Draft 

Advisory Board on Radiation and Worker Health

National Institute for Occupational Safety and Health

SC&A Evaluation of Feasibility and Utility of Subcontractor 

Exposure Potential Comparison 

Response Paper

Revision 0

Contract No. 75D30119C04183

Prepared by

Bob Barton, CHP

SC&A, Inc.

2200 Wilson Blvd., Suite 300

Arlington, VA 22201-3324

December 18, 2023 

DISCLAIMER

This is a working document provided by the Centers for Disease Control and Prevention (CDC) 

technical support contractor, SC&A for use in discussions with the National Institute for 

Occupational Safety and Health (NIOSH) and the Advisory Board on Radiation and Worker 

Health (ABRWH), including its Working Groups or Subcommittees. Documents produced by 

SC&A, such as memorandum, white paper, draft or working documents are not final NIOSH or 

ABRWH products or positions, unless specifically marked as such. This document prepared by 

SC&A represents its preliminary evaluation on technical issues.

NOTICE: This document has been reviewed to identify and redact any information that is 

protected by the Privacy Act 5 U.S.C. § 552a and has been cleared for distribution. 
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Table of Contents

List of Tables................................................................................................................... 2

1 Introduction and Background.................................................................................... 3

2 Records Available for Analysis ................................................................................. 3

3 Summary of Bioassay Data (1991–1997)................................................................. 5

4 Feasibility and Potential Path Forward ..................................................................... 8

5 SC&A Commentary on Utility of Proposed Comparison ......................................... 10

6 Summary Conclusions............................................................................................ 11

7 References ............................................................................................................. 12

Appendix A: ProRad Database Files Not Relevant to Potential Comparison of 

Subcontractor and Prime Contractor Exposure Potential ....................................... 13

List of Tables

Table 1. Summary of SRS ProRad data files and relevance to potential subcontractor 

comparison........................................................................................................... 4

Table 2. Overview of total bioassay samples per radionuclide per year for prime 

contractors............................................................................................................ 6

Table 3. Overview of total bioassay samples per radionuclide per year for 

subcontractors...................................................................................................... 6

Table 4. Overview of unique individuals sampled per radionuclide per year for prime 

contractors............................................................................................................ 7

Table 5. Overview of unique individuals sampled per radionuclide per year for 

subcontractors...................................................................................................... 7

Table 6. Overview of total bioassay samples per radionuclide per year for Bechtel 

employees ............................................................................................................ 8

Table 7. Overview of unique individuals sampled per radionuclide per year for Bechtel 

employees ............................................................................................................ 8

Table A1. Summary of ProRad files not relevant for subcontractor and prime contractor 

exposure analyses.............................................................................................. 13
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1 Introduction and Background

The Savannah River Site (SRS) Work Group last met on March 23, 2023. During that meeting, a 

member of the work group proposed that a quantitative comparison be made of the exposure 

potential between subcontractors and prime contractors (ABRWH, 2023, pp. 114–132). 

Specifically, a Board member summarized the proposed evaluation as follows: 

suppose you look at the bioassay data of these short-term workers where data 

does exist. And the . . . point estimate and distribution is way out of hand of what 

the overall cohort is. That tells me something. If it falls right in the middle, that 

also tells me something. [ABRWH, 2023, p. 130] 

At the conclusion of the March 2023 SRS Work Group meeting, SC&A was tasked with 

evaluating the feasibility and utility of such a comparison and reporting back to the work group. 

This report summarizes SC&A’s evaluation of feasibility and commentary on the overall utility 

of such an effort moving forward. 

Section 2 gives an overview of the available electronic database records provided by SRS for 

consideration in this feasibility and utility study. Section 3 describes in further detail those 

database files that may have merit in answering the proposed question, in particular the bioassay 

database. Section 4 presents SC&A’s perspective on the feasibility of further analysis, and 

section 5 provides additional commentary on the utility of performing such evaluations. Finally, 

section 6 summarizes the previous sections for SRS Work Group discussion. 

2 Records Available for Analysis

Subsequent to the March 2023 meeting of the SRS Work Group, the National Institute for 

Occupational Safety and Health (NIOSH) provided SC&A with a suite of data files collectively 

titled “SRS_ProRad.” SC&A found that eight of these files are salient to the proposed 

comparison of subcontractors and prime contractors; these eight files are described in table 1. 

