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

FROM: Robert Anigstein and John Mauro, SC&A 

SUBJECT: Updated Review of Occupational Internal Dose at GSI 

DATE: May 30, 2012 

Update of “Review of ‘Site Profiles for Atomic Weapons Employers That Worked Uranium 

and Thorium Metals - Appendix BB: General Steel Industries,’ Battelle-TBD-6000, 

Appendix BB,” Occupational Internal Dose

Background

On May 21, 2012, Ted Katz asked SC&A to report on our reviews of the residual period at GSI. 

However, the evaluation of exposures to residual contamination at GSI, as presented in 

Appendix BB, section BB.6: “Residual Contamination” (Allen and Glover 2007), is based on 

the evaluation of occupational internal dose described in section BB.5. We therefore needed to 

review Allen and Glover’s internal exposure assessment during the period of AEC operations, as 

well as during the residual period. 

Intakes During Uranium Handling Operations—DCAS Assessment

Allen and Glover (2007) based the intake rate of airborne uranium during uranium handling 

operations on that of a uranium slug production operator listed in the parent document, TBD6000 (Allen 2011, Table 7.8).1

 The listed intake, 651 pCi per calendar day, was assumed to 

reflect an annual exposure of 2,000 h. The annual exposure to uranium handling at GSI was 

based on the purchase orders from the Mallinckrodt Chemical Works, which specified a monthly 

cost as well as an hourly charge. These purchase orders provide a means of estimating the time 

spent handling uranium during various periods. Allen and Glover calculated the average 

exposure per calendar day by dividing the intake listed in TBD-6000 by 2,000 h, the nominal 

work-year, and then multiplying it by the duration of uranium handling operations during each 

year, derived from the purchase orders. They then increased this amount by 1% to account for 

the increased specific activity of uranium resulting from activation during betatron irradiation. 

Intakes During Uranium Handling Operations—SC&A Observations

Allen and Glover (2007) listed the intakes derived by the above model in units of dpm/calendar 

day. However, these intakes were based on the value 651 pCi per calendar day in TBD-6000. 

The authors did not convert the units; consequently, these intakes were understated by a factor of 

2.22 (1 pCi = 2.22 dpm). Subsequent dose reconstructions that were audited by SC&A utilize 

these values as dpm, and are consequently in error. Whereas this pathway makes a small and 

usually insignificant contribution to doses to organs outside the respiratory tract, it has a 

significant impact on the reconstruction of doses to the lungs. 

 1

 The original reference was to the 2006 version of this document. The relevant parameter values are unchanged 

in the revised version.

Updated Review of Occupational Internal Dose at GSI 1 SC&A –May 30, 2012 

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. 
Updated Review of Occupational Internal Dose at GSI 2 SC&A –May 30, 2012 

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.

An observation with a lesser impact concerns the monthly hours for the period January 1, 1953–

June 30, 1958. Although NIOSH assumes that the uranium operations started on January 1, 

1953, the first available purchase order covers the period March 1, 1958–June 30, 1958. It 

stipulates an estimated cost of $500/mo, at an hourly rate of $16. This implies an expenditure of 

31.25 h/mo, or 375 h/y. Since this is the first extant purchase order, it is reasonable and claimant 

favorable to assume this annual rate for the period January 1, 1953–June 30, 1958. Allen and 

Glover (2007), citing later purchase orders that stipulate a cost of $450/mo, assume an exposure 

duration of 337.5 h/y during this entire period, effectively ignoring the first purchase order. 

Intakes Between Uranium Handling Operations—DCAS Assessment

To estimate the intakes of uranium between periods of uranium handling operations, Allen and 

Glover (2007) derived a surficial contamination based on the deposition of uranium aerosols 

during uranium handling operations. They assumed this surficial activity would become 

resuspended following the uranium handling operations, resulting in a constant airborne 

concentration following the uranium handling operations. 

Allen and Glover (2007) modeled the areal uranium concentrations by citing the DWA (daily 

weighted average) air concentration for the operator involved in uranium slug production and 

canning of 198 dpm/m3 (Allen 2011, Table 7.6). They assumed that this concentration prevailed 

only during the time that the GSI workers were actually handling the uranium metal. Since, 

according to the authors’ scenario, the workers spent one-half of the time setting up and taking 

down the shot, and one-half performing the actual exposure from the betatron control room, they 

were in the room with the uranium metal for only one-half of the total time devoted to uranium 

handling operations. The authors did not reduce the duration of the intake of uranium aerosols 

by that fraction, but they did reduce the time the uranium was suspended in the air and was 

settling to the floor. They multiplied the airborne dust loading of 198 dpm/m3 by the assumed 

terminal velocity of uranium aerosols of 7.5 × 10-4 m/s to obtain an accumulation rate of 

0.1485 dpm m-2

 s

-1. They integrated this rate over the reduced hours of uranium handling during 

one year to obtain an areal concentration. They then applied a resuspension factor (RF) of 

1 × 10-6 m

-1 to obtain an airborne uranium concentration and consequent intake rate for the 

periods between uranium handling operations. 

