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Shibata, Akira; Nakamura, Natsuki; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Zairyo Shiken Gijutsu, 62(1), p.35 - 40, 2017/01
Welding between irradiated and un-irradiated type 316 stainless steel is demanded for in-pile IASCC tests in Japan Materials Testing Reactor. Specimens were made from type 316 stainless steel which was irradiated up to 6
10
n/m
(
1 MeV) in Reactor and welding tests of irradiated and un-irradiated type 316 stainless steels were performed to confirm integrity of the welding. Relationship between heat input and amount of Helium bubbles in welding bead was evaluated and hardness test was performed. It appeared that there is threshold value of heat input for welding without problem.
Shibata, Akira; Wakui, Takashi; Nakamura, Natsuki; Futakawa, Masatoshi; Maekawa, Katsuhiro*; Naka, Michihiro
Zairyo Shiken Gijutsu, 62(1), p.41 - 47, 2017/01
Nuclear reactor fuel cladding material has been gradually replaced from Zircaloy-4 to Zr-Nb alloys such as M5. To reveal the origin of good corrosion resistance of Zr-Nb alloys, evaluation on oxide layer of fuel cladding tube Zircaloy-4 and M5 was performed. Nano-indentation with spherical indenter was performed on oxide layer of those materials. Test results of the indentation were evaluated by the inverse analysis using Kalman filter and Finite Element Method. The results analysis shows that the oxide layer of M5 has more ductility compare from that of Zircaloy 4. Thus, oxide layer of Zircaloy4 could be injured by smaller strain compare from that of M5.
Shibata, Akira; Kato, Yoshiaki; Taguchi, Taketoshi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Nuclear Technology, 196(1), p.89 - 99, 2016/10
Times Cited Count：6 Percentile：49.29(Nuclear Science & Technology)Cladding material Zircaloy-4 is gradually replaced by M5 (Zr-Nb alloy) and other new Nb added Zirconium alloys which are expected to have long operating life. Corrosion tests on Zircaloy-4 and M5 were performed in various hydrogen concentrations in water to research corrosion properties of those alloys. Specimens were exposed under PWR conditions. Increase of oxide layer was analysed by weight gain and observation. Electro chemical impedance spectroscopy was performed to compare corrosion properties. And effect of dissolved hydrogen concentration on increase of oxide layer of M5 is smaller than that of Zircaloy-4. M5 is less affected by local uniformity of dissolved hydrogen concentration and is more suitable as PWR fuel cladding. Results of Electro chemical spectroscopy shows that structural significant difference existed in oxidizing reaction of Zircaloy-4 and M5.
Xiong, Z.; Naoe, Takashi; Wan, T.; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Procedia Engineering, 101, p.552 - 560, 2015/03
Times Cited Count：1 Percentile：62.19(Engineering, Multidisciplinary)Very high-cycle fatigue behaviour of SUS316L, which is used as the structural material of the spallation neutron sources, was investigated through the ultrasonic fatigue test with the strain rate of 10
s
. Cross-sectional hardness distributions of the fatigue-failed specimens for solution annealed (SA) and cold worked (CW) 316L were measured to understand the cyclic hardening or softening. In addition, the tensile tests of the fatigue-failed specimens were performed at room temperature. Furthermore, the nonlinear ultrasonic system was used for evaluating the dislocation density variation. The results showed the cyclic hardening in the region of very high-cycle fatigue in the case of SA. In contrast, in the case of 10%CW, cyclic softening occurred when the number of cycles below 10
and followed by cyclic hardening. In the case of 20%CW, cyclic softening was observed when the number of cycles below 10
, while cyclic hardening occurred subsequently.
Wan, T.; Naoe, Takashi; Wakui, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Applied Mechanics and Materials, 566, p.629 - 636, 2014/06
A double-walled liquid mercury target vessel, which consists of outer and inner walls, is being globally developed for MW-class spallation neutron sources. When proton beams bombard a mercury target, pressure waves are generated due to the rapid thermal heat deposition. These pressure waves trigger impulsive vibrations in the mercury vessel, and cause cavitation damage to the inner wall of the vessel. In this study, the dependency of the vibration behavior of the mercury vessel on the damage is systematically investigated through numerical simulations and experiments, for inner wall damage characterized by hole diameters of 1, 5, 10, 20, and 40 mm. A method referred to as wavelet differential analysis is developed, and a parameter referred to as average intensity is derived for a quantitative damage evaluation. Both the numerical simulation and experimental results show that the average intensity is damage-sensitive and depends on the damage feature size. The critical damage hole diameter is estimated to be 10 mm during damage evaluation.
