ML19309H464
| ML19309H464 | |
| Person / Time | |
|---|---|
| Issue date: | 04/04/1980 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
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| REF-WM-26 NUDOCS 8005130316 | |
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Text
s 8005130 7/h O
REP 0hf 0F THE RADIOLOGICAL ASSESSMENT OF THE PROPOSED MT. TAYLOR PROJECT
1.0 INTRODUCTION
The New Mexico Environmental Improvement Division (NMEID) requested technical assistance from the NRC in the review of the Mt. Taylor Uranium Mill Project proposed by Gulf Mineral Resources Company (" Gulf"), a division of the Gulf 011 Corporation. The most recent version of that proposed project was submitted in the Groundwater Discharge Plan dated February 1980.1 In a March 3,1980, meeting between the NMEID and the NRC concerning technicai assistance on the proposed project it was agreed that the NRC would provide (1) a report on the radiological assessment and (2) a report on the tailings management system evaluation and coments and recommended license conditions resulting from the NRC review.
1.1 BACKGROUND
The Mt. Taylor Project is to be located near San Mateo New Mexico, which is approximately 16 miles northeast of Grants, New Mexico. The project has as its major components a deep underground mine, a processing mill with a capacity of approximately 1.5 million tons of ore per year, and tailings disposal facilities.
The mine is located 1/2 mile north of San Mateo and the proposed mill is to be located in lower San Lucas Canyon, approximately 3 miles north of the mine site.
Gulf proposes to dispose of tailings waste from the Mt. Taylor Uranium Mill in La Polvadera Canyon in an area a,pproximately 4 miles north-northwest of the mill site. A parallel series of dragline excavated trenches for burial of tailings solids would be located in the E1/2 of Section 15, T14N, R8W, a slimes settling pond (s), and an evaporation pond would comprise the La Polvadera Canyon tailings facilities. During the planned project life from 1982 through year 2003, approximately 12.6 million tons of tailings would be buried.
This tonnage represents one-half of the mine ore production minus five percent for dissolution during processing. The remaining 50 percent of the mill tailings would be used for mine backfill.
Although the proposed tailings management system will be described in more detail in the forthcoming evaluation report the following major system components are briefly described to aid in the understanding of anticipated system behavior:
. 1.
Tailing Trenches.
Tailings would be discharged in a slurry to dragline excavated 50-foot deep trenches. Waste water would be decanted from the trenches and routed through a below grade intermediate settling pond. The disposal trenches would be covered and reclaimed as soon as the trenches are filled and the tailings develop enough strength to support the load of the cover (ap3roximately 50-foot thickness).
Each trench would be covered wit 1 material being excavated from the next, adjacent, parallel trench.
2.
Settling Pond (s)
The intermediate settling pond (s) would intercept suspended slimes in the tailings waste water and the clear water would be transported to an evaporation pond for disposal.
It is proposed that the pond (s) would be covered after slimes consolidate and dry.
Because of the highly toxic nature of the slimes and because of the large anticipated volumes that will accumulate in the settling pond (s), a preliminary determination from the tailings management evaluation is that the slimes be allowed to dry and consolidate to a moist state and be transported to the tailings trenches for final disposal.
3.
Evaporation Pond The evaporation pond would have sufficient capacity to store and evaporate all liquid wastes.
In the tentative reclamation plan liquids would be allowed to evaporate at the end of project life and the residual salts would be disposed of in dragline trenches similar to those used for burial of tailings.
It should be noted that the radiological assessment provided in this report is. based on assumptions concerning the tailings management system.
Because the tailings management system evaluation has not been completed, an attempt has been made in this report to point out features of the system which were significant with respect to radiological impacts and steps which should be taken to ensure the impacts are minimized.
1.2 CONTENTS OF" REPORT This report presents the assessment by the NRC staff of the incremental radiological impacts resulting from the operation of the proposed project and the methodology used to perform the evaluation.
Components of the evaluation include the following estimations:
(1) annual releases of radioactive materials from the mill, tailings management system, and mine; (2) resulting concentrations at the restricted area boundaries for the above-noted sources; and (3) resulting dose commitments
- to nearby individuals and the population within 80 km (50 miles). The calculated results are compared to measured background radiation and applicable
- Individual and population dose commitments are defined in ref. 2.
! regulatory requirements. All potential pathways that are likely to contribute a significant fraction of the dose commitments have been included in the analysis. Note that the radiological impacts contributed by the mining operation are discussed separately in Sect. 9.0.
As a predictive analysis, the results of the radiological assessment are dependent ur, and sensitive to many input design parameters.
Changes in paramete values used in the estimation of radioactive releases (Table 1) result in different calculated dose comitments.
Because a preliminary determination of compliance with applicable regulations is made by this assessment, future significant modifications to the facility's design or operation, which would affect the assumptions made here concerning effluent releases, will require a revised analysis.
2.0 ESTIMATED RELEASES A sumary of the information and data assumptions used to calculai.a the annual releases of radioactive materials from the mill and the tailiscs management system is presented in Table 1.
The estimated annual releases are outlined in Table 2.
Further, more detailed descriptions of release estimates are provided in Appendices A and B.
The proposed schedule for operation of the tailings management system (Fig. 1) was used in the estimation of the parameters and releases for the tailings trenches and
.__. the evaporation ponds.
3.0 EXPOSURE PATHWAYS Potential environmental pathways by which people could be exposed to radioactive materials resulting from the project are presented schematically in Fig. 2.
The pathways of concern for the dirborne effluents include inhalation of radioactive materials in the air, external exposure to radioactive materials in the air or deposited on ground surfaces, and ingestion of contaminated food products (i.e., vegetables, meat, and milk).
There will be no planned or routine releases of radioactive waste materials directly into surface waters. Although the analysis of impacts to groundwater has not been completed, preliminary results indicate that, while there will be some seepage of radioactive liquids fror" the evaporation 1
ponds or tailings trenches, this seepage should not reach the groundwater system.
Therefore, in this analysis seepage is not considered to be a significant pathway of human exposure. A brief presentation of the i
projected impacts to ground and surface waters will be provided in the tailings management evaluation report.
[
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6 1
, Table 1.
Informa. ion and data used to estimate annual releases of radioac Ive materials from the Mt. Taylor Uranium Mill and Tailings Management System Parameter definition Parameter value(s)a I.
General data A.
Ore processing rate MT/ year 1,295,482 B.
Average ore grade, % U 038 0.32 C.
Bulk are equilibrium concentration of U-238 903.61 and each radioactive daughter, pCi/g D.
Operating time, days / year 340 E.
Mill lifetime, years 22 F.
Uranium recovery rate, %
95 II. Ore storage and handling A.
Truck-dumping are dust loss rate, Ib/ ton 0.1 B.
Fraction of input to storage, %
100 C.
Ore dust loss rate related to ore pad handling 0.05 activities,lb/ ton D.
Ore dust loss rate from dumping are to the 0.20 grizzly,lb/ ton E.
Annual average dyst loss rate by windblown 32.85 emissions, g/m -year F.
Reduction factor due to chemical spraying and 50 wetting of ore, 1 G.
Fraction of ore equilibrium radon content released 40 in handling and grizzly operations, %
H.'
Specific radon flux from ore storage, pCi/mZ-see Rn-222 1.0 pCi/g Ra-226 1.
Dust-to-ore activity concentration ratio, 2.5 dimensionless J.
Orestoragearea,ha(acres)d 5.0(12.34)~
III. Product operations (yellowcake drying & packaging)
A.
Fraction of yellowcake product released from 0.lb drying and packaging operations, %
8.
Annual yellowcake production, MT/ year 3916.80 C.
P,roduct purity, %
85 IV. Tailings impoundment system A.
General parameters 1.
Fraction of U to tailings, %
5 Fraction of Th to tailings, %
95 Fraction of Pb to tailings 5 99.8 Fraction of Ra.to tailings, 5 99.8 2
2.
Annual average dust loss rate, g/m -year 387.99 3.
Dust-to-tails activity ratio, dimensionless 2.5 4.
Dusting reduction factor for water cover, 80 moisture, and chemical agents, %
5.
Specific radon flux from exposed beach, 2
pCi Rn-222/m -sec 1.0 pCi Ra-226/g 6.
Total area of tailings, ha (acres)d 91 (225) 7.
Total area of settling pond, ha (acres)d 8.1 (20) 8.
Total area of evaporation pond, ha (acres)d 81 (200)
. Parameter definition Parameter value(s)a e
B.
Specific tailing cells parameters 1.
Trench I e-Trench area, ha (acres) 8.3 (20.45)
Operational lifetime, years 4.0 Drying time, years 1.0 2.
Trench 2 Trench area, ha (acres) 16.6 (40.9)
Operational lifetime, years 5.0 Drying time, years 1.0 3.
Trenches 3, 4, and 5 each Trench area, ha (acres) 16.6 (40.9)
Operational lifetime, years 3.0 Drying time, years 1.0 4.
Trench 6 Trench area, ha (acres) 16.6 (40.9)
Operational lifetime, years 4.0 Drying time, years 2.5 d
C.
Evaporation and settling ponds 1.
Settling cond Total area, ha (acres) 8.1 (20)
Operational lifetime, rears 22.0
-~
Drying time, years 2.5 2.
Evaporation pond Total area, ha (acres) 81 (200)
Operational lifetime, y,'ars 22.0 Drying time, years 2.5 3.
Concentration levels predicted for ponds, pC1/11ter U
720,25 83 Th Ra 4900 Pb 162 aParameter values presented here are those selected by the NRC staff for vie in its radiological impact assessment of the Gulf Mineral Resources Comparj, Mt. Taylor Mill facility project. They represent conservative sel61ons from ranges of potential values in instances where available data ha;< been insufff-cient and/or not specific.
b ased on information provided in NUREG/CR-1216, ANL/ES-84, " Radioisotopic B
Composition of Yellowcake," December 1979.
cFigur.e 1 presents a time profile of the tailings impoundment operation for each trench and pond.
dInformation on the size of the ore storage area and on the evaporation and settling p;,nds is taken from (the) " Groundwater Discharge Plan for the Mt. Taylor Uranium Mill," Gulf Mineral Resources Company, February 1980.
' Reported thorium concentration appears to be too low considering ore processing rate, solubility of thorium, and concentration of radium.
. Table 2.
