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Wakui, Takashi; Takagishi, Yoichi*; Futakawa, Masatoshi
Zairyo, 73(6), p.520 - 526, 2024/06
Cavitation damage is one of crucial issues to predict the structural endurability of the mercury targets for highly intensive pulsed neutron sources. Based on the comparison with numerical simulation on the pit shape and results of the basic test, the cavitation bubble collapsing was assumed to be resulted in the micro jet with the impact velocity of 160-200 m/s, imposing then impact pressure of 3-4 GPa at the input power simulating the operation condition in the mercury targets. It was statistically understandable that cavitation damage evolution was proportional to 4th power of the input power approximately, as taking the aggressivity of cavitation bubbles, the distribution of the maximum diameter of grown bubbles and the space of distribution of bubbles in the mercury into account.
Wakui, Takashi; Takagishi, Yoichi*; Futakawa, Masatoshi; Tanabe, Makoto*
Jikken Rikigaku, 23(2), p.168 - 174, 2023/06
Cavitation damage on the inner surface of the mercury target for the spallation neutron source occurs by proton bombarding in mercury. The prediction method of the cavitation damage using Monte Carlo simulations was suggested taking variability of the bubble core position and impact pressure distribution into account. The impact pressure distribution was estimated using the inverse analysis with Bayesian optimization was conducted with comparison between cavitation damage distribution obtained from experiment and the cumulative plastic strain distribution obtained from simulation. The average value and spread of maximum impact pressure estimated assuming the Gaussian distribution were 3.1 GPa and 1.2 
m, respectively. Simulation results reproduced experimental results and it can be said that this evaluation method is useful.
Iwata, Keiko; Hata, Kuniki; Tobita, Toru; Hirota, Takatoshi*; Takamizawa, Hisashi; Chimi, Yasuhiro; Nishiyama, Yutaka
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 7 Pages, 2021/07
Onizawa, Kunio; Suzuki, Masahide
JSME International Journal, Series A, 47(3), p.479 - 485, 2004/07
In the structural integrity assessment of reactor pressure vessel, fracture toughness values are estimated by assuming that the radiation effect on fracture toughness is equivalent to that on Charpy properties. Therefore, it is necessary to establish the correlation between both properties especially on irradiation embrittlement. In this paper, we present the fracture toughness data obtained by applying the master curve approach that was adopted recently in the ASTM test method. Materials used in this study are five ASTM A533B class 1 steels and one weld metal. Neutron irradiation for Charpy-size specimens as well as standard Charpy-v specimens was carried out at the Japan Materials Testing Reactor. The shifts of the reference temperature on fracture toughness due to neutron irradiation are evaluated. Correlation between the fracture toughness reference temperature and Charpy transition temperature is established. Based on the correlation, the optimum test temperature for fracture toughness testing and the method to determine a lower bound fracture toughness curve are discussed.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Tsai, C.-C.*; Ishikura, Shuichi*; Ikeda, Yujiro
JAERI-Research 2003-005, 70 Pages, 2003/03
JAERI-Research-2003-005.pdf:12.08MB
A liquid-mercury target system for the MW-scale target is being developed in the world. The moment the proton beams bombard the target, stress waves will be imposed on the beam window and pressure waves will be generated in the mercury by the thermally shocked heat deposition. Provided that the negative pressure generates through its propagation in the mercury target and causes cavitation in the mercury, there is the possibility for the cavitation bubbles collapse to form pits on the interface between the mercury and the target vessel wall. In order to estimate the cavitation erosion damage due to pitting, two types of off-line tests were performed: Split Hopkinson Pressure Bar (SHPB), and Magnetic IMpact Testing Machine (MIMTM). The data on the pitting damage at the high cycle impacts up to 10 million were given by the MIMTM. As a result, it is confirmed that the mean depth erosion is predictable using a homologous line in the steady state with mass loss independently of testing machines and the incubation period is very dependent on materials and imposed pressures.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Hino, Ryutaro; Date, Hidefumi*; Takeishi, Hiromasa*
International Journal of Impact Engineering, 28(2), p.123 - 135, 2003/02
JAERI is carrying out research & development to construct the a of spallation neutron source facility, which may bring us innovative science fields. A high power proton beam will be injected into a liquid mercury target to produce neutrons. The mercury vessel will consequently be subjected to the pressure waves generated by rapid thermal expansion. The pressure waves will propagate from the liquid mercury into the vessel solid metal, and back again. The pressure waves may induce erosion at the interface between the solid metal vessel and the liquid mercury under certain loading conditions, e.g. impact. In order to investigate the impact erosion damage due to the pressure wave, we have carried out impact experiments using a modified conventional split Hopkinson pressure bar apparatus on mercury filling a small chamber. Surface degradation in the form of many pits was observed and the ranking order of damage was found to be A6061
316SS@Inconel600Maraging steel, which is the same as that of hardness.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Hino, Ryutaro
Journal de Physique, IV, 10, p.Pr9_237 - Pr9_242, 2000/00
no abstracts in English
Nishiyama, Yutaka; Fukaya, Kiyoshi; Onizawa, Kunio; Suzuki, Masahide; Nakamura, Terumi*; ; Sato, Akira*; Yoshida, Kazuo*
Small Specimen Test Techniques (ASTM STP 1329), 0, p.484 - 494, 1998/00
no abstracts in English
Onizawa, Kunio; Suzuki, Masahide
ISIJ International, 37(8), p.821 - 828, 1997/08
Times Cited Count：3 Percentile：35.19(Metallurgy & Metallurgical Engineering)no abstracts in English
Kumamaru, Hiroshige; Murata, Hideo; ; Kukita, Yutaka
The 3rd JSME/ASME Joint Int. Conf. on Nuclear Engineering (ICONE),Vol. 1, 0, p.217 - 222, 1995/00
no abstracts in English
