ML19263E482

Draft Reg Guide 3.XXX, Calculational Models for Estimating Radiation Doses to Man from Airborne Radioactive Matls Resulting from U Milling Operations

ML19263E482
Person / Time
Issue date:	05/31/1979
From:	NRC OFFICE OF STANDARDS DEVELOPMENT
To:
References
RTR-REGGD-3.051, TASK-OS, TASK-RH-802-4 REGGD-03.XXX, REGGD-3.XXX, NUDOCS 7906180748
Download: ML19263E482 (5)

Text

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May 1979 A

U.S. NUCLEAR REGULATORY COMMISSION Division 3

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DRAFT REGULATORY GUIDE AND VALUE/ IMPACT STATEMENT s, v

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b CALCULATIONAL MODELS FOR E'S]IMTING RADIATION DOSES TO MAN FROM AIRBORNE,,RADI0 ACTIVE MATERIALS RESULTING FROM URANIUMsMICflNG OPERATIONS

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g:Q ' b 2357 247 p}8%f l}ND; This regulatory guide and the associated value/ impact statement are being issued in draft fom to involve the public in the early stages of the development of a regulatory position in this area. They have not received complete staff review and do not represent an official NRC staff position.

Public consents are being solicited on both drafts, the guide (including its implemntation schedule) and the value/ impact statement. Corrients en the value/.mpact statement should be acccmeanied by succorting data. Convents on both drafts should be sent to the Secretary of the Comissien. U.S. 'luclear Regulatory Cemission, Washington, D.C. 20555. Attention: Cocketing ano Service Brancn. by g yg Recues.s for single cooles of issued guides and draft guides (which may be reproduced) or for olacement en an autcmatic distribution list for single copies of future guides and draf t guides in specific divisions should be trade in writing to the U.S. Nuclear Regulatory Ccenission, Washington D.C. 20555. Attention:

Director. Division of Technical Infomation and Document Ccntrol.

7906180 W8

TABLE OF CONTENTS P. age A.

INTRODUCTION.

1 2

B.

DISCUSSION.

2 1.

Uranium Hill Source Terms..

2.

Critical Exposure Pathways...............

3 3.

Required Dose Estimates.

4 3.1 Individual Doses.

4 3.2 PoLulation Doses.................

6 4.

Use of This Guide....

7 C.

REGULATORY POSITION 8

1.

Concentrations in Environmental Media.........

8 1.1 Radionuclide Accumulation on the Ground.

9 11 1.2 Total Air Concentrations.

~ 1.3 Vegetation Concentrations.............

13 1.4 Meat and Milk Concentrations...........

14 1.5 Concentrations at Different Times...

15 2.

Dose Calculations for Individuals.

17 2.1 Inhalation Doses.................

17 2.2 External Doses..................

18 2.3 Ingestion Doses..................

19 2.4 Individual Dose Totals..............

20 3.

Population Dose Calculations..

21 3.1 Regional Population Doses.............

22 3.2 Continental Population Doses...........

26 3.3 Total Population Dose Commitments 27 D.

IMPLEMENTATION..............

28 REFERENCES 41 LIST OF SYMBOLS......

44 2357 248 iii 4

O TABLE OF CONTENTS (Continued)

Page APPENDIX A - Site-Specific Information and Data Used by the NRC Staff in Performing Radiological Impact Evaluations for Uranium Milling Operations 52 APPENDIX B - Staff Methodology for the Computation of 100-Year Environmental Dose Commitments.

57 APPENDIX C - Radon Dose Conversion Factor.

61 REFERENCES FOR APPENDIX C.

62 DRAFT VALUE/ IMPACT STATEMENT.

63 9

zw 20 O

9

.3 iv

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LIST OF TABLES Table P_ age 1

Isotopes and Particle Sizes for Which Direct Air Concen-trations (C values) are Required as Input Data.

29 aidp 2

Environmental Transfer Coefficients.........

30 3

Inhalation Dose Conversion Factors...

31 32 4

Dose Conversion Factors for External Exposure.......

5 Food Consumption Rates Used for Calculating Doses to Individuals.

33 6

Ingestion Dose Conversion Factors.

34 7

Average Agricultural Productivity Factors for Various States.

35 8

Food Consumption Rates Used for Calculating Doses to 36 Populations.

9 Age Distribution of Population, Average and Per Capita Consumption Rates, and Fractions Used in the Absence of Site-Specific Data 37 10 Continental Pcpulation Doses per kCi of 222Rn Released in 38 1978 11 Projected Population of the United States, 1978-2100.

39 A-1 Plant, Plant Operations, Meteorological, and Environmental Data Routinely Used by the NRC Staff in Performing Radi-ological Impact Evaluations.

53 B-1 Comparison of Staff and Conventional Techniques for Environmental Dose Commitment Calculation......

60 LIST OF FIGURES.

Page Figure a

1 Schematic Diagram of Information Flow and Use for Dose Calculations....

40 2357 250 v

A.

INTRODUCTION Analyses of radiation doses to the public, or individual members thereof, resulting from the radioactive effluents from uranium mills are required to be made by the NRC staff for the following purposes:

1.

Evaluating compliance with 40 CFR Part 190, " Environmental Radiation Protection Standards for Nuclear Power Operations,"*

2.

Evaluating compliance with the "as low as is reasonably achievable" (ALARA) criterion embodied in 10 CFR Part 20, " Standards for Pro-tection Against Radiation," and 3.

Evaluating overall radiological impact as part of the complete environmental impact assessment required by the National Environ-mental Policy Act (NEPA) of 1969 (Public Law 91-190, 83 Stat. 852).

This regulatory guide describes basic features of calculational models employed by the NRC staff for such evaluations and suggests values for various parameters used in the estimation of radiation doses to man from uranium milling operations.

Specifically, this guide addresses the calculation of radiation doses to man from previously estimated environmental radioactivity concentrations in air.

The environmental radioactivity concentrations in air required for this calculation result from extensive and detailed analyses of effluent release rates and atmospheric dispersion phenomena.

Staff guidance concerning the estimation of facility release rates (source terms) or the calculation of airborne concentrations from estimated source terms (atmos-p'ieric dispersion) has not yet been prepared.

The preparation and issuance of appropriate guidance in these areas is planned for the future.

In the interim, however, considerable information on methodologies currently used by the staff for source term calculations and analyses of atmospheric disper-sion is available in NUREG-0511, " Generic Environmental Impact Statement on Uranium Milling" (Ref. 1) and in NUREG/CR-0553, "The Uranium Dispersion and Dosimetry (UDAD) Code" (Ref. 2).

AThe limits on individual dose equivalent contained in 40 CFR Part 190 become effective as of December 1, 1980, for doses resulting from the milling of uranium ore.

2357 251 1

B.

DISCUSSION This guide describes models used by the NRC staff to estimate the radi-ological impacts resulting from uranium mills for the purpose of evaluating compliance with 40 CFR Part 190 and 10 CFR Part 20 as well as assessing over-all environmental radiological impacts in accordance with NEPA.

1.

URANIUM MILL SOURCE TERMS A uranium mill, unlike other fuel cycle facility types, goes through phases in its life cycle in which both the composition and the magnitude of it radioactive emissions (and associated impacts) vary greatly.

For this reason, the NRC staff will perform impact evaluations for each individual mill at different stages of its existence.

Typically, a uranium mill will operate for a period of years during which there will be radon and particulate releases from the ore storage pile, the mill itself, and the tailings disposal area.

During this operational period, both particulate and radon releases from the tailings pile may be somewhat limited by maintaining the pile at least partially under water.

Mechanical sprinkler systems or chemical stabilizing agents may also be used to inhibit air suspension by wind action of radioactive tailings dust.

Upon the cessation of actual milling, the tailings pile is normally allowed to dry by process of natural evaporation until it is ready for stabilization.

In this postoperational, prestabilization period, there are essentially no releases from the ore storage pile or the actual mill.

However, as the tailings pile dries, releases of radon and particulates from this source may increase, reaching a maximum prior to implementation of measures required to achieve long-term stabilization.

After stabilization and reclamation of the tailings area, there should be no further radioactive particulate releases.

However, small quantities of radon.may continue to diffuse upward from the tailings and may be released to the atmosphere.

These continuing radon releases, though small, will likely persist for tens of thousands of years.

2357 252 2

Depending on the specific details of the site, facility, effluent controls, and stabilization program, maximum individual particulate exposure could occur either during the last year of actual milling or the last year prior to stabilization of the tailings.

Maximum individual doses due to radon releases are likely to occur during the last year prior to stabilization.

The radioactive isotopes comprising uranium mill radioactivity releases are mostly those belonging to the 238U and 23su decay series.

The 23sU series members amount to less than 5 percent of total releases aad are routinely disregarded because of their insignificant contributic, to overall radiol-ogical impact.

2.

CRITICAL EXPOSURE PATHWAYS Exposure pathways of concern for airborne releases from uranium mills normally include inhalation of airborne radioactive material, ingestion of vegetable and animal products contaminated via deposition, and direct external exposure to radiation emitted by airborne activity and activity deposited on ground surfaces.

Liquid exposure pathways are not usually of concern because there are usually no discharges to surface water of siquid effluents.

Liquid pathways may exist, however, and need to be included if significant.

All individual exposure pathways of significance will be evaluated at locations where the exposure pathway and a dose receptor actually exist at the time the analysis is made.

Also, the applicant may take into account any real phenomena or actual exposure conditions that may be present.

Such conditions could include actual values for agricultural productivity, dietary habits and food sources, residence times, measured environmental transport factors, or similar values determined for a specific site.

However, if the analysis is based on existing conditions and if potential changes in land use and food pathways could result in exposures significantly higher, the applicant should provide reasonable assurance that a monitoring and surveil-lance program will be performed on a regular and continuing basis to deter-mine if such changes have occurred.

g 2357 253 3

3.

REQUIRED DOSE ESTIMATES 3.1 Individual Doses Evaluations of the dose received by an exposed individual are made to satisfy the requirements of both 40 CFR Part 190 and 10 CFR Part 20.

The EPA regulation, 40 CFR Part 190, speaks to individual radiation doses from all pathways and all nuclear power and fuel cycle facilities combined, except that exposure from radon and its daughters need not be included.

10 CFR Part 20 includes a requirement to keep all radiation exposures "as low as is reason-ably achievable" (ALARA).

ALARA is a general concept that has not to date been interpreted in the form of numerical design objectives for uranium mills as it has for light-water-cooled nuclear reactors (see Appendix I, " Numerical Guides for Design Objectives and Limiting Conditions for Operation to Meet the Criteria 'As Low As Is Reasonably Achievable' for Radioactive Material in Light-Water-Cooled Power Reactor Ef fluents," to 10 CFR Part 50, " Domestic Licensing of Production and Utilization Facilities").

However, a case-by-case evaluation will be made to ensure that doses are kept as low as is reasonably achievable.

ALARA evaluations will address all releases, includ-ing radon and its daughters, and will consider population doses as well as individual doses.

For the purpose of evaluating compliance with 40 CFR Part 190, the whole body and organ doses to any individual, considering all pathways combined, from all activity releases except radon and its daughters are evaluated for:

a.

The last year of actual mill operation, and b.

The last year prior to tailings pile reclamation.

These evaluations are adequate for assessing ALARA compliance except that exposure to radon and its daughters is to be included and radon and daughter exposure for the first year after tailings pile reclamation is so to be evaluated.

Postreclamation exposure to radon and its daughters be evaluated at the location of greatest radon concentration where unrestricted land use after mill decommissioning may be permitted.

2357 254 O

4

Exposed individuals are characterized with regard to food consumption, occupancy, and other use of the region in the vicinity of the mill site.

All physiological and metabolic parameters for the exposed individuals are assumed to have those characteristics that represent the averages for the general population.

Although specific individuals will almost certainly display dietary, recreational, and other living habits considerably different from those suggested here and actual physiological and metabolic parameters may vary considerably, the HRC staff considers the use of these reference values to be acceptable because the actual physiological and metabolic charac-teristics of specific individuals cannot usually be determined.

