Effect of zirconium fuel cladding oxidation on water boiling in PWR: A molecular dynamics study

Abstract

Clarifying the mechanism of water boiling on the zirconium fuel cladding in the pressurized water reactor (PWR) is crucial for the safety and design of reactors. The underlying mechanism remains largely unclear so far. In this study, the molecular dynamics method is employed to investigate the boiling behavior of water on zirconium (Zr) surfaces with varying degrees of oxidation (pure Zr, perfect zirconia ZrO₂, and zirconium reconstructed through oxidation reaction Zr-O). The phase change behavior of water, the accompanying heat transfer characteristics at the solid-liquid interface, and the energy distribution on different surfaces are analyzed under two heating temperatures of 600 K and 650 K. The results indicate that the oxidation of Zr significantly influences the phase change behavior of water. Compared to Zr, the non-uniform distribution of oxygen atoms on the Zr-O surface increases the thermal resistance of both the solid conductive layer and the solid-liquid interface, whereas the ordered arrangement of oxygen atoms in ZrO₂ solid enhances heat transfer at the solid-liquid interface. The efficient heat transfer at the solid-liquid interface on ZrO₂ allows water molecules to gain greater kinetic energy to overcome the potential energy barrier for explosive boiling. This study provides a theoretical foundation for understanding the effect of oxide deposition of Zr cladding on water boiling in PWR.