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General Steel Industries 

Layout man Beta Skin Dose 

Response Paper 

National Institute for Occupational Safety and Health

Division of Compensation Analysis and Support 

January 8, 2015 

By David Allen

Reviewed by James W. Neton, Ph.D., CHP 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.
Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

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BACKGROUND SUMMARY

The Advisory Board Work Group (WG) on TBD 6000 reviewed many potential exposure 

scenarios for the General Steel Industries’ (GSI) Appendix and the Special Exposure Cohort 

Petition (SEC) petition. These discussions resulted in an agreed-upon method for most exposure 

scenarios and assumptions to be used in a revised GSI Appendix BB. These included: (1) The 

technique to determine beta dose calculations for Betatron Operator and (2) a Layout man

exposure scenario for the photon dose calculations from working on freshly x-rayed castings.

NIOSH used the agree-upon-methodology to calculate the beta dose for the Layout man. The 

beta dose for the betatron operator was also calculated in the revision, which is a separate issue 

in the Appendix revision. During the revision, NIOSH found the already agreed-upon parameters 

and exposure scenario resulted in a beta skin dose overestimate for the Layout man. 

In a 2014 review of Appendix BB (SCA 2014), Sanford Cohen & Associates (SC&A) concluded 

their calculated beta dose to the Layout man larger than the Appendix BB revision. Following the 

review, NIOSH and SC&A exchanged e-mails and files to understand SC&A’s revised position 

on the agreed-upon parameter and exposure scenarios for beta dose calculations to the Layout 

man. NIOSH recognized the need to discuss beta dose potential, as well as, an exposure scenario 

from working on freshly x-rayed castings. SC&A appears to have modified the agreed-upon 

approach for beta-dose calculations, which caused a dose over-estimate. 

 

This is a response paper to SC&A’s proposed change to the agreed-upon scenario for dose 

recalculation for the Layout man. We have outlined below the agree-upon approach, examined

SC&A recent proposal, and have recommended a revised approach to estimate the beta-skin dose 

to the whole body and the extremities (e.g., hands and forearms) in our response. 

AGREED-UPON SCENARIO 

The scenario for the Layout man’s photon dose who worked outside of the betatron building on a 

single large casting during most of a shift assumed:

1. Casting was repeatedly x-rayed using a short shot routine (i.e., 3-minute shots with 12 

minutes between). That meant 5321

 short-shots were performed before the Layout man

received the casting. 

2. It took 15 minutes (after the last shot) before the Layout man began casting work.

3. The Layout man worked on this single large casting for a full shift. (The only exception is

being interrupted by other castings discussed.) The work was interrupted to mark-up a freshly 

x-rayed casting near completion, according to a [redacted for privacy] statement.

 

1 The number of short shots is based on page 7 of the January 12, 2014 SC&A memo (SCA 2014) dealing with 

calculating gamma dose to the layout man. The steel was assumed to have 30 hours of prior betatron exposure 

according to the December 5, 2013 SC&A memo dealing with calculating beta dose to the betatron operator (SCA 

2013).

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 3 of 14 

4. The castings that would interrupt the Layout man’s work were assumed to: (1) have been 

exposed to long shots of 60 minutes; and (2) x-rayed 400 times just before the Layout man’s 

casting work started (SCA 2014 p. 7). 

5. The Layout man’s exposure duration ranged from 15 minutes up to 8 hours and 15 minutes 

following the single large casting x-ray. The exposure, after interruption of castings, ranged 

from 15 to 90 minutes (75 minutes of exposure). New freshly-x-rayed interrupting casting 

was assumed to take place after the 75 minutes of exposure. 

6. Work on the interrupting casting was assumed to take 10% of the shift, based on a statement 

of the [redacted for privacy] . [redacted for privacy] said that the Layout man would 

typically spend a full 8-hour shift marking-up a large casting. He added the Layout man

could sometimes be interrupted to mark-up a casting that had just been radiographed and 

close to shipment (SCA 2014 page 7). The scenario assumed the remaining single largecasting work was 90% of the work for each shift.