Applicants are encouraged to use information and data applicable to a specific region or site when possible.

Where site-specific information and data are used, its origin or derivation should be documented for the NRC staff's review.

In this guide, the term " dose" is used instead of the more precise term

" dose equivalent," as defined by the International Commission on Radiological Units and Measurements (ICRU). When applied to the evaluation of internal deposition of radioactivity, the term " dose," as used here, includes the prospective dose component arising from retention in the body beyond the period of environmental exposure, i.e., the committed dose equivalent.

The committed dose equivalent is evaluated over a period of 50 years.

The committed dose equivalent per unit intake, either by inhalation or ingestion, usually varies by age as well as by organ.

For the purpose of calculating collective (population) doses, the population has beta assumed to be composed of four age groups:

infants (0 to 1 year), children (1 to 11 years), teenagers (11 to 17 years), and adults (17 years and older).

Four sets of ingestion-dose conversion factors are presented later in this guide, one for each of these four age groups.

Available data are not suffi-cient to permit the calculation of age-specific dose conversion factors for inhalation exposure, and adult dose conversion factors are assumed to apply for all age groups for this exposure pathway.

2357 255 5

3.2 Population Doses Evaluations of population doses resulting from uranium milling opera-tions are required to satisfy NEPA stipulations with respect to assessing the total environmental impact associated with the operation of each facil-ity.

Calculated estimates of resulting population doses therefore need to reflect, insofar as practicable, the overall radiological impact of each uranium mill over the duration of its existence.

For a typical uranium mill life cycle, the total radiological impact is composed of the impacts of the three major phases of existence:

the operational phase, the postoperational prereclamation phase, and the post-reclamation phase.

The first two phases may involve substantial releases of radon gas and particulates but are of relatively short duration.

The postreclamation phase involves only small releases of radon, but these releases may persist for periods of tens of thousands of years.

For each separate mill life-cycle phase, the average annual radiological impact will be estimated by the NRC staff by use o-f the following basic procedure:

Annual average releases over the duration of the particular mill a.

phase will be estimated for each isotope.

b.

The radiological impact resulting from 1 year of average releases will be evaluated in terms of population dose, using the EPA con-cept of " environmental dose commitment" (Ref. 3).

The environmental dose commitment will be evaluated for a period of 100 years follow-ing release.

The total dose commitments for the operational and prereclamation phases will be calculated by multiplying the annual population dose commitments by the number of years the mill is expected to be in each phase.

The sum of these two products then represents an approximation of the combined radi-ological impact of the facility prior to tailings pile reclamation.

The annual popui= tion dose commitments from postreclamation radon releases are also calculated and represent the continuously recurring impact of this residual activity source.

Consideration of particulate releases will generally be limited g egraph-ically to the area within 80 km (50 mi) of the mill site.

Within this area, 2357 256 6

G exposure pathways requiring assessment include all those considered in the evaluation of maximum individual exposure.

Outside the 80-km (50-mi) radius, only radon and daughters require consideration.

4.

USE OF THIS GUIDE Present NRC staff practice with regard to the calculation of radio-active emission rates from uranium milling facilities involves the character-ization of such releases by radionuclide, particle size, and density (Ref. 1).

The data required as input for use of the calculational models described in this guide consist of annual average air concentrations resulting directly from such releases at specific locations (not including resuspended air con-centrations of radicactive materials previously deposited on ground surfaces).

The required input air concentrations are denoted in this guide, for a parti-cular location, by the symbol Cadip (in pCi/m ), where the subscripts indicate 3

air concentration (a), direct (d), radionuclide (i), and particle size (p).

Direct air concentrations required are those for values of the subscripts i and p as identified and defined in Table 1.

The primary calculational tool employed by the staff in performing radi-ological impact evaluations of uranium milling operations is a staff-modified version of the Uranium Dispersion and Dosimetry (UDAD) Code (Ref. 2), developed at the Argonne National Laboratory.

In the staff code, currently called 238 UDAD4-MOD 2, only five primary radionuclides in the U decay chain are treated explicitly as source terms.

These radionuclides are 238U, 230Th, 22cRa, 21 Pb, and 222Rn.

Release rates for these radionuclides are required for each potential onsite source (for particle sizes 1 through 4 in Table 1).

For 222Rn daughters, which grow in during transport of 222Rn from the site, the resulting ingrowth concentrations (particle size 5 in Table 1) are also required.

These 222Rn daug

s include 218po, 214Pb, 214Bi, 2toPb, and 21 Po, The dosimetry model accounts for releases and ingrowth of other radionuclides, using assumptions of secular equilibrium.

O 2357 257 7

Appendix A identifies and describes the various other site-specific infor-mation and data routinely used by the NRC staff in performing radiological impact assessments for uranium milling facilities.

Appendix B provides a more detailed discussion of the method used in this guide for calculating environmental dose commitments.

Appendix C provides a detailed explanation of the derivation of the radon dose conversien factor used in this guide.

C.

REGULATORY POSITION Equations and other data by which the NRC staff will estimate radiation exposure for individuals and the population in general are presented below.

These equations are appropriate for the exposure pathways that the staff routinely considers in its evaluations.

In addition, other pathways that may be present because of a;ique conditions at a specific site should be considered if they are likely to provide a significant contribution to total dose.

A pathway is considered significant if a conservative evaluation yields an additional dose increment of more than 10 percent of the total from all other pathways considered in this guide.

1.

CONCENTRATIONS IN ENVIRONMENTAL MEDIA As discussed in Section B.4, annual average direct air concentrations are required as input data for use in the equations that follow.

These equa-tions yield resulting concentrations in environmental media of interest, including total air concentrations, ground surface concentrations, and concen-trations in edible vegetation, meat, and milk.

These concentration calcu-lations are explicitly performed only for certain members of the 238U decay chain.

Concentrations in environmental media of other chain members are inferred from those for which concentrations are explicitly calculated.

The basic calculational procedure first involves treatment of the direct air concentrations to obtain ground surface concentrations and resuspended air concentrations.

Resuspension of radioactive materials deposited on ground surfaces is not treated as a loss mechanism for ground concentrations.

For 2757 258

~

8

this reason, deposition of resuspended air concentrations onto ground surfaces is not considered.

Resuspended particulate concentrations in air are added to the airborne concentrations arising directly from the source to obtain total air concentrations.

The calculated total air concentrations are then used to obtain total deposition rates onto vegetation (resuspension losses of activity deposited on vegetation are assumed to be accounted for by the application of a weathering half-life).

Total deposition rates and ground concentrations are used to compute concentrations in various vegetation types, including hay and forage.

Radionuclide concentrations in hay and animal forage are initial inputs for the calculation of radionuclide concentrations in meat and milk ingested by man.

This basic calculational process, the resulting environmental media concentrations, and the exposure pathways for which they are used are indicated schematically in Figure 1.

1.1 Radionuclide Accumulation on the Ground Radionuclide ground concentrations are computed from the calculated airborne particulate concentrations arising directly from onsite sources (not including air concentrations resulting from resuspension).

Resuspended particulate concentrations are not considered for evaluating ground concentra-tions.

The direct deposition rate of radionuclide i is calculated, using the following relationship:

Odi "

adip V (1)

P where C

is the direct air concentration of radionuclide i, particle adip 3

size p, in pCi/m ;

D is the resulting direct deposition rate of radionuclide i, di in pCi/m2 per sec; and V

is the deposition velocity of particle size p, in m/sec (see p

Table 1).

2357 259 3

9

The concentration of radionuclide i on a ground surface due to constant deposition at the rate D ver time interval t is obtained from di

~1 - exp[-(A. + A )t]~

Cg (t) = Ddi A

+A j

il e

where C g(t) is the ground surface concentration of radionuclide i at time 2

t, in pCi/m ;

t is the time interval over which deposition has occurred, in sec; A

is the assumed rate constant for environmental loss, in sec-2; e

and A

is the radioactive decay constant

• for radionuclide i, in j

-2 sec The environmental loss constant, A, corresponds to an assumed half-time e

for loss of environmental availability of 50 years (Ref. 1).

Thi: carameter accounts for downward migration in soil and loss of availability dca to chemical binding.

It is assumed to apply to all radionuclides deposited on the ground.

Ground concentrations are explicitly computed only for 2380, 230Tt 22GRa, and 22 Pb.

For all other radionuclides, the ground concentration is assumed equal to that of the first parent radionuclide for which the ground concentration is explicitly calculated.

For 2toPb, ingrowth from deposited 22cRa can be significant.

The concentration of 21oPb on ground due to 22cRa deposition is calculated by the staff, using the standard Bateman formulation and assuming that 22cRa decays directly to 220Pb.

Using i = 6 for 22cRa and i = 12 for 21 Pb (see Table 1), the following equation is obtained:

D t~

^12 d6 1-e~A$2t

-Agt,e'A$2

+e (3)

Cgyp(Pb ~ Ra) =

3, p

6 12 6

12 where g12(Pb -- Ra) is the incremental 2toPb ground concentration resulting C

from 22cRa deposition, in pCi/m ; and 2

s Radiological decay constants employed by the NRC staff are obtained from data given in Reference 4.

10 2357 260

A*

is the effective rate constant for loss by radioactive decay and migration of a grcund-deposited radionuclide and is equal to A

^, in secd.

n e

1. 2 Total Air Concentrations For use of the models described in this guide, air concentrations arising directly from onsite sources are required for each receptor location as a function of particle size (for particulates).

Direct air concentrations are assumed to include the effects of depletion by deposition (particulates) or ingrowth and decay in transit (for radon and its daughters).

In order to compute inhalation doses, the total air concentration of each radionuclide at each location (as a function of particle size) is computed as the sum of the direct air concentration and the resuspended air concentration:

Caip(t) = Cadip + Carip(t)

(4) where C

is the direct air concentration of radionuclide i, particle adip size p, (constant), in pCi/m ;a aip(t) is the total air concentration of radionuclide i, particle C

size p, at time t, in pCi/m ; and 3

pjp(t) is the resuspended air concentration of radionuclide i, C

particle size p, at time t, in pCi/m.

3 The resuspended air concentration is computed using a time-dependent and particle-size-dependent resuspension factor, which, for deposits of age t years, is defined by

-A t R (t) = (0.01/V )10-5 e R (for t 5 1.82 yr)

(Sa) p p

R (t) = (0.01/V )10-9 (for t > 1.82 yr)

(5b) p p

2357 261 11 N

where R 't) is the ratio of the resuspended air concentration to the ground r

p concentration, for a ground concentration of age t yr, of particle size p, in m-1; A

is the assumed decay constant of the resuspension factor R

(equivalent to a 50-day half-life), 5.06 yr-1; 0.01 is the deposition velocity for the particle size for which the initial resuspension factor value is 10-5/m, in m/sec; 10-5 is the initial value of the resuspension factor for particles with a deposition velocity of 0.01 m/sec, in m-1; 10-9 is the terminal value of the resuspension factor for particles with a deposition velocity of 0.01 m/sec, in m-1; and 1.82 is the time required to reach the terminal resuspension factor, in yr.

The basic formulation of the above expression for the resuspension factor, the initial and final values, and the assigned decay constant derive from experimental observations (Ref. 1).

The decrease with age primarily accounts for agglomeration with other larger particles.

The inverse relationship to deposition velocity physically accounts for decreased resuspendibility of larger particles; mathematically, it eliminates mass balance problems for the 35 pm particle size.

Based on this formulation, the resuspended air concentration is given by

~1-exp[-(Aj+A)(t-a)]

3 R

arip(t) = 0.01Cadip (Aj A )

10 p

exp[-Aj(t a)] - exp(-Ajt)~

_4

... + 10 6(t)

(3.156 x 107)

(6) pi where a

is equal to (t - 1.82) if t > 1.82 and is otherwise equal to zero, in yr; 6(t) is zero if t 5 1.82 and is unity otherwise, dimensionless; b2 12

A*

is the effective removal constant for radionuclide i on soil, 1

in yr-1; and 3.156x107 is sec/yr.

