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NUREG/CR-3235, Technical Assistance for Regulatory Development: Review and Evaluation of the EPA Standard 40CFR191 for Disposal of High-Level Waste, Volume 1
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Issue date:	04/30/1983
From:	Ortiz N, Wahi K; Office of Nuclear Material Safety and Safeguards, Sandia
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NUREG/CR-3235 SAND82-1557 WH TECHNICAL ASSISTANCE FOR REGULAT.ORY DEVELOPMENT:

REVIEW AND EVALUATION OF THE EPA STANDARD 40CFR191 FOR DISPOSAL OF HIGH-LEVEL WASTE VOLUME 1 EXECUTIVE

SUMMARY

N. R. Ortiz K. K.* Wahi*

Manuscript Completed: April 1983 Date Published: April 1983 Sandia National Laboratories Albuquerque, New Mexico 87185 operated by Sandia Corporation for the Uo S. Department of Energy Prepared for Division.of Waste Management Office of Nuclear Material Safety ~nd Safeguards Washington, o.c. 20555 NRC FIN No.- A-1165

Science Applications, Inc.

OTHER VOLUMES OF SAND82-1557 NUREG/CR-3235 Main

Title:

Technical Assistance*for Regulatory Development: Review and Evaluation of the EPA Standard 40CFR191 for Disposal of High~

Level Waste.

Volume 1

Executive Summary N. R. Ortiz. K. Wahi

Volume 2 .A Simplified Ana.lysis of a Hypothetical High-Level Waste Repository in a Basalt Formation R. E. Pepping. M. s. Chu. M.. D. Siegel Volume 3 A Simplified Analysis of a Hypothetical High-Level Waste*Repository in a Tuff Formation M. D. Siegel. M. S. Chu Volume 4 A Simplified Analysis of a Hypothetical High-Level Waste Repository in a Bedded Salt

.Formation R. E. Pepping. M. s. Ch~. M. D.. Siegel Volume 5 Health.Effects Associated with Unit Radio-nuclide Releases to the Environment J. c. Helton Volume 6 Calcuiation of Health Effects Per Curie Release for Comparison with the EPA Standard G. E. Runkle

ABSTRACT The Environmental Protection Agency (EPA) has prepared a draft Standard (40CFR191, Draft 19)[1] which, when finalized, will provide the overall system requirements for the geologic disposal of radioactive waste. This document (Vol. l) provides an "Executive Summary" of the work performed at Sandia National Lab6ratories, Albuquer~u*, NM. {SNLA) under contract to the US Nuclear Regulatory Commission (NRC) to analyze certain aspects of the draft Standard~ The issues of radionuclide release limits, interpretation, uncertainty, achievability, and assess-ment of compliance with respect t6 the requirements of *th~

draft Standard are addressed based on the detailed analyses presented in five companion volumes to th.is report.

iii

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Introduction The Environmental Protection Agency (EPA) has prepared a draft Standard (40CFR191. Draft 19)[1] which. when finalized will provide the overall syste~ requirements for the geologic disposal of radioactive waste. Volume 1 of this series of reports provides an "Executive summary" of the work performed at Sandia National Laboratories. Albuquerque. N~ (SNLA) under contract to the US Nuclear Regulatory Commission to analyze certain aspects of the draft Standard. There.are five compan-ion volumes to this report that _describe. in detail. the analyses carried out. Analyses of hypothetical repositories in three candidate media (Vols. 2. 3. 4) were performed to address the issues of interpretation, achievability, uncertainty, and

co~pliance with respect to the requirements of ihe draft Sta_ndard. An analysis investigating the health effects associ-ated with unit radionuclide releases (Vol. s) was performed to ascertain the release limits of the draft Standard and their relationship to .the assumed health ~ffects. Calculations of health effects *per curie of release. similar to those in Volume 5, were carried out for the purpose of showing the effects of uncertainty (Vol .. 6) in defining the release limits.

Radionuclide Release Limits.

The objective of the draft Standard is to set forth .require-ments that will ensure public health and safety by minimizing

the riskB associated with the permanent disposal of nuclear wastes. In an attempt to establish release limits for various radionuclides. the EPA selected a limit on long-term risks of 1,000 health effects (i.e .* latent cancer fatalities) over 10,000 years for a 100,000 -metric ton of heavy metal (MTHM) repository (for reasonably foreseeable releases). This is*

equivalent to ten health effects per 1,000 MTHM. The EPA determined the release limit for a given radionuclide by calculating the number of curies that, if released to the accessible environment, will not cause more than ten.health effe~ts per 1.000 MTHM over 10,000 years. Using the same health effects constraint. SNLA calculated independently the number of curies for each radionuclide as described in Volumes of this report. The results are compared with the EPA release limits in Table 1. The t~o sets of release limits are seen to be very similar. with the exception of 99Tc.

The release limits shown in Table l are derived. both by EPA and SNLA~ by using single point values for the input parameters or variables that are known to have uncertainties. The effect of these uncertainties was scoped in the present study by performing calculations in which ranges and distributions were assigned to the distribution coefficients (Rd), river dis-charge, regional erosion rates. and _exchange factor between the.

TABLE .l A Com paris on of cumu lativ e Rele ase Limi ts to the Acce ssibl e Envi ronm ent for 10.00 0 Year s Afte r Disp osal Prop osed Rele ase' Rele ase Limi t From Half -Life Limi tb (cur ies per Tabl e 1-lc (cur ies Radi onuc lide (yea rs)a 1000 MTHM) per 1000 MTHM)

Am241 458 10 Am243 7370 14 4 4 Cl4 5730 200 Csl35 2.18 3.E6 2000 2625 Csl37 30.2 500 I Np23 7 505 I',.) 2.14E 6 20 17 I Pu238 86 400 Pu239 437

2. 44E4 100 Pu24 0* 145 6580 100 153 Pu242 3.79E 5 100 Ra22 6 148 1600 3 NE Sr90 28.1 80 Tc99 83 2.12E 5 2000 35.08 8 Snl26 l.E5 80 83 Any othe r alph a-em ittin g 10 radio nucl ide Any othe r radio nucl ide whic h 500 does not emit alph a part icles a From Ref. 2 b From Ref. l c From Volume 5 NE no estim ate

surface water and soil compartments. A sample comparison with the EPA calculation is presented in Figure 1. which shows the health effects associated with one curie of a given radio-nuclide when the ingestion pathways are considered.

The results of this analysis suggest that the release limits for 241Am. 243Amand 237Np may be overly conservative and may warrant a re-examination by the EPA. Also. the EPA release limit for 135cs would appear not to be restrictive enough and may also warrant some reconsideration.

Although the results .in Volume 6 generally suggest that the EPA made assumptions conservative enough to cover the uncertainties expected in the input variables considered by SNLA. they do not establish that the EPA release limits proposed in the Standard are overly conservative. However. SNLA did.not address all the uncertainties in the input parameters. A more complete compar-ison and discussion is included in Volume 6.

Interpretation of the Requirements The draft Standard requires high-level waste repositories to be designed to provide a reasonable expectation that for 10.000 ye~rs after disposal: (1) reasonably foreseeable releases of waste to the accessible environment are projected to be less than the quantities in Table 1. and (2) very unlikely releases of waste to the accessible environment are projected to be less than ten times the quantities in Table 1. The draft Standard defines: (1) "reasonably foreseeable releases" as releases of radioactive wastes to the accessible' .environment that are esti-mated to have more than one chance in 100 of occurring within 10.000 years. and (2) "very unlikely releases" a~ releases of radioactive wastes to the accessible environment that are estimated to have between one chance in 100 and one chance in 10.000 of occurring within 10,000 years.

The draft Standard uses. but does not define. the word "release."

The interpretation of this word affects the manner in which compliance is assessed. Two possible interpretations are:

Interpretation 1: The word "release" defines a unique scenario*

leading to radionuclide release. The draft Standard is applied independently to the probability of release for each scenario.

scenarios are events. features, and processes. both natural and human induced, that could conceivably alter the natural state of the disposal site and result in human exposure to radionuclides released from the underground facility.

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Interpretation 2:

A "release" involves all scenarios that may result in discharges to the environment during .the regulatory period. The magnitude of the discharge is given by its correspond-ing EPA Release Ratio.* Estimation of the.

probabiliiy of exceeding a given value of the EPA Release Ratio includes contributions from all scenarios.

Analyses were performed based on the above interpretations. In the analyses of the hypothetical basalt repository (Vol. 2).

compliance assessment was investigated in terms of *Interpreta-tion 1 and 2. In the analysis of the hypoth~tic~l tuff repository (Vol. 3),,_compliance assessments were made using a modified version of Interpretation 1 such that the scenario probability (and not release probability) determined the allowable r~lease limit. In th~ analysis of a hypothetical bedded salt repository (VOL 4). -the results* of the direct-hit scenarios are presented individually in conformance with Inter-pretation 1: the results of the four ground-water transport scenarios are combined as suggested by Interpretation 2.

The results discussed in Volume 2 indicate that_ the number .of predicted violations to the draft Standard will vary depending on the selected interpretation.

As discussed in Volume 2. we feel that Interpretation 2 is more in the* spirit of the risk-based requirements of the draft Standard. since it considers all sources producing a release greater or equal to the specified, release limits. EPA should clarify the intended interpretation.

Achievability of the Requirements Si~plified analyses of hypothetical repositories in basalt.

tuff. and bedd~d salt* formations have been p~rformed with the in.tent of predicting integrated releases to the accessible environment and cqmparing them to the release limits of the draft Standard. Each of the interpretations stated above has been used in expressing the re-ults of these analyses in terms of the release limits of the draft.Standard~ An appropriate set*

of scenarios has been *chosen for analysis in each of the three media; i.e., the scenarios chosen for a given medium are, in.

general. different fro~ the ones chosen for the other two media. Table 2.summarizes the postulated scenarios for hypo-thetical repositories in basalt. tuff~ and bedded salt. A

*obtaine.d by summing over all radionuclides the ratio of the integrated' discharge to the release limit. For a given radionuclide., the release limit is the value given in Table 1 or ten times that, depending on the probability of release-

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TABLB 2 Sconario c Analyzed for Hypothe ticQl Repou!to riee ln Basalt, Tuff, and Bedded Salt Hoot Scenario Number and Descrip tion lllledlum Scenario 1 Scenal'lo 2 Scenat'lo 3A Routine Scenario 38 Scenaz,lo 3C Fracture s Bo.. ehole Borehole 81111dt release with la denue Boz,ehole connecti on to connecti on to connectl on to no dlaruptl oa basalt upper aquifer: .Upper aqul fer: uppez, aquifer; mldng cell leach llmlted: leach 11ml ted:

oource model 10-4 7 10-5 7 per year pez, year Scenario s 1 & 18 ScenCLrlo* 2 & 28 Scenario 3 I 1. No z,etaz,da tloa Scene.t'lo 4 Scen&t'los 5 & 58 Scenai,lo 6

!Both use rock Retat'da tlon In Retardat ion ln Tuff Both experien ce Retal'da tlon es

°'I In any ft'BCture d layez,a matrix diffusio n and the vertical some fracture d layers due to porous v ltd c or.-

dev i tr l f 1ed tuff 300 ft. rise In water table ln Scenado 1; 18, Rock mCLtrlx gradien t Is un- zeollta11 accessib le envlz,oo-dlffualo n In soma. fracture d 5. Retarda tion ao ment 8 miles from affected by thermal layez,s ln fz,e.ctured 1*ulse In each. ln Scenario 1 l'eposlto l'y leyez,u 28 uses the mlxlng cell source model 58. Retardat ion ea ln Scenario 18 S<:enarlo l Scenat'io 2 Scenado 3 U-tube fonned b~ Scenat'lo 4 Scenario 5 Scenal'lo 6 U-tube fon11ed by U-tube formed by U-tube formed by Bedded a failed shaft two or moz,e bore- Canlstel ' direct Brine pocket Salt a failed shaft two or moz,e boz,e- hit; npld *and seal and one or holes; water eeal and one or penetrat ion mol'e boz,ehole a; holes; t1atel' dlz,ect movement o.-lglna tes fl'om more borehole s; originat es from water orlglnat ea and return11 to of radlonu clldes water oz,lglnat em and l'eturno to to 8Ul'face from and l'Bturn11 prhauy aqulfor fl'om and l'otul'n; to primal'y aquifer secondar y aquifer to aecondal'y aquifer

lea~h-limited source model is implied unless stated otherwise in Table 2. The discharge location (accessible environment) is at a distance of one mile in all cases. except for Scenario 6 in tuff where this distance is eight miles.

The above analyses were .performed using the SNLA Risk Assess-ment Methodology (3,4,5]. The methodology also incorporates uncertainty and sensitivity techniques ~o calculate consequences (integrated discharges) and the associated release probabilities. Ranges and distributions are assigned to those input variables, from the set of variables needed to define ground-water and radionuclide transport, that are kno.wn to have significant uncertainties. A Latin Hypercube .Sampling (LHS) technique [5] is then used to sample input values to be used in the calculation of ground-water and radionuclide transport.

A quantitative description of the degradation of the.waste form and its release at the boundary of the engineered barrier is provided by a "source model.". Three different source models were utilized in the present work:

Source #1 This is a leach-limited source model. A different leach-rate range is chosen for each medium. A range of 10-3 to 10-7/yr is ~sed 1

for tuff. and a maximum range of 10-4 to

. 10-7iyr is used for basalt and bedded salt.

The complete inventory of waste is assumed to be available for leaching.

Source. #2 This leach-limited source has the same range as source fl in terms of release rate, but the amount of. waste available for transport is reduced. Each borehole. allows only the penetrated waste -in the particular backfilled storage room to be available for transport.

Source #3 This source resembles Source #2 but allows the backfilled rooms to be modeled as a mixing cell where wasteforms are leached uniformly. Solubil-ity limits are allowed to apply to radionuclide concentrations in the mixing cell.

Only the repository in bedded salt was analyzed with all three source models. -

Although the draft Standard has defined a r~gulatory p~riod of 10,000 years, the present analysis was carried out. to a total of 50,000 years. and the results are presented in increments of 10,000 year~~ Thi~ was done in order to assess the adequacy of the 10,ooo~yr period of regulation.

An examination of the results from the basai"t analyses indi-cates that Scenario l does not violate the EPA release limits when using Interpretation 1. during the first so.ooo years.

Slight violations do occur for Scenario 2 in each of the five 10.000-yr increments. The Scenario 3 results show a strong

, dependence on the type of source model used. In Scenario JA.

no violations occurred during the first. second. and fifth 10.000-yr period. In Scenarios 3B and JC. large to very large violations o~curred in each of th~ five 10.000-yr periods considered.

In the tuff analysis *. it was assumed that all the scenarios considered were reasonably foreseeable.

During the first 10~000-yr period. Scenarios i. lB. 3. 4 and 5 show very slight to slight violation of the draft Standard limits: Scenarios SB and 6 sho~ no violation and Scenarios 2 and 2B show large violations. In general. the number of vectors* or the extent of violation. or both. tend(s) to increase in each of the.

subsequent 10.000-yr periods analyzed.* This increaie. however.

is gradual and typically within an order of magnitude.

As with the basalt results. the bedded salt results were evaluated using Interpretations 1 and/or 2. The grotind-wa~er transport scenarios (Scenarios 1-4) were repeated using three different source models, and the results are ~valuated using Interpretation 2. Substantial variations in the results occur when different source models are used. Gross violations occur when source fl is used. No violation occurs during the first 10,000 years for Source #2: violations during the subsequent 10.000-yr petiod are extremely minor. No violations occur during any of the five 10,000-yr periods wh~n Source i3 is used. Interpretation 1 was used in presenting the results of Scenari~s 5 and 6. The direct hit scenario. Scenarios. indi-cates a slight violation during the first 10,oob-yr period.

The brine-pocket penetration scenario. Scenario 6, indicates~

relatively large violation of the EPA limit.

The results for all three media for the first 10,000 years are summarized in Table 3. Sample plots 6f probability of exceeding release r~tio on the abcissa are shown in Figure 2 for basalt. Figure 3 for tuff, and Figures 4 and 5 for*bedded salt. A direct comparison among the three different media is not recommended due mainly to the fact that the scenarios analyzed are different.

Conclusions and Recommendations Based on the results of the: analyses performed by SNLA. the following co*nclusions and recommendations are presented.

A vector. in the present context, r~presents a complete s~t of input values selected by the sampling program to carry out a transport calculation. Different vectors represent different combinations of input parameter values ..

TABLE 3 summary of Results of Simplified Analysis for Hypothetical Repositories 1n Basalt. Tuff. and Bedded Salt

(10.000-yr period)

Host scenario Number and Description Medium Interpretation *l BASALT Scenario 1 Scenario 2 Scenario 3A Scenario 38 Scenaqo JC p*ercent No 3\ No -20, -10, violations violations violations maximum 1.3 -1.000~ -100.

release rat.io contrib. Cl4 several Several radio-nuclides Interpretation 82 BASALT percent No violations (Using Scenarios 1. 2 & JA) violations Modified Interpretation #1 TUPP Scenarios Scenarios Scenario 3 Scenario 4 Scenarios Scenario i l and lB 2 and 2B- 5 and SB percent l\ l\ 10\ 8\ l\ l\ 3\ none none violations maximum 2.4 1.7 207 22 .9 1.9 7.9 release ratio

cont rib. Tc99 Tc99 U234 0234 Tc99 Tc99 Cl4 radio- Np237 U236 nuclldes U238 Np237 U23'6 Interpretation #1 BEDDED Source

Scenario 1 Scenario 2 Scenario 3 Scenario 4 SALT percent 1 61\ 59\ 27\ 2a,*

violations 2 no . l\ <n DO violation violation 3 no no DO DO v1olat1on violation violation violation maximum l 44 43 25 25 release 2 1.6 1.2 ratio cont.rib. l 0234 0234 U234 U234 radio- Am243 Am243 U236 0236 nuclide& U236 U236 U238 U238 U238 U238 2 Am24J+ u234+

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Interpretation ftl lnterp~et!tion 92 BEDDED Scenario 5 scenario 6 Scenar;ios l, 2, 3 & 4 SALT percent Very Some source l large violations violations slight violations S1>urce 2 no violat;i.ona violation *source 3 no violations

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The radionuclide release limits in the draft Standard are in agreement with the values calculated by SNLA with the exception of 99Tc. The draft Standard allows a lower release limit for 99Tc.

In general. the health effects (per curie) 6alculated by EPA for the ingestion pathways are higher than the ranges calculated by SNLA. The exceptions are 126sn and 135cs. The resu.lts of this analysis for 241Am. 243Am and 237Np indicate that the release limits for these radionuclides may be overly conservative and may warrant a*

)

re-examination by the EPA. Also. the EPA release limit for 135cs would appear not to be restrictive enough according to the results of this analysis and. again, may warrant some reconsideration.

The results suggest that higher releise limits could be tolerated if the health effects per curie calculated in the present analysis were to be the basis for such a decision.

However. the results do not establish that the release limits in the draft Standard are overly conservative.

It is necessary to clearly state the intended interpre-tation in the draft standard as to how the terms "reasonably foreseeable" and "very unlikely" releases should actually be applied._ In other words. is it the scenario probability or the probability of release? .

Further, should the release probabilities be considered for individual scenarios (conditional) or all pertinent scenarios with a composite release probability?

-

The results of the analyses for the reference basalt site

performed under Interpretation 1 showed a small probabil-ity of violating the draft EPA Standard for Scenarios 2 and 3A. Under Interpretation 2, the same analyses indi-cate total compliance with the draft Standard, underscoring the need for a clear interpretation.

Sorption of radionuclides by s.everal thousand feet of zeoli ti zed .tuff may limit the release of actinides below the EPA release limits even in the absence of solubility constraints. .

Violati6ns ~f the draft Standard for Scenirios 1. lB, 3, 4. and 5 in tuff are due to discharges of 99Tc and 14c. Retardation due to matrix diffusion, however, could significantly reduce the discharge of these nuclides under realistic ground-water flow rates.

If the radionuclides do not flow through thick sequences of zeolitized tuff. discharges of U and Np under oxidizing conditions may be much larger than the EPA limits.

Drilling-related. direct-hit scenarios in sedimentary basins indicate slight violations of the draft Standard.

Brine pockets in bedded salt may pose~ significant prob-lem in complying with the draft Standard. Therefore. site characterization should directly address the question of identifying any brine pockets that may be present.

Analyses performed with different source models show the importance of the source-term assumption on compliance estimates. In general. the mixing-cell source model gives significantly lower releases. and hence discharges. to the accessible environment.

A majority of the vectors examined in all scenarios pro~

duced radionuclide releases below the limits set by the draft *standard. In general. violations of the Standard occurred only when the most conservative assumptions were used or when combinations of input data produced ground-water flow rates that were unrealistically high . .

A practical difficulty in implementing the draft Standard is the lack of our ability to assign reliable numerical values to the. scenario probabilities. The methodology to assess compliance with the Standard is. nevertheless, available as has been demonstrated by this and other similar studies. -

The predicted radionuclide releases over 10.000-yr inter-vals. from 10.000 to so.ooo years. are not significantly higher than for the first 10.000 years. The maximum release ratio over the so.ooo years increases by a factor of two to three.

SNLA strongly recommends thai detailed performance an~lyses be carried out for repositories in ba~alt and tuff {similar to the on~ performed for bedded salt in [i.4]) to assure that important variables. processes. or event~ have riot been overlooked in the simplified analyses.

REFERENCES

1. "Environm ental Radiation Protection Standards for Manage-ment and Disposal of Spent Nuclear Fuel. High~Leve l and* Transuran ic Radioactiv e Wastes. 11 40CFR191.

(Working Draft :fl:19 >.* Federal Register, March 19. 1981.

2. Weast. w. E .* 1974~ Handbook of Chemistry and Physics (55th edition). CRC Press. Cleveland . OH.

3. Cranwell.

R. M.* J. E. Campbell. and others.* "Risk Method-ology for Geologic Disposal of Radioactiv e Waste:

Final Report." Sandia National Laborator ies, SAND~Sl-2573. NUREG/C.R-:-2452. 1982.

4. Cranwell. R. M** R. v. Guzowski. J. E. Campbell. and N. R.

Ortiz, "Risk Methodolo gy for Geologic Disposal of Radioactiv e Waste: Scenario Selection Procedure ."* . I Sandia National L.aborator ies ~ SANDS0-1429. NUREG/CR- I 1667. 1982. .

5. Iman. R. L .* J.M. Davenport . and D. K. Zeigler. "Latin-Hypercube Sa.mp ling: Program User's Guide. " sand_ia National Laborator ies. SAND79-1473. 1980.

NRC FORM 335 1 REPORT NUMCER /Amgn~a ~i: D(;CJ l U.S. NUCLEAR REGULATORY COMMISSION 111111 NUREG/CR-3235, vol.

018.LIOGRAPHIC DATA SHEET SAND82-1557 4 TITLE AND SUBTITLE {-"!dcl Volum~ No, 1f appropr,a~J 2 (Leav~ Olllft/c J Technical Assistance for Regulatory Development:

Review- and Evaluation of the Draft EPA Standard 3 RECIPIENTS ACCESSION NO 40CFR191 For Disposal of High-Level Waste 7 AUTHOR ISi Executive Summary 5 DATE REPORT CO\IPLETED Fuel Cycle Risk Analysis Division MONTH I YEAR

April 1983 9 PERFORMING 9RGANIZATION NAME ANO MAILING ADDRESS (Include Z,p Code} DATE REPORT ISSUED Sandia National Laboratories MONTH I YEAR Fuel Cycle Risk Analysis April 1983 Di vision 9413 6 (L~av~ Otan/r I Albuquerque, NM 87185 t-------- --------- _.;..---- -----1 B 12 SPONSORING ORGANIZATION NAME AND MAILING ADDRESS (lnclud~ Z,p Code}

(Leav~ 01ank J 10 PROJECT/TASK/WORK UNIT NO Division of Waste Management

.Office of Nuclear Material Safety and Safeguards 11 FIN NO U.S. Nuclear Regulatory Commission NRC FIN A 1165 Washington, DC 20555 Task 3 13 TYPE OF REPORT Formal Report l"PE RICO COVERED llnclu1,v~ Oate1)

July .1981 - April 1983

15 SUPPLEMENTARY NOTES 14 (Leav~ orank J 16 ABSTRACT 1200 words or less)

The Environmenta l Protection Agency (EPA) has prepared a.draft Standard (40CFR191, Draft 19) which, when finalized, will govern the geoiogic disposal of radioact.1. ve waste. This document (Vol. 1) provides an *

"Executive Summary" of the work performed at Sandia National Laboratories ,

Albuquerque, _N.M. (SNLA) under a contract to the U.S. Nuclear Regulat9ry Commission (NRC) to analyze certain aspects of the draft Standard.* The issues of radionuclide release limits, interpretatio n, uncertainty, achievability , and assessment of compliance with respect to the require-ments of the draft Standard are addressed based on the detailed analyses presented in five companion volumes to this report.

17 KEY WOROS AND DOCUMENT ANALYSIS 17a OESCRIP1.0F,S 17b IDENTIFIERS.OPEN ENDED TERMS 18 AVAILABILITY STATEMENT 19 SECURITY CLASS /Th,s r~oortJ 21 NO OF PAuES Unlimited Unclassified 20 SECUAI TY CLA~ /Th*J P1J~/ 22 PRICE Unclassi.tiea 0 s

IIIRCFORMJJ5 111111

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NUREG/CR-3235 SAN D82-1557 Vols. 2, 3, and 4 Technical Assistance for Regulatory Development: Review and Evaluation of the Draft EPA* Standard 40CFR 191 for Disposal of High-Level Waste

A Simplrf1ed Analysis of a Hypothetical Repository 1n a Basalt Formation

A Simplrf1ed Analysis of a Hypothetical Repository 1n a Tuff Formation

A Simplified Analysis of a Hypothetical Repository rn a Bedded Salt Formation Prepared by Fuel Cycle Risk Analysis D1v1s1on Sandia National Laboratories April 1983 Prepared. for U S Nuclear Regulatory Comm1ss1on

OTHER VOLUMES OF SAND82-l557 NUREG/CR-3235 Main 'l'itle:

T.echnical Assistance for R,egulatory Development: Review and Evaluation of the EPA Standard ~OCFRl~l for Disposal of High-Level Waste ..

Volume 1 Executive su~mary N. R~ Ortiz, K. Wahi Volume 2 A Simplified Analysis of a Hypothetical High-

.Level .waste*Repository in a Basalt Formation R. E. Peppirig, M. S. Chu, M. D. Siegel Volume 3 A Simplified Analysis*of a Hypothetical*High-Level Waste Repository in a Tuff Formation.

M. D. Siegel, M. S. Chrt Volume. 4 .*

A Simplified Analysis of a Hypothetical High-Level Waste Repository in a Bedded Salt Formation -

R. E. Pepping. M. s. Chu. M. D. Siegel Volume 5 H~alth Effects Ass~ciated with Unit Radio-nuclide Releases to the Environment J. c. Helton Volume 6 Calculation of Health Effects PerCurie Release for Comparison with the EPA Standard G.. E. Runkle

Volume 2

A Simplified Analysis of a Hypothetical Repository in a Basalt Form111tic:m

NURE G/CR -3235 SAND 82-15 57 WH TECHNICAL ASSISTANCE FOR REGULATORY DEVELOPM REVIEW AND EVALUATION OF THE DRAFT*EPA STANDARD ENT:.

40CF R191 FOR DISPOSAL OF HIGH-LEVEL WASTE VOL. 2 A SIMP LIFIE D ANALYSIS OF A HYPOTHETICAL REPOSITOR Y

IN A BASALT FORM.l\TION R. E. Pepp ing M. S. Chu M. D. Sieg el Manu scrip t Comp leted : Apri l 1983 Date Publ ished : Apri l 1983 with cont ribut ions from:

R. v. Guzo wski*

Sand ia Nati onal Labo rator ies Albu querq u~, New Mexi co 87185 oper ated by Sand ia Corp orati on for the U. s. Depa rtmen t of Energ y Prep ared for Divi sion of Wast e Mana geme nt Offi ce of Nucl ear Mate rial Safe ty and Safe guar ds Hash ingto n, n.c. 20555 NRC ~.,IN. No. A-11 65

Ene rgy Mana genen t and Tech nolog y

ABSTRACT An anal ysis of a hypo theti cal nucl ear wast e repo sitor y in a.ba salt form ation has been -perf orme -

d to dem-onst rate the appl icati on of exist ing* anal ytica l tools to the asses smen t of* comp lianc e of the repo sitor y with the draf t EPA Stan dard , 40CFR 191 (Dra ft #19) . The tools have been deve loped by Sand ia Natio nal Labo rator ies for use by NRC in such analy ses. The hypo theti cal site is based on desc ripti ve and quan titat ive data for a cand idate basa lt repo .sitor y in the early stage s of site char acte rizat ion.

The effe cts of unce rtain ty in the inpu t data on the asses smen t of comp lianc e are demo nstra ted; Othe r sourc es of unce rtain ty resu lting from inter pret ation of the stan -

dard and its prob abili stic natu re are discu ssed

. The re-sults of the calc ulati ons prese nted indic ate that

. ance with the draf t stand ard may be achie ved comp li-depen d*ing . On how the* term "rele ase" is inter prete d~ name ly, is the re-lease due to a uniqu e (sing le) even t or does it invo lve all prob able scen arios .

iii

TABLE OF CONTENTS Chapte r

1. INTRODUCTION ....... ....... ....... ....... ....... 1

2. THE DRAFT. EPA STANDARD, 40CFR1 91 . . . . . . . . . . . . . . . 4 2.1 Interp retatio ns of the Draft Stand ard.... . 4 2.2 Implem entatio n of Differ ent Interp retatio ns. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 - Estima tion of Probab ilities of Scenar ios.. 9 3* THE REFERENCE BASALT SI TE . . . . . . . . . . . . . . . . . . . . . . 11

4. WASTE AND REPOSITORY DESC RIPTI ON.... ......... .. 16 4.1 vvaste ....... ....... ....... .....-. . . . . . . . . . . 16 4.2 Subsur face Facilit y ....... ....... ... ~.... 16 5* GEOCHEl lI STR:Y . *. . . . . . . . . . . . . . . . . . . _....... ... -. . . . .

0

- 18 5 .1 Retard ation Factors . . . . . . . . . . . . . . . . . . . . . . 18 5.2 Solubi lity ....... _..... ....... ....... ..... 23 5.3 Matrix Diffu sion. ....... ....... ....... ... 23

6. GROUNDWATER TRANSPORT MODEL ... ..... ... *. . .. .... 25

7. SCENARIOS ANALYZED . , , . , .** , ...*... . _. . . . . . * . . . . . 27 7.1 Scenar io-! Routine Releas e ....... .... .. 28 7.2 Scenar io 2 Fractu res in Dense Basalt .. 32 7 ._3 Scenar io 3 Boreho le . _....... ....... ... . 34

8. RESULTS OF DEMONSTRATION ANAL YSES ......... ...... 44

9. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 REFERENCES * . .. . . * * . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . R-1 V

APPENDICES APPENDIX A -- RADIONUCLIDE RETARDATION A-1

1. Calculation of the Retardation Factor.... A-1

2. Estimation of Utilization Factor .... ..... A-3 APPENDIX B -- REDOX CONDITIONS IN THE REFERENCE REPOSITORY AND APPROPRIATE VALUES OF Rd *************.****** ** , ***** ** * * *

B-1

1. Redox Conditions .*............. ; ..... ~. .. B-1

2. Available Data for Values of Ra.......... B-2 APPENDIX C -- AN APPROXIMATE TREATMENT OF MATRIX DIFFUSION AS A RETARDATION MECH.Ai.'HSH . C-1 APPENDIX D -- CALCULATION OF THERMAL BUOYANCY GRADIENT ................... .......... D-1 APPENDIX E THE MIXING CELL SOURCE* MODE.L ......... E-1 APPENDIX F RATIONALE FOR THE SELECTION OF SCENARIOS ANALYZED IN BASALT . . . . . . . . . . F-1 APPENDIX G -- GEOCHEMICAL AND HYDRAULIC PARAMETER . DATA. . . . . . * . . . . . * . . . . * . . . . . . G-1 V1

LIST OF FIGURES Figure Page*

1. General Geologic Features of the Referenc e Basalt Reposito ry Site . . . . . . . . . . . * . . . . . . . . . . . . 12 2, Stratigr aphic Cross-S ection of* Hypothe tical Reposito ry in Basalt . . . . . . . . . . . . . . . . . . . . * . * . . . 13

3. Routine ' Release Scenario (Scenari o i) ........ . 31

4. Fracture d Dense Basalt Scenario (S~enari o 2) .. 1l

5. Borehole Scena:['.io ( Scenario 3 ). . . . . . . . . . . . * . . * . 37

6. Scenario 1 CCDF - 1st lO~OOO_ Years 45 7* Scenario 1 CCDF 2nd* 10,000 Years 46

8. Scenario l CCDF - 3rd 10,000 Years ........ .... 47

9. Scenario l.CCDF - 4th 10,000 Years 48

10. Scenario l CCDF - 5th 10,000 Years 49

11. Scenario 2 CCDF - 1st 10,000 Years ........ .... so

12. Scenario 2 CCDF - 2nd 10,000 Years ........ .... 51

13. Sce.nario .2 CCDF - 3rd 10,000 Years 52

14. Scenario 2 CCDF - 4th 10,000 Years ... *......... . 53

15. Scenario 2 CCDF 5th 10,000 Years ........ .... 54

16. Scenario 3A CCDF - 1st 10,000 Years 55

17. Scenario 3A CCDF - 2nd 10,000 Years 56

18. Scenario 3A CCDF - 3rd 10,000 Years 57 19, Scenario 3A CCDF - 4th 10,000 Years 58

20. Scenario 3A CCDF - 5th 10,000. Years ............ 59

21. All Scenario CCDF - 1st 10,000 Years ....... ** .. 60

22. All Scenario CCDF - 2nd 10,000 Years 61 vii

LIST OF FIGURES (continued)

Figure

23. All Scenario CCDF - 3rd 10,000 Years 62

24. All Scenario CCDF 4th 10,000 Years 63

25. All Scenario CCDF - 5th 10,000 Years 64

26. Scenarios 3B and 3C (leach limited) CCDFs -

1st 10,000 Years . . . . . . . . . . . . **. .. . . . . . . . . . . . . . . . . . 65

27. Scenarios 3B and- 3C (leach limited) CCDFs -.

2Il.d 10, o*oo Years . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 66

28. Scenarios 3B and 3C (leach limited) CCDFs -

3rd 10,000 Years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6**7

. 29. Scenarios 3B and 3C (leach limited) CCDFs -

4th 10,000 Years . . .. * . . . . . . . . . . . . . . . . . . . . . . . . . * . . . 68"

30. Scenarios 3B and 3C (leach limited) CCDFs -

5th 10,000 Years . . . . . . . . .. . . .. . . . . . . . . . . . . . . . . . . . . 69 B-1 ~d Data ........................... ~ .* . . . . . . . . . . . . B-3 C-1 Idealized Fracture Geometry * . . . . . . . . . . . . . . . . . . . . C-2 Breakthrough Curve Depicting Behavior. of Equation Cl: C(t)=C0 erfc(17) ...***..****.*..... *.. C-5 D-1 Water Column Assumed for Thermal*Buoyancy Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. . . . . . . . . D-1 D-2 Isotherms Used in Calculating Thermal Buoyancy ** D-3 E-1 Implementation of the Mixing Cell Source Model for }TWFT/DVM *******.. ~ *** **..*. * . . . . . . . . . . . . . . . . . * *E-3 E-2 Effects of the Mixing Cell Assurnptuion on

Integrated Discharge Relative to the Leach-Limited Source Mode 1 . . . . . . . . . . . . . . . . . . * . . . . . * * . *

E-5 .

viii

TABLES Ta ble

1. Cu mu lati ve Re lea ses to the Ac ces sib le En vir -

onm ent for 10, 000 Ye ars Af ter Di spo sal ..* .** ... *s

2. Re fer enc e Hy dra uli c Pro per tie s *.. ... ... ... .** **

14

3. Inv ent ory of Re fer enc e Re pos ito ry **. .** ..* **. ..

17

4. Ge och em ica l En vir onm ent of Str ati gra ph ic La yer s in Ba sal t Re pos ito ry

.. . ~ ..* .** .** **. *.. 21

5. Rd Ran ges . . *. Cl

o D

o ** o o ** Cl o * * ** o * *

o ... o

o *

o o *

o 22

6. Ran ges of So lub ili tie s of Se lec ted Ele me nts Use d for Ba sal t Re fer enc e Re pos ito ry Co nd itio ns. 24

7. Oa ta Ran ges and Di str ibu tio Va ria ble s ... *.. ... ..* ..* *.. ns for Ad dit ion al

.** .* *. . . . . * * . . . * . * * * * *2 9

8. Sc ena rio 2 .: EPA Ra tio s of Ra dio nuc lid e Dis cha rge s int o Aq uif er I-M c> e *

0 0 0 35

9. Sc ena rio 3: EPA Ra tio s of Ra dio nuc lid es

<ieo*o*o 40

10. Sc ena rio 3A: EPA Ra tio s Sum ri1ed Ov er Al l Ra dip nuc lid es .*. .*. ... .. ..*

.*. ... . 41 11 . Me an Va lue s of Co ntr ibu tio

{10 0 Ve cto rs) for Sc ena rions to the EPA Sum 3B wit h Le ach -

Lim ite d Sou rce . a o . " o * * * *

o o o Cl). o o o a .... a * * * "

~ Cl o o

42 C-1 Sc ena rio 2 Dis cha rge s Wi tho ut Roc k Ma trix Re tar dat ion *** **. *** *** *.*

- - *** *** *** * : .** ~ *** C-8 C-2 Sun una ry of Ef fec ts of Di ffu Ma trix on TID o e sio n Int o Roc k ooeeoeoeDo eoo******.*o*

o*ooo*o***

C-9 C-3 Ve cto r 15 Da ta Use d to Est im ate Re tar dat ion Due to Di ffu sio n int o the Roc k Ma trix * . . * * .* * * * . *C- 10 C-4 Ve cto r 24 Da ta Use d to Est im ate Re tar dat ion Due to Di ffu sio n int o the Roc k Ma trix ... .*. .**

C-1 1 C-5 Ve cto i 62 Da ta Use d to Est im ate Re tar dat ion Due to Di ffu sio n int o the

Ro ck Ma trix *** .** ..*

C-1 2 lX

LIST OF TABLES (continued)

Table D-1 Hydraulic Gradients Produced by Thermal Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . *. _.. D-2 G-1 Ranges of Rd Values for Basalt Host Rock. G-1 G-2 Ra Values for Basalt *******.******...* ~.. G-2 G-3 Ra Ranges in Basalt Aquifer . . * * * * * . . * * * . . . G-3 G-4 Basalt Hydraulic Parameters ..**.*.....***. G-4 X

1. INTRODUCTION In the near future, the EPA is expected to issue a proposed standard (40CFR19 1) governin g the geologic dispo-sal of radioac tive wastes. A 180 day period is expected for public comment on the st.andard . Other governm ent agen-cies, such as the NRC, are also expected to comment on the standard . Saridia is funded by.the NRC- to provide informa tion and insight useful.i n preparin g these comments ~ .The objec-tive of this effort is to perform calculat ions similar to those.pe rformed by EPA in developi ng their standard 1 (Draft

19). We have calculat ed integrat ed discharg es of radio-nuclides in plausib le sce.riario s. A number of media have been proposed as candidat e hosts for nuclear waste reposi-itories; bedded salt, domed salt, basalt, tuff and granite .

This report documen ts analyses of a hypothe tical reposito ry in basalt.

In order to assess complian ce with the draft standard ,

it is necessar y to normaliz e the predicte d integ*ra ted dis-charges to the release limits prescrib ed in the standard .

Two differe nt interpre tations of the standard , along with

their respecti ve methods of impleme ntation are presente d in Chapter 2. Also presente d is a short discussi on on the estimati on of scenario probabi lities.

The charact eristics of the referenc e basalt site in this study were chosen.t o be consiste nt with our current understa nding of the proposed candida te reposito ry site in>order to determin e the realism of the assume~ EPA repo:-

sitories . Chapter 3 describe s the referenc e site in this study. First, the general charact eristics of the site and* surround ing region are describe d; then, the strati-graphy and litholog y of the referenc e site are presente d.*

Chapter 4 describe s the referenc e reposito ry and the radioac tive waste*s stored. This includes the waste inventor y, the waste form, the waste canister s and the leaching behavio r.

Chapter 5 presents the geochem ical paramet ers used in the analysis . The geochem ical *environm ent of each subsur-face layer has been describe d. Special emphasis has been placed on the calculat ion of retardat ion factors nuclides in basalt. we assumed that the transpo rt of of radio-radionu clides in basalt takes place exclusiv ely in par-tially filled fracture s. Retarda tion factors were cal-culated using distribu tion coeffici ents for radionu clides in secondar y minerals in the fracture s.

Chap ter 6 descr ibes the groun dwate r trans port model used in these analy ses. The flow is repre sente d by a two-d imens iona_ l Darci an mode l. Sand ia's distr ibute d quasi -

veloc ity metho d (DVM) 2 was used to calcu late radio nucli de.tr ansp ort.

Chap ter 7 descr ibes the scena rios analy zed in calcu la-ting the integ rated relea, ses of radio nucli des for times to 50,00 0 years . A base case routi ne-re lease scena rio up two disru ptive scena rios were analy zed.* and Chap ter 8 prese nts resul ts of nume rical calcu latio_ ns, and comp ares them to the requi remen ts of the EPA Stand ard.

Chap ter 9 state s the concl usion based on the resul ts

. of our study .

It would be misle ading to claim that the resul ts.

these model calcu latio ns can provi de a detai led descrof iptio n of the perfo rmanq e of a real repos itory . A large amoun o_f unce rtain ty in the resul ts is introd uced by the paucit of geoch emica l and hydro logic al data (expe rimen tal and ty field )

relev ant to the desig n of a waste repos itory in basa lt for-matio ns. In addit ion, it was impo ssible to provi de exact mathe matic al descr iption s_ of flui,d flow and radio nucli de migra ,tion due to the comp le xi ty of this syste m and the and budg etary cons train ts. Howe ver, with bette r in-si time tu measu remen ts or site chara cteriz ation , and addit ional re-sourc es, the realis m and accur acy of these calcu latio could be great ly impro ved. ns It shoul d be noted _that the resul ts prese nted here re-prese nt a first attem pt at the type of an~ly ses that repo sitor ies will requi re. real The motiv ation for perfo rming a demo nstra tion analy sis at this time is twofo ld. First we gain exper ience in ident ifyin g neces sary assum ption ,

s, areas of spars e data or weak mode ls, and poten tial probl with imple menti ng the draft stand ard. ems Secon dly, the nume r-ical predi ction s indic ate the likeli hood that the hypo the-tical repos itory comp lies with the draft stand ard.

It there -

fore indic ates the impor tance of valid ating assum ption impro ving data for any real candi date repos itory that s and simil ar. is Appe ndice s A throu gh G descr ibe sever al assum ption s and mathe matic al appro ximat ions that we have devel oped order _to estim ate radio nucli de disch arges from the repos in itory . Appen dix A outli nes and deriv es a new metho d -

for appro ximat ion of.th e retar datio n facto r for radio nucli de migra tion in fract ured media . Appen dix B descr ibes conce ption of the geoch emica l envir onme nts along possiour nucli de migra tion paths and discu ss~s the unce rtain ty ble relat ed to choic es of relev ant value s of radio nucli de distr ibuti on coeff icien t (R ). In Appen dix C, a metho to appro ximat e the radio nucli de retar datio n cause d by d matri x diffu sion is discu ssed. In Appen dix D, verti cal hydr aulic gradi ents induc ed by therm al effec ts are cal-culat ed. Appen dix E descr ibes an optio nal sourc e mode l,

the mixin g cell, used in some of the analy ses. Appen F discu sses the ratio nale for scena rio selec tion. Appen dix dix G summ arizes the data range s for Ra and hydra ulic param eters in basa lt, with appro priate refer ences noted

2. THE DRAFT EPA STANDARD, .40CFR191 The Environmental Protection Agency (EPA) has*prepared a working. draft of its proposed generally applicable stan-.

dard for the protection of publfc health from the ge.ologic disposal of radioactive wastes * . The standard is expressed in terms of the total integrated discharge of the radionu-clides comprising the wastes tothe accessible environment.

In Table 1 a list is given of radionuclides expected in the radioactive waste inventory and the corresponding EPA release limits. since events and processes leading to radionuclide relea~e will generaliy result in the release of mixtures of radionuclides, a sum rule is imposed on mixtures of radio-nuclide discharges: * *

~ 1. for reasonably foreseeable release.s Q,

EPA Sum= Ll.

l.

EPA, l.

< 10. for very unlikely releases where Qi is the integrated discharge over 10,000 years of radionuclide i and EPA. is the release limit of radionuclide*

i in the draft standar~. Qi and EPAi are scaled for the a-mount of waste in the geologic repository according to the assumed 1000 metric tons of heavy metal (MTHM).

In the draft EPA Standard, a "reasonably foreseeable" release is defined as any release expected to occur with a probability of greater than 0.01 in the 10,000 year per-iod addressed by the. standard. A "very unlikely release" is defined as any release expected to occur with a proba~

bility of less than 0.01 but greater than 0.0001 in the 10,000 year period~ Any release with a probability of occurrence of less than b.0001 in the 10,000 year period need not be considered in the analJses. 3 *.

2.1 Interpretations of the Draft Standard In attempting to assess compliance. with the draft standard, *one is faced with the difficult task of how*

best to formulate the test for compliance. The intended interpretation of the standard is also subject to debate.

Table 1 Cumulat ive Releases to the Accessi ble Environm ent for 10,000 Years After Disposa l!

EPA Release Limit Radionu clide (Curies per 1000 MTHM*).

Americ+/-u m-241 10 I

Americiu m-243 4 Carbon-1 4 200 Cesium-1 35 2000 Cesium-1 37 500 Iodine-1 29 500 Neptuniu m-237 20 Plutonium ...:.238 400

Plutoniu m-239 100, Plutoniu m-240 10.0

. Plutoniu m-242

100 Radium-2 26 3 Stroritiu m-90 80 Techneti um-99 2000 Tin-126 80 Any other alpha.- . 10 emitting radio-nuclide

Any other radio- 500 nuclide *which does*

riot emit alpha par-ticles

M'rHM denotes metric

tons of heavy met.al.

-5'-

As a result of the uncertainties in .input data, computer models, and the ability of models to represent the,physical system, there ~xist inherent uncertainties in the calcula~

tions required to assess compliance. It will be shown.in later sections that a fraction of the input vectors* lead to violations of the standard. Typically, the parameter values constituting the vectors that apparently "violate" the standard are at the conservativ~ extreme of the ranges assigned to those parameters. Clarification from EPA may be necessary as .to how uncertainty in compliance assessment should be treated.

For example,* the standard uses, but does not define, the word "release". The interpretation of this word affects the manner in which compliance is assessed. We offer two interpretations below;.*

Interpretation 1: The word "release" defines a unique ~vent or scenario ~eading to radionuclide*

release. The draft EPA Standard is applied inde-p~ndently to each scenario *

.Interpretation 2: A "release" involves all events or processes that may result in discharges to the enviro.nment during the regulato.ry period. The mag-nitude of the discharge is given by its corresponding EPA Sum. The standard could be rephrased as saying, for example, "Values 9f EPA Sum greater than 1 shall qccur with a probability of less than 0.01 in 10;000*

years".

Estimation of*the probability of exceeding a* given value of EPA Sum includes contributions from all scenarios.

We have performed analyses based on both interpreta-tions.

2.2 Implementation of Different Interpretations Interpretation 1:

The probability assigned to the scenario indicates whether values of the EPA Sum will be. compared to 1 or 10.

Different values of the EPA sum result from different com-binations of input data chosen by the sampling procedure. 4 Thus, there is a sampling error in the *assessment of com-pliance *.

See page 27.for a definition of "vector".

The. results of calcula tions are presen ted in the form of a Compli mentary Cumula tive Distrib utioq*F unctio n (CCDF) as sugges ted by EPA 3 ~ Such a CCDF is illustr ated in. the followi ng diagram .

I*

max EPA>

For N input vectors sampled for the scenar io, the plotted curve enable s.one to see what fractio n (if any) of the N vect_or s produc e a value of the EPA Sum greate r than some value denoted by EPA>. In this* exampl e, the shaded area indica tes that a* fractio n of the vectors do violate the standa rd.

Interp retatio n 2 Accord ing to this interpr etation , the analys t is pre-sumed to have the same set of scenari os and probab ilities as in Interp retatio n 1. Each scenari o is again analyze d to estima te the EPA Sum as in -Interp retatio n 1. Howeve. r, with this interpretatio n, compliance is estimated by con-structing a CCDF from all scenarios. The construction of*.

this CCDF .is aided by 'first constructing a plot of proba-bility versus the EPA Sum for each scenario. An important point should be made regarding the probabilitie s used in the construction of the CCDF;* namely, that the probabil-*

ity used is that of the scenario's occurrence and the particular combination of the input data used in the cal-culation of the EPA Sum.

Construction of the CCDF then in.eludes contribution s from all scenarios analyzed and expected to produce an EPA Sum greater than a given value, EPA>.* The probability, p 5 , associated with EPA>is given by

= r, Ps

Pc (EPA Sum> EPA>ls) s Nuraber of vectors with EPA

= r, Sum> EPA> for scenario, s.

5 N where Psis the probability of scenario *s, and Pc is the

¢onditiorial probability of the state of the repository, given scenarios. The last step, substitution for Pc' follows from the fact that the LHS method selects Hin-put vectors with equal probability. For simplicity, we write Ps Ps =

N

Construction of the CCDF is illustrated3 in the following d1agram for the case of two scienarios where, for clarity, the EPA limit is .superimposed on the CCDF plot.

/EPA Limit p**

2 p'

1 X

0 XX X 0

X 0 0 X

0 xx r

EPA Sum EPA>

p' 1

Com plia nce wit h the dra ft min ed by com par ison of the con EPA Sta nda rd is the n det er-stru cte d CCDF wit h an "en ve~

lop e" def ine d by the sta nda rd and illu str ate d in the dia gra m.

The sha ded are a in the dia gra m def str uct ed CCDF out sid e of the EPA ine s the par t of the con -

com plia nce wit h the sta nda rd. lim it and ind ica tes non -

2.3 Est ima tion of Pro bab ilit ies of Sce nar ios

/

Alt hou gh the met hod s dev elo ped at San dia may be. use d wit h ran ges and dis trib uti ons bil ity , we hav e use d fix ed val for p , the sce nar io pro ba-ues in5 thi s ana lys is. The sit e we hav e assu med for thi s act eri zed suf fic ien tly to allo ana lys is has not bee n cha r-w est ima tio n of. the pro ba-bil itie s. Sin ce the dra ft EPA Sta nda rd req uir es thi s in-for ma tion and , sin ce it may intr int o est ima tes of com plia nce , odu ce fur the r unc ert ain ty it is app rop ria te in thi s wor k to dis cus s the lik ely sou rce s of the pro b~ bil itie s.

Sou rce 1. Of the sce nar ios to be ana lyz ed, the ana lys t*

may hav e rea son to bel iev e tha l

t the pro ces ses \

inv olv ed are sto cha stic in nat cas e, met hod s ma y*e xis t to est ure . In suc h a ima te thi s pro -

bab ilit y wit h the fin al unc ert ain ty in the est iljt ate res ult ing from unc ert dat a and the acc ura cy. of mo del ain ty in inp ut s use d to per -

form the est ima te. At lea st one atte mp t has bee n mad e to add res s fau ltin g wit h inp ut dat a des cri bin g exi in thi s man ner st!n g .fa ult den -

sit y and str ess sta tes req uir ed.

Sou rce 2. His tor ica l dat a may be ava ilab le tha t cou ld be ext rap oi'a ted int o the fut ure to est ima te pro bab ilit ies of som e sce nar ios

. An exa mp le of *use of suc h dat a is the est ima tio n of ex-plo rat ory dri llin g for pet rol eum res our ces .

In the ref ere nce sit e ana lys is of a hyp oth e-tic al nuc lea r was te rep osi tor y in bed ded sal t, dri llin g rec ord s for sim ilar sit es wer e use d to est ima te the pro bab ilit y of fut ur~ exp lo-rat ory dri llin g int o the rep osi tor y.

Source 3. In the absence of historical records and de-tailed understanding of the processes invol-ved, expert judgement may*be used to estimate scenario probabilities. The Delphi method is one example of the many ways in which expert judgement can be used.

The use of expert judgement is implicit in Source l and Source 2, since unquantifiable jud.gements must be made as to the applicability of. the data and models.

_.10-I

3. THE REFERENCE BASALT SITE The reference* basal~ repository is located in the cen-ter of a drainage basin within a region of flood _basalts.

This reference site is shown schematically in Figure 1.

Mountains along the northern, northwestern and southwestern edges of the site are zones of recharge to the groundwater ..

system. A major river, River C, flows through the site from the northwest to the southeast. The deeper ground water near the repository site discharges to the upper unconfined aquifers west of moun,tain Ml.

This region is underlain_ by a sequence of basaltic lava flows. The sequence of flows contains sedimentary beds of regional extent. Overlying*the volcanic rocks is an unconfined aquifer consisting 0£ alluvial sand and gravel. The geologic cross-section at the Reference Site (A.;.A' cut) is shown schematically in Figure 2. The repo-sitory is located in the middle of a dense basalt forma-tion. Overlying this horizon is a sequence of four layers of alternating interflows and dense basalts.* Above these four layers lies*a water-bearing interbed (Layer I-V) con-sisting mainly of sandstone and clay. Above interbed I-V is a basalt formation consisting of three members with dis-tinct chemical signatures. This basalt formation is overlain by a major confined aquifer system (Layer I-M) predominantl y composed of tuffac_eous siltstones and sandstone. Above aqui-fer. I-M lies a basalt formation (J) which, in turn, is over-lain by an unconfined ~quifer (UA)~

. Ranges of horizontal and vertical hydraulic conduct-ivity (Kh,Kv) and effective porosity for each layer are presented in Table 2. These ra~ges are also summarized in Table 4 of Appendix G along with the appropriate ref-ere~c~s. To be consistent with-a real. basalt site, a normal distribution was assigned to each range of porosity.

A lognormal distribution was assigned to the Kh data range.

The sample population for K that was used in this work was determined by the follo~ing method. A lognormal dis-tribution was assigned :to the K data*range in Ta~le 2.

Then using the Latin Hypercube ~arnpling. Technique (LHS),

Kv_values were sampled. The sampled values were then sub-tracted from Kv(max). The resulting sample population is skewed toward the high end*of the range. For this system, this procedure produces more conservative estimates of discharge than those of the standard lognormal distribution .

N River C s

A'

.\

. i I

I I

I Subsurface Facility . Site

. I I I

I

.. , A f

f;

!j J

0 5 Miles Figure 1. General Geologic Features of the Reference Basalt Repository Site SYMBOL OF THICKNESS LAYER (ft) A

~ -

UA 200 UNCONFINED AQUIFER J 850 BASALT FLOWS 1-M 150 INTE;RBED H 150 BASALT FLOWS G 200 BASALT FLOWS F 690 BASALT FLOWS 1-v 10 INTERBED E 690 BASALT FLOWS D 60 INTERFLOW C 50 COL/ENT B 150 INTERFLOW A 300 DENSE BASALT W?M UNDERGROUND FACILITY Figure 2. Stratigraphic Cross-Sectio n of Hypothetical Repository in Basalt Table 2 Refer ence Hydra ulic Prope rties*

Horiz ontal Verti cal Hydr aulic Hydr aulic Cond uctiv ity Cond uctiv ity Effec tive Layer {ft/d ) {ft/d ) Poro sity A (10-:- 8 10- 5 ) (lo- 7 10- 4 ) (10- 3 0.025 )

(10- 3 - 10~ 1 ) (lo- 3 - 10- 1 )

B (10- 2 - 0.120 )

{10- 8 *~ 10- 3 )

C (10- 7 - 10- 2 ) cio- 3 -*0.0 25)

D {10 10- 1 ) cio 10- 1 ) (10- 2 -0.12 0)

E (10-8 3 ) (10- 1 - 10- 2 ) (10 0.120 )

(10- 1 -

I-V 10) (10-2 - 1) co .1 - 0.2)

F {10- 6 2 ) (10- 6 .,. 10- 2 ) (10""'. 3 - 0.120 )

G (10-4 - 10> (10 10) (10~ 3 - 0.120 )

H (10- 4 - 10 2 ) (lo 10 2 ) (10~,3 - 0.120 )

I-M (1 - 150) (10-1 - 15) (O.l - 0 .'2)

J (10-4 - 2000) (10- 4 - 2000) (10 0.120 )

UA {l - 10 4 ) (O.l - 0.3)

The refer ences for the data in this table are. inclu in Table 4 qf Appen dix G. Also, the range s of the ded verti cal cond uctiv ity of all the layer s, excep t Layer UA, have been combi ne.d into a singl e range to repre sent, a "unifo rm" verti cal' cond uctiv ity for the host rock syste m.

A 70 percent rank correlation4 is assumed to exist between porosity and hydraulic conductivity. This minimizes the occurrence of physically unreasonable combinations of these variables.

The horizontal hydraulic grad!ents in I-V, I-Mand UA are assumed to have a range of 10- to 10- 2 . The vertical gradient is assumed to be upward and small in magnitude~

4. WASTE AND REPOSITORY DESCRIPTION 4.1 Waste The inventory ( T*able 3) assumed in this work* is equal to half the-projected accumulation of 10-year-old spent fuel in the United States by the year 2010. This would contain a total of.103,250 BWR and 60,500 PWR assemblies~ a total of 46,800 metric tons of heavy metal (MTHM). The criteria for selection of key radionuclides are described in detail..elsewhere 7 .

In addition* to these criteria, all radionuclides specified in the Re~

lease Limit Table of the EPA Standard-are included in this inventory list.

All canisters containing the wastes are*assumed to have a life of 1,000 years after emplacement. At year 1,000, all canisters fail simultaneously and radionuclide release begins. Radionuclide release is. assumed to be determined by a. constant leach rate of th.e waste form.

The waste matrix is assumed to dissolve at an annual rate of 10- 4 to.10- 7 of the originai mass. Radionuclides are assumed to be uniformly distributed throughout the matrix so .that their release rate is directly proportional to the matrix dissolution rate: this is also known as con-gruent dissolution.

4~2 Subsurface Facility The reference subsurface facility is a mined facility at a depth of 3 ~ 000 feet below the surface. A description of the facility is summarized in the following data.

Areal.dimensions -- 9,840 feet x 7,870 feet Number of.storage rooms 120 Storage room dimensions length = 3,560 feet width = 100 feet height = 40 feet Porosity of backfilled region -- 18.percent Table 3 Inventory of Reference Repository (Spent fuel from 46,800 MTHM)

Radionuclide Half Life Curies (at time=O)

Pu240 6.76E3 2.1E7 U236 2.39E7 l.OE4 Th232 l.41El0 l.7E-5 Ra228 6.7 4.7E-6 Cm245 8.27E3 8.4E3 Pu241 14.6 3.2E9 Am241 433. 7.SE7 Np237 2 .14E6 l.SE4 U233 l.62E5 1.8.

Th229 7300. l.3E-3 Crn246 4710. l.6E3 Pu242 3.79E5 7.5E4 U238 4 .51E9 l.5E4 Pu238 89. 9.4E7 U234 2.47E5 3.5E3 Th230 8.E4 0 .19 Ra226 1600. 3.SE-4 Pb210 21. 3.3E-5 Am243 7650. 6.6E5 Pu239 2.44E4 l.4E7 U235 7.1E8 7.SE2 Pa231 3.25E4 0.25 Ac.227 21.6 S.2E-2 Tc99 2.14E5 6. lES

!129 l.6E7 l.5E3 Snl26 l.OES 2.2E4 Sr90 28.9 2.4E9 Cl4 5730~ 3.SE4 Csl35 2.0E6. l.3E4 Csl37 30. 3.5E9

-i7-

5. GEOCHEMISTRY 5.1 Retardation Factors One of the most important barriers to the movement of dissolved radionuctides in ground water is retardation due to the interaction between radionuclides and the geologic medium. The retardation factor is defined as the ratio of the velocity of the fluid to the velocity of the retarded radionuclide. A radionuclide with a retardation factor of 10 would travel at one-te.nth the velocity of the ground water. A general expression for the retardation factor is given by: 8 (5.1) where

= utilization factor Rd = sorptfon ratio of radionuclide in-ml.g.

p = grain density of rock in g/cm3

'95eff = effective porosity of rock matrix The utilization factor (.JI) is the fractional volume of the rock matrix that interacts with the fluid. For flow in porous media, "'approaches unity *. In fractured.media such as basalt, ground water travels almost exclusively in fractures. Most of the bulk rock matrix does not inter-act.with the fluid; under these conditions, 'f/, may be much less than unity. It will be shown that a simpler expres-sion than Equation (5.1) can be used to calculate the retardation factor if we make certain assumptions about .JI.

At the reference site, nearly all of the fractures in the basalts are assumed to be lined with secondary 1

mineralization. We have assumed that the ground water comes. in contact only with the secondary minerals.

Therefore, the volume of the rock matrix that interacts with the fluid is equal to the volume of the secondary mineralization. The utilization factor can be calcula-

.ted as volume of secondary mineralization total rock volume The volume of secondary mineralization is equal to a fraction or multiple *(f) of the volume of open space remaining in the fractures (fracture porosity). For a unit volume of rock matrix, the utilization factor can be calculated*as f

fracture porosity

"' - 1 - total porosity If we assume

¢fracture then Therefore Equation (5.1) becomes R = 1 + f RdP (5.3)

In our calculations, we have assumed that the ori-ginal fractures .have been on the average one-half filled with secondary minerals. Therefore, : f = 1 *and R = 1 + RaP (5.4)

In this study, Equation (5.4) rather than the more general Equation (5.1), has been used to calculat e R for fracture d media. Note that the values of Rd and p for the seconda ry minerals must be used in the equation . A more detailed derivati on of Equation (5.3) is given in Appe~dix A.

The sorption ratio Rd for radionu clides in rock-water systems is defined as, mass on solid phase per unit.mas s of solid (5.5)

= mass in solution per unit volume of solution Calcula tions of radionuc lide disch~rg e from a re~

pository are sensitiv e to values of Ra. 0 The magnitud e of Ra is. influenc ed by many fac~ors includin g solution

.compos ition, pH, Eh and tempera ture. Laborato ry measure -

ments of Rd have been made under a variety of physico -.

chemica l conditio ns. The geochem ical environm ent along*

postula ted groundw ater flow pat_hs must be characte rized in order to choose the Ra values that w~r obtained 7

under the most relevant laborato ry cond1 t1ons. * .

The geochem ical environm ent that was postulat ed for each stratigr aphic layer shown in Figure* 2 is describe d in Table 4. Equatio~ (5.1), with a utilizat ion factor of uriity, was used to calculat e the retardat ion factois for layers which are assumed to be porous. Equation (5.4) was used for layers in which ground water flows predom-inantly through fracture s. The redox potentia l_along the flow path and the nature of the minerals which interac t with the fluid are also describe d in Table 4.

. Table 5 shows the ranges and distribu tions of R used in this study.. For basalt and seconda ry minera1s it was assumed that data ranges obtained from experi-mental measurem ents mark the 95 percent confiden ce level interva l *. From these limits, new*rang es for the 99.9 percent confiden ce level were generate d and are shown.

in Table 5. The last column of the table shows the.ran-ges of Ra in sandsto ne/siltst one for use in the unconfin ed aquifer Iayer. Appendic es B. and_ G contain a descrip tion of.the data set from which.th e Rd values were selected and a discussi on of the Eh~pH conditio ns in each stratum .

Table 4 Geochemical Environment of Stratigraphic Layers in Basalt Repository Type of Redox Layer Medium Conditions Mineralogy A Fractured Reducing Secondary minerals B Fractured Reducing Secondary minerals C Fractured Reducing Secondary minerals D Fractured Reducing Secondary minerals E Fractured Reducing Secondary minerals I-V Porous Oxidizing. Secondary minerals F Fractured Reducing Secondary minerals G Fractured Reducing Secondary minerals H Fractured Reducing. Secondary minerals I-M Porous Oxidizing Secondary minerals J. Fractured Reducing *Secondary minerals UA Porous Oxidizing Sandstone/silt Density of secondary minerals =* 2. 3 g / cm 3 Density *of rock in layer I-V and I-M = 3. 3 g/cm3 Table 5 Rd Range s* (mi/ g)

Reduc ing Oxidi zing Reduc ing Oxid izing Eleme nt SM** SM** Basa lt Sand stone /Silts tone Cm, Am ( 25., 2.0E6 ) (25., 2.0E6 ) ( 3 3. , 300.) (l.OE -2, l.OES )

Pu ( 45

I 5.2E3 ) ( 3 7. , L5E4 ) (0.35 , 4.24E 4) (l.OE -2, l.OE4 )

Np ( 1. 5, 2.8E4 ) ( 4. 0, 430.) (1.7, l.56E 3) (.1. OE-2, 50. )

u ( 4*. 0, l.3E3 ) (2.4, L5E4 ) ( 34. , 57. ) ( l.OE- 2, l. OE4)

Th (25., 2.0E6 ) ( 2 5. , 2. OE6-) ( 3 3. , 300.) (l.OE -2, l. OE4)

Pa ( 25., 2.0E6 ) ( 25

I 2.0E6 ) ( 3 3. , 300.) {l.OI :-2, 1. OE4)

Ac {25., 2 _-OE6) (25., 2.0E6 ) ( 3 3. , 300.) ( 1. OE-2, l.OE4 )

Pb ( 1 7. , 5.8E3 ) ( 1 7. , 5.8E3 ) {68*., 320.) (l.OE -2, l-OE4 )

Ra ( 1.7 * , S.8E3 ) ( 1 7. , 5.8E3 ) ( 68., 320.) (1.0E -2, 500.)

Sn ( 1 7. , 5.8E3 ) ( 1 7., 5.8E3 ) ( 68. , 320.) ( 1. OE-2, 500.)

Tc {0.2, 750. j (0.6, 10.0) (0.2, 4.16E 4) ( 1. 0 E- 2 , . 1

0 E 3 )

I (0.7, 6 .o ). (0.7, 6.0) 0 ( 1. OE-2, 100.)

Sr (0.8, l.38E 3) (185. , 590.) (67., 600.) (l.OE -2, 500.)

Cs {97., l.3E6 ) { 97., L3E6 ) { 51. 2. OE3.)

I { 1. OE-2, l.OE4 }

C o. o. . 0. o.

Distr ibuti on of Rd: Logno rmal

More comp lete data range s and their appro priate refer ences are comp iled in Table s 1, 2, and 3 of Appen dix G.

- SM = Secon dary Mine1 :als 5.2 Solubility The determination of solubilities of ~adionuclides in ground water associated with a repository in basalt requires a detailed knowledge of the aqueous geochemistry ot these radionuclides. ,Until detailed calculations can be made, the *solubility ranges*employed to characterize the bedded salt reference site environment 9 have been used *in this study (Table 6). The upper limits of these.

ranges are probably too high. The solubilities of these elements in waters from the basalt repository would be.

lower than those in the salt brines due to the lower ionic strength and higher pH o_f the water in t:he basalt.

5.3 Matrix Diffusion In. our calculations,. we have assumed that the radionuclide retardation caused by diffusion into the basalt m~trix is negligible. This assumption leads to conservative (high) estimates of integrated discharge.

It will be shown later .that for several calculations this conservative estimate contributed to an apparent

violation of the draft EPA Standard. 1 In Appendix C, a method to appro*ximate the retardation' due to matrix diffusion is outlined.*._ It is shown* that the retardation calculated in this manner has the potential to reduce all discharges to levels below the EPA stariqard*.

Tab le 6 Rang es of Sol ubi litie s of Sele cted Elem Used for Bas alt Refe renc e Rep osit ory Con ents ditio ns*

Elem ent Mass Frac tion (g/g )

Tc l.lE -9. - 9.4E -5 I No.L imit Sn 6.6E l.SE -4 Cs No Lim it Ra 8.lE l.2E -5 Th l.lE 5.7E ~6 u L6E 2.0E -2 Np l.3E -25 4,7E -7 Pu l.7E 3.SE -4 Am Not .imi t Cni No Lim it Pb i.6E -ll - 3.9t -5 Pa* l .4E- 7 - 7 .lE- 4 c No Lim it Sn 2.2E 2.SE -3 Ac No Lim it

Da ta are calc ulat ed from the solu bili ty data used in a bedd ed salt repo sito ry ana lysi s. 9 Valu es a.re con._

fide nce inte rva ls for an assu rned .log norm tion . al dist ribu -.

6. GROUUDWATER TRANSPO RT MODEL In the calcul ations of radion uclide transp ort it is assume d that ground water flows upward from the vicinit y.*

of th.e reposi tory to an aquife r, wllereup ori it moves hori-zontal ly toward the biosph ere *. This flow is modell ed as being quasi-t wo-dim ensiona l and describ ed by Darcy's Law:

q = O/A = KI (6.1) where Q is the vol.um etric flow rate through an area A, normal to the flow. dire~ti on,. I is the hydrau lic gradie nt, K is the hydraµ lic *condu ctivity , and q is the Darcy *veloc-ity. \fuen the flow .passes through a series of, layers with differe nt hydrau lic .proper tie*s ,* an "effec tive" hydrau lic*

conduc tivity may be calcula ted by

I:i Li K = (6.2)

Li -L, 1

K, 1

with Li= thickne ss of layer i Ki= hydrau lic conduc tivity of layer i The total ground water travel time is given by L,

Time = L ].

( 6. 3) where Vi is the inters titial ground water veloci ty in layer i and is equal to q/¢., with ¢i *being the effecti ve porosi ty of layer i. 1 When a radio. nuclid e {RN) is transp orted by ground water the radion uclide trave l time {TR~) is increa sed by its re- ,

tardat ion factor . This is given by T RN. .. L RN

_L_i_._R_1_*_.

{6.4) i V, l.

where R.RN is the retard ation factor of radion uclide RN in 1 ayer

l.

1.

rhe Distri bute~ Veloc ity ~ethod {DVM) has been*

develo ped.by Sandia to simula te long chains of*rad io-

nuclid es transp orted by ground water *.

In this study we calcu lated the averag e veloc iti o( radion uclide s using Eq.uat ion ( 6. 4). . The.n. the. DVM code. was used. to calcu late the discha rges of radion uclide *~ .*,.

7. SCENARIOS ANALYZED Large uncertainties were associated t.iith many. of the

input variables in the model. These variables were assumed to be distributed according to user-specifie d probability distribution s and ranges, rather than point values. The 4

Latin Hypercube Sampling (LHS) technique was used to se-lect the input variables. A sample of 100 *vectors was g~nerated with this technique. Each vector consists of a particular combination of input variable values where the ith component of the vector corresponds to the *sampled value of t~e ith variable.

Radionuclide discharge rates for each vector were calculateq at some specified location. Discharge rates we~e integrated for 10,000 year periods from Oto 50,000 years.

The integrated discharge for each 1 radionudlide was then divided by its EPA release limit to assess com-pliance of that vector with the draft EPA Standard.

Three sce~arios were analyzed for the basalt reference repository *. A "no-disruptio n" base *cq.se scenario and two scenarios involving disruption of the repository w~re con-sidered. Both of the latter two scenarios are consistent with the. geologica.l setting described in Chapter 3. The

.disruptions involve the int.reduction of a zone of high hy-draulic. conduct.ivity and could be caused by either natural or artificial processes.

Bas~d on the inventory and toxicity of each radio~

nuclide, the following chains of radionuclide s were

.considered:

The fis sio n and act iva tio n*p

~o duc t rad ion ucl ide s Tc9 9, Snl 26, Sr9 0, Cl4 , Csl 35, and I12 9, Csl 37 wer e als o con sid ere d in thi s wo rk.

Tab le 7 sho ws the dat a ran add itio nal var iab les use d in ges and dis trib uti on s for som e

ar ios . the cal cul ati on s of the se sce n-Two sou rce mo del des cri pti ons The fir st sou rce mo del ass um wer e use d in thi s ana lys is.

es tha t the sol id ma trix con ing the wa ste .tad ion ucl ide s tai n-(e. g., spe nt fue l ele me nts or bo ros ilic ate gla ss) bre aks dow n at a con sta nt rat e. Th is is the so cal led "le ach -lim ite d lea se the n.o ccu rs at a rat e sou rce mo del ". Ra dio nuc lid e re-det erm ine d by the inv ent ory eac h dif fe' ren tia l mas s inc rem in ity lim its a.re not use d at all ent tha t is rel eas ed.

So lub il-sim pli cit y, r*ad ion ucl ide s are wit h thi s sou rce mo del . For dis trib ute d thr oug hou t the sol ass um ed to be. hom oge neo usl y sou rce mo del is mo st eas ily id ma trix . The lea ch- lim ite com par ed wit h the req uir em ent d of 10C FR6 0. Sim ply sta ted , s*

10C FR6 0 req uir es tha t rel e~s rat es not exc eed a spe cif ied e rat e of 10- 5 /ye ar. The rel eas e rat e is equ al to the .re cip roc al of the lea ch per iod .

The sec ond sou rce mo del reg ion s can be mo del ed as a ass um es tha t the bac kfi lle d mix ing ce ll. The wa ste ma trix sti ll is ass um ed to dec om pos e at a con sta nt rat e. How eve r, the rad ion ucl ide s are ass um ed wa ter in the mix ing cel l. Ra to ins tan tan eou sly mix wit h 1 **

'ba ck fil ied reg io~ s is sen sit dio nuc lid e rel eas e fro m the ive to the rad ion ucl ide con tra tio n in the mix ing cel l. cen -

Th is mo del is dis cus sed fur the in Ap pen dix E. Not .e tha t eve r n

is cho sen , it is pos sib le tha whe n the mix ing cel l mo del (if the ir sol ub ilit y lim its t for cer tai n rad ion ucl ide s are suf fic ien tly hig h) the tr~ nsp ort is eff ect ive ly lea ch lim ite d.

NWFT/DVM allo ws use r-s ele cti als o has an alg ori thm for aut on of the sou rce mo del . It om atic sou rce mo del sel ect ion In. the sce nar ios to be des cri .

nec ess ary con dit ion s to sel ect bed , onl y. Sce nar io 3 had the the mix ing cel l mo del " For com par iso n, thi s sc~ nar io was als o ana lyz ed wit h the lea ch-lim ite d sou rce mo del imp ose d.

7.1 Sce nar io l -- Ro utin e Re lea se In thi s sce nar io, it was mi gra tes int o the rep osi tor y ass um ed tha t gro und wa ter of the rep osi tor y. When the and sat ura tes the por e vol um e wa ste can ist ers fai l at 1,0 00 yea rs, thi s col um n of wa ter ,

hav ing the *cr oss -se cti opa l* are a

Table 7 Data Ranges and Distributions for Additional Variables Range Distribution Leach.Period (year} 104 - 10 7 Log Uniform Horizontal gradient in 10-4 10.:... 2 Uni-form aquifer Conductivity of borehole 0~05 - so Log Uniform Porosity of borehole o.os - 0.5

Normal Vertical upward gradient in Scenarios l ahd 2

sx10-3 - 3x10-2 Uniform Vertical upward gradient in Scenario 3 3xlo-3 - 2xlo- 2 Uniform Dispersivity (ft) so of the repo sitor y, slow ly trans ports leach ed and radio nucl ides vert icall y throu gh the basa lt laye disso lved rs to the*

.aqui fer syste m I-Ma nd then hori zont ally throu gh the aqui fer to a disch arge poin t 1 mile down grad ient. In our base case

.and in the othe r scen arios , it was assum ed that there

exist ed littl e or rio natu ral verti cal* grad ient. A temp eratu re field in the vicin .ity of the repo sitor y, due to the from the deca ying wast es, produ ces an upwa rd hydr heat gene rated aulic grad -

ient due to therm al buoy ancy of the groun d wate

r. .For our base. case , we estim ated that this therm al buoy gene rated a hydr aulic grad ient rangi ng from SxlO anc~ effe ct 2 - to 3x10 -

This grad ient is assum ed *to be cons tant along a vert ical colum n whic h has the hydr aulic cond uctiv by Equa tion (6.2 ). The deriv ation of this calc ity given ulati on is

pres ente d in more deta il in Appe ndix D. It was also assu -

med that the upwa rd flow of groun d wate r into aqui fer I-M does not alter .the natu ral hydr aulic grad ient in that aqui -

fer. Figu re 3 sche mati cally show s the trans port route this scen ario. in Integ rated disch arge s for each vect or were calc ulate d at a dista nce of 1 mile down grad ient in aqui fer I-M. The resu lts.o f these calcu latio ns are as follo ws.

The inte -

grate d disch arge s for eac*h actin ide radio nucl ide zero for all vect ors. For the*f issio n prod uct were all radio nu-clide s, there were some smal l disch arge s but they below the EPA relea se limi ts. This was true for were all of the 10,00 0~yr . incre ment s of the 50,0 00-y r. all five tota l perio d of anal ysis.

In this scen ario, all 100 ~ecto rs resu lted limi ted sourc e as deter mine d by the auto mati c in a leach -

sourc ectio n algo rithm of NWFT/DVM~ The algo rithm sele e sel-cts the

sour ce mode l based large ly on the antic ipate d resid ence time of the groun d wate r in the near field .

)

DISCHARGE AT ONE MILE DOWN 1-M i M AQUIFER :

~-*1-*-. - --:, .. .. :

H I l

G F

1-V E FLOW J lo.

D C

B CROSS SECTIONAL AREA

!/ !/ OF FLOW COLUMN A

UNDERGROUND FACILITY = 9840' X 7872' figure 3. Routine Release Scenario (Scenario 1) 7.2 Scenario 2 -- ~ractures -in Dense Basalt This scenario is based on the assumption that the

. hydrologic properties of the dense basalt unit (Layer A) containing the subsurface facility ha.VE! been altered.

Specifically, this scenario assumes that the hydraulic conductivity and porosity have been'increased due to the repository-induced fracturing of the rock strata. The generation of these new fractures could be caused by one or more of several processes: thermal stress from waste heat, mechanical stress from the construction of the re-pository, or the. occurrence of an earthquake swarm. The potential increase in conductivity and porosity can enhance the upward migration of radionuclides released from the.

subsurface facility.

