Draft

Advisory Board on Radiation and Worker Health

National Institute for Occupational Safety and Health

SC&A Review of NIOSH Response to SC&A’s Supplemental 

Review of M&C Work Group Issues

Response Paper

Revision 0

Contract No. 75D30119C04183

Prepared by

Joe Fitzgerald, MS, MPH

SC&A, Inc.

2200 Wilson Blvd., Suite 300

Arlington, VA 22201-3324

April 25, 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.

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Table of Contents

1 Introduction............................................................................................................... 3

2 General Comments................................................................................................... 4

3 Specific Comments................................................................................................... 5

3.1 Finding 1: Subsurface inside (pipe sediments)................................................... 5

3.2 Finding 2: Use of Mound surrogate data ............................................................ 8

3.3 Other NIOSH comments .................................................................................... 9

4 Summary and Conclusions..................................................................................... 16

5 References ............................................................................................................. 17
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1 Introduction

At the request of the Metals and Controls Corporation (M&C) Work Group (tasked on March 3, 

2022), SC&A issued a “Supplemental Review of M&C Work Group Issues” on August 22, 2022 

(SC&A, 2022). The tasking was for SC&A to focus on any remaining lines of inquiry or 

outstanding issues relevant to the work group’s final review of the Special Exposure Cohort 

(SEC)-00236 petition evaluation report (ER) that would benefit from additional assessment. As

SC&A noted in the introduction to that review (SC&A, 2022, p. 6): 

This review is based on the available record of work group discussions, former 

worker input, and supporting documents, including NIOSH and SC&A reports, 

responses, white papers, and presentations. However, it does not represent a 

consensus among SC&A staff and is intended to be responsive to the work 

group’s request for a timely and supplemental means to inform final work group 

deliberations on M&C. It should be emphasized that in matters of interpreting 

plausibility and sufficient accuracy in the context of exposure modelling and 

bounding assumptions, there is obviously a high degree of professional judgment 

involved. The purpose of this review is to consider all such interpretations so that 

the Advisory Board on Radiation and Worker Health (Board) is in the best 

possible position to complete its review of the M&C evaluation report.

To accomplish its supplemental review, SC&A pursued three lines of inquiry:

1. Line of Inquiry 1: Are the conditions and work activities associated with the M&C 

residual period unusual or different such that (a) standard modeling procedures do not 

apply and (b) exposure potentials higher than those addressed by ORAUT-OTIB-0070, 

revision 01 (NIOSH, 2012; “OTIB-0070”), and Battelle-TBD-6000, revision 1 (NIOSH, 

2011; “TBD-6000”), and supporting exposure pathway bounding analyses may have 

resulted? 

2. Line of Inquiry 2: Are the exposure pathway bounding methods prescribed by the ER 

and subsequent National Institute for Occupational Safety and Health (NIOSH) reviews 

appropriate and consistent with how other Atomic Weapons Employer (AWE) sites have 

been addressed? 

3. Line of Inquiry 3: Are the available source term, survey data, and other information 

applied by NIOSH to support its dose bounding methods sufficiently accurate and 

plausibly applied? 

SC&A’s supplemental review had two findings and two observations (SC&A, 2022): 

• Finding 1. The back application of a high 1995 sediment survey result to bound inside 

subsurface activities is not adequately supported by information for M&C worker 

activities from the earlier residual time period.
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• Finding 2. The application of surrogate data from the Mound project to provide a dustloading factor for M&C subsurface activities does not satisfy the Board’s surrogate data 

policy. 

• Observation 1. The use of blended decontamination and decommissioning (D&D) 

characterization survey data from 1984 and 1992 to support a bounding dose for outside 

subsurface activities may not be necessarily bounding for work in nonuniform soil 

contamination, given the presence of hot spots that existed during the residual period at 

M&C.

• Observation 2. References to the M&C safety and health manual, U.S. Nuclear 

Regulatory Commission (NRC) inspection results, operator training, and other 

programmatic considerations do not necessarily substantiate the conservatism of the 95th 

percentile soil contamination value being applied. 

On January 13, 2023, NIOSH issued its response to SC&A’s supplemental review. This paper 

provides SC&A’s assessment of NIOSH’s response, organized into general and specific 

comments.

2 General Comments

NIOSH repeats the comment throughout its response to SC&A’s supplemental review that it 

does not find any “new technical information or technical justifications,” and couples that with 

the observation that NIOSH and SC&A “have done extensive work” on each issue and have 

“previously agreed” on them. 

SC&A disagrees with NIOSH’s first comment and finds the second not consistent with the 

purpose and intent of the work group’s tasking. For the M&C work group review, it is not 

apparent that anyone has previously surfaced the presence of confined spaces and their impact on 

the assumed dust loading factor and levels of airborne radioactive contaminants. No one has 

brought up the implications to drainage pipe sediment levels of coagulant wire lubricant being 

released during the residual period. And while highly contaminated scale has been mentioned, no 

one has previously raised the issue of aerosolization or volatilization of such scale during pipe 

cutting. These are among the new issues that are highlighted in SC&A’s supplemental review 

and, as noted in that report, add to the uncertainty surrounding the work activities, potential 

source terms, and exposure levels upon which NIOSH’s models for M&C are based.

While the implication is that the preceding is neither new information nor technical in nature, it

represents key questions on how available information and data are being interpreted. As for 

agreement being already achieved with SC&A, it should be noted that the two findings from this 

supplemental review address additional considerations upon which the Board may base its

judgment regarding dose reconstruction with sufficient accuracy; they are not a reassessment of 

the results of SC&A’s past reviews of proposed dose reconstruction models. 
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3 Specific Comments

Sections 3.1 and 3.2 focus on NIOSH’s response to the two supplemental review findings, 

drawing from the relevant analyses and conclusions in NIOSH’s response paper. Sections 3.3–

3.5 respond to the rest of NIOSH’s analyses and conclusions (addressing, for example, the two 

observations), which do not impact the SEC evaluation directly but influence the modelling 

assumptions being made or comparisons with other AWE sites or operations. 

