Secondary hydriding experiments and simulation on zr-1%nb claddings

During LOCA (Loss of Coolant Accident) the sign of pressure difference on the two sides of cladding is reversed and the atmosphere is oxidative due to the steam. Subsequently the ballooning, burst and double-sided oxidation of the cladding can occur. Not only the oxygen but also the hydrogen can have an effect, it can diffuse into the alloy, making it brittle. In order to understand the behaviour of the cladding under these circumstances, secondary hydriding experiments were conducted in MTA EK. The alloy that was the subject of these experiments is the sponge-based Zr-1%Nb. We analysed the on-line measured data and the results of post-test examinations. And we have written a stand-alone program that contains the high temperature oxidation kinetics (mass gain and oxide layer growth) of such cladding. Simulations were made for all the experiments, and the experimental data was used for evaluation.