Release of Iodine from Defective Fuel Elements Following Reactor Shut-down

Data from a reactor operating with a single defective fuel element were used to develop a physically based model for describing the increased release of iodine to the primary coolant following reactor shutdown. Transport of iodine from the fuel-to-sheath gap of the element to the primary coolant is described by a diffusion process. The model has been used to predict the timing of the increased release.