Draft 

ADVISORY BOARD ON

RADIATION AND WORKER HEALTH

National Institute for Occupational Safety and Health

REVIEW OF THE NIOSH SITE PROFILE FOR THE

AMES LABORATORY

Contract No. 200-2009-28555

SCA-TR-SP2013-0044, Revision 0

Prepared by

U. Hans Behling, PhD, MPH 

S. Cohen & Associates 

1608 Spring Hill Road, Suite 400 

Vienna, Virginia 22182 

August 2013 

DISCLAIMER

This is a working document provided by the Centers for Disease Control and Prevention (CDC) technical 

support contractor, SC&A for use in discussions with the National Institute for Occupational Safety and 

Health (NIOSH) and the Advisory Board on Radiation and Worker Health (ABRWH), including its 

Working Groups or Subcommittees. Documents produced by SC&A, such as memorandum, white paper, 

draft or working documents are not final NIOSH or ABRWH products or positions, unless specifically 

marked as such. This document prepared by SC&A represents its preliminary evaluation on technical 

issues. 

NOTICE: This report has been reviewed to identify and redact any information that is protected by the 

Privacy Act 5 U.S.C. § 552a and has been cleared for distribution.
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S. COHEN & ASSOCIATES: 

Technical Support for the Advisory Board on 

Radiation & Worker Health Review of 

NIOSH Dose Reconstruction Program

Document No.

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REVIEW OF THE NIOSH SITE PROFILE FOR THE 

AMES LABORATORY Page 2 of 84 

Task Manager:

_____________________________ Date:____________ 

U. Hans Behling, PhD, MPH 

Supersedes:

N/A

Project Manager:

_____________________________ Date:____________ 

John Stiver, MS, CHP 

Reviewer(s):

John Mauro 

John Stiver 
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TABLE OF CONTENTS

Acronyms and Abbreviations ..........................................................................................................7

1.0 Executive Summary ...........................................................................................................10

1.1 Technical Approach and Review Criteria ..............................................................10

1.2 Summary of Issues .................................................................................................11

1.2.1 Occupational Environmental Dose ............................................................11

1.2.2 Occupational Internal Dose ........................................................................12

1.2.3 Occupational External Dose ......................................................................13

1.3 Organization of the Report.....................................................................................13

2.0 Introduction and Scope of Audit ........................................................................................14

2.1 A Summary of Events that Prompted Review of ORAUT-TKBS-0055, 

Rev. 03 ...................................................................................................................14

2.2 Scope and Objectives of Audit ..............................................................................17

3.0 Relevant Background Information .....................................................................................19

3.1 Site/Facility Descriptions .......................................................................................19

3.1.1 Uranium and Thorium Facilities ................................................................19

3.1.2 Other Facilities ...........................................................................................20

3.2 Major Operations and Processes ............................................................................20

3.2.1 Uranium Metal Production ........................................................................20

3.3 Thorium and Metal Production ..............................................................................26

4.0 Review of Section 4.0 of the Ames Site Profile: Occupational Environmental Dose ......28

4.1 Uranium and Thorium Intakes ...............................................................................29

4.2 Synchrotron Operations .........................................................................................30

4.3 Ames Laboratory Research Reactor Operations (1965–1977) ..............................36

4.1 Environmental Doses from Research and Development Facilities (1942–

Present) ..................................................................................................................41

4.2 Significant Environmental Event ...........................................................................46

5.0 Estimates of Occupational Internal Dose ...........................................................................51

5.1 Estimates of Uranium Exposure from Inhalation and Ingestion ............................51

5.2 Resuspension During Period with No Uranium Operations ..................................59

5.3 Thorium Exposure from Thorium Contamination After 1954 ..............................60

5.4 Thorium Exposures During Operational Periods That Were Not Considered 

by NIOSH ..............................................................................................................65

5.4.1 Thorium Bioassay Data..............................................................................65

5.4.2 AEC Survey Data .......................................................................................66

5.4.3 Thorium Processes and Source Term Data ................................................67

5.5 Tritium Exposures ..................................................................................................68

5.6 Fission Product Intakes ..........................................................................................68

5.6.1 Use of NUREG-1400 for Modeling Intakes at the Hot Lab ......................68
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5.6.2 Intakes of Fission Products from Decontamination and 

Decommissioning of the Ames Laboratory Research Reactor ..................69

5.7 Failure to Address Uranium and Thorium Blowouts for the Assessment of 

Episodic Intakes .....................................................................................................70

5.7.1 Quantities of Uranium and Thorium Metal Produced ...............................70

5.7.2 Estimated Frequency of Blowouts .............................................................71

5.7.3 Assessment of Airborne Contamination Levels Associated with 

Blowouts ....................................................................................................72

6.0 Occupational External Dose ..............................................................................................75

6.1 Unmonitored External Dose ..................................................................................75

6.2 Coworker Dose Model – 1952 to the Present ........................................................77

7.0 References ..........................................................................................................................80

Appendix A: Interview with Dr. March 12, 2006, by Dr. Arjun Makhijani, 

SC&A .....................................................................................................................85 

Appendix B: AEC Survey Report Findings and Recommendations ............................................89 

Appendix C: 2006 Bihl Memo ....................................................................................................120 

Appendix D: 1947 Fulmer Report (pages 36–42).......................................................................123 

Appendix E: Telephone Interview with Mr. on January 3, 2007 .....................130 

Appendix F: Thorium Bioassay Data for Ames Workers ...........................................................134 

Appendix G: Discussions Relating to the 250-Workday Requirement for SEC Status .............140 

Appendix H: Memorandum from Dr. Skoog to Dr. Spedding ...................................................152
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LIST OF TABLES

Table 2-1. Feasibility Findings for SEC-00038, August 13, 1942 through 

December 31, 1954 .....................................................................................................16

Table 2-2. Feasibility Findings for SEC-00075, January 1, 1955 through 

December 31, 1970 .....................................................................................................16

Table 2-3. Feasibility Findings for SEC-00166, January 1, 1955 through 

December 31, 1960 .....................................................................................................17

Table 3-1. Major Activities Associated with the Ames Project ....................................................27

Table 4-1. Environmental External Doses ....................................................................................28

Table 4-2. Summary of Environmental Intakesa ...........................................................................28

Table 4-3. Survey of Fenceline Gamma Dose Rates around the Synchrotron Facility with 

the Beam Directed West .............................................................................................31

Table 5-1. Chemistry Building Uranium Intakes (pCi/d) .............................................................51

Table 5-2. Physical Chemistry Annex 1 Uranium Intakes (pCi/d) ...............................................51

Table 5-3. Physical Chemistry Annex 2 Uranium Intakes (pCi/d) ...............................................52

Table 5-4. Uranium Excretion in Personnel, Group 1 ..................................................................54

Table 5-5. Uranium Concentrations among 48 Ames Workers ....................................................54

Table 5-6. Uranium Air Concentrations associated with the Production of 

Uranium Metal at Annex 1 .........................................................................................55

Table 5-7. Default intakes for Ames Laboratory ..........................................................................57

Table 5-8. Summary of Urine Bioassay Data for Thorium ..........................................................65

Table 5-9. Internal Dose Estimates for a Thorium Blowout* (rem) .............................................73

Table 5-10. Internal Dose Estimates for a Uranium Blowout* (rem) ...........................................73
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LIST OF FIGURES

Figure 3-1. Physical Chemistry Annex (Little Ankeny) North View ...........................................22

Figure 3-2. South View of Little Ankeny .....................................................................................23

Figure 3-3. Floor Plan of Little Ankeny Production Facility for Uranium and Thorium .............24

Figure 4-1. Cartoon about the Fires in the Reduction and Casting Processes and 

the Role of the Local Firemen ....................................................................................49

Figure 4-2. Cartoon about Frequent Explosions and Keeping Secretarial Staff 

on the Ames Project ....................................................................................................50

LIST OF EXHIBITS

Exhibit 4-1. 1961 Survey Synchrotron .........................................................................................32

Exhibit 4-2. Fenceline Dose Rates for Synchrotron Beam Directed West ...................................33

Exhibit 4-3. Fenceline Dose Rates for Synchrotron Beam Directed Eastward ............................35

Exhibit 4-4. Air Sampling Locations for 1A for the Weather Tower ...........................................38

Exhibit 4-5. Air Sampling Locations for 2A for Spedding Hall ...................................................39

Exhibit 4-6. Summary Data for Airborne Activity Levels for These Two Sampling 

Locations are Cited in Tables 7 and 8 of Voss (1975) ...............................................40

Exhibit 5-1. Locations Selected by NIOSH for Determining 

Removable Contamination Levels ..............................................................................63

Exhibit 6-1. Table IV of Klevin 1952 ...........................................................................................78
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Acronyms and Abbreviations

Advisory Board

or Board Advisory Board on Radiation and Worker Health 

AEC U.S. Atomic Energy Commission 

ALRR Ames Laboratory Research Reactor 

AWE Atomic Weapons Employer 

cc cubic centimeter

cm2 square centimeter

Ci curie 

CFR Code of Federal Regulations 

D day 

D&D decontamination and decommissioning 

DOE U.S. Department of Energy 

dpm/m3

 disintegrations per minute/per cubic meter 

EEOICPA Energy Employees Occupational Illness Compensation Program Act of 

2000 

ERDA Energy Research and Development Administration 

FMPC Feed Materials Production Center

GM geometric mean

GSD geometric standard deviation 

HEPA high-efficiency particulate air

hr hour 

ICRP International Commission on Radiological Protection 

IMBA Integrated Modules for Bioassay Analysis 

ISU Iowa State University 

kg kilogram 

kV kilovolt 

L liter

LAT lateral

lbs pounds 

m3 cubic meter

MDA minimum detectable activity 

MDL minimum detection level
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MED Manhattan Engineer District 

MeV megaelectron-volt, 1 million electron-volts 

Mg magnesium

mg milligram 

mL milliliter 

mR milliroentgen

MRD minimum recordable dose 

mrem millirem 

MW megawatt 

N/A Not applicable 

NCRP National Council on Radiation Protection and Measurements 

NIOSH National Institute for Occupational Safety and Health 

ORAUT Oak Ridge Associated Universities Team 

ORNL Oak Ridge National Laboratory 

pCi/d picocurie per day 

POC probability of causation 

R&D research and development 

s second

SC&A S. Cohen and Associates (SC&A, Inc.) 

SEC Special Exposure Cohort 

SRDB Site Research Database Reference 

TBD technical basis document 

Th thorium 

ThF4 thorium-fluoride 

ThO2 thorium dioxide 

TLD thermoluminescent dosimeter 

T.N.T. trinitrotoluene 

U uranium 

U3 O8 uranium oxide 

UF4 uranium tetrafluoride

U.S.C. United States Code 

yr year 

ZnCl zinc chloride 
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β beta 

γ gamma 

μCi microcurie 

μg microgram 

§ section or sections
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1.0 EXECUTIVE SUMMARY

This draft report presents S. Cohen and Associates’ (SC&A, Inc.) evaluation of the Site Profile 

for the Ames Laboratory, ORAUT-TKBS-0055, Rev. 3 (ORAUT 2012a). This draft report was 

prepared at the request of the Advisory Board on Radiation and Worker Health (Advisory 

Board). Authorization for the preparation of this report is described in Section 2 of the report. 

As part of our evaluation, SC&A also reviewed numerous other documents that were considered 

relevant including the following: 

• Select documents that were referenced in the Ames Laboratory Site Profile

• Documents contained in the National Institute for Occupational Safety and Health 

(NIOSH) Site Research Database (SRDB)

• Relevant reference texts and scientific studies cited in the open literature

• Personal memoirs/manuscripts; worker interviews; and memoranda/letters that provide 

critical insight on attitudes, work conditions/practices and events that surround the Ames 

Project

1.1 TECHNICAL APPROACH AND REVIEW CRITERIA

The approach used by SC&A to perform this review includes, but is not limited to, the 

procedural protocols described in Standard Operating Procedure for Performing Site Profile 

Reviews (SC&A 2004). Approved by the Advisory Board on March 18, 2004, SC&A’s protocol 

reflects the following review criteria:

(1) Completeness of data sources

(2) Technical accuracy

(3) Adequacy of data 

(4) Consistency with other site profiles 

(5) Regulatory compliance

Deficiencies pertaining to these review criteria are noted as “issues.” Our review of the Ames 

Laboratory Site Profile identified a total of 23 issues. Twenty-two (22) of the issues are regarded 

as “findings” and represent deficiencies that may require correction due to their potential adverse 

impact(s) on dose reconstruction. A single issue designated as an “observation” corresponds to 

an issue with limited significance for affecting dose reconstruction. 

The purpose of this review is to provide the Advisory Board with an independent assessment of 

issues that surround the Ames Site Profile. Findings identified in our review are expected to 

Issues

Findings Observations 
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provide the Advisory Board with a preliminary overview of potential issues that may impact the 

feasibility of dose assessment.

SC&A’s draft report with its preliminary findings will subsequently undergo a multi-step 

resolution process. Resolution includes a transparent review and discussion of draft findings 

with members of the Advisory Board’s Work Group and select personnel representing 

NIOSH/Oak Ridge Associated Universities Team (ORAUT). This resolution process is intended 

to ensure that each finding is evaluated on its technical merit in a fair and impartial manner.

1.2 SUMMARY OF ISSUES

SC&A’s review of ORAUT-TKBS-0055, Rev. 03 (ORAUT 2012a), principally focused on the 

following three sections of the Ames Laboratory Site Profile:

• Section 4.0 – Occupational Environmental Dose 

• Section 5.0 – Occupational Internal Dose

• Section 6.0 – Occupational External Dose

Of the 22 preliminary findings identified in this review, 9 findings pertained to Occupational 

Environmental Dose, 11 to Occupational Internal Dose, and 2 to Occupational External Dose. 

A brief statement for each of the 22 findings is presented below. However, the reader is 

cautioned that nearly all findings are based on a substantial body of data in the text that is further 

supported by the attached appendices. A more complete understanding and judgment of merit in 

behalf of these findings may, therefore, require a full review of this draft report. 

1.2.1 Occupational Environmental Dose 

Finding #1: Derived environmental intakes of U and Th, as given in Table 4-7 of the TBD, are 

improperly referenced and appear without technical basis.

Finding #2: NIOSH provides no basis for the “assumed” losses of 0.1% of U and Th to the 

environment and fails to identify a value for resuspension. 

Finding #3: NIOSH’s selection of personnel at the Ames Laboratory Research Reactor (ALRR) 

Facility as the target population is inappropriate and results in dose estimates that are not 

claimant favorable. 

Finding #4: NIOSH’s selection of data from the 1961 survey conducted at the Synchrotron 

Facility defines fenceline dose rates that are 1 to 2 orders of magnitude lower than other 

measurements reported in the survey when beam direction was shifted from a westerly to 

easterly direction. 

Finding #5: SC&A concludes that the 1961 survey measurements, which were limited to 

gamma dose rates, were incomplete and may have substantially underestimated total exposure by 

excluding the contribution of particulate radiation. 
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Finding #6: Statements in Section 4.3 of the Ames Site Profile are factually incorrect. For all 

years for which reported environmental sampling data (1974, 1975, 1976), there were two 

sampling sites (not one, as stated by NIOSH) that provided data in behalf of air concentrations 

and corresponding dose estimates. 

Finding #7: The nearly “instantaneous” 100-fold reduction of U and Th environmental intakes 

that represent the transition of the uranium and thorium metal production facilities at the end of 

1953 to research and development (R&D) facilities in 1954 are improperly modeled. Also not 

included in the model are the contribution of blowouts to environmental contamination and the 

persistence of these radionuclides in the environment post-1953. 

Finding #8: Environmental intakes cited in Table 4-7 of the Ames technical basis document 

(TBD) are based on unsupported assumptions and model parameters, which moreover are 

inconsistent with parameter values used to model worker intakes inside the hot laboratory 

described in Section 5.0 of the TBD. 

Finding #9: Uranium and Th blowouts represent significant environmental events that should 

be included in Section 4.5 of the Ames TBD for the assessment of environmental exposures. 

1.2.2 Occupational Internal Dose 

Finding #10: Available empirical bioassay and air-sampling data for Annex 1 workers are 

substantially higher than modeled/surrogate data assigned by NIOSH. 

Finding #11: NIOSH further minimized the intake value of 853 pCi/d for Annex 1 production 

workers by assigning the “distribution” as a constant. 

Finding #12: Default intake rates defined in Table 5-8 of the Ames TBD are improper for 

absorption Types F or S.

Finding #13: The scaling of uranium intake values based on (1) facility and (2) job function is 

without technical support and conflicts with statements given in the Ames Site Profile.

Finding #14: Although NIOSH briefly acknowledged the occurrence of “frequent fires and 

explosions” associated with the production of uranium metal, no attempt was made to assess 

potential intakes of these episodic events.

Finding #15: Technical Basis for Estimating the Maximum Plausible Dose to Workers at 

Atomic Weapons Employer Facilities, ORAUT-OTIB-0004, Rev. 03 (ORAUT 2006), is 

referenced for estimating non-operational intakes. OTIB-0004 was canceled before Rev. 03 of 

the Ames Site Profile (ORAUT 2012a) was issued. Moreover, the much higher intake values for 

inhalation and ingestion during non-operating years (i.e., 1954–1976) are inconsistent with 

intake values for operating years (1942–1953) as given in Table 5-8 of the Ames TBD.

Finding #16: NIOSH’s approach for deriving estimates of thorium intakes from residual 

contamination post-1954 does not make the best use of survey data reported by Klevin (1952) 

and use of ORAUT-OTIB-0070, Rev. 01 (ORAUT 2012b). 
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Finding #17: Given the availability of credible data, NIOSH’s exclusion of thorium exposure in 

dose reconstruction is not justified. 

Finding #18: Due to the fact that very little is known about the design features and technical 

specifications of the Hot Lab and the absence of worker monitoring/facility survey data, the 

applicability of NUREG-1400 (Hickey et al. 1993), Section 1.2, for use in dose reconstruction 

lacks technical merit and credibility for a facility that operated between 1943 and 1951. 

Finding #19: Although Section 5.4.2 of the Ames TBD is titled, “Fission Product Intakes from 

Research Reactor Operations and Decontamination and Decommissioning,” NIOSH restricted 

intakes to two activation products that are arbitrarily based on a 1977 Energy Research and 

Development Administration (ERDA) gross beta air concentration limit.

1.2.3 Occupational External Dose 

Finding #20: By means of documented anecdotes/testimonials regarding potential frequencies 

of blowouts, technical data for a specific blowout documented at Feed Materials Production 

Center (FMPC), and reasonable assumptions, SC&A derived significant U and Th intakes and 

associated organ doses that are applicable to workers at the Ames Laboratory, but were not 

considered/included in ORAUT-TKBS-0055 (ORAUT 2012a). 

Finding #21: SC&A’s concerns about the use of the same surrogate data sources and 

questionable assumptions for deriving external dose for Ames’ workers exposed to uranium 

closely parallel those related to uranium intakes as cited in Findings #10 and #13. 

Findings #22: Given the availability of highly credible and site-specific data for deriving 

external doses from thorium exposure, NIOSH’s decision to exclude said exposures/doses is not 

justified.

1.3 ORGANIZATION OF THE REPORT

This draft report was written and organized as a “stand-alone” document by including summary 

information/data from various sources used to support our findings in the text of this report. For 

most of the 22 findings, additional information is provided by the attached appendices that either 

represent select portions or the full text of documents considered relevant to our findings. 

Findings identified by SC&A are confined to Sections 4.0, 5.0, and 6.0 of this report and closely 

track the topical sequence of Sections 4.0, 5.0, and 6.0 of the Ames Laboratory Site Profile.
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2.0 INTRODUCTION AND SCOPE OF AUDIT

Under the Energy Employees Occupational Illness Compensation Program Act of 2000 

(EEOICPA) and federal regulations defined in Title 42, Part 82, Methods for Radiation Dose 

Reconstruction Under the Energy Employees Occupational Illness Compensation Program, of 

the Code of Federal Regulations (42 CFR Part 82), the Advisory Board on Radiation and Worker 

Health (Board) is mandated to conduct an independent review of the methods and procedures 

used by NIOSH and its contractors for dose reconstruction. As contractor to the Board, S. Cohen 

and Associates (SC&A, Inc.) has been charged to support this effort by independently evaluating 

site profiles as requested by the Board that correspond to specific facilities at which energy 

employees worked and were exposed to ionizing radiation. 

In a teleconference held by the Advisory Board on February 7, 2013, SC&A was tasked to 

review/evaluate the Site Profile for Ames Laboratory (ORAUT-TKBS-0055, Rev. 03), which 

was issued on January 3, 2012. The Board’s request for the review of ORAUT-TKBS-0055, 

however, was made under circumstances that differed from previous reviews performed by 

SC&A, as briefly explained below. 

2.1 A SUMMARY OF EVENTS THAT PROMPTED REVIEW OF 

ORAUT-TKBS-0055, REV. 03 

Revisions to the Ames Site Profile. The first Site Profile for Ames Laboratory, ORAUT-TKBS0055, Rev 00 (ORAUT 2007a) was issued on June 22, 2007. Since then, the Ames Site Profile 

was revised four times: Rev. 00 PC-1 on August 20, 2008 (ORAUT 2008); Rev. 01 on 

December 18, 2009 (ORAUT 2009); Rev. 02 on January 14, 2011 (ORAUT 2011); and Rev. 03 

on January 3, 2012 (ORAUT 2012a). 

While some of the aforementioned revisions resulted in an increase in assigned dose, others 

decreased the dose, and still others decreased in an earlier revision and increased in a subsequent 

revision, as summarized below: 

• Revision 01 increased uranium intakes for researchers in the Ames Chemistry Building 

from August 1942 through December 1953. This change remained in Revisions 02 and 

03. Revision 01 also added lateral (LAT) exposure dose estimates to occupational 

medical exposure.

• External dose for unmonitored workers for some job categories before 1946 increased in 

Revision 01, remained the same in Revision 02, but increased again in Revision 03. 

• External dose for unmonitored workers between 1946 and 1953 decreased for all job 

categories and locations in Revision 01, remained the same in Revision 02, but increased 

in Revision 03. 

• Revision 02 increased uranium intakes for all employees in the Chemistry Building for 

the period January 1954 through May 1976. These higher intakes remained unchanged 

in Revision 03. All occupational medical exposures were eliminated in Revision 02 

and Revision 03. 
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Special Exposure Cohort (SEC) Classes Added. During this time period, NIOSH added classes 

to SEC-00038 in 2006 (NIOSH 2006), SEC-00075 in 2007 (NIOSH 2007), and SEC-00166 in 

2010 (NIOSH 2010) to cover three separate groups of employees based on work location and job 

description. While the classes added in 2006 and 2007 included specific workers performing 

specific tasks in designated buildings, the 2010 class determined that the information available 

about worker job description, work location, or movement about the site was insufficient to 

determine if an employee worked in the affected area(s).

In 2011, NIOSH designated a fourth class [SEC-00185 (NIOSH 2011)] that encompasses all 

previous Ames SEC periods from August 13, 1942, to December 31, 1970, and designates all 

Ames employees (including predecessor agencies, contractors, and subcontractors) who were 

employed for a number of workdays aggregating at least 250 workdays. In Section 1.3.4 of 

ORAUT-TKBS-0055, Rev. 03 (ORAUT 2012a), NIOSH states the following: 

. . . This SEC, SEC-00185 does not make any new information available for the 

feasibility of performing dose reconstructions between the dates of August 13, 

1942, and December 31, 1970. . . . 

. . . NIOSH has determined that site-specific and claimant-specific data available 

for Ames Laboratory for this entire period are insufficient to enable it to 

determine that a specific work group was not potentially exposed to radioactive 

material releases or possible subsequent contamination. Based on this 

information, NIOSH has determined that the previously proposed SEC class 

definitions cannot be based on or limited to job titles or duties. [Emphasis 

added.] 

It must also be noted that SEC-00185 was revised to change the covered period’s start date from 

January 1, 1942, to August 13, 1942, the start of the Manhattan Engineer District (MED), known 

later as the Manhattan Project. 

In behalf of these four SEC classes, NIOSH in Revision 03 of ORAUT-TKBS-0055 (ORAUT 

2012a) provides the following statements and guidance for the dose reconstruction of Ames 

workers who were employed after December 31, 1970, as well as for workers who were 

employed prior to 1970 but who are not eligible for inclusion in SEC-00185: 

Although NIOSH cannot bound doses for certain areas and periods as described 

in the SECs, internal and external data that become available for an individual 

claim (and that can be interpreted using existing NIOSH dose reconstruction 

processes or procedures) and applicable dose reconstruction methods that are 

defined in Sections 4, 5, and 6 of this site profile, will be used to complete partial 

dose reconstructions for workers who worked during the SEC periods but are 

not eligible for the SEC. 

