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Journal Articles

Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe$$_2$$

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Matsumura, Hiroki*; Hori, Fumiya*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; et al.

Science Advances (Internet), 9(30), p.2736_1 - 2736_6, 2023/07

JAEA Reports

Development of wide range monitor for HTTR; Improvement for heat resistance performance against heat cycle

Kozawa, Takayuki; Suganuma, Takuro; Homma, Fumitaka; Higashimura, Keisuke*; Ukai, Takayuki*; Saito, Kenji

JAEA-Technology 2023-007, 24 Pages, 2023/06

JAEA-Technology-2023-007.pdf:2.24MB

To improve the reliability of the HTTR wide range monitor in a high-temperature environment, structural changes of the wide range monitor were investigated. It was clear that the structure for directly joins of the MI cable core wire and metal tube instead of the joins with lead wire is the most reliable method with shortest way. From a result of the thermal cycle tests and high temperature endurance tests for a mock-up connecting this connection parts, it was clear that the soundness of the connection part was maintained under the usage conditions of the HTTR.

Journal Articles

Low-temperature magnetic fluctuations investigated by $$^{125}$$Te-NMR on the uranium-based superconductor UTe$$_2$$

Fujibayashi, Hiroki*; Kinjo, Katsuki*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 92(5), p.053702_1 - 053702_5, 2023/05

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Large reduction in the $$a$$-axis knight shift on UTe$$_2$$ with $$T_c$$ = 2.1 K

Matsumura, Hiroki*; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 92(6), p.063701_1 - 063701_5, 2023/05

Journal Articles

Change of superconducting character in UTe$$_{2}$$ induced by magnetic field

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Physical Review B, 107(6), p.L060502_1 - L060502_5, 2023/02

 Times Cited Count:2 Percentile:94.06(Materials Science, Multidisciplinary)

Journal Articles

Drastic change in magnetic anisotropy of UTe$$_2$$ under pressure revealed by $$^{125}$$Te-NMR

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Physical Review B, 105(14), p.L140502_1 - L140502_5, 2022/04

 Times Cited Count:3 Percentile:72.4(Materials Science, Multidisciplinary)

Journal Articles

Improving the safety of the high temperature gas-cooled reactor "HTTR" based on Japan's new regulatory requirements

Hamamoto, Shimpei; Shimizu, Atsushi; Inoi, Hiroyuki; Tochio, Daisuke; Homma, Fumitaka; Sawahata, Hiroaki; Sekita, Kenji; Watanabe, Shuji; Furusawa, Takayuki; Iigaki, Kazuhiko; et al.

Nuclear Engineering and Design, 388, p.111642_1 - 111642_11, 2022/03

 Times Cited Count:0 Percentile:35.78(Nuclear Science & Technology)

Following the Fukushima Daiichi Nuclear Power Plant accident in 2011, the Japan Atomic Energy Agency adapted High-Temperature engineering Test Reactor (HTTR) to meet the new regulatory requirements that began in December 2013. The safety and seismic classifications of the existing structures, systems, and components were discussed to reflect insights regarding High Temperature Gas-cooled Reactors (HTGRs) that were acquired through various HTTR safety tests. Structures, systems, and components that are subject to protection have been defined, and countermeasures to manage internal and external hazards that affect safety functions have been strengthened. Additionally, measures are in place to control accidents that may cause large amounts of radioactive material to be released, as a beyond design based accident. The Nuclear Regulatory Commission rigorously and appropriately reviewed this approach for compliance with the new regulatory requirements. After nine amendments, the application to modify the HTTR's installation license that was submitted in November 2014 was approved in June 2020. This response shows that facilities can reasonably be designed to meet the enhanced regulatory requirements, if they reflect the characteristics of HTGRs. We believe that we have established a reference for future development of HTGR.

Journal Articles

Slow electronic dynamics in the paramagnetic state of UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.

Journal of the Physical Society of Japan, 91(2), p.023707_1 - 023707_5, 2022/02

 Times Cited Count:11 Percentile:93.25(Physics, Multidisciplinary)

$$^{125}$$Te NMR experiments in field ($$H$$) applied along the easy magnetization axis (the $$a$$-axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe$$_2$$. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 30$$-$$40 K, where the spin susceptibility along the hard magnetization axis (the $$b$$-axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in $$H|a$$. We suggest that UTe$$_2$$ would be located on the paramagnetic side near an electronic phase boundary, where either the magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.

