ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller I MJW Technical Services

Page 1 of 24

DOE Review Release: 03/09/2012

Document Title:

Dose Reconstruction During Residual 

Radioactivity Periods at Atomic Weapons 

Employer Facilities

Document Number: ORAUT-OTIB-0070

Revision: 01

Effective Date: 03/05/2012

Type of Document: OTIB

Supersedes: Revision 00

Subject Expert(s): Mutty M. Sharfi

Approval: Signature on File Approval Date: 02/17/2012

Mutty M. Sharfi, Document Owner

Concurrence: Signature on File Concurrence Date: 02/16/2012

John M. Byrne, Objective 1 Manager

Concurrence: Signature on File Concurrence Date: 02/16/2012

Edward F. Maher, Objective 3 Manager

Concurrence: Vickie S. Short Signature on File for Concurrence Date: 02/16/2012

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 03/05/2012

James W. Neton, Associate Director for Science

New Total Rewrite Revision Page Change

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 2 of 24

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

03/10/2008 00 Approved new technical information bulletin to establish a process for 

estimating dose to workers at AWE Facilities during residual 

radioactivity periods. Incorporates formal internal and NIOSH review 

comments. Training required: As determined by Task Manager. 

Initiated by Joseph S. Guido.

03/05/2012 01 Revises the source term depletion rate from 0.01 day-1 to 0.00067 

day-1, removes NUREG-1400 source term approach, and deletes 

Attachment B. References updated. Incorporates formal internal 

and NIOSH review comments. Constitutes a total rewrite of the 

document. Training required: As determined by the Objective 

Manager. Initiated by Mutty M. Sharfi.
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 3 of 24

TABLE OF CONTENTS

SECTION TITLE PAGE

Acronyms and Abbreviations ............................................................................................................... 5

1.0 Introduction .............................................................................................................................. 6

2.0 Scope....................................................................................................................................... 6

3.0 Background Information ........................................................................................................... 6

3.1 Resuspension Models .................................................................................................. 6

3.1.1 Resuspension Factor ........................................................................................ 7

3.1.2 Resuspension Rate........................................................................................... 9

3.1.3 Mass Loading ................................................................................................. 10

3.2 Computer Models ....................................................................................................... 10

3.3 Deposition Velocity ..................................................................................................... 12

3.4 Decline of Resuspension Factor with Time................................................................. 12

3.5 Source Term Depletion............................................................................................... 13

3.6 Ingestion Considerations ............................................................................................ 13

4.0 Guidance ............................................................................................................................... 13

4.1 Internal Dose Calculations.......................................................................................... 13

4.1.1 Consideration of Bioassay Data ...................................................................... 13

4.1.2 Maximizing Conditions .................................................................................... 15

4.1.3 Surface Activity ............................................................................................... 15

4.1.4 Exponential Interpolation................................................................................. 15

4.1.5 Computer Models............................................................................................ 16

5.0 Conclusions ........................................................................................................................... 16

6.0 Attributions and Annotations .................................................................................................. 16

References ........................................................................................................................................ 17

ATTACHMENT A, DERIVATION OF RESUSPENSION FACTORS USING 

RESRAD-BUILD-PROBABILISTIC...................................................................... 19
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 4 of 24

LIST OF TABLES

TABLE TITLE PAGE

3-1 Resuspension factors measured under various conditions....................................................... 8

3-2 Parameters for normal and lognormal maximum likelihood models of 

resuspension factor data..........................................................................................................9

3-3 Derivation of weighted indoor resuspension rate.................................................................... 10

3-4 Evaluation of the technical basis for the building occupancy scenario using the 

RESRAD-BUILD and DandD models ..................................................................................... 11

4-1 Calculated source-term depletion rates during residual periods for various sites.................... 14

4-2 Adjustment factors to account for depletion of source term during the residual 

period.....................................................................................................................................14

5-1 Recommended methods ........................................................................................................ 16

A-1 Input parameters....................................................................................................................21

A-2 Input values............................................................................................................................21

A-3 Calculated resuspension factor.............................................................................................. 24

LIST OF FIGURES

FIGURE TITLE PAGE

3-1 Resuspension factor range from mechanical and wind resuspension stresses ........................ 7

3-2 Cumulative probability function for resuspension factor............................................................ 9

3-3 Inhalation pathway in DandD and RESRAD-BUILD programs ............................................... 10

A-1 Removable fraction ................................................................................................................ 22

A-2 Air release fraction .................................................................................................................22

A-3 Source lifetime .......................................................................................................................23

A-4 Air exchange rate...................................................................................................................23
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 5 of 24

ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

AWE Atomic Weapons Employer

d day

DOE U.S. Department of Energy

dpm disintegrations per minute

FGR Federal Guidance Report

hr hour

m meter

min minute

mo month

mrem millirem

NIOSH National Institute for Occupational Safety and Health

NRC U.S. Nuclear Regulatory Commission

pCi picocurie

s second

TIB technical information bulletin

U.S.C. United States Code

yr year

§ section or sections

μg microgram
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 6 of 24

1.0 INTRODUCTION

Technical information bulletins (TIBs) are not official determinations made by the National Institute for 

Occupational Safety and Health (NIOSH) but are rather general working documents that provide 

historic background information and guidance concerning the preparation of dose reconstructions at 

particular sites or categories of sites. They will be revised in the event additional relevant information 

is obtained about the affected site(s). TIBs may be used to assist NIOSH staff in the completion of 

individual dose reconstructions.

