ORAU Team

NIOSH Dose Reconstruction Project

Technical Basis Document for the Y-12 National Security Complex 

– Site Description

Document Number:

ORAUT-TKBS-0014-2 

Effective Date: 09/09/2004

Revision No.: 00 PC-1 

Controlled Copy No.:_______

Page 1 of 30

Subject Expert: Karin Jessen

Document Owner

Approval: Signature on File Date: 11/19/2003

William E. Murray, TBD Team Leader

Approval: Signature on File Date: 11/19/2003

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Date: 11/19/2003

Richard E. Toohey, Project Director

Approval: Signature on File Date: 11/21/2003

James W. Neton, OCAS Health Science Administrator

Supersedes:

None

TABLE OF CONTENTS

Section

Record of Issue/Revisions ...................................................................................................................

Page

3

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

2.1 Introduction................................................................................................................................. 5

2.2 Operating Contractors.................................................................................................................6

2.3 Site Activities ..............................................................................................................................6

2.4 Site Processes............................................................................................................................7

2.4.1 Electromagnetic Enrichment (1943–1947)........................................................................ 10

2.4.2 Feed Preparation for Enrichment Operations (1943–1947) .............................................. 10

2.4.3 Uranium Recovery and Recycle Operations (1944–1951)................................................ 10

2.4.4 Uranium Salvage Operations (1947–1951) ...................................................................... 10

2.4.5 Uranium Preparations and Recycle for Weapon Component 

Operations (1949–1995)................................................................................................... 10

2.4.6 Uranium Forming and Machining for Weapon Component Operations 

(1949–1995).....................................................................................................................11

2.4.7 Weapon Component Assembly Operations (1952–1995)................................................. 11

2.4.8 Stockpile Stewardship and Maintenance (1996–2003)..................................................... 11

2.5 Facilities....................................................................................................................................11

2.6 Waste Treatment and Disposal Operations............................................................................... 15

2.7 Criticality Accident.....................................................................................................................16
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 2 of 30

2.8 Radionuclides and Radiation Sources....................................................................................... 17

2.8.1 Uranium ...........................................................................................................................17

2.8.2 Recycled Uranium............................................................................................................ 17

2.8.3 X-Ray and Electron Generating Equipment...................................................................... 17

2.8.4 Radionuclide and Neutron Sources .................................................................................. 17

2.8.5 Special Nuclear Material................................................................................................... 18

2.8.6 Transuranics ....................................................................................................................18

2.8.7 Thorium............................................................................................................................18

2.8.8 Lithium .............................................................................................................................19

2.9 Solubility and Insolubility ........................................................................................................... 19

References ........................................................................................................................................22

Glossary ............................................................................................................................................24

Attachment B – Site Description ........................................................................................................ 25

LIST OF TABLES

Table Page

Table 2.3-1. Radionuclides of concern........................................................................................ 7

Table 2.4-1. Process chronology of operations........................................................................... 8

Table 2.4-2. Key uranium operations .......................................................................................... 9

Table 2.5-1. Key uranium facilities............................................................................................ 13

Table 2.8.4-1. Known sealed radiation sources ........................................................................... 17

Table 2.9-1. Chemical formulas and solubility class.................................................................. 20

Table 2.9-2. Solubility of material for various buildings and work areas 

as calculated by DOSE 66(a) code......................................................................... 21
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 3 of 30

RECORD OF ISSUE/REVISIONS

ISSUE 

AUTHORIZATION 

DATE

EFFECTIVE 

DATE

REV. 

NO. DESCRIPTION

Draft 10/31/2003 00-A Technical Basis Document for the Y-12 National 

Security Complex – Site Description. Initiated by 

William E. Murray.

11/19/2003 11/19/2003 00 First approved issue. Initiated by William E. 

Murray.

11/19/2003 09/09/2004 00 PC-1 Deletes unused reference on page 22. Initiated 

by William E. Murray.

Approval:

William E. Murray, TBD Team Leader

Signature on File____________ _09/08/2004

Judson L. Kenoyer, Task 3 Manager

Signature on File_________________08/27/2004 

Richard E. Toohey, Project Director

Signature on File_________________08/30/2004 

James W. Neton, Associate Director for Science

Signature on File____________ _09/09/2004
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 4 of 30

ACRONYMS AND ABBREVIATIONS

AEC Atomic Energy Commission

Ci Curie

CEDE Committed Effective Dose Equivalent

CY Calendar Year

DNFSB Defense Nuclear Facilities Safety Board

DOE Department of Energy

DU Depleted Uranium

EU Enriched Uranium

HEU Highly Enriched Uranium

IAEA International Atomic Energy Agency

ICPP Idaho Chemical Processing Plant

ICRP International Commission on Radiological Protection

keV kiloelectron volt

kg kilogram

LLW Low Level Waste

mCi millicurie

MED Manhattan Engineering District

MeV megaelectron volt

mg milligram

NPDES National Pollutant Discharge Elimination System

ORGDP Oak Ridge Gaseous Diffusion Plant

ORNL Oak Ridge National Laboratory

ORO Oak Ridge Operations

ORR Oak Ridge Reservation

RWP Radiological Work Permit

RCRA Resource Conservation and Recovery Act

RU Recycled Uranium

SM Source Material

SNM Special Nuclear Material

SRS Savannah River Site

TEC Tennessee Eastman Corporation

TRU Transuranic

UNH Uranyl nitrate hexahydrate

WETF West End Treatment Facility
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2.1 INTRODUCTION 

The Y-12 Plant (currently, the Y-12 National Security Complex) 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) and consists of approximately 531 buildings that cover more than 

7.5 million square feet of space. Construction of Y-12 was initiated in late 1942 and completed in 

1943 as part of the Manhattan Engineering District (MED). 

The specific mission of Y-12 was to separate fissionable isotopes of uranium (235U) for use in atomic 

weapons. Of the four wartime Manhattan Project plants, Y-12 was one of the most urgently needed 

because it was thought to be the fastest and surest of the gambles in its race with Germany to build 

an atomic bomb. At its peak, Y-12 employed approximately 22,000 workers. Today, Y-12 is focused 

on support of US Nuclear Defense Policies.

The information in this part is based on reports and other sources of information that are not 

classified. In some cases, classified documents have been redacted to allow their release as 

unclassified information. We are fully aware that more information is available that may be of use in 

reconstructing worker doses. However, due to classification restrictions, such information can not be 

included in this document.

The First Era – 1942 to 1947

Mission: Uranium Isotope Separation

The Y-12 Plant, conceived in 1942 by the MED of the U.S. Army Corps of Engineers (USACE), was 

constructed by Stone and Webster Construction Company at a cost of about $427 million. Prior to 

completion, the operating contractor, the Tennessee Eastman Company (TEC) of Kingsport, TN, 

moved its people in to start operations. The first building to begin operations was the Calutron pilot 

plant/training building (9731) in the fall of 1943.

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

succeeded in its mission. In a little over 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 Second Era – 1947 – 1992

Mission: Manufacturing Nuclear Weapons Components During the Cold War

The Y-12 Plant eventually became one of twelve production facilities with a unique role. Its new 

mission was to produce the key components of nuclear weapons and test devices needed for the 

expanding nuclear weapons stockpile, and for the safekeeping of our nation’s highly enriched uranium 

(HEU) stockpile. Many supporting tasks were given to Y-12, notably the production of the enriched 

lithium urgently needed for the thermonuclear program in the 1950’s and 1960’s. Y-12 succeeded in 

carrying out these challenging missions in developing state-of-the-art technologies demanded by new 

weapons designs over a period of almost 50 years.

The Third Era – 1992 to present

Multiple New Missions

The Nation’s stockpile of nuclear weapons was reduced by 90% during this time. The number of 

operational buildings was reduced and Y-12’s manufacturing technology was transferred to industry, 

where allowed. Ongoing missions include: 
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 6 of 30

• Storing HEU for the Department of Energy (DOE) 

• Disassembling weapons/components to study aging and other effects

• Producing a small number of nuclear weapons parts and assemblies

• Decontaminating and decommissioning of unused buildings

• Conducting major efforts in environmental and waste management. 

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. 

2.2 OPERATING CONTRACTORS

The TEC was the original Y-12 contractor under agreement with the USACE. On January 1, 1947, in 

accordance with the Atomic Energy Act of 1946, all atomic energy activities including Y-12 were 

turned over to the United States Atomic Energy Commission (U.S. AEC). During the same year, the 

MED was disbanded and TEC was replaced by Carbide and Carbon Chemicals Corporation as the Y12 site contractor. The name “Y-12,” a code name for the plant during the Manhattan Project, has 

been in use since that time. The following is a list of the site prime contractors throughout Y-12’s 

history.

Operating Contractor Period

Tennessee Eastman Corporation 1943 to 1947

Carbide and Carbon Chemicals Corporation 1947 to 1950

Carbide and Carbon Chemicals, Division of 1951 to 1956

 Union Carbide and Carbon Corporation

Union Carbide Nuclear Company, Division of 1957 to 1963

 Union Carbide and Chemicals Corporation

Union Carbide Corporation, Nuclear Division 1963 to 1984

Martin Marietta Energy Systems, Incorporated 1984 to 1994

Lockheed Martin Energy Systems 1994 to 1998

BWXT Y-12, L.L.C. 1998 to present

2.3 SITE ACTIVITIES

From inception, Y-12 was specifically designed to enrich uranium via an electromagnetic separation 

process. The actual device used for enrichment, the Calutron (from California University Cyclotron

The early operations at Y-12 were narrowly focused. The primary hazards at the facility were 

uranium-bearing chemicals including, but not limited to: 

), 

used a massive magnetic field to separate isotopes of uranium based on slight differences in mass. 

