ORAU TEAM

Dose Reconstruction

Project for NIOSH

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

Page 1 of 39

Document Title:

Weldon Spring Plant – Site Description

Document Number: ORAUT-TKBS-0028-2 

Revision: 00

Effective Date: 06/24/2005

Type of Document: TBD

Supersedes: None

Subject Experts: Craig A. Little and Laura McDowell-Boyer

Document Owner

Approval: Signature on File Approval Date: 06/20/2005

Robert Meyer, TBD Team Leader

Approval: Signature on File Approval Date: 06/20/2005

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 06/20/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 06/24/2005

James W. Neton, Associate Director for Science

 New Total Rewrite Revision Page Change

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

PLEASE DISCARD / DESTROY ALL COPIES OF THE PRIOR REVISION.
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 2 of 39

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

03/24/2005 00-A New technical basis document for the Weldon Spring Plant – Site 

Description. Initiated by Robert Meyer.

04/27/2005 00-B Incorporates internal review comments. Initiated by Robert Meyer.

06/10/2005 00-C Incorporates NIOSH review comments. Initiated by Robert Meyer.

06/24/2005 00 First approved issue. Training is not required. Initiated by Robert 

Meyer.
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 3 of 39

TABLE OF CONTENTS

Section

Publication Record ..............................................................................................................................

Page

2

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

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

2.2 Site Activities and Processes ......................................................................................................7

2.2.1 Site Location and History....................................................................................................7

2.2.2 Site Development and Operations......................................................................................8

2.2.2.1 Site Acquisition and Development (1954 to 1957) ..................................................... 9

2.2.2.2 Plant Operations (1957 to 1967).............................................................................. 10

2.2.2.3 Department of Defense Control (1967 to 1985) ....................................................... 22

2.2.2.4 Monitoring and Maintenance (1975 to 1985)............................................................ 22

2.2.3 Summary of Processed Nuclear Materials........................................................................22

2.2.4 Site Remediation..............................................................................................................23

2.3 Releases to the Outdoor Environment ...................................................................................... 24

2.3.1 Airborne Emissions ..........................................................................................................25

2.3.2 Waterborne Emissions .....................................................................................................25

2.4 Accidents ..................................................................................................................................27

2.5 Health Protection Practices....................................................................................................... 28

2.5.1 Operational Period (1957 to 1967) ...................................................................................28

2.5.1.1 Badging ...................................................................................................................29

2.5.1.2 Radiological Exposure and Access Control ............................................................. 29

2.5.2 Postoperational Period (1975 to Present).........................................................................30

2.5.2.1 Badging (post-operational)....................................................................................... 31

2.5.2.2 Radiological Exposure and Access Control ............................................................. 31

References ........................................................................................................................................33

Glossary ............................................................................................................................................37
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LIST OF TABLES

Table

2-1 Chronological summary of thorium operations .......................................................................

Page

11

2-2 Description of WSP buildings ................................................................................................. 12

2-3 Partial list of job titles and locations during operational phase................................................ 17

2-4 Partial cost center history cross-referenced with work groups ................................................ 20

2-5 Listing of work groups and units............................................................................................. 21

2-6 Location and height of stacks at the WSCP ........................................................................... 21

2-7 Annual uranium and thorium mass receipts (kg) .................................................................... 23

2-8 History of radioactive effluent-generating activities (1957 to 2002)......................................... 25

2-9 Estimated annual discharges to stacks (kg) ........................................................................... 26

2-10 Estimated annual discharges to raffinate pits ......................................................................... 27

2-11 Estimated annual discharges to sewer................................................................................... 27

2-12 Tolerated dose limits in 1955 ................................................................................................. 28

2-13 Guides for prescribing restricted work based on radiation exposure in 1965 .......................... 29

LIST OF FIGURES

Figure

2-1 Weldon Spring Plant location ...................................................................................................

Page

8

2-2 Weldon Spring Plant site..........................................................................................................9

2-3 Wet solvent extraction of uranium .......................................................................................... 12

2-4 Sampling plant flow diagram .................................................................................................. 14

2-5 Digestion, purification, and denitration.................................................................................... 14

2-6 Reduction and hydrofluorination process ............................................................................... 15

2-7 UF6 conversion to uranium metal ........................................................................................... 16
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ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

BZA breathing-zone air

Ci curie

CSS chemical stabilization and solidification

CEDE committed effective dose equivalent

CFR Code of Federal Regulations

cm centimeter

DOE U.S. Department of Energy

EDE effective dose equivalent

EPA U.S. Environmental Protection Agency

ft foot

HEPA high-efficiency particulate air

hr hour

kg kilogram

km kilometer

L liter

m meter

MCW Mallinckrodt Chemical Works

mg milligram

mR milliroentgen

mrem millirem

NIOSH National Institute for Occupational Safety and Health

NLO National Lead Company of Ohio

NPL National Priorities List

ORAU Oak Ride Associated Universities

RI/FS remedial investigation/feasibility study

SWTP Site Water Treatment Plant

TNT trinitrotoluene

TSA Temporary Storage Area

WSCP Weldon Spring Chemical Plant

WSP Weldon Spring Plant

WSQ Weldon Spring Quarry

WSRP Weldon Spring Raffinate Pits

WSSRAP Weldon Spring Site Remedial Action Project
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 6 of 39

U.S.C. United States Code

yd yard

yr year
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2.1 INTRODUCTION

This technical basis document describes the Weldon Spring (WSP) site operations and historical 

health protection practices by Mallinckrodt Chemical Works (MCW), the site’s operator. The 

information in this document is for the evaluation of internal and external exposures to unmonitored 

and monitored workers, and dose reconstructors can use this information as a supplement to

individual monitoring data. 

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

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

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

These documents may be used to assist the National Institute for Occupational Safety and Health 

(NIOSH) in the completion of the individual work required for each dose reconstruction.

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

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

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

Occupational Illness Compensation Program Act of 2000 [42 U.S.C. Sections 7384l(5) and (12)]. This 

document supports the evaluation of worker dose from WSP operations and processes. 

OCAS-IG-001, External Dose Reconstruction Implementation Guideline (NIOSH 2002a), and 

OCAS-IG-002, Internal Dose Reconstruction Implementation Guideline (NIOSH 2002b), provide 

additional guidance on these processes. 

WSP operations played an important role in the U.S. development of nuclear power and nuclear 

weapons. Operations focused on processing of uranium and thorium from feed stocks to metal and 

other intermediate products for use at other facilities. The purpose of this TBD is to provide 

information on WSP facilities and operations critical to evaluation of the total occupational dose. This 

TBD also describes nuclear materials of potential concern.

2.2 SITE ACTIVITIES AND PROCESSES

2.2.1

The 220-acre Weldon Spring Chemical Plant (WSCP) site is about 2 miles southwest of the 

community of Weldon Spring and the junction of Missouri State Route 94 and U.S. Highway 40/61 

(Figure 2-1). The site contained 44 buildings and support structures as well as remnants of a railroad 

system, four raffinate pits, and two small ponds. An 8.7-acre limestone quarry, used in part to deposit 

radioactive wastes from the WSCP, is part of the WSP site, although it is about 4 miles southwest of 

the plant. Figure 2-2 shows the WSCP and raffinate pits. 

Site Location and History

In April 1941, the U.S. Department of the Army acquired 17,232 acres surrounding what is now the 

WSCP as the site for an explosives production facility known as the Weldon Spring Ordnance Works. 

From November 1941 to January 1944, the Atlas Powder Company operated the Ordnance Works for 

the Army to produce trinitrotoluene (TNT) and dinitrotoluene explosives. The Ordnance Works began 

operating again in 1945 but was closed and declared surplus in April 1946. By 1949, all but about 

2,000 acres had been transferred to the state of Missouri and the University of Missouri.

In 1956, approximately 220 acres of the former Ordnance Works were transferred to the U.S. Atomic 

Energy Commission (AEC) for construction and operation of a Feed Materials Plant to process 

uranium and thorium ore concentrates, which operated from 1957 through 1966 (U.S. Army 1976). 

Construction was completed in February of 1957; the date of initial operation was June of 1957 (MCW 
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Figure 2-1. Weldon Spring Plant location. 

1957). Nuclear materials in the form of natural uranium concentrates were being stored at the site 

prior to the start of operations, but “since they were not processed, they did not engender operational 

losses” (DOE 1986a). Thus, it is reasonable to assume exposures prior to operational startup were 

negligible. This is the WSCP referred to in this document. The raffinate pits were originally part of the 

WSCP, but are referred to separately in this document as the Weldon Spring Raffinate Pits (WSRP) 

because they were managed separately from the other area of the WSCP in the post-operational 

period. In 1958, a 9-acre quarry site was transferred to the AEC, which is referred to as the Weldon 

Spring Quarry (WSQ) in the following discussion.

In August 1967, the WSCP was returned to U.S. Army control for construction of an herbicide 

production facility (U.S. Army 1976), but the AEC retained custody of the WSQ and the WSRP. 

Decontamination of the transferred WSCP facilities was attempted between 1968 and 1970, but 

abandoned because of cost. The U.S. Department of Energy (DOE) gained responsibility for the 

WSCP in 1985 and began site characterization and remediation in 1985. The quarry was placed on 

the U.S. Environmental Protection Agency’s (EPA) National Priorities List (NPL) in 1987, and the 

listing was expanded to include the WSCP and associated waste storage areas in 1989. 

2.2.2

Before remediation, four periods of WSP site history can be identified: 

Site Development and Operations
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Figure 2-2. Weldon Spring Plant site (adapted from several 

documents).

• Plant acquisition and development (1954 to 1957)

• Operations (1957 to 1967) 

• Department of Defense Control (1967 to 1985) 

• Monitoring and Maintenance (1975 to 1985). 

The following sections provide more detailed descriptions of these activities. These descriptions are 

summarized from U.S. Army (1976) and Meshkov et al. (1986) unless otherwise noted. 

2.2.2.1 Site Acquisition and Development (1954 to 1957)

In August 1956 Congress officially approved transfer of 205 acres of the former Ordnance Works 

property from the Army to AEC. An additional 15 acres were later transferred to the AEC for 

expansion of waste storage capacity. The AEC began designing a feed materials plant in 1954 and 

constructed the plant now referred to as the WSCP in 1956 and 1957 on this property for processing 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 10 of 39

uranium and thorium feed stocks into metal and intermediate products. This facility replaced a more 

limited plant of similar operational capability in St. Louis (on Destrahan Street). The WSP facility was 

initially designed specifically to process uranium mill concentrates (yellow cake) produced elsewhere 

in the United States and Canada. These materials were shipped to the WSP site for sampling to 

determine payment. Fractions of the total mill concentrates were processed through chemical 

treatment operations. Other fractions, after sampling, were shipped to other DOE facilities for further 

processing.

