Nuclear Core Design For A Small PWR Utilizing TRISO Fuel Embedded In SiC Matrix

TRISO coated particle has been successfully introduced in high temperature gas cooled reactor, it has the benefits of retaining fission products, high burnup, and proliferation resistance. which would have great potential using into small and medium sized reactors.With the help of CASMO-4E/SIMULATE-3 code package, this paper aims to combine the advantages of TRISO fuel concept with mature PWR technology to design a 350MWt small PWR core using TRISO particles embedded in SiC matrix. The fuel kernel of TRISO particle is initially UO2. On that basis, a small PWR core design utilizing TRISO fuel with MOX fuel kernel is conducted by replacing the UO2 fuel kernel with MOX fuel kernel. Core physical and safety margin analysis are performed for the two designed cores to ensure reactor core safety. In order to meet the requirements of small reactors, the objective of the core design is single batch refueling, long core life and soluble boron free operation.First, a benchmark calculation of CASMO-4E is perfonned with MCNP-4C benchmark code. By conducting TRISO fuel lattice calculations using CASMO-4E and MCNP-4C separately, and then comparing the k? deviations calculated with different fuel processing models, the effects on fuel homogenization calculation made by double heterogeneity of TRISO fuel is investigated. and thus the feasibility of CASMO-4E code to conduct TRISO fuel assembly calculation is verified. The calculation results show that for both the UO2 fuel kernel and MOX fuel kernel, the impacts on fuel homogenization calculation made by double heterogeneity of TRISO fuel are very small, and the kj, deviations are within 5‰. As a consequence. it is doable to calculate the TRISO fuel assembly with fuel homogenization model, namely CASMO-4E is proven feasible to conduct TRISO fuel assembly calculation.Then, with the purpose of core design and by using the CASMO-4E/SIMULATE-3 code package, TRISO fuel design and core basic design with UO2 fuel kernel are completed by discussing the properties using TRSIO fuel into PWR technology. Through adding Pu-240 into UO2 fuel kernel, arranging Gd2O3-UO2 rods and control rods in the core, core reactivity is effectively controled and soluble boron free operation is achieved. Subsequently, on the basis of UO2 fuel kernel core design, a small PWR core design of TRISO fuel with MOX fuel kernel is completed when replacing the UO2 fuel kernel by MOX fuel kernel in the core. The fuel rod picth is enlarged from 2.4cm to 2.5cm to soften the neutron spectrum. And with the proper design of Gd2O3-UO2 rods and control rods in the core, core reactivity is effectively controled and soluble boron free operation is achieved. The average discharge burnup of TRISO fuel cores with UO2 fuel kernel and MOX fuel kernel are 56.6MWd/kg and 57.6MWd/kg respectively, and both cores achieve six-year core life without refueling. Core physical and safety margin analysis indicate that, no matter with UO2 fuel kernel or MOX fuel kernel, both TRISO fuel core designs meet the safety requirements well, and the fuel temperatures are greatly reduced compared with conventional PWR's.