Draft

Advisory Board on Radiation and Worker Health

National Institute for Occupational Safety and Health

A Review of NIOSH’s Program Evaluation Report 

DCAS-PER-051, “Weldon Spring Plant” 

Contract No. 75D30119C04183

Document No. SCA-TR-2023-PER051, Revision 1 

Prepared by

Ron Buchanan, PhD, CHP

SC&A, Inc.

2200 Wilson Blvd., Suite 300

Arlington, VA 22201-3324

September 21, 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.

NOTICE: This report 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.
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SC&A, Inc. technical support for the Advisory Board on Radiation and Worker Health’s 

review of NIOSH dose reconstruction program

Document title A Review of NIOSH’s Program Evaluation Report DCAS-PER-051, 

“Weldon Spring Plant”

Document number SCA-TR-2023-PER051

Revision number 1 (Draft)

Supersedes 0 (Draft)

Effective date September 21, 2023

Task manager Kathleen Behling [signature on file]

Project manager Bob Barton, CHP [signature on file]

Document reviewer(s) Bob Barton, CHP [signature on file]

Record of revisions

Revision number Effective date Description of revision

0 (Draft) 8/10/2023 Initial issue

1 (Draft) 9/21/2023

Revision issued to expand SC&A’s subtask 2 

evaluation of the revised Weldon Spring TBD, 

sections 3–6, described in section 4.
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Table of Contents

Abbreviations and Acronyms........................................................................................... 4

1 Statement of Purpose............................................................................................... 5

2 Relevant Background Information Pertaining to Facility Operations, Potential 

Source Terms, and Worker Monitoring Protocols............................................................ 6

2.1 Facility operations .............................................................................................. 6

2.2 Source terms...................................................................................................... 6

2.3 Internal and environmental monitoring............................................................... 7

2.4 External and ambient monitoring........................................................................ 7

3 Subtask 1: Identify the Circumstances that Necessitated DCAS-PER-051 .............. 9

3.1 Chronology of events that necessitated PER-051.............................................. 9

3.2 SC&A’s comments ........................................................................................... 10

4 Subtask 2: Assess NIOSH’s Specific Methods for Corrective Action...................... 13

4.1 Overview of SC&A’s review of Weldon Spring site profile................................ 13

4.2 SC&A’s comments ........................................................................................... 13

5 Subtask 3: Evaluate the PER’s Stated Approach for Identifying the Number of DRs 

Requiring Reevaluation of Dose.................................................................................... 14

5.1 NIOSH’s selection criteria ................................................................................ 14

5.2 SC&A’s comments ........................................................................................... 15

6 Subtask 4: Conduct Audits of a Sample Set of Reevaluated DRs Mandated by 

DCAS-PER-051 ............................................................................................................ 16

7 References ............................................................................................................. 17
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Abbreviations and Acronyms

ABRWH, Board Advisory Board on Radiation and Worker Health

DCAS Division of Compensation Analysis and Support 

DoD U.S. Department of Defense 

DOE U.S. Department of Energy 

DOL U.S. Department of Labor 

DR dose reconstruction 

EEOICPA Energy Employees Occupational Illness Compensation Program Act 

mrem millirem

NA not applicable 

NIOSH National Institute for Occupational Safety and Health

ORAUT Oak Ridge Associated Universities Team

PER program evaluation report 

pCi/mg picocurie per milligram

POC probability of causation 

Ra radium 

Rn radon 

RU recycled uranium 

SEC Special Exposure Cohort 

SRDB Site Research Database

TBD technical basis document

Th thorium 

U uranium 

UF4 uranium tetrafluoride

WLM working-level-month 

WSP Weldon Spring Plant 

WSRP Weldon Spring Raffinate Pits 

WSQ Weldon Spring Quarry 
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1 Statement of Purpose

To support dose reconstruction (DR), the National Institute for Occupational Safety and Health 

(NIOSH) and the Oak Ridge Associated Universities Team (ORAUT) assembled a large body of 

guidance documents, workbooks, computer codes, and tools. In recognition of the fact that all 

these supporting elements in DR may be subject to revision, provisions exist for evaluating the 

effect of such programmatic revisions on the outcome of previously completed DRs. Such 

revisions may be prompted by document revisions due to new information, misinterpretation of 

guidance, changes in policy, and/or programmatic improvements. 

