SEC Petition Evaluation Report

Petition SEC-00143 

Report Rev #: 0 Report Submittal Date: April 16, 2010

Subject Expert(s): Lori Arent, Ray Clark, Monica Harrison-Maples, Robert Morris, Eugene W. Potter, 

Bryce Rich, Edward D. Scalsky, Billy P. Smith

Site Expert(s): N/A

Petition Administrative Summary

Petition Under Evaluation 

Petition # Petition 

Type Petition Receipt Date Petition Qualification Date DOE/AWE Facility Name

SEC-00143 83.13 April 29, 2009 September 11, 2009 Weldon Spring Plant 

Petitioner Class Definition

All employees of the Department of Energy, Department of Energy contractors, or subcontractors who worked in 

any area at the Weldon Spring Plant in Weldon Spring, Missouri, during the applicable covered operational period 

from January 1, 1957 through December 31, 1966. 

Class Evaluated by NIOSH 

All employees of the Department of Energy, Department of Energy contractors, or subcontractors who worked in 

any area at the Weldon Spring Plant in Weldon Spring, Missouri, during the applicable covered operational period 

from January 1, 1957 through December 31, 1967. 

NIOSH-Proposed Class(es) to be Added to the SEC

None 

Related Petition Summary Information 

SEC Petition Tracking #(s) Petition Type DOE/AWE Facility Name Petition Status

SEC-00144 83.13 Weldon Spring Plant Merged with SEC-00143 

Related Evaluation Report Information 

Report Title DOE/AWE Facility Name

N/A N/A

ORAU Lead Technical Evaluator: Monica Harrison-Maples ORAU Review Completed By: Karin Jessen

Peer Review Completed By: [Signature on file] 4/16/2010 

Mark Rolfes Date

[Signature on file] 4/19/2010 SEC Petition Evaluation Reviewed By: 

Brant Ulsh Date

[Signature on file] 4/21/2010 SEC Evaluation Approved By:

Stuart L. Hinnefeld Date
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Evaluation Report Summary: SEC-00143, Weldon Spring Plant

This evaluation report by the National Institute for Occupational Safety and Health (NIOSH)

addresses a class of employees proposed for addition to the Special Exposure Cohort (SEC) per the 

Energy Employees Occupational Illness Compensation Program Act of 2000, as amended, 42 U.S.C. 

§ 7384 et seq. (EEOICPA) and 42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as 

Members of the Special Exposure Cohort under the Energy Employees Occupational Illness 

Compensation Program Act of 2000. 

Petitioner-Requested Class Definition

Petition SEC-00143 was received on April 29, 2009, and qualified on September 11, 2009. The 

petitioner requested that NIOSH consider the following class: All employees of the Department of 

Energy, Department of Energy contractors, or subcontractors who worked in any area at the Weldon 

Spring Plant in Weldon Spring, Missouri, during the applicable covered operational period from 

January 1, 1957 through December 31, 1966. 

Class Evaluated by NIOSH

Based on its preliminary research and finding that shut-down activities were occurring at Weldon 

Spring Plant through 1967, NIOSH extended the petitioner-requested class. NIOSH evaluated the 

following class: All employees of the Department of Energy, Department of Energy contractors, or 

subcontractors who worked in any area at the Weldon Spring Plant in Weldon Spring, Missouri, 

during the applicable covered operational period from January 1, 1957 through December 31, 1967. 

NIOSH-Proposed Class to be Added to the SEC

Based on its full research of the class under evaluation, NIOSH has obtained uranium bioassay 

monitoring data, airborne dust study data with uranium and thorium applications, environmental air 

concentration measurements, personnel whole-body dosimetry, and medical diagnostic X-ray records 

for the Weldon Spring Plant. Based on its analysis of these available resources, NIOSH found no part 

of the class under evaluation for which it cannot estimate radiation doses with sufficient accuracy. 

Feasibility of Dose Reconstruction

Per EEOICPA and 42 C.F.R. § 83.13(c)(1), NIOSH has established that it has access to sufficient 

information to: (1) estimate the maximum radiation dose, for every type of cancer for which radiation 

doses are reconstructed, that could have been incurred in plausible circumstances by any member of 

the class; or (2) estimate radiation doses of members of the class more precisely than an estimate of 

maximum dose. Information available from the site profile and additional resources is sufficient to 

document or estimate the maximum internal and external potential exposure to members of the 

evaluated class under plausible circumstances during the specified period.

Health Endangerment Determination

Per EEOICPA and 42 C.F.R. § 83.13(c)(3), a health endangerment determination is not required 

because NIOSH has determined that it has sufficient information to estimate dose for the members of 

the evaluated class.
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Table of Contents

SEC Petition Evaluation Report for SEC-00143 ................................................................................... 9

1.0 Purpose and Scope ................................................................................................................. 9

2.0 Introduction ........................................................................................................................... 9

3.0 SEC-00143, Weldon Spring Plant Class Definitions .......................................................... 10

3.1 Petitioner-Requested Class Definition and Basis ................................................................ 10

3.2 Class Evaluated by NIOSH ................................................................................................. 11

3.3 NIOSH-Proposed Class to be Added to the SEC ................................................................ 11

4.0 Data Sources Reviewed by NIOSH to Evaluate the Class .................................................. 12

4.1 Site Profile Technical Basis Documents (TBDs) ................................................................ 12

4.2 Technical Information Bulletins (TIBs) .............................................................................. 13

4.3 Facility Employees and Experts .......................................................................................... 13

4.4 Previous Dose Reconstructions ........................................................................................... 14

4.5 NIOSH Site Research Database .......................................................................................... 15

4.6 Documentation and/or Affidavits Provided by Petitioners ................................................. 15

5.0 Radiological Operations Relevant to the Class Evaluated by NIOSH ................................ 15

5.1 Weldon Spring Plant and Process Descriptions .................................................................. 16

5.1.1 Materials Processed at Weldon Spring Plant ........................................................... 17

5.1.2 Buildings and Activities at Weldon Spring Plant .................................................... 19

5.1.3 Plant Shutdown Activities ....................................................................................... 22

5.2 Radiological Exposure Sources from Weldon Spring Plant Operations ............................. 23

5.2.1 Internal Radiological Exposure Sources from Weldon Spring Plant Operations .... 23

5.2.1.1 Uranium .................................................................................................... 25

5.2.1.2 Uranium Decay Products and Other Impurities ....................................... 25

5.2.1.3 Recycled Uranium .................................................................................... 26

5.2.1.4 Thorium .................................................................................................... 27

5.2.1.5 Radon ........................................................................................................ 27

5.2.1.6 Thoron ...................................................................................................... 28

5.2.2 External Radiological Exposure Sources from Weldon Spring Plant Operations .. 30

5.2.2.1 Photon ....................................................................................................... 31

5.2.2.2 Beta ........................................................................................................... 32

5.2.2.3 Neutron ..................................................................................................... 33

5.2.3 Incidents .................................................................................................................. 33

6.0 Summary of Available Monitoring Data for the Class Evaluated by NIOSH .................... 34

6.1 Available Weldon Spring Plant Internal Monitoring Data .................................................. 35

6.1.1 Uranium Urinalysis Monitoring Data ...................................................................... 35

6.1.2 Thorium In Vivo Chest Counting Data .................................................................... 38

6.1.3 Airborne Dust Studies ............................................................................................. 39

6.1.4 Environmental ......................................................................................................... 46

6.2 Available Weldon Spring Plant External Monitoring Data ................................................. 46

6.2.1 Film Badges ............................................................................................................. 46
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6.2.2 Medical .................................................................................................................... 47

6.2.3 Environmental ......................................................................................................... 47

7.0 Feasibility of Dose Reconstruction for the Class Evaluated by NIOSH ............................. 48

7.1 Pedigree of Weldon Spring Plant Data ................................................................................ 48

7.1.1 Internal Monitoring Data Pedigree Review ............................................................. 49

7.1.2 External Monitoring Data Pedigree Review ............................................................ 52

7.2 Evaluation of Bounding Internal Radiation Doses at Weldon Spring Plant ....................... 52

7.2.1 Evaluation of Bounding Process-Related Internal Doses ........................................ 52

7.2.1.1 Urinalysis Information and Available Data .............................................. 52

7.2.1.2 Airborne Levels ........................................................................................ 53

7.2.2 Evaluation of Bounding Ambient Environmental Internal Doses ........................... 54

7.2.3 Methods for Bounding Internal Dose at Weldon Spring Plant ................................ 54

7.2.3.1 Methods for Bounding Operational Period Internal Dose ........................ 55

7.2.3.2 Methods for Bounding Ambient Environmental Internal Dose ............... 58

7.2.4 Internal Dose Reconstruction Feasibility Conclusion ............................................. 58

7.3 Evaluation of Bounding External Radiation Doses at Weldon Spring Plant ...................... 59

7.3.1 Evaluation of Bounding Process-Related External Doses ....................................... 59

7.3.1.1 Personnel Dosimetry Data ........................................................................ 60

7.3.1.2 Alternative Data Sources for Bounding External Dose ............................ 61

7.3.2 Evaluation of Bounding Ambient Environmental External Doses .......................... 61

7.3.3 Weldon Spring Plant Occupational X-Ray Examinations ....................................... 62

7.3.4 Methods for Bounding External Dose at Weldon Spring Plant .............................. 62

7.3.4.1 Methods for Bounding Operational Period External Dose ....................... 62

7.3.4.2 Methods for Bounding Ambient Environmental External Doses ............. 64

7.3.5 External Dose Reconstruction Feasibility Conclusion ............................................ 64

7.4 Evaluation of Petition Basis for SEC-00143 ....................................................................... 64

7.4.1 Radon ....................................................................................................................... 64

7.4.2 Thorium Bioassay .................................................................................................... 65

7.4.3 Recycled Uranium ................................................................................................... 65

7.4.4 Thorium Disequilibrium .......................................................................................... 65

7.4.5 Lost or Missing Records .......................................................................................... 66

7.4.6 Accidents/Incidents ................................................................................................. 66

7.4.7 Ambient Environmental Exposure .......................................................................... 66

7.4.8 Contamination Control ............................................................................................ 67

7.4.9 Medical Exposure .................................................................................................... 67

7.4.10 Neutron Dose ........................................................................................................... 68

7.5 Other Potential SEC Issues Relevant to the Petition Identified During the Evaluation ...... 68

7.6 Summary of Feasibility Findings for Petition SEC-00143 .................................................. 69

8.0 Evaluation of Health Endangerment for Petition SEC-00143 ............................................. 70

9.0 Class Conclusion for Petition SEC-00143 .......................................................................... 70

10.0 References ........................................................................................................................... 73

Attachment One: Data Capture Synopsis............................................................................................. 79
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Tables 

Table 4-1: No. of Weldon Spring Plant Claims Submitted Under the Dose Reconstruction Rule ...... 14

Table 5-1: Annual Uranium and Thorium Mass Receipts (kg) ........................................................... 17

Table 5-2: Chronological Summary of Thorium Operations at Weldon Spring Plant ........................ 19

Table 5-3: Mass and Percentage of Feed Materials ............................................................................. 23

Table 5-4: History of Dust-Generating Activities at Weldon Spring Plant ......................................... 23

Table 5-5: Potential Internal Radionuclide Exposure for Production Buildings ................................. 24

Table 5-6: Maximum Recycled Uranium Contaminant Levels ........................................................... 27

Table 5-7: Thoron and Isotopic Daughters .......................................................................................... 29

Table 5-8: Beta and Gamma Emissions of Primary Interest ................................................................ 31

Table 5-9: Default Photon Energy Distribution for Weldon Spring Plant Materials........................... 32

Table 5-10: Forms for Reporting High Urinary Uranium Results ....................................................... 34

Table 6-1: Urinary Uranium and Thorium Count Data in the SRDB Documents ............................... 35

Table 6-2: Personnel Quarterly and Annual Average Urinary Uranium Concentration Range 

Analysis—Monday Before Work Samples ......................................................................... 37

Table 6-3: Personnel Quarterly and Annual Average Urinary Uranium Concentration Range 

Analysis—Friday After Work Samples ............................................................................... 38

Table 6-4: Dust Concentrations for Uranium Production Jobs ............................................................ 40

Table 6-5: Dust Concentrations for Thorium Production Jobs ............................................................ 41

Table 6-5 and its associated notes span five pages. ............................................................................ 41

Table 6-6: Average Annual Gamma Exposure (mR) by Job Category ............................................... 47

Table 6-7: Average Annual Beta Exposure (mR) by Job Category ..................................................... 47

Table 7-1: Statistical Evaluation of CER Database and SRDB Results for Urinary Uranium, 1957-

1959 ..................................................................................................................................... 49

Table 7-2: Statistical Evaluation of CER Database and SRDB Results for Urinary Uranium, 1960-

1964 ..................................................................................................................................... 50

Table 7-3. Numbers of Urinary Uranium Results and Individuals Represented in the CER Database

 ............................................................................................................................................. 51

Table 7-4: Activity Ratios of Uranium Decay Products and Other Impurities to Thorium-230 Activity 

in Weldon Spring Raffinate Pits .......................................................................................... 56

Table 7-5: Intakes of Uranium Decay Products and Other Impurities Based on Raffinate Pit 

Measurements ...................................................................................................................... 56

Table 7-6: Summary of Feasibility Findings for SEC-00143 .............................................................. 69

Figures 

Figure 5-1: Map of Weldon Spring Chemical Plant and Raffinate Pits ................................................ 16

Figure 5-2: Decay and Buildup of Thorium-228 and Daughters Following Processing ....................... 29
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SEC Petition Evaluation Report for SEC-00143

1.0 Purpose and Scope

This report evaluates the feasibility of reconstructing doses for all employees of the Department of 

Energy, Department of Energy contractors, or subcontractors who worked in any area at the Weldon 

Spring Plant in Weldon Spring, Missouri, during the applicable covered operational period from 

January 1, 1957 through December 31, 1967. It provides information and analyses germane to 

considering a petition for adding a class of employees to the congressionally-created SEC. 

This report does not make any determinations concerning the feasibility of dose reconstruction that 

necessarily apply to any individual energy employee who might require a dose reconstruction from 

NIOSH. This report also does not contain the final determination as to whether the proposed class 

will be added to the SEC (see Section 2.0). 

This evaluation was conducted in accordance with the requirements of EEOICPA, 42 C.F.R. pt. 83, 

and the guidance contained in the Division of Compensation Analysis and Support’s (DCAS) Internal 

Procedures for the Evaluation of Special Exposure Cohort Petitions, OCAS-PR-004.1

2.0 Introduction 

Both EEOICPA and 42 C.F.R. pt. 83 require NIOSH to evaluate qualified petitions requesting that the 

Department of Health and Human Services (HHS) add a class of employees to the SEC. The 

evaluation is intended to provide a fair, science-based determination of whether it is feasible to 

estimate with sufficient accuracy the radiation doses of the class of employees through NIOSH dose 

reconstructions.2 

42 C.F.R. § 83.13(c)(1) states: Radiation doses can be estimated with sufficient accuracy if NIOSH 

has established that it has access to sufficient information to estimate the maximum radiation dose, 

for every type of cancer for which radiation doses are reconstructed, that could have been incurred in 

plausible circumstances by any member of the class, or if NIOSH has established that it has access to 

sufficient information to estimate the radiation doses of members of the class more precisely than an 

estimate of the maximum radiation dose.

 

Under 42 C.F.R. § 83.13(c)(3), if it is not feasible to estimate with sufficient accuracy radiation doses 

for members of the class, then NIOSH must determine that there is a reasonable likelihood that such 

radiation doses may have endangered the health of members of the class. The regulation requires 

NIOSH to assume that any duration of unprotected exposure may have endangered the health of 

members of a class when it has been established that the class may have been exposed to radiation 

during a discrete incident likely to have involved levels of exposure similarly high to those occurring 

during nuclear criticality incidents. If the occurrence of such an exceptionally high-level exposure has 

not been established, then NIOSH is required to specify that health was endangered for those workers 

who were employed for at least 250 aggregated work days within the parameters established for the 

 

1 DCAS was formerly known as the Office of Compensation Analysis and Support (OCAS).

2 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 C.F.R. pt. 82 and 

the detailed implementation guidelines available at http://www.cdc.gov/niosh/ocas.
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class or in combination with work days within the parameters established for other SEC classes 

(excluding aggregate work day requirements). 

NIOSH is required to document its evaluation in a report, and to do so, relies upon both its own dose 

reconstruction expertise as well as technical support from its contractor, Oak Ridge Associated 

Universities (ORAU). Once completed, NIOSH provides the report to both the petitioner(s) and to the 

Advisory Board on Radiation and Worker Health (Board). The Board will consider the NIOSH 

evaluation report, together with the petition, petitioner(s) comments, and other information the Board 

considers appropriate, in order to make recommendations to the Secretary of HHS on whether or not 

to add one or more classes of employees to the SEC. Once NIOSH has received and considered the 

advice of the Board, the Director of NIOSH will propose a decision on behalf of HHS. The Secretary 

of HHS will make the final decision, taking into account the NIOSH evaluation, the advice of the 

Board, and the proposed decision issued by NIOSH. As part of this decision process, petitioners may 

seek a review of certain types of final decisions issued by the Secretary of HHS.

3

3.0 SEC-00143, Weldon Spring Plant Class Definitions 

 

The following subsections address the evolution of the class definition for SEC-00143, Weldon 

Spring Plant. When a petition is submitted, the requested class definition is reviewed as submitted. 

Based on its review of the available site information and data, NIOSH will make a determination 

whether to qualify for full evaluation all, some, or no part of the petitioner-requested class. If some 

portion of the petitioner-requested class is qualified, NIOSH will specify that class along with a 

justification for any modification of the petitioner’s class. After a full evaluation of the qualified 

class, NIOSH will determine whether to propose a class for addition to the SEC and will specify that 

proposed class definition. 

In this case, the petitioner-requested class differs from the covered period as determined by the 

Department of Energy (DOE) Office of Health, Safety and Security, which lists the time period as 

1955-1967. There is no evidence of the existence of radioactive materials onsite prior to 1957, when 

construction was completed and operations were begun. The earliest indication of radioactive 

material onsite is the start of operations in June 1957. Documentation indicates that the Atomic 

Energy Commission (AEC) decided early in 1966 to close the Weldon Spring Plant site at the end of 

that year. The workforce began to decline as employees sought other employment. Shutdown 

activities occurred throughout 1967. 

3.1 Petitioner-Requested Class Definition and Basis

Petition SEC-00143 was received on April 29, 2009, and qualified on September 11, 2009. The 

petitioner requested that NIOSH consider the following class: All employees of the Department of 

Energy, Department of Energy contractors, or subcontractors who worked in any area at the Weldon 

Spring Plant in Weldon Spring, Missouri, during the applicable covered operational period from 

January 1, 1957 through December 31, 1966.

The petitioner provided information and affidavit statements in support of the petitioner’s belief that 

accurate dose reconstruction over time is impossible for the Weldon Spring Plant workers in question. 

 

3 See 42 C.F.R. pt. 83 for a full description of the procedures summarized here. Additional internal procedures are 

available at http://www.cdc.gov/niosh/ocas.
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NIOSH deemed the following information and affidavit statements sufficient to qualify SEC-00143 

for evaluation: 

The SEC-00143 petitioner provided an affidavit that included the statement: “To the best of 

my knowledge and research, there are no monitoring records/measurements to account for 

exposures to thorium.” 

Records show that in 1958, 44 kg of thorium were received at the Weldon Spring Plant. An 

interview with a senior chemical processing engineer formerly employed at Weldon Spring 

indicates that the thorium was not processed (Personal Communication, 2009g). The next 

indication of thorium material onsite at Weldon Spring Plant is November 6, 1963 (i.e., fiscal 

year 1964), when the first chemical processing operations involving thorium began. Thorium 

operations are summarized in Table 2-1 of the TBD for Weldon Spring Plant – Site Description

(ORAUT-TKBS-0028-2). While there are personnel and area monitoring data that can be 

evaluated to estimate thorium exposure at Weldon Spring Plant, NIOSH concurred that the 

sufficiency of area monitoring data for thorium is uncertain.

Based on its Weldon Spring Plant research and data capture efforts, NIOSH determined that it has 

access to uranium urinalysis, medical X-ray, and film badge external dosimetry data for Weldon 

Spring Plant workers during the time period under evaluation. However, NIOSH also determined that 

records related to potential thorium exposure may not be sufficient for adequate reconstruction of 

internal exposure. NIOSH concluded that there is sufficient uncertainty to support, for at least part of 

the requested time period, the petition basis that internal thorium radiation exposures and radiation 

doses may not have been adequately monitored at Weldon Spring Plant, either through personal 

monitoring or area monitoring. In addition, the petition identified a number of concerns which 

individually are not supported; however, NIOSH concurred that en masse these concerns warranted

evaluation of their relevance to and impact on the dose reconstruction of individual Weldon Spring 

Plant workers. The information and statements provided by the petitioner qualified the petition for 

further consideration by NIOSH, the Board, and HHS. The details of the petition basis are addressed 

in Section 7.4. 

3.2 Class Evaluated by NIOSH

Based on its preliminary research and finding that shutdown activities were occurring at Weldon 

Spring Plant through 1967, NIOSH extended the petitioner-requested class to include 1967. 

Therefore, NIOSH defined the following class for further evaluation: All employees of the 

Department of Energy, Department of Energy contractors, or subcontractors who worked in any area 

at the Weldon Spring Plant in Weldon Spring, Missouri, during the applicable covered operational 

period from January 1, 1957 through December 31, 1967. 

3.3 NIOSH-Proposed Class to be Added to the SEC

Based on its research of the class under evaluation, NIOSH has obtained uranium bioassay monitoring 

data, airborne dust study data with uranium and thorium applications, environmental air concentration 

measurements, personnel whole-body dosimetry, and medical diagnostic X-ray records for the

Weldon Spring Plant. Based on its analysis of these available resources, NIOSH found no part of the 

class under evaluation for which it cannot estimate radiation doses with sufficient accuracy. 
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4.0 Data Sources Reviewed by NIOSH to Evaluate the Class

As a standard practice, NIOSH completed an extensive database and Internet search for information 

regarding the Weldon Spring Plant site. The database search included the DOE Legacy Management 

Considered Sites database, the DOE Office of Scientific and Technical Information (OSTI) database, 

the Energy Citations database, the Atomic Energy Technical Report database, and the Hanford 

Declassified Document Retrieval System. In addition to general Internet searches, the NIOSH 

Internet search included OSTI OpenNet Advanced searches, OSTI Information Bridge Fielded 

searches, Nuclear Regulatory Commission (NRC) Agency-wide Documents Access and Management 

(ADAMS) web searches, the DOE Office of Human Radiation Experiments website, and the DOENational Nuclear Security Administration-Nevada Site Office-search. Attachment One contains a 

summary of Weldon Spring Plant documents. The summary specifically identifies data capture 

details and general descriptions of the documents retrieved. 

In addition to the database and Internet searches listed above, NIOSH identified and reviewed 

numerous data sources to determine information relevant to determining the feasibility of dose 

reconstruction for the class of employees under evaluation. This included determining the availability 

of information on personal monitoring, area monitoring, industrial processes, and radiation source 

materials. The following subsections summarize the data sources identified and reviewed by NIOSH. 

4.1 Site Profile Technical Basis Documents (TBDs) 

A Site Profile provides specific information concerning the documentation of historical practices at 

the specified site. Dose reconstructors can use the Site Profile to evaluate internal and external 

dosimetry data for monitored and unmonitored workers, and to supplement, or substitute for, 

individual monitoring data. A Site Profile consists of an Introduction and five Technical Basis 

Documents (TBDs) that provide process history information, information on personal and area 

monitoring, radiation source descriptions, and references to primary documents relevant to the 

radiological operations at the site. As part of NIOSH’s evaluation detailed herein, it examined the 

following TBDs for insights into Weldon Spring Plant operations: 

• TBD for Weldon Spring Plant – Introduction, ORAUT-TKBS-0028-1; Rev. 00 PC-1; June 30, 

2008; SRDB Ref ID: 45869 

• TBD for Weldon Spring Plant – Site Description, ORAUT-TKBS-0028-2; Rev. 00; June 24, 2005; 

SRDB Ref ID: 20186 

• TBD for Weldon Spring Plant – Occupational Medical Dose, ORAUT-TKBS-0028-3; Rev. 00; 

June 24, 2005; SRDB Ref ID: 20187 

• TBD for Weldon Spring Plant – Occupational Environmental Dose, ORAUT-TKBS-0028-4; Rev. 

00; June 28, 2005; SRDB Ref ID: 20188 

• TBD for Weldon Spring Plant – Occupational Internal Dose, ORAUT-TKBS-0028-5; Rev. 00; 

June 28, 2005; SRDB Ref ID: 20189 

• TBD for Weldon Spring Plant – Occupational External Dose, ORAUT-TKBS-0028-6; Rev. 00; 

June 24, 2005; SRDB Ref ID: 20190 
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• Site Profiles for Atomic Weapons Employers that Refined Uranium and Thorium, Battelle-TBD6001; Rev. F0; December 13, 2006; SRDB Ref ID: 30673 

4.2 Technical Information Bulletins (TIBs) 

A Technical Information Bulletin (TIB) is a general working document that provides guidance for 

preparing dose reconstructions at particular sites or categories of sites. NIOSH reviewed the 

following TIBs as part of its evaluation:

• TIB: Dose Reconstruction from Occupationally Related Diagnostic X-Ray Procedures, ORAUTOTIB-0006; December 21, 2005; SRDB Ref ID: 20220

• TIB: Estimation of Ingestion Intakes, OCAS-TIB-009; April 13, 2004; SRDB Ref ID: 22397

• TIB: Estimation of Neutron Dose Rates from Alpha-Neutron Reactions in Uranium and Thorium 

Compounds, ORAUT-OTIB-0024; April, 7, 2005; SRDB Ref ID: 19445

• TIB: Assignment of Missed Neutron Doses Based on Dosimeter Records, ORAUT-OTIB-0023; 

May 14, 2008; SRDB Ref ID: 43937

• TIB: Default Assumptions and Methods for Atomic Weapons Employer Dose Reconstructions, 

Battelle-TIB-5000; April 2, 2007; SRDB Ref ID: 32016

4.3 Facility Employees and Experts

To obtain additional information, NIOSH interviewed nine former Weldon Spring Plant employees. 