Estimated annual releases of radioactive materials from the a
Mt. Taylor Uranium Hill and Tailings Management System Estimated annual releasesD (C1/ year)
U-238 Th-230 Ra-226 Pb-210 Rn-222 Ore storage and handling 1.14E-Old 1.14E-01 1.14E-01 1.14E-01 1.43E+03 activitiesc Gri:21y and apron feeder 1.46E-01 1.46F-01 1.46E-01 1.46E-01 2.34E+02 Yellowcake drying and 1.04E+00 5.45E-02 2.18E-03 2.18E-03 0.0 packaging Tailings trenches' Trench 1 5.35E-03 1.02E-01 1.07E-01 1.07E-01 3.48E+03 Trench 2 1.07E-02 2.04E-01 2.14E-01 2.14E-01 6.96E+03 Trench 3 1.07E-02 2.04 E-01 2.14 E-01 2.14E-01 6.96E+03, Trench 4 1.07E-02 2.04E-01 2.14E-01 2.14E-01 6.96E+03 Trench 5 1.07E-02 2.04E-01 2.14E-01 2.14E-01 6.96E+03 Trench 6 1.07E,-02 2.04E-01 2.14E-01 2.14E-01 6.96E+03 Scttling pond 6.82E-05 5.87E-04 4.00E-03 1.32E-04 1.32E+02 Evaporation pond 6.90E-04 5.94E-03 4.05E-02 1.34E-03 1.32E+03 aRefer to Table 1 for emission control reduction factors, b eleases of other isotopes in the U-238 decay chain have been included in this radio-R logical impact evaluation. These releases are, assumed to be identical to those calculated and presented here for parent isotopes; e.g., the release rates of Pb-210 and Po-210 are taken to be identical to that of Ra-226.
cRadioactive emissions contributed from truck unloading, ore handling, and other ore pad activities are included, as well as those from windblown emissions.
dThe notation 1.14E-01 denotes 1.14 x 10'I.
eRefer to Fig. I for time profile of operating schedule for tailings and evaporation pond impoundnent areas.
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9-4.0 RADIATION DOSE COMMITMENTS TO INDIVIDUALS The nearest known residence to the mill is the Lee Ranch, located approximately 4.6 km (2.9 miles) southwest of the mill. The nearest known residence to the tailings is the San Miguel Ranch, located approximately 8.34 km (5.2 miles) northeast of the mill.
The nearest town is San Mateo which is located approximately 5.7 km (3.6 miles) south of the mill.
A nearby residence in the prevailing wind direction from the mill is the Marcus Ranch, located 9.49 km {5.9 miles) west-southwest of the mill.
Table 3 presents a summary of the individual dose commitments calculated for the locations identified above. At these locations it was assumed that individuals ingest meat from cattle which graze 0.56 km (0.35 mile) west of the mill site.
It is assumed that milk pathway exists for and that locally grown vegetables are consumed at each location excluding the San Miguel Ranch.4 5.0 RADIATION DOSE COMMITMENTS TO POPULATIONS The annual 100-year environmental dose commitments received by the (regional) population within 80 km (50 miles) of the site are presented in Table 4.
The projected population distribution data (Table 5), based
_ on the year 2000, were used to do the estimation.4 Releases of radon gas yield radiological impacts which occur over a range of thousands of miles from a release source.
Impacts of radon releases from the facility that occur. within 80 km (50 miles) of the' site have been included in the tabulation of the regicnal population dosu connitments (Table 4). Transcontinental radon-222 impacts have also been evaluated.
Table 6 includes t'otal environmente.1 dose commitments received by both regional and extra-regional populations. A grand total of 100-year environmental dose commitments received by all populations is also presented.
6.0 EVALUATION OF RADIOLOGICAL IMPACTS ON THE PUBLIC Dose commitments to individuals at the locations noted in Sect. 4 were calculated for the purpose of evaluating compliance with the limits specified by the U.S. Environmental Protection Agency's (EPA) 40 CFR Part 190, "Rdiation Protection Standards for Normal Operations of the Uranium Fuel Cycle," which will be effective for uranium milling operations in December 198G. Under 40 CFR Part 190, total doses to any organ of an offsite individual are limited to 25 millirems / year, excluding contributions from radon-222 and its radioactive daughters.
Table 7 provides a comparison of the calculated dose commitments to individuals with the 40 CFR Part 190 limits.
Doses in this table are lower than total doses tTable 3) because contributions from radon-222 and its daugh'ers have been omitted.
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Table 3.
Annual dose cocnit:::ents to individuals from radioactive releases from the fit. Taylor Mill facility Dose Coneitment (millirem / year)
Bronchial Location Exposure oathway Total body Bone Luno epitheliuma Nearest residence to mill Inhalation 2.32E-Olb 6.38E+00 1.48E+01 1.14E+01 Lee Ranch External from ground 5.98E-01 5.98E-01 5.98E-01 5.98E-01 (4.6 km SW of mill)
External from cloud 1.68 E-01 1.68E-01 1.68E-01 1.68E-01 Ingestion Vegetable 2.26E-01 2.78E+00 2.26E-01 2.26E-01 i
Meate 1.33E+00 1.68E+01 1.33E+00 1.33E+00 Milk 2.27E-02 2.78E-02 2.27E-02 2.27E-02 Total 2.58E+00 E.68E+01 1.72E+01 1.37E+01 Nearest residence to tailings Inhalation 1.04E-01 2.78E+00 6.69E+00 2.21E+00 San Miguel Ranch External from ground 4.58E-01 4.58E-01 4.58E-01 4.58E-01 (8.34 km NE of mill)
Externalfromcloud 1.63E-01 1.63E-01 1.63E-01 1.63E-01 Ingestion MeatC 1.33E+00 1.68E+01 1.33E+00 1.33E+00 i
Total 2.06E+00 2.02E+01 8.64E+00 4.16E+00 Nearest town Inhalation 1.19E-01 3.05E+00 8.33E+00 1.29E+01 San Mateo External from ground 2.40E-01 2.40E-01 2.40E-01 2.40E-01
~~'
~(5.7 km S of mill)
External from cloud 1.95E-01 1.95E-01 1.95E-01 1.95E-01
~
Ingestion Yeoetable 9.0SE-02 1.15E+00 9.08E-02 9.08E-02 Met.tc 1.33E+00 1.68E+01 1.33E+00 1.33E+00 Milk 9.15E-03 1.03E-01 9.15E-03 9.15E-03 Total 1.98E+00 2.16E+01 1.02E+01 1.48E+01 Nearby residence in prevail-Inhalation 4.50E-02 1.24E+90 2.87E+00 2.83E+00 ing wind direction from External from ground 1.29E-01 1.29E-01 1.29E-01 1.29E-01 the mill External from cloud 4.27E-02 4.27E-02 4.27E-02 4.27E-02 Marcus Ranch Ingestion (9.49 km WSW of mill)
Vegetable 4.84E-02 5.96E-01 4.84E-O'.
4.84E-02 MeatC 1.33E+00 1.68E+01 1.33E+00 1.33E+00 Milk 4.85E-03 5.28E 4.86E-03 4.86E-03 Total 1.60E+00,
1.89E+01 4.42E+00 4.38E+00 aDoses to the bronchial epithelium result from the innalation of the short-lived radioactive daughters of Rn-222.
bThe notation 2.32E-01 denotes 2.32 x 10-1 I
Cingestion doses result from the consumption cf the meat of cattle grazed 0.56 km W of the mill, dThere is no milk or vegetable pathway at this location.
1
- 11 _
Table 4 Annual 100-year environmental dose comitments to regional population resulting from the operation of Mt. Taylor Uranium Mill Annual environmental dose comitments (EDC), person-rem /yr Exposura Pathway
'4 hole Body Bone Lung Bronchial epithelium Inhalation 4.35E-Ol' l.18E+01 2.37E+01 1.90E+02 External from Ground 2.82E+00 2.82E+00 2.82E+00 2.82E+00 External frdi Cloud 3.20E+00 3.20E+00 3.20E+00 3.20E+00 Vegetable Ingestion 1.83E+00 2.46E+01 1.83E+00 1.83E+00 Meat Ingestion 1.01E-01 1.50E+00 1.01E-01
'l.01E-01 Milk Ingestion 1.24E-01 1.40E+00 1.24E-01 1.24E-01 TOTAL 8.51E+00 4.53+01 3.18E+01 1.98E+02 Estimated population dose from natural ba ckgroundC 1.04E+04 1.31E+04 1.05E+04 3.98E+04 Ratio of total annual regional population dose to that from natural background 8.15E-04 3.47E-03 3.03E-03 4.38E-03
~_.
- The notation 4.35E-01 denotes 4.35 x 10'I.
b Doses presented for the bronchial epithelium are these resulting fmm inhalation of short-lived Rn-222 daughters.
CSource:
G. L. Montet et al., Descriptions of United States Uranium Resource Areas. a Supplement to the Generic Environmental Imoact Statement on Uranium Millino, Report NUAEG/CR-0597, ANL/ES-75. Prepared by Argonne National Laboratory for the U. S. Nuclear Regulatory Commission, June 1979. (Colorado Plateau Region data).
)
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Table 5.
Population Distribution for Year 2000*
f N
NNE NE ENE E
WNW NW NNW KILOMETERS 0.0 22.5 45.0 67.5 90.0 112.5 135.0 157.5 180.0 202.5 225.0 247.5 270.0 292.5 315.0 337.5 1.0-2.0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 2.0-3.0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 3.0-4.0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 4.0-5.0 0
0 0
0 0
0 0
0 12 49 0
0 0
0 0
0 5.0-10.0 0
0 0
0 0
0 0
0 627 0
0 20 0
0 0
0 10.0-20.0 0
801 0
0 0
0 0
0 0
0 0
0 0
0 0
0 20.0- 30.0 0
0 0
0 0
0 0
0 2689 0
0 0
0 0
0 0
30.0-40.0 0
0 0
0 0
~ 0 660 0
392 0 24938 2170 2372 0
0 0
40.0-50.0 0
0 0
0 0
0 1908 1429 4156 0
0 0
1229 1097 0
0 gj 50.0-60.0 2902 0
0 6554 0
0
.285 0
0 0
1549 0
0 0
1914 2587 60.0-70.0 0
0~
0 0
0 1658 0
0 0
0 0
0 0
3467 2355 0
70.0-80.0 0
0 0
0 0
C 0
0 2640 0
0 0
539 0
0 0
1.0-80.0 2902-801 0 6554 0
1658 2853 1429 10516 49 26487 2190 4140 4564 4269 2587 TOTAL 1-80 Kit POPULATION IS 70999 PERSONS a.
Currently available population distribution data provided by Gulf Mineral Resources Co. Extrapolation to year 2000 based on staff estimate of regional growth.
Tatig 6.
Total envirorvental dose commitgents (EDC) over the life of the Mt. Taylor mill facility Total envireneental dose comitments (EDC) person-ren Whole Body Bone Luno Bronchial epithelium IOC's received by 1.99E+02 1.01E+03 6.71E+02 5.30E+03
- ecple within 80 km of the mill C
Fraction of Background B.15E-04 3.47E-03 3.03E-03 4.98F 33
~
EDC's received by 3.05E+03 4.09E+04 6.73E+02 1.93E+04 ec:le beyond 80 km of the mill d
Traction of Background 4.78E-06 6.41E-05 1.05E-06 6.04E-06
" rand Total EDC's 3.25E+03 4.19E+04 1.34E+03 2.46E+04 received over all
- opulations
- Total EDC's shown are the combined result of operational and post-operational releases for the entire duration of 24.5 years.