This site profile provides internal and external exposures that might coincide 

with work periods that fall within the SEC periods. There are varying types of 

exposures that can be applicable during the SEC periods to dose reconstructions 

for employees who do not qualify for the SEC(s). The periods in which doses can 
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and cannot be reconstructed for a particular claim should be identified when 

writing the Dose Reconstruction Report. For dose reconstruction of claims with 

employment during the SEC period (see Section 1.3.4), all Ames employees are 

included and the dose reconstruction is a “partial reconstruction” by default. 

This designation should be included in the Dose Reconstruction Report. 

[Emphasis added.] 

Tables 2-1, 2-2, and 2-3 summarize NIOSH’s assessment regarding the feasibility of performing 

partial dose reconstructions from internal and external exposures for workers ineligible for SEC 

status. Workers ineligibility for SEC status may be due to (1) cancer type, and/or 

(2) employment prior to 1970 of fewer than 250 workdays. 

For ineligible workers, a partial dose reconstruction may, therefore, be based on internal and 

external sources defined in the second column of Tables 2-1, 2-2, and 2-3 and described in 

Sections 4, 5, and 6 of Revision 03 of the Ames Site Profile (ORAUT 2012a). 

Table 2-1. Feasibility Findings for SEC-00038, August 13, 1942 through 

December 31, 1954 

Source of Exposure Dose Reconstruction is Feasible Dose Reconstruction is NOT 

Feasible

Internal dose: — —

Uranium X —

Thorium/plutonium — X

Thoron — X

External dose: — —

Uranium beta/gamma X —

Thorium/plutonium beta/gamma — X (except 1953 and 1954)

Neutron — X

Occupational medical x-ray X —

Table 2-2. Feasibility Findings for SEC-00075, January 1, 1955 through 

December 31, 1970 

Source of Exposure Dose Reconstruction is Feasible Dose Reconstruction is NOT 

Feasible

Internal — —

Th-232 and progeny — X

Ambient environmental X —

External — —

Gamma X —

Beta X —

Neutron N/A —

Ambient environmental X —

Occupational medical x-ray X —
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Table 2-3. Feasibility Findings for SEC-00166, January 1, 1955 through 

December 31, 1960 

Source of Exposure Dose Reconstruction is Feasible Dose Reconstruction is NOT 

Feasible

Internal dose: — —

Uranium and progeny X —

Thorium and progeny X —

Other radionuclides (Research 

Building) — X 

External dose: — —

Gamma X —

Beta X —

Neutron X —

Occupational medical x-ray X —

2.2 SCOPE AND OBJECTIVES OF AUDIT

SC&A’s past approach to the review of other site profiles closely followed the protocol 

described in Standard Operating Procedure for Performing Site Profile Reviews (SC&A 2004). 

For the Ames Laboratory Site Profile, this standard review process is considered inappropriate 

due to the fact that, for earlier time periods of facility operations, Ames workers were either not 

monitored for exposure or available records pertaining to worker monitoring; claimant-specific 

job duties and work locations; process descriptions and source-term data were insufficient to 

perform complete dose reconstructions. Hence, for the period of August 13, 1942, to December 

31, 1970, NIOSH recommended the addition of the SEC-00185 class that includes all workers 

for all areas of the Ames Laboratory.

SC&A’s review of the Ames Laboratory Site Profile for the period of August 13, 1942, through 

December 31, 1970, will, therefore, assess and evaluate Sections 4, 5, and 6 of the Ames Site 

Profile, as well as all claimant-specific and facility-specific data that are available and considered 

appropriate for a partial dose reconstruction in behalf of individuals who do not qualify for 

inclusion in the SEC. This may include the review of documents that under more normal 

circumstances would have a low priority among other available sources and would, therefore, not 

be given consideration for use in dose reconstruction. Among these are a 1952 Atomic Weapons 

Employer (AEC) survey (Klevin 1952), personal memoirs/manuscripts, worker interviews, and 

memoranda that provide a critical insight on attitudes, work conditions/practices, and events that 

surround the Ames Project. 

For facility operations after 1970, SC&A’s review of Sections 4, 5, and 6 of ORAUT-TKBS0055, Revision 03, will follow the traditional protocols (SC&A 2004) with the following review 

objectives:

(1) Completeness of information and data sources for all workers and time periods of facility 

operation 

(2) Technical accuracy and reliability of the data

(3) Claimant favorability in instances when assumptions, surrogate data, and/or coworker 

models are used
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(4) Consistency with other site profiles 

(5) Compliance with Federal Regulations pertaining to EEOICPA and with guidance 

documents established by NIOSH and its contractors 
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3.0 RELEVANT BACKGROUND INFORMATION

3.1 SITE/FACILITY DESCRIPTIONS

The Ames Laboratory is located on the Iowa State University (ISU) campus in Ames, Iowa. 

Although the Ames Laboratory was not formally established until 1947 by the AEC, work at 

Iowa State College began in 1942 when Dr. Frank Spedding, a professor of physical chemistry at 

the college, agreed to establish and direct a chemical and metallurgical research program that

complemented the MED’s Metallurgical Laboratory in Chicago. 

In the beginning, the Ames Project was first and foremost an academic laboratory that was

concerned with metallurgical research, studies on physical/chemical properties that investigated

such parameters as melting points/viscosities of metals, chemicals reactivity, and separation of

select fissile metal compounds and their reduction to pure elemental metals. The vast majority of

personnel involved in research activities were academics that included professors, graduate 

students, and technical support personnel with varying knowledge in chemistry and other 

sciences.

Within months, Ames researchers were successful in developing a chemical reduction process

for converting uranium tetrafluoride (UF4) to a highly purified uranium metal. Because this 

process was efficient and cost effective, the Ames Project was expanded to include the largescale production of purified uranium and later thorium metal. Thus, research and production 

became an integrated operation in which the production processes were an extension of research 

efforts, and continuing research reflected failures and problems encountered at the production 

level. To some extent, problems encountered in the production phase were likely affected by the 

need to hire workers from the local community who were neither familiar with the hazardous 

nature of materials employed nor the basic protocols of industrial safety. 

3.1.1 Uranium and Thorium Facilities

For research and development and for the production of uranium and thorium metal, a total of 

four campus buildings were utilized by the Ames Project l. These included the following: 

• Chemistry Building (Gilman Hall) was utilized for analytical research and process 

development 

• Physical Chemistry Annex I was used for the production of 1,000 tons of uranium ingots 

• Physical Chemistry Annex II was used for the recovery of uranium turnings and 

production of 300 tons of uranium ingots 

• Metallurgical Building (Wilhelm Hall) was used for various research and the production 

of thorium metal
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3.1.2 Other Facilities 

Other facilities with significant potential for radiation exposure included the following: 

• Physics Building was used for R&D that supported other work at Ames. Work included 

the development of analytical equipment, the operation of an 80-MeV synchrotron, and 

studies of nuclear fission and the shielding properties of various materials.

• Research Building (Spedding Hall) started operation in 1951 and was used to investigate 

the properties of various metals. This facility included a 150-kV accelerator that 

produced 14 MeV neutrons; a hot canyon and hot cell; and a glovebox. 

• Synchrotron Building housed two electron accelerators (up to 80 MeV) that upon 

interaction with a target produced high-energy gammas that in turn interacted with nuclei 

to release neutrons, protons, and alphas. This facility operated between 1949 and 1971 

and was decommissioned in the early 1990s. 

• Ames Laboratory Research Reactor (ALRR) was a 5-MW, heavy-water-moderated 

reactor that employed 93% enriched U-235 and started operation in 1965. Research 

included various material studies and analysis of decay products of nuclear fission. The 

reactor operated until 1977 and was decommissioned in 1981. The primary radiological 

concern at this facility was airborne tritium.

3.2 MAJOR OPERATIONS AND PROCESSES

The two major operations that contributed to radiation exposures among personnel at the Ames 

Laboratory involved the production of purified uranium (1942–1945) and thorium metal (1945–

1953). 

3.2.1 Uranium Metal Production 

Chemistry Building. Initial protocols for the purification of uranium metal were tested in the 

Chemistry Building. The Chemistry Building consisted of a basement and first floor. Besides 

basic chemical and metallurgical research on uranium and its compounds, a key research 

directive was to develop a chemical reduction process that would lend itself to the large-scale

production of highly purified uranium metal. 

Up until 1942, virtually no uranium metal in its pure form had been produced in significant 

quantities. At the time, uranium was generally available in the form of an impure uranium oxide

that required initial purification by ether extraction. At the beginning of the Ames Project, it was

thought that the oxides of uranium could be reduced to form a salt slag and a purified uranium 

metal. Early attempts to reduce uranium oxide by hydrogen, carbon, aluminum, magnesium, and 

calcium met with limited success and low yields, due to temperature melting problems of

uranium oxide and interactions with crucibles used to contain the chemical mixture. 

In these reduction experiments, oxygen presented the principal obstacle in reducing the uranium 

to pure metal. This obstacle was overcome in August 1942, when uranium oxide (U3O8) was 
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replaced with UF4 (i.e., green salt) and successfully reduced with a calcium liner. Within weeks, 

research produced pure uranium ingots weighing several pounds. In total, about 4,000 pounds of 

purified uranium metal had been produced by the research staff in the Chemistry Building late in 

1942. 

The successful reduction of UF4 to pure uranium metal by Ames researchers led to a contract

with Iowa State to produce 100 pounds of uranium per day in a pilot plant until such time that 

companies like Mallinckrodt and DuPont could integrate the Ames process into their own plant. 

Because research and process development of the Ames Project were performed/supervised by 

trained chemists, who at a minimum understood the chemical toxicity, volatility, and potentially

explosive reactivity of materials under investigation, standard laboratory precautions were taken. 

Moreover, the Chemistry Building with its ventilation hoods was designed for work with 

hazardous materials. Thus, on a relative scale, radiological exposures (in particular internal 

exposures associated with inhalation and ingestion) were likely lower among researchers that 

included faculty members, graduate students, and laboratory support personnel. 

This conclusion is based on personal interviews with Dr. F.H. Spedding, Director of the Ames 

Project, and others by Carolyn S. Payne and reported in her 1992 PhD thesis, “The Ames 

Project: Administrating Classified Research as a Part of the Manhattan Project” (Payne 1992). 

In one of the many interviews with Dr. Spedding, C.S. Payne (1992) reported the following 

comments: 

As long as the chemists were involved in research with the various elements, 

typical laboratory precautions were taken . . . ventilation hoods were being 

used . . . [and] there were few examples of safety breaches or carelessness by the

scientists at the Ames Project. The production area though presented quite a 

different problem. Scientists generally had security clearance, so they knew with 

what they were working . . . [but] workers often from the community had to be 

hired who were often unfamiliar with even routine practices. [Emphasis added.] 

Dr. Spedding’s comments were further supported by comments made by Dr. during 

an interview with SC&A (Dr. A. Makhijani) on March 12, 2006 (see Appendix A for full 

transcript of interview).

Dr. Makhijani: Did you go to Little Ankeny [where uranium metal was 

manufactured in large amounts]? 

Dr. First I went to predecessor of little Ankeny. At this place they had a 

way of preparing a steel cylinder and putting a lime liner in it. Then they put in 

UF4 mixed with magnesium and put some lime freshly baked so as to decompose 

the hydroxide. That was the way the metal was prepared. Then they put in UF4. 

After the heating, the reduction occurred and uranium metal separated out. Some 

of the guys who worked there refused to wear masks. They would wear them 

when the director was there and then take them off when he left. They were farm 

boys and did not worry about the green powder. There was this one fellow; 
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Annex I (“Little Ankeny”). For the uranium production pilot plant, a small World War I wooden 

structure was selected. This facility that resembled a house was located on the southeastern edge 

of the campus, and at one time served as a women’s gymnasium, a popcorn laboratory used by 

the college’s agricultural department, and, in 1942, was used for storage. 

Important to an understanding of radiological environments that were encountered by uranium

(and subsequently thorium) production workers between the years 1943 and 1954 is a brief 

description of this building that would officially be called the Physical Chemistry Annex I and

nicknamed by workers as “Little Ankeny” after a war munitions plant in Ankeny, Iowa. 

Figures 3-1 and 3-2 show the simple wooden structure that, after a series of additions, became 

known as Annex I or Little Ankeny. 

Figure 3-1. Physical Chemistry Annex (Little Ankeny) North View
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Figure 3-2. South View of Little Ankeny

In her PhD thesis, titled The Ames Project: Administrating Classified Research as a Part of the 

Manhattan Project, C.S. Payne (1992) provided the following description: 

. . . The College gave the building to the project and immediately the chemists had 

the dirt floor in the garage area replaced with concrete so that casting could take 

place in this area. The chemists set up the reduction laboratory in the original 

part of the building where the popcorn lab had been located. The building shortly 

began to expand in a most curious pattern. The porch was used for the especially 

dirty work, the least secret of the process. However, when it became too cold to 

work on the porch, a canvas would be added followed by a crude set of walls and 

finally a new roof. A new porch appeared and the process repeated itself. . . 

After the building became available, a machine shop at the production site 

became the second necessity. Wilhelm* heard of a small machine shop owned 

and managed by Bill Maitland for sale in Ames west of Grand Avenue near the 

railroad. Maitland made garden tools normally, but he could no longer obtain 

the metal he needed because of war-time restrictions on material priorities. 

Wilhelm examined the shop contents and discovered that Maitland would sell all 

his tools and equipment for $8,000. After consulting with Spedding, both men 

contacted Maitland and bought the entire shop, moving the equipment along with 

Bill Maitland to the campus production building. . . . [Emphasis added.] 

Production equipment, unlike lathes, motors, and small tools from Maitland, was 

much harder to procure. For example, reduction furnaces were especially hard 
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to obtain. The small reduction furnace in the Chemistry Department used to 

produce most of the metal earlier was not big enough for a large-scale production 

plant. Luckily for the Ames operation, the Metallurgical Laboratory had ordered 

two 40,000 watt reduction furnaces for what they called “Site B,” but when the 

Ames pilot plant needed to be established as a production facility, those furnaces 

were diverted to Ames. Mixers and grinders for processing metals like calcium 

and later magnesium and vacuum casting apparatus were also purchased from 

various producer . . . 

* Harley A. Wilhelm was a metallurgist and professor of chemistry at Iowa State and was Associated 

Director.

A floor plan of the original structure that, along with subsequent additions became known as 

Annex I or “Little Ankeny,” is provided in Figure 3-3. 

Figure 3-3. Floor Plan of Little Ankeny Production Facility for Uranium and Thorium 

(Note: Heavy dotted line identified original buildings.)

Uranium metal production at Annex I began in January of 1943. Ames received the UF4 from 

three sources—Mallinckrodt, DuPont, and Harshaw. Production rose from 3,600 pounds per 

week early in January 1943 to about 5,600 pounds in the last week of that month. During 

this time, reduction of UF4 to uranium metal was performed by means of either calcium or 

magnesium. However, by March, magnesium became the reductant of choice. 

Peak production of uranium metal was reached in July 1943, with 130,000 pounds per month. 

During peak production periods, Ames operated 24 hours per day and 7 days per week. By
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December 1945, a total of 2,000,000 pounds (or 1,000 tons) of uranium ingots had been 

produced at Ames, and UF4 reduction and uranium metal casting shifted from Ames Laboratory 

to three companies that included Electromet, Mallinckrodt, and DuPont. 

In addition to the reduction of UF4 to uranium metal, Figure 3-3 also identifies numerous other 

critical processes that were performed at the Annex I facility. These included the following: 

• In preparation of the reduction process, UF4 and Mg had to be “ground and chopped” into 

smaller pieces.

• UF4 and Mg were subsequently screened, and ferrous contaminants were removed by 

magnets.

• Following a successful reduction and the formation of a uranium “biscuit,” the biscuit 

was stamped and sent to the melting and casting room. 

• In the casting process, a vacuum induction furnace heated/melted the biscuit in a crucible, 

which discharged the molten uranium into a graphite mold in the shape of rods that 

varied between 1.5 to 5 inches in diameter and 20–30 inches in length. 

• A cropping was cut from one end of the rod for physical and chemical evaluation, and 

each rod was stamped with an ID number and crated for shipment. 

Based on the above-cited information, it is reasonable to conclude that Iowa State’s uranium 

production facility was neither designed for nor equipped with the necessary safety systems 

needed to process large quantities of uranium and minimize worker exposure, as acknowledged 

by C.S. Payne (1992) in the following statements: 

There was a basic conflict trying to balance safety with accomplishing the work in 

time to win the war . . . [and] much of the early work was not done under the best 

of conditions . . . For example, most of the tools that had been obtained from Bill 

Maitland’s garden shop in down-town Ames were hand-driven so power 

apparatus had to be adapted and added to them. Also many of the grinders, 

cutting mills, and machining tools were originally manufactured for other 

industrial purposes and naturally did not have all the necessary safety features 

for working with uranium. It took months to obtain fans that were needed for 

proper ventilation in the building and since much of the work took place in hot 

months without the luxury of air conditioning, respirators and masks, though 

required for particularly dusty work, were sometimes discarded for worker 

comfort. [Emphasis added.] 

Failure to enforce basic safety precautions among process workers at Annex I was also 

acknowledged by , one of the , who recalled the following: 

I was acting as either or for a crew of from six to 

sixteen people. . . In a situation of that type it often falls on the immediate 

supervisor to make some decisions with his own judgment. I would say that we 

were perhaps guilty on erring on the side of, “well, lets get the job done and not 

worry too much about this or that safety rule”. . . (C.S. Payne 1992) 
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According to statements provided by Dr. F.H. Spedding in 1967 and acknowledged by C.S. 

Payne (1992), there were some people on the Ames Project who ignored all safety rules, as given 

in the following: 

[Redacted]

Beginning in 1943, Annex I was used for process development, as well as early production of 

thorium metal.

Chemistry Annex II. In September of 1943, concurrent with the production of uranium metal 

from virgin material, Ames developed a uranium recovery program from scrap metal turnings 

produced at Ames and at all other MED sites. Uranium recovery was done in the Chemistry 

Annex II Building, a one-story brick building, also known as the former Credit Union Building. 

In April 1944, this development work became a production operation. 

In the recovery process, metal turnings were first collected in barrels and examined by hand to 

identify uranium turnings. Segregated uranium turnings were then subjected to a magnetic 

separator that removed smaller iron and other ferrous impurities before being sent to a cutting 

machine. After being washed, rinsed, dried, and again passed over a magnetic separator, the 

cleaned uranium turnings were pressed into briquettes (about 1-inch thick and 4.25 inches in 

diameter). Lastly, briquettes were taken to the casting room to be melted and cast into ingots.

Over a 2-year period, Ames recovered in excess of 600,000 pounds of scrap uranium using this 

process. In December of 1945, this recovery process was taken over by Metal Hydrides in 

Massachusetts and by a recovery facility at the Hanford Site in Washington. 

3.3 THORIUM AND METAL PRODUCTION

Metallurgy Building. Interest in thorium (Th-232) as a source for producing the fissile U-233 by 

the Th-232 (η,γ) U-233 reaction began at Iowa State as early as 1943. Here too, the Ames 

Project served the dual role of analytical R&D and implementation of a pilot production 

program. Key research studies involved the chemical separation of thorium from uranium 

contained in monazite sand and the reduction of thorium oxide (ThO2) or ThF4 to pure metal.

In 1944, preliminary tests successfully demonstrated that the addition of zinc chloride (ZnCl) as 

a booster resulted in the formation of a zinc-thorium alloy, which when heated to high 

temperatures under vacuum produced purified thorium metal. 

Thorium biscuits were subsequently melted and recast either into ingots of up to 150 pounds or 

machined into suitable targets for use in atomic piles. By December 1946, Ames had produced 

4,500 pounds of thorium metal. Research and development on thorium were conducted in both 
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the Chemistry Building and Annex I. In other words, during 1944 and 1945, thorium production 

took place in the same building as large-scale uranium production; thereafter, production shifted 

to the Metallurgy Building until 1954, when production was halted. In total, 65 tons of purified 

and recast thorium metal were produced under the Ames Project.

Table 3-1 summarizes major activities and locations for the Ames Project between 1942 and 

1954, when metal production/casting ceased. 

Table 3-1. Major Activities Associated with the Ames Project

Building Dates Major Activities 

Chemistry Building 1942–1954 ? • Basic chemical/metallurgical research pertaining to uranium, 

thorium, plutonium, beryllium, cerium

Chemistry Building 1942–1945 • Chemical/metallurgical research on uranium

• Process development for uranium metal production 

Chemistry Building 1943–1944 • Process development for uranium recovery from turnings 

• Thorium reduction experiments and process development 

Annex I 1943–1945 

1943–1949 • Uranium metal reduction/production and casting of uranium 

• Process development and early production of thorium metal 

Annex II 1944–1947 • Recovery and casting of uranium metal from turnings 

Metallurgy Building 1947–1954 • Production and casting of thorium metal 
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4.0 REVIEW OF SECTION 4.0 OF THE AMES SITE PROFILE: 

OCCUPATIONAL ENVIRONMENTAL DOSE

In the Introduction of Section 4.0, NIOSH provides the following comments: 

Occupational environmental dose refers to the dose received by workers on the 

site but outside facilities (e.g., buildings). . . . 

Occupational environmental dose was not measured (direct radiation dosimeters) 

until 1953, when workers were badged (Martin 2006a,b), and it was not

calculated from environmental media concentrations until 1962. Sources of 

potential environmental exposures (releases to the environment) were not 

measured until 1962 (Voss 1963). [Emphasis added.]

Sections 4.1 through 4.5 of the Ames TBD provide estimates of environmental external and/or 

internal exposures from the following source terms during their times of operation: 

• Uranium/Thorium Production Period (1942–1952) 

• Synchrotron Operations (1949–1971) 

• Ames Laboratory Research Reactor (ALRR) Site (1965–1977) 

• Ames Laboratory R&D Activities (1942–Present)

• Significant Environmental Event 

Based on various assumptions and models, NIOSH estimated/derived annual external doses 

(mrem/yr) and daily intakes (pCi/d) that are presented in Tables 4-6 and 4-7 of ORAUT-TKBS0055 (ORAUT 2012a) and reproduced below as Tables 4-1 and 4-2. 

Table 4-1. Environmental External Doses 

(To be applied only to unmonitored workers) 

Location Dates Dose

(mrem/yr)a Distribution

Skyshine from Synchrotron Building 1949–June1971 25 Constant

Ar-41 from ALRR 1965–1977 1 Constant

All other R&D Buildings (see list in Section 4.4) All Negligible N/A a The energy range for all environmental external dose is assumed to be 100% 30–250 keV.

Table 4-2. Summary of Environmental Intakesa

Dates Radionuclide/adsorption Intake (pCi/d) Distribution

August 1942–1953 U (assume U-234); Type M or S 5 Constant

1954–present U (assume U-234); Type F,M, or S 0.05 Constant

June 1954–April 1953 Th-232, Ra-228, Th-228; all Type M 0.07 each Constant

1954–present Th-232, Ra-228, Th-228; Type M or S 0.0007 each Constant

1965–1977 Tritium 2,700 Constant

1943–1981 Fission products per Table 4-2 Per Table 4-2 Constant a Apply the environmental intakes in this table if no occupational intakes are applied for the same radionuclide and 

the same period in accordance with the instructions in Table 5-8.
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Presented below is SC&A’s assessment of these environmental exposure estimates for 

credibility, claimant favorability, and completeness.

4.1 URANIUM AND THORIUM INTAKES

Section 4.1 of the Ames TBD offers the following explanation for the derived upper-bound 

environmental intakes of (1) 5 pCi/day for U (modeled as U-234, Type M or S) and 

(2) 0.07 pCi/day each for Th-232, Th-228, and Ra-228 for years 1942–1954: 

There were no documents found that stated the room and hood ventilation stacks 

on the facilities had filters. Concentrations of uranium dust were measured in 

the operation rooms (Voss 1978). To estimate a bounding dose outside the 

facilities, it was assumed that losses of 0.1% of the uranium or thorium as dust in 

a facility were emitted continuously and dispersed from ground level in 

accordance with local and regional meteorological conditions (see Figure 4-1) 

(Voss 1981) and a standard Gaussian atmospheric dispersion computer model 

(Napier et al. 2004). When resuspension is included, the daily intake rate of 

uranium (modeled as 234U, type M or S) was 5 pCi. This intake applies outside 

Physical Chemistry Annex 1 for August 1942 through August 1945 and outside 

Physical Chemistry Annex 2 for 1944 through 1954. In addition, daily intakes of 

232Th, 228Th, and 228Ra at 0.07 pCi each apply to Annex 1 for June 1946 through 

1949 and to the Metallurgy Building for 1950 through April 1953. [Emphasis 

added.] 