Journal Articles

Inhomogeneous superconducting state probed by $$^{125}$$Te NMR on UTe$$_2$$

Nakamine, Genki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Journal of the Physical Society of Japan, 90(6), p.064709_1 - 064709_7, 2021/06

 Times Cited Count:14 Percentile:86.92(Physics, Multidisciplinary)

Journal Articles

Anisotropic response of spin susceptibility in the superconducting state of UTe$$_2$$ probed with $$^{125}$$Te-NMR measurement

Nakamine, Genki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Physical Review B, 103(10), p.L100503_1 - L100503_5, 2021/03

 Times Cited Count:27 Percentile:93.57(Materials Science, Multidisciplinary)

Journal Articles

Superconducting properties of heavy fermion UTe$$_2$$ revealed by $$^{125}$$Te-nuclear magnetic resonance

Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; Li, D.*; et al.

Journal of the Physical Society of Japan, 88(11), p.113703_1 - 113703_4, 2019/11

 Times Cited Count:57 Percentile:95.27(Physics, Multidisciplinary)

Journal Articles

Effect of copper addition on precipitation behavior near grain boundary in Al-Zn-Mg alloy

Matsuda, Kenji*; Yasumoto, Toru*; Bendo, A.*; Tsuchiya, Taiki*; Lee, S.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Marioara, C. D.*; Lervik, A.*; Holmestad, R.*; et al.

Materials Transactions, 60(8), p.1688 - 1696, 2019/08

 Times Cited Count:13 Percentile:61.87(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

$$^{125}$$Te-NMR study on a single crystal of heavy fermion superconductor UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 88(7), p.073701_1 - 073701_4, 2019/07

 Times Cited Count:56 Percentile:94.87(Physics, Multidisciplinary)

We report $$^{125}$$Te-NMR studies on a newly discovered heavy fermion superconductor UTe$$_2$$. Using a single crystal, we have measured the $$^{125}$$Te-NMR Knight shift $$K$$ and spin-lattice relaxation rate $$1/T_1$$ for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static ($$K$$) and dynamical susceptibilities ($$1/T_1$$) in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate $$1/T_2$$, when the field is applied along the easy axis of magnetization (=$$a$$ axis). This behavior suggests the development of longitudinal magnetic fluctuations along the $$a$$ axis at very low frequencies below 20 K.

Journal Articles

Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; Maeda, Tomoyoshi*; Matsuda, Kenji*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

 Times Cited Count:26 Percentile:83.85(Materials Science, Multidisciplinary)

Journal Articles

Investigation of absorption characteristics for thermal-load fluctuation using HTTR

Tochio, Daisuke; Honda, Yuki; Sato, Hiroyuki; Sekita, Kenji; Homma, Fumitaka; Sawahata, Hiroaki; Takada, Shoji; Nakagawa, Shigeaki

Journal of Nuclear Science and Technology, 54(1), p.13 - 21, 2017/01

 Times Cited Count:1 Percentile:10.85(Nuclear Science & Technology)

GTHTR300C is designed and developed in JAEA. The reactor system is required to continue a stable and safety operation as well as a stable power supply in the case that thermal-load is fluctuated by the occurrence of abnormal event in the heat utilization system. Then, it is necessary to demonstrate that the thermal-load fluctuation should be absorbed by the reactor system so as to continue the stable and safety operation could be continued. The thermal-load fluctuation absorption tests without nuclear heating were planned and conducted in JAEA to clarify the absorption characteristic of thermal-load fluctuation mainly by the reactor and by the IHX. As the result it was revealed that the reactor has the larger absorption capacity of thermal-load fluctuation than expected one, and the IHX can be contributed to the absorption of the thermal-load fluctuation generated in the heat utilization system in the reactor system. It was confirmed from there result that the reactor and the IHX has effective absorption capacity of the thermal-load fluctuation generated in the heat utilization system. Moreover it was confirmed that the safety estimation code based on RELAP5/MOD3 can represents the thermal-load fluctuation absorption behavior conservatively.

