U.S. NUCLEAR REGULATORY COMMISSION March 1982 

REGULATORY GUIDE 

OFFICE OF NUCLEAR REGULATORY RESEARCH 

Regulatory Guide 3.51 

(Task RH 8024) 

CALCULATIONAL MODELS FOR ESTIMATING 

RADIATION DOSES TO MAN FROM AIRBORNE RADIOACTIVE 

MATERIALS RESULTING FROM URANIUM MILLING OPERATIONS

USNRC REGULATORY GUIDES 

Regulatory Guides are Issued to describe and make available to the 

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them is not required. Methods and solutions different from those set S-out In the guides will be acceptable If they prnvlde a basis for the 

findings requisite to the issuance or continuance of a permit or license by the Commission. 

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UNITED STATES 

NUCLEAR REGULATORY COMMISSION 

WASHINGTON, D. C. 20555 

August 4, 1982 

ERRATA 

Regulatory Guide 3.51, March 1982

CALCULATIONAL MODELS FOR ESTIMATING RADIATION DOSES TO MAN 

FROM AIRBORNE RADIOACTIVE MATERIALS RESULTING FROM URANIUM MILLING OPERATIONS 

Table 3, "Inhalation Dose Conversion Factors," on page 31 of this guide has the following typographical errors: 

1. Under "Uranium Ore Dust," the 2 38 U bone dose value in the second row 

of the first column should read 7.29E+01 instead of 7.92E+01. 

2. Under "Coarse Tailings Particulates," the.first value for 2 2 6Ra for 

the whole body dose should read 3.90E+01 instead of 4.90E+01.
CONTENTS 

Page 

A. INTRODUCTION ................... ........................ I 

B. DISCUSSION ................... ......................... I 

1. Uranium Mill Source Terms ...... ............ .... 2 

2. Critical Exposure Pathways ......... ............... 3 

3. Required Dose Estimates ............ ................ 3 

3.1 Individual Doses ............ ................. 3 

3.2 Population Doses ............ ................. 5 

4. Use of This Guide ............ ................... 6 

C. REGULATORY POSITION ................ .................... 7 

1. Concentrations in Environmental Media ..... ......... 7 

1.1 Radionuclide Accumulation on the Ground .......... 8 

1.2 Total Air Concentrations .... ............. .... 10 

1.3 Vegetation Concentrations ....... ............. 12 

1.4 Meat and Milk Concentrations .............. .... 14 

1.5 Concentrations at Different Times ........... .... 15 

2. Dose Calculations for Individuals .............. .... 16 

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 .. ........ ... 26 

D. IMPLEMENTATION .......... ....................... .... 27 

REFERENCES ................ ........................... .... 43 

LIST OF SYMBOLS ................... ......................... 47 

VALUES OF CONSTANTS .......... ....................... .... 51 

APPENDIX A - Site-Specific Information and Data Used by the NRC 

Staff in Performing Radiological Impact Evaluations for 

Uranium Milling Operations ...... ................. .... 53 

iii
CONTENTS (Continued)

APPENDIX B - Staff Methodology for the Computation of 100-Year 

Environmental Dose Commitments ..... ............... .... 59 

APPENDIX C - Radon Dose Conversion Factor ........ ............ 63 

REFERENCES FOR APPENDIX C ........ .................... .... 64 

VALUE/IMPACT STATEMENT ......... ...................... .... 65

iv
TABLES 

Table Page 

1 Isotopes and Particle Sizes for Which Direct Air Concen

trations (Cadip values) Are Required as Input Data .... 29 

2 Environmental Transfer Coefficients ................ ... 30 

3 Inhalation Dose Conversion Factors .... ............ ... 31 

4 Dose Conversion Factors for External Exposure ........... 32 

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 

Populations ........ ........................ ... 36 

9 Age Distribution of Population, Average and Per Capita 

Consumption Rates, and Fractions Used in the Absence of 

Site-Specific Data ....... .................... ... 37 

10 Continental Population Doses per kCi* of 2 2 2 Rn Released in 

1978 ............. ... ........................... 38 

11 Projected Population of the United States, 1978-2100 . . 39 

12 Conversion Factors into SI Units .... ............ .... 41 

A-1 Plant, Plant Operations, Meteorological, and Environmental 

Data Routinely Used by the NRC Staff in Performing Radi

ological Impact Evaluations .... ............. ..... 54 

B-1 Comparison of Staff and Conventional Techniques for 

Environmental Dose Commitment Calculation ........... ... 61 

FIGURES 

Figure Page 

1 Schematic Diagram of Information Flow and Use for Dose 

Calculations ...... ....... ....................... 40 

See Table 12.

v
A. INTRODUCTION 

The NRC staff is required to make analyses of radiation doses to the public, 

or individual members thereof, resulting from the radioactive effluents from 

uranium mills 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 Protection Against 

Radiation," and 

3. Evaluating overall radiological impact as part of the complete environ

mental impact assessment required by the National Environmental Policy Act (NEPA) 

of 1969 (Public Law 91-190, 83 Stat. 852). 

This regulatory guide describes basic features of calculational models 

used 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. 

Information on the approach used for estimating source terms is included 

in the Final Generic Environmental Impact Statement on Uranium Milling, 

NUREG-0706 (Ref. 1). The methodology used by the staff for calculating 

atmospheric dispersion is documented in the MILDOS code user's manual, 

NUREG/CR-2011 (Ref. 2). 

B. DISCUSSION 

This guide describes models used by the NRC staff to estimate the radio

logical impacts resulting from uranium mills for the purpose of evaluating 

compliance with 40 CFR Part 190 and 10 CFR Part 20 and of assessing overall 

environmental radiological impacts in accordance with NEPA.

I
1. URANIUM MILL SOURCE TERMS 

A uranium mill, unlike other types of fuel cycle facilities, goes through 

phases in its life cycle in which both the composition and the magnitude of 

its radioactive emissions (and associated impacts) vary greatly. For this 

reason, the NRC staff will perform impact evaluations for each individual mill 

at different phases of its existence. The three principal uranium mill life

cycle phases discussed in this guide are (1) operational (milling), (2) tailings 

pile drying and stabilization, and (3) reclamation. 

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 

curtailed by maintaining the pile at least partially under water. Mechanical 

sprinkler systems or chemical stabilizing agents may also be used to inhibit 

the suspension in air of radioactive tailings dust by the wind. 

When actual milling ceases, the tailings pile is normally allowed to dry 

by natural evaporation until it is ready for stabilization. When the tailings 

are wet, there are essentially no particulate releases from the tailings pile. 

However, as the tailings pile dries, releases of radon and particulates from 

this source may increase, reaching their 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, are likely to persist for 

tens of thousands of years. 

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 stabili

zation 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 2 3 8U and 235U decay series. The 2 3 5U series 

radionuclides amount to less than 5 percent of total releases and are routinely

2
disregarded because of their insignificant contribution to overall radiological 

impact. 

2. CRITICAL EXPOSURE PATHWAYS 

Three exposure pathways of concern for airborne releases from uranium mills 

are (1) inhalation of airborne radioactive material, (2) ingestion of vegetable 

and animal products contaminated via deposition, and (3) 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 liquid effluents. Liquid pathways 

may exist, however, and methodology similar to that used in Regulatory 

Guide 1.109, "Calculation of Annual Doses to Man from Routine Releases of 

Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, 

Appendix I," should be used for evaluating intakes via the liquid pathway. 

However, ingestion dose factors from Table 6 should be used in converting 

intakes to doses. 

All individual exposure pathways of significance will be evaluated at loca

tions 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, occupancy 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 significantly higher exposures, the applicant should 

provide reasonable assurance that a monitoring and surveillance program will 

be performed on a regular and continuing basis to determine if such changes 

have occurred. 

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 

Environmental Protection Agency (EPA) regulation, 40 CFR Part 190, speaks to

3
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. The NRC regulation, 10 CFR Part 20, includes a require

ment to keep all radiation exposures "as low as is reasonably 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 been 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 Reason

ably Achievable' for Radioactive Material in Light-Water-Cooled Nuclear Power 

Reactor Effluents," 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, including 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 for all pathways combined and from all 

activity releases except radon and its daughters are evaluated for (1) the 

last year of actual mill operation and (2) the last year prior to tailings 

pile reclamation. These evaluations are adequate for assessing ALARA compliance 

except that exposure to radon and its daughters should be included and radon 

and daughter exposure for the first year after tailings pile reclamation should 

also be evaluated. Postreclamation exposure to radon and its daughters should 

be evaluated at the location of greatest radon concentration where unrestricted 

land use after mill decommissioning may be permitted. 

Exposed individuals are characterized by food consumption, occupancy, and 

other uses 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 various age groups in 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 NRC staff considers the use of these reference values to be 

acceptable because the actual physiological and metabolic characteristics of 

specific individuals cannot usually be determined. Applicants are encouraged 

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

4
When site-specific information and data are used, their 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." 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 been 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 in this guide, one for each of 

these four age groups. Available data are not sufficient 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. 

3.2 Population Doses 

Evaluations of population doses resulting from uranium milling operations 

are required to satisfy NEPA requirements for assessing the total environmental 

impact associated with the operation of each facility. 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, the total radiological impact is composed of 

the impacts of the three major phases of its existence: the operational phase, 

the prereclamation phase, and the postreclamation 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 phase, the average annual radiological impact 

will be estimated by the NRC staff using the following basic procedure:

5
1. Annual average releases over the duration of the particular mill phase 

will be estimated for each radionuclide. 