2 The notation 1.99E+02 denotes 1.99 x 10,
~~
~ ~ hatio of dose comitment from operation of mill to that from natural background (from Table 4).
aa':io of EDC's to occulation dose commitment due to Rn-222 from background. Back estfrated en the basis of year 2000, a U. S. population of 260.4 million persons, ground values each person receiving 100 mil 11 rems / year to the whole body, bene, and lung and 500 millirems / year to the brcnchial epithelium.
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t e As indicated in Table 7, the radiation dose comitment to the bone of an individual living at the Lee Ranch residence would slightly exceed (by 5%) the EPA limit and the dose comitment to the lung would be a significant fraction (66%) of the EPA limit.* The calculated bone doses result primarily from the ingestion of meat from animals grazing west of the mill site and result from ingestion by grazing cattle of contaminated vegetation; the contamination consists of fugitive dust from from the ore storage and handling areas.
Implementation of a strict program to minimize fugitive dust from the ore storage and handling areas should ensure that the actual ingestion doses are reduced to within limits.
The results of the required radiological monitoring program (Sect.11.0) must be used to verify that compliance with 40 CFR Part 190 is achieved.
It should be noted that an 80% dust particulate reduction factor for uncovered tailings trenches was used throughout the facility's operation and drying of the tailings. That is, through dust control techniques, such as spigotting of the tailings slurry over exposed tailings beaches, only 20% of the tailings trench area is assumed to be dry and available for dusting at any time.
(See Table 1, Part IV and Figure 1 for data and assumptions used in modeling releases from the tailings impoundment system.
The schedule used in the model for excavation, filling, and reclamation of trenches does not exactly correspond with what is proposed, but is considered appropriate because of uncertainties concerning actual behavior of the system.) Additionally, a dusting reduction factor of 50% for chemical spraying or wetting of the ore pad was used in the analysis.,This factor significantly reduces the doses that would otherwise result.
The concept of developing separate, below-grade tailings disposal trenches in stages is a positive feature of the facility in that, among other things, it minimizes the area available for dusting.
Furthermore, Gulf proposes to cover tailings within a trench as soon as possible after deposition; the ability to do this is dependent on a number of l
factors which, at present, are uncertain, e.g., required drying time for a filled trench. There is, in any case, a need to develop a formal dust control program.. As a license condit on, it is recommended that a t
formal, dccumented program for tailings dust mntrol, including implementation of supplementary dust suppression methods suca as wetting, sprinkling, and/or chemical-retardation spraying of the tailings dteing the operational and drying periods be developed.
Under 10 CFR Part 20, air concentrations of radioactive materials in unrestricted areas are limited to maximum permissible concentrations (MPCs). Table 8 presents the results of the staff's evaluation of compliance with 10 CFR Part 20 for calculated annual average air concentrations for restricted area boundary locations 0.4 km south-southeast, 0.3 km
- This analysis was based on land use information supplied by Gulf that grazing immediately southeast of the mill site would not occur.
Consumption of meat grazed at locations to the immediate southeast would result in higher ingestion doses.
. Table 7.
Comparison of annual dose commitments to individuals with EPA Radiation Protection Standards (40 0FR Part 130)a Calculated ann al dose comitments (millirem / year) location Excosure cathway Total body Bone Luno Lee Ranch Inhalation
- 2. 31 E-01b 6.36E+00 1.48E+01 -
(4.6 km SW of mill)
External exposure 4.81E-02 4.81E 4.81E-02 Ingestion Vecetable 2.25E-01 2.76E+00 2.25E-01 Meate 1.33E+00 1.68E+01 1.33E+00 Milk 2.27E-02 2.47E-01 2.27E-02 Total 1.86E+00 2.62E+01 1.64E+01
' EPA limit 2.5E+01 2.5E+01 2.5E+01 Fraction of EPA limit 7.44E-02 1.05E+00 6.58E-01 San Miguel Ranch Inhalation 1.03E-01 2.75E+00 6.68E+00 (8.34 km NE of mill)
External qxposure 2.80E-02 2.80E-02 2.80E-02 Ingestion 0 Meate 1.33E+00 1.68E+01 1.33E+00 Total 1.46E+00 1.96E+01 8.01E+00 EPA 1imit
- 2. 5E+01 2.5E+01 2.5E+01
~ ~
~~ ' -
Fraction of EPA limit 5.84E-02 7.82E-01 3.20E-01 San Mateo Inhalation 1.18 E-01 3.02E+00 S.33E+00 (5.7 km S of mill)
External Exposure 3.07 E-02 3.07 E-02 3.07E-02 Ingestion Vegetable 8.96E-02 1.12E+00 8.96E-02 Meate 1.33E+00 1.68E+01 1.33E+00 Milk 9.11 E-03 1.02E-01 9.11E-03 Total 1.58E+00 2.llE+01 9.79E+00 EPA limit 2.5E+01 2.5E+01 2.5E+01 Fraction of EPA limit 6.32E-02 8.43E-01 3.92E-01 Marcus Ranch Inhalation 4.48E-02 1.22E+00 2.87E+00 (9.49 km WSW of mill)
External Exposure 9.76E-03 9.76E-03 9.76E-03 I
Ingestion Vegegable 4.81E-02 5.89E-01 4.81E-02 Meat 1.33E+00 1.6SE+01 1.33E+00 Milk 4.85E-03 5.27E-02 4.85E-03 Total 1.44E+00 1.87E+01 4.26E+00 EPA limit 2.5E+01 2.5E+01 2.5E+01 Fraction of EPA limit 5.76E-02 7.47E-01 1.70E-01 a 40 CFR Part 190 specifically excludes any doses and dose comitments arising from the releases of radon and daughters.
b The notation 2.31E-01 denotes 2.31 x 10'I c Meat ingestion doses result from consumption of the meat of cattle grazed 0.56 km_W of the mill.
d There exists 'no vegetable or milk pathway at this location.
9
I.
t 9
Table H.
Comparlson of air cor.tentration'. during mill operation with NRC adiation protection standards (10 CFR Part 20J 3
Total air concentratinns.,pC fm,,of_ iso _t,op,es_ _
WL Concentrationsd U-238 U-234 Th-230 Ra.226 Pb-210 Bi-210 Po-210 b
10 CFR Part 20 limits 5.0E400 4.0E+00 8.0E-02' 2.0E+00 4.0E+00 2.0E+02 7.0E+00 3.3E-02 Predicted values:
SSE restricted area 2.9E-01 2.9E-01 8.8E-02 7.8E-02 7.8E-02 7.8E-02 7.8E-02 1.2E-03 boundary (0.4 km SSE of mill)
Fraction of Ilmit 5.8E-02 7.2E-02 1.10E+00 3.9E-02 1.9E-02 3.9E-04 1.1E-02 3.6E-02 d
Sum of fractions = 1.33E*00 W restricted area 9.4E-02 9.4E-02 6.8E-02 6.7E-02 6.7E-02 6.7E-02 6.7E-02 5.4E-04 boundary (0.3 km W of mill)
Fraction of limit 1.9E-02 2.3E-02 8.5E-01 3.3E-02 1.7E-02 3.3E-04 9.5E-03 1.6E-02 e
a Sum of fractions = 9.7E-01 m
E restricted 1.4E-01 1.4E-01 5.7E-62 5.2E-02 5.2E-02 5.2E-02 5.2E-02 4.6E-04 area boundary (0.4 km Eof mill)
Fraction of limit 2.9E-02 3.6E.02 7.1E-01 2.6E-02 1.3E-02 2.6E-04 7.4E-03 1.4E-02 Sum of fractions = 8.3E-01 Lee Ranch (4.6 km 3.6E-03 3.6E-03 9.2E-04 7.8E-04 9.0E-04 7.8E-04 7.7E-04 1.6E-04 SW of mill) fraction of Ilmit 7.2E-04 9.0E-04 1.1E-02 3.9E-04 2.3E-04 3.9E-06 1.1E-04 4.8E-03 Sum of fractions = 1.9E-02 a
WL denotes " working level". A one-WL concentration is defined to be any combinatipn of air concentrations of the short-lived Rn-222 daughters '
Po-218 Pb-214 Bi-214, and Po-214 that, in one liter of air, will yield a total of 1.3x105 Mey of alpha particle energy in their complete decay to Pb-210. Predicted values given for outdaor air are those calculated on the basis of actual ingrowth from released Rn-222.
b Values given are from 10 CFR Part 20, Appendix B. Table !!, Col. 1.
C The notation 8.0E-02 denotes 8.0x10-2, d Compilance with 10 CFR Part 20 is not achieved if the sum of the fractions is greater than 1.
That is If radionuclides A, B and C are present in concentrations C concentrationsshalf,beIlmhtedsothatthefollowingrelationshipexists:and if the applicable maximum per1nissible concentrations (MPCs) are NPC, MPC C,C B
A B
C (C/MPC)+(Cg/MPC)+(C/MPCI'I*
A g
B C
C I
l
west, and 0.4 km east of the mill, and at the nearest residence (Lee Ranch) which is located 4.6 km southwest of the mill, Con:entrations at other boundary locations were calculated and found to be smaller than those presented in Table 8.
As indicated by the table, the individual isotopes are not all below the MPC limits.
(0bviously, the sum of the fractions of the 1:,Mividual isotopes also exceeds the MPC limit for a mixture. *)
Compliance with the MPC limit for thorium-230 (Th-230) is not achieved in the analysis primarily due to fugitive dust emissions from the ore storage and handling areas even though a 50% reduction factor for dusting from the ore pad is used. Calculations indicate that the MPC for Th-230 would be exceeded at the proposed mill exclusion area boundary.
Extending the exclusion area boundary to the property boundary immediately S-SE-E of the mill would result in Th-230 effluent concentrations of about 0.50 and 1.33 MPC for ore processing rates of 2100 and 4200 tpd, respectively. Therefore, it is recommended that the exclusion area boundary be extended to near the property boundary southeast of the mill.
This is not considered a serious problem for the following reasons:
a.
The high Th-230 concentrations at exclusion area boundaries immediately to the southeast of the mill are primarily due to ore storage and handling (including grizzly) effluents.
A firm effluent control program should ensure the effluent 1imits
~
are met.
b.
As proposed, Gulf will start processing ore at a rate of 2100 tpd for a period of four years.
Monitoring results will be available after the first and following years for extrapolating to effluent concentrations which would be expected at a rate of 4200 tpd.
This will provide a firm basis for determining whether limits will actually be exceeded, and process modification
.necessary, before operating the mill at the full capacity assumed in this assessment.
