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Forwards Final Radiological Assessment of Dawn Mining Co U Mill to Document Technical Assistance Being Provided in Connection W/License Renewal.Revisions Made Per 820129 & 0305 Comments.Revised Computer Printout Encl
	ML20054F320
Person / Time
Issue date:	06/01/1982
From:	Scarano R; NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Strong T; WASHINGTON, STATE OF
References
	REF-WM-33 NUDOCS 8206160079
	Download: ML20054F320 (39)
	v • d • e

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gg WMUR:DMG JLinehan WM_33 HPettengill REBrowning Mr. T.R. Strong, Head JBMarti o o

S Radiation Control Section Department of Social and Health Services 8

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State of Washington 4 ' O.s

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Olympia, Washington 98504 f

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Dear Mr. Strong:

Ng In response to your technical assistance request, enclosed is 6hstaff D

I[

radiological assessment of the Dawn Mining Company Uranium Mill 'e9 347 to the license renewal review.

This is the final version of the a

report, which was submitted to you for comment on November 16, 1981.

We have received your coments and additional information transmitted to us by letters dated January 29, 1982, and March 5, 1982.

Based on your comments and on more recent site-specific data you have provided, the followir.g revisions to the draft assessment have been made (selected pages of the revised input information from the revised computer printout are attached):

a.

Correction of the geographical location specified for the town of Ford, Washington.

b.

Update of emission control factors to reflect the most recent available information from the Department of Social and Health Services (DSHS) on progressive tailings management plans and actual stack sampling data.

c.

Update of normalized release rates used in the draft, to reflect the most recent technical information available.

d.

The actual nearest residence was not included in the tables of the assessment, since it was not shown by the analysis to be a critical receptor.

However, a copy of the analysis results at this receptor location has been attached for your information.

In addition, please note that we have revised Appendix B to a shortened format recently adopted by our staff. Details pertaining to the DIST:

TICKET NO:

8206160079 820601 PDR WASTE 0FC

_____[_.

WM-33 PDR

,___j____________,___________j,___________j_,_________

NM1E :

DATE :82/05/27 hY

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33/DMG/82/05/17/0 JJN I 1982

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methodology for transport, deposition and resuspension mechanisms, as / ),

i wellastheequations,tablesandassumptionsusedforconcentrationandf dose calculations are available in published applicable regulatory ~ ',

guides and NUREG documents, which are referenced. These revisions.to thh draft assessment have been previously discussed between Mr. G. Gnugno,1100my y L!

7 staff and Mr. D. Peterson of OSHS in a May 17, 1982 telephone

'. c i

conversation.

Based on this discussion, Mr. Peterson concluded 'that we \\'

S have adequately addressed the DSHS ' comments on the draft assessm(nt.

4 As discussed in our telephone conversation on January 15, 1982,'my staff will be available to respond to questions and participate in public hearings in support of this technical evaluation.

In addition, since T

our word processing systems are not compatible, we will provide, at your request, editorial assistance in making minor modifications you find W,

necessary in adapting the assessment to your environmental statement.

q Shoula you have any questions on this submittal, 91 ease do not. hesitate to contact Mr. D. Gillen of my staff (301-427-4538).

0!! tnal S$8netys 8

R. A. Scar'ag Ross A. Scarano, Chief Uranium Recovery Licensing Branch Division of Waste Management l

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4

FINAL RADIOLOGICAL ASSESSMENT OF THE DAWN MINING COMPANY URANIUM MILL FORD, WASHINGTON MAY, 1982 PROJECT WM-33 PREPARED BY THE U.S. NUCLEAR REGULATORY COMMISSIE.

WASHINGTON, D.C.

FOR THE DEPARTMENT OF SOCIAL AND HEALTH SERVICES STATE OF WASHINGTON TO DOCUMENT TECHNICAL ASSISTANCE BEING PROVIDED IN CONNECTION WITH THE LICENSE RENEWAL i

4-1 4.

RADIOLOGICAL ASSESSMENT

4.1 INTRODUCTION

This section presents the NRC staff's assessment of the radiological impacts of the Dawn Uranium Mill for license renewal of the facility.

An assessment was recently performed to evaluate the impacts of the new below grade tailings impoundment.

Since the completion of that assessment, more information has become available relating to the operational plan of the mill (Ref. 1, 2, 3, 4).

For this reason, the values presented here in the various tables are different from those in the previous assessment of the new tailings impoundment.

Major components of the staff's evaluation documented here have included detailed assessments of the following:

(1) annual releases of airborne radio-active materials from the mill and all tailings storage areas; (2) resulting incremental radioactivity concentrations in air and in other environmental media; and (3) resulting incremental radiation dose commitments to individuals and populations.

The calculated results are compared to natural background radiation exposures and applicable regulatory limits.

All potential airborne exposure pathways likely to contribute a significant fraction of total expo-sures have been included in the analysis.

Dose commitments resulting from all releases are presented and discussed.

The values presented for the annual emission rates and annual dose commitments represent the year of highest expected radioactive emissions from operation.

The NRC staff understands that Dawn Mining Company is planning to cover greater portions of the inactive tailings areas, thus reducing impacts from annual emissions.

As a calculational analysis, the results of this evaluation are dependent upon, and sensitive to, values chosen for the many necessary input parameters.

Changes in input parameter values used in this assessment would necessarily result in changes to the calculated results.

Significant modifications to the Dawn facility's design or mode of operation, which would affect the assumptions made here concerning effluent releases, would necessitate a revised analysis to confirm or qualify the conclusions drawn here.

Additionally, the results of the complex mathematical analysis presented here have inherent levels of uncertainty which are difficult to quantify.

4.2 ESTIMATED RADI0 ACTIVITY RELEASES This assessment is based on an evaluation of radioactivity releases from the various components of the entire Dawn facility during the year of expected highest radioactive emission from the operation.

Incrementai annual dose commitments due to releases are predicted to be highest during this year.

