Draft 

ADVISORY BOARD ON 

RADIATION AND WORKER HEALTH 

National Institute for Occupational Safety and Health 

REVIEW OF THE SITE PROFILE FOR THE CLARKSVILLE 

AND MEDINA PLANTS 

Contract No. 200-2009-28555 

SCA-TR-SP2012-0007, Rev. 0

Prepared by 

Joseph Fitzgerald 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, Virginia 22182 

Saliant, Inc. 

5579 Catholic Church Road 

Jefferson, Maryland 21755

February 2012 

Disclaimer 

This document is made available in accordance with the unanimous desire of the Advisory Board on 

Radiation and Worker Health (ABRWH) to maintain all possible openness in its deliberations. However, 

the ABRWH and its contractor, SC&A, caution the reader that at the time of its release, this report is predecisional and has not been reviewed by the Board for factual accuracy or applicability within the 

requirements of 42 CFR 82. This implies that once reviewed by the ABRWH, the Board’s position may 

differ from the report’s conclusions. Thus, the reader should be cautioned that this report is for 

information only and that premature interpretations regarding its conclusions are unwarranted.

 
Effective Date: 

February 22, 2012 

Revision No. 

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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

Document No. 

SCA-TR-SP2012-0007 

Effective Date: 

February 22, 2012 

S. COHEN & ASSOCIATES: 

Technical Support for the Advisory Board on

Radiation & Worker Health Review of 

NIOSH Dose Reconstruction Program Revision No. 0 – (Draft) 

Review of the Site Profile for the Clarksville 

and Medina Plants Page 2 of 32 

Task Manager: 

________________________ Date: ___________ 

Joseph Fitzgerald 

Supersedes: 

N/A 

Project Manager: 

________________________ Date: ___________ 

John Stiver, PhD, CHP 

Reviewer(s); 

 John Stiver 

Record of Revisions 

Revision 

Number Effective Date Description of Revision 

0 (Draft) 02/22/2012 Initial issue 
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February 22, 2012 

Revision No. 

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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

TABLE OF CONTENTS 

Acronyms and Abbreviations ..........................................................................................................5 

1.0 Executive Summary.............................................................................................................7 

1.1 Summary of Findings...............................................................................................9 

1.1.1

......................................................................................9 

Finding 1: Unsupported Assumptions for Modeling Depleted 

Uranium Exposures

1.1.2

................................................................................................9 

Finding 2: Potential Thorium Exposure Pathway Not Addressed for 

Medina Plant

1.1.3

....................10 

Finding 3: Use of Pantex Tritium Dose Experience as Surrogate for 

Upper Bound for Clarksville/Medina Plants is Questionable

1.1.4

.....................................................................10 

Finding 4: N/P Ratio Method Cited has been Replaced with 

Correction Factor for NTA Film Coupled with MCNP-Based 

Estimate for Missed Doses below 0.5 MeV Energy Threshold; 

However, Questions Remain

1.1.5

..........................................11 

Finding 5: Inadequate Consideration of Potential Exposures 

Resulting from Handling of “Broken Arrows”

1.1.6

................................................................................................11 

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

1.1.7

...........................................................................................12 

Finding 7: Lack of Dose Records and Source Term Characterization 

Data for Clarksville/Medina leads to Use of Inadequately Justified 

Surrogate Data

1.2 Strengths ................................................................................................................12 

1.3 Opportunities for Improvement .............................................................................13 

2.0 Scope and Introduction ......................................................................................................14 

2.1 Review Scope.........................................................................................................14 

2.2 Assessment Criteria and Methods..........................................................................15 

2.2.1 Objective 1: Completeness of Data Sources.............................................15 

2.2.2 Objective 2: Technical Accuracy..............................................................16 

2.2.3 Objective 3: Adequacy of Data.................................................................16 

2.2.4 Objective 4: Consistency among Site Profiles..........................................16 

2.2.5 Objective 5: Regulatory Compliance and Quality Assurance ..................16 

2.3 Report Organization...............................................................................................17 

3.0 Vertical Issues....................................................................................................................18 

3.1

...............................................................................................................18 

Finding 1: Unsupported Assumptions for Modeling Depleted Uranium 

Exposures

3.2

.......................................................................................................................20 

Finding 2: Potential Thorium Exposure Pathway Not Addressed for Medina 

Plant

3.3

...........................................21 

Finding 3: Use of Pantex Tritium Dose Experience as Surrogate Upper 

Bound for Clarksville/Medina Plants is Questionable

3.4

.........................22 

Finding 4: N/P Ratio Method Cited has been Replaced with Correction 

Factor for NTA Film Coupled with MCNP-Based Estimate for Missed Doses 

below 0.5 MeV Energy Threshold; However, Questions Remain
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NOTICE:

3.5

...............................................................................24 

Finding 5: Inadequate Consideration of Potential Exposures Resulting from 

Handling of “Broken Arrows”

3.6

............................................................................................................24 

Finding 6: Use of Surrogate Pantex External Dose Distribution for 

Clarksville/Medina “Exposure Groups” Belies Lack of Dose Records in 

Earlier Years, Dosimeter Uncertainty Information, and Definitive Operational 

Information

3.7

........................26 

Finding 7. Lack of Adequate and Complete Source Term Characterization 

and Dose Records Preclude Use of Clarksville/Medina Site Data

4.0 Overall Adequacy of the Site Profile as a Basis for Dose Reconstruction ........................27 

4.1 Objective 1: Completeness of Data Sources.........................................................27 

4.2 Objective 2: Technical Accuracy..........................................................................27 

4.3 Objective 3: Adequacy of Data.............................................................................27 

4.4 Objective 4: Consistency among Site Profiles and Other NIOSH Documents ....28 

4.5 Objective 5: Regulatory Compliance and Quality Assurance ..............................28 

4.6 Inconsistencies and Editorial Errors in the Site Profile .........................................29 

5.0 References..........................................................................................................................30 

Attachment 1: Summary of Site Expert Interviews......................................................................32 
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ACRONYMS AND ABBREVIATIONS 

Advisory Board 

or ABRWH Advisory Board on Radiation and Worker Health 

AEC U.S. Atomic Energy Commission 

CATI Computer-Assisted Telephone Interview 

CFR Code of Federal Regulations

Ci curie 

cm3 cubic centimeter 

d day 

DOE U.S. Department of Energy 

dpm disintegrations per minute 

DU Depleted Uranium 

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000 

g gram 

HE High Explosive 

HEPA High Efficiency Particulate Air 

HHS Department of Health and Human Services 

hr hour 

IAAP Iowa Army Ammunition Plant 

ICRP International Commission on Radiological Protection 

INRAD Intrinsic Radiation measurements 

IREP Interactive RadioEpidemiological Program 

MCNP Monte Carlo N-Particle Transport Code 

MDL minimum detectable level 

MeV million electron volts 

MHSMC Mason and Hanger-Silas Mason Company 

mrem millirem 

n/p neutron-photon ratio 

NIOSH National Institute for Occupational Safety and Health 

NTA Nuclear Track Film Type A 

ORAUT Oak Ridge Associated Universities Team 

OTIB Oak Ridge Associated Universities Team Technical Information Bulletin 

pCi picocurie 

RST Radiological Safety Technician 

RTG Radioisotope Thermoelectric Generator 

SC&A S. Cohen & Associates (SC&A, Inc.) 

SEC Special Exposure Cohort 

SNL Sandia National Laboratory 

SRDB Site Research Database 
Effective Date: 

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NOTICE:

TBD Technical Basis Document 

TIB Technical Information Bulletin 

W28 Nuclear weapons system 

yr Year 
Effective Date: 

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1.0 EXECUTIVE SUMMARY 

This draft report presents the results of an independent review conducted by S. Cohen and 

Associates (SC&A) of ORAUT-TKBS-0039, Site Profile for Clarksville Base Weapons Storage 

Area and Modification Center with Supplementary Guidance for Medina Base (ORAUT 2006a), 

or Clarksville/Medina technical basis document (TBD), which was issued by the National 

Institute for Occupational Safety and Health (NIOSH) as a summary site profile document. 

SC&A conducted this review during the period August 2010 through November 2011. 

This review was conducted in accordance with the Advisory Board on Radiation and Worker 

Health’s Data Access and Interview Procedures (ABRWH 2009a) and SC&A’s Board-approved 

Standard Operating Procedure for Performing Site Profile Reviews (SC&A 2004). SC&A 

evaluated the site profile for completeness, technical accuracy, adequacy of data, compliance 

with regulatory objectives, and consistency with other site profiles. Review criteria and methods 

are described in greater detail in Section 2.0 of this report. 

The Clarksville and Medina Plants were 2 of 13 weapons storage areas (or “modification” 

centers) established in the 1940s under the Armed Forces Special Weapons Project. The 

Clarksville Base was constructed on a site adjacent to Fort Campbell, Kentucky, in the mid- to 

late-1940s, with the first weapons components arriving in July 1949. The Medina Base was 

constructed on 3,700 acres of Lackland Air Force Base near San Antonio, Texas, by the Air 

Force and the Atomic Energy Commission (AEC) between 1953 and 1955, with the first 

weapons components arriving in 1955. 

