ORAU TEAM

Dose Reconstruction

Project for NIOSH

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

Page 1 of 38

Document Title:

Portsmouth Gaseous Diffusion Plant – 

Site Description

Document Number: ORAUT-TKBS-0015-2 

Revision: 01

Effective Date: 10/04/2006

Type of Document: TBD

Supersedes: Revision 00

Subject Experts: Marquis P. Orr and Paul J. Demopoulos

Approval: Signature on File Approval Date: 09/05/2006

Paul J. Demopoulos, Document Owner

Approval: Signature on File Approval Date: 09/06/2006

John M. Byrne, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 09/05/2006

Edward F. Maher, Task 5 Manager

Concurrence: Signature on File Concurrence Date: 10/03/2006

Kate Kimpan, Project Director

Approval: Brant A. Ulsh Signature on File for Approval Date: 10/04/2006

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

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

REVISION AND DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 2 of 38

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

11/21/2003 00 First approved issue. Initiated by Mark Notich.

10/04/2006 01 Revision initiated for biennial review and to incorporate recent 

direction from NIOSH to include DOL review comments. Revised to 

change from a page change (Rev 00 PC-1-A) to a revision (Rev 01-

A) as a result of worker outreach comments from PACE Local 5-689 

and SPFPA Local 66 04/16/2004 meeting. Approved issue of 

Revision 01. Section 2.3.12 was added to reflect new information on 

building X-770 facilities. Table 2-15 was also added. Three 

references were added. Added a Purpose and Scope subsection to 

the Introduction (Section 2.0). Three references were added. No 

sections were deleted. No further changes occurred as a result of 

internal formal review. Incorporates NIOSH formal review 

comments. This revision results in no change to the assigned dose 

and no PER is required. Training required: As determined by the 

Task Manager. Initiated by Paul J. Demopoulos.
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 3 of 38

TABLE OF CONTENTS

Acronyms and Abbreviations ...............................................................................................................5

2.1 Introduction................................................................................................................................. 7

2.1.1 Purpose..............................................................................................................................8

2.1.2 Scope................................................................................................................................. 8

2.2 Site Description...........................................................................................................................8

2.3 Site Activities ............................................................................................................................10

2.3.1 Gaseous Diffusion Cells – Buildings X-326, X-330, and X-333......................................... 10

2.3.1.1 Building X-333 ................................................................................................... 10

2.3.1.2 Building X-330 ................................................................................................... 10

2.3.1.3 Building X-326 ................................................................................................... 11

2.3.2 Fluorine Generation Facility and Fixed Feed Facility – Building X-342 & X-342A ............. 12

2.3.3 Fixed Feed Facility – Building X-343 ................................................................................12

2.3.4 Feed Manufacturing Plant – Building X-344......................................................................12

2.3.5 Special Nuclear Materials Storage – Building X-345.........................................................13

2.3.6 Maintenance – Building X-700..........................................................................................14

2.3.7 Decontamination, Cleaning, and Recovery – Building X-705............................................ 14

2.3.8 Oxide Conversion Facility – Building X-705E....................................................................15

2.3.9 Analytical Labs, Process and Materials – Building X-710 ................................................. 15

2.3.10 Compressor Shop – Building X-720 .................................................................................15

2.3.11 Aluminum Smelter and Recovery – Building X-744G........................................................16

2.3.12 Test Loop Facility – Building X-770 ..................................................................................16

2.4 Site Processes..........................................................................................................................16

2.4.1 Recent History of the Cascade.........................................................................................16

2.4.2 Feed Material for the Cascade .........................................................................................17

2.4.3 Atmospheric Emissions from the Cascade .......................................................................17

2.4.4 Liquid Discharge from the Facility.....................................................................................18

2.4.5 Solid Waste Generation....................................................................................................18

References ........................................................................................................................................34

Glossary ............................................................................................................................................36
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TABLE TITLE PAGE

2-1 Major facilities at PORTS............................................................................................ 19

2-2 Radionuclides of concern in Building X-333................................................................ 20

2-3 Radionuclides of concern in Building X-330................................................................ 21

2-4 Radionuclides of concern in Building X-326................................................................ 22

2-5 Radionuclides of concern for Buildings X-342 and X-342A......................................... 23

2-6 Radionuclides of concern for Building X-343 .............................................................. 24

2-7 Radionuclides of concern for Building X-344 .............................................................. 25

2-8 Radionuclides of concern in Building X-345................................................................ 26

2-9 Radionuclides of concern in Building X-700................................................................ 27

2-10 Radionuclides of concern in Building X-705................................................................ 28

2-11 Radionuclides of concern for Building X-705E............................................................ 29

2-12 Radionuclides of concern for Building X-710 .............................................................. 30

2-13 Radionuclides of concern for Building X-720 .............................................................. 31

2-14 Radionuclides of concern in Building X-744G............................................................. 32

2-15 Radionuclides of concern in Building X-770................................................................ 33

2-16 Reactor returns fed to cascade................................................................................... 33

LIST OF FIGURES

FIGURE TITLE PAGE

2-1 Portsmouth Gaseous Diffusion Plant ............................................................................ 9

2-2 Photograph of PORTS from about 1988....................................................................... 9
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ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

Ci curie

cpm counts per minute

DAC Derived Air Concentration

DOE U.S. Department of Energy

DU depleted uranium (uranium with less than 0.7% 235U)

EEOICPA Energy Employees Occupational Illness Compensation Program Act

ERP Extended Range Product

FY Fiscal Year

GDP Gaseous Diffusion Plant

HASA High Assay Sampling Area

HEU highly enriched uranium (over 20% 235U)

kg kilogram

km kilometer

LAW Low Assay Withdrawal

lb pound

MTU metric tons of uranium

MeV million electron volts

mo month

mrem millirem

NIOSH National Institute for Occupational Safety and Health

POC probability of causation

PGDP Paducah Gaseous Diffusion Plant

PORTS Portsmouth Gaseous Diffusion Plant

PPE personal protective equipment

ppm parts per million

RPM Radiation Protection Manual

RU recycled uranium

TBD technical basis document

TRU transuranic (elements with an atomic number greater than uranium i.e., <92)

UF6 uranium hexafluoride 

UF4 uranium tetrafluoride

USEC United States Enrichment Corporation

U.S.C. United States Code
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 6 of 38

yr year

α alpha radiation

β beta radiation

γ gamma radiation

§ Section
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2.1 INTRODUCTION

Technical basis documents (TBDs) and site profile documents are not official determinations made by 

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

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

dose reconstructions 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 the NIOSH staff in the completion of the individual work required for each dose 

reconstruction.

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

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

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

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

EEOICPA defines a DOE facility as “any building, structure, or premise, including the grounds upon 

which such building, structure, or premise is located ... in which operations are, or have been, 

conducted by, or on behalf of, the Department of Energy (except for buildings, structures, premises, 

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

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

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

facility encompassed by EEOICPA.

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

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

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

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

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

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

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

determined in accordance with the POC [probability of causation1

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

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

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

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

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

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

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

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

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

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

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

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

derived:

] guidelines established under 

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

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

restrict the “duty” to nuclear weapons work.

 

1 The U.S. Department of Labor is ultimately responsible under the EEOICPA for determining the POC. 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 8 of 38

• Radiation from naturally occurring radon present in conventional structures

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

2.1.1

This Site Description TBD presents a brief description of the facilities and processes that have been 

used in processing and enriching uranium. The Portsmouth Gaseous Diffusion Plant (PORTS) 

processed thousands of tons of uranium through diffusion cascades for 47 yr beginning in 1954. The 

majority of the uranium feed materials PORTS received was slightly enriched from the Paducah

Gaseous Diffusion Plant (PGDP), but some was recycled material obtained from spent reactor fuel.

Purpose

The PORTS site profile provides supporting technical data to evaluate the total PORTS 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 PORTS facilities.

2.1.2

The site description gives some general information on where some of the processes occurred and 

some details of the processes. This may include when and where the processes occurred and details 

of the product produced. 

Scope

This part of the site profile describes the site (Section 2.1), the site facilities (Section 2.2), and historic 

site processes (Section 2.3). 

2.2 SITE DESCRIPTION

PORTS is in Pike County, Ohio, approximately 112 km (70 miles) south of Columbus, Ohio. The 

Federal reservation covers approximately 3,714 acres and contains 109 buildings and individual 

plants with approximately 500 acres of roofed area. 

