Page 1 of 29

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

NIOSH Response to Short-lived 

Radionuclide Issues Raised in Comment 5 

of SC&A’s NTS Resuspension Issues Status 

Report 

White Paper 

Rev. 0-A 

National Institute for Occupational Safety and Health 

June 6, 2016

Dennis Strenge 

Oak Ridge Associated Universities Team

Reviewed by Mark Rolfes

Division of Compensation Analysis and Support
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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

PURPOSE

This is the National Institute for Occupational Safety and Health’s (NIOSH) response to

Comment 5 of the Status Report on Resuspension Issues at the Nevada Test Site (Sanford Cohen 

and Associates [SC&A] 2015). This white paper describes the analysis method used to estimate

the environmental dose from short-lived radionuclides during the period 1963 to 1972 at the 

Nevada Test Site (NTS). Results of the analysis method are presented to illustrate the impact of 

various assumptions.

SUMMARY OF RESULTS

The results show that the method used to estimate the internal dose from short-lived

radionuclides is favorable to claimants. The treatment of refractory elements enhancing their

activity results in higher doses is compared to not making corrections to the primary data.

Results are presented for the Small Boy and Little Feller I shots. The calculated dose values are

similar to the values previously presented in the NTS Environmental Technical Basis Document 

(TBD) (ORAUT 2012). Some changes to the values in the TBD have occurred as a result of 

modifications to the evaluation and application of dose correction factors.

BACKGROUND

The NTS Environmental TBD was reviewed by SC&A and concerns were expressed in the 

Status Report on Resuspension Issues at the Nevada Test Site (SC&A 2015). The 5th comment in

this report dealt with the evaluation of inhalation and ingestion dose from short-lived

radionuclides. 

Summary of the Issue

Comment 5 is stated as follows: 

Derivation of the concentration of relatively short-lived radionuclides in soil for January 1, 

1963, employed the Hicks’ tables (Hicks 1982) for the Small Boy event that occurred on July 14, 

1962. In fact, the contamination in soil on January 1, 1963, reflects fallout from numerous tests

that resulted in surface contamination, such as the Sedan test on July 6, 1962, and Little Feller

II on July 7, 1962, which occurred shortly before Small Boy, and Little Feller I that occurred

after Small Boy on July 17, 1962. As such, NIOSH should address whether tests shortly before 

and after Small Boy on July 14, 1962, could also have contributed substantively to the fallout

levels in soil derived for January 1, 1963. In a related matter, the protocol used in the TBD to 

account for fractionation is overly simplistic and appears to rely primarily on the Small Boy 

event. NIOSH will need to demonstrate that the approach used to account for fractionation does 

not substantively underestimate doses.

Draft responses to this issue have been submitted and reviewed by SC&A. The following is the 

response submitted for review.
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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The evaluation report (ER) for Special Exposure Cohort (SEC)-00055 (NIOSH, 2006), which

covers the time period of January 27, 1951 to December 31, 1962, specifically discusses the 

inability to reconstruct doses between the cessation of testing in July of 1962 and the end of that

year. The last paragraph of Section 4.5 states:

Above-ground testing at the NTS began on January 27, 1951, and concluded on 

July 17, 1962. NIOSH considers reconstruction of internal doses at the NTS

feasible for periods after cessation of atmospheric testing beginning on January

1, 1963. During the period of atmospheric testing, the source term to which

workers were exposed changed with each detonation, due mainly to re-suspension

and mixing of fallout caused by the blast waves. After the final above-ground test,

NIOSH considers the radiological source term to be sufficiently stable so as to

allow assumptions adequate for dose reconstruction. The extension of the SEC

period through December 31, 1962, approximately six months after the last 

atmospheric test, allows time for the stabilization of the source term and for decay

of the shorter-lived radionuclides associated with the final atmospheric tests.

In addition, the ER for SEC-0084 (NIOSH 2007) describes a model for the reconstruction of 

environmental internal doses beginning on January 1, 1963. Thus, the ERs for the SECs are clear 

on the time period for which environmental doses can be reconstructed.

After reviewing the above response, SC&A indicated the following in an email:

We continue to believe that it is possible to derive exposures during this time period, and that 

these exposures (for workers not covered by the SEC) might be significant relative to the 

exposure post-January 1, 1963, the time period where NIOSH has developed a protocol to 

reconstruct these environmental exposures.

The current analysis adheres to the NIOSH position that evaluation of environmental internal

dose cannot begin prior to 1963. 

Summary of Analyses Performed 

In response to the comment, the following analyses have been performed to investigate the 

impact of the assumptions: 

1. Review the analysis method and assumptions in detail. 

2. Perform evaluations for alternate assumptions regarding treatment of refractory elements.

3. Perform evaluations using Hicks data from Little Feller I.

The NTS Environmental TBD (ORAUT 2012) evaluates internal dose based on annual intake

rates of selected radionuclides by year, starting in 1963. The intake rates are given in Table 4-7 

of the NTS Environmental TBD. The intake rates were maximized based on air monitoring data.

The resulting intakes include strontium-90 intakes by year. For 1966 and later years, the 
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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

strontium-90 intake is constant at 1.55 Bq/yr. For the years 1963 to 1965, the intake rate was

scaled upward to account for early resuspension at a higher rate.

