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NIOSH Response to SC&A Review of 

ORAUT-RPRT-0081 (SRS)

Response Paper

National Institute for Occupational 

Safety and Health

June 27, 2019

Mike Mahathy

Oak Ridge Associated Universities Team

Reviewed by Timothy Taulbee

Division of Compensation Analysis and Support 

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 2 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

PURPOSE

In 2017, NIOSH produced ORAUT-RPRT-0081, Appropriateness of Using 1997 Gross Alpha 

Air Sampling Data as a Method of Bounding Thoron Intakes at the SRS H-Area Tank Farm 

Between 1972 and 1994 (ORAUT 2017a), which calculated the lognormal distributions of the air 

concentration due to thoron for three different periods (1982–1983, 1984–1985, and 1990) for 

comparison to the 1997 data (Sigg, et al. 1997). Subsequently, the Advisory Board on Radiation 

Worker Health tasked SC&A with reviewing the methodology and rationale presented in 

ORAUT-RPRT-0081. This resulted in SC&A issuing Memorandum: SC&A Review of RPRT0081 Methods for Thoron Dose Reconstruction (SC&A 2018). This NIOSH white paper 

responds to SC&A observations in that memorandum.

SC&A OBSERVATIONS AND NIOSH RESPONSES

SC&A Observation 1

To characterize and bound potential thoron exposures for the period October 1972–1995, NIOSH 

analyzed data from three periods: 1982–1983, 1984–1985, and 1990. However, the actual temporal 

coverage of the data constitutes only approximately 8% of the period of interest. It is not known 

whether additional air sampling data are available to evaluate the temporal gaps in the NIOSH

analysis.

SC&A acknowledges that the data comparison presented for the years that were analyzed 

demonstrates that the 1996 derived thoron exposures significantly bound the limited earlier data by 

an order of magnitude or more for these periods. Therefore, further data capture and analysis may 

not be deemed necessary to assure the approach is bounding.

NIOSH Response

ORAUT-RPRT-0081 proposed to use thoron air concentrations reported in Sigg, et al. 1997, not 

data from 1996, to derive thoron doses for the period 1972 through 1994 (ORAUT 2017a). 

However, these same data can be used to derive thoron doses through 1997.

In order to assess whether thoron air concentrations fell below the results captured in 1997, 

NIOSH collected additional air monitoring data for the H Tank Farm (HTF) that were recorded 

in the years 1999 and 2000. By that time, SRS used the process shown in Figure 1 to determine 

whether air samples contained thoron (Westinghouse 1998). Only filters and planchets meeting 

the condition were recounted after 24 hours for thoron. Less than 1 percent of all samples were 

suspected to have thoron contamination.
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure 1: Air Sample Flowchart.
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Thoron Air Concentrations, 2000 

For 2000, NIOSH identified 60 samples for which both 6- and 24-hour counts were performed. 

Table 1 provides the location of these 60 samples. The location of these samples represents 

similar locations used for a Westinghouse study that sampled Tanks 11 through 17 and general 

areas within the H Tank Farm (Sigg, et al. 1997). These results are provided in Attachment A, 

Table A-1. NOTE: Only the samples given in Table 1 below indicated thoron. Hundreds of 

samples were taken at or around Tanks 11 through 15 for which counting revealed no indication 

of thoron. 

Table 1: Thoron Sample Locations. 

Location Description No. of results

HTF 241-57H Evaporator system 1

HTF DB-2 GA Diversion box general area 1

HTF TK 10-12 E Tanks 10 and 12 east 7

HTF TK 13 N Tank 13 north 1 

HTF TK 13-16 BERM Tanks 13 through 16 berm 5

HTF TK 30 Annulus Tank 30 annulus 1

HTF TK 39 Annulus Tank 39 annulus 2

HTF TK 9-12 GA Tanks 9 through 12 general area 7 

HTF PP 5&6 Pump Pit 5&6 35

The tank farms employ a network of transfer lines to transfer wastes between the waste tanks, 

process units, and various Savannah River Site (SRS) areas (i.e., H Area, S Area, and Z Area). 