Descriptions of the remaining files not listed in table 1 can be found in appendix A. 
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Table 1. Summary of SRS ProRad data files and relevance to potential subcontractor 

comparison

File name

# Entries 

(rows) Relevant? SC&A comments

SRS_INDIVIDUAL 165,022 Yes –

subcontractor 

identification

This database contains social security 

number (SSN), name, termination date, and 

company for each energy employee (EE). 

The “company” designation includes whether 

the EE was a subcontractor or not and 

identifies Bechtel workers who generally 

served as the prime contractor construction 

trade workers. While the termination dates 

are provided, no hire dates or other work 

duration information is provided. The listed 

termination dates span all the way from 1950 

through 2023. Finally, in many cases there is 

a “craft code” listed with the EE’s personnel 

entry.

srs_organ_dose 18,790 Yes – internal 

dose estimates

This database contains evaluated committed 

dose equivalent for individual EEs, starting in 

1945 and extending through 2022. The file 

provides each EE’s SSN and full name, 

allowing the identification of subcontractors 

and prime contractors. Only 484 of the 

18,790 entries occurred during the period of 

interest (1991–1997).

SRS_EXTERNAL_

DOSIMETRY_LEG

ACY

2,071,483 Yes – external 

dose

Contains external dosimetry (deep, shallow, 

and neutron dose) results beginning in 1973 

and extending through 2003. Area codes are 

provided beginning in 1982. The file also 

provides SSN numbers, which would allow 

the identification of subcontractors and prime 

contractors. The file does not specify the 

actual exposure period (i.e., actual wear 

period) other than indicating the badge cycle 

when it was assigned and whether it was a

visitor, temporary, monthly, or quarterly 

badge.

SRS_EXTREMITY

_DOSE_YTD_SUM

549,986 Yes – external 

dose

Contains annual extremity dose values for 

four locations on the body, starting in 1952 

and ending in 2023. While the file does not 

contain SSN numbers, it does contain a 

unique employee number and full name of 

the EE that would allow identification of 

subcontractors and prime contractors.

SRS_EXTREMITY

_DOSIMETRY_LE

GACY

101,045 Yes – external 

dose

Contains extremity shallow dose 

measurements starting in 1990 and includes 

actual body location (e.g., left ankle, right 

hand, right wrist, back, chest, etc.). The 

entries include a facility code and an SSN 

number that would allow identification of 

subcontractors and prime contractors.
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File name

# Entries 

(rows) Relevant? SC&A comments

SRS_WHOLE_BO

DY_YTD_DOSE_S

UMMARY

605,455 Yes – external 

dose

This database contains a listing of combined 

internal and external doses for EEs, starting 

in 1945 and extending to early April 2023. 

The database does contain a unique 

employee ID number and full name that 

would allow for delineation of subcontractors 

and prime contractors. However, internal 

doses are not reported until 2003, though 

over 115,000 annual external dose records 

are available for 1991–1997.

SRS_INDV_NONT

RITIUM_LEGACY

434,062 Yes – bioassay 

results

Contains in vitro bioassay results beginning 

in 1986 and ending in 2004. The major 

radionuclide categories are plutonium, 

uranium, and fission products (i.e., Sr-90), as 

well as trivalent actinides and neptunium. 

The database contains EE SSNs and 

names, which allow the identification of 

subcontractors versus prime contractors. 

Facility codes are also often included with 

the bioassay result.

SRS_INCIDENT_D

ATA_CEDE

3,549 Yes – incident 

dose evaluation

Lists documented incidents extending from 

1945 into 2023. Of the 3,549 entries, 84 

pertain to the 1991–1997 period; only 3 of

the 84 provide an incident description. While 

not explicit, the database appears to provide 

an SSN associated with each entry. Also 

provided are a security badge number and 

the full name of the EE involved, which 

should allow identification of subcontractors 

and prime contractors.

Of the eight database files described in table 1, “SRS_INDV_NONTRITIUM_LEGACY” is 

likely the most relevant to the proposed evaluation of subcontractor and prime contractor 

records, as this would be the vehicle used in development of any subsequent co-exposure model. 

Section 3 characterizes this database to illustrate the amount of data and worker coverage 

contained in the dataset for the period of interest (1991–1997). 

3 Summary of Bioassay Data (1991–1997)

This section analyzes the main bioassay database, “SRS_INDV_NONTRITIUM_LEGACY,” to 

determine the number of samples and individual workers, by year and radionuclide type, for 

subcontractors and prime contractors. SC&A only considered nonbaseline urinalysis samples

that had a void date from 1991−1997 (or, if a void date was unavailable, the receipt date was 

used) and did not include fecal samples. Based on these criteria, SC&A identified 238,491 

bioassay samples for characterization and notes that only 601 of these samples were greater than 

zero (~0.25 percent). 