2. The radiological impact resulting from 1 year of average releases 

will be evaluated in terms of population dose using the EPA concept of "environ

mental dose commitment" (Ref. 3). The environmental dose commitment will be 

evaluated for a period of 100 years following release as per the procedure 

used by EPA in setting the standards in 40 CFR Part 190. 

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 

represents an approximation of the combined radiological impact of the facility 

prior to tailings pile reclamation. The annual population 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 geograph

ically to the area within 80 km (50 mi) of the mill site. Within this area, 

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 and these are treated separately 

from particulate releases (see Regulatory Position 3.2). 

4. USE OF THIS GUIDE 

Present NRC staff practice with regard to the calculation of radioactive 

emission rates from uranium milling facilities involves the characterization 

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 concentra

tions of radioactive materials previously deposited on ground surfaces). The 

required input air concentrations for a particular location are denoted in 

this guide by the symbol Cadip (in pCi/m 3 ), where the subscripts indicate 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.

6
The primary calculational tool employed by the staff in performing radi

ological impact evaluations of uranium milling operations is the MILDOS code 

(Ref. 2), a modified version of the Argonne National Laboratory Uranium Disper

sion and Dosimetry (UDAD) Code (Ref. 4). As used by the NRC staff, the MILDOS 

code has only five primary radionuclides in the 2 3 8 U decay chain that are 

treated explicitly as source terms. These radionuclides are 23 8 U, 2 3 °Th, 22 6 Ra, 

2 1°Pb, and 2 2 2 Rn. Release rates for these radionuclides are required for each 

potential onsite source (for particle sizes 1 through 4 in Table 1). For 2 2 2 Rn 

daughters, which grow in during transport of 2 2 2 Rn from the site, the resulting 

ingrowth concentrations (particle size 5 in Table 1) are also required. These 

2 2 2 Rn daughters include 2 18 Po, 2 14 Pb, 2 1 4 Bi, 2 1 °Pb, and 2 1°Po. The dosimetry 

model accounts for releases and ingrowth of other radionuclides, using 

assumptions of secular equilibrium. 

Appendix A identifies and describes the various other site-specific 

information 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 environ

mental dose commitments. Appendix C provides a detailed explanation of the 

derivation of the radon dose conversion 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 from uranium mills 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 unique 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 equations

7
yield resulting concentrations in environmental media of interest, including 

total ground surface concentrations, air concentrations, and concentrations in 

edible vegetation, meat, and milk. These concentration calculations are 

explicitly performed only for certain radionuclides of the 2 38 U decay chain. 

Concentrations in environmental media of other radionuclides of the chain 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 

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 concen

trations. The direct deposition rate of radionuclide i is calculated, using 

the following relationship: 

Ddi ". CadipVp 

p

8
where

C adip is the calculated direct air concentration of radionuclide i in 

particle size p in pCi/m 3 ; 

Ddi is the resulting direct deposition rate of radionuclide i 

in pCi/m 2 per sec; and 

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

p Table 1). 

The concentration of radionuclide i on a ground surface due to constant 

deposition at the rate Ddi over time interval t is obtained from 

"" - exp[-(Xi + Xe)t] (2) Cgi~t :di xI ¥ + 

where 

C(t) is the calculated ground surface concentration of radionuclide i 

at time t in pCi/mr2 ; 

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

xe is the assumed rate constant for environmental loss in sec-1; 

and 

xi is the radioactive decay constant* for radionuclide i in 

sec-1. 

The environmental loss constant Xe corresponds to an assumed half-time 

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

accounts for downward migration in soil and loss of availability due to 

chemical binding. It is assumed to apply to all radionuclides deposited on 

the ground. 

Radiological decay constants employed by the NRC staff are obtained from 

data given in Reference 5.

9
Ground concentrations are explicitly computed only for 2 3 8 U, 2 30 Th, 22 6 Ra, 

and 2 10 Pb. For all other radionuclides, the ground concentration is assumed 

equal to that of the first parent radlonuclide for which the ground concentra

tion is explicitly calculated. For 2 1°Pb, ingrowth from deposited 2 2 6 Ra can be 

significant. The concentration of 2 1°Pb on the ground due to 2 2 6Ra deposition 

is calculated by the staff, using the standard Bateman equation and ignoring 

the very-short-lived daughter radionuclides. This is equivalent to assuming 

that 22 6Ra decays directly to 2 1°Pb. Using i = 6 for 2 26 Ra and i = 12 for 

21°Pb (see Table 1), the following equation is obtained: 

S a 2Dd6 [I- e-l2t e-At - e'l2t] Cgl(Pb + Ra) = 12d6 • 1- 2 + e 6 • e2 (3) 

g12 6 L 12 6 A12 j() 

where 

C gl(Pb <- Ra) is the incremental 2 1 °Pb ground concentration resulting from 2 26 Ra deposition in pCi/m 2 ; and 

A* is the effective rate constant for loss by radioactive 

n decay and migration of a ground-deposited radionuclide 

and is equal to An + Ae in sec-1. 

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 M = Cadip + Carip(t) (4) 

where 

C is the calculated direct air concentration of radionuclide i 

adip in particle size p in pCi/m 3 ;

10
C aip(t) is the calculated total air concentration of radionuclide i 

in particle size p at time t in pCi/m 3 ; and 

C arip(t) is the calculated resuspended air concentration of radionu

clide i in 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 

R p(t) = (0.01/Vp )10- e-ARt (for t < 1.82 yr) (5a) 

R p(t) = (0.01/Vp )10- (for t > 1.82 yr) (5b) 

where 

R p(t) is the ratio of the resuspended air concentration to the ground 

concentration for a ground deposit of age t yr for particle 

size p in m-1 ; 

XR is the assumed decay constant of the resuspension factor 

(equivalent to a 50-day half-life), 5.06 yr-'; 

0.01 is the deposition velocity for the particle size for which 

the initial resuspension factor value is 10-5/m in m/sec; 

I0-5 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

11
C arip t) = O.01C adipO-5 

exp 

+ 10-4 6(t)

(W! + xR)

:3.156 x 107) (6)

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 < 1.82 and is unity otherwise, dimensionless; 

Xý is the effective removal constant for radionuclide i on soil 1 in yr- 1 ; and

3.156 x 107 is the number of seconds per year.

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 as given in Table 1. Particulate 

daughters of 2 2 2 Rn (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 Concentrations 

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:

Di = E CaipVp 

p

(7)

where

D. is the total deposition rate, including deposition of resus pended activity, of radionuclide i in pCi/m 2 per sec.

12
Concentrations of released particulate materials 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 

above-ground vegetables, potatoes, other edible below-ground vegetables, 

pasture grass, and hay. Vegetation concentrations are computed using the 

following equation: 

1 - exp('hwtv +CBi() 

Cvi = DiF rEv Y X w ] + Cgi VI (8) 

where 

B vi is the soil-to-plant transfer coefficient for radionuclide i 

and vegetation type v (pCi/kg(wet) plant per pCi/kg(dry) soil); 

C vi is the resulting concentration of radionuclide i in vegetation v in pCi/kg(wet weight); 

Ev is the fraction of the foliar deposition reaching edible por

tions of vegetation v, dimensionless; 

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

p is the assumed soil areal density for surface mixing, 

240 kg(dry weight)/m2 ; 

t is the assumed duration of exposure while vegetation v is 

v~ growing in sec; 

Y is the assumed yield density of vegetation v in kg(wet v weight)/m2 ; and 

Xw is the decay constant accounting for weathering losses (equivalent 

to a 14-day half-life), 5.73 x 10-7 sec- 1. 

The value of Ev is assumed to be 1.0 for all above-ground vegetation and 0.1 

for all below-ground vegetables (Ref. 6). The value of tv is taken to be 60 

days, except for pasture grass for which a value of 30 days is assumed. The 

yield density Yv is taken to be 2.0 kg/mn, except for pasture grass for which 

a value of 0.75 kg/m 2 is applied. Values of the soil-to-plant transfer 

coefficients B vi are provided in Table 2.

13
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 = QFbi(FpgCpgi + FhChi) (9) 

where 

Cbi is the resulting average concentration of radionuclide i in 

meat in pCi/kg; 

Chi is the concentration of radionuclide i in hay (or other stored 

feed) in pCi/kg(wet weight); 

C is the concentration of radionuclide i in pasture grass in 

pgi pCi/kg(wet weight); 

F bi is the feed-to-meat transfer coefficient for radionuclide i 

in pCi/kg per pCi/day ingested (see Table 2); 

F pg,Fh are the fractions of the total annual feed requirement assumed 

to be satisfied by pasture grass or locally grown stored feed 

(hay), respectively, dimensionless; and 

Q is the assumed feed ingestion rate, 50 kg(wet weight)/day 

(Ref. 6). 

The equation used to estimate milk concentrations from cows ingesting 

contaminated feed is 

Cmi = QFmi(F pgC pgi + Fh C hi) (10) 

.where 

C mi is the resulting average concentration of radionuclide i in 

milk in pCi/L; and 

F .i is the feed-to-milk transfer coefficient for radionuclide i 

Fmi in pCi/L per pCi/day ingested (see Table 2).

14
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 during 

the final year of actual mill operation, for an operational lifetime of To 

years, the value of the time variable t appearing in Equations 2, 3, 4, and 

6 is set equal to T0 (in appropriate units). The resulting concentration 

values are those predicted for the end of the final year of operation and 

are assumed to represent average values existing over that year. 

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 TO, the operational lifetime. Residual ground concentra

tions at the end of the final prereclamation year are then determined by 

Cgi(Td) = Cgi(To)exp[_Xi(Td)] (11) 

where 

Cgi(Td) is the residual ground concentration of radionuclide i resulting 

from operational releases at the end of the Td-year drying 

period in pCi/m 2 ; 

C i(T ) is the ground concentration of radionuclide i at the time of 

gi 0 mill shutdown in pCi/m 2 ; and 

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

prior to reclamation per yr. 