In this document, the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy (DOE) facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act of 2000 [42 U.S.C. § 7384l(5) and (12)].

2.0 SCOPE

The purpose of this document is to provide guidance for estimating dose to workers at Atomic 

Weapons Employer (AWE) facilities during periods when NIOSH determined there was “significant 

residual contamination” in its Report on Residual Radioactive and Beryllium Contamination at Atomic 

Weapons Employer Facilities and Beryllium Vendor Facilities (NIOSH 2006) or any update to that 

report. These periods are referred to as the “residual radioactivity period”. Consideration of exposure 

during these periods is required in accordance with amendments to the EEOICPA program contained 

in Public Law 108-375.

For employment during the residual period, only the radiation exposures defined in 42 U.S.C. § 

7384n(c)(4) (i.e., radiation doses from DOE-related work) must be included in dose reconstructions; 

that is, internal or external radiation exposure from commercial sources of exposure is not 

reconstructed. For example, exposure from the manufacture and distribution of commercial uranium 

and/or thorium products would not be reconstructed for the residual period (NIOSH 2010a).

Under subparagraph B of 42 U.S.C. § 7384n(c)(4), however, radiation from a source that cannot be 

reliably distinguished from radiation covered under subparagraph A (i.e., radiation doses from DOErelated work) is considered part of the employee’s radiation dose during the residual period and must

be reconstructed (NIOSH 2010a).

During the residual period, doses from radiation or radiation-generating devices that were used at the 

AWE facility for commercial purposes that are distinguishable from the noncommercial sources are 

not included in the dose reconstruction. This includes, but is not limited to, doses from: (1) 

nondestructive testing devices such as radiography units, (2) process or flow gauges that employ 

radioactive sources, (3) moisture or density gauges, (4) electrostatic eliminators, and (5) radiationgenerating laboratory instruments, such as X-ray diffraction units (NIOSH 2010a).

3.0 BACKGROUND INFORMATION

3.1 RESUSPENSION MODELS

Methodology for the calculation of airborne radionuclide activity from particulate surface contamination 

has been expressed as either a “resuspension factor” or “resuspension rate” (Sehmel 1980). As an 

alternative, a “mass loading” approach has been applied in which the concentration of soil in air is 

used along with the assumption that the particulate in soil and air contains the same proportion of 

contaminant (Linsley 1978; Anspaugh et al. 1975).
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 7 of 24

3.1.1 Resuspension Factor

A resuspension factor is the ratio of the radionuclide airborne concentration per unit air volume 

divided by the surface concentration per unit area and is generally reported in units of m-1

. 

Resuspension factors have been extensively reviewed in the literature (Stewart 1964; Linsley 1978; 

Sehmel 1980; Brodsky 1980; DOE 1994) and have been reported to range from 10-10 m-1 to 10-2 m-1

(Sehmel 1980). A summary of these data is presented in Figure 3-1 (from Sehmel 1980).

Figure 3-1. Resuspension factor range from mechanical and wind resuspension stresses (Sehmel 

1980, Figure 2). 

Application of resuspension factors in dose assessment has been studied by a number of authors. 

Generally, early conclusions of a value of 10-6 m-1 under quiescent conditions and a factor of 10 higher 

(10-5 m-1

) under conditions of moderate activity (Stewart 1964) have been supported by later analysis 

(Brodsky 1980). 
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 8 of 24

The U.S. Nuclear Regulatory Commission (NRC) conducted an extensive review of resuspension 

factors for the purpose of estimating internal exposure of future occupants of decommissioned 

facilities and published these data in the NUREG/CR-5512 series of documents (Kennedy and 

Strenge 1992; Beyeler et al. 1999, Abu-Eid et al. 2002). Table 3-1 contains a summary of the 

resuspension factors for indoor facilities based on the NRC research in 1999. The NRC initially 

proposed a resuspension factor in the form of a probability density function, with a median value of 

5 × 10-5 m-1 (Figure 3-2). The NRC approach was based on the loose contamination present and, if 

applied to total surface contamination, would have to be adjusted by the fraction of the total 

contamination that is removable. A typical value used is 10% (Beyeler et al. 1999). 

Table 3-1. Resuspension factors measured under various conditions (Beyeler et al. 1999, 

Figure 5-11).

Experimental condition Resuspension factor (m-1)

Normal room ventilation 3.3E-8

Walking (14 steps/min) 9.1E-6

Walking (36 steps/min) 6.9E-5

Walking (100 steps/min) with wind stress (hair dryer directed toward floor) 1.5E-4

Undisturbed 1.5E-5 to 3.6E-4

Fans on 3.4E-5 to 1.6E-3

Vibration (dolly) 1.2E-4 to 1.9E-4

Fans + vibration 1.2E-4 to 1.5E-2

Vigorous sweeping by two workmen 1.02 × 10-2 to 4.2 × 10-2

Vigorous work activity, including sweeping 1.9E-4

Vigorous walking 3.9E-5

Light work activity 9.4E-6

Rapid air circulation 7.1E-4

Additional analysis on resuspension factors was published by the NRC in NUREG-1720 (Abu-Eid et 

al. 2002). The justification for the revision was the fact that the earlier analysis used data from both 

freshly deposited and aged deposits. It was the NRC contention that, for application at 

decommissioned facilities (which was the intended purpose of the analysis), values from fresh 

deposits would be overly conservative. In addition, data from additional studies were included in the 

2002 analysis. The proposed resuspension factor selected (because this NUREG is still a draft 

document) was expressed as both a normal and lognormal distribution (Table 3-2) with a 

90th-percentile value of 9.6 × 10-7 m-1 (lognormal fit).
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 9 of 24

Figure 3-2. Cumulative probability function for resuspension factor (RFO) (Beyeler et al. 1999, Figure 

5-7).

