SC&A Status Report for the Metals and 

Controls Corporation SEC Petition Evaluation 

of Petition 236

Prepared by

John Mauro, PhD, CHP

Robert Anigstein, PhD

Prepared for the Advisory Board on Radiation and Worker Health

Meeting in Redondo Beach, CA

December 12–13, 2018
Metals and Controls Corporation

 Located in Attleboro, MA

 Approximately 30 miles south of Boston

 Covered time periods:

 AWE Operations:

January 1, 1952–December 31, 1967

SEC Granted under Petition SEC-00149

 Residual Period: 

January 1, 1968–March 21, 1997

SEC Petition 236 currently under evaluation

2
M&C Timeline of Key Activities and Events

3
Scope of Petition 236

 Who: All facilities construction and

maintenance workers

 Work Location: Metals and Controls Corp.

(M&C) in Attleboro, MA, in:

 Buildings 4, 5, 10 interior areas

 Buildings 5, 10, 11, 12, 17 exterior areas

 Time Period: January 1, 1968, through

March 21, 1997 (i.e., the residual period)

4
Historical Overview

 April 5, 2017 – SEC Petition Evaluation Report (Petition 236)

Issued

 August 24, 2017 – NIOSH/DCAS Presents to Advisory Board

 Petitioner raises concerns that all not all exposure pathways addressed

 Board tasks SC&A review

 October 24–26, 2017 – Interviews conducted with petitioners and

former employees

 February 12, 2018 – SC&A issues review of SEC Petition

 Identifies 3 Findings and 5 Observations

 Includes recommendations for pathways not previously addressed: 

 HVAC Maintenance

 Subsurface Maintenance in Building 10

 Burial Area Subsurface exposures

 February 22, 2018 – NIOSH/DCAS memo on SC&A review

5
Historical Overview

 April 23, 2018 – NIOSH/ORAUT issues white paper on

subsurface exposure models

 May 3, 2018 – Work Group on M&C meets

 Discusses SC&A review

 Petitioner raises additional concerns

 September 12, 2018 – Matrix issued

 Incorporated feedback from SC&A, Work Group Members, 

NIOSH/ORAUT, and Petitioners

 3 SC&A Findings

 5 SC&A Observations

 10 Petitioner-raised Issues

 September 17, 2018 – SC&A issues white paper response to

April 23 NIOSH/ORAUT Subsurface Model

 October 18, 2018 – NIOSH/DCAS memo response to Sept. 17

white paper
Historical Overview

 October 24, 2018 – NIOSH/ORAUT issues maintenance

exposure model white paper

 Adds roof/overhead exposure pathway

 November 20, 2018 – Work Group on M&C meets

 Discusses current NIOSH/ORAUT pathways

 Preliminary SC&A feedback on models

 Petitioner raises additional concerns

 November 29, 2018 – SC&A issues response to

maintenance exposure model white paper

7
Issues Associated with the Specific Approach 

Used in the ER

 Observation 1: SC&A suggests that a more appropriate approach

to deriving the chronic airborne concentration of uranium and

thorium from resuspension during the residual period would be to

use the mean value of the swipe data (i.e., 12.3 dpm/100 cm2, as

opposed to the 95th percentile value of 54.8 dpm/100 cm2) and an

RF of 1E-5/m, as opposed to 1-E6/m.

 Observation 2: The distinction between production and nonproduction workers should be better defined in the ER.

 Observation 3: NIOSH should consider adopting the approach

used in the TBD and ER for Carborundum and General Steel

Industries for deriving ingestion doses during the residual period.

8
Issues Not Explicitly Addressed in the ER

Finding 1: Based on interviews with workers held October 24–

October 26, 2017, SC&A found that many unique maintenance 

and repurposing activities were performed during the residual 

period by many workers who were not aware of any residual 

radioactivity. These activities could have resulted in external 

exposures that are not addressed in the ER, including:

1. Recurring subsurface maintenance and repurposing activities

in contaminated soil, conduits, and pipelines beneath

Building 10

2. Outdoor activities in the vicinity of the low-level radioactive

waste burial grounds

9
Issues Associated with the Specific Approach 

Used in the ER

 Finding 2: NIOSH incorrectly transcribed some of the Landauer film

badge dosimetry reports and incorrectly calculated annual 95th

percentile external penetrating doses to workers in the residual

period.