Residual resuspended air concentrations resulting from operational releases 

are determined at the end of the final prereclamation year by

15
C arip(Td) = 0.01C adipO-9 exp[-Ki(Td)] 

ari dadip( Td)] 1 

X i-eP(A~) (3.156 X 107) (12) 

where 

Cadip is the direct air concentration of radionuclide i in particle size p resulting from operational releases in pCi/m 3 ; and 

C ar (T d is the residual resuspended air concentration of radionuclide i 

CaripTd in particle size p resulting from operational releases at the 

end of the Td-year drying period in pCi/m 3 . 

Ground and resuspended air concentrations resulting from postoperational 

releases at the end of the final prereclamation year are calculated using Equa

tions 2, 3, 4, and 6 with the value of t equal to T . These concentrations are 

then incremented by the residual concentrations due to operational releases. 

These residual concentrations are calculated using Equations 11 and 12 to obtain 

the required totals. Total air concentrations and concentrations in vegetation, 

meat, and milk are then calculated from the total ground and resuspended 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 

when environmental concentrations resulting from plant operations are expected 

to be at their highest level.

16
2.1 Inhalation Doses 

Inhalation doses are calculated from the total radionuclide concentration 

in air, including resuspended material. The inhalation dose conversion factors 

for radioactive particulate materials used in this analysis are presented in 

Table 3. With the exception of the dose conversion factors presented for "mass 

average lung," these dose conversion factors have been computed by Argonne 

National Laboratory's UDAD computer code (Ref. 4) in accordance with the Task 

Group Lung Model (TGLM) of the International Commission on Radiological Protec

tion (Ref. 7). Dose conversion factors for the mass average lung have been 

computed by mass-averaging the UDAD-calculated dose conversion factors for the 

four regions of the TGLM: nasopharyngeal, tracheobronchial, pulmonary, and 

lymph. Ordinarily, the dose computed specifically for the pulmonary region is 

reported or presented as the "lung" dose. For the principal lung dose contribu

tors (uranium and thorium), doses computed for the mass average lung are slightly 

higher than those calculated for the pulmonary region. The net overall effect, 

considering all radionuclides, is thus a slight increase in the reported lung dose. 

In addition to the physical characteristics of the particulate matter 

involved, use of the TGLM demands the assignment of a solubility class, denoted 

by Y (years, slowly soluble or insoluble), W (weeks, moderately soluble), or D 

(days, quite soluble). Solubility classifications have been assigned on the 

basis of experimental data reported and summarized by Kalkwarf in NUREG/CR-0530 

(Ref. 8). These data indicate that thorium, lead, and polonium are 100% class Y 

in ore, yellowcake, or tailings dusts. Radium was determined to be best 

characterized by the split-solubility classification 10% class D, 90% class Y. 

Uranium in ore dust was determined to be 100% class W; uranium solubility for 

tailings dusts was not analyzed and is assumed to be class Y. Data for uranium 

in yellowcake were mixed and showed a pronounced dependence on the specific 

source of the yellowcake sample. Results reported by Kalkwarf indicate a 

split-solubility classification is appropriate, and on review of those results 

(particularly those given on page 55 of Reference 8), the staff has assumed 

uranium in yellowcake to be 50% class D and 50% class Y. The computed inhalation 

dose conversion factors are given in Table 3. 

Doses to the bronchial epithelium from 2 2 2 Rn and short-lived daughters 

are computed based on the assumption of indoor exposure with 100% occupancy.

17
The dose conversion factor for bronchial epithelium exposure from 2 2 2 Rn is 

derived as follows (see Appendix C for detailed basis): 

1. 1 pCi/m 3 2 2 2 Rn in outdoor air will yield an average indoor concentra

tion of about 5 x 10-6 Working Level (WL).* 

2. Continuous exposure to 1 WL = 25 cumulative working-level months 

(WLM) per year. 

3. 1 WLM = 5000 mrem (Ref. 9). 

Therefore, 

1 pCi/m 3 2 2 2 Rn x (5 x 10-6 pCi-- ) x (25 WL 

mrem• 

x (5000 w- = 0.625 mrem 

and the 2 22 Rn 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 

equation: 

d.(inh) = . aipDCF ijp(inh) (13) 

ip 

where 

d.(inh) is the inhalation dose to organ j in mrem/yr; and 

DCF. (inh) is the inhalation dose conversion factor for radionuclide i, 

iJP 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 hours per day at a dose rate of 70 percent of the outdoor 

One WL concentration is defined as any combination of short-lived radioactive 

decay products of 2 2 2 Rn per liter of air that will release 1.3 x 105 MeV of 

alpha-particle energy during their radioactive decay to 2 1OPb.

18
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: 

d.(ext) = 0.825 Z.c aiDCF ij(cld) + C giDCF ij(gnd) (14) 

where 

C ai is the total air concentration of radionuclide i in pCi/m 3 ; 

d.(ext) is the external dose to organ j in mrem/yr; 

DCF. (cld) is the dose conversion factor for cloud exposure from radio

nuclide i to organ j in mrem/yr per pCi/mr3 ; 

DCF ij(gnd) is the dose conversion factor for ground exposure from radio

nuclide i to organ j in mrem/yr per pCi/m 2 ; and 

0.825 is the effective reduction factor because of structural 

shielding for indoor exposure periods. 

2.3 Ingestion Doses 

Ingestion doses are routinely calculated for ingestion of vegetables 

and meat (beef, unprocessed pork, and lamb). Milk 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. 6), usually involving washing, peeling, boiling, 

etc. The following equation is used to compute the annual radionuclide 

intake via ingestion: 

Iik = UmkCmi + UbkCbi + 0.5 E-AUvkCvi (15) 

where 

I A is the activity ingestion rate of radionuclide i by an 

individual in age group k in pCi/yr;

19
Umk, Ubk are milk (in L/yr) and meat (in kg/yr) ingestion rates for 

an individual in age group k; 

U A is the ingestion rate of vegetable category v for age group 

k in kg(wet weight)/yr; and 

0.5 is the fraction of vegetable activity remaining after food 

preparation, dimensionless. 

Ingestion doses are then computed by 

dj ig = E-•likDCF ijk (ing). (16) 

i 

where 

djk(ing) is the ingestion dose for organ j of an individual in age 

group k in mrem/yr; and 

DCF ijk(ing) is the ingestion dose conversion factor for radionuclide i in 

organ j of an individual in 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 2 2 2 Rn 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: 

d. (tot) = d.(inh) + d.(ext) + d.(ing) (17) 

where 

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

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--

20
1. all dose contributions from radiation emitted by 2 2 2 Rn, 2 1 8Po, 2 14 Pb, 2 14 Bi, and 2 1 4 po will be excluded, and 

2. all dose contributions from radiation emitted by 2 1 °Pb, 2 10 Bi, 

and 2 1 0 Po formed by decay of released 2 2 2 Rn 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 2 2 2Rn 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 ratds over a 1-year period is computed 

for (1) the period of actual uranium milling and (2) the period of time after 

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 technique 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 phases of 

the mill life cycle: operational (milling) and prereclamation. For these two 

time intervals and for the postreclamation era, annual population dose commit

ments resulting from transcontinental dispersion of 22 2 Rn are also evaluated.

21
3.1 Regional Population Doses

Population doses resulting from environmental radioactivity concentrations 

in the region of the site are evaluated for all exposure pathways considered 

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 population and agricultural productivity within a distance 

of 80 km (50 mi). Individual localized population centers lying beyond this 

distance should also be considered if their inclusion 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 (1) divide the geographical site region into segments by radius 

and direction, (2) establish average individual doses within each segment, 

(3) multiply these individual doses by the estimated population lying within 

each segment, and (4) 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 22.50 sectors) and con

centric circles drawn at distances of 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 

70, and 80 km. The 13 circles and 16 radii then form a grid composed of 192 

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 of each annulus. 

The population dose in the site region from inhalation and external 

exposure pathways is computed by the staff using the following equation: 

M (inh + ext) = 10- 4P s[djs (inh) + d js(ext)] (18) 

3 5s

22
where

djs (ext) is the average external dose to organ j in segment s in 

mrem/yr; 

djs (inh) is the average inhalation dose to organ j in segment s in 

mrem/yr; 

M.(inh+ext) is the resulting population dose from inhalation and external 

exposure pathways in rem/yr; 

P5 is the population residing in segment s; and 

10-3 is the 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 quantity 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 fruit 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: 

1. The site region is divided into segments and each segment is assigned 

a productivity rate for each food category (vegetables, meat, and milk in kg/yr 

per km2); 

2. The average activity concentrations for each food type are computed 

and multiplied by the segment productivity factor and by the segment area; 

3. Total activity content of the regional food production is then 

determined by summing over the segments; and 

4. Population doses are determined assuming that all food produced in 

the region is consumed by a population with the same age distribution 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.

23
The available raw data should be projected forward in time to provide a 

reasonable 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 radionuclide concentrations in vegetables: 

Cvis (avg) = Wvs Cvis (19) 

v 

where 

is the average concentration of radionuclide i in vegetable 

type v produced in segment s in pCi/kg(wet weight); 

Cvis(avg) is the average concentration of radionuclide i averaged over 

all types of vegetables in segment s in pCi/kg; and 

W vs is the weighting factor for vegetable type v in segment s 

(fraction of total production), dimensionless. 

