ORAU TEAM

Dose Reconstruction

Project for NIOSH

Oak Ridge Associated Universities I Dade Moeller & Associates I MJW Corporation

Page 1 of 10

Document Title:

Y-12 National Security Complex – 

Introduction

Document Number: ORAUT-TKBS-0014-1 

Revision: 01

Effective Date: 10/24/2006

Type of Document: TBD

Supersedes: Revision 00

Subject Expert: William E. Murray

Approval: Signature on File Approval Date: 10/23/2006

William E. Murray, Document Owner

Approval: Signature on File Approval Date: 10/18/2006

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 10/17/2006

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 10/23/2006

Kate Kimpan, Project Director

Approval: Brant A. Ulsh Signature on File for Approval Date: 10/24/2006

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

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

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 2 of 10

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

01/06/2004 00 New document for the Y-12 National Security Complex – Y-12 Site 

Profile. First approved issue. Initiated by William E. Murray.

11/24/2004 00 PC-1 Deletes acronyms and abbreviations for DOL IREP, and OWCP on 

page 3. Revises information on page 4 to incorporate changes from 

DOL and NIOSH Office of General Counsel (OGC). First approved 

page change revision. Initiated by William E. Murray.

Approval:

William E. Murray, TBD Team Leader

Signature on File_______________________________10/26/2004 

Judson L. Kenoyer, Task 3 Manager

Signature on File_______________________________10/26/2004 

Richard E. Toohey, Project Director

Signature on File_______________________________11/04/2004 

James W. Neton, Associate Director for Science

Signature on File_______________________________11/24/2004 

10/11/2005 00 PC-2 Page change initiated to incorporate recent direction from NIOSH to 

include details for the definition of a DOE facility on pages 4 and 5. 

No sections were deleted. Second approved page change revision. 

Retraining is not required. Initiated by William E. Murray.

Approval:

William E. Murray, TBD Team Leader

Signature on File_______________________________10/06/2005 

Judson L. Kenoyer, Task 3 Manager

Signature on File ______________________________10/04/2005 

Richard E. Toohey, Project Director

Signature on File_______________________________10/04/2005 

James W. Neton, Associate Director for Science

Signature on File_______________________________10/11/2005 

10/24/2006 01 Approved Rev 01 initiated to incorporate Y-12 National Security 

Complex Special Exposure Cohort class descriptions in a new 

section. Text was added or modified on pages 5 and 6. Headings 

and citations were added for the Technical Basis Documents. A 

Reference section was added with the TBD references. The 

Acronyms and Abbreviations page was adjusted per usage. No 

sections were deleted. Constitutes a total rewrite of the document. 

Incorporates formal internal and NIOSH review comments. This 

revision results in no change to the assigned dose and no PER is 

required. Training required: As determined by the Task Manager. 

Initiated by William E. Murray.
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 3 of 10

TABLE OF CONTENTS

SECTION TITLE

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

PAGE

4

1.1 Purpose ...................................................................................................................................5

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

1.3 Special Exposure Cohorts........................................................................................................9

1.3.1 March 1943 to December 1947 ....................................................................................9

1.3.2 January 1948 to December 1957..................................................................................9

References ........................................................................................................................................ 11 
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 4 of 10

ACRONYMS AND ABBREVIATIONS

DOE U.S. Department of Energy

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

HEU highly enriched uranium

HHS U.S. Department of Health and Human Services

MED Manhattan Engineering District

NIOSH National Institute for Occupational Safety and Health

ORAU Oak Ridge Associated Universities

POC probability of causation

TBD technical basis document

U.S.C. United States Code

Y-12 Y-12 National Security Complex

μm micrometer

§ section or sections
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 5 of 10

1.1 PURPOSE

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 historic background information and guidance to assist in the preparation of 

dose reconstructions for particular sites or categories of sites. The documents will be revised in the 

event additional relevant information is obtained about the affected site(s). These documents may be 

used to assist NIOSH staff in the completion of the individual work required for each dose 

reconstruction.

