ORAU TEAM

Dose Reconstruction

Project for NIOSH

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

Page 1 of 11

Document Title:

Weldon Spring Plant – Introduction

Document Number: ORAUT-TKBS-0028-1 

Revision: 00

Effective Date: 06/28/2005

Type of Document: TBD

Supersedes: None

Subject Experts: Craig A. Little and Robert Meyer

Document Owner

Approval: Signature on File Approval Date: 06/22/2005

Robert Meyer, TBD Team Leader

Approval: Signature on File Approval Date: 06/22/2005

Judson L. Kenoyer, Task 3 Manager

Concurrence: Signature on File Concurrence Date: 06/22/2005

Richard E. Toohey, Project Director

Approval: Signature on File Approval Date: 06/28/2005

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-0028-1 Revision No. 00 Effective Date: 06/28/2005 Page 2 of 11

PUBLICATION RECORD

EFFECTIVE 

DATE

REVISION

NUMBER DESCRIPTION

03/24/2005 00-A Technical basis document for the Weldon Spring Plant – Introduction. 

Initiated by Robert Meyer.

04/20/2005 00-B Incorporates internal review comments. Initiated by Robert Meyer.

05/20/2005 00-C Incorporates responses to NIOSH comments. Initiated by Robert 

Meyer.

06/16/2005 00-D Incorporates an additional change per a NIOSH comment. Initiated 

by Robert Meyer.

06/28/2005 00 First approved issue. Training is not required. Initiated by Robert 

Meyer.
Document No. ORAUT-TKBS-0028-1 Revision No. 00 Effective Date: 06/28/2005 Page 3 of 11

TABLE OF CONTENTS

Section

PUBLICATION RECORD ....................................................................................................................

Page

2

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

1.0 Introduction......................................................................................................................................5

References ........................................................................................................................................11
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ACRONYMS AND ABBREVIATIONS

AEC U.S. Atomic Energy Commission

CFR Code of Federal Regulations

DOE U.S. Department of Energy

DOL U.S. Department of Labor 

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 2000

HVL half-value layer

IREP Interactive RadioEpidemiological Program 

IMBA Integrated Modules for Bioassay Analysis (computer program)

NIOSH National Institute for Occupational Safety and Health

ORAU Oak Ridge Associated Universities

TBD technical basis document

U.S.C. United States Code

WSCP Weldon Spring Chemical Plant

WSP Weldon Spring Plant

WSQ Weldon Spring Quarry

WSRP Weldon Spring Raffinate Pits
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1.1 INTRODUCTION

Oak Ridge Associated Universities (ORAU) leads the ORAU Team in support of the National Institute 

for Occupational Safety and Health (NIOSH) in conducting activities under the Energy Employees 

Occupational Illness Compensation Program Act of 2000 (EEOICPA). The purpose of this Site Profile 

is to support the ORAU Team with documentation of historical practices at the Weldon Spring Plant 

(WSP). This WSP Site Profile contains technical basis information the ORAU Team can use to 

evaluate the total occupational radiation dose for EEOICPA claimants. Dose reconstructors can use 

the information in this Site Profile to evaluate internal and external dosimetry data for unmonitored 

and monitored workers, and to serve as a supplement to, or substitute for, individual monitoring data. 

Technical basis documents (TBDs) and Site Profile documents are general working documents that 

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

of sites. They will be revised in the event additional relevant information is obtained about the 

affected site(s). These documents may be used to assist NIOSH in the completion of the individual 

work required for each dose reconstruction.

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

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

employer facility” or a “Department of Energy facility” as defined in the EEOICPA (42 U.S.C. § 7384l 

(5) and (12)). 

