ML20127K963

Forwards Proposed Technical Position on Concentration Averaging & Encapsulation.Further Rev to Position May Be Warranted

ML20127K963
Person / Time
Issue date:	06/26/1992
From:	Bangart R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	AFFILIATION NOT ASSIGNED
Shared Package
ML20127K956	List: IA-92-345, Forwards Proposed Technical Position on Concentration Averaging & Encapsulation.Further Rev to Position May Be Warranted ML20127K954 ML20127K963
References
FOIA-92-345 NUDOCS 9301260292
Download: ML20127K963 (12)

Text

. _ _ _

1 JUN 2 C 1992-ATTENTION: Commission Licensees

SUBJECT:

Proposed Concentration Averaging and Encapsulation Technical Position, Revision in Part

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The regulation, " Licensing Requirements for Lanc Disposal of Radioactive Waste,"

10 CFR Part 61, establishes a waste classification system basea on the concen-tration of specific radionuclides contained in the waste. The regulation also states, at il01.55(a)(8), that, "The concentration of a racionuclide [in waste) may be averaged over the volume of the waste, or weight of the waste if the units '

[on the values tabulated in the concentration tables] are expressed as nanocuties per gram" [ text acced for clarity].

A technical position on Radioactive Waste Classification was initially developed in 1983. This initial position included a section, " Concentration Volumes and Masses," which provided guidance to waste generators on the interpretation cf

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il61.55(a)(8) as it" applies tt, a variety of different types and forms of low-

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level M ster Beca'usel of"t'h Fdesirability of attempting to achieve consistent waste classification.

practices. e ,7 e among;the,Comission' ...v and _ Agreement ' State regula- .

tory authorities',fand;bec'au,seioff the {im, pact sofrwaste; classification positions

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on other programsL(e.gp,q00E!s m apw .y +_ program c.

,.;to; accept; greater.than; Class;C waste), Ay m wm s ; - ,

this' propose,d i,position expands upo i; cfurther definespand feplaces the guidance g

proviced in Section C.3 of the original 1983 Technical Position.n The-recom- j Y

mendations a'n'cT'aidance~

g provided in this proposed technical position are 0" acceptable meth5cs'by which specific waste types may be classifiec acainst the ti.bulated concentration values defined in Tables 1 and 2 of $61.55. \ ,

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The 1983 technical position also addressed three additional topics:

(1) Materials accountability programs, including acceptable appicaches for f (a) determining radionuclide concentrations and-(b) demonstrating com- t pliance with waste classification requirements; i

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l (2) Determination and verification of radionuclide concentrations and correlations; and )

(3) Reporting of waste infonration on shiprent manifests.

On th.' last topic, the Comission has recently proposed arrendtrents to 10 CFR Parts 20 and 61 on low-level waste shipment manifest information and reporting (57 FR 145C0 dated April 21,1992). Following the outcome cf the rulemaking process, a further revision of the 1983 technical position is planned.

The proposed technical position on concentration averaging and encapsulation, which represents a revision, in part, to the 1983 technical position, is enclosed. Coments on this technical position paper should be received prior to August 26, 1992, and sent to Chief, Rules and Directives Review Cranch, U.S.

Nuclear Regulatory Comission, Washington, D.C. 20555. Questions may be referred to W. Labs, U.S. Nuclear Regulatory Comission, Mail Stop SE-2 OWFN, Washir: ton, DC 20555, telephone (301)504-2569. A final technical position will be issued following NRC staff review of the coments receive.c. lhe information collections contained in the technical position have,been approved under OMB number 315.0 .0014. ...- ,.

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Richard L. Bangart, Directo ,

Division of low-Level Waste Management and Decomissioning, NMSS

Enclosure:

As stated

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[ proposed) Technical Position on Concentration Averagina and Encapsulation l I

i A. INTRODUCTION -

1 l

] The suitability of radioactive waste for near-surface disposal necessitates j the proper classification of that waste. The regulation, Licensing Requirements i

h for Land Disposal of Radioactive Waste," 10 Cfk Part 61, establishes a waste-1 classification system based on the concentration of specific radionuclides

! contained in the waste. Theregulatfonalsostates,at$$61.55(a)(8),that, "The concentration of a radionuclide [in waste) may be averaged over the volume i

of the weste, or weight of the waste if the units [on the values tabulated in l tne concentration tab bs) are expressed as nanocuries per gram" [ text added for clarity).

