Hazards Assessment

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

respiratory regions and swallowed, thereby delivering little radiation dose to the

lung tissues. Because plutonium is poorly absorbed in the gut, very little dose is

attributed to the larger particles that are cleared from the body by this process.

Small particles are deposited deeper in the lung and are cleared very slowly,

producing a much larger dose per unit activity inhaled. Extremely small particles

tend to be exhaled and not deposited.

Isotopic mixture. Characterization of the isotopic mixture is important to the

accuracy of both dose calculations and contamination measurements. When the

inventory or quantity released is expressed as the total activity (Ci or Bq) of a

mixture of isotopes, the total often includes the 241Pu activity. Because 241Pu

decays almost exclusively by beta emission, it contributes little to the internal dose

from a mixture of Pu isotopes. Also, the fraction of 241Am (from decay of 241Pu) in

plutonium can vary greatly, depending on the degree of irradiation and the time

since the plutonium was chemically separated from the reactor fuel.

Characterization of contamination from a plutonium mixture is often done by

detecting the low-energy photons emitted by 241Am, which requires knowledge of

the activity of 241Am compared to the other isotopes in the mixture.

(d) Developing Event Scenarios. The properties of the hazardous material do not

significantly affect the manner in which this step of the hazards assessment is

performed.

(e) Estimating Potential Event Consequences. For the scenarios developed in the

previous step, this step determines the area potentially affected, the need for protective

actions, and the time available to take those actions. The way these consequences are

determined depend on properties of the hazardous material.

For plutonium and its compounds, inhalation during plume passage is the most

important exposure process in the early phase of an emergency. After passage of

a plume, exposure to material deposited on the ground will dominate. Therefore,

the following features should be considered when selecting and applying

calculational models:

Inhalation pathway dose. For any realistic mixture of plutonium isotopes, the great

majority of the dose will be by the inhalation pathway. Therefore, the model

selected to estimate consequences of an atmospheric plutonium release must be

able to calculate the total effective dose equivalent (TEDE) to an individual

exposed by inhalation.

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