Impact of Secondary Effects on the Reduction of Fission Product Source Terms in Class IX Reactor Accidents

A more realistic examination of the potential radiological consequences of a hypothetical line-break, core melt type of accident (Class IX) reveals inherent release suppression processes that have not been fully evaluated in the Reactor Safety Study. These include the chemical effect of strongly reducing conditions in the reactor vessel, the retention of condensed materials on the internal surface, and the attenuation of the radioactive source in the containment building by the rapid settling of a highly concentrated aerosol. Both new experimental data and the Three Mile Island experience have been helpful in developing these concepts; however, the lack of sufficient data still leaves some conclusions open to question.