1 i

j A technical position on Radioactive Waste Classification was initially developed 4

in 1983. This initial position included a section, " Concentration Volumes.and

} Masses," which provided guidance to waste generators on the interpretation of i

, $561.55(a)(8) a as it applies to a variety of different types and fr.ms of;10w-m i level m'

,,.q'Thi' waste. - g .-:s~

v w ms position expandsEupon, further defines,.and replaces the l guidaSce prev'i'dhEi[SEtlSn"bNf"thiIohgin'al 1983 ? ' Technical Position. The recommendations'ahdgiiidInNYroYike'd3tEO[ffiN$lEllos'ition_areacceptable

'me'thods.by whieh specifi[EasikMeEkN#bN5Yii'iE5lUgii$25t[ tabulated

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, concentration valust defined in' Tab 1 E I M h h M M N h N b N " # '.~

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1. "A* c U t- B. DISCUSSION

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\ Each shipment of radioactive waste-to a licensed operator of-a land disposal j

facility must be accompanied by a shipment manifest.--In the manifest, then j

shipper / consignor-licensee must classify and clearly-identify reaste as Class

} A,- Class' B. or Class C in accordance with $61.55. -Determination of the-classification of waste involvesitso considerations. First, consideration must .

'be given to the_ concentration of.long-lived radionuclides in the': waste with

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respect to the values in Table 1.of $61.55. . Second,_ consideration must be

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giventothe,;concentrationofshort'livedradinnuclidesinthewastewith;

- i respect to the values in Table 2 of 561.55.

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Vaste is determined to be generally unacceptable for near-surface disposal if it contains any of the radionuclides listed in Tables 1 and 2 of S61.55 in l concentrations exceeding the applicable limits established for the individual radionuclides.

C. _ REGULATORY POSITION Volumes and Masses for Determination of Concentration!

Paragraph 61.55(a)(8) states that, for the purposes of waste classification, the concentration of a radionuclide may be averaged over the volume of the waste, or the weight of the waste for those concentration units in Table 1 that are expressed as nanocuries per gram. This requirement needs interpretation due to different types and forms of low-level waste. Principal considerations include:

(1) whe-ther the distribution of radionuclides within the waste can be considered to be reasonably homogeneous; (2) whether the "as generated" waste has been processed and, if so, what is the mass / volume of the processed waste; (3) whether the waste includes mixtures of various waste types; (4) whether the waste includes I mixtures of the same waste type  : ..but

. . .at differ,ing, rad

r. . . s.. n.ioactivity

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...s.v levels; and (5)- -whether....... mthe volume,.of 4 nwi nnuthewanunu,.

waste container,:nnrm, u a -if u pw sed to represent the volume  %

+of vthecwaste,,,is,s,ignif,icantly

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.m volume of the waste itself,'and the differential vol tw ,

. u.v .u a u.. ume. consists largely of. void,i space.

With respect to the above considerations many waste streams may be considered to be homogeneous for purposes of waste classification. Such waste streams would include, for example, spent ion-exchange resins, filter media, solidified liquid, or contaminated soil. Contaminated trash waste streams, which are composed of a variety of miscellaneous materials, may be considered homogencous for purposes of waste classification when placed in containers. To the extent that contamin-ated trash and contaminated soil are reasonably packaged in a disposal container, 1

It should be noted that waste acceptance requirements for Agreement State l

N, disposal f acilities (e.g. , requirements for encapsulate;d wastes or activated metals) may differ from this guidance. Waste generator $ shoul_d consult

_. specific disposal site license conditions prior to classifying these wastes. )

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the volumetric-averaged concentration of radionuclides in these waste streams can be based on the fill-volume of the container. Alternatively, the volume of the container can be calculated from the weight of the container contents divided by the density of the contents. A representative density based on a representative distribution of materials as they occur in waste may be used.