2.2.2.2 Plant Operations (1957 to 1967) 

The WSCP was operated for AEC by the Uranium Division of MCW from 1957 to 1966. The WSCP 

processed materials from June 1957 to December 1966. Shutdown procedures were completed in 

1967. DOE (2000a) estimated the employment at the site for the Uranium Division at about 600 

employees, of whom about 300 would have handled the materials. Four types of nuclear material 

were processed in the DOE-owned WSCP: natural uranium, depleted uranium, slightly enriched 

uranium, and natural thorium (DOE 1986a). The following paragraphs describe the use of these 

materials at the WSCP. 

Natural Uranium: Natural uranium was received as continental ore concentrates that were refined to 

extract the uranium, after which the uranium was converted to various compounds and metal forms 

and shipped off the site. Processing of natural uranium was a continuous operation during the life of 

the plant. 

Depleted Uranium: Uranium depleted in 235U isotope below its natural isotopic abundance ratio was 

received and processed on an intermittent basis. This form of uranium was used primarily in product 

development activities and flow-sheet improvements. Use was confined primarily to pilot plant 

activities.

Slightly Enriched Uranium: Uranium enriched to 1% or less 235U by weight was also received and 

processed on an intermittent basis. This type of uranium was typically received in the form of scrap 

metal or residues. The uranium contents were recovered, processed to various chemical forms, and 

shipped off the site. The coefficient of variation about the values assigned to all flows of this type of 

material was slightly greater than that for natural uranium, primarily because of the heterogeneous 

nature of receipts.

Natural Thorium

An average of 1.2 × 107 kg (1.4 × 104 tons) of uranium-containing material was processed per year 

(DOE 1986a). Natural uranium processing accounted for more than 97% of the nuclear materials 

throughput. Total material balance closures (i.e., percent of material accounted for) for natural 

uranium, depleted uranium, and slightly enriched uranium for the 10 yr of plant operations were 

99.94%, essentially 100%, and 99.27%, respectively. An average of 3.1 × 105 kg (350 tons) of natural 

thorium was processed per year during 1964 through 1966, with an associated total material balance 

closure of 98.52%. 

: Natural thorium was typically received in either a nitrate or an oxide form and 

processed on an intermittent batch basis in the refinery and oxide production/firing systems. Only a 

limited area of the WSCP (refinery and pilot plants) was exposed to the material. In addition, Dupree 

(1979) stated that approximately 3.6 × 105 kg (400 tons) of “impure thorium nitrate and enriched 

uranium” were processed starting in 1965. MCW (1966) summarized operations with thorium as 

shown in Table 2-1. 
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Table 2-1. Chronological summary of thorium operations. 

Operation title Building 1963 1964 1965 1966

TNT crystal repackaging 403 Nov-Dec May-Sep

301 Oct-Dec

Denitration of TNT crystals & sol drying-hand 

unloading

103 Nov-Dec May-Aug 

Denitration of TNT crystals & sol drying-vacuum 

uploading

103 Sep-Dec

Denitration of TNT liquor & sol drying-vacuum 

uploading

103 Jan-Jul

Denitration by fluid bed-product packaged in 

drums

403 May-Jul

Denitration by fluid bed-liquor feed & sol 

product

403 Aug-Dec Jan; Jun-Sep

Denitration of TNT liquor-scoop & pail transfer 

to sol tank

103 Oct-Nov

Sol drying-vacuum uploading 103 Aug-Dec Jan; Jun-Sep

Tho2 high firing-recast furnace 301 Nov-Dec May-Sep

Tho2 high firing-billet heaters 301 Oct-Dec Jan-Dec Jan; Jun-Sep

Tho2 product packaging 403 Nov-Dec May-Jul; Sep-Dec Jan-Sep

103 Aug

301 Oct-Dec Jan; Jun-Sep

Rotary kiln calcining of sump cake 301 Apr-Jul

Digest feed repackaging 101 Apr-Aug

Scrap digestion & raffinate disposal 103 May-Sep

Extraction 105 Jun-Sep

The WSCP’s main activity was to convert uranium concentrate to uranium trioxide (UO3), uranium 

tetrafluoride (UF4), and uranium metal. The material received at the plant was yellowcake (uranium

concentrate). Figure 2-3 shows a schematic diagram of a wet solvent extraction method used for UF4

production. Before entering the refinery, the ore concentrate underwent a sampling and preparation 

process in the sampling plant. Table 2-2 lists the WSCP buildings and the activities that took place in 

them (MCW 1962, 1964; Meshkov et al. 1986). 

Building 101 was the sampling building. Ore concentrate of about 60% to 70% uranium content 

arrived in drums. Concentrate in opened drums was sampled using one of the two sampling 

methods—auger or mechanical sampling—and the drums were emptied into hoppers at the top of the 

building. From the hoppers, material was transferred to portable hoppers for transfer to the refinery 

(Figure 2-4). Yellowcake dust was collected in three large dust collectors, each with its own stack. 

Some yellowcake was repackaged in drums and shipped out; the rest was put into hoppers and 

moved to Building 103 for digestion. The dust collection system was vacuum cleaned from time to 

time, and the collected dust was reprocessed. Uranium dust was washed off the drums, equipment, 

and floors, and this dust was also reprocessed.

UO3 (sometimes known as orange oxide) was produced, or refined, in three steps: Digestion, 

purification by solvent extraction, and denitration (Figure 2-5). Building 103 was the first building of 

the refinery plant. Concentrate was brought in hoppers to the top of the building where there was one 

dust collector with one stack to collect yellowcake dust. The concentrate was heated and digested 

with nitric acid to produce a solution of uranyl nitrate. The digested material was passed to 

Building 105 in liquid form where pure uranyl nitrate solution was extracted and remained in liquid 

form. The highly purified uranyl nitrate solution was evaporated and pumped to gas-fired denitration 

pots in Building 103 where the remaining water was removed, producing pure UO3. According to 

Meshkov (1986), this was the dustiest part of the process. Impurities generated in the purification 

process were bled off in the raffinate, which was pumped to pits. This raffinate contained a 

conglomerate of radionuclides including thorium and radium in small concentrations.
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Figure 2-3. Wet solvent extraction of uranium (adapted from US Army 1976). 

Table 2-2. Description of WSP buildings.

a

Building Description Dates Operations performed

101 Sampling Plant Jun 1957–1966 Preparation and sampling building designed to process 

approximately 75 tons of low-assay uranium ore 

concentrates per day. Housed equipment and facilities for 

drying, grinding, screening, blending, and sampling of ore 

concentrates and process residues. Incoming ore 

concentrates and residues were stored in drums on 

concrete pad.

Area 102 A&B Refinery Tank Farm Jun 1957–1966 Provided facilities for unloading, storing, and transferring 

liquid process material required in the refinery operation 

and were supplied or handled in tank-car and tank-truck 

quantities.

103 Digestion and Denitration 1957–1966 Originally the nitrating, denitrating, and raffinate 

processing and storage area.

• The northern digestion section received uranium ore 

concentrates that were digestion and transferred as a 

slurry to Building 105 where the solvent was purified 

by extraction. 

• The middle denitration section received the purified 

uranium nitrate solution, which was denitrated to 

yield uranium nitrate solution, which was further 

denitrated to yield U03. During later years, thorium 

products were also processed in this building.

104 Lime Storage Facility for storing lime.

105 Extraction Feb 1957–1966 Purification building. Previously used for producing a 

highly purified uranyl nitrate hexahydrate (UNH) solution 

by means of extraction columns, process vessels, 

evaporators, and tributyl phosphate and hexane reaction 

tanks.
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Table 2-2 (Continued). Description of WSP buildings.

a

Building Description Dates Operations performed

106 Refinery sewer sampling Used as a sampling station for process waste streams.

108 Nitric acid plant 1957–1966 Used for recovering and reconcentrating nitric acid and 

oxides of nitrogen.

109, 110 West Drum Storage, 

East Drum Storage

Used to store drums containing ore concentrates and 

process residues.

201 Green Salt Building Feb 1958–1966 Used for converting U03 to U02 and UF4. 

202 A&B Green Salt Tank Farm 1957–1966 Used for tank car unloading and storage of hydrofluoric 

acid (HF) and ammonia.

301 Metals Building Apr 1958–1966 Used for converting UF4 to uranium metal. 

302 Magnesium Building 1957–1966 Powdered magnesium handling building used for storage 

of magnesium.

Pad 303 Served as a material storage pad.

401 Steam Plant 1956–1966 Steam-generating plant including coal conveyor and coal 

yard.

403 Chemical Pilot Plant 1957–?? Demonstration of pilot operations.

404 Metallurgical Pilot Plant 1957–?? Provided facilities for metal processing studies, ceramic 

work, and metal testing; housed metallurgical pilot plant.

405A & B Pilot Plant Maintenance 1957 Building 405A was a small shop and storage building 

spare pilot plant equipment storage. The dust collectors 

and vacuum cleaning system for Buildings 403 and 404 

were on Pad 405B.

406 Warehouse 1956 Served as a warehouse and office area.

407 Laboratory 1957 Used as an analytical chemistry laboratory. 

408 Maintenance and Stores 1956 Contained numerous maintenance shops, office area, 

garage, receiving and shipping area, decontamination 

room, and a large storage area.

409 Administration 1957 Contained offices for administrative staff.

410 Services Building 1957 Contained the main gate, administrative offices, plant 

security office, health and safety office, kitchen, dining 

room, laundry facility for contaminated clothing, and clean 

and contaminated locker rooms with shower facilities.

412 Electrical Substation Substation for electrical supply.

413 Cooling Tower and Pump 

House

Water-cooling tower and pump house

414 Salvage Building 1956 Served as a salvage shop and equipment storage space.

415 Process Incinerator Incinerator for process materials.

417 Paint Shop ?? Served as the paint shop.

426 Water Tower Used for water storage (elevated water storage tank).

427 Primary Sewage 

Treatment Plant

Served as the primary sewage treatment plant for the site.

428 Fuel Gas Plant Storage facility for fuel gas.

429 Water Reserve Facilities Water storage (pump house and ground storage tank). 

Also noted to have been a propane gas storage facility.

430 Ambulance Garage Used as an ambulance garage.

43l Laboratory Sewer 

Sampler

Used as a sampling station for process waste streams.

432 Main Sewer Sampler Used as a sampling station for process waste streams.

433 Garage Large equipment garage area. 

434 Storage Ore concentrate storage building.

435 Storage Salvageable equipment storage.

436 Storage Salvageable equipment storage.

437 Records Retention

Building

Facility used for storage and retention of records.

438 Storage Salvageable equipment storage.

439, 443 Fire Training and 

Storage Building

Facility used for fire training purposes and storage.

441 Cylinder Storage Facility used for storage of UF6 cylinders.

a. Adapted from U.S. Army (1976).
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Figure 2-4. Sampling plant flow diagram (adapted from US Army 1976). 

Figure 2-5. Digestion, purification, and denitration (adapted from US Army 1976). 
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UO3 was packaged into transfer hoppers and transferred from Building 103 to the top of Building 201, 

the green salt (UF4) plant. Figure 2-6 shows the reduction and hydrofluorination process used to 

produce UF4. Hydrogen gas reduced UO3 to uranium dioxide (UO2). 

