Fernald SEC Petition Review

Status Update

Brad Clawson, Chair, Fernald Work Group 

John Stiver, SC&A Team

Presented to the Advisory Board on Radiation and Worker Health

Idaho Falls, Idaho

July 16–17, 2013
Work Group Review: Overview

• April 19, 2006: SEC Petition qualified

– “All employees who worked in all facilities at the Feed Materials Production 

Center (FMPC) in Fernald, Ohio, from Jan 1, 1951 through Dec 31, 1989”

• November 3, 2006: NIOSH Evaluation Report issued

– “NIOSH found no part of the class under evaluation for which it cannot 

estimate radiation doses with sufficient accuracy.”

• November 10, 2006: SC&A Site Profile Review 

• July 2, 2007: SC&A SEC PER Review

• August 2007  July 2013: 16 Work Group meetings

• May 24, 2011, ABRWH Meeting: SC&A presents detailed summary of SEC 

issues (as of April 2011)

– O:\AB Document Review\Fernald\SC&A Work Products for SEC Issues Resolution

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Status - Work Group SEC Issues

1. Coworker Model for Uranium Internal Exposures – open

2. Validation of the HIS-20 database – closed*

3. Recycled Uranium (RU) – closed*

4. Use of radon breath data for reconstructing doses from inhalation of Ra226 and Th-230 – closed*

5. Review of radon emissions from the K-65 silos and associated exposures 

- moved to site profile discussions

6. Reconstruction of internal exposures from inhalation of Th-232

6A: DWE Data (1953–1967) – conditional closure**

6B: Chest Counts (1968–1989) – closed***

* Work Group recommendation.

** New coworker model introduced by DCAS since closure recommendation in 2011.

*** SEC: 1968–1978 for all workers (based on mg thorium data). 1979–1989 moved to site 

profile discussions March 2013 WG meeting.

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Original Description of Issue –

Concerns regarding the completeness and adequacy of the uranium 

bioassay data available for dose reconstruction and supporting the 

Fernald internal dosimetry coworker model (OTIB-0078)

Status of Issue –

Numerous white paper exchanges and Work Group meeting discussions 

from inception to July 1, 2013, Work Group teleconference

At July 1, 2013, Work Group teleconference, the Work Group passed a 

motion to recommend to the Board that a class of workers comprising 

subcontractor employees at Fernald from January 1, 1951, through 

December 31, 1983, be added to the SEC

Open Issue (#1): Coworker Model for Uranium 

Internal Exposures – Subcontractor Employees

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Coworker Model for Uranium Internal Exposures –

Subcontractor Employees, continued

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Central Issues

• Subcontractors were employed at Fernald from the beginning of operations 

in 1951 

• Subcontractors were not included in the routine bioassay program until 1986, 

when Westinghouse took over the M&O contract from NLO 

• The uranium bioassay coworker model does not include subcontractor 

samples prior to 1986

• Prior to the March 2013 WG meeting, DCAS located 939 hardcopy bioassay 

records for about 180 subcontractors collected over a 9 -year period from 

1969 to 1985

• These uranium bioassay data are extremely limited and there aren’t enough 

data to make meaningful OPOS comparisons for these earlier years

• SC&A observed bioassay records for a group of subcontractors from 1969 

that appeared to be very high compared to the prime contractor data
Coworker Model for Uranium Internal Exposures –

Subcontractor Employees, continued

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March – July 2013 key activities and findings

• As proof of principle, the WG asked DCAS to perform “best-estimate” intake 

evaluations for these subcontractors using their data and compare this to what they 

would have received from the 95th percentile of the coworker model

• The second aspect of this comparison exercise was for DCAS/ORAUT to identify 

subcontractor claimants from the pre-1986 era with employment data

• If the best-estimate intake values were all bounded by what would have been 

assigned via the coworker model, this would be a very powerful piece of evidence 

that the surrogate data in the coworker model were appropriate for subcontractors

• NIOSH’s response showed that depending on the solubility class, the 95th percentile 

of the coworker model would bound intakes for some of the subcontractors, but not 

all

• SC&A observed that the NIOSH coworker doses for claimants extended far beyond 

the periods of bioassay intake, which biased results in favor of the coworker model

• SC&A also observed that the assumptions used for the non-claimants were arbitrary 

and constrained potential intake, again favoring the coworker model

• Even so, the comparison strongly suggests that the coworker model is not bounding 
Coworker Model for Uranium Internal Exposures –