The TBDs that comprise this Site Profile provide supporting technical data to evaluate, with claimantfavorable assumptions, the total WSP occupational radiation dose that can reasonably be associated 

with a worker’s radiation exposure. This dose results from exposure to external and internal radiation 

sources in WSP facilities, occupationally required diagnostic X-ray examinations, and onsite 

environmental releases. In addition, this Site Profile includes the dose that might have occurred while 

the worker was not monitored, or the dose that might have been missed. Over the years new and 

more reliable scientific methods and protection measures have been developed. This Site Profile 

identifies methods needed to account for these changes. The analyses for this Site Profile used the 

NIOSH Interactive RadioEpidemiological Program (IREP) and Integrated Modules for Bioassay 

Analysis (IMBA) computer codes to evaluate doses. 

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

Site Profile describes the evaluation of uncertainty for WSP exposure and dose records.

1.2 SITE PROFILE DESCRIPTION

The Site Profile consists of this introductory document and five major TBDs: Site Description, 

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

Occupational External Dosimetry. Some of these have attachments that provide critical data for dose

reconstructors. In some cases, data and information specific to the WSP were unavailable. In such 

situations, the analysis examined TBDs that describe similar processes at other facilities to discern 

the situation at the WSP. 

1.2.1

The WSP Site Description TBD (ORAUT-TKBS-0028-2) discusses facilities and processes used in the 

processing of uranium concentrates and other uranium compounds from 1957 through 1966. WSP

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

These operations focused on processing uranium and thorium from feed stocks to metal and 

Site Description
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intermediate products for use at other facilities. This TBD contains documentation to assist in the 

evaluation of worker dose from WSP operations and processes.

Site History and Operations

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

Spring Chemical Plant (WSCP) as the site for an explosives production facility known as the Weldon 

Spring Ordnance Works. By 1949, the ordnance works had been shut down and 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 (the WSCP) to 

process uranium and thorium ore concentrates; this plant operated from 1957 through 1966. This Site 

Profile refers to the raffinate pits that were originally part of the WSCP as the Weldon Spring Raffinate 

Pits (WSRP) because they were managed separately in the postoperational period. In 1958, a 9-acre 

quarry site was transferred to the AEC; this is referred to as the Weldon Spring Quarry (WSQ). 

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

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

In 1985, the U. S. Department of Energy (DOE; an AEC successor agency) regained responsibility for

the WSCP and began site characterization and remediation. The quarry was placed on the National 

Priorities List in 1987; the listing was expanded to include the chemical plant area and associated 

waste storage areas in 1989. 

Prior to remediation, there were four periods of the WSP site and WSCP history: Plant acquisition and 

development (1954-1957), operations (1957-1966), initial cleanup (1967-1969), and maintenance 

(1969—1985). The periods of concern for this Site Profile Document (SPD) are those during which the 

U.S. Department of Energy (DOE) or its predecessor agencies (the U.S. Atomic Energy Commission 

until 1975 and the Energy Research and Development Administration until 1977) had contractors on 

some or all of the WSP. These include the operational period (1957 through 1966) and the monitoring 

and remediation periods (1975 to present). The monitoring period, from 1975 through 1984, applies 

only to the raffinate pits and quarry areas because DOE did not assume control of the chemical plant 

until 1985. Part 2 of this Site Profile contains a more detailed description of these activities. 

During its operation by the Uranium Division of Mallinckrodt Chemical Works from 1957 to 1966, the 

WSCP processed four types of nuclear material: natural uranium, depleted uranium, slightly enriched 

uranium, and natural thorium (DOE 1986). 

• Natural uranium was received as 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. The processing of natural uranium was a continuous operation during the life of the 

Plant. 

• Uranium depleted in the 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. Its use was confined primarily to pilot 

plant activities. 

• Uranium enriched to 1% or less 235U by weight was received and processed on an intermittent 

basis. This form of uranium was typically received in scrap metal or residues. The uranium 

contents were recovered, processed to various chemical forms, and shipped off the site. 
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• Natural thorium was typically received in either a nitrate or oxide form and processed on an 

intermittent batch basis in the refinery and oxide production/firing systems.