The basic information, data, and assumptions used to estimate radioactivity releases are summarized in Table 4.1.

The estimated release rates contributed by each

4-2 Table 4.1 Principal Parameter Values Used in the Radiological Assessment of the Dawn Mining Company Uranium Project Parameter Value(s)*

A.

General Data Average ore grade, % Ua0s 432.0 0.153 Ore concentration, pCi/g U-238 and daughters 3

Ore processing rate, MT/d 430.0 Days /yr operational 346 B.

Ore Storage Pile (s) i Actual area, acres 13.6 Annual average dust loss rate, g/m yr 42.0 i

2 Dust / ore activity ratio 2.5 l

Reduction factor for chemical spraying and wetting, %

50.0 Release rate for truck dumping and ore pad activities, %

3.3 x 10 8 Specific Rn-222 flux from ore piles, h*2[226 1.0 l

l C.

Hoppers and Feeders l

Release rate for ore feeding, %

1.15 x 10 3 Dust / ore activity ratio 2.5 Reduction factor for dust control, %

85.0 i

Fraction of Rn-222 equilibrium ore content released, %

20.0 D.

Crushing and Grinding Release rate for crushing and grinding, %

8.0 x 10 8 Efficiency of particulate loss control, %

91.0 i

Dust / ore activity ratio 2.5 Fraction of Rn-222 equilibrium ore content released, %

20.0 E.

Fine Ore Storage Release rate for fine ore activities, %

4.6 x 10 8 Efficiency of particulate loss control, %

75.0 Dust / ore activity ratio 2.5 Fraction of Rn-222 equilibrium ore content released, %

20.0 See footnotes last page of table.

4

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Parameter Value(s)*

F.

Yellowcake Drying and Packaging Yellowcake production rate, MT/ year 214.0 Release rate of yellowcake product to atmosphere, kg/hr 1.16'x 10 8 Activity ratio of Th-230 to U-238 in yellowcake 0.5 Activity ratio of Ra-226 to U-238 in yellowcake 0.1 Activity ratio of Pb-210 to U-238 in yellowcake 0.1 Yellowcake purity, %

79.0 E.

Tailings Impoundment System General parameters Fraction Th to tailings, %

99.5 Fraction Ra and Pb to tailings, %

99.9 2

Annual average dust loss rate, g/m yr 420.0 Dust / tails activity ratio 2.5 Dusting reduction factor for water cover, moisture, and chemical agents, %

80.0 Specific Rn-222 flux from exposed beach, 2

pCi/m -sec 1.0 pCi/g Ra-226 i

Abandoned tailings impoundment l

Total area, acres 59.2 Dust reduction factor from progressive reclamation, %

97 - 100 Fraction U to tailings, %

9.2 Tailings activities, pCi/g U-238 62.1 Th-230 672.

Ra-226 674.

Pb-210 674.

Inactive tailings impoundment Total area, acres 47.0 Fraction U to tailings, %

6.0 Reduction factor of dust loss by chemical stabilization, wetting and progressive reclamation, %

80.0 - 100.

Tailings activities, pCi/g U-238 40.5 Th-230 672.

Ra-226 674.

Pb-210 674.

See footnotes last page of table,

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4-4 Table 4.1 (Continued)

Parameter Value(s)*

Below grade tail;r,gs impoundment Total area, acres 27.2 Fraction of U to tailings, %

6.0 Reduction factor of dust loss by water cover, and below grade disposal, %

99.0 Tailings activities, pCi/g U-238 25.9 Th-230 430.

Ra-226 432.

Pb-210 432.

Parameter values presented here are those selected by the NRC staff for use in its radiological impact assessment of the Dawn Mining Company uranium mill project. Whenever possible, these values are based on information submitted by the Dawn Mining Company and the State of Washington's Department of Social and Health Services (Refs. 1, 2, 3, 4).

In instances where avail-able data have been insufficient and/or not specific, reasonably conservative estimates have been made.

4-5 facility component are presented in Table 4.2.

This table is based on the assumption that releases from the new below grade tailings impoundment will continue to be controlled by water cover and below grade protection against windblown dusting, such that 99 percent of potential releases will be abated.

More detailed information pertaining to the evaluation of radioactivity releases is provided in Appendices A and B.

4.3 EXPOSURE PATHWAYS Potential environmental pathways by which people could be exposed to radioactive materials resulting from the project are presented schematically in Figure 4.1.

The pathways of concern for the airborne effluents include inhalation of radioactive materials in the air, external' exposure to radio-active materials in the air or deposited on the ground, and ingestion of contaminated food products (vegetables, meat and milk).

4.4 RADIATION DOSE COMMITMENTS TO INDIVIDUALS The estimated radiation dose at each individual receptor depends on the distance and direction of the receptor with respect to each of the sources, as well as the wind directional frequency toward the receptor from each of the sources.

The dose decreases with distance as the radioactive particulates are dispersed and depleted by deposition, and their concentration decreases.

The direction of the reference point with respect to the mill is important because the average concentration of particulates is higher downwind.

Prevailing winds in the site vicinity are out of the SSW and SW sectors (see Appendix B Table B.2).

The most critical nearby receptor is located 0.41 miles (0.66 km) NNW of the mill, and the nearest residence in the prevailing wind direction is 0.53 miles (0.86 km) NE of the mill.

There is a closer residence to the mill, however impacts at this location were found to be lower than those presented here, because the location is infrequently downwind from the sources.

In addition, the licensee has reported the location of a residence in the prevailing wind direction 0.62 miles (1.0 km) ENE of the mill.

This location was also assessed and impacts are presented.

The nearest population center is Ford, Washington 0.99 miles (1.60 km) ENE of the mill.

Table 4.3 presents the calculated annual dose commitments received by people living at these locations.

For each of these locations, it was assumed that individuals would have access to, and consume as part of their normal diet, vegetables grown locally at the residence and beef fed by grazing in an area approximately 0.4 km N of the mill.

