Fuel cooling under steam venting conditions

A new approach to analyzing the degradation of fuel cooling during severe accidents in CANDU reactors is presented. Thermal-hydraulic models are developed that quantify the process of coolant stratification and the depletion of liquid inventory in fuel channels. These models are particularly applicable to small loss of coolant accidents accompanied by failure of emergency coolant injection (LOCA/LOECI). Heatup of the fuel and pressure tubes under stratified conditions in the fuel channels is modelled and, coupled with a simple, conservative fission product release model, enables scoping assessments of radioactivity release from the fuel to be performed