7. The full-shift dose from the interrupting casting was calculated by multiplying the dose per 

casting by 6.4, which is the average number of castings that could be processed through this 

scenario in an 8-hour shift. 

8. The initial dose rate from the castings was calculated by first using MCNP to determine the 

production rate of each isotope. This production rate, combined with the decay constant for 

each isotope, was used to determine the buildup of each isotope. The build-up time for the 

short-shot scenario was 26.6 hours (532 shots of 3 minutes each). This was 26.6 constant 

hours of exposure to the x-ray beam without the 12 minutes per shot of additional decay 

time. Similarly, the long-shot scenario used 400 hours of continues x-ray-beam exposure.

9. The dose for each scenario was calculated for contact, 1 foot and 1 meter distances from the 

casting. The beta dose to the hands and forearms was calculated by applying the contact 

dose for 90% of the time and the 1 meter dose for the remaining 10% of the time. The dose 

to the rest of the skin of the body was calculated by applying the 1-foot dose for 90% of the 

time and the 1-meter dose for 10% of the time. 

NEW SC&A SCENARIO

In December 2014, memorandum, SC&A revised its position that the beta-dose calculations used 

will vary significantly from a gamma-dose approach (SCA 2014a). The distinct difference in the 

calculation is that no single large-casting approach exists. The SC&A model uses only 

interrupting casting scenarios, even though a GSI [redacted for privacy] this activity “might sometimes” 

happen. In addition, the interrupting casting scenario was changed from being created by 100% 

long shots to being created by 64% short shots and 36% long shots. Lastly, SC&A used a 30 

hour continuous x-ray of the castings prior to the Layout man receiving the casting. This is 

different than the Layout man exposure scenario used for the gamma dose calculation, which 

was based on 400 hours for long shots (used for the interrupting casting) or 1596 minutes for 

short shots (used in the single large casting calculation). 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 4 of 14 

NIOSH RESPONSE 

NIOSH reevaluated the applicability of the gamma dose scenario to the estimation of beta dose. 

As a result, propose a change to the values and techniques employed in the estimation of beta 

dose to the skin because:

1. The physical impossibility of the betatron irradiation scenarios that were used in both the 

originally agreed-upon model and the scenario used in SC&A’s recent review paper; and 

2. The excessively long irradiation times used to bound photon dose were considered acceptable 

because the photon dose from the irradiated steel was a small (~0.2%) component of the 

overall photon dose. Thus, bounding calculation use in this case was considered acceptable. 

This is not necessarily true for the beta exposure scenario.

Please note that Table 6 of Appendix BB Rev.1 for the estimated photon dose to the Layout man

from the irradiated steel at 20.8 mrem/year (out of the total 9000 mrem/year total photon dose.) 

Casting Interruption Occurrences 

We propose using the already-agreed-upon value of 10% of the work shift for casting that 

interrupts the work. 

NIOSH is not aware of any basis to remove a single large-casting scenario from the calculation. 

The [redacted for privacy] indicated that a casting “might sometimes” interrupt the work; however, 

the Layout man would normally work on a single casting the full 8- hour shift. This assumes that 

10% of the time each shift represents an interrupting casting appears to be favorable. 

Fraction of Short/Long Shot 

NIOSH proposes using this ratio in the calculations for both the single large casting and the 

interrupting casting

In the original SC&A report (SCA 2008), referenced and quoted in its January 12, 2014, memo 

(SCA 2014), the scenario used was that of a single large-casting created 100% short shots and 

the interrupting casting created by 100% long shots. Then, in its latest calculations, SC&A 

provided a mixture of short and long shots for the interrupting casting and eliminated the single 

large casting scenario. The ratio of short and long castings in the latest memo was taken from 

betatron operator calculations (64% short / 36% long). However, that ratio was the amount of 

time each type of casting was worked within the betatron building. 

The ratio was based on the number of shots being 10% long shots and 90% short shots and 

applying the length of time each type of shot took. The Layout man would be marking the 

locations for a shot or for a defect found in a shot. The time necessary to do this work would be 

unaffected by how long the x-ray exposure occurred for that shot. That means it would take just 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

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as long to mark a location for a short shot as it would to mark a location for a long shot. The 

appropriate ratio should be 10% long shots and 90% short shots. 

