Efficiency of various strategies of short term countermeasures in case of a severe nuclear accident
F.Charpin, H. Mansoux
IRPA-10: 10. international congress of the International Radiation Protection Association Hiroshima (Japan) 14-19 May 2000, P-11-280.
In case of a severe nuclear accident at PWR plants, countermeasures should be initiated in the short term by authorities to reduce the consequences of the atmospheric radioactive releases on the neighbouring population. Various factors influence the level of protection afforded by the countermeasures. For instance, a too early intervention would lead to a lack of efficiency in terms of dosimetric impact if the actual evolution of the accident is not considered. Thus, implementation of countermeasures should be optimized. The characteristics of the release also influence this efficiency. The accidental scenario in this study is considered as the most severe accident envisaged in France, and constitutes the basis for emergency plans.
The basic protective actions in the early phase of the accident are the evacuation of the population, the sheltering, and the intake of stable iodine to saturate the thyroid gland. These countermeasures can be combined in strategies, for example, sheltering followed by evacuation when the situation threatens to get worse, or evacuation combined with iodine distribution for the people who may be exposed in the radioactive plume.
In general, the projected doses (those without applying any countermeasure) are compared with those expected for a particular countermeasure or strategy, the dosimetric efficiency being estimated for the total duration of the release. In this paper, an in-depth analysis associates the kinetics of the release with the corresponding evolution of the dosimetric efficiency of countermeasures. This is done at different times in the short term of the accident and for various distances from the accidented plant. Results are presented for different strategies initiated at various times. This work is intended to improve the management of a major nuclear accident in its early phase.