Table 3-2. Parameters for normal and lognormal maximum likelihood models of resuspension factor 

data (Abu-Eid et al. 2002, Table 5).

Statistical model Sample mean

Sample standard 

deviation

90th-percentile 

resuspension factor

Normal fit to 5 site mean RFs 4.74E-7 m-1 3.11E-7 m-1 8.7E-7 m-1

Lognormal fit to 5 site mean RFs log10 = -6.433 log10 = 0.3247 9.6E-7 m-1

3.1.2 Resuspension Rate

Resuspension rates indicate the fraction of a material that is released per unit time (units of hr-1 are 

common). Some authors report the resuspension rates as applicable to outdoor environments to 

calculate downwind contaminant concentrations and ground deposition (Sehmel 1980; Till and Meyer 

1983), while others apply them in the indoor setting to determine exposure to occupants (Healy 1971). 

Healy cited studies that showed that the resuspension rate can exceed 1 × 10-3 hr-1 for particles on 

noncarpeted surfaces. Based on a review of resuspension data and assumptions about the amounts 

of time spent at different activities indoors, Healy estimated a time-weighted average resuspension 

rate of 5 × 10 -4 hr-1 for a house (Table 3-3). The corresponding air activity x is determined by the 

expression: 

x = [(resuspension rate)(surface contamination level)(area contaminated)]/[(volume)(air changes/hr)] (3-1)
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 10 of 24

Table 3-3. Derivation of weighted indoor resuspension rate (Healy 1971, p. 32).

Activity (description)

Duration 

(hr/d)

Resuspension 

rate

Vigorous activity in area. Includes cleaning or children at active play or running 1 5E-3 hr-1

Active. Normal traffic in the room. Children at normal play 5 1E-3 hr-1

Moderate. Low traffic with reading, watching TV and occasional movement 6 1E-4 hr-1

Quiet. No movement. Room unoccupied 12 1E-6 hr-1

Average rate 5E-4 hr-1

Resuspension rates are used in the RESRAD-BUILD computer program to incorporate the 

contribution to airborne radioactivity from the resuspension of freshly deposited material (Figure 3-3).

Figure 3-3. Inhalation pathway in DandD and RESRAD-BUILD programs

(Biwer et al. 2002, Figure 2-2).

3.1.3 Mass Loading

An approach used to calculate the airborne concentration in outdoor areas due to resuspension of 

soils is to multiply the surface soil concentration (activity per unit mass) by the average mass loading 

of the atmosphere (mass per unit volume), yielding an air concentration in units of activity per unit 

volume (Anspaugh et al. 1975). Anspaugh et al. suggests a default value of 100 μg/m3 based on 

particulate concentrations in 30 nonurban locations. This same approach was adopted by the NRC in 

NUREG/CR-5512 for the residential scenario for exposure outdoors, using a mass loading value of 

100 μg/m3 (Beyeler et al. 1999).

3.2 COMPUTER MODELS

Two common computer models for the estimation of exposure from residual radioactive contamination 

inside building structures are RESRAD-BUILD (Yu et al. 1994) and DandD (McFadden et al. 2001). 

RESRAD-BUILD was developed for DOE by Argonne National Laboratory and DandD was developed 

for the NRC. Both models are intended to either develop activity-based release criteria for facility 

decommissioning or to demonstrate compliance with dose-based criteria. Table 3-4 is a summary of 

the capabilities of both of these models. Although both programs are suitable for modeling exposure 

from residual contamination in indoor environments, DandD is much more simplistic (Figure 3-3) with 

fewer input parameters and assumptions and is likely to be more appropriate for situations in which 
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 11 of 24

the requisite parameters for RESRAD-BUILD are either not available or highly variable (such as 

airflow rates and building dimensions).

Table 3-4. Evaluation of the technical basis for the building occupancy scenario using the RESRADBUILD and DandD models (Biwer et al. 2002, Table 2-1).

Component RESRAD-BUILD DandD Remarks

Source 

description

• Up to 10 sources

• Volume, area, line, or point source 

of any dimension

• Floor is contaminated

• Infinite area source for 

the direct exposure 

pathway

Handling of 

radionuclides

• 67 principal radionuclides

• Half-lives 6 mo or longer

• In secular equilibrium with 

progeny of half-lives less than 

6 mo

• 249 primary 

radionuclides 

• Half-lives 10 min or 

longer

• In secular equilibrium 

with progeny if halflives are (1) less than 

9 hr and (2) less than 

one-tenth the listed 

parent half-life

DandD has many more 

short-lived radionuclides 

in its database.