In this document the word “facility” is used as a general term for an area, building, or group of 

buildings that served a specific purpose at a site. It does not necessarily connote an “atomic weapons 

employer facility” or a “Department of Energy [DOE] facility” as defined in the Energy Employees 

Occupational Illness Compensation Program Act [EEOICPA; 42 U.S.C. § 7384l(5) and (12)]. 

EEOICPA defines a DOE facility 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 Department of Energy (except for buildings, structures, premises, 

grounds, or operations ... pertaining to the Naval Nuclear Propulsion Program)” [42 U.S.C. § 

7384l(12)]. Accordingly, except for the exclusion for the Naval Nuclear Propulsion Program noted 

above, any facility that performs or performed DOE operations of any nature whatsoever is a DOE 

facility encompassed by EEOICPA.

For employees of DOE or its contractors with cancer, the DOE facility definition only determines 

eligibility for a dose reconstruction, which is a prerequisite to a compensation decision (except for 

members of the Special Exposure Cohort). The compensation decision for cancer claimants is based 

on a section of the statute entitled “Exposure in the Performance of Duty.” That provision [42 U.S.C. § 

7384n(b)] says that an individual with cancer “shall be determined to have sustained that cancer in the 

performance of duty for purposes of the compensation program if, and only if, the cancer ... was at 

least as likely as not related to employment at the facility [where the employee worked], as 

determined in accordance with the POC [probability of causation1

As noted above, the statute includes a definition of a DOE facility that excludes “buildings, structures, 

premises, grounds, or operations covered by Executive Order No. 12344, dated February 1, 1982 (42 

U.S.C. 7158 note), pertaining to the Naval Nuclear Propulsion Program” [42 U.S.C. § 7384l(12)]. 

While this definition contains an exclusion with respect to the Naval Nuclear Propulsion Program, the 

section of EEOICPA that deals with the compensation decision for covered employees with cancer 

[i.e., 42 U.S.C. § 7384n(b), entitled “Exposure in the Performance of Duty”] does not contain such an 

exclusion. Therefore, the statute requires NIOSH to include all occupationally derived radiation 

exposures at covered facilities in its dose reconstructions for employees at DOE facilities, including 

radiation exposures related to the Naval Nuclear Propulsion Program. As a result, all internal and 

external dosimetry monitoring results are considered valid for use in dose reconstruction. No efforts 

are made to determine the eligibility of any fraction of total measured exposure for inclusion in dose 

reconstruction. NIOSH, however, does not consider the following exposures to be occupationally 

derived:

] guidelines established under 

subsection (c) ...” [42 U.S.C. § 7384n(b)]. Neither the statute nor the POC guidelines (nor the dose 

reconstruction regulation) define “performance of duty” for DOE employees with a covered cancer or 

restrict the “duty” to nuclear weapons work.

• Radiation from naturally occurring radon present in conventional structures

 

1 The U.S. Department of Labor is ultimately responsible under the EEOICPA for determining the POC. 
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 6 of 10

• Radiation from diagnostic X-rays received in the treatment of work-related injuries

NIOSH is supported by the Oak Ridge Associated Universities (ORAU) Team in conducting dose 

reconstructions under EEOICPA. This Site Profile represents a specific support mechanism to the 

ORAU Team about documentation of historical practices at the Y-12 National Security Complex, 

referred to as Y-12. This Site Profile can be used to evaluate both internal and external doses for 

both monitored and unmonitored workers and can serve as a supplement to, or substitute for, 

individual monitoring data. The document provides a Site Profile of Y-12 that contains technical basis 

information that the ORAU Team can use to evaluate the total occupational radiation dose for 

EEOICPA claimants. 

The document also provides supporting technical data to evaluate the total Y-12 occupational 

radiation dose that can reasonably be associated with the worker’s radiation exposure. This dose 

results from exposure to external and internal radiation sources in Y-12 facilities; to Y-12 

occupationally required medical X-ray examinations, and to onsite environmental releases. 

Techniques are also included to estimate the dose that could have occurred while the worker was not 

monitored or inadequately monitored, dose that could have been missed due to analytical detection 

limits, or dose to workers whose monitoring records are incomplete (i.e., missed dose). Over the 

years new and more reliable scientific methods and protection measures have been developed. The 

methods needed to account for these changes are also identified in this document. 