Figure 2-6. Reduction and hydrofluorination process (adapted from US Army 

1976). 

The next step was hydrofluorination, in which UO2 was transformed to UF4 or green salt. Excess 

hydrogen fluoride (HF) gas from the process was filtered through carbon filters to recover uranium, 

which was recycled to black oxide (U3O8). Discharge from the UF4 reactor system was mechanically 

collected, crushed, and blended to obtain desired particle sizes. There were two additional dust 

collectors on the roof of Building 201 associated with the system to collect UF4 dust, and there was a 

reverter in the building to convert UF4 into U3O8. 

Green salt was packaged in transfer hoppers and moved to Building 301, the metals plant. 

Magnesium was used to convert UF4 to solid uranium metal in a multistep process. Figure 2-7 depicts 

this process. The reaction occurred in refractory-lined steel “bomb” shells, which were charged with a 

mixture of green salt and magnesium chips. Green salt and magnesium were mixed in a blender; the 

mixture was then placed in individual steel shells at the filling machine and sent to the furnaces for 

firing. Within the furnace, the shell was heated to about 500°F and the charge was ignited electrically. 

Once ignited, the reaction proceeded spontaneously. Complete shells were moved to an outdoor 

cooling pad for about 3 days. The process generated green salt dust. UF4 and magnesium fluoride 

(MgF), with 1% to 2% of residual uranium in various forms, were discharged from several dust 

collectors at the ground level on the south side of the building. A rotary kiln in Building 301 calcined 

uranium metal chips to convert them to U3O8. One standard dust collector was used for the dusty 

discharge, mostly U3O8, produced in this operation.
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Figure 2-7. UF6 conversion to uranium metal (adapted from US Army 1976). 

Uranium fuel cores were produced in Building 301. Uranium billets were extruded to rods of suitable 

size to produce cores for use in reactors. The rods were straightened, cut to lengths, heat treated, 

degassed, machined, inspected and shipped. Rods or tubes approximately 22 ft long were 

straightened and fed to a six-spindle automatic machine, which turned off a thin layer of material from 

the outside diameter and sectioned them into about 8.5-inch lengths. The rough cores were then 

treated at 950°F in a vacuum furnace to remove hydrogen gas from the metal. Degassed cores were 

heat treated in molten salt at 1,350°F and quenched in water at 130°F to randomize the grain 

structure. Cores were further machined to remove the warp and oxide layer that resulted from heat 

treatment and degassing. Holes were drilled in the solid core, and it was reamed to final size. Good 

cores were inspected in an ultrasonic machine to ensure that the grain structure was neither too small 

nor too large. A dimensional inspection was performed to ensure that specifications were met. All 

acceptable cores were packaged in boxes and shipped by rail directly to reactor sites.

The Analytical and Research Laboratories were housed in Building 407. The Analytical Laboratory 

had four sections. The Production Section had laboratories for process control, uranium 

accountability, sampling, and specifications testing. The Spectrographic Section measured impurities 

in raw materials and in finished products. The Method Development Section provided analytical 

procedures for the laboratory. Equipment included infrared and ultraviolet spectrophotometers, vapor 

phase chromatograph, X-ray spectrometer, ultra-high-vacuum equipment, an isotope ratio mass 

spectrometer, and a time-of-flight mass spectrometer. The Special Analysis Section performed 

analytical work for the research laboratory and pilot plants in addition to running production and 

uranium inventory samples. 

The Research Laboratory consisted of three sections. The Dry Chemistry Section was concerned 

with problems in fluoride chemistry and with metallurgical studies. The Wet Chemistry Section 
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worked on such studies as the digestion and extraction of raw material feeds, solvent quality, uranyl 

nitrate purity, and nitric acid recovery. The Instrumental Techniques Section used a wide variety of 

optical equipment: X-ray diffraction equipment for qualitative and quantitative analysis, and electron 

and optical microscopes for particle-size distribution studies, identification of minerals, and studies of 

physical properties.

Buildings 403 and 404 housed the Chemical and Metallurgical Pilot Plants, respectively. The 

chemical and metallurgical pilot plants had development facilities on a scale intermediate between the 

laboratory and the plant. After new processes and equipment were demonstrated on a small scale in 

the laboratory, they were investigated further in the pilot plants. Research was performed on the 

design, installation, and operation of an integrated fluid-bed system for producing uranium trioxide, 

uranium dioxide, and green salt. Also studied in the chemical pilot plant was a process for the 

simultaneous denitration of uranyl nitrate and reduction of UO3. The metallurgical pilot plant was 

equipped for large-scale development of the bomb-reduction step of the process. 

Table 2-3 lists job titles and locations for the plant during its operational phase. These were taken 

from an anonymous list that accompanied a memorandum (Dupree 1979) written to describe a visit by 

Mont Mason to Oak Ridge. The notes were presumed to have been made by Mason, who was head 

of Health and Safety for Mallinckrodt for a number of years. 

Table 2-3. Partial list of job titles and locations during operational phase. 

Job title Job type Job location or building*

103 DX men Porter Refinery – Digestion and Denitration (103)

105 DX men Porter Refinery - Extraction (105)

201 DX men Porter Green Salt Plant (201)

201 Production Office porter Porter Green Salt Plant (201)

301 DX men Porter Metals Building (301)

408 porter Porter Maintenance (408)

Accountability Lab Technical Analytical Laboratory (407)

Assistant foreman Supervisory Stores (408)

Assistant Superintendent Supervisory Green Salt Plant (201)

Auxiliary dissolving Operator Operator Refinery – Digestion and Denitration (103)

Blending Operator Operator Metals Building (301) – Conversion

Bomb Cooling Operator Operator Metals Building (301) – Conversion

Bomb Unloading Operator Operator Metals Building (301) – Conversion

Capping & Tamping Operator Operator Metals Building (301) - Conversion 

Carpenter Carpenter Maintenance Department (408)

Casting Operator Operator Metallurgical Pilot Plant (404)

Ceramics Operator Operator Metallurgical Pilot Plant (404)

Clerical and Steno Clerical Stores (408)

Clerical and Steno Clerical Production Control office

Control Technical Analytical Laboratory (407?)

Decontamination room DX Porter Various process buildings?

Digester Operator Operator Refinery – Digestion and Denitration (103)

Dingot Chipping Operator Operator Metals Building (301) – Conversion

Dishwasher Labor Analytical Laboratory (407?)

Draftsmen Draftsmen Engineering 

Electrician Electrician Maintenance Department

Employee Benefits officer Clerical Industrial Relations

Engineer Engineer Maintenance Department (408)

Engineer Engineer Engineering 

Extrusion Press Operator Operator Metals Building (301) – Fabrication and Extrusion

Feed Operator Operator Refinery – Digestion and Denitration (103)

Filling Operator Operator Metals Building (301) – Conversion

Fluoride Chemistry technician Technical Research Laboratory

Foreman Supervisory Stores (408)
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 18 of 39

Table 2-3 (Continued). Partial list of job titles and locations during operational phase.

Job title Job type Job location or building*

Foreman Supervisory Warehouse (406)

Foreman Supervisory Sampling Plant (101)

Foreman Supervisory Maintenance Department (408)

Foreman Supervisory Metallurgical Pilot Plant (404)

Foreman Supervisory Wet (Chemical?) Pilot Plant (403)

Forge Press Operator Operator Metallurgical Pilot Plant (404)

Furnace and Saw Operator Operator Metallurgical Pilot Plant (404)

Furnace Operator Operator Green Salt Plant (201)

Furnace Operator Operator Metals Building (301) – Conversion

General foreman Supervisory Refinery (103-105)

General Foreman Supervisory Green Salt Plant (201)

General Foreman Supervisory Metals Building (301)

General Foreman Supervisory Maintenance Department (408)

General Labor Labor Boiler House (401)

General Labor Labor Water Plant (429?)

General Office Clerical Health Department (410)

General Office Clerical Industrial Engineering 

General Office Clerical Engineering

General Office Clerical Industrial Relations

General Office Clerical Safety and Fire

General Office Clerical Accounting

General Office Clerical Purchasing

General Office Clerical Administrative Services (409)

General Office Clerical Payroll (409?)

General Office Clerical Tabulating Office

General Office Clerical Research Laboratory (407?)

General Office Clerical Production Technical Department

Guard Plant protection Plant Wide

Guard Captain Plant protection Plant Wide

Guard Lieutenant Plant protection Plant Wide

HF Operator Operator Green Salt Plant (201)

Industrial Hygiene Industrial Hygiene Health Department (410)

Inspectors Inspector Safety and Fire 

Jolter Operator Operator Metals Building (301) – Conversion

Laborer Laborer Maintenance Department (408)

Lathe Operator Operator Metals Building (301) – Fabrication and Extrusion

Lead Operator Operator Metallurgical Pilot Plant (404)

Lid Chipping Operator Operator Metals Building (301) – Conversion

Locker room porters Porter Services Building (410?)

Machine maintenance Laborer Maintenance Department (408)

Magnesium Building Operator Operator Metals Building (301) - Conversion

Maintenance Clerks Clerical Maintenance Department (408)

Messenger Messenger Administrative Services

Metallurgical technician Technical Research Laboratory

Methods Development Technical Analytical Laboratory

Misc. digestion Operator Operator Refinery – Digestion and Denitration (103)

Motor and equipment Tagger Labor Accounting (409?)

Nitric Acid Operator Operator Refinery – Digestion and Denitration (103)

NOK Operator Operator Refinery – Nitric Acid in Hexane (NAH)

Office and Steno Clerical Analytical Laboratory (407)

Oiler Laborer Maintenance Department (408)

Operator Operator Wet (Chemical?) Pilot Plant (403)

Operators Operator Sampling Plant (101)

Packaging Operator Operator Refinery – Digestion and Denitration (103)

Packaging Operator Operator Green Salt Plant (201)

Painter Painter Maintenance Department (408)

Pipe Maintenance Laborer Maintenance Department (408)
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 19 of 39

Table 2-3 (Continued). Partial list of job titles and locations during operational phase.