Uranium enrichment was the primary activity at PORTS. Uranium is a naturally occurring radioactive 

element that consists of three isotopes: 238U (99.276%), 235U (0.719%), and a trace amount of 234U 

(0.0057%) (DOE 1997, p. 20). The enrichment process increases the concentration of 235U, which is 

needed to manufacture low enriched (less than 20% 235

U) nuclear fuel necessary for commercial 

nuclear power plants and highly enriched (more than 20% 235U) material for the U.S. Navy propulsion 

program and atomic weapons. In 1952, construction began on the gaseous diffusion plant (GDP) in 

Piketon, Ohio, which later became known as the Portsmouth Gaseous Diffusion Plant. Uranium 

enrichment began in 1954 and continued until May 2001, when operations were consolidated at 

PGDP (USEC 2003). 

The historical records indicate that the plant enriched uranium for government programs and 

commercial nuclear power plants at levels ranging from a few to up to 97% 235U. In 1991, production 

of the highly enriched uranium (HEU) stopped and the plant mission changed to uranium enrichment 

for commercial reactors. From its initial construction until 1986, the site was operated by Goodyear 

Atomic Corporation. In 1986, Martin Marietta Energy Systems, Inc. took over operation of the facility 

after Goodyear decided not to take part in the rebid. The Energy Policy Act of 1992 (Public Law 102-

486) transferred responsibility for PORTS from DOE to a newly created entity, the United States 

Enrichment Corporation (USEC), which has leased and operated the facility since July 1, 1993 (USEC 

2003). 

Figures 2-1 and 2-2 show PORTS. 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 9 of 38

Figure 2-1. Portsmouth Gaseous Diffusion Plant.

Figure 2-2. Photograph of PORTS from about 1988. 
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2.3 SITE ACTIVITIES

Plant Facilities

Table 2-1 shows the major facilities at PORTS. Each of these areas was critical to the operation of 

the plant. 

2.3.1

The main process buildings at PORTS (X-326, X-330, and X-333) contain the cascades, which are a 

series of compressor, heat exchanger, control valve and motor, converter stages, and supporting 

piping arranged in stages, cells, and units that progressively increase the concentration of the 235U 

isotope in the uranium hexafluoride (UF6) feed. 

Gaseous Diffusion Cells – Buildings X-326, X-330, and X-333

Enrichment occurs as the UF6 passes through semiporous barriers in the converter stage. These 

barriers allow the lighter 235U to pass through more easily, which results in a gas with a slightly higher 

percentage of 235U (enriched) on one side of the barrier and a slightly lower percentage (depleted) on 

the other side. The enriched UF6 gas flows up towards the top of the cascade while the depleted UF6

gas flows toward the bottom. 

An individual converter stage enriches the UF6 gas stream approximately 0.0043%. The PORTS 

cascade consists of 4,080 stages in the three process buildings. The facility was able to enrich 

uranium to nearly 100% 235U. 

2.3.1.1 Building X-333

The initial enrichment process occurred in Building X-333. It is equipped with 80 enrichment cells, 

each of which has eight isotopic stages, for a total of 640 stages. All cells contain the largest-size 

converter in the system (designated X-33 or 000). As with all the cascade buildings, the enrichment 

stages are installed on the second floor with the auxiliary systems and control rooms on the ground 

floor. The two floors provide approximately 65 acres of floor space. Reactor-grade material can be 

drawn off through the Low Assay Withdrawal (LAW) station in the west-central section of the building 

(DOE 2000a, p. 17). Table 2-2 shows the radionuclides of concern associated with Building X-333. 

(Note: For readability, all tables in this TBD are at the end of the text.)

X-333 Internal Dose Issues: Most uptakes of uranium indicate a fast absorption type unless otherwise 

identified in the bioassay records. Because the concentration of both the 235U and 234U are increased 

by the enrichment process, and the 234U has a shorter half-life than the 235U, most of the annual 

internal dose will be from 234U.

X-333 External Dose Issues

2.3.1.2 Building X-330

: There is a potential for exposure to 99Tc when conducting maintenance 

of cascades due to plating out within the system. Because Building X-333 is used as a backup to the 

X-330 tails facility, depleted uranium (DU) may concentrate in this facility (see Section 2.3.1.2) (Hill

and Strom 1993, p. 16.6). The secular equilibrium pair 234Th/234mPa is an external skin dose hazard if 

no personal protective equipment (PPE; e.g., gloves, coveralls, or full-face respirators) is used. A 

2,000-cpm limit to the skin amounting to about 20 mrem of skin exposure was used as a screening 

action limit (HP-103, p.1-RPM).

The X-330 process building carried out the intermediate stages of the enrichment process. It is 

equipped with 1,100 stages. Five hundred stages (50 cells) have the X-31 or 00-size equipment, 600 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 11 of 38

stages (60 cells) are equipped with X-29 or 0-size converters. The two floors provide a total of 

55 acres of floor space. The original tails withdrawal station is in the northeast corner of the building. 

It has been modified to allow the withdrawal of product as well as tails (DOE 2000a, p. 18). Table 2-3 

identifies the radionuclides of concern for Building X-330.

X-330 Internal Dose Issues: Most uptakes of uranium indicate a fast absorption type unless otherwise 

indicated in the bioassay records. Most of the annual internal dose will be from 234U.

X-330 External Dose Issues

2.3.1.3 Building X-326

: There is a potential for exposure to 99Tc during maintenance of 

cascades due to plating out within the system. Due to the tails or DU concentrating in this facility, the 

234Th/234mPa secular equilibrium pair fed by 238U could be an external dose issue. That pair is an 

external skin dose hazard if no PPE is used. A 2,000-cpm limit to the skin amounting to about 

20 mrem of skin exposure was used as a screening action limit (HP-103, p. 1-RPM). 

The PORTS cascade is able to enrich uranium to more than 97% 235U. The X-326 building is the final 

and highest stage enrichment cascade. The building is equipped with 2,340 stages, 720 stages (60 

cells) with X-27 size equipment and 1,620 stages, including the purge stages, with X-25 size 

equipment. The two floors have a total of 58 acres of floor space. A withdrawal station is in the 

southwest corner of the ground floor, it is designed to withdraw the HEU product (BJC 2000, p. 20). 

The purge facilities are in the south end of the X-326 building. They were used to vent light 

contaminants in the UF6 stream before the flow entered the high assay enrichment equipment. The 

purge systems vented entrapped air, Freon, and such lightweight isotopes as 99Tc from the UF6

stream. Because of its low atomic weight and relative volatility, technetium tends to concentrate at 

the top of the gaseous diffusion cascade, where it becomes an inhalation, ingestion, and effluent 

concern when the cascade is vented or opened for maintenance. Technetium as pertechnetate 

(TcO4) is also difficult to remove from skin and can therefore cause significant skin dose from 

contamination. Detection and classification of technetium exposure is difficult because its low-energy 

beta (maximum 0.293 MeV) is often masked by the higher energy (maximum 2.29 MeV) beta from 

234mPa (DOE 2000b, p. 2-16). 

Facilities in Building X-326 include the Extended Range Product (ERP) Station, the High Assay 

Sampling Area (HASA), the Top Product Withdrawal Station, mobile side withdrawals, side feeds, and 

light gas purge stages. Radiochemicals including UF6, U3O8, and uranyl fluoride (UO2F2) are likely to 

be present in these facilities (Hill and Strom 1993, p.14.7). In addition, contaminated waste is 

currently stored in the X-326 L Cages under special security requirements. Table 2-4 identifies the 

radionuclides of concern in Building X-326.

X-326 Internal Dose Issues: As in the other cascade buildings, most uptakes of uranium indicate a 

fast absorption type unless otherwise documented in the bioassay records. Most of the annual 

internal dose will be from 234U. In addition, Table 2-4 shows time and sources for processing of HEU. 

Intake of 99Tc should be considered during maintenance of cascades due to plating out within the 

system or in the maintenance of the purge equipment. Technetium-99 was a significant 

environmental release radionuclide from 1975 to 1994. 

