The role of probabilistic events in the application of the justification criterion

Probabilistic events (potential accidents) at large industrial installations, specifically nuclear power plants, play a major role in the public debate. According to the IAEA (ICRP) criteria an installation is only justified if it results in a net benefit for the society. It is logical and in accord with the importance assigned by public opinion that probabilistic events be included in a justification evaluation. This also entails an assessment of the probability of occurrence and the consequences of such events. As regards the consequences, however, one has to keep in mind that the impact on a given society depends, for example, on an absolute number of casualties but also to a great extent on the fraction of the population involved. For the application of the optimisation criterion it has been recommended that a beta factor be used to describe the more than linear increase in risk aversion which occurs as the level of risk to a single individual increases. Potential applications of this methodology are addressed as well as some of the problems which may be encountered