A program evaluation report (PER) critically evaluates the effects that a given issue or 

programmatic change may have on previously completed DRs. This includes a qualitative and 

quantitative assessment of potential impacts. Most important in this assessment is the potential 

impact on the probability of causation (POC) of previously completed DRs with POCs less than 

50 percent. 

On February 16, 2023, the Advisory Board on Radiation and Worker Health (Board) tasked 

SC&A to reviewDCAS-PER-051, “Weldon Spring Plant” (NIOSH, 2015; “PER-051”). In 

conducting a PER review, SC&A is committed to perform the following five subtasks, each of 

which is discussed in this report: 

• Subtask 1: Assess NIOSH’s evaluation and characterization of the issue addressed in the 

PER and its potential impacts on DR. Our assessment intends to ensure that the issue was 

fully understood and characterized in the PER. 

• Subtask 2: Assess NIOSH’s specific methods for corrective action. When the PER 

involves a technical issue that is supported by documents (e.g., white papers, technical 

information bulletins, procedures) that have not yet been subjected to a formal SC&A 

review, subtask 2 will include a review of the scientific basis and/or sources of 

information to ensure the credibility of the corrective action and its consistency with 

current/consensus science. Conversely, if such technical documentation has been 

formalized and previously subjected to a review by SC&A, subtask 2 will simply provide 

a brief summary and conclusion of this review process. 

• Subtask 3: Evaluate the PER’s stated approach for identifying the universe of potentially 

affected DRs and assess the criteria by which a subset of potentially affected DRs was 

selected for reevaluation. The second step may have important implications where the 

universe of previously denied DRs is very large and, for reasons of practicality, NIOSH’s 

reevaluation is confined to a subset of DRs that, based on their scientific judgment, have 

the potential to be significantly affected by the PER. In behalf of subtask 3, SC&A will 

also evaluate the timeliness of the completion of the PER. 

• Subtask 4: Conduct audits of DRs affected by the PER under review. The number of 

DRs selected for audit for a given PER will vary. (It is assumed that the Board will select 

the DRs and the total number of DR audits for each PER.)

• Subtask 5: Prepare a written report that contains the results of DR audits under 

subtask 4, along with our review conclusions. 
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2 Relevant Background Information Pertaining to Facility Operations, 

Potential Source Terms, and Worker Monitoring Protocols

The following information was obtained from the most current revisions of the Weldon Spring 

technical basis documents (TBDs) to present the relevant background for this report. Older 

versions of the TBDs will be referred to as applicable in the appropriate sections of our review of 

PER-051. 

2.1 Facility operations

The facilities covered under the Energy Employees Occupational Illness Compensation Program 

Act (EEOICPA) are the Weldon Spring Plant (WSP), Weldon Spring Quarry (WSQ), and the 

Weldon Spring Raffinate Pits (WSRP). In this document, the term “WSP site” is used when it is 

unnecessary to distinguish between the plant, the quarry, and the raffinate pits. The WSP site was 

operated for the U.S. Atomic Energy Commission as a feed materials plant to process uranium 

and thorium ore by the Uranium Division of Mallinckrodt Chemical Works. 

There were four periods for the WSP site: 

1. site acquisition and development, 1954–1957 

2. operational, 1957–1966 

3. the U.S. Department of Energy (DOE) did not control WSP during the period 1967–1985 

and WSRP and WSQ during the period 1967–1974; the U.S. Department of Defense 

(DoD) controlled those Weldon Spring facilities during these periods 

4. remediation, 1985–2002 

WSP employment is covered under EEOICPA only during the operational (1957–1966) and 

remediation (1985–2002) periods, when the U.S. Atomic Energy Commission, the U.S. Energy 

Research and Development Administration, and DOE had contractors and radioactive materials 

at WSP. 

WSQ and WSRP employment is covered during the operational period (1957–1966), the period 

1975–1984, and the remediation period (1985–2002). 

2.2 Source terms

The radionuclides of concern are those that make up 95 percent of the potential internal dose. 