NIOSH selected individuals based on their known experience and likelihood that they would be 

knowledgeable about (1) workplace radiation fields, hazards, and practices to control worker 

exposure; (2) potential radionuclide intakes as evidenced by workplace controls, monitoring policies 

and procedures, and bioassay data; and (3) measurements of the beta, photon, and neutron exposure to 

workers.

• Personal Communication, 2009a, Personal Communication with Former Weldon Spring Plant 

Chemical Operator and Pipefitter; Telephone Interview by ORAU Team; October 23, 2009; 

SRDB Ref ID: 76964

• Personal Communication, 2009b, Personal Communication with Former Weldon Spring Plant 

Utility Operator; Telephone Interview by ORAU Team; October 24, 2009; SRDB Ref ID: 76968

• Personal Communication, 2009c, Personal Communication with Former Weldon Spring Plant 

Employee; Telephone Interview by ORAU Team; October 25, 2009; SRDB Ref ID: 76962

• Personal Communication, 2009d, Personal Communication with Former Weldon Spring Plant 

Chemical Operator and Rigger; Telephone Interview by ORAU Team; October 25, 2009; SRDB 

Ref ID: 76965
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• Personal Communication, 2009e, Personal Communication with Former Weldon Spring Plant 

Production Operator; Telephone Interview by ORAU Team; October 25, 2009; SRDB Ref ID: 

76967

• Personal Communication, 2009f, Personal Communication with Former Weldon Spring Plant 

Metallurgical Engineer; Telephone Interview by ORAU Team; October 26, 2009; SRDB Ref ID: 

76969

• Personal Communication, 2009g, Personal Communication with Former Weldon Spring Plant 

Employee; Telephone Interview by ORAU Team; October 27, 2009; SRDB Ref ID: 76966

• Personal Communication, 2009h, Personal Communication with Former Weldon Spring Plant 

Design Engineer; Telephone Interview by ORAU Team; October 29, 2009; SRDB Ref ID: 76970

• Personal Communication, 2009i, Personal Communication with Former Weldon Spring Plant 

Health Technician and Health Supervisor; Telephone Interview by ORAU Team; November 6, 

2009; SRDB Ref ID: 76963

4.4 Previous Dose Reconstructions

NIOSH reviewed its NIOSH OCAS Claims Tracking System (NOCTS) to locate EEOICPA-related 

dose reconstructions that might provide information relevant to the petition evaluation. Table 4-1 

summarizes the results of this review. (NOCTS data available as of March 12, 2010) 

Table 4-1: No. of Weldon Spring Plant Claims Submitted Under the Dose Reconstruction Rule

Description Totals

Total number of claims submitted for dose reconstruction 258 

Total number of claims submitted for energy employees who meet the definition criteria for the class 

under evaluation (January 1, 1957 through December 31, 1967) 244 

Number of dose reconstructions completed for energy employees who meet the definition criteria for 

the class under evaluation (i.e., the number of such claims completed by NIOSH and submitted to the 

Department of Labor for final approval)

180

Number of claims for which internal dosimetry records were obtained for the identified years in the 

evaluated class definition 207 

Number of claims for which external dosimetry records were obtained for the identified years in the 

evaluated class definition 192 

NIOSH reviewed each claim as well as the transcripts from the computer-assisted telephone 

interviews (CATI) to determine whether internal and/or external personal monitoring records could be 

obtained for the employees. Of the 244 claims submitted for energy employees whose employment 

meets the definition criteria for the class under evaluation, three have not yet received a dosimetry 

response from the Department of Energy (DOE), five have been administratively closed, and forty-six 

have been pulled either because of an SEC designation for other employment or for administrative 

reasons. Of the remaining 190 claims, as indicated in the table above, 180 have completed dose 

reconstructions submitted to the Department of Labor (DOL) for final approval. 
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4.5 NIOSH Site Research Database

NIOSH also examined its Site Research Database (SRDB) to locate documents supporting the 

assessment of the evaluated class. Eight hundred forty-four documents in this database were 

identified as pertaining to the Weldon Spring Plant site. These documents were evaluated for their 

relevance to this petition. The documents include historical background on radiation safety program 

descriptions and policies, external and internal radiation reports, survey and routine monitoring 

summary reports, description of health and safety-related studies, environmental reports, exposure 

incident reports, and air sample reports. 

4.6 Documentation and/or Affidavits Provided by Petitioners

In qualifying and evaluating the petition, NIOSH reviewed the following documents submitted by the 

petitioners:

• Petition Form B for SEC-00143; April 29, 2009; OSA Ref ID: 108678 (Form B, 2009a)

• Petition Form B for SEC-00144; April 29, 2009; OSA Ref ID: 108677 (Form B, 2009b)

• Portion of Correspondence Regarding Record Center, correspondence to Dr. T. F. Mancuso with 

an attached conference agenda; Mont G. Mason; 1972; OSA Ref ID: 108678 (Mason, 1972)

• Portions of the Draft Review of the NIOSH Site Profile for the Weldon Spring Site in Weldon 

Spring, Missouri; S. Cohen & Associates; February 2009; OSA Ref ID: 108678 (SCA, 2009)

• Portions of Transcript from the 31st Meeting of the Advisory Board on Radiation and Worker 

Health; July 6, 2005; OSA Ref ID: 108678 (ABRWH, 2005a)

• Portion of Correspondence Regarding Mallinckrodt SEC Recommendation, correspondence to 

The Honorable Michael O. Leavitt; Advisory Board on Radiation and Worker Health; September 

15, 2005; OSA Ref ID: 108678 (ABRWH, 2005b)

• Page from Draft Review of the NIOSH Site Profile for Mallinckrodt Chemical Company, St. Louis, 

Missouri; S. Cohen & Associates; January 31, 2005; OSA Ref ID: 108678 (SCA, 2005)

• Portion of Worker Radiation Dose Records Deeply Flawed, Volume 6, Number 2 of “Science for 

Democratic Action”; Arjun Makhijani and Bernd Franke; November 1997; OSA Ref ID: 108678 

(Makhijani, 1997) 

5.0 Radiological Operations Relevant to the Class Evaluated by 

NIOSH

The following subsections summarize both radiological operations at the Weldon Spring Plant site 

from January 1, 1957 through December 31, 1967 and the information available to NIOSH to 

characterize particular processes and radioactive source materials. From available sources NIOSH has 

gathered process and source descriptions, information regarding the identity and quantities of each 

radionuclide of concern, and information describing processes through which radiation exposures may 
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have occurred and the physical environment in which they may have occurred. The information 

included within this evaluation report is intended only to be a summary of the available information. 

5.1 Weldon Spring Plant and Process Descriptions 

ATTRIBUTION: Section 5.1 was completed by Monica Harrison-Maples and Ray Clark, Oak Ridge 

Associated Universities (ORAU). The rationales for all conclusions in this document are explained in 

the associated text.

The AEC began designing a feed materials plant in 1954. In 1956 and 1957, the AEC constructed a 

plant (now referred to as the Weldon Spring Plant) for the purpose of processing uranium and thorium 

feed stocks into metal and intermediate products. Construction was completed in February 1957. 

Initial operations began in June 1957, and the plant operated through December 1966 (DOE, 1957, p. 

28-46; Niedermeyer, 1976). The plant was designed specifically to process uranium mill concentrates 

(yellowcake) produced elsewhere in the United States and Canada. These materials were shipped to 

the Weldon Spring Plant 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 (ORAUT-TKBS-0028-2). Shutdown 

procedures for the plant were initiated and completed in 1967 (ORAUT-TKBS-0028-2). During 

shutdown, several buildings were used for interim storage of drummed yellowcake. In August 1967, 

the Weldon Spring Plant site was returned to U.S. Army control for construction of an herbicide 

production facility (Niedermeyer, 1976). Figure 5-1 shows a map of the Weldon Spring Plant site. 

Figure 5-1: Map of Weldon Spring Chemical Plant and Raffinate Pits

Source: Adapted from ORAUT-TKBS-0028-2. 
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The Health Protection program in place when operations began at the Weldon Spring Plant site in 

1957 is not specifically detailed in any of the technical reports available at this time. However, since 

Mallinckrodt Chemical Works transferred many of its activities and employees from the Destrehan 

Street site in St. Louis, at the startup of the Weldon Spring Plant, it is likely that the Weldon Spring 

Plant program closely resembled that documented in the report titled Mallinckrodt Chemical Works 

Health Program Policies, Status, and Summary (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, the design of the Weldon Spring Plant “took advantage of the 

Company’s and the Atomic Energy Commission’s accumulated wealth of experience concerning the 

handling of health and contamination problems encountered in uranium processing” (FleishmanHillard, 1967). The Weldon Spring Plant layout was planned with the goal of minimizing the spread 

of contamination; advanced dust-control systems were used, and onsite 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” (Fleishman-Hillard, 

1967). 

5.1.1 Materials Processed at Weldon Spring Plant

ATTRIBUTION: Section 5.1.1 was completed by Ray Clark and Monica Harrison-Maples, Oak Ridge 

Associated Universities (ORAU). The rationales for all conclusions in this document are explained in 

the associated text.

The Weldon Spring Plant site was operated by the Uranium Division of Mallinckrodt Chemical 

Works and processed materials from June 1957 through December 1966. DOE estimates that 

approximately 600 employees worked at the site for the Uranium Division; of those 600 employees, 

300 would have handled the materials processed at the Weldon Spring Plant site (DOE, 2000). Four 

types of nuclear material were processed in the DOE-owned Weldon Spring Plant: (1) natural 

uranium, (2) depleted uranium, (3) slightly-enriched uranium, and (4) natural thorium (DOE, 1986). 

Table 5-1 summarizes the total material receipts by fiscal year of operation.

Table 5-1: Annual Uranium and Thorium Mass Receipts (kg)

Table 5-1 and its corresponding notes span two pages.

Fiscal 

Yeara

Natural Uranium 

Material

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

Notes:

Source: ORAUT-TKBS-0028-2 
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a The fiscal year begins on July 1st of the previous calendar year and ends on June 30th of the calendar year corresponding 

to the designated fiscal year. Thorium received in fiscal year 1964 was actually processed in November and December of 

1963, as shown in Table 5-2 of this report.

b Includes the startup period in fiscal year 1957.

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 natural uranium was a continuous operation throughout the life of the plant (DOE, 

1986). Some plant documentation and interviews with former Weldon Spring Plant workers show 

that the feed material was “ore.” This issue was explored with a chemical engineer who was 

associated with the Weldon Spring chemical processes (Personal Communication, 2009g) as well as

with a former health physicist (Personal Communication, 2009h) and another former employee 

(Personal Communication, 2009c). All three individuals confirmed that raw ore was never processed 

at the Weldon Spring Plant. They explained that the term “ore” was often used to describe ore 

concentrates.

Depleted uranium was received as metal and various intermediate chemical forms, processed on an 

intermittent basis, and used primarily in product development activities. This form of uranium was 

used primarily in product development activities and flow-sheet improvements. Use was confined 

primarily to Pilot Plant activities (DOE, 1986). 

 

Uranium enriched to 1% or less uranium-235 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 

(DOE, 1986). 

An average of 1.2 × 107

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

(DOE, 1986). Natural uranium processing accounted for more than 98% of the nuclear materials 

throughput. 

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 (DOE, 1986). The same 

processing equipment was used for thorium and uranium processing (Personal Communication, 

2009g). Only a limited area of the Weldon Spring Plant was exposed to thorium, as described in 

Table 5-2 and Table 6-5. Thermal denitration of thorium nitrate, followed by sol-gel processing, was 

used to produce thorium dioxide, which is also known as thoria or thorium oxide. Thorium nitrate 

solution or thorium nitrate tetrahydrate (TNT) crystals were placed in a reaction pot and reacted with 

steam. The reaction product, low density ("light") thorium oxide, precipitated to the bottom of the 

reaction pot. After cooling, the low density thorium oxide was hand-scooped or vacuum-scooped 

from the reaction pot and placed in a sol tank. (Eventually it was found that vacuum scooping 

introduced too much air and resulted in a poor quality product.) Demineralized water was added to 

the sol tank and the solution was acidified using nitric acid. The solution in the sol tank was agitated 

at mildly elevated temperature becoming the "sol". A stable sol was attained when the ionic charge on 

individual particles in solution was sufficient for the particles to repel each other and did not aggregate 

or flocculate. The sol was decanted and dried, becoming a "gel" (NLCO, 1966; Sloat, 1965). A gel, 

as discussed in this context, is a solid glassy ceramic-like material which can be oxidized, or "fired", 

at high temperature to drive off volatile impurities and complete the processing. 
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Table 5-2: Chronological Summary of Thorium Operations at Weldon Spring Plant

Operation Title Building 1963 1964 1965 1966

TNT crystal repackaging 403 Nov-Dec May-Sep - - 

TNT crystal repackaging 301 - Oct-Dec - - 

Denitration of TNT crystals and sol dryinghand unloading 103 Nov-Dec May-Aug - - 

Denitration of TNT crystals and sol dryingvacuum unloading 103 - Sep-Dec - - 

Denitration of TNT liquor and sol dryingvacuum unloading 103 - - Jan-Jul - 

Denitration by fluid bed-product packaged in 

drums 403 - - May-Jul - 

Denitration by fluid bed-liquor feed and sol

product 403 - - Aug-Dec Jan; 

June-Sep

Denitration of TNT liquor-scoop and pail 

transfer to sol tank 103 - - Oct-Nov - 

Sol drying-vacuum unloading 103 - - Aug-Dec Jan; 

Jun-Sep

Thorium dioxide high firing-recast furnace 301 Nov-Dec May-Sep - - 

Thorium dioxide high firing-billet heaters 301 - Oct-Dec Jan-Dec Jan; 

Jun-Sep

Thorium dioxide product packaging 403 Nov-Dec May-Jul; 

Sep-Dec Jan-Sep - 

Thorium dioxide product packaging 103 - Aug - - 

Thorium dioxide product packaging 301 - - Oct-Dec Jan; 

Jun-Sep

Rotary kiln calcining of sump cake 301 - - - Apr-Jul

Digest feed repackaging 101 - - - Apr-Aug

Scrap digestion and raffinate disposal 103 - - - May-Sep

Extraction 105 - - - Jun-Sep

Notes:

Source: Created with information from Weldon Spring Feed Materials Plant, Summaries of Dust Concentrations at 

Production Jobs (MCW, 1958-1966).

- Indicates that no operations were conducted.

5.1.2 Buildings and Activities at Weldon Spring Plant

ATTRIBUTION: Section 5.1.2 was completed by Ray Clark and Monica Harrison-Maples, Oak Ridge 

Associated Universities (ORAU). The rationales for all conclusions in this document are explained in 

the associated text.

Weldon Spring Plant’s main activity was converting uranium concentrate (yellowcake) to uranium 

trioxide, uranium tetrafluoride, and uranium metal. Before entering the refinery, the ore concentrate 

underwent a sampling and preparation process in the sampling plant. Described below are some of 

the buildings and activities associated with the yellowcake conversion process and outside the 

yellowcake conversion process that had potential for radiological exposure occurring at the Weldon 

Spring Plant site. 

BUILDINGS INVOLVED IN THE YELLOWCAKE CONVERSION PROCESS

Described below are some of the buildings and activities associated with the yellowcake conversion 

process that had potential for radiological exposure occurring at the Weldon Spring Plant site. 
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Building 101 

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. 

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 (Meshkov, 1986, pp. 27-28). 

Building 103 

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 (Meshkov, 1986, p. 31). Following processing in Building 105, 

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 uranium trioxide (ORAUTTKBS-0028-2, p. 13). In 1967, Building 103 was transferred to the Army for herbicide production. 

Building 105 

Building 105 was the purification building where a highly purified uranyl nitrate hexahydrate (UNH) 

solution was produced by means of extraction columns, process vessels, evaporators, and tributyl 

phosphate and hexane reaction tanks (ORAUT-TKBS-0028-2, p. 13). In 1967, Building 105 was 

transferred to the Army for herbicide production. 

Building 201 

Building 201 (Green Salt Building) was used for converting uranium trioxide to uranium dioxide and 

uranium tetrafluoride. Excess hydrogen-fluoride gas from the process was filtered through carbon 

filters to recover uranium, which was recycled to black oxide (U3O8). Discharge from the uraniumtetrafluoride 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 uranium-tetrafluoride dust, and there was a reverter in the building to convert 

uranium tetrafluoride into U3O8. The green salt was then packaged in transfer hoppers and moved to 

Building 301 for conversion into solid uranium metal (Meshkov, 1986, p. 22). 

Building 301 

As previously mentioned, magnesium was used to convert uranium tetrafluoride into solid uranium 

metal using a multistep process in Building 301. The reaction occurred in refractory-lined steel 

“bomb” shells that were charged with a mixture of green salt and magnesium chips. The green salt 

and magnesium were mixed in a blender, and the mixture was then placed into individual steel shells 

at the filling machine where the shells were then sent to the furnaces for firing. Within the furnace, 

the shells were heated to about 500°F and the charge was electrically ignited. Once ignited, the 

reaction proceeded spontaneously. Complete shells were moved to an outdoor cooling pad for about 

three days. Besides uranium metal, the process generated uranium tetrafluoride and magnesium 

fluoride (MgF), with 1% to 2% of residual uranium in various forms, were discharged from several 
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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 (ORAUT-TKBS-0028-2, p. 15). 

BUILDINGS OUTSIDE THE YELLOWCAKE CONVERSION PROCESS

Described below are some of the buildings and activities outside the yellowcake conversion process 

that had potential for radiological exposure occurring at the Weldon Spring Plant site. These activities 

may have been in support of the primary mission but were not directly part of that process. 

Building 301 

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. All acceptable cores were packaged in boxes and 

shipped by rail directly to reactor sites (Niedermeyer, 1976, p. 46). 

Buildings 403/404 

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 these 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. A process for the simultaneous denitration of uranyl nitrate and 

reduction of uranium trioxide was also studied. The Metallurgical Pilot Plant was equipped for largescale development of the bomb-reduction step of the process (Niedermeyer, 1976, p. 47). 

Building 407 

The Analytical and Research laboratories were housed in Building 407. The Analytical laboratory 

had four sections: (1) production, (2) spectrographic, (3) method development, and (4) special 

analysis. 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. The special analysis section performed analytical work for the Research laboratory and 

Pilot Plants, in addition to running production and uranium inventory samples (Niedermeyer, 1976, 

pp. 35-36). 

The Research laboratory consisted of three sections: (1) dry chemistry, (2) wet chemistry, and (3) 

instrumental techniques. The dry chemistry section was concerned with problems in fluoride 

chemistry and with metallurgical studies. The wet chemistry section 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 for qualitative 

and quantitative analysis, particle-size distribution studies, identification of minerals, and studies of 

physical properties (Niedermeyer, 1976, p. 36). 

Waste Streams

Between 1958 and 1964, in order to contain process wastes from the plant, four raffinate pits were 

constructed in the southwest portion of the Weldon Spring Plant site. Pits 1 and 2 were constructed in 
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1958, and were used for almost two years. The design volume of each of these two pits was 14,000 

m3

 (500,000 ft3) (NLCO, 1977). 

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 operation 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) (NLCO, 1977, p. 20). 

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 into 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 1986; ORAUT-TKBS-0028-2). The raffinates from thorium-232 

processing were deposited in Raffinate Pit 4.

In 1958, the AEC acquired the Weldon Spring Quarry, which was previously part of the U.S. Army’s 

Weldon Spring Ordnance Works (ORAUT-TKBS-0028-2). The Weldon Spring Quarry was first used 

by the Weldon Spring Plant site 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, uranium- and 

radium-contaminated building rubble, equipment, and soils were deposited into the Weldon Spring 

Quarry following demolition of the Mallinckrodt Chemical Works’ Destrehan Street Feed Plant. In 

1966, approximately 13,500 ft3 of drummed and bulk 3%-thorium residues were deposited in the 

Weldon Spring Quarry (ORAUT-TKBS-0028-2). 

5.1.3 Plant Shutdown Activities

ATTRIBUTION: Section 5.1.3 was completed by Ray Clark and Monica Harrison-Maples, Oak Ridge 

Associated Universities (ORAU). The rationales for all conclusions in this document are explained in 

the associated text.

In early 1966, the AEC decided to close Weldon Spring Plant at the end of the year because the plant 

was made obsolete by more cost-efficient processes. 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 (initiated in 1967), hoppers 

and process lines were emptied and dust collectors and other points of material accumulation were 

cleaned out. All access ports were used to remove as much of the pure uranium compounds as 

possible from the production equipment. By the end of 1967, these shutdown activities were 

terminated and the facilities were awaiting turnover to the Department of Defense (DOD) for use as an 

herbicide facility. The transfer of facilities to DOD had begun by March 1968. 

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 were outside the primary production lines in building 

sumps and in secondary pieces of process equipment and piping without routine access ports. 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. 
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5.2 Radiological Exposure Sources from Weldon Spring Plant Operations 

ATTRIBUTION: Section 5.2 was completed by Robert Morris and Eugene W. Potter, M.H. Chew and 

Associates, Inc. The rationales for all conclusions in this document are explained in the associated 

text.

The primary feed material at Weldon Spring Plant was natural uranium in the form of yellowcake. 

Weldon Spring Plant also processed depleted uranium and slightly-enriched (up to 1%) uranium, as 

well as natural thorium. Table 5-3 lists the quantity and percentage of each type of feed material 

processed.

Table 5-3: Mass and Percentage of Feed Materials

Material Mass (kg) Percent of Total Mass

Natural Uranium 122,015,944 98.43

Depleted Uranium 167,823 0.14

Slightly-Enriched 

Uranium

842,585 0.68

Natural Thorium 941,347 0.76

Total 123,967,712

Source: ORAUT-TKBS-0028-2 

The following subsections provide an overview of the internal and external exposure sources for the 

Weldon Spring Plant class under evaluation.

5.2.1 Internal Radiological Exposure Sources from Weldon Spring Plant Operations

ATTRIBUTION: Section 5.2.1 was completed by Robert Morris and Eugene W. Potter, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

The principal source of internal deposition of radionuclides for the Weldon Spring Plant site was 

inhalation of dust generated during the operations, initial cleanup, and maintenance periods. Table 5-

4 lists the history of dust-generating operations.

Table 5-4: History of Dust-Generating Activities at Weldon Spring Plant

Period Activity

June 1957-December 1966

Operation of the uranium feed materials plant

• Uranium concentrates converted to uranium trioxide, uranium tetrafluoride, and 

uranium metal

• Some thorium processing between 1965 and 1966

• Raffinate from processing removed and sent to raffinate pits

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

year between 1958 and 1964

December 1966 Plant closed

• Hopper and process lines emptied

• Dust collectors cleaned out

1967 Site used as interim storage depot for yellowcake later shipped to other plants for 

refining and processing

Source: This table was modified from Table 5-1 in ORAUT-TKBS-0028-5. 
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Table 5-5 shows the potential radionuclide exposure for production buildings at the Weldon Spring 

Plant site.

Table 5-5: Potential Internal Radionuclide Exposure for Production Buildings

Building 

Number Building Description Potential Radionuclide Exposures

101 Sampling

Natural uranium dust

Radium-226

Thorium-230

Polonium-210

Lead-210

Radon-222 and its short-lived decay products

Thorium-232 and decay products (in 1966)

103 Digestion

Natural uranium dust (as yellowcake and uranium trioxide)

Radium-226

Thorium-230

Polonium-210

Lead-210

Radon-222 and its short-lived decay products

Thorium-232 and decay products ( beginning November 

1963) 

105 Purification Uranium dust or thorium (in 1966)

Radon-222 and short-lived decay products

108 Acid Recovery Radon gas and its decay products

201 Uranium Tetrafluoride (Green Salt) Plant Uranium exposure as green salt dust or natural thorium 

(1965-1966)

301 Metals Plant

Uranium as green salt dust and U3O8 or natural thorium 

(1965-1966)

Thorium-232 and decay products (beginning November 

1963)

403 Chemical Pilot Plant

Natural uranium dust

Radium-226

Thorium-230

Polonium-210

Lead-210

Radon-222 and its short-lived decay products

Thorium-232 and decay products (starting November 1963)

404 Metallurgical Pilot Plant Uranium as green salt dust and U3O8 or natural thorium 

(1965-1966)

407 Analytical and Research Laboratories

Natural uranium dust

Radium-226

Thorium-230

Polonium-210

Lead-210

Radon-222 and its short-lived decay products

Thorium-232 and decay products (1965-1966)

Source: This table was modified from a table in ORAUT-TKBS-0028-2.
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5.2.1.1 Uranium

ATTRIBUTION: Section 5.2.1.1 was completed by Eugene W. Potter, M.H. Chew and Associates, Inc. 

The rationales for all conclusions in this document are explained in the associated text.

During the entire operations period, the Weldon Spring Plant facility primarily handled uranium 

concentrates (e.g., yellowcake) received from uranium-milling facilities, consisting of uranium-234, 

uranium-235, and uranium-238 in their natural abundances with very low concentrations of decay 

products. Historical documents report that Weldon Spring did not receive the high-quality 

pitchblende ores that were processed at the Mallinckrodt Destrehan Street facility (St. Louis) (Ingle, 

1991). Although some plant documents mention the receipt or processing of “ores,” it appears that 

this term actually referred to ore concentrates (Personal Communication, 2009c; Personal 

Communication, 2009g; Personal Communication, 2009h). The plant processed uranium concentrates 

into uranium trioxide, uranium tetrafluoride, and uranium metal (Meshkov, 1986). Uranium dioxide 

was an intermediate product in the conversion of uranium trioxide to uranium tetrafluoride (ORAUTTKBS-0028-2). Production at Weldon Spring waned during the later part of its operational period. 

