M&C Work Group Review of 

SEC-Related Issues

Meeting of the Advisory Board on Radiation and Worker 

Health, M&C Work Group

July 13, 2023

Josie Beach, Chairperson

1
Background

• M&C Work Group tasked SC&A to review remaining lines of

inquiry or outstanding issues relevant to Work Group’s

review of SEC-00236 evaluation report (ER).

• SC&A issued “Supplemental Review of M&C Work Group

Issues” on August 22, 2022.

• NIOSH responded on January 13, 2023, and SC&A on

April 25, 2023.

• M&C Work Group met on May 12, 2023. SC&A presented its

supplemental report and NIOSH presented its response.

2
SEC issues for M&C: Work Group perspective

• No monitoring data for residual period at M&C, 1968–1997. NIOSH considers

1995 pre-D&D drainage pipe sediment concentrations as “relevant source

term” data for bounding purposes.

• NIOSH bounding approach:

• Back-applies 95th percentile of 1995 pre-D&D Priority 1 pipe sediment measurements to bound potential “inside subsurface” exposures for M&C

maintenance workers.

• Compares M&C maintenance activities to other AWE sites (non-SEC).

• Applies “extreme conservatism” to account for “intrusive activities, high exposure

conditions, uncertain facility activities, or unknown contamination sources”(NIOSH,

2023a).

• The question is whether the 1995 pre-D&D survey measurements are sufficiently informative about exposures during the M&C residual period to

support NIOSH’s bounding approach as being sufficiently accurate under EEOICPA and 42 CFR Part 83.

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NIOSH “inside subsurface” bounding exposure 

model

• NIOSH applies highest Building 10 subsurface drain line sediment

concentration of total uranium and calculates 95th percentile of

6,887 pCi/g for bounding uranium in M&C subsurface maintenance

activities, concluding that these Priority 1 drain lines contained the

“highest subsurface radioactive material concentrations to which

workers were exposed” (NIOSH, 2018).

• Assumes dust loading equal to 95th percentile of Mound project air

sampling and worker occupancy of 2 months.

• Intrusiveness of activities is seen by NIOSH as comparable to other

AWE facilities (non-SEC), with D&D worker handling of pipe removal

similar to that of M&C maintenance workers.

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SC&A supplemental review: Inside subsurface

• SC&A finds that unaddressed and uncertain source terms and elevated

exposure pathways may have been present during M&C residual period:

• Elevated workplace airborne contamination due to confined spaces

• Cutting of pipe containing contaminated scale leading to airborne release

• Concentration of pipe sediment due to discharge of coagulant

• SC&A concludes that the back application of a high 1995 sediment

survey result to bound inside subsurface activities may not be adequately supported by information for M&C worker activities from

the earlier residual period.

• Work Group concern: Insufficient information exists to address these

uncertainties, and reliance on “extreme conservatism” to bound

potentially higher or unknown exposures is not a plausible approach to compensate for inadequate or insufficient information.

5
AWE comparability

• NIOSH’s original ER position: M&C had passive exposures 

consistent with ORAUT-OTIB-0070 and Battelle-TBD-6000 

models. Compares well with other AWEs (non-SEC).

• Revised position:

• Workers identified intrusive activities for which six exposure models 

and bounding values developed.

• “Extreme conservatism” applied for M&C models to account for 

intrusive activities, high exposure conditions, uncertain facility 

activities, or unknown contamination sources (NIOSH, 2023a).

• SC&A finds M&C to be comparable to facilities with more 

intrusive activities; for example, those related to facility 

renovation as defined by NRC and found at Linde. 

6
Linde precedent: SC&A and NIOSH positions

• SC&A (2022) views Linde precedent as having two precepts, 

based on deliberations by Linde and SEC Work Groups at the 

time:

1. “Less precision or technical accuracy can be tolerated if the exposure 

of a worker cohort is relatively low.”

2. “The use of a high exposure or concentration values based on these 

data to bound or represent that of other workers in a facility or on a 

site for long time periods would not be appropriate if their exposure 

potential could be higher, conditions were different, or if there is lack 

of information upon which to make those judgments.”

• NIOSH disagrees that second precept also applies to M&C: Linde 

exposures were higher and there are more relevant source term 

data for M&C.

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Linde precedent: SC&A response

• SC&A’s (2023) response to NIOSH finds:

• Information is lacking on newly identified exposure concerns.

• D&D era source terms and conditions not clearly reflective of 

entire M&C residual period.

• Radiological controls were not in place for M&C workers, as they 

were for D&D-era workers.

• Potential exposure levels may have been relatively higher at Linde, 

but SEC question is sufficient accuracy of proposed bounding level.

• Reliance on “extreme conservatism” to compensate for 

inadequate or insufficient information may not be plausible and 

appropriate.

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Exposure potential: Confined spaces

• SC&A: 

• Confined space work at M&C not reflected in exposure modeling. 

Leads to increased dust loading and resuspension of contaminant 

particulates and aerosols.

• Surrogate use of Mound project data used for M&C dust loading 

factor does not account for confined space effects.

• NIOSH acknowledges that “potential particulate 

enhancement in confined space[s]” represents new 

information but is not a source term issue (NIOSH, 2023b). 

• This issue is unresolved.

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Exposure potential: Contaminated scale

• Accumulation of contaminated scale on inside of piping confirmed, with 

one survey exceeding 1,000,000 dpm/100 cm2 for a 4-inch mainline 

drain being cut and removed (source of contaminated scale unknown – may be covered or uncovered).