When relying on the state-average production data given in Table 7, the NRC 

staff will use values of Wv that have been selected to roughly correspond 

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 

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 

Qfi = E GfsAsCfis (20) 

s 

where 

As is the area of segment s in kin2 ; 

Cfis is the concentration of radionuclide i in food category f in 

segment s in pCi/kg(wet weight); 

Gfs is the productivity factor for food f in segment s in kg/yr 

per km2 ; and

24
Qfi is the gross activity content of radionuclide i in food 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 Qfi values determined by 

Equation 20 that are ingested by the various age groups. The following rela

tionship applies: 

F F pkU fk (21) Ffk = FpkUfk 

k 

where 

Ffk is the fraction of the production of food type f ingested by 

individuals in age group k, dimensionless; 

F pk is the fraction of the regional population belonging to age 

group k, dimensionless; and 

U fk is the average consumption rate in kg/yr or L/yr (for milk or 

other liquids) of food type f for an individual in age group k 

(see Table 8 for values). In the absence of suitable site

specific information, the NRC staff will assume average consump

tion rates for the population at large as given in Table 8 and 

population age fractions and fractional 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 2 EfQfiFfkDCFijk(ing) (22) 

fik 

where 

Ef is a factor to account for activity remaining after food prepara

tion, dimensionless; and 

M.(ing) is the resulting regional population dose from food ingestion 

for organ j in rem/yr.

25
The value of Ef is assumed to be 0.5 for vegetables and 1.0 for meat 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 

Substantial contributions to the total population dose may arise from the 

transport of released 2 2 2 Rn across the North American continent. Formation of 

long-lived 2 1°Pb from 2 2 2 Rn may result in both inhalation and ingestion doses 

not only to people in the United States, but to people in Canada and Mexico as 

well (Ref. 10). 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 2 2 2 Rn from four specific locations in the western United 

States. The location closest to the mill site should be used. The population 

doses provided 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 2 2 2 Rn 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 2 2 2 Rn 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. 

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 operational (milling), prereclamation 

(pile drying), and postreclamation phases. The total radiological impact due 

to emissions during the first two phases is estimated by multiplying the annual

26
impacts by the durations and summing. Total annual impacts for each of the 

three phases are obtained by 

M. = M.(inh + ext) + M.(ing) + M.(Rn) (23) 

where 

M. is the annual committed population dose to organ j in rem/yr; 

and 

M.(Rn) is the annual continental population dose from 2 2 2 Rn and its 

3 daughters to organ j in rem/yr. 

Total impacts over the first two phases are obtained by 

M.(m&d) = T M.(m) + TdMj(d) (24) 

where 

M.(d) is the annual committed population dose to organ j during 

the drying phase in rem/yr; 

M.(m) is the annual committed population dose to organ j during 

the milling phase in rem/yr; 

M.(m&d) is the aggregate committed population dose to organ j over 

the milling and drying phases in rem; and 

To,Td are the durations of the operational and pile-drying phases, 

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 operation of a typical uranium mill. 

D. IMPLEMENTATION 

The models specified in this guide are being used by the NRC staff in 

evaluating radiological impact in connection with applications for uranium 

mill licenses and renewals.

27
Table 1

ISOTOPES AND PARTICLE SIZES FOR WHICH DIRECT AIR 

CONCENTRATIONS (Cadip VALUES) ARE REQUIRED AS INPUT DATA

Particle Size Group Characteristics (Ref. 1)

Particle 

Size Group*

p 

p 

p 

p 

p

-1 

-2 

-3 

-4 

-5

Diameter 

Range, pm 

1 to 10 

10 to 80

Mean 

Diameter, pm

1.0 

1.0 

5.0 

35.0 

0.3

Density, 

g/cm-3

8.9 

2.4 

2.4 

2.4 

1.0

Unit Density 

Activity--Median 

Aerodynamic Equivalent 

Diameter (AMAD), 

pm

3.0 

1.5 

7.75 

54.0 

0.3

Deposition 

Velocity, m/sec 

1.0 x I-2 

1.o0 10

1.0 X 1O-2 

8.82 x 10-2 

0.3 x 10-2

Particle Size Group Index**

Radionuclide

uranium-238 

thorium-234 

protactinium-234 

uranium-234 

thorium-230 

radium-226 

radon-222*** 

polonium-218 

lead-214 

bismuth-214 

polonium-214 

lead-210 

bismuth-210 

polonium-210

Particle size groups are 

dust; p = 2, 3, or 4 for 

growth concentrations of

assigned to effluents as follows: 

fugitive ore and tailings dusts; p 

particulate daughters.

p = 1 for yellowcake 

= 5 for 2 2 2 Rn air inThe entry "C & R" indicates that the particular Cadip value is explicitly calculated 

by the staff and required as input for use of the models, equations, and data describec 

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. 

The air concentration of 2 2 2 Rn is also calculated by the staff and is required as 

input for use of this guide; 2 2 2 Rn gas is not assigned a particle size.

29

C&R 

se 

se

i 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14

C&R 

se 

se

C&R 

se 

se

se 

&R 

& R

C 

C

C& R 

se 

se

C 

C

se 

&R 

&R 

se

se 

&R 

& R C 

C

C 

C

se 

se 

se 

se 

se 

C&R 

se 

se

se 

&R 

&R 

se 

se 

se 

se

se 

se 

se 

se 

C& R 

se 

se

se 

se 

se 

se 

se 

C&R 

se 

se

& 

& 

&

R 

R 

R

C 

C 

C 

C 

C 

C

se 

C&R 

se 

se

se 

&R & R 

& R
Table 2

ENVIRONMENTAL TRANSFER COEFFICIENTS*

Transfer Coefficent

U Th Ra

Plant/Soil (B vi) 

(pCi/kg plant - wet weight)/(pCi/kg

Edible Above Ground 

Potatoes 

Other Below Ground 

Pasture Grass 

Stored Feed (Hay)

2.5 

2.5 

2.5 

2.5 

2.5

soil1 

10- 3 

10- 3 

10- 3 

10- 3 

10- 3

x 

x 

x 

x 

x

- dry weight) 

4.2 x -3 

4.2 x 10 

4.2 x 10-3 

4.2 x 10.3 

4.2 x 10

Beef/Feed (Fbi)

(pCi/kg per pCi/day)

Milk/Feed (Fmi) 

(pCi/L per pCi/day)

3.4 x 10

6.1 x 10

2.0 x 10

5.0 x 10

Sources for these data include References 11-14.

