Abstract
(Englisch)
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This project had the specific objectives of detennining whether; (i) the focus of the severe accidents (SA) research is consistent with that of the regulatory authorities, (ii) the results obtained so far by SA research satisfy the regulatory concerns and (iii) what should be the future prograins, that Will address the potential future regulatory needs into next century.
The project work consisted of Workshops to which the partners contributed. The partners represented their respective regulatory organizations or their technical support organizations. A Questionnaire based on the objectives, listed above, was prepared and sent to several European regulatory authorities. The Questionnaire was also sent to United States Nudear Regulatory Conirnission, Japanese Nudear Safety Conmiission and the regulatory authorities of Hungary, Slovakia, Slovenia and Czech Republic. Responses have been received from nine European organizations, four Eastem European organizations, Japanese Safety Conmiission and the United States Nudear Regulatory Conrniission (USNRC). The responses showed differences between the attitudes of the various regulatory organizations towards SA research accomplishment and needs. Clearly, the responses obtained have statistical value since a wide spectrum of regulatory organizations have contributed, although no statistical analysis was performed. Insights obtained from their responses have been combined and are reported here.
In addition to the analysis of the responses to the Questionnaire, a critical review of the severe accident phenomenological research conducted in the World for the past 20 years was perfonned. The accomplishments made by this research activity were exaniined and related to the needs of the regulatory organisations as evidenced by the responses to the Questionnaire, referred to above. The research accomplishments were also related to the requirements of the severe accident management guidance (SAMG) and its implementafion. The impact of the more recent approaches e.g. the probabilistic safety assessment (PSA) and the risk informed regulations was examined and their needs related to the accomplishments of the severe accident research performed so far. In this context the accomplishments of the SA research, sponsored by the European Commission in the fourth framework program, were reviewed. This has lead us to summarize the state of resolution of the SA issues with respect to die needs of the regulatory organisations. lt was found that most regulatory organisations state diat they have employed the results obtained, and die insights gained, from die SA research for regulatory decision making. They have also used the same for establishing greater confidence in either die regulations they have proposed or in reviewing die actions that die licensees (plants) have proposed for preventing or mitigating die consequences of severe accidents. The specific needs for further research, that the majority of the regulatory organisations [or their technical support aorganisations (TSO~s)] have indicated, have been classified in the report and recommendations have been made on the future directions of die SA research. The highest priority for füture SA research has been assigned to die resolution of the issue of ex-vessel meltidebris coolability to achieve stabilization and termination of die postulated severe accident.
The recommendations provided in the report, although, quite general, may not apply to all countries and plants. Some of the SA issues and recommendations, particularly with respect to the application of die SAMG, may require plant specific modifications.
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