CFD simulation of the zircaloy/steam oxidation in the CANDU fuel channel experiments: CS28-2

Oxidation of zircaloy cladding exposed to a high temperature steam is an important phenomenon for the safety analysis of CANDU reactors during a postulated loss-of-coolant accident (LOCA), since this zircaloy/steam reaction is highly exothermic and results in a hydrogen production. The CS28-2 high temperature experiment represents this accident scenario well. As a part of a CFD (Computational Fluid Dynamics) simulation for the CS28-2 experiment, a zircaloy/steam reaction model is implemented into a commercial CFD code, CFX-10, because the present version of the CFX-10 code does not include a surface reaction model. First, the present oxidation model for the CFX-10 code is validated against the model correlations implemented into the CFX-10 code, and then applied to the simulation of the CS28-2 experiment. The CFX predictions of a temperature rise in the heater rods are compared with the temperature measurements to confirm the validity of the oxidation heat release calculated by the present model. Furthermore, the prediction of a hydrogen generation as a byproduct of the oxidation reaction is validated against the amount of the collected hydrogen in the experiment. (author)