General Atomics 

Special Exposure Cohort 

Evaluation Report

LaVon B. Rutherford, CHP

NIOSH

Division of Compensation Analysis and Support

July 29, 2014

Idaho Falls, Idaho
Background

 NIOSH issued Evaluation Report (ER) in September 

2006 for SEC-00064 (84.141) 

 Presented ER to the Advisory Board on Radiation 

and Worker Health (Board) December 11, 2006

 Board agreed with NIOSH recommendation to add a 

class to the Special Exposure Cohort (SEC)

1 §83.14 petition is a petition submitted to NIOSH by a petitioner whose dose could not be reconstructed by 

NIOSH
Background(cont.)

 In June 2010 NIOSH completed a review of the SEC 

class definitions (consistency, applicability, and 

whether NIOSH needed to act to correct an existing 

class definition)

 We recognized a need to adjust the existing class 

definition from workers in specific buildings to 

include “All employees...”

 Waited for “Litmus case” to serve as the petitioner 

for an 83.14 ER
 Sanford Cohen & Associates (SC&A) completed a review 

of the General Atomics Site profile in October 2013 

 In June 2014, NIOSH received a potential “Litmus claim” 

 June 17, 2014: NIOSH informed a General Atomics 

claimant that we were unable to reconstruct the 

radiation dose for the claim

 July 1, 2014: NIOSH received an 83.14 SEC petition

 July 17, 2014: NIOSH approved and issued the 

evaluation report

Background(cont.)
Site Information

 Location: La Jolla, California

 Private contractor for the Atomic Energy 

Commission (AEC) from 1960 – 1969

 Operated under licenses first issued by the AEC and 

later by the state of California

 Performed an array of radiological research and 

production activities involving various radionuclides

• Uranium (Enriched, Normal, Depleted and Recycled)

• Plutonium

• Thorium

• Fission and activation products

• Tritium
Radiological Operations

 Developed and fabricated reactor fuels

 Operated three on-site Training Research Isotopes 

General Atomics (TRIGA ) reactors

 Fusion research

 Experimental criticality test facilities 

 Experimental operations with radioactive materials

 Special nuclear material and radioactive tracers in 

laboratories

 Operated four linear accelerators (LINACs)
Internal Monitoring Data

 Bioassay monitoring are available from the start of 

AEC operations

• Samples analyzed for gross alpha or uranium activity

• Appears to be random sampling based on perceived potential 

for internal exposure

 No routine personal or area monitoring for internal 

exposures to thorium, plutonium during the AEC 

period

• Whole body counting started 1966. However, they’re not 

useable.

• Twelve experimental whole body counts for thorium 1966

• One whole body count for thorium 1969
Internal Monitoring Data (cont.)

 Bioassay monitoring for fission products 

beginning in the early 1960s

• Incident based until 1963

 Bioassay for tritium started in 1965

 No thoron measurements although routine 

reference to thoron contamination on air 

samples
External Monitoring Data 

 External monitoring data are available from the 

start of AEC operations

 Film badges sensitive to beta, gamma, and neutron 

were issued for individuals working in areas with 

potential for neutron exposure
First Petition Evaluation Infeasibilities 

 Since this was an 83.14, NIOSH did not address 

feasibility for each radionuclide. Once NIOSH 

identifies an exposure that cannot be reconstructed 

NIOSH moves forward with an 83.14 petition

 NIOSH identified an infeasibility in reconstructing 

thorium exposures and tritium prior to 1965

• No personal or area monitoring data specific to Thorium

• Diverse operations with thorium and no correlation with 

other radionuclides

• No tritium data prior to 1965
First Petition Class 

 Early in the program, NIOSH did not ask DOL if they 

could administer a class as defined

 Can DOL identify the locations people worked?

 Early in the program, NIOSH did not recognize the 

potential of worker movements through various 

facilities

 Were there maintenance workers that supported all the bldgs?

 Were there access controls for each of the facilities that would 

control movement of workers?
First Petition Class (cont.)