Equation 6 yields the resuspended air concentration of radionuclide i in particle size p because of deposition over time span t, in years.

Total air concentrations are computed using Equations 6 and 4 (in that order) for all particulates in particle sizes 1 through 4 (see Table 1).

Particulate daughters of 222Rn (particle size 5 in Table 1) are not assumed to be depleted because of deposition and are also not assumed to resuspend.

1.3 Vegetation Conce.'.trations As illustrated in Figure 1, vegetation concentrations are derived from ground concentrations and total deposition rates.

Total deposition rates are given by the following summation:

D.=

C.V (7) 1 alp p P

where D

is the total depositicn rate, including deposition of resus-j 2

pended activity, of radio.mclide i, in pCi/m pr sec.

Concentrations of released particulate matericis can be environmentally trans-ferred to the edible portions of vegetables, or to hay or pasture grass con-sumed by animals, by two mechanisms -- direct foliar retention and root uptake.

Five categories of vegetation are treated by the staff.

They are edible ah ve ground vegetables, potatoes, other edible below ground vegetables, pz grass, and hay.

Vegetation concentrations are computed using the following equation:

1 - exp(-A t )

B C. VI (8)

• V C.=0FE

+

vi irv YA g1 y

p 2357 263 13

B is the soil-to plant transfer coefficient for radionuclide yj i, vegetation type v, dimensionless; C

is the resulting concentration of radionuclide i, in vegeta-5 tion v, in pCi/kg; E

is the fraction of the foliar deposition reaching edible por-y tions of vegetation v, dimensionless; F

is the fraction of the total deposition retained on plant surfaces, 0.2, dimensionless; p

is the assumed soil areal density for surface mixing, 240 2

kg/m ;

t is the assumed duration of exposure while growing of vegeta-tion v, in sec; Y

is the assumed yield density of vegetation v, in kg/m ; and 2

y A,

is the decay constant accounting for weathering losses (equivalent to a 14-day half-life), 6.73 x 10-7 sec-1 The value of E is assumed to be 1.0 for all above ground vegetation and 0.1 for all be ow ground vegetables (Ref. 5).

The value of t is taken to y

be 60 days, except for pasture grass where a value of 30 days is assumed.

The yield density, Y, is taken to be 2.6 kg/m, except for pasture grass 2

y where a value of 0.75 kg/m is applied.

Vanes of the soil-to plant transfer 2

coefficients, By4, are provided in Table 2.

1.4 Meat and Milk Concentrations Radioactive materials can be deposited on grasses, hay, or silage that are eaten by meat animals that are in turn eaten by man.

The equation used to estimate radionuclide concentrations in meat is Cbi

• Ofbi(F C j+FCh hi)

(9) pg pg where C

is the resulting average concentration of radionuclide i in bi meat, in pCi/kg; b

14

9 C

is the concentration of radionuclide i in hay (or other stored hi feed), in pCi/kg; C

is the concentration of radionuclide i in pasture grass, in pgj pCi/kg; F

is the feed-to-meat transfer coefficient for radionuclide i, bi in pCi/kg per pCi/ day ingested (see Table 2);

are the fractions of the total annual feed requirement assumed fpg,Fh to be satisfied by pasture grass or locally grown stored feed (hay), respectively, dimensionless; and Q

is the assumed feed ingestion rate, 50 kg/ day (Ref. 5).

The equation used to estimate milk concentrations from cows ingesting contaminated feed is m1(F C

.+FCh hi)

(10)

C. = QF pg pg1 m1 where C

is the resulting average concentration of radionuclide i in g5 milk, in pCi/f; and F,5 is the feed-to-milk transfer coefficient for radionuclide i, in pCi/2 per pCi/ day ingested (see Table 2).

1. 5 Concentrations at Different Times Maximum doses to individuals are calculated for the last year of mill operation and for the last year prior to tailings pile reclamation.

This section explains the procedures used by the NRC staff to obtain annual average environmental media concentrations for these years.

In order to estimate average environmental media concentrations durinc the final year of actual mill operation, for an operational lifetime of Tg years, the value of the time variable t appearing in Equations 2, 3, 4, and 6 is set equal to T - 0.5 year (in apprcoriate units)'

The resulting con-g centration values are those predicted for the midpoint of the final year of operation and are assumed to represent averaye values existing over that year.

2357 265 15

Environmental concentrations existing during the final prereclamation year result from postoperational releases and residual contamination due to releases during the period of mill operation.

Because direct air concentra-tions from operational releases vanish, environmental concentrations due to operational releases, at the time of reclamation, arise only from residual ground and resuspended air concentrations.

Ground concentrations at the end of the milling period are calculated using Equations 2 and 3, with the value of t set to T, the operational lifetime.

Residual ground concentra-g tions at the midpoint of the final prereclamation year are then determined by Cg (T

- 0.5) = Cgj(T )exp[-A (T - 0.5)]

(11) j d

g d

where Cg (T )

is the ground concentration of radionuclide i at the time of j g mill shutdown, in pCifm ;

2 g (T C

- 0.5) is the residual ground concentration of radionuclide i resulting j d from operational releases, 0.5 year prior to the end of the T year drying period, in pCi/m ; and 2

d T

is the duration of time required to dry the tailings pile d

prior to reclamation, in yr.

Residual resuspended air concentrations resulting from operational releases are determined for the midpoint of the final prereclamation year by Carip(T - 0.5) = 0.01C 10-9 exp[-A (T - 0.5)].

d adip d

4 1

exp(-A T )

j (3.156 x 107)

(12) x A.

1 where C

is the direct air concentration of radionuclide i in particle adip size p resulting from c,perational releases, in pCi/m ; and 3

Carip(T -0.5) is the residual resuspended air cer.ecntration of radionuclide i d

in particle size p resulting from cperational releases, 0.5 year prior to the end of the T ye r drying period, in pCi/m.

3 d

2357 266 16

Ii

.g Ground and resuspended air concentrations resulting from postoperational releases, at the midpoint of the final prereclamation year, are calculated using Equations 2, 3, 4, and 6 with the value of t equal to T - 0.5 year.

d These concentrations are then incremented by the residual concentrations due to operational releases, calculated using Equations 11 and 12 to obtain the required totals.

Total air concentrations and concentrations in vegeta-tion, meat, and milk are then calculated from the total ground and resus-pended air concentrations.

2.

DOSE CALCULATIONS FOR INDIVIDUALS Doses to individuals are calculated for inhalation, external exposure to air and ground concentrations, and ingestion of vegetables, milk, and meat.

Internal doses are calculated using dose conversion factors that yield the 50 year committed dose equivalent, i.e., the entire dose received over a period of 50 years following either inhalation or ingestion.

The annual doses are actually the 50 year committed dose equivalents resulting from a 1 year exposure period.

The 1 year exposure period is taken to be the year (s) when environmental concentrations resulting from plant operations are expected to be at their highest level.

2.1 Inhalation Doses Inhalation doses are computed using total air concentrations obtained from Equation 4 (resuspended air concentrations are included) and the dose conversion factors presented in Table 3.

These dose conversion factors have been computed by Argonne National Laboratory's UDAD Code (Ref. 2) in accord-ance with the Task Group Lung Model (TGLM) of the International Commission on Radiological Protection (Ref. 6).

Inhalation dose conversion factors for the lung are weighted averages over the nasopharyngeal, tracheobronchial, lymph, and pulmonary regions of the TGLM.

Dose's to the bronchial epithelium from 222Rn and short-lived daughters are computed based on the assumption of indoor exposure with 100% occupancy.

2357 267 17

The dose conversion factor for bronchial epithelium exposure from 222Rn is derived as follows (see Appendix C for detailed basis):

a.

1 pCi/m3 222En in outdoor air will yield an average indoor concentra-tion of about 5 x 10-6 Working Level (WL).*

b.

Continuous erposure to 1 WL = 25 cumulative working level months (WLM) per year, c.

1 WLM = 5000 mreh: (Raf. 7).

Therefore W'

'M 1 pCi/m3 222Rn x (5 x 10-8 pCi/m ) x (25 WL )

3 x (5000

• ) = 0.625 mrem and the 222Rn bronchial epithelium dose conversion factor is taken to be 0.625 mrem /yr per pCi/m.

3 Inhalation doses are computed by the staff by use of the following d (inh) =

C DCF j

aip jjp(inh)

(13) ip where d (inh) is the inhalation dose to organ j, in mrem /yr; and j

DCF.. (inh) is the inhalation dose conversion factor for radionuclide i, 1]p organ j, and particle size p, in mrem /yr per pCi/m.

3 2.2 External Doses External doses resulting from exposure to air and ground activity concen-trations are computed, using the dose conversion factors presented in Table 4 and assuming 100 percent occupancy at a given location.

Indoor exposure is assumed to occur 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> per day at a dose rate of 70 percent of the outdoor A

One WL concentration is defined as any combination of short-lived radio-active decay products of 222Rn, per liter of air, that will release 1.3 x 105 MeV of alpha particle energy during their radioactive decay to 21oPb.

18 2

b

dose rate, which is equivalent to a dose reduction factor for structural shielding of 0.825.

The following equation is used by the staff to calculate external doses:

ai gj 4j(gnd)

(14) d)(ext) = 0.825 C DCFjj(cid) + C DCF i

where 3

C,5 is the total air concentration of radionuclide i, in pCi/m ;

d (ext) is the external dose to organ j, in mrem /yr; DCFjj(cid) is the dose conversion factor for cloud exposure for radio-3 nuclide i, organ j, in mrem /yr per pCi/m ;

DCFjj(gnd) is the dose conversion factor for ground exposure for radio-2 nuclide i, organ j, in mrem /yr per pCi/m ; and 0.825 is the effective reduction factor because of structural shie; ding for indoor exposure periods.

2.3 Ingestion Doses Ingestion doses are routinely calculated for ingestion of vegetables and meat (beef, unprocessed pork, and lamb).

Hilk ingestion doses are also computed if that pathway exists at the time of licensing.

Ingestion doses are based on environmental concentrations established using Equations 8, 9, and 10, ingestion rates given in Table 5, and dose conversion factors given in Table 6.

Ingestion doses from vegetable consumption are computed under the assumption that an average of 50 percent of the initial activity will be lost in food preparation (Ref. 5), usually involving washing, peeling, boiling, etc.

The following equation is employed to compute the annual radionuclide intake via ingestion:

I mk'mi

• bk bi + 0.5 U C (15) ik vk y; v

where

,I is the activity ingestion rate of radionuclide i by an ik individual in age group k, in pCi/yr; 2357 269 19

re milk (in 2/yr) and meat (in kg/yr) ingestion rates for Umk'Ubk age group k; U

is the ingestion rate of vegetable category v for age group vk k, in kg/yr; and 0.5 is the fraction of vegetable activity remaining after food preparation, dimensionless.

Ingestion doses are then computed by ik ij k(i"9)

(

}

p(ing) =

I 0 d

i where p(ing) is the ingestion dose for organ j, age group k, in mrem /yr; d

and ijk(ing) is the ingestion dose conversion factor for radionuclide i, DCF organ j, age group k, in units of mrem /pCi ingested.

2.4 Individual Dose Totals Individual doses are calculated by the NRC staff for purposes of evalu-ating compliance with 10 CFR Part 20 and 40 CFR Part 190.

For evaluating compliance with 40 CFR Part 190, dose contributions from 222Rn and daughters are excluded.

Total doses to individuals are calculated for both purposes using the following equation, which sums the dose contributions from inhala-tion, external dose, and ingestion:

jk(tot) = d (inh) + d)(ext) + djk(ing)

(17) d j

where jk(tot) is the total dose to organ j of an individual in age group k d

from all exposure pathways, in mrem /yr.

To evaluate compliance with 40 CFR Part 190, the staff will compute total doses to appropriate individual receptors, using the above equation and all other models, data, and assumptions described in this guide, except that 2357 270 g

20

a.

All dose contributions from radiation emitted by 222Rn, 2tapo, 214Pb, 214Bi, and 214Po will be excluded, and b.