Two stages of separation and enrichment were required. The first and larger stage, designated 

Alpha, produced slightly enriched feed material for the second stage, known as the Beta Stage. The 

Alpha and Beta chemical operations were required to produce feed material for the calutrons, to 

recover valuable waste and by-products, and to produce the final material for use in an atomic 

weapon.

• Uranium oxide (U3O8) 

• Uranium dioxide (UO2),

• Uranium trioxide (UO3), 

• Uranium hexafluoride (UF6),

• Ammonium diuranate [(NH4)2U2O7],
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 7 of 30

• Uranyl nitrate [UO2(NO3)2], 

• Uranium peroxide (UO4 ∙2H2O), 

• Uranium tetrachloride (UCl4), 

• Uranium pentachloride (UCl5), and 

• Uranium tetrafluoride (UF4) 

In addition, bulk quantities of industrial chemicals, e.g. carbon tetrachloride (CCl4), hydrogen peroxide 

(H2O2), dibutyl carbitol (C12H26O3), nitric acid (HNO3), and hydrochloric acid (HCl), were used or 

produced at the plant. Because Y-12 was basically a heavy industry site, many other common 

industrial materials, such as, asbestos, solvents, acids, alkalis, and oils, were used and available for 

potential worker exposure. 

Electromagnetic operations at Y-12 continued for a number of years after 1947. However, these 

activities were chiefly directed toward research on new radionuclides for medical or other uses.

Over the following years, Y-12 became a highly sophisticated nuclear weapons component 

manufacturing facility and development engineering organization. The plant receives, stores, and 

protects uranium and lithium materials and parts; dismantles nuclear weapons components; and 

serves as a government repository for enriched uranium (EU). In addition, Y-12 has many treatment, 

storage, and disposal facilities for hazardous and radioactive materials. Today, the primary mission of 

Y-12 consists of dismantling nuclear weapons components, storing nuclear material, pursuing new 

technologies, and serving as the Department of Energy’s (DOE) primary repository for HEU. Table 

2.3-1 shows the radionuclides of concern at Y-12. Some building numbers and their corresponding 

radionuclides are not available at this time.

Table 2.3-1. Radionuclides of concern

Radionuclide Type of emission

Radioactive 

half life (y) Building number

Solubility

class

99Tc Beta 2.13 x 105

228Th Alpha 1.91 9201-1, 9201-5, 9202, 9204-4, 9206, 

9215, 9766

230Th Alpha 7.54 x 104 9215, 9720-5 100% S

232Th Alpha 1.45 x 1010 9201-5, 9207-5, 9215, 9998 100% S

234U Alpha 2.47 x 105 N/A(a) S,M,F

235U Alpha, some gamma 7.4 x 108 N/A S,M,F

236U Alpha 2.34 x 107 N/A S,M,F

238U Alpha 4.47 x 109 N/A S,M,F

237Np Alpha 2.14 x 106 9201-5, 9202, 9215, 9720-5 100% S

238Pu Alpha 86.4 9201-5, 9720-5 100% S

239Pu Alpha 2.4 x 104 N/A

241Am Alpha 4.32 x 102 9212 100% S

2.4 SITE PROCESSES 

Over the years, the mission of Y-12 has evolved from uranium isotope separation to a multitude of 

new missions. Manufacturers conduct their own research using unique machinery available at Y-12 

as well as expertise throughout the Oak Ridge Complex. In addition, Y-12 provides landlord services 

for DOE as well as other types of management, such as the Transportation and Safeguards Division, 

and the Oak Ridge National Laboratory. Other responsibilities include environmental restoration and 

waste management; putting facilities into a safe, legally compliant condition for shutdown; and 

providing protection of government property. Tables 2.4-1 and 2.4-2 summarize Y-12 processes and 

operations from the very beginning to the present.
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Table 2.4-1. Process chronology of operations

Building 1943-1948 1949-1951 1952-1963 1964-1995 1996-2003

9201-1 Tracks 1 and 2, α - I 

calutrons (uranium 

enrichment)

Uranium enrichment 

operations

Uranium salvage 

operations

Fusion energy 

research operations

General 

manufacturing for 

tooling, including 

work for others. 

Almost all clean 

work.

9201-2 Tracks 3 and 4, α - I 

calutrons (uranium 

enrichment)

Uranium enrichment 

operations

COLEX Lithium/Hg 

enrichment 

operations

Development/research 

operations

ORNL

9201-3 Track 5, α - I 

calutrons

Uranium enrichment 

operations

Uranium salvage 

operations

Fusion energy 

research operations

Currently used for 

office space.

9201-4 Tracks 6 and 7, α -

II calutrons (uranium 

enrichment)

Uranium enrichment 

operations

COLEX Lithium/Hg 

enrichment 

operations

Engineering and 

administrative facilities

Awaiting D&D

9201-5 Tracks 8 and 9, α -

II calutrons (uranium 

enrichment)

Uranium enrichment 

operations

COLEX Lithium/Hg 

enrichment 

operations

Normal/depleted 

uranium press, rolling, 

and machining 

operations

Normal/depleted 

uranium press, 

rolling, and 

machining 

operations

9202 α and chemical 

preparation/recover

y operations

Uranium product 

recovery operations

Uranium process 

development & 

improvement 

operations

Uranium process 

development & 

improvement 

operations

Technology 

Development

9203 235U analysis and 

initial uranium 

product processing

Uranium product 

recovery operations

Recovery and 

salvage operations

Y-12 production 

development and 

research operations

Technology 

Development

9204-1 Tracks 1 and 2, ß -

calutrons (uranium 

enrichment)

Uranium enrichment 

operations

Stable isotope 

separation operations

Fusion energy 

research operations

ORNL facility, 

however BJC 

occupies office 

space

9204-2 Tracks 3 and 4, ß 

calutrons (uranium 

enrichment)

Uranium enrichment 

operations

Uranium assembly 

operations

Uranium assembly 

operations

Uranium assembly 

operations

9204-3 Tracks 5 and 6, ß 

calutrons (uranium 

enrichment)

Uranium enrichment 

operations

Stable isotope (e.g., 

copper) separation 

operations

Stable isotope (e.g.,

copper) separation 

operations

ORNL facility

9204-4 Tracks 7 and 8, ß 

calutrons (uranium 

enrichment)

Uranium enrichment 

operations

ELEX Lithium/Hg 

pilot-scale operations

Normal/depleted 

uranium press and 

rolling operations

Depleted uranium 

press operations and 

quality evaluations 

for weapon 

components storage

9206 ß chemical recycle 

and product 

processing

Uranium product 

recovery/salvage

Uranium chemical 

processing and metal 

production operations

Uranium chemical 

processing and metal 

production operations

Currently undergoing 

deactivation. No 

longer an MAA, D&D 

scheduled for future.

9207 Uranium salvage 

operations

Uranium 

recovery/salvage

Maintenance/salvage 

operations

ORNL biological 

research Operations

ORNL facility, mostly 

vacated.

9211 Uranium salvage 

operations

Uranium salvage 

and product 

recovery operations

Uranium salvage and 

product recovery 

operations

ORNL biological 

research operations

ORNL biological 

research operations

9212 ß product 

processing

Uranium 

conversion/recovery 

operations

UF6 conversion, 

chemical operations, 

and weapon 

production operations

Chemical operations 

and weapons 

production operations

Chemical operations 

and weapons 

production 

operations

9215 -- -- Enriched uranium 

machining and metal 

finishing operations

Enriched uranium 

machining and metal 

finishing operations

Enriched uranium 

machining and 

metal finishing 

operations

9998 -- Normal uranium H-1 

foundry operations

Depleted uranium H-1 

foundry operations

Depleted uranium H-1 

foundry operations

Depleted uranium H1 foundry 

operations
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Table 2.4-2. Key uranium operations

Key uranium operations Buildings involved

Dates of 

operation

Electromagnetic Enrichment: Y-12 processed roughly 50,000 kg of UCl4 in 

calutrons that were housed in both alpha and beta enrichment buildings. To 

obtain a desired enrichment, UCl4 was processed through many calutrons and 

recycled frequently. Alpha operations enriched up to 20 – 30% 235U. Beta 

operations were designed to further enrich partially enriched, alpha recycle 

material up to 95% 235U. Enriched U compounds were recovered and converted 

to oxide for shipment or recycled for further alpha or beta enrichment. DU was 

removed from process equipment and disposed of through building vents and 

storm sewer drains.

Alpha buildings 9201-1,2,3,4,5 

Beta buildings 9204-1,2,3,4

1943–1947

Feed Preparation and Product Processing: Volatile UCl4 was the chemical 

form of U 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 U 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 heated conditions inside a chemical 

reactor bowl for roughly eight hours and then purged with nitrogen to exhaust 

phosgene vapors from the system. From both methods, UCl4 crystals were 

collected and loaded in calutrons.

9202, 9203, 9206, 9212

9202 and 9203 housed alpha U 

feed preparations and product 

recovery operations. They also 

handled EU, DU and normal U.

9206 was used to recover beta 

product with higher enrichment 

levels (>50%). Highly enriched 

material was converted to UCl4 for 

further enrichment.

9212 received ~ 4,700 kg of UF6

with an average 235U content of 

30% between 1945-1947.

1943–1947

Uranium Recovery and Recycle: Y-12 stopped enriching U after WWII and 

operations now centered on U recovery and recycling of residual U found on 

equipment and scrap material. Operations included mechanical scraping and 

brushing, nitric acid washing, and distillation and recovery of solid U compounds 

adhered to surfaces. Uranium contaminated materials included condensates, 

scrubber solutions, raffinates, destructive distillates, oils, and miscellaneous 

residues. These facilities handled mostly normal U and DU.

