BWR of Fukushima NPPs and others: safeguard systems, severe accidents, accidental situations, proceedings

GRS Cologne (Germany)

Abstract

The physical and chemical processes governing beyond design basis accidents (BDBA) and the progression into severe accidents are very complex, often involving many simultaneous phenomenological interactions, for which detailed experimental information is not available in all cases. Nevertheless, large progress has been made over the last more than 25 years after the two severe accidents in TMI-2 and Chernobyl NPPs to gain knowledge about severe accident phenomena and the NPP reaction to it.

The typical design of BWRs (Japanese and German NPPs) is discussed and main principles and differences in the severe accident progression before reactor pressure vessel failure are explained. A distinction of two accident classes for BWRs is needed, as the containment conditions depend on the release location a) through a leak into the drywell or b) through the safety valves into the water of the wetwell. Examples are provided with some illustration of typically different conditions inside the containment.

These general explanations should help drawing conclusions related to the Fukushima severe accident and especially the containment conditions. Further details are provided by the papers of AREVA given in the same SFEN conference.