Intakes Between Uranium Handling Operations—SC&A Observations

In our review of TBD-6000, we observed that an RF of 1 × 10-6 m

-1 might be low by about an 

order of magnitude (SC&A 2007). This value is cited by Abu-Eid et al. (2002) for screening 

analyses of the building occupancy scenario by the Nuclear Regulatory Commission (NRC). 

However, this scenario is for the release of buildings following decontamination and 

decommissioning (D&D). As stated in the issues resolution matrix, “There are two key 

assumptions that underlie the use of such a value. First, the surface contamination occurred 

sometime in the past, and no new contaminants are being introduced. Second, 

“It is assumed that surfaces will be cleaned or washed during decommissioning. 

This will remove most of the loosely bound and some of the more tightly bound 

particles. Following the above discussion, surfaces that have been cleaned would 
Updated Review of Occupational Internal Dose at GSI 3 SC&A –May 30, 2012 

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.

be expected to have a smaller RF than surfaces that have not been cleaned, given 

the same levels of surface contamination. [Abu-Eid et al. 2002, p 4] 

Clearly, neither of these assumptions apply to an operating facility that performs work on 

uranium . . . .” (SC&A 2009) 

The current revision of this document (Allen 2011) retains this original value. If the RF were 

increased by a factor of 10, the airborne dust loading and the consequent intakes would increase 

in the same proportion. 

We observe an inconsistency in the modeled intakes of uranium during the uranium handling 

operations and in the accumulation of uranium deposited on floors and other surfaces. In 

modeling the intake during uranium operations, Allen and Glover (2007) assumed that the 

uranium remained airborne during the entire time of uranium operations, so that betatron 

operators and other workers continued to be exposed to the uranium aerosols even while the 

betatron was operating and no workers were in the shooting room. If that were the case, the 

uranium would also have continued depositing on the floor during this time, whereas the authors 

assumed that the deposition only occurred while the workers were in the shooting area, and 

apparently stopped once they were in the control room. Furthermore, there are different accounts 

of the uranium radiography procedures from former betatron operators, including accounts of 

brief “corner shots,” presumably to determine the amount of defective metal in the casting that 

needed to be sawed off, as well as shots of “betatron slices.” Evidence was also found for the 

radiography of relatively thin ingots produced at Weldon Spring, which would have required 

shorter radiographic exposures and would thus have led to a higher fraction of time spent by 

operators in the shooting room, in the proximity of the uranium. A consistent, reasonable, and 

claimant-favorable approach would be to assume continuous deposition during the entire period 

of uranium handling operations, thus doubling the areal concentration accumulated during one 

year. 

The highest duration of uranium handling operations, 437.5 h/y, was during the period July 1, 

1961–June 30, 1962. Allen and Glover (2007) used this duration to calculate the upper bound of 

the areal uranium concentration: 1,170 dpm/100 cm2

. They assumed that this concentration 

prevailed from July 1, 1961, until the end of the residual period, December 31, 1993. The 

uranium intakes during the residual period were calculated by multiplying the areal concentration 

by the RF, then multiplying by the inhalation rate and by the average work hours. If, as 

discussed above, the areal concentration were doubled and the RF increased by a factor of 10, the 

daily uranium intakes would increase by a factor of 20. A further increase would result from 

increasing the exposure duration from 2,400 to 3,250 hours per year, the value currently accepted 

by NIOSH for external exposure assessments at GSI. The net result would be to increase the 

intake from 0.932 to 24.97 dpm per calendar day. 

External Exposure During Residual Period

Allen and Glover (2007) assigned the highest external exposure rate measured during the 1989 

GSI FUSRAP survey (Cottrell and Carrier 1990), 90 μR/h at the surface of a vacuum cleaner, to 

workers employed at GSI during the residual period. We concur that this is a claimant-favorable 
Updated Review of Occupational Internal Dose at GSI 4 SC&A –May 30, 2012 

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.

 

assumption; however, we observe that, for consistency with other time periods, the exposure 

duration should be increased from 2,400 hours to 3,250 hours per year. 