Due to the scarcity of information on consumption of locally produced milk, it was conservatively assumed that a local milk ingestion pathway existed at each nearby location.

4.5 RADIATION DOSE COMMITMENTS TO POPULATIONS The annual 100 year environmental dose commitments received by the (regional) population within 50 miles (80 km) of the site are presented in Table 4.4.

4-6 Table 4.2 Estimated Annual Releases of Radioactive Materials Resulting from the Dawn Mining Company Uranium Project

Annual releases, Curie / year **

Release source U-238 Th-230 Ra-226 Pb-210 Rn-222 Ore storage 3.74E-03t 3.74E-03 3.74E-03 3.74-03

-7.50E+02 Hopper and feeders 2.78E-04 2.78E-04 2.78E-04 2.78E-04 1.29E+01 Grinding and crushing 1.16E-03 1.16E-03 1.16E-03 1.16E-03 1.29E+01 Fine ore storage 1.85E-03 1.85E-03 1.85E-03 1.85E-03 1.29E+01 Yellowcake stackstt 2.18E-03 1.09E-05 2.18E-06 2.18E-06 0.0 Tailings impoundments Abandoned pile 4.75E-04 5.14E-03 5.16E-03 5.16E-03 5.10E+03 Inactive pile 8.05E-04 1.34E-02 1.35E-02 1.35E-02 2.03E+03 Below grade pile 2.99E-05 4.96E-04 4.98E-04 4.98E-04 1.50E+03

Releases are based on estimates for the most critical year of mill operation (1983).

- Releases of all other isotopes in the U-238 decay series are also included in the radiological impact analysis.

These releases are assumed to be identical to those presented here for parent isotopes.

For instance, the release rate of U-234 is taken to be identical to that for U-238.

Release rates of Pb-210 and Po-210 are assumed equal to that given for Ra-226.

tThe notation 3.74E-03 is read as 3.74 x 10 3 or 0.00374.

ftYellowcake stack releases are based on actual stack sampling data collected by Dawn Mining Company - (See Refs. 1, 2 and Appendix A).

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4-8 Table 4.3 Annual Dose Commitments to Individuals in the Vicinity of the Dawn Mining Company Uranium Mill (mrem / years)

Exposure Whole Bronchial Location Pathway

Body Bone Lung Epithelium Nearest resident Inhalation **

0.18 5.07 7.33 246.

in prevailing External ground 4.07 4.07 4.07 4.07 wind direction External cloud 0.44 0.44 0.44 0.44 0.9 km NE Ingestion-Vegetable 1.09 13.0 1.09 1.09 Heat #

0.27 3.41 0.27 0.27 Milk 0.27 2.81 0.27 0.27 Total 6.32 28.8 13.5 252.

Nearby resident Inhalation **

0.22 6.17 9.79 361.

0.7 km NNW External ground 4.17 4.17 4.17 4.17 External cloud 0.51 0.51 0.51 0.51 Ingestion Vegetable 1.07 12.7 1.07 1.07 Meat #

0.27 3.41 0.27 0.27 Milk 0.26 2.76 0.26 0.26 Total 6.50 29.7 16.1 367.

Nearby resident Inhalation **

0.13 3.64 5.19 217.

1.0 km ENE External ground 2.98 2.98-2.98 2.98 External cloud 0.46 0.46 0.46 0.46 Ingestion Vegetable 0.81 9.69 0.81 0.81 Meat #

0.27 3.41 0.27 0.27 Milk 0.20 2.10 0.20 0.20 Total 4.85 22.3 9.91 222.

Nearest town, Inhalation **

0.05 1.36 1.88 113.

Ford, Washington External ground 1.27 1.27 1.27 1.27 1.6 km ENE External cloud 0.43 0.43 0.43 0.43 Ingestion Vegetable 0.33 3.92 0.33 0.33 Meat #

0.27 3.41 0.27 0.27 Milk 0.08 0.85 0.08 0.08 Total 2.43 11.2 4.26 115.

See footnotes last page of table

4-9 Table 4.3 (Continued)

Doses are integrated over a 50 year period from one year of inhalation or ingestion.

- Doses to the whole body, lungs, and bone are those resulting from the inhalation of particulates of U-238, U-234, Th-230, Ra-226, Pb-210, and Po-210.

Doses to the bronchial epithelium are those resulting from the inhalation of radon daughters.

Ingestion doses result from the consumption of the meat of cattle grazing 0.4 km N of the mill.

l I

.4-10

' Table 4.4 Annual Environmental Dose Commitments to the Regional

. Population Within a 50-mile Radius Resulting from the Dawn Mining Company Uranium Mill Ar.nual Environmental Dose Commitments (EDC), person-rem / year

Exposure Pathway Whole Body Bone Lung Bronchial Epithelium **

Inhalation 0.14 4.30 1.85 254.

External from ground 0.65 0.65 0.65 0.65 External from cloud 3.94 3.94 3.94 3.94 Vegetable ingestion 3.93 67.4 3.93 3.93 Meat ingestion 0.14 2.54 0.14 0.14 Milk ingestion 0.23 2.89 0.23 0.23 Total 9.03 81.7 10.7 263.

Estimated population dose from natural background 53,800 70,700 54,300 241,000 Ratio of total annual regional population dose to that from natural backgroundt 0.0002 0.0012 0.0002 0.0011

Doses to the whole body, lung, and bone are those resulting from the releases of particulates of U-238, U-234, Th-230, Ra-226, and Pb-210.

Inhalation doses to the bronchial epithelium are those resulting from the inhalation of radon daughters.

fBackground doses are based on the regional population size of 430,790 and background radiation doses presented in Reference 5.

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4-11 The population distribution data (Table 4.5), projected to the year 1990, were used to do the estimation.

Releases of radon gas yield radiological impacts which occur over a range of thousands of miles from a release source.

