ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller I MJW Technical Services

Page 1 of 23 

DOE Review Release 03/18/2013 

Document Title:

A Method for Estimating Stable Metal Tritide 

Exposures to Tritium Ancillary Workers 

Based on Swipe Data in Rooms SW-8, SW13, SW-150 and R-108 at the Mound 

Laboratory 1968 to 1989

Document Number: ORAUT-RPRT-0057

Revision: 00

Effective Date: 03/07/2013

Type of Document: Report

Supersedes: None

Subject Expert(s): Karin A. Jessen, Samuel L. T. Chu, Robert L. Morris, Leo G. Faust, Melton H. Chew, 

Eugene W. Potter, Billy Smith

Approval: Signature on File Approval Date: 03/05/2013

Karin A. Jessen, Document Owner

Concurrence: Signature on File Concurrence Date: 03/06/2013

Daniel H. Stempfley, Objective 4 Representative

Concurrence: Vickie S. Short Signature on File for Concurrence Date: 03/06/2013

Kate Kimpan, Project Director

Approval: Signature on File Approval Date: 03/07/2013

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-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 2 of 23

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

03/07/2013 00 This report defines a dose reconstruction method for Mound workers 

who may have been incidentally exposed to stable metal tritide (SMT) 

compounds in the SW/R Tritium Complex (SRTC), but who were not 

assigned to directly handle SMTs. SMTs are type S tritium 

compounds that are insoluble in lung fluids. The method defines an 

annual intake of SMTs based on a claimant-favorable estimate of 

removable tritium surface contamination, a chronic resuspension 

factor (5 ×10-5 m-1) that modifies the surface contamination level 

resulting in an airborne radioactivity concentration, and full-time 

worker occupancy (2000 hr/yr) in the contaminated area. The 

method is applicable for the period March 6, 1980 through December 

31, 1999. March 5, 1980 is the date when SEC-00171, which covers 

every potentially-exposed tritium worker, ends. December 31, 1999 

is the date when there is confidence that the dosimetric problems 

associated with SMT exposure were adequately addressed by the 

Mound radiation safety staff. The method may also be useful for 

reconstruction of doses associated with non-presumptive cancers 

during the SEC-00171 period. Incorporates formal internal and 

NIOSH review comments. Training required: As determined by the 

Objective Manager. Initiated by Karin A. Jessen.
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 3 of 23

TABLE OF CONTENTS

SECTION TITLE PAGE

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

1.0 Executive Summary ................................................................................................................. 6

2.0 Introduction .............................................................................................................................. 6

3.0 Workplace Description ............................................................................................................. 7

4.0 Survey Data and Contamination Levels ................................................................................... 9

4.1 Survey Data.................................................................................................................. 9

4.2 Data Gaps .................................................................................................................... 9

4.3 Fitting Contamination Data to Lognormal Distributions and Establishing 

a Favorable Estimate of Contamination Levels........................................................... 12

4.4 Conversion of Survey Data Into Units of Activity......................................................... 15

5.0 Resuspention Factor.............................................................................................................. 17

6.0 Breathing Rate, Occupancy Factor and Particle Size ............................................................. 17

6.1 Breathing Rate ........................................................................................................... 17

6.2 Occupancy Factor ...................................................................................................... 18

6.3 Particle Size ............................................................................................................... 18

7.0 Calcuation of Annual Intake ................................................................................................... 18

7.1 Calculation of Annual Intake ....................................................................................... 18

7.2 Tabulation of Annual Intake ........................................................................................ 18

8.0 Calculation of Organ Dose ..................................................................................................... 19

9.0 Intake During the SEC-00171 Period and After 1989 ............................................................. 19

9.1 Intake Before March 6,1980, the Sec-000171 Period ................................................. 19

9.2 Intake After 1989 ........................................................................................................ 19

10.0 Guidance to Dose Reconstructors.......................................................................................... 20

References ........................................................................................................................................ 21

