General Steel Industries (GSI)

Special Exposure Cohort 

David Allen

Dose Reconstruction Health Physics Team Leader

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support

June 2012

Santa Fe, NM
Background

 General Steel Industries (GSI) was classified as 

an Atomic Weapons Employer (AWE) facility 

from 1953 to 1966

 Residual contamination period through 1993

 Performed radiography examinations of uranium 

metal using betatrons

 No correction of defects or other manipulation 

of uranium metal was reported
Sources of Radiation: Internal

 Dust from uranium corrosion

 Dust from activated steel
Sources of Radiation: External

 Direct radiation from betatrons

 Activated steel

 Uranium

 Radiography with isotopic sources

 Portable x-ray machines
Betatrons

 Two betatron buildings on site, new and old

• Old betatron was built in 1952 and was reported to 

have a maximum energy of 24 MeV

• New betatron was moved from Eddystone, 

Pennsylvania, to Granite City in 1963 and was 

reported to have a maximum energy of 25 MeV

 Photon energy was high enough to cause 

activation
Betatron Buildings
Activated Steel

 Betatron energy was high enough to cause 

activation of steel castings

 MCNP, a computer program, was used to model 

this activation using favorable scenarios

• Reported intensity

• Drawings of the aluminum compensator and ion 

chamber

• Maximum electron energy

• Reported distances between betatron and castings
Isotopic Sources

 Two 500 mg Ra-226 sources until 1962

• Used fishing pole technique to place sources

• Interview with former operator described technique 

details

• Sources used both inside a radiography room in 6 

building and throughout the plant
Isotopic Sources—cont.

 Purchased two Co-60 sources in 1962

• Discontinued use of Ra-226 at the request of the state 

of Illinois

• Purchased two Co-60 sources in 1962

• Sources were 260 mCi and 280 mCi

• Sources were to be used in the radiography room

• Workers reported sources also used throughout the 

plant
Isotopic Sources—cont.

 St. Louis Testing

• Contracted to perform some radiography as well as 

provide other services (instrument calibration)

• Used 50 Ci Ir-192 source and 10 Ci Co-60 source on 

site at various times

• GSI employees were not involved with radiography 

performed by St. Louis Testing
Other Sources of Radiation

 GSI owned two portable x-ray machines

• GE OX-250

• Andrex

 Reports of the frequency and location of use are 

conflicting

• The few memories of machines indicate infrequent 

use

• Former supervisor indicated machine was tested 

when bought and not used again
Data Sources: Film Badges

 Film badge dosimetry from Landauer

• Covers November 1963 through 1972

• Only those associated with radiography were issued 

film badges

• Weekly exchange

• Reporting level of 10 mrem

• 99.7% of readings less than reporting level
Data Sources: Film Badges—cont.

 Prior to 1963, film badges were worn

• Unable to locate reports of film badges

• Information from interviews and pictures of former 

workers show film badges being worn

• One former worker provided a film badge summary 

report
Data Sources: NRC

 Co-petitioner obtained GSI documents from 

Nuclear Regulatory Commission (NRC) via a 

Freedom of Information Act (FOIA) request

 Documents mainly licenses and applications for 

licenses and renewals

 License first granted in 1962 prior to purchase of 

Co-60 sources
Data Sources: NRC—cont.

 Information includes:

• Drawing and radiation surveys of radiography room

• Type and strength of isotopic sources (Ra-226 and Co60)

• Sparse information on source utilization and previous 

exposures

• Detail drawing of new betatron building

• Survey outside new betatron shooting room with 80 

Ci Co-60 source exposed
Data Sources: Former Workers

 Many workers were interviewed at various times 

by various people (Co-petitioner, NIOSH, SC&A)

 Some interviews were group settings and some 

individual
Data Sources: Former Workers—cont.

 Information includes:

• Work practices when using source outside 

radiography room

• Violations of practices both routine and abnormal

• Frequency and duration of x-rays using the betatrons

• Badge practices including removing film badge when 

working outside betatron building
Dose Estimate: Internal

 Uranium modeled using uranium slug 

production values from Battelle-TBD-6000

• Slug production involved some abrasive work while 

GSI did not perform any destructive work on the 

uranium metal

 Dose from uranium fission and activation 

products were included in the estimate

 Internal dose from activated castings was 

considered by assuming an individual 

continuously ground on a freshly activated 

casting
Use of TBD-6000

 All TBD-6000 tasks involve uranium metal

 All tasks inherently include moving uranium metal 

as well as other operations

 Moving the metal is the least airborne causing 

evolution

 All tasks in TBD-6000 are bounding for GSI

 The lowest task is most plausible
Dose Estimate: External

(Betatrons)

 New Betatron building was modeled in MCNP

 Model was checked against a 1971 80 Ci Co-60 

source survey

 Building model was then used to determine dose 

rates outside the building when betatron was 

operating at various locations and orientations
Dose Estimate: External—cont. 

(Betatrons)

 Dose rate at the film badge storage location was 

determined for each orientation

 Orientations were chosen based on weekly dose 

rate at badge rack for each orientation 

consistent with the utilization described by the 

operators
Dose Estimate: External—cont.

(Betatrons)

 Hours per week of each orientation was then 

used to determine dose at various locations 

while betatron was operating

 Dose from steel and uranium after operations 

was determined and added to this dose
Dose Estimate: External—cont.

(Betatrons)

 Typical durations for x-rays of steel and uranium 

were assessed from worker interviews

 Separate dose estimates were derived for each

 The two dose estimates were combined using 

uranium work frequencies derived from 

purchase orders
Dose Estimate: External

(Layout man)

 Operators often marked castings for upcoming 

shots outside the betatron building

 When performing this work, film badges were 

not worn (kept in the betatron building)

 Exposed to betatron radiation while it was 

operating and to activated steel
Dose Estimate: External—cont. 

(Layout man)

 Dose from betatron determined using worst-case 

location and orientation frequencies previously 

determined

 Dose from activated steel determined using 

worst-case scenario for moving castings into and 

out of the betatron building.
Dose Estimate: External

(Co-60 sources)

 A 1962 survey around the radiography room was 

used in combination with source utilization 

reported by the Atomic Energy Commission 

(AEC)

 Source strength and reported work practices 

outside the radiography room were used to 

determine that dose

 Highest of the two scenarios to be used
Dose Estimate: External

(Ra-226 sources)

 Source strength and reported work practices 

outside the radiography room were used to 

determine that dose

 Assumed radiography room did not exist before 

1962

 Information since then indicates it did exist and 

was routinely used

 Estimate for radiography room was done by 

SC&A
Dose Estimate: External

(St. Louis Testing Sources)

 Reported that GSI radiographers did not help St. 

Louis Testing perform radiography

 Estimate based on continuous occupancy at the 

boundary
Dose Estimate: External

(Portable X-rays)

 Reported frequency of use was very low

 Qualitative estimate used to estimate dose 

would be lower than other potential sources
Residual Contamination

 Operational airborne assumed to deposit on 

surfaces

 Airborne assumed to be present when people were 

handling uranium

 Estimated the surface contamination then 

resuspended it

 External dose based on vacuum cleaner contact 

reading (higher than from surface contamination)