Building 

description

• Up to a three-room structure 

• Air exchange

• One large structure

• Air exchange is not 

explicitly modeled

Receptor location 

with respect to 

source

Up to 10 receptor locations at any 

distance from the source

Only one receptor at a 

fixed location (specified 

by Federal Guidance 

Report 12a geometry) 

with respect to the source

RESRAD-BUILD has an 

external exposure model 

to handle any sourcereceptor configuration.

Pathways • Direct external exposure from 

surface source

• Inhalation of airborne radioactive 

particulates

• Inadvertent ingestion of source 

material directly

• Inadvertent ingestion of deposited 

materials

• Exposure to deposited materials

• Exposure due to air submersion

• Inhalation of aerosol indoor radon 

progeny

• External exposure due 

to surface source

• Inhalation of 

resuspended surface 

contamination

• Inadvertent ingestion 

of surface 

contamination

RESRAD-BUILD is a 

more sophisticated code 

and can model sitespecific situations.

Time 

dependence

• 10 time steps in a single run

• Calculates average timeintegrated dose over the exposure 

duration

• Radionuclide concentration 

changes with radioactive ingrowth, 

decay, and mechanical erosion

• A single time step

• Calculates average 

time-integrated dose 

over 1-yr duration

• Radionuclide 

concentration changes 

with radioactive 

ingrowth and decay

Air concentration • Dynamic air quality model 

• Different source release 

mechanisms: diffusion and 

particulate injection

Simple and static linear 

relationship between air 

concentration and 

contamination

DandD assumes infinite 

source, and air 

concentration is derived 

from the resuspension 

factor, whereas in 

RESRAD-BUILD there is 

uniform depletion of 

source over the source 

lifetime.
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 12 of 24

Component RESRAD-BUILD DandD Remarks

Ingestion 

pathway

• Direct ingestion of removable 

material

• Ingestion of deposited material

Direct ingestion of 

removable material

RESRAD-BUILD also 

considers ingestion from 

deposited materials.

External 

exposure 

pathways

• Directly from the source 

• Materials deposited on the floor

• Air submersion

Directly from the source RESRAD-BUILD 

considers two more 

external exposure 

pathways.

Shielding 

correction

Eight shielding materials No shielding correction

Transport of 

contamination 

from one room to 

another

• With an indoor air quality model

• Air exchange between the rooms

and with outside air

• The deposition and resuspension 

of particulates

• Radioactive decay and ingrowth

No transport considered

H-3 (tritium) Special H-3 model for volume 

source

No special H-3 model

Radon Radon diffusion and radon flux 

model

Not included Not required for NRC 

compliance.

a. Eckerman and Ryman (1993).

3.3 DEPOSITION VELOCITY

The deposition velocity characterizes the rate at which particles in the air deposit on a surface. 

Deposition velocity is determined experimentally by measuring the amount of material deposited per 

unit area during a particular time interval and dividing by the time-integrated air concentration at a 

particular reference height (Till and Meyer 1983). In addition, deposition velocities can be estimated 

empirically by considering the terminal settling velocity (which is a function of particle size and 

density) and factors related to atmospheric turbulence and Brownian motion (Till and Meyer 1983). 

Based on terminal settling velocity alone, a value of 0.00075 m/s has been used in previous Project 

documents [ORAUT-OTIB-0004 (ORAUT 2006) and Battelle-TBD-6000 (Battelle 2011)] to estimate 

the surface contamination from airborne radioactive contamination. As an alternative, a loguniform 

distribution, with minimum and maximum values of 2.7 × 10-6 m/s and 2.7 × 10-3 m/s, has been 

proposed by the NRC for use in RESRAD-BUILD (Biwer et al. 2002).

3.4 DECLINE OF RESUSPENSION FACTOR WITH TIME

Decrease in particulate resuspension with time has been well-documented in experimental studies in 

outdoor environments (Sehmel 1980; Till and Meyer 1983). Measured resuspension factor “half-lives” 

in the range of 35 days to years have been reported (Sehmel 1980). Models for this effect have been 

proposed in the form of a constant (steady-state component) and a second component with an 

exponential term. For example, Linsley (1978) reported an expression: 

K(t) = [10-6 exp(-0.01t) + 10-9

] m-1 (3-2)

where

t = days, and with the 10-6 factor being replaced by 10-5 for periods of “regular disturbance by 

vehicular or pedestrian traffic.”

Fewer data are available on the variation of resuspension factors with time in indoor environments. 

However, Healy (1971) recommends a decay constant value of 0.1 d-1

, which represents the effects of 

source depletion with time. While no experimental studies were identified for indoor facilities, an 
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 13 of 24

exponential decrease in resuspension is expected to occur due to conservation of mass and the 

depletion of easily suspended contaminants.

3.5 SOURCE TERM DEPLETION

The half-life of the surface contamination is given by (Steward 1964):

1

2

0.693 hr A T

KnR = (3-3)

where

A = is the contaminated area

K = resuspension factor

n = ventilation rate (air changes per unit time)

R = room volume 

R = A × H

H = room height

Therefore the decay constant (λ) is

λ = KnH (hr-1

) (3-4)

Expressed in units of d-1 this becomes

λ = 24KnH (d-1

) (3-5)

NUREG-1720 (Abu-Eid et al. 2002) presents an analysis of experimental data from a uranium 

processing facility. Measurements were collected over a weekend during which uranium operations 

were not conducted. Analysis of these data to determine the rate at which the airborne activity was 

being depleted yielded an average time constant of 0.0378 hr-1 and a minimum value of 0.00946 hr-1

. 

