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Wakui, Takashi; Saito, Shigeru; Futakawa, Masatoshi; Sakai, Tomoki*; Mori, Kotaro*
no journal, ,
One of dominant factors to determine the lifetime of the structural components used under high irradiation environment is radiation damage. The indentation test will be applied to understand the degradation in mechanical properties. In this study, the technique evaluating mechanical properties from the combination of the indentation test with inverse analysis and the numerical tensile experiment is proposed. In order to confirm that this technique can evaluate changes in mechanical properties, it was applied to ion irradiated 316L stainless steels. The numerical model consists of multi layers whose mechanical properties are dependent on the DPA distribution. The material constants of each layer were identified. The numerical tensile experiments were conducted by using identified material constants. These results are compared with the PIE results of SNS. As the results, it was confirmed that this technique is effective to evaluate the mechanical property degradation due to irradiation.
Meigo, Shinichiro; Iwamoto, Yosuke
no journal, ,
The material displacement damage index of displacement per atom (dpa) is obtained by the particle flux and the displacement cross section. However, the experimental data of the displacement cross section was scarce, so our group conducted the measurement using proton beams. So far, the experimental data of protons up to 30 GeV were obtained using FFAG at Kyoto University, RCNP at Osaka University, and RCS and MR at J-PARC. In the projectile protons energy region above several GeV, it was found that the cross section was almost constant regardless of the energy. This tendency is against the expectation because the heat deposition given by the proton increases as projectile energy due to the relativistic theory. We conducted the experiment with 120 GeV protons at Fermi National Laboratory (FNAL) to obtain the data for high-energy regions. The first experiment was successfully finished by February. The experimental data will be presented as a rapid communication. We will experiment with 430-GeV protons at HiRadMat in CERN to extend the energy region. Additionally, a new facility plan at J-PARC with 400-MeV protons to study material radiation damage will be presented in this talk.
Naoe, Takashi; Wakui, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Saruta, Koichi; Teshigawara, Makoto; Haga, Katsuhiro
no journal, ,
A mercury target vessel installed in the J-PARC, made of 316L stainless steel, with 3 mm thick at the beam window is damaged due the cavitation caused by the proton beam-induced pressure waves. To prolong the lifetime of the vessel, we have adopted the damage mitigation techniques consisting of surface improvement, gas microbubble injection, and double-walled beam window structure. To monitor the acoustic vibration of the vessel by the pressure waves, the laser Doppler vibrometer and microphone has been installed in the helium vessel and correlation between the proton beam power and gas microbubble injection were investigated during the beam operation. Beam window of the used vessel was cut to inspect the cavitation erosion on the interior surface and validate the effect of mitigation techniques. In the workshop, recent progress of the cavitation damage inspection, the correlation between the beam induced acoustic vibration and damage, and beam power dependency on damage will be presented.
Saito, Shigeru; Wakui, Takashi; Tsukada, Manabu*; Yamashita, Naoki; Sano, Naruto; Dai, Y.*; Futakawa, Masatoshi
no journal, ,
Post irradiation examination (PIE) of the MEGAPIE (MEGAwatt Pilot Experiment) project has been performed on the samples allotted to JAEA. In the experiments, specimens for tensile test are prepared by taking from the component of the MEGAPIE target such as the beam window (BW) of T91. The irradiation temperatures were about 250 
C and the displacement-damage levels ranged between 0.75 and 1.74 dpa. After the tensile tests, SP specimens are prepared from the grip part of the tested tensile specimens. Testing temperatures for SP tests ranged from -150C to 250C. From the area of the load-displacement curves (LDC) of the SP tests, ductile-brittle transition temperature (DBTT) was evaluated. Comparison of these data with previous STIP data showed similar values. In addition, the yield stress and ultimate tensile strength were calculated from the SP tests results by applying the conversion equation. These were compared with the results of the tensile tests and found to be in good agreement.