Reactivity Control Method for Direct Use of Spent Pressurized Water Reactor Fuel in CANDU Reactors (DUPIC)

A method to reduce the fuel composition heterogeneity effect on the core performance parameters has been studied for DUPIC fuel, which is made from spent pressurized water reactor (PWR) fuel by a dry refabrication process. This study focuses on the reactivity control method, which uses slightly enriched, depleted, or natural uranium to minimize the additional cost on the manufacturing of DUPIC fuel, when adjusting the excess reactivity of the spent PWR fuel. To reduce the variation of isotopic composition of the DUPIC fuel, interassembly mixing operations were assumed to be carried out three times. Three options have been considered: reactivity control by slightly enriched and depleted uranium, reactivity control by natural uranium for high-reactivity spent PWR fuels, and reactivity control by natural uranium for intermediate-reactivity spent PWR fuels. The results of this study have shown that the reactivity of DUPIC fuel can be tightly controlled with the minimum amount of fresh uranium feed. For reactivity control by slightly enriched and depleted uranium, all spent PWR fuel can be utilized as DUPIC fuel, and the fraction of fresh uranium feed is 3.4% on the average. For reactivity control by natural uranium, ~88% of spent PWR fuel can be utilized as DUPIC fuel when intermediate-reactivity spent PWR fuels are used, and the amount of natural uranium feed needed to control the DUPIC fuel reactivity is negligible.