Using LEU+Th mixed oxide fuel in CANDU reactors

Thorium-based fuel alternatives for PHWR/CANDU were extensively explored in the last decades, given the Thorium economic benefits and CANDU reactors flexibility. Both 37-and 43-element bundles were studied in this paper. The uranium enrichment ranged between 5 and 10 wt% U235, while the Th/U ratio was 1.5 ÷ 2.333. The (LEU+Th)O2 fuel bundles are supposed to be loaded in every channel of the CANDU core, in a homogenous "once-through Thorium" (OTT) core. Transport cells calculations were performed for the (LEU+Th)O2 fuel using the lattice codes DRAGON and WIMS and the associated nuclear data library based on ENDF/B-VII. The mixed oxide fuel is meant to replace the CANDU one, therefore key features were investigated to assess its economic performances: maximum burnup, power peaking factors, relative fissile yield and utilisation. The results are encouraging, due to this fuel potential to reach higher fuel burnup. (authors)