For Clarksville, maintenance and quality assurance was performed by Sandia Corporation (later 

Sandia National Laboratory) in conjunction with the U.S. Navy; from 1958 to 1965, this function 

was supported by Mason and Hanger-Silas Mason Company (MHSMC). In 1965, the 

Clarksville mission was transferred to Pantex and other facilities, but the facility was not 

officially transferred to the Army until 1969 (the AEC continued to manage the site until 1967, 

with uncertainty regarding its status in 1967–1969, although there were no weapon components 

handled during that period) (ORAUT 2006a). 

For Medina, corresponding activities were likewise performed by Sandia, AEC, and the Air 

Force from 1955 until MHSMC assumed responsibilities in 1959 (MHSMC was contracted in 

1958).1 In January 1966, the Medina mission was transferred to Pantex and the complex 

transferred to the Air Force. 

Storage of nuclear systems at Clarksville was in an underground tunnel and bunker complex at 

the site, with additional above-ground structures, such as gravel gerties, igloos, and conventional 

brick structures used variously for maintenance and storage. At Medina, similar storage 

facilities, bunkers, igloos, and gravel gerties were constructed to support weapons modification, 

maintenance, and later, disassembly. As noted in the site profile, Medina’s mission included 

performing “stockpile surveillance, modifications, retrofits, and weapon retirements,” as well as 

“inspections for corrosion and replacement of tritium reservoirs” (ORAUT 2006a). 

1

 However, the Department of Labor has only approved the site’s applicability under Energy Employee 

Occupational Illness Compensation Program Act (EEIOCPA) for 1958–1966. 
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Radiological source terms at both modification centers primarily consisted of potential exposure 

pathways for plutonium, uranium (enriched and depleted), tritium, polonium, and radon. Internal 

dose would be due to surface particulate contamination from uranium, plutonium, or polonium 

present on weapons components being handled; depleted uranium (DU) contamination at the 

burning grounds (from burning of high explosives); airborne tritium from component leaks; and 

elevated natural radon levels in structures. External dose would primarily consist of the beta, 

gamma, and neutron fields associated with direct handling of nuclear weapons components, with 

the nature of these fields varying by weapon type and work activity involved. Additional 

exposure source terms consisted of occupational medical dose from routine medical x-rays and 

onsite occupational environmental dose due primarily to tritium emissions. 

SC&A conducted data capture visits at Pantex and at Sandia National Laboratory for purposes of 

locating both classified and unclassified documents pertaining to Clarksville and Medina in 

August 2010, August 2011, and November 2011. Interviews were also conducted with former 

workers for both sites. The purpose of these interviews was to obtain first-hand accounts about 

past radiological controls, personnel monitoring programs, and site operations. 

 

This draft report was prepared at the request of the Advisory Board and covers ORAUT-TKBS0039, Site Profile for Clarksville Base Weapons Storage Area and Modification Center with 

Supplementary Guidance for Medina Base (ORAUT 2006a). As part of its evaluation, SC&A 

also reviewed other documents that were considered relevant, including the following: 

 Relevant technical information bulletins (TIBs) 

 Select documents that were referenced in the Clarksville/Medina Site Profile, particularly 

the Pantex Site Profile 

 Documents contained in the NIOSH Site Research Database (SRDB) 

 Documents retrieved from data capture at Pantex and Sandia National Laboratory 

 Documented interviews conducted with former Clarksville and Medina workers 

This review found that the NIOSH site profile for Clarksville/Medina, while acknowledging the 

lack of personnel monitoring data and useable site characterization information, did not 

adequately address the implications and shortcomings of applying what is effectively “surrogate” 

data from both the Iowa Army Ammunition Plant (IAAP) and the Pantex Plant as bounding dose 

estimates for operations at the two modification centers. Some of these implications include 

differing operations, varying time periods, and uncertain dosimetry and work procedures. While 

it is understood that such comparisons offer the only relevant characterization information 

available in lieu of actual site-specific data, more substantiation is necessary to justify the broad 

application of such data (albeit guidance on such substantiation was not available at the time of 

the initial site profile in 2006; it has since been codified into both NIOSH (OCAS 2008) and 

Advisory Board (ABRWH 2010) policy statements. Another implication is the carryover of 

deficiencies and dose reconstructability issues for IAAP and Pantex, as identified during their 

respective Special Exposure Cohort (SEC) evaluation reviews by NIOSH and the Advisory 

Board. Findings such as the inability to reconstruct dose with sufficient accuracy for DU at 

Pantex for 1958–1983, and corresponding Pantex Work Group findings governing dose 
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reconstructability of thorium exposures, will have clear implications for Clarksville and Medina 

dose reconstructions that will need to be addressed in the site profile. In terms of scope, SC&A 

also finds that the site profile fails to include any characterization of potential exposures that may 

have been associated with “broken arrow” systems that were handled at the two sites, as well as 

other non-routine handling of damaged systems received from the military. 

1.1 SUMMARY OF FINDINGS 

A summary of SC&A’s primary findings for the Clarksville/Medina site profile is presented 

below. Detailed discussions of all findings and observations can be found in Section 3.0 of this 

report, “Vertical Issues.” 

1.1.1 Finding 1: Unsupported Assumptions for Modeling Depleted Uranium Exposures 

The recent Pantex Work Group SEC deliberations and recommendation for the feasibility of 

dose reconstruction for DU at the Pantex Plant have direct relevance to the site profile for 

reconstructability of DU at Clarksville/Medina Plants. The systems dismantled there included 

the W28 and other systems containing oxidized DU. No routine bioassay or limited air 

monitoring were conducted during the scope and timeframe of operations. No respiratory 

protection was provided system handlers, and the contamination control program was limited to 

smearing components and a reported use of a “portable glovebox.” A clear exposure potential 

existed for DU for all workers involved in surveillance and retrofit activities at the Clarksville 

and Medina plants. The cited dose reconstruction methods contained in the current site profile 

are not supportable based on more recent research and deliberations by both NIOSH and the 

Advisory Board. 

Potential exposure would have been present when specific weapons systems were first received 

at Clarksville and Medina. To date, the only timeframe available for maintenance and quality 

assurance activities (i.e., in-service surveillance) is 1958 for the W28 system. This would 

encompass the designated EEOICPA period at Medina, but would exclude the earlier years at 

Clarksville (which received components as early as 1949). Research is continuing by both 

NIOSH and SC&A regarding the DU exposure potential for systems that predated the W28 that 

may have contained oxidized uranium components. 

An exposure pathway for the burning grounds at Clarksville and Medina existed for DU, given 

the contamination that likely existed on the high explosives that were burned. The site profile 

states that air sampling measurements and intakes by the burning ground operators for similar 

operations at Pantex would be bounding for those at Clarksville (and by association, Medina). 

SC&A agrees that based on available documentation, the operations were similar and exposures 

likely representative, and that the recommended dose estimation approach, therefore, would be 

bounding. 

1.1.2 Finding 2: Potential Thorium Exposure Pathway Not Addressed for Medina Plant 

At the Medina Plant in the 1960s, weapon system casements containing thorium were handled 

during surveillance and maintenance resulting in an exposure potential from thorium oxide, 
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which is not addressed in the Clarksville/Medina site profile. No bioassay program was 

conducted for workers during these operations, and no air sampling results for thorium have been 

located. 

A thorium contamination source term was acknowledged for Pantex weapons disassembly 

operations in that site profile [specifically, ORAUT-TKBS-0013-5 (ORAUT 2006c)]. During 

the Pantex Work Group review of the NIOSH Evaluation Report for Petition SEC-00068, a 

proposal was made by NIOSH “to determine a ratio of airborne thorium to DU in the workplace” 

as a means to bound potential airborne thorium exposure based on the 1989 “bounding” DU 

event (Ruhter et al. 2011). An activity ratio of thorium-232 to DU was calculated to be 0.018 to 

1. However, with the subsequent HHS action to approve an SEC class based on the inability to 

use the 1989 event as a bounding exposure for DU at Pantex, there remains no clear approach to 

estimate thorium dose from weapons system surveillance, maintenance, and disassembly 

activities, either at Pantex or at the two modification centers in question. 

SC&A does not agree that the NIOSH methodology presented in the Pantex TBD is bounding of 

potential exposures to thorium or can be supported by available technical information. The 

NIOSH “check of reasonableness” provided is based on 258 worker urinalysis samples from 

1992–1996. However, neither the operational conditions nor samples taken could be 

representative of the 1960s–1980s era at Pantex, nor the early 1960s at Medina or Clarksville. 

1.1.3 Finding 3: Use of Pantex Tritium Dose Experience as Surrogate for Upper Bound 

for Clarksville/Medina Plants is Questionable 

In the absence of tritium monitoring records, NIOSH will apply a 122 mrem/year upper bound 

dose for production operators at Clarksville and Medina Plants based on the maximum annual 

dose recorded for similar operators at Pantex during the height of disassembly operations there in 

the 1970s–1980s timeframe. Similarly, a 1,200 mrem dose is assigned for any production 

operator, quality specialist, or quality control inspector at Clarksville in 1962, the year a major 

tritium leak was experienced, based on the 1989 leak at Pantex. These assumptions were made 

based on an assumption that “disassembly [at Pantex having been] similar to maintenance 

activities [at Clarksville/Medina],” without any confirmation or evaluation regarding the 

similarity of the operations involved (disassembly versus surveillance/maintenance). Another 

question is whether there were confounding differences in the conduct of operations and 

radiological controls between the mid-1950s at satellite “modification” centers (i.e., Clarksville 

and Medina) and the peak disassembly era at Pantex, which was later in the 1980s–1990s. While 

the use of surrogate data in this case is justifiable, a more objective rationale needs to be 

provided that the Pantex tritium dose data would be bounding for that at Clarksville and Medina. 