X-326 External Dose Issues: Consider exposure to 99Tc from maintenance of cascades due to plating 

out within the system. During times of processing HEU, neutron radiation may have been present in 

higher than average amounts due to the alpha–neutron reaction on fluorine (75 mrem yr-1) (Cardarelli 

1997;p. 8). 
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In general, all the process building work areas were physically hot, but normally clean and 

uncontaminated, except when equipment was opened for repair, maintenance, or modifications. 

Multiple small “puff” or “jet” releases of UF6 occurred during connection and disconnection of feed and 

product storage cylinders or from broken instrument lines or connection piping. In general, PPE was 

used only for specific maintenance activities and not during the connection or disconnection of 

cylinders. The majority of contamination and personnel exposure to UF6 and hydrogen fluoride (HF) 

gas in the process buildings occurred during cylinder moves (DOE 2000a, p. 18). 

2.3.2

The X-342 facility contains equipment to vaporize and sample UF6 before feeding it to the cascades 

and to generate pure fluorine gas (F2) for the uranium recovery operations. Fluorine is generated by 

the electrolytic conversion of hydrogen fluoride, which also produces sodium fluoride, lithium fluoride, 

and potassium fluoride as waste products. While chemically hazardous, the fluorine generation 

operation presented little or no radiological hazard to the workers. Table 2-5 identifies the 

radionuclides of concern for Building X-342 and the Fixed Feed Facility in Building X-342A. 

Fluorine Generation Facility and Fixed Feed Facility – Buildings X-342 and X-342A

X-342 and X-342A Internal Dose Issues: Vaporization of UF6 from transport cylinders would allow for 

the uptake of uranium as a fast absorption type unless otherwise documented in the bioassay 

records. Most of the annual internal dose will be from 234U. In addition, Table 2-5 shows time and 

sources for processing of feed materials. 

X-342 and X-342A External Dose Issues

2.3.3

: Ambient gamma, beta, and neutron radiation may be of 

concern in this area. 

At first, UF6 feed and product material could be input or withdrawn from the cascades at virtually any 

point. Later, fixed feed facilities were installed in Buildings X-342A and X-343 using autoclaves to 

heat the cylinders and feed UF6 gas into the cascade. The mobile input and withdraw facilities have 

not been used since 1991. Contamination and exposure in the fixed feed facility was more chemical 

than radiological in nature and occurred during cylinder connection and disconnections. Table 2-6 

shows the radionuclides of concern in Building X-343, and Table 2-5 shows the radionuclides of 

concern in Buildings X-342A and X-342. 

Fixed Feed Facility – Building X-343

X-343 Internal Dose Issues: As in Building X-342, uranium uptake should be considered as a fast 

absorption issue unless otherwise documented in bioassay records. Most of the annual internal dose 

will be from 234U. 

X-343 External Dose Issues

2.3.4

: Ambient gamma, beta, and neutron radiation may be of concern in this 

area. 

Uranium tetrafluoride (UF4; green salt) was converted to UF6 in the X-344 Feed Manufacturing Plant. 

The UF4 feedstock used in Building X-344 was of normal enrichment from either Mallinckrodt 

Chemical Works or National Lead of Ohio (Fernald). According to plant records, none of the UF4

contained recycled uranium (RU) (BJC 2000, p. 42). The plant used direct fluorination tower reactors 

to convert UF4 to UF6 before feeding it into the cascade. The Feed Manufacturing Plant operated 

from May 1958 until February 1962, producing a total of 11,890 MTU of UF6 feed for the cascade 

(BJC 2000, p. 36). 

Feed Manufacturing Plant – Building X-344
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The direct fluorination towers operated by dropping powdered green salt through a rising column of 

hot elemental fluorine gas (F2). The resultant UF6 gas was drawn off, filtered, condensed, and 

transferred to storage cylinders to be fed into the cascade. Excess F2 was recovered and unreacted 

material (ash) was collected and re-fed to the tower. Working conditions in the area were harsh. 

During operation, the area around the towers was hot and noisy and the air was filled with dust and 

smoke. Because fluorine is such an extremely reactive gas, the towers were high-maintenance items 

that required constant repair and upkeep. 

In the mid-1950s, PORTS evaluated the seriousness of contamination in work areas by calculating a 

“Contamination Index” based on the level of contamination and square footage of the work area. A 

three-tiered approach categorized work areas as Red, Orange, or Clean. An index of greater than 75 

was designated a “Red Job” assignment, an index of 10 to 75 was considered “Orange,” and anything 

less than 10 was considered “Clean.” The specific formula used for determining the contamination 

index was not available; however, Building X-344 was designated a permanent Red job assignment in 

1955, and employees were furnished company-issued undergarments, coveralls, head covers, and 

shoe covers or shoes. Showering was also a postjob requirement for any Red job assignments. 

Despite these formal controls, inspection reports and appraisals indicate that the requirements were 

not enforced and that adherence was inconsistent (DOE 2000a, p. 40). 

Building X-344 houses the feed autoclaves for natural assay as well as the sampling facility for large 

UF6 cylinders. Radiochemicals including UF6, U3O8, and UO2F2 were likely sources for both internal 

and external exposure. 

Uranium recovery material from Building X-705 was transferred to Building X-344 in the form of UO2F2

to blend with the UF4 steam. Although no direct use of RU occurred in Building X-344, recovered 

uranium from Building X-705 may have contained transuranic (TRU) isotopes from the small quantity 

of RU processed by PORTS. Additionally, because purge gas from the cascades was processed in 

Building X-344, 99Tc could have been present (DOE 2000a, p. 95). Facilities in this building include 

feed autoclaves for natural assay. Sampling of large UF6 cylinders also occurred here (Hill and Strom 

1993, p. 16.6). Table 2-7 shows the nuclides of concern for Building X-344. 

X-344 Internal Dose Issues: Uranium intakes indicate type S for these facilities; see the Internal Dose 

section of this TBD for further information. 

X-344 External Dose Issues

2.3.5

: Exposure to 99Tc is a potential from maintenance of cascades due to 

plating out within the system. Fluorination towers were 100 mR/hr on contact during normal 

operations and 50 mR/hr at 12 in. High beta fields are possible due to accumulation of progeny. Ash 

tower spills of 6 R/hr beta/0.7 R/hr gamma at contact are an issue. This exposure rate could have 

occurred during clearing of ash plugs from the towers (DOE 2000a, p. 45). 

The vaults on the north and south sides of Building X-345 store or stored HEU. The central area 

houses a HASA and a small laboratory. The entire building has been designated as having fixed 

radiological contamination (Yggdrasil Institute 2003). DOE describes the sampling facility as a source 

of fluoride and uranium emissions (DOE 2000a, p. 43). Table 2-8 identifies the radionuclides of 

concern for Building X-345. 

Special Nuclear Materials Storage – Building X-345

Due to its high atomic weight, and because 230Th is a decay product of 234U, it tends to concentrate 

with the highly enriched 235U stored in Building X-345. This makes the alpha-emitting 230Th an 

inhalation hazard for workers in the area. The U.S. Nuclear Regulatory Commission has given 230Th a 
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lung clearance classification of S (slow), which is equivalent to the Federal Guidance Report No. 11 

class Y (years) (NRC 1992, p. 2). 

X-345 Internal Dose Issues: Most uptakes of uranium indicate a fast absorption type unless otherwise 

indicated in the bioassay records. Note that both 230Th and 234U should be considered as predominant 

radionuclides.

X-345 External Dose Issues

2.3.6

: Ambient gamma and neutron radiation are of concern.

The building is used for equipment maintenance support for nonradioactive or low-level radioactively 

contaminated equipment from the diffusion cascade. It houses the Chemical Cleaning and 

Operations, the Converter/Weld Shop, and the Radiation Calibration Laboratory. The Calibration 

Laboratory housed sealed sources of 137Cs, 226Ra, and an X-ray machine for component repair 

inspections. It operated as long as the cascades were in use. The major use of the Barrier Shop was 

final assembly and repair of converters. The Converter Shop performed welding operations on the 

converters. Contaminated equipment could be repaired in the maintenance areas of the shops. 

Radiochemicals such as UF6, U3O8, and UO2F2 are likely, as well as hazardous chemicals such as 

hydrogen fluoride, trichloroethylene, other solvents; polychlorinated biphenyl-contaminated oils, 

welding gases, mercury, and toxic metals (Hill and Strom 1993, p. 16.7). Work techniques and 

procedure requirements for the use and availability of PPE improved through the years, but a lack of 

compliance and enforcement was a recurring problem (DOE 2000a, p. 28). Table 2-9 identifies the 

radionuclides of concern in Building X-700. 

