SEC Petition Evaluation Report 

Petition SEC-00018 

Rev # 0 Submittal Date: 06-13-2005 

Petition Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Submittal Date DOE/AWE Facility Name 

SEC-00018 83.13 02-24-05 Y-12 Plant 

Feasible to Estimate Doses with Sufficient Accuracy? 

Single Class Multiple Classes Determination Established for All Classes 

Yes No X Yes No Yes X No 

Initial Class Definition 

All Control Operators that worked in building 9201-5 and the Beta Building at Y-12 from January, 1944 

through December, 1945. 

Proposed Class Definition (Abbreviated) 

All DOE, DOE contractors, or subcontractors, or AWE employees who worked in uranium enrichment 

operations or other radiological activities at the Y-12 facility in Oak Ridge, Tennessee from March, 1943 

through December, 1947. 

Related Petition Summary Information 

SEC Petition Tracking #(s) Petition Type DOE/AWE Facility Name Petition Status 

SEC-00026 83.13 Y-12 Plant Evaluation Completed 

SEC-00028 83.13 Y-12 Plant Evaluation in Progress 

Lead Technical Evaluator: Signature on File 

LaVon Rutherford 

6/10/2005 

Date 

Reviewed By: Signature on File 

James W. Neton 

6/10/2005 

Date 

Approved By: Signature on File 

Larry J. Elliott 

6/13/2005 

Date 

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Evaluation Summary 

This evaluation report by the National Institute for Occupational Safety and Health (NIOSH) covers a 

class of employees proposed for addition to the Special Exposure Cohort (SEC) in Petition 00018, 

which qualified for evaluation on February 3, 2005. This petition requested NIOSH to consider all 

“control operators” that worked in building 9201-5 and the Beta Building at the Y-12 facility in Oak 

Ridge, Tennessee from January 1944 through December 1945. Subsequently, two additional petitions 

on behalf of employees at the Y-12 facility qualified for evaluation. Petition 00028 qualified for 

evaluation on April 29, 2005; the initial proposed class definition was “all steamfitters, pipefitters and 

plumbers who worked at Y-12 from October, 1944 through December, 1957.” Petition 00026 

qualified for evaluation on May 9, 2005; the initial proposed class definition was “all Tennessee 

Eastman Corporation employees at the Y-12 Plant that conducted laboratory equipment cleaning work 

from 1943 through 1947.” Based on knowledge of facility records and information available for years 

prior to and after the petition class time frames and the operating years of the calutrons, the evaluation 

was expanded to cover the entire “calutron” period of uranium enrichment operations at the Y-12 

facility. In addition, the class start date was established based on the completion of the Pilot Plant 

building shell in March 1943. Therefore, this evaluation covers the time period of March 1943 

through December 1947. 

Feasibility of Dose Reconstruction 

The feasibility determination for the class of employees covered by this evaluation report is governed 

by the requirements of the Energy Employees Occupational Illness Compensation Program Act of 

2000 (EEOICPA) and 42 C.F.R. § 83.13(c)(1). This section of the rule states that “Radiation doses 

can 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 in plausible circumstances by any member of 

the class, or if NIOSH has established that it has access to sufficient information to estimate the 

radiation doses of members of the class more precisely than an estimate of the maximum radiation 

dose.” 

NIOSH has established in this evaluation that it lacks 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. Although NIOSH has completed dose 

reconstructions for workers employed during the 1943 – 1947 time period, these reconstructions were 

either for individuals who worked in areas and operations not involving radioactive materials and 

exposures or they were for individuals for whom the limited information available to NIOSH was 

sufficient for dose reconstruction, based on the type of cancer the individual incurred and the 

individual’s complete work history, which may have involved work during other time periods and 

other facilities. NIOSH is not able to estimate the maximum internal radiation doses, however, for all 

cancer types for members of the class specified under the class definition established by NIOSH 

below. Specifically, members of this class may have had intakes of uranium compounds associated 

with calutron operations, for which existing area monitoring data and source term and process 

information are inadequate to estimate maximum radiation doses. In addition, members of this class 

may have had intakes of radionuclides and external radiation exposures associated with other 

2
 
radiological activities occurring during the petition time period, as mentioned in a 1946 TEC History 

report including: 

• Developing and distributing beneficial radioactive isotopes, 

• Developing a neutron monitor and testing the monitor with a neutron source, 

• Maintenance and use of a large 226Ra sealed source for radiographic examinations, and 

• Extraction of Thorium. 

There are no area monitoring data, source term, or process information for these radiological activities 

to estimate the maximum radiation doses associated with these activities. On these bases, NIOSH 

finds that it is not feasible to estimate radiation doses with sufficient accuracy for members of the 

class. 

Health Endangerment 

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by EEOICPA and 42 C.F.R. § 83.13(c)(3). Under these requirements, if it is not feasible to 

estimate with sufficient accuracy radiation doses for members of the class, NIOSH must also make a 

determination whether or not there is a reasonable likelihood that such radiation doses may have 

endangered the health of members of the class. The regulation requires NIOSH to assume that any 

duration of unprotected exposure may have endangered the health of members of a class when it has 

been established that the class may have been exposed to radiation during a discrete incident likely to 

have involved levels of exposure similarly high to those occurring during nuclear criticality incidents. 

If the occurrence of such an exceptionally high level exposure has not been established, then NIOSH 

is required to specify that health was endangered for those workers who were employed for a number 

of work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC (excluding aggregate work day requirements). 

This NIOSH evaluation 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, as described above. NIOSH is not aware of any report 

of such an occurrence at the facility until 1958. NIOSH finds the primary radiation exposure hazard 

to employees involved in the calutron activities resulted from episodic inhalations of radionuclides 

that cumulatively result in chronic exposures. Members of the class involved in other radiological 

activities would also have incurred internal and external chronic radiation exposures. Consequently, 

NIOSH has specified that health was endangered for those workers covered by this evaluation who 

were 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 established for one 

or more other classes of employees in the SEC. 

Proposed Class Definition 

This evaluation defines a single class of employees for which NIOSH cannot estimate radiation doses 

with sufficient accuracy and whose health may have been endangered by such radiation doses. This 

class includes employees of DOE or DOE contractors or subcontractors who worked in uranium 

enrichment operations or other radiological processes at the Y-12 facility in Oak Ridge, Tennessee 

during the period from March 1943 through December 1947 and who were employed for a number of 

work days aggregating at least 250 work days or in combination with work days within the parameters 

3
 
(excluding aggregate work day requirements) established for classes of employees presently included 

in the SEC. Under this proposed class definition, “working in uranium enrichment operations or other 

radiological activities” means any work in which the employee might have been routinely present, 

during the specified period, within the uranium enrichment buildings or other buildings where 

radiological activities occurred. 

4
 
 

1.0 Purpose 

The purpose of this report is to provide an evaluation of the feasibility of reconstructing the doses for 

employees who worked in uranium enrichment operations or other radiological activities at the Y-12 

facility in Oak Ridge, Tennessee from March 1943 through December 1947. The evaluation was 

initially based on SEC Petition 00018 which defines a class limited to “All Control Operators that 

worked in Building 9201-5 and the Beta Building at Y-12 from January 1944 through December 

1945.” Subsequently, two additional petitions on behalf of employees at the Y-12 facility qualified 

for evaluation. Petition 00028 qualified for evaluation on April 29, 2005; the initial proposed class 

definition was “all steamfitters, pipefitters and plumbers who worked at Y-12 from October, 1944 

through December, 1957.” Petition 00026 qualified for evaluation on May 9, 2005; the initial 

proposed class definition was “all Tennessee Eastman Corporation employees at the Y-12 Plant that 

conducted laboratory equipment cleaning work from 1943 through 1947.” Based on information 

obtained regarding data availability for the period during which uranium was enriched at the facility 

using “calutrons,” NIOSH expanded the scope of this evaluation to cover the entire period of these 

operations and all buildings where these or other radiological operations occurred from 1943 through 

1947. 