LIST OF TABLES

TABLE TITLE PAGE

7-1 Annual intakes in μCi ............................................................................................................. 18
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 4 of 23

LIST OF FIGURES

FIGURE TITLE PAGE

1 SW/R Complex layout – first floor.............................................................................................8

2 Typical contamination swipe locations in Room SW-150........................................................ 10

3 Typical contamination swipe locations in Room SW-13.......................................................... 11

4 Typical contamination swipe locations in Room R-108........................................................... 11

5 Typical contamination swipe locations in Room SW-8............................................................ 12

6 Typical high, low, and average swipe values reported on the health 

physics trend sheets ..............................................................................................................13

7 Available swipe sample populations....................................................................................... 14

8 Swipes and average worker tritium dose by period for Room R-108, 1983 

to 1989...................................................................................................................................14

9 Swipes and average worker tritium dose by period for Room SW-8, 1980 

to 1989...................................................................................................................................15

10 Estimate of swipe sample counts in four rooms at Mound...................................................... 16

11 Calibration of PC-5 based on paired LSC counts ................................................................... 17
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 5 of 23

ACRONYMS AND ABBREVIATIONS

ABRWH Advisory Board on Radiation and Worker Health

AMAD activity median aerodynamic diameter

cm centimeter

cpm counts per minute

DCAS Division of Compensation Analysis and Support

DCF dose conversion factor

DE dose equivalent

DOE U.S. Department of Energy

dpm disintegrations per minute

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

GM geometric mean

GSD geometric standard deviation

hr hour

IMBA Integrated Modules for Bioassay Analysis

LN(TH) trachea, bronchi, bronchioles, alveolar ducts, and sacs

LS liquid scintillation

m meter

MAE minimum absolute error

NIOSH National Institute for Occupational Safety and Health

NRC Nuclear Regulatory Commission

ORAU Oak Ridge Associated Universities

ORAUT Oak Ridge Associated Universities Team

R Research

RF resuspension factor

SEC Special Exposure Cohort

SMT stable metal tritide

SRDB Ref ID Site Research Database Reference Identification number

SRTC SW/R Tritium Complex

SW Semi-Works

WG Working Group

yr year

μCi microcurie

μm micrometer
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 6 of 23

1.0 EXECUTIVE SUMMARY

The report defines a dose reconstruction method for Mound workers who may have been incidentally 

exposed to stable metal tritide (SMT) compounds in the SW/R Tritium Complex (SRTC), but who were 

not assigned to directly handle SMTs. SMTs are type S tritium compounds that are insoluble in lung 

fluids. The method defines an annual intake of SMTs based on a claimant-favorable estimate of 

removable tritium surface contamination, a chronic resuspension factor (5 ×10-5 m-1

) that modifies the 

surface contamination level resulting in an airborne radioactivity concentration, and full-time worker 

occupancy (2000 hr/yr) in the contaminated area.

The method is applicable for the period March 6, 1980 through December 31, 1999. March 5, 1980 is 

the date when SEC-00171, which covers every potentially-exposed tritium worker, ends. December 

31, 1999 is the date when there is confidence that the dosimetric problems associated with SMT 

exposure were adequately addressed by the Mound radiation safety staff. The method may also be 

useful for reconstruction of doses associated with non-presumptive cancers during the SEC-00171 

period.

The estimate of removable tritium surface contamination is based on analysis of more than 60,000

tritium swipe results taken in Rooms SW-150, SW-13, R-108 and SW-8. In some periods all of the 

surface contamination data for a period of time and specific location are available. In those cases the 

full set of data are fit to lognormal distributions and the 95th percentile values are used. For other

periods only “high, low, and average” trend data are available. In those cases the geometric mean 

(GM) of the high data are used. For some years the results must be combined on a time-weighted 

basis, with preference given to 95th percentile values when they are available.