Maintenance – Building X-700

X-700 Internal Dose Issues: Most uptakes of uranium indicate a S absorption type unless otherwise 

indicated in the bioassay records. 

X-700 External Dose Issues

2.3.7

: Technetium-99 deposits along with TRU elements and uranium progeny 

were likely present, as well as ambient gamma and neutron radiation. 

The uranium recovery facility recovered approximately 38.2 MTU of triuranium octoxide (U3O8) during 

its period of operation (1958 to 2001). Although the facility underwent many safety and process 

improvements, the basic operation remained unchanged. Uranium-bearing solutions, scrap, and 

waste materials were dissolved and chemically treated to extract the uranium. The uranium-bearing 

slurry was kiln-dried to form U3O8, which was sent to the oxide conversion plant in Building X-705E for 

conversion to UF6 for cascade feed. A very small percentage of impurities and radioactive isotopes 

traveled with the U3O8 and concentrated in the ash from the oxide converter. Most impurities and 

metals remained in solution and concentrated in the sludge of the X-701B settling pond or in the 

precipitate of the heavy metals recovery operation (BJC 2000, pp. 36-39). Contaminants in Building 

X-705 such as UF6, UO2F2 (fine dust), uranyl nitrate, and U3O8 (from calciners) are likely. TRU 

elements such as 237Np, 238Pu, 239Pu, 240Pu, and 241Am were present from flame tower ash and the 

MgF2 traps from the oxide conversion facility (Building X-705E) (Hill and Strom 1993, p. 16.8). 

Table 2-10 identifies the radionuclides of concern for Building X-705. 

Decontamination, Cleaning, and Recovery – Building X-705

X-705 Internal Dose Issues: Uranium intakes indicate class S for these facilities; see ORAUT (2004,

2005) for additional information. All TRU elements along with 99Tc are of concern in this area. 

Uranium-bearing solutions, scrap, and waste materials were dissolved and chemically treated to 

extract uranium. A flame tower operated in the facility from 1958 to 1965. Although an Oak Ridge 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 15 of 38

National Laboratories report indicated potential internal exposures to insoluble and enriched oxides, 

monitoring at the time was not adequate (DOE 2000a, p. 46). In vivo monitoring (lung counting) for 

insoluble uranium and 237Np began in 1965. 

X-705 External Dose Issues

2.3.8

: Ambient gamma, beta, and neutron radiation may be of concern in this 

area.

The Oxide Conversion Facility in Building X-705E provided the capability to generate UF6 directly from 

uranium oxide (U3O8). The first conversion process used screw-fed, stirred-bed reactors that proved 

difficult to maintain and had inadequate production capabilities. They were replaced in 1959 with a 

direct fluorination flame tower, which was improved and enlarged in 1967. The enlarged conversion 

facility operated until 1978. In sum, the Oxide Conversion Facility operated from 1957 to 1978 and 

produced about 233 MTU of UF6 (DOE 2000a, p. 18). Operation of the Oxide Conversion Facility 

required continual maintenance and repair. The system was beset with airborne uranium 

contamination, burn-through of the fluorination towers, leakage from the cold traps and product 

withdrawals, and system breaches (DOE 2000a, p. 20). Table 2-11 shows the radionuclides of 

concern for Building X-705E. 

Oxide Conversion Facility – Building X-705E

X-705E Internal Dose Issues: Uranium intakes indicate class S for these facilities. All TRU elements 

along with 99Tc are of concern in this area. Permissible air levels were exceeded during handing of 

oxide powders, changing the tower feed screw, connecting and disconnecting pigtails, and performing 

maintenance on cold traps plugged with foreign materials (DOE 2000a, p. 46). In vivo monitoring for 

insoluble uranium and 237Np began in 1965. 

X-705E External Dose Issues

2.3.9

: Ambient gamma, beta, and neutron radiation may be of concern in this 

area.

The facilities in this area include electrical substations, special analytical laboratories, and process 

and materials technology areas. Sealed radioactive sources containing 22Na, 99Tc, 252Cf (40.2 mCi – 

1999), 133Ba, or 137Cs were used for instrument calibration and may be found in the instrument 

technology area. A small radiographic room was used to test welds, small valves, sample containers, 

and other components for internal soundness and integrity. The presence of UF6, UO3, and UO2F2

along with TRU elements is also likely due to the handling of enriched product (Hill and Strom 1993, 

p. 16.10). Table 2-12 shows the radionuclides of concern for Building X-710. 

Analytical Labs, Process and Materials – Building X-710

X-710 Internal Dose Issues: Most uptakes of uranium should be considered a fast absorption type 

unless otherwise documented in the bioassay records. 

X-710 External Dose Issues

2.3.10

: Ambient gamma, X-ray, beta, and neutron radiation may be of concern 

in this area. Calibration sources including 22Na, 99Tc, 133Ba, 137Cs, or 252Cf were used for instrument 

calibrations. 

Each cell in the cascade contained a compressor, heat exchanger, and converter. The compressor 

shop was a precision machine shop where compressors could be disassembled, decontaminated, 

repaired, and modified. The concrete pad outside the compressor shop served as an outdoor 

Compressor Shop – Building X-720
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 16 of 38

cleaning and decontaminating area for compressors and other large equipment from the cascades. 

Steam, high-pressure water, degreasers, and chemical solvents were sprayed to clean and 

decontaminate the equipment before moving it into the shop. Runoff from the cleaning pad entered 

the storm drain system. Table 2-13 shows the radionuclides of concern for Building X-720. 

X-720 Internal Dose Issues: Most uptakes of uranium indicate a fast absorption type unless otherwise 

indicated in the bioassay records. 

X-720 External Dose Issues

2.3.11

: Ambient gamma and beta radiation may be of concern in this area. 

Facilities include an aluminum smelter to extract aluminum from process equipment. Waste and 

scrap was stored pending offsite disposal. Uranium in the form of UF6, UO3, and UO2F2 along with 

TRU elements are expected (Hill and Strom 1993, p. 16.9; DOE 2000a, p. 52). Table 2-14 shows the 

radionuclides of concern for Building X-744G. 

Aluminum Smelter and Recovery – Building X-744G

X-744G Internal Dose Issues: Most uptakes of uranium indicate a fast absorption type unless 

otherwise indicated in the bioassay records. 

X-744G External Dose Issues

2.3.12

: Ambient gamma and neutron radiation may be of concern in this area.

Facilities included test loop equipment that may have been involved in the development of the 

cascade equipment. In the early 1980s for about 3 yr the facility was used as a guard training center. 

(SPFPA 2005) There have been many pieces of equipment that had been used in processing that 

were stored in the facility. This included process pipes, instrument lines, pumps, and other equipment 

associated with the test loops. Contamination surveys have indicated low removable α contamination 

levels of less than 100 dpm/ 100 cm2. However, fixed contamination levels of greater than 500,000 

dpm/100 cm2 have been reported. This was associated with an external β/γ radiation level of about 

0.02 mrem/hr (USWA 2005). 

Test Loop Facility – Building X-770

The amount of uranium present in the stored equipment in Building 770 was estimated in 2002 as 

approximately 0.1 Ci of total uranium. The percent enrichment could have varied. A total of 759 g of 

235U was estimated (DOE 2002). Table 2-15 shows the radionuclides of concern for Building X-770.

X-770 Internal Dose Issues: Most uptakes of uranium indicate a fast absorption type unless otherwise 

indicated in the bioassay records. TRU materials were also potentially present (DOE 2002; UF6 and 

UO2F2 and TRU). 

X-770 External Dose Issues

2.4 SITE PROCESSES

: Ambient gamma, beta, and neutron radiation may be of concern in this 

area.

2.4.1

Production of HEU ended in 1991 when 1,680 cascade stages were retired in place. They were 

cleaned of large deposits and mothballed between fiscal year (FY) 1993 and FY 1998. A total of 240 

Recent History of the Cascade
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X-27 and 180 X-25 cascade stages remained in operation through 2001; they were used for product 

withdrawal and side feeding. 