In any case, it is recommended that the applicant be required by license condition to establish a control program that shall inclrade written procedures and instructions concerning wetting or chemical spraying of the ore handling ~and storage areas to achieve the maximum practicable reduction.
As discussed above with regards to 40 CFR Part 190 limits, actual compliance with 10 CFR Part 20 during operation of the facility will have to be determined using the results of the radiological monitoring program.
If operational results show that MPC levels are exceeded, further review will be necessary to determine whether operational procedures or design modifications to increart emission control will have to be instituted or whether the restricted a.;a boundary needs to be extended so that compliance with 10 CFR Part 20 can be achieved.
- The sum of the. fractions obtained by dividing the concentration of each isotope by the corresponding MPC cannot exceed 1 (footnote e to Table 8),
so that the total contribution by a mixture of isotopes will not exceed i
the whole-body dose limit of 0.5 rem per calender year for an individual in an unrestricted area (as defined in 10 CFR Part 20).
l
. 7.0 0CCUPATIONAL DOSE Uranium mills are designed and built to minimize exposure of both the mill workers and the general public to radiation.
Occupational exposures for workers are required to be monitored and kept below regulatory limits.
In addition, protection measures to reduce cccupational exposures are periodically reviewed and revised in accordance with the requirement to make such exposures as low as is reasonably achievable.
The scope of this NRC staff review has not included a review of the in-plant radiological safety program proposed for the mill.
- However, occupational exposures can be characterized in general terms. Special studies at selected mills have shown that the exposures of mill workers to airborne radioactivity are normally below 25% of the maximum pennissible concentrations given in Appendix B of 10 CFR Part 20 and that gxternal exposures are normally less than 25% of 10 CFR Part 20 limits.D,0 A recent review 7 of mill exposure data by the NRC staff has indicated that only a few uranium mill employees may have exceeded, over a one-year period,1S to 20% of the permissible exposure to are dust, 25% of the permissible exposure to yellowcake, or 10% of the pennissible exposure to radon concentrations. Except for a few individuals, the combined exposure of an average worker to these radioactive components over a one-year period probably does not exceed 25% of the total pennissible exposure.
8.0 RADIOLOGICAL IMPACT ON BIOTA OTHER THAN MAN Although no guidelines concerning acceptable limits of radiation exposure have been established for the protection of species other than man, it is generally agreed that the limits for humans are also conservative for those species.8-15 Doses from gaseous effluents to terrestrial biota (such as birds and mammals) are quite similar to those calculated for man and arise from the same dispersion pathways and considerations.
Because the effluents of the mill will be monitored and maintained sithin safG radiological protection limits for man, no adverse radiological impact is expectdd for resident biota.
9.0 RADIOLOGICAL ASSESSMENT FOR THE MT. TAYLOR MINE Preliminary mine input data provided by Gulfl6 as well as staff estimated parametersi7 on mine radon releases were used to calculate the annual releases of radon-222 from the mine. These are presented in Table 9.
Utilizing the meteorological data obtained for the proposed mill site (Table B.2), the staff calculated annual air concentratios.s for two locations:
(1) the town of San Mateo (5.7 km south of Fee mill) and (2) the Lee Ranch (4.6 km south of the mill). These estimo ced concentrations were smaller than the MPC limits specified in 10 CFR %rt 20. The
(
compliance comparison is presented in Table 10.
l l
able 9.
Information and data used to estimate radon releases from the San Mateo Mine".
1.
Location of mine vents 4.62 km SSW of mill a 2.
Height of vents relative to mill center 41.0 meters 3.
Exit velocity of vents 6.18 m/sec 4 Annual emission of radon from mine vents 1.22 x 10 C1/yearb 5
5.
Ore grade 0.32 % U 038 6.
Ore production of mine 1295482 MT/ year
"?alues based on infomation provided by NMEIO.
b Yalue based on NUREG/CR-0627. PNL-2888IO Table 10.
Comparison of estimated radioactive air concentrations with NRC Radiation Protection Standards (10 CFR Part 20) for the San Mateo Mine.
Concentrations of radon daughters pCi/m3 Location Wla
. Pb-210 Bi-210 Po-210 San Mateo 6.86E-03b 2.79E-04 2.5BE-07 6.75E-12 (5.7 km S of mill)
Fraction of limits
- 2.08E-01 6.98E-05 1.29E-09 9.64E-13 Lee Ranch 4.27E-03 4.55E-04 8.11E-07 4.00E-11 (4.6 km SW of mill)
Fraction of limits" 1.29E-01 1.14E-04 4.06E-09 5.71E-12 a
WL denotes " working level." A one-WL concentration is defined to be any combination of air con-eentrations of the short lived Rn-222 daughterg Po-218. Pb-214. B1-214. and Po-214, which, in j
1 liter of air, will yield a total of 1.3 x 10 decay to Pb-210.
MeV of alpha particle energy in their complete DThe notation 6.86E-03 denotes 6.36 x 10-3, c
Limits given in 10 CFR Part 20 for Wg and for concentrations of Pb-210. B1-210. and Po-210 are 0.033 WL and 4.0, 200 and 7.0 pCf/m. respectively.
. l The individual inhalation dose commitments resulting from the exposure to radon and its daughters were calculated for the town of San Mateo, the location of the nearest residence to the mine. A sumary is presented i
in Table 11. A comparison of these doses with the total calculated doses resulting from the mill facility (Table 3) shows that the dose contribution of the mine is smaller, except for the dose to the bronchial i
epithelium which is due to the higher release of radon-222 at the mine.
The total 100-year environmental dose coninitments to the regional and Sect. 5)gional population were also calculated (in the same manner as in extra-re l
Table 12 presents both the dose commitments within and beyond 80 km (50 miles) of the site. The doses to the bronchial epithelium to the regional population and the total dose to the extra-regional population are significantly larger than the doses received from the mill facility (see Table 6). This is because the radon emission from the mine is significantly larger than that from mill sources.
10.0
SUMMARY
OF RADIOLOGICAL IMPACTS On the basis of this predictive analysis which is reasonably conservative in its assumptions, it is considered likely that dose commitments from the proposed Mt. Taylor Mill facility operations would meet the 25 millirem / year limit imposed by 40 CFR Part 190 for maximum offsite dose to any oraan of any individual, excluding contributions from radon-222 and its radioactive decay products (see Table 7). Although calculations indicate the 25 millirem / year limit could be slightly exceeded at one location, strict effluents controls should prevent this from happening.
The analysis also indic'ates that, although the mill operations, as proposed, may not comply with the total maximum permissible concentration (MPC) limits from the facility calculated at the restricted area boundary.
strict control of effluents during_ actual operr.tlon should ensure
\\
the MPC 1fiiBts are met. Measurements to tie tikenTi~part of thi -
radiological monitoring program must be used to confirm that effluents l
from the mill facility operation meet the limits of 10 CFR Part 20 and 40 CFR Part 190. Although a degree of conservatism is maintained in calculation of source terms (because of uncertainties concerning the unknown effect of certain site-specific factors, e.g., topographic features), the resultant predicted environmental concentrations, and thus the corresponding doses, being so c. lose to regulatory limits clearly indicate the need for strict control of mill emissions.
In addition to the planned program of staged covering and reclamation of tailings, a formal documented program of fugitive dust control at the tailing trenches and the ore handling and storage' areas should be developed i
and followed.
Furthermore, frequent checks of yellowcake stack emission control devices should be required.
l i
,p-r-m--
Table 11. Annual inhalation dose commitmeats to individuals from radioactive releases from the San Mateo Mine to the town of San Matec.
Dose Comitment Organ (millirems / year) i Whole body 2.0BE-03 Bone 6.47E-02 4
Lung 1.75E-02 b
Brcnchial epithelium 9.83E+02 a
The notation 2.08E-03 denotes 2.08 x 10'3 DDoses to the bronchial epithelium result from the inhalation of the short-lived radioactive daughters of Rn-222.
~
Table 12.
l Environmental (100-year) Dose Comitments (EDC) areceived by populations as a result of radon released from the San Mateo Mine,
Total EDC's, person-rem Whole Body Bone Lung Broncnial Epithelium D
EDC's received by people 9.51E+02 3.05E+03 1.15E+03 5.23E+04 within 80 km of the mill C
Fraction of Background 4.14E-03 1.06E-02 4.97E-03 5.98E-02 EDC's received by people 2.52E+04
- 3. 38 E+05 5.54E+03 1.60E+05 beyond 80 km of the mill d
Fraction of Background 4.40E-05 5.90E-04 9.67E-06 5.59E-05 Total EDC's received over 2.62E+04 3.41E+05 6.69E+03 2.12E+05 all populations a
iotal EDC's are the combined result of radon releases over the lifetime of the facility (22 years),
b 2
The notation 9.51E+02 denotes 9.51 x 10,
C Ratio of average annual EOC's to regional population dose from natural background, d
Ratio of average annual EDC's to population dose commitment due to Rn-222 from background.
See Table 6. footnote c.
. The evaluation of the tailings impoundment radiological source term included the assumption made by Gulf that tailings in trenches would be dry enough to reclaim after a one year drying period. This assumption may prove to be unrealistic (a presentation of Gulf's proposal will be provided in the tailings management evaluation reportl. The tailings slurried to the trenches would be 20-40% solids and would consist of approximately 60% (by dry weight) slimes (-200 meshl and 40% sands. The slimes are a low density, " fat" clay.
In short, the deposite.1 tailings may not behave as is predicted by Gulf and reclamation of the tailings may be delayed resulting in a larger source term for radon.
In addition, the foundation for the reclamation cover may be less firm (stable) than is predicted by Gulf.
(Similarly, a larger quantity of moisture retained in the tailings could lead to problems with seepage to groundwater.)
For this reason Gulf should continue /reinstitute research into methods of ensuring the tailings drain and consolidate as rapidly as is now thought to be possible.
i 11.0 RADIOLOGICAL. MONITORING PROGRAM i
Although an evaluation of the proposed radiological environmental monitoring program was not within the scope of this radiological assessment, a few comments are necessary considering the importance of this part of Gulf's proposal. As was noted earlier in this report, project activities, as currently proposed by Gulf, may result in effluents which would cause
-~ ~
violations of 10 CFR 20 and 40 CFR 190 limits if not better controlled.
It is only through implementation of a thorough and comprehensive radiological environmental monitoring program that the most significant effluent sources can be identified and controls developed to minimize the effluents.
In general, the radiological environmental monitoring program should be based on that which is outlined in Generic Environmental Impact Statement on Uranium Milling (GEIS).18 Additionally, the guidance presented in NRC Staff Technical Position on Operational Radiological Monitoring Programsl9 should be used-in developing the program.
Specific details ~
of the program should be firmly established and made a license condition
~
prior to authorizing the proposed operations.