3.6 INGESTION CONSIDERATIONS

If inhalation intakes are calculated from air concentrations, ingestion intakes are to be considered. 

The ingestion rate, in terms of disintegrations per minute (dpm) for an 8-hour workday, can be 

estimated by multiplying the air concentration in dpm per cubic meter by a factor of 0.2 (NIOSH 2004). 

To adjust this to ingestion intake per calendar day, the calculated ingestion rate is multiplied by 250 

workdays per year and divided by 365 d/yr. The same f1 value as that used for inhalation dose 

calculations is to be used for ingestion dose calculations (NIOSH 2004).

4.0 GUIDANCE

4.1 INTERNAL DOSE CALCULATIONS

4.1.1 Consideration of Bioassay Data 

If bioassay data from the residual period might be affected by continued site operations (nonAEC/DOE), it is necessary to account for the fact that only a portion of the exposure during the 

residual period is from resuspended residual contamination versus exposure due to continued site 

operations. Therefore, calculated intakes must be adjusted by a weighting factor to account for the 

continued depletion of the operational source term during the residual period. The source-term 

depletion rates during the residual radiation periods have been previously determined for the four 
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 14 of 24

sites listed in Table 4-1 (NIOSH 2010b; Battelle 2011; ORAUT 2008; ORAUT 2011). In these cases, 

contemporary estimates of airborne radioactivity at the beginning and end of each site’s residual 

radiation period were used to estimate the effective exponential clearance of the contamination over 

an extended period for each site. 

Table 4-1. Calculated source-term depletion rates 

during residual periods for various sites.

Facility Depletion rate (d-1)

Blockson 0.00076

Dow Madison 0.00027

General Atomics 0.00116

Simonds Saw and Steel 0.00049

Average 0.00067

Based on the average depletion rate of 0.00067 d-1, source term depletion adjustment factors are 

presented in Table 4-2. This average depletion rate should be used for facilities without site-specific 

data. 

Table 4-2. Adjustment factors to account for depletion 

of source term during the residual period.

Year Factor

1* 1.00E+00

2 7.83E-01

3 6.13E-01

4 4.80E-01

5 3.76E-01

6 2.94E-01

7 2.31E-01

8 1.81E-01

9 1.41E-01

10 1.11E-01

11 8.67E-02

12 6.79E-02

13 5.32E-02

14 4.16E-02

15 3.26E-02

16 2.55E-02

17 2.00E-02

18 1.56E-02

19 1.23E-02

20 9.60E-03

21 7.51E-03

22 5.88E-03

23 4.61E-03

24 3.61E-03

25 2.83E-03

26 2.21E-03

27 1.73E-03

28 1.36E-03

29 1.06E-03

30 on 8.32E-04

* Year one is applied to the first year of the residual period.
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 15 of 24

4.1.2 Maximizing Conditions

Overestimating methods for residual radioactivity periods are presented in ORAUT (2006) and 

Battelle (2011).

4.1.3 Surface Activity

Estimates of internal dose from surface activity measurements are accomplished using resuspension 

factors (Section 3.1.1) for indoor calculation and mass loading factors (Section 3.2) for outdoor areas 

(or where surface activity is available in activity per unit mass).

Application of resuspension factors requires some information on the average surface contamination 

level in the facility. If this value is not known, an estimate could be made based on typical airborne 

radioactivity levels during operations [or worst-case values based on data from ORAUT (2006) or 

Battelle (2011)]. Using estimated airborne radioactivity levels, surface activity can be estimated using 

a deposition velocity and duration. This approach enables the estimation of airborne activity due to 

residual surface activity that has been deposited during operations. Values of 0.00075 m-1 and 1 year 

of deposition velocity and duration, respectively, would be favorable to claimants.

To ensure an assessment that is favorable to claimants, a resuspension factor of 1 × 10-6 m-1 should 

be used for undisturbed areas to estimate airborne activity from surface contamination. This value is 

consistent with the research (Section 3.1.1), and bounding at the 95th percentile based on a 

probabilistic analysis using RESRAD-BUILD (Attachment A). In cases, where the contaminated area 

is still involved in active operations, a site-by-site analysis of the appropriateness of the 1 × 10-6 m-1

resuspension factor should be done.

Application of a mass loading approach could be appropriate for outdoor areas or for indoor areas 

where there is debris that has been characterized as activity per unit mass. Based on the analysis 

reviewed by the NRC, a value of 100 μg/m3 is favorable to claimants and should be applied.

4.1.4 Exponential Interpolation

Contemporary estimates of airborne radioactivity (directly measured or calculated using surface 

activity measurements) can be used in conjunction with measurements of airborne activity during the 

operational period to develop an exposure matrix during the residual radioactivity period. Based on 

an understanding of the removal mechanisms (Section 3.4), an exponential model should be used to 

fit the operational period data and the postoperational data. In practice, the postoperational airborne 

activity and the operational activity would be related by the following equation:

( )( ) e λt A residual period A operations − = × (4-1)

where

t = the length of time between the two air concentration measurements (residual and 

operational)

This equation is then solved for λ. Calculation of intakes between the measured operational and 

residual period values should be based on integration of Equation 4-1 on an annual basis. 