In the calculations. of radionucl.ide releases, the following assumptions were made-(Figure 4):

1. The fractured zone is located above the subsurface facility in the dense basalt unit (Layer A).

2. The fractures* in the dense basalt layer occur inunediately after closure of the subsurface facility.

3. The fractured zone has the same cross-sectional.area as that of the subsurface fac{liiy, i.e.~ 9840' x 7872', and it extends upward *through all of Layer A.

4. The hydraulic conductivity of*the fractured zone is arbitra~ily increased by two orders of *magnitude and the porosity is increased*

by a factor of four. That is, Kfractured basalt = 100 ° Kaense basalt

~fractured basalt= 4 * ~dense basalt

5. The vertical 1:1ydraulic:gradi 7nt is the_~ame as t~~tused in Scenario 1, i.e., SxlO to 3xl0 .. .

DISCHARGE AT ONE MILE DOWN 1-M t 1-M AQUIFER

-l

I . l" .. *..*.*. .. .: =--* .....

H I I I G

F 1-v E

t D I C

B r

',~ ,';'.!rr/f ~::-~

, .... ,...,.,,__/1.).,~'" I": FRACTURED ZONE 1:., I/

A UNDERGROUND FACILITY Figure 4. Fractured Dense Basalt Scenario (Scenario 2)

The same 100 vectors as those used in the routine-release scenario were used in the calculatio ns of inte-grated discharge s of radionucli des in this scenario. Two calculatio ns were performed . The discharge s were calcula-ted at a location 1 mile down gradient in Aquifer I-M.

Table 8.lists the radionucli des and the vectors that showed violation of the draft EPA Standard.

Table 8 also shows that few of the sampled input vectors violate the draft EPA .Standard during the first 10,000 years.

In these calculatio ns, however, the effective retardatio n due to diffusion into the rock matrix was ignored. A method for estimating the magnitude of this effect is described in Appendix* c. When the retardatio n, due to rock matrix diffusion calculated by this method, is taken into account, it is possible that no *vectors violate the draft EPA Standard.

For readers familiar with the technical criteria of 10CFR60, it is worth mentioning that of all the "violating "

vectors listed in Table 8, all except one {vector #24) have leach rates greater ~han 10-5/year. Also, all vectors ex-

cept two ( #=4 and :/f:71) 'have a groundwat er travel time fror.i.

the repository to the discharge location greater than i,000 years.

For Scenario 2, all 100. vectors used the leach-lim ited source model.as determined by the automatic source selection algorithm of NWFT/DVM.

7.3 Scenario 3 -- Borehole This scenario assumes that there exists a borehole or a zone of high conductiv ity that connects the repository to the unconfined upper aquifer (Layer UA). This zone is of very small areal extent (Figure 5). The h~gh conduc-tivity zone could be related to *one of the following:

borehole

degraded shaft seal

disturbed rock zone around a borehole or shaft.

This last mode can occur during relaxation of emplaceme nt stres~es or as a result of an earthquak e.

Tabl e 8 Scen ario 2

. EPA Rati os* of Radi onuc lide Disc harg es Into Aqu ifer I-M 0-10 ,000 *yea rs:

Vec tor# 14c 5

1. 34 71 1.15 77 :L. 22 10,0 00-2 0,00 0 year s:

Vec tor#

62 1.18 65 1. 68 20,0 00-3 0,00 0 yea~ s:

Vec tor#

5 1.29 25 1.08

.. 62 3.43 65 2.00 87 2.04 30,0 00-4 0,00 0 year s:.

Vec tor # 99Tc 234u 236u 2380 5 4.21 IS 1.27 20 2 .27 25 4.09

62 L42 65 1.99 87 2.22 Table 8 {Continu ed) 40,000-5 0,000 years:

Vector# 234u 236 0 238u 4 1.22

.15 2.54 20 2.88 24 3.61 1.43 1.61 87 1.42

EPA Ratio is the ratio of integrat ed discharg e of radionu clide {over 10,000 years) to the allowed EPA Release Limit.

UA t ..~'... * ..*. - '*.*. *.*

~ *.; . *...... * . . * *...* *. *.** -\.*=*==-=...;.;.......;__._......,__.......____

e,- *** .* *

" * . * *** **.* .. ~o. *:*,:.

J 1-M H---- ------ ------ 11-- ------ -----

G

------ ---1 F

1-v-- ------ -----1 L--- ----- ----

E co _____ _____ __

a_____ _____ ____--1

~L-- L------------ ----- ----- -

A .

SUBSURFACE FACILITY Figure 5. Borehole Scenario (Scenario 3)

The following assumptions were used in the calculations of this scenario:

1. Cross-sectional area of this disruptive zone is 2 square feet.

2. Hydraulic conductivity of this zone has a range of 0.05 ft/day to 50 ft/day. A lognormal dis-tribution is assigned to this range.

3. Porosity of this zone has a range of 0.05 to 0.5. A normal distribution is assigned to this range.

4. *The hydraulic gradient *in UA is unperturbed due to the smallness of this. zone *.

s. The same head difference typical of thermal buoyancy as calculated in Appendix C, is assumed here. However, due.to the extra 1,000 foot path .. length between r~M and UA the vertical upward gradient between the repository and aquifer UA is reduced to the range 3xlo 2xlo- 2 * *

6. Layer' UA is compo'sed mainly of s~ndstone/

siltstone and is characterized by.an oxi-dizing envlrorimerit.

7. The redox potential in the small disruptive zone is reduci~g and the roqk. type.is fresh basalt *..

a. The discharge location i s l mile down gra-dient in aquifer UA.

9. The entire radionuclide inventory in the repository .is available for leaching*and t:c:ansport.

Three variations of this scenario were analyzed. In Scenario 3A, al.l 100 vectors .chose the mixing cell source model as determined by the automatic source selection al-gorithm of NWFT/DVM.

Integrated discharges of each radionuclide were. calcu-lated for each vector and divided by the EPA Release Limit to produce the "EPA Ratio". Table 9 show.s those radionu-clides and vectors that produce EPA.Ratios of magnitude exceeding one. For each vector, the EPA Ratios were then summed over all radionuclides , and the results are shown in Table 10.

For comparison, Scenario 3B was also analyzed with the leach-limited source model imposed. The range of leach rate was 10- 4 to 10- 7 per year. With this source model, too many vectors gave large discharges to* list each violating vector as in Tables 9 and. 10. In.Table 11, we show the mean values for the 100 vectors for each radionuclide that had a sigriificant discharge. From.this table, the main contrib~-

ting radionuclides appear to be 243Am, 240Pu, 239Pu~ and 234U. The third variation, Scenario 3C, was also analyzed with the leach-lirn~ted so~ ce model; but the range of leach rate was 10- to 10 7 per year.

Table 9 Scenario 3A EPA Ratios of Radionuclides 243Am:

Vector i 10 4-2x10 4 4

2xl0.-3xl0 4 4 3xl0 -4xl0

4 Years Years Years 13 1.30 1.15 36 2.34 1.93 Table 10 Scenario 3A EPA Ratios Sununed Over All Radionuclides 10 4 -2x104 2x104-3x104 3x10 4 -4x104* 4xl() 4 -sx104 Vector # rears i:ears i:ears .i:ears 13 1.4 1.20 36 2_.49 2.25 1.73 1.55 Table 11 Mean Values of Contributions to the EPA Sum (100 Vectors) for Scenario 3B With Leach-Limited Source*

Radionuclide 10,000.year period 1 2* 3 4 5 240 Pu 8.56 9.75 3.23 1.87 .69 236 u .12 ~34 .46 .64 .56 245 Cm .01 .02 .02 .01 .01 241 Am . as .02 .02 . .01 .01 237 Np .31 .78 .97 .81 .99 233 u .01 .07 .13 .25 .31 229 Th .01 .08 .21 .49 .78 242 Pu .06 .14 .12 .18 .16 238 u .15 .35 .49 .66 .54 234 u .34 .82 1.15 1. 52 1.22 230 Th .* 01 .05 .10

22 * .30 226 Ra .02 .20. .48 .91 1.24 210 Pb o. .03 .06 .13 .19 24:3 Am 1.35 . 3.83 2.60 1.84 1.16 239 Pu 9.02 17.95* 12.38 13.91 10.19 235 u .01 .02 .03 .04 .04 231 Pa o. o. .01 .01 .02 227 Ac o. .01 .03 .os .08 99 Tc .05 .07 .06 .06 .06 126 Sn o. .04 .06 .04 .03 14 C .13 .04

01 o. o.

The Range of leach rate is 10-4 to 10- 7 per year

-42..;..

This page intentionally left blank.

8. RESULTS OF DEMONSTRATION ANALYSES For this demonstration , three basic scenarios and several variations on them have been analyzed in detail. A detailed analysis of scenario probabilities has not been performed due to constraints on the allowed effort and the fact that site characterizat io_n is in its early stages. The three scenarios analyzed are assumed to form a complete set of mutually exclu-sive scenarios describing the repository over the 0-10,000 year interval.

L s

Ps = 1 The three scenarios analyzed have been discussed previously.

We assume the following probabilities :

Scenario, s Description Ps......

1 The undisturbed site 0.33 2 The large areal extent, 0.01 high conductivity zone, e.g., fractures 3 The small areal extent, 0.66 high conductivity zone, e.g., a borehole Calculations have been performed for the three scenarios to estimate values of the EPA Sum during each 10,000 year*in-terval from zero to 50,000*years following closure. Thus, for Interpretatio n 1, five CCDFs have been constructed for each of the three scenarios (Scenarios 1, 2, and 3A). For Interpretatio n 2, a total of five .CCDFs have been constructed. The CCDFs based on Interpretatio n 1 appear in Figures 6 through 20. CCDFs based on Interpretatio n 2 appear in Figures 21 through 25.

For Scenarios 1 and 2, the automatic source selection algo-rithm of NWFT/DVM selected leach-limited sources for all 100 vec-tors. For Scenario 3A, the algorithm selected the mixing cell source model for all 100 vectors. Scenarios 3B and 3C were eval-uated with the leach-limited source model imposed. These results are shown in Figures 26 through 30.

10° SCENARIO 1 1sT 10,ooo*v.Rs

==

UJ cs: 10- 1 0.

w EPA C, LIMIT.

-zw C

w 0

)( 10-2 w

u.

0 0

zw

, 10-3 0

w a:

u.

10-4 _ _..........................................._ ___._..,__i......................_ __..._.....__.__._..-.....,.,,

10- 2 . -0

. 1 0.

EPA SUM Figure 6. Scenario 1 CCDF - 1st 10,000 Years SCENARIO 1

e 2 ND 10,000 YRS V,

. : 10- 1 . EPA w

C, LIMIT

-wz C*

w 0

t'.i 10- 2 lL-0 0

z_

w 5w 10~ 3 cc lL \..

I ii EPA SUM Figure 7. Scenario 1 CCDF - 2nd 10,000 Years 10+0 . I SCENARIO 1 3rd 10,000 YRS. EPA LIMIT

E

. :J en

<t 10- 1 0.

w C,

-zw Q

w 0 10-2 )*

w u.

-0 0

zw

J 10-3 0

w a:

u.

EPA SUM Figure 8. *Scenario 1 CCDF - 3rd.10,000 Years SCENARIO 1 4th 10,000 YRS EPA LIMIT

~

en

< 10- 1 a.

w C,

z cw

.w

~ 10-2 w

LL 0

o.

z

~ 10-3 0

w a:

LL 10+1 EPA SUM Figure 9. Scenario 1 CCDF - 4th 10,000 Years

'\

":""48-

10° SCENARIO 1

~ 5 TH 10,000 YRS U)

a. 10- 1 EPA w LIMIT

.CJ

.z C

LU w

0

)( 10- 2 w

LL 0

0 z

w

> 10- 3 0

w a:

u.

1~4'---'l.-.-..~.&....1..-..~-----........,_~l..-'-l...&..1-~--_.,_._...,_._...~

10- 2 EPA SUM Figure 10. Scenario 1 CCDF - 5th 10,000 Years

s

(/) SCENARIO 2

<( 1 ST 10,000 YRS.

C.

w C,

-zw 0

w CJ w

LL o*

CJ zW*

, . 10-3 0

w ff 1 o- 4 '----'---'-...1...1....1.JJ.......__....__..__._L.A.,&,~-..............-...~.......--__._...-............w

. 10-3 10+1 EPA SUM Figure 11. Scenario 2 CCDF - 1st 10,000 Years

-so-

~

> SCENARIO 2 en EPA LIMIT

< 10- 1 2 ND 10,0 00 YRS.

a.

w C,

z cw w

(.)

w LL 0

(.)

zw

-::> -3 0 10 w

a:

u.

10+ 1

EPA SUM Figur e 12. Scena rio 2 CCDF - 2nd 10,00 0 Years

-51.-

10+0

E u, SCENARIO 2 ct 3RD 10,000 YRS.

a.

w C,

Z cw w

(J

)(

w u.

0 (J

zLU 10-3 a::,

w a:

u.

10-4 L---L-L.L.LJ..U.J u....---1.--1..........JJ.1,'"-_..--..l-l. ........&1.1.o--...-..........

. . "10~3 10-2 .

10-:1 10+ 0

10+1 EPA SUM Figure 13. Scenario 2 CCDF -.3rd 10,000 Years

-52

E U) SCENARIO 2

.c:i:

D.

10- 1 *4TH 10, 000 YRS

w C,

-z C

LIJ w

~ 10- 2 .

W u.

0 U*

z*

LIJ.

, 10~3

'O UJ r.c

. u.

10~2 .. -1 10 1 EPA SUM rigu r~ 14 * . sce ~ar io.2 CCDF ~ 4th, 10,0 00 Yea rs

-5.3 -

. 10+ 0

~ I

, SCENAR.10 2

I

(/)

<t: 10- 1 5TH 10,000 YRS.

0.

w C,

-z C*

UJ UJ.

0 X 10- 2 UJ LL 0

0 z

w 5 10-3 w

a:

LL 10-4 .......___,__._.....,_.................___...___..,......_...................___.................~..____.__..._...&...L..L.LI..U 10-3 10+ 1 EPA SUM Figure 15. Scenario 2 CCDF - 5th 10,000 Years

. SCENARIO 3 A

E

> 1ST 10,0 00 YRS.

en EPA LIMIT

<t a.

w C,

-wz C

L w

u w

u.

0 u

z a

w w

10-3 C:

u.

EPA SUM Figu re 16. Scen ario 3A CCDF - 1st 10,00 0 Year s

-ss-

10+ 0 SCENARIO 3A EPA 2nd 10,0 00 YRS SUM

. :1:

en ct 10- 1 a.

w C,

z

-w C

w (J i 10-2 w

LL 0

(J zw

, . 10-3 0

W*

a:

LL 10-4 10-3 10+ 0 EPA SUM Figur e 17. Scena rio 3A CCDF - 2nd 10,00 0 Years

. I I I l ii I I 11111" EPA

~ LIMIT (j)

<t 10- 1 .

C.

LU C, SCENARIO 3A z

-C UJ 3rd 10,00 0 YRS UJ

~

10- 2 w

u.

0 0

z UJ

, 10- 3 0

w a:

u.

. EPA SUM Figure 18. Scena rio 3A CCDF - 3rd 10,000 Years

~

. :)

CJ) 10- 1 SCENARIO 3A 4th 10,000 YRS EPA C. /LIMIT w

C,

-zw C

-2 w 10

(.)

w u..

0

(.)

zw 10-3 0

w C:

u..

. 10-4 10-3 10- 2 10- 1 10- 0 10+ 1 EPA SUM Figure 19. Scenario 3A CCDF - 4th 10,000 Years 10+ 0 EPA

. :E LIMIT

(/'J c=: 10- 1 SCENARIO 3A Q;,

w 5th 10,0 00 YRS_

c.,

z Cl w

w

()

X 10- 2 w

u. \

0

(.)

z w

, 10- 3 0

w C:

u.

.10+ 0 EPA SUM Figu re 20. Scen ario 3A CCDF - 5th 10,00 0 Year s

ALL SCENARIOS EPA

( INTERPRETATION 2)

LIMIT

E. 1st 10,000 YRS.

U)

<t 10- 1 a.

UJ C,

-zw C

UJ U

)(

10- 2 w

u.

0

(.)

z UJ

> 10- 3 0

UJ a:

u.

10+ 0 .

EPA SUM Figure 21. All Scenario CCDF - 1st 10,000 Years EPA

l: LIMIT (fJ .

C.

UJ C, ALL SCENA RIOS

-wz C

(INTERPRETATION 2) .

2nd 10,00 0 YRS UJ u

X w

u.

0 u>

z LU

=> 1 o- 3 0

LU C:

u.

O-4 r , 1 , , ,, I 1

10- 3 10- 2 10+ 0 .

EPA SUM Figure 22. All Scenar io CCDF - 2nd 10,000 Years EPA LIMIT

E 10-1 ALL SCENARIOS

/

Cl) (INTERPRETATION 2)

a. 3RD 10,000 YRS.

. LU C,

-z C

LU LU

(..)

X LU u.

0 u> 1 o- 3 zLU 0

LU C:

LL.

10-4 ...__,__,_....................._.......___....,..i-i,......___,.--'--&....l-'-',JU...,....~U-.1-'--'-U..LU 10-3

\

EPA SUM Figure 23. All Scenario CCDF - 3rd 10,000 Years

E

J en C. ALL SCENARIOS EPA LIMI T w

(INTERPRETATION -2)

CJ

-wz C

4th 10,0 00 YRS.

lU u 10-2 w

LL 0

(.)

z w*

J 0

UJ a:

LL EPA SUM Figu re 24. All Scen ario CCDF - 4th 10,00 0 Year s EPA LIMIT

~

en

<

10- 1 C.

w ALL SCENARIOS . _

C,

. (INTERPRETATION *2}

-zw C 5TH 10,000 YRS.

w 0 10-2 w.

LL 0

0 z

UJ 5 10-3 w

a:

LL 10- 4 _________........._J,,,,1.,,1,.........___._ __._..................._....__.__._._.........._ _ _......_......,..,.

10-3 EPA SUM Figure 25~ All Scenario CCDF - 5th 10,000 Years

~64-

SCENARIO 38 4

~ (LEACH RATE: 10- 7 )

U)

~

0.

UJ I

"z 0

UJ SCENARIO 3C

, (LEACH RATE:

I '

I UJ u 10-s 7 )

X UJ u.

0

> EPA

z u LIMIT UJ

> ~.

0 w

0::

u. 1ST 10,000Y RS 10=4 ..._..._.................__._........................_....__............I.Ll,i,..--i.,....i....i ..J....&.L.L-.u..... .....................___.__........,"'4..1 10-2 10+0 EPA SUM Figure 26. Scenario s 3B.and 3C (Leach Limited)

CCDF - 1st 10,000 Years SCENARIO 38

E (LEACH RATE:

U) / 1 o.;.4 .;.. t 0-1 >

~ 10- 1 w

(!J

-zC W*

SCENARIO 3C

(LEACH RATE: .

w 10-5 7 ).

0 ts 10-2 LL 0

0 zw EPA LIMIT

, . ~

0 10-3*

w 2ND a:

LL 10,000 YRS.

10-4 .__.........-............._.__..._.-...,...__........~....._--.-.............~---.........------..................

10-2 10- 1 10+.o 10+1 10+2 10+ 3 10+4

EPA SUM Figure 27.. Scenarios 3B and 3C (_Leach Limited)

CCDf ~ 2nd 10 1 000 Years SCENARIO 38 (LEACH RATE:

~ 10-4-10-7)

(J) a.

w C, SCENARIO 3C

~ (LEAGH RATE:

C w 10-s-10"'.'7) w

()

w LL.

0

()

z EPA LIMIT w

=>

0 3RD w

a: 10,000 u.

. YRS.

10-4 .........--.....-.........-....-....-....--..._,_~..........._._...........~...__....._.~.............--.--'-'..LU.IM 10-2 .10-1 10+0 10+1 10+3 10+4 EPA SUM Figure 28. Scenarios 3B and 3C (Leach Limited)

CCDF - 3rd 10,000 Years

~

Cl) a.

w C,

_/

z SCENARIO 3C

-w C LEACH RATE:

w *10- 5 7 )

u X

w u.

0

() . 4TH 10,000 YRS z

w

> EPA LIMIT 0

w*

a: ~

u.

104 1--.L....L..u..L.WL.--L-.L.J..J.JJ .1.J.L...-L..1.-U.U.~-L.'-J...L.LW &___J~u..Ll,UI.---..L..1..-M.w 10- 2 10+ 4 EPA SUM Figure 29~ Scenarios 3B and 3C (Leach Limited)

CCDF - 4th 10,000 Years SCENARIO 38

~ / (LEACH RA TE:

=:,

en 10-S-1 o- 7 )

< . 10*- 1 C.

LU

. C, /

z C

LU SCENARIO 3 C .

(LEACH RATE: .

LU u . 10-4 7 )

>< 1* 0- 2 LU LL 0

(.)

EPA LIMIT z

LU 5TH . ~

5 10-3. .10,000 w

a: YRS.*

u.

10-4 ~.i.....a......u .~....-...,_,_L LU.I....._.I..J ,...u.LUJ.L... ..;.L....a.....i. ...&1o1.u-..& ....1~~__..--~

10- 2 10-1 10+0 EPA SUM Figure 30. Scenario s 3B and* 3C. (.leach Limited)

CCDF*- 5th 10,000 Years

-6 9.;.

All five CCDFs for Scenario 1 *(F.igures 6 through 10) show compliance with the EPA li¢it. Note that Interpretation 1 is implicit when the CCDF is for a.single scenario. The CCDF re-

sults for Scenario 2 (fractures in dense basalt) are presented in Figures 11 through 15. All five of these figures indicate a violation of the EPA limit, with each successive 10,000-yr.

period showing a greater degree of violation. As in Scenario 1, the leach-limited source model had been chosen by the computer model in Scenari.o 2. The. dominating radionuclidI!, in

t ms 0£ their contribution -to the EPA Sum, appear to be C and 99 Tc.

tn the first of the three variations of the borehole scen-ario, Scenario 3.A, the automatic source. selection algorithm chose the mixing cell model. The CCDF plots for Scenario 3A are given in Figures 16 through 20. Although some violations are apparent in the ~0,000 to 50,000-yr. period, none of the vectors exce~d the EPA limit during the first 10,000-yr. period, which is the period of.primary concern.

In an attempt to apply Interpretation 2 to the analysis, Scenarios 1, 2; an~ JA were assigned probabilities such that their sum was equal to L Composite CCDFs were then construc-ted and compared to the EPA limit "envelope". Recall that when scenario probabilities are inherent in predicting the*probabil-ity of a given release, two different EPA limits (EPA Surns,of l or 10) -are in effect, depending on the range of r.elease prp- .

bability. The composite CCDFs are shown in Figures 21 through 25, and it is seen that the frequency of violation is extremely small. This re-emphasizes the importance of, the manner in which the standard could be interpreted.*

The finai set of CCDF results, Figures 26 through 30, are included to demonstrate_.the effect of meeting the release *rate limit criterion of the proposed Rule (10CFR60) *

. The release rate and the leach rate are considered to be synonymous for demonstration purposes of this study. A leach-e- .

limited source model was imposed to obtain Scenario JB (leach ra_!: :* 10:j ? per year) and Scenario 3C .. (leach rate:

10 5 - 10 per year) respons*es. The EPA Sums associated with certain vectors of Scenario 3B are consistently higher than the corresponding vectors of Scenario 3C, as expected. Neverthe-less, .considerable violations of the EPA limit are indicated

by each of the-two leach-limited variations of Scenario 3. By contrast, the violations in Scenario 3A are not nearly as large or as fr.equent. This too is to be expected, since the mixing cell permits. the solubility limit to be the controlling para-meter instead of leach rate.

9, CONCLUSIONS The ana lys es pre sen ted tic al too ls cou ld be use d to dem ons trat e how the exi stin ana ly-ass ess com plia nce wit h thegdra EPA Sta nda rd. A det ail ed dev elo ft pm ent of pro bab ilit ies of see n~

ari as wil l be nee ded in 6rd er to sme nt. As sit e cha rac ter iza tio per for m a mor e rea lis tic ass es-n pro cee ds, .on e may exp ect i@-

pro vem ent s in the inp ut dat a ove r tha t ass um ed in thi s ana lys is.

Am big uiti es in the dra ft to ass ess com plia nce hav e bee n sta nda rd and ass um ptio ns nec ess ary ide nti fie d. The se wil l nee d to be cla rif ied , jus tifi ed, or fur the r dev elo ped bef ore a rel iab ass ess me nt of com plia nce can be le mad e.

,. Two int erp ret ati ons of the i

sen ted whi ch sho uld be dis cus sed dra ft sta nda rd hav e bee n pre -

I fur the r, esp eci all y in lig ht of the unc ert ain ties in bot h the sce nar io pro bab ilit y and the est ima ted E~A Sum . Int erp ret ati on 1 is com put atio ple ri sin ce sce nar ios may be a~a nal ly the sim -

pos tul ate d. lyz ed one at a tim e as the y are It is als o eas ier to com pre hen to the unc ert ain ty in sce nar io d int uit ive ly. Due wh eth er or not com plia nce is ach pro bab ilit y, arg um ent s as to iss ues , iev ed are red uce d to two bas ic

1. Ass ura nce tha t the sce nar io pro bab ilit y is: gre ate r tha n 10- 2 (th e c~n ser va~

tiv e ass um ptio n), betw een 10-and 10~ 2 (ar gua ble if unc ert ain ty pro bab ilit y is lar ge) , or les s in the 4 tha n 10- (ne gli gib le) .

2, Con fide nce tha t the con seq uen ces sub sta nti all y les s tha n the allo are max imu m. we d Co mp uta tion ally , Int erp ret uti liz e but see ms to be mor e in ati on 2 is mor e dif fic ult to the spi rit of ris k ass ess me nt as it has bee n app lied to. nuc lea der s all sou rce s of a giv en con r rea cto ~s. in tha t it con si-seq uen ce (EP A Sum ). An oth er dif fic ult y in imp lem ent ing thi ma tion of sce nar io pro bab ilits int erp ret ati on is the est i-ies , Un cer tain ty in sce nar io pro bab ilit y cou ld be acc omm oda lea st in pri nci ple , by per for min ted in thi s int erp ret ati on, at g a sam plin g of a pro bab ilit y dis trib uti on assu med to des crib pea r tha t the qua nti ty of int ere e eac h sce nar io. It wou ld ap-st, as far as the sta nda rd is con cer ned , is the pro bab ilit y of rel eas e (re gar dle ss of wha sce nar ios or eve nts con trib ute t to it) . The ref ore , in our

opi nio n, Int erp ret ati on 2 is pre dif fic ult ies tha t hav e not bee fer abl e in spi te of som e n tot all y res 6lv ed, The results of analyses for this reference basalt site performed under Interpretation 1 showed as.mall probability (a few percent) of violating the draft EPA Standard for Sce-narios 2 and 3A without imposition of.the 10CFR60.requiremen ts on the release rate. Under Interpretation 2, the same analyses indicate nearly total compliance with the draft EPA Standard.

Of course, both of these results are subject to sampling error.

Future analyses *Should explicitly address the sampling error.

Analyses performed with different source models.show the importance of the source term assumption on compliance esti-mates.

APPENDI:X A RADIONUCLIDE RETARDATION

1. Calcu lation of the Retar datio n Facto r The retar datio n facto r R for an aqueo us radio nucli de trave ling in a porou s mediu m is speci es or a usual ly de-fined as:

veloc ity of groun d water (l)*

R =

.velo city of radio nucli de The value of R can be calcu lated - by:

(2)

R = 1 + R

P

d where

= the radio nucli de sorpt ion ratio in ml/gm P = grain densi ty of rock in gra/cm3

</Jeff = effec tive poro sity that contr ibu-tes to the flow path; in porou s media , ¢eff = ¢tota l" A more gener al expre ssion that is valid for porou s as well as fract ured media for a unit volurn ~ of rock, may be de-fined as follo ws:

r-1.r total mass of radio nucii de in rock- water syste m R = =

mass of radio nucli de in water (3)

A-1

For porous media, it is shown below that this expression is equivalent to Equation (2).

Let:

ex = concentration of radionuclide in solution in gm/ml' CMX = concentration of radionuclide adsorbed by the rock in gm/gm MR = mass of nuclide in r:ock in grams Then for a unit volume of porous rock, Mx = CX

. ¢eff ( 4)

MR = CMX (l-<l>eff)P ( 5)

= {6)

From Equation (3),

( 7)

R =

substituting terms yields:

Cx. ¢eff + CMX (l- ¢eff)

P R = (8)

Cx -* *¢eff CMX l - ¢e£f R = l+-*P* ( 9)

Cx 0eff A-2

bu t (se e Eq uat ion 5.5 )

the ref ore ,

. R = . p .

In gen era l how eve r, the flu id is no t in co nta ct wi th en tir e roc k ma ss. We int rod the uce th.e uti liz ati on fac tor to co rre ct R for thi s eff ec , if, in Eq uat ion s (2) and (8) ,

t.

R =

e- ( 10)

x

( 11) .

.wh ere ~ is the vol um e fra cti wi th the *flu id. on of the roc k tha t int era

cts

2. Es tim ati on of Ut iliz ati on Fa cto r In the ref ere nce rep osi of the fra ctu res are lin ed tor y we hav e ass um ed tha t*m ost der the se co nd itio ns, we .can wit h sec ond ary rni ner als . 10 Un -

als o sim pli fy, the exp res sio der ive an exp res sjio n for if, and n for R. If we ass um e tha t the flu id in the fra ctu res int era cts on ly wit h sec ond mi ner als , *th en ary

=

wh ere PsM and VsM are

the mi ner als in the un it vol um den sit y and

vol um e of sec ond ary e

*is the co nc en tra tio n of rad of roc k, res pe cti ve ly, CSMX ond ary mi ner als in gm /gm . ion ucl ide ads orb ed by the sec -

A-3

Let

. fraction of rock)

VsM* = (.volume. of s<;>lid) rock in unit X composed of

volume of rock ( secondary minerals.

= (1 - ¢T) *

1P

unit volume where

¢T - total porosity.

If we assume-th at ¢T=::.¢eff' then Equation {10) becomes, 1

R ~ CX * </Jeff + .if,

Cm,ix * {.l ¢ef f)

Psr-1 {12 }

ex* ¢ef.f Let which gives, (l - ¢eff)

R ::::: 1 + 1/J*

RdSM

p SM * (13)

¢eff Note that in t,his scenario, RdSM and PsM refer to the so~ption ratio and density,o f secondary minerals, and that¢ ff refers to the basalt matrix. The utiliza-tion ffctor 1/1 is the volume fraction of the rock matrix occupied* by secondary minerals.

Intuitivel y; we would expect that the amount of

secondary mineraliz ation in the basalt can be related to the vo 8rne of the.fractu res. At Hanford, for exam-ple, Long 1 examined 3 flows in the Grande Ronde. He found that nearly all the fractures contained some filling and that.more than 75 percent of the fractures were filled completely * . If we assume that the frac,...

. ture_s that contribute to the effective porosity are, on the average, one-half filled, i.e.,

"original" unfilled

fracture porosity = 2

residual_ porosity A-4

Th en VSM = re si du al po ro si ty

- ¢e ff an d Ip =

V so lid ro ck *

(1 4)

Th is ex pr es si on ca as fo llo w s: n be us ed to si m pl ify Eq ua tio n (1 3)

R = l + KdSM.

p ..

(/)ef f SM . (1 - (/J eff )

or ,

R l + Kd SM

PS M (1 5)

I

!t.

I.

In th e mo re ge t vo lu m e of se co nd ar ne ra l ca se , we ca n as su m e th at th I.

e o-f th e vo lu m e of y m in er al iz at io n is a m ul tip le (f ) [-'.

re si du al co nn ec te d ,..

1.*

tio ns (1 4) an d (1 po re sp ac e. Eq ua -

5) be co me , !

r ll r,*

1**.

.,. = 1,.

Y'- i:.

(1 4a ) t;'~*

J; ..

. J.

1.

R i (1 5a ) Ii i

I A- 5

APPENDIX B REDOX CONDITIONS IN THE REFERENCE REPOSITORY AND APPROPRIATE VALUES OF Rd

. A large amoun t of uncer tainty in our estim ates of radion uclide discha rge is introd uced by a lack of *know-,.

ledge about the geoche mical enviro nment that *may.b e en-count ered by the migra ting nuclid es and by the pauci ty of reliab le values ot radion uclide sorpti on ratios * (Ras) releva nt to this study. In this sectio n we will descr ibe the assum ptions we have made in chara cteriz ing the geo-chemi cal enviro nment and in choos ing appro priate values of Ras for our calcu lation s.

1. Redox Condi tions The diffic ulties encou ntered in attem pting to predi ct the Eh-pH enviro nment of natura l system s from eithe r theor etical consid eratio ns, or*fro m direc t mea-surem ents1 h~ve been discus sed iri detai l by sever al autho rs. 1

1 113 Discu ssions of t}:l.e proba ble nature of the geoche mical enviro nment within t~e Hanfo rd Site and subsu rface mine.s are given by Sato , Smi th 14 , and Guzow ski, et*a1. 1 5 Field measu remen ts and theor etical calcu lation s based on observ ed miner al assem blages in basal tic enviro nment s sugge st that ground water , in conta ct with basal t, will have a low Eh (-0.40 to

- 0.55) , a high pH (9.4 - 10), and moder ate tempe ra-.

tures (30 - so 0 c). These Eh-pH condi tions may be ex-pected near the repos itory in part of Layer A in Figure 2 and along fresh basal t fractu res expose d by faulti ng or drilli ng in other layers as descri bed in the hypot hetica l disrup tion scena rios. In our char-acteri zation of the repos itory, we have not consid -

ered the oxida tion poten tial of air and foreig n mat-erials introd uced .into the basal t during opera tion and

cons tructi on of the repos itory. The two interb eds I-V and I-Mar e assume d to be relati vely active aquif er system s, and are, theref ore, assum ed to.be oxidiz ing and sligh tly alkali ne.

In the "bas~" (no disrup tion) case, we have assu-med that in all basal t layers , ground water flows throug h fractu res lined with second ary miner als. The observ ed fractu re-fil l consi sts of amorp hous silica ,

zeoli tes, calcit e, and nontr onite. 1 0 None of these B-1

minerals ha~e appreciable oxidizing power. Althou~g nontronite contains Fe 3 , it forms under reducing conditions.* At low .

pH, the dissolution of iron-bearing minerals in basalt and pre-cipitation of ferric oxyhydroxides will proceed under reducing conditions. 11 For these reasons, we have assumed that the geo-chernicai environment of partially filled fractures in basalt is reducing. *

2. Available Data for Values of Rd The large amount of experimental error reported for de-*

terminations of Ras and the questionable utility of this parameter for accurate calculations of radionuclide retardation have been discussed by several authors. 1 5-22 The values for the ranges of radionuclide, Ras, that were used in this report are presented in Table 5 (main text}. The data were supplied by several researchers and are reviewed in Guzowski, et ai. 15 Histograms of the number of det~rminations of Ras for each radionuclide for the substrates under several geocnemical environments considered are shown in Figure B-1. *.

It is clear th.at there are relatively few reliable determina-tions of Ras for the geochemical conditions relevant to this study.* The large majority of data has been obtained for ba-salt under an oxidizing atmosphere, a condition that we do not feel is relevant to the geological system under consider-ation *

. In mos~ ?ases, the ranges of Rd values rep?~'!=-e? for re-;-

ducing conditions overlap those reported for oxidizing condi-tions. For this reason, we have used the more limited number of data obtained under oxygen-free conditions to est~mate the ranges of Rd for reducing environments and we have supplemented these data with values obtained.under oxidizing conditions where necessary. No data are available for several elements: Cm, Pa, Ac, Th, and Pb. Based on similarities in solubility, valence and ionic radii, the following chemical homgl'ogs have been as*su-med: (Am= Cm, Pa, Ac, Th} and (Pb= Ra). 1 No yalues of the .

Ras of Cs*, I, Ra, or Am in contact with basalt under reducing "

conditions are available. The Ras of these elements are assu-med to be insensitive to redox conditions: values under oxidi-zing conditions were used for our calc~lations *.

B-2

'-J

12 Secondary Minerals -

10

-- Reducing Conditions 8 --

6 4

2 .

0 I I Cs I I I I

.1:'U Np u Ra Tc I I

Sr I

' Grou p I ' Pb I Am 60 --

so 40

--... Secondary MineFals Oxidizing Conditions 30 ..

t:11 i:: 20

0

ri

.µ 10 ~

!IS i::

ri 0 I e

1-1

.l:'U Np u Ra Tc -I Sr Cs Group I Pb I Am (I)

.µ 20

I-0 (I) 16 -- Basalt - Reducing

'O Conditions

~

4-1 12 ---

0 1-1 8 -

~z (I) 4 ...

0 Pu Np u Ra Tc I Sr Cs I

Group I . Pb I I Am I

140 -

120

-- Basalt Oxidizing 100 80

-* Conditions 60 -

40 -*

20 .

0 I Pu Np u Ra Tc I Sr Cs Grou p I Pb Am Group I= Cm, Pa, Ac, Th Figure B_-1. Rd Data B-3

APPENDIX C AN APPROXIMATE TREATMENT OF MATRIX DIFF USIO N AS A RETARDATION MEC HAlH SM We hav e ass'u med tha t grou ndw mig rati on occ ur pred omi nan tly thro ater flow and rad ion ucli de ugh num erou s narr ow ver tica l fea ture s in the bas alt. He hav e also effe ct of such a flow assu mpt ion on atte mpt ed to show - the ces ses exp ecte d to reta rd rad ion ucli the che mic al sor ptio n pro -

de mig rati on and enh anc e the con tain men t c~p abi lity of the rep osit ory . In doin g so, we hav e give n up the trad itio nal poro us med ium exp ress ion for the reta rda tion fac tor of the form R 2:'

-PRa

¢ (1 - ¢)

in favo r of the form R

-- .PRd as disc uss ed in App endi x A.

A few rad ion ucli des are ess ica l sor ptio n, i.e ., Ra::::: 0. Speent iall y unf !tar ded ~y chem -

ina te the. EPA .Sum for mos t vec tors .

cifi call y, C and 9 Tc dom -

pro duc ing larg e val* ues of the EPA Sum . For sce nar ios invo lvin g maj or hyd rau lic con -

nec tion s betw een the sub surf ace fac ilit y and ove rlyi ng aqu i-fers , e. g_., bor eho les, thes e rad ion ucli des may be of mos t

con cern in lice nsin g con side rati ons

. In sce nar ios res ulti ng in enh ance men t of the rep osit ory hyd frac ture s in den se bas alt, tran spo rau lic pro per ties , e.g .,

rt may sti ll be dom inat ed by ** flow thro ugh narr qw frac ture s.

For thes e cas es, we may hav e ove rest ima ted *the rele ase s by reta rda tion mec hani sm" neg lect ing a pot ent ial A num ber of auth ors hav e disc con tam inan ts into *the rock mat rix uss ed the diff usio n of for- cas es sim ilar to tha t whi ch we hav e assu med , nam ely tran spo ture s in rela tive ly imp erm eabl e rock rt ~2r~ g.gh narr ow. frac -.

.2 3 , ' The trea tme nt pre sen ted her e is ess ent iall y tha t of Eric kso n and For tney 26 who hav e used this effe ct in the des ign of radi onu cl~d e mi-gra tion exp erim ents in non -we lded tuf esti mat e the pot ent ial imp orta nce of fs. We wou ld like *to this mec hani sm in ra-dio nuc lide reta rda tion . The val idit y of the met hod , as der ived and imp lem ente d her e, res ts on a num ber. of assu mp-C-1

tions which will be made.* Neverthel ess, the results will demonstra te the potential importance of this retardatio n mech-*

anism and the importance of understand ing it better.

Consider the idealized fracture geometry depicted in Fig-ure C-1 below:

XL z co VRN cf>m H C ( t)

L Figure C-1.

Idealized Fracture Geometry A fracture

of width H and length L is _assumed to exist in a

rock matrix with a porosity, <t>m* At time t = 0 a constant radionucl ide con~entra tion, C , is introduced at the fracture

, inlet. Ari expression for the 0 time dependent concentra tion, C(t), at the outlet is desired. The rock is assumed to be infinite in the x~directio n with the contamina nt concentra tion in the rock r CR ( x, ~) , maintained at zero at x =. + _oo. . In the fracture, radiopucl ide t~ansport is assumed to be purely ad- .

vectiv w~th the contamina nt t ans~orted at~ spe~d, vaN' .with 7 7 no variation of the concentra tion in the x-d1.rect1o n w_1th1n the fractu*re ... Dispersion in the z-directio n in the fracture is neglected . *tn the rock, transport is assumed to.be purely diffusive and iri the x-directio n . . For .this situation , trans-port in the fracture is assumed to be described by C-2

ac + v ac + 2 ao at az Ir ot = 0 wher e co Q =

0 f q(x, z, t)dx and q is the conta mina nt conc entra tion in the rock matr ix desc ribed by aq

=

at ax 2 wher e Deft is the effec tive diffu sion coef ficie nt RR is the stand ard porou s mediu m retar datio n in the rock and facto rock . Matc hing the conta mina nt flux in the x-di r for the recti on at the fract ure- rock inter face gives the conc entra tion of con-tami nant at the fract ure exit (z = L),

C (t) = C0 erfc (7]) (Cl) wher e

. 0mRRL /neff /RR 7/ =

HvRN Jt - z/vRN A "brea kthro ugh time ", tB, may be defin ed as that valu e of

~' wher e C(tB )/C = 1/2. The effe ct of the early the erfc func tion will be addr essed below . This tail of 0

value of 7/ will be deno ted by 77 , .whic h. has a nuine rical 0 value

of C-3

approximatel y TJ 0 = 0.48 The expression for 7] may be solved fort, giving tB =

L t RRL) r*ffj 2

VRN + H:RN71o . . RR In the absence of diffusion into the rock matrix (D £ - 0),

radionuclides would be expected to appear at the exitfi~

high concentration at time L/vRN" Thus, we may define a*

. retardation for this mechanism, RMD RMD = ti(v:J= l + _R_R_L_v-:-:-f-f

.I I

I If*there is some chemical retardation in the fracture, then vRN ~s retarded relative to.the fluid velocity, vf 1 ,. by the chemical reta.rda tion factor, Reh, so that

= 1 +

As will be shown, retardation factors resulting from use of this.form cart be very large. Transport calculations have not been performed for times long enough to dsmonstrate this effect. Thus, we do not have the results of numerical cal-culations of the total discharge to be compared to the EPA limits. It is not clear.that*th e current version of the DVM transport model could be used for such a calculation due to the skewed shape of the breakthrough curve. We can,*

however, make a bounding estimate of the total integrated discharge-ba sed on simple consideration s which should be

.f,iPlicab1 to_one-membe r radionuclide decay chains such as C and 99 Tc *.

Con sid er the foll ow ing bre akt hro dep icti ng the beh avi or of Equ atio ugh cur ve (Fi gur e c-2 )

n Cl, Ca __ __ __ __, ....... __ _ _.. __ - -.- ......

c' Tun *t B

Fig ure C-2 . Bre akt hro ugh Cur ve De pic ting Beh of EqG atio n Cl: C(t )=C erf c(~ avi or.

0 )

C c*o = max imu m dis cha rge .ra te

= est ima ted bou nd of the dis cha rge rat e for tin es l~s s tha n .TR in th~ abs Tun = tim e o*f tra nsp ort in theencabs e of ma trix di~ fus ~on enc e of ma trix dif -

fus ion L/vR N. . . *.

TR =

reg ula tor y tim e lim it, e.g ., 10 4 yea rs tB = est ima ted bre akt hro ugh bim e wit h ma trix dif fus ion as a ret ard atio n mec han ism The sha ded are rep res ent s the tot al int egr ate d dis cha rge ,

TID ,. tha t we see k to bou nd.

The onl y ass um ptio n nec ess ary is ,tha t the sha pe of the dis cha rge cur ve be cur ved upw ard ,

as. dep icte d, for tim es les s tha n t 8

Thi s ass um ptio n has not ,be en inv est iga ted , but seem s rea son abl e.

The sha ded are a.i s bou nde d by the are a of the tria ngl e.

of bas e (TR - T ) and hei ght ,

un

C',

1 l TID < - C' (T - T R un ) =- C O

2. 4., Ct 0 Tun >

c-s

where the last step follows from similar triangles . The maximum *discharge rate i.s given from the transport calcu-lation performed without matrix diffusion .

No decay corre.ction s have been considered .. In fact, the c6rrection terms already introduced are sufficien t to significa ntly reduce the calculated discharge s.

To implement these results for the multi-lay ered reference basalt system, we will assume the radionucl ide migration path to be made up of a series of idealiz~d fractures through each of the layers of the reference repository (except the thin sandstone layer). The subsur-face facility is treated as an extended source releasing radionucl ides through these idealized fractures. Discharge s from the.last set of fractures are collected by.the over-lying aquifers. Lateral variations in propertie s are neg-

.lected *. We seek an equivalen t single fractur~ represent a-tion of the actua.l multi-laye red system.

The fluid transport time is given by L,

Tfl = Li 1.

vfl,i

=-=-I:

q i Li¢h,i layers where qi~ the Darcy velocity which is the same in each layer, i, and *Li is the thicknes_s of the ith layer. ¢h i is the effective porosity assumed to be dominat~d by fr~c-tures. The transport time for the migrating contamina nt, tB'* is given by L, L, R. (md*) L,R, (md).R, (ch)

.).

tB = Li J.

.v, (md)

J. .

= I:i l. l.

v:RN, i

= --'

i 1 ].

V '

1. ..

f].,l.

= l:E L . R . ( md ) R . ( ch ) (/>

l. l. l. h,1 q i So that C-6.

t Li L*</J .R. (ch)R, (md) 1, h,1 1 1 Reff = B ------.-=

"-L---*</J-h-.-,_i_ _ __

Tfl - L..J 1 i

Here, we have as.sumed the Darcy velocity and fluid vel-ocity to be related by

=

Finally, to implement these results, we will make the following assumptions.

1. </Jm, i = an approximate relation.-.

ship consistent with data on basalt 1 S

2. Reh = i. + RaP as in Appendix A

3. Deff = 2 X 10- 7 cm2 /sec.

4. *. H = .os cm l'

To demonstrate the effect of diffusion into the rock matrix on estimates of the integrated discharge,th ree ..

vectors of Scenario 2 have been chosen which led to vio-lations of the EPA draft standard. The integrated dis-charges for these vectors are sununarized in Table C-1.

Applying the approximate treatment discussed above yields results presented in Table C-2. Data used in these cal-culations are presented ~n Tables C~J, 4, and* s.

It shouid be noted from this. summary of results that the estimated contribution to the *EPA S'um 1 is the. estimated integrated discha;i:-ge from time*zf;!ro to T. Thus, for Vector 15, for example, we estimate the ~otal discharges, integrated to 50,000 years, divided by their EPA limits, and summed over all radionuclides to give *a val'ue of. less than 0.140. Similarly; for Vector 62, the 50,000 year upper bound estimated for the EPA/Sum ii:!> 0.2. The results for Vector 24 must be qualified. The method developed for this estimation is based on the treatment of a single-membered radioactive decay chain. All-of the dominant con-

_.tributors to the EPA Sum in Vector 24 are members of longer C-7

Table C-1 SCENARIO 2 Discharges With0ut Rock Matrix Retardation.

Vector 15 Period

<xears) 0~10 4 10-20,000 20-30,000 30-40,000 40-50,000 EPA Sum .68 . 34 .079 1.27 2.55 Tc99* 1.27 2.55 Cl4 .68 .32 .OS Vector 24 EPA Sum .093 .044 .015 1. 02 6.97 236U .19 1.42

238U .25 1. 61 234U .ss 3.61 Vector 62 EPA Sum .81 1.57 3.46 1.42 Tc99 0 1.18 3.43 1.42 C14 .81 ~39 C-8

Tab le C-2 Sum mary of Effe cts of Diff usio n Into Rock Mat rix on TID* . Con trib utio ns to the EPA Sum less than .001 are omi tted . No corr ecti ons for deca y have been incl ude d.

SCENARIO 2 Vec tor 15 Vec tor 24 Tc99 Cl4 Vec tor 62

--- -- -- 234U

--- - 236U

--- - 238U --irc 99

--- -- cl4 Reff 6.4E ll 2.1E 4 2.3E 9 2;3E 9 2.3E 9 2.0E 9 l.8E 4 Tfl (yr) l.2E 3 l.2E 3 l.1E 3 l.1E 3 l.1E 3 l.1E 3 l.1E 3 T8 (yr) 7.4E l4 2.5E 7 2.4E l2 2.4E l2 2.4E l2 2.3E l-2 2.1E 7 n c 0 (Ci/ yr) 22.3 1.15 I .22 .10 .093 33.2 1.4

\0 Con trib utio ns to EPA Sum TR = l.E4 .oos .007 2.* E4 .021

.030 3.E4 .049

.070 4.E4 .088

.127 5.E4 .40

.200

To tal inte grat ed disc harg e

Table C-3 SCENARIO 2 Vector 15 Data Used to Estimate*Retardation*

Due to Diffusion Into the Rock Matrix i L, ¢.J. v;fl Rmd

l. l. Rhost Rfracture Tc99 1 150. .0537 2.449 .5859E+05 28.36 .3216E+l0 2 150. .0750 1.754 ** 4100E+05 . 28. 36 .6132E+10 3 50. .0129 10.23 .2552E+06 28.36 .6411E+08 4 60. .0967 1.360 .3106E+05 28.36 .3981E+l0 5 690. .0887 1.483 .3416E+05 28.36 .3887E+ll

O 6* 10. .1639 .8026 33.91 33,91 1.000

-~* 7 690.

625 2.105 ,4988E+05 28. 36 . .1984E+ll 0 a 200. * .0587 . 2. 240 .5329E+05 28.36 .5101E+l0 9 150. .0600 2.193 .5212E+05 28.36 .3984E+l0 c14 l 150. .0537 2.449 1.000 1.000 1936.

2 150. .0750 1.754 1.000 1.000. 5273 *.

3 so*. .0129 10.23 1.000 1.000 9.855 4 60. .0967 1.360 1.000 1.000 4520.

5 690. *.0807 1.483 1.000 1.000 .4012E+05 6* 10. .1639 .8026 1.000

1.000 .i.000 7 690. .0625 2.105 1.000 1.000 .1402E+05 8 200. .0587 2.240 1.000 1.000 3375.

9 150. .0600 ,2.193 1.000 1.000 2696.

No matrix diffusion assumed in Layer 6. ,

Table.C-4 SCENARIO 2 Vector 24 Data Used to Estimate Retardation Due to Diffusion Into the Rock Matrix. (Caveats in the text on p. C-7 with regard* to longer decay chains should be notecl.}.

L*1 i fl ch ch (ft) ¢.1 vi Rhost Rfracture Rmd U234, U236, U238

~-------~

1 150. .0484 2.619 2 2455. 10. 20 . .3678E+08 150. .0440 2.878 2711.

3 50. 10.20 ,30?8E+08

,0125 10.09 9817. 10.20 nI 4 60. .1017 .8559E+06 1.246 1103. 10.20 .6139E+08

..... 5 690. .0675 1.07G

..... 6* 1724 . 10.20 * .3231E+09

10. ,1438 .8808 1317 *

.7 690. 131 7. 1.000

.0639 1. 98.1 1827. 10.20 8 200. .0552 .2907E+09 2.297 2138. 10.20 .6329E+08 9 150. .0708

1.790 1639. 10.20 .7687E+08

NG matrix difl~sion assumed in Lay~r 6.

Table C-5 Vector 62 Data Used to Estimate Retardation Due to Diffusion Into the Rock Matrix fl Ch Ch i L, l.. fDi V*

l.. Rhost Rfracture Rmd Tc99.

1 150. .0422 3.326 7215.

2 150. 5.348 .3391E+08

.0931 1.506 3095. 5. 348 3 so. .1565E+09

.0140 10.04 . 2242E+05 5. 348 .

4 60. . 0694 .1277E+07 2.021 4260 . 5 .348 . 3570E+.08 5 690. . 0786 1.784 3725 .

6 5.340 .5213E+09

10. .1694 .8276 76.98 76.98 7 690. .0753 1.000 1.861 3899. 5.348 .4808E+0.9 n 8 200. .0735 1.907 4002.

I 9 150 *. 5.348 .1330E+09 i,:... .0742 1.890 3964. 5 ._348 ._ 1015E+09

"' Cl4 1 150. .0422 3.326 1. 000

2 1.000 879.8 150. .0931 1.506 1.000 3 1.000 9460.

50. .0140 10.04 1. 000 1.000 4 60. 11.65

.0694 2.021* 1.000 1.000

1568.

5 690. .0786 1.784 1.000 6 1.000 .2617E+OS

10. .1694 .8276 1.000 1.000 7 690. .0753 1.000 1.861 1. 000 1.000 .2306t:+05 8 200. .0735 1.907 1.000 9 1.000 6216.

150. ~0742

1. 890 1. 000 1.000 4789.

decay chain s. The effec t of other chain membe rs on these est-imates has not been inves tigate d quant itativ ely.

Other violat ing v~cto rs for this scena rio h~ve been in-vestig ated with this method and simil ar improv ement observ ed.

The accura cy of the estim ates would be improv ed by estim ating discha rges at times earlie r than tB and corres pondi ngly larger value s of ~

Howev er, the treatm ent giv~n is suffic ient to 0

demon strate the poten tial impor tance of diffus ion into the rock matrix as a retard ation mecha nism.

C-13

)

APf'ENDIX D CALCULA TION OF THERMAL BUOYAi.'l'CY GRADIENT .

Conside r a cylindr ical volume of fluid with length L and *average tempera ture T immersed in a medium of average tempera ture T (T>T ), (F'igure D-1). The differen ce_ in tempera ture p~oduce~ an upward force on the volume of fluid.

The v~lbcity 2 the fluid in the cylindr ical volume. can*be describe d by: 1 * . . . * *

V -a.dTK (D-1) with V = Darcy velocity of fluid a = average linear coeffici ent of thermal expansio n of fluid AT = T-T 0 K = Hydraul ic conduct ivity of medium T

L T T 0

l

.Figure D-1. Water Column Assumed for Thermal Buoyanc y Calcula tion

\

D-1

Since Darcy velocit y is equal to the produc t of hydrau lic gradie nt (I},, and conduc

. tivity, the upward gradie nt is given by* .

I = aL1T (D-2}

The temper ature field around a reposi tory at the Han-ford Site (46,800 MTHM spent fuel} has been calcula ted for variou s times after closure . Figure D-2 presen ts the re-sults of these calcula tions at f3ooo, 4,000, and 30,000 years after reposit ory closure . 2

The upward gradie nt for each time period is calcula ted as follow s: the 11 disturb ed zone 11 is assume d to be 4 km wide and has a height 6£ 400 meters above the reposi tory. The average temper ature T of this disturb ed zone is calcula ted by T =

-1 L

f TdL.

T 0 is the_ average backgro und teniper ature of_the disturb ed zone calcula ted from the natura l geother mal field. The hydrua lic gradien t is then obtaine d* by using Equatio n (D-2),

i.e., I= a(T~T }.

. . 0 '

The results of the calcula tions are shown in Table D-1.

Table D-1 Hydrau lic Gradie nts Produce d by Therma l Effect s T( c}

0 a(T) 0 c- 1

- - !o(OC} Gradie nt 1,000 year 98.2° 53.2° 608xlo - 6 0.027 4,000 year 101.s 0 53.2° 608x!0 - 6 0.030 10,000 *year 64.3° 53.2° 513xl0 - 6 Q.006 D-2

45°C 300 50°C

[ 200 UJ u

...~

1/)

100 ss c0 ci

...J c(

0

~

.....a:

.,oo

200 di 1000 YEARS

&0°c

.1

. 65°C

~-r-"""

I -- 10°c

.J.O *2.0 .,.o 0 1.0 HORIZONTAL DISTANCE (kml 2.0 J.O I

4.0 el 4000 YEARS

/00 45°c 300 50°C I

WI 200 u

zc(

VI i5 100 ss c 0

...J

~

0 ---

~ *100 eo*c 60"C

> --6S°C

-200 NOTE:

10°c REPOSITORY LCCATEO I

AT 10, 01 COO='IQttiATES

.J.O *2.0 .,.o 0 t.O 2.0 J.0 40 HORIZONTAi. DISTANCE (kmJ IJ 30000 YEARS" Figure D-2. Isotherms Used in Calculatin g Thermal Buoyancy, ifrom Reference .2 8 D-3

APPENDIX E THE MIXING CELL SOURCE MODEL In Sourc e #3 we allow the back filled regio ns to be mode led as a mixin g cell in which flowi ng groun d water is assum ed to mix with radio nucli des in the volum e of the mixin g cell. The conce ntrati on of radio nucli des relea sed from _the back filled regio ns is then given by the unifo rm conc entra tion in the mixin g cell. This model can be cal-culat ed analy tical ly for a singl e stabl e speci es.

Let V = mixin g cell volum e, C = radio nucli de conce ntrati on in water in the mixin g cell, L = rate of radio nucii de input into V from waste -form leach ing, Q = rate of water flow throu gh v..

In the mixin g cell mode l, we assum e the leach rate, L, to be a const ant_f ractio nal rate, AL of the initi al inven in the waste form,. N , tory 0

L =

The conta minan t conce ntrati on in the mixin g cell is descr ibed by dC V *dt- - L - QC (El)

.If we let Ao = Q/V.

E-1.

the solution of Equation (El) is, C ( t) . - (E2)

Q For small t, tL C (t) =

V Thus the concent ration of the radionu clide increase s linearly with time from zero.

The asympto tic release rate QC 00 can be obtained f rain Equation . ( E2 ) with t - oo :

QC 00 = L Thus, a~ long times, the release rate approach es a value governed by the rate of waste-fo rm leaching . The release rate from the-mixi ng cell is then less than or equal to, the release rate given by conside ration of the waste form leaching alone.

For decaying radionu clide chains, this model is im-plemente d numeric aily in NWFT/DVM accordin g to the compart -

ment model_ sh.own in Figure E-1. Radionu clides remainin g in the waste form ar.e represen ted by Compart ments, R. The waste-fo rm breakdow n rate governs transfer from Compart -

ments R to Compartm ents u. The inventor y in Compartm ents U is examine d"along with the water volume in the mixing cell and solubil ity l_imits to transfer all or part of that invento ry into the mixing cell. The mixing cell inventor y is denoted by Compartm ents N. The mixing cell is flushed constan tly to give a release source (S) of E-2

production decay

_; -1 i i +l R [ } ~ ] ~ I I

I I

! leaching I

I u

1 '

~

I I

i J

disso1ution

~ I I

I

' t t precipitation N

I. J ~ J

?I,, r 1 I.

flushing s

Figure E-1. Implementation of the Mixing Cell Source Model for NWFT/DVM.

E-3

where Ni is the inventory of radionuclide i in the mixing cell* compartment.

When solubility limits are applied, radionuclides may be transferred from Compartments N to Compartments U, re-presenting precipitation. For large solubility limits*, Com-partments U are emptied as quickly as* they are f il_le<i.

Horizontal transfers between a compartment, i, and compartments i + 1 or i - 1 represent decay and/qr produc-tion.

The effect. of various source models can be illustrated by considering the total integrated discharge of the contam-inant, Di t*

D*,"

l. =

f0 s.l. dt For a leach or solubility limited source, Si is a constant.

For the *mixing ce.11,

Si is . initially zero and approaches an asymptotic value determined by the leach* or solubility limit.

The discharge is illustrated in Figure E-2.

The integrated discharge is numerically equal.to the area under the plot of s., versus t. Due to its low* initial value, the mixing cell aiways gives lower values of S, and Di at any finite time, 'than a leach or solubility limitea model.

It should be kept.in mind that, the leach-limited source will be depleted at an earlier time, and the the total release will be the same for all models given sufficient time.

E-4

Leach Limited I .-.

/"'

' /

/

/'

/

/.

/ /\

Mixing Cell

/

I

/,

t Time After Onset of Releas e Figure E-2. Compar ison of Radion uclide Releas es in the Mixir.g Cell and the Leach-Limited Source Models E-5

APPENDIX F RATIONALE FOR. THE SELECTION' OF*

SCENAR!OS ANALYZED IN BASALT In these analyses, we have chosen scenarios which are both credible and consisteri t with the character istics of a real ba-salt site currently being studied. It is felt that contamina nt transport by ground water to an aquifer is the dominant trans-port mode. The first step, therefore, was to examine scenarios involving groundwat er transport to an aquifer. The path of this transport *from the undergroun d facility could either be upward or downwa.rd, to an upper or lower aquifer, resp~ctiv eiy.

An upward path was chosen for our analyses for the following reasons:

1. No indication exists that there is a downward gradient from the subsurface facility to the lower aqu.ifer at the candidate site, 2~ A lack of knowledge of the character istics

of the lower aquifer for the real*site:

that is, data involving flow direction ,

discharge location and hydraulic p~oper-ties are very limited and inconsiste nt. *

3. Based on expert judgement, the groundwat er travel time from the undergroun d facility to the accessible environme nt via a lower aquifer is .likely to be much longer. than via an upper aquifer. In other words, the lower aquifer path would probably be of much le.ss radiologic al consequenc e than the upper case.

No Disruption Scenario With an upward path*chose n, a base case (no disruption )

Scenario 1, was selected with the following rationale. :

1. Thecross -sectiona l area of the whole undergroun d facility was used as the.

cross~sec tional area of the upward flow column. This is the largest areal ex-tent that can carry the wastes from the undergroun d facility.* This is a conser-vative approach *.

F-1

2. Little or no natural upward gradient is indicated by the data from the real site.

Therefore , an upw~rd gradient that could be produced by the thermal buoyancy re-sulting from waste.hea t was used in the analyses.

3. The "shortest" path .to the accessible environme nt was selected. First a loca-tion one mile down gradient in the first aquifer above the undergroun d facility .

was chosen as the "accessibl e environme nt".

Then a "vertical" path, rather than.a "zig-zag11 path, to the upper aquifer was used

{see fi~ures below).

lrnile 1 mile r- 0

'I I

I I

I Vertical Path Zig-Zag Path Each horizonta l segment in the *zig-zag path is* a high conductiv ity zone in an interflow or an interbed layer. It was felt that the vertical segments in this path could be represente d by one vertical segment as in the "vertical path"-

case. Available data on interflow and- interbed zones of the real site suggest that the total travel time of ground water in the horizonta l segments would most probably be longer than that in the 1-mile-dis tance within the aquifer in the "vertical path" case.

Therefore, a "vertical path" to the upper aquifer was chosen for our analyses.

F-2*

Disrupti on Scenario s The disrupti on scenario s we chose involved the intro-

.duction of a high conduct ivity zone between the undergro und facility and the upper aquifer. One scenario (Scenari o 2) involves a high conduct ivity zone of a large areal extent and another scenario (Scenari o 3) a zone of small areal ex-tent. For Scenario 2, the dense basalt layer containi ng the undergro und facility was assumed to be fracture d by either earthqua kes or stresses (mechan ical or thermal) related to the proximi ty of the u~dergro und facility . The same ratio-nales as ( 1), ( 2), and (. 3) in the "no <;iisrupt ion" scenario were appl~ed here. Scenario 3 involves a small area of high conduct ivity. This could be a borehol e, a degraded shaft, or fracture d rock around a borehole or a shaft. We feel that the two scenario s selected represen t events of high or.credi ble probabi lity' and possibly of high conse-quences for the time period of interes t ..

No massive disrupti on scenario , e.g., faulting , was consider ed in our analyses . Due to the time constra int of this work, no detailed analysis of the probabi lity of oc-currence of massive disrupti on could be perform ed. We fee~, however , that the probabi lity of having a massive disrupti on through or near the undergro und facility at.a site with these charact eristics during the time period of interes t, should be v~ry small.

F-3

APPENDIX G GEOCHEMICAL AND HYDRAULIC PARAMETER DATA Table G-1 Ranges of Rd Values *for Basalt Host Rock lSecondary Minerals)

Element Ranges 1 in Table 5 Ranges Fro' Literatur e Am 2.SEl, 2.0E6 1.9~2, 2.SlES

pu 4.SEl, 5.2E3 l.1E2, 2.20E3 u 4 *. .OEO, l.3E3 l.2El, 4~50E2 Np I.SEO, 2.8E4 9.0EO, 4.60E3 Ra, Sn, Pb 1. 7El, 5.8E3 5.0El, 2.00E3 l Ranges expanded to represent .001-:-.999 quantiles 0

2 Values from literature review (see Table G-2),

assumed to represent .5-0.95 quantiles G-1

Table G-2 R Values for Basalt (Secondary ~inerals, 0.05-0.95 quantiles)

Element Value Ref Conunent 1 Am l.9E2 29 normal po 2 , GR-1, interbed/altered 2.51E5 29 basalt, 23-6.0° C, ave. value Pu l.1E2 29 normal po 2 , GR-1, interbed/altered 2.2E3 29 l~w po 2 , GR-1, fracture minerali-zation, ave. value+ s.d.

l.2El 29 normal po 2 , GR-1, interbed/altered 4.SE2 29 normal po 2 , GR-1, fracture miner-alization, Gooc, median value+ s.

d. for several temp., contact times, etc.

Np 9.0EO 29 normal po 2 , GR-1, interbed/altered 4.65E3 30 hydrazine reducing agent, altered basalt, GR-2 Ra, Sn, 5.0El 29 normal po 2 , GR-1, . interbed/al tered Pb 2.0E3 29 normal po_ 2 , GR-1, interbed/ altered 1 Experimental .conditions are described including redox or at-'

rnospheric. conditions, water used (see Ref. 31), type of rock and nature of the value quoted: average or absolute value

+ standard deviation (s.d.).

G-2

Table G-3 Rd Ranges in Basalt Aquifer (nl/g)

Rd Ranges Radionuclide in Table*5 Rd Ranges Ref. Comment of Rationale 1.n Ref.

Am (10-2 - 10 5 ) 300-134,000 32 Aquifer of Salt dome, pH6....:8 8-11 35 Sandstone, pH6 Pu 1,100-33,000 32 II 20-64 34 Sandstone, pH6.8

' u 2.89-10,900 32 Aquifer of salt dome, pH6-8 7.45 - 65.3 33 Alluvium, pH8 Np (10- 2 - 5oJ 27 34 Argillite 44 . 35 Argillite, pH8.2

( 10 500) . 7-500 32 Aquifer of.salt dome, pH6.:.8 109-569 33 Alluvium, pH8.S G-3

Table G-4 Basalt Hydraulic Parameters_

Range of Data Reference Parameter Range in Table 2 in Available Ref.

Conductivity in l.OEO - l.OE4 9.9 36, Table 14 Aquifer (ft/day) 1 - 2E4 37 Porosity in 0.1 - 0.3 0.1 - 0.15 36, Table 13 Aquifer 0.2 37 Conductivity in l.OE-7 - l.OEO 2.BE 0.28 36, Table 11 Host Rock(ft/day)

Porosity in l.lE 2.0E-1 l.OE l.OE-2 37,Table 3 Host Rock l.OE-3 - 36,Table 13 G-4

REFERENCES

1. "Environment al Radiation Protection Standards for Management and Disposal of Spent Nuclear Fuel, High-Level and,Transura nic Radioactive Wastes," 40CFR191, (Working Draft #19), 1981.

2. Campbell, J. E., D. E.* Longsine, and M. Reeves, Sandia National Laboratories , "Risk Methodology for Geologic Disposal of Radioactive Waste: The Distributed Velo-city Method of Solving the Convective-D ispersion Equa-tion," Report SAND80-0717, NUREG/CR-137 6, 1980.

3. Egan, D. J~, Environmenta l Protection Agency, Public Presentation at the Symposium on Uncertaintie s Associ-ated With the Regulation of the Geologic Disposal of High-Level Radioactive Wastes, Gatlingburg, TN, March 9-13*, 1981.

4. Iman, R. L., J. M. Davenport, and D~ Ka Zeigler, San~

dia National*Lab oratories, "Latin-Hyperc ube Sampling:

Program User's Guide," Report SAND79-1473, 1980~

5. Donath, F. A., and R. M. Cranwell, "Probabilist ic Treatment of Faulting," in Geologic Media, Arner ... Geo-physical Union Monograph, 1981.

6. Cranwell, R. M., J.E. Campbell, and others, Sandia National Laboratories , "Risk Methodology for Geologic Disposal.of Radioactive Waste: Final Report," SAND-81-2573, NUREG/CR-245 2, 1982.

7. Pepping, R. E., and G. E. Runkle, Sandia National Laboratories, "Risk Methodology for Geologic Dispo-sal of Radioactive Wastes: Decay Chain Representa-tion for Geologic Transport of Radioactive Wastes,"

Report.SANDB l-0065, NUREG/CR~237 6, 1981.

8. . Fontes, J. C. , I. Neretnieks, and others, IAEA,.

Vienna, "The Application of Isotope Techniques in the Assessment of Potential Sites for the Disposal of High--level Radioactive Wastes," in preparation, 1982. *

9. Muller, A. B., N. c. Finley, and F. Pearson; Jr.,

Sandia National Laboratories ,. "Geochemical Parame-ters Used in the Bedded Salt Reference Repository Risk Assessment Methodology, "*Report SAND81-0557, NUREG/CR-199 6, 1981.

R-1

10. Long,. P. E. *, Rockwel l Hanford Operatio ns, Richland ,

Washing ton, "Charac terizatio n and Recogni tion of Intra Flow Structur es, Grande Ronde Basalt," Report RHO-BWI -LD-10, 19?8.

11. Sato, M., "Geochem ical Environm ents in Terms of Eh and pH," in Econ. Geol., vol. 55, P*. 928-961, 1960.

12. Garrels, R. M., and c. L. Christ, Solution s,* Minerals and Equilib ria, Harper and Row, New York.

13. Stumm, w., and J. J. Morgan, Aquatic Chemist ry, Wiley, New York, 1970.

14~ Smith, M. J., G. J. Anttonen , and other, Rockwel l Hanford Oper~tio ns, Richland ~ Washing ton, "Enginee *red Barrier Developm ent for a Nuclear Waste Reposito ry in

Basalt, " Report RHO-BWI ~ST-7, 1980.

15. Guzowsk i, R. v., F. B. Nimick, and A. B * .Muller, Sandia Nationa l Laborat ories, "Reposi tory Site Definiti on in Basalt: Pasco Basin, Washing top," Report SAND81- 2088,

NUREG/C R-2352, 1982;

16. Harder, H., "Synthe sis of Iron Layer Siiicate Minerals

Under Natural Conditio ns," in Clay and Clay Minerals ,

vol. 26, p. 65-72, 1978.

17.

Erdal, .B. *R., B *. P. Bayhurs t, and others, "Parame ters

_Affecti ng Radionu clide Migratio n in Geologic Media,"

in Scienti fic. Basis* for Nuclear wa*ste Managem ent,. vql.

2, c. J. M. Northrup , Jr., Ed., Plenum, N.Y., p. 609-

_616, 1980.

18. Wolfsbe rg, K., B. P. Bayhurs t, and others, Los Alamos Nationa l Laborato ry,. "Sorptio n-Desor ption.St udies on Tuff, I: Initial Studies with.Sam ples from the J-13 Drill Site,_ Jackass Flats, Nevada," Report LA-7480- MS, 1979.

19. Relyea, J. F., D. Rai, and R. J. Serne, Interac tion of Waste Radionu clides with Geomedia Program Approach and Progres s," in.Scie ntific Basis for.Nuc lear Waste

Managem ent, vol. 1, G. J. McCarth y, Ed., Plenum, N.Y.,

1979. . *

20. Relyea, *J. F*., R~ J. S!;:!rne, and;D. Rai, Battelle Pac-ific Northwe st Laborat ories, Richland , Washing ton, "Methods for Determi ning Radionu clide Retarda tion Factors: Status Report,*" Report.P NL-3349 , 1980.

R-2.

.21. Hoste tler, D. D., R. J. Serne, and A. Brand stette r, Batte lle Pacif ic Northw est Labor atorie s, "Statu s of Sorpti on Inform ation Retrie val System ," Repor t PNL-3 139, 1979.

22. Reardo n, E. J., "Kd's -- Can They be Used* to Des-cribe Rever sible Ion Sorpti on React ions in Contam -

.inan t Migra tion?" in Ground Water , vol. 19,*p .

279-28 6, 1981.

23. Neret nieks, I., Diffus ion in the Rock Matrix : An Impor tant Facto r in Radio nuclid e Retar dation ?, .in Journ . Geoph ysical Resea rch, vol. 85, *BS, p. 4379-4397, 1980.

24. Grisak , G. E., and J. *F. Picken s, An Analy tical Soluti on for Solute TraJ?.s port Throug h Fractu red Media with Matrix . Diffus ion, in Journ . Hydro logy, vol. 52, p. 47-57, 1981.

25. *Tang, D. H., E. o. Fr ind, and E. A. Sudick y, "Con-tamin ant. Trans port .in. Fractu red Porou s Media : .An-:-

alytic al Soluti on for a Single Fract ure," in*wa ter Resou rce Res~a rch, vol. 17, 3, p. 555-56 4, 1981.

2 6 *. Ericks on, K. L. , and D. R. Fortne y, . Sandi a Natio nal Labor atorie s, ":Preli minary Trans port Analy ses for Desig n of the Tuff Radio nuclid e Migra tion.F ield Exper iment ," Repor t SANDS l-1253, 1981.

27. Merki n, J. H., Free Conve ction Bound ary Layer s on Axi-Sy mmetr ic and Two-D imensi onal Bodie s of .Az:bi -.

trary Shape in a Satura ted Porou s Medium , in Int-ernati onal Journ al of Heat and Mass Trans fer, vol.

i 22, P* 1461-1 462, 1979 *.

I

28. King, I. P.*, D. B. McLau ghlin, W. R. Norto n, R. G.

Baca, and R. c. Arnet t, Rockw ell-In ternat ional, "Par-ametr ic and Sensi tivity Analy sis of Waste Isolat ion in a Basal t Medium , 11 Repor t RHO-B WI-C-9 4, 1981.

29. *serne ; .J *. , Pacifi c Northw est Labor atorie s, memor andum to A.* B *. Mulle r (SNLA ), This report

s1.,1mmariz:ed data

. from the follow ing repor ts: PNL-:-281 7, PNL-31 4*6, PNL-

2797 and RHO-BWI quart erly repor ts for 1979 and 1980, May 13, 1981.

30. Deju, R. A., Ed., Rockw ell Hanfo rd Operp tions, ."Basa lt Water Isolat ion Proje ct, Quart erly Repor t, Octob er 1, 1980-D ecemb er 31, 1980," Repor t RHO... ;BWI-8 1-100-I Q, 86 P*., 1981.

R-3

I 1-1

31. Guzow ski, R. v., F. B. Nimick , and A. B. Mulle r, Sandia Natio nal Labor atorie s, "Repo sitory Site Defin ition in Basal t: Pasco Basin, Washi ngton, " Repor t SANDS l-2088, NUREG /CR-23 52, 1982.

32. *Erdal , B. R.,-Lo s Alamos Labor atorie s~ "Labo ratory Stu-dies of Radio nuclid e Distri bution s Betwe en Sel*ec ted Groun dwater s and Geolo gic Media: Annua l Repor t, Octob er l, 1978-S eptem ber 20,. 1979, "*Rep ort LA-80 88-PR, 1979.

33. Erda!, B. R., Los Alamo s Labor atorie s, "Labo ratory Mea-surem ents*o f Radio nuclid e Distri bution Betwe en Selec ted Groun dwater and Geolo gic Media ," Repor t LA-687 7-MS, 1979.

34. Seitz , M. G., P. G. Ricke rt, s. M~ Fried, A. M. Friedm an, *I and M. J. Stein dler, Argonn e Natio nal Labor atory, "Stu- i dies of Nucle ar Waste Migra tion in Geolo gic Media : An- I nual Repor t, Novem ber 1976-- octobe r 1977," Repor t ANL-7 8-8, 1978.

35. Barne y, G. s., and P. D. Ander son, Pacif ic Northw est Lab-orator y; The Kinet ics and Rever sibili ty of Radio nuclid e*

Sorpti on Reacti ons with Rocks: Progre ss Repor t for 1978, in Task 4 Second Contr actor Inform ation Meetin g, vol.

II, R. J. Se~ne , Ed., Repor t PNL-S A-7352 , p. 161-21 8, 1979.

36. Rockw ell Intern ationa l, Rockw ell. Hanfo rd Opera tions, - "Ba-s.alt Waste Isolat ion Proje ct Refere nce Condi tions for Long-T erm Risk*A sse~sm ent _Calc ulatio ns," Inform al Repor t RHO-B WI-LD, -36, Janua ry 1981.

37. Veatc h, M. D., Pacif ic Northw est Labor atory, "Asses sment of Effec tive~e ss of Geolo gic Isolat ion System s," Repor t PNL-2 859, April 1980.

R-4

Volume3*

A Simplified Analysis of a f-lypoth,tical. Repository in a T"'ff Formotlo*n

NUREG/CR-3235 SAND82-1557 WH TECHNICAL ASSISTANCE FOR REGULATORY DEVELOPMENT:

REVIEW AND EVALUATION OF THE EPA STANDARD 40CF R191 FOR DISPOSAL OF HIGH-LEVEL WASTE VOL. 3 A SIMPLll:FIED ANALYSIS OF A HYPOTHETICAL REPOSITORY IN A TUFF FORMATION Malc olm D. Sieg el Marg aret s. Y. Chu Manu scrip t Comp leted : Apri l 1983 Date Publ ished : Apri l 1983 Sand ia Natio nal Labo ra.to ries Albu querq ue, New Mexico 87185 oper ated by Sand ia Corp orati on for the

u. s. Depa rtmen t of Ener gy Prep ared for Divi sion of Wast~ Mana geme nt Offi ce of Nucl ear Mate rial Safe ty and Safe guar ds Wash ingto n, o.c. 2_0555 NRC FIN. No. A-11 65

ABSTRACT Potential radionucl ide releases from a hypotheti cal tuff repository have bee~ calculated and compared to the limits set by the EPA Draft Standard 40CFR191._ The importanc e of *several*

parameter s and model assumption s to the estimated discharge s has been evaluated~ The areas that were examined included the radionucl ide solubiliti es and sorption. the descriptio n of the local hydrogeolo gy and the simulation of containme nt transport

_in the presence of fracture flow and matrix diffusion . The

uncertain ties in geochemic al* and hydrogeol ogical parameter s

were represente d by assigning realistic ranges and probabili ty distributi ons to these variables . The Latin Hypercube sampling technique was used to produce combinatio ns (vectors) of values of the input variables . Ground-wa te*r flow- was described by Darcy's Law and radionucli de travel time was adjusted* using calculated retardatio n factors. Radionucl ide discharge s were calculated using the Distribute d Velocity Method *(DVM). The discharge s were integrated over five successiv e 10.000 year periods. The degree df complianc e of the repository with the

standard in each scenario was.illus trated by the use of Complemen tary Cumulativ e Distributi on Functions (CCDF).