These transfer lines are connected to diversion boxes that contain removable pipe segments to 

complete the desired transfer route. The use of diversion boxes allows flexibility in waste

movement. The diversion boxes are usually underground, constructed of reinforced concrete, 

and either sealed with waterproofing compounds or lined with stainless steel. Pump pits are 

intermediate pump stations in the tank farm transfer systems. They contain pump tanks and 

hydraulic pumps or jet pumps. The pits are constructed of reinforced concrete and have a 

stainless-steel liner. Some pump pits are associated with diversion boxes. 

NIOSH used Equation 3-7 in ORAUT-RPRT-0084 to derive the thoron concentration in air for 

each recorded set of 6-hour and 24-hour results (ORAUT 2017b). Many of the recorded counts 

appear to be rounded to the closest 100, which limits the number of significant digits. As a 

reminder, thoron was found in less than 1 percent of the air sampling data. Looking further at 

the results for the year 2000, the thoron data can be broken into two smaller distributions: (1)

concentrations measured at Pump Pit 5&6; and (2) concentrations measured at all other HTF 

sampling stations, as shown in Figure 2 (SRS, 2015). In both distributions, the 95th- and 99thpercentile concentrations are about an order of magnitude less than the 1997 values. Thoron air 

contamination appeared to be persistent at Pump Pit 5&6. Table 2 provides summary statistics 

for the two distributions along with the summary statistics reported for 1997, as published in 

ORAUT-RPRT-0081.
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 2: Thoron Concentration Summary Statistics by Location (μCi/cc). 

Location N GM 95th 99th GSD

HTF PP 5&6 34 5.9 x 10-11 1.3 x 10-10 1.8 x 10-10 1.6

Thorium Tanks/Other 29 7.6 x 10-12 2.1 x 10-11 3.1 x 10-11 1.8

Year 1997 Locations 22 2.8 x 10-11 2.7 x 10-9 1.8 x 10-8 15.9

Figure 2: H Tank Farm Map.

Source: SRS, 2015
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure 3 shows the plot for the Pump Pit 5&6 distribution; Figure 4 shows the plot for the 

Thorium Tanks/Other distribution. 

Although the concentrations at Pump Pit 5&6 were higher than those measured for the tanks, 

Pump Pit 5&6 was isolated from most of the waste tanks where measurements were taken (see 

Figure 2 above). It is unlikely that operations or construction trade workers would have worked 

near those tanks full time. Operations workers would have been assigned tasks across the tank 

farm; construction trade workers would have been assigned to specific jobs with lesser 

frequency.

Figure 3: Thoron Air Concentration, HTF PP 5&6. 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure 4: Thoron Air Concentration, HTF Tanks/Other. 

Figure 5 shows H Tank Farm and Pump Pit 5&6 in comparison to the major areas E, F, S, and Z 

(SRR, 2015). Given the distance from H Tank Farm to those areas and the lack of thorium 

source terms, it is reasonable to assume that thoron concentrations in major areas E, F, S, and Z 

would not exceed those recorded for H Tank Farm. 

Finally, the distribution of the thoron air concentration reported for 1997 in ORAUT-RPRT-0081 

is sufficient to bound thoron exposures of workers in thorium storage areas, as documented in the 

report, through 1997. 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Figure 5: H Tank Farm in Comparison to Site Major Areas.

Source: SRR, 2015

Thoron Air Concentrations, 1999 

NIOSH also identified job-specific, thoron-daughter, air-concentration data taken in November 

and December 1999 (SRS Air Data 1999a; SRS Air Data 1999b). While the data were not taken 

from the same tanks for which data were obtained for Sigg, et al. 1997 (Tanks 11 through 17), 

the 1999 data do represent tanks known to hold thorium (Tanks 40 and 51) (Thames 2000). 

