ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 26

Document Title:

Dose Reconstruction During 

Residual Radioactivity Periods 

at Atomic Weapons Employer Facilities

Document Number: ORAUT-OTIB-0070

Revision: 00 

Effective Date: 03/10/2008

Type of Document OTIB

Supersedes: None

Subject Expert(s): Joseph S. Guido

Site Expert(s): N/A

Approval: Signature on File Approval Date: 02/08/2008

Joseph S. Guido, Document Owner

Concurrence: Signature on File Concurrence Date: 02/11/2008

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 02/08/2008

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 02/15/2008

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 03/10/2008

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. 00 Effective Date: 03/10/2008 Page 2 of 26

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.
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 3 of 26

TABLE OF CONTENTS

SECTION TITLE

1.0 Purpose ......................................................................................................................................

PAGE

5

2.0 Background Information..............................................................................................................5

2.1 Resuspension Models ........................................................................................................5

2.1.1 Resuspension Factor..............................................................................................6

2.1.2 Resuspension Rate ................................................................................................7

2.1.3 Mass Loading .........................................................................................................9

2.2 NUREG-1400 Methodology..............................................................................................10

2.3 Computer Models (RESRAD-BUILD; DandD) ..................................................................10

2.4 Deposition Velocity...........................................................................................................10

2.5 Decline of Resuspension Factor with Time.......................................................................10

2.6 Source Term Depletion ....................................................................................................12

2.7 Ingestion Considerations..................................................................................................13

3.0 Guidance ..................................................................................................................................13

3.1 Internal Dose Calculations................................................................................................13

3.1.1 Consideration of Bioassay Data............................................................................ 13

3.1.2 Maximizing Conditions.......................................................................................... 13

3.1.3 Source Term......................................................................................................... 13

3.1.4 Surface Activity..................................................................................................... 14

3.1.5 Exponential Interpolation ...................................................................................... 14

3.1.6 Computer Models ................................................................................................. 15

4.0 Conclusions ..............................................................................................................................15

5.0 Attributions and Annotations ..................................................................................................... 16

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

ATTACHMENT A, DERIVATION OF RESUSPENSION FACTORS USING RESRADBUILD-PROBABILISTIC ......................................................................................20

ATTACHMENT B, THORIUM SOURCE TERM DATA.......................................................................26
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 4 of 26

LIST OF TABLES

TABLE TITLE

2-1 Derivation of weighted indoor resuspension rate......................................................................

PAGE

9

2-2 Evaluation of the technical basis for the building occupancy scenario using the 

RESRAD-BUILD and DandD codes ....................................................................................... 11

3-1 Adjustment factors to account for depletion of source term during the residual 

contamination period..............................................................................................................13

3-2 Efficiency methods for AWE residual radioactivity period dose reconstruction ....................... 14

4-1 Summary of recommended methods ..................................................................................... 16

A-1 Input parameters....................................................................................................................22

A-2 Input values............................................................................................................................22

A-3 Calculated resuspension factor.............................................................................................. 25

LIST OF FIGURES 

FIGURE TITLE PAGE

2-1 Resuspension factor range from mechanical and wind resuspension stresses ........................ 6

2-2 Resuspension factors measured under various conditions....................................................... 7

2-3 Cumulative probability function for RF......................................................................................8

2-4 Parameters for normal and lognormal ‘maximum likelihood’ models of RF data....................... 8

2-5 Inhalation pathway in DandD and RESRAD-BUILD codes....................................................... 9

A-1 Removable fraction ................................................................................................................23

A-2 Air release fraction ................................................................................................................. 23

A-3 Source lifetime .......................................................................................................................24

A-4 Air exchange rate................................................................................................................... 24
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 5 of 26

1.0

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 to assist in 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. 

PURPOSE

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 facility” as defined in the Energy Employees 

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

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

Weapons Employers (AWEs) after operations were performed for the Manhattan Engineering District 

(MED) or Atomic Energy Commission (AEC) during periods when “significant residual contamination” 

existed as determined by Report on Residual Radioactive and Beryllium Contamination at Atomic 

Weapons Employer Facilities and Beryllium Vendor Facilities (NIOSH 2006). These time periods are 

referred to as the “residual radioactivity period” and are listed in the DOE Worker Advocacy Website 

as covered time periods for the purpose of determining eligibility for the EEOICPA program. 