Annual impacts of radon releases from the facility that occur within 50 miles (80 km) of the site are listed in Table 4.4.

Impacts resulting from the entire life of the mill for both regional and extra-regional populations are given in Table 4.6.

Also listed in Table 4.6 are total impacts received by the continental population.

4.6 EVA'.UATION OF COMPLIANCE WITH REGULATORY LIMITS Dose commitments to individuals at the locations noted in Section 4.4 were cal-culated for the purpose of evaluating compliance with the limits specified by the U.S. Environmental Protection Agency's (EPA) 40 CFR Part 190, " Radiation Protection Standards for Normal Operations of the Uranium Fuel Cycle." 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 4.7 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 (Tsble 4.3) because contributions from radon-222 and its daughters have been omitted.

The 40 CFR Part 190 dose commitments are based on the most critical year of milling releases (1983).

However, this release scenario has a short-term dura-tion, since the inactive tailings impoundment will be totally covered by soil by 1985.

At this stage, the doses are expected to be significantly lower than those presented in Tables 4.3 and 4.7, and hence well within EPA standards.

As indicated in Table 4.7, calculated individual doses to the bone at the nearby residences achieve the 25 mrem per year limit.

However, it should be noted that over 75% of the calculated impacts at these locations are attributable to the ingestion pathway.

These calculations are directed toward identifying the maximal impact to individuals and therefore, are based on the assumption that all of the fresh beef, pork, lamb, vegetables, and milk consumed by the nearby population is locally produced.

A survey reported by the milling operator (Ref. 2) describes the food consumption pattern of residents within 1 kilometer of the Dawn mill.

This survey indicates that an individual would not likely be solely dependent on local food production as assumed by the analysis.

An individual's diet would more likely include significant guantities of commer-cially obtained foods not produced locally.

This would lead to much lower contributions from the ingestion pathway, and dose commitments would then be well within EPA standards.

In addition, while the predictive analysis indicates that doses reaching the EPA limit are possible, it should be emphasized that the analysis conducted provides a conservative indication of the potential dose commitments.

The inherent levels of uncertainty associated with this type of analysis are such that close evaluation of empirical data obtair.ed through environmental moni-toring should be used as the primary basis for actual compliance determinations.

D Table 4.5 Projected 1990 Population Distribution Mile Radius of the Dawn Mining Company Uranium Mill N

NNE NE Er E

ESE SE SSE S

SSW SW WSW W

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 3

3 10 10 3

6 5

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5 5

4.0- 5.0 5

16 16 16 5

31 21 21 21 10 5

5 16 10 10 5

5.0-10.0 52 52 31 26 52 52 31 31 21 52 16 16 21 10 10 10 10.0-20.0 52 105 52 210 105 52 52 31 52 52 21 52 441 52 21 21 20.0-30.0 105 278 52 970 970 1259 210 52 540 52 21 52 52 21 37 10 30.0-40.0 53 53 53 319 6462 9668 15193 14044 159 159 53 21 53 32 159 11 40.0-50.0 2242 11 11 319 3299 36614 187655 8050 159 159 1699 53 27 21 11 11 50.0-60.0 106 11 11 319 319 93360 10407 7551 159 53 212 382 27 11 11 11 4=

60.0-70.0 106 11 377 2273 106 3186 1062 262 159 32 552 159 106 11 11 11 1.

70.0-80.0 5236 11 11 1989 2210 2989 658 212 584 32 53 1179 212 11 11 11 ro 1.0-80.0 7970 564 656 6488 13561 147253 215320 30285 1895 626 2647 1929 975 194 306 121 4

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4-13 Table 4.6 Cumulative Environmental Dose Commitments (100 year) to Continental Populations from the Operation of the Dawn Mining Company Uranium Mill for 33 Years Total Environmental Dose Commitments. (EDC), Person-Rem Whole Body Bone Lung Bronchial epithelium EDCs received by the population within 80 km of the mill 284 2,580 338 7,820 EDCs received by the population beyond 80 km of the mill 2,330 31,400 526 10,700 Total EDCs received by the continental population 2,610 34,000 864 18,500 Fraction of background

2.07E-06**

2.70E-05 6.85E-07 2.94E-06

Background values estimated on the basis of year 1993 continental population of 382 million people, each person receiving 100 millirem / year to the whole body, bone, and lung and 500 millirem / year to_the bronchial epithelium.

- The notation 2.07E-06 denotes 2.07 x 10 6 or 0.00000207.

4-14 Table 4.7 Comparison of Annual Dose Commitments to Individuals with EPA Radiation Protection Standards (40 CFR 190)*

Calculated annual dose commitment (mrem / year)**

Location Exposure Pathway Whole body Bone Lung Nearest resident Inhalation 0.18 5.07 7.33 in prevailing External exposure 0.09 0.09 0.09 wind direction Ingestion 0.9 km NE Vegetable 1.09 13.0 1.09 Meatt 0.27 3.41 0.27 Milk 0.27 2.81 0.27 Total 1.90 24.4 9.05 EPA limit 25.0 25.0 25.0 Fraction of limit 0.04 0.98 0.36 Nearby resident Inhalation 0.22 6.16 9.78 0.7 km NNW External exposure 0.10 0.10 0.10 Ingestion Vegetable 1.07 1?. 7 1.07 Meatt 0.27 3.41 0.27 Milk 0.26 2.75 0.26 Total 1.92 25.1 11.5 EPA limit 25.0 26.0 25.0 Fraction of limit 0.08 1.00 0.46

(

Nearby resident Inhalation 0.13 3.63 5.19 1.0 km ENE External exposure 0.07 0.07 0.07 Ingestion Vegetable 0.81 9.68 0.81 Meatt 0.27 3.41 0.27 Milk 0.20 2.10 0.20 Total 1.48 18.9 6.54 EPA limit 25.0 25.0 25.0 Fraction of limit 0.06 0.76 0.26 See footnotes last page of table.

l l

i 4-15 1

i Table 4.7 (Continued) t I

Calculated annual-dose commitment (mrem / year)**

Location Exposure Pathway.

