Page 1 of 15

DOE Review Release 05/02/2019

Summary Site Profile for the S-50 Oak Ridge 

Thermal Diffusion Plant

ORAUT-TKBS-0054 Rev. 01

Effective Date: 04/15/2019

Supersedes: Revision 00

Subject Expert(s): Michalene Rodriguez

Document Owner 

Approval: Signature on File

Michalene Rodriguez, Document Owner

Approval Date: 04/10/2019

Concurrence: Signature on File

John M. Byrne, Objective 1 Manager

Concurrence Date: 04/10/2019

Concurrence: Signature on File

Scott R. Siebert, Objective 3 Manager

Concurrence Date: 04/10/2019

Concurrence: Vickie S. Short Signature on File for

Kate Kimpan, Project Director

Concurrence Date: 04/10/2019

Approval: Signature on File

James W. Neton, Associate Director for Science

Approval Date: 04/15/2019

FOR DOCUMENTS MARKED AS A TOTAL REWRITE, REVISION, OR PAGE CHANGE, REPLACE THE PRIOR 

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION. 

New Total Rewrite Revision Page Change
Document No. ORAUT-TKBS-0054 Revision No. 01 Effective Date: 04/15/2019 Page 2 of 15

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION 

NUMBER DESCRIPTION

12/08/2006 00 New document to describe the S-50 Liquid Thermal Diffusion Project 

to enable the preparation of dose reconstructions. First approved 

issue. Attributions and Annotations added to document. 

Incorporates formal internal and NIOSH review comments. There is

no change to the assigned dose and no PER is required. Training 

required: As determined by the Task Manager. Initiated by Paul A. 

Szalinski.

04/15/2019 01 Revision initiated to update Section 3.0 on occupational medical 

dose with updated K-25 information. Added Section 1.3 to describe 

the Special Exposure Cohort class applicable to S-50 employees. 

Provided additional information in Section 2.0 about site operations. 

Updated boilerplate language and references. No changes occurred 

as a result of formal internal review. Incorporates formal NIOSH 

review comments. Constitutes a total rewrite of the document. 

Training required: As determined by the Objective Manager. 

Initiated by Michalene Rodriguez. 
Document No. ORAUT-TKBS-0054 Revision No. 01 Effective Date: 04/15/2019 Page 3 of 15

 

TABLE OF CONTENTS

SECTION TITLE PAGE

Acronyms and Abbreviations ............................................................................................................... 4

1.0 Introduction .............................................................................................................................. 5

1.1 Purpose........................................................................................................................ 6

1.2 Scope........................................................................................................................... 6

1.3 Special Exposure Cohort.............................................................................................. 6

2.0 Site Description........................................................................................................................ 6

2.1 S-50 Oak Ridge Thermal Diffusion Plant ...................................................................... 6

2.2 Nuclear Energy for the Propulsion of Aircraft Project .................................................... 9

3.0 Occupational Medical Dose.................................................................................................... 10

4.0 Occupational Environmental Dose ......................................................................................... 10

5.0 Occupational Internal Dose.................................................................................................... 11

6.0 Occupational External Dose................................................................................................... 11

7.0 Attributions and Annotations .................................................................................................. 11

References ........................................................................................................................................ 12

Glossary ............................................................................................................................................ 14

LIST OF TABLES

TABLE TITLE PAGE

2-1 S-50 building and/or equipment number and description.......................................................... 9

3-1 X-ray guidance for S-50 workers............................................................................................ 10

LIST OF FIGURES

FIGURE TITLE PAGE

2-1 S-50 plant and auxiliary buildings............................................................................................. 7

2-2 Isotope separation columns ..................................................................................................... 8
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ACRONYMS AND ABBREVIATIONS

AWE Atomic Weapons Employer

DOE U.S. Department of Energy

DOL U.S. Department of Labor

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

ft foot

kW kilowatt

lb pound

NEPA Nuclear Energy for the Propulsion of Aircraft (Project)

NIOSH National Institute for Occupational Safety and Health

ORAU Oak Ridge Associated Universities

ORNL Oak Ridge National Laboratory

PER program evaluation report

psig pounds per square inch gauge

SEC Special Exposure Cohort

SRDB Ref ID Site Research Database Reference Identification (number)

U.S.C. United States Code

§ section or sections
Document No. ORAUT-TKBS-0054 Revision No. 01 Effective Date: 04/15/2019 Page 5 of 15