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 contamination period, only the radiation exposures defined in 42 

U.S.C. § 7384n(c)(4) [i.e., radiation doses received from DOE-related work] must be included in dose 

reconstructions. That is, internal or external radiation exposure, associated with commercial sources 

of exposure, is not reconstructed. For example, the exposure incurred from the manufacture and 

distribution of commercial uranium and/or thorium products would not be reconstructed during the 

residual contamination period (NIOSH 2007). 

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 received 

from DOE related work) is considered part of the employee’s radiation dose and must be 

reconstructed (NIOSH 2007). 

During the residual contamination period, doses associated with radiation or radiation generating 

devices that were used at the AWE facility for commercial purposes that are distinguishable from the 

non-commercial sources are not included in the dose reconstruction. This includes, but is not limited 

to, doses from: 1) non-destructive 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) radiation generating laboratory instruments, such as x-ray diffraction units (NIOSH 2007). 

2.0

2.1 RESUSPENSION MODELS

BACKGROUND INFORMATION

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). 

Alternatively, a “mass loading” approach has been applied in which the concentration of soil in air is 
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 6 of 26

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

contaminant (Linsley 1978; Anspaugh et al. 1975). 

2.1.1

Resuspension factors are the ratio of the radionuclide airborne concentration per unit air volume 

divided by the surface concentration per unit area and are 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 2-1 (from Sehmel 1980). 

Resuspension Factor

Figure 2-1. 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). 
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The 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). Figure 2-2 below (Beyeler et al. 1999) 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 2-3). Note that 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 (Beyeler et al. 1999). A typical value used is 10% (Beyeler et al. 

1999). 

Figure 2-2. Resuspension factors measured under various conditions (Beyeler et al. 1999, 

Figure 5-11). 

Additional analysis on resuspension was published by the NRC in 2002 with the publication of 

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’s contention that, 

for application at decommissioned facilities (which was the intended purpose of the analysis), values 

from fresh deposits would be overly conservative. Additionally, data from additional studies were

included in the 2002 analysis. The proposed value (since this NUREG is still a draft document)

selected was expressed as both a normal and lognormal distribution (Figure 2-4) with a 90th

percentile value of 9.6 × 10-7 m-1 (lognormal fit).

2.1.2

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 in 

order 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 

Resuspension Rate
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Figure 2-3. Cumulative probability function for RF (release fraction) (Beyeler et al. 1999, Figure 5-7). 

Figure 2-4. Parameters for normal and lognormal ‘maximum likelihood’ models of RF data (Abu-Eid 

et a. 2002, Table 5). 

(Healy 1971). Healy cited studies that showed that the resuspension rate can exceed 1 × 10-3 h-1 for 

particles on non-carpeted surfaces (Healy 1971). Based on a review of resuspension data and 

assumptions regarding the amounts of time spent at different activities indoors, Healy estimated a 

time-weighted-average resuspension rate of 5 × 10 -4 h-1 for a house (Table 2-1). The corresponding 

air activity (x) is determined by the expression (Healy 1971): 

x = [(resuspension rate)(surface contamination level)(area contaminated)]/[(volume)(air changes/hr)]

Resuspension rates are used in the RESRAD-BUILD code to incorporate the contribution to airborne 

radioactivity from the resuspension of freshly deposited material (Figure 2-5, below).
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Table 2-1. Derivation of weighted indoor resuspension rate (Healy 1971, p. 32). 

Activity (description) Duration Resuspension rate

Vigorous activity in area. Includes cleaning or children at active play 

or running

1 hr/day 5 × 10-3 h-1

Active. Normal traffic in the room. Children at normal play 5 hr/day 1 × 10-3 h-1

Moderate. Low traffic with reading, watching TV and occasional 

movement

6 hr/day 1 × 10-4 h-1

Quiet. No movement. Room unoccupied 12 hr/day 1 × 10-6 h-1

Average Factor 5 × 10-4 h-1

Figure 2-5. Inhalation pathway in DandD and RESRAD-BUILD codes (Biwer et al. 2002, Figure 2-2). 

2.1.3

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. suggest 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).

Mass Loading
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2.2 NUREG-1400 METHODOLOGY

NUREG-1400 (Hickey et al. 1993) provides a method for calculation of potential airborne emissions 

based on the total amount of radioactive material processed or stored. The methodology was 

developed for the determination of potential radionuclide intake and determination of the need to 

perform air sampling. The amount of material that may be inhaled by a worker (I) is determined as:

Potential Intake = Q × 10-6 × R × C × D 

Where, 

Q = quantity of material handled

R = release fraction (0.01 for nonvolatile powders; 0.001 for solids)

C = confinement factor (0.01 for glovebox; 0.1 for fumehood; 1.0 for open work area)

D = dispersability factor (10 if cutting, grinding, and heating are performed)

10-6 represents the fraction of the material in process that is available for intake.