Subcontractor Employees, continued 

7 

0

200000

400000

600000

800000

1000000

1200000

1400000

pci Intake

Type M DR integrated intake

0.E+00

2.E+06

4.E+06

6.E+06

8.E+06

1.E+07

1.E+07

1.E+07

2.E+07

2.E+07

pCi Intake

Type S DR integrated intake

Coworker integrated intake
Coworker Model for Uranium Internal Exposures –

Subcontractor Employees, continued

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March – July 2013 key activities and findings

• At the July 1, 2013, WG teleconference, DCAS agreed that the uranium coworker 

model was not bounding for the subcontractors prior to the mid -1980s

• It was determined that the hardcopy data supported a separate coworker model for 

subcontractors in 1984 and 1985, but not prior

Table 1: Fernald CW Subcontractor Results in Hardcopy

Year No. of Individuals Results

1969 12 52

1971 13 85

1972 6 17

1973 3 4

1981 16 35

1983 38 164

1984 82 275

1985 67 307

1986 79 370
Coworker Model for Uranium Internal Exposures –

Subcontractor Employees, continued

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March – July 2013 key activities and findings

• Research revealed that uncontrolled subcontractor uranium exposure potential 

existed as early as mid-1952 and likely since the beginning of uranium handling in 

1951:

• (SRDB 3230, pg. 118) Dated August 7, 1952: 

[Redacted] has the difficult problem of getting management and supervisors educated in 

the fields of good housekeeping practices, general health and safety supervision and 

enforcement procedures which will insure proper control of uranium contamination with 

hundreds of contractor and subcontractor personnel running around “loose” in the work 

areas. However, the sooner National Lead of Ohio management and the top management 

of the construction contractor know the AEC requirements for health and safety in the plant, 

the sooner bad practices will be curtailed. [Emphasis added.]

• At July 1, 2013, WG teleconference, the WG passed a motion to recommend to the 

Board that a class of workers comprising subcontractor employees at Fernald from 

January 1, 1951, through December 31, 1983, be added to the SEC
Issue #6A: Reconstruction of Internal Exposures from the 

Inhalation of Th-232 (DWE Data)

• Description: Use of BZ and GA sampling data and associated daily 

weighted exposures (DWEs) to reconstruct Th-232 intakes

• Central Issues 

– Data Adequacy and Completeness 

• Sufficient DWE Data to Bound Internal Doses from Th-232 in all Thorium 

buildings from 1954–1967

– Given Adequate Data, are NIOSH’s Proposed Methods Sufficiently 

Robust to Reconstruct Doses in Accordance with 42 CFR 83 Accuracy 

Requirements?

• Status

– March 2008 – June 2013 

• Numerous white papers exchanged

• NIOSH produces 5 Revisions of the DWE Coworker Model 

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Review: Daily Weighted Exposure (DWE) Concept 

• Introduced by AEC HASL in 1953 

• Monitoring concept was transferred to the FMPC staff; used at FMPC since 

the beginning of site operations since 1954 

• DWE reports - summaries of data prepared by the FMPC Industrial Hygiene 

and Safety (IH&S) staff for use by management 

– Provided Estimate of Average Worker Exposure by Job Type 

– Used to Assess and Control Radioactive Dust Levels in a Plant (not to 

assess intakes) 

– Provided a Standardized Methodology through FMPC History 

• Based on Gross Alpha Air Activity Concentration (AAC) Measurements 

– Applicable to Workplace Alpha Emitters (U, RU, Th, U, and Th Progeny) 
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Review: DWE Description

• Time-Weighted Alpha Air Concentration (AAC)

– Job- and Building-specific

– Several Tasks per Job (3 to >20)

– High, Low, and Average AAC in dpm/m3 Reported for Each 

Task Associated with a Job

– Time to Complete Each Task Reported

– Sample Type (BZ, GA)

• BZ – Most Job-specific Tasks

• GA – Ambient, Typically Less Contributor to Dose (e.g., 

cafeteria, washroom)
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DWE Reports - Summary

• Job-Specific DWE Represents:

– Task-weighted Average Air Concentration of Given Alpha 

Emitter (e.g., Th-232)

– For Specific Day(s)

– For the Monitored Worker(s)

– Time Weighting is Crucial

• Link between the AAC at a location and time to potential 

worker exposure

• In Reality - have a Distribution of DWEs for Workers in Any Given 

Job (key concept)

– There was Spatial and Temporal Variation in AAC Experienced 

by Any Given Worker

– No Uncertainty Analysis
DWE Uncertainty Analysis 

Davis and Strom 2008 – Highlights

• Reviewed six HASL reports covering five sites that were visited between 1948 and 1955 

to characterize radiological hazards arising from the use of U, U ore, Th, or Ra-226/Rn222

• 63 job titles for which DWEs are reported. Each job title was held by 1 to 12 employees 

from a total of 165 employees across the sites

• Job titles involve from 1 to 13 operations, and each operation is characterized by 1 to 27 

air samples. A total of 428 air samples are reported.