According to the TBD for internal dose, ORAUT-TKBS-0028-5, revision 04 (ORAUT, 2017), 

the radionuclides of concern at the WSP site for DR are the naturally occurring isotopes of 

uranium ((U)-234, U-235, and U-238), their decay products (primarily thorium (Th)-230 and 

radium (Ra)-226), isotopes of natural thorium (Th-228 and Th-232) and their decay products, 

and recycled uranium (RU).

2.2.1 Uranium

ORAUT-TKBS-0028-5 (ORAUT, 2017) recommends that, for the purposes of DR, it be

assumed that all uranium processed at the WSP site was natural uranium from 1957 through 
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1962, with a specific activity of 683 picocuries per milligram (pCi/mg). After 1962, all uranium 

is assumed to be enriched to 1 percent, with a specific activity of 973 pCi/mg. 

2.2.2 Radon and thoron

The three radon isotopes generated during the decay of U-235, U-238, and Th-232 are radon 

(Rn)-219, Rn-222, and Rn-220, respectively. Due to the limited amount of enriched uranium 

(which contains U-235) processed at the WSP site, there was no large source of Ra-223 and, in 

turn, Rn-219. The risks associated with Rn-219 were insignificant due to its extremely short halflife (4 seconds) and small source term. Therefore, ORAUT-TKBS-0028-5, revision 04 

(ORAUT, 2017), considers only the inhalation intakes for Rn-222 (radon) and Rn-220 (thoron) 

to be potentially significant. 

2.2.3 Recycled uranium

It should be assumed that all the uranium that the WSP site processed beginning in 1961 was 

RU. For the periods that include RU (i.e., after 1960), RU contaminant mass concentrations are 

provided in section 5.6.1.3.3 of ORAUT-TKBS-0028-5, revision 04 (ORAUT, 2017). 

2.3 Internal and environmental monitoring

The following summarizes the internal intake monitoring at the WSP site. SC&A obtained this 

information from ORAUT-TKBS-0028-4, revision 04 (ORAUT, 2020), and 

ORAUT-TKBS-0028-5, revision 04 (ORAUT, 2017). 

2.3.1 Operational period, 1957–1966

Urine bioassay was the primary method of determining uranium intakes during the production 

phase. There has been no indication so far that a routine urine sampling program was 

implemented for thorium. No urine bioassay data for thorium have been found in the worker 

files.

2.3.2 DoD period, 1967–1985 

There did not appear to be DOE contractor personnel present during the DoD period. No 

bioassay monitoring records have been located for this period. 

2.3.3 Remediation period, 1985–2002

An extensive bioassay monitoring program was conducted from 1991 to 2001 to detect intakes 

greater than 100 millirem (mrem) committed effective dose equivalent.

2.4 External and ambient monitoring

The following summarizes external monitoring methods at the WSP site. SC&A obtained this 

information from ORAUT-TKBS-0028-4, revision 04 (ORAUT, 2020), and ORAUT-TKBS0028-6, revision 01 (ORAUT, 2013e).

2.4.1 Operational period, 1957–1966

Employees who worked in radiological areas were monitored, and their exposures should be 

accounted for in their normal dosimetry results. However, documents obtained to date do not 
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contain monitoring data that describe the ambient exposure rate at the WSP site during the 

operational period. 

2.4.2 DoD period, 1967–1985 

There did not appear to be DOE contractor personnel present during the DoD period, and no 

external monitoring records have been located for this period. In addition, there are no records of 

site surveys being conducted until 1982, except for a 1975 aerial radiological survey. 

2.4.3 Remediation period, 1985–2002

Personnel external monitoring was provided as needed during the remediation period. External 

ambient exposure monitoring was conducted at the site beginning in 1982 by perimeter 

monitoring, as detailed in section 4.3.2 and summarized in table 4-6 of ORAUT-TKBS-0028-4, 

revision 04 (ORAUT, 2020). 
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3 Subtask 1: Identify the Circumstances that Necessitated 

DCAS-PER-051

3.1 Chronology of events that necessitated PER-051

3.1.1 ORAUT-TKBS-0028-3: Occupational medical dose

NIOSH issued revision 00 of ORAUT-TKBS-0028-3 on June 24, 2005 (ORAUT, 2005a), and 

revision 01 on January 30, 2013 (ORAUT, 2013a). NIOSH reevaluated all noncompensated 

claims using the current version of the TBDs; therefore, PER-051 did not address specific 

changes in revision 01 compared to revision 00 that could lead to an increase in assigned dose. 

