Public Exposures and Environmental Impacts

DOE-STD-6003-96

appropriate for the fusion isotopes involved, the accident scenario, and the public mitigative

actions (if any) being considered.

Acute dose is defined for specific organs depending on what short-term exposure is the

best predictor of acute health effects. For example, the acute lung dose is typically the 1-yr

CED, and the bone marrow acute dose is typically considered as the 7-day CED or 100% of the

7-day CED plus 50% of the 830th day CED. Thus, for the same exposure time periods, the

acute dose is always less than (or equal to for very short half-lives) the 50-yr CED.

Early dose is the 50-yr CED from the first 7 days of exposure following the onset of an

accident, specifically the inhalation and cloudshine doses during plume passage, inhalation from

resuspended/re-emitted isotopes during the first 7 days, and the groundshine dose from the first

7 days. This dose measure is appropriate when contemplating the need for short-term public

mitigative actions. The early dose is generally calculated for the most exposed individual (MEI)

of the public, assumed to reside at the site boundary or (for release elevated above ground

level) where the plume reaches the ground.

Two-hour (prompt) dose is the 50-yr CED resulting from the first 2 hours of exposure fol-

lowing the onset of an accident, as in DOE 6430.1A. This dose measure implicitly assumes

evacuation within 2 hours.

Chronic dose is the 50-yr CED from 50-yr exposure after an event, specifically from

inhalation of resuspended or re-emitted isotopes, groundshine, and ingestion of radionuclides.

This dose measure is appropriate when contemplating whether long-term public mitigative

actions are needed and, if so, when and for how long. When calculated for an individual, the

chronic dose should include reasonable assumptions about the fraction of time an individual

resides at the site boundary and the fraction of food produced at that location. Because of the

long time scales, the chronic dose is more appropriately calculated for the "average" resident of

the surrounding area.

The factor χ is the instantaneous concentration of a radioactive or hazardous material (in

becquerels per cubic meter or grams per cubic meter) at a given location distant from the point

where the material is released into the environment. The factor Q is the amount of material

released, expressed in grams or becquerels; Q′ is the rate of material release emission from a

continuous point source. The ratios χ/Q and χ Q ′ are determined by the atmospheric condi-

tions, the distance between the source and distant location atmospheric transport, and the time

since release. For further explanation, see Slade (AEC 1968).

2.2 Public Exposures and Environmental Impacts

A significant part of 10 CFR 20 is directed toward protecting the public, the environment,

and workers from the risks of exposure to radiation. Part of 40 CFR 61 is also concerned with

protecting the public from chronic exposure to radiation. In addition, exposures to workers, the

public, and the environment must be kept "as low as reasonably achievable" (ALARA).

"Reasonably achievable" levels are typically a fraction of those allowed by 10 CFR 20 and

40 CFR 61.