Irradiation-induced property change of C/C composite for application of control rod elements of very high-temperature reactor (VHTR)

Shibata, Taiju ; Sumita, Junya ; Takagi, Takashi*; Makita, Taiyo*; Fujita, Ichiro; Sawa, Kazuhiro

VHTR is one of the Generation-IV reactor systems and being developed internationally. Since the core components in the VHTR will be used at severe temperature condition, it is important to develop heat-resistant ceramic composite material. JAEA is carrying out the application study on two-dimensional (2D-) C/C composite to the control rod of VHTR. 2D-C/C composite of CX-270G grade, graphitized at 2800 C, was used to evaluate the change of material properties by neutron irradiation. The samples were irradiated by JMTR at 600 C up to the neutron fluence of 8.210 n/m (E1.0MeV) corresponding to 1.2 dpa. The irradiation-induced dimensional change, thermal conductivity, coefficient of thermal expansion and Young's modulus were evaluated. The test results were evaluated in comparison with the irradiation database of graphite of JAEA. It was shown that the graphite database is effective to support the evaluation of the irradiation test results of the graphitized C/C composite.