All dose contributions from radiation emitted by zioPb, 2toBi, and 21oPo formed by decay of released 222Rn will be excluded.

With reference to Table 1 of this guide, the dose contributions eliminated for the purpose of evaluating compliance with 40 CFR Part 190 include those due to any radiation emitted by (a) radionuclides for which i = 7, 8, 9, 10, or 11 and (b) radionuclides present in particle size category p = 5 (radon daughters).

The staff will add to dose totals computed for evaluating compliance with 40 CFR Part 190 any known significant doses resulting from any other light-water-cooled nuclear power generating or fuel cycle facilities, as appropriate (excluding doses from 222Rn and its daughters as stipulated above and excluding doses from any radioactive materials released by nuclear or other facilities or operations not included under 40 CFR Part 190).

3.

POPULATION DOSE CALCULATIONS Population doses are calculated, using the environmental dose commitment concept with an integrating period of 100 years (Ref. 3).

Under this approach, radiological impacts for a given release of activity are integrated over a time interval of 100 years following the release.

The 100 year environmental dose commitment resulting from average release rates over a 1 year period is computed for (a) the period of actual uranium milling and (b) the period of time af ter the cessation of milling during which tailings are allowed to dry prior to final stabilization and reclamation.

The NRC staff's rationale for the selection and use of a 100 year integrating period and the staff's tech-nique for computing environmental dose commitments are addressed in Appendix B to this guide.

Population doses resulting from particulate and radon releases are evalu-ated over the general region of the facility site for the first two mill-life-cycle time spans (, nilling operation and prestabilization postoperation phases).

For these.two time intervals, and for the postreclamation era, annual popula-tion dose commitments resulting from transcontinental dispersion of 222Rn are also evalu'ated.

2357 271 21 f

3.1 Regional Population Doses Population doses resulting from environmental radioactivity concentra-tions in the region of the site are evaluated for all exposure pathways con-sidered in the evaluation of maximum individual doses; other pathways should also be considered if they are likely to result in an increase of more than 10 percent to the total result.

Regional population dose commitments are generally computed on the basis of the popula' ion and agricultural productiv-c ity within a distance of 80 km (50 mi).

Individual localized population centers lying beyond this distance should also be considered if their inclu-sion would increase the population dose estimates by more than 10 percent.

3.1.1 Inhalation and External Doses Inhalation and external doses are computed by the NRC staff, using the identical models, equations, data, and assumptions as previously described for individual dose calculations in regulatory positions 1 and 2 of this guide.

The procedure for calculating regional population doses from those pathways is to (a) divide the geographical site region into segments by radius and direction, (b) establish average individual doses within each segment, (c) multiply these individual deles by the estimated population lying within each segment, and (d) sum over all segments.

The population distribution required is that projected for the final year of mill operation.

The appropriate population projection should be presented for each segment formed by radii extending outward from the site and bisecting the 16 compass directions (forming 22.5 sectors) and con-centric circles drawn at distances of 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, and 80 km.

The 14 circles and 16 radii then form a grid com-posed of 224 individual segments.

Average doses over the population within each segment are computed by the NRC staff along the segment directional centerline at a distance midway between the inner and outer boundaries.

The population dose in the site region from inhalation and external exposure pathways is computed by the staff, using the following equation:

2357 272 22

M (inh + ext) = 10-3 P,[djs(inh) + djs(ext)]

(18) j s

where d (ext) is the average external dose to organ j in segment s, in mrem /yr; p(inh) is the average inhalation dose to organ j in segment s, in d

mrem /yr; M (inh + ext) is the resulting population dose from inhalation and external j

exposure pathways, in rem /yr; P

is the population residing in segment s; and 3

10-3 is a conversion factor from millirem to rem.

3.1.2 Food Ingestion Doses Collective population doses from food ingestion are calculated on the basis of the region's agricultural productivity rather than its population.

This is because the total population dose from food pathways is proportional to the total amounts of radionuclides in all food produced in the region rather than the number of people exposed.

The model employed by the NRC staff considers population doses resulting from radioactive contamination of vegetable, meat, and milk products produced in the region.

For population dose calculations, the vegetable category includes f ruit and grain crops as well.

The procedure followed by the staff to compute food ingestion doses is similar to that used for inhalation and external doses and is composed of the following procedural steps:

a.

The site region is divided into segments and each segment is assigned a productivity rate for each food category (vegetables, 2

meat, and milk, in kg/yr per km );

b.

The average activity concentratioris for each food type are computed and multiplied by the segment productivity factor and by the segment area; c.

Total activity content of the regional food production is then determined by summing over the segments; and 2357 273 23

d.

Population doses are determined assuming that all food produced in the region is consumed by a population with the same age distri-bution as the U.S. population.

Agricultural productivity data required for use in this analysis are generally available on a county-by county basis for a relatively recent year.

The available raw data should be projected forward in time to provide a reason-able estimate of productivity during the final year of mill operation.

If other means are not available, the NRC staff considers it acceptable to assume that regional agricultural productivity will remain in constant proportion to the U.S. population.

Should other site-specific data not be available, the staff will rely on the statewide average productivity data presented in Table 7.

The following equation is used to obtain segment average radio-nuclide concentrations in vegetables:

Cvis( V9) "

W C (19) vs vis v

C ;3 is the averao' concentration of radionuclide i in vegetable y

type v produced in segment s, in pCi/kg; Cvis(avg) is the average concentration of radionuclide i, averaged over all types of vegetables, in segment s, in pCi/kg; and W

is the weighting factor for vegetable type v in segment s vs (fraction of total production), dimensionless.

When relying on the state-average production data given in Table 7, the NRC staff will use values of W that have been selected to roughly correspond y

to the fractions of the three vegetable types in the average diet.

From Reference 1, these W values are 0.78 for above ground vegetables, 0.20 for y

potatoes, and 0.02 for other below ground vegetables.

The gross activity content of the regional food production for each food type (vegetables, meat, or milk) is obtained by O

G AC (20) fi fs 3 fis s

2357 274

(

24

where 2

A is the area of sagment s, in km ;

3 C

is the concentration of radionuclide i in food category f in fjg segment s, in pCi/kg; G

is the productivity factor for food f in segment s, in kg/yr fs 2

per km ; and Qg is the gross activity content of radionuclide i in food f, f

in pCi/yr.

Since the food produced may be eaten at different rates by different age groups and since ingestion dose conversion factors are also age dependent, it is necessary to establish the fractions of the Q g values determined by f

Equation 20 that are ingested by the various age groups.

The following rela-tionship applies:

U pk fk (py)

F

=

fk

{Fpk fk U

k where F

is the fraction of the production of food type f ingested by fk individuals in c.ge group k, dimensionless; F

is the fraction of the regional population belonging to age pk group k, dimensionless; and U

is the average consumption rate of food type f for an indi-fk vidual in age group k (see Table 8 for values).

In the absence of suitable site-specific information, the NRC staff will assume average consumption rates for the population at large, as given in Table 8, and population age fractions and frac-tional consumption rates, as given in Table 9.

Using values obtained from Equations 20 and 21, total population inges-tion doses from all food categories are calculated by M)(ing) = 10-3 E Q j fkOCFijk(ing)

(22)

F ff fik

)

2357 275 25

where E

is a factor to account for activity losses during food prepara-7 tion, dimensionless; and M (ing) is the resulting regional population dose from food ingestion j

for organ j, in rem /yr.

The value of E is assumed to be 0.5 for vegetables and 1.0 for meat f

and milk.

Fractions of the population belonging to the various age groups used in Equation 20 are determined from U.S. census data in the absence of site-specific information (see Table 9 for values).

3.2 Continental Population Doses Substantiai contributions to the total population dose may arise from the transport of released 222Rn across the North American continent.

Forma-tion of long-lived 21oPb from 222Rn may result in both inhalation and ingestion doses to people in Canada and Mexico, as well as in the United States (Ref. 8).

In order to estimate population doses occurring beyond the immediate region of the site, the staff makes use of the data presented in Table 10.

These data consist of estimates of population doses resulting from 1,000-Ci releases of 222Rn from four specific locations in the western United States.

The location closest to the mill site should be used.

The population doses pro-vided are those that would have resulted from releases during calendar year 1978, including doses to Canadian and Mexican populations, and are based on the use of the environmental dose commitment concept with an integrating period of 100 years.

For projected releases of 222Rn in future years, resulting population doses are computed by assuming those doses to be proportional to the U.S.

population (use the population data provided in Table 11).

The anticipated annual 222Rn release, in kCi, is multiplied by the appropriate population doses from Table 10, and these results are then multiplied by the ratio of the projected U.S. population for the year of release to the 1978 U.S.

population.

2357 276 C

26

S 3.3 Total Population Dose Commitments Population doses over the site region and the North American continent are computed on an annual basis for the milling, pile drying, and postreclama-tion uranium mill life-cycle phases.

The total radiological impact due to emissions during the first two phases is estimated by multiplying the annual impacts by the durations and summing.

Total annual impacts for each of the three phases are obtained by j = M (inh + ext) + M (ing) + M (Rn)

(23)

M j

j where M) is the annual committed population dose to organ j, in rem /yr; and M (Rn) is the annual continental population dose from 222Rn and its j

daughters to organ j, in rem /yr.

Total impacts over the first two mill-life-cycle phases are obtained by M (m&d) = T M (m) + T M (d)

(24) j gj dj where M (d) is the annual committed population dose to organ j during j

the drying phase, in rem /yr; M (m) is the annual committed population dose to organ j during j

the milling phase, in rem /yr; M (m&d) is the aggregate committed population dose to organ j over j

the milling and drying phases, in rem; and T,T are the durations of the operational and pile drying phases, g d respectively, in yr.

The calculation, compilation, and presentation of these population doses is considered by the NRC staff to represent a reasonably complete description of the radiological impact incurred by the cperation of a typical uranium i

mill.

2357 277 27 4

D.

IMPLEMENTATION Portions of the models specified in this guide have been used by the NRC staff in evaluating current uranium mill licensing applications.

Except in those cases in which an applicant proposes acceptable alternative methods for performing the evaluations described herein, the methods to be described in this guide will be used for radiological impact evaluations for uranium mills with license applications docketed after the implementation date to be specified in the active guide.

This implementation date will not be later than December 1, 1980.

2357 278 9

C 28

O TABLE 1 ISOTOPES AND PARTICLE SIZES FOR WHICH DIRECT AIR CONCENTRATIONS (C M S) ARE R W ED AS IN M DATA adip Unit Density Activity-Median Aerodynamic Equivalent Particle Diameter Mean

Density, Diameter (AMAD),

Deposition Size Group

• Range, mm.

Diameter, mm g/cm3 mm Velocity, m/sec p=1 1.0 8.9 2.98 1.0 x 10_2 p=2 1.0 2.4 1.55 1.0 x 10-2 p=3 1 to 10 5.0 2.4 7.75 1.0 x 10 -2 p=4 10 to 80 35.0 2.4 54.2 8.82 x 102 p=5 0.3 1.0 0.3 0.3 x 10 Particle Size Group Index**

i Radionuclide p=1 p=2 p=3 p=4 p=5 1

uranium-238 C&R C&R C&R C&R 2

thorium-234 se se se se 3

protactinium-234 se se se se 4

uranium-234 se se se se 5

thorium-230 C&R C&R C&R C&R 6

radium-226 C&R C&R C&R C&R 7

radon-222***

se se se se 8

polonium-218 se se se se C&R 9

lead-214 se se se se C&R 10 bismuth-214 se se se se C&R 11 polonium-214 se se se se se 12 lead-210 C&R C&R C&R C&R C&R 13 bismuth-210 se se se se C&R 14 polonium-210 se se se se C&R AParticle size groups are assigned to effluents as follows:

p = 1 for yellowcake dust; p = 2, 3, or 4 for fugitive ore and tailings dusts; p = 5 for 222Rn air in-growth concentrations of particulate daughters.

value is explicitly calculated Theentry"C&R"indicatesthattheparticularC,M0els, equations,anddatadescribed by the staff and required as input for use of the in this guide.