SC&A’s Comments and Findings 

From the statement cited above, SC&A interprets the derivation of 5 pCi/d for U-234 intake and 

the 0.07 pCi/d intake for Th-234, Th-228, and Ra-228 to be principally based on the following: 

(1) Measured uranium dust in operations rooms (associated with Annex 1, Annex 2, and 

Metallurgy Building), as reported by Voss (1978); 

(2) An assumed continuous loss of 0.1% to the outside; and 

(3) The “inclusion of resuspension.” 

A review of Voss (1978), Environmental Monitoring at Ames Laboratory Calendar Year 1978, 

reveals a 58-page report that as its title suggests is limited to environmental sampling results for 

the year 1978. The focus of the 1978 sampling effort includes liquid and air releases of 

fission/activation products from the ALRR. The report neither makes reference to uranium and 

thorium metal production nor cites data for air concentrations for indoor air, as implied by 

NIOSH.

Finding #1: Derived environmental intakes of U and Th, as given in Table 4-2 above are 

improperly referenced and appear without technical basis.

For a more credible derivation of thorium values, SC&A recommends the use of data cited in a 

1952 AEC survey (Klevin 1952). Klevin (1952) reported (1) a daily weighted thorium air 
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concentration of 530 dpm/m3, and (2) a daily weighted maximum thorium air concentration of 

3,100 dpm/m3 for the Metallurgical Building (see page 3 of Appendix B).

Finding #2: NIOSH provides no basis for the “assumed” losses of 0.1% of U and Th to the 

outside and fails to identify a value for resuspension. 

4.2 SYNCHROTRON OPERATIONS

Although the synchrotron operated from 1949 to 1971, no dosimeters were provided to staff at 

the facility until after 1952, and no routine γ/η dose-rate measurements were made outside of this 

facility. In 1961, a facility survey was conducted that included a gamma dose-rate survey at the 

fenceline that surrounded the Synchrotron facility (Ames 1961). To estimate external exposure 

from the operation of the synchrotron, NIOSH stated the following: 

The ALRR (now the Applied Science Complex) is about 750 ft from the nearest 

part of the Synchrotron Building, and construction or operations at the two 

facilities overlapped, at a maximum, from 1962 to 1971. Skyshine from both 

heavy particles and photons decreases at rates equal to or greater than the 

reciprocal of the square of the distance (1/r2) from accelerator facilities (NCRP 

2003). If it is conservatively assumed that all of the radiation field measured in 

the 1961 survey was from skyshine, the dose rate at the ALRR would have been 

less than 0.13 mrem/hr during the worst-case operation and less than 

0.013 mrem/hr during routine operations. On the main campus of the University, 

the dose rate would have decreased to less than about 0.00025 mrem/hr during 

routine operations. 

It is favorable to claimants to use the environmental external dose from 

synchrotron operations at the ALRR for full-time exposure (2,000 hr/yr) for all 

locations at 25 mrem/yr for the period from 1949 to 1971. [Emphasis added.] 

Fenceline readings used by NIOSH are defined in Table 4-1 of the Ames Site Profile and as a 

convenience to the reader are reproduced herein as Table 4-3. As noted in Table 4-3, fenceline 

doses corresponded to the beam directed west. 
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Table 4-3. Survey of Fenceline Gamma Dose Rates around the Synchrotron Facility with 

the Beam Directed West

Location Dose rate 

(mrem/hr)a Location Dose rate (mrem/hr)a

1 0.75–1 14 1.8

2 3.5 15 1.8

3 7 16 1.8

4 6 17 1.6

5 5.5 18 1.5

3 7 19 1.5

7 4.75 20 1.75

8 3.5 21 1.6

9 2.6 22 1.6

10 1.5 23 1.5

11 2 24 0.75–1

12 2 25 4.5

13 1.8 — — a

 Background reading in the beam direction (see location 3-6) before turning on the 

beam was 0.5 to 1.0 mrem/hr.

Source: Ames 1961, p. 7

SC&A’s Comments and Findings 

SC&A questions NIOSH’s selection of model parameters, as well as the claim that, “It is 

favorable to claimants to use the environmental external dose from synchrotron operations at the 

ALRR for full-time exposure (2,000 hr/yr) for all locations at 25 mrem/yr for the period” 

[Emphasis added.] for the following reasons: 

(1) Selection of the target population. In Section 4.0, NIOSH defined Occupational 

environmental dose as “. . . the dose received by workers on the site but outside facilities 

(e.g., buildings).” [Emphasis added.] 

Based on this definition, the target population would be limited to maintenance workers, 

groundskeepers, security personnel, etc., who were assigned fulltime to outdoor duties at 

the ALRR at a distance of 750 feet from the source.

If such persons existed at the ALRR, they would also have existed at much closer 

distances that include areas at or within the fenceline that surrounds the Synchrotron 

Facility (see Exhibit #4-1).

Distances from the Synchrotron to the fenceline that surround this facility are included in 

the 1961 survey data and are provided here as Exhibit 4-2. For the 25 survey points, 

fenceline distances range from 55 to 325 feet and with dose rates ranging from <1 mR/hr 

to 7 mR/hr. For a full-time exposure (2,000 hr/yr), these dose rates would convert to 

annual doses of 2,000 mR to 14,000 mR. Dose rates within the fenceline must, therefore, 

be assumed even higher.
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Exhibit 4-1. 1961 Survey Synchrotron 
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Exhibit 4-2. Fenceline Dose Rates for Synchrotron Beam Directed West 
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(2) Choice of Survey Data. Section 4.2 of the Ames Site Profile states: 

The fenceline gamma dose rates measured in the radiation survey ([Ames 

1961]) were worst case and were produced with the maximum beam 

current on a target and direction that would produce maximum dose rates 

at the fenceline [Attribution#2]. . . . [Emphasis added.] 

SC&A’s review of the Ames (1961) survey data, however, identified other dose-rate 

measurements that are substantially higher than those selected by NIOSH. Exhibit 4-3 

identifies dose rate measurements: 

. . . recorded with the main beam projected northeast-ward direction. 

The beam was detected along the cyclone fence 55’ west of the northeast 

corner of the fence that surrounds the synchrotron site. The power level 

during the run of this survey was 60 to 65 MeV. [Emphasis added.] 

Exhibit 4-3 identifies multiple fenceline dose rates greater than 100 mrem/hr, which 

implies that NIOSH’s “claimant-favorable” dose of 25 mrem per year would have been 

received in less than 15 minutes spent at these locations.

(3) Accuracy and Completeness of Survey Data. Footnote “a” in Table 4-1 in ORAUTTKBS-0055 (ORAUT 2012a) (and reproduced above as Table 4-3) states that 

“Background reading in the beam direction (see locations 3-6) before turning on the 

beam was 0.5 to 1.0 mrem/hr” [Emphasis added]. 

Accuracy. It is uncertain what this “background reading” represents, since this would 

translate to an annual dose between 4,400 and 8,900 mrem, which is more than 100-fold 

higher than ambient dose rates in the U.S. On the assumption that the observed 

background levels of 0.5 to 1 mrem/hr were correct, one explanation may be the 

contribution of stored radioisotopes produced at the synchrotron. 

Completeness. Survey dose-rate measurements cited in the 1961 survey (Ames 1961) 

were limited to gamma radiation. As stated in Section 2.1.8 of the Ames Site Profile: 

. . . The synchrotron room housed two electron accelerators that could 

project electrons up to 80 MeV onto a target, which produced highenergy gamma rays that interacted with nuclei to release neutrons, 

protons, and alpha particles (Ames 1967). The accelerators were 

operated from a Control Room where there was a safety gate that 

prohibited access to the synchrotron room when the beam was on (Ames 

1967). In many cases, the products of these reactions were 

radioactive, . . . In addition, the synchrotron was used to probe nuclear 

structures and to provide radioisotopes for nuclear spectroscopy. . . 

[Emphasis added.] 
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Exhibit 4-3. Fenceline Dose Rates for Synchrotron Beam Directed Eastward

 
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Findings Associated with Environmental Exposures Associated with the Operation of the 

Synchrotron 

Finding #3: NIOSH’s selection of personnel at the ALRR Facility as the target population is 

inappropriate and results in dose estimates that are not claimant favorable. At a minimum, 

survey data/dose rates cited in Exhibit 4-2, which reflect Synchrotron fenceline measurements, 

should be considered. 

Finding #4: NIOSH’s selection of data from the 1961 survey conducted at the Synchrotron 

Facility defines fenceline dose rates that are 1 to 2 orders of magnitude lower than other 

measurements reported in the survey when beam direction was shifted from westerly to easterly

direction. For bounding estimates of environmental doses, fenceline data cited in Exhibit 4-3 

should be considered. 

Finding #5: SC&A concludes that the 1961 survey measurements, which were limited to 

gamma dose rates, were therefore incomplete and may have substantially underestimated total 

exposure by excluding the contribution of particulate radiation. 

4.3 AMES LABORATORY RESEARCH REACTOR OPERATIONS (1965–1977)

The 5-MW, heavy-water-moderated research reactor is about 1.5 miles northwest of the ISU 

campus. Operation of the reactor resulted in airborne emissions of H-3, Ar-41, and small 

quantities of fission and activation products. 

In behalf of environmental exposures associated with ALRR operations, Section 4.3 of the Ames 

Site Profile states the following:

. . . not all workers at the ALRR have recorded doses. In addition, environmental 

doses from gaseous effluents released from the operating reactor were not 

monitored. However, environmental doses to the public from airborne releases 

were calculated and reported (Voss 1975, 1976, 1977). The only air monitoring 

station in the vicinity of the reactor was on the roof of the reactor building, as 

shown in Figure 4-3.

Environmental Monitoring at Ames Laboratory: Calendar Year 1974 was the first 

annual report to provide gamma spectroscopy of environmental media samples 

(Voss 1975); subsequent annual reports (Voss 1976, 1977) provided similar 

results. The average release estimates from these reports were used to determine 

the estimated environmental dose to offsite workers from gaseous releases from 

reactor operations. From the effluent data, it was shown that the contribution to 

radioactivity in air from ALRR operations consisted principally of 41Ar and 

tritium (Voss 1975, 1976, 1977). An atmospheric dispersion model, which used 

annual average meteorological data for Ames and an exposure model (Napier et 

al. 2004; [Napier 2006]), was used to determine external dose rates from the 41Ar 

and inhalation intake estimates for the tritium.

At the fenceline location with the highest dose from gaseous effluents, the 

average annual dose to a person for the entire year (8,760 hours) was estimated 
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to be 4.2 mrem from 41Ar during the years of reactor operation. An offsite worker 

who worked full time at this location would not have been exposed for more than 

2,080 hr/yr, which would result in a submersion dose of about 1 mrem/yr. 

At the fenceline location with the highest concentration of tritium effluents, the 

average annual intake of tritium to a person for the entire year (8,760 hours) was 

estimated to be about 2.9 μCi/yr during the years of reactor operation. An offsite 

worker who worked full time at this location would not have been exposed for 

more than 2,080 hr/yr, which would result in an intake of tritium of about 

0.7 μCi/yr or 2,700 pCi/d. [Emphasis added.] 

SC&A’s Comments and Findings 

SC&A reviewed the referenced annual environmental reports, including the first, Environmental 

Monitoring at Ames Laboratory: Calendar Year 1974 (Voss 1975). Contrary to statements 

contained in Section 4.3 of the Ames Site Profile (and cited above), Voss (1975) provided the 

following statements and data:

From Section B. Environmental (pp. 17 and 18 of Voss 1975): 

Air samples are collected from two different locations at the Ames Laboratory on 

a daily (except weekends) basis for the purpose of monitoring the particulate 

radioactivity content of the atmosphere. The sites are located at the ALRR 

weather tower site and the roof of Spedding Hall. . . . The specific isotopes for 

which the filter papers are examined are: Be-7, Ce-144, Cs-137, Nb-95, Ru-106, 

plus any other unknown which might be observed. [Emphasis added.] 

Exhibits 4-4 and 4-5 identify the two air sampling locations as: 1A for the Weather Tower

location, which is about 500 feet from the ALRR, and 2A for Spedding Hall, which is just 

beyond the 1-mile radius of the ALRR.

Summary data for airborne activity levels for these two sampling locations are cited in Tables 7 

and 8 of Voss (1975) and reproduced herein as Exhibit 4-6. The data imply that at Site 2a 

(Spedding Hall), which is more than 1 mile from the ALRR, air concentrations were 

substantially higher than at the 1A location within the fenceline perimeter of the ALRR.
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Exhibit 4-4. Air Sampling Locations for 1A for the Weather Tower 
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Exhibit 4-5. Air Sampling Locations for 2A for Spedding Hall 
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Exhibit 4-6. Summary Data for Airborne Activity Levels for These Two Sampling 

Locations are Cited in Tables 7 and 8 of Voss (1975) 

From Section C. Impact (p. 26 of Voss 1975): 

From the effluent data it has been shown that the contribution to the 

environmental radioactivity in air from Ames Laboratory operations consisted 

principally of Ar-41 and tritium. 

Applying principles of meteorological diffusion to the stack effluent . . . the 

[following] estimates have been made at the exclusion fence:
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Individual dose at Fence Line for 1974 

Radionuclide Millirem (max) Millirem (Avg)

Ar-41 2.86 2.15

H-3 (tritium) 0.05 0.04

TOTAL 2.91 2.19

Finding #6: Statements in Section 4.3 of the Ames Site Profile are factually incorrect. For all 

years for which Voss reported environmental sampling data (1974, 1975, 1976), there were two

sampling sites that provided data in behalf of air concentrations and corresponding dose 

estimates.

Observation #1: Doses derived by NIOSH are lower than those reported by Voss. Admittedly, 

both sets of doses are small, which makes these differences of limited significance.

4.1 ENVIRONMENTAL DOSES FROM RESEARCH AND DEVELOPMENT

FACILITIES (1942–PRESENT)

NIOSH identified a total of seven facilities as R&D facilities that are located on the main campus 

of ISU. In behalf of these facilities, NIOSH stated the following:

U and Th Exposures 

. . . there was no monitoring of radiation exposure or contamination of the 

personnel or environmental areas around and among these facilities. As research 

facilities, the quantities of radioactive materials involved in the R&D work were 

small compared to the production facilities. 

. . . Principal sources would have been uranium, thorium, and fission products

from the hot canyon/hot cell in the Research Building. Because of the smaller 

amounts of radioactive materials in the R&D facilities in comparison with those 

in the production facilities, the releases from the R&D facilities were assumed to 

be one one-hundredth of the releases from the production facilities. That 

assumption resulted in daily environmental intakes of 5 × 10-2 and 7 × 10-4 pCi/d 

for uranium and thorium, respectively. . . . for workers exposed around the R&D 

facilities, a daily intake of 5 × 10-2 pCi of 234U and 7 × 10-4 pCi each of 232Th, 

228Ra, and 228Th . . . [Emphasis added.] 

Exposures to Fission Products 

A hot laboratory was operated in the Chemistry Building, but was replaced in 

1951 by a “hot canyon/hot cell” in the Research Building. In the 1940s, the hot 

laboratory was used to study extraction of plutonium from irradiated uranium by 

means of ion exchange columns. 
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. . . The uranium and plutonium were separated from one another and from the 

fission products using 1 kg samples of uranium, from the pile, which had an 

activity of 5 curies.

Releases were estimated from this operation by making the following assumptions

(see Bihl 2006 for details of the calculation): 

• A total annual throughput of the laboratory of 50 Ci/yr 

• An airborne fraction of 0.002 for boiling liquids 

• Filtration efficiency for average particle sizes of 99.5% [high-efficiency 

particulate air (HEPA) filters were just being developed during this 

period] 

These assumptions produce a total release of fission products of 5 × 108 pCi/yr.

Using the least dispersive approach recommended by the National Council on 

Radiation Protection and Measurements (NCRP) in Publication 123 (NCRP 

1996), the ground-level annual average air concentration would have been 

13.2 pCi/m3. Using the inhalation rate of 2,400 m3/yr and converting to a daily 

intake results in 87 pCi/d. 

Using the recommended fission product ratios for 180-day cooled fuel from 

Fission and Activation Product Assignment for Internal Dose-Related Gross Beta 

and Gross Gamma Analyses ([ORAUT 2007b]), an 87-pCi/d intake of fission 

products is assigned to specific radionuclides as listed in Table 4-2. 
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Table 4-2. Annual environmental fission product intakes from the hot laboratory 

in the Chemistry Building (1943–1981) 

Radionuclide Relative fraction Intake (pCi/d)

Ce-141 0.0221 1.92

Ce-144 0.2191 19.1

Cs-134 0.0054 0.470

Cs-137 0.0208 1.81

Eu-155 0.0014 0.122

Fe-55 0.0172 1.50

Nb-95 0.2492 21.7

Pm-147 0.0546 4.75

Ru-103 0.0321 2.79

Ru-106 0.0844 7.34

Sr-89 0.0558 4.85

Sr-90 0.0157 1.37

Y-91 0.0911 7.93

Zr-95 0.1311 11.4

Because maximizing assumptions were used for most of the parameters in this 

analysis, the distribution is an upper bound (constant). [Emphasis added.] 

SC&A’s Comments and Findings Pertaining to Environmental Exposures from R&D Activities 

Given the paucity of empirical environmental monitoring data, NIOSH’s decision to employ 

surrogate data and models that are based on assumptions/extrapolation is commendable, as long 

as the resultant estimates of external doses and intakes are fundamentally sound and favor the 

claimants.

SC&A’s review of Section 4.4 of the Ames Site Profile identified findings pertaining to 

(1) intakes of U and Th, and (2) intakes of fission products, as explained below. 

Environmental Intakes of U and Th. As quoted above, NIOSH twice states that “. . . as research 

facilities, the quantities of radioactive materials involved in the R&D work were small compared 

to the production facilities.” 

Among the seven facilities identified as R&D facilities is Wilhelm Hall (formerly the 

Metallurgy Building). As described in Section 2.2.2 of the Site Profile (and briefly discussed in 

Section 3.2 of this report), Wilhelm Hall was the principal facility for the production of 

thorium that also experienced numerous blowouts. Environmental releases during the 

production periods and blowouts undoubtedly resulted in a steady buildup of Th-232/-228 and 

Ra-228 until the end of 1953. Table 4-7 of the Site Profile identifies environmental intakes 

during this time (i.e., 1943–1953) of 0.07 pCi/d for each of the three radionuclides. 

The inhalation intake of 0.07 pCi/d would correspond to the combined air concentration 

representing the (1) continuous airborne releases from Wilhelm Hall as the operating research 

facility and (2) the resuspension of past ground contamination representing years of production. 

Thus, the transition from operational to R&D status in 1953 to 1954 and the corresponding 

100-fold reduction of intake from 0.07 pCi/d to 0.0007 pCi/d for the three nuclides does not

account for the long-term persistence of these nuclides as ground contaminants and their 
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resuspension. [Note, for indoor environments, NIOSH defines the transition from facility 

operation to post-operational time periods by means of a depletion factor as given in ORAUTOTIB-0070 (ORAUT 2012b).] 

Inspection of Table 4-7 of the Ames Site Profile shows the identical “instantaneous” 100-fold 

reduction of U intakes from 5 pCi/d to 0.05 pCi/d during the transition from 1953 and 1954, 

respectively.

Finding #7: The nearly “instantaneous” 100-fold reduction of U and Th environmental intakes 

that represent the transition of the uranium and thorium metal production facilities at the end of 

1953 to R&D facilities in 1954, as defined in Table 4.7, are improperly modeled. Also not 

included in the model are the contribution of blowouts to environmental contamination and the 

persistence of these radionuclides in the environment post-1953. 

Environmental Intakes of Fission Products. Estimates of environmental intakes from the 

operation of the Hot Laboratory as defined in Table 4-2 of the Site Profile were principally 

based on five modeled parameters. The only parameter that was based on documented 

information involved the quoted statement taken from page 40 of Fulmer (1947): 

A hot laboratory, capable of handling 5 curies through the adsorption process, 

was designed and built. The method proved successful in a number of runs. The 

uranium and plutonium were separated from one another and from the fission 

products using 1 kg samples of uranium from the pile, which had an activity of 

5 curies. (Fulmer 1947) [Emphasis added.] 

The remaining parameters used in the derivation of environmental intakes of fission products 

were based on assumptions stated in a memorandum authored by Bihl 2006 (Subject: 

“Estimated Releases from the Hot Laboratory in Ames Chemistry Building”).

Enclosed herein as Appendix C is the Bihl 2006 memo, which provides the following assumed 

parameters: 

(1) An annual throughput of 50 pCi/y (or about 10 kg of uranium from the pile) 

(2) An airborne release fraction of 0.002 

(3) The hot lab air-exhaust was filtered with an efficiency of 99.5% for all particle sizes

(4) An air concentration that is based on the NCRP Report 123 (NCRP 1996) model for the 

Atmospheric Screening Level I: Vent Air (which includes the default value of 0.3 m3/s 

exhaust ventilation rate)

Justification for the assumed annual throughput of 50 Ci fission products and fission-product 

release fraction of 0.002 was based on the following statements: 

Since this was an experimental lab, not a production facility, it was assumed that 

the throughput was 10 times the maximum inventory, or 50 Ci/yr. [Emphasis 

added.] 
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And: 

It was assumed due to activities in the hot lab described as experiments on 

techniques for separating the plutonium out of the irradiated fuel, that .002 of the 

inventory went airborne (from DOE Handbook 3010 worst case for boiling liquid, 

page 3-1 [DOE 1994]. 

Questions Pertaining to Annual Throughput, Release Fraction, and Filter Efficiency 

SC&A’s review of the 1947 report (Fulmer 1947) titled, History of the Ames Project Under the 

Manhattan District to December 31, 1946, suggests that (1) the throughput of 50 Ci/yr of fission 

products assumed by Bihl (2006) may have been considerably higher, and (2) the assumed 

airborne fraction of 0.002 for “worst case/boiling liquids” does not apply to the extraction 

method(s) used at Ames and may not represent the “worse case.”

Enclosed herein as Appendix D are pages 36 through 42 of the Fulmer (1947) report, which 

provide a description of the dry fluoride process used at Ames for the separation of plutonium 

from highly volatile fission products and uranium (see pages 38–40).

Regarding annual throughput quantities, Fulmer (1947) states the following (Appendix D, 

bottom of page 40):

A hot laboratory, capable of handling 5 curies through the adsorption process, 

was designed and built . . . 

After appreciable amounts of plutonium became available from the piles it 

appeared that it would have to be obtained in the metallic state and extremely free 

from light element impurities, if it was to be used for weapons. An extensive

“purity” program was set up in cooperation with the various sites and the Ames 

Project took part in this program. [Emphasis added.] 

Don Bihl’s unsupported assumption that the airborne release fraction of fission products was 

subject to a filter with an efficiency of “99.5% for all particle sizes” (before release to the 

environment) must be questioned in context with statements made by Dr. During 

an interview with Dr. Makhijani (SC&A), which included questions of his involvement in the 

plutonium separation at the Ames Laboratory, Dr. shared the following comments:

Arjun: Could you tell me about the plutonium separation research? 

Dr. We received uranium metal we made in our laboratory. We made tons 

of it.

Arjun: That was non-irradiated material. 

Dr. Yes. It was irradiated in Chicago. We would take some of those 

irradiated metal slugs and dissolve them and extract out the fission products and 

separate them to prepare the technique for isolating the plutonium from it. There 

were others in the country doing separation research also: Berkeley, Oak Ridge 
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and maybe some at Los Alamos. I went to the Bureau of Standards in DC and 

they had a small plutonium research program going. Then I went to Columbia 

where they had leftovers from the time Fermi was there. There was a small 

program at MIT. . . . 

Arjun: You did not have glove boxes when you worked with irradiated material? 

Dr. We had crude devices – a hood with a stream of air. We knew better 

than to breathe that stuff. [Emphasis added.] 