2.3 COMPUTER MODELS (RESRAD-BUILD; DANDD)

Two common computer models that are available 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). The RESRAD-BUILD code was developed for the Department of Energy (by 

Argonne National Laboratory) while the DandD code was developed for the Nuclear Regulatory 

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

decommissioning or to demonstrate compliance with dose-based criteria. Table 2-2 below is a 

summary of the capabilities of both of these codes. Although both codes are suitable for modeling 

exposure from residual contamination in indoor environments, the DandD code is a much more 

simplistic code (Figure 2-5) with fewer input parameters and assumptions and is likely more 

appropriate in situations where the requisite parameters for the RESRAD-BUILD code are either not 

available or highly variable (such as airflow rates and building dimensions).

2.4 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). Deposition velocities can also 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 program 

documents [ORAUT-OTIB-0004 (ORAUT 2006), Battelle-TBD-6000 (Battelle Team 2006a), and 

Battelle-TBD-6001 (Battelle Team 2006b)] to estimate the surface contamination resulting from 

airborne radioactive contamination. Alternatively, 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 the 

RESRAD-BUILD code (Biwer et al. 2002).

2.5 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” 
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Table 2-2. Evaluation of the technical basis for the building occupancy scenario using the RESRADBUILD and DandD codes (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 months or longer

• In secular equilibrium with progeny 

of half-lives less than six months

• 249 primary radionuclides 

• Half-lives 10 minutes or longer

• In secular equilibrium with 

progeny if half-lives are (1) less 

than 9 hours and (2) less than 

one tenth the listed parent halflife

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 FGR 12 

geometry) with respect to the 

source

RESRAD-BUILD has 

an external exposure 

model to handle any 

source-receptor 

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 

site-specific 

situations.

Time dependence • 10 time steps in a single run

• Calculates average time integrated 

dose over the exposure duration

• Radionuclide concentration 

changes with radioactive ingrowth, 

decay, and mechanical erosion

• A single time step

• Calculates average timeintegrated dose over one-year 

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 RESRADBUILD there is 

uniform depletion of 

source over the 

source lifetime.

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
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 12 of 26

Component RESRAD-BUILD DandD Remarks

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

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 reported an expression (Linsley 1978): 

K(t in days) = [10-6 exp(-0.01t) + 10-9]m-1 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 recommends a decay constant value of 0.1 d-1 which represents the effects of source 

depletion with time (Healy 1971). While no experimental studies were identified for indoor facilities, 

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

depletion of easily suspended contaminants.

2.6 SOURCE TERM DEPLETION 

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

T1⁄2 = KnR

0.693A hr

where

A = is the contaminated area

K = resuspension factor

n = ventilation rate (airchanges per unit time)

R = room volume, rearranging and realizing that R = A * H (height of room)

λ = KnH, hr-1 

Expressed in units of day-1 this becomes

λ = 24KnH, day-1 

Accordingly, the assumption of a 1% per day source depletion factor (consistent with research 

summarized in Section 2.5, above) would be achieved solely from removal by the ventilation system 

for resuspension factors of 8x10-5 m-1 (assuming a nominal ventilation rate of 1 air change per hour 

and a room height of 5 meters). Increases in either of these factors would result in a higher depletion 

rate. This application assumes that depletion through removal in the ventilation system is the only 

source of reduction, which is known not to be the case.

NUREG-1720 presents an analysis of experimental data from a uranium processing facility. 

Measurements were collected over a weekend during which uranium operations were not being 

conducted. Analysis of this data to determine the rate at which the airborne activity was being 
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 13 of 26

depleted yielded an average time constant of 0.0378 hr-1 and a minimum value of 0.00946 hr-1(AbuEid et al. 2002). 

2.7 INGESTION CONSIDERATIONS

In the case where inhalation intakes are calculated from air concentrations, ingestion intakes are also 

to be considered. The ingestion rate, in terms of 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 days per year. The same f1-value as used for inhalation dose 

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

3.0

3.1 INTERNAL DOSE CALCULATIONS

GUIDANCE

3.1.1

When bioassay data collected during the residual period may be impacted by continued site 

operations (non-AEC/DOE) it is necessary to account for the fact that only a portion of the exposure 

during the residual contamination 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. A 

source term depletion factor of 1% of the surface activity per day based on Section 2.6 is suggested 

for this purpose. Use of this 1% depletion factor is favorable to claimants, based on the depletion 

behavior reported above; however, to account for the observed steady-state resuspension conditions 

(Linsley 1978), this factor is held constant after 3 years. Calculated depletion factors based on a 1% 

per day depletion rate are presented in Table 3-1, below.