This evaluation was conducted in accordance with the requirements of EEOICPA, 42 C.F.R. pt. 83 

and the guidance contained in NIOSH’s Internal Procedures for SEC Evaluations, OCAS-PR-004. It 

provides information and analyses germane to considering a petition for adding a class of employees 

to the SEC. It does not provide any determinations concerning the feasibility of dose reconstruction 

that necessarily apply in the particular case of any individual energy employee who might require a 

dose reconstruction from NIOSH. 

2.0 Introduction 

EEOICPA and 42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the 

Special Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program 

Act of 2000, requires NIOSH to evaluate qualified petitions requesting HHS to add a class of 

employees to the SEC. The evaluation is intended to provide a fair, science-based determination of 

whether or not it is feasible to estimate with sufficient accuracy the radiation doses of the class of 

employees through NIOSH dose reconstructions.1

 If it is not feasible, the regulation requires NIOSH 

to make a determination with respect to the health endangerment of the class of employees. 

NIOSH is required to document the evaluation in a report, which is provided to the petitioners and to 

the Advisory Board on Radiation and Worker Health. The Board will consider the NIOSH evaluation 

report, together with the petition, comments of the petitioner(s) and such other information as the 

Board considers appropriate, to make recommendations to the Secretary of HHS on whether or not to 

add one or more classes of employees to the SEC. Once NIOSH has received and considered the 

advice of the Board, the Director of NIOSH will propose decisions on behalf of HHS. The Secretary 

of HHS will make final decisions, taking into account the NIOSH evaluation, the advice of the Board, 

1

 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 C.F.R. pt. 82 and 

the detailed implementation guidelines available at www.cdc.gov/niosh/ocas. 

5
 
 

 

 

 

 

 

and the proposed decision issued by NIOSH. As part of this final decision process, the petitioner(s) 

may seek a review of certain types of proposed decisions issued by NIOSH.2 

This NIOSH report provides a summary of the methods and findings of the NIOSH SEC petition 

evaluation for employees of DOE or DOE contractors or subcontractors who worked in uranium 

enrichment activities or other radiological processes at the Y-12 Plant in Oak Ridge, Tennessee over 

the period of operation from March 1943 through December 1947. The Y-12 facilities’ primary 

mission during this time period was the enrichment of uranium using an electromagnetic isotope 

separator known as a calutron. 

3.0 Initial Class Definition and Petition Basis 

SEC Petition 00018, qualified on February 3, 2005, requested HHS to consider the addition to the 

SEC a class of employees including all control operators that worked at Y-12 in Oak Ridge, 

Tennessee in building 9201-5 and the Beta Building from January 1944 through December 1945. The 

petitioner, who worked at the facility during this time period, asserted by affidavit that the petitioner 

did not receive or witness monitoring of radiation exposures or radiation doses of control operators. 

Records available to NIOSH support the petitioner’s statement that such employees were not 

personally monitored by radiation badges, urinalysis, or other means. Although the facility did have a 

program of area monitoring during the time period specified, a review by NIOSH of the records from 

this program had already identified concerns about their adequacy for dose reconstruction for the time 

period during which the calutrons (discussed below) and associated radiological operations were in 

operation, from March 1943 through December 1947. Accordingly, the evidence provided by the 

petitioner qualified the petition for further consideration by NIOSH, the Board, and HHS and NIOSH 

expanded the scope of the evaluation to cover the entire period from March 1943 – December 1947 

and to cover all employees with apparent potential for radiation exposures. 

4.0 Data Resources 

NIOSH identified and reviewed data resources to determine the availability of information relevant to 

determining the feasibility of dose reconstruction for the class of employees covered by the petition. 

This included determining the availability of information on personal monitoring, area monitoring, 

industrial process, and radiation source materials. The following sections summarize the resources 

identified and reviewed. 

Site Profile or Technical Basis Documents 

NIOSH reviewed portions of the site profile NIOSH issued on November 24, 2004 for the facility 

covered by the petition: Technical Basis Document for the Y-12 National Security Complex – Y-12 

Site Profile (ORAU 2004d). The Technical Basis Documents (TBDs) contained within this Site 

Profile provide process history information, information on personal and area monitoring, radiation 

source descriptions, and references to primary documents relevant to the radiological operations at the 

facility. 

Previous Dose Reconstructions 

2 See 42 C.F.R. pt. 83 for a full description of the procedures summarized here. Additional internal procedures are 

available at www.cdc.gov/niosh/ocas. 

6
 
NIOSH reviewed its dose reconstruction database, NIOSH OCAS Claims Tracking System (NOCTS), 

to identify dose reconstruction cases under EEOICPA that might provide information relevant to the 

petition evaluation. Table 1 below provides a results summary of this review for the 

March 1943 – December 1947 time frame. 

Table 1: Y-12 Claims Submitted Under Dose Reconstruction Rule for 1943-1947 

Description Total 

Number of cases submitted for energy employees who meet the 

revised class definition employment period criteria. 810 

Number of dose reconstructions completed for energy employees 

who were employed at Y-12 during the years identified in the 

revised class definition. 

135 

Number of cases for which internal dosimetry records were 

obtained for the identified years in the revised class definition. 0 

Number of cases for which external dosimetry records were 

obtained for the identified years in the revised class definition. 0 

NIOSH reviewed each claim to determine whether NIOSH had been able to obtain internal and/or 

external personal monitoring records on the employee or area monitoring data that could be used in 

the place of personal data. NIOSH had not been able to obtain any personal monitoring records but 

had obtained some area monitoring data for use in conducting dose reconstructions. NIOSH also 

reviewed the interviews conducted with claimants for these cases to determine whether they had 

provided relevant information for dose reconstruction. The interviews provided some information that 

might be useful for dose reconstructions (i.e., work locations, hours worked, and hazards 

encountered). 

The 135 cases for which NIOSH has completed dose reconstructions involving employees who 

worked for Y-12 during (but not limited to) the March 1943 – December 1947 “calutron” period 

involved circumstances that allowed for the use of either an overestimating or an underestimating dose 

reconstruction methodology, as described in NIOSH internal procedure OCAS-PR-003, Performing 

and Reporting Dose Reconstructions. These methods make use of relatively limited and case-specific 

information that are not necessarily sufficient to demonstrate the feasibility of estimating radiation 

doses for a class of employees, which may include individuals for whom these methods are 

inappropriate. 

More specifically, the overestimating methodology uses overestimates of radiation exposures to limit 

the need for additional research and analysis for cases that apparently did not involve a compensable 

level of radiation dose and, hence, for which a more precise determination of the doses received by the 

employee would delay without any benefit to the claimants the completion of the dose reconstruction 

and the resolution of the related claims. The underestimating methodology similarly uses 

underestimates of radiation exposures to limit the need for additional research and analysis, but in this 

case the dose reconstruction process is abbreviated at the point it becomes apparent that the case 

7
 
 

involved a compensable level of radiation dose, allowing the claimants to be compensated more 

expeditiously. Neither of these methods is useful when only a comprehensive and maximally detailed 

dose reconstruction can establish whether or not the individual incurred a compensable level of 

radiation dose. 

