Vacancies and interstitial type dislocation loops of two fusion reactor candidate materials (V-4Cr-4Ti and F82H) after fission and fusion neutron irradiation were studied by positron annihilation lifetime spectroscopy. Fusion neutron irradiation was performed in the FNS of JAERI, and fission neutron irradiation was performed in the KUR of Kyoto University. The neutron irradiation dose was about 10-6 to 10-4dpa, and the irradiation temperatures were room temperature and 673K. In the irradiation at room temperature, the defects (mainly dislocation loops) in both alloys were detected even at a low irradiation dose of 10-6dpa and the mean lifetime of positrons increased as the irradiation dose increased. The effects of the fission and fusion neutron irradiation on the point defect production were almost the same if they were compared at the same dpa. This could be explained by the fact that the number of sub-cascades, which was an important factor for the defect formation at room temperature, was proportional to dpa in these metals. In contrast, an effect of cascade size was found for the irradiation at 673 K. Dislocation loops were detected only in the fusion-neutron-irradiated F82H at 673 K.

Point Defect Formation in V-4Cr-4Ti and F82H Irradiated with Fission and Fusion Neutrons. K.Sato, T.Yoshiie, Q.Xu, Y.Satoh, E.Wakai, C.Kutsukake, T.Nishitani: Materials Transactions, 2005, 46[3], 445-9