SEC Petition Evaluation Report 

Petition SEC-00038 

Report Rev # 0 Report Submittal Date 04-09-06_

Subject Expert(s): Jim Berger, Dan Stempfley 

Site Expert(s): N/A 

Independent Technical Reviewer: N/A 

Petition Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Qualification Date DOE/AWE Facility Name 

SEC-00038 83.13 September 23, 2005 Ames Laboratory 

Feasible to Estimate Doses with Sufficient Accuracy? 

Single Class Multiple Classes Determination Established for All Classes 

Yes No X Yes No X Yes No X 

Petitioner Class Definition 

All scientists, production workers, technicians, salaried graduate students, physical plant workers, maintenance, administrative and 

support staff, and subcontracted workers who worked at the Ames Laboratory, Ames Laboratory campus, and/or AEC/DOE 

facilities/locations including: Annex 1, the old women’s gymnasium, “Little Ankeny,” Chemistry Building, and/or Wilhelm Hall from 

January 1, 1942 through December 31, 1955. 

Proposed Class Definition 

Employees of the DOE or DOE contractors or subcontractors who were monitored or should have been monitored while working at 

the Ames Laboratory in one or more the following facilities/locations: Chemistry Annex 1 (also known as “the old women’s 

gymnasium” and “Little Ankeny”), Chemistry Annex 2, Chemistry Building (also known as “Gilman Hall”), Research Building, or 

the Metallurgical Building (also known as Harley Wilhelm Hall) for a number of work days aggregating at least 250 work days during 

the period from January 1, 1942 through December 31, 1954, or in combination with the work days within the parameters established 

for one or more other classes of employees in the SEC. 

Related Petition Summary Information 

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

NONE 

Related Evaluation Report Information 

Report Title DOE/AWE Facility Name 

NONE 

ORAU Lead Technical Evaluator: 

(Document Owner) Signature on file 

 

4/09/2006 

Mike Mahathy Date 

Peer Review Completed By: Signature on file 4/10/2006 

Lavon Rutherford Date 

SEC Petition Evaluation Reviewed By: Signature on file 4/10/2006 

Jim Neton Date 

SEC Evaluation Approved By: Signature on file 4/10/2006 

Larry Elliott Date 
SEC-00038 FINAL Ames Laboratory

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SEC-00038 FINAL Ames Laboratory

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Evaluation Report Summary: SEC-00038, Ames Laboratory 

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

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

Energy Employees Occupational Illness Compensation Program Act of 2000, as amended, 42 USC 

(EEOICPA) and 42 CFR 83, Procedures for Designating Classes of Employees as Members of the 

Special Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program 

Act of 2000. 

Petitioner Requested Class Definition

Petition SEC-00038, qualified on September 23, 2005, requested NIOSH to consider the following 

class: All scientists, production workers, technicians, salaried graduate students, physical plant 

workers, maintenance, administrative and support staff, and subcontracted workers who worked at 

the Ames Laboratory, Ames Laboratory campus, and/or AEC/DOE facilities/locations including: 

Annex 1, the old women’s gymnasium, “Little Ankeny,” Chemistry Building, and/or Wilhelm Hall 

from January 1, 1942 through December 31, 1955.

NIOSH Proposed Class Definition

This evaluation defines a single class of employees for which NIOSH cannot estimate radiation doses 

with sufficient accuracy. This class includes: Employees of the DOE or DOE contractors or 

subcontractors who were monitored or should have been monitored while working at the Ames 

Laboratory in one or more of the following facilities/locations: Chemistry Annex 1 (also known as 

“the old women’s gymnasium” and “Little Ankeny”), Chemistry Annex 2, Chemistry Building (also 

known as “Gilman Hall”), Research Building, or the Metallurgical Building (also known as Harley 

January 1, 1942 through December 31, 1954, or in combination with work days within the parameters 

established for one or more other classes of employees in the SEC. 

Feasibility of Dose Reconstruction

The feasibility determination for the class of employees covered by this evaluation report is governed 

by the requirements of the Energy Employees Occupational Illness Compensation Program Act of 

2000 (EEOICPA) and 42 C.F.R. § 83.13(c)(1). This section of the rule states that “Radiation doses 

can be estimated with sufficient accuracy if NIOSH has established that it has access to sufficient 

information to estimate the maximum radiation dose for every type of cancer for which radiation 

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

the class, or if NIOSH has established that it has access to sufficient information to estimate the 

radiation doses of members of the class more precisely than an estimate of the maximum radiation 

dose.” 

NIOSH has established in this evaluation that it does not have access to sufficient information to 

estimate either the maximum radiation dose incurred by any member of the class or to estimate such 

radiation doses more precisely than a maximum dose estimate. The sum of information from the 

available resources is not sufficient to document or estimate the potential maximum internal and 

external exposure to members of the class, under plausible circumstances during the period of 

radiological operations at Ames Laboratory. 
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Health Endangerment

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by EEOICPA and 42 C.F.R. § 83.13(c)(3). Under these requirements, if it is not feasible to 

estimate with sufficient accuracy radiation doses for members of the class, NIOSH must also make a 

determination whether or not there is a reasonable likelihood that such radiation doses may have 

endangered the health of members of the class. The regulation requires NIOSH to assume that any 

duration of unprotected exposure may have endangered the health of members of a class when it has 

been established that the class may have been exposed to radiation during a discrete incident likely to 

have involved levels of exposure similarly high to those occurring during nuclear criticality incidents. 

If the occurrence of such an exceptionally high level exposure has not been established, then NIOSH 

is required to specify that health was endangered for those workers who were employed for a number 

of work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC (excluding aggregate work day requirements). 

The NIOSH evaluation did not identify any evidence from the petitioners or from other resources that 

would establish that the class was exposed to radiation during a discrete incident likely to have 

involved exceptionally high level exposures. However, the evidence reviewed in this evaluation 

indicates that some workers in the class may have accumulated substantial chronic exposures through 

episodic intakes of radionuclides, combined with external exposures to gamma, beta, and potentially 

neutron radiation. Consequently, NIOSH has determined that health was endangered for those workers 

covered by this evaluation who were employed for a number of work days aggregating at least 250 

work days within the parameters established for this class or in combination with work days within 

the parameters established for one or more other classes of employees in the SEC. 
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Table of Contents 

Evaluation Report Summary: SEC-00038, Ames Laboratory ................................................................ 3

1.0 Purpose and Scope.......................................................................................................................... 7

2.0 Introduction .................................................................................................................................... 7

3.0 Petitioner Requested Class/Basis and NIOSH Proposed Class/Basis ............................................ 8

4.0 Data Sources Reviewed by NIOSH................................................................................................ 9 

4.1 Site Profile Technical Basis Documents (TBDs) .................................................................. 9 

4.2 ORAU Technical Information Bulletins (OTIBs)................................................................. 9 

4.3 Facility Employees and Experts .......................................................................................... 10 

4.4 Previous Dose Reconstructions ........................................................................................... 10 

4.5 NIOSH Site Research Database .......................................................................................... 11 

4.6 Ames Laboratory Website................................................................................................... 11 

4.7 ORISE Center for Epidemiologic Research Database ........................................................ 11 

4.8 Documentation and/or Affidavits Provided by Petitioners ................................................. 12

5.0 Radiological Operations Relevant to the Proposed Class ............................................................ 12 

5.1 Ames Laboratory Plant and Process Descriptions............................................................... 12 

5.2 Ames Functional Areas ....................................................................................................... 14 

5.2.1 Uranium Metal Production...................................................................................... 15 

5.2.2 Uranium Metal Casting ........................................................................................... 15 

5.2.3 Uranium Scrap Recovery ........................................................................................ 15 

5.2.4 Thorium Metal Production ...................................................................................... 15 

5.2.5 Thorium Metal Casting............................................................................................ 16 

5.2.6 Studies of Uranium and Thorium Properties........................................................... 16 

5.2.7 Studies of Plutonium Properties .............................................................................. 16 

5.2.8 Development of Analytical Procedures................................................................... 16 

5.3 Characterization of Radiological Exposure Sources from Ames Operations...................... 17 

5.3.1 Alpha Particle Emissions......................................................................................... 18 

5.3.2 Beta Radiation Fields .............................................................................................. 18 

5.3.3 Neutron Exposures .................................................................................................. 19 

5.3.4 Photon Exposures .................................................................................................... 19

6.0 Summary of Available Monitoring Data for the Proposed Class................................................. 19 

6.1 Ames Laboratory External Monitoring Data....................................................................... 19 

6.2 Ames Laboratory Internal Monitoring Data........................................................................ 20 

6.2.1 Uranium Internal Monitoring ..................................................................................... 20 

6.2.2 Thorium and Thoron Internal Monitoring............................................................... 22 

6.2.3 Plutonium Internal Monitoring................................................................................ 22 

6.3 Ames Laboratory Air Sampling Data.................................................................................. 22 

6.4 Ames Laboratory Area Surveys .......................................................................................... 24 

6.5 Summary of Monitoring Data ............................................................................................. 24
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7.0 Feasibility of Dose Reconstruction for the Proposed Class ......................................................... 25 

7.1 Analysis of Data Sufficiency and Reliability ...................................................................... 25 

7.2 Internal Radiation Doses at Ames Laboratory .................................................................... 26 

7.2.1 Process-related Internal Doses at Ames Laboratory ............................................... 26 

7.2.1.1 Urinalysis Information and Available Data........................................... 26 

7.2.2 Ambient Environmental Internal Radiation Doses at Ames Laboratory................. 27 

7.3 External Radiation Doses at Ames ...................................................................................... 27 

7.3.1 Process-related External Radiation Doses at Ames Laboratory.............................. 28 

7.3.1.1 Beta and Gamma Characterization........................................................ 28 

7.3.1.2 Neutron Field Characterization ............................................................. 28 

7.3.1.3 External Monitoring .............................................................................. 28 

7.3.2 Ambient Environmental External Radiation Doses at Ames Laboratory ............... 29 

7.3.3 Ames Laboratory Occupational X-ray Examinations ............................................. 29 

7.4 Evaluation of Petition Basis for SEC-00038....................................................................... 30 

7.5 Summary of Feasibility Findings for Petition SEC-00038.................................................. 30

8.0 Evaluation of Health Endangerment for Petition SEC-00038...................................................... 30

9.0 NIOSH Proposed Class for Petition SEC-00038.......................................................................... 31

10.0 References .................................................................................................................................... 33 

Tables 

Table 4-1: Ames Laboratory Claims Submitted Under Dose Reconstruction Rule1 ............................ 11

Table 5-1: Timeline of Ames Activities................................................................................................ 14

Table 6-1: Uranium Excretion Study Results Grouped by Potential/Severity...................................... 21 

Table 6-2: Results Summary for Ames Laboratory Individuals in MED Uranium Excretion Studies. 22 

Table 6-3: 1943 Uranium Air Samples (General Area) ........................................................................ 23 

Table 6-4: Summary of Monitoring Data1 for the Ames Laboratory................................................... 24

Table 7-1: Summary of Feasibility Findings for SEC-00038 ............................................................... 30 
SEC-00038 FINAL Ames Laboratory

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SEC Petition Evaluation Report for SEC-00038

1.0 Purpose and Scope 

This report evaluates the feasibility of reconstructing doses for employees who worked at specified 

facilities during a specified time. It provides information and analyses germane to considering a 

petition for adding a class of employees to the congressionally-created Special Exposure Cohort 

(SEC). 