Our calculatio ns suggest the following conclusion s for the hypotheti cal tuf~ repository : (1) sorption of radionucl ides by zeolitized tuff is an effective barrier to the migration of.

actinides even in the absence of solubility constrain ts; (2) violation s of the EPA Draft standard can still occur due to discharge of 99Tc *and 14c. Ret~rdatio n due to matrix dif-fusion. however. may eliminate discharge of these nuclides for realistic ground-wa ter flow rates; (3) in the absence of sorp-tion by thick sequences of zeolitized tuff, dischaige s of u and Np under oxidiz,ing conditions might exceed the EPA standard.

Under reducing condition s. however, the low solubilit ies of these elements may effective ly control radionucl ide release.

iii

TABLE OF CONTENTS Page

1. INTRODUCTION

. 1

2. GEOLOGY AND HYDROLOGY OF THE REPOSITORY SITE 2

2.1 Regi onal geol ogy and hydr olog y

2. 2 L_ocal geol ogy and hydr olog y 2 6

3.. WASTE AND REPOSITORY DESCRIPTION 10 3.1 Wast e 3.2 Subs urfa ce faci lity 10 10

4. SITE GEOCHEMISTRY AND RADIONUCLIDE RETARDAT ION 13 4 .1 Geoc hemi cal envh ;onm ent .

4.2 Sorp tion rati os 13 4.3 Solu bilit y limi ts of radi onuc lide s 13

4. 4 Rad ionu clide retar d.at ion 15 15

5. GROUND-WATER TRANSPORT MODEL 18

6. DESCRIPTION OF SCENARIOS AND CALCULATIONS 20 i.1 Intr6 duct ion 6.2 Scen ario s 1. 3. 4 and lB: Alte rnat e repr esen ta- 20 tion s of reta rdat ion in weld ed tuff laye rs 6.3 Scen ario *5: Effe ct~ of chan ges in. the wate 23 tabl e r

6. 4 s*cen ario

6: Acc essib le envi ronm ent at eigh t tni 34 6.5 Scen ari6 s 2 and 2B: Impo ttanc e of solu bili ty les 42 limi ts to disc harg e 47

7. CONCLUSIONS AND .RECOMMENDATIONS.

53

-App endi x A -- HYDROGEOLOGICAL MODEL OF THE HYPO THETICAL TUFF REPOSITORY SITE AND ITS RELATIONSHIP TO DATA FROM THE NEVADA TEST SITE 55 A.l

Phy sica l prop ertie s of weld ed. tuff A.2 Ver tica l hydr auli c grad ient 55 A.3 Hor izon tal hydr auli c grad ient 56 65 Appe ndix B -- GEOCHEMI_STRY AND RADIONUCLIDE RETARDATION "67 B.l Geoc hemi cal envi ronm ent of the hypo thet ical tuff site B.2 Rad ionu clide solu bili ties 67 B.3 Radi onuc lide sorp tion ratio s 68 71 V

TABLE OF CONTENTS (contin ued)

Append ix C -- Al?PROXI.MATIONS FOR ADAPTING ONE-DIMENSIONAL POROUS MEDIA RADIONUCLIDE TRANSPORT MODELS TO THE ANALYSIS OF TRANSPORT IN JOINTED POROUS 'ROCK 76 REFERENCES 95 vi

LIST OF FIGURES Figure

l. Regional Topography of the Hypothetical Tuff Site 3

2. Regional Cross Section of the Repository Site 4

3. Lo~al Cross Section of the Repository Site 5

4. Scenario 1 25

5. Scenario 3

26

6. Scenario 4 27

7. Scenario lB 28

a. Complementary Cumulative Distribution Functions for Scenarios 1. lB. 3 and 4 29

9. Scenario 5 35

10. Scenario SB 3.6

11.

Complementary cumulative Distribution Functions for Scenarios 1. 5 and SB 38

12. Scenario 6 43

13. Complementary Cumulative Distribution Functions for Scenarios 1 and 6 44

14. Scena~ios 2 and 2B 48 15.. Complementary Cumulative Distribution Functions for Scenarios 1. 2 and 2B 49 A-1 Ranges of, Hydraulic Conductivity Determined by Different Me~hods 58 A-2 Calculation of Thermal Buoyancy Gradient 61 A-3 Far Field Temperature Profile Along the Vertical Centerline for Gross Thermal Loading _/

of *75 kW/Acre 62 vii

LIST OF FIGURES (continued) '

Figure A-4 Temperature Increase Hisiories at 307 and 711 Meters Below the surface of the Earth for Spent Fuel at 100 kW/Acre 64 C-1. Schematic Diagrams of Porous.and Jointed Porous Rock 80

.viii

LIST OF TABLES Tab le

1. Str ati gra ph y of Hy pot het ic~ ! Tu Sit e ff 7

2. Ran ges of Hy dro geo log ic Par am ete rs 8

3. Inv ent ory of Re fer enc e Re pos ito ry 12

4. Ran ges of Rd Va lue s Sam ple d by La tin Hy per cub e 14

5. Ele me nt So lub ilit ies Used in Mix Ca lcu lat ion s ing Ce ll 16

6. De scr ipt ion s of Sce nar ios 22

7. Number of Vio lat ing Ve cto rs. Ma*

Re lea se Rat i.os and Sum of Re lea ximum se Ov er All Ve cto rs for Eac h 10, 000 Ra tio s Yea r Per iod 32

8. Pro per .tie s of Ve cto rs Which Vio Sta nda rd in Sce nar io lB lat e EPA 33

9. Number of Vio lat ing Ve cto rs. Max Re lea se Ra tio s and sum of Re lea imum se ove r Al l Ve cto rs for Eac h 10. 000 Ra tio s Yea r Per iod 37

10. Pro per tie s of Ve cto rs Which EPA Sta nda rd in Sce nar io SB Vio lat e 41 A-1 Pro per tie s of. Fra ctu red Tu ff 57 A-2 Sou rce s of Dat a for Rar iges of Hy Par am ete r Va lue s dro geo log ic 59 A-3 Hy dra uli c Gra die nts As soc iate d Eff ect s I wit h The rma l 63 A-4 Hy dra uli c Gra die nts As soc iate d Eff ect s I I wit h The rma l 63 B-1 An aly ses of Wa ters fro m the Nev ada Te st Sit e 68 B-2 Co nse rva tism of. Lab ora tor y De ter of Rd mi nat ion s*

72 ix

LIST OF TABLES (continued)

Table -Page B-3 Sources of Data for.Ranges of Rd Values for Vitric Tuff 73

.B-4 Sources of Data for Ranges of Rd Values for Zeolitize~ Tuff 74 B-5 Sourc*es of Data for Ranges of Rd Values for Devitrified ruff 75 C-1 Definition .of Terms 77 C-2 Applicati9n of Equivalent Porous Medium Criteria 93 X

ACKNOWLEDGEMENTS Mich ael Read e of C.G. S .* Inc. coll ecte d and synt much of the hydr ogeo logic data from the Neva hesi zed was used in this repo rt. The equi vale nt poro us da Test Site that appr oxim ation used in thes e calc ulat ions medi a K. L. Eric kson . Divi sion 1843 . Sand ia .Natwas iona deri ved by l Labo rato ry.

Appe ndix C was writ ten from info rmat ion and text seve ral arti cles and note s by Dr. Eric kson . Paul cont aine d in Divi sion 9413 , Sand ia Nati onal Labo rator y. prov Dav is.

criti cism s of an earl ier draf t of this *rep ort. ided valu able

xi

1. INTRODUCTION In the nea r fut ure . the EPA is exp ecte d to issu e 40CFR1 dra ft stan dar d for the geo log ic dis pos al of rad ioa ctiv e 91. a was tes. Dur ing a 180 day per iod . gov NRC are exp ecte d to comment on the stan ernm ent age nci es suc h as by the NRC to pro vid e info rma tion and dar d. San dia is fun ded par ing the se com men ts. The obj ect ive ins igh ts use ful in pre -

per form cal cul atio ns sim ilar to tho se of thi s eff ort is to dev elo pin g the dra ft stan dar d. We hav per form ed by EPA in dis cha rge s of rad ion ucl ide s in pla usi e cal cul ate d inte gra ted of med ia hav e bee n pro pos ed as can didble sce nar ios . A nuniber was te rep osi tor ies : bed ded sal t. domedate hos ts for nuc lea r gra nit e. Thi s rep ort doc ume nts ana lys sal t. bas alt *. tuf f and sat ura ted zon e of a vol can ic tuf f formis of a r~p osi tory in the atio n.

The con cep tua l mod el of the rep our cur ren t und erst and ing of theosi tory sit e.i s con sist ent wit h cha tuf f env iron men ts cur ren tly bein g sturac ter isti cs of vol can ic Ene rgy . It mus t be stre sse d tha t we die d by the Dep artm ent of acc ura tely mod el any spe cifi c rea l sithav e not atte mp ted to the ava ilab le dat a are n6t suf fiq ien t e. At the pre sen t tim e unc ert ain ties exi st in the cha rac teri for thi s pur pos e. Lar ge and sor ptio n of rad ion ucl ide s. in the zat ion of the sol ubi liti es reg ion al and loc al hyd rog eolo gy and in des crip tion of the men t of con tam ina nt tran spo rt due to the mat hem atic al tre at-dif fus ion . We fee l. how eve r. tha t in fra ctu re flow and ma trix cal cul ate d rea son abl e upp er lim its of thi s ana lys is. we hav e rad for a gen eric tuf f rep osi tory und er rea ion ucl ide dis cha rge our cal cul atio ns we hav e also atte mp ted list ic con diti ons . In tiv e imp orta nce of the afo rem enti one d to* eva lua te the r&l a-the esti ma ted rad ion ucl ida rele ase . are as of unc erta inty to App end ices A-t hro ugh c des crib e in det mat hem atic al app rox ima tion s tha ail the assu mp tion s and t we use App end ix A we dis cus s the dat a *obt a.in d in our ana lys is. In Mo unta in at the Nev ada Tes t Sit e whi ched from stu die s .of Yucca rea list ic lim its to* hyd rog eol ogi cal par wer e use d in set tin g*

cal cul atio ns. The assu mpt ion s use d to ame ters use d in our gra die nts for the hyp oth etic al rep osi cal cul ate hyd rau lic cus sed . In App end ix B. the geo che mfctor y sit e are als o dis -

Mo unta in is des crib ed. The dat a whi chal env ir-o nme nt a_t Yucca rea list ic val ues of rad ion ucl ide sor ptiower e use d to esti ma te Kd' s) and sol ubi liti es are also dis cus n rat ios (Rd 's or.

cal cul atio ns we hav e use d a reta rda tionsed . In some. of our the eff ect s oi ma trix dif fus ion for 99T fac tor whi ch inc lud es 1*291.

App end ix C con tain s a der iva tion c. and 14c and we* hav e use d to ada pt our one -dim ens of the app ro*x ima tion s por t mod el* to the ana lys is ~f tran spo ion al por ous .me dia tra ns- .

rt in join ted por ous roc k.

2. GEOLOGY AND HYDROLOGY OF THE REPOSITORY SITE 2.1 Regiona l Geology and Hydrolog y A map of the topograp hic ietting. and a regiona l cross-se ction of the reposito ry site. are showri in Figures l

and 2 respecti vely. The r~posito ry (point R) is located in Mouritai n A on the flanks of a large volcanic caldera . The repo~ito ry horizon lies approxim ately 3000 fee*t below the surface within a Tertiary volcanic tuff aguitard (Unit 3) in the saturate d zone. In Mountain A. the water table is 1500 feet below the surface and 1500 feet -abo~e the re~osito zy. The tuff aguitard is composed of layers of moderat ely welded to nonwelde d tuff units and extends several thousand s of feet below the reposito ry horizon.. On a regiona l scale. the tuff aqui tard is underla in bt a Paleozo ic elastic aquitard (Unit 2) and a*

Paleozo ic carbona ta aquifer *(Uni~ 1). The basal no-flow boundary of the regionil ground-w ater system* li~s at the base of the carbona te aquifer.

Above the tuff *quitarc i lies a denseli welded and highly ~rac-tured Tertiary tuff aqui"fer. This uriit reaches a maximum thicknes s of about 1000 feet at Mountai n A. In the washes adjacen t to the mountain . the water table lies* within the tuff aquifer. The _pie*zom etric surface approach es the land surf ace gradual ly along the A~D section in Figures land 2: at point D water flows freely in wells at* the surface .

The lateral boundar ies of the regional grotind-:- water system are approxim ately coincide nt* with the *edg*es of Figure 1. Th_e areas north ot Mesa A and Me~a B. 6omprise the northern ~order of the system. The eastern and s6uthea stern limits of the basin are marked by a seiies of mountain s and ridges. A ~ountain range in the* southwe st marks* another bou_ndary of the system. The

northw est border at the regiona l system is not well defined .

however . t~~ ar~a to the west of Mesa A is* knowri to belong to another hydroge ologic system.

Recharg e to the ground-w ater system through precipi tation occurs only above the SOOO'foot contour marked in Fig~re 1.

Due to the high evapora tion potentia l in this region. onfy about 15 ~ercent of 15 inches of raihfall infiltra tes t6 the water table in areas above this eleva*tio n. The ground.:..water system is* sluggish because of the small amount of recharge *.

The hydraul ic gradien ts are low to moderate cio-4 to 10-3) except .in regions where the rocks in the saturate d zone are relative ly imperme able. The regional ground-w ater flow is south-so utheast through the reposito ry and soutb-so uthwest in the southern portions of Figure 1.

CA .~

,.,_l OE~-

MESA P.

I I

--~r-

-,...? I .. J I

/ "/ /11

/ I / / I

/ I I \

/ FLAT A I \

FLAT B.

IU Q

Q -

0

.:i:

. Q.

~

I CJ I 0

\ Q.

O*

\ ....

\

KEY \

\

- - - LINE AT SECTION

* * * * * .5000 ft CONTOUR

0 2 4 8 8 MILES I I I I REGIONAL TOPOGRAPHY Figure i. Regional Topography of the Hypothetical Tuff Repository Site.

REGIONAL CROSS SECTION NNW.

R B A C* SSE 5000 D 4 -~---~~----------------

. 5 ---~---

i

=

,c.. 0 .3 I -

,c:,. z I 0 2

.:,c. I

-~.

_, -sooo w

1 1:I~ -

_sz_

ENGINEERED FACILITY WATER TABLE 1

-10.000

. 1,11 FAULT NO FLOW BOUNDARY 0 5

SCALE Figure 2. Regional Cross Section of Hypothetical Repository Site.

Unit 1: Paleozoic carbonate aquifer;_Unit 2: Paleozoic elastic aquitard; Unit 3: Tuff aquitard; Unit 4: Tuff aquifer.

LOCAL CROSS SECTION NNW SSE 8000 MOUNTAIN A R

5000 4000

--2...z..

WASH A I

VI t- 3000 K 1* C

...w>w ____ ____ _ .sz. ____H _

2000 1000

, ~

1V D

B A

0 ..__ __.._ __.,ii..,.._

0

__.__ _ _ _ _ _ _ _ _--i._ __.__ _ _ _ _ _,,__, J......L..---l-------.....--'---------'

1 6 7 ..

.. DISTANCE (miles)*

KEY

ENGINEERE'.D *FACILITY .

~2- WATER TABLE

~\, FAULT Figure 3 *. Local Cross Section of Hypoth etical Tuff Reposi tory Site. .

2.2 Local Geology and Hydrology A detailed cross section at the repository is shown in Fig-ure 3. In Table 1. the stratigraphy for the site is described in more detail. An explanatioh of the petrological terms can be found in the section on Geochemistry.

In the vicinity of the volcanic caldera. the tuff layer* are underlain only by granitic batholiths: all pre-existing rocks have been destroyed by volcanic eruptions. The *tuff units thi'n with increasing distance from the volcanic centers as shown in Figure 2.

The engineered facility is located in the middle of Unit A, a densely welded member of the tuff aquitard. This unit is a devitrified tuff. composed primarily of alkali feldspar.

tridymite and cristobalite.

Layer B. directly above the repository horizon. is a nonwelded zeolitized tuff composed primarily of clinoptilolite. The water table lies in layer G which is similar in composition to Layer c. Layers E and I have not undergone devitrification. They have retained their original glassy nature and are designat~d as "vitric" in Table 1.

The geochemical and hydrological characteristics of these layers are determined primarily by the mineralogy and the degree ~f welding of the rocks. The local flow~system and radionuclide retardation will in turn be st'rongly influenced by these characteristics. In Table 2. the ranges and types of distribu*tion for several hydrogeologic parameters are described for the different types of .tuff. Data from pump tests. labor-

~tory ~easurements of matrix porosity of intact cores. and .

calculations based on fracture aperture and density were used to bound reasonable limits-for hydraulic.conductivity and poro-sity. Observations of the orientation of fractures in volcanic tuffs at the Nevada Test site (1.2) suggest that two sets of vertical fractures dominate the joint system. In such systems.

fluid flowing in the horizontal direction will effectively encounter only one set of fractures. Fluid flowing in the vertical direction will ehcounter both sets of fractures. In our calculattons. therefore. we have assumed that values of hydraulic conductivity and effective porosity in the vertical direction are twice the values in the horizontal direction.

The assumptions and methods used to delimit the ranges of hydraulic propert-ies are discussed in more detail in Appendix A. The wid~ ranges of values ~or the~e para~eters cor~espond to the limit*s of values of published data obtained fro.m the different measurement te~hniques described above. It ~ill be I

Ta ble l STRATIGRAPHY OF HYPOTHET ICAL TUFF SIT E DEGREE OF WELDING THICKNESS ROCK TYPES CFT) COMMENT NA ALLUVIUM DENSE 60 -42 5 DEVITRIFIED 14 5 NONWELDED VITRIC DENSE 15 0 DEVITRIFIED 90 0 WATER TABLE AT DISTANCE=& MILES OG NONWELDED Cl::

I':(

ZEOLITIZED 47 5 WATER TABLE.AT E-IF MODERATE DISTANCE=O MILES H

, E DEVITRIFIED 27 0 MODERATE VITRIC

~D NONWELDED 18 0 ZEOLI TI ZED 15 0

~c DENSE, DEVITRIFIED

~B NONWELDED 25 0 ZEOLITIZED 30 0

~A DENSE *OEVITRIFIED 40 0* REPOSITORY HORIZON I

Table 2 RANGES OF HYDROGEOLOGIC PARAMETERS Densely We.lded Moderately Welded

Nonwelded Parameter

Tuff Tuff Tuff.

Hor1zontal hydraul1c 2x10-5_30 3x10-5_5 10-5-2 conduct1v1ty (ft/day) (LU)' (UO ( LN)

Hor1zontal effect1ve 4.4xl0.,.4-0.32 0.03-25 20-48 poros1ty (%) 1 1 ( LN) ( LU) ( N)

Hor1zontal :hydraul1c 1xl o-3_, xl o-1 1xl o-3 __ , xl o-1 1xl o-3_, xl o-1 grad1ent ( LU) ( LU) ( LU)

Vert1cal hydraul1c lx10-2-4x10-2 1x10-2-4xlo-2 1x10-2-4xlo-2 grad1ent (U) (U) (U)

Gra1n dens1ty 2.3 2.2 l. 7 (g/cm3)

Hor1zontal fracture 4.4xl0.-4,-0.32 o.0~0.06 porosity(%)

Total Poros1ty (%) . *,3-10 10-38 20-50 1

Type of d1$tr1but1on 1s 1nd1cated 1n parenthes1s for var1able sampled by Lat1n Hypercube Sample: (LU)-log un1form; (LN)~lognormal; (U)-un1form.

Values of these propert1es 1n the vert1cal d1rect1on are 2x the values 1n the hor1zontal d1rect1on.

-a-

shown in Chapt_er 6 that th1s unc erta inty in be rela ted to the unc erta inty in the resµ lts the inpu t. data can Hyp ercu be ~amp ling tecq niqu e. ( 18) .and the by the Lati n Cum ulat ive Dis trib utio n Fun ctio n (6). com plem enta ry The repo sito ry site is exte nsiv ely bloc k ~au the wat er tabl e lies in the .tuf f aqu itar d lted , con sequ entl y, upl ifte d bloc k) and in the tuff aqu ifer bene near Mou ntai n A (an wash es and flat s (dow n-dr oppe d bloc ks). ath the adja cen t

_The wat er tabl e in the vici nity of the repo in Figu re 3. Near Mou ntain A, the piez ome sito ry is indi cate d with in Uni t H and para llel s the top of thistric surf ace lies hor izon tal hyd raul ic grad ient near the repo laye r-. The rang e 10- l to 10-3 . App roxi mate ly 2 mile s sito ry is with in the repo sito ry, the wate r tabl e ente rs. the tuff from the

aqu GD and the grad ient decr ease s to:a rang e of 10-2 to 10-4Lay ifer Cin er This chan ge in grad ient is dUe to the com bine .

stra tigr aph y, con tras ts in hyd raul ic con duc d effe cts of incr ease d rech arge *. at elev atio ns abov e 5000 tivi ty, and calc ulat ions . how ever .* we have sam pled the feet . In our over a rang e of 10-l to 10-3 for con serv atishori zon tal grad ient m.

The bloc k faul ting can crea te loca l abru ver tica l fau lts whe re rela tive ly perm eablpte chan ges in head at are abu tted aga inst impe rmea ble laye rs. Forwat er-b eari ng zone s.

calc ulat ions , how ever . we have igno red thes the purp ose of.o ur gen eiti es. The wate r lies more than 1000 e loca l hete ro~

face at all poin ts alon g sect ion ARBC. *Loc feet .belo w the sur-wate r tabl e will not sub stan tial ly affe ct al chan ges in the port on the scal e of our mod el; the wat er radi onu clid e tran s-

~ep rese rited by stra igh t-lin es in iigu re 3. tabl e, ther efor e, is In all of the rele ase scen ario s (exc ept scen have assu med that radi onu clid es trav el ver ario s 2 and 2B) we eng inee red fac ility to the wat er.t able undetica lly from the ther mal buoy ancy rela ted to the heat gen eratr the infl uen ce of was te. We have also assu med that the volu meed by the emp lace d wate r flow thro ugh .the repo sito ry is not larg of annu al grou nd-ciab ly pert urb the regi ona l .flow syst em. e *eno ugh to app re-wate r to the repo sito ry will be suff icie nt Sup ply of grou nd repo ~it~ ry at ~11 time s~du ring the 50,0 00 to satu rate the est. This assu mpt ion adds anot he*r elem ent year peri od of inte r-*

our calc ulat ions and will be disc usse d furt of con serv atis m to her in App end ix~-

,-----------------------c---- ---

3. WASTE AND REPOSITORY DESCRIPTION 3.1 Waste The inventory (Table 3) assumed in this work is equal to half the projected accumulation of 10-year-old spent fuel in the United States by the year 2010. This would contain a total of 103.250 BWR and 60.500 PWR assemblies: a total of 46.800 metric

't;ons of heavy metal (MTHM). All radionuclides specified in the Release Limit Table of the EPA Standard.are includ~d in this inventory list.

Based on the inventory and toxicity of each radionuclide the following chains of radionuclides were considered:

(1) 240Pu ~ 236 0 .._..232Th ~ 228Ra (2) 245Cm ~ 241Pu ~241A.m ~ 237N. p ~ 233 0 229T*h

~

(3) 246cm ~ 242Pu ~238 0 ~234 0 ~230Th _..226Ra

, ._ . t

238Pu ~ 210Pb (4) 243Am .-..+: 239Pu ~ 235 0 ~231Pa ~ 227Ac The fis~i-0n and a6tivation product radionuclides 99Tc~

129 1

126sn. 90sr. 14c. 13Scs. and 137cg were also considered in this work.

All canisters containing the wastes are assumed to have a life of 1.000 years after emplacement. At year 1.000. all canisters fail simultaneously and. radionuclide release begins. Radio-nuclide release is assumed to. be determined by a constant rate of breakdown of the waste form. The waste matrix is assumed to dissolve at an annual rate of 10-3 to 10-7 of the original mass. Radionuclides are assumed to be uniformly distributed throughout the matrix so that their release rate is ~irectly proportional to th~ matrix dissoltition rate.

3.2 Subsurf~ce Facility The reference, subsu.rface facility ts cl_ mined facility a.t a.

depth of 3. ooo feet below th'e surface. A description of the facility .is s_ummarized as follows:

Areal dimerisions 2.000 acres (8.7lxl07ft2)

(Reference 3. Table Cl)

Height= 23 ft.

Rep. Volume= B.71x107 ft2 x 23 ft= 2.ox109ft3 Extraction Ratio= 20% (Reference 3. p. 88)

Porosity of Backfill= 20%

P6rosity volume of depository~ a.ox107ft3 Table 3 INVENTORJ OF REFERENCE REPOSITORY (SPENT FUEL FROM 46,800 MTHM)

Radionuclide Half Life Curies Pu2,40 6.76E3 2.1E7 U236 2.39E7 l.OE4 Th232 l.41El0 l.7E-5 Ra228 6.7 4.7E-6 Cm245 8.27E3 B.4E3 Pu241 14.6 3.2E9 Am241 4.33. 7.5E7 Np237 2.14E6 l.SE4 U233 1. 62ES 1.8 Th229

7300-. l.3E-3 Cm246 4710. .. 1. 6E3 Pu242 3.79E5 7.5E4 U238 4.51E9 l.5E4 Pu238 89.

9. 4E7 U234 2.47ES 3.SE3 Th230 8.E4 0.19 Ra226 1600. 3.SE-4 Pb210 21. 3.3E-5 Am243 7650. 6.6ES Pu23*9 2.44E4 l.4E7 U235 7.1~8 7.5E2 Pa231 3.25E4 0.25 Ac227 21.6

5.2E-2 Tc99 2.14ES 6.lES I129 l.6E7 l.SE3 Snl26 l.OE5 2.2E4 Sr90 28.9 2.4E9 Cl4 5730.

3.5E4 Csl35 2.0E6 l.3E4 Csl37 30. 3.5E9

4. SIT E GEOCHEMISTRY AND RADION UCLIDE RETARDATION 4 .1 Ge och em ica l Env iron m*e nt of the Hy pot het ica l Tu ff Sit e The mi gra tio n rat e of rad ion ucl ide in the tuf f rep osi

~i ll dep end on the int era cti on s bet we en the dis sol ved tor y sit e spe cie ~

and the ioc k ma trix and bet wee ri in the liq uid pha se. Imp ort ant the dif fer en t aqu ~ou s spe cie s mu st be cha rac *ter ize d* inc lud e thegeo che mic al par am ete rs wh ich po sit ion , pH, Eh, and tem per atu ma jor and min or ele me nt com -

min era log y of :tu ff lay ers thr oug re of the gro und wa ter and the mi gra te. h wh ich the rad ion ucl ide s The lith olo gy of eac h tuf f un it is des cri bed in Tab le 1. The y in our hyp oth eti cal tuf f sit e vit ric or de vit rif ied . A mtire are cla ssi fie d as zeo liti zed ,

era log y may be fou nd in Ap pen dixdet ail ed dis cus sio n of the mih -

rep osi tor y sit e is ass um ed to* be B. The gro und wa ter in the wa ter sim ila r to tha t des cri bed a sod ium -po tas siu m- bic arb ona te at the Nev ada Tes t Sit e. The Eh by Wi nog rad and Tho rda rso n {4) diz ing and the pH is bet wee n 7.2 is ass um ed to be mi ldl y ox i-po sit ion of wa ter fro m the vi" cin and 8.3 . The che mic al com -

jus tif ica tio n for the abo ve ass umity of _Yucca Mo unt ain and the in Ap pen dix B. The tem per atu re ptio ns are des cri bed in de tai l in the far fie ld of the rep osi torass um ed in the _tr ans por t leg s 40° C. '!'h is ran ge is bas ed on they sit e is bet we en ~o 0 c and Mo unt ain (3) . -ge oth erm al gra die nt at Yuc ca 4.2 So rpt ion Ra tio s The_ sor pti on rat io (Rd.)* is an exp of the amo unt of rad ion ucl ide bou eri me nta lly det erm ine d rat io am oun t of riu clid e in a vol um e of nd to a sol id pha se to the sol id *. iiq uid in con tac t wit h the gra ms rad ion ucl ide s per Rd {m l/g) =. gra ms rad ion ucl ide per mlgrawa m roc k ter Va lue s for range_s of Rd for the at the ref ere nce rep osi tor y sit dif fer en t typ es of tuf f fou nd e

ran ges are bas ed pri ma rily on a are giv en in Tab le 4. The se sor pti on rat io stu die s by sci en rev iew of the res ult s of (5- 10) . tis ts at Los Ala mo s La bor ato rie s

The deg ree of con ser vat ism for Ap pen dix B. Ele me nts for wh the se ran ges is dis cus sed in ich are enc los ed in bra cke ts in Tab no sor pti on dat a. are pub lish ed to Ra val ues of che mic al hom olo le 4. The y hav e bee n ass ign ed abl e (11 ). To our kno wle dge , the gs for wh ich dat a are av ail -

re are no -ac cep tab le dat a ~or r

I:

I.

Table 4 RANGES OF Rd (ml/g) VALUES SAMPLED BY LATIN HYPERCUBE Zeol1t1zed V1tr1c Oev1tr1f1ed *. Tuff w1th Element Tuff Tuff Cl 1nopt1 lo l 1te Sr, [Ra, Pb, Sn] 117-300 50-450 290-213,000 Cs 429-8600 120-2000 615-33,000 Pu 70-450 80-1400 250-2000 Am, [Cm, Pa, Th, Ac] 85-360 190-4600 600-9500 Np 5-7 5-7 4.5-31 u 0-11 .1-14 5-15 I, 14c 0 0 0 Tc 0-2 0.3-1.2 0.2-2 Np sorption on vitric tuff: the sorption ratio range for devi-trified tuff .was assigned to this medium.

4.3

Solubility Limits of Radionuclides The solubility limits that were assigned to each element in this study are listed in Table 5. Based on data available at this time *. the values in the table are approximate upper bounds for the solubilities of these elements in a volcanic tuff environment~ The determination of solubilities of radionuclides in ground water associated with a repository in tuff requires experimental studies and calculations describ-ing the possible interactions between nuclides and ligands over a range of temperatures. water compositions and redox condi-tions. The theoretical calculations are not within the scope of this contract and to our tnowledge have not been carried out.

Few experimental data describing radionuclide solubility in tuff are available at this time. Due to the time con-stratnts of this contract. we have compiled this list of solu-bility values from a limited amount of experimental data and solubilities calculated from a limited review of thermochemical data (12-16). A discussion of the conservatism of these data may be found in Appendix B.

4.4 Radionuclide Retardation The.following expression was used to describe radionuclide retardation in layers of zeolitized tuff in all scenarios.*

(4.1)

Where is the effective porosity of the rock is the grain density of the rock

is the radionuclide sorption ratio (ml/g)

The calculation of retardation in moderately and densely welded tuff layers was different in each scenario. In scenarios 3 and

4. expression 4.1 was used for moderately welded tuff layers.

It was assumed that all radionuclides were unretarded in densely welded layers in scenarios 1,. 3. 4. s. and 6. In scenarios 1. s. and 6 it was assumed that all tadionuclides were unretarded in moderately welded tuff layers also.

Detailed descriptions of the scenarios and rationales f.or these representations ot retardation are found in the next section.

Table 5 ELEMENT SOLUBILITIES USED IN MIXING CELL CALCULATIO~S Solubility Element gig

Reference Pu 2.4x10-4 u 2.4x10-S

Th 15

2.Jx10-7 13 Ra 2.Jx10....:a 16 Cm 2.sx10-ll Am 2.4x10-12

Np 15 2.4x10-8 .15 Pb 2.1x10-6 Pa 2.3x10-2

Ac 13 no limit Tc no limit

I no limit

Sn lx10-3

13 s~ 2x10.._6 13.16 Cs no limit C 3x10-S *

See discussion in Appendix B In scenarios lB. 2, 2B, and SB matrix diffusion for Tc, 14c.

and I was included eiplicitly in .the calculations of radio-nuclide retardation:

R = 1 +

'f',n A ~ 1- ) *

(

p . *( 1-¢ ~n 1 +R* d

In j) (4.2)

Wher.e . 'P,n

,J. == matrix porosity E = fracture porosity*

p* = grain density of rock matrix Rd = radionuclide sorption ratio* (ml/g).

The derivation of ~his expression and constraints on its use are discussed in Appendix c.

i r..

5. GROUNDWATER TRANSPORT MODEL*

In the calculations of radionuclide transport it is assumed that ground~water flow is described by Darcy's Law:

q = Q/A = KI (5.1) where. Q is the volumetric flow ~ate through an area A, normal to the flow direction, I is the hydra~lic gradient, K is the hydraulic conductivity, and q .is the Darcy velocity. When the flow passes through a series of layers with different hydraulic*

properties, an "effective" hydraulic conductivity may,be calcu-lated by

I:i L.

l.

K - _L.

{ 5 *. 2)

I:i K, l.

l.

with Li= thickness of layer i Ki= hydraulic conductivity of layer i The total groun~-water tra~el time is given by L.

Time = 1:* l v.l.

(5.3) i=l where Vi is the interstitial ground-water velocity in layer*i and is equal to q/ </, i, where <Pi* is the effective poros-ity of layer .i. We have assumed that *<Pi and Ki are correlated and r2 = 0.70. The ~eometry of the flow path is described fo~ each scenario in Section 6.

When a radionuclide {RN) is transported by ground water, the*

radionuclide travel time {TRN> is increased by its retarda-tion factor. This is given by.

L.

R. RN

=Li l v.l.

l.

(5.4)

-18"'.'"

wher e R.RN

,1 is the retar datio n facto r of .radi onuc lide RN in layer

1.

The Dist ribu ted Velo city Method (DVM) (17} has been by San,d ia to simu late long chain s of radio nucl ides deve loped by groun d wate r. In this study we calcu lated the avera trans port ed city of *radi onuc lides using Equa tion (5.4) . The DVM ge velo -

then used to calc ulate the disch arge s of radio nucl ides. code was

6. DESCRIPTIONS OF SCENARIOS AND CALCULATIONS

6.1 Intioduction The conce~tual model of our _hypothetical repository site is consistent with our qurrent understanding of the characteris-tics of ~olcanic tuff environments being studied by the Department of Energy. We have not attempted to accurately model any particular real site: at the *present time the avail-.

able data are not sufficient f6r this purpose. Lirge tincer-tainties exist iri the cha*racterization of the solubilities' and so.tption of radionuclide's, in the description of _the reglonal and local hydrogeology and in the mithematical treatment of coritaminant traniport in t~e presence of fracture flow and matrix diffusion. In our calculations, we have attempted to evaluate the relative importance of.these areas of uncertainty to the estimated radionuclide discharge. We have calculated radionuclide release for several scenarios using different com-binations of the following as~umptions:

A. Release rate of radioriuclides from the engineered facility

1. limited by leach rate

2. solubility limited B Representation of retardation of radionuclides in moderately welded units

l. no retardation

2. porous media approximations with zeolit~ Ra's

3. poious media approximations with Ra's for vitric or devitrified tuff

c. Matrix diffusion

1. no credit given for retardation by matrix diffusion-

2. calcuiation of r*tard~tion of 99Tc, 1291, anal4c in welded units D. Distance to accessible environment

1. one mile

2. eight miles E. Flow path

1. vertical path ind gradient controlled by thermal effect

2. horizotital migration only F. Location of water table

1. in zeolitiied tuff

2. in densely welded tuff (300 ft above present day level)

The char~6teristics of each scenario are summarized in Table 6. The release rate of radionucli~es fr~m the engineered f~cility was set equal to the leach rate c10-3 to 10-7 of the original inventory) in all scenarios except*scenario 2B.

The mixing cell option of NWFT/DVM was used in the scenario 2B and.wil l be describe d in more detail in Section 6.5.

The uncerta inties in geochem ical and hydroge ological paramet ers were represen ted by assignin g realisti c ranges. and probabi lity distribu tions to these variable s. The Latin Hypercub e Sampling Techniqu e (18) was used to produce 106 combina tions {vectors )

of values of the input variable s. Integrat ed* radionu clide dis-charges foi five successi ve 10.000 year periods were calculat ed as describe d in Section 5. A release ratio was calculat ed for eadh vector by ~ividing the magnitud e of .the discharg e of each radionu clide by the correspo nding EPA release limit (19. 23) and then summing over all radionu clides.* The results are presente d as probabi lity distribu tions of the release .ratios for each scenario {Comple mentary Cumulat ive Distribu tion Function s) (20). The curv~ indicate s *the ability of the J reposito ry site to limit tbe release of radionu clides and to comply with the Draft EPA Standard . They also illustra te how our ability to assess the complian ce of a reposito ry with the EPA Draft Standard is affected by the uncerta inty in the input*

data.

We have not made quantit ,tive estimate s of the probabi lity of occurren ce of any of the scenario s. We have assumed only that ea~h of the scenario s is an "anticip ated event" (corresp onding to a "reasona bly foreseea bie release" in the EPA Draft Standard (19-)). We feel tha:t the scenario s have a reasonab l_e .probabi l-ity of occurren ce within the 10.000 year regulato ry period.

The water table is at least 1.000 feet below the land surface at all points within the hypothe tical reposito ry site of our analyse s. All of the scenario .s require that a well be drilled at least to the depth of the water table and that the radio-.

nucl ides are withdraw n continuo usly for 10 ._ooo years or *1on-ger. We have based our subjecti ve estima~e of the probabi lity of drilling at the hypothe tical tuff site on estimate s of the water. hydrocar bon and heavy metal ore potentia l of the Nevada Test Site. our estimate of the probabi lity of a pluvial period and subsequ ent rise in the water table at the reposito ry site (scenari o 5) is based on informat ion conc~rn ing past climatic changes at NTS {22).

EPA release ratio~ ~ Q*/EPA*

kl 1 1 ,. where Q 1* is the integrat ed release of radionuc lide i and EPAi is the EPA release limit for radionuc lide i for the 10.000 year interva l.

For "reasona bly foreseea ble releases " the_ EPA release ratio must be less than or equal to unity for complian ce.

Table 6 DESCRIPTIONS OF SCENARIOS VERTICAL. CLIMATIC DISTANCE BETWEEN REPRESENTATION OF RETARDATION IN WELDED UNITS GRADIENT [HANGE CAUSES DEPOSITORY ANO DENSELY ANO MODERATELY WELDED CONTROLLED BY 300 FT RI SE I N POINT OF DISCHARGE MODERATELY WELDED ONLY THERMAL PULSE WI\TER Tl\f3LE FRACTURED POROUS POROUS MATRIX MEDIUM MEDI UM MEO I UM WITH l MILE 8 MILE DIFFUSION WITH NO - WITH DEVITRIFIED TUFF SCENAIUU PUl*IP PUMP MUUEL RETARDATION ZEOL ITES OR VITRlC TUFF YES NO YES NO

1 X X X X

18 X X X X I

I\.)

N #2 X X X X I

28 X X X X

3 X X X X

4 X X X X

5 X X X X

58 X x. X X

6 X X X X leach

Scenarios 2 and 28 differ from each* other in their treatment of the source tenn. Scenario 2 was a limited source term with no solubilit y limits. In scenario 2B we used the mixing cell option of NWFT/DVM which allows iolubilit y limits to constrain the rat~ of radionucl ide release from the re~ositor y.

6.2 Scen arios 1. 3. 4. and lB: Alte rnate repr esen tatio ns of retar datio n in weld ed tuff laye rs Scen ario 1 - The "Base Case" Scen ario l can be cons idere d the base case scen analy ses of the hypo theti cal tuff site (Figu re ario in our 4). The majo r geol ogic al barr iers to radio nucl ide migr ation are the laye rs of zeol itize d tuff above the repo sitor y. The magn vert ical hydr aulic grad ient is deter mine d by a itude of the buoy ancy effe ct of wate r heate d by the repo sitor y as desc ribed in Appe ndix A.

Grou nd wate r and radio nucl ides from the *repo sitor along tbe v~rt ical grad ient to the top of the y will trav el wate r table and then migr ate hori zont ally down the horiz onta l hydr aulic grad ient. The horiz onta l grad ient is calcu lated as the sum the regio nal grad ient plus a comp onent relat ed of to the upwe lling heate d wate r from the repo sitor y (~ee Appe ndix A.3) .

At a dista nce of one mile from the repo sitor y.

a well pump s wate r from this uppe r satur ated unit . The majo r barr ier to horiz onta l trans port of the radio nucl ide is retar zeol itize d laye r G. datio n in the Laye rs of zeol itize d tuff are treat ed as porou s medi a in the fluid trans port and retar datio n calc ula-tions . Laye rs of mode ratel y or dens ely weld ed tuff are as porou s medi a in the trans port calc ulati ons treat ed but it is assum ed that no retar d~tio n o~cti rs in these layer ~. Sinc e no cred it is given to retar datio n in the weld ed unit s. the calc charg e may be an uppe r bound for relea se asso ciate ulate d dis-d with the fluid trans port path desc ribed abov e.

Scen arios 3 and 4 -Poro us media appro xima tions weld ed tuff laye rs for mode ratel y Scen arios *3 and 4 diffe r from s.cen ario 1 only in the treat ment .

of retar datio n in the mode ratel y weld ed tuff laye rs (Figu res 5 and 6). In both scen ~rios th~se laye rs are treat ed as medi a. Mod erate ly weld ed tuffs are char acter ized porou s by phy~ ical and chem ical prop ertie s that are inter ~edi ate betw een dens el~

weld ed devi trifi ed tuffs and nonw elded zeol itize d tuffs . In scen ario 3. Ra valu es of zeol itize d tuff (Tab le 4) are used to calc ulate retar datio n facto rs. These calc ulati prov ide a lowe r bound to disch arge from the site ons may

1. 3, and 4. Ra value s for vitri c tuffs and devifor trifi scen arios ed tuffs are used to calc ulate retar datio n in laye rs E and F resp ectiv ely in scen ario 4. Valu es of all othe r

the same as in corre spon din~ vect ors of scen ario varia bles are 1.

Scenario lB - Matrix diffusion in w~lded tuff layers Scenaci6 iB (Figure 7} differs from scenario 1 onlj by the inclusion rif matrix diffusion in calculations of radionuclide retardation in moderately and densely welded tuf£. layers. The calculation of a retardation factor which includes the effects of matrix diffusion has been described in Equation 4.2 and in Appendix c~. At present, it 6~n only be ~hown that this expres-sion is valid foe radionuclides with Ra= o (K. Erickson, personal communication). Foe scenario lB, therefore, retarda-tion due to matrix diffusion was considered only foe 1291, 99T~ and 14c (see Table 4}.

Results Radionuclide discharge rates foe each vector were calculated.

Discharge ia tes were integca t,ed for 10,000 year periods from o to 50,000 years. The results of the calculations are pr~sented.

as Compleme~tary Cumulative Distribution Functions for each 10;000 year period in Figures-SA-SE. (20) The number of vec-tors that violate the EPA Standard, the maximum violation and the sum of the release ratio over all vectors are presented in Table 7. For these scenarios, all violations of the EPA Stan-dard ace due to discharges of 99Tc and 1 4c. The effect of retardation in the moderately welded units on the integrated discharge can be assessed by comparing the values for scenarios 3 and 4 to corresponding values foe scenario 1. It can be seen

.that discharge is decreased for the first 40,000 y~acs and increased in the petiod from 40.000 to* so.coo ya~rs r~lative to scenario- 1 . . Comparison of the results for scenario lB with those for scenario l shows that although discharge of the cadionuclides is decreased significantly by matrix diffusion.

violations of the EPA release limit still occur.

The charadteristics of the three vectors whose radionuclide discharges violate the EPA Standard ace shown in Table 8. When these values of hydraulic gradient and Darcy velocity are com-pared* to the ranges of hydrogeologic parameters sampled by the LHS for input, it can be seen that the high radionuclide dis-charges ace due primarily to large ground..,.water. fluxes. These annual ground-water discharges rarige from 2 percent to* 7 percent of the present day recharge of the Pahute Mesa ground-water sy~~em at the Nevada Test Site (21. 22}. In Appendix A it is shown that this fraction is unrealistically high for Yucca Mountain. Therefore, _we can conclude that violations of the EPA Standard for a ground-water flow path similar to scenario lB is very unlikely.

SCENARIO 1 1 mile well; moderate= fiactured; thermal buoyancy; no pluvial LEG LAYERS WELDING - RETARDATION LENGTH (ft) 1 A dense - no retardation 200 2 B nonwelded - porous - zeolites 300 3 C dense - no retardation 250 4 D nonwelded - porous - zeolites 150

5 E moderate - no retardation 180 6 F moderate - no retardation 270 7 G nonwelded - porous - zeolites 5280 FLOW PATH WELL TO SURFACE G . NONWELDED F

MODERATE E MODERATE D NON WELDED C DENSE B NON WELDED A DENSE

.LAYER WELDING KEY Ill DEPOSITORY OJ LAYERS WITH NO RETARDATION

[1] LAYERS WITH RETARDATION Figure 4 SCENARIO 3 1 mile well: moderate; porous zeolite: thermal buoyancy:

no*pluvial LEG LAYERS WELDING - RETARDATION LENGTH (ft) 1 A dense - no retardation 200 2 B nonwelded - porous - zeolites 300 3 C dense - no retardation 250 4 D nonwelded - porqus - zeolites 150 5 E moderate - porous - zeolites 180 6 F moderate - porous -. zeolites 270 7 G nonwelded - porous - zeolites 5280 FLOW PATH WELL TO SURFACE G NO NW ELD ED F MODERATE E MODERATE D NONWELDED C DENSE 8 NONWELDED A DENSE LAYER WELDING Figure 5 SCENARIO 4 l mile well; moderate= porous, vitric or devitrified tuff, thermal buoyancy LEG LAYERS WELDING - RETARDATION LENGTH (ft) l A dense - no retardation 200 2 B nonwelded - porous - zeolites 300 3 C dense - no retardation 250 4 D nonwelded - porous - zeolites 150 5 E moderate - porous - vitric 180 6 F moderate - porous - devitrified 270 7 G nonwelded - porous - zeolites 5280 FLOW PATH WELL TO SURFACE G NON\y.ELDED F

MODERATE-DV E MODERATE-VITRIC D. NO NW ELD ED C DENSE B NONWELDED

A DENSE LAYER WELDING Figure 6 SCENARIO lB l mile well; matrix diffusion. thermal buoyancy: no pluvial LEG LAYERS WELDING - RETARDATION LENGTH (ft) l A

dense - matrix diffusion 200 2 B nonw~lded - porous - zeolites 300 3 C dense - matrix diffusion 250 4 D nonwelded - porous - zeo lites 150 5 E moderate - matrix diffusion 180 6 F . moderate - matrix diffusion 270 7 G nonwelded - porous - zeolites 5280 FLOW PATH WELL TO SURFACE G NONWELDED F MODERATE E MODERATE D NONWELDED C DENSE B NONWELDED A. DENSE LAYER WELDING KEY

.DEPOSITORY

[si] LAYERS WITH MATRIX DIFFUSION

[I] LAYERS WITH RETARDATION (POROUS MEDIA)

Figure 7 SCENARIO 1, 3, 4, 1B CCDF-1ST 10000 YEARS. SCENARIO 1, 3, 4, 1B CCDF-2ND 10000 YEARS 100 ______.......,..r"""""""T""~r-r-,"TTM"r--r-r-r-l'"TTTrr-~'T"T"TTTTR

-1 -1 10 10

> 1 0

zw*

, -2 _..1 2 0 10 10 I w N

a: 18 I.O I u.

-3 -3 10 10 18- -4 10

-3 2 1 1 10 10 10 10° 10 10- 2 10- 1 10° 10 1

RELEASE RATIO RELEASE RA TIO Figure 8.a. Figure B.b Figure 8. Complementary Cumulative Distribution Functions for Scenarios 1. lB. 3, and 4:

Alternate R~presentations of Retardation in Welded Tuff Units.

l = base case: lB = base case with matrix diffusion; 3 = zeolites; 4 = vitric or devitrified

SCENARIO 1, :S, 4, 1B CCDF-3RD 10000 YEARS. SCENARIO 1, 3, 4, 1B CCDF-4TH 10000 YEARS 10 0 10-1 10""' 1 0

z I

~ 10-2 1B/ 10-2 *-*-

w 0 0 UJ I 0:

u.

1 10-3 10-3 --

3,4 10-2 10-1 . 100 . 10-2 10"'.'1 1*00 RELEASE RATIO

RELEASE RATIO Figure 8.c Figure 8.d

SCENARIO 1, 3, 4, 18 CCDF-5TH 10000 YEARS 100 0

z..

.~ 10- 2 0

w a:

LL 18 10- 4 ..._...L....i-J....I...I..Uu.i._~-L..JU-L;U..U....__.~..1..L.U..U.L-L-iU...JLL.l..UJ.U 10- 3 RELEASE RATIO Figure B.e Table 7 NUMBER Of VIOLATING VECTORS, MAXIMUM Of RELEASE RATIOS AND SUM -Of RELEAS~ RATIOS*

OVER.ALL VECTORS FOR EACH 10,000 YEAR PERIOD Scenar1o 0-10,000yr 10,000-20,000yr 20,000-30,000yr 30,000-40,000yr 40,000-50,000yr l l* 4. 7 8 4 2.4** 5.9 3. l 2.9 2.0

2. 5*** 12. 1 16.5 17 .0 10.7 3 1 1 1 4 8 1.9 6~2 1.4 3 .1 2.3 2.2 10. 2 4.8 12.0 14.4 4 1 1 1 6 8 1.9 6. l 1.4 1.5 3.4

2. l 10. l 4.6 10.6 15. 6 w lB 1 1 2 1 2 N

1. 7 3.9 2.2 1.5 1.5 1.8 5.7 5.0 3 .1 5.2

number of violating vectors out of 106.vectors analyzed

- maximum release ratio _

- - sum of release ratios for all 106 vectors

Tab.le. 8 PROPERTIES OF VECTORS WHICH VIOLATE EPA STANDARD IN SCENARIO 1B VECTOR '3 24 51 PARAMETER Maximum R* for Tc 10827 7570 14364 Average vertka l 0.32 0 .13 0.41 Darty velocity (ft/yr)

Vertical hydraulic o.. 04 0.03 0.03 gradien t Average hor1zontal 0.17 0.88 0.36 Darcy veloc1ty (ft/yr)

Horizontal hydraulic 0.02 0.08 0.02 gradien t Total ground~water 10197 3781 6069 travel t1me (yr)

Discharge** (ft3/yr) 2.1x107 l. l xlO 7 3.6xl07

. Maximum rel ease 1.2 3.9 1.5 ratio***

R = retardat ion factor

- annual recharge ~f regional ground-water system 1s approxim~tely 5x108 ~t3/yr

- - maximum during 50,000 year period

6.3 Scenarios

Effects of changes in the water table In scenarios. the water table has risen 300 feet during a plu-vial period and is located. in the densely welded tuff of layer H. Radionucl~des migiate from the repo~itory to this layer undet the influ~nce of the vertical hydraulic gradient (Figure 9). The zeolitized tuff of layer G is not a barrier to horizontal radionuclide. migration in this scena.rio. In this calculation we have assu~ed. that no retardation occtirs in layer H . . Ground water and dissolved radionuclides are pumped from the aqui£er from a well located one mile from the tepository.

In all other resp~cts. this sceriario is eqtiivalent to scenario

1. .

Scenario sa (Fig~re 10) differs from scenaiio 5 by the inclu-sion of matrix diffusion in calculations of radionuclide retar-dation in the moderately and densely welded layers A. c.*E, F *

.and H. As in scenario lB. retardation by matrix diffusion was considered only for 129r, 99T~. and 14c.

Results The results of the calculations for scenario 5 are presented in Figures llA~llE and in Table 9. It can be seen that the lack of retardation in the horizontal transport leg.has resulted in discharges that are much larger than those calculated for scenario 1. Violation of the EPA Release limit results from discharges 6f 236u. 233u~ 238u, 234u~ 237Np. 99Tc. arid 14c. In the first 10.000 year period, violations are due pri~

marily to releases of 99Tc and 14c. After 30,000 years, .

releases of other radionuclides comprise the major part of the discharge~ '

Results from scenario SB are summarized in Figures llA-llE and in Table 9. Matrix diffusion decreases the discharges of* 99 Tc and 14c to levels below the EPA* release limit during the first 10,000 years~ After 20,000 years. the release of 236u, 237Np~ 233u, 238u, and 234u may exceed the EPA Standaid.

The properties of the vectors which violate the EPA. Standard* in scenario SB are described in Table 10. The large radionuclide releases associated with vectors 3, 24, and 51 are due to their large ground-water discharge r-tes and short travel times. In vectors 72 a~d 85, .ihe high horizontal Darcy velocity is indicative of the short travel time associated with the horizontal legs (0.03-0.6 yr). Although the retardation factors*

SCENARIO 5 1 mile well; moderate = fractured; thermal buoyancy: pluvial LEG LAYERS WELDING - RETARDATION LENGTH (ft) 1 A dense - no retardation 200 2 B nonwelded - porous - zeolites 300 3 C dense - no retardation 250-4 D nonwelded - porous - zeolites 150 5 E moderate - no-retardation 180 6 F moderate - no retardation 270 7 G nonwelded - porous - zeolites 475 8 H dense - no retardation 5280 FLOW PATH WELL TO SURFACE H DENSE G NONWEL.DED F MODERATE E MODERATE D NONWELDEO C DENSE B NONWELDED A DENSE LAYER WELDING Figure 9 SCENARIO SB 1 mile well; matrix diffusion. thermal buoyancy: pluvial LEG LAYERS WELDING - RETARDATION LENGTH (ft) l A dense - matrix diffusion 200 2 B nonwelded - porous - zeolites 300 3 C dense - matrix diffusion 250 4 D nonwelded - porous - zeolites 150 5 E . mqderate matrix diffusion 180 6 F moderate - matrix diffusion 270 7 G nonwelded - porous - zeolites 475 8 .H dense - matrix diffusion 5280 FLOW PATH WELL TO SURFACE H DENSE G NONWELDED F MODERATE E MODERATE D NONWELDED C DENSE B NONWELDED A DENSE LAYER WELDING Figure 10

-3.6-

Table 9 NUMBER OF VIOLATING VECTORS, MAXIMUM OF RELEASE RATIOS ANO SUM OF RELEASE RATIOS OVER ALL VECTORS FOR EACH 10,000 YEAR PERIOD Scenario 0-10,000yr 10(000-20.000yr 20;000-30,000yr 30,000-40,000yr 40,000-50,000yr

5. 3* 6 . 11 14 16 7.9*U 6.2 20.9 43.7 54.0 13.4*** 29.6 54.2 102. 1 178.8 58 0 1 3 4 4 0.90 2. 1 19.3 42 .1 53.4 1.1 5.9 28.8 75.9 153.0 6 0 1 1 4 3 0 .1 1. 5 1.6 4.4 2.2 w

0. 1 2.5 3.7 12.5 7.6

-.J 2 11 14 19 20 19 207 85 87 57 55 667 392 461 424 434 2B 8 10 16 17 19 22 24 21 20 21 62 114 116 123 130

number of v1olattng vectors out of 106 vectors analyzed

- maximum release ratio

- - sum of release ratios for all 106 vectors

SCENARIO 1, 5, 5B CCDF-1ST 10000 YEARS SCENARIO 1, 6, 6B CCDF-2ND 10000 YEARS 100 ,--_,__.........,___.._..............__,.......-,..,,,.,_,.-..-.-TTTmr-~T"TTTlffl 10- 1 10- 1

. (.}

z I w

, 10-2 L,.J 10-2 CD 0 I w a:

LL

....-1

--s 10- 3 10-3 58--

58--- ---s 1 _.;

10 -4 . 1 - -..............L.UIJ..U.L-.!.-'-'~~--'-.1....1.JLLLLILL-JL.l.-'-l,..&..LJ.U.-.L.-'-J..u..&.W 1o-:-4 l.-"-'--'-l,..&.lU.L-.L.....L..1...LLLJLLL.-.J.-......__..LU.J.1__.L-1--J.__._....___,_...,..........

. 10-3 10-2 10-1 10 0 101 102 10- 3 10~2

10- 1 100 10 1 10 2 RELEASE RATIO RELEASE RATIO

Figure 11.a Figure 11.b Figure 11. Complementary Cumulative Distribution Functions for scenarios l, 5 and 5B:

Effects of Changes in the Water Table on Discharge.

1 = base case; 5 = water table rise: SB= water table rise with matrix diffusion.

SCENARIO 1 0 5 0 SB CCDF-3RD 10000 YEARS SCENARIO 10 5, SB CCDF-4TH 10000 YEARS 10-1 10-1

()

~

w

, 10-2 I 0 10-2 w UJ

\0 a:

I LL.

10-3 1--.

10-3 . 1 ---- 58--

1 o*4 ._........................__._...................LU.-....................u..u..i"--_.__.U...UW.U..-- ..........._ 10-4 .__........__....L..LI.J........_..._...L..Ll..&.JL.U..-~.................___._ WJu.r.llI___..___._~ lllJ 10-3 10-2 100 10-3. 10-2 10-1 100 101 102 RELEASE RATIO RELEASE RATIO Figure 11. c Figure 11.d

SCEN~RIO 1, 5, SB. CCDF;.STH 10000 YEARS 1

.10~

CJ z

w 10-2 0

LU 5,58 a:

LL 1--

10-4 ..._..__._.........i,,1.U.1,..---'-...J...1........._..U.-...__._~........___.___._.,........,""-_,_~LUU 10-3 10-2 10-1 100 101 102 RELEASE RA TIO

Figure 11. e

_)

Table 10 PROPERTIES OF VECTORS WHICH VIOLATE EPA STANDARD IN SCENARIO SB VECTOR 3 24 51 72 85 PARAMETER Maximum R for U 32 27 23 47 35 Maximun R for Np 41 37 39 52 68 Maximum~ for re 10827 20063 26659 13866 14888 Average vertical 0.3 0.16 0.43 0.04 0.07 Darcy velocity (ft/yr)

I A

'j' Vertical gradient 0.04 0.03 0.03 0.03 0.04

. Average horizontal 0.03 0.002 2x10-4 1.5. 169 Darcy velocity (ft/yr)

Horizontal gradient 0.02 0.08 0.02 0.02 0.03 Total ground-water -1024 2585 2203 7877 4939 travel time (yr)

Discharge (ft3/yr) 2.7xlo7 1.4x107 3.8x107 3.Sx106 6.lx107 Maximum release ratios U234 16 26 1.9 0 0 Np237 8. 7 7xio-5 12 0 0

Tc99 0

- 0 0 2.6 3.5

TOTAL 44.4 48.7 53.4 2.6 3.5

for Tc in leg a are high for thes e vec tors resp ecti vely ). the high Darc y velo (507 6 and 2569

city indi cate s that this leg is not a bar rier to mig ratio n of this radi onu clid e.

6.4 Sce nari o 6: Acc essi ble envi ronm ent at eigh t mile s At the hyp othe tica l repo sito ry site . the wate r tabl e pass es from the nonw elde d zeo li ti zed aqui tard ( laye lyin g den sely weld ed aqu ifer (lay er H) at r G) into

the ove r-ima tely two mile s from the dep osit ory. In a dist aric e of appr ox-pos tula ted that a wel l eigh t mile s from the scen ario 6. we have draw s grou nd wat er and radi onu clid es from repo sito ry with -

scen ario diff ers from scen ario l by the add this aqu ifer .

This tran spo rt in the nonw elde d unit and by six itio nal one mile in the den sely weld ed tuff laye r.* No reta rdat mile s of tran spo rt den sely weld ed laye r. ion occu rs in the Res ults The resu lts of the calc ulat ion a~e pres ente and in Tab le 9. It can be seen that the d in Figu res 13A -13E add of trav el thro ugh laye rs G and H~e duce the itio nal seve n mile ~

the firs t 10.0 00 year s to leve ls beld w the disc harg e duri ng Disc harg es of the unre tard ed radi onu clid es EPA rele ase lim it.

vect ors* 12. 76. 77. and 105. how ever . exce 99Tc and 14c in afte r 10.0 00 yea rs. Due to time con stra ints ~d the EPA lim it mat rix diff usio n on dis~ harg e was- not calc . the* effe ct o~

path of scen *ario 6. It was show n prev ious ulat ed for the flow that mat rix diff usio n in 900 feet of weld ly in scen ario . lB disc harg e of .99T c and 14c for the abov e veced tuff decr ease d the EPA Stan dard . it can be assu med . ther efor tors belo w the diff usio n wou ld elim inat e all viol atio ns e. that mat rix for a flow path sim iiar to. scen ario 6.. of the EPA Stan dard SCENARIO &

8 mile well: moderat e= fracture d: thermal buoyancy : no pluvial LEG LAYERS WELDING - RETARDATION .LENGTH (ft) 1 A dense - no retardat ion 200 2 B nonwelde d - porous - zeolites 300 3 C dense - no retardat ion 250 i) -

4 nonwelde d porous - zeolites 150 5 E moderate - no retardat ion 180 6 F moderate - no retardat ion 270 7 G nonwelde d - porous - zeolites 11000 8 H dense - no retardat ion. 31000 FLOW PATH MILES 0 2. 4 6 8

-.--- -----... WELL TO SURFACE G - NONWELDED F - MODERATE E - MODERATE

---- -- ~LAYE R H-DENSE D - NONWELDED C - DENSE B - NONWELDED A - llENSE LA YER-WELDIN G Figure 12 SCENARIO 1, 8 CCDF-1ST 10000 YEARS SCENARIO 1, 8 CCDF-2ND 10000 YEARS 10 0 . 100=-'"T'"""-r-T"',,..,..,rn--,--,-r-rrTTTT"--r""'T""T"T'TTT'IT--r-T"TTTT~

. 1 10-1 II 10- 1

> 6 0

z w

I

,:,. ::, 10- 2 10- 2 I

a UJ a:

........--1 LL.

,...--6 .,........-6 10- 3 10- 3 10- 4 .__._...._.................~.__--...........___._._................__............................... 10- 4 .___._..._,_..........Ll.4-__._._...................__._..._._................._..._.__._.....................

10- 3 10-2 10-1 100 10 1 10-3 10-2 10-1 10° 101 RELEASE RA TIO RELEASE RA TIO Figure 13.a Figure 13.b Figure 13. Complementary Cumulative Distribution Functions for Scenarios 1 and 6:

Accessible environment at eight miles.

1 = base case; 6 = 8 miles

SCENARIO 1, 8 CCDF-3RD 10000 YEARS O SCENARIO 1, 8 CCDF-4TH 10000 YEARS 10 10-1 10- 1 0

l z

~-

U1 .

w 10*2

, 10- 2 I 0 w 1/

a:

u.

10- 3 10- 3 1 o-4 L...-.-'-..L...L.J..U..llL-_.j._._...........u.u_..__..........~~__._....._.&...L.I..U.,

10- 2 10- 1 10° 10*3 10-2 10- 1 100 10 1 RELEASE RATIO RELEASE RATIO Figure 13.c Figure 13.d

Q SCENARIO 1, 8 CCDF-STH 10000 YEARS 10

(.) (

z

~. 10- 2 0

w cc u.

10-4 '---'-J......L.L.1,;W..........L...J...J....&..Uu.L.---1-L.J....&-L.L,Ll,l~..U....i......JU-IJJ.I 10- 3 10- 2 10- 1 10° RELEASE RA TIO Figure 13.e 6.5 Scenarios 2 and 2B: Importance of solubility limits to discharge We consider scenario **2 (Figure 14) our. "worst case 11 scenario.

The source term is entirely leach-limited ; the solubility

. limits* of radionuclid~ s are not specified. Ground water migrates laterally from the depository. Due to the block faulting and dip of the tuff units in*the ,repository site, the lateral fluid flow path cuts across several stratigraphi c layers~ At a distance of one mile from the repository, water and radionuclides are pumped by a well that.extends to a depth I

of 3,000 feet. Technetium, 1291 and 14c ate retarded by m~trix diffusiQn in the densely welded layers A *nd c. Layer B is tiighly sorbent zeolitic tuff which retards the move-ent of the other isotopes_. This scenario has a shorter path length and thinner sequence of zedlitized tuff than the .other sce-narios.

Scenario 2B differs from scenario 2 only in th-* calculation of the source term. We have used the mixing-cell option of NWFT/DVM for*this scenario (17,23)~ For each time step, the mass of a-radionuclid e that is assumed leached from the waste form is compared to the maximum amount th~t is consistent with a user-specifie d solubility limit; The solubility limits are listed in Tabl~ 5 and are discussed in detail in section 4.3 and in Appendix B. The sm~ller of these two amounts of radio-nuclide is transported in that time step.

Results Results of calculations for scenarios 2 and .2B are summarized in Figures 15A-15E and in Table 9. Discharges in scenario 2 are the highest calculated in this study and lead to large.vie-.

lations of the EPA Standard. During the first.10,000 years, releases of 234u, 237Np, 238u and 236u account for 94 percent of the sum of.the EPA release ratios. During the fifth

10,000 year interval they continu~ to dominate discharge and account for 85 percent of the vi6lation of the EPA Standard.

The importance of solubility limits ih controlling discharge in scenario 2B can be seen in the.figures and table. The ~um of the release ratios for all uranium species is reduced by an order of magnitude and Np dischatge is decreased by a.factor of 30 for.the first 10,000 year int~rval. Discharges of these radionuclide s, however, still are in excess of the EPA stan7 dard. The solubiiities that were assumed for uranium and neptunium were based oh experimental studies under oxic condi-tions. They are upper bounds for the solubilities : under reducing conditions the solubilities of U and Np are several orders of magnitude lower. We feel that the transport of SCENARIOS 2 and 2B 1 mile borehole; matrix diffusion:

no thermal buoyancy or pluvial LEG LAYERS . WELDING - RETARDATION LENGTH (ft) 1 A dense - matrix diffusion 2600 2 B nonwelded - zeolitized 300 3 C dense - matrix diffusion 2600 FLOW PATH C

B WELL TO SURFACE A

DENSE NON WELDED DENSE LAYER WELDING Figure 14

_49.:..

SCENARIO 1, 2, 2B CCDF-1S.T 10000 YEARS

. SCENARIO 1, 2, 28 CCDF-2ND 10000 YEARS 100...-T""T"1"1"TTT..-,...,....,,......,..,-r-,-,rTTn..-.,-T",..........-...,...,......,.,,_.......,~

100c-,r-r,-TITTTr-..,,..TTTm-r-rn~-r.-n-nnr--,-T"T"MTmr""-r-r-PT,m 10- 1 10- 1 0

z UJ

=> 10- 2 0

w 10-2 a:

I LL

.i:,.

I.O I

1 ' 28 2 1.0-3 10- 3 1 28 2

\ \ \ I 10-4 10-4 .__...................._._._._~..._.,_~u.wJ.--L..LU...UU..-Ull..U.J:,uAL--L....U.U~

L--l'-I...L.I.I.JJJ.Jl--l,,....U...LLW1.......L~WW.---..LU.JJ.W.__._.u..L.wu.;.-L.LUJlUJ 10-3

10-2 10- 1 100 101 10-3 10- 2 10-1 10*0 101 RELEASE RATIO .

RELEASE RATIO Figure 15.a Figure 15.b Figure 15. Cumulative Complementary Distribution Functions for Scenarios 1, 2 and 2B:

Importance. of Solubility Limits to Discharge.

1 = base case; 2 = leach-limited; 2B = solubility-limited

SCENARIO 1, 2, 28 CCDF*4TH 10000 YEARS SCENARIO 1, 2, 28 CCDF-3RD 10000 YEARS 10 0 ~-rTTTTffl""-r-T""TTTTrTr-T""T"TTTTTIT--r-..-.r-n......---.-,.-rTn,-~-

10-1 10- 1 u

z w

I ::> 10- 2 10- 2 U1 0 .

0 I

w a:

LL 10-3 28 2 10-3 1 28 .2

\ / \ \ I 10-4 ....................u.&.W._._..................................u...LJWL-....L..11J.ULW-..L.1,.JUllJ.L-...JLI.i.WW 10- 4 .__..........UJJJJ~...L.L..UJJJJ---L..1.J.JWJ.11-.L....LLL.ilW..........JL.U..UIWJL--l-.u.J.J.wJ 10-3 10- 1 100 101 10- 3 10-1 10° 101 RELEASE RATIO RELEASE RA TIO Figure 15.c Figure 15.d

SCENARIO 1, 2, 2B CCDF-5TH 10000 YEARS 100 ~~TTmT---r"'T"T"1Tffl'l"--r-T"TT'lrTn,-~,..,.....,.n,r--....,........_.......-..,......._ _ _

10- 1 0

zw

, 10- 2 0

w a:

u.

1-- 28 ~2 10-3 10-4"-J-..LL.LW.I_.._..J....LJW.LIL-L.~W"-_._U..U..LW-...L.I-UI.JWL.....J...L.UW.U 10-3 10- 2 10- 1 10° 101 10 2 10 3 RELEASE RA TIO

. Figure 15. e radion uclides along the flow path describ ed in scenar ios 2 and 2B is less likely than transp ort as ~ascrib ed in the other scenar ios. The calcula ted violati ons of the EPA Standa rd,

therefo re, should not be interpr eted a~ an indica tion that release s from a reposi tory in tuff are likely .

7 .. _CONCLUSIONS AND RECOMMENDATIONS Esti mate s of pote ntia l radi onuc lide rele ases from faci litie s in geol ogic form ation s are an inte gral HLW stor age tech ntca l basi s.fo r the regu latio n of nucl ear part of the At pres ent. the avai labl e data is insu ffic ient wast e disp osal .

mode l any real repo ~ito ry siie s. Larg e unc erta to accu rate ly

the char acte riza tion of the solu bili ties and sorp intie s exis t in nucl ides . in the desc ripti on of th~ regi tion of radi o-geol ogy and in the math ema tical treat menonal and loca l hydr ?-

port in the pres ence of frac ture flow andt matr of cont amin ant tran s-feel , howe ver, that it is poss ible to plac e real ix ijiff usio n. We li~i ts on radi onuc lide disc harg e for a gene ric isti c uppe r tuff iepo sito ry. We have also .atte mpt ed to assehypo thet ical ance of the vari atio n of seve ral vari able s and ss the impo rt-tion s to the calc ulat ions of radi onuc lide rele mod~ l assum p-itor y in ~he satu rat~ d zone of a .~olc anic tuff ase from a repo s-site .

Our calc ulat ions sugg est the follo wing conc luiio hypo theti cal_ tuff repo sito ry desc ribe d in this ns for the pape r:

1) Sorp tion of radi onuc lide s by seve ral thou sand zeol itize d tuff may limi t the rele ase of acti nidefeet of the EPA rele ase limi ts even in the abse nce of s belo w solu bili ty I con stra ints .

2) All viol atio ns of the EPA Draf t Stan dard in the case 11 are due to disc harg es of 99Tc and 1 4 c.

11 base Reta tion due to ~atr ix diff usio n, howe ver, coul d elim rda:-

disc harg e of thes e nucl ides unde r real istic .grou inat e flow rate s. nd-w ater

3) If the iadi onuc lide s do not flow thro ugh thic k of zeol itize d tuff , disc harg es of u and Np.u sequ ence s nder cond ition s may be mu~h larg er than the EPA limi oxid izin g redu cing cond ition s, howe ver, the. low solu bili ts. Unde r thes e elem ents may redu ce thei r disc harg es to ties of .

the EPA limi t. leve ls belo w

4) The radi onuc lide rele ase limi ts set by Dra ft 19 Stin dard are p~ob ably achi eva~ le for a repo sito of th~ EPA sim ilar to the hypo thet ical site desc ribe d in ry site repo rt. The majo rity of the vect ors exam ined this I,. scen ario s prod uced radi onuc lide rele ases belo w in all set by the draf t stan dard . In gene ral, viol atiothe limi ts stan dard occu rred only when the most cons erva tive ns of the assu mpti ons were used or when com bina tions of prod uced grou nd-w ater flow rate s that were unre inpu t data high . alis tica lly We feel that the following topics merit further investigation by the NRC:

1) Detailed calculations of limiting solubilities of uranium.

neptunium and radium under geochemical conditions expected at the tuff site. *

2) Calculations of the potential retardation of actinides due to matrix diffusion in welded tuff.

3) .Calculations of the sensitivity of radionuclide discharges to assumptions about radionuclid& speciation.

4) A study of the frequency of oil and water drilling and mineral exploration in areas like Yucca Mountain. All of the scenarios examined in this ihvolve human intrusion. A study of the probability of such activities in areas like Yucca Mountain would yield valuable insights about the safety of such a repository site.

APPENDIX A HYDROGEOLOGICAL MODEL OF THE.HYPOTHET'ICAL TUFF REPOSITORY SITE AND ITS RELATIONSHIP TO DATA FROM THE NEVADA TEST SITE A *ajor objec tive in the progra m of simpl ified repos itory analys es perfor med ~t Sandia is the d~fin ition of a hypoth e-tical site which exhib its hydro geolog ical chara cteris tics which might be found at real poten tial repos itory sites. We have.

define d our iefere nce tuff site to be consi stent with availa ble hydro geolog ic data from the Nevada Test Site.

Where certai n data are not availa ble from the real site. we have postu lated pr~pe rties that are physi cally reason able for the refere nce site. We have not attemp ted to accur ately repres ent the Nevad a Test Site in our analys es; instea d we have mo~ele d a hypoth e-tical site which is intern ally s~lf-c onsis tent.

A.l Physi cal prope rties of welded tuff The tuff units at the refere nce tu~f repos itory are descri bed as dense ly welded . moder ately welded or nonwe lded. Dense ly welded tuff units are highly fractu red; the block s betwee n fractu res have low inter stitia l matrix poros ity. Nonwe lded tuff units have few fractu res but have a high matrix poros ity.

This dual poros ity of the rock must be consid ered when model -

ling fluid flow . . We have used data from the UE25a -l drill core log to obtain reason able values of fractu re densi ty. apertu re width and orien tation in the tuff units (1,2). The maximum.

minimum and median of. the range of values

of these param eters for differ ent tuff ~ithol ogies are shown in Table A-1.

We have repres ented the fractu re system as two sets of perpen -

dicula r vertic al fractu res. Value s of horizo ntal fractu re poros ity {Eh) are calcu lated by where Na is the obser~ ed fractu re densit y in the core, e is an estim ate of the averag e inclin ation of the fractu res from the horizo ntal plane, arid His the fractu re apertu re width observ ed under a petrog raphic micros cope. Horiz ontal hydra ulic condu ctivit y for a ~aral lel array of plana r fractu res is given (24) by:

(P: ).* (-'1_2 :"""'a"-~-:-o---e-> )

_s_1_*

where:

p = density of* Water= 1.0 gm/cm3 g = 9.8lx10 2 cm/sec2

µ = viscos ity of water= 1.0 centip oise In the assume d joint system . fluid flowing in the horizo ntal directi on will effecti vely encoun ter only one set of fractu res. Fluid flowing in the vertica l directi on will encoun ter both sets of fractur es. For this reason . values of h~drau lic conduc tivity and fractur e porosi ty in the veitic al directi on are twice the horizo ntal values .

The hydrau lic conduc tivity is very sensiti ve to change s in fractu re apertur e~ In welded zones. the majori ty of fractur e~

are 5-20 micron s wide; the maximum observe d width was 150 micron s (1. 2). Fractu res in nonweld ed *zones were genera lly filled with secdnd ary minera ls. For these units. apertu re widths of 0-5 micron s are probab ly realis tic and were used to estim~ te the hydrau lic proper ties in Table A-1 . . Result s of .

calcul ations using a 150-mi cton apertu re width a.r:e also shown in the table. Ranges of values presen ted for total porosi ty are taken from data in referen ces 4 and 25.

In Figure A-1. tI:ie ranges of values of matrix hydrau lic conduc -

tivity of unfrac tured cores of tuff measur~ d .in the labora tory are compar ed to the values calcula ted from fractu re proper -

ties. The values are based on data compile d in referen ces 4.

22. and 25. Values of the bulk hydrau lic conduc tivity. as measur ed by actual pump tests at the Nevada Test Site. are also shown. Data obtaine d in these tests reflec t contrib utions from fluid flow in both the fractur es and the rock matrix between joints. It can be seen that flow in fractur es may domina te.the bulk hydrau lic conduc tivity of densely welded tuffs. wherea s fluid flow in the por~us rock matrix domina tes the proper ties of nonwel ded units. Both fractur e flow and porous flow are import ant for modera tely welded tuffs. The insigh ts gained from Figure A-1 were used to estima te reason able ranges for effecti ve porosi ty and hydrau lid conduc tivity for the Latin Hyper~ ube Sample Program (18). The data ranges and the shape of their distrib utions are tabulat e~ in Table 2 of the main text. Refere nces for simila r values in the literat uie are describ ed in Table A-2. ~he shapes of the frequen cy distrib utions were estima ted by compar ing the median values to the upper and l.ower 1 imi ts of the data ranges of the differe nt types of hydrau lic conduc tivity and poro~i ty.

A.2 Vertic al Hydrau lic Gradie nt There are insuff icient data in the open literat ure. at presen t to estima te vertic al hydrau lic gradie nts at the Nevada Test Table A-1 PROPERTIES OF FRACTURED TUFF Densely Welded Moderately Nonwelded Tuff Welded Tuff - Tuff

Fracture Aperture H (microns) min 5 5 0 median 12 12 5 max - 150 150 5 (150)+

Apparent Fracture Density -Na (ft-1) min 0.2 () 0 median 1.2 0.4 0.1 max 4.8 0.8 0.3

Inclination of Fractures from Horizontal - () 42° 00°_

Horizontal Fracture Porosity-'- h(%)

min 4.4xio-4 0 0 medi_an 6.4xio-3 2.2x10-3 9.sxio-4 max 0.32 0.06 2.ax10- 3 (0.09)+

Horizontal Fracture Hydraulic conductivity (KH) - (ft/day) _

min 2. 6x10-5 . 0 0 median 2.1x10- 3 7 ~ 5xlo-'-4 - 5. 5x10-S max _ 16. 7 2.9 l.7xio- 4 (4.5)+

Total Po~osity (%) 3-10 10-38 20-50

References (1. 2)

+Values corresponding to aperture width of 150 microns.

a, 10-2

10- 3

iii::

t{;{\i 10- 1 --------- -.&...... .,,.........._ _ _ _ ___.__...__ _ _ ___.

