TO: Advisory Board on Radiation and Worker Health Work Group on TBD-6000 

FROM: Robert Anigstein and John Mauro, SC&A 

SUBJECT: Update of Doses from External Exposure at GSI 

DATE: January 12, 2014 

Update of Doses from External Exposure at General Steel Industries 

During the December 19, 2013, meeting of the ABRWH Work Group on TBD-6000, SC&A was 

asked to provide an update to our previously calculated doses to GSI employees from external 

exposure to penetrating radiation. Agreement had already been reached on limiting photon doses 

to plant personnel during the Radium Era, which, for purposes of dose reconstruction, spanned 

the period October 1, 1952–December 31, 1962. Agreement had also been reached on photon 

doses to administrative personnel, with the understanding that such doses shall be assigned only 

if it can be conclusively established that the employee in question performed administrative 

functions, that the employee’s work station was remote from the production areas of the plant, 

and that the employee did not frequently enter the production areas. Finally, agreement had been 

reached on doses to the skin from β rays. The present memo presents the results of our analyses 

of limiting photon doses during the period of AEC operations following the Radium Era (i.e., 

January 1, 1963– June 30, 1966), and neutron doses during the entire period of AEC operations. 

We have estimated annual photon doses during the Post-Radium Era based on two exposure 

scenarios: the betatron operator and the layout man. Whichever scenario yields the higher 

probability of causation should be employed in an individual dose reconstruction. 

1 Betatron Operator 

1.1 Photon Dose from Hypothetical Residual Radiation from the Betatron Apparatus 

As discussed by Anigstein and Olsher (2012, Section 2.1.1), the limiting photon dose to betatron 

operators is based on the hypothetical exposure to residual radiation from the betatron apparatus 

in the posteroanterior orientation. This exposure scenario yields a maximum effective dose of 

26 mrem/week, as listed in Table 1—the annual dose is listed in Table 2. This limiting dose 

should be assigned to betatron operators during the Post-Radium Era. 

Table 1. Effective Dose to Betatron Operator from External Exposure 

Photons Neutrons Source of radiation 

mrem/week mrem/shift 

Betatron residual 26 

Uranium handling 0.50 

Uranium radiography 1.16 

Steel radiography 0.65 

Update of Doses from External Exposure at GSI -1- SC&A –January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

1.2 Neutron Exposures 

Betatron operators were also exposed to delayed neutrons from photofission and photoactivation 

of irradiated uranium and to neutron radiation in the control room during the radiography of 

uranium and of steel castings. 

1.2.1 Exposure to Neutrons from Irradiated Uranium 

The exposure of the betatron operator to neutrons from irradiated uranium was simulated by 

using the delayed neutron feature of MCNPX. We used the code to model neutron emission 

resulting from photofission and photoactivation in a slice from a uranium dingot, 18 in 

(45.72 cm) in diameter and 4 in (10.16 cm) thick, as a function of time following exposure to the 

betatron x-ray beam. Such a disk, radiographed at a distance of 6 ft from the betatron target, 

would intercept a major portion of the x-ray beam and thus represents a limiting exposure 

scenario. The exposure was assumed to take place in the Old Betatron Building—the MCNPX 

model, shown in Figure 1, included the walls, floor, and roof of the shooting room. We assumed 

Update of Doses from External Exposure at GSI -2- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

 

that the operator’s exposure began 5 s after the betatron was turned off and lasted for 15 min. He 

was assumed to be at a distance of 1 m from the uranium metal during one-half of this time— 

location 1, marked by an asterisk in Figure 1—and at a distance of 1 ft during the remaining 

time—location 2 in Figure 1. The MCNPX model of the betatron, shown in Figure 1, includes 

the platinum target inside the porcelain doughnut, the ionization chamber, and the aluminum 

compensator that serves to flatten the x-ray beam in order to produce a more uniform exposure 

across its cross-section. The electromagnets, which are not in the path of the primary beam, are 

not part of the model. 

MCNPX was used to tabulate the effective dose from delayed neutrons in a series of time bins. 