Consideration of Bioassay Data 

Table 3-1. Adjustment factors to 

account for depletion of source term 

during the residual contamination 

period.

Year Factor

1 1

2 0.03

3 on 0.0007

3.1.2

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

Battelle Team (2006a,b), and are summarized in Table 3-2 below. 

Maximizing Conditions

3.1.3

Estimates of internal dose from source term data can be performed using the NUREG-1400 (Hickey 

et al. 1993) methodology (Section 2.2) or by applying a resuspension rate (Section 2.1.2). 

Source Term

Application of NUREG-1400 methodology requires that the total annual material handled be used in 

the calculation. A specific evaluation would have to be performed based on knowledge of the facility 

and processes in order to determine appropriate release fraction and dispensability factors. Without 
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Table 3-2. Efficiency methods for AWE residual radioactivity period dose reconstruction. 

Document Applicability Summary

ORAUT 2006 AWE facilities, subject to applicability 

matrix in attachment B.

Add one year of additional exposure based 

on operational exposure matrix.

Battelle Team 2006a AWE uranium metal facilities. Inhalation–413 pCi/d (uranium)

Ingestion–Tabulated value (Battelle Team 

2006a, Table 7.9).

Battelle Team 2006b AWE uranium refineries. Inhalation–413 pCi/d (uranium)

Ingestion–Tabulated value (Battelle Team 

2006a, Table 8.30).

additional information, favorable to claimant values of 0.01 for release fraction and 10 for 

dispersability should be used.

Application of the resuspension rate methodology requires knowledge of the volume of area into 

which the material is released and the associated ventilation rate. Selection of an appropriate release 

rate could be based on knowledge of the facility characteristics, otherwise a favorable to claimant

value of 5 × 10-3 hr-1 could be used (Healy 1971).

3.1.4

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

factors (Section 2.1.1) for indoor calculation and mass loading factors (Section 2.3) for outdoor areas 

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

Surface Activity

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

level present 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 Team 2006a,b)]. Using estimated airborne radioactivity levels, surface activity can 

be estimated using a deposition velocity and duration. This approach would allow the estimation of 

airborne activity due to residual surface activity which has been deposited during operations. Values 

of 0.00075 m-1 and 1 year would be favorable to claimant estimates of deposition velocity and 

duration, respectively.

To ensure a favorable to claimant assessment, a resuspension factor of 1x10-6 m-1 should be used to 

estimate airborne activity from surface contamination. This value is consistent with the research 

presented in Section 2.1.1, and bounding at the 95th percentile based on a probabilistic analysis 

using RESRAD-BUILD presented in Attachment A. 

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 favorable to claimant value of 100 μg/m3 should be applied.

3.1.5

Contemporary estimates of airborne radioactivity (either 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 2.5), an exponential model should be used to 

fit the operational period data and the post-operational data. In practice, the post-operational airborne 

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

Exponential Interpolation
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A(residual period) = A(operations) * e -λtwith t being the length of time between the two air 

concentration measurements (residual and operational). This equation is then solved for the factor 

λ. Calculation of intakes between the measured operational and residual period values should be 

based on integration of the equation above on an annual basis. 

If no data are available for airborne radioactivity levels during the operational period, a favorable to 

claimant value can be estimated based on applicable values based on data from Battelle Team

(2006a,b) (uranium facilities) or Attachment B (thorium facilities).

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

depletion factor of 1% per day (Section 2.6) 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 3 years (as in Section 3.1.1). 

3.1.6

Application of either the RESRAD-BUILD or DandD computer models (Section 2.3) would yield a 

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

assessment would only be as robust as the input parameters on which the calculations are based. If 

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

appropriate. The DandD code, being a more simplistic model, would require less of a detailed 

understanding of the exposure conditions and may be more appropriate for situations in which 

knowledge of facility conditions is limited.

Computer Models

4.0

Table 4-1 below presents a summary of the methods reviewed for estimation of internal exposure to 

residual radioactivity at AWE facilities

CONCLUSIONS
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Table 4-1. Summary of recommended methods. 

