Review of DCAS-PER-051 for the 

Weldon Spring Plant, Weldon Spring, 

MO

Ron Buchanan, PhD, CHP

Advisory Board on Radiation and Worker Health, 

Subcommittee for Procedure Reviews

November 16, 2023
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Weldon Spring site profile revisions that 

triggered PER-051

 ORAUT-TKBS-0028-3 (TBD-3), occupational medical dose, rev. 01, 

issued January 30, 2013

 ORAUT-TKBS-0028-4 (TBD-4), occupational environmental dose, 

rev. 01, issued May 17, 2013

 ORAUT-TKBS-0028-5 (TBD-5), occupational internal dose, rev. 01, 

issued March 15, 2013; rev. 02, issued May 21, 2013

 ORAUT-TKBS-0028-6 (TBD-6), occupational external dose, rev. 01, 

issued February 6, 2013

 DCAS-PER-051, “Weldon Spring Plant,” issued March 4, 2015, to 

address changes in dose reconstruction (DR) procedures using the 

revised site profile documents
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Weldon Spring facilities

 Weldon Spring Plant (WSP), Weldon Spring Quarry (WSQ), 

and the Weldon Spring Raffinate Pits (WSRP)

 Referred to as the “Weldon Spring Plant” in general

 Operated by 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
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Four periods of site operations

1. Site acquisition and development: 1954–1957

2. Operational: 1957–1966

3. Post-operational: 1967–1985. U.S. Department of Defense 

(DOD), not the U.S. Department of Energy (DOE), controlled:

• WSP during the post-operational period 1967–1985

• WSRP and WSQ during 1967–1974

4. Remediation: 1985–2002
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EEOICPA coverage

 WSP employment is covered:

– Operational period (1957–1966)

– Remediation period (1985–2002)

 WSQ and WSRP employment is covered:

– Operational period (1957–1966)

– Post-operational period (1975–1984)

– Remediation period (1985–2002)
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Radionuclides of dose significance

 Natural uranium (NU) processed 1957–1962

 After 1962, all uranium is assumed to be enriched to 1%

 Natural thorium

 Recycled uranium (RU) was processed beginning in 1961

 Radon-222 and radium-228 considered to be potentially 

significant for DR
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Internal monitoring

 Operational period (1957–1966): uranium urine bioassays, no 

records of thorium monitoring

 Post-operational period (1967–1985): no DOE contract 

personnel bioassay monitoring appears to have been 

conducted during this period

 Remediation period (1985–2002): extensive bioassay 

monitoring program was conducted from 1991 to 2001
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External monitoring

 Operational period (1957–1966): Employees in radiological 

areas were monitored. No ambient exposure rates recorded 

during the operational period.

 Post-operational period (1967–1985): No record of external 

monitoring for DOE contract personnel. No site surveys until 

1982, except for a 1975 aerial radiological survey. Site external 

ambient exposure monitoring began in 1982.

 Remediation period (1985–2002): Personnel external 

monitoring was provided during the remediation period. 
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DCAS-PER-051 for Weldon Spring 

ORAUT-TKBS-0028-3, -4, -5, and -6

 There were several technical basis document (TBD) changes 

that covered all operational time periods and job types. 

Therefore, no claims were excluded from further evaluation 

based on job types or employment period.

 Changes included:

– Change in assumed isotopic ratios for uranium ore concentrates

– Addition of a neutron-to-photon ratio

– Addition of a geometry correction factor for external dose

– Addition of a thoron exposure dose

– Change in RU contaminate fractions

– An increase in the radon exposure estimate.
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SC&A’s review of PER-051

 February 16, 2023: The Subcommittee for Procedure Reviews 

(SPR) tasked SC&A to review DCAS-PER-051, “Weldon Spring 

Plant.”

 August 10, 2023: SC&A issued “A Review of NIOSH’s 

Program Evaluation Report DCAS PER-051, ‘Weldon Spring 

Plant.’”

 September 21, 2023: SC&A issued revision 1 of “A Review of 

NIOSH’s Program Evaluation Report DCAS PER-051, ‘Weldon 

Spring Plant.’”
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SC&A’s subtask 1 review of PER-051

 Subtask 1: Identify the circumstances that necessitated PER-051.

 SC&A reviewed rev. 01 of TBD-3, TBD-4, and TBD-6; rev. 02 of 

TBD-5; and PER-051. 

 SC&A found that PER-051 addressed the changes in these 

revisions that could potentially result in increases in internal and 

external dose assignments. 

 Additional changes in the revisions were for other purposes and did 

not result in a potential increase in assigned dose. 