Pump Pit 5&6 would also have been used to transfer waste to these tanks. 

Table 3 below provides derived concentrations of thoron daughters. Table 4 provides summary 

statistics for these derived concentrations. The geometric mean, 95th- and 99th-percentiles 

derived for these results are much less than the statistics derived for 1997, and for samples taken 

from Pump Pit 5&6 in the year 2000. The 1999 statistics are comparable to the statistics derived 

from the sampling of Thorium Tanks/Other in the year 2000 (see Table 2). While the 

concentrations given for 1997 in Table 2 are sufficient to bound intakes of thoron daughters 

through 1999, concentrations derived from the sampling of Pump Pit 5&6 are reasonable for 

bounding thoron intakes from the year 2000 forward. 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 9 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 3: Thoron Daughter Concentrations, 1999.

Tank End Date Concentration 

(μCi/cc)

HTF TK 40 11/10/1999 3.08 x 10-12

HTF TK 40 airlock 11/10/1999 3.20 x 10-12

HTF TK 40 airlock 11/12/1999 1.12 x 10-11

HTF TK 40 airlock 11/17/1999 3.13 x 10-12

HTF TK 40 airlock 11/18/1999 4.17 x 10-12

HTF TK 40 airlock 11/23/1999 5.06 x 10-12

HTF TK 40 airlock 12/17/1999 3.36 x 10-12

HTF TK 40 airlock 12/28/1999 3.18 x 10-12

HTF TK 40 annulus 11/18/1999 1.39 x 10-11

HTF TK 40 coppus 12/28/1999 2.15 x 10-12

HTF TK 40 exhaust 11/10/1999 7.10 x 10-13

HTF TK 40 hut 11/10/1999 6.34 x 10-12

HTF TK 40 hut 11/11/1999 2.36 x 10-12

HTF TK 40 hut 11/18/1999 3.21 x 10-12

HTF TK 40 hut 11/23/1999 1.18 x 10-11

HTF TK 40 hut 12/17/1999 2.41 x 10-12

HTF TK 40 hut 12/18/1999 1.03 x 10-12

HTF TK 40 hut 12/28/1999 1.99 x 10-12

HTF TK 40 purge 11/12/1999 2.26 x 10-11

HTF TK 40 purge 11/20/1999 3.24 x 10-12

HTF TK 40 purge 12/29/1999 2.89 x 10-11

HTF TK 40 RBA 11/17/1999 5.98 x 10-12

HTF TK 40 RBA 11/18/1999 4.83 x 10-12

HTF TK 51 annulus 11/18/1999 7.58 x 10-12

Source: SRS Air Data 1999a; SRS Air Data 1999b

Table 4: Statistics for Thoron Daughter Concentrations, 1999. 

Statistic Concentration (μCi/cc)

GM 4.34 x 10-12

95th percentile 1.82 x 10-11

99th percentile 3.30 x 10-11

GSD 2.39

Finally, based on results identified for 1999 and 2000, the distribution of the thoron air 

concentrations reported for 1997 in ORAUT-RPRT-0081 is sufficient to bound thoron exposures 

of workers in thorium storage areas, as documented in NIOSH 2012, not only through 1997 but 

also through 1999. 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 10 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.

SC&A Observation 2

Based on the comparison of the limited air sampling data for the period of interest, it is clear that the 

1996 thoron assessments bound the exposure potential for the earlier periods evaluated in RPRT0081.

Finally, RPRT-0081 does not specify how NIOSH intends to assign thoron exposures to the relevant 

claimant population at SRS. RPRT-0081 (p. 12) states: 

NIOSH concludes that concentrations of thoron daughters reported in the 1997 study are 

sufficient to bound thoron exposures of workers in thorium storage areas. [Emphasis added.] 

It is not clear if this methodology is intended to apply only to tank farm workers or any worker in an 

area of SRS where thorium might have been stored. Additionally, it is not clear whether NIOSH 

intends to assign the geometric mean, the 95th percentile, or the 99th percentile as presented in 

Table 3-1 of RPRT-0081. RPRT-0081 should explicitly define how the proposed dose reconstruction 

approach would be implemented.