1.1.4 Finding 4: N/P Ratio Method Cited has been Replaced with Correction Factor for 

NTA Film Coupled with MCNP-Based Estimate for Missed Doses below 0.5 MeV 

Energy Threshold; However, Questions Remain 

NIOSH finds available neutron dose records “unreliable,” and proceeds to apply neutron-tophoton dose (n/p) ratios, which were calculated from Pantex post-1993 dosimeter data “because 

the work performed at Clarksville Base and the Pantex Plant were similar” (ORAUT 2006a). 
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From an analysis of Pantex neutron data by Strom (Strom 2004), n/p ratios were determined and 

a 95th percentile ratio of 1:6 was calculated as an upper bound for direct weapons system 

handling. A maximum ratio of 1:4 was determined for the early era (1949–1956) when Po-Be 

initiators were handled. However, during an Advisory Board review of the same n/p ratio 

approach at another site, the limitations of relying on such ratios, particularly with respect to 

energy dependent NTA film, were recognized and alternatives were considered. 

Accordingly, NIOSH has moved from its former n/p ratio approach to one of estimating neutron 

dose at Pantex for 1952 to 1977 by applying a correction factor. The correction factor consists of 

three elements, including (1) correction for the energy threshold of NTA film, (2) angular 

response of NTA film, and (3) NTA track fading. NIOSH proposes to apply the Monte Carlo NParticle Transport Code (MCNP) program to determine the fraction of the neutron dose 

equivalent that would fall below a 0.5 MeV threshold. As noted in its May 18, 2011, 

memorandum to the Pantex Plant Work Group, SC&A had a number of questions related to the 

use of MCNP for this purpose, the most important of which was how MCNP would bound 

neutron dose for the range of systems assembled and disassembled for the period 1951–1991 at 

Pantex (Fitzgerald 2011a). 

For Clarksville/Medina, an additional question is whether the activities at the modification 

centers would be sufficiently similar such that the Pantex correction factor would be bounding 

for neutron exposures at the two sites? This issue is particularly important recognizing that an 

n/p ratio of 1:4 (vs. 1:6 at Pantex) would have been applied for 1949–1956 at Clarksville, given 

the exchange of Po-Be initiators that was being performed during that early period of the 

weapons program. (This was not performed at Pantex.) 

1.1.5 Finding 5: Inadequate Consideration of Potential Exposures Resulting from 

Handling of “Broken Arrows” 

There are historic accounts of damaged weapon systems being received, examined, and handled 

at both Clarksville and Medina Plants during their respective operating periods. However, the 

site profile does not acknowledge these potential exposure sources, nor provide any guidance 

regarding characterizing and estimating potential personnel doses that may have been received 

by the workers involved. In terms of non-routine exposures, these sources may be important, in 

that potential contamination would likely have been greater for workers involved with 

disassembly, inspection, and handling of damaged components. 

1.1.6 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 

As noted in the site profile, “external dosimetry records for Clarksville Base are sparse and the 

connection between the dose records and the worker may be missing...” and that “statistical 

analysis of doses received at Clarksville cannot be performed with the few records found to date” 

(ORAUT 2006a). The site profile indicates that a relatively small number of positive results 

were found after 1960 for Clarksville (a limited database for MHSMC workers was maintained 

by Pantex after that date). It also notes that “because Clarksville and Pantex were operated by 
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the same contractor, it is reasonable to assume that identical dosimetry service was provided for 

both sides.” 

While the similarity of the source terms involved is acknowledged, SC&A finds the backextrapolation of surrogate data to unduly “stretch” the enabling criteria later defined by the 

Advisory Board for such an approach. There is no objective information provided to substantiate 

that the handling of components during surveillance and maintenance activities in 1949–1958 at 

Clarksville presented a comparable upper bound dose as the period 1952–1958 at Pantex 

(240 mrem/yr at 95th percentile for unmonitored workers). In the latter case, plant construction 

and startup activities dominated the early part of the period in question, which would have 

limited potential radiation exposure, whereas at the modification centers, actual systems and 

components were being directly handled from the beginning. Likewise, while very limited 

records exist for that period, one interviewee cited by NIOSH indicates that the “maximum 

reported radiation dose was as high as 1 rem/yr from 1949 to 1952 (ORAUT 2006a). While 

NIOSH has assigned the higher dose value of 1,040 mrem/yr from 1959–1960 at Pantex for 

Clarksville Group 1 workers, the basis for applying any Pantex annual dose as a surrogate 

bounding dose for Clarksville and Medina should be re-examined in the context of current 

surrogate data policies. 

SC&A has another concern regarding the site profile’s use of Pantex external dose data. In 

SC&A’s 2007 site profile review for Pantex (SC&A 2007), a series of findings were made 

regarding the reliability of early recorded deep dose (Hp10), how calibration and dosimeter 

processing were performed by outside vendors, how the current dose estimation methodology 

assigned exposures from skin contamination, and how missed photon doses for monitored 

workers should be reflected in the derivation of photon and neutron doses for unmonitored 

workers. NIOSH agreed to review the external dose findings from SC&A’s site profile review in 

that context and clarify its dose estimation approach keying on these SC&A findings. 

1.1.7 Finding 7: Lack of Dose Records and Source Term Characterization Data for 

Clarksville/Medina leads to Use of Inadequately Justified Surrogate Data 

The approach adopted for both Clarksville and Medina plants in the absence of almost all sitespecific monitoring data and operational information, particularly for the pre-MHSMC contract 

period, is to use surrogate data from the Pantex Plant, given the assumed “similarity” of 

operations. However, no objective information is provided in the site profile as an evaluative 

basis for this wholesale application of data from another site. The only source of validation is 

essentially the interview of one former worker, who provides his recollections of operations and 

radiation exposure conditions for the 1950s and 1960s. While a legitimate case can be made for 

the similarity of maintenance activities at Clarksville/Medina and full disassembly in later years 

at Pantex, substantiation of a more objective and evaluative nature needs to be provided in the 

site profile to warrant such a sweeping use of surrogate data. 

1.2 STRENGTHS 

The TBD discusses the site, activities occurring at the site, and the characteristics of radiation 

exposure. It addresses the historic scope of operations, physical layout, job categories, and 
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NOTICE:

various radiological source terms at the respective plant sites. The sections on Occupational 

Medical Dose, Occupational Environmental Dose, and “Assessing Occupational Internal Dose 

from Elevated Radon Concentrations” are particularly well done, with detailed tables containing 

site-specific information. While SC&A questions the basis for applying Pantex exposure data, 

the tabular display of dose calculation parameters and IREP input parameters, as in Table 5-5, is 

a clear and effective means to guide dose reconstructors. Given the scarcity of site-specific 

information (that is not classified) for the two sites, the authors have done a commendable job in 

presenting a well organized synopsis of dose reconstruction methods that leverage those in 

similar operations at Pantex (albeit, it is not always clear that Medina, which is only addressed in 

the appendices, mirrors Clarksville’s operations and source terms as closely as inferred in the site 

profile). The site profile is also candid in its appraisal of the availability and value of dosimetry 

data for the two sites, making it clear that much of it is has not been located or is of little use in 

dose reconstruction. 

1.3 OPPORTUNITIES FOR IMPROVEMENT 

While the TBD provides detailed information concerning the history, scope of activities, and 

facilities at Clarksville, and to a lesser extent, Medina, there are bases and assumptions that can 

be strengthened and improved. Recommendations to support these bases and assumptions, as 

well as completeness of dose reconstruction efforts, include: 

 Evaluation of the exposure potential related to early surveillance and maintenance 

activities at the “modification” facilities, such as Clarksville and Medina, as compared 

with disassembly operations at Pantex 

 Identification of a possible thorium source term for potential exposure consideration at 

Medina 

 Further searches for missing internal and external dose records for the two sites, which 

would strengthen the site-specific database and reduce the reliance on surrogate dose 

distributions from Pantex 

 Linkage of external dosimetry information with actual personnel identifiers 

 Review and inclusion of “broken arrows” and other non-routine sources of exposure 

SC&A understands that site profiles are living documents, which are revised, refined, and 

supplemented with NIOSH technical information bulletins (TIBs) as required to help dose 

reconstructors. Site profiles are not intended to be prescriptive or necessarily complete in terms 

of addressing every possible issue that may be relevant to a given dose reconstruction. However, 

future revisions in the Medina and Clarksville site profiles would serve to mitigate some of the 

gaps and issues raised in this report. 
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2.0 SCOPE AND INTRODUCTION 

The review of the site profiles for the Median and Clarksville Plants was authorized by the 

Advisory Board at its February 9–11, 2010, meeting in Manhattan Beach, California, and was 

conducted between August 2010 and November 2011 by SC&A’s team of health physicists and 

technical personnel. The Pantex Work Group asked that these site profiles be linked to the 

ongoing Advisory Board SEC review of the Pantex Plant, given the similar operations conducted 

at these plants and at Pantex, and recognizing that source term information and exposure 

potential issues would be similar. Therefore, research being conducted within the Pantex SEC 

review was relevant to SC&A’s parallel review of the site profiles for these two plants. The 

pertinent records reviewed were both classified and unclassified, and were located at various 

Department of Energy (DOE) record repositories. This review was performed in accordance 

with Data Access and Interview Procedure (ABRWH 2009a), which provides for appropriate 

onsite coordination and data access protocols in conjunction with the Advisory Board, NIOSH, 

and DOE, and with Department of Energy Classification Review of Documents (ABRWH 

2009b), which provides for appropriate security clearance reviews. 