This Site Profile can be a tool when performing dose reconstructions for Y-12 workers. The 

Integrated Modules for Bioassay Analysis computer program is a tool useful for internal dose 

calculations. Information on measurement uncertainties is an integral component of the NIOSH 

approach. This document describes how to evaluate uncertainty associated with exposure at Y-12 

and the Y-12 dosimetry records.

1.2 SCOPE

The Site Profile is divided into six TBDs: This Introduction, Site Description, Occupational Medical 

Dose, Occupational Environmental Dose, Occupational Internal Dose, and Occupational External 

Dosimetry. After this Introduction, each TBD has an accompanying attachment that provides critical 

data for the specialists reconstructing the doses. 

Site Description

The Site Description TBD (ORAUT 2005) presents a brief description of the facilities and processes 

used at Y-12 to develop nuclear weapons and weapons components since the early 1940s. Y-12 is in 

the eastern section of the Oak Ridge Reservation in Oak Ridge, Tennessee. The plant occupies 

811 acres and consists of 531 buildings with more than 7.5 million square feet of floor space. 

Construction of Y-12 was initiated in late 1942 and completed in 1943 as part of the Manhattan 

Engineering District (MED). Prior to completion, the operating contractor, the Tennessee Eastman 

Company, moved people in to start operations. The first building to begin operations was the 

Calutron pilot plant and training building in the fall of 1943.

Despite technical problems, this first-of-a-kind electromagnetic isotope separation (Calutron) plant, 

succeeded in its mission. In about 2 years, the uranium fuel was separated for the Hiroshima nuclear 

weapon. The gaseous diffusion process at the K-25 Site was the MED’s backup for enriching 

uranium. Because this process was workable and much less costly, Y-12 was shutdown in December 

1946, and employment was cut drastically.
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The Y-12 Plant eventually became one of 12 production facilities with a unique role. From 1947 to 

1992, its missions were to produce the key components of nuclear weapons and the test devices 

needed for the expanding nuclear weapons stockpile and to safeguard the nation’s highly enriched 

uranium (HEU) stockpile. Other tasks included the production of the enriched lithium urgently needed 

for the thermonuclear program in the 1950s and 1960s. Y-12 successfully carried out these missions 

in developing state-of-the-art technologies demanded by new weapons designs over almost 50 years. 

From 1992 to the present, the Nation’s stockpile of nuclear weapons was reduced by 90%. The 

number of operational buildings at Y-12 was reduced, and the Plant’s manufacturing technology was 

transferred to industry where allowed. By the end of 1992, 50 research and development agreements 

were negotiated between Y-12 and governmental and commercial entities. Informally termed “Work 

for Others,” challenging problems were successfully solved for other Federal agencies. Ongoing 

missions include storing HEU for DOE, disassembling weapons components to study aging and other 

effects, producing a small number of nuclear weapons parts and assemblies, decontaminating and 

decommissioning unused buildings, and conducting major efforts in environmental and waste 

management. 

Occupational Medical Dose

The Occupational Medical Dose TBD (ORAUT 2006a) provides information about the dose that 

individual workers received from chest X-rays taken as a condition of employment. These included 

chest X-rays taken during preemployment (preplacement), periodic, and termination physical 

examinations. All workers received chest X-rays prior to employment or placement and at termination 

from 1943 through the present. However, the frequency of periodic chest X-rays varied over time and 

with the worker’s age. 

Both the X-ray equipment and the techniques used for taking X-rays have changed over the years. 

These factors have been considered in determining the dose that a worker received from the X-ray. 

When there was a doubt about the technique used, the assumptions which are most favorable to 

claimants have been made to ensure that the worker’s dose has not been underestimated. The 

technique parameters considered include tube current and voltage, exposure time, filtration, sourceto-skin distance, the view (posterior-anterior or lateral), and any other factor that could affect the dose 

received by the worker.

The doses to other exposed organs from the chest X-rays have also been calculated. The calculated 

dose takes into account the uncertainty associated with each of the parameters mentioned above. 

The doses received by the various organs in the body are presented in the tables for convenient 

reference by the dose reconstructors.