Isotope Production Rate 

NIOSH proposes adjusting the production rate to properly account for the chosen scenarios.

The production rate of isotopes in steel was calculated using MCNP. 

That production rate assumes the betatron beam is exposing the steel for the entire shot scenario 

(i.e., during the actual irradiation and in between shots) and the created isotopes are always 

decaying. In reality, the isotopes are only created when the betatron beam is on and the beam is 

not always on. The short shot scenario assumes a 3-minute shot followed by 12 minutes of time 

between shots. The long shot scenario assumes a 60 minute shot followed by 15 minutes between 

shots. There is therefore a considerable amount of time that the production of an isotope stops 

while the decay of that isotope continues resulting in a lower concentration of the isotope. To 

correct for the effect of this non-continuous exposure, an effective production rate must be 

determined using the technique discussed in Appendix A of this response paper. 

Impossible Scenario

In the scenarios for both the short and long shots, the assumption has been that the casting was xrayed continuously for many hours prior to the Layout man receiving the casting. The SC&A 

calculation in the December 2014 memo used 30 hours of prior exposure for both the long and 

short shots. Every 75 minutes, a new freshly exposed casting is moved to the Layout man. For 

the short shots, the x-ray exposure to the casting occurs for 3 minutes out of every 15 minutes it 

is being examined in the betatron building. For the long shots, it is 60 minutes out of every 75 

minutes. With these parameters, it would take 150 hours to achieve 30 hours of x-rays to the 

casting using the short shot scenario while the long shot scenario would take 37.5 hours to 

complete. Clearly it is not physically possible for a casting to be examined in the betatron room 

for 37.5 hours and provided to the Layout man every 75 minutes. Such a scenario that would 

result in the highest yet physically possible dose is one in which 2 castings are alternated 

repeatedly. 

For the long-shot scenario, the interrupting casting scenario would start with casting A being xrayed for 60 minutes followed by a 15 minute break for the casting to be moved out of the 

betatron building so the Layout man can begin working on it. During the 15 minutes, casting B 

is moved into the betatron building. For the next 60 minutes, casting B is x-rayed while the 

Layout man works on casting A. Once this x-ray is completed, the next 15 minutes is used to 

switch the castings back and the process repeats. For short shots, the exact same scenario would 

apply except the shot time is 3 minutes and the time between shots is 12 minutes so the process 

would repeat every 15 minutes instead of 75 minutes. 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 6 of 14 

For the single large casting on which the Layout man works most of the shift, there is still an 

issue of being physically impossible. For gamma exposure to the Layout man, the short shot 

scenario uses 532 shots of 3 minutes each. Including the 12 minutes between shots, requires 

about 5.5 days to complete this number of shots. But, it’s assumed the Layout man would be 

exposed to a freshly-exposed casting for every shift worked. Even if he worked only one shift 

per day, the scenario requires a casting to be x-rayed for 5.5 days every 24 hours. A similar 

situation can be seen for the long shot scenario of 400 prior shots as well as the scenario of 30 

continuous hours of x-rays.

Again, a scenario that yields the highest dose, while still being physically possible, is one in 

which two castings are alternated. The first is x-rayed for 24 hours just before the Layout man

begins working on the casting. It is important to note that this 24 hour period is not one 

continuous x-ray but rather an x-ray routine matching the short or long shot scenarios. At the end 

of the 24 hour period, the casting is moved to the Layout man and a second casting is placed in 

the betatron building for a 24 hours period of x-rays. After another 24 hours, the castings switch 

places and this process continues. 

It is important to note that the effective production rate calculated in an appendix to this paper is 

correct for a consistent routine of intermittent production. In the case of the single large casting, 

there are two different intermittent production periods. The first being the x-ray and film change 

routine and the second being the 24-hour period that this routine is performed followed by the 24 

hours outside the betatron building for which no x-ray exposures occurs. The appendix begins on 

page 9 of this document and discusses this calculation.

