A Spent-Fuel Combination Method for Minimizing Composition Variability of DUPIC Fuel

A combination method of spent pressurized water reactor (PWR) fuel is proposed that adjusts the fuel composition for direct use of spent PWR fuel in Canada deuterium uranium (CANDU) reactors (DUPIC). This method reduces the composition heterogeneity (variation) of the DUPIC fuel caused by directly reusing spent PWR fuel as DUPIC fuel feedstock. In this study, a combination method was used to find the optimum mixture composition from the spent PWR fuel database by minimizing the composition variation of the major fissile isotopes ²³⁵U and ²³⁹Pu. The simulation results have shown that the combination method can reduce the composition variation of ²³⁵U and ²³⁹Pu to 0.11 and 1.40%, respectively, through assemblywise mixing operation only. It is also believed that the result could be improved further through a rodwise combination technique if the isotopic composition of each spent PWR fuel rod is known by direct measurement during the DUPIC fuel fabrication process.