The entry "se" indicates that radionuclide is assumed to be in secular equilibrium with the next-higher-up parent for which the direct air concentration is explicitly calculated.

AAA The air concentration of 222Rn is also calculated by the staff and is required as input for use of this guide; 222Rn gas is not assigned a particle size.

2357 279 29

C TABLE 2 ENVIRONMENTAL TRANSFERS COEFFICIENTS

• U Th Ra Pb I. Plant / Soil (Byj)

~3

-3

-2

-3 a.

Edible Above Ground 2.5 x 10 4.2 x 10 1.4 x 10 4.0 x 10

-3

-3

-3 b.

Potatoes 2.5 x 10 4.2 x 10~

3.0 x 10 4.0 x 10

-3

-3

-2

-3 c.

Other Below Ground 2.5 x 10 4.2 x 10 1.4 x 10 4.0 x 10

-3

-3

-2

-2 d.

Pasture Grass 2.5 x 10 4.2 x 10 1.8 x 10 2.8 x 10

-3

-3

-2

-2 e.

Stored Feed (Hay) 2.5 x 10 4.2 x 10 8.2 x 10 3.6 x 10 II. Beef / Feed (Fbi)

~4

~4

~4

~4 (pCi/kg per pCi/ day) 3.4 x 10 2.0 x 10 5.1 x 10 7.1 x 10 III. Hilk/ Feed (F,9)

~4

-6

~4

~4 (pCi/E per pCi/ day) 6.1 x 10 5.0 x 10 5.9 x 10 1.2 x 10 A

Sources for these data include References 9-12.

))

t 30

s O

TABLE 3 INHALATION DOSE CONVERSION FACTORS 4

mrem /yr per pCi/m2 3

Particle Size = 0.3 micron 2toPb 2iopo Whole Body 7.46E+00 1.29E+00 Bone 2.32E+02 5.24E+00 Kidney 1.93E+02 3.87E+01 Liver 5.91E+01 1.15E+01 Mass Average Lung 6.27E+01 2.66E+02 Particle Size = 1.0 micron 2380 2349 230Th 22sRa 2toPb 21opo 3

Density = 8.9 g/cm Whole Body 1.44E+00 1.64E+00 1.37E+02 3.97E+01 9.42E+00 1.77E+00 Bone 2.42E+01 2.64E+01 4.90E+03 3.97E+02 2.87E+02 7.22E+00 Kidney 5.53E+00 6.30E+00 1.37E+03 1.40E+00 2.39E&O2 5.33E+01 Liver 0.

O.

2.82E+02 4.94E-02 7.32E+01 1.59E+01 Mass Average Lung 2.13E+03 2.42E+03 2.37E+03 3.04E+02 2.49E+01 1.12E+02 Particle Size = 1.0 micron 238g 234U 230Th 22sRa 21oPb 21opo 3

Density = 2.4 g/cm Whole Body 1.65E+00 1.87E+00 1.66E+02 3.40E+01 8.24E+00 1.54E+00 Bone 2.78E+01 3.03E+01 5.95E+03 3.40E+02 2.56E+02 6.29E+00 Kidney 6.33E+00 7.22E+00 1.67E+03 1.20E+00 2.13E+02 4.64E+01 e

Liver 0.

O.

3.43E+02 4.22E-02 6.53E+01 1.38E+01 Mass Average Lung 2.88E+03 3.28E+03 3.22E+03 4.04E+02 3.38E+01 1.48E+02 Particle Size = 5.0 microns 238U 234U 2 aoth 22sRa 21oPb 21opo Whole Body 1.16E+00 1.32E+00 1.01E402 4.47E+01 1.00E+01 1.96E+00 Bone 1.96E+01 2.14E+01 3.60E+03 4.47E+02 3.11E+02 7.99E+00 Kidney 4.47E+00 5.10E+00 1.00E+03 1.57E+00 2.59E+02 5.89E+01 Liver 0.

O.

2.07E+02 5.55E-02 7.93E+01 1.76E+01 Mass Av rage Lung 1.24E+03 1.42E+03 1.38E+03 1.87E+02 1.45E+01 7.01E+01 Particle Size = 35.0 microns 238g 234U 230Th 22sRa 21 Pb 2topo C.

Whole Body 7.92E-01 9.02E-01 5.77E+01 4.40E+01 9.66E+00 1.93E+00 Bone 1.34E+01 1.46E+01 2.07E+03 4.40E+02 3.00E+02 7.84E+00 Kidney 3.05E+00 3.47E+00 5.73E+02 1.55E+00 2.50E+02 5.79E+01 Liver 0.

O.

1.19E+02 5.47E-02 7.65E+01 1.73E+01 Mass Average Lung 3.33E+02 3.80E+02 3.71E+02 6.38E+01 3.91E+00 2.58E+01 2357 281 31

t TABLE 4 OOSE CONVERSION FACTORS FOR EXTERNAL EXPOSURE Dose Factors for External Doses from Air Concentrations (mrem /yr per pCi/m )

a Radionuclide Skin Whole Body

• 23sU 1.05E-05 1.57E-06 234Th 6.63E-05 5.24E-05 234mPa 8.57E-05 6.64E-05 2340 1.36E-05 2.49E-06 230Th 1.29E-09 3.59E-06 22 era 6.00E-05 4.90E-05 222Rn 3.46E-10 2.83E-06 218Po 8.18E-07 6.34E-07 214Pb 2.06E-03 1.67E-03 214Bi 1.36E-02 1.16E-02 214Po 9.89E-07 7.66E-07 2topb 4.17E-05 1.43E-05 Dose Factors for External Doses from Grcund Concentrations (mrem /yr per pCi/m )

2 Radionuclide Skin Whole Body

• 238U 2.13E-06 3.17E-07 2'4Th 2.10E-06 1.66E-06 234mPa 1.60E-06 1.24E-06 234U 2.60E-06 4.78E-07 23 Th 2.20E-06 6.12E-07 22sRa 1.16E-06 9.47E-07 222Rn 6.15E-08 5.03E-08 21spo 1,42E-08 1.10E-08 214Pb 3.89E-05 3.16E-05 2 *Bi 2.18E-04 1.85E-04 214Po 1.72E-08 1.33E-08 22 Pb 6.65E-06 2.27E-06 A

Doses to internal body organs are assumed to be the same as computed for the whole body.

2357 282 C

32

m.

9 TABLE 5 FOOD CONSUMPTION RATES USED FOR CALCULATING DOSES TO INDIVIOUALS Ingestion Rates by Age Group *

(kg/yr)

Infant Child Teen Adult I. Vegetables (Total) 47.8 76.1 105.

a.

Edible Above Ground 17.3 28.9 39.9 b.

Potatoes 27.2 42.2 60.4 c.

Other Below Ground 3.?

5.0 5.0 II. Meat (Beef, Fresh Pork, and Lamb) 27.6 44.8 78.3 III. Milk (2/yr) 208.

208.

246.

130.

• All data are taken from Reference 5.

Ingestion rates are averages for typical farm households.

No allowance is routinely credited for portions of year when locally grown or home grown food may not be available.

2357 283 33

TABLE 6 INGESTION DOSE CONVERSION FACTORS Internal 00se Conversion Factors by Organ and Age (mrem per pCi ingested) 238U 234g 234Th 230Th 226 Raw 2toPb 21ogj 210po Age Group Organ Infant Wh. Bod 3.33E-04 3.80E-04 2.00E-08 1.06E-04 1.07E-02 2.38E-03 3.58E-07 7.41E-04 Bone 4.47E-03 4.88E-03 6.92E-07 3.80E-03 9.44E-02 5.28E-02 4.16E-06 3.10E-03 Liver 0.

O.

3.77E-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 8.71E-04 4.33E-02 2.08E-04 1.26E-02 Child Wh. Bod 1.94E-04 2.21E-04 9.88E-09 9.91E-05 9.87E-03 2.09E-03 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 jg Liver 0.

O.

1.51E-08 1.78E-04 1.84E-05 1.22E-02 1.02E-03 2.43E-03 Kidney 5.24E-04 5.98E-04 8.02E-08 8.67E-04 4.88E-04 3.67E-02 1.15E-04 7.56E-03 Teenager Wh. Bod 6.49E-05 7.39E-05 3.31E-09 6.00E-05 5.00E-03 7.01E-04 5.66E-08 1.23E-04 Bone 1.09E-03 1.19E-03 1.14E-07 2.16E-03 4.09E-02 1.81E-02 6.59E-07 5.09E-04 Liver 0.

O.

6.68E-09 1.23E-04 8.13E-06 5.44E-03 4.51E-06 1.07E-03 Kidney 2.50E-04 2.85E-04 3.81E-08 5.99E-04 2.32E-04 1.72E-02 5.48E-05 3.60E-03 Adult Wh. Bod 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 7.67E-04 8.36E-04 8.01E-08 2.06E-03 4.60E-02 1.53E-02 4.61E-07 3.56E-04 Liver 0.

O.

4.71E-09 1.17E-04 5.74E-06 4.37E-03 3.18E-06 7.56E-04 Kidney 1.75E-04 1.99E-04 2.67E-08 5.65E-04 1.63E-04 1.23E-02 3.83E-05 2.52E-03 Nu (J7 m

'sJ Adult whole body and bone dose conversion factors for 22sRa have been obtained from Reference 5 and are based on applicable models and data from Reference 13.

22cRa whole body and bone dose conversion factors for other IN) age groups have been computed by assuming the same proportion to adult whole body and bone dose factors as

(([

given in Reference 14.

All other dose conversion factors are directly from Reference 14.

O

e S

TABLE 7 AVERAGE AGRICULTURAL PRODUCTIVITY FACTORS FOR VARIOUS STATES State-Average Productivity *

(kg/yr p3r km )

2 State Vegetables Meat Milk i

Arizona 580 1,040 1,130 Colorado 2,800 3,200 1,400 Idaho 14,200 2,000 3,400 Montana 1,800 2,000 370 Nevada 18 510 230 New Mexico 280 1,150 460 South Dakota 2,400 6,400 3,600 Texas 1,200 5,300 2,100 Utab 370 790 1,800 Washington 10,700 1,600 6,000 Wyoming 320 1,400 230 aData presented are based on a staff survey and analysis of available data on agricultural productivity for 1973.

2357 285

,j 35

C TABLE 8 FOOD CONSUMPTION RATES USED FOR CALCULATING DOSES TO POPULATIONS Average Consumption Rates *

(kg/yr)

Food Category Infants Children Teens Adults I. Vegetable Pathway A.

Berries and Tree Fruit 0.

54.1 63.9 49.2 B.

Fresh Vegetables **

1.

Potatoes 0.

27.2 42.3 60.4 2.

Other root veg.

O.

3.4 5.0 5.0 3.

Leafy vegetables 0.

5.8 9.4 13.9 4.

Other above ground vegetable.s 0.

11.4 19.5 26.3 C.

Processed Vegetables 1.

Potatoes 0.

2.3 3.6 5.2 2.

Other root veg.

O.

0.9 1.4 1.4 3.

Leafy vegetables 0.

0.4 0.6 0.8 4.

Uther above ground vegetables 0.

14.4 24.6 32.8 D.

Grain, Rice, and Wheat 0.

118.2 136.2 90.8 Total Vegetables 0.

238.1 306.5 285.5 II. Heat Pathway A.

Beef and Lamb **

0.

21.8 35.9 64.0 B.

Unprccessed Pork **

0.

5.9 8.9 14.3 C.

Poultry and Processed Pork 0.

21.0 33.2 49.6 Total Meat O.

48.7 78.0 127.9 III. Milk Pathway A.

Fresh Milk **

207.6 207.6 246.0 129.6 B.

Milk Products 0.

27.2 45.4 46.7 Total Milk 207.6 234.8 291.4 176.3 All data are taken rom Reference 5 and are representative of average consumption rates by individuals at farm residences.

nn These food categories are evaluated for individual doses from ingestion pathways.