2.1 REVIEW SCOPE 

This report provides a review of the technical basis document related to historical occupational 

exposures at Medina and Clarksville, ORAUT-TKBS-0039, Site Profile for Clarksville Base 

Weapons Storage Area and Modification Center with Supplementary Guidance for Medina Base

(ORAUT 2006a). 

To date, the site profile has not been supplemented by site-specific TIBs, but there are two 

generic TIBs that provide additional guidance to the dose reconstructor: 

 ORAUT-OTIB-0006, Technical Information Bulletin: Dose Reconstruction from 

Occupationally Related Diagnostic X-ray Procedures, Rev. 03-D, December 21, 2005 

(ORAUT 2005) 

 ORAUT-TIB-0055, Technical Basis for Conversion from NCRP Report 38 Neutron 

Quality Factors to ICRP Publication 60 Radiation Weighting Factors for Respective 

IREP Input Neutron Energy Ranges, June 5, 2006 (ORAUT 2006b) 

SC&A also reviewed other pertinent documents, including those cited on the NIOSH SRDB. 

SC&A has critically reviewed the Medina/Clarksville TBD, as well as supplementary and 

supporting documents, against the following three evaluation criteria: 

 Determine the completeness of the information gathered by NIOSH, with a view to 

assessing its adequacy and accuracy in supporting individual dose reconstructions

 Assess the technical merit of the data/information

 Assess NIOSH’s guidelines for the use of the data in dose reconstructions
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SC&A’s review of the Clarksville/Medina site profile and supplemental documentation focuses 

on the quality and completeness of the data that characterized the facility and its operations and 

on the use of these data in performing dose reconstruction. The review was conducted in 

accordance with SC&A Standard Operating Procedure for Performing Site Profile Reviews

(SC&A 2004), which was approved by the Advisory Board. 

The review is directed at “sampling” the site profile analyses and data for validation purposes. 

The review does not provide a rigorous quality control process, whereby actual analyses and 

calculations are duplicated or verified. The scope and depth of the review are focused on aspects 

or parameters of the site profile that would be particularly influential in dose reconstructions, 

bridging uncertainties, or correcting technical inaccuracies. 

The Clarksville/Medina site profile document serves as site-specific guidance to support dose 

reconstructions for EEOICPA claimants. It provides the health physicists who conduct dose 

reconstructions on behalf of NIOSH with consistent general information and specifications to 

support their individual dose reconstructions. This report was prepared by SC&A to provide the 

Advisory Board with an evaluation of whether and how the TBD can support dose reconstruction 

decisions. 

The basic principle of dose reconstruction is to characterize the radiation environments to which 

workers were exposed, and to determine the levels of exposure the workers received in that 

environment through time. The hierarchy of data used for developing dose reconstruction 

methodologies is dosimeter readings and bioassay data, coworker and workplace monitoring 

data, and process description information or source term data. 

 

2.2 ASSESSMENT CRITERIA AND METHODS 

SC&A is charged with evaluating the approach set forth in the site profiles that is used in the 

individual dose reconstruction process. These documents are reviewed for their completeness, 

technical accuracy, adequacy of data, consistency with other site profiles, and compliance with 

the stated objectives, as defined in SC&A (2004). This review is specific to the Clarksville/ 

Medina site profile; however, items identified in this report may be applied to other facilities, 

especially facilities with similar source terms, exposure conditions, and mobile workforces. The 

review identifies a number of issues and discusses the degree to which the site profile fulfills the 

review objectives delineated in SC&A’s site profile review procedure (SC&A 2004). 

2.2.1 Objective 1: Completeness of Data Sources 

SC&A reviewed the site profile with respect to Objective 1, which requires SC&A to identify 

principal sources of data and information that are applicable to the development of the site 

profile. The three elements examined under this objective are (1) determining if the site profile 

made use of available data considered relevant and significant to the dose reconstruction, 

(2) investigating whether other relevant/significant sources are available, but were not used in the 

development of the site profile, and (3) determining if worker input was considered in the 

development of the site profile. 
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2.2.2 Objective 2: Technical Accuracy 

Objective 2 requires SC&A to perform a critical assessment of the methods used in the site 

profile to develop technically defensible guidance or instructions, including evaluating field 

characterization data, source term data, technical reports, standards and guidance documents, and 

literature related to processes that occurred at both Clarksville and Medina plants. The goal of 

this objective is to analyze the data according to sound scientific principles, and then evaluate 

this information in the context of dose reconstruction. 

2.2.3 Objective 3: Adequacy of Data 

Objective 3 requires SC&A to determine whether the data and guidance presented in the site 

profile are sufficiently detailed and complete to conduct dose reconstruction, and whether a 

defensible approach has been developed in the absence of data. In addition, this objective 

requires SC&A to assess the credibility of the data used for dose reconstruction. The adequacy 

of the data identifies gaps in the facility data that may influence the outcome of the dose 

reconstruction process. For example, if a site did not monitor all workers exposed to neutrons 

who should have been monitored, this would be considered a gap and thus an inadequacy in the 

data. An important consideration in this aspect of our review of the site profile is the scientific 

validity and claimant favorability of the data, methods, and assumptions employed in the site 

profile to fill in data gaps. 

2.2.4 Objective 4: Consistency among Site Profiles 

Objective 4 requires SC&A to identify common elements within site profiles completed or 

reviewed to date, as appropriate. In order to accomplish this objective, the Clarksville/Medina 

TBD was compared to other TBDs, particularly those referenced in the site profile and those 

related to frequently visited facilities. This assessment was conducted to identify areas of 

inconsistencies and determine the potential significance of any inconsistencies with regard to the 

dose reconstruction process. 

2.2.5 Objective 5: Regulatory Compliance and Quality Assurance 

Objective 5 requires SC&A to evaluate the degree to which the site profile complies with stated 

policy and directives contained in 42 CFR Part 82. In addition, SC&A evaluated the TBD for 

adherence to general quality assurance policies and procedures utilized for the performance of 

dose reconstructions. 

SC&A’s draft report and preliminary findings will subsequently undergo a multi-step resolution 

process. Resolution includes a transparent review and discussion of draft findings with members 

of the Advisory Board Working Group, petitioners, claimants, and interested members of the 

public. Prior to and during the resolution process, the draft report is reviewed by the DOE Office 

of Health, Safety, and Security to confirm that no classified information has been incorporated 

into the report. 

All review comments apply to Rev. 00 of the Clarksville/Medina site profile document, which is 

the most recently published version. Site expert interviews were conducted with former and 
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NOTICE:

current Clarksville/Medina site workers to assist SC&A in obtaining a comprehensive 

understanding of the radiation protection program, site operations, and historic exposure 

experience. The Attachment to this report contains a summary of the collective interviews 

conducted by SC&A during the course of this review and approved by interviewees. 

2.3 REPORT ORGANIZATION 

In accordance with directions provided by the Advisory Board and with site profile review 

procedures prepared by SC&A and approved by the Advisory Board, this report is organized into 

the following sections: 

(1) Executive Summary 

(2) Scope and Introduction 

(3) Vertical Issues 

(4) Overall Adequacy of the Site Profile as a Basis for Dose Reconstruction 

Based on the issues raised, SC&A prepared a summary list of findings, which is presented in the 

Executive Summary. Issues are designated as primary findings if SC&A believes they represent 

deficiencies that need to be corrected and pose the potential for substantial impact on at least 

some dose reconstructions. Issues can be designated as secondary findings if they simply raise 

questions, which, if addressed, would further improve the site profile and may possibly reveal 

deficiencies that will need to be addressed in future revisions of the site profile. Detailed 

analyses of the primary and secondary findings are provided in Section 3.0 of this report. 

Section 4.0 summarizes the evaluation of the TBD with respect to the stated objectives. 
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3.0 VERTICAL ISSUES 

3.1 FINDING 1: UNSUPPORTED ASSUMPTIONS FOR MODELING DEPLETED 

URANIUM EXPOSURES 

The Clarksville/Medina site profile cites the Pantex Occupational Internal Dose TBD (ORAUT 

2006c, pg. 26) for its source term assumptions for calculating a claimant-favorable dose estimate 

for disassembly and maintenance workers for which no bioassay monitoring was performed. It 

assumes that “about half a cup (118 cm3) of oxidized DU was available for resuspension.” By 

assuming a “density of UO2 of 11 g/cm3

,” an “estimated mass of UO2 of 1,300 grams of which 

about 1,140 grams is DU” would be available for resuspension (ORAUT 2006a). It then applies 

an assumed airborne release fraction and respirable fraction, coupled with other assumptions for 

ventilation, work day, and breathing rate to derive an assumed “upper bound” intake value of 

3.99 × 10-3 grams or 1,600 pCi per weapon disassembled. With an assumed average of “50 

surveillance/disassembly operations” conducted by a Clarksville/Medina worker per year 

(doubled for the “MHSMC years”), a chronic annual inhalation of 80,000 pCi of DU (219 pCi/d) 

is projected as a “constant upper bound for 1949 through 1957, and twice that rate for 1958 

through 1965” (ORAUT 2006c). 