The evaluation timeframe of 1991–1997 was chosen to begin where the previous Special 

Exposure Cohort (SEC) recommendation to include a class of workers (subcontractors) for 
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whom internal dose was determined to be infeasible (i.e., through 1990) and end when 

significant corrective action was enacted by SRS. Tables 2 and 3 summarize the total number of 

bioassay samples by year and radionuclide for prime and subcontractors, respectively. The 

radionuclides monitored via bioassay include trivalent actinides (americium/curium/californium 

(Am/Cm/Cf)), neptunium, plutonium, strontium, uranium (enriched uranium/depleted 

uranium/main isotopes of uranium). It should be noted that for the tables in this section, when 

isotopic bioassay samples are reported (i.e., plutonium (Pu)-238/Pu-239 and uranium 

(U)-234/U-235/U-238), the totals and percentages are reflective of each individual isotopic 

sample due to the fact they were identical or had negligible differences. As seen in the tables, 

prime contractors generally made up 80–90 percent of the available bioassay samples.

Table 2. Overview of total bioassay samples per radionuclide per year for prime 

contractors

Radionuclide 1991 1992 1993 1994 1995 1996 1997 All years

Trivalent

actinides

625 

(90.8%)

518 

(89.0%)

303 

(87.3%)

331 

(81.3%)

849 

(80.4%)

942 

(81.9%)

1,588 

(82.2%)

5,156 

(83.7%)

Np-237 122 

(89.1%)

284 

(87.4%)

280 

(87.2%)

260 

(89.7%)

253 

(89.1%)

271 

(92.2%)

673 

(89.3%)

2,143 

(89.1%)

Pu-238, 

Pu-239

9,664 

(76.4%)

11,541 

(83.6%)

8,253 

(82.5%)

6,963 

(83.0%)

6,465 

(84.3%)

5,718 

(84.0%)

7,717 

(84.3%)

56,321 

(82.2%)

Sr-90 2,707 

(75.5%)

6,507 

(80.7%)

4,165 

(80.7%)

3,820 

(81.1%)

3,723 

(82.7%)

3,277 

(81.8%)

2,926 

(82.5%)

27,125 

(80.8%)

Enriched 

uranium

3,141 

(83.1%)

4,939 

(82.8%)

3,768 

(82.5%)

1,023 

(83.2%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 12,871 

(82.8%)

Depleted 

uranium

14 

(82.4%)

3 

(75.0%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 17 

(81.0%)

U-234, U-235, 

U-238

8 

(100.0%)

4 

(80.0%)

14 

(82.4%)

2,508 

(82.3%)

3,670 

(84.3%)

2,973 

(82.0%)

2,849 

(79.9%)

12,026 

(82.3%)

All uranium 3,179 

(83.2%)

4,956 

(82.8%)

3,810 

(82.5%)

8,547 

(82.4%)

11,010 

(84.3%)

8,919 

(82.0%)

8,547 

(79.9%)

48,968 

(82.4%)

Table 3. Overview of total bioassay samples per radionuclide per year for 

subcontractors

Radionuclide 1991 1992 1993 1994 1995 1996 1997 All years

Trivalent 

actinides

63 

(9.2%)

64 

(11.0%)

44 

(12.7%)

76 

(18.7%)

207 

(19.6%)

208 

(18.1%)

345 

(17.8%)

1,007 

(16.3%)

Np-237 15 

(10.9%)

41 

(12.6%)

41 

(12.8%)

30 

(10.3%)

31 

(10.9%)

23 

(7.8%)

81 

(10.7%)

262 

(10.9%)

Pu-238, Pu-239 2979 

(23.6%)

2265 

(16.4%)

1,754 

(17.5%)

1,427 

(17.0%)

1,207 

(15.7%)

1,090 

(16.0%)

1,435 

(15.7%)

12,157 

(17.8%)

Sr-90 880 

(24.5%)

1,554 

(19.3%)

998 

(19.3%)

890 

(18.9%)

781 

(17.3%)

728 

(18.2%)

622 

(17.5%)

6,453 

(19.2%)

Enriched 

uranium

639 

(16.9%)

1,024 

(17.2%)

799 

(17.5%)

207 

(16.8%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 2,669 

(17.2%)

Depleted 

uranium

3 

(17.6%)

1 

(25.0%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 4 

(19.0%)

U-234, U-235, 

U-238

0 (0.0%) 1 

(20.0%)

3 

(17.6%)

538 

(17.7%)

682 

(15.7%)

653 

(18.0%)

716 

(20.1%)

2,593 

(17.7%)

All uranium 642 

(16.8%)

1,028 

(17.2%)

808 

(17.5%)

1,821 

(17.6%)

2,046 

(15.7%)

1,959 

(18.0%)

2,148 

(20.1%)

10,452 

(17.6%)
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Similarly, tables 4 and 5 summarize the total individuals sampled by year and radionuclide for 

prime and subcontractors, respectively. Similar to the number of bioassay samples in total, the 

number of individual prime contractors monitored by year was generally 75 to 90 percent. 

