Thermalhydraulics studies examining the feasibility for introducing slightly enriched uranium fuel into the Embalse CANDU reactor

A joint study on the technical feasibility of using 0.9% slightly enriched uranium (SEU) fuel in the Embalse CANDU reactor was performed by Atomic Energy of Canada Limited (AECL) and Nucleoeléctrica Argentina S.A. (NASA). The feasibility study focused on the following technical areas: reactor physics and fuel management, fuel performance, and safety. Part of the safety assessment involved detailed thermalhydraulics analyses of three accident scenarios for a full core of SEU fuel bundles: (i) slow loss-of-reactivity control (LORC) event, (ii) large-break loss-of-coolant accident (LBLOCA) with emergency core cooling system (ECCS) available, and (iii) end-fitting failure. Other accident scenarios possibly encountered during the demonstration irradiation exercise or transition core have also been examined. It is concluded that introducing SEU fuel into the Embalse CANDU reactor is feasible. Clear advantages (e.g., fuel cost saving, increase in fuel exit burnup, and reduction in spent fuel volume) have been identified. The reduction in maximum bundle powers and the shift of the maximum bundle-power location to the inlet of the channel for the SEU fuel improve operating and safety margins. These margins are higher with the CANFLEX SEU fuel than the 37-element SEU fuel, due to lower linear powers and improved thermalhydraulic design.