For example, there is a clear need to sample air particulates at the restricted area boundaries inmediately west and southeast of the mill to enable measurements of rMius.uclide concentrations at those critical locations.
As part of the program to ensure compliance with 40 CFR 190 exposure limits, Gulf should be required by license condition to conduct an annual survey of land use (grazing, inhabited residences, wells, etc.) in the area within 8 km (5 miles) of the mill and submit a report to the State.
The report should describe any differences in land use from that assumed in support of this first radiological assessment.
i i
t I
k
REFERENCES FOR SECTION 4 1.
Gulf Mineral Resources Company, Ground Water Discharge Plan, Mt. Taylor Uranium Mill Project, New Mexico, February 1980.
Docket WM-26.
2.
U.S. Nuclear Regulatory Commission, " Calculational Models for Estimating Radiation Doses to Man from Airborne Radioactive Materials Resulting from Uranium Milling Operations," Task RH 802-4, May 1979.
3.
Gulf Mineral Resources' Company letter to HMEID, dated February 22, 1980.
4.
NMEID letter to NRC, dated November 28, 1978, Docket WM-26.
5.
B. R. Metzger, " Nuclear Regulatory Commission Occupational Exposure Experience at Uranium Plants," Conference on Occupational Health Experience with Uranium, Report ERDA-93, Washington, D.C., 1975.
6.
International Atomic Energy Agency, Safety Series No. 43, Manual on Radiation Safety in Uranium and Thorium Mines and Mills, IAEA, Vienna, 1976.
7.
Fuel Processing and Fabrication Branch, U.S. Nuclear Regulatory Commission, Presentation to the Environmental Subcommittee of the Advisory Subcommittee on Reactor Safeguards, Occupational Radiation Exposure Control at Fuel Cycle Facilities, January 26, 1978.
8.
S. I. Auerbach, " Ecological Considerations in Siting Nuclear Plants.
The Long-Term Biota Effects Problem," Nucl. Saf.12: 25-35 (1971).
9.
Proceedings of the Environmental Plutonium Symposium, Report LA-4756, Los Alamos Scientific Laboratory, Los Alamos, N. Mex.,1971, and A Proposed Interim Standard for Plutonium, Report LA-5483-MS, Los Alamos Scientific Laboratory, Los Alamos, N. Mex., 1974.
- 10. Enewetak Radiological Survey, USAEC Report NV0-140, Nevada Operations Office, Las Vegas, Nev., 1973.
l l
11.
N. A. Frigerio, K. F. Eckerman, and R. S. Stowe, " Background Radiation I
as a Carcinogenic Hazard," Rad. Res.
62: 599 (1975).
l 12.
A. H. Sparrow et al., " Chromosomes and Cellular Radiosensitivity,"
l Rad. Res. 32:915 (1967).
- 13. Radioactivity in the Marine Environment, Report of the Committee on Oceanography, National Academy of Sciences-National Research Council, Washington, D.C.,1971.
14.
R. J. Garner, " Transfer of Radioactive Materials from the Terrestrial Environment to Animals and Man," Environ.'
Control 2: 337-85, 1971.
I 15.
S. E. Thompson, Concentration Factors 'of Chemical Elements'in Edible Aquatic Organisms, USAEC Report UCRL-50564, rev.1, October 1972.
- 16. Gulf Mineral Resources Company, " Responses to NRC Questions Dated December 28, 1979", dated April 1979.
17.
P. O. Jackson et al., Radon-222 Emissions in Ventilation Air Exhausted from Underground Uranium Mines, Report NUREG/CR-0627, PNL-2888 Rev., Pacific Northwest Laboratories, September 1979; the mine ore rate of 4200 tons / day; and a letter from L. C. Schwendiman, Pacific Northwest Laboratories, to W. E. Thompson, U.S. Nuclear Regulatory Commission, re radon emission from underground uranium mines, dated November 15, 1979.
18.
U.S. Nuclear Regulatory Commission, Draft Generic Environmental Impact Statement on Uranium Milling, Report NUREG-0511, April 1979, Vol.
1, pp.10-8 through 10-13.
19.
U.S. Nuclear Regulatory Commission, Uranium Recovery Licensing Branch, " Proposed Branch Position for Operational Radiological Environmental Monitoring Programs for Uranium Mills," no date.
1
Appendix A CALCULATION OF SOURCE TERMS Introduction The radiological assessment for the Mt. Taylor Mill facility was accomplished by use of the MILDOS computer code.
The input to the computer code consists of site-specific data, as well as generalized staff estimates of sources from the mill and tailings management system. Among the site-specific data are the source terms; that is the estimated quantity of radioactivity released in a specific period of time.
This analysis includes the following mill sources:
1.
the ore pad and its related activities, 2.
the grizzly and apron feeder, 3.
yellowcake drying and packaging.
The evaporation pond and tailings trench area sources are presented in Appendix B.
Some general parameter values which are significant in the calculations contained herein are 1.
the annual process rate, 1,295,482 MT/ year, 2.
the ratio of radioactivity in the ore dust to that of the bulk ore, 2.5 3.
fraction of U-238 in yellowcake, 95%
fraction of Th-230 in yellowcake, 5%
fraction of Pb-210 and Ra-226 in yellowcake, 0.2%
The Ore Pad Particulate emissions from.the ore pad result from:
1.
truck delivery of ore,.
2.
handling cre on pad, 3.
windblown emission, Radon gas emissions are based on a specific Rn-222 flux of 2
1.0 pCi/m -sec Rn-222 pCi/gm Ra-226 (Table 1) 1.
Truck unloading Release rate 0.1 lb/ ton = 0.1 lb/2000 lb = 5 x 10 s (ref. 1) 5 x 10 5 x 1295482 MT/ year x 108 g/MT x 903.61 pCi/g x 10 12 Ci/pCi x 2.5 = 1.46 x 10 1 Ci/ year.
l A-1
2.
Handling Release rate 0.05 lb/ ton = 0.05 lb/2000 lb = 2.5 x 10 5 (ref. 1) 2.5 x 10 5 x 1295482 MT/ year x 106 g/MT x 903.61 pCi/g x 10 12 Ci/pci x 2.5 = 7.32 x 10 2 C;.jear.
3.
Windblown emissions Dusting rate for ore pad 32.85 g/m year (Table 1) 2 2
32.85 g/m year x 903.61 pCi/g x 2.5 x 4047 m / acre 2
x 12.344 acres x 10 12 Ci/pCi = 3.70 x 10 3 Ci/ year.
4.
Radon-222 released from ore pad 1p
-sec x 903.61 pCi/g (Ra-226) x 3.156 x 107 sec/ year g
x 12.344 acres x 4047 m / acre x 10 22 = 1426 Ci/ year.
2 Sum total of particulate ore pad emissions:
1.46 x 10 1 Ci/ year 7.32 x 10 2 Ci/ year 3.70 x 10 3 Ci/ year 2.23 x 10 1 Ci/ year x 50% reduction * (ref. 2)
= 1.11 x 10 1 Ci/ year Total ore pad radon emission:
1426 Ci/yr Grizzly Release rate 0.2 lb/ ton = 0.2 lb/2000 lb = 10 4 (ref. 1) 10 4 x 1295482 MT/ year x 106 g/MT x 903.61 pCi/g x 2.5 x 10 22 Ci/pci = 2.93 x 10 1 Ci/ year Particulate emissions = 2.93 x 10 1 Ci/ year x 50% reduction
= 1.46 X 10 1 Ci/ year Radon released at the grizzly is conservatively assumed to be 20% (the radon emanation power of ore) of the equilibrium ore content of radon.
The estimated release is likely to be. greater than the actual release at
^50% reduction is assumed to be achieved by means of chemical spraying and/or wetting.
A-2
this point.
This approach is taken to account for nonspecific, small releases from other steps in the other ore-handling processes which are not explicitly modeled.*
20% x 1295482 MT/ year x 108 g/MT x 903.61 pCi/g x 10 12 Ci/pCi = 234.12 Ci/ year Rn-222 emissions = 234.12 Ci/ year Yellowcake drying and packaging The yellowcake releases from the packaging and drying processes are based on the following assumption, as well as the general parameters mentioned in page A-1:
1.
Yearly yellowcake production of 3916.8 MT/ year (Table 1) 2.
Operation time is:
340 days / year 3.
Approximately 0.1% of the yellowcake product is released in the drying and packaging process:
(Ref. 3) 3916.80 MT/ year x 0.1% = 4.32 MT/ year Total particulate release is 4.32 MT/ year Radioactive particulate emission:
4.32 MT/ year x 3.33 x 10 7 Ci U-238 x 0.85 g U-238 x 0.85 g U 0, 3
g g U 0s g yellowcake 3
x 108 g/MT = 1.04 x 10 1 Ci/ year U-238 1.04 x 10 16 Ci/ year x 0 h re
= 5.45 x 10 2 Ci/ year Th-230 r
1.04 x 10 1 Ci/ year x 0b5re
= 2.18 x 10 3 Ci/ year each of r
Pb-210 and Ra-226 l
Radon release from the yellowcake activities is assumed to be negligible.
l l
Summary Except for the yellowcake source terms, the U-238, U-234, Th-230, Ra-226, Pb-210 quantities are considered to be in secular equilibrium.
In general, "The conveyor, grinding, leaching and counter-current decantation (CCD) operations are relatively insignficant sources when compared with those which are included in the analysis.
A-3 l
radioactive emissions which are not explicitly calculated are assumed to be equal to the next higher-up parent in the decay chain.
The MILDOS code also accounts for mechanisms such as ingrowth of radon daughters, resuspension, deposition, all of which are further explained in Appendix B.
4 REFERENCES FOR AF/ENDIX A
~
1.
"APCD itining Worksheet," prepared by William Reef, Colorado Department of Health, for Enviro-Test, Ltd., March 1978.
2.
U.S. Environmental Agency, Technical Guidance for Control of Industrial Process Fugitive Particulate Emissions, Report EPA-45013-010, March 1977.
3.
M. H. Momeni et al., Radioisotopic Composition of Yellowcake, An Estimation of Stack Relere
' tes, Report NUREG/CR-1216, ANL/ES-84, i
Argonne National Laboratofy,' December 1979.
e i
A-4 4
l f
Appendix B DETAILED RADIOLOGICAL ASSESSMEfiT O
e
Appendix B DETAILED RADIOLOGICAL ASSESSMENT Supplemen'.al infomation is provided below which describes the models, data, and assumptions utilized by the staff in perfoming its radiological impact assessment of the Mt. Taylor Urantum Mill. The primary calculational tool employed by OS'e staff in performing this assess-rrent is.1ILDOS, an NRC-modified version of the UDAD (Uranium Dispersion and Dosimetry) computer code originated at Argonne National Laboratory.1 B.1 ANf.U L RADI0 ACTIVE MATERIAL RELEASES Estinated a.anual activity releases for the Mt. Taylor Uranium Mill are provided in Table 2.