The following recommendations are provided to dose reconstructors:

1. For workers who are known to have worked directly with SMT (a list identifying SMT workers 

exists):

• Calculate SMT dose to the organ of interest assuming all of the tritium measured in urine 

bioassay samples is the result of SMT intakes. 

• Calculate dose to the organ of interest assuming the tritium excreted in urine is entirely 

associated with exposure to soluble tritium compounds, such as tritiated water.

2. Select the result that provides the highest dose to the organ of interest. 

3. For all other workers who were monitored for tritium:

• Calculate dose to the organ of interest assuming the tritium excreted in urine is entirely 

associated with exposure to soluble tritium compounds, such as tritiated water.

• Calculate SMT dose to the organ of interest using the method specified in this report. 

• Add both quantities to determine the dose to the organ of interest.

2.0 INTRODUCTION

Most of the tritium exposure at Mound was associated with tritiated water which is soluble in biological 

fluids, is quickly excreted, and is readily measured using urine bioassay. This kind of tritium exposure 

is amenable to dose reconstruction using ordinary methods (ORAUT 2007). In contrast, some metal 

tritide compounds are insoluble and are retained in the lung and other respiratory tissues for long 
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 7 of 23

times, potentially causing high doses to the respiratory tract and much small doses to all other organs 

or tissues. Consequently a different approach to dose reconstruction is required in situations where 

exposure to insoluble metal tritides may have occurred. These insoluble metal tritide compounds are 

often called “stable metal tritides” (SMTs). 

This report documents a method for SMT dose reconstruction that may be used at Mound. The 

method requires knowledge of the tritium contamination levels present in the work place and includes

assumptions about a chronic resuspension of workplace contamination, occupancy times in the 

contaminated workplace, and breathing rate of the worker. 

By the late 1990s D&D was underway at Mound and the problems associated with dosimetry of SMTs 

were recognized and adequately addressed. The Mound Internal Dosimetry TBD that first addressed 

SMTs was published in January 2000 (BWXT 2000). Consequently this dose reconstruction method 

is not necessary after December 31, 1999. 

SEC-00171 (HSS 2010) has been approved for all Mound workers who had a tritium bioassay 

between March 1, 1959 and March 5, 1980. Tritium workers were identified as being coincident with 

workers who may have been exposed to elevated and unmonitored levels of occupationally enhanced 

radon, which was the basis for the SEC. In effect everyone who could have been exposed to SMT 

prior to March 6, 1980 is already in an SEC Class. 

The dose reconstruction method described in this report is intended for use as a “best estimate” 

method for SMT exposures for workers who did not directly handle SMTs. This guidance is applicable 

for exposures that may have occurred after March 5, 1980 and before 2000. It may also be useful for 

dose reconstruction for non-presumptive cancers at earlier dates. 

Guidance for dose reconstruction for the specifically identified people who directly handled SMT is 

also provided. 

Although this report is applicable only at the Mound site, the approach defined in this report may be 

applied at any site where SMT exposure may have occurred if sufficient contamination survey data 

are available.

3.0 WORKPLACE DESCRIPTION

Tritium research, development, analytical recovery, enrichment, and surveillance activities occurred in 

the SW/R Tritium Complex (SRTC) on the Mound Laboratory site. The SW/R Tritium Complex 

consisted of the Semi-Works (SW) Building and two rows of rooms in the adjacent Research (R) 

Building that were converted to tritium operations. Figure 1 shows the floor plan layouts of the SRTC. 

SRTC tritium operations started in these rooms in the 1960s and continued beyond the 1980s.

The focus of this report is the following four rooms in the SRTC:

• SW-150, which housed the gas synthesis, high pressure gas loading, pinch weld, gas 

tungsten arc welding, and component functional testing systems.

• SW-13, which housed the gas synthesis system, the tritiated water synthesis and sampling 

system, and the metallurgical analysis processes.