JAEA Reports

HTTR thermal load fluctuation test (non-nuclear heating test); Confirmation of HTGR system response against temperature transient

Honda, Yuki; Tochio, Daisuke; Nakagawa, Shigeaki; Sekita, Kenji; Homma, Fumitaka; Sawahata, Hiroaki; Sato, Hiroyuki; Sakaba, Nariaki; Takada, Shoji

JAEA-Technology 2016-016, 16 Pages, 2016/08

JAEA-Technology-2016-016.pdf:2.84MB

A system analysis code is validated with the thermal-load fluctuation absorption test with nun-nuclear heating by using the High Temperature Engineering test Reactor (HTTR) to clarify the High Temperature Gas-cooled Reactor (HTGR) system response against temperature transient. The thermal-load fluctuation absorption test consists on the thermal load fluctuation tests (non-nuclear heating) and heat application system abnormal simulating test (non-nuclear heating). The HTGR reactor response against temperature transient is clarified in the thermal load fluctuation test (non-nuclear heating). The Intermediate Heat Exchanger (IHX) reactor response against temperature transient is clarified in the heat application system abnormal simulating test (non-nuclear heating). With the two HTTR non-nuclear heating test, HTGR system response against temperature transient is obtained.

Journal Articles

Spin model of O$$_{2}$$-based magnet in a nanoporous metal complex

Soda, Minoru*; Homma, Yuki*; Takamizawa, Satoshi*; Kawamura, Seiko; Nakajima, Kenji; Masuda, Takatsugu*

Journal of the Physical Society of Japan, 85(3), p.034717_1 - 034717_9, 2016/03

 Times Cited Count:1 Percentile:11.63(Physics, Multidisciplinary)

Inelastic neutron scattering experiments are performed on the nanoporous metal complex Cu-${{it trans}}$-1,4-cyclohexanedicarboxylic acid (Cu-CHD) adsorbing O$$_{2}$$ molecules to identify the spin model of the O$$_{2}$$-based magnet realized in the host complex. It is found that the magnetic excitations of Cu-CHDs adsorbing low- and high-concentration O$$_{2}$$ molecules are explained by different spin models, the former by spin dimers and the latter by spin trimers. By using the obtained parameters and by assuming that the levels of the group of the highest energy states are reduced because of the nonnegligible spin dependence of the molecular potential of oxygen, the magnetization curves are explained quantitatively.

Journal Articles

The Operation status of the superconducting cavity for CERL main linac; Toward the deep understanding inside the superconducting cavity with high current beam

Numata, Naoto*; Asakawa, Tomoyuki*; Sakai, Hiroshi*; Umemori, Kensei*; Furuya, Takaaki*; Shinoe, Kenji*; Enami, Kazuhiro*; Egi, Masato*; Sakanaka, Shogo*; Michizono, Shinichiro*; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.566 - 570, 2015/09

no abstracts in English

JAEA Reports

Outline of device to confirm the responsiveness of control systems for HTTR

Homma, Fumitaka; Hirato, Yoji; Saito, Kenji

JAEA-Technology 2014-010, 64 Pages, 2014/05

JAEA-Technology-2014-010.pdf:35.55MB

After an accident at Fukushima Daiichi Nuclear Plant, the High Temperature Engineering Test Reactor (HTTR) should be kept shut-down till adaptability to the new nuclear safety regulation established by the Nuclear Regulation Authority (NRA) will be confirmed. However, we have to keep the operational ability for the HTTR is indispensable. The operation training for the HTTR using the simulator of light water reactors is not effective. Because the HTTR is the only test reactor in the world and one has many characteristics different from light water reactors. It is an urgent problem to utilize the device which confirms the responsiveness of the control systems for the HTTR (simulator) as a simulator for operation training. This report shows specifications of device, results of simulation and the matter which we should carry out in future.

Journal Articles

Development of operation and maintenance technology for HTGRs by using HTTR (High Temperature engineering Test Reactor)

Shimizu, Atsushi; Kawamoto, Taiki; Tochio, Daisuke; Saito, Kenji; Sawahata, Hiroaki; Homma, Fumitaka; Furusawa, Takayuki; Saikusa, Akio; Takada, Shoji; Shinozaki, Masayuki

Nuclear Engineering and Design, 271, p.499 - 504, 2014/05

 Times Cited Count:5 Percentile:43.51(Nuclear Science & Technology)

The long term high temperature operation using HTTR was carried out to establish the technical basis of HTGR in the high temperature test operation mode during 50-day since January till March, 2010. It is necessary to demonstrate the stability of plant during long-term operation in order to attain the stable supply of the high temperature heat to the planned heat utilization system of HTTR. Test data obtained in the operation were evaluated for the technical issues which were extracted before the operation. As the results, Stability and reliability of the components and facility was demonstrated by evaluating the heat transfer performance of high temperature components, the performance of pressure control to compensate helium gas leak, the reliability of the dynamic components such as helium gas circulators, the performance of heat-up protection of radiation shielding. Through the operation, the technical basis for the operation and maintenance technology of HTGRs was established.

63 (Records 1-20 displayed on this page)