Ore concentrates containing 60% to 70% yellowcake were sampled on receipt in Building 101. Some 

of the material was repackaged into drums and some sent directly for processing. The concentrates 

were digested with nitric acid in Building 103 to produce uranium-nitrate solution that was then 

purified by solvent extraction in Building 105 and denitrated in Building 103 to produce uranium 

trioxide. Uranium trioxide was converted to uranium tetrafluoride (green salt) in Building 201. Green 

salt was one of the final products of the plant. 

Uranium metal was produced using magnesium to convert uranium tetrafluoride to the metallic form

in Building 301. A rotary kiln was used to convert uranium metal chips to U3O8. Uranium fuel cores 

were also produced in Building 301 and shipped directly to reactor sites. 

The process wastes from uranium processing were sent to four raffinate pits, constructed between 

1958 and 1964. The uranium-process wastes contained relatively low-level concentrations of 

uranium. The radionuclide of most concern in the raffinate pits was thorium-230, due to its high 

activity concentration and its radiotoxicity. Thorium-230 is discussed further in Section 5.2.1.2 of this 

evaluation report. It is estimated that 152,382 kg of natural uranium, 46 kg of depleted uranium, and 

2,808 kg of slightly enriched uranium was discharged in to the raffinate pits (DOE, 2000, Table 2-23, 

p. 86). 

Additional details regarding uranium processing are contained in ORAUT-TKBS-0028-2. The annual 

uranium and thorium mass receipts are shown in Table 5-1 of this evaluation report. 

5.2.1.2 Uranium Decay Products and Other Impurities

ATTRIBUTION: Section 5.2.1.2 was completed by Eugene W. Potter and Bryce L. Rich, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

Uranium decay products and other impurities were present in the uranium ore concentrates processed 

at the Weldon Spring Plant. No bioassay program was in place for these materials since they were 

considered a minor hazard of the operations as compared to the uranium itself. The Weldon Spring 

Historical Dose Estimate (Meshkov, 1986) is a historical offsite dose estimate study that estimates the 
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activities of thorium-230 and radium-226 in yellowcake to be 5% and 1% of uranium-238 activity, 

respectively. The final Weldon Spring Plant product was essentially pure uranium, with thorium-230 

and other impurities having been removed in the raffinates and sent to the disposal pits. 

Raffinate Pits 1, 2, and 3 received mostly uranium raffinates, and Pit 4 received both uranium and 

thorium raffinates. In the first three pits, thorium-230 constituted greater than 80% of the total 

activity. An upper estimate of the thorium-230 activity in the ore concentrates is 100% of the 

uranium-234 activity (its parent), or 50% of the total uranium activity (approximately 0.34 nCi/mg 

uranium). Measurements of the activity concentrations in Raffinate Pits 1, 2, and 3 can be used to 

determine the relationship between thorium-230 and other impurities during the initial uranium 

processing in Building 101 before any separations occurred. The shorter-lived decay products for 

which no raffinate measurements were made (e.g., lead-210 and polonium-210) can be assumed to be 

present similarly to the measured activity level of the radium-226 parent in the raffinate pits (see 

Table 7-4 below). Following the purification of the uranium during the initial processing of the ore 

concentrates to uranium trioxide, the removal of the uranium decay products would have eliminated 

them as a potential exposure source in the general operating areas of the plant. There was some 

natural thorium (e.g., thorium-232 and thorium-228) present in the uranium ore concentrates, which 

was also separated and sent to the raffinate pits. Measurements of thorium-232 in the raffinate pits 

were made by alpha spectroscopy, but these measurements were not considered to be reliable because 

of the interference from the thorium-230 alpha peak. Measurements of thorium-228 in Raffinate Pits 

1, 2, and 3 are available to NIOSH (MK-Ferguson, 1989). Given that radium-228 (the parent of 

thorium-228) was largely removed by the milling process, and that thorium-232 (the parent of radium228) has a long half-life, the build-up of thorium-228 in the short term is minor. Meanwhile the 

thorium-228, which was originally in approximate equilibrium with thorium-232, decays significantly 

because of a half life of only 1.9 years. The delay time from milling to processing of 1.2 years 

equates to an approximate thorium-228 activity to thorium-232 activity of 65% (65% equilibrium). 

Using this relationship, the amount of thorium-232 can be estimated from the thorium-228 

measurements.

5.2.1.3 Recycled Uranium

ATTRIBUTION: Section 5.2.1.3 was completed by Eugene W. Potter, M.H. Chew and Associates, Inc. 

The rationales for all conclusions in this document are explained in the associated text.

In 1999, DOE initiated the complex-wide Recycled Uranium Mass Balance Project, which identified 

the Weldon Spring Plant as a site that likely received recycled uranium in relatively small quantities of 

materials after 1961 (ORAUT-TKBS-0028-2). The significance of these shipments of recycled 

uranium is that this material contained trace amounts of residual transuranic elements (including 

plutonium and neptunium), fission products (such as technetium), and reactor-produced uranium 

isotopes (such as uranium-236) (DOE, 2000). 

Contaminant radionuclides in recycled uranium that could be dosimetrically significant are plutonium 

(assume plutonium-239), neptunium (neptunium-237), and technetium (technetium-99). Site records 

do not include the level of detail needed for an accurate estimate of the amount of recycled material 

received and processed at the Weldon Spring Plant site. However, greater than 99% (by weight) of 

the slightly enriched uranium received at the Weldon Spring Plant site was from Fernald (DOE, 2000, 

p. 1,130). For the purpose of this evaluation, the uranium source term is considered to be: 

• Prior to 1961, natural uranium,
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• 1961-1967, recycled uranium.

For the periods that included recycled uranium, Table 5-6 contains maximum values for the recycled 

uranium contaminants as a fraction of uranium intake based on material that is likely to have been 

received by Weldon Spring (DOE, 2000, p. 1,140). 

Table 5-6: Maximum Recycled Uranium Contaminant Levels

Contaminant

Average 

Concentration 

(ppbU)

Observed Range 

(ppbU)

Bounding Valuea

ppbU pCi/μgU pCi/pCiU

Plutonium 2.9 0.60-15 6.3 3.9E-04 5.7E-04

Neptunium-237 390 55-3,200 1,800 1.3E-03 1.9E-03

Technetium-99 8,600 800-19,000 21,000 0.36 0.53

Note:

a Calculated as the 95th percentile of an unblended uranium trioxide PUREX source, assuming a lognormal distribution. 

This provides the highest values for the two subgroups of recycled uranium likely received by Weldon Spring (DOE, 

2000).

5.2.1.4 Thorium

ATTRIBUTION: Section 5.2.1.4 was completed by Robert Morris, M.H. Chew and Associates, Inc. 

The rationales for all conclusions in this document are explained in the associated text.

Thorium processing operations at the Weldon Spring Plant site began in November 1963. These 

operations are included in the chronological summary of thorium operations found in ORAUT-TKBS0028-2, Table 2-1. 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 101, 103, 

105, and 301(Argonne, 1985). 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 Weldon Spring Plant site was exposed to the material. An average of 3.1 × 

105

 kg of natural thorium was processed per year during 1964 through 1966, with an associated total 

material balance closure of 98.52% (DOE, 1986; ORAUT-TKBS-0028-2). Wastes were deposited in 

Raffinate Pit 4.

The AEC acquired the Weldon Spring Quarry in 1958 as a location to dispose of thorium residues as 

well as uranium- and radium-contaminated building rubble and equipment and soils from the 

Destrehan Street site. These materials were deposited into the Weldon Spring Quarry between 1959 

and 1966. The estimated maximum thorium-232 concentration in materials deposited in the Weldon 

Spring Quarry was 4200 pCi/g (DOE, 1991; ORAUT-TKBS-0028-5).

5.2.1.5 Radon

ATTRIBUTION: Section 5.2.1.5 was completed by Eugene W. Potter, M.H. Chew and Associates, Inc. 

The rationales for all conclusions in this document are explained in the associated text.

As indicated in Section 5.2.1.1 of this report, there is no suggestion in the historical records that the 

Weldon Spring Plant facility ever processed the high-activity concentration pitchblende, which 

contained significant concentrations of radium. The ore concentrates processed at Weldon Spring 

were a relatively small source of radon because most of the radium in the ore was removed in the 
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milling process, which occurred elsewhere. Radium is the parent of radon in the naturally occurring 

decay chain. 

The radon trapped in the ore concentrates was released during the acid digestion process in Building 

103. The off gasses containing radon and nitrogen oxides from the digestion process were sent to the 

acid recovery plant (Building 108). This plant was the prime source of radon emission and was 

estimated as being between 12 and 34 Ci/year based on throughput (Meshkov, 1986, p. 48). 

Impurities generated in the uranyl-nitrate purification process were bled off in the raffinate, which 

were pumped to raffinate pits. The raffinate contained a conglomerate of radionuclides, including 

small concentrations of thorium and radium (Unknown, 1967; ORAUT-TKBS-0028-2). Due to the 

presence of water in the pits, wastes disposed of in the raffinate pits were not a significant source of 

airborne radionuclides during the operational period. It is unlikely that a significant portion of the 

sediments became sufficiently dry to be considered a source term, even though the report, Weldon 

Spring Site Environmental Monitoring Report, Calendar Year 1983 reported that Pits 1 and 2 could 

become dry during the summer months (Bechtel, 1984). The report, Study of Radioactive Waste 

Storage Areas at ERDA-Weldon Spring Site concluded that the inherent consistency of the raffinate 

material precluded sufficient drying, and the pits did not pose a significant source of airborne 

contaminants (NLCO, 1977). Radon measurements in the pit area in the late 1970s and early 1980s 

(before remediation) averaged 0.92 ± 1.0 pCi/L, indicating that the pits were not a major source of 

radon (Meshkov, 1986, p. 101). This value is limiting for the operational period since the amount of 

radium-226 in the pits was at its maximum at the end of operations, and it would not have decayed or 

leached out of the pits significantly before the measurements were made.

Prior to 1963, the quarry only contained drummed thorium wastes that were likely submerged and not 

a significant source of radon. In 1963 and 1964, an estimated 38,000 m3 of uranium- and radiumcontaminated rubble, equipment, and soil were placed in the quarry following demolition of the 

Destrehan Street site, with a majority of this waste not submerged, providing a potential source of 

radon exposure (Unknown, 1967; ORAUT-TKBS-0028-4). Measurements in the quarry area in the 

late 1970s and early 1980s (before remediation) averaged 0.65 ± 0.41 pCi/L, indicating that the quarry 

was not a major source of radon (Meshkov, 1986, p. 101). As in the case of the raffinate pits, this 

value would be limiting for the operational period.

5.2.1.6 Thoron

ATTRIBUTION: Section 5.2.16 was completed by Bryce L. Rich, M.H. Chew and Associates, Inc. The 

rationales for all conclusions in this document are explained in the associated text. 

Thoron is the second daughter product of thorium-228, and after a couple of weeks, following the 

processing of thorium ores for thorium purification, can be considered to be in full equilibrium with 

the parent, thorium-228. Thorium-228 is the third daughter product of the long-lived thorium-232, 

and is generally in 40-65% equilibrium for materials processed at the Weldon Spring Plant. The 

degree of equilibrium is dependent upon both the decay of thorium-228 (without replenishment from 

the 5.7 year half life of radium-228) after removal of the thorium daughters and the time it takes the 

radium-228 to build into equilibrium with thorium-232. 
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Figure 5-2: Decay and Buildup of Thorium-228 and Daughters Following Processing

Thoron was present and a portion was released during the processing and storage of thorium at the 

Weldon Spring Plant and the associated waste storage locations. The thoron, with its subsequent 

daughter products, would act as a potential source of internal exposure in the thorium process 

buildings and at waste storage locations. 

There are several aspects of the release and buildup of thorium daughter products that mitigate the 

exposure to thoron in process and storage configurations. These include the following: 

• Because of the very short half life of thoron (56 seconds), much of the isotope decays within the 

material matrix; therefore, the diffusion distance in soils is in the range of approximately one inch. 

Only the quantities of thoron in the first inch of material represent the source term. Table 5-7 

provides the half life information for thoron and its daughters. 

• In process equipment, the release of thoron gas is largely contained within the containment system 

and/or the ventilation system. Essentially, the dose from exposure to thoron comes entirely from 

the daughters lead-212 and bismuth-212. A thoron working level (WL) requires 375 pCi/l thoron 

and polonium-216 to produce measured daughter products lead-212 and bismuth-212 at 7.5 pCi/l. 

Table 5-7: Thoron and Isotopic Daughters

Isotope Half Life Atoms/7.5 pCi • MeV/atom PAEC1 MeV per 7.5 pCi

Radon-220 56 sec 23 14.6 335

Polonium-216 0.15 sec <1 Incl - 

Lead-212 10.64 hr 15476 7.8 1.21E+5

Bismuth-212 60.6 min 1469 7.8 0.12E+5

Polonium-212 0.3 μsec - Incl - 

Thallium-208 3 min 73 no • - 

Total 1.33E+5

Notes: 1 Potential Alpha-Energy Concentration (PAEC)
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The primary focus of the radiological safety programs for thorium was to define the air concentrations 

in the work place, the results of which provided the means of limiting worker exposures to levels 

below the permissible levels. Weldon Spring Plant records do not indicate specific analyses to define 

the concentrations of thoron daughter activities; however, it was standard practice to provide delayed 

counts on the air samples for up to 96 hours to allow the short- lived radon and thoron daughter 

products to decay. 

5.2.2 External Radiological Exposure Sources from Weldon Spring Plant Operations

ATTRIBUTION: Section 5.2.2 was completed by Ray Clark, Monica Harrison-Maples, and Edward 

D. Scalsky, Oak Ridge Associated Universities (ORAU). The rationales for all conclusions in this 

document are explained in the associated text.

The principal source of external radiation doses for members of the evaluated class, other than 

medical X-rays required as a condition of employment, was direct beta-gamma exposures from 

uranium processing. The uranium processed at the Weldon Spring Plant site was natural, slightly 

enriched, and depleted uranium. The natural uranium, which accounted for more than 97% of the 

nuclear materials throughput, was received as continental ore concentrates. A limited amount of 

thorium was also processed at the Weldon Spring Plant site from November 1963 through 1966, the 

chronology of which is presented in ORAU-TKBS-0028-2. Although low, there was also some 

potential for external exposure associated with working in proximity to the raffinate pits and quarry. 

Uranium and thorium processing generated several chemical and radioactive waste streams, which 

were piped into the raffinate pits. 

External ambient exposure at the Weldon Spring Plant site would have been a result of gamma and Xray radiation emitted from radionuclides in the ore concentrate stored on the site during the 

operational period, and to a lesser extent from radionuclides in the raffinate pits and quarry. 

Considerable shielding would have occurred at the quarry from the water covering most of the 

deposited materials. An aerial radiological survey of the Weldon Spring Plant site (Jobst, 1976) 

indicated that for most of the site the normal terrestrial gamma exposure rate was 3 to 6 μR/hour at 1 

meter above ground level, and the average cosmic exposure rate was approximately 4 μR/hr. 

Summary reports indicate that natural uranium was the radiological material that the workers came

into contact with most frequently. Radiation fields most often consisted of a complex mixture of beta 

and gamma energies. There was a low potential to encounter neutrons in several buildings (discussed 

further in Section 5.2.2.3 of this report). The relative magnitude of each type of exposure can be 

found in employee records. The majority of the exposure would have consisted of beta particles, 

which, depending on the energy spectrum of the particles, can deliver substantial doses to bare skin in 

relatively close proximity to the source, but which do not penetrate deeply into the body. 

Table 5-8 lists the beta and gamma emissions of the radionuclides of major external exposure concern. 

ORAUT-TKBS-0028-6 (Figures 6-1 to 6-3) shows complete decay chains of uranium-238, uranium235, and thorium-232. Protactinium-234m is likely the most important contributor to skin dose 

because of its frequent high-energy beta emission. Protactinium-234m also emits higher energy 

gamma rays, albeit less frequently, than other radionuclides of concern at the Weldon Spring Plant 

site. 
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Table 5-8: Beta and Gamma Emissions of Primary Interest

Radionuclide Beta Energy 

(MeV, max.)

Gamma Energy 

(MeV)

Uranium-238 None None

Thorium-234 0.10 (19%) 0.063 (3.5%)

0.193 (79%) 0.093 (4%)

Protactinium-234m 2.28 (99%) 0.766 (0.2%)

1.00 (0.6%)

Uranium-235 None

0.144 (11%)

0.163 (5%)

0.186 (54%)

0.205 (5%)

Thorium-231

0.205 (15%)

0.287 (49%) 0.026 (15%)

0.304 (35%) 0.084 (6.5%)

Uranium-234 None 0.053 (0.1%)

Thorium-232 None 0.059 (0.19%)

0.126 (0.04%)

Radium-228 0.0389 (100%) 0.0067 (6 x 10-5%)

Actinium-228

0.983 (7%) 0.338 (11.4%)

1.014 (6.6%) 0.911 (27.7%)

1.115 (3.4%) 0.969 (16.6%)

1.17 (32%) 1.588 (3.5%)

1.74 (12%) - 

2.08 (8%) - 

(+33 more • s) - 

Thorium-228 None

0.084 (1.19%)

0.132 (0.11%)

0.166 (0.08%)

0.216 (0.27%)

Bismuth-212

1.59 (8%) 0.040 (1%)

2.246 (48.4%) 0.727 (11.8%)

- 1.620 (2.75%)

Lead-208 None 2.614 (100%)

Notes: 

Source: Radiological Health Handbook, 1998 

A more complete list for uranium and thorium progeny can be found in the Radiological Health 

Handbook, 1998

5.2.2.1 Photon

ATTRIBUTION: Section 5.2.2.1 was completed by Ray Clark and Edward D. Scalsky, Oak Ridge 

Associated Universities (ORAU). The rationales for all conclusions in this document are explained in 

the associated text.

Weldon Spring Plant records indicate that depleted and enriched uranium were routinely handled with 

some shielding, but the type and amounts of shielding are not known. Enriched and depleted uranium 

received at the Weldon Spring Plant site for processing is assumed to have been relatively fresh with 

little or no ingrowth of decay products having occurred at the time that the material was processed at 

the Weldon Spring Plant site. 
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Protactinium-234m is a decay product in the uranium-238 decay chain that emits a 2.29-MeV beta 

particle. The bremsstrahlung photons associated with this high energy beta are in the intermediate 

energy range (30 to 250 keV). Protactinium-234m was present in equilibrium quantities for most 

depleted uranium that was processed at the Weldon Spring Plant site. 

Although enriched uranium has significantly less ingrowth of protactinium-234m, uranium-235 and 

its decay products emit a 185.7-keV photon 57% of the time and a 143.8-keV photon 11% of the time. 

These photons dominate the measured photon energy spectra. Natural uranium was processed in 

Buildings 101, 103,105, 106, 108, 109, 110, 201, 301, 403, 404, 405 A & B, 407, 414, 415, and 431, 

as well as Area 102 A & B. Slightly enriched uranium was processed in Buildings 103, 105, 201, and 

301. Depleted uranium was processed in Buildings 403 and 404. Natural thorium was processed in 

Buildings 103, 105, 201, and 301. The default assumptions for the distribution of the photon energies, 

as defined for the purpose of dose reconstruction for the Weldon Spring Plant site, are relayed in 

Table 5-9. 

Table 5-9: Default Photon Energy Distribution for Weldon Spring Plant Materials

Energy Natural 

Uranium

Depleted 

Uranium

Slightly Enriched 

Uranium

Natural 

Thorium

<30 keV 0% 0% 0% 0%

30-250 keV 50% 40% 100% 25%

>250 keV 50% 60% 0% 75%

Source: ORAUT-TKBS-0028-6 

5.2.2.2 Beta

ATTRIBUTION: Section 5.2.2.2 was completed by Ray Clark, Monica Harrison-Maples, and Edward 

D. Scalsky, Oak Ridge Associated Universities (ORAU). The rationales for all conclusions in this 

document are explained in the associated text.

Beta radiation fields are usually the dominant external radiation hazard in facilities that involve 

contact work with unshielded forms of uranium. This was the case at the Weldon Spring Plant site for 

natural and depleted uranium work. The most common exposure at the Weldon Spring Plant site was 

to natural uranium, but depleted uranium was present at the site on an intermittent basis; in addition, 

slightly-enriched uranium (less than 1% uranium-235 by weight) was also present at times in the form 

of scrap metal or residues. Table 5-8 provides the energies of the beta emissions from the primary 

isotopes of concern at the Weldon Spring Plant site. 

Beta doses were determined by the use of film badges. Several studies were done to evaluate the time 

required to perform potentially high exposure jobs, to determine the shielding that could be applied to 

reduce the beta exposures, and to determine the primary exposure source during various phases of the 

job. The Health and Safety program employees provided reports to management at the Weldon 

Spring Plant that were used to evaluate worker exposures, and thus determine who should be rotated 

or removed from exposure sources in order to ensure individuals’ doses were below the existing 

standards. 

Additional beta exposure data are available for lathe operators and for jobs in the casting area. These

data are from a study of various operations and times of exposure in the casting area (MCW, unknown 

date). 
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5.2.2.3 Neutron

ATTRIBUTION: Section 5.2.2.3 was completed by Ray Clark, Monica Harrison-Maples, and Edward 

D. Scalsky, Oak Ridge Associated Universities (ORAU) and Leo G. Faust, M.H. Chew and Associates, 

Inc. The rationales for all conclusions in this document are explained in the associated text.

The Weldon Spring Plant was operated as an integrated facility for the conversion of uranium ore 

concentrates and small quantities of recycled scrap to pure uranium trioxide, uranium tetrafluoride, 

and uranium metal (DOE, unknown date). During these processes and during the storage of uranium 

tetrafluoride, neutrons were not anticipated at the Weldon Spring Plant. Any neutrons would have 

resulted from the alpha-neutron reaction from uranium tetrafluoride (green salt) or processing the 

slightly-enriched (<1%) uranium. 

Most Weldon Spring operational employees were involved with the processing of natural and depleted 

uranium and were assigned the regular beta-gamma dosimeter badge monitors. However, in a special 

study at the Feed Materials Production Center site (Fernald), neutron measurements were made in and 

around the arrays of drums of stored uranium tetrafluoride, up to 2% enrichment, to determine the 

potential for neutron exposures. The study included the use of Landauer Neutrak-ER dosimeters as 

area badges over the period of one quarter, and a special survey using a Nuclear Research Corporation 

Model NP-2 portable neutron meter. The results of the study indicate neutron exposures were 

minimal: a maximum of 0.089 mrem/hour for the area badges, and less than the minimum detectable 

(0.02 mrem/h) for the portable neutron monitor. Calculations performed for Battelle-TBD-6001 on 

similar materials are in agreement with the Fernald measurement data and support the conclusion that 

neutron dosimetry is not needed when processing uranium tetrafluoride under these parameters 

because there is no significant potential for neutron exposures. 

Even though the Weldon Spring Plant received enriched uranium, it was always <1%; therefore, the 

potential for neutron exposure was very low. The slightly-enriched uranium was processed in 

Buildings 103, 105, 201, and 301, and those employees that processed the slightly-enriched uranium 

were assigned special neutron dosimeter badges to be worn in conjunction with their regular film 

badge dosimeters. Neutron dose results for these Weldon Spring employees have not been located, 

plausibly because there was no measured neutron dose. 

5.2.3 Incidents

ATTRIBUTION: Section 5.2.3 was completed by Lori Arent, M.H. Chew and Associates, Inc. The 

rationales for all conclusions in this document are explained in the associated text.

NIOSH did not identify any documented accidents at the Weldon Spring Plant site that resulted in 

exceptionally high personnel exposure levels (such as a criticality event). Interviews conducted with 

former site employees discussed several anecdotal radiological or contamination events, but none of 

the people interviewed reported that the events resulted in exceptionally high exposures (Personal

Communication, 2009a; Personal Communication, 2009b; Personal Communication, 2009c; Personal 

Communication, 2009e; Personal Communication, 2009f; Personal Communication, 2009h). 

The Health and Safety Division maintained annual logbooks of forms and memos for employees with 

high urinary uranium concentrations. Investigation reports were also included in the logs (for Action 

Level 2 exposures and above). Descriptions of the data forms in Table 5-10 are included to 

demonstrate Weldon Spring’s management of and response to high bioassay results (Weldon, 1960; 
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Weldon, 1961; Weldon, 1962-1965). The Weldon Spring Urinary Uranium Program procedures for 

1960 and 1963 provide additional information on the bioassay program and use of these forms 

(MCW, 1962; MCW, 1960).

Table 5-10: Forms for Reporting High Urinary Uranium Results

Form No. Form Title Description

7274 High Exposure Incident Report

Includes the following information: 

Employee name, department, job, type of exposure 

(film badge or urinary uranium with corresponding 

units), sample date, a description of the incident or 

occurrence, process or equipment to which the high 

exposure was attributed, and follow-up and remedial 

actions.

7273

Report of High Urinary Uranium Concentration

Report on Action Level Urinary Uranium 

Concentrations (Rev 9-60)

Multiple employee names with their action level 

category (Action Level 1 to 4), and sample date. 

Beginning in September 1960 the following 

information was pre-printed on the form:

• Action Level 1 Monday 0.030 to 0.100 mg/l 

• Action Level 1 Friday 0.060 to 0.100 mg/l

• Action Level 2 0.100 to 0.200 mg/l

• Action Level 3 0.200 to 0.300 mg/l

• Action Level 4 >0.300 mg/l

7357 Urinary Uranium Data for Week

Weekly summary of the Monday/Friday average 

urinary uranium concentrations by location, number 

of operators participating, percent of employees

sampled with results less than the action level, and 

the names of the "peak men" (highest exposed 

employees).

7463 Urinary Uranium

Weekly summary of the Monday/Friday samples by 

cost center, concentration ranges, number of 

employees in each range, names of employees above 

the Monday or Friday limits (>0.030 or 0.060 mg/l 

respectively), and the number of scheduled and 

reporting employees.