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

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

National Institute for Occupational Safety and Health (NIOSH). This report does not make the final 

determination as to whether or not the proposed class will be added to the SEC (see Section 2.0). 

This evaluation was conducted in accordance with the requirements of the Energy Employees 

Occupational Illness and Compensation Program Act (EEOICPA), 42 U.S.C. §§ 7384-7385, 

Procedures for Designating Classes of Employees as Members of the Special Exposure Cohort Under the 

Energy Employees Occupational Illness Compensation Program Act of 2000, 42 C.F.R. pt. 83, and the 

guidance contained in the Office of Compensation Analysis and Support’s Internal Procedures for the 

Evaluation of Special Exposure Cohort Petitions, OCAS-PR-004. 

2.0 Introduction 

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

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

evaluation is intended to provide a fair, science-based determination of whether or not it is feasible to 

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

reconstructions.1 

42 CFR § 83.13(c)(1) states: Radiation doses can be estimated with sufficient accuracy if NIOSH has 

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

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

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

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

estimate of the maximum radiation dose.

 

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

radiation doses for members of the class, NIOSH must also make a determination whether or not there 

is a reasonable likelihood that such radiation doses may have endangered the health of members of the 

class. The regulation requires NIOSH to assume that any duration of unprotected exposure may have 

endangered the health of members of a class when it has been established that the class may have been 

exposed to radiation during a discrete incident likely to have involved levels of exposure similarly 

high to those occurring during nuclear criticality incidents. If the occurrence of such an exceptionally 

high level exposure has not been established, then NIOSH is required to specify that health was 

 

1

 NIOSH dose reconstructions under EEOICPA are performed using the methods promulgated under 42 CFR 82 and the 

detailed implementation guidelines available at www.cdc.gov/niosh/ocas. 
SEC-00038 FINAL Ames Laboratory

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endangered for those workers who were employed for at least 250 aggregated work days either solely 

under the employment or in combination with work days within the parameters established for other 

SEC classes (excluding aggregate work day requirements). 

NIOSH is required to document the evaluation in a report. For development of the evaluation report, 

NIOSH relies on its own dose reconstruction expertise as well as technical support from Oak Ridge 

Associated Universities (ORAU). Upon completion, the report is provided to the petitioners, the 

public, and to the Advisory Board on Radiation and Worker Health. The Board will consider the 

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

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

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

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

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

and the proposed decision issued by NIOSH. The petitioner(s) may also seek a review of certain types 

of final decisions issued by the Secretary of HHS.2

 

3.0 Petitioner Requested Class/Basis and NIOSH Proposed Class/Basis 

Petition SEC-00038, qualified on September 23, 2005 requested that NIOSH consider the following 

class: All scientists, production workers, technicians, salaried graduate students, physical plant 

workers, maintenance, administrative and support staff, and subcontracted workers who worked at 

the Ames Laboratory, Ames Laboratory campus, and/or AEC/DOE facilities/locations including: 

Annex 1, the old women’s gymnasium, “Little Ankeny,” Chemistry Building, and/or Wilhelm Hall 

from January 1, 1942 through December 31, 1955.

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

is not feasible to estimate the radiation doses of this class of employees with sufficient accuracy. 

NIOSH considered the following information and affidavit statements to be sufficient to qualify SEC00038 for evaluation. 

An affidavit asserted that there were periods of inadequate radiological monitoring at Ames 

Laboratory and periods for which radiological monitoring records and data are unavailable, 

respective to the operation of this facility from 1942 through 1955 (Affidavit, 2005). The 

petitioner’s belief was justified during NIOSH’s review of available monitoring data for the period 

of operations at Ames Laboratory from January 1, 1942 through December 31, 1955. Although 

limited uranium urinary excretion data (studies from 1942-1945), thorium air sampling data (from 

1952-1953), personal external radiation exposure data (starting in October 1952), and area 

radiological monitoring data (from 1942-1943 and post 1951) exist, there are many apparent gaps 

in dosimetry information. 

Based on its research, NIOSH revised the requested class to include two additional buildings, 

Chemistry Annex 2 and the Research Building; both were associated with the Atomic Energy 

Commission (AEC) activities at Ames Laboratory. In addition, it was identified that “Little Ankeny,” 

the old women’s gymnasium, and Annex 1 (Chemistry Annex 1) were the same building. The worker 

 

2

 See 42 CFR 83 for a full description of the procedures summarized here. Additional internal procedures are available at 

www.cdc.gov/niosh/ocas. 
SEC-00038 FINAL Ames Laboratory

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description was also modified to include all people who worked for DOE or under DOE contractors; 

this includes all former AEC workers. Based on the information provided in History and Current 

Radiological Condition of the Ames Laboratory (Voss, 1979 ) and An Assessment of the Causes, 

Mitigation Efforts, and Current Status of Thorium-232, Uranium-238, and Beryllium Contamination 

in Wilhelm Hall at Ames Laboratory (Hokel, 1998), all AEC related operations were terminated at 

Ames by 1954. The end date of AEC operations at Ames was therefore assumed to be December 31, 

1954 for the purposes of this evaluation. Therefore, the NIOSH-proposed class includes employees of 

the DOE or DOE contractors or subcontractors who were monitored or should have been monitored 

while working at the Ames Laboratory in one or more of the following facilities/locations: Chemistry 

Annex 1 (also known as “the old women’s gymnasium” and “Little Ankeny”), Chemistry Annex 2, 

Chemistry Building (also known as “Gilman Hall”), Research Building, or the Metallurgical Building 

(also known as Harley Wilhelm Hall) for a number of work days aggregating at least 250 work days 

during the period from January 1, 1942 through December 31, 1954, or in combination with work 

days within the parameters established for one or more other classes of employees in the SEC. 

Based on the discussions with individuals who were interviewed and documentation obtained by 

NIOSH during research for this report, dosimetry information that would permit the performance of 

dose reconstructions with sufficient accuracy for the period immediately following AEC operations at 

Ames is available. However, as this information is outside of scope of this evaluation, based on the 

petitioner and proposed class definitions, further evaluation of this information has not been included 

in this report as to permit evaluation of the proposed class in a timely manner. 

4.0 Data Sources Reviewed by NIOSH 

NIOSH identified and reviewed data sources to determine the availability of information relevant to 

determining the feasibility of dose reconstruction for the class of employees requested by this petition. 

This included determining the availability of information on personal monitoring, area monitoring, 

industrial processes, and radiation source materials. The following sections summarize the data 

sources identified and reviewed. 

4.1 Site Profile Technical Basis Documents (TBDs) 

A site profile has not been written for Ames Laboratory. Not having a site profile does not 

automatically lead to a determination that dose reconstructions cannot be completed, nor is a site 

profile necessary to complete dose reconstructions. 

4.2 ORAU Technical Information Bulletins (OTIBs) 

An ORAU Technical Information Bulletin (OTIB) is a general working document that provides 

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

NIOSH reviewed the following OTIBs describing the methods for dose reconstruction to consider 

their usefulness for reconstructing doses of members of the proposed Ames SEC class: 

• OTIB: Internal Dose Overestimates for Facilities with Air Sampling Programs, ORAUT-OTIB0018; August 9, 2005 

• OTIB: Analysis of Coworker Bioassay Data for Internal Dose Assignment, ORAUT-OTIB-0019; 

October 7, 2005 
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• OTIB: Estimation of Neutron Dose Rates from Alpha-Neutron Reactions in Uranium and Thorium 

Compounds, ORAU-OTIB-0024; April 7, 2005 

• OTIB: Application of Internal Doses Based on Claimant-Favorable Assumptions for Processing 

as Best Estimates, ORAU-OTIB-0033; April 20, 2005

4.3 Facility Employees and Experts 

NIOSH interviewed a former Health Physicist at Ames Laboratory on November 1, 2005 (Personal 

Communication, 2005). The health physicist reported that until the early 1950s, personal monitoring 

for radiological exposure was only performed as part of the annual medical physical. He believes that 

little or no documentation exist regarding the actual history of the Health Physics Program at Ames 

Laboratory for the period of 1942 through the early 1950s, which includes the time period of uranium 

and thorium operations. He said that during his tenure, thorium production operations were mostly 

limited to the Metallurgical Building (now Harley Wilhelm Hall). Some thorium research was also 

conducted in the Chemistry Building. He also stated that when external monitoring was put in place, 

everyone with a potential for external exposure was monitored. However, there was no indication of 

how the exposure potential was determined. The information gained from the telephone conference 

with a former Ames Health Physicist is consistent with the documentation reviewed by NIOSH during 

the evaluation of SEC Petition 00038. 

NIOSH interviewed nine staff members from Ames Laboratory on October 17 and October 18, 2005. 

These staff members provided a history of early work performed at Ames Laboratory and also 

provided a walking tour of Ames Laboratory in which they discussed buildings that had been used in 

the MED/AEC work, or where these buildings had been located. These staff indicated that additional 

documentation and data had been sent several years ago to the University of Rochester, the Health and 

Safety Laboratory (HASL) Records Center, and Argonne West (Wessels, 2005). Records that were 

once stored at the University of Rochester and the HASL Records Center have since been sent to the 

Atlanta Records Center and the Germantown Records Center where NIOSH previously searched for 

Ames Laboratory documents. NIOSH identified one memorandum during the Atlanta Records Center 

search that discussed medical monitoring for the applicable period but no additional individual 

monitoring records were discovered for the period evaluated in this report. NIOSH did not locate 

radiological monitoring or exposure data pertinent to 1942 through 1952 operations at Ames 

Laboratory during the records search at the Germantown Records Center. In addition, Health and 

Safety staff from Ames Laboratory indicated that certain medical monitoring records may be stored in 

the Department of Energy (DOE) Oak Ridge Operations (ORO) records vault (Payne, 1992). NIOSH 

performed a search for Ames Laboratory records at the DOE ORO records vault and did discover 

several Ames related documents. However, none of these documents contained individual monitoring 

data or records pertinent to this evaluation report. 