NIOSH and ORAU Research Documents 

The NIOSH and ORAU site research databases were reviewed for documents to support the 

evaluation of the petitioning class. The documents identified for review from this search are listed in 

Attachment 1. The reports include information on dust studies, radon sampling, dose rate surveys, 

urinalysis data, the radiological control program, medical monitoring, feed materials, and process 

description information for the Y-12 site. 

Documentation and/or affidavits provided by the Petitioners 

In qualifying and evaluating the petition, NIOSH reviewed the following documents submitted by the 

petitioners: 

1) An affidavit received on November 24, 2004 from the petitioner documenting the petitioner’s 

belief that neither area nor personal radiation monitoring was conducted for the proposed class 

of employees. [SEC 00018] 

2) Documents received on February 8, 2005 from the petitioner indicating that radiation 

exposures and doses to members of the initial proposed class were not monitored, including 

technical reports that identified dosimetry and related information that are unavailable. [SEC 

00026] 

3) An affidavit received on March 28, 2005 from the petitioner documenting the petitioner’s 

inability to obtain monitoring records for certain members of the initial proposed class of 

employees. [SEC 00028] 

5.0 Summary of Available Monitoring Data 

Only area monitoring techniques were used to measure and provide data to support the control of 

radiation exposure to workers during the March 1943 – December 1947 operating period. No 

personal internal or external monitoring data are available for Y-12 employees working prior to 1948 

(Souleyrette, 2003). The area monitoring data include condenser R chamber results measuring 

external penetrating exposures adjacent to the control cubicles in the alpha- and beta-calutron 

buildings and approximately 900 records of area monitoring results on radiological dust 

concentrations associated with the various uranium enrichment processes. 

Several retrospective radiological exposure studies have been conducted at Y-12 in the past. [See the 

ORAU Centers for Epidemiologic Research site reports: http://www.orau.gov/cer/reports.htm] 

Records used in these studies have been retrieved, maintained, and are available for use to reconstruct 

certain radiation doses. 

Condenser R Chamber Measurements 

Records indicating a concern about exposure to X rays for personnel adjacent to the calutrons were 

located commencing August 11, 1943 (Sterner 1943, Hall 1943, Schmidt 1944a and 1944b, Hull 

1944, Marks 1944a and 1944b, Brosemer 1944). This radiation was generated primarily from the 

8
 
rectifier units within high voltage circuitry of the calutrons. Initial exposure measurements appear to 

have been made using Kodak photographic film (Sterner 1943). Hall (1943) refers to exposure 

measurements that had been made indicating elevated X-ray exposures both in front (cubicle 

operator's position) and back sides of the cubicles. Metal shielding had been installed over the glass 

on the back side of the cubicle in response to these measurements. Apparently, General Electric 

conducted similar tests that were in the "same order of magnitude" as the earlier measurements. Later, 

Marks (1944a 1944b) conducted measurements using 0.25 R, condenser R chambers (Victoreen 

Manufacturing Co.). These measurements indicated that, due to variations in the rectifier tubes, there 

were similar variations in exposures adjacent to the cubicles, but that typically the position of the 

control operators in front of the cubicle did not exceed the 0.1 R/d tolerance level. The maximum safe 

stay-time next to the rear doors of the cubicle was 4 hours in a day (Schmidt 1944a). These 

measurements taken sporadically during the evolving development of the calutrons indicated that the 

external radiation exposure hazard from the rectifier tubes (X ray) was known in the Fall of 1943. It is 

not clear when engineering controls were initiated, but most of the monitoring conducted in the spring 

of 1944 was conducted to test what appears to have been "sight glasses" for the operators. 

Measurements were conducted with no glass present, regular glass, "ruby" glass, and lead glass. At 

some time during the operation of the calutron units prior to 1944, lead glass was installed in the 

operator area and measured exposure rates were reported as "negligible" (Kerr 2005). Additional 

information (Tankersley 2005) indicated that leaded glass was installed at the viewing ports to reduce 

exposure rates at that location to less than the tolerance level. Documentation also indicates there was 

a "metal back, which is always in place when the cubicle is in operation" that reduced exposure rates 

to "0.1 - 0.2 R/d." The maximum dose rate to which a worker could be exposed appears to have 

occurred at the window or viewing ports. 

Area Dust Monitoring Data 

Dust concentration measurements were first performed at the Y-12 plant in May 1944; however a 

formal air dust monitoring program was not established until April 1945. Prior to the establishment of 

the program, samples were collected only at selected locations. The samples were initially collected 

using a “polaragraph” supplied by Eastman Kodak and later via ionization chambers. 

The formal dust monitoring program established in 1945 provided a system for monitoring all 

production buildings. Each building was divided into separate sections or rooms in which permanent 

monitoring stations utilizing air filtration collection devices were placed. Based on the documents 

reviewed, sampler locations were chosen to be proximate to locations where personnel spent the 

majority of their time. In addition to routine monitoring, some monitoring targeted specific 

operations. However, all dust monitoring conducted from 1944 through 1947 appears to have 

consisted of general area air sampling, based on the sampling documentation available. NIOSH has 

not located documentation indicating that any of the samples measured breathing zone exposures. 

NIOSH also lacks information on the frequency of the sampling during this period. An ORAU report 

(ORAU 2001) does indicates that workers employed at the Y-12 Plant from 1943-1947 had a high 

potential for internal intakes because of the processes performed at the facility and the dust monitoring 

data is consistent with this report. The data indicates that uranium dust was a substantial exposure 

problem and indicates the relative differences in exposure levels for different areas and operations. 

Sampling results for some operations indicated essentially no dust exposure hazards during most 

sampling periods. For example, calutron operators appear to have been exposed to very little or no 

contaminated dust during normal operating conditions, which is consistent with the fact that the 

interior of the calutrons was maintained in a vacuum state during their operation. However, 

9
 
 

concentrations of several hundred and several thousand percent above the calculated maximum air 

concentration (MAC) were measured during some calutron cleaning and uranium recycling 

operations. 

NIOSH has not located any area dust monitoring for the other radiological processes covered under 

Section 6.1.4 of this report. 

6.0 Summary of Radiological Operations Relevant to the Class 

The following subsections summarize the radiological operations at the Y-12 facility from March 

1943 to December 1947 and the information available to NIOSH to characterize particular processes 

and radioactive source materials. The principal source of information for these sections is the Y-12 

site Profile (ORAU 2004d) which contains process and source descriptions. It also presents available 

information regarding the identity and quantities of each radionuclide of concern, as well as 

information describing the process through which the radiation exposures of concern may have 

occurred and the physical environment in which they may have occurred. 

6.1 Plant and Process Descriptions 

The Y-12 Plant, now the Y-12 National Security Complex, was initially constructed in the fall of 1942 

by engineers of the Manhattan Engineering District (MED) of the U.S. Army corps of Engineers. The 

specific mission of Y-12 was to separate fissionable isotopes of uranium (235U) from uranium 

feedstock, using an electromagnetic separation process within a “calutron”, for use in the Hiroshima 

atomic bomb. The Y-12 Plant is located at the eastern section of the Oak Ridge Reservation in Oak 

Ridge, Tennessee. The plant occupies approximately 811 acres (0.67 mile wide and 3.2 miles long). 

The Stone and Webster Construction Co. of Boston, MA served as the general engineering contractor 

for the facility which eventually reached a cost of well over $400 million. Tennessee Eastman 

Company (TEC) of Kingsport, TN was selected as the operating contractor for the facility. 

Production of elements of the calutrons and the supporting infrastructure were divided between three 

major contractors to avoid overload and to increase the rate at which installation could proceed. 

General Electric produced power supply equipment, Allis-Chalmers produced the magnets and 

electrical generators, and Westinghouse produced the process tanks and other mechanical parts. 