1.2.2

The WSP Occupational Medical Dose TBD (ORAUT-TKBS-0028-3) provides information about doses 

received by individual workers from X-rays that were required as a condition of employment. Three 

reports for Mallinckrodt workers (1955 – 1957) and WSP workers in the period from 1958 through 

1966 reference the frequencies and types of X-ray examinations; however, no protocol for frequency 

of a chest X-ray as a function of job category is available nor is there reference to any other type of Xray examination. For the post-1985 remediation period, chest X-rays might have been performed on 

some workers, but might not have been mandatory on an annual basis. Respirator users or asbestos 

workers were probably required to have a chest X-ray during the first medical examination, after which

X-ray examinations occurred every 2 or 5 years depending on the work performed (Lopez 2004). 

Occupational Medical Dose

Although the TBD analysis assumed that WSP radiological practices followed standards of medical 

practice to minimize dose to the patient, types of equipment, technique factors, and machine 

calibrations are not known. Some medical X-ray examinations were apparently administered on the 

site, with films read by an offsite radiologist (Thornton and Johnson 1965). Another report indicates 

that chest X-ray examinations occurred at Barnes Hospital Laboratories (Mason 1955; Quigley and 

Mason 1963). 

Organ dose estimates for occupational X-ray examinations administered at the WSP are provided for 

the period from 1955 through 1966 using default dose estimates from the Technical Information 

Bulletin: Dose Reconstruction from Occupationally Related Diagnostic X-Ray Procedures (ORAU 

2003) for chest X-rays. These default values apply to any year before 1970, and assume minimal 

beam collimation and a half-value layer (HVL) of 2.5 mm Al.

During the post-1985 period, X-ray examinations were performed but records are not available, so 

default estimates for lateral and posterior-anterior chest x-rays have been provided from the Technical 

Information Bulletin: Dose Reconstruction from Occupationally Related Diagnostic X-Ray Procedures

(ORAU 2003). The post-1985 estimates assume beam collimation and an HVL of 4.0 mm Al.

Doses to other exposed organs from chest X-ray examinations have been calculated. The calculated 

dose takes into account the uncertainty associated with machine type, examination frequency, and job 

classification. This TBD presents doses received by organs in the body in tabular form for more 

convenient reference by dose reconstructors.

1.2.3

The WSP Occupational Environmental Dose TBD (ORAUT-TKBS-0028-4) considers doses that 

workers received when working outside buildings; from inhalation of or direct exposure to radioactive 

materials in the air; and from direct exposure to radionuclides in the soil. Exposure to these sources 

can result in an internal dose to the whole body or individual organs from inhaling radioactive 

materials, or could result in a whole- or partial-body external dose from deposited radionuclides or 

submersion in a cloud of radioactive material. 

Occupational Environmental Dose

The WSCP processed uranium (

235,238U) and thorium (232Th) ore concentrates and some scrap metal

during its operational period. Waste materials associated with uranium and thorium processing at the 

chemical plant and other facilities were disposed of in the quarry. Radiological risks associated with 

the 235U decay series were probably much lower than those of the 238U series because the abundance 
Document No. ORAUT-TKBS-0028-1 Revision No. 00 Effective Date: 06/28/2005 Page 8 of 11

of 235U in natural uranium ore concentrates represents less than 5% of the activity in natural uranium, 

and because the WSP processed only a small amount of slightly enriched uranium. 

Radionuclide concentrations in WSP outdoor areas are based on limited environmental 

measurements at the site. The total amount of uranium emitted to the atmosphere has been 

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

(DOE 1986). Based on methods and data in these two reports, the estimated uranium activity emitted 

from the Plant ranged between 1 and 5 Ci/yr. An estimate of radon release, based on the amount of 

uranium processed during the operational period, ranges from 12 to 34 Ci/yr, assuming radium activity 

was 1% of uranium activity, radon was in equilibrium with radium, and all radon was released. 

Beginning in 1981, annual environmental monitoring reports 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. The TBD analysis used

these data to derive annual estimates of intake for 1957 to 2004. 

Measured air concentrations of radon during the operational period are not reported in the literature. 

Therefore, a simplistic screening-level model was used to estimate air concentrations at the WSCP. 