For spent ion exchange resins and filter media, care needs to be taken to differentiate between the volume of the waste form and the volume of the waste container. Although free volume should be reduced to the extent practicable, these wastes may be contained within a< disposable domineralizer or liner with some waste-free volume. In such cases, the volume or weight used for waste classification should be the displaced volume or dewatered weight of the resins or filter media rather than the gross internal volume of the container or the weight of the resins prior to dewatering.

Mixing of similar homogeneous waste streams

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Mixing of similar homogeneous waste streams (e.g., spent ion-exchange resins or contaminated soils).is permissible. However, mixing with the sole intent to dilute radionuclide concentrations to lower a waste's classification is not permitted.

Under this guideline the classification of the mixture using the sum of fractions rule specified in 561.55 should be based on either (a) the highest nuclid,e concentrations in any of the individual waste streams contributing

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tog t!e mixture; or (b) the volumetric or weight averaged nuclide concentrations of the mixture, provided that the concentrations of the individual waste stream contribgors to the mixture are within a factor of 10 of the concentration of the resulting mixture. In either case, in accordance with Section III of '

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Appendix,F y to 10 CFR Part 20, the licensee classifying the waste must have in placeaquglitycontrolprogramtoensurecompliancewiththewaste classification provisions of S61.55. As part of this quality control program, if the cla fication of a mixture is based on the volumetric or weight-averaged nuclide concentration of the mixture, as allowed under (b) above, the licensee responsible for classification of the waste should prepare retain .

with manife documentation, and have available for inspection, a record ion

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classificatica of a wete stream contributing to the mixture. I i

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$ol,j_dified o d and absorbed liquids i 1

j Classification of liquids or ion-exchange resins solidified in a manner to  ;

j achieve homogeneity should be based on the volume or mass of the solidified j_ mass. Because absorbed liquid wastes do not appreciably bind nuclides, classi-l- fication of absorbed liquids should be based on the volume or mass of the l liquids prior to absorption.

I Mixing of activated or contaminated components j for large components such as contaminated pumps, heat exchangers, or neutron-I activated components, the waste classification volume or weight should be taken to be the total weight or displaced volume of the component (i.e., void volume

subtracted from the envelope volume). Mixtures of activated or contaminated components in a disposal cont.ainer are permissible. In this case, because of ~

! the non-homogeneity of the waste, the classification of,the combined waste- )

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! within the disposal. container, for-the:predominantly" gamma-emitting nuclides (e.g,, Co-60, Nb-94 Cs2137/B5{$5b5hNfd[b"eI$aNu^p'oUEheIhfgYe'sYav'e'ra"gE ' ^~

concentration

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. s.,a nn pieces  : 3of components ownudw a. ,

that may:;w.result from operational considerat.+ 1- ions, e.g.,r apackaging For_all'other nuclides, and+(transportation).

< :n n; " n,~.,e considered individually, the classification of the combined waste should be basedonthevolumetric-orweidtaveraged'concentrationofthecombined-S components,: provided that all the concentrations within the individual components in the container are within a-factor of 10 of_ the averaged concentration.

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For activated or contaminated component wastes containing both gamma- and non gamma emitting radionuclides, otherwise complying with the above guidance, the sum of the fractio $s- rule described in SS61.55(a)(7) would apkly. Under d51 this. guidance, the sum;of the fractions rule would involve-summing (1) the fraction of- the appropriate $61iSS. Table -1 or 2 concentration values as'sociated with the in e component,-piece, or section containing the highest concentrations of gamme m o emitting radionuclides and (2) the average fraction of= concentration values i 4

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associated with each of the non gamma-caitting radionuclides associated with all components, pieces, or sections in the disposal container. In either case, in accordance with Section III of Appendix F to 10 CFR Part 20, the licensee classifying the mixture of contaminated or activated components must have in place a quality control program to ensure compliance with the waste classification provisions of $61.55. As part of this. quality control program, if the classification of the mixture of contaminated or activated components is based on the volumetric- or weighted-averaged nuclide concentrations in

• he components as a whole, as allowed above, the licensee responsible for classification of the waste should prepare, retain with manifest documentation, and have available for inspection, a record documenting the licensee's waste classification analyses. The record or analyses should show that the averaging of concentrations over the components as a whole was not undertaken solely to lower the classification of any of the indiv,idual-components.

