Nuclear fuel rod cladding oxidation and hydrogen production model based on diffusion theory in a multiphase environment of ZrO₂, α-Zr(O), and β-Zr at high temperatures (1273 K–1800 K)

This paper proposes a mathematical model for the oxidation process of zirconium under the theory of oxygen diffusion in Zircaloy. The model considers ZrO₂, α-Zr(O), and β-Zr phases at high temperatures (1273 K–1800 K) in an equivalent fuel rod. The model also considers the heat transfer phenomenon, the decay heat after shutdown, the heat released by the oxidation reaction, the loss of coolant water in the core and the heat transported by the steam produced. A computer program was coded in the C++ environment. The accident scenario of a BWR short term station blackout was simulated with this model. The results are compared with the ones obtained using MELCOR and RELAP/SCDAP codes. The comparison yielded an approximate result for total hydrogen production at the end of the simulation, with a difference of −2.7% compared with RELAP/SCDAP, and a difference of −1.11% with MELCOR. With the present model it is possible to calculate the growth of ZrO₂, α-Zr(O), and β-Zr phases through the cladding.