4.4 Previous Dose Reconstructions 

NIOSH reviewed its dose reconstruction database, NIOSH OCAS Claims Tracking System (NOCTS), 

to identify dose reconstruction cases under EEOICPA that might provide information relevant to the 

petition evaluation. Table 4-1 provides a results summary of this review for the period of January 1, 

1942 through December 31, 1954 (Data available as of: March 6, 2006). 
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Table 4-1: Ames Laboratory Claims Submitted Under Dose Reconstruction Rule1

Description Totals 

Total number of cases submitted for energy employees who meet the proposed class definition 

criteria 36 

Number of dose reconstructions completed for energy employees who were employed during the 

years identified in the proposed class definition2 2 

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

proposed class definition 2 

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

proposed class definition 4 

Note: 

1

The first AMES EEOICPA claim was received in NOCTS on May 17, 2002. This table includes claims in NOCTS 

dating from May 17, 2002 through March 6, 2006. 

2

One dose reconstruction was completed for an individual having both Ames and ORNL employment. However, the 

dose reconstruction was completed using only ORNL data. 

NIOSH reviewed each individual claim to determine whether internal and/or external personal 

monitoring records could be obtained. NIOSH was not able to obtain personal radiological monitoring 

data representative of the class of workers defined in the SEC Petition for an employee represented in 

an individual claim that has been submitted for dose reconstruction under EEOICPA for the time 

period from January 1, 1942 through December 31, 1954. Twenty claims filed for this period 

contained medical X-ray information. 

4.5 NIOSH Site Research Database 

The NIOSH Site Research Database (SRDB) was reviewed for documents to support the evaluation of 

the proposed class. The documents identified during this review were evaluated for pertinence to this 

petition. Identified documents contained event histories, external dosimetry data from 1952 through 

2004, air sampling/dust sampling data from 1942 and 1952, bioassay/urinalysis results from 1952 

through 1953, process descriptions, materials handled, and Ames Laboratory activities from 1942 

through 2004. 

4.6 Ames Laboratory Website 

NIOSH was granted access to the Ames Laboratory website, known as the Ames Laboratory 

Documents for Former Worker Program Review, which provided Adobe PDF images of Ames 

documents (with title, author, and year) detailing the history of Ames Laboratory, the processes used, 

the locations of processes, and some references to additional documents that may contain information 

regarding personnel health and safety (Ames Web, 2005). 

4.7 ORISE Center for Epidemiologic Research Database 

Medical examination data for 104 Ames Laboratory employees are available in a dataset at the Oak 

Ridge Institute for Science and Education (ORISE) Center for Epidemiology Research (CER) for the 

time period of 1943 through1947 (ORAU, 2006). 
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4.8 Documentation and/or Affidavits Provided by Petitioners 

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

petitioners: 

1. Submission - Form B Standard OMB (SEC Form B, 2005); SECIS Document ID: 9075 

2. Occupational Exposures to Thorium and Beryllium, Paul Klevin, Ames Laboratory, Ames 

Laboratory, pages 1–73; SECIS Document ID: 9074 

3. The Ames Project, Administering classified research as part of Manhattan Project at Iowa State 

College, 1942 – 1945, Carolyn Stilts Payne, Iowa State University, 1992, pages 1- 298; SRDB Ref 

ID: 18851 

4. Urinary Excretion Studies, published in Industrial Medicine on the Plutonium Project, Survey and 

Collected Papers Edited by Robert S. Stone, M.D., McGraw-Hill Book Co. 1951, pp. 243-255; 

SECIS Document ID: 9087

5. Affidavit from submitter to OCAS containing notarized affidavit stating that no monitoring 

records exist for Ames Laboratory employees in the 1942 – 1955 period except for small subsets 

for limited time periods and with no documented methods or protocols; SECIS Document ID: 

9119 (Affidavit, 2005).

5.0 Radiological Operations Relevant to the Proposed Class 

The following subsections summarize the radiological operations at the Ames Laboratory from 

January 1, 1942 to December 31, 1954 and the information available to NIOSH to characterize 

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

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

of concern, and information describing the process through which the radiation exposures of concern 

may have occurred and the physical environment in which they may have occurred. The information 

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

5.1 Ames Laboratory Plant and Process Descriptions 

In 1942, a small metallurgical research program was established at Iowa State College (now Iowa 

State University) for the purpose of supporting the atomic energy activities at the University of 

Chicago. The original contract with the Office of Scientific Research and Development included 

development of a process for production of large quantities of high purity uranium for use as fuel in 

piles (nuclear reactors) and fundamental studies of the properties of materials to be used in these piles. 

Work under this contract was initially conducted in the Chemistry Building. It was in this facility that 

a process for producing highly pure metallic uranium was developed. The process was so successful 

that the contract was expanded to include production of the uranium metal on a pilot plant scale. As a 

result, the Ames Laboratory was established and the contract was transferred from the Office of 

Scientific Research and Development to the Manhattan Engineer District (MED). Since 1942, the 

Ames Laboratory has continued to support the MED and atomic energy and nuclear development 

activities of the U.S. Atomic Energy Commission and its successor organizations, the Energy 

Research and Development Agency and the Department of Energy. However, production of uranium 

ended by 1946 and production of thorium materials ended by 1954 (Voss, 1979; Hokel, 1998). 

In the fall of 1942, a pilot plant was set up in a remodeled single-story wooden building that had been 

previously used as a women’s gymnasium and also as a garage for college vehicles. This pilot plant, 
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which became known as Physical Chemistry Annex #1 or “Little Ankeny,” was used to produce large 

quantities of uranium metal and to cast uranium metal into the desired/necessary shapes for use in the 

development of fuels for nuclear reactors. During the early years, 1942 and 1943, of operation at 

Physical Chemistry Annex #1, the open porch was enclosed (to control dusty operations), and 

additions were constructed to accommodate increases in uranium production levels and new projects 

(Payne, 1992). The uranium production and casting operations at the Ames Laboratory continued in 

Physical Chemistry Annex #1 until early 1945 when uranium production was turned over to 

commercial firms (IS-T 2564). 

The machining of uranium metal to produce the shapes required for atomic piles resulted in large 

quantities of turnings and other scrap. As a result, in 1943, a method for the recovery of uranium from 

machining waste and scrap was developed at Ames. In 1944, a production-scale operation was 

established in a newly constructed one-story brick building, known as Physical Chemistry Annex #2. 

This uranium recovery operation continued until December 1945 (ISC-10). 

Thorium was a potential alternative to uranium and plutonium as a source of “fuel” for nuclear piles 

(ISC-10; Hokel, 1998). Soon after start-up of the uranium production at Ames Laboratory, 

development of a process for producing thorium metal was initiated. In 1943, thorium production was 

initiated at Physical Chemistry Annex #1 facility. Refinement of the thorium process continued 

through late 1946. By that time, approximately 4,500 pounds of thorium metal had been produced by 

the Ames Laboratory (ISC-10). In 1947, Ames was declared a major AEC research facility and the 

primary focus of the Ames Laboratory production program shifted from uranium production to 

thorium production. In 1949, production of thorium was relocated to the newly constructed 

Metallurgy Building where production continued until 1954 (Hokel, 1998). 

Beginning in 1942, along with uranium and thorium production operations, the Ames Laboratory 

conducted a variety of metallurgical research and bench-scale studies related to MED/AEC nuclear 

energy programs. Separation and purification of rare earths, such as yttrium, cerium, scandium, 

gadolinium, and lanthanum were the primary metallurgical research activities conducted at Ames 

Laboratory. The production and fabrication of beryllium crucibles and other special forms was another 

major operation. Ames Laboratory also conducted studies on properties of thorium and uranium alloys 

and corrosion-resistant coatings for uranium metal and alloys. Many of these activities continued 

beyond the end of World War II. The Chemistry Building was originally the site of these activities 

(ISC-10). In May 1947, the AEC established Ames Laboratory as one of its major laboratories for 

materials research. With the establishment of Ames Laboratory as one of AEC’s major laboratories, 

the Metallurgy Building was constructed to house some of the major activities of the newly formed 

center. Research and development activities continued to be conducted in the Chemistry Building and 

in the Metallurgy Building (Hokel, 1998). 

Available documents from January 1, 1942 through February 29, 1952 do not address the disposal of 

radioactive waste or the control and monitoring of air and liquid effluents. There are references to an 

incident involving the release of thorium to the sanitary drain system in the 1951/1952 time frame, 

resulting in contamination at the Ames City Wastewater Treatment Facility (Voss, 1979; Hokel, 

1998). Uranium tetrafluoride contamination of the ground surface around Annex #1 required removal 

and off-site disposal of the contaminated soil (Payne, 1992). 
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A summary of AEC activities at Ames Laboratory during the period covered by the petition are 

presented in Table 5-1. 

Table 5-1: Timeline of Ames Activities 

Operation Dates1 Building Activity 

Uranium Metal Production February 1942 – August 1942 Chemistry Process Development 

Uranium Metal Production August 1942 – December 1942 Chemistry Production 

Uranium Metal Production December 1942 – August 1945 Annex I Production 

Uranium Scrap Recovery Late 1943 – Early 1944 Chemistry Process Development 

Uranium Scrap Recovery Early 1944 – December 1946 Annex 2 Production 

Uranium Metal Casting December 1942 – January 1945 Annex 1 Process Development and 

Production 

Thorium Metal Production August 1943 – June 1946 Annex 1 Process Development 

Thorium Metal Production June 1946 – Late 1949 Annex 1 Production 

Thorium Metal Production Early 1950 –December 1954 Metallurgy Production 

Studies of Plutonium 

Properties 

Summer 1943 –December 19472 Research Research 

Plutonium/Fission Product 

Separations 

Start Date Unknown –December 

19542

Research and 

Chemistry 

Research and Hot Cell Work 

Thorium Metal Casting June 1946 – Late 1949 Annex 1 Production 

Thorium Metal Casting Early 1950 – Late 1954 Metallurgy Production 

Studies of Uranium and 

Thorium Properties 

Spring 1942 – December 19542 Chemistry Research 

Development of Analytical 

Procedures 

Spring 1943 – December 19543 Chemistry Research 

Annex 1 Demolition 1953 NA NA 

Notes: 

1

Exact start/end dates may vary, depending on reference. Those listed are the most common or the apparent 

consensus. Also, seasons, rather than months, were often provided. 2

No end dates provided in references. Also, no documentation to show these activities were conducted past 1954. 3

No end dates provided in references. Also, it is reasonable to assume development of lab procedures would have 

continued using low level laboratory sources. 