3.1 Finding 1: Subsurface inside (pipe sediments)

3.1.1 Cleaning blocked drain lines – first comment

NIOSH cites an M&C worker interview that indicated they “cut the line with a snap cutter [and] 

replace[d] the line” (NIOSH, 2023, p. 2) and contends that maintenance workers during the 

residual period used “common practices similar to those used by D&D workers to remove the 

Priority 1 drain lines (e.g., pipe removal versus cleanout)” (NIOSH, 2023, p. 3). NIOSH 

interprets the M&C worker’s description as meaning those workers were not “cleaning out 

blocked drain lines,” as SC&A states, and that it “resembles the decontamination and 

decommissioning (D&D) work the health physicist describes” (NIOSH, 2023, p. 2) in a second 

worker interview quoted by SC&A and reproduced by NIOSH (2023, p. 3): 

I think that one of the differences that I would suggest is that these remediation 

workers are not handling the material inside the piping because usually it is dealt 

with in some way that it is a sealed entity. In many cases when there was piping 

or ductwork, the idea was not to take material out of it and clean it. The idea was 

to get rid of it. On the other hand, the maintenance worker’s job is to clean 

the pipe. So, I think the difference is the proximity to the source term, the 

handling of the source term, and their physical presence near the source 

term was probably a little different. [NIOSH, 2017a, p. 6; emphasis added] 

3.1.1.1 SC&A response

NIOSH’s citation of SC&A’s second interview quote (which was taken from a NIOSH interview 

summary, NIOSH, 2017a) reinforces our original comment that M&C maintenance workers 

cleaned the pipes. According to this interview, a knowledgeable worker saw a distinct difference 

between how D&D workers handled extraction of piping versus the cutting of piping as 

performed by M&C maintenance workers who were unclogging pipes. In the first quote cited, to 

“replace the line” for a M&C maintenance worker would likely still have involved “cleaning out 

blocked drain lines” before installing a new segment, entailing more handling and closer 

proximity, with the potential for higher exposure. This is consistent with commentary provided 

by another interviewee, who emphasized the contrast between the controlled manner in which 

D&D workers performed such work as compared with M&C maintenance workers (NIOSH, 

2017b, p. 6). 

3.1.2 Cleaning blocked drain lines – second comment

NIOSH (2023, p. 3) indicates that it and SC&A:

have done extensive work on the subsurface model and have previously agreed, as 

shown in the following: 
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SC&A believes the impacts of the conservatism of the assumptions applied 

to the model are greater than the impacts of the uncertainties associated 

with the material dilution and extraction. Taken in combination, SC&A 

believes that the methods and assumptions used by NIOSH to reconstruct 

internal doses to M&C workers involved in subsurface maintenance and 

repurposing activity in Building 10 during the residual period are 

scientifically sound and claimant favorable [SC&A [2021], PDF p. 15]. 

3.1.2.1 SC&A response

As pointed out in the supplemental review (SC&A, 2022), there are uncertainties associated with 

other potential exposure pathways during the M&C residual period that have not been addressed 

in past reviews of the inside subsurface model. These include those related to the presence of 

confined work spaces, the volatilization or aerosolization of contaminated scale during pipe 

cutting, and the potential concentration of drain pipe sediment due to the regular discharge of a 

known coagulant. The scientific soundness and claimant favorability of the model, as based on 

its current scoping of exposures, are not as much in question as are its full treatment of all 

potential exposure pathways, including those identified in SC&A’s supplemental review. 

Beyond the technical adequacy of the model itself is the question of its plausibility, given, as the 

former Board chairman put it for the SEC review for Linde, “we may have a bounding dose, but 

is it a plausible bounding dose, given how little information we have and the fact that most of 

these people probably weren’t engaged in the activity that we have done the dose reconstruction 

for?” (ABRWH, 2011, p. 124). Is it plausible to back apply pre-D&D sediment values over a 27-

year residual period given the lack of actual source term and monitoring data for M&C 

maintenance activities during that time period, compounded by “intrusive activities, high 

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

2023, p. 17)? 

3.1.3 Materials released into drains

NIOSH contends that the “premise in the SC&A review is inaccurate,” in that the release of 

coagulant oil during the residual period by High Flux Isotope Reactor (HFIR) operations did not 

introduce higher concentrations of “covered uranium and thorium from AWE operations (1952–

1967) to the subsurface” (NIOSH, 2023, p. 12). NIOSH also repeats its summary from the SEC 

ER of the NRC investigatory surveys that led that agency to be “satisfied that the interiors of 

Buildings 3, 4, and 10 were sufficiently decontaminated and they released Buildings 3, 4, and 10 

for unrestricted use” (NIOSH, 2023, p. 12). More specifically, NIOSH stated that “wire 

operations during the residual period did not process radioactive materials; therefore, most 

material rinsed into the drains was non-radioactive except for residual contamination that 

remained in cracks and crevices” (NIOSH, 2023, p. 12). 

