Area IV of the Santa Susana 

Field Laboratory

SEC-00234

Lara Hughes, PhD, CHP

Health Physicist

Division of Compensation Analysis and Support

Advisory Board on Radiation and Worker Health, 114th meeting

Santa Fe, NM

December 1, 2016

Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Petition History

 SEC-00234 - NIOSH finding is dose reconstruction not 

feasible for existing claim

• Claimant identified in July 19, 2016 

• Petition received on August 2, 2016

• October 11, 2016 NIOSH evaluation report issued 

 SEC-00093: class added to SEC for 1955-1958 based 

on lack of internal monitoring pre-1959

 SEC-00156: Class added to the SEC for 1959-1964 

based on incomplete bioassay, air and process 

monitoring pre-1965
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Site History

 Area IV established in 1953

• In 1955 nuclear operations became Atomics International (AI)

• Rocket testing operations became Rocketdyne

 AI merged with Rocketdyne in 1984 as part of Rockwell 

International

 Boeing-owned since 1996 

 DOE operational part refered to as “ETEC”
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Site History (cont.)

 2,850 acres total

 Simi Hills, Ventura County; 

30 miles northwest of Los 

Angeles

 4 administrative and 

operational areas (Area I-IV)

 Area IV (290 acres) is the 

only covered area (ETEC)
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Area IV SSFL - Site Operations

 Nuclear reactor programs, 1955-1980

• Development and operation of 10 test reactors

• Operation of criticality test facilities

 Nuclear support operations,1956-present

• Reactor fuel manufacturing

• Disassembly of used reactors and fuels

• Production of radioactive sources
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Area IV SSFL - Site Operations

 Nuclear support operations - cont.

• Reactor fuel manufacturing

• Disassembly of used reactors and fuels

• Production of radioactive sources

• Research on fuel reprocessing

• Preparation of waste for disposal

 Non-nuclear programs, 1966-1998

• Liquid metal technologies
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Rationale for Additional Class

 Continued evaluation and issues resolution of Area 

IV SSFL found exposure potential for Americium 

and Thorium

• Am and Th not detected by available internal monitoring 

methods

 Internal coworker model is limited in scope 

• U, Pu, MFP

• Does not address Th and progeny

• Does not address 241Am
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Rationale for Additional Class - cont.

 Sources of Am and Th 

• Routine reactor operations, shutdowns, modifications, 

refueling

• SRE, U-Th metal alloy core used from 1960-1964

• AETR (1960-1974) used Th fuel cores

• RMDF: used reactor fuel storage 

• Hot Lab: SRE fuel disassembly in 1974 and 1976

• Research on fuel reprocessing in Engineering Test Building

• Fuel decladding operations
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Rationale for Additional Class - cont.

 Sources of Am and Th

• Research involving special isotopes

• Nuclear operations ended in 1980

• Nuclear support operations ended in 1988
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Sources of Available Information

 Site Profile and Technical Information Bulletins and 

Procedures

 NIOSH Site Research Data Base 

 Existing claimant files

 Electronic data bases

 Interviews with former Area IV SSFL employees

 Scientific publications
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary of Information Available 

for Dose Reconstruction

 Internal monitoring data

• Gross alpha and beta

• Uranium, plutonium, mixed fission products

• Limited data available for Am-241 and Thorium

• Internal monitoring limited to radiation workers handling 

unencapsulated material

• Coworker models completed, but limited in scope
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary of Information Available 

for Dose Reconstruction

 External monitoring data available for all years 

 Assigned based on job/exposure potential

• Beta/gamma: pocket or pencil dosimeters, film dosimeter 

and TLD

• Neutron: NTA film, n:p ratio assigned

• 4665 individuals enrolled in external dosimetry program 

(1955-1999)

• NIOSH has developed external coworker model
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Feasibility Conclusion

 NIOSH lacks sufficient monitoring, process or source 

information to estimate potential internal doses from 

thorium or americium from 1965 through 1988

 NIOSH believes that it has sufficient data to 

reconstruct external doses to all workers at the site

 NIOSH will use individual personal monitoring data or 

applicable coworker data for partial dose 

reconstructions as appropriate
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Definition Finding

All employees of the Department of Energy, its predecessor 

agencies, and their contractors and subcontractors who 

worked in any area at Area IV of the Santa Susana Field 

Laboratory in Ventura County, California, from January 1, 

1965 though December 31, 1988, 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 for one or more other 

classes of employees included in the Special Exposure 

Cohort. 
Department of Health and Human Services

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Summary

Feasibility Findings for Area IV SSFL SEC-00234

Source of Exposure Dose Reconstruction

Feasible

Dose Reconstruction NOT 

Feasible

Internal

- Uranium, Plutonium, Mixed 

Fission Products

X (1965 present) X (1958-1964)

- Americium, Thorium (and 

progeny)

X (1988-present) X (1965-1988)

External 

-Beta-Gamma X

- Neutron X

- Occupational Medical X-ray X