Lastly, model parameters assumed by Bihl (2006) for deriving environmental intakes of fission 

products (described in Section 4.4) should also be compared to the model used by NIOSH in 

Section 5.4.1 of the Ames Site Profile. Section 5.4.1, “Fission Product Intakes from Early Fuel 

Research,” derives worker intakes within the hot laboratory by means of a model described in 

NUREG-1400, Air Sampling in the Workplace (Hickey et al. 1993). The equation from 

NUREG-1400 is based on the following:

I = Q × 10-6 × R × C × D

where

I = intake

Q = source term release for 1 year = assumed to be 50 Ci

R = release fraction = 0.01

C = confinement factor = 0.1 assuming material was handled in some containment 

D = dispersibility factor = 10 for heating or chemical reactions

A comparison of parameters used by Bihl (2006) for modeling environmental intakes versus 

those defined in NUREG-1400 (Hickey et al. 1993) and selected for worker intakes within the 

hot laboratory identify (1) a 5-fold difference for the release fraction (i.e., 0.01 versus 0.002) and 

(2) a 20-fold difference in the “confinement” factor (i.e., 0.1 versus the 0.005% filter failure for 

particulate removal).

Finding #8: Environmental intakes cited in Table 4-2 are based on unsupported assumptions 

and model parameters, which moreover are inconsistent with parameter values used to model 

worker intakes inside the hot laboratory described in Section 5.0 of the TBD. 

4.2 SIGNIFICANT ENVIRONMENTAL EVENT

Regarding significant environmental releases/exposures, NIOSH limited its discussion to the 

following event: 

The only significant environmental event in the history of the Ames Laboratory 

was the release to the environment from operations that occurred from July 1951 

through August 1952. . . . 

. . . Most Ames Laboratory workers were not exposed to the radioactive materials 

released during this event and were not involved in responding to the event. . . . 
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Thus, no additional dose is recommended for occupational environmental dose 

for any workers. [Emphasis added.] 

These statements conflict with earlier statements contained in Section 2.3 of the Ames TBD that 

include the following: 

There were frequent small explosions and fires associated with the uranium and 

thorium production operations (Payne 1992) cited as many as six small fires in a 

single day; these fires contributed to work-area contamination and potential 

airborne radioactive material exposures. No records were found to indicate that 

air sampling or contamination control was associated with these fires. [Emphasis 

added.] 

Additionally, NIOSH’s limited reference to Payne (1992) understates the magnitude of these 

events and their contribution to environmental releases and worker exposures that involved fires 

and/or explosions during the reduction phase of UF4 and ThF4 to metal and subsequent 

grinding/machining of U and Th ingots. 

SC&A’s awareness of these discrete radiological events with a high potential for significant 

radiation exposures at the Ames Laboratory were prompted by a two-volume document that 

represents a doctoral dissertation authored by Carolyn Stilts Payne and submitted to the Graduate 

faculty of ISU in 1992. Part 1 of the dissertation is titled, The Ames Project: Creation, 

Organization, and Purposes of the Ames Project; and Part 2: Issues of Administration. It should 

be noted that Dr. Payne’s thesis was accepted by the Graduate Committee and is archived in the 

U.S. Library of Congress. 

At the time of the Ames Project, little was known about the behavior and properties of materials 

and the chemical processes employed in the reduction of UF4 and ThF4 to pure metal biscuits. 

The reduction reaction was highly exothermic, in which internal temperatures reached levels 

well above the 1,500oC melting point of the steel container. Thus, it was critical that the 

refractor liner, which separated the reactants from the steel container, was not breached. As 

noted below, the use of wet material and/or improper lining of the bomb retorts resulted in 

numerous fires and explosions. 

In her dissertation, Dr. Payne provides several accounts of discrete radiological events, as 

summarized below: 

Mr. Premo Chiotti was working with Dr. Wilhelm and me [i.e., Dr. F. Spedding]

on the reduction of thorium fluoride to thorium metal. Mr. Chiotti was adding a 

booster to the reaction in a room a few doors down the hall from my office. 

Suddenly there was a terrific explosion which blew out several of the windows in 

the front of the chemistry building. When I came out of my office to see what had 

happened, the corridor was filled with dust about six feet above the floor to the 

ceiling. I was relieved to see that Mr. Chiotti had not been injured, but he looked 

very dazed and was pacing up and down the corridor. As I passed him, I heard 

him muttering, “I must have misplaced that decimal point, I must have misplaced 

that decimal point.” (Ref. 324) 
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. . . Improper handling or lack of attention to properly lining the bomb retorts 

could cause blowout problems when the uranium reaction came into contact with 

the steel or iron in the bomb containers. . . . Some days that was quite a chore; 

there were at least six explosions in one day because some wet raw lime being 

mixed in the bomb retort containers adversely affected the reduction experiment. 

(Ref. 267) . . . 

Once an explosion blew out the south wall of Little Ankeny in the early hours of 

the morning; by then explosions were so commonplace that the workers went 

outside and pushed the wall back in as far as they could . . . 

Incidentally, that was the day that several secretaries threatened to resign and 

one Army officer received a rather suspicious wound. Secretaries, who were at 

an office attached to the production plant, had to pass through the firing pit 

area in order to get outside the building. After that series of explosions, they 

were wary of staying any longer in a potentially dangerous work environment. 

Spedding, however, convinced all but two of them to stay after he promised to 

strengthen the wall between the office and the operations area and to cut a door 

to the outside directly from their office. That same day Major H.A. Savigny, an 

Army officer who also happened to be the Area Engineer came to investigate 

the problem after the third explosion. While he was there, another explosion 

occurred, and, of course, he immediately ran for the door. As he was talking to 

someone a few moments later, he suddenly grabbed his leg, and a small piece of 

metal fell from a burned hole in the seat of his pants. Others, however, thought it 

might be somewhat hard to justify his “bravery” since it was apparent what he 

was doing when he was injured. (Ref. 268) [Emphasis added.] 

. . . Fires were also a danger at several steps in the process. Magnesium could 

shoot a flame several feet in length sometimes setting anything in its path on fire. 

Until the proper insulation techniques were learned, uranium cutting or 

machining caused fires when the cutting blade struck such a hard metal. 

Controlling these special chemical fires with lime or graphite became a common 

practice that every worker had to learn. (Ref. 365). [Emphasis added.] 

Occasionally, more than plant security was threatened by secrecy. Because the 

chemicals were volatile, frequent fires erupted. Since the Ames fire department 

could not come into the buildings that housed the production plant or the 

research activities because of secrecy requirements, the College allowed the 

firemen and equipment to come, but remain outside in the event a fire went out of 

control. Luckily, the workman [sic] were always able to use the lime and 

powdered graphite around the production building to squelch any flames (Ref. 

267). [Emphasis added.]

The above-cited references in Dr. Payne’s thesis correspond to the following sources: 

Ref. 267 – Kooser, 8; Frank H. Spedding. “Explosions,” Spedding Manuscript, 4-5; 

Daane, Spedding. Wilhelm Interview, 1967, 25. 
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Ref. 324 – Frank Spedding, “Humorous Story Concerning Explosions and Education,” 

Spedding Manuscript, 2. 

Ref. 365 – Frank Spedding, interview with Hacker 1980, 18-19; Frank Spedding, “The 

Day the Wall Blew Out of Little Ankeny,” Spedding Manuscript; Frank Spedding, 

“Explosions,” Spedding Manuscript. 

Ref. 268 – Frank Spedding. “The Green Hornet,” Spedding Manuscript, 3-4. The story 

was also repeated in varying detail in the following sources: Adolf Voigt interview with 

the author 1990, 6; Spedding, Wilhelm, Daane interview 1967, 15–16. 

The limited role of the Ames fire department and the response of secretaries were acknowledged 

and referenced to in cartoons that were illustrated in the local newspaper, as shown in 

Figures 4-1 and 4-2. 

Figure 4-1. Cartoon about the Fires in the Reduction and Casting Processes and 

the Role of the Local Firemen
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Figure 4-2. Cartoon about Frequent Explosions and Keeping Secretarial Staff

on the Ames Project

Finding #9: U and Th blowouts represent significant environmental events that should be 

included in Section 4.5 of the Ames TBD for the assessment of environmental exposures. 

Numerous interviews with and anecdotal accounts by Dr. Frank Spedding, Director of the Ames 

Project, as well as other coworkers, consistently describe bomb explosions and fires as 

commonplace, routine events during the years of the Ames Project (see Appendix E, “Telephone 

Interview with Mr. ”).

Explosions and fires involved many kilograms of either uranium or thorium metal that released 

substantial quantities of radioactivity in the form of metal vapor and/or micro-particulates within 

the work area and environment. 

In summary, the absence of documentation/records pertaining to blowouts should not be used to 

dismiss these events as insignificant; on the contrary, the absence of formal documentation of 

these events and assessment of their radiological impacts on workers and the environment should 

serve as evidence of radiological standards and practices that were lax and poorly enforced, 

especially during the earlier years of the Ames Project.
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5.0 ESTIMATES OF OCCUPATIONAL INTERNAL DOSE

Section 5.0 of the Ames Laboratory Site Profile states that radionuclides of interest for internal 

dose include uranium, thorium, tritium, and fission products. However, based on available 

information, NIOSH determined the following: 

(1) For the period August 13, 1942, through December 31, 1954, internal doses from the 

production and casting of thorium metal cannot be reconstructed

(2) For the period January 1, 1955, through December 31, 1970, internal doses from 

maintenance and renovation activities of the thorium production areas of Wilhelm Hall 

(aka the Metallurgy Building) cannot be determined for all workers at Ames Laboratory

(3) For the period January 1, 1955, through December 31, 1960, internal doses from 

radionuclides other than uranium (i.e., fission products) cannot be determined for any 

worker 

5.1 ESTIMATES OF URANIUM EXPOSURE FROM INHALATION AND 

INGESTION

Estimates of uranium intakes derived by NIOSH are given in Tables 5-1, 5-2, and 5-3 of the 

Ames Laboratory Site Profile. Tables 5-1 and 5-2 identify intakes for personnel assigned to the 

Chemistry Building and Annex 1, respectively, and were based on data cited in Christofano 

and Harris (1960). Table 5-3 provides data for uranium scrap recovery at the Annex 2, which is 

based on data from Battelle (2011). For convenience to the reader, these tables have been 

reproduced below: 

Table 5-1. Chemistry Building Uranium Intakes (pCi/d)

Period Inhalation Ingestion

Aug 1942–December 1953 8.5a,b 0.09b

a. No data were available for determination of intakes in the Chemistry Building; therefore, it was 

assumed that research activities would have one-hundredth the intake of production activities, since 

uranium metal production was moved to the Physical Chemistry Annex 1.

b. Values are for workers assumed to work in research or production full time. For supervisors, assume

one-quarter of the intake; for all other employees (clerical, janitorial, security, etc.), assume one-tenth of 

the supervisor’s intake. 

Table 5-2. Physical Chemistry Annex 1 Uranium Intakes (pCi/d)

Period Inhalation Ingestion

Aug 1942–December 1945 853a 8.7a

a. Values are for workers assumed to work in research or production full time. For supervisors, assume

one-quarter of the intake; for all other employees (clerical, janitorial, security, etc.), assume one-tenth of 

the supervisor’s intake. 
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Table 5-3. Physical Chemistry Annex 2 Uranium Intakes (pCi/d)

Period Inhalation Ingestion

January 1942–December 1950 6,061a 124 a

January 1951–December 1953 5,556a 114a

a. Values are for workers assumed to work in research or production full time. For supervisors, 

assume one-quarter of the intake; for all other employees (clerical, janitorial, security, etc.), 

assume one-tenth of the supervisor’s intake.

In support of these estimated uranium intakes, NIOSH stated the following: 

Because it is not clear if there were clerical, janitorial, or nontechnical personnel 

and other types of researchers working in these buildings, and it is not known

what precautions might have been taken for contamination control, it can be 

assumed that all individuals who worked in the buildings had some potential for 

exposure to uranium. 

The data in Tables 5-1 and 5-2 were derived from data in Christofano and 

Harris (1960). In Christofano and Harris (1960), there is a description of the 

process for metal reduction that is similar to the process used at Ames 

Laboratory for production of uranium metal (Fulmer 1947). The primary 

difference appears to be that at Ames Laboratory the process used granulated 

calcium metal and at AWE sites the process used magnesium. Fulmer (1947) 

describes the process using magnesium, and it appears to be similar enough to be 

representative of the intakes at Ames Laboratory. [Emphasis added.] 

. . . The intakes in Tables 5-1, 5-2, and 5-3 were compared to the few actual 

bioassay results found for workers in approximately the same period. Chapter 7 

in Stone (1951), “Uranium Excretion Studies,” provided data from a series of 

uranium bioassays obtained from Ames Laboratory workers in 1944 and 1945. Of 

special interest was a series of samples from the supposedly highest exposed 

worker at Ames Laboratory and samples from the most highly exposed group of 

workers at the Laboratory (21 samples from 11 workers). . . The average 

bioassay result for the group of highest exposed workers was 75 μg/L. Assuming 

chronic intake for 1 year before the bioassay, the estimated intakes were: 

• Absorption type F: 390 μg/d, 260 pCi/d 

• Absorption type M: 1,670 μg/d, 1,100 pCi/d 

• Absorption type S: 45,400 μg/d, 31,000 pCi/d. [Emphasis added.]

SC&A Comments

SC&A reviewed the modeled data representing Tables 5-1, 5-2, and 5-3 in context with the 

limited bioassay data referenced by NIOSH [i.e., Chapter 7 in Stone 1951; also referenced was 

Ferretti et al. 1951] as well as other data that include toxicological data and spot air sampling 

data. 

Assessment of Tables 5-1, 5-2, and 5-3 from the Ames TBD. Estimates of uranium intakes at 

each of the three facilities are not only based on surrogate data, but their uncertainty is further 
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enhanced by multiple layers of assumptions that are purely speculative, as illustrated in the 

following example:

(1) Data in Table 5-2 are based on surrogate data defined in Christofano and Harris (1960) for 

production workers at Annex 1. 

(2) As defined in footnote a of Table 5-1, intakes at the Chemistry Building are defined for 

full-time researchers and are “assumed” at 1/100th the intake of full-time production 

workers at Annex 1 defined in Table 5-2 (or 853 pCi/d/100 = 8.5 pCi/d). 

(3) For supervisors at the Chemistry Building, daily intakes are assumed at 25% of the fulltime research or 8.5 pCi/d/4 = 2 pCi/d (see footnote “b” of Table 5-1); and for all other 

employees, daily intakes are assumed at one-tenth (1/10th) of the supervisor’s intake (or 

2 pCi/d/10 = 0.2 pCi/d. 

Similar reduced, fractional intakes for supervisors and all other employees are defined for 

Annex 1 and Annex 2. 

Assessment of Bioassay Data Reported by Ferretti et al. (1951). Between September 1943 and 

March 1945, a total of 48 workers at the Ames Laboratory were evaluated for urinary excretion 

of uranium that principally resulted from exposure to UF4 salt at the Annex 1 facility. To avoid 

contamination, urine sample collection involved the following protocol: 

Upon leaving work Saturday noon, the men were given a clean bottle enclosed 

within two large envelopes. They were instructed to remove the outer envelope at 

home after carefully washing their hands. The second envelope was to be opened 

after bathing Sunday evening or Monday morning. The urine sample was to be 

passed into the bottle after again washing the hands . . . [Emphasis added.] 

The 48 subjects were grouped by their supervisors into four groups that reflected the potential for 

uranium exposure. Group 1 was expected to be highest and Group 4 the lowest. Grouping was 

based on the following criteria: 

Those who were probably exposed to the greatest amount were classed as group 

1; those exposed to the next highest amount made up group 2; those with very 

little but continuous exposure constituted group 3; and those with only occasional 

incidental exposure formed group 4. [Emphasis added.] 

Data for the maximally exposed Group 1 are shown in Table 5-4 below. It should be noted that 

for the 11 individuals, there were 21 data points, which reflect some individuals who were 

assessed more than once at intervals of a few weeks or months. For example, case (worker) # 

was assessed times and case # was assessed times, with each having a maximum 

excretion value of μg/L. 

Case (worker) # was subjected to additional evaluation, since this individual was believed to 

have had more exposure than any other individual on the Ames Project. His exposure began in 

 and ended . Ten analyses made from 

ranged from μg to μg of uranium per liter. (Note: Case # of Group 1 most likely 
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represents the individual as referenced by 

, as well as by 

A summary of bioassay results for all 48 Ames workers are shown in Table 5-5. 

Table 5-4. Uranium Excretion in Personnel, Group 1

(Source: Ferretti et al. 1951) 

Sample Case Amount, μg/liter

1 1 40

2 1 96

3 2 52

4 3 86

5 3 50

6 4 100

7 4 44

8 4 70

9 4 200

10 5 123

11 5 96

12 5 74

13 6 84

14 6 200

15 6 73

16 7 48

17 7 40

18 8 29

19 9 25

20 10 12

21 11 31

— — 75 (avg)

Table 5-5. Uranium Concentrations among 48 Ames Workers 

(Source: Ferretti et al. 1951) 

Group No. No. of Subjects No. of Samples Avg. Urine Conc.

(μg/L)

Max. Urine Conc. 

(μg/L)

1 11 21 75 200

2 26 46 130

3 11

20

14 16 33

4 6 6 <5 7

Assessment of Toxicological Data. During this period (1943–1944), select workers were also 

evaluated by medical personnel who were concerned about the toxicological effects of uranium, 

fluorine, and magnesium on function. Analyses focused on sulfur, sugar, 

albumin, F+, and other ionic species in blood/urine. In a report dated June 1, 1944, by Samuel 

Schwartz, MD, analyses in behalf of individuals classified as being in the “heavy exposure” 
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group suggested values indicative of abnormal functions (Schwartz 1944). In his conclusions, 

Dr. Schwartz stated that:

In general, fortunately, the tests indicate less abnormality than I would have 

expected from the amount of exposure these men are getting. The one exception 

to this statement is the almost consistent elevation of serum sulfur which is

indicative of probably slight disfunction. function tests almost

uniformally normal. In only the heaviest exposure group is there significant 

change in metabolism. 

While these observations are highly suggestive of radiological impacts associated with uranium

exposure, the toxicological effects of uranium, as well as several other agents (including F+), 

cannot be ruled out. For this reason, non-radiometric analyses are of limited value to dose 

reconstruction. 

Air Sampling during Uranium Metal Production. Routine air sampling in the workplace can 

provide credible estimates of internal doses from the inhalation of airborne contaminants. This is 

especially true for breathing-zone air samples. SC&A’s review of available documents showed 

data for only 12 air samples taken in May, June, and July of 1943. However, among the 12 area 

spot-samples taken, only 6 specifically identified uranium as the analyte. Table 5-6 below 

identifies the results of the 6 uranium area air samples by dates, location, and work activity at the 

Annex 1 facility. 

Table 5-6. Uranium Air Concentrations associated with the Production of

Uranium Metal at Annex 1 

Date Work Location Operation Air Concentration

(μg/m3) (pCi/m3)

6/16/1943 Near Jolter Bomb loading 53.3 36

6/16/1943 Near Micropulverizer Grinding (lime, slo-set) 1,080 738

6/16/1943 Near Riffle Mg processing 85 58

7/10/1943 Sample Room Metal grinding 63.5 43

7/12/1943 Cut-off Room Metal cutting 420 328

7/12/1943 Slag Room Opening bomb 153 105

The range for area air concentrations associated with the routine production of uranium metal at 

Annex 1 varied from 36.4 pCi/m3

 to 738 pCi/m3 with an average of 218 pCi/m3. On the 

unconservative assumption that area air-sampling values approximate breathing zone air 

concentrations, the average daily intake is 2,100 pCi, with a maximum value of about 7,100 pCi 

for grinding operation. These two values should be compared to Table 5-2 of the Ames TBD, 

which shows a maximum value of 853 pCi/d. 

SC&A Findings 

Uranium intakes were defined in Tables 5-1, 5-2, and 5-3 for three facilities (i.e., Chemistry, 

Building, Annex 1, and Annex 2, respectively) for workers who were assumed to be 

“maximally” exposed. Based on job descriptions (e.g., supervisors, clerical, janitorial, security, 

etc.), intakes are assumed to be 0.25 and 0.025, respectively of intake values cited in each of the 
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three tables. NIOSH based these values on surrogate data derived from data in Christofano and 

Harris (1960), Battelle (2011), and multiple levels of unsupported assumptions. 

NIOSH sought validation for these data by comparing intakes in Tables 5-1, 5-2, and 5-3 of the 

Ames TBD to the few actual bioassay results reported by Ferretti et al. in Chapter 7 in Stone 

(1951). For comparison, bioassay data selected by NIOSH involved the average urine excretion 

value of 75 μg/L (or 51.225 pCi/L) for the maximally exposed workers designated as Group 1. 

IMBA runs yielded the following intakes: 

• Absorption Type F: 260 pCi/d 

• Absorption Type M: 1,100 pCi/d 

• Absorption Type S: 31,000 pCi/d 

Based on these results, NIOSH stated:

If the geometric mean of the data is used, the estimated intakes are smaller . . . 

For type M, this range is still consistent with the intakes in Tables 5-1, 5-2, and 

5-3. [Emphasis added.] 

Uranium intake values defined in Tables 5-1, 5-2, and 5-3 of the Ames TBD are re-introduced 

with other data in Table 5-8, “Default intakes for Ames Laboratory (if no bioassay results are 

available),” in the Ames Site Profile. Findings cited below reference data provided in Table 5-8 

of the Ames Site Profile, which is reproduced herein as Table 5-7. 

Finding #10. Available empirical bioassay and air-sampling data for Annex 1 workers are 

substantially higher than modeled/surrogate data assigned by NIOSH. 

For absorption Type M, the average excretion concentration value of 75 μg/L (or 51.225 pCi/L) 

yields an intake of 1,100 pCi/d. This value is 29% higher than NIOSH’s assumed value of 

853 pCi/d for Annex 1 production workers, as given in Table 5-2 of the Ames TBD.

Equally, empirical air sampling data cited in Table 5-6 above would yield an average intake of 

2,100 pCi/d and a maximum intake of over 7,000 pCi/d for Annex 1 workers exposed to various 

chemical forms of uranium.

Finding #11: NIOSH further minimized the intake value of 853 pCi/d for Annex 1 production 

workers by assigning the “distribution” as a constant (see Table 5-7 below).

By assigning a “constant” distribution, NIOSH implied that the 75 μg/L (or 51.225 pCi/L) value 

was a maximal excretion value, when in fact it was the average excretion value for Group 1 (see 

Tables 5-4 and 5-5 above). 

Finding #12: Default intake rates defined in Column 6 of Tale 5-7 below are improper for 

absorption Types F or S.

It is technically incorrect for an intake value that represents (or is assumed to represent) 

absorption Type M to be used for absorption Types F or S. For example, NIOSH calculated an 

intake of 31,000 pCi/d in behalf of the average excretion value of 75 μg/L (or 51.225 pCi/L) 
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excretion value reported by Ferretti et al. (1951). Based on guidance provided in Table 5-8 

(Exhibit 5-1), the dose reconstructor would, nevertheless, be expected to select the 853 pCi/d 

intake value for absorption Type S in behalf of an Annex 1 production worker. 

