SC&A’s Review of DCAS-PER-092 for 

the Weldon Spring Plant, Weldon 

Spring, MO

Ron Buchanan, PhD, CHP

Advisory Board on Radiation and Worker Health, 

Subcommittee for Procedure Reviews

September 29, 2022
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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 operation

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 processed beginning in 1961

 Radon (Rn)-222 and radium (Ra)-228 considered to be 

potentially significant for dose reconstruction (DR)
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Internal monitoring

 Operational period, 1957–1966: Uranium urine bioassays, no 

records of thorium monitoring.

 DoD 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.

 DoD period, 1967–1985: No record of external monitoring for 

DOE contract personnel. No site surveys until 1982, except for 

a 1975 aerial radiological survey.

 Remediation period, 1985–2002: Personnel external 

monitoring was provided during this period. Site external 

ambient exposure monitoring began in 1982.
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Weldon Spring environmental dose site profile

 ORAUT-TKBS-0028-4, revision 00, issued June 28, 2005

 ORAUT-TKBS-0028-4, revision 01, issued May 17, 2013

 ORAUT-TKBS-0028-4, revision 02, issued March 29, 2017

 ORAUT-TKBS-0028-4, revision 03, issued September 8, 2017

 DCAS-PER-083, issued January 7, 2019, to address changes 

in DR procedures using ORAUT-TKBS-0028-4, revision 03

 ORAUT-TKBS-0028-4 revision 04, issued March 27, 2020 

(“TBD-4”)
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DCAS-PER-092 for Weldon Spring TBD-4

 Issued on March 29, 2021.

 Addressed changes in DR procedures for Weldon Spring 

facilities as a result of the issuance of ORAUT-TKBS-0028-4, 

rev. 04.
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TBD-4 rev. 04 changes that could increase 

assigned doses

 Environmental intakes of Rn-222 and Ra-228 were added for 

1963 through 1966.

 Uranium (U)-234 intakes were added for the Weldon Spring 

Quarry for the years 1990, 1991, 1993–1996, and 1998–2001.

 Onsite ambient gamma doses from 1957 to 1966 were 

previously applied as a constant value, but rev. 04 included 

geometric standard deviation values that are to be applied to 

the lognormal distribution for ambient gamma doses.
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SC&A’s review of PER-092

 On February 15, 2022, the Advisory Board on Radiation and 

Worker Health Subcommittee for Procedure Reviews (SCPR) 

tasked SC&A to review DCAS-PER-092, “Weldon Spring Plant”

 On June 9, 2022, SC&A issued “A Review of NIOSH’s Program 

Evaluation Report DCAS-PER-092, ‘Weldon Spring Plant’”
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Subtask 1: Identify the circumstances that 

necessitated PER-092

 PER-092 addressed the changes in revision 04 of the site 

profile that could potentially result in increases in internal and 

external dose assignments. 

 These changes included:

– Addition of Rn-222 and Ra-228 for 1963–1966

– U-234 intakes added for WSQ for certain years during 1990–2001

– Use of lognormal distribution for external ambient doses for 1957–1966
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Subtask 1: SC&A evaluation of changes that 

necessitated PER-092

 SC&A reviewed TBD-4 rev. 04 and PER-092. 

 SC&A found that PER-092 addressed the changes in rev. 04 

that could potentially result in increases in internal and external 

dose assignments. 

 Additional changes in rev. 04 were for other purposes and did 

not result in a potential increase in assigned dose. 

 SC&A had no findings or observations pertaining to subtask 1.
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Subtask 2: Assess NIOSH’s revision of site 

profile

 NIOSH revised ORAUT-TKBS-0028-4 from rev. 03 to rev. 04 to 

modify the DR methodology to reflect best estimate DR 

methods and to update radionuclide intake values and intake 

years.

 SC&A reviewed TBD-4 rev. 04 and found:

– The radionuclide intake values were correct and appropriate as a 

function of the years listed in tables 4-3 and 4-4.