According to SC&A( 2008, Section 2.1.4), 

After the metal has been irradiated for a period of time, the dose rate from the metal 

is the sum of contributions from the activation and subsequent decay of nuclides that 

were created during the period of exposure. To calculate the dose rate at a time after 

the end of the exposure, we performed a numerical integration over the doses in the 

individual time bins. [Further details are found in the cited location.] 

The resulting dose per 8-h shift, assuming an average of 6.4 radiographic exposures per shift 

(480 min/shift ÷ [60 min/shot + 15 min setup] = 6.4), is listed in Table 1. The contribution of the 

uranium handling scenario to the annual neutron effective dose, listed in Table 2, was calculated 

by multiplying the dose per shift by the number of shifts devoted to uranium radiography during 

a given year. 

Table 2. Annual Effective Dose to Betatron Operator from External Exposure 

Betatron residual Annual number of shifts Neutrons (mrem/y) 

Year photonsa 

(rem) Uranium Steel Uranium 

handling 

Control room 

U Steel 

Total 

1952-1957 — 54.69 351.56 27.1 63.6 227.1 317.8 

1958 — 46.48 359.77 23.1 54.1 232.4 309.5 

1959-1960 — 42.19 364.06 20.9 49.1 235.1 305.1 

1961 — 48.44 357.81 24.0 56.3 231.1 311.4 

1962 — 35.16 371.09 17.4 40.9 239.7 298.0 

1963 1.30 9.57 396.68 4.7 11.1 256.2 272.1 

1964 1.30 3.52 402.73 1.7 4.1 260.1 265.9 

1965 1.30 2.56 403.69 1.3 3.0 260.7 265.0 

1966b 1.30 0.80 202.32 0.4 0.9 130.7 132.0 

a

 Assuming 50 weeks/y of exposure 

b During contract period: January 1–June 30 

Update of Doses from External Exposure at GSI -3- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

1.2.2 Exposure to Neutrons in Control Room During Uranium Radiography 

The neutron exposure of the betatron operator during uranium radiography was simulated with 

MCNPX. The operator was assumed to be in the control room of the Old Betatron Building, 1 m 

from the wall that faced the shooting room—see position 3, marked by an asterisk in Figure 2. 

The resulting dose, based on an assumed uranium radiographic exposure of 60 min per shot and 

6.4 shots per shift, is listed in Table 1. The contribution of this scenario to the annual neutron 

effective dose, listed in Table 2, was calculated by multiplying the dose per shift by the number 

of shifts devoted to uranium radiography during a given year. 

Update of Doses from External Exposure at GSI -4- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

1.2.3 Exposure to Neutrons in Control Room During Radiography of Steel Castings 

SC&A (2008, Section 2.2.1) described the assessment of stray radiation from the betatron during 

the radiography of a heavy hollow axle. In the present analysis, we re-evaluated the neutron 

exposure of the betatron operator, using the latest release of MCNPX. We assumed the operator 

to be seated at the desk in the control room, as shown in Figure 3. The MCNPX model is 

illustrated in Figure 4. 

The neutron dose to the betatron operator from this scenario was calculated on the assumption 

that during 64.29% of the shifts, he spent 3 min of each 15 min at the desk in the control room, 

which is the time for each of the short shots, while during the remaining shifts, which were 

devoted to long shots, he spent 60 of each 75 min at this location. The result is listed in Table 1. 

To calculate the contribution of this scenario to the annual neutron effective dose, we postulated 

that the betatron operator receiving the highest neutron dose spent the maximum number of shifts 

Update of Doses from External Exposure at GSI -5- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

during a given year radiographing uranium, which, as shown in Table 1, produced a higher dose 

per shift than the radiography of steel. We assumed that the remainder of his work year was 

spent radiographing steel. The annual neutron dosefrom the radiography of steel, listed in 

Table 2, was calculated by multiplying the dose per shift by the number of shifts devoted to 

radiography of steel during a given year. 