• R-108, which housed and tritium recovery operations that included solid tritiated metal 

compounds, gas recovery, and purification from other tritium-handling processes.
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• SW-8, which housed the effluent removal system and was involved in tritium enrichment, 

recovery process technology, and the processing and containment of tritium-contaminated 

scrap from Mound activities as well as scrap generated at other DOE sites.

 

Figure 1. SW/R Complex layout – first floor (SRDB Ref ID 26833).

SW-150

SW-13

SW-8

R-108
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 9 of 23

Mound had a comprehensive tritium urinalysis program. Workers who entered these rooms 

participated in this program. 

The identities of the small number of primary SMT workers who were involved with the direct handling 

and processing of SMTs are known (Chew et al 2012). Urine bioassay results for these specifically 

identified workers should be interpreted as though they were entirely associated with exposure to 

SMT if the organ of interest is in the respiratory tract. Digestive tract organs and tissues should also 

be evaluated as it is possible that the dose to these organs may be larger if the exposure is evaluated 

as an insoluble form as opposed to a soluble form of tritium.

Unlike the primary SMT workers, the only plausible mechanism for SMT intake for support and 

ancillary workers was via resuspended removable surface contamination. Under this circumstance, 

the urinalysis program could fail to detect SMT intakes with adequate sensitivity. 

4.0 SURVEY DATA AND CONTAMINATION LEVELS

4.1 SURVEY DATA

The routine contamination swipe data used in this report were obtained from a set of Building 

Contamination Surveys (Wipe Samples) Reports for the R and SW Buildings. More than 10,900 

SRDB documents and more than 220,000 pages were reviewed. Twenty-nine (29) of those reports 

contained swipe data reported on a routine basis for Rooms SW-150, SW-13, R-108, and SW-8 for 

the period between 1968 and 1989 (Caldwell 1991). Additional citation information for the source 

documents is in the Reference section identified as author “Unk.”. Typical locations in the rooms 

where swipe samples were taken are shown in Figure 2, Figure 3, Figure 4 and Figure 5. 

In general, when only the high, low and average swipe values were reported, as shown in Figure 6, 

the high value, each of which is an independent data point, was used as discussed in Section 4.3. 

Figure 7 shows the yearly swipe sample populations of the four rooms in the 22-year period. A total 

of 60,264 swipe data values were used for all four rooms. 

4.2 DATA GAPS

Figure 7 shows swipe sample data availability for the rooms during the operational period from 1968 

to 1989. Gaps exist in the swipe data. The gap periods could be an entire year or could be several 

months within a given year. This raises the question of what work or incident (if any) had occurred 

during the data gap periods that could cause anomalies of the trending on either side of the gap.

The developmental and production work with the SMTs occurred primarily in SW-150 and SW-13 in 

the SW/R Tritium Complex. This work was done throughout the period from 1968 through 1989 

(SRDB Ref ID 107797). The developmental and production work was well defined and would not 

deviate from the functionality of the equipment housed in the rooms. Incidents that cause a SMT 

release are reportable and dose assessments would have been performed for the personnel that were 

exposed. For these rooms, the swipe results on either side of the gap periods can be used to 

extrapolate data in the gap periods.

The tritium scrap recovery work in R-108 was the primary work during the intermittent gap periods 

beginning in the 1980s. The recovery of SMT contaminated scraps occurred in 1984 (SRDB Ref IDs 

107797, 116978 and 116979). SW-8, which housed the effluent removal system and was involved in 

the processing and containment of tritium-contaminated scrap from Mound activities as well as scrap 

generated at other DOE sites. These rooms are susceptible to “off-spec” scrap materials that could 

have impacted the contamination level within the data gap periods.
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 10 of 23

Figure 2. Typical contamination swipe locations in Room SW-150.

