Overview of Beyond-design Basis Accident Management with Particular Reference to Severe Accident Scenarios in German Pressurized Water Reactors

Over the last 10 years, emergency procedures have been developed by Framatome ANP (formerly Siemens KWU), which act both to prevent core melt events and to mitigate effects of severe accidents. A general overview will be presented of the administration and interactions between organisations and institutions involved when an accident occurs in a German nuclear power plant . The operating manual concept for accident management in German pressurized water reactors will be explained. The most important preventive and mitigative emergency procedures will be described. Finally the use of mitigative measures and their implementation in a German PWR will be discussed. In summary it can be seen that in German PWRs a number of steps have already been taken to counteract severe accidents. This applies to both the establishing of emergency response teams within and outside of the plant as well as the accident management measures, for which hardware and procedures have been installed and written. In the area of beyond design basis accident management the main emphasis has been on preventing core damage and the failure of the reactor pressure vessel. The majority of beyond- design-basis procedures have been written for this area of the accident spectrum. Nevertheless, these procedures can often also be used for mitigative purposes. Despite predominantly concentrating on preventive measures, procedures have also been devised that are only applied when the core has already been damaged or the reactor pressure vessel has already failed. For these mitigative measures additional procedures have been written and changes to the plant hardware have been made. (authors)