All enrichment operations were halted in 2001 when USEC transferred enrichment operations to 

PGDP. Operating equipment was cleaned of gross contamination and large deposits before being 

placed in dry storage. 

From 1997 to mid-1998, the active stages in Building X-326 were used to down-blend 14 MTU of HEU 

stored on site. The HEU-UF6 in storage was diluted as part of a Memorandum of Understanding 

between DOE and USEC. Other uranium-bearing materials with greater than 20% enrichment were 

shipped off site (BJC 2000, p. 24). 

A fire on December 9, 1998, destroyed one and damaged two other cells in the purge cascade in 

Building X-326. The accident investigation team hypothesized that a loss of cooling to aluminum 

process equipment caused the fire. The equipment became so hot that an aluminum–uranium 

hexafluoride reaction (which is highly exothermic) took place. The fire released an undetermined 

quantity of radiological materials (NRC 1999). 

2.4.2

During operations, more than 330,000 MTU of UF6 passed through the PORTS cascades (BJC 2000, 

p. 22). The major sources of feed material were PGDP and the K-25 plant at Oak Ridge. The feed 

manufacturing plant in Building X-344 and Oxide Conversion Plant in Building X-705 produced a small 

percentage of the UF6 feed stock and some UF6 was received directly from commercial sources. 

Feed Material for the Cascade

Of the 330,000 MTU fed to the PORTS cascade, 1,094.66 MTU contained RU from spent nuclear fuel 

(BJC 2000, p. 22). The RU came from many sources over many years of operation. Table 2-16 

shows the source and quantity of reactor returns fed to the cascade. 

RU was first fed to the cascade during startup in 1955 when UF6 feed was manufactured at PGDP 

from UO3 received from Hanford and Savannah River Site reactor tails. In addition, the normal PGDP 

feed material contained an estimated 1-ppm 99Tc contamination. The UO3 from the Savannah River 

and Hanford Site canyon systems were contaminated before 1967 with 237Np, plutonium, and 99Tc at 

an estimated 0.18 ppm, 0.4 ppm, and 6.65 ppm, respectively, and after 1967 at 0.068 ppm, 

0.021 ppm, and 6.65 ppm, respectively (BJC 2000, p. 19). 

2.4.3

Cascade operation released a variety of contaminants to the air. Chief among them were uranium, 

fluorine, fluorides, and Freon. A May 2000 DOE report identifies the following contaminants released 

through the top and side purge cascades in Building X-326: uranium, 99Tc, HF, F2, chlorine, SO4, 

SO2F2, Freon 114, ClF4, and CF4 (DOE 2000c). Uranium and technetium were the major release 

elements from the cold recovery and wet air evacuation systems in Buildings X-330 and X-333 (DOE 

2000a, p. 72). 

Atmospheric Emissions from the Cascade

Because of the lack of air sampling data, the full quantity of uranium, fluorine, and other atmospheric 

discharges from the cascade operation cannot be known. In addition, the design of PORTS facilitated 

accidental or intentional venting through unregulated and unmonitored outlets. One source estimates 

that 20 to 30 tons of fluorine were vented annually during operation of the facility (DOE 2000a, p. 72). 

While fluorine releases may have some correlation with uranium releases because airborne UF6

hydrolyzes with atmospheric water to form hydrogen fluoride, UO3, and U3O8, , a close correlation is 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 18 of 38

not possible because the plant design required the use of free fluorine and fluoride compounds, which 

were vented to the atmosphere. It is, therefore, impossible to estimate the radiological impacts 

resulting from the release of 20 to 30 tons of fluorine. 

PORTS did not perform continuous vent monitoring of radionuclides or fluorides until the middle of the 

1980s. Grab samples and some space recorders were used to estimate the quantity of released 

materials, but the unreliability of space recorders and inaccuracy of grab sampling when compared to 

continuous monitoring systems indicate that emissions may have been underestimated. Accidents 

and deliberate events resulted in several large atmospheric releases at the facility. A cylinder rupture 

in 1978 vented more than 6,000 kg (13,000 lb) of UF6 inside the fixed feed facility. In 1985, operators 

released over 50 kg (110 lb) of uranium into the atmosphere from Building X-333 when the wet traps 

overloaded and operators ignored alarms (BJC 2000, pp. 20-27). 

2.4.4

Liquid effluents from PORTS contributed a large portion of total emissions from the facility. Water and 

degreasing solvents from the decontamination facilities were sent to the X-701B holding pond at rates 

as high as 500,000 gal/mo until the pond was closed in 1988. An active uranium recovery program in 

Building X-705 used nitric acid to dissolve uranium-bearing solids and produce U3O8 feed for the 

oxide converters. Effluents from the uranium recovery operation and decontamination activities were 

routed to the X-701B holding pond, which drained through a small stream to the Scioto River. 

Liquid Discharge from the Facility

During FY 1975, sludge sample from the bottom of the X-701B holding pond showed concentrations 

of 99Tc, uranium, plutonium, neptunium, and various heavy metals. It was estimated that 1,415 g of 

99Tc as well as 0.03 g of plutonium and 3.3 g of neptunium were present in the sludge (BJC 2000, 

pp. 32-36). Once or twice each year the pond was dredged and the sludge was dumped in 

containment ponds on either side of X-701B to dry before being shipped off the site. Airborne 

exposure could have occurred during the drying and handling operations. 

2.4.5

The PORTS facility had a continuing program to recover as much uranium as possible from all scrap 

materials. A strict Go/No-Go criterion was used to evaluate all solid and liquid waste products; all 

material with sufficient uranium content was sent to the uranium recovery operation in Building X-705. 

Filter media, incinerator ash, magnesium fluoride traps, and scrap metals with recoverable uranium 

went through a solvent extraction process that involved dissolving the uranium (and other metals) in 

nitric acid and then separating the uranium by solvent extraction and drying. The dried U3O8 was fed 

to the oxide converters where it was converted to UF6 and fed to the cascades (DOE 2000a, 

pp. 18-20; BJC 2000, pp. 35-37). 

Solid Waste Generation

Oxide conversion work in X-705 presented the most hazardous radiological and chemical exposures 

to PORTS workers. The original plant design was inefficient and generated large quantities of 

airborne and surface contamination from the manual handling of uranium powder. A design change in 

1965 installed additional gloveboxes and automated controls to grind the U3O8 into a fine powder and 

feed it to the fluorination towers. However, leaks and equipment maintenance problems still 

generated large uranium contamination and exposure problems for the workers. 

Early exposure levels were so high that, in 1965, two oxide conversion workers were found to have 

high enough insoluble uranium lung burdens that they were put on permanent restricted duty. One 

worker still had significant lung burden when he retired in 1985 (DOE 2000a, p. 18). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 19 of 38

Table 2-1. Major facilities at PORTS. 

Building 

No. Name Dates of 

Operation Activities

X-326 Gaseous Diffusion Process Building 1954–1991 High Assay Product 

X-330 Gaseous Diffusion Process Building 1954–2001 Intermediate process and tails withdrawal

X-333 Gaseous Diffusion Process Building 1954–2001 Initial enrichment and reactor product

X-342A Fixed Feed Facility 1954–2001 Feed UF6 to Process line

X-342 Fluorine Generation Facility 1954–2001 Generate elemental F2 for converters

X-343 Fixed Feed Facility 1954–2001 Feed UF6 to Process line

X-344 UF6 Feed Manufacturing Plant 1958–1962 Conversion of UF4 to UF6

X-345 Special Nuclear Material Storage 1978–2003 Highly enriched uranium storage

X-700 Maintenance Building 1954–2003 Large component repairs

X-705 Decontamination & Cleaning Building 1954–2003 Equipment wash & uranium recovery

X-705E Oxide Conversion Plant 1957–1978 Convert U3O8 to UF6

X-710 Labs, Electrical and I&C Shops 1954–2003 Testing, calibration, and repair

X-720 Compressor Shop 1954–2003 Disassembly and repair of compressors

X-744G Smelter and Aluminum Recovery 1954–1978 Recover aluminum from scrap

(Source: DOE 2000c, p. 16)
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 20 of 38

Table 2-2. Radionuclides of concern in Building X-333. 