2357 286 36

TABLE 9 IhI AGE DISTRIBUTION OF POPULATION, AVERAGE AND PER CAPITA CONSUMPTION RATES, AND FRACTIONS USED IN THE ABSENCE OF SITE-SPECIFIC DATA Average Total Consumption Rates **

Age Fraction of (kg/yr)

Group Population

• Vegetables Meat Milk Infants 0.0179 0.

O.

207.6 Children 0.1647 238.1 48.7 234.8 Teenagers 0.1957 306.5 78.0 291.4 Adults 0.6217 235.5 127.9 176.3 Fraction of Regional Production Ingested by Each Age Group Age Group Vegttchles Meat Milk Infants 0.

O.

0.0178 Children 0.1416 0.0780 0.1850 Teenagers 0.2167 0.1485 0.2728 Adults 0.6415 0.7735 0.5244 AAge fractions given reflect average values for the entire U.S. population indicated by 1970 census data, as reported in Reference 15.

AAConsumption rates given are from Table 8 and are not those used for, or appropriate to, the calculation of maximum individual doses.

2357 287 37 4

C TABLE 10 CONTINENTAL POPULATION DOSES PER kCi 0F 222RN RELEASED It' 1978 Population Doses Casulting from a 1-kCi Release of 222Rn During 1978, organ-rem

• Bronchial Whole Pulmonary Release Site Epithelium Body Lung Bone Casper, Wyoming 56.

8.8 2.0 120.

Falls City, Texas 72.

S. 8 1.6 77.

Grants, New Mexico 52.

6.2

1. 8 110.

Wellpinit, Washington 43.

9.0

1. 7 120.

Average 56.

8.0

1. 8 110.

A Values given are based on data reported in Reference 8 and amended for inclusion in Reference 1.

Exposure pathways considered include inhalation and ingestion.

Isotopes considered include 222Rn and its short-lived daughters, 2toPb, 2io8i, and 2toPo.

A 100 year integrating period was used in the application of the environmental dose commitment concept.

2357 28E L

E 38

-~

9 TABLE 11 PROJECTED POPULATION OF THE UNITED STATES, 1978-2100 Projected U.S.

Projected U.S.

Population, Population, Year millions

• Year millions

• l l

1978 218.4 1992 247.4 1979 220.2 1993 249.3 1980 222.2 1994 251.1 i

1981 224.2 1995 252.8 1982 226.3 1996 254.4 1983 228.5 1997 255.9 1984 230.7 1998 257.5 1985 232.9 1999 258.9 1986 235.1 2000 260.4 1987 237.2 2025 287.5 1988 239.4 2050 291.1 1989 241.5 2075 291.9 1990 243.5 2100 293.0 1991 2+5.5 APopulation projections through the year 2000 are from Reference 16.

Later projections were obtained from Reference 8 and are based on a predicted growth rate obtained from Reference 17.

2357 289 39

DIRECT AIR RESUSPENDED AIR CONCENTRATION CONCENTRATIONS pCkm' pCum" (Cadip's)

(C,ip's)

\\

u u

[

\\

\\

DIRECT TOTAL AIR USED TO COMPUTE INHALATION DOSE AND EXTERNAL DOSES FROM DEPOSITION CONCENTRATIONS SUBMERSION IN A CONTAMINATED pCum'sec pCum s (D "'I I0 di alp I f l f

\\

[

\\

GROUND TOTAL CONCENTRATIONS DEPOSITION pCUm pCUm'~sec a

(C,'s)

(D;p's)

\\

\\

/

m USED TO COMPUTE EXTERNAL DOSES FROM CONTAMINATED GROUND PLANE VEGETATION CONCENTRATIONS

- {

USED TO COMPUTE VEGETABLE CUk INGESTION DOSES vi

\\

/

/

N MEAT CONCENTRATIONS USED TO COMPUTE MEAT (BEEF) pCilkg INGESTION DOSES (Cbi "I

/

N MILK

+

CONCENTRATIONS m

USED TO COMPUTE MILK pCL1 INGESTION DOSES (C,g's)

\\

/

FigurO 1.

Schematic Diagram Of Information Flow and Use For Dose Calculations 2357 290

REFERENCES 1.

" Generic Environmental Impact Statement on Uranium Milling," USNRC Report NUREG-0511, Office of Nuclear Materials Safety and Safeguards, April 1979.

2.

M. H. Momeni, Y. Yuan, and A. J. Zielen, "The Uranium Dispersion and Dosimetry (UDAD) Code," US NRC Report NUREG/CR-0553.

3.

" Environmental Radiation Dose Commitment:

An Application to the Nuclear Power Industry," Environmental Protection Agency, EPA-520/4-73-002, 1974.

4.

D. C. Kocher, " Nuclear Decay Data for Radionuclides Occurring in Routine Releases from Nuclear Fuel Cycle Facilities," USNRC Report ORNL/NUREG/

TM-102, August 1977.

5.

J. F. Fletcher and W. L. Dotson (compilers), " HERMES - A Digital Computer Code for Estimating Regional Radiological Effects from the Nuclear Power Industry," Hanford Engineering Development Laboratory, HEDL-TME-71-168, December 1971.

6.

ICRP Task Group on Lung Dynamics, " Deposition and Retenc;nn Models for Internal Dosimetry of the Human Respiratory Tract," Health Physics 12:181, 1966.

7.

National Academy of Sciences--National Research Council, "The Effects on Populations of Exposure to Low Levels of Ionizing Radiation," Report cf the Advisory Committee on the Biological Effects of Ionizing Radiation (BEIR), U.S. Govern. ment Printing Office, 1972.

8.

C. C. Travis et al., "A Radiological Assessment of Radon-222 Released from Uranium Mills and Other Natural and Technologically Enhanced Sources,"

Oak Ridge National Laboratory Report ORNL/NUREG-55, USNRC Report NUREG/

CR-0573, 1979.

3 2357 291 u

REFERENCES (Continued) 9.

Y. C. Ng et al., " Prediction of the Maximum Dosage to Man from the Fallout of Nuclear Devices, Handbook for Estimating the Maximum Internal Dose from Radionuclides Released to the Biosphere," USAEC Report UCRL-50163, Part IV, 1968.

10.

R. S. Booth et al., "A Systems Analysis Methodology for Predicting Dose to Man from a Radioactivity Contaminated Terrestrial Environment,"

Proceedings of the Third National Symposium on Radioecology, USAEC Report CONF-710501, Oak Ridge, Tenn., pp. 877-893, 1971.

11.

R. J. Garner, " Transfer of Radioactive Materials from the Terrestrial Environment to Animals and Man," CRC Press, Cleveland, Ohio, 1972.

12.

L. L. McDowell-Boyer et al., " Review and Recommendations of Dose Conver-sion Factors and Environmental Tranport Parameters for 2toPb and 22cRa,"

Oak Ridge National Laboratory Report ORNL/NUREG-56, USNRC Report NUREG/

CR-0574, 1979.

13.

International Commission on Radiological Protection, " Recommendations of the International Commission on Radiological Protection," ICRP Publication 10A, Pergamon Press, New York, 1971.

14.

G. R. Hoenes and J. K. Soldat, " Age-Specific Radiation Dose Commitment Factors for a One-Year Chronic Intake," Battelle Pacific Northwest Laboratories, USNRC Report NUREG-0172, November 1977.

15.

" Environmental Analysis of the Uranium Fuel Cycle, Part II - Nuclear Power Reactors," U.S. Environmental Protection Agency, EPA-520/

2} 292 9-73-003-C, November 1973. 42

S REFERENCES (Continued) 16. U.S. Bureau of the Census, " Projections of the Population of the United States: 1977-2050," Current Population Reports Series P-25, No. 704, U.S. Government Printing Office, Washington, D.C. 20402, 1977. 17. " Development of the Methodology Relevant to U.N. Global Projections," paper presented to the Ad Hoc Group of Experts on Demographic Projec-tion, U.N. Fund for Public Activities, Population Division, New York, 7-11 November 1977. 2357 293 P 43

LIST OF SYMBOLS Symbol Description a Equal to (t - 1.82) if t > 1.82 and otherwise ewal to zero, in yr 2 A Area of segment s, in km 3 B Soil-to plant transfer coefficient for radionuclide i, yj vegetation type v, dimensionless C Direct air concentration of radionuclide i, particle adip 3 size p, resulting from operational releases, in pCi/m 3 C Total air concentration of radionuclide i, in pCi/m ai aip(t) Total air concentration of radionuclide i, particle size C 3 p, at time t, in pCi/m y5p(t) Resuspended air concentration of radionuclide i, particle C size p, at time t, in pCi/ma Carip(T - 0.5) Residual resuspended air concentration of radionuclide d i in particle size p resulting from operational releases, 0.5 year prior to the end of the T 'Y" # d"Y "9 P*"I d' I d 3 in pCi/m C Resulting average concentration 31 radionuclide i in bi meat, in pCi/kg C Concentration of radionuclide i in food category f in fj3 segment s, in pCi/kg C }}}[ }Qd 44

o LIST OF SYMBOLS (Continued) gi(t) Ground surface concentration of radionuclide i at time C 2 t, in pCi/m - 0.5) Residual ground concentration of radionuclide i resulting g4(T C d from operational releases, 0.5 year prior to the end of 2 I the T year drying period, in pCi/m d Cgj(T ) Ground concentration of radionuclide i at the time of g 2 mill shutdown, in pCi/m C g(Pb +- Ra) Incremental 2toPb ground concentration resulting from g 2 22sRa deposition, in pCi/m C Concentration of radionuclide i in hay (or other stored hi feed), in pCi/kg C,9 Resulting concentration of radionuclide i in milk, in pCi/2 C Concentratiw of radionuclide i in pasture grass, in pgj pCi/kg C. Resulting concentration of racionuclide i, in vegetation vi v, in pCi/kg C Average concentration of radionuclide i in vegetable is type v produced in segment s, in pCi/kg Cvis(avg) Average concentration of radionuclide i, averaged over all types of vegetables, in segment s, in pCi/kg 2357 295 45

o i LIST OF SYMBOLS (Continued) DCFjj(cid) Dose conversion factor for cloud exposure for radionuclide i, organ j, in mrem /yr per pCi/m 3 DCFjj(gnd) Dose conversion factor for ground exposure for radionuclide i, organ j, in mrem /yr per pCi/m2 DCFijk(ing) Ingestion dose conversion factor for radionuclide i, organ j, age group k, in units of mrem /pCi ingested CCFjjp(inh) Inhalation dose conversion factor for radionuclide i, organ j, and particle size p, in mrem /yr per pCi/m3 D Resulting direct deposition rate of radionuclide i, in di pCi/m2 per sec D Total deposition rate, including depos; tion of resuspended j activity, of radionuclide i, in pCi/m per sec 2 d (ext) External dose to organ j, in mrem /yr j d)(inh) Inhalation dose to organ j, in mrem /yr p(ing) Ingestion dose for organ j, age group k, in mrem /yr d jk(tot) Total dose to organ j of an individual in age group k d from all exposure pathways, in mrem /yr djs(ext) Average external dose to organ j in segment s, in mrem /yr 2357 296 46

LIST OF SYMBOLS (Continued) js(inh) Average inhalation dose to organ j in segment s, in d mrem /yr E Factor to account for activity losses during food prepara-f tion, dimensionless E Fraction of the foliar deposition reaching edible portions y of vegetation v, dimensionless F Feed-to-meat transfer coefficient for radionuclide i, bi in pCi/kg per pCi/ day ingested (see Table 2) F Fraction of the production of food type f ingested by fk individuals in age group k, dimensionless G F,9 Feed-to-milk transfer coefficient for radionuclide i, in pCi/f per pCi/ day ingested (see Table 2) Fractions of the total annual feed requirement assumed Fpg,F h to be satisfied by pasture grass or locally grown stored feed (hay), respectively, dimensionless F Fraction of the regional population belonging to age pk group k, dimensionless F Fraction of the total deposition retained on plant r surfaces, 0.2, dimensionless G Productivity factor for food f in segment s, in kg/yr fs 2 per km 2357 297 9 47

l LIST OF SYMBOLS (Continued) l Activity ingestion rate of radionuclide i by an individual ik in age group k, in pCi/yr M Annual committed population dose to organ j, in rem /yr j M (d) Annual committed population dose to organ j during the j drying phase, in rem /yr M (ing) Resulting regional population dose from food ingestion j for organ j, in rem /yr M (inh + ext) Resulting population dose from inhalation and external j exposure pathways, in rem /yr M (m) Annual committed population dose to organ j during the j milling phase, in rem /yr M (m&d) Aggregate committed population dose to organ j over the j milling and drying phases, in rem M (Rn) Annual continental population dose from 222Rn and its j daughters to organ j, in rem /yr p Assumed soil areal density for surface mixing, 240 kg/m 2 P Population residing in segment s 3 Q Assumed feed ingestion rate, 50 kg/ day Q; Gross activity content of radionuclide i in food f, in f pCi/yr 2357 298 48