The trending of tritium doses to workers as determined through urine analyses can serve as an 

indicator of unspecified high activity operations in any given time period. Figure 8 shows the 

relationship between the swipes and the average worker tritium dose, by period, for Room 108 from 

1983 to 1989. Figure 9 shows the relationship between the swipes and average worker tritium dose, 

by period, for Room SW-8 for years 1980 to 1989. The average doses were the average dose for the 
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 11 of 23

Figure 3. Typical contamination swipe locations in Room SW-13.

Figure 4. Typical contamination swipe locations in Room R-108.
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Figure 5. Typical contamination swipe locations in Room SW-8.

top 50% of annual doses obtained from the HP_TRITIUM Table in the MESH database (Chew et al 

2012). The dose value trending is overlaid onto the data gap periods in both Figures.

Both of these graphs indicate that the doses were not trending upward as a result of unusual high 

activity during operations or scrap recovery that could result in increased uptakes during the gap 

periods. This supports the position that the swipe results on either side of the gap periods can be 

used to extrapolate data in the gap periods for R-108 and SW-8.

4.3 FITTING CONTAMINATION DATA TO LOGNORMAL DISTRIBUTIONS AND 

ESTABLISHING A FAVORABLE ESTIMATE OF CONTAMINATION LEVELS

For some periods of time the entire contamination swipe data set measured for a particular room is 

available. In other periods only “high, low and average” trend data (see Figure 6) are available. And 

for some periods no swipe data are available as discussed in Section 4.1. When full data sets and 

trend data are available for the same period, full data sets are preferred. 

When all measured swipe values for a period are available these data are fit to a lognormal 

distribution to define the 95th-percentile contamination levels for that period of time, using the 

following approach.
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 13 of 23

Figure 6. Typical high, low, and average swipe values reported on the health

physics trend sheets.

The 95th-percentile contamination values are developed by: (1) plotting the “z scores” of the data on 

the x axis and the natural logs of the data on the y axis; and (2) using the plotted data to determine a 

linear equation and the associated fit parameter, R2 (ORAUT 2006). The linear equation is in the form 

of Equation 1:

(1)

Where:

y = natural log of the data

m = slope of the line

x = z-score

b = Y axis intercept

y mx b = +
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 14 of 23

Figure 7. Available swipe sample populations (Chu 2013).

Figure 8. Swipes and average worker tritium dose by period for Room R-108, 1983 to

1989 (Chew et al 2012). 

10

100

1000

10000

1968196919701971197219731974197519761977197819791980198119821983198419851986198719881989

Swipe Data Population

SW-150

SW-13

SW-8

R-108

0

1

2

3

4

5

6

7

0

50

100

150

200

250

300

350

400

Jan-83

May-83

Sep-83

Jan-84

May-84

Sep-84

Jan-85

May-85

Sep-85

Jan-86

May-86

Sep-86

Jan-87

May-87

Sep-87

Jan-88

May-88

Sep-88

Jan-89

May-89

Sep-89

Dose (mrem)

Number of Swipes

Swipes Average dose for Top 50% (mrem)
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 15 of 23

Figure 9. Swipes and average worker tritium dose by period for Room SW-8, 1980 to 

1989 (Chew et al 2013).

For a lognormal distribution, the geometric mean (GM), which is also the 50th percentile, is equal eb; 

the geometric standard deviation (GSD) is equal to em; and the 95th percentile is equal to GM ∗

GSD1.645.

When only trend data are available, a reasonable assumption of contamination level for that period is 

obtained by calculating the GM value of the “high” values reported in the trend data, as described 

above. For years in which both trend data and 95th percentile data must be combined, this is done by 

time-weighted averaging of the values.

Figure 10 shows the resulting “high estimate” swipe contamination activity levels values for the rooms 

that were used to calculate the airborne contamination. Depending on the availability of data, Figure 

10 represents 95th percentile of swipe data, or the GM of high trend data, or the higher of the two 

when a combination of the two are used.