6.1.1 Construction and Facilities Summary 

The priority associated with the wartime mission to develop an atomic bomb created a need for rapid 

production of enriched uranium. The physical theory, process chemistry, and methods of construction 

for each building or set of calutron units were developed concurrently with construction and 

operation, so that each set of units served as a pilot plant for the next group. Just as soon as buildings 

were completed, TEC moved its people in to operate them. During its mission, the uranium 

enrichment operations were in a constant state of improvement and innovation which resulted in major 

increases in the number and efficiency of operational calutrons. At its peak in mid-1945, the Y-12 

Plant employed over 22,000 workers, including administrative and support staff, calutron operators, 

calutron chemical recycle operators, machinists, construction staff, and scientific research staff. Over 

the March 1943 – December 1947 time period, the Y-12 Plant employed over 50,000 individuals. 

Table 2 presents a brief chronological summary of significant developments at Y-12 and descriptions 

of buildings involved in the enrichment operation. As indicated in Table 3 the first building shell 

10
 
completed was the Pilot Plant 9731 in March 1943. Although the bulk treatment facility 9202 was not 

completed until October 1943, initial testing and storage of radiological material may have occurred in 

the Pilot Plant. 

11
 
Table 2: Process Chronology and Building Descriptions 

Datea Building Event Description/Building Use February 1943 Ground breaking and construction begins at Y-12. 

March 1943 9731 The first building shell is completed. The building is known as the Pilot plant. Initial testing would h

October 1943 9202 Bulk treatment facility designed to convert UO3 (from Mallinckrodt Chemical Works) to UO2, to UCL

used in the alpha calutron sources. The chemical conversions (reduction, chlorination, sublimation) ar

October 1943 9203 235U Analysis (mass spec.), control analyses, and initial product processing. 

October 1943 9205 Uranium isotopic analysis (fission count). 

November 1943 9731 Known as the Pilot Plant, the first calutron units built at Y-12 (2 alpha, 2 beta) are constructed here. T

training facility. 

January 1944 9201-1 Contained alpha – 1 calutron tracks 1 and 2. Track 1 first operational in January, track 2 operational b

March 1944 9204-1 Contained beta calutron tracks 1 and 2. Track 1 first operational in March, track 2 operational by follo

March 1944 9201-2 Contained alpha – 1 calutron tracks 3 and 4. Track 3 first operational in March, track 4 by following A

March 1944 First shipment of partially enriched uranium goes to Los Alamos. Spring 1944 The peak of construction work in Oak Ridge – 47,000 workers (Wilcox, 1997). June 1944 9201-3 Contained alpha – 1 calutron track 5. July 1944 9201-4 Contained alpha – 2 calutron tracks 6 and 7. Track 6 first operational in July, track 7 by following AuSeptember 1944 9204-2 Contained beta calutron tracks 3 and 4. Track 3 operational in September, track 4 operational by follo

September 1944 9201-5 Contained alpha – 2 calutrons tracks 8 and 9. Track 8 operational in September, track 9 operational by November 1944 9206 Beta chemical recycling and product processing. November 1944 9733-3 Chemical control analysis. 

November 1944 Y-12 starts converting HEU oxide (final product from the beta calutrons) to green salt for shipment. December 1944 9204-3 Contained beta calutron tracks 5 and 6. Track 6 operational by December, track 5 operational by follo

January 1945 9207 Uranium salvage operations. 

February 1945 9733-4 Chemical control analysis. 

May 1945 Peak Y-12 operating workforce reached at this time (22,482 employees). September 1945 All alpha calutrons utilized for producing low-enriched uranium are shut down. The gaseous diffusion 

required enriched uranium suitable for use as beta calutron feed. 

November 1945 9212 Beta product processing November 1945 9204-4 Contained beta calutrons tracks 7 and 8. Track 8 operational by November, track 7 operational by fol

January 1946 9211 Uranium salvage. December 1946 All beta calutrons stop production of enriched uranium, K-25 is supplying all the highly enriched uran

beta calutrons (in 9204-3) and the experimental calutrons in 9731 are left operational and utilized for sexperimental basis trying to improve efficiency of the calutrons. 

May 1947 TEC’s contractor duties end. TEC is replaced by Carbide & Carbon Chemicals Co., a predecessor to U

Mid-year 1947 

-

1951 

Y-12 overall mission shifts towards reducing K-25 enriched uranium to metal and subsequent machinicomponents. Additionally, salvage operations involved recovering EU from all non-product componeoperations. Calutron parts and associated equipment containing small amounts of uranium were clean

operations were primarily done in Buildings 9206, 9207, and 9211 

a Dates associated with buildings reflect time of initial operation. Information sources: 1991 Compere; 1997 W

12 
6.1.2 Alpha and Beta Calutron Operations 

During the March 1943 – December 1947 time period, the operations at Y-12 primarily involved the 

use of the electromagnetic separation process to enrich uranium in 235U, with the enriched product 

being shipped to Los Alamos for production of atomic weapons. The electromagnetic separation 

process involved the use of “calutrons” which were essentially production scale mass spectrographs. 

In the calutron, atoms or groups of atoms contained in a uranium source (“charge bottle”) are ionized 

and accelerated to a given electrical potential. The ions are then introduced into a magnetic field 

through which they move at a velocity which is a function of their mass and charge. Ions are then 

collected in receivers positioned at locations that can be predicted on the basis of the ion’s size and 

charge. 

Major items required for efficient calutron operation are well designed magnets and associated power 

supplies, high-voltage triodes for close current control, a special high voltage, high current x-ray 

cable, and large vacuum systems to keep the materials processed in the calutron contained under 

negative pressure. Major constraints on the efficiency of the separation process were the recycle, 

handling, and chemical separations of the enriched uranium deposited on the walls of the calutrons. 

Though improvements were made, initially only about 4 % of the uranium in the source actually 

arrived in the receivers through the electromagnetic separation process; 96% remained in the source, 

coated the electrodes, or splattered all over the liner of the calutron. The remaining uranium had to be 

recovered from the equipment though labor intensive cleaning operations involving 20 persons per 

calutron. 

Until the latter part of 1945, Y-12 converted UO3 to UCl4 , which then served as the feed material 

enriched in 235U using two calutron stages, termed “alpha” and “beta.” Enriched product (~ 10% 235U) 

obtained from the alpha calutrons was used as feed for the beta calutrons which then further processed 

the product until it was sufficiently enriched for use in weapons 

Eventually, the Y-12 plant came to contain five alpha enrichment buildings and 4 beta enrichment 

buildings. The calutrons were generally arranged within these buildings in continuous oval or 

rectangular arrangements called “racetracks”. Each alpha track consisted of 96 calutron tanks with 

electromagnets between, arranged in an oval (alpha-1) or rectangle (alpha-2). Oval alpha tracks were 

122 ft long, 77 ft wide and 15 ft high. The beta tracks consisted of 36 units each, in the form of a 

rectangle. At the peak, there were a total of 1,152 production calutrons at Y-12. 

In late 1945, Y-12 discontinued the use of the alpha calutron stage, changing the process to receive 

UF6 from the Oak Ridge Gaseous Diffusion Plant (“K-25” Plant), which was converted to UCl4 and 

used directly as feedstock in the beta calutrons. After 1947 the calutron were no longer used to 

support production. One track of 36 beta calutrons and the experimental calutrons were left 

operational and utilized experimentally for several more years in an attempt to improve efficiency of 

the calutrons. 

