Study on breakaway oxidation of Zry-4 fuel cladding

Negyesi, M.

This study deals with high-temperature steam oxidation behavior of Zry-4 fuel cladding. The experimental conditions correspond to the loss of coolant accident (LOCA) of LWRs. Oxidation tests were carried out at 1273 K employing two experimental techniques. The effect of the heat-up conditions on the subsequent isothermal oxidation rate were investigated. Furthermore, the effect of specimen surface roughness on the oxidation behavior was treated. The oxidation rate during the isothermal exposure was substantially suppressed at higher degrees of oxidation upon the heat-up. Consequently, the well-known "breakaway" effect, which results in accelerated oxidation rate, was found to be significantly delayed. The effect of the surface roughness on the oxidation behavior appeared to be rather minor under the test conditions of this study. The effect of the degree of oxidation upon the heat-up showed to be crucial and needs to be further addressed when evaluating the "breakaway" effect.