 Finding 3: NIOSH incorrectly calculated annual 95th percentile

beta skin doses to workers in the residual period.

 Observation 4: Exposures experienced by High Flux Isotope

Reactor workers cannot be used “as supporting evidence to validate

the bounding method used in Section 7 of this report” as stated on

page 24 of the ER.

 Observation 5: SC&A is concerned that it may be inappropriate to

use external dosimetry data collected during the last year of AWE

operations as the basis for bounding the external doses during the

residual period.

10
Summarized Petitioner Comments

1. Concerns that the operational period monitoring data are not applicable

because to those workers had knowledge of contamination and safety

procedures while M&C workers did not

2. 1982 surveys limited in scope and may have missed contamination

3. 1992 surveys limited to burial area

4. Concerns regarding the 1-month duration assumption

5. 1995 drainage system survey only looked at uranium, not thorium

6. Concerns regarding bounding thorium inside drains

7. 1985 surveys limited in scope

8. Concerns that the HVAC model does not allow for residue from

operations that may have been in ducts

9. Roof penetrations should have undepleted source term

10. 1982 surveys only covered accessible areas

11
Objectives of Work Group

Primary Objectives – Address Potential SEC Issues 

 Do we have sufficient data and understanding of M&C

worker activities to reconstruct doses during the residual

period?

 Do we have consensus on what are and are not SEC

issues?

Secondary Objectives – Address Site Profile Issues

 Can we achieve consensus on scientifically sound and

claimant-favorable assumptions regarding scenarios,

pathways of exposure, data, models, and parameters?

12
Exposure Pathways

Indoor

Locations: Buildings 4, 5, 10 

(predominately Building 10)

Pathways:

1. Above Ground – Full Time

2. Maintenance and

Repurposing

Outdoor

Locations: Buildings 5, 10, 

11, 12, 17 exterior areas 

Pathways:

1. Above Ground – Perhaps

Full Time

2. Maintenance and

Repurposing

13
Major Scenarios

 Building 10 HVAC maintenance

 Building 10 roof and overhead

 Subsurface inside Building 10

 Subsurface areas outside Building 10

14
Building 10 HVAC Maintenance

Internal dose from HVAC filter replacement in 

Building 10

 NIOSH has fully adopted SC&A’s suggested approach to this

exposure scenario as described in SC&A’s 2/12/2018 report.

 This scenario was discussed at the 11/20/2018 Work Group

meeting. There appeared to be general consensus that the

approach makes use of sufficient data representing the time

period of interest and that the models and assumption are

scientifically sound and claimant favorable.

 The limiting dose is 1.77 mrem/hr effective dose commitment to

the extra-thoracic airways (the limiting exposure pathway).

15
Building 10 Roof and Overhead

Internal dose from periodic maintenance work performed by M&C workers 

in the rafters and upper levels of Building 10 during the residual period

NIOSH Analysis

 Hundreds of alpha, beta, and gamma surveys, including wipe surveys of the

upper levels of Building 10 and also the roof in the early 1980s

 NIOSH reconstructed the doses to these workers using these assumptions:

 Upper 95th percentile of the survey data – 8.99 dpm/100 cm2

 10% of the measured contamination levels was removable

 A resuspension factor of 1E-4/m

 Occupancy time of 1 month per year (173 hours or 22 work days per year)

SC&A Analysis

 SC&A estimated contamination levels on surfaces ~ 20% higher

 We concur with all other NIOSH assumptions

 We derive an annual effective dose commitment of about 0.01 mrem/yr
Subsurface Building 10 – Internal Exposures

Internal dose to M&C workers involved in periodic subsurface 

maintenance and repurposing activities in Building 10 during the residual 

period.