Data sources

Recommended methodology

Air sample Surface contamination

Source 

Operational term

Postoperational OperationalPostoperational

X X Exponential fit of operational and post operational

data.

X Calculate annual intake quantities based on a source 

term depletion factor of 1% per day (Section 2.6).

X 

Exponential fit of post operational data and estimate 

of operational airborne radioactivity based on ORAUT 

(2006), Battelle Team (2006a,b), or Attachment B 

(thorium facilities).

X x 

Conversion of surface activity to airborne 

concentrations using resuspension factor or 1x10-6 

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 1% per day (Section2.6).

x 

Conversion of post operational surface activity data to 

airborne concentrations using resuspension factor of 

1x10-6. Estimate of operational airborne radioactivity 

based on ORAUT (2006), Battelle Team (2006a,b), or 

Attachment B (thorium facilities). Exponential fit of 

two quantities.

x Estimate of potential intake using NUREG-1400 

(Hickey et al. 1993) intake fraction.

5.0

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

section of this document.

ATTRIBUTIONS AND ANNOTATIONS
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 17 of 26

REFERENCES

Cited 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]

AEC (U.S. Atomic Energy Commission, 1955, Horizons, Inc., Cleveland, Ohio, Occupational 

Exposure to Airborne Contaminants, HASL-Horizons-1, New York Operations Office, New 

York, New York, February 21. [SRDB Ref ID: 16125]

AEC (U.S. Atomic Energy Commission, 1958, Nuclear Metals, Inc., Cambridge Massachusetts,

Occupational Exposure to Radioactive Dust, HASL-49 (NMI-3), New York Operations Office, 

New York, New York, August 12. [SRDB Ref ID: 10504]

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; 

1975. [SRDB Ref ID: 16567] 

Battelle Team, 2006a, Site Profiles for Atomic Weapons Employers that Worked Uranium and 

Thorium Metals, Battelle-TBD-6000, Rev. F0, Richland, Washington, December 13. [SRDB 

Ref ID: 30671] 

Battelle Team, 2006b, Site Profiles for Atomic Weapons Employers that Refined Uranium and 

Thorium Metals, Battelle-TBD-6001, Rev. F0, Richland, Washington, December 13.

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. [SRDB Ref ID: 23558]

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.

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.

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.

Healy, J. W., 1971, Surface Contamination: Decision Levels, LA-4558-MS, Los Alamos Scientific 

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

Hickey, E. E., G. A. Stoetzel, D. G. Strom, G. R. Cicotte, C. M. Wiblin, and S. A. McGuire, 1993, Air 

Sampling in the Workplace, Final Report, NUREG-1400, U.S. Nuclear Regulatory 
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 18 of 26

Commission, Office of Nuclear Regulatory Research, Washington, D.C., September. [SRDB 

Ref ID: 20129]

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]

Klevin, P. B., and J. [illeg], 1953, Lindsay Chemical Company, Industrial Hygeine Survey, Part I, 

Occupational Exposure to Thorium Dust and Thoron, Lindsay-1, U.S. Atomic Energy 

Commission, New York Operations Office, New York, New York, January 21. [SRDB Ref ID: 

9041]

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

NRPB-R75, Harwell, Didcot, Oxon.

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 Material 

Safety and Safeguards, Washington, D.C., April. [SRDB Ref ID: 40435]

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, Office of Compensation Analysis and Support, Cincinnati, Ohio, December. [SRDB 

Ref ID: 29386]

NIOSH (National Institute for Occupational Safety and Health), 2007, Radiation Exposures Covered 

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

Compensation Program Act, OCAS-IG-003, Rev. 0, Office of Compensation Analysis and 

Support, Cincinnati, Ohio, November.

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.

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. 

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]
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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. 00 Effective Date: 03/10/2008 Page 20 of 26

ATTACHMENT A 

DERIVATION OF RESUSPENSION FACTORS USING RESRAD-BUILD-PROBABILISTIC

Page 1 of 6 

LIST OF TABLES

TABLE TITLE

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

PAGE

22

A-2 Input values............................................................................................................................22

A-3 Calculated resuspension factor.............................................................................................. 25

LIST OF FIGURES

FIGURE TITLE PAGE

A-1 Removable fraction ................................................................................................................23

A-2 Air release fraction ................................................................................................................. 23

A-3 Source lifetime .......................................................................................................................24

A-4 Air exchange rate................................................................................................................... 24

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: 

T λ H

f fC C a R b

R surf n

24 = (Yu et al. 1994, equation J.4.10-5)