NIOSH Response

NIOSH proposes to use these data to assign dose to workers assigned to areas where thorium was 

stored through 1999, but limited to the dates of material storage and to specified years in 

identified buildings. Storage locations are listed in Addendum 3 of the SEC-00103 SRS 

evaluation report (NIOSH 2012). Those locations are 773-A (1972 – 2007), 235-F (1975-1998), 

M Area (1972-1992), 100 K basin (1972-2005), 100 L basin (1980-2007) and 244-H, or the 

RBOF (1972-2004). Quantities of Th-232 are known to exist in Tanks 11, 12, 13, 14, 15, 40, 42,

and 51 (Thames 2000) though thorium is primarily stored in Tanks 12 and 15; these are the tanks 

where the thoron air concentration study was performed and presented in Sigg et al. 1997. In 

Building 773-A, thorium was used in several labs over time; however, specific storage locations 

are not known. Thorium was also stored in vaults in both M Area and 235-F. For example, a 

claimant who worked at SRS from 1972 through 1995, but who worked only in a thorium 

storage area from 1980 through 1984, would be assigned thoron dose only for 1980 through 

1984.

HP area codes (ORAUT 2016) listed on quarterly dosimetry reports through 1990 will be used to 

identify workers that worked in those locations. In some cases, SRS did not have a separate HP 

area code for a location, such as F Tank Farm from 1972 through 2003. In these cases, the HP 

area code for the overlying area, F Area for F Tank Farm, will be used to identify workers who

potentially worked at the thorium storage location. HP sometimes assigned subcontract 

construction trade workers to an HP code for Central Shops (CS) or for a specific trade such as 

laborer (8L) rather than a specific area. Using the HP area code for an area will likely include 

more workers than would be included with a specific HP area code for the location. Table 5 lists 

HP area codes by location or craft.
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 11 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 5: Location Identifiers for Thoron Dose Assignment. 

Location Start 

Year

End 

Year

Area Code

in 1972

Area Code

in 1973

Area Code 

in 1990

Area Code 

in 2004

773-A 1972 2007 5A 5A, A15, A18 SRT

235-F 1975 1998 1A 2F, 3F, 8F, 

5F

F03, F08, 

F05 235

M-Area 1972 1992 3A 3M M03 none

100-K Basin 1972 2005 10A 1K K01 NMM

100-L Basin 1980 2007 9A 1L L01 LLL

244-H 1992 2004 2A 2F, 2H, 5H, 

6H

F02, F05, 

H02, H05, 

H06

RBO

F/H Tank 

Farms 1992 2007 2F, 2H 2H, 1H, 3H

H02, H01, 

H03 H05, 

H06

EPT, FTF, 

HTF

Construction 

(craft) 1992 2007 12E, 12Z

7A, 7J, 7R, 

7T, 8A, 8B, 

8C, 8H, 8I, 

8K, 8L, 8M, 

8P, 8S, 8T

J02, J03, 

J12, J24, 

J20, J06, 

J14, J31, 

J18, J17, 

J21, J10, 

J08, J05

Use 

occupation 

given in 

NOCTS

Doses Calculated for Year 1997 Air Concentration Data 

NIOSH proposes to use the lognormal fit of the distribution of the 1997 thoron air concentration 

given in ORAUT-RPRT-0081 for all workers in thorium locations with a 100% occupancy rate 

through 1999. Table 6 provides the parameters used in the distribution. Table 7 provides the 

dose conversion factors used in the dose calculations in units of rem/working level month 

(WLM), as presented in Tables 6-1 and 8-1 in DCAS-TIB-011, Dose Conversion Factors for 

Radon WLM (NIOSH 2018). 

Table 6: Lognormal Distribution Parameters, 1997 Data. 

