Formation of partially constrained precipitates such as hydride blisters and oxide nodules have been reported on surfaces of Zr-alloy components of pressurised heavy water reactors and is associated with a large increase in volume. Such a change in volume imposes large stresses in the material surrounding the precipitate and may facilitate stable crack growth through delayed hydride cracking. In this work, the stress field of the partially constrained precipitates with different depth and aspect ratio has been computed using a finite element method. The computed stress field is used to predict the region in the matrix in which radial hydride is likely to form and fracture, by taking into consideration grain-size, texture and multi-axial state of stress. For a hypothetical crack just below the precipitate, stress intensity factors are estimated using material properties for both unirradiated and irradiated pressure tube materials. The results are compared with the threshold stress intensity factors required for crack growth due to delayed hydride cracking.

据报道，在加压重水反应堆的Zr合金部件表面上形成了部分受约束的沉淀物，例如氢化物水泡和氧化物结核，这与体积的大幅增加有关。体积的这种变化在沉淀物周围的材料中施加了很大的应力，并可能通过延迟的氢化物开裂而促进稳定的裂纹扩展。在这项工作中，使用有限元方法计算了具有不同深度和纵横比的部分受约束的析出物的应力场。考虑到晶粒尺寸，织构和应力的多轴状态，计算出的应力场用于预测基体中可能形成放射状氢化物并破裂的区域。对于在析出物正下方的假想裂纹，应力强度因子是使用未辐照和辐照压力管材料的材料属性估算的。将结果与因氢化物开裂延迟而导致裂纹扩展所需的阈值应力强度因子进行比较。