Protection of nuclear power plants against external events

The different aspects for the selection of external events to be accounted for in designing nuclear power plants and in defining load assumptions are illustrated: 1) In case of earthquake the severest possible events according to the state of science and technology are assumed. 2) For events where it is not or only to a certain extent possible to apply this method, e.g. in the load case airplane crash, load assumptions are defined in a combined probabilitic-deterministic way. By the example of plant protection, it is shown that by integrating all measures for protecting against interference of third parties (sabotage) or other external events, optimum protection concepts may be achieved. In all considerations on interference of third parties or other external events, one has to take into account that absolute protection is not possible. Nevertheless, it may be confirmed that nuclear power plants not only have a much higher level of protection than other, non-nuclear plants with equal or even higher potential hazard, but also that they meet the requirement not to increase significantly the current risk of society. (orig./HP)