1.0 INTRODUCTION

Technical basis documents and site profile documents are not official determinations made by the 

National Institute for Occupational Safety and Health (NIOSH) but are rather general working 

documents that provide historical background information and guidance to assist in the preparation of 

dose reconstructions at particular Department of Energy (DOE) or Atomic Weapons Employer (AWE) 

facilities or categories of DOE or AWE facilities. They will be revised in the event additional relevant 

information is obtained about the affected DOE or AWE facility(ies). These documents may be used 

to assist NIOSH staff in the evaluation of Special Exposure Cohort (SEC) petitions and the completion 

of the individual work required for each dose reconstruction.

In this document the word “facility” is used to refer to an area, building, or group of buildings that 

served a specific purpose at a DOE or AWE facility. It does not mean nor should it be equated to an 

“AWE facility” or a “DOE facility.” The terms AWE and DOE facility are defined in sections 7384l(5) 

and (12) of the Energy Employees Occupational Illness Compensation Program Act of 2000 

(EEOICPA), respectively. An AWE facility means “a facility, owned by an atomic weapons employer, 

that is or was used to process or produce, for use by the United States, material that emitted radiation 

and was used in the production of an atomic weapon, excluding uranium mining or milling.” 42 U.S.C. 

§ 7384l(5). On the other hand, a DOE facility is defined as “any building, structure, or premise, 

including the grounds upon which such building, structure, or premise is located ... in which 

operations are, or have been, conducted by, or on behalf of, the [DOE] (except for buildings, 

structures, premises, grounds, or operations ... pertaining to the Naval Nuclear Propulsion Program);” 

and with regard to which DOE has or had a proprietary interest, or “entered into a contract with an 

entity to provide management and operation, management and integration, environmental 

remediation services, construction, or maintenance services.” 42 U.S.C. § 7384l(12). The Department 

of Energy (DOE) determines whether a site meets the statutory definition of an AWE facility and the 

Department of Labor (DOL) determines if a site is a DOE facility and, if it is, designates it as such.

Accordingly, a Part B claim for benefits must be based on an energy employee’s eligible employment 

and occupational radiation exposure at a DOE or AWE facility during the facility’s designated time 

period and location (i.e., covered employee). After DOL determines that a claim meets the eligibility 

requirements under EEOICPA, DOL transmits the claim to NIOSH for a dose reconstruction. 

EEOICPA provides, among other things, guidance on eligible employment and the types of radiation 

exposure to be included in an individual dose reconstruction. Under EEOICPA, eligible employment 

at a DOE facility includes individuals who are or were employed by DOE and its predecessor 

agencies, as well as their contractors and subcontractors at the facility. Unlike the abovementioned 

statutory provisions on DOE facility definitions that contain specific descriptions or exclusions on 

facility designation, the statutory provision governing types of exposure to be included in dose 

reconstructions for DOE covered employees only requires that such exposures be incurred in the 

performance of duty. As such, NIOSH broadly construes radiation exposures incurred in the 

performance of duty to include all radiation exposures received as a condition of employment at 

covered DOE facilities in its dose reconstructions for covered employees. For covered employees at 

DOE facilities, individual dose reconstructions may also include radiation exposures related to the 

Naval Nuclear Propulsion Program at DOE facilities, if applicable. No efforts are made to determine 

the eligibility of any fraction of total measured exposure for inclusion in dose reconstruction.

NIOSH does not consider the following types of exposure as those incurred in the performance of 

duty as a condition of employment at a DOE facility. Therefore these exposures are not included in 

dose reconstructions for covered employees (NIOSH 2010):

• Background radiation, including radiation from naturally occurring radon present in 

conventional structures

• Radiation from X-rays received in the diagnosis of injuries or illnesses or for therapeutic 

reasons
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1.1 PURPOSE

This document provides guidance for partial dose reconstructions for EEOICPA-covered employees 

who worked at the S-50 Oak Ridge Thermal Diffusion Plant (S-50) from July 9, 1944, through 

December 31, 1951.

1.2 SCOPE

Section 1.3 discusses the SEC applicable to S-50 employees. Section 2.0 describes the site and its 

operations. Section 3.0 provides guidance for the determination of occupational medical dose. 