Sources: Weldon, 1960; Weldon, 1961; Weldon, 1962-1965; MCW, 1960; MCW, 1962

6.0 Summary of Available Monitoring Data for the Class Evaluated 

by NIOSH

The following subsections provide an overview of the state of the available internal and external 

monitoring data for the Weldon Spring Plant class under evaluation.
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6.1 Available Weldon Spring Plant Internal Monitoring Data

ATTRIBUTION: Section 6.1 and its related subsections were completed by Lori Arent and Billy P. 

Smith, M.H. Chew and Associates, Inc., and Monica Harrison-Maples, Oak Ridge Associated 

Universities (ORAU). The rationales for all conclusions in this document are explained in the 

associated text.

Details regarding the various analyses used and the associated minimum detectable activities are 

presented in the Technical Basis Document for the Weldon Spring Plant-Occupational Internal Dose 

(ORAU-TKBS-0028-5). A summary of the available internal data applicable to this evaluation is 

presented below.

6.1.1 Uranium Urinalysis Monitoring Data 

The ORAU Center for Epidemiological Research (CER) database contains nearly 30,000 uranium 

urinalysis records collected during the period from 1957 through 1966 for approximately 1,800 

employees. Data fields include the employee social security number, name, clock number, sample 

data, department/job/area, and results in units of mg/l (CER Data, 2009). 

ORAUT-TKBS-0028-5 contains a table of composite uranium urine data for routine monitoring 

during the years 1958 through 1966, with the median, 95th percentile, maximum concentration results, 

and the number of records for each year. There are also tables for each individual year where the data 

are summarized by cost center. These tables were created from the records in the CER database. 

Table 6-1 shows the urinary uranium and thorium count data found in the SRDB documents. The 

table shows (identified by an X in the appropriate row and column) the months and years in which 

raw data and/or quarterly and annual summary data are available. 

Table 6-1: Urinary Uranium and Thorium Count Data in the SRDB Documents

Table 6-1 and its corresponding notes span two pages.

Year

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

SepOct

Nov

Dec

Data Description SRDB

Sources

1957 X X X X X X X X X Raw urinary uranium results by individual name 9213a

1958 X X X X X X X X X Raw urinary uranium results by individual name 9213a

15634b

1959 X X X X X X X X X X X X

Raw urinary uranium results by individual name (Jan-Apr)

Quarterly average urinary uranium results by name/clock no.

Yearly average urinary uranium summary table

15634b

15898c

15907d

1960 X X X X X X X X X X X X

High urinary uranium log (names and results)

Quarterly average urinary uranium results by name/clock no.

Quarterly & annual average urinary uranium summary tables

15874e

15898c

13763d

15901d

1961 X X X X X X X X X X X X

High urinary uranium log (names & results) (Jul-Dec)

Quarterly average urinary uranium results by name/clock no.

Quarterly & annual average urinary uranium summary tables

15865e

15898c

13735d

13736d

13745d

13752d
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Table 6-1: Urinary Uranium and Thorium Count Data in the SRDB Documents

Table 6-1 and its corresponding notes span two pages.

Year

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

SepOct

Nov

Dec

Data Description SRDB

Sources

1962 X X X X X X X X X X X X

High urinary uranium log (names & results) (Jul-Dec)

Quarterly average urinary uranium results by name/clock no.

Quarterly average urinary uranium summary tables

15890f

15898c

13732d

1963 X X X X X X X X X X X X High urinary uranium log (names & results)

Quarterly average urinary uranium by group no. (no names)

15890f

15866g

1964 X X X X X X X X X X X X High urinary uranium log (names & results) 15890f

1965 X X X X X X X X X X X X

List of employees providing urine samples for uranium & 

dates (no data)

Monthly average urinary uranium by group no. (no names)

15890f

15914g

1966 X Chest count summary results for thorium 12400h

Notes:

a USAEC NYOO Form NY-99 with plant name and mailing address, analyze for x in urine, sample no., sample type, date 

and hour of sample collection, sample description (typed employee name, plant & job), and results (handwritten). NOTE: 

some plant and job information appears to be for the Mallinckrodt Destrehan Street facility (St. Louis), but the address on 

the form is listed as Weldon Spring.

b Logbook with handwritten dates, names, and results organized alphabetically; clearly identifies St. Louis and Weldon 

Spring data.

c MCW Form 7184, computer printout with clock no., name, department, period, date, average urinary uranium results by 

quarter for Monday and Friday samples.

d Tables published in the Personnel and Environmental Monitoring Reports prepared quarterly and annually. Data include 

the number and names of employees with average urinary uranium concentrations above Monday and Friday action levels, 

as well as the percent of employees in each concentration range by cost center.

e Logbook for high urinary uranium results containing forms as described in Table 5-10. 

f Logbook for high urinary uranium results containing forms as described in Table 5-10 for 1962-1964; “Urinary Uranium 

Collection Report” for 1965 with handwritten names and dates (no data).

g Computer printout with group no., no. of employees monitored, and average, high and low urinary uranium results by 

month or quarter.

h Based on a memo (Ingle, 1991) summarizing thorium chest counting results (no names; semi-quantitative results only).
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Tables 6-2 and 6-3 include summaries of the average urinary uranium data that were readily available 

from the Mallinckrodt Chemical Works Uranium Division Personnel and Environmental Monitoring 

reports prepared quarterly and annually in the 1959-to-1963 timeframe. 

Table 6-2: Personnel Quarterly and Annual Average Urinary Uranium Concentration Range Analysis—Monday 

Before Work Samples

Average Urinary Uranium Concentration 

Number of Results by Concentration Range (mg/l)

Year Period 0.000-0.009 0.010-0.019 0.020-0.029 >0.030

Total No. 

Personnel 

Monitored

SRDB Ref 

ID

1958 Annual - - - 10 - 15907

1959

Quarter 1 - - - - - N/A

Quarter 2 - - - - - N/A

Quarter 3 265 79 7 1 352 15907

Quarter 4 494 91 16 5 606 15907

Annual - - - 1 - 15907

1960

Quarter 1 281 145 28 2 456 15901

Quarter 2 214 234 31 5 484 15901

Quarter 3 260 212 46 5 523 15901

Quarter 4 166 218 46 2 432 13763

Annual 481 466 43 0 990 13763

1961

Quarter 1 191 224 67 4 486 13752

Quarter 2 241 183 28 4 456 13745

Quarter 3 195 219 29 1 444 13736

Quarter 4 237 162 13 0 412 15375

Annual 434 454 41 0 929 16375

1962

Quarter 1 159 124 28 2 313 13732

Quarter 2 379 274 34 3 690 13732

Quarter 3 236 110 2 4 352 13732

Quarter 4 - - - - - N/A

Annual - - - - - N/A

1963

Quarter 1 130 198 104 13 445 15866

Quarter 2 163 196 107 11 477 15866

Quarter 3 277 301 71 18 667 15866

Quarter 4 86 215 124 16 441 15866

Annual - - - - - N/A

Notes:

- indicates no data. 
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Table 6-3: Personnel Quarterly and Annual Average Urinary Uranium Concentration Range Analysis—Friday 

After Work Samples

Average Urinary Uranium Concentration

Number of Results by Concentration Range (mg/l)

Year Period 0.000-0.009 0.010-0.019 0.020-0.029 0.030-0.059 >0.060

Total No. 

Personnel 

Monitored

SRDB Ref 

ID

1959 Annual - - - - 14 - 13735

1960

Quarter 1 56 61 25 44 11 197 13752

Quarter 2 35 88 33 40 15 211 13745

Quarter 3 42 61 54 58 12 227 13763

Quarter 4 46 84 55 55 9 249 13763

Annual 73 173 106 98 19 469 13763

1961

Quarter 1 25 50 70 65 6 216 13752

Quarter 2 40 67 61 36 7 211 13745

Quarter 3 44 67 60 30 2 203 13736

Quarter 4 69 100 51 28 4 252 13735

Annual 72 168 138 66 7 451 13735

1962

Quarter 1 18 38 21 36 2 115 13732

Quarter 2 69 143 58 57 4 331 13732

Quarter 3 31 70 24 19 4 148 13732

Quarter 4 - - - - - - N/A

Annual - - - - - - N/A

1963

Quarter 1 53 116 53 56 9 287 15866

Quarter 2 46 91 51 45 9 242 15866

Quarter 3 80 114 42 58 7 301 15866

Quarter 4 42 80 66 75 14 277 15866

Annual - - - - - - N/A

Notes:

- indicates no data. 

Weldon Spring Plant Urinary Uranium Program procedures provide additional information on the 

bioassay program (MCW, 1960; MCW, 1962). Fluorometric urinalysis procedures used at the 

Weldon Spring Plant are also available to NIOSH (Weldon, unknown date-a; Weldon, unknown dateb).

6.1.2 Thorium In Vivo Chest Counting Data

From July 11 through July 27, 1966, Oak Ridge Y-12 personnel provided a portable whole-body 

counter for in vivo lung region measurements to evaluate the thorium lung burdens of employees at 

the Weldon Spring Plant site. A total of 200 measurements were collected for 148 employees. 

Twenty minute counts were made in a shielded geometry using a 9-inch sodium iodide crystal 

adjacent to the workers back while the worker was in a supine position (Hibbs, 1966). According to a 

knowledgeable health physicist, the most exposed individuals were highly likely to be included in the 

population of monitored individuals and were much more likely to be counted than workers who were 

less exposed (Personal Communication, 2009h). The individual results were summarized without 

identifying information in a memo (Ingle, 1991) as negative, trace, or positive with the following 

interpretation:

• Negative: Net counts less than 60 counts per 20 minutes had less than the detectable amounts of 

thorium in their lungs. 
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• Trace: Net counts in more than 60, but less than 204 counts per 20 minutes. 

• Positive: Net counts in excess of 204 counts for 20 minutes. A person who showed 204 counts for 

20 minutes was considered to have at least one lung burden. 

The overall results showed that workers involved in principal exposure positions in Plants 101 

(Sampling), 103 (Digestion, Denitration, Packaging), 301 (Metals), and 403 (Chemical Pilot), and the 

Maintenance and Health and Safety personnel had a more frequent occurrence of “trace” detections. 

No workers monitored during this period had a “positive” designation (Ingle, 1991), and 

consequently, the maximum observed count rate can be specified as 204 counts per minute in the 

thallium-208 region of interest (thallium-208 is a gamma emitter in the thorium-228 decay chain). 

Information regarding the Oak Ridge counting technique, calibration, interpretation, limit of 

sensitivity, and error details used at the Weldon Spring Plant are available to NIOSH. This 

information may assist in interpretation of the in vivo count data. The Weldon Spring calibration was 

based on the response to a “Remab” manikin loaded with a 42-mg thorium source in equilibrium, 

which was considered to be typical of the source to which employees might have been exposed. The 

result was a calibration factor of 8.2 net counts per 20 minutes per mg of thorium. 

The ORAU CER database contains 148 in vivo individual lung-region counting results measured 

during July 1966. The 2.6 MeV-gamma from thallium-208, a daughter of thorium-228, was used in 

the evaluation of thorium burdens. Data fields include the employee name, pay status (wage or 

salary), job/area, sample data, and results in units of net counts per 20 minutes (CER Data, 2009). 

The information in the job/area field was evaluated to understand the kinds of workers who were 

evaluated with these in vivo measurements. Forty-five chemical operators were monitored, 19 of 

whom were associated with Building 103 where thorium denitration occurred. The other chemical 

operators were associated with Building 101 (3 employees), Building 201 (5), Building 301 (7), 

Building 403 (7), and Building 404 (4). Twenty-one foremen and supervisors were monitored. Other 

monitored job titles included: millwrights (10), pipefitters (9), technicians (9), riggers (7), chemists 

(6), yard operators (6), instrument mechanics (5), and machinists (4). The remaining monitored job 

titles accounted for no more than two people each; specific location data were not associated with 

these jobs. 

6.1.3 Airborne Dust Studies

A summary of the Weldon Spring Plant dust studies for various production jobs from 1957 through 

1966 was published (MCW, 1958-1966). The studies evaluated the Weldon Spring worker 

environment relative to airborne uranium and thorium dusts. Component task concentrations were 

time-weighted and integrated to give a daily weighted average (DWA) concentration for the job. 

Work group indices were obtained by weighting the daily averages for jobs by manpower 

distributions for each plant. This index was calculated to account for job rotations within each work 

group. Both breathing zone and general area air samples were collected and the samples were 

analyzed by direct alpha count with laboratory scintillation counters. For uranium, a counting delay 

of 24 hours was employed to permit decay of short half-lived daughters; the delay time for thorium 

counting was 100 hours. Tables 6-4 and 6-5 include the summary dust concentrations for uranium 

and thorium production jobs respectively. ORAUT-TKBS-0028-5 provides a summary of the dust 

study results and descriptions of the sampling protocols and calculations. In some instances the 

original air sample data that were used to calculate DWA values are available. 
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Table 6-4: Dust Concentrations for Uranium Production Jobs

Plant Name 

& No. Materials Work Group Title 

No. of 

Job 

Titles 

Daily Weighted Average (DWA) Index per Year for Workgroup 

(μg/m3) 

195819591960196119621963196419651966

Sampling

101

Uranium 

concentrates

Sampling & 

Repackaging 11 65 55 45 55 32 31 20 60 - 

Digest/

Raffinate/

Acid 

103-108

Uranium 

concentrates & 

scrap

DigestRaffinate 4 17 7

a 7 20a - 11 8 7 -

Extraction 

105

Uranium 

concentrate 

feeds

Extraction 5 4 - 3 - 5 - 2 2 - 

Refinery Pot 

Room 

103

Uranium 

trioxide & 

uranyl nitrate 

hexahydrate

Denitration 

(Pot Room) 4 117 42a 70 17a,b 22c - 45c 16 - 

Green Salt

201

Uranium 

trioxide to 

uranium 

tetrafluoride

Green Salt 8 40 37 37 53 53 16 16 22 - 

Metals 

301

Natural uranium 

as uranium 

tetrafluoride & 

U3O8

Dingot 

Reduction 11 - 37a 115 65 - 150 150d 78 50

Metals

301 Uranium Metal-other 

than reduction 10 - - e 44 52 63 40 55 10a

Metals

301

Uranium metalnatural Core Area 11 - - 20 - - - - - - 

Chemical 

Pilot 403 & 

Scrap Plant

Uranium Pilot/Scrap 

Plants 10 - - - 50f - 50f 50f 50f 50f

Metal Plant

404 Uranium Special 

Projects 4 - - - - - 320a 190a g - 

Notes:

Source: Information used to create this table is from MCW, 1958-1966. 

- indicates no data

a An index was not calculated; this is a DWA for one job title.

b Airline masks were specified for shaking bags in dust collectors during uranium trioxide packaging; if no allowance was 

made, the concentrations would range about 10 times this value. 

c Airline masks were specified for shaking bags in dust collectors during uranium trioxide packaging; if no allowance was 

made, the concentrations would range about 10 times this value. Uranium trioxide packaging was one of three job titles 

that contributed to the index per year for the Denitration (Pot Room) work group title. d Airline masks were used for dingot cleaning by sandblasting during dingot reduction; no allowance was made for the use 

of the respirator. Dingot cleaning by sandblasting one of six job titles that contributed to the index per year for the 

Denitration (Pot Room) work group title.

e An index was not calculated; this is a DWA for two job titles. For each of the two job titles, the individual DWA result 

was 13 ug/m3

. 

f Overall average (not weighted).

g An index was not calculated; the individual DWAs for 3 job individual titles were 42, 72, and 92 μg/m3

. 
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Table 6-5: Dust Concentrations for Thorium Production Jobs

Table 6-5 and its associated notes span five pages.

Plant Name 

& No. Materials

Work Group 

Title & Cost

Centera Job Titleb Time Periodc Workers/Day

Daily Weighted Average (DWA) 

Concentrations 

(alpha d/m/m3) 

Notes

1963 1964 1965 1966

Sampling

101

Extracted 

thorium-natural

Sampling

0402 Oven drying ThO2 sol-pan 

transfer Mar 1965 2 - - 3 - 

Test date: Mar 30, 1965. Five ovens 

operated on a 24-hour cycle at 400 

lbs/oven. Experimental, intermittent 

operation.

Oven drying ThO2 sol-vacuum 

unload Aug 1965 2 - - 16 - 

Test date: Aug 9, 1965. 

Experimental, intermittent 

operation.

Repackaging ThO2 feeds for 

digestion-drum dumping Apr-Aug 1966 1 - - - 9 

Total project operating time 

estimated at 1 week or 10 shifts 

intermittent operation.

Repackaging ThO2 feeds for 

digestion-hopper packaging Apr-Aug 1966 1 - - - 12 Total project operating time 

estimated at 1 week or 10 shifts.

Repackaging ThO2 feeds for 

digestion-outgoing drum 

conveyor

Apr-Aug 1966 1 - - - 7 

Total project operating time 

estimated at 1 week or 10 shifts 

(empty drums).

Refinery

103

Extracted & reextracted 

thorium-232 & 

daughters

DigestRaffinate

0501 Hopper feed & digestion Apr-May 1966 3 - - - 6 

Test date: Apr 22, 1966. One 

hopper (15,000 pounds) made 1 tank 

batch, 20,000 lbs/day product on 

first cycle; recycle is liquid feed. 

Raffinate treatment & disposal May-Sep 1966 3 - - - 2 - 

Misc. digestion of drummed 

scrap-wet feed May-Sep 1966 2 - - - 4 

Test date: May 3, 1966. Material 

was damp to wet; floor sweepings 

were used as feed. Non-routine job.
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Table 6-5: Dust Concentrations for Thorium Production Jobs

Table 6-5 and its associated notes span five pages.

Plant Name 

& No. Materials

Work Group 

Title & Cost

Centera Job Titleb Time Periodc Workers/Day

Daily Weighted Average (DWA) 

Concentrations 

(alpha d/m/m3) 

Notes

1963 1964 1965 1966

Refinery 

Pot Room

103

Extracted 

thorium-natural

Pot Room

0502d Pot denitration & sol dryinghand transfers

Nov-Dec 1963; 

May-Aug 1964 6 88 88 - - 

Test dates: Nov 1963 and May 

1964. Airline masks used to enter 

pot sections.

Pot denitration (crystals) & sol 

drying-vacuum unload Aug-Dec 1964 6 - 60 - - 

Test samplings for vacuuming and 

packaging collected from Sep 1964 

to Oct 1965. Airline masks 

prescribed for entrance into pot or 

packaging sections. Small crucibles 

packaged.

Pot denitration (liquor) & sol 

drying-vacuum unload Jan-Aug 1965 6 - - 48 - 

Airline masks prescribed for 

packaging and unloading; half-face 

dust respirators (Comfo) for misc. 

attending duties in pot sections. 

Small crucibles packaged.

Sol drying (fluid bed sol)-

vacuum unload

Aug 1965-Jan 

1966; Jun-Sep 

1966

6 - - 38 38

Packaging in small crucibles (500 

lbs). Comfo respirators prescribed 

in pot sections.

Pot denitration-hand unload & 

bucket dump to sol tank Oct-Nov 1965 6 - - 144 - 

Pot denitration used for special 

project and to maintain production 

at scheduled rate when fluid bed was 

down. Airline masks prescribed for 

dumping and scooping. Comfo 

respirators were used for vacuuming 

and packaging activities. 

ThO2 repackaging-multi-purpose 

hood Aug 1964 2 - 260 - - Short-term operation. Airline masks 

used in hood.

DWA index for the Pot room 

work group

Apr 1964-Dec 

1965 - - 78 50 - 

For Apr-Dec 1964, approximately 

45% of the effort (manpower) was 

on thorium jobs. For 1965, 

approximately 50% of the effort was 

on thorium jobs. Results are yearly 

indices and represent DWAs for 3 

job titles.
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Table 6-5: Dust Concentrations for Thorium Production Jobs

Table 6-5 and its associated notes span five pages.

Plant Name 

& No. Materials

Work Group 

Title & Cost

Centera Job Titleb Time Periodc Workers/Day

Daily Weighted Average (DWA) 

Concentrations 

(alpha d/m/m3) 

Notes

1963 1964 1965 1966

Extraction

105

Extracted 

thorium and 

thorium-232 

daughters

Extraction Pumper decanter, pulse column, 

strippers, and NOK (product 

liquor)

Jun-Sep 1966 9 - - - 2 - 

Metals 

301

Extracted 

thorium-natural

Metals-other 

than 

Reduction

0702

High-firing 1,000 lb crucibles at 

recast (furnace)

Nov-Dec 1963; 

May-Sep 1964 6 21 21 - - 

Test dates included Dec 1963, May 

1964, and Oct 1964. Airline masks 

used for entrance into enclosure for 

thermocouple change and 

inspection; operation performed 7

days/week.

TNT repackaging Oct-Dec 1964 2 - 3 - - 

Test date: Oct 5, 1964. For part of 

this period, crushing was done 

externally by electric grabs and 

transferred to the refinery without 

repacking TNT.

High-firing 500 lb crucibles in 

billet heaters 

Sep 1964-Jan 

1966; 

Jun-Sep 1966

3 - 11 11 11

Test date Nov 4, 1964. Four heaters 

were installed, each handling a 500-

lb crucible on a 24-hourcycle.

Repackaging ThO2 in recast 

enclosure

Oct-Dec 1965;

Jan 1966;

Jun-Sep 1966

2 - - 2060 

(55) 55

The DWA result of 2,060 d/m/m3 is 

for Oct 1965; airline masks and 

cover clothing were used inside the 

transfer enclosure which exhausted 

to the dust collector. 

Test dates: Sep 16, 1965 

(experimental batch) and Sep 27, 

1965- improvements were 

recommended. 

The DWA result of 55 d/m/m3 is for 

Nov 1965 and later. 

Test dates: Feb 24, 1966 and Jul 14, 

1966. Airline masks were used for 

all scooping operations.
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Table 6-5: Dust Concentrations for Thorium Production Jobs

Table 6-5 and its associated notes span five pages.

Plant Name 

& No. Materials

Work Group 

Title & Cost

Centera Job Titleb Time Periodc Workers/Day

Daily Weighted Average (DWA) 

Concentrations 

(alpha d/m/m3) 

Notes

1963 1964 1965 1966

Kiln calcining of NLO sump 

cake Apr-Jul 1966 3 - - - 20

Test dates: Apr 21, 1966; Jun 8-9, 

1966. Comfo (MSA) dust 

respirators used on dumping 

platform and at packaging stations. 

Feed was normally wet, ranging 

from damp to a surface water layer.

DWA index for the Metals 

(other than Reduction) work 

group

May 1964-Dec 

1965 - - 17 113 - 

For 1964, approximately 50% of the 

(manpower) effort was on thorium 

jobs, but none (on thorium) during 

the first 4 months. For 1965, 

approximately 60% of effort was on 

thorium jobs. Results are yearly 

indices and represent DWAs for 2 to 

3 job titles.

Scrap Plant

403

Extracted 

thorium-natural

Scrap Plant

0601 e TNT crystals-repackaging Nov-Dec 1963;

May-Sep 1964 6 15 15 - - Equivalent production rate of 1 ton of ThO2/day.

ThO2 repackaging-from recast 

crucibles

Nov-Dec 1963;

May-Sep 1964 6-8 290 290 - - 

After Sep 1964, smaller crucibles 

were used. Airline masks were used 

on all scooping operations; 

operations conducted inside multipurpose walk-in hoods. Exhaust

was filtered by auto-air-mat (paper 

rolls). Manpower for 1964 was 

variable (5 in May to 15 in Jul); 

normal manpower was 6 to 8. ThO2

repackaging included 

screening, blending, and product 

packaging.

ThO2 repackaging-from billet 

heater crucibles Sep 1964-Oct 1965 4 - 20 20 - 

Test date: May 24, 1965. Airline 

masks used on all scooping 

operations. Shallow crucibles could 

be scooped with breathing zone 

more distant from the opening than 

with recast crucibles (lower 

concentrations observed). Longhandles scoops were used in the 

blender drum.
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Table 6-5: Dust Concentrations for Thorium Production Jobs

Table 6-5 and its associated notes span five pages.

Plant Name 

& No. Materials

Work Group 

Title & Cost

Centera Job Titleb Time Periodc Workers/Day

Daily Weighted Average (DWA) 

Concentrations 

(alpha d/m/m3) 

Notes

1963 1964 1965 1966

Fluid bed denitration-product to 

drums May-Jul 1965 6 - - 44 - Test date Jun 1965. Experimental 

use of NLO liquor during May.

Fluid bed denitration-wet feed & 

product

Aug 1965-Jan 

1966;

Jun-Sep 1966

6 - - 29 29 Liquor feed and sol product at 1 

ton/day production rate.

DWA index for Scrap Plant 

work group

Nov 1963-Dec 

1965 - 180 117 28 - 

The 1963 index was for a 6-man 

group (Nov-Dec) with 17% of 

manpower on thorium. The 1964 

index was for a 6-man group with 

60% of manpower on thorium. The 

1965 index was for a 12-man group 

(Jan-Jun) and a 6-man group (JulDec) with 80% of manpower on 

thorium. Results are yearly indices 

and represent DWAs for 2 to 3 job 

titles.

Notes: 

Source: Information used to create this table is from MCW, 1958-1966. 

- indicates no data

a “Cost Center” refers to an employer charge code. Cost center codes are published in some TBDs and can be used for identifying employee work areas. b “Job Title” is the term used in the referenced report; this term more accurately represents a task description rather than an employee job title. 

c

 “Time Period” was recorded from the air sampling data sheets and was estimated if date ranges were incomplete. d Manpower in this group ranged from 18 to 21 men during the years 1963 through 1965; base production rate was 1 ton ThO2/day. e Average production rate was 1 ton ThO2/day.
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6.1.4 Environmental 

Available occupational environmental monitoring data include summarized results of uranium air 

concentration measurements made at the site perimeter and two offsite locations from 1959 to 1965 

(Meshkov, 1986) and general air sample results collected onsite during the cleaning of six 5-ton 

hoppers in 1960 (Holt, 1960a). Estimated average perimeter air concentrations and onsite air 

concentrations during the hopper cleanout are provided in ORAUT-TKBS-0028-4 for 1957 to 1967 

for the chemical plant, quarry, and raffinate pit locations. 