If no data are available for airborne radioactivity levels during the operational period, a value that is

favorable to claimants can be estimated based on applicable values based on data from Battelle

(2011).
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 16 of 24

If no data are available for airborne radioactivity levels during the residual period, a source term 

depletion factor of 0.00067 d-1 (Section 2.5) can be used in conjunction with the available operational 

period data. To account for the observed steady-state resuspension conditions (Linsley 1978), source 

term depletion should be held constant after 30 years (as in Table 4-2).

4.1.5 Computer Models

Application of either the RESRAD-BUILD or DandD models (Section 2.2) would yield a detailed 

assessment of exposure conditions based on input assumptions. However, such an assessment 

would only be as accurate as the input parameters on which the calculations were based. If such 

parameters could be determined with confidence, application of such a method would be appropriate. 

DandD, being a more simplistic model, would require a less detailed understanding of the exposure 

conditions and might be more appropriate for situations in which knowledge of facility conditions is 

limited.

5.0 CONCLUSIONS

Table 5-1 presents the methods reviewed for estimation of internal exposure to residual radioactivity 

at AWE facilities.

Table 5-1. Recommended methods.

Air sample Surface contamination

Operational Recommended methodology

Postoperational OperationalPostoperational

X X Exponential fit of operational and postoperational 

data.

X Calculate annual intake quantities based on a source

term depletion factor of 0.00067 d-1 (Section 3.5).

X

Exponential fit of postoperational data and estimate 

of operational airborne radioactivity based on ORAUT 

(2006) or Battelle (2011).

X X

Conversion of surface activity to airborne 

concentrations using resuspension factor* or 1 × 10-6

m-1 followed by an exponential fit of derived levels.

X

Conversion of surface activity to airborne 

concentrations using resuspension factors. Calculate 

annual intake quantities based on a source term 

depletion factor of 0.00067 d-1 (Section 3.5).

X

Conversion of postoperational surface activity data to 

airborne concentrations using resuspension factor* of 

1 × 10-6 m-1

. Estimate of operational airborne 

radioactivity based on ORAUT (2006) or Battelle 

(2011). Exponential fit of two quantities.

* In cases, where the contaminated area is still involved in active operations, a site-by-site analysis of the appropriateness of 

the 1 × 10-6 m-1 resuspension factor should be done.

6.0 ATTRIBUTIONS AND ANNOTATIONS

All information requiring identification was addressed via references integrated into the reference 

section of this document.
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 17 of 24

REFERENCES

Abu-Eid, R. M., R. B. Coddell, N. A. Eisenburg, T. E. Harris, and S. McGuire, 2002, Re-evaluation of 

the Indoor Resuspension Factor for the Screening Analysis of the Building Occupancy 

Scenario for NRC’s License Termination Rule, NUREG-1720, Draft Report for Comment, U.S. 

Nuclear Regulatory Commission, Office of Nuclear Material Safety and Safeguards, 

Washington, D.C., June. [SRDB Ref ID: 22400]

Anspaugh, L. R., J. H. Shinn, P. L. Phelps, and N. C. Kennedy, 1975, “Resuspension and 

Redistribution of Plutonium in Soils,” Health Physics, volume 29, number 4, pp. 571–582; 

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Battelle, 2011, Site Profiles for Atomic Weapons Employers that Worked Uranium Metals, BattelleTBD-6000, Rev. 1, June 1. 

Beyeler, W. E., W. A. Hareland, F. A. Durán, T. J. Brown, E. Kalinina, D. P. Gallegos, and P. A. Davis, 

1999, Residual Radioactive Contamination from Decommissioning, Parameter Analysis, 

NUREG/CR-5512 Vol. 3., Draft Report for Comment, U.S. Nuclear Regulatory Commission, 

Office of Nuclear Regulatory Research, Washington, D.C., October [SRDB Ref ID: 77730]

Biwer, B. M., S. Kamboj, J. Arnish, C. Yu, and S. Y. Chen, 2002, Technical Basis for Calculating 

Radiation Doses for the Building Occupancy Scenario Using the Probabilistic RESRAD-BUILD 

3.0 Code, NUREG/CR-6755, U.S. Nuclear Regulatory Commission, Office of Nuclear 

Regulatory Research, Washington, D.C., February. [SRDB Ref ID: 91669]

Brodsky, A., 1980, “Resuspension Factors and Probabilities of Intake of Material in Process (Or ‘Is 10-

6 a Magic Number in Health Physics?’),” Health Physics, volume 39, number 6, pp. 992–1000. 

