Draft 

ADVISORY BOARD ON 

RADIATION AND WORKER HEALTH 

National Institute for Occupational Safety and Health 

SC&A CLARIFYING QUESTIONS FOR FERNALD ISSUES 

MATRIX – DRAFT WORKING DOCUMENT 

Contract No. 211-2014-58081 

SC&A, Inc. 

2200 Wilson Boulevard, Suite 300 

Arlington, VA 22201-3324 

Saliant, Inc. 

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February 2018 

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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SC&A, INC.: Technical Support for the Advisory Board on Radiation and 

Worker Health Review of NIOSH Dose Reconstruction Program

DOCUMENT TITLE: SC&A Clarifying Questions for Fernald Issues Matrix – Draft 

Working Document

REVISION NO.: 0 (Draft)

SUPERSEDES: N/A

EFFECTIVE DATE: February 22, 2018

PROJECT MANAGER: John Stiver, MS, CHP [signature on file]

Record of Revisions

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0 (Draft) 2/22/2018 Initial issue
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TBD FINDINGS 7, 8: URANIUM- AND RADIUM-POOR RAFFINATE 

MATERIAL

BACKGROUND

Current dose reconstruction methods have been developed for potential internal exposures to 

raffinate material by utilizing the indicator radionuclides of radium and uranium along with 

appropriate contaminant ratios. In the former case, radon breath analysis was used to estimate a 

radium body burden which can then be used with source term data to reconstruct the dose from 

other contaminants present in the raffinate material. In the latter case, uranium urinalysis results 

are used with appropriate ratios to other unmonitored contaminants. However, using these two 

methods becomes problematic when addressing any potential exposures to uranium- and radiumpoor raffinate material. 

This issue has most recently been discussed at the December 2014 and July 2017 Fernald Work 

Group meetings. In December 2014, NIOSH had tacitly proposed a framework by which daily 

weighted exposure studies conducted in Plant 2/3 could be applied to reconstruct doses to 

uranium- and radium-poor raffinate source terms (see ABRWH 2014, pages 128–150). During 

the July 2017 Work Group meeting, NIOSH’s position was essentially twofold (see ABRWH 

2017, pages 13–25):

 Due to the nature of the raffinate process, existing engineering controls, and source term 

characteristics (raffinate material was a wet slurry), no internal exposure potential existed 

for uranium- and radium-poor raffinate material.

 In the event that any internal exposures did occur to uranium- and radium-poor raffinate 

material, such exposures would be considered not reconstructable with sufficient 

accuracy and thus would be included in the currently existing Special Exposure Cohort 

(SEC) for thorium.

During that meeting, NIOSH indicated they had a formal rationale for their conclusions but that 

the document had not been transmitted to the Work Group or SC&A at that time (ABRWH 2017,

page 24). To date, SC&A does not believe it has received any new documentation specific to 

radium- and uranium-poor raffinate material. The most current response from NIOSH takes the 

form of a traditional matrix and states the following concerning TBD Findings 7 and 8 (NIOSH 

2017b):

10/24/2017: NIOSH’s position is that there was little potential for exposure to 

uranium- and radium-poor raffinates, since they were liquids that were pumped to 

disposal pits. If there were exposures to uranium- and radium-poor raffinates, 

doses from those exposures cannot be reconstructed with sufficient accuracy, 

given the information available to NIOSH. Any such exposures occurred within 

the period of the existing “thorium” SEC class. Therefore no further SEC action 

is required, and doses resulting from exposure to uranium- and radium-poor 

raffinates will not be included in partial dose reconstructions.
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DISCUSSION

The NIOSH response states that there was little potential for exposure to uranium- and radiumpoor raffinates. However, specific documentation or references (whether it be descriptions of the 

specific process streams and equipment utilized, interviews with former workers in the area, or 

other such justification) has not been provided with respect to this issue. Furthermore, NIOSH 

states that any such exposures (if the potential existed) cannot be reconstructed with sufficient 

accuracy.