6.2 Available Weldon Spring Plant External Monitoring Data

ATTRIBUTION: Section 6.2 and its related subsections were completed by Billy P. Smith, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

External monitoring data available to NIOSH consist of film badge results representing the entire 

operational period under evaluation. NIOSH does not have access to area survey or monitoring 

records beyond what is described in Section 6.1.3 of this report, Airborne Dust Studies. 

Details regarding the various analyses used and the associated minimum detectable activities are 

presented in the Technical Basis Document for the Weldon Spring Plant in ORAUT-TKBS-0028-6. 

A summary of the available external data applicable to this evaluation is presented below.

6.2.1 Film Badges 

NIOSH has access to the ORAU CER database which contains nearly 8,000 film badge records 

collected from 1957 to 1967 for approximately 1,850 employees. Data fields include the employee's 

last name, social security number, date, beta results (i.e., mrem), gamma results (i.e., mrem), total 

records (identified as TORECS), the number of weeks that the reported doses did not exceed the 

administrative limits (identified as OKGAMWKS), and the number of weeks the individual was 

monitored during the year (identified as MONWKS) (CER Data, 2009).

Table 6-6 in ORAUT-TKBS-0028-6 summarizes several different formats in which health personnel 

recorded external dosimetry information for the Weldon Spring Plant site. Many of the dosimetry 

reports did not specify the reporting units, but a June 16, 1956, memorandum from K. E. Brandner to 

J. W. Miller details the change from roentgen and rep to rad for both gamma and beta radiation 

(ORAUT-TKBS-0028-6). The memorandum specifies that, beginning June 18, 1956, units for both 

gamma and beta radiation “should be standardized to the ‘rad’ unit.” Table 6-6 of ORAUT-TKBS0028-6 includes descriptions of personal monitoring summary records and reports, descriptions of 

how the result quantities are noted in the reports, and NIOSH’s interpretation of zeros and blanks in 

the monitored exposure results. 
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Tables 6-6 and 6-7 provide the annual average gamma and beta dose (mR) by job category from 1957 

through 1966. 

Table 6-6: Average Annual Gamma Exposure (mR) by Job Category

Job Category 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966

Engineer 110 102 43 121 83 75 94 244 170 94

Equipment Operator 135 - 135 168 154 151 176 177 164 278

Foreman 233 85 150 183 190 186 154 130 192 102

Laboratory Worker 220 89 71 71 134 175 204 285 575 155

Manager 52 - 37 517 102 41 142 112 78 64

Non-Radiation Job 125 - 48 96 105 72 93 226 181 33

Operator 305 129 151 234 369 371 640 516 413 298

Safety, Security 168 75 265 59 65 83 415 273 119 183

Unknown 411 48 85 141 170 223 184 294 292 248

Worker 240 132 67 142 140 216 317 303 198 177

Table 6-7: Average Annual Beta Exposure (mR) by Job Category

Job Category 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966

Engineer 228 23 191 579 486 572 277 308 186 90

Equipment Operator 190 1 878 1170 710 788 283 279 514 190

Foreman 328 45 492 1293 804 919 1336 735 637 257

Laboratory Worker 382 133 343 463 796 724 367 327 340 278

Manager 107 35 199 1160 1099 403 204 128 91 181

Non-Radiation Job 248 135 123 378 538 204 224 243 142 50

Operator 761 274 1122 2642 2695 1648 1309 1018 884 297

Safety, Security 198 60 94 170 301 463 107 98 197 91

Unknown 524 128 297 890 1427 1146 338 401 453 205

Worker 697 93 472 923 1070 1107 780 354 473 317

6.2.2 Medical

NIOSH has access to the ORAU CER database which contains over 9,900 medical diagnostic X-ray 

records for approximately 2570 employees collected during the period 1957 to 1967. Data fields 

include the employee name, date, number of X-rays, area of X-ray (e.g., chest PA LL, thumb), age, 

race, sex, "origin" or type of X-ray (e.g., pre-employment, routine, termination, special, re-exam), and 

diagnosis (e.g., yes/no) (CER Data, 2009).

Table 3-4 in ORAUT-TKBS-0028-3 shows the organ dose estimates for chest X-rays (rem) for the 

period of pre-1970. 

6.2.3 Environmental 

Table 4-12 in ORAUT-TKBS-0028-4 shows the estimated maximum site-wide ambient dose exposure 

to workers for years 1957-1967. 
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7.0 Feasibility of Dose Reconstruction for the Class Evaluated by 

NIOSH

The feasibility determination for the class of employees under evaluation in this report is governed by 

both EEOICPA and 42 C.F.R. § 83.13(c)(1). Under that Act and rule, NIOSH must establish whether 

or not it has access to sufficient information either to estimate the maximum radiation dose for every 

type of cancer for which radiation doses are reconstructed that could have been incurred under 

plausible circumstances by any member of the class, or to estimate the radiation doses to members of 

the class more precisely than a maximum dose estimate. If NIOSH has access to sufficient 

information for either case, NIOSH would then determine that it would be feasible to conduct dose 

reconstructions. 

In determining feasibility, NIOSH begins by evaluating whether current or completed NIOSH dose 

reconstructions demonstrate the feasibility of estimating with sufficient accuracy the potential 

radiation exposures of the class. If the conclusion is one of infeasibility, NIOSH systematically 

evaluates the sufficiency of different types of monitoring data, process and source or source term data, 

which together or individually might ensure that NIOSH can estimate either the maximum doses that 

members of the class might have incurred, or more precise quantities that reflect the variability of 

exposures experienced by groups or individual members of the class. This approach is discussed in 

DCAS’s SEC Petition Evaluation Internal Procedures which are available at 

http://www.cdc.gov/niosh/ocas. The next four major subsections of this Evaluation Report examine:

• The sufficiency and reliability of the available data. (Section 7.1) 

• The feasibility of reconstructing internal radiation doses. (Section 7.2) 

• The feasibility of reconstructing external radiation doses. (Section 7.3) 

• The bases for petition SEC-00143 as submitted by the petitioner. (Section 7.4) 

7.1 Pedigree of Weldon Spring Plant Data

This subsection answers questions that need to be asked before performing a feasibility evaluation. 

Data Pedigree addresses the background, history, and origin of the data. It requires looking at site 

methodologies that may have changed over time; primary versus secondary data sources and whether 

they match; and whether data are internally consistent. All these issues form the bedrock of the 

researcher’s confidence and later conclusions about the data’s quality, credibility, reliability, 

representativeness, and sufficiency for determining the feasibility of dose reconstruction. The 

feasibility evaluation presupposes that data pedigree issues have been settled. 
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7.1.1 Internal Monitoring Data Pedigree Review

ATTRIBUTION: Section 7.1.1 was completed by Lori Arent and Robert Morris, M.H. Chew and 

Associates, Inc. The rationales for all conclusions in this document are explained in the associated 

text.

Uranium in Urine Data

The ORAU CER obtained electronic files along with hardcopy records of uranium in urine results 

from a prior epidemiology effort headed by Dr. T. F. Mancuso. In December 1979, the data were 

subjected to a 10% sampling validation prior to being accepted for use by CER (MCW, 1979). Data 

from the CER database were extracted into a Microsoft Access table (CER Data, 2009) and the CER 

data were compared to the applicable hardcopy records in the SRDB. 

For the period from 1957 through 1959, raw urinary uranium results are available to NIOSH as 

hardcopy documents located in the SRDB. A statistical evaluation was conducted to determine the 

number of the SRDB results that were successfully captured in the CER database. Five percent of the 

available hardcopy urinalysis results were compared with the entries in the CER database and the 

results of the evaluation are presented in Table 7-1. 

Table 7-1: Statistical Evaluation of CER Database and SRDB Results for Urinary Uranium, 1957-1959

Year

Evaluation Periods 

Covered in SRDB 

Documents

No. of SRDB 

Resultsa 

No. of SRDB 

Resultsa Matched 

in CER Database

SRDB Resultsa

Captured in 

CER Database 

(%) 

No. of 

Errors found 

in CER 

Databaseb 

SRDB 

Ref ID 

1957 Apr-Jul 56 34 61% 4 9213

1958 Jan-Apr; Aug-Dec 49 44 90% 0 9213; 

15634

1959 Jan-Apr 31 29 94% 1 15634

Notes:

Sources: Weldon, 1957-1958; Weldon, 1958-1959 a The number and percent of SRDB results refer to individual urinalysis. 

b Errors include minor date (several days) or result (hundredths or less of a decimal place) discrepancies and do not affect 

dose reconstruction outcomes. 

For the period from 1960 through 1964, NIOSH has access to hardcopy documents (located in the 

SRDB), including logbooks of high urinary uranium results reported on MCW Forms 7273, 7274, and 

7463; descriptions of these forms are included in Table 5-10. All of the available SRDB results were 

compared with the CER database results and the findings of this evaluation are presented below in 

Table 7-2. 
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Table 7-2: Statistical Evaluation of CER Database and SRDB Results for Urinary Uranium, 1960-1964 

Year

Evaluation 

Periods Covered 

in SRDB 

Documents

No. of SRDB 

Resultsa 

No. of SRDB 

Resultsa

Matched in 

CER Database

SRDB Resultsa

Captured in 

CER Database 

(%) 

No. of 

Errors found 

in CER 

Databaseb 

SRDB 

Ref ID 

1960 Jan-Dec 407 165 41% 3 15874

1961 Jan-Dec 162 76 47% 0 15865

1962 Jan-Dec 79 44 56% 7 15890

1963 Jan-Dec 101 100 99% 1 15890

1964 Jan-Aug 78 78 100% 1 15890

Notes:

Sources: Weldon, 1960; Weldon, 1961; Weldon, 1962-1965 a The number and percent of SRDB results refer to individual urinalysis.

b Errors include minor date (several days) or result (hundredths or less of a decimal place) discrepancies and do not affect 

dose reconstruction outcomes.

While there are nearly 2,900 urinalysis results in the CER database for 1965 and over 2,100 results for 

1966, NIOSH does not have hardcopy results for 1965-1966. NIOSH does have the 1965 urinary 

uranium collection report with handwritten names and dates, which implies that samples were 

collected; however, NIOSH is not sure this is a one-to-one correlation (i.e., the name/date of 

collection corresponding to an individual sample result). In addition, there are checkmarks and dates 

crossed out that make the collection reports difficult to interpret (Weldon, 1962-1965). The CER 

database does not include any results for 1967, nor does NIOSH have hardcopy urinalysis data for this 

year.

As demonstrated in Tables 7-1 and 7-2, the Microsoft Access table (which contains data extracted 

from the CER database) appears to be a faithful reproduction of the uranium in urine sample results 

for 1958 and 1959, as well as for January 1963 through August 1964. 

For 1957, 61% of the hardcopy records were represented in the CER database. NIOSH has access to 

various handwritten logs of bioassay urine processing results on New York Atomic Energy 

Commission Form NY-99 (Weldon, 1957-1958), but it is difficult to determine if the results are for 

Weldon Spring Plant workers during the period when both the Mallinckrodt Destrehan Street Facility 

(St. Louis) and Weldon Spring Plant were operating. For example, some records with a Weldon 

Spring mailing address have St. Louis job titles/locations (e.g., Plant 6). There are many results that 

have a generic job title (e.g., office, operator, etc.) that could be assigned to either location. There are 

also results for AEC employees and possibly for United Nuclear Corporation workers from the 

Hematite Plant (concurrent operations). Because of these uncertainties, NIOSH did not include these 

data with the CER data.

For the period from 1960 through 1962, the data in the Microsoft Access tables appear to be accurate 

but are incomplete, including less than half of the uranium in urine sample results that were 

recognized contemporarily as being elevated and worthy of management attention. NIOSH has 

extracted the Microsoft Access data into an Excel spreadsheet and has added the missing elevated 

urinary uranium data. The number of urinary uranium results, both originally in the CER database 

and those added from other documentation, and the number of individuals represented in the CER 

database by year are shown in Table 7-3. 
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Table 7-3. Numbers of Urinary Uranium Results and Individuals Represented in the CER Database

Year

No. of Results in 

Original CER 

Database

No. of SRDB 

Results Added to 

CER Database

New Total No. of 

Results in CER 

Database

No. of Workers 

Represented in CER 

Databasea 

1957 1,038 0 1,038 815

1958 1,872 0 1,872 1,207

1959 2,284 14 2,298 1,053

1960 4,396 242 4,638 1,019

1961 4,184 86 4,270 945

1962 3,083 36 3,119 811

1963 3,481 0 3,481 664

1964 3,476 0 3,476 636

1965 2,980 0 2,980 604

1966 2,128 0 2,128 511

Total 28,926 378b 29,304 1,890c

Notes:

Source: CER Data, 2009

a Includes number of workers for SRDB hardcopy results added by NIOSH.

b Of the 378 results added, 331 (88%) were equal to or above the lower limit of Action Level 1 (i.e., 0.03 mg/l) and 47 

(12%) were below this level; the results lower than Action Level 1 were typically follow-up samples on dates -after a 

recorded high result. A total of 116 results were listed as Action Level 1 through Action Level 4 (i.e., no numerical 

result); these results were added to the CER database at the upper bound of the stated action level range. [Example: 

“Action Level 1” with a range up to 0.1 mg/l was entered as < 0.1 mg/l in the CER database.] Action Level ranges are 

described in Table 5-10. c This value is the number of individual names represented in the CER database, including the data added by NIOSH. This 

is not a sum of the number of workers for each year. An individual worker routinely has results for multiple years.

For 1965, there are 2,980 results in the CER database representing 604 individuals. For 1966, there 

are 2,128 results representing 511 individuals (Table 7-3). Taking the decreased production rates into 

account, the numbers of sample results and workers represented in 1965 and 1966 appear reasonable 

when compared with previous years. Although hard-copy data for these years have not been 

discovered, NIOSH believes it is reasonable to assume the CER data are complete and accurate for 

1965 and 1966. 

According to a health physicist who was recently interviewed by NIOSH, the most highly exposed 

workers were always captured in the bioassay program. Any high uranium-in-urine sample was 

promptly re-sampled using 24-hour catches. Follow-up medical monitoring of individuals with 

elevated results was overseen by the assigned physician (Personal Communication, 2009h). 

There are over 29,000 urinary uranium results available for 1,890 individuals during the 1957 through 

1966 timeframe. More than 330 “high-biased” results (i.e., results that were above the reporting 

threshold) were added following the data capture and review efforts. The few errors noted in the CER 

database as compared to the hardcopy records were minor date or result discrepancies. In summary, 

NIOSH believes the CER database is of sufficient quality to use to bound internal doses for Weldon 

Spring Plant employees.

Thorium Whole-Body/Chest Count Data

The thorium in vivo counting data described in Section 6.1.2 are available in a spreadsheet derived 

from CER data. Unlike the hardcopy summary report (Ingle, 1991), the spreadsheet contains 
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individually identifiable data. The number of individuals and the total number of analyses in the 

spreadsheet match the hardcopy summary information. The spreadsheet data are entirely consistent 

with the data summarized in the hardcopy report. 

7.1.2 External Monitoring Data Pedigree Review

ATTRIBUTION: Section 7.1.2 was completed by Monica Harrison-Maples, Oak Ridge Associated 

Universities (ORAU). The rationales for all conclusions in this document are explained in the 

associated text.

As discussed in Section 6.2.1 of this report, NIOSH has access to film badge records for 

approximately 1,850 employees over the evaluated period. 

There are documented reports of the practice of nearly universal external monitoring using film 

badges (Mason, 1955, p. 21), with confirmatory accounts from former Weldon Spring workers stating 

that workers (other than female administrative workers) were required to wear a combination film

badge/security badge (Personal Communication, 2009b; Personal Communication, 2009e; Personal 

Communication, 2009f). 

In summary, the available external dosimetry monitoring data are available in sufficient quantity and

quality to adequately represent external beta and photon dose for the Weldon Spring Plant class under 

evaluation for the period from January 1, 1957 through December 31, 1967. NIOSH did not identify 

any neutron dosimetry data; therefore, a pedigree review of neutron external dosimetry data was not 

possible. 

7.2 Evaluation of Bounding Internal Radiation Doses at Weldon Spring Plant

The principal source of internal radiation doses for members of the class under evaluation was 

inhalation of particulate radiological materials during routine operations, initial cleanup, and 

maintenance periods. Ingestion is routinely assessed by NIOSH concurrently with inhalation 

exposure. The following subsections address the ability to bound internal doses, methods for 

bounding doses, and the feasibility of internal dose reconstruction. 

7.2.1 Evaluation of Bounding Process-Related Internal Doses

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related internal doses of members of the class under evaluation. 

7.2.1.1 Urinalysis Information and Available Data 

ATTRIBUTION: Section 7.2.1.1 was completed by Robert Morris and Eugene W. Potter, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

Uranium

Urine bioassay was the primary method of determining uranium intakes during the operational period. 

The bioassay program was set up in accordance with the general health physics practices of the 

period. Grab (single-void) urine samples were collected and analyzed for uranium by 
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photofluorimetric analysis. Results of the photofluorimetric analysis were reported as the mass of 

uranium in milligrams, or sometimes micrograms, per liter of urine (ORAUT-TKBS-0028-5). 

From 1957 to mid-May 1959, urine sampling was conducted at random times during the week. From 

mid-May 1959 through September 1959, sampling occurred primarily on Fridays. Starting in October 

1959, the routine sampling program was changed to a workgroup monitoring program and continued 

through 1966. Under this program, one or more persons from each operational group in the plant 

were sampled each week. The selected individuals were asked to submit samples on Monday 

morning, Friday after work, and the following Monday morning. The sample from each person was 

added to their individual summary. Each exposed person was scheduled three or more times per year. 

Unexposed persons were scheduled less frequently. Workers also submitted urine samples as part of 

the hiring and termination processes. A repeat sample was required if the result of the Monday 

morning sample was greater than 100 μg/L or if the result of the Friday afternoon sample was greater 

than 200 μg/L. Special urine samples were required for known or suspected significant intakes 

(MCW, 1965; ORAUT-TKBS-0028-5). 

Details on the reporting levels, minimum detectable amounts, and uncertainties are available to 

NIOSH (MCW, 1965; ORAUT- TKBS-0028-5). Many Weldon Spring Plant workers were assigned 

to the St. Louis facility before being assigned to Weldon Spring. All of the urine data reports contain 

data from both facilities. When no other specific information is available, it is reasonable to assume 

that Weldon Spring/Mallinckrodt Chemical Works uranium urine data starting in 1957 is associated 

with Weldon Spring Plant. 

Data summaries covering most of the operational period have been discovered. In addition, NIOSH 

has located approximately 28,000 urine bioassay results for the operational period (See Section 6.0). 

Tables 5-8 through 5-17 of ORAUT-TKBS-0028-5 provide median, 95th-percentile, and maximum 

concentrations for routine urine bioassay samples by year. These data are adequate to support 

bounding the dose from uranium intakes because the program was specifically designed so that 

workers not sampled in a given period would be represented by the workgroup sample. 

7.2.1.2 Airborne Levels 

ATTRIBUTION: Section 7.2.1.2 was completed by Robert Morris and Eugene W. Potter, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

Whereas the matter of uranium intake bounding is addressed above in Section 7.2.1.1, no further 

discussion of uranium airborne levels will be provided. Uranium airborne data are available as 

detailed in Section 6.1.3 and specifically in Table 6-4 for use on a case-by-case basis if applicable. 

Thorium airborne dust concentrations were routinely measured and evaluated throughout the 

operating period. These data, in the form of DWA concentrations, were summarized for the thorium 

processing period of 1963 through 1966 (MCW, 1958-1966) and are reproduced in Table 6-5. 

Reduction in actual intake rate due to use of respiratory protection is not incorporated in the 

calculation of DWA. Thorium airborne dust levels are of particular interest because no thorium 

bioassay method was available until the mobile in vivo counter became available for a one-time use in 

1966. When combined with the methods and assumptions described in Site Profiles for Atomic 

Weapons Employers that Refined Uranium and Thorium (Battelle-TBD-6001) and Default 
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Assumptions and Methods for Atomic Weapons Employer Dose Reconstruction (Battelle-TIB-5000), 

the DWA thorium data can be used to define bounding thorium intake rates, as discussed in Section 

7.2.3. 

7.2.2 Evaluation of Bounding Ambient Environmental Internal Doses

ATTRIBUTION: Section 7.2.2 was completed by Robert Morris and Eugene W. Potter, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

An evaluation of the ambient environmental internal radiation doses from releases of 

particulates/aerosols of uranium, the associated recycled uranium contaminants, and decay products 

(e.g., thorium-230) is not necessary because the most highly exposed plant employees were monitored 

by routine uranium bioassay sampling, either individually or as members of a workgroup. Thus, these 

doses are accounted for in the process-related internal dose evaluations. 

In the few years that thorium-232 was processed, operational area dust measurements (see Section 

6.1.3 of this evaluation report) are available. Two hundred whole-body count measurements for 

thorium were also collected for 148 employees, with a good cross section of Weldon Spring Plant 

workers being represented (see Section 6.1.2 of this evaluation report). Thus, thorium can also be 

accounted for in the assignment of process-related dose. 

Measured air concentrations of radon are not available for the operational period. However, the 

maximum occupational ambient environmental exposure for radon may be calculated using the 

method in ORAUT-TKBS-0028-4. The estimate of radon releases based on throughput, mainly from 

the acid recovery plant, is between 12 and 34 Ci/year (see Section 5.2.1.5). The screening model in 

the National Council of Radiation Protection and Measurements (NCRP) Report No. 123 (NCRP, 

1996) was used to perform the calculations. Default parameters were used with the exception of 4.2 

m/s for wind speed (Weidner, 1982) and 10 m for stack height (estimated). The concentration at the 

receptor (within 100 m of the acid recovery plant), corresponding to a release of 34 Ci/year, was 

rounded to 80 Bq/m3

. ORAUT-TKBS-0028-4 added 11 Bq/m3 to this value, since the concentration 

including background was desired. (Background is omitted in this analysis. Using a 2,000-hour/year 

occupational exposure period and an outdoor environmental radon daughter equilibrium factor of 

30%, which is the upper limit of measured factors for the Weldon Spring Plant (MK-Ferguson, 2001), 

the result is 0.076 working-level month (WLM)/year. This value is the maximum occupational 

ambient environmental exposure for radon for the entire operational period. 

7.2.3 Methods for Bounding Internal Dose at Weldon Spring Plant

The following subsections summarize the methods for bounding internal dose at the Weldon Spring 

Plant.
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7.2.3.1 Methods for Bounding Operational Period Internal Dose

ATTRIBUTION: Section 7.2.3.1 was completed by Robert Morris, Eugene W. Potter, and Bryce L. 

Rich, M.H. Chew and Associates, Inc. The rationales for all conclusions in this document are 

explained in the associated text.

Uranium, Uranium Decay Products, and Recycled Uranium Contaminants

The Weldon Spring Plant’s urine bioassay monitoring program for uranium was extensive. The urine 

bioassay data are readily available to bound the dose to uranium isotopes for both monitored and 

unmonitored workers. Summary statistics have been published in ORAUT-TKBS-0028-5 in several 

tables that include the median, 95th percentile, and maximum result for each year of processing, as 

well as a breakdown of the results by year for each cost center (operational area). During this 

evaluation, a limited amount of additional data was found in hardcopy records and has been handentered into the NIOSH database. The analysis in Section 7.1.1 indicates that the additional data has a

negligible impact on the statistics of the dataset.

As discussed in ORAUT-TKBS-0028-5, prior to 1961, doses are bounded by assuming that all 

uranium processed contained natural uranium isotopic abundances. Between 1961 and 1962, doses 

are bounded by assuming that all uranium processed was recycled natural uranium. From 1963 to 

1967, doses are bounded by assuming that all uranium processed was enriched (1%) recycled 

uranium, even though the overwhelming majority of uranium processed remained as natural uranium 

(98.4%). Although the contaminant concentrations in recycled uranium were not documented for 

Weldon Spring, there is evidence that nearly all slightly enriched uranium that was processed came 

from the Feed Materials Processing Center (Fernald) (DOE, 2000, Figure B.1-10) where the 

contaminant concentrations in recycled uranium were well documented. Using the conservative 

contaminant concentrations from Fernald (as cited in ORAUT-TKBS-0028-5) together with the 

assumption that all uranium processed after 1961 contained these contaminants bounds the dose from 

the recycled uranium contaminants. 

As noted in Section 5.2.1.3, Table 5-6 contains maximum values for the recycled uranium 

contaminants as a fraction of uranium intake. For long-term workers, the exposures would certainly 

have been less than the maximum values listed in the table because the workers typically rotated jobs 

and often worked in various areas of the plant. The maximum values documented in Table 5-6 are 

high enough to bound shorter-term employment exposures with a proportionally higher recycled 

uranium contaminant exposure time.

The doses from uranium decay products are also bounded by using ratios from intakes determined by

uranium bioassay. It should be noted that the thorium-230 intakes are determined from the maximum 

ratio of thorium-230 to uranium and that ore concentrate processing is the only source of exposure to 

thorium-230 at Weldon Spring. Measurements of the activity concentrations in Raffinate Pits 1, 2, 

and 3 can be used to determine the relationship between thorium-230 and other impurities during the 

initial uranium processing in Building 101 before any separations occurred. The shorter-lived decay 

products for which no raffinate measurements were made (e.g., lead-210 and polonium-210) can be 

assumed to be present at the same activity as their radium-226 parent in the mill concentrate feeds. 