Facility/Process: X-333 LAW Area

Years of operation: 1954 – 2001

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 5.03E-1 

U-235 F F-S 2.83E-2 

U-236 F F-S 1.74E-3 

U-238 F F-S 4.67E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 6.81E-5

Pu-238c S M-S 4.29E-5 X 

Pu-239c S M-S 4.29E-5 X 

Pu-240c S M-S 4.29E-5 X 

Am-241c S M-S 4.29E-5 X 

Th-228 S F-S 4.42E-5 

Th-230 S F-S 8.23E-5 

Th-231 S F-S Trace

Th-232 S F-S 1.04E-5 

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with 

234-Th)

X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their derived air concentration (DAC) on conservative modes (Radiation 

Protection Manual (RPM,) p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 21 of 38

Table 2-3. Radionuclides of concern in Building X-330. 

Facility/Process: X-330 process facilities and tails withdrawal

Years of operation: 1954 – 2001

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 7.44E-1 

U-235 F F-S 3.33E-2 

U-236 F F-S 2.46E-3 

U-238 F F-S 2.20E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 8.22E-5 

Pu-238c S M-S 1.03E-5 X 

Pu-239c S M-S 1.03E-5 X 

Pu-240c S M-S 1.03E-5 X 

Am-241c S M-S 1.03E-5 X 

Th-228 S F-S 1.51E-5 

Th-230 S F-S 8.36E-5 

Th-231 S F-S Trace

Th-232 S F-S 1.66E-5 

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with 

Th-234) 

X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their derived air concentration (DAC) on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 22 of 38

Table 2-4. Radionuclides of concern in Building X-326. 

Facility/Process: X-326 process facilities and ERP, HASA and PW

Years of operation: 1954 – 2001 (1991 for HASA)

Radionuclides 

of concern

Most probable 

absorption type 

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234c F F-S 9.12E-01

U-235c F F-S 3.16E-02

U-236c F F-S 2.64E-03

U-238c F F-S 5.33E-02 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 9.58E-05

Pu-238d S M-S 1.79E-05 X 

Pu-239d S M-S 1.79E-05 X 

Pu-240d S M-S 1.79E-05 X 

Am-241d S M-S 1.79E-05 X 

Th-228 S F-S 1.15E-04

Th-230 S F-S 3.47E-04

Th-231 S F-S Trace

Th-232 S F-S 3.6 ×E-06

Th-234 M F-S Trace X 

Pa-234m M M-S (In equilibrium with 234Th) X 

a. Always use bioassay information to determine absorption class, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern. 

c. UF6 and UO2F2 are considered type F materials (Hill and Strom 1993. p. 14.7). U3O8 is considered type S 

(Hill and Strom 1993, p. 14.7). Most material should be UF6 feed. Most bioassay results indicate that 

uranium acts as a type F material (Hill and Strom 1993, p. 14.5). To be favorable to claimants, assume 

type S unless otherwise indicated in the bioassay records.

d. Americium and plutonium not distinguished in analysis.
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Table 2-5. Radionuclides of concern for Buildings X-342 and X-342A. 

Facility/Process: X-342 Fluorine Generation Facility and X-342A Fixed Feed Facility

Years of operation: 1954 – 2001

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 8.46E-1 

U-235 F F-S 3.48E-2 

U-236 F F-S 4.69E-3 

U-238 F F-S 1.14E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 3.3E-4 

Pu-238c S M-S 1.33E-5 X 

Pu-239c S M-S 1.33E-5 X 

Pu-240c S M-S 1.33E-5 X 

Am-241c S M-S 1.33E-5 X 

Th-228 S F-S 1.05E-4 

Th-230 S F-S 1.06E-4 

Th-231 S F-S Trace

Th-232 S F-S Trace

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 24 of 38

Table 2-6. Radionuclides of concern for Building X-343. 

Facility/Process: X-343 Fixed Feed Facility

Years of operation: 1954 – 2001

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 8.0E-1 

U-235 F F-S 3.45E-2 

U-236 F F-S 2.31E-3 

U-238 F F-S 1.57E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 8.78E-5 

Pu-238c S M-S 6.26E-5 X 

Pu-239c S M-S 6.26E-5 X 

Pu-240c S M-S 6.26E-5 X 

Am-241c S M-S 6.26E-5 X 

Th-228 S F-S 2.49E-5 

Th-230 S F-S 1.95E-4 

Th-231 S F-S Trace

Th-232 S F-S Trace

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with

Th-234) 

X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 25 of 38

Table 2-7. Radionuclides of concern for Building X-344. 

Facility/Process: X-344 UF4 conversion to UF6 conversion facility Cylinder Transferring and Transfer Facility

Years of operation: 1958 – 1962 and 1962 – 2001

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 Sc F-S 7.44E-1 

U-235 Sc F-S 3.20E-2 

U-236 Sc F-S 4.9E-4 

U-238 Sc F-S 2.23E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 2.37E-5 

Pu-238d S M-S 3.48E-6 X 

Pu-239d S M-S 3.48E-6 X 

Pu-240d S M-S 3.48E-6 X 

Am-241d S M-S 3.48E-6 X 

Th-228 S F-S 9.95E-6 

Th-230 S F-S 1.42E-4 

Th-231 S F-S Trace

Th-232 S F-S Trace

Th-234e M F-S Trace X 

Pa-234me M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Absorption type for this facility has indicated class S in many bioassay results. 

d Americium and plutonium not distinguished in analysis.

e Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 26 of 38

Table 2-8. Radionuclides of concern in Building X-345. 

Facility/Process: X-345 SNM Storage Area – HEU storage

Years of operation: 1954 – 2003

Radionuclides 

of concern

Most probable 

absorption type

Absorption Type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 9.78E-1 

U-235 F F-S 1.68E-2 

U-236 F F-S 1.19E-3 

U-238 F F-S 2.16E-3 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 2.04E-3 

Pu-238c S M-S Trace X 

Pu-239c S M-S Trace X 

Pu-240c S M-S Trace X 

Am-241c S M-S Trace X 

Th-228 S F-S Trace

Th-230d S F-S 1.2E-1 

Th-231 S F-S Trace

Th-232 S F-S Trace

Th-234e M F-S Trace X 

Pa-234me M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-230 is a significant inhalation hazard in this building; see Section 2.3.5.

e. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 27 of 38

Table 2-9. Radionuclides of concern in Building X-700. 

Facility/Process: Converter Shop and Cleaning Area

Years of operation: 1954 – 2003

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 Sc F-S 5.97E-1 

U-235 Sc F-S 3.14E-2 

U-236 Sc F-S 2.55E-3 

U-238 Sc F-S 3.64E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 1.37E-3 

Pu-238d S M-S 5.24E-5 X 

Pu-239d S M-S 5.24E-5 X 

Pu-240d S M-S 5.24E-5 X 

Am-241d S M-S 5.24E-5 X 

Th-228 S F-S 3.74E-4 

Th-230 S F-S 3.17E-3 

Th-231 S F-S Trace

Th-232 S F-S 3.23E-4 

Th-234e M F-S Trace X 

Pa-234me M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Absorption type for this facility has indicated class S in many bioassay results. 

d. Americium and plutonium not distinguished in analysis.

e. Thorium-234/Pa-234m are found in equilibrium and are type M for GDPs. Technetium-99 is type F for 

GDPs that based their DAC on the more conservative modes (RPM, p. 15).
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Table 2-10. Radionuclides of concern in Building X-705. 

Facility/Process: X-705 Decontamination and Recovery

Years of operation: 1954 – present

Radionuclides 

of concern

Most probable 

absorption type

Absorption Type 

rangea Activity fraction

Significant to 

external exposureb

U-234 Sc F-S 8.87E-1 

U-235 Sc F-S 3.43E-2 

U-236 Sc F-S 1.86E-2 

U-238 Sc F-S 5.88E-2 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 1.60E-4 

Pu-238d S M-S 8.79E-5 X 

Pu-239d S M-S 8.79E-5 X 

Pu-240d S M-S 8.79E-5 X 

Am-241d S M-S 8.79E-5 X 

Th-228 S F-S 1.30E-4 

Th-230 S F-S 6.66E-4 

Th-231 S F-S Trace

Th-232 S F-S 3.37E-5 

Th-234e M F-S Trace X 

Pa-234me M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Absorption type for this facility has indicated class S in many bioassay results. 

d. Americium and plutonium not distinguished in analysis.

e. Thorium-234/Pa-234m are found in equilibrium and are type M for GDPs. Technetium-99 is type F for 

GDPs that based their DAC on the more conservative modes (RPM, p. 15).
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 29 of 38

Table 2-11. Radionuclides of concern for Building X-705E. 

