Accident-Tolerant-Fuel Performance Analysis of APMT Steel Clad/UO₂ Fuel and APMT Steel Clad/UN-U₃Si₅ Fuel Concepts

While Zircaloy-based claddings have been the workhorse for the nuclear power industry for decades, they have also demonstrated problems, particularly regarding accident scenarios. Work has been performed to assess the viability of stainless steel–based cladding in traditional light water reactors. This paper assesses the reactivity penalty of moving to stainless steel cladding using Monteburns, while attempting to minimize this penalty by increasing the fuel pellet radius and decreasing the cladding thickness. Fuel performance simulations using BISON have also been performed to quantify gains or losses in structural integrity when moving to thinner, stainless steel claddings. Thermal and irradiation creep, along with fission gas swelling, thermal swelling, and fuel relocation, are accounted for in the models for both Zircaloy and stainless steel claddings. Additional models for the lower-oxidation stainless steel APMT are also invoked where available, with irradiation data for HT9 used as a fallback in the absence of appropriate models. In this study the isotopic vectors within each natural element are varied to assess potential reactivity gains if advanced enrichment capabilities were levied toward cladding technologies. Recommendations on cladding thicknesses for a robust cladding as well as the constitutive components of a less penalizing composition are provided.