The source term of “about a half cup” of oxidized DU being available for resuspension is not 

apparent in the referenced 2006 Pantex Occupational Internal Dose TBD, nor is any reference to 

the dose estimation approach cited above. That TBD notes that “from 1961 to 1965, most 

disassemblies were performed at the Medina and Clarksville plants” and that “before about 1980 

nuclear weapon disassembly operations were generally free of contamination” (ORAUT 2006c, 

pg. 24). It assumes that “it is claimant-favorable to assign unmonitored workers an intake that is 

the same as that from 1980 to 1993, “because documentation on the number of disassemblies and 

partial disassemblies and the contamination levels are not specifically available.” For that 

period, the 2006 Pantex Occupational Internal Dose TBD assigns to Production Technicians, 

RSTs, and Quality Assurance Technicians either 1.3 pCi/day for Type M inhalation or 

19 pCi/day for Type S inhalation. 

In the updated version of the Internal Dose TBD (ORAUT 2007), it is likewise recommended 

that the intake values for 1980 to 1993 be used for earlier intakes, observing that the median 

excretion rate of 0.375 dpm/day of the (then) 34 available DU bioassay samples taken in 1963–

1967 compared favorably with the median excretion rate of 0.188 dpm/day, assuming chronic 

intake for the samples collected in 1990 following the contamination incident that occurred in 

1989. As has been noted in SC&A’s site profile review for Pantex (SC&A 2007) and in its 

reviews of the Pantex SEC Evaluation Report (NIOSH 2008), there are a number of concerns 

with the dose estimation approaches for DU in both the Clarksville/Medina site profile and the 

referenced methods in the Pantex site profile. 

First, the assertion contained in the referenced Pantex TBD that disassembly operations before 

1980 were relatively contamination free is apparently based on the assumption that oxidation of 

the DU in certain systems would take some years before becoming a significant contamination 

issue during disassembly. As discussed in the Pantex Work Group, interviews with 

knowledgeable site experts indicate that such corrosion began almost immediately at the time of 
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fabrication, and would be exacerbated by environmental conditions, such as high humidity. 

Therefore, the earlier assembly and disassembly activities, such as those at Clarksville and 

Medina during their operating periods, cannot be assumed to involve minimal contamination. 

Therefore, the source-term assumption in the Clarksville/Medina site profile of “one-half cup” or 

118 cm3 of DU does not have any clear basis as derived from the Pantex TBD (assuming such a 

referenced estimate is, in fact, provided in that TBD). 

Second, assuming that the current Pantex TBD (ORAUT 2007) approach is substituted for that 

cited above in the Clarksville/Medina site profile, SC&A has already found, and the Pantex 

Work Group has accepted, that the back-extrapolation of the Pantex 1989 DU contamination 

incident bioassay data is not adequate as a means to bound annual DU intakes and doses during 

disassembly of the W28 system (considered having the highest exposure potential for DU) 

beginning in 1958. As noted in SC&A’s memorandum to the Pantex Work Group on October 

11, 2011 (Fitzgerald 2011b), the basis for this conclusion included: 

 NIOSH’s finding that the 1984–1989 W28 campaign represents greater exposure 

potential than prior years is based largely on interviews with several managers 

who were asked whether they believed that particular event presented a higher 

exposure potential than for other systems and events from earlier years. 

However, these were subjective recollections that were not backed up by reliable, 

comparative data or facts. SC&A’s interviews with another like knowledgeable 

Pantex manager found a different recollection: that the 1989 depleted uranium 

(DU) contamination incident was not the worst one experienced at Pantex, just 

the one that finally garnered management’s attention; that at least two others may 

have been worse. No analytic comparisons with earlier reliable bioassay results, 

air sampling results, or contamination results are available or have been 

presented by NIOSH to make an objective case, in this regard. 

 In the Site Profile and Petition Evaluation Reports, the original bases provided by 

NIOSH for reliance on the 1990 bioassay data set was, variously: because it was 

the “oldest set of data that provides isotopic determination of uranium alpha 

activity in urine samples and has significant data to perform statistical analysis;” 

and because it was the “most comprehensive set of depleted uranium intake data 

found in the Pantex records,” and it represented “large, known high quality, 

intakes from exposures expected to be above normal operational exposures.” 

SC&A agrees with these earlier NIOSH rationales that the 1990 set is the “best” 

DU data set available from the standpoint of quality and quantity, just not 

necessarily the bounding one required for dose reconstruction with sufficient 

accuracy. 

 NIOSH’s use of relatively contemporary data (1990) to bound potential exposures 

from 1958–1989 necessitates at least some corroboration that essential attributes 

of operations can be normalized during this lengthy time period, e.g., number of 

units handled at one time, personnel handling practices, extent of uranium 

corrosion, contamination control practices, etc. This has not been accomplished 

and invalidates the assumed representativeness of exposure pathways in 1990 as 

compared with those from as much as thirty years earlier. 
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While it is noted in the Clarksville/Medina site profile that “portable gloveboxes with HEPAfiltered exhausts” were used to contain oxidized DU when weapons underwent inspections, 

maintenance, and refurbishment during the Sandia years, it is not known how regularly and 

effectively such controls were applied, how much contamination was removed and resuspended 

from cleaning rags that were used to wipe down oxidized and contaminated components, and 

how much of the DU contamination was in the respirable range. (On this last point, substantial 

uptake by workers in the 1989 contamination event renders this question less important – the 

exposure potential via inhalation of DU particles proved significant.) 

An exposure pathway for the burning grounds at Clarksville and Medina existed for DU, given 

the contamination that likely existed on the high explosives that were burned. The site profile 

states that air sampling measurements and intakes by the burning ground operators for similar 

operations at Pantex would be bounding for those at Clarksville (and by association, Medina). 

As noted in the Clarksville/Medina site profile: 

The estimated intake at Pantex was 130 pCi/d of DU based on the 95th percentile 

air concentration for the cleanup activities. It is assumed this intake rate applies 

as well to Clarksville workers involved in burning high explosives. The intake is 

an upper-bound estimate so the distribution is a constant. (ORAUT 2006a) 

SC&A agrees that the operations were similar and exposures representative; the recommended 

dose estimation approach using the 95th percentile distribution should be bounding. 

In conclusion, the recent Work Group SEC deliberations and recommendation for the feasibility 

of dose reconstruction for DU at Pantex have direct relevance to the site profile for 

reconstructability of DU at Clarksville/Medina Plants. The systems dismantled there included 

the W28 and other systems containing oxidized DU. No routine bioassay and limited air 

monitoring were conducted during the scope and timeframe of operations. No respiratory 

protection was provided system handlers, and the contamination control program was limited to 

smearing components and the reported “portable glovebox.” A clear exposure potential exists to 

DU for all workers involved in surveillance and retrofit, as well as assembly and disassembly 

activities at Clarksville and Medina Plants, and the proposed dose reconstruction methods 

contained in the current site profile are not supportable. 

3.2 FINDING 2: POTENTIAL THORIUM EXPOSURE PATHWAY NOT 

ADDRESSED FOR MEDINA PLANT 

Thorium was known to figure in historic weapons systems and was a contamination concern in at 

least four systems dating back to the 1960s (SC&A 2007). While it is stated in ORAUT-TKBS0013-5 (pg. 35) that “there is no record of disassembly of thorium weapons before 1980, it is 

clear that there were early modifications of one of the aforementioned systems that was retired in 

1966. 

At the Medina Plant in the 1960s, weapons system casements containing thorium were handled 

during surveillance and maintenance resulting in an exposure potential from thorium oxide, 

which is not addressed in the Clarksville/Medina site profile. No bioassay program was 
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conducted for workers during these operations and no air sampling results for thorium have been 

located. As noted in the Pantex site profile, “...information on source terms of weapons 

containing thorium is classified, as is the number or percentages of weapons that contain 

thorium.” Therefore, source term characterization in lieu of personnel monitoring data or air 

sampling measurements is problematic. 

During the Pantex Work Group review of the NIOSH Evaluation Report for Petition SEC-00068 

(NIOSH 2008), a proposal was made by NIOSH “to determine a ratio of airborne thorium to DU 

in the workplace” as a means to bound potential airborne thorium exposure based on the 1989 

“bounding” DU event (Ruhter et al. 2011). An activity ratio of thorium-232 to DU was 

calculated to be 0.018 to 1. However, with the subsequent HHS action to approve an SEC class 

based on the inability to use the 1989 event as a bounding exposure for DU at Pantex, there 

remains no clear approach to estimate thorium dose from weapons system surveillance, 

maintenance, and disassembly activities, either at Pantex or at the two modification centers in 

question. 