The other uranium streams (e.g., recycled uranium) had been previously processed and contained 

essentially no thorium. Table 7-4 gives the results of a statistical analysis of raffinate pit 

measurements. The data were taken from the 1989 Waste Assessment Radiological Characterization 

of the Weldon Spring Site Raffinate Pits (MK-Ferguson, 1989).
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Table 7-4: Activity Ratios of Uranium Decay Products and Other Impurities to 

Thorium-230 Activity in Weldon Spring Raffinate Pits

Pits 1 and 2 Pit 3 Pit 4

Isotope Mean 95% UCL Mean 95% UCL Mean 95% UCL

Ra-226 0.028 0.060 0.019 0.041 0.029 0.099

Ra-228 0.0033 0.0071 0.0038 0.0092 0.090 0.38

Th-228 0.0028 0.0062 0.0054 0.012 0.12 0.45

Th-232a 0.0043 0.0095 0.0083 0.018 0.13 0.49

Notes: a Measurements of thorium-232 in Raffinate Pits 1, 2, and 3 were not used due to alpha peak interference from thorium230 (MK-Ferguson, 1989). Thorium-232 was calculated assuming that thorium-228 was in 65% equilibrium, except for 

Pit 4 where reliable measurements were available.

The mean values in Table 7-4 represent the amount of each isotope that as a fraction of thorium-230 

an employee would have been exposed to over the long term. It is unlikely that any employee would 

have been continuously exposed to fractions greater than the 95% of the upper confidence limits; 

therefore, the 95% upper confidence limits of the ratios to thorium-230 in Table 7-4 can be used to 

bound the intakes from the other potentially important radionuclides. The data for Pit 4 were not used 

in this analysis since natural thorium wastes were deposited there. The results are shown in Table 7-5. 

Notes:

a Indicates the higher value of intakes based on Pits 1 & 2 (Column 2) and intakes based on Pit 3 (Column 3).

b Measurements not available; assumed to be equal to the intake of radium-226. 

Thorium

Thorium intake rates will be based on DWA air sample concentration measurements of thorium dust 

taken during thorium processing operations; these data are summarized in Table 6-5. Although in vivo

chest count data for thorium may be useful for individual dose reconstructions, these data are not 

useful for bounding exposures for the evaluated class because the measurements represent only one 

point in time, near the end of the multi-year thorium processing campaign. The bounding intake rate 

method based on DWE takes no credit for use of air-purifying or air-supplied respiratory protection 

equipment. 

The air sample data used in the DWA analysis were counted after an appropriate delay to eliminate 

the short-lived radon-220 and radon-222 progeny interference with the measurement. The measured 

alpha air concentration will be assumed to be associated only with thorium-232 and thorium-228, 

which are the isotopes found in thorium processed at the Weldon Spring Plant site. No uranium is 

Table 7-5: Intakes of Uranium Decay Products and Other Impurities Based on Raffinate Pit Measurements

Isotope Intakes based on Pits 1 and 2 

(nCi/mg-U)

Intakes based on Pit 3 

(nCi/mg-U)

Bounding Intakes 

(nCi/mg-U)a

Pb-210b 0.020 0.014 0.020

Po-210b 0.020 0.014 0.020

Ra-226 0.020 0.014 0.020

Ra-228 0.0024 0.0031 0.0031

Th-228 0.0021 0.0040 0.0040

Th-230 0.34 0.34 0.34

Th-232 0.0032 0.0061 0.0061
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assumed to have been present in the thorium work area. The actual equilibrium between the thorium 

isotopes and their progeny is unknown and changes with time after chemical purification. The 

isotopic assumptions in Section 5.6.1.2 of ORAUT-TKBS-0028-5 are reasonable and will contribute 

to a bounding evaluation. Therefore, the measured alpha activity will be partitioned in a 1-to-1 ratio 

of thorium-232 to thorium-228. In addition, radium-228, which is a beta emitter that would not have 

been detected in the gross alpha count, will be added in a 1-to-2 ratio of thorium-232 to radium-228. 

Intake rates will be reported in units of activity per day for use in a chronic exposure scenario. This 

chronic scenario assumes an exposure of 24 hours per day, 365 days per year. For inhalation, the 

intake rate will be based on the product of DWA, breathing rate (1.2 m3

 per hour), and number of 

working hours per year. For ingestion, the intake rate will be based on the guidance in the document, 

Estimation of Ingestion Intakes (OCAS-TIB-009). Normalization to adjust the number of work hours 

per year to conform to the 24 hours per day, 365 days per year exposure scenario will be performed in 

both cases.

Uncertainty in the DWA will be computed in accordance with Section 3.8 of Battelle-TIB-5000, 

which provides an approach for estimating overall uncertainty when only summaries of the timeweighted average data are available. The uncertainty is evaluated by fitting lognormal distributions to 

the data for each job title and performing a Monte Carlo simulation. The method described in Section 

2.1.2.2 of Battelle-TIB-5000 may be used to determine the lognormal parameters for each task used in 

the simulation based on the minimum, maximum, mean, and number of observations. Furthermore, 

the parameters in Table 3.9 of Battelle-TIB-5000 will be incorporated in the simulation to account for 

the lack of representativeness of air samples. When the actual location of a worker is not known, the 

maximum measured DWA for that period of time and full-time occupancy during the work day will 

be assumed.

Radon 

Conservative estimates of the amount of radon released based on the amount of uranium processed 

during the operational period were discussed in Section 7.2.2. Operations at the acid recovery plant, 

the main radon release point, were carried out in large hoods. Therefore, the radon would have been 

released into the outside air. Assuming that the outside air could have been drawn back into the 

building and that the indoor equilibrium factor was 0.5, rather than the 0.3 used for outdoors in 

Section 7.2.2, the estimated maximum intake is 1.3 WLM/year for 100% occupancy for 2000 hrs/year.

Thoron 

As described in Section 5.2.1.6, there are several aspects of the release and buildup of the daughter 

products that mitigate the exposure to thoron in process and storage configurations. 

From November 1963 through September 1966, natural thorium was processed on an intermittent 

batch basis in the refinery and oxide production/firing systems at the Weldon Spring Plant; therefore 

NIOSH’s evaluation of operational exposures to thoron at Weldon Spring is confined to those years. 

During 1966 (the maximum production year), the Weldon Spring Plant processed approximately 

100,000 kg of thorium per month for six months, or up to 5,000 kg of thorium per day. Typical 

thorium processing at other facilities averaged < 1,000 kg of thorium per day; thus, NIOSH believes 

this to be a very conservative default level to assume for bounding thoron releases. NIOSH 

recognizes that the thorium processing was not continuous, but rather was operated more on a batch 

basis. Given the specific activity of thoron in thorium feed materials, and assuming the feed materials 

were received with at least a one-year delay since processing, it is possible to calculate the amount of 
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thoron in process per day (approximately 0.3 Ci thoron) during the period of the maximum production 

rate. By assuming a conservative equilibrium factor for a plant configuration with large buildings and 

engineered ventilation (0.02), it is possible to determine the concentration of thoron and its daughters 

to achieve 1 WL. The release fraction (RF) can be calculated by measuring the particulate thorium in 

the working environment of the process equipment, compared to the inventory amounts in process. 

The thoron releases are expected to be less than the particulate materials, since the gaseous state will 

be more easily captured by the ventilation systems. Maximizing assumptions can be applied on a 

case-by-case basis to occupancy factors, release fractions, and diffusion rates. 

Potential exposure to thoron is mitigated by several factors, as discussed in Section 5.2.1.6, including 

the very short half-life of thoron and the resulting limitations on the diffusion distance within the 

material matrix, and the effective shielding provided by the thorium processing apparatus. Thus, 

thoron is not a potential source of exposure to be broadly accounted for across the evaluated class of

Weldon Spring workers. It is possible to bound the dose from the release of thoron and thoron 

daughters during processing activities and during storage of thorium materials at Weldon Spring 

during the three-year period of thorium operations, as applicable, on a case-by-case basis.

7.2.3.2 Methods for Bounding Ambient Environmental Internal Dose

ATTRIBUTION: Section 7.2.3.2 was completed by Robert Morris and Eugene W. Potter, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

ORAUT-TKBS-0028-4 lists relevant monitoring or other data pertinent to estimating environmental 

internal dose. Although available data enable dose reconstruction, in this evaluation, workers are 

assumed to be maximally exposed to conditions that potentially existed in operational areas. Ambient 

environmental dose is accounted for in the operational dose information. 

7.2.4 Internal Dose Reconstruction Feasibility Conclusion 

ATTRIBUTION: Section 7.2.4 was completed by Robert Morris and Eugene W. Potter, M.H. Chew 

and Associates, Inc. The rationales for all conclusions in this document are explained in the 

associated text.

This evaluation concludes that NIOSH can bound internal dose (reconstruct dose with sufficient 

accuracy) for members of the class under evaluation. NIOSH located sufficient personnel monitoring 

data to support bounding internal uranium and thorium exposures at the Weldon Spring Plant for the 

evaluated period of January 1, 1957 through December 31, 1967. This feasibility conclusion is based 

on the collective availability of bioassay (urinalysis), thorium in vivo, and air sampling data in 

sufficient quantity and quality for the entire evaluated period to adequately represent the class under 

evaluation. Supporting information exists related to workplace activities, area monitoring, and 

associated source terms.
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7.3 Evaluation of Bounding External Radiation Doses at Weldon Spring Plant

ATTRIBUTION: Section 7.3 was completed by Edward D. Scalsky, Oak Ridge Associated Universities

(ORAU). The rationales for all conclusions in this document are explained in the associated text.

The principal source of external radiation doses for members of the evaluated class, other than 

medical X-rays required as a condition of employment, was direct beta-gamma exposures from 

processing uranium feed stocks to metal and other intermediate products for use at other AEC 

facilities across the weapons complex. A limited amount of thorium was also processed at Weldon 

Spring from November 1963 through 1966. 

NIOSH has located individual external monitoring records for Weldon Spring Plant employees 

associated with uranium and thorium material processing during the operational period under 

evaluation. As expected, the highest doses were received by operations workers in the plant’s 

processing areas. Documentation retrieved from the site verifies that the existing personnel external 

monitoring was sufficient to detect the photon and beta radiation from significant sources of radiation, 

as reflected in the individual external monitoring records. Although a routine monitoring program for 

neutrons did not exist at the Weldon Spring Plant, personnel working directly with slightly-enriched 

uranium materials were assigned neutron dosimeter badges to be worn in conjunction with the regular 

film badges; but, no neutron dose results for Weldon Spring Plant employees were located, plausibly 

because there were no measured neutron doses. Neutron measurements made on drums of stored 

uranium tetrafluoride and calculations performed on materials similar to that at Weldon Spring (and 

documented in the Mallinckrodt Site Profile) provide indications that there was no need for neutron 

dosimetry because there was minimal neutron exposure potential. If required, neutron doses for 

operational personnel working with slightly-enriched uranium and other operational personnel 

working with natural and depleted uranium could be determined from the Battelle-TBD-6001 

measurements and information discussed in Section 5.2.2.3. 

Thorium processing also contributed to external exposure to Weldon Spring personnel. The amount 

of thorium processed at Weldon Spring represented less than 1% of the total amount of natural, 

depleted, and enriched uranium processed, making the thorium contribution to the external exposure 

relatively minor. However, the external exposure from the thorium processing operations would be 

accounted for in the personnel film badge dosimeter records. 

The following subsections address the ability to bound external doses, methods for bounding doses, 

and the feasibility of external dose reconstruction. 

7.3.1 Evaluation of Bounding Process-Related External Doses

ATTRIBUTION: Section 7.3.1 and its related subsections were completed by Edward D. Scalsky, Oak 

Ridge Associated Universities (ORAU) and Billy P. Smith, M.H. Chew and Associates, Inc. The 

rationales for all conclusions in this document are explained in the associated text.

As reported in Section 6.2.1 of this report, NIOSH has access to the ORAU CER database which 

contains nearly 8,000 film badge records collected from 1957 to 1967 for approximately 1,850 

Weldon Spring Plant employees. Individual dosimetry data are the preferred data source for 

evaluating the external radiation doses for members of the Weldon Spring Plant class. A subset of the 

class, comprised of female administrative support personnel, was unmonitored and thus necessitates 
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that bounding methods for unmonitored employees be used to evaluate those potential external 

radiation doses. 

As reported in Section 6.2 of this report, no area survey or monitoring records beyond airborne dust 

studies are available. 

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related external doses of members of the class under evaluation.

7.3.1.1 Personnel Dosimetry Data

NIOSH has located records documenting the external monitoring program for beta and photon 

exposure at the Weldon Spring Plant. As reported in Section 6.2.1, NIOSH has nearly 8,000 external 

personnel dosimetry results. While a limited routine external monitoring program for neutron 

exposure did exist at the site for areas processing slightly-enriched uranium, the neutron dosimeter 

results have not been located by NIOSH, plausibly because no positive doses were observed. NIOSH 

conducted interviews with former Weldon Spring Plant workers who stated that they routinely wore a 

film badge (Personal Communication, 2009a; Personal Communication, 2009b; Personal 

Communication, 2009c; Personal Communication, 2009e Personal Communication, 2009f; Personal 

Communication, 2009h; Personal Communication, 2009i). A review of the CATI interview reports 

for information on the routine use of radiation dosimeters also supports the existence a routine 

badging program at the Weldon Spring Plant. 

Photon

The available personnel external monitoring data, in the form of film badge results, provide external 

photon/gamma dose information for the personnel working during the operational period at the 

Weldon Spring Plant. These data are sufficient to support bounding photon dose for members of the 

class under evaluation, as described in Section 7.3.4.1. 

Beta

The CER database includes almost 8,000 film badge records from 1957 to 1967 for approximately 

1,850 employees and contains the beta doses and the necessary information needed to aid in the 

completion of dose reconstructions for most individuals. These data can be used to reconstruct beta 

dose for members of the class under evaluation. The available personnel monitoring data include data 

that represent the maximally-exposed worker group and work scenario during the Weldon Spring 

Plant operational period. 

Neutron

Considering that significant neutron doses were not anticipated at the Weldon Spring Plant, a 

conclusion that is supported by the Mallinckrodt study mentioned in Section 7.3, the neutron 

monitoring that was employed was limited to the workers assigned to processing slightly-enriched 

uranium at the Weldon Spring Plant facility. These workers were most likely to be exposed to 

neutron radiation. The employees who were determined to be less likely to be exposed to neutron 

radiation were not monitored for neutrons. Because of the alpha-neutron reaction from uranium 

tetrafluoride, very low neutron radiation exposures to unmonitored workers may have occurred in 
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buildings that processed uranium.4 NIOSH has considered the potential source of neutrons resulting 

from alpha-neutron reactions and determined that in the cases where NIOSH needs to apply 

unmonitored neutron dose for members of the class, it can apply the methods approved in ORAUTOTIB-0024 to support bounding the neutron dose. The applicability of this method will be assessed 

on a case-by-case basis for individual dose reconstructions. 

As previously mentioned, neutron dose results for the Weldon Spring employees who were involved 

with processing slightly-enriched (<1%) uranium have not been located, plausibly because there was 

no measured neutron dose to record. In the absence of measured dosimeter doses, the primary method 

for assigning potential neutron dose is in the determination of missed neutron dose, as described in the 

NIOSH document, External Dose Reconstruction Implementation Guideline (OCAS-IG-001). 

7.3.1.2 Alternative Data Sources for Bounding External Dose

As indicated in Section 5.2.2.2, additional beta exposure data are available for bounding external 

doses. These data are from radiation surveys in the 301 Core Area (Holt, 1960b), from drum surveys 

(Drum survey, unknown date), and from studies to determine the exposure rates and the sources of 

exposure for specific operations in the Casting Area and for lathe operations (MCW, unknown date). 

These can be used to support NIOSH’s ability to bound doses for groups of workers in the evaluated 

class.

7.3.2 Evaluation of Bounding Ambient Environmental External Doses

ATTRIBUTION: Section 7.3.2 was completed by Edward D. Scalsky, Oak Ridge Associated 

Universities (ORAU). The rationales for all conclusions in this document are explained in the 

associated text.

An aerial radiological survey of the Weldon Spring Plant indicates that for most of the site, the normal 

terrestrial gamma exposure rate is 3 to 6 μR/hour at 1 meter above ground level, and the average 

cosmic exposure rate is approximately 4 μR/hour (Jobst, 1976). For continuous exposure over a year, 

this represents an annual ambient dose of 61 to 88 mrem/year. 

Elevated terrestrial exposures over the raffinate pits and the quarry were observed, indicating the 

presence of man-made changes from the natural radioisotopes. Based on the results of the aerial 

survey, gamma radiation exposure rate isopleths drawn in the immediate vicinity of the plant and 

centered on the raffinate pits indicated exposure rates ranging from 116 to 164 microR/hour with 

decreasing levels ranging from 11.8 to 31.8 microR/hour at approximately 1,000 feet from the pits 

(Jobst, 1976). These measurements represent the terrestrial radiation only. The average cosmic 

exposure rate of 4 microR/hour should be added to the isopleths to compute the total exposure rate for 

personnel within the site boundary (Jobst, 1976). 

Weldon Spring employees working in these areas would be monitored and their exposure accounted 

for in their normal dosimetry results. Since all employees in operational areas were required to wear 

film dosimeters, there would not be unmonitored employees subject to exposure in those areas. 

Therefore, doses to Weldon Spring employees for whom dosimetry results are not available would be 

bound by the dose that is accounted for in the occupational dose for the evaluated class. The aerial 

 

4 Buildings with a potential for neutron exposure are listed in Section 5.2.2.3. 
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survey information can be used for the purpose of a more precise estimate, applied on a case-by-case 

basis for individual dose reconstructions. 

7.3.3 Weldon Spring Plant Occupational X-Ray Examinations 

ATTRIBUTION: Section 7.3.3 was completed by Edward D. Scalsky and Monica Harrison-Maples, 

Oak Ridge Associated Universities (ORAU). The rationales for all conclusions in this document are 

explained in the associated text.

As part of the requirements for employment at the Weldon Spring Plant from 1955 through 1966 (the 

operational period) all employees received periodic physical examinations. The frequency and type of 

X-ray examinations are referenced in reports for Weldon Spring Plant workers from 1955 through 

1966 (MCW, 1965). These references clearly indicate that chest X-ray examinations were performed 

annually from 1955 through 1966, and medical records indicate that both posterior-anterior (PA) and 

lateral (LAT) views were taken. There is no indication that photofluorography was ever used at the 

Weldon Spring Plant site. 

7.3.4 Methods for Bounding External Dose at Weldon Spring Plant

There is an established protocol for assessing external exposure when performing dose reconstructions 

(these protocol steps are discussed in the following subsections): 

• Photon Dose 

• Beta Dose

• Neutron Dose 

• Medical X-ray Dose

7.3.4.1 Methods for Bounding Operational Period External Dose

ATTRIBUTION: Section 7.3.4.1 was completed by Edward D. Scalsky, Oak Ridge Associated 

Universities (ORAU). The rationales for all conclusions in this document are explained in the 

associated text.

NIOSH has access to sufficient dosimetry records for individual workers exposed to beta and photon 

radiation during operations at Weldon Spring. 

Photon Dose

Photon doses can be reconstructed using available film badge results for individual workers exposed 

to photon radiation during operations at the Weldon Spring Plant for all years of the evaluated period. 

NIOSH analyzed available Weldon Spring Plant worker data in an attempt to develop a profile of 

exposure for each type of job at the Weldon Spring Plant site. Job titles, as reported in computerassisted telephone interviews, were utilized. There were over 70 different job titles identified for 

Weldon Spring Plant workers. These titles were grouped into nine categories, roughly representing 

the reported job titles. Table 6-8 of ORAUT-TKBS-0028-6 presents the annual average gamma 

exposures calculated for each category and shows that the operator category received the greatest 

exposure to gamma rays for most years. This analysis supports the contention that the operator 

category of workers at the Weldon Spring Plant site is included in the group of workers representing 
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the maximally-exposed work group and work scenario during the Weldon Spring Plant operations 

period. 

Extensive external dose information for Weldon Spring workers is available for the operational 

period. The records in the CER database are sufficiently detailed to support a bounding dose for the 

applicable exposure source of concern. While the operator category represents the maximimallyexposed work group among badged workers, unmonitored workers would not be expected to be 

represented in this worker category. Therefore, the engineer job category represents a more 

reasonable representation of unmonitored workers who would infrequently, if ever, be subjected to the 

exposures associated with processing work. By using the engineer job category and the associated 

doses, a conservative bounding dose estimate can be determined for the Weldon Spring workers who 

did not have a permanent badge. Therefore, the operator job category represents the maximally 

exposed work group, which NIOSH can use as the bounding exposure scenario. On an individual 

basis, additional information specific to the worker will be used to refine the bounding approach. 

Beta Dose

The method used to determine the beta dose is the same as that used for the photon dose. The total 

beta dose is the sum of the readings of all film badges for the entire work history for which the 

individual was exposed to beta radiation. 

As with the gamma doses, the beta doses were analyzed and determined for the nine job categories 

that roughly represent the 70 reported job titles mentioned in the photon discussion. Table 6-8 of 

ORAUT-TKBS-0028-6 lists the annual average beta exposures calculated for each category. As can 

be seen from the table, average exposure to beta radiation, similar to photon radiation, was 

substantially greater for those in the operator category than for any other job category. Therefore, as 

seen with respect to photon exposure, the operator job category represents the maximally exposed 

work group, which NIOSH can use as the bounding exposure scenario. Additional information 

specific to the worker will be used to refine the bounding approach on a case-by-case basis.

Neutron Dose

Based on the studies described in Section 5.2.2.3, it has been determined that neutron radiation was 

not a source of significant exposure at the Weldon Spring Plant and no further analysis is required. 

Medical X-ray Dose

Although NIOSH has not located specific parameters associated with occupational medical X-rays 

(i.e., specific information on the X-ray devices), default values of entrance kerma developed for the 

three most commonly-used occupational medical diagnostic procedures are available in ORAUTOTIB-0006. Additionally, a document titled Calculations and Assumptions Used in ORAUT-TKBS0028-3 Rev. No. 01 Weldon Spring Plant Technical Basis Document for Occupational Medical 

Exposure provides details for occupational medical exposures at the Weldon Spring Plant site for 

available X-ray equipment and dose calculations (Morris, 2007). The ORAUT-OTIB-0006 values can 

be used to support bounding the medical X-ray dose for the time period under evaluation. These 

default values are upper limit values developed from review of patient doses as reported in the 

literature, machine characteristics, and knowledge of X-ray procedures used during different time 

periods. These default values can be used in lieu of actual measurement data or entrance kerma 

derived from technique factors to bound the occupational X-ray exposures for the Weldon Spring 
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Plant site. NIOSH believes this methodology supports its ability to bound occupational medical X-ray 

doses (reconstruct the medical X-ray dose with sufficient accuracy) for the class under evaluation. 

7.3.4.2 Methods for Bounding Ambient Environmental External Doses

ATTRIBUTION: Section 7.3.4.2 was completed by Billy P. Smith, M.H. Chew and Associates, Inc. and 

Edward D. Scalsky, Oak Ridge Associated Universities (ORAU). The rationales for all conclusions in 

this document are explained in the associated text.

Ambient environmental dose for monitored workers is accounted for in an individual’s recorded dose. 

Potential ambient environmental dose for unmonitored workers, such as non-badged administrative 

personnel, is bounded by the available data for monitored individuals as assessed in this report, but 

can be evaluated on an individual case-by-case basis in accordance with the method described in 

ORAUT-TKBS-0028-4. The methods in ORAUT-TKBS-0028-4, coupled with the background dose 

as determined by the aerial surveys, supports NIOSH’s ability to assess ambient environmental dose 

more precisely than a bounding dose estimate for the Weldon Spring class evaluated in this report 

(Jobst, 1976). 

7.3.5 External Dose Reconstruction Feasibility Conclusion 

ATTRIBUTION: Section 7.3.5 was completed by Edward D. Scalsky, Oak Ridge Associated 

Universities (ORAU). The rationales for all conclusions in this document are explained in the 

associated text.

NIOSH concludes that the external dose reconstruction for members of the evaluated class is feasible 

based on the available personal external monitoring data, the analysis of the film badge results for the 

various job categories, survey data obtained during studies to determine the time to perform specific 

job functions and necessary shielding, and if necessary, a determination of missed and unmonitored 

neutron dose using the methods described in Section 5.2.2.3 for personnel working in buildings that 

processed uranium (because of the alpha-neutron reaction from uranium tetrafluoride). In addition, 

doses from the required medical X-rays and ambient environmental doses can be determined with 

sufficient accuracy for the evaluated class.

7.4 Evaluation of Petition Basis for SEC-00143

ATTRIBUTION: Section 7.4 and its related subsections were completed by Monica Harrison-Maples, 

Oak Ridge Associated Universities (ORAU). The rationales for all conclusions in this document are 

explained in the associated text.

The following subsections evaluate the assertions made on behalf of petition SEC-00143 for the 

Weldon Spring Plant site. 

7.4.1 Radon 

SEC-00143: The petitioner is concerned that the measured air concentration of radon during the 

operational period at Weldon Spring is not reported in the literature.

Response: NIOSH investigated the ability to assess radon concentrations during the operational 

period. As described in Section 5.1.1 of this report, the materials processed at Weldon Spring did not 
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include radium bearing “raw” ores and thus did not produce significant amounts of radon relative to 

unprocessed uranium ore. Section 5.2.1.5 of this report provides detail on radon generating materials 

and their disposition at the site. NIOSH is able to conservatively estimate the maximum radon 

released given the uranium source term, as described in Section 7.2.3 of this report.

7.4.2 Thorium Bioassay 

SEC-00143: The petitioner is concerned that no quantitative in vitro bioassay results have been found 

for thorium.

Response: No quantitative in vitro bioassay results for thorium exist at Weldon Spring. NIOSH uses 

various methods to bound internal exposure in the absence of bioassay data. The default exposure 

approach for the Weldon Spring Plant is based on the review of thorium air sampling results from 

samples taken during thorium processing at the site. The daily weighted average concentration for air 

monitoring data from the 1957-through-1966 period will be used to bound the exposures during those 

periods for which there are no bioassay analyses available for thorium. Section 7.2.3.1 of this report 

provides additional detail on how this will be achieved.