Tr.ey are based ca the data and assumptions given in Table 1 and described elsewhere in Sect.1.1. with the exception of the annual average dusting rate for exposed tailings sands.
Tnis dusting rate is calculated in accordance with the following equation:
x 3156
- IU' 1 a,r,.
(s-1) e T, is the annual average frequency of occurrence of wind speed group s. dimensionless;
., is the dusting rate for tailings sands at the average wind speed for wind speed group
- a. for particles <20 um in diameter, g/m2 sec; x is the annual dust loss per unit area, g/mi year; 3.156 x 107 is the number of w.onds per year; 0.5 is the fraction of the total d.ist loss constituted by particles <20.so in diameter.
dimensionless.3 Tr.e salues of A, and T, utilized by the staff are as given in Table E.1.
The calculated value of the annual dusting rate. M. is 387.99 g/mi year. Annual curie releasts from the tailings piles are tnen given by the following relationship:
J = t.3(1 - f,)f,(1332)(2.5)(1 x 10-12).
(B-2) where A is the assumed beach area of the pile, m2; fy is the fr' action of the dusting rate controlled by mitigating actions, dimensionless; f, is the fraction of the ore content of the particular nuclide present in the tails; 5 is the annual release for the particular beach area. Ci/ year; B-3
l. l- % 7 ;..
~
- a
.A_A-B-4 Toble B.1. Parameter values for sesoulation of anneet duetag reis for espeesd teilings sends 8
Wind speed Average wind Dusting rate. A, Frequency of occurrence.F, group (knots) speed lmph)
(g/m'
- sec)*
Site 1 (milli Site 2 (tainniest o-3 1.5 0
4-4 5.5 0
7-10 ta0 3.92 X 10*'
a19068 a24774 11 -18 155 9.68 X 10-8 o.o8434 411977 17-21 21.5 571X 10-'
O.02733 o.03o35
>21 2&O 108 X 10**
a01323 0.01518
- Dustent rate as a function of wind speed is computed by the MILDOS code.
- Wind speed frequencies are obtained from annual joint frequtncy osta presentedin Tables B.2 and IL3.
1332 is the assumed specific activity, pCi/g; 2.5 is the dust-to-tails activity ratio; 1 x 10-12 is et/ pct, For the mill site, the amounts of tailings area exposed as a function of time were assumed using Fig. I and Table 1.
Required mitigating actions to reduce dusting were assumed to reduce dust losses by 80t.
Dust losses from the ore storage pile were estimated assuming they would be about 10t of ttiose fenm en equivalent area of tailings beach and using the meteorological data for site 1 (see Table B.2 and Appendix A).
B.2 ATMOSPHERIC TRANSPORT Tne staff analysis of offsite air concentrations of radioactive materials has been based on meteorological data collected from July 8,1976, to Septenter 3,1976, and from November 24, 1976, to January 21, 1977, for site 2 and from February.1976 to February 1977 for site 1.2 The collected meteorological dad is entered into the MILD 05 code as input in the form of a joint frequency distribution by stsbility class, wind speed group, and direction. The joint frequency data employed by the staff t er this analysis are presented in Tables B.2 and B.3.
The dispersion model employed by the MILD 01 code is the basic straight-line Gaussian plume model.1 Ground-level, sector-averaged con:entrations are computed using this snodel and are corrected for decay and in due to deposition losse's (growth in transit (fer randen-222 and daughters) and for depletion for particulate material). Area sources are treated using a virtual point-source technique. Resuspension ir.to the air of particulate material initially deposited on ground surfaces is treated using a resuspencion factor that depends on the age of the deposited material and its particle size. For the isotopes of concern here, the total air concentration including resuspension is about 1.6 times the ordinary air concentration.
The assumed particle size distribution, particle density 3 source are presented in Table B.4
~ and deposition velocities for each B.3 CONCENTRATIONS IN ENVIRONMENTAL MEDIA Information provided below describes the methods and data used by the staff to determine the cencentrations of radioactive materials in the environmental tredia of concern in the vicinity of the site.
These include concentrations in the air (for inhalation and direct external exposure), on the ground (for direct external exposure), and in meat 3nd vegetables (for ingestion expcsure). Concentration values are computed explicitly by the MILDOS code for uranium-238, thorium-230, radium-226, and radon-222 (air only), and lead-210. Concentrations of other isotopes of concern are assumed to be equal to those of the next higher-up parent for which the air concentration is explicitly calculated.
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i e
e B-7 Table B.4. Physical cherecteristics assumed for porticutete meterief re4eenes D.ameter Density Deposition velocity AMAD'
- ""'Y"*
3 (um)
(o/cm )
(cm/sec)
(um)
Crusher dusts 1.0 2.4 1.o 1.56 Yellow cake dusts 1.0 8.9 1.0 2.98 Taihnes, are pile dusts 5.0 (30%)
2.4 1.0 7.75 35.0 (70%)
2.4 8.8 54.2 Ingrown redon deughters 1.o o.3 0.3
' Aerodynamic equivalent diameter, used in calculating inhalation doses.
Source: M. Momeni, Y. Yuan, and A. J. Zeelen, The Uranium Desper:4m erNf Dosimetry (UDAD1 Code, Report NUREGCR 0553, ANUES.72, Argonne National Laboratory, May 1979.
E.3.1 Air concentrations Ordinary, direct air concentrations are computed by the MILDOS code for each receptor location, from each activity source, by particle size (for particulates). Direct air concentrations com-pated by MILDOS include depletion by deposition (particulates) or the effects of ingrowth and decay in transit (radon and daughters). To compute inhalation doses, the total air concentra-tion of each isotope at each location, as a function of particle size, is computed as the sum of the direct air concentrat on and the resuspended air concentration:
i C
(t)=C
+C c.
p-gF7(t),
(B-3) n...
w where g (t) is the total air concentration of isotope f. particle size p, at tine :. pCi/m3; C
p gg is the direct air concentration of isotcpe i, particle size y, for e constar.t. pCi/m3; C
g (t) is the resuspended air concentration of isotope i, particle size y, at time e, C
pC1/m3 The resuspended air concentration is computed using a time-dependent resuspension factor,
.9(:) defined by
? (t) = (1/r.)10-5 exp(-L. ) (for : < 1.22 years),
(B-4a) e r
a
?p( ) = (1/7 )10-9 (for > 1.82 years),
(B-4b) 7 where l
y.(:) is the ratio of the resuspended air concentration to the ground concentration, r
for a ground concentration of age t years, of particle size p. m-1; r is the deposition velocity of particle size p, cm/sec; 7
is the assumed decay constant of the resuspension factor (equivalent to a 50-day ly half-life), 5.06 year-1; 10*5 is the initial value of the resuspension factor (for particles with a depo'sition velocity of I cm/sec), m-1;
I B-8 10*S is the teminal value of the resuspension factor (for particles with a deposition velocity of I cm/sec), m-1; 1.B2 is the time required to reach the terminal resuspension factor, years.
The basic fomulation of the above expression for the resuspension factor, the initial and final valces, and the assigned decay constant are derived from experimental observations.s The inverse relationship to deposition velocity eliminates mass balance problems involving resuspension of trare than 100% of the initial ground deposition for the 35-um particle size (see Table B.4). Based on this formulation, the resuspended air concentration is given by 1 - exp[-( A * + 1 )(* - a) '
g p
C (t) = 0.01C 104 yg afpd 43.,3) p
+ 10'N(t) <(exp[-A *(e - :)] - exp(-A
- )'
~
g g
3 I- (3.156 x 10 ),
(B-5) 7 i
u
).
where c is equal to (t - 1.B2) if * > 1.82 and is equal to zero otherwise, years; s(:) is zero if e < 1.82 and is unity otherwise, dimensionless; A
- is the effective decay constant for isotope i on soil, year-1; g
0.01 is the deposition velocity for the particle size for which the initial resuspension factor value is 10-s per meter, m/see; 3.156 x 107 is sec/ year.
Tctal air concentrations are computed using Eqs. B-5 and B-3 for all particulate effluents.
Radon daughters that grow in from released radon are not depleted due to deposition losses and are therefore not assumed to resuspend.
B.3.2 Ground concentrations Radionuclide ground concentrations are computed from the calculated airborne particulate con-centrations arising directly from onsite sources (not including air concentrations resulting fron resuspension). Resuspended particulate concentrations are not considered for evaluating ground concentrations.
The direct deposition rate of radionuclide i is calculated, using the following relationship:
-Ddi *
- adip p '
I where C,jg is the direct air concentration of radionuclide i particle size p, pCi/m3; p
gg is the resulting direct deposition rate of radionuclide i, pCi/m2.seg; U
is the deposition velocity of particle size p, m/sec (see ref. 4).
7 i
j l
1 B-9 The concentration of radionuclide i on a ground surface due to constant deposition at the rate D over time interval e is obtained from dg
.1-exp[-(Ag + 1 )t]-
g(t) = Ddi A
C g + 1,
~
where g (t) is the ground surface concentration of radionuclide i at time *, pCi/m ;
C g 2
e is the time interval over which deposition has occurred sec; 1, is the assumed rate constant for envirv. mental loss, sec-It A is the radioactive decay constant
- for radionuclide i sec"I.
g The environmental loss constant,1. cc cesponds to an assumed half-time for loss of enviro 9-mental availability of 50 years.3,This v 'smeter accounts for downward migration in soil and loss of availability due to chemical binding. It is assumed to apply to all radionuclides deposited on the ground.
Ground concentrations are explicitly computed only for uranium-238, thorium-230, radium-226 and lead-210. For all other radionuclides, tne ground concentration is assumed equal to that of the first parent radionuclide for which the ground concentration is explicitly calculated.
For lead-210, ingrowth from deposited radium-226 can be significant. The concentration of lead-210 c. tr.c ground due to radium-226 deposition is calculated by the staff, using the standard htWn formulation and assuming that radium-226 decays directly to lead-210. If i = 6 ior radvc -226 and i = 12 for lead-210," the following equation is obtained:
- PI'#8)~'*PI-AI2).
1 r I~#*PblI2*)
12 d6 6
8 C 12(Pb - Ra) =
+
(E.7) where d2(Pb - Ra) is the incremental lead-210 ground conc =ntration resulting from radie-226 C
deposition, pCi/m ;
2
- r* is the effective rate constant for loss by radioactive decay and migration of a ground-deposited radionuclide and is equal to a
- A
- S'C'!*
r.
s B.3.3 Vece*ation concentrations Vegetatic. concentrations are derived from ground concentratias and total deposition rates.