The NTS Environmental TBD includes evaluation of the dose from short-lived fission and

activation products starting in 1963, based on the last atmospheric shots in 1962. The shots were

Small Boy (July 13, 1962) and Little Feller I (July 17, 1962). The dose results were based on the 

Small Boy data as that provided a higher estimate of dose. The comments from the Working 

Group suggested that the Little Feller I and Sedan shot results also be considered. The Sedan

shot was an underground shot (635 feet) that resulted in atmospheric releases. Because of the 

uncertainty regarding release of activity to the surface and the relative releases of volatile and

refractory materials, the analyses have not used the data for the Sedan shot. 

This white paper describes the evaluation of the additional correction factors to account for the 

dose from short-lived fission and activation products for years 1963 to 1972. The correction 

factors are applied by multiplying the strontium-90 dose by the correction factor for each year to

get the total dose to each organ. The resulting doses are small and are only retained for a few

organs as given in Table 4-9 of the TBD, and are discussed below. 

ANALYSIS METHOD FOR SHORT-LIVED RADIONUCLIDE DOSE

The following discussion provides details of the analysis method, including changes compared to

the initial analysis. This is the analysis method described in the current NTS Environmental

TBD text and in Attachment A (ORAUT 2012).

Overview of Data and Analysis Method 

The evaluation of dose from short-lived radionuclides is based on the relative dose compared to

the dose from intake of strontium-90. The intake of strontium-90 is provided in the TBD and is

used as the basis for the estimation of dose from the short-lived radionuclides. The fraction of 

dose from strontium-90 is evaluated first for specific organs and as a function of time following 

the shot for full years of 1963 through 1972. Then the correction factor is evaluated for each

organ by integration of the curve of dose fraction as a function of time. The inverse of the 

integral over one year is the correction factor for that year.

The basis for the activity of each radionuclide present as a function of time is data provided in

reports by Hicks (Hicks 1981; Hicks 1982). The data presented in the Hicks papers give the 

relative activity of radionuclides present following several of the atmospheric test shots at NTS.

The values were based on runs of the ORIGEN computer program. The following is a summary

of the calculations performed to estimate the ground concentrations (Hicks 1981). The input to 

the ORIGEN program was the total number of fissions per kiloton. The total burst was for

1.43E17 fissions in a fuel element composed of 1 kg each of U-235, U-238, and Pu. The fission

yield is not that of a nuclear device, so the values were corrected by a relative fission yield which

includes the refractory fraction (RF) for each element. 152 fission products and 25 neutroninduced activation products were included. Presumably, the activity of neutron-induced 
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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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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activation products included consideration of structural materials present. There would be 

differences for balloon shots, tower shots, ground level shots, and underground shots. 

The result is the fractionated inventory of each radionuclide at time zero. For refractory

radionuclides, a refractory fraction was applied by Hicks for each radionuclide in the analysis.

This was done to represent the off-site activity, allowing for enhanced on-site deposition of 

refractory elements (Hicks 1982). Application of the refractory fraction is the only treatment of 

deposition of activity as the analysis did not include any atmospheric transport or deposition

calculation.

The results were decayed for times from 1 to 21 hours, 1 to 300 days, and 1 to 50 years. This

gives the activity of each radionuclide as a function of time for a 1 kt fission yield. The external

dose for each time was evaluated by Hicks and the ground concentrations were normalized to

give a dose rate of 1mR/hr at 12 hours. Therefore, the ground concentrations values are relative

values, not absolute values.

The volatile elements used in the analysis by Hicks are:

• Ge,

• As,

• Se,

• Br,

• Kr,

• Rb, 

• Mo, 

• Tc,

• Cd,

• In,

• Sn,

• Sb,

• Te,

• I,

• Xe,

• Cs,

• W,

• Au, and

• Pb.
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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

The refractory elements 1

1 Although elemental strontium is assumed to be refractory, the isotope Sr-90 is treated as a volatile because it is

a progeny of Kr-90 and Rb-90, which are volatile and were in existence while on-site deposition was occurring. Mo99 and Tc-99 are treated as refractory by Hicks (1981) without a reason for the treatment.

used in the analysis by Hicks are:

• Be,

• Na,

• Mn, 

• Fe,

• Co,

• Cu,

• Sr,

• Y,

• Zr,

• Nb,

• Ba,

• Rare Earths,

• Th,

• U,

• Np,

• Pu,

• Am, and

• Cm.

The actual application of volatile versus refractory assumptions was based on data provided by

Hicks for the Pacific test shots and summarized in Table A-8 of the NTS Environmental TBD 

(ORAUT 2012), which is shown here as Table 1. Because the selection of volatile versus 

refractory assumptions included comparison of measured and estimated concentrations, the 

representations by Hicks are used in the current analyses. The table is reproduced here with the 

relative ratios adjusted to show the refractory fraction of 0.4 for the purely refractory

radionuclides. The tests Small Boy and Little Feller I were assigned refractory fractions of 0.4 

by Hicks. The refractory fractions for mass number chains 91, 140, and 141 were calculated as

described below. This table includes a large number of radionuclides including many with very

short half-lives that will not be present after a short period of time. The actual number of 

radionuclides included in the present analysis is much smaller and is based on the radionuclides 

included in the Hicks (1981) “days” and “years” tables.

