Station blackout at Browns Ferry Unit One: iodine and noble-gas distribution and release

This is the second volume of a report describing the predicted response of Unit 1 at the Browns Ferry Nuclear Plant to a postulated Station Blackout, defined as a loss of offsite power combined with failure of all onsite emergency diesel-generators to start and load. The Station Blackout is assumed to persist beyond the point of battery exhaustion and the completely powerless state leads to core uncovery, meltdown, reactor vessel failure, and failure of the primary containment by overtemperature-induced degradation of the electrical penetration assembly seals. The sequence of events is described in Volume 1; the material in this volume deals with the analysis of fission product noble gas and iodine transport during the accident. Factors which affect the fission product movements through the series of containment design barriers are reviewed. For a reactive material such as iodine, proper assessment of the rate of movement requires determination of the chemical changes along the pathway which alter the physical properties such as vapor pressure and solubility and thereby affect the transport rate. A methodology for accomplishing this is demonstrated in this report