Update of Doses from External Exposure at GSI -6- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

2 Layout Man 

SC&A (2008, Section 2.4.2) discussed the exposure assessment of the layout man. A brief 

updated description of this scenario was presented by Anigstein and Olsher (2012, 

Section 2.1.2). The primary source of photon exposure was the stray and scattered radiation from 

the betatron during the radiography of steel castings. The photon dose was assessed at two 

locations: 10 ft to either side of the railroad track used to transport castings into the New 

Betatron Building. The location northwest of the tracks received a 72% higher photon exposure 

—the exposure at this location, reported by Anigstein and Olsher (2012, Table 2), remains 

unchanged. 

The neutron dose to the layout man was re-evaluated for the present analysis. The assessment 

used the same exposure geometry as the photon exposure assessment. As it happened, a worker 

at the location that experienced the higher photon exposure received the lower neutron dose. 

However, the difference between the neutron doses at the two locations was only 12%. Since the 

numerical values of the photon exposures were an order of magnitude higher than the neutron 

doses, the neutron dose at the northwest location—the same location that was adopted for the 

photon exposure assessment—was assigned to the layout man. 

The assessment of this worker’s photon exposure to irradiated steel was based on the description 

presented by SC&A (2008, Section 2.4.2), 

The layout man marked up the steel after all shots were completed; therefore, the 

portion of his time marking up the steel that had been subjected to long shots and 

short shots is not the same as the fraction of long shots and short shots performed 

with the betatron. According to , a former GSI supervisor, 

the layout man would typically spend a full shift of 8 h marking up a large casting. 

However, he might sometimes be interrupted to mark up a casting that has just been 

radiographed and is close to being shipped. . . . We characterized that scenario as 

involving long (one-hour) shots. . . . We assumed that 10% of his shift consisted of 

such activity, while 90% was devoted to marking up a single large casting that had 

been subjected to multiple short shots . . . . Because marking the steel requires 

continuous close contact with the metal, we assumed that he was at a distance of 1 ft 

(30.48 cm) 90% of the time and at 1 m the remaining 10%. 

During the shifts involving the long-shot scenario, the layout worker was assumed to work on a 

succession of castings that had each been subjected to 400 exposures prior to his shift, and to 

spend 75 min marking up each of these castings. He would have marked up an average of 6.4 

such castings during such a shift. During each of the remaining shifts, he was assumed to mark 

up a single casting that had been subjected to 532 short shots. 

The results of the updated analysis are presented in Table 3. 

Update of Doses from External Exposure at GSI -7- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.
 
 

 

Table 3. External Exposure of Layout Man to Direct Penetrating Radiation 

Betatron Duration Exposure Neutron dose Source of radiation 

duty cycle h/shift mR/shift mrem/shift 

Short shots–90% — — 0.02 Irradiated steel 

Long shots– 10% — — 0.03 

Betatron 41% 8 22.11 1.4 

Total 22.2 1.4 

Annual No. shifts/y 

406.25 

R/y 

9.0 

mrem/y 

554 

References 

Anigstein, R., and R. H. Olsher. 2012. “Response to ‘Battelle-TBD-6000 Appendix BB General 

Steel Industries: Dose Estimates for Betatron Operations’.” 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/scarespon2dcasgsi.pdf. 

Nuclear Regulatory Commission (U.S.) (NRC). 2009. “General Steel Industries Byproduct 

Materials License for Cobalt-60, Budd Company Model 41706 Sealed Source not to exceed 1 

curie in a single source,” ADAMS acquisition number ML093480290. 

S. Cohen & Associates (SC&A). 2008. “Review of ‘Site Profiles for Atomic Weapons 

Employers That Worked Uranium and Thorium Metals - Appendix BB: General Steel 

Industries,’ Battelle-TBD-6000, Appendix BB, Rev. 0” (March 17, 2008). 

http://www.cdc.gov/niosh/ocas/pdfs/abrwh/scarpts/sca-gsisp-r1.pdf 

Update of Doses from External Exposure at GSI -8- SC&A – January 12, 2014
 

NOTICE: This report has been reviewed for Privacy Act information and has been cleared for distribution. 

However, this report is pre-decisional and has not been reviewed by the Advisory Board on Radiation and Worker
 

Health for factual accuracy or applicability within the requirements of 42 CFR 82.