30

Pb

10-2 

0- 3 

10

0- 2 

0- 2

1.4 

3.0 

1.4 

1.8 

8.2

x 

x 

x 

x 

x

10-3 

i0-3 

10- 3 

10- 2 

10- 2

4.0 

4.0 

4.0 

2.8 

3.6

x 

x 

x 

x 

x

5.1 x 10

5.9 x 10

7.1 x 10.4

1.2 x 10.4
Table 3

INHALATION DOSE CONVERSION FACTORS

Conversion Factor, mrem/yr per pCi/rn3

Radon Decay Products 

Particle Size = 0.3 micron 

Density = 1.0 g/cm3 

AMAD = 1.0 microns 

Whole Body 

Bone 

Kidney 

Liver 

Mass Average Lung 

Yellowcake Dust 

Particle Size = 1.0 micron 

Density = 8.9 g/cm3 

AMAD = 3 microns 

Whole Body 

Bone 

Kidney 

Liver 

Mass Average Lung 

Uranium Ore Dust 

Particle Size = 1.0 micron 

Density = 2.4 g/cm3 

AMAO = 1.5 microns 

Whole Body 

Bone 

Kidney 

Liver 

Mass Average Lung 

Fine Tailings Particulates 

Particle Size = 5.0 microns 

Density = 2.4 g/cm3 

AMAD = 7.75 microns 

Whole Body 

Bone 

Kidney 

Liver 

Mass Average Lung 

Coarse Tailings Particulates 

Particle Size = 35.0 microns 

Density = 2.4 g/cm3 

AMAD = 54 microns 

Whole Body 

Bone 

Kidney 

Liver 

Mass Average Lung

210 Pb 210 po

7.46E+O0 

2.32E+02* 

1. 93E+02 

5. 91E+O1 

6. 27E+01

1.29E+00 

5. 24E+00 

3.87E+01 

1. 15E+01 

2.66E+02

238U 2 3 4 U 2 3OTh 226Ra 2 1OPb 2 10po

9.82E+00 

1. 66E+02 

3.78E+01 

0.0 

1. 07E+3

1. 12E+01 

1. 81E+02 

4. 30E+01 

0.0 

1. 21E+3

1. 37E+02 

4. 90E+03 

1. 37E+03 

2.82E+02 

2.37E+03

3. 58E+01 

3. 58E+02 

1. 26E+00 

4.47E-02 

4. 88E+03

4.66E+00 

1.45E+02 

1. 21E+02 

3. 69E+01 

5. 69E+02

5. 95E-01 

2.43E+00 

1. 79E+01 

5. 34E+00 

3.13E+02

23 8U 234 U 2 30

Th 2 26Ra 2 1

oPb 2 10 po

4. 32E+00 

7. 92E+01 

1. 66E+01 

0.0 

1. 58E+02

4.92E+00 

7.95E+01 

1. 89E+01 

0.0 

1. 80E+02

1. 66E+02 

5.95E+03 

1. 67E+03 

3.43E+02 

3. 22E+03

3. 09E+01 

3. 09E+02 

1. 09E+00 

3.87E-02 

6. 61E+03

4. 36E+00 

1. 35E+02 

1. 13E+02 

3.45E+01 

7.72E+02

4.71E-01 

1. 92E+00 

1. 42E+01 

4.22E+00 

4.20E+02

2 3 8 U 2 3 4 U 230 Th 2 2SRa 2 1

OPb 2 10 po

1.16E+00 

1. 96E+01 

4.47E+00 

0.0 

1. 24E+03

1. 32E+00 

2. 14E+01 

5. 1OE+00 

0.0 

1. 42E+03

1. O1E+02 

3. 60E+03 

1. OOE+03 

2. 07E+02 

1. 38E+03

4. OOE+01 

4.OOE+02 

1. 41E+00 

4.97E-02 

2.84E+03

4.84E+O0 

1. 50E+02 

1. 25E+02 

3.83E+01 

3. 30E+02

7. lOE-01 

2.89E+00 

2. 13E+01 

6. 36E+00 

1.88E+02

2 3 8 U 2 3 4 U 2 3 OTh 2 2 6 Ra 2 1OPb 2 1 0 po

7.92E-01 

1. 34E+01 

3. 05E+O0 

0.0 

3. 33E+02

9.02E-01 

1. 46E+01 

3.47E+00 

0.0 

3. 80E+02

5. 77E+01 

2.07E+03 

5. 73E+02 

1. 19E+02 

3.71E+02

4.90E+01 

3.90E+02 

1. 38E+00 

4.85E-02 

7. 64E+02

4.43E+00 

1. 38E÷02 

1. 15E+02 

3.51E÷01 

8. 70E+01

7.28E-01 

2. 96E+00 

2. 19E+01 

6. 52E+00 

5. 75E+01

Read 2.32E+02 as 2.32 X 102 = 232.

31
Table 4

DOSE CONVERSION FACTORS FOR EXTERNAL EXPOSURE 

Dose Factor for External Dose 

from Air Concentrations 

mrem/yr per pCi/m 3

Radionuclide

2 3 8 U 

2 3 4 Th 2 3 4 m 

234UPa 

2 3 OTh 

226Ra 

222Rn 

218po 

214pb 

214Bi 

214po 

21opb

Skin 

1. 05E-05** 

6.63E-05 

8.57E-05 

1. 36E-05 

1.29E-09 

6. OOE-05 

3.46E-10 

8.18E-07 

2. 06E-03 

1. 36E-02 

9.89E-07 

4.17E-05 

Dose Factor 

from Ground 

mrem/vr Der

Whole Body* 

1.57E-06 

5.24E-05 

6.64E-05 

2.49E-06 

3.59E-06 

4.90E-05 

2.83E-06 

6.34E-07 

1.67E-03 

1.16E-02 

7.66E-07 

1.43E-05 

for External Dose 

Concentrations 

DCi/m 2

Radionuclide

2 3 8 U 234Th 

2 3 4 m 

234UPa 

23OTh 

2 2 6 Ra 

2 2 2 Rn 

218po 

2 1 4 Pb 

2 1 4 Bi 

214po 

21%p

Skin

2.13E-06 

2. 1OE-06 

1. 60E-06 

2. 60E-06 

2.20E-06 

1. 16E-06 

6.15E-08 

1.42E-08 

3.89E-05 

2.18E-04 

1.72E-08 

6.65E-06

Whole Body* 

3.17E-07 

1.66E-06 

1.24E-06 

4.78E-07 

6.12E-07 

9.47E-07 

5.03E-08 

1.10E-08 

3.16E-05 

1.85E-04 

1.33E-08 

2.27E-06

to be the

32

*Doses to internal body organs are assumed 

same as computed for the whole body. "**Read as 1.05 x 10-5 or 0.0000105.
Table 5

FOOD CONSUMPTION RATES USED FOR CALCULATING 

DOSES TO INDIVIDUALS 

Ingestion Rate by Age Group,* kg/yr 

Infant Child Teen Adult 

Vegetables (Total) - 47.8 76.1 105. 

Edible Above Ground - 17.3 28.9 39.9 

Potatoes - 27.2 42.2 60.4 

Other Below Ground - 3.3 5.0 5.0 

Meat (Beef, Fresh Pork, 

and Lamb) - 27.6 44.8 78.3 

Milk (L/yr) 208.0 208.0 246.0 130.0 

*All data are taken from Reference 6. 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.

33
Table 6

INGESTION DOSE CONVERSION FACTORS

Internal Dose Conversion Factor by Organ and Age, mrem per pCi ingested

Age Group 

Infant 

Child 

Teenager 

Adult

Organ 

Wh. Bod 

Bone 

Liver 

Kidney 

Wh. Bod 

Bone 

Liver 

Kidney 

Wh. Bod 

Bone 

Liver 

Kidney 

Wh. Bod 

Bone 

Liver 

Kidney

2 3 8U 

3.33E-04 

4.47E-03 

0 

9.28E-04 

1. 94E-04 

3.27E-03 

0 

5.24E-04 

6.49E-05 

1. 09E-03 

0 

2. 50E-04 

4.54E-05 

7.67E-04 

0 

1.75E-04

2 3 4 U 

3.80E-04 

4.88E-03 

0 

1. 06E-03 

2.21E-04 

3. 57E-03 

0 

5.98E-04 

7. 39E-05 

1.19E-03 

0 

2.85E-04 

5.17E-05 

8.36E-04 

0 

1. 99E-04

234Th 

2. OOE-08 

6.92E-07 

3.77E-08 

1. 39E-07 

9.88E-09 

3.42E-07 

1.51E-08 

8.02E-08 

3.31E-09 

1. 14E-07 

6. 68E- 09 

3.81E-08 

2.13E-09 

8.01E-08 

4.71E-09 

2.67E-08

2 "Th 

1. 06E-04 

3.80E-03 

1.90E-04 

9. 12E-04 

9.91E-05 

3.55E-03 

1. 78E-04 

8.67E-04 

6. OOE-05 

2.16E-03 

1. 23E-04 

5.99E-04 

5.70E-05 

2. 06E-03 

1.17E-04 

5.65E-04

2 2SRa* 2 1OPb

1.07E-02 

9.44E-02 

4.76E-05 

8.71E-04 

9.87E-03 

8.76E-02 

1. 84E-05 

4.88E-04 

5. OOE-03 

4.09E-02 

8.13E-06 

2. 32E-04 

4.60E-03 

4.60E-02 

5.74E-06 

1.63E-04

2.38E-03 

5.28E-02 

1. 42E-02 

4.33E-02 

2.09E-03 

4.75E-02 

1. 22E-02 

3.67E-02 

7. 01E-04 

1. 81E-02 

5.44E-03 

1.72E-02 

5.44E-04 

1.53E-02 

4.37E-03 

1.23E-02

*Adult whole body and bone dose conversion factors for 226Ra have been obtained from Reference 6 and 

are based on applicable models and data from Reference 15. 22 'Ra whole body and bone dose conversion 

factors for other age groups have been computed by assuming the same proportion to adult whole body and 

bone dose factors as given in Reference 16. All other dose conversion factors are directly from 

Reference 16. 

S( (

3. 58E-07 

4. 16E-06 

2.68E-05 

2.08E-04 

1. 69E-07 

1. 97E-06 

1.02E-05 

1. 15E-04 

5. 66E-08 

6. 59E-07 

4.51E-06 

5.48E-05 

3.96E-08. 

4.61E-07 

3.18E-06 

3.83E-05

7.41E-04 

3. 1OE-03 

5.93E-03 

1.26E-02 

3.67E-04 

1. 52E-03 

2.43E-03 

7.56E-03 

1. 23E-04 

5.09E-04 

1. 07E-03 

3.60E-03 

8. 59E-05 

3.56E-04 

7.56E-04 

2.52E-03
Table 7 

AVERAGE AGRICULTURAL PRODUCTIVITY FACTORS FOR VARIOUS STATES

State 

Arizona 

Colorado 

Idaho 

Montana 

Nevada 

New Mexico 

South Dakota 

Texas 

Utah 

Washington 

Wyoming

State-Average Productivity,* 

Vegetables Meat 

580 1,040 

2,800 3,200 

14,200 2,000 

1,800 2,000 

18 510 

280 1,150 

2,400 6,400 

1,200 5,300 

370 790 

10,700 1,600 

320 .1,400

x available data

Data presented are based on a staff survey and analysis of 

on agricultural productivity for 1973.

35

kg/yr per kln2 

Milk 

1,130 

1,400 

3,400 

370 

230 

460 

3,600 

2,100 

1,800 

6,000 

230

available data
Table 8

FOOD CONSUMPTION RATES USED FOR CALCULATING 

DOSES TO POPULATIONS

Average Consumption Rates,* kg/yr)

Food Category Infants Children Teens

Vegetable Pathway

Berries and Tree Fruit 

Fresh Vegetables** 

1. Potatoes 

2. Other root veg. 

3. Leafy vegetables 

4. Other above-ground 

vegetables 

Processed Vegetables 

1. Potatoes 

2. Other root veg. 

3. Leafy vegetables 

4. Other above-ground 

vegetables 

Grain, Rice, and Wheat 

Total Vegetables 

Meat Pathway 

Beef and Lamb** 

Unprocessed Pork** 

Poultry and Processed 

Pork 

Total Meat 

Milk Pathway (L/yr) 

Fresh Milk** 

Milk Products

Total Milk

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0

54.1 

27.2 

3.4 

5.8 

11.4

2.3 

0.9 

0.4

63.9 

42.3 

5.0 

9.4 

19.5 

3.6 

1.4 

0.6

14.4 24.6 

118.2 136.2 

238.1 306.5

0 

0 

0 

0

21.8 

5.9

21.0 

48.7

207.6 

0 

207.6

207.6 

27.2

35.9 

8.9 

33.2 

78.0

246.0 

45.4

234.8 291.4

All data are taken from Reference 6 and are representative of average 

consumption rates by individuals at farm residences.