Table 5-7. Default intakes for Ames Laboratory 

(if no bioassay results are available)

Job Category

or task/Building

Dose calculation parameters IREP input parameters

Period Material Mode Absorption

Type of f1 pCi/d Distribution Type

Parameter 

1

Researcher/Chemistry 

Buildinga

Aug 1942–

Dec 1953

Natural 

uranium

Chronic 

inhalation

F, M, or S 8.5 Constant Dose 

Researcher/Chemistry 

Buildinga

Aug 1942–

Dec 1953

Natural 

uranium 

Chronic 

ingestion

0.02 with F, M; 

0.002 with S

0.09 Constant Dose 

All employees in 

Chemistry Building

Jan 1954–

May 1976 

Natural 

uranium 

Chronic 

inhalation

F, M, or S 4.1 Constant Dose 

All employees in 

Chemistry Building

Jan 1954–

May 1976 

Natural 

uranium 

Chronic 

ingestion

0.02 with F, M; 

0.002 with S

0.68 Constant Dose 

Researcher in hot 

lab/Chemistry Building

1943–1951 Fission 

products

Chronic 

inhalation

Use most 

favorable to the 

claimant, for 

Sr-90 use F

See Table 

5-7 

Constant Dose 

Researcher, production 

technician, anyone 

involved daily with 

uranium in Annex 1a 

Aug 1942–

Aug 1945

Natural 

uranium

Chronic 

inhalation

F, M, or S 853 Constant Dose 

Researcher, production 

technician, anyone 

involved daily with 

uranium in Annex 1a 

Aug 1942–

Aug 1945

Natural 

uranium

Chronic 

ingestion

0.02 with F, M; 

0.002 with S 

8.7 Constant Dose 

All employees in Annex 

1 

Sep 1945–

Dec 1953 

Natural 

uranium 

Chronic 

inhalation 

F, M, or S 17.5 Constant Dose 

All employees in Annex 

1 

Sept 1945–

Dec 1953

Natural 

uranium

Chronic 

ingestion 

0.02 with F, M; 

0.002 with S 

1.6 Constant Dose 

Researcher, production 

technician, anyone 

involved daily with 

uranium in Annex 2a

Jan1944–

Dec 1953

Natural 

uranium

Chronic 

inhalation

F, M, or S 6,061 

through 

1950, 

5,556 

from 1951 

to 1953

Constant Dose 

Researcher, production 

technician, anyone 

involved daily with 

uranium in Annex 2a

Jan1944–

Dec 1953

Natural 

uranium

Chronic 

ingestion

0.02 with F, M; 

0.002 with S

124 

through 

1950; 114 

from 1951 

to 1953

Constant Dose 

All employees in Annex 

2 

Jan 1954–

1972 

Natural 

uranium 

Chronic 

inhalation 

F, M, or S 124.7 Constant Dose 

All employees in Annex 

2 

Jan 1954–

1972 

Natural 

uranium 

Chronic 

ingestion 

0.02 with F, M; 

0.002 with S

11.2 Constant Dose 

Anyone routinely in 

Wilhelm Hall 

(Metallurgy Building)

1955–present Th-232 Chronic 

inhalation

M or S See Table 

5-5 

Constant Dose 

Anyone routinely in 

Wilhelm Hall

1955–present Th-232 Chronic 

ingestion

5E-4 with M; 

2E-4 with S

See Table 

5-5 

Constant Dose 

Anyone routinely in 

Wilhelm Hall

1955–present Ra-228 Chronic 

inhalation

M See Table 

5-5 

Constant Dose 

Anyone routinely in 

Wilhelm Hall

1955–present Ra-228 Chronic 

ingestion

0.2 See Table 

5-5 

Constant Dose 
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Job Category

or task/Building

Dose calculation parameters IREP input parameters

Period Material Mode Absorption

Type of f1 pCi/d Distribution Type

Parameter 

1

Anyone routinely in 

Wilhelm Hall

1955–present Th-228 Chronic 

inhalation

M or S See Table 

5-5 

Constant Dose 

Anyone routinely in 

Wilhelm Hall

1955–present Th-228 Chronic 

ingestion

5E-4 with M; 

2E-4 with S

See Table 

5-5 

Constant Dose 

Reactor workers and 

D&D workers

1965–1981 Tritium Total of all 

modes

N/A N/A Lognormal, 

see Table 5-6 

for GSD

Dose; see 

Table 5-6 

Workers involved with 

D&D of reactor,

including former reactor 

workers

1978–1981 Co-60 or 

Zn-65 

Chronic 

inhalation

Type S 3,300 Constant Dose 

Workers involved with 

D&D of reactor, 

including former reactor 

workers

1978–1981 Co-60 or 

Zn-65 

Chronic 

ingestion

Type S 660 Constant Dose 

Anyone routinely in 

Applied Science Center

1982–present Tritium Total of all 

modes

N/A N/A Constant 8.6 

mrem/yr a

 Values are for workers assumed to work in research or production full time. For supervisors, assume 0.25 of the intake; for all 

other employees (clerical, janitorial, security, etc) assume one-tenth of the supervisor’s intake (0.025 of the intake in the table).

Finding #13: The scaling of uranium intake values based on (1) facility and (2) job function is 

without technical support and conflicts with statements given in the Ames Site Profile.

For example, NIOSH states that “. . . for workers involved in research . . . in the Chemistry 

Building, an exposure of one-tenth of the workers involved in the production operations is 

assumed . . .” Values for supervisors were assumed at 0.25 (or 1⁄4) of the intake of researchers/ 

production workers, and for all other employees (clerical, janitorial, security, etc.) assume 0.025 

(or 1/40th).

This rigid scaling of intakes based on location and job description imposes unreasonable burden 

on the dose reconstructors and conflicts with the following statements contained in Section 1.3 of 

the Site Profile:

NIOSH added classes to the SEC in 2006, 2007, and 2010 to cover three separate 

groups of employees based on work location and job description. While the 

classes added in 2006 and 2007 included specific workers performing specific 

tasks in designated buildings, the 2010 class determined that the information 

available about worker job description, work location, or movement about the 

site was insufficient to determine if an employee worked in the affected area(s). 

[Emphasis added.] 

Should data pertaining to job function become available, scaling factors that more closely 

resemble the ratios of excretion values reported by Ferretti et al. (1951) for Groups 1, 2, and 3 

should be considered (see Table 5-5 above). Based on group averages, intake ratios of 1.0, 0.6, 

and 0.2 are more likely to represent production workers, supervisors, and all others. 

For ingestion intakes of uranium, NIOSH stated that “. . . The rationale used in inhalation 

intakes for reduced fractions for other workers is applied to ingestion intakes as well.” Thus, 
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SC&A findings associated with inhaled intakes of uranium apply equally to ingestion intakes as 

well.

Finding #14: Although NIOSH briefly acknowledged the occurrence of “frequent fires and 

explosions” associated with the production of uranium metal, no attempt was made to assess 

potential intakes of these episodic events. Potential doses from uranium blowouts are discussed 

in combination with thorium blowouts in Section 5.7 below. 

5.2 RESUSPENSION DURING PERIOD WITH NO URANIUM OPERATIONS

To estimate exposure during non-operations for the Chemistry Building, NIOSH stated the 

following: 

. . . The daily intake rates for the Chemistry Building can be estimated by 

reducing the generic exposure estimate from ORAUT ([2006]) by a factor of 10 to 

account for the conclusion of the work, the standard laboratory precautions that 

were in place, and the production time at about 50% of full time in the Chemistry 

Building. [Emphasis added.] 

Finding #15: ORAUT (2006) referenced above for estimating non-operational intakes 

corresponds to ORAUT-OTIB-0004, Rev. 03, Technical Basis for Estimating the Maximum 

Plausible Dose to Workers at Atomic Weapons Employer Facilities. It should be noted that 

OTIB-0004 was canceled before Rev. 03 of the Ames Site Profile [ORAUT-TKBS-0055 

(ORAUT 2012a)] was issued. Moreover, the much higher intake values for inhalation and 

ingestion during non-operating years (i.e., 1954–1976) make no sense when compared to intake 

values for operating years (1942–1953), as given in Table 5-8 of the Ames TBD (see Table 5-7 

above) and briefly summarized below: 

For non-operating years (1954–1976): 

All Workers in Chemistry Building

• Inhalation of 4.1 pCi/d 

• Ingestion of 0.68 pCi/d 

For the operating years (1942–1953), intake for the maximally exposed Researcher

identifies:

• Inhalation of 8.5 pCi/d 

• Ingestion of 0.09 pCi/d 

Note: During the same operating years, Supervisors, and all others would be assigned 

the following intakes: 

Supervisor: 

• Inhalation: 8.5/4 = 2.1 pCi/d 

• Ingestion: 0.09/4 = 0.0225 pCi/d 
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All Others: 

• Inhalation: 8.5/40 = 0.2125 pCi/d

• Ingestion: 0.09/4 = 0.00225 pCi/d 

5.3 THORIUM EXPOSURE FROM THORIUM CONTAMINATION AFTER 1954 

The Ames Laboratory Site Profile restricted its assessment of thorium exposures to residual 

contamination following the production of 65 tons of thorium metal in 1954. This decision was 

based on the conclusion “. . . that it was not feasible to complete dose reconstruction for internal 

dose for thorium, plutonium, and thoron for 1942 through 1954 (NIOSH 2006) and, therefore, 

internal dose is not addressed here for those radionuclides during those years.” 

Inhalation intakes from residual contamination for years 1955 through 2010 are principally based 

on past survey data reported in a 1998 report (Hokel 1998 et al.) titled, An Assessment of the 

Causes, Mitigation Efforts, and Current Status of Th-232, U-238, and Beryllium Contamination 

in Wilhelm Hall at Ames Laboratory. 

NIOSH summarized survey data contained in Hokel et al. (1998) as follows: 

From Section 5.2 (pp. 39–41) 

. . . Starting in 1984 and continuing through the early 1990s, surveys were 

conducted in Wilhelm Hall to determine locations of contamination left from the 

early production years. This information is in Hokel et al. (1998). The following 

discussion using data from Hokel et al. and Klevin provides an estimate for 

intakes by workers in Wilhelm Hall from 1955 to the present. A summary of the 

air concentrations and daily inhalation and ingestion intakes is provided in 

Table 5-5. 

All the data in Hokel et al. (1998) were reviewed and considered. Much of the 

data was related to locations that were hard to access and considered not to be 

an inhalation issue. There was one set of data that had floor surveys made in 

1988, but these locations all had fixed activity, indicating that this was from beta 

radiation (see Appendix 6 of Hokel et al.). For this reason, the recommendation 

for assessing dose from thorium from 1954 through the present was provided. 

The accessible areas of the building, including rooms, air ducts, hallways, 

stairwells, transformer rooms, etc., were surveyed starting in 1984. The data in 

Hokel et al. present an overview of the survey results. In 1996, some 

measurements were made using an Alpha Continuous Air Monitor in the subbasement pipe tunnels and in large vertical void spaces in the stairwells. All of 

these results were less than background for thorium, thoron, or radon (Hokel et 

al. 1998). Therefore, the results used for this estimation are from a pipe tunnel 

survey that showed removable contamination on smears ranging from 

background (3 dpm) to 1,224 dpm. These numbers are high for generally 

accessible areas and with the possibility of the contamination becoming 

resuspended. Although other survey numbers in the report with removable 
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contamination are higher, they are in locations that are inaccessible (in a drain 

line), hard to reach (inside a drawer), or small (edge of a sink), or the 

contamination was fixed. [Emphasis added.] 

SC&A reviewed the Hokel et al. (1998) survey report for its credibility and use in assessing 

inhalation intakes for the years 1955 through 2010. Exhibit 5-1 corresponds to page 13 of Hokel 

et al. (1998) and identifies the following salient information: 

• The “Pipe Tunnel Special Surveys of East Tunnel” was conducted on November 15, 

1995, or more than 40 years after Wilhelm Hall was used for the production of thorium 

metal.

• The purpose of the “Special surveys” of the Pipe Tunnel was to test the effectiveness of 

the “water wash down method.” 

• The location of this survey (i.e., the pipe tunnel) has little to no relevance to areas of 

Wilhelm Hall where workers were engaged in the production of thorium metal (see 

photos #10 and #11 of Exhibit 5-1).

• The statement that “initial analyses showed removable contamination levels on the 

smears ranging from background levels (approximately 3 disintegrations per minute 

(dpm)) to 1,224 dpm.” (The obvious deficiency in these two contamination levels is the 

unit area that was smeared was not identified. It can only be assumed to be 100 cm2.) 

For deriving a “removable contamination” value, NIOSH adopted the “1,224 dpm” value cited in 

Exhibit 5-1; and due to the uncertainty regarding the surface area sampled, increased the value to 

2,000 dpm for an assumed sampling area of 100 cm2, as described in the Attribution and 

Annotation statement #19 of the Ames TBD.

For estimating thorium inhalation quantities at Wilhelm Hall on November 15, 1995, NIOSH 

employed the 2,000 dpm/100 cm2 as follows (p. 41 of the Ames Site Profile): 

A removable surface concentration of 2,000 dpm/100 cm2

 of thorium in 

equilibrium with its progeny was assumed. This means the 232Th activity was 

approximately 200 dpm/100 cm2. Applying a resuspension factor of 10-4. 

Air concentrationTh-232 = (200 dpm/100 cm2)(10-4/m)(100 x 1002) = 2 dpm/m3

The value of 2 dpm/m3 on November 15, 1995, when the survey of the pipe tunnel 

occurred, represents an upper bound. [Emphasis added.] 

For estimating the starting air concentration at the end of the production period (i.e., 1955), 

NIOSH stated the following (p. 41 of TBD): 

Because survey information in the building just after cessation of the thorium 

operations was not available, the Klevin data were used to represent air 

concentrations in 1955 with the caveats provided below: . . . 
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Reference to the “Klevin data” corresponds to a survey conducted by the AEC in 1952 and 

authored by Paul B. Klevin. This survey report titled, Ames Research Laboratory Occupational 

Exposure to Thorium and Beryllium, is enclosed herein as Appendix B. Data selected by NIOSH 

from Klevin (1952) involved average general air samples as given in Table III (page 11) with 

exclusion of Room 303 (Drying and Calcining Area) and the Seminar Room/(Lunch Room). 

Using the 95th percentile of the geometric distribution of remaining air concentration values cited 

in Table III of Klevin (1952), NIOSH calculated an air concentration of 479 dpm/m3 for airborne 

concentration at Wilhelm Hall in 1955. 
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Exhibit 5-1. Locations Selected by NIOSH for Determining

Removable Contamination Levels

(Source: Hokel et al. 1998, page 13) 
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From these two data points (representing air concentrations on January 1, 1955, and November 

15, 1995), NIOSH derived a removal rate (i.e., λ) value of 3.7 × 10-4/day or 0.134/yr that was 

used for estimating daily intakes (inhalation and ingestion) for years 1955 through 2010 as given 

in Table 5-5 of the TBD. For 1955, Table 5-5 recommends an air concentration of 

448 dpm/m3 for Th-232.

SC&A Comments and Findings 

NIOSH’s approach for modeling intakes from residual contamination during the non-operational 

period of 1955 through 2010 was based on two data points that were separated in time by 

14,929 days.

For November 15, 1995, the data point of 2 dpm/m3 of air represents a single adjusted smear 

sample taken in the East Pipe Tunnel, which is located in the sub-basement of Wilhelm Hall. 

Based on location, this smear sample has a limited relevance to those areas of Wilhelm Hall that 

were utilized for the production of thorium and resultant residual contamination levels during the 

non-operational period of 1955 through 2010. 

The second data point assigned to January 1, 1955, was derived from general air samples taken 

in March of 1952 (see Table III of Appendix B). These data define thorium air concentrations 

based on alpha activity for thorium that assumes equilibrium of Th-232 with Th-228. Thus, the 

95th percentile air concentration of 479 dpm/m3 assigned to Th-232 at t=0 by NIOSH is a factor 

of 2 too high. This error applies to all values defined in Table 5-5. 

Although the Klevin (1952) time-weighted air concentrations for workers were reviewed by 

NIOSH, these data were dismissed as not relevant (p. 41 of TBD): 

Klevin (1952) did a thorough survey during operations, including breathing-zone 

task-specific air concentrations, time-weighted air concentrations for various 

workers, and general room air concentrations. . . . 

The Klevin air concentrations for specific tasks during production and the timeweighted averages are not relevant for Wilhelm Hall after 1954. [Emphasis 

added.] 

Surprisingly, for the 22 workers assessed by Klevin (1952), their average time-weighted air 

concentration to thorium was 530 dpm/m3

. For Th-232, this would correspond to only 

275 dpm/m3

, which is slightly more than one-half the value of 479 dpm/m3 assumed by NIOSH. 

Additionally, a review of Appendix B identifies several other credible options by which the 

Klevin (1952) operational survey data in combination with ORAUT-OTIB-0070, Rev. 01, 

Dose Reconstruction during Residual Radioactive Periods at Atomic Weapons Employer 

Facilities (ORAUT 2012b), can be used to derive exposure estimates from residual 

contamination. 

Finding #16: NIOSH’s approach for deriving estimates of thorium intakes from residual 

contamination post-1954 does not make the best use of survey data reported by Klevin (1952) 

and use of ORAUT-OTIB-0070, Rev. 01 (ORAUT 2012b). 
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5.4 THORIUM EXPOSURES DURING OPERATIONAL PERIODS THAT WERE 

NOT CONSIDERED BY NIOSH

Justification for the decision not to consider/assess thorium exposure during the operational 

period of 1942 through 1954, which produced 65 tons of thorium, was explained in Section 1.3.1 

of the TBD, which states: 

NIOSH . . . found that the monitoring records, process descriptions, and source 

term data available [for thorium/plutonium and thoron (see Table 1-1)] are not 

sufficient to perform complete dose reconstructions . . . [Emphasis added.] 

The inverse of these statements and Table 1-1 of the TBD suggest that for uranium, a complete 

dose reconstruction can/will be performed using available monitoring records, process 

descriptions, and source term data. 

However, NIOSH’s method for deriving uranium, as evaluated by SC&A in Section 5.1 above, 

employed a combination of surrogate data [i.e., data derived from Christofano and Harris (1960); 

and Battelle (2007)] and layers of unsupported assumptions defined in footnotes assigned to 

Tables 5-1, 5-2, and 5-3. The relative merit by which NIOSH derived uranium exposures 

should, therefore, be compared to thorium data considered suitable for dose reconstruction, as 

discussed below. 

5.4.1 Thorium Bioassay Data 

Four datasets were found to contain bioassay data for thorium representing urine samples 

collected on the following dates: April 13, 1952; May 12, 1952; April 11, 1953; and May 11, 

1953. As discussed below, the significance of dates for these four datasets is their temporal

relationship to the AEC’s radiation survey conducted on March 18–21, 1952 (Klevin 1952). 

Enclosed herein as Appendix F are redacted copies of the four datasets, which identify sample 

dates, task(s) performed by each individual, and observed concentrations of thorium in urine 

samples. (Note: Datasets #1 and #2 report urine concentrations in the units of γ/Liter of urine, 

and datasets #3 and #4 in the units of γ/200 cc of urine). Table 5-8 provides summary data in 

behalf of the four bioassay datasets. Tasks which corresponded to the highest urine excretion 

values included calcining and hydrofluorination, metal reduction, final casting, and solution of 

Th nitrate (see Appendix F). At this time, the quantitative interpretation of thorium urine 

concentrations must await an understanding of the unit value of “γ,” based on the fact that the 

colorimetric analysis assumes that “γ” equates to microgram (μg).

Table 5-8. Summary of Urine Bioassay Data for Thorium 

(see Appendix F)

Set # Sampling Date No. of Samples Thorium Range

(γ/L)

Urine Conc. (γ/L) 

Average

1 4/13/1952 5 15–35 21

2 5/12/1952 15 10–80 23.7

3 4/13/1953 7 0–15 5.7

4 5/11/1953 15 0–90 13.7
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A relative comparison of thorium concentration values among the four sets identifies a marked 

reduction in exposure between sets #1 and #2 versus sets #3 and #4. Undoubtedly, this 

difference can be explained by the impacts of the radiological survey and resultant 

recommendations made by the AEC on March 18–21, 1952, but not issued as a report until July 

14, 1952 (Klevin 1952). 

As stated on page 3 of the 1952 Survey Report: 

This survey was made with the following objectives in mind: 

1. To gather data from which estimation of the daily weighted average exposure 

can be determined for the personnel working on the AEC project; 

2. To suggest the physical and procedural changes which should be made in 

order to correct excessive exposure. [Emphasis added.] 

AEC Recommendations. Pertaining to the second objective, the AEC audit team cited a total of 

36 recommendations (see pp. 10 through 13 of Appendix B), which were facility engineering 

controls for specific processes involving (1) thorium production, (2) calcining and 

hydrofluorination, (3) handling of thorium crude (ThF4), and (4) metal casting. AEC 

recommendations pertaining to procedural changes included the introduction of the most basic 

health physics practices and protocols for worker safety (see recommendations #29–#36). 

5.4.2 AEC Survey Data 

Independently or in combination with bioassay data summarized above, quantitative survey data 

reported by the AEC in 1952 for the Ames Laboratory provide key information that satisfies

regulatory requirements for dose reconstruction defined in §82.14 of 42 CFR 82. 

Among applicable data provided in the AEC Survey Report are the following: 

• Breathing Zone Air Samples that are facility-specific and task-specific for a total of 54 

operations that involved the production of thorium metal (see Table II and Figures #2 

through #8 in Appendix B).

• An Assessment of Daily Weighted Average Inhalation Exposures to Thorium/Thoron 

among 22 Ames workers representing a total of 15 different assigned tasks in the 

production of thorium metal (see Table I in Appendix B). 

• Average Air Concentrations for Thorium and Thoron Based on General Air Sampling. 

General air sampling was performed at discrete locations of Wilhelm Hall. Locations 

critical in the production of thorium included Rooms 203, 303, 307, and 33 (see Table III 

and Figures #2 through #8 in Appendix B).

• Location- and Task-Specific Smear Contamination and Dose Rate Data for Rooms 303, 

204, and 33 (see Table IV in Appendix B).
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5.4.3 Thorium Processes and Source Term Data 

In a 1947 report titled, History of the Ames Project under the Manhattan District to December 

31, 1946, E.I. Fulmer, Assistant Director of the Ames Project, provided a comprehensive 

summary of processes and source terms for thorium (Fulmer 1947). Relevant sections of the 

report include II, Section 1.4 – Production and Casting of Thorium Metal; II, Section 2 – 

Fabrication of Uranium and Thorium; II, Section 4.2 – Thorium Alloy Studies; and III, Section 4 

– Thorium Chemistry including purification of thorium compounds by liquid-liquid extraction. 

In Section 1.4 of the report, Fulmer provided the following information regarding the production 

of thorium metal.

Soon after the large scale bomb reduction of uranium was in successful 

operation, similar approaches were made on the reduction of thorium. In August, 

1943, attempts were made to reduce a number of thorium compounds in a bomb. 

The first attempts were unsuccessful due to the high melting point of thorium and 

the great stability of its compounds. Later, small amounts of thorium were 

produced by reducing ThF4 with metallic calcium using iodine as a “booster”. 

The yields were low and the metal was obtained in small pellets which were very 

difficult to recast into solid metal. In August, 1944, ZnCl2 was tried as a 

“booster” and solid biscuits of thorium-zinc alloy were obtained in good yields. 

Within three months the conditions necessary for good yield had been well 

enough established to allow expansion of the process to the use of a reduction 

bomb 6 inches in diameter. . . . By June 1946, most of the details had been 

worked out successfully and the bomb reduction of thorium fluoride was ready for 

expansion to large scale production. 

The process, as [sic] use in December, 1946, was a metallothermic reduction of 

thorium fluoride by metallic calcium. Zinc chloride was used to provide 

additional heat, to give a more fusible slag, and to form a low-melting allow of 

thorium which would collect in the form of a solid biscuit. The reduction was 

carried out in an iron bomb 7 inches in diameter and 45 inches long. This bomb 

was lined with a layer of dolomitic oxide compacted into place around a steel 

mandrel with a pneumatic jolter. The charge was placed in the bomb which was 

then closed and the reduction started by preheating in a gas-fired furnace. The 

bomb was allowed to cool after the reaction and the biscuit of thorium-zinc alloy 

removed and cleaned. This method produced a biscuit of about 39 pounds of 

thorium-zinc alloy with better than 96 per cent [sic] yield of thorium. . . . By 

December 31, 1946 over 4500 pounds of thorium had been cast for shipment to 

other sites. [Emphasis added.] 

Production of thorium metal continued at Annex I (i.e., Little Ankeny) until 1949. Starting in 

1947 and continuing through the end of 1953, production and casting of thorium metal was also 

conducted in the Metallurgy Building. Total production of thorium at both facilities amounted to 

65 tons (or 130,000 pounds). 
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In summary, based on the availability of urine bioassay data, the comprehensive AEC survey of 

1952, and detailed process and source-term data, SC&A concludes the following: 

In the regulatory hierarchy of data considered suitable for dose reconstruction, available data for 

the reconstruction of internal doses associated with the production of thorium metal are

considerably higher than data used by NIOSH in the dose reconstruction for uranium cited in 

Tables 5-1, 5-2, and 5-3 of the Ames TBD. 

Finding #17: Given the availability of credible data, NIOSH’s exclusion of thorium exposure in 

dose reconstruction is not justified. 

5.5 TRITIUM EXPOSURES

Section 5.3 of the Ames TBD evaluated tritium exposures associated with the ALRR, which was 

a 5 MW heavy-water-moderated reactor that operated from February 1965 through December 

1977. Decontamination and decommissioning of the ALRR was completed in 1981. 

Personnel at the ALRR were monitored for tritium and should have bioassay and dose records. 