Worker type Air Concentration (μCi/cm3) 

95th percentile 2.67 x 10-09

50th percentile 2.84 x 10-11

GSD 15.83
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 12 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 7: Dose Conversion Factors (rem/WLM). 

Worker type DCF

Lung 6.2

ET1 943.83 

ET2 0.45

Kidney 0.24

Bone Surface 0.21

Prostate 0.0091

Stomach 0.01

Colon 0.015

Source: NIOSH, 2018

Example Dose Reconstructions 

Viable examples of employment were written that demonstrate higher bounds of doses and 

probability of causation (POC) for all sets of workers and locations listed in Table 8. The 

examples are:

1. Chemist, Building 773-A, employment 1/1/1973–12/31/2007, lung cancer 

2. Electrician, Building 773-A, employment 1/1/1975–12/31/1990, lung cancer 

3. Electrician, H Tank Farm, employment 1/1/1990–12/31/1993, lung cancer 

4. Engineer, H Tank Farm, employment 1/1/1982–12/31/1982, lung cancer 

5. Maintenance worker, Building 773-A, employment 1/1/1973–12/31/2007, stomach cancer 

6. Janitor, Building 773-A, employment 1/1/1973–12/31/2007, ET1 

7. Operator, H Tank Farm, employment 1/1/1973–12/31/2007, colon cancer 

8. Janitor, H Tank Farm, employment 1/1/1973–12/31/2007, ET2 

9. Electrician, Building 773-A, employment 1/1/1975–12/31/1990, kidney cancer 

10. Maintenance worker, Building 773-A, employment 1/1/1973–12/31/2007, bone surfaces 

cancer

11. Maintenance worker, Building 773-A, employment 1/1/1973–12/31/2007, prostate cancer 

Cancer diagnosis date for all eleven cases is 1/1/2008. All workers are assumed to have been 

diagnosed at age 60 and are assumed to have no history of smoking.
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 13 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Table 8: Dose Reconstruction Scenarios. 

Scenario Job Title Facility Employment 

Dates

Years of 

Exposure Diagnosis Annual Dose (rem) PoC %

1 Chemist 773-A 1/1/1973 -

12/31/2007 35 Lung 0.287 95.93%

2 Electrician 773-A 1/1/1975 -

12/31/1990 16 Lung 0.287 94.34%

3 Electrician H Tank 

Farm

1/1/1990 -

12/31/1993 4 Lung 0.287 80.79%

4 Engineer H Tank 

Farm

1/1/1982 -

12/31/1982 1 Lung 0.287 52.45%

5 Maintenance 

worker 773-A 1/1/1973 -12/31/2007 35 Stomach 0.0005 2.37%

6 Janitor 773-A 1/1/1973 -

12/31/2007 35 ET1 (160.0) 43.699 99.79%

7 Operator H Tank 

Farm

1/1/1973 -

12/31/2007 35 Colon 0.001 3.97%

8 Janitor H Tank 

Farm

1/1/1973 -

12/31/2007 35 ET2 (161.0) 0.021 18.58%

9 Electrician 773-A 1/1/1975 -

12/31/1990 16 Kidney 0.011 29.99%

10 Maintenance 

worker 773-A 1/1/1973 -12/31/2007 35 Bone surfaces 0.010 35.14%

11 Maintenance 

worker 773-A 1/1/1973 -12/31/2007 35 Prostate 0.0004 1.04%

Doses Calculated for the Year 2000 Pump Pit 5&6 Air Concentration Data 

NIOSH proposes to use the lognormal fit of the distribution of the year 2000 thoron air 

concentration data given in this report for all workers in thorium locations with a 100% 

occupancy rate from the year 2000 forward. Table 6 previously provided the parameters used in 

the distribution. Table 9 below provides thoron air concentrations (from Pump Pit 5&6) used in 

the dose calculations in units of rem/working level month (WLM). 

Table 9: Lognormal Distribution Parameters, Year 2000 Data. 