SC&A notes that audits that occurred in the 1950s noted on several occasions that an operator 

was shoveling solvent cake with measurements in the range of 40 to 69 dpm/m3(SRDBs 29301, 

29330, and 29340) in the Plant 3 hot raffinate building. About 90 minutes per shift were spent 

doing this by raffinate operators. In 1955 (SRDB 29340), it was noted an operator was pushing 

material down a pipe (or maybe chute?) into the drumming station in the hot raffinate building 

that came from the Oliver filter, but this was low-radioactive material and no respirator was 

worn. No respiratory equipment was noted on a couple of occasions throughout the surveys. 

Auditors noted use of an air hose to unplug a chute (SRDB 43291, 43299). The control panel 

area of the Plant 3 hot raffinate building measured 122 dpm/m3(SRDB 29340). Other general 

area measurements were as high as 237 dpm/m3. Most measurements, however, were much less, 

say 1 to 20 dpm/m3(background about 0.23 c/m). While SC&A acknowledges that many of 

these exposures were to hot raffinates on the upstream end of the process, there remains a 

concern that there could have also been exposures to radium- and uranium-poor (cold) raffinates 

on the back end of the operation, notwithstanding that the material was contained in piping 

during normal operations. 

A number of studies are available in which daily weighted exposures (DWE) were calculated for 

Plants 2 and 3 (SRDBs 41050, 41063, 41084, 41111, and 41126). While most DWE values were 

less than 70 dpm/m3alpha (MAC, or maximum allowable concentration), some Plant 3 areas 

exceeded the MAC (the mobile hoppers, 3rd level of denitration, and 4th level denitration) 

(SRDB 41050). Some of these studies determined DWE values for hot raffinate workers. While 

the results were typically low, about 0.1 to 0.2 times the MAC (SRDB 41063, 41084, and 

41126), the studies demonstrate that exposures can be calculated. Exposures therefore were 

recorded for workers from raffinate operations, although the exposures were not necessarily 

related to exposure to the raffinate itself.

While it is not immediately clear whether such DWE studies are appropriately representative and 

could be applied to potential exposures to uranium- and radium-poor raffinate material (namely 

Th-230), a substantive discussion on what data is available and why it cannot be used to 

reconstruct doses would help clarify the decision to close the issue. Such discussions also 

provide programmatic transparency to the claimants and other interested parties. 

SC&A Clarifying Question 1: What specific documentation or references (whether it be 

descriptions of the specific process streams and equipment utilized, interviews with former 

workers in the area, or other such justification) was used by NIOSH in concluding that exposures 

to uranium- and radium-poor raffinate material are negligible? Or alternately, what evaluation 

and analysis was performed to determine that air sampling data available for Plant 2/3 is not 

appropriate for partial dose reconstruction and should be included in the SEC for Th-232?
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TBD FINDINGS 9 AND 11 AND SEC FINDING 3: RECYCLED URANIUM 

CONTAMINANT RATIOS (PU, NP, TC)

BACKGROUND

SC&A’s review of Revision 03 of the Fernald Internal Technical Basis Document (NIOSH 

2017a) noted that the agreed-upon parameters for recycled uranium contaminants had changed 

for the period of 1961–1972. The originally agreed-upon parameters were described in a 2011 

NIOSH white paper, Issues Related to the Ability to Bound Internal Dose from Recycled 

Uranium Trace Level Contaminants at Fernald (NIOSH 2011):

The period of interest for RU contaminants at Fernald is 1961 (see references 

above). The initial phases post 1961 to 1973 were in the 5 ppbPu from Hanford, 3 

ppbPu for SRS range. Process sub group 6A is a fair representation of the receipt 

data from Hanford – with blending, and processing the concentrations will 

decrease, with an equivalent increase in the subgroup #8, MgF stream from both 

concentration of some activity in the MgF and a significant reduction in the 

uranium in this process stream. Due to the fact that DR for claimants to date have 

used defaults (Pu at 100 ppbU) an administrative decision to continue default at 

100 ppbU for the 1961 to 1970, while defaulting at 400 ppbU during the 1973 

through 1985 period. 

Specifically, the assumed contaminant concentration of plutonium had decreased by an order of 

magnitude from 100 ppb Pu to 10 ppb Pu on a uranium mass basis (the other contaminant ratios 

for neptunium and technetium decreased accordingly).