Example: Three equally sized (by volume) pieces of a control rod blade are contained in a liner. The pieces.respectively contain concentrations of Nb-94 which are 0.8, 0.7;;and 0.5 of tne.A ble 1 value for Nb-94.of 0.2 curies per

, cubic meter.dThipieces alsoscontain.Ni-59:in. concentrations of t44, 22 and 11 curies per cubic meter.mThese concentrations are 0.2, 0.1, and 0.05 of the Table 1 valuelfor.Ni-59 of 220 curies per cubic meter, respectively. The Ni-59 concentrationft..in.the three pieces are all within a factor of 10 of the average concentration of Ni-59 in the three pieces considered together (i.e., ,

26 curies per' cubic meter). The sum of the fractions for the pieces in the liner would be calculated by summing 0.8 (the' fraction for the highest  !

gamma-emitting piece) and 0.12 (the fraction for the non gamme-emitting activity averaged over all three pieces). The sum, 0.92, would qualify.the liner as containing Class C waste.

Mixing of cartridge filters The classification of disposal containers containing multiple cartridge filters should-follow the guidance for mixing ~of activated or contaminated components..

-Because of the non-homogeneity of the waste, the classification of combined m~ cartridge filters containing the predominately gamma-emitting nuclides (e.g.,

aCo-60,Nb-94.hCs-137)shouldbebaseduponthehighestaverageconcentrationin j i 5 1:

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l any of the individual filters contained in the disposal container. For all other nuclides, considered individually, the classification of the combined cartridge filters should be based on the vclumetric- or weight-averaged con- I centration within the combined filters, provided that all the concentrations j within the individual filters in the container are within a factor of 10 of I the averaged concentration.  !

For cartridge filter wastes containing both gamma- and non gamma-emitting {

radionuclides, otherwise complying with the above guidance, the sum of the fractions rule described in SS61.55(a)'(7) would apply. Under this guidance the sum of the fractions rule would involve summing (1) the fraction of the appropriate 661.55 Table 1 or 2 concentration valves associated with the filter containing the highest concentrations of gamma-emitting radionuclides, and (2) the average fraction of concentraticn values associated with each of the non gamma-emitting radionuclides associated with all the filters in the disposal container. See example under, " Mixing of activated or contaminated components." In either case, in accordance with Section III of Appendix F to 10 CFR Part 20, the licensee classifying the mixture of cartridge filters must have in place a quality control program to ensure compliance with the waste classification provisions of $61.55. As part of this quality control program, )

if the classification of the mixture of cartridges filters is based on the volumetric- or weighted-averaged nuclide concentrations in the combined filters as allowed above, the licensee responsible for classification of the waste should prepare;' retain with manifest documentation, and have available for inspection, a record documenting the_ licensee's waste classification analyses. The record or analyses should show that the averaging of concentra-tions over the the combined filters was not undertaken solely to lower the classification of any individual filter.

Waste in high-integrity containers In the case of cartridge filters stabilized by emplacement within high integrity containers, the volume or weight used to determine waste classification should be calculated over the displaced volume or weight of the cartridge filter itself rather than the gross volume or weight of the container. Similarly, the volume and mass considered for purposes of waste classification of dewatered ion-exchange resins and filter media placed into high integrity containers should be the t 6

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volume and mass of the contained t;aste. In both these casos, disposal in a high integrity container i:, not considered to alter the as-buried concentrations of radioactivity.

Encapsulation of solid material For routine wastes such as filter cartridges or sealed sources centered in an encapsulated mass, classification may be based on the overall volume of the final solidified mass, provided that: (1) the volume and attributes of the encapsulated waste comply with the constraints established in Appendix C; (2) the solidified mass meets the waste form structural stability criteria of S61.56 for Class B and Class C waste; and (3) the disposal unit containing the encapsulated mass is segregated from disposal units containing class A wastes wh.ich do not meet the structural stability renoirements in SS61,56(b). Under the above provisions, additional protection is provided through the shielding, lack of dispersibility, or identulability of the encapsulated mass; and, for Class C encapsulated waste, by the land disposal facility operational require-ments in S$61.52(a)(2). This additional protection has been considered in the classification position developed in Appendix C and has been balanced against the hypothetical radiological impact caused by potential interactions between assumed intruders and the encapsulated mass.