Summary of SC&A Observations

In summary, we present the following issues and observations regarding the assessment of 

occupational internal doses, as presented by Allen and Glover (2007). We list them in order of 

significance, starting with the issue that has the greatest potential impact on internal doses. 

 Intakes of uranium during uranium handling operations are understated by a factor of 2.22, 

due to a failure to convert the units (pCi to dpm) of the intake by a slug production operator 

listed in TBD-6000. 

 A resuspension factor of 1 × 10-6 m-1 is inapplicable to an operating facility. An RF of 1 × 

10-5 m

-1 represents a more reasonable value. 

 The model of the buildup of uranium on contaminated surfaces, which assumes deposition 

took place only when the workers were in the shooting room with the uranium metal, is 

inconsistent with the calculation of intakes of uranium aerosols during uranium operations, 

which were assumed to occur during the entire time of uranium operations. We recommend 

modeling the deposition as persisting during the entire period of uranium operations. 

 Intakes during January 1, 1953–June 30, 1958 were based on 337.5 h/y. We believe that 

uranium handling operations during this period should be based on the first extant purchase 

order, dated March 6, 1958, which implies an expenditure of 375 h/y. 

 External exposures during residual period should be based on an exposure duration of 3,250 

hours per year to be consistent with other assessments 

Further SC&A Observation on Exposure Assessments for the Residual Period

Allen and Glover (2007) assumed a constant level of surficial contamination during the residual 

period, based on the maximum calculated contamination level during the operational period. We 

agree that this is certainly a claimant-favorable assumption. However, since the maximum 

surficial contamination reported by Cottrell and Carrier (1990) was 540 dpm/100 cm2

, NIOSH 

could avail itself of the methodology recommended in OTIB-0070 (Sharfi 2012), in the 

following manner. 

Allen and Glover (2007) assumed that the highest contamination level resulted from operations 

during the period July 1, 1961–June 30, 1962. If this level were increased to 

2,340 dpm/100 cm2

, as we recommended, one could derive an exponential rate of decline from 

the midpoint of this period, January 1, 1962, to March 16, 1989, 2

 as follows: 

2

 Cottrell and Carrier (1990) reported that the survey was performed in March 1989. We use the middle of the 

month in this calculation. 
  = rate of change of surficial contamination 

= 0.0539 dpm/100 cm2

 per year

A(t) = areal activity concentration at time t

= 540 dpm/100 cm2

 t = 27.2 y 

A0 = 2,340 dpm/100 cm2

The first of the above equations could be used to calculate the contamination level and hence the 

intake rate during each year of the residual period. 

Updated Review of Occupational Internal Dose at GSI 5 SC&A –May 30, 2012 

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.
Updated Review of Occupational Internal Dose at GSI 6 SC&A –May 30, 2012 

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.

References

Abu-Eid, R. M., et al. 2002. “Re-evaluation of the Indoor Resuspension Factor for the Screening 

Analysis of the Building Occupancy Scenario for NRC’s License Termination Rule: Draft 

Report for Comment,” NUREG-1720. http://www.nrc.gov/reading-rm/doccollections/nuregs/staff/sr1720/.

Allen, D., and S. Glover. 2007. “Site Profiles for Atomic Weapons Employers That Worked 

Uranium and Thorium Metals - Appendix BB: General Steel Industries,” Battelle-TBD-6000, 

Appendix BB, Rev. 0. http://www.cdc.gov/niosh/ocas/pdfs/tbd/b-6000-apbb-r0.pdf. 

Allen, D. 2011. “Site Profile for Atomic Worker Employers that Worked Uranium Metals,” 

Battelle-TBD-6000 Rev. 1. http://www.cdc.gov/niosh/ocas/awedocs.html#b6000. 

Cottrell, W. D., and R. F. Carrier. 1990. “Results of the Radiological Survey at the Granite City 

Steel Facility, Granite City, Illinois,” ORNL/RASA-89/10. Oak Ridge, TN: Oak Ridge National 

Laboratory. 

S. Cohen & Associates (SC&A). 2007. “Draft Review of Battelle-TBD-6000, Site Profiles for 

Atomic Weapons Employers That Worked Uranium and Thorium Metals.” 

S. Cohen & Associates (SC&A). 2009. “Issue Resolution Matrix for SC&A Findings on TBD6000.” (October 14, 2009) 

Sharfi, M. M. 2012. “Dose Reconstruction During Residual Radioactivity Periods at Atomic 

Weapons Employer Facilities,” ORAUT-OTIB-0070, Rev. 01. 

http://www.cdc.gov/niosh/ocas/pdfs/tibs/or-t70-r1.pdf.