SC&A does not agree that the NIOSH methodology presented in the Pantex TBD is bounding of 

potential exposures to thorium or can be supported by available technical information. The 

NIOSH “check of reasonableness” provided is based on 258 worker urinalysis samples from 

1992–1996. However, neither the operational conditions nor samples taken could be 

representative of the 1960s–1980s era at Pantex or the early 1960s at Medina or Clarksville. 

3.3 FINDING 3: USE OF PANTEX TRITIUM DOSE EXPERIENCE AS 

SURROGATE UPPER BOUND FOR CLARKSVILLE/MEDINA PLANTS IS 

QUESTIONABLE 

As noted in the site profile, routine tritium intakes likely occurred at both Clarksville and Medina 

Plants beginning with the arrival of reservoirs in the mid-1950s. While it is clear that this 

exposure source was recognized at both locations, and air monitoring and personnel bioassay 

monitoring performed, limited records have been found. In the absence of such records, NIOSH 

will apply a 122 mrem/year upper bound dose for production operators at Clarksville and Medina 

Plants based on the maximum annual dose recorded for similar operators at Pantex during the 

height of disassembly operations there in the 1970s–1980s timeframe. Similarly, a 1,200 mrem 

dose is assigned for any production operator, quality specialist, or quality control inspector at 

Clarksville in 1962, the year a major tritium leak was experienced, based on the 1989 leak at 

Pantex. 

These assumptions were made based on an assumption that “disassembly [at Pantex, having 

been] similar to maintenance activities [at Clarksville/Medina],” without any confirmation or 

evaluation regarding the similarity of the operations involved (disassembly versus 

surveillance/maintenance). One option would be interview information from a worker involved 

with both types of activities at both Clarksville/Medina and Pantex (a number of workers from 

the former plant finished their careers at the latter plant). Another question is whether there were 

differences in the conduct of operations and radiological controls between the mid-1950s at 

satellite “modification” centers (i.e., Clarksville and Medina) and the peak disassembly era at 

Pantex, which was later. There is also no consideration given by NIOSH of potential exposures 
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to chemical forms of tritium other than the gaseous from reactivity over time. While the use of 

surrogate data in this case is justifiable, a more objective rationale needs to be provided that the 

Pantex tritium dose data would be bounding for that at Clarksville and Medina. 

3.4 FINDING 4: N/P RATIO METHOD CITED HAS BEEN REPLACED WITH 

CORRECTION FACTOR FOR NTA FILM COUPLED WITH MCNP-BASED 

ESTIMATE FOR MISSED DOSES BELOW 0.5 MEV ENERGY THRESHOLD; 

HOWEVER, QUESTIONS REMAIN 

In the site profile, NIOSH finds available neutron dose records “unreliable,” and proceeds to 

apply n/p ratios, which were calculated from Pantex post-1993 dosimeter data, “because the 

work performed at Clarksville and the Pantex Plant were similar” (ORAUT 2006a). From an 

analysis of Pantex neutron data by Strom (2004), n/p ratios were determined and a 95th percentile 

ratio of 1:6 was calculated as an upper bound for direct weapons systems handling. A maximum 

ratio of 1:4 was determined for the early era (1949–1956), when Po-Be initiators were handled. 

However, during an Advisory Board review of the same n/p ratio approach at another site, the 

limitations of relying on such ratios, particularly with respect to energy-dependent NTA film, 

were recognized and alternatives were considered. 

Accordingly, NIOSH has moved from its former n/p ratio approach to one of estimating neutron 

dose at Pantex for 1952 to 1977 by applying a correction factor. The correction factor consists of 

three elements, including (1) correction for the energy threshold of NTA film, (2) angular 

response of NTA film, and (3) NTA track fading. NIOSH proposes to apply the MCNP program 

to determine the fraction of the neutron dose equivalent that would fall below a 0.5 MeV 

threshold. The input parameters for the MCNP run include: 

 Weapons-grade plutonium metal with a spontaneous fission neutron spectrum (average 

energy of 1.934 MeV) 

 RDX Moderator with a thickness of 0, 1, 2, and 4 inches 

 A symmetrical 3-meter tall concrete silo with 12-inch thick walls and a 12-inch thick 

ceiling and floor 

 Point source located 1 meter above the floor 

 Operator and observer distances of 60 cm and 240 cm, respectively 

As noted in SC&A’s draft memorandum of May 18, 2011, to the Pantex Work Group (Fitzgerald 

2011a), SC&A has a number of questions regarding how MCNP will be applied under the 

following circumstances: 

 What happens when the moderator is thicker than 4 inches? Is 4 inches an 

appropriate thickness for very large weapons? The assumed thickness of the 

moderator should reflect the range of thickness of actual weapon systems. A 

sensitivity analysis of HE thickness in its actual range should be conducted. 

 How is “direct” or “close contact” by workers addressed? The position of the 

source term in relation to the worker was assumed to be 60 cm (~2 feet) and 240 
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cm (~8 feet). Interviewed workers indicated the source term was handled 

directly. In particular, pits were held in workers’ laps for cleaning. As observed 

during the tour, workers now handle pits on stands and on trolleys. With the 

advancement of time, these stands and transports facilitated less direct contact 

with the radioactive constituents as compared with direct handling in the earlier 

years of Pantex assembly and disassembly operations. 

 How is dosimetry geometry addressed? Work with multiple radiological sources 

increases the likelihood of posterior-anterior exposure. 

 How is the presence of multiple units (including those in storage) addressed? 

Within a cell or bay and RTG storage vaults, shipping and receiving areas, and 

magazines, the workers (including Material Handlers and security) could be in 

the proximity of multiple weapons at one time including multiple pits. This could 

include the same or different units. During worker interviews, it was indicated 

that 10 components could be worked on at the same time while 10 components 

were in staging. This situation was more common historically than in more 

modern times. 

 What consideration is given to the light elements present in the weapons system 

and their impact on neutron energy? 

 What consideration is given to the joint presence of pits and RTGs in the 

weapon? 

 How is unit specific angular dependence demonstrated and bounded? 

 The source term quantity used in MCNP modeling is not specified making 

validation of the resulting neutron fluence difficult. 

 The MCNP model focuses on only assembly/disassembly scenarios, and excludes 

workers handling, storing, inventorying, transporting and receiving, and 

guarding accountable materials.

Most importantly, NIOSH needs to demonstrate how its proposed parameters for MCNP will 

result in a bounding neutron dose estimate for the range of systems assembled and disassembled 

for the period of 1951–1991 at Pantex, as well as the years of operations at Clarksville and 

Medina. The INRAD reports reviewed by SC&A for different weapons systems show large 

variability in the neutron dose rate, depending on the distance from the source, the angle of 

exposure, and the configuration of the particular unit. Where neutron spectral measurements are 

available in the INRAD reports, the data can be used for benchmarking the results obtained by 

MCNP for a single component or weapon. It is also of note by SC&A that documents dated 

1962 and 1963 discuss new assembly of weapons systems was taking place at Clarksville and 

Medina, which has not been addressed by NIOSH in the site profile for these sites. This factor 

raises additional external dose concerns from both photon and neutron doses to workers in the 

early years of these sites. 

For Clarksville/Medina, an additional question is the one raised earlier, i.e., would the activities 

at the modification centers be sufficiently similar such that the Pantex correction factor would be 

bounding for neutron exposures at the two sites? This issue is particularly important, 
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recognizing that an n/p ratio of 1:4 (vs. 1:6 at Pantex) would have been applied for 1949–1956 at 

Clarksville, given the exchange of Po-Be initiators that was being performed during that early 

period of the weapons program (this was not conducted at Pantex). 

3.5 FINDING 5: INADEQUATE CONSIDERATION OF POTENTIAL EXPOSURES 

RESULTING FROM HANDLING OF “BROKEN ARROWS” 

There are historic accounts of damaged weapons systems being received, examined, and handled 

at both Clarksville and Medina during their respective operating periods. However, the site 

profile does not acknowledge these potential exposure sources, or provide any guidance 

regarding characterizing and estimating potential personnel doses that may have been received 

by the workers involved. In terms of non-routine exposures, these sources may be important, in 

that potential contamination would likely have been greater for workers involved with 

disassembly, inspection, and handling of damaged components. 

For Clarksville, interviewees mention a “unit that came from North Carolina” that had been in an 

accident, which they had subsequently disassembled (SC&A 2010). It was also mentioned that 

they had handled several damaged systems in transit to Pantex for dismantlement, including 

those involved in the Palomares accident (SC&A 2010). Apparently, Clarksville received a 

number of other systems damaged while in the military inventory during its operating period. 

The history at Medina is less clear from interviews, but should be researched in this regard to 

ensure appropriate guidance to dose reconstructors when this activity is cited in ComputerAssisted Telephone Interview (CATI) accounts. 

3.6 FINDING 6: USE OF SURROGATE PANTEX EXTERNAL DOSE 

DISTRIBUTION FOR CLARKSVILLE/MEDINA “EXPOSURE GROUPS” 

BELIES LACK OF DOSE RECORDS IN EARLIER YEARS, DOSIMETER 

UNCERTAINTY INFORMATION, AND DEFINITIVE OPERATIONAL 

INFORMATION 

As noted in the site profile, “external dosimetry records for Clarksville Base are sparse and the 

connection between the dose records and the worker may be missing...” and that “statistical 

analysis of doses received at Clarksville cannot be performed with the few records found to date” 

(ORAUT 2006a). The site profile indicates that a relatively small number of positive results 

were found after 1960 for Clarksville (a limited database for MHSMC workers was maintained 

by Pantex after that date). It also notes that, “because Clarksville and Pantex were operated by 

the same contractor, it is reasonable to assume that identical dosimetry service was provided for 

both sides.” 