Table 4. Overview of unique individuals sampled per radionuclide per year for prime 

contractors

Radionuclide 1991 1992 1993 1994 1995 1996 1997 All years

Trivalent 

actinides

335 

(89.3%)

184 

(86.8%)

153 

(81.0%)

187 

(82.7%)

222 

(81.9%)

327 

(81.5%)

961 

(85.0%)

515 

(90.7%)

Np-237 62 

(84.9%)

175 

(86.6%)

233 

(87.6%)

244 

(89.1%)

223 

(89.2%)

246 

(91.8%)

420 

(94.0%)

792 

(87.2%)

Pu-238, Pu-239 6,425 

(73.9%)

7,159 

(81.5%)

5,325 

(80.6%)

4,562 

(80.9%)

4,335 

(82.5%)

4,130 

(82.7%)

5,111 

(103.9%)

11,066 

(74.6%)

Sr-90 2,321 

(74.7%)

3,517 

(80.7%)

2,968 

(80.0%)

2,818 

(80.5%)

2,866 

(81.8%)

2,815 

(81.7%)

2,082 

(64.0%)

6,803 

(77.2%)

Enriched 

uranium

1,797 

(79.3%)

3,051 

(81.0%)

2,273 

(79.5%)

920 

(82.5%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 4,341 

(78.8%)

Depleted 

uranium

14 

(82.4%)

3 

(75.0%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 17 

(81.0%)

U-234, U-235,

U-238

1 

(100.0%)

3 

(75.0%)

14 

(82.4%)

1,562 

(78.9%)

1,916 

(79.8%)

1,735 

(79.1%)

1,852 

(90.5%)

2,870 

(76.4%)

All uranium 1,800 

(79.3%)

3,052 

(81.0%)

2,276 

(79.5%)

1,972 

(78.8%)

1,916 

(79.8%)

1,735 

(79.1%)

3,150 

(153.9%)

5,296 

(77.5%)

Table 5. Overview of unique individuals sampled per radionuclide per year for 

subcontractors

Radionuclide 1991 1992 1993 1994 1995 1996 1997 All years

Trivalent 

actinides

53 

(9.3%)

40 

(10.7%)

28 

(13.2%)

36 

(19.0%)

39 

(17.3%)

49 

(18.1%)

74 

(18.5%)

170 

(15.0%)

Np-237 11 

(15.1%)

27 

(13.4%)

33 

(12.4%)

30 

(10.9%)

27 

(10.8%)

22 

(8.2%)

51 

(11.4%)

127 

(14.0%)

Pu-238, Pu-239 2,273 

(26.1%)

1,620 

(18.5%)

1,279 

(19.4%)

1,079 

(19.1%)

922 

(17.5%)

864 

(17.3%)

831 

(16.9%)

3,777 

(25.5%)

Sr-90 786 

(25.3%)

842 

(19.3%)

744 

(20.0%)

681 

(19.5%)

637 

(18.2%)

630 

(18.3%)

559 

(17.2%)

2,022 

(22.9%)

Enriched 

uranium

470 

(20.7%)

717 

(19.0%)

587 

(20.5%)

195 

(17.5%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 1,171 

(21.2%)

Depleted 

uranium

3 

(17.6%)

1 

(25.0%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 4 

(19.0%)

U-234, U-235,

U-238

0 (0.0%) 1 

(25.0%)

3 

(17.6%)

418 

(21.1%)

485 

(20.2%)

458 

(20.9%)

426 

(20.8%)

892 

(23.8%)

All uranium 470 

(20.7%)

717 

(19.0%)

587 

(20.5%)

532 

(21.2%)

485 

(20.2%)

458 

(20.9%)

426 

(20.8%)

1,560 

(22.8%)

Another subgroup of workers that may be of interest for comparison are those employed by 

Bechtel Savannah River Inc. (“Bechtel”), which served as the construction branch of the prime 

contractor. The total numbers of samples and individual workers monitored via bioassay for 

Bechtel are shown in tables 6 and 7, respectively. Similar to the proportion of subcontractor 
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records, Bechtel employees were generally between 10 and 20 percent of the monitored results 

and population. 