Worker type Thoron Air Concentration (μCi/cm3) 

95th percentile 1.3 x 10-10

50th percentile 5.9 x 10-11

GSD 1.6
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 14 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

NIOSH revised dose reconstructions for all scenarios where the end of employment exceeded 

1999. Those are scenarios 1, 5, 6, 7, 8, 10, and 11. Table 10 below provides the revised dose 

reconstruction scenarios. For comparison, Table 10 includes the probability of causations 

previously presented in Table 8. 

Table 10: Modified Dose Reconstruction Scenarios. 

Scenario Job Title Facility Employment 

Dates

Years of 

Exposure Diagnosis

Annual 

Dose 

(rem)

PoC% Previous 

PoC%

1 Chemist 773-A 1/1/1973 -

12/31/2007 35 Lung 0.287 95.93% 95.93%

5 Maintenance 

worker 773-A 1/1/1973 -12/31/2007 35 Stomach 0.0005 2.37% 2.37%

6 Janitor 773-A 1/1/1973 -

12/31/2007 35 ET1 (160.0) 43.699 99.78% 99.79%

7 Operator H Tank 

Farm

1/1/1973 -

12/31/2007 35 Colon 0.001 3.91% 3.97%

8 Janitor H Tank 

Farm

1/1/1973 -

12/31/2007 35 ET2 (161.0) 0.021 17.83% 18.58%

10 Maintenance 

worker 773-A 1/1/1973 -12/31/2007 35 Bone surfaces 0.010 33.19% 35.14%

11 Maintenance 

worker 773-A 1/1/1973 -12/31/2007 35 Prostate 0.0009 0.99% 1.04%
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

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This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

REFERENCES

NIOSH (National Institute for Occupational Safety and Health), 2012, SEC Petition Evaluation 

Report for SEC-00103, Savannah River Site, Addendum 3, November 20. [SRDB 

158744] 

NIOSH (National Institute for Occupational Safety and Health), 2018, Technical Information 

Bulletin: Dose Conversion Factors for Radon WLM, DCAS-TIB-011, Rev 05, NIOSH

Division of Compensation Analysis and Support, June 28. [SRDB Ref ID: 175105] 

ORAUT (Oak Ridge Associated Universities Team), 2016, Evaluation of Health Physics Area 

and Health Physics Department Codes to Identify Neptunium Workers at the Savannah 

River Site, ORAUT-RPRT-0077, Rev. 00, November 8. [SRDB Ref ID: 163179] 

ORAUT (Oak Ridge Associated Universities Team), 2017a, Appropriateness of Using 1997 

Gross Alpha Air Sampling Data as a Method of Bounding Thoron Intakes at the SRS 

H-Area Tank Farm Between 1972 and 1994, ORAUT-RPRT-0081, Rev. 00, April 7. 

[SRDB Ref ID: 166258] 

ORAUT (Oak Ridge Associated Universities Team), 2017b, Two-Count Filter Method for 

Measurement of Thoron Progeny in Air, ORAUT-RPRT-0084, Rev. 00, March 27. 

[SRDB Ref ID: 166030] 

SC&A (Sanford Cohen & Associates), 2013, SC&A Review of Addendum 3 to the NIOSH 

Savannah River Site Special Exposure Cohort (SEC-00103) Evaluation Report, 

September. [SRDB Ref ID: 165637] 

SC&A (Sanford Cohen & Associates), 2018, Memorandum: SC&A Review of RPRT-0081 

Methods for Thoron Dose Reconstruction, October 11. [SRDB Ref ID: 175137] 

Sigg, et al, 1997, Personnel Exposures from Periodic Venting of Radon Gas from High-ThoriumContent Tanks at H-Tank Farm, WSRC-TR-97-0033, Rev. 0, R. A. Sigg, R. H. Ross, and 

A. H. Weber, Westinghouse Savannah River Company, Savannah River Site, Aiken, 

South Carolina, April 8. [SRDB Ref ID: 49677] 