 
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Table 1: Far-Field Refractory Enrichment Ratios Modified by the Small Boy Refractory Ratios

Radionuclide Refractory Fraction Ratio

Be-7 0.4

Na-24 0.4

Mn-54 0.4

Fe-55 0.4

Fe-59 0.4

Cu-64 0.4

Cu-67 0.4

W-181 1.0

W-185 1.0

W-187 1.0

W-188 1.0

U-237 0.4

U-239 0.4

U-240 0.4

Np-239 0.4

Np-240m 0.4

Np-240 0.4

Am-241 0.4

Cm-242 0.4

Ge-75 1.0

Ge-77 1.0

As-77 1.0

Se-77m 1.0

Ge-78 1.0

As-78 1.0

As-79 1.0

Se-79m 1.0

Br-80 1.0

Se-81m 1.0

Se-81 1.0

Br-82 1.0

Se-83 1.0

Br-83 1.0

Kr-83m 1.0

Br-84 1.0

Kr-85m 1.0

Kr-87 1.0

Kr-88 1.0

Rb-88 1.0

Rb-89 1.0

Sr-89 1.0

Sr-90 1.0

Y-90 1.0

Sr-91 0.85

Y-91m 0.85

Y-91 0.85

Sr-92 0.4
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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Radionuclide Refractory Fraction Ratio

Y-92 0.4

Sr-93 0.4

Y-93 0.4

Y-94 0.4

Y-95 0.4

Zr-95 0.4

Nb-95 0.4

Zr-97 0.4

Nb-97m 0.4

Nb-97 0.4

Nb-98 0.4

Mo-99 0.4

Tc-99m 0.4

Mo-101 1.0

Tc-101 1.0

Mo-102 1.0

Tc-102 1.0

Tc-102 1.0

Ru-103 1.0

Ru-103m 1.0

Tc-104 1.0

Ru-105 1.0

Rh-105m 1.0

Rh-105 1.0

Ru-106 1.0

Rh-106 1.0

Rh-107 1.0

Pd-107m 1.0

Pd-109 1.0

Ag-109m 1.0

Pd-111m 1.0

Pd-111 1.0

Ag-111m 1.0

Ag-111 1.0

Pd-112 1.0

Ag-112 1.0

Ag-113 1.0

Ag-115 1.0

Cd-115m 1.0

Cd-115 1.0

In-115m 1.0

Cd-117 1.0

In-117m 1.0

In-117 1.0

Cd-118 1.0

In-118 1.0

Cd-119 1.0

In-119m 1.0

In-119 1.0
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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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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Radionuclide Refractory Fraction Ratio

Sn-121 1.0

Sn-123m 1.0

Sn-123 1.0

Sn-125 1.0

Sb-125 1.0

Sb-126 1.0

Sn-127 1.0

Sb-127 1.0

Te-127 1.0

Sn-128 1.0

Sb-128m 1.0

Sb-128 1.0

Sn-129m 1.0

Sn-129 1.0

Sb-129 1.0

Te-129m 1.0

Te-129 1.0

Sb-130m 1.0

Sb-130 1.0

I-130 1.0

Sb-131 1.0

Te-131m 1.0

Te-131 1.0

I-131 1.0

Te-132 1.0

I-132 1.0

Te-133m 1.0

Te-133 1.0

I-133 1.0

Xe-133m 1.0

Xe-133 1.0

Te-134 1.0

I-134 1.0

I-135 1.0

Xe-135m 1.0

Xe-135 1.0

Cs-136 1.0

Cs-137 1.0

Ba-137m 1.0

Xe-138 1.0

Cs-138 1.0

Cs-139 1.0

Ba-139 1.0

Ba-140 0.82

La-140 0.82

Ba-141 0.60

La-141 0.60

Ce-141 0.60

Ba-142 0.4
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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Radionuclide Refractory Fraction Ratio

La-142 0.4

La-143 0.4

Ce-143 0.4

Pr-143 0.4

Ce-144 0.4

Te-132 1.0

I-132 1.0

Te-133m 1.0

Te-133 1.0

I-133 1.0

Xe-133m 1.0

Xe-133 1.0

Te-134 1.0

I-134 1.0

I-135 1.0

Xe-135m 1.0

Xe-135 1.0

Cs-136 1.0

Cs-137 1.0

Ba-137m 1.0

Xe-138 1.0

Cs-138 1.0

Cs-139 1.0

Ba-139 1.0

Ba-140 0.82

La-140 0.82

Ba-141 0.60

La-141 0.60

Ce-141 0.60

Ba-142 0.4

La-142 0.4

La-143 0.4

Ce-143 0.4

Pr-143 0.4

Ce-144 0.4

Pr-144 0.4

Pr-145 0.4

Cd-146 0.4

Pr-146 0.4

Pr-147 0.4

Nd-147 0.4

Nd-149 0.4

Pm-149 0.4

Pm-150 0.4

Nd-151 0.4

Pm-151 0.4

Pm-152 0.4

Sm-153 0.4

Sm-155 0.4
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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Radionuclide Refractory Fraction Ratio

Eu-155 0.4

Eu-157 0.4

Eu-158 0.4

Eu-159 0.4

Ge-159 0.4

Tb-161 0.4

Source: ORAUT 2012, Table A-8.

