SEC Petition Evaluation Report 

Petition SEC-00064 

Report Rev #_ 1 Report Submittal Date ____09-20-06___________ 

Subject Expert(s): Cindy Bloom, Shelby L. Gubin, Kenny Fleming, Robert Vogel, 

and Robert Hysong

Site Expert(s): Not Applicable 

Petitioner Administrative Summary 

Petition Under Evaluation 

Petition # Petition 

Type 

Petition A 

Receipt Date DOE/AWE Facility Name 

SEC-00064 83.14 July 17, 2006 General Atomics 

Proposed Class Definition 

All AWE employees who were monitored or should have been monitored for exposure to ionizing radiation 

while working at the following General Atomics locations: Science Laboratories A, B, and C (Building 2); 

Experimental Building (Building 9); Maintenance (Building 10); Service Building (Building 11); Buildings 21 

and 22; Hot Cell Facility (Building 23); Waste Yard (Buildings 25 and 26); Experimental Area (Buildings 27 

and 27-1); LINAC Complex (Building 30); HTGR-TCF (Building 31); Fusion Building (Building 33); Fusion 

Doublet III (Building 34); SV-A (Building 37); SV-B (Building 39); and SV-D (no building number) for a 

number of work days aggregating at least 250 work days from January 1, 1960, through December 31, 1969, or 

in combination with 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: James M. Mahathy ORAU Review Completed By: Michael S. Kubiak

Peer Review Completed By: [Signature on file] 9/26/06 

LaVon Rutherford Date 

SEC Petition Evaluation Reviewed By: [Signature on file] 9/26/06 

Jim Neton Date 

SEC Evaluation Approved By: [Signature on file] 11/03/06 

Larry Elliott Date 
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Evaluation Report Summary: SEC-00064, General Atomics 

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

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

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

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

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

Compensation Program Act of 2000. 

NIOSH-Proposed Class Definition

The NIOSH-proposed class includes all Atomic Weapons Employer (AWE) employees who were 

monitored or should have been monitored for exposure to ionizing radiation while working at the 

following General Atomics locations: Science Laboratories A, B, and C (Building 2); Experimental 

Building (Building 9); Maintenance (Building 10); Service Building (Building 11); Buildings 21 and 

22; Hot Cell Facility (Building 23); Waste Yard (Buildings 25 and 26); Experimental Area (Buildings 

27 and 27-1); LINAC Complex (Building 30); HTGR-TCF (Building 31); Fusion Building (Building 

33); Fusion Doublet III (Building 34); SV-A (Building 37); SV-B (Building 39); and SV-D (no 

building number) for a number of work days aggregating at least 250 work days from January 1, 1960, 

through December 31, 1969, 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

Per EEOICPA and 42 C.F.R. § 83.14(b), NIOSH has established that it does not have sufficient 

information to complete dose reconstructions for individual members of the class with sufficient 

accuracy. NIOSH does not have access to sufficient personal monitoring data, or workplace 

monitoring data, to adequately determine the total potential intake of radioactive materials for workers 

in the proposed class. 

Health Endangerment Determination

The NIOSH evaluation did not identify evidence from the petitioners or from other sources that would 

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

exceptionally high-level exposures, such as nuclear criticality incidents or other events involving 

similarly high levels of exposures. However, the evidence reviewed in this evaluation indicates that 

some workers in the class may have accumulated chronic exposures through intake of radionuclides 

and from direct exposure to radioactive materials. Consequently, NIOSH has determined that health 

may have been 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-00064, General Atomics ................................................................. 3 

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

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

3.0 NIOSH-Proposed Class Definition and Petition Basis................................................................ 8 

4.0 Radiological Operations Relevant to the Proposed Class ........................................................... 8 

4.1 General Atomics Plant Description.................................................................................... 8 

4.2 General Atomics Functional Areas .................................................................................. 10 

4.2.1 LINAC Facility..................................................................................................... 12 

4.2.2 Experimental Building (E Building) .................................................................... 12 

4.2.3 Critical Assembly Facility.................................................................................... 12 

4.2.4 Science Laboratories ............................................................................................ 13 

4.2.5 Hot Cell Facility ................................................................................................... 13 

4.2.6 Waste Yard/Incinerator ........................................................................................ 13 

4.2.7 Reactor Facilities.................................................................................................. 13 

4.2.8 Other Locations.................................................................................................... 14 

5.0 Summary of Available Monitoring Data for the Proposed Class.............................................. 14 

5.1 General Atomics Internal Monitoring Data...................................................................... 15 

5.2 General Atomics External Monitoring Data..................................................................... 16 

5.3 General Atomics Workplace Monitoring Data................................................................. 17 

6.0 Feasibility of Dose Reconstruction for the Proposed Class ...................................................... 17 

6.1 Feasibility of Estimating Internal Exposures ................................................................... 17 

6.2 Feasibility of Estimating External Exposures .................................................................. 18 

7.0 Summary of Feasibility Findings for Petition SEC-00064........................................................ 19 

8.0 Evaluation of Health Endangerment for Petition SEC-00064................................................... 19 

9.0 NIOSH-Proposed Class for Petition SEC-00064 ...................................................................... 20 

10.0 References ................................................................................................................................. 21 

Table 

4-1: General Atomics Facilities That Conducted Radiological Work................................................... 11 
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SEC Petition Evaluation Report for SEC-00064

1.0 Purpose and Scope 

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

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

petition for adding a class of employees to the Congressionally-created 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 

NIOSH, with the exception of the employee whose dose reconstruction could not be completed, and 

whose claim consequently led to this petition evaluation. The finding in this report is not the final 

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

report will be considered by the Advisory Board on Radiation and Worker Health (the Board) and by 

the Secretary of Health and Human Services (HHS). The Secretary of HHS will make final decisions 

concerning whether or not to add one or more classes to the SEC in response to the petition addressed 

by this report. 

