SEU 43 extended burnup fuel performance from safety viewpoint

Presently, INR Pitesti is developing an advanced CANDU fuel, SEU43 (Slightly Enriched Uranium fuel bundle with 43 elements). Compared with the current design, SEU43 will have higher power capability and higher burnup potential. Fuel burnup with 1.2 percent SEU is about 22 MWd/kg U, which is three times the burnup usually achieved in CANDU-6 reactors fuelled with natural uranium. SEU 43 fuel bundles have reduced outer element linear powers, providing an opportunity to increase the power output of the CANDU 6 reactor. In this study, consequences of a postulated large loss of coolant accident (LOCA) were used as an indicator to determine the power increase. The power-uprating potential was determined by increasing the power in a SEU43 fuelled channel to the point where the predicted consequence in terms of fuel behaviour are the same as the consequences for a 37 -element fuelled channel operating at current nominal powers. This paper describes the effect of the design changes of SEU43 bundle on CANDU-6 reactor safety and the analysis performed to determine the increase in nominal reactor power for a full core of SEU43 fuel so that consequences of postulated large break loss of coolant accidents (LOCA) are not increased relative to a 37-element bundle fuelled core. An analysis of the consequences of a large break LOCA will provide a limit on the reactor power increase from the current nominal power. Because of the lower outer element linear power ratings of SEU43 fuel, as compared with those of 37-element fuel, there is a potential for an increase in reactor power without a decrease in safety margins. (authors)