Prior Casting Irradiation Time 

The amount of time the castings are irradiated prior to the Layout man receiving them is 

inconsistent with that used for the gamma exposure calculation. For the gamma dose, this source 

of exposure was small compared to other sources. Therefore it is only necessary to have a 

bounding scenario for the gamma dose and it is not necessary for it to be consistent with the beta 

dose. 

We can resolve the issue for beta dose in a favorable manner is to assume the physicallypossible scenarios continue indefinitely until the isotopes reach an equilibrium value. This 

equilibrium value is below the value that would be achieved from continuous x-ray exposure. 

For many of the isotopes, assuming this equilibrium value will have little affect because their 

relatively short half-life will produce an equilibrium value with any reasonable estimate of prior 

exposure time. The concentration of longer lived isotopes would be overestimated to some extent 

but the dose from those isotopes is only a portion of the overall dose so overestimating that 

portion does not produce a large overestimate of the Layout man’s dose. 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 7 of 14 

RESULTS OF THE PROPOSED APPROACH

Using the effective production rate approach proposed in our response paper, the doses to the 

Layout man for various exposure scenarios are calculated in Table 1 to provide values for the 

beta dose rates in mrad per 8-hour shift. These values are not prorated to any scenario; rather 

they represent the dose rate if the depicted scenario were undertaken for the entire shift. For the 

single large casting scenario, the Layout man exposure occurs 15 minutes to 8 hours and 15 

minutes following irradiation of the casting. For the interrupting casting scenario, the Layout 

man exposure starts 15 minutes after the casting irradiation and ends 15 minutes or 75 minutes 

after that for the short and long shot scenarios respectively. Table 2 combines the values in Table 

1 using parameters discussed in this white paper. Assuming an average of 406.25 shifts per year, 

the annual beta dose to the Layout man would be 264 mrad to the hands and forearms and 147 to 

the rest of the skin. The short and long shot values in the table are based on 10% of the time 

being 1 meter away and 90% of the time being close (contact for hands and forearms, 1 foot for 

other skin). The composite value is based on 90% of the dose coming from castings irradiated 

from the short shot routine and the remaining 10% from the long shot routine. The combined 

values are calculated by assuming the single large casting dose accounts for 90% of the Layout 

man’s time with the interrupting casting representing the remaining 10% of the time.

Table 1 – Layout man Beta Dose per 8 hour Shift (unadjusted)

Table 2 – Layout man Beta Dose per 8 hour Shift (combined scenarios)

Short (mrad/shift) Long (mrad/shift) Composite (mrad/shift)

H&F single casting 0.279 2.392 0.491

H&F interrupting 

casting 1.614 6.219 2.075 

Combined H&F 0.649

skin single casting 0.150 1.273 0.262

skin interrupting casting 0.995 3.719 1.267

Combined skin 0.363

 Single Casting Interrupting Castings

mrad/

shift

mrad/

casting

casting/ 

shift

mrad/shift

Short shot contact 0.305 0.055 32 1.751

Short shot 1 ft. 0.161 0.033 32 1.063

Short shot 1 m 0.052 0.012 32 0.387

Long shot contact 2.610 1.055 6.4 6.753

Long shot 1 ft. 1.366 0.621 6.4 3.974

Long shot 1 m 0.436 0.221 6.4 1.416

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

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REFERENCES

SCA 2008, S. Cohen & Associates, Review of “Site Profiles for Atomic Weapons Employers that 

Worked Uranium and thorium Metals – Appendix BB: General Steel Industries,” Battelle-TBD6000, Appendix BB, Rev 0., SCA-TR-TASK1-0024, April 21, 2008. 