Job title Job type Job location or building*

Plant Porter Porter Plant-wide

Pot room Operator Operator Refinery – Digestion and Denitration (103)

Production Clerk Clerical Sampling Plant (101)

Production Clerk Clerical Refinery (103-105)

Production Clerk Clerical Green Salt Plant (201)

Production Clerk Clerical Metals Building (301)

Production Machinist Operator Metallurgical Pilot Plant (404)

Production Operator Operator Metallurgical Pilot Plant (404)

Pulse column Operator Operator Refinery (105/108)– Nitric Acid in Hexane (NAH)

Pumper decanter Operator Operator Refinery (105/108)– Nitric Acid in Hexane (NAH)

Raffinate Operator Operator Refinery (103) – Digestion and Denitration 

Recovery Operator Operator Refinery (103) – Digestion and Denitration 

Residue Operator Operator Metallurgical Pilot Plant (404)

Rigger Rigger Maintenance Department (408)

Sampling plant DX men Porter Sample plant

Saw Operator Operator Metals Building (301) – Fabrication and Extrusion

Shift assistant foreman Supervisory Refinery

Shift foreman Supervisory Refinery

Shift Foreman Supervisory Green Salt Plant – 201

Shift Foreman Supervisory Metals Building (301)

Shift Foreman Supervisory Metallurgical Pilot Plant (404)

Shift Foreman Supervisory Wet (Chemical?) Pilot Plant (403)

Slag Building Operator Operator Metals Building (301) – Conversion

Special analysis Technical Analytical Laboratory

Special techniques technician Technical Research Laboratory

Specification testing Technical Analytical Laboratory

Spectrographic Technical Analytical Laboratory

Stenographer Clerical Maintenance Department (408)

Storekeeper Stores Stores (408)

Stripper Operator Operator Refinery (105/108)– Nitric Acid in Hexane (NAH)

Sump Operator Operator Metals Building (301) – Fabrication and Extrusion

Superintendent Supervisory Refinery (103-105)

Superintendent Supervisory Metals Building (301)

Superintendent Supervisory Maintenance Department (408)

Superintendent Supervisory Production Technical Department

Supervisor Supervisory Production Control office

Technical Technical Metallurgical Pilot Plant (404)

Technical Technical Wet (Chemical?) Pilot Plant (403)

Technical Services Staff Technical Production Technical Department - Sampling Plant (101)

Technical Services Staff Technical Production Technical Department – Refinery

Technical Services Staff Technical Production Technical Department -Green Salt Plant – 201

Technical Services Staff Technical Production Technical Department – Metals Building (301)

Tinner Laborer Maintenance Department (408)

Utility Operator Operator Green Salt Plant (201)

Vacuum techniques technician Technical Research Laboratory (407)

Warehouse Yard Operator Operator Sampling Plant (101)

Warehouse Yard Operator Operator Refinery (103-105)

Warehouse Yard Operator Operator Green Salt Plant – 201

Warehouse Yard Operator Operator Metals Building (301)

Warehouse Yard Operator Operator Various

Welder Welder Maintenance Department (408)

Wet chemistry technician Technical Research Laboratory (407)

* A question mark denotes disagreement in the various documents that describe jobs or locations.

Table 2-4 provides a partial history of cost center designations from MCW (1966) that could be useful 

in understanding job types or classifications. However, these designations are not suggested for 

cross-referencing job titles and locations with time or dosimetry card entries. An October 25, 1983, 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 20 of 39

memorandum from Dupree to the MCW file of the Oak Ridge Associated Universities (ORAU) worker 

epidemiology study reported on a trip to MCW (Dupree 1983). Item five of that memorandum states, 

“Beginning in 1954 the [cost center] codes changed about once every 6 months. Documentation of 

changes was made only to the extent that was necessary to obtain the money for the UD [Uranium 

Division] operations from the government.” Assuming that the practice continued into the WSP

operations of 1956 and beyond, using cost center codes to help assess worker dose may not be 

reliable. 

Table 2-4. Partial cost center history cross-referenced with work groups. Work group Cost center name Cost center code numbers

Title

Group 

unit no.

11/59 

& 4/60 7/60 7/61 7/62 7/63 7/64 1965 1966

Sampling Plant 0402 Sampling 310 310 310 310 110 110 110 110 Repackaging

Digest-Raffinate 0501 Refinery 321 321 321 321

Extraction 0503 320 320 320 320 120 120 120 120

Pot Room (Denitration) 0502 320 320 320 320 120 120 120 120

Green Salt Plant 0401 Green Salt 320 320 320 320 120 120 120 120

Dingot Production 0701 Dingot Reduction 330 330 330 330 150 150 150 150

Dingot Machining 0702 Extrusion General 360 360 360 340 180 180 180 180

200

301-Other than Dingot 

Production

0702 Extrusion General 200 200 200

Extrusion Extrusion General 359

Extrusion, Recast, Kiln 0703 Gamma Extrusion (Dingot 

Extrusion

361 361 361 351 210

0703 Alpha Extrusion (Dingot 

Conversion to Rods)

364 352 220

0703 Metal Plant Scrap Activity 358 280

Vacuum Outgassing 363 363

Core Area 0704 Core Fabrication 362 362 362 366 250

365 367

366 368

369

Building 403 Chemical Process 

Development

420 420

Development 450 450

0601 Scrap Plant 290 290 290 290

Building 404 Metallurgical Development 410 410

0602 Special Projects 460 460 460 460 460 460

Table 2-5 lists work groups and units as taken from MCW (1966). The table is not dated; in 

conjunction with data in Tables 2-2 and 2-3, it is useful in ascertaining the worker’s job type. 

Table 2-6 lists the buildings that produced most of the air discharges and summarizes the types of 

discharge and stack heights. 

The processing of uranium and thorium generated several chemical and radioactive waste streams, 

which were piped to the raffinate pits. The solids settled to the bottom of the pits, and the supernatant 

liquids were decanted to the plant process sewer that drained off the site to the Missouri River. Of the 

discards (i.e., material known to have been disposed of via plant stacks, sewers, and raffinate pits 

rather than shipped off the site), approximately 67% of the uranium and essentially all of the thorium 

went to the raffinate pits (DOE 1986a).

Between 1958 and 1964, four raffinate pits were constructed in the southwest portion of the site to 

contain process wastes from the plant (NLO 1977). Pits 1 and 2 were constructed in 1958, and were 

used for almost 2 yr. The design volume of each of these two pits was 14,000 m3 (500,000 ft3

). 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 21 of 39

Table 2-5. Listing of work groups and units. 

Group 01 Unit 01 Clean up

Unit 02 Laundry Operations

Unit 03 Custodians

Group 02 Unit 01 Storekeepers

Unit 02 Yard Operators

Group 03 Unit 01 Tool and Die Makers

Unit 03 Painters

Unit 04 Carpenters

Unit 06 Riggers

Unit 07 Welders

Unit 18 Tinners

Unit 12 Millwrights

Unit 13 Oilers

Unit 11 Machinists

Unit 20 Auto Mechanics

Unit 14 Pipefitters

Unit 17 Instrument Mechanics

Group 01 Unit 01 Clean up

Group 04 Unit 01 Green Salt Plant

Unit 02 Sampling Plant

Group 05 Unit 01 Refinery Digest, Etc.

Unit 02 Pot Room, Etc.

Unit 03 Extraction in 105

Unit 04 Water Plant

Group 06 Unit 01 Building 403

Unit 02 Building 404

Group 07 Unit 01 Dingot Production and Mag

Unit 02 Dingot Machining

Unit 03 Extrusion, Recast & Kiln

Unit 04 Core Area

Group 08 Unit 02 Electricians

Group 09 Unit 01 Boiler House

Group 10 Unit 01 Guards

Group 11 Unit 01 Dishwasher

Table 2-6. Location and height of stacks at the WSCP (Meshkov et al. 

1986 Table 3.2).

Building 

number

Number 

of stacks Discharge

Height of 

stack (meters)

101 2-3 Yellowcake dust 35

103 1 Yellowcake dust 23

Several UO3

201 6 UO2, UF4, and U3O8 14-34

301 Several UF4 and MgF with 1% uranium 23

1 U3O8

Because of the high production rate, the first two raffinate pits filled rapidly, requiring the construction 

of the third and, eventually, fourth pit. Pit 3 was constructed and put into use in 1959 with a design 

volume of 127,000 m3 (4.5 × 106 ft3

). Pit 4 was constructed and put into operation in 1964, and its

design volume was 340,000 m3 (12 × 106 ft3

).

In 1958, AEC acquired the WSQ, which was previously part of the U.S. Army’s WS Ordnance Works 

(Bechtel 1985a). The WSQ was first used for storing radioactive waste in 1959, when an estimated 

150 m3 (5,400 ft3

) of drummed 3.8%-thorium residues were placed there. In 1963 and 1964, uraniumand radium-contaminated building rubble, equipment, and soils were deposited in the Quarry following 

demolition of the MCW’s Destrehan Street Feed Plant. In 1966, approximately 13,500 ft3 of drummed 

and bulk 3%-thorium residues were deposited in the WSQ. 

In 1965 and 1966, first pure and then impure thorium oxide was processed, initially on a pilot scale in 

Buildings 403 and 404 and later on a large scale in Buildings 103, 105, and 301. Wastes were 

deposited in Raffinate Pit 4.

In early 1966, the AEC decided to close WSCP at the end of the year because more cost-efficient 

processes made the plant obsolete. The workforce began to decline as employees sought other 

employment. Decontamination of the buildings and equipment for unrestricted use were not part of 

the AEC shutdown directive. Under the shutdown procedures, hoppers and process lines were 

emptied, and dust collectors and other points of material accumulation were cleaned out. All access 
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ports were used to remove as much of the pure uranium compounds as possible from the production 

equipment. 

2.2.2.3 Department of Defense Control (1967 to 1985) 

As noted, the plant was closed at the end of 1966 and shutdown procedures were initiated in 1967. 

Only a few pounds of pure compounds were present in any single piece of equipment. The bulk of 

the radiological materials that remained on the site was outside the primary production lines in 

building sumps and in secondary pieces of process equipment and piping without routine access 

ports. For a short time after closure, some of the buildings were used for interim storage of drummed 

yellowcake from other mills. This yellowcake was later shipped to various plants for refining and 

processing.

AEC returned the WSP facility to the Army in 1967 (DOE 2003) for the purpose of using portions of 

the feed materials plant for the production of Herbicide Orange to meet needs in Southeast Asia. 

AEC maintained control of Building 434 (which had been used for the storage of ore concentrates), a 

51-acre tract encompassing the four raffinate pits, Building 438, and the WSQ. 

The Army selected Buildings 103 and 105 for herbicide production, with blending and packaging to 

occur adjacent to Building 101. Construction of the herbicide facility began in December 1968 but 

was terminated when the project was canceled in early 1969. Cleanup and shutdown work was 

conducted on the site until June 1969. The Army began decontamination and equipment removal in 

Buildings 103 and 105 in March 1968. About 6,000 yd3 of highly contaminated and unrecoverable 

material were hauled to the quarry 4 miles south on Highway 94. About 2,400 tons of contaminated 

scrap was shipped via rail and truck to a Knoxville, Tennessee contractor. Another AEC contractor, 

National Lead Company of Ohio (NLO), received 20 railcars and one truckload of stainless-steel 

piping, valves, vessels, and spare parts. Approximately 135 barrels of uranium oxide were recovered 

from the buildings. A high-pressure hot-water solution containing an acidic wetting agent was used to 

partially decontaminate Buildings 103 and 105. Portions of some concrete floors were removed and 

covered with tar and new concrete to mask radiological contamination. In June of 1969, the Kansas 

City District of the U.S. Army Corps of Engineers obtained custody of the 169-acre tract containing the 

WSCP. Because the herbicide production program was cancelled in 1969, no major activities took 

place between 1969 and 1985. 