3.1.3.1 SC&A response

The release of nonradioactive coagulant oil to drain lines was done separately from any HFIR 

operational radioactive releases and may have had a collateral influence on how AWE-related 

uranium and thorium contamination already in the piping would have concentrated over the 

years following those original discharges. In fact, in its response, NIOSH supports this 

interpretation by making the case that “wire operations during the residual period did not process 
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radioactive materials; therefore, most material rinsed into the drains was non-radioactive except 

for residual contamination that remained in cracks and crevices” (NIOSH 2023, p. 12). SC&A 

agrees with NIOSH that the wiring operations did not contribute radioactive materials to the 

drain lines. It was the coagulant oil itself that may have consolidated the uranium and thorium 

already entrained in the pipes (“cracks and crevices”) that would have impacted the covered 

AWE material from prior years (the resulting sediment would not have been distinguishable 

between AWE and HFIR residual contamination). The AWE sediment was clearly present within 

the system following the cessation of AWE operations; any later introduction of oil-based 

coagulant solutions within that system may have collected and concentrated the uranium and 

thorium already present in that system and led to higher sedimentation to which M&C 

maintenance workers would have been exposed. This concern represents a new issue that has not 

been addressed. 

3.1.4 Drain line contamination

NIOSH contends that cutting of drain lines with contaminated scale exceeding 1,000,000 

disintegrations per minute per 100 square centimeters (dpm/100 cm2

) would constitute “isolated 

hot spots,” not a systemic condition, and that in any case, it does not believe there is any 

evidence that even higher activity levels might have existed. (NIOSH, 2023, p. 16). NIOSH also 

notes it was a clay pipe, not a metal pipe, that showed the elevated radioactive scale.

3.1.4.1 SC&A response

NIOSH presents no evidence that this contaminated scale would not have been present elsewhere 

in the piping system, could have involved both metal and clay pipes, or that even higher activity 

levels may have been present elsewhere in the pipe network. NIOSH fails to address the source 

of this concern: the U.S. Department of Energy’s (DOE’s) Bridgeport Brass AWE hazard 

assessment, where it was warned that pipe cutting involving internal radioactive contamination 

could lead to airborne releases that may involve worker exposure (DOE, 1996, PDF p. 48). 

NIOSH’s reliance on “mass-based sample data” and “soil-sampling plans” does not address the 

simple question raised: Given that an AWE hazard assessment raised this general worker 

exposure concern, can this potential exposure pathway at M&C be characterized and bounded?

This concern represents a new issue that has not been addressed.

3.1.5 D&D measurements

NIOSH contends that it is not “back-applying conservative D&D measurements” from 1995 in 

its bounding method for subsurface inside and that it “incorporated extreme conservatism in its 

modeling to account for intrusive activities, high exposure conditions, uncertain facility 

activities, or unknown contamination sources” (NIOSH, 2023, pp. 16–17). Further, NIOSH and 

SC&A “have done extensive work on this issue” and have already agreed on a bounding method 

(NIOSH, 2023, p. 17). 

3.1.5.1 SC&A response

This appears to be inexact terminology on the part of SC&A. NIOSH is noting that compared 

with SC&A’s statement, it is actually “back-applying measurements taken by M&C and NRC 

Contractors before D&D” (NIOSH, 2023, p. 16; emphasis added). There is no disagreement, as 

that meaning was the intent of SC&A’s statement. SC&A’s use of the term “D&D” referred to 

D&D-related sampling in 1995 for characterization purposes, a meaning made clear in the first 
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sentence (and footnote) of SC&A’s review of the subsurface inside model in section 3.2.2.1 of its 

supplemental review (SC&A, 2022, p. 19). SC&A’s point, as elaborated in the supplemental 

review, is to question how confident one can be to take these 1995 survey measurements and 

apply them back over the previous 27 years of the residual period. NIOSH refers to the “extreme 

conservatism in its modeling to account for intrusive activities, high exposure conditions, 

uncertain facility activities, or unknown contamination sources” (NIOSH, 2023, p. 17), but this 

NIOSH approach employs a maximized value to compensate for the lack of any actual data for 

the period in question. When is the back application of a modeled bounding value based on a 

much later set of pre-D&D measurements plausible? For the M&C evaluation, this is ultimately 

a Board judgment and decision. Regarding previous agreement between SC&A and NIOSH, our 

earlier general comment applies: This supplemental review addresses additional considerations 

upon which the Board may base its judgment regarding dose reconstruction with sufficient 

accuracy; it is not a reassessment of the results of SC&A’s past reviews of proposed dose 

reconstruction models. 

3.1.6 Applying the 1995 sediment survey result

NIOSH (2023, pp. 17–18) clarifies that it did not use one high 1995 sediment survey result to 

create its model (in response to SC&A’s finding that “the back application of a high 1995 

sediment survey result to bound inside subsurface activities is not adequately supported by 

information for M&C worker activities from the earlier residual time period” (SC&A, 2022, 

p. 23)). 

3.1.6.1 SC&A response

SC&A’s finding is directed at the bounding value adopted by NIOSH, based on the 95th 

percentile equivalent of 6,888 picocuries per gram (pCi/g), which is clearly based on the 1995 

pre-D&D survey measurements.

3.2 Finding 2: Use of Mound surrogate data

3.2.1 Site characterization

NIOSH observes that SC&A’s characterization of potential confined spaces at M&C (various 

manholes, trenches, pits, and vault spaces) is not clear on what vault spaces are being referred to 

and believes manholes would not be a significant source term problem (NIOSH, 2023, p. 21). 