During the Fernald Work Group teleconference held on July 28, 2017, NIOSH indicated that the 

change was due to a re-examination of this earlier period and the determination that the majority 

of recycled uranium lots received prior to 1973 were all likely less than 10 ppb (ABRWH pp.

34–37). It is worth noting that during the Work Group discussion in July 2017, NIOSH 

acknowledged that certain processes resulted in contaminants being concentrated above the 

ratios observed upon receipt (in particular the magnesium-fluoride reduction process). However, 

NIOSH’s position was that such operations were short in duration and thus would not represent a 

consistent source of exposure (ABRWH pp. 35–36).

NIOSH’s position is echoed in the most recent version of the issues matrix (NIOSH 2017b),

which states:

NIOSH’s use of the 10 ppb Pu in RU through 1972 is based on the lot data found 

in Attachment C of the Ohio Field Office Report [DOE 2000]. From a quick 

review of the lots identified as being processed prior to 1973, it appears that more 

than 95% of the identified Pu concentrations are below 1 ppb. Of those that are 

above 1 ppb Pu, most of those are still below 10 ppb Pu. This means that any 

potential to exposures to RU with Pu concentrations great than 10 ppb would be 

considered rare and to be short in duration. The remaining and thus majority of 

any worker’s exposure time would have been associated with materials well 

below the recommended default level of 10 ppb Pu. Therefore, NIOSH cannot 
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identify any reason to believe that any worker could have an exposure for which 

the recommended default level of 10 ppb Pu would not be adequately conservative 

and bounding.

SC&A’s concerns about the magnesium fluoride concentration process were reflected in SC&A 

2012 and 2017. SC&A 2012 stated the following:

The topic of whether the original defaults (e.g., 100 ppb Pu) would adequately 

bound Plant 5 metal production workers and associated Plant 1 millwrights who 

were exposed to high constituent concentrations in MgF2 in the pre-1973 period 

was discussed in the April and August 2011 Work Group meetings... At that time, 

SC&A contended that if chemical concentration of downblended material was the

sole mechanism that resulted in the high concentrations in MgF2 documented in 

DOE 2000 [Recycled Uranium Project Report], then the higher defaults (e.g., 400 

ppb Pu) would apply during the entire period of metal production employing RU, 

and not just after POOS receipts began in 1973. The discovery of NLO [1985, 

titled: “Processing 168 MTU of UO3 Containing Recycle Contaminants”] among 

the 49 new references identified...was a key factor in SC&A’s acceptance of the 

original defaults for the 1961–1972 timeframe.

DISCUSSION

SC&A examined the original Recycled Uranium Project Report (DOE 2000) to identify which 

recycled uranium lots are applicable to the pre-1973 timeframe. Unfortunately, the original 

report does not identify a specific date with each lot sample; however, the report does indicate on 

page 577 that additional information on each lot sample can be provided upon request. It appears 

that NIOSH made such a request and received additional working documents and database files 

as indicated on page 3 of NIOSH 2011. In addition, NIOSH 2011 contains a chart which shows 

average plutonium contaminant ratios as far back as 1965 (this chart is shown as Figure 1, 

below).
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Figure 1. Chart from 2011 NIOSH Document: Issues Related to RU Dose Reconstruction 

Draft 01 8-5-11 (NIOSH 2011)

SC&A located a database that appears to contain the expanded information on the recycled 

uranium analysis contained in DOE 2000. This database can be located at the following network 

location: [

]. This database contains a date 

column (column “AC” on the “U_Recycle_Final” tab); however, a date was only specified on 

995 of 3,737 total entries (~27% of the total entries). Examination of entries that specified a date 

indicate that the earliest receipt was from August 1962, which indicated 942.5 Pu ppb. The next 

dated sample found is dated May 1974.