This evaluation, in which NIOSH provides its findings on both the feasibility of estimating radiation 

doses of members of this class with sufficient accuracy and on health endangerment, was conducted in 

accordance with the requirements of both EEOICPA and 42 C.F.R. pt. 83. 

2.0 Introduction 

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

HHS add a class of employees to the SEC. The evaluation is intended to provide a fair, science-based 

determination of whether it is feasible to estimate, with sufficient accuracy, the radiation doses of the 

proposed class of employees through NIOSH dose reconstructions.1

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

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

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

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

report, together with the petition, comments of the petitioner(s) and such other information as 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 a decision on behalf of HHS. The Secretary 

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

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

petitioner(s) may seek a review of certain types of final decisions issued by the Secretary of HHS.2

1

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

the detailed implementation guidelines available at www.cdc.gov/niosh/ocas. 

2

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

available at www.cdc.gov/niosh/ocas. 
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3.0 NIOSH-Proposed Class Definition and Petition Basis 

This NIOSH report provides a summary of the methods and findings of the NIOSH SEC evaluation 

for all AWE employees who were monitored or should have been monitored for exposure to ionizing 

radiation while working at the following General Atomics locations: Science Laboratories A, B, and 

C (Building 2); Experimental Building (Building 9); Maintenance (Building 10); Service Building 

(Building 11); Buildings 21 and 22; Hot Cell Facility (Building 23); Waste Yard (Buildings 25 and 

26); Experimental Area (Buildings 27 and 27-1); LINAC Complex (Building 30); HTGR-TCF 

(Building 31); Fusion Building (Building 33); Fusion Doublet III (Building 34); SV-A (Building 37); 

SV-B (Building 39); and SV-D (no building number) for a number of work days aggregating at least 

250 work days from January 1, 1960, through December 31, 1969, or in combination with work days 

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

The evaluation responds to Petition SEC-00064, which was submitted by an EEOICPA claimant who 

was employed as an electronic fabricator, lab technician, and senior lab technician at the facility 

during this period, and whose dose reconstruction could not be completed by NIOSH due to a lack of 

sufficient dosimetry-related information. The NIOSH determination that it is unable to complete a 

dose reconstruction for a EEOICPA claimant is a qualified basis for submitting an SEC petition 

pursuant to 42 C.F.R. § 83.9(b). 

4.0 Radiological Operations Relevant to the Proposed Class 

The following subsections summarize radiological operations at General Atomics from January 1960 

to December 1969, 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 processes 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. 

4.1 General Atomics Plant Description 

General Dynamics Corporation established the General Atomics Division in San Diego, California, to 

develop commercial applications for nuclear technology. General Atomics performed an array of 

radiological research and production activities at its Torrey Pines Mesa facility in La Jolla, California 

(General Atomics, 1998). General Atomics operated under licenses first issued by the Atomic Energy 

Commission (AEC) and later by the State of California. The General Atomics source term includes 

depleted, normal, and highly-enriched uranium [typically greater than 20% and up to 93.5% (SNM696) U-235 by mass]. This uranium was in the form of scrap, fresh reactor fuel, and irradiated reactor 

fuel comprised of uranium, activation products, and fission products. Thorium was used in fuel 

fabrication work. Plutonium work was also done on site. Four linear accelerators (LINACs) and 

several nuclear reactors were employed. Sealed sources were used for instrument calibrations and 

other work. By-product materials (Atomic Numbers 3-83) and tritium were also used. 
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General Atomics performed irradiation and time-of-flight studies with four LINACs; developed and 

fabricated reactor fuels; operated three on-site TRIGA reactors (Training/Research/Isotopes General 

Atomics); performed fusion research (since the mid-1960s); ran experimental criticality test facilities; 

used an “experimental” facility that is understood to have conducted a diverse set of tests with 

radioactive materials; and worked with special nuclear material (SNM) and radioactive tracers in its 

laboratory facilities. Hot Cells were used for handling radioactive materials associated with high 

radiation fields or very large quantities of radioactive materials that might be subject to processes 

resulting in dispersion. Operations conducted in these hot cells included post-irradiation examinations 

of DOE fuels, structural materials, and reactor dosimetry materials; and mechanical inspection of 

irradiated fuel. Development and manufacture of Experimental Beryllium Oxide Reactor (EBOR) 

fuel, tritium extraction, and experiments to test plutonium transport using plutonium oxide were also 

performed in hot cells. 

Fuel fabrication involved working with uranium (up to 93.5% U-235 by mass) and thorium. 

Radioactive materials were coated, blended, compounded, heated, rolled, extruded, machined, 

compacted, and eventually made into fuel elements. There were many tasks required for fuel 

fabrication whereby raw materials were converted to usable fuel assemblies. 

General Atomics reclaimed highly-enriched uranium (HEU) from non-irradiated NERVA (Nuclear 

Engines for Rocket Vehicle Applications) scrap fuel. The scrap was identified as being in Scrap 

Groups III (uranium compounds such as oxides) and IV (combustibles such as paper, tissue wipes, 

filters, etc.). The scrap materials were to be shipped from the Westinghouse Electric Corporation’s 

Astrofuel Facility in Cheswick, Pennsylvania, to General Atomics for processing into uranium oxides 

(Type III recovered uranium: UO2, UO3, and U3O8). SNM in the form of uranium-bearing impure 

scrap materials (e.g., oxides or carbides) was processed to recover and purify the contained uranium. 