 SC&A had no findings but did have one observation for ORAUTTKBS-0028-6 pertaining to subtask 1.
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SC&A’s observation for subtask 1

Observation 1: Use of neutron-to-gamma ratio

Section 2.0 of PER-051 states that the revisions to the TBDs included the 

addition of a neutron-to-photon ratio. However, it appears that revision 00 of 

ORAUT-TKBS-0028-6 (2005) contains the same neutron-to-photon ratio 

recommendations as revision 01 (2013), as follows:

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

depleted and low enriched UF4 [uranium tetrafluoride] 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 

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.
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NIOSH’s review of claims under PER-051

 NIOSH issued rev. 00 of TBD-3, TBD-4, and TBD-6 in 2005, 

and rev. 01 in 2013. 

 NIOSH issued rev. 00 of TBD-5 in 2005, and rev. 01 and 02 

in 2013. 

 Under PER-051, NIOSH reevaluated all noncompensated 

claims using the current version of the TBDs; therefore, NIOSH 

did not address specific changes in rev. 01 compared to rev. 00 

(or rev. 02 compared to rev. 00 or 01 for TBD-5) that could lead 

to an increase in assigned dose.
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SC&A’s subtask 2 review of PER-051

 Subtask 2: Assess NIOSH’s specific methods for corrective 

action, including a review of TBD-3, TBD-4, TBD-5, and TBD-6.

 SC&A had previously reviewed rev. 00 of TBDs-3–6 in 2009.

 Rev. 01 of TBDs-3–6, and rev. 02 of TBD-5 had not been 

reviewed by SC&A. 

 SC&A’s review of Weldon Spring TBDs 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.
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SC&A’s review of sections 3–6 of 2013 TBD

 Determined if the revisions contained technically correct 

methodology and information. 

 Evaluated appropriate references as needed. 

 Analyzed changes that could decrease or increase assigned 

dose. 

 Did not identify any findings or observations concerning 

sections 3–6 of the 2013 Weldon Spring TBD.

 Summarized the changes that have the potential to increase 

assigned dose in section 3.2 of SCA’s report.
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SC&A’s comments on subtask 2

 SC&A confirmed that the 2013 revisions incorporated in 

Weldon Spring TBD-3, TBD-4, TBD-5, and TBD-6 were 

scientifically sound. 

 SC&A finds NIOSH corrective actions to be appropriate since 

NIOSH reevaluated all Weldon Spring noncompensated claims 

and reworked the applicable claims using the revised TBDs.

 There are no findings associated with subtask 2.
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SC&A’s subtask 3 review of PER-051

 Subtask 3: Evaluate the PER’s stated approach for identifying 

the number of DRs requiring reevaluation of dose

 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.
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Subtask 3: Removal of DRs not requiring 

reevaluation of dose

 NIOSH removed 174 claims for the following reasons:

– 4 claims: DRs were completed using the revised TBDs

– 5 claims: pulled from DR by the U.S. Department of Labor (DOL)

– 112 claims: previous DR resulted in a POC of ≥50%

– 46 claims: part of Mallinckrodt Special Exposure Cohort (SEC)

– 2 claims: no verified Weldon Spring employment and DR did not use Weldon 

Spring TBDs

– 2 claims: employment only included the construction period prior to the start of 

any radiological operations

– 3 claims: removed prior to being evaluated further for the following reasons: 

• 1 claim: met the Mallinckrodt SEC criteria 

• 1 claim: employment was outside the covered period for the site

• 1 claim: returned to NIOSH for a new DR for other reasons, will be revised 

using the current TBDs
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Subtask 3: Evaluation of remaining claims

 Dose for the remaining 112 claims was recalculated using the 

current revisions of the TBDs and other applicable documents. 

The reevaluation found:

– 101 claims: The resulting POC was below 45%.

– 8 claims: Resulted in a POC greater than 50%. NIOSH will request that 

DOL return the eight claims for reevaluation.

– 3 claims: Had a POC between 45% and 50%. For those 3 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% for each claim.
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Subtask 3: SC&A’s evaluation of selection 

process

 SC&A found that 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 one observation associated 

with subtask 3.
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SC&A’s observation for 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 nonSEC 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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SC&A’s subtask 4 review of PER-051

Subtask 4: Conduct audits of a sample set of reevaluated DRs mandated by PER- 051

SC&A suggests that 2–3 DR claims be selected for review from the WSP site 

during the operational period (1957–1966). Since the TBDs have undergone major 

revisions, a complete DR review will be performed. SC&A suggests that the 

selection process should attempt to include the following criteria:

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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Summary of SC&A’s evaluation of site profile

 SC&A’s review of ORAUT-TKBS-0028-3, -4, and -6, rev. 01, 

identified no findings or observations.

 SC&A’s review of ORAUT-TKBS-0028-5, rev. 02, identified no 

findings or observations.
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Summary of SC&A’s evaluation of PER-051

 SC&A’s review of PER-051 identified no findings and two 

observations: 

– Observation 1: Use of neutron-to-gamma ratio 

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

SEC

 SC&A requests that: 

– NIOSH select appropriate claims for review under subtask 4

– The SPR task SC&A with the evaluation of selected claims
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Questions?