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Abstract

From 10 to 12 November 1986 some 80 delegates met under the auspices of the CEC working group on the safety of light-water reactors. The participants from EC Member States were joined by colleagues from Sweden, Finland and the USA and met to discuss the subject of severe accidents in LWRs. Although this seminar had been planned well before Chernobyl, the "severe-accident-that-really- happened' made its mark on the seminar. The four main seminar topics were: (i) high source-term accident sequences identified in PSAs, (ii) containment performance, (iii) mitigation of core melt consequences, (iv) severe accident management in LWRs. In addition to the final panel discussion there was also a separate panel discussion on lessons learned from the Chernobyl accident. These proceedings include the papers presented during the seminar and they are arranged following the seminar programme outline. The presentations and discussions of the two panels are not included in the proceedings. The general conclusions and directions following from these two panels were, however, considered in a seminar review paper which was published in the March 1987 issue of Nuclear Engineering International. As major points of agreement following from the seminar one can mention: (i) Existing safety margins in nuclear power plants are considerable and would go a long way in coping with severe accidents and their consequences. (ii) Severe accidents are very unlikely but cannot be ignored. (iii) Probabilistic risk studies will, by their very nature, never give completely absolute values of risk. PSA and PRA are, however, excellent tools to analyse plants and to identify weaknesses in plant design by looking at dominant sequences. (iv) Reactor containment is crucial as it is the last barrier against spreading radioactive material and thus protecting the public. (v) Not all phenomena that could occur inside containment are sufficiently well understood today to put them aside. Examples cited: hydrogen generation, deflagration and detonation, steam explosion and pressure spikes, direct heating. (vi) Given a severe accident, the most likely containment failure is long-term overpressure failure. Source terms associated with this failure mode should be reasonably modest and may not lead to early fatalities. (vii) Early containment failure modes (or bypass modes) could be important contributors to total risk and cannot be ignored. (vii) The objectives of severe accident management are basically twofold: (a) to prevent containment failure, (b) to limit containment release.

Additional information

Authors: CEC CEC - BRUXELLES (BELGIUM), CEC - BRUXELLES (BELGIUM)
Bibliographic Reference: EUR 11019 EN (1987) FS, 292 P., BFR 950, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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