Revision to Cerro Grande White Paper
Rev. 1, April 4, 2011

Since this dose is below the level regarded as significant, and because current practice is the
assignment of a larger dose based on claimant favorable assumptions for environmental
internal dose, it is unnecessary to include dose estimated during exposure during the Cerro
Grande fire.

6. References

e Eberhart, C., “Measurements of Air Contaminants during the Cerro Grande Fire at Los
Alamos National Laboratory,” LA-14250, Los Alamos National Laboratory, August 2010

e International Commission on Radiological Protection (ICRP), No. 23, Report of the Task
Group on Reference Man (ICRP 23), Adopted October 1974, Pergamon Press, 1975.

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1

3.

3.1.

Revision to Cerro Grande White Paper
Rev. 1, April 4, 2011

Introduction

Formerly, a white paper was written to provide a technical basis for an overestimate of dose to
workers with potential intakes of radioactive material while working on the Los Alamos site
during the Cerro Grande fire of May, 2000, With this re-evaluation, a modified estimate
methodology is based upon the results of an updated study from August 2010 (Eberhart 2010),
which presents an in-depth analysis of the field data from the fire.

Radionuclides

Radiological releases resulting from the fire are described in the reference. The primary
dosimetric consideration was suspended radon decay products that had accumulated for many
year's on vegetation and on the forest floor. Concentrations of plutonium, americium, and
depleted uranium were also measured; however, these results were considered to be, in
general, consistent with measurements made outside the fire period (Eberhart 2010). Gamma
spectroscopy identified only naturally-occurring radionuclides. For the purpose of an
overestimate of potential inhalation to Los Alamos workers, intakes for plutonium, americium,
and uranium are calculated based on the highest measured value, without considering likely
background inhalation rates.

The concentration values were chosen based only upon the maximum measured result for each
radionuclide, Two isotopes of plutonium, ?38Pu and 239Pu, were considered, since detectable
concentrations are available in the reference.

Methodology

Intakes were estimated using the maximum measured concentrations from four radionuclides
listed in the tables in the reference. The values are listed in the table. Total intakes were
calculated using the relation below.

3 *,
Total intake = Concentration (m2) + Inhalation rate (TM Trour) + Exposure time (hours)

Breathing Rate Assumptions
Standard breathing rate assumptions are unlikely to apply to emergency workers responding

to the fire. For this reason, the breathing rate was adapted from ICRP (1975), Table 120, as
shown,

Vy = f «Vi + time (minutes)

Where:
Vn = Volume of air per minute
f= Frequency of inhalation breaths per minute (min)

Vr Tidal volume, which varies with activity level

VRID UNGLASSIFE

Mi. Gleasiflasiion @

Page 1 of 3

This is a working document prepared by NIOSH 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.



Revision to Cerro Grande White Paper
Rev. 1, April 4, 2011.

In this case, fand Vr were selected for an adult performing heavy work from the reference (Table
120), with the result below,

Vy = 21min“ + 2030 mL 60 MIN), = 2.56E +06 M267,
3.2. Additional Assumptions
Additional assumptions are listed below:
= A bounding intake is used to overestimate worker internal dose consequences;

= Individuals were assumed to spend the entire 60-hour period at the location of the highest
potential intake;

«The highest measured values for each alpha-emitter were identified from the data in
Eberhart (2010). These values are listed in the table;

«A 60-hour exposure period is assumed;
= A ‘Heavy Work’ breathing rate was assumed for the entire 60-hour period;

» Respiratory protection was not worn;

4, Calculated Intakes

Intakes calculated from the methodology described above are listed in the table.

7 i ‘ Concentration Total Intake
Radionuclide Date Location (aci/m?) (dpm/m®) (dpm) e
Am-241 May 12 1251 3.79 E-03 0.043
Pu-238 May 13 652 2.78 E-04 0.023
Pu-239 May 13 4723 1.05 E-03 0.17
U-234 May 13 17094 1.44 E-04 0.59

5. Recommendation

The dose estimation methodology in section 3, above, is likely to bound any actual doses due to
conservative assumptions for location, exposure time, and breathing rate. However, the listed
intakes are unlikely to represent a significant dose to any potential claimant. Doses were
estimated using the IMBA program, assuming an acute inhalation of each of the listed intakes,
over a number of organs, and assuming cancer was diagnosed in May 2010. The highest
resulting dose was 1.06 E-04 rem, or 0.1 millirem, for an assumed 736Pu, absorption Type S,
intake and the thoracic lymph nodes (LN(TH)) as the internal organ assumed for dose
reconstruction. All other organs, including lung, bone, and red bone marrow, were
approximately an order of magnitude or more less than this value. The other radionuclides for
all possible absorption types, also resulted in lower doses.

* Eberhart 2010, Table A-16.
? Ibid, Table A-17.
* Ibid, Table A-18.
“ibid, Table A-19.

Page 2 of 3
This is a working document prepared by NIOSH 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.