Because no site-specific ambient gamma data were available for the WSCP during the operational 

period, this analysis evaluated ambient dose rates for the Feed Materials Plant in Fernald, Ohio, as 

reported in ORAU (2004). The reported net average dose rate for 1956 to 1970 was 0.18 mrem/hr, or 

1,576 mrem/yr for continuous exposure. When this dose rate estimate is applied to the WSP 

operational period, the WSP site background rate of 99 mrem/yr (Bechtel 1986) is added to derive an 

ambient dose rate of 1,675 mrem/yr for continuous exposure. This corresponds to a 2,000-hr 

exposure of 382 mrem. Between 1982 and 2000, thermoluminescent dosimeters monitored ambient 

exposure at many perimeter locations around the WSCP, the WSRP, and the WSQ. These data are 

summarized in this TBD, which summarizes estimated ambient onsite dose for the WSRP, WSCP, 

and WSQ for periods between 1957 and 2004. 

1.2.4

The WSP Occupational Internal Dosimetry TBD (ORAUT-TKBS-0028-5) discusses the internal 

dosimetry program and develops estimates of potential intakes. Radionuclides of concern at the site

include naturally occurring isotopes of uranium (234U, 235U, and 238U) and their decay products 

(primarily 230Th and 226Ra). Due to the amount of material processed, the primary radionuclides of 

concern for internal radiation dose are the uranium isotopes. Because WSP processed some natural

thorium, dose reconstructors should consider 232Th and its decay products, 228Ra and 228Th. 

Occupational Internal Dosimetry

The primary modes of intake were chronic and acute inhalation. The internal dosimetry program 

required routine monitoring of environmental radon and thoron and their decay products when an 

individual was likely to receive an annual intake of 10% or more of the annual limit of intake. 

According to Revision 7 of the Internal Dosimetry Program Technical Basis Manual (DOE 2001), that 

threshold was never exceeded. Bioassay (urine) data estimate the activity of the radionuclide 

excreted in the urine following an inhalation. This TBD discusses these data, including history, 

sensitivity, and pertinent nuances of methods and data. 

Urine bioassay data represent the primary information available to quantify uranium intake for the 

worker who is the subject of a claim. However, data are not always available for individual workers. 

These data can be supplemented by workgroup monitoring data, because essentially continuous 

bioassay monitoring of a worker was simulated by sampling at least one worker in the group each 

week, with Monday – Friday – Monday sampling for “exposed” workers. 
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Workgroup data have been reconstructed from urine data for all WSP workers by cost center. 

Solubility classes for 234U, 235U, 238U, 228Th, 230Th, and 232Th are summarized by location. Descriptive 

statistics of uranium concentration in urine are summarized by year and by cost center for available 

worker records. For 1958, available uranium in urine data is summarized. A more detailed analysis 

of “Monday” and “Friday” urine samples is summarized for each year from 1959 through 1966. 

No quantitative in vitro or in vivo bioassay results have been found for thorium. Based on the 

assumption that thorium operations at Fernald were reasonably similar to those at WSP, this TBD 

suggests the use of the methods used in the Fernald TBD to assess natural thorium intakes. Under 

these assumptions, the claimant-favorable assumption results in an annual intake of approximately 

60 nCi of 232Th per year. 

1.2.5

The WSP Occupational External Dosimetry TBD (ORAUT-TKBS-0028-6) describes methods and 

concepts for measuring occupational external dose to workers. It provides technical data dose 

reconstructors can use to evaluate, with claimant-favorable assumptions, external occupational doses 

that can reasonably be associated with worker radiation exposures. 

Occupational External Dosimetry

During the operational period, external exposure at WSP was monitored using a two-element film 

badge that could distinguish between gamma and beta exposure. During the post-1985 remedial 

action period, WSP had a DOELAP accredited dosimetry program. During operations, badges were 

assigned to all workers who had a reasonable expectation of receiving a radiation dose or who 

worked in a “badged” area. During the remedial action period, all workers on the site probably wore 

dosimeters. 