7.4.3 Recycled Uranium

SEC-00143: The petitioner is concerned that the Weldon Spring Plant site was identified as a site that 

likely received recycled uranium in relatively small quantities of materials after 1961, and site records 

do not include the level of detail needed for accurate estimates of the amount of recycled material 

received and processed at Weldon Spring Plant. It is known that the plant received shipments from 

other DOE sites that processed and shipped recycled uranium, in fiscal years 1962 through 1967, but 

amounts of recycled uranium versus natural uranium are not known. 

Response: NIOSH investigated the receipts and processing of recycled uranium at the Weldon Spring 

site and acknowledges that limited quantities of recycled uranium were received at Weldon Spring for 

processing. The fact that the quantities of recycled uranium are unknown led DOE to assume, as a 

worst case, that all uranium received after 1962 was recycled uranium. DOE acknowledges that this 

assumption leads to the worst-case quantities of transuranic elements. These quantities do not 

represent what was actually processed, and in fact, DOE estimates these quantities to be significantly 

less (0.0 gm of plutonium-239, 12.3 to 15.3 grams of neptunium-237, and 4.9 to 6.1 grams of 

technetium-99, as compared to the worst case 2.4 grams, 330 grams, and 7,200 grams of plutonium, 

neptunium, and technetium respectively). For the purpose of defining the ability to bound dose for the 

evaluated class in this report, the maximum quantities have been considered as the source term for this 

evaluation.

7.4.4 Thorium Disequilibrium

SEC-00143: The petitioner is concerned that thorium-228 and thorium-232 may not have been in 

equilibrium following chemical purification of natural thorium feed materials. In vivo measurements 

were performed on some Weldon Spring Plant workers for thorium in 1966. The overall results 

showed that workers in Areas 101, 103, 301, 403, Maintenance, and Health and Safety (which were 

principal exposure positions) had a more frequent occurrence of trace detection. The quantification of 

thorium depositions from these in vivo thallium-208 measurements is therefore, uncertain without the 

knowledge of the degree of equilibrium of the thallium with the thorium-232 parent.
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Response: The in vivo measurement data available to NIOSH have not been used as part of the 

methodology to bound thorium dose for the evaluated class. In some individual cases, the in vivo

counts made in July 1966 may be useful, but it is more likely to be disregarded during dose 

reconstruction due to uncertainty about when the intake may have occurred and the solubility of the 

thorium compounds. The cases where such use of the in vivo counts would be necessary would be 

limited to those with very specific circumstances and information. 

7.4.5 Lost or Missing Records

SEC-00143: The petitioner is concerned about a memo concerning possible lost medical records at 

Weldon Spring Plant. Mont Mason (deceased) could not find one complete set of medical files, which 

had originally been titled, Terminated from Weldon Thru 4/28/66. 

Response: NIOSH has investigated the possibility of lost medical records as described in the Mason 

memo. It was unclear from the original memo if any records were in fact lost. Mont Mason indicated 

the problem might have been a simple filing error and asked for all medical records to be sent to Oak 

Ridge, Tennessee to resolve the discrepancy. NIOSH has interviewed epidemiologists familiar with

Mont Mason and the work he did with the Weldon Spring records. One person interviewed recalled 

two data capture trips to the Weldon Spring Plant site where the boxes were thoroughly reviewed oneby-one for health and safety records, standard operating procedures, manuals, monitoring records, 

exposure records, medical records, incident reports, etc. The person interviewed was unaware of any 

missing records or any data gaps. In addition, NIOSH has a letter from T. F. Mancuso specifically 

requesting to the AEC that the records mentioned by M. Mason not be destroyed. NIOSH concludes, 

from the above interview and from the review of the data holdings for the Weldon Spring Plant site 

that these records were in fact saved from destruction by the efforts of Mr. Mason and Dr. Mancuso. 

NIOSH has no other evidence of the loss of any significant number of records or data gaps. 

7.4.6 Accidents/Incidents

SEC-00143: The petitioner is concerned that all accidents may not have been documented sufficiently 

or that the records might not be readily available and that accidents and incidents could have lead to 

acute intakes and/or contamination that greatly exceeded normal levels.

Response: NIOSH has conducted a thorough investigation into documentation that gives no indication 

of significant accidents or incidents at the facility. While several events were identified, through 

document searches and interviews with former workers, there were no indications of events that could 

have resulted in exceptionally high personnel exposures or exposures that are not already accounted 

for within the data in the available records. Section 5.2.3 of this report provides additional detail on 

NIOSH’s investigations and findings related to incidents.

7.4.7 Ambient Environmental Exposure

SEC-00143: The petitioner is concerned about the lack of “any thorium data,” and believes that there 

“is no basis to estimate thorium releases prior to 1967.” The petitioner has also expressed a belief and 

concern that thorium was first stored and used at Weldon Spring as far back as 1958, and that 

significant quantities of thorium in the Weldon Spring Quarry were not routinely sampled until after 

1985.
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Response: NIOSH must presume that the petitioner’s concern about a lack of “any thorium data” in 

conjunction with the phrase “is no basis to estimate thorium releases prior to 1967” refers to potential 

internal exposure due to thorium released into the environment. As described in this report, the 

earliest thorium processing at the site began in 1963 (DOE, 1986). Prior to that, there are no 

indications of any processing of the material, only limited storage onsite and disposal at the Quarry. 

NIOSH does have DWA concentration air monitoring data from the years 1957 through 1966. The 

data (1957-1966) encompasses the span of thorium processing at the site.

SEC-00143: The petitioner is concerned about the lack of atmospheric monitoring data for Weldon 

Spring Plant during the operational period; thus, leading to insufficient data for assigning unmonitored 

workers internal environmental dose during the operational period. In addition, the petitioner is 

concerned about the TBD’s use of environmental dose from protracted Fernald estimated data. 

Response: The atmospheric monitoring data for Weldon Spring Plant during the operational period are 

limited, but sufficient to calculate estimated intakes of radioactive airborne particulates and radon, as 

described in Section 4.2.3.1 of ORAUT-TKBS-0028-4. These calculations pertain to both operational 

personnel and unmonitored personnel. As noted in Section 7.2.2 of this report, the most highly 

exposed plant employees were monitored or accounted for through monitoring or airborne dust 

measurements. These exposures would be bounding for unmonitored workers. This evaluation does 

not depend on the use of environmental data from Fernald estimated data.

7.4.8 Contamination Control 

SEC-00143: The petitioner is concerned that there was a lack of: routine personnel contamination 

monitoring; a consistent and documented badging policy with geometry correction factors; a

comprehensive bioassay program that encompassed all the major isotopes brought onsite; and an 

onsite environmental monitoring program for unmonitored workers that have resulted in gaps in some 

of the information and data.

Response: These broad statements were the basis for qualifying the petition. These concerns resulted 

in the evaluation of the petition for Weldon Spring Plant. The responses to these concerns are 

encompassed in this report. 

7.4.9 Medical Exposure 

SEC-00143: The petitioner is concerned that there is very little information available concerning the 

Weldon Spring Plant site’s occupational medical procedures, equipment, X-ray exam frequency, etc. 

The petitioner is also concerned that there is no mention made of the frequency of retake exams 

performed, as well as no indication whether photofluorography exams were conducted at Weldon 

Spring Plant.

Response: Although NIOSH has not located specific policy guidance associated with the performance 

of occupational medical X-rays, the dose associated with occupational medical X-rays can be assessed 

using the default values of entrance kerma, developed for the three most commonly used occupational 

medical diagnostic procedures, as available in ORAUT-OTIB-0006, Dose Reconstruction from 

Occupationally Related X-Ray Procedures. These values can be used to support bounding the 

medical X-ray dose for the time period under evaluation. 
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7.4.10 Neutron Dose

SEC-00143: The petitioner is concerned about a lack of documentation and detail as related to neutron 

doses at Weldon Spring Plant.

Response: As discussed in Section 5.2.2.3 of this report, given the processing performed at the 

Weldon Spring Plant, the only source of neutron production would have resulted from the alphaneutron reaction associated with uranium tetrafluoride. This reaction has been studied at other 

facilities in the DOE complex; the conclusion of these studies is that at the level of enrichment of the 

uranium received at Weldon Spring Plant, there was no possibility of significant neutron exposure, 

and therefore no neutron dosimetry was necessary. 

7.5 Other Potential SEC Issues Relevant to the Petition Identified During the 

Evaluation

ATTRIBUTION: Section 7.5 was completed by Monica Harrison-Maples, Oak Ridge Associated 

Universities (ORAU). The rationales for all conclusions in this document are explained in the 

associated text.

During the feasibility evaluation for SEC-00143, three issues were identified that needed further 

analysis and resolution. The issues and their current status are:

ISSUE: A concern with the identification of the feed material processed at Weldon Spring arose early 

in this evaluation. During a review of interview reports, it was identified that former workers referred 

to the feedstock brought into the facility in several different ways, including “ore.” The uranium 

progeny inherent in pitchblende ore causes very different exposure concerns as compared to those 

associated with pre-processed ores. 

RESPONSE: NIOSH investigated this concern and found the use of the term “ore” to be inaccurate. 

According to interviews with a number of former Weldon Spring Plant workers, the Weldon Spring 

Plant accepted ore concentrates for processing, but never received raw ore (Personal Communication, 

2009c; Personal Communication, 2009g; Personal Communication, 2009h). As discussed in Section 

5.1.1, it was common practice at the site to refer to uranium concentrates that were milled in the 

western United States as ore. This information regarding ore that was derived from the interviews is 

further supported by the historical Weldon Spring Plant work reports that were reviewed by NIOSH. 

ISSUE: During an interview, NIOSH was informed by a former worker that isotopes other than 

uranium or thorium were used as radiotracers. The interviewee stated that only him and three other 

workers (names were provided) worked with these tracers (Personal Communication, 2009g). 

RESPONSE: An interviewee reported that three tracer isotopes, molybdenum-99, europium, and

vanadium-48, were used in bench-top operations (Personal Communication, 2009g). The

molybdenum-99 was used in mCi quantities and the other isotopes were used in much smaller 

quantities. NIOSH considered the doses which could result from intakes of these tracer radionuclides 

and found that they would contribute a negligible amount of additional risk to the limited number of 

workers that may have come in contact with them. The committed effective doses were calculated to 

be on the order of a few mrem/year for the molybdenum-99, a tenth of a mrem/year for the europium 

isotope with the highest dose coefficient, and a hundredth of a mrem/year for the vanadium-48. From 
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the perspective of potential external exposure, the tracers would have been used in columns on a 

bench top, which would absorb or shield betas. The potential gamma exposure would be included in 

the results on the film badges. 

ISSUE: During the initial review of Weldon Spring Plant documentation, NIOSH identified a single 

reference to a Building 441 as a facility used for storage of uranium hexafluoride cylinders. No other 

reference to any storage or use of uranium hexafluoride cylinders was located in the documentation. 

NIOSH performed additional research to determine if uranium hexafluoride was stored on the Weldon 

Spring site for any reason and if so, during what time frame, and how much may have been stored at 

the site.

RESPONSE: In addition to document research, NIOSH conducted former worker interviews to try to 

confirm the presence of uranium hexafluoride cylinders onsite. During interviews, two former 

workers provided information that uranium hexafluoride was never processed at the Weldon Spring 

Plant; neither had heard of uranium hexafluoride cylinders being stored at the Weldon Spring Plant 

(Personal Communication, 2009h; Personal Communication, 2009g). As a result of a review of the 

source documentation attributed by Table 2-2 of ORAUT-TKBS-0028-2 (the only reference to 

Building 441 as a storage location for uranium hexafluoride cylinders), NIOSH believes this reference 

in ORAUT-TKBS-0028-2 may be an error. No such reference to Building 441 being used in this 

capacity was located in the source documentation.

7.6 Summary of Feasibility Findings for Petition SEC-00143

This report evaluates the feasibility for completing dose reconstructions for employees at the Weldon 

Spring Plant site from January 1, 1957 through December 31, 1967. NIOSH found that the available 

monitoring records, process descriptions and source term data available are sufficient to complete 

dose reconstructions for the evaluated class of employees.

Table 7-6 summarizes the results of the feasibility findings at Weldon Spring Plant for each exposure 

source during the time period from January 1, 1957 through December 31, 1967. 

Table 7-6: Summary of Feasibility Findings for SEC-00143

January 1, 1957 through December 31, 1967

Source of Exposure Reconstruction Feasible Reconstruction Not Feasible

Internal1 X 

Uranium X 

Uranium decay products & other impurities X 

Recycled uranium X 

Thorium X 

Radon X 

Thoron X 

External X 

Gamma X 

Beta X 

Neutron X 

Occupational Medical X-ray X 

Note:

1 Internal includes an evaluation of urinalysis (in vitro), airborne dust, and lung (in vivo) data
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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As of March 12, 2010, a total of 258 claims have been submitted to NIOSH for individuals who 

worked at the Weldon Spring Plant and are covered by the class definition evaluated in this report. 

Dose reconstructions have been completed for 180 individuals (~69.8%). 

8.0 Evaluation of Health Endangerment for Petition SEC-00143

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by both EEOICPA and 42 C.F.R. § 83.13(c)(3). Under these requirements, if it is not 

feasible to estimate with sufficient accuracy radiation doses for members of the class, NIOSH must 

also determine that there is a reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. Section 83.13 requires NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If 

the occurrence of such an exceptionally high-level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those workers who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

NIOSH’s evaluation determined that it is feasible to estimate radiation dose for members of the 

NIOSH-evaluated class with sufficient accuracy based on the sum of information accessible from 

available resources. Modification of the class definition regarding health endangerment and minimum 

required employment periods, therefore, is not required. 

9.0 Class Conclusion for Petition SEC-00143

Based on its full research of the class under evaluation, NIOSH found no part of said class for which it 

cannot estimate radiation doses with sufficient accuracy. This class includes all employees of the 

Department of Energy, Department of Energy contractors, or subcontractors who worked in any area 

at the Weldon Spring Plant in Weldon Spring, Missouri, during the applicable covered operational 

period from January 1, 1957 through December 31, 1967. 

NIOSH has carefully reviewed all material sent in by the petitioner, including the specific assertions 

stated in the petition, and has responded herein (see Section 7.4). NIOSH has also reviewed available 

technical resources and many other references, including the SRDB, for information relevant to SEC00143. In addition, NIOSH reviewed its NOCTS dose reconstruction database to identify EEOICPArelated dose reconstructions that might provide information relevant to the petition evaluation. 

These actions are based on existing, approved NIOSH processes used in dose reconstruction for 

claims under EEOICPA. NIOSH’s guiding principle in conducting these dose reconstructions is to 

ensure that the assumptions used are fair, consistent, and well-grounded in the best available science. 

Simultaneously, uncertainties in the science and data must be handled to the advantage, rather than to 

the detriment, of the petitioners. When adequate personal dose monitoring information is not 

available, or is very limited, NIOSH may use the highest reasonably possible radiation dose, based on 

reliable science, documented experience, and relevant data to determine the feasibility of 

reconstructing the dose of an SEC petition class. NIOSH contends that it has complied with these 
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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standards of performance in determining the feasibility or infeasibility of reconstructing dose for the 

class under evaluation. 
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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10.0 References 

42 C.F.R. pt. 81, Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol. 67, No. 85/Thursday, p 22,296; May 2, 2002; SRDB Ref ID: 19391 

42 C.F.R. pt. 82, Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 

19392 

42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the Special 

Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 

2000; Final Rule; May 28, 2004; SRDB Ref ID: 22001 

42 U.S.C. §§ 7384-7385 [EEOICPA], Energy Employees Occupational Illness Compensation 

Program Act of 2000, as amended

ABRWH, 2005a, Portions of Transcript from the 31st Meeting of the Advisory Board on Radiation 

and Worker Health (ABRWH); July 6, 2005; OSA Ref ID: 108678, pp. 52-53

ABRWH, 2005b, Portion of Correspondence Regarding Mallinckrodt SEC Recommendation, 

correspondence to The Honorable Michael O. Leavitt; Advisory Board on Radiation and Worker 

Health; September 15, 2005; OSA Ref ID: 108678, p. 54

Argonne, 1985, Preliminary Draft-1 Weldon Spring Historical Dose Estimate: A Study of Radiation 

Doses from Uranium and Thorium Reprocessing; Argonne National Laboratory; November 1985; 

SRDB Ref ID: 72152 

Battelle-TBD-6001, Site Profiles for Atomic Weapons Employers that Refined Uranium and Thorium, 

Rev. FO; Battelle Team Dose Reconstruction Project for NIOSH; December 13, 2006; SRDB Ref ID: 

30673 

Battelle-TIB-5000, Default Assumptions and Methods for Atomic Weapons Employer Dose 

Reconstruction, Rev. 00; Battelle Team Dose Reconstruction Project for NIOSH; April 2, 2007; 

SRDB Ref ID: 32016 

Bechtel, 1984, Weldon Spring Site Environmental Monitoring Report, Calendar Year 1983; Bechtel 

National, Inc. (Bechtel); June 1984; SRDB Ref ID: 12530 

CER Data, 2009, 1957-1967 Weldon Spring Data from the Center for Epidemiological Research 

(CER) Database, tblMCW SEC Urinalysis 1957-1967; Oak Ridge Associated Universities CER 

Database Results; spreadsheet dated November 3, 2009; SRDB Ref ID: 76556 

DOE, unknown date, Background Report for the DOE Weldon Spring Site; Department of Energy 

(DOE); unknown date; SRDB Ref ID: 72145 

DOE, 1957, A Description of the Feed Materials Production Facilities—St. Louis Plants and Weldon 

Spring Plants; Department of Energy (DOE), St. Louis Area Office; August 1957; SRDB Ref ID: 

17122 
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DOE, 1986, Historical Nuclear Materials Balance Report for the Former AEC-Owned Weldon Spring 

Chemical Plant Weldon Spring, Missouri, DOE/OR-872; Department of Energy (DOE); July 1986; 

SRDB Ref ID: 8252 

DOE, 1991, Internal Dosimetry Program Technical Basis Manual, Rev. 0, DOE/OR/21548-241; 

Department of Energy (DOE); November 1991; SRDB Ref ID: 79457 

DOE, 2000, DOE Ohio Field Office Recycled Uranium Project Report, Final; Department of Energy 

(DOE); May 15, 2000; SRDB Ref ID: 3644 

Drum survey, unknown date, Weldon Spring Plant Drum Surveys; performed by C. Barkshire, W. 

Reyland, and J. Horner; unknown date; SRDB Ref ID: 14745 

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

Processing Operations, 1942-1967; Fleishman-Hillard, Inc.; September 30, 1967; SRDB Ref ID: 

6538 

Form B, 2009a, Petition Form B for SEC-00143; April 29, 2009; OSA Ref ID: 108678, pp. 1-18 

Form B, 2009b, Petition Form B for SEC-00144; April 29, 2009; OSA Ref ID: 108677 

Hibbs, 1966, In Vivo Monitoring of Mallinckrodt Employees, includes cover letter; R. F. Hibbs; 

August 16, 1966; SRDB Ref ID: 11804 

Holt, 1960a, Decontamination of Five-Ton Portable Hoppers for Shipment, correspondence to W. L. 

Utnage; D. L. Holt; August 8, 1960; SRDB Ref ID: 14974 

Holt, 1960b, 301 Core Area Radiation Survey, correspondence to W. L. Utnage; D. L. Holt; October 

18, 1960; SRDB Ref ID: 14943 

Ingle, 1991, Mallinckrodt Chemical Works: Four Plant Study Classifications of Radium, Radon, and 

Thorium Exposure, memo to files; J. Nicolas Ingle; September 16, 1991; SRDB Ref ID: 12400 

Jobst, 1976, Aerial Radiological Survey of the Weldon Spring Chemical Plant (St. Charles, Missouri)-

Date of Survey: November 22, 1975; Joel E. Jobst; April 1976; SRDB Ref ID: 14355 

Makhijani, 1997, Portion of Worker Radiation Dose Records Deeply Flawed, Volume 6 Number 2 of 

“Science for Democratic Action”; Arjun Makhijani and Bernd Franke; November 1997; OSA Ref ID: 

108678, p. 68 

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

Mason; February 21, 1955; SRDB Ref ID: 13180 

Mason, 1972, Portion of Correspondence Regarding Record Center, correspondence to Dr. T. F. 

Mancuso with an attached conference agenda; Mont G. Mason; 1972; OSA Ref ID: 108678, pp. 20-22 

MCW, unknown date, Shielded and Unshielded Average Time Required for Lathe Operations and 

Percent of Working Day to Establish Maximum Available Exposure at Operator’s Position; 

Mallinckrodt Chemical Works (MCW); Unknown date; SRDB Ref ID: 14938 
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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MCW, 1958-1966, Summaries of Dust Concentrations at Production Jobs-Weldon Spring Feed 

Materials Plant; Mallinckrodt Chemical Works (MCW) Uranium Division; 1958-1966; SRDB Ref 

ID: 15000 

MCW, 1960, Urinary Uranium Program; Mallinckrodt Chemical Works (MCW) Uranium Division, 

Health and Safety Department; Effective January 1, 1960; SRDB Ref ID: 62354 

MCW, 1962, Scheduled Urinary Uranium Program; Mallinckrodt Chemical Works (MCW) Uranium 

Division Health and Safety Department; January 12, 1962; SRDB Ref ID: 14964 

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

Uranium Division; March 16, 1965; SRDB Ref ID: 14998 and 11821 

MCW, 1979, Results from Verification of All Records for a 10% Sample of Employees Listed on the 

Work History File using Hard Copy Source Documents at ORAU, computer printout used for 

verification; Mallinckrodt Chemical Works (MCW); December 14, 1979; SRDB Ref ID: 76634 

Meshkov, 1986, Weldon Spring Historical Dose Estimate, ANL/EES-TM-308; N. Meshkov, P. 

Benioff, J. Wang, and Y. Yuan; July 1986; SRDB Ref ID: 13117 

MK-Ferguson, 1989, Waste Assessment Radiological Characterization of the Weldon Spring Site 

Raffinate Pits, Rev. 0, DOE/OR/21548-062; MK-Ferguson Company and Jacobs Engineering Group; 

August 1989; SRDB Ref ID: 12541 

MK-Ferguson, 2001, Internal Dosimetry Program Technical Basis Manual-Weldon Spring Site 

Remedial Action Project, Rev. 7, DOE/OR/21548-241; MK-Ferguson Company and Jacobs 

Engineering Group; December 2001; SRDB Ref ID: 32724 

Morris, 2007, Calculations and Assumptions Used in ORAUT-TKBS-0028-3 Rev. No. 01 Weldon 

Spring Plant Technical Basis Document for Occupational Medical Exposure; Robert L. Morris; 

December 28, 2007; SRDB Ref ID: 40732 

NCRP, 1996, Screening Models for Releases of Radionuclides to Atmosphere, Surface Water, and 

Ground, Report 123; National Council on Radiation Protection & Measurements (NCRP); 1996; 

SRDB Ref ID: 79896 

Niedermeyer, 1976, Assessment of Weldon Spring Chemical Plant in St. Charles County, Missouri; 

Glenn J. Niedermeyer; March 1, 1976; SRDB Ref ID: 13478 

NLCO, 1966, Thorium Precipitation Pilot Facility-Pilot Plant, Project Proposal; National Lead 

Company of Ohio (NLCO); August 1966; SRDB Ref ID: 28949 

NLCO, 1977, Study of Radioactive Waste Storage Areas at ERDA-Weldon Spring Site, NLCO-1144; 

National Lead Company of Ohio (NLCO); April 25, 1977; SRDB Ref ID: 3583 and 3576 

OCAS-IG-001, External Dose Reconstruction Implementation Guideline, Rev. 02; Division of 

Compensation Analysis and Support (DCAS); Cincinnati, Ohio; August 25, 2006; SRDB Ref ID: 

29929 
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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OCAS-PR-004, Internal Procedures for the Evaluation of Special Exposure Cohort Petitions, Rev. 0; 

Division of Compensation Analysis and Support (DCAS); Cincinnati, Ohio; September 23, 2004; 

SRDB Ref ID: 32022 

OCAS-TIB-009, Estimation of Ingestion Intakes, Rev. 0; Division of Compensation Analysis and 

Support (DCAS); Cincinnati, Ohio; April 13, 2004; SRDB Ref ID: 22397 

ORAUT-OTIB-0006, Dose Reconstruction from Occupationally Related Diagnostic X-Ray 

Procedures, Rev. 03 PC-1; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction 

Project for NIOSH; December 21, 2005; SRDB Ref ID: 20220 

ORAUT-OTIB-0023, Assignment of Missed Neutron Doses Based on Dosimeter Records, Rev. 01; 

Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; May 14, 

2008; SRDB Ref ID: 43937 

ORAUT-OTIB-0024, Estimation of Neutron Dose Rates from Alpha-Neutron Reactions in Uranium 

and Thorium Compounds, Rev. 00; Oak Ridge Associated Universities (ORAU) Team Dose 

Reconstruction Project for NIOSH; April 7, 2005; SRDB Ref ID: 19445 

ORAUT-TKBS-0028-1, TBD for Weldon Spring Plant – Introduction, Rev. 00 PC-1; Oak Ridge 

Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; June 30, 2008; 

SRDB Ref ID: 45869 

ORAUT-TKBS-0028-2, TBD for Weldon Spring Plant – Site Description, Rev. 00; Oak Ridge 

Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; June 24, 2005; 

SRDB Ref ID: 20186 

ORAUT-TKBS-0028-3, TBD for Weldon Spring Plant – Occupational Medical Dose, Rev. 00; Oak 

Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; June 24, 

2005; SRDB Ref ID: 20187 

ORAUT-TKBS-0028-4, TBD for Weldon Spring Plant – Occupational Environmental Dose; Rev. 00; 

Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; June 28, 

2005; SRDB Ref ID: 20188 

ORAUT-TKBS-0028-5, TBD for Weldon Spring Plant – Occupational Internal Dose, Rev. 00; Oak 

Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; June 28, 

2005; SRDB Ref ID: 20189 

ORAUT-TKBS-0028-6, TBD for Weldon Spring Plant – Occupational External Dose, Rev. 00; Oak 

Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for NIOSH; June 24, 

2005; SRDB Ref ID: 20190 

Personal Communication, 2009a, Personal Communication with Former Weldon Spring Plant 

Chemical Operator and Pipefitter; Oak Ridge Associated Universities (ORAU) Team Dose 

Reconstruction Project for NIOSH; October 23, 2009; SRDB Ref ID: 76964
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Personal Communication, 2009b, Personal Communication with Former Weldon Spring Plant Utility 

Operator; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for 

NIOSH; October 24, 2009; SRDB Ref ID: 76968

Personal Communication, 2009c, Personal Communication with Former Weldon Spring Plant 

Employee; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for 

NIOSH; October 25, 2009; SRDB Ref ID: 76962

Personal Communication, 2009d, Personal Communication with Former Weldon Spring Plant 

Chemical Operator and Rigger; Oak Ridge Associated Universities (ORAU) Team Dose 

Reconstruction Project for NIOSH; October 25, 2009; SRDB Ref ID: 76965

Personal Communication, 2009e, Personal Communication with Former Weldon Spring Plant 

Production Operator; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project 

for NIOSH; October 25, 2009; SRDB Ref ID: 76967

Personal Communication, 2009f, Personal Communication with Former Weldon Spring Plant 

Metallurgical Engineer; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction 

Project for NIOSH; October 26, 2009; SRDB Ref ID: 76969

Personal Communication, 2009g, Personal Communication with Former Weldon Spring Plant 

Employee; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for 

NIOSH; October 27, 2009; SRDB Ref ID: 76966

Personal Communication, 2009h, Personal Communication with Former Weldon Spring Plant Design 

Engineer; Oak Ridge Associated Universities (ORAU) Team Dose Reconstruction Project for 

NIOSH; October 29, 2009; SRDB Ref ID: 76970

Personal Communication, 2009i, Personal Communication with Former Weldon Spring Plant Health 

Technician and Health Supervisor; Oak Ridge Associated Universities (ORAU) Team Dose 

Reconstruction Project for NIOSH; November 6, 2009; SRDB Ref ID: 76963 

Radiological Health Handbook, 1998, Handbook of Health Physics and Radiological Health, 3rd

edition; Bernard Shleien, Lester A. Slaback, Jr., and Brian Kent Birky; 1998; SRDB Ref ID: 22737 

SCA, 2005, Select Page from Draft Review of the NIOSH Site Profile for Mallinckrodt Chemical 

Company, St. Louis, Missouri, Contract No. 200-2004-03805; S. Cohen & Associates (SCA); January 

31, 2005; OSA Ref ID: 108678, p. 66 

SCA, 2009, Select Pages from Draft Review of the NIOSH Site Profile for the Weldon Spring Site in 

Weldon Spring, Missouri, Contract No. 200-2009-28555; S. Cohen & Associates (SCA); February 10, 

2009; OSA Ref ID: 108678, pp. 28-50 and SRDB Ref ID: 74616 

Sloat, 1965, Test Conversion of Thorium Nitrate to Thorium Oxide, RL-SEP-775; R. J. Sloat; October 

22, 1965; SRDB Ref ID: 52857 

Unknown, 1967, Weldon Spring Raffinate Pits and Quarry Task Force Report; Unknown author; June 

1, 1967; SRDB Ref ID: 3645, pp. 50-66 
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Weidner, 1982, Weldon Spring Storage Site Environmental Monitoring Report for 1979 and 1980; R. 