NIOSH 2011 seems to indicate that for the period prior to 1973, Subgroup 6A (UO3 from 

Hanford) was utilized in arriving at 10 Pu ppb. However, it is not clear if the Subgroup 6A data 

was extrapolated backwards from post 1973 to the earlier period. If data is being back 

extrapolated, further discussion of the use of this data as a substitute may be warranted. NIOSH 

2011 further states:

This RU was blended with existing materials, including natural uranium to meet 

enrichment specifications and others. The MgF buildup would be reflective of a 

concentration from single digit contaminants from the blending and processing 

to the default of 10 ppbPu. 

The analytical basis for assuming the MgF contaminant buildup would be bounded at 10 ppbPu 

is not clear. However, based on the recent discussions in ABRWH 2017, it appears that the 
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position is not that contaminants would be bounded at 10 ppbPu but rather that the short duration 

of these concentrating activities would be “averaged out” over a full year of uranium processing 

activities.

SC&A Clarifying Question 2: How was NIOSH able to determine which lots were processed 

prior to 1973 as was indicated in Figure 1 (above) as well as the most recent responses contained 

in NIOSH 2017b?

SC&A Clarifying Question 3: NIOSH 2011 indicates that for the period prior to 1973, 

Subgroup 6A (UO3 from Hanford) was utilized in arriving at 10 Pu ppb, though it is not clear if 

this assumption is still being utilized. It is also not clear if the Subgroup 6A data was 

extrapolated backwards from post-1973 to the earlier period. If data is being back extrapolated, 

further discussion of the use of this later data as a substitute may be warranted.

SC&A Clarifying Question 4: What analytical basis was used to determine the potential 

contaminant ratios experienced by workers involved in the MgF process in the 1961–1972 

period? Furthermore, what is the analytical basis used to conclude that workers exposed to the 

MgF source term would be sufficiently “averaged out” with exposures to other less contaminated 

recycled uranium?

THORIUM COWORKER MODEL FINDING 6: THORON PARAMETER 

SELECTION

BACKGROUND

NIOSH developed a model for assigning exposures to thoron from thorium storage operations in 

its white paper, Fernald Dose Reconstruction Methodology for the Post Special Exposure Cohort 

(SEC) Period, 1979–2006 (NIOSH 2014), which was also migrated into Appendix B of NIOSH 

2017a. SC&A reviewed NIOSH 2014 and had the following finding related to thoron (SC&A 

2014):

Finding 6: The underlying assumptions employed in NIOSH 2014a to reconstruct 

doses to thoron are not well established or referenced. The assumptions 

concerning thorium source term inventory, release fraction, equilibrium factor, 

occupancy time, and specific activity of thoron must be thoroughly defined based 

on credible documentation and site specific records.

This issue was initially discussed in during the December 2014 Fernald Work Group meeting 

(ABRWH 2014) and again during the July 2017 Work Group meeting. After discussions at the 

latter meeting, the following actionable items were indicated by NIOSH as under their purview:

1. Specific analysis of Building 65 to estimate potential thoron doses (ABRWH 2017, page 

170). 

2. Further discussion of the release fraction assumed: 1×10-4(ABRWH 2017, page 170).

3. Justification for the chosen occupancy times (ABRWH 2017, pages 172–173).
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DISCUSSION

NIOSH 2017b provides additional discussion of parameter selection for the thoron dose 

reconstruction model. Actionable Item 1 (above) was discussed in NIOSH 2017b under item 2 

found after the matrix; this discussion included a quantitative assessment of Building 65 working 

levels based on an air sampling measurement of 267 pCi/l made in Building 65 in 1996. The 

analysis shows that thoron estimates using the Building 65 empirical data comport well with the 

site-wide thoron estimates developed in NIOSH’s thoron model.

A qualitative discussion of the assumed release fraction (Actionable Item 2, above) is contained 

under item 5 in NIOSH 2017b. In that discussion, NIOSH indicated that stored materials tended 

to have lower release fractions due to the short half-life of the material, which would not allow 

for significant diffusion within the source material. Furthermore, NIOSH states that the chosen 

release fraction of 10-4 when used in combination with other assumed parameters matches 

reasonably well with thoron working level estimates calculated using an empirical measurement 

from Building 65. It must be noted that release fractions generally range from 10-3 to 10-4 and 

thus NIOSH’s chosen value is at the low end of the potential range. No additional documentation 

in the form of referenced studies or measurements was provided to justify the lower release 

fraction. 