3.2.1.1 SC&A response

To clarify, vault spaces are typically concrete enclosures used to surround large pieces of 

equipment or utility areas. Regarding NIOSH’s comment about manholes, SC&A simply 

identified all the obvious confined spaces at M&C and made the statement: “it is not apparent 

how the Mound project addressed considerations related to resuspension or dust loading in a 

confined space, such as the various manholes, trenches, pits, and vault spaces at M&C in which 

maintenance workers actively worked” (SC&A, 2022, p. 31). As emphasized in former worker 

interviews, it was not uncommon to be working in a trench doing routine utility repairs or pipe 

cleanouts for days and up to a week (NIOSH, 2017c, pp. 1–2). One installation project in 

Building 10 involved the cutting out of an existing drain line and installation of new equipment, 

piping, and large tanks, necessitating a trench 100 feet long, with a depth of 8–10 feet in places, 

that was worked in for 6 months in 1983–1984 (NIOSH, 2017d, p. 11). NIOSH does not respond 
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to the central question posed: In applying the Mound surrogate data to derive a dust loading 

factor, did they address confined space considerations? From a larger perspective, did they 

consider the impact of confined spaces on their modeled airborne resuspension of uranium and 

thorium? The answer appears to be “no” in both cases. Confined spaces represent a new issue 

that has not been addressed. 

3.2.2 Surrogate data

NIOSH cites SC&A’s finding 2 (that surrogate data from the Mound project do not satisfy the 

Board’s surrogate data policy) but does not respond directly. NIOSH merely observes that it has 

committed to revisit OTIB-0070 in terms of how surrogate data are applied at other sites and 

cites the previous SC&A conclusion that while the Mound data can be applied, they may not be 

sufficiently conservative due to other factors (e.g., moisture of soil, dust loading variables). 

NIOSH, while indicating that it will consider SC&A’s previous points, concludes it “did not find 

where SC&A provided any new technical information or technical justification to indicate why 

the proposed approach is not considered bounding” (NIOSH, 2023, p. 22). 

3.2.2.1 SC&A response

NIOSH did not respond to the finding. Instead of addressing whether confined space issues 

would make a difference in applying the Mound data to M&C exposure pathway modeling and if 

so, how that could be mitigated in resulting dust loading and other airborne concentration 

estimates, NIOSH does not provide a direct answer. Instead, what is provided is an account of a 

past NIOSH and SC&A exchange where it is acknowledged that the dust loading factors in 

OTIB-0070 will need to be “uniquely evaluated at each site” and that “one size will not fit all” 

(NIOSH, 2023, pp. 21-22). NIOSH’s proposed application of Mound project data for deriving 

the M&C dust loading factor does not satisfy the Board’s surrogate data policy for site and 

process similarity given disparities between the sites for confined space conditions. This is a new 

concern that bears on the technical accuracy and plausibility of NIOSH’s model.

3.3 Other NIOSH comments

Sections 3.3.1–3.3.8 address the balance of NIOSH’s responses for the two SC&A observations 

and other issues.

3.3.1 Controlled D&D and typical maintenance work

NIOSH objects to SC&A’s quoting of a former worker to characterize the intrusiveness of M&C 

maintenance work because the health physicist cited was “not present during maintenance work” 

(NIOSH, 2023, p. 4). NIOSH then provides interview quotes from other M&C maintenance 

workers to refute or qualify the statements of that health physicist and to illustrate that 

contamination monitoring was being performed and maintenance workers were performing work 

under a sound safety and health program. NIOSH concludes that “the statement in SC&A’s 

supplemental review might incorrectly lead the reader to believe that Texas Instruments found

spreading dust clouds of contamination throughout the plant to be an acceptable practice” 

(NIOSH, 2023, p. 6). However, NIOSH also makes the qualifying statement that “NIOSH 

acknowledges that some aggressive activities briefly resulted in a dusty environment and 

elevated exposure” (NIOSH, 2023, p. 6).
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3.3.1.1 SC&A response

SC&A’s only purpose in presenting alternate points of view from worker interviews was to 

provide a more diverse commentary on plant conditions during the residual period.1

1 SC&A does not judge the validity of interviewee comments at face value but accepts them as individual 

perspectives based on unique experience, some of which may not be apparent to an outside reviewer. For 

clarification, it may be useful to re-interview the health physicist in question to reconcile their commentary and 

experience with that of the other workers interviewed by NIOSH.

The 

interviewee’s comment was simply intended to contrast what that worker understood as the 

difference between the work environment during Texas Instruments-managed D&D-related 

activities (“controlled”) and that of M&C maintenance activities (“uncontrolled, unconfined, 

aggressive”) (NIOSH, 2017a, pp. 4–5). Clearly, recollections back over the decades by former 

maintenance workers and other personnel can and do often vary. However, NIOSH’s final 

statement admitting “some aggressive activities briefly resulted in a dusty environment and 

elevated exposure” is the salient one before the work group. Such intrusive work at close 

proximity within ditches and pits would have exposed M&C maintenance workers to not only 

resuspended dust but also volatized aerosols and fumes from welding and machine tool cutting of 

contaminated piping, all of which would have been concentrated by confined spaces. This is the 

context of SC&A’s citation of the interview comment, not to characterize how Texas Instruments 

may have managed its contamination control program. 

3.3.2 Routine equipment maintenance

NIOSH clarifies that its equipment discussion is related to “tasks when workers penetrated the 

concrete floor, accessed the subsurface, or went into the overhead to make connections” 

(NIOSH, 2023, p. 7). It is further clarified that “a few substantial pieces of equipment were left 

in place with residual contamination in inaccessible locations” (NIOSH, 2023, p. 7). 

3.3.2.1 SC&A response

SC&A’s question, here, regards the repurposing of M&C equipment, which does not appear to 

be addressed in terms of covered exposure to M&C workers performing later maintenance on 

that equipment during the residual period. While the SEC-00236 ER does cite the contamination 

surveys performed and that a few substantial pieces of equipment were left in place with residual 

contamination in inaccessible locations, NIOSH does not address whether later repurposing of 

M&C equipment may have led to exposures to the workers performing the repurposing and 

whether later maintenance on such equipment would have been a potential exposure pathway. 

