Development of evaluation method of residual stress for graphite component of HTGR by micro-indentation method, 1 (Contract research)

Sumita, Junya ; Shibata, Taiju ; Tada, Tatsuya; Sawa, Kazuhiro

In High Temperature Gas-cooled Reactor (HTGR), graphite materials are used as core internal structural components. The neutron irradiation and thermal gradient induce residual stress of graphite components which is a crucial factor to determine the lifetime of them. It is hence important to measure and assess the stress for lifetime extension of the components. Since the residual stress gives characteristics change to the micro-indentation behavior, it is possible to evaluate the residual stress to measure indentation depth. Therefore, in order to evaluate the change of residual stress of graphite components non-destructively, we are now developing the indentation method to evaluate it. This report showed the relationship between indentation depth and residual stress based on experimental data obtained by changing the stress condition of graphite specimen parametrically.