EC research on accident prevention and mitigation of severe accident consequences

This paper deals with the European Union (EU) research activities conducted at present and those planned under the next EURATOM Framework Programme through multi-partner scientific co-operation projects in the area of reactor safety. The objective of EU research in reactor safety is twofold: in the short term, to contribute to the development of risk reduction techniques in nuclear installations and, in the long term, to maintain a high level of nuclear expertise in the EU (thereby keeping the nuclear option open). The emphasis in this paper is placed on the strategy, the motivations and the key actors of these European research programmes. Some examples of technological achievements for LWRs of present and future generation are given in the specific areas of accident prevention and mitigation of severe accident consequences. Ensuring the safety of nuclear installations and of the entire fuel cycle becomes particularly demanding in countries where large-scale evacuation and land contamination are 'practically' prohibited for accidents because of high population density. In this case, increased safety assurance is provided in the plants (in line with the requirements of the regulatory authorities) with the ultimate aim to substitute evacuation, as an additional layer to the traditional defence-in-depth strategy. Maintaining the fission product boundaries intact under all conceivable reactor conditions is the main purpose of the preventive measures, but this might no longer be possible in the highly hypothetical case when severe fuel damage has begun. Therefore, a great deal of research and technological developments in reactor safety is focusing on accident management strategies, based not only on accident prevention but also on the mitigation of their consequences if prevention failed. Mitigation measures may consist in engineered dedicated safety systems added to the reactor or in severe accident management (SAM) measures proposed to the emergency control team responsible for severe accident management. (author)