SC&A’s Review of 

DCAS-PER-087, 

“Clarksville and 

Medina Modification 

Centers”

Ron Buchanan, PhD, CHP

Joe Fitzgerald, MS, MPH

Advisory Board on Radiation and Worker 

Heath, Subcommittee for Procedure Reviews

November 3, 2021
Introduction

◆ The Clarksville Modification Center (CMC) was 

located in Clarksville, TN; covered period 1949-1967

◆ The Medina Modification Center (MMC) was located 

in San Antonio, TX; covered period 1958-1966 

◆ The two sites were under contract to the U.S. Atomic 

Energy Commission to support nuclear weapons and 

weapon components maintenance and storage

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Program evaluation report 

DCAS-PER-087

◆ Issued January 18, 2019, for the Clarksville and 

Medina Modification Centers

◆ Earlier revisions to ORAUT-TKBS-0039 primarily 

resulted in decreases (or no change) to dose 

estimates

◆ PER-087 (NIOSH, 2019) was issued because 

revision 03 of ORAUT-TKBS-0039 (NIOSH, 2017) 

could increase some external doses assigned 

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Potential areas of external dose 

increase

◆ Lumbar-spine (L-S) x-ray examination dose to some organs 

could increase because of the use of L-S exam doses as listed 

in ORAUT-OTIB-0006, revision 03 PC-1 (NIOSH, 2005)

◆ Dose to lower torso organs could increase for some workers 

due to establishing a scaling factor for workers who held 

weapon pits in their laps in the sitting position 

◆ Unmonitored external shallow dose increased for all years due 

to the incorporation of ORAUT-OTIB-0086, revision 01 

(NIOSH, 2016a), into the Pantex technical basis document 

(TBD), ORAUT-TKBS-0013-6 (NIOSH, 2016b) 

4
Internal dose 

◆ No changes in revision 03 of the TBD resulted in 

an increase in internal dose

◆ PER-087 does not contain internal dose 

modification recommendations

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TBD for Clarksville and Medina 

Modification Centers

◆ Initial dose reconstructions (DRs) were based on 

using complex-wide methods or other documents

◆ ORAUT-TKBS-0039, revision 00 (NIOSH, 2006)

◆ ORAUT-TKBS-0039, revision 01 (NIOSH, 2012)

◆ ORAUT-TKBS-0039, revision 02 (NIOSH, 2013)

◆ ORAUT-TKBS-0039, revision 03 (NIOSH, 2017)

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Cases to be evaluated under DCASPER-087

◆ Because of the variety of DR methods used in 

the past, no populations of claims were excluded 

from reevaluation based on their being 

unaffected by the latest changes

◆ All claims associated with the CMC and the MMC 

were considered

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SC&A’s review of PER-087 and TBD 

revision 03

◆ On March 15, 2021, the Advisory Board on Radiation and 

Worker Health tasked SC&A to review DCAS-PER-087 and the 

associated site profile, ORAUT-TKBS-0039, revision 03

◆ SC&A issued revision 1 of its review on September 28, 2021 

(SC&A, 2021), addressing:

– Subtask 1: Identify the circumstances that necessitated PER-087

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

including a review of ORAUT-TKBS-0039, revision 03

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

number of DRs requiring reevaluation of dose

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

mandated by PER-087

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SC&A’s review of PER-087 subtask 1

◆ Subtask 1: Identify the circumstances that 

necessitated PER-087

◆ SC&A’s evaluation:

– SC&A found that NIOSH correctly identified the 

changes in revision 03 of the TBD and addressed them 

in PER-087

– SC&A had no observations or findings concerning 

subtask 1

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SC&A’s review of PER-087 subtask 2

◆ Subtask 2: Assess NIOSH’s specific methods for 

corrective action, including a review of ORAUT-TKBS0039, revision 03

◆ SC&A’s review methodology:

– Evaluation of status of findings from SC&A’s review of TBD 

revision 00

– Review of TBD revision 03 that necessitated PER-087

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Previous SC&A evaluation of 

ORAUT-TKBS-0039, revision 00

◆ The Board tasked SC&A to conduct a technical 

review of revision 00 of ORAUT-TKBS-0039

◆ SC&A’s (2012) review identified findings that 

could impact the reconstruction of worker doses 

◆ SC&A identified seven findings concerning 

internal and external DR

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SC&A’s internal dose findings from 

review of TKBS-0039, revision 00

◆ SC&A had four findings about internal dose 

(findings 1, 2, 3, and 5)

◆ All internal dose findings were rendered 

moot by the designation of a Special 

Exposure Cohort (SEC) class for all 

employees at Clarksville and Medina for 

the operational years in question due to the 

inability to reconstruct internal doses

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SC&A’s external dose findings from 

review of TKBS-0039, revision 00

◆ Finding 4: Neutron-to-photon ratio method cited has been replaced 

with correction factor for neutron film coupled with Monte Carlo NParticle (MCNP)-based estimate for missed doses below 0.5 MeV 

energy threshold; however, questions remain

◆ Finding 6: Use of surrogate Pantex external dose distribution for 

Clarksville/Medina “exposure groups” belies lack of dose records in 

earlier years, dosimeter uncertainty, and definitive operational 

information

◆ Finding 7: Lack of dose records and source term characterization 

data for Clarksville/Medina leads to use of inadequately justified 

surrogate data

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Status of finding 4 from review of 

TKBS-0039, revision 00

◆ Finding 4: N/P ratio method cited has been replaced with 

correction factor for neutron film coupled with MCNP-based 

estimate for missed doses below 0.5 MeV energy threshold

◆ In subsequent NIOSH revisions of TKBS-0039, the MCNP 

approach was supplanted by use of correction factors with an 

overall correction factor of 2.9

◆ SC&A evaluated the individual correction factors and the 

resulting correction factor of 2.9 and is satisfied with this 

resolution; SC&A considers finding 4 resolved

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Status of finding 6 from review of 

TKBS-0039, revision 00

◆ Finding 6: Use of surrogate Pantex external dose 

distribution for Clarksville/Medina

◆ NIOSH reworked all the previous claims per 

DCAS-PER-087, using revision 03 of the TBD 

and OTIB-0086; therefore, changes in external 

dose assignments were accounted for

◆ SC&A is satisfied with this resolution and 

considers finding 6 resolved

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Status of finding 7 from review of 

TKBS-0039, revision 00

◆ Finding 7: Use of surrogate data for Clarksville is 

not adequately addressed in TBD

◆ SC&A did not find that finding 7 was adequately 

addressed in revision 03 of the TBD

◆ SC&A recommends that the original finding 7 

remain open as finding 1 of this PER-087 review

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Issues in TBD revision 03 that 

necessitated PER-087

◆ Three technical issues addressed in TBD 

revision 03 that resulted in the issuance of PER087:

1. Surrogate organ 

2. Pits in lap adjustment

3. Shallow dose

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SC&A’s evaluation of TBD rev. 03 

issues that resulted in PER-087

1. Surrogate organ – SC&A finds the surrogate organ 

changes in TBD revision 03 were correctly addressed in 

PER-087 

2. Pits in lap adjustment – While SC&A concurs with the 

derivation of the scaling factor of 0.125, SC&A questions 

the application of it as stated on page 27 of TBD 

revision 03 (refer to observation 1 on slide 19)

3. Shallow dose – SC&A concurs that ORAUT-OTIB-0086, 

revision 01, should be used for assignment of shallow 

dose, per the Pantex external dose TBD

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Observation 1

Observation 1: Scaling factor needs clarification

TBD revision 03, page 27, instructs the dose reconstructor 

to multiply the 95th-percentile glovebox correction factor 

(2.19*(1.34)1.645) by 0.125; however, this equals 0.44, which 

would lower the actual dose assigned

It would appear that the wording in the first paragraph on 

page 27 of TBD revision 03 should instruct the dose 

reconstructor to use the following scaling factor:

Scaling factor = (1.0 × 7/8 + 2.19*(1.34)1.645 × 0.125) = 1.32

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SC&A’s review of PER-087 subtask 3