Based on NIOSH 2017b, an occupancy time of 25% or 3 months per year was assumed. 

However, no further information or discussion is provided to justify that assumption. 

Finally, NIOSH calculates working level months per year (WLM/yr) as ~0.5 WLM/yr in NIOSH 

2017b. However, NIOSH 2017a calculates a thoron dose assignment of 1.5 WLM/yr for “1954-

1989, various storage sites Available for release.” It is not clear if the calculated thoron doses in 

NIOSH 2017b are meant to replace the estimates provided in NIOSH 2017a. 

SC&A Clarifying Question 5: What additional resources, references, or documentation (if any) 

were consulted in determining that the originally assumed release fraction of 10-4is the most 

appropriate?

SC&A Clarifying Question 6: NIOSH 2017b indicates that the occupancy factor should remain 

at 25% (3 months per year) for the period from 1954 to 1989 but does not provide any additional 

justification or discussion. It is also not clear if the assumption of 1 month of exposure per year 

from 1990 to 2006 still applies. SC&A requests clarification as to how the currently assumed 

occupancy times were substantiated.

SC&A Clarifying Question 7: It is not clear what the final thoron dose assignment is intended 

to be, as NIOSH 2017a and NIOSH 2017b contain different estimates. In addition, SC&A asks 

for clarification on the calculation steps presented in NIOSH 2017b, as it appears the conversion 

from working levels to working level-months in NIOSH 2017b may be in error. 

REFERENCES

ABRWH 2014. Transcript: Teleconference Meeting of the Advisory Board on Radiation and 

Worker Health, Fernald Work Group. December 4, 2014.
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ABRWH 2017. Transcript: Teleconference Meeting of the Advisory Board on Radiation and 

Worker Health, Fernald Work Group. July 28, 2017.

DOE 2000. Recycled Uranium Project Report, DOE 00-0001, U.S. Department of Energy, Ohio 

Field Office. May 15, 2000. [SRDB Ref. ID 3644]

NLO 1985. DOE Contact Report, Processing 168 MTU of UO3 Containing Recycle 

Contaminants, National Lead of Ohio, Inc. July 31, 1985. [SRDB Ref. ID 33901]

NIOSH 2011. Issues Related to the Ability to Bound Internal Dose from Recycled Uranium 

Trace Level Contaminants at Fernald, Draft 01, National Institute for Occupational Safety and 

Health, Office of Compensation Analysis and Support, Cincinnati, Ohio. August 5, 2011.

NIOSH 2014. Fernald Dose Reconstruction Methodology for the Post Special Exposure Cohort 

(SEC) Period, 1979–2006, White Paper, Revision 2, National Institute for Occupational Safety 

and Health, Cincinnati, Ohio. June 23, 2014.

NIOSH 2017a. Feed Materials Production Center – Occupational Internal Dose, ORAUTTKBS-0017-5, Revision 03, National Institute for Occupational Safety and Health, Office of 

Compensation Analysis and Support, Cincinnati, Ohio. March 30, 2017.

NIOSH 2017b. Issues Resolution Matrix for Fernald Site Profile and SEC Petition, Revision 05, 

National Institute for Occupational Safety and Health, Office of Compensation Analysis and 

Support, Cincinnati, Ohio. October 24, 2017.

SC&A 2012. SC&A’s Response to NIOSH’s Subgroup 10a Impact Analysis Dated November 1, 

2011, Revision 0, SC&A, Inc., Vienna, VA. February 6, 2012.

SC&A 2014. Review of Proposed NIOSH Methods for Reconstructing Thorium Doses at Fernald 

(1979–2006), Revision 0, SC&A, Inc., Vienna, VA. November 24, 2014. 

SC&A 2017. Draft Review of Oraut-TKBS-0017-5, Revision 03, Feed Materials Production 

Center – Occupational Internal Dose, SCA-TR-2017-SP004, Revision 0, SC&A, Inc., Arlington, 

VA. July 6, 2017.