Occupational Environmental Dose

The Occupational Environmental Dose TBD (ORAUT 2006b) applies to workers who were not 

monitored for external or internal radiation exposure. The occupational environmental dose received 

by unmonitored workers is limited to exposures received while outside buildings and within the 

perimeter of the Y-12 Plant. Buildings and other operational units occupy the vast majority of the land 

area at Y-12. The two exposure pathways identified are inhalation of uranium in ambient air from 

operational releases and direct external radiation from radionuclides in soils and outdoor surfaces, as 

well as shine from buildings and operational units.

Other radionuclides have been used at Y-12, but the primary source of airborne radioactive material 

has been uranium from operations that have occurred over the years. Due to the complexity of the 

terrain surrounding Y-12 and the release mechanisms from the production facilities compounded by 

the limited dispersion distances, traditional dispersion and transport models were considered 
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 8 of 10

unsuitable. An empirical approach based on the limited ambient air-monitoring data was used to 

estimate 234/235U and 238U air concentrations for all years. This approach used the annual release 

estimates independently reconstructed by previous studies to generate annual air concentrations for 

four locations within Y-12. Annual intakes were then calculated for 234/235U and 238U. 

There are two potential sources of external exposures received by workers at the Y-12 facility: 

Exposures from the deposition of radionuclides released as a consequence of facility operations and 

exposures received from radiation emanating from buildings and storage areas. External exposures 

were estimated using the results of a comprehensive radiological scoping survey. The analysis of the 

results from the scoping survey was used to generate a statistical range of exposure values.

Occupational Internal Dose 

The Occupational Internal Dose TBD (ORAUT 2006c) discusses the internal dosimetry program. 

Uranium isotopes in various chemical and physical forms have been the primary contributors to the 

workers’ internal radiation doses, but other radionuclides were also handled and recycled uranium 

introduced other radionuclides. At times the processed uranium compounds might have contained 

impurities with radiological health implications, but the primary focus on internal dose control has been 

on uranium compounds and alloys over a wide range of 235U enrichment. 

Uranium compounds handled at Y-12 range from highly soluble to very insoluble. Several particle 

size studies in uranium process areas have been conducted. For different processes, particle sizes 

ranged from less than 1 to over 10 μm. A positive correlation was reported between uranium octoxide 

particle size and process temperature. 

During and immediately after World War II, a uranium urinalysis program based on fluorometry was 

used in conjunction with medical examinations to monitor for kidney damage from exposure to soluble

uranium compounds. In 1950, production workers were placed on a uranium urinalysis program to 

estimate internal exposure. The program was expanded to include certain maintenance workers in 

1954. At present, workers with a potential for internal exposures in excess of 100 mrem/year

committed effective dose equivalent are required to participate in the urinalysis program. Until 1989, 

routine urinalysis focused on enriched, normal, and depleted uranium, tritium, and plutonium. 

Analyses for other radionuclides were performed on an as-needed basis. Where available, the TBD 

provides laboratory detection limits for all urinary bioassay methods over time. Fecal samples were 

used in follow-up investigations when urinalysis or in vivo measurements indicated the likelihood of a 

substantial intake. Fecal sampling was discontinued several times in the past, but was reinstated in 

1998 due to changes in workplace exposure conditions. If a work area has predominantly insoluble 

airborne uranium, current workers with a moderate to high exposure potential submit urine and fecal 

samples. The detection limit for fecal analysis is provided. 

Whole-body counting was not routinely practiced at Y-12. The primary in vivo detection method was 

chest counting, which was put into routine use in 1961. Chest counting was done for 235U, 238U, 

thorium (inferred from 228Ac and/or 212Pb), 237Np, 60Co, and 95Zr. Reported detection limits are 

provided.

Occupational External Dosimetry

The Occupational External Dosimetry TBD (ORAUT 2006d) discusses the program for measuring skin 

and whole–body doses to the workers. The methods for evaluating external doses to workers have 

evolved over the years as new techniques and equipment have been developed. The dose 

reconstruction parameters, Y-12 practices and policies, and dosimeter types and technology for 

measuring the dose from the different types of radiation are discussed in this section. Attention is 

given to the evaluation of measured doses due to beta, gamma, and neutron radiations. Test results 
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 9 of 10

are tabulated for various dosimeters exposed under different exposure geometries to different

radiation energies.