3.3.3 Intrusive nature of maintenance work

NIOSH contends that the “intrusiveness” of work at M&C ought to be judged in terms of 

“applying standard industrial hygiene or nuclear industry resuspension factors to a source term” 

(NIOSH, 2023, p. 8). NIOSH also observes that Norton Co. and Vitro Manufacturing were not 

added to the SEC because of the intrusiveness of their activities, and that the “source term at the 

Linde Ceramics Plant was considerably larger than M&C’s” (NIOSH, 2023, p. 10). It was also 

observed that the only data NIOSH could use in the Linde SEC-00107 ER were “air samples 

taken during jackhammering,” and that NIOSH’s approach for Linde was unlike that for M&C 

because for M&C NIOSH had developed “separate models of the highest maintenance exposure 
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scenarios, using scenario-specific pre-D&D data, which resulted in much smaller doses 

(71 mrem/yr CED [millirem per year committed effective dose])” (NIOSH, 2023, p. 10). 

3.3.3.1 SC&A response

The use of the standard exposure model for M&C, as founded on OTIB-0070 and TBD-6000 and 

complemented by exposure pathway bounding, can be predicated on no work activities during 

the residual period being so intrusive or disruptive that they would have “altered the materials 

present and placed employees close to the disturbed materials”2

2 This criterion was cited for the SEC-00173 evaluation of the Norton Company AWE.

(NIOSH, 2020, slide 7). If such 

activities “briefly resulted in a dusty environment and elevated exposure” as acknowledged by 

NIOSH (2023, p. 6), the question becomes whether that level of exposure can be characterized 

and bound by an approach that presupposes more passive exposures (i.e., OTIB-0070 and 

TBD-6000) but requires six bounding models to address intrusive activities at M&C. 

This is compounded by additional uncertainties identified by SC&A’s supplemental review: 

confined space concentration of particulates and gases, potential coagulant concentration of pipe 

sediments, and release of contaminated scale from pipe cutting. Even the brevity of exposure is 

open to question, given feedback from M&C maintenance workers that they performed work in 

trenches for up to a week at a time and in one case, for up to a 6-month period, all under 

confined space conditions. While the question of how intrusive work activities may have been at 

M&C is obviously a subjective one, SC&A believes there is clear evidence that maintenance 

activities during the M&C residual period were unique in terms of their level of intrusiveness 

(excavations, pipe cleaning, pipe cutting), work environments (confined spaces), and uncertain 

or unknown source terms (contaminated pipe sediments, presence of coagulants, contaminated 

scale, confined space concentration of airborne particulates). While other AWE sites, such as 

Carborundum and Dow Madison had residual work activities (e.g., welding, torch-cutting, soil 

excavation) similar to those of M&C maintenance workers, the difference is the aforementioned 

level of intrusiveness and uncertain or unknown source terms. Ultimately, NIOSH acknowledges 

the “high exposure conditions” and “unknown contamination sources” that may have been

associated with such M&C intrusive activities (NIOSH, 2023, p. 17) in developing its bounding 

models. 

3.3.4 NRC regulatory direction

NIOSH acknowledges that hot spots identified during the burial ground remediation were higher 

than 30 pCi/g, but that “NIOSH’s statement was explicitly about the airline installation process” 

(NIOSH, 2023, p. 18). Further, “NIOSH does not construe the lack of NRC regulatory direction 

to signify the elevated levels were merely above background, but less than release criteria 

(30 pCi/g), as SC&A states,” but that “when M&C reviewed documented surveys of the airline 

debris, M&C determined those contamination levels to be below applicable NRC release 

criteria” (NIOSH 2023, p. 18). 

3.3.4.1 SC&A response

SC&A accepts NIOSH’s clarification of this issue.
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3.3.5 Blended D&D characterization survey data 

In response to SC&A’s observation 1, regarding the use of blended D&D characterization data, 

NIOSH notes that the 95th percentile is applied as opposed to a maximum value for hot spots, 

given that they are limited exposures and not a normally expected condition (NIOSH, 2023, 

p. 20). 

3.3.5.1 SC&A response

SC&A accepts NIOSH’s clarification of this issue given the availability of soil measurements.

3.3.6 95th percentile

NIOSH responds to SC&A’s observation 2 by noting that it was not using the M&C safety and 

health manual, NRC inspection results, operator training, and other programmatic considerations 

to justify using the 95th percentile (NIOSH, 2023, p. 23). 

3.3.6.1 SC&A response

NIOSH appears to misunderstand the essence of this observation. As noted in the basis for 

SC&A’s observation 2 (SC&A, 2022, p. 37): 

The claim “that M&C’s area monitoring assures that the 95th percentile soilcontamination value is conservative based on routine surveys of Building 10 

during the first 14 years of the residual period (1968-1981)” (NIOSH, [2021], 

pp. 7–8) is not necessarily substantiated by the assumed strength of the M&C 

radiological surveillance program. Without corroborating accounts or evidence 

regarding the actual implementation of non-HFIR workplace contamination 

surveillance procedures at M&C, assurance cannot be placed solely on typical 

HFIR-specific survey results or the assumed implementation of procedural 

requirements such as the M&C safety manual or NRC inspection requirements. 

[Emphasis added.] 

Whether using these program documents to justify, or to demonstrate, corroborate, illustrate, or 

show that such monitoring procedures and oversight “assures” that the 95th percentile soil 

contamination value is conservative is a distinction with little difference. SC&A stands by its 

observation that the program references NIOSH cites “do not necessarily substantiate the 

conservatism of the 95th percentile soil contamination value being applied” (SC&A, 2022, 

p. 37). 

