Abstract The ZrO2 oxide layers of Zr-based fuel claddings have been intensively studied to unveil their oxidation mechanisms in high temperature pressurized water. Nevertheless, there has been insufficient research on their mechanical properties, which are key factors determining the resistance to grid-to-rod fretting damage in normal Pressurized Water Reactor (PWR) operation. An experimental approach was applied to examine the tribological behavior of time-dependent oxide layers on both Zr cladding and grid, which were prepared in simulated PWR conditions for up to 360 days. It was found that the wear rate of pre-oxidized Zr cladding suddenly dropped with increasing oxide thickness of both the cladding and grid. The increase of surface roughness with oxide growth on the Zr-based grid could result in a rapid increase of wear damage by third-body abrasion. The well-developed columnar structure of the ZrO2 oxide layer could have a detrimental effect on the resistance to plastic deformation due to the enlarged grain size and relaxation of compressive residual stress by tetragonal to monoclinic ZrO2 transformation and crack formation. Consequently, ZrO2 oxide layers formed on fuel cladding and spacer grid under high temperature pressurized water show sufficient ductility to accommodate plastic deformation, which results in enhanced fretting wear resistance.

中文翻译：

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ZrO2 氧化层对核燃料棒微动磨损性能的影响

摘要 已经深入研究了 Zr 基燃料包壳的 ZrO2 氧化层，以揭示其在高温加压水中的氧化机制。然而，对其力学性能的研究还不够充分，而这些力学性能是决定正常压水堆 (PWR) 运行中栅-杆微动损伤阻力的关键因素。应用一种实验方法来检查 Zr 包层和网格上随时间变化的氧化层的摩擦学行为，这些氧化层在模拟 PWR 条件下制备了长达 360 天。结果表明，预氧化 Zr 包层的磨损率随着包层和格栅的氧化物厚度的增加而突然下降。Zr 基网格上随着氧化物生长而增加的表面粗糙度会导致第三体磨损造成的磨损损伤迅速增加。ZrO2 氧化层发达的柱状结构可能对抗塑性变形产生不利影响，这是由于四方向单斜 ZrO2 转变和裂纹形成导致的晶粒尺寸增大和压缩残余应力松弛。因此，在高温加压水下在燃料包壳和隔栅上形成的 ZrO2 氧化层显示出足够的延展性以适应塑性变形，从而增强了抗微动磨损性。ZrO2 氧化层发达的柱状结构可能对抗塑性变形产生不利影响，这是由于四方向单斜 ZrO2 转变和裂纹形成导致的晶粒尺寸增大和压缩残余应力松弛。因此，在高温加压水下在燃料包壳和隔栅上形成的 ZrO2 氧化层显示出足够的延展性以适应塑性变形，从而增强了抗微动磨损性。ZrO2 氧化层发达的柱状结构可能对抗塑性变形产生不利影响，这是由于四方向单斜 ZrO2 转变和裂纹形成导致的晶粒尺寸增大和压缩残余应力松弛。因此，在高温加压水下在燃料包壳和隔栅上形成的 ZrO2 氧化层显示出足够的延展性以适应塑性变形，从而增强了抗微动磨损性。