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Double diffusive dissolution model of UO$$_{2}$$ pellet in molten Zr cladding

Ito, Ayumi*; Yamashita, Susumu   ; Tasaki, Yudai ; Kakiuchi, Kazuo ; Kobayashi, Yoshinao*

The rapid dissolution of UO$$_{2}$$ in molten Zr that could occur during fuel-cladding liquefaction at high temperatures and its kinetics were reformulated considering the convective mass transfer and the chemical effect at the UO$$_{2}$$/Zr interface. The mass transfer coefficient of U was obtained as a correlation including the aspect ratio term by CFD analysis. To explain the gap between the rapid dissolution rate observed in the experiments and the density-driven convective mass transfer, we introduced an idea in which the eutectic melting at the UO$$_{2}$$/Zr interface promotes the grain detachment owing to infiltration of the U-Zr-O liquid into the UO$$_{2}$$ grain boundaries. The developed model was validated with UO$$_{2}$$-Zr crucible experiments at 2273 and 2373 K. The calculated mass percentage ratios of U/Zr agreed with the measurements and the transition times from rapid saturation to precipitation were consistent with the metallographic observations.



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Category:Nuclear Science & Technology



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