Facility/Process: X-705E Oxide Conversion

Years of operation: 1957 – 1978

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 Sc F-S 8.87E-1 

U-235 Sc F-S 3.43E-2 

U-236 Sc F-S 1.86E-2 

U-238 Sc F-S 5.88E-2 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 1.60E-4 

Pu-238d S M-S 8.79E-5 X 

Pu-239d S M-S 8.79E-5 X 

Pu-240d S M-S 8.79E-5 X 

Am-241d S M-S 8.79E-5 X 

Th-228 S F-S 1.30E-4 

Th-230 S F-S 6.66E-4 

Th-231 S F-S Trace

Th-232 S F-S 3.3E-5 

Th-234e M F-S Trace X 

Pa-234me M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Absorption type for this facility has indicated class S in many bioassay results. 

d. Americium and plutonium not distinguished in analysis.

e. Thorium-234/Pa-234m are found in equilibrium and are type M for GDPs. Technetium-99 is type F for 

GDPs that based their DAC on the more conservative modes (RPM, p. 15).
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 30 of 38

Table 2-12. Radionuclides of concern for Building X-710. 

Facility/Process: X-710 Analytical Labs, Process and Materials

Years of operation: 1954 – 2003

Radionuclides 

of concern

Most probable 

absorption type

Absorption Type 

rangea Activity fraction Significant to external exposureb

U-234 F F-S 9.18E-1 

U-235 F F-S 2.70E-2 

U-236 F F-S 1.75E-2 

U-238 F F-S 4.69E-2 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 1.80E-3 

Pu-238c S M-S 7.25E-4 X 

Pu-239c S M-S 7.25E-4 X 

Pu-240c S M-S 7.25E-4 X 

Am-241c S M-S 7.25E-4 X 

Th-228 S F-S 3.49E-4 

Th-230 S F-S 3.94E-3 

Th-231 S F-S Trace

Th-232 S F-S 4.61E-5 

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 31 of 38

Table 2-13. Radionuclides of concern for Building X-720. 

Facility/Process: X-720 Compressor Shop& High Bay

Years of operation: 1954 – 2003

Radionuclides 

of concern

Most probable 

absorption type 

Absorption Type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 7.77E-1 

U-235 F F-S 3.45E-2 

U-236 F F-S 8.9E-4 

U-238 F F-S 1.86E-1 X 

Tc-99 M F-M Trace X 

Np-237 S M-S Trace

Pu-238c S M-S 3.08E-4 X 

Pu-239c S M-S 3.08E-4 X 

Pu-240c S M-S 3.08E-4 X 

Am-241c S M-S 3.08E-4 X 

Th-228 S F-S 5.64E-4 

Th-230 S F-S 4.68E-4 

Th-231 S F-S Trace

Th-232 S F-S Trace

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 32 of 38

Table 2-14. Radionuclides of concern in Building X-744G. 

Facility/Process: X-744G Smelter for Aluminum recovery

Years of operation: 1961 – 1983

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 9.44E-1 

U-235 F F-S 3.26E-2 

U-236 F F-S 2.57E-3 

U-238 F F-S 1.88E-2 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 4.61E-4 

Pu-238c S M-S 2.2E-4 X 

Pu-239c S M-S 2.21E-4 X 

Pu-240c S M-S 2.21E-4 X 

Am-241c S M-S 2.21E-4 X 

Th-228 S F-S 3.08E-4 

Th-230 S F-S 1.04E-3 

Th-231 S F-S Trace

Th-232 S F-S 4.92E-5 

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with Th-234) X

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 33 of 38

Table 2 -15. Radionuclides of concern in Building X-770. 

Facility/Process X-770 Test Loop Equipment

Years of operation: 1961 – 1983

Radionuclides 

of concern

Most probable 

absorption type

Absorption type 

rangea Activity fraction

Significant to 

external exposureb

U-234 F F-S 9.44E-1 

U-235 F F-S 3.26E-2 

U-236 F F-S 2.57E-3 

U-238 F F-S 1.88E-2 X 

Tc-99 M F-M Trace X 

Np-237 S M-S 4.61E-4 

Pu-238c S M-S 2.21E-4 X 

Pu-239c S M-S 2.21E-4 X 

Pu-240c S M-S 2.21E-4 X 

Am-241c S M-S 2.21E-4 X 

Th-228 S F-S 3.08E-4 

Th-230 S F-S 1.04E-3 

Th-231 S F-S Trace

Th-232 S F-S 4.92E-5 

Th-234d M F-S Trace X 

Pa-234md M M-S (In equilibrium with Th-234) X 

a. Always use bioassay information to determine absorption type, when available.

b. Uranium-238 feeds Pa-234m with a high-energy beta that is also of concern.

c. Americium and plutonium not distinguished in analysis.

d. Thorium-234/Pa-234m are found in equilibrium and are absorption type M for GDPs. Technetium-99 is 

type F for GDPs that based their DAC on conservative modes (RPM, p. 15). 

Table 2-16. Reactor returns fed to cascade. 

Fiscal year Amount fed 

(MTU)

Enrichment 

(%235U) Source Remarks

1955 105.8 0.64 – 0.68 Paducah

1956 54.5 0.64 – 0.68 Paducah Fed May – Sept. 1955

1956 293.4 0.64 – 0.68 Oak Ridge

1957 6.2 0.64 – 0.68 Paducah

1958 64.2 0.64 – 0.68 Paducah

1970 168.1 0.64 – 0.68 Paducah Fed Oct. & Nov. 1969

1974 398.8 0.64 – 0.68 Paducah Fed Jan. 1974

1974 – 1978 1.86 2 – 50 PORTS Oxide Conversion

1968 – 1977 0.15 78 – 80 Division of International Affairs

1977 – 1998 0.15 78 – 97 Babcock & Wilcox

1969 – 1993 0.07 78 AEC Office of Safeguards & Materials 

Management

1997 – 1998 1.10 56 – 82 France

1997 – 1998 0.33 80 NUMEC

TOTAL 1,094.66

Source: BJC (2000, p. 22, Table 2.2.2.5-1). 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 34 of 38

REFERENCES

ANL (Argonne National Laboratory), 2003, “Uranium Hexafluoride,” 

http://web.ead.anl.gov/uranium/about/index.cfm, June. 

BJC (Bechtel Jacobs Company LLC), 2000, Recycled Uranium Mass Balance Project, Portsmouth, 

Ohio Site Report, BJC/PORTS-139/R1, U. S. Department of Energy, Office of Environmental 

Management, Washington, DC. 

Cardarelli, J., II, 1997, NIOSH Health Hazard Evaluation Report, HETA 96-1298-2651, National 

Institute for Occupational Safety and Health, Cincinnati, Ohio. 

DOE (U. S. Department of Energy), 1997, Linking Legacies Connecting the Cold War Nuclear 

Weapons Production Processes to Their Environmental Consequences, Office of 

Environmental Management, Washington, DC. 

DOE (U. S. Department of Energy), 2000a, Independent Investigation of the Portsmouth Gaseous 

Diffusion Plant, Volume 1, “Past Environment, Safety, and Health Practices,” Office of 

Oversight Environment, Safety, and Health, Washington, DC. 

DOE (U. S. Department of Energy), 2000b, Guide of Good Practices for Occupational Radiological 

Protection in Uranium Facilities, DOE Standard DOE-STD-1136-2000, DOE ES&H Technical 

Information Services, August 2000. 

DOE (U. S. Department of Energy), 2000c, Independent Investigation of the Portsmouth Gaseous 

Diffusion Plant, Volume 2, “Current Environment, Safety, and Health Practices”, Office of 

Oversight Environment, Safety, and Health, Washington, DC. 

DOE (U. S. Department of Energy), 2002, Hazard Identification and Facility Categorization, PHS-SM0770-0040, Rev 0, October.

HP-103, RPM HP-103 “Monitoring Skin Decontamination,” Training Lesson Plan. 