Whole body Bone Lung Nearest town, Inhalation 0.48 1.35 1.87 Ford, Washington External exposure 0.03 0.03 0.03 1.6 km ENE Ingestion Vegetable 0.33 3.91 0.33 Meatt 0.27 3.41' O.27 Milk 0.81 0.85 o0.81 Total 1.92 9.55 3.31 EPA limit 25.0 25.0 25.0 Fraction of Limit 0.08 0.38 0.13

40 CFR Part 190 excludes any contributions resulting from the releases of radon and its daughters.

- Dose commitments are based on most critical year of milling releases (1983).

l fMeat ingestion doses result from consumption of meat from cattle grazed 0.4 km N of the mill site.

i 4

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4-16 Table 4.8 Comparisons of Air Concentrations During Mill Operation with 10 CFR Part 20 Limits for Unrestricted Areas Total air concentrations, pCi/m, of radionuclides, 3

U-238 U-234 TH-230 Ra-226 Pb-210 WL*

i concentration 10 CFR Part 20 limits **

l 3.00E+00 4.00E+00 3.00E-01 2.00E+00 4.00E+00 3.33E-02 Restricted area boundary (0.3 km NE) 6.80E-03t 6.80E-03 7.51E-03 7.52E-03 7.51E-03 1.16E-03 Fraction of limit 2.27E-03 1.70E-04 2.50E-02 3.76E-03 1.88E-03 3.49E-02 Restricted area boundary (0.2 km W) 3.25E-03 3.25E-03 5.17E-03 5.18E-03 5.17E-03 1.47E-03 Fraction of limit 1.08E-03 8.13E-04

1. 72E-02 2.59E-03 1.29E-03 4.43E-02

WL denotes " working level." A one-WL concentration is defined to be any combination 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 1.3 x 105 Mev of alpha particle energy in their complete decay to Pb-210.

Predicted values given for outdoor air are those calculated on the basis of actual ingrowth from released Rn-222.

C* Values given are from 10 CFR Part 20, Appendix B, Table II, Column 1.

tThe notation 6.80E-03 denotes 6.80 x 10 3, or 0.0068.

l l

l

4-17 under 10 CFR Part 20, air concentrations in unrestricted areas are limited to maximum permissible concentrations (MPCs).

Table 4.8 presents the results of the staff's evaluation of compliance with 10 CFR Part 20 for calculated annual average air concentrations for selected restricted area boundary locations.

As indicated by the results presented in Table 4.8, there does not appear to be any problem in meeting the MPC limits specified in 10 CFR Part 20.

In addition to the locations evaluated in Table 4.8, other locations along the restricted area boundary were evaluated but were found to have lower computed average air concentrations.

4.7 OCCUPATIONAL RADIATION EXPOSURE Uranium mills are designed, built, and operated to minimize exposure of bnth 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 occupational 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 percent of the maximum permissible concentrations given in Appendix B of 10 CFR Part 20 and that external exposures are normally less than 25 percent of 10 CFR Part 20 limits (Refs. 6 and 7).

A recent review (Ref. 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,15 to 20 percent of the permissible exposure to ore dust, 25 percent of the permis-sible exposure to yellowcake, or 10 percent of the permissible 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 percent of the total permissible exposure.

4.8 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 (Refs. 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 within safe radiological protection limits for man, no adverse radiological impact is expected for resident biota.

4.9

SUMMARY

OF RADIOLOGICAL IMPACTS AND CONCLUSIONS This predictive analysis is based on reasonably conse ~st.ive assumptions and, for the annual estimated impacts, on the worst year of operation for release.

As previously stated, this worst release scenario is one of short duration.

4-18 In addition, information submitted by the applicant (Ref. 2) indicates that the predicted significant ingestion dore commitments are based on conservative assumptions regarding the consumption of locally produced foods.

Thus, the actual dose commitments are most likely within EPA standards.

Calculated impacts to the regional and continental populations are estimated to be small fractions of the contribution from natural background radiation.

Also estimated annual ambient air concentrations of radionuclides indicate that even at the highest level of expected releases, the mill appears to be in com-pliance with 10 CFR Part 20 NRC Radiation Protection Standards for unrestricted areas.

The results of this predictive analysis will be confirmed by comparison to the i

monitoring data collected by the operator.

Existing license conditions stipu-late that the operator conduct a comprehensive effluent and environmental radiological monitoring program.

These conditions require that the program meet minimum specifications as presented in U.S. NRC Regulatory Guide 4.14,

" Radiological Effluent and Environmental Monitoring at Uranium Mills," and in U.S. NRC Regulatory Guide 4.15, " Quality Assurance for Radiological Monitoring Programs (Normal Operations) - Effluent Streams and the Environment." The results of this monitoring program are reported to the State of Washington, Department of Social and Health Services at six-month intervals.

Moreover, the operator is required to conduct and document semi-annual land use surveys of the nearby er.vironment.

These surveys are reported to the State of Washing-ton on an annual basis.

Significant changes in regional population, grazing or land cultivation patterns near the mill would be included in a revised analysis, and could alter the conclusions in this assessment.

As an Agreement State, the State of Washington (Department of Social and Health Services) will continue to review the operator's future submittals to determine compliance with existing standards.

4-19 References 1.

" Principal Parameters for Radiological Assessment," Dawn Mining Company, May 1980.

2.

" Input Data for the Radiological Assessment of the Dawn Mining Company Uranium Mill," Newmont Services, Ltd., March 13, 1981.

3.

Letter from Robert R. Mooney, State of Washington, Department of Social and Health Services to Ross Scarano, U.S. NRC, January 29, 1982.

4.

Memorandum (with enclosures) from Don Peterson, State of Washington, Department of Social and Health Services to George Gnugnoli, U.S. NRC, March 5, 1982.

5.

