Heat transfer effectiveness for cooling of Canadian SCWR fuel assembly under the LOCA/LOECC scenario

The effectiveness of heat transfer from the fuel rods to the moderator in a Canadian, pressure-tube type, Super-Critical Water-cooled Reactor (SCWR) has been assessed for the postulated loss-of-coolant accident (LOCA) coupled with the total loss of emergency core cooling (LOECC) event using the safety analysis code “SCTRAN”. A radiation heat-transfer model, including a two-dimensional heat conduction solution scheme, has been incorporated into the SCTRAN code for this assessment. The assessment result shows that the combined radiation heat transfer from the fuel rods to the fuel channel and natural convective heat transfer from the fuel rods to the steam are effective in removing decay heat for the LOCA/LOECC scenario. Maximum cladding temperatures of fuel rods in inner and outer rings of the fuel assembly in the highest-power channel are predicted at 1278°C and 1192°C respectively, which are lower than the melting point of the modified stainless-steel cladding. Sensitivity analyses of several analytical parameters on the predicted maximum cladding temperatures have been performed.