The material was accumulated from several sources (both on-site and off-site), including 

out-of-specification SNM product, process equipment, scrap, waste, and solid residue from liquid 

evaporation. Some of the materials came from the facility recovery operations. 

The steps used for uranium material extraction and purification are described in SNM License 696 

(SNM-96). In addition to the production, research, and recovery activities conducted with uranium 

and SNM, General Atomics also worked with thorium materials. Thorium was one of the 

radionuclides used in the initial stages of operation; such use continued through the operational 

period. Thorium was used in Building 2 (Science Laboratories) for testing mixtures and components 

of fuel assemblies. The thorium operations conducted in Building 2 included grinding of thorium, 

high-temperature heating under vacuum, and fabrication of thorium-uranium gel. Undetermined 

amounts of thorium were used in Building 9 (Experimental Building); operations included extrusion, 

rolling, cutting, milling, lathing, and casting of metal. Research and development of reactor fuel 

pellets using uranium and thorium was one of the activities conducted in Building 23 (Hot Cell 

Facility). When work was performed in hot cells, there was the potential for exposure during the 

transport of radioactive materials to and from the Hot Cells and during maintenance of equipment. 
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Radioactive materials containing thorium and other radionuclides were volume-reduced at, stored at, 

and shipped from the Waste Yard (Buildings 25 and 26). Information regarding the total quantities 

and activities of individual radionuclides handled at the Waste Yard has not been identified. 

Coated thorium fuel pellets were irradiated in the linear accelerator building (LINAC Complex or 

Building 30). Other research activities involving thorium were also conducted at the LINAC 

Complex. Criticality testing of fuel elements containing thorium was routinely conducted at the 

Critical Assembly Facility (Building 31); thorium compaction also occurred in this facility. 

Fabrication and testing of HTGR (High Temperature Gas Cooled Reactor) fuel was performed in 

Buildings 37 (SV-A) and 39 (SV-B). One of the primary uses of thorium at General Atomics was in 

the fabrication of Th-U fuel. Potential exposure to thorium in these Sorrento Valley areas resulted in 

part from the transport and handling of materials, maintenance of fabrication equipment, and airborne 

leaks from the thorium conversion furnace (SNM-696). 

Records suggest that thorium was routinely used in the aforementioned buildings. However, based on 

available documentation (General Atomics, 1964; SNM-696), the transfer, storage, and use of thorium 

in other radiological buildings was also likely. NIOSH has not located documentation on the amount 

of thorium used and processes employed in these remaining buildings or on the level of thorium 

activity in any specific locations of the facility. 

4.2 General Atomics Functional Areas 

Some of the larger radiological operations involved the Fuel Fabrication Facility, the Hot Cell Facility 

(Building 23), the reactors, and the linear accelerator. In addition, there were a number of research 

and development and small-scale manufacturing projects on going in the General Atomics research 

and experimental buildings. Although many of the facilities were operational by 1960, some were 

moved or constructed during the 1960s. This evaluation report identifies the functional areas and 

facilities where thorium was handled, used, or processed. A list of these facilities is shown in Table 

4-1; these thorium facilities are discussed in the successive report sub-sections. 
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Table 4-1: General Atomics Facilities That Conducted Radiological Work 

Building Process 

Building 2 

Science Laboratories A, B, and C 

Radiological and chemical laboratories 

Building 9 Experimental Building (E Building) Many radiological operations, including fuel 

element development and Pu storage 

Building 10 Maintenance Building Radioanalytical laboratory and Health 

Physics 

Building 11 Service Building Shipping and receiving of radioactive 

materials 

Building 21 (TRIGA) Housed three TRIGA reactors 

Building 22 TRIGA Fuel Fabrication 

Building 23 (Hot Cell Facility) Multiple radiological operations 

Buildings 25 and 26 Waste handling, minimization, processing, 

and storage; SNM storage; and a gamma 

counting facility 

Building 27 (Experimental Area Building #1) Preparation of target samples for neutron 

irradiation; post-irradiation radiochemical 

separations 

Building 27-1 (Experimental Area Building #1 – 

Bunker; also contained ‘Strontium Facility’) 

Neutron activation; yttrium production; and 

research and development 

Building 30 (LINAC Complex) High-energy electron accelerators 

Building 31 (HTGR-TCF) Also called the 

Critical Assembly Facility 

Testing of fuel elements 

Building 33 (Fusion Building) Study of controlled thermonuclear reactions 

Building 34 (Fusion Doublet III) Research in magnetic fusion technologies 

(involving short-lived radiation sources) 

Building 37 (SV-A) Fabrication of fuel elements; SNM 

Building 39 (SV-B) Fabrication and testing of fuel assemblies for 

HTGR; SNM 

SV-D (no building number) Assembled thermionic and thermoelectric 

fuel elements; SNM 
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4.2.1 LINAC Facility 

The LINAC facility began operating in 1962 and was used for a variety of research activities. Early 

experiments investigated the intensity of delayed radiations from the fission of uranium-238, 

uranium-235, plutonium-239, and thorium-232 (General Atomics, 1964). 

Administrative controls coupled with physical interlocks were used to ensure the safety and protection 

of LINAC personnel. Any material registering over twice background on an alpha, beta, or gamma 

detector was considered radioactive (SNM-69). 