 Because of this a number of classes were defined 

based on the buildings where the exposures may 

have occurred

 General Atomics class was defined by buildings 

where work with thorium may have occurred

 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 (Bldg. 2).....
Site Profile Review

 October 2013 SC&A reviewed the site profile

 SC&A identified a number of issues associated with 

our dose reconstruction approach for the SEC period 

and the residual period

 NIOSH reviewed: the issues identified by SC&A; the 

site profile; and supporting documentation

 From the review NIOSH identified additional 

infeasibilities that are included in this evaluation
Additional Infeasibilities

Uranium, Plutonium, Thorium (Fuel Fabrication)

 No personal or area monitoring data specific to these 

radionuclides during 1960-1964 period

 No routine personal or area monitoring data specific to 

radionuclides other than uranium during the entire AEC period

• Whole body counts starting in 1966 were not useable

 Isotopic ratios of airborne activity and gross alpha bioassay 

cannot be established

 The site profile currently uses a back extrapolation method from 

1965-1968 period to address exposures in the 1960-1964 period 

and data outside the operational period for plutonium
Fission and Activation Products

 Incident based bioassay program starting in the early 1960s

 Some routine operations involving potential for exposure to 

mixed fission and activation products

• Work with irradiated fuels

• Y-90 production

• Experimental facility work 

 During a portion of the AEC period the incident based monitoring 

would not support a co-worker model and it’s not clear based on 

the number of activities involving the potential exposure to fission 

and activation products that the routine bioassay program 

covered all of the activities

Additional Infeasibilities (cont.)
Tritium/Metal Tritides

 General Atomics began monitoring for Tritium in 1965

• NIOSH has identified 194 bioassay samples from 1965 

through 1969

 Metal tritides were present during the operational period 

with no indication of any analysis performed to determine 

the type of tritide

 NIOSH has determined that, without the knowledge of the 

type of metal tritide present at General Atomics, 

sufficiently accurate dose assessment cannot be made

Additional Infeasibilities (cont.)
Thoron

 No personal or area monitoring data for thoron are available 

for the entire AEC period

 Routine reference to thoron interference on air samples

 Site profile uses thoron data from 1975 for the operational 

period

 NIOSH has determined that the approach in the site profile 

does not provide a reasonable assessment of the potential 

exposures to thoron during the operational period

Additional Infeasibilities (cont.)
External Exposures

 External exposure issues were identified during site 

profile review that questioned the ability to reconstruct 

external exposures to unmonitored workers 

 NIOSH has determined that it is unable to define 

individual worker exposure scenarios for those workers 

that were not monitored for external exposure

 NIOSH has determined that it cannot estimate 

unmonitored external beta, gamma, and neutron 

exposures for the AEC period

Additional Infeasibilities (cont.)
Infeasibilities Summary

 NIOSH does not have access to sufficient personnel 

monitoring, workplace monitoring, or source term data to 

estimate potential internal exposures to unmonitored 

radionuclides, including unmonitored uranium, thorium and 

progeny, plutonium, tritium, and fission and activation 

products and resulting doses for the class of employees 

covered by this evaluation

 NIOSH does not have access to sufficient personnel 

monitoring, workplace monitoring, or source term data to 

estimate unmonitored external beta, gamma, and neutron 

exposures for the class of employees covered by this 

evaluation
Health Endangerment

 The evidence reviewed in this evaluation indicates that some 

workers in the class may have accumulated chronic radiation 

exposures through intakes of radionuclides and 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. 
Dose Reconstructions

 NIOSH intends to use any internal and external monitoring data 

available for individual claims to support partial dose 

reconstruction for claims not qualifying for inclusion in the SEC

 In addition, NIOSH’s position on occupational medical dose did 

not change. NIOSH will continue to reconstructed this dose.

 A number of the issues identified by SC&A with the site profile 

will be resolved with this petition evaluation. NIOSH will work 

with the Advisory Board’s work group and SC&A to resolve the 

remaining issues

 Once all issues are resolved NIOSH will revise the site profile to 

include the findings of this petition evaluation and the resolution 

from the findings of the site profile review
Current Class 

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 

(Bldg. 2); Experimental Building (Bldg. 9); Maintenance (Bldg. 10); 

Service Bldg. (Bldg. 11); Bldgs. 21 and 22; Hot Cell Facility (Bldg. 23); 

Waste Yard (Bldg. 25 and 26); Experimental Area (Bldg. 27 and 27-1); 

LINAC Complex (Bldg. 30); HTGR-TCF (Bldg. 31); Fusion Bldg. (Bldg. 

33); Fusion Doublet III (Bldg. 34); SV-A (Bldg. 37); SV-B (Bldg. 39); SVD (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 included in 

the SEC
Recommended SEC Class

All Atomic Weapons Employees who worked for 

General Atomics at its facility in La Jolla, California, 

during the period from January 1, 1960 through 

December 31, 1969, for a number of work days 

aggregating at least 250 work days, occurring 

either solely under this employment or in 

combination with work days within the parameters 

established by one or more other classes of 

employees included in the Special Exposure Cohort
Recommendation

 For the period January 1, 1960 – December 31, 

1969, NIOSH finds that radiation dose estimates 

cannot be reconstructed for compensation 

purposes

Class Feasibility Health Endangerment

January 1, 1960 –

December 31, 1969 No Yes