Response of a LWR pressure vessel to severe-accident loadings

In the recent emphasis on nuclear safety, structural studies of nuclear reactor vessels have been directed toward evaluating their response during severe loading incidents or accidents including even core meltdown - however improbable these accidents may be. The present paper will address some of these problems. The ultimate load carrying capacity of an unflawed nuclear pressure vessel is estimated. The measure of the maximum pressure that the vessel can resist during quasistatic loading is a useful quantitative estimate of overall vessel strength. The paper than analyzes two structural problems during a hypothetical meltdown. In the initial stage, the molten core mixture drops into the lower portion of the pressure vessel, resulting in both temperature and pressure rises. Subsequently, a vapor explosion may occur as a result of the molten metal coming in sudden contact with the water in the lower portion of the vessel. The explosion is postulated to propel a slug of molten metalup the vessel barrel that eventually impacts the upper head of the vessel potentially generating missiles in the containment building. The reactor vessel at Indian Point, New York is used as a prototype of this analysis.