4.2.2 Experimental Building (E Building) 

The Experimental Building was involved in much of the initial fuel development work conducted 

onsite. The first major operation conducted within the facility was the fabrication of TRIGA reactor 

fuel elements (UZrH, a uranium-zirconium hydride alloy). There were two radiologically-controlled 

areas within the structure, designated as Zones A (South Control Zone: A-1, A-2, and A-3) and B (Hot 

Suite: B-1, B-2, and B-3). All operations with the potential to generate particulate matter were 

conducted in hoods or glove boxes, or were serviced by portable ductwork attached to an exhaust 

system. Procedural and administrative controls were in place to minimize exposure; these controls 

typically helped the health physics group to protect personnel. There were two SNM storage vaults 

located adjacent to the east wall of the facility and a security storage area designed to store materials 

in Zone A for short periods of time. 

Undetermined amounts of thorium were used in the Experimental Building in fuel fabrication 

experiments involving extrusion, rolling, cutting, milling, lathing, and casting of metal. 

4.2.3 Critical Assembly Facility 

This facility consisted of two buildings contained in a fenced area between the LINAC Complex and 

TRIGA / Experimental Area Building #1. The facility was used to conduct many critical and 

sub-critical assembly experiments. These buildings, also referred to as Building 31, were collectively 

referred to as the Critical Assembly Facility. The buildings were used to support the Marine GasCooled Reactor (MGCR) and HTGR programs (General Atomics, 1961). In addition to these two 

buildings, a fuel assembly building was located in the area. Fuel assemblies were irradiated with 

accelerator-produced neutrons or with neutron triggers (e.g., PoBe or PuBe sources). The design of 

the fuel and assembly was such that if an undesired criticality were to occur, the fuel would either 

rapidly expand (Russell, 1967) or the sub-critical fuel beds would separate (Pound, 1974), inducing 

the neutron excursion to terminate. Criticality testing of fuel elements containing thorium was 

conducted at this facility. 
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4.2.4 Science Laboratories 

The Science Laboratories were composed of three two-story, arc-shaped buildings forming an annular 

ring around the central library and cafeteria buildings. The Science Laboratories contained 150 

individual laboratories and associated offices. Much of General Atomics work in chemistry, 

experimental physics, electronics, metallurgical research, reactor physics, and thermoelectricity was 

performed in these buildings. Thorium was used in the Science Laboratories for testing mixtures and 

components of fuel assemblies. Operations included grinding of thorium, high-temperature heating 

under vacuum, and fabrication of thorium-uranium gel. 

4.2.5 Hot Cell Facility 

The Hot Cell Facility (HCF) was constructed in 1959 and used primarily to facilitate remote 

inspection of irradiated, highly-radioactive HTGR and TRIGA fuel (General Atomics, 1960). 

Approximately 12% of the building footprint was taken up by the hot cell (SNM-69). A hot cell was 

made up of 3 sections: the high-level cell (HLC), low-level cell (LLC), and the metallurgy cell (MC). 

The HLC was used as a remotely operated “hot” machine shop to cut open and section irradiated fuel 

samples for inspection. The MC was used for analytical inspection and research activities, including 

the sample preparation that entailed grinding, polishing, and mounting. The LLC was used as an 

interface between the other “hot” cells and other areas of the building, and housed all shipping cask 

off-loading and packaging operations. Thick (up to 42-inch), high-density concrete walls were in 

place to minimize personnel exposure to penetrating radiation. In addition to uranium and other fuel 

constituents, thorium materials were handled in the hot cell facility. 

4.2.6 Waste Yard/Incinerator 

The waste processing facility includes several buildings, collectively referred to as Building 25. The 

facility was used for waste handling, minimization, processing, and storage; SNM and by-product 

material storage; and as a gamma-counting facility. Liquid wastes generated on the site were treated 

by placing them in evaporation pools. Only authorized personnel were allowed into the fenced-off 

incinerator area; they were required to wear a film badge and a self-reading dosimeter, and to submit 

bioassay samples for analysis (SNM-69). Several locations were used within the waste processing 

facility area to store radioactive materials, including TRIGA Hot Storage, a temporary storage yard, 

the Butler Building, and the By-Products Vault. Radioactive materials containing thorium were 

volume-reduced at, stored at, and shipped from the Waste Yard. Information regarding the total 

quantities and activities of individual radionuclides handled at the Waste Yard has not been identified. 

4.2.7 Reactor Facilities 

Three separate TRIGA reactors (Mark I, Mark F, and Mark III) were operated within Building 21; 

each reactor was individually licensed (R-38, R-67, and R-100, respectively). The original building, 

constructed in 1957, housed the Mark I reactor. The building was later expanded to the east and then 

to the north (1966) to house the Mark F and III reactors, respectively. The Mark I, F, and III reactors 

were all below-ground pool reactors (General Atomics, 1969). They were designed to: provide 

university training; provide a source of neutrons and/or gamma radiation for research; aid 

investigations of the effects of radiation on materials; and produce radioisotopes. 
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The Mark I, which was graphite-reflected, was operated routinely at steady-state thermal levels up to 

250 kW; it could also be operated in pulsed mode. The Mark F reactor (also known as the Advanced 

TRIGA Prototype and the FLAIR [Flash Irradiation Reactor]), which was water-reflected, operated 

routinely at steady-state thermal power levels up to 1500 kW and also could be operated in pulsed 

mode. The Mark III reactor, also water-reflected, operated routinely at steady-state thermal levels up 

to 1500 kW. 

The core of the TRIGA reactor contained reactor fuel, dummy fuel assemblies, and one or more 

neutron source holders. Workers may have been exposed to external and internal radiation during fuel 

loading and maintenance. Thorium was a fuel mixture constituent during some of these operations. 

4.2.8 Other Locations 

Due to the diversity of General Atomics operations, there was a significant potential for thorium 

storage, handling, or use in any of the buildings or work areas associated with radiological activities. 

