Fission product transport analysis in a loss of decay heat removal accident at Browns Ferry

This paper summarizes an analysis of the movement of noble gases, iodine, and cesium fission products within the Mark-I containment BWR reactor system represented by Browns Ferry Unit 1 during a postulated accident sequence initiated by a loss of decay heat removal (DHR) capability following a scram. The event analysis showed that this accident could be brought under control by various means, but the sequence with no operator action ultimately leads to containment (drywell) failure followed by loss of water from the reactor vessel, core degradation due to overheating, and reactor vessel failure with attendant movement of core debris onto the drywell floor. The analysis of fission product transport presented in this paper is based on the no-operator-action sequence and provides an estimate of fission product inventories as a function of time within 17 control volumes outside the core, with the atmosphere considered as the final control volume in the transport sequence. The paper includes discussion of fission product transport calculation features, control volumes, loss of decay heat removal accident sequence, and results, i.e., predicted radioactive inventories in major reactor zones