D LIST OF SYMBOLS (Continued) R (t) Ratio of the resuspended air concentration to the ground p concentration, for a ground concentration of age t yr, of particle size p, in m-1 t Time interval over which deposition has occurred, in sec l T Duration of time required to dry the tailings pile prior l d to reclamation, in yr T,T Durations of the operational and pile drying phases, g d respectively, in yr t Assumed duration of exposure while growing of vegetation y S v, in sec U Average consumption rate of food type f for an individual fk in age group k (see Table 8 for values) Milk (in 2/yr) and meat (in kg/yr) ingestion rates for Ug,Ubk age group k U Ingestion rate of vegetable category v for age group k, vk in kg/yr V Deposition velocity of particle size p, in m/sec (see p Table 1) W Weighting factor for vegetable type v in segment s (frac-s tion of total production), dimensionless 2357 299 49

s S LIST OF SYMBOLS (Continued) Y Assumed yield density of vegetation v, in kg/m2 y 6(t) Zero if t 5 1.82 and unity otherwise, dimensionless A, Assumed rate constant for environmental loss, in sec-1 A Radioactive decay constant for radionuclide i, in sec-1 4 Aj Effective removal constant for radionuclide i on soil, in yr-1 A* Effective rate constant for loss by radioactive decay and migration of a ground-deposited radionuclide and equal to A + ^, in sec" n e A Assumed decay constant of the resuspension factor R (equivalent to a 50-day half-life), 5.06 yr-1 A Decay constant accounting for weathering losses (equivalent to a 14-day half-life), 6.73 x 10-7 sec-1 10 '3 Terminal value of the resuspension factor for particles with a deposition velocity of 0.01 m/sec, in m-1 10-5 Initial value of the resuspension factor for particles with a deposition velocity of 0.01 m/sec, in m-1 10-3 Conversion factor for millirem to rem O.01 Deposition velocity for the particle size for which the initial resuspension factor value is 10-5/m, in m/sec 2357 300 50 O

LIST OF SYMBOLS (Continued) 0.5 Fraction of vegetable activity remaining after food preparation, dimensionless 0.825 Effective reduction factor because of structural shielding for indoor exposure periods 1.82 Time required to reach the terminal resuspension factor, in yr 3.156 x 107 Sec/yr 2357 301 0 51

t APPENDIX A SITE-SPECIFIC INFORMATION AND DATA USED BY THE NRC STAFF IN PERFORMING RADIOLOGICAL IMPACT EVALUATIONS FOR URANIUM MILLING OPERATIONS Table A-1 lists and partially describes most of the information and data commonly used by the NRC staff in performing its uranium mill radi-ological impact evaluations. All the data detailed in Table A-1 are not always available on a site-specific basis, in which case the staff will employ conservative estimates or assumptions. In some situations, the data identified in Table A-1 may not be adequate, so the staff will attempt to secure additional information. This situation may arise, for instance, when operations at more than one site are involved and the staff is required to evaluate combined impacts. In most cases, however, provision of the data identified in Table A-1 allows the staff to completely fulfill its respon-sibilities with regard to the preparation of a thorough, knowledgeable, and technically sound radiological impact evaluation. 2357 102 t 52

/ _. 9 TABLE A-1 PLANT, PLANT OPERATIONS, METEOROLOGICAL, AND ENVIRONMENTAL DATA ROUTINELY USED BY THE NRC STAFF IN PERFORMING RADIOLOGICAL IMPACT EVALUATIONS I. PHYSICAL PLANT DATA A. Detailed site plot plan (overlaid on topographic map, with scale and true north arrow) clearly identifying all locations of 1. Site property boundaries 2. Raw ore storage pads 3. Primary crushers 4. Secondary crushers 5. Crushed ore storage areas 6. Ore grinders 7. Yellowcake dryer and yellowcake dryer stack

• 8.

Yellowcake packaging area and exhaust stack 9. Tailings impoundments rnd their boundaries 10. Any heap leach piles atd their boundaries 11. Restricted area boundaries if different from site property boundaries 12. Fences B. Plant operations data 1. General data Ore processing rates for all crushers and grinders, a. MT/d; hr/d and d/yr operational by weight, average, and range b. Raw ore grade, % Ua03 c. Fractions of uranium, thorium, radium, and lead in raw ore expected to flow through to tailings d. Expected yellowcake purity, % U 03 3 by weight, average, and range, MT/yr produced Expected calendar years of initial ore milling, final e. ore milling, and completion of tailings area reclamation nPart of the input to the NRC staff's impact assessment computer code consists of X, Y,-and Z coordinates for various release and receptor locations. 'The staff routinely determines these coordinates with respect to the topographic elevation at the location of the yellowcake dryer stack. 2357

03 53

Table A-1 (Continued) 2. Ore storage data Areas of each pile or bin complex, in m a. 2 b. Ore storage masses c. Ore grades, % Ua0 by weight 3 d. Antidusting measures routinely implemented Anticipated dusting rates, in MT/yr e. f. Anticipated 222Rn releases, in Ci/yr g. Fractions of input ore sent to storage 3. Crushing, grinding data Description of ventilation air filtration equipment a. b. Design efficiency of exhaust filters c. Minimum efficiencies of exhaust filters d. Filter testing procedure and schedule if applicable Fraction of time filters not operational or used e. f. Any measured effluent concentrations g. Stack heights and airflows h. Anticipated release rates, in kg/hr i. Anticipated 222Rn release rate, in Ci/yr j. Fractions of ore throughput reaching filters as dust 4. Yellowcake drying and packaging data Processing rates, MT/hr, for drying and packaging if a. different b. Hr/d and d/yr drying and packaging operations are carried out Description of all ventilation air filtration equipment c. with design, expected, and minimum efficiencies d. Filtration equipment testing procedures and frequencies e. Any measured effluent concentrations f. Stack heights and airflows g. Anticipated release rates, in kg/hr, for the dryer stack, the packaging area ventilation exhaust, and any yellowcake storage area ventilation exhausts S. Tailings impoundment system data Complete physical, chemical, hydr) logical, and radi-a. ological description ( 2357 04 3 54

Table A-1 (Continued) b. Total area, surface areas expected to be under water, saturated, moist, and dry (indicate surface moisture contents used as basis of estimates) c. Description of antidusting measures routinely implemented and their expected effectiveness d. Anticipated dusting rates for saturated, moist, and 2 dry surface areas, in g/m per sec e. Anticipated 222Rn release rates for underwater, saturated, 2 moist, and dry surface areas, Ci/yr per m f. Estimated drying time required prior to initiation of reclamation procedures and basis g. Estimated time required to stabilize and reclaim after drying and basis h. Postreclamation estimated 222Rn release rate, Ci/yr 2 per m, and basis II. METEOROLOGICAL DATA A. Joint frequency data 1. National Weather Service (NWS) station data a. Locations of all NWS stations within 80 km (50 mi) b. Available joint frequency distribution data by wind direction, wind speed, and stability class (3-dimen-sional numerical array) c. Period of record by month and year d. Height of data measurement 2. Onsite meteorological data a. Location and heights of instrumentation b. Description of instrumentation c. Minimum of 1 full year of onsite joint frequency distribution data broken down by wind direction, wind speed, and stability class (3-dimensional array) with a joint data recovery of 90 percent or more B. Miscellaneous data 1. Annual average mixing depth heights 2. Description (general) of regiutal climatology, particularly including frequencies and durations of extreme wind speeds 2357 305 55

Table A-1 (Continued) III. ENVIRONMENTAL DATA A. A detailed topographic map of the area within 8 km (5 mi) of the site showing the locations of all 1. Site boundaries 2. Lands owned, leased, or otherwise controlled (including mill site claims) by the applicant 3. Lands privately owned 4. Lands under the jurisdiction of the U.S. Bureau of Land Management 5. Lands otherwise publicly held 6. Lands useable and available for grazing 7. Private residences or other structures used by the general public 8. Vegetable or other crops, identified by type 9. Private, public, and industrial water wells and natural springs 10. Milk animals (cows or goats) 8. Regional data (within 80 km) 1. Population distributions by direction (16) and radius (0.5, 1, 2, 3, 4, 5,10, 20, 30, 40, 50, 60, 70, and 80 km) for a recent year (no earlier than 1970), for the last year of expected milling (approximate), and for the last year prior to completion of tailings area reclamation (approximate), with expected age group fractions (if available) 2. Available county food production data, in kg/yr, for vegetables (by type and totals), meat (all types), and milk; and any available future predictions by local governmental, industrial, or institutional organizations 2357 306 56

S APPEN'0IX B STAFF METHODOLOGY FOR THE COMPUTATION OF 100-YEAR ENVIRONMENTAL DOSE COMMITMENTS A primary objective of the NRC staff's radiological impact analysis is to e estimate the aggregate radiological impact of the evaluated facilities. In attempting to achieve this goal, the staff employs the concept of environmental dose commitment (EDC) and uses an integrating period of l 100 years. In adopting this general calculational approach, the staff has also endeavored to select and employ a specific calculational scheme suitable for routine use, both by the NRC staff and uranium milling license applicants. The specific technique used by the staff is, for this reason, greatly simplified but somewhat less comprehensive in comparison with other published approaches for EDC computation. This appendix describes the staff's technique for EDC evaluation and addresses the rationale for selecting a 100 year integrating period. Ordinarily, to compute maximum individual doses, the staff uses environmental concentrations calculated for the final year of the particular phase of milling operations. The duration of the milling phase is most often estimated to be 15 to 20 years, while drying of tailings piles may require from 2 to 5 years or slightly longer. The lengths of these time intervals define the value of the time variable "t" that appears in Equa-tions 2, 3, 4, and 6 of regulatory position 1, Concentrations in Environ-mental Media, of this guide. The staff technique for evaluating regional population EOCs for an integrating period of 100 years following activity release involves artifi-cially setting the value of t to 101 years. The specific procedural steps taken by the staff in the calculation of 100 year EDCs are then as otherwise described in regulatory positions 1 and 3 and as follows: 1. Obtain all necessary input direct air concentrations, as identified 'in Table 1, for average release rates (by isotope) over the time interval of the mill life-cycle phase being evaluated. 2357.07 57

t 2. Evaluate all required environmental media concentrations by means of the equations provided for this purpose in regulatory position 1, using a value of 101 years for the variable t appearing in Equations 2, 3, 4, and 6. 3. Based on the environmental media concentrations computed for t = 101 years, using appropriate population, agricultural, and other data as described in regulatory position 3, calculate the regional population doses for all exposure pathways for an exposure period of 1 year. 4. Sum the computed doses, as appropriate, over all exposure pathways. These calculational procedures actually result in the computation of the population dose commitments resulting from a 1 year exposure period to environmental concentrations existing during the 101st year of releases at the constant rates employed. The similarity of thi: result to the desired EOC (the population dose commitments resulting from a 100 year period of exposure to environmental concentrations resulting from constant releases over a 1 year time period) is illustrated in Table B-1, which provides a comparison of staff and conventional methodologies for EDC computation. This table has been organized to display the component parts of each calcu-lational method. Line-by-line equivalence of these component parts can be readily demonstrated under conditions of constant population, population distribution, and agricultural productivity in the site region. The staff has elected to use the approach described, rather than the more conventional approach, and a 100 year integrating period, primarily because of the following reasons: 1. The major exposure pathways are dominated by doses resulting from airborne activity, which decreases rapidly (the resuspension factor has a half-life of about 50 days); 2. The major dose impact of ground concentrations arises from the food ingestion pathways, which depend on estimates of agricultural productivity (forecast data for food productivity in specific areas are rare and are considered to be potentially unreliable); 2357 103 58