Sections 4.0 through 6.0 discuss environmental, internal, and external dose, respectively. Attributions 

and annotations, indicated by bracketed callouts and used to identify the source, justification, or 

clarification of the associated information, are presented in Section 7.0

1.3 SPECIAL EXPOSURE COHORT

The Secretary of the U.S. Department of Health and Human Services has designated a class of S-50 

employees as an addition to the SEC based on the findings and recommendations of NIOSH and the 

Advisory Board on Radiation and Worker Health Board (Leavitt 2006):

July 9, 1944, through December 31, 1951

Employees of the Department of Energy predecessor agencies and their contractors or

subcontractors who were monitored or should have been monitored while working at 

S-50 Oak Ridge Thermal Diffusion Plant (S-50) for a number of work days aggregating 

at least 250 work days during the period from July 9, 1944 through December 31, 1951, 

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

classes of employees in the SEC.

NIOSH has determined that there is insufficient information either 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 or to estimate the radiation doses 

of members of the classes more precisely than a maximum dose estimate (NIOSH 2006). However, 

NIOSH intends to use any available information to conduct partial dose reconstructions for this period 

for workers who do not meet the class definition. NIOSH has determined that only occupational 

medical dose can be reconstructed (NIOSH 2006). Partial dose reconstructions can be conducted 

using the information in this technical basis document. 

2.0 SITE DESCRIPTION

2.1 S-50 OAK RIDGE THERMAL DIFFUSION PLANT

S-50 was a wartime uranium enrichment facility constructed in 1944 adjacent to the Oak Ridge 

Gaseous Diffusion Plant (K-25) in Oak Ridge, Tennessee, by H. K. Ferguson Company and operated 

by Fercleve Corporation, a wholly owned subsidiary of H. K. Ferguson Company that was organized 

for the sole purpose of operating the plant. Groundbreaking for the facility took place on July 9, 1944, 

and construction was complete on October 31, 1944. The main process building dimensions were 

522 ft long by 62 ft wide by 75 ft high; the building had a concrete floor and foundation with steel 

frames, sides, and roof (MED 1947). The building housed 2,142 columns, each 48 ft tall and 5 in. in 

diameter. Uranium enrichment began on September 16, 1944, before construction was complete. 

Thermal diffusion operations shut down on September 9, 1945 (Prince 2005). Figure 2-1 shows the 

thermal diffusion plant and associated buildings.
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Figure 2-1. S-50 plant (left of power plant for K-25) and auxiliary buildings (Fandom 2019).

The S-50 plant was originally intended to supply high concentrations of 235U feed to the Y-12 Plant 

until the gaseous diffusion process at K-25 could get into large-scale production (Author unknown ca. 

1947). However, in June 1945 S-50 feed material was first fed to K-25 instead of Y-12 (Author 

unknown ca. 1947). There was a tremendous amount of emphasis placed on high production output 

at this facility. Processed uranium from the plant was eventually used as feed material for the Y-12 

facility, where it was further enriched; some of this material was used in the bomb dropped over 

Hiroshima (“Little Boy”). Operations at S-50 generally continued around the clock. The number of 

individuals Fercleve employed reached a maximum of 1,600 in April 1945 (MED 1947). 

Feed material came from Harshaw Chemical Company of Cleveland, Ohio, in nickel shipping 

containers as uranium hexafluoride (UF6). The liquid thermal diffusion process at S-50 increased 235U 

enrichment from natural (0.71%) to 0.85% (MED 1947).

The process to enrich uranium at S-50 consisted of isotope separation columns, each of which 

contained three concentric pipes. One-hundred and two columns were arranged to form an operating 

unit called a rack (MED 1947). High-pressure (1,000-psig) steam passed through the innermost 

nickel pipe, which was inside a copper pipe. UF6 was batch-charged into the gap between the nickel 

and copper pipes at about 1,500 psig. The nickel and copper pipes were inside the outermost steel 

pipe. Cold water passed between the steel pipe and the outer wall of the copper pipe. The 

enrichment process used convective flow, whereby the lighter 235U molecules tended to move upward 
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along the hot nickel pipe wall while the heavier 238U molecules moved downward along the cold 

copper wall (MED 1947). A graph of the production output from S-50 (Percentage of Original 

Theoretical Maximum Output) showed the racks operated at less than 5% until January 1945, at 

which time the production increased gradually to a maximum of approximately 90% in June 1945 

(MED 1947).

