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Reactor Physics Assessment of Thick Silicon Carbide Clad PWR Fuels

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Master's thesis

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High temperature tolerance, chemical stability and low neutron affinity make silicon carbide SiC a potential fuel cladding material that may improve the economics and safety of light water reactors LWRs. Thick SiC cladding 0.089 cm is easier and thus more economical to manufacture than SiC of conventional Zircaloy Zr cladding thickness 0.057 cm. Five fuel and clad combinations are analyzed Zr with solid UO2 pellets, reduced fuel fraction thick SiC Thick SiC with annular UO2 pellets, Thick SiC with solid UO2BeO pellets, reduced coolant fraction annular fuel with thick SiC Thick SiC RCF, and Thick SiC with solid PuO2ThO2 pellets. CASMO-4E and SIMULATE-3 have been utilized to model the above in a 193 assembly, 4-loop Westinghouse pressurized water reactor PWR. A new program, CSpy, has been written to use CASMOSIMULATE to conduct optimization searches of burnable poison layouts and core reload patterns. All fuelclad combinations have been modeled using 84 assembly reloads, and Thick SiC clad annular UO2 has been modeled using both 84 and 64 assembly reloads. Dual Binary Swap DBS optimization via three Objective Functions OFs has been applied to each cladfuelreload case to produce a single reload enrichment equilibrium core reload map. The OFs have the goals of minimal peaking, balancing lower peaking with longer cycle length, or maximal cycle length. Results display the tradeoff between minimized peaking and maximized cycle length for each cladfuelreload case. The presented Zr reference cases and Thick SiC RCF cases operate for an 18 month cycle at 3587 MWth using 4.3 and 4.8 enrichment, respectively. A 90 capacity factor was applied to all SiC cladding cases to reflect the challenge to introduction of a new fuel. The Thick SiC clad annular UO2 84 reload cores and Thick SiC UO2BeO exhibit similar reactor physics performance but require higher enrichments than 5.

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  • Inorganic Chemistry

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