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Journal Articles

Integrity evaluation for welding of irradiated and un-irradiated type 316 stainless steels

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$$times$$10$$^{25}$$ n/m$$^{2}$$($$>$$ 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.

Journal Articles

Evaluation of mechanical properties of oxide layers of fuel cladding material Zircaloy-4 and M5 oxidized under PWR condition using Nano indentation with spherical indenter

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.

Journal Articles

Corrosion properties of Zircaloy-4 and M5 under simulated PWR water conditions

Shibata, Akira; Kato, Yoshiaki; Taguchi, Taketoshi; Futakawa, Masatoshi; Maekawa, Katsuhiro*

Nuclear Technology, 196(1), p.89 - 99, 2016/10

 Times Cited Count:6 Percentile:51.31(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.

Journal Articles

Mechanical property change in the region of very high-cycle fatigue

Xiong, Z.; Naoe, Takashi; Wan, T.; Futakawa, Masatoshi; Maekawa, Katsuhiro*

Procedia Engineering, 101, p.552 - 560, 2015/03


 Times Cited Count:1 Percentile:62.88

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$$^2$$ s$$^{-1}$$. 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$$^6$$ and followed by cyclic hardening. In the case of 20%CW, cyclic softening was observed when the number of cycles below 10$$^7$$, while cyclic hardening occurred subsequently.

Journal Articles

Damage evaluation by impulsive response in structure filled with liquid

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.

Journal Articles

Very high cycle fatigue in pulsed high power spallation neutron source

Xiong, Z.*; Futakawa, Masatoshi; Naoe, Takashi; Maekawa, Katsuhiro*

Advanced Materials Research, 891-892, p.536 - 541, 2014/03

 Times Cited Count:7 Percentile:95.07

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.

Journal Articles

A Novel ultrasonic evaluation process for cavitation damage by combination of attenuation and higher harmonics

Wan, T.; Wakui, Takashi; Naoe, Takashi; Futakawa, Masatoshi; Maekawa, Katsuhiro*; Wan, T.*

Jikken Rikigaku, 13(4), p.387 - 394, 2013/12

The mercury target system is used for MW-scale neutron sources in the Japan Spallation Neutron Source. During this operation, cavitation damage is imposed on the mercury target vessel. It is very important to nondestructively evaluate the cavitation damage from the viewpoints of the structural integrity evaluation and lifetime estimation of the mercury target vessel. In this study, the cavitation damage was evaluated using a nonlinear ultrasonic method. First, the cavitation damage was imposed on plate specimens using an electro-Magnetic IMpact Testing Machine with 108 impact cycles. Nonlinear ultrasonic imaging was used to evaluate the damage. We found that the damping factor and higher harmonics of reflected waveforms from the damaged area can be used to evaluate the damage. An effective cavitation damage evaluation process has been developed based on our results. The evaluation process successfully detected minimal cavitation damage with peak-to-peak roughness of about 25 $$mu$$m.

JAEA Reports

Result of study on storage plan for irradiated components generated at MLF in J-PARC

Kinoshita, Hidetaka; Wakui, Takashi; Matsui, Hiroki; Maekawa, Fujio; Kasugai, Yoshimi; Haga, Katsuhiro; Teshigawara, Makoto; Meigo, Shinichiro; Seki, Masakazu; Sakamoto, Shinichi; et al.

JAEA-Technology 2011-040, 154 Pages, 2012/03


In the MLF, relatively high level irradiated components will be generated. Therefore, these components can not be kept in standard facilities. For the irradiated components at the MLF, the storage plan using the facilities in the Nuclear Science Research Institute has been studied, but the concrete plan is not decided yet. In this report, outline of the components, prehistory of the studying for storage, schedule of the component generation and status of the possible facility, which is a hot laboratory, are described. Resulting from the comparison between the generation schedule and the plan of the hot laboratory, the difference is very large. Present status of the hot laboratory and the cost estimation of the modification to use for storage of the MLF components were studied. Using the hot laboratory seems not to have advantage from the view point of cost and modification method. Therefore, the study on a new storage facility construction will be started as soon as possible.

JAEA Reports

Influence of Great East Japan Earthquake on neutron source station in J-PARC

Sakai, Kenji; Sakamoto, Shinichi; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Kasugai, Yoshimi; Tatsumoto, Hideki; et al.