INTERNAL EXPOSURES

Parameter SC&A 2018 10/24/2018 White 

Paper

Contamination 

level 5,878.1 pCi/g 6,887.84 pCi/g

Dust loading 200 μg/m3 220 μg/m3

Breathing rate 2.5 m3/hr 1.2 m3/hr

Exposure duration 184 hr/yr 173 hr/yr

U Inhalation rate 20 Bq/yr Not provided

Dose 15.6 mrem/yr effective 

dose commitment Not provided

17
Subsurface Building 10 – External Exposures

NIOSH

Used film badge data from the end of the AWE period as the underpinning of 

the methods used to reconstruct external exposures to M&C workers during 

the residual period.

SC&A

Had reservations on this strategy

 Modeled same worker is exposed to the high-end concentrations of

radionuclides in the subsurface environment for all subsurface-related

activities in Building 10 (1 month per year )

 External dose conversion factors associated with an effective infinite slab of

contaminated soil (e.g., FGR No 12)

 Using these assumption, SC&A obtains effective dose commitment of

12.75 mrem/yr and skin dose of 32.5 mrem/yr

 Comparable doses to NIOSH model

18
SC&A direct contamination of skin for downhole workers (new 

exposure pathway in November 29, 2018, white paper 

response)

 Soil contamination level 5,878.1 pCi/g uranium

 Soil residue on skin of 10 mg/cm2

 DCF of 40 mrem/hr per dpm/cm2 for uranium with shortlived progeny

 0.67 mrem/hr skin dose

Subsurface Building 10 – External Exposures

19
Substitute Data Considerations for Building 10 

Analyses

A number of important points can be made for using the 

1990 data:

 Use of 95th percentile data

 High chronic dust loading (220 μg/m3), especially for moist 

soil

 Same person involved in all subsurface maintenance and 

repurposing activities

 Notwithstanding these bounding assumptions, the doses are 

extremely small

 Actual bioassay data collected in the 1990s reveal internal 

exposures that are well below the modeled doses

20
Outside Areas: Internal Exposures

NIOSH

 Considerable surface and subsurface data were collected in

many outdoor areas in 1984 by the NRC and again in the early

1990s

 2,391 soil samples were collected prior to remediation

 1,629 samples were analyzed for gross alpha

 762 samples were collected for uranium and thorium and analyzed using 

isotopic identification

 95th percentile gross alpha and uranium concentration of

117.86 pCi/g

 95th percentile gross alpha and thorium concentration of

87.5 pCi/g

 Occupancy 1 month per year by the same person

 Dust loading of 220 μg/m3
Outside Areas: Internal Exposures

SC&A Above-ground Exposures – Use similar assumptions

 For above-ground internal exposures: SC&A suggests assuming 

average soil contamination, 2,000 hours/yr exposure duration and a 

chronic dust loading of about 200 micrograms/m3.

 For subsurface exposures: SC&A suggests that NIOSH derive the 

upper 95th percentile of the radionuclide concentrations observed in 

subsurface samples, along with an exposure duration of perhaps 

200 hours per year and a dust loading of about 200 μg/m3 as the 

basis for estimating internal doses associated with outdoor 

subsurface work.

 Using 95th percentile of all outdoor data, 200 μg/m3, and 

2,000 hours/yr, SC&A derives an effective dose commitment of 

4.556 mrem/yr.
SC&A Conclusions

Doses to M&C workers during the residual period can 

be reconstructed in a scientifically sound and claimantfavorable manner by using upper end values of the 

contamination levels measured during the 1980s and 

1990s, along with appropriately conservative 

assumptions regarding airborne dust loadings and 

exposure durations.

23
Additional Petitioner Comments Raised During 

November 20 Work Group Meeting

1. More explicit consideration of thorium exposures

2. Explicit consideration of internal exposures associated

with welding operations

24