For instance, thorium was likely handled in a radiochemistry laboratory located in the Maintenance 

Building, and the Service Building was used for receiving and shipping radioactive materials and 

components. Based on available information, NIOSH cannot rule out the possible existence of 

thorium contamination in any General Atomics radiological work area. Consequently, all General 

Atomics radiological work areas are included in the proposed SEC class. 

5.0 Summary of Available Monitoring Data for the Proposed Class 

The primary data used for determining internal exposures are derived from personal monitoring data, 

such as urinalyses, fecal samples, and whole-body counting results. If these are unavailable, the air 

monitoring data from breathing zone and general area monitoring are used to estimate the potential 

internal exposure. If personal monitoring and breathing zone area monitoring are unavailable, internal 

exposures can sometimes be estimated using more general area monitoring, process information, and 

information characterizing and quantifying the source term. 

This same hierarchy is used for determining external exposures to the cancer site. Personal 

monitoring data from film badges or thermoluminescent dosimeters (TLD) comprise the primary data 

used to determine such external exposures. If there are no personal monitoring data, then exposure 

rate surveys, process knowledge, and source term modeling can sometimes be used to reconstruct the 

potential exposure. 

A more detailed discussion of the information required for dose reconstruction can be found in 

OCAS-IG-001, Internal Dose Reconstruction Implementation Guide, and OCAS-IG-002, External 

Dose Reconstruction Implementation Guide. These documents are available at: 

http://www.cdc.gov/niosh/ocas/ocasdose.html. 
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5.1 General Atomics Internal Monitoring Data 

During the AWE operational period for General Atomics (1960 through 1969), some workers were 

monitored by bioassay; however, bioassays were not routine at General Atomics until October 1963. 

NIOSH has reviewed available data, which appear to be from random sampling, and identified 1,188 

bioassay results through September 1963 (ORAUT, 2006). NIOSH has identified 1,577 bioassay 

records for the period October through December 1963. These results are gross activity results. 

NIOSH has identified 17,188 results from October 1963 through December 1969. According to the 

data available to NIOSH, most results were for in vitro sampling. A majority of the samples collected 

from 1960 through 1963 were analyzed for gross beta, gross alpha, and U-235. Most of the in vitro

bioassay data available for the period October 1963 through December 1969 show that samples were 

analyzed for gross alpha or for uranium activity. The bioassay program incorporated gross counting 

methods to determine exposure to uranium, and the analytical methods used were not well 

documented. Determination of the specific internal exposures to other radionuclides, including 

thorium-232, thorium-238, plutonium, and americium, did not occur within the AWE operational 

period (ending December 31, 1969). NIOSH has located no in vitro results for exposure to thorium. 

Further, NIOSH has not found any evidence to suggest that in vitro bioassay for thorium exposure was 

ever performed at General Atomics. 

General Atomics began monitoring for tritium exposure by bioassay in September 1965. NIOSH has 

identified 194 tritium bioassay records for the period November 1965 through December 1969. 

General Atomics implemented an in vivo analysis program in 1966. The Helgeson mobile counter 

was brought to the site a few times each year. The perceived potential for internal exposure was the 

early basis for including a worker in the in vivo bioassay program. Many individual measurement 

spectra are included with results identifying the radionuclide and quantity measured. Background and 

calibration measurements were also observed in the records provided by Helgeson (Helgeson, 1966). 

The first U-235 lung counting results (~1966 through 1967) were considered "experimental" by 

Helgeson, and were either associated with some large uncertainty or assumed to be invalid. Workers 

were chosen for lung counts based on their potential for U-235 exposure and the results of their 

uranium urinalyses (Helgeson, 1969). The early General Atomics U-235 in vivo measurements are 

indicators that a worker had the potential for U-235 exposure. 

In addition to the Helgeson in vivo analysis, General Atomics conducted its own in-house in vivo

measurements beginning in 1966. The subject sat in an office chair lined with 0.25-inch thick lead 

and a 4” x 4” NaI(Tl) detector operated in a lap geometry. 

The in vivo bioassay program was not used in 1966 to routinely monitor for exposures to thorium, 

although twelve workers were analyzed for thorium in March of that year. These results were 

reported to be experimental and final results were not provided by Helgeson (Helgeson, 1966). 

Available records indicate that a thorium in vivo result was reported for only one worker in 1969, who 

was reported to have no thorium activity (Helgeson, 1969). 
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5.2 General Atomics External Monitoring Data 

External whole body dosimetry results are available for monitored General Atomics workers for the 

entire AWE operational period (January 1960 through December 1969). NIOSH has 27,661 external 

monitoring records available for that period. Initially, external dosimetry services using film badges 

were provided by R. S. Landauer, Jr. and Company. In July 1961, those services were transferred to 

Radiation Detection Company; however, in 1965 they were transferred back to R. S. Landauer, Jr. and 

Company. Personnel working in areas where potential neutron exposure could occur were issued film 

badges sensitive to beta, gamma, and neutron radiation. Otherwise, personnel were issued film badges 

sensitive to only beta and gamma radiation. 

No details on the Radiation Detection Company dosimeter design or film type are currently available, 

but site documentation suggests that the film badge was comparable to the Landauer design. Film 

badge detection thresholds for R.S. Landauer, Jr. and Company badges were reported in January 1961 

as 10 mrem from gamma, 40 mrem from beta, and 20 mrem from fast neutrons. Other documentation 

indicates that film badge detection thresholds in the early days were assumed to be as high as 50 mrem 

for gamma and 60-80 mrem for beta. 

In addition to the badge dosimeters, personnel used direct- or indirect-reading dosimeters, such as 

personal ion chambers. It is unclear whether these additional dosimeters detected low-energy X-rays. 