For unmonitored workers and those whose records have not been located, NIOSH has 

categorized them into four groups, as provided in Table 6-4 of the site profile. These groups, 

defined by exposure potential (extensive work with pits/full-time exposure; entered radiation 

areas, but did not handle pits; exposure equivalent to 500 hr/yr; infrequent entry into radiation 

areas; exposure equivalent to 200 hr/yr; and did not enter radiation areas; exposure from 

environmental sources only), included operators, inspectors, material handlers, and various 

support workers. The site profile finds that, “operations at Clarksville Base between 1959 and 
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1965 were similar to those at the Pantex Plant, and MHSMC operated both facilities,” and 

therefore, “statistical information from the Pantex External Dosimetry TBD (ORAUT 2006d) 

was used to provide guidance for unmonitored workers at Clarksville for the MHSMC years.” 

Accordingly, NIOSH applied the Pantex dose distribution, with an adjustment to replace zero 

dose readings by MDL/2 for the monthly reporting period. The unmonitored dose value for 

1949–1958 is estimated as much lower than that for later years, but is seen as valid for that 

period of time (the “Sandia years”), because “workers handled components rather than 

performing intimate handling of pits, so doses would be expected to be smaller than those for 

MHSMC operations” (ORAUT 2006a). The site profile goes on to state: 

This is mostly consistent with [Interviewee]’s recollections in that [the 

Interviewee] indicated that maximum doses of 1 rem occurred up to 1952 and that 

all doses were less than 100 mrem after that [ORAUT 2006a]. A small number of 

external dose data have been found for 1949 through 1957. Of those dose 

records, 28 worker-years of data have been found for nine Sandia workers who 

did surveillance on nuclear capsules. There were no results for 1949, only two 

for 1950, and only one each for 1956 and 1957. (ORAUT 2006a) 

The circumstances for the Medina Plant are similar, in that a Pantex external dose database exists 

for MHSHC workers at Medina for the period April 1959 through 1966, but does not include 

dose records for Sandia workers at the site before that time (it is noted that none have been 

located). The database for MHSHC workers has been corrected and recompiled in “Medina 

Dose Records, 1959–1966” (Martin 2006), with the Pantex dose distribution being applied for 

Medina as it is for Clarksville, given the similarities of their respective, albeit limited, badge data 

and similar operations (ORAUT 2006a). 

While the similarity of the source terms involved is acknowledged, SC&A finds the backextrapolation of surrogate data to stretch the enabling criteria defined by the Advisory Board for 

such an approach. There is no objective information provided to substantiate that the handling of 

components during surveillance and maintenance activities in 1949–1958 at Clarksville 

presented as low an upper bound dose as the period 1952–1958 at Pantex (240 mrem/yr at 95th

percentile for unmonitored workers). In the latter case, plant construction and startup activities 

dominated the early part of the period in question, which would have limited potential radiation 

exposure, whereas at the modification centers, actual systems and components were directly 

handled. Likewise, while very limited records exist for that period, one interviewee cited by 

NIOSH indicates that the “maximum reported radiation dose was as high as 1 rem/yr from 1949 

to 1952 (ORAUT 2006a). While NIOSH has assigned the higher dose value of 1,040 mrem/yr 

from 1959–1960 at Pantex for Clarksville Group 1 workers, the basis for applying any Pantex 

annual dose as a surrogate bounding dose for Clarksville and Medina should be re-examined in 

the context of current surrogate data policies. 

SC&A has another concern regarding the site profile’s use of Pantex external dose data. In 

SC&A’s 2007 site profile review for Pantex, a series of findings were made regarding the 

reliability of early recorded deep dose (Hp10), how calibration and dosimeter processing were 

performed by outside vendors, how the current dose estimation methodology assigned exposures 

from skin contamination, and how missed photon doses for monitored workers should be 
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reflected in the derivation of photon and neutron doses for unmonitored workers. SC&A noted 

during the May 2, 2011, Pantex Work Group meeting that while these were site profile issues in 

nature, some of them involved incorrect adjustment factors or values that would affect the 

accuracy of dose estimates if used as stated. NIOSH agreed to review the external dose findings 

from SC&A’s site profile review in that context. It was agreed in the Pantex Work Group that 

the SC&A site profile review lays out these concerns in detail, including the implications of a 

1980 DOE investigation report that cited deficiencies in how the dosimetry program was 

administered and with the credentials of the Pantex personnel responsible for that program. 

NIOSH’s response during the May 4, 2010, meeting confirmed that these concerns were not 

likely of SEC significance and accordingly, NIOSH agreed at that time to follow-up and clarify 

its dose estimation approach keying on the SC&A site profile review findings. 

3.7 FINDING 7. LACK OF ADEQUATE AND COMPLETE SOURCE TERM 

CHARACTERIZATION AND DOSE RECORDS PRECLUDE USE OF 

CLARKSVILLE/MEDINA SITE DATA 

The site profile acknowledges that “no records were found indicating bioassays were performed 

or internal dose was assessed for workers at Clarksville Base.” It adds that, likewise, “no data 

were found for air samples or urinalyses.” For tritium, it is noted that “no air sample or tritium 

bioassay results for Clarksville Base were found.” For a major accident involving a tritium 

release, the site profile verifies that “no documentation of the accident or any information about 

the amount of tritium that might have leaked has been found.” For uranium exposure, it is noted 

that “no records were found indicating that bioassay was performed on workers to determine 

uptake of DU.” For potential DU exposures from the Burning Grounds at Clarksville, “there is 

no information concerning the amount of high explosives or DU contamination burned at 

Clarksville...” For external monitoring, the site profile acknowledges that “statistical analysis of 

doses received at Clarksville cannot be performed with the few records found to date,” and that 

“few dosimetry records have been found for Clarksville; those that have been found do not 

always identify the person receiving the radiation dose.” With respect to the dosimeter badges, 

themselves, it is noted that “results from film badges were reported on ‘cardex’ dosimetry 

records...however, records from these dosimeters have not been found in the SNL archives” 

(ORAUT 2006a). Finally, the neutron doses of record at Clarksville are unreliable, and dose 

reconstructors should not use them” (ORAUT 2006a). 

The approach adopted for both Clarksville and Medina Plants in the absence of almost any sitespecific monitoring data and operational information, particularly for the pre-MHSMC contract 

period, is to use surrogate data from the Pantex Plant, given the assumed “similarity” of 

operations. However, no objective information is provided in the site profile as an evaluative 

basis for this wholesale application of data from another site. The only source of validation is 

essentially the interview of one individual, who provides recollections of operations and 

radiation exposure conditions for the 1950s and 1960s. While a legitimate case can be made for 

the similarity of maintenance activities at Clarksville/Medina and full disassembly in later years 

at Pantex, substantiation of a more objective and evaluative nature needs to be provided in the 

site profile to warrant such a sweeping use of surrogate data.
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4.0 OVERALL ADEQUACY OF THE SITE PROFILE AS A BASIS FOR 

DOSE RECONSTRUCTION 

The SC&A procedures call for both a “vertical” assessment of a site profile, for evaluating 

specific issues of adequacy and completeness and a “horizontal” assessment, considering how 

effectively the profile satisfies its intended purpose and scope. This section addresses the latter 

objective in a summary manner by assessing: 

(1) How, and to what extent, does the site profile satisfy the five objectives defined by the 

Advisory Board? 

(2) How usable is the site profile as a generalized technical resource for the dose 

reconstructor when individual dose records are unavailable? 

(3) Have generic technical or policy issues been identified that transcend any single site 

profile and need to be addressed by the Advisory Board and NIOSH? 

4.1 OBJECTIVE 1: COMPLETENESS OF DATA SOURCES 

As noted in Finding 7 above, site-specific data are largely lacking or incomplete. Even for 

occupational medical x-ray exams, no records were found and no information regarding “x-ray 

equipment manufacturers, models, examination techniques, and exposure rates for those 

techniques has been found” (ORAUT 2006a). For the environmental source term 

characterization, “no records on environmental releases from Clarksville Base have been 

discovered.” 

4.2 OBJECTIVE 2: TECHNICAL ACCURACY 

As noted above, given that the key dose parameters are founded on upper bound surrogate values 

from the Pantex Plant (or in the case of occupational environmental doses from tritium, from 

IAAP), there is little intrinsic accuracy for the dose estimates made for Clarksville and Medina. 

Arguably, the most accurate source term estimations are radon daughter levels at Clarksville, for 

which actual building measurements were made in later years. The environmental tritium source 

term would likely be accurate, given the identical components being handled and similar 

circumstances of handling at Clarksville and Medina. The uranium and plutonium source terms 

due to component contamination are largely surmised, based on experience at Pantex and 

interview accounts, but without comparative analysis of operations or actual systems handled. 

As noted previously, the use of n/p ratios from Pantex operational experience does not 

necessarily account for earlier neutron sources at Clarksville, nor does it account for the 

technical shortcomings of relying on NTA film readings. 

