Review of Overall NIOSH 

Response and SEC Issues under 

Consideration for M&C

Joe Fitzgerald, MS, MPH

Bob Barton, CHP

Advisory Board on Radiation and Worker Health, M&C 

Work Group

December 6, 2023
2

Chronology

 March 3, 2022: M&C Work Group tasked SC&A to focus on any remaining lines of 

inquiry or outstanding issues relevant to work group’s review of SEC-00236 evaluation 

report

 August 22, 2022: SC&A issued supplemental review based on:

– Record of work group discussions

– Former worker input

– Supporting NIOSH and SC&A reports, responses, white papers, and presentations

 January 13, 2023: NIOSH issued response paper to SC&A’s supplemental review

 April 25, 2023: SC&A issued review of NIOSH response

 May 12 and July 13, 2023: M&C Work Group meetings

 August 22, 2023: NIOSH issued response to SC&A’s April 2023 review
3

SC&A supplemental review: Findings and 

observations

 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 period.

 Finding 2: The application of surrogate data from the Mound project to provide a dustloading factor for M&C activities does not satisfy the Board’s surrogate data policy.

 Observation1: The use of blended 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, NRC inspection 

results, operator training, and other programmatic considerations do not necessarily 

substantiate the conservatism of the 95th percentile soil contamination value being 

applied.
4

Intrusive nature of M&C maintenance work

 M&C maintenance activities 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 and scale, presence of 

coagulants, repurposed equipment).

 Like Linde Ceramics, M&C better fits 

“building renovation” scenario under 

NUREG/CR-5512 (NRC, 1992) than it 

does “building occupancy” scenario that 

typifies OTIB-0070 resuspension 

assumptions for other AWEs.

 NIOSH responds that “intrusiveness” 

should be judged “applying standard 

industrial hygiene or nuclear industry 

resuspension factors to a source term” 

and that the “source term at the Linde 

Ceramics Plant was considerably larger 

than M&C’s” (NIOSH, 2023a).

 SC&A agrees M&C dose levels are 

relatively low compared with some SEC 

sites but are comparable to others 

(e.g., Pantex, Blockson, Sandia).
5

Concern with subsurface inside bounding 

concentration: Presence of coagulants

 A vegetable-based mineral oil that was used in Building 10 for drawing 

wire had the properties of a coagulant. Upon discharge to the drainage 

system, M&C workers found it would frequently “plug up the drains” 

(ORAUT, 2017).

 The discharged oil may have consolidated and concentrated drainpipe 

sediments, including existing AWE uranium and thorium.

 Question: During active Building 10 operations (through 1981), would 

regular releases of coagulants have led to more frequent and substantial 

blockages, involving elevated uranium and thorium as a function of the 

consolidation properties of the coagulant oil on sediments?
6

Presence of coagulants: NIOSH updated 

(August 2023) response

 As part of TBD updating, NIOSH will:

– Identify locations of wire machines in Building 10 and overlay their locations above the drain

lines to indicate distance from Priority 1 drain lines.

– Mark up drain lines with flow paths to determine which lines were downstream of coagulant

sources

 NIOSH will also consider that:

– Weston could have noted and collected coagulant when they characterized drain lines

– Airborne hazard associated with cleaning clogged pipes minimal because material was wet;

coagulants functioned as glue, reducing resuspension and respirability of source term

– No information found in literature supporting solvent properties of vegetable/mineral oils that

made up coagulant

 NIOSH determined it can bound exposures associated with unclogging pipes while 

accounting for effects of nonradioactive coagulant to the drain line source term
7

Presence of coagulants: SC&A response

 Whether or not Weston would have identified and collected coagulant during characterization does 

not comport with coagulant mechanism: They are substances that serve to neutralize normally 

repulsive electrical charge of sediments in solution such that they can consolidate, forming floc.

 Coagulants are not “sticky” or function as “glue” (NIOSH, 2023b).

 Whether specific coagulant involved had “solvent” properties is speculative: Specific chemical and 

physical properties of coagulant, fixed contamination, and liquid within drain pipes are not known.