SRR, 2015, Tank 16 Special Analysis for the Performance Assessment for the H-Tank Farm at 

the Savannah River Site, SRR-CWDA-2014-00106, Rev. 1, Savannah River 

Remediation, LLC; February. [SRDB Ref ID: 176619, PDF p. 19] 

SRS, 2015, Savannah River Site F and H Area Tank Farms: NRC Onsite Observation Visit, July 

28-29, 2015, PowerPoint presentation, Savannah River Site, July 28. [SRDB Ref ID: 

176618, PDF p. 30] 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 16 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

SRS Air Data, 1999a, Workplace Job Specific Air Sampling Filter Results for 1999, Savannah 

River Nuclear Solutions, Savannah River Site, provided to NIOSH on May 28. [SRDB 

Ref ID: 176627] 

SRS Air Data, 1999b, Process Air Sampling Results for 1999, Savannah River Nuclear 

Solutions, Savannah River Site, provided to NIOSH on May 28. [SRDB Ref ID: 176628] 

Thames, 2000, HLW Stack Samples and Thoron, memorandum from R. D. Thames to E. M. 

Perett and J. D. Gall, Westinghouse Savannah River Company, Savannah River Site, 

Aiken, South Carolina, November 20. [SRDB Ref ID: 105017] 

Westinghouse, 1998, Air Sample Calculations and Data Sheets, Westinghouse Savannah River 

Company, Savannah River Site, Aiken, South Carolina, July 27. [SRDB Ref ID: 175894, 

PDF p. 10] 
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 17 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

ATTACHMENT A

Table A-1: Thoron Air Concentration Data, Year 2000. 

Location Date 6-hr 

dpm

24-hr 

dpm

Thoron 

Concentration 

(μCi/cc)