Hill, R. L., and D. J. Strom, 1993, Internal Dosimetry Technical Basis Manual for Portsmouth and 

Paducah Gaseous Diffusion Plants, PNL-8723 (UC-607), Pacific Northwest Laboratories, 

Battelle Memorial Institute, Richland, Washington, June. 

NRC (U.S. Nuclear Regulatory Commission), 1999, “Notice of Violation and Proposed Imposition of 

Civil Penalty,” EA-99-080, letter from J. E. Dyer to J. N. Adkins, U.S. Enrichment Corporation, 

June 29. 

NRC (U. S. Nuclear Regulatory Commission) 1992, New Exposure Limits for Airborne Uranium and 

Thorium, Information Notice No. 92-34, , May 6.

ORAUT (Oak Ridge Associated Universities Team), 2004, Technical Basis Document for the 

Portsmouth Gaseous Diffusion Plant – Occupational Internal Dose, ORAUT-TKBS-0015-5, 

Rev. 00, Oak Ridge, Tennessee. 

ORAUT (Oak Ridge Associated Universities Team), 2005, Technical Basis Document for the 

Portsmouth Gaseous Diffusion Plant – Occupational External Dose, ORAUT-TKBS-0015-6, 

Rev. 00, Oak Ridge, Tennessee. 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 35 of 38

Radiation Protection Manual, Portsmouth Facility, “Acceptable Plant Limits for radiation and 

Radioactive Contamination(4/1/1963), Section 243.5 (7/1/1975) and GAT/GDP-1073, vol 2 pg 

4.3-35 (5/10/1990). 

SPFPA (Security, Police, Fire and Professionals of America), 2005, Job Description.

USWA (United Steel Workers of America Union) 2005, Radiological Surveys of Building X-770. 

USEC (United States Enrichment Corporation), 2003, ”The history of PORTS,” 

http://www.usec.com/v2001_02/HTML/Facilities_PortsOverview.asp, accessed August 21.

Yggdrasil Institute 2003, “A Guide to Key Facilities and Sites at the Portsmouth Gaseous Diffusion 

Plant,” http://www.earthisland.org/yggdrasil/portsmouth_gdp.html, accessed August 20. 
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 36 of 38

GLOSSARY

alpha radiation 

A positively charged particle ejected spontaneously from the nuclei of some 

radioactive elements. It is identical to a helium nucleus that has a mass number of 4 

and an electrostatic charge of +2. It has low penetrating power and a short range (a 

few centimeters in air). The most energetic alpha particle will generally fail to 

penetrate the dead layers of cells covering the skin and can be easily stopped by a 

sheet of paper. Alpha particles are hazardous when an alpha-emitting isotope is 

inside the body. 

becquerel 

The derived SI unit of radioactive decay equal to 1 disintegration per second. 37 billion 

(3.7 × 1010) becquerels = 1 curie (Ci). 

beta particle (beta radiation) 

A charged particle emitted from a nucleus during radioactive decay, with a mass equal to 

1/1837 that of a proton. A negatively charged beta particle is identical to an electron. A 

positively charged beta particle is called a positron. Large amounts of beta radiation may 

cause skin burns, and beta emitters are harmful if they enter the body. Beta particles may be 

stopped by thin sheets of metal or plastic. 

cascade

The process system that is used to separate the isotopic streams of 235U and 238U in gaseous 

diffusion plants.

cylinder

A large steel container used to store UF6. Cylinders are typically about 3.7 m (12 ft) long by 

1.2 m (4 ft) in diameter and weigh about 9.1 to 12.7 metric tons (10 to 14 tons) when full of 

depleted UF6. 

deep dose equivalent

The dose equivalent at the respective depth of 1.0 cm in tissue.

depleted UF6 

UF6 with a lower isotopic fraction of 235U than found in natural uranium. 

depleted uranium

Uranium having a percentage of 235U smaller than the 0.7% found in natural uranium. It is 

obtained from spent (used) fuel elements or as byproduct tails, or residues, from uranium 

isotope separation.

derived air concentration (DAC)

The concentration of radioactive material in air and the time of exposure to that radionuclide, in 

hours. A Nuclear Regulatory Commission licensee may take 2,000 hr to represent one ALI, 

equivalent to a committed effective dose equivalent of 5 rem (0.05 sievert).

dose equivalent

The product of absorbed dose in tissue multiplied by a quality factor, and then sometimes 

multiplied by other necessary modifying factors at the location of interest. It is expressed 

numerically in rem or sieverts (see 10 C.F.R. § 20.1003).
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 37 of 38

enriched UF6 

UF6 with a higher isotopic fraction of 235U than found in natural uranium. 

enrichment

An isotopic separation process that increases the portion of the 235U isotope in relation to 238U 

in natural uranium. In addition to the enriched uranium, this process also produces uranium 

depleted in 235U (see depleted UF6 and tails).

exposure

As used in the technical sense, exposure refers to a measure expressed in roentgens (R) of 

the ionization produced by photon radiation (i.e., gamma and X-rays) in air.

gamma radiation (gamma rays) 

High-energy, short wavelength, electromagnetic radiation emitted from the nucleus. Gamma 

radiation frequently accompanies alpha and beta emissions and always accompanies fission. 

Gamma rays are very penetrating and are best stopped or shielded by dense materials, such 

as lead or depleted uranium. 

gaseous diffusion plant 

A facility where uranium hexafluoride gas is filtered, 235U is separated from 238U, 

increasing the percentage of 235U from 1 to about 3%. The process requires enormous 

amounts of electric power. 

half-life 

The time in which one half of the atoms of a particular radioactive substance disintegrate into 

another nuclear form. Measured half-lives vary from millionths of a second to billions of years. 

Also called physical or radiological half-life 

in vitro 

From the Latin, in glass, isolated from the living organism and artificially maintained, as 

in a test tube. 

in vivo 

From the Latin, in one that is living, occurring within the living.

monitoring of radiation 

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

contamination present in a region, as a safety measure, for the purpose of health or 

environmental protection. Monitoring is done for air, surface and ground water, soil 

and sediment, equipment surfaces, and personnel (for example, bioassay or alpha 

scans). 

neutron

An uncharged elementary particle with a mass slightly greater than that of the proton, and 

found in the nucleus of every atom heavier than hydrogen. 

rad 

The special unit for radiation absorbed dose, which is the amount of energy from any type of 

ionizing radiation (alpha, beta, gamma, neutrons, etc.) deposited in any medium (e.g., water, 

tissue, air). A dose of 1 rad means the absorption of 100 ergs (a small but measurable 

amount of energy) per gram of absorbing tissue (100 rad = 1 gray).
Document No. ORAUT-TKBS-0015-2 Revision No. 01 Effective Date: 10/04/2006 Page 38 of 38

radiation

Alpha, beta, neutron, and gamma ray (i.e., photon) radiation.

Radiation Exposure Monitoring System (REMS)

An online DOE database that contains records of personal dosimetry information.

radioactivity

The spontaneous emission of radiation, generally alpha or beta particles, often 

accompanied by gamma rays, from the nucleus of an unstable isotope. Also, the rate 

at which radioactive material emits radiation. Measured in units of becquerels or 

disintegrations per second.

rem

(1) The amount of ionizing radiation required to produce the same biological effect as one rad 

of high-penetration X-rays. (2) A unit for measuring absorbed doses of radiation, equivalent to 

1 roentgen of X-rays or gamma rays. 

roentgen

A unit of radiation exposure equal to the quantity of ionizing radiation that will produce 1 

electrostatic unit of electricity in 1 cc of dry air at 0°C and standard atmospheric pressure. 

sievert (Sv) 

The international system (SI) unit for dose equivalent equal to 1 Joule/kg. 1 sievert = 

100 rem.

Shallow Dose Equivalent (SDE)

The dose equivalent at the respective depth of 0.07 mm of the skin or an extremity.

tails

The product stream of depleted UF6 (i.e., lower isotopic fraction of 235U than found in natural 

uranium) that results from the enrichment process. For gaseous diffusion at PORTS, tails are 

loaded into cylinders and placed in a UF6 cylinder storage yard.

uranium hexafluoride (UF6) cylinder storage yard

Storage yards at the Paducah and Portsmouth Gaseous Diffusion Plants and Oak Ridge K-25 

site. These yards maintain cylinders containing depleted UF6. The cylinders, which typically 

weigh 10 and 14 tons, contain depleted UF6 that has cooled to a solid form.