• Drain pipes were frequently cut and cleaned out with power tools and 

cutting torches.

• SC&A: Such pipe cutting may have released fine aerosols that would have been concentrated by confined spaces (trenches, pits).

• NIOSH: Responds that such contamination would have constituted “isolated hot spots” and not a systemic condition.

• Work Group finds this exposure potential remains uncertain and 

unresolved.

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Exposure potential: Coagulants 

• Mineral oil used for drawing wire in Building 10 had properties of coagulant. Upon discharge to

drainage system, M&C workers found it would frequently “plug up the drains” (NIOSH, 2017).

May have concentrated existing drain pipe sediments, including uranium and thorium.

• NIOSH (2023a): SC&A’s premise is “inaccurate” in that HFIR operations had not introduced higher

concentrations of “covered uranium and thorium from AWE operations” and “wire operations

during the residual period did not process radioactive materials.”

• SC&A: Releases of nonradioactive coagulant oil to drain lines was done separately from any HFIR

operational radioactive releases and may have influenced how AWE-related uranium and thorium

contamination already in piping would have concentrated over the years.

• Work Group finds increased exposure potential associated with higher source term

concentrations of AWE contaminants in drainage pipes remains uncertain and unresolved.

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Comparability of D&D and M&C work activity: 

Drain line removal

• NIOSH finds M&C maintenance workers used “common practices 

similar to those used by D&D workers to remove Priority 1 drain lines 

(e.g., pipe removal versus cleanout)” (NIOSH, 2023a).

• SC&A found from interviews that M&C maintenance workers likely 

handled pipe cleaning more intrusively than did D&D workers for pipe 

removal. Key difference were the “controlled” radiological work 

procedures employed in D&D compared with none for M&C 

maintenance workers.

• Are M&C inside subsurface exposures sufficiently different from other 

AWEs and D&D-related activities that normal models do not apply?

12
Comparability of M&C maintenance to D&D 

and other AWE sites

• Additional Petitioner comments submitted to the Work Group

Chair May 27, 2023:

• “D&D workers were simply cutting out the drain lines whole and intact,

sealed prior to removal, and under carefully controlled conditions.”

• M&C maintenance workers would “clear the lines using conventional

plumbing methods, and only after those efforts failed, would they cut

out the closed section of the drain as a last resort, and even then, it was

done without sealing the removed line to prevent release of any

contaminants it might have contained.”

• Work Group finds that while pipe removal by M&C maintenance

workers as compared with D&D era workers had some analogous steps, the former would have likely been more intrusive with no

radiological controls.

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Summary concerns on the subsurface model

• Intrusive work activities by maintenance workers at M&C during the residual period led to potential

exposures for which there are no available monitoring data.

• NIOSH applies 1995 D&D survey data as basis for an upper bound for residual period exposure. For

radiological data from one time period to be considered informative about exposures during another time

period, there should be sufficient similarity of conditions and processes between the two periods.

• Although NIOSH has proposed a claimant-favorable “inside subsurface” bounding concentration

(6,887 pCi/g), there remains uncertainty about source terms and exposure pathways during the residual

period, 1968–1997.

• There is insufficient information available to account for the exposure contribution of confined spaces, pipe

scale releases, and released coagulants in a workplace not controlled as a radiation environment, unlike that

of the later D&D era at M&C from which NIOSH draws its data.

• The application of “extreme conservatism” in formulating the proposed upper bound concentration to

account for “intrusive activities, high exposure conditions, uncertain facility activities, or unknown

contamination sources” is not a plausible approach to compensate for inadequate or insufficient

information.

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Proposed Work Group conclusion

• Because of the identified differences between the two 

periods (residual vs. D&D era), there is insufficient basis to 

conclude that radiological data from D&D efforts (including 

pre-D&D surveys) are sufficiently informative about 

exposures arising during the entirety of the M&C residual 

period to be applied in the manner proposed by NIOSH.

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References

National Institute for Occupational Safety and Health. (2017). Documented communication SEC-00236 with 

[Former Worker #7] on Metals and Controls Corp October 25, 2017. SRDB Ref. ID 169938

National Institute for Occupational Safety and Health. (2018). Metals and Control Corp. maintenance exposure model [White paper]. https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-metcontmaintwem-102418-508.pdf

National Institute for Occupational Safety and Health. (2023a). NIOSH response to SC&A’s supplemental review of M&C Work Group issues [Response paper]. https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-sca-mcwgissues- 508.pdf

National Institute for Occupational Safety and Health. (2023b). NIOSH’s response to SC&A’s supplemental review of M&C Work Group issues [PowerPoint slides]. M&C Work Group meeting, May 12, 2023. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/pres/2023/dc-metcontwgissues-051223-508.pdf

Petitioner. (2023, May 27). Special Exposure Cohort Petition SEC00236 [Written comments to Josie Beach, M&C 

Work Group Chair, following May 12, 2023, M&C Work Group meeting].

SC&A, Inc. (2022). Supplemental review of M&C Work Group issues (SC&A-TR-2022-SEC002, rev. 0). https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-metcontwgissues-508.pdf

SC&A, Inc. (2023). SC&A review of NIOSH response to SC&A’s supplemental review of M&C Work Group issues [Response paper]. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-reviewmetcontwgissues-508.pdf

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