JAEA-Technology 2011-039, 121 Pages, 2012/03


This report investigates the behavior, damage and restoration of a neutron source station of the MLF at the Great East Japan Earthquake and verified the safety design for emergency accidents in the neutron source station. In the MLF, after an occurrence of the Earthquake, strong quakes were detected at the instruments, the external power supply was lost, all of the circulators shut down automatically, and the hydrogen gas was released. The leakages of mercury, hydrogen and radio-activation gases did not occur. While, the quakes made gaps between the shield blocks and ruptured external pipe lines by subsidence around the building. But significant damages to the components were not found though the pressure drop of compressed air lines influenced on a target trolley lock system and so on. These results substantiated the validity of the safety design for emergency accidents in the source station, and suggested several points of improvement.

Journal Articles

Influence of Great East Japan Earthquake on neutron target station in J-PARC

Sakai, Kenji; Futakawa, Masatoshi; Takada, Hiroshi; Sakamoto, Shinichi; Maekawa, Fujio; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; et al.

Proceedings of 20th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-20) (USB Flash Drive), 6 Pages, 2012/03

This report investigates behaviors and damages of each component in a neutron target station of the MLF at the J-PARC at the time of the Great East Japan Earthquake (GEJE). At the date of the GEJE, in the MLF, strong quakes were detected at several instruments, an external power supply were lost, all of the circulation systems were shut down automatically, and a hydrogen gas was released as planned. Leakage of activation liquids and gases did not occur. While, the quakes made gaps between shield blocks and ruptured external pipe lines for air and water by subsidence. But significant damages on the components of the target station were not found though a loss of compressed air supply affected lock systems with air cylinders and pneumatic operation values. These results substantiated a validity of safety design on the target station for emergency accidents.

JAEA Reports

Horonobe Underground Research Laboratory Project; Synthesis of phase I investigation 2001 - 2005, Volume "Geological disposal research"

Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; Sasamoto, Hiroshi; Yoshikawa, Hideki; Shibata, Masahiro; et al.

JAEA-Research 2011-001, 193 Pages, 2011/03


This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project, of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological conditions obtained from the surface-based investigations in the Horonobe Underground Research Laboratory project as an example of actual geological environment.

JAEA Reports

Establishment of advanced integration technology for site characterization of deep geological repository; Development of information synthesis and interpretation system; Annual report 2007 (Contract research)

Osawa, Hideaki; Ota, Kunio; Hama, Katsuhiro; Sawada, Atsushi; Takeuchi, Shinji; Amano, Kenji; Saegusa, Hiromitsu; Matsuoka, Toshiyuki; Miyamoto, Tetsuo; Toyoda, Gakuji; et al.

JAEA-Research 2008-085, 742 Pages, 2008/11


This report shows the results the project for the establishment of comprehensive site characterization technology, entrusted from Natural Resources and Energy Agency, Ministry of Economy, Trade and Industry Natural Resources and Energy Agency in 2007.

Journal Articles

Microbubble formation at a nozzle in liquid mercury

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:17.33(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 $$mu$$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.

Journal Articles

Wettability effect on bubble formation at orifice type nozzle

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 $$mu$$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 $$mu$$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.

JAEA Reports

Basic approach to solute transport analysis utilizing information from surface-based investigations at two generic underground research laboratories

Maekawa, Keisuke; Sawada, Atsushi; Ota, Kunio; Kurikami, Hiroshi; Kunimaru, Takanori; Funaki, Hironori; Hama, Katsuhiro; Takeuchi, Shinji; Amano, Kenji; Saegusa, Hiromitsu; et al.

JAEA-Review 2007-011, 8 Pages, 2007/03


In the current programme for research and development on the technical aspects of geological disposal, it is of significance to establish techniques for evaluating solute transport with a direct link to surface-based investigations through the processes of data interpretation, modelling and parameter designation within the immediate five years following the H17 Project. This report presents a basic approach to promoting multidisciplinary research activities involving field investigations and relevant solute transport analysis.

JAEA Reports

Horonobe Underground Research Laboratory project synthesis of phase I investigation 2001-2005 volume "Geological Disposal Research"

Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Nishimura, Mayuka; Kobayashi, Yasushi; Hiramoto, Masayuki; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; et al.