• A significant fraction of workers (i.e., 104 of 165, or 63%) were exposed above the 

contemporary MACs

• Focused on variability in observations as evidenced in the air sample data themselves, 

which dominates the DWA uncertainty

• Sources of uncertainty and variability:

– measurement uncertainty, variability, and mistakes in data processing and communication, and 

the representativeness of air samples to what a worker actually breathed

– Variability arises due to uncertainty in aerosol particle size distributions, process variability, 

placement of air samplers, changes in ventilation

• Ran Monte Carlo simulations to generate distributions of discrete DWE and log-normal 

fits to DWE

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Davis and Strom 2008 – Highlights (continued)

• Log-normal fits allow for the possibility that exposures can be larger or 

smaller than those actually observed

• Upper 95th percentile of the GSD value is about 4, and the upper 99th

percentile is between 7 and 8. 

– Supports a GSD of 5 when a concentration measurement is available, but 

there is no information on uncertainty.

• Using the distribution of all air samples from a plant without time weighting 

or assignment to specific jobs does not produce a DWE or GSD that is 

representative of any individual worker for that site.

• The means of unweighted site-wide average concentrations exceed the 

DWAs for all workers in 60 of 63 cases.

• The site-wide average concentration is a biased estimator of exposure, but 

it can be used in making compensation decisions when it is required to be 

favorable to a claimant.

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Fernald Thorium Buildings and Timeline

Reference - White Paper on the Use of FMPC DWE Reports for Estimation of Chronic

Daily Intake Rate, Rev. 3, Robert Morris, Oak Ridge Associated Universities Team, Cincinnati, 

Ohio. October 2010.
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Fernald DWE Data and Coworker Models

• March 2008 – NIOSH Posted for Review

– 160 DWE Reports for the plants identified in the previous slide

– Spreadsheets with Sample DWE Data for Th-232 Plants for 1955, 1966, Plant 6 for 1960

y = 2.0336x + 0.8273

R2 = 0.949

-6

-4

-2

0

2

4

6

8

-3 -2 -1 0 1 2 3 LN(MAC)

z-score

Lognormal Fit to DWE (MAC)

Data

Linear (Data)

Sample data for 1955

Data used

Plant Year Workers

Job 

DWE Tasks

1 1955 12 12 45

4 1955 66 45 94

9 1955 119 31 273

Totals 197 88 412
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Fernald DWE Data and Coworker Models

• March 2008 – June 2013 

– Numerous white papers exchanged

– NIOSH produces five Revisions of the DWE Coworker Model 

– March 2009 NIOSH CW Model Rev. 2

• Questionable statistical approach, unwarranted level of granularity (year, building, job)

• July 2009: SC&A Review – 20 findings related to uncertainty and modeling approach

– October 2010: NIOSH CW Model Rev. 3

• Incorporated uncertainty from Davis and Strom (2008)

• Assigns the highest DWE for a given building in a given year to all workers in that building/year 

combination with a GSD of 5

• SC&A agreed in principle with that approach, with the caveat that NIOSH demonstrate the 

feasibility of implementation

– November 2012 – SC&A analysis demonstrates it was not possible to place workers in a 

given facility in a year 

– June 2013 NIOSH CW Model Rev. 5 – Like Rev. 3, it is a one size model, but assigns the 

highest DWE for the entire site to all workers for each year of thorium production (no 

attempt to place workers in particular buildings)
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Limiting Daily Weighted Exposure (MAC) for Plants and Years Where Thorium was Processed

Location 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967

Plant 1 N/A* 23.4 6.1 2.2 1.4 3.0 0.7 0.9 1.5 0.9 1.0 0.9 1.4 1.7

Plant 4 6.4 4.5 1.3 - - - - - - - - - - -

Plant 6 - - - - - 2.6 6.2 25.0 4.0 22.3 - - - -

Plant 8 - - - - - - - - - - - - 10.1 -

Plant 9 N/A 215.1** N/A - - - - - - - - - - -

Pilot Plant 5.9 N/A 2.0 - - - - - - - 5.9 N/A N/A N/A

Fernald DWE Data and Coworker Models (continued)

*N/A = No daily weighted exposure reports are available.

**The highest DWE value in 1955 was 686 MAC but included dust loads above the physiological tolerance 

level for unprotected breathing. Application of a respiratory protection factor would decrease this DWE 

value to less than 20 MAC. 215 MAC was adopted as the limiting case since it involved jobs within the 

physiological tolerance level for unprotected breathing and did not require a respiratory factor correction.