In the event that records are either incomplete or unavailable, NIOSH constructed a coworker 

tritium dose model for years 1965–1981, as given in Table 5-6 of the Ames TBD. 

SC&A Comments

SC&A has not been given access to the raw data that defines estimates of tritium exposures for 

unmonitored coworkers. On the assumption that available tritium monitoring records were 

objectively evaluated, SC&A has no comments/findings. 

5.6 FISSION PRODUCT INTAKES

Worker exposure to fission products at the Ames Laboratory may have come from two sources: 

(1) a Hot Lab that was operated in the Chemistry Building and (2) the decontamination and 

decommissioning of the ALRR. 

5.6.1 Use of NUREG-1400 for Modeling Intakes at the Hot Lab

Between 1943 and 1951, workers at the Ames hot laboratory separated plutonium from 

uranium and their associated fission products. In the absence of empirical survey/bioassay data, 

Table 5-7 of the Ames TBD provides modeled estimates based on a generic formula defined in 

NUREG-1400: Air Sampling in the Workplace (Hickey et al. 1993): 

Ip = Q × 10-6 × R × C × D Eq. 5.6.1

where,

Q = total quantity of unencapsulated material 

R = release fraction

C = confinement factor

D = dispersibility
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SC&A Comments and Findings 

The intent of NUREG-1400 is to assist licensees in establishing air sampling programs that 

conform with recommendations in the 1992 Regulatory Guide 8.25, Revision 1, Air Sampling in 

the Workplace (NRC 1992), and the regulatory requirements stated in 10 CFR Part 20. Thus, 

modifying factors for the intake Ip are based on licensed facilities that reflect current-day 

timeframes of operation. For example, NUREG-1400 states that the 10-6 factor cited in Equation 

5.6.1 represents a rule of thumb that applies “. . . when normal precautions are taken [and] a 

worker is not likely to have an intake Ip exceeding 10-6 of the material being handled . . .” 

[Emphasis added]. 

As previously referenced in Section 4.4 of this report, a mere glimpse of the design and 

operational conditions that describe the Hot Lab in the 1940s was offered by Dr. in 

response to questions during an interview with SC&A (see Appendix A): 

Arjun: You did not have glove boxes when you worked with irradiated material? 

Dr. We had crude devices – a hood with a stream of air. We knew better than to 

breathe that stuff. [Emphasis added.] 

Finding #18: Due to the fact that very little is known about the design features and technical 

specifications of the Hot Lab and the absence of worker monitoring/facility survey data, the 

applicability of NUREG-1400, Section 1.2, for use in dose reconstruction lacks technical merit 

and credibility for a facility that operated between 1943 and 1951. 

5.6.2 Intakes of Fission Products from Decontamination and Decommissioning of 

the Ames Laboratory Research Reactor 

Section 5.4.2 of the Ames TBD states:

During D&D operations, radiation protection appeared to be acceptable for the 

time. . . There is no evidence that bioassay for other radionuclides [i.e., fission 

projects] was performed. However, during D&D of the reactor, which included 

dismantlement, cutting, grinding, etc., it can be expected that some intakes from 

activation products occurred. [Emphasis added.] 

This research reactor operated with 93% enriched U-238 fuel for a period of 12 years (1965–

1977). Thus, in addition to activation products, one must also expect substantial contamination 

from fission products. For estimates of intakes, NIOSH stated: 

A reasonable estimate of intakes from D&D of the reactor can be made by using 

the gross beta air concentration limit from 1977 (1 × 10-9 μCi/mL) (ERDA 1977) 

based on the most conservative beta emitter (90Sr). [Emphasis added.] 

Intakes for D&D workers were further adjusted by means of an assumed occupancy factor of 0.5 

(or 1,000 hours/year) with supervisory and other personnel receiving one-fourth of the intake of 

D&D workers.
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Inspection of the Ames TBD Table 5-8 (“Default intakes for Ames Laboratory (if no bioassay 

results are available”) (see Exhibit #5-1 above) identifies that intakes from D&D activities of the 

ALRR are restricted to two activation products: Co-60 or Zn-65 as Types S. 

Finding #19: Although Section 5.4.2 of the Ames TBD is titled, “Fission Product Intakes from 

Research Reactor Operations and Decontamination and Decommissioning,” NIOSH restricted 

intakes to two activation products that are arbitrarily based on a 1977 ERDA gross beta air 

concentration limit. SC&A regards the default intake (that is limited to a choice of one of two 

activation products as surrogate for fission products) as qualitatively incomplete and 

quantitatively without technical basis/support. 

5.7 FAILURE TO ADDRESS URANIUM AND THORIUM BLOWOUTS FOR THE 

ASSESSMENT OF EPISODIC INTAKES

In two previous draft reports, Review of the Ames Laboratory Special Exposure Cohort (SEC) 

Petition SEC-0038 (SC&A 2006) and An Assessment of Worker Eligibility Criteria For Less 

Than 250-Days Employment: Ames Case Study (SC&A 2007a), SC&A identified to the 

Advisory Board the relatively common radiological incidents of chemical explosions or 

“blowouts” at the Ames facility in context with the 250-workday requirement. In response to 

SC&A’s concern, the Board appointed an ad hoc work group chaired by Dr. James Melius to 

further evaluate this issue. The work group requested SC&A to (1) review all available 

records/sources that would establish the frequency of such events, and (2) provide scoping 

calculations that would assess reasonable estimates of potential internal exposures associated 

with a single event. A third SC&A draft report was issued in June 2007 in order to satisfy this 

request. A full text of the third SC&A draft report titled, The Relevance of the 250-Workday 

Requirement to Potential Exposures Associated with a Single Blowout (SC&A 2007b), is 

enclosed herein as Appendix G. As a convenience to the reader, salient elements of this report 

(Appendix G) are summarized below. 

5.7.1 Quantities of Uranium and Thorium Metal Produced 

Data regarding the potential quantities of uranium and thorium that might have become 

volatilized and airborne as a result of blowouts during the reduction of UF4/ThF4 to metal at 

Ames Laboratory can be found in a 1947 document titled, History of the Ames Project Under the 

Manhattan District to December 31, 1946 (Fulmer 1947). This document was compiled by E.I. 

Fulmer, who served as Assistant Director to Dr. F.H. Spedding, Director of the Ames Project. 

Sections 1.1 and 1.4 of the report provide the following information pertaining to the reduction 

of UF4 and ThF4 to pure metal. 

Uranium. Section 1.1 of the report emphasizes that the principal objective of the Ames Project 

was the production of uranium metal, which originally was based on the chemical reduction of 

UF4 by calcium metal in a refractory-lined steel bomb. In the first quarter of 1943, however, 

calcium was replaced by magnesium for the reduction, and by July 1943, uranium metal 

production reached 130,000 pounds per month. Production of uranium metal was performed 

exclusively in the remodeled one-story wooden building identified as the Physical Chemistry 

Annex I. 
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Uranium production ceased by January 1, 1945, after producing a total of about 

2,000,000 pounds. Over the 2-year production period, reduction of UF4 commonly involved 

steel pipes measuring 6 inches in diameter by 36 inches in length (however, larger pipes of up to 

10 inches in diameter by 36 inches in length were also used). A successful reduction yielded a 

biscuit that was typically 42 pounds of uranium metal. 

In Section 1.4 of the report, Fulmer (1947) provided the following information regarding the 

production of thorium metal. 

Soon after the large scale bomb reduction of uranium was in successful 

operation, similar approaches were made on the reduction of thorium. . . . By 

June 1946, most of the details had been worked out successfully and the bomb 

reduction of thorium fluoride was ready for expansion to large scale production. 

The process, as [sic] use in December, 1946, was a metallothermic reduction of 

thorium fluoride by metallic calcium. . . . This method produced a biscuit of 

about 39 pounds of thorium-zinc alloy with better than 96 per cent [sic] yield of 

thorium. . . . By December 31, 1946 over 4500 pounds of thorium had been cast 

for shipment to other sites. [Emphasis added.] 

On the unconservative assumption that the total of 4,500 pounds of pure thorium had been 

produced between June 1946 and December 1946 by means of 39-pound thorium-zinc biscuits 

with ~96% yield of thorium, a minimum of 120 reductions may be assumed for the 7-month 

period (or about 4 reductions per week). 

Production of thorium metal continued at Annex I (i.e., Little Ankeny) until 1949. Starting in 

1947 and continuing through the end of 1953, production and casting of thorium metal was also 

conducted in the Metallurgy Building. Total production of thorium at both facilities amounted to 

65 tons (or 130,000 pounds). 

Furthermore, assuming that the size of the bomb retorts remained constant after 

December 1946, a total of around 3,500 ThF4 bombs were reduced between June 1944 and 

December 1953, yielding an average of seven reductions per week.

5.7.2 Estimated Frequency of Blowouts 

As noted in Appendix G and Section 5.7 above, official statements made by Dr. Frank Spedding 

attest to the fact that uranium and thorium blowouts were episodic events that were not 

uncommon during the entire production period. 

From Spedding’s statement that “...I remember one night we had an explosion that blew the 

whole south end of the building out and being an old wooden building, when things quieted 

down we all went outside and shoved the wall back in again and went to work” [Emphasis 

added], it is reasonable to conclude that this and other blowouts were not perceived as potential 

radiological threats, since no attempt was made to limit the time of exposure or to mitigate 

subsequent exposure by decontamination efforts, engineering controls/building modification, or 

the use of respiratory protection. 
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Dr. Spedding’s assessment of these episodic events and their casual acceptance was confirmed in 

a separate interview conducted by SC&A with a former Ames Laboratory employee, 

, on January 3, 2007. Transcript of the interview is enclosed herein as Appendix E. In 

response to the question of the frequency of blowouts, stated “. . . Oh, I would say 

maybe once a week” (see pp. 2–3 of Appendix E). 

5.7.3 Assessment of Airborne Contamination Levels Associated with Blowouts 

Although no radiological incident/investigative reports were found in behalf of the Ames 

Laboratory, there was a blowout incident at Fernald on April 5, 1954, which provides data that 

are applicable to Ames.

Summarized below are descriptions and data contained in a report issued by J.H. Noyes et al. 

(1954) on April 5, 1954, titled Committee Investigative Report of Thorium Blender Incident – 

March 15, 1954. 

From Section 2.0: 

On March 15, 1954, personnel were attempting to blend a batch of thorium 

fluoride, calcium metal and zinc chloride preparatory to the reduction of the 

charge. After some delay in starting the blending operation and after 

unsuccessful attempts to properly seat a Gemco valve on the blender, a puff of 

dust appeared at the mouth of the blender; then a short flame; followed at 

3:13 p.m. by a sheet of flame that extended horizontally from the blender a 

distance of about 45 feet over an arc segment of 38 feet. The duration of the 

flame is estimated at less than 10 seconds during which time two persons... 

received serious burns which subsequently proved fatal, and two others received 

minor burns. Three additional persons received minor hand burns while assisting 

the injured. Physical damage to the equipment is estimated at about $700. 

Approximately 50 lb. of thorium were unaccounted for following the incident. 

The building was vacated and all activities stopped until an adequate 

investigation established such factors contributing to the accident as an 

examination of the building and equipment could offer. [Emphasis added.]

From Section 7.1: 

The blending of a charge of thorium fluoride using calcium metal and zinc 

chloride is similar to the process utilized by Iowa State College, at Ames, Iowa... 

[Emphasis added.]

The charge that was being blended when the incident occurred consisted of the 

following: 

100.0 lb. thorium fluoride 

10.0 lb. zinc chloride 

35.9 lb. calcium metal 

. . . Examination of the blender after the accident showed it to be nearly empty. . . 
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These data suggest that 50 lbs (or about 50%) of the 100 lbs thorium charge were likely to have 

been volatilized and dispersed by the high temperature that characterizes this exothermic 

chemical reduction of ThF4. Thus, data involving a thorium blowout at FMPC in 1954 were

used to model internal exposures from inhaling airborne contaminants in the first few minutes 

following a blowout, and from resuspension of residual surface contamination for a period of 

30 days (or 193 workhours). This time interval was selected on the unconservative assumption 

that the frequency of blowouts may have occurred on a monthly bases. 

Applying FMPC data to Ames, a 50% volatilization of a typical UF4 or ThF4 charge would have 

released about 21 lbs of U and about 19.5 lbs of Th into the air/environs at the Ames Annex I/ 

Little Ankeny facility.

By means of these quantities, building dimensions for Annex 1, and assumptions stated in 

Section 6.0 of Appendix G, SC&A derived the internal dose estimates for a single thorium or 

uranium blowout as given in Tables 5-9 and 5-10, respectively.

Table 5-9. Internal Dose Estimates for a Thorium Blowout* (rem) 

Radionuclide/ 

Solubility

Amount 

Inhaled 

(μCi)

Bone Surface Lung

1 yr 5 yr 10 yr 30 yr 1 yr 5 yr 10 yr 30 yr

Th-232 Type S 4.4E-02 0.1 1.3 3.6 13.7 2.6 5.1 7.3 11.4

Th-228 Type S 4.4E-02 0.3 1.4 2.0 2.0 29.3 34.2 34.2 34.2

Th-232 Type M 4.4E-02 4.6 26.0 53.7 153 1.8 2.0 2.0 2.3

Th-228 Type M 4.4E-02 12.2 39.0 43.9 45.8 19.5 21.2 21.2 21.2

Total — — 12.7 67.7 103 214.5 53.2 62.5 64.7 69.1

* Dose estimates include inhalation exposures resulting from the first 5 minutes of a blowout and from resuspension 

of contaminants for a 30-day work-period. Not included are exposures to kidneys, liver, and other organs.

Table 5-10. Internal Dose Estimates for a Uranium Blowout* (rem)

Radionuclide/ 

Solubility

Amount 

Inhaled 

(μCi)

Bone Surface Lung

1 yr 5 yr 10 yr 30 yr 1 yr 5 yr 10 yr 30 yr

U-238 Type S 0.186 0.012 0.043 0.076 0.14 12.4 17.9 19.9 22.7

U-235 Type S 0.009 0.001 0.002 0.004 0.01 0.67 0.94 1.06 1.17

U-234 Type S 0.186 0.014 0.050 0.080 0.15 15.8 21.9 24.7 27.5

U-238 Type M 0.186 0.360 0.760 1.030 1.44 8.26 8.94 8.94 8.94

U-235 Type M 0.009 0.020 0.040 0.050 0.07 0.47 0.47 0.47 0.47

U-234 Type M 0.186 0.400 0.820 1.100 1.65 11.0 11.0 11.0 11.0

Total — — 0.81 1.71 2.34 3.43 50.94 61.15 66.07 71.78

* Dose estimates include inhalation exposures resulting from the first five minutes of a blowout and from

resuspension of contaminants for a 30-day work-period. Not included are exposures to kidneys, liver, and other 

organs.

Exposure to the lungs and bone surface from a single incident suggests substantial doses that 

increase with time, as shown in Table 5-3 and Table 5-4 above. The selection of 5-, 10-, and 

30-year periods corresponds to critical time intervals between exposure and the induction period 

for cancer development. 
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Finding #20: By means of documented anecdotes/testimonials regarding potential frequencies 

of blowouts, technical data for a specific blowout documented at FMPC, and reasonable 

assumptions, SC&A derived significant U and Th intakes and associated organ doses that are 

applicable to workers at the Ames Laboratory, but were not considered/included in ORAUTTKBS-0055. 
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6.0 OCCUPATIONAL EXTERNAL DOSE

In Section 6.0 of the Ames TBD, NIOSH stated the following: 

Workers at Ames Laboratory received external radiation doses between 1942 and 

1952 that were largely unmonitored. Pocket chambers were [sic] available that 

might have been used to monitor external doses, but very few records could be 

found . . . 

An upper bound of the total external exposures cannot be made for SEC-00038 

workers because external doses from beta and gamma radiation resulting from 

exposure to thorium and its daughters or plutonium cannot be reconstructed 

due to a lack of information on the percentage of thorium daughter in-growth

(up to 1954, when thorium operations ended) (NIOSH 2006). However, external 

dose from potential exposure to uranium from 1942 to 1953 can be estimated. 

[Emphasis added.] 

6.1 UNMONITORED EXTERNAL DOSE

In Section 6.3.1 of the Ames TBD, NIOSH derived external doses for uranium exposure using 

the same surrogate data and assumptions that had been used for deriving estimates of uranium 

intakes, as given by the following: 

To estimate reasonable external doses from the uranium processes before 1953, 

the methods described in three documents (Battelle 2011, Christofano and Harris 

1960, and [ORAUT 2010]) were used. These documents are representative of the 

potential external exposures encountered at Ames Laboratory because the 

processes developed there were similar to processes at AWE sites. . . . 

Exposure levels in these documents were converted to annual doses. These doses 

are provided for the Chemistry Building, Physical Chemistry Annex 1, and 

Physical Chemistry Annex 2 in Tables 6-4, 6-5, and 6-6 below. 

SC&A’s Comments and Findings 

Finding #21: SC&A’s concerns about the use of the same surrogate data sources and 

questionable assumptions for deriving external dose for Ames’ workers exposed to uranium 

closely parallel those related to uranium intakes. These concerns must be addressed, but for the 

purpose of expediency will not be repeated here. 

However, a concern that needs further discussion is NIOSH’s failure to include external doses 

from exposure to thorium (1) for years 1943–1949 during early production of thorium metal in 

Annex 1 and (2) for years 1947–1953 that correspond to large-scale production and casting of 

thorium metal at the Metallurgy Building (aka Wilhelm Hall).
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Justification for the Inclusion of Thorium External Exposure 

SC&A questions both the need for and purpose of NIOSH’s statement that “. . . An upper 

bound of the total external exposure cannot be made . . . due to the lack of information on the 

percentage of thorium daughter in-growth. . . .” [Emphasis added.] 

It is likely that the “age” of separated thorium that was processed at the Ames Laboratory was 

highly variable, as suggested by statements contained in a letter authored by Allen P. Skoog 

M.D., Head of the Ames Laboratory Safety Group, to Dr. Spedding dated September 12, 1952 

[Dr. Skoog’s letter (Skoog 1952) is enclosed herein as Appendix H]. 

In his five-page letter, Dr. Skoog responded to numerous issues and suggestions raised by the 

AEC in their survey of the Ames Laboratory in March of 1952, including problems associated 

with “aged” thorium: 

From pp. 3–4 

In connection with thorium and uranium processing the health physicists work in 

close conjunction with the production groups in all health matters. It should be 

called to the attention of all concerned that the operations in the production of 

thorium metal at the Ames Laboratory are not stable industrial processes. The 

area actually is a research pilot plant in which new developments are constantly 

being made. At present this pilot plant, when in operation, is called upon to do 

the work of several times the originally-designed capacity. One of the major 

problems in the mesothorium disposal aspect of our general problem lies in the 

raw material T.N.T. Originally the T.N.T. was shipped directly from the 

Lindsay Light and Chemical Corporation and was newly manufactured. Since 

the first scale-up of thorium production, this basic material has been shipped by 

the New York Office from its Middlesex, N.J., storage area. Recently, after we 

noticed increased activity, we were informed that they were shipping material 

which might have been in storage up to 6 yrs. The radioactive elements, 

especially mesothorium, have built up by a factor of 5 to 10 in this older T.N.T. It 

is these problems that cause most of our headaches. [Emphasis added.] 

In the absence of more definitive information regarding the “age” of the separated thorium and 

the degree of Ra-228 ingrowth, an upper bound estimate of external exposures would 

conservatively assume full equilibrium. However, the need for the use of an upper bound/full 

equilibrium assumption becomes irrelevant when empirical dose rate measurements are 

available. 

Included in the March 18–21 radiological survey of the Metallurgical Building at the Ames 

Laboratory, the AEC assessed both beta and gamma dose rates at key locations of the thorium 

production/operational areas, as given in Table IV of Klevin (1952) (see Appendix B). For 

example, shown as Exhibit 6-1 are beta and gamma dose rates associated with thorium reduction, 

casting, machining, and storage. These and other dose rate measurements cited in Table IV 

represent empirical site-specific, area-specific, and task-specific thorium dose rate 
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measurements that are available for the reconstruction of external dose for years 1943 through 

1952. 

In the hierarchy of data that may be used in the reconstruction of external dose, SC&A concludes 

that the credibility of available data for deriving external thorium doses exceeds those used by 

NIOSH for deriving external doses from uranium exposures. 

Findings #22: Given the availability of highly credible and site-specific data for deriving 

external dose from thorium exposure, NIOSH’s decision to exclude said exposures/doses is not 

justified.

6.2 COWORKER DOSE MODEL – 1952 TO THE PRESENT 

Table 6-7 of the Ames TBD identifies coworker doses for the years 1952 to 2005 at the 50th and 

95th percentile for unmonitored workers with potential exposure to beta, gamma, and/or neutron 

sources. The derivation of annual coworker doses was based on the following statements 

contained in Section 6.3.1.2 of the Ames TBD: 

Extensive dosimetry records have been found for Ames Laboratory workers; 

however, many of the records for 1965 to 1981 do not identify the person 

receiving the radiation dose. If a worker was monitored but cannot be identified 

in the dosimetry records, that individual must be considered unmonitored and 

assigned a dose in each year for which no clearly identified records exist. 

The coworker data study for Ames Laboratory included all available dosimetry 

records from 1952 through 1981 (Martin 2006c). All dose results were analyzed, 

including zeros and blank values, to determine the 50th - and 95th -percentile 

doses for each year for beta, gamma, and neutron exposures (McCartney 2006). 

The results of the analysis are summarized in Table 6-7. The missed dose 

recommended for monitored workers in Table 6-8 was added to the 50th - and 

95th -percentile values in Table 6-7. Specifically, half of the maximum annual 

missed doses were added to the reported annual doses, except the reported 

positive doses, in which case the maximum missed dose was reduced by the dose 

corresponding to one badge exchange (because it is not possible that all 

individual badge results were zero if a positive annual dose was reported). 

[Emphasis added.] 
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Exhibit 6-1. Table IV of Klevin 1952 
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SC&A Comments and Findings 

Our review of raw dosimetry records and NIOSH’s assembly of these records in a spreadsheet 

format (McCartney 2006) confirms NIOSH’s claim of “extensive dosimetry records” and the fact 

that “. . . many of the records for 1965 to 1981 do not identify the person receiving the radiation 

dose” [Emphasis added]. For example, a review of dosimetry records for 1966 show that of the 

241 badged personnel, only 42 (or 17.4%) individuals could be identified by name. 

Nevertheless, annual doses were derived in behalf of all badged personnel, which proved useful 

in the construction of the coworker model summarized in Table 6-7 of the Ames TBD. 

In addition, SC&A selected a small number of individuals in order to verify the assignment of a 

total annual dose against raw recorded data and NIOSH’s assigned dose from potential missed 

dose defined either by minimum recordable dose (MRD/2) or by minimum detection limit 

(MDL/2).

Our limited review verifies that potential missed doses assigned to monitored persons who 

represent the coworker dose model correctly used one-half of the “minimum reportable dose” 

(MRD/2) as well as the recommended minimum detection level (or MDL/2) cited in Table 6-1 

for the various time periods. 

Regarding Table 6-7 for assigning dose to unmonitored workers or unmonitored periods for 

monitored workers, SC&A has no findings. 
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7.0 REFERENCES

10, CFR Part 20, 1991. Standards for Protection Against Radiation, 56 FR 23391, May 21, 

1991, Nuclear Regulatory Commission, Washington DC.

42, CFR Part 82, 2001. Methods for Radiation Dose Reconstruction Under the Energy 

Employees Occupational Illness Compensation Program, of the Code of Federal Regulation, 

Office of the Federal Register, National Archives and Records Administration, Washington DC.

Ames (Ames Laboratory) 1961. “Synchrotron Building Radiation Survey,” U.S. Atomic Energy 

Commission, Iowa State University, Ames, Iowa. May 16. [SRDB Ref ID: 25766] 

Ames (Ames Laboratory) 1967. 25th Year Open House: 1942–1967, April 7–8, 1967, Iowa 

State University, Ames, Iowa. [SRDB Ref ID: 18830] 

Battelle 2007. Default Assumptions and Methods for Atomic Weapons Employer Dose 

Reconstructions, Battelle-TIB-5000, Rev. 00, Battelle, Pacific Northwest Division, Richland, 

Washington. April 2, 2007. 

Battelle 2011. Site Profiles for Atomic Weapons Employers that Worked Uranium Metals, 

Battelle-TBD-6000, Revision 1, Battelle, Pacific Northwest Division, Richland, Washington. 