Figure 2-2. Isotope separation columns (Wikipedia 2019).

Losses of UF6 were common during S-50 operations, with UF6 often escaping into the air or cooling 

water (MED 1947). The losses usually resulted from internal or external breaks in columns or other 

parts of the process, which were caused by failure of the materials under the high operating 

pressures. Other losses resulted from improper handling of open connections and from operational 

mistakes due, in part, to the number of new employees at the facility and the emphasis on high 

production rates. From March through July 1945, monthly losses of UF6 ranged from 247 to 1,826 lb 

(Prince 2005). Accountability records showing losses for other months of operation are unavailable. 

The released UF6 would rapidly oxidize and form uranyl fluoride (UO2F2) (Prince 2005), which would 

either exhaust through the building roof or settle to the process building floor. Operators were 

required to have a gas mask on their persons at all times for emergencies (MED 1947). 

The S-50 plant ceased enrichment operation in September 1945, shortly after the war ended (MED 

1947). The uranium enrichment process at S-50 was unique in that it was the only production-scale 

liquid thermal diffusion facility ever built. S-50 closed because it had become evident that the liquid 

thermal diffusion process would not be competitive with the gaseous diffusion process. Once the 
Document No. ORAUT-TKBS-0054 Revision No. 01 Effective Date: 04/15/2019 Page 9 of 15

 

S-50 plant was placed in standby mode, the Carbide and Carbon Chemical Corporation assumed 

custody of the facility (MED 1945). 

In 1946, Carbide and Carbon Chemical Corporation performed an inspection of the S-50 plant. Due 

to the cost, labor, and necessary security it would take to maintain the plant in standby mode, it was 

recommended that certain buildings not being used at the S-50 plant be dismantled for salvage (see 

Table 2-1) (Author unknown ca. 1947). A memorandum dated January 22, 1948 (Belcher 1948), 

reveals the main process building, F-01, had been demolished. Radiation surveys of the concrete 

floor slab revealed beta/gamma radiation was below the U.S. Atomic Energy Commission tolerance 

levels; however, fixed alpha contamination was present (Belcher 1948). It should be noted that the 

survey results of the slab were not attached to this document. The condition and the timeframe of the 

demolition of the remaining auxiliary buildings is unknown: Laboratory No. 1 (housed mass 

spectrometer equipment), Laboratory No. 2 (housed alpha-counting equipment), administration 

building, cafeteria, canteen, tank farm, change house (showers and lockers), machine shop, storage 

shed (stored raw material), warehouse, and switch house.

Table 2-1. S-50 building and/or equipment number and description. 

Building and/or 

equipment number Description

F-01 Main Process Building

F-02 Pump House

F-03 Water Treatment Plant

F-06 Boiler Plant

F-07 Materials and Conditioning Building

F-24 Propane Tank

F-25 Transfer Rack

F-26 Time Office

F-28 Time Office

F-29 Gasoline Filling Station

F-31 Inflammable Storage

2.2 NUCLEAR ENERGY FOR THE PROPULSION OF AIRCRAFT PROJECT

From May 1, 1946, through December 31, 1951, the S-50 facilities were used to conduct feasibility 

studies for the Nuclear Energy for the Propulsion of Aircraft (NEPA) project. The NEPA operations 

were conducted by Fairchild Engine and Aircraft Corporation (NIOSH 2006). 

Documentation indicates that in 1950 NEPA was involved with Oak Ridge National Laboratory 

(ORNL) to (1) perform studies to delineate the most feasible types of supersonic aircraft nuclear 

power plants, (2) perform research aimed at solving the problems involved in the liquid-metal-cooled 

type of reactor with the aim of constructing a 1,000-kW prototype in Oak Ridge, and (3) exploratory 

research on problems of other reactor cycles that might be employed in future models (Ellis and 

Thompson 1950). In addition, joint ORNL-NEPA groups were established to develop the details of the 

shielding and control system designs (Ellis and Thompson 1950). 