Energy distributions for uranium processes were evenly split between the 30- to 250-keV range and 

the greater-than-250-keV range. For thorium processes, three-fourths of the photons were likely to be 

above 250 keV, with the remainder between 30 and 250 keV. Electron energies are all considered to 

have been greater than 15 keV. Neutron energies, if present, were probably spread between 0.1 and 

2 MeV. 

This TBD discusses the process used to evaluate measured film densities and determine dose, as 

well as a bias correction to be applied to WSP recorded dose values. It also discusses historical 

administrative practices and explores common issues such as the handling of zero readings, missing 

entries, and changes in exposure geometry. It explores dosimetry of photons, neutrons, and 

electrons in some detail. It discusses treatment of data for unmonitored individuals. Other topics 

include limits of detection, dose-to-organ-dose conversion factors, and measurement uncertainty.

During the operational period of the Plant, maximum missed annual photon doses might have been as 

high as 600 mR if badges were exchanged on a biweekly basis. Monthly and quarterly exchanges 

are estimated to have maximum missed annual photon doses of 300 and 100 mR, respectively. 

During the remedial action period, missed annual photon doses were probably no higher than 60 

mrem for monthly exchanges. 

During the operational period, the estimated maximum missed electron dose for weekly badge 

exchanges was as high as 2,080 mrep annually. Semimonthly and monthly exchanges would result 

in missed annual electron doses as high as 960 and 480 mrep, respectively. Monthly badge 

exchanges during the remedial action period would have led to maximum missed annual doses of no 

more than 60 mrem. 
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In summary, all five technical TBDS for WSP provide, to the extent that information specific to the 

Plant was available, detailed information, data, explanations, and references for use during the 

reconstruction of worker doses (including WSQ, WSRP, and WSCP workers). In lieu of information 

specific to WSP, the analysis examined TBDs that describe similar processes at other facilities to 

estimate doses at the WSP. The Weldon Spring TBD User Guide (ORAUT-USGD-0028) combines 

key data from each TBD into a single document to enable more efficient use of the information by 

dose reconstructors.
Document No. ORAUT-TKBS-0028-1 Revision No. 00 Effective Date: 06/28/2005 Page 11 of 11

REFERENCES 

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), 1986, Historical Nuclear Materials Balance Report for the Former 

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

Ridge Operations Office, July, 1986.

DOE (U.S. Department of Energy), 2001, Internal Dosimetry Program Technical Basis Manual: 

Weldon Spring Site Remedial Action Project, Rev. 7, DOE/OR/21548-241, Oak Ridge 

Operations Office, Oak Ridge, Tennessee, December.

Lopez, T., 2004, “Regarding x-ray protocol for remediation workers at Weldon Spring,” memorandum 

to file, MFG Inc., Fort Collins, Colorado, September 1.

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

February 21. ORAU Project Document #030000740.

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. 

ORAU (Oak Ridge Associated Universities), 2003, Technical Information Bulletin: Dose

Reconstruction from Occupationally Related Diagnostic X-Ray Procedures, ORAUT-OTIB0006, Oak Ridge, Tennessee. December 9. 

ORAU (Oak Ridge Associated Universities), 2004, Technical Basis Document for the Fernald

Environmental Management Project - Occupational Environmental Dose, ORAUT-TKBS-0017-

4, Oak Ridge, Tennessee.

Quigley, J. A., and M. G. Mason, 1963, Epidemiological Study of Uranium Workers – Feasibility, NLO 

S-512, MCW 25141-M, Report of Work Completed through the Contract Period. 

Thornton, W. T., and W. A. Johnson, 1965, Review of Mallinckrodt Chemical Works, October. 

U.S. Army (Department of the Army), 1976, Assessment of Weldon Spring Chemical Plant in St. 

Charles County, Missouri, Office of the DA Project Manager for Chemical Demilitarization and 

Installation Restoration, Aberdeen Proving Ground, Maryland, March.