9202, 9203, 9206, 9212

9202, 9203 received DU, slightly 

EU, and normal U.

9206 was the main U recovery 

and recycle facility and housed 

sanding, grinding, chemistry and 

incinerator operations.

1945–1951

1950s–1990s

Uranium Salvage: Salvage operations involved recovery of U from materials not 

considered production equipment, such as liquid and solid waste materials from 

maintenance/cleanup activities such as mop water, laundry washes, and floor 

drain residues. Combustible materials such as wood, rags, sponges, filter paper, 

and carbon solids were burned in muffle furnaces and incinerators to recover U. 

Other salvage operations included mechanical scraping and brushing, nitric acid 

washing, and distillations a recovery of U compounds.

9206, 9207, 9211

9206 housed salvage operations 

and process operations were 

similar to 9207 and 9211.

9207, 9211 processed incinerated 

solid waste and recovered normal 

and slightly EU.

1945–1951

Uranium Preparation/Recycle: Y-12 began a continuous growth of U weapons 

component manufacturing operations handling a variety of U compounds and 

enrichment. EU prepared for reduction to metal involved conversion of UF6 to 

UF4 purification of uranyl nitrate solutions, precipitation for U recovery, and then 

reduction to U metal.

9202, 9206, 9211, 9212

9212 housed the largest chemical 

operations for EU purification, 

recovery and chemical conversion, 

as well as normal and DU 

machining operations.

1952–1995

Uranium Forming/Machining: Y-12 had operations capable of casting, rolling, 

and machining U metal. These operations handled EU, DU and normal U. 

Uranium was pressed, rolled, shaped, and machined into finished weapon 

components.

9201-5, 9204-4, 9215, 9998

9201-5, 9204-4 housed DU

9215 housed EU

9998 contained H-1 foundry 

operations that included DU 

recycle and parts manufacturing.

1952–1995

Uranium Component Assembly: Machined components were sent through 

finishing operations that included drilling, welding, brazing, polishing and final 

specification checks. Bldg. 9202 was primarily used for early pilot scale 

operations that involved design and implementation of fabrications and assembly 

processes and final inspection procedures. Assembly operations generally were 

not associated with significant releases of U compounds. Any measurable 

amounts of U wee recovered and recycled back into the production stream. U 

was routinely recovered from articles such as rags, paper towels, oils and liquid 

waste products. Process exhaust stacks were equipped with HEPA filtrations a 

periodically inspected for buildup of U.

9202, 9204-2, 9204-2E

9204-2, 9204-2E housed uranium 

assembly operations.

1952–1995
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2.4.1

Uranium was enriched for use in atomic weapons by processing large amounts of UCl4 in calutrons. 

These operations were housed in the Alpha buildings (Buildings 9201-1, 9201-2, 9201-3, 9201-4, and 

9201-5) and Beta buildings (Buildings 9204-1, 9204-2, 9204-3, and 9204-4) that contained the first 

and second stages, respectively, of the enrichment processes. 

Electromagnetic Enrichment (1943–1947) 

2.4.2

Feed preparation involved conversion of large quantities of uranium oxides (including UO2, UO3, and 

U3O8) into UCl4 - the feed material for the calutrons. Most operations were done in Buildings 9202, 

9203, 9206, and 9212.

Feed Preparation for Enrichment Operations (1943–1947) 

2.4.3

An elaborate system of mechanical and chemical processes was used to recover and recycle uranium 

feed and product material that had 235U content worth recovering. These operations were primarily 

done in Buildings 9202, 9203, and 9206.

Uranium Recovery and Recycle Operations (1944–1951) 

2.4.4

Salvage operations involved recovering EU from all non-product components or byproduct of the 

operations. Calutron parts and associated equipment containing small amounts of uranium were 

cleaned and decontaminated. Some uranium was recovered for future use, while that in wash fluids 

was discharged to East Fork Poplar Creek. Scraps and materials that could not be decontaminated 

were buried within the Oak Ridge Reservation (ORR). These operations were primarily done in 

Buildings 9206, 9207, and 9211.

Uranium Salvage Operations (1947–1951) 

2.4.5

Uranium for weapon production was first processed in recovery, purification, and conversion 

operations. From about 1949 to 1964, Y-12 received cylinders of 93.5% UF6 as feed material for 

nuclear weapon parts manufacturing. Once purified and converted to its metallic form, uranium was 

transferred to metal processing operations for forming and shaping the metal into weapon part 

configurations. After 1964, the majority of EU processed at Y-12 was recycled from nuclear weapons 

stockpiles. Uranium recycle and purification processes continued through present day operations. 

These operations were primarily done in Buildings 9202, 9206, and 9212. Recycled uranium (RU) 

contains transuranic (TRU) material (e.g. plutonium, neptunium), fission products, (e.g. technetium), 

and reactor-generated uranium products (e.g. 236U). Thus, the processing and re-enrichment of RU 

may present an increased potential hazard for occupational and environmental exposure that is 

greater than that normally associated with the processing of un-irradiated uranium. The RU 

encompassed a variety of material forms. These included uranyl nitrate solutions (UNH), molten UNH, 

uranium oxide (UO2), UO3, UF4, uranium metal, uranium alloys, and a variety of associated wastes. 

Y-12 was involved with highly enriched RU processing operations at five different locations. Until the 

early 1970’s, chemical processing of highly enriched RU occurred in the 9212 complex, and later in 

Building 9206. The EU product was stored in Building 9720-5. The S-3 ponds served as 

impoundment for process wastewater until the mid-1980’s. After the ponds were closed, the RU 

process wastewater was treated by a variety of methods at the West End Treatment Facility (WETF). 

Uranium Preparations and Recycle for Weapon Component Operations (1949–1995) 
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2.4.6

Formed uranium metal parts were machined into finished weapon parts and then transferred to Y-12 

assembly operations. Numerous buildings were needed to support these diverse operations and the 

buildings were frequently modified to meet changes in production needs. These operations were 

primarily done in Buildings 9201-5, 9204-4, 9215, and 9998. Depleted uranium (DU) operations for 

the production of weapon components have existed at Y-12 since the early 1950’s. DU is a form of 

uranium consisting of over 99.8% 238U and less than 0.72% 235U by mass. The DU and DU alloy 

operations typically included melting and casting, forging and rolling into plates, forming or extruding 

into shapes, and final heat treating to obtain desired properties. The depleted forms were then 

machined into the final design specifications for weapons components. Buildings 9998, 9215, 9201-5, 

and 9204-4 housed the majority of Y-12’s DU processing operations. Particle or dust collectors, such 

as cyclones and bag houses, were used in most of the processes to capture the larger sized particles. 

Airborne losses from the foundry and other operations were fairly large from 1948 to 1956. When 

production levels increased, additional filters were installed sometime in 1955. Potentially large 

uranium losses may have occurred in 1954 and July 1956, because minimal dust was collected or 

filtered compared to the amount of uranium collected after the new filtering equipment was operating 

efficiently. The losses during 1956 were estimated from stack monitoring to be about 0.1 kg of DU per 

day. Continuous monitors were installed on the exhaust stacks in the mid 1950’s.

Uranium Forming and Machining for Weapon Component Operations (1949–1995) 

2.4.7

Weapon parts were assembled into finished products, inspected and tested against design criteria, 

and then shipped off-site. The majority of these operations were housed in Buildings 9204-2 and 

9204-2E. Tables’ 2.4.7-1 and 2.4.7-2 show the key operations over time at Y-12.

Weapon Component Assembly Operations (1952–1995) 

2.4.8

DOE is responsible for maintaining the safety and reliability of the Nation’s weapons. Y-12 supports 

DOE in their mission by providing resources to address safety, programmatic and operational 

considerations. This includes maintaining critical skills and physical assets for weapons production 

and maintaining critical technology.

Stockpile Stewardship and Maintenance (1996–2003) 

2.5 FACILITIES

Building 9731: The first building to become operational was the Calutron pilot plant building, 9731, in 

the fall of 1943. This building, also known as XAX/XBX, contained two each of the Alpha and Beta 

calutrons. This facility was also used as a training facility. During the first four months, only 4% of the 

uranium in the source “charge bottle” actually ended up in the receivers, while the remaining 96% 

either remained in the source, coated the electrodes, missed the receiver slits, and/or was splattered 

all over the liner. All side streams were collected in order to recover EU. A major concern was the 

growing amount of partially EU in recycle streams that needed to be purified and further enriched.

Building 9212 Complex: The 9212 Building Complex includes buildings 9212, 9809, 9812, 9818, 

9815, and 9980. More than 100 operations or processes have been performed in this complex. The 

largest building, 9212, has four wings, A, B, C, and D, and its primary activity was uranium recovery. 

Originally, this complex recovered HEU from the calutrons. After WW II, the 9212 building was 

expanded to accommodate the increased production of uranium from the Oak Ridge Gaseous 

Diffusion Plant (ORGDP) and to provide the capability to recover uranium from waste materials. In 

1948, new structures were built between the four wings. In 1951, the E Wing was added to facilitate 
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the casting and machining of uranium components. The UF6 conversion facility in the D wing was 

shutdown in 1964, essentially stopping the introduction of new HEU metal in the weapons stockpile.

Building 9212 currently performs four primary functions:

• Casting of HEU metal, 

• Accountability of HEU from plant activities,

• Recovery of HEU in a form suitable for storage,

• Serving as the U.S. source of all HEU used in test, research, or propulsion reactors and for 

isotope production.