Table 6. Overview of total bioassay samples per radionuclide per year for Bechtel 

employees

Radionuclide 1991 1992 1993 1994 1995 1996 1997 All years

Trivalent 

actinides

7 (1.0%) 0 (0.0%) 1 (0.3%) 5 (1.2%) 12 

(1.1%)

80 

(7.0%)

157 

(8.1%)

262 

(4.3%)

Np-237 22 

(16.1%)

76 

(23.4%)

58 

(18.1%)

35 

(12.1%)

12 

(4.2%)

7 (2.4%) 17 

(2.3%)

227 

(9.4%)

Pu-238, 

Pu-239

1,964 

(15.6%)

2,383 

(17.3%)

1,319 

(13.2%)

893 

(10.6%)

701 

(9.1%)

499 

(7.3%)

579 

(6.3%)

8,338 

(12.2%)

Sr-90 1,055 

(29.4%)

2,658 

(33.0%)

1,062 

(20.6%)

825 

(17.5%)

619 

(13.7%)

401 

(10.0%)

305 

(8.6%)

6,925 

(20.6%)

Enriched 

uranium

532 

(14.1%)

1,588 

(26.6%)

776 

(17.0%)

190 

(15.4%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)

Depleted 

uranium

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)

U-234, U-235,

U-238

0 (0.0%) 0 (0.0%) 2 

(11.8%)

349 

(11.5%)

486 

(11.2%)

351 

(9.7%)

362 

(10.2%)

1,550 

(10.6%)

All uranium 532 

(13.9%)

1,588 

(26.5%)

782 

(16.9%)

1,237 

(11.9%)

1,458 

(11.2%)

1,053 

(9.7%)

1,086 

(10.2%)

7,736 

(13.0%)

Table 7. Overview of unique individuals sampled per radionuclide per year for Bechtel 

employees

Radionuclide 1991 1992 1993 1994 1995 1996 1997 All years

Trivalent 

actinides

8 (1.4%) 2 (0.5%) 2 (0.9%) 3 (1.6%) 5 (2.2%) 21 

(7.7%)

36 

(9.0%)

53 

(4.7%)

Np-237 18 

(24.7%)

45 

(22.3%)

51 

(19.2%)

36 

(13.1%)

11 

(4.4%)

7 (2.6%) 14 

(3.1%)

119 

(13.1%)

Pu-238, 

Pu-239

1297 

(14.9%)

1,588 

(18.1%)

933 

(14.1%)

668 

(11.8%)

511 

(9.7%)

390 

(7.8%)

328 

(6.7%)

2,387 

(16.1%)

Sr-90 985 

(31.7%)

1,304 

(29.9%)

719 

(19.4%)

566 

(16.2%)

460 

(13.1%)

343 

(10.0%)

273 

(8.4%)

1,840 

(20.9%)

Enriched 

uranium

514 

(22.7%)

1,113 

(29.5%)

603 

(21.1%)

183 

(16.4%)

0 (0.0%) 0 (0.0%) 0 (0.0%) 1,396 

(25.3%)

Depleted 

uranium

0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%)

U-234, U-235, 

U-238

0 (0.0%) 0 (0.0%) 3 

(17.6%)

287 

(14.5%)

336 

(14.0%)

261 

(11.9%)

213 

(10.4%)

534 

(14.2%)

All uranium 514 

(22.6%)

1,113 

(29.5%)

603 

(21.1%)

391 

(15.6%)

336 

(14.0%)

261 

(11.9%)

213 

(10.4%)

1,499 

(21.9%)

4 Feasibility and Potential Path Forward

As noted in section 3, access to an electronic set of bioassay data is available for the period of 

interest (1991–1997). Drawing on past experience with similar analytical efforts, SC&A believes 

that the most relevant example is found in ORAUT-RPRT-0102, revision 00 (ORAUT, 2021; 

“RPRT-0102”), which compares the magnitude of plutonium (Pu-238 and Pu-239) bioassay 
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results for four different groups of workers at the Los Alamos National Laboratory (LANL): 

(1) Johnson Controls (JC), (2) Environmental Safety and Health (ESH), (3) Nuclear Materials 

Technology (NMT), and (4) other workers not fitting into the prior three categories.

Such a comparison is relatively simplistic because it only compares the magnitude of plutonium 

in urine (rather than a metric specific to individual workers) over several years at LANL (1996–

2001). Drawbacks to this type of analysis include: 

• Does not account for potential data dominance. 