The Hicks data were used to calculate the total (relative) internal dose for selected times from

five days to 10 years. The fraction of internal dose to each organ for each time was evaluated.

The resulting curve of fraction of dose from strontium-90 versus time was integrated for annual 

periods to give the total fraction of dose from strontium-90 per year. For example, for 1963 the 

integration started at 172 days and continued one year, considering the time of the shot on July 

14, 1962. The inverse of this integral value was applied as a correction factor to the internal dose 

calculated using the strontium-90 intakes from Table 4-7 (ORAUT 2012), as discussed above. 

The above approach is claimant favorable because it considers the activity of short-lived

radionuclides to all have started in July of 1962, the date of the last above-ground shot. There

were many above-ground shots from 1951 to 1962 of higher yields that also contributed to the 

strontium-90 activity on the ground. The assumption that all of the short-lived radionuclide 

activity is related to the maximum strontium-90 activity results in an overestimate of dose.

Analysis Steps

The starting point in the analysis is the data from Hicks for a specific shot, using the data for

decay times of days and years. The data are corrected to represent the activity deposited near the

test site. The data provided by Hicks included multiplication by the refractory fraction to

represent the relative activities at off-site locations. This application was reversed by dividing by

the refractory fraction for each radionuclide using the volatile/refractory designations as provided 

by Hicks and summarized in Table 1 above. This provides an estimate of the initial 

relative activities near the location of the test shot in the cloud without consideration for

deposition at the test site. The activity in the deposited material near the test shot site could be 

different because of preferential deposition of the refractory material. Therefore, the relative

values were again divided by the refractory fractions.

Hicks used effective refractory fractions for three decay chains (below). The effective refractory

fractions are for chains in which some of the radionuclides are volatile and some are refractory.

RF = refractory fraction for the shot (0.4 for Small Boy and Little Feller I) 

Mass chain 91: 

RF91 = 0.75 + 0.25xRF = 0.85 for Small Boy and Little Feller I 
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Mass chain 140: 

RF140 = 0.70 + 0.30xRF = 0.82 for Small Boy and Little Feller I 

Mass chain 141: 

RF141 = 0.33 + 0.67xRF = 0.60 for Small Boy and Little Feller I

Although the reasoning for the above equations is not immediately obvious from the decay

chains, the results are reported to agree generally within experimental error with measured soil 

concentrations (Hicks 1982). 

The next step is the evaluation of the fraction of dose from strontium-90.

The adjusted data sets are used for input to the analysis that provides the fraction of the dose

during each year that is from strontium-90 relative to the dose from strontium-90 plus short-lived

radionuclides. The Hicks data provide the relative activity of the radionuclides, which is

sufficient for the current analysis because the output desired is the relative dose from the 

radionuclides. 

The relative activity of each radionuclide for a specific time (from five days to 10 years) is

entered into a spreadsheet that evaluates the relative dose from each radionuclide using 

inhalation or ingestion dose factors. The list of radionuclides excludes the radionuclides 

included in Table 4-7 (Am-241, Pu-238, Pu-239/240, Co-60, Cs-137, Sr-90, Eu-152, Eu-154, and

Eu-155), except for strontium-90, because the dose from these radionuclides is included in other

parts of the dose evaluation and assignment. Including them in this analysis would be a 

duplication of dose. The guidance in the TBD directs the dose reconstructor to include internal 

dose based on the intakes of the radionuclides in Table 4-7 as part of the environmental dose.

The time period of interest starts about six months after the shot. Therefore, the activity of

yttrium-90 will be in equilibrium with and equal to that of strontium-90. The ytrrium-90 activity

is set to the strontium-90 activity in the relative dose analysis.

Because strontium-90 stays in the body for much more than a year, the dose factors used for

strontium-90 are the dose from one year of intake, with the dose integral ending at the end of the 

first year. These dose factors have been evaluated using the IMBA computer program. The

other radionuclides in the analysis are based on the 50-year dose commitment value although the 

dose for many of the short-lived radionuclides is received during the first year. This results in a

smaller value for relative dose from strontium-90 which is claimant favorable in the estimation

of dose from the short-lived radionuclides. 

The relative dose from strontium-90 is evaluated for times from 5 days to 3650 days (10 years)

for all internal organs of interest (and for which dose conversion factors are available.) The

array of relative dose values is entered into a spreadsheet that evaluates the correction factors for

specific organs for each year of the 10-year period. The starting time is January 1, 1963, using 
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the data offset from the time of the shot to the end of 1962, as in Table 2. 

Table 2: Days Offset from Time of Shot to January 1, 1963

Shot Name Days Offset to January 1, 1963

Little Feller I 169

Small Boy 172

The curve of relative dose from strontium-90 is integrated for each annual period, using the 

curve fit by Excel as either linear or polynomial (quadratic). The integral value is averaged over 

a 365-day period. The inverse of this integral is the correction factor to be used to estimate the 

dose from strontium-90 and associated short-lived fission and activation products. 