2.2.2.4 Monitoring and Maintenance (1975 to 1985)

The AEC did not have any contractors performing work on the 52 acres surrounding the WSRP and 

the 9-acre WSQ until August of 1975, when it contracted with National Lead of Ohio to perform 

environmental monitoring in the pits and the quarry. In 1981, Bechtel National, Inc. assumed 

management and maintenance responsibility for the pits and quarry. In 1985, custody of the chemical 

plant was transferred from the Army to DOE (DOE 2004a). 

2.2.3

In 1986, DOE prepared Historical Nuclear Materials Balance Report for the Former AEC-Owned 

Weldon Spring Chemical Plant (DOE 1986a), which summarized the types and quantities of nuclear 

materials received and processed through WSP. This DOE report indicated that four types of nuclear 

materials were processed during the operational period of WSP: 1) natural uranium, 2) depleted 

uranium, 3) slightly enriched uranium, and 4) natural thorium. The great majority of material 

processed at WSP was natural uranium (approximately 98% of the total mass of processed

materials). 

Summary of Processed Nuclear Materials
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The natural uranium was received as ore concentrates, from which uranium was extracted and 

converted to various compounds and metal forms and shipped off the site. Depleted uranium was 

received as metal and various intermediate chemical forms, processed on an intermittent basis, and 

used primarily in product development activities. Slightly enriched uranium was processed on an 

intermittent basis only, and was typically received in the form of scrap metal or residues. Natural 

thorium was received in either a nitrate or an oxide form and processed on an intermittent basis in the 

refinery (DOE 1986a). Table 2-7 summarizes the total receipts by fiscal year of operation. 

Table 2-7. Annual uranium and thorium mass receipts (kg) (DOE 1986a).

Fiscal yeara Natural uraniummaterial

Depleted uranium 

material

Slightly enriched 

uranium material

Natural thorium 

material

1958b 8,000,407 128 0.4 44

1959 12,898,013 11,255 0 0

1960 15,032,283 30,203 0 0

1961 15,546,776 94,260 0 0

1962 16,009,091 22,225 0 0

1963 18,873,351 0 94,695 0

1964 16,661,427 47 265,323 13,111

1965 11,445,290 2,769 441,977 313,699

1966 7,077,000 6,936 27,700 614,693

1967 472,339 0 12,890 0

Totals 122,015,977 167,823 842,585 941,347

a. Fiscal year begins on July 1 of the previous calendar year and ends on June 30 of the calendar year corresponding 

to the designated fiscal year.

b. Includes startup period in FY 1957.

In 1999, DOE initiated the complex-wide Recycled Uranium Mass Balance Project (DOE 2000a), 

which identified WSP as a site that likely received recycled uranium in relatively small quantities of 

materials after 1961. The significance of these receipts of recycled uranium is that this material 

contains trace amounts of residual transuranic elements (including plutonium and neptunium), fission 

products (such as technetium), and reactor-produced uranium isotopes (such as 236U) (DOE 2000a). 

Site records do not include the level of detail needed for accurate estimate of the amount of recycled 

material received and processed at WSP. It is known that the plant received shipments of uranium 

materials from other DOE sites that processed and shipped recycled uranium from fiscal years 1962 

to 1967 (the period of recycled uranium shipment), but the amounts of recycled uranium versus 

natural uranium are not known. Due to the lack of information about recycled uranium quantities, the 

May 15, 2000, DOE report addressing WSP recycled uranium (DOE 2000a) assumes that all uranium 

receipts after 1961 (71,413,060 kg) were recycled, which is a large overestimate of the actual quantity 

because the same document reports that the majority of material processed through WSP was natural 

uranium.

2.2.4

In 1985, DOE proposed designating control and decontamination of the chemical plant, raffinate pits, 

and quarry as a major project to be called the Weldon Spring Site Remedial Action Project 

(WSSRAP). In July 1986 a DOE project office was established on the site, and the project 

management contractor for the WSSRAP was a partnership of MK-Ferguson Company and Jacobs 

Engineering Group, Inc. The quarry was placed on the EPA NPL in July 1987. The chemical plant 

and raffinate pits were added to the NPL in March 1989.

Site Remediation

The purpose of the WSSRAP was to eliminate potential hazards to the public and environment and to 

make surplus real property available for other uses to the extent possible. The scope of work 

included dismantling the 44 WSCP buildings and structures and disposing of both radiologically and 

chemically contaminated structural materials and soils. The project also disposed of as much material 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 24 of 39

as possible (including water, sludge, abandoned waste materials, and structural materials) from the 

raffinate pits, quarry, and nearby properties (DOE 2000b). 

The Record of Decision for the Management of the Bulk Wastes at the Weldon Spring Quarry (ANL 

1990) was signed in September 1990. The quarry bulk wastes were excavated and placed in the 

Temporary Storage Area (TSA) at the WSCP site based on an accelerated cleanup strategy involving 

limited characterization, a focused Remedial Investigations/Feasibility Study (RI/FS), and a limited 

baseline risk evaluation. Excavation of approximately 120,000 yd3 of WSQ bulk wastes was 

completed in October 1995 (DOE 2003). Material at the TSA was eventually placed in the onsite 

engineered disposal facility referred to as the Disposal Cell. Following bulk waste excavation, the 

selected remedy for residual contamination at the quarry site is long-term monitoring to verify that 

conditions at WSQ are protective of human health and the environment. 

Remedial investigations were conducted at the chemical plant and raffinate pits areas in 1988 and 

1989 under the Comprehensive Environmental Response, Compensation, and Liability Act RI/FS 

process. These investigations included characterization of groundwater, on-site soil contamination, 

contaminated sediment in off-site surface drainages, lakes, surface water and springs, and 

radiological contaminants in the raffinate wastes. The Record of Decision for Remedial Actions at the 

Chemical Plant Area of the Weldon Spring Site (DOE 1993) identifies the selection of the final 

remediation and disposal method for the chemical plant and bulk wastes for the quarry (DOE 2003). 

Remediation activities included the removal of contaminated soil, demolition and removal of remaining 

concrete pads and foundations that supported the 44 structures and buildings, removal and treatment 

of the raffinate pits wastes, and disposal of site wastes in an onsite engineered disposal facility (DOE 

2004b). Remediation via removal was completed in 2002, and DOE decided that remediation of the 

shallow groundwater aquifer under the former WSCP would involve institutional controls and 

monitoring to achieve remediation objectives (DOE 2004b).

Several temporary staging areas and process structures were constructed or commissioned for the 

purpose of treating or storing excavated wastes and raffinate pit water during the remediation 

process. Two water treatment facilities were used: A Quarry Waste Treatment Plant and the Site 

Water Treatment Plant (SWTP). A TSA for the WSQ bulk wastes was an area designed and 

designated on the WSCP to store excavated waste before placement in the Disposal Cell. A 

Chemical Stabilization and Solidification (CSS) facility operated to produce a grout for use in the 

engineered disposal facility. By mixing the contaminated raffinate pit sludges with fly ash and 

Portland cement, the plant provided a means for managing the contaminants as well as a material to 

fill voids and increase the structural stability of the facility. The full-scale CSS plant began operation 

in mid-1998. On November 13, 1998, the CSS plant completed dredging and processing sludge from 

Pit 3, treating approximately 122,000 yd3 of sludge since April 1998. More than 75 million gallons of 

water with an average of 8 to 10% solids was pumped through the dredge. The sludge was screened 

for oversized materials then thickened with a polymer before it was blended with binder materials and 

transferred to the Disposal Cell. Approximately 188,000 yd3 of grout were produced in the process. 

Demolition work on the SWTP was initiated on April 23, 1999, with activities completed in late June 

1999. As of 2002, construction of the Disposal Cell was 85% complete and nearly 1.5 million yd3 of 

contaminated wastes had been placed in it. Final site grading for the raffinate pits, Ash Pond, TSA, 

SWTP, Frog Pond, and material storage areas was performed in 2000.

2.3 RELEASES TO THE OUTDOOR ENVIRONMENT

Table 2-8 summarizes the activities that released radionuclides to the Weldon Spring environment. 

The following discussion is restricted to the periods for which the WSP has been listed as a “covered 

facility” according to the DOE Office of Worker Advocacy list (DOE 2004a), which are from 1955 to 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 25 of 39

1967 and from 1975 to the present. Operations did not begin until 1957; thus, this discussion is 

limited to a beginning date of 1957. The site did not have AEC or DOE contractors performing work at 

WSCP outside of these periods (DOE 2004a). 

Table 2-8. History of radioactive effluent-generating activities (1957 to 2002). 

Date Event

1957–1966a Operation of uranium feed materials plant.

Uranium concentrate converted to UO3, UF4, and uranium metal.

Some thorium processing. 

Raffinate from the processing removed to raffinate pits.

14,500 metric tons of uranium materials received for processing and sampling per year 

from 1958 to 1964.

Some thorium processed from 1965 to 1966.

Uranium and thorium residues disposed of in the WSQ. 

Dec 1966a Plant closed; hopper and process lines emptied; dust collectors cleaned out.

1975-1985 Site remained essentially undisturbed.

1986-2002 Remediation involving excavation of contaminated soils and rubble. 

a. Expanded from Meshkov et al. (1986).

2.3.1

According to Meshkov et al. (1986), air concentrations of uranium were measured during the WSCP 

operational period along the plant site perimeter, around buildings on the site, and at the south edge 

of the quarry. Air concentrations of radon were measured from 1979 through 2000 around the 

chemical plant, pits, and quarry perimeters (Meshkov et al. 1986; Weidner and Boback 1982; Bechtel 

1983a, 1983b, 1984, 1985a, 1986; MK-Ferguson 1987; 1988; 1989; 1990; 1991; 1992; 1993; 1994; 

1995; 1996; 1997; 1998; 1999; 2000a; and 2001a). Air concentrations of particulates were measured 

during some of the postoperational period. This information suggests that air emissions were of 

potential concern not only during operational activities when radionuclide-laden dust was created, but 

also from subsequent contamination of the surrounding terrain. 

Airborne Emissions

The total amount of uranium emitted to the atmosphere during the operational period (1957 to 1966)

has been estimated from monitoring data (Meshkov et al. 1986) and a materials balance study (DOE 

1986a). Table 2-9 summarizes the reported atmospheric discharges from the materials balance 

study, which were engineering estimates derived from airflows and other process factors along with 

stack-monitoring data. Based on these two methods, the amount of uranium activity emitted from the 

plant is estimated to range between approximately one and 5 Ci/yr. Release rates for uranium decay 

products (230Th, 226Ra, and 210Pb) were also estimated by Meshkov et al. as a fixed percent of the 

(estimated) amount of released 238U. An estimate of radon release based on the amount of uranium 

processed during the period ranged from 12 to 34 Ci/yr. 