Building 9212 also supports the International Atomic Energy Agency (IAEA) in sampling surplus EU, 

the packaging of HEU for offsite shipment, and producing specialized uranium compounds and metal 

for research reactor fuel.

Building 9202: Building 9202 became operational late in 1943. This is a bulk treatment facility and 

was designed to process UO3 to UO2 to UCl5 to UCl4 – the feed material for the Alpha Calutron 

sources.

Building 9203: Building 9203 became operational in November 1943. In this building, UCl4 was 

made from UO2 for the Alpha Calutron feed (the sources were called “charge bottles”). Other 

activities included washing Alpha collector pockets to recover the product, developing two different 

Beta chemical recycle processes (precipitation and electrochemical and later extraction processes), 

analytical chemistry labs, and mass spectrometry and fission counting labs to determine enrichment 

levels (assays).

Alpha Buildings and Beta Buildings: Over the course of one year starting in 1943, Y-12 put into 

operation eight of nine electromagnetic enrichment process buildings, including five first-stage 

enrichment operations called alpha buildings (9201-1, 9201-2, 9201-3, 9201-4, 9201-5) and three 

second-stage enrichment operations called beta buildings (9204-1, 9204-2, 9204-3). A fourth beta 

building, 9204-4, was operating by November 1945. As part of the war effort, Y-12 processed roughly 

50,000 kilograms of UCl4, in both the Alpha and Beta calutron buildings. The calutrons were arranged 

in large groups called "racetracks", typically with 96 calutrons per alpha track and 36 calutrons per 

beta track (1248 calutrons total). Each building typically housed two tracks. To obtain a desired 

enrichment, UCl4 was processed through many calutrons and recycled frequently. Alpha operations 

enriched uranium up to 20-30% 235U. Beta operations further enriched alpha recycle material up to 

95% 235U. Enriched uranium compounds were recovered and converted to an oxide form for 

shipment to Los Alamos, or recycled for further alpha or beta enrichment. The DU was removed from 

process equipment and disposed of through building vents and storm sewer drains.

Building 9206 Complex: Building 9206, centrally located at Y-12, has been used extensively for the 

chemical processing of uranium. Related structures that house supporting or process services and/or 

equipment, are 9768, 9720-17, 9409-17, 9510-2 and 9767-2 and the east and west tank farm pits.

The 9206 facility has carried out several EU processes and activities (times in parentheses):

• Chemical recycle, charge preparation, HEU recovery, and product processing for the 

electromagnetic process (1945-1946),
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• Recovery of EU from programs at Y-12 and many other sites (1947-1994),

• Production of uranium compounds for other sites (1949–1972), 

• Conversion of UF6 to UF4 to uranium metal for weapons (1954–1964),

• Casting and machining of HEU metal for weapons (1955–1965),

• Recovery of HEU from the Savannah River Site (SRS) solutions and other scrap for return to 

SRS as uranium metal (1972–1989),

• Conversion of excess HEU metal to oxide feed for the Portsmouth Gaseous Diffusion Plant 

(1980–1985),

• Storage of in-process materials (1950–present).

The following non-enriched uranium processes and activities at the 9206 facility include (times in 

parentheses):

• Recycling DU chips (1951-late 1950’s),

• Production of uranium compounds for other sites (1949-1972),

• Canning of normal-assay uranium slugs for nuclear reactor use (1950-1952),

• Storage of in-process materials (1950-present).

Building 9720-5: Building 9720-5 is used as a warehouse for short and long term storage of strategic 

materials. Built in 1944, it has been renovated several times. This building serves as a 

shipping/receiving facility for Special Nuclear Material (SNM) and the primary storage facility for 

interim and prolonged low maintenance storage of HEU.

Building 9215: Building 9215 was used to manufacture parts from DU and EU. The uranium was 

pressed, rolled, shaped, and machined into finished weapon components. 

Building 9995: Building 9995 is used as an analytical laboratory to assay nuclear components. The 

building allowed Y-12 to move into the forefront of the Nuclear Weapons Complex plant in the 

analytical chemistry field during the years following 1952. 

See Table 2.5-1 for the key uranium facilities.

Table 2.5-1. Key uranium facilities

Facility Facility Description

Building 9201-4, 

Alpha 4

Constructed in 1945

Mission: originally used for electromagnetic separation of uranium, later used for lithium isotopes separation.

Square footage: 562,000 square feet

Status: Facility is deteriorating, but in good condition, currently shut down, however all major Y-12 plant 

utilities run through this facility as well as the entire electrical system.

Concerns: large quantities of mercury and other hazardous materials, such as asbestos, lithium, lithium 

hydroxide, and mixed wastes. 

Building 9201-5, 

Alpha 5

Constructed in 1945

Mission: process and manufacture depleted uranium and non uranium materials. Beryllium, lithium, and depleted 

uranium in various forms are stored in this facility. Combustibles contaminated with enriched uranium are also 

stored in 9201-5.

Square footage: 591,500 square feet of space. 

Status: Plans to relocate the arc melting operation to the 9998 H-1 foundry.

Concerns: EU, DU
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Facility Facility Description

Building 9201-

5N/5W, Alpha 

5N/5W

Constructed in 1972

Mission: machine depleted uranium

Square footage: 80,500 square feet 

Status: Work for others

Concern: Some risk of depleted uranium exposure or uptake to workers 

Building 9204-2, 

Beta 2

Constructed in 1954

Mission: manufacture non-nuclear components for weapon production, includes salvage and recycle of weapon 

components made from lithium hydride and lithium deuteride, storage of these and other lithium-based materials for 

possible reuse. Today's lithium operations are generally industrial types: non-nuclear, non-radiological, chemical, 

foundry, and metal working processes.

Square footage: 270,000 square feet 

Status: Much of the original equipment has been replaced or upgraded by the lithium process replacement project 

and other projects since the late 1980s with significant improvements in safety, waste minimization, and process 

control.

Concerns: EU

Building 9204-2E, 

Beta 2E

Constructed in 1969

Mission: (1) processing cleaning, assembling, welding, and preparing nuclear components for shipment; (2) 

disassembling, storing, and preparing non-nuclear components for shipment; (3) dismantlement, and (4) quality 

evaluation and component certification. 

Square footage: 151,200 square feet

Status: Operations resumed in March 1996.

Concerns: A major hazard is the significant quantities of special nuclear material (SNM). While the risks are 

relatively low, the workers are exposed to radiological and industrial hazard and to possible nuclear criticality. 

Building 9204-4, 

Beta 4

Constructed in 1949

Mission: disassembly, testing, and storage of warhead components produced at Y-12. Sections of this facility have 

become active as part of receipt, storage, and shipping (RSS) operations.

Other activities: quality evaluation (QE), are being performed under special operation packages. The mission of 

this facility is being moved to Building 9204-2E. In addition, depleted uranium and non-uranium metals are 

processed in this facility. Plans are to relocate this activity to Buildings 9212, 9996, and 9998.

Square footage: 273,000 square feet. 

Status: DU and non-uranium metals are processed in the facility.

Concerns: presence of significant quantities of SNM and hazardous substances; while the risks are relatively low, 

workers are exposed to hazardous substances and to possible nuclear criticality. 

Building 9206

Related 

structures: 9768, 

9720-17, 9409-

17, 9510-2, 9767-

2, and east and 

west tank farm 

pits

Constructed in 1946

Mission: It was used to recover enriched uranium from scrap and trash. However, it is in stand-down with limited 

operations, due to conduct of operations concerns identified by the DNFSB.

Square footage: 67,294 square feet 

Status: currently undergoing deactivation.

Concerns: A major hazard is the presence of significant quantities of SNM and hazardous substances. While the 

risks are relatively low, the workers are exposed to hazardous substances and to possible nuclear criticality.

Building 9212 

Complex

Related 

structures: 9212, 

9809, 9812, 9818, 

9815, 9980

Constructed in 1940s

Mission: It is used for recovery, purification, and processing of enriched uranium into usable products or forms 

suitable for storage.

Square footage: 311,325 sq. ft. 

Concerns: The major hazards are nuclear, radiological, and hazardous chemicals present in the facility, and 

standard industrial hazards. Significant events: 1) the required annual test of the baghouse Halon system did not 

test all required components; 2) CSA requirements were not strictly enforced; and 3) there was uptake of 

radiological material by workers. An internal investigation by the contractor resulted in a detailed report that 

identified the causes of the uptake and the recommendations to prevent a recurrence. The uptake resulted in a 

committed effective dose equivalent of 5 mrem for all of the attested workers. The Price-Anderson Amendment Act 

audit conducted in October 1996 focused on this event.

Status: The facility is in stand-down with limited operations due to conduct of operations concerns.

Building 9215 Constructed in 1950

Mission: It was used to manufacture parts from depleted and enriched uranium. Portions of this facility have 

become active as part of RSS operations. The remainder will be reactivated as part of the enriched uranium 

operations restart.

Square footage: 157,000 square feet 

Status: EU machining and metal finishing operations.

Concerns: The major hazard is the presence of significant quantities of enriched and depleted uranium.

Building 9720-5 Constructed in 1944

Mission: It is used for storing enriched uranium weapons parts, assemblies, and other SNM for Y-12. 

Square footage: 53,949 square feet

Status: Storage facility

Concerns: The major hazard is a significant quantity of SNM. 

Building 9995 Constructed in 1952 

Mission: It is an analytical laboratory used, among other tasks, to assay nuclear components. This facility is 

maintained as a continuing operation.
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Facility Facility Description

Square footage: 84,000 square feet

Status: Plant laboratory, analysis of waste

Concerns: hazardous and mixed waste

Building 9202 Constructed in 1942

Mission: It is used as a bulk treatment facility and was designed to produce feed material used in the Alpha 

Calutron sources.