(Currently available pocket dosimeters designed for low-energy X-ray detection report the lower end 

of the energy range as 20 to 40 keV. Dosimeters not specifically designed for low-energy X-ray 

detection have thresholds of about 80 keV.) Extremity dosimeters were used in some operations, such 

as during removal of irradiated samples from the TRIGA reactors (Gurren, 1966). Results from the 

pocket dosimeters were logged by staff on a routine basis. Some on-site readings are included in the 

available individual dosimetry records. 

Site documentation indicates that during the 1960 to 1961 timeframe, film badges, fast and thermal 

neutron detection equipment, and direct- and indirect-reading pocket dosimeters were irradiated to 

evaluate the radiation recorded on each device. Beginning in early 1960, indium foils were 

incorporated into personnel security badges in case of a criticality event (Ray, 1960). By July 1961, 

all personnel film holders were equipped with a built-in threshold detector for neutron dose 

evaluations in the event of a criticality (Bold, 1961). Badges were exchanged on a bi-monthly 

frequency at General Atomics in 1960 and 1961 (Bold, 1962). In 1962, badges were exchanged 

monthly (Bold, 1968); this frequency was likely used until 1996 when quarterly exchanges were 

begun. 

According to 1961 correspondence, “Special Tests for Employees Working Around BeO,” special 

radiation tests, X-rays, and spirograms were conducted for employees working in the vicinity of BeO 

(Bethard 1961a, 1961b, 1961c, and 1961d). No additional documentation detailing occupationallyrequired medical X-ray examinations has been identified. NIOSH’s review of data for EEOICPA 

claimants who worked at General Atomics suggests that X-rays were given annually. To date, no 

information regarding equipment and techniques specific to General Atomics has been located. 
SEC-00064 FINAL General Atomics

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5.3 General Atomics Workplace Monitoring Data 

Engineering controls to reduce radiation/radioactivity exposure appear to have been present 

throughout the site. General Atomics conducted routine air monitoring, but noted inadequacies in the 

frequency and quality of its program in the early years. NIOSH has no documentation that suggests 

thorium was specifically monitored by air sampling. 

Surface area wipe-testing was performed periodically at General Atomics, but it is unclear whether 

direct contamination surveys were routinely performed. Several incidents involving radioactivity 

releases and occurrences of contamination were documented (Hughes, 1964; Hughes, 1967; Hughes, 

1969; Kesting, 1964; Kesting, 1969; Lepper, 1963). At least one incident, in 1968, involved the 

LINACs whereby both long- and short-lived radionuclides were potentially released. Because 

thorium was irradiated at the accelerators, it is plausible that thorium was released during one or more 

incidents. 

6.0 Feasibility of Dose Reconstruction for the Proposed Class 

42 C.F.R. § 83.14(b) states that HHS will consider a NIOSH determination that there was insufficient 

information to complete a dose reconstruction, as indicated in this present case, to be sufficient,

without further consideration, to conclude that it is not feasible to estimate the levels of radiation 

doses of individual members of the class with sufficient accuracy. 

In the case of a petition submitted to NIOSH under 42 C.F.R. § 83.9(b), NIOSH has already 

completed research to determine that a dose reconstruction cannot be completed for an employee at 

the DOE or AWE facility. This determination by NIOSH provides the basis for the petition by the 

affected claimant. NIOSH has further considered defining the extent of the class of employees who 

are similarly affected, as indicated by the completed research, and hence, as a class of employees, 

dose reconstruction is similarly not feasible. 

This section of the report summarizes research findings by which NIOSH determined that it lacked 

sufficient information to complete the relevant dose reconstruction and on which basis it has defined 

the class of employees for which dose reconstruction is not feasible. NIOSH’s determination relies on 

the same statutory and regulatory criteria that govern consideration of all SEC petitions. 

6.1 Feasibility of Estimating Internal Exposures 

As indicated in Section 5.1, NIOSH has identified no evidence to suggest that a bioassay monitoring 

program for thorium exposure existed at General Atomics during the AWE operational period from 

January 1, 1960 through December 31, 1969. As indicated in Section 4.0, potential for thorium 

intakes existed throughout the radiological areas of the General Atomics facility, with no identifiable 

correlation between thorium activity levels and the uranium activity levels found in the workplace. 

Concentrated thorium was commonly produced or used during radiological operations and 

experiments. Consequently, although a uranium bioassay monitoring program existed during portions 

of the defined period, the uranium bioassay results are not adequate to allow the bounding of worker 

doses due to potential thorium intakes. 
SEC-00064 FINAL General Atomics

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NIOSH does not have air monitoring program documentation or air monitoring data relative to the 

worker breathing zones or for the work areas containing concentrated thorium activities at General 

Atomics. Given the lack of evidence of any thorium-specific monitoring program, NIOSH has 

determined that there are insufficient air monitoring data available to support reconstruction of 

thorium-specific internal doses with sufficient accuracy. Further, NIOSH lacks sufficient process and 

source term information to adequately assess potential thorium doses that may have occurred due to 

the diverse radiological operations at General Atomics. 

Given the data currently available to NIOSH, it is not possible to adequately reconstruct the internal 

doses that would have resulted from intake of thorium at General Atomics from January 1960 through 

December 1969. Consequently, NIOSH is unable to adequately estimate total internal exposures for 

the General Atomics AWE operational period. Prior to the start of routine bioassay in October 1963, 

NIOSH is unable to reconstruct any internal doses from any radionuclide. Internal dose due to intake 

of uranium can be reconstructed for exposures starting in October 1963, and tritium doses can be 

estimated after September 1965. 

Some limited documentation is currently available to match radiological workers to specific locations; 

however, many of these workers were likely assigned to multiple locations. Therefore, the proposed 

class cannot be restricted to a specific job title or occupation. Thorium was used or potentially used, 

handled, or stored in the locations included in the class definition. 