June 17, 2011. 

Bihl, D.E., 2006. “Estimated Releases from the Hot Laboratory in Ames Chemistry Building,” 

memorandum to file, Pacific Northwest National Laboratory, Richland, Washington. December 

29, 2006. [SRDB Ref ID: 29227] 

Christofano, E., and W. B. Harris, 1960. “The Industrial Hygiene of Uranium Refining,” 

Archives of Environmental Health, volume 1, pp. 438–460 (reprinted). [SRDB Ref ID: 15774] 

DOE (U.S. Department of Energy) 1994. Airborne Release Fractions/Rates and Respirable 

Fractions for Nonreactor Nuclear Facilities, Volume 1 – Analysis of Experimental Data, DOEHDBK-3010-94, Washington, DC. December.

ERDA (Energy Research and Development Administration) 1977. Standards for Protection 

Against Radiation, Manual Chapter 0524, Washington, DC. March 30. [SRDB Ref ID: 11595] 

Ferretti, R.J., G.R. Price, and S. Schwartz, 1951. Uranium Excretion Studies, In Industrial 

Medicine on the Plutonium Project, Survey and Collected Papers, Edited by Robert S. Stone, 

M.D. McGraw-Hill Book Co. [SRDB Ref ID: 739]

Fulmer, E.I., 1947. “History of the Ames Project under the Manhattan District to December 31, 

1946,” Report ISC-10, December 9, 1947. Springfield, Virginia. [SRDB No. 18823, pp. 6–7] 
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Hickey, E.E., G.A. Stoetzel, D.J. Strom, G.R. Cicotte, C.M. Wiblin, and S.A. McGuire, 1993. 

Air Sampling in the Workplace, NUREG-1400, U.S. Nuclear Regulatory Commission, Office of 

Nuclear Regulatory Research, Washington, DC. September. [SRDB Ref ID: 20129] 

Hokel, B.W., J.H. Withers, W.P. Waters, and K.J. Ewing, 1998. An Assessment of the Causes, 

Mitigation Efforts, and Current Status of 232Th, 238U, and Beryllium Contamination in Wilhelm 

Hall at Ames Laboratory, Iowa State University, Ames Laboratory, Ames, Iowa. April. [SRDB 

Ref ID: 18848] 

Klevin, P.B., 1952. Ames Research Laboratory Occupational Exposures to Thorium and 

Beryllium, U.S. Atomic Energy Commission (AEC), New York Operations Office, Health and 

Safety Division, New York, New York. [SRDB Ref ID: 18942] 

Martin, J.B., 2006a. “ALRR Workers Badged?” E-mail to D.B. Shipler (Pacific Northwest 

National Laboratory), Dade Moeller & Associates, Richland, Washington. November 2006. 

[SRDB Ref ID: 29257, p. 2] 

Martin, J.B., 2006b. “Unbadged Workers at the Synchrotron,” E-mail to D.B. Shipler (Pacific 

Northwest National Laboratory), Dade Moeller & Associates, Richland, Washington. November 

1, 2006. [SRDB Ref ID: 29256] 

Martin, J.B., 2006c. Ames Laboratory Dose Records, 1952–2005, Dade Moeller & Associates, 

Richland, Washington. [SRDB Ref ID: 29229] 

McCartney, K.A., 2006. Statistical Analysis of Ames Laboratory External Dose Records (1952–

2005), Dade Moeller & Associates, Cincinnati, Ohio. [SRDB Ref ID: 30977] 

Napier, B.A., D.L. Strenge, J.V. Ramsdell Jr., P.W. Eslinger, and C.J. Fosmire, 2004. GENII 

Version 2 Software Design Document, PNNL-14584, Pacific Northwest National Laboratory, 

Richland, Washington. November. [SRDB Ref ID: 24168] 

Napier, B.A., 2006. GENII Version 2 Users’ Guide, PNNL-14583, Pacific Northwest National 

Laboratory, Richland, Washington. August. [SRDB Ref ID: 30771] 

NCRP (National Council on Radiation Protection and Measurements) 1996. Screening Models 

for Releases of Radionuclides to Air, Surface Water, and Ground Water, Report 123, Bethesda, 

Maryland. 

NCRP (National Council on Radiation Protection and Measurements) 2003. Radiation 

Protection for Particle Accelerator Facilities, Report 144, Bethesda, Maryland. 

NIOSH (National Institute for Occupational Safety and Health) 2006. SEC Petition Evaluation 

Report, Petition SEC-00038, Rev. 0, Office of Compensation Analysis and Support, Cincinnati, 

Ohio. April.
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NIOSH (National Institute for Occupational Safety and Health) 2007. SEC Petition Evaluation 

Report, Petition SEC-00075, Rev. 0, Office of Compensation Analysis and Support, Cincinnati, 

Ohio. May. 

NIOSH (National Institute for Occupational Safety and Health) 2010. SEC Petition Evaluation 

Report, Petition SEC-00166, Rev. 0, Division of Compensation Analysis and Support, 

Cincinnati, Ohio. July. 

NIOSH (National Institute for Occupational Safety and Health) 2011. SEC Petition Evaluation 

Report, Petition SEC-00185, Rev. 0, Division of Compensation Analysis and Support, 

Cincinnati, Ohio. June. 

Noyes, J.H., et al. 1954. Committee Investigation Report of Thorium Blender Incident – 

March 15, 1954. April 5, 1954. [SRDB Ref ID: 3635] 

NRC (U.S. Nuclear Regulatory Commission) 1992. Regulatory Guide 8.25, Revision 1, Air 

Sampling in the Workplace, Washington, DC.

ORAUT (Oak Ridge Associated Universities Team) 2006. Technical Information Bulletin: 

Technical Basis for Estimating the Maximum Plausible Dose to Workers at Atomic Weapons 

Employer Facilities, ORAUT-OTIB-0004, Rev. 03 PC-2, Oak Ridge Associated Universities 

Team, Cincinnati, Ohio. December 6, 2006. 

ORAUT (Oak Ridge Associated Universities Team) 2007a. Site Profile for Ames Laboratory, 

ORAUT-TKBS-0055, Rev. 00, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

June 22, 2007. 

ORAUT (Oak Ridge Associated Universities Team) 2007b. Technical Information Bulletin: 

Fission and Activation Product Assignment for Internal Dose-Related Gross Beta and Gross 

Gamma Analyses, ORAUT-OTIB-0054, Rev. 00 PC-1, Oak Ridge Associated Universities 

Team, Cincinnati, Ohio. November 19, 2007. 

ORAUT (Oak Ridge Associated Universities Team) 2008. Site Profile for Ames Laboratory, 

ORAUT-TKBS-0055, Rev. 00 PC-1, Oak Ridge Associated Universities Team, Cincinnati, 

Ohio. August 20, 2008. 

ORAUT (Oak Ridge Associated Universities Team) 2009. Site Profile for Ames Laboratory, 

ORAUT-TKBS-0055, Rev. 01, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

January 18, 2009. 

ORAUT (Oak Ridge Associated Universities Team) 2010. Technical Basis Document: Basis 

for Development of an Exposure Matrix for the Mallinckrodt Chemical Company St. Louis 

Downtown Site and the St. Louis Airport Site, St. Louis, Missouri, ORAUT-TKBS-0005, 

Rev. 03, Oak Ridge Associated Universities Team, Cincinnati, Ohio. November 22, 2010. 
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ORAUT (Oak Ridge Associated Universities Team) 2011. Site Profile for Ames Laboratory, 

ORAUT-TKBS-0055, Rev. 02, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

January 14, 2011. 

ORAUT (Oak Ridge Associated Universities Team) 2012a. Site Profile for Ames Laboratory, 

ORAUT-TKBS-0055, Rev. 03, Oak Ridge Associated Universities Team, Cincinnati, Ohio. 

January 3, 2012. 

ORAUT (Oak Ridge Associated Universities Team) 2012b. Dose Reconstruction During 

Residual Radioactivity Periods at Atomic Weapons Employer Facilities, ORAUT-OTIB-0070, 

Rev. 01, Oak Ridge Associated Universities Team, Cincinnati, Ohio. March 5, 2012. 

Payne, C.S., 1992. The Ames Project: Administering Classified Research as a Part of the 

Manhattan Project at Iowa State College, 1942-45, PhD Dissertation of Carolyn Stilts Payne, 

Iowa State University, Ames, Iowa. [SRDB Ref ID: 18851] 

SC&A 2004. SC&A Standard Operating Procedure for Performing Site Profile Reviews, Rev. 1. 

S. Cohen & Associates, McLean, Virginia. May 13, 2004. 

SC&A 2006. Review of the Ames Laboratory Special Exposure Cohort (SEC) Petition,

SEC-00038, SCA-SEC-TASK5-0031, Rev. 0. SC&A, Inc., McLean, Virginia. June 5, 2006. 

SC&A 2007a. An Assessment of Worker Eligibility Criteria for Less Than 250-days 

Employment: Ames Case Study, S. Cohen & Associates, Vienna, Virginia. January 11, 2007. 

SC&A 2007b. The Relevance of the 250-Workday Requirement to Potential Exposures 

Associated with a Single Blowout, S. Cohen & Associates, Vienna, Virginia. June 2007. 

Skoog, A.P., 1952. Letter from Allan P. Skoog, M.D. to Dr. F.H. Spedding, Director Regarding 

Environmental Health Conditions – Ames Laboratory, Ames Laboratory Safety Group. 

September 12, 1952. [SRDB Ref ID: 18813] 

Stone, R.S. (editor), 1951. Industrial Medicine on the Plutonium Project, National Nuclear 

Energy Series, Manhattan Project Technical Section, Division IV, Plutonium Project Record, 

Vol. 20. [SRDB Ref ID: 739] 

Schwartz, S., 1944. Letter Report of Studies of Personnel at Ames, Iowa, University of Chicago, 

Metallurgical Laboratory, Chicago, Illinois. June 1, 1944. 

Voss, M.D., 1963. Survey of Environmental Radioactivity, Report No. 1, Iowa State University, 

Ames Laboratory, Ames, Iowa, December 31. [SRDB Ref ID: 25165] 

Voss, M.D., 1975. Environmental Monitoring at Ames Laboratory Calendar Year 1974, IS3613, Iowa State University, Ames Laboratory, Ames, Iowa. May. [SRDB Ref ID: 25446] 

Voss, M.D., 1976. Environmental Monitoring at Ames Laboratory Calendar Year 1975, IS3856, Iowa State University, Ames Laboratory, Ames Iowa. May. [SRDB Ref ID: 25445] 
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Voss, M.D., 1977. Environmental Monitoring at Ames Laboratory Calendar Year 1976, IS4139, Iowa State University, Ames Laboratory, Ames Iowa. April. [SRDB Ref ID: 25444] 

Voss, M.D., 1978. Environmental Monitoring at Ames Laboratory Calendar Year 1978, IS4679, Iowa State University, Ames Laboratory, Ames, Iowa. April 1979. [SRDB Ref ID: 

18839] 

Voss, M.D., 1981. Environmental Summary for Ames Laboratory Calendar Year 1981, IS-4798, 

Iowa State University, Ames Laboratory, Ames, Iowa. April. [SRDB Ref ID: 25429] 
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APPENDIX A: INTERVIEW WITH DR. , MARCH 12, 2006, 

BY DR. ARJUN MAKHIJANI, SC&A

Draft notes sent to Dr. for approval on March 13, 2006. Written corrections received on 

March 16, 2006, and incorporated. .

This account of the interview is not verbatim. The conversational style has been retained to give 

a flavor for how the interview was conducted and of the nature of the conversation. 

Dr. Arjun Makhijani explained that he was a part of a team that was providing the Advisory 

Board with technical support on the DOE worker compensation law, and that he was at the 

beginning stages of looking at the petition for a Special Exposure Cohort filed by 

 and others for the Ames Laboratory. They discussed a good time for the interview and 

Dr. decided to give an interview then and there. 

Dr. Makhijani: I understand that you worked on plutonium separation research at Ames 

Laboratory. I have found information about the uranium and thorium processing, but not much 

about the plutonium separation work. Could you tell me about it? 

Dr. : All our work was written up in a series of reports with numbers that had CC in them. 

Our studies on the fission products were described there. 

Dr. Makhijani: Do you have these CC reports? 

Dr. : No. I was not allowed to take them. Secrecy at the time. You should try to find 

them. They may be at the Iowa State University archives.

Dr. Makhijani: Could you tell me about the plutonium separation research?

Dr. : We received uranium metal we made in our laboratory. We made tons of it.

Dr. Makhijani: That was non-irradiated material.

Dr. : Yes. It was irradiated in Chicago. We would take some of those irradiated metal 

slugs and dissolve them and extract out the fission products and separate them to prepare the 

technique for isolating the plutonium from it. There were others in the country doing separation 

research also; Berkeley, Oak Ridge and maybe some at Los Alamos. I went to the Bureau of 

Standards in DC and they had a small plutonium research program going. Then I went to 

Columbia, where they had leftovers from the time Fermi was there. There was a small program 

at MIT.

Dr. Makhijani: Did you have any air-monitoring data or urinalysis or other such data for the 

people in the lab doing plutonium research? 

Dr. : We did have one who took 

care of testing all of us in the analytical chemistry laboratory. tested for uranium and also 

thorium, and would take blood samples. . After the 

project, . You might try to locate about the 
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monitoring. [In his review of the interview, Dr. informed Dr. Makhijani that had 

passed away.]

Dr. Makhijani: Was that monitoring for uranium and thorium in the production and testing areas 

for metal production? 

Dr. : Yes.

Dr. Makhijani: Do you remember any sampling for bioassay or air monitoring in the chemistry 

labs where the plutonium separation research was done? 

Dr. : Actually we did not pay too much attention to the toxicology of it [in the separations 

research areas]. We knew we should not be breathing it. We did not wear masks all the time but 

we wore them at the times when we were doing something like burning scrap uranium and 

converting it to black oxide. There was particulate matter that went up the hood. I am sure that 

carried fission products. 

Dr. Makhijani: You did this burning with irradiated uranium? 

Dr. : Yes, we practiced first on non-irradiated uranium. I was the who prepared 

and practiced uranium hydride. I had the idea that if I can find a way to make uranium hydride, 

then we could separate the uranium from the fission products. But that turned out to be wrong. 

The hydride particle size is so big that the amount of FP you could separate was too tiny. You 

had to actually dissolve the uranium chemicals to get a good separation. That was the reason for 

the loss of interest on uranium hydride. 

Dr. Makhijani: How much irradiated material did you get per batch and how hot was it? 

Dr. : Can’t give quantitative figures, but we handled roughly 100 grams at a time. The 

shipments were half a kilogram or so. 

Dr. Makhijani: What about the level of irradiation? Were the slugs in lead containers? 

Dr. : Yes they were. We often drove to Chicago and brought them back in the trunk of our 

car. There were three of us— and myself. [See Dr. book, 

All Things Nuclear, p. 206.] I’ll tell you a story that’s been written. The three of us were driving 

back from Chicago one day in February 1943 or 1944. Around 3 a.m., we had a flat tire out 

there on the Iowa prairie. We got out in the snow – there was snow coming down – but the jack 

was out of order. It would only lift the car up three or four inches. Then the three of us had the 

same idea at the same time. We jacked up the car three or four inches; then we put the uranium 

cylinders under the axle and lowered the car down on them. Then we raised the car some more, 

put another stack of uranium rods, and then jacked up the car again. Fortunately the length of the 

cylinder was more than the jack would raise the car so we were able to do the job. Otherwise I 

might still be out there on the Iowa prairie. And I learned something very important about 

uranium. It is very good to hold up cars. 

Dr. Makhijani: How long did the plutonium separation research work go on at Ames? 
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Dr. : Well, it started in about 1943 and continued as long as I was there, which was until 

1946 when I had to decide; what am I going to do? Am I going to work the rest of my life with 

plutonium? I knew and I asked him bluntly; is the main effort going to be to 

make more bombs? He said yes, that’s what it is funded for. 

Dr. Makhijani: Do you still teach there occasionally?

Dr. : I did , but after they don’t call on me. 

Dr. Makhijani: Did you ever measure the level of radiation of the rods you were working on in 

your research? Was there ever a GM tube that was put on them to get an idea of the level? 

Dr. : Once I used a sample of uranium that was not clad in aluminum. It was bare uranium 

metal that had been exposed in a reactor. Under these conditions, you start out with bright shiny 

uranium that turns brown and gray and black as U3O8 builds up. I took some of that [black 

oxide] and scraped it off and then I measured the total radioactivity per milligram and I 

compared that with the radioactivity of unoxidized metal. The oxide had a lower level. I made 

the correction for the oxide part. You know the eight atoms of oxygen and three of uranium in 

U3O8 – and then they came out to be the same. That told me that no segregation of fission 

products took place during oxidation. 

Dr. Makhijani: Do you remember the number? 

Dr. : No.

Dr. Makhijani: You did not have gloveboxes when you worked with irradiated material? 

Dr. : We had crude devices – a hood with a stream of air. We knew better than to breathe 

that stuff.

Dr. Makhijani: Did you go to Little Ankeny [where uranium metal was manufactured in large 

amounts]? 

Dr. : First I went to predecessor of little Ankeny. At this place they had a way of preparing 

a steel cylinder and putting a lime liner in it. Then they put in UF4 mixed with magnesium and 

put some lime freshly baked so as to decompose the hydroxide. That was the way the metal was 

prepared. Then they put in UF4. After the heating, the reduction occurred and uranium metal 

separated out. Some of the guys who worked there refused to wear masks. They would wear 

them when the director was there and then take them off when he left. They were farm boys and 

did not worry about the green powder. There was this one fellow;

. 

Dr. Makhijani: Does that say that Iowa farm boys are healthy and strong? 

Dr. : Yes. Too bad is not available to interview. He died recently. 
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Dr. Makhijani: So it seems like the conditions in the uranium metal production areas must have 

been very dusty? 

Dr. : Yes. Yes, UF4 was of most concern. The air was also dusty from lime. That’s good, 

because that gave a matrix to sweep up the smaller amounts of radioactive materials. There were 

hand brushes to clean the area. I don’t remember vacuum cleaners being used though. 

Dr. Makhijani: I think I have the preliminary information I need at this stage. I will send you 

the interview for checking to correct any errors I may have made.

Dr. : I hope you don’t mind my stories and jokes. 

Dr. Makhijani: Not at all. On the contrary, I will leave them in. They make the interview more 

interesting. Thanks so much for your time and for giving me an interview on the spur of the 

moment? 

End of interview. 
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APPENDIX B: AEC SURVEY REPORT FINDINGS AND 

RECOMMENDATIONS
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APPENDIX C: 2006 BIHL MEMO
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APPENDIX D: 1947 FULMER REPORT (PAGES 36–42)
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APPENDIX E: TELEPHONE INTERVIEW WITH 

MR. ON JANUARY 3, 2007

Behling: Today is January 3rd, 2007. This is Dr. Hans Behling, and I am interviewing Mr. 

. Will you please identify yourself for the record and perhaps give us your mailing 

address?

: This and my address is . 

Behling: Mr. , let me just ask a few questions that will clarify what your role was at 

Ames Laboratory? Can you give us the years in which you were employed?

: Well, I am not really sure, but I believe that I started there in either and I 

was there for years.

Behling: So, you were there from approximately through . 

: Yes.

Behling: Can you give us a brief description and is it possible that you might have had several 

types of jobs, but can you give us an overview as to what type of work you were doing at that 

time?

: I worked at what they called the Building, and we got I believe thorium, 

but I am not really sure. It was a white substance that was put into trays that were long and 

narrow and then they were put into a furnace to be heated and dried. 

Behling: Were you a member of the team? In other words, were you considered a 

 worker? 

: Yes.

Behling: Okay. And you believe that the material in question was thorium. 

: Well, I was told that later on, but I really don’t know. 

Behling: As a matter of record, I do believe that it had to be thorium because the uranium 

production stopped before your time of employment. So, I agree with your recall that it was 

likely thorium. Let me ask you, when you were working as a worker, were you given 

any special training about handling the material? Were you given respirators to wear during the 

working hours? Were you given anti-contamination clothing or gloves? Can you describe the 

working conditions?

: I was given none of the stuff you just mentioned. We did have to take a shower at the 

end of the day, and we had khakis and a T-shirt or shirt that they laundered and furnished to us 

and that is about it. 
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Behling: So there were no anti-contamination clothing or gloves that you wore other than the 

khakis and T-shirt that were given to you and washed by the Ames Laboratory facility – that was 

the only precaution taken? 

: Right.

Behling: And the shower at the end of a day. 

: That is right.

Behling: Did people routinely take showers or do you know people who decided that they were 

not interested in taking a shower? 

: Well, the people that I worked with – we all had to take a shower, and we just 

automatically did it.

Behling: Do you remember ever being monitored for internal exposure? In other words, was 

there any attempt to assess what you may have breathed in in terms of thorium that would be 

measured by various assays? Today, for instance, we would use urinalysis; we would ask you to 

give us a urine sample and that would be analyzed for thorium or, in some cases, fecal analysis 

where a 24-hour stool sample would be analyzed for thorium. Do you remember ever being 

given any of these tests—urinalysis, fecal analysis to assess what you might have had in your 

body? 

: No, we were never given anything like that.

Behling: Okay. Let me talk about specific events, which, as I had mentioned to you, are part of 

my interest here in talking to you. And that is, when we talk about discrete events, I am talking 

about unusual events that are not necessarily part of the normal working environment. Events 

that I am specifically looking to get some information on involve blowouts or explosions, as well 

as potential fires that might have resulted. Do you remember any of those particular incidents 

during the timeframe when you were working – explosions, blowouts, fires? 

: Yes, basically there would be an explosion then a blowout where it would knock out an 

outside wall of a building. 

Behling: Let me ask you again, focusing on these discrete events—explosions, blowouts— what 

happened when there was such an event? Was there an attempt to get people out of the building 

or did you stay in the building? Were you asked in some instances to assist with the fire? What 

happened during these explosions? And, I am going to ask you to describe not only what you 

may have been doing but perhaps other coworkers who were sharing in that same work 

environment. 

: Well, I have to go back quite a ways; no, we stayed right in the building and we helped 

with the cleanup; and we seemed like we took it for granted that there could be an explosion. 

Behling: During these explosions, do you remember, was there visible contamination that you 

could see in the air, such as a cloud of dust, material that was airborne that you were breathing 
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in? Do you remember anything about the explosions that stands out in terms of visual things— 

contamination that involved airborne dust or anything like that? 

: I am afraid that I cannot bring myself to remember anything like that. 

Behling: Was there any attempt to decontaminate after such an event? In other words, were 

there vacuum cleaners used to pick up the dust that might have been dispersed into the work 

environment or any attempt to clean up surface areas of any contamination that might have 

resulted from the explosion? Do you recall any clean-up activities?

: No. No. 

Behling: So, by in large, you would continue working unless you were involved in putting out 

the fire or restoring a wall that may have been knocked out. But in essence, you did not run out 

of the building and avoid any potential exposures.

: Correct.

Behling: Do you have any feel—and I am obviously asking a question that might be very 

difficult for you—but do you have any feel for how often these events occurred? 

: Oh, I would say maybe once a week. 

Behling: Once a week?

: I would say that – yes.

Behling: Is that correct? Let me ask you something else, during the timeframe when you said 

that you were there between and , do you remember an inspection that was done by 

the Atomic Energy Commission in March of 1953? Do you recall that particular event? There 

was a three-day inspection that was conducted by the Atomic Energy Commission. They 

assessed the working conditions in various facilities, including the Building, by the 

Atomic Energy Commission. Do you remember that inspection? 

: No, I am afraid I don’t. 

Behling: Do you keep in touch with any of the coworkers that you worked with during that 

timeframe assuming that they may still be alive?

: Well, the fellows that I worked with in the room where we 

, thorium, I guess it was, I’m sure have passed on by now. They were older than I was by 

quite a bit. But, no not from the end of it, I do not recall socializing with them.

Behling: So, right now, you do not have anyone that you stay in touch with that you worked 

with during that timeframe.

: No.
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Behling: Let me ask you this, and I guess I should have asked earlier, are you a claimant 

yourself?

: Am I what?

Behling: Are you a claimant? In other words, have you filed a claim for any health effects—

cancer—that is associated with your work? 

: 

Behling: I needed to ask that question, and I am to hear that your answer is . Well, 

unless you have something else to add, I thank you for your time; but let me give you my phone 

number, if you think of something that I should have asked or you failed to mention, let me give 

you my phone number. It is area code . 