These food categories are evaluated for individual doses from 

pathways.

ingestion

36

Adults

49.2 

60.4 

5.0 

13.9 

26.0

5.2 

1.4 

0.8

32.8 

90.8 

285.5

64.0 

14.3 

49.6 

127.9

129.6 

46.7 

176.3
Table 9 

AGE DISTRIBUTION OF POPULATION, AVERAGE AND PER CAPITA CONSUMPTION 

RATES, AND FRACTIONS USED IN THE ABSENCE OF SITE-SPECIFIC DATA

Fraction of 

Population* 

0.0179 

0.1647 

0.1957 

0.6217

Age Group 

Infants 

Children 

Teenagers 

Adults

Average Total Consumption Rates,** kg/yr 

Vegetables Meat Milk 

0 0 207.6 

238.1 48.7 234.8 

306.5 78.0 291.4 

285.5 127.9 176.3 

Fraction of Regional Production 

Ingested by Each Age Group 

Vegetables Meat Milk 

0 0 0.0178 

0.1418 0.0780 0.1850 

0.2167 0.1485 0.2728 

0.6415. 0.7735 0.5244

Age fractions given reflect average values for the entire U.S. population 

indicated by 1970 census data, as reported in Reference 17. 

Consumption rates given are from Table 8 and are not those used for, or 

appropriate to, the calculation of maximum individual doses.

37

Age 

Group 

Infants 

Children 

Teenagers 

Adults
Table 10 

CONTINENTAL POPULATION DOSES PER kCi OF 2 2 2 Rn RELEASED IN 1978 

Population Dose Resulting from a 1-kCi 

Release of 2 22 Rn During 1978, organ-rem*

Release Site

Bronchial 

Epithel i um

Casper, Wyoming 

Falls City, Texas 

Grants, New Mexico 

Wellpinit, Washington

Average

56. 

72. 

52.

8.8 

5.8 

8.2

43. 9.0

56. 8.0

Values given are based on data reported in Reference 10 and amended 

for inclusion in Reference 1. Exposure pathways considered include 

inhalation and ingestion. Isotopes considered include 2 2 2 Rn and 

its short-lived daughters, 2 10 Pb, 2 1 6Bi, and 2 1°Po. A 100-year 

integrating period was used in the application of the environmental 

dose commitment concept.

38

Whole 

Body

Pulmonary Lung Bone

2.0 120.

1.6 

1.8

1.7 

1.8

77.

110.

120. 

110.
Table 11

PROJECTED POPULATION OF THE UNITED STATES, 1978-2100

Projected U.S. 

Population, 

millions*

218.4 

220.2 

222.2 

224.2 

226.3 

228.5 

230.7 

232.9 

235.1 

237.2 

239.4 

241.5 

243.5 

245.5

Year 

1992 

1993 

1994 

1995 

1996 

1997 

1998 

1999 

2000 

2025 

2050 

2075 

2100

Projected U.S. 

Population, 

millions* 

247.4 

249.3 

251.1 

252.8 

254.4 

255.9 

257.5 

258.9 

260.4 

287.5 

291.1 

291.9 

293.0

Population projections through the year 2000 are from Reference 18. Later 

projections were obtained from Reference 10 and are based on a predicted 

growth rate obtained from Reference 19.

39

Year 

1978 

1979 

1980 

1981 

1982 

1983 

1984 

1985 

1986 

1987 

1988 

1989 

1990 

1991
DIRECTC, TOTALAI USED TO COMPUTE INHALATION DOSE 

DEPOSITION CONCENTRATIONS . AND EXTERNAL DOSES FROM 

P cSUBMERSION IN A CONTAMINATED 

) (ip)ATMOSPHERE 

NFROM CONTAMINATED GROUND PLANE 

CONCENTRATIIO N EPS I5USDTOCMPIOVGTAL 

IIVEGETATIONNE 

CCONCENTRATIONSC USED TO COMPUTE VEGETABLE 

-pCkg -INGESTION DOSES 

CONCENTRATIONS USED TO COMPUTE MEAT IBEEF) 

pCilkg INGESTION DOSES 

FC bi S) f 

CNCENTRATIONS USED TO COMPUTE MILK 

pLa e, INGESTION DOSES 

Figure 1. Schematic Diagram of Information Flow and Use For Dose Calculations

40
Table 12 

CONVERSION FACTORS INTO SI UNITS 

Conversion 

Old New Factor from 

Units* SI Units Old to New Unit 

Activity Concentrations (Environmental) 

Airborne Particulates and Gas pCi-m- 3 Bq-m- 3 3.70E-02 

Liquids (Water, Milk, etc.) pCi.L-' Bq.L- 1 3.70E-02 

Solids (Soil, Sediment, pCi-kg- 1 Bq-kg-I 3.70E-02 

Vegetation, Food Stuff, etc.) 

Activity Concentrations (Effluent) 

Gas (Air) (PCi-mL-i)** Bq-m-3 3.70E+10 

Liquid (pCi.mL-i)** Bq.L-i 3.70E+07 

Exposure Rate (Environmental) pR-h-1 C-kg-i'h-i 2.58E-10 

Absorbed Dose mrad Gy 1.OOE-05 

Dose Equivalent mrem Sv 1.OOE-05 

Dose Equivalent Rate mrem-yr-' Sv-yr-1 I.OOE-05 

(Commitment) 

*Sanctioned for temporary use. 

"**Adopted because of established convention and use in maximum permissible 

concentration (MPC) tabulations.

41
REFERENCES* 

1. U.S. Nuclear Regulatory Commission (USNRC), Office of Nuclear Materials 

Safety and Safeguards, "Final Generic Environmental Impact Statement on 

Uranium Milling," NUREG-0706, September 1980. 

2. D. L. Strenge and T. J. Bander, "MILDOS--A Computer Program for Calculating 

Environmental Radiation Doses from Uranium Recovery Operations," USNRC 

Report NUREG/CR-2011 (PNL-3767), April 1981. 

3. Environmental Protection Agency, "Environmental Radiation Dose Commitment: 

An Application to the Nuclear Power Industry," EPA Report EPA-520/4-73-O02, 

1974. 

4. M. H. Momeni, Y. Yuan, and A. J. Zielen, "The Uranium Dispersion and 

Dosimetry (UDAD) Code," USNRC NUREG/CR-0553. 

5. 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. 

6. 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. 

7. International Commission on Radiological Protection Task Group on Lung 

Dynamics, "Deposition and Retention Models for Internal Dosimetry of the 

Human Respiratory Tract," Health Physics 12:181, 1966. 

8. D. R. Kalkwarf, "Solubility Classification of Airborne Products from 

Uranium Ores and Tailings Piles," USNRC Report NUREG/CR-0530, January 1979. 

*NUREG-series reports are available at current rates through the GPO Sales 

Program, ATTN: Sales Manager, U.S. Nuclear Regulatory Commission, Washington, 

D.C. 20555, or from the National Technical Information Service, Springfield, 

Virginia 22161. 43
REFERENCES (Continued)

9. National Academy of Sciences--National Research Council, "The Effects 

on Populations of Exposure to Low Levels of Ionizing Radiation," Report 

of the Advisory Committee on the Biological Effects of Ionizing Radiation 

(BEIR), U.S. Government Printing Office, 1972. 

10. 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. 

11. 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," U.S. Atomic Energy 

Commission (USAEC) Report UCRL-50163, Part IV, 1968. 

12. 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. 

13. R. J. Garner, "Transfer of Radioactive Materials from the Terrestrial 

Environment to Animals and Man," CRC Press, Cleveland, Ohio, 1972. 

14. L. L. McDowell-Boyer et al., "Review and Recommendations of Dose Conver

sion Factors and Environmental Transport Parameters for 2 1°Pb and 2 2 6 Ra," 

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

CR-0574, 1979. 

15. International Commission on Radiological Protection, "Recommendations 

of the International Commission on Radiological Protection," ICRP 

Publication 1OA, Pergamon Press, New York, 1971.

44
REFERENCES (Continued)

16. 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. 

17. U.S. Environmental Protection Agency, "Environmental Analysis of the 

Uranium Fuel Cycle, Part II - Nuclear Power Reactors," EPA Report EPA-520/ 

9-73-003-C, November 1973. 

18. 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. 

19. "Development of the Methodology Relevant to U.N. Global Projections," 

paper presented to the Ad Hoc Group of Experts on Demographic Projection, 

U.N. Fund for Public Activities, Population Division, New York, 7-11 

November 1977.

45
SYMBOLS 

Description Symbol

A 

B 

Cadi 

C. 