" Descriptions of United States Uranium Resource Areas," a supplement to the Draft GEIS, Argonne National Laboratory, NUREG/CR-0597, ANL/ES-75, June 1979.

i 6.

B. R. Metzger, " Nuclear Regulatory Commission Occupational Exposure Experience at Uranium Plants," Conference on Occupational Health Experience with Uranium, Report ERDA-93, Washington, DC, 1975.

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.

5. 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 Sym)osium, Report LA4756, Los Alamos Scientific Laboratory, Los Alamos, i. Mex.,1971, and A Proposed Interim Standard for Plutonium, Report LA-5483-MS, Los ATamos Scientific Laboratory, Los Alamos, N. Mex.,1974.

10.

Enewetak Radiological Survey, USAEC Report NV0-140, Nevada Operations Office, Las Vegas, Nevada, 1973.

i 11.

N. A. Frigerio, K. F. Eckerman, and R. S. Stowe, " Background Radiation as a Carcinogenic Hazard," Rad. Res. 62:599 (1975).

12.

A. H. Sparrow et al., " Chromosomes and Cellular Radiosensitivity,"

Rad. Res. 32:915 (1967).

13.

Radioactivity in the Marine Environment, Report of the Committee on Oceanography, National Academy of Science-National Research Council, Washington, DC, 1971.

14.

R. J. Garner, " Transfer of Radioactive Materials from the Terrestrial Environment to Animals and Man," Environ. Control 2:337-85, 1971.

4-20 15.

S. E. Thompson, Concentration Factors of Chemical Elements in Edible Aquatic Organisms, USAEC Report UCRL-50564, Rev. 1, October 1972.

A-1 APPENDIX A CALCULATION OF SOURCE TERMS FOR MILLING OPERATIONS Introduction The radiological assessment for the operation of the Dawn Mining Co'npany Uranium Mill _was performed using the MILDOS computer code.

The input to the computer code consists of site-specific data and staff estimates of the radio-active effluents from the mill and tailings management systems (Refs. A.1-A.6).

The site specific data was based on Dawn Mining Company and State of Washington Department of Social and Health Services information.

The source term calcula-tions for the tailings impoundment are described in Appendix B.

Source terms are defined as the estimated quantity of radioactivity released in a specific period of time.

The mill sources addressed in this appendix are:

1.

The ore pad and its related activities.

2.

Mill hoppers and feeders.

3.

Grinders and crushers.

4.

Fine ore storage and transfer of fine ore.

5.

Yellowcake drying and packaging.

Some general parameter values which are necessary to these calculations are:

1.

The annual ore processing rate is 148,780 MT/ year.

2.

The ratio of radioactivity in the ore dust to that of the bulk ore is 2.5.

3.

The bulk ore activity for U-238, Th-230, Ra-226, and Pb-210 is 432 pCi/g.

Ore Pad Activities Particulate emissions from the ore pad are the result of:

1.

Truck delivery of ore.

2.

Ore pad handling by front-end loaders and other equipment.

3.

Windblown emission.

Radon gas emissions are estimated on a specific Rn-222 flux (Ref. A.1) of m sec Rn-222 1.0 pCi/g Ra-226 1.

Truck Unloading l

The release rate is estimated by the staff to be (Ref. A.2):

0.025 lb/ ton = 0.025/2000 = 1.25 x 10 5 release fraction

l A-2 The particulate release is then:

148,780 MT/ year x 106 g/MT x 2.5 x 10 12 Ci/pCi x 1.25 x 10 5 x 432 pCi/g = 2.01 x 10 3 Ci/ year 2.

Handling The release rate is estimated to be (Ref. A.2):

4 0.037 lb/ ton = 0.037/2000 = 1.85 x 10 5 release fraction.

The particulate release is then:

148,780 MT/ year x 106 g/MT x 2.5 x 10 12 Ci/pCi x 1.85 x 10 5 x 432 pCi/g = 2.97 x 10 3 Ci/ year 3.

Windblown Emission The dusting rate for the ore pad is 42 g/m year (Ref. A.1) 2 The particulate release is then:

2 2

42 g/m year x 432 pCi/g x 2.5 x 5.5 x 104 m x 10 12 Ci/pCi = 2.49 x 10 3 Ci/ year 4.

Radon-222 Release from Ore Pad The staff estimates radon release to be 2

1.0 pCi/m -sec 222 x 432 pCi/g x 3.156 x 107 sec/ year x 10 12 Ci/pCi x 5.5 x 104 m2 = 750 Ci/ year Total ore pad emissions for U-238, Th-230, Ra-226, Pb-210 (secular equilibrium):

2.01 x 10 3 Ci/ year 2.97 x 10 3 Ci/ year 2.49 x 10 3 Ci/ year 7.47 x 10 3 Ci/ year x 50 percent.'eductiort (Ref. A.3)

= 3.74 x 10 3 Ci/ year Total ore pad radon emission is 750 Ci/ year.

4

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Hoppers and Feeders

' ~

The release'ratet s estimated to be (Ref. A.2):

i q

O 023 lb/ ton = 0.023/2000 = 1.15 x 10 5 release fraction.

The particulate release is then:

148,780 MT/ year x 108 g/MT x 2.5 x 432 pCi/g x 1.15 x 10 5 x 10 12 Ci/pCi = 1.85 x 10 8 Ci/ year.

A reduction factor of 85% (Ref. A.2) is assumed because of the negative pressure created by the crusher bag house collection system.

Thus, the particulate release for U-238, Th-230, Ra-226, and Pb-210 is estimated to be:

1.85 x 10 3 Ci/ year x 15% (Ref. A.2) = 2.78 x 10 4 Ci/ year.

The radon release in based on a staff estimate that 20 percent of the secular equilibrium content of radon escapes at this stage of the ore processing.

This estimate also accounts for radon released from other sources such as the leaching, CCD, and other circuits in the mill, which are not specifically addressed.