Square footage: 128,800 square feet

Status: Technology development

Concerns: U processed materials

Building 9731 Constructed in 1943

Mission: It is the Calutron Pilot Plant Building and was also used for training of supervisors.

Square footage: 37,300 square feet

Status: Standby mode

Concerns: The amount of partially EU in recycle streams that needed to be purified and further enriched. 

Building 9203 Constructed in 1942

Mission: Calutron feed production, washing alpha collector pockets to recover the product, developing beta 

chemical recycle processes, analytical chemistry labs, and mass spectrometry and fission counting labs to 

determine enrichment levels.

Square footage: 30,800 square feet

Status: Technology development

Concerns: RU

2.6 WASTE TREATMENT AND DISPOSAL OPERATIONS

The S-3 Ponds: Between 1951 and 1984, four seepage pits known as the S-3 ponds were used to 

dispose of over 2,700,000 gallons of a variety of liquid wastes including concentrated acids, caustic 

solutions, mop waters, and byproducts from the uranium recovery processes, including uranium and 

other heavy metals. These unlined pits, referred to at one time as a "witch's cauldron," were designed 

to allow liquid either to evaporate or percolate into the ground. Various metal impurities and 

radionuclides stripped from HEU during the solvent extraction steps in Buildings 9212 and 9206 

[approximately 10% to 30% of RU, Pu, Np, and technetium (Tc)] were discharged with the dilute nitric 

acid and other process-derived acid wastewater to the S-3 ponds prior to the mid 1980’s.

The S-3 Ponds served as an impoundment for process wastewater until the mid-1980’s. The four 

earthen basins comprising the S-3 ponds had no direct discharge to any local creek or river tributary. 

After the ponds were closed, RU process wastewater was treated by a variety of methods at the West 

End Treatment Facility (WETF). New Hope Pond (see below) served as a surface water 

impoundment that captured entrained solids from rainwater and secondary wastewaters.

Clean-up and closure of the ponds began in 1984. The site has been covered with gravel and clay, 

paved, lined, and it is now used as a parking lot. Sludge removed from the sediments of the ponds is 

stored in above-ground tanks. The S-3 ponds were finally closed in 1989 in accordance with the 

Resource Conservation and Recovery Act (RCRA) act. Prior to capping the ponds, sludge samples 

were taken from each pond to ascertain the airborne (internal) exposure potential for workers placing 

the cap materials. Based on the first evaluation, no special precautions were needed for this work, 

other than the normal requirements for handling DU. However, the second evaluation included the 

effects from thorium (Th) and strontium (Sr) and concluded the material should be treated as a 

mixture of 45 wt. % 230Th and 228Th. 

West End Treatment Facility, Building 9616-7: Beginning in the mid-1980’s, after closure of the S3 ponds, the WETF was constructed for treating mixed low level waste (LLW) and LLW- contaminated 

wastewater generated by Y-12 production and other DOE Oak Ridge Reservation (ORR) processes. 

Nitrate wastewater contaminated with EU was mixed with much larger quantities of wastewater 

contaminated with DU. The EU component was diluted to less than normal assay uranium. 
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Wastewaters are discharged into East Fork Poplar Creek, under the National Pollutant Discharge 

Elimination System (NPDES) permit.

In 1997, sludge from the WETF was analyzed for radionuclides. Elevated levels of 228Th, 230Th, and 

237Np were found. Sampling is now conducted on an ongoing basis. Both the tanks as well as 

incoming tankers are sampled periodically. 

New Hope Pond: New Hope Pond was constructed and placed in operation in the 1950’s to provide 

a retention basin on East Fork Poplar Creek at the east end of Y-12. The pond facilitated mixing of 

water and offered a sampling point for rainwater runoff, once-through cooling water, steam plant boiler 

blow-down, and secondary production process wastewaters. The pond also functioned to remove any 

suspended contamination from rainwater, miscellaneous releases from various tank farms and 

storage yards, and inadvertent releases from process buildings.

In 1973, New Hope Pond was dredged, and the resultant sludge was transferred to a basin located on 

Chestnut Ridge. In 1983, samples were taken to determine if the sediment that had accumulated in

the pond was hazardous. It was concluded that the data from the leach test showed no hazardous 

material per the RCRA definition.

2.7 CRITICALITY ACCIDENT

On June 16, 1958, there was an accidental, prompt–critical neutron chain reaction that occurred in a 

solution system at Y-12. The accident occurred in the C-1 Wing of the 9212 building, in a 55-gallon 

stainless steel drum. The cause of the accident was a super-critical quantity of highly enriched uranyl 

nitrate solution being accumulated in the drum due to a leaky valve.

The accident occurred in a process phase that was a temporary arrangement encompassing portions 

of a new and an old installation. Both installations were necessary to maintain production during an 

interim phase of remodeling a process. This temporary arrangement split the responsibility for the 

operation among three different supervisors in three physically separated areas. This contributed to 

the cause of the accident by complicating communications and control. The incident occurred while 

they were draining material thought to be water from a safe geometry, 5-inch storage pipes, into an 

unsafe geometrical drum. 

Eight employees were in the vicinity of the drum. Based on their reported proximity to the drum and 

on the activation of the indium foil strip in their badges, these eight employees received the highest 

radiation doses of any who may have been exposed. One of the eight employees was within three to 

six feet of the drum. The other seven employees were from 15 to 50 feet away. Special, post hoc 

methods were used to determine the neutron and gamma exposures of the employees involved. 

As employees left the plant for the day, their badges were collected and taken to the secondary 

control center to obtain activity readings on the indium foil. A list was compiled of the 31 employees 

with potentially significant neutron doses. These employees were routed through the medical test 

routine. 

During this incident 1.3 X 1018 fissions occurred. (See TID-5360, Suppl. 2, p. 25; USAEC Serious 

Accidents Issue #136, 8-25-59; USAEC Health and Safety Information Issue # 82, 9-5-58; 1959 

Nuclear Safety, Vol. 1, #2, p. 59.)
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2.8 RADIONUCLIDES AND RADIATION SOURCES

The three main exposure fields at Y-12 are from process and other radioactive materials, radiation 

generating equipment (x-rays and accelerators), and criticality or nuclear accidents. The most 

common process materials are EU (235U) and DU (238U). Both radionuclides are primarily alpha 

emitters. Most of the external dose from DU results from 234Th and 234Pa (protactinium) daughter 

products. The assumption is that all U activity is due to 234U. 

2.8.1

Uranium is a naturally occurring radioactive element that is used for nuclear reactor fuel and in 

nuclear weapon components. The two principal natural isotopes are 235U (0.7%) and 238U (99.3%). 

Natural U also includes a trace amount of daughter 234U by mass (0.0057%). The 234U activity is more 

significant as the 235U enrichment increases. When hit by thermal neutrons, uranium can achieve 

nuclear fission, in which the 235U isotope splits into fragments and releases energy. The DU contains 

less than 0.7% 235U and has an isotopic distribution by mass of 0.001% 234U, 0.199% 235U, and 99.8% 

238U. The EU contains more than the natural concentration of 235U, typically in the range of 0.99% to 

99% by mass. A common isotopic distribution by mass is 1% 234U, 93% 235U, and 6% 238U.

Uranium

The first known records for EU below 20 %235U are dated in calendar year (CY) 1947. At that time, 

the product had been produced by the electromagnetic process at Y-12. Subsequent to CY 1947, the 

below 20% 235U product was produced by the diffusion plants.

2.8.2

The RU is defined as any uranium that has been irradiated in a reactor. As a result, RU contains TRU 

material, fission products and reactor generated uranium products. The primary buildings and 

facilities that handled RU were: 9212, 9206, WETF and S-3 ponds. In addition, RU is stored 9720-5. 

Recycled Uranium

2.8.3

The x-ray or electron generating equipment used at Y-12 includes linear electron beams, electron 

beam welders, scanning electron microscopes, x-ray photoelectron spectrometers, secondary ion 

mass spectrometers, enclosed beam diffraction equipment, and medical diagnostic x-ray equipment. 

The emitted energy range is from 15 keV to 9 MeV.

X-Ray and Electron Generating Equipment

2.8.4

The most common radionuclide source facilities are segmented gamma scanners containing 169Yb 

(Ytterbium) (emits 63.1 keV gamma ray), a 60Co (1.33 and 1.17 MeV gamma rays) well source used 

for calibration of radiation monitoring equipment, and 252Cf spontaneous fission (average energy 2 

MeV) neutron sources used for non-destructive testing and material inventories. 

Radionuclide and Neutron Sources

Three gamma-ray sources, 4.55 mg 226Ra, 23.0 mg 226Ra, and 250 mCi 60Co, are used in the 

calibration of personnel meters and low range radiation instruments. A nine-Ci 60Co source is used in 

the calibration of high range survey meters. A large gamma source, 15 Ci 60Co, is used in the 

Radiographic Laboratory. The types of sources and location are in Table 2.8.4-1. 

Table 2.8.4-1. Known sealed radiation sources

Sources Building

Ra-Be, Po-Be 9203
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Ra, Co, Ta, Po-Be 9983

Po-Be, 226Ra 9737, 9201-2, 9204-3

226Ra 9212

226Ra, Co 9212

226Ra 9206,9706-2

2.8.5

There is a wide variety of special nuclear material (SNM), source material (SM), and other nuclear 

materials accounted for at Y-12. The various materials include EU above 20% of 235U, EU below 20% 

of 235U, DU, normal uranium, Th, enriched lithium (Li) (40%, 60% and 95% 6

Li), deuterium, Pu, and 

233U.