• Does not look at more specific time periods (e.g., annual). 

For the first bullet, SC&A notes that a time-weighted one-person-one-statistic (TWOPOS) 

approach could be employed to account for situations in which individual employees may have 

submitted significantly more samples during the desired evaluation period compared to the 

majority of monitored employees over the same period. For the second bullet, SC&A 

recommends that any potential analysis be performed at yearly intervals since the primary 

question under consideration is not only whether SEC-0103 should be extended but also, if it is 

extended, what would be an appropriate cutoff point post 1990? 

In addition, the work group may want to consider expanding the analysis to other radionuclides 

described in section 3 of this report (e.g., strontium (Sr)-90, U-238, U-235, Am/Cm/Cf, and 

neptunium (Np)-237). Finally, it may be possible for at least some of these radionuclides to be 

parsed not only by year and worker type (subcontractor and prime contractor) but also by work 

area. However, this level of granularity may make reaching any conclusions based on the 

available dataset more problematic (e.g., if plutonium was higher for one group in A Area but 

lower for the same group in F Area).

SC&A recommends that, if the work group elects to proceed with such a comparison, 

NIOSH/Oak Ridge Associated Universities Team (ORAUT) may be in the best position to 

perform the analysis. NIOSH already develops co-exposure models that would contain the same 

essential steps as the comparison suggested previously in this section. During the March 2023 

work group meeting, NIOSH has already indicated that the process would be relatively easy, 

specifically:

I believe that what Dr. Lockey’s referring to would be a coexposure model. I 

would point out that we have not finalized that development yet, but we could do 

so relatively quickly -- well, I believe relatively quickly, or at least get something 

on paper. [ABRWH 2023, p. 115] 

In addition, as noted previously, the vast majority of relevant bioassay entries (i.e., greater than 

99 percent) were zero or negative, which would necessitate using multiple imputation in any sort 

of quantitative comparison. Should the work group elect to proceed with the comparison study, it 

seems the most efficient path forward in any potential analysis would be for NIOSH to use its 

established modules for calculating the TWOPOS values of the groups of interest. 
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5 SC&A Commentary on Utility of Proposed Comparison

SC&A noted during the March 2023 SRS Work Group meeting that it has reservations 

concerning the utility of such a subcontractor comparison because it may not fully illuminate the 

primary SEC issue being discussed (ABRWH, 2023, pp. 120–121, 124–125, 129). These 

reservations were also echoed by the work group chairperson (ABRWH, 2023, pp. 117–118, 

123, 128). Recent SEC discussions involving SRS recommended the addition of a class of 

workers up through 1990 based on the uncertainty around the appropriate collection and analysis 

of radiation work permit (RWP) job-specific bioassay. This uncertainty would most likely 

disproportionately affect subcontractors, whose work may have been transient and short term but 

of potentially higher exposure potential than the prime contractors who were more likely to be on 

a routine monitoring program. 

As noted in section 3, SC&A was able to separate electronic bioassay records for subcontractors 

and prime contractors. However, SC&A was not able to identify job-specific bioassay records 

within the available dataset (i.e., there is no specific designation for RWP-driven job-specific 

bioassay). Given the noted deficiencies identified in the collection of job-specific bioassays (i.e., 

only 21 percent compliance with the program, as identified in the late 1990s), along with the 

small fraction of job-specific bioassays compared to routine bioassays (NIOSH, 2020), it is 

logical to assume that any such comparison of electronic records would primarily be for those on 

a routine monitoring program. Therefore, it is SC&A’s opinion that such a comparison may not 

sufficiently inform the work group as to what the missing1 RWP-job-specific bioassays may 

have indicated as far as exposure potential. 

1 In this instance, “missing” refers to the Westinghouse Savannah River Company and U.S. Department of Energy

findings of noncompliance with the RWP-driven job-specific bioassay, not that the bioassays were 

collected/analyzed but are simply unavailable.

SC&A also notes that NIOSH compared exposure potential between subcontractors and prime 

contractors in the report, “Practical Implications of the Bootstrap Uncertainty Analyses on Coexposure Models” (NIOSH, 2021), for the period 1972–1990. That report concluded, in part: 

Subcontractor CTWs [construction trade workers] exposures were generally lower 

than prime CTWs between 1972 and 1990, however there is no practical 

difference between subcontractor CTWs and the current combined CTW model. 

