ORAU Team

NIOSH Dose Reconstruction Project

Technical Basis Document for the Y-12 National Security Complex 

– Y-12 Site Profile

Document Number:

ORAUT-TKBS-0014-1 

Effective Date: 11/24/2004

Revision No.: 00 PC-1 

Controlled Copy No.: ______

Page 1 of 7

Subject Expert: William E. Murray

Approval: Signature on File Date: 01/07/2004

William E. Murray, TBD Team Leader

Approval: Signature on File Date: 01/07/2004 Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Date: 01/07/2004

Richard E. Toohey, Project Director

Approval: Signature on File Date: 01/09/2004 James W. Neton, OCAS Health Science Administrator

Supersedes:

None

TABLE OF CONTENTS

Section 

Record of Issue/Revision................................................................................................2 

Page

Acronyms and Abbreviations..........................................................................................3 

1.0 Y-12 Site Profile....................................................................................................................4
Effective Date: 01/06/2004 Revision No. 00 Document No. ORAUT-TKBS-0014-1 Page 2 of 7

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 12/01/2003 00-A New draft document for the Y-12 National 

Security Complex – Y-12 Site Profile. Initiated by 

William E. Murray.

Draft 12/22/2003 00-B Incorporates comments from NIOSH and internal 

review. Initiated by William E. Murray.

01/06/2004 01/06/2004 00 First approved issue. Initiated by William E. 

Murray.

01/06/2004 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). 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 
Effective Date: 11/24/2004 Revision No. 00 PC-1 Document No. ORAUT-TKBS-0014-1 Page 3 of 7

ACRONYMS AND ABBREVIATIONS

Ac Actinium

CFR Code of Federal Regulations

CEDE Committed Effective Dose Equivalent

Co Cobalt

DOE Department of Energy

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

HEU Highly Enriched Uranium

HHS Department of Health and Human Services

IMBA Integrated Modules for Bioassay Analysis

LD Laboratory detection limit

MED Manhattan Engineering District

Np Neptunium

NIOSH National Institute for Occupational Safety and Health

ORAU Oak Ridge Associated Universities

Pb Lead

TBD Technical Basis Document

TEC Tennessee Eastman Corporation

U Uranium

U.S.C. United States Code

Y-12 Y-12 National Security Complex

Zr Zirconium
Effective Date: 11/24/2004 Revision No. 00 PC-1 Document No. ORAUT-TKBS-0014-1 Page 4 of 7

1.0 Y-12 SITE PROFILE

The National Institute for Occupational Safety and Health (NIOSH) is supported by Oak Ridge 

Associated Universities (ORAU) and others, the ORAU Team, in conducting dose reconstructions 

under the Energy Employees Occupational Illness Compensation Program Act of 2000 (EEOICPA). 

This Site Profile represents a specific support mechanism to the ORAU Team concerning 

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 to be used by

the ORAU Team 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 may 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 diagnostic x-ray examinations, and to on-site environmental releases. Also 

included are techniques to estimate the dose that may have occurred while the worker was not 

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

limits, or 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 (IMBA) computer code 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.

The Site Profile is divided into five Technical Basis Documents (TBDs); Site Description, Occupational 

Medical Dose, Occupational Environmental Dose, Occupational Internal Dose, and Occupational 

External Dosimetry. Each TBD has an accompanying attachment that provides critical data for the 

specialists reconstructing the doses. 

Technical Basis Documents and Site Profile Documents are general working documents that provide 

guidance concerning the preparation of dose reconstructions at particular sites or categories of sites. 

They will be revised in the event additional relevant information is obtained about the affected site(s).

These documents may be used to assist NIOSH 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 facility” as defined in the Energy Employee 

Occupational Illness Compensation Program Act of 2000 (42 U.S.C. § 7384l (5) and (12). 

The Site Description TBD (ORAUT-TKBS-0014-02) 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 located 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 
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Tennessee Eastman Company (TEC) moved people in to start operations. The first building to begin 

operations was the Calutron pilot plant/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 two years, the uranium fuel was separated for the Hiroshima 

nuclear weapon. The gaseous diffusion process at the K-25 Site was the Manhattan Project’s backup 

for enriching uranium. Since this process was workable and much less costly, Y-12 was shutdown in 

December 1946 and employment was cut drastically. 

The Y-12 Plant eventually became one of twelve production facilities with a unique role. From 1947 to 

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

needed for the expanding nuclear weapons stockpile, and safeguard our 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 was reduced and Y-12’s manufacturing technology was transferred to 

industry, where allowed. By the end of 1992, fifty 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. 

The Occupational Medical Dose TBD (ORAUT-TKBS-0014-03) 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 pre-employment (pre-placement), 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 most claimant favorable assumptions have 

been made to ensure the worker’s dose has not been underestimated. The technique parameters 

considered include tube current and voltage, exposure time, filtration, source to 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-ray have also been calculated. The calculated 

dose also 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.

The Occupational Environmental Dose TBD (ORAUT-TKBS-0014-04) 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 
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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 is 

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 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 levels 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.

The Occupational Internal Dose TBD (ORAUT-TKBS-0014-05) discusses the internal dosimetry 

program. Uranium isotopes in various chemical and physical forms have been the primary 

contributors to the workers’ internal radiation dose but other radionuclides were also handled. At 

times the uranium compounds processed may 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 one 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 control 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. Currently, workers with a potential for internal exposures in excess of 100 mrem y-1 committed

effective dose equivalent (CEDE) 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. Laboratory detection limits 

(LD) are provided for all urinary bioassay methods over time, where available. 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 that 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.
Effective Date: 01/06/2004 Revision No. 00 Document No. ORAUT-TKBS-0014-1 Page 7 of 7

The Occupational External Dosimetry TBD (ORAUT-TKBS-0014-06) 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 doses measured from exposure to beta, gamma, and neutron radiation. 

Test results are tabulated for various dosimeters exposed to different exposure geometries and 

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 photon and neutron dose is 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. In Attachment F, the use of the 

parameters presented in Section 6 is discussed to aid the dose reconstructor in preparing dose 

reconstructions for long-term Y-12 workers.