Estimated Safety Significance of Generic Safety Issue 61.

摘要

The potential threat posed by transient initiated accident sequences involving BWR systems capable of releasing steam into the wetwell airspace and thereby pressurizing the containment has been examined. The study estimates the likelihood of a rupture in one of a number of high pressure steam lines which pass through the wetwell airspace before entering the suppression pool. The study outlines the postulated accident sequences, estimates their frequency, and calculates containment response to the proposed steam discharges using the computer code CONTEMPT4. Based on the predicted containment response, the investigation estimates the probability of core melt, the possible fission product release and the associated consequences. The study concludes that, while some of the sequences could potentially result in core melt and cause significant releases of fission products, the frequency of these sequences are judged to be sufficiently small to remove them as significant contributors to public risk.