An analysis of containment failure by a steam explosion following a postulated core meltdown in a light water reactor

The Reactor Safety Study (WASH-1400) assessed the probability of containment failure via a steam explosion during a postulated core meltdown accident to be 10−2. Large uncertainties were attached to this probability and research has continued to reduce the uncertainty. In this paper, we discuss the possible consequences of a steam explosion for a specific reactor system (Zion Nuclear Station—Pressurized Water Reactor). It is our opinion, based on the analysis performed, that generation of large mass missiles by the explosion is unlikely, while small mass missiles, although more likely would not pose a threat to the containment. We do not mean to imply that steam explosions can be disregarded during a postulated meltdown accident, but rather that emphasis should now be placed on how the explosion affects the overall core meltdown accident instead of causing a direct failure.