Beginning in 1981, annual environmental monitoring reports have provided estimates of air 

concentrations of particulate radionuclides and of radon at the WSCP and WSQ. These estimates 

reflect emissions during the later maintenance period and throughout remediation activities. Because 

the site remained in the monitoring and maintenance phase from 1975 to 1985, data from the period 

from 1981 to 1985 could be useful for estimating emissions from 1975 to 1980.

2.3.2

Waterborne emissions from the WSP site have been a result of discharge of solubilized radionuclides 

to surface water or groundwater. The four raffinate pits at the WSCP and the WSQ presented 

conditions where contaminated sludge, soil, and rubble were covered or partially covered with 

standing water. During the operational period (1957—1967), the raffinate pits at the WSCP were a 

Waterborne Emissions
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 26 of 39

Table 2-9. Estimated annual discharges to stacks (kg).

a

Fiscal yearb Natural uranium Depleted uranium

Slightly enriched 

uranium Natural thorium

1958 —c —c —c —c

1959 —c —c —c —c

1960 7,200 —c —c —c

1961 7,200 0 0 0

1962 7,200 0 0 0

1963 7,200 0 0 0

1964 7,483 0 0 0

1965 4,200 0 300 0

1966 4,158 0 0 0

1967 100 0 0 0

Total 44,741 0 300 0

a. From Table 7 in DOE (1986).

b. Fiscal year begins on July 1 of the previous calendar year and ends on June 30 of the calendar year corresponding 

to the designated fiscal year.

c. No values given for these years.

source of radionuclides that were discharged to surface water. After the WSP operations ceased in 

1967, a small but continuous discharge at the process sewer outfall occurred (Weidner and Boback 

1982). During operations and in the years following plant closure, leaching of sediments in the pits 

and quarry provided a route of discharge to groundwater (Weidner and Boback 1982).

The four raffinate pits received neutralized residues and waste streams from the various processing 

steps at the WSCP (Ficker 1981). The sludges in all the pits are essentially the same with the 

exception of those in Pit 4, because the latter was used predominantly during thorium processing. 

The pits were used as settling lagoons: The solids would settle out as a sludge, and the remaining 

supernatant would overflow to the plant process sewer. The solids were mostly acid insoluble 

compounds contained in the original ore material as well as hydroxides and precipitates that formed 

when the raffinates were neutralized with lime. 

About 30% of the residues in Pits 1, 2, and 3 came from the uranium metal production step. 

Magnesium fluoride was produced as a scrap material during the reduction of UF4 to uranium metal, 

and the slag contained about 5% uranium. This uranium was leached from the slag and then washed 

to remove the remaining soluble uranyl nitrate. The washed slag, almost uranium free, was pumped 

to the pits. In addition to residues from thorium processing, Pit 4 also contains drums and rubble 

dumped during plant closure (Ficker 1981).

During the operational period, the total amount of uranium discarded to the raffinate pits was 

measured, and it is reported in the materials balance study cited earlier (DOE 1986a). Table 2-10 

summarizes the recorded discharges to the raffinate pits. 

When the raffinate pits were in use, the supernatant solution from Pits 1 through 3 was decanted and 

fed to the plant storm sewer system via buried pipes (Weidner and Boback 1982). Sewage treatment 

effluent added to this flow, and the combined wastewater was discharged off the site into a natural 

streambed. The discharge point, called the process sewer outfall, was within a fenced right-of-way 

that enclosed the stream all the way to the Missouri River. Table 2-11 lists the estimates of 

discharges to the sewer from the materials balance study (DOE 1986a). Supernatant from Pit 4 was 

never decanted, which is why Table 2-11 does not indicate thorium discharges to the sewer. 

While the majority of the thorium and uranium in the raffinate pits and quarry is insoluble, their 

progeny are likely to be more soluble. Therefore, both the WSCP and WSQ pose a potential source 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 27 of 39

Table 2-10. Estimated annual discharges to raffinate pits (kg).

a

Fiscal yearb Natural uranium Depleted uranium

Slightly enriched 

uranium Natural thorium

1958 —c —c —c —c

1959 —c —c —c —c

1960 46,193 —c —c —c

1961 12,502 0 0 0

1962 8,831 46 0 0

1963 18,448 0 0 0

1964 35,243 0 0 2,469

1965 13,069 0 2,828 16,170

1966 18,067 0 (20) 26,809

1967 29 0 0 30,750

Total 152,382 46 2,808 76,198

a. From Table 7 in DOE (1986).

b. Fiscal year begins on July 1 of the previous calendar year and ends on June 30 of the calendar year corresponding 

to the designated fiscal year.

c. Discharges to raffinate pits in AEC Fiscal Years 1958 and 1959 were held in inventory as “potentially recoverable.” 

Beginning in AEC Fiscal Year 1960, all previous and then current releases to the raffinate pits were treated as 

discharges and removed from the operating inventory as they occurred.

Table 2-11. Estimated annual discharges to sewer (kg).

a

Fiscal yearb Natural uranium Depleted uranium

Slightly enriched 

uranium Natural thorium

1958 —c — — —

1959 — — -- —

1960 3,472 — — —

1961 6,461 0 0 0

1962 4,304 0 0 0

1963 6,374 0 0 0

1964 3,239 0 0 0

1965 1,254 0 979 0

1966 1,411 0 0 0

1967 205 0 0 0

Total 26,720 0 979 0

a. From Table 7 in DOE (1986).

b. Fiscal year begins on July 1 of the previous calendar year and ends on June 30 of the calendar year corresponding to 

the designated fiscal year.

c. — = no values given for these years.

of groundwater contamination near the WSP site. Ongoing remediation involves active monitoring of 

the groundwater in this region.

2.4 ACCIDENTS

No information is currently available about accidental releases of radioactive materials to the 

environment during operation of the WSP. If additional information becomes available, it will be 

assessed for value and added to this section as appropriate. 

Dupree (1979) cites two accidental exposures of workers which occurred during plant operations and 

were described by Mason during a visit to ORAU in August 1979. In one instance, a worker overfilled 

a pot with molten uranyl nitrate solution which spilled onto the floor. While attempting to turn off the 

valve, he fell into the material on the floor. He was hospitalized and ultimately returned to work 

approximately 11 weeks after the accident. A full report of the incident was made (MCW 1961). In the 

other case, a worker inhaled soluble uranium while trapped in a dust enclosure. The notes report that 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 28 of 39

the worker suffered from “CNS effect” (presumably central nervous system effect). Mason further 

speculated that this reaction was due to the chemical toxicity of the uranium exposure. There are no 

notes about longer-term effects on either employee. 

2.5 HEALTH PROTECTION PRACTICES

2.5.1

The health protection program in place when operations began at the WSP in 1957 is not specifically 

detailed in any of the technical reports available at this time. However, since MCW transferred many 

of its activities and personnel from the Destrehan Street site in St. Louis at the startup of the WSP, it 

is likely that the program in place closely resembled that documented by Mason (1955). If anything, 

changes to the health protection program were likely more effective due to experience gathered in 

previous years of involvement in uranium-processing operations. According to a descriptive report of 

the Mallinckrodt contributions between 1942 and 1967 (Fleishman-Hillard 1967), the design of the 

WSP “took advantage of the Company’s and the Atomic Energy Commission’s (AEC’s) accumulated 

wealth of experience concerning the handling of health and contamination problems encountered in 

uranium processing.” The WSP layout was planned with the goal of minimizing the spread of 

contamination; advanced dust-control systems were used, and on-site health facilities were provided. 

This 1967 document states, “...existing health programs were continued... at the new site, and a 

number of supplemental programs were initiated at the Weldon Spring plant.” 

Operational Period (1957 to 1967)

A 1965 revision of the Summary of Health Protection Practices for the MCW Uranium Division is 

documented in MCW (1965). The policies and basic principles underlying the health protection 

program are described, and information is included about survey meter checks, film-badging 

procedures, bioassay procedures, and restrictions on work assignments based on previous 

accumulated exposures. It is likely that this represents a revision of the 1955 program, but it is not 

clear what or when specific changes were made over the intervening years.

Both the 1955 and 1965 documents rely on AEC standards of radiation exposure to the extent that 

health protection decisions were made about worker rotation based on a comparison of monitored 

personnel exposures with these standards for radiation workers (i.e., individuals in controlled areas). 

Table 2-12 summarizes the 1955 document’s list of tolerated cumulative doses in use at MCW. In 

addition, the 1955 document states that the goal was to keep each individual cumulative exposure at

no greater than one-half of the tolerance when averaged over 3 months. The methods claimed for 

controlling exposure are shielding, semi-remote operations, and worker rotation.

Table 2-12. Tolerated dose limits in 1955. 

Type of radiation Tolerated dose limit

Beta 500 mrepa/wk, whole body or part

Gamma 300 mR/wk, whole body or part

Beta & Gamma 500 mrepa/wk, whole body or part

Not specified 1,500 mrepa/wk hands and forearms

a. rep = roentgen-equivalent-physical, an obsolete unit of absorbed dose 

for types of radiation other than X-rays and gamma rays; replaced by 

the gray.

Table 2-13 lists the WSP guides for prescribing restricted work so that AEC standards would not be 

exceeded (MCW 1965). Work restriction involved temporary relocation of the affected personnel from 

usual duties until the cumulative average was at an acceptable level. 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 29 of 39

Table 2-13. Guides for prescribing restricted work based on radiation exposure in 1965. 

Type of radiation or 

radioactive material

Dose limit

Gamma 3 rem per 3 consecutive calendar months.

10 rem per 12 consecutive calendar months.

5 rem per 12 months averaged over employment beginning 1955.

Beta 10 rem beta + gamma to whole body per 3 consecutive months.

30 rem beta + gamma to whole body per 12 consecutive months.

25 rem beta + gamma to whole body per 3 consecutive months.

75 rem beta + gamma to whole body per 12 consecutive months.

Internal radioactive 

materials (when principal 

effect of the material is 

radiation dose to tissues)

50% of the acceptable body burden specified in the recommendations of the 

National Council on Radiation Protection and Measurements (NBS 69).

Time-weighted exposure concentration averaged over any 4-week period exceeds 

more than 5 times the quantity in Table 1 of AEC Appendix 0524.

Uranium Average urine concentrations for 3 evenly spaced samples over a 72-hr period 

exceeds 0.15 mg/L and one sample exceeds 0.25 mg/L.

Time-weighted exposure air concentration averaged over 5 consecutive workdays 

exceeds 0.25 mg/m3.

Concentration in exposure air averaged over a 1-hr exposure exceeds 2.0 mg/m3 

(a reduction factor of 5 is allowed for a well-fitted mechanical respirator, and a 

factor of 50 for positive pressure respirator).

Uptake by other than inhalation suspected or known, average urine concentrations 

for 3 evenly spaced samples over a 72-hr period exceeds 0.10 mg/L.