Special Nuclear Material

Since the weapons material flow was initiated, pure metal has been shipped and received as 100% 

uranium. The SNM metal generated in the early days of weapons production at Y-12 was not as pure 

as that produced subsequently. The primary impurity was carbon.

2.8.6

The primary sources of transuranic materials (TRU) [238-240Pu and 237Np] were RU from the Savannah 

River Site (SRS) and the Idaho Chemical Processing Plant (ICPP). The Rocky Flats Plant (RFP) 

returned HEU parts that had potential TRU contamination, and special development projects. Y-12 

proactively evaluated RU receipts from its inception against a specification that would maintain 

uranium as the dominating dose hazard. Dose estimates did not indicate a significant TRU problem. 

Compared to the current regulatory monitoring criteria, it would not warrant the initiation of special 

bioassay sampling beyond that needed for uranium. Recent workplace sampling confirms that the 

historical specification ensured that uranium was the dominating radiological hazard, even against 

current regulatory requirements. The exception was waste streams as evidenced by sludge samples 

from the WETF. The other radionuclides present were: 99Tc, 237Np, 238-240Pu, and 241Am.

Transuranics

2.8.7

The first record of Th at Y-12 was in January 1947. At that time, the inventory was used in research 

and development studies primarily by Oak Ridge National Laboratory (ORNL) personnel at Y-12. It 

was not until FY 1952 that the Th activity increased significantly. Shipments and receipts were 

primarily between Y-12 and ORNL. 

Thorium 

Processing of Th at Y-12 began in the early 1960’s. The Th metal in pellet form was pressed into 

electrodes and two arc meltings were made. The metal from these melts was pressed and/or rolled, 

formed, and machined. Metal scraps and chips were salvaged and also pressed into electrodes to be 

used in the arc-melting process.

The following activities by facility occurred as part of the process:

• Pellet/scrap preparation, arc melting, crop and trim machining, and sawing occurred in 9205-1,

• Mold press sintering, ingot forging, canning and annealing after first cold roll, and final 

inspection/assembly were preformed in 9204-4,

• Ingots were canned prior to first cold roll in 9201-1,
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• Cold rolling was conducted in 9215,

• Decanning, cleaning, and final plating was conducted in 9206,

• Decanning and machining activities were conducted in 9766,

• Development activities were performed in 9202.

Sludge samples were taken from the S-3 ponds prior to capping to determine whether there was any 

airborne (internal) exposure potential for workers placing the cap materials. No special precautions 

were needed for this work, other than the normal requirements for handling DU. However, there was 

a dramatic increase in the exposure potential of 228Th and 230Th that contributed to 90% of the internal 

exposure potential.

2.8.8

Significant quantities of Li material were machined and crushed to fine dust. Some unmeasured 

quantity ends up in the ventilation system, as mop water, cleanup solutions, and in non homogeneous 

salvage awaiting recovery.

Lithium

Impurities that are present in the Li metal react with deuterium. In many cases, the reaction 

productions distill out the lithium deuteride at the reaction temperatures and condense wherever the 

vessel is cooler (lid and upper 2 or 3 inches of the reactor). This represents a loss of deuterium which 

is not accounted for.

2.9 SOLUBILITY AND INSOLUBILITY

Y-12 has mainly processed U in the form of UO2 and U metal. Chemical conversions from UNH to 

both UO2 and U metal are performed as well. Although the solubility class for U metal is not 

addressed by the guidance documents, experience at U process facilities has shown that U metal 

generally behaves as a Class M compound. However, the possibility of slow oxidation of a significant 

portion of the surface of the metal to UO2 and/or U3O8 over time must be considered.

Y-12 has defined a Class Q as a mixture of 90% Class W and 10% Class Y. The Class Q represents 

the circumstance when there is only a thin layer of UO2 on the surface of uranium metal. It may also 

provide a reasonable representation of the solubility half-time that has been observed for UO2 that has 

not been “high-fired” (approximately 120–140 days) than would the assumed half-time for Class W (50 

days). However, the use of the International Commission on Radiological Protection (ICRP), 

Publication 66 lung model would overcome the need for the contrived compound Class Q since Type

M assumes 90% of the material has a half-time of 140 days. Under the ICRP Publication 66 lung 

model, only U that is “high-fired” UO2 or the product of slow oxidation of U metal should be classified 

as Type S. 

Y-12 uses three default solubility assumptions for workers who participate exclusively in the urine 

bioassay program (see Section 5 for more detail): 

• 100% Type S

• 75% Type S/25% Type M

• 50% Type S/50% Type M 
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These defaults are designed to be conservative and provide adequate protection for workers while, at 

the same time, being representative of the actual exposure material. The defaults are determined by 

the Radiological Work Permit (RWP) bioassay indicator code, the last character of the RWP identifier. 

When working with soluble materials such as uranyl nitrate, the solubility may be defaulted to 100% 

Type M or 100% Type F, depending on the material. However, to be conservative, persons working 

exclusively with soluble U are defaulted to 50% Type M/ 50% Type S. If an individual uses RWPs that 

indicate the work is with insoluble U materials, such as uranium oxide, then the solubility should be 

determined by dose calculation software. If the RWP indicates work with U has both a soluble and 

insoluble component, then the solubility will be defaulted to 25% Type M/75% Type S. If the RWP is 

for low exposure potential insoluble U requiring urinalysis only, then the solubility is defaulted to 100% 

Type S. The RWP bioassay indicators used for routine U handling jobs are ‘F’, ‘Y’, ‘W’, and ‘M’ and 

are summarized in Table 2.9-1.

Table 2.9-1. Chemical formulas and solubility class

Chemical formula Chemical name Solubility class (a)

(NH4)2U2O7 ammonium diuranate(b) M

CCl4 carbon tetrachloride 

C12H26O3 dibutyl carbitol 

HCl hydrochloric acid 

H2O2 hydrogen peroxide 

HNO3 nitric acid

UF6 uranium hexafluoride F

UO2 uranium dioxide S

U3O8 uranium oxide S

UCl5 uranium pentachloride

UO4 ∙2H2O uranium peroxide

UCl4 uranium tetrachloride M

UF4 uranium tetrafluoride M

UO3

(c) uranium trioxide M

UO2(NO3)2 uranyl nitrate F

UO2(NO3)2 x 6H20 uranyl nitrate hexahydrate (UNH)

a. F, M, S are inhalation solubility classes established by the ICRP. F material is very soluble, 

M class material is moderately soluble, S material is relatively insoluble.

b. Ammonium diuranate is known to contain U as UO3 and should not be assigned to a single 

inhalation class. The solubility of U oxides is very dependent on heat treatment. The rate of 

oxidation may also affect solubility.

c. ICRP Publications 54 (ICRP 1988) notes that there is evidence from animal studies that 

industrial UO3 may behave more like class S material; UF4 may behave more like class S 

material depending on the method used to produce it.

Historically from 1990 to 1998, the default solubility class for internal dose assessments was 90% W 

and 10% Class Y for both EU and DU. Almost all internal exposures at Y-12 involve U that has either 

been enriched or depleted in 235U through the process of gaseous diffusion.

In 1999, DOE gave the Y-12 Radiological Control Dosimetry Department permission to use the ICRP 

Publication 66 lung model for estimating intakes and doses received by personnel. Prior to this, the 

ICRP-30 lung model was used from 1989-1999. The ICRP 66 report includes a considerably more 

detailed respiratory tract model than ICRP-30. The default material assumptions recommended in 

ICRP-66 more closely reflect those observed at Y-12.

A number of Y-12 studies has been conducted in an attempt to better characterize the work area with 

regard to material solubility at Y-12 using the Dose 66 Code. These studies include a three month 

investigation using participants from various areas during October to December 1999, recalculation of
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 21 of 30

solubility of 1999 incident investigations, and a review of the 2000 incident investigation. The results 

of these studies have been combined and are given in Table 2.9-2.

Table 2.9-2. Solubility of material for 

various buildings and work areas as 

calculated by DOSE 66(a) code

Building N(b) %Type S %Type M

9202 1 51 49

9206 2 31 69

9212 48 68 32

9215 54 82 18

9995 4 78 22

9998 2 64 36

9201-5 2 36 64

9201-5N 12 77 23

9204-2E 5 89 11

9204-4 8 74 26

9704-2 1 0 100

a. DOSE 66 code was developed and validated during 

CY 2000 at Y-12. This code utilizes the more recent 

ICRP 66 methodology for inhalation intakes

b. N represents the number of data points

Y-12 developed the Dose 66 code and it was validated and verified in CY 2000. This code utilizes the 

ICRP 66 methodology for inhalation intakes. A major advantage of the DOSE-66 code is the 

calculation of a derived mixture for intake material class when both urine and fecal bioassay data is 

available. The code calculates an intake based on fecal bioassay results only. It then estimates an 

intake based on the urine results. If the fecal and urine intake estimates differ by a significant amount 

(set by the user), it adjusts the solubility of the material until the urine estimate of intake matches that 

of the fecal data.

Uranium is considered to be primarily an internal dosimetric hazard since it emits alpha particles, beta 

particles and only weak gamma and x-ray photons. Y-12 is rather unique in that workers are 

assumed to be routinely exposed to low levels of U. This chronic intake assumption places a 

premium on accurately assessing Committed Effective Dose Equivalent (CEDE) values received by 

workers. Review of the DOSE 66 data reveals the high correlation between the assumed solubility 

type and estimated CEDE values when urine bioassay data alone is used. As the solubility of the 

material is increased, the CEDE value drops dramatically. This phenomenon, coupled with the 

potential for exposure of workers to varying solubility mixtures, illustrates the importance of solubility 

in internal dose assessments. The preferred bioassay method for areas and work that could lead to 

significant insoluble U intakes is fecal sampling. For areas and work functions that could lead to 

intakes that are both soluble and insoluble, urine sampling alone is sufficient provided the insoluble 

intakes result in CEDE less than 100 mrem.
Effective Date: 09/09/2004 Revision No. 00 PC-1 Document No. ORAUT-TKBS-0014-2 Page 22 of 30

REFERENCES

ATSDR. 1992. Agency for Toxic Substances and Disease Registry. Public Health Assessment 

Guidance Manual. U.S. Department of Health and Human Services, Atlanta, Georgia. 