6.2 Feasibility of Estimating External Exposures 

This evaluation responds to a petition based on NIOSH determining that internal radiation exposures 

to thorium could not be reconstructed for a dose reconstruction referred to NIOSH by the Department 

of Labor. As noted above, HHS will consider this determination to be sufficient without further 

consideration to determine that it is not feasible to estimate the levels of radiation doses of individual 

members of the class with sufficient accuracy. Consequently, it is not necessary for NIOSH to 

evaluate the feasibility of reconstructing external radiation exposures for the class covered by this 

report. 

However, for the record, NIOSH considers the adequate reconstruction of occupational external 

radiation doses for General Atomics workers feasible. Available records indicate that General 

Atomics workers were monitored for external whole-body exposures. Adequate reconstruction of 

external dose is considered possible by using claimant-favorable assumptions as well as applicable 

protocols specified in various complex-wide Technical Information Bulletins (TIBs). 

In addition, NIOSH considers the adequate reconstruction of medical dose for General Atomics 

workers feasible by using claimant-favorable assumptions as well as applicable protocols specified in 

the complex-wide TIB ORAUT-OTIB-0006, Technical Information Bulletin: Dose Reconstruction 

from Occupationally Related Diagnostic X-Ray Procedures. 
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7.0 Summary of Feasibility Findings for Petition SEC-00064 

This report evaluated the feasibility for estimating the dose, with sufficient accuracy, for General 

Atomics employees from January 1, 1960, through December 31, 1969. NIOSH determined that it 

lacks bioassay data and air monitoring results necessary to reconstruct the internal exposures at the 

facility during this time period. Consequently, NIOSH finds that it is not feasible to estimate with 

sufficient accuracy the radiation doses resulting from internal exposures received by members of this 

class of employees. 

NIOSH has documented herein that it cannot complete the dose reconstruction(s) related to this 

petition. The basis of this finding is specified in this report, which demonstrates that NIOSH 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. Members of this class at General Atomics may have received internal intakes from exposure 

to thorium at the plant. NIOSH lacks sufficient information, including biological monitoring data, air 

monitoring information, and process and radiological source information that would allow it to 

estimate the potential intake(s) of thorium, and the resulting dose to which the proposed class may 

have been exposed. 

 

8.0 Evaluation of Health Endangerment for Petition SEC-00064 

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

governed by EEOICPA and 42 C.F.R. § 83.14(c) and § 83.13(c)(3). Pursuant to these requirements, if 

it is not feasible to estimate with sufficient accuracy radiation doses for members of the class, NIOSH 

must determine that there is a reasonable likelihood that such radiation doses may have endangered 

the health of members of the class. The regulations require NIOSH to assume that any duration of 

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

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

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

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

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

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

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

employees in the SEC. 

NIOSH has determined that members of the class were not exposed to radiation during a discrete 

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

criticality incidents. However, the evidence reviewed in this evaluation indicates that some workers in 

the class may have accumulated chronic radiation exposures through intake of radionuclides and from 

direct exposure to radioactive materials. Consequently, NIOSH is specifying that health may have 

been 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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9.0 NIOSH-Proposed Class for Petition SEC-00064 

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

with sufficient accuracy. The NIOSH-proposed class includes all AWE employees who were 

monitored or should have been monitored for exposure to ionizing radiation while working at the 

following General Atomics locations: Science Laboratories A, B, and C (Building 2); Experimental 

Building (Building 9); Maintenance (Building 10); Service Building (Building 11); Buildings 21 and 

22; Hot Cell Facility (Building 23); Waste Yard (Buildings 25 and 26); Experimental Area (Buildings 

27 and 27-1); LINAC Complex (Building 30); HTGR-TCF (Building 31); Fusion Building (Building 

33); Fusion Doublet III (Building 34); SV-A (Building 37); SV-B (Building 39); and SV-D (no 

building number) for a number of work days aggregating at least 250 work days from January 1, 1960, 

through December 31, 1969, or in combination with work days within the parameters established for 

one or more other classes of employees in the SEC. 
SEC-00064 FINAL General Atomics

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10.0 References 

42 C.F.R. pt. 81, Guidelines for Determining the Probability of Causation Under the Energy 

Employees Occupational Illness Compensation Program Act of 2000; Final Rule, Federal 

Register/Vol. 67, No. 85/Thursday, p 22296; May 2, 2002; SRDB Ref ID: 19391 

42 C.F.R. pt. 82, Methods for Radiation Dose Reconstruction Under the Energy Employees 

Occupational Illness Compensation Program Act of 2000; Final Rule; May 2, 2002; SRDB Ref ID: 

19392 

42 C.F.R. pt. 83, Procedures for Designating Classes of Employees as Members of the Special 

Exposure Cohort Under the Energy Employees Occupational Illness Compensation Program Act of 

2000; Final Rule; May 28, 2004; SRDB Ref ID: 22001 

42 U.S.C. §§ 7384-7385 [EEOICPA], Energy Employees Occupational Illness Compensation 

Program Act of 2000; as amended 

Bethard, 1961a, Bethard, W. F., 1961a, memorandum to H. B. Fry, General Atomics, “Highlights of 

the Medical Department 4/22/61 thru 5/22/61,” May 23; SRDB Ref ID: 20217 

Bethard, W. F., 1961b, memorandum to H. B. Fry, General Atomics, “Highlights of the Medical 

Department 5/21/61 thru 6/22/61,” June 22; SRDB Ref ID: 20217 

Bethard, W. F., 1961c, memorandum to H. B. Fry, General Atomics, “Highlights of the Medical 