C aip( 

Carip( 

C arip (T 

Ct

Cf

Cgi( 

C gi(T 

C gi(T

Cg12 (Pb <- Ra

C 

C

a Equal to (t - 1.82) if t > 1.82 and otherwise equal to 

zero in yr 

Area of segment s in km2 

Soil-to-plant transfer coefficient for radionuclide i and 

vegetation type v, (pCi/kg(wet) plant per pCi/kg(dry) soil) 

Calculated direct air concentration of radionuclide i in 

particle size p resulting from operational releases in pCi/m 3 

Total air concentration of radionuclide i in pCi/m 3 

Calculated total air concentration of radionuclide i in 

particle size p at time t in pCi/m3 

t) Calculated resuspended air concentration of radionuclide i 

in particle size p at time t in pCi/m3 

Residual resuspended air concentration of radionuclide i 

d) in particle size p resulting from operational releases at 

the end of the Td-year drying period in pCi/m3 

bi Resulting average concentration of radionuclide i in meat 

in pCi/kg 

Concentration of radiorluclide i in food category f in 

is segment s in pCi/kg(wet weight) 

t) Calculated ground surface concentration of radionuclide i 

at time t in pCi/m 2 

d) Residual ground concentration of radionuclide i resulting 

from operational releases at the end of the Td-year drying 

period in pCi/m2 

"Ground concentration of radionuclide i at the time of mill 

shutdown in pCi/m 2 

) Incremental 2 1°Pb ground concentration resulting from 

226Ra deposition in pCi/m 2 

Concentration of radionuclide i in hay (or other stored 

'hi feed) in pCi/kg(wet weight) 

Resulting average concentration of radionuclide i in milk 

in pCi/L

47
CP 9 

C 

Cvi 

Cvis(a• 

DCF ij(c 

DCF ij(gi 

DCF ijk(i 

DCFijp(i

D

d (ex 

d (ir 

djk(ir 

djk(t, 

d s(e> 

d s(it

SYMBOLS (Continued) 

Concentration of radionuclide i in pasture grass in pCi/kg 

(wet weight) 

Resulting concentration of radionuclide i in vegetation v 

in pCi/kg(wet weight) 

Average concentration of radionuclide i in vegetable type 

is v produced in segment s in pCi/kg(wet weight) 

vg) Average concentration of radionuclide i averaged over all 

types of vegetables in segment s in pCi/kg(wet weight) 

Id) Dose conversion factor for cloud exposure from radionuclide 

i to organ j in mrem/yr per pCi/m3 

nd) Dose conversion factor for ground exposure from radionuclide 

i to organ j in mrem/yr per pCi/m 2 

ng) Ingestion dose conversion factor for radionuclide i in 

organ j of an individual in age group k in mrem/pCi ingested 

nh) Inhalation dose conversion factor for radionuclide i, 

organ j, and particle size p in mrem/yr per pCi/m3 

Resulting direct deposition rate of radionuclide i in 

rdi pCi/m 2 per sec 

Total deposition rate, including deposition of resuspended 

1i activity, of radionuclide i in pCi/m 2 per sec 

<t) External dose to organ j in mrem/yr 

nh) Inhalation dose to organ j in mrem/yr 

1g) Ingestion dose for organ j of an individual in age group k 

in mrem/yr 

t) Total dose to organ j of an individual in age group k 

from all exposure pathways in mrem/yr 

xt) Average external dose to organ j in segment s in mrem/yr 

nh) Average inhalation dose to organ j in segment s in mrem/yr 

Ef Factor to account for activity remaining after food pre

paration, dimensionless 

Ev Fraction of the foliar deposition reaching edible portions 

of vegetation v, dimensionless

48
F

M

M.(inh +

M

SYMBOLS (Continued) 

F bi Feed-to-meat transfer coefficient for radionuclide i, 

in pCi/kg per pCi/day ingested (see Table 2) 

Ffk Fraction of the production of food type f ingested by 

individuals in age group k, dimensionless 

F Feed-to-milk transfer coefficient for radionuclide i 

mi in pCi/L per pCi/day ingested (see Table 2) 

IFh Fractions of the total annual feed requirement assumed 

to be satisfied by pasture grass or locally grown stored 

feed (hay), respectively, dimensionless 

Fpk Fraction of the regional population belonging to age 

group k, dimensionless 

F Fraction of the total deposition retained on plant 

r surfaces, 0.2, dimensionless 

G fs Productivity factor for food f in segment s in kg/yr 

per km2 

Activity ingestion rate of radionuclide i by an individua 

in age group k in pCi/yr 

M. Annual committed population dose to organ j in rem/yr 

.(d) Annual committed population dose to organ j during the 

drying phase in rem/yr 

ing) Resulting regional population dose from food ingestion 

for organ j in rem/yr 

ext) Resulting population dose from inhalation and external 

exposure pathways in rem/yr 

W(m) Annual committed population dose to organ j during the 

milling phase in rem/yr 

m&d) Aggregate committed population dose to organ j over the 

milling and drying phases in rem 

(Rn) Annual continental population dose from 22 2 Rn and its 

daughters to organ j in rem/yr 

p Assumed soil areal density for surface mixing, 240 kg(dry 

weight)/m

2 

P5 Population residing in segment s 

Q Assumed feed ingestion rate at 50 kg(wet weight)/day

49

M j(

M.

M j (
SYMBOLS (Continued) 

Qfi Gross activity content of radionuclide i in food f in 

pCi/yr 

R pt) Ratio of the resuspended air concentration to the ground 

concentration for a ground deposit of age t yr for particle 

size p in m-1 

t Time interval over which deposition has occurred in sec 

Td Duration of time required to dry the tailings pile prior 

to reclamation in yr 

T Duration of the operational phase in yr 0 

tv Assumed duration of exposure while vegetation v is growing 

in sec 

Ufk Average consumption rate of food type f for an individual 

in age group k (see Table 8 for values) in L/yr or kg/yr 

U mk,Ubk Milk (in L/yr) and meat (in kg/yr) ingestion rates for an individual in age group k 

U vk Ingestion rate of vegetable category v for age group k, in 

kg(wet weight)/yr 

V Deposition velocity of particle size p in m/sec (see Table 1) 

W Weighting factor for vegetable type v in segment s (fraction vs of total production), dimensionless 

Yv Assumed yield density of vegetation v, in kg/m 2 (wet weight) 

6(t) Zero if t < 1.82 and unity otherwise, dimensionless 

X Assumed rate constant for environmental loss in sec- 1 

Xi Radioactive decay constant for radionuclide i in sec- 1 

lxý Effective removal constant for radionuclide i on soil in yr-1 

I 

X* Effective rate constant for loss by radioactive decay and 

n migration of a ground-deposited radionuclide and equal to 

Xn + Xe in sec- 1 

XR Assumed decay constant of the resuspension factor (equivalent 

to a 50-day half-life), 5.06 yr- 1 

Xw Decay constant accounting for weathering losses (equivalent 

to a 14-day half-life), 5.73 x 10-7 sec- 1

50
VALUES OF CONSTANTS

Terminal value of the resuspension factor for particles 

with a deposition velocity of 0.01 m/sec 

Initial value of the resuspension factor for particles 

with a deposition velocity of 0.01 m/sec 

Deposition velocity for the particle size for which the 

initial resuspension factor value is 1O- 5 /m 

Fraction of vegetable activity remaining after food 

preparation, dimensionless 

Effective reduction factor because of structural shielding 

for indoor exposure periods 

Time required to reach the terminal resUspension factor

10- 9m-1 

10- 5 m-1 

0. Olm/sec 

0.5 

0.825 

1.82 yr

51
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 radiological 

impact evaluations. All the data detailed in Table A-1 are not always avail

able 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 responsibilities with regard to the preparation of a 

thorough, knowledgeable, and technically sound radiological impact evaluation.

53
Table A-i

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 and their boundaries 

10. Any heap leach piles and their boundaries 

11. Restricted area boundaries if different from 

boundaries 

12. Fences

site property

B. Plant operations data 

1. General data 

a. Ore processing rates for all crushers and grinders, 

MT/d; hr/d and d/yr operational 

b. Raw ore grade, % U3 08 by weight, average and range 

c. Fractions of uranium, thorium, radium, and lead in raw 

ore expected to flow through to tailings 

d. Expected yellowcake purity, % U30 8 by weight, average 

and range, MT/yr produced 

e. Expected calendar years of initial ore milling, final 

ore milling, and completion of tailings area 

reclamation 

Part 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. 

A list of all such locations should be given in the radiological assessment.

54
Table A-1 (Continued)

2. Ore storage data 

a. Areas of each pile or bin complex, m2 

b. Ore storage masses 

c. Ore grades, % U308 by weight 

d. Antidusting measures routinely implemented 

e. Anticipated dusting rates, MT/yr 

f. Anticipated 2 22 Rn releases, Ci/yr 

g. Fractions of input ore sent to storage 

3. Crushing, grinding data 

a. Description of ventilation air filtration equipment 

b. Design efficiency of exhaust filters 

c. Minimum efficiencies of exhaust filters 

d. Filter testing procedure and schedule if applicable 

e. Fraction of time filters not operational or used 

f. Any measured effluent concentrations 

g. Stack heights and airflows 

h. Anticipated release rates, kg/hr or kg/MT yellowcake 

processed 

i. Anticipated 2 2 2 Rn release rate, Ci/yr 

j. Fractions of ore throughput reaching filters as dust 

4. Yellowcake drying and packaging data 

a. Processing rates, MT/hr, for drying and packaging if 

different 

b. Hr/d and d/yr drying and packaging operations are 

carried out 

c. Description of all ventilation air filtration equipment 

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, kg/hr, for the dryer 

stack, the packaging area ventilation exhaust, and any 

yellowcake storage area ventilation exhausts 

h. Annual yellowcake yield, MT/yr 

5. Tailings impoundment system (including evaporation or 

settling ponds) data 

a. Complete physical, chemical, hydrological, and radio

logical description 

b. Total area, surface areas expected to be under water, 

saturated, moist, and dry (indicate surface moisture 

contents used as basis of estimates)

55
Table A-i (Continued)

c. Description of antidusting measures routinely implemented 

and their expected effectiveness 

d. Anticipated dusting rates for saturated, moist, and 

dry surface areas, g/m2 per sec 

e. Anticipated 2 2 2 Rn release rates for underwater, saturated, 

moist, and dry surface areas, Ci/yr per m2 

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 2 2 2 Rn release rate, Ci/yr 

per M2 , 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 odsite 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 regional climatology, particularly 

including frequencies and durations of extreme wind speeds 

III. ENVIRONMENTAL DATA 

A. A detailed topographic map of the area within 8 km (5 mi) of the 

site showing the locations of all1. Site boundaries 

2. Lands owned, leased, or otherwise controlled (including 

mill site claims) by the applicant

56
Table A-1 (Continued)

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) 

B. Regional data (within 80 km) 

1. Population distributions by direction (16) and radius (for 

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, kg/yr, for vegetables 

(by type and totals), meat (all types), and milk; any 

available future predictions by local governmental, industrial, 

or institutional organizations

57
APPENDIX 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 

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 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 by uranium milling license applicants. The specific tech

nique 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 environ

mental concentrations calculated for the final year of the particular phase of 

milling operations. The duration of the operational (milling) phase is most 

often estimated to be 15 to 20 years, while drying of tailings piles in the 

prestabilization phase 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 Equations 2, 3, 4, and 6 of Regulatory Position 1, Concentrations 

in Environmental Media, of this guide. 