Sources of bias, workplace radiation field characteristics, responses of the different beta/gamma and 

neutron dosimeters in the workplace fields, and the adjustments to the recorded dose measured by 

these dosimeters during specific years are discussed in detail. There are sources of potential dose 

that could be missed because of the limitations of dosimetry systems and the methods of reporting 

low doses. This missed dose is discussed as a function of facility location, dosimeter type, year, and 

energy range. The uncertainty in both photon and neutron doses are discussed and standard error is 

given over time for various dosimeters. The complexities and uncertainties in applying organ dose 

conversion factors to the adjusted dose of record are discussed. The use of the parameters 

presented in Section 6.0 is discussed in Attachment F to aid the dose reconstructor in preparing dose 

reconstructions for long-term Y-12 workers. 

1.3 SPECIAL EXPOSURE COHORTS

1.3.1

Based on the findings and recommendations of NIOSH and the Advisory Board on Radiation and

Worker Health, the Secretary of the U.S. Department of Health and Human Services (HHS) has 

determined that, for the period from March 1943 to December 1947, the only radiological exposures at 

Y-12 for which doses can be reconstructed are those that resulted from occupational medical X-rays. 

As a consequence, internal exposures are not reconstructed for those years.

March 1943 to December 1947

Beginning from 1948, the occupational environmental internal dose from uranium can be calculated

using the data provided in Y-12 National Security Complex – Occupational Environmental Dose

(ORAUT 2006b).

1.3.2

Based on the findings and recommendations of NIOSH and the Advisory Board on Radiation and

Worker Health, the Secretary of the HHS has determined that, for the period from January 1948 to 

December 1957, there is insufficient bioassay or air-sampling data to reconstruct:

January 1948 to December 1957

1. Internal thorium dose for employees who worked in buildings where thorium operations took 

place (Buildings 9201-3, 9202, 9204-1, 9204-3, 9206, and 9212). 

2. Internal dose for cyclotron workers (employees who worked in Building 9201-2). These 

workers might have accumulated substantial chronic exposures through episodic intakes of a 

variety of radionuclides that were produced during the cyclotron operation period.

NIOSH determined that it is possible to reconstruct or bound occupationally required medical doses 

and external gamma, beta, and neutron doses. NIOSH also found that sufficient bioassay data from 

January 1948 to December 1957 are available for reconstruction of internal doses for workers:

1. With potential for exposure to uranium or recycled uranium contaminants (

238Pu and 239Pu in 

lesser quantities, 237Np, and 99Tc) 

2. Involved in plutonium operations when plutonium was enriched with the calutrons.
Document No. ORAUT-TKBS-0014-1 Revision No. 01 Effective Date: 10/24/2006 Page 10 of 10

REFERENCES

ORAUT (Oak Ridge Associated Universities Team), 2005a, Technical Basis Document for the Y-12 

National Security Complex – Site Description, ORAUT-TKBS-0014-2, Rev. 01 PC-1, Oak 

Ridge, Tennessee, October 11. 

ORAUT (Oak Ridge Associated Universities Team), 2006a, Technical Basis Document for the Y-12 

National Security Complex – Occupational Medical Dose, ORAUT-TKBS-0014-3, Rev. 00 PC3, Oak Ridge, Tennessee, April 18. 

ORAUT (Oak Ridge Associated Universities Team), 2006b, Y-12 National Security Complex – 

Occupational Environmental Dose, ORAUT-TKBS-0014-4, Rev. 01, Oak Ridge, Tennessee, 

July 20. 

ORAUT (Oak Ridge Associated Universities Team), 2006c, Y-12 National Security Complex – 

Occupational Internal Dose, ORAUT-TKBS-0008-5, Rev. 02, Oak Ridge, Tennessee, August 

3. 

ORAUT (Oak Ridge Associated Universities Team), 2006d, Technical Basis Document for the Y-12 

National Security Complex – Occupational External Dose, ORAUT-TKBS-0008-6, Rev. 00 PC3, Oak Ridge, Tennessee, May 11.