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

number of DRs requiring reevaluation of dose

◆ NIOSH’s search resulted in a total of 172 claims

◆ 122 claims were removed for various reasons:

– 51 previous DRs resulted in a probability of causation (POC) >50 percent

– 49 were included in the SEC

– 11 were duplicate claims identified in the initial search

– 11 were evaluated under a PER for Pantex

◆ 50 claims were recalculated using revision 03 of TKBS-0039 in 

conjunction with PER-087

◆ Rework of all 50 claims resulted in new POCs below 45 percent

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SC&A’s evaluation of NIOSH’s claim 

selection process for subtask 3

◆ SC&A determined that the selection criteria used 

by NIOSH for previously completed DRs that 

require reevaluation under DCAS-PER-087 were 

valid 

◆ SC&A had no findings or observations associated 

with subtask 3

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SC&A’s review of PER-087 subtask 4

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

mandated by PER-087 

◆ SC&A recommended:

– At least one DR be selected for review from each of the CMC and MMC 

sites during the respectively covered periods 

– Each of the DRs needs to include the requirement of assigning:

• L-S x-ray examination dose

• Lower torso dose due to handing weapons pits in the lap

• External shallow dose

– If all these exposures cannot be located in a single DR for each site, then 

additional DRs that do contain these elements will be needed

◆ Currently, SC&A has no findings or observation concerning subtask 4

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Summary

◆ Finding 1: The use of surrogate data for 

Clarksville was not adequately addressed in TBD 

revision 03 (i.e., original finding 7 from SC&A’s 

2012 review of TBD revision 00 remains open)

◆ Observation 1: Scaling factor needs clarification

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Questions?

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References

National Institute for Occupational Safety and Health. (2005). Dose 

reconstruction from occupationally related diagnostic x-ray procedures (ORAUTOTIB-0006, rev. 03 PC-1). https://www.cdc.gov/niosh/ocas/pdfs/arch/tibs/or-t6-

r3-p1.pdf

National Institute for Occupational Safety and Health. (2006). Site profile for 

Clarksville Base Weapons Storage Area and Modification Center with 

supplementary guidance for Medina Base (ORAUT-TKBS-0039, rev. 00). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/clarkmed-r0.pdf

National Institute for Occupational Safety and Health. (2012). Site profile for 

Clarksville Modification Center with supplementary guidance for the Medina 

Modification Center (ORAUT-TKBS-0039, rev. 01). 

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

National Institute for Occupational Safety and Health. (2013). Site profile for 

Clarksville Modification Center with supplementary guidance for the Medina 

Modification Center (ORAUT-TKBS-0039, rev. 02). 

https://www.cdc.gov/niosh/ocas/pdfs/arch/clarkmed-r2.pdf

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References 2

National Institute for Occupational Safety and Health. (2016a). Pantex external 

coworker model (ORAUT-OTIB-0086, rev. 01). 

https://www.cdc.gov/niosh/ocas/pdfs/tibs/or-t86-r1.pdf

National Institute for Occupational Safety and Health. (2016b). Pantex Plant –

Occupational external dose (ORAUT-TKBS-0013-6, rev. 03). 

https://www.cdc.gov/niosh/ocas/pdfs/tbd/pantex6-r3.pdf

National Institute for Occupational Safety and Health. (2017). Site profile for 

Clarksville Modification Center with supplementary guidance for the Medina 

Modification Center (ORAUT-TKBS-0039, rev. 03). 

https://www.cdc.gov/niosh/ocas/pdfs/tbd/clarkmed-r3.pdf

National Institute for Occupational Safety and Health. (2019). Clarksville and 

Medina Modification Centers (DCAS-PER-087). 

https://www.cdc.gov/niosh/ocas/pdfs/pers/dc-per87-508.pdf

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References 3

SC&A, Inc. (2012). Review of the site profile for the Clarksville and Medina 

Plants (SCA-TR-SP2012-0007, rev. 0). 

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

SC&A, Inc. (2021). A review of NIOSH’s program evaluation report DCAS-PER087, “Clarksville and Medina Modification Centers” (SCA-TR-2021-PER087, 

rev. 1). https://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-per87-r1-508.pdf

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