JAEA-Research 2007-045, 140 Pages, 2007/03


This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project (HOR), of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological environments and derive future subjects based on the results. The design methods of geological disposal were reviewed based on the recent knowledge and the advertences were identified. Then the parameters for virtual design of engineered barrier system, backfill deposition hole and tunnel were set up based on actual geological conditions obtained from the surface-based investigations in HOR as an example of actual geological environment. The conceptual structure from site investigation and evaluation to mass transport analysis was represented as a work flow at first. Then following this work flow a series of procedures for mass transport analysis were carried out based on actual geological conditions obtained from the surface-based investigations in HOR to illustrate the functioning of the work flow and the applicability of this methodology. Consequently, knowledge that will help follow-up or future execution and planning activities was obtained.

Journal Articles

Laser surface alloying of SUS316 stainless steel with Al-Si; Effect of substrate temperature on structure and properties of modified layer

Zherebtsov, S.*; Maekawa, Katsuhiro*; Hayashi, Terutake*; Futakawa, Masatoshi

JSME International Journal, Series A, 48(4), p.292 - 298, 2005/10

The effect of temperature on the structure and properties of the type 316 stainless steel alloyed with Al-Si has been reported in the present paper. It has been found that four different types of structure are formed in the alloyed zone depending on the temperature of the substrate. These structures differ from each other in phase composition, microhardness and relation to cracking. Hard, crack-free microstructures are formed at temperatures of about 350 and 750 $$^{circ}$$C. Maintaining the temperature of the sample at 350 $$^{circ}$$C a uniform, crack-free layer with a high hardness is produced by laser alloying with an energy density of 0.76 W/mm$$^{2}$$.

JAEA Reports


Makino, Hitoshi; Sawada, Atsushi; Maekawa, Keisuke; Shibata, Masahiro; Sasamoto, Hiroshi; Yoshikawa, Hideki; Wakasugi, Keiichiro; Koo, Shigeru*; Hama, Katsuhiro; Kurikami, Hiroshi; et al.

JNC TN1400 2005-021, 148 Pages, 2005/09



Journal Articles

Effect of proton beam profile on stress in JSNS target vessel

Kogawa, Hiroyuki; Ishikura, Shuichi*; Sato, Hiroshi; Harada, Masahide; Takatama, Shunichi*; Futakawa, Masatoshi; Haga, Katsuhiro; Hino, Ryutaro; Meigo, Shinichiro; Maekawa, Fujio; et al.

Journal of Nuclear Materials, 343(1-3), p.178 - 183, 2005/08

 Times Cited Count:8 Percentile:49.64(Materials Science, Multidisciplinary)

A cross-flow type (CFT) mercury target with flow guide blades, which has been developed for JSNS, can suppress the generation of stagnant flow region especially near the beam window where the peak heat density is generated due to spallation reaction. Then, a flat type beam window has been applied to the CFT target from the viewpoint of suppressing dynamic stress caused by a pressure wave, which has been estimated with a mercury model of the linear equation of state. The recent experimental results obtained by using a proton beam incidents to mercury led that a cutoff pressure model in the equation of state of mercury caused a suitable dynamic stress with experimental results. Dynamic stress analyses were carried out with the cutoff pressure model, in which the negative pressure less than 0.15 MPa was not generated. The generated dynamic stress in the flat beam window became much larger than that in a semi-cylindrical type window. However, the generated stress in the semi-cylindrical type beam window was over the allowable stress of SS316L under the peak heat density of 668 W/cc. In order to decrease the dynamic stress in the semi-cylindrical beam window, the incident proton beam was defocused to decrease the peak heat density down to 218 W/cm$$^{3}$$. As a result, the dynamic stress could be suppressed less than the allowable stress. On the other hand, due to defocus of the proton beam, high heat density was generated on the end of the flow guide blades, which caused high thermal stress exceeding the allowable stress. To decrease the thermal stress, several shapes of the blade ends were studied analytically, which were selected so as not to affect the mercury flow distribution. A simple thin-end blade showed low thermal stress below the allowable stress.

JAEA Reports

Shielding design for target trolley for a spallation neutron source in the J-PARC project

Tamura, Masaya; Maekawa, Fujio; Harada, Masahide; Haga, Katsuhiro; Konno, Chikara

JAERI-Tech 2005-020, 58 Pages, 2005/03


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