Total deposition rates are given by the following summation:
Dg=
C,gpp, (B-Ba)
F r
Radiological decay constants employed by the NRC staff are obtained from data given in ref. 6.
l l
'I l
a I
B-10 where O is the total deposition rate, including deposition of resuspended activity, of g
radionuclide i, pC1/m2.sec, Concentrations of released particulate materials can be environmentally transferred to the edible portions of vegetables, or to hay or pasture grass consumed by animals, by two nechanisms - direct foliar retention and root uptake. Five categories of vegetation are treated by the staff. They are edible above-ground vegetables, potatoes, other edible below-ground vegetables, pasture grass, and hay. Vegetation concentrations are computed using the following equation:
'l-exp(-ljyf Cyg
- U T,E
+Cg(Eg/P),
(B-8b) g y
ahere E
is the soil-to-plant trantfer factor for isotope i, vegetation type v. dimensionless; yg r
is the resulting concentration of isotope i, particle size p, in vegetation v.
Cygg pCi/kg; E, is the fraction of the foliar deposition reaching edible portions of vegetation v, dimensionless; T, is the fraction of the total deposition retained on plant surfaces, 0.2, dimensionless;
? is the assumed areal soil density for surface mixing, 240 kg/m ;
2 is the assumed duration of exposure while growing for vegetation v sec; ty J is the assumed yield density of vegetation v,' kg/m ;
2 y
),, is the decay constant accounting for weathering losses (equivalent tc a 14-day half-life), 5.73 x 10*7 per second.
~he value of G is assumed to be 1.0 for all above-ground vegetation and 0.1 for all below-
- round vegetables.6 The value of t is taken to be 60 days, except for pasture grass where a v
,alue of 30 days is assumed. The yield density.
I... is taken to be 2.0 kg/m2 except for
- as ure grass, where a value of 0.75 kg/mi is applied. Values of the soil-to-plant transfer
- cefficients, Eye, are provided in Table B.S.
Table 8.5. Environmental transfer coefficients Uranium Thorium Radium Lead Plant! soil (B,)
l Edible scove ground 2.5E-03 4.2E-03 1.4 E-02 4.oE-03 j
Potatoes 2.5E-o3 4.2E-03 3.oE 4.oE-03 Other below ground 2.3E-03 4.2E-03 1.4 E-02 4 oE-03 Pasture grass 2.5 E-03 4.2E-43 1.8E-02 2.8E-02 Stored feed (hav) 2.5E-03 4.2E-03 8.2E-02 3.6E-02 8eef/ feed (73), pO/kg per pCi/ day 3 4E-04 2.0E-04 5.1E-04 7.1E-04 Milk / feed (7,,,,), pC/hter per pci/ day 6.1E-04 5.oE-06 5.9E-04 1.2E-04 i
Source: U.S. Nuclear Regulatory Commission, Ca!cularena Models for Estimating r
Pa&ation Doses to Man from Airborne Ratlocactwe Matersals Resulting from Uranium OperaDons. Task RH Bo24. May 1979.
I
i e
B-11 B.3.4 Meat concentrations Padioactive materials can be deposited on grasses, hay, or silage, which are eaten by meat ar.imals, which are in turn eaten by man. It has been assumed that meat animals obtain their entire feed requirement by grazing six months per year and by eating non locally grown stored feed the remainder of the year. The equation used to estimate meat concentrations is C3g = GT3g(0.33C
+ 0.0Cht),
(B-9) where C.,i is the concentration of-isotope i in pasture grass, pCi/kg; n
hi is the concentration of isotope i in hay or other stored feed, pCi/kg; C
3g is the resulting concentration of isotope i in meat, pC1/kg; C
3g is the feed-to-meat transfer factor for isotope 5, pCi/kg per pCi/ day jee Table B.5);
E Q is the assumed feed ingestion rate 50 kg/ day; 0.33 is the fraction of the total annual feed requirement assumed to be satisfied by pasture grass; 0.0 is the fraction of the total annual feed requirement assumed to be satisfiea by locally grown stored feed (hay).
The equation used to estimate milk concentrations from cows ingesting contaminated feed is C,9 = QF,9 (0.33 Cpgg + 0.0 Chi)
(B-9a) where C,4 is the resulting average concentration of radionuclide 1 in milk, in pCi/I; and Fmi is the feed-to-milk transfer coefficient for radionuclide i, in pC1/2 per pCi/ day ingested (See Table B.5)
B.4 DOSES TO INDIVIDUALS ~
2 Coses to individuals have been calculated for inhalation, external exposure to air and ground concentrations, and ingestion of vegetables and meat. Internal doses are calculated by the staff using dose conversion factors that yield the 50-year dose cornitment, that is, the entire dcse insult received over a period of 50 years following either inhalation or ingestion. Annual doses given are the 50-year dose commitments resulting from a one-year exposure period. The one-year exposure period was taken to be the final year of mill operation when environmental concentrations resulting from plant operations are expected to be near their highest level.
B.4.1 Inhalation doses Inhalation doses have been computed using air concentrations obtained by Eq. B-3 (resuspended air concentrations are included) for particulate materials and the dose conversion factors presented in Table B.6 (refs.1 and 7). _
Doses to the bronchial epithelium from raden-222 and short-lived daughters were computed based.
on the assumption of indoor exposure at 100% occupancy. The dose conversion factor for bronchial epithelium exposure from radon-222 is derived as follows:
1.
1 pC1/m3 of raden-222 = 5 x 10-5 working level (WL),*
2.
continuous exposure to 1 WL = 25 cumulative working level months (Ni) per year, 3.
1 WLM = 5000 millirems.e "One WL concentration is defined as any combination of short-lived radioactive decay products of radon-222 in 1 liter of air that will release 1.3 x 105 MeV of alpha particle energy during their radioactive decay of lead-210.
l e
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N O en af laa e, e4 N 9 en en me me e.
N O.ea ena de es eJ NO as as e, m. as N 5 deasasasas e S e og m.a p 9 e== N O N g g e a e e e =80 eeeeeNe 0 9 9 a e e *=
T S ? y e=
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& 4 e e o e e 86 8 e *
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== 0
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-e S
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S O N 8%s== N 4 O N N== N O 3 N N== N 8 O N se== N O O N==== 8%S 83 eOOOOO S9OOOce S S 33940 S900000 O 9000OO
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3 e e e e o e 2 9 e * * *
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e est m e e a=
a est est e est se a g y N y==
8 et est p.- a se e
ass 0
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C e N apt est *ts se e N - est egg est e N M art N set e== msg N N su a
- O
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=a 4 est eoeee+
ast g**e e, est eee***
sat g+++,e est g s.
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9 e se e e em 3 0 e em em== p est e9 Z 5 08% 9 88% W6 889 19eeNee Z 0 3 4 88% O O 1 9 8m 83 >=== em 1 4 C
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9 9 se & N W
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9 6 3e e o e ee 30 e e e ee 3e e oe o e 3e e e e e e 39 e p==== O J89 0 e *= ** O==
e se=*** O S S 9*== s*e @ est 8
0 8
0 9
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S S
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9 889 9 9
9 &
G 4 S S e8 ee ene e ins 9 as S ins 9 eaa e N D Pe 9 D.e 4 e.e G
=
- 8 p
ee 8 ee 0 ee 0
- 8 S
i o
o B-13 Therefore, (1 pC1/m2 of radon-222) 5 x 10-5 25 y 5000 *i.$'*5
= 0.625 millirem ;
thus the radon-222 bronchial epithelium dose conversion factor is taken to be 0.625 millirem year-1 pCi-1 m-3 B.4.2 External doses External doses from air and ground concentrations are computed using the dose conversion factors provided in Table B.7 (ref.1). Doses were computed based on 100% occupancy at the particular location. Indoor exposure was assumed to occur 14 hr/ day at a dose rate of 70% of the outdoor dose rate.
B.4.3 Incestion doses Ingestion doses have been computed for vegetables, meat, and milk. Ingestion doses reported are based on concentrations obtained using Eqs. B-8 and B-9. ingestion rates given in Table B.8. and dose conversion factors given in Table B.9 (ref.1 and 9). Vegetable ingest computed assuming an average 50% activsty reduction due to food preparation.jon doses were Ingestion doses to infants. children and teenagers were c3mputed but found to be equivalent to or less than doses to adults.
Table 8.7. Dese converson factors for external esposure Isotope -
skin Whole body Dose factors for aoses from air concentrations.
millirem vur*' pCi m'3 4 236 1.oSE-05 1.57E-06 h 234 6.63E- 05 5.24E-05 Pa 234 8.578 05 6.64E 05 U 234 1.36E-oS 2.49E-06 4 23o 1.29E-09 3.59E-o6 Ra-226 6.coE-05' 4.9eE-05 Rn-222 3.46E-to 2.83 E-06 4218 8.18E-07 6.34 E-07 Pt>214 2.o6E-03 1.67E-03 Bi-214 1.36 E-02 1.16 E-02 Po 214 9.89E-07 7.66E-07 N21o 4.17E-05 1.43E-05 Dose factor for doses fro n ground concentrations /
millirem year oCi m-2 U238 2.13E-06 3.17 E-07 T4234 2.loE-06 1.66E.06 Pe234 1.6cE-06 1.24 E-06 tJ234 2.SoE-06 4.78E-07 TN230 2.2oE-06 6.12E-07 4 226 1.16E-06 9.47E-07 Rn.222 6.15E-08 5.o3E-0E 6 218 1.42E-08
- 1. toe-08 N 214 3.89E-oS 3.16E-05 8i-214 2.18E-04 1.85E-04 6 214 1.72E-08 1.33E-08 N21o 6.65E-06 2.27E-06 I
i
i e.
e B-14 Table B.S. Assumed food inpstion rates.* kg/ year Infant Child Teen Adult f
Vegetables 0.0 47.8 76.1 105 Edible above ground 0.0 17.3 28.9 39.9 Potatoes 0.0 27.2 42.2 60.4 Other below ground 0.0 3.3 5.0 5.0 Heat (beef and lamb) 0.0 27.6 44.8 78.3 Milk (liters / year) 208.0 208.0 246.0 130.0
'legastion rates are averages for typical rural farm households. No allowance is credited for portions of year when locally or home grown food may not be avadable.
Source-U.S.
Nuclear Regulatory Commission. Cs/culational Models for Estimarrng Radiaroon Ooses to Man from Airbome Radioactiw Materials Resulting from Uranium Milling Operations.
Task RH 802 4. May 1979.