 However, what is clear: During M&C residual period, drain pipes contained both in-solution 

suspended sediments and fixed sediment contamination of varying degrees, for which regular 

introduction of oil-based coagulant was know by M&C workers to cause the blockage of drain 

pipes, requiring cleanout.

 SC&A concludes that presence of coagulant oils within the M&C drainage system may have led to 

increased concentrations of uranium- and thorium-contaminated sediments for which upper bound 

exposure estimates may not be feasible.
8

Concern with aerosolization of contaminated 

scale

 Accumulation of contaminated scale on inside of piping confirmed, with one survey of 

interior surface contamination exceeding 1,000,000 dpm/100 cm2 for a 4-inch vitreous 

clay mainline drain being cut and removed.

 During M&C residual period, drain pipes were frequently cut, repaired, replaced, and 

cleaned out, using power tools such as saws, drills, grinders, and powered snakes, as 

well as cutting torches.

 As noted by DOE in its hazard assessment of Bridgeport Brass AWE, “the residual 

uranium could eventually be released . . . through intrusive work activities such as pipe 

cutting and removal,” and that “it is possible that under certain conditions (such as 

cutting through a steel pipe with a cutting torch) surface activity attached to the steel 

could be released with the steel particles” (DOE, 1996).

 Such pipe cutting may have released fine aerosols that would have been concentrated 

by the confined space (trenches, pits) atmospheres where such work was performed.
9

Aerosolization of contaminated scale: NIOSH 

updated response

 NIOSH considers snap cutting or sawing more routine than torch cutting of steel pipes.

 NIOSH did not select cutting of drain lines as a bounding scenario for M&C, in contrast to the 

Bridgeport Brass hazard assessment concern with cutting of steel drain lines.

 NIOSH reviewed the exposure assessment in DOE’s model and found that the ratio of assigned 

doses to source term level for Bridgeport Brass compares favorably to M&C.

 NIOSH notes that the 1,000,000 dpm/100 cm2 was not for “scale” but for interior pipe surface 

contamination, and that it was for a vitreous clay pipe, not cast iron. NIOSH notes that scale and 

rust are associated with cast iron pipes.

 Regarding whether contaminated scale deposits are an isolated or systemic source term, NIOSH 

“relies on available source-term data because of the comprehensiveness exercised by Weston and 

Texas Instruments” (NIOSH, 2023b). Illustrative interior pipe “scale” survey data provided.

 NIOSH performed a dose assessment based on the source term calculation model in the 

Bridgeport Brass hazard assessment, using the 1,000,000 dpm/cm2 survey measurement. 
10

Aerosolization of contaminated scale: SC&A 

response

 M&C workers used wide array of powered tools to cut and clean out pipes. These 

mechanized tools would have volatilized and suspended fine particles and fumes. Torchcutting example from Bridgeport Brass AWE was highlighted by SC&A in its 

supplemental review to substantiate exposure pathway involved with cutting pipes with 

in-pipe surface contamination (scale).

 Comparative use of Bridgeport Brass pipe and surface contamination parameters for 

modeling M&C exposure is problematic: M&C had different or uncertain conditions, 

processes, source terms, and surface contamination thickness.

 NIOSH’s conclusion on scale only being associated with cast iron pipes is not 

corroborated: 1,000,000 dpm/100 cm2 in-pipe surface contamination was found in 

vitreous clay mainline pipe.

 NIOSH appears to lack sufficient and representative survey data for in-pipe contaminant 

scale (or interior pipe surface contamination) to provide an adequate basis for an upper 

bound source term.
11

Aerosolization of contaminated scale: NIOSH 

survey data and SC&A response 

 NIOSH: Caged Area (Areas 1 and 4) – typically less than 3,000 dpm/100 cm2

SC&A: Survey data from “near-surface recirculation piping,” not drain pipes (Weston 1996)

 NIOSH: Locations 4 and 5, supporting assay laboratories – concentration of 500 pCi/g total U

