Comparison of two kinetic approaches for modeling of radial hydride fraction in zirconium-based fuel rod cladding

Theoretical models simulating the kinetics of the radial hydride fraction in the zirconium cladding of fuel rods are developed to predict their hydride embrittlement degree and to justify the safety regimes for the storage and handling of spent nuclear fuel. Currently, there are a number of kinetic models based on different assumptions, approximations and experimental datasets used for their verification. These models can be divided into two groups according to the assumption on how they define the radial hydride fraction fr precipitated at the current time step: directly from physically based equations (Approach 1) or through engineering correlations for the cumulative radial hydride fraction (Approach 2). The present study investigates the effect of this single assumption on the simulation results of kinetic models. It is shown that Approach 1 assumes a higher relative role for hydrides precipitated at low temperatures than Approach 2 in its current form.