DE~SELY MODERATELY ZEOLITIZED WELDED WELDED NONWELDED TUFF TUFF TUFF RANGES OF VALLI.ES OF HYDRAULIC CONDUCTI VITY DETERMINED BY DIFFERENT METHODS

~

MAX VALUES USED IN

~

EGJ]* MEDIAN CALCULATI ONS FRACTURES MATRIX BULK .~ MIN AND LHS

Figure A-1 Table A-2 SOURCES OF DATA FOR RANGES* OF HYDROGEOLOGIC PARAMETER VALUES

Simi lar Value Param eter Value From Liter ature Refer ence Comment Hydr aulic cond uctiv ity 2 5 X 10~

of dense ly welde d tuff Calcu lated from data in (ft/d ay) Table A-1 in this repo rt.

30 19 22 Table 3 (Tiva Canyon)

Hydr aulic cond uctiv ity 3 X 10- 5 of mode rately welde d 22 Table 3 (Topopah Sprin gs) tuff (ft/d ay) 4.4 X 10- 5 10 pp. 38 - 39 5 2.9 Calc ulate d from data in Table A-1 round ed up to I

u, value of 5 I.O I 2.1 22 Table 3 (Topopah Sprin gs)

Hydr aulic cond uctiv ity 10 - 5 1.] X 10 - 5 of nonw elded tuff 10 pp. 38 - 39 (ft/d ay) 2 2.3 .25 Table A-1 Effec tive poro sity of dense ly welde d tuff 4.4 X 10- 4

(") Calc ulate d from data in Table A-1 in this repo rt.

0.32 Calc ulate d from data in Table A~l in this repo rt.

Effec tive poro sity of 0.03 mode rately welde d tuff Maximum fract ure poro sity

(%) calcu lated from data in Table A-1 in this' repo rt for mode rately welde d tuff 25 25 22 Table 3 (Tiva Canyon)

r------------------------,------------------------- - - -

Table A-2 (Continued)

Effective porosity of 20 - 19.8 4 Table 5, p. C45, minimum nonwelded tuff ('I,) for zeolitized tuff 48 48.3 4 Table 5, p. C45, maximum for zeolitized tuff Total porosity of 3 :5 4 p. C32 densely weided tuff (T.) 10 10 4 p. C32 I

CTI' 0

I Total porosity of 10 10 .4 p. C32 moderately welded tuff ('I,) 38 35 4 p. C32 Total porosity of 20 35- 4 p. C32 nonwe_lded tuff

('f.) 50 50 4 p. C32

Ranges for Table 2. Values tabulated here are for hydraulic properties in the horizontal direction.

Site with an acceptab le degree of certaint y. In our referenc e site. we have assumed that the vertical gradien t in the vicin-ity of the reposito ry will be dominate d by a thermal bouyancy gradien t related to the heat generate d by the decay of the radioac tive waste. The calculat ion of the thermal bouyancy gradien t is describe d below.

\

Conside r a cylindri c~! volume of fluid with length Land average temp~ra ture T immersed in a medium of average tempera-ture T 0 (T>T 0 ). (Figure A-2). The differen ce in tempera-ture produces an upward force on the volume of fluid. The velocity of the fluid in the cylindri cal volume can be describe d (26) by:

v - a L\TK (A-1) with v = Darcy velocity of fluid a = average coeffici ent of thermal expansio n of fluid L\T = .T - T 0 K = hydrauli c conduct ivity of medium I

L T Figure (A-2)

Since Darcy velocity is egual to the product of hydrauli c gra-dient (I) and conduct ivity. the upward gradien t is given by I = a.L\T (A-2)

-,.61-

The temperature field a.rou'nd a .repository in tuff fo.r spent fuel at 75 kW/Ac.re thermal loading has been calculated

( 3)

0 200 400 600 yr Repos1t*ory

--'5

800 E

. Depth 1000 C.

(11

. c:i 1200 Temperature 1400 1600 1800 2000~~~-----o.~~..._~..J,__._~~~._~--'

0 20 40 60 80 100 120 140 Temperature (° C)

Figure (A-3) Far~Field Temperature Profile Along the Vertical Centerline for Gross Thermal Loading of 75 .kW/Acre Figu~e A-3 shows the temperature profile along the vertical centerline of the repository as a function of depth and time after closure. Th~ *"disturbed zone" is assumed to e~tend from the repository to 470 mete.rs.below sutface where the water table lies. The average temperature of this disturbed zone is calculated by:

wher e L ii the dista nce from the repo sitor y to and is equa l io 330 mete rs. T is the ijVer age the wate r.tab le backg round temp eratu re of the same zone as0 calcu lated from the natu ral geoth erma l field . The ambi ent temp eratu re at the horiz on is 50°C . Unde r these assum ption s, the repo sitor y grad ients calcu lated are show n in Tabl e A-3: hydr aulic Table A-3 Time Afte r Clos ure (yr} T (°Cl T0 (OC) a ( l/°C) .* Grad ient 500 73 50 6.0lx l0 ... 4 l.4xi o-2 5,000 85 so 6.6ax 10-4 2.3x1 0-2 50,00 0 65.4 50 5.54x 10-4 0.sx1 0-3

. More rece nt field work indic ates that the ambi peia tuie at the repo sitor y horiz on will be 35°Cent rock tem-(27). This temp eratu re corre ~pon ds to an avera ge ambi ent temp 30°C . Tabl e A-4 show s the calcu lated upwa rd grad eratu re of temp eratu re is assum ed. ient when this Tabl e A-4 Time (yr) T (OC) To (°Cl a ( 1/oC l Grad ient 500 73 30 6.01x 10-4 2.6x1 0- 2 s.ooo 85 30 6.68x 10-4 3.7x io-2 50,00 0 65.4 30 5.54x 10-4 l. 9x10 - 2

Therm al histo ries at*30 7 and 711 mete rs below the repo sitor y wit~ a 100 kW/A cre therm al load ing have surfa ce for a lated and are prese nted in Figu re A-4 (27). From been calcu -

these curv es.

it is appa rent that the peak temp eratu re occu rs befo re 10.00 0

ye~r s afte r cl~su re of the faci lity. The hydi aulic grad ient at 500 year s ior an avera ge ambi ent temp eratu re of 50°C was selec -

ted as a lowe r bound for our calc ulati ons. The gzad ient at 5,000 year s with the avera ge ambi ent temp eratu re used as the uppe r boun a**for the vert ical hydr aulic of 30°C was rang e of vert ical hydr aulic grad ients of 1x10 -2 grad i*nt. A was samp led by the Latin Hype rcube Samp le techn to 4x10 -2 ique for the trans port calc ulati ons.

60 50 0

0

~

40 w

(/)

<(

w I 0:

0

°'I

,i:,. z 30 w

0:

J 0:

w 20

~

E w

t-10 0.1-~1-~--.1-.LJ..JU..::~-L--L....L...Jw...J..LI.JL-----l~L--11-=:;IU-L'-'-~..L-_._...........................~_.____.._._...._............,..

1 10 YEARS AFTER EMPLACEMENT Figure A-4. Temperature lncrease Histories at 307 and 711 Meters Below the Surface of the Earth for SF at 100 kW/acre.

The volume of annual recharge at the reposito ry site places a

. constra int on the maximum flow thr*ough the reposito ry under the influenc e of this thermal gradien t. The maximum vertica l dis-charge calculat ed from the vectors sampled by the LHS techniqu e was 3. 6x107 ft3/yr (vector #:51). This is .approxi mately 7 .

percent of the volume of ground water moving through the Pahute Mesa gro~rid-w ater system of the Nevada Test Site. The.

area of the reposito ry comprise s less than 0.1 percent of the area of this flow.sys tem. Although all of the recharge in this

-ystem is limited to areas above 5000-ft elevatio n. this volume of ground-w ater flow through the reposito ry is probably unreali stically high. As discusse d in Section 6 (Table 7).

nearlY all of the vectors whose radionu clide releases violated the EPA Standard in scenario s 1. 3. 4 *. s. 6. lB. and SB were characte rized by similarl y unreali stic flows.

Most of the other vectors consider ed in these calculat ions* had ground-w ater discharg es at least an order of magnitud e smaller than vector

51.

A.3 Horizon tal Hydraul ic Gradien t We have consider ed two contribu tions to the horizon tal hydraul ic gradien t in our calculat ions. One compone nt is the regiona l gradien t of the undistur bed site. Static water levels from four wells near Yucca Mountain were used to estimaie

.ranges -of the regional horizon tal gradien t. Three of the wells have similar static .water levels ( - 2400 ft) while the fourth and only well which is actually on Yucca Mountain has an ano-malously high head ( - 3400 ft) ( 22). The range of regiona 1 hydraul ic gradien ts was set to spa~ the highest and !~west values/ that could be calculat ed from these data. The LHS-rou -

tine. thsrefor e. sampled a range of 10-l to 10-3.

The second compone nt to the horizon tal gradien t is a local gradien t related to the local rise in the water table above the reposito ry due to the thermal bouyancy effect describe d pre~

viously. We can place an upper bound on this rise in water table (D.Z) by assuming that the heated water in the cylinder -

describe d in Figure A-2 is constrai ried to expand only in the upward (Z) directio n. By applying Archime des* Princip le. we can show that the height of the heated cylinder cari ~e related to the height of a cylinder of water of equal weight at the backgrou nd teinpera ture T . Since the height of the cylinde r of*

water at tempera ture T iquals the distance from the reposito ry to the water table we 8an

~ . . calculat

. e '1Z as follows:

w = 7Tr2gp(L+ AZ) - rrr2gpL (Archime des* Piincipl e) (A-3)

AZ = L ( Pl P - 1) (A-4) where P,P = average density of water at T0 and .T. respectively L = height of cylinder of water at temperature T0 .

r az == rise of water table radius of cylinder of water w = weight of water in both cylinders If V equals the volume of the cyiinder of water at temperature T

then 0 w = PV = p (V + a V) *(A-5) dV = aV.6.T (A-6) p = w/V(l + a .6.T) = P/(1 + a !.lT) (A-7) where aT and AV refer to differences in temperature and volume between the two cylinders and a is the average coefficient of thermal expansion of the fluid. Substituting (A-7 into A-4) we . '

obtain: I

.1Z = La tlT (A-8)

We have shown that a 4T is equal to Iv. the vertical hydraul1c gradient (equation A-2) . . we ~an therefore calculate~Z for each inptit vector in our calculations by rising the value of iv sampled by the LHS technique. The horizontal hydraulic gradient (IH) used in our transport calculations is set equal to the sum of the regional gradient and the local gradient: *

(A-9) where:

IRS = valtie of regional horizont~l hydraulic gradient sampled by the L~S Iv = value of vertical gradient sampled by LHs*

L = sum of vertical leg lengths in transport path X = sum of horizontal leg lehgths in transport path APPENDIX B.

GEOCHEMISTRY AND RADIONUCLIDE RETARDATION B.l - Geoch emical Enviro nment of the Hypot hetica l Tuff Site The miner alogy of each rock unit at the hypot hetica l tuff site is descri bed in Table 1. The miner alogy and chemi cal compo tion of a tuff unit depend in part upon its coolin g histor y si- and degree of post-d eposi tional altera tion. Vitric tuffs are por-ous tuffs which are compo sed of pumice or fragm ents of glass shards which have underg one a moder ate to. s*1 ight degree of weldin g. Their chemi cal compo sition is simple : the sum Si02

+ Al203 + K20 + Na 2o is greate r than 95 weigh t perce nt.

Minor eleme nt£ includ e ca. Mgi Cl. F and trans ition metal s.

Alter ation of the glass to clay is ubiqu itous in minor a~oun ts and locall y may be nearly compl ete. Devit rified tuffs are chemi cally very simila r to vitric tuffs but are quite dif-feren t in their minera logy and physic al prope rties. They are compo sed prima rily of fine-g rained aggre gates of sanad ine cristo balite . They may contai n pheno crysts of amphi boles, and clinop yro~e ne and feldsp ar as well as lithic clasts . Low-te peratu re altera tion of devit rified tuffs is not signif icant: m-access of ground water to the rocks is limite d by the low inter stitia l poros ity. Zeoli tized tuffs are the produ cts low tempe rature altera tion of nonwe lded volca nic ash. Theyof are compo sed prima rily of the zeolit es clino ptilol ite, morde nite, and analci me.

An averag e chemi cal compo sition of the ground water (6) is shown in Table B-1. The water is classi fied as a sodium -

potass ium-b icarbo nate ~ater by Winog rad ~t al. (4). Local ly the compo sition of ground water is depen dent upon lithol ogy.

Water assoc iated with vitric tuffs is highe st in silic~ .

sodium . *calciu m and magne sium where as ground water in zeoli tic*

tuffs is deplet ed in the bivale nt cation s (28). The pH of these water s ranges from near-n eutral to sligh tly alkali ne (7.2-8 .5). The :Eh of the ground water in the repos itory hori-zon is unknow n. Dissol ved oxygen conte nts from sever al shallo wells at the Nevada Test Site are fairly high ( - 5 ppm) (29).w The conce ntrati ons of severa l redox *indic ators and.th e altera tion featur es of- the mafic miner als in sever al uni ts indica te that oxidiz ing condi tions preva iled at one time .below the water table (9). N~gat ive redox poten tials and low levels of dissol ved oxygen , howev er, have been measu red in sectio ns of a drill hole in the Crater Flat Tuff (33). These obser vation are consi stent with measu red values of sulfid e in the ground - s water and the occurr ence of pyrite (FeS ) in the rock mat-rix. The measu remen ts are subje ct to a 2 large amoun t of TABLE B-1 ANALYSES OF WATERS FROM THE NEVADA TEST SITE (mg/1) 1 2 Well Species J-13 USW-Hl 2 USW-VH1 Na+ 47.00 74.90 97.10 K+ 4.70 5.10 4. 30 ca 2 + 13.00 7.20 10.30 Mg2+ 2.00 0.40 1. 90 Ba 2 + 0.20 0.01 Q.04 sr 2 + 0.06 0.02 0.08 2

HC0 3 + CO 3 - 130.00 c1- 7.70

' 2-so 4 21.00 N0 2 - 5.60 3

F- 1. 70 Si02 61.00 11. 00. 53.40 pH 7.1-8.3 TDS >294.00 1 LA-7480-MS - reference 6 2 LA-:8847-PR -.reference 8 uncertainty and must be confirmed by further investigations. In light of this uncertainty. we assumed that the ground waters at the hypothetical repository are oxidizing. The importance of redox to both the solubilities and Ra values for the radio-nuclides that were conside~ed in our calculations will be dis-cussed below.

B.2 Radionuclide Solubilities As discussed in Section 4.3. we have attempted to estimate upper bounds for the radionuclide solubilities at the tuff repository. These limits were s~t after a limited review of available* experimental data and theoretical calculations. Most of the redox-sensitive elements are least soluble under reduc-ing conditions. In light of the uncertainty concerning the redox conditions at Yucca Mountain and in order to ensure that our calculated releases are conservative. we have used the estimated radionuclide solubilities for oxic conditions in our calculations.

The estim ated solu bilit y* limi t for each elem ent cuss ed belci w. In this disc ussi on. a pH= 8 and is dis-com posi tion simi lar to J-13 wate r (Tab le B-1) a grou nd-w ater a-re assu med.

Pu: Exp er irnen ta 1 'stud ies revie wed by Wood and Rai sugg est that Pu solu bilit y is rela tive ly inse ( 15) to redo x ~ond ition s .. They sugg este d a valu e of nsit iie 4x10 -lO M from thei r data ; A more cons erva tive valu e of 10-3 M (2.4 xio- 4 g/g) was used in orde acco unt for the poss ible dom inanc e of a Pu-c arbo r to comp lex (12) . nate

~: Uran ium sol~ Ei~i ty coul d be very high if cons

(>10 -2M) co 3 1s pres ent .. How ever. the grou nd- ider able wate r com posi tion at NTS (6.8 ) does not supp ort pos sibi lity . We have used the expe rime ntal data this pres ente d in (15) to set_ the U solu bili ty limi 2.4x io- 5 g/g. Unde r redu ~ing cond ition s the t. at solu bili ty woul d be seve ral orde rs of mag nitud e lowe r.

Th: The dom inan t spec ies at Th is prob ably Th(O va~u es abov e 5 (13. 31.3 2). We used the reacH)i at. pH.

t1~n :

0 .

Th (OH) 4 .:::::: Th02 ( s) + 2H20 to estim ate the solu bilit y limi t at 2.Jx 10-7 g;g pH=B. The -sol ubil ity is not sens itive to at redo x.

Ra: Radi um i~ anot her elem ent whos e solu bili ty is tive ly inse nsit ive to redo x. Its solu bili ty isrela -

trol led prim arily .by RaS0 4(s) or RaC 03(s i. The con-valq e from (16) is a very cons erva tive uppe r boun Ra solu bili ty at the tuff site . d for Few .data are avai labl e to e~ti mate cm solu bili natu ral wate rs. In a O.lM NaCl solu tion at pH= ty in cm solu bili ty was 10-l lM. The solu bili ty decr 3.the at lowe r pH (14) . A cons erva tive valu e of 10-1ease s (2.S x10- 11g/ g) was used in the calc ulat_ ions . 0 M Am solu bili ty has been stud ied by Wood and Rai They sugg est that a valu e of 7xio -12 Mis reas (15) .

over a ,ide rang e of redo x cond ition s. Com plexi onab le c1-. S04-

or N03 _wil l not be sign ifica nt. ng by N..12.: Nept uniu m is leas t solu ble unde r r~du cing cond c10-l OM) (15) . At an Eh= +0.2 6 and pH=7 the ition s bili ty of Np0 2 (c) is appr oxim ately 2.4x 10-B g/g. solu -

Pb: PbC03 or Pbso 4 will limit the solubility of lead in an oxic tuff environment to less than 10-6 M. If any sulfide is present, PbS will precipitate and fur-.

ther decrease the solubility.

Pa: Little data are available for protactinium solubility in natura1*waters. We use the reactions:

. . 0 Pa4+ + 4QH-::;:!:Pa (OH) 4 Pao 2 + 2H 2 o=: Pa4+ + 40H-to set the solubility limit at 2.3x10-2 M.

We had no data to estimate the*solubility of actinium; we therefore assumed that it had no solubility limit in our calculations.

Tc: Tc is least soluble under r~ducing conditiong and precipitates as Tco 2 . Under oxidizing conditions it is probably present as TcOi and is very soluble. .

We have assumed that it has no solubility limit in our calculations (13, 16).

I, Cs: These elements probably have no limiting solubilities under repository conditions (13, 16).

Sri: We have assumed that these redox-insensitive reactions determine.tlle solubility of tin (13, 16):

sn4~ + 4H 20 = Sn(OH)~ + 4a+: log K = -57 Sn(OH) 4 (s) = sn4+ + 40H-: log K = -0.87 I

The solubility of Sr is probably set by strontianit~

Srco 3 (13, 16). At pH=8, the reported 1jo ppm of HC03 + co 32- (Table B-1) is dominantly bicar-bonate and [CO~- ] is about 10-SM. Log K5 of Srco 3 is -9.6 whicll means the solubility of.~r is about 2x10-6g/g. * .

C: We set the solubility limit of Cat a level con~

sistent with the doncentration of HCOi in J-13 water (-26 ppm carbon in a .solution of 130 ppm HCOi).

B.3 Rad ionu clid e Sorp tion Rati os The rang es of radi onu clid e dist ribu (Ra) used in our calc ulat ions are list ed tion in coe ffic ient s valu es were chos en afte r a revi ew.o f the pub Tab le 4. The stud ies that were cond ucte d at Los Alamos lish ed exp erim enta l (LANL) thro ugh June , 1981 , (5-1 0). Nat iona l Lab orat ory

.. Ra valu es from batc h expe rime lowi ng con diti ons were incl uded in nts obta ined unde_r *the fol-the rang es show n in Tab le 4.

tem p~ra ture = 22°c soli d: solu tion rati o= 1:20 atm osph ere= oxid izin g par ticl e size = 106- 500 mic rons wat er= J-tJ wate r pre- equ ilib rate d with the rock sam ple roc ks= sam ples from UE2 5a-l , G-1 and J-13 dril l hole s

Para met ric stud ies by LANL scie ntis the mea sure d Ra valu es are depe nden t uponts (5-1 0)_ sugg est that

-par ame ters list ed abov e. The cons erva tismall of the letit ed und er thes e ~xp erim enta l con ditio ns of the data col-natu ral con diti ons -~pe cted at the tuft r~p~ith resp ect to d~s crib ed in Tab le B-2. 6sit ory site is For seve ral el.em ents , Ra valu es obta ined und exp erim enta l con diti ons can vary up er thes e to 3 orde rs of mag nitu de betw een sam ples of the sa~e bulk min eral ogy valu e are- stro ngly depe nden t upon the abun . The ~eas ured Ra eral s such as mon tmo rillo nite , the dura tion danc e of mino r min-and upon the met~ od used to mea sure the con of the expe rime nt sorb ed radi onu clid e. Valu es obta ined from cen trat ion of the men ts are alm ost alwa ys sign ific antl y high deso rpti on exp eri-tain ed ~rom sorp tion expe rime nts. The data er than thos e ob-b~ac ket the high est aver ag~ Ra valu es obta rang es in Tab le 4 deso rpti on expe rime nts and the low est ined from valu e. The refe renc es for si~i lar valuaver es age sorp tion Rd desc ribe d in Tab les B-1 to B-5. in the lite ratu re are TABLE B-2 CONSERVATISMl OF LA.BORATORY

. DETERMINATIONS OF Rd (LANL)

ELEMENT PARAMETER Pu Am u Sr Cs Ba Ce Eu Tc Radionuc lide Concentra tiqn *O ND ND ND 0 ND Solid/Sol ution Ratio ND ND ND -o* -0 ND Ionic Strength ND ND ND *-* _::it

-* -* -* ND Temperatu re ND 0 + + + + it it ND Particle Size -0 +O +O +O* +O* +O* 0 0 ND TYPE EXPERIMENT:

Batch vs. Column ND ND -* -* ND ND Eh (Atmosphe re) + 0 + 0 0 0 .0 0 +

KEY: -+ Conserva tive Not conservat ive o Little effect

Inconclus ive or interactio n effects ND Not determine d 1 Assuming the following experimen tal condition s:

T = 22°C Atmosphe ric condition s (in air)

Solid: Solution = 1:20 106-500 micron particle size range Batch experimen t Element-s pecific concentra tion J-13 water Table B-3 SOURCES OF DATA FOR RANGES! OF Rd VALUES FOR VITRIC TUFF Eleme nt Value Refere nce2 Comme nt3 Am 85 6(27) JA-18 . minimu m sorpti on value 360 6(27) JA-18 . maximu m sorpti on value Pu 70 6(27} JA-18 . minimu m sorpti on value 1.

450 6(27) JA-18 . maximu m sorpti on value u 0.01 conse rvativ e lower limit 11 9(8) YM-54 . YM-22 (devi trifie d) max. or ave. desor ption value Np 5 10(12) YM-49 . Gl-188 3 (devi trifie d).

(ave. sorpti on value - s.d.)

7 10(12) Gl-188 3 (devi trifie d). (ave.

sorpti on value + s.d.)

Sr 117 8(10) Gl-129 2. sorpti on averag e 300 9(1) YM-5. desorp tion averag e Cs 429 8(10) Gl-129 2. sorpti on averag e 8600 9(1) YM-5. Cs desor ption averag e Tc 0.01 conse rvativ e lower limit 2 7(16) YM-48 . desorp tion averag e (glas s+ zeolit es)

I 0 6(25) *conse rvativ & value 1

Ranges in Table 4.

2 R~fere nces are numbe red in biblio graph y: numbe r in paran theses is table numbe r in the refere nce.

3 rnform ation given includ es: rock sample numbe r. miner alogy if differ ent from that stated at top of table. type of value (s.d. = standa rd devia tion of averag e value ). Avera ges includ e contr ibutio n from severa l partic le size fracti ons and conta ct times .

\

Table B-4 SOURCES OF DATA FOR RANGES OF Rd -VALUES FOR ZEOLITIZED TUFF Element Value Reference2 Comment3 Am 600 6(32) JA-37, sorption average 9500* 9(6) YM-38, desorption average Pu 250 9(6} YM-38, sorption average 2000 9(6} YM-38, desorption average u 5 9(8} YM-38, sorption average 15 9(8) YM-38, desorption average Np 4.5 10(12) YM-49, (average sorption value - s. d.)

31 10(12} Ul2G-RNM9, single sorption value for 3 wk. contact time Sr 290 6(21} JA-37, sorption average 213,000 8(10} Gl-2698, desorption average Cs 615 6(21} JA-37, sorption average 33,000 3 (Al} YM-49, desorption average Tc 0.2 3 (Al} YM-49, sorption average 2 3 {Al} YM-49, deso~ption average I 0 6(25) conservative value 1

Ranges in Table 4.

2 see note 2, Table B-3.

3 see note 3, Table B-3.

Table B-5 SOURCES OF DATA FOR RANGES 1 OF Rd VALUES

FOR DEVITRIFIED TUFF Ele.ment Value Refe.renc e 2 Comment3 Am 180 9(4) YM-5.4, minimum sorption value

4600 9(6) YM~22, desorpti on average PU 84. 9(6) YM-54, sorption average 1400 9(6) YM-22. desorpti on average u l. 2 \ 9 (7) YM-22, sorption average

( 106-500 µ m) 14.3 9(7) YM..:s4, desorpti on average

(<106 µm)

Np 5 10(12) YM-49, Gl-1883 (devitri fied).

(a~e. sorption . value - s.d.)

7 10(12) Gl-1883 (devitri fied), (ave.

s~rption v~lue + s.d.)

Sr 53 6(19) JA-32, desorpti on average 450 8(10) Gl-1982, maximum sorption value Cs 123 6(19) *JA-32. sorption average 2020 8(10) Gl~l982. desorpti on average Tc 0.3 3(Al) sorption average 1.2 3(Al) d~sorpti on average I 0 6(25) conserv ative value 1 . .

Ranges in Table 4~

2 .

see note 2, Table B-3.

3 . * *

Informa tion includes : *rock sample number, type of value, particle size fraction if not all fraction s were consider ed in average. Maximum values are maxima for several size

fraction s. samples or contact times.

APPENDIX C APPROXIMATIONS FOR ADAPTING POROUS MEDIA RADIONUCLIDE TRANSPORT MODELS TO ANALYSIS OF TRANSPORT IN JOINTED POROUS ROCK C.l Intro ducti on This attach ment summ arizes resul ts of initi al analy ses (34. 35. 36) to devel op equiv alent poroµ s media mode ls for analy sis of trans port in jointe d porou s rock. Much of text and appro ach are taken from (36). First . the equatthe and under lying assum ption s used to descr ibe radio nucli de ions trans port in both porou s and jointe d porou s media are summ arized . Gene ral' cond itions are then defin ed for which trans port in joint ed poiou s rock can be appro iimat ed occur ring in equiv alent porou s media havin g effec tive as poro sities defin ed by joint a~ert ure. orien tatio n spaci ng. An expre ssion for the retar datio n facto r and equiv alent porou s media trans poyt equat ions is derivin ed.

the nume rical crite ria for. use of the porou s media trans port *~ext equat ions are deriv ed. Then nume rical crite ria for porou s media appro ximat ion are deriv ed fo~ a spec ificuseflowof the syste m. The equat ions descr ibing flpw throu gh a system of joint s which form plate -like regio ns df joint ed rock prese nted. It is shown that the crite ria for the use:are of a porou s media appro ximat ion can be deriv ed from solut ion of these equat ions. The speci fic crite ria for this system are shown to be equiv alent to those defin ed for the gener Defin ition s of*the *sym bols used in this discu ssion areal case.

summ arized in Table C-1 and descr ibed in Figur e C-1.

C.2. Radio nucli de Trans port in Porou s and in Joint ed.Po rous Media Porou s Media Consi der a reaso nably homog eneou s porou s mediu m. shown schem atica lly in Fig. C-1, which has avera ge effec tive poro sity~ and grain densi ty Ps* Assume that the phys icai and chem ical prop ertie s of the rock can be consi dered unifo and conti nuou s. *Let the pore space be fully satur im ated. and assum e that flow is relat ively unifo rm throu ghou t space . Also, let sorpt ion of radio nucli des by the that pore rock resul t from only reve~ sible proce sses such as adsor ption or ion Table C-1 DEFINIT ION OF TERMS symbol Defini t*ion matrix porosi ty(*)

Ps grain density (g/cc)

C radion uclide concen tration in flowirig fluid (g/ml) q* radion uclide concen tration on solid phase (g/g) sorptio n equilib rium distrib ution coeffi cient. = q'/C (ml/g) radion uclide concen tration .on surface of solid phase (g/cc) local radion uclide concen tration in solid phase (g/cc) q bulk radion uclide concen tration in porous matrix (g/cc)

V bulk-m ass average veloci ty of f~uid (cm/se c).

(inter stitial or joint fluid veloci ty)

V averag e veloci ty of fluid in x directi on Ccm/sec' )

X directi on of fluid flow (cm)

X/V mean residen ce time of fluid (sec)

R retarda tion fa6tor for radion uclide transp ort in porous media( *)

E porosi ty of rock associa ted with joints (*)

m void volume (assoc iated with joints) per unit volu-e of porous matrix = E/(1-E) (*)

volume of plate-l ike regions of porous matrix (cm3l joint apertu re (_cm) 2b joint spacing or width of plate- like region s of porous matrix . (cm)

1. Table C-1 (contin ued) symbol

Defini tion*

K bulk sorptio n distrib ution coeffi cient: = q/c = R¢

(*)

D molecu lar diffusi on coeffic ient of radion uclide (cm2/se c)

Q tortuo sity (*)

effecti ve diffusi on coeffic ient of radion uclide in porous matrix = D¢/a2K (cm2/se c) effecti ve interfa cial resista nce to mass transfe r (sec-1)

R*J retarda tion factor for equiva lent porous media approx imatio n= l+K/m (*)

z direcii on of diffusi on, perpen di~ular to rock-f luid

interfa ce (cm) mass of radion uclide on rock matrix per unit contro l volume (g) mass of .radion uclide .in pore water per unit contro l volume (g) mass of xadion uclide in flowing fluid in joint per unit control .volum e (g) iadion uclide decay consta nt (sec-1)

/\

C solutio n to transp ort equatio ns for A= o I

a interfa cial area per unit volume of bulk rock= 1/b =

2m/H (cm-1)

/\

to.s elapsed time require d for C/Co to reach a value- of o.s a De/b2 (sec-1)

Table C-1 (continued)

Symbol Definition 0 t-x/v (sec) y DeK/b2 (sec-1) w x/mv (sec)

Yw effective bed length (cm) \.

g (cm)

=dimensionless variables (A) POROUS ROCK 1zL X (B) JOINTED POROUS ROCK POROUS MATRIX

- - - - o*********~*~*

- - - - *r. .......................... !t_H

...................... .i I I I I I I 1

I I I I t o I I I I I I It I 1

~ ~ : ** *- ** ~.L..!...!..!-!- ***...:..! *

+

-* * *

J I. * * * * * * * * * * * - . *

o!_...J_ *

2b (A) I I I I I t I I I I I I I I I t I I I* I I I 1*1 (B) I I ~ I *

... . . -* .~-* .

I I I I I I t I I I JOINT I

CX) 0 I

Matrix -porosity=¢ Matrix porosity .= ¢ train Density = Ps Fracture porosity= E Grain density = p s

Volume*of plate-like regions _of= VP porous matrix Plate thickness = 2b Joint aperture = H Figure C-1. Schematic Diagrams of Porous (A) and Jointed Porous Rock (B) ~

Coordinate system is same for both diagrams. Origin_for z coordinate -is at center of block.

exchange, and let fluid-phase concentrations be sufficiently dilut~ so that sorption can be represented by linear isotherms of the form q 1 = KdC* where c, Ka, and q 1 are the radionuclide concentration in the flowing fluid, the sorption equilibrium distribution coefficient, and the radionuclide concentration associated with the solid phases, respectively.

Furthermore, assume that the radionuclide concentration C is due only to dissolved species. For such media,, the following assumptions are generally made:

Assumption A: The interstitial fluid velocity profile can be approximated by the bulk mass-average pore fluid velocity V.

Assumption B: The cross section of the pores. is sufficiently small so that the radionuclide concentration in the pores can be considered cross-sectionally uniform.

Assumption C: Local sorption equilibrium exists between pore water and mineral phases.

I When these conditions obtain, then for constant-valued parameters, the basic equation describing radionuclide transport. is the material balance for the flowing fluid I

__,,_ decay ac = ~

y_

v.c = terms for .reaction (C-1) at R {

dispersion where R is the retardation factor given by R = 1 + (1 - ¢)P5 Kd/¢, and it is assumed that essentially all pore space is available to fluid flow.

Jointed media Now consider a jointed, but otherwise reasonably homogeneous, porous medium which has*porosity ¢ and grain density Ps associated with the bulk porous matrix and has porosity E associated with the joints, as determined from j6int aperture H, orientation, and spacing 2b (Figure C-lb).

Let fluid flow occrir primarily in the joints, and convective radio nucli de trans port in the bulk porou s rock be negli gible Let the joint s be linea r, have recta ngula r cross -sect .

appro xima tely unifo rm dimen sions , and have const ant and ions. of

conti nuou s physi cal and chem ical prop ertie s. Furth ermo re.

asstim e that the joint s and porou s matri x are fully -satu rated and let the regio ns of porou s rock bound ed by the joint s have, ,

appro xima tely unifo rm, plate -like shape and volum e Vp.

Again assum e that the radio nucli de conc entra tion c only resul ts.fro m disso lved speci es. Also assum e that radio nucli retar datio n, relat ive t6 conve ctive trans port in the de is due to molec ular diffu sion in the pore water and joint s, simul taneo us sorpt ion by the soliq phase s of the bulk rock.

Again let sorpt ion of radio nucli des by the Lock resul t from only rever sible proce sses, and let the conc entra tion C be suffi cient ly small so that sorpt ion can be repre sente d by linea r isoth erms. and radio nucli de diffu sion- throu gh water by Fick 1 s law. Assume that the plate thick ness the 2b.

pore suffi cient ly small so that_ radio nucli de conc entra tions is resul ting from diffu sion are non- trivia l over the entir e thick ness of the plate . -

Three other assum ption s, analo gous to Assum ptions A-C for porou s media need t~ be made for jointe d.por ous media . In mode ling radio nucli de trans port in joint ed media , it is gene rally assum ed that the veloc ity profi les .in the joint s also can *be appro ximat ed by the bulk mass- avera ge fluid veloc ity v in the joint s, again obtai ned from an appro priat hydro logic mode l. Howe ver, it canno t be assum ed that e conc entra tion in th~ fluid in the joint s gene rally will be cross -sect ional ly unifo rm or that local sorpt ion equil ibriu m, gene rally exist s betwe en bulk phase s. Inste ad the follow ing assum ption s are usual ly made:

Assum ption Bl: Joint apert ures are suffi cient ly small so that in the joint s. diffu sion of radio nucli des in *the fluid phase can be appro ximat ed as a quasi -stea dy state proce ss which is repre sente d by a *1ine ar drivi ng force expre ssion .

Assum ption Cl: Local sorpt ion equil 1bria exist at the inter face betwe en flowi ng fluid and bulk rock and betwe en pore water and solid phase s of the porou s matri x.

When these condition s obtain, then for constant-v alued parameter s. radionucl ide transport can be described by the following *eguations :

(material balance for the fluicl in the joint) ac . .: . -* 1 an decay at + v

V c + -mat *= = terms for reaction

{ dispersio (C-2) n (flux expression at the interface between flowing fluid and bulk rock) 2.9. .!. (C -g./K} = terms for { decay at Rf . s . reaction (C-3)

(material balance for the bulk rock) aq *.

DeV 2 g.1

_._1 { decay at = terms for (C-4) reaction where.

q.dV l . p (C-5)

The terms in these expression s are detined in Table C-1 and Figure C-L . De is the effective radionucl ide diffusion coefficie nt for the bulk porous rock: K is the bulk sorption distributi on coefficien t between porous matrix and external*

solution: mis *the void volume (based on joint aperture, orientatio n, and spacing per unit volume of porous matrix:

Rf is an effective interfacia l resistance to mass transfer:

qi is the local concentra tion in the'porous rock: qs is the.value of qi at the interface bet~een matrix and flowing fluid, and the Laplacian v72 is defined in a coordinat e system convenien t for describing diffusion in porous rock.

C.3 Eg~ivalent Porous Media Approximation Qualitatively, it should be evident from the preceding discussion that radionuclide transport in the jointed porous rock described above could be approximated as occurring in an equivalent porous media if the joint aperturi H, joint spacing 2b, and the physical and chemical properties of the radionuclides and bulk rock were such that the conditions described by Assumptions Bl and Cl reduced to the conditions described in Assumptions Band C respectively. These

equivalent porous media assumptions can be stated as Assumption B2: Radionuclide concentrations in the flowing fluid can be considered approximately cross-sectionally uniform.

Assumption C2: The bulk rock can be considered approximately*to be in local sorption

~quilibrium with fluid flowing in the joints.

In the paragraphs below, quantitative criteria, which determine when the above two conditions are valid, are developed in terms of the joint aperture H, spacing 2b, and the fundamental parameters describing the physical and*

chemical properties of the. bulk rock. The expression for the retardation factor Rj to be used in the equivalent porous media equation is also develo~ed. .

Criteria for equivalent porous media approximation Let x denote a sp~tial coordinate .in the direction of bulk fluid motion, and let*D be the radionuclide diffusion coefficient (assumed constant) £or dilute aqueous solutions of the nuclide. A criterion for approximately uniform radionu-clide concentrations i.n the flowing flu1d is that the average

residence time x/v for the flowing fluid is much greater than the relaxation tim~ for a concentration gradient. The equi-libration time for a plane sheet which has thickness H/2 and one face maintained at~ constant concentration is approxi-mately H2/4D (37) and should be a ~easonably geneial esti-mate of the ~elaxation time for a concentr~tion gradient. The desired criterion is then x/v >> H2/4D or x/v ~ A1 H2/4D, where A1 is an .appropriate constant, on the order of 10 to 106. In previous analyses (34, 35) of specific cases in jointed porbus rock, the preceding criterion was derivea using the solutions to the tran~port equations for porous rock.

The valu e of the *con stan t Ai so obta ined vari ed and 24.

Ther efor e. a reas onab le crit erio n betw ~en 23 cros s-se ctio nall y unif orm radi onuc lide conc entr for appr oxim ately the flow ing fluid shou ld be atio ns in x/v > 6H2 /D . (C-6 )

Bu.!_ k_roc t.

For the bul~ rock to be appr oxim equi libri um with th~ flui d flow ing* in ately in loca l sorp tion the join ts. radi onuc lide

~onc entr atio ns in the plat e-lik e regi ons must sect iona lly unifo rm. Agai n a crite rion for such be neat ly cros s-mate ly unifo rm conc entr atio ns is that the mean appr oxi-

x/v of the flow ing flui d is much grea ter than resid ence time time for a conc entr atio n grad ient . Foll owin g the rela xati on argu men ts. that crit erio n _would be x/v >> b2 /De. the prec edin g diff usio n of radi onuc lide s into t~e poro us matr How ever.

the conv ectiv e tran spor t of radi onuc lide s rela ix will reta rd flui d moti on. The mean resid ence time of the tive to bulk .

woul d be grea ter than the fluid resid ence time radi onuc lide s part icul ar. if radi onuc lide conc entt atio ns in x/v. In are inde ed near ly unif orm. then the radi onuc lide the bulk tock time ~oul d be gr~a ter than the fluid resid ence . resid ence fac*t or of Rj, the reta rdat ion fact or defi ned belo time by a join ted medi a. Then the prec edin g crit erio n can w for les~ rest ricti Ve form as* be ~tat~ d in Rj *X/V >>b2 /De or .x/v >> A2b2 /RjD e, wher e A2 agai n is an appr opri at~ cons tant . on to 100. It is shown late r that the orde r of 10 RjDe:::: KDe/m = </>Dta.2m =<l>D(l - E)/a. 2E, and that a typi cal valu e fo~ A woul d be abou t fore , a reas onab le crit erio n for 2 so.

Ther e-appr oxim ate loca l sorp tion equi libri um shou ld be b2 m__ 2 Q2

K V -

> 50 KD e = 50 if, " ( l E_ E

) * !L_

D (C-7 ) .

Retar dation factor for equiv alent pdrous media appr6 ximat ion By defin ition, the interf acial resist ance Rf to mass transf er (Eq.C- 3) is propo rtiona l to the fluid phase conce ntrati on gradie nt perpe ndicu lar to the interf abe betwee n bulk tock and. flowin g fluid. As that conce ntrati on gradie decre ases, the resist ance Rf decrea ses corres pondi ngly, andnt for suffic iientl y small gradie nts~ that is, nearly cross-sectio nally unifor m .conce ntratio ns in the joirits , Eg. C-3 redu~e s to gs= ic. Furthe rmore , for appro ximat ely cross-sectio nally unifor m radion uclide conce ntrati ons in the bulk rock, Eg. C-4 reduce s to qi~~ consta nt, which implie s q 6 ~_qi, and Eq. C-5 reduce s to q ~ Qi, which implie s

q ~Kc. Then, Eqs. C-2 to C-5 reduce to ac + v

ot R.

J vc = terms for decay reacti on

{ dispe rsion (C-8)

Eq. C-8 is analog ous to Eg. C-1 for porou s media .

. An expre ssion for the r~tard ation factor Rj for jointe d

. porous media can now be derive d in terms of measu rable fundam ental paiam eters.

In gener al, a retard ation factor can be define d as the ratio of the mass of solute in the rock-w ater system to the mass ot* solute in the fluid in a unit contr~ l volum ~. In a jointe d porous media this d~fin ition can be expres sed as:

M R.= r + Mp*+ Mf (C-9)

J where :

I Mf = mass of radion uclide in water in fractu res in a unit contro l volume Mm= mass of radion uclide in the porou s matrix bound by fractu tes iri a unit contro l volum e Mr.= ma~s of radion uclide sorbed onto solid phases of porous matrix in unit volum e Mp= mass of radion uclide in.por e water of porous matrix in unit volume When the local equilib rium assump tions defined above obtain .

then:

E c

unit volume (1 - E } unit volume Mr= (1 - ¢}P 5 KdC * (l - E)

unit volume therefo re:

EC + [(l - cf>) P5 KdC + <PC] (1 - E )

Rj =

EC R. = 1 +

J (1~*)*[¢(1+ p (l s

-<P)

¢ Kd)l (C-10) which is the d~sired expres sion.

The criteri on in Equatio n C-7 can now be derived .

By defini tion:

m = E / ( l -:- E *)

therefo re. R. = 1 + K/m. (C-11)

J Now. if most of the porosi ty of the bulk rock is avail-able .to radion* uclide diffusi on. and if surface diffusi on at the minera l surface s is neglig ible. the effecti ve diffusi on coeffi cient De for porous rock often is defined by De= D/a2R or De= D/a2[1 + (1 - ¢>PsKd /¢J.

where a2 is a tortuo sity fact~r for the porous matrix .

Further more. for most jointed media. the porosi ty t associa ted with the joints will be relativ ely small and much less than</ ,. Since m = E)(l_- E ). K/m >> 1. and Rj :::::- K/m.

From the definit ions of Kand D. it then follows that RjDe ::: ¢ D( 1 ~ E ) /E a2. as mention ed in the preced ing section . Since x/v > sob2/Rj De* Equatio n C-7 can be easily derived by substi tution .

I C.4. Criteria and Retardation Factor Der1ved from Solution of I . the Transport Equations

. In this section the preceding principles are illu£trated

using the transport equations for a specific flow system.

Consider transport of a radionuclide through a uniform,*

jointed porous medium illustrated in Figure C-'lb. -Let t]1.e nuclide be initially present in the inventory but not subsequently generated as a daughter product. Let flow in the joints and diffusion int9.the bulk rock be one-dimensio nal.

Assume that no competing chemical reactions occur and that radionuclide transport resulting from dispersion in the direction of flow is small relative to convectiv~ transport.

Let x, y. and z be rectangular Cartesian coordinates where x is again parallel to flo~ and z is perpendlctila r to the intetface between flowing fluid and bulk rock. For relatively uniform joint spacing, Eqs. c~2 to C-4 then become

ac ac !. Q9. l at + V ax +

m at = -lC - -q m (C-12)

~ _l_

-at Rf (C - qs/K) = -lq (C-13) 2 aq. _ 0 a g1.. -lq, (C-14)

__ 1. e--* = . l.

at az2 b .

where q =. 1/b L qidz: ). .is the tadionuclide decay constant.'

and appropriate0 initial and boundary conditions are *as follows: C(z,O) = o for z ~ o: C(O,t) = O fort$ o. and C(O,t) = c 0 e-Xt for t > o: qi(x.z,O) = o for o s z ~ b.

and x 2: o: aqi(x,O.t)/oz = o for x *~ o *and t ~ o.

Solution of transport equations If, for the above initial and boundary conditions, and ~i are the solutions to Eqs. t-12 to C-14 for 'X = o, it

8. ~.

can be verified by direct substitution that for }.. >O, the solutions to Eqs. C-12 to C-14 using ihe above initial and boundary conditions are given by c = ee-Xt, q = ~e-Xt*, a.nd Qi= G1e-Xt. For l= o. details of the method of .

solution are given by Rosen (38. 39) for the analogous equations for flow around spherical rather than plate-like

. regions. A similar solution is given by Erickson (34, 35) for a fluid flowing through a single fracture between two parallel

_:_99_

plates in which radionuclide diffusion perpendiculai to the fracture was limited to a finite penetration depth. By substituting the appropriate expression form. that is

/(1 - E ). in the single fracture result. the solution can be obtained for flow through a system of joints which form several plate-like regions of porous rock. such as shown on Fig. C-lb. The resulting solution is in the form of an infiriite integ~al which requires numerical evaluation~

,However. for sufficiently large values of xiv. the integral approaches a relatively simple asympototic expression. In particular. if x/v ~ so mb 2 /KDe* then

/\

ctc ::::::

.!. + .!. erf (C-15) 0 2 2 where O= De/2b2: 9= t - x/v: Y= DeK/b2: w = x/mv:

g = YRf. It should be noted that the expression x/v ~ 50mb2/KDe is equivalent to yw ~ so.

Derivation of numeri6al criteria for assumption ~2 For g/yw = a constant >O and sufficiently large Yw. the argument of the error function in Eq. C-15 becomes

[(206/YW) - l]/2(g/yw)ll2, and at a given value of g/yw.

depends only on *the ratio 09/Yw. It then can be seen by e

analogy with Rosen's discussion 139) that for Yw ~ so. the

shape of the breakthrough curve C(O.w) is relatively

unaffected by values .of g/Yw $ 0.01. This implies that a criterion for approximately cross-sectionally uniform concentrations in the flowing fluid would be g/yw = Rf/W ~ 0.01. or X/V ~ 100 mRf.

We ca~ now obtain the criterion in terms of fundamental properties of the bulk rock .from Equation (C-13). In general.

at the interface between flowing .fluid and bulk. rock.

aq/&t =*-aD8Ci/Bz. Thi term a is the interfacial area _per unit volume of bulk rock: Ci the local radionuclide.

concentration. and C -in Eqs. C-2 and C-3 should be defined more precisely here as the average value of Ci for the cross section of the joints. The term 8Ci/&z generally monotonically decreases nonlinearly from its value at the fluid-rock interface to a value of zero at distance H/2 from the interface. The value of 8Ci/&z at the interface then would be at least twice the average value. We can obtain expressions form and a in terms of b ~nd H by referring to

Figure C-lb. For the bulk rock:

E 2 m = - H

C2b} =

_H (C-16) l - f 2b

{2b}

a =. interfa cial area uriit volume - 2 *{2b}

{2b) 3 2

=

1 b =

2m*

H (C-17)

If the average of -oC./az is .approx imated by (C-qs/K )/{H/4) .

then at the interfa ce!

(C-18)

(C-19)

From Eq. C~l3, if A= O (C-20) therefo re 2

mRf S H ./160. (C-21)

The criteri on for approx imately cross- sectio nally uniform concen tiation .in the flowing fluid. can now be written as x/v ~ lOOH2/1 6D or x/v ~ 6H2/o. which is identic al to Eg.

C-6. .

Deriva tion of retarda tion factor for equiva lent porous media and numeri cal criteri on for assump tion C2 A The right side of Eg. C-15 is symme tric~l about the value of C/C 0 = 0.5 .. For a given valueA of t. t . is defined 0 01 as the elapsed time require d for C/C to reach a value of 0

0.01. and to.S* to.99* and 80.s are defined analog ously. For suffici ently small radion uclide concen tration s giadien ts in the joints {i.e. Assump tion C2).

Rf- o and g = YRf ~ O. From Eg. C-15 and approp riate value~ ~f the ~rror functio n. therefo re t - t 0.99 0.01 = 6.6 (C-22) 1/2 O0. 5 (3Yw) and for )'w > 50 t - t 0.99 0.01 0 < 0.54 o.5 This implies that as Yw becomes large. the spread in the breakthrough curve becomes small relative to the distance its midpoint has traveled. This is because the time interval by which the value of ~/C 0 = 0.01 precedes the value of t1c 0 = 0.5, and the interval by which the value of ~/C 0 = 0.99 trails, become small relative to Oo.s or (t 0 . 5 - x/v). For example. when Yw > so. the intervals are about twenty-five percent or less of 0 0 . 5 . Furthermore. from Eq. C-15 when C/C 0 = o.s. the argument of the error function is equal to zero and 2a0o.s/Yw = l. Using the definitions in Table C-1 we obtain:

to.s = (l + K/m)x/v (C-23) and if vo.s = x/to.s* then:

vo.s = v/(1 + K/m}. (C-24) and R. = V = 1 + K/m (C-25)

J vo.s which is equivalent to Eq. C-11.

Therefore. as yw becomes large. ecx.t) approaches eco.t - Rjx/v) and C(z.t) approaches e-At~(O.t - R.x/v). which is the solution to

' J' the corresponding form of Eq. C-1~

.ac + L oc A R, C (C~26) at R. ox J J Due to the inherent uncertainties associated with analyses of.

radionuclide transport in geologic media. a 27~ spread in the value of c about to.s probably is not serious. and values of Yw? so should be sufficiently large for Eqs. C-12 to c~14 to be approximated by.Eq. C-26. Furthermore. the criterion Yw? so. or x/v ~ SOmb2/KDe* is the same as that given by Eq. C-7 for approximate local sorpiion equilibrium between.

bulk phases .

. c.s. Discussion Application of equivalent porous medium criteria to the hypothetical tuff site. I The criteria described for Assumptions B2 and Cl (Equations C-6 and C-7 respectively) were evaluated for the welded tuff units of the hypothetical repository site.

Equation C~7 can be ~ritten in terms of the parameters listed in Tables 2 and A-1 as

X/V > so~ {l/N2D) * ( Q 2;ct,) * ( ,E /1- E) = A3 (C-27) where:

D = ionic diffusion constant a = tortuosity X ;:: path length in fractured media V = Darcy velocity+ fracture porosity

<J, ;:: matrix porosity of unfractured .blocks p = grain density of rock E ;:: fracture porosity= 2NH for our system where N = fracture density: H = fracture aperture The criterion was evaluated for densely and moderately welded tuff uni ts. for in'dividual beds as well as for the entire welded tuff thickness. The maximum~ *median and minimum values of the ranges.used for the LHS input variables were used *to evaluate the term (Aj). The. results are presented in Table C-2.

Table C-2

. A3 max A1 min A3 median*

X 200 ft 200 ft 100 ft*

6.4x10-3 8.Bxlo-6 l. 3x10-4

<P 0.03 0.10 0.06 N 6.5 ft-1 o_. 21 ft. -1 1. 6 ft. -:-1 K 60 ft/day* 4x10-s ft/day 4.2 ft/day i 4x10-~ *1x10-2 2x10-2 V 375 ft/day* 0.045 ft/day 0.646 ft/day X/V 0.533 day 4.4xlo3 day 155 day A3 0.19 day 0.045 day 0.031 day where:

i = vertical hydraulic gradient D = 10-S cm2/sec = 3.i9xlo-l ft2/yr Q' = 1.0 K = hydraulic conductivity in LHS range for densely welded units*

V = iK/

It can be seen from these calcula tions that the criteri on*

x/v ?A3 holds for the conditi ~ns encoun tered at fhe tuff site.

The criteri on in equatio n C-6 can also, be evalui ted from the above data. The condit ion x/v~6H 2/o is equiva lent to x/v ?: o. 6 sec. when an average apertu re with H of 10 micron s and D=lo-5 cm2/se c are assume d. The values of fluid residen ce time x/v listed in. Table C-2 all exceed this value.

Theref ore both of the criteri a require d for the equiva lent porous media are met for the hypoth etical tuff site.

SUMMARY

If the criteri a given by Eqs. C-6 ~nd C-7. for

approx imately cross- section ally uniform radion uclide concen trati6n s in the flowing fluid and bulk rock are satisfi ed. then radion uclide transp ort in jointed porous rock can be approx imated as occurri ng in equiva lent porous media.

Flow can be describ ed by the approp riate form of Eq. C-1.

where the retarda tion factor is given by Eq. C-10 to C-11.

The criter ia and retarda tion factor are given in terms of fundam ental physic al and chemic al parame ters~ Those which can be.eva luated in the labora tory include the radion uclide diffus ion coeffi cient D for dilute aqueou s solutio n. the distrib ution coeffi cient Ka fo*r sorptio n equilib rium betwee n

pore water and miner~ l phases~ the tortuo sity factor a. grain density Ps* and porosi ty¢ of the bulk rock. Parame ters which must.b e evalua ted from field data include the joint spacin g 2b and apertu re H. averag e fluid veloci ty v. and porosi ty E ass6cia ted with the joints. The last parame ter is determ ined from joint apertu re. orienta tion. and spacin g.

In terms of parame ters* evalua ted from labora tory data.

fhe distrib ution coeffic ient Ka and the ratio.D /a2 genera lly domina te Eqs .. C-7 and C-10 and also involv e the greate st uncert ainties . For very porous ro6k and for chemic ally-si mple radion uclides . evalua tion of Ka and D/a.2*

is n6t .diffic ult. Howeve r. for rock having very "tight" .

porosi ty arid (or) fot chemic ally-co mplica ted radion uclide s.

much labora tory and analyt ical work is require d to determ ine approp ~iate "~ffec tive" values . In terms of parame ters obtaine d from field data *. Eqs. C-6. C-7. and C-10 are most sensit ive to joint apertu re H. joint spacing 2b. and porosi ty E.

Evalua tion of H inhere ntly involve s consid erable uncert aihty.

which corresp onding ly affects evalua tion of E. Evalua tion of the averag e fluid velocit y. v involve s many uncert ainties which can substa ritially affect use of Eqs. C-6 and C-7.

\

REFERENCES

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Preli mina ry Repo rt on the Geolo gy and Geop hysicR. B.*

s ai Drill Hole UE25 a-l Yucca Moun tain. Nevad a Test Site.

U. s. G. s. Open File Repor t 79-12 44. 1979.

2. Sykes . M. L .* Heike n. G. H.* and Smyth . J~ R .* Mine ralog and Petro logy of Tuff Units from the UE25 a-l Drill Site. y Yucca Moun tain. Nevad a. Los Alamo s Natio nal Labo ratory Repo rt LA~81 39-MS ! 1979.

3. Johns tone.

J. K ** and Wolfs *berg. K. eds .* Evalu ation Tuff as a Medium for a Nucle ar Waste Repo sitory : an of Inter im Statu s Repo rt on the Prop ertie s of*Tu ff. Sandi a Natio nal Labo rator ies Repor t SANDB0-1464. 1980.

4. Wino grad. r. J: and Thord arson . W.* Hydro geolo gic and Hydro chemi ca.l Frame work. South -Cent ral Great Basin .

Neva da-Ca liforn ia; with Speci al Refer ence to the Nevad a Test Site. u. S. G. S. Prof. Pap. 712-C . 1975.

5 *. Wolfs berg. K ** Sorpt ion-D esorp tion Studi es of Nevad a Test Site Alluv ium and Leach in~ Studi es of.Nu clear Test Debr is, Los Alamo s Scien tific Labo ratory Repo rt LA-72 16-MS . 1978.

6. Wolfs berg. K.* Bayh urst. B. P. and other s. Sorp tion-Deso rption Studi es on Tuff I. Initi al studi es with samp le* fro~ the J-13 Diill Site. Jacka ss Fl~ts , ~evad a.

Los Alamo s Scien tific Labo ratory Repo rt LA~74BO-MS. 1979.

7. Vine. E~ N.* *Agu ilar.* R. D. and other s. Sorp tion-Deso rption Studi es on Tuff II. A conti nuati on of studi es with samp les from Jacka ss Flats . Nevad a. and initi al studi es with samp les from Yucca Moun tain. Nevad a. Los Alamo s Scien tifi~ Labo ratory Repo rt L~-81 10-MS . 1980.

8*. Erdal , B. R .* Dani els. w. R.. and Wolf sberg . K ** *eas .*

Resea rch and Devel opmen t relat ed to Nevad a Nucle ar Stora ge Inves tigat ions. Janua ry 1 - March 31. 1981. WasteLos Alamo s Scie ntific Labo ratory Repo rt LA-88 47-PR . 1981.

9. Wolfsberg . K.* Aguilar. R. D. and others. Sorption-Desorptio n studies on Tuff III. A continuat ion of studies with samples from Jackass *Flats and Yucca Mountain.

Nevada. Los Alamos National Laboratory Report LA-8747-MS.

1981.

10. Erdal. B ..R .* Daniels. W. R.* Vaniman. D. T. and Wolfsberg . K.* Research and Developme nt related to the Nevada Nuclear waste Storage Investiga tions. April 1 -

June 30. 1981. Los Ala~os National Laboratqr y Report LA~8959-P R. 1981.

11. Guzowski. R. v .* Nimick. F. B. and Muller. A. B .*

Repositor y Site Definition in Basalt: Pasco Basin.

Washingto n. Sandia National Laborator ies Report.

SANDBl-20 88. NUREG/CR -2352. 1982.

12. Wolfsberg t K.* Diniels.* W.R .. Erdal. B. R. and Vaniman.

D. T .* Research and Developme nt Related to the Nevada Nuclear Waste Storage Investiga tions. April 1 - June 30.

1982. Los Alamos National Laboratory Report LA-9484-PR .

1982.

13. Letter From F. Nimick. Sandia National Laborator ies. to L. Rossbach. NRC.

Subject:

Prelimina ry calculatio ns of solubiliti e$ of* radionucli des in basalt groundwat ers.

dated April 27. 1982 .. Available in NRC PDR for inspection and copying for a *fee. *

14. Rai, D and serne, R. J., Solid Phases and Solution Species of Different Elements in Geologic Environme nts, Battelle, Pacific Northwest Laborator ies Report PNL-2651, 1978 ..

15. Wood. B. J. and Rai, Dhanpat, Nuclear Waste Disposal:

Actinide *Migration from Geologic Repositor ies, Battelle, Pacific Northwest Laborator ies Report PNL-SA-.9549. 1981.

16. Muller, A. B., Finley. N. c. and Pearson. F. J., Geo-chemical Paramet~r s used in the Bedded Salt Reference Repositor y Risk Assessmen ts Methodolo gy, Sandia National Laborator ies Report, SAND81-0557, NUREG/CR-1996, 1981.

17. Campbel l, J.E., Longsine , D. E. and Cranwel l, R. M., Risk Methodo logy for Geologic Disposa l of Radioac tive Waste:

The NWFT/DVM Compute r Code Users Manual, Sandia Nationa l Laborat ories Report SANDBl-0886, Novembe r 1981.

18. Iman, R. L., Davenpo rt, J.M. and Zeigler, D*. M., Latin Hypercub e Sampling (Program Users Guide), Sandia Nationa l Laborat ories Report SAND79-1475, January , 1980.

19. Environm ental Protecti on Agency. "Environ mental Radiatio n Protecti on Standard s for Managem ent and Disposa l of Spent Nuclear Fuel, High-Le vel and Transur anic Radioac tive wastes," Working Draft #19 40CFR191. Availab le in NRC PDR for inspecti on and from the EPA.

20. cranwel l, R. M., and others, Risk Methodo logy for Geologic Disposa l of Radioac tive Waste: Final Report, Sandia Nationa l Laborat ories Report SAND81- 2573, NUREG/Clf-2452, Decembe r 1982.

21. Rush, F. E., Regiona l Ground-W ater Systems in the Nevada Test site area, Nye, Lincoln, and Clark Countie s, Nevada:

Nevada Depirtm ent of Conserv ation and Natural Resourc es.

Water Resource s - Reconna issance Series Report 54, 1970 *.

22. Re*ade, M. T. and McKay, E. D. Geology and Hydrolog y of Yucca Mountain and Vicinity . Nevada Test Site.

C~S/8116 R028, C.G.S .* Inc.~ Urbana. rllinois 61801. 1982.

23. Pepping. R. E .* Chu. M. s. and Siegel. M. D** A Simplifi ed Analysis of a Hypothe tical High-Le vel Waste Reposito ry in a Basalt Formatio n, Sandia Nationa l Laborat ories Report.

SAND82-1557. NUREG/CR-3.235. v. 2. 1982.

24. Freeze. i. A. and Cherry, J. A.* Groundw ater.

Pr~ntice -Hall Inc., Englewoo d Cliffs. N.J., 1979.

25. Guzowsk i, R. V., Nimick, F. B.* Siegel. M. D. and Finley.

N. c .. Reposito ry Site Definiti on in Tuff: Yucca Mountai n, Nevada, Sandia' National Laborat ories Report SAND82-2105. NUREG/CR-2937., to be publishe d.

26. Merkin, J. H..* Fiee Convection Boundary Layers on

.Axi-Symmetric and Two-Dimensional Bodies of Arbitrary

Shape* in a Saturated Porous Medium. Int. J. Heat Mass Transfer. v. 22, pp. 1461-1462, i979.

47. Interim Reference Repository Conditions for Spent Fuel and Comm*ercial High Level Nuclear Waste Repositories in Tuff.

Battelle Project Management Division (ONWl) NWTS-12, September 1981.

28. White, A. F., Claassen, H. c. and Benson, L. v .. The Effect of Dissolution of Volcanic Gl~ss on the Water Chemistry in a Tuffaceous Aquifer, Rainier Mesa. Nevada, Geological Survey Water-Supply Paper 1535-Q, 1980.

29. Winograd, I. J. and Robertson. F. N., Deep oxygenated Ground Water Anomaly or Common Occurrence?, Science, v .. 216, pp. 1227.-1230, 1982.

30. Allard, B., Solubilities of Actinides in Neutral or Basic Solutions, in Proceedings of the*Actinides 1981 Conferenc~: Oxford, Pergamon Press. 1982.

31. Letter from J. Serne, Battelle Pacific Northwest Laboratories~ to A. Muller, Sandia National Laboratories,

Subject:

Sorption Data for Radionuclides in Basalt Ground-Water Systems, dated May 13, 1981. Available in NRC PDR for inspection and copying for a fee.

32. Bae.s. c. F. and Mesmer, R. E. The Hydrolysis of cations.

Wiley Interscience; John Wiley and Sons. New York. N. Y.,

1976 .

. 33. Daniels, w. R., Erdal, B. R.* Vaniman, D.* T., Wolfsberg, K.* Research and Development Related to the Nevada Nuclear Waste Storage Investigations, Januaty l - March 31, 1982, Los Alamos National Laboratory Report LA-9327~ 1982.

34. Erickson, K. L .* Preliminary Rate Expressions for Analysis of Radionudlide Migration Resultirig from Fluid Flow Through Jointed Media, Scientific *aasis for Nuclear waste Management. Volume 2: New York. Plenum Press. p. 729-738.

1980. .

-98...:.

35. Eiickson. K. L., Fundament al Approach to the Analysis of Radionucl ide Transport Resulting fiom Fluid Flow Through Jointed Medi~. s~~dia National *Laborator ies Repbrt

.SANDB0-0 457, 1981.

36. Erickson, K. L .* Approxima tions for Ada_pting Porous Media Radionucl ides Transport Models to Analysis of Transport in Jointed Porous' Rock. Scientific Basis for Nucl_ear

Waste Managemen t. Volume 6: in press.

37. Crank. J., The Mathemati cs of Diffusion (2nd ed.).

Oxford, Clarendon Press. pp. 49-53. 1975.

~8. Rosen, J. B~. Kinetics *o~ a Fixed Bed System for Solid Diffusion into Spherical Par~icles: Jour. Chem. Phys .*

v. 20. no~ 3, pp. 381-393. 1952.

39. Rosen, J.B .* General Numerical Solution for Solid Diffusion in Fixed Beds: Ind. Eng. Chem .* v. 46, pp.

1590. 1954.

Volume 4 A Simplified Analysis of a Hypothetical Repository in a Bedded S-alt Formation

NUREG/CR-3235 SAND82-1557 WH TECHNICAL ASSISTANCE FOR REGULATORY DEVELOPMEtJT:

REVIEW AND EVALUATION OF THE DRAFT EPA STANDARD 40CFR191

-FOR DISPOSAL OF HI.GH-LEVEL WASTE VOL. 4 A SIMPLIFIED ANALYSIS OF A HYPOTHETICAL REPOSITORY IN A BEDDED SALT FORMATim1 R. E. Pepping M. S. Chu M. D. Siegel Manuscript Completed: April 1983 Date Published: April 1983 with contributions from:

Pei-Lin Tien*

Adel A. Bakr*

Sandia National Laboratories Albuquerque, New Mexico 87185 operated by Sandia Corporation for the

u. s. Department of Energy Prepared for Division of Waste Management Office of Nuclear Material Safety and Safeguards Washington, D. c. 20555 NRC FIN. No. A-1165

Science Applications, Inc.

ABSTRACT An ana lys is of a hyp oth etic tor y in a bed ded sal t for ma tion al nuc lea r was te rep osi -

ons tra te the app lica tio n of exi has bee n per for me d to dem -

stin g ana lyt ica l too ls to*

the ass ess me nt of com pl.i anc e of*

the rep osi tor y wit h the dra ft EPA Sta nda rd, 40C FR1 91 (Dr bee n dev elo ped by San dia Na tion aft #19 ). The too ls hav e al Lab ora tor ies for use by NRC in suc h ana lys es. The hyp oth etic al sit e is bas ed on dat a tha t are rep res ent ativ e of the con tin ent al u.s . The eff ect bed ded sal t geo log ies in s of unc ert ain ty in the inp ut dat a on the ass ess me nt of ted . Oth er sou rce s of unc ert ain com plia nce are dem ons tra-pre tat ion of the sta nda rd and ty res ult ing from int er-its. pro bab ilis tic nat ure are dis cus sed . The res ult s of the cal cul atio ns pre sen ted ind ica te tha t com plia nce wit h ach iev ed for the gro und wat er tra the dra ft sta nda rd may be nsp ort sce nar ios dep end ing on whi ch sou rce mod el *is use d.

(di rec t can iste r hit or bri ne The pen etr atio n sce nar ios poc ket hit ) ind ica te pot en-tia lly ser iou s con seq uen ces : how gat ed by pro per sit e sel ect ion eve r, .the se cou ld be mi ti-and .in stit uti ona l con tro ls.

-ii i-

Table of Contents Page.

I. Introduc tion ..*. .*. *.*.**.. . **.****. ******* 1 II. The Draft EPA Standard ........ ........ ..... 2 III. Sequence of Discussi on . . . . . . . . .. . . . . . . . . . . . 4 IV. The Hypothe tical Reposito ry **** ** * * * * * * * * * *

5 V. Radionu clide Release Scenario s and Probabi lities ******** *...*.*** ******** *.* 16 VI. Compute r Models (NWFT/DVM) Used for Groundw ater Transpo rt Scenario s .*.***.* ** 28*

A. The Groundw ater Transpo rt Scenario s (ffi'lFT/DVM) * ~ *****.. ~....... 28 B. Penetra tion Scenario s . * * * * * * * . * * . * . * * *

38

c. Constru ction of the CCDFs ***.*.** *.**.. 40 D. ~erisiti vity Arialysis Results *****.** *.* 56 VII. Conclusi ons . . . . . . .. . . .. . . . . . . . .. . . . . . . . . . . 58 Appendix A. The Mixing Cell Source Model

(Source #3) ******** *** * * * * * * * * * ***

A-1 Appendix B. Geohydr ologic Data for Bedded Salt *** B-1 Referenc es ...* ........ ....*... ....*... ........ .... R-1 V

Figures Page

1. General Setting of the Bedded Salt Refer-ence Site (Plan View) ..****..***. .*..**..*. 6

2. Schematic Cross-Section s Across the Subbasin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . 8

3. Floor Plan of the Reference Underground Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . 13

4. The U-Tube Flow and Migration Pattern for the Groundwater Transport Scenario .******** 18

5. Scenario 2 Geometry .......................... 22

6. Reference Area, A, Containirig M Spherical Br* 1ne

, Pockets . .rn . . . . . . . ** . . . . . . . . . . . . . . . . . . . . . 27

7. Flow and Transport Network Assumed by ID'VFT/DV~1 . * * * * * .. * . * * * * * * * * * * * * * * * * * * * * * * * * *

29

8. CCDF for Scenario 5, Direct Hit Scenario 42

9. CCDF for the Brine Pocket Penetration Scenario . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . 45

10. CCDFs for the Groundwater Transport Scenario With Source #1 ************ ******.*.* 46-48

11. CCDFs for the Groundwater Transport Scenaiio With Source #2 ************ ****.*.* 49-51

12. CCDFs for the Groundwater Transport Scenario With Source #3 **.*******.** ******** 52-54 A~l Implementatio n of the Mixing Cell Source Model for NWFT /DVM * * * * * * * * * * . . * * * * * * * . * * * * *

A-3 Vl.

Tables Page

1. Release Limits in the Draft EPA Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Stratigrap hic Units, Lithology , and Thickness of Hypotheti cal Bedded Salt Repository Site ********* *****.**** **** 9-10

3. Hydraulic Properties of Geologic Units, Bedded Salt Site ********** *~******* ******** 12

4. Radionucl ide Inventorie s (Ci) at Time of Closure (t=O) .: .**.**.*.* .**.****** ***** 15

5. Lengths .and Elevations Correspon ding to Figure 7 for the Groundwat er Trans-port Scenarios ****..*** ....****** .*..*..*** 30

6. Hydraulic Properties and Sampled Distrib\!ti ons ~ ..... *. . . . . . . . . . . . . . . . . . . . . . . 31

. 7. NWFT/DVM Source Models * * * * * * * * * * * * * * * * * * * * . * . 34

8. Sorption Data, Bedded Salt Site .***..*..* *...

35

9. Solubility Limits of Various Radionucl ides .** 37

10. Repository Hazard Index ********** ********** ** 38

11. Probabili ties (per 10,000 yr) and Conse-quences for the "Direct Hit" Scenario ***** ~ 41

12. Probabili ties {per 10,000 yr) and Conse-quences for the Brine Pocket Scenario ****** 44 B-1 Ra Ranges in Aquifer (Bedded Salt) *********.

B-1 B-2 Bedded Salt Hydraulic Parameter s ***.****** *** B-2 V11

_Tables Page

1. Release Limits in the Draft EPA Standard . . . . . . . . . . . . . . *. . . . . . . . . . . . . . . . . . . . . .3

2. Stratigr aphic Units, Litholog y, and Thickne ss of Hypothe tical Bedded Salt Reposito ry Site ........ ........ ........ 9-10

3. Hydrauli c* Properti es of Geologic Units, Bedded Salt Site . . . * . . * * . . * . * . *.. . . . . . . . . . . . 12

4. R~dionu clide Invento ries (Ci) at Time of Closure (t=O) .... , . . . . . . . . . . . . . . . . . . . . . . 15

5. Lengths and Elevatio ns Corresp onding*t o Figure 7 for the Groundw ater Trans- 0 port .Scenari os . . . . . . . . . . . . . . . . . . *. . ... . .. . . . . . 30

6. Hydraul ic Properti es and Sampled Distribu

. tions. . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . 31

7. NWFT /DVM Source Models . . . . * * . . . . . . . . . . . . . . . . . 34

8. Sorption Data, Bedded Salt Site ...*.... ....... 35

9. Solubil ity Limits of Various Radionu clides* .*. 37

10. Reposito ry Hazard Index . . * * . . . . . * * * . * * * * . . . . . 38

. 11. Probabi lities (per 10,000 yr) and Conse-quences *for the "Direct Hit" Scenario ***..* 41 12 .. Probabi lities (per 10,000 yr) and Conse-quences

for the Brine Pocket Scenario .***.*

44 1

Vl.l.l.

I. Intro ducti on Backg round The Envir onme ntal Prote ction Agenc y (EPA) has draft ed a stand ard *for prote ction again st highl y radio activ e waste s to be store d under groun d. The stand ard, which will apply to all geolo gic .repo sitor ies, is still being devel oped an inter nal worki ng draft is avail able [l]. The Nucle and ar Regu latory Cornm i15sion (NRC) will enfor ce the stand ard, is devel oping appro priat e Feder al regul ation s [2]. and To assig n quan titati ve, that. is, nume rical value s such facto rs as relea se of radio nucli des from a geolo to gic repos itory , the EPA used simpl e comp uter mode ls [3].

The agenc y expec ts the NRC to use comp uter mode ling to asses s

comp liance with the EPA Stand ard. To suppo rtNRC , Sandi a

Natio nal Labo ratori es~ (SNL) is devel oping comp uter mode that may be used in such* a comp liance asses smen t [4] ls

~ We expec t that NRC will use the model s to evalu ate appli tions for licen se to const ruct actua l repo sitor ies. ca-The Depar tment of Energ y (DOE) is also invol* ved in that it selec ts actua l s.ites for geolo gic repo sitor ies and subm its appli catio ns to const ruct them. *To deter mine their suita bilit y for waste dispo sal, the DOE .is inve gatin g basa lt and tuff flows , bedde d salt and grani te sti-for-matio ns, and salt domes . Some of these geolo gic forrna tioris are beirtg chara ct~ri zed, but no spec ific sites -

have yet been selec ted. Neith er are they mode led in enoug h de-tail to evalu ate any given site to the rigor ous comp liance requi remen t,s set down by the draft EPA Stand ard. Howe ver, whate ver "infor matio n does exist can be suppl emen ted with gener al infor matio n taken from such sourc es as simil ar .

forma tions or host- rock descr iptio ns, hydra ulic prop ertie s, and geoch emica l chara cteri stics . We can then apply the mode ls thus devel oped to evalu ate a simil ar but hypo thetic al repos itory . Using the capa bility of SNL mode ls as a base, we then deter mine how well the hypo thetic al site meets the draft EPA Stand ard: does it comp ly; Scena rios To *selec t scena rios for d.eta. iled analy sis, we used the resul ts of risk analy sis metho ds devel opme nt progr ams at SNL [SJ. In.th at work a numbe r of scena rios were iden~

tifie d that may be impo rtant in unde rstan ding .risks real repo sitor ies. Most of those scena r"ios invol ved from flowi ng groun dwate r intru ding into the back filled regio ns of the repos itory . Vario us water -bear ing geolo gic strat a were the sources of.groundwat er as well as potential paths for migrating radionuclide s.

After considering the previous scenario development efforts and the details of the-repositor y (discussed below),

we chose two types of scenarios: groundwater transport and penetration. In the first type of scenario, radionu-clides are presumed to be released at low rates over ah extendeq period. Radionuclides are transported to the accessible environment by the natural, or slightly per-turbed, groundwater flow system. In penetration scenarios, radionuclide s are transported rapidly to the acce.ssible environment over a short period.

II. The Draft EPA Standard The EPA assumes that natural or man-induced disruptions will cause the repository 1:.o release some radionuclide s ahd that they will find their way to the accessible environ-ment.* In Draft #19 of its standard, the EPA sets the limits for total integrated discharges that may be expected from such disruptions (Equation (1)):

Q.

EPA Sum = I: l.

(1)

i. EPA, l.

where: total integrated release of radionuclide i

= release limit for radionuclide i.

The sum over*i includes all radionuclide s present in the waste *. The proposed rele~se limits are listed in Table 1.

A more detailed discussion of the draft EPA Standard, its interp~etatio ns and implementatio n in assessing compli-ance are.presented elsewhere [6,7].

The accessible environment is "any location on the surface where radionuclides may be released or any aquifer that may be contaminated by radiohuclides at a distance of 1 mile from the perimeter of the underground facility."

Tab1 e*1

.Rele ase Limi ts in the Draf t EPA Stan dard Radi onuc lide Rele ase Limi t Amer icium -241 10 Amer iciuin -243 4

Carb on -

200.

Cesiu m-13 5 - - - - 2000 Cesiu m-13 7 500 Nept unium -237 - - - - - - - 20 Pluto nium :-238 400 P lut6n i um-23 '9 100 p*1u toni um-2 40 100 Pluto nium -242 - - - - - - - 100 Radiu m-22 6 - - -

3 Stron tium. .:.90 - - - - 80 Tech netiu m-99 2000 Tin-1 26 80 Any othe r alph a-em itting radio nu~l ide - - ~ - - - - - - - 10 Any othe r radio nucl. ide which does not emit alpha part icles - - - - . - - - 500

-3:-

III. Sequence of Discussion Below we will discuss our *findings as follows:

1, Description of the hypothetical repository

-rock types found at the site

-hydraulic properties of the rock formations

-properties of any aquifers

-sizes of various formations,

2. Scenarios -- such situations or potential st~tes of the repository that may lead to release of radionuclide s -- and their probabilities of occurrence,

3. Models -- description and details of their application to this c!nalysis,

4. Required geochemical data,

5. Quantitative data -- numerical results from this analysis: how much, when, how long?

As we discuss our findings, we are assuming that the reader is famil1ar with the problems of disposal of radio-active wastes and the methods developed at SNL to address them.

IV. The Hypoth etical Reposi tory If we are to use the SNL models to verify compli ance with the draft EPA Standa rd, we need a descrip tion of the reposi tory to be license d. The descrip tion should include the geolog ic, hydrol ogic, and geoche mical proper ties of

the site; the shape, size, and layout of the engine ered undergr ound facilit y; and the nature of the nuclea r waste.

Bedded Salt Site The bedded salt reposit ory site is located in a subsid iary basin within a major sedime ntary basin. The crust of the region sank, allowin g sedime nts to accumu late.

Beginn ing 300 million years ago, within this depress ed region , small blocks of the crust were displac ed along deep-s eated faults, creatin g a system. of subbas ins sepa-rated by baseme nt uplifts . The subbas in where the site is located (Figure 1) is bounded on the north by Uplift A and on the south by Arch M. - River C, approx imately 40 to 50 miles to the north, flows eastwa rd. A small river, River R, about 25 miles to the east, flows northw est to southe ast. The uplift and the arch are bounde d by high-angle reverse faults that steepen with depth, indica ting that the subbas in is a block of crust that was uplifte d with respec t to surroun ding region s. The subbas in is situate d within a tecton ically stable region that is associ ated with a shield area to the north. Severa l faults strike northw est just ~outh of the uplift, but the rest of the subbas in lacks evidenc e of faultin g or volcani sm.

