Soft X-ray irradiation induced metallization of layered TiNCl

Kataoka, Noriyuki*; Tanaka, Masashi*; Hosoda, Wataru*; Taniguchi, Takumi*; Fujimori, Shinichi; Wakita, Takanori*; Muraoka, Yuji*; Yokoya, Takashi*

Journal of Physics; Condensed Matter, 33(3), p.035501_1 - 035501_6, 2021/01

https://doi.org/10.1088/1361-648X/abbbc3

SR study of an layered organic superconductor -(BEDT-TTF)HgBr

Sato, Kazuhiko*; Fujita, Hidemi*; Katayama, Kazuhiro*; Taniguchi, Hiromi*; Ito, Takashi; Oishi, Kazuki*; Higemoto, Wataru

Physica B; Condensed Matter, 404(5-7), p.597 - 599, 2009/04

https://doi.org/10.1016/j.physb.2008.11.122

Zero-field muon spin relaxation and high-field transverse muon spin rotation have been measured for an organic superconductor -(BEDT-TTF)HgBr. No anomaly is found in zero-field relaxation spectrum at the superconducting transition temperature, 4.2 K. The muon Knight shift determined by transverse muon spin rotation at 6 T exhibits Curie-Weiss like behavior down to 2 K, whereas static magnetic susceptibility shows a peak around 30 K. The muon Knight shift does not scale with the magnetic susceptibility at low temperatures.

SR study of an antiferromagnetic insulator (BEDT-TTF)(TCNQ)

Sato, Kazuhiko*; Fujita, Hidemi*; Sato, Ryosuke*; Taniguchi, Hiromi*; Higemoto, Wataru

Physica B; Condensed Matter, 374-375, p.102 - 105, 2006/03

https://doi.org/10.1016/j.physb.2005.11.026

Zero-field SR measurements for an antiferromagnetic Mott insulator (BEDT-TTF)(TCNQ) were performed in order to study the microscopic magnetic properties of this organics. Slight increase of the relaxation rate is observed below 20K owing to the antiferromagnetic ordering of BEDT-TTF dimers, whereas clear muon precession signal is observed below 3K owing to the antiferromagnetic ordering of TCNQ. Below 3K, there exist at least two antiferromagnetic domains whose volume fractions changes with temperature.

Single-crystal growth of group III nitride semiconductors by slow cooling of their melts under high pressure

Utsumi, Wataru; Saito, Hiroyuki; Taniguchi, Takashi*; Aoki, Katsutoshi

Oyo Butsuri, 74(5), p.593 - 596, 2005/05

https://ci.nii.ac.jp/naid/10015722572

New method of the single crystal growth of GaN is introduced, which is based on the slow cooling of its melt under high pressure. Applying high pressures above 6 GPa prevented decomposition into Ga and nitrogen and allowed the congruent melt of GaN at high temperature. Using a large volume high pressure-temperature apparatus, high quality single crystals of GaN were successfully synthesized. This technique is also applied for the synthesis of other nitride crystals such as AlN-GaN alloy and InN.

Report on the 18th International Conference on High Pressure Science and Technology (AIRAPT-18)

Shimizu, Hiroyasu*; Utsumi, Wataru; Kume, Tetsuji*; Kondo, Tadashi*; Shimizu, Katsuya*; Sotani, Tomohiro*; Taniguchi, Takashi*; Nakamura, Kazutaka*

Koatsuryoku No Kagaku To Gijutsu, 11(4), p.334 - 338, 2001/12

https://ci.nii.ac.jp/naid/10007402307

no abstracts in English

Evaluation of Coupled Thermo-Hydro-Mechanical Phenomena in the Near Field for Geological Disposal of High-Level Radioactive waste

Chijimatsu, Masakazu*; Fujita, Tomoo; Sugita, Yutaka; Taniguchi, Wataru

JNC TN8400 2000-008, 339 Pages, 2000/01

JNC-TN8400-2000-008.pdf:30.96MB

Geological disposal of high-level radioactive waste (HLW) in Japan is based on a multibarrier system composed of engineered and natural barriers. The engineered barriers are composed of vitrified waste confined within a canister, overpack and buffer material. Highly compacted bentonite clay is considered one of the most promising candidate buffer material mainly because of its low hydraulic conductivity and high adsorption capacity of radionuclides. In a repository for HLW, complex thermal, hydraulic and mechanical (T-H-M) phenomena will take place, involving the interactive processes between radioactive decay heat from the vitrified waste, infiltration of ground water and stress generation due to the earth pressure, the thermal loading and the swelling pressure of the buffer material. In order to evaluate the performance of the buffer material, the coupled T-H-M behaviors within the compacted bentonite have to be modelled. Before establishing a fully coupled T-H-M model, the mechanism of each single Phenomenon or partially coupled phenomena should be identified. Furthermore, in order to evaluate the coupled T-H-M phenomena, the analysis model was developed physically and numerically and the adequacy and the applicability was tested though the engineered scale laboratory test and in-situ test. In this report, the investigative results for the development of coupled T-H-M model were described. This report consists of eight chapters. In Chapter l, the necessity of coupled T-H-M model in the geological disposal project of the high-level radioactive waste was described. In Chapter 2, the laboratory test results of the rock sample and the buffer material for the coupled T-H-M analysis were shown. The rock samples were obtained from the in-situ experimental site at Kamaishi mine. As the buffer material, bentonite clay (Kunigel V1 and Kunigel OT-9607) and bentonite-sand mixture were used. In Chapter 3, in-situ tests to obtain the rock property were shown. As ...

