核破砕中性子源水銀標的容器の材料劣化評価に対する押込み試験技術の適用

抄録

Irradiation damage is one of the main factors determining the lifetime of the mercury target vessel for spallation neutron source in J-PARC. In order to understand material degradation of the used vessels, it is planned to conduct an evaluation using inverse analyses with indentation tests on the structural materials of the used vessels and numerical experiments. This evaluation technique was applied to two kinds of ion-irradiated materials with different displacement damage doses, in which the irradiation condition was simulated. It could be confirmed that the ultimate strength increased, and the total elongation decreased with increasing irradiation. These trends are similar to the material degradation behaviors which have been reported by using small specimen’s tensile tests as taking the scatters into account. Furthermore, the decrease in the total elongation with increasing temperature and the fatigue strength of the irradiated materials are discussed because the vessels are subjected to repeated thermal load, and the temperature of the vessel is estimated to be over 140 °C at the rated maximum beam power.