The staff technique for evaluating regional population EDCs for an inte

grating period of 100 years following activity release involves artificially 

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 I and 3 and as follows: 

1. Obtain all necessary input direct air concentrations, as identified 

in Table 1 of the guide, for average release rates (by radionuclide) over the 

time interval of the phase being evaluated. 

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.

59
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 environ

mental concentrations existing during the 101st year of releases at the constant 

rates employed. The similarity of this result to the desired EDC (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-I, which provides a comparison of staff and conventional 

methodologies for EDC computation. This table has been organized to display 

the component parts of each calculational 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 for the 

following reasons: 

1. The major exposure pathways are dominated by doses resulting from 

airborne activity, which decreases rapidly in the absence of a continuing 

source (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); 

3. Inordinate computational difficulties 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 

environmental concentrations at distances between 20 and 80 km (32 and 50 mi) 

from the site at which routine atmospheric dispersion calculations cannot 

generally yield results with sufficient accuracy to justify accounting for 

minor perturbations.

60
NRC Staff EDC Calculational Technique* 

(Defined as population dose commitments 

resulting from a 1-year period of exposure 

to environmental concentrations present 

during the 101st year of constant releases)

Conventional EDC Calculational Technique 

(Defined as population dose commitments 

resulting from a 100-year period of exposure 

to environmental concentrations resulting 

from constant releases over a 1-year period)

Exposure 

Line Interval, yr

1 

2 

3 

0'• 4 

5 

6 

94 

95 

96 

97 

98 

99 

100 

101

100 - 101 II 

it 

it 

II 

II II 

{I 

II 

'S 

II

Release 

Interval, yr

100 

99 

98 

97 

96 

95

7 

6 

5 

4 

3 

2 

1 

0

101 

100 

99 

98 

97 

96

8 

7 

6 

5 

4 

3 

2 

1

Average Time 

Difference, yr

0 

1 

2 

3 

4 

5

93 

94 

95 

96 

97 

98 

99 

100

Exposure 

Interval, yr

0 

1 

2 

3 

4 

5

93 

94 

95 

96 

97 

98 

99 

100

1 

2 

3 

4 

5 

6

94 

95 

96 

97 

98 

99 

100 

101

Release 

Interval. yr

0-1 0 -II 

If 

If 

II 

I!

II 

II 

It 

I' 

II 

II 

II 

'I

Average Time 

Difference, yr

0 

1 

2 

3 

4 

5 

93 

94 

95 

96 

97 

98 

99 

100

Table B-i 

COMPARISON OF STAFF AND CONVENTIONAL TECHNIQUES FOR ENVIRONMENTAL DOSE COMMITMENT CALCULATION

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 condi

tions described in the text, can be shown to be mathematically identical.

(
APPENDIX C 

RADON DOSE CONVERSION FACTOR 

The basis on which the NRC staff has relied for its radon daughter 

inhalation dose conversion factor consists of the following major component 

parts: 

1. The indoor working level (WL) concentration resulting from an outdoor 

2 2 2 Rn concentration of 1 pCi/m 3 is approximately 5.0 x 10-6 WL. 

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. 

3. The committed dose equivalent to the bronchial epithelium (basal cell 

nuclei of segmented bronchi) per unit WLM exposure is 5000 mrem (5 rem). 

These component parts enter into the following equation, which yields the 

2 2 2 Rn inhalation dose conversion factor used by the staff: 

5.0 x 10-6 WL x 25 WLM/yr 5000 mrem 0.625 mrem/yr 

pCi/mf3 WL WLM" pCi/m3 

Each of the three components identified above are derived from the following 

sources and data: 

1. 5 x 10-6 WL per pCi/m 3 of 2 2 2 Rn is established by the assumed indoor 

air concentration ratios for 2 2 2 Rn, 2 18 Po, 214 Pb, and 2 14 Bi 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 for Appendix C). 

2. 25 WLM/yr per WL concentration is derived 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 to a 1-WL concentration. This 

aqstimed breathing rate would result in an average individual receiving about

63
0.5 WLM as a result of the same length of exposure to air at a 1-WL concentration. 

The following relationship applies: 

12 WLM/yr-WL (8760 hr/yr) x 40 hr/wk x 52 wk/yr x 0.5 = 25 WLM/yr-WL 

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. 1, 2, and 3 of 

Appendix C) to the figure of 0.5 rad/WLM as reported in the BEIR Report 

(page 148 of Ref. 3 of Appendix C). 

The NRC staff considers the above basis for its 2 2 2 Rn inhalation dose 

conversion factor to be both sound and reasonable. The staff acknowledges that 

radon dosimetry is extremely complex and strongly influenced by assumed environ

mental 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 mucous layers, etc., the staff has 

endeavored to use physical, environmental, and other data reasonably 

representative of average conditions. 

REFERENCES FOR APPENDIX C 

1. Environmental Protection Agency, "Potential RAdiological Impact of Airborne 

Releases and Direct Gamma Radiation to Individuals Living Near Inactive 

Uranium Mill Tailings Piles," EPA Report EPA-520/1-76-001, January 1976. 

2. Environmental Protection Agency, "Environmental Analysis of the Uranium 

Fuel Cycle, Part I--Fuel Supply," EPA Report EPA-520/9-73-003-B, 

October 1973. 

3. National Academy of Sciences--National Research Council, "The Effects 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.

64
VALUE/IMPACT STATEMENT

1. PROPOSED ACTION 

1.1 Description 

The proposed action consists of the development and publication of a 

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 population of the entire United States, and doses to the population 

of the North American Continent. 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 and NRC regulations, evaluating impacts of releases as 

part of the overall ALARA evaluation, and evaluation of environmental impacts 

to meet NEPA requirements. 

1.2 Need 

Radiological impact evaluations for routine releases from uranium mills 

have been carried out in the past, and numerous new and repeat evaluations will 

probably be required in the future. Past evaluations have been prepared 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 evolution 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 needed to be corrected. 

The proposed action includes the publication of state-of-the-art analytical 

models, including environmental transport models and data, models and data for 

human dosimetry, and appropriate data for receptor characteristics. An example

65
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 

1.3.1 NRC 

The 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 will have available a reliable reference document explaining 

NRC's evaluation techniques. If evaluations can be conducted more uniformly, 

other agencies concerned with radiological and health impacts would benefit 

from these evaluations as they 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 proposed regulatory guide. Benefits will be 

derived from more easily predicting and understanding the results of NRC 

evaluations. Some differences from past evaluation techniques have been 

incorporated in this guide, but based on public comment, the degree and effects 

of such alterations appear to be minimal. 

1.3.4 Public 

The public will derive a benefit from the availability of a reference 

document explaining NRC evaluation techniques, and a further benefit will be 

derived from the increase in quality of NRC evaluations and subsequent licensing 

decisions and regulatory requirements.

66
2. TECHNICAL APPROACH

The technical approach to be used is based in part on contract work pre

pared by staffs of the Argonne National Laboratory, the Pacific Northwest Labora

tory, and the Oak Ridge National Laboratory. This approach reflects techniques 

currently being adopted for use in review of uranium milling license applica

tions and license renewal applications by the Office of Nuclear Material Safety 

and Safeguards. Comments on the technical approach were solicited by the 

issuance of Draft Regulatory Guide RH 802-4 for public comment. The comments 

received were evaluated and modifications were made to the guide where 

appropriate. 

3. PROCEDURAL APPROACH 

In its preliminary value/impact assessment, the staff considered several 

procedural approaches for carrying out the proposed action and selected the 

publication of a regulatory guide. 

4. STATUTORY CONSIDERATIONS 

4.1 NRC Authority 

The product document establishes routine procedures by which NRC will 

evaluate radiological impacts of routine airborne releases from uranium mills. 

These evaluations will be and are being used in "as low as is reasonably achiev

able" determinations to evaluate compliance with NRC regulations, to evaluate 

compliance with EPA's 40 CFR Part 190 regulation, and to evaluate environmental 

impacts as part of NRC's overall NEPA determination. 

4.2 Need for NEPA Assessment 

The proposed action on calculational models did not require an environmental 

impact statement as it was 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.

67
5. RELATIONSHIP TO OTHER.-EXISTING OR PROPOSED REGULATIONS OR POLICIES 

No potential conflicts with other agencies have been identified. However, 

the proposed regulatory guide will be a principal tool in the implementation 

of EPA regulation 40 CFR Part 190. Implementation of 40 CFR Part 190 is an 

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 EPA regulation. 

6. SUMMARY AND CONCLUSIONS 

Guidance on routine procedures for evaluating the radiological impact of 

routine airborne releases of radioactive material from uranium mills should be 

developed and published in a regulatory guide.

68
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