3.1.2 ORAUT-TKBS-0028-4: Occupational environmental dose

NIOSH issued revision 00 of ORAUT-TKBS-0028-4 on June 28, 2005 (ORAUT, 2005c), and 

revision 01 on May 17, 2013 (ORAUT, 2013b). NIOSH reevaluated all noncompensated claims 

using the current version of the TBDs; therefore, PER-051 did not address specific changes in 

revision 01 compared to revision 00 that could lead to an increase in assigned dose. 

3.1.3 ORAUT-TKBS-0028-5: Occupational internal dose

NIOSH issued revision 00 of ORAUT-TKBS-0028-5 on June 28, 2005 (ORAUT, 2005d), 

revision 01 on March 15, 2013 (ORAUT, 2013c), and revision 02 on May 21, 2013 

(ORAUT, 2013d). NIOSH reevaluated all noncompensated claims using the current version of 

the TBDs; therefore, PER-051 did not address specific changes in revisions 01 and 02 compared 

to revision 00 that could lead to an increase in assigned dose. However, PER-051 did list some 

general changes that could impact assigned internal dose: 

• change in assumed isotopic ratios for uranium ore concentrates

• addition of a thoron exposure dose 

• change in RU contaminate fractions

• an increase in the radon exposure estimate 

3.1.4 ORAUT-TKBS-0028-6: Occupational external dose

NIOSH issued revision 00 of ORAUT-TKBS-0028-6 on June 24, 2005 (ORAUT, 2005e), and 

revision 01 on February 6, 2013 (ORAUT, 2013e). NIOSH reevaluated all noncompensated 

claims using the current version of the TBDs; therefore, PER-051 did not address specific 

changes in revision 01 compared to revision 00 that could lead to an increase in assigned dose. 

However, PER-051 did list some general changes that could impact assigned external dose: 

• addition of a neutron-to-photon ratio 

• addition of a geometry correction factor for external dose 

3.1.5 DCAS-PER-051

On March 4, 2015, NIOSH issued DCAS-PER-051 (NIOSH, 2015) for the WSP site, which 

addressed changes in DR procedures using the latest 2013 revisions of the Weldon Spring TBDs, 

as given in sections 3.1.1–3.1.4. 
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3.2 SC&A’s comments

SC&A reviewed the sequence of revisions of the Weldon Spring TBDs and PER-051. SC&A 

found that PER-051 addressed the changes in the TBDs that could potentially result in increases 

in internal and external dose assignments by (1) reevaluating all noncompensated Weldon Spring 

claims and (2) reworking the applicable claims using the latest version of the TBDs as of the 

PER-051 date of March 2015. 

SC&A reviewed the changes in the 2013 revisions of the TBDs. The following subsections 

summarize the changes that have the potential to increase assigned dose.

3.2.1 ORAUT-TKBS-0028-3: Occupational medical dose

Revision 01 of ORAUT-TKBS-0028-3 (ORAUT, 2013a) includes the following changes that 

may increase assigned occupational medical dose: 

• Includes skin doses for all areas of skin (refer to tables 3-2 and 3-3). 

• Recommends using revision 04 of ORAUT-OTIB-0006, “Dose Reconstruction from 

Occupational Medical X-ray Procedures” (ORAUT, 2011), whereas ORAU-TKBS-0028-

3, revision 00, recommended using ORAUT-OTIB-0006, revision 03 (ORAUT, 2005b). 

3.2.2 ORAUT-TKBS-0028-4: Occupational environmental dose

Revision 01 of ORAUT-TKBS-0028-4 (ORAUT, 2013b) includes the following changes that 

may increase assigned occupational environmental dose: 

• Added factors for calculation of RU contaminant activity based on parts per billion or 

picocurie of uranium in section 4.2.2.1, page 11. 