ChemRisk Repository No. 4002

ATSDR. 2003. Agency for Toxic Substances and Disease Registry. Public Health Assessment for 

Oak Ridge Reservation, Public Comment Release. U.S. Department of Health and Human 

Services, Atlanta, Georgia.

BWXT Y-12, L.L.C, Radiological Control Organization, Technical Basis Document, 2001, Technical 

Basis for the External Dosimetry Program at the Y-12 National Security Complex, RCO/TBD007, Rev. 3

BWXT Y-12, L.L.C. Recycled Uranium Mass Balance Project Y-12 National Security Complex Site 

Report, December 2000, Y/LB-16,036, Rev. 1.

ChemRisk. 1993. Oak Ridge Health Studies, Phase 1 Report, Volume ll – Part A, Dose 

Reconstruction Feasibility Study 

ChemRisk. 1999. Reports of the Oak Ridge Dose Reconstruction, Vol. 5, Task 6, Uranium Releases 

from the Oak Ridge Reservation - Review of the Quality of Historical Effluent Monitoring Data 

and a Screening Evaluation of Potential Off-Site Exposures

DOE Standard, Guide of Good Practices for Occupational Radiological Protection in Uranium 

Facilities. U.S. Department of Energy: DOE-STD-1136-2000;2-16; 2000

Health Physics Progress Report, November 1,1950 – December 31, 1950

ICRP (International Commission on Radiological Protection), 1994, “Human Respiratory Tract Model 

for Radiological Protection”, ICRP Publication 66, Annals of the ICRP, volume 24, numbers 1-

3, Pergamon Press, Oxford, England.

Linking Legacies, Connecting the Cold War Nuclear Weapons Production Processes to Their 

Environmental Consequences, DOE/EM-0319, Office of Environmental Management, U.S. 

Department of Energy, January 1997.

McLendon, J.D. 1958. Accidental Radiation Excursion at the Oak Ridge Y-12 Plant, Part II - Health 

Physics Aspects of the Accident. Report Y-E4-591. November 1958. ChemRisk Repository 

No. 931.

Oliver, B.O. 9/14/99, Request for White Papers Regarding Recycled Uranium Contaminated with 

Transuranics at the Y-12 Plant. Memo to J.A. Allard

Owings, E. 1995. Historical Review of Accountable Nuclear Materials at the Y-12 Plant. Report 

Y/EXT-00153/DEL Rev 

Oxley, L.S. Technical Basis Document for the External Dosimetry Program at the Y-12 National 

Security Complex, August 2, 2001, RCO/TBD-007, Rev. 3
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Patton, F.S., Googin, J.M., and Griffith, W.L. 1963. Enriched Uranium Processing. Pergamon Press. 

1963. ChemRisk Repository No. 2912.

Snapp,L.M. Technical Basis Document for the Internal Dosimetry Program, March 5, 2003, 

RCO/TBD-024, Rev. 4

Rucker, T.L., Slack, J.D., Fleming, K.N., Stevens, S.W., Moody, R.M., Johnson, C.M., Green, S.W., 

Uranium Lung Solubility Class Selection at Bechtel Jacobs Company LLC-Operated Facilities

Veinot, K.G., Souleyrette, M.L., Technical Basis for Solubility Determination and Bioassay Sampling 

Protocols at Y-12 National Security Complex, March 12, 2003, RCO/TBD-040, Rev. 1

Wilcox, Jr., William J. An Overview of the History of Y-12 – 1942-1992. American Museum of Science 

and Energy, Oak Ridge, Tennessee. 2001, 76 pages.
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 24 of 30

GLOSSARY

In preparation
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 25 of 30

ATTACHMENT B – SITE DESCRIPTION

TABLE OF CONTENTS

Section

B.1 Sources of Exposure.................................................................................................................

Page

26

B.2 Chronology Y-12 Uranium Operations ...................................................................................... 26

B.3 Y-12 Facilities ...........................................................................................................................28

B.4 Solubility of Radionuclides and Other Chemicals ...................................................................... 29

LIST OF TABLES

Table Page

Table B.1-1. Radionuclides of concern...................................................................................... 26

Table B.1-2. Known sealed radiation sources ........................................................................... 26

Table B.2-1. Primary uranium operations.................................................................................. 27

Table B.2-2. Process chronology of operations......................................................................... 27

Table B.3-1. Key uranium facilities............................................................................................ 28

Table B.4-1. Radionuclides and solubility class......................................................................... 29

Table B.4-2. Radioelements and default solubility class............................................................ 30

Table B.4-3. Radiological work permit bioassay indicators for routine uranium handling jobs ... 30

Table B.4-4. Solubility of material for various buildings and work areas 

as calculated by DOSE 66(a) code......................................................................... 30
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 26 of 30

B.1 SOURCES OF EXPOSURE

Y-12 became a highly sophisticated nuclear weapons component manufacturing facility and 

development engineering organization. The plant receives, stores, and protects uranium and lithium 

materials and parts; dismantles nuclear weapons components; and serves as a government 

repository for enriched uranium. In addition, Y-12 has many treatment, storage, and disposal facilities 

for hazardous and radioactive materials. Today, the primary mission of Y-12 consists of dismantling 

nuclear weapons components, storing nuclear material, pursuing new technologies, and serving as

the DOE primary repository for HEU. Table B.1-1 shows the radionuclides of concern and its 

associated buildings. Table B.1-2 shows the location of known sealed radiation sources. Some 

building numbers and their corresponding radionuclides are not available at this time.

Table B.1-1. Radionuclides of concern

Radionuclide Type of emission

Radioactive 

half life (y) Building number

Solubility 

class

99Tc Beta 2.13 x 105 Not available

228Th Alpha 1.91 9201-1, 9201-5, 9202, 9204-4, 

9206, 9215, 9766

230Th Alpha 7.54 x 104 9215, 9720-5 100% S

232Th Alpha 1.45 x 1010 9201-5, 9207-5, 9215, 9998 100% S

234U Alpha 2.47 x 105 Not available S,M,F

235U Alpha, some gamma 7.4 x 108 Not available S,M,F

236U Alpha 2.34 x 107 Not available S,M,F

238U Alpha 4.47 x 109 Not available S,M,F

237 Np Alpha 2.14 x 106 9201-5, 9202, 9215, 9720-5 100% S

238Pu Alpha 86.4 9201-5, 9720-5 100% S

239Pu Alpha 2.4 x 104 Not available

241Am Alpha 4.32 x 102 9212 100% S

Table B.1-2. Known sealed radiation sources

Sources Building

Ra-Be, Po-Be 9203

Ra, Co, Ta, Po-Be 9983

Po-Be, 226Ra 9737, 9201-2, 9204-3

226Ra 9212

226Ra, Co 9212

226Ra 9206,9706-2

B.2 CHRONOLOGY Y-12 URANIUM OPERATIONS 

Tables B.2-1 and B.2-2 contain descriptions of historical Y-12 uranium process operations. Specific 

key buildings and their functions are highlighted to better understand the Y-12 uranium operations. Y12 experienced significant changes from their original mission of electromagnetic enrichment to their 

current multiple missions of storing HEU, weapons disassembly, and major efforts in environmental 

and waste management. 
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 27 of 30

Table B.2-1. Primary uranium operations

Key uranium operations Buildings involved

Dates of 

operation

Electromagnetic Enrichment Alpha buildings 9201-1,2,3,4,5 Beta buildings

9204-1,2,3,4

1943–1947

Feed Preparation and Product Processing 9202, 9203, 9206, 9212 1943–1947

Uranium Recovery and Recycle 9202, 9203, 9206, 9212 1945–1951,

1950s–1990s

Uranium Salvage 9206, 9207, 9211 1945–1951

Uranium Preparation/Recycle 9202, 9206, 9211, 9212 1952–1995

Uranium Forming/Machining 9201-5, 9204-4, 9215, 9998 1952–1995

Uranium Component Assembly 9202, 9204-2, 9204-2E 1952–1995

Stockpile Stewardship and Maintenance 9201-5, 9204-4, 9215 1952–2003

Table B.2-2. Process chronology of operations

Building 1943-1948 1949-1951 1952-1963 1964-1995 1996-2003

9201-1 Tracks 1 and 2, α - I 

calutrons (uranium

enrichment) 

Uranium 

enrichment 

Uranium salvage Fusion energy research Manufacturing for 

tooling, work for 

others. Clean work.

9201-2 Tracks 3 and 4, α - I 

calutrons (uranium 

enrichment)

Uranium 

enrichment 

operations

COLEX Lithium/Hg 

enrichment operations

Development/research 

operations ORNL

9201-3 Track 5, α - I 

calutrons

Uranium 

enrichment 

Uranium salvage Fusion energy research Office space.

9201-4 Tracks 6 and 7, α - II 

calutrons (uranium 

enrichment)

Uranium 

enrichment 

operations

COLEX Lithium/Hg 

enrichment operations

Engineering and 

administrative facilities Awaiting D&D

9201-5 Tracks 8 and 9, α – 

II calutrons (uranium 

enrichment)

Uranium 

enrichment 

operations

COLEX Lithium/Hg 

enrichment operations

Normal/depleted 

uranium press, rolling, 

and machining 

operations

Normal/depleted 

uranium press, rolling, 

and machining work.