SCA 2013, Memo from Robert Anigstein and John Mauro, SC&A, Review of Skin Doses at GSI, 

December 5, 2013 

SCA 2014, Memo from Robert Anigstein and John Mauro, SC&A, Update of Doses from 

External Exposure at General Steel Industries, January 12, 2014 

SCA 2014a, Memo from Robert Anigstein and John Mauro, SC&A, Review of “Site Profiles for 

Atomic Weapons Employers that Worked Uranium Metals Appendix BB – General Steel 

Industries,” Revision 1, December 10, 2014 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.
Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 9 of 14 

APPENDIX 

Calculation of Buildup from Intermittent Production

CONTINUOUS BUILDUP

The buildup of radionuclides created in steel during the x-ray by a betatron can be described 

mathematically by the following equations: 

Equation 1 

 

C = the number of atoms of a particular nuclide 

P = the production rate of that nuclide (atoms per sec)

λ = the decay constant for that nuclide (sec-1) 

Solving for C produces Equation 2 

 

Equation 2 produces a smooth buildup curve approaching an equilibrium value where the 

production rate equals the decay rate. By inserting infinity for time, it can be seen that the 

equilibrium value would be P/ λ. This smooth buildup curve is shown as the upper curve in 

figure A1. The equation assumes the nuclides are continuously created at the same time that they 

are continuously decaying. 

However, in the case of GSI, a casting is x-rayed for a period of time and then the betatron is 

turned off while that film is collected. A new film is put in place and the betatron head is 

repositioned. This intermittent production combined with a continuous decay leads to a sawtoothed pattern shown as the lower curve in figure A1 on the next page. 

(continued) 

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with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 10 of 14 

Figure A1 – Continuous and Intermittent Buildup Curves

It can be seen more clearly in Figure 2 that this saw-toothed pattern will also build up to an

equilibrium value but that value will be lower than the continuous production curve. 

 

Figure A2 – Intermittent Buildup Curve

INTERMITTENT EXPOSURE

For our purposes, it is necessary to find the value of the peaks of the saw tooth curve. That 

would represent the activity in the casting immediately after the x-ray exposure. In order to find 

the value of the peaks, it is first noted that the peaks follow a similar continuous buildup pattern, 

the shape of which is dictated by the decay constant. Therefore, an equation for a continuous 

buildup curve that matches the peak values can be constructed if a new equilibrium value is 

determined that adjusts for the intermittent production rate. 

In order to find this new equilibrium value, it is first noted that the concentration at the first peak 

(C1) is equal to equation 2 if the time is set equal to the length of time of the x-ray exposure (3 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 11 of 14 

minutes for the short shot scenario). The full cycle time from the end of one x-ray to the end of 

the next x-ray is 15 minutes for the short shot scenario. Therefore, the continuous buildup 

equation depicting the peaks of the saw toothed pattern would have to start 15 minutes prior to 

the end of the first shot. 

Equation 3 

Peff = the effective production rate

t1 = the shot time (amount of time the actual x-ray beam is turned on) 

tc1 = cycle time (amount of time from the end of one x-ray to the end of the next x-ray)

Rearranging the equation to solve for Peff/λ provides the next equation. 

Equation 4 

By replacing P/λ in equation 2 with Peff/λ above and assuming time equals zero 15 minutes prior 

to the end of the first shot, a new continuous buildup curve can be produced as shown in figure 

A3.

Figure A3 – Intermittent Buildup Curve and Effective Continuous Curve

This new curve eventually reaches an equilibrium value of Peff/λ. The effect of this adjusted 

production rate will depend on the half-life of the particular isotope. Table A1 below shows the 

adjustment for both the short and long shot scenarios for the longest and shortest lived isotopes 

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ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 12 of 14

 

used in the GSI beta dose calculation. The adjustment in the table is the adjustment to the 

equilibrium value. 

Table A1 – Parameters for Effective Production Rate

Short Shots Long Shots

Shot time (minutes) 3 60

Cycle time (minutes) 15 75

Adjustment for Fe53 

(8.51 minute half-life)

.307 .995

Adjustment for Mo99 

(65.94 hr. half-life)

.200 .801

It can be seen that in the case of Fe-53, the long shot adjustment is small (nearly 1). This is 

due to the fact that the 60 minute x-ray is long enough to nearly reach and the equilibrium 

value (approximately 7 half-lives). Since it nearly reaches equilibrium during a single shot, 

the intermittent production has little effect on the maximum value. For a longer lived 

isotope, the adjusted equilibrium is nearly proportional to the fraction of the cycle time that 

the isotope is actually being produced (60 min/75 min or 3 min/15 min). 

