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Yada, Hiroki; Takaya, Shigeru; Morohoshi, Kyoichi*; Yokoi, Shinobu*; Miyagawa, Takayuki*
Mechanical Engineering Journal (Internet), 10(4), p.23-00044_1 - 23-00044_13, 2023/08
To develop rationalized maintenance plans for nuclear power plants, the characteristics of each plant must be considered. For sodium-cooled fast reactor (SFR) plants, constraints on inspections exist due to the specialty that equipment retaining sodium must be handled, which is one of the important points that must be considered in maintenance rationalization. In this study, we propose a maintenance optimization scheme, which is a design support tool, using risk information to develop a maintenance strategy based on the system based code (SBC) concept. The SBC concept intends to provide a theoretical procedure to optimize the reliability of structure, system and components (SSCs) by administrating every related engineering requirements throughout the life of the SSCs from design to decommissioning. ASME Boiler and Pressure Vessel Code, Code Case, N-875 was developed based on the SBC concept. The purpose of this study is to establish detailed procedures for the maintenance optimization scheme based on the procedure in Code Case N-875. Furthermore, a quantitative trial evaluation of the core support structure of the next SFR under development in Japan is also performed using the maintenance optimization scheme.
Ikesue, Shunichi*; Morita, Hideyuki*; Ishii, Hidekazu*; Sago, Hiromi*; Yokoi, Shinobu*; Yamamoto, Tomohiko
Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 8 Pages, 2021/07
In this paper, a new method is proposed for the nonlinear sloshing condition of a cylindrical tank, which can evaluate the vertical load acting on the roof and the horizontal load acting on the sidewall. This method is a combination of simplified equations for the liquid surface level and velocity proposed in the past study and the new pressure model modified from the existing model. A long calculation time as CFD analysis is not needed, because this method is consisted of simplified equations. The validity of this method was confirmed by comparing them with the CFD and the test. And future issues on the improvement of this method were clarified from the result.
Lustikova, J.*; Shiomi, Yuki*; Yokoi, Naoto*; Kabeya, Noriyuki*; Kimura, Noriaki*; Ienaga, Koichiro*; Kaneko, Shinichi*; Okuma, Satoshi*; Takahashi, Saburo*; Saito, Eiji
Nature Communications (Internet), 9, p.4922_1 - 4922_6, 2018/11
Times Cited Count：32 Percentile：84.16(Multidisciplinary Sciences)Honda, Tomohiro*; Minoshima, Yusuke*; Yokoi, Yuki*; Takayanagi, Toshiyuki*; Shiga, Motoyuki
Chemical Physics Letters, 625, p.174 - 178, 2015/04
Times Cited Count：5 Percentile：19.13(Chemistry, Physical)Electron attachment dynamics to the guanine-cytosine (G-C) base pair in the gas phase isstudied using DFT and molecular dynamics. The potential energy surface of the G-C anion isconstructed with the empirical-valence-bond method using force-field information obtained from long-range corrected DFT calculations. Ring-polymer molecular dynamics simulations predict that theinitial dipole-bound anion readily converts into the valence-bound anion within 0.1 ps and proton-transfer occurs subsequently within 10 ps. The same process was found in classical simulations, buton a much slower time scale. This result suggests that nuclear quantum effects are important inunderstanding DNA damage by low-energy electrons.
Negi, Tateyuki; Umeda, Koji; Matsuo, Koichi*; Asamori, Koichi; Yokoi, Koichi*; Ohara, Hidefumi*
Butsuri Tansa, 64(2), p.153 - 165, 2011/04
The wide band MT method is recognized as an effective method for identifying deep resistivity structures in the crust. In the method, natural variations in the electric and magnetic fields of the earth are acquired over a wide range of frequencies. World wide, thunderstorm activity produces magnetic fields at frequencies above 1Hz. These natural phenomena create strong MT source signals over the entire frequency spectrum. However, magnetic fields at frequencies below 1Hz activate intermittently, because they are caused by the interaction between solar wind and the magnetosphere and therefore, long recording times are required to obtain usable readings. In noisy regions, the signals may be contaminated by DC train signals and other coherent noise, such as occur in western Japan. When magnetic field data are contaminated by such noise, it is difficult to remove or segregate the contaminated data from the usable data. In the paper, we showed the validity of the new weighted stacking method using survey data contaminated by coherent noise.
Negi, Tateyuki; Umeda, Koji; Matsuo, Koichi*; Asamori, Koichi; Yokoi, Koichi*; Ohara, Hidefumi
Butsuri Tansa, 63(5), p.395 - 408, 2010/10
In the MT-survey, it is important for the reliability evaluation of inversion result to evaluate acquired data quality. We suggested new reliability parameters, "Predict Phase Error (PPE)", "Acquired Curve Roughness (ACR)", "Error Bar Level (EBL)" to evaluate acquired data quality that was depend on the skill and experience of MT surveyor. We examined the relation between noise level and numerically expressed parameters. As a result, extremely high correlation coefficient was recognized between noise level and PPE. PPE was expected available parameter to evaluate the noise level of acquired MT data. We suggested combination of PPE, ACR, and EBL to keep the objectivity and stability for the reliability evaluation.
