Study on in-core behavior of PWR fuel under power transient; Influence of waterside corrosion

Yanagisawa, Kazuaki

(1)The waterside corrosion for the pressurized PWR fuel had no effect on the fuel failure occurred by the ballooned/rupture mechanism but that for the unpressurized PWR fuel had a significant effect to preventing the fuel from the failure occurred by the melt/brittle mechanism. The corroded film tended to minimize the temperature gradient across the cladding, to prevent the additional oxide formation and to reduce the hoop stress raised during the quench. As a result, the failure threshold of the corroded fuel was higher than that of the standard fuel. (2) The peak axial strain for the pressurized fuel increased with the increase of the oxide film, where the maximum was 4% for the 40 micron oxide film. However, the peak axial strain for the unpressurized fuel was within 1% irrespective to the oxide film thickness.