Analysis of Fuel End Temperature Peaking

Abstract

During normal operation and refuelling of CANDU®¹ fuel, fuel temperatures near bundle ends will increase due to a phenomenon called end flux peaking. Similar phenomenon would also be expected to occur during a postulated large break LOCA event. The end flux peaking in a CANDU® fuel element is due to the fact that neutron flux is higher near a bundle end, in contact with a neighbouring bundle or close to heavy water coolant, than in the bundle mid plane, because of less absorption of thermal neutrons by Zircaloy or heavy water than by the UO₂ material. This paper describes Candu Energy experience in analysing behaviour of bundle due to end flux peaking using fuel codes FEAT, ELESTRES and ELOCA².