[p. 7] 

NIOSH (2021) was presented to the SRS Work Group on March 23, 2021, and also to the full 

Advisory Board on Radiation and Worker Health (“Board,” ABRWH) on April 15, 2021, at 

which time the Board voted to recommend subcontractors at SRS be added as an SEC class. 
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6 Summary Conclusions

SC&A’s evaluation of the potential for a meaningful comparison of prime and subcontractors 

identified the following conclusions:

• A suite of database files was provided by SRS and contained various dosimetry 

information, including external dosimetry, internal bioassay monitoring, incident 

documentation, employee information (e.g., subcontractor or prime contractor), facility 

designations, and radiation work permit information. 

• Eight of the files contained information relevant to any potential comparison of exposure 

potential between subcontractors and prime contractors.

• The most relevant database file contained 238,491 bioassay results for both 

subcontractors and prime contractors during the period of interest (1991–1997), of which 

only ~0.25 percent of the total bioassay results had results greater than zero.

• Bioassay results measured the following radionuclides: trivalent actinides, neptunium, 

plutonium, strontium, and uranium.

• Subcontractors generally represented 0–20 percent of the population monitored via 

bioassay (i.e., prime contractors represented 80–90 percent of the population monitored 

via bioassay).

• The prime contractor construction branch (Bechtel Savannah River Inc.) also generally 

represented 10–20 percent of the population monitored via bioassay.

• SC&A believes the best potential path forward would be to calculate the TWOPOS 

values by year for the groups of interest (e.g., subcontractors, prime contractors, prime 

construction workers).

• The most efficient execution of any comparison study is likely to be performed by 

NIOSH, as the framework is already in place via standard co-exposure modeling modules 

currently used by NIOSH as well as methods for dealing with the large portion of zero or 

less-than-zero results. 

• SC&A maintains that any potential comparison may not reflect the exposure potential of 

the RWP-driven, job-specific bioassay, which had notable incompleteness (i.e., only 

21 percent compliance as found in 1997) and was the basis for the Board recommending 

the inclusion of an SEC class for subcontractors for 1972–1990.
Effective date: 12/18/2023 Revision No. 0 (Draft) Response Paper Page 12 of 14

NOTICE: This document has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.

7 References

Advisory Board on Radiation and Worker Health. (2023). Savannah River Site (SRS) meeting 

Wednesday, March 22, 2023 [Transcript of teleconference meeting]. 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2023/wgtr032223-508.pdf 

National Institute for Occupational Safety and Health. (2020). NIOSH response to SC&A 

comments on ORAUT-RPRT-0092 [Response paper]. 

https://ftp.cdc.gov/pub/FOIAREQ/182968_red-508.pdf 

National Institute for Occupational Safety and Health. (2021). Practical implications of the 

bootstrap uncertainty analyses on co-exposure models [White paper]. 

https://ftp.cdc.gov/pub/FOIAREQ/184554-508.pdf

Oak Ridge Associated Universities Team. (2019). Evaluation of bioassay data for subcontracted 

construction trade workers at the Savannah River Site [Redacted version] (ORAUT-RPRT-0092, 

rev. 00). https://www.cdc.gov/niosh/ocas/pdfs/orau/oraurpts/or-rprt-92-r0-508.pdf

Oak Ridge Associated Universities Team. (2021). Assessment of Los Alamos National 

Laboratory plutonium bioassay programs 1996 to 2001 (ORAUT-RPRT-0102, rev. 00). 

https://www.cdc.gov/niosh/ocas/pdfs/orau/oraurpts/or-rprt-102-r0-508.pdf
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Appendix A: ProRad Database Files Not Relevant to Potential 

Comparison of Subcontractor and Prime Contractor Exposure 

Potential 

Table A1. Summary of ProRad files not relevant for subcontractor and prime contractor 

exposure analyses

File name

# Entries 

(rows) Relevant? SC&A comments

SRS_[various 

years]_PRORA

D_SIGN_IN_D

ATA

4,497,761 No – out of 

period

Contains a series of six databases (parsed by time period 

because of their size) that contain RWP sign-in/sign-out 

times, thermoluminescent dosimeter (TLD) numbers, and 

accrued dose during the indicated period. However, these 

files are out of the period of interest as they represent 

RWP sign-in sheets from January 2004 through April 

2023.

SRS_AREA_M

ONITORING_F

ACILITIES

774 No – out of 

period

Contains area code designations used at SRS 2000−2023 

(e.g., area code F087 represents the 235-F Office 202-B 

starting in 2004).

SRS_EXTERN

ALDOSIMETR

Y_VISITOR_L

EGACY

34,749 No – out of 

period

Contains a list of visitor badges issued starting in 1966 

through May 1990. 

