Implementation of PAR-Systems in German LWRs

During the last decade, several concepts of mitigation have been developed and tested to limit the hydrogen concentrations in the containment atmosphere during the course of a severe accident. Extensive efforts have been given, especially in Germany, Canada and France, to investigate the use of passive auto-catalytic recombiners (PAR). Investigations were carried out at GRS, sponsored by the German Ministry of Environment, Nature Conservation and Nuclear Safety (BMU), to develop the basic requirements for the implementation of a PAR-system in large dry containments. Based on the outcome of these research efforts in Germany it was recommended by the Reactor Safety Commission (RSK) in March 1998 to implement a hydrogen mitigation system, based on catalytic recombiners, in large dry containments of German PWR plants. Most of the PWR-containments and two BWR-containments, where only the wet-well is inerted, have been equipped with a PAR-system. The process of PAR-implementation is ongoing. (authors)