The correction factors are next used to estimate the internal dose from the short-lived fission and

activation products. The IMBA program was used to calculate the internal dose to each organ

from the intake of 1 Bq of strontium-90 type F material during a 1-year period. The dose from

just the short-lived radionuclides is then calculated as shown in Equation 1. 

Equation 1. Annual dose from short-lived radionuclides based on Sr-90 intake rates. 

 

Where, 

Dosesl(year,i) = dose to organ i from short-lived radionuclides during a given year based 

on intake of strontium-90, rem, 

DCFi = strontium-90 dose conversion factor for 1-year intake of 1 Bq, to organ 

i, rem/Bq,

CF(year,i) = factor giving the dose from strontium-90 and short-lived radionuclides 

to organ i during a specific year, and

IntakeSr90(year) = intake of strontium-90 for a specific year from Table 4-7, Bq/year. 

Note that the correction factor, CF(year,i) includes the dose from strontium-90 and is always

greater than or equal to 1.0. The subtraction of 1 in the equation removes the strontium-90 dose.

The dose from strontium-90 is included when the intakes of Table 4-7 of the NTS TBD are

applied in a dose reconstruction.

This evaluation of dose is different from the method used in the previous analysis. Previously, 

the correction factors were applied to the dose commitment from strontium-90 in years after the 

first year. However, the dose factors for the short-lived radionuclides are 50-year dose 
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commitments and include all possible dose from each radionuclide for the year of intake. The

correction factors are developed for the year of intake.

ANALYSIS RESULTS

The dose analysis has been performed for inhalation and ingestion intake routes for the two shots 

indicated above. The doses have been evaluated using the method described above in which the 

refractory fractions have been removed (by dividing the activity by the refractory fraction) twice

to represent the relative activity in soil near the test location. Additional analyses have been

performed for inhalation dose for the Small Boy test. These additional analyses were performed

to investigate the impact of increasing the activity of the refractory radionuclides by removing 

the refractory fraction. First the analysis was done without removing the refractory fractions,

and then the analysis was done after removing the refractory fractions once. The first analysis

represents the relative activities at an off-site location (per suggestion by Hicks) and the second

analysis represents the relative activities at the source location without consideration of 

deposition. 

The following tables provide the results of the inhalation correction factor analysis for the shots. 

For each analysis two tables are presented. The first is based on Table 4-8 of the NTS 

Environmental TBD (ORAUT 2012) and provides the correction factors for estimation of organ

dose from the strontium-90 dose. The second is based on Table 4-9 in the NTS Environmental

TBD and gives the calculated dose to selected organs for each year from 1963 to 1972. Only the 

doses greater than 0.0005 rem are included and presented to three significant figures.
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Table 3: Annual Inhalation Dose Correction Factors for Various Organs 

Based on Deposition from Event Small Boy

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Skin, Adrenals, Thymus, 

Small Intestine, Spleen, 

Muscle, Uterus, Pancreas, 

Kidneys, Breast, Testes, 

Esophagus, Ovaries, Brain, 

Stomach, Thyroid, Gall 

Bladder

1,500 477 231 136 79 26 14 8.8 6.2 4.5

Upper Large Intestine 784 250 120 70 46 19 12 8.8 6.6 5.1

Urinary Bladder 499 170 84 50 33 23 6.0 3.9 2.8 2.1

Lungs 54,201 16,814 7,865 4,515 2,920 2,041 482 322 232 175

Extra Thoracic Regions 1,258 428 214 151 87 57 40 29 23 18

Lower Large Intestine 439 144 70 41 27 13 8.3 5.9 4.4 3.4

Colon 525 173 85 50 33 31 18 12 8.4 6.3

Liver 13,459 6,631 4,399 3,292 2,630 1,660 626 350 228 162

Red Bone Marrow 82 23 12 7.8 5.4 3.9 3.0 2.3 1.9 1.6

Bone Surface 192 78 43 28 19 14 11 8.8 7.1 5.9
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Table 4: Annual Inhalation Dose (Rem) from Short-Lived Activity from Event Small Boy

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Liver 0.003 0.001 Negla Negl Negl Negl Negl Negl Negl Negl

Bone Surface 0.003 0.001 Negl Negl Negl Negl Negl Negl Negl Negl

Lower Large 

Intestine

0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

ETb(ET2), LNc(ET), 

LN(THd

) 

0.002 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lung 0.012 0.002 0.001 Negl Negl Negl Negl Negl Negl Negl

ET1 1.305 0.243 0.088 0.050 0.029 0.018 0.013 0.009 0.007 0.006

a

Negl means the dose is less than 0.0005 rem and is negligible. b

ET=extra-thoracic region. c

LN=lymph node. d

TH=thoracic.
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Table 5: Annual Inhalation Dose Correction Factors for Various Organs Based on 