Curren t seismi city in the region is localiz ed along the uplift, which is the domina nt structu ral feature and the focus of any seismic energy release ; most earthqu akes in the area have foci in the baseme nt. In the past, only a few earthqu akes with intens ities betwee n V and VI on the Modifie d Mercal li Intens ity Scale have been registe red, and none with destru ctive intens ities of VII and above. Accord ingly, this region is in Zone 1 on a seismi c-risk map, which means that minor earthqu ake damage may be expecte d in the next 100 years. Howeve r, the level of shaking hazard s is expecte d to be less than 0.04g, where g is the accele ration due to gravity .

Active subsur face dissolu tion* is eviden t along the northe rn and eastern margin s of the subbas in; collaps e feature s such as sinkho les, depres sions, small faults, and fractur es are common within the salt dissolu tion zone, which is at least 10 miles from the site. The mean rates of salt dissolu tion range from 19 feet (6 m) to 1150 feet N

1 REFERENCE SITE 0 SCALE 40 MILES Figure 1. General Setting of the Bedded sa*1 t Reference Site (Plan View).

(350 m) per 10,000 years. Salt dissolu tion along the north side is slower than along the east side of the subbas in.

The subbas in is a relativ ely shallow , contin ental-interio r basin. The Precam bri.an baseme nt is at most, 10,000 feet below the surface . The reposi tory is located in the center of Unit SA (Figure 2), which consis ts of 1,000 to 1,200 feet of evapor ites, mainly halite with small amount s of anhydr ite and dolomi te (Table 2). Unit SA is overla in by Unit FSA, which ranges in thickn ess fro~ 550 to 850 feet and consis ts of siltsto ne; sandsto ne, salt and anhydr ite. Unit FSA is an aquita rd slowing the downwa rd moveme nt of ground water. Overla ying the PSA.un it is 300 to 900 foot-th ick Unit D, which consis ts of sand and clay, and is a minor aquife r. Unit O, which. overlay s Unit D, is between 50 to 300 feet thick and is the major unconfi ned aquife r in the area. The major constit uents of Unit Oare sand and clay, with small amount s of gravel and some caliche that thinly

.covers the surfac e.

Below Unit SA is Unit CF, which ranges from 1,750.

to 2,050 feet in thickne ss and is compos ed predom inantly of halite , anhydr ite, and clay. CF is also an aquita rd.

Below Unit CF is Unit WP, which is from 2,300 to 4,200 feet thick and. consis ts mainly of shale, limesto ne, . and sandsto ne. This unit, which is brine- satura ted, is consid ered an aquife r but with such low conduc tivity that.no pumpin g at all ~akes place.

Geoche mical analyse s of shale sample s from Unit WP show an average total organic carbon conten t of 2.4 percen t. The sedime nts of the layers deposi ted after Unit WP show a totai*o rganic carbon. conten t of up to 5.38 percen t.* Kerogen color, which indica tes therma l maturi ty when plotted agains t kerogen type, shows that sample s from this unit are in transit ion betwee n maturi ty

.and immatu rity, and that those of post Unit WP never reached temper atures high enough to genera te hydroc arbons .

This means that, since the site* is. away from any potenti a_l.

hydroc arbon reservo ir-, intensi ve explor ation and drillin g will not likely take place within the area.

About 50 miles west of the site, the shallow aquife rs (Units O and DL are recharg ed at a rate of betwee n 0.2 and 1.0 inch/y ear, but dischar ge ~long the eastern margiri of the subbas in. In these aquife rs, _the ground water.f lows slowly from west to east, several _ inches to a few-fe et per year. Flow in the overly ing aquife rs is driven by gravity .

The aquife r Units .o and D dip over a range of 10 to 50 feet N a PSA SA WP PRECAMBRIAN BASEMENT 0 50 MILES HORIZONTAL SCALE w b E PSA SA WP PRECAMBRIAN BASEMENT o* 50MILES HORIZONTAL SCALE*

Figure 2. Schematic Cross-Sections Across the Subbasin.

Table 2 Stratigraphic Units, Lithology, and Thickness of Hypothetical Bedded Salt Repository Site Unit Thickness {Ft) Lithology % Thickness.

0 50 - 300 silt 45 clay sand 50 gravel caliche <S D 300 - 900 shale 30 clay s.1ltstone 7 sandstone 60 conglomerate limestone <3 PSA 550 - 850 anhydrite *7 clays tone 8 salt 23 mudstone 22

~iltstone 28 sandstone 12

{cont 'ct)*

Table 2 (Cont'd)

Stratigraphic Units, Lithology, and Thickness of Hypothetical Bedded Salt Repository Site Unit Thickness (Ft) Lithology % Thickness SA 1000 - 1200 dolomite 13 anhydrite 22 claystone 5 salt 59.

mudstone 1

siltstone <l sandstone CF 1750 - 2050 dolomite <5 anhydrite 20 clays tone 15 salt 50 mudstone 5 siltstone 5 sandstone <1 WP 2300 - 4200 limestone 55 sandstone 9 claystone ! 36 shale J per mile. This results in a head gradie nt of 2 to 10 x 10- 3

drivin g horizo ntal flow within Units O and D. Vertic al gradie nts in Units O and Dare dowriwa rd and small in magni-tude. The disper sivity of Units O and Dis small, less than 100 feet, and typica lly tens of feet.

Unit WP recharg es very slowly -- much slowe.r than the shallow aquife rs -- a few huridred miles vrnst of the site and discha rges severa l hundred miles southe ast of the subbas in.

The briny ground water in this unit flows slowly , mostly from west to east, at a rate of a few inches per year.

Its hydrau lic gradie nt Jaries between 10 and 30 feet/m ile, i.e., from 2 to 6 x 10-

The vertica l hydrau lic gradien t in this unit, howeve r, is steep (about 1), and is directe d upward .

Table 3 lists ranges of horizo ntal and vertic al hydrau lic conduc tivities and porosi ties for each unit.

Values of *condu ctivitie s for the O and D units mean that approx imately 50 percen t of conduc tivity measur e-ments made in these units would fall in the given range.

For the remain ing units, the values indica te that 85 percen t of the measur ements would fall in the given range.

Engine ered Underg round Facilit y The DOE has conceiv ed a design for a subsur face facilit y where nuclea r wastes can be emplace d [8-lO]o We will use this facilit y for our analys es. Since the facilit y has already been describ ed elsewh ere [11], we will presen t only the few gross feature s that are import -

ant to our analys es. The reader is caution ed that the reposi tory being modeled is hypoth etical.

Dimens ions -- The mined reposit ory, which is located at a depth of 2,300 feet, has a storage area that extends over a 3,000- acre rectang ular area (15,370 ft by 8,600 ft).

A shaft pillar area extends 2,000 feet horizo ntally away from the waste* storage area, the "panha ndle" area shown in Figure 3.

Each storage room in the design is 4,000 feet (long) by 17.5 feet (wide) by 19 feet (high). For our calcula -

tions, we will assume the height to be 15 feet to accoun t for creep closure that takes place over the operat ional life of the reposi tory. The centra l co~rid ors, which are 18.5 feet (wide) by 19 feet (high), will also be calcula ted as being 15 feet (high).

Table 3 Hydraulic Properties of Geologic Units, Bedded Salt Site*

Horizontal Vertical.

Hydraulic Hydraulic Conductivity Conductivity Porosity Unit (ft/d} (ft/d) (dimensionless) 0 4 - 25 0.4 - 3 0.1 - 0.2 D 0.4 - 2.5 0.04 - 0,25 0.05 - 0.1 PSA 10 10- 2 10 10- 3 0.01 - 0.05 SA 10- 7 10- 3 10- 8 10- 4 0.001 - 0.01 CF 10 10- 3 10 10- 4 0.005 - 0.05 WP 10- 5 10- 2 10- 6 10- 3 0.01 - 0.05

Please refer to Table B-2 in Appendix B for original source and reference.

10~1 50ft 5220 U

// - j

'/

fl CONFINEMENT '/

RETURN AIRW AY (FL -199 0 ft) ft

. J ol co :

.. 'I 0

. 0

,.. I:

. I I-' u, (0 w

I co CONF~JEMENT1... _ .. _,,_

-RETURN

..........-+-+-f- --+

/J AIR\"IAY (FL -199 0 ft)

I I

' ,.I

(

N t I '\

.... ~ I ......

PHASE I AND II PHAS E Ill u

290 ft CROSS CUT 2000 -ACR E MINE *1000 -ACR E FUEL ASSEMBL V EXPANSION STORAGE ROOM Figur ~ J. Floor Plan of the Refer ence Under groun d Faci lity. FL-2 050. ft

{Sha fts are locat ed in the panha ndle sectio ri)

Capacity -- The 'mine can accept unreproc essed spent fuel assembl ies from approxim ately 86,000 metric tons of heavy metal (MTHM). This translat es to about 204,000 canister s containi ng either one assembly from a pressuri zed water reactor (PWR) or two from a boiling water reactor (BWR). The cylindri cal *caniste rs, which are 14 inches in diameter and 15 feet long, are to be placed in vertical holes drilled into the floor of the storage rooms. Total volume of excavate d salt is 1.56 x 108 cubic feet.

Backfill -- After wa$te emplacem ent is complete d, the mine is backfill ed with crushed salt, leaving a residual porosity of 20 percent.

Waste Inventor y The draft EPA Standard requires that all radionu clides in the waste inventor y (Tabie 1) be consider ed. However, we have found through experien ce that a subset of *the inven-tory (Table 4) dominate s the response and is sufficie ntly represen tative of the total inventor y to estimate complian ce.

Therefo re, we will use that subset in this study.

The inventor y listed in Table 4 is that of the full reposito ry at the time it is sealed closed (t = O).

Although the inventor y varies from canister to canister because _of reactor type (BWR/PWR), we will assume that each canister contains a uniform fraction of the entire inventor y: 1/204,00 0, that is, 4.9 x 10- 6 .

Table 4 Radionuclide Inventories* (Ci) at Time of Closure (t = 0)

Half-Life Radioisotope (years) Ci at t=O Pu240 6.76E3 4,6E7 U236 2, 39E7 3. 2E.4 Th232 1. 41El0 3.2E-5 Ra228 6.7 9.0E-6 Cm245 8. 27E3 3,3E4 Pu241 14.6 4.4E9

Am241 433. 2.0EB Np237 2.14E6 4.0E4 U233 l.62E5 8.0 Th229 7300 .. 1. 2E-2 Cm246 4710. 6.6E3 Pu242 3.79E5 1. 3E5 U238 4,51E9 3.0E4 Pu238 89. \ 3. lEB U234 2.47E5 1. OES Th230 8.E4 16.8 Ra226 1600. 8.lE-2 Pb210 21. 1. BE-2 Am243 7650. 1. 7E6' Pu239* 2.44E4 3. 2E7

0235 7.1E8 l.6E3 Pa231 3.25E4 3.4 Ac227 21.6 1.4 Tc99 2.14E5 1. 3E6 Il29 l.6E7 3.0E3 Snl26 1. OE5 5.2E4 Sr90 28.9 4.8E9 Cl4 5730. 4.8E4 Csl35 2.0E6 3.3E4 Csl37 30. 6.7E9

Inventories correspond to 86,000 metric tons of heavy metal V. Radionuclide Release *scenarios and.Probabilities The three types of scenarios with radionuclide trans-port that we analyzed were groundwater transport, drilling into a canister, and brine pocket penetration.

In all cases, the sealed repository is violated either

because mineshaft seals f~il or because exploratory drill holes penetrate the underground engineered facility. The draft EPA Standard requires that each radionuclide release have an associated probability assigned to it. Since all

. scenarios that we considered were caused by either. the shaft 1

seal failing or by drilling, we had to determine the likeli-hood that!

either would . happen.

Since Unit WP has low hydraulic* conductivity and ground-water flows through it. extremely slow°ly -- a few inch.es* per year -- we will ignore it as a ~ource of groundwater or a migration path.

Wells sunk into Unit WP could shorten the path of radionuclide~ to the accessible environment. However, because of its tightness, salinity, and overlying units of greater transmissivity, we do_not feel that wells are likely to be drilled into the lower-units for the extraction of water. Also, the natural discharge loca-tion for the unit is more than 100 miles away. With the groundwater moving at 1 mile/1,000 years (5.28 inches/

year) it would take over 100,000 years for the radionu-clides to escape. This time is much greater than the 10,000-year limit set by the draft EPA Standard.

We should note that the objective of this study is to choose and analyze a set 6£ representative scenarios.

As will be shown, the. scenarios chosen will indeed be important scenarios in the compliance assessment of the assumed repository*. This is not to say that they are the only scenarios,. A full scenario development, char-acterization, and analysis is beyond the scope of this' work.

Probability of Seal Failure Without a detailed study of the properties of sealing materials, we can only assume a non-mechanistic probability of their failure. Thus, we assume that:

Probability of )

shaft seal failure} = 0.001 at 1000 years }

For our calculations, we also assume that the shaft seal remains defective throughout the calculation, that is, it is not resealed.

Groundwater Transport Scenarios In order that the Units (0 and b) overlying the back-filled repository be able to transport radionuclides, two hydraulic conduits are required between them. One allows water to enter and contact the canisters. The other carries

,contaminated water back to the geologic units. The two conduits and the repository would thus form a U-shaped path, called a U-tube (Figure 4).

The vertical conduits could be formed along former mine shafts leading to the repository whose seals had failed. Another possibility would be an inadvert~nt pene-tration by exploratory drill holes made by future genera-tions seeking petrochemicals or evaporite minerals.

In Figure 4, the conduit to the left is either a mine shaft whose seal.has failed, or a borehole. The one to the right is a borehole. Water is driven through the u~

tube by the head difference between the vertical conduits and the units overlying the,reposi~ory. The difference is caused by the water flowing horizontally 1

through Units 0 and D.

Below, we analyze two variations of the characteris-tics of the *overlying aquifer. In one we assume that' Unit O is nearly saturated and that the vertical legs of Figure

,4 connect with it. Water and radionuclides flow from the backfilled regions back into Unit o. Once there, the

radionuclides are transported through the unit.

In the other variation, we assume that Unit O has been depleted, say for irrigation. Unit Dis then the migration path for radionuclides, although slower be-cause of its lower conductivity.

Probability of U-Tube Formation -- To determine the likelihood that a borehole will intrude into the :repository; we first assume that the drilling rate into the 3,000-acre tract is 1~9 x 10- 3 /year. This rate is relativeiy low for drilling into strata containing bedded salt [4]. However, it is a reasonable value considering the thermal maturity of the strata, discussed previously in the description of the report. The floor space of the engineered facility co-vers a smaller area than that of its gross extent, typically UNIT OORD ... _G,...flOUNDWA°lER FLOW ... ...

I'-.-

PSA ! 4 HEAD DIFFERENCE

. t

'~

'I I

I-'

l i 00 I

SA ! ... ... ... 1 BACKFILLED REGION Figure 4. The- U-Tube Flow and Migration Pattern for the Groundwater Transport Scenario.

25 *percent or less extracti on ratio. In- the assumed design,. this fraction is less. than 10 percent [8-10].

For the calculat ions presente d in this report, we assumed this fraction to be about 15 percent. Thus, the.num ber of borehole s expected to penetra te the back-filled regions in 10,000 years is:

19 X 0.15 = 3 We can thus assume that three borehole s are expected to penetra te the backfill ed regions during the 10,000- year period.

However , other factors enter the picture. If water is to flow through a U-tube, there must be enough driving head. For example, in the case where water origina tes in Unit O and returns loaded with iadionu clides, there is a minimum distance that must separate the vertica l legs of the U-tube. This distance is determin ed by applying the DNET Model [12]. The water in the U-tube's entry leg is fresh until it comes into contact- with the salt. There-fore, the exit leg contains *saturate d brine, which is heavier . Given the hydraul ic gradien t of tinit 0, the minimum downdip separati on calculat es as 11,500 feet.

In the case where water originat es from and returns to Unit D,*both vertical legs are filled with brine.

Therefo re, there is no differen ce in their weights and two or more holes, regardle ss of separati on, may form a success ful U-tube, as long as both penetra te the.back -

filled regions.

To impleme nt all our assumpt ions, we further assume that explora tory drilling is a Poisson process with a dis-tributio n on the number of borehole s into the 450-acre (15 percent of 3,000) target area given by P(n) = *( 5) n!

where: A.T = 3.

In the Unit O case, where we require a minimum distance of 11,500 feet, we must adjust the value of AT~ The adjust-ment needed is a scaling of the val~e of AT by the ratio of the target area to 3,000 acres.

We will consider four variations of the U-tube scenario. In .two of the variations, Unit O will .be assumed to transport the radionuclides . In the other two, Unit D will be assumed to transport:.*the radionuclide s.

For each of the assumed major transporting units, two ty~es of vertical conduits (Figure 4) will be considered.

In all the U-tube scenarios analyzed, the vertical conduit at the right in Figure 4 will be assumed to be formed by one or mc:ire*borehol es. The conduit at the left of Figure 4 will be assumed to be one or more failed shaft seals in one 'case, and one or inore boreholes in the other. In the discussion that follows, probabilities for these scenarios will be given. In order to describe .the hydraulic properties of the vertical iegs, conditional probabilitie s will also be needed to describe the number of boreholes tha~ may occur. These will also be given in the following discussion:

Scenario 1 ~- Water originates in and returns to Unit o.

The entrance leg is a shaft whose seal has failed and the exit leg is one or more boreholes. Both legs an:? separated by at least 11,500 feet*. The. size of the target area (Figure 3) is approximated as:

Area= (17,000 - 11,500) x 8,600 feet 2 - 1,086 acres.

Thus, we scale >. T appropriately to get ( >. T) ' :

1,086 Acres

(>.T)' = >.T = 1.09 (6) 3,000 Acres Using Equation (5), P(O) = 0.34 and the probability of one or* more holes penetrating the target is p~ 1 = 1 - 0.34 = 0.66.

Therefore, the probability that Scenario 1 will occur is:

pl= p shaft

P 0.001

0.66: 6.6xlo- 4 (7)

We can now use Equatio n (5) to. genera te a condit ional probab ility, Pc(n) distrib ution on the number of bore-holes in the 1,086 x 15 percert t target area:

n 1 2 3 4 5 6

7. > S Pc(n) 0.56 0.30 0~11 0.03 0.01 0.0011 l.7xl0 -d* nil Scenar io 2 -- Water origina tes from and returns to Unit o. Both legs *of the U-tube are two or more boreho les separa ted by at least 11,500 feet. Since any two boreho les separa ted by that distanc e can form a succes sful U-tube ,

we need a convol ution of probab ilities of boreho les in differe ntial. target areas at greate r than minimum sep~ra -

tion. To avoid this compli cated compu tation, we presen t a simpli fied treatm ent to estima te the number of boreho les, ignorin g the 2,000- ft long "panha ndle" of the reposi tory since no waste is stored there (Figure 5).

The two 2,700- ft section s at each end of the reposi -

tory are targets fbr the boreho les forming a U-tube with those at the opposi te end. The size of each target area is thus 2,700 feet x 8,600 feet= 533 acres. Theref ore, adjust ing XT gives us,

533 (AT) I - A T - - - =0.53. (8) 3000 The probab ility that there will be no boreho les in a target area that is 15 percen t of 533 acres is Q.59

[Equat ion (5)], so that the probab ility of one or more boreho le at each end is*

P 2 = (1 - .59) 2 = 0.17. (9)

I. . .-- --

15,400 ,1 --- ~-I I I I

I I

IT=

N I I N

I I . I

._ I I 0 11,500 ft *1 0

I <D I I CX)

I I

1 I

I I .

PANHANDLE I I I I

~2700 ft~-l~* --10,0 00 ft ____.-.. ~1-. 2700 ft-I Figure 5. Scenario 2 Geometry \

However, in orde~ to perform our calculatio ns, we need the distributi on of the number of boreholes . This number can be generated from Equation (5) to give us a condition al probabili ty distributi on of boreholes in each target area:

n 1 2 3 4. 5 6 > 7

.7549 .2031 .0364 .0049 .0005 .00005 nil.

Scenario 3 -- Water originates in and returns to Unit D. One leg of the U-tube is a shaft whose seal has failed and the other is one or more boreholes at any distance, not exceeding the size of the backfilled regions.

We use the same calculatio ns as for Scenarios land 2.

However, we do not adj"ust for target area and insfead use

>.T = 3. Using Equation (5), we calculate the probabili ty of one or more boreholes penetratin g the target area as P> 1 = 0.95 so that the probabili ty of this scenario occurring is:

P3 = Pshaft

P~1 = 0.001

0.95 = 9.Sxio- 4 (10)

Thus, the condition al probabilit y distributi on on the number of *boreholes is:

n PcM n ~chl l 0.16 6 o.os 2* 0.24 7 0. 0.2 3 0.24 8 0.01 4 0.18 9 0.003 5 0.11 10 0.001

> 11 nil.

Scenario 4 -- Water originates in and returns to Unit D. Both legs of the U-tube are boreholes with no minimum separation . No adjustmen t of >.Tis needed and we use

>. T = 3. By using Equat1.on {5), we cal cu late the prob-ability of two or more boreholes penetratin g the target area as P> 2 = 0.80 _ P . The condition al probabili ty of distributi on is 4 n ~cM n P cJE.)

2 0~28 7 0.03 3 0.28 8 0.01 4 0.21 9 0.003 5 0.13 10 0.001 6 0.06 > 11 nil.

II

- I

1

Since we cannot assume Unit Oto be both saturated and depleted, we assume each of these possibilities to be equally probable. This translates to an additional factor

.of 1/2 on the probabilities above. Also, we treat only one scenario at a time. For example, we do not consider a U-tube formed by a failed shaft ~eal which, after sub-sequent drilling, becomes a U-tube with boreholes providing additional water conduits. Thus, the shaft seal failures compete with boreholes for U-tube formation~ Including the factors of 1/2 for Unit O vs Unit D scenarios, we calculate probabilities for the mutually exclusive scenarios, Pi' pl I

= 1/2 pl (1 1/2 P2)

P2 I

= 1/2 P 2 - (1 1/2 P1)

P3 I

= 1/2 P3 (1 1/2 P4)

P*

.4 I

= 1/2 P4 (1 1/2 P3)

In su~ary, the probability assigned to each scenario, p, I I l.S:

l.

Scenario p. P* I

-1 -l.-

1 .00066 .00030 2 .17 .0850

'l

.J .00095 .00029 4 .80 .40 Penetration Scenarios Scenario 5: The canister "direct hit."

In this scenario, the radionuclides move to the surface directly and rapidly. While sinking a borehole, possibly while exploring for minerals, the drill bit strikes a waste canister and brings. a fraction of the contents to the su:r-

face.

In the scenarios pre~iously described, we determined that in 10,000 years, 19 boreholes could be expected over the 3,000 acre site. The same probability applies to this pene tratio n scena rio. Each boreh ole will prob abili ty of makin g a "dire ct hit". on a canishave ter. The a fixed prob abili ty is determ ined by comp aring the area of the waste canis ters with that of the facil ity.

Since there are 204,0 00 canis ters, each with an end

~rea df 1.15 foot 2 , any drill bit pene tratin g the back-fille d repos itory has a prob abili ty of hitti ng a canis of ter 2.04

10.5 cani sters *

1.15 foot 2 /cani ster (11) 15,37 0 feet* 8,600 feet

= 1. 8

10- 3

For n boreh oles, the prob abili ty of N direc t hits will be given by a binom ial distr ibuti on, n!

P(N,n ) = ~~~~~- (12)

N! (n-N) !

Thus, the prob~ bility of N hits is:

00 P(N) = L n=N p(n)

P(N,n ) (13) 00

= L n=N n!

where AT= 19 and Phit = l.8E- 3 A more detai led analy sis of this scena rio migh the spati al exten t of the drill bit, the drill ing t,i,nc lude direc tion, and the distr ibuti on of waste withi n the canis ter.

Scenario 6: Brine pocket pen~tration We have not had time duiing this study ~o analyze this scenario. in detail. However, it has been suggested as a potentially important scenario to be considered when analyzing risks from nuclear waste disposal [13].

The suggestion is that for a specific repository site, approximately i borehole in 27 will hit a brine.pocket

[13]. Therefore, we use this number with some other assumptions to decribe this scenario~

We use the probabilistic expression of Equation (13) because conceptually , the canister "direct hit" scenario is the same as that of the brine pocket penetration (Figure 6), the brine pocket now being the target, rather than the canister. Therefore, we have to develop an expression for Phit" As indicated in Figure 6, we assume that M brine pockets exist below the horizon of the* subsurface facility, with an area, Am. Each brine pocket is spherical with a cross-section al area, a, projecting to the surface. We assume that the ratio of total brine pocket area, Ma, to Am is a constant, a, i.e.,

Ma = a Am.

The constant a then gives the probability that a random drill bit will penetrat~ a brine pocket. A value of 1/25 was given for a with no mention of the thickness of the salt layer [13]. However, since we are concerned only with the lower half of the salt layer, we will assume that a = 1/2 *

1/25 = 0.02 This value will be used for Phit in Equation (13) to evaluate this scenario.

(0 8

8 8

Figure 6. Reference Area, A.n, Containing M Spherical Brine Pockets. (tach brine pocket has a*

projected area, a, at the surface.)

VI. Computer Models (NHFT/DVM) Used for Groundwater Transport Scenarios We used different models to estimate discharges expected from the various scenarios. For groundwater transport (U-tube) scenarios,* we. used the I:TI'lFT/DVM model [14] developed at SNL for the NRC. For the pen-etration scenarios, we used more simplistic model~.

A. The Groundwater Transport Scenarios (NWFT/DVM)

This model is used to calculate time-depende nt discharge rates of radionuclides into the accessible environment for the four groundwater transport scenar-ios. Figure 7 shows the simple network of points and distp.nces used in .the calculations . In the figure, "L 11 indicates th~ length between junctions at elevations, 11 d 11 ; and "p" .is the hydraulic pressure of the aquifer.

The numerical values assigned to the J's and d's vary from scenario to scenario. *These values are presented in Table 5.

The upper horizontal legs represent the overlying aquifer, either Unit O or Unit D, the vertical legs represent the borehole(s) or failed shaft, and the lower horizontal le~, 1 Pepresents the backfilled region.

6 We used the Latin Hypercube Sampling Method [15] to select input data for flow and transport calculations (Table 6). For example, to calculate discharges* in each groundwater. transpOrt scenario, we chose 50 combinations of input data (vectors) from the distribution s in the table. We repeated this procedure three times so as to observe the effects of sampling error on the calculated discharges.

In order to avoid physically unreasonable combina-

.tions of porosity and hydraulic conductivity , we assumed a rank cbrrela,tion of 0.7 when sampling these parameters for any feature [15]. Leg 6 is the backfilled repository, which is a hydraulic "short circuit" between legs 4 and and has c:1n arbitrarily high hydraulic conductivity of 10 g

feet/day.

The NWFT/DVM Model also requires that we assign a value to the cross-section al area of this "short circ.uit".

Depending on the source model (see below), we 1ssign an end-view, cross-section al area of 1.3 x 10 5 f t , if the entire waste inventory is available to access by ground-water. If the available fraction is proportional to the UNIT O OR D I d1 I\..)

\0 d2 d3 d4 I P1: :

P4.

' 11 .i.2 13 UNIT PSA 14 15 UNIT SA d5 Fi9u re 7.

Flow and Tran spor t Netw ork Assu med by NWFT/DVM.

Table 5 Lengths and Elevations Correspon ding to Figure 7 for the. Groundwat er Transport Scenarios .

Index, i: 1* 2 3 4 5 6 lengths, 1.

1 (feet)

I 1

.Ul 10.0, 000 17,370 5,280 2,000 1,878. 17,370 C 0 ltj.,.,

1-1 1-1 E-t ra 2 102,000 15,370. -5, 280 1,986 1,878 C 15,370 1-1 QJ a, C)

~Cf.l ra 3 100,000 17,370 5,280 1,500 1,378 17,370 3: ~

'O f..l C 0

l ~

0 4 102,000 15,370 5,280 1-1 1,486 1,378 15,370 c.,

Elevation s, d, (feet) l.

I r/l 1 859 159 37 0 -1,841 -1,841

~* 0 ltJ *ri 1-1 1-1 E-t* ra

~ 2 859 145 37 0 -1,841 -1,841 1-1 a, QJ C)

~ Cf.l ra

~ .µ 3 359 ~341 -463 -500 -1,841 *-1,841

'O H

§&

0 1-1 c.,

4 359 -355 -463 -so*o -1,841 -1,841 Table 6 Hydraulic Properties and Sampled Distributions*

Conductivities are assumed to. be lognormally .distributed.

Porosi.ties are assumed to be normally distributed. The given ranges specify the 0.001 and 0.999 quantiles of the assumed distributions.

0.001 0.999 Property Quantile Quantile

1. Hydraulic Conductivity (ft/day) of Unit 0 0.15 680.

2. Porosity of Unit 0 0.1 0. 2 .*

3 *. Hydraulic Coriductivi ty.

(ft/day) of Unit D O. 015" 68

4. Porosity of Unit D 0.05 0.1

5. Hydraulic Conductivity

.( ft/day) of Failed Shaft o.os 50.0 6 .. Porosity of Failed* Shaft o.os 0 .. s

7. Hydi;-aulic Conductivity (ft/day) of Boreholes 0.05 25.0

8. Porosity of Boreholes o.os o.s

The references* and data ranges supporting the .assumed values for the rock units in this table are given in Appendix B.

. \'

number of boreholes, the cross-section al area can be de-duced by the number of borehole.s multiplied by the cross-sectional area of the penetrated storage room (262.5 ft 2 ).

Actually, since leg 6. is a "short-:-circu i t" anyway, these assignments are of little practical value, but are assigne~

because the model requires them.

Note.that we have consistently assumed the maxi-mum lateral separation between the vertical legs for sim-plicity. Due to the density.diffe rence between fresh water and brine, a minimum distance of 11,500 ft between legs -4 and 5 is required to push the brine upward in leg 5 for Scenarios 1 and 2. Therefore, the assumption of maximum later~l separation is fairly representativ e for those sce-narios. For the remaining two*u-tube scenarios, the actual separation between legs 4 and~ could be small~r. However, due to the assumption of a "short circuit" through leg 6, the separation derined in the computer raodel is immaterial.

The cross-section al area of the U-tube legs { 1 , i )

depends on whether the legs are mineshafts (2,000 f~ 42 5

) or 2

boreholes (0.8 fooi /hoie). We ~lso ~ssume that the inlet and outlet pressures (p and p ) are zero since the aqui-fers ar~ unconfined.

1 ** 4 .

We have neglected dispersivity in our ffilFT/DVM cal-culatibns. We-feel this is justified since the dispersi-vity is s.mall for the assumed repository.

More import-antly, the effect of dispersi vi ty is to make the leadin*g edge of the discharge curve more* diffus*e. Since :we are calculating time-integrat ed discharges, we expect little error from the neglect of dispersion.* The error is lar-ges~ when integration begins or ends *during the diffuse part of the discharge. The effect. is to assign a .portion of the discharge to the adjacent 10,000-year period.

In our calculations, we have assumed three models for NWFT/DVM, each describing a different source of nu-clide release (Table 7). We did not perform detaiied modeling of each source; the sources are simply assump- .*

tions chosen to demonstrate their efficacy.

Source #1 -- This source complies with the release rate limit imposed by NRC [2l, that is, 10- 5 /year of the entire radionficlide inventory at i,000 years. 0e have assumed that the inventory is.homogeneo usly dispersed throughout the wasteform so that if Ni(t) denotes the ith radionuclide in th~ inventory at time t, in the absence of releas e, the releas e rate*o f that radion uclide is (10-S to 10-7) x N, (t). We assume that the entire waste inven tory is availa ble i for transp ort. .

Source #2 -- This source has the same range as Source .

1 in terms of releas e rate, but the amoun t of \\Taste avail -

able for transp ort is redtice d. E~ch boreh ole allows only the amoun t of waste in the* partic ular penet rated backf illed storag e room to be availa ble for transp ort. This model would be valid if we assume d* the. flow throug h the backf illed region s *to be locali zed to the vicin ity of the boreh ole (there a~e 106 storag e rooms ).

Source #3 -- Thfs source resem bles Source #2 but.al lows the backf illed rooms to be modele d as a mixing cell where wastef orrns are leache d.unif ormly (Appen dix A). The range of leach rat.e has been change d- to allow a more rapid rate in the breakd own of wastef orms. The calcu lated discha rges thus show how a less stable wastef orm can be compe nsated if mixing mecha nisms can be assum ed. We also allow solu-,,

bility limits to apply to radion uclide conce ntrati ons in the mixing cell.

Geoch emical Data We assume that retard ation of radion uclide s occurs

only in the aquife r uni ts ( 0 and D) of the transp ort path. The retard ation factor , R, is thus given by

( 1-<P)

R = 1 + Ra P .<j) (14) where P = the assume d rock densit y (2. 7 g/ c~3 )

¢= the unit's poros ity (see Table 6)

Rd= the,so rption ratio* (Table 8)

We use the symbo l Rd to signif y an exper iment ally-d eterm ined radion uclide distri butio n coeffi _cient where* we do not assum e that equili brium has been achiev ed. Althou gh they are called "sorp tion ratios ," there is no assura nce that sorpti on is.the only chemi cal proce ss occur ring during the exper iment s. We use the te 7m.Kd. in ~ts cl~ss ical sense, ~.e., ideal ion ex-change equili brium involv ing tr~ce const ituen ts.

Table 7 NWFT/DVM Source Models Available Leach Rate**

Model Source Fraction of (Release} Leach Rate Number Type . Inventory Range (yr- 1 } Distribution 1 Leach Limited 1.00 10- 5 to 10- 1 Log Uniform 2 Leach *Limited . .jj.*.

':I' of boreholes 10- 5 to 10- 7 Log Uniform IOo*

3 Mixin9 Cell # of boreholes 10- 3 to 10- 7 Log Uniform 106*

I I

106 denotes the number of storage rooms in the repository

~-----~~-

Tabl e 8 Sorp tion Data ,

Bedd ed Salt Site

Perc enti les of assum ed Elem ent logn orrna l dist ribu tion 0.00 1 0.99 9 Cm 10 2 105 Am 50 10 4 Pu 30 10 4 Np 2 400 u .01 270 Th 103 10 5 Ac 10 2 105 Pb 100 500 Ra 100 500 Pa 0.01 10 4 Sr 1.0 2000 c*s o.. 01 3000 I 0.01 100 Sn 0.01 5*00 Tc 0.01 3 14c is assum ed to be com plete d unre tard ed, i.e. , Ra=O .

Sup port ing data and refe renc es are summ arize d in Appe ndix B.

The LHS method is. used to select values from the distri-butions for. each input vector according to the distributions given in Table 8. Data appearing in Table 8 are taken from Reference [16] and the supplemental information fror.i the open literature.

Solubility limits are needed for Source #3 to treat concentration limits on each radionuclide . These data are presented in Table 9. Elements not appearing in Table 9 are assumed to have unlimited solubility.

The sources for the data used in compiling the ranges for the hydrogeologi c and goechemical variables are identi-fied in Appendix B.

-36..;.

Ta ble 9 So lub ili ty Lim its of Va rio us Ra dio nu cli des The giv en ran ges spe cif y the 0.0 01 and 0.9 99 qu an an ass um ed log no rm al dis til es of t~i bu tio n.

Ran ge of So lub ili ty Lim it (gm /gm )

Ele me nt 0.0 01 qu an til e 0.9 99 qu an til e Pu l.6 E- 16 4.0 E-4 u l,6 E- 8 3,0 E-2 Th 1.1 £-9 5.8 E-6 Ra 7.9 E-1 2 l,3 E- 5 Np l.3 E- 25 S.O E-7 Pb 2.S E-1 1 4.0 E-5 Pa l,4 E- 7 7,2 E-4 Sn 6.3 E-1 7 *l.6 E- 4 Tc l.9 E- 9 9.5 E-5 Sr 2,2 E-6 2.8 E-3

_;3 7-

B. Penetr ation Scenar ios The penetr ation scenar ios are quite differe nt from our usual analys es; therefo re, the manner *in which we evalua ted their conseq uences is discuss ed here. For each, the consequ ence of the. scenar io depend s on the time of its occurre nce and each* consequ ence depend s on the in-ventor y at the time of penetr ation.

As a measur e of the time-de penden t conseq uence, Table 10 shows the hazard represe nted by the waste invento ry_in terms of EPA release l.imi ts. \'le obtaine d the table by evalua ting Equatio n (1) for the entire invento ry.

Table 10 Reposi tory Hazprd Index Time (yr) EPA Sum (Eq. (1))

1,000 8 .~E7 1,500 4.3E6 2,000 2.SE6 5,000 8.9E5 10,000 6.4ES In the direct hit scenari o,* for exampl e, to use Table 10

to find.th e haz~rd on a per-ca nister basis, divid~ its value in the second column by 204;000 (the number of canist ers). The penetr ation scenar ios have been des-cribed in terms of the number of boreho les expecte d to cause them, indepe ndent'o f when these boreho les occur.

Since the conseq uences are time depend ent, it is essen-tial for consequ ence evalua tion that a time of occurre nce be assume d. The assump tion made, is that the N hits con-sidered , occur uniform ly over the period of intere st.

For the "direc t hit" scenar io, the period is the 9900 years followi ng loss of admin istrativ e contro l after 100

years *. For the brine pocket scenar io, the period is the 9000 years follow ing contain ment lifetim e (1000 years) when all waste packag es are assumed to fail simulta n~

eously and comple tely. Thus, for N hits causin g the scenar. ios, each is ass urned to occur at a time, t j, where t*J =

9900 N

(j ~) + 1*00 "direct hit"

{ 15) .

9000 N

(j ~) + 1000 brine po'cket In the "direct hit" case, we assume that a fraction, fo = 1/4 of the canister contents are removed.

Thus, a 1-borehole, direct hit occurs at 5050 years with a consequence (Table 10) of approximately ,

C (1) . =

direct hit 1/4 * = 1.1 (16) 204,000 For the brine pocket scenario, we assume that the pres-**

sure in the pocket is relieved by expelling a.fraction of its volume. This brine flows up the borehole into a back"".'

filled room. We assume that the backfilled rooms have become resaturated before the waste packages fai°l a_t 1000 years.

When a waste package fails, its contents are assumed to be re.leased uniformly to the entire volume of water in the bac~filled regions, at a constant rate over a period, T .

Thus, _at time tj, the fraction of wastes that have been released is f1:

l:j - 1000 f1 = T We assume that the brine flow will be of short duration and will remove only those radionuclides in the water volume in the immediate vicinity of the borehole. No modeling was used to test this assumption. We assumed that 1/40 of the water in the backfilled room is mixed with the flowing brine and released to the accessible environment. This choice corresponds to the water volume contained in a .100-foot length ( 50 feet either way from the borehole) of the 4, 000-ft.

long room.

The consequen ce from this scenario is obtained by evaluating Equation 1 (through. interpolat ion of Table 10) with the assumptio ns made, EPA ~um(tj))

C(N) (17) brine pocket (

106 We will assume T = 100,000 years. For example, a one brine-poc ket scen~rio occurs at tj = 5,500 years and has a consequen ce of approxima tely, 5

( 8. 9 X 10 ) =

9.45

\ 106 Since both penetratio n scenarios involve a relatively small fraction of the waste inventory , we do not consider them as competing \vith the groundwat er transport scenarios .

The boreholes that cause them, *hm*1ever, may also contribute to the U-tube formation. We have neglected the small per-turbation the penetratio n scenarios may have on the conse-quence of the groundwat er transport scenarios .

C. Construct ion of the CCDFs As we dis.cussed in volume 2, assessing complianc e with the draft EPA Standard should probably combine all scenarios to produce a final CCDF. However, for the scenarios analyzed, it is. more illuminati ng to examine them individua lly. \rle will first present the penetratio n scenarios followed by the groundwat er transport scenarios . CCDFs for the groundwat er transport scenarios have been constructe d for *each of the three source models described previously .

Scenario 5: The "Direct Hit" Penetratio n Scenario Equation (13) was evaluated to give probabili ty, P(N),

of the N-hit scenario. Equation (15) gives the time, tj, for each of the N 'direct hits. Values from Table 10 were interpola ted a.t t. to give values of the EPA Sum, as illu-strated in Equatidn (16). These results are presented in Table 11 and Figure 8. As can *be seen in Figure 8, this scenario, when considered by itself, is *in slight violation of the draft EPA Standard.

Table 11 Probabilities (per 10,000 yr) and Consequences for the "Direct Hit" Scenario*

Consequence N P(N) (EPA Sum) 0 9.82E-l 0 1 3.33E-2 1.09 2 5.59£-4 3. 6.5 3 6.26£-6 6.18 4 6.27E-8 40.40

Contributions with probabilities of less than 10- 4 need not be considered.

EPA LIMIT

(/)

D.

w C,

z 0 VIOLATION w

w 0

)(

LU LL

. EPALIMIT 0

~ "DIRECT HIT"

l SCENARIO a

c:t 3

~ 10-a:'

~

104 --~~~~-L.~~---L~~-.I-~~~~~

10 1 EPA SUM Figure 8. CCDF for Scenario 5, Direct Hit Scenario.

(The Shaded Area Indicates Violation of the Draft EPA Standard.)

Scenar io 6: Brine.P ocket Penetr ation Scenar io Equatio n (13) was used with Ph't = .02 to-eva luate probab ilities~ P(N), of N brine pociet penetr ations that release radion u6lides . Equatio n (15) was used to evalua te t, and the EPA Sum was evalua ted accord ing to Equatio n (i7). Table 10 values were interpo lated to give values

at t .* These results are tabulat ed in Table 12 and the resuiti ng CCDF is presen ted in Figure 9. As can ~e seen from Figure 9, this scenar io, when consi~ ered by itself, violate s the draft EPA Standa rd.

Scenar ios 1-4: Ground water Transp ort Scenar ios We evalua ted the ground water transp ort scenar ios for three source -term assump tions discuss ed previo usly:

Source #1: 1ractio nal release of 1~~ 5 to 10- 7 /year of entire invento ry, Source #2.: fractio nal release of 10-5 to 10~7/y ear of a portion of the invento ry, given by consid ering the number of boreho les *and assigni ng one roomfu l of waste to each boreho le,

.Source #3: fractio nal ~eleas e rate from the waste form .of 10-3 t.o 10-7 with the waste-fractio n assump tion of Source #2. In additio n~ we con~id ered solubi lity li-mits and mixing assume d in the back-filled regions (Appen dix A).

In additio n, for these scenar ios, we sampled the variab les require d for the analys is from the ranges given in-Tab les 6, 7, 8, and 9 by.the LHS techniq ue [15]. We cnose 50 combin ations of input and calcula ted an EPA Sum (Equat ion 1) for each. Also, we chose two addi_ti onal in-depend ent sample s of 50 vectors each to estima te the effect s of samplin g_ error.

We calcula ted radion uclide dischar ge rates for 50, ooo*

years follow ing waste emplac ement. We integra ted these discha rge rates over each of the five 10,000 -year period s*

and evalua ted Equat ion(!) . Thus, we calcula ted a CCDF for each of the five 10,000 -year periods , for each of the three indepen dent samples and for each of the source term assump tions. When approp riate, room number and release rates were also sample d. Figure s 10, 11, and 12 give the resulti ng CCDFs.

Table 12

. Probabilities (per 10,000 yr) and Consequences for the Brine Pocket Scenario Consequence N P(N) (EPA Sum) 0 .942 0 1 .0565 9.21 2 .0017 24.0 3 3. 39E.:...5 38.0 10°

~

)

U) EPA LIMIT

<(

D.

w

(!J 10- 1 BRINE POCKET SCENARIO

-w a

z I

.i::.

w VI 0 I >< 10-2 w

LL 0

.~

m 10-3

<(

m 0

a:

a.

10-4 ~ _ _ _ _ _ _ _.___ _ _ _ _ ___........__._........_ _ _ _ _ __

10-1 100 101 102 EPA SUM Figure 9. CCDF for the Brine Pocket Penetrat..ion Scen<1rio.

( The Shaded Ar eds Ind Leu t~..? Vi olat.i.'on of the Draft EPA Standat"'d. )

ALL SCENARIO CCDF- ALL SCENARIO CCDF -

1st 10000 YEARS 2nd 10000 YEARS I

.;:. EPA **EPA

°'I SOURCE #1 SOURCE #1 10-4 10-4 10-2 .. +2 10+0 10 10-3 10-1 10+1 10+3 c> .c>

(a) (b)

Figure 10. CCDFs for the Groundwater Transport Scenarios*

With Source #1.

ALL SCE NAR IO CCD F- ALL SCENARIO CCD F -

3RD *100 00 YEARS 4TH 100 00 YEARS I

~ 10-2 EPA EPA I A a.

10-4 SOURCE #1 SOURCE #1 10-4 10-3 10- 1 10+1 10+3 10-3 10- 1 10+ 1 10+3 c> c>

(c)

(d}

Figq re 10. CCDFs for the Grou ndw ater Tran spor t Sce With Sou rce #1. nari o

ALL SCENARIO CCDF- 5TH 10000 YEARS 10+ 0 I EPA

""'I 0)

SOURCE #1 1 o-4 ..----.............--....................._...................................._..i.___~..w.._.................,

10-3 10+3

C .

(e) iigure 10. CCU~s for U1e GrounJwater Transport Scenario With Source #1.

ALL SCENARIO CCDF - ALL SCENARIO CCDF -

1ST 10000 YEARS 2ND 10000 YEARS 10- 1 10~ 1

\0 I

I I\

Q.

10-2 EPA" I\

a.

10-2 10-3 10-3

. -4 SOURCE*-#2 SOURCE #2 10 10-4 10-3

10-2 10- 1 10+0 10+ 1 10-3 10-2 10- 1

10+ 0 10+ 1 c> *C>

(a) (b)

Figure 11 .. CCDFs for the Groundwat er Transport Scenario With Source #2.

ALL SCIENARIO CCDF- ALL SCENARIO CCDF-3RD 10000 YEARS* 4 TH 10000.YEARS 10- 1 10- 1 I

U1 /\ 10-2 .

Q.

10-2 0

I Q.

SOURCE #2 *souRCE #2 10-4 .._..........~......__--.......................------.............__....._._~...... 1o-4 ._...............................__........__......................___._....._...............__....._,...._._......~

10-3 10-2 10- 1 10+ 0 . 10+1 10-3 .

c>

(c)

Figure 11. CCDFs for the Groundwater Transport Scenario With Source #2

ALL SCENARIO CCDF- 5TH 10000 YEARS

.10+0 10- 1 I

l.Jl 1--'

I A 10-2 Q.

10-3 .

SOURCE #2 (e)

Figure 11. CCDFs for the Grouhdwater Transport Scenario With Source #2 .

ALL SCENARIO CCDF- ALL SCENARIO CCDF~

1ST 10000 YEARS 2ND 10000 YEARS 10- 1 10- 1 EPA EPA~ LIMIT~

I LIMIT a.

01

N I a. 10-2 10-2 SOURCE #3

10~3 SOURCE #3 .

10-4a.__--............................___.___....._...........~..._..-................. 10-4 .___._.............-J-.......___.._._~ -......_._.........._.___...

10-3 10*2 10-1

10+0 10-3 10-+<>

Figure 12. CCDFs for the Groundwater Transport Scenario With Source #3

ALL SCENARIO CCDF - ALL SCENARIO CCDF -

3RD 1000 0 YEARS 4 TH 1000 0 YEARS 1 o+ 0

r-----.. . . . .......----.-.. . . . . _.. . .,--__. . . ,. . .,

10- 1 EPA 10- 1 EPA LIMIT --. LIMIT ---.._

I l11 w "

a._)

I

a. 10-2 10-2 SOURCE #3 SOURCE #3 10-3 10-3 1o-4 .___.__...__.,.. . . . . . .....____. .___.. . . . . _..___. . . . . .~ 1o-4 .____..._._. . . . . . .......__ __.__._._...~-...__.._._._......-.......

10-3 10-2 10~ 1 10+0 10-3 Figure 12. CCDPs for the Groun dwater Trans port Scena rio With Source #3

ALL SCENARIO CCDF- 5TH 10000 YEARS 10+0 r - - - -.........._ . . . . . . - r ~ . - - . . - - ~ . . - - ~ - - . - - -......

10-1 EPA LIMIT

~

I V1

.i:,.

I A 10-2 Q

SOURCE #3 10-3 1o-4 ...___----_........______.__........_.____. . . . . ~...,

10-3. 1o+o (e)

Figure 12. CCDFs for the Groundwater Transport

. Scenario With Source #3

The thre e trac es*s how n*in each figu eva luat ion s with the thre e inde pen den re.r esu lt from t sam plin gs of 50 vec tors each .* The ver tica l spre ad sen ts an esti mat e of sam plin g erro r in thes e plo ts rep re-asso ciat ed with the LHS 'rne thod . As.c an be*s een , the kam piin g erro r is sma ll ave~ mos t of the curv e.

All scen ario s eva luat ed with Sou rce yie ld larg e disc har ges . #1 (Fig ure 10)

The res ults ind icat e a vio lati on of the dra ft EPA Stan dard in each of per iod s. the five 10,0 00- yea r The sce nar ios eva luat ed with Sou rce

2 (Fig ure 11) res ult in muc h low er disc har ges , and it app ears tha t com""'.

plia nce i~ ach ieve d ~ur ihg the firs The res ults ind icat e tha t.th e mag nitut 10,0 00- yea r per iod .

de of the vio lati on is very sma ll.

All scen ario s,* whe n eva luat ed with cate tha t com plia nce r;1ay be ach ieve Sou rce #3, ind i-d, pro vide d tha t the mix ing cel l assu mpt ion can be 'jus App end ix A, the rele ase rate with tifi ed. As show.n in this type of sou rce assu mpt ion sho uld asy mpt otic a~ly app roac h tha t give n by the was te-f orm des crip tion alon e (Ta ble 7). Sinc e we

assu med a less . stab le was tefo rm, in con jun ctio n with the mix ing cel l mod el, we can infe r tha t the tim e req uire d to ach ieve tha t asy mpt otic re.l ease to the time s for whi ch disc harg es wer rate was long com pare d e calc ula ted . The imp orta nce of the rele ase rate assu mpt ion is ind icat ed by com pari ng Fig ures 10, 11, and 12.

D. Sensi tivity Analy sis Resul ts For the ground water transp ort scena rios we applie d standa rd sensi tivity analy sis method s to the calcu lated discha rges as measu red by the EPA Sum ( Equat ion l) [ 17] ..

The result s of .this analy sis indica te the relati ve i~port ance of the variou s data used in the transp ort calcu lation s (Table s 6 throug h 9)

The impor tant variab les determ ined by this analy sis are tabula ted here:

Scena rio

Source

1 and #2 #3 l Rd (U), T s ( U) 1 T 2 Rd ( U), T s ( U) 1 T 3 Ra ( U), ( U) ~

T Kua s T 4 Rd ( U) , T s ( U)

Kua I T In this table, Ra(U) = Uraniu m sorpti on ratio (Table 8),

T = Leach period (recip rocal of Table 7),

S(U) *= Uraniu m solub ility limit (Table 9),

Kua= Hydra ulic condu ctivity of the upper aquife r, Unit O or D ( Table 6) ~

1

The variab les appea ring ~n the table are those that contro l the time of onset of discha rge {break throug h) and the rate of discha rge, For slowly varyin g discha rge rates.

Integr ated\

Disch arge) * ( T _ Break ~hroug h)

( Disch arge/ ( Rate Time where T denote s the end of the period of intere st, e.g.,

T = 10,000 years~

For Sour ce #3 the vari able s cont rolli ng

.thro ugh time do not appe ar to be as impo rtan the brea k-Sour ces #1 and #2. This is like ly due to t as for the lead ing edge of the disc harg e puls e. the shap e of As show n in Appe ndix A, the mixi ng cell mode l *giv es.a (sou rce term for NWFT/£VM) that is init iallrele ase rate to the leac h rate , y prop ortio nal T - , and incr ease s line arly with init iall y. For the leac h limi ted sour ces, time the disc harg e rate is near ly a step -fun ctio n. Thus , we expe sens itiv ity to vari able s cont rolli ng the time ct a larg er of brea k-thro ugh for shar ply defi ned brea kthr ough s than for the slow ly incr easi ng brea kthr ough s typi cal of Sour ce #3.

Of note is the impo rtanc e of the sorp tion solu bili ty limi t valu es of Uran ium. Sinc e ratio and we calc ulat ed disc harg es for a mixt ure of radi onuc lide s,

.the influ enci ng all radi onuc lide s may be expe cted vari able s to be most impo rtan t e.g. , T , Ku . The appe aran ce of spec ific vari able s indr catB s the domi nanc e elem ent-in the mixt ure. of the elem ent( s)

I VII. Conclusions From the analyses presented here, we can draw several conclusions and make recommendations:

Drilling-related direct-hit.scenarios in sedimentary basins -indicate only slight violations of the draft EPA standard.

Brine pockets in bedded salt may pose a significant problem in complying with the draft EPA Standard.

Therefore, site. characterization should directly address the question of identifying any brine pockets that may be present. If few brine pocket~ and low drilling rates can be expected, the probability of this scenario can be kept ;Low. Our modeling of this scenario is admittedly simplistic. Impermeable back-fills may be expected in actual designs serving to limit the ~mount of waste*-that may mix with the flowing brine. aefining the description of this scenario

is clea~ly needed. For example, we assumed that (l/4o)*x (1/106) of the entire waste inventory came into contact with the flowing brine. This fraction ..

represents some 48 canisters distributed over a 100-foot length of the storage room.

In fact, one may expect

the brine to flow predominantly in the vicinity of the borehole, contacting a much smaller fraction of the waste and reducing the consequences of this scenario.

The descriptions of flow along such a borehole and in the backfilled room, as well as the description of brine pocket characteristics require further analys~s.

One would expect a description in terms of the fraction of the waste contacted and the amount of flow expected; only such a description would be useful in analyzing '

such scenarios.

The.importance of the groundw.ater transport scenarios in contributing to estimates of releases may be.great or small, depending on the source model chosen. Since they all result from drilling, steps should be taken to keep future drilling rates low. A reduction in the consequence may be achieved if the assumptions used in Sources #2 and #3 can be justified. Clearly, the fraction of waste available to flowing groundwater, solubilities, and mixing processes must be understood to estimate the importance of their contribution.

Unfortunately, we have not analyzed any processes in the area adjacent to a repository. Such analyses would be needed to make definitive statements on these assumptions.

An

impo.rta nt assumpti on that has been made througho ut this analysis should be noted. We have assumed failed shafts and borehole s to remain open througho ut the calcula-tional period of 50,000 years. In fact, they are likely to close due to creep, unless the groundw ater flowing through them dissolve s enough salt to ~eep. the conduit open. We have not investig ated this assumpt ion in detail.

The capabil ity to address it with the DNET Model [12]

is currentl y being develope d.

It should be noted that, in general, we have not addresse d the entire set of scenario s develope d in Referenc e

[SJ. We have addresse d a subset of scenario s that we feel may be importa nt. Judging from the results calculat ed, these scenario s are indeed importan t for any reposito ry similar to the one we have assumed.

A practic al difficul ty in impleme nting the draft EPA

.Standar d is the lack of our ability to assign reliable numeric al values to the scenario probab ilities. The methodo logy to assess complian ce with the standard is, neverth eless, availabl e as has been demonst rated by this and other similar studies *.

APPENDIX A Th~ Mixing Cell Source Model (Source #3)

In Source #3*we allow the backfilled regions to be modeled as a mixing .cell in which flowing groundwat er is assumed to mix with radionucl ides in the volur:1e of the mixing cell. The concentra tion of radionucl ides released from the backfilled regions is then given by the uniform concentra tion in the mixing cell. This model can be calculated analytica lly for a*single stable species.

Let V = mixing cell volume, C = radionucli de' concentra tion in water in the mixing cell, L =*rate *of radionucli de input into v* from waste form leaching,

and, Q = rate of water flow through V.

In the mixing cell model we assume the leach rate, L, to be given as a constant fractiona l rate, AL' of the initial inventory in the waste form, N ,

0 The contamina nt concentra tion in the mixing cell is described .by

. dC V-- = *L - QC (A. l) dt

.If we let A0 = Q/V A-1

the solutio n of A.l is C(t)

=~

(

1-e. o)

- X t (A. 2)

For small t, C(t) = J:JL_

_v Thus the concen tration of the radion uclide increas es linear ly from zero.

The asympt otic release rate QC 00 can be obtaine d from Equatio n (A.2) with t - oo:

QC 00 = L Thus, for long times, the release rate approa ches a value govern ed by the rate of 'waste- form leachin g. The release rate from the mixing cell is then less than or equal to the prescr ibed waste-f orm leach ~ate.

For decayin g radion uclide chains , this model is implem ented numeri cally in tnvFT/DVM accord ing to the compar tment model shown in Figure A-1.

A-2

PRODUCTION DECAY i-1 i+1 R

LEACHING D

I ~' .

!)::I w

I u

D DISSOLUTION

PRECIPITATION N

I I . D FLUSHING s

Figure A-1. Implementation.of the Mixing Cell Source Model for NWFT/DVM

Radio rtucli des remai ninq in the waste form are repre sente by Comp artme nts, R. The waste -form break down rate. goverd trans fer from Comp artme nts R to Comp artme nts u. ns The

inven tory in Comp artme nts u is exami ned along with water volum e in the mixin g cell and solub ility limitthe s

trans fer all or part of that inven tory into the mixin to g

cell. The mixin g cell inven tory is denot ed by Comp artme nts N. The mixin g cell is flush ed const antly to give a relea se sourc e (S} of When solub ility limit s are appli ed, radio nucli des.

may be.tr ansfe rred from* comp artme nts N to Comp artme nts repre senti ng preci pitat ion. For large solub ility limit U, Comp artme nts U may be empty . 'nJ,en, trans fer to Comp s, artme nts N may occur direc tly along the dotte d paths of Figur e A-1.

Horiz ontal trans fer betwe en radio nucli des comp artme nt, i, and comp artme nts i + l or i - l repre sents decay produ ction . and A-4

APPENDIX B Geohydro log.ic Data for Bedded Salt Table B-1 Ra Ranges in Aquifer* (Bedded Salt)

Radionu clide Media** Ra Range (ml/g) Referenc es a 50-1,000 40,41,59 ,60,74,7 7 Am b 700-10 4 20,21,28 ,33,34,3 7, 40,41,53 ,69,74 a 300-3,00 0 24,40,48 ,55,56,5 8 60-63,76 ,77 Pu b 20,21,24 ,28-32,3 7 41,S3,54 ,69,76,7 7 a 0 57 u

b 1-270 26, 27, 33, 34, 41 a 2-40 41,58,60 ,61,74 Np b 2-400 20,21,41 ,59-61,7 4 a 0-100 19,22,34 ,51,52,5 9,60, Fission 64 Products (Cs)

.b 70-3,000 20,21,24 ,28,30,3 3*,34, 41-43,45 -47,51-5 3,65, 70,73,76 ,78,80.

These data are in oxidizin g, relative fresh {potable ) water (pH 6-8; salinity < 5,000 ppm)

- a-Qua rtz and clean sedimen ts; b-dirty and clayey sedimen ts.

B-1*

TABLE B'"'.'2 Bedded Salt Hydraulic Parameters Parameter Range in Table 6 Range of Data Reference Explanation and/or Main Text in Available Ref.

Conductivity in 0.15-680 9.4-37 81 A range of 4-25 (0.25-0.75 Aquifer (ft/day) 8 82 quantiles) was expanded to 0.15-680 to represent 0.001'"'.'0.999 quantiles Porosity in 0.1-0.2 0.1-0.2 83,84 NA Aquifer Gradient in l.E l.E-2 2.E-3 87 Aquifer (ft/ft)

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NRC FOAM 335 1. REPORT NUMBER (Assigned by DDCJ 111-811 U.S. NUCLEAR REGULATORY COMMfSSION NUREG/GR~3235 Vols. 2,3 and 4 BIB!,.IOGRAPHIC DATA SHEET SAND82-l557 ' .

4. TITLE AND SUBTITLE (Add Volume No.* if appropriare}

2. (Leave blank)

Technical Assistance for Regulatory Development: .Review and Evaluation of the Draft EPA Standard 40CFR19T for Disposal

3. RECIPIENT'S ACCESSION NO.

of High-Level Waste

7. AUTHOR(S)

5. DATE REPORT COMPLETED Fuel Cycle Risk Analysis Division MONTH I YEAR April

1983

9. PERFORMING ORGANIZATIO N NAME AND MAILING ADDRESS- (Include Zip Code)

DATE REPORT ISSUED Sandia National Laboratories Fuel Cycle Risk Analysis MONTH I YEAR April_ 1983 Division 9413 6. (Leave blank)

Albuquerque,. New Mexico 87185

8. (Leave blank)

12. SPONSORING ORGANIZATIO N NAME AND MAILING ADDRESS (Include Zip Code)

Diviston of Waste Management 10. PROJECT/TAS K/WORK UNIT NO.

Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission 11. FIN NO.

NRC FIN A 1165 Washington, D. C. 20555 Tr1c.k ~

13. TYPE OF REPORT I PERIOD COVE RED /Inclusive dares)

Formal Report Jul.v 1981-Aoril 1983

15. SUPPLEMENT ARY NOTES 14. (Leave blank J

16. ABSTRACT (200 words or less)

Analyses of a hypothet ical nuclear waste repository i"n each _of th.ree geologic media

(.basalt, tuff and bedded salt) have been performed to assess compliance with the Draft

(#19) EPA Standard 40CFR191 .. Hypo the ti cal sites are based on represent ative gailltkfor geologies fn the continental U.S. The effects of uncertafn ties in the input data and in the interpret ation of the standard on the assessment of compliance are demonstrated.

results of the calculatio n$ indicate: l) For basalt media, compliance with the draft* The stan-dard may be achieved depending on how the .term 11 *release 11 is interpret ed; namely, is the release due to a unique (single) event or does it i"nvolve all probable s*cenarios. 2) For tuff rnedi"a, sorptfon of radionuclides is an effective barrier to acti"nide migration th*e absence of solubiHt y constrain ts. Discharges of 99rc and 14c may cause violatfoneven s of ir the draft standard; however, retardatio n due to matrix diffusion may eliminate discharge of these radionuclfdes for realistic conditions. For short groundwater travel times to the accessibl e environment, discharges of uranium and neptunium could exceed the draft standarc under oxidizing conditions if the radionuclides do not pass through thick sequences of sor bent zeolotized tuff. 3) For bedded salt media, co~pliance depends on the source model us*ed. Penetration scenarios (direct canister hit or brine pocket hit) indicate potential serious consequences. However, thes.e. could be mitigated by proper site selecthm and ly ins-ti tutiona l controls.

17. KEY WORDS AND DOCUMENT ANALYSIS 17a. DESCRIPTORS 17b. IDENTIFIERS/ OPEN-ENDED TERMS

18. AVAILABILIT Y STATEMENT 19. SECURITY CLASS {Th,s repcrrJ 21. NO. OF PAGES Unclassif iorl Unlimited 20. SE CURI TY CLASS (This page} 22. PRi°CE llnrl::.cc,-if 'iorf s N RC FOAM 335 111-811

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NUREG/CR-3235 SAN D82-1557 Vols. 5 and 6 Technical Assistance for . .

Regulatory Developm.ent: Review and Evaluation* of the Draft _

EPA Standard 40CFR*191 for Disp*osa-1 of High7Level *-Waste

Health Effects Associated with Unit Radionuclide Releases to the Environment

*ca1culati9n of Health Effe<::ts per Curie Release for Comparison with the EPA Standard Prepared by Fuel Cycle Risk Analysis Division Sandia National Laboratories

. April 1983 Prepared for U.S. Nuclear Regulatory Commission

OTHER VOLUMES OF SAND82-1557 NUREG/CR-3235 Main

Title:

Technical Assistance for Regulatory Development: Review and Evaluation of the EPA Standard 40CFR191 for Disposal of High-Level Waste.

Volume 1 Executive summary N. R. Ortiz. K. Wahi Vo.lume 2 A Simplified Analysis of a Hypothetical High-Level Waste Repository in a Basalt Formation R. E. Pepping. M. S. Chu. M. D. Siegel Volume 3 A Simplified Analysis of a Hypothetical High-Level Waste Repository in a Tuff Formation M. D. Siegel. M. S .. Chu Volume 4 A Simplified Analysis of a Hypothetical High-Level Waste Repository in a Bedded Salt Formation R. E. Pepping. M. *s. Chu. M. D. Siegel Volume 5 Health Effects Associated with Unit Radio-nuclide Releases to the Environment J. c. Helton Volume 6* Calculation of Health Effects Per Curie Release for Comparison with the EPA Standard G. E. Runk'le

Volume 5 Health Effects Associated with Unit Radionuclide Releases to the Environment

llliREG/CR-323 5 SAND82-1557 WH TECHNICAL ASSISTANCE FOR REGULATORY DEVELOPt-IBNT:

REVIEW Alil> EVALUATION OF THE DRAFT EPA STANDARD 40CFR191 FOR DISPOSAL OF HIGH-LEVEL WASTE VOL. 5 HEALTH EFFECTS ASSOCIATED WITH UNIT RADIONUCLIDE RELEASES TO THE ENVIRONMENT J. c. Helton

Manuscript Completed: April 1983 Date Published: April 1983 Sandia National Laboratories Albuquerque, New Mexico 87185

Operated by Sandia Corporation for the U. S. Department of Energy

.Prepared for Division of Waste Management Office of Nuclear Material Safety and Safeguards Washington, n.c. 20555 NRC FIN. No. A-1165

Arizona

. State University

ABSTRACT Simple models are presented for the estimation.o f individual and population health effects (i.e., latent cancer fatalities) for long-term radionuclide releases to-the surface environment. These models were suggested by techniques employed by the Environmenta l ProtectiQn Agency in the development of a proposed standard for the disposal of high-level radioactive waste. The modeling approach is based on the use of asymptotic solutions to mixed-cell models in conjunction with appropriate usage rates~ dose factors, risk* factors, and population esti-mates. Although the modeis are simple, it is felt that they can be used in prelimirtary investigation s of topics in high-level waste 'disposal such as potential importance of individual radionuclide s, relative importance of dif-ferent release patterns or exposure pathways, and rela-tionships between individual and population.ex posures.

The use of the models is illustrated by calculating the population health effects along various exposure pathways for the radionuclides considered in the proposed Environ-mental Protection Agency Standard. The results of these calculations are compared with the calculated population exposures on which the proposed Environmenta l Protection Agency Standard is based.

iii

TABLE OF CONTENTS CHAPTER

l. Overview 1-1 l.l Preliminary Comments 1-1 l.2 Computational Approach 1-1 l.3 Computat;.ional, Results ** 1-7 l.4 Comparison With Environmental Protection 1-22 Agency Results l.5 Discussion 1-32

2. Mixed-Cell Models 2-1

3. Release to Surface Water 3-1 3.l Preliminary Comments 3-1 3.2 Exposure From Water Consumption 3-3 3.3 Exposure From Fish Consumption 3-4 3.4 Exposure From Inhalation of Suspended 3-6 Sediment 3.5 Exposure From Water Immersion 3-8 3.6 Exposure from Shoreline Se~iment 3-9 3.7 Exposure From Suspended Sediment 3-11

.4. Release to Soil 4-1 4.l Preliminary Conunents 4-1

4.2 Exposure From Plant Consumption 4-5 4.3 Exposure From Milk Consumption 4-7 4.4 Exposure From Meat Consumption 4-9 4 .. 5 Exposure From Inhalation of Suspended Soil 4-9 4.6 Exposure From Soil 4-11 4.7 Exposure From Suspended Soil 4-13 5 .. Irrigation ~..:fter Release to Surface Water 5-1 5.1 Preliminary Comments 5-1 5.2 Exposure From Plant Consumption 5-4 5.3 Expos.ure From Milk consumption . 5-5 5.4 Exposure From Meat Consumption 5-9 REFERENCES R-1 V

LIST OF. FIGURES FIGURE ' .PAGE 2-1 Flows Associa ted With a Single Uniform ly- 2-2 Mixed Cell With No Radiom.i clide Partitio n-ing Between a* Liquid and: a So*lid....Phase*

2-2 Flows Ass.ocia ted *With. a ..Single :Urriform ly- 2-5 Mixed Cell With Radionu ciidePa rtitionin g Between a Liquid and a Solid.Ph ase*

,. t* *'

. ~ . .,. ..

.: ~** "'

H ... ,..:,,. ,*,

V1

LI ST OF TABLES TABLE PAGE 1- 1 He alt h Ef fe cts pe r Cu rie Re lea se d fo r Di ffe en t Re lea se Mo des r- 1- 2 1- 2 Cu mu lat ive Re lea se s to the Ac ce ss ib le En me nt fo r 10 ,00 0 Ye ars vir on - 1- 3 Af ter Di sp os al Pr op os by th e En vir on me nta l ed Pr ot ec tio n Ag en cy 1- 3 Va ria bl es Ap pe ari ng in Ta ble s 1-4 1 1- 5 an d 1- 6 1- 8 1- 4 Ex po su re to Or ga n As so cia ted W ith Ca nc er to Ra dio nu cli de I fo J Du e 1- 12 r Re lea se s to Su rfa ce W ate r 1- 5 Ex po su re to Or ga n As so cia ted W ith Ca nc er to Ra dio nu cli de I fo J Due. 1- 13 r Re lea se s to So il 1- 6 Ex po su re to Or ga n As so cia ted W ith .C an ce r to Ra dio nu cli de I fo J Du e . 1- 15 r Re lea se s to Su rfa ce W ate r W ith Su bs eq ue nt Us e of Su rfa ce \*l ate r fo r Li ve sto ck an d Sp rin kl er Ir rig at io n 1- 7 Po pu lat io n He alt h Ef fe ct s fo r 1. Cu rie Ra

. nu cli de Re lea se s to dio - 1- 16 Su rfa ce W ate r 1- 8 Po pu lat io n He alt h Ef fe cts fo r 1. Cu rie Ra nu cli de Re lea se to So dio - 1- 17 il 1- 9 Po pu lat io n He alt h Ef fe cts fo r 1. Cu rie Ra nu cli de Re lea se to Su dio - 1 8 rfa ce W ate r wi th Su b-se qu en t Us e of Su rfa ce *wa t.e r fo r Li ve sto an d Sp rin kl er Irr ig ck at io n 1- 10 Or ga ns an d Ri sk Fa cto rs Co ns ide red 1-* 21 1- 11 Va ria bl es Us ed in Ca lcu lat io n of Re su lts se nt ed in Ta ble s 1~ 7, Pr e- 1- 23 1- 8 an d 1- 9 1- 12 He alt h Ef fe cts pe r Cu rie Re lea se d fo r Re lea to a Ri ve r se s 1- 24 V1 1

1. Ove rvie w 1.1 Pre lim ina ry Com men ts The Env iron men tal Pro tec tion Age per form ed an ana lys is of the pop ncy has rec ent ly ula tion hea lth eff ect s ass oci ate d wit h a rele ase to the of sel ect ed rad ion ucl ide s con tain sur fac e env iron men t ed in hig h-l eve l was te (Sm 81). Tab le 1-1 cqn tain s a syn ops is of the pop u1a tion hea lth .eff ect s cal cul ate d in the Env iron men tal Pro tec tion Age ncy ana lys is due to a one cur ie rele ase of eac h of the ind ica ted rad ion ucl ide s ove r an ext end ed per iod of tim e.

In tur n. the val ues con tain ed in thi s tab le wer e use d in the der iva tion of the Env iron men tal Pro tec tion Age ncy 's dra ft stan dar d for the geo log ic dis rad ioa ctiv e was te (En 80) . - Spe cifi pos al of hig h-l eve l to allo w 100 0 hea lth eff ect s (i.e cal ly, it was dec ide d

., lat ent can cer fat al-itie s) ove r a.10 ,00 0 yea r per iod per 100 ,000 me tric ton s of hea vy met al (MTHM) use d as rea cto r fue l. For eac h rad ion ucl ide . the allo wab le rele

.ov er a 10. 000 yea r per iod was obt ase iim it per 100 0 MTHM ain ed by div idin g 10 hea lth eff ect s by the hea lth eff rele ase to sur fac e wat er giv en. in ect s per cur ie for a Tab le 1-1 . The pro -

pos ed stan dar d and the ~es ults of lati on are giv en in Tab le 1-2 . the ind ica ted cal cu-Rel eas es to sur fac e wat er are pro lik ely , ten ded to dom inat e hea lth bab ly the mos t eff ect s in the Env iron -

men tal Pro tec tion Age ncy cal cul atio and wer e use d in the der iva tion ns show n in Tab le 1-1 ;

of the pro pos ed stan dar d giv en iri Tab le 1-2 . For the se rea son s, i t was dec ide d to exa min e the cal cul atio ns rel ate exp osu re path way *. Spe cifi cal ly, d to the sur fac e-w ate r it was dec ide d to exa min e the Env ~ro nme ntal Pro tec tion Age ncy cal cul atio ns by

dev elo pin g sim ple mod els of the sam e typ e tha t the y

_use d and ther i usin g the se mod els and pop ula tion exp osu res and hea to pre d1c t ind ivid ual lth ~ff ect s. In thi s dev elop men t; the dos e and risk fac Run kle et al. (Ru 81) are use d. tor s pre sen ted in 1.2 Com put atio nal App roac h*

The com put atio nal res ult s the use of sim ple lin ear mod els pre sen ted are obt ain ed wit h tn rep res ent rad ion ucl ide mov eme nt. Spe cifi cal ly. the mod els con sid ere d are of the form dX/ dt = R - AX , (1.1 )

1-1

Table 1-1. Hea:l th .. Effed:.s per Curie Released for Different Release Modes*

. -* .R~1e.a.ses. tQ: : . *. *Reiease$ \o: ., : . R~:l.~ases;*,to_.:'* :.... Releases to Nuclide ,, . . . . a-;Riv~r ,:~n* Oc_ean.: . ,,. - Land-, Su.rfclt:,e- , -~: the Air

, ~ 14 4.58 E::.:*2 ' * . 2 .58 *E- 5 *,.. 2'~04 E- -4 Ni;-s.9* .*

Sri. 90:.

-1;;;2ft~:1

,:

1:gf EL g:

9*.,7s.* E.:;. ;4 . ... ,1\.63 E- 2 Zr-,.9.3 *: , : .. ~.:: ..::..'*.*.. :.:. .

Tc-*99 *. *

2-~as* E;_* 4 * * ., _. i.04 £.::..' 6 .,.. *3...*.67 E- 5

.. . -~*......... **.. ..'..: *'

Sn-126 . *.* * ... 1.20. £-,..~: 1 _ * :* > . ,:c-7 .86c E.,.,6*: : :<4".13. E~ ::-2 * -*.:.: 1.12 E- 1 I~i29 ... 1'.~~ .t:.: 2, _:* ,< ., 9*. 6_2;}-::~: : : : ,_ :* .. 2.:31 E~_-:5, -* . _. -~: .tJs E- 3 Cs-135: *. J*.:81 E~ 3 ,:, .:' * '.<: l;SS* E---:5 * .* * .:. 4~01 E.:;._-4* *: '" : .:: -7'*.36 E- 4" Cs-i37 1:~_~8 ,"£.~/*2. ;*,:*_1.tfo E".",c.s* .....* : *s.6°2* E~ 4'. ..,. :* ~' : : .-6:~~t E- 3 Sm-151 .: *:;~:: **....

Ra-226 .. .. ,, ~** :~ ::.-: . . . . . , .... '. -: ::.: /~ **, ~'.}.:* :.:. *.- ...... '.: .. *,,

u.:.z.34* * . :: *: .7:" :: ~.-.. ::. :;: "":: -~*-, ; '. .. >.. _.:*. *.~-: -~ ' . ... ,.. :: ....

Np-2~7_ . . . ': .$~$,(¥::-::J::/:. ~; :..Z~.44~ t~ fl.~.-':':. : : .i'!z{ E.~ :-3 .. .* a~:63 E- 2 Pu-238. '*2*.;;29*E-*-2::,:*:::::**:.z~*3g'*E.: S ., .* 3-.21:E_.s:3 .:*1*~47 E- 2

.* * ~-ti;?~~ .*. i l~~?: i~.J.* : ., ..:* *

1:31-- E;:;,f >~:- * ~ s~~s . E~ ,,:2** * ;.::'. :: i*~sJ.a E- 2

~: : ::-t}:}J-C/}itti:/ i }ltr'., :~{!! ~= !

=::***** r,::~i'F!~--_-:i:!:!f[!:f ,.i?{~t!:?_.,!:!! ~-!

....... :- __ , .......... __ ,: --**** N ,.',_.-.. ( * *: : . * : ,: :*:,*:.

. . ... ~-

1-2

Tabl e, 1--2*. dmil lativ e Rele ases *:to the Acce ss":ib le Envi ronm for 10 ~ 000 Years* Afte r Disi; :osal Proposed' by* theent Envi ronm ental Prot ectio p Agency**

Prop psed Rele ase. Rele ase Limi.t Fran Balf -Lif ea Limi.tb( curi es per Tabl e 1-lc (cur ies Radi onuc lide (yea rs) i.ooo Ml'HM) per 1000 Ml'HM)

Ame rici~ 241 458. 10 13.9 *

. Ame riciu m-24 3" ,.737 0 *. ,,: 3. 73 Carb on-1 4 5730 200 218. 3

Cesi un-1 35 3.D, 2000 2624 .7.

Cesiu m-13 7 30.2 500 505. 0 1 ..7E:7 ..

- .*--::* .. - ..... - .... *:: -~- ::*

.Nept unium -237 . .

2.14a :i 20 16.8

. --.:*: .:. -~...-: *.*.: **~* :::*. ,:-: . ., -* .... -*

Plut ani~ 238. '. 86~:: .. :.*. :::**. ,,400 ii".

Plutdniom,.;.239-

.. C *.*

-* ~- ..... *- ~ ::. -* ...... ;- ..

'** .2;.44E4.' -~100 ,:. -* .*.:*144~5 Pluta ri.um -240 6580 . 100 153. 1 Plu ~2 42 3.79E 5 100 147. 9

., : ;,( *; .-:... ~:* ,;'; ':*::'

~-. ::~* ~:* --~- ';:-:'} '* ~:;*. *- ' ; :; ,*

Strcnt:i.ulir.90 **:* ~-.. *:.:: *:.::. :28. l 0

,,

-.:-so ..::. -.

