Bayesian estimation of core damage frequency incorporating historical data on precursor events

Data from a recent report analyzing precursors to severe core damage accidents are presented as additional evidence combined with the results of engineering risk analyses through the use of Bayes' theorem. Calculations are performed based on various definitions of increasing core damage: mild to severe core damage (no melting of fuel), full-scale core melt, and worse-case accidents. The Reactor Safety Study alone and combined with other published probabilistic risk assessment study results is also used. Assuming various core damage levels exist, the result of the Bayesian calculations indicate that the evidence, including precursor events, may not alter significantly core damage frequency estimates