Reactor Safety Study (WASH-1400) and its implications for radiological emergency response planning

The methodologies developed for the Reactor Safety Study provide a more realistic assessment of consequences associated with a nuclear power reactor accident than techniques previously used. The consequence model includes among other refinements (1) a time dependent atmospheric dispersion treatment that accounts for weather variations during the progression of the accident, (2) dosimetry that accounts for multiple exposure modes to an individual, and (3) a statistically based population evacuation treatment. With this methodology it has been established that radiation dose to the bone marrow is dominant in determining early fatalities and that the magnitude of this dose is controlled by the external radiation from ground deposited radioactive materials. Initial studies for emergency planning purposes indicate that early fatalities are sensitive to the details of radioactivity release (amount of activity, thermal content of the cloud, etc.). They are less sensitive to variations in weather following the release. In contrast, latent fatalities are governed primarily by the total amount of activity released, not the details of the release. Evacuation can be effective in reducing early fatalities but has little impact upon latent fatalities. The reduction in early fatalities realized through reduction of early dose suggests that there may be alternatives to massive evacuations, such as sheltering followed by selective population relocation