Investigation of Multifarious Zircaloy-Water Oxidation Models on Core Degadation in a Typical SBO Accident

Cladding oxidation is a particularly important process which can affect the process of core melting. Synchronously, hydrogen released from zircaloy-water reaction is a threat to the integrity of containment. Up to now, multifarious zircaloy-water oxidation models are applied in different severe accident analysis programs. In order to investigate the influence of different cladding oxidation models on the core degradation process, a station blackout (SBO) accident model of CPR1000 nuclear power plant (NPP) was established and simulated by modifying the cladding oxidation model in this work. Five oxidation relations were chosen for evaluating thermal hydraulic, metal oxidation and core degradation analysis. Thermal hydraulic characteristics of five types remain consistent before core oxidation. For more concerned hydrogen production, the results show that the ratio of the maximum hydrogen production to the minimum is approximately 2.5 times in comparison of the different oxidation models. Four core nodes temperature distributions at different time points are selected to analyze the core node degradation process, which can help readers understand the effect of different models on core degradation more intuitively. The oxidation heat generated is consistent with that of hydrogen production, indicating that the core degradation time in the case of less hydrogen produced is delayed than that of more hydrogen produced. It follows that different oxidation models have great influence on the core oxidation behavior, which is of great significance to understand different oxidation models of zircaloy and the core degradation behavior of severe accident. It is critical to choose the appropriate model to simulate the whole severe accident.