3.3.7 NIOSH’s response to SC&A’s conclusion comment

NIOSH first cites SC&A’s conclusion:

Precedent suggests that while less precision or technical accuracy can be tolerated 

if the exposure of a worker cohort is relatively low, 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. As noted in the Board’s 

deliberations on the Linde residual period, the question of where to draw the line 
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for applying such bounding constructs is a subjective one, weighing the precision 

(or accuracy) of the bounding assumption and data, as well as the plausibility of 

their application to the target worker population. [SC&A, 2022, p. 36] 

NIOSH then appears to parse SC&A’s conclusion, citing the low exposure precept and 

attributing it to M&C, followed by the application of a “high exposure” for bounding purposes, 

and attributing it to the Linde case. NIOSH finds that the Linde case does not apply to M&C 

because the potential exposure level is much higher (5,479 mrem/yr CED). NIOSH goes on to 

note that it has a “more complete data set” with which to work for M&C and a better 

understanding of M&C work processes than it did with Linde (NIOSH, 2023, p. 24). 

3.3.7.1 SC&A response

In its conclusion, SC&A is not referring to a specific value (e.g., Linde’s), but any site 

monitoring data not related to the actual operations in question being back extrapolated over a 

long period of time with a formulation that is made ultra conservative to compensate for the lack 

of data and to address the inherent uncertainties and unknowns of that approach. These policy 

approaches, and his concerns about them, were articulated more fully by Dr. James Melius, 

former chair of the Board, in the Linde proceedings. As the Chair stressed in that discussion, 

when information is lacking for affected worker populations, the application of generalized 

bounding doses, no matter how maximized, may not be appropriate (ABRWH, 2011, pp. 121–

123). As the Chair explained: 

To me, the lack of information — and we have no sampling data during this 

renovation time period. We have very little information on what was done at the 

site during this time period and who was involved, and how many people were 

involved, that it seems to me that [it] is just as appropriate to be designated a 

Special Exposure Cohort. 

I think putting it into our terms, we may have a bounding dose, but is it a 

plausible bounding dose, given how little information we have and the fact that 

most of these people probably weren’t engaged in the activity that we have done 

the dose reconstruction for? [ABRWH, 2011, pp. 123–124] 

As noted in the supplemental review, this statement suggests that the use of a high exposure or 

concentration value based on a later set of specific workplace data to bound or represent that of 

earlier workers in a facility or on a site, particularly over a lengthy time period, would not be 

appropriate if their exposure potential could be higher, work conditions were different, or if there 

is lack of information upon which to make that judgment. Regarding conservatism, while any 

measurement can be made extremely conservative by the multiple layering of favorable 

assumptions and statistical 95th percentile values, the Board’s original question remains: Where 

do we draw the line with the application of bounding values? (SC&A, 2022, p. 30). 

3.3.8 NIOSH’s response to lines of inquiry conclusions

3.3.8.1 Line of inquiry 1

Are the conditions and work activities associated with the M&C residual period 

unusual or different such that (a) standard modeling procedures do not apply and 
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(b) exposure potentials higher than those addressed by OTIB-0070 and TBD-6000 

and supporting exposure pathway bounding analyses may have resulted? [SC&A, 

2022, p. 7] 

SC&A’s supplemental review compared AWE sites (as illustrated in table 1 of the report) and 

found that: 

The active and intrusive nature of the described maintenance work at M&C 

during the residual period clearly exceeded the residual period conditions and 

activities at other AWEs, as described in their corresponding evaluation reports 

and site profiles, and what would be assumed under OTIB-0070 for application of 

its resuspension and volumetric soil values. It falls within the continuum of postoperational intrusive activities ranging from Norton and Vitro (very active, D&Dlike activities) to that of Linde (renovation activities), with M&C being closer to 

the latter, but without the radiological protection controls, protective equipment, 

and personnel monitoring that were typical of formal D&D programs. [SC&A, 

2022, p. 14] 

Based on where such intrusive activities would have “altered the materials present and placed 

employees close to the disturbed materials” (NIOSH, 2020, slide 7), the standard exposure 

model, as founded in OTIB-0070 and TBD-6000 and complemented by exposure pathway 

bounding, may not be sufficiently accurate or complete. At M&C during the residual period, 

maintenance workers conducted intrusive work activities, including cutting pipes containing 

contaminated scale, cleaning out contaminated pipe sediment, performing subsurface 

construction, and providing maintenance support for utilities in various subsurface, confined 

spaces for sometimes extended periods of time. Unlike D&D workers, M&C maintenance 

workers were unaware of the radiological contamination and conducted these activities with no 

radiological control program implemented, no apparent health physicist presence, and no 

radiological control oversight.

While NIOSH claims that it has “demonstrated that M&C exposure potentials are not higher than 

those addressed by ORAUT-OTIB-0070 and ORAUT-TBD-6000” (NIOSH, 2023, p. 11), it has 

not fully considered potential exposure pathways attributable to the intrusive nature of M&C 

maintenance work, with new issues identified by SC&A’s supplemental review such as confined 

space atmospheres, coagulant oil discharges, and airborne releases of contaminant scale during 

pipe cutting. This is in addition to the six exposure models that have been deemed necessary to 

bound intrusive activities at M&C that could not be addressed under OTIB-0070 and TBD-6000. 