Mixing of dissimilar waste streams Classifications may also be needed in situations involving a mixture of miscellaneous waste materials - e.g., situations in which contaminated valves, piping,;or similar components are placed in containers mixed with other trash; or miscellaneous trash or components are mixed with other radioactive materials such as resins or filters. In such cases, because of potential differences in waste interactions with the disposal environment, waste classification involy-ing averaging the total activity over the total volume or mass of the waste in the contain^er will be accepted provided that the classification of the mixture is not lower' than the highest waste classification of any individual components  ;

of the mixture. This provision does not apply to small concentrated microcurie '

1 1 sources of waste such as check sources or gauges which may be mixed with contami- ;

nated trash waste streams. The activity of such check sources or gauges may be averagedove{thetrashvolume. I h } { 7 -

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l Alternative provisions Under 561.58, the Commission, upon request, may authorize other provisions for )

the classification and characteristics of waste on a specific basis if, after evaluation of the specific characteristics of the waste, disposal site and method of disposal, it finds reasonable assurance of compliance with the l performance objectives in Subpart C of 10 CFR Part 61. I l

Alternatives to the determination of radionuclide concentrations for waste classification purposes, other than those defined in this technical position, may be considered acceptable. If the approaches in this technical position are incorporated as disposal facility license conditions, alternatives would require the approval of or otherwise be authorized by the NRC or Agreement State regulatory agency .(e.g., the disposal facility may need to apply for a license I amendment from the NRC or Agreement State regulatory agency). The alternatives could be considered acceptable if (1) reasonable assurance is found that the alternative classification approach will result in compliance with the performance objectives in Subpart C of 10 CFR Part 61, and (2) the concentration of the radionuclide is determined to be based on the volume or weight of the j waste as defined in'SS61.55 (a)(8). }

Table 1 provides a summary of the primary aspects of the above guidance.

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)l Table 1 Volumes and Masses for Determination of Concentration-l 1

Waste Type Allowable Classification Volume or Mass 4 Contaminated trash or soil Reasonable fill volume of container / mass of waste (<10% void)*

Absorbed liquids ' Volume / mass of liquid prior to _ absorption

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Solidified liquids. Volume / mass of solidified mass Solidified ion-exchange-resins Volume / mass of solidified mass *

.Dewatered ion-exchange resins in Displaced volume /dewatered mass of high integrity containers ion-exchange' resins Filter cartridges in high integrity Displaced volume / mass of filters

• containers Activated components . Full density volume / mass of components

• Encapsulated filter cartridges Volume / mass of solidified mass when or sealed sources encapsulated in accordance with the ^

s guidance provided in' Appendix C

• If homogenity' maintained in solidified mass Mixtures of waste streams subject to additional guidance defined in text.

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A A A A A A APPENDIX C

' POSITION ON ENCAPSULATION OF SEALE0 SOURCES AND OTHER SOLID LOW-LEVEL RADI0 ACTIVE WASTES Encapsulation can mitigate dispersion of waste and can also provide additional shielding to limit external radiation fields, If provided to meet the stability 1

criteria of $61.56(b) and coupled with the technical requirements for land i

disposal facilities in subpart 0 of 10 CFR Part 61 (specifically, S61.52),

encapsulation will limit the impacts from both (1) the direct exposure, i

inhalation, and ingestion pathways associated with potential intruder-waste interactions and (2) the potential exposure pathways to individual members of the public involving groundwater and agricultural products.

i The amount of credit allowed for encapsulation, though, needs to be limited so that extreme measures cannot be taken solely for the purposes of. dilution. To be consistent with the NRC's policy on volume reduction and to limit extremely large " point sources" of radioactivity in the disposal site, limits on minimum and maximum encapsulated waste volumes and masses, nuclide activities and radiation levels are established.

These bounding conditions are as follows:

(1) The minimum solidified volume or mass for encapsulation should be that .

which can reasonably be expected to increase the difficulty of an inadver-tent intruder moving the waste by hand following the loss of institutional control over the disposal site. This minimum size or weight should pre-clude any significant movement without the assistance of mechanical equipment.