".\:

..- .: ::;-:.- ~::.- ~- ~: : _: :: '; .:: ~ ~:- :*:* .: .**; . . . *..: .. _..: t- -~{ -:~: ... ~,> -:~

2000 * :-:*.::*.:.:".'::. ***. 35;087-..7

... -** ' ;:. *=- '::" *-:; '-.. :. - .. **_ ::.. :~~ ,;. .-.. . .., ***. ' ..._ 1

~. .* ,* .

:-' .*... * ~ . /..* . : ,;. C*:1 ; < ~-*I:::.~-:;*.!.".;-:.:

. *.,SQ:.*,t *.. :. :'*::: :: :. ** ::, E *.'. \83'. 3

*r ~*** . . *:*****

....i *: '\' ..* -~-

-: \ '

"Any :othe r alpha-," ... *- : . . . _. . .

.** =: .*.. :-.:.

\

~ ; **. :'... *..:*- ~-~ _:_.:~~'. :-: *: *. :_._, . ,

': emit.ting' '.Rldio,,,,* . . . " - *: :'. ,:,..-:. ,': ...... .

:.:..::, :',nu dide . *:.: : - .:: .;..., .i:. :: : .*, ::_ :* *~ , ;: ,, >: :: ..:: 2.. .. -

~-\.-~:~~=o::*;~;:~*-*.:*:* , ..... .. : .: .. *:*

~::

..,. .::* :'. *:, ..: ..-. :L.r;*.: ... :-.:.

doe2 f not -:-emit*: .:: : -. ., :";. .. -:-

alp ha:: ~~!~ :,.::: :.<, - *

I * '* * -: .f' ~-~ ' '.

- ,; ; .... :::: '.*.'~.::::~ \ ; ;:-:-::::*:.

.'... * ** ' .* ,

I ... : ** . ** * *': ,. ... '

.::;. ~-: . .... ' - .* *.

a Fnm (We74) b Fran (En8 0) c Deri ved fn:m "Rel ease s to:a Rive r" in Tabl e 1-1.

1-3

where Xis the amount of radionu clide in *some region of interes t (units: Ci),, R is the rate of radionu clide input to-this region (units: Ci/yr) and A is a rate constan t for movemen t out of that region (units: yr- 1 ).

The solution of the precedin g equation is given by X(t) = e-Atxo + (R/A}(l. e -At) ' ( ]:. 2) where X(O) = Xo* Further, when A is_posi tive as is the case for situatio ns consider ed in this present ation, the asympto tic or steady state solution to.(l.l) is given by SX = R/A . (1.3)

.It is this latter solution which will be used in the developm ent of dose and risk results to be presente d.

The equation appearin g in (1.1) is used to represen t three differen t situatio ns. The first situatio n is a radionu clide release to a surface -

water body. Here, for each radionu clide conside red, R = TD(I)/T and A= F/VW , * (1.4) where TD(I) equals total release for radionu clide I (units: Ci) over a time period of length T (units: .yrs)

F equals the flow rate out of the water body under con-siderati on {units: L/yr), and VW equals the volume o~ the water body {units: L). For complet eness. the rate constan t A appearin g in (1.4) should also contain a term represe nt-ing radioac tive decay. However, as this term would be very

~mall relative to F/VW for the r~dionu clides conunonl y con-sidered in the geologic disposal - of high-le vel waste, i t is omitteQ . Radionu clide releases over relative ly long time periods will be consider ed. In particu lar, dose fac-tors which provide a 70. year dose commitm ent from a 70.

year chronic exposure will be used. Therefo re, T must be signific antly greater than 70. years. The coeffic ient A is derived from the assumpti on that the surface- water body can be treated as a uniform ly mixed cell such that a radionu clide can leave the cell only by outward movemen t.

1-4

of wate r. Addi tiona l discu ssion of Rand A can be obtai ned in* Chap ter 3.

The secon d situa tion is a radio nucli de relea se to

_soil. Here, for each radio nucli de consi dered , R i.s defin ed as in (1.4) and A is defin ed by S{I)* ER (1. - S(I))* RO ALOG (2.).

A= DP*( l. - PO)*D E + DP*PO*SA*lOOO. + HLIFE (.I) , (1.5) where S(I) repre sents radio nucli de parti tioni ng betwe en the liqui d and solid pha~e s of the soil and is defin ed in Table 1-5 (unit s: unitl ess~, ER repre sents erosi on per unit area (unit s: kg/m per yr), DP repre sents rate depth of soil *(uni ts: m), PO repre ~ents poro sity of soil (unit s:

unitl ess), DE repre sen}s mean parti cle dens ity of soil mate rial (µnit s: kg/m ), RO repre sents runof f rate .

per unit area (unit s: L/ra2 per yr), SA repre sents perce satur ation of pore space in soil (units *: unitl ess), nt is the natur al logar ithm of 2. and HLIF E(I) is the half- ALOG (2.)

life of radio nucli de I (unit s: yr). Due to the slowe r proce sse-s assoc iated with radio nucli de movem ent in soil, radio decay is incor porat ed into the expre ssion appea ring activ e in (1.5) . The coeff icien t A is deriv ed from the assum p-tions that the soil can be treat ed as a unifo rmly mixed cell with a water phase and_ a*sol id phase such that (1) a radio nucli de* is parti tione d betwe en.th e water and solid phase s on the basis of *a distr ibuti on coeff icien t and a radio nucli de can leave the cell only by radio activ (2) e decay or movem ents of water and solid s. Addi tiona l discu ssion of A can be obtai ned in Chap ter.4.

The third situa tion is radio nucli de depo sition on crops due to sprin kler irrig ation . In this case, R = FRET *TD(I )*FRI V/T and A= ALOG (2.)/W HRHL , (1.7).

where TD(I ), T and ALOG (2.) are alrea dy-de fined , FRET is 1-5

the fraction. of. dep9sited ra,dionuc:!l~des. in spr:inkle:r:- .. .

irrigation ini t'ially retained. on plants J units*: . . *... : .

unitless), FRIV is the fraction of the river *rec:eiv::... *

ing the radionuclide. release used _fo~ spri,nkter irri~

gation (un:i.ts: ~nitle~s) .* and \{HRHL. is the_ weathe;i;:-:-*

ing half' life ':i:or radionuclides deposited by sprinkler ...

irrigation (units: . yrs). The: variables ir and A are derived from the assumption that the radionuclides retained on plants d~e to sprinkler irrigation,can be treated as being in a uniformly::--mixed cell* such *tha,t

radionuclides qan enter this cell'only'by deposition*

on plants and can leave the cell only by weathering.

Due tc::> the generally short:. wea:thering_ hc1.lf l:i. ves. which ..

a:re eoh~-id~red, . ;r-adioaGtive decay ls omi t,ted in the. ..

definition. qf A ...*.**. _Addit:ional di~etlssion oni the . .

der.ivation of I\, and- A is pr_9yided

in *9ha.pter s.

. " Fo;r. each. o:f. the s;i tµatloh$ . :,inp:i.ca,te~. ,,ip. the tJ1_r.~e ....

precegin,g: para,g:ta."pns:, .. ra.d.;i.on,µc,lide to;9v~):nei1t ~an be. rep:-- .

resehi:g_ci* PY a:.* di.f_fere.i:itial equati_on. :of* the. io'.:rm given* ....

. in (1 ;1J~ . , As*. *t:nd:i.¢ai:ed :in ( ,l ~ 3) /. ~P-¢)J. of. )::.h~se equa; . : .

. tTqris \vi}Lha\ie' an ~sy'mptotic*; solutton: p~f- the.'.forµC R/A *...

.. "\flhich: j::epf~s~nti( .the.' *amp:unt:. ol .ra<lioriu_cl:ide ip-'j:h¢'. sys::.. :: . .

'te'm at* *steacI '. state.*

F"roin this solution ,, steacr

state*

~bbh~,~'ntr:at.io~s: *:c~iii b~. : :bbt?-i'h_ed':: by. *aivi:r'1tg by:*

oriate vblume

or *mass*. - .. *For radi6'nuc1rde I aha* rerease:: ... *.

tr~-:- ~ppr9~:*. *.

to SU/fa{~ -~a;tei-_/. fh~ sf:e~dy~§tat:e :~~lii!-~?r*' Ji *.* : ,. . >: :*

c

~ .. . -*. -. -~--

.. ,; .. , ..... ,*. ::*-:./ .... *.,.:::*:**;. ** :* *:*:* .... ~..'* ... ,..

Sftnit:~r calculations ~Iii° yieii~,*~f~hd'y..::~tate concentra-tions for release to soil and deposition on plants due to sprinkler irrigation.

. -*-' ~-

Once the concentrations indicated in the preceding paragraph are known, t~~y,1 ,gan b~::* ustad:= t9 ca*lculate indi-vidual exposure rates.. 'ln turn,"' mi.il tip'iica tion of these exposure rates by appropriate dose factors will yield i~dj._ v.:i,.~Jl~l ,~p.s~, . .[ate.s,*... Tp.ep, ,. multi-pli1:::ati9ncc by risk ,... '"',*,**.

0 fa.btors' wi1T\r*ield in.dlviduai'* cancer .. risk:* .Fina.1ty*, .... **.*****

multiplication of individual dose and risk by popula-

tion size. will yield pop'!,].J,.1;3.-t:ic:>_n dos_~ and. population i risk. Tabies :**1.:.."4, 1-5 *and' 1-:6* cont~in selected formulas I

I I.

for individual dose (units: rem/ind) and associated popu-.

-lation - size {units*: ---- ind). *Tab-le *].---3 contains definitions for variables used in .Tabl.es 1-4, 1-5 and 1-6. Detailed derivations for all relations are given later in the pre-I .. sentati0n .. * - However; a*l*l were derived* as *already indi-"

cated_ *. __'l'hat _ is, .an -.asympto:ti<:;:. concentra_tion was obta_ined_

i'l:i each* substra*te of iriter*e*st**. Next,* .theise concentrations were used in conjunction with individual usage rates and

dose factors to obtain individµaJ ... da.se. Then, mul tipli-cation by the appropriate risk* fa*_ctor yields individual*..

risk, and multiplication by the indicated population siz~.

yields population -dose and risk~- Due to the assumed lin.:..

earity of m.any of_th.e rela:tion.s, mllltiplication by popu---

lation size often *re*sults in con'sideiable. simplification of the algebrai~ express,j,QI1$ :f.or p.op9.lati.Q11. dose and ris_k.

The appearance of the. factor* 70 .. in. many *of. the expres- *--

sions results from the. fact that _dose_ .factors for a 70 ..

year dos~-- cbmm.l.ttneht from::a:, 70. }e~r"'ch.toiii\:: exposure are b~Jng_ l.,!S~q _for_ .i_nger~t.i,or:i .?,nd _inl:i,aJ...atiqn..~"- -.Mul tiplicatiqn_**:

or a' "brie :year* 'chronic . ( i ..:e{: ,* ~s:*sur.nesi to: he: the same over'.

0 an entire lifetim~) expos\.ire i'ate by-'thes'e" factors yields the \?1i~~:~-e~ ~OS'.~ ...s<=>.r_nmi t.m~n ~.: . ,, '.: ......... ..

l.~ Compµtationai B,esq,1, t$ *.

This section preserit::s ;p6.-pulciti6n health effects ol;>.ta.:l_q~d wJ_th the. re,latio.ns given .. in .Tab.l.es .1-4, 1-5 ~ an,cL*

l;,;;;6 ~-' ...Th'es*e restiTts*. a):.-e_-*pre\~,ent*e*d- in ;:fab}e'~ . 1-7, 1-8 *anci ..

1-9 and were calcui"ated .*foii""totai.' "discharge of 1. curie pe~. ra.qionµcl;i.d.~ .Ci, .. e._,. rp(r L. ':'7: ) .. * ) ..... The...,.q.pse factors ....,.:_.,

us'~a-*'fn th~s*e* *c'a:i'ctiiations* are* ~:i,ven:.:rn* ia-t>i.es 2 .1, * **2 ~ 2 . .

and 2. 3 of Runkle et al. ( Ru81 r.. ,. 'Th"E/ 6aric'ers and associ-

ated risk faqtors useci a+!= ,l.i,$ted .. in. Tctble , 1-10. For each

--~:x:i56su:rJ--.rn6de;*the" ihaiciitecla.**'pop'uiatf6n":1i.e'a1 th effect is'*

. *:, 1~+/-::!~fetf+if~=t~:zt}~a*~fg;~tli!?:il~~;l~igxt~U~~ (r~-~~;;Sir:

WT(I) = 1.), and concentration,*f~{.ios;"(r~-~-, CRDM(I),

CRDMT (I), C.RSP (I), CRWJ; ( ::J:)) _are taken . fro:m... Tables A-8 . a11d

gtf~*~.r

:~~ttlf:!e~t:l~~f6{~~~j~[!f1~*;i~*~~f$::"*!~;~!c~N~~!~; ,

and soil are the same as those given Tri-fhe Environmental-P.rotect.:i..op Agency analysig f_or.: .. $edi:ne.nt, ( Sqt.81, Table, ,5,::-5);

"'frowevifr;' ai1:*:~:d,}fffr!~i\f'6h. }:tiefJ;q::j~en:f~:'i tnJlcated 'as' 'l:5eincf zero in the preceding 't'a:bie \'ie"re 'a.ss.fgnecit.he value of 1.

fq_:r: . qµr -,~~9:}y_:5-_~s. __ ... _T_h~_ ,Ez:i:v,,ironmentc:1.-1-:, P:t;:Qt~.qJ.ion Agency.- ..m?-y have' used *'di°ff*erent di*stribt.iti*on::.:c:6e.f1icfi~_ri'ts fo'r - soiT "c:a.*1-culations but their document~t.10~ a.'bes ric/t make this clear l":"'7.

Table l-3. Variables A_E:pearing in Tables l-4, l-5 and l-6 Variable Defi:h:itio n

AIRClliI Concentra tion of suspended solids in air (units: kg/

m3) . . .

AIDG(2.) Natural logarit.,m of 2.

Area of soil (units: m2)

CMLK Indiviwa l. milk cnnsurrpti on (units: L/yr)

CMI' Individua l CEat cons~tio n (units: kg/yr)

CPLT Individua l plant con.sunpti on (units: kg/yr)

CRDM(I) Concentra tion ratio for radionucl ide I from diet to milk (units: Ci/L per Ci/day)

CRDMl'(I) Concentra tion ratio for radionucl ide I frcm diet to neat (units: Ci/kg per Ci/day)

CRSP(I) Concentra tion ratio for radionucl ide I fran soil to plant (units: unitless)

CRWF(I) Concentra tion ratio fur radionucl ide I frcF.l water to fish (units: ci/kg per ,ci/L)

DCDEF(I) Distribut ion ooefficie nt for radionucl ide I (units:

Ci/kg per Ci./L)

DE Mean particle density of soil ne.terial. (units: kg/m3)

DENSITY ~ particle density for external exposure calculati ons

. (units: kg/m3) .

DEPI'H Depth to which ra.di.onuc lides are assumed to be CDncen-trated on surface for extenial e:xp:>sUre calculati ons (units: m)

DFIDIT(I ,l,J) Ibse factor for ground exposure to o~gan J fran radio-nuclide I (units: rem/hr per. Ci./m2-) .

DF.EXT( I, 2,J) Same. as DFEXr(I.,l ~J) hit for water i.mrersion (units:

rem/hr per Ci/rrr)

1-8

Ta bl e 1- 3. (co nti nu ed )

Va ria bl e De fin iti on DF EX T( I,3 ,J) Same as PFEXT(1;1 J) bu t fo r ai r in me rsi oh (u re m/ hr pe r Ci /m3) ni ts:

DF IN G( I,J ) :COse fa ct or fo r ex po su re ra di on uc lid e I (u ni ts: to or ga n J from in ge sti on of rem pe r Ci /y r)

DF IN H{ I,J ) Sarne as DF IN G( I,J

) bu t fo r in ha la tio n DFSH Co ns tan t re la tin g fis h pr od uc tio n to riv er fla kg /y r pe r L/ yr ) ,.,r (u ni ts:

DMLK In di vi du als su pp or ted ,

by mi lk pr od uc tio n (u m2) ni ts: inc l/

DMr In di vi du als su pp or ted by r.e at pr od uc tio n (u m2) ni ts: in d/

DP Depth of so il (unit;.s:

m)

DPLT In di vi du als su pp or ted m2) by pl an t pr od uc tio n (u ni ts: irn V DPOP Co ns tan t re la tin g po pu lat io n siz e to riv er fla in d pe r L/ yr ) ,.,r (u ni ts:

DSL Po pu lat io n de ns ity fo r in ha la tio n an d ex te ca lc ul at io ns (u ni ts: rn al ex po su re ind/m2)

ER Er os io n. ra te (u ni ts:

kg/m2 pe r yr )

F Ri ve r flO N ra te (u ni ts:

L/ yr )

FMLK Fr ac tio n of lan d us ed fo r mi lk pr od uc tio n (u un itl es s) ni ts:

FMr Fr ac tio n of lan d us ed fo r rre at pr od uc tio n (u un itl es s) ni ts:

FPLT Fr ac tio n of lan d us ed to grCM pl an ts fo r huma co ns um pti on (u ni ts: n un itl es s) 1- 9

Table 1-3. (continued)

Variable Definition FREI' Fraction of radionuclides in sprinkler irrigation initially retained on plants (units: unitless}

FRIV Fraction of river used for sprinkler irrigation (units: unitless}

HLIFE(I) Half-life for radiouclide I (units: yr)

PDEN . Plant density (units: kg/m2 }

PMLK P:Lant consurrption by dairy cattle (units: kg/day)

PMI' Plant consumption by beef cattle (units: kg/day) ro Ibrosity of soil (units: unitless}

POROSIT Porosity for external exposure calculations (units:

unitless)

REXARSD Exposure to suspended sediment (units: hr /yr)

REXARSL EXfX)sure to suspended* soil (units: . hr /yr)

REXTSD Exposure to sedit:ient (units: hr/yr}

REXTSL EXfX)sure to soil (units: hr/yr)

REX.'IWAT Exposure water (units: hr/yr}

RINGWAT Water ingestion rate (units: L/yr}

RINHAIR Inhalation rate (units: m3/yr}

RO Runoff rate (units: L/m2 per yr}

SA Percent saturation of pore space in soil (units:

unitless)

T Length of radionuclide discharge (units: yr}

TD(I} Total discharge of radionuclide I (units: Ci) 1-10

Ta ble 1-3 . {co nti nu ed }

Va ria ble De fin itic n Fr ac tio n of ye ar th at ind

.ivid sus pen ded sed im en t (u nit s: ua l is e:,q;osed to

un itl es s)

TMINSL Fr ac tio n of ye ar th at ind ivi sus pen ded so il (u nit s: undu al is exp:>sed to itl es s)

We at. rer ing ha lf lif e fo r rad ion uc lid es dep ::is ite d by sp rin kle r irr ig ati on {u nit s: yr )

Wa ter co nsu rrp tic n by da iry ca ttl e (u nit s: L/d ay}

WM1' Wa ter co ris un pti on by be ef ca ttl e (u nit s: L/d ay) wr (I) Wa ter tre atm en t fac tor for rad ior ruc lid e I {u nit un i.t les s) s:

70 . Av era ge lif e ex pe cta nc y (u nit s: yr )

1-1 1

Table 1-4. Exposure to Organ Associated With Cancer J Due to Radionuclid e I for Releases to .surface Water Exoosure From Water Consumotion Individual RINGWAT*T D(I)*WT(I)*D FING(I,J)/(F* T)

(rem/ind)

Pop. Size DPOP*F*T/70 .

(ind)

Exnosure From. Fish Consumotion Individual : TD(I)*CRWF (I)*DFSH*DF ING(I,J)/(DPO P~F*T)

(rem/ind)

Pop. Size DPOP*F*T/70 .

(ind)

Exoosure From Inhalation of SUsoended Sediment Individual : DCOEF( I) *TD( I) *AIRCON*RIN HAIR*TMINSD *DFINH(I, J)/( F*T)

(rem/ind)

. i Pop. Size DPOP*F*T/70 .

(ind) i Exoosure From Water Immersion Individual : TD(I)*REXT WAT*DF(I,2 ,J)*7.E4/(F*T )

(rem/ind)

Pop. Size DPOP*F*T/70 .

(ind)

Exposure From Shoreline Sediment Individual : DCOEF(I)*TD (I)*DEPTH*D ENSITY*(l.-P OROSIT)*F~X TSD (rem/ind) *DFEXT(I,l ,J)*70./(F*T )

Pop. Size : DPOP*F*T/70 .

(ind)

Exposure From SUsoended Sedim~nt Individual DCOEF(I)*TD (I)*AIRCON* REXARSD*D FEXT(I,3,J)*7 0./{F*T)

(rem/ind) .

Pop. Size DPOP*F*T/70 .

(ind) 1-12

Ta ble 1-5 . Ex po sur e to org an As soc iat ed Wi th Ca nce r J Du e to Ra dio nu cli de I for Re lea ses to So il Ex ore ssi on s Int rod uc ed to SL 'ID lifv No tat ion S(I ) = IXDEF{I)*(l. - PO

)*DE/(IX JJEF(I)*(l. - PO)*DE + Po*lOOO

.* )

(un its : un itl es s)

A( I) = S(I )*E !V (D P* {l. -

PO)*DE) + (l. - S(I ))* Ro /(D P* PC ?.1 000 .)

+ AIL G(. 2. )/H LIF E(I )

(un its : yr - 1 ) .

FA C(I ) = 1./ (A {I) *D P* (L - PO)*DE)

(un its : ~ yr/ kg )

Ex oo sur e Fr an .Pl an t Co nsu

!ic tic n Ind ivi du al : CPLT*TD( I) *FAC( I) *CRSP(

(re m/ ind ) I) *DFJN-3( I, J) / (T*AR)

Pop. Siz e AR*FPLT*DPLT*T/70.

(io o)

Ex:oosure Fra n Mi lk Con.suIT Ption In div idu al: TD(I)*FAC{I)*CR (l;"en/ irx l) SP(I)*PMrK"C.RCM(I)*CMLK*D

. FJNi(I,J)/(T*AR}

Po p. Siz e : AR*FMI.I<*DMU<*T/70.

(irx:i}

.Exoosure Fra n Me at Co nsu np tio n In div idu al: TD(I)*FAC(I)*CRS (re m/irx i) P(I)*PMI'*CRDMI'(I)*CMI'*DFI.."1:

. i(I,J)/(T*.r\R.)

Po p. Siz e : AR*FMI'*rMI'*T/70.

(in d.)

1-1 3

Table 1-5. (cont inued )

Exoo sure From Inhal ation of Susoe nded Soil Indiv idual : TD(I) *FAC (I)(AI RCON *RINH AIR*T MINS L*DF INH(I ,J)/(T* AR)

(rem /ind)

Pop. Size : AR*DSL*T/70.

(ind)

Ext>o sure Frbm Soil Indiv idual : TD(I) *FAC (I)*DE PTH* DENS ITY*( l. - PORO SIT)*REXTSL (rem /ind)

I

DFEXT( I ,1,J) *70 ./( T*AR)

\:

Pop. Size : AR*DSL*T/70.

(ind)

ExPo sure From Susoe nded Soil Indiv idual TD ( I) *FAC( I) *AIRCON*REXARSL*DFEXT( I.,3 ,J) *70 ./(

T*AR)

(rem /ind)

Pop. Size : AR*DSL*T/70.

(ind. )

1-14

Tab le 1-6 . Exp osu re to Org an Ass ocia ted Wit h Can cer J Due to Rad ion ucli de I for Rel ease s to Sur fac e Wat er Wit h Sub sequ ent Use of Sur face Wa ter for Liv esto ck and Spr ink ler Irri gat ion Exp c,su re From Pla nt Con sum otio n Ind ivid ual PRET*TD(I) *FRIV*WHRHL*CPLT*DFING (rem /ind ) ( I ,J)/ ( T*AR*PDEN*ALcx;( 2.) )

Pop . Siz e : AR*FPLT*DPLT*T/70.

(ind )

ExP osu re From Mil k Con sum otio n Ind ivid ual a: FRET*TD(I)*FRIV*WHRH L*PMLX*CRD~(I)*CMLK*DFING(I,J)

(rem /ind ).

/(T*AR*PDEN*AL(X;(2.))

Ind ivid ual b: TD( I)*W MLK *CR D~(

I)*C ~LK *DF ING (I,J) /(F* T)

(rem /ind )

Pop . Siz e AR*FMLK*DMLK*T/70.

(in d.)

ExP osu re From Mea t Con sum otio n Ind ivid ual a: FRET*TD(I)*FRIV*WHRH L*PMT*CRD~(I)*C..~T*DFING(I,J)

(rem /ind )

/(T*AR*PDEN*ALCG(2.))

Ind ivid ual h: TD( I) '*WM'i'*CRDMT( I)

'*CMT*DFING{ I; J)/( F*T)

(rem /ind )

Pop . Siz e : AR*FMT*DMT*T/70.

(ind )

aEx pos ure from .rad ion ucl ide s dep osit ed py spr ~nk ler irri gat ion whi ch are sub seq uen tly use d as on pla nts anim al fee d.

bEx pos ure from rad ion ucl ide s in wat er use d for live sto ck.

)

1-1 5

Table 1-7. Population Health Effects for 1. *curie Radionucl ide Releases to Surface Water NUCLIDE WRHETOTa FHHETOTb INSDTOTc *EXSDTOTe EXARSDTf

. Cl4 2.0SE-05 2.58E-04 9.95E-16 o. o* 1.98E:..20 NI59 5.75E-05 l.55E-05 5.34E-14 o. o. o.

SR90 3.91E-02 3.17E-03 2.lSE-11 2.18E-10 o. 6.78E-19 ZR93 S.89E-06 5.25E-08 7.24E-ll 1. 61E-ll 3.42E-08 4.71E-17 TC99 2.00E-06 8.lOE-08 2.22E-14 5.24E-ll o. 8.19E-20 SN126 4.68E-04 3~79E-03 3.55E-13 7.26E-09 l.27E-07 l.86E-14 I129 8.87E-05 3.60E-06 4.35E-15 6.86E-09 6.35E-09 2.54E-17 CS135 l.60E-:-04 8.65E-04 4.89E-13 2.66E"'-ll o. 7.91E-19 CS137 9.72E-04 5.255-03 2.95E-12 4.03E-07 l.19E-06 L 33E-14 SM:151 l.26E-05 8.53E-07 l.90E-ll l.OSE-io* 2.03E-07 1 *.14E-12 RA226 2.34E+OO 3.17E-Ol 2.07E-09 l.31E-06 1. BlE-06 2.13E-14 U234 4.39E-03 2.37E-05 S.36E-09* 4.76E-10 3.lOE-08 2.19E-16 NP237 s.04E-03 1. 36E-04 7.90E-10 l.45E-07 l.98E-08 2.05E-16 PU238 l.73E-04 l.64E-06 7 .69E-08 6.0SE-11 3.67E-08 l.92E-16 PU239 2.87E-03 2.72E-05 3.04E-06 4.84E-ll 2.23E-08 l.SBE-16 PU240 2.87E-03 2.72E-05 3.04E-06 5.65E-ll 3.67E-08 l.84E-16 AM241 3.21E-03 2.17E-04 5.14E-07 l.57E-08 2.54E-06 2.54E-14 PU242 2.68E-03 2.53E-05 2.83E-06 4.44E-ll 3.llE-08 l.44E-16 AM243 3.22E-03 2.18E-04 5.llE-07 1.25E-07 1.84E.:...os

l *. 98E-13

.awRHETOT Total health effects from drinking water bFHHETOT - Total health effects from eating fish cINSDTOT -: Total health effects from inhalation of se.diment dEXWRTOT - Total health effects from water itnersion eEXSDTOT - Total heal th effects from external exposure

to sediment fEXARSDT - Total heal th effects from external exposure to suspended sediment 1-16

Tab le 1-8 . Pop ulat ion Hea lth Eff ects -for 1. Cur ie Rad ionu clid e Rel ease to Soi l NUCLIDE PLHETOTa MKHETOTb HTHETOTc INSLTOTd EXSLTOTe EXARSLTf Cl4 2.0S E-04 S.3SE-OS l.67 E-0 5 NI59 4 .89E -13 0, 9 ,}4E -18 l.36 E-0 5 1. 97E-06 l.89 E-0 7 SR90 2.16 E-0 3 3 .75E -05 2,2 7E- ll o. o.

3,40 E-06 9.56E-,.Q9 o. 3,02 E-1 6 ZR93 1. 29E -06 l.40 E-1 0 l.15 E-0 7 TC99 l .27E.;_08 6,02-E-06 8,31 E-1 5 8,97 E-0 7 4,87 E-07 9,42 E-07 SN126 2,lO E-0 6 1.14 E-07 l.09 E-l l o. 4.03 E-1 7 4,41 E-07 1. 74E -10 6.26 E-0 5 9,18 E-1 2 Il29 3.19 E-0 6 4,15 E-07 2,43 E-08 CS135 2,14 E-1 2 3,13 E-0 6 l.25 E-1 4 4.86 E-0 5 l.27 E-0 5 5,lO E-07 CS137 .2.4 8E- 04 6.47 E-05 2.03E"'"l0 o. 3,29 E-1 6

2. 61E-06 l,03 E-0 9 4 .lSE -04* 4,65 E-1 2 SM151 6,80 E-0 6 7.38 E-10

8,92 £-08 RA226 3. 72E -09 4.00 E-0 5 2,25 E-1 0 l.12 E-0 2 l.94 E-0 3 9.99 E-04 U234 8. 71E-07 7.63 E-04 9.00 E-1 2 4.17 E-0 3 4.52 E-05 3.72:E:-06 NP237 l.86 E-0 6 1.08 E-0 5 7.61 E-1 4 2,26 E-0 5 2.46 E-09 l.19 E-0 8 PU238 3.88 E-0 7 9.74 E-0 6 l.Ol E-1 3 l.47 E-0 5 6.37 E-10 5 ,39E -10 3,56 E-0 6 PU239 9.lS E-0 4 1. 70E -06 8.91 E-1 5 3.97 £-08 3,36 E-08 5.30 E-0 4 3.89 E-0 6 PU240 8, 91E -04 3.87 E-08 2.76 E-1 4 3.28 £-08 5.lS E-0 4 6.2.4 E-06 3.12 E-1 4 AM241 5.30 E-0 4 5.75 E-08 2.78 £-07 PU242 9,28 E-0 5 4.60 E-0 4 4.60 E-1 2 8.60 E-0 4 3. 73£- 08 3.16 E-08 AM243 4,97 £-04 5.47 E-0 6 2.54 E-1 4 7.13 E-04 7.74 E-08 3.74 E-07 l.23 E-0 4 4 .45£-,.03 4.7 9E- ll aPLHETOT - Tot al hea lth effe cts from plan t ing esti on due to radi onu clid e upta ke by plan ts from soi l hr-IKHETOT - Tot al hea lth effe cts from milk ing esti on

to radi onu clid e upta ke by plan ts from due soi l cMTHETOT - Tot al hea lth effe cts from meat ing esti on due to radi onu clid e upta ke by plan ts from soi l dtNS LTO T- Tot al hea lth effe cts from inh alat ion . of sus -

pend ed soi l eEXSLTOT - Tot al hea lth effe cts from exte rna l exp osu re to soi l

fEX ARS LT- Tot al hea lth effe cts from exte rna l exp osur e to susp end ed soi l 1-17

Ta ble 1- 9, Po pu lat ion He alt h Ef Ra dio nu cli de Re lea se fe cts fo r 1, Cu rie Wi th Su bs eq ue nt Use ofto Su rfa ce Wa ter fo r Li ve sto ck an d Sp rinSu rfa ce W ate r kl er Irr ig at io n NUCL:J:DE IPLRHETa PLHETOTb IRPLHETC Cl 4 l.1 2E -0 4 NI59 2.0 5E -04 J.1 7E -0 4 3.l OE -04 l.3 6E -0 5 SR90 2.l OE -01 3.2 3E -04 ZR93 2.1 6E -03 2.1 3E -O l 3,1 7E -05 1. 29 E- 06 TC99 l.OBE-05 3.3 0E -05 SN126 8.9 7E -07 l.1 7E 2 .52 E- 03 -O S

!12 9 2.l OE -06 2,5 2E -03 4.7 8E -04 3.1 9E -06 CS135 8.6 2E -04 4.8 1E -04 CS137 4.8 6E -05 9. llE -0 4 5.2 4E -03 2.4 8E -04 SM151 6.8 0E -05 5.4 8E -03 RA226 6,BOE-06 7,4 8E -05 l.2 6E +O l l,1 2E -0 2 U234 2,3 6E -02 l.2 6E +O l NP237 4.1 7E -03 2.7 8E

2. llE -0 2 -02 PU238 2.2 6£ -0 5 2,7 2E -02 9.3 4E -04 1.4 7E -05

PU239 LS SE -02 9,4 8E -04 PU240 9.l SE -0 4 l.6 4E l,5 5E -0 2 -02 AH241 8.9 1E -04 l.6 4E -0

1. 73E-02 2 PU242 5.J OE -04 1. 78 E-0 l,4 4E -0 2 2 AM243 8,6 0£ -0 4 l.5 3E -0 2 l.7 4E -0 2 7 .13 E- 04 1.8 1£ -02 aIPLRHET -T ot al he alt h ef fe ct s from pl an t fo lia r de po sit io n in ge sti on du e to bPLHETOT - To tal he alt h ef fe cts fro to rad ion uc lid e up tak e m pl an t in ge sti on du e by pl an ts fro m so il CIRPLHET - IPLRHET +

PLHETOT 1-1 8

Table 1-9. (continu ed)

NUCLIDE IMKRHETd IMKWHETe MKHETOTf IRMKHETg Cl4 2.92E-05 l.69E-05 5.35E-05 9.95E-05 NI59 4.51E-05 2.60E-05 1. 97E-06 7.30E-05 SR90 3.66E-03 2.llE-03 3.75E-05 5.81E-03 ZR93 . 3.44E-09 1. 99E-09 l.40E-10 S.57E-09 TC99 S.84E-06 3.37E-06 4.87E-07 9.70E-06 SN126 l.37E-04 7.91E-05 l.14E-07 2.16E-04 1129 6 .* 23E-05 3.60E-05 4.lSE-07 9.86E-,.05 CS135 2.25E-04 l.30E-04 1. 27E-05 3.67E-04 CS137 l.36E-03 7.88E-04 6.47E-05 2.22E-03 SM151 7.38E-09 4.27E-03 7.38E-10 1.24E-08 RA226 2.19E+OO l.27E-00

l.94E-03 3~46E+OO U234 2.57E-04 l.(i.SE-04 4.52E-05 4.SOE-04 NP237 2.94E-06 1. 70E-06 2.46E-09 4.65E-06 PU238 4.0SE-08 2.34E-08 6.37E-10 6.46E-08 PU239 .* 6.73E-07 3.88E-07 3.97£-08 l.lOE-06 PU240 6. 72E-07 3.88E-07 3.87E-08 l.lOE-06 AM241

l.88E-06 l.08E-06 5.75£-08 3.02E-06 PU242 6.26E-07 3.625-07 3.73E-08 1.02E-06 AM243 l.88E-06 l.09E-08 7.74£-08 3/0SE-06 dIMKRHET - Total health effects from foliar depositi on and subseque ~~ plant use in milk producti on eIMKWHET - Total health effects from water used for milk cattle f~IKHETOT- Total health effects from milk ingestio n due to radionu clide uptake by plants from soil gIRMKHET - IMKRHET + IMKWHET + MKHETOT 1-19

Tab le 1-9 . (Co ntin ued )

NUCLIDE IHTRHETh H1TWHETi HTHETOTj IRHTHETk C14 9. llE- 06 4.3 9E- 06 Nl59 4.Jl E-0 6 l.67 E-0 5 3.0 2E- 05 2.0 7E- 06 1. 89£ -07 6.5 7E- 0~

SR90 3 .32E.-04 l.60E...;04 ZR93 3.4 0E- 06 4.9 4E- 04 2.~83E-06 l.36 E-0 6 l. lSE -07 TC99 l.13 E-0 5 4.3 1E- 06 5.44 E-0 6 9 .42 £-0 7. 1. 77E -05 SN126 5.30 E-0 4 2.55 E-0 4 Il2 9 4 .4.l E-0 7 7.8 5E- 04 3.64 E-0 6 l.75 E-0 6 2.4 3E- 08 CS135 9.0S E-0 6 5.4 1E- 06 4.3 6E- 06 5.lO E-0 7 l.39 E-0 5 CS137 5.SOE-05 2.6 5E- 05 SH151 2.6 1E- 06 8.4 1E- 05 8.93 E-0 7 4.3 0E- 07 8.9 2E- 08 RA226 l.13E+OO 1.4 1E- 06 5.4 3E- Ol 9.9 9E- 04 l.67E+OO U234 2. llE -05 l.02 E-0 5

_NP237 J.72 E-0 6 3.5 0E- 05 l.42 E-0 5 6.86 E-0 6 l.19 E-0 8 PU238 3.4 3E- 08 2.ll E-0 5 l.65 E-0 8 5.3 9E- 10 5.1 4E- 08 PU239 5.6 9E- 07 2.74 E-0 7 PU240 3.3 6E- 08 8.7 7E- 07 5.69 E-0 7 2.7 4E- 07 3.2 8E- 08 AH241 9.07 E-0 6 8.7 5E- 07 4.37 E-0 6 2.7 8E- 07 1.3 7E- 05 PU242 5.3 0£- 07 2.5 5E- 07 AN243

J.16 E-0 8 8.1 6E- 07 9.12 E-0 6 4.3 9E- 06 3. 74E-07 1.3 9E- 05 hIMTRHET - to hea lth eff ect s from fol iar dep and sub seq uen t pla nt use in mea osi tion t pro duc tion iIMTWHET - Tot al hea lth eff ect s from wat er pro duc tion . use d for meat

\1THETOT - Tot al hea lth eff ect s from mea t to rad ion ucl ide upt ake by pla ntsing est ion due from soi l kIRMTHET - UlTRHET + IMTWHET + MTHETOT 1-2 0

Table 1-10. Organs and Risk Factors Conside red Risk Factor EPAa Risk Factor Sandiab Organ/C ancer (cancer/ ind-rem) (cancer/ ind-rem )

Bone l.OOE-5 9.75E-6 Red Marrow/

Leukemi a 4.00E-5 2.85E-5c Lung 4.00E-5 2.SE-5 Liver 1. OOE-5 GI-LLI 2.00E-5 Stomach l.15E-5d Pancreas 3.85E-6d Other GI 3.85E-6d Thyroid 1. OOE-6.

Kidney 1. OOE-5 Breast 2.88E-5e Other 7.00E-s 3.60E-5e aFrom Table 4.3-1 of (Sm81) bFrom Table 3. 4 of (Ru81) cDose factor for bone used

<loose factor for GI-LLI used eDose factor for total body used 1-21

{ see

Sm8 1, p. 93) . The val ues var iab les are ind ica ted . in Tab use d for all oth er le 1-1 1.

To gen era te the val ues for IMK Tab le 1-9 , it was nec ess ary WHET and IMTWHET in to kno w the are a AR und er con sid era tio n. Th is was obt ain ed by ass um ing irr iga tio n rat e IRAT of 300 tha t an L/m 2 per yr was use d.

The n, AR can be exp res sed in term s of IRA T, F and FRI V.

1.4 Com par iso n Wit h Env iro nm ent al Pro tec tio n Age ncy Re sul ts The Env iro nm ent al Pro tec rel eas e to sur fac e wa ter are tio n Age ncy res ult s for a pre sen ted in Tab le 1-1 2.

As alr ead y not ed, it is the num ber s app ear ing in the col um n lab ele d "TOTAL" of thi s tab le tha t wer e use d in obt ain ing the Env iro nm ent al Pro tec tio n Age ncy dra ft sta nda rd for rad ion ucl ide rel

ge olo gic dis pos al *fo r hig h-l eas es in the con tex t of eve l wa ste ; the se num ber s wer e obt ain ed by sum min g the num ber s in the oth er co l-umn s and rep res ent tot al pop ula tio n hea lth eff ect s. The pop ula tio n hea lth eff ect s in thr oug h "p = s*i are now com col um ns lab ele d "p = l" par ed wit h rel ate d res ult s in Tab les 1-7 , 1-8 and 1-9 .

The res ult s for dri nki ng wa in col um n p = l of Tab le 1-1 ter ing est ion app ear ing Tab le 1-7 we re cal cul ate d wit 2 and col um n WRHETOT of h mo del s tha t are ess en-tia lly ide nti cal . Thi s sim ila rity ten ds to be by the dif fer enc es in not ati obs cqr ed on use d in thi s rep ort and in {Sm and der iva tio n tec hni que

81) . Th ere for e, the com -

pu tat ion al app roa ch use d in the two dev elo pm ent s wi ll be com par ed. Much of the app are nt dif fer enc e ari ses fro m the nat ure of the dos e fac tor s use d. In thi s reg ard ,

the rea der is rem ind ed tha t the dos e fac tor s in {Sm 81) for ing est ion and inh ala tio n yie ld a 50. yea r dos e com -

mit me nt from a 1,. yea r exp osu re. In con tra st, in our ana lys is the dos e fac tor s for yie ld a 70. yea r dos e com mit ing est ion and inh ala tio n men t fro m a 70. yea r chr oni c exp osu re. For the for me r qos e

of a 1. yea r ing est ion or inh fac tor s, mu ltip lic ati on fac tor pro vid es the 50. yea r ala tio n rat e by the dos e of exp osu re; for the lat ter com mit men t fro m the 1. yea r dos e fac tor s, mu ltip lic ati on of the ave rag e ann ual ing est ion or inh ala tio n rat e by the dos e fac tor pro vid es the

yea rs wh ich res ult s fro m 70. dos e com mit men t Ov er 70.

yea rs of exp osu re.

1-2 2

Table 1-11. Variable s Used in Calculati on of Results Presented in Tables 1-7, 1-8 and 1-9

-Variable Definitio n Variable Definitio n AIR<;ON '3.5E-9 kg/m3 (Bon73, Table 1.4-5) PDEN 2. kg/m2 (Nu76, p. 1.109-55 )

CMLK 110. L/yr (Nu76, Table D-1) PMLK 50. kg/day (Nu76, Table A-10)

CMT 95. kg/yr (Nu76, Table D-1) PMT 50. kg/day (Nu76, Table A-10)

CPLT 190. kg/yr (Nu76, Table D-1) PO .5 (To70, *Table 4-25)

DE 2800. kg/m3 (Cu73, Table 34-20) POROSIT .5 (To70, Table 4-25)

DENSITY 2800. kg/rn3 (Cu73, Taule 34~20) REXARSD' 8.3 *hr/yr (Nu76, Table D-1)

DEPTH .025 m REXARSL 8760. hr/yr (Nu76, Table D-1)

DFSH 3.3E-7 kg/L (Sm81, p. 87) REXTSD 8.3 hr/yr (Nu76, Table D-1)

DMLK l.5E-3 ind/m2 (Sm81, P* 91) REXTSL 8760 hr/yr (Nu76, T~ble D-1)

DMT 2.lE-4 ind/m2 (SmBl, .p. 91) REXTWAT 8.3 hr/yr (Nu76, Table D-1)

DP .!Sm (SmBl, p. 85) RINGWAT 370. L/yr (Nu76, Table D-1)

DPLT l.OE-3 ind/m 2 (Sm81, p. 91) RINHAIR 7300 ~ 3 /yr (Nu76, Table D-1)

DPOP 3.3E-7 ind-yr/L (Sm81, P* 86) RO 510 L/rn2-yr (To70, Table 2-22)

DSL 6.67E-5 ind/m2 (SmBl, P* 91) SA .5 (To70, Figure 4-2)

ER .35 kg-yr/m2 (To70, Table 2-33) TMINSD 9.SE-4 (Nu76, Table D~l)

FMLK .25 (SM81, P* 89) TMINSL 1. (Nu76, Table D-1)

FMT .25 (Sm81, P* 89) WHRHL .038 yr (Boo81)

FPLT .5 (Sm81, p. 89) WMLK 60 L/day (Nu76, Table A-10)

FRET .25 (BooBl) WM': SOL/day (Nu76, Table A-10)

FRIV 1.

1-23

Ta ble 1- 12 . He alt h Ef fe cts pe r Cu rie Re lea sed fo r Re lea se s to a Ri ve ra Drinking Freshldater Sur Above face Inh alat ion Ext ern al Ext erna l Water f tsh. C"ro of (lose - Dose -

~c l Ide TOTAL Kn9esUon lnges tio11 lnges tpston Hilk Beef ResuspendeCI Ground Air lnges tion Ing esti on Materia I Con tam. Submen ion (p .. 1) (p .. 2) (p ., 3) (p Q 4). (p "' 5) (p 6) a (p "' 7) (p "' 8)

C- 14 4.5 8*E - 2 7.40 E- 5 5.59 E- 4 2 .99 E-2 1.11 E- 2 4.l OE -3 1.46 Ni- 59 E-12 o.o u.o Sr- 90 1.21 E- l 8.0 3 E- J 6.6 6 E- 5 1.05 E- l 7.79 E- 3 1.04 E- 4 7 .81 E- 7 Zr- 93 0.0 o.o Tc- 99 2.85 E- 4 2.4 2 E- 5 6.* 02 E- 7 l.92 E- 4 6 .25 E- 5 5.8 2 E- 6 4 .92 Sn-126 1.2 0 E- l !.41 E- 3 E-10 0.0 u.a

. 7 .01 E- 3 6.66 E- 3 2.95 E- 4 2.09 [;,. 3 3.71 E-J-12!1 1.08 E- 2 l.63 E- 3 6 1.02 E- l 5.61 E- 9 4 .05 E- 5 6 .4J E- 3 2 .114 E- J l .84 E- 4 1.2 2 Cs-135 3.81 E- 3 2.55 E- 4 E- 8 9 .19 E- 5 1.54 E-12 1.69 E- 4 2.13 E- 3 9.99 E- 4 2.65 E- 4 l".12 E- 7 Cs-137 1.98 E- 2 2.01 E- 3 1.33 E- 3 7.83 E- 3 2.08 o.o o.o

>>.1 51 E- 3 5 .55 E- 4 7.51 E- 8 5 .96 £- 3 3.JS E-10 Ra-226 U-234 Mp-237 5.96 E- l I.JO E- l *2. 15 £-3 4.6U E- l 9.21 E- 5 3.9 0£- 4 Pu-2 JB 2.29 E- 2 3.9 2 [- 3 2.28 E- 3 LO J E- l 4 .95 E- l 2 .22 £- 8 1.42 E- 2 3.03 E.:.. 8 1,16 E- 9 fu-239 6,92 E- 2 4 .32 E- 3 2.5 0 E- 3 2.40 E- J S.l 6E -5 2 .63 E-!3 2.51 E- 2 5.3 9 E- 8 2.0 6 E- 9 Pu-21.10 6.53 E- 2 4.32 E- J 2.51 E- 3 3.6 9 E- 2 3.24 E- 4 1.71 2.37 E- 2 S.16 E- B E-12 Aa-241 7,19 E- l 1.97 E- 9 J.41 [- 2 5.8.6 E- 'l 3.00 LJ2 E:- l 5.47 E- l 5 .61 E- l B.3 2 E- 4 E-12

!lu- 242 6.76 E- l l.91 E- 6 LU E- 2 8 .61 E- 3 l.b4 4.1 0 E- l 2.38 E- l . 2.43 E- 2 *4,44 E- E-10

~2 i!J 2.68 E 0 B 4 .29 E- B 3.62 E- 2 6.07 E- 4 3.1 3.38 E-*K° l.40 E- 2 2 ,13 E 0 3.28 0 E-12 E- l 1.55 E- 5 8 .93 E- 2 1.1 3 E- l

&.61 E- 9 aT his ta bl e is a re pr in t of Ta ble *D -2 of (Sm 8l} o 1-2 4

From (3.1.2 -6) in (Sm81 ), the popul ation expos ure from a releas e to a river is given by

( 1. 8) where s repres ents popul ation exposu re to organ o 00 from radign uclide n for path*p (in this case, p = 1),

PR* repres ents the size of the popul ation expose d each year to drinki ng water, Iw repres ents indivi dual water consum ption per year, Dnop repres ents the dose factor to organ o from radion uclide n for path p,* Qnp repre-sents the total releas e of radion uclide n for path p, and R repres ents annua l river discha rge. From the relati ons in Table 1-4, the same popul ation expos ure is given by RINGW AT*Tb (I)*WT (I)*DF ING{I, J)*DPO P/70. ( 1. 9)

The expre ssions for popul ation exposu re in (1.8) and (1.9) are essen tially the same as the follow ing corres ponde nces ~xist:

PR/R = DPOP = 3.3E-7 ind-yr /L* in both analys es 1603 L/yr in EPA analy sis Iw -* RINGWAT =

370 L/yr in prese nt analy sis Qnp = TD{I) = 1. Ci in both analys es WT{ I) = 1. in both analy ses.

The differ ence betwee n the expre ssions Dno and DFING {I,J)/7 0 *. arises from the nature of tRe dose*

facto rs: this is best seen by first calcu lating an indivi dual dose commi tment and then conve rting to

a popul ation dose commi tment.

1-.25

. From (3.1.2-1) in (Sm81), the SO. year dose commitment to an individua*l from the radionuclides in water ingested during 1. year is gi~en by (1.10)

For the preceding relation, Dinop and On are being considered functions of time DinopCt) an~ OnpCt) such

.that DinopCt) is the total dose commitment to an indi-vidual from_ birth to time t and Onp(t) is the total radionuclide release from time O to time t. Then,

DI~ 0 p(t) and O~p(t) represent the derivatives of these functions with respect to time and thus corre-spond to annu.al individual dose commitment rate at time t and annual discharge rate at time t. Multiplication*

of the expression in (1.10) by population size PR yields the population dose commitment rate *

(1.11)

Now, integration ca:1 be used to ecover Snap for a time*

perio~ of length Tin the following 7 manner:

(1.12}

=

which yields the relation in (1.8).

In comparison, Table 1-4 provides the following expression for a, 70. year dose commitment to an indi-vidual from a chronic 70. year exposure:

RINGWAT*TD (I) *WT (I) *DFING (I, J} / ( F*T) * (1.13) 1-26"

The expressi on for total populati on size is derived from the assumpt ions that the size of the populati on exposed to drinking water each year is DPOP*F, that the time period consider ed is of length T, and that the average life expect~n cy is 70. years. Thus, if Tis signific ant-ly larger thari 70., then the total number of individu als exposed is given by DPOP*F* T/70~ (1.14)

Now, multipl ication of the expressi ons in (1.13) and (1.14) yields the relation in (1.9).

The use of deri va ti ves and integral s in ( 1 .10) , ( 1.11) ,

and (1.12) tends to obscure the relation between the expres-sions in (1.8) and (1.9). Therefor e, the expressi on in (1.10) for individu al dose commitm ent will be reconsid ered with an average annual discharg e rate rather than a time varying discharg e rate obtained by differen tiating QnpCt).

Specifi cally, with the assumpti on that a total discharg e

of size Qnp takes place over a time period of length T,

the expres"S ion £Or 50. year dose cornmi tment to an individu al *from 1. year of exposure in (1.10) becomes (1.15) and so the dos~ commitm ent to an individu al from 50. years of exposure can be estimate d as

( 1.16)

The expressi on for lifetime dose commitm ent .in (1.16) from the Envirori mental Protecti on Agency analysis is compara ble to the similar expressi on in (1.13) for lifetime dose commitm ent.. For* both expressi ons, multipl ication by total populati on size for the time per1od consider ed will yield populat ion dose. The populati on for (l.lfr) is PR*T/50 . = DPOP*R* T/50. (1.17) while the populati on for (1.13) is given in (1.14). Now, multipl ication of the expressi ons in ( 1.16) and ( 1.1 7) will yield *( 1.8). Similarl y, multipli catiop. of the expressi ons in (1.13) and (1.14) will yield (1.9).

1-27

Ov era ll, .the res ult s app ear ing for ing est ion in Tab les 1-1 2 and 1-7 drin kin g wat er are qui te sim ilar . In mos t cas es, the diff ere nce was .les

mag nitu de; how eve r, in a few cas s tha n one ord er of es the dif fer enc e was gre ate r. As bot h app roa che s use d the sam e tech niq ue to cal cul ate sur fac e wat er con cen trat are dui to.t he wat er ing esti on rateion , the dif fere nce s cer s con side red and the dos e and s assu med , the can -

risk fac tor s use d.

The org ans and risk fac tor s use d for*

ing est ion and inh ala tion cal cul atio ns are giv en in Tab le 1-1 0. Fur the r, the dif -

fere nce s in the dos e fac tor s con side red 'has alre ady bee n dis cus sed .

The res ult s for .fre shw ater in colu mn p = 2 of Tab le 1-1 3 andfish ing esti on app ear ing 1-7 wer e cal cul ate d wit h mod els colu mn FHHETOT of Tab le tha t are ess ent iall y ide nti cal . Aga in, the res ult s are the res ult s are wit hin an ord er sim ilar ; in mos t cas es, of mag nitu de. Hqw ever , in som e cas es, the diff ere nce is clo ser to two ord ers of ma gni tud e.* As for wat er ing esti on, duc ed by the can cer s, dos e fac tors dif fer enc es are int ro-Alt hou gh mos t of the con cen trat ion and risk fac tor s use d.

fish use d in the two ana lyse s are rat ios from *wa ter to is als o intr odu ced her e (see Tab sim ilar , som e var iati on le 5-2 of (Srn Bl} and Tab le A-8 of (Nu 76)) *.

The res ult s for pla nt ing esti on p = 3 of Tab le 1-1 2 and colu mn IRPL app ear ing in colu mn cal cul ate d wit h sim ilar mod els. HET of Tab le 1-9 are Bot h mod els hav e a sub -

mod el for rad ion ucl ide bui ld-u p irri gat ion and a sub mod e! for rad on pla nts due to spr ink ler ion ucl ide bui ld-u p in

.so il. For IRPL HET , the pop ula tion hea lth cia ted wit h the se two sub mod els eff ect s ass o-are giv en in. the colu mns lab ele d IPLRHET and PLHETOT, res no suc h dis tin ctio n is mad e in the pec tive ly, in Tab le 1-9 ;

(Sm 81). res ult s pre sen ted in For bot h ana lys es, a rad ion ucl ide assu med to tak e pla ce to soi l thro rele ase is ugh spr ink ler irri ga-tio n wit h 50 per cen t of the soi l bei ng use d to grow pla nt ma teri al for dir ect hum an Env iron men tal Pro tec tion Age ncy con sum ptio n. In the stud y (Sm 81), it. is assu med tha t a .5 cur ie rele ase to the soi l for eac h rad ion ucl ide tak es pla ce; for the gen era ted Tab le 1-9 , a 1. cur ie cal cul atio ns tha t rele ase is assu med to tak e pla ce. The refo re, as the mod res pec t to rad ion ucl ide inp ut, the els are lin ear wit h app rop riat e com par ison betw een the ing esti on rate s sho uld cat ed val ues for IRPLHET div ide d be mad e wit h the ind i-by 2. Bot h mod els use the sam e exp one ntia l mod el for rad pla nts due . to spr ink ler irri gat ion ion ucl ide bui ld-u p on (i.e .,

the sub mod e!

1-2 8

used in determ ining IPLRH ET); .howev er, some of the param eters used within the model were differ ent (e.g.,

.20 for fracti on of radion uclide s initia lly retain ed in the Enviro nment al Protec tion Agenc y analy sis.an d .25 in our analy sis). Both models also use simila r expon ential model s to repres ent radion uclide build- up in the soil (i.e., the submo del used in determ ining PLHET OT). In the Enviro nment al Protec tion Agenc* y analy sis, radion u-clide remov al is by w~ter flow and radioa ctive decay.

Our analy sis includ es those two remov al mecha nisms and also solid- mater ial outflo w. Howev er, the models may diffe r in some detail s (e.g., . the exact manne r in which the rate consta nts for radion uclide outflo w in water were determ ined) and in the actua l param eters used in the analys es (e.g., water outflo w rates, distri butio n coeff icient s). Howev er, the final calcu lated health effec ts are gener ally within an order of magni tude of each other. The differ ences are proba bly due*to the differ ent cance rs, dose factor s and risk factor s con-sidere d and. to the differ ent values used *for the same or simila r param eters. Also, the inclus ion of soil remov al (i.e., erosio n) in the calcu lation of PLHETOT may have an effec t.

The result s for milk ingest ion appea ring.i n column p = 4 of Table* 1-12 can be compa red with the sum of the values appea ring in column s IMKRHET and MKHETOT of Table 1-9. In both analys es, it is assume d that 25 perce nt of the availa ble land is used to grow plarit mate-rial* for use in milk produ ction. The values for IMKRHET resul t from the rc;1dio nuclid es retain ed on plants due to-sprin kler.i rrigat ion and the values for MKHETOT resul t from the radion uclide s in plants due to uptake from soil.

As for direc t plant ingest ion,* the result s* in Table

1-12 are the sum of these two paths .

Also,* as a. 1 *.curie releas e was consid ered in the* gener ation of the resul ts contai ned in Table 1-9, the prope r compa rison is betwee n the *va.lue s in Table 1-12 and one-h alf of the sum of IMKRHET and MKHETOT. As radion uclide conce ntrati on in plants for.an imal feed was determ ined in the same manne r as radion uclide conce ntratio n in plants for human con-sumpt ion, the discus sion in. the preced ing paragr aph is also releva nt to the presen t. compa rison. There is a consid erable amoun t of differ ence betwee n the milk inges tion result s in the Enviro nment al Prote ction Agenc y analy sis and in our analy sis. Althou gh the result s are simil ar for some radion uclide s, for other :radio nuclid differ enc~ of up to three orders of magni tude exists . es a These differ ences are probab ly caused by factor s of the 1-29

type .already indicated~ However, to identify the major causes of these difference s, it would be necessary to compare *calculatio ns for the same radionucli des_on a parameter -by-param eter basis. The health effects that result from radionucli des in livestock water for dairy cattle are indicated in column* IMK\lHET of Table 1-9.

This path is not included in the calculatio n of the results presented in Table 1.12.

The results for beef ingestion appearing in column p = 5 of. Table 1-12 can be compared with the sum of values appearing in columns IMTRHET and MTHETOT of Table 1-9. As the calculatio ns for.beef ingestion are the same as _those for milk-inge stion except for the us~ of appropria te concentra tion ~atios .and ingestion rates, the discussion for milk ingestion also* pertains to beef ingestion. Overall, the results for heef inges-tion for the two analyses are more similar than those for- milk ingestion. For most radionucl ides, the results are within one order of magnitude . However, in some cases~ this_diffe rence goes up to approxima tely two orders of magnitude . .The h~al th effects that result from radionucli des in livestock water for beef cattle are indicated in column tMTWHET of Table 1-9. As for milk consumptio n, this path is not included in the calculatio n of the results presented in.Table 1-12 *.

Results in. the Environme ntal Protection Agency analysis for health effects due to inhalation of *sus-pended material, external exposure due to ground con-taminatio n and external exposure due to suspended material in air are presented in columns p = 6, p = 7, and p = 8, respective ly, of Table 1-12. Similar results for our analysis are presented in columns INSLTOT, EXSLTOT, and EXARSLT, respective ly, of Table 1-8. As our analysis was for a total release of 1. curie, the values in Table 1-12 should be compared with one-half the correspond _ing values in Table 1-8. Generally , the results in our analysis are one to two orders of magni-tude below cor*respon ding results in Table 1-12. . In the Environme ntal Protection Agency analY-sis, it is assumed that all radionucl ides in the soil are concenttr ated on the surface for the calculatio n of the exposure modes*

now under considera tion (see Equations (3.1.5:-9) and (3.1.5-10) in (Sm81)). This alone is sufficien t to cause discernab le difference s between tJ1e results.

1-30

To dete rmi ne inh alat ion exp osu re, Pro tect ion Age ncy obta ined susp end the Env iron men tal ed rad ion ucli de con~

cen trat ion thro ugh mu ltip lica tion of surf ace rad ion ucli de con cen trat ion (un its: Ci/r n2) by a resu spe nsio n fac tor of 10-9 m-1 (Sm 81, p. 92) . In con tras t, we obta ined susp end ed rad ion ucli de con cen trat ion by mu ltip nuc lide con cen trat ion (un its: ci/m lica tion of soi l rad io-

3) by an assu med *con cen-trat ion qf susp end ed mat eria l in air of 3. SE-9 kg/m 3 .* For an assu med amo unt X of a par ticu lar rad ion ucli de in a soi l reg ion of area AR, the Env iron men tal Pro tect ion Age ncy I

. I app roac h yie lds a susp end ed con cen trat ion of I (X/A R)* lo- 9 = X*l o- 9 /AR Ci/r n3 (1.1 8) whi ie our app roac h yiel ds a susp end ed rad ion ucli de con cen -

trat ion of (X/( AR* .15* 280 0.*. 5))* 3.SE -9

= (X/A R}* l~7E -ll Ci/~ 3. (1.1 9)

Thu s, this diff ere nce alo ne.w ill cau se the res ults from Tab les 1-12 and 1-8 for inh alat ion of rad ion ucli des and ext ern al exp osu re to susp end ed rad ion ucli des to dif fer by a fac tor of. app roxi mat ely 59.

Sim ilar ly, for grou nd exp osu re, we assu me tha t only the

.rad ionu clid es in the top 2. 5 cm of the so.il . are ava ilab le for ext ern al exp osu re. Thu s, as our soi l was assu med to be dee p and *the Env iron men tal Pro tect 15. cm ion *Age ncy ana lysi s assu med tha t all rad ion ucli des . in soi l wer* e

on the surf ace , this diff eren ce alon e wil l cau se the res ults from Tab le 1-12 and 1-8 for grou nd.e xpo sure to dif fer by a fac tor of 6. Oth er diff eren ces are due to the can cers , dos~ fac tors and risk fac tors con side red ,and to the ind ivid ual para met ers used in dete rmi ning the amo unt of each rad ion ucli de in soi

l.

In sum mar y, the. pop ulat ion hea lth ana lysi s wer e gen eral ly wit hin one mag nitu de of the res ults obta ined Pro tect ion Age ncy ana lysi s.

effe cts in our to .two ord ers of in the Env iron men tal How ever , in som e cas es, the diff ere nce s wer e clo ser to thre e ord As. the two ana lyse s u*sed sim ilar moders of mag nitu de.

els, thes e dif fer -

enc es are due prim aril y to the can cers , dose fac tors ,

1-31

and risk factors used and to the parameters actually us.ed within the models. If desired, the exact cause of the differences can be determined.fo r individual radio-nuclides and specif,ic exposure pathways.from a parameter by.parameter comparison of.the two calculations .

1.5 Discussion overall; it is f~lt that the computationa l relationships indicated in Tables 1-4, 1-5 and 1-6 will yield conservative results. For example, no radio-nuclide removal by *sedimentation is considered in the results related to surface-wate r concentration in Table 1-4. However, the individual using these relati.onship s has a great deal of control on the conservatism of the final calculated' results through the selection Qf inges-tion* rates, concentration ratios, risk factors, constants used in the definition of population *size, and other

parameters.

The relationships presented in Tables 1-4, 1-5 .and 1-6 provide a conven.:i.ent way to observe the differences between exposures* to indi viduais and populations. In.

particular, the exposure to individuals can vary dramat-ically while population exposure.rem ains unchanged. This results from the assumed linearity of the processes con~

sidered.. Thus, while length of* release and size of river receiv~ng the release will affect individual exposure; these properties \~ill not affect_ population exposure obtained. with th~ models in use.

_Computation al relationships of the form given in Tables 1-4, 1-5 and 1-6 provide a way of comparing hazards from different 'substances. They could be used

.to compare risks between artificially and naturally occurring radioactivity '. Also, *there is nothing in the models which is inherently.ti ed to radioactive materials~

T}:lerefore, provided *appropFiate. dose and risk factors were defined, they*could be used to calculate the con-sequences associated with noriradioacti~ e pollutants. In turn, s*uch values could be used in *the comparison of the.

risks associated with wast~ disposal and the risks asso-ciated with ot}:ler activities ... In making such comparisons,

-it is essentia*1 that. the compared* risks be calculated in the same manner and w.1th. the' same degree of conservatism* .

Otherwise,. *the comparisons

a*re rr:ieaningless. Hopefully, with re.lat;ively* simple models such as those in Tables 1-4, 1-5 and 1:...6, it would be possible to treat all the substances considered in the same manner.

1-32.

Th e co m pu ta tio na an d 1- 6 pr ov id e l re la ti on sh ip s a wa y to sc re en in Ta bl es 1- 4, 1-ra di on uc li de s to fo r th e m os t ap 5 co ns id er in th e. pr op ri at e di sp os al of hi gh re gu la ti on of ge

-l ev el w as te . Th e co ns eq ue nc es ol og ic at ed . w it h a un it as re le as e of ea ch ra di on uc so ci -

in te re st ..ca n be li de of po ss ib le ca lc ui at ed . Th es e co ns eq ue nc be w ei gh te d by es ca n th en th e in ve nt or y of On ce th is .h as be th e ra di on uc li de en do ne fo r al l pr es en t.

at io n of th e re ra ia ti ve si ze of th di on uc li de s, co ns id er -

pr ov id es on e wa e w ei gh te d co ns y to se le ct _t he eq re gu la to ry co ns ra di on uc li de s fo ue nc es id er at io n. r U nf or tu na te ly , ma 1- 4, 1- S* an d 1- 6 ny of th e va ri ab w il l be im pr ec is le s us ed in Ta bl ys is . el y kn ow n in an y es Th e re la ti ve si m an al -

.th es e ta bl es pe pl ic it y of th e. re la rm its an ea sy in ti on sh ip s in un ce rt ai nt y in sp ec ti on of th e in di vi du al va ri a- ef fe ct s of ef fe ct is li ne ar bl es .

Q ui te of te

. Fo r ex am pl e, a do n, th is in ge st io n ra te w ub lin g of th e w D is ce rn m en t of th il l do ub le th e as so ci at ed co at er e ef fe ct s of va ns eq ue nc es .

si bl y co rr el at ed ri at io n in se ve ra

). va ri ab le s is m i {p os -

te ch ni qu es ex is or e di ff ic ul t.

t w hi ch ca n be us Ho we ve r, .

ed in su .ch an al ys es ( Im 78 ).

Ta bl es 1- 7,

1- 8 he al th ef fe ct s an d 1- 9 pr es en t fo r th e va ri ou s th e po pu la ti Ta bl es i- 4, ;1..-5 pa th w ay s co ns id er on an d 1- 6 w ith . a re ed in in di vi du al pa ra m le as e of 1. C i.

et er s us ed in th Th e ar e in di ca te d in e as so ci at ed ca Se ct io n ~- 3~ It lc ul at io ns in ve st ig at e th e is of te n po ss ib ef le to re pr od uc in g ar i en fe ct s of ot he r pa ra m et er s w ith ti re ca lc ul at io n. ou t f I

ef fe ct s fo r a w Fo r ex am pl e, th e at er in ge st io n ra he al th I,:'

p. 86 ) ra th er th te of 60 3. L /y r i an 37 0. L/ yr ca n (S rn 81 , I, pl yi ng th e re su be ob ta in ed by m i*.'

lt s ul ti - ;.:.

60 3. /3 70 .. Th e co in co lu m n WRHETOT of Ta bl e 1- 7 r*

m bi ne d ef fe ct s of by L ca n be ob ta in ed va ri ou s. re le as e by ta ki ng ap pr op m od es ,*,.

of va lu es ih Ta bl ri at e li ne ar co m '

1*

es f,. .7 , 1- 8 an d 1- 9. Fo bi na tio ns po pu la ti on he al th r ex am pl e, th e !

ef fe ct s fo r ea ch w at er an d pl an t ra di on uc li de du e !

in ri ve r w ith 10 pe ge st io n re su lt in g fr om a re le as to rc en t of th e ri ve e to a ir ri ga ti on ar e gi ve n by r us ed fo r fl oo d (

1.*WRHETOT + .l* PL HE TO T. ( 1. 20 )

St ic h re la ti on sh ip an d di ff er en t as s ca n be us ed to in ve st ig at e di ff er en t si su m pt io ns ab ou t te s a sp ec if ic si te .

i..

1- 33 i.

i

This discussion ends with a caveat. The models presented are very simple and propably tend to over-estimate health effects. They will certainly do so if one is suffi6iently aggressive in seeking out conservative values for the individual parameters in the models. Therefore, care must be exercised in the interpretation and presentation of model predictions.

In particular, care must be taken in comparing results obtained with these models with results obtained with other methods. However, there is also an advantage to this simplicity. It permits consideration of different hazards at an equivalent level of complexity.

1-34

2. Mixed-Cel l Models

.The exposure calculatio ns presented in later chapters are based on radionucl ide concen~ra tions obtained by ujing one compartme nt mixed-cel l models. For releases .to sur-face water, no radionucli de partitioni ng within the cell is considered . However, for releases to soil, such parti-tioning is considered . To facilitate presentat ion of the later exposure calculatio ns, derivation s are presented in this chapter for the different ial equations which underlie the models in use. This presentati on is adapted from

Sections B-2 arid B-3 of Helton and Finley (He82).

The different ial equation for a single uniformly -

mixed cell without radionucli de partitioni ng between a liquid and a solid phase is presented first. The situ.a-tion under considera tion is indicated in Figure 2-1. The cell is assumed to have a constant volume VW (units: L).

Further, it is ass:umed that water enters and leaves the cell at a rate RW (units: L/yr) and that a rc;1.dionucl ide with decay constant ;\(units: yr-1) enters *the cell at a rate R (units: Ci/yr). It is desired to determine the amount X(t) (units: Ci) of the radionucl ide present in the cell at time t (units: yrs) .. The basic assump-tion used in deriving X(.t) is that the cell* is uniformly -

mixed: mathemati cally, this means that the radionucl ide concentra tion C(t) (units: Ci/L) at any time t i s given by c(t) = x(t)/vw *. ( 2 .1)

A different ial equation representi ng the rate of change of X(t) is now derived. Then, X(t) can be obtained by solving this equation. The derivativ e dX(t)/dt (units: Ci/yr) is defined by the limit X(t +At) X(t)

( 2. 2)

L\t and represents the rate at which X(t} is changing. In turn, this rate is equal to the\differ ence between the rate R1 (units: Ci/yr) at which the radionucl ide is entering the cell and the rate R (units: Ci/yr) at which the radionucli de is leaving2 the cell. The rate 2-1

r rw rw...

, r

.~

\

\ I

'vw

1x(t)

R: .rate at which* radionuc lide enters cell (units: Ci/yr)

RW: rate at.which water enters and leaves cell (units: .L/yr)

X: decay constan t for radionuc lide (units: yr-) 1 VW: volume of water in cell (units: L)

X (t) :

amount of radionu clide in cell at

time t (uni ts: Ci)

Figuie 2-1. Flows Associat ed With a Single Unifo~m ly-Mixed Cell With no Radionu clide Partitio ni~g Between a Liquid and a Solid Phase.

2-2

R 1 is give n by R .. The rate R2 is the com pone nts: a rate due to phy sica l flow sum of two out of the cel l, and a rate due to radi oac tive deca y.

The rate due to*

phy* sica l flow is equa l to the prod uct of . the radi onu clid e con cen trat ion X(t) /VW in the* cell and the rate of wat er flow RW out of the cell ; the rate due to deca y *is equ al to the prod uct of the. deca y con stan t ;\

X(t) of radi onu clid e pres ent. Thu s,. and the amo unt R1 =Ra nd R = [(RW/VW) + ;\] X(t) ,

2 (2.3 )

and henc e, the desi red equa tion is give n by dX( t)/d t = R - ~

1 2

= R - [(RW /VW) + A] X(t) . ( 2. 4)

Also asso ciat ed with the prec edin g equ atio valu e L!On ditio n X(O) = x , whic h repr esen n is an init ial radi onu clid e pres ent at time 0 ts the amo unt* of t = O.

Thus , dete rmin atio n of X(t) redu ces to of an init ial valu e prob lem of the form the solu tion d X( t ) / d t = R - AX ( t } ~ X ( 0 ) = Xo , ( 2. 5)

whe re A= (RW/ VW) + ;\, (2. 6)

Such prob lems .are reia tive ly easy to solv ble solu tion tech niqu es incl ude sepa rati e and app lica -

on of vari able s;.

intr odu ctio n of inte grat ion fact ors, and app lica tion of Lap lace tran sfor ms. The prec edin g tech niqu es are dis-cuss ed in intr odu ctor y text s on diff ere ntia and lead to the- foll owi ng uniq ue solu tion l equ atio ns valu e prob lem in (2.~ ): for the init ial X(t) . = e-A t Xo. + (R/A )(l - e-A t). ( 2. 7) 2-3

If the initial value condition is X(O) = 0, then the preceding solution becomes X(t) = (R/A){l - e-At). (2.8)

Further, regardless of the initial value condition, the steady state or asymptotic sol~tion SX to which any solu-tion of (2.5) converges is given by sx = lim. X(t) t-.oo .

= lirn [e-At Xo + (R/A)(l - e-At)J t -.co

= R/A, ( 2. 9) provided A > 0.

The differential equation for a single uniformly-mixed cell with radionuclide partitioning between a liquid and a solid phase* is pr,esented next. The. situ...;

ation under consideration is indicated in Figure 2~2.

The cell is. assumed to have a constant volume VW (units:

L) and to contain a constant mass MS of solid material (units: kg). Further,* it is assumed that water enters and leaves the cell at a rate RW (units: L/yr), that solid material enters and leaves the cell at a rate

RS (units: kg/yr), and that a radionuclide with decay constant A(units: yr-1) enters the cell at a rate R (units: Ci/yr). The partitioning of the radionuclide between the liquid and solid phases of the system is assumed to be described by the ratio cone. of radionuclide sorbed to solids AW/MS KD = cone. of radionuclide dissolved in water = AW/VW (2.10) 2-4

r A

' (

rw .....

rw~

rs ~

r rs '-,.

4 -l -I. __J I I

'\ \ ..

'\

\v w '*m s \ x(t )

R: rat e at whi ch rad ion ucl ide ent ers cel l.

(un its: Ci/ yr)

RW: rat e at wh ich *wa ter ent ers and lea ves cel l (un its: L/y r)

RS: rat e at whi ch sol id ma ter ial ent ers and lea ves cel l (un its: kg/ yr)

. 'A.: dec ay con sta nt for rad ion ucl 1de

{un its: yr- 1)

VW: vol ume of wat .er in cel l (ul') i ts:

L)

MS: mas s of sol ids in cel l (un its:

kg)

X(t ): amo unt of rad ion ucl ide in cel l at tim ~ t (un its: Ci)

Fig ure 2-2 , Flo ws Ass oci ate d Wit h a Sin gle Un Mix ed Cel l Wit h Rad ion ucl ide Par ifor mly -

Bet wee n a Liq uid and a Sol id Pha titi oni ng se.

2-5 i

I.

wher e AS (uni ts: Ci) is the :amou nt of radio nucl ide in the syste m sorbe d to solid s and*A W (uni ts:

Ci) is the amou nt of radio nucl ide in the syste m disso lved in wate r. The. ratio in (2.10 ) is know n as a KD-v alue or a distr ibut ion coef ficie nt.

It is desir ed to deter mine the amou nt X(t) (uni ts:

Ci) of the radio nucl ide pres ent in the cell at time t (uni ts: yr). Thre e basic assum ption s unde rlie the deriv ation of X(t) . Firs t, *it is. assum ed that radio nucl ide is unifo rmly distr ibut ed throu gh the -

the cell and is part ition ed betw een the liqui d and solid phas es on the basi s of its distr ibut ion coef ficie nt.

vatio n for this part ition ing is prese nted in A deri~

the next para grap n. Seco nd, it is assum ed that the flow of wate r and solid mate rial out of the cell is the on.1,y invo lved in the phys ical trans port of the radio mech anism nucl ide.

Thir d, it is assum ed*th at all radio nucl ides asso ciate d with a phas e, liqui d or solid , *rema in with that phas e in move ments out of the cell. In essen ce, the cell is treat ed as a unifo rmly mixed "ves sel" in whic h the radio nucl ides are parti tione d betw een the liqui solid phas es on the basis of the distr ibut ion d and coef fi-cien t and such that radio nucl ides can be carri ed out of this "ves sel" and out of the syste m only by move ments of wate r or solid mate rial.

A deriv ation for the part ition ing of a radio -

nucli de.be twee n* the liqui d and solid phas es of a syste m is now pres ente d. The follo wing nota tion is used in the deriv ation :

X = amou nt of radio nucl ide in syste m (uni ts:

Ci),

XS = amou nt of radio nucl ide in syste m sorbe d to solid s (uni ts: Ci),

xw* = amou nt of radio nucl ide in syste m disso lved in wate r (uni ts: Ci),

MS = mass of solid in syste m (uni ts: kg)'

vw = .volu me of wate r in syste m (uni ts: L)

2-6

Assu me X, MS, VW, and KD are know n for the syste m unde r cons ider atio n. Now, XS and XW are dete rmin ed. Sinc e KD _= (XS/M S) (XW/ \7W) -l and X = XS + XW, * (2.1 1) we have that (KD) (MS) = (XS) (VW) (xw) -1 and XW = X - xs.

(2.12 )

Thus ,

(KD) (MS) = (XS) (VW-) (X - xs)- 1. (2.1 3)

Furt her, mul tipli cati on by (X - XS) give s (KDH MS)( X) - (KD) (MS) (XS) = (XS)( VW) (2.l4 )

or (KD) (MS) {X) - [(KD ) (MS) + VW] XS, (2.1 5) and henc e (KD) (MS) ]

XS = [ (KD) (MS) + VW X. (2.1 6)

Furt her, sinc e XW = X - XS, (2.1 7)

The rela tion s in (2.16 ) and (2.1 7) repr esen t t~e desi red ,

part ition ing.