4.4 Conversion of Survey Data Into Units of Activity

Nuclear Measurements Corporation PC-5 windowless gas flow proportional counters were generally 

used to count tritium contamination control swipes at Mound prior to August 1993. The PC-5 is a 

“gross beta” counter with variable beta particle detection efficiency that is proportional to the energy of 

the beta emission. High energy beta emitters, such as strontium-90, are typically counted with greater 

than 50% efficiency and the efficiency is reduced as the energy of the beta emissions decreases. The

PC-5 used at Mound exhibited some low, but undefined, counting efficiency for tritium beta particles. 

Consequently, the PC-5 data are reported in counts per minute (cpm). In order for a PC-5 counter 

result to be quantitative and be reported in units of disintegrations per minute (dpm), a calibration 

factor must be determined.

By 1990, the Packard “Tricarb” liquid scintillation (LS) counter was introduced at Mound for 

quantitative measurement of tritium on contamination control swipes. For tritium compounds, (e.g., 

0

1

2

3

4

5

6

7

0

100

200

300

400

500

600

700

Jan-80

Jul-80

Jan-81

Jul-81

Jan-82

Jul-82

Jan-83

Jul-83

Jan-84

Jul-84

Jan-85

Jul-85

Jan-86

Jul-86

Jan-87

Jul-87

Jan-88

Jul-88

Jan-89

Dose (mrem)

Number of Swipes

Swipes Average dose for Top 50% (mrem)
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 16 of 23

Figure 10. Estimate (i.e. 95th percentile of all data or GM of “high” trend data or the higher of the two 

for combined data sets) of swipe sample counts in four rooms at Mound (Chu and Potter 2013).

tritiated water) that completely dissolve in the counting cocktail, LS systems are able to provide 

quantitative results – the “actual activity” because the factors that affect counting efficiency are 

measured and compensated using the transformed spectral index of the external standard quench 

parameter called tSIE.

Some SMTs are insoluble so the assumption of complete solubility is not valid. The energy from beta 

rays originating inside a SMT particle can be absorbed inside the particle before reaching the particle 

surface where it becomes available for measurement, or for delivery of dose to the surrounding tissue. 

For low energy beta rays (average 5.7 keV) emitted during the decay of tritium, self-absorption can

approach 100% when the particles are large (> 10 μm) because only the energy from betas emitted 

from the particle surface are available for measurement.

The problem of SMT activity quantization has been addressed authoritatively in DOE-HDBK-1129-

2008 Appendix E (DOE 2008). The term “observed activity” is introduced for radiation protection and 

dosimetry purposes. Observed activity is the activity that is detected by the analytical method. 

Therefore the LS counter data in dpm reports the observed activity of a contamination control swipe. 

DOE-HDBK-1129-2008 Appendix E demonstrates that individual dose calculations can be made 

using observed activity data without the need to determine actual activity.

Tritium swipe counting records are available documenting the results of swipes counted on both an 

LS counter and on a PC-5 system (SRDB Ref IDs: 81787, pdf pp. 8-247; 81788, pdf pp. 2-628; 

81907, pdf pp. 425-700; 81908, pdf pp. 58-62; 81909, pdf pp. 2-692). A sample of 356 of these data 

pairs were transcribed for evaluation in a spreadsheet titled “Mound LSC & PC5 Comparison” (SRDB 

0

1000

2000

3000

4000

5000

6000

7000

High Swipe Data (cpm/100cm2) 

SW-150

SW-13

SW-8

R-108
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Ref IDs: 81787, pdf pp. 28-38, 44, 50, 60, 70, 80, 90, 100, 110; 81788, pdf pp. 2, 20). The PC-5 

counting efficiency value for each paired sample (discussed below) is calculated by dividing the PC-5 

count rate in cpm by the observed activity in dpm, as measured by the LS counter. The sample of 

356 pairs was reduced to 133 pairs. This was done by eliminating the 14 instances in which the PC-5 

counting efficiency was undefined, which means the LS observed activity equaled zero. Others were 

eliminated because the PC-5 efficiency was judged to be implausibly high for tritium (i.e., > 10%).