Xiong, Z.*; Futakawa, Masatoshi; Naoe, Takashi; Maekawa, Katsuhiro*
Advanced Materials Research, 891-892, p.536 - 541, 2014/03
Times Cited Count：7 Percentile：94.67(Engineering, Mechanical)Very high cycle fatigue degradation of type 316L austenitic stainless steel, which is used as the structural material of neutron spallation sources under intensive neutron irradiation environment, is investigated by using an ultrasonic fatigue testing machine. The strain rate imposed on the structure of neutron spallation source is almost equivalent to that produced in the testing machine. The temperature on the surface was controlled by the air-cooling. The effect of strain rate on the fatigue strength is recognized to increase the fatigue limit.
Bucheeri, A.; Kogawa, Hiroyuki; Naoe, Takashi; Futakawa, Masatoshi; Haga, Katsuhiro; Maekawa, Katsuhiro*
Journal of Nuclear Science and Technology, 45(6), p.525 - 531, 2008/06
Times Cited Count：2 Percentile：16.99(Nuclear Science & Technology)A mercury target for pulsed neutron sources is being developed in JAEA. Cavitation will be induced by pressure waves which are caused by high intense proton beam injection into the target. Microbubbles with 50 to 200 
m in diameter injected in mercury are plausibly effective to mitigate cavitation. The mitigation is dependent on the conditions of bubble size and population. It is important to understand bubble formation behavior in mercury to develop microbubble injection method. CFD simulations were carried out to investigate the bubble formation behavior in mercury. Bubbles in stagnant mercury were visualized with X-ray to observe the formation behavior of bubbles at a micro-gas-nozzle and compared with the simulation results. It was found that high surface tension makes the bubble to grow around the outer surface of the nozzle in stagnant and makes it larger until its effect becomes small in the flow. The bubble diameter in stagnant increases with increasing the contact angle.
Bucheeri, A.; Kogawa, Hiroyuki; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Jikken Rikigaku, 7(4), p.331 - 336, 2007/12
A mercury target system will be installed in Japan Proton Accelerator Complex (J-PARC). High intense proton beams injected into the target will induce cavitation by pressure waves. Injection of microbubbles with 50 to 200 m in diameter into mercury may be effective to reduce cavitation damage. Bubble generation in mercury is difficult because of its poor wettability. Therefore, we artificially change wetting condition in water to simulate bubble formation in poor wetting conditions. Experimentally, visualization of bubble growth at an orifice type nozzle of 100 m in diameter was done by a high-speed CCD camera. Wetting condition on the orifice surface was worsen by coating it with a water-repellent. Computational Fluid Dynamics simulation was carried out under stagnant water to understand the effect of wettability on bubble formation from the orifice nozzle. It was found that the bubble diameter depends on contact angle and it increases as wetting become worse.
Bucheeri, A.; Kogawa, Hiroyuki; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
no journal, ,
A high-power liquid mercury target system for spallation neutron source is being developed in Japan Atomic Energy Agency. Cavitation will be induced by pressure waves which are caused by high intense proton beam injection into mercury. Injection of microbubbles in mercury with 50 to 200m in diameter may be effective to mitigate the cavitation. The effectiveness is dependent on bubble size and population. To investigate the behavior of bubble formation in mercury from a nozzle and develop microbubbles injection technique, numerical simulation on bubble injection in stagnant and flowing mercury were carried out using a Computational Fluid Dynamics (CFD) code. The simulation in stagnant showed that bubble grew around the outer wall of the nozzle. Bubble computed under flowing condition was smaller than that in stagnant due to the drag and shearing fources induced by mercury flow.
Osone, Ryuji; Bucheeri, A.; Kurishita, Hiroaki*; Kato, Masahiro*; Yamasaki, Kazuhiko*; Maekawa, Katsuhiro*; Naoe, Takashi; Futakawa, Masatoshi
no journal, ,
Liquid mercury target system for high power spallation neutron sources is being developed. When high intensity proton beams are injected into the target, pressure waves are generated by the thermal shock in mercury and pitting damage will be imposed on the target vessel. Bubble injection into mercury is effective to mitigate the pressure waves. In this work, we propose a method of fabricating meso-nozzle for bubble injection. The method is based on powder metallurgy by inserting thin glass fibers into a metal powder matrix to create a green compact, followed by sintering at a temperature between the melting points of the powder and the fiber. SUS316L and molybdenum powders were used as the nozzle matrix materials. In order to investigate optimum sintering condition, experiments were performed at different combination of pressing load and sintering temperature. We found that in molybdenum high relative density and straight hole with circlar cross section were obtained.
