Community Research and Development Information Service - CORDIS


Probabilistic Accident Consequence Uncertainty Assessment: Countermeasures Uncertainty Assessment, EUR 18821

Funded under: FP5-EAECTP C


Accident consequence assessment codes are used to evaluate the risks of hypothetical accidents at nuclear plants, allowing for the range of atmospheric conditions that could occur at the time of the accident. The codes include an allowance for the effect of countermeasures, such as sheltering, evacuation and stable iodine tablets, in reducing doses following such accidents.
Uncertainty analyses have been undertaken on various aspects of the predictions of such codes. This report describes a project to use expert judgement to determine distributions on the values of some of the parameters used in the countermeasures modules of accident consequence assessment codes. The distributions obtained are appropriate for use only in such calculations and should not be used for emergency response in the event of an accident.
In the codes countermeasures are taken once calculated doses are above preset intervention levels (doses defined by international bodies such as the IAEA). Whether in real situations emergency managers will act accordingly is hard to predict. Uncertainties associated with these decisions are termed ¿volitional¿ uncertainties. These uncertainties, however, cannot be assessed by expert judgements as they express the decision at stake in an emergency situation. Uncertainties on the times to implement countermeasures and on the times for the general population to respond to these measures can be assessed by experts, as they represent "lack-of-knowledge" uncertainties. This paper will describe the difference in approach of both types of uncertainties and will show the results of aggregating expert judgements on the latter type of uncertainties in early countermeasures strategies. Ten experts from seven European countries provided subjective assessments.

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