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 (1/h), 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:

T λ H

ff R a R b

R

F 24 = (Yu et al. 1994, equation J.4.10-6)
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 21 of 26

ATTACHMENT A 

DERIVATION OF RESUSPENSION FACTORS USING RESRAD-BUILD-PROBABILISTIC

Page 2 of 6

Since RESRAD-BUILD probabilistic 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:

n

h n in i i n Dinh (t) FF IR C ED(t) ⋅⋅⋅⋅⋅= DCF (Yu et al. 1994, equation D.3)

where

D (t) n

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),

C (t) n

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 dudration (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 

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

analytical solution (based on equation J.4.10-6) and comparing them with the RESRAD-BUILD output 

air activity value (provided on the detailed output report). Note that the requisite parameters 

necessary to perform this comparison are only available for the deterministic RESRAD-BUILD 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 

percent. 

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, 4) air exchange rate. A deterministic value of room 

height (2.5 m) was selected to represent a reasonable, albeit favorable to claimant approximation. 

The default distributions applied (as documented in Appendix J of Yu et al. 1994), are based on a 

detailed literature review conducted by Argonne National Laboratory and are summarized in Table A1 and graphically depicted in Figures A-1 – A-4, below. Detailed analysis of these distributions are 

provided in Appendix J to Yu et al. 1994.
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 22 of 26

ATTACHMENT A 

DERIVATION OF RESUSPENSION FACTORS USING RESRAD-BUILD-PROBABILISTIC

Page 3 of 6

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

From Yu et al. 1994, Figure J.14

Air release fraction

(unitless)

Probabilistic Triangular distribution 

Minimum = 1E-6, 

Maximum = 1

Most likely = 0.07

From Yu et al. 1994, Figure J.13

Source lifetime

(d)

Probabilistic Triangular distribution

Minimum = 1,000 

Maximum = 100,000

Most likely = 10,000

From Yu et al. 1994, Figure J.15

Air exchange rate 

(1/h)

Probabilistic Truncated lognormal distribution

Mean = 0.4187

Standard deviation = 0.88

Lower quantile = 0.001

Upper quantile = 0.999

From Yu et al. 1994, Figure J.9

Height

(m)

Deterministic 2.5 Realistic, favorable to claimant

value

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

Value Type Value Comment

Source activity

(pCi/m2)

Deterministic 1000

Source area

(m2) 

Deterministic 36

Breathing rate

(m2/d)

Deterministic 28.8 Equal to 1.2 m3/h

Indoor fraction

(unitless)

Deterministic 0.23 Equal to 2000 h/y

Time fraction

(unitless)

Deterministic 1 Single room model

Exposure duration

(d)

Deterministic 365
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 23 of 26

ATTACHMENT A 

DERIVATION OF RESUSPENSION FACTORS USING RESRAD-BUILD-PROBABILISTIC

Page 4 of 6

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

Figure A-2. Air release fraction (from Yu et al. 1994, Figure J.13). 
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 24 of 26

ATTACHMENT A 

DERIVATION OF RESUSPENSION FACTORS USING RESRAD-BUILD-PROBABILISTIC

Page 5 of 6

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

Figure A-4. Air exchange rate (from Yu et al. 1994, Figure J.9)
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 25 of 26

ATTACHMENT A 

DERIVATION OF RESUSPENSION FACTORS USING RESRAD-BUILD-PROBABILISTIC

Page 6 of 6 

Results

Table A-3, below 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 4.5E-7 is derived.

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
Document No. ORAUT-OTIB-0070 Revision No. 00 Effective Date: 03/10/2008 Page 26 of 26

ATTACHMENT B

THORIUM SOURCE TERM DATA

This attachment contains a summary of general area air sample results gathered from operational air 

sampling studies conducted by the Health and Safety Laboratory (HASL). Studies conducted at 

indicated facilities were reviewed and air sample results which were deemed indicative of general 

area conditions. Breathing zone and process samples were excluded. 

Facility

Summary of general area 

airborne radioactivity data Reference

Horizons GM – 4.8 dpm/m3

GSD – 2.8 dpm/m3 

95th percentile -26 dpm/m3

AEC 1955

Nuclear Metals, 

INC

GM – 1.2 dpm/m3

GSD – 3.9 dpm/m3 

95th percentile -11 dpm/m3

AEC 1958

Lindsay GM – 41 dpm/m3

GSD – 4.0 dpm/m3 

95th percentile -411 dpm/m3

Klevin 1953