Consequences of class 9 accidents on the LWR design

Recent considerations on the experience from the occurrence of accidents in LWR, together with investigations and studies in several laboratories in the world have led to the nuclear safety regulatory bodies in some countries to introduce the class 9 accidents concept in their licensing procedures. This type of accident delivers a great amount of radioactivity to the media due to core meltdown with the loss of the containment integrity. The problem has been treated taking into account a new release category, the so-called beed (Best Estimate Empirical Data) in the emergency planning and in modifications in the plant design to mitigate the radiological effects of such accidents so an adequate level of nuclear risk to the population can be guaranteed. (author)