 

SECOND INTERMITTENT EXPOSURE

The Layout man beta dose scenario for GSI utilizes two types of castings. One casting on which 

the Layout man works for the entire shift (single large casting) and the other is a freshly exposed 

casting that interrupts this work periodically (interrupting casting). Both types of castings are 

exposed many times prior to the Layout man working on them. 

For the interrupting casting, the maximum starting dose rate would be associated with the 

equilibrium value for each isotope. That equilibrium would have to be adjusted based on the 

shot time and cycle time as described above. 

For the continuous casting, the same adjustment is necessary however since the Layout man is 

working on this casting the entire shift, an additional adjustment is necessary. The proposed 

scenario in the body of this white paper is for two castings to be worked in an alternating 

fashion. The scenario calls for one casting to be x-rayed during a 24 hours period while another 

casting is being worked on by the Layout man. The castings and switched every 24 hours. 

While the casting is in the betatron building, the x-ray exposure is not continuous but intermittent 

according to the short or long shot routine. The equation for the intermittent exposure described 

above can be used to determine the appropriate equilibrium value for this period. However, it 

would not accurately represent the equilibrium value of the casting without accounting for the 

second 24 hour period when the casting is outside the betatron building. A new equilibrium 

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with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

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Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 13 of 14 

activity must be calculated in this case that not only reduces the production rate for the 

intermittent exposure between shots but also for the intermittent exposure periods in and out of 

the betatron building. 

In order to find this value, the same technique described above will work. However, that 

technique relies on a single consistent cycle time. In this case, we would have one cycle 

consisting of the shot time and time between shots and a second cycle consisting of 1 day in the 

betatron building and one day outside of the building. The new adjusted production rate (Peff2/λ) 

can be found the same way as the first adjusted production rate by simply substituting the first 

effective production rate (Peff/λ) for P/λ in equation 4. The new shot time and cycle time must 

also be substituted for t1 and tc1. This results in the following equation:

Equation 5 

Where t2 and tc2 represent the production time (24 hours) and the total cycle time (48 hours) for 

the larger intermittent exposure period. Figure A4 depicts a continuous buildup function using 

these equilibrium values.

Figure A4 – Intermittent Buildup Curves and Two Effective Continuous Curve

In Figure A4, you can see the saw toothed curve actually includes another saw toothed curve on 

the buildup side of the curve. Another curve follows the first buildup side but continues to 

increase above the second peak of the saw toothed curve. This is the continuous curve using 

Peff/λ and is identical to figure A3 with the scales changed. An additional line shows a 

continuous curve that matches each peak of the larger saw toothed curve. That is the continuous 

buildup function using Peff2/λ as the equilibrium value. 

Table A1 is reproduced as Table A2, with the second cycle parameters included and the 

adjustment values recalculated.

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.
Response Paper General Steel Industries Layout Man Beta Skin Dose January 8, 2015 

Page 14 of 14 

Table A2 – Parameters for Effective Production Rate (Two Different Intermittent Periods)

Short Shots Long Shots

Shot time (minutes) 3 60

Cycle time (minutes) 15 75

Production time (hours) 24 24

2nd cycle time (hours) 48 48

Adjustment for Fe53 (8.51 minute half-life) .307 .995

Adjustment for Mo99 (65.94 hr. half-life) .113 .451

Comparing these values to the values in table A1, it can be seen that this additional decay period 

has no effect on the equilibrium value for the short lived isotope. The isotope essentially decays 

away during the 24 hour decay period and starts from zero each time. For the long lived isotope, 

a noticeable effect can be seen. 

This working document prepared by NIOSH’s Division of Compensation Analysis and Support (DCAS) or its contractor for use in discussions 

with the ABRWH or its Working Groups or Subcommittees. Draft, preliminary, interim, and White Paper documents are not final NIOSH or 

ABRWH (or their technical support and review contractors) positions unless specifically marked as such. This document represents preliminary 

positions taken on technical issues prepared by NIOSH or its contractor. NOTICE: This report has been reviewed to identify and redact any 

information that is protected by the Privacy Act 5 USC §552a and has been cleared for distribution.