• Added table 4-1, page 20, for annual median intake values for WSCP, WSRP, and WSQ. 

• Added table 4-2, page 22, for maximum sitewide median intake values to comply with

ORAUT-PROC-0031, “Site Profile and Technical Basis Document Development,” 

revision 04 (ORAUT, 2012). 

• Revised sections 4.2.1, page 9, and 4.2.2.1, pages 9–11, to more specifically target the 

radionuclides of concern and source terms that contribute to 95 percent of the potential 

internal dose. 

• Revised section 4.2.3.1, pages 11–16, concerning the approach for determining annual 

intake of radionuclides during the operational period to optimize the use of available sitespecific monitoring data. 

• Added table 4-3, page 23, consisting of the annual median values for environmental 

external onsite ambient dose during the operational period. 

• Added section 4.4, pages 27–28, as a summary of environmental doses for use by dose 

reconstructors and provided tabulated inhalation intakes and ambient dose default values. 
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3.2.3 ORAUT-TKBS-0028-5: Occupational internal dose

Revision 01 of ORAUT-TKBS-0028-5, March 15, 2013 (ORAUT, 2013c), and revision 02 of 

ORAUT-TKBS-0028-5, May 21, 2013 (ORAUT, 2013d), include the following changes that

may increase assigned occupational internal dose: 

• The specific activity for slightly enriched (1 percent) uranium in section 5.2.1 of 

revision 01, page 13, was adjusted to agree with the formula in DOE’s “Guide of Good 

Practices for Occupational Radiological Protection in Uranium Facilities” (DOE, 2001). 

• Section 5.2.2 of revision 01, pages 13–14, related to uranium decay products, was edited 

to reflect the fact that the early uranium mills may not have been effective in removing 

thorium, and therefore the dose reconstructor should increase the amount of Th-230 and 

daughters used in DR calculations. 

• The maximum concentrations for certain decay products at the WSRP and WSQ were 

eliminated in section 5.2.2 of revision 01, pages 13–14. 

• A discussion was added in section 5.2.3 of revision 01, page 14, on potential intakes from 

thoron. 

• Site-specific ratios of Th-230 to other contaminants were developed in section 5.6.1.1 of 

revision 01, pages 38–39, for DR applications during the period of initial uranium 

processing. 

• Daily weighted-average concentrations for thorium dust measurements were added as 

attachment A of revision 01. These values were used to create table 5-22, page 41, of 

thorium intakes in section 5.6.1.2. Thoron guidance was also added to this section. 

• A statement was added in section 5.6.1.1 of revision 01, page 38, to use Friday urine 

sampling data statistics to avoid underestimating intakes. 

• The estimated annual exposure from radon was increased in section 5.6.1.3 of 

revision 02, pages 42–43, to 12.4 working-level-months (WLMs) per year.

• Section 5.2.4 of revision 01, page 16, concerning RU contaminants, was updated. 

• Th-232 intake rates were updated in section 5.6.1.2 of revision 01, page 40, to reflect an 

8-hour workday normalized to a calendar year for each of the years of Th-232 operations. 

• Equations were included in the text in section 5.6.1.2 of revision 01, page 40, regarding 

calculation of the median and 95th percentiles of the Th-232 intake rates. 

• The indoor radon equilibrium factor was modified from 0.5 to 0.7 in section 5.6.1.3 of 

revision 02, page 43. This increased the radon intake value from 8.8 WLM per year to 

12.4 WLM per year. 

• Table 5-23, page 44, was added in section 5.7 of revision 01, and revised in revision 02, 

to provide the dose reconstructor with a summary of intake information for DR that 

reflects the major changes outlined here. 
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3.2.4 ORAUT-TKBS-0028-6: Occupational external dose

Revision 01 of ORAUT-TKBS-0028-6 (ORAUT, 2013e) includes the following changes that

may increase assigned occupational external dose: 

• Section 6.3.11, page 30, includes a correction factor of 2.1 to account for workerradiation source geometry to be applied to the measured and missed photon doses for 

operators, material handlers, and trade workers to avoid underestimating dose. Organs 

most affected by this are those in the lower torso (stomach, pancreas, ovaries, etc.). 