6.1.3 Calutron-related Enrichment Processes 

Significant efforts were required to produce feed material for the calutrons, to salvage and recycle 

uranium, and to produce the final material suitable for use in an atomic weapon. A very brief 

discussion of these operations is presented here; detailed discussions are available in Compere, 1991. 

13
 
Feed Preparation and Product Processing 

Volatile UCl4 was the uranium chemical form fed to alpha and beta electromagnetic enrichment 

operations. UCl4 was produced using one of two chemical conversions involving UO3 and carbon 

tetrachloride. The first method was liquid phase chlorination in which uranium and carbon 

tetrachloride were heated under pressure. The UCl4 crystals formed were collected and placed in 

charge bottles which were then loaded into calutrons for U enrichment. A second method was vapor 

phase chlorination in which carbon tetrachloride was gradually added to UO3 and under heated 

conditions inside a chemical reactor bowl for roughly eight hours and then purged with nitrogen to 

exhaust phosgene vapors from the system. UCl4 crystals were collected and loaded into “charge 

bottles” to be placed into calutrons. 

Uranium Recovery and Purification 

Enriched uranium salvage and recycle chemistry was a small batch operation. The operation was 

divided into several phases, which included calutron dismantling and washing, calutron component 

salvage, housekeeping salvage, uranium purification, chlorination, and hexafluoride conversion. 

The recovery and purification efforts were extensive because, even with the most efficient of the 

calutrons, only 20% of the charge material reached the receiver; the rest of the ionized uranium halide 

vapor had to be recovered from wherever it settled and condensed into various chemical forms. The 

calutron liner, the ion source, and the receiver contained a variety of uranium compounds, including 

tetrachloride, oxychloride, carbides, and oxides, as well as loose metal. Operations to recover 

uranium included vacuum cleaning, concentrated nitric acid leaching, and several manual cleaning 

operations using dilute nitric acid. 

All of the operations described above had a common characteristic shared by many other Y-12 

operations: they reclaimed uranium primarily in the form of a uranyl nitrate-nitric acid solution. After 

uranium was removed from process equipment and put into recycle streams, a variety of processes 

were used to purify and concentrate it so that it could be oxidized, chlorinated and returned to the 

calutrons. The nitrate solutions, together with salvage and reclamation from laundry, plant cleanup 

operations, and floor drains represented a significant uranium stream. 

Final Product Production 

The highly enriched uranium obtained from the beta calutrons was recovered as uranium oxide and 

then converted to UF4 (green salt) prior to shipment. The process involved a high temperature 

reduction of the UO3 to UO2, followed by hydrofluorination with anhydrous HF. 

6.1.4 Other Radiological Activities 

Inherent to the developmental nature of the uranium enrichment process, TEC scientists performed a 

variety of radiological experiments, tests and special projects. Examples of some of these activities, 

documented in a second quarter 1946 TEC History Report are: 

14
 
 

 

•	 A program for developing and distributing beneficial radioactive isotopes began during 

the first half of 1944; 

•	 Development of a battery operated neutron monitor; 

•	 Maintenance and use of a large 226Ra source for radiographic examinations; 

•	 Assaying of samples of enriched isotopes of iron, chromium, and lithium; 

•	 A study of the relative behavior of thorium and uranium in ether extractions; and 

•	 Development of a rapid procedure for the separation of trace amounts of thorium from 

large amounts of uranium prior to colorimetric estimation with “Thoron.” 

NIOSH has been unable to obtain any detailed information concerning these activities and any 

associated radiological safety procedures and occupational exposures. 

6.2 Radiological Exposure Sources 

The most substantial radiological exposures documented at Y-12 for the period covered by this report 

were potential internal intakes, resulting from inhalation of particles comprised of various forms of 

uranium. The primary exposure pathway was via inhalation of particles contaminated with uranium in 

various forms during operations involving handling and preparation of feed materials and during the 

recovery, recycling, and salvage processes. Uranium-bearing chemicals present at the facility during 

the subject time period included (but are not limited to): 

• Uranium oxide (U3O8) 

• Uranium dioxide (UO2) 

• Uranium trioxide (UO3) 

• Uranium hexafluoride (UF6) 

• Ammonium diuranate [(NH4)2U2O7] 

• Uranyl nitrate [UO2(NO3)2] 

• Uranium peroxide (UO4 ·2H2O) 

• Uranium tetrachloride (UCl4) 

• Uranium pentachloride (UCl5) 

• Uranium tetrafluoride (UF4) 

The 235U and 238U contained in these compounds are primarily alpha emitters; 235U also emits a 185­

keV photon in 54% of its decays and short lived 238U decay products (234Th, 234mPa, and 234Pa) are 

beta and photon emitters. 

6.2.1 Raw Materials Sources 

Materials used as feed materials for calutron operations varied over time. Ultimately, both alpha and 

beta calutron charge bottles were loaded with UCl4 which was obtained from processing UO3 via 

various chemical processes (liquid- or vapor-phase chlorination). Initially, UO3 (natural quality) was 

obtained from Mallinckrodt Chemical Works for this purpose. Calutron wash solutions (uranyl 

nitrate-nitric acid solution) obtained during cleaning (recycling) operations were also converted to 

back to UO3 for subsequent conversion to UCl4. Starting in late 1945, UO3 was obtained from 

hexafluoride conversion of enriched UF6 obtained from the Oak Ridge Gaseous Diffusion Plant (“K15
 
25” Plant). The UCl4 ultimately obtained from this conversion was sufficiently enriched for use as 

feed for the beta calutrons and the alpha stage of the refinement process was shut down. 

6.2.2 Calutron Operations 

The calutrons units were closed systems, operated under a high vacuum, and therefore provided little 

potential for internal exposure to the operators during operation. As discussed in section 5.0, the 

primary hazard to calutron control operators during operations (typically located on stools in front of 

control panels) was due to X-rays generated from the high voltage equipment. Surveys were 

performed and results were documented in a series of memos (Kerr 2005). Specific sources of the X 

rays were determined to be rectifier tubes in both the alpha and beta control cubicles. Based on the 

documents reviewed, the maximum radiation occurred at the rear of the cubicle (where it did not 

present a significant exposure potential) and at lower level ports. Lead glass was installed over the 

ports to reduce the radiation levels at some point prior to 1944. 

6.2.3 Miscellaneous Chemical Processing 

Radiation exposures at Y-12 during the 1943 to 1947 time period resulted from uranium in various 

forms and occurred primarily in locations where uranium was either received, analyzed, chemically 

converted, recycled and/or purified. Section 6.1.1 contains a table summarizing the building locations 

in which these various activities occurred. Document sources (Tankersley 2005) indicate a potential 

for particularly high exposure to UCl4 in the alpha chemistry sublimation and bottle filling operations 

and during the beta chemistry UCl4 production and bottle filling work. Document sources indicate a 

potential for high exposure to uranium oxides (via dust inhalation) during UCl4 production and during 

the recovery of uranium salts from the calutrons in preparation for the recycling process (Tankersley 

2005). 

7.0 Evaluation of Feasibility of Dose Reconstruction 

The feasibility determination for the class of employees covered by this evaluation report is governed 

by EEOICPA and 42 C.F.R. § 83.13(c)(1). Under this Act and rule, NIOSH must establish whether or 

not it has access to sufficient information to either 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 to estimate the radiation doses of members of 

the class more precisely than a maximum dose estimate. If NIOSH were to have access to sufficient 

information for either case, then it would be determined that it was feasible to conduct dose 

reconstructions. 