Deposition from Event Little Feller I

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Skin, Adrenals, Thymus,

Small Intestine, Spleen,

Muscle, Uterus, Pancreas,

Kidneys, Breast, Testes,

Esophagus, Ovaries, Brain,

Stomach, Thyroid, Gall

Bladder

432 159 77 45 29 20 6.5 4.8 3.7 2.9

Upper Large Intestine 165 58 30 18 12 8.7 6.6 5.1 4.1 3.4

UrinaryBladder 646 176 56 26 15 5.2 3.4 2.4 1.8 1.4

Lungs 15,794 4,801 2,175 1,223 780 171 105 71 52 39

Extra Thoracic Regions 500 160 76 44 29 13 9.5 7.1 5.5 4.4

Lower Large Intestine 108 41 22 14 9.8 7.2 5.6 4.4 3.6 3.0

Colon 105 41 22 14 9.8 7.2 5.6 4.4 3.6 3.0

Liver 3,804 1,866 1236 297 108 58 37 25 19 14

Red Bone Marrow 25 19 4.8 3.5 2.8 2.3 2.0 1.7 1.5 1.3

Bone Surface 29 13 7.8 5.4 4.1 3.2 2.6 2.2 1.9 1.6
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Table 6: Annual Inhalation Dose (Rem) from Short-Lived Activity from Event Little Feller I

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Liver 0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bone Surface/Red

Bone Marrow

Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lower Large Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

ETa(ET2), LNb(ET),

LN(THc) 

0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lung 0.003 0.001 Negl Negl Negl Negl Negl Negl Negl Negl

ET1 0.519 0.090 0.031 0.014 0.009 0.004 0.003 0.002 0.001 0.001

a

ET=extra-thoracic region. b

LN=lymph node. c

TH=thoracic.
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The following two sets of tables provide the results of the ingestion correction factor analysis for 

the two shots. 

Table 7: Annual Ingestion Dose Correction Factors for Various Organs 

Based on Deposition from Event Small Boy

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Skin, Adrenals, Thymus,

Small Intestine, Spleen,

Muscle, Uterus, Pancreas,

Kidneys, Breast, Testes,

Esophagus, Ovaries, Brain,

Stomach, Thyroid, Gall

Bladder

139 61 37 26 19 15 12 10 8.4 7.2

Bladder 56 18 9.1 5.6 3.8 2.7 2.1 1.6 1.3 1.1

Bone Surface 5.7 3.2 2.2 1.8 1.6 1.4 1.3 1.3 1.3 1.3

Stomach 380 131 65 39 26 18 31 17 11 7.9

Small Intestine 107 36 22 16 12 10 8.4 7.3 6.4 5.8

Upper Large Intestine 392 175 63 32 19 13 9.1 6.8 5.3 4.2

Lower Large Intestine 306 151 38 20 12 8.2 5.9 4.4 3.4 2.8

Colon 346 170 70 34 20 13 9.5 7.1 5.5 4.3
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Table 8: Annual Ingestion Dose (Rem) from Short-Lived Activity for Various Organs Based on 

Deposition from Event Small Boy

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Adrenals, Breast, Brain,

Skin, Kidney, Muscle,

Pancreas, Esophagus,

Liver, Ovaries, ETa, ET1,

ET2, LNb(THc), LN(ET), 

Lungs, Spleen, Testes,

Thymus, Thyroid, Uterus,

Gall Bladder

Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bladder Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bone Surface Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Stomach Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Small Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Upper Large Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lower Large Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Colon Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

NOTE: All values are less than 0.0005 rem. a

ET=extra-thoracic region. b

LN=lymph node. c

TH=thoracic.
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Table 9: Annual Ingestion Dose Correction Factors for Various Organs Based on 

Deposition from Event Little Feller I

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Adrenals, Breast, Brain, Skin, 

Kidney, Muscle, Pancreas, 

Esophagus, Liver, Ovaries, 

ETa

, ET1, ET2, LNb(THc), 

LN(ET), Lungs, Spleen, 

Testes, Thymus, Thyroid, 

Uterus, Gall Bladder

91 29 14 7.7 5.0 3.5 2.6 2.0 1.5 1.3

Bladder 11 5.2 3.4 2.5 2.0 1.7 1.5 1.3 1.2 1.1

Bone Surface 3.1 1.7 1.3 1.1 1.1 1.1 1.1 1.1 1.1 1.1

Stomach 103 34 17 10 6.6 4.7 5.4 4.5 3.8 3.3

Small Intestine 65 27 17 12 10 8.0 6.8 5.9 5.3 4.7

Upper Large Intestine 153 27 17 12 9.0 7.2 5.9 4.9 4.2 3.7

Lower Large Intestine 86 42 38 20 12 8.2 5.9 4.4 3.4 2.8

Colon 124 61 14 10 7.2 5.7 4.7 3.9 3.3 2.9

a

ET=extra-thoracic region. b

LN=lymph node. c

TH=thoracic.
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Table 10: Annual Ingestion Dose (Rem) for Various Organs Based on Deposition from Event Little Feller I

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Adrenals, Breast, Brain, 

Skin, Kidney, Muscle, 

Pancreas, Esophagus, 

Liver, Ovaries, ETa

, ET1, 

ET2, LNb

(THc), LN(ET),

Lungs, Spleen, Testes, 

Thymus, Thyroid, Uterus, 

Gall Bladder

Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bladder Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bone Surface Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Stomach Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Small Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Upper Large Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lower Large Intestine Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Colon Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