For the period evaluated in this report, the number of staff at Ames Laboratory peaked at about 600 

workers. The approximate production totals for this time period included the following: uranium 

metal, 2,000,000 pounds; uranium scrap recovery, 600,000 pounds; and thorium metal, 130,000 

pounds (through December 31, 1953). In 1953, following the termination of uranium metal production 

and the relocation of thorium production, the Chemistry Annex #1 was demolished. Thorium 

production continued to be done in the Metallurgy Building (Harley Wilhelm Hall). In 1972, Physical 

Chemical Annex #2 was also demolished. The Chemistry Building (currently known as Gilman Hall), 

the Research Building, and the Metallurgy Building are still being used by Ames Laboratory and the 

Iowa State University (Payne, 1992; Hokel, 1998). 

5.2 Ames Functional Areas 

Ames Laboratory operations included the following functional areas: 

• Uranium Metal Production 

• Uranium Metal Casting 

• Uranium Scrap Recovery 
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• Thorium Metal Production 

• Thorium Metal Casting 

• Studies of Uranium and Thorium Properties 

• Studies of Plutonium Properties 

• Development of Analytical Procedures 

5.2.1 Uranium Metal Production 

The process for production of uranium metal, developed by Ames Laboratory, utilized the reduction 

of uranium tetrafluoride by calcium metal. Uranium tetrafluoride was finely ground and mixed with 

an excess of metal calcium powder. This mixture (or charge) was placed into a refractory-lined iron 

container. A fuse wire, inserted into this charge, was electrically heated to initiate a thermite reaction, 

which resulted in molten uranium metal and calcium fluoride. The more dense uranium collected in a 

“biscuit” at the bottom of the container. Later improvements to the process replaced calcium with 

magnesium and entailed preheating the charge before the thermite reaction was initiated. The final 

process was capable of producing biscuits weighing up to approximately 42 pounds. Large quantities 

of highly pure uranium metal were produced at a reduced cost by this process. In July 1943, the 

production rate peaked at approximately 130,000 pounds per month (ISC-10). 

5.2.2 Uranium Metal Casting 

Casting of the metal into ingot shapes was performed by placing biscuits of uranium metal into a 

graphite crucible, heating the metal charge in a vacuum to melt it, and allowing the liquid metal to 

flow from the crucible into a graphite mold. This process resulted in uranium ingots up to 100 pounds 

that were both cast and machined on site or were provided to other fabrication facilities to produce 

desired shapes for use in atomic piles (ISC-10). 

5.2.3 Uranium Scrap Recovery 

Machine turnings and scrap were sorted by hand to remove large pieces of uranium metal, large 

foreign objects, and non-uranium scrap. A magnetic separator was then used to remove magnetic 

impurities, such as pieces of iron. Turnings were then cut, washed, rinsed, and dried and, again, hand 

inspected and passed over the magnetic separator to remove foreign matter. The remaining turnings 

and scrap were then pressed into small briquettes about one inch long and four and a quarter inches in 

diameter. The briquettes were cast into larger ingots in the same manner as described in Section 5.2.1 

for the biscuits of uranium metal (ISC-10). This work was isolated to Annex 2. 

5.2.4 Thorium Metal Production 

The initial process implemented in 1943 for producing thorium metal, developed by the Ames 

Laboratory, was similar to that for production of uranium metal. This process utilized the reduction of 

powdered thorium tetrafluoride with calcium metal. The metallic calcium was later replaced with zinc 

chloride and calcium fluoride. This mixture (or charge) was placed into a refractory-lined container 

and the reduction reaction was initiated by preheating the materials in a gas-fired furnace. The 

resulting thermite reaction produced a biscuit of thorium-zinc metal alloy, weighing approximately 39 
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pounds. Further heating of the thorium-zinc alloy drove off the zinc, leaving pure thorium metal (ISC10). 

Ames Laboratory prepared the purified feed for the reaction by dissolving thorium nitrate in nitric and 

oxalic acids, precipitating the thorium oxalate, drying the precipitate in trays, hydrofluorinating the 

precipitate to thorium tetrafluoride and crushing the thorium tetrafluoride to a fine powder. This 

process was used until thorium operations ceased at Ames Laboratory. 

5.2.5 Thorium Metal Casting 

Casting thorium into ingot shapes was performed by placing biscuits of thorium metal into a beryllia 

crucible, heating the metal charge in a vacuum to melt it, and allowing the liquid metal to flow from 

the crucible into a graphite mold. This process resulted in ingots of up to approximately 150 pounds 

being produced that were either machined on site or provided to other fabrication facilities to produce 

desired shapes for use in atomic piles (ISC-10; Kelvin, 1952). 

5.2.6 Studies of Uranium and Thorium Properties 

Ames Laboratory conducted a wide variety of research projects related to the chemical and physical 

properties of uranium and thorium. These projects included studies of the properties of thorium and 

uranium metal alloys, studies of thorium refractories, and studies regarding the properties of corrosion 

coatings for uranium metal and alloys (ISC-10; Iowa State University, date unknown). These studies 

also included the use of reprocessed uranium in quantities around 200 micrograms at a time. It should 

be noted that several employees could be working with these size samples concurrently. The work was 

conducted in the basement of the Chemistry Building (Fourtes, 2006). 

5.2.7 Studies of Plutonium Properties 

Ames Laboratory conducted laboratory studies on the physical and chemical properties of plutonium. 

These studies resulted in the development of techniques for separating plutonium and fission products 

from uranium metal and also resulted in the development of methods for analyzing plutonium, fission, 

and activation products. Chemical processes for large-scale separation of plutonium and fission 

products from the irradiated uranium power reactor fuel rods were also developed and tested. 

A shielded “hot canyon” handling facility with remote manipulators, capable of handling irradiated 

fuel containing up to five curies of fission products, was added in the Iowa State University’s 

Research Building to support the separations work (ISC-10; Iowa State University, date unknown). 

The research work associated with plutonium ended with the termination of AEC related activities at 

Ames in 1954 (ISC-10; Hokel, 1998). 

5.2.8 Development of Analytical Procedures 

Methods for routine analysis of fission products were developed at the Ames Laboratory. These 

activities resulted in the discovery of previously unidentified isotopes of phosphorus-33, promethium144, antimony-125, and five total isotopes of ruthenium and rhodium. Research on the parentdaughter relationship of strontium-90/yttrium-90 was also conducted. 
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Pioneering research in applications of alpha and beta spectroscopy and mass spectroscopy to identify 

specific radionuclides was part of the development of laboratory methods. A process for separating 

uranium-233 from thorium rods was also developed at Ames Laboratory (ISC-10; Iowa State 

University, date unknown; Iowa State University, 1961). The uranium-233 work ended with the 

termination of thorium processing work at Ames in 1953 (ISC-10; Hokel, 1998). 

5.3 Characterization of Radiological Exposure Sources from Ames Operations 

The potential sources of radiological exposure from operations that were performed at Ames 

Laboratory from January 1, 1942 through December 31, 1954 included uranium metal production, 

uranium scrap recovery, uranium and thorium metal casting, thorium metal production, uranium and 

thorium metal machining, and other special projects. 

Uranium and thorium metal production involved several dusty operations that resulted in work-area 

contamination and potential worker inhalation and ingestion (ISC-10). The principal sources of 

surface contamination and airborne dust were from the processes of grinding uranium fluoride into a 

fine powder, transferring the uranium fluoride powder from the grinder, and then mixing and loading 

the powder charge into the reduction crucible. Because the uranium had been separated from radium 

and its decay chain, radon-222 was not a potential inhalation concern (ISC-10). The principal sources 

of thorium surface contamination and airborne dust were from the processes of preparing and drying 

the fine powder and mixing and loading the powder charge into the reduction crucible. 

Examples of controls that were implemented at the Ames Laboratory include the use of local exhaust 

ventilation for potentially dusty uranium production operations. Exhaust ventilation was also provided 

for the general work areas at the Ames Laboratory. Ames Research Laboratory Occupational 

Exposure to Thorium and Beryllium suggests that these ventilation systems were initially considered 

inadequate and improvements were recommended (Klevin, 1952). Recommendations regarding 

surface cleaning were also made. The recommendations included replacing dry sweeping and the use 

of compressed air with methods that would reduce the potential for generating airborne dust (Klevin, 

1952). However, the records do not clearly indicate the extent (if any) to which these 

recommendations were implemented. 

There were also frequent small explosions and fires associated with the uranium metal production 

process (Payne, 1992). In The Ames Project: Administering Classified Research as a Part of the 

Manhattan Project at Iowa State College, 1942-45 (Payne, 1992), it was cited that as many as six 

small fires occurred in a single day; these fires contributed to work-area contamination and potential 

airborne uranium exposures. There are no records indicating that sampling for radiation exposure 

associated with these fires was performed. 

Personal protection used in potential dusty operations included the use of laboratory-provided clothing 

and gloves as well as restrictions on eating and smoking in areas where radioactive materials were 

handled. Although respiratory protection measures, such as gas masks and dust masks, were provided 

and their use was encouraged, the use of respiratory protection measures was not rigidly enforced at 

the Ames Laboratory. It was also indicated that personnel were recommended to shower (or bathe) at 

the end of the workday, but records suggest that all workers did not comply with this recommendation 

(Klevin, 1952; SEC Form B, 2005; Payne, 1992). 

 
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The specific sources of exposure are relayed in the following sections. 

5.3.1 Alpha Particle Emissions 

Alpha particle emissions from the radioactive materials handled at Ames Laboratory present the 

greatest potential for exposure through internal deposition via inhalation and ingestion (alpha particles 

do not present an external exposure hazard). The principal alpha-emitting radioactive materials 

associated with Ames Laboratory operations were natural uranium and natural thorium. Processed 

natural uranium consists of approximately equal activities of uranium-238 (4.20 MeV and 4.15 MeV 

alpha particles) and uranium-234 (4.77 MeV and 4.72 MeV alpha particles) (Radiological Health, 

1970). There are smaller amounts of uranium-235 (approximately 1/20 of the activity levels of 

uranium-238 or uranium-234) with alpha particles of 4.40 MeV and 4.36 MeV. Thorium-232 emits 

alpha particles of 4.01 MeV and 3.95 MeV, and the natural thorium decay series includes 6 daughter 

products that also emit alpha particles with energies ranging from 5.34 MeV to 8.78 MeV. The 

abundance of these daughter product emissions depends on the state of equilibrium with the thorium232 parent, which is, in turn, a factor of the time elapsed since the thorium process feed material was 

separated: a parameter which has not been determined from the review of available documents. 

