AP-1000 fuel assembly performance with UO₂ and UO₂/U₃Si₂ fuels and silicon carbide cladding from the viewpoint of neutronics

ABSTRACT

Accident Tolerate Fuels have been highly researched since the Fukushima disaster. To improve the safety of the AP-1000 fuel assembly, an advanced fuel, UO₂/U₃Si_2, is considered. In addition, the silicon carbide (SiC) cladding that has the capability of reducing oxidation is compared with the baseline Zircaloy for AP-1000 fuel assembly along with the two different fuel cases (UO₂ and UO₂-U₃Si₂). The present study focuses on the neutronic performance of the UO₂/U₃Si₂ fuel and thus the main neutronic parameters such as the fuel cycle length, pin power distribution, atom density evolution of main isotopes, and the reactivity feedback coefficients are evaluated. An increase of 6.72% in the criticality period is introduced when 70%UO₂-30%U₃Si₂ fuel with SiC cladding is considered. The pin power peaking factors, fuel temperature coefficients, and moderator temperature coefficients of the proposed fuel result in very few changes. For instance, the maximum pin power distribution difference between 70%UO₂-30%U₃Si₂ and UO₂ fuel with SiC cladding is 0.001, which is negligible. Thus, its performance is as good as the traditional UO₂ fuel from the neutronic aspects and controlling power distribution.

KEYWORDS:

• UO₂/U₃Si₂
• silicon carbide
• neutronic parameters
• criticality period
• power distribution

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Notes on contributors

Farrokh Khoshahval

Farrokh Khoshahval is with Reactor and Nuclear Safety Research School, Nuclear Science and Technology Research Institute (NSTRI). He received his BSc degree in Electrical Engineering and Master’s and PhD degrees in Nuclear Engineering from Shahid Beheshti University, Iran. His research areas include neutronic, thermal-hydraulic analysis, nuclear fuel management, and heuristic optimization methods.