Fission Product Behaviour in the PHTS following Fuel Failure Occurrence: New Developments

Abstract

Recent studies using commercial reactor experience have shed more light on the behaviour of PHTS fission product evolution following failed fuel occurrence. Simulation capabilities of recently developed software tools such as STAR and VISUAL_DETECT permit characterization of failed fuel present in a Unit at any particular time and enable prediction of future evolution of the concentration of fission products in the PHTS. Also, empirical techniques have been developed for differentiating between iodine releases due to the initiation of a new fuel defect (or degradation of an existing one) from iodine spiking due to fuel-to-sheath gap washout.