The preparation and loading uranium and thorium powders into reduction crucibles were dusty 

operations with a potential for airborne contamination and surface contamination of facilities, 

equipment, and personnel. Machining of metallic uranium and thorium also had a potential for 

producing airborne and surface contamination. Chip fires associated with uranium machining resulted 

in airborne contamination. Research and development on plutonium separations processes and 

plutonium properties presented potential exposures to plutonium-239, with alpha emissions of 5.46 

MeV and 5.16 MeV. However, these operations were typically performed wet and involved smaller 

quantities of radioactive materials than those used for uranium and thorium production operations 

(Iowa State University, date unknown). 

5.3.2 Beta Radiation Fields 

Beta radiation was the dominant external source of radiation associated with activities involving 

contact with unshielded sources of uranium, such as the uranium metals production, uranium scrap 

recovery, and uranium machining processes at Ames Laboratory. 

For processed natural uranium, the dominant beta radiation was likely from the uranium-238 decay 

products. The most energetic of these beta particles is 2.29 MeV from Pa-234m. Thorium metal 

production and machining operations also involved unshielded contact with sources of beta radiation. 

While thorium-232 itself does not emit beta particles, five of the daughter radionuclides in the natural 

thorium decay series do have beta emissions, ranging in energy up to a maximum of 2.26 MeV 

(Radiological Health, 1970). The abundance of these daughter product emissions depends on the state 

of equilibrium with the Th-232 parent, That, in turn, is a factor of the time elapsed since the thorium 

process feed material was separated. The ratios of thorium to daughters were not documented in the 

information reviewed by NIOSH for this evaluation report. 
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5.3.3 Neutron Exposures 

Neutron exposure could have resulted from plutonium research and development activities. This work 

was performed in the Hot Canyon, but details on the experiments and separations are not available 

(ISC-10; Iowa State University, date unknown). Ames Laboratory performed varying extraction and 

reduction experiments, including the plutonium research, for which the neutron levels and energy 

spectra were not recorded or documented. 

5.3.4 Photon Exposures 

Photons from processed natural uranium are primarily from the Th-234 daughter of U-238 and are in 

the energy range of 30 – 250 KeV. There are higher energy photons – up to 1.00 MeV - from another 

uranium-238 daughter, Pa-234m, but the abundance of these photons is less than 1%. Thorium-232 

itself has no photons; however, many of the daughter radionuclides in the natural thorium decay series 

do emit photons. These photons have an energy range up to a maximum of 2.61 MeV (Radiological 

Health, 1970). The abundance of these daughter product photon emissions depends on the state of 

equilibrium with the thorium-232 parent, which is, in turn, a factor of the time elapsed since the 

thorium process feed material was separated. This parameter has not been determined from the review 

of available documents. 

Photon exposure rates up to 22 mR/h were reported for a thorium storage area, suggesting that this 

raw material for the thorium production operations was not newly separated. Research and 

development activities also entailed work with radioactive materials having photon emissions. The 

available documents do not include sufficient details of such activities to determine the levels and 

energies of the associated photon emissions. 

6.0 Summary of Available Monitoring Data for the Proposed Class 

Some personal and area monitoring data for the proposed class of Ames Laboratory employees 

evaluated in this report are available for intermittent periods from January 1, 1942 through December 

31, 1954. These data have been compiled in the NIOSH Site Research Database and are summarized 

below. 

6.1 Ames Laboratory External Monitoring Data 

Two film badge results were identified for 1944 with results in units of “Average Roentgens/8 hour 

days during week” (Tyrout, 1944) which were applicable to this evaluation. No other external 

dosimetry data appears to be available before October 1952. In An Assessment of the Causes, 

Mitigation Efforts, and Current Status of Thorium-232, Uranium-238, and Beryllium Contamination 

in Wilhelm Hall at Ames Laboratory (Hokel, 1998), the AEC made a recommendation from a March 

1952 study to install a personnel monitoring service which would include film badge service and 

radiation monitoring. Based on this recommendation NIOSH assumes that prior to that date there was 

not a routine external radiation monitoring program at Ames Laboratory in Wilhelm Hall, the 

Chemistry Building, the Research Building, Annex 1, and Annex 2. 

1953 records indicate about 166 workers were monitored with a total of about 3,200 results, most of 

which were reported as total dose. NIOSH found over 7,800 results for about 190 workers in 1954. 
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These results are reported in a mixture where some have beta and gamma results and some are 

reported in total dose only. This data was collected at the origin of a formal monitoring program at 

Ames and provides general film badge and direct reading (pocket chamber) data. Although some 

quality check records are available, this documentation and data does not provide sufficient supporting 

information that relates to the early operations that were performed during the time period evaluated 

in this report. Therefore, further evaluation and development of this data, as it relates to the later 

period work, was not performed. 

Although NIOSH obtained neutron monitoring results for workers in the Ames Laboratory Research 

Building for part of 1953 and 1954, there is no documentation to indicate these workers were involved 

with thorium research or other AEC sponsored activities. NIOSH discovered no evidence of 

individual neutron monitoring, or the acknowledgement of potential neutron exposures, prior to 1953. 

The personnel interview of November 1, 2005, as described in Section 4.3, indicated that although 

there was no indication obtained of how exposure potential was determined, once an external 

monitoring program was initiated, everyone with a potential for external exposure was monitored. 

Based on the information reviewed for this evaluation, the formal personnel monitoring program at 

Ames was not fully developed until after the period evaluated in this report. 

6.2 Ames Laboratory Internal Monitoring Data 

A search of all documents and data available to NIOSH located limited bioassay data for the period 

from January 1, 1942 through December 31, 1954. As summarized below, only limited in vitro

bioassay data, and the associated analysis of the monitoring data is available for 1942 through 1943 

and 1952 through 1953. 

6.2.1 Uranium Internal Monitoring 

Ames Laboratory initially monitored employees for radiation exposure by medical testing to look for 

abnormalities in blood chemistry (Payne, 1992). This practice was discontinued in 1946 (Payne, 

1992). No direct mention of radiological monitoring was identified in individual medical monitoring 

records. However, a specific code (the letter “T”) appears to have been used to identify uranium blood 

test results for Ames Laboratory employees. This was a medical test that looked for abnormal albumin 

results as an indicator of exposure to uranium. The 1946 Myers correspondence reports that highly 

exposed employees were sampled monthly by urinalysis and other employees were sampled quarterly 

through 1945 (Myers, 1946). Only thirty-four uranium bioassay records have been found for Ames 

Laboratory employees for that time period. 

The thirty-four bioassay samples were collected by the Army Corps of Engineers in July, August, and 

September of 1944 and were analyzed for uranium (“X ion”). The analytical results ranged from 0 

Mg/l to 0.3 Mg/l, but no information was provided on the method used to analyze these samples. The 

Army Corps of Engineers stated that at that time, no tolerance value had been established for the X 

ion, but that the report results were about the same as those obtained from other groups handling the 

same special materials (Tyrout, 1944). 

In addition to these results, a uranium excretion study was performed at Ames Laboratory between 

1943 and 1945 (Industrial Medicine, 1951). This study was part of a Manhattan Engineer District 
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(MED) study of 86 individuals exposed to different uranium compounds at Ames, Chicago, and Oak 

Ridge. Forty-eight individuals from Ames Laboratory were sampled. Exposure was determined to be 

mostly due to uranium tetrafluoride salt (green salt). Only men were sampled for the study. The 

individuals in the test were put into one of four groups according to their presumed exposure to 

uranium, with Group one (1) having the highest exposure potential and Group four (4) having the 

lowest. Results of the study for the four groups are shown in Tables 6-1 and 6-2. 

Table 6-1: Uranium Excretion Study Results Grouped by Potential/Severity 

Group 1 Group 2 Group 3 Group 4 

Sample 

# Case 

Amount 

(μg/l) Sample 

# Case Amount (μg/l) 

Sample 

# Case Amount (μg/l) 

Sample 

# Case Amount (μg/l) 

1 1 40 1 12 15 1 32 24 1 43 <3 

2 1 96 2 13 17 2 33 27 2 44 <3 

3 2 52 3 14 13 3 34 7 3 45 7 

4 3 86 4 15 38 4 35 9 4 46 <3 

5 3 50 5 16 21 5 36 19 5 47 <3 

6 4 100 6 17 40 6 37 22 6 48 9 

7 4 44 7 18 21 7 38 22 –– –– –– 

8 4 70 8 19 33 8 38 18 –– –– –– 

9 4 200 9 19 58 9 38 3 –– –– –– 

10 5 126 10 20 33 10 38 3 –– –– –– 

11 5 96 11 21 54 11 39 5 –– –– –– 

12 5 74 12 22 64 12 40 16 –– –– –– 

13 6 84 13 23 10 13 41 15 –– –– –– 

14 6 200 14 23 16 14 42 33 –– –– –– 

15 6 73 15 24 11 –– –– –– –– –– –– 

16 7 48 16 24 11 –– –– –– –– –– –– 

17 7 40 17 25 87 –– –– –– –– –– –– 

18 8 29 18 25 64 –– –– –– –– –– –– 

19 9 25 19 25 80 –– –– –– –– –– –– 

20 10 12 20 26 130 –– –– –– –– –– –– 

21 11 31 21 27 80 –– –– –– –– –– –– 

–– –– –– 22 28 108 –– –– –– –– –– –– 

–– –– –– 23 29 64 –– –– –– –– –– –– 

–– –– –– 24 29 64 –– –– –– –– –– –– 

–– –– –– 25 30 28 –– –– –– –– –– –– 

–– –– –– 26 31 43 –– –– –– –– –– –– 

75 

(average) 

46 

(average) 

16 

(average) 

<5 

(average) 

Note: 

–– indicates no data 
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Table 6-2: Results Summary for Ames Laboratory Individuals in MED Uranium Excretion Studies 

Group Number of % of samples containing uranium per liter 

Individuals 

Number of 

Samples 0-10 μg 10-20 μg 20-40 μg 40-80 μg 80-200 μg 

4 6 6 100 0 0 0 0 

3 11 14 35 29 35 0 0 

2 20 26 0 23 27 31 19 

1 11 21 0 5 14 43 38 

Source: Industrial Medicine, 1951 

The Manhattan Engineer District performed a separate urinary excretion study of one male Ames 

Laboratory employee from March 1943 though June 1945 (Industrial Medicine, 1951). At that time, 

the Laboratory believed this employee had received the most exposure to uranium of any Ames 

employee at the facility, although the support for this belief was not included in the reference 

document. Results from 10 analyses made from September 1944 through June 1945 ranged from 24 to 

200 μg/liter of uranium. Large scale operations involving uranium were curtailed at Ames Laboratory 

in June 1945. Results of 50 urine samples obtained after the end of exposure starting in August 1945 

ranged from 5 to 10 μg/liter of uranium. 