Additional information was obtained through the telephone interviews with S-50 claimants (NIOSH 

2006) and one follow-up interview with an S-50 claimant (ORAUT 2006). It was learned from these 

interviews that S-50 (NEPA) employees fabricated blocks that contained enriched uranium and 

graphite as potential fuel for a nuclear-powered airplane. In addition, the employees recovered 

enriched uranium using nitric acid solutions. The recovered enriched uranium was used to fabricate 

the uranium and graphite blocks. One interviewee stated, “the place was highly radioactive given the 

enriched 235U they were handling” (ORAUT 2006). According to documented interviews with other 

claimants, activation analysis studies might have taken place at S-50 on items that had been 

irradiated at ORNL. In addition, employees during this period might have been exposed to 
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contamination remaining from the earlier liquid thermal diffusion projects in this facility. To date it is 

unknown which building or buildings on the S-50 grounds housed the NEPA project. Also unknown 

are the radiological conditions of the buildings occupied by NEPA employees. 

3.0 OCCUPATIONAL MEDICAL DOSE

In October 1944, the Fercleve Corporation began its official medical program with preemployment and 

termination examinations performed at the Carbide and Carbon Chemicals Corporation dispensary. 

Preemployment physical examinations were required for all S-50 employees and included their 

medical history, a physical examination, blood and urine samples, and an X-ray of the chest (MED 

1946). S-50 employees also received interval examinations, including a film of the chest, based on 

the employee’s exposure to hazardous materials, but the frequency of these examinations is unknown 

(MED 1946). On termination, S-50 workers received a physical examination, blood and urine 

analysis, and a chest X-ray (MED 1946). 

A review of medical records for S-50 employees did not reveal any medical X-ray examinations. 

However, X-ray information can be derived from K-25 knowledge because both plants shared the 

Carbide dispensary. NIOSH (2006) concluded that adequate reconstruction of medical dose for S-50 

workers is possible by using assumptions that are favorable to claimants based on the information in 

the technical basis document for K-25 (ORAUT 2013) and by using applicable protocols in ORAUTOTIB-0006, Dose Reconstruction from Occupational Medical X-Ray Procedures (ORAUT 2018). 

Dose reconstructors should follow the guidance in the current version of ORAUT-TKBS-0009-3, Oak 

Ridge Gaseous Diffusion Plant (K-25) – Occupational Medical Dose (ORAUT 2013), and/or ORAUTOTIB-0006, Dose Reconstruction from Occupational Medical X-Ray Procedures (ORAUT 2018) when 

evaluating the dose from X-rays for S-50 employees. It should be noted that the medical dispensary 

at K-25 did not have X-ray equipment available until October 1944 (MED 1946). Before this date, 

K-25 employees received their medical X-rays at the Oak Ridge Hospital in Oak Ridge, Tennessee 

(MED 1946). The dose from X-rays can be included from the Oak Ridge Hospital because it is a 

covered facility (ORAUT 2017). For July 9 through September 30, 1944, even though this time is 

before the inception of their official medical program, it is also assumed that S-50 workers received 

their medical X-rays at the Oak Ridge Hospital. For all years of employment, the frequency and type 

of procedures should be obtained from the current version of the technical basis document for K-25

(ORAUT 2013). Depending on the date of employment, dose values should be obtained from the 

documents listed in Table 3-1. 

Table 3-1. X-ray guidance for S-50 workers. 

Applicable dates Facility Document for dose values

07/09/1944–09/30/1944 Oak Ridge Hospital ORAUT-OTIB-0006, Dose Reconstruction from 

Occupational Medical X-Ray Procedures (2018)

10/01/1944–12/31/1951 Oak Ridge Gaseous 

Diffusion Plant

ORAUT-TKBS-0009-3, Oak Ridge Gaseous Diffusion 

Plant (K-25) - Occupational Medical Dose (2013)

4.0 OCCUPATIONAL ENVIRONMENTAL DOSE

NIOSH determined in the SEC petition evaluation report (NIOSH 2006) that it lacks sufficient 

personnel monitoring, air monitoring, or source term data to adequately reconstruct any internal or 

external occupational exposures at the S-50 plant. As a consequence, NIOSH finds that it is not 

feasible to estimate with sufficient accuracy the radiation doses from internal or external ambient 

exposures at the S-50 plant.
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5.0 OCCUPATIONAL INTERNAL DOSE

Review of the available information concludes that bioassays were not obtained during the years of 

concern (1944 to 1951). This conclusion is based on the lack of information on bioassays and 

monitoring and the recommendations for treatment of exposures to workers and medical personnel 

when a worker “breathed process material” (MED 1947; Various ca. 1945). 