The radon release is computed as:

148,780 MT/ year x 108 g/MT x 10 12 Ci/pCi x 20% x 432 pCi/g = 12.9 Ci/ year i

Grinding and Crushing The release 'o a is estimated to be (Ref. A.2):

r 0.16 lb/ ton = 0.16/2000 = 8 x 10 5 release fraction.

l The particulate release is then:

148,780 MT/ year x 108 g/MT x 432 pCi/g x 2.5 x 8 x 10 5 x 10 12 Ci/pCi = 1.29 x 10 2 Ci/ year.

This emission point has an emission control device (bag house), which the applicant estimates (Ref. A.4) at 91 percent efficiency.

Thus, the particulate souce term is then:

1.29 x 10 2 Ci/ year x 9% = 1.16 x 10 3 Ci/ year.

?

m

m_

t A-4 1

The staff estimates ~that the radon source ~ term will be approximately'the same as that for _the hopper and feeder:

12.9 Ci/ year for the same reasons as mentioned before.

Fine Ore Storage i

The staff estimates loss from loading in, loading out, and transfers of ore to and from the fine ore storage area.

The release rate for each of these four activities is estimated (Ref. A.2) to be 0;023 lb/ ton each.

i

Thus, 4 x 0.023 lb/ ton = 0.092/2000 = 4.6 x 10 5 release fraction.

The particulate source term for U-238, Th-230, Ra-226, and Pb-210 is estimated te be:

148,780 MT/ year x 106 g/MT x 2.5 x 4.6 x 10 5 x 432 pCi/g x 10 12 Ci/pCi =

7.39 x 10 3 Ci/ year.

The efficiency of emission control is estimated to be 75 percent (Ref. A.2),

so the particulate source term reduces to:

7.39 x 10 3 Ci/ year x 25% = 1.85 x 10 3 Ci/ year.

l Again, the radon source term is estimated to be 12.9 Ci/ year.

Yellowcake Drying and Packaging The yellowcake production rate is reported by the applicant to-be 214 MT/ year.

(Ref. A.5)

The applicant reports the yearly emission rates of 5.71 x 10 3 MT/ year for the dryer and of 4.08 x 10 3 MT/ year for packaging.

The total release rate is i

then 9.79 x 10 3 MT/ year.

I The U-238 particulate source term is:

9.79 x 10 3 MT/ year x 106 g/MT x 3.33 x 10 7 Ci/g U-238 x 0.85 4

x 0.79 = 2.18 x 10 3 Ci/ year, where 0.85 is the percent of uranium in U 0s 3

j and 0.79 is the reported purity of yellowcake.

The Generic Environmental Impact Statement on Uranium Milling (Ref. A.6) reports that the activity of Th-230 in yellowcake is 0.5 percent that of U-238 and that activity of Ra-226 and Pb-210 are each 0.1 percent that of U-238.

yv m s 1:- -

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I A-5 The Th-230 source term is:

2.18 x 10 3 Ci/ year x 0.5% = 1.09 x 10 5 Ci/ year.

7 The Pb-2]0 and Ra-226 source terms are:

2.18 x 10 3 Ci/ year x 0.1% = 2.18 x 10 8 Ci/ year.

Radon release from yellowcake operations is assumed to be negligible.

Summary Except for the yellowcake source terms, the U-238, U-234, Th'-230, Ra-226, and Pb-210 quantities are considered to be in secular equilibrium.

In general, 1

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, and deposition, all of which are further explained in NUREG/CR-2011 (The Documentation for the MILDOS code).

REFERENCES FOR APPENDIX A A.1. Table 4.1, Section 4.

A.2. " Fugitive Dust Emissions," Colorado Department of Health, Air Pollution Control Division, Stationary Sources Section, September 30, 1981.

A.3. " Principal Parameters for Radiological Assessmerit " Dawn Mining Company Uranium Mill, May 1980.

A.4 Memorandum (with enclosures) from Don Peterson, State of Washington, Department of Social and Health Services, to George Gnugnoli, U.S.

NRC, March 5, 1982.

A.5. " Input Data for the Radiological Assessment of the Dawn Mining Company."

Newmont Services, Ltd., March 13, 1981.

A.6. " Generic Environmental Impact Statement on Uranium Milling," NUREG-0706, U.S. Nuclear Regulatory Commission, September 1980.

B-1 APPENDIX B DETAILED RADIOLOGICAL ASSESSMENT Supplemental information is provided below which describes the models, data, and assumptions utilized by the staff in performing its radiological-impact assessment of the Dawn Mining Company Uranium Project.

The primary calcula-tional tool employed by the NRC staff in performing this assessment is MILDOS (Ref. B.1), an NRC-modified version of the UDAD (Uranium Dispersion and Dosimetry) computer code originater' at Argonne National Laboratory (Ref. B.2).

B.1 ANNUAL RADI0 ACTIVE MATERIAL RELEASES Estimated annual activity releases for the Dawn Mining Company Uranium Project are provided in Table 4.2.

They are based on the data and assumptions given in Table 4.1 and described elsewhere in Section 4, with the exception of the -

annual average dusting rate for exposed tailings sands. This dusting rate is calculated in accordance with the following equation:

M = 3.156 x 107 RF F) 0.5 ss s

where F is the annual average frequency of occurrence of wind speed s

group s, dimensionless; R

is the dusting rate for tailings sands at the average wind s

speed for wind speed group s, for particles 120 pm diameter, 2

g/m -sec; M

is the annual dust loss per unit area, g/m _yp; 2

3.156 x 107 is the number of seconds per year; and 0.5 is the fraction of the total dust loss constituted by particles 1 20 pm diameter, dimensionless.