SRDB Ref ID PDF Page

HTF PP 5&6 1/31/2000 5000 1600 3.36 x 10-11 175888 135

HTF TK 10-12 E 1/31/2000 1400 390 1.20 x 10-12 175888 152

HTF TK 13-16 BERM 1/31/2000 1400 405 1.18 x 10-12 175888 151

HTF TK 9-12 GA 1/31/2000 600 363 2.81 x 10-13 175888 151

HTF TK 30 Annulus 2/7/2000 538 164 7.88 x 10-12 175888 164

HTF PP 5&6 2/15/2000 6000 800 1.40 x 10-10 175888 191

HTF TK 13 N 2/28/2000 1398 600 1.54 x 10-12 175888 274

HTF TK 13-16 BERM 2/28/2000 1810 800 1.68 x 10-12 175888 274

HTF TK 9-12 GA 2/28/2000 1810 700 1.85 x 10-12 175888 274

HTF PP 5&6 3/6/2000 3600 1400 2.19 x 10-10 175888 299

HTF TK 39 Annulus 3/6/2000 600 400 4.11 x 10-12 175888 298

HTF TK 39 Annulus 3/6/2000 800 400 8.27 x 10-12 175888 299

HTF PP 5&6 4/13/2000 5000 2000 7.00 x 10-11 175893 9

HTF TK 10-12 E 4/17/2000 2000 600 2.05 x 10-12 175893 3 

HTF PP 5&6 4/24/2000 5000 1000 1.03 x 10-10 175893 5

HTF PP 5&6 4/27/2000 4400 2800 3.70 x 10-11 175893 7 

HTF PP 5&6 5/8/2000 5000 2000 6.48 x 10-11 175893 11

HTF PP 5&6 5/15/2000 4000 1000 8.21 x 10-11 175893 13 

HTF TK 10-12 E 5/15/2000 2000 600 1.65 x 10-12 175893 15

HTF PP 5&6 5/16/2000 5000 1000 6.90 x 10-11 175893 17 

HTF PP 5&6 6/9/2000 4000 2000 2.19 x 10-11 175889 43

HTF PP 5&6 6/9/2000 4000 1000 4.26 x 10-11 175889 45

HTF TK 10-12 E 6/12/2000 2000 200 2.34 x 10-12 175889 57

HTF TK 10-12 E 6/19/2000 2000 300 1.95 x 10-12 175889 85

HTF TK 10-12 E 6/26/2000 800 500 3.50 x 10-13 175889 99

HTF 241-57H 7/10/2000 1800 600 1.40 x 10-12 175889 167

HTF TK 10-12 E 7/10/2000 4000 800 4.14 x 10-12 175889 158

HTF TK 13-16 BERM 7/10/2000 2000 600 1.81 x 10-12 175889 157

HTF TK 10-12 E 7/24/2000 2000 800 1.54 x 10-12 175889 204

HTF TK 13-16 BERM 7/31/2000 2000 800 1.40 x 10-12 175889 239

HTF TK 13-16 BERM 8/7/2000 2000 600 1.63 x 10-12 175889 272

HTF TK 9-12 GA 8/7/2000 2000 800 1.46 x 10-12 175889 272

HTF PP 5&6 8/15/2000 6000 2000 1.04 x 10-10 175889 281

HTF PP 5&6 8/21/2000 6000 2400 3.35 x 10-11 175889 311
Response Paper NIOSH Response to SC&A Review of ORAUT-RPRT-0081 June 27, 2019

Page 18 of 18

This is a working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution. 

Location Date 6-hr 

dpm

24-hr 

dpm

Thoron 

Concentration 

(μCi/cc)

SRDB Ref ID PDF Page

HTF PP 5&6 8/23/2000 5000 2000 3.03 x 10-11 175890 3 

HTF PP 5&6 8/23/2000 6000 2200 1.78 x 10-11 175890 9

HTF PP 5&6 8/26/2000 5600 2000 7.69 x 10-11 175890 7 

HTF PP 5&6 8/27/2000 5000 1200 1.41 x 10-10 175890 20

HTF PP 5&6 8/28/2000 5000 2000 3.83 x 10-10 175890 22

HTF PP 5&6 8/28/2000 4000 2000 7.44 x 10-11 175890 31

HTF PP 5&6 8/28/2000 5000 2000 1.67 x 10-10 175890 39

HTF PP 5&6 8/29/2000 6000 2400 1.90 x 10-10 175890 48

HTF PP 5&6 9/4/2000 4000 2000 9.47 x 10-11 175890 54

HTF TK 9-12 GA 9/4/2000 2800 2000 9.70 x 10-13 175890 98

HTF PP 5&6 9/5/2000 4000 2000 3.07 x 10-10 175890 69

HTF PP 5&6 9/6/2000 4000 2000 6.21 x 10-11 175890 77

HTF PP 5&6 9/6/2000 5000 1600 3.02 x 10-10 175890 78

HTF PP 5&6 9/6/2000 4000 1000 2.51 x 10-10 175890 82

HTF PP 5&6 9/8/2000 2800 800 1.20 x 10-09 175890 86

HTF PP 5&6 9/21/2000 4000 2000 3.66 x 10-11 175890 144

HTF PP 5&6 9/25/2000 10000 3000 8.67 x 10-10 175890 174

HTF TK 9-12 GA 9/25/2000 1000 600 1.72 x 10-12 175890 195

HTF PP 5&6 9/27/2000 6000 1500 3.64 x 10-10 175890 184

HTF DB-2 GA 10/16/2000 2000 200 2.33 x 10-12 175891 10

HTF TK 9-12 GA 10/16/2000 3000 400 3.36 x 10-12 175891 10

HTF TK 9-12 GA 10/16/2000 5000 2000 3.88 x 10-12 175891 117

HTF PP 5&6 11/13/2000 8000 3000 4.94 x 10-11 175891 126

HTF PP 5&6 12/11/2000 4000 2000 2.70 x 10-11 175891 211

HTF PP 5&6 12/22/2000 8000 3000 1.31 x 10-10 175891 240

HTF PP 5&6 12/30/2000 5000 2000 1.24 x 10-10 175891 267