HHS Special Exposure Cohort Designation:

Clarksville Modification Center, Ft. Campbell, Clarksville, Tennessee

HHS Designation of Additional Members of the 

Special Exposure Cohort 

under the 

Energy Employees Occupational Illness Compensation Program Act of 2000 

Designating a Class of Employees 

Clarksville Modification Center, Ft. Campbell

Clarksville, Tennessee
HHS Special Exposure Cohort Designation:

Clarksville Modification Center, Ft. Campbell, Clarksville, Tennessee

Page 2

I. Designation 

I, Kathleen Sebelius, Secretary of Health and Human Services, designate the class 

of employees defined in Section II of this report for addition to the Special Exposure 

Cohort (SEC), as authorized under the Energy Employees Occupational Illness 

Compensation Program Act of 2000 (EEOICPA), 42 U.S.C. § 7384q.

August 23, 2012 [Signature on File]

Date Kathleen Sebelius

II. Employee Class Definition

All employees of the Department of Energy, its predecessor agencies, and 

their contractors and subcontractors who worked at the Clarksville 

Modification Center, Ft. Campbell, in Clarksville, Tennessee, from August 1, 

1949, through December 31, 1967, for a number of work days aggregating at 

least 250 work days, occurring either solely under this employment, or in 

combination with work days within the parameters established for one or 

more other classes of employees included in the Special Exposure Cohort.

III. Designation Criteria and Recommendations

Pursuant to 42 U.S.C. § 7384q, for the class defined in Section II of this report, the 

Secretary has determined, and the Advisory Board on Radiation and Worker Health 

(Board) has recommended, that

(1) It is not feasible to estimate with sufficient accuracy the radiation dose that 

the class received; and

(2) There is a reasonable likelihood that such radiation dose may have 

endangered the health of members of the class.

The SEC final rule states in 42 C.F.R. § 83.13(c)(1) that it is feasible in two situations 

to estimate the radiation dose that the class received with sufficient accuracy. First, 

the rule states that radiation doses may be estimated with sufficient accuracy if 

NIOSH has established that it has access to sufficient information to estimate the 

maximum radiation dose for every type of cancer for which radiation doses are 

reconstructed that could have been incurred under plausible circumstances by any 

member of the class. Alternatively, radiation doses may be estimated with sufficient 

accuracy if NIOSH has established that it has access to sufficient information to 

estimate the radiation doses of members of the class more precisely than a 

maximum dose estimate.

The Board, pursuant to 42 U.S.C. § 7384q, advised the Secretary to designate the 

class as an addition to the SEC in a letter received by the Secretary on August 1, 

2012.
HHS Special Exposure Cohort Designation:

Clarksville Modification Center, Ft. Campbell, Clarksville, Tennessee

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IV. Designation Findings

Feasibility of Estimating Radiation Doses with Sufficient Accuracy

The Secretary established the feasibility determination for the class of employees 

covered by this report based upon the findings summarized below.

• The principal sources of internal radiation exposures for members of the 

Clarksville Modification Center, Ft. Campbell proposed class included exposures 

to tritium as a gas, weapons-grade plutonium, highly-enriched uranium, depleted 

uranium, polonium-210 in a Po-Be neutron generator, and small activities of 

cesium-137 during the assembly, inspection, and disassembly of weapons 

components.

• NIOSH has found that air monitoring for tritium was called for in the plant 

operating procedures. However, NIOSH has been unable to located recorded 

results of this monitoring. NIOSH has also identified a lack of information 

indicating urinalysis or other forms of internal monitoring were conducted to 

monitor for intakes of uranium, plutonium, or tritium. 

• NIOSH has located very little documentation as to quantities of radiological 

materials shipped to the Clarksville Modification Center, Ft. Campbell, for 

processing or testing. It is clear from reports and worker communication that the 

Clarksville employees worked with uranium, tritium, and plutonium. However, 

without additional documentation, NIOSH is unable to ascertain the quantities or 

forms of the source materials that may have been used or stored on site at any 

time during the period under evaluation. 

• In the absence of adequate internal dose monitoring criteria and adequate 

personnel monitoring data, NIOSH has not found sufficient general area air 

sampling, breathing zone air sampling, site survey, or source term information to 

allow it to bound potential internal exposures, or to demonstrate that workers 

were adequately monitored for potential exposures. Therefore, NIOSH finds that 

it is not feasible to estimate with sufficient accuracy the total internal dose for 

workers at the Clarksville Modification Center, Ft. Campbell, in Clarksville, 

Tennessee, during the period from August 1, 1949, through December 31, 1967.

• The principal sources of external radiation exposures for members of the 

Clarksville Modification Center, Ft. Campbell proposed class included exposures 

to weapons-grade plutonium, highly-enriched uranium, depleted uranium, 

polonium-210 in a Po-Be neutron generator, a cobalt-60 radiography source, an 

iridium-192 radiography source, and small activities of cesium-137 during the 

assembly, inspection, and disassembly of weapons components.

• NIOSH determined that it has access to annual dosimetry reports for Clarksville 

Modification Center, Ft. Campbell from 1949 through 1959 and weekly report

from 1960 through the end of operations in 1965. However, NIOSH intends to 

investigate the use of neutron-to-photon ratios based on data from similar 

operations to support reconstructing external neutron doses for members of the 

proposed class.
HHS Special Exposure Cohort Designation:

Clarksville Modification Center, Ft. Campbell, Clarksville, Tennessee

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• NIOSH has also identified no information describing the medical X-ray 

examination requirements for the evaluated period at the site. NIOSH intends to 

use the available methodology for the era to support reconstructing medical Xray for members of the proposed class.