Matsuo, Koichi*; Yokoi, Koichi*; Negi, Tateyuki*; Kasagi, Toshio*; Takahashi, Takeharu*; Teshima, Minoru*
JNC TJ5410 2005-001, 142 Pages, 2005/03
JNC-TJ5410-2005-001.pdf:18.35MB
The present document is to report the result of resistivity monitoring by using MT(Magnetotelluric) method near the site proposed for the Horonobe Underground Research Program at Horonobe-cho, Hokkaido by the Japan Nuclear Cycle Development Institute. The stationary MT observation system, installed near the HDB-1 borehole on November 2002, was moved to a site at the Hokusei-en, 4km west of the first site. This system is monitoring for the depth of underground resistivity. 0bservation data at the Hokusei-en from February 1st 2004 to January 31st 2005 was added in the investigation in 2004 fiscal year. But, data cannot be acquired from July 8th to November 11th of 2004 due to the disconnection trouble of the optical fiber cable for data transfer.The results were as follows
Yokoi, Koichi*; Takahashi, Takeharu*; Negi, Tateyuki*
JNC TJ5410 2004-001, 205 Pages, 2004/03
JNC-TJ5410-2004-001.pdf:42.0MB
The present document is to report the results of resistivity monitoring by using MT(Magnetotelluric) method around the site proposed for the Horonobe Underground Research Program at Horonobe-cho, Hokkaido by the Japan Nuclear Cycle Development Institute. One stationary MT observation system was installed near the HDB-1 drilling hole at the north of Horonobe-cho on November 2002.
Matsuo, Koichi*; Negi, Tateyuki*; Yokoi, Koichi*; Takahashi, Takeharu*; Teshima, Minoru*
JNC TJ5410 2004-002, 188 Pages, 2004/02
JNC-TJ5410-2004-002.pdf:109.99MB
The present document is to report the results of geophysical survey by electromagnetic method around a site proposed for the Horonobe Underground Research Program at Horonobe-cho, Hokkaido by the Japan Nuclear Cycle Development Institute. Remote-reference AMT(Audio-frequency magnetotelluric) method was carried out at 59 stations over 4 km2 in the area of Hokushin in Horonobe-cho. Two dimensional and three dimensional resistivity inversion analysis was carried out and the resistivity structure from the surface to 1,000m below sea level became clear. The resistivity structure was studied by comparing geological structure presumed from existing geological information. Resistivity contour lines extends NNW-SSE trend in plan of resistivity that is coincident with geological structure. The resistivity distribution was good agreement with existing electrical resistivity log data. At 500m below sea level, the resistivity of South-West part from presumed Omagari-fault was ranges from 1 to 3 ohm-m, and that of North-East part is ranges from 3 to 7 ohm-m.
Yokoi, Koichi*; Yoneda, Yoshihiro*; Takahara, Hiroyuki*; Moriya, Toshifumi*
PNC TJ1380 96-002, 68 Pages, 1996/03
None
Yokoi, Koichi*; Noguchi, Yoshifumi*; Morita, Masaya*; Nakamura, Naoaki*; Takahara, Hiroyuki*; Moriya, Toshifumi*
PNC TJ1380 95-004, 235 Pages, 1995/03
None
Cho, Hisashi*; Yokoi, Koichi*; Noguchi, Yoshifumi*; Morita, Masaya*; Nakamura, Naoaki*; Takahara, Hiroyuki*; Moriya, Toshifumi*
PNC TJ1380 94-001, 1308 Pages, 1994/03
None
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Moyoshi, Taketo*; Yokoi, Mai*; Soda, Minoru*; Yasui, Yukio*; Kobayashi, Yoshiaki*; Sato, Masatoshi*; Igawa, Naoki; Kakurai, Kazuhisa
no journal, ,
no abstracts in English
Negi, Tateyuki; Umeda, Koji; Matsuo, Koichi*; Asamori, Koichi; Yokoi, Koichi*
no journal, ,
no abstracts in English
Otani, Tomoyuki*; Yokoi, Kosuke*; Okazaki, Kazunari*; Nishimura, Yuki*; Kojima, Satoru*; Kuboshima, Koji*; Sasao, Eiji
no journal, ,
The orientation of microcracks was measured using the MIU-3 core penetrating the Tsukiyoshi fault to clarify the relation of the microcrack distribution near the fault. Attitude of microcracks in quartz grains in granite are measured under the optical microscope with the universal stage using three perpendicular thin sections. The healed microcracks was probably formed prior to the sealed microcracks. Both healed and sealed microcracks with moderate dip appears near the fault. The distribution of microcracks with moderate dip shows that the preferred orientation of microcracks near the fault is different from that far from the fault. The distribution of the sealed microcracks with moderate dip is narrower than that of the healed microcracks. This shows that the healed microcracks with moderate dip was developed in the intact granite at the earlier stage of the faulting history, and the sealed microcracks was in the weak fault zone which has repeated rupturing and healing at the later.