The values of R and F utilized by the staff are as given in Table B.1.

s 3

~

B-2 Table B.1-Parameter values'for calculation of annual dusting rate for exposed tailings sands Wind Speed Avarage Wind Dusting Rate Frequency of 2

Group, knots Speed, mph (R ), g/m.sec*

Occurrence-(F )**

3 s

0-3 1.5 0

0 4-6 5.5 0

0 10 10.0 3.92 x 10 7 0.38011 11-16 15.5 9.68 x 10 8 0.18314' 17-21 21.5 5.71 x 10 5 0.04671-

>21 28.0 2.08 x 10 4 0.00993.

Dusting rate as a function of wind speed is computed by 'the MILDOS code-(Ref. B.1).

- Wind speed frequencies obtained from annual joint frequency data presented in Table B.2.

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B-4 The calculated value of the annual dusting rate, M is 420 g/m yr.

Annual 2

curie releases from the tailings piles are then given by the following relationship:

5 = MA (1-f ) It (C) (2.5 x 10 d)

(B-2) c where A

is the assumed beach area of the pile, m ;

~

2 f

is the fraction of the dusting rate controlled by mitigating c

actions, dimensionless; f

is the fraction of the ore' content of the particular nuclide t

present in the tails; 5

is the annual release for the particular beach area, Ci/yr; C

is the assumed raw ore activity, pCi/g; 2.5 is the dust to tails activity ratio; and 10 12 is Ci/pCi.

The tailings impoundments consist of three areas:

(1) the abandoned tailings area (59.2 acres); (2) the inactive tailings area (47 acres); and (3) the below grade tailings area (27 acres).

The abandoned tailings area is no longer in use and consists of old tailings from processing ore with an estimated average activity of 675 pCi/g.

At present only 3 percent of this area is not covered by wood chips or other cover material, and it is estimated that it will be totally covered by 1985.

The inactive tailings area is being stabilized by a soil cover.

At present approximately 10 acres is exposed, and as drying progresses, more cover will be applied to exposed areas.

The staff has estimated a 90 percent reduction factor of dusting for the present assessment.

As the interim stabilization cover is applied to the rest of this area, particulate emissions would effectively be eliminated.

The,.esent below grade tailings disposal area is in operation, and the staff has assumed a 99 percent reduction factor for dusting because of water cover and other dust reduction conditions which occur with use of below grade impoundments.

Dust losses from the ore storage piles were estimated by assuming they would be about 10 percent of those from an equivalent area of tailings beach.

Calculated dust losses were reduced by 50 percent to account for dust loss control measures agreed to by the operator.

/

r B-5 B.2 ATMOSPHERIC TRANSPORT The staf f analysis of of fsite air concentrations of radioactive materials was based on five years of meteorological data collected at Spokane, Washington, over the period 1967 through 1971 (Ref. B.3).

The collected meteorological data were entered into the MILD 05 code as input, in the form of a joint frequency distribution by stability class, wind speed group, and direction.

The joint frequency data employed by the staff for this analysis are presented in Table B.2.

The dispersion model employed by the MILDOS code is the basic straight-line Gaussian plume model (Ref. B.1).

Ground-level. sector-average concentrations are computed using this model and are corrected for decay and ingrowth in transit (for Rn-222 and daughters) and for depletion due to deposition losses (for particulate material).

Area sources are treated using a virtual point source technique.

Resuspension into the air of particulate material initially deposited on ground surfaces is treated using a resuspension factor which depends on the age of the deposited material and its particle size (Ref. B.1).

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, and deposition velocities for each source are presented in Table B.3.

Table B.3 Physical characteristics assumed for particulate material releases Deposition Diameter Density Velocity AMAD*

Activity Source pm g/cm cm/sec pm 3

Activity Source Crusher dusts 1.0 2.4

1. 0 1.55 Yellowcake dusts 1.0 8.9

1. 0 2.98 Tailings, ore pile dusts 5.0 (30%)

2.4 1.0 7.75 Tailings, ore pile dusts 35.0 (70%)

2.4 8.8 54.2 Ingrown Rn daughters 0.3 1.0 0.3 0.3

Aerodynamic equivalent diameter, used in calculating inhalation doses (Ref. B.4).

P B-6 B. 3 CONCENTRATIONS IN THE ENVIRONMENTAL MEDIA AND THE DOSE COMMITMENT METHODOLOGY Details on the methodology for computation of the transport, deposition, resuspension mechanisms, as well as the equations, tables and assumptions utilized for concentration and dose calculations are described in the following references available from the National Technical Information Service or the GPO Sales Program:

The Generic Environmental Impact Statement on Uranium Milling.

NUREG-0706 September 1980 (Ref. B.5)

Regulatory Guide 3.51 " Calculational Models for Estimating Radiation Doses to Man from Airborne Radioactive Materials Resulting from Uranium Milling Operations." G rch 1982 (Ref. B.4)

MILD 05 - A Computer Program n.r Calculating Environmental Radiation Doses from Uranium Recovery Operations.

NUREG/CR-2011 April 1981.

(Ref. B.1)

References for Appendix B B.1 U.S. Nuclear Regulatory Commission, " MILD 05 - A Computer Program for Calculating Environmental Radiation Doses from Uranium Recovery Operations,"

NUREG/CR-2011, April 1981.

B.2 M. Momeni, et al., " Uranium Dispersion and Dosimetry (UDAD) Code," Argonne National Laboratory Report, ANL/ES-72, NUREG/CR-0553, May 1979.

B. 3 " Wind Distribution of Pasquill Stability Classes - Spokane, Washington, 1967-1971," National Climatic Center, Asheville, North Carolina.

B.4 U.S. Nuclear Regulatory Commission, " Calculational Models for Estimating Radiation Doses to Man from Airborne Radioactive Material Resulting from Uranium Milling Operations," Regulatory Guide 3.51, March 1982.

B.5 " Final Generic Environmental Impact Surement on Uranium Milling," U.S.

Nuclear Regulatory Commission, NUREG-0706, September 1980.

-

ML20054F320

Contents

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4.1 INTRODUCTION

SUMMARY

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ML20054F320

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4.1 INTRODUCTION

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