• Because the monitored individuals would have been those workers with direct 

exposure to the devices being maintained at the plant, it is reasonable to assume 

that these badges represent the maximally-exposed individuals. Based on this 

data availability, and the available dose reconstruction methods, NIOSH believes 

that is feasible to reconstruct external dose, including occupational medical 

doses, with sufficient accuracy for all Clarksville Modification Center, Ft. 

Campbell employees during the time period from August 1, 1949, through 

December 31, 1967.

• NIOSH finds that it has access to sufficient personnel and area monitoring data, 

and sufficient process and radiological source information, to support assessing 

external dose, including occupational medical dose, with sufficient accuracy. 

However, NIOSH lacks access to sufficient information and documentation that 

would allow it to estimate with sufficient accuracy the potential internal 

radiological exposures to which the proposed class may have been subjected at 

the Clarksville Modification Center, Ft. Campbell employees during the time 

period from August 1, 1949, through December 31, 1967.

• NIOSH has documented that it cannot complete the dose reconstructions related 

to this petition with sufficient accuracy for the employees who worked at the 

Clarksville Modification Center, Ft. Campbell employees during the time period 

from August 1, 1949, through December 31, 1967. The basis of this finding 

demonstrates that NIOSH does not have access to sufficient information to 

estimate either the maximum radiation dose incurred by any member of the class 

or to estimate such radiation doses more precisely than a maximum dose 

estimate for that period.

• Although NIOSH found that it is not possible to completely reconstruct radiation 

doses for employees who worked at the Clarksville Modification Center, Ft. 

Campbell employees during the time period from August 1, 1949 through 

December 31, 1967, NIOSH intends to reconstruct external exposures and use 

any internal monitoring data that may become available for an individual claim 

during this period (and that can be interpreted using existing NIOSH dose 

reconstruction processes or procedures) to support a partial dose reconstruction 

for individuals employed at the Clarksville Modification Center, Ft. Campbell, 

during the period from August 1, 1949, through December 31, 1967, but who do 

not qualify for inclusion in the SEC.
HHS Special Exposure Cohort Designation:

Clarksville Modification Center, Ft. Campbell, Clarksville, Tennessee

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• Pursuant to 42 C.F.R. § 83.13(c)(1), NIOSH determined that there is insufficient 

information to either: (1) estimate the maximum radiation dose, for every type of 

cancer for which radiation doses are reconstructed, that could have been 

incurred under plausible circumstances by any member of the class; or (2) 

estimate the radiation doses of members of the class more precisely than a 

maximum dose estimate.

• The Board concurred with the NIOSH evaluation and recommended the 

proposed class for addition to the SEC.

 Health Endangerment

The Secretary established the health endangerment determination for the class of 

employees covered by this report based upon the findings summarized below.

(1) Pursuant to 42 C.F.R. § 83.13(c)(3), NIOSH established that there is a 

reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. Pursuant to 42 C.F.R. § 83.13(c)(3)(ii), 

NIOSH specified a minimum duration of employment to satisfy this health 

endangerment criterion as “having been employed for a number of work days 

aggregating at least 250 work days within the parameters established for this 

class or in combination with work days within the parameters (excluding 

aggregate work day requirements) established for one or more other classes 

of employees in the Cohort.”

(2) NIOSH did not identify any evidence from the petitioners or from other 

resources that would establish that the class was exposed to radiation during 

a discrete incident likely to have involved exceptionally high-level exposures, 

such as a nuclear criticality incident, as defined under 42 C.F.R. § 

83.13(c)(3)(i). 

(3) The Board concurred with NIOSH’s finding that the health of the class may 

have been endangered and defined the class according to the 250-work day 

requirement specified under 42 C.F.R. § 83.13(c)(3)(ii).

V. Effect and Effective Date of Designation

The Secretary submits this report on the designation of one additional class to the 

SEC for review by Congress, pursuant to 42 U.S.C. §§ 7384l(14)(C)(ii) and 

7384q(c)(2)(A), as amended by the Ronald W. Reagan National Defense 

Authorization Act for Fiscal Year 2005, Pub. L. No. 108-375 (codified as amended in 

scattered sections of 42 U.S.C.). Pursuant to 42 U.S.C. § 7384l(14)(C)(ii), as 

amended by the Ronald W. Reagan National Defense Authorization Act for Fiscal 

Year 2005, Pub. L. No. 108-375 (codified as amended in scattered sections of 42 

U.S.C.), the designation in this report will become effective 30 days after the date of 

this report’s submission to Congress “unless Congress otherwise provides.”
HHS Special Exposure Cohort Designation:

Clarksville Modification Center, Ft. Campbell, Clarksville, Tennessee

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VI. Administrative Review of Designation

The health endangerment determination of the designation provided in this report 

may be subject to an administrative review within HHS, pursuant to 42 C.F.R. § 

83.18(a). On the basis of such a review, if the Secretary decides to expand the class 

of employees covered by this designation, the Secretary would transmit a 

supplementary report to Congress providing the expanded employee class definition 

and the criteria and findings on which the decision was based.