Table 8.9. Ingestion dose conversion factors, mdlirems/pci.ingessed Age group Organ U-238 B234 Th.234 Th 230 Ra 226 Pt>210 Bi-210 Po 210 Infant Who#e body 3.33E-04 3.80E-04 2.00E-08 1.06 E -.04 1.07 E-02 2.38E-03 3.58E-07 7.41E-04
- Bon, 4.47 E-03 4.88E-03 6.92E-07 3.80 E-03 9.44E-02 5.28E-02 4.16E-06 3.10E-03 Uver 0
0 3.7 7 E-08 1.90E-04 4.76E-05 1.42E-02 2.68E-05 5.93E-03 Kidney 9.28E-04 1.06E-03 1.39E-07 9.12E-04 8.71 E-04 4.33E-02 2.08E-04 1.26E-02 Osild Whole body 1.94 E-04 2.21 E-04 9.88E-09 9.91E-05 9.87E-03 2.00E-43 1.69E-07 3.67E-04 Bone 3.27E-03 3.'57E-03 3.42E-07 3.55E-03 8.76E-02 4.75E-02 1.97E-06 1.52E-03 Uver 0
0 1.51 E-08 1.78E-04 1.84 E-05 1.22E-02 1.02E-05 2.43E-03 Kidney 5.24 E-04 5.90E-04 8.01 E -d'3
&67E-04 4.88E-04 3.67E-02 1.15E-04 7.56E-03 Teenager Whole body 6.49E-05 7.39E-05 3.31 E -09 6.00E-05 5.00E-03 7.01E-04 5.66E-08 1.23E-04 Sone 1.09E-03 1.19E-03 1.14E -07 2.16E-03 4.90E-02 1.81E-02 6.59E-07 5.09E-04 Uver 0
0 6.68f -09 1.23E-04 8.13 E-06 5.44E-03 4.51E-05 1.07E-03 Kidney,
2.50E-04 2.85E-04 3.81E 4 5.99E-04 2.32E-04 1.72E-02 5.48E-05 3.60E-03 Adult Whole body
- 4.54E-05 5.17E-05 2.13E-09 5.70E-05 4.60E-03 5.44E-04 3.96E-08 8.59E-05 Bone 7.67 E-04 8.36E-04 8.CI E-08 2.06E-03 4.60E-02 1.53E-02 4.61E-07 3.56E-04 Uver 0
0 4.71E-09 1.17E-04 5.74E-06 4.37E-03 3.18E-08 7.56E-04 Kidney 1.75 E. 04 1.99E-04 2.67E-08 5.65E-04 1.63E-04 1.23E-02 3.83E-05 2.52E-03 l
l t
~
e,
e 8-15 REFERENCES FOR APPENDIX B 1.
'4. Momeni, Y. Yuan, and A. J. Zie1en, O.e traniw-Dispersicn and Desimetr4 (LTat:) Code, Rep >rt NUREG/CR-0553, ANL/ES-72. Argonne National Laboratory, May 1979.
2.
Gu1f Mineral Resources Co., Prevention of Significant Detericration Application, Mt.
Taylor Uranium #f!I Project, New Mexico, March 1979.
3.
U.S. Nuclear Regulatory Comission Generio Ihvironmental Irpast Statement on Umnium uf1 Zing, Report NUREG-0511 April 1979.
4.
U.S. Nuclear Regulatory Comission, CaIeuZatier.a1 Nodels for Isticating Radiation Doses to Man frcn Airbcrne Radioactive Materials Resulting from Urantun Hilling Opentions, Task RH 802-4, May 1979.
5.
D. C. Kocher, Mieur Decay Data for Radic:uclides Dec:aring in Routine Peteases frcm N; ear 5%st cycle reciZities, Report ORNL/NUREG/TM-102, Oak Ridge National Laboratory.
August 1977.
6.
J. F. Fletcher and W. L. Dotson (compilers). EIR'ES - A Digital Cc9puter Code for Esti-matina Re2ional Radiological Effects frort the Mlear Pouer Industry, Report HEDL-TME-78-168. Hanford Engineering Development Laboratory, December 1971.
7.
D. R. Kaikwarf, Solubility C:assificatien of Airborne Products fron Uranium cres and Taf;fngs PfIes, Report NUREG/CR-0530 PNL-2830, Pacific Northwest Laboratory, January 1979.
8.
National Academy of Sciences-National Research Council, N.s Effects on PeguZations of E:pceure to Lcv Levels of Iontaing Radiaticn, Report o Biological Effects of Ioniaing Radiation (BEIR Report)f the Adviscry Co-rittee cn the U.S. Government Printing Office, 1972.
9.
G. R. Hoenes and J. K. Soidat, Age-S esific Radiation Cces Ccn;ersion Fa:tcre for a Cne-Iaar Chronic Intake, Report NUREG-0152 prepared by Battelle Pacific Northwest Laboratories.
e 4
6 Y "ad,
...-~.m,.
g
Appendix C CALCULATION OF GAMMA RADIATION ATTENUATION FOR RECLAIMED TAILINGS TRENCHES Assuming soil to be composed mainly of SiO, the mass attenuation coeff'cient 2
for a 1-to 2-MeV gamma ray is 0.0518 cm /g.1 (Most of the dose rate from a 2
typical natural emitter is in this range.2) Assuming the gamma radiat'on from the uncovered tailings pile to be approximately 12 R/ year (same as for the Bear Creek project) and the bulk density of the soil to be 1.6 g/cm, the 3
effect of the 16 m (52 ft) of soil materials proposed would reduce tre gamma radiation to approximately 1.07 x 10 ss R per year.
I/I = exp[-(pen /p)px] = exp[-(0.0518 cm /g)(1.6 g/cm )(1585 cm)]
2 a
g
= 8.92 x 10 ss.
I = (8.92 x 10 ss),12 R/ year) = 1.07 x 10 se R/ year.
The area's background t-adiation dose from all sources of radioactivity, including the contribution from fallout, is approximately 147 mR/ year.3 Thus, the gamma radiation from the deposited tailings after reclamation would be insignificant compared to the natural background radiation.
' - ~
~~
~
REFERENCES FOR APPENDIX C U.S. Department of Health, Education, and Welfare, Radiological Health s.
Handbook, U.S. Government Printing.0ffice, Washington, D.C., January 1970, p. 139.
2.
H. May and L. D. Marinelli, " Cosmic Ray Contribution to the Background of Low Level Scintillation Spectrometry," Chap. 29 in The Natural Radiation Environment, J. A. S. Adams and W. M. Lowder, Eds., University of Chicago Press, Chicago, 1964.
3.
Gulf Mineral. Resources, Co., " Environmental Report, Mt. Taylor Uranium Mill Project, New Mexico." Volume 2, Section 2.9.
l C-1
-_,9
~
e Appendix D CALCULATIONS OF REQUIRED THICKNESS OF COVER MATERIALS Introduction As a result of milling operations, tailings are deposited in trenches and buried with soil cover.
Most of the radionuclides would not be subject to airborne emission under a relatively thin cover of soil.
However, radon gas does escape from the tailings trenches by diffusion through the pore spaces.
The mechanism is more fully _ developed in the Generic Environmental Impact Statement on Uranium Milling (GEIS) published by the NRC staff.1 Based on recent findings of NRC research studies (Ref. 2) the most significant factor af fecting the radon attenuation prcperties of soil covers is the ar. aunt of moisture retained by the soil.2 The model used herein to estimate the radon flux is that proposed in Appendix P of the GEIS.1 Calculation of Bare Tailings Radon Flux Although the tailings may still be fairly moist (15%-40% moisture) after reclamation, the NRC staff estimates that it would be unrealistic to assume that these levels of moisture would be maintained over a long period of time.
Based on an assumption of 8% residual moisture (dry tailings), the bare tailings flux is calculated using the approach outlined in Appendix P of the GEIS1:
J
=C p
E 4 A O /P (I) g Ra t t where J6 radon-222 flux at the' surface of the bare tailings
=
2 i
(pCi/m -sec)
C, concentration of radium-226 in the tailings solids (pCi/g)
{
=
g l
density of the tailings solids (g/cm )
p
=
3 E
=
emanating power of tailings (dimensionless)
D effective bulk diffusion coefficient for radon from the
=
I tailings solids (cm /sec) 2 Pt Porosity for tailings solids (dimensionless)
=
A
=
decay constant for radon-222 (2.1 x 10 8 sec 1) 1 The following parameter values were selected to model the long-term conditions for the Mt. Taylor Mill tailings disposal trenches:
CRa 1332.02 pCi/g
=
1.6 g/cm3 p
=
D-1
E 0.20
=
'D /P
=
2 t g 0.0131 cm /sec (assuming tailings sand has 8% residual 2
moisture )
Given these parameter values, the bare tailings radon flux is J,
706.98 pCi/m -sec.
=
2 Calculation of Cover Requirements 4
The thickness of cover materials required to attenuate the radon flux to the proposed flux limit of 2 pCi/m -sec (ref. 1) is primarily dependent upon the 2
bare tailings flux and the moisture retention capacity of the cover material used.
Based on site specific information,3 the cover material should retain about 8% moisture levels.
Thus, the diffusion coefficient for the cover attenuation was chosen to reflect this residual moisture content.
The equation for calculating the radon flux from the covered tailings disposal trenches is (refs. 1 and 2):
J = J, exp ( - 4 A / (D,/P) x )
(2) where
~ ~
~ ~ '
~
J
=
radon flux from the surface after attenuation by cover material (pCi/m -sec) 2 J,
bare tailings flux.(pCi/m sec)
=
2 i
D
=
alternate diffusion coefficient of cover material a
2 (cm /sec) (ref. 2) l P
=
porosity of the cover material (dimensionless)
A
=
decay constant for radon-222 (2.1 x 10 8 sec 1) depth of the cover material (cm)
X
=
The value based on 8% moisture for the diffusion is D,/P = 0.0131 cm /sec (ref. 2) 2 Since the proposed depth of cover is 52 ft. (1585 cm), then D,/P I,/p D
(ref. 2).
No depth adjustment is necessary,* and thus D,/p = 0.0131 cm /sec.
2
- See Fig. 5.6 of ref. 2.
D-2
4e b
Using the bare flux computed, the depth required to meet a flux of 2 pCi/m -sec 2
can be obtained from the following rearrangement of Eq. (2):
- 4 (0 /P)/A - (in J/J ) - (0.03281)
(3) x =
3 g
where depth of cover in feet x =
and 0.03281 converts em to feet Solving for x:
x = - 4 (0.0131cm /sec)/(2.1x10 6sec 2) z In [ (2 pCi/m -sec)/(706.98 pCi/m -sec) ]-(0.03281) 2 2
15.21 feet x
=
REFERENCES FOR APPENDIX D 1.
U.S. Nuclear Regulatory Agency, Draft Generic Eraironmental Impact Statement on Uranium Milling, Report NUREG-0511, April 1979.
2.
Ford, Bacon & Davis Utah, Inc., Characterization of Uranium Tailing Cover Materials for Radon Flux Reduction, Report NUREG/CR-1081, FBDU 218-2, January 1980.
3.
Woodward-Clyde Consultants," Evaluation of Alternative Tailings Management Methods, Mt.' Taylor, New Mexico," Mt. Taylor Uranium Mill Project, Gulf Mineral Resources, Co., Appendix B, April 1978, Waste WM-26.
l D-3 l
l l