Observation 1: Use of neutron-to-gamma ratio

Section 2.0 of PER-051 (NIOSH, 2015, p. 1), states that the revisions to the TBDs included the 

addition of a neutron-to-photon ratio. However, it appears that revision 00 of ORAUT-TKBS0028-6 (ORAUT, 2005e) contains the same neutron-to-photon ratio recommendations as 

revision 01 (ORAUT, 2013e), as follows. 

ORAUT-TKBS-0028-6, revision 00, section 6.2.4.2, states:

Using the results of gamma and neutron dose rate measurements performed on 

depleted and low enriched UF4 [uranium tetrafluoride] drums, a neutron-togamma ratio was developed. Natural uranium was addressed as well. The results 

of this analysis were that a neutron-to-gamma ratio of 0.1, lognormally distributed 

with a geometric standard deviation of 1.71 and an upper 95% ratio limit of 0.23, 

should be applied in those areas where there is the potential for neutron dose from 

uranium fluoride compounds. [ORAUT, 2005e, p. 19] 

ORAUT-TKBS-0028-6, revision 01, section 6.3.4.2, states: 

Using the results of gamma and neutron dose rate measurements performed on 

depleted and low-enriched UF4 drums, a neutron-to-gamma ratio was developed. 

The results of this analysis were that a neutron-to-gamma ratio of 0.1, 

lognormally distributed with a geometric standard deviation of 1.71 and a 95th

percentile ratio of 0.23, should be applied in those areas where there is the 

potential for neutron dose from uranium fluoride compounds. [ORAUT, 2013e, 

p. 24] 

SC&A has previously reviewed1

 the WSP TBDs and the revisions made to the TBDs. 

1 SC&A’s WSP TBD review reports can be found on the Weldon Spring Plant page of the NIOSH website at

https://www.cdc.gov/niosh/ocas/weldonsp.html. 
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4 Subtask 2: Assess NIOSH’s Specific Methods for Corrective Action

NIOSH initially released revision 00 of sections 3–6 of the Weldon Spring TBD in June 2005 

(ORAUT, 2005a, 2005c, 2005d, 2005e). NIOSH released revision 01 of sections 3–6 and 

revision 02 of section 5 of the Weldon Spring TBD between January 30 and May 21, 2013 

(ORAUT, 2013a, 2013b, 2013c, 2013d, 2013e). These revisions to the Weldon Spring Plant 

TBD included several changes that would cause an increase in calculated doses. NIOSH did not 

find that a detailed list of changes made to the TBD was necessary because all four sections were 

revised, and the changes cover all operational time periods and job types. Therefore, as a 

corrective action, NIOSH did not exclude any Weldon Spring claim from further evaluation 

based on job type or employment period but revaluated all previous Weldon Spring claims with 

POCs <50 percent. 

SC&A had previously reviewed revision 00 of sections 3–6 of the Weldon Spring TBD in 2009 

(SC&A, 2009). However, revision 01 of sections 3–6 and revision 02 of section 5 of the Weldon 

Spring TBD had not been reviewed by SC&A. Therefore, subtask 2 of PER-051 included a 

review of the scientific basis and/or sources of information to ensure the credibility of the 

corrective action and its consistency with current/consensus science as described in the following 

section.

4.1 Overview of SC&A’s review of Weldon Spring site profile 

SC&A reviewed revision 01 of sections 3–6 and revision 02 of section 5 of the Weldon Spring 

2013 TBD to determine if they contained technically correct methodology and information and 

referred to appropriate references as needed. SC&A analyzed changes that could decrease or 

increase assigned dose. SC&A did not identify any findings or observations concerning sections 

3–6 of the Weldon Spring 2013 TBD. SC&A summarized the changes that have the potential to 

increase assigned dose in section 3.2 of this report and had two observations there concerning 

PER-051, but there were no findings or observations involving the revised TBDs. 

