V型凹口对液态熔盐堆用核石墨构件应力分析的影响

摘要

本文利用了一个根据球床模块堆(Pebble Bed Modular Reactor,PBMR)用核石墨材料辐照性能数据编写的用户自定义材料模型(User defined Material model,UMAT),按照美国橡树岭国家实验室(Oak Ridge National Laboratory,ORNL)的液态燃料熔盐试验堆(Molten Salt Reactor Experiment,MSRE)用核石墨构件尺寸,为钍基熔盐堆(Thorium-based Molten Salt Reactor,TMSR)设计了一款方型核石墨构件.利用新编UMAT对该核石墨构件进行了初步的应力分析.分析结果表明,在没有预制裂纹的情况下辐照梯度越大核石墨构件中心区域最大主应力值越大,构件的断裂位置可能出现在构件中心位置处;对于有V型凹口预制裂纹的情况,应力集中部位均出现在预制裂纹尖端附近,这将可能导致裂纹尖端附近出现裂纹扩展,从而引起构件断裂失效.%Background: Nuclear graphite has served as neutron moderator, reflector and structural material in the liquid molten salt reactor (MSR) due to its excellent irradiation performance and mechanical properties at high temperature. During the life time of reactors, the properties of nuclear graphite will be changed due to the irradiation damage.Purpose: The aim is to studythe effect of V-shape notch on stress analysis of nuclear graphite component for liquid MSR. Methods:A user-defined material model (UMAT) was used to model the irradiation behavior of nuclear graphite component. The finite element method was used to develop numerical models for the stress analysis of nuclear graphite component.Results and Conclusion: The stress of nuclear graphite component increases as the irradiation gradient. What's more, the stress results of nuclear graphite component without crack and with V-shape crack are different. In the absence of a V-shape crack, the fracture position of the square-shaped graphite component may occur at the center of the structure. In the case of having a V-shape crack, the crack propagation may occur near the crack tip of the nuclear graphite component, which may cause fracture failure of the component.