Review of DCAS PER-083 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
2

Weldon Spring site profile, 2013

 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. 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
3

Weldon Spring site profile, 2017

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

rev. 02, issued March 29, 2017

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

rev. 03, issued September 8, 2017

 ORAUT-TKBS-0028-5 (TBD-5), occupational internal dose, rev. 03, 

issued March 14, 2017

 ORAUT-TKBS-0028-5 (TBD-5), occupational internal dose, rev. 04, 

issued August 31, 2017

 DCAS-PER-083, “Weldon Spring Plant TBD Revision,” issued 

January 7, 2019, to address changes in 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 WSP 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 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-083 for Weldon Spring TBD-4 and 

TBD-5

 NIOSH issued rev. 02 and 03 of TBD-4 and rev. 03 and 04 of 

TBD-5 in 2017. 

 Several technical basis document (TBD) changes could 

increase the assignment of environmental and internal intakes 

and resulting doses.

 Changes include:

– Consistent use of RU intakes started in 1961, not after 1961 

– Contribution of RU contaminants to internal dose

– Specific activity of 1% enriched uranium (EU)
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SC&A’s review of PER-083

 February 16, 2023: The Subcommittee for Procedure Reviews 

(SPR) tasked SC&A to review DCAS-PER-083, “Weldon Spring 

Plant TBD Revision”

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

Program Evaluation Report DCAS PER-083, ‘Weldon Spring 

Plant TBD Revision’”

 September 22, 2023: SC&A issued rev. 1 of “A Review of 

NIOSH’s Program Evaluation Report DCAS PER-083, ‘Weldon 

Spring Plant’”
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SC&A’s subtask 1 review of PER-083

 Subtask 1: Evaluate changes that necessitated PER-083.

 SC&A reviewed TBD-4 rev. 02 and 03, TBD-5 rev. 03 and 04, and 

PER-083. 

 SC&A found that PER-083 addressed the changes in these TBD 

revisions that could potentially result in increases in internal and 

external dose assignments. 

 Additional changes in the TBD revisions were for other purposes 

and did not result in a potential increase in assigned dose. 

 SC&A had no findings or observations for TBD-4 and TBD-5 

pertaining to subtask 1.
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NIOSH’s review of claims under PER-083 for 

RU in 1961

 In considering the last TBD revisions, NIOSH reviewed all 

Weldon Spring Plant claims completed between March and 

September 2017 concerning RU starting in 1961 versus RU 

starting after 1961. 

 Only one claim had employment in 1961. NIOSH reviewed the 

DR for that claim and found that RU intakes were assigned in 

1961. Therefore, no further consideration for this issue was 

necessary.
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NIOSH’s review of claims under PER-083 for 

RU and EU

 NIOSH reevaluated all applicable Weldon Spring claims and 

reworked the appropriate claims using the revised TBDs.
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SC&A’s subtask 2 review of PER-083

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

of site profile.

 SC&A had previously reviewed rev. 00 of TBD-4 and TBD-5 in 2009.

 SC&A reviewed rev. 01 of TBD-4 and rev. 01 and 02 of TBD-5 in 

subtask 2 of their 2023 review of DCAS-PER-051.

 Rev. 02 and 03 of TBD-4 and rev. 03 and 04 of TBD-5 had not been 

reviewed by SC&A. 

 SC&A’s review of Weldon Spring TBD-4 and TBD-5 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 2017 TBD-4 and TBD-5

 Determined if the revisions contained technically correct 

methodology and information.

 Evaluated appropriate references as needed. 

 Analyzed changes that could decrease or increase assigned 

dose. 

 Summarized the changes that have the potential to increase 

assigned dose for TBD-4 (section 3.2.1 of SC&A’s report) and 

for TBD-5 (section 3.2.2).
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SC&A’s comments on subtask 2

 SC&A confirmed that the revisions incorporated in the Weldon 

Spring TBD-4 and TBD-5 were scientifically sound. 

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

NIOSH reevaluated all applicable Weldon Spring claims and 

reworked the appropriate 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-083

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

the number of DRs requiring reevaluation of dose.

 NIOSH conducted a search for all claims with employment at 

any one of the three Weldon Spring facilities in the NIOSH 

claims tracking system (NOCTS). 

 NIOSH conducted a keyword search of DR reports for the word 

“Weldon.” 

 These searches identified 330 unique claims.
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Subtask 3: Removal of DRs not requiring 

reevaluation of dose

 NIOSH removed 190 claims for the following reasons:

– 3 claims: Completed with the current TBDs

– 126 claims: Had a POC equal to or greater than 50%

– 51 claims: Pulled from DR, primarily due to inclusion in the Mallinckrodt Special 

Exposure Cohort (SEC)

– 7 claims: Active at NIOSH at the time of the search and would be completed 

using the current TBDs

– 2 claims: No employment at Weldon Spring. They had been identified because 

the DR report mentioned Weldon Spring but there was actually no employment 

there, and the Weldon Spring TBDs were not used to estimate the dose.

– 1 claim: Met the criteria for the Mallinckrodt SEC and the DR was done prior to 

the designation of that SEC class. Therefore, it was removed from evaluation 

under PER-083.
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Subtask 3: Evaluation of remaining 140 claims

 The remaining 140 claims were to be reevaluated under this 

PER as follows:

– 2 claims were returned to NIOSH for a new DR (for other reasons) 

before the evaluation occurred. A new DR for these two claims would 

be completed using the current revisions of the TBDs. Therefore, the 

two claims were removed from further consideration under PER-083.

– 138 claims were reevaluated using the current revisions of the TBDs 

and all other applicable procedures.
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Subtask 3: Results of reevaluation of 138 

claims

 The reevaluation of remaining 138 claims under PER-083 resulted 

as follows:

– 129 claims had POC values that remained below 45%.

– 4 claims resulted in a POC between 45% and 52%. For those claims, the 

Interactive RadioEpidemiological Program (IREP) was run 30 times at 10,000 

iterations per NIOSH procedures. The resulting POC was less than 50% for 

all four claims.

– 5 claims resulted in a POC greater than 50%. 

 NIOSH will provide the U.S. Department of Labor (DOL) with the list 

of all the claims evaluated under this PER. Further, NIOSH will 

request that DOL return the five claims that would now result in a 

POC greater than 50%. 
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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-083 are reasonable. 

 SC&A had no findings or observations associated with 

subtask 3.
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SC&A’s subtask 4 review of PER-083

 Subtask 4: Conduct audits of a sample set of reevaluated DRs 

mandated by PER-083.

 SC&A suggests that 2–3 DR claims from the WSP site during 

the covered period be selected for a focused review.

 SC&A suggests that the claims selected should attempt to 

include the following criteria:

– Environmental intakes consisting of exposure to EU (1963–1966) and 

RU (1961–2001) contaminates

– Internal intakes consisting of exposure to EU (1963–1966) and RU 

contaminates (1961–2002)
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Summary of SC&A’s evaluation of site profile

 SC&A’s review of ORAUT-TKBS-0028-4, rev. 02 and 03, 

identified no findings or observations.

 SC&A’s review of ORAUT-TKBS-0028-5, rev. 03 and 04, 

identified no findings or observations.
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Summary of SC&A’s evaluation of PER-083

 SC&A’s review of PER-083 identified no findings or 

observations.

 SC&A requests:

– 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?