Cladding of nuclear fuel with iron based alloy: Penalty and solution

Abstract

Replacing zirconium-based alloys fuel cladding by that of iron in nuclear fuel of Light Water Reactors (LWRs) needs increasing the fuel enrichment to achieve the same core cycle length. The penalty of using iron based alloys fuel cladding in LWRs can be overcome by direct recycling of nuclear spent fuel in CANDU reactors. The problems associated with using zirconium-based alloys fuel cladding in LWRs is not significant in the case of CANDU reactors. This is because CANDU reactors discharge the spent fuel with low burnup which is in the withstand tolerance of zirconium-based alloys and the moderator acts as an effective heat sink in case of severe accident.The case studied in this research is direct recycling of the spent fuel discharged from the European Advanced Pressurized Water Reactor (EU-APWR) in CANDU-6 reactor. The calculations using MCNPX computational code showed that replacing fuel clad from zircaloy-4 to stainless steel-348 requires increasing the fuel enrichment from 4.95 %w U-235 to 6.8 %w U-235 with an increase of 37%. After direct spent fuel recycling in CANDU-6, the total burnup of the fuels cladded with zircaloy-4 and with stainless steel-348 are about 70 and 96 GWd/t, respectively with an increase of about 37% in the case of the fuel cladded with stainless steel which compensates the increase of the enrichment.