Department 6/24/61 thru 9/18/61,” September 18; SRDB Ref ID: 20217 

Bold, 1961, memorandum from F. O. Bold to W. H. Ray, Progress Report for Period May 16, 1961 

through June 15, 1961; June 19, 1961; General Atomics Corporation; SRDB Ref ID: 20367

Bold, 1962, memorandum from F. O. Bold to W. F. Bethard, Health Physics Operations Report for 

Period January 15, 1962 through February 15, 1962, General Atomics Corporation; SRDB Ref ID: 

20367

Bold, 1965, memorandum from F. O. Bold to E. A. Long, Health Physics Report for the period 

October 1 through October 31, 1965, November 10, 1965; General Atomics Corporation; SRDB Ref 

ID: 20369 

Bold, 1968, Radiological Safety Guide, GGA-417 (Rev. 3/68), Bold, F. O., 1968; General Atomics 

Corporation; San Diego, California; SRDB Ref ID: 17859 

General Atomics, 1960, General Atomics Division of General Dynamics Corporation and Holmes & 

Narver, Inc., 1960, Draft Safety Study for the General Atomic Hot Cell Facility, San Diego and Los 

Angeles, California; December 21, 1960; SRDB Ref ID: 17538 

General Atomics , 1961, General Atomics Division of General Dynamics Corporation and Holmes & 

Narver, Inc., 1961, Safety Study for the General Atomic Hot Cell Facility, San Diego and Los 

Angeles, California, GA-1953, San Diego and Los Angeles, California; January 21, 1961; SRDB Ref 

ID: 17939 
SEC-00064 FINAL General Atomics

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General Atomics, 1962, A Report on General Atomics Division of General Dynamics, General 

Atomics Corporation; SRDB Ref ID: 20409 

General Atomics, 1964, A Report on General Atomics Division of General Dynamics, General 

Atomics Corporation; SRDB Ref ID: 20410 

General Atomics, 1969, Instruction Manual for the Torrey Pines TRIGA Reactors, GA-7275, 

February 11, 1969; SRDB Ref ID: 20366 

General Atomics, 1998, General Atomics Hot Cell Facility Decommissioning Plan, PC-000423/4, 

February 2, 1998; General Atomics Corporation; SRDB Ref ID: 18096 

Gurren, 1966, memorandum from E. J. Gurren to F. O. Bold, Hand Exposure of S. Oxley at Triga 

Facility -7-01-1966; July 5, 1966; General Atomics; SRDB Ref ID: 17917 

Helgeson, 1966, Helgeson Nuclear Services, Report of Whole Body Counting for General Atomics, 

March 21, 22, and 23; Pleasanton, California; May 3, 1966; SRDB Ref ID: 19024 

Helgeson, 1969, Helgeson Nuclear Services, Report of In Vivo Counting for Gulf General Atomics, P. 

O. Box 608, San Diego, California 92111 Work Performed on May 26-29, 1969; Pleasanton, 

California; July 3, 1969; SRDB Ref ID: 20403 

Hughes, 1964, memorandum from G. J. Hughes to F. O. Bold, Urine Bioassays of G. Hughes and R. 

House, March 20, 1964; General Atomics; SRDB Ref ID: 17928 

Hughes, 1967, memorandum from G. J. Hughes to F. O. Bold, Report of Fire in Controlled Area on 

12-28-66, January 3, 1967; General Atomics; SRDB Ref ID: 17914 

Hughes, 1969, memorandum from G. J. Hughes to F. O. Bold, Contamination in Clean High Bay, 

FFF, January 24, 1969; General Atomics; SRDB Ref ID: 17975 

Kesting, 1964, memorandum from H. L. Kesting and R. J. Cockle to F. O. Bold, High Radiation 

Field in LINAC Flight Path Area, January 30, 1964; General Atomics; SRDB Ref ID: 17889 

Kesting, 1969, memorandum from H. L. Kesting to F. O. Bold, Contamination Incident in Lab L-218, 

January 29, 1969; General Atomics; SRDB Ref ID: 17974 

Lepper, 1963, memorandum from F. R. Lepper to F. O. Bold, 1963, Radioactive Spill in L-403, 

September 19, 1963, General Atomics; SRDB Ref ID: 17890 

ORAUT, 2006, Microsoft Access Database containing results of General Atomics bioassay results; 

entered from General Atomics data sheets, 2006. 

ORAUT-OTIB-0006, Oak Ridge Associated Universities Team, 2003, Technical Information 

Bulletin: Dose Reconstruction from Occupationally-Related Diagnostic X-Ray Procedures, Rev. 03 

PC-1, Cincinnati, Ohio; December 21, 2005. 
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Ray, 1960, Log Book Entry for Room L-540 dated 12-19-1960 signed by W. H. Ray, January 25; 

General Atomics; SRDB Ref ID: 17534 

Russell, 1967, Thermionic Critical Experiment Spectrum Measurements: Description and Safety 

Analysis, Russell, J. L., Jr.; GAMD-8346, September 8, 1967; SRDB Ref ID: 20353 

SNM-69, Special Nuclear Materials License 69 (Docket 70-72), 1963; General Atomics; La Jolla, 

California; March 29, 1963; SRDB Ref ID: 19011 

SNM-69, Amendments 1-62, Special Nuclear Materials License 69 (Docket 70-72) – Amendments 1 

through 62; multiple dates; General Atomics; La Jolla, California; SRDB Ref ID: 19012 and 19013 

SNM-696, Special Nuclear Materials License 696 (Docket 70-734); multiple dates; General Atomics; 

La Jolla, California; SRDB Ref ID: 19014