Modeling and simulation of hydrogen behavior in Zircaloy-4 fuel cladding

Multidimensional simulations of hydrides during fuel rod lifecycle

“…Hydrogen diffusion, precipitation, and dissolution were recently implemented in BISON; the model is described in detail in [13]. In this work we expanded upon the existing model so that it can be used for lifecycle analysis of fuel rods.…”

“…In BISON, the user specifies a fixed instantaneous hydrogen pickup fraction, so that the average total concentration of hydrogen C H (including dissolved hydrogen and hydrogen as ZrH x ) in the cladding is roughly proportional to the thickness of the oxide layer [13]:…”

“…2 can be approximated by Thus, the flux boundary condition for hydrogen diffusion into the cladding is nearly proportional to the growth rate of the oxide layer. This hydrogen pickup model was implemented in BISON by [13] along with a model for oxidation. However, BISON includes several oxidation models that are independent of the hydrogen pickup model and that encompass normal operation as well as accident conditions such as loss of coolant accidents (LOCA).…”

“…We have therefore coupled the hydrogen pickup model directly to the existing oxidation models in BISON. For brevity, we only describe the most commonly used oxidation model that is used during normal irradiation; this is the same EPRI/KWU/CE model that was used by [13].…”

Integrated Computational Modeling of Water Side Corrosion in Zirconium Metal Clad Under Nominal LWR Operating Conditions

“…Existing models 41 for the hydrogen behavior (diffusion and hydride precipitation) in Zr use simplified expressions for reaction (precipitation and dissolution) rates to solve for the hydrogen concentration in the metal matrix (solid solution form) and the total concentration of hydrogen in all hydrides without regard to their sizes. While the partition of hydrogen into the matrix and the hydrides is important, the existing models do not provide more detailed information, such as the number density and the size distribution of the hydrides, which is valuable to mechanics modeling and failure probability analysis of the fuel-cladding system.…”