Okamura, Shigeki*; Hirayama, Tomoyuki*; Yokoi, Shinobu*; Somaki, Takahiro*; Miyagawa, Takayuki*; Uchita, Masato*; Yamamoto, Tomohiko; Miyazaki, Masashi; Fukasawa, Tsuyoshi*; Fujita, Satoshi*
no journal, ,
no abstracts in English
Yamamoto, Tomohiko; Miyazaki, Masashi; Watakabe, Tomoyoshi; Miyagawa, Takayuki*; Uchita, Masato*; Yokoi, Shinobu*; Somaki, Takahiro*
no journal, ,
no abstracts in English
Fukasawa, Tsuyoshi*; Hirayama, Tomoyuki*; Yokoi, Shinobu*; Hirota, Akihiko*; Somaki, Takahiro*; Yukawa, Masaki*; Miyagawa, Takayuki*; Uchita, Masato*; Yamamoto, Tomohiko; Miyazaki, Masashi; et al.
no journal, ,
The seismic integrity of sodium-cooled fast reactor (SFR) designs in nuclear power plants is of paramount importance. Based on the static loading test, this study investigates the force-displacement relationship and load transference in a three-dimensional seismic isolation system that is envisaged for use in reactor buildings. In SFR designs, the necessity for thin-walled structures to maintain high-temperature structure integrity can unintentionally compromise the seismic design. Consequently, addressing horizontal and vertical seismic forces become vital for ensuring seismic resilience. Currently, there are no specific codes or standards governing the integration of Three-dimensional seismic isolation systems into nuclear reactor buildings. However, current guidelines for the design of horizontal seismic isolation systems emphasize the necessity to clarify the force-displacement relationship and load transfer under conditions of superimposed horizontal and vertical loads. This study involves static loading tests performed on a half-scale specimen, which is subjected to horizontal and vertical loads exceeding the design basis ground motions for the SFR. The findings affirm that the system's horizontal supporting function maintains the segregation of horizontal and vertical load transference, even under seismic loads that exceed the design basis ground motions.
Yokoi, Shinobu*; Yamamoto, Tomohiko; Miyazaki, Masashi; Tanaka, Masaaki; Yamane, Yuma*; Nishiwaki, Yoshinori*; Sago, Hiromi*; Morita, Hideyuki*; Iwasaki, Akihisa*; Ikesue, Shunichi*
no journal, ,
The design basis ground motions have been revised to improve the seismic resistance of nuclear power plants. The reduction of seismic forces not only horizontally but also vertically has required more critical than in the past to ensure the seismic resistance of components. Notably, the design of a Sodium-Cooled Fast Reactor will require reducing the seismic forces applied to the components because of the components with thin wall thickness. To overcome this problem, the authors plan to introduce a seismic isolation system. When the sloshing wave height is small, it can be approximated with a linear vibration model. However, when the sloshing wave height increases and the sloshing becomes nonlinear, it is necessary to evaluate the wave height using other methods such as numerical analysis. Although the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing. This paper reports on the development plan and an overview of the evaluation method for nonlinear sloshing wave height and load applied to cylindrical tanks.
Sago, Hiromi*; Yamamoto, Tomohiko; Miyazaki, Masashi; Tanaka, Masaaki; Yokoi, Shinobu*; Yamane, Yuma*; Nishiwaki, Yoshinori*; Morita, Hideyuki*; Iwasaki, Akihisa*; Ikesue, Shunichi*; et al.
no journal, ,
The design basis ground motions have been revised to improve the seismic resistance of nuclear power plants. The reduction of seismic forces not only horizontally but also vertically has required more critical than in the past to ensure the seismic resistance of components. Notably, the design of a Sodium-Cooled Fast Reactor will require reducing the seismic forces applied to the components because of the components with thin wall thickness. To overcome this problem, the authors plan to introduce a seismic isolation system. When the sloshing wave height is small, it can be approximated with a linear vibration model. However, when the sloshing wave height increases and the sloshing becomes nonlinear, it is necessary to evaluate the wave height using other methods such as numerical analysis. Although the evaluation of nonlinear sloshing wave height is important, there are few examples which quantitatively evaluate the wave height of nonlinear sloshing. This paper reports the results of the sloshing water test carried out to obtain test data for the construction of the evaluation method and the results of the reproduction analysis carried out using the VOF method.