[SRDB Ref ID: 52086]

DOE (U. S. Department of Energy), 1994, Airborne Release Fractions/Rates and Respirable Fractions 

for Nonreactor Nuclear Facilities, DOE-HDBK-3010-94, Washington, D.C., December. [SRDB 

Ref ID: 56569]

Eckerman, K. F., and J. C. Ryman, 1993, Federal Guidance Report No. 12: External Exposure to 

Radionuclides in Air, Water, and Soil, EPA-402-R-93-081, U.S. Environmental Protection 

Agency, Office of Radiation and Indoor Air, Washington, D.C. [SRDB Ref ID: 11997]

Healy, J. W., 1971, Surface Contamination: Decision Levels, LA-4558-MS, University of California, 

Los Alamos Scientific Laboratory, Los Alamos, New Mexico. [SRDB Ref ID: 40445]

Kennedy, W. E., Jr. and D. L. Strenge, 1992, Residual Radioactive Contamination from 

Decommissioning. Technical Basis for Translating Contamination Levels to Annual Total 

Effective Dose Equivalent, Final Report, NUREG/CR-5512, Vol. 1 (PNL-7994), U.S. Nuclear 

Regulatory Commission, Office of Nuclear Material Safety and Safeguards, Washington, D.C., 

October. [SRDB Ref ID: 23558]

Linsley, G. S., 1978, Resuspension of the Transuranium Elements – A Review of Existing Data, 

NRPB-R75, National Radiological Protection Board, Harwell, Didcot, Oxford, England. [SRDB 

Ref ID: 63425]
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McFadden, K., D. A. Brosseau, W. E. Beyeler, and C. D. Updegraaf, 2001, Residual Radioactive 

Contamination from Decommissioning, User’s Manual, DandD Version 2.1, NUREG/CR-5512, 

Vol. 2 (SAND2001-0822P), U.S. Nuclear Regulatory Commission, Office of Nuclear 

Regulatory Research, Washington, D.C., April. [SRDB Ref ID: 40435]

NIOSH (National Institute for Occupational Safety and Health), 2004, Estimation of Ingestion Intakes, 

OCAS-TIB-009, Rev. 0, Office of Compensation Analysis and Support, Cincinnati, Ohio, April 

13.

NIOSH (National Institute for Occupational Safety and Health), 2006, Report on Residual Radioactive 

and Beryllium Contamination at Atomic Weapons Employer Facilities and Beryllium Vendor 

Facilities, December. [SRDB Ref ID: 29386]

NIOSH (National Institute for Occupational Safety and Health), 2010a, Radiation Exposures Covered 

for Dose Reconstructions under Part B of the Energy Employees Occupational Illness 

Compensation Program Act, OCAS-IG-003, Rev. 1, Division of Compensation Analysis and 

Support, Cincinnati, Ohio, October 5.

NIOSH (National Institute for Occupational Safety and Health), 2010b, Technical Basis Document for 

Atomic Energy Operations at Blockson Chemical Company, Joliet, Illinois, DCAS-TKBS-0002, 

Rev. 03, Division of Compensation Analysis and Support, Cincinnati, Ohio, December 20.

ORAUT (Oak Ridge Associated Universities Team), 2006, Estimating the Maximum Plausible Dose to 

Workers at Atomic Weapons Employer Facilities, ORAUT-OTIB-0004, Revision 3 PC-2, Oak 

Ridge, Tennessee, December 6.

ORAUT (Oak Ridge Associated Universities Team), 2008, Site Profile for General Atomics, Rev. 00, 

ORAUT-TKBS-0045, Oak Ridge, Tennessee, September 26.

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Rev. 01, ORAUT-TKBS-0032, Oak Ridge, Tennessee, April 18.

Sehmel, G. A., 1980, “Particle Resuspension: A Review,” Environment International, volume 4, 

pp.107–127.

Stewart, K., 1964, “The Resuspension of Particulate Material from Surfaces,” Chapter NA, pp. 63–74 

Surface Contamination, First Edition, B. R. Fish, editor, Pergamon Press, Oxford, England.

Till, J. E., and H. R. Meyer, 1983, Radiological Assessment – A Textbook on Radiological Dose 

Analysis, NUREG/CR-3332, U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor 

Regulation, Washington, D.C., September. [SRDB Ref ID: 40438]

Yu, C., D. J. LePoire, C. O. Loureiro, L. G. Jones, and S. Y. Chen, 1994, RESRAD-BUILD: A 

Computer Model for Analyzing the Radiological Doses Resulting from the Remediation and 

Occupancy of Buildings Contaminated with Radioactive Material, ANL/EAD/LD-3, University of 

Chicago, Argonne National Laboratory, Argonne, Illinois, November. [SRDB Ref ID: 40436]
Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 19 of 24

LIST OF TABLES

TABLE TITLE PAGE

A-1 Input parameters....................................................................................................................21

A-2 Input values............................................................................................................................21

A-3 Calculated resuspension factor.............................................................................................. 24

LIST OF FIGURES

FIGURE TITLE PAGE

A-1 Removable fraction ................................................................................................................ 22

A-2 Air release fraction .................................................................................................................22

A-3 Source lifetime .......................................................................................................................23

A-4 Air exchange rate...................................................................................................................23

Methodology

The air concentration (Cn

) in a one-room air quality model under equilibrium conditions for a surface 

source of long-lived radionuclide contamination in which the contamination covers the entire floor can 

be expressed as (Yu et al. 1994, Equation J.4.10-5): 

24

n R surf

a

R b

f fC C

T λ H = (A-1)

where

Cn = air concentration of radionuclide n in the room (pCi/m3

),

fR = removal fraction of the source material

f = fraction of removed material that becomes indoor dust (air release fraction),

Csurf = surface concentration (pCi/m2

),

TR = time to remove material from the source (source lifetime) (d), a

b λ = air exchange rate (hr

-1

), and

H = height of compartment (m).