Bucheeri, A.; Kurishita, Hiroaki*; Kato, Masahiro*; Naoe, Takashi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Maekawa, Katsuhiro*
no journal, ,
Mercury target system for high power spallation neutron sources is being developed. Proton beam will be injected into the target. Pressure waves will be generated and cavitation damage will be imposed on the target vessel. Injection of microbubbles may be effective to act as a cushion against pressure waves. Numerical simulations were carried out to investigate the optimum generation of microbubbles taking into account; wettability, bubbler size, gas flow rate, and liquid flowing velocity. It was found that orientation with respect to flowing liquid and bubbler geometry are essential parameters. The fabrication method uses Mo and 316L SS powders and glass fibers of 100 m in diameter. Sintering at a temperature between melting point causes glass to evaporate leaving a hole and densify the powder. Green compacts were prepared at various compressive loads and then subjected to sintering. The hole exhibited straightness and a circular cross-section, and was free from powder and glass.
Yokota, Hitoshi*; Sato, Hidetomo*; Suzuki, Tetsuya*; Maekawa, Katsuhiro*; Kurata, Yuji
no journal, ,
Liquid lead-bismuth is a candidate material of a spallation target and a coolant of accelerator driven systems for transmutation of high-level radioactive wastes. Compatibility of steels and lead-bismuth is one of critical issues. In order to solve the problem, Al powder alloy coating on 316SS was investigated. The Al alloy coating was conducted by scanning a YAG laser beam on Al-Ti-Fe sheets under Ar gas environment. Coating parameters are chemical compositions of sheet material, scanning rates of laser beam etc. Cracks often formed in the coating layer when Al contents in sheet material were high. From detail analyses, knowledge of crack formation was obtained in Al powder alloy coating using this method.
Zhihong, X.*; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
no journal, ,
Very high cycle fatigue degradation of type 316L austenitic stainless steel, which is used as the structural material of neutron spallation sources under intensive neutron irradiation environment, is investigated by using an ultrasonic fatigue testing machine. The strain rate imposed on the structure of neutron spallation source is almost equivalent to that produced in the testing machine. The temperature on the surface was controlled by the air-cooling. The effect of strain rate on the fatigue strength is recognized to increase the fatigue limit.
Xiong, Z.; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
no journal, ,
An austenitic stainless steel, SUS316L is currently being used in the liquid mercury pulsed spallation neutron source as the structural material of the mercury enclosure vessel, so called target vessel. The target vessel suffers cyclic loading in which the total number of cycles in the service life is higher than 210
, with a high strain rate of 50 1/s at maximum under intensive proton and neutron irradiation environment. In present work, the very high cycle fatigue strength was investigated using the specimens that had the different dislocation density at room temperature. The tensile strength and hardness of the failed specimen were measured to understand the change in mechanical properties during fatigue test in addition to the fatigue strength evaluation. It was found that the fatigue failure still occurred in the very high cycle region. The fatigue strength was increased with the dislocation density. For the SA 316L, cyclic hardening, the hardness was increasing with the number of cycles, was observed. However, 10% CW316L showed obvious softening, the hardness decreased while the number of cycles was less than 106 and then increased while the number of cycles was beyond 10.
Xiong, Z.; Naoe, Takashi; Futakawa, Masatoshi; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Maekawa, Katsuhiro*
no journal, ,
An enclosure vessel of liquid mercury spallation target, which is made of 316L stainless steel, is suffered from the cyclic loading due to the proton beam-induced pressure waves. The number of loading cycles will be beyond 10 to giga-cycle region throughout the expected service life. In and around giga-cycle region, the fatigue failure occurs under the conventionally defined fatigue limit. In addition to the cyclic loading, the strain rate at the beam window of the target vessel reaches to 50 1/s at the maximum, which is much higher than the conventional fatigues. In this work, ultrasonic fatigue tests were conducted with controlling specimen surface temperature to investigate effects of the temperature and the work hardening that simulates the irradiation embrittlement on very high-cycle fatigue strength of 316L SS. The experimental result showed that the obvious fatigue limit was not observed up to 10
cycles, and the fatigue strength was reduced about 75% of R.T. around 250 
C regardless of the work hardening, which was the conceivable maximum temperature of the beam window at the 1 MW operation.
Sun, X.*; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*
no journal, ,
Mercury target for pulsed spallation neutron source has been installed at the Materials and Life science experimental Facility (MLF) in the Japan Proton Accelerator Research Complex. At the moment of the proton beams bombard the target, pressure waves will be generated due to the thermal shock. On the process of the pressure wave propagation, negative pressure induces the cavitation which causes pitting damage on the inner surface of the target vessel. In the MLF, microbubbles injection into the flowing mercury is carrying out in order to mitigate the pressure waves. In this study, the effect of microbubbles on cavitation damage by microsecond-scale negative pressure was investigated through the vibratory horn tests in the bubbly water.
