Composition adjustment on direct use of spent pressurized water reactor fuel in CANDU

In the DUPIC fuel cycle, spent pressurized water reactor (PWR) fuel is refa bricated as a DUPIC fuel by a dry process. Because the spent PWR fuel compo sition depends on the initial enrichment and burnup conditions of PWR fuel, the composition of DUPIC fuel is not uniquely defined. To reduce the effec ts of such a composition heterogeneity on core performance, an adjustment o f DUPIC fuel composi tion was studied. The composition adjustment was made in two steps: mixing two spent PWR fuel assemblies of higher and lower Pu c ontents and blending in fresh uranium with the mixed spent PWR fuels. Becau se the fuel and core performances depend on both the absolute amount of fis sile isotopes and the ratio of major fissile isotope contents, a parametric study was performed to determine the reference compositions of U-235 and P u-239. The reference enrichments of U-235 and Pu-239 were determined such t hat the DUPIC core performance is comparable to that of a natural uranium c ore with high spent PWR fuel utilization and low fuel cycle cost. Under thi s condition, it is possible to utilize 90% of spent PWR fuels as the DUPIC fuel formula. On average, the amounts of slightly enriched and depleted ura nium used for blending correspond to 8.6 and 10.6%, respectively, of the ma ss of candidate spent PWR fuels.