Design study of buffer material from the view of thermal condition

Taniguchi, Wataru; Suzuki, Hideaki*; Sugino, Hiroyuki*; Matsumoto, Kazuhiro*; Chijimatsu, Masakazu*; Shibata, Masahiro

JNC TN8400 99-052, 73 Pages, 1999/12

JNC-TN8400-99-052.pdf:3.83MB

For the buffer of geological disposal of High-level radioactive waste (HLW) in Japan, it is expected to maintain its low water permeability, self-sealing properties, radionuclides adsorption retardation properties, thermal conductivity, etc. It is considered that compacted bentonite or a compacted sand-mixtured bentonite that satisfy many of the expected properties mentioned above are superior. JNC (Japan Nuclear Fuel Development Corporation) has studied the measurement method for the properties of buffer and measured to use the measurement results for the design and performance assessment analysis. Also, we have conducted the design of engineered barrier and underground facility based on assuming geological condition. For the design of engineered barrier and underground facility, high thermal conductivity of buffer is design requirement to avoid mineralogical alternation. Also, the design is not conducted using the density of buffer less than the bulk density (powder-mass density). Therefore, the bulk density (powder-mass density) is one of the design requirements. In this report, the thermal properties and the bulk density (powder-mass density) of the buffer material is measured. Then thermal analysis in the near field is conducted using the measurement results, and we studied the relationships between the dry density, sand-mixtured ratio, water content and thickness of the buffer to satisfy the design requirement from the view point of thermal condition, based on the temperature constraint of the buffer.

Fundamental properties of geoenvironment for design study of repository

Taniguchi, Wataru; Hasegawa, Hiroshi; Iwasa, Kengo; Sato, Toshinori

JNC TN8400 99-053, 66 Pages, 1999/11

JNC-TN8400-99-053.pdf:4.27MB

To develop appropriate designs, as well as the manufacture, installation and construction technologies for the engineered barrier system and disposal facilities, it is necessary to evaluate physical properties of the rock mass that relate to mechanical stability analysis, thermal analysis, and seismic analysis (hereinafter referred to as "mechanical properties", "thermal properties", and "dynamic properties"). Since H3 Report, these physical properties have been broadly collected from the open literature, including field measurement data, as well as in-situ data obtained in the Tono area and at the Kamaishi Mine, in order to obtain more reliable data and to promote understanding of the deep geological environment for the purpose of design. These collected data have been added to databases on rock properties developed in H3. Thus, this report contains the upgraded databases on rocks, which include the features from a wide range of geological environments in Japan. In this report, rock types are classified into groups that have equivalent properties from the viewpoint of engineering, based on these databases of rocks. Then, design values of physical properties for the classified rock groups are determined by considering the correlation between each physical property. To date, the mechanical properties and thermal properties have been generally treated separately from each other. Here, the mechanical properties and thermal properties are determined by applying relationships between effective porosity and both mechanical and thermal properties. For the mechanical properties and dynamic properties, depth dependence are also taken into consideration.

Dynamic mechanical properties of buffer material

Takachi, Kazuhiko; Taniguchi, Wataru

JNC TN8400 99-042, 68 Pages, 1999/11

JNC-TN8400-99-042.pdf:2.74MB

The buffer material is expected to maintain its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. over a long period of time. Natural clay is mentioned as a material that can relatively satisfy above. Among the kinds of natural clay, bentonite when compacted is superior because (1)it has exceptionally low water permeability and properties to control the movement of water in buffer, (2)it fills void spaces in the buffer and fractures in the host rock as it swells upon water uptake, (3)it has the ability to exchange cations and to adsorb cationic radioelements. In order to confirm these functions for the purpose of safety assessment, it is necessary to evaluate buffer properties through laboratory tests and engineering-scale tests, and to make assessments based on the ranges in the data obtained. This report describes the procedures, test conditions, results and examinations on the buffer material of dynamic triaxial tests, measurement of elastic wave velocity and liquefaction tests that aim at getting hold of dynamic mechanical properties. MWe can get hold of dependency on the shearing strain of the shearing modulus and hysteresis damping constant, the application for the mechanical model etc. by dynamic triaxial tests, the acceptability of maximum shearing modulus obtained from dynamic triaxial tests etc. by measurement of elastic wave velocity and dynamic strength caused by cyclic stress etc. by liquefaction tests.

Study of vibration behavior of deep underground cavity and internal structure (2); Cooperative project of JNC with National Research Institute for Earth Science and Disaster Prