核工程石墨断裂力学研究进展

s main candidates for Gen- nuclear power reactors,both high temperature gas cooled reactors and molten salt reactors use nuclear graphite as a neutron moderator and core structural material.During the operation of nuclear reactors,nuclear graphite will withstand common mechanical loads,thermal stresses under different operating conditions,radiation deformation and seismic actions,resulting in complex stress effects on the graphite components.As micro-damage inside the material continues to accumulate,local stress concentration at keys,grooves,and other discontinuities can even induce macroscopic cracks,which will affect the dimensional integrity of the entire core structure and threaten the safety of the reactor.Therefore,it is necessary to study the damage and fracture mechanics characteristics of nuclear graphite,which can improve the reliability of safety assessment of core structure.This paper first introduces the research status of fracture mechanics of nuclear graphite from the following aspects:material failure criteria,fracture criteria,R-resistance curve,nonlinear fracture mechanics models,and multi-scale analysis methods.Then,the standard test methods used to determine the fracture parameters of nuclear graphite are summarized,and the research progress is reviewed in conjunction with commonly used test methods.Finally,the future development trend of fracture mechanics research on nuclear graphite is prospected from three aspects:the impact of service environments,characterization of fracture process zone,and size effects.This study can provide some reference for proposing or improving fracture mechanics models of nuclear graphite,a basis for selecting experimental methods to obtain fracture parameters of nuclear graphite,and provide ideas for the direction of research on fracture mechanics of nuclear graphite.