In making determinations of feasibility, NIOSH begins by evaluating whether current or completed 

NIOSH dose reconstructions demonstrate the feasibility of estimating with sufficient accuracy the 

potential radiation exposures of the class (identified in section 6.0 of this report). If not, NIOSH 

systematically evaluates the sufficiency of different types of monitoring data, process and source or 

source term data, which together or individually might assure NIOSH can estimate either the 

maximum doses members of the class might have incurred, or more precise quantities that reflect the 

variability of exposures experienced by groups or individual members of the class. This approach is 

specified in the SEC Petition Evaluation Internal Procedures (NIOSH 2004) available at 

www.cdc.gov/niosh/ocas. 

16
 
The evaluation that follows examines separately the availability of information necessary for 

reconstructing internal and external radiation doses of members of the class. 

7.1 Completed Dose Reconstructions 

As discussed under section 4.0 of this evaluation, the 135 cases for which NIOSH has completed dose 

reconstructions involving employees who worked for Y-12 during (but not limited to) the 1943-1947 

period involved circumstances that allowed for the use of either an overestimating or an 

underestimating dose reconstruction methodology. The completion of these dose reconstructions is 

not sufficient to demonstrate the feasibility of estimating radiation doses for the class of employees 

covered by this evaluation. In particular, the overestimates of radiation dose included in some of these 

dose reconstructions do not establish estimates of the maximum radiation dose, for every type of 

cancer, for members of the class defined in this evaluation, nor do they demonstrate that NIOSH can 

estimate the radiation doses of the class more precisely than an estimate of the maximum radiation 

doses. The overestimates applied to employees who did not routinely work in the uranium enrichment 

buildings or radiological processes at the Y-12 facility or who incurred cancers for which the 

maximum relevant radiation doses can be estimated. The overestimates would not apply to employees 

who worked routinely in the uranium enrichment buildings of the facility. 

7.2 Internal Radiation Doses 

No individual monitoring records (either in vivo or in vitro) are available indicating either direct or 

indirect measurement of internal exposures at the Y-12 Plant prior to 1948. As indicated in section 

5.0, workers employed at the Y-12 Plant during the 1943-1947 period had a high potential for internal 

intakes because of the processes performed at the facility. The principal source of internal radiation 

doses for members of the class was uranium particulate material aerosolized through enrichment and 

chemical processing activities. This aerosolized dust could be inhaled by individuals in the area 

which would be deposited in the respiratory tract. This dust would also settle onto surfaces and be 

available for resuspension back into the air where it could be inhaled or ingested in the body by 

transfer from contaminated surfaces via hand to mouth. There were other radiological activities 

identified in 6.1.4 (e.g., Thorium extraction) where internal exposure could have occurred as well, 

although these other radiological activities were conducted on a laboratory or pilot scale. 

It appears that uranium compounds exhibiting all solubility classes would have been present in 

various operations at the Y-12 Plant prior to 1948 (ORAU 2004f). Chemically soluble forms in 

solution, moderately soluble compounds, and relatively insoluble compounds could have been 

encountered by site workers. Monitoring of urine to assess internal exposure, however, did not 

commence at Y-12 until 1948. 

The subsections below summarize the extent and limitations of information available for 

reconstructing the internal doses of members of the class. Most of the information summarized below 

is provided in greater detail in the individual TBDs available for the Y-12 Plant. 

7.2.1 Urinalysis Information and Available Data 

No urinalyses data are available for the Y-12 Plant prior to 1948 (ORAU 2001). Urine sampling 

began at the Y-12 Plant in 1948 to identify internal exposures to personnel. 

17
 
Although NIOSH has assessed the use of surrogate urinalysis data for use in reconstructing dose 

(ORAU 2005a), NIOSH finds that the urinalysis data for the later years would not be representative of 

the urine activity during the 1943 to 1947 time period when the calutrons were in operation. In some 

cases, dosimetry data (i.e., urine data, film badges, fecal sampling) obtained from a later period or 

different location or facility can be applied as a surrogate for data that are unavailable, using statistical 

models to account for potential differences. Use of such “surrogate” data, however, requires that the 

processes and radiological materials involved in the different time periods be similar and comparable. 

Although NIOSH has access to urinalysis data at Y-12 during later periods, the processes during later 

periods are not similar or comparable to the processes during the 1943 to 1947 time period, when the 

calutrons were operating. The calutron operations required significant manual work to recover the 

uranium from the calutrons. 

7.2.2 Information and Available Data Regarding Other Types of Bioassay 

NIOSH has not located any additional records of in vitro (e.g., fecal, sputum, nasal, etc.) or in vivo 

(e.g., whole body, lung, or other organ count) analyses. 

7.2.3 Airborne Dust Levels 

As discussed in section 5.0, NIOSH has access to approximately 900 air sample results for the time 

frame covered by the petition (ORAU 2001). These records comprise general area air samples taken 

in various locations within buildings and also during various operations. The sampling strategy and 

frequencies used are not known and hence NIOSH cannot determine whether the data represents high, 

low, or average concentrations to which a worker would be exposed. Nor do the records indicate 

whether there was monitoring for dust concentrations during non routine activities. Furthermore, 

NIOSH cannot determine whether operations personnel who had low radiation exposure potential 

while operating the calutrons, supported the recycling and cleaning activities that involved high 

radiation dust exposures, or whether these operators were present during the cleaning. NIOSH does 

have documentation, however, indicating that the operation of some calutrons continued while 

recycling and cleaning activities were conducted at other calutrons, indicating a potential for operators 

to be exposed to high dust levels. 

NIOSH reviewed the available site information that described process activities conducted during the 

time period of the proposed class. The calutron operations were unique among uranium production 

and enrichment operations. The inefficiency of the calutron operations, coupled with the continuous 

attempts at increasing the production efficiency, required a substantial amount of time for 

disassembly, recovery of product, and maintenance activities. These operations would have exposed 

the workers to substantial airborne concentrations, as indicated by the general area air sampling results 

that are available to NIOSH. However, without breathing zone measurements for these manual 

activities, NIOSH cannot establish maximum exposure scenarios. Similarly, surrogate data from later 

years at Y-12 or a similar facility cannot be used because the operations involving the calutrons during 

the 1943 to 1947 time period were unique. 

NIOSH also cannot establish maximum exposure scenarios based on source term and process data. 

As discussed above, the levels of enrichment of the source materials and the production rate of the 

operations varied substantially and are not documented for this period of operations. The manual 

recycling and cleaning activities are not comparable to any operations for which NIOSH has access to 

adequate monitoring data. 

18
 
As indicated in section 6.1.4, NIOSH has documentation that supports that other radiological activities 

were occurring at Y-12 during the evaluation period. NIOSH has no air monitoring data, source term, 

or process information associated with these activities. Therefore, NIOSH cannot establish a 

maximum internal exposure scenario for these activities. 

7.2.4 Radon 

NIOSH has not located records of area radon concentrations for the Y-12 Plant during this time 

period. During site operations prior to 1948, radon levels at the site would be close to 

environmental background levels due to the receipt of pre-processed uranium compounds 

(primarily UO3). The pre-processing of uranium compounds removed the radium from the 

material. The radium is the parent radionuclide for radon and has a 1600 year half life. There 

would be minimal buildup during the time the ore was processed and the material leaving the Y12 site. Also, NIOSH has not located any records indicating that radium bearing ores or wastes 

were received or processed at Y-12 during the time period covered by this evaluation. 

NIOSH can estimate maximum doses associated with such potential exposure using surrogate data 

from other uranium metal plants. NIOSH has radon data from later years at uranium processing 

facilities that processed material with similar radium content in greater quantities. Therefore, for 

the purpose of estimating radon exposures, the data would be similar and comparable to that at Y12 during the 1943 – 1947 time period. Hence, these surrogate data would enable NIOSH to 

develop claimant-favorable estimates of the potential radon exposure at Y-12 during the 1943 to 

1947 time period. 