6.2.2 Thorium and Thoron Internal Monitoring 

NIOSH has identified ninety bioassay (urine) samples that were collected in March 1952 by AEC and 

analyzed for thorium (AEC, Urine Samples; AEC, Various Samples). NIOSH has also identified 

approximately 70 bioassay (urine) samples were collected by AEC in 1953 and analyzed for thorium 

(AEC, Urine Samples; AEC, Various Samples). NIOSH did not, however, identify any thorium 

bioassay analysis prior to March 1952. 

6.2.3 Plutonium Internal Monitoring 

The potential for plutonium exposures existed during the plutonium property studies performed at 

Ames. The plutonium property studies were performed concurrently with the period when uranium 

metal processing studies occurred at Ames (through 1946). NIOSH did not identify any indication that 

plutonium bioassay analyses were performed for any period when the potential for plutonium 

exposures existed at Ames Laboratory.

6.3 Ames Laboratory Air Sampling Data 

NIOSH has not located any documentation indicating that Ames Laboratory conducted a routine air 

sampling program for uranium, plutonium, or thorium during the period evaluated in this report. 

However, NIOSH did find twenty-two general area air dust (uranium) samples that were collected in a 

special study performed in May, June, and July of 1943 by the Army Corp of Engineers (Friedell, 

1943, Iowa State College, 1943. The purpose of the sampling was not identified in the documentation 

associated with the sampling results. These results are shown in Table 6-3. 
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Table 6-3: 1943 Uranium Air Samples (General Area) 

Sampled Area Job Function Analyte Sample Date 

Sample 

Flow Rate 

(Cu ft./min) 

Sample Activity 

(μg/m3) 

Slow Set Room –– Not Specified 5/10/1943 3 4,360 

Magnesium Room –– Not Specified 5/10/1943 3 188 

Loading Dock –– Not Specified 5/10/1943 3 615 

Near Jolter Bomb loading Not Specified 6/16/1943 3 2,830 

Near 

Micro-pulverizer 

Grinding 

(Lime, Slow Set) Not Specified 6/16/1943 3 37,100 

Near Riffle Magnesium 

Processing Not Specified 6/16/1943 3 3,420 

Near Jolter Bomb Loading Uranium 6/28/1943 3 53.3 

Near 

Micro-pulverizer 

Grinding 

(Lime, Slow Set) Uranium 6/28/1943 3 1,080 

Near Riffle Magnesium 

Processing Uranium 6/28/1943 3 85 

Sample Room Metal Grinding Not Specified 7/10/1943 3 707 

Cut-off Room Metal Cutting Not Specified 7/12/1943 3 2,240 

Slag Room Opening Bomb Not Specified 7/12/1943 3 3,300 

Cut-off Room Metal Cutting Uranium 7/15/1943 3 420 

Sample Room Metal Grinding Uranium 7/15/1943 3 63.5 

Slag Room Opening Bomb Uranium 7/15/1943 3 153 

Slag Room Opening Bomb Uranium 7/15/1943 3 153 

Cut-off Room Metal Cutting Uranium 7/31/1943 3 420 

Sample Room Metal Grinding Uranium 7/31/1943 3 63.5 

Slag Room Opening Bomb Uranium 7/31/1943 3 153 

Note: 

–– indicates no known data

NIOSH also has approximately 700 general air samples (thorium samples collected in an AEC study 

performed in March 1952 (Klevin, 1952), approximately 270 breathing zone air samples (collected 

during this same time frame/study), and air sampling for Wilhelm Hall (performed by Iowa State 

University in February 1953 (Hokel, 1998). The AEC study includes thorium, although the specific 

radionuclide can not be assumed without equilibrium data and thoron results (Klevin, 1952). The 

methodology in use at that time for estimating thoron concentrations was dependent on assumptions 

of thorium decay series equilibrium and equivalent sample collection efficiency for the various 

members of the thorium decay series present in airborne dust (Klevin, 1952). Because of the lack of 
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source information that would permit validation of the estimates of the actual thoron concentrations, 

NIOSH did not perform further evaluation of the thoron data provided in the AEC study. 

6.4 Ames Laboratory Area Surveys 

The March 1952 study documented in Ames Research Laboratory Occupational Exposure to Thorium 

and Beryllium (Klevin, 1952), documents alpha, beta, and gamma radiation measurements were made 

and documented in the thorium refining and processing areas (separate surveys of the same areas have 

been performed and documented in more recent years). The data demonstrate that Wilhelm Hall was 

contaminated from thorium operations. Further confirmation is available from a roof survey in 1984 

and survey of exhaust ducts in the basement of the Hall in 1991 (Hokel, 1998). NIOSH has not 

located documentation indicating contamination levels in Annex 1 at the times of its demolition in 

1953.

6.5 Summary of Monitoring Data 

A summary of monitoring data obtained for Ames Laboratory from January 1, 1942 through 

December 31, 1955 is provided in Table 6-4. 

Table 6-4: Summary of Monitoring Data1 for the Ames Laboratory 

Available Data Qualifications on Data 

External Dosimetry Data Limited monitoring data has been 

identified for external exposures 

resulting from Ames Laboratory 

work performed in 1953 through 

1954, but no work area assignment 

or location has been designated in 

that data. 

No data, applicable to reconstructing 

thorium or plutonium dose for the 

proposed class, are available for Ames 

Laboratory workers prior to 1953. 

Neutron Dosimetry Data No data has been identified for 

monitoring neutron exposure from 

the uranium or thorium operations or 

the bench scale processing of 

plutonium performed at Ames during 

the period evaluated in this report. 

None 

Internal Dosimetry Data Results from a uranium excretion 

study in 1943 through 1945 and 

samples collected by the Army 

Corps of Engineers in 1944 for 

uranium exposure. 

Limited data on thorium and thoron 

exposures are available for the 

period of March 1952 through 1953. 

No data, applicable to reconstructing 

thorium or plutonium dose for the 

proposed class, are available for Ames 

Laboratory workers prior to 1952. 
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Table 6-4: Summary of Monitoring Data1 for the Ames Laboratory 

Available Data Qualifications on Data 

Air Sampling/ Environmental 

Sampling Data 

Limited air (dust) sampling data is 

available for uranium operations in 

1943. These uranium samples were 

taken in 1943. 

Limited thorium/ thoron and no plutonium 

(pre-1947) air sample results exist for the 

period prior to March 1952. Limited data 

are available for the period of March 1952 

through 1953. 

Note: 

1

Summary is for January 1, 1942 through December 31, 1954 

7.0 Feasibility of Dose Reconstruction for the Proposed Class 

The feasibility determination for the proposed class of employees covered by this evaluation report is 

governed by EEOICPA and 42 CFR § 83.13(c)(1). Under this Act and rule, NIOSH must establish 

whether or not it has access to sufficient information to either, estimate the maximum radiation dose 

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

under plausible circumstances by any member of the class, or to estimate the radiation doses to 

members of the class more precisely than a maximum dose estimate. If NIOSH has access to 

sufficient information for either case, then it would be determined that it was feasible to conduct dose 

reconstructions. 

In making determinations of feasibility, NIOSH begins by evaluating whether current or completed 

NIOSH dose reconstructions demonstrate the feasibility of estimating with sufficient accuracy the 

potential radiation exposures of the class. If not, NIOSH systematically evaluates the sufficiency of 

different types of monitoring data, process and source or source term data, which together or 

individually might assure NIOSH can estimate either the maximum doses members of the class might 

have incurred, or more precise quantities that reflect the variability of exposures experienced by 

groups or individual members of the class. This approach is specified in the SEC Petition Evaluation 

Internal Procedures available at www.cdc.gov/niosh/ocas. 

The evaluation that follows examines separately the availability of information necessary for 

reconstructing internal and external radiation doses of members of the proposed class. 

7.1 Analysis of Data Sufficiency and Reliability 

Performing internal and external dose reconstructions requires worker monitoring data or source term 

and process information. Worker monitoring data includes data from members of the proposed class 

as well as data from workers outside the proposed class who were performing jobs with higher 

exposure potentials. Using worker monitoring data provides a means of calculating claimant-favorable 

and maximum potential radiation doses for class members who were unmonitored or have gaps in 

their monitoring records. In the case of this evaluation, the thorium and plutonium data sets are 

insufficient to permit a complete evaluation for the purposes of estimating internal and external 
SEC-00038 FINAL Ames Laboratory

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exposures with sufficient accuracy for members of the proposed class. Therefore, further evaluation of 

the pedigree of any of the data (including the uranium data) was not performed. 

7.2 Internal Radiation Doses at Ames Laboratory 

The principal source of internal radiation doses for members of the proposed class would have been 

due to inhalation and ingestion of radiological contaminants during the performance of pilot projects, 

uranium laboratory and production activities, and thorium laboratory and production activities. Other 

potential sources of internal exposure at Ames Laboratory included bench scale work associated with 

plutonium separation experiments. 

Information in the NIOSH Site Research Database, information obtained from the Ames Laboratory 

website, and information in the affidavit provided by the petitioner indicates a substantial potential for 

internal exposure hazard from thorium and uranium (and their progeny) while performing work at the 

Ames Laboratory. In addition, the potential for thoron exposures existed during the time period 

evaluated in this report. The potential for these exposures is supported by the radiological conditions 

discovered during the performance of more recent contamination surveys and 1988 decontamination 

efforts at the Ames Laboratory facilities (Hokel, 1998). The authors of An Assessment of the Causes, 

Mitigation Efforts, and Current Status of Thorium-232, Uranium-238, and Beryllium Contamination 

in Wilhelm Hall at Ames Laboratory (Hokel, 1998) assumed that the spread of contamination was (at 

least in part) a result of airborne contaminants transported throughout the Ames Laboratory facilities 

as a result of the radiological activities that occurred from January 1, 1942 until thorium operations 

was discontinued in 1954. 

Limited individual monitoring records are available for uranium exposures, and no individual 

monitoring records are available for thorium or plutonium exposures at Ames Laboratory from 

January 1, 1942 through February 1952. Limited individual and area results for thorium and thoron 

sampling are available after that period but the data are not sufficient for reconstruction of internal 

doses. As a result of these limitations and changes in processes and exposures prior to the 1952 

monitoring, and with routine monitoring beginning in the 1954-1955 timeframe, NIOSH cannot 

establish a maximum internal exposure scenario that addresses all of the internal exposure potential 

for the petitioning class, and therefore cannot estimate their internal doses with sufficient accuracy. 