4.2 SC&A’s comments 

SC&A confirmed that the revisions incorporated into Weldon Spring ORAUT-TKBS-0028-3, 

ORAUT-TKBS-0028-4, ORAUT-TKBS-0028-5, and ORAUT-TKBS-0028-6 were scientifically 

sound. Since NIOSH reevaluated all Weldon Spring noncompensated claims and reworked the 

applicable claims using the revised TBDs, SC&A finds NIOSH’s corrective actions to be 

appropriate. 

SC&A has no findings associated with subtask 2. 
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5 Subtask 3: Evaluate the PER’s Stated Approach for Identifying the 

Number of DRs Requiring Reevaluation of Dose

5.1 NIOSH’s selection criteria

According to section 3.0 of PER-051, NIOSH created a database to search for all claims using 

the search terms “Weldon Spring Plant,” “Weldon Spring Raffinate Pits,” and “Weldon Spring 

Quarry” to develop a list of all claims that may have had employment at the Weldon Spring site. 

The original search resulted in 286 potentially affected claims. Claims were excluded from 

reevaluation based on the following: 

• Four claims were removed because the DRs were completed using the revised TBDs. 

• Five claims had been pulled from dose reconstruction by the U.S. Department of Labor 

(DOL) and were removed from the list.

• 112 claims were removed because the previous DR resulted in a POC of 50 percent or 

greater.

• 46 of the claims also had employment at Mallinckrodt and were part of the Special 

Exposure Cohort (SEC) at that facility.

• Two claims were excluded because they had no verified Weldon Spring employment and 

the Weldon Spring TBDs were not used in the DR. 

• Two claims were excluded because the employment only included the construction 

period prior to the start of any radiological operations. 

• Three claims were removed prior to being evaluated further. One was determined to meet 

the Mallinckrodt SEC criteria. A DR for this claim was done prior to the designation of 

the Mallinckrodt SEC, but no DR would now be necessary for a compensation decision. 

The second was removed because the employment was outside the covered period for the 

site. The third claim was returned to NIOSH for a new DR for other reasons. That claim 

will be revised using the current revision of the TBDs. 

This resulted in 112 claims remaining for reevaluation. Dose for the remaining 112 claims was 

recalculated using the current revisions of the TBDs and any other applicable documents. The 

following is a summary of the reevaluation of 112 remaining claims: 

• The resulting POC for 101 of the claims was below 45 percent. 

• Eight of the claims resulted in a POC greater than 50 percent. 

• Three claims had a POC between 45 percent and 50 percent. For those three claims, the 

Interactive RadioEpidemiological Program was run 30 times at 10,000 iterations per 

NIOSH procedures, and the resulting POC was still less than 50 percent for each of those 

claims.

PER-051 states that NIOSH will provide the DOL with the list of all the claims evaluated under 

this PER. Further, NIOSH will request that DOL return the eight claims that would now result in 

a POC greater than 50 percent. 
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5.2 SC&A’s comments

The selection criteria used by NIOSH for previously completed DRs that required reevaluation 

under PER-051 are reasonable. SC&A had no findings but did have an observation associated 

with subtask 3. 

Observation 2: Eliminating claims due to being reevaluated under an SEC

PER-051 indicates that 46 of the claims were removed from the reevaluation list because the 

energy employees also had employment at Mallinckrodt and were part of the SEC at that facility. 

However, a claim may also have a non-SEC cancer that would need to be reevaluated using the 

revised Weldon Spring documents for medical coverage. How does NIOSH assure that a claim 

does not have additional non-SEC cancers before removing it from consideration under a PER? 
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6 Subtask 4: Conduct Audits of a Sample Set of Reevaluated DRs 

Mandated by DCAS-PER-051

Previous sections of this report described changes introduced in revisions of WSP TBDs that

could increase the dose assigned for the periods covered for the WSP site. 

For SC&A to satisfy its commitment under subtask 4, SC&A suggests that two or three DR

claims be selected for review from the WSP site during the operational period (1957–1966). 

Instead of a focused review of the claims, SC&A suggests that SC&A perform a complete DR 

review of the claims, since the TBDs have undergone major revisions with many changes. 