SC&A: Specific to only one Building 10 activity

 NIOSH: Areas 3 and 4 – total uranium concentration of 1,864 pCi/g

SC&A: Represents total loose pipe sediment and debris, not just scale 

 NIOSH: Reliance on “beta scintillator data” to represent scale activity

SC&A: Beta scintillator used to identify, not quantify, scale activity; Weston emphasized limitations 

of any direct measurements given pipe surface irregularities, geometry, presence of blockages and 

liquids

 NIOSH: Reliance on Weston methodology for “hypothetical dose and exposure rate” (Weston 

1997)

SC&A: May not be sufficiently accurate for bounding source term for scale
12

Aerosolization of contaminated scale, 

NIOSH exposure model calculation 

 NIOSH used source term concentration calculation method provided in 

Bridgeport Brass AWE hazard assessment

– Applied 1,000,000 dpm/100 cm2 survey value to model dose associated with cutting 

through a contaminated pipe

 NIOSH found that adding calculated dose to other subsurface data 

increases worker dose from 71 to 96 mrem CED

 NIOSH concludes not an SEC issue
13

Aerosolization of contaminated scale, NIOSH 

exposure model calculation: SC&A response

 SC&A finds:

– NIOSH has not demonstrated that the as-high-as-1,000,000 dpm/100 cm2 value is

bounding in-pipe surface contamination or scale value at M&C during residual period

– Additional survey data are few in number, some are not applicable, and overall, not

representative of drain pipes at M&C

– Bridgeport Brass source term values are based on actual U-238 surface activity

measurements; those model parameters do not necessarily extend to M&C

(particularly “T,” thickness of interior pipe surface activity, which can involve significant

uncertainty and is unknown for M&C)

– Increasing 95th percentile by factor of 2 goes beyond mere conservatism to extreme

means to compensate for uncertainty of application

 SC&A concludes not enough M&C-specific information and survey 

data to support use of Bridgeport Brass model
14

Concern with subsurface inside bounding 

concentrations: Confined space effects

 Presence and effect of extensive confined space work at M&C not 

reflected in exposure modeling. Leads to increased resuspension of 

contaminant particulates and concentration of aerosols.

 Prevalence of confined space work at M&C differentiates it from other 

AWEs.

 Mound project data used for M&C dust loading factor do not account for 

confined space effects and are therefore not an acceptable surrogate 

under Board guidelines.
15

Confined space effects: NIOSH updated response

 M&C workers not actually in trench installing Beckett line for full 6 months

 Drain line work typically done in trenches located 2–3 feet below facility 

grade with building ventilation, not considered confined space in standard 

industrial practice

 Priority 1 drain lines only made up small area of Building 10; workers 

recollected confined space work in other areas not associated with 

radiological source term

 “NIOSH is committed to reviewing recent suggestions to upgrade its dust 

loading models, including enhancement factors and confined spaces, and 

will consider incorporating methods suggested by SC&A in their 

supplemental review” (NIOSH, 2023b).
16

Confined space effects: SC&A response

 Beckett line work was highlighted to demonstrate not all M&C work was small, 

short-duration utility replacement or repair work; however, such maintenance 

work was intermittent and task related.

 Ergonomics matter: Breathing zone of workers would have been in closer 

proximity to bottom of trenches near drain pipes being cut and cleaned out.

 SC&A’s finding is for the sufficient accuracy of Mound project data as a 

surrogate, given that confined space effects are lacking for it. 

– The issues NIOSH raised—proportion of building with confined spaces, proximity to 

radiological sources, degree of contamination, etc.— are mitigating but do not change 

SC&A’s finding.

 SC&A considers this to be a TBD issue and, with NIOSH’s commitment to review 

it, recommends this be pended for further follow up. 
17

NIOSH table 2, “Additional information to augment 

SC&A’s Comparison of AWE sites table 1” 

 Intent of new table is to provide “context regarding the intrusive types of 

work performed at the other AWE sites where the Advisory Board agreed 

with NIOSH’s ability to bound exposures during residual period work” 

(NIOSH, 2023b).

 Intrusive work activities cited include grinding, general machine shop 

maintenance, construction and maintenance of water lines, cleaning and 

decontamination activities, steel-mill maintenance activities, filtration and 

duct system maintenance, general nuclear production facility 

maintenance, metal sanding, excavations, subsurface utility maintenance, 

facility maintenance, and heavy machinery operations.
18

NIOSH table 2: SC&A response

 SC&A does not dispute intrusive activities highlighted by NIOSH for other AWEs.