2.5.1.1 Badging

According to Mason (1955) health protection program document, “each employee except office 

females wears (a) combination film badge-security badge.” The stated procedure was to change 

these badges biweekly “or more often as indicated.” Film monitors were placed at selected points 

throughout process areas to serve as integrating area monitors, and routine meter surveys were used 

to detect hot spots and provide information for decisions about protective measures. Data from these 

area monitors or meter surveys have not been found at this point.

The MCW (1965) health protection program document states that personnel in operating areas of the 

plant and in some laboratories wore badges continuously while at work and exchanged them monthly

for processing. Permanent badges were assigned to persons who frequently went into badged areas. 

Spare badges were available for persons having a casual need to enter badged areas. Badges other 

than operations badges were exchanged on a 3-month schedule.

2.5.1.2 Radiological Exposure and Access Control

Workers at the WSP had the potential for exposure to airborne radionuclides from uranium or thorium 

ore processing and to external radiation from the onsite radioactive materials. Film badges and 

bioassay were used to evaluate actual exposures throughout the operational history. Measures were 

taken to control potential exposures to below AEC standards. According to Mason (1955) these 

measures involved:

1. Instituting a work permit program (aimed primarily at protecting maintenance workers in

hazardous areas), which involved establishing time limits and survey meter checks for areas 

with radioactive materials
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 30 of 39

2. Conducting investigations and counseling to study causes for exposure trends or unusual 

individual exposures and to educate employees about protective measures

3. Providing shielding, semi remote operations, and worker rotation to control exposure

4. Providing work clothing from the skin out for personnel working in regulated areas (where 

radioactive materials were processed and handled), which could not be worn outside of these 

areas except under cover clothing

5. Use of respirators as specified by the MCW Health Department

6. Instituting a job time-limit program, for personnel who worked routinely in areas wherein the 

exposure rate was known to be above the AEC-based tolerance limits

MCW (1965) is more general than Mason (1955), but it is reasonable to assume all of the above 

measures were still in place based on language in the 1965 report.

2.5.2

During the monitoring and maintenance period (1975 to 1985), contractors to the Energy Research 

and Development Administration and DOE maintained the integrity of embankments of the pits, 

controlled vegetation, and conducted environmental sampling for assessment in relation to the

maintenance role. Documentation of the health protection program in place for these workers has not 

been found. However, NLO (1977) states, “no personnel are employed or directly assigned to the 

Weldon Spring site”, and “NLO personnel perform sampling and engineering duties on assignment 

from the Feed Materials Production Center, Fernald, Cincinnati, Ohio.” Therefore, exposures to 

radionuclides on the WSP site were limited because the site was essentially undisturbed during this 

period and the external exposure rate and airborne concentrations of radioactivity were minimal in 

terms of potential short-term exposures to caretakers (NLO 1977).

Postoperational Period (1975 to Present)

During the remediation period (1985 to present), the WSSRAP project management contractor

implemented health protection practices in compliance with DOE guidelines and regulations on 

occupational radiation protection (DOE 1981, 1986b, 1989, 10 C.F.R. pt. 835). Because inhalation 

was recognized as the primary pathway of concern at the WSP site in relation to worker exposure

during active remediation (i.e., excavation and dismantling of structures), the focus of the radiation 

protection program was to control dust emissions and prevent inhalation intakes (MK-Ferguson 

2001b). Intake by ingestion was considered possible, but less of a potential dose hazard than 

inhalation. Administrative controls were implemented to minimize ingestion hazards by limiting eating, 

drinking, and smoking in contamination areas; by using personal protective equipment such as 

coveralls, face shields, and gloves; and by meeting monitoring requirements. 

Active remediation began in 1993 with the dismantlement of structures at the WSCP and the removal 

of bulk wastes at the WSQ. Applicable DOE guidelines and regulations were specified in 10 CFR pt.

835 at that time. Monitoring to assess internal exposure hazards to remediation workers included 

area monitoring for airborne radionuclides other than radon and thorium, area monitoring for radon 

and thorium, breathing-zone air (BZA) samplers, and bioassay. In work areas where long-lived 

airborne radioactivity concentrations were likely to exceed 2% of the DOE-established limit, BZA 

sampling was conducted on 25% of the workers spending more than 1 hr/day in the area. Bioassay 

requirements included baseline, routine, special, contamination incident, and exit urine samples 

analyzed for uranium for radiological workers who were likely to receive 100 or more mrem/yr
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 31 of 39

committed effective dose equivalent (CEDE) and who declared pregnancy and routinely entered 

controlled areas. The BZA-sampling results were used to determine bioassay participation.

According to the WSSRAP project management contractor (MK-Ferguson 2000b), “external dose 

rates are very low at the WSP site. General area external beta dose equivalent rates are at 

background levels (i.e., 0.03-0.05 mrem/hr)”, with external gamma dose equivalent rates ranging from 

background (about 60 mrem/yr) to about 113 mrem/yr for continuous exposure in general areas. 

These exposure rates were expected to remain constant for the duration of site remediation. The use 

of nuclear density gauges by remediation workers increased the gamma radiation fields near the 

equipment (3 mrem/hr at 30 cm from the source), so control measures were instituted in these special 

areas to limit worker exposure. Raffinate sludge could produce a contact gamma dose rate in the 

range of 1 to 3 mrem/hr (with shallow dose equivalent rates up to 10 mrem/hr). Therefore, most 

raffinate sludge treatment and disposal activities were performed remotely to limit exposure. 

2.5.2.1 Badging (post-operational)

Information on badging procedures during the monitoring and maintenance period (1975 to 1985) is 

not available. For the remediation period (1985 to present), the following information has been 

derived from documentation generated by the project management contractor for the WSSRAP, which 

was a partnership of MK-Ferguson Company and Jacobs Engineering Group, Inc. 

According to the January 2000 External Dosimetry Technical Basis Manual (MK-Ferguson 2000b), the 

“WSSRAP has provided personnel dosimetry to radiological workers since October 1986,” just 

following the establishment of the DOE office on the site. According to this manual, only one worker’s 

monitoring results indicated an external effective dose equivalent (EDE) above 100 mrem/yr (the 

results for this worker were 170 mrem EDE in 1994). In addition, the highest measured shallow dose 

equivalent was 1,450 mrem (in 1994), and all measured extremity dose equivalents were less than 

this value. Therefore, the DOE regulated action level of 5,000 mrem annual shallow and extremity 

dose equivalent was never exceeded. Therefore, during the fourth quarter of 1995, the number of 

dosimeters issued to personnel was reduced by approximately 95% due to completion of many of the 

activities that could have resulted in a significant external dose in relation to DOE regulations and 

because future WSSRAP activities were judged to be similar to previous activities, which did not lead 

to significant exposure. The issuance was reduced to include only declared pregnant workers who 

entered controlled areas and those radiological workers likely to receive 100 mrem EDE in 1 yr from 

external sources or 5,000 mrem shallow dose equivalent to the skin or any extremity. The issuance 

decision was made by the Worker Protection Supervisor based on area radiation monitoring results 

and estimated exposure times. 

2.5.2.2 Radiological Exposure and Access Control

Access to the WSP was limited to authorized personnel during the maintenance period by a 7-ft

chain-link cyclone fence topped with three strands of barbed wire. The site was completely enclosed 

by Army-owned areas, and security patrols were provided by the Army to hinder unauthorized access 

(NLO 1977).

During active remediation, measures were taken to control potential internal and external exposures 

according to DOE guidelines, many of which are noted above. Access to areas in which exposures 

could exceed regulatory limits was administratively controlled. The Worker Protection Supervisor (or 

designee) made decisions about access to areas based on area monitoring that evaluated external 

exposure rates as well as air concentrations of radionuclides including radon, thorium, and progeny 

(MK-Ferguson 2000b, 2001b).
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 32 of 39

Workplace intake controls included:

• Area decontamination

• Air-handling units equipped with high efficiency particulate air (HEPA) filters

• Dust suppression using water sprays

• Dust elimination using surface wipe down and/or HEPA vacuuming

• Plastic dust barriers

• Limiting work area access to essential personnel and equipment

• Prohibiting eating, drinking, smoking, and chewing in the work area

• Training for hazard recognition prior to entry in controlled areas 

Respiratory protection was required when workplace control measures were not possible or 

sufficiently effective, and the need for such was generally assessed when annual intakes of 

radionuclides other than radon, thorium, and progeny were likely to result in dose equivalents 

exceeding 100 mrem CEDE, or when intakes of radon, thorium, and progeny were likely to result in 

dose equivalents above 500 mrem CEDE.
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 33 of 39

REFERENCES

10 C.F.R. pt. 835, Occupational Radiation Protection, Final Rule, Code of Federal Regulations. 

AEC (U.S. Atomic Energy Commission), AEC Manual Chapter 0524, Washington, DC. 

ANL (Argonne National Laboratory), 1990, Record of Decision for the Management of the Bulk 

Wastes at the Weldon Spring Quarry, no document number available, Chicago, Illinois. 

Bechtel (Bechtel National, Inc.), 1983a, Weldon Spring Site (WSS) Environmental Monitoring Report, 

Calendar Year 1981, no document number available, Oak Ridge, Tennessee, May.

Bechtel (Bechtel National, Inc.), 1983b, Weldon Spring Site (WSS) Environmental Monitoring Report, 

Calendar Year 1982, no document number available, Oak Ridge, Tennessee, May.

Bechtel (Bechtel National, Inc.), 1984, Weldon Spring Site Environmental Monitoring Report, Calendar 

Year 1983, DOE/OR/20722-16, Oak Ridge, Tennessee, June.

Bechtel (Bechtel National, Inc.), 1985, Weldon Spring Site Environmental Monitoring Report, Calendar 

Year 1984, DOE/OR/20722-58, Oak Ridge, Tennessee, July.

Bechtel (Bechtel National, Inc.), 1986, Weldon Spring Site Annual Site Environmental Monitoring 

Report, Calendar Year 1985, DOE/OR/20722-101, Oak Ridge, Tennessee, September.

DOE (U.S. Department of Energy), 1981, Environmental Protection, Safety, and Health Protection 

Program for DOE Operations, DOE 5480.1A, August.

DOE (U.S. Department of Energy), 1986a, Historical Nuclear Materials Balance Report for the Former 

AEC-Owned Weldon Spring Chemical Plant, Weldon Spring, Missouri, DOE/OR-872, Oak 

Ridge Operations Office, Oak Ridge, Tennessee, July.

DOE (U.S. Department of Energy), 1986b, Environmental Protection, Safety, and Health Protection 

Program for DOE Operations, DOE 5480.1B, September. 

DOE (U.S. Department of Energy), 1989, Radiation Protection for occupational Workers, DOE 

5480.11, January. 

DOE (U.S. Department of Energy), 1993, Record of Decision for Remedial Action at the Chemical 

Plant Area of the Weldon Spring Site, DOE/OR/21548-376, September 1993, Weldon Spring, 

Missouri. 

