Santa Susana Field Laboratory Special 

Exposure Cohort/Site Profile Update 

Lara Hughes, PhD CHP

Division of Compensation Analysis and Support

November 2014

Redondo Beach, CA 
 Background 

 Area IV of the Santa Susana Field Laboratory (SSFL)

• Covered Period: 1955 – present

• Two Special Exposure Cohort (SEC) classes: 1955 – 1964

 Canoga Avenue Facility

• Covered Period: 1955 – 1960

• SEC class: 1955 – 1960

 DeSoto Avenue Facility

• Covered Period: 1959 – 1995, 1998

• SEC class: 1959-1964

 Downey Facility

• Covered Period: 1948-1955

• SEC Class: 1948-1955
Historical Site Assessment of the Area IB Santa Susana Field Laboratory Ventura County, California, Volume 1 – Methodology Prepared by Sapere Consulting Inc. and The Boeing Company for the 

Department of Energy under contract DE-AC03-99SF21530, May 2005. 
Work Group History

 Met in 2008, 2009, 2010, and Oct. 16, 2014

 SEC Evaluation Reports (ERs) delivered, 2009 

and 2010

 Board contractor reviewed Technical Basis 

Document (TBD) , Area IV ER in 2008 and 2009
Issues Discussed

 Site definition and operations timeline 

 Incidents

 Internal monitoring issues, internal coworker 

model

 External monitoring issues, external coworker 

model

 Neutron approach/NTA film data

 Environmental approach from stack releases

 Tritium plumes
Dates and Documents

 Documents in discussion 

• Neutron-Photon ratio white paper (June 14, 2010)

• Internal Coworker Model - ORAUT-OTIB-0080 (March 14, 2014)

 NIOSH draft documents to release

• External Coworker Model - ORAUT-OTIB-0077 

• TBD revisions to include most recent guidance on neutrons, 

coworker models and environmental approach
NIOSH work since 2010

 2010

• Continuing discussion and issue resolution with internal 

data

• NIOSH negotiating with Boeing trying to obtain SSFL 

scanned dosimetry records to complete coworker models

• NIOSH analyzes neutron/photon data and releases white 

paper with n/p approach 

• Internal, external and environmental TBDs were revised, 

mainly to include SEC language
NIOSH work since 2010 (cont.) 

 2011

• Continuing negotiation with Boeing about scanned 

records and data base information

• NIOSH discovers issue with Boice data base and 

abandons using it for coworker studies

• NIOSH drafts revised versions of SSFL TBDs but they 

remain pending resolution of issues with coworker 

studies
NIOSH work since 2010 (cont.) 

 2012

• Boeing decides to release scanned records of worker 

dosimetry files in January

• NIOSH ORAU receives data 3/7/2012, consisting of over 

14,000 files

• Data entry and coworker model development take place 

from May 2012 to January 2013
NIOSH work since 2010 (cont.) 

 2013

• Internal and external coworker models completed and 

reviewed

• External model is pending approval awaiting issue 

resolution on neutrons

 2014

• OTIB-0080 – internal coworker model approved 03/2014

• Issue resolution of OTIB-0077 restarted (neutron 

approach)
Coworker models overview

 Internal (OTIB-0080)

• Plutonium model – 1965-1986

• Uranium model – 1965- 1988

• Gross beta model - 1965-1991

 External (OTIB-0077 – draft)

• 175,024 data points

• Sitewide model: photon, electron, neutron

• Area IV model: photon, electron

• DeSoto model: photon, electron
Neutron Photon Ratio

 Bounding approach for unmonitored 

neutrons

 Time span: 1956-1987

 1180 Paired neutron and photon 

measurements around reactor facilities 

analyzed

 Lognormal fit to data

 Site wide neutron photon ratio of 1.73 with a 

GSD of 2.76
Neutron Approach

 Site wide/unknown work location: use n:p 

ratio

 Accelerator exposure: use NTA film with 

correction factor 

 Reactor exposure: use n:p ratio as indicated 

in NIOSH white paper 

 Fuel handling: research indicates that SSFL 

reactor n:p ratio is bounding
Path Forward

 Issue External Coworker Model

 Incorporate neutron guidance in revised TBDs

 Issue resolution with SC&A regarding 

coworker models and neutron approach

 Remaining SEC issues

 Remaining Site Profile issues
Questions?