Neutronic and burnup characteristics of potential dual‐cooled annular (Th‐233U‐235U)O2 fuel for the advanced pressurized water reactors: An assembly‐level analysis

Summary Many efforts are now being made to ensure nuclear power plant safety and efficiency. One of these is the use of dual‐cooled annular fuel, which is an internally and externally cooled annular fuel with many advantages in heat transfer characteristics and neutron thermalization. Another is the tendency to use thorium‐containing fuel to extend the fuel cycle and reduce plutonium production. Hence, in this study, the performance of dual‐cooled annular fuel fueled by a new suggested thorium‐based fuel, namely (Th‐233U‐235U)O2, has been presented and investigated from a neutronic point of view in an AP1000 reactor assembly. The neutronic and safety properties of the envisaged dual‐cooled annular assemblies are compared to those of two hypothetical reference assemblies fueled with UO2 and (Th‐233U)O2. The primary neutronic goal is to achieve a longer cycle length than the proposed reference assemblies while retaining or improving safety parameters over the reference assemblies. The obtained results show that the studied dual‐cooled annular assemblies have a longer criticality period than the reference designs. Other safety parameters, such as the power peaking factor, the delayed neutron fraction, and the moderator and fuel temperature coefficients, demonstrate that dual‐cooled annular assemblies have favorable safety parameters compared to UO2 or (Th‐233U)O2. However, this analysis would benefit from a more detailed burnup simulation based on a full core modeling, as well as a comprehensive thermal‐hydraulic analysis in conjunction with a neutronic analysis. This paper presents a neutronic feasibility analysis of using (Th‐233U‐235U)O2 fuel in some proposed dual‐cooled assemblies for fueling the next generation of advanced pressurized water reactors, such as Westinghouse Electric Company's AP1000 design. The effect of (Th‐233U‐235U)O2 fuel and suggested assemblies on the variation of multiplication factor and thus discharge burnup is first investigated in this paper. Other critical safety parameters' behavior has also been evaluated and compared to two references design fueled by UO2 or (Th‐233U)O2. Based on the analysis methods and results, the use of (Th‐233U‐235U)O2 fuel in dual‐cooled annular assemblies can achieve higher discharge burnup and favorable safety coefficients. Other important results have been presented and discussed in the paper