The resuspension factor is defined as the ratio of the air activity to the surface activity. Using the 

notation above, the resuspension factor RF can be expressed as (Yu et al. 1994, Equation J.4.10-6):

T λ H

f f R a R b

R

F 24 = (A-2)

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Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 20 of 24

Because the RESRAD-BUILD probabilistic module does not directly provide an air activity output, it is 

necessary to derive it based on the inhalation dose output value based on the relationship (Yu et al. 

1994, Equation D.3):

( ) ( ) n nn D t F F IR C t ED DCF inh in i = ×× × × × i h (A-3)

where

( ) n D t inh = total effective dose equivalent due to inhalation of radionuclide n in compartment I

from time t to t + ED (mrem),

Fin = fraction of time spent indoors (indoor fraction) (dimensionless),

Fi = fraction of indoor time that is spent at compartment i (time fraction) (dimensionless),

IR = inhalation rate (m3 d-1

),

( ) n C t i = average concentration of radionuclide n (pCi/m3

) over the exposure duration ED

starting at time t in the indoor air of compartment i,

ED = exposure duration (d), and n DCFh = inhalation dose conversation factor for radionuclide n (mrem/pCi). 

The appropriateness of this methodology for deriving the air activity (and in effect the resuspension 

factor) was verified by calculating these values using both the described technique and the closed 

form analytical solution (based on Yu et al. 1994, Equation J.4.10-6) and comparing them with the 

RESRAD-BUILD output air activity value (provided on the detailed output report). The requisite 

parameters necessary to perform this comparison are only available for the deterministic RESRADBUILD cases.

Input Values

The probabilistic module of RESRAD-BUILD allows any parameter to be specified as a probability 

density function. The resultant output is provided for the 5th through 100th percentile in intervals of 

5%. 

The resuspension factor at the 95th percentile was calculated using default probability density 

functions for the following parameters: (1) removable fraction, (2) fraction of removed material that 

becomes indoor dust, (3) time to remove material, and (4) air exchange rate. A deterministic value of

room height (2.5 m) was selected to represent a reasonable approximation that is favorable to 

claimants. The default distributions applied (as documented in Appendix J of Yu et al. 1994) are 

based on a detailed literature review by Argonne National Laboratory and are summarized in 

Table A-1 and shown in Figures A-1 to A-4. Detailed analyses of these distributions are provided in 

Appendix J of Yu et al. (1994).

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Table A-1. Input parameters (sensitive).

Value Type Value Comment

Removable fraction

(unitless)

Probabilistic Triangular distribution

Minimum = 0

Maximum = 1.0

Most likely = 0.1

Yu et al. 1994, Figure J.14

Air release fraction

(unitless)

Probabilistic Triangular distribution 

Minimum = 1E-6, 

Maximum = 1

Most likely = 0.07

Yu et al. 1994, Figure J.13

Source lifetime

(d)

Probabilistic Triangular distribution

Minimum = 1,000 

Maximum = 100,000

Most likely = 10,000

Yu et al. 1994, Figure J.15

Air exchange rate 

(hr

-1

)

Probabilistic Truncated lognormal distribution

Mean = 0.4187

Standard deviation = 0.88

Lower quantile = 0.001

Upper quantile = 0.999

Yu et al. 1994, Figure J.9

Height

(m)

Deterministic 2.5 Realistic value that is favorable to

claimant 

Table A-2. Input values (insensitive – no impact on analytical results).

Value Type Value Comment

Source activity (pCi/m2) Deterministic 1,000

Source area (m2) Deterministic 36

Breathing rate (m2 d-1) Deterministic 28.8 Equal to 1.2 m3/hr

Indoor fraction (unitless) Deterministic 0.23 Equal to 2,000 hr/yr

Time fraction (unitless) Deterministic 1 Single-room model

Exposure duration (d) Deterministic 365

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Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 22 of 24

Figure A-1. Removable fraction (Yu et al. 1994, Figure J.14).

Figure A-2. Air release fraction (Yu et al. 1994, Figure J.13).

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Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 23 of 24

Figure A-3. Source lifetime (Yu et al. 1994, Figure J.15).

Figure A-4. Air exchange rate (Yu et al. 1994, Figure J.9)

Results

Table A-3 presents the calculated resuspension factor based on the RESRAD-BUILD probabilistic 

model runs for the inputs described above. At the 95th percentile, a resuspension factor of 4.5 × 10-7

is derived.

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Document No. ORAUT-OTIB-0070 Revision No. 01 Effective Date: 03/05/2012 Page 24 of 24

Table A-3. Calculated resuspension factor.

Statistic (%) Resuspension factor

5 2.6E-09

10 5.2E-09

15 7.1E-09

20 9.5E-09

25 1.2E-08

30 1.6E-08

35 2.0E-08

40 2.3E-08

45 2.9E-08

50 3.3E-08

55 4.2E-08

60 5.0E-08

65 6.0E-08

70 7.6E-08

75 9.3E-08

80 1.3E-07

85 1.6E-07

90 2.2E-07

95 4.5E-07

100 2.6E-06

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