 This is not a new issue: NIOSH responded similarly to the same question raised by the Work 

Group in 2020 and concluded that “the pathways leading to internal exposures from alphaemitting radionuclides such as uranium and thorium are identical for workers at all of these 

sites: the inhalation and ingestion of resuspended, contaminated dust.” (NIOSH, 2020)

 The intent of SC&A’s supplemental review table 1 was to take exception to this broad 

characterization of M&C maintenance activities as being no different than those of other 

AWEs

– SC&A’s table 1, backed by M&C worker interviews, shows that M&C maintenance activities

were unique, by degree, proximity, and nature, in bringing workers close to elevated

radiological source terms.

 SC&A finds that while residual period activities cited by NIOSH in table 2 somewhat resemble 

those at M&C, NIOSH by its action to derive six bounding exposure models for intrusive 

activities at M&C acknowledges they were distinct from more passive scenarios of OTIB0070 and TBD-6000 and from experience at other AWEs.
19

Data applicability: NIOSH updated response

 NIOSH validated a bounding source term and applied appropriate resuspension/dust 

loads for various operations described by interviewees.

 One of the primary reasons for Weston drainage system characterization in 1995 was to 

quantify risk to ongoing drain line maintenance workers, which was still ongoing.

 Although the frequency of clogged drains may have increased over time, techniques to 

unclog drains did not change throughout residual period.
20

Data applicability: SC&A response

 SC&A’s supplemental review: “The use of a high exposure or concentration value 

based on a set of specific workplace [pre-D&D sediment survey] 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).

 Different conditions and process may have led to higher exposure potentials in the pre1995 residual era than accounted for by the inside subsurface bounding source term 

model:

– Presence of coagulant oils in drain lines, cutting and cleaning of pipe with contaminated scale, 

and confined spaces

 Precedent for considering data applicability can be found with Board’s SEC 

recommendation for Linde Ceramic renovation period. 

– Basis for judgment parallels considerations for M&C and is documented in HHS designation.
21

Worker protection: NIOSH updated response and 

SC&A response

 NIOSH: “Work practices such as those specified in the Work Group’s 

concern [that maintenance workers were unaware of radioactive 

contamination and operated without radiological controls and health 

physics oversight] do not affect the source term or any of the ‘three legs 

of the stool’ that form NIOSH’s bounding method” (NIOSH, 2023b).

 SC&A: Distinct differences between how workers conducted their work, 

the conditions and processes of that work, and the radiological controls 

under which they performed their activities lead to greater uncertainty 

over any comparison between D&D-era exposure potentials and those of 

the pre-1995 residual period (Linde Ceramics precedent).
22

Claimant-favorable assumptions: NIOSH 

updated response

 Information presented at the August 16, 2023, Advisory Board 

meeting is inaccurate, especially regarding ORAUT-OTIB-0070 

(NIOSH, 2023b)

 SC&A and the Work Group are misinterpreting NIOSH’s use of 

“extreme conservatism” to mean “implausibly high” (NIOSH, 

2023b)
23

Claimant-favorable assumptions: SC&A response

 SC&A questions the application of standard modeling approaches (as provided in OTIB-0070 

and TBD-6000) for unique conditions and processes at M&C; makes the “thoughtful 

selection” of appropriate resuspension and dust loading factors important.

 NIOSH itself found that the M&C ER “models resuspension (OTIB-0070) and does not 

specifically address potential exposures from digging, snaking/replacing clogged drain lines, 

or repurposing M&C equipment” (NIOSH, 2017). 

 SC&A goes further and has identified coagulants, scale, and confined spaces.

 SC&A has cited NIOSH’s defined application and scope of “extreme conservatism” precisely 

as given and in the context it was given by NIOSH in its January 2023 response paper. Its 

application is manifest in the substantial conservative assumptions and statistical margins 

relied upon in M&C bounding models.