The subsections below summarize the extent and limitations of information available for 

reconstructing the internal doses of members of the class evaluated in this report. 

7.2.1 Process-related Internal Doses at Ames Laboratory 

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related internal doses of members of the proposed class. 

7.2.1.1 Urinalysis Information and Available Data

Ames Laboratory initially monitored employees for radiation exposure by medical testing to look for 

abnormalities in blood chemistry (Payne, 1992). This practice was discontinued in 1946 (Payne, 

1992). No direct mention of radiological monitoring was identified in individual medical monitoring 

records. However, a specific code (the letter “T”) appears to have been used to identify uranium blood 

test results for Ames Laboratory employees. This was a medical test that looked for abnormal albumin 
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results as an indicator of exposure to uranium. The 1946 Myers correspondence reports that highly 

exposed employees were sampled monthly by urinalysis and other employees were sampled quarterly 

through 1945 (Myers, 1946). 

The data from the uranium excretion studies for the workers at the Iowa State College, summarized in 

Section 6 of this report, were reviewed for their potential application in reconstructing dose for the 

class in this petition. This excretion study also included an evaluation of the highest exposed 

individual at Ames for the period of September 1944 to July 1945. This individual’s exposures ranged 

from 24 to 200 μg/l (Industrial Medicine, 1951). 

Although this uranium internal data would be useful in estimating internal uranium doses for Ames 

workers, further development/evaluation of this data as not performed based on the lack of thorium 

and plutonium data for the same time period, which prevents bounding/establishing a maximum 

internal exposure scenario for the proposed class evaluated in this report. 

Routine air monitoring data can be used to support development of an internal exposure model. As 

discussed in Section 6, NIOSH has uranium air sample data from 1943 and thorium air sample data 

from 1952. No air sampling data was available for any plutonium activities. Based on NIOSH’s 

review of the available data, there is no indication that a routine air sampling or monitoring program 

existed at Ames prior to 1953. After review of the air sample data, NIOSH has determined the data 

does not provide sufficient information to support establishing a bounding exposure scenario. As a 

result, the estimation of doses resulting from internal exposures to uranium, thorium, thoron, or 

plutonium, from the available air monitoring data, for the period of January 1, 1942 through 

December 31, 1954 can not be reconstructed or estimated with sufficient accuracy for the proposed 

class defined in this evaluation. 

7.2.2 Ambient Environmental Internal Radiation Doses at Ames Laboratory 

There is no evidence that any environmental or ambient air monitoring for the purpose of internal 

exposure assessment was performed at Ames Laboratory prior to March 1952. As discussed in Section 

8.2.2, some thorium and thoron area air sampling was performed for a limited time frame after that 

period. Given the lack of adequate process-related air monitoring data and bioassay data, NIOSH did 

not further evaluate the feasibility of dose reconstruction for environmental/ambient exposures 

received at Ames during the period evaluated in this report. 

7.3 External Radiation Doses at Ames 

The principal source of external radiation doses for members of the proposed class would have been 

due to exposures to photon (gamma) and electron (beta) radiation. Likely, the primary source of 

gamma radiation exposures would have been from the thorium activities. The primary source of beta 

radiation exposures would have been from the uranium activities. As discussed in Section 6, neutron 

exposures are also possible. 

Other than two film badge monitoring results from 1944, no individual external monitoring records 

are available for the class of Ames Laboratory workers who worked during the period from January 1, 

1942 through September 1952. Although NIOSH has some source term information for this period, 

this information is inadequate to reconstruct maximum exposure scenarios. The limited data available 
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for the period from October 1952 through December 31, 1954 are also inadequate for estimating doses 

from external exposures with sufficient accuracy. The subsections below summarize the extent and 

limitations of information available for reconstructing the external doses of members of the class 

evaluated in this report. 

7.3.1 Process-related External Radiation Doses at Ames Laboratory 

The following subsections summarize the extent and limitations of information available for 

reconstructing the process-related external doses of members of the proposed class. 

7.3.1.1 Beta and Gamma Characterization

As discussed in Section 5, the most dominant source of beta radiation was associated with uranium 

work, primarily hands-on work associated with unshielded processing and machining work that 

occurred until 1946 at Ames. The specific source of beta radiation from this work was from the 

uranium-238 decay products. The most energetic of these beta particles was 2.29 MeV. In addition, 

the potential for beta exposures also existed during unshielded production and machining of thorium. 

This beta exposure would have been due to emissions from thorium daughter radionuclides ranging in 

energy up to a maximum of 2.26 MeV (Radiological Health, 1970). As previously discussed 

throughout Sections 5, 6, and 7, source term information relating to thorium operations and 

processing, which prevents the identification of the ratios or abundance of thorium daughters, is not 

adequate to permit reconstructing dose for the proposed class with sufficient accuracy. 

Gamma radiation from processed natural uranium is primarily from the thorium-234 daughter of 

uranium-238 and is in the energy range of 30 KeV – 250 KeV. There are higher energy photons, up to 

1.00 MeV, from another uranium-238 daughter, protactinium-234m. However, the abundance of these 

photons is less than 1%. Thorium-232 itself has no photons, but many of the daughter radionuclides in 

the natural thorium decay series do emit photons. These photons have an energy range up to a 

maximum of 2.61 MeV (Radiological Health, 1970), which could be assumed for dose reconstruction. 

However, the abundance of these daughter product photon emissions depends on the state of 

equilibrium with the thorium-232 parent, which is, in turn, a factor of the time elapsed since the 

thorium process feed material was separated. NIOSH does not have this information, and cannot 

estimate the quantity of these daughter product photon emission from thorium daughter radionuclides. 

7.3.1.2 Neutron Field Characterization

The work associated with plutonium and the research associated with thorium and uranium in the 

laboratories had the highest potential for exposure to neutrons. While the potential for exposure to 

neutrons existed at Ames Laboratory, NIOSH has insufficient details, relating to source term 

information for the plutonium work or enrichment information relating to the thorium or uranium 

work, to characterize the possible neutron field or energies. NIOSH does not have this information, 

and cannot estimate the potential neutron exposures for this proposed class as evaluated in this report. 

7.3.1.3 External Monitoring

There is no evidence that sufficient beta-gamma external radiation exposure monitoring (through 

personal dosimetry) or area radiation monitoring applicable to evaluating personnel external 
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exposures was performed for any Ames Laboratory personnel prior to October 1952.External 

exposure data, mostly penetrating, is available for some workers starting in October 1952. Although a 

health physicist who worked at Ames Laboratory indicated that everyone with exposure potential was 

monitored, data were not found for all potentially exposed workers. 

Based on the knowledge of the processes and types of uranium handled at Ames coupled with the 

available data from other uranium processing facilities, sufficient uranium data exist. However, 

NIOSH did not proceed with the development of a uranium scenario because external doses from beta 

and gamma radiation resulting from exposure to thorium and its daughters or plutonium cannot be 

reconstructed due to the lack of information on the percentage of thorium daughter in-growth ( up to 

1954 when thorium operations ceased). Based on the limitations with the external exposure 

information, the conclusion is that NIOSH cannot bind the total external exposures or establish a 

sufficiently accurate dose reconstruction method for members of the proposed class evaluated in this 

report. 

7.3.2 Ambient Environmental External Radiation Doses at Ames Laboratory 

There is no evidence that any environmental or ambient external radiation exposure monitoring was 

performed for any Ames Laboratory area prior to March 1952. As discussed in Section 8.1, some 

limited external dosimetry data was available after that period. Given the lack of adequate processrelated external exposure monitoring data, NIOSH did not further evaluate the environmental/ambient 

exposures received at Ames during the period evaluated in this report. 

7.3.3 Ames Laboratory Occupational X-ray Examinations 

As revealed in the NIOSH review of the current individual claims, twenty claims, for the timeframe 

evaluated in this report, contained medical X-ray information. However, the data supplied by DOE for 

these claims does not always indicate the purpose of the medical X-rays (whether the X-rays were preemployment, routine, or non-routine). Based on a review of the claims for those cases where X-ray 

information exists, each employee in the class had (or should have had) a pre-employment chest Xray, an annual chest X-ray, and an annual pelvic fluoroscopy exam. This is supported by the 

information in the PhD dissertation of Carolyn Stilts Payne and a memorandum concerning the 

progress of the Special Materials Division of the Medical Section (Payne, 1992; Ferry, 1944). In 

addition, to the pre-employment X-rays, termination chest X-rays were also given (Myers, 1946). 

Employees that worked with beryllium were given monthly x-rays through 1946 (Myers, 1946). 

Payne reported that employees also received annual chest x-rays (Payne, 1992).Employees handling 

fluorides, which would include at least some members of the proposed class, also received preemployment and annual pelvic X-rays as a condition of employment. An upper bound for exposure 

for occupational medical X-rays can be established using the procedure titled Occupational X-Ray 

Dose Reconstruction for DOE Sites, as well as the stated requirements for pre-employment and annual 

X-rays. 

In summary, NIOSH can reconstruct the medical X-ray dose for the class of Ames Laboratory 

workers in the class defined in this evaluation report with sufficient accuracy. All workers would be 

assigned pre-employed chest X-rays and termination chest-X-rays to all workers. Employees working 

with beryllium from 1942 through 1946 would be assigned monthly chest X-rays. Employees 
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handling fluorides would be assigned annual pelvic X-rays. Starting in 1950, all workers would be 

assigned annual chest X-rays. 

7.4 Evaluation of Petition Basis for SEC-00038 

The petition basis provided in petition SEC-00038 was that there were periods of inadequate and/or 

lack of monitoring. 

Based on the description of processes and exposure scenarios in Section 5, workers involved in each 

of those processes should have been monitored for external (beta and gamma) exposures and for 

internal exposures to radionuclides, particularly uranium and thorium-232 and its daughters. As 

discussed in Section 6, very little monitoring data exist. Although it appears that internal doses from 

exposures to uranium production and casting can be reconstructed, external exposures resulting from 

production and casting of thorium metal for 1953 and 1954 cannot be reconstructed. Doses for all 

workers resulting from exposures to occupationally required medical X-rays can be reconstructed. 

There is insufficient monitoring data and source term information to reconstruct all other doses with 

sufficient accuracy. Therefore, NIOSH finds that the petition basis has been supported. 