NIOSH determined in the SEC petition evaluation report (NIOSH 2006) that it lacks sufficient 

personnel monitoring, air monitoring, or source term data to adequately reconstruct the internal 

exposures at S-50. As a consequence, NIOSH finds that it is not feasible to estimate with sufficient 

accuracy the radiation doses from internal exposures during S-50 operations.

6.0 OCCUPATIONAL EXTERNAL DOSE

NIOSH considers the available external monitoring data and methods inadequate for performing 

external dose reconstruction at S-50. NIOSH determined in the SEC petition evaluation report 

(NIOSH 2006) that it lacks sufficient personnel monitoring, area monitoring, or source term data to 

adequately reconstruct the external exposures at S-50. As a consequence, NIOSH finds that it is not 

feasible to estimate with sufficient accuracy the radiation doses from external exposures during S-50 

operations.

7.0 ATTRIBUTIONS AND ANNOTATIONS

All information requiring identification was addressed via references integrated into the reference 

section of this document.
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REFERENCES

Author unknown, ca. 1947, S-50 Plant: Historical, Economic, and Production Data. [SRDB Ref ID: 

99053]

Belcher, F. H., 1948, “Completion of Demolition of Building F-01 and Removal of Equipment from 

Building F-06 S-50 Area,” memorandum to S. R. Sapirie, Atomic Energy Commission, Oak 

Ridge Operations Office, Oak Ridge, Tennessee, January 22. [SRDB Ref ID: 88614]

Ellis, C. B., and W. E. Thompson, 1950, The Aircraft Nuclear Propulsion Project Quarterly Progress 

Report for Period Ending August 31, 1950, ORNL-858, Carbide and Carbon Chemicals 

Company, Oak Ridge National Laboratory, Oak Ridge, Tennessee, December 4. [SRDB Ref 

ID: 101927]

Fandom, 2019, image of S-50 plant and auxiliary buildings, Wikia, Inc. [SRDB Ref ID: 175495]

Leavitt, M. O., 2006, HHS Designation of Additional Members of the Special Exposure Cohort under 

the Energy Employees Occupational Illness Compensation Program Act, Designating a Class 

of Employees from S-50 Oak Ridge Thermal Diffusion Plant (S-50), Oak Ridge, Tennessee, 

U.S. Department of Health and Human Services, Office of the Secretary, Washington, D.C., 

November 9. [SRDB Ref ID: 78920]

MED (Manhattan Engineer District), 1945, collection of weekly and monthly operations reports, U.S. 

Department of War, U.S. Army Corps of Engineers, Oak Ridge, Tennessee. [SRDB Ref ID: 

30779]

MED (Manhattan Engineer District), 1946, Manhattan District History, Book I - General, Volume 7 -

Medical Program, U.S. Department of War, U.S. Army Corps of Engineers, December 31. 

[SRDB Ref ID: 40434]

MED (Manhattan Engineer District), 1947, Manhattan District History, Book VI Liquid Thermal 

Diffusion (S-50) Project, U.S. Department of War, U.S. Army Corps of Engineers, May 21. 

[SRDB Ref ID: 8623]

NIOSH (National Institute for Occupational Safety and Health), 2006, SEC Petition Evaluation Report,

Petition SEC-00060, Office of Compensation Analysis and Support, Cincinnati, Ohio, 

August 4. [SRDB Ref ID: 33588]

NIOSH (National Institute for Occupational Safety and Health), 2010, Radiation Exposures Covered 

for Dose Reconstructions Under Part B of the Energy Employees Occupational Illness 

Compensation Program Act, DCAS-IG-003, Rev. 1, Division of Compensation Analysis and 

Support, Cincinnati, Ohio, October 5. [SRDB Ref ID: 88929]

ORAUT (Oak Ridge Associated Universities Team), 2006, “Interview with S-50 Claimant,” SECIS 

Non-Submitter Communication ID 75, Oak Ridge, Tennessee, July 28. [SRDB Ref ID: 

175096]

ORAUT (Oak Ridge Associated Universities Team), 2013, Oak Ridge Gaseous Diffusion Plant (K-25)

– Occupational Medical Dose, ORAUT-TKBS-0009-3, Rev. 01, Oak Ridge, Tennessee, March 

28. [SRDB Ref ID: 123796]
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ORAUT (Oak Ridge Associated Universities Team), 2017, Guidance on Assigning Occupational 

X-Ray Dose Under EEOICPA for X-Rays Administered Off Site, ORAUT-OTIB-0079, Rev. 02, 

Oak Ridge, Tennessee, June 15. [SRDB Ref ID: 166967]

ORAUT (Oak Ridge Associated Universities Team), 2018, Dose Reconstruction from Occupational 

Medical X-Ray Procedures, ORAUT-OTIB-0006, Rev. 05, Oak Ridge, Tennessee, August 13. 