A*differential equation representing the rate of change cif X(t) is now derived. .Then, X(t) can be obtained by solving this equation. The following deri-vation is similar to that previously presented for a uniformly-mixed cell without partitioning. As for that case, dX(t}/dt is equal to the difference between the rate R1 at which the radionuclide is entering the cell and the rate R2 at which the radionuclide is leaving the cell. The rate R1 is given by R. The rate R2 is the sum of three.components: a rate due to physical flow out of the cell with solid material, a rate due to physical flow out of the cell with water, and a rate due to radioactive decay. The two rates due to physical flow are equal to the products of the concentrations XS(t)/MS and XW(t)/VW with the flow rates RS and RW, where XS(t) represents the amount of radionuclfde in the*cell sorbed to solid mate-rial and*XW(t) represents the amount of radionuclide in the cel'l dissolved in water. The functions XS(t) and XW(t} can be obtained from (2.16) and (2.17). The rate due to decay is equal to the proffuct of the decay constant and the amount X(t) of radionuclide present. Thus, R {2.18) and

[XS(t)/MS](RS] + [XW(t)/VW] [RWJ + i\ X(t)

.= (KD) (MS)

[ ( KD ) ( MS ) + VW J [ t )]

X(

[RS]

MS

[From (2.16) and (2.17)]

.= [

S(RS)

MS +

( 1. - S) (RW) vw + i\] X(t) ( 2 .19) 2-8

wh ere

( KD ) (MS )

S = (KD ) ( MS ) + VW (2. 20 )

He nce , the de sir ed eq ua tio n is giv en by dX (t) /dt = R1 - R2

+

( 1. - S) ( RW) vw +;\] X( t).

{2 .21 )

Al so as so cia ted wi th the pre ce din g eq ua tio n is an va lue co nd iti on X(O ) = in iti al Xo

Th us, de ter mi na ti6 n of of an in iti al va lue pro X( t) red uc es to the so lut ble m of the for m ion

dX ( t) / dt =. R - AX ( t),

X( 0} = Xo , (2. 22 )

wh ere S(R S) . ( 1. - S )( RW)

A= MS + vw + A (2. 23 )

wi th S de fin ed as in (2. 20 to the pre ce din g in iti al ). Va rio us for ms of the so lut ion (2 .8) , an d'( 2.~ }. va lue pro ble m are giv en in (2 .7) ,

2-9

3 * . Rele ase to Surf ace \*late r*

3 .1 Prel imin ary Cor:i ments Popu latio n expo sure s and r~su ltan t heal th effe cts are now calc ula~ ed for radi onuc lide rele ase to body .

a surf ace~ wate r In part icul ar, WRD S(I,j ),WR HE(I ,J) and WRH are dete rmin ed for expo sure from wate r cons ETOT(I) ump tion, wher e WRDS (I, J) = popu latio n dose (uni ts:

rems ) to orga n asso ciate d with canc er J from

radi onu-clid e I, WRH E(I,J ) = numb er of occu rren ces of canc er Jin popu latio n* due to radi onuc lide I, WRHETOT(I) = tota l numb er of canc ers in popu latio n due to radi onuc lide I.

Sim ilirl y, FHD S(I,J ), FHH E(I,J ) and FHHE TOT(

mine d for fish inge stion ; INSD DS{I ,J), HlSD I) are dete r-HE(I ,J) and INSD TOT( I) are dete rmin ed for inha latio n of susp ende d sedi men t; EXW RDS (I,J), EXW RHE( I,J) and EXW RTOT (I) are dete rmin ed for wate r imm ersio n: EXS DDS (I,J),

EXSD HE{I ,J) and EXSD TOT( I) are dete rmin ed for exte rnal shor elin e sedi men ts; and EXA RSD D(I,J ), EXA expo ~ure from RSDH (I,J) and EXARSDT( I) are deter .min ed for exte rnal expo sure fror:1 sus-pend ed sedi men ts.

The quan titie s indi cate d in the prec edin g para grap h are obta ined in -the follo wing mann er. .Fir radi onuc lide expo sure rate s are dete rmin ed. st, indi vidu al Then , thes e expo sure rate s are used in conj unct ion wit.h appr opri ate dose and risk fact ors to yiel d indi vidu al dose and risk ,

for sele cted orga ns and canc ers . . Next , thes e indi vidu al dose s and risk s are mul tipli ed by popu latio n size to obta in popu latio n dose and risk for .::iel ected canc ers. Furt her, as many alge brai c sim plifi orga ns and cati ons as poss ible are carr ied out; due to the natu re of the mod-els used , this resu lts in rela tive ly simp le expr essio ns for popu latio n dose and risk whic h are inde pend ent of*

the popu latio n size , rive r size~ and time peri od con-side red. Fina lly, popu latio n risk from the vari ous canc ers is summ ed to give an*o vera ll popu latio n risk estim ate *.

3-1

It is assum ed that the surfa ce-w ater body unde cons idera tion can be repre sente d as a sing le unifo r mixe d cell as desc ribed by the diffe rent ial equa rmly -

tion appe aring in (2,5) . For radio nucl ide I, it is assum ed that a relea se of size TD(I ) (uni ts: Ci) takes place into the surfa ce wate r over a time perio d of leng th T (uni ts: yrs). Furt her, for use in (2,5) , it is assum ed that the annu al disch arge (uni ts: Ci/y r) for radio nucl ide I is given by TD(I )/T, Thus , for each radio nucl ide, the asym ptoti c conc entra tion (uni ts:.

Ci/L ) in the surfa ce wate r is given by*

CW(I ) = TD(I )/F*T (3,1) wher e F deno tes the annu al flow (unit s: L/yr) of the rive r whic h cons titut es the surfa ce wate r body unde r cons idera tion.

As in the EPA anal ysis (Srn8 1), it is assum ed that popu latio n size and fish prod uctio n are linea r, neou s func tions of river flow p, That is, it homa ge~

is assum ed that POP= DPOP*F ( 3. 2) and FSH = bFSH*F ( 3. 3) wher e POP= popu latio n (uni ts: ind*) supp orted by rive r DPOP = cons tant (uni ts: ind per L/yr )

FSH = fish prod uctio n (uni ts: kg/y r) supp orted by rive r DFSH = cons tant *(uni ts: kg/y r per L/yr ). . I Furt her, with an assum ed life expe ctanc y of 70, yr, the tota l popu latio n TP (uni ts: ind) supp orted by the rive r over a time perio d of leng th*T is

indiv idua ls.

3-2

(

[:

l I

TP = DPOP*F *T/70. ( 3. 4) 3.2 Exposu re From Water Consum ption The popula tion exposu res and resulta nt health effects are now calcula ted for water. ingesti on.

It folloi.vs from (3.1) that the amount of radion uclide I ingeste d by an in:divi dual (units: Ci/yr) is given by CW(I)*R INGWAT *WT(I) = RINGW AT*TD (I)*WT( I)/F*T, (3.5) where*

RINGWAT = individ ual water ingest ion.rat e (units:

L/yr)

WT(I) = water treatm ent remova l factor for radio-nuclid e.I (units: unitle ss).

Thus, the dose. (units: rem/ino .) to the organ associa ted with cancer J aue.to radion uclide I and the resulta nt can-cer risk (units: cancer /ind) are given by RINGW AT*TD( I)*WT(I )*DFIN G(I,J)/F *T ( 3. 6) and RINGW AT*TD (I)*WT (I)*DFI NG(I,J) *RISK( J)/F*T, (3.7) respec tively.

Popula t.ion exposu re and risk now follow from the expres sions in (3.6) and (3.7). Specif ically, with use of the relatio n in ( 3 *. 4) ,

WRDS(I ,J) = [RINGW AT*TD (I)*WT( I)*DFIN G(I,J)/F *T]

[DPOP *F*T/70 .]

= RINGWAT-*TD( I) *WT( I). *DFING ( I ,J) *DPOP/ 70. (3.8) 3-3

and WRHE (I, J) = [RINqWAT*TD (I) *VlT (I) *DFIN G (I, J) *RISK ( J) /F*T]

[DPO P*F*T /70.]

= RINGWAT*TD (I) *HT (I) *DFIN G ( I, J) *RISK ( J)

DPO P/70. *(3.9 )

Thus, the total cance rs from radio nucli de I are given by WRHETOT(I) = ~JWR HE(I, J) . (3.10 )

3.3 Expos ure from Fish Consu mptio n The popu lation expos ures and resul tant healt h effec are now calcu lated for fish inges tion. ts It follow s from (3.2) and (3.3) that avera ge indiv idual fish consu mptio n is*

(DFSH *F)/(D POP*F ) = DFSH/DPOP . (3.11 )

Thus, it follow s from (3.1) that the amoun t of radio nucli de I inges ted byan indiv idual from fish consu mptio n (unit s:

Ci/yr ) is given by CW( I j *CRWF (I)*.( DFSH/ DPOP)

= TD(I)* CRWF (I)*DF SH/(D POP*F *T) (3.12 )

where CRWF (I) - conce ntrati on ratio for radio nucli de I from water to fish (unit s: Ci/kg per Ci/L) .

3-4

Th us , th e do se (u w ith ca nc er J du ni ts : re m /in d) to th e or ga n as so ci at ed e to ra di on uc li de ca nc er ri sk {u ni I an d th e re su lt an t ts : ca nc er /in d) ar e gi ve n by (T D (I) *C RW F( I)* D FS H *D FI ~G (I, J) )/( D PO P* F* T) (3 .1 3) an d (T D (I) *C RW F( I)* D FS H *D FI N G (I, ~) *R IS K (J )) .

I

/(D PO P* F* T) I (3 .1 4) re sp ec ti ve ly .

Po pu la tio n ex pr es si on s in ( ex po su re an d ri sk no w fo llo w =r o~

3. 13 ) an d ( 3. 14 th e of th e re la ti on ). Sp ec if ic al ly , w ith in (3 .4 ), us e FH D S( I,J ) = I [TD(I)*C~WF(I)*DFSH*DFING(I,J)]

/[D PO P* F* TJ I !

DP OP *F *T /7 0 .:

= TD (I )* CR W F( I) *D FS H *D FI N G (I ,J) /7 0 (3 .1 5) an d FH H E( I,J ) = l[T D( I) *C RW F( I) *D FS H *D FI NG (I ,J )*

RI SK (J )]

/[D P~ P* F* TJ !* ID PO P* F* T/ 70 .1

= TD (I )* CR W F( I) *D FS H *D FI NG (I ,J )*

RI SK (J )/7 0.

(3 .1 6)

Th us , th e to ta l ca nc er s fro m ra di on uc li de I ar e gi ve n by 3- 5 ..

FHHETOT ( I ) =* L J *FHHE ( I , J) * . (3.17) 3.4 Exposure *From Inhalation of Suspended Sediment The population exposures and resultant heaith effects are now calculated for inhalation of suspended sediment.

For this calculation and* for subsequent exposure calcula-tions involving sediment, it is assumed that sediment con-centration CSED(I) (units: Ci/kg) of the 1th radionuclide is given by CSED(I) = DCOEF(I)*CW(I)

= DCOEF(I)*TP(I}/F*T (3.18)

[From (3.1)]

where DCOEF(I) = distribution cpeffici~nt for radionuclide I (units:

Ci/kg per Ci/L)~

Hence, the amount of radionuclide I inhaled by an individ-ual (units: Ci/yr) is given by CSED(I)*AIRCON*RINHAIR*TMINSD

= DCOEF(I)*TD(I)*AIRCON*RINHAIR*TMINSD /F*T , (3.19) where AIRCON = concentration of suspended sediment in the air (units: kg/m3), ..

. RINHAIR = rate of inh~lation (units: ~3/yr),

TMINSD = fraction of year that individual is exposed to suspended sediment (units: unitless) .

.Thus, the dose (units: rem/ind) to the organ associated with cancer J due to radionuclide I and the resultant can-cer risk (units: cancer/ind) are given by

\.. 3-6

[DCOEF (I) *TD (I) *AIRCON*RINHAIR *TMINSD*DFIN'H ( I ,J)] /[F*T]

(3.20) and

[PCOEF(I)*TD(I)*AIRCON*RINHAIR*TMINSD*DFINH(I,J)

RISK(J)]/[F*T] ,

(3.21) respectively.

Population exposure and ris~ now follow from the expressions in (3.20) and (3.2l). Specifically, with the use of the relation in (3.4),

INSDDS(I,J) = {[DCOEF(I)*TD(I)*AIRCON*RINHAIR*TMINSD

DFINH ( I ,J)] /[F~TJ} * {DPOP*F*T /70 .}

= [DCOEF(I)*TD{i)*AIRCON*RINHAIR*T~IN~D

DFINH(I,J)*DPOP]/70.

(3.22) and INSDHE (I, J) = { [DCOEF (I) *TD (I) *AIRCON*RI N'.HAIR *TMINSD

-*Dr'DrH(I ,J) *RISK(J)J/[F*TJ} * {oPOP*F*T/70 *}

= rDCOEF(I)*TD(I)*AIRC~t>7*RINHAIR*TMINSD

DFINH(I,J)*RISK(J)*DPOP]/70.

(3.23)

Thus, the total cancers from radionuclide I are given by 3-7 I f

I"

INSD TOT( I) = .EJ INSD HE(I, J) . (3.24 )

3. 5 Ex,oo sure From Wate r Imme rsion The popu latio ri expo sures and resu ltant heal th effec ts are now calcu lated for wate r inune rsion . The exte rnal exoo -

sure (uni ts: rem/i nd} to the organ asso ciate d with can--

cer J due to radio nucl ide I and the resu ltant canc er risk (uni ts: canc er/in d} are given by CW(I )*RE XTW AT*D FEXT (I,2,J )*70. *1000 .

= TD(I) *REX TWA T*DF EXT( 'I,2,J) *7.E4 /F*T (3.25 )

[From (3.1) ]

and TD(I) *REX TWA T*DF EXT( I,2,J) *7.E4 *RIS K(J)/ F*T , (3.26 )

wher e REXT.WAT = expo sure rate to conta mina ted wate r (uni ts: hr/y r),

70. = avera ge life expe ctanc y (qni ts: yr/in ~)

1000 . = liter s per cubic mete r (unit ~i L/m3 ).

The facto rs 70. yr/in d and 1900 . L/m 3 appe ar in (3.25 )

to prod uce nece ssary unit conv ersio ns.

Popu latio n expo sure ..and risk now foll'o w from the expr essio ns in (3.25 ) and (3.26 ). Spec ifica lly, with use . of *the relat ion in (3.4) ,

EX HR DS (I,J ) = [TD (I) *R EX TW AT *D FE XT (I,2 ,J) *7. E4 /F* T]

[D PO P* F* T/7 0.]

= TD (I)* RE XT WA T* DF EX T(I ,2,J )*D PO P*l .E3 (3. 27 )

and EX WR HE (I,J ) = [TD (I) *R EX TW AT *D FE XT (I,2 ,J)* 7.E 4*R ISK (J)

/F* T]* [D PO P* F* T/7 0.]

= TD (I) *R EX T\l AT *D FE XT (I,2 ,J)* RIS K( J)

D PO P* l.E 3.

(3. 28 )

Th us, the to tal ca nc ers fro m rad ion uc lid e I are giv en by EXHRTOT (I) =LJ EXWRHE (I, J) . (3. 29 )

3.6 Ex po sur e Fro m Sh bre lin e Se dim ent Th e po pu lat ion ex po sur es are now ca lcu lat ed fo r and re su lta nt h~ alt h Sf ex ter na l ex po sur e to sh fec ts me nt. Fo r the se ca lcu lat ion s,. or eli ne se di -

de ter mi ne a su rfa ce rad it is fir st ne ce ssa ry to ion uc lid e co n6 en tra tio n.

th is, it is ass um ed th To do at al l rad ion uc lid es dow tai n de pth in t.h e sed im n to ac er -

en t are

co nc en tra me nt su rfa ce . Th en, the su rfa ce co nc en ted on the se di-(b ni ts: Ci/ m 2 ) f~ r rad ion uc lid e tra tio n CS UR F(I )

I is giv en by CS UR F(I ) = CS ED (I)* DE PT H* DE NS ITY *(l

. - PO RO SIT )

= DC OE F(I )*T D(I )*D EP TH

D EN SIT Y* (l. - PO RO SIT )

/F *T ,

( 3 . 30)

[Fr om (3. 18 )]

3-9

wher e DEPT H= depth to which radio nucl ides are assum ed to be conc entra ted on surfa ce (uni ts: m),

DENS ITY= mean part icle dens ity of sedim ent (unit s:

kg/m 3 ), '

POROSIT = poro sity of sedim ents (uni ts: unit less) .

Henc e, the exte rnal expo sure (unit s: rem/ ind) to the orga n asso ciate d with .canc er J due to radio nucl ide I and the resu ltant canc er risk (unit s: canc er/in d) by are given CSUR F(I)* REXT SD*D FEXT (I,-l,J )*70.

= [DCO EF(I) *TD( I)*DE PTH* DENS ITY* (l. PORO SIT)/ F*T]

[RE XTSD *DFE XT(I ,l,J)* 70.]. {3.31 )

[From (3.30 )]

and

[ DCOEF (I) *TD (I) *DEPTH*DENSITY* { l. - PORO SIT) /F*T ]

[RE XTSD *DFE XT(I ,l,J)* 70.]* R~SK (J) ,

(3.32 ) .

resp ectiv ely, wher e REXTSD = expo sure rate to sedim ent (uni ts:. hr/y r),

70. = avera ge life expe ctanc y (uni ts: yr/in d) .

. *Pop ulati on expo sure and risk now follo w from expr essio ns in {3.31 ) and (3.32 ). Spec ifica lly, the.

with use of the relat ion in (3.4) ,

3-10

EX SD DS (I,J ) = [DC OE F(I )*T D(I )*D EPT H*D EN SIT Y

(1 . - PO RO SIT )/F *T] *[R EX TS D* DF EX T(I ,l,J )

70 .]* [DP OP *F* T/7 0.]

= DC OE F(I )*T D(I )*D EPT H*D EN SIT Y

{*1 . - PO RO SIT )*~ EX TSD *D FEX T(I ,l,J )*D PO P (3. 33) and EX SD HE (I,J ) = [DC OE F(I )*T D(I )*D EPT H*D EN SIT Y

(l . - PO RO SIT )/F *T] *[R EX TSD

D FEX T(I ,l,J )

70 .]* RIS K(J )*[ DP OP *F* T/7 0.]

= DC OE F(I )*T D(I )*D ~PT il*D EN SIT Y* (l. - POR OSI T)

RE XT SD *D FEX T(I ,l,J )*R ISK (J)*

DP OP . (3. 34)

Th us, the tot al can cer s fro m rad ion ucl ide I are giv en by EXSDHET {I) =. LJ EXSDHE (I' J)

. (3.- 35) 3.7 Ex pos ure Fro m Sus pen ded Sed ime nt The po pu lat ion exp osu res and are now cal cu lat ed £or ext res ult an t he alt h eff ec ts

_er nal exp osu re fro m sus pen sed im ent . The ex ter na l exp ded org an ass oc iat ed wit h can cerosu re {u nit s: rem /in d) to the the res ult an t can cer ris k J due to rad ion uc lid e I and

~.

(un its : can cer /in d) are giv en 3-1 1

CSED(I)*AIRCON*REXARSD*DFEXT(I,3,J)* 70.

= [DCOEF(I)*TD(I)*AIRCON*REXARSD*DFE XT(I,3,J)*70.J

/[F*T]

(3~36)

[From (3.18)]

and

[DCOEF(I)*TD(I)*AIRCON*REXARSD*DFE XT(I,3,J)*70~*RISK(J)]

/[F*T] ,

( 3. 37) respectively, where REXARSD = exposure rate to suspended sediMent (units:

hr /yr),

70. = average life expectancy (units:* yr/ind).

Population exposure and risk now follow fro~ the expressions in (3.36) qnd (3.37). Specifically, with use of the relation in (3.4),

EXARSDD( I, J) = {[DCOEF (I) *TD (I) *AIRtON*REXARSD

DFEXT (I, 3, J) *70. ]/[ F*TJ} * {DPOP*F*T/70 *}

DCJEF (I) ""TD (I) *AIRC:J!\I* REXARSD

DFEXT(I,3,J)*DPOP

{ 3. 38) and 3-12

EXARSDH (I, J) = { [DCOEF (I) *TD(_ I) *AIRCON*REXARSD

DFEXT(I,3,J)*70.*RISK(J)]

. / [F*T]} * {DPOP*F*T /70 *}

= DCOEF{I)*TD{I)*AIRCON*REXARSD

DFEXT(I,3,J)*DPOP*RISK{J) * (3.39)

Thus, the total cancers from radionuc.lide I are given by EXARSDT(I) = ~J EXARSDH(I,J) . (3.40)

3-13

4. Rele ase to Soil 4.1 Preli mina ry Comm ents Popu latio n expo sures and resu ltant heal th effe are now ,calc ulate d for radio nucl ide relea se to cts soil .

In part icula r, PLD S(I,J ), PLHE (I,J) and PLHE TOT(

I) are deter mine d for expo sure from p'lan t consu mptio n, wher e PLDS (I,J) = popu latio n dose (uni ts: rems ) to organ asso ciate d with canc er J from radio nucl ide I, PLHE (I,J) == numb er of occu rrenc es of canc er J in popu latio n due to radio nucl ide I, PLHE TOT( I) = tota l numb er of canc ers in popu la-tion due to radio nucl ide I.

Simi larly , MKD S(I,J) , MKH E(I,J) and MKHETOT(I) are deter mine d for milk consu mptio n; MTD S(I,J) , MTH E(I,J) and MTHETOT (I) are

deter mine d for meat* cons umot INSL DS(I ,J),,I NSL HE(I ,J) and INSL TOT( I) are deter ion; mine d for inha latio n of suspe nded soii; EXSL DS(I, J), EXSL HE(I, J) and EXSL TOT( I) are deter mine d for exte rnal expo sure, from soil; and EXAR SLD( I,J), EXAR SLH( I,J) and EXAR SLT(I )

are dete r-mine d for exte rnal expo sure from suspe nded soil.

The prece ding quan titie s are deter mine d in a mann er sini lar to that used in Chap ter 3.

It is assum ed that the regio n unde r cons idera tion can be repre sente d as a sing le unifo rmly -mix ed cell as desc ribed by the diffe rent ial equa tion appe aring in (2.21 ).

A spec ific form of this equa tion is now deriv ed for use in this chap ter. The follo wing symb ols are intro duce d for use in this deriv ation :

X(I) = amou nt of radio nucl ide I in soil (uni ts: Ci),

XS(I ) = amou nt of radio nucl ide I in soil sorbe d to solid mate rial (unit s: Ci),

XW(I ) = amou nt of radio nucl ide I in soil disso lved in wate r (unit s: Ci) ,

DP = depth of soil (unit s:

m) '

AR = area of soil (unit s: m2)'

4.-1

ER = erosio n rate per unit area (units : kg/m2

. per yr),

RO = runof f rate per unit area (units : *L/m2 per yr),

DCOEF (I) = distri butio n coeff icient for radion u-clide I (units : Ci/kg per Ci/L) ,

MS= mass of solid m~ter ial in soil (units :

kg),

VW = volume of water in soil (.units : L) I.

PO= poros ity of soil (units : unitle ss),

DE= mean partic le densit y of soil mater ial (units : kg/m3 ), ..

SA= perce nt satura tion of pore space ,in soil (units : uni tless) .

Radio nuciid e partit ionin g is consid ered first. The solid mass MS and the water volume VW in the soil are given by MS AR*DP *(l. - PO)*DE (4.1) and

vw = AR*DP*PO*SA*lOOO * { 4. 2)

Thus, the factor S(I) used in the .deter minat ion of radio- .

nuclid e partit ionin g betwee n the liquid and solid phases of a syste~ is gi~en by DCOEF (I)*MS S(I) = DCOEF (I)*MS *+ VW [From (2.20) ]

DCOEF (I)*AR *DP*(l . - PO)*DE

= -==o:--:c::-::o:--::E::-::F~(::-:I::-)::-*-:-A:-R,,. . . . ,. *. ;,.D.....P"""*....,.(~1-.-_-p--o:c-::-)*~D=:E=-+---A--R_,*_D_P_*_P_O_*.,...S_A___,..*~l-0_0_0

= DCOE F(l)*(l ~ - PO)*DE DCOE F(I)*{ l. - PO)*DE + PO*SA *looo (4.3) 4-2

Hen ce, i t foll ows from (2.1 6) and (2.1 7), tha t the par titi oni ng of racU onu clid e I betw een the liqu id anc,l sol id pha ses of the syst em is give n by XS ( I ) = S{ I) *X ( I ) and XW ( I ) = [L - S ( I ) ] *X ( I ) . ( 4. 4 )

The des ired equ atio n can now be con par ticu lar, it foll ows from (2.2 1) stru cted . In tha t dX( I)/d t = R(I) - [XS (I)/M S]*A R*E R

- [ XW ( I ) /VW] *AR* RO A*X (I)

S(I) *X( I) } *

= R(I) - { AR* D?* (l. ~ PO)*DE *A~*~R

[l. - S(I) ]*X (I)) .

- { AR* DP*P O*SA *lOO O{*A R*~O -. ;\*X (I)

[ From ( 4. 1), ( 4. 2 ) , ( 4. 4) J

= R(I) ~ A(I )*X (I) , (4.5 )

whe re S(I) *ER [ 1 * .- S ( I ) ]

RO A(I ) = DP* (l. - PO)* DE + DP*P O*SA

lOO O + A * (4.6 )

For rad ion ucli de I, the deca y con stan t A is give n by I

[

\ = ALOG(2 * )/HL IFE (I) ,

( 4. 7) whe re HLI FE( I) = hal f-li fe of rad ion ucli de I (un its: yr) .

4-3

As in di ca ted in (2 .. 9) ,

the eq ua tio n in (4 .5) the as ym pto tic so lu tio is giv en by n to R/A (.I) = TD (I) /T *A (I)

(4 .8) wh ere the sec on d pa rt of the pr ec ed ing eq ua lit fro m the ass um pti on th y fol low s at the an nu al dis ch arg Ci /y r) fo r rad ion uc lid e (u ni ts:

e I is giv en by TD (I) /T fo r ea ch rad ion uc lid e, .

the asy mp tot ic co nc en tra Th us ,.

(u ni ts: Ci /kg ) in the so il is tio n giv en by CS L( I) = [T D{ I)/ T* A{ I)] /M S

= [T D( I)] /[T *A (I) *A R* DP *(l

. - PO )*D E]

[Fr om (4 .1) ]

= TD (I) *F AC (I) /T* AR (4 .9) wh ere the fa cto r FA C( I) ve nie rtc e an d .is de fin ed is int ro du ce d fo r no tat io na l co n-

. by FA C( I) = [A (I) *D P* (l.

- PO )*D E] -l . (4. 10 )

It is no ted th at FA C( I) th e are a AR of the so il co nta ins no ter m wh ich de pe nd s on len gt h T of the tim e pe reg ion un de r co ns id er ati on or the rio d un de r co ns id er ati on In sim ila rit y to the En an aly sis , th e fol low ing vir on me nta l Pr ot ec tio n Ag fo r the reg ioh un de r co pa ram ete rs ar e ass um ed to be enc y ns ide rat ion : kno wn FP LT = fra cti on of lan d us ed hum an co nsu mp tio n (u nito gro w pl an ts fo r ts: un itl es s) ,

FMLK = fra cti on of lan d use d fo (u ni ts: r mi lk pr od uc tio n un itl es s) ,

FMT = fra cti on of lan d us ed fo r (u ni ts: me at pr od uc tio n un itl es s} ,

4-4

DPLT = num ber of peo ple sup port ed ')

per m-<- by pla nt pro duc tion (uni ts~ in~/ m2) ,

D.MLK = num ber of peo ple sup por ted per m2 by milk pro duc tion (un its: ind/ m2) ,

DMT = num ber .of pe.o ple sup por ted per m2 Dy wea t pro duc tion (un its: ind/ m2)

DSL = pop ulat ion d*en si ty for inh alat ion and ext er-nal exp osu re calc ul~ tion s (un its:

ind/ m 2 ).

The prec edin g var iabl es lead to the foll owi ng pop ulat ion s for use in late r exp osu re calc ula tion s:

TPPL T = AR* FPLT *DP LT*T /.70. (4.1 1)

TPMLK = AR*FMLK*DMLK~T/70.

TPMT = AR*FMT*D~lT*T/70. (4.1 3)

TPSL = AR* DSL *T/7 0. , (4.1 4) whe re TPPL T = tota l pop ulat ion exp osed to pla nt ing esti on

. (un its: ind ),

TPMLK = tota l pop ulat ion exp osed to milk con sum ptio n (un its: ind ),

TPMT = tota l pop ulat ion exp osed to mea t con sum ptio n (un its: ind ),

TPSL = tota l pop ulat ion for inh alat ion and ext ern al exp osu re calc ulat ion ~ (un its: ind ),

70. = ave rage life exp ecta ncy (un its: yr) .

4.2 Exp osur e From Pla nt Con sum ptio n The pop ulat ion exp osu res and res are now calc ula ted for pla nt ing esti ulta nt hea lth effe cts on . . It foll ows from (4.9 ) tha t. the amo unt of radi o.nu clid e I ing este d by an ind i-*

vid ual (un its: Ci/y r) is give n by 4-5

CPLT*CS L(I)*CRS P(I)

= CPLT*T D(I)*iAC (i)*CRSP (I)/T*AR , (4.15) where CPLT = individu al plant consump tion (units: kg/

yr)-,

CRSP(I) = ~oncent ration ratio from soil to plant for radionu clide I (units: Ci/kg per Ci/kg).

Thus, the dose (units: rem/ind) to the organ associat ed with cancer J due to radionu clide I and the .resultan t can-cer risk (units: cancer/i nd) are given by CPLT*TD (I)*FAC( I)*CRSP( I)*DFING (I,J)/T*A R (4.16) and CPLT*T D(I)*FAC (I)*CRSP (I)*DFIN G(I,J)*R ISK(J)/T *AR, (4.17) respecti vely.

Populati on exposure and risk now follow from the expressi ons in (4.16) and (4.17). Specific ally, with use

of the relation in (4.11),

PLDS(T, J) = [CPLT*T D(I)*FAC (I)*CRSP (I)*DFIN G(I,J)/T* AR]

[AR*FPL T*DPL~* T/70.]

= CPLT*TD (I}*FAC( I)*CRSP( I)DFING (I,J)*FPL T

DPLT/70 . (4.18) and 4-6

PLH E(I,J } = [CPL T*T D(I) *FA C(I} *CR SP{I }*D FING {I,J)

RIS K(J} /T*A R]*[ AR* FPL T*D PLT *T/7 0.]

= [CPL T*T D(I) *FA C(I) *CR SP(I }*D FISG (I,J)

RIS K(J) *FPL T*D PLT ]/70.

(4.1 9)

Thus , the tota l canc ers from radi onu clid e I are give n by PLHE'TOT ( I). = rJ PLHE ( I , J) . (4.2 0) 4,3 Exp osur e From Milk Con sum ption The pop ulat ion expo sure s and resu' ltan t are now calc ulat ed for milk inge stio n. hea lth effe cts It*fo llow s from (4.9 ) that the amo unt of radi onu clid e I inge sted by an indi vidu al {un its: Ci/y r) is give n by CSL( I)*C RSP{ I)*PM LK*C RDM (I)*C MLK

{4.2 1)

- TD(I )*FA C{I) *CR SP(I )*PN LK* CRD M{I) *CM LK/T *AR whe re PMLK = plan t cons ump tion by dair y catt le (un its:

kg/d ay},

CRDM(I) = con cent ratio n rati o from diet to milk for radi onu clid e I (un its: Ci/L per Ci/d ay),

CMLK = indi vidu al milk cons ump tion (un its:

L/y r).

Thu s, the dose (un its:

rem /ind ) to the with canc er J due to radi onu clid e I and orga n asso ciat ed canc er risk (un its: canc er/in d) are givethe resu ltan t n by 4-7

TD (I_) *FAC (I) *CRSP (I) *PMLK*CRDM( I) *CML..T<*DFING (I, J) /T*AR (4.22) and

[TD(I)*FAC(I)*CRSP(I)*PMLK*CRDM(I)*CMLK*DFING(I,J)

RISK(J)]/[T*AR] (4.23) respectively.

Population exposure and risk now follow from the expressions in (4.22) ann (4.23-). Specifically, w~th use of the relation in (4.12);

MKDS (I, J) = {[TD (I) *FAC (I) *CRSP (I) *P:-1LK*CRDM (I) *C'1LK

DFI NG (I, J)] /[T*AR]} *{AR*FMLK*DMLK*T /70.}

= [TD {I) *FAC (I) *CRSP (I) *P~1LK*CRD~ {I) *C:*!LK

DFIN'G (I, J) *FMLK*DMLK] /70. (4.24) and MKHE(I,J) {[TD(I)*FAC(I)*CRSP(I)*PMLK*CRDM(I)*CMLK

DFI~G(I,J)*RISK(J)]/[T*AR]}*{AR*FMLK*DMLK

T/70.}

= [TD(I)*FAC(I)*CRSP(I)*PMLK*CRDM(I)*CMLK

DFING(I,J)*RISK(J)*FMLK*DMLK]/70. (4.25) 4-8 I.

I

/:

I".

Th us, the to tai ca nc ers fro m* rad ion uc lid e I are giv en by MKHETOT ( I) = :EJ MKHE { I' J) . (4. '26 )

4.4 Ex po sur e Fro m Me at Co nsu mp tio n Th e po pu lat ion ex po sur fo r me at con sum pti on are es and re su lta nt he alt h de ef fe cts .*

mi lk co nsu mp tio n wi th the ter mi ne d the sam e as tho se ex ce pti on s th at PMT, fo r CM T, FMT and DMT are use d ins tea d of PM LK, CR CR DM T(I ),

FMLK and DMLK, res pe cti ve DM (I), CMLK, ly, wh ere PMT = pla nt con sum pti on by .be ef ca ttl e (u nit s:

kg /da y),

CR DM T(I ) = co nc en tra tio n ra tio fro m di et to me at for rad ion uc lid e I (u nit s:

Ci /kg pe r Ci /da y),

CMT = ind ivi du al me at* co nsu mp tio n (u nit s: kg /

yr) and the rem ain ing two va ria ble s are de fin ed af ter Th us, (4. 14 ).

MT DS {I, J} = [TD (I)* FA C(I

)*C RS P{I )*P MT *C RD MT (I)* CM T

D FIN G( I,J} *F MT *D NT ]/7 0.

4 (4. 27 )

.*MTHE( I, J) - [TD ( I} *FA C (I) *CR SP( I} *PM T*CRDMT (I) *CM T..

D FIN G( I,J )*R ISK (J) *F MT *D MT ]/7 0. (4. 28 )

and MTHETOT ( I) = LJ MTHE ( I 'J) . (4. 29 )

4.5 Ex po sur e Fro m In ha lat ion of Su spe nd ed So il Th e po pu lat ion ex sur es fo r inh ala tio n of sus pepo and re su lta nt he alt h ef nd ed so il are de ter mi ne fe cts sam e ma nn er as tho se for d in the wi th the ex ce pti on s th at inh ala tio n of sus *pe nd ed sed im en t ins tea d of CS ED (I) , TP CS L( !), TP SL and TM INS L and TMINSD, res pe cti ve ly, .ar e use d wh ere 4-9

TMINSL = fract ion of year that indiv idual is expos ed to suspe nded soil (unit s: . unitl ess).

Spec ifica lly, the amoun t of radio nucli de inhal ed by an indiv idrial (unit s: Ci/yr ) is given by CSL(I)*AIRCON*RINHAIR*TMINSL (4.30 )

= TD( I) *FAC (I) *AIRCON*RINHAIR*TMHlSL/T*AR

Thus, the dose (unit s: rem/i nd) to the organ assoc iated with cance r J due to radio nucli de I and the resul tant can-cer risk (unit s: cance r/ind ) are given by TD(I)* FAC(I )*AIR CON* RINH AIR*T MINS L*DFI NH(I,J )/T*A R (4.31 )

and

[ TD( I) *PAC (I) *AIRCON*RI1UIAIR*n1INSL*DFINH (I, J)

RISK( J)]

/[T*A R] ,

(4.32 )

respe ctive ly.

Popu lation expos ure and risk now follow from the expre ssion s in (4.31 ) and (4.32 ). Spec ifica lly, with use of the relat ion in (4.14 ),

INSL DS(I, J) = j[TD(I )*FAC (I)*AI RCON *RINH AIR*T MINS L

DFIN H(I,J) ]/[T*A RJ} * {AR*D SL*T/ 70.}

= TD(I)* FAC(I )*AIR CON* RINHA IR*TM INSL

DFIN H(I,J) *DSL /70. (4.33 )

4-10

and INSLH E(I,J) - {[TD(I )*FAC( I)*AIR CON*R INHAIR *TMIN SL

DFIN H(I,J)* RISK( J)]/[T* AR]f * {AR*D SL*T/7 0}.

= [TD(I)* FAC(l) *AIRC ON*RI NHAIR *TMIN SL

DFIN H(I,J)* RISK( J)*DS L]/70. (4.34)

Thui, the total cance rs from radion uclide I are given by INSLTOT (I) = LJ HTSLHE ( I , J) (4.35) 4.6 Expos ure From Soil The popul ation exposu res and result ant health effec ts for extern al exposu re from soil are determ ined in the same manne r as those for extern al exposu re from

~edim ent with the excep tions that CSL(I ), TPSL and REXTSL are used instea d of CSED( I), TP and "REXTSE~, respe ctivel y, where REXTSL = exposu re rate to soil (units : hr/yr ).

First, as was done in (3.30) , it is neces sary to conve rt the soil conce ntrati on CSL(f) (unils : Ci~kg) to a stir-face conce ntrati on CSURF (I) (units : Ci/m ), where .

C~URF (I) = CSL(I) *DEPT H*DEN SITY*( l. - POROS IT)

= TD(I)* FAC(I) *D.EPT H*DEN SITY*( l. POROS IT)/T*A R (4.36)

Hence , the extern al exposu re (units : rem/in d) to the organ assoc iated with cancer J due to radion uclide I and the result ant cancer risk (units :. cance r/ind) are* given by 4-11

CSURF(I)*REXTSL*DFEXT(I,l,J)*70.

= [TD(I)*FAC(I)*DEPTH*DENSITY*(l. POROSIT)/T*AR]

[REXTSL*DFEXT(I,l,J)*70.J (4.37) and

[TD(I)*FAC(I)*DEPTH*DENSITY*(l. - POROSIT)/T*AR]

[REXTSL*DFEXT(I,l,J)*70.]*RISK(J) , (4.38 respectively.

Population exposure and risk now follow fror:1 the expressions in (4.37) and (4.38). Specifically, with use of th~ relatibn in (4.14),

EXSLDS(I,J) = [TD(I)*FAC(I)*DEPTH*DENSITY*(l. - POROSIT)

/T*AR]*[REXTSL*DFEXT(I,l,J)*70.]

[AR*DSL*T/70.]

= TD(I)*FAC(I)*DEPTH*DENSITY*(l. - POROSIT)

REXTSL*DFEXT{I,l~J)*DSL (4.39) and 4-12

I EXSLHE(I, J} = [TD(I}*FAC (I}*DEPTH *bENSITY* (l. - POROSIT)

/T*AR] * [REXTSL*DFEXT (I, 1, J) *70.] *RISK ( J ).

[AR*DSL* T/70.]

= TD(I}*FAC (I}*DEPTH* DENSITY*( l *. - POROSIT)

REXTSL* DFEXT(I,l, J)*RISK(J} *DSL. (4.40}

Thus; the toial cancers from radionucli de I are given by EXSLTOT (I) = LJ E..XSLHE (I, J). (4.41) 4.7 Exoosure. From Susoended Soil' The population exposures and result~nt health effects for external exposure from suspended soil are determi~ed in the same manner as those for external exposure from suspended sediment with the exceptions that CSL(I),

and REXARSL are used instead of CSED(I) and REXARSD, respectiv ely, where REXARSL = exposure rate to suspended soil (units:

hr/yr}.

The 'external exposure (units: rem/ind} to the organ associate d with cancer J due to radionucl ide i and the resultant cancer risk (units:* cancer/ind ) are given by CSL(I)*AIR CON*REXA RSL*DFEX T(I,3,J}*70.

= [TD(I}~FAC (I}*AIRCO N*REXARS L*DFEXT(I ,3,J)*70.]

/[T*AR] (4.4;2) 4-13

and

[TD (I) *FAC (I) *~IRCON*REX..\RSL*DF:SXT( I, 3, J) *70. *RISK( J)]

/ [T*AR] ,

(4.43) C\

respectively.

Population exposure and ris'k now follow from the expressions in (4.42) and (4,.43). Specifi_cally, with use of _the relation in ( 4. 14),

EXARSLD(I,J) = {[TD(I)*FAC(I)*AIRCON*REXARSL*DFEXT(I,3,J)

70.J/[T*AR]}*{AR*DSL*T/70.}

= TD (I) *FAC (I) *AIRCON*REXARSL *DFEXT( I, 3, ,J) *!)SL

( 4. 44) .

and EXARSLH (I, J) = { r.TD (I) *FAC (I) *.l\.IRCON* REXARSL

DFE;XT (I, 3, J)

70.*RI~K(J)i/[T*AR]}*{AR*DSL*T/70.}

= TD(I)*FAC(I)*AIRCON*REXARSL*DFEXT(I,3,J)

RISK(J)*DSL.

(4.45)

Thus, the total cancers from radionuclide I are given by EXARSLT(I) = ~J EXARSLH(I,J) * (4.46) 4-14

5. Irrigation After Release to Surface Hater 5.1 Preliminary Comments Population exposures and resultant health effects are now calculated for irrigation after a radionuclide release to a surface-water body. Similar calculations are considered in Chapter 4. However, there the only uptake mode consid-.

ered is direct uptake from soil to plant. In this chapter the.additional uptake modes resulting from radionuclides retained on plants due to sprinkler irrigation and from radionuclides in drinking water for milk and beef cattle are considered. In particular, IPLRDS(I,J), IPLRHE(I,J) and IPLRHET(I) are determined for exposure resulting from human ingestion of plants containing radionuclides depos-ited by sprinkler irrigation,, where

IPLRDS(I,J) = po~ulation dose (units: rems) to organ associated with cancer J due to radionuc_lide I, IPLRHE(I,J) = number of occurrences of cancer J in population due to radionuclide I, IPLRHET(I.) = total number of cancers fn popula-tion due to radionuclide I.

Further, IMK;RDS (I, J) , IMKRfiE (I, J) and H1KRHET (I) are determined for that part of the dose from milk ingestion which results from milk cattle* ingesting radionuclide.s deposited on feed due to sprinkler irrigation, where IMKRDS(I,J) = population dose (units: rems) to organ associated with cancer J due to radionuclide I,*

IMKRHE(I,J) = number of occurrences of cancer J in population due to radionuclide I, IMKRHET(I_) = total number of cancers in population due to radionuclide I.

Similarly, IM.KWDS(I,J), HlKWHE(I.,J) and. IMKWHET(I) are determined for that part of the dos~ from milk ingestion which results from milk .cattle ingesting radionuclides in their drinking water. In like manner, IMTRDS(I,J),

IMTRHE(I,J), IMTRHET(I), IMTWDS(I,J), IMTWHE(I,J) and IMTWHET(I) are determined for human ingestion of beef.

5-1

The prec~ ding quant iti~s are determ ined in a mann~ r simila r to that used in Chapt er 4.

As alread y indica ted, this sectio n *consi ders foliar depos ition due to sprink ler irriga tion. The conce ntra-tion of radion uclide retain ed on, or in a plant, as the resul t of sprink ler irriga tion is determ ined by solvin g a diffe rentia l equati on which repres ents the change in this conce ntr~ti on as the differ ence betwee n the rate at which the radion uclide is contam inatin g the plant and the rate at which the radion uclide is being remove d by weath ering~ This equati on is dC(t) /dt = D(t) "'">-w( t) ( 5. 1 )

where C(t) = conce ntratio n of radion uclide on plant mate-rial* ( in Ci/kg) ,

D(t) rate of radion uclide depos ition (in Ci/kg /

yr), and

~ = rate consta nt for remov al by weath ering (in w yr-1),

With the initia l condi t.ion C ( 0) = 0 and the assum ption that D(t) has a consta nt value D, the preced ing equati on has the soluti on (5.2)

. which provid es the conce ntratio n due to foliar depos ition.

The weath ering half- life is oft<.:n taken to be 14 days.

This yield~ a value for ">,. w of 18 .1 yr- 1 . It is pointe d* out that 1 - e Awt approa ches 1 rapidl y. With t = 0.17 yr, the value is 0.95, and with t = 0.25 yr, the value is 0.99, Thus., the length of time for irriga tion is proba bly not critic al. The depos ition rate D is giyen by*

D = FRET*C WAT*I RAT/PD EN, ( 5 -* 3 )

5-2

.wher e FRET = frat ion bf depos ited radio nucli des retai~ ed on crops , often taken to be 0.25 (dime nsion -

less) ,

CWAT. = conce ntrati on of radio nucli de in irrig ation water (in Ci/L) ,

IRAT = irrig ation rate (in L/m2 /yr), and PDEN = stand ing crop (in kg/m 2 ).

The value s indic ated for Aw and ~R~T are .wide ly used appea r to come from a study by Miloo urn.a nd Taylo r [Mi65 <;1-nd

].

The manne r in which the relat ions in (5.2) and will be used is now indic ated. First , for simp licity(5.3) the asym ptotic value for C(t) will be used. That is, the conc entra tion C (unit s: Ci/kg ) due to folia r depo sition as a resul t of sprin kler irrig ation is taken as C = D/A w = .FR_ET*C\* 1AT*IR AT/"Aw *PDEN * ( 5 .4)

Value s for the varia bles in (5.4) are now obtai ned for radio nucli de I in the conte xt of the situa tion under con-sider ation . From (3.1) ,

CWAT (I) = TD(I )/F*T . ( 5. 5)

Furth er,.

!RAT = FRIV *F/AR , (5.6) where FRIV = fract ion of river used for sprin kler irrig a-tion (unit s: unitl ess).

Also, Aw = ALOG (2.)/W HRHL , (5.7) 5-3

where WHRHL = weather ing half-lif e for radionu clides depos-ited by sprinkle r irrigati on {units: yrs).

Thus, the concent ration C{I) _{units: Ci/kg) of radionu-clide I. on plants due to sprinkle r irrigati on is given by C(I) = [FRET*TD(I)*FRIV*WHRHL]

/[T*AR*P DEN*ALO G(2.)] (5.8) 5.2 Exposure Fr6~*Pla nt Consump tibn The popula.t ion exposure s and resultan t health effects are now determin ed for human ingestio n of plants contain -

ing radionu clides deposite d by sprinkle r irrigati on. It follows from ( ~-. 8) that the amount of radionu clide I ingested by an individu al (units: Ci/yr) is given by C (I) *CPLT = [FRET*TD( I) *FRIV*v-JBRHL*CPLT]

/[T*AR*P DEN*ALO G(2.)] (5 ~9)

Thus, the dose (units: rem/ind) to the organ associat ed with cancer J due to rap.ionu clide I and the resultan t cancer *risk (units: cancer/ ind) are gi.ven

by

[FRET*TD (I)*FRIV* WHRHL* CPLT*DF ING(I,J)]

/[T*AR*PDEN.*ALOG.( £. )] (5.10) and

['FRET*TD( I) *FRIV*WHRliI/Ci:'LT*DFING (I, J) *RISK( J)].

/[T*AR*P DEN*ALO G(2.)] , (5.11) respecti vely.

5-4

Population exposure'and risk now follow from the e~pressions in (5.10) and (5;11). Specifically, with use of the relation in (4.11) for total population available for plant consumption, IPLRDS(I,J) = {[FRET*TD(I)*FRIV*WHRHL:,._CPLT*DFING (I,J)]

/ [T*AR*PDEN*ALOG ( 2 *. ) ] } * {AR*FPLT*DPLT*T /70 .}

- [FRET*TD(I.)*FRIV*WHRHL*CPLT*DFING(I, J)

FPLT*DPLT]/[PDEN*ALOG(2.)*70.J (5.12) and IPLRHE ( I ,J) = { [FRE'r*TD( I) *FRIV*WHRHL*CPLT*DFING(.I ,J).

RISK(J)]/[T_*AR*PDEN*ALOG(2. )] }

{AR*FPLT*DPLT*T/70 .}

= [FRET*TD(I)*FRIV*WHRHL*CPLT*DFING(I, J)

RISK(J)*FPLT*DPLT]/[PDEN*ALOG(2.)*7

. :* .. 0.]

(5.13)

Thus, the total cancers from radionuclide I are given by (5.14) 5.3 Exposure From Milk Consumption The population exposures and resultant health effects are now determined for milk ingestion. Two sets of d~ter-minatibns are. made * . ,The ,.first is for that part of. exposure and health effects *which results from foliar; *deposition of radiontlclides. due to *sprinkler irrigation. The.* second is 5-5

for tha t par t of exp osu re and hea lth from rad ion ucli des in wat er give n to effe cts whic h res ults

.liv esto ck.

It foll ows from (5.8 ) tha t the I ing este d by an ind ivid ual (un its: amo unt of rad ion ucli de dep osit ion and sub seq uen t plan t use Ci/y r) due to fol iar give n by in milk pro duc tion is C(I)*PMLK*CRDM(I)*CMLK

= {[FR ET* TD( I)*F RIV *WH RHL ]/[T* AR*

PDE N*A LOG (2.)J }

{PMLK*CRDM(I);CMLK}

= [ FRET* TD (I) *FRIV*\'lHRHL* PMLK* CRDM (I) *CMLK]

/[T* AR* PDE N*A LOG (2.)] .

(5.1 5)

Thu s, the dose (un its: rem /ind ) to the orga n asso ciat ed with can cer J due to rad ion ucli de I and the res ulta nt can -

cer risk (un its: can cer/ ind ) are give n by

[FRET*TD{ I) *FRIV*WHRHL*PMLK*CRDl1( I) *Cl-;L K

DF ING (I ,J) ]/ [T*AR*PDEN*ALOG( 2.)]

(5.1 6).

and

[FRET*TD(I)*FRIV*WHRHL*PMLK*CRDM(I)*CMLK

DF ING (I,J) *RIS K(J) ]/[T *AR *PD EN* ALO G(2

.)] , (5.1 7).

resp ecti vel y.

Pop ulat ion exp osu re and risk now foll exp ress ion s in (5.1 6) and (5.1 7). ow .from the Spe ci£ ical ly, with use of the rela tion in (4.1 2) for tota l pop ulat ion ava ilab le for mil. k con sum ptio n, 5-6

IMKRD S(I,J) :::: {[FRET* TD(I)*FR IV*WHR HL*PML K*CRDM (I)

CMLK *DFING (I,J)]/[T *AR*PD EN*~OG (2.)J}

{AR*FM LK*DML K*T/70} .

= [FRET*T D(I)*FRI V*WHRH L*P.MLK *CRDM( I)*CMLK

DFIN-G ( I ,J) *FMLK*DMLK] / [ PDEN*ALOG( 2.) *70. J (5.18) and IMKRHE (I, J) * = {[FRET~ TD(I)*FR IV*WHR HL*PML K*CRDM (I)

- CMLK *DFING (I,J)*RI SK(J)]/[ ~*AR*P DEN

ALOG ( 2. ) J} * {AR*FMLK*DMLK*T /70 };

- [FRET*T D(.I) *FRIV*HHRHL*PMLK*CRDM( I) *CMLK

DFING (I,J)*RI SK(J)*F MLK*D MLK]

/[PDEN *ALOG (2.)*70. ] * (5.19)

Thus, the total cancer s from radion uclide I are .given by IMKRHET (I) = 1:J IMKRHE ( I ,J) * (5.20)

It folio~s from (j.1) that the amount of radion uclide

r ingeste q by an individ ual (units: Ci/yr) due to water used for milk cattle is given by CW( I) *WMLK*CRDM( I) *CMLK = TD( I )*Wrt'JLK*CRDM( I) *CMLK/ F*T, ( 5. 21) 5-7

wher e .

WMLK = wate r cons ump tion by dair y catt le (uni ts:

L/da y). .

Thus , the dose (uni ts: rem/ ind) to the orga n asso ciate d with canc er J due to radi onuc lide I and the resu ltan t canc er risk {uni ts: canc er/in d) are give n by TD(I)*WMLK*CRDM(I)*CMLK*DFING(I,J)/F*T (5.2 2) and TD ( r*) *WMLK*CRDM( I) *CMLK*DFING (I, J) *RIS K( J) /F*T (5.2 3) resp ecti vely .

Popu latio n expo sure and risk now *foll ow fro~

expr essi ons in (5.2 2) and (5.2 3). the Spe cific ally , with use of the rela tion in (4.12 ) for tota l popu latio for milk consu r.1pt io'n, n avai labl e IMK WDS (I,J) = [TD( I)*W MLK *CRD M(I)* CML K*DF ING( I,J)/F *T]

[AR*FMLK*DMLK*T/70.]

= [TD(I)*WMLK*CRDM(I)*CMLK*DFING(I,J)*AR

FMLK*DMLK]/[F*70.] ( 5. 24) .

and IMKWHE (I, J.) = [TD (I) *WMLI<*CRDM( I) *CMLK*DFING ( I ,J) *RIS K(J)

/F*T]*[AR*FMLK*OMLK*T/70.]

= [TD (I) *WMLI<*CRDM( I) *CMLK*DFING ( I ,J) *RIS K( J) .

AR*FMLK*DMLK]/[F*70.] * (5.2 5) 5-8

Thus , the tota l canc ers from radio nucl ide I are given by IMKWHET (I, J) = EJ* I~1KWHE (I, J) . (5.26 )

Unlik e all earl ier calcu latio ns for popu latio n the varia bles F and AR did not drop out of the effe cts, expr essio ns in (5.24 ) and (5.25 ).

Howe ver, if one assum es that the irrig atio n rate IRAT (unit s: L/m2 per yr) is know n, it is poss ible t<;:> remo ve F and AR. Spec ifica lly, F*FR IV = AR*IRAT (5.27 )

and so AR/F = FRIV /IRAT . (5.28 )

Now, with use of the relat ion in (5.28 ), the equa

.(5.2 4) and (5.25 ) can be rewr itten as litie s in IMKW DS(I, J) = [TD(I )*WM LK*C RDM (I)*C MLK* DFIN G(I,J) *FRIV

FML K*DM LK]/[ IRAT *70.] (5.29 )

and IMKWHE ( I ,J) * - [TD( I) *WMLK*CRDM (I) *CMLK* DFING (I, J) *RISK ( J).

FRIV *FML K*DM LK]/[ IRAT *70.] . (5.3 0) 5,4 Expo sure From Meat Cons umpt ion The popu latio n expo sures and resu ltant heal th' effec ts*

for meat consu mptio n are deter mine d in the same mann er as those for milk consu mptio n with the exce ption PMT,* CRDM T{I), CMT, FMT, .DMT and WMT are used s that inste ad of PMLK, CRDM (I), CMLK, FMLK, DMLK and WMLK; resp ectiv ely.

5-9

Thu s, IMT RDS (I,J) = [FRE T*TD (I)*F RIV* WHR HL* PMT *CR DMT (I)*C MT

DF ING (I,J) *FM T*D MT] /[PD E~* ALO G(2

.)*7 0.] ,

(5.3 1)

IMT RHE (I,J) = [FRET*TD(I)*FRIV*WHRHL*PMT*CRDMT(I)*C i'-1T

DF ING (I,J) *RIS K(J) *FM T*D MT]

/[PD EN* ALO G(2 .)*7 d.J (5.3 2)

IMT WD S(I,J ) = [TD (I)*W MT* CRD MT( I)*C MT* DFIN G(I, J)*A R

FM T*D MT] /[F* 70.] .

= [TD (I)*W MT* CRD MT( I)*C MT* DFIN G(I, J)*F RIV

FM T*D MT] /[IR AT* 70.]

(5.3 3) and IMT WIE (I,J) = [TD (I)*W MT* CRD MT( I)*C MT* DFI NG( I,J)*

RISK (J)

AR *FM T*D MT] /[F* 70.J

= [TD (I)*W MT* CRD MT( I)*C MT* DFI NG( I,J)* RISK (J)

FR IV*F MT* mIT / [IRA T*7 0.] .

(5.3 4).

5-10

The total cancers from radionuclide I are given by IMTRHET =~J IMTRHE(I,J) (5.35) and IMTWHET =LJ I MTWHE { I , J ) * (5.36) 5-11

Reference s

. Bon73 Bond, R. G. and C. P. Straud (Ed.s.), 1973, Handbook of Environme ntal Control, Vol. 1, CRC .Press, Cleveland ,

OH.

Boo81 Boone, F. w., Y. c. Ng, ahd J. M. Palms, i981 "Terrestr ial Pathways of Radionucl ide Particula tes,"

Health Physics 41 1 735-747.

Cu73 Cummins, A. B. and I. A .. Given (Eds.), 1973, SME Mining Engineerin g Handbook, Society of Minin~

Engineers , Littleton , co.

En80 Environme ntal Protection Agency, 1980, Environme ntal Radiation Protection _ Standards for Managemen t and Disposal of Spent Nuclear Fuel, High-Leve l and Transuran ic Radioactiv e Wastes, 40CFR191 . (\'lorking Draft No. 16, October 21, 1980) *

Im78 Iman, R. L., J. c. Helton, and J. E *. Campbell, 1978, Risk Methodolog y for Geologic Disposal of Radioactiv e Waste: Sensitivi ty Analysis Technique s, SAND78-09 12, Sandia Labaorato ries, Albuquerq ue, NM.

He82 Helton, J. c. and N. c. Finley, 1982, PATHl Self-Teaching Curriculim : Example Problems for Pathways-T o-Man Model,

SANDBl.;...2377, Sandia National Laborator ies,..

Albuquerq ue, NM.

Mi65 Milbourri, G. M. and R. Taylor, 1965, "The Contami-nation of Grassiand s With Radioactiv e Strontium :

I, Initial Retention and Loss," Radiation Botany 5, 337-347.

Nu76 Nuclear Regulatory Commissio n, 1976, Calculatio n of Annual Doses to Man From Routine Releases of Reactor Effluents for the Purpose of Evaluatin g Complianc e With 1 OCFR Part *- 50,

Appendix I, .

Regulatory Guide 1.109, u.s. Nuclear Regulatory Commissio n, Washingto n, DC.*

Ru81 Runkle, G. E., R. M. Cranwell, and J. D. Johnson, .

1981,* Risk Methodolog y for Geologic Disposal of Radioactiv e Waste: Dosimetry and Health Effects, SANDB0-13 72, Sandia National Laborator ies, Albu-querque, NM.

R-1

Sm81 Smith, J.M., T. w. Fowler, and A. s. Goldin, 1981, Environme'ntal Pathway Models for Estimating Population Health Effects From Disposal of High-Level Radioactive Waste in Geologic Repositories, EPA520/5-80-002 (Draft June 8, 1981), Ehvironmental Protection Agency, Washington, DC.

To70 Todd, D *. K. (Ed.), 1970, The \'later Encyclopedia, Water Information Center, Huntington, NY.

We74* Weast, w. E., 1974, Handbook of Chemistry and Physics (55th edition), CRC Press, Cleveland, OH.

R-2

Volume 6 Calculation of Health Effects per Curie Release for Corilpari$QM

. with

. the EPA Standard

I NUREG/CR-3235 SAND82-1557 WH TECHNICAL ASSISTANCE.FOR REGULATORY DEVELOPMENT:

REVIEW AND EVALUATION OF, THE DRAFT EPA STA_NDARD 40CFR191 FOR DISPOSAL OF HIGH-LEVEL WASTE

. VOL. 6 CALCULATION OF HEALTH EFFECTS PER*

CURIE RELEASE FOR COMPARISON WITH THE EPA_STANDARD GENE E. RUNKLE*

Manuscr ipt Complete d: April 1983 Date Publishe d: April 1983 Sandia Nationa l Laborat ories*

Albuque rque. New Mexico 87185 operated by Sandia Corpora tion for the

u. s~ Departm ent of Energy Prepared for Division of Waste Managem ent

- office of Nuclear Materia l Safety and Safegua rds Washing ton. D.C. 20555 NRC FIN. No. A-1165

Raytheo n Service Company

ABSTRACT The Env iron men tal Pro tect ion Age ncy (EPA) stan dard for geo logi c disp osal of high is deve lopi ng a

-lev el (40C FR1 91) base d on radi oac tive rele ases (exp radi oac tive was tes tha t may resu lt in 1,00 0 hea lth effe cts (i.e ress ed in curi es}

fata liti es) over a 10,0 00 year peri od. Hea ., late nt canc er calc ulat ions were used by EPA to esta blis h lth effe cts lim its. The Fuel Cyc le Risk .An alys is Div isio the curi e rele ase Nat iona l Lab orat orie s was requ este d by the n of San dia Com miss ion (NRC)' High -Lev el Was te Lice nsin Nuc lear Reg ulat ory to perf orm calc ulat ions , usin g the meth odol g Man agem ent Bran ch the Risk Asse s.sm ent Met hodo logy Prog ram, to ogy deve lope d unde r resu lts from the EPA ana lysi s. The inte nt com pare with the insi ght s into the degr ee of con serv atism in was to prov ide some per curi e valu es pres ente d by the EPA stan the hea lth effe cts made to enco mpa ss all the unc erta inty in the dard . No atte mpt was

~sed in the calc ulat ions and ~ome of the mod inpu t para met ers used in this ana lysi s are diff eren t from thos elin g assu mpt ions Thre e sets of calc ulat ions of hea lth effe cts e of the EPA .*

per cur ie rele ase were perf orm ed in this ana {can cei deat hs) calc ~lat iona l meth ods, the resu lts of the lysi s. The ana pot enti al imp lica tion of thes e resu lts upon lysi s. and ihe lim its of the EPA .are disc usse d in this rep the curi e rele ase ort.

r I'

/..

r I'

1.

r 1*

i r

I j*

i I

I.

iii II

.TABLE OF CONTENTS 1.0 Int.roduction . ........~ ................... ........... . 1 2.0 Description of the EPA/SANDIA Analysis .....*...* .... 3 2.1 Ingestic;,n. ,.................... *.. *~ .......... . 9 2.1.1 Dose Factors and Health Effects Estima.tes . .* ..... ~ ................. . -9 2.1.2 Population at Risk ...*. ~ *.***.**..**. 9 2.1.3 Quantity Intake of Radionuclides ...*. 13' Drinking Water .....*....... 17 2.1.3~2 Fish .. .. ~ .................. ." .. 17 2.1.3.3 Crops .*........... ** .**...**. 17 2.1.3.4 Milk . ................... .. . 17 2.1.3.5 Beef . ................... ... . 18 2.2* Inhalation .....***....***..... *.*.*............ 19 2.2.1 Dose Factors and Health Effects Est-imates ........ ..................

19 2~2.2 Population at Risk.:...***.*..**..**.** 19 2.2.3 Quantity Intake of Radionuclides ...** 20 2 =3 .External ExPosure . ......*...........* . . * . . .. . . 20 2.3.1 Dose Factors . .

and Health Effects.

Estimates........ ..................... 20 2.3.2 Population at Risk.............. ..... 20

2. 3. 3. Exposu~e Level ..*.*...*..***.*... ..... 20 2.3.3.1 Contaminated Soil *....**.** 20 2.3.3.2 Contaminated Air ...*..***** 21 3.0 Description of the SANDIA Analysis ***.**..****.*.*. 21 V

TABLE OF CONTENTS (Cont'd)

PAGE 4.0 Description of SAMPLED SANDIA Analysis .... ~ .... ~ .... 31 5.0 Results and Discussion ............................ . 34 References.**... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 vi

FIGURES 5.1 Deaths Per curie Calcul ated with Sample d Kd Ranges and No Adsorp tion onto Solid Phase of the Surface Water for Pathwa ys 1-5 ....... ..*.. 38 5.2 Deaths Per Curie Calcul ated with Sample d Kd Ranges and No Adsorp tion onto Solid Phase of the Surface Water for Pathwa ys 6-8 . . . . . . . . . * . . 39 5.3 Deaths Per curie ~alcul ated with sample d Kd R*anges and Aqsorp tion onto Solid Phase of the surface Water for Pathwa ys 1-5 *.*..* ...... 41

5.4 Deaths Per -Curie Calcul at~d with Sample d Kd Ranges and Adsorp tion onto Solid Phase of the Surface Water for Pathwa ys 6-8 . . . . * . . . . . . . 42 vii

TABLES 2 .1 Environmental Transport Input Parameters. . . . * . . . . . 5

2. 2 Distribution Coefficients _(Kd) Assumed by EPA..... 7

-2°.3 Radionuclide Concentrations in the-Surface Water and Soil From the Pathways Analysis.......... ... 8

2. 4

Heal th Effects Conversion Factors (EPA)........... 10 2.5 Ingestion. Inhalation and External Exposure Rates Assumed by EPA.............. .............. 14 2.6 Crop and Animal Parameters Assumed by EPA......... 15 2.7 Concentration Ratios Assumed by EPA............... 16 3.1 Basic Equations for Calculating Radionuclide Concentrations for Various Pathways.......... ... 22 3.2 Concentration Ratios for Human and Animal Food Sources (Used in Reference Site Analysis) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

24 3.3 Ingestion. Inhalation and External Exposure Rates for an Averag-e Individual (Used in Sandia Reference Site Analysis) ***....*........... ....* 25 3.4 Crop and Animal Parameters (Used in Sandia Reference Site Analysis) *...*...*....*.*.. ...... 26 3.5 Dose Conversion Factors - Ingestion (remiCij . . . . . . . . . . . . . . . . . . . ~........... ... . . . . . . . 27 3.6 Dose Conversion Factors - Inhalation

( rem/Ci ) ...... ~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.7 Dose Conversion Factors - External .*...........*... 29 3.8 Cancer Risk Estimates Used in the SANDIA Analysis. 30 viii*

TABLES (C on t'd ).

4.1 La tin Hy per cub e Sam ple ...

.*. ..* -~ .* ... ... .* ... ... ..

32 4.2 Va ria ble s Wh ich Af fec t the Ph of the Su rfa ce En vir onm ent ysi cal De scr ipt ion

..................... . 33 5.1 Ind ivi du al Pat hw ays and Do sim etr y and He al. th Ef fec ts Co mp ari son Ta ble Ex De ath s'. Pe r Cu rie ... ... .* ... pre sse d as 35 5.2 Pat hw ays and Do sim etr y and He alt h Ef fec ts

Co mp ari son Ta ble ... ... ...

37 ix

.l.O Introdu ction The Environ mental Protec tion Agency (EPA) is develo ping a

.standa rd for geolog ic dispos al of high-le vel radioa ctive wastes that would limit the curie release s to the access ible enviro n-ment of the variou s radion uclides found in high-le vel waste.

The EPA guidan ce establi shes that the release s of radion uclides to the access ible environ ment from the wastes from 100.000 Metric Ton of Heavy Metal (MTHM) should not result in excess of 1.000 health effects (i.e .* latent cancer fatalit ies) over a 10.000 year period . The process by which EPA establi shed the*

release limits consis ted of two steps. In the first step. the projec ted release s of radioa ctivity from a generic geolog ic reposi tory in variou s geolog ic media (bedded .salt. domed salt.

granit e. basalt and shale) were calcula ted and in the second step. the potent ial excess cancer deaths from. the release s were estima ted. A set Qf calcula ted health effect s per curie release d into the ~nviron ment for all the radion uclide j consid ered in the EPA analys is was establi shed t.o estima te the potent ial health hazard . The EPA analys es of the variou s media were used to select the limit of 1.000 health effed~ s over 10.000 years for a 100.000 MTHM reposi tory. The 1.000* health effects criter ia was then used to establ ish the release limits for .indivi dual radion ucl ides. The NV.clea r Regula tory Commis sion (NRC) reques ted the Fuel Cycle Risk Analys is Divisio n of Sandia Nation al Labora tories (SNL) to perform an evalua tion using the method ology develop ed under the Risk Assessm ent Method ology Program (FIN:A -1192) to calcul ate the health effects that may result from the release of one curie of each of variou s radion uclides to the biosph ere. The intent of this two week effort was to provide some insigh ts into the degree of conser vatism in the health effect s per curie values calcula ted by the EPA. The intent was not to presen t values to replace the EPA curie values . but rather to perform calcul ations simila r to the EPA analys is *that would provid e some perspe ctive on the EPA release limits . No attemp t was made to bound all of the uncert ainty in the input parame ters in the pathway modeli ng effort . to encomp ass all the possib ilities of release or to addres s the uncert ainties in the dose conver -

sion factors and health effects estima tes. The calcul ations presen ted in this report were designe d to flag.p otenti al prob~

lems with the EPA release limits that may warran t furthe r anal-

. ysis.

Three sets of calcula tions were perform ed in this work.

The firs*t set of calcul ations (EPA/SANDIA Analys is) used the Pathwa ys Model develop ed at Sandia (Helton and.Ka estner. 1981) and the input parame ters (e.g .* distrib ution coeffi cients (Kd).

concen tration ratios . dose conver sion factor s. risk estima tes.

etc.) and the health effects calcul ationa l method s from the EPA. A second set of calcula tions (SANDIA Analys is) was made using. the Pathwa ys Model (Helton arid Kaestn er. 1981) and the 1

Dosime try *and Health Effect s Model (Runkl e. et aL. 1981). In these calcul ations the input parame ters to the Pathwa ys Model were selecte d from those used in demon strating the Risk Assess -

ment Method ology (descri bed in Cranwe ll. et al .* 1982). The referen ce site used in this demon stration was based on a hypo-thetic al site and generic parame ters repres enting severa l sites throug hout the United states . The EPA point value for the distrib ution coeffi cients (Kd) for the variou s radion uclides were used in the analys is. The third set of calcul ations (SAMPLED SANDIA Analys is) were perform ed using a statist i.cal techniq ue to sample an assigne d range of values for some of the input parame ters to the Pathwa ys Model. A distrib ution was assigne d to each range of values . This approa ch can be used to repres ent some of the uncert ainty in the calcula ted results due to input data uncert ainties . Many other uncert ainties have not been addres sed in this analys is and includ e uncert ainties in the concen tration ratios . the dose conver sion factor s. and the risk estima tors of health effect s. to name only a few.

There are severa l differe nces in the *modeli ng approa ches used in this analys is that may affect the results and are therefo re detaile d below. First. for calcul ating the health effect s per curie release for the water based pathwa y. the EPA inp~t a unit curie source over* 10.000 years (i.e .* 10-4 *

Ci/yr) into the surface (river) water to calcul ate the drinkin g water and fish intake s. For the land based pathwa ys (which

includ e ingesti on of crops. beef and milk). EPA input a 0.5 curie source into the sc:>ilco mpartm ent over 10.000 years (i.e .*

5 x 10- 5 Ci/yr) to estint,ii te the soil concen tration s. and furthe r assume d that 50% *,of the contam inated land was used for crop produc tion for direct human consum ption. 25% for milk produc tion and 25% for beef produc tion.

In the analys es {EPA/SANDIA. SANDIA. SAMPLED SANDIA) pre-sented in this report . a unit curie source was input to the liquid. phase of the surface water over 10.000 years (i.e **

10-4 Ci/yr) and the interch ange betwee n the surfac e water and the soil compar tments of the Pathwa ys Model determ ined the soii conc*e ntratio n. The calcul ations perform ed* by the Pathwa ys Model resulte d in an input of 2.3E-3 Ci to*the soil over the 10.000 year period . Iri additio n. the fractio nal partiti oning of. land use (assume d by EPA) was not incorp orated in this.

analys is.

Second . the EPA analys is consid ered a popula tion detrim ent that was based on a linear relatio nship of popula tion to the flow rate in a river for the water based pathwa ys and was line-.

arly propor tional to the area of land for the land based path-ways. In the approa ch used by EPA. it is import ant to note 2

that the area (A) canc eled out of the equ base d inge stio n calc ulat ion. whic h elim atio n for the land tion ship betw een area and pop ulat ion. inat ed the line ar rela -

The Risk Asse ssm ent Met hodo logy used for base d on the risk to an aver age indi vidu this ana lysi s was a pop ulat ion risk by rela ting the rive r flow al and was conv erte d to lati on den sity {pe rson s/!) assu med by EPA rate to the popu -

pop ulat ion for the wat er base d ~ath way s.

to esti mat e the pa*th ways the den sity (per sons /m ) defi ned* For the land base d plie d by the area con side red in the refe renc by EPA was mul ti-(Cra nwe ll et al .* 198 2). The land area was e site ana lysi s defi ned as 40 km X 2 km on both side s of a rive r (160 km2 ). that fall with in the floo d plai n of the rive was assu med to (cro ps. beef and milk ) for the pop ulat ion. r and to prov ide food

the pop ulat ion is a line ar func tion of the With this appr oach .

dou blin g the area wil l resu lt in a dou blin assu med area and g of the pop ulat ion.

The thre e calc ulat iona l meth ods for the EPA/

and SAMPLED SANDIA Ana lyse s are deta iled SANDIA. SANDIA resp ecti vely . Cha pter 5 is a summary of the in Cha pter s 2-4.

in this ana lysi s. resu lts calc ulat ed 2.0 Des crip tion of the EPA/SANDIA Ana lysi s The EPA/SANDIA Ana lysi s used the Env iron men Mod el deve lope d at San dia (He lton and *Ka tal Path way s

.inp ut para met ers used by EPA in thei r ana estn er. 1981 ) and the para met *rs incl ude d con cen trat ion rati os. lysi s. The inpu t cons ump tion rate s. dose conv ersi on fact ors hum an and anim al The se calc ulat ions were desi gned to esti mat and risk esti mat es.

per curi e rele ase by emp loyi ng the Risk Asse e the hea lth e-ff ects deve lope d at SNL and the EPA inpu t para met ssm ent Met hodo logy ers .

. The Path way s Mod el (He lton and esti mat e the radi onu clid e con cen tratiKae stne r. 1981 ) was used to ons in the surf ace wat er and soil com part men ts foll owi ng a 10-4 curi into the surf ace wat er for a 10.0 00 yea r peri e/ye ar rele ase plif ied ana lysi s pres ente d in this r~p ort. od. For the sim-of two com part men ts. soil and surf ace wat a syst em con sist ing er.

this situ atio n. the math ema tica* 1 form ulat ion was used . For clid e con side red is a syst em of two diff ere for each radi onu -

the foll owi ng form : ntia l equ atio ns of dX1 /dt = hl - (~ + k21) Xl + k12 X2 (1).

dX2 /dt = h2 + k21 Xl - (~ + ko2 + k12) X2 whe re Xi is the amo unt (un its: Ci) of radi part men t i (1 ... soil . 2 - surf ace wat er). onu clid e in com-of radi onu clid e inpu t (un its: Ci/y r) to com hii s the i:ate part men t i. and X 3

is the decay constant {units:. yr-1) for the radionuclide under conslderation. The kij is the rate constant for move-ment from compartment j to compartment i *. where i = O denotes a flow from compartment j to an area outside the modeled system.

Each coefficient. kij~ is of the following form:*

kiJ" = (1 - Sj)RWij + Sj RS i j .* {2)

VW*) MS*

J where VWj denotes the v9lume of water in compartment j (units: t). MSj denotes the mass of solids in compartment j (units: kg). RWij denotes the rate at which water flows from com~artment j to compartment i (units: i/yr). _and RSij denotes the rate at which solid material flows from compartment j to compartment i (uni ts: - kg/yr). Further. the unitless quantity Sj represents the effects of radionuclides partitioning in compartment j and is defined by s.

J

= . Kd jMS Kd*MS*

Jw. * (3}

) J + *J where Kdj is the distribution coefficient in compartment j for the radionuclide under consideration (units:* i/kg}. The nonzero values for the VWj, MSj* RWij and RSij for the site described in this section are given in Table 2.1.

The system of equations in (1) can be_ reformulated in matrix not~tion as dx/dt = h + Kx. (4) where X = [:~]

For_this analysis h 1 was assumed to be 10-4 curies/yr and h2 was assumed to be O. As the system under-consideratio n is completely open. the equations repre*ented in (1) and (2) have a unique asymptotic solution. sx *. where sx = -K-1.h. {6}

For the analysis presented in this report. the asymptotic solu-tions indicated in (6) were used instead of time-dependent solutions. Variables a1 to R4 were used to introduce vari-:-

ance in the exchange rate between subzones and may be sampled from a user-specified range. For this analysis. a mid-point value (see Table 2.1) was assumed.

4

Table 2.1 Environm *ental Transpo rt Input Paramet ers (Helton and Kaestne r. 1981)*

Surface Water:

VW2 = Volume of Water *2.2x1ol0 2_

- Mass of Solid kg

6. ax1os. (:~)

= Rate of mass outflow to 1.1x10 11 (R 3 ) kg/y soil subzone

= Rate of water outflow to -

surface water in next zone

= Rate of solid outflow to surface in next zone Rate of water outflow to soil subzone Soil:

VW1 = Volume of water *2.ox1ol0 2_

MS1 = Mass of solid 1.1x10 11 kg RW21 =Rate.o f water outflow to 4.oxiolO CR~>- i/y surface water RS21 = Rate of mass outflow to 0.0 (kg/y) surface water Assumed Values:

R1= 1.0 Variable s to introduc e variatio n in the subzones indicate d above.

R2= 1.0 Variatio ns were not consider ed in the EPA/SANDIA or the SANDIA R3;,. 10-3 analyses . therefor e these varia-bles were assigned the point val-

. R4= 9.0 ues given in this table .

5

Also for this analy sis. the radio nucli desw ere assum ed to be relea sed*t o the liqui d phase of the surfa ce water no adsor ption onto the soJid parti culat e phase of the. surfa Furth er.

water was*e onsid ered. This would repre sent a situa tion where ce there are no Kd effec ts in the water . In an alter nativ e scen ario. that consi ders river flood ing. parti culat es are carri ed onto the surro undin g land mass and contr ibute a*lar radio nucli de burde n to the soil. This analy sis place d the ge radio nucli de solel y in the liqui d phase of the surfa ce water as assum ed by the EPA. Howe ver. the distr ibuti on .

coeff Kd. was taken into accou nt in the radio nucli de conc entra tion t. icien the soil subzo iie. The point value s for the Kd value s for in radio nucli des that were used in this analy sis and also by the EPA are given in.Ta ble 2.2. The EPA data (unle ss other wise the speci fied) were obtai ned from perso nal comm unica tion with Smith . EPA. Montg omery . Alaba ma. Since . the initi al work J.M.

1981. these EPA param eters and the envir onme ntal calcu latio in have been publi shed in £mith . et al .* 1982. ns In the analy sis prese nted in this secti sourc e was input .to the liqui d phase of the on. a unit curie water over 10.00 0 years and the interc hang es betwe en the surfa ce water and soil comp artme nts of the Pathw ays Mode*1 deter mined . the soil the conc entra tion. The resul ts of the Pathw ays analy sis are given in Table 2 .3 for the* surfa ce water and soil comp artme nts.

These . radio nucli de conce ntrati ons were used to calcu late

. healt h effec ts (canc ei death s) per curie relea se. T~e calcu the latio ns of the cumu lative healt h eff-ec ts over time. T. may -

summ arized by the follow ing gener al equat ion *

be RSK. .