7.5 Summary of Feasibility Findings for Petition SEC-00038 

This report evaluated the feasibility for completing dose reconstructions for employees at Ames 

Laboratory from January 1, 1942 through December 31, 1954. NIOSH found that the monitoring 

records, process descriptions and source term data available are not sufficient to perform complete 

dose reconstructions for the proposed class of employees. 

Table 7-1 summarizes the results of the feasibility findings at Site Name for each exposure source for 

the time period January 1, 1942 through December 31, 1954. 

Table 7-1: Summary of Feasibility Findings for SEC-00038 

Source of Exposure Dose Reconstruction is Feasible Dose Reconstruction is NOT 

Feasible 

Internal X 

-Uranium X 

-Thorium/Plutonium X 

-Thoron X 

External X 

-Uranium Beta-Gamma X 

-Thorium/Plutonium Beta-Gamma X (except 1953 and 1954) 

-Neutron X 

-Occupational Medical X-ray X 

8.0 Evaluation of Health Endangerment for Petition SEC-00038 

The health endangerment determination for the class of employees covered by this evaluation report is 

governed by EEOICPA and 42 CFR § 83.13(c)(3). Under these requirements, if it is not feasible to 

estimate with sufficient accuracy radiation doses for members of the class, NIOSH must also 
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determine that there is a reasonable likelihood that such radiation doses may have endangered the 

health of members of the class. The regulation requires NIOSH to assume that any duration of 

unprotected exposure may have endangered the health of members of a class when it has been 

established that the class may have been exposed to radiation during a discrete incident likely to have 

involved levels of exposure similarly high to those occurring during nuclear criticality incidents. If the 

occurrence of such an exceptionally high level exposure has not been established, then NIOSH is 

required to specify that health was endangered for those workers who were employed for a number of 

work days aggregating at least 250 work days within the parameters established for the class or in 

combination with work days within the parameters established for one or more other classes of 

employees in the SEC. 

This NIOSH evaluation did not identify any evidence from the petitioners or from other resources that 

would establish that the above class was exposed to radiation during a discrete incident or similar 

conditions resulting from the failure of radiation exposure controls and likely to have produced levels 

of exposure similarly high to those occurring during nuclear criticality incidents. NIOSH is not aware 

of any report of such an occurrence at the facility during this period. NIOSH finds the primary 

radiation exposure hazards to employees resulted from episodic inhalations of radionuclides, and from 

unmonitored exposures to beta, gamma and neutron radiation that cumulatively resulted in chronic 

exposures. Consequently, NIOSH is specifying that health was endangered for those workers covered 

by this evaluation who were employed for a number of work days aggregating at least 250 work days 

within the parameters established for this class or in combination with work days within the 

parameters established for one or more other classes of employees in the SEC. 

9.0 NIOSH Proposed Class for Petition SEC-00038 

This evaluation defines a single class of employees for which NIOSH cannot estimate radiation doses 

with sufficient accuracy. This class includes employees of the DOE or DOE contractors or 

subcontractors who were monitored or should have been monitored while working at the Ames 

Laboratory in one or more of the following facilities/locations: Chemistry Annex 1 (also known as 

“the old women’s gymnasium” and “Little Ankeny”), Chemistry Annex 2, Chemistry Building (also 

known as “Gilman Hall”), Research Building, or the Metallurgical Building (also known as Harley 

Wilhelm Hall) for a number of work days aggregating at least 250 work days during the period from 

January 1, 1942 through December 31, 1954, or in combination with work days within the parameters 

established for one or more other classes of employees in the SEC. 
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10.0 References 

42 CFR 81, Guidelines for Determining the Probability of Causation Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule, Federal Register/Vol. 67, No. 

85/Thursday, p 22296; May 2, 2002; SRDB Ref ID: 19391

42 CFR 82, Methods for Radiation Dose Reconstruction Under the Energy Employees Occupational 

Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 19392

42 CFR 83, Procedures for Designating Classes of Employees as Members of the Special Exposure 

Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 2000; Final 

Rule; May 28, 2004; SRDB Ref ID: 22001

ISC-10, History of the Ames Project Under the Manhattan District to December 31, 1946, Iowa State 

College; December 9, 1947; SRDB Ref ID: 18823

IS-T 2564, The Ames Project: History of the Ames Laboratory’s Contributions to the Historic 

Manhattan Project, 1942-1946, Iowa State University; 2003; SRDB Ref ID: 18859

ORAU-OTIB-0018, Rev. 01, Internal Dose Overestimates for Facilities with Air Sampling 

Programs, ORAU; August 9, 2005; SRDB Ref ID:19436

ORAUT-OTIB-0019, Rev. 01, Analysis of Coworker Bioassay Data for Internal Dose Assignment,

ORAU; October 7, 2005; SRDB Ref ID: 19438

ORAU-OTIB-0024, Rev. 00, Estimation of Neutron Dose Rates from Alpha-Neutron Reactions in 

Uranium and Thorium Compounds, ORAU; April 7, 2005; SRDB Ref ID: 19445

ORAU-OTIB-0033, Rev. 00, Application of Internal doses Based on Claimant-Favorable 

Assumptions for Processing as Best Estimates, ORAU; April 20, 2005; SRDB Ref ID: 19457

ORAUT-PROC-0061m Rev.00, Occupational X-Ray Dose Reconstruction for DOE Sites, ORAU; 

December 1, 2004; SRDB Ref ID: 20214

EC-00012-2, SEC Petition Evaluation Report; time period of 1946 through 1957 (SEC-00012-2, 

Mallinckrodt Destrehan Street Facility; National Institute of Safety and Health (NIOSH), draft 2; July 

21, 2004; SRDB Ref ID: Currently Not Assigned 

AEC, Urine Samples, Urine Samples (1952-1953) for Ames Laboratory, U.S. AEC New York 

Operations Office Health and Safety Division; 1953; SRDB Ref ID: 8965

AEC, Various Samples, Various Urine, Air Dust and Slag Samples (1952-1953) for Ames 

Laboratory, U.S. AEC New York Operations Office Health and Safety Division; 1953; SRDB Ref 

ID: 8966

Affidavit, 2005, Letter from SEC-00038 Submitter to OCAS addressing the deficiencies in the letter 

dated July 25, 2005. SECIS ID: 9019
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Ames Web, 2005, Ames Laboratory Documents for Former Worker Program Review, Ames 

Laboratory protected web site; Ames Laboratory; 2005; Will not be located in SRDB or SECIS

DOE, 2001, Characteristics of Uranium and Its Compounds, Characteristics of Uranium and Its 

Compounds, U.S. Department of Energy Office of Environmental Management; 2001; SRDB Ref ID: 

22168 

Ferry, 1944, Progress Report of the Special Materials Division of the Medical Section, memorandum 

from Captain John L. Ferry, Corps of Engineers, to Colonel S. L. Warren; E.S. Engineer Office; 

January 3, 1944; SRDB Ref: 14490

Friedell, 1942, Supplemental Report to Complete Preliminary Survey of Plans Engaged in Production 

of Materials; Captain H. L. Friedell, Corps of Engineers; December 23, 1942; SRDB Ref ID: 8967

Friedell, 1943, Letter to Name Redacted, Dust Samples; Iowa State College; July 13, 1943; SRDB 

Ref ID: 8960 

Fourtes, 2006, Correspondence Between Dr. Fourtes and National Institute for Occupational Safety 

and Health (NIOSH); March 23, 2006; SECIS ID: 9626

Hokel, 1998, An Assessment of the Causes, Mitigation Efforts, and Current Status of 232TH, 238U, and 

Beryllium Contamination in Wilhelm Hall at Ames Laboratory; Bruce W. Hokel, et al, Ames 

Laboratory; 1998; SRDB Ref ID: 18848

Industrial Medicine, 1951, Uranium Excretion Studies—Industrial Medicine On The Plutonium 

Project, Survey and Collected Papers; Edited by Robert S. Stone, M.D., McGraw-Hill Book Co.; 

1951, SRDB Ref ID: 739 

Iowa State University, date unknown, Iowa State University Institute for Atomic Research; author 

and date not provided; SRDB Ref ID: 18856 

Iowa State College, 1943, Laboratory Records; Iowa State College; 1943; SRDB Ref ID: 8969

Iowa State University, 1961, Welcome to the Ames Laboratory of the Atomic Energy Commission; 

Iowa State University, Technical Information Office; October 31, 1961; SRDB Ref ID: 18831

Klevin, Occupational Exposures to Thorium and Beryllium; Paul Klevin, Ames Laboratory, Ames 

Laboratory, pages 1–73; SECIS Document ID: 9074 

Klevin, 1952, Ames Research Laboratory Occupational Exposure to Thorium and Beryllium; Paul B. 

Klevin, U.S. AEC New York Operations Office Health and Safety Division; July 14, 1952; SRDB 

Ref ID: 18942 

Myers, 1946, Medical Clearance on Terminated Madison Square Area Contracts, Letter from Name 

Redacted to the District Engineer; Manhattan District, Oak Ridge, Tenn. Corps of Engineers; March 

8, 1946; SRDB Ref ID: Currently Not Assigned 
SEC-00038 FINAL Ames Laboratory

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ORAU, 2006, Personal communication between ORAU Team with, Oak Ridge Associated 

Universities, Center for Epidemiology Research; January 19, 2006; SRDB Ref ID: 22167

Payne, 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; 1992; SRDB Ref ID: 18851

Personal Communication, 2005, Personal communication between ORAU Team, with former Health 

Physicist, Ames Laboratory; November 1, 2005. SECIS Non-Submitter Communication ID: 47

Radiological Health, 1970, Radiological Health Handbook, Revised Edition; Public Health Service, 

U. S. Department of Health, Education, and Welfare; January 1970; Publicly Available—Not 

Included in SRDB

SEC Form B, 2005, Special Exposure Cohort (SEC) Petition – Form B; submitted by petition 

representative Name Redacted; June 29, 2005; SECIS ID: 9075

Tyrout, 1944, Letter from Richard A. Tyrout to Frank Spedding Regarding Urine Sample Results; 

Corps of Engineers; November 21, 1944; SRDB Ref: 8959

Urinary Excretion Studies, published in Industrial Medicine on the Plutonium Project, Survey and 

Collected Papers Edited by Robert S. Stone, M.D., McGraw-Hill Book Co. 1951, pp. 243-255; 

SECIS ID: 9087

Voss, 1979, History and Current Radiological Condition of the Ames Laboratory; letter from Milo D. 

Voss of Ames Laboratory to William E. Mott of DOE transmitting document; December 3, 1979; 

SRDB Ref ID: 18840

Wessels, 2005, Personal communications with Ames Laboratory; October, 17 – 18, 2005; SECIS 

Non-Submitter Communication ID: 47