It appears the solution to these unknown or uncertain exposure potentials is that NIOSH has 

“incorporated extreme conservatism in its modeling to account for intrusive activities, high 

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

2023, p. 17). The work group will need to judge whether such “extreme conservatism” in the 

service of NIOSH’s bounding analyses can be considered plausible given the level of uncertainty 

and lack of information about M&C maintenance worker exposure during the residual period. 
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3.3.8.2 Line of Inquiry 2

Are the exposure pathway bounding methods prescribed by the ER and 

subsequent NIOSH reviews appropriate and consistent with how other AWE sites 

have been addressed? [SC&A, 2022, p. 7] 

SC&A examined (1) whether the NIOSH bounding approach for exposure pathways applied to 

M&C is consistent with past practice and precedent for AWE residual periods, and (2) whether 

dose reconstruction methods for these pathways can be considered plausible and sufficiently 

accurate. Like other AWEs, M&C had residual contamination resulting from earlier uranium and 

thorium operations, and work activities that were similar. However, the nature of some of the 

M&C maintenance activities differed by the degree of its intrusiveness, which placed some 

workers in close proximity to elevated contamination sources in normally inaccessible locations. 

As already noted, SC&A found several new issues that bear on the potential exposure of M&C 

maintenance workers that bring into question the bounding approach for subsurface inside 

exposures, leading to finding 1. 

While NIOSH contends its exposure pathway bounding methods are appropriate and consistent 

with how other AWE sites are addressed, it does not address the increased exposure potential 

posed by confined space atmospheres, nor does it adequately consider the implications of 

coagulant oil discharges and airborne contaminant scale releases to its subsurface inside 

exposure pathway analyses. The necessity of complementing the normal application of OTIB0070 and TBD-6000 with six exposure pathway models that incorporate “extreme conservatism” 

to address these and other uncertain or unknown exposures at M&C sets it apart from how other 

AWEs have been addressed in the past. 

3.3.8.3 Line of Inquiry 3

Are the available source term, survey data, and other information applied by 

NIOSH to support its dose bounding methods sufficiently accurate and plausibly 

applied? [SC&A, 2022, p. 7] 

A guiding principle that NIOSH follows for addressing the “uncertainty around the work 

performed” or the “complete understanding of the work performed” is that it is “NOT an issue 

when the bounding doses are very low, and specifically, during AWE residual periods such as at 

M&C” (NIOSH, 2020, slide 14). However, as pointed out by SC&A’s supplemental review, the 

question of determining a bounding dose in the absence of sampling data during the AWE 

residual period and applying sufficient conservatism to it is not without precedent and carries 

with it the question of plausibility. As pointed out during the Board’s Linde review, if “carried to 

an extreme, we could take any site . . . and we could come up with what we think is the highest 

possible exposure at that site that would occur, and that would be bounding, and apply that to 

everybody that ever worked at the site” (ABRWH, 2011, p. 129). However, the essential 

questions, as the former Board Chair put it, are “is that a plausible bound? And then, who are we 

trying to characterize?” (ABRWH, 2011, p. 129). 

NIOSH’s response, that it has “incorporated extreme conservatism in its modeling to account for 

intrusive activities, high exposure conditions, uncertain facility activities, or unknown 

contamination sources” (NIOSH, 2023, p. 17) at M&C for the residual period, raises the very 
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concern raised by Dr. Melius during the Linde AWE proceedings that contributed to the Board’s 

decision on that SEC evaluation. In the absence of source term and monitoring data for the 

facility time period in question, is it plausible to incorporate what NIOSH terms “extreme 

conservatism” in its bounding value for inside subsurface exposures based on information from a 

much later time frame (27 years), from a different operation (pre-D&D), and with different work 

conditions when attempting to address what NIOSH terms “intrusive activities, high exposure 

conditions, uncertain facility activities, or unknown contamination sources”? (NIOSH, 2023, 

p. 17)? 

While NIOSH notes that M&C dose estimates are relatively low and it has “a more complete 

data set to characterize M&C and a better understanding of M&C maintenance work than we had 

with Linde” (NIOSH, 2023, p. 24), it has not addressed the increased exposure potential posed 

by confined space atmospheres, nor does it similarly consider the implications of coagulant oil 

discharges and airborne contaminant scale releases to its exposure pathway analyses. NIOSH 

may claim that the extreme conservatism of its modeling would bound even these exposure 

pathways, but in the absence of validating information, such a claim may be considered by the 

work group to be unfounded and implausible. 

4 Summary and Conclusions

SC&A was tasked by the M&C Work Group to focus on any remaining lines of inquiry or 

outstanding issues relevant to the work group’s final review of the SEC-00236 ER that would 

benefit from additional assessment. The supplemental review pursued several new issues that 

heretofore had not received attention. This has led to two findings that derive from SC&A’s 

premise as stated in its review: “The use of a high exposure or concentration value based on a set 

of specific workplace [pre-D&D sediment] data to bound or represent that of other workers in a 

facility or on a site, particularly over a lengthy time period, would not be appropriate if their 

exposure potential could be higher, conditions were different, or if there is a lack of information 

upon which to make that judgment” (SC&A, 2022, p. 36). 