9202 Alpha and chemical 

preparation/recovery 

operations

Uranium product 

recovery operations

Uranium process 

development & 

improvement 

operations

Uranium process 

development & 

improvement 

operations

Technology 

Development

9203 235U analysis and 

initial uranium 

product processing

Uranium product 

recovery operations

Recovery and salvage 

operations

Production 

development and 

research operations

Technology 

Development

9204-1 Tracks 1 and 2, ß -

calutrons (uranium 

enrichment)

Uranium 

enrichment 

operations

Stable isotope 

separation operations

Fusion energy research 

operations

ORNL facility, 

however BJC 

occupies office space

9204-2 Tracks 3 and 4, ß 

calutrons (uranium 

enrichment)

Uranium 

enrichment 

operations

Uranium assembly 

operations

Uranium assembly 

operations Uranium assembly 

operations

9204-3 Tracks 5 and 6, ß 

calutrons (uranium 

enrichment)

Uranium 

enrichment 

operations

Stable isotope (e.g., 

copper) separation 

operations

Stable isotope (e.g.,

copper) separation 

operations

ORNL facility

9204-4 Tracks 7 and 8, ß 

calutrons(uranium 

enrichment)

Uranium 

enrichment 

operations

ELEX Lithium/Hg pilotscale operationsNormal/depleted 

uranium press and 

rolling operations

DU press operations, 

quality evaluations for 

weapon components 

storage

9206 ß chemical recycle 

and product 

processing

Uranium product 

recovery/salvage

Uranium chemical 

processing and metal 

production operations

Uranium chemical 

processing and metal 

production operations

Currently undergoing 

deactivation. D&D 

scheduled for future.

9207 Uranium salvage 

operations

Uranium recovery/ 

salvage

Maintenance/salvage 

operations

ORNL biological 

research Operations

ORNL facility, mostly 

vacated.

9211 Uranium salvage 

operations

U salvage and 

product recovery 

operations

U salvage and product 

recovery operations

ORNL biological 

research operations ORNL biological 

research operations

9212 ß product 

processing

Uranium 

conversion/ 

recovery operations

UF6 conversion, 

chemical operations, 

and weapon 

production

Chemical operations 

and weapons 

production operations

Chemical operations 

and weapons 

production operations

9215 -- -- Enriched uranium Enriched uranium Enriched uranium 
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 28 of 30

Building 1943-1948 1949-1951 1952-1963 1964-1995 1996-2003

machining and metal 

finishing operations

machining and metal 

finishing operations

machining and metal 

finishing operations

B.3 Y-12 FACILITIES

Table B.3-1 lists the key facilities and gives details of the facility, including the year of construction 

and current status of the building.

Table B.3-1. Key uranium facilities

Facility Facility Description

Building 9201-4, Alpha 4 Constructed: 1945

Mission: Electromagnetic separation of U, lithium isotopes separation.

Square footage: 562,000 square feet.

Status: Deteriorating, shut down; all utilities run through facility.

Concerns: EU hazardous materials and mixed wastes. 

Building 9201-5, Alpha 5 Constructed: 1945

Mission: Process and manufacture DU and non uranium materials. Storage of DU 

in various forms and combustibles contaminated with EU.

Square footage: 591,500 square feet. 

Status: Plans to relocate the arc melting operation to the 9998 H-1 foundry.

Concerns: EU, DU

Building 9201-5N/5W, Alpha 

5N/5W

Constructed: 1972

Mission: Machine DU.

Square footage: 80,500 square feet 

Status: Work for others

Concerns: Some risk of DU exposure or uptake to workers 

Building 9204-2, Beta 2 Constructed in 1954

Mission: Manufacture non-nuclear components for weapon production. Salvage, 

recycle, store lithium materials. Industrial lithium operations.

Square footage: 270,000 square feet.

Status: Original equipment replaced/upgraded by lithium process project.

Concerns: EU

Building 9204-2E, Beta 2E Constructed: 1969

Mission: Processing, cleaning, assembling, welding, and preparing nuclear 

components for shipment; other non-nuclear work.

Square footage: 151,200 square feet

Status: Operations resumed in March 1996.

Concerns: significant quantities of SNM.

Building 9204-4, Beta 4 Constructed: 1949

Mission: Disassembly, testing, and storage of Y-12 warhead components. 

Square footage: 273,000 square feet. 

Status: DU and non-uranium metals are processed in this facility. 

Concerns: Significant quantities of SNM. 

Building 9206

Related structures: 9768, 9720-

17, 9409-17, 9510-2, 9767-2, and 

east and west tank farm pits

Constructed: 1946

Mission: Recover EU from scrap/trash. It is in stand-down, limited work. 

Square footage: 67,294 square feet.

Status: currently undergoing deactivation

Concerns: Significant quantities of SNM and hazardous substances. 

Building 9212 Complex

Related structures: 9212, 9809, 

9812, 9818, 9815, 9980

Constructed: 1940’s

Mission: Recovery, purification, and processing of EU.

Square footage: 311,325 sq. ft. 

Status: Facility is in stand-down with limited operations. 

Concerns: Major hazards are nuclear, radiological, and chemicals. 
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 29 of 30

Facility Facility Description

Building 9215 Constructed: 1950

Mission: Manufacture parts from DU and EU. Will be reactivated as part of the EU 

operations restart.

Square footage: 157,000 square feet 

Status: EU machining and metal finishing operations.

Concerns: Significant quantities of DU and EU.

Building 9720-5 Constructed: 1944

Mission: Storing EU weapons parts, assemblies, and other SNM. 

Square footage: 53,949 square feet.

Status: Storage Facility

Concerns: Significant quantity of SNM. 

Building 9995 Constructed: 1952 

Mission: Analytical laboratory.

Square footage: 84,000 square feet

Status: Plant laboratory, analysis of waste

Concerns: hazardous and mixed waste

Building 9202 Constructed: 1942

Mission: Bulk treatment facility, produced feed material for Alpha Calutrons.

Square footage: 128,800 square feet.

Status: Technology development

Concerns: U processed materials

Building 9731 Constructed: 1943

Mission: Calutron Pilot Plant Building used for training.

Square footage: 37,300 square feet.

Status: Standby mode

Concerns: Partially EU in recycle streams that needed to be purified and further 

enriched.

Building 9203 Constructed: 1942

Mission: Calutron feed production, washing alpha collector pockets to recover the 

product, developing beta chemical recycle processes, mass spectrometry and 

fission counting labs to determine enrichment levels.

Square footage: 30,800 square feet.

Status: Technology Development

Concerns: RU

B.4 SOLUBILITY OF RADIONUCLIDES AND OTHER CHEMICALS

Workers at Y-12 routinely perform work with various compounds of uranium. These compounds have 

differing retention times and clearance pathways. Since the clearance of soluble materials is primarily 

through the blood, urine bioassay is the preferred method for detecting these forms of compounds. 

For insoluble compounds, the material is cleared from the lungs. The majority of the insoluble 

material will be excreted via the feces, with only a small fraction clearing through the urine. Tables 

B.4-1 and B.4-2 show the solubility class of different radionuclides and radioelements.

Table B.4-1. Radionuclides and solubility class

Radionuclides Solubility class

99Tc F and M

237Np M

238Pu M

239Pu S

241Am M
Effective Date: 11/19/2003 Revision No. 00 Document No. ORAUT-TKBS-0014-2 Page 30 of 30

Table B.4-2. Radioelements and default solubility class

Radioelement Solubility class

Am M

Np M

Pu S

Sr S

Tc M

3

H Vapor

U As determined by RWP

Y-12 uses three default solubility assumptions for workers who participate exclusively in the urine 

bioassay program: 100% Type S, 75% Type S/25% Type M and 50% Type S/50% Type M. These 

defaults are designed to be conservative and provide adequate protection for workers while at the 

same time being representative of the actual exposure material. Table B.4-3 summarizes the 

bioassay indicators.

Table B.4-3. Radiological work permit bioassay indicators for routine uranium handling jobs

Bioassay 

indicator Solubility Bioassay method

F Primarily (>75%) insoluble. Derived solubility will be determined 

by DOSE 66

Bi-monthly urine and fecal 

sampling

Y Primarily (>75%) insoluble but low exposure potential. Assumed 

solubility for dose calculations is 100% Type S.

Quarterly urine sampling

M Insoluble component between 25% and 75%. Assumed 

solubility for dose calculations is 75% Type S and 25% Type M.

Quarterly urine sampling

W No insoluble component expected. Assumed solubility for dose 

calculation is 50% Type S and 50% Type M.

Quarterly urine sampling

A number of studies have been conducted in an attempt to better characterize the work areas at Y-12 

with regard to material solubility. These studies have included a three month investigation using 

participants from various areas during October to December 1999. The results are shown in Table 

B.4-4.

Table B.4-4. Solubility of material for 

various buildings and work areas as 

calculated by DOSE 66(a) code

Building N(b) %Type S %Type M

9202 1 51 49

9206 2 31 69

9212 48 68 32

9215 54 82 18

9995 4 78 22

9998 2 64 36

9201-5 2 36 64

9201-5N 12 77 23

9204-2E 5 89 11

9204-4 8 74 26

9704-2 1 0 100

a. DOSE 66 code was developed and validated during CY 2000 at Y-12. 

This code utilizes the more recent ICRP 66 methodology for inhalation intakes. 

b. N represents the number of data points.