4.3 OBJECTIVE 3: ADEQUACY OF DATA 

As noted under Finding 7 above, pertinent data sources for internal and external dose are largely 

lacking for Clarksville and Medina Plants, particularly for the early years of operation before 

MHSMC assumed operational management of the two sites. NIOSH compensates for the lack of 
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site-specific source term characterization information and monitoring data by applying that of 

Pantex, given the similarity of operations. While it is clear that no alternative approach may be 

possible under the circumstances, it is also clear that the extensive use of surrogate data in this 

manner entails justification through a comparative analysis of operations, dosimetry, and 

radiological controls to demonstrate the feasibility of applying surrogate data. This comparison 

has only been done on a qualitative basis, with an assumption of “similarity” based on the nature 

of activities and interview accounts. Unless additional monitoring data have been found since 

the issuance of this site profile, NIOSH needs to provide this additional validation. 

Data sources for occupational medical, environmental, and radon sources, while not necessarily 

available, have more bearing in site-specific conditions and source term characterization, as 

provided in the site profile. For example, the frequency and type of medical x-ray examinations 

are based on worker interviews and practices at the time, as normalized at various other sites. 

Occupational environmental releases are based on identical tritium-containing components and 

release experience at IAAP. Radon source terms are based on actual measurements inside 

containments at a later time period for Clarksville. However, even in these instances, the lack of 

site-specific data creates uncertainties: 

 Were the exhaust and filtering characteristics at Clarksville and Medina similar to those 

at IAAP? 

 Were the exposure pathways to workers present in the environs of the two facilities more 

or less exposed to environmental releases than those at IAAP? 

 While radon measurements were made at Clarksville, inside levels were inferred for 

Medina, based on being “more like” Pantex than Clarksville given soil characteristics and 

geological concentrations of radium. However, were the physical characteristics of the 

various buildings at Medina sufficiently different than those at either Pantex or 

Clarksville to warrant a higher upper bound (e.g., more air-tight, less ventilated 

structures)? 

4.4 OBJECTIVE 4: CONSISTENCY AMONG SITE PROFILES AND OTHER 

NIOSH DOCUMENTS 

SC&A has conducted reviews of methodologies applied for weapons assembly/disassembly 

facilities at the IAAP and the Pantex Plant, which share operational similarities to the activities 

conducted at the Clarksville and Medina Plants. The Clarksville/Medina site profile adopts 

much of the dose distributions and methods from the Pantex TBD, with the exception of the 

occupational environmental source term for tritium, which comes from the IAAP site profile. 

The IAAP site profile (ORAUT 2004), in turn, adopted the bounding dose values and approach 

used in the Pantex TBD for uranium and radon. In these cases, it is not a question of consistency 

as opposed to adoption of surrogate data in lieu of site-specific information for Clarksville and 

Medina. 

4.5 OBJECTIVE 5: REGULATORY COMPLIANCE AND QUALITY ASSURANCE 

SC&A reviewed the site profile with respect to Objective 5, which requires SC&A to evaluate 

the degree to which the site profile complies with stated policy and directives contained in 
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42 CFR 82. In addition, SC&A evaluated the site profile for adherence to general quality 

assurance policies and procedures utilized for the performance of dose reconstructions. 

The key issue in this context is what information is being substituted, given the lack of individual 

monitoring data at Clarksville and Medina, as noted repeatedly in this review. Where individual 

monitoring data are lacking, three types of “quantitative” information can be applied (42 CFR 

82, 2002): 

a) Monitoring data from co-workers, if NIOSH determines they had a common 

relationship to the radiation environment; 

b) A quantitative characterization of the radiation environment in which the covered 

employee worked, based on an analysis of historical workplace monitoring 

information such as area dosimeter readings, general area radiation and 

radioactive contamination survey results, air sampling data; or 

c) A quantitative characterization of the radiation environment in which the 

employee worked, based on analysis of data describing processes involving 

radioactive materials, occupational tasks and locations, and radiation safety 

practices. 

This issue was addressed at the November 2010 Advisory Board meeting in Santa Fe, New 

Mexico, and this “quantitative” approach in lieu of site-specific data was reaffirmed. While 

radiological monitoring data are lacking for both Clarksville and Medina, a quantitative source 

term characterization based on site-specific information is not evident in the site profile. In lieu 

of this characterization, surrogate data from the Pantex Plant (and for environmental releases of 

tritium, IAAP) are used. However, where surrogate site data are to be applied, as is the case for 

Clarksville and Medina, it is incumbent on NIOSH to provide a clear basis for doing so, as 

prescribed by governing procedures for applying surrogate data. Given that the surrogate data 

policy was not in place at the time of TBD issuance in 2006, that review remains to be 

accomplished. 

4.6 INCONSISTENCIES AND EDITORIAL ERRORS IN THE SITE PROFILE 

Page 20 of 69 of the site profile (Section 4.0, 1st paragraph) states that “complete disassemblies 

were not performed at Clarksville Base,” yet on page 15 of the same document, it points out that 

disassembly of the weapon pit was required to remove the initiator, which was at the pit center. 

It is assumed that this should be interpreted as a partial disassembly activity. This should be 

clarified.
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5.0 REFERENCES 

42 CFR Part 82. Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule, Federal Register/Vol. 67, 

No. 85/Thursday, May 2, 2002, p. 22314. 

ABRWH 2009a. Data Access and Interview Procedures, Advisory Board on Radiation and 

Worker Health, 2009. 

ABRWH 2009b. Department of Energy Classification Review of Documents, Advisory Board 

on Radiation and Worker Health, 2009. 

ABRWH 2010. Criteria for the Use of Surrogate Data, Advisory Board on Radiation and 

Worker Health. May 14, 2010. 

Fitzgerald, J., 2011a. Memorandum to the Pantex Plant Work Group, Neutron Dose Estimation, 

May 18, 2011. 

Fitzgerald, J., 2011b. Memorandum to the Pantex Work Group, Basis for SC&A’s Position on 

Bounding Internal Exposure to Uranium at Pantex, October 11, 2011. 

Martin 2006. Medina Dose Records, 1959–1966, memorandum to file, Dade Moeller & 

Associates, Richland, Washington, May 6, 2006. [SRDB Ref ID: in process] 

NIOSH 2008. SEC Petition Evaluation Report, SEC-00068, Pantex Plant, August 5, 2008. 

OCAS 2008. The Use of Data from Other Facilities in the Completion of Dose Reconstructions 

under EEOICPA, OCAS-IG-004, Rev. 00. Office of Compensation and Analysis Support, 

National Institute for Occupational Safety and Health, Cincinnati, Ohio. August 21, 2008. 

ORAUT 2004. ORAUT-TKBS-0018, Technical Basis Document for Atomic Energy Operations 

at the Iowa Army Ammunition Plant (IAAP), Rev. 00, April 16, 2004. 

ORAUT 2005. ORAUT-OTIB-0006, Technical Information Bulletin: Dose Reconstruction from 

Occupationally Related Diagnostic X-ray Procedures, Rev. 03-D, December 21, 2005. 

ORAUT 2006a. Site Profile for Clarksville Base Weapons Storage Area and Modification 

Center with Supplementary Guidance for Medina Base, ORAUT-TKBS-0039, Oak Ridge 

Associated Universities, Cincinnati, Ohio, November 14, 2006. (same as McConn 2006). 

ORAUT 2006b. ORAUT-TIB-0055, Technical Basis for Conversion from NCRP Report 38 

Neutron Quality Factors to ICRP Publication 60 Radiation Weighting Factors for Respective 

IREP Input Neutron Energy Ranges, June 5, 2006. 
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However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.

NOTICE:

ORAUT 2006c. Technical Basis Document for the Pantex Plant – Occupational Internal 

Dosimetry, ORAUT-TKBS-0013-5, Rev. 00. Oak Ridge Associated Universities, Cincinnati, 

Ohio, July 27, 2006. 

ORAUT 2006d. Technical Basis Document for the Pantex Plant – Occupational External 

Dosimetry, ORAUT-TKBS-0013-6, Rev. 00. Oak Ridge Associated Universities, Cincinnati, 

Ohio, July 27, 2006. 

ORAUT 2007. Technical Basis Document for the Pantex Plant – Occupational Internal 

Dosimetry, ORAUT-TKBS-0013-5, Rev. 01. Oak Ridge Associated Universities, Cincinnati, 

Ohio, June 22, 2007. 

Ruhter, P. and B. Smith (M.H. Chew & Assoc., Inc); D. Bihl (Dade Moeller & Assoc.); and M. 

Rolfes (NIOSH) 2011. Pantex Bounding Uranium and Thorium Intakes, August 5, 2011. 

SC&A 2004. Standard Operating Procedure for Performing Site Profile Review, Sanford Cohen 

& Associates, 2004. 

SC&A 2007. Pantex Plant Site Profile Review, Sanford Cohen & Associates, October 14, 2007. 

SC&A 2010. Interview with Charles Dean, August 20, 2010. 

Strom, D.J., Log Probability Analysis of Grouped Pantex Photon and Neutron Dosimeter Data, 

Pacific Northwest National Laboratory, Richland, Washington, 2004. [SRDB Ref ID: 21850]. 
Effective Date: 

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ATTACHMENT 1: SUMMARY OF SITE EXPERT INTERVIEWS 

[To be provided at a later date]