Rev. 5 DCAS Coworker model uses limiting DWE for each year
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Fernald DWE Data and Coworker Models (continued)

Year

# Total 

Samples

Concentration (dpm/m3)

Corresponding 

Intake (nCi/d)

# Total 

Thorium BZ 

Samples

Concentration (dpm/m3)

Corresponding 

Intake (nCi/d)

GM GSD

95th

Percentile GM GSD 95th Percentile

1964 63 31.8 4.1

330.1 (4.7 

MAC) 1.04 16 43.7 2.4 574.3 (8.2 MAC)1 1.801

1965 67 73.7 7.1

1852.4 (26.5 

MAC) 5.82 21 117.0 2.4 484.6 (6.9 MAC) 1.52*

19662 N/A

1967 61 69.8 4.1

705.5 (10.1 

MAC) 2.22 43 118.2 3.7 1027.3 (14.7 MAC) 3.23*

[1] Per the NIOSH text document, they plan to use the 95th percentile of thorium breathing zone samples only.

[2] NIOSH does not plan to use these data, but rather use the DWE values for the Stokes Furnace Operator in 1964 (4.1 N.C.G. or 

roughly 5.85 MAC – 1.3 nCi/d).

[3] NIOSH plans to use the higher of the DWE values for 1965 or 1967 for this year unless bounded by Plant 1.

*These values do not bound the current 95th percentile values presented in ‘Summary of Thorium Intake 

Rate Guidance DRAFT TO DCAS 05-30-13.docx’ found at [O:\AB Document Review\Fernald\Items from 

Mar03_2013 WG mtg\Item 10 Method for Using DWE]. Thus, Plants 1 and 8 DWEs are bounding.

NIOSH has Th air sampling data from the Pilot Plant from 1965 and 1967 and planned to use 

the 95th % of BZ samples for each year and the higher for 1966. They would then compare to 

Plants 1 and 8 DWE and use the highest for that year
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Fernald DWE Data and Coworker Models

• July 1, 2013, WG teleconference meeting

– WG requested summary data for limiting DWEs proposed in Rev. 5 coworker model

Year

# of Job Types 

Evaluated in 

Thorium Plants

Limiting 

Plant/DWE

# of DWE’s for 

Limiting Plant

Duration of Limiting Plant 

Study

Duration 

days

1954 14 Plant 4 14 Unspecified

1955 59 Plant 9 32 5/17/1955 – 10/31/1955 167

1956 51 Plant 1 20 Jan-Dec 1956 365

1957 22 Plant 1 22 Unspecified

1958 12 Plant 1 12 Aug – Nov 1958 92

1959 67 Plant 1 12 8/26/1959 – 10/1/1959 36

1960 70 Plant 6 58 3/1/1960 – 6/22/1960 113

1961 82 Plant 6 70 Aug-Oct 1961 61

1962 83 Plant 6 72 Feb-Mar 1962 28

1963 81 Plant 6 72 Oct-Nov 1963 31

1964 19 Pilot Plant 2 3/1/1964 – 10/31/1964 244

1965 16 Plant 1 16 Feb-Sept 1965 212

1966 29 Plant 8 14 Unspecified

1967 17 Plant 1 17 Unspecified

Average 44 31 135
Summary – Issue 6A Th-232 Coworker Model for 1954–1967 

Based on DWE

• DWE data adequacy and completeness do not appear to be a problem for 

thorium buildings from 1954–1967 for purpose of constructing a bounding 

coworker model for Th-232

– Job types appear to be well represented

– Sufficient DWEs exist for each year and limiting plant to ascertain bounding 

job type

– GSD of 5 accounts for uncertainties

– Air dust study duration per year available for 10 of 14 years

• Ranges from 28 to 356 days, average of 135 days

– 1965–1967: “proof of concept” comparison shows that 95th percentiles based 

on DWE data from Plants 1 and 8 are bounding

– High dust loads identified in historic communications reflected in AAC samples

• Does not appear to be systematic suppression of high results

• Dust studies used for process improvement, not intake assessment

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SUMMARY

• Work Group recommends full Advisory Board review and action regarding 

dose reconstructability of subcontractor exposure at Fernald for:

– Uranium from 1951 through 1983, when the uranium bioassay coworker 

model is not bounding for subcontractors

• Work Group recommends acceptance of NIOSH’s ability to reconstruct 

thorium exposures from 1954 through 1967 based on the thorium 

coworker model based on DWE.

• Completes remaining SEC issues for petition period.

• Work Group will continue to focus on resolving remaining site profile 

issues.

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Questions?

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