As mentioned in section 6.1.4, Maintenance and use of a large 226Ra source for radiographic 

examinations was occurred at Y-12 during the evaluation period. However, this source was a 

sealed source and would not have provided a significant potential for radon exposure. 

7.3 External Radiation Doses 

As discussed in Section 6.2, potential external radiation exposures at Y-12 during the 1943 – 1947 

time period would have occurred primarily in buildings and areas where uranium was either received, 

analyzed, chemically converted, enriched, recovered as final product or for recycling, processed as 

waste, and/or packaged/shipped from the site. External exposures from material processing could have 

occurred in the control operators’ cubicles of the calutron tracks, any of the material handling 

operations, chemical operators that converted oxides of uranium to uranium tetrachloride for feed 

material into the calutrons, and from miscellaneous activities adjacent to these areas. 

Exposure to neutron radiation also was possible at Y-12. Neutron exposures would have occurred 

primarily from (α, η) reactions with the alpha particles emitted from highly enriched uranium 

interacting with low-Z material (e.g., fluorides and oxides of uranium), but also from other neutron 

sources that were present at the site, as indicated in 6.1.4. These sources included both neutron 

emitting instrument calibration sources (e.g. Po-Be, Pu-Be, Ra-Be, and Am-Be), particle accelerators, 

and neutrons emitted from fissile material testing that took place onsite. 

Occupational medical exposures to x rays, when such screening x rays are a condition of employment, 

are also included in EEOICPA dose reconstructions. During this time period, individuals at the Y-12 

site were required to have pre-employment, annual, and termination chest X-ray examinations. The 

19
 
X-ray examinations were performed at the Y-12 clinic or the Oak Ridge Hospital using a Type 1 

Photoflourographuc unit. 

The subsections below summarize the extent and limitations of information available for 

reconstructing external doses of members of the worker classes addressed by this report. More 

information is provided in greater detail in the Y-12 Site Profile and additional reports (ORAU 2004b 

and c) that have been written supporting the site external dosimetry TBD (ORAU 2003). 

7.3.1 Film Badge Monitoring 

Information in the site external dosimetry TBD documents that film badge monitoring did not 

commence at the Y-12 site until 1948. [A database maintained by ORAU’s Center for Epidemiologic 

Research (CER) indicates individual external dosimetry records beginning the first week of January 

1948.] 

As discussed earlier, in some cases, dosimetry data obtained from a later period or different location 

can be applied as a surrogate for data that are unavailable, using statistical models to account for 

potential differences. Use of such “surrogate” data, however, requires that the processes and 

radiological materials involved in the different time periods be similar and comparable. Although 

NIOSH has access to dosimetry data on external radiation exposures at Y-12 during later periods, the 

processes during later periods are not similar or comparable to the processes during the 1943 – 1947 

time period, when the calutrons were operating. The later activities at Y-12 were primarily associated 

with uranium metal manufacturing and processing. Hence, the surrogate external dosimetry data 

cannot be used for estimating external exposure for workers during the period covered by this report. 

7.3.2 Gamma/X-ray, Beta, and Nonspecific Beta-Gamma Exposures 

The external radiation dose at the Y-12 site arose primarily from personnel X-ray exposure adjacent to 

the calutrons during enrichment activities and the handling and processing of uranium as feed and 

product. As documented in claimant interviews and photographs of the operation, calutron control 

operators were positioned immediately in front of the calutron control panels. The majority of the 

operator’s day was spent in this position, observing the calutrons to ensure that the equipment was 

operating properly. The primary radiation hazards to these individuals came from exposure to X rays 

generated from the high voltage units used for the operation of the calutrons. 

NIOSH has access to the results of fixed location radiation surveys conducted at Y-12 conducted in 

1943 to 1944 (ORAU 2001). As indicated in section 5.0, these radiation surveys were performed 

around the calutrons to determine the necessary controls needed to reduce the operator’s external 

exposures through improvements in shielding, such as the selection of lead glass for the window and 

ports to reduce operator exposure. NIOSH can establish a maximum potential exposure for this 

activity for the March 1943 – December 1947 time period using the dose rate information from these 

surveys. 

Personnel were also involved in chemically converting uranium oxide compounds (typically UO3) 

received from atomic weapons employer (AWE) sites into volatile uranium tetrachloride at Y-12 for 

use as feed material into the calutron tracks. Further chemical processing of these materials was also 

necessary to recover the product material. This material was also later converted into other chemical 

forms for use in metal production. Contact exposure rate measurements are available for uranium 

20
 
compounds that were processed at Y-12 during this period and are sufficient for estimating external 

exposures. 

Employees at Y-12 would have received some exposure to beta radiation. These beta exposures 

would have arisen from the uranium progeny 234Pa, 234Th, and 234mPa from the forms of uranium 

feedstock used during this period at Y-12. The UO3 produced at Mallinckrodt Chemical Works and 

received at Y-12 for conversion into UCl4 feed material for the calutrons would have originally been 

relatively pure uranium, devoid of the early progeny. These early progeny would build back into 

equilibrium conditions over an approximate 5 month period of time during shipping/storage and 

would be available to cause contact, absorbed dose rates of approximately 204 mrad/hr (HEW 1970) 

when handled. Similar contact, absorbed dose rates of approximately 200 mrad/hr would be 

associated with other uranium compounds at the Y-12 Plant during the 1943 to 1947 calutron 

operations. 

NIOSH can develop a maximum beta exposure using the beta dose rates from the surface of cast 

uranium metal. As indicated above, a significant amount of information is known about the beta dose 

rates from uranium metal (EG&G 1988). NIOSH can use this dose rate as a maximum and/or NIOSH 

can use surrogate data from Y-12 data from later years. Although the processes were different the 

product or source, uranium metal was the same and therefore would have similar dose rates. 

More detail addressing how gamma, beta, and neutron radiation doses could be estimated is provided 

in sections 6.4 and 6.5 of the Y-12 external dosimetry TBD (ORAUT 2003) and in supporting reports 

(ORAU 2004b and ORAU 2004c). 

As indicated in section 6.1.4, NIOSH has documentation that supports that other radiological activities 

were occurring at Y-12 during the evaluation period. NIOSH has no external monitoring data, source 

term, or process information associated with these activities. Therefore, NIOSH cannot establish a 

maximum external exposure scenario for these activities. 

7.3.3 Neutrons 

Exposures to neutron radiation were a minor external exposure hazard during the period covered by 

this evaluation report (October 1943 through December 1947) at the Y-12 site. Exposure to neutron 

radiation was possible at Y-12 either directly from neutron sources that were present at the site or 

indirectly from (α, η) reactions during processing of enriched uranium. A report discussing the 

historical evaluation of the neutron measuring film badge (ORAU 2004c) indicates that in 1949 

neutron sensitive films were added to the film badge (Souleyrette, 2003). No personal neutron 

measurements were made at Y-12 prior to that time. 

NIOSH has estimated neutron exposures estimates for the types of uranium compounds that were 

handled and processed at Y-12 during the October 1943 – December 1947 time period (ORAU 

2005c). These estimates are based on the (α, η) reactions and dose rates measured from these types of 

material. Similar estimates could be made at the Y-12 Plant that would provide an overestimate to 

individual neutron exposure. 