Finding 1 is that “the back application of a high 1995 sediment survey result to bound inside 

subsurface activities is not adequately supported by information for M&C worker activities from 

the earlier residual time period” (SC&A, 2022, p. 36). NIOSH’s disputes that coagulant oil could 

have introduced higher concentrations of covered uranium and thorium from AWE operations 

into the drains, a response that SC&A finds does not comport with the possible physical and 

chemical reactions that this known coagulant may have had on already entrained uranium and 

thorium in the cracks and crevices of the M&C drainage system. NIOSH disputes, without 

evidence, that cutting of drain lines with contaminant scale found to exceed 1,000,000 dpm/100 

cm2

 is a systemic issue for M&C exposure potential, notwithstanding DOE’s emphasis on this 

exposure concern in its hazard assessment for the Bridgeport Brass AWE. NIOSH questions the 

distinction SC&A draws between how the exposure potential of D&D workers is smaller 

compared with M&C maintenance workers when performing pipe cutting and removals but 

references a worker account that supports the interpretation that the latter’s job is also to clean 

the pipe prior to repair (versus removal for D&D), and that, therefore, there would have been a 

difference in physical proximity and source term. NIOSH did not address the impact of confined 

space atmospheres on its bounding exposure assumption for inside subsurface work, such as 
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drain line cleaning, despite there being scientific evidence that this would have likely led to 

higher airborne concentrations of radioactive contaminants and intakes. 

Apropos to this confined space issue is SC&A’s finding 2, that the “application of surrogate data 

from the Mound project to provide a dust loading factor for M&C subsurface activities does not 

satisfy the Board’s surrogate data policy” (SC&A, 2022, p. 37). NIOSH does not address the 

central question of the likely impact posed by confined space atmospheres but instead dismisses 

the review as not providing “any new technical information or technical justifications to indicate 

why the proposed approach is not considered bounding” (NIOSH, 2023, p. 22). 

NIOSH’s generic response, as stated in the preceding quote and repeated throughout its report, 

appears to key on two threshold criteria for what information it deems is acceptable for the work 

group to consider. First, that any new information or justification apparently needs to be 

“technical” to be valid, without explaining how that is defined in this context. Second, that this 

same information needs to justify why NIOSH’s modeling approach is not bounding. On matters 

of dose reconstruction with sufficient accuracy, including the basis and application of bounding 

exposure values, it is the Board that ultimately weighs the scientific validity of information it 

chooses to consider in its SEC deliberations on such matters and whether NIOSH’s justification 

based on “reliable science, documented experience, and relevant data” (Methods for Radiation 

Dose Reconstruction, 2002, p. 22332) is similarly adequate. On such matters, the burden of 

justifying its bounding approach belongs to NIOSH. Obviously, the work group can request that 

NIOSH provide additional justification in light of new information that brings into question the 

accuracy, conservatism, or plausibility of its approach. 

SC&A’s role in response to its tasking was to inform work group deliberations by identifying 

“any remaining lines of inquiry or outstanding issues” that needed to be addressed by the M&C 

work group (SC&A, 2022, p. 6). It has done so in a deliberate manner by applying its three lines 

of inquiry and identifying remaining issues that were not addressed or not fully considered in 

previous NIOSH and SC&A reviews.

5 References

Advisory Board on Radiation and Worker Health. (2011). 75th meeting Thursday February 24, 

2011 [Transcript]. https://www.cdc.gov/niosh/ocas/pdfs/abrwh/2011/tr022411.pdf 

Methods for Radiation Dose Reconstruction under the Energy Employees Occupational Illness 

Compensation Program Act of 2000, 67 Fed. Reg. 22314 (May 2, 2002) (to be codified at 

42 CFR pt. 82). https://www.cdc.gov/niosh/ocas/pdfs/42cfr82/42cfr82.pdf

National Institute for Occupational Safety and Health. (2011). Site profiles for Atomic Weapons 

Employers that worked uranium metals (Battelle-TBD-6000, rev. 1). 

https://www.cdc.gov/niosh/ocas/pdfs/tbd/bat-6000-r1.pdf

National Institute for Occupational Safety and Health. (2012). Dose reconstruction during 

residual radioactivity periods at Atomic Weapons Employer facilities (ORAUT-OTIB-0070, 

rev. 01). https://www.cdc.gov/niosh/ocas/tibsnum.html#tib70
Effective date: 4/25/2023 Revision No. 0 (Draft) Response Paper Page 18 of 18

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.

National Institute for Occupational Safety and Health. (2017a). Documented communication 

SEC-00236 with [Former Worker #3, joined by Former Worker #4] on Metals and Controls Corp 

October 24, 2017. SRDB Ref. ID 169925 

National Institute for Occupational Safety and Health. (2017b). Documented communication 

SEC-00236 with [Former Worker #3] on Metals and Controls Corp October 24, 2017. SRDB 

Ref. ID 169920 

National Institute for Occupational Safety and Health. (2017c). NIOSH notes October 24 – 26, 

2017: Interviews for Metals and Controls [DCAS external memorandum to Metals and Controls 

SEC Working Group]. SRDB Ref. ID 192920 

National Institute for Occupational Safety and Health. (2017d). 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. (2020, September 2). SEC-00236 Metals 

and Controls Corp. NIOSH response to working group comments [PowerPoint presentation to 

the Metals and Controls Corp. Work Group]. https://ftp.cdc.gov/pub/FOIAREQ/182969-508.pdf 

National Institute for Occupational Safety and Health. (2021). Response to comments from the 

Metals and Controls Corp. Work Group meeting held on September 2, 2020 [Response paper]. 

https://ftp.cdc.gov/pub/FOIAREQ/184642_red-508.pdf 

National Institute for Occupational Safety and Health. (2023). 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 

SC&A, Inc. (2021). Metals and Controls Corp. exposure pathway evaluation (SC&A-TR-2021-

SEC004, rev. 0). SRDB Ref. ID 190928 

SC&A, Inc. (2022). Supplemental review of M&C Work Group issues (SCA-TR-2022-SEC002, 

rev. 0). https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-metcontwgissues-508.pdf 

U.S. Department of Energy. (1996). Hazard assessment for the General Motors site, Adrian, 

Michigan (DOE/OR/21950-1017). SRDB Ref. ID 14422