B. Weidner and M. W. Boback; April 19, 1982; SRDB Ref ID: 14356 

Weldon, unknown date-a, Procedure for Uranium in Urine; Weldon Spring Plant (Weldon); 

Unknown date; SRDB Ref ID: 14954 

Weldon, unknown date-b, Standardization and Reproducibility of Health and Safety Department 

Fluorimetric Method of Analysis; Weldon Spring Health and Safety Department (Weldon); Unknown 

date; SRDB Ref ID: 15008 

Weldon, 1957-1958, Various Handwritten Log of Bioassay Urine Processing Results on New Youk

Atomic Energy Commission Form NY-99; Various dates throughout 1957 and 1958; SRDB Ref ID: 

9213 

Weldon, 1958-1959, Various Handwritten Log of Bioassay Urine Processing Results; Various dates 

throughout 1958 and 1959; SRDB Ref ID: 15634 

Weldon, 1960, Various Bioassay Urine Reports, Including Personnel with High-Uranium-in-Urine 

Concentrations; Weldon Spring Health and Safety Department (Weldon); January 1-June 30, 1960; 

SRDB Ref ID: 15874 

Weldon, 1961, Various Bioassay Urine Reports, Including Action Level Urinary Uranium 

Concentrations; Weldon Spring Health and Safety Department (Weldon); January-December 1961; 

SRDB Ref ID: 15865 

Weldon, 1962-1965, Various Bioassay Urine Reports, Including Action Level Urinary Uranium 

Concentrations and Collection Reports; Weldon Spring Health and Safety Department (Weldon); 

1962-1965; SRDB Ref ID: 15890 
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Attachment One: Data Capture Synopsis

Table A1-1: Summary of Holdings in the SRDB for the Weldon Spring Plant

Data Capture Information Data Capture Description Completed Uploaded 

into SRDB

Primary Site/Company Name: Weldon Spring 

Plant

1955-1967; 1975-present (remediation); DOE

Other Site Names: 

Mallinckrodt

Weldon Spring Chemical Co.

Weldon Spring Site Remedial Action Project 

(WSSRAP) 

WSS

Successor Contacts: 

URS-Formerly MK-Ferguson - Brad Giles, 

Vice-President Environmental, Health, Safety, 

and Security, 208-386-7899 (Data Capture 

performed)

Covidien-Formerly Mallinckrodt - Pat Duft, 

Chief Counsel, 314-654-6314, Confirmed 

Mallinckrodt did not retain records of personnel 

or operations.

Bechtel National Inc Records for this period 

were transferred to Kansas City FRC (Data 

Capture performed)

Jacobs Engineering - Ann Katoh, Risk 

Management, 626-578-3552, Confirmed 

records were with MK-Ferguson.

Uranium in the air at Y-12, depth doses in a slab phantom for low energy 

monoenergetic photons, environmental audit, historical overview, internal 

contamination during decontamination/decommissioning, long-term 

surveillance and maintenance, radiation incident, dose calculations, former 

Army Ordnance Works information, and Weldon Spring quarry/plant/pits 

information.

02/25/2010 26

State Contacted: Missouri Department of 

Natural Resources (MODNR) Rhonda Loveall

Summary of radiation monitoring data, inspection report, site history, 

engineering evaluation, characterization results, closure reports, sitespecific soil guidelines, effluent levels of uranium, environmental 

monitoring reports, radon control and emissions, groundwater 

contamination, interviews with two MODNR employees, feasibility study, 

radiological surveys, soil sampling, safety and health plan, and a 

radiological control manual.

10/03/2008 66

Claimant Work products from inter-agency working groups formed for a study of 

occupational hazards and illnesses in the DOE contractor workforce.

04/18/2005 1 
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-1: Summary of Holdings in the SRDB for the Weldon Spring Plant

Data Capture Information Data Capture Description Completed Uploaded 

into SRDB

Department of Labor/Paragon Annual environmental monitoring reports, Cotter Corporation visit report, 

Surplus Facilities Management Program reports, and monthly progress 

reports.

12/30/2008 18

DOE Germantown Historical nuclear materials balance report, historical review of the 

Mallinckrodt airport cake, and historical dose estimate information with 

facility descriptions.

12/17/2003 3 

DOE Legacy Management - Grand Junction 

Office

Description of the Feed Materials Production facilities, federal facility 

agreement, operating history, hazardous ranking, contamination surveys 

and instrumentation, site material accountability, disposal of uranium 

contaminated building debris, rubble and residues, historical dose 

estimates, proposed remedial action information, environmental monitoring 

reports, and characterization reports.

09/02/2009 92

DOE Legacy Management - MoundView 

(Fernald Holdings, includes Fernald Legal 

Database)

Analysis of water samples, bioassay monthly reports, radon monitoring 

reports, environmental reports, decommissioning study, Fernald quarterly 

report, major thorium campaigns at NLO/Fernald, health and safety reports, 

electrolysis of UO2 at Mallinckrodt, plant procedures and records, Slightlyenriched Recovery Facility (SERF) Program, radioactive waste 

management, stabilization of raffinate pits, thorium accountability, and 

metallic scrap recycling and disposal of radioactive residues.

05/30/2008 49

Researcher at Southern Illinois University, 

Edwardsville Personal Files

Weldon Spring plot plans and historical summaries, interest in commercial 

use of Weldon Spring Plant, contamination information, disposal of 

Weldon Spring materials, long-term management of existing radioactive 

materials, raffinate pits, trip report, and quarry surveillance information.

11/05/2008 26

EML Library Dust problems in refining and fabrication of uranium and the correlation 

between alpha surface contamination and air concentration.

02/15/2005 2 

Internet - Department of Energy (DOE) Weldon Spring Plant remedial action cleanup activities. 04/27/2005 1 

Internet - DOE Comprehensive Epidemiologic 

Data Resource (CEDR)

No relevant data identified. 03/02/2010 0 

Internet - DOE Hanford Declassified Document 

Retrieval System (DDRS)

Irradiation Processing Department monthly report and a test conversion of 

thorium nitrate to thorium oxide.

03/02/2010 2 

Internet - DOE OpenNet Linking Legacies Appendix B: The Eight Major Processes of the Nuclear 

Weapons Complex.

03/02/2010 1 

Internet - DOE OSTI Energy Citations No relevant data identified. 03/02/2010 0 

Internet - DOE OSTI Information Bridge Survey of the wetlands and floodplains at Weldon Spring Plant, quarterly 

reports, quarry residuals scoping document, quarterly environmental 

summary, alloyed dingot status, beta-to-alpha transformation 

characteristics, and remedial action information.

03/02/2010 14
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-1: Summary of Holdings in the SRDB for the Weldon Spring Plant

Data Capture Information Data Capture Description Completed Uploaded 

into SRDB

Internet - Google Engineering evaluation of contaminated water in quarry, inherent problems 

conducting dose assessments, air and personal monitoring, Edward 

Mallinckrodt Jr. papers, U238 burn, recycled uranium and transuranics, site 

history, waste management information, and environmental reports.

03/02/2010 22

Internet - National Academies Press (NAP) No relevant data identified. 03/02/2010 0 

Internet - National Nuclear Security 

Administration (NNSA) - Nevada Site Office

No relevant data identified. 03/02/2010 0 

Internet - NRC Agencywide Document Access 

and Management (ADAMS)

Letter from MO Department of Natural Resources requesting additional 

information regarding DOE's plans to recycle scrap metal at the Weldon 

Spring Plant.

03/02/2010 1 

Internet - Washington State University (U.S. 

Transuranium and Uranium Registries)

No relevant data identified. 03/02/2010 0 

Lawrence Berkeley National Laboratory 

(LBNL)

Status report and hazards survey. 02/07/2007 2 

Los Alamos National Laboratory (LANL) Radioactive waste disposal and low-level mixed waste streams for the DOE 

complex.

12/06/2007 2 

NARA Atlanta Annual summary off-site environmental monitoring report, criticality 

safeguards manual, analytical bioassay procedures, Extraction Plant design 

criteria and health program, concerns for recycling materials, incident 

reports, Mallinckrodt recovery of uranium from residues, monitoring of 

employees for thorium burdens, various preliminary proposals, operating 

procedures, sale of residues at the St. Louis Airport Site, off-site 

environmental sampling program, thorium operations at Mallinckrodt, trip 

report, and information on uranium refining processes.

10/20/2005 39

NARA Kansas City Radiological surveys, area TLD results, bioassay results and logs,

description of Latty Avenue wastes, radiological and chemical 

characterization reports, engineering evaluation for the disposition of the 

raffinate pits, environmental monitoring reports, 1969 listing of buildings & 

occupancy, pit sludge data, radiological concentrations and exposure rates, 

removal of uranium from Building 434, work diary and release of Weldon 

Spring property, and occupational radiation exposure reports.

08/15/2009 61

National Institute for Occupational Safety and 

Health (NIOSH)

Personnel files. 10/21/2009 24

NIOSH OCAS Claims Tracking System 

(NOCTS)

Safety investigation and occupational summary. 11/18/2009 2 

ORAU Team Site information and documented communications. 12/03/2009 21
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-1: Summary of Holdings in the SRDB for the Weldon Spring Plant

Data Capture Information Data Capture Description Completed Uploaded 

into SRDB

Oak Ridge Institute for Science Education 

(ORISE)

Dosimetry database. 11/03/2009 1 

ORO Vault Site visit reports, radiation surveys, air sample data, area monitor badges, 

bioassay results, personnel exposures, drum surveys, health and safety 

manual, maintenance job history sheets, refinery pre-operational and 

startup, summary of health protection practices, health physics procedures, 

and a raffinate radioactivity survey.

04/11/2006 134

MFG Inc. Files External and internal dosimetry technical basis manuals, green salt 

production area Building 201 dust study report, Mallinckrodt claims X-ray 

dosimetry, and a summary of a site visit by M. E. Mason.

03/01/2010 16

Savannah River Site (SRS) Dosimetry visitor cards and the procurement of thoria. 08/26/2008 3 

Southern Illinois University Shipping documents, classified material receipts, ammonia oxidation 

process, list of real property, map of Mallinckrodt site, uranium exposures 

within the nuclear industry, burn area no. 9 data, plant capacity and 

expansion estimates, Weldon Spring stockpile information, and disposal of

radioactive wastes.

10/18/2008 44

Unknown Urine and air dust samples, radiological survey, air pathway analysis, 

engineering evaluation of waste disposal, environmental reports, 

radiological characterization, significant events, radon flux monitoring, 

health and safety survey, employee exposures, epidemiological studies, 

decommissioning study, plant history, internal dosimetry technical basis 

manual, trip reports, progress reports, off-site population radiological 

assessment, record of decision for remedial action, remedial investigations, 

and material inventories.

06/08/2009 230

URS Corporate Records at Boise, IA Building health and safety plan, site characterization data, environmental 

impact statement, remedial investigation report, waste assessment, 

radiological characterization of the raffinate pits, feasibility study for 

remedial action, radon data, results of soil sampling, vicinity properties 

remediation, work packages, and dismantlement risk assessment reports.

12/10/2009 36

US Army Corps of Engineers Decontamination of storage site, Continental Mining and Milling Company 

assets seized by Commercial Discount Corporation, and a uranium residues 

historical synopsis.

03/19/2008 3 

Westinghouse Site (Hematite-MO) Urine sample results, service dates for counted employees, and employee 

exposure records. 

04/08/2009 5 

Total 947
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

DOE CEDR

http://cedr.lbl.gov/

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

3 0 

DOE Hanford DDRS

http://www2.hanford.gov/declass/

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

51 2 

DOE OpenNet

http://www.osti.gov/opennet/advancedsearch.jsp

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

46 1 
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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring" AND "Jacobs Engineering"

DOE OSTI Energy Citations

http://www.osti.gov/energycitations/

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

464 0 

DOE OSTI Information Bridge

http://www.osti.gov/bridge/advancedsearch.jsp

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

377 14

Google

http://www.google.com

COMPLETED 03/02/2010

"WSS" "Weldon Spring"

"Weldon Spring Chemical Co."

"Weldon Spring Plant" americium, OR Am241, OR Am-241, OR "AM 

241", OR 241Am, OR 241-Am, OR "241 Am"

"Weldon Spring Plant" ionium, OR Th230, OR Th-230, OR "Th 230", 

OR 230Th, OR 230-Th, OR "230 Th"

"Weldon Spring Plant" polonium, OR Po210, OR Po-210, OR "Po 

210", OR 210Po, OR 210-Po, OR "210 Po"

3,239,119 22
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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring Plant" thorium, OR thoria, OR Th232, OR Th-232, 

OR "Th 232", OR 232Th, OR 232-Th, OR "232 Th", OR "Z metal", 

OR Z-metal, OR myrnalloy, OR "chemical 10-66", OR "chemical 

1066", OR "chemical 10 66", OR "chemical 18-12"

"Weldon Spring Plant" "chemical 1812", OR "chemical 18 12", OR 

"chemical 10-12", OR "chemical 1012", OR "chemical 10 12", OR 

UX1, OR UX2, OR Th-234, OR Th234, OR "Th 234", OR TH-234, 

OR 234-Th, OR 234Th, OR "234 Th"

"Weldon Spring Plant" tritium, OR H3, OR H-3, OR mint, OR HTO

"Weldon Spring Plant" uranium, OR U233, OR U-233, OR "U 233", 

OR 233U, OR 233-U, OR "233 U", OR U234, OR "U 234", OR U-234, 

OR 234U, OR 234-U, OR "234 U", OR U235, OR "U 235", OR U-235, 

OR 235-U, OR 235U, OR "235 U", OR U238, OR "U 238", OR U-238

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "americium" OR "Am241" 

OR "Am-241" OR "Am 241" OR "241Am" OR "241-Am" OR "241 

Am" OR "ionium"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "Th230" OR "Th-230" OR 

"Th 230" OR "230Th" OR "230-Th" OR "230 Th" OR "neptunium" 

OR "Np237" OR "Np-237"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "Np 237" OR "237Np" OR 

"237-Np" OR "237 Np" OR "palm" OR "palmolive" OR "polonium" 

OR "Po210" OR "Po-210"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "Po 210" OR "210Po" OR 

"210-Po" OR "210 Po" OR "thorium" OR "thoria" OR "Th232" OR 

"Th-232" OR "Th 232"
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "232Th" OR "232-Th" OR 

"232 Th" OR "Z metal" OR "Z-metal" OR "myrnalloy"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "chemical 10-66" OR 

"chemical 1066" OR "chemical 10 66" OR "chemical 18-12" OR 

"chemical 1812" OR "chemical 18 12" OR "chemical 10-12" OR 

"chemical 1012" OR "chemical 10 12"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "UX1" OR "UX2" OR "Th234" OR "Th234" OR "Th 234" OR "234-Th" OR "234Th" OR "234 

Th" OR "tritium"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "H3" OR "H-3" OR "mint" 

OR "HTO" OR "uranium" OR "U233" OR "U-233" OR "U 233" OR 

"233U"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "233-U" OR "233 U" OR 

"U234" OR "U 234" OR "U-234" OR "234U" OR "234-U" OR "234 

U" OR "U235"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "U 235" OR "U-235" OR 

"235-U" OR "235U" OR "235 U" OR "U238" OR "U 238" OR "U238"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "238-U" OR "238U" OR "238 

U" OR "U308" OR "U 308" OR "U-308" OR "308-U" OR "308U" OR 

"308 U"
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "black oxide" OR "brown 

oxide" OR "green salt" OR "orange oxide" OR "yellow cake" OR 

"UO2" OR "UO3" OR "UF4"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "UF6" OR "C-216" OR "C616" OR "C-65" OR "C-211" OR "U3O8" OR "uranium extraction" 

OR "uranium dioxide" OR "uranium hexafluoride"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "uranium tetrafluoride" OR 

"uranium trioxide" OR "plutonium" OR "Pu-238" OR "Pu238" OR "Pu 

238" OR "238Pu" OR "238-Pu" OR "238 Pu"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "Pu-239" OR "Pu239" OR 

"Pu 239" OR "239Pu" OR "239-Pu" OR "239 Pu" OR "Pu-240" OR 

"Pu240" OR "Pu 240"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "240Pu" OR "240-Pu" OR 

"240 Pu" OR "Pu-241" OR "Pu241" OR "Pu 241" OR "241Pu" OR 

"241-Pu" OR "241 Pu"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "radium" OR "Ra-226" OR 

"Ra226" OR "Ra 226" OR "226-Ra" OR "226Ra" OR "226 Ra" OR 

"Ra-228" OR "Ra228"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "228Ra" OR "228-Ra" OR 

"228 Ra" OR "radon" OR "Rn-222" OR "Rn222" OR "Rn 222" OR 

"222Rn" OR "222-Rn"
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "222 Rn" OR "thoron" OR 

"Rn-220" OR "Rn220" OR "Rn 220" OR "220Rn" OR "220-Rn" OR 

"220 Rn" OR "protactinium"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "Pa-234m" OR "Pa234m" OR 

"Pa 234m" OR "234mPa" OR "234m-Pa" OR "234m Pa"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "strontium" OR "Sr-90" OR 

"Sr90" OR "Sr 90" OR "90-Sr" OR "90Sr" OR "90 Sr" OR "oralloy" 

OR "postum"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "tuballoy" OR "uranyl nitrate 

hexahydrate" OR "UNH" OR "K-65" OR "sump cake" OR "accident" 

OR "air count" OR "air dust"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "air filter" OR "airborne test" 

OR "alpha" OR "belgian congo ore" OR "beta" OR "bioassay" OR 

"bio-assay" OR "breath" OR "breathing zone"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "BZ" OR "body burden" OR 

"calibration" OR "chest count" OR "columnation" OR "contamination" 

OR "curie" OR "denitration" OR "denitration pot"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "derby" OR "regulus" OR 

"derived air concentration" OR "DAC" OR "dose" OR ""dosimeter" 

OR "dosimetric" OR "dosimetry" OR "electron"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "environment" OR "EtherWater Project" OR "exposure" OR "exposure investigation" OR 

"radiation exposure" OR "external" OR "F machine" OR "fecal" OR 

"feed material"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "femptocurie" OR "film" OR 

"fission" OR "fluoroscopy" OR "Formerly Utilized Sites Remedial 

Action Program" OR "FUSRAP" OR "gamma-ray" OR "gamma ray" 

OR "gas proportional"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "gaseous diffusion" OR 

"health" OR "health instrument" OR "health physics" OR "H.I." OR 

"HI" OR "HP" OR "highly enriched uranium" OR "HEU"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "hydrofluorination" OR "in 

vitro" OR "in vivo" OR "incident" OR "ingestion" OR "inhalation" OR 

"internal" OR "investigation" OR "isotope"

"Weldon Spring Plant" OR "Weldon Spring Chemical Co" OR 

"Weldon Spring Site Remedial Action Project" OR " WSSRAP" OR 

"WSS" OR "Mallinckrodt" OR "WSCC" "isotopic" OR "isotopic 

enrichment" OR "JS Project"

Weldon Spring AND "National lead" -ocas -niosh – eeoicpa

Weldon Spring AND "Bechtel National" -ocas -niosh - eeoicpa

Weldon Spring AND Feguson -ocas -niosh - eeoicpa

Weldon Spring AND jacobs -ocas -niosh – eeoicpa

Weldon Spring AND "Bbechtel National" OR "Jacobs Engineering" 

OR "National lead" OR MK-Ferguson -orau -eeoicpa -niosh -

mallinckrodt -wss -wscc -"Weldon Spring Site"
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

National Academies Press

http://www.nap.edu/

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

819 0 

NNSA - Nevada Site Office

www.nv.doe.gov/main/search.htm

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

0 0 

NRC ADAMS Reading Room

http://www.nrc.gov/reading-rm/adams/webbased.html

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

104 1 
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Table A1-2: Database Searches for the Weldon Spring Plant

Database/Source Keywords/Phrases Hits Uploaded into 

SRDB

"Weldon Spring" AND "Jacobs Engineering"

U.S. Transuranium & Uranium Registries 

http://www.ustur.wsu.edu/

COMPLETED 03/02/2010

"Weldon Spring Plant"

"Weldon Spring Chemical Co."

"Weldon Spring Site Remedial Action Project"

"WSSRAP"

"WSS" "Weldon Spring"

"Mallinckrodt" "Weldon Spring"

"Weldon Spring" AND "National lead"

"Weldon Spring" AND Bechtel

Weldon Spring AND Ferguson

"Weldon Spring" AND "Jacobs Engineering"

64 0 

Table A1-3: OSTI Documents Ordered for Weldon Spring Plant

Document Number Document Title Requested Data Date Received

NLCO-1102 (Rev. 1) Weldon Spring Radioactive Waste 

Management Plan, June 17, 1974

11/10/2009 Have not received

TID-5295 Uranium Oxide Refinery TBP 

Hexane Process, Jan 1, 1956

11/10/2009 Have not received

ORISE-98-0084 Verification Survey of the Composite 

and Annex Building Construction 

Sites and the Subcontractor Parking 

Lot, Dec 1, 1997

11/10/2009 Have not received

TID-7573-PAPER 7; AD-R036343 Evaluation of the Weldon Spring 

Sampling Plant, Paper 7 of AEC and 

Contractor SS Materials 

Management Meeting, May 19-22, 

1958

11/10/2009 Have not received

MCW-1379 Production of Ionium from a 

Pitchblende Residue, Jul 28, 1955

11/10/2009 Have not received 

MCW-1391 Recovery of Ionium and Uranium 

from Raffinate, Apr 1, 1957

11/10/2009 Have not received

MCW-1408 Pilot Plant Production of Ionium 11/10/2009 Have not received
SEC-00143 04-16-10 Rev. 0 Weldon Spring Plant

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Table A1-3: OSTI Documents Ordered for Weldon Spring Plant

Document Number Document Title Requested Data Date Received

Concentrate, Nov 1, 1957

M-5208 Health Hazards Resulting from the 

Casting of Uranium Metal at 

Mallinckrodt Chemical Works, Jul 2, 

1953

11/10/2009 Have not received

MCW-1396 Sampling and Testing Procedures for 

Special Products, Jan 1, 1956

11/10/2009 Have not received

MCW-1384 Causes of Refinery Tank Explosion 

on December 7, 1955. Interim 

Topical Report, Mar 1, 1956

11/10/2009 Have not received