A linear regression analysis of the 133 data pairs was performed using Statgraphics Centurion XV to 

obtain the slope of the calibration model as represented in Figure 11. Recognizing that outliers could 

significantly impact the analysis the “minimum absolute error” (MAE) analysis method was used 

instead of the more common “least squares” method. The MAE method is more robust and lowers 

the impact of outliers on the regression analysis. This regression analysis reveals the slope of the line 

to be 0.054. So the PC-5 observed counting efficiency for tritium is nominally 5%. The counting 

efficiency factor is assumed to be accurate to one significant figure.

 Figure 11. Calibration of PC-5 based on paired LSC counts.

5.0 RESUSPENTION FACTOR

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

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

ORAUT-OTIB-0070, Rev. 01, Dose Reconstruction During Residual Radioactivity Periods at Atomic 

Weapons Employer Facilities (ORAUT 2012) includes a summary of literature reviews pertaining to 

RF. The U.S. Nuclear Regulatory Commission (NRC) literature review is given emphasis in OTIB0070. The median RF value developed in that review, 5 ×10-5 m-1

, is used in this dose reconstruction 

method. The resuspension factor is assumed to be accurate to one significant figure.

6.0 BREATHING RATE, OCCUPANCY FACTOR AND PARTICLE SIZE

6.1 BREATHING RATE

The standard ICRP 66 (ICRP 1994a) occupational breathing rate,1.2 m3

/hr, is assumed in this dose 

reconstruction method.
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6.2 OCCUPANCY FACTOR

Full time occupancy, 2000 h per year, is assumed for this dose reconstruction method. This value 

may be proportionally adjusted to account for partial year exposures. 

6.3 PARTICLE SIZE

The standard particle size distribution, 5-μm AMAD, is assumed for this dose reconstruction method.

7.0 CALCUATION OF ANNUAL INTAKE 

7.1 CALCULATION OF ANNUAL INTAKE 

Intake rate is calculated as shown in Equation 2:

(2)

Where:

I = SMT intake quantity (μCi)

CPC-5 = Contamination swipe data as counted by a PC-5 proportional counter (cpm/100 

cm2

).

EffPC-5 = Counter efficiency (cpm/dpm)

CF = Conversion Factor of 4.505 × 10-7 μCi/dpm

100 = Constant that converts 100 cm2 to m2 

RF = Resuspension Factor (m-1) 

Br = Worker’s breathing rate of 1.2 m3

/hr (ICRP 1994a)

T = Exposure time of 2,000 working hr/yr.

7.2 TABULATION OF ANNUAL INTAKE 

The intake rate of SMT for each year, 1969 through 1989, is shown in Table 7-1 to one significant 

figure. The data and calculations used to produce this table are available in a spreadsheet (Chu and 

Potter 2013). For years 1990 through 1999, data for 1990 are assumed.

Table 7-1. Annual intakes in μCi. 

Year

Room SW 150

(μCi/year)

Room SW 13

(μCi/year)

Room R 108

(μCi/year)

Room SW 8

(μCi/year)

1969 3E-01 NA NA 3E+00

1970 NA NA NA NA

1971 NA NA NA NA

1972a 1E-01 NA NA 9E-02

1973 NA NA NA NA

1974 NA 2E-01 NA NA

1975a 1E-01 2E-01 NA 7E-01

1976 2E-01 6E-02 NA 2E-01

1977 2E-01 1E-01 NA 1E-01

1978 1E-01 8E-02 NA 1E-01

1979 4E-02 3E-02 NA 1E-01

1980 2E-02 3E-02 NA 1E-01

1981 2E-02 4E-02 NA 8E-02
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 19 of 23

Year

Room SW 150

(μCi/year)

Room SW 13

(μCi/year)

Room R 108

(μCi/year)

Room SW 8

(μCi/year)