[SRDB Ref ID: 172596]

Prince, R. P., 2005, Compilation of Historical Document Reference Sources for Project S-50, Liquid

Thermal Diffusion Plant, ETTP-736, Bechtel Jacobs Company, East Tennessee Technology

Park, Oak Ridge, Tennessee, May. [SRDB Ref ID: 17169]

Various authors, ca. 1945, collection of memoranda and surveys related to radiation hazards and 

medical treatment at S-50. [SRDB Ref ID: 16643]

Wikipedia, 2019, image of isotope separation columns, Wikimedia Foundation, San Francisco, 

California. [SRDB Ref ID: 175496]
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GLOSSARY

contamination

Radioactive material in undesired locations including air, soil, buildings, animals, and persons.

dose

In general, the specific amount of energy from ionizing radiation that is absorbed per unit of 

mass. Effective and equivalent doses are in units of rem or sievert; other types of dose are in 

units of rad, rep, or grays.

dose reconstruction

Process of analyzing the available information including evaluation of historical methods and 

data to estimate the dose a person could have received from one or more radiation exposures.

enrichment

Isotopic separation process that increases the percentage of a radionuclide in a given amount 

of material above natural levels. For uranium, enrichment increases the amount of 235U in 

relation to 238U. Along with the enriched uranium, this process results in uranium depleted in 

235U. 

exposure

(1) In general, the act of being exposed to ionizing radiation. (2) Measure of the ionization 

produced by X- and gamma-ray photons in air in units of roentgens.

gaseous diffusion enrichment

Process by which uranium hexafluoride (UF6) is filtered through a series of semipermeable 

molecular barriers to separate the lighter 235U from the heavier, more naturally abundant 238U.

gaseous diffusion plant

Facility where uranium hexafluoride (UF6) gas is filtered to enrich the 235U and separate it from 

238U. The process requires enormous amounts of electric power and results in an increase in 

235U enrichment from 1% to about 3%.

ionizing radiation

Radiation of high enough energy to remove an electron from a struck atom and leave behind a 

positively charged ion. High enough doses of ionizing radiation can cause cellular damage. 

Ionizing particles include alpha particles, beta particles, gamma rays, X-rays, neutrons, 

high-speed electrons, high-speed protons, photoelectrons, Compton electrons, 

positron/negatron pairs from photon radiation, and scattered nuclei from fast neutrons. 

liquid thermal diffusion

Uses the transfer of heat across a thin liquid to accomplish isotope separation. By cooling a 

vertical film on one side and heating it on the other, the lighter 235U gas molecules will diffuse 

toward a hot surface, while the heavier 238U gas molecule will diffuse toward a cold surface. 

monitoring

Periodic or continuous determination of the presence or amount of ionizing radiation or 

radioactive contamination in air, surface water, groundwater, soil, sediment, equipment 

surfaces, or personnel (for example, bioassay or alpha scans). In relation to personnel, 

monitoring includes internal and external dosimetry including interpretation of the 

measurements.
Document No. ORAUT-TKBS-0054 Revision No. 01 Effective Date: 04/15/2019 Page 15 of 15

occupational medical dose

Dose from X-ray procedures performed for medical screening of workers as part of an 

occupational health program. Doses from X-rays used to diagnose diseases or injuries, even 

if incurred on the job, are not considered occupational and are therefore not eligible to be 

included in dose reconstruction under the Energy Employees Occupational Illness 

Compensation Program Act of 2000.

radiation

Subatomic particles and electromagnetic rays (photons) with kinetic energy that interact with

matter through various mechanisms that involve energy transfer. See ionizing radiation.

radiograph

Static images produced on radiographic film by gamma rays or X-rays after passing through 

matter. In the context of the Energy Employees Occupational Illness Compensation Program 

Act of 2000, radiographs are X-ray images of the various parts of the body used to screen for 

disease.

X-ray

See radiograph.