– The external onsite ambient dose values recommended in tables 4-6 

and 4-7 were correctly converted from a continuous exposure of 

8,760 hours/year (rev. 03) to 2,500 hours/year (rev. 04).

 SC&A had no findings about rev. 04 of ORAUT-TKBS-0028-4.
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Subtask 2, observation 1: Documentation in 

site profile

 SC&A did identify two documentation errors in rev. 04 of 

ORAUT-TKBS-0028-4:

– Figure 4-2: This figure is referred to in the next-to-last paragraph on 

page 14, but it appears that it was omitted in rev. 04 of TBD-4.

– Table 4-7: Footnote “a” of this table refers to “Table 4-5,” when it should 

read “Table 4-6.”

 SC&A’s review of rev. 04 has not previously been presented to 

the work group or NIOSH. Therefore, this observation remains 

to be addressed.
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Subtask 2: Assess NIOSH’s specific methods 

for corrective action in PER-092

 SC&A found that PER-092 addressed the changes in rev. 04 

that could potentially result in increases in internal and external 

dose assignments.

 SC&A had no findings or observations about PER-092.
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Subtask 3: Evaluate PER approach for identifying 

the number of DRs requiring reevaluation of dose

 NIOSH performed:

– Search of the NIOSH Claims Tracking System (NOCTS) database for 

employment at any of the three Weldon Spring sites.

– Text query using the keyword “Weldon Spring” in DR reports of 

previously completed claims. 

 The combined search identified a total of 338 cases.
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Subtask 3: Removal of DRs not requiring 

reevaluation of dose

 NIOSH removed 284 cases from this list for the following reasons:

– 51 cases: because they had been “pulled” from DR primarily due to inclusion 

in the Special Exposure Cohort.

– 135 cases: because the previous evaluation of the cases yielded probability 

of causation (POC) values ≥50 percent.

– 1 case: because it was returned for other reasons and would be processed 

using revision 04 of TBD-4.

– 7 cases: because they had no Weldon Spring employment or visits during the 

covered period. 

– 90 cases: because they were not affected by the changes in the revised TBD 

primarily; those were monitored individuals for which no environmental dose 

was assigned.
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Subtask 3: Evaluation of remaining cases

 Dose for the remaining 54 cases was recalculated using 

revision 04 of ORAUT-TKBS-0028-4 and all other applicable 

procedures.

 The resulting POC for all 54 claims was less than 45%.
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Subtask 3: SC&A’s evaluation of selection 

process

 SC&A found the selection criteria used by NIOSH for 

identifying previously completed DRs that required reevaluation 

under PER-092 are appropriate. 

 SC&A had no findings or observations associated with 

subtask 3.
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Subtask 4: Conduct audits of a sample set of 

reevaluated DRs mandated by PER-092

 SC&A suggest that DR cases be selected for review from the 

WSP site during the covered period. The combination of 

selected DRs needs to include the requirement of assigning:

– Environmental intakes of Rn-222 and Ra-228 during all or part of 

1963–1966

– Environmental intake of U-234 at the WSQ during all or part of 1990, 

1991, 1993–1996, and/or 1998–2001

– Onsite external ambient gamma dose during all or part of 1957–1966

 One, two, or three cases can be selected depending on how 

many are needed to address the required three dose 

assignments.
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Summary of SC&A’s evaluation of site profile

 SC&A’s review of ORAUT-TKBS-0028-4, rev. 04, identified no 

findings.

 SC&A did have an observation concerning documentation in 

the site profile:

– Figure 4-2 is missing.

– Table 4-7: footnote “a” needs to be revised.
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Summary of SC&A’s evaluation of PER-092

 SC&A’s review of PER-092 identified no findings or 

observations.

 SC&A does request that NIOSH select appropriate cases for 

review under subtask 4 and that the SCPR task SC&A with the 

evaluation of selected cases.
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Questions?