(2) The maximum solidified volume or mass for encapsulation (from which concentrations are determined) should be 0.2m3 or 500Kg (typical 55 gallon drum). Larger volumes and masses may be used for encapsulation but no credit beyond the volume or mass indicated should be considered when determining waste concentrations.

Note:. The bounding volumes and weights in (1) and (2) will ensure that the potential radiological impacts from encapsulated-discrete source dis-posals.are within the envelope of impacts which would be calculated if the radioactivity was homogeneously distributed throughout-the encapsulating media...

(3) The maximum amount of gamma-emitting radioactivity (e.g., Cs-137/Ba-137, Nb-94) or radioactive material that should be encapsulated is that which, if- creditfis taken for a 500 year decay period, would result in a dose rate of'1,ess than 0.2p5v/hr (0.02 mrem /hr) on the surface of the encapsu-lating media (refer to foonote 1, following page). The calculation to

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! determine compliance with this criterion may consider the minimum attenua- ,

j tion factor provided by the shielding properties of the encapsulating media )

i but, in no case, should this facter exceed an attenuation factor that would

! be provided by 15 inches of concrete encapsulating material (refer to

footnote 2). Furthermore, the maximum C5-137/Ba-137. gamma emitting activ-ity that should be encapsulated in a single disposal container is 1.1 TBq (30 curies) (refer to footnote 3).

3 i (4) The maximum amount of any radionuclide that should be encapsulated in a

single disposal container intended for disposal at a commercial LLW dis-

! posal facility is that which, whpn averaged over the waste and the encap--

! sulating media, does not exceed the maximum concentration limits for

! Class C waste at defined in Tables 1 and 2 of S61~.55 (refer to footnote 4,

followingpage).

} (5) In all cases when a discrete source of radioactive solid waste is i encapsulated written procedures should be established-to ensure that the radiation source (s) is-reasonably centered within the encapsulating media.

[ Footnotes

! 1 Presuming the inadvertent intruder has contact with the encapsulated waste

as generally defined in the intruder-agricultural scenario (reference NUREG-0945), this dose rate would result in an annual exposure of less than 1/10 of that which would be received if the radioactivity was homogenized over a soil volume equivalent-to the encapsulating media. This factor of 10 takes-

{ into consideration the possibility that the intruder may be. exposed to both I>

1 (1) other encapsulated waste which may be excavated from the disposal ,

! trenches without mixing with uncontaminated cover material and (2) other homogenized waste. '

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l 2 i The15inchesofconcreteshielding/Ba-137couldsatisfythe0.2pS encapsulated 30 Ci source of Cs-137 (0.02 mrem /hr) dose criteria (bounding case). Additional shielding ,

thicknesses from the encapsulating or disposal unit materials could be expected to be in existence after 500 years but because:of uncertainties

! :regardingshieldingorientationsandeffectlvenessfollowingthistime i period, no greater credit is considered appropriate. Furthermore

attenuationofdoseprovidedbythis-limitedamountofshieldingIs;the such

that, absent any shielding. intruder doses would still be expected to be

1 less than doses which would be received if the radioactivity was I

homogenized over a soil. volume equivalent to the encapsulating media.

) 3 The 30-curie limit on L any encapsulated, gamma-emitting radionuclide or i radioactive material results from the application of the: dose rate and shielding criteria.in bounding condition-3 for waste containir.g Cs-137,.

^ the most prevalent gamma-emitting isotope for which encapsulation may be-appropriate. The 30-curie limit has been selected to provide assurance

' that intruders will not-receive doses (e.g. , from larger activities of waste emitting radiation at lower energies) greater than 1/10 of that-which would be received-if the radioactivity was homo'genized over a mil volume equivalent to the encapsulating media. *j ,

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I ' Reasserting the applicability of Tables 1 and 2 of 561.55 emphasizes that, for alpha- or beta-emitting radionuclides, encapsulation under bounding conditions 1 through 3 does not classification tables in the regulations. provide As aan exemption result, to the the largest activity of transuranic, encapsulated in 0.2m3 other than Pu-241 and Cm-242, which can be is about 1.1GBq (30 mci), presuming the density of the tncapsulating mass is 1.3 gm/cm3 The density of the material used for encapsulating not exceed 2.5gm/cm3 alpha and beta emitting radionuclides should

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