', l.J

= Q. .

1]

O:k DF. . k 1]

HE . k)

J POP * *T J

(7) where RSK*1]* = heal~ h effec ts (canc er death s) per curie relea

.of radio nucli de i via pathw ay j (inge stion *. se inhal ation or exter nal)

= quan tity intak e per year (via inges tion or inhal ation ) or* expos ure (exte rnal) to radio nucli de i via pathw ay j '(Ci/y )

dose conve rsion facto r to calcu late the dose comm itmen t to organ . k from radio nucli de i via pathw ay j (rem/ Ci}

6

Table 2.2 Distribution Coefficients (Kd)

As.sumed by EPA 3

Radionuclide Kd Value (cm /gm)

Am241 2000 Am243 2000 Cs135 200 Csl37 200 I129.

0 Np239 15 Pu239 2000 Pu240 2000 Pu242 2000 Sz:90 20 Tc99. 0 Snl26 250 7

I.

Table 2.3 Radionuclide Concentrations in the Surface Water and Soil From the Pathways Analysis Radionuclide Surface Water Soil (Ci/!!.) . (Ci/kg)

Am241 5.26E-18 l.13E-15 Am243 5.26E-18 7.02E-15 Csl35 5.26E-18 1. OSE-15 Csl37 5.26E-18 7.66E-17 I129 5.26E-18 9.57E-19 NP237 5.26E-18 7.99E-17 PU239 5.26E-18 9.lOE-15 PU240 5.26E-18 6.54E-15 PU242 5.26E-18 l.04E-14 SR90 5.26E-18 4.56E-17 TC99 5.26E-18 9.57E-19 SN126 5.26E-18 l.31E-15 8

= he alt h ef fe cts co nv ers ion po ten tia l fa ta l ca nc ers fa cto r to es tim ate the fro m the do se co mm itm en t to org an k.v ia pa thw ay j(h ea lth ef fe ct s) rem POP*J = po pu lat ion ex po sed to the pa thw ay j (p ers on s) do se co mm itm en t fro m*

T ;:

'tim e in ter va l of the ca lcu an aly sis (an d EPA) the tim lat io n. Fo r th is to be 10 ,00 0 ye ar s. e ~n ter va l wa s ass um ed Th e th re e *pa thw ay s inc lud (in clu de s se ve ra l su bp ath ed in th is an aly sis we re the in ge sti on su te. The ca lcu lat io ns wa ys ), in ha lat io n an d ex ter na l ex po -

ea ch of the se pa thw ay s are of he alt h ef fe cts pe i cu rie 2.3 , ies p~ cti ve ly . de tai led in su bs ec tio ns re lea se fo r 2.1 . 2.2 an d 2.1 In ge sti on Th e in ge sti on pa thw fro m. va rio us su bp ath wa ys ay co ns ist s of' in tak e of ra di on uc lid es pl an ts. mi lk an d me at. inc lud ing dr ink ing wa ter Th , fis h, us ed the fo llo wi ng co mp e ca lcu lat io ns fo r the se su bp ath wa ys es tim ate s (2) po pu lat io n- on en ts: (1) do se fa cto rs an d he alt h co mp on en t is dis cu sse d be at ris k an d (3) qu an tit y in tak e. Ea ch sub pa thw ay s.

low wi th ref ere nc e to the va rio us

2. l;l Do se Fa cto rs an d He alt h Ef fe cts Es tim ate s Th e do se co nv ers ma tes pe r rem of ex p~ion fa cto rs an d the he h ef su re we re tak en fro m Taalt fe ct s es ti~

rad ion uc lid e, the pr od uc ble 2.4 . Fo r ea ch fa cto rs and he alt h ef fe cts t of the in ge sti on do se co mm itm en t al l or ga ns . Th e sum ma tio co nv ers ion fa cto rs we re summed ov er ef fe cts fro m al l of the n was us ed to ca lcu lat e the he alt h

.to rs us ed by EPA re pr es en su bp ath wa ys . Th e do se co nv ers ion fa c-an in di vi du al wh ich re su t a SO -ye ar do se com mi tm ent (re m) to cu rie of the ra di on uc lid lts fro m the in iti al int ak e of on e e.

2.1 .2 Po pu lat ion at Ri sk EPA us ed the flo w po pu lat ion to es tim ate ra the te of the wo rld 's riv er s an d the wo rld a giv en riv er flo w ra te . po pu lat ion th at ca n be su pp or ted by wo rld po pu lat ion . wa s ap Th is ra tio . of the flo w ra te to the co ns ide red in th is an alypli ed to the flo w ra te of the riv er la tio n fo r the dr ink ing sis (1 .9E l31 /yr ) to de fin e the po pu -

pe rso ns wa s us ed fo r the wa ter . A re su lti ng po pu lat ion of 6.3 E6 re lat ed the wo rld 's av era EPA/SANDIA ca lcu lat io ns . EPA als o to the wo rld 's riv er flo wge fis h co ns um pti on ra te* (lo lO kg /yr )

. ra te {3 El6 I/y r) to es tim ate the 9

Tab le 2.4 HEAL TH EFFECTS COHVERSION FACTORS, (FATAL CANCERS FOR ALL ORGANS EXCEP HEAL TH EFFECTS/MAN REM T OVARIES AND TESTES. GENETIC EFFEC TS TO FIRST GENERATION FOR OVARIES AND TESTES)

BONE RED MARROW LUNGS LIVER GI-LL I THYROID KIDNEYS OTHERORGAN OVARIES TESTES WALL 1.000E-05 4.000E-05 4,000E-05 1.000E-05 2.000E-05. 1.000E-06 1.000E-05 7.000E-05 2.000E-05 2.000E-05 NLCLIDE DEPENDENT INPUT DATA NUCLIDE PATHWAY (INHALATION AND INGEST IQN:REM/CI INTAK DOSE C(}lf.lITMENT FACTORS E AIR SUBMERSIQN:REJ.1/Y PER CI/M **3 GROUND CONTAMINATIQN:REM/Y PER CI/M

- 2 l ORGAN BONE RED HARROW LUNGS LIVER GI-LL I TH.YROID KIDNEYS OTHERORGAN WALL OVARIES TESTES.

C-14 INHALl 8.460E+o0 2.420E+Ol 6.l80E+o0

. INHAL2 8.880E+o0 7.220E+o0 6.480E+o0 7.920E+o0 8.460E+QO 2.420E+ol 6.l80E+OO 8.880E+OO l.410E+01 5.290E+OO 5.420E+o0 INGEST 7.220E+OO 6.480E+OO 7.920E+OO 1.410E+01 1.170E+o3 3.380E+o3 8.490E+o2 1.230E+03 5.290E+OO 5.420E+OO EXT AIR 0.0 l.460E+o3 8.890E+02 1.060E+o3 1.920E+03 0.0 0.0 0.0 0.0 7.360E+02 7.230E+02 o.o

0.0 0.0 EXT GND o.o o.o o.o n.o o.o o.o 0.0 O~O O~O o.o o.o o.o NI-59 INHALl 1.290E+o4 2.150E+o3 8.470E+o3 INHAL2 4.983£+03 7.120E+02 2.150E+o3 2.150E+03 2.150E+03 1.290E+04 2.150E+o3 8.470E+03 4.980£+03 2.150E+03 2.150E+OJ INGEST 9.670E+03 1.610E+o3 1.610E+o3 3.560£+02 2.150E+03 2.150£+03 2.150E+03 3.320E+o3 9.700E+02 2.150E+03 2.150E+o3 EXT AIR o.o 1.610E+o3 1.6H>E+o3 1.610E+o3 0.0 o.o 0.0 0.0 0.0 o.o 1.6.lOE+OJ 1.610E+o3 .

EXT GND 0.0 0.0 o.o o.o 0.0 o.o o.o 0.0 o.o o.o 0.0 0.0 0.0 SR-90 INHALl 3.210£+05 1.210E+05 8.540£+06 INHAL2 1.930£+04 9~310E+05 3.740E+o3 3.740E+03 3.000E+o6 1.lOOE+06*4.920E+04 1.490E+o4 1.510E+05 J.740E+03 3,730E+o3 INGEST 5.SOOE+04 1.540E+o4 1.540E+04* 2.410E+05 1.200E+o6 4.300E+o5 1.570£-02 5.710E+o3 1.540E+04 1.540E+04 EXT AIR o.o 1.980E+05 5.99CJE+03 5.990E+o3 0.0 o.o 0.0 0.0 0.0 9.500E+04 5.990E+o3 5.990E+03 EXT GND o.o o.o 0.0 o.o ZR-93 INHALl 1.470E+o3 o.o o.o o.o 1.750E+03 5.850E+04 2.930E+o3 7.160E+03 o.o. o.o 0.0 o.o I o.o 0.0 o.o HIHAL2 4.120E+03 2.460E+o3 3.080E+o4 2.110E+o3 6.980E+03 l.600E+o3 1.360E+o3 2,SOOE:+03 l.040E+03 1.320E+o3 1.~70E+02 INGEST 1.970E+o2 3.340E+o2 3.900E+o1 1.430E+02 1.750£+04 1.320E+o3 2,1JOE+o3 l.460E+o3 4.950E+02 EXT AIR o.o 1.690E+o1 1.990E+o2 2.470E+o2 1.360E+o3 0.0 o.o o.o . 0.0 0.0 o.o 1,340E+o2 EXT GND 1.7BOE+o4 1.780E+o4 1.780E+o4 1.780E+o4 1.780E+o4 1.780E+04

. 0.0 o.o 1.780E+o4 1.780E+04*1.780E+04 o.o 1.780E+04 TC-99 INHAU 2.* 420E+02 2.150E+o2 5.220E+04 4.210E+02 INHAL2 2~420E+02 2.150E+02 5.220E+04 4.210E+02 1.660E+o3 9.460E+o3 3.070E+02 8.870E+o2 2.120E+02 2.120E+02 INGEST 1.660E+OJ 9.460E+03 3.070E+o2 8.870E+02 2.120E+02 3.61 OE+o2 3.220E+02 0.0 6.280E+02 3.200£+03 1. 41 OE+04 2.120E+02 EXT AIR 0.0 0.0 0.0 4 .580E+02 2 .140E+o2 3.170£+02 3. 170£-+02 EXT GND o.o o.o o.o 0.0 0.0 o.o 0.0 o.o o.o o.o o.o o.o o.o o.o *o.o 0.0 o.o Tak en from Sm ith, et al. , 198 2 10

Table 2~4 (~ontinu ed)

ORGAN BOIIE . RED MARROW LUNGS LIVER Gl-LLI THYROID KIDNEYS OTHERORGAN OVARIES TESTES WALL SN-126 INHALl 1.580E+o5.1.580E+o5 1.270E+o6 4.i90E+o3 7,600£+-04 1.230£+-03 6.160E+03 6.160E+-03 6.160E+03 INHAL2 6.160E+o3 1.580E+05 1.580E+o5 l.270E+o6 4.190£+03 7.600E+o4 1.230E+o3 6.160E+o3 6.160E+o3 6.l60E+03 6.160£+03 INGEST 8.570E+04 8.57DE+04 3.llOE+oJ 1.690E+o3 1.1SCE+o5 4.990E+o2 2.830E+o3 2;820E+o3 2.820£+03 2.820£+03 EXT AIR 1.150E+o71.l50E+o7 l.150E+o71.150E+o7 1.150E+o7 t.150E+o7 l.150E+071.150E+-071.150E+o7 EXT GND 1.150E+-07 2.090E+o5 2.090E+o5 2.090E+-05 2.090E..05 2.090E+-05 2.090£+05 2.090£+o5 2.090E**05 2.090£+-05 2.090E+o5 1-129 INHALl 5.790£+02 6.050E+o2 7.SSOE+-02 4.660E+o2 4,280E+-01 5.000E+06 4,490E+o2 2.050E-t03 3.780E+02 3;5]QE+02 UlllAL2 5.790E+o2 6.05DE+o2 7.880E+-02 4.660E+-02 4.280E+01 5.000E+06 4,490E-t02 2.050E-t03 3.7BOH02 3.57C£-+02 HIGEST 9.020E..02 9.420E..02 1.790E+-02 7.240E+o2 6.700E+01 7.8COE+o5 7,020E+-02 3,180E+-03 5.920E+02 5.SSOE+-02 EXT AIR 1,450E+05 1,310E+o5 4.850E+04 3,600E+-04 1.150E+04 1,010£+05 5.380E+04.9.540E+-04 3.400E+04 1,310E*05 EXT GNo* 8.730[+03 7,870E..03. 2.910E+o3 2,160£+03 6.900E+o2 6.0~0E-+03 3.2~0E+03 5.730E+o3)2.040E+03 7.880E-t03 CS-135 WHALl 7.470E+03 7.470E+o3 6.400[+02 7.470E+03 8,51GE+01 7.480[+03 7.470E+03 4,400[+03 7.470::'.+03 7.4701:-l-03 INHAL2 7.470£+03 7.470£..03 6,400E+o2 7,470E+oJ* 8:510£-+01 7.40C£-t03 7.470E+03 4,400E+03 7,470E+03 7.4,CE+o3 INGEST .1.120E+041. 120E+o4 O.O 1.120£+04 5.JSOE+021,130E-t041;120E+04 6,610E+o31.120E+04 1.120E+o4 EXT AIR o.o o.o . o.o o.o 0.0 0.0 0.0 o.o o.o 0.0 .

EXT GND o.o o.o o.6 o.o* o.o o.o o.o o.o o.o o.o CS-137 IN11AL1 4.540£+04 4.910E+o4 1,620E+o4 5.230E+o4 1.600E+04 4.4]0E+04 5.130E+04 J.260E+04 5.000E+04 4.440E+o'4 IN11AL2 4.540£+04 4.910E+04 :t.620E+04 5,230E+o4 1.600£-+04 4.47GE+04 5.130E+04 3,260E+04 5.000E+o4 4.440£+04 INGEST 6.820E+o4 7.380E+04 1.990£+04 7,87UE+04 2.590£+04 6.720E+o4 7.7JOE-t04 4,910E+04 7.540E+o4 6.680£+04 EXT- AIR 4;660E+o6 4.450E+o6 3,600E+o6 3.180E+06 2.750E+o6 4,020E+o6 3.380E+06 3,810£+06 1.390E+06 4.240£+06 EXT GND 8.290£-t-04 7.920E+o4 6.400E+04 5.650E+04 4.900E+o4 7.150£+04 6.030£+04 6.790£+04 2.490E+04 7.550C+o4 SM-151 HIHALl 5.100E+02 2.090E+o2 6. 780E+o4 1. 900E+03 3.040E+03 1.920E+01 5;540E+02 1.090£+03 1.470E+01 UIIIAL2 1.070E-+01 4.910E+03 1.940E+03 1,590E+o4 1,890E+o4 2.810E+Ol 1.040E+02 5.380E+03 1.190£+03 LOSOE+o2 1.030E+02 UIGE*ST 4.910E-l{)O 3.200E+OO 1,0SOE-01 1..730£+01 5.850E+o3 1.030£-01 5.520E+o0 2.340£+01 5.660E+OO 5.360E-01 EXT AIR 2.440E+Ol 2.130E+o1 4,240E+OO 2.350E+OO 2.920£+00 9.060E+OO 7.020E+OO 3.070£+01 3.920E+OO EXT GND 3.86uE+01 4.590E+o0 4.000E+OO 7.960£-01 4.410E-01 5.480£-01 1.700£+00 1.320E+OO 5.780E+o0 '7.360£-01 7.300E+o0 RA-226 I11HAL1 1.100E+07 9,800E+05 2.810E+07 3.400E+o5 l.OOOE+o5 3.* 400£+05 3.490E+o5 4,600E+o6 3 *.400E+05 3.400£+05 INHAl.2 1.100E+o7 9.800£+05 2.810E+o7 3.400E+05 1.000E+o5 3.400E+05 3;490£..05 4.600E+o6 3.400E+05 ItlGEST 3.40DE+o5 6,320E+o7 2.140£+06 2,710£+02 1,870E+o6 8.160E+-05 8.010E+o5 5.790E+o6 7.790E+o6 8.060E+05 8.010E+05 EXT*AIR 1.500E+o7. 1.390E+o7 1.270E+o7 1, 120E+07 1.030E+07 l.280E+o7 1.060Ef{)7 1.180Eto7 9.900E+-06 EXT GND 1.130E+07 2~520E+o5 2~3.40E+o5 2.070£+05 1.850[-+05 1.ii90£+05 2.* 120£-+05 1.750E+o5 2.210E+o5 1.630E+o5 1.890E+o5 U-234 INHALl 2.000E+07 8.100E+05 2.730E+o8 5.900£+05 5.480E+o4 5.900[+05 8.700E+o5 IHHAL2 9.800£+06 5.900£+05 5.900E+05 5.900E+07 2.400E+o6 2.800E+o7 1.700E+o6 4.790£+04 1.700E+o6 2.500E+o6 5.500E+06 1.700E+o6 1.700£+06 INGEST 2.000E+o7 8.000E+o5 8,230E+o2 5.800E-t05 8~860E+o4 5.800E+05 8.500E+05 1,700E+o6 EXT AIR 5.800£+05 5.BOOE+05 2,940E+03 2.640E+03 1.030E+o3 7.640£+02 8.560E+o2 1.280E+03 8.130£+02 2.490E+03 6.640£+02 2.090E+03 EXT GND 5.630E+02 5.050£+02 1.970E+o2 1.460E-l-02 1.640£+02 2.460E+02 1.560E+02 4.780~-+02 1.270£+02 4.000E+02

. NP-237

JNIIALl 9.o~oE+o8 3.0lOE+oS 2.900E-t08 4.020£+08 1.JSOE-l-05 3.000£+06 5.200E+o7 8,500[+07 1.800[+06 5.800[+06 INIIAL2 2.240E+09 7.470E+o8 3.000E+o7 9.910E+08 1.260E+05 7,400[+06 1.280E+o8 1.900E+o8 INGEST 4.600£+06 1,§00E+o7 1.900E+o7 6.200E+o6 8,870E+o2 8.200E+o6 1,460E+o5 6.080E+o4 1.100E+o6 1.600£+06 3.900£+04 1.200E+o5 EXT AIR 3.270Et06 3,0JOE+o6 1.790E+061.560E+06 1.130E..06 2.150£+06 1.500E+o6 EXT GND 2.050£+06 1.020E+06 2.410E+06 7.250E *04 6, 720E+04 3.970£+04 3 .460E +o4 2. 50UE +04 4.470E f()4 3. 340E +04 4. 570E-+04 2.270E+04 5. 350E+o4 11

Table 2 .4 (continued)_

ORGAN.

BONE RED MARROW LUNGS LIVER GI-LLI . THYROID KIDNEYS OTHERORGAN OVARIES TESTES UALL.

PU-238 ItlHALl *7.910E+o8 2.640E+o8 3.090E+o8 3.550E+o8 6,200E+04 2.600E+o6 4.600E+07 7.600E+o7 1.600E+06 5.000E+o6 INHAL2 2.030E+o9 6.770E+o8 3.200E+07 9.070E+08 5.510E+o4 6.600E+06 1.170Et08 1.730E+08 4.100E+06 1.300E+07 WGEST 5.000E+o5 1.700E+05 7.890E-02 2.200E+05 1,lOOE+05 l.640E+03 2.910E+04 4.320E+04 1.03DE+o3 3.200E+03 EXT AIR 1.260E+03 1.090E+03 3.020E+02 l.33DE+02 4.45CE+02 2.460E+02 1.770E+02 l.660E+03 1.B60E+02 l.320E+03

EXT GND 2.470E+o2 2.140E+o2 5.920E+Ol 2.600E+Ol 8.710E+01 4,810E+01 3.460E+Ol 3.250E+02* 3.640E+Ol 2.580E+02 PU-239 INHALl 9.120E+08 3.040E+08 2.940E+08 4.040Et08 5.7BOE+o4 3.000E+06 5.200E+o7 8.600E+o7 l.8QOE+06 5.800E+06

INHAL2 2.280E+o9 7.610E+08 3.000E+07 l.OOOE+09 5,130E+o4 7.400E+o6 l.300E+OB l,920E+08 4.600E+06 l.500E+07 INGEST 5.700E+05 1~900E+05 6.090£--02 2.500E+o5 9,850E+o4 1.850E+OJ 3.220E+o4 4.820E+o4 1.l50E+03 3.600E+03 EXT AIR 6.410E+o2 5.610E+02 l.710E+02 9.JBOE+Ol 1.900E+o2 1.890E+02 l.230E+02 7.220E+02 1,170E+02 6.110E+02 EXT GND 1.220E+o2 1.070E+02 3.240£+01 1.7BOE+o1 3.600E+ol 3.590E+ol 2.330E+o1 1.370E+o2 2.210E+01 1,160E+02 PU-240 INHALl 9.130E+08 3.040E+OB 2.950E+08 4.050E+OB 5.820E+o4 3.000E+06 5.200E+07 8.600E+07 1.800E+05 5.800E+06 IUHAL2 2.280E+09 7,600E+08 3.100E+07 1.010E+Q9.5.170E+04 7.400E+06 l.300E+OB l.940E+08 4.600£+06 l.500E+07 IllGEST 5.700E+05 l.900E+05 8.32CE-02 2:SOOE+05 9.9JOE+04 l.84GE+03 3.220E+04 4.830E+04 1.150E+03 3.600E**03*

EXT AIR l.160E+03 1.000£+03 2.890E+02 1.400E+o2 J.9SOE+02 2.530E+02 1.7SOE+02 l.460E+o3 1.60DE+02 1.170E+03 EXT GIID 2.250£+02 1.960£+02 5.640E+01 2.720E+Ol 7.790£+01 4.930E+Ol 3.470E+01 2.S50E+o2*3.520E+01 2.280E+o2

. AM-241 IIIHALl . 9.430E+08 3.l40E+08 3.1JOE+08 4.l90E+-08 6.520E+04 3.lOOE+06 5.400E+07 8.900E+07 1.900E+06 6.000E+o6 Illl!AL2 2.35GE+09 7.830E+08 3.200E+07 1.040E+09 6,110E+04 7.700E+06.1.340E+08 l.990E+08 4.800E+06 1.500£+07 IHGEST 1. 900E+07 6.400E +06 1. 270E+02 8. 500E+06 1.100E+o5 6. 320E+04 1. 1OOE+06 1. 600E+06 3. 940E;-04 1. 2COE+05 EXT AIR 2.720E+05 2.4SOE+05 1.010E+05 8.300E+04 5.6SOE+04 l.J80E+o5 8.800E+04 1.440E+05 8.510E+04 1.250E+05 EXT GHD . ~ 420E+04 1.300£+04 5.JOOE+o3 4.330E+Ol 2,960E+-03 7.210E+OJ 4.590£+03 7.500E+oJ 4o440El-03 5.570Er03 PU-242 INHALl 8.690£+08 2.890£+08 2.800£+08 3.850£+08 5.51DE+o4 2.S00E+o6 5.000£+07 .8.200£+07 1.800£+06 5.500£+06 INHAL2 2,170E+09 7.220£+08 2.900E+07 9.56DE+D8 4.900E+04 7.100E+D6 1.23DE+OB .1.840E+08 4.40DE+D6 1.400£+07 INGEST 5.400E+o5 1.800E+05 1.600E-01 2.400£+05 9.400E+04 1.760E+03 3.060E+D4 4.600E+04 1.090E+03 J.42GE+03 EXT AIR 1.0~0E+03 8.9JOE+D2 2~360E+D2 9.J70E+01 J.650E+02 1.770E+o2 1.32CE+02 1.390E+03 l.Sl,E102 l,100E+03 EXT GND 2.030E+o2 1. 750£+02 4.630E+Ol 1 ~840E+01 7. 160E+01 J.470E,+01 2. 590E+01 2. 72DE +02 2. 9i.iC:+01 2. 170E+-02 AM-243 IllHALl 9.430E+D8 1~560E+09 3.0JOE+08 4.210£+08 3,220E+05 3~ 100E~06 5.400E+07 8.900E+07 1.9DOE+06 6:0GOE+06

INHAL2 2.340£+09 3.870E+09 3.lOOE+07 1.040E+09 1.5DOE+-05 7.70DE+06 1.3~ul+OB 1.990E+08 4.800£+06 1.500E+07 INGEST 1.900E+07 3.200E+07 9.640£+02 8.500E+06 1.490£+05 6.340E+04 1.100E+o5 1.600E+o6 4.d70E+04 1.200E+o5 EXT AIR 2.170E+06 2,010£+06 1.060E+06 9.140£+05 6.490E+OS 1.3JOE+o6 8.970E+05 1.290E+o6 6,760E+05 1.410E+06 EXT GND 5.290E+04 4.880E+04 2.630E+04 2.260£+04 1.610E+04 3.2EOE+o4 2.210£+04 3.150£+04 1.650£+04 3.480E+o4 12

popu latio ~ inta ke of fish (3.3E -7 kg per pers on/!

estim ate of 3.3E -7 kg per pers on/! is the s~me )~ The EPA as l kg/y e fish inta ke. Ther efor e. for the EPA/SAND assu ming a tion s a 1 kg/y r cons ump tion of fish and the same IA calc ula-us~d for the drin king wate r calc ulat ions *{6~3E6 popu latio n*

assu med.

pers ons) were The popu latio n for the land -bas ed inge stio n in'ta calc ulat ed by mul tiply ing the dens ity (per sons kes was

/m 2 ) prov ided by EPA for the thre e subp athw ays by the area hyp othe tica l refe renc e* site anal ysis ( 160 km2)cons ider ed in the et al., 1982 ). The popu latio ns used in thes e (Cra nwel 1. .

latio ns were subp athw ay calc u-I CROP 160 km 2 ** l.OE

- 3 pers on

= 1. 6ES pers ons 2*

m MILK 160 km 2

l.SE - 3 pecs on - 2.4E S pers ons m2 BEEF 160 km 2

2 . 1 E_ 4 pecs on = 3*. 4E4 .Pe*r sons .

' m2 2.1. 3 Qua ntity Inta ke of Radi onuc l ides

The quan tity irita ke of a radi onuc lide the ~on cent ratio n of the radi onuc lide in.th eis food dep~ nden t upon the rate of inta ke or cons ump tion. The EPA/SAND sour ce and util ized th*e equa tions . for each subp athw ay avai IA calc ulat ions Path ways Mod el and subs ti'tu ted the appr opri ate labl e .in the valu es. In some case s, the mod eling appr oach es EPA para mete r betw een EPA and the Path ways Mod el, and in thes diff ered inpu t para mete rs were sele cted from thos e used e case s, the site anal ysis (Cra nwe ll. et al.', 1982 ). The EPAin the refe renc e used in the ana lisis are give n with each equa tion poin t valu es mari zed in Tabl es 2.s and 2.6. The radi onuc lide and are sum-conc entr atio n rati os were take n from a com pute depe nden t by J.M . Smit h. EPA. and are give n in Tabl e 2.7 r outp ut prov ided lishe d in Smit h. et. al., 1982 ). The equa tion s (rec entl y pub-inge stio n subp athw ays are defi ned in Sect ions .2.l. *for the vari ous 2.1. 3.5. 3~l to 13

Table 2.5 Ingestio n. Inhalati on and Externa l Exposure iates Assume(J by EPA Ingestio n Rates Water Consump tion by Humans 6.03E02 1/yr.

Plant Consump tion by Humans 1. 94E02 'kg/yr Milk Consump tion by Humans l.12E02 1/yr Beef Consump tion by Humans 8.SEOl kg/yr Fish Consump tion by Humans l.OEOO kg/yr Inhalati on Rate Average Air Consump tion by Humans 8.40E03m 3/y Annual Externa l Exposure Submers ion in Air 1/3 year Grounds hine from Soil* 1/3 year

.i

An effectiv e depth of O.lSm was assumed for soil by EPA.

14 J

Tab le 2.6 Crop and Anim al Par ame ters Assumed by EPA Ani mal Con sum ptio n Rat es Pla nt Con sum ptio n by Dai ry Cows 5.0E Ol kg/d ay Pla nt Con sum ptio n by Bee f Cows 5.0E Ol kg/d ay Spr ink ler Irri gat ion for Cro ps Ir_r igat ion Rat e

3. OE02 9../m 2/y*

Ret enti on* Fra ctio n 2.5E -Ol*

Stan ding Crop _

7.16 E-O l kg/m 2 Rat e Con stan t for Wea ther ing (kc., ) l.8E 01y -l (13. 75 day hal f-li fe)

Irri gat ion Tim e(~ )

l.7E -l y e-1'.c.>~

4.65 E-2 Spr ink ler Irri gat ion for Pas ture Irri gat ion Rat e 3.0E 02 9../m 2/y*

Ret enti on Fra ctio n 2.5E -Ol*

Stan dil). g Cro p 2.8E -Ol kg/m 2 Rat e Con stan t for Wea ther ing (~c.,) 1. 8E0 1 y-1 (13. 75 day hal f-li fe)

Irri gat ion Tim e (~)

l.7E -l y e-1'.c.>~

4.65 E-2

Th ese para met ers wer e not defi ned in the the refo re the valu es used in refe ren ce EPA Ana lysi s:

dem ons trat e the SNL Risk Ass essm ent Met site ana lysi s to sub stit ute d for the calc ula tion . hod olog y w~r e 15

Table 2.7 Concentration Ratios Assumed by EPA FISH/WATER PASTURE MILK/FEED BEEF/FEED (Ci/kg per CROP/SOIL (FEED)/SOIL (dar

kg_) (da}".

kg)

Ci/ll) (dimensionless) (dimensionless) kg. ll kg. kg Am241 2.5El O.llE-2. 0.74E-2 0.36E-4 O.l6E-5 Am243 2.5El 0.22E-3 O.lSE-2 0.36E-4 0.16E-5 CS135 4.0E2 O.lOE-5 0.17E-4 0.56E-2 0.14E-l CS137 4.0E2 0.85E-2 *. 0.14EO 0.56E-2 0.14E-l 1129 l.5El 0.19E-7 0.68E-7 0.99E-2 0.70E-2 NP237 l.OEl 0.16E-7 0.65E-7 0. SOE:-.5 0.20E-3 Pu239 3.5E2 0.59E-4 0.36E-3 0. 5_3E-7 0.19E-7 PU240 3.5E2 0.19E-3 0.12E-2 O.SJE-7 0.19E-7 Pu242 3.5E2 0.40E-5 0.24E-4 0.45E-7 0.41E-6 SR90 5.0EO 0.21EO 0.86EO 0.24E-2 0.30E-3 TC99 1. 5El O.l4E-5 0.28E-3 0.99E-2 0.87E-2 SN126 3.0E3 0.77E-5 0.31E-4 0.12E-2 0.80E-1

.16"

2.1.3. l Drinkin g Water amt of nuclid e nuclide cone ) ra~e of ~ater) intake per year= (in surface water * ( 1ngest1 on Ci/y = (Ci/1) * (6031/y )

2.1.3.2 Fish amt of nuclid e nuclide cone in) (cone ) r~te of.fish )

intake per year= ( surface water .

ratio * ( 1ngest1 on Ci/y = (Ci/2.) * (1/kg) ** (l. 0 kg/y) where cone ratio cone of nuciide in fish

=

cone of nuclide in water 2.1.3.3 CroQs

amt of nuclid e nu~lide cone) r~ te of. crop) intake per year= ( 1n crops * ( 1ngest1 on Ci/y = (Ci/kg) * (194 kg/y) nuclide cone nu~lid e.conc) (cone ) (

in crops ( cone due to )

= 1n soil

ratio + sprink ler irrigat ion Ci/kg= (Ci/kg) * {dimen sionles s) + (Ci/kg) where cone ratio = cone of nuclide in crops cone of nuclide in soil nuclide nuclide retenti on cone in irrigat ion cone due* fractio n *surfa ce* rate to = l water sprink ler rate consta nt irrigat ion* for weathe ring standin g crop ciJkg -( 1 ) (0~2s * (Ci/1)

JOO 1/m2/y~

- 18.05 .y-1 0.716 kg/m2 J (o.9sJs )

2

l. 3

4 Mi 1 k amt of nuclide nuclide cone) r~te of.milk )

intake per year= ( in milk * ( 1ngest1 on 17

Ci/y = (Ci/l ) * (1121 /y) nucli ae cone nucli de cone ) (cone J (* consu in milk = ( in dairy feed

ratio *. of contamptio n rate *)

minat ed feed Ci/l = (Ci/k g).* /day

kg) *

~kg

l

/

\50 day

M_)

where cone ratio = cone of nucli de in milk intak e of nucli de per day nucli de cone in nucli dairy and beef feed =. ( in de soil cone) *(con e) co~~c ~!~e to)

ratio + ( sprin kling .

pastu re.

Ci

= (Ci/k g) * (dime nsion less) + (Ci/k g) kg where cone: ratio = cone of nucli de in pastu re cone of nucli de in soil nucli de nucli de reten tion cohc in irrig ation cone due fract ion *sur face

rate to = 1 water .

sprin kling rate const ant pastu re for ~eath ering stand ing crop Ci/kg I- 1 * (Ci/l )

300

=,18 .05 0.28 kg/m 2 2 . 1. 3 . 5 Beef amt of nucli de nu~li de*co nc) r?te of. beef) intak e per year = ( in beef * ( inges tion Ci/y = (Ci/k g) * (85 kg/y) nucli de*co nc nucli de cone) *(con sump tion )

in beef rate *of

= ( in beef feed

conta mina ted

feed 18

Ci/k g=

( ckgi)

.* *(day

kg) kg. kg * (50 kg/d ay) wher e cone rati o = .cone of nucl ide in beef inta ke of nucl ide per day nucl ide cone calc ulat ed the same as dair y feed in beef feed - ' (See 2.1. 3.4) 2.2 Inha latio n The inha iatio n path way cons ider s inha led radi onuc that are resu spen ded from the soil . The EPA lide s radi onuc lide conc entr atio ns throu gh mul tipli cati obta ined susp ende d radi onuc lide s conc entr atio n (exp resse d in Ci/m on of surf ace pens ion fact or of 10-9 m-l (Smi th. et al.. 2) by a resu s-1982 tras t, in this anal ysis the susp ~nde d-ra dion uclid ). In con-

tion was obta ined by mui tiply ing .the soil conc e ~ori cent ra-entr by an as~u med *con cent ratio n of s~sp ende d mat eria atio n (Ci/ kg) 3.SE -9 kg/m 3 . The latt er conc entr atio n of susp l in air of was take n from the* listi ng of vari ous soil typeende d mat eria l Hand book of Envi ronm ~nta l Con trol. *V9lume 1 (Bons in the CRC 1973 ). d and stra ud.

2.2. 1 Dose Fact ors and He~ lth Effe cts Esti mate s The dose conv ersio n fact ors .(rem /Ci) path way were take n from Tabl e 2.4.a nd were for mul the inha latio n appr opri ~te heal th effe cts estim ates for the or~a tipli ed by the side red. INHALl dose fact ors are for inso lubl ns con-mat eria l reta ined in the lung for long biol ogic e CY clas s) whil e INHAL2 dose fact ors are for more solu ble al half -tim es, inha led mat eria l and resu l.t in more dose to the CW clas s) orga ns. .For this com para tive calc ulat ion. the othe r body comm itmen t .fac tors were mul tipli ed by the INHA L2 dose mato rs and summed over all orga ns for each heal th effe cts esti -

radi side red. onuc lide con-

~

2.2~ 2 Popu latio n at Risk The popu latio n at risk for the inha latio calc ulat ed by mul tiply ing the popu latio n densn path way was sons /m2) prov ided by EPA and the area cons iderity (6.7F,:-5 per-eren ce site anal ysis (160 km2) . The area depeed in the *ref-tion of l.1E 4 pers ons was used for thes e calc ulat nden t popu la-ions .

19

2.2.3 Quan t~ty Intak e of Radi onuc lides amt of nucl ide intak e per year = (

nu7l ide. cone) 1n soil cone of suspe ~dedJ *( aver age~

(:mate rial

brea thing in air rate Ci/y =(C i/kg )'* (3.SE -9 kg/m3 ) * (8400 m3/y ).

2.3 Exte rnal Expo sure EPA cons idere d exte rnal expo sure trom conta mina ted and air in thei r anal ysis. The. sofl conc entra tions soil by the Pathw ays Mode l (see Table 2.3) were used to calc ulate d exte rnal expo sure for. this comp ariso n anal ysis estim ate the

. deta iled in Subs ectio n 2~2 for calc ulati ng the . radi6 The appro ach conc entra tion in the air was used to estim ate the airnucl ide trati ons for the air subm ersio n expo sure calc ulati ons. conc en-assum ed expo sure time of 1/3 year was mult iplie d by An conc entra tion and the ~ir conc entra ~ion to estim ate the soil expo sure leve l. the 2.3. l Dose Fact ors and Heal th Effe cts Estim ates The dose conv ersio n facto rs for the air expo sure pathw and for the soil expo sure pathw ay were mult ay appr opria te heal th effe cts estim ates (Tab le iplie d by the med over all organ s for e~ch iadib nucl ide. 2. 4) and were sum.-

2.3~2 Popu latio n at Risk The popu iatio n dens ity of (6.7E -5 perso 2 ) prov ided by EPA was mult iplie d by the area of 160 km2ns/m the refer ence site anal ysis. Agai n. the area cons depe idere d in tion of l.1E4 per~o ns* was used for the calc ulati on nden t popu la-soil expo sure. of air and 2.3.3 Expo sure Leve l 2.3.3 .1 conta mina ted soil Expo sure Leve l= '(nu~ lide. cone) so-1 1*\ effe ctive \*

1n SOll * (dens ity/ * ( depth /

(exp~

time sure)

= (Ci)

. kg 20

2.3.3.2 ~ontami nated Air nu 7lide. cone) exp?sure )

Exposur e Level= ( in soil * ( time

=

(~:)

3.0 Descrip tion of the SANDIA Analysis The SANDIA health effects per curie release values were calculat ed using the modeling appro.ach es and input paramet ers presente d in the Pathways Model (Helton and Kaestne r, 1981) and the Dosimet ry and Health Effects Model (Runkle, et al., 1981).

The two compartm ent system of the Pathways Model, describe d in Chapter 2, was used in this analysis . The input paramet ers (distrib ution coeffici ents (Kd) and variable s to vary flo_w between subzone s) to*the Pathways Model were assumed to be the point values presente d in Table 2.1. The dose convers ion fac-tors (70 year intake/7 0 year dose commitm ent), concent ration ratios, environm ental paramet ers and health effects estimate s from the Risk Assessm ent Methodo logy (Cranwe ll, et al., 1982) were used to calculat e the SANDIA health effects per curie values. The average individu al risk estimate s were converte d.

to populati on risk by multiply ing the density values assumed by EPA (in persohs/ m2) and the area consider ed in the referenc e site analysis for the land-bas ed pathway s. The populati on estimate s for drinking water and fish intake -were based on a

linear relation shi~ of world populati on to the river flow rate of the world's rivers and the flow rate of the .river consider ed in the* referenc e site analysis . The equation s used in the calculat ions for the ingestio n, inhalati on and externa l expo-sures ar~ given in Table 3. l. The input paramet ers that were used in the calcul~t ions are gi~en in Tables 3.2-3~8 . The dose conversi on factors used in the Risk Assessm ent Methodo logy conside r a 70 year chronic intake and estimate a 70 year dose commitm ent. The 70 year dose comrni tment is essenti ally equi va.-

lent to the so year dose commitm ent (conside red by EPA), how-ever, the 70 year chronic intake. must be adjusted to account for the -143 generati on that can occur in 10,000 years.

Therefo re. the health effects estimate s were divided by a fac-tor of 70 for estimati ng the health effects per curie release values.

Ma*ny of the paramet ers used in the SANDIA Analysi s are

.differe nt from thoQe preesent ed in the EPA analysis and may be the source of some of the differen ces between the SANDIA and EPA health effects per curie values. For example , in *the'

21

Table 3.1 Basic Eguatiqn s for Calcula ting Radionu clide

Concent rations for Various Pathways WATER BASED (1) Drinking Water Intake (Ci/yr)= Water Consump tion (370 2./yr)

Water Treatme nt Factor (1.0)

Water Cone. (Ci/2.)

(2) Fish (kg/yr) = Fish Consump tion (6.9 kg/yr)

Water/ Fish Cone. Factor (CF)a *Water Cone. (Ci/1)

LAND WITHOUT IRRIGATION (3) Plant Cone. (Ci/kg) = Soil/Pla nt cFa *Soil cone.* (Ci/kg)

\

(4) Plant Intake (Ci/yr) = Plant C6nsump tion (190.0 kg/yr)

Plant Cone. (Ci/kg)

(5) Milk Intake (Ci/yr) = [Dairy Cow Consump tion of Plants (50 kg/day)

Plant ~one. (Ci/kg)

+ Dairy Cow Drinking Rat~ Per Day (60.0 2./day)

Water Cone. (Ci/1))

Milk/Di et CFa

Milk Consump tion Rate {110.0 l/yr)

(6) Meat Intake (Ci/yr) = [Beef Cattle Consump tion of Plants (50 kg/d~y)

Plant Cone. (Ci/kg)

+ Beef Cattle Drinking Rate Per Day (500 l/day)

Water Cone. (Ci/1)]

Beef /Diet cFa

M~at Consump tion Rate (95.0 kg/yr)

LAND WITH IRRIGATION (7) Deposit ion Rate (Ci/kg-y r)=Retai ned Fraction on Plant (~25)

-wate.r Cone. (Ci/l) *

[Rate Irrigati on (300 1/m2-yr )/Plant Density (5.2 kg/m2)]

(8) Rate Constan t for Weather ing (yr-1) ~ 1n2/.038 4 yr (14 Day Halt* Life)

(9) Plant Cone. *(Ci/kg) = [Soil/Pl ant CFa *Soil Cone.

(Ci/kg)]

+ [(Depos ition Rate (Ci/kg)/ Weather ing Rate (yr-1))

{l ~ [Exp -ln2/.03 84

Irrigati o~ Time (.17 yr)]}

Plant. Beef. Milk Consump tions with Irrigati on are Calculat ed Using Formulas 4-6 and the Plant Cone. (9).

asee Table 3.2 These.c oncentra tion factors are radionu clide depende nt.

22

Table 3.1 (Cont inued )

INHALATION (10) Air Cone. (Ci/m 3) = Soil Cone. (Ci/k g)

Conc entra tion of *suspe nded Mate rial in the Air

( 3. SE-9 kg/m3 ).

(11) Inhal ation (Ci/y r) = Air Cone. (Ci/m 3)

Breat hing Rate (8000 m3/yr )

EXTERNAL (12) Air Subm ersio n= (6.llE S hrs (Life time E~po sure)

)

Air Cone. (C1/m 3)

(13) Soil Expo sure= [2.04E S hrs (1/3 year Expo sure for 70 years )

Soil Cone. (Ci/k g)~ Soil Dens ity (2.8E 3 kg/m3 )

soil Depth (.02S m)]

(14) Sedim ent Ex~os tire = [l.OSE 3 hrs (15 hrs/y r- fo~ 70 years )

Sedim ent Cone. (Ci/k g)* Sedim ent Dens ity (2.6E 3kg/m 3)

Sedim ent Depth (.02S m)]

(15) Water Imme rsion ~ (1.06E 3 hrs (15 hrs/y r for 70 years

)

Water Cone. (Ci/1 )

1000 l/m3) 23

Table 3.2 Concentration Ratios for Human and Animal Food Sources (Used in Reference Site Analysis)

CROP/SOIL Radionuclide FISH/WATER (Ci/kg eer Ci/1!.2 PASTURE/SOIL

{dimensionles s) {day .

MILK/FEED kg/k~ . 2.)

BEEF/FEED (day* kg/kg* kg)

AM 2.SEOl 2.SE-04 5.0E-06 2.0E-04 cs 2.0E03 l.OE-02 l.2E-02 4.0E-03 I 1. SEOL 2.0E-02 6.0E-03 2.9E-03 NP l.OEOl 2.SE-03 5.0E-06 2.0E-04 Pu 3.SEOO 2.SE-04 2.0E-06 1. 4E-05 .

SR 3.0EOl l.7E-02 B.OE-04 6.0E-04 TC 1. SEOl 2.SE-01 2.SE-02 4.0E-01 SN 3.0E03 2.SE-03 2.SE-03 8.0E-02

Taken from USNRC (1977) 24

Table 3.3 Ingestion . Inhalation and External Exposure Rates for an Average Individua l (Used in Sandia Reference Site Analysis)

Ingestion Rates Water Consumpti on by Humans 3 . 7 E02 2./yr Plant Consumpti on by Humans 1.9 E02 kg/yr Milk Consumpti on by Humans 1.1 E02 1/yr Beef Consumpti on by Humans 9. 5 EOl k*g/yr Fish Consumpti on by Humans 6.9 EOO kg/yr Inhalation Rate Average Air Consumpti on by Humans 8.0 E03 m3 /yr External Exposure Rates Submersio n in Air 8.7 E03 hr/yr Groundshi ne from Soil 2.9 E03 hr/yr*

An effective depth of 0.025 m was assumed for soil and sediment.

Taken from USNRC (1977) and USDOE (1979) 25

Tab le 3.4 Cro p and Anim al Par ame ters .

(Use d in San dia Ref eren ce Si~ e An~ lysi s)

Ani mal Con sum ptio n Rat es Pla nt Con sum ptio n by Dai ry cow s 5.0E Ol kg/d ay Wat er Con sum ptio n by Dai ry Cows 6.0E Ol 1/da y Pla nt Con sum ptio n by Bee f cows 5.0E Ol kg/d ay Wat er Con sum ptio n by Beef - Cows 5.0E Ol ll./d ay Spr ink ler Irri gat ion of Cro ps and -Pa stur e

Irri gat ion Rat e 3.0E 02 l/m2 Ret enti on Fra ctio n

2. SE-- 01 Star idin g Cro p (Pla nt Den sity )

5.2E OO kg/m 2 Con stan t Rat e of Wea ther ing <~w> . l.8E Q1 yr-1 (14 day hal f life )

Irri g'~t ion* Time (,)

l.7E -01 yr e-AwT 4.65 E-0 2 I

!I

[,

26

Table 3.5 Dose Conversion Factors - Ingestion (rem/Ci)

(70-year intake/70-year dose commitment)

TOTAL BODY BONE LUNG GI TRACT SR90 1. 01E8 4.07E8 o.o l.53E7 TC99 3.51E3 8.76E3 l.11E3 2.89E4 SN126 1. 68E5 5.88E6 0.0 1. 70E6

!129 6.41E5 2.29E5 0.0 3.11E4 CS135 5. 55E5. 1. 35E6 1. 42ES 2.9SE4 CS137 4.96E6 \5.53E6 8. 5 lES

l.48E5 NP237 . 2.77E6 6.80E7 0. 0 :. S.56E6 Pu239 9.SlES 3.91E7 0.0 4.66E6 Pu240 9.SOES 3.91E7 0.0 4.7SE6 Pu242 9~16ES 3.63E7 0.0 4.57E6 AM241 2. 75E.6 4 .*OBE7 0.0. 5.19E6 AM243 2.68E6 4.07E7 o.o 6.09E6 Taken from Runkle. et al .* 1981.

27

Table 3.6 Dose C.onver sion Factor s - Inhala tion (rem/C i)

(70-yea r *intake /70-ye ar dose commit ment)

I TOTAL BODY BONE LUNG .. GI TRACT I SR90 l.35E8 2~17E9 8.67E7 6. 31E6 TC99 3.51E3 8.76E3 7.32E6 S.28ES SN126 9.39ES 2~35E7 8.47E7 l.11E6 il29 4.80ES 1.73~5 0.0 l.*SSE4 CS135 4.17ES l.01E6 S.91E6 1. 48E4 CS137 3.72E6 4~15E6 3.SSE7 7.3SE4 NP237 6.93E9 1. 66Ell 3.78E9 3.44E6 Pu239 7.93E9 3.26El l 1. 22El0 2.89E6 Pu240 7.91E9 3.26El l 1. 22El0 2.9SE6 Pu242 7.63E9 3.02El l l.18El0 2.83E6 AM241 6.86E9

1. 03Ell 4.39E9 3.22E6 AM243 6.70E9 l.03El l 4.16E9 3.78E6 Taken from Runkle . et al .* 1981.

28

Table 3.7 Dose Conversion Factors - External TOTAL BODY SOIL AIR (rem/hr/Ci/m 2l . Crem/hr/Ci/m 31 SR90 0.0 2.40E-l TC99 0.0 S.BOE-2 SN126 9.00EO l.32E4 1

Il29 4

SOE-1 l.80El CS135 o.b 2.BOE-2 CS137 4.20EO 4.70E2 NP237 l.40EO 1. 45E2 Pu239 7.90E-4 S.60E-2*

Pu240 1. 30E~3 6.SOE-2 Pu242 l.10E~3 5.lOE-2 AM241 1. BOE-1 l.BOE-1

AM243 1. 30EO 1. 40E2 Taken f~om Runkle. et al .* 1981.

29,

Table 3.8 Cancer Risk Estimates Used in the SANDIA Analysis Organ Dose Individual Risk Commitment Associated Type of Cance*r per rem* With This Cancer Type Leukemia 2.9E-05 Bone Lung 2. SE-0.5 Lung GI Tract 1. 9E-:-05 GI Tract B,reast 2.9E-05 Total Body Bone 9. 8.E-06 Bone All Other 3.6E-05 Total Body

Based

. on a lifetime J?lateau period for the solid tumor cancers .

. Taken from Runkle et al*., 1981.

30

inge stion calc ulati ons for land- based . food sour ces.

cont ribb tions from crop irrig atio n wete taken the. .

the SANDIA Anal ysis. Also . the intak e of co.nt into acco unt in wate r by the anim als that prov ide milk and beefamin at.ed drink ing was cons idere d. In cont rast. the EPA cons idere d only conta mina ted forag e by the milk and b~ef prod ucin~ the intak e of anim als.

4.0 Desc ripti on of SAMPLED SANDIA Anal ysis This set of calcu latio ns was perfo rmed .to the unce rtain ty that resu lts from vari abil ity incoi;is the ider some of para mete rs. Howe ver. only a few of the param eters inpu t and the unce rtain ti~s in many othe r aspe dts of the were varie d_

mode effo rt were not addr essed . In this anal ysis. the Pathw ling Mode l utili zed a set of samp led inpu t param eters sel~ ays the Litir i Hype rcube samp ling t~chn ique (Iman . et al cted by The distr ibut ion coef ficie titi (Kd) and varia bles to .* 1980 ).

flow rates betw een vario us subzo nes were samp led and adju st the desc ripti on and assig ned distr ibut ion of each inpu t the rang e.

are defin ed in Tabl e 4 .1 ~ The res.u l ts of the anal ysisparam eter

. sent a 3a vari ation in the inpu t data for those varia re pre-with a log-n orma l or norm al distr ibut ion assig ned to bles range s~ Thos e varia bl~s with a unifo rm or log-u nifor thei r tribu tion assig ned w~re samp led'o ver the entir e rang m dis-ables 1 to 4. thai adjus ~ the flow rates . are furth e. Vari -

in Table

4.2. Fifte en runs of the comp uter code were er desc ribed each with a diffe rent samp led set of inpu t vari able made .

s.

outp ut of each comp uter run (in the form of radio nucl The cent ratio n in the soil. and surfa ce wate r) was proc essed ide con~

Dos imetr y and Heal th Effe ct* Comp uter Code . ~nd h~al by the (canc er death s) per curie relea *se were calc ulate d. th ~tfe cts trati on ratio s. dose conv ersio n facto rs and risk estim The conc en-in this anal ysis are desc ribed in Chap ter 3. ates used The popu latio n for the wate r based pathw ays was based the linea r relat ions hip betw een river flow rate on and desc ribed abov e. *To estim ate the popu latio n at risk popu latio n calc ulati on. the* flow rate of. the river was varie d for this pled varia ble (R 1 )'.and the popu latio n was adju by the sam-sted fpr each .

of the fifte en comp uter runs. The popu latio n for the based and- exte rnal pathw ays was based on the dens ity land EPA and the area of the refer ence site *of 160 kma~. defin ed by popu lat~o ns~ whic h are area depe nden t,.we re kept cons Thes e the fifte en comp uter runs for land* bas.e a and exte rnal tant for p*ath ways .

As discu ssed in Chap ter 3. the heal th effe cts per curie relea ~e were divid ed by 70 to acco unt for the tions that can occu r in a 10,00 0 year perio d. - 143 gene ra-Two type s of calcu latio ns were perfo rmed depe nding whet her or not adso rptio n was allow ed to influ ence on phase {par ticul ates ) of the surfa ce wate r. For the the solid firs t set

. 31

.Table 4.1 Latin *Hypercube Sample TITLE-LHS PATH EPA

-RANDOM SEED= Sll46S26750425l7 NUMBER OF VARIABLES= 12 SAMPLE SIZE= 15 DISTRIBUTION AND RANGE ASSUMED FOR EACH VARIABLE Variable Distribution Assumed Range l Uniform .250 to 2.00 Scale Factor Rivr Disch_rg 2 Log Uniform l.OOOE-02 to 1.00 Scale Factor Water Xchng 3 Log uniform l. OOOE-04 to l.OOOE-02 .Scale .Factor Solid Xchng 4 Uniform 3.00 to 15.0 Regional Erosion Rate 5 .Log Normal l. OOOE-02 to 2.500E+0S KD for CM(AM) 6 Log Normal l.OOOE-02 to l.OOOE+04 KD for Pu 7 Log Normal l.OOOE-02 to 50.0 KD for NP 8 Log Normal L OOOE-02 to l.OOOE+03 KD for TC 9 Log Normal l.OOOE-02 to 3.000E+03

KD for SR 10 Log Normal l.OOOE-02 to l.OOOE+04 KD for cs 11 Log Normal l.OOOE-02 to l.OOOE+03 KD for I 12 Log Normal l.OOOE-02 to l.OOOE+03 KD for SN 32

Table 4.2 Variables Which Affect the Physical Description

, of the Surf ace Environment scale factor used to introduce variation in hydrologic properties. New values for water flow from the soil compartment to the ground-water compartment are obtained by multiplication with this factor. As the reference site was defined with an annual rainfall of l m. use of R1 amounts. in a crude way. to varying the rainfall from .25 m to 2 m. This is only approximate. as the indicated rates do not. move in a strictly linear manner with rainfall: however. it is felt that thi~ provides a way of varying between wet and dry conditions. (Units:

Unitless: Range: .25. 2.: .Sampling Dist.: Uniform.)

scale factor used to introduce variation in water move-ment between the s6il compartment and the surface water compartment. New values for such movements are obtained by multiplication of the pore volume of the soil com-partment by R2 . This variable is introduced to allow for variation in water movements which might result from runoff. irrigation or overbank flooding. (Units:

yr-1: Range: 10-2. 100: Sampling Dist.: Log Uniform.)

scale factor used to introduce variation in solid move-ment between the.soil compartment and the surface water compartment. New values for such movements are obtained by multiplication of the mass of solids contained in a soil compartment by*R 3 . This variable is introduced to allow for variation in solid movements which might result .from runoff. irrigation or overbank floodirig.

(Units: yr-1; Range: 10-4. 10-2: sampling ,

Dist.: Log Uniform.)

regional erosion rate. (Units: cm/1000 yr: Range: 3**

15.: Sampling Dist.: Uniform.)

33

of calculations . the radionuclides were input into the surface water with no adsorption onto the solid phase (particulates ) of the water (i.e .* Kd = O for all radionuclide s in the water).

However.*the Kd influence in the.soil compartment was consid-*

ered. This technique is similar to the procedures used by EPA in their analysis and in the EPA/SANDIA and SANDIA calculations .

When flooding of a river occurs. the particulates sus-pended in the*surface water may carry the adsorbed radionu-clides onto the surrounding land mass. If adsorptio~ of radio~

nuclides onto solid phase of the surface water is ignored.

there is a .much. smaller quantity. of a radionuclide carried to the soil compartme~t by the surface water. In the second set of c*a1culations . the radionuclides were allowed to adsorb onto the solid phase of the surface water as well as the liquid phase. The exchange to.the soii compartment was influenced by the particulates suspended in the water. and the distribution cioefficients- (Kd) determined the partition of~ radionuclide between the solid and liquid phase-s. The results of this anal-ysis ItJ.aY simulate exchange that could occur with flooding and erosion or with irrigation and erosion.

s.o Results and Discussion The health effects per cutie release for the indiiidual pathways are given in Table 5.1. The EPA values were taken from* the Health Effects per Curie Release Model and Subpathway Table provided to the author by the EPA. A slightly revised version of this table was published in-Smith~ et al .* 1982.

These values represent the health effects (deaths) per curie release. The EPA/SANDIA values were calculated using the pro-cedures outlined in Chapter 2. This procedure utilized the Pathways Model and point Kd values provided by EPA to calc_ulate the radionuclide concentration s in the s*oil and surface water.

Other parameters .(e.g .* dose conversion factors. heal th effects estimates. etc~) from EPA were also used. 'l'he SANDIA values were calculated with Pathways Model and Dosimetry and Health Effects ~odel rising th* 70-ye~r intake/ 70-year dose commitment factors. environmenta l parameters and risk estimates used in the reference site analtsis. However. the same point* Kd v~lues from EPA (and used in the EPA/SANDIA calculations* ) were used in the analysis.

There is good agreement between t'he EPA and .the EPA/SANDIA results *for the drinking water and the fish pathways for most of the radionuclides .. Marked differences are noted for the crop. milk and meat subpathways. EPA assumed that o.s curies were released to the soil over the 10.000-year interval and further assumed that 50% of the contaminated land was used for crop production for ditect human consumption. 25% for milk*

34

Table 5.1 Individ ual Pathway s and Dosimet ry and Health Effects Compari son Table Express ed as Deaths Per Curie Drinkin g Inhala- Externa l Externa l Water_ Fish CCOI! Milk Meat tion Soil Air Ani241 EPA 1.29E-l 3.7E-3 5.SE-1 8.2E-4 2.7E-6 2.2E-5 1.4E-5 2.9E-13 EPA/San dia 1. 32E-l 5.45E-3 6.lBE-3 2.62E-'-5 l.24E-7 *3.03E-7 2.72E-5 4.34E-15 Sandia 3.23E-3 l.SlE-3 3.42E-5 l.84E-8 8.00E-8 2.27E-7 6.84E-7 1. 02E-14.

Am243 EPA 3.4E-l l.2E-2 2.lEO 3.2E-3 1. SE-5 5 .. 7E-5 7.3E-5 3.0E-12 EPA/San dia l.06E-l 4. 4E-.3 S.03E-3 2.17E-5 l.03E-7 4.74E-6 7 .O.lE-4 2.43E-13 Sandia 3.25E-3 l.52E-3 4.62E-5 2.lOE-8 9.28E-8 1.* 40E-6 3.0SE-5 4.97E-13 Csl35 EPA .. 2.6E-4 1. 7E-4 2.lE-3 9. 9E..:.4 2. 6E-4. 2.4E-10 () 0 EPA/San dia* 1.113E-4 1. 21E..:.4 . 8.24E-6 Sandia :)..62E-4 6.02E-3 5.79E-6

5. llE-6 1. 3E-6 3.0lE-12 o.o 0.0 4,33E-6 1. 66E-7 1.0lE-1 1 o.o 1. 49E-17 Csl37 EPA 2.lE-3 1. 3E-3

7; SE-3 2.11f.:.3*

EPA/San d,ia 5.SE-4 1. 9E-9 1. SE-4 8.4E-12 2.0E-3 1. 33E-3 9.25E-5 6.42E-5 1. 71E-5 Sandia 1. 71E-12 1. 6E-5 7.53E-15

9. 79E.-4 3.65E-2 l. lSE-5 l.40E-5 S.09E-7 . 4. 42E-12 1. 09E-6 *1. 82E:_f4 Il29 EPA 1. 6E-3 4.0E-5 6.4E-3 2.4E-3 . 1. BE-4 1. 5E-9 .l. lE-5 1. SE-13 EPA/San dia 1. 63E-3 4.04E-5 7.32E-s 8.02E-5 6.03E-6 l.64E-14 1. 48E-8 2.0SE-18 Sandia 8.95E-5 2.SOE-5 8.89E-7 5.95E-7 3.12E-8 1. 63E-15 1. 45E-9 8.70E-18 v.> Np23'.7 EPA l.3E-l 2.2E-3 4.6E-l 9.2E-5 3.9E-4 2.2E~S 1. OE-4 4. 7E-12 VI EPA/San dia 1. 3E-l 2.lSE-3 5.84E-3 3.23E-6 1. 38E-5 1. 87E-8 3.76E-8 2.03E-8 Sandia 5.0SE-3 9.48E-4 S.28E-5 2.86E-8 l.25E-7 2.47E-8 3.77E-7 5.SSE-15 Pu239 EPA 4.3E-3 2.SE-3 2.SE-2 S.4E-8 2.lE-9 3.lE-2* 1. 9E.-7 1.0E-15 EPA/San dia 4.31E-3 2 ,*SE-3 1. 97E-4 1.19E-9 Sandia 4.52E-11 2.37E-6 2.47E-6

l.09E-16

2. 90E-3

1. 89E-4 4.SOE-5 7.83E-9 6.07E-9 S.42E-6 2.43E-8 2.SSE-16 Pu240 EPA 4.3E-3 2.SE-3 2.4E-2 5.2E-8 2.0E-9 2.2E-5 3.SE-7 2.0E-15 EPA/San dia 3. 31E-3 1. 92E-3 l,SSE-4 9.67E-10 3.70E-11 1. 71E-6 3.48E-6 l.48E-16 Sandia 2.90E-3 l.89E-4 4.03E-5 7,42E-9 5.73E-9 3.89E-6 2.87E-8 2.lSE-16 PU242 EPA* 4.lE-3 2.4E-3 2.4E-2 4.4E-8 4.3E-8 2.lE-5 3.SE-7 l.SE-15 El;'A/San dia 4.lOE-3 2;38E-3 1. SSE-4 9.22E-10 8.92E-1 0 2.SBE-6 5.17E-6 2.lBE-16 Sandia 2.70E-3 1. 76E-4 4.41E-5 7.48E-9 5.81E-9 5.76E-6 3. 87E-8' 2.69E-16 Sr90 EPA 8.0E-3 6.0E-5 l.OE-1 7.BE-3 l.OE-4 2.6E-8 0 0 EPA/San dia 7.99E-3 6. 63E..:5 4.78E-4 1. 46E-4 Sandi~ 3.94E-2 2. 20E-2. 4. 6-SE-4 3.74E-5

1. 95E-6 1.42E-l l 0.0 o.o 3.07E-6 1. 92E-10 o.o 5.53E,-18 Tc99 EPA 2.4E-5 EPA/San dia Sandia 2.39E-5 2.02E-6 6.0E-7 5.95E-7 5.64E-7 l.9E-4

1. OSE-6

' 2. llE-8 6.3E-5

. l. lBE-6 5.SE-6 l.lOE-7 6.2E-10 6.96E-1 5 0

0.0

- 0 0.0 5.70E-8 9.93E-8 8.30E-1 5 o.o 2.SOE-20

Snl26 EPA l.4E-3 7.0E-3 6.7E-3 2.9E-4 2.lE-3 1. 7E-8 4.6E-4. 2. 6E-ll EPA/San dia . 1. 38E-3 6.83E-3 6.19E-'S 8.22E-6 *s.82E-5 2.62E-1 0 8.54E-4 3.91E-13 Sandia 4. 72E-4 2.64E-2

B.49E-6 1. 72E-6 6 .14E-6 l.82E-10 3.98E-5 8.74E-12

prod ucti on and 25\ for beef prod ucti on. The tion s calc ulat ed by the Path way s Model used soil con cen tra-tion . depe nden t upon the flow rate s betw een an asym ptot ic solu -

face wate r subz ones . and were base d on a diffthe soil and sur-than the EPA ana lysi s. The calc ulat ions perf eren t inpu t rate r ways Mod el resu lted in an inpu t of 2.3E orm ed by the Path -

-3 Ci the 10.0 00 year p~ri od. Ano ther con trib utor to the soil over betw een the EPA and EPA/ SANDIA valu es is to .the diff eren ce inpu ~ to the plan ts via spri nkle r irri gati the diff eren t rate of tion s pres ente d in this repo rt.* the inpu t on. For the calc ula-

.tion was 2.SE -7 Ci/y r. whi le EPA assu med a to pl~n ts by irri ga-Ci/y r. This diff eren ce of grea ter than two valu e of 5.0E -5 in the inpu t rate is refl ecte d in the resu orde rs of mag nitu de lts.

Gen eral ly. the SANDIA hea lth effe sma ller than the EPA valu es for mos t ofctstheper curi e valu es are*

diff eren ce app ears to be due to dift eren ces path s and this con cen trat ion fact ors. dose con vers ion fact in the inpu t rate s.

time s used in the calc ulat ions .

Aga in. theors and expo sure are affe cted by diff eren ces in the inpu t .rat land base d path way s es.

When the hea lth effe cts per curi e valu es from SANDIA are summed over subp athw ays 1-5 EPA and wat er. fish . crop . milk and mea t) and 6-B (inc lude s drin king exte rnal soil and exte rnal air) the SANDIA (inc lude s inha lati on.

all case s (Tab le 5. 2). Some valu es -dif fer valu es are lowe r in by fact ors of

grea ter than 102; how ever . path way s 1-5 do var iati on as path way s 6-8. The risk of adv not show as much from paih way s 6-8 is lowe r than the risk from erse hea lth effe cts ther efor e. the diff eren ce note d in path way path way s 1-5:

ican t. We have not atte mpt ed to acco unt* for s 6-8 is less sign if-ence s; but the in~u t rate s *. dose fact ors, all the diff er-*

tati os used irt the two anal yses appe ar to and con cen trat ion diff eren ces. acco unt for the majo r The resu lts. of the SANDIA SAMPLED in Cha pter 4) are pres ente d grap hica lly calcin ulat ions (des crib ed Figu The Kd rang es and the R to R vari able s were res 5.1 to 5.4.

the Lati n Hyp ercu be Sam1plin g 4tech niqu e for s~m pled usin g pop ulat ions for the vari ous subp athw ays. defi this ana lysi s. The 2.1~ 2; 2.2. 2: and 2.3. 2. were used in this ned in Sec tion s lati on for the drin king *wat er and fish inta ana lysi s. The popu -

the sam pled vari able , Rl, to accr iunt for chan kes were adju sted by flow . ~he pop ulat ion for land base d path way ges .in the iive r for all 15 calc ulat ions . s was held con stan t In Figu res 5.1 and 5.2 the resu lts are give when . ther e was no adso rpti on of the radi onu n ior the case phas e of the surf ace wat er. The subp athw ays clid .e onto the soli d 5.1) and 6 to 8 (Fig ure 5.2} were summed and 1 to 5 (Fig ure and minimum valu es of the fift een com pute r the mean , maximum runs are pres ent. ea 36

Table 5.2 Pathway and Dosimetry and Health Effects Comparison Table Health Effects Per Curie Radionuclide EPA Pathways.1-5 EPA Pathways 6-8 Am241 EPA 7.0E-1 2.0E-2 Sandia

4.8E-3 9.lE-7 Am243

EPA 2.SEOO 2.0E-1 Sandia 4.8E-3 3.2E-5 Csl35 EPA* 3.8E-3 l. lE-7 Sandia 6. 2E-_3 l.OE-11 Csl37 EPA L4E-2 6.0E-3 Sandia 3.BE-2 l. lE-6

1129 EPA l. lE-2 9.2E-5 Sandia l.2E-4 l. SE-9 Np237 'EPA S.9E-l 2.SE-3 Sandia 6.lE-3 4.0E-7 Pu239 EPA 3.2E-2 3.7E-2 Sandia 3.lE-3 5.4E-6 Pu240 EPA .3. lE-2 3.SE-2 Sandia 3.lE-3 3.9E-6 Pu242 EPA 3.lE-2 3.7E-2 Sandia 2.9E-3 S.8E-6 Sr90 EPA l . 2E-l 7.9E-7 Sandia 6.2E-2 l.9E-10 Tc99 EPA .2. 9E-4 4.9E-10 Sandia 2.BE:-6 8.3E-15 Snl26 EPA* l. 7E-2 l.OE-1

Sandia 2.7E-2

. 4. OE-:-5 37

101 . VARIED K PATitS 1-5 0

10° C 0

0 0 0 0 0

0 0 0

0 A

9 M

a.

HIGH LOW MEAN EPA I

Zl>J>u 2<<>i>u i42J>u ec>sr -re 12'1sn 2,1Am 2tsAml:J&cs mes 1291 ~p-(1) VARIED X, RANGES {L.\TIN HYPERCUBE SAMPLE)

. (2) INPUT OF RADJONUCUDE TO LIQUID PHASE OF SURFACE WATER.

Figure 5. l.

Deaths per curie calculat ed with sampled Kd ranges and no adsorpti on* onto solid phase of the surface water for Pathways 1-5.

38

VARIED K PATHS 8-8 0

D 0 0 -0 D

0 0

0 Ii 0

0 9 j i A . HIGH V LOW M MEAN o EPA 2:>>pu 2'°Pu 2~u SOSr ~c 128sn 241Arn 2'3Am1~ mes 129 1 2S7Np (1) VARJED JC., RANGES (LATIN HYPERCUBE SAMPLE)

- (2) . INPUT OF RADJONUCUDE TO LIQUJD PHASK OF-SURFACE YATER.

Figure 5. 2.

Deaths per curie calculated with sampled Kd ranges and no adsorption onto solid phase of the s-urface water for Pathways 6-8.

39

along with the point values from EPA. In general, the EPA values for pathways* 1-5 are higher than the results calculated.

with the sampled values. The exceptions are 126sn, 135cs and 137cs. The sum of pathways 1-5 is dominated by the water based pathways and, since the populations are adjusted by the sampled variable Rl, the results are clustered. If a constant population were assumed for the calculation and the flow rate were varied, the results would vary in an approximately linear fashion. That is, a one order of magnitude variation in the flow rate would result in a one ~rder variaiion in the response. In pathways 8, there is more variability than in Paths 1-5; however the EPA values are always higher than the deaths per curie values calculated by the sampled values~

In Figures 5.3 and 5.4 the results are presented for the case when adsorption of the. radionuclide .. onto the* solid phase was assumed. The partitioning was determined by the distribu.- i

.I tion coefficients (td).

This approach significantly atfects I the soil concentration and the resu,,lting risk to the human population .. For the analysis that considers adsorption, th~

EPA values for both the 1-5 and 6-8 pathways are generally within the range or*only slightly higher than the results using the sampled ranges, for most radionuclides ..

Of note are the EPA values for 241Am, 243Am and 237Np for pathways l_.5 (Figure 5.3). The results of this analysis for 241Am*and 243Am*indicate that the release limits for these radionuclides may be overly conservative and may warrant a reexamination .by*the EPA. Also, the EPA release limit for 135cs would appear not.to be restrictive enough from the results*of this analysis and again may warrant some recon-sideration.

Although these results certainly do not establish that the EPA release limits proposed in the .Standard are overly conser-vative, generally they do suggest that the allowed release lim-its might be higher if the h~alth effects per cu~ie calculated in this analysis were used. *

40

101 _________V,.:.:I\R=l=ED::::;....::c""-----~--'Pc....;N.=T=H=S__l__--=-6--------,

0 10° 0 0 0

I l 0

0

~

i f t

t 0 l

, 0 tJ

~

....I'll

.F:

~

A A .

HIGH V LOW M MEAN 0 EPA 2'JDJ>u 2'°Pu 2Rpu OOSr "Tc 1~n 2 1

' Am 243Am 1~s mes 129 1 237Np

( l) VARIED Kd RANGFS (LATIN HYPERCUBE SAMPLE)

(2) INPUT OJi' RADJONUCIJDE ro LIQUID AND SOIJD PHASE OF SURFACE WATER Figure 5.3.

Deat~s_per curie calculated with sampled K~ ranges and ad~orption ~hto solid pha~~ of the surface wat~t for Pathways 1-5.

41

*VARIED K

'-="'- -----..:...:.:.=

PAfflS S-8

-=-=------;....._~

0 0

0 0 0

0 0

0 1t.

V M

HIGH*

I.OW MEAN l

o EPA 10- ~

I 10~-+ -~--~.........~ - - - ~ - - - - - . ~ - - r ~ - . - ~ - - ~ - - . . - ~ - . - ~ - - - ~ ~ - - - J DJlu 2<<>J>u 2 ttpu DOsr "Tc 1"sn " 1Am 243Aml36cs 137Cs I ~p (1) VARIED X. RANGES (J£11TIN HYPERCUBE SAPlPLE)

-(2) INPUT or *RADJONUCUDE TO UQUJD AND SOIJD PHASE or SURFACE WATER.

Figure 5.4.

Deaths per curie calcula ted with sampled Kd ranges and adsorp tion onto s9lid phase of the surfac e water for Pathwa ys 6-8.

42

References Bond. R .. G.* and C. P. Stra.ud (Eds.), CRC Press. Handbook of Environmental Controlr Volume l, 1973.

Cranwell. R. M., J.E. Campbell, J. c. H~lton, R. L. Iman, D. E. Longsine. N. R. Ortiz. G. E. Runkle. and M. J.

Shortencarier. Sandia National Laboratories. "Risk Methodology for .Geologic Disposal of Radioactive Waste: Final Beport, 11

SANDBl-2573. NUREG/CR-2452. 1982. .

Helton. J. c .. and P. c. Kaestner, Sandia National Labota~

tories. "Risk Methodology for Geologic Disposal of Radioactivi Waste: User*s Manual Pathways Model," SAND78-1711. NUREG/

CR-1636, 198.1.

Iman. R. L .* J.M. Dave~port. and D. K. Leigler. Sandia National Laboratories, "Latin Hypercube Sampli~g Program User*s Guide." SAND79-1473. January 1980.

Runkle. G. E., R. M. Cranwell. and J. D. Johnson. Sandia National Laboratories, 11 Risk Methodology for Geologic Disposal

. of Radioactive Waste: Dosimetry and Health Effects," SANDB0-1372. NUREG/CR-2166, 1981.

Smith. J.M., T. W~ Fowler. and A. S. Goldin, U.S. Environ~

mental Ptotection Agency, Montgomery. Alabama, "Draft -- Envi-ronmental Pathway Models for Estimating Population Health

Eff~cts From Disposal of High-Level Radioactive Waste in Geologic Repositories," EPA 520/5-80-002, July 19~1.

S~ith. J.M .* T. W. Fowler and A~ S. Goldin. U.S. Environmental Protection Agency. Montgomery. Alabama. "Environmental Pathways Model for Estimating ~opulation Health Effects from Disposal of High-Level Radioactive Waste in Geologic Repositories, 11 EPA 520/5-80-002, December 1982).

U.S. DOE (U.S. *Department of Energy), Office of Nuclear Waste Management. Washington, DC. "Environmental Aspects of Commer-cial Radioactive Waste Management. 11 DOE/ET-0029, UC-70. l:,979.

U. s. NRC CU. S. Nuclear Regulatory Commission), Office of *stand-ards Development. 11 Calculations of'Annual.Doses to Man From Routine Releases of Reactor Effluents for the Purpose of Evalu-ating Compliance Mith 10 CFR, Part* so. Appendix I, 11 Regulatory Guide 1.109. 1977. *

43

NRC FORM 335 _1. REP_QR_T !"_U~M,B!: R ~ssigned bv DDCJ 111-811 U.S. NUCLEAR REGULATORY COMMISSION Bl~LIOGRAPHIC DATA SHEET NUREG/CR-3235~ Vols. 5 and 6

. SAND82-1557

4. TITLE AND SUBTITLE (Add Volume No., if apfr~riare)

2. (Leave blank)

Technical Assistance for Regu a ory Development: Review and Evaluation of the Draft EPA*Standard 40CFR191 for Disposal 3. RECIPIENT'S ACCESSION NO.

of High..:.Level Waste

7. AUTHOR (Sl 5. DATE REPORT COMPLETED Fuel Cycle Risk Analysis Division MONTH I-YEAR April . 1983

9. PERFORMING ORGANIZATION NAME AND MAILING ADDRESS (Include Zip Code) DATE REPORT ISSUED Sandia National Laboratorjes MONTH I YEAR Fuel Cycle Risk Analysis April 1983 Division 9413 6. (Leave blank)

.Albuquerque, NM 87185

8. (Leave blank)

12. SPONSORING ORGANIZATION NAME AND*MAI LING ADDRESS (Include Zip Code)

10. PROJECT/TASK/WORK UNIT NO.

Division of Waste Management Office of Nuclear Material Safety and Safeguards 11. FIN NO.

U.S. Nuclear Regulatory Commission A1165 Washington, DC 20555 Task 3 *

13. TYPE OF REPORT Fonna l Report I PERIOD COVERED (Inclusive.dates)

July 1981 *- April 1983

15. SUPPLEMENTARY NOTES 14. (Leave blank)

16. ABSTRACT (200 words or less)

!Simple models are presented for the estimation of individual and population health effects.

for long-term radionuclide* releases to the surface environment. In volume 5, models based bn the use of asymptoti'c solutions to mixed cell models in conjunction with appropriate usage rates,, dose factors, risk factors, and population estimates are demons,trated. These lsimple models may be us*eful in evaluating topics such as the potential importance of indi-lvidual radionucli'des, different release patterns or exposure pathways, a'nd the relationshi1 between indivi'dual and population expos*ures*. tllustrative model calculations* are compared wtth th.e calculated population exposures on whtcti the. Draft (#19) EPA Standard 40CFR191 is based. ln Volume 6, s imp 1e models are employed to provide i ns*i ghts into the degree of con-servatism in the health effects* per curte value pres-ented by* the.* draft s~tandard. _No attemp is made to encompass all .uncertai'nty i'n the input parameters* us*e tn th.e calculations, and*

some o:f the mode 1 i ng assumptions use~ i'n th.i's* ana lys*i s are different from thos*e of the EPA. Three sets* of calculaUons of health effects* (c~ncer deaths*} per curte releas:e are*

pres*ented and discussed i'n terms* of thei'r potenttal *implications* upon the curte rel ease 1 imits of the EPA draft standard. *

17. KEY WORDS AND DOCUMENT ANALYSI_S 1 7a. DESCRIPTORS

17b. IDENTIFIERS/OPEN-ENDED TERMS

18. AVAILABll,..ITY STATE.MENT uJ*ncs1cURll:fCL'(f5S a.s.s.1. 1.e.

(Th,s reporrJ 21. NO. OF PAGES

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NUREG/CR-3235, Technical Assistance for Regulatory Development: Review and Evaluation of the EPA Standard 40CFR191 for Disposal of High-Level Waste, Volume 1

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6.3 Scenarios

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