DOE (U.S. Department of Energy), 2000a, Ohio Field Office Recycled Uranium Recovery Report, no 

document number available, Ohio Field Office, Springdale, Ohio. 

DOE (U.S. Department of Energy), 2000b, “Weldon Spring Site Remedial Action Project: Cleanup 

Activities,” Office of Environmental Management, Washington, DC,

http://www.em.doe.gov/wssrap/cleanup.html, web page date 10/02/00.

DOE (U.S. Department of Energy), 2003, Environmental Monitoring Plan, DOE/OR/21548-424, Rev. 

10, Oak Ridge Operations Office, Weldon Spring Site Remedial Action Project, Oak Ridge, 

Tennessee, January. 
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DOE (U.S. Department of Energy), 2004a, “Weldon Spring,” Office of Environmental Management, 

Office of Worker Advocacy, Washington, DC, 

http://tis.eh.doe.gov/beta/eren/advocacy/faclist/showfacility.cfm.

DOE (U.S. Department of Energy), 2004b, Record of Decision for the Final Remedial Action for the 

Groundwater Operable Unit at the Chemical Plant Area of the Weldon Spring Site, 

DOE/GJ/79491-936a, Office of Legacy Management, Weldon Spring Site Remedial Action 

Project, Weldon Spring, Missouri, January.

Dupree, E. A., 1979, “Mallinckrodt Chemical Works – Visit from Mont Mason, August 21-24, 1979,” 

internal memorandum to A. P. Polednak, September 5, Oak Ridge Associated Universities, 

Oak Ridge, Tennessee. 

Dupree, E. A., 1983, “Visit to MCW Corporate Headquarters,” memorandum to file, October 25, Oak 

Ridge Associated Universities, Oak Ridge, Tennessee. 

Ficker, C. F., 1981, Environmental Monitoring Program for DOE Weldon Spring, Missouri Site, 

NLCO-009EV, Special UC-70A, National Lead Company of Ohio, Cincinnati, Ohio. 

Fleishman-Hillard, 1967, Fuel for the Atomic Age, Completion Report on St. Louis-Area Uranium 

Processing Operations, 1942-1967, St. Louis, Missouri.

Mason, M., 1955, Mallinckrodt Chemical Works Health Program, Policies, Status, and Summary, 

Mallinckrodt Chemical Works, St. Louis, Missouri. 

MCW (Mallinckrodt Chemical Works), 1961, Summary Report: Chemical Operator Burned With 

Molten Uranium Salt Solution, Health and Safety Department, Uranium Division, Weldon 

Spring, Missouri, June 1, 1961. 

MCW (Mallinckrodt Chemical Works), 1962, Tour Guide Book, Feed Materials Plant, Uranium 

Division, Weldon Spring, Missouri, February. 

MCW (Mallinckrodt Chemical Works), 1964, Weldon Spring, An Introduction, Uranium Division, St. 

Charles, Missouri. 

MCW (Mallinckrodt Chemical Works), 1965, Summary of Health Protection Practices (Revised 1965), 

Health/Safety Department, Uranium Division, Weldon Spring, Missouri. 

MCW (Mallinckrodt Chemical Works), 1966, Summaries of Dust Concentrations at Production Jobs, 

Life of Operation – from Year 1957 through 1966, Uranium Division, St. Charles, Missouri. 

Meshkov, N., P. Benioff, J. Wang, and Y. Yuan, 1986, Weldon Spring Historical Dose Estimate, 

ANL/EES-TM-308, Argonne National Laboratory, Argonne, Illinois, July. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1987, Weldon Spring Site Annual 

Environmental Monitoring Report, Calendar Year 1986, DOE/OR/21548-T1, St. Charles, 

Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1988, Weldon Spring Site Annual 

Environmental Monitoring Report, Calendar Year 1987, DOE/OR/21548-015, St. Charles, 

Missouri. 
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MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1989, Annual Environmental 

Monitoring Report, 1988, For the Weldon Spring Site Remedial Action Project, 

DOE/OR/21548-079, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1990, Annual Environmental 

Monitoring Report, 1989, For the Weldon Spring Site Remedial Action Project, 

DOE/OR/21548-129, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1991, Annual Environmental 

Monitoring Report, 1990, For the Weldon Spring Site Remedial Action Project, 

DOE/OR/21548-193, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1992, Weldon Spring Site 

Environmental Monitoring Report for Calendar Year 1991, Revision 1, DOE/OR/21548-283, St. 

Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1993, Weldon Spring Site 

Environmental Report for Calendar Year 1992, DOE/OR/21548-372, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1994, Weldon Spring Site 

Environmental Report for Calendar Year 1993, DOE/OR/21548-436, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1995, Weldon Spring Site 

Environmental Report for Calendar Year 1994, DOE/OR/21548-512, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1996, Weldon Spring Site 

Environmental Report for Calendar Year 1995, DOE/OR/21548-592, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1997, Weldon Spring Site 

Environmental Report for Calendar Year 1996, DOE/OR/21548-676, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 1998, Weldon Spring Site 

Environmental Report for Calendar Year 1997, DOE/OR/21548-730, St. Charles, Missouri. 

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Environmental Report for Calendar Year 1998, DOE/OR/21548-773, St. Charles, Missouri. 

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Environmental Report for Calendar Year 1999, DOE/OR/21548-845, St. Charles, Missouri. 

MK-Ferguson (MK-Ferguson and Jacobs Engineering Group), 2000b, External Dosimetry Technical 

Basis Manual, Weldon Spring Site Remedial Action Project, DOE/OR/21548-441, Rev. 7, 

Weldon Spring, Missouri. 

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NBS (National Bureau of Standards), 1959, Maximum Permissible Body Burdens and Maximum 

Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure. 

Report 69, US Government Printing Office, Washington, DC.

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Implementation Guideline, OCAS-IG-001, Rev. 1, Office of Compensation Analysis and 

Support, Cincinnati, Ohio.

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Implementation Guideline, OCAS-IG-002, Rev. 0, Office of Compensation Analysis and 

Support, Cincinnati, Ohio.

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ERDA-Weldon Spring Site, NLCO-1144 (Special), Cincinnati, OH, April, 1977.

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Charles, County, Missouri, Office of the Deputy Assistant Project Manager for Chemical 

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Report for 1979 and 1980, NLCO-1176 (Special, UC-11), Feed Materials Production Center, 

National Lead Company of Ohio, Cincinnati, Ohio, April.
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 37 of 39

GLOSSARY

annual dose equivalent

The dose equivalent received in a year, expressed in units of rem or sievert.

alpha particles

Positively charged particles of discrete energies emitted by certain radioactive materials; alpha 

particles usually expend their energy in short distances and will not usually penetrate the outer 

layer of skin; they are a significant hazard only when taken into the body where their energy is 

absorbed by tissues.

U.S. Atomic Energy Commission (AEC)

Original agency established for nuclear weapons and power production; a predecessor to the 

Energy Research and Development Agency and the U.S. Department of Energy.

beta radiation

Radiation consisting of charged particles of very small mass (i.e., the electron) emitted 

spontaneously from the nuclei of certain radioactive elements. Most (if not all) of the direct 

fission products emit beta radiation. The beta particle is physically identical to an electron 

moving at high velocity.

curie (Ci)

A special unit of activity. One curie equals 3.7 × 1010 nuclear transitions per second.

dose equivalent (H) 

The product of the absorbed dose D, the quality factor Q, and any other modifying factors. 

The special unit is the rem. When D is expressed in gray, H is in sieverts, where 

1 sievert equals 100 rem.

dosimeter

A device used to measure the quantity of radiation received. A holder with radiation-absorbing 

elements (filters) and an insert with radiation-sensitive elements packaged to provide a record 

of absorbed dose or dose equivalent received by an individual. 

dosimetry

The science of assessing absorbed dose, dose equivalent, effective dose equivalent, etc., 

from external or internal sources of radiation. 

dosimetry system

A system used to assess dose equivalent from external radiation to the whole body, skin, or 

extremities. This includes the fabrication, assignment, and processing of dosimeters as well 

as interpretation and documentation of the results.

exposure

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

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

extremity

That portion of the arm extending from and including the elbow through the fingertips, and that 

portion of the leg extending from and including the knee and patella through the tips of the 

toes.
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 38 of 39

film

In general, a packet that contains one or more pieces of film in a light-tight wrapping. When 

developed, the film has an image caused by radiation that can be measured using an optical 

densitometer.

gamma rays

Electromagnetic radiation (photons) originating in atomic nuclei. Gamma rays are physically 

identical to X-rays, the only essential difference being that X-rays do not originate in the 

nucleus. 

hydrofluorination

Chemical conversion to a form containing fluorine.

isotope

One of a set of chemically identical species of atom which have the same atomic number but 

different mass numbers (different isotopes of an element having the same number of protons 

but different numbers of neutrons and thus different atomic numbers).

neutron

A basic particle that is electrically neutral weighing nearly the same as the hydrogen atom.

operating area

Designation of major onsite operational work areas.

photon

A unit or "particle" of electromagnetic radiation consisting of X- or gamma rays. 

quality factor (Q)

A modifying factor used to derive dose equivalent from absorbed dose.

radiation

Alpha, beta, neutron, and photon radiation. 

radioactivity

The spontaneous emission of radiation, generally alpha or beta particles, gamma rays, and 

neutrons from unstable nuclei.

radionuclide

A radioactive isotope of an element, distinguished by atomic number, atomic weight, and 

energy state. 

raffinate

A term loosely applied to waste from the uranium or thorium extraction step. Solids that result 

from the neutralization of this waste are also called raffinates. 

rem

A unit of dose equivalent equal to the product of the number of rad absorbed and the quality 

factor. The word derives from roentgen equivalent in man. 
Document No. ORAUT-TKBS-0028-2 Revision No. 00 Effective Date: 06/24/2005 Page 39 of 39

roentgen

A unit of exposure to gamma (or X-ray) radiation. It is defined precisely as the quantity of 

gamma (or X-) rays that will produce a total charge of 2.58 × 10-4 coulomb in 1 kilogram of dry 

air. An exposure of 1 roentgen is approximately equivalent to an absorbed dose of 1 rad in 

soft tissue for higher (more than about 100 kilovolt-electron) energy photons.

shallow absorbed dose

The absorbed dose at a depth of 0.007 centimeter in a material of specified geometry and 

composition.

shallow dose equivalent (Hs) 

Dose equivalent at a depth of 0.007 centimeter in tissue.

shielding

Any material or obstruction that absorbs (or attenuates) radiation and thus tends to protect 

personnel or materials from radiation.

sievert

The International System unit for dose equivalent, where 1 sievert equals 100 rem.

skin dose

Absorbed dose at a tissue depth of 7 milligrams per square centimeter. 

whole-body dose

Commonly defined as the absorbed dose at a tissue depth of 1.0 cm (1000 mg/cm2

); however, 

also used to refer to the recorded dose.

X-ray

Ionizing electromagnetic radiation of external nuclear origin.