A Critique of Three Methodologies for Estimating the Probability of Containment Failure Due to Steam Explosions

At least three distinct approaches have been employed for estimating the conditional probability of containment failure due to steam explosions within the pressure vessel of a water-cooled nuclear reactor. These approaches, which involve varying degrees of subjectivity and objectivity, are reviewed. It is concluded that, given the current state of knowledge, all approaches involve significant uncertainties; no method is currently capable of credibly defending any given value of failure probability or a narrow uncertainty range.