NOTE: All values are less than 0.0005 rem. a

ET=extra-thoracic region. b

LN=lymph node. c

TH=thoracic.
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Table 11: Annual Inhalation Dose Correction Factors for Various Organs Based on Deposition

from Event Small Boy Without Refractory Fraction Adjustments

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Skin, Adrenals, Thymus, 

Small Intestine, Spleen, 

Muscle, Uterus, Pancreas, 

Kidneys, Breast, Testes, 

Esophagus, Ovaries, Brain, 

Stomach, Thyroid, Gall 

Bladder

908 330 166 99 66 47 18 11.8 8.4 6.3

Upper Large Intestine 450 165 85 52 35 19 12 8.8 6.6 5.1

Urinary Bladder 407 150 77 46 31 22 6.0 3.9 2.8 2.1

Lungs 20,188 7,016 3,462 2,047 1349 955 181 119 84 63

Extra Thoracic Regions 453 155 78 66 32 19 12 8.8 6.6 5.2

Lower Large Intestine 291 109 57 35 24 9.8 6.8 5.0 3.9 3.1

Colon 335 120 61 36.9 25 18.5 12.3 8.8 6.6 5.1

Liver 2,742 1,351 896 671 109 58 37 25 19 14

Red Bone Marrow 30 12 7.1 4.9 3.6 2.8 2.2 1.8 1.5 1.3

Bone Surface 31 14 8.4 5.9 4.4 3.5 2.8 2.3 2.0 1.7
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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Table 12: Annual Inhalation Dose (rem) for Various Organs Based on Deposition

from Event Small Boy Without Refractory Fraction Correction

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Liver 0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bone Surface Negl Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lower Large 

Intestine

0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

ETa(ET2), 

LNb

(ET), LN(THc),

0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lung 0.004 0.001 Negl Negl Negl Negl Negl Negl Negl Negl

ET1 0.469 0.088 0.032 0.022 0.010 0.006 0.004 0.003 0.002 0.001

a

ET=extra-thoracic region. b

LN=lymph node. c

TH=thoracic.
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Table 13: Annual Inhalation Dose Correction Factors for Various Organs Based on Deposition

from Event Small Boy with One Refractory Fraction Adjustment

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Skin, Adrenals, Thymus, 

Small Intestine, Spleen, 

Muscle, Uterus, Pancreas, 

Kidneys, Breast, Testes, 

Esophagus, Ovaries, 

Brain, Stomach, Thyroid, 

Gall Bladder

1156 416 211 127 85 60 65 35.7 23.1 16.3

Upper Large Intestine 480 181 95 58 39 27 19 15 11 9.2

Urinary Bladder 407 150 77 46 31 22 6.0 3.9 2.8 2.1

Lungs 25,352 7,991 3,786 2,191 1,425 999 247 176 132 103

Extra Thoracic Regions 698 243 123 92 51 33 23 17 13 10

Lower Large Intestine 351 128 66 40 27 20 15 11 9.0 7.3

Colon 369 137 71 43.7 30 21 16 12 9.5 7.7

Liver 6,074 2,993 1,986 1,486 808 264 140 89 62 46

Red Bone Marrow 42 12 7.0 4.7 3.4 2.6 2.1 1.7 1.4 1.2

Bone Surface 60 26 15 10 7.2 5.5 4.3 3.5 2.9 2.4
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

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Table 14: Annual Inhalation Dose (rem) for Various Organs Based on Deposition

from Event Small Boy with One Refractory Fraction Correction

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Liver 0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bone Surface 0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lower Large Intestine 0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

ETa(ET2), LNb(ET), 

LN(THc

) 

0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lung 0.006 0.001 Negl Negl Negl Negl Negl Negl Negl Negl

ET1 0.724 0.137 0.050 0.030 0.017 0.011 0.007 0.005 0.004 0.003

a

ET=extra-thoracic region. b

LN=lymph node.

c

TH=thoracic.

Table 15: Annual Inhalation Dose (rem) for Various Organs Based on Deposition

from Event Small Boy – Current TBD

Organ 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972

Liver 0.002 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Bone Surface 0.001 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002

Lower Large Intestine 0.001 Negl Negl Negl Negl Negl Negl Negl Negl Negl

ET(ET2)a, LNb(ET), 

LN(THc

) 

0.002 Negl Negl Negl Negl Negl Negl Negl Negl Negl

Lung 0.008 0.002 0.001 0.001 Negl Negl Negl Negl Negl Negl

ET1 1.635 0.248 0.164 0.164 0.146 0.138 0.138 0.138 0.138 0.138

a

ET=extra-thoracic region. b

LN=lymph node.

c

TH=thoracic.
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GENERAL CONCLUSIONS

The purpose of application of the refractory fractions by Hicks (1981, 1982) was to estimate the 

relative activities of refractory and volatile radionuclides at off-site locations. The phenomenon of 

fractionation is described by Hicks (1982) as follows.