SC&A does suggest that the selection process should attempt to include the following criteria to 

address some of the major changes in the TBDs: 

1. occupational medical x-rays with skin cancer(s)

2. environmental intakes consisting of exposure to uranium, thorium, and RU contaminants 

3. environmental external ambient exposure 

4. internal intakes consisting of exposure to uranium ore concentrates, thorium, 

RU contaminants, thoron, and radon 

5. external photon dose for an operator, material handler, or trade worker 
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7 References

National Institute for Occupational Safety and Health. (2015). Weldon Spring Plant (DCASPER-051, rev. 0). https://www.cdc.gov/niosh/ocas/pdfs/pers/dc-per51-r0.pdf

Oak Ridge Associated Universities Team. (2005a). Weldon Spring Plant – Occupational medical 

dose (ORAUT-TKBS-0028-3, rev. 00). https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon3.pdf

Oak Ridge Associated Universities Team. (2005b). Dose reconstruction from occupationally

related diagnostic x-ray procedures (ORAUT-OTIB-0006, rev. 03). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/tibs/or-t6-r3.pdf

Oak Ridge Associated Universities Team. (2005c). Weldon Spring Plant – Occupational 

environmental dose (ORAUT-TKBS-0028-4, rev. 00). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon4.pdf

Oak Ridge Associated Universities Team. (2005d). Weldon Spring Plant – Occupational internal 

dose (ORAUT-TKBS-0028-5, rev. 00). https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon5.pdf

Oak Ridge Associated Universities Team. (2005e). Weldon Spring Plant – Occupational 

external dosimetry (ORAUT-TKBS-0028-6, rev. 00).

https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon6.pdf

Oak Ridge Associated Universities Team. (2011). Dose reconstruction from occupational 

medical x-ray procedures (ORAUT-OTIB-0006, rev. 04). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/tibs/or-t6-r4.pdf

Oak Ridge Associated Universities Team. (2012). Site profile and technical basis document 

development (ORAUT-PROC-0031, rev. 04). 

Oak Ridge Associated Universities Team. (2013a). Weldon Spring Plant – Occupational medical 

dose (ORAUT-TKBS-0028-3, rev. 01). https://www.cdc.gov/niosh/ocas/pdfs/tbd/weldon3-r1.pdf

Oak Ridge Associated Universities Team. (2013b). Weldon Spring Plant – Occupational 

environmental dose (ORAUT-TKBS-0028-4, rev. 01). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon4-r1.pdf

Oak Ridge Associated Universities Team. (2013c). Weldon Spring Plant – Occupational internal 

dose (ORAUT-TKBS-0028-5, rev. 01). https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon5-

r1.pdf

Oak Ridge Associated Universities Team. (2013d). Weldon Spring Plant – Occupational internal 

dose (ORAUT-TKBS-0028-5, rev. 02). https://www.cdc.gov/niosh/ocas/pdfs/arch/weldon5-

r2.pdf

Oak Ridge Associated Universities Team. (2013e). Weldon Spring Plant – Occupational 

external dosimetry (ORAUT-TKBS-0028-6, rev. 01). 

https://www.cdc.gov/niosh/ocas/pdfs/tbd/weldon6-r1.pdf
Effective date: 9/21/2023 Revision No. 1 (Draft) Document No.: SCA-TR-2023-PER051 Page 18 of 18

NOTICE: This report 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.

Oak Ridge Associated Universities Team. (2017). Weldon Spring Plant – Occupational internal 

dose (ORAUT-TKBS-0028-5, rev. 04). https://www.cdc.gov/niosh/ocas/pdfs/tbd/weldon5-r4.pdf

Oak Ridge Associated Universities Team. (2020). Weldon Spring Plant – Occupational 

environmental dose (ORAUT-TKBS-0028-4, rev. 04). 

https://www.cdc.gov/niosh/ocas/pdfs/tbd/weldon4-r4-508.pdf

SC&A, Inc. (2009). Review of the NIOSH site profile for the Weldon Spring Site in Weldon 

Spring, Missouri (SCA-TR-TASK1-0028, rev. 0). 

https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-weldonsp-r0.pdf

U.S. Department of Energy (DOE). (2001). Guide of good practices for occupational 

radiological protection in uranium facilities (DOE-STD-1136-2000, Change Notice No. 3). 

SRDB Ref. ID 4617