As indicated in section 6.1.4, NIOSH has documentation that indicates that Y-12 was working on 

developing a battery operated neutron monitor during the evaluation period. The documentation 

indicates that a neutron generator was used for the calibration of this instrument. However, NIOSH 

21
 
has no monitoring or source term data concerning the dose rates associated with this neutron 

generator. Therefore, NIOSH cannot determine the maximum radiation exposure from this activity. 

7.3.4 Occupational Medical X rays 

As indicated in section 7.3, the x rays were performed during the 1943 to 1947 period at the Y-12 

clinic or the Oak Ridge Hospital using a Type 1 Photoflourographuc unit. Although no exposure date 

is available for medical X rays at Y-12 during the 1943 to 1947 period, surrogate data was used in the 

Y-12 Site Profile (ORAU 2004a) to develop an exposure matrix. The site profile documents the 

method and feasibility of reconstructing these medical exposures. Therefore, NIOSH can determine 

the maximum exposures from occupational medical x rays. 

7.4 Summary of Feasibility Findings 

Table 4 below summarizes the results of the feasibility findings at the Y-12 site for each exposure 

source for the time period 1943 through 1947. 

Table 3: Summary of Feasibility 

Source of Exposure Maximum Exposure can 

be determined 

Maximum Exposure 

cannot be determined. 

Internal X 

- Urinalysis X 

- Airborne Dust X 

- Radon X 

External X 

- Gamma X 

- Beta X 

- Neutron X 

- Occupational Medical X 

ray 

X 

This report evaluated the feasibility for completing dose reconstructions for workers at the Y-12 site 

from the time that radioactive material might have first been brought onto the site (October 1943) 

through the end of routine enrichment operations using electromagnetic separation (December 1947). 

NIOSH found that records associated with determining internal and external exposures were 

insufficient to estimate doses with sufficient accuracy for this class of employees. 

This conclusion was based, in part, on the finding that employees involved in the calutron uranium 

enrichment process were exposed to levels of airborne uranium products that cannot be determined 

because of the absence of bioassay data for the time period and the lack of air sampling sufficient to 

develop maximum exposure scenarios and hence to estimate maximum internal doses. Furthermore, 

NIOSH is unable to estimate such doses based on source term and process information for lack of 

documentation on the varying levels of enrichment of the source materials and on the production rate 

of the operations, and because the manual recycling and cleaning activities are unique and not 

comparable to any operations for which NIOSH has access to adequate monitoring data. Therefore, 

NIOSH is unable to estimate doses associated with internal exposures with sufficient accuracy for 

employees involved in the calutron uranium enrichment process operated at the Y-12 Plant during this 

22
 
period. NIOSH did find that external exposures associated with the calutron uranium enrichment 

process could be estimated through a combination of available dose rate data, measured dose rates 

from similar material, and source term information. 

For employees involved in other radiological activities, mostly experimental and developmental in 

nature as indicated in Section 6.1.4 of this report, NIOSH is unable to estimate any radiation doses 

whether resulting from internal or external exposures. NIOSH has essentially no source term and 

process information, let alone any monitoring data, from which to estimate such doses. 

Note: The determination by NIOSH that it cannot estimate radiation doses with sufficient accuracy 

for members of this class does NOT necessarily mean that NIOSH cannot estimate ANY radiation 

doses with sufficient accuracy for ALL members of this class. In a case in which a member of this 

class incurred a cancer not included among the 22 specified cancers covered by EEOICPA and hence 

requires a dose reconstruction (or would otherwise be left without a remedy), it is possible that 

NIOSH could reconstruct some or all of the radiation doses relevant to the individual’s cancer in 

conformance with 42 C.F.R. pt. 82. 

8.0 Evaluation of Health Endangerment 

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by EEOICPA and 42 C.F.R. § 83.13(c)(3). Under these requirements, if it is not feasible to 

estimate with sufficient accuracy radiation doses for members of the class, NIOSH must also 

determine that there is a reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. The regulation requires NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If 

the occurrence of such an exceptionally high level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those workers who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

This NIOSH evaluation 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 or similar conditions 

resulting from the failure of radiation exposure controls and likely to have produced levels of 

exposure similarly high to those occurring during nuclear criticality incidents. NIOSH is not aware of 

any report of such an occurrence at the facility during this period. NIOSH finds the primary radiation 

exposure hazard to employees resulted from episodic inhalations of radionuclides that cumulatively 

resulted in chronic exposures. This report documents substantial exposures from this hazard. 

Additionally, employees in the class involved in other radiological activities, separate from the 

calutron enrichment process, may have incurred substantial external, as well as internal, radiation 

exposures. Consequently, NIOSH is specifying that health was endangered for those workers 

covered by this evaluation who were 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 established for one or more other classes of employees in the SEC. 

9.0 Proposed Class Definition 

23
 
 

This evaluation defines a single class of employees for which NIOSH cannot estimate radiation doses 

with sufficient accuracy and whose health may have been endangered by such radiation doses. This 

class includes employees of DOE or DOE contractors or subcontractors who worked in uranium 

enrichment operations or other radiological processes at the Y-12 facility in Oak Ridge, Tennessee 

during the period from March 1943 through December 1947 and who were employed for a number of 

work days aggregating at least 250 work days or in combination with work days within the parameters 

(excluding aggregate work day requirements) established for classes of employees presently included 

in the SEC. Under this proposed class definition, “working in uranium enrichment operations or other 

radiological activities” means any work in which the employee might have been routinely present, 

during the specified period, within the uranium enrichment buildings or other buildings where 

radiological activities were present. 

10.0 References 

EEOICPA (Energy Employees Occupational Illness Compensation Program Act of 2000, as amended, 

42 U.S.C. §§ 7384-7385). 

42 C.F.R. pt. 82. Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule, May 2, 2002. 

42 C.F.R. pt. 83. Procedures for Designating Classes of 

Employees as Members of the Special Exposure Cohort Under the Energy Employees Occupational 

Illness Compensation Program Act of 2000; Final Rule, May 28, 2004 

Compere, 1991, The U.S. Calutron Program for Uranium Enrichment: History, Technology, 

Operations, and Production, October 1991. 

EG&G 1988, Health Physics Manual of Good Practices for Uranium Facilities, June 1988 

HEW, 1970, Radiological Health Handbook, US Department of Health, Education, and Welfare, p. 

204, January 1970. 

Kerr, 2005, Miscellaneous memos from, and to TEC personnel supplied from George Kerr in 

February, 2005. 

NIOSH (National Institute for Occupational Safety and Health) 2004, Internal Procedures for the 

Evaluation of Special Exposure Cohort Petitions, OCAS-PR-004, Revision 0, Cincinnati, Ohio, 

September 23, 2004. 

ORAU (Oak Ridge Associated Universities) 1993, Data Collection, Validation, and Description for 

the Oak Ridge Nuclear Facilities Mortality Study, Oak Ridge Tennessee, 1993. 

ORAU 2001, Radiation Dosimetry Information Resource Evaluation, Y-12 Plant, Oak Ridge 

Tennessee, October 31, 2001. 

ORAU 2003, Technical Basis Document for the Y-12 National Security Complex – Occupational 

External Dosimetry, ORAUT-TKBS-0014-6, Rev. 00, Oak Ridge, Tennessee, November 19, 2003. 

24
 
ORAU 2004a, Technical Basis Document for the Y-12 National Security Complex – Occupational 

Medical Dose, ORAUT-TKBS-0014-3, Rev. 00 PC-1, Oak Ridge, Tennessee, September 9, 2004. 

ORAU 2004b, Technical Report 2004-0888, Historical Evaluation of the Film Badge Dosimetry 

Program at the Y-12 Facility in Oak Ridge, Tennessee, Part 1 – Gamma Radiation, 2004. 

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