The phenomenon of fractionation is due to both chemical and physical separation 

of the radionuclides. Chemical separation occurs in the first few minutes. At zero

time, everything in the vicinity of the device is vaporized. As the fireball cools to

about 3000oC the FeO and soil components form liquid droplets in which the

refractory elements dissolve (Ad60). The fireball cools to the melting point of soil 

and iron oxides, ~1500oC, in about 20 sec (Mi63, St58). The solidified droplets 

contain the refractory elements, while the volatile elements and their radioactive

daughters remain in the gas phase. In 6-8 minutes, when the cloud has cooled to 

ambient temperature, ~50oC, the volatile elements (except for Kr and Xe) and 

their daughters condense on the surface.

The volatile phase consists of those elements in the gas phase when the liquid droplets solidify.

The refractory phase consists of those elements in the liquid droplets when they solidify. The

volatile/refractory ratio is the ratio of the amounts of volatile phase to the refractory phase.

The solid particles in the cloud of nuclear debris fall to earth at different velocities and from

different altitudes. This process has the effect of separating the debris by particle size along the 

path of the cloud. Thus, the refractory phase and the volatile phase are partially physically

separated, a process taking hours or days.

Off-site fallout is characterized by an excess of volatile phase, because the smaller particles tend

to be deposited farther from ground zero.

The application of the refractory fraction (inverse of the volatile/refractory ratio) was to account

for preferential deposition as the cloud moved downwind and off-site. The selection of the value 

to use for refractory fractions was based on the comparison of calculated and measured soil

concentrations as a function of distance from the test shot (Hicks 1982). The results of the 

analyses indicated that the volatile/refractory ratio increased from about one near the shot site to

over three at long distances off-site. The application of refractory fractions by Hicks is

summarized as follows:

• For air drops and balloon shots, no fraction was assumed by setting RF to 1.0.

• For low tower, surface, and underground shots, a refractory fraction of 0.4 was applied.

• For all other shots a refractory fraction of 0.5 was applied. 

• The two shots evaluated for July of 1962 were Small Boy (low tower) and Little Feller I 

(surface), and have a refractory fraction of 0.4 (Hicks 1981). 
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

Page 28 of 29

This is a 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.

For the present analysis, the results are needed for distances closer to the shot representing onsite locations. This is the reason the Hicks data were adjusted by reversing the refractory 

fraction correction. 

A summary of the doses in the tables in the previous section is given in the following table. 

Table 16: Summary of Dose Results for ET1 from Inhalation

Event Analysis ET1 Dose (rem) Ratio to Small Boy, 

TBD Method

Source

Small Boy TBD Method 1.305 1.00 Table 4

Little Feller I TBD Method 0.519 0.40 Table 6

Small Boy No refractory 

adjustment

0.469 0.36 Table 12

Small Boy One refractory 

adjustment 

0.724 0.55 Table 14

Small Boy Current TBD 1.635 1.25 Table 15

The results indicate the application of the refractory fraction once, to represent off-site activities,

results in the lowest doses from inhalation intakes. As the refractory fraction is removed from

the analysis, once and then twice, the doses increase. This indicates that the analysis method

used in the NTS Environmental TBD is favorable to claimants. The same is true for the

ingestion intake analyses. Consequently no change to the method used in the TBD is

recommended. Minor changes to the values in the TBD have occurred as a result of

modifications to the evaluation and application of dose correction factors. Specifically, removal

of the radionuclides in the TBD Table 4-7 from the correction factor analysis reduced the

resulting doses because it increased the fraction of the dose from strontium-90.

REFERENCES

Hicks, 1982, Calculation of the concentration of any radionuclide deposited on the ground by

off-site fallout from a nuclear detonation; Harry G. Hicks; Health Phys.; 1982; 42:585-600.

Hicks, 1981, UCRL-53152 Pt. 8, Results of Calculations of External Gamma Radiation

Exposure Rates from Fallout and the Related Radionuclide Compositions – Operations Nougat

through Bowline, 1962-1968; Harry G. Hicks, Lawrence Livermore National Laboratory;

Livermore, California; July, 1981; SRDB Ref ID: 1851

NIOSH, 2006, SEC Petition Evaluation Report for Petition SEC-00055, Nevada Test Site;

NIOSH (National Institute for Occupational Safety and Health); Cincinnati, Ohio; April 14,

2006; SRDB Ref ID: 150574
White Paper: NIOSH Response to Comment 5 of SC&A’s NTS Resuspension Issues Status Report

Page 29 of 29

This is a 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.

NIOSH, 2007, SEC Petition Evaluation Report for Petition SEC-00084, Nevada Test Site;

NIOSH (National Institute for Occupational Safety and Health); Cincinnati, Ohio; September 26,

2007; SRDB Ref ID: 77699

ORAUT, 2012, ORAUT-TKBS-0008-4, Technical Basis Document for the Nevada Test Site –

Occupational Environmental Dose, Rev 03; Oak Ridge Associated Universities Team (ORAUT)

Dose Reconstruction Project for NIOSH; August 24, 2012; SRDB Ref ID: 117890

SC&A, 2015, Status Report on Resuspension Issues at the Nevada Test Site, Rev. 0; Not PA

Cleared (Draft); Sanford Cohen and Associates (SC&A); Vienna, Virginia; July 15, 2015; SRDB

Ref ID: 151961