: . 

Behling: That is correct. And, my first name is Hans H-A-N-S and last name Behling, B as in 

boy E-H-L-I-N-G.

: B-E-H-L-I-N-G.

Behling: Yes. I think that you have given me the information that I am looking for. And, I will 

forward to you by mail a transcript of this interview so that you have assurance that I did not say 

anything that you did not state in this interview; and, if you have any additional comments or 

questions, do call me. 

: Okay.

Behling: Well, I appreciate your cooperation, Mr. . 

: Well, I am glad that I could help.

Behling: Thank you so much. 

: Thank you. 
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APPENDIX F: THORIUM BIOASSAY DATA FOR AMES WORKERS
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APPENDIX G: DISCUSSIONS RELATING TO THE 250-WORKDAY 

REQUIREMENT FOR SEC STATUS

WORKING DRAFT

THE RELEVANCE OF THE 250-WORKDAY REQUIRMENT TO POTENTIAL 

EXPOSURES ASSOCIATED WITH A SINGLE BLOWOUT

Contract No. 200-2004-03805 

Task Order No. 5 

Prepared by 

S. Cohen & Associates

1608 Spring Hill Road, Suite 400 

Vienna, Virginia 22182 

June 2007 

DISCLAIMER

This is a working document provided by the Centers for Disease Control and Prevention (CDC) technical 

support contractor, SC&A for use in discussions with the National Institute for Occupational Safety and 

Health (NIOSH) and the Advisory Board on Radiation and Worker Health (ABRWH), including its 

Working Groups or Subcommittees. Documents produced by SC&A, such as memorandum, white paper, 

draft or working documents are not final NIOSH or ABRWH products or positions, unless specifically 

marked as such. This document prepared by SC&A represents its preliminary evaluation on technical 

issues.

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1.0 INTRODUCTION AND STATEMENT OF PURPOSE

For Special Exposure Cohort (SEC) class eligibility, regulations defined in Title 42, Part 83, 

Section 83.13 of the Code of Federal Regulations (42 CFR Part § 83.13) currently specify a 

minimum aggregate of 250 workdays. An exception to this requirement is provided in 

§83.13(c)(3)(i), which involves exposure to “...discrete incidents likely to have involved 

exceptionally high levels of exposures, such as nuclear criticality incidents or events involving 

similarly high levels of exposures resulting from the failure of radiation protection 

controls.” [Emphasis added.] 

In two previous draft reports (Review of the Ames Laboratory Special Exposure Cohort (SEC) 

Petition SEC-0038 issued in June 2006 and An Assessment of Worker Eligibility Criteria issued 

in January 2007), SC&A identified to the Advisory Board the relatively common radiological 

incidents of chemical explosions or “blowouts” at the Ames facility in context with the 

250-workday requirement. In response to SC&A’s concern, the Board appointed an ad hoc 

working group chaired by Dr. James Melius to further evaluate this issue. The working group 

requested SC&A to (1) review all available records/sources that would establish the frequency of 

such events, and (2) provide scoping calculations that would assess reasonable estimates of 

potential internal exposures associated with a single event. The enclosed draft report attempts to 

satisfy this request.

2.0 RELEVANT BACKGROUND INFORMATION

Data regarding the potential quantities of uranium and thorium that might have become 

volatilized and airborne as a result of blowouts during the reduction of UF4/ThF4 to metal at 

Ames Laboratory can be found in a 1947 document entitled, History of the Ames Project Under 

the Manhattan District to December 31, 1946. This document was compiled by E.I. Fulmer, 

who served as Assistant Director to Dr. F.H. Spedding, Director of the Ames Project. 

Sections 1.1 and 1.4 of the report provide the following information pertaining to the reduction 

of UF4 and ThF4 to pure metal. 

Section 1.1 of the report emphasizes that the principal objective of the Ames Project was the 

production of uranium metal, which originally was based on the chemical reduction of UF4 by 

calcium metal in a refractory-lined steel bomb. In the first quarter of 1943, however, calcium 

was replaced by magnesium for the reduction, and by July 1943, uranium metal production 

reached 130,000 pounds per month. Production of uranium metal was performed exclusively in 

the remodeled one-story wooden building identified as the Physical Chemistry Annex I, known 

locally as Little Ankeny. 

Uranium production ceased by January 1, 1945, after producing a total of about 

2,000,000 pounds. Over the 2-year production period, reduction of UF4 commonly involved 

steel pipes measuring 6 inches in diameter by 36 inches in length (however, larger pipes of up to 

10 inches in diameter by 36 inches in length were also used). A successful reduction yielded a 

biscuit that was typically 42 pounds of uranium metal.
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In Section 1.4 of the report, Fulmer provided the following information regarding the production 

of thorium metal.

Soon after the large scale bomb reduction of uranium was in successful 

operation, similar approaches were made on the reduction of thorium. In August, 

1943, attempts were made to reduce a number of thorium compounds in a bomb. 

The first attempts were unsuccessful due to the high melting point of thorium and 

the great stability of its compounds. Later, small amounts of thorium were 

produced by reducing ThF4 with metallic calcium using iodine as a “booster”. 

The yields were low and the metal was obtained in small pellets which were very 

difficult to recast into solid metal. In August, 1944, ZnCl2 was tried as a 

“booster” and solid biscuits of thorium-zinc alloy were obtained in good yields. 

Within three months the conditions necessary for good yield had been well 

enough established to allow expansion of the process to the use of a reduction 

bomb 6 inches in diameter. . . . By June 1946, most of the details had been 

worked out successfully and the bomb reduction of thorium fluoride was ready for 

expansion to large scale production.

The process, as use in December, 1946, was a metallothermic reduction of 

thorium fluoride by metallic calcium. Zinc chloride was used to provide 

additional heat, to give a more fusible slag, and to form a low-melting allow of 

thorium which would collect in the form of a solid biscuit. The reduction was 

carried out in an iron bomb 7 inches in diameter and 45 inches long. This bomb 

was lined with a layer of dolomitic oxide compacted into place around a steel 

mandrel with a pneumatic jolter. The charge was placed in the bomb which was 

then closed and the reduction started by preheating in a gas-fired furnace. The 

bomb was allowed to cool after the reaction and the biscuit of thorium-zinc alloy 

removed and cleaned. This method produced a biscuit of about 39 pounds of 

thorium-zinc alloy with better than 96 per cent yield of thorium. . . . By 

December 31, 1946 over 4500 pounds of thorium had been cast for shipment to 

other sites. [Emphasis added.] 

On the unconservative assumption that the total of 4,500 pounds of pure thorium had been 

produced between June 1946 and December 1946 by means of 39 pounds thorium-zinc biscuits 

with ~96% yield of thorium, a minimum of 120 reductions may be assumed for the 7 month 

period (or about 4 reductions per week). 

Production of thorium metal continued at Annex I (i.e., Little Ankeny) until 1949. Starting in 

1947 and continuing through the end of 1953, production and casting of thorium metal was also 

conducted in the Metallurgy Building. Total production of thorium at both facilities amounted to 

65 tons (or 130,000 pounds). 

Furthermore, assuming that the size of the bomb retorts remained constant after December 1946, 

a total of around 3,500 ThF4 bombs were reduced between June 1944 and December 1953, when 

thorium production ceased.
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3.0 FREQUENCY OF BLOWOUTS 

As previously noted in two separate reports issued to the Advisory Board, official monitoring 

records and radiological incident reports for Ames Laboratory are essentially non-existent. Since 

the issuance of these reports, further efforts have yielded no additional documentation that would 

quantify the number or frequency of blowouts, fires, and other radiological incidents. 

However, previous SC&A reports included excerpts of official statements made by Dr. Frank 

Spedding, Director of Ames Laboratory (as well as by others), that uranium and thorium 

blowouts were commonplace events, as given in the following statements:

Interview with Dr. Frank H. Spedding by Dorothy Kehlenbeck, July 5, 1961 (page 7): 

Interviewer: It seems to me I remember there were a few explosions over in Little Ankeny, too, 

weren’t there? [Emphasis added.] 

Spedding: Yes, these caused quite a bit of concern. We were reducing the uranium with 

magnesium and the magnesium, of course, as you know, when ground into finely divided 

state is the active ingredient in flash powder. The chopped up magnesium was mixed 

with uranium salt and put in a steel container and then heated in a furnace. And 

occasionally the magnesium and the uranium would start alloying with the steel 

container, punching a hole in it and giving rise to an explosion which was intensely 

brilliant, just as if they’d shot off a ton of flash powder inside the building. And the 

building actually appeared to glow and expand, although actually it didn’t, it was a 

brilliant light coming out of it and this caused a good deal of comment. Well, one day—

the explosions were really set off, we found later, by moisture. We were buying line [sic]

from St. Louis, having it hard fired, and then having it set up here. But in the spring 

things became moist and the shipments got damp coming to Ames so we suddenly had a 

flurry of explosions. Fortunately in chemistry, my experience has been that whenever 

anyone expects that there might be an explosion, nobody gets hurt. It’s only when you 

don’t expect something that you get hurt so our men were usually down behind a wall 

when the explosion took place and it did no harm. Although I remember one night we 

had an explosion that blew the whole south end of the building out and being an old 

wooden building, when things quieted down we all went outside and shoved the wall 

back in again and went to work. Another difficulty I had with explosions was, during 

this same period we had employed a number of girls to do the business part of the project 

and when we had six of these in one day and set the building afire they all resigned in 

mass, although I did persuade about half of them to stay with us assuring them that the 

explosions were under control and that they would not damage them. [Emphasis added.]
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Excerpts from F.H. Spedding Manuscript 2, Humorous Story Concerning Explosions and 

Education

Mr. Premo Chiotti was working with Dr. Wilhelm1 and me [i.e., Dr. F. Spedding] on the 

reduction of thorium fluoride to thorium metal. Mr. Chiotti was adding a booster to the 

reaction in a room a few doors down the hall from my office. Suddenly there was a 

terrific explosion which blew out several of the windows in the front of the chemistry 

building. When I came out of my office to see what had happened, the corridor was filled 

with dust about six feet above the floor to the ceiling. I was relieved to see that Mr. 

Chiotti had not been injured, but he looked very dazed and was pacing up and down the 

corridor. As I passed him, I heard him muttering, “I must have misplaced that decimal 

point, I must have misplaced that decimal point.”

1 Dr. Harley Wilhelm was the Associate Director of the Ames Laboratory and Mr. Premo Chiotti was a 

scientist at the Ames Laboratory when it was under contract to the U.S. Atomic Energy Commission.

These testimonials support the following assumptions: 

(1) Blowouts involving the reduction of UF4 and ThF4 were episodic events that were not 

uncommon during the entire period of facility operation. 

(2) From Spedding’s statement that “...I remember one night we had an explosion that blew 

the whole south end of the building out and being an old wooden building, when things 

quieted down we all went outside and shoved the wall back in again and went to 

work,” it is reasonable to conclude that this and other blowouts were not perceived as 

potential radiological threats, since no attempt was made to limit the time of exposure or 

to mitigate subsequent exposure by decontamination efforts, engineering controls/ 

building modification, or the use of respiratory protection. 

4.0 ASSESSMENT OF AIRBORNE CONTAMINATION LEVELS 

ASSOCIATED WITH BLOWOUTS

Although no radiological incident/investigative reports were found in behalf of the Ames 

Laboratory, there was a blowout incident at Fernald on April 5, 1954, which provides data that 

are applicable to Ames. 

Summarized below are descriptions and data contained in a report issued by J. H. Noyes et al. on 

April 5, 1954, entitled Committee Investigative Report of Thorium Blender Incident – March 15, 

1954. 

From Section 2.0: 

On March 15, 1954, personnel were attempting to blend a batch of thorium 

fluoride, calcium metal and zinc chloride preparatory to the reduction of the 

charge. After some delay in starting the blending operation and after 

unsuccessful attempts to properly seat a Gemco valve on the blender, a puff of 

 
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dust appeared at the mouth of the blender; then a short flame; followed at 

3:13 p.m. by a sheet of flame that extended horizontally from the blender a 

distance of about 45 feet over an arc segment of 38 feet. The duration of the 

flame is estimated at less than 10 seconds during which time tow persons... 

received serious burns which subsequently proved fatal, and two others received 

minor burns. Three additional persons received minor hand burns while assisting 

the injured. Physical damage to the equipment is estimated at about $700. 

Approximately 50 lb. of thorium were unaccounted for following the incident. 

The buildings was vacated and all activities stopped until an adequate 

investigation established such factors contributing to the accident as an 

examination of the building and equipment could offer. [Emphasis added.]

From Section 7.1: 

The blending of a charge of thorium fluoride using calcium metal and zinc 

chloride is similar to the process utilized by Iowa State College, at Ames, Iowa...

[Emphasis added.] 

The charge that was being blended when the incident occurred consisted of the 

following:

100 lb. thorium fluoride

10 lb. zinc chloride 

35.9 lb. calcium metal 

. . . Examination of the blender after the accident showed it to be nearly empty. . . 

These data suggest that 50 lbs. (or about 50%) of the 100 lbs. thorium charge were likely to have 

been volatilized and dispersed by the high temperature that characterizes this exothermic 

chemical reduction of ThF4. 

Applying these data to Ames, a 50% volatilization of a typical UF4 or ThF4 charge would have 

released about 21 lbs. of U and about 19.5 lbs. of Th into the air/environs at the Ames’ Annex I/ 

Little Ankeny facility.

5.0 ESTIMATES OF AIRBORNE CONTAMINATION LEVELS

Figure 1 provides a floor plan of Little Ankeny. The heavy dotted line identifies the original 

building. Within the heavy dotted line, the lower right-hand side identifies the “Reduction 

Area.” Unfortunately, the floor-plan does not include a scale that would permit an assignment of 

physical dimensions of the reduction area and surrounding rooms. However, available 

photographs, reproduced herein as Figures 2 and 3, depict the north and south view of the 

building and offer a crude measure of the building’s physical dimensions. Based on relational 

dimensions of windows, doors, and automobiles (parked on the north side), an estimate of about 

800 ft2 is appropriate for the reduction area; for the entire building (inclusive of add-ons), an area 
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of about 6,000 ft2 is estimated. The low profile of the building further suggests a standard 

ceiling height of 8 to 9 feet. 

Figure 1. Floor Plan of Little Ankeny Production Facility for Uranium and Thorium

Figure 2. Physical Chemistry Annex (Little Ankeny) North View
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Figure 3. South View of Little Ankeny

6.0 ASSUMPTIONS USED FOR MODELING AN ACUTE 

INTAKE/DOSE FROM A BLOWOUT

Potential inhalation exposures from blowouts associated with the reduction of UF4 or ThF4 at 

Ames Laboratory are affected by a host of parameters. While some parameters can be defined 

empirically from historical data, others require reasonable but claimant-favorable assumptions. 

For estimating potential workers’ doses, the following model is proposed. 

(1) Assume one blowout per month for the entire period of facility operations. 

(2) For either Unat or Thorium, a typical charge of 40 lbs. is assumed. This value is based on 

historical data for Ames.

(3) For a blowout, 50% of the charge is assumed to have been reduced to metal and 50% is 

assumed to remain in the fluoride form. 

(4) Due to the explosive nature of a blowout (i.e., blown-out windows, doors, etc.), it is 

assumed that as much as 75% of the charge is released to the outside, with only 25% 

remaining indoors. 

(5) For the metallic form, solubility Type S is assumed; for the fluoride form, solubility 

Type M is assumed.

(6) Based on the documented radiological incident data at Fernald, essentially all of the 

charge is assumed to escape from the bomb retort.
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(7) For simplicity, about 10 lbs. (or 4,540 g) of natural uranium or Th-232 (in equilibrium 

with Th-228) are suspended uniformly in air at time zero throughout Annex I building 

having an interior volume of about 50,000 ft3 (or ~1,350 m3). This would yield an initial 

air concentration of 3.36 g/m3 of Unat or Th-232/-228. 

(8) Due to the intense heat generated by the blowout, we will assume a 5-minute period for 

contaminants to condense and settle out. During this 5-minute period, the worker is 

assumed to have a breathing rate of 2 m3/hr with an air concentration of 3.36 g/m3, as 

discussed in bullet #7 above. (In behalf of a radiological incident at Pantex, NIOSH 

assumed a breathing rate of 3 m3/hr for a period of 5 minutes (see ORAUT-TKBS-0013-

5). 

(9) In the absence of any cleanup effort, the uniform deposition of 4,540 g of Unat or 

Th-232/-228 is assumed to have deposited onto 6,000 ft2 (or 540 m2), yielding a surface 

concentration of 8.4 g/m2. 

(10) Due to operation of machinery, human activity, building ventilation, and continued 

production of uranium and thorium metal, resuspension of contamination from floors and 

machinery would continue to create airborne levels for the next 30 days (or the next 

blowout). 

For the intermittent period of 30 days between successive blowouts, the following empirical data 

may be used to estimate the air concentration and inhalation of thorium that is likely to have 

reached a steady-state contamination level resulting from successive blowouts.

In a 1952 AEC survey/audit conducted at the Ames Laboratory, the working environment of 

22 production workers was evaluated. A breakdown of the daily weighted thorium exposure of 

the production personnel were as follows: 

Average Weighted Daily Exposure: 530 dpm/m3

 Max Weighted Daily Exposure: 3,100 dpm/m3

For modeling the 30-day post-episodic exposure, SC&A will use the unconservative average

value of 530 dpm alpha per m3

, and further make the unconservative assumption that the thorium 

alpha activity was contributed equally between Th-232 and Th-228. 

For the post-incident period of 30 days, a normal breathing rate of 1.2 m3/hr is assumed for a 

9-hour workday, yielding a total of 193 workhours. 

Estimate of Thorium Intakes Per Blowout 

• First 5 minutes = (3.36 g/m3)(2 m3/60 min.)(5 min.) 

= 0.56 g total thorium
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The intake of 0.56 g thorium is equal to the intake of 0.06 μCi of Th-232 and 0.06 μCi of 

Th-228. 

• For balance of 30 days = (530 dpm/m3)(1.2 m3/hr)(193 hr/30 days) 

= 122,748 dpm/30 days 

Assuming an equilibrium condition, an intake of 0.028 μCi is estimated for Th-232 and 

for Th-228. 

Further, assuming that one-half of the thorium existed as metal (or oxide) with a 

solubility Type S and one-half existed as ThF4 with Type M solubility, the following 

dose estimates are derived.

Table 1. Internal Dose Estimates for a Thorium Blowout* (rem)

Radionuclide/ 

Solubility

Amount 

Inhaled 

(μCi)

Bone Surface Lung

1 yr 5 yr 10 yr 30 yr 1 yr 5 yr 10 yr 30 yr

Th-232 Type S 4.4E-02 0.1 1.3 3.6 13.7 2.6 5.1 7.3 11.4

Th-228 Type S 4.4E-02 0.3 1.4 2.0 2.0 29.3 34.2 34.2 34.2

Th-232 Type M 4.4E-02 4.6 26.0 53.7 153 1.8 2.0 2.0 2.3

Th-228 Type M 4.4E-02 12.2 39.0 43.9 45.8 19.5 21.2 21.2 21.2

Total — — 12.7 67.7 103 214.5 53.2 62.5 64.7 69.1

* Dose estimates include inhalation exposures resulting form the first 5 minutes of a blowout and from

resuspension of contaminants for a 30-day work-period. Not included are exposures to kidneys, liver, and other 

organs.

Estimates of Uranium Intakes Per Blowout

• For the first 5 minutes = (3.36 g/m3)(2 m3/60 min.)(5 min.) 

= 0.56 g Natural Uranium 

The intake of 0.56 g Unat is equal to the following activities:

U-238 = 0.186 μCi

U-235 = 0.009 μCi

U-234 = 0.186 μCi

• For the 30-day post-incident period, the uranium air concentration will unconservatively

be scaled to the thorium data. This assumes a time-weighted average air concentration of 

1.2 mg/m3

. For a breathing rate of 1.2 m3/hr and 193 work-hours, an intake of 0.278 g is

estimated for the 30-day post-incident period. The intake of 0.278 g of Unat equals the 

following activities:
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U-238 = 0.093 μCi

U-235 = 0.0044 μCi

U-234 = 0.093 μCi

Table 2. Internal Dose Estimates for a Uranium Blowout* (rem)

Radionuclide/ 

Solubility

Amount 

Inhaled 

(μCi)

Bone Surface Lung

1 yr 5 yr 10 yr 30 yr 1 yr 5 yr 10 yr 30 yr

U-238 Type S 0.186 0.012 0.043 0.076 0.14 12.4 17.9 19.9 22.7

U-235 Type S 0.009 0.001 0.002 0.004 0.01 0.67 0.94 1.06 1.17

U-234 Type S 0.186 0.014 0.050 0.080 0.15 15.8 21.9 24.7 27.5

U-238 Type M 0.186 0.360 0.760 1.030 1.44 8.26 8.94 8.94 8.94

U-235 Type M 0.009 0.020 0.040 0.050 0.07 0.47 0.47 0.47 0.47

U-234 Type M 0.186 0.400 0.820 1.100 1.65 11.0 11.0 11.0 11.0

Total — — 0.81 1.71 2.34 3.43 50.94 61.15 66.07 71.78

* Dose estimates include inhalation exposures resulting form the first five minutes of a blowout and from

resuspension of contaminants for a 30-day work-period. Not included are exposures to kidneys, liver, and other 

organs.

7.0 SUMMARY CONCLUSIONS

The Ames Laboratory operated on the Iowa State University campus between 1942 and 1953. In 

the beginning, the Ames Project was primarily a metallurgical research laboratory that 

investigated the chemical properties of various heavy metals that were of interest to the 

Manhattan Project. A major focus was the reduction of uranium and thorium compounds to pure 

elemental metal.

Within months, Ames researchers pioneered a chemical reduction process for converting UF4 to 

a highly purified uranium metal. Because this process was efficient and cost effective, the Ames 

Project was expanded to include the large-scale production of purified uranium and later thorium 

metal. Thus, research and production became an integrated operation in which production 

processes were an extension of research efforts, and ongoing research reflected failures and 

problems encountered at the production level. 

Of the many difficulties affecting worker health and safety was the ability to safely execute the 

highly exothermic reduction of uranium and thorium in devices called bomb retorts. Chemical 

impurities and trace amounts of water resulted in blowouts or chemical explosions that 

frequently also resulted in fires. 

Formal documentation or investigation of these incidents do not exist, but are acknowledged in 

personal interviews and memoirs by key personnel, including the Director of the Ames Project.

After 1953, the production of uranium and thorium metal by means of the Ames protocols was 

transferred to other facilities, including the Feed Materials Production Center (FMPC) in 

Fernald, Ohio. Data involving a thorium blowout at FMPC in 1954 was used to model internal 

exposures from inhaling airborne contaminants in the first few minutes following a blowout, and 
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from resuspension of residual surface contamination for a period of 30 days (or 193 workhours). 

This time interval was selected on the assumption that the frequency of blowouts may have 

occurred on a monthly bases. 

Exposure to the lungs and bone surface from a single incident suggests substantial doses that 

increase with time, as shown in Table 1 and Table 2 above. The selection of 5-, 10-, and 30-year 

periods corresponds to critical time intervals between exposure and the induction period for 

cancer development.

REFERENCES 

Corbett, J.D. 2001, Frank Harold Spedding 1902-1984, “A Biographical Memoir by John S. 

Corbett,” Biographical Memoirs, Volume 80, The National Academy Press, Washington, DC. 

Fulmer, E.I. 1947, “History of the Ames Project under the Manhattan District to December 31, 

1946,” Report ISC-10, December 9, 1947. Springfield, Virginia. 

Kehlenbeck, D.S. 1961 Interview with Dr. Frank H. Spedding, Special Collections Department

University of Iowa Libraries (Tanya Zanish-Belcher, Head, Special Collections Department), 

Iowa City, Iowa 52242-1420 

Noyes, J.H. and others 1954, “Committee Investigation Report of Thorium Blender Incident – 

March 15, 1954.” SRDB Ref ID: 3635. April 5, 1954. 

Payne, C.S. 1992. The Ames Project: Administering Classified Research as a Part of the 

Manhattan Project at Iowa State College, 1942-45, PhD Dissertation of Carolyn Stilts Payne, 

Iowa State University, Ames, Iowa (SRDB Ref ID: 18851). 
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APPENDIX H: MEMORANDUM FROM DR. SKOOG TO DR. SPEDDING
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