0 3. Inordir, ate computational ::ifficulties are involved in routinely taking into account growth trends not amenable to description by very simple mathematical functions; and 4. The vast majority of resulting population exposure results from environnental concentrations at distances between 20 and 80 km from the site at which routine atmospheric dispersion calculations cannot generally yield results with sufficient accuracy to justify accouriting for minor perturbations. 4 ~ Il 2357 309 O 59

TABLE B-1 COMPARISON OF STAFF AND CONVENTIONAL TECHNIQUES FOR EDC CALCULATION NRC Staff EDC Calculational Technique

• Conventional EDC Calculational Technique Defined as:

Population dose commitments Defined as: Population dose com::litments resulting from a 1 year pericd of exposu.-e resulting from a 100 year period of exposure to environmental concentrations present to environmental concentrations resulting during the 101st year of constant releases. from constant releases over a 1 year period. Exposure Release Average Time Exposure. Release Average Time Line Interval, yr Interval, yr Difference, yr Interval, yr Interval, yr Dif ference, yr 1 100 - 101 100 - 101 0 0-1 0-1 0 2 99 - 100 1 1-2 1 3 98 - 99 2 2-3 2 4 97 - 98 3 3-4 3 5 96 - 97 4 4-5 4 6 95 - 96 5 5-6 5 N 94 7-8 93 93 - 94 93 u 95 6-7 94 94 - 95 94 Ln 96 5-6 95 95 - 96 95 N 97 4-5 96 96 - 97 96 98 3-4 97 97 - 98 97 99 2-3 98 98 - 99 98 ] 101 100 1-2 99 99 - 100 99 0-1 100 100 - 101 100

• This table has been purposely organized to portray a line-by-line similarity between staff and conventional EDC computation methods.

Computation by both methods is broken down into component parts that, under con-ditions described in the text, can be shown to be mathematically identical.

~ D APPENDIX C RADON DOSE CONVERSION FACTOR The basis on which the NRC staff has relied for its radon daughter inhala-tion dose conversion factor consists of the following major component parts: 1. The indoor working level (WL) concentration resulting from an outd',or is approximately 5.0 x 10-6 WL; 3 222Rn concentration of 1 pCi/m 2. The number of cumulative working level months (WLM) exposure per year for an average individual at a constant concentration of one WL is 25 WLM/yr; and 3. The committed dose equivalent to the bronchial epithelium (basal 9 cell nuclei of segmented bronchi) per unit WLM exposure is 5000 mrem (5 rem). O These component parts enter into the following equation, which yields the 222Rn inhalation dose conversion factor used by the staff: 5.0 x 10-6 WL 25 WLM/yr 5000 mrem _ 0.625 mrem /yr X a WL WLM ~ l pCi/m3 1 pCi/m Each of the three components identified above derive from sources and data identified below: 3 of 222Rn is established by the assurned indoor 1. 5 x 10-6 WL per pCi/m air concentration ratios for 222Rn, 218po, 214Pb, and 214Bi of 1.0/0.90/0.51/and 0.35. These concentration ratios and the derived conversion factor are representative of conditions in a reasonably well-ventilated structure (Refs. 1 and 2). 2. ,25 WLM/yr per WL concentration derives from the assumption that an average individual's average breathing rate will be about 50 percent of that of a working miner. A WLM is defined, in terms of exposure to a working miner, as one month's occupational exposure 2357 311 61 l

M f 8 t . JJ.....-. o I 4 to a 1-WL concentration. This assumed breathing rate would result in an average individual receiving about 0.5 WLM as a result of the same length of exposure to air at a 1-WL concentration. The H following relationship applies: (8760 hr/yr) x x 0.5 = 25 W yr M 40 r/ k x 52 k/yr 3. Five rem /WLM is the value derived from applying a quality factor ^ (QF) of 10 for alpha radiation to convert from rad to rem (Refs. i 1, 2, and 3) to the figure of 0.5 rad /WLM as reported in the BEIR l Report (page 148 of Ref. 3). i m = The NRC staff considers the above basis for its 222Rn inhalation dose conversion factor to be both sound and reasonable. The staff acknowledges I that radon dosimetry is extremely complex and strongly influenced by assumed environmental and biological conditions. In view of the large variations induced by rather small changes in the assumed free-ion fraction, relative equilibrium, thickness of the intervening tissue and mucuous layers, etc., the staff has endeavored to use physical, environmental, and other data N reasonably representative of average conditions. REFERENCES FOR APPENDIX C l 1. " Potential Radiological Impact of Airborne Releases and Direct Gamma I Radiation to Individuals Living Near Inactive Uranium Mill Tailings fl Piles," Environmental Protection Agency, EPA-520/1-76-001, January 1976. 2. "Environmantal Analysis of the Uranium Fuel Cycle, Part I--Fuel Supply," [ Environmental Protection Agency, EPA-520/9-73-003-B, October 1973. x, 3. National Academy of Sciences--National Research Council, "The Effects j on Populations of Exposure to Low Levels of Ionizing Radiation," Report of the Advisory Committee on the Biological Effects of Ionizing Radiations (BEIR), November 1972. 2357

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2 9 DRAFT VALUE/ IMPACT STATEMENT 1. PROPOSED ACTION 1.1 Description The proposed action consists of the development and publication of a l routine methodology for assessing the radiological impacts of routine radio-active releases from uranium mills. These radiological impacts include doses to exposed individuals, doses to the population within an 80-km (50-mi) radius, doses to the entire U.S. population, and doses to the entire world population. Evaluations made using the published methodology would serve several regulatory and licensing purposes for which the methodology must be suitable. These purposes include evaluating compliance with 40 CFR Part 190, evaluating impacts of releases as part of the overall ALARA evaluation, and evaluation of environ-mental impacts to meet NEPA requirements. 1.2 Need for the Proposed Action Radiological impact. evaluations for routine releases from uranium mills have been carried out in the past and numerous new and repeat evaluations will likely be required in the future. Past evaluations have been prepared in-house by NRC personnel or by personnel from national laboratories under contract. These assessments have lacked a uniformity of approach and purpose for numerous reasons, the most important being the absence of a standardized ~ routine procedure. Other reasons include, but are not limited to, the evolu-tion of new models, techniques, and data; the development of new concerns requiring new methods of analysis; and the problems associated with having evaluations prepared by different groups of people. This situation definitely needs to be corrected. The proposed action incluaes, as part of the develop-ment process, the assembly of state-of-the-art analytical models, including environmental transport models and data, models and data for human dosimetry, 2357 ;13 63

and appropriate data for receptor characteristics. An example of the problems to be addressed by this effort is the evaluation of the long-term time-integrated impact of mill tailings piles, heretofore assessed by NRC only in terms of the impact during a single year.

1. 3 Value/ Impact of the Proposed Action 1.3.1 NRC Completion of the proposed action is estimated to require from 0.5 to 1.0 man year of effort.

Associated costs include resource materials not presently available, printing and copying costs, and costs for normal office supplies. No travel costs are anticipated. No additional research or technical assistance contract costs in support of this effort are anticipated. The possibility exists that further developments may indicate the advisability of efforts incurring travel or contract costs. .he document conveying the results of the proposed action will be a useful tool and should result in substantial benefits to NRC. These include upgrading the quality of future evaluations, particularly with regard to uniformity, completeness, and the application of more up-to-date methods and data. Other benefits will include greater flexibility in personnel assignments and reduced allocations of personnel time to completing evaluations.

1. 3. 2 Other Government Agencies Other agencies may participate in carrying out the proposed action in terms of review and comment services.

Upon completion of the proposed action, other agencies will have available a reliable reference document explaining NRC's evaluation techniques. If evaluations can be conducted more uniformly, there will be a benefit to other agencies concerned with radiological and health inipacts in that they may become more familiar with a routine approach and require less time to review NRC evaluations. 1.3.3 Industrial and Public Interest Groups Clearly predictable impacts on these groups include the costs involved in familiarizing themselves with the product document and in revies and comment 2357 214 A

efforts. Benefits will be derived from more easily predicting and understanding the results of NRC evaluations. It is assumed that some differences from past evaluation techniques will be incorporated in the product document and that such changes would altet he results of past and future evaluations. The degree and effects of such alterations are presently undefinable. 1.3.4 Public The public will suffer the nonetary costs and benefits of completing and implementing the proposed action. The public will derive a benefit from the availability of a reference document explaining NRC evaluation techniques and, hopefully, a further benefit will be derived from the increase in quality of NRC evaluations and subsequent licensing decisions and regulatory requirements.

1. 4 Decision on the Proposed Action The proposed action should be undertaken immediately on a priority basis.

S 2. TECHNICAL APPROACH The technical approach to be used is based in part on contract work prepared by staffs of the Argonne National Laboratory and the Oak Ridge National Laboratory. This approach reflects techniques currently being adopted for use in review of uranium milling license applications and license renewal applications by the Office of Nuclear Material Safety and Safeguards. Comments on the technical approach are being solicited by the issuance of the draft guide for public comment. 3. PROCEDURAL APPROACH 3.1 Procedural Alternatives Possible SD procedures that may be used to carry out the proposed action include the following: 2357

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Regulation Regulatory Guide ANSI Standard, endorsed by a Regulatory Guide Branch Posii. ion NUREG 3.2 Value/ Impact of Procedural Alternatives Preparation of a NUREG report is inappropriate because the product document includes staff positions. An acceptable ANSI standa M is neither available nor currently under preparation. The subject matter of the product document is intended to convey informa-tional material as to the purposes, mechanisms, and minimum requirrments of e NRC evaluations. It is also intended to demonstrate acceptable e/aluation models for use by license applicants. Publication of a regulation is viewed as inappropriate because the strength of law is unnecessary anJ would not allow the flexibility often required in such matters wherein changing scientific, technical, and regulatory bases may be expected. Branch positicas, although sometimes prepared for guidance of this sort, enjoy only limited distribution and are usually followed by a regulatory guide if they prove useful. In this case, no branch position has been prepared, nor is one expected. 3.3 Decision on Procedural Approach A regulatory guide should be prepared. e 4. STATUTORY CONSIDERATIONS 4.1 NRC Authority The product document will establish routine procedures by which NRC will evaluate radiological impacts of routine releases from uranium mills. 66 2357 316

These evaluations will be used in "as low as is reasonably achievable" determinations to evaluate compliance with NRC regulations, to evaluate com-pliance with EPA's 40 CFR Part 190 regulation, and to evaluate environmental impacts as part of NRC's overall NEPA determination. l 4.2 Need for NEPA Assessment The proposed action does not appear to require an environmental impact statement as it is not "a major Commission action significantly affecting the quality of the environment" as detailed in paragraph 51.5(a)(10) of 10 CFR Part 51. l S. RELATIONSHIP TO OTHER EXISTING OR PROPOSED REGULATIONS OR POLICIES No potential conflicts with other agencies have been identified. How-ever, the product document will be a principal tool in the implementation Implementation of 40 CFR Part 190 is an 9 of 40 CFR Part 190, issued by EPA. NRC responsibility. There is some possibility that backfitting requirements may result from implementation of 40 CFR Part 190. Such possible requirements will not result from the proposed action but rather from the original EPA regulation. 6.

SUMMARY

AND CONCLUSIONS The proposed action consists of developing and publishing guidance on routine procedures for evaluating the radiological impact of routine releases of radioactive material from uranium mills. The recommended procedural approach is to publish the product document in the form of a regulatory guide to be issued as soon as possible. There is a present and growing need for guidance in this area. 2357.I7 67

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