 If NIOSH’s bounding model cannot account for M&C’s “intrusive activities, high exposure 

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

without resorting to extreme conservatism, sufficient accuracy and plausibility become 

concerns.
24

AWE equipment: NIOSH updated response and 

SC&A response

 NIOSH: has previously responded to this concern. AWE operations were 

decontaminated and decommissioned, and all radioactive material was 

removed during 1955–1968: “contaminated noncombustible scrap 

material and machinery were collected in 55-gallon steel drums and 

disposed of” (Sowell, 1985).

 SC&A: NIOSH’s response does not address the potential exposure 

pathway posed to M&C maintenance workers from moving, repurposing, 

and subsequent maintenance of AWE-era equipment that remained 

during the residual period. D&D activities would not have addressed 

residual contamination under and within AWE-era machinery and 

equipment that was not decontaminated and decommissioned.
25

Burial area: NIOSH updated response and SC&A 

response

 NIOSH: Regarding the Work Group comment that intrusive M&C activities 

included “excavating contaminated soils, including those near or within 

radioactive waste burial sites” (ABRWH, 2023), NIOSH noted that it has 

developed a model to bound exposure during subsurface work in areas 

outside of Building 10, including the burial ground.

 SC&A: has already addressed its concerns about the subsurface outside 

bounding approach in previous Work Group discussions and has no new 

technical information to add.
26

Work Group findings, August 2023

 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 prior to pre-D&D characterization, 1968–1995. [dates corrected]

 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” may not be a plausible approach to compensate for inadequate or 

insufficient information.
27

Work Group proposed 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.
28

SC&A conclusions

 SC&A’s review of NIOSH’s August 22, 2023, response paper did not identify information 

or analyses that materially affect the Work Group’s concerns and proposed conclusion.

 NIOSH has a pathway to address the confined space issue, which is acknowledged as a 

TBD concern.

 Uncertainties remain for source terms related to in-pipe contaminated sediments (due to 

the presence of coagulants) and interior surface contamination (scale) during the pre1995 M&C residual period.

– These were the basis for finding 1 of SC&A’s supplemental review 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).

 Uncertainties compounded by:

– Undetermined worker exposure due to repurposing of AWE-era machinery and equipment

– Intrusiveness of M&C maintenance worker activities as compared with other AWEs
29

References (1 of 3)

Advisory Board on Radiation and Worker Health, Metals and Controls Work Group. (2023, 

August 16). Update: M&C Work Group review of SEC-related issues [PowerPoint slides]. 

153rd Meeting of the Advisory Board on Radiation and Worker Health, Augusta, GA. 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/pres/2023/bd-metcontsec236issues-081623-

508.pdf

National Institute for Occupational Safety and Health. (2017). 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. (2021, Jan. 21). 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. (2023a, Jan. 13). 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
30

References (2 of 3)

National Institute for Occupational Safety and Health. (2023b, August 22). NIOSH response 

to “SC&A review [April 2023] of NIOSH response [January 2023] to SC&A’s supplemental 

review of M&C Work Group issues [August 2022]” [Response paper]. 

https://www.cdc.gov/niosh/ocas/pdfs/dps/dc-metcontwgissues-082223-508.pdf

Oak Ridge Associated Universities Team. (2017), Documented communication SEC-00236 

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

169938

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-metcontwgissues508.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
31

References (3 of 3)

Sowell, L. L. (1985). Radiological survey of the Texas Instruments site Attleboro, 

Massachusetts: Final report. SRDB Ref. ID 94371 PDF pp. 6–123.

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

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

U.S. Nuclear Regulatory Commission. (1992). Residual radioactive contamination from 

decommissioning: Technical basis for translating contamination levels to annual total 

effective dose equivalent (NUREG/CR-5512, PNL-7994, Vol. 1). 

https://www.nrc.gov/docs/ML0522/ML052220317.pdf

Weston [Roy F. Weston, Inc.]. (1996). Texas Instruments Incorporated Attleboro Facility: 

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PDF pp. 6–31.

Weston [Roy F. Weston, Inc.]. (1997). SNM license termination hypothetical radiological 

dose and exposure rate assessment priority 2 drain lines (SNM-23/70-33). SRDB Ref. ID 

197835