SRS_EXTREM

ITY_DOSE_CY

CLE_SUMMAR

Y

81,147 No – out of 

period

Contains annual extremity dose values for various 

locations on the body (e.g., upper left extremity quadrant, 

lower left quadrant, etc.) beginning in 2004.

SRS_EXTREM

ITY_DOSE_DE

TAIL

302,375 No – out of 

period

Contains specific extremity dosimeter results, as well as 

whole-body dosimeter results during the same wear 

period, starting in 2004.

SRS_FACILIT

Y

28 Unknown –

undated

Contains an undated short list of mainly non-numerical 

facility codes for the A Area.

SRS_FETAL_

DOSE

1,491 No – out of 

period

Contains dosimetry information, including whole-body 

dosimeter and fetal monitoring measurements. The 

records begin in 2003.

SRS_INDIVID

UAL_LGCY

10,704 Unknown –

undated

Contains a list of SRS visitors by name and SSN;

however, no dates are provided.

SRS_INDV_IN

VITRO_SAMP

LES

332,390 No – out of 

period

Contains in vitro bioassay results beginning in November 

2003 and ending in 2011.

SRS_INDV_TR

ITIUM_LEGAC

Y 

857,050 No – out of 

scope

Contains individual tritium urinalysis results beginning in 

1989 and ending in 2003. SC&A notes that the primary 

evaluation of job-specific bioassay completeness (ORAUT, 

2019) specifically omitted tritium monitoring as not being 

relevant to SEC discussions; therefore, SC&A finds the 

data contained in this database are not relevant in the 

context of this report. 

SRS_Invivo_C

ount

46,037 No – lacking 

dose 

information

Contains a list of whole-body and chest count dates by EE 

(including the name and SSN). The file does not contain 

any results.
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File name

# Entries 

(rows) Relevant? SC&A comments

SRS_LIFETIM

E_DOSE_SUM

165,022 No – lacking 

period 

specific 

data

Contains a single listing for individual EEs by unique 

employee number and contains the accrued dose over, 

presumably, their entire employment at SRS (no dates are 

given). Dose data include deep dose, committed effective 

dose equivalent from both tritium and non-tritium intakes, 

offsite dose, and the sum of all three dose assessments.

SRS_RWP 27,810 No – out of 

period

Contains information on specific RWPs, including the 

activation and expected closure date, type (standing work 

permit or job-specific permit), area, survey information, 

measured contamination, etc. However, the database 

does not begin until October 2003.

SRS_RWP_RE

QUEST

12,508 No – out of 

period

Contains a list of RWP requests including a description of 

the work to be performed, location, estimated length, 

required equipment, potential hazard descriptions, etc. 

However, the database does not begin until October 2003.

SRS_RWP_RE

QUIRED_ANA

LYSIS

270,334 No – out of 

period

Explicitly identifies the RWP number and the required 

bioassay analysis to be performed. However, the database 

does not begin until October 2003.

SRS_RWP_TA

SK

132,887 No – out of 

period

Contains a list of RWPs and an associated four-digit 

number to describe the task (the database also contains 

sporadic written comments describing the RWP task) as 

well as estimates of the accrued external dose that is to be 

expected when performing the individual tasks. However, 

the database does not begin until October 2003. 

SRS_TLD_Are

a_assigns

84,558 No – out of 

period

Contains a list of dosimeter issuance dates, locations, and 

results. The database does not appear to identify any 

specific EEs who wore each dosimeter; rather, it lists the 

employee number of the EE who issued the badge. 

However, the entries do not begin until December 2003.

SRS_TLD_AS

SIGNS (also 

listed as 

SRS_TLD_AS

TMT)

744,409 No – out of 

period

Contains a list of dosimeter issuance to individual EEs that 

includes a unique employee number, facility code, 

issue/return dates, and monitoring results (deep, lens of 

the eye, shallow, and neutron dose). However, the entries 

do not begin until January 2004.

SRS_WHOLE_

BODY_DOSE_

DETAIL

484,520 No – lacking 

dose 

information

Contains a list of combined internal and external doses for 

EEs starting in 1945 and extending to early April 2023. 

The database does contain a unique employee ID number 

and full name that would allow identification of 

subcontractors and prime contractors. It should be noted 

that dose breakdowns by pathway (deep dose, shallow 

dose, neutron dose, tritium intake and non-tritium intake) 

are not apparent until 2003. Only 93 of the 484,520 entries 

are during the period 1991–1997.