1982 6E-02 8E-02 NA 1E-01

1983 8E-02 1E-01 4E-02 4E-05

1984 1E-01 1E-01 3E-02 8E-02

1985 2E-01 2E-01 6E-02 9E-02

1986 1E-01 1E-01 7E-02 1E-01

1987 7E-02 1E-01 8E-02 1E-01

1988 7E-02 1E-01 1E-01 2E-01

1989 5E-02 1E-01 8E-02 7E-02

1990–1999 5E-02 1E-01 8E-02 7E-02

a. Data for SW-150 are very limited in 1972 and 1975; and for SW-8 in 1975

8.0 CALCULATION OF ORGAN DOSE

The NIOSH approach for calculating SMT intakes and doses from urine bioassay data is provided in 

ORAUT-OTIB-0066 (ORAUT 2007). ORAUT-OTIB-0066 implements the ICRP Publication 71 

recommendations for SMT aerosols. In this instance the SMT intakes are calculated based on air 

concentrations rather than urine bioassay, so the modifications to the urine bioassay model discussed 

in ORAUT-OTIB-0066 Appendix A are not necessary.

Table 7-1 lists the intake rates for the calculation of doses from SMTs for the organs of interest. Enter 

intake rates into IMBA as normal and organ doses will be calculated. 

9.0 INTAKE DURING THE SEC-00171 PERIOD AND AFTER 1989

9.1 INTAKE BEFORE MARCH 6,1980, THE SEC-000171 PERIOD

As discussed in Section 2.0, all workers who may have been exposed to SMT prior to March 6, 1980 

may also have been exposed to unmonitored radon and consequently are members of the SEC00171 class. 

Although NIOSH found that it is not possible to completely reconstruct radiation doses for the SEC00171 class, HHS stated in the July 14, 2010 designation of the class (HSS 2010) that any internal 

monitoring data that may become available for an individual claim that can be interpreted using 

existing NIOSH dose reconstruction processes or procedures will be used. 

Therefore, dose reconstructions for individuals who were monitored for tritium at the Mound Plant 

during the period from March 1, 1959 through March 5, 1980, but who do not qualify for inclusion in 

SEC-00171 class, due to having a non-presumptive cancer or due to a short employment duration,

may be performed using the annual intake data and method in this report to the extent appropriate. 

9.2 INTAKE AFTER 1989

SMT intakes after 1989, the last year when survey data were analyzed, are expected to be the same 

as the intake in 1989, because no additional SMT was introduced into the workplace until the D&D 

period began. By the late 1990s D&D was underway at Mound and the problems associated with 

dosimetry of SMTs was recognized and adequately addressed. The Mound Internal Dosimetry TBD 

that first addressed SMTs was published in 2000 (BWXT 2000).

Therefore the annual intake established for 1989 should be applied to years 1990 through 1999, and 

this method is not applicable after December 31, 1999.
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 20 of 23

10.0 GUIDANCE TO DOSE RECONSTRUCTORS

Apply the following guidance to complete SMT dose reconstruction for Mound workers monitored for 

tritium exposure at any time during the period March 6, 1980 through December 31, 1999.

1. For workers who are known to have worked directly with SMT (a list identifying SMT workers 

exists):

• Calculate SMT dose to the organ of interest assuming all of the tritium measured in urine 

bioassay samples is the result of SMT intakes. 

• Calculate dose to the organ of interest assuming the tritium excreted in urine is entirely 

associated with exposure to soluble tritium compounds, such as tritiated water.

• Select the result that provides the highest dose to the organ of interest. 

2. For all other workers who were monitored for tritium:

• Calculate dose to the organ of interest assuming the tritium excreted in urine is entirely 

associated with exposure to soluble tritium compounds, such as tritiated water.

• Calculate SMT dose to the organ of interest using the method specified in this report.

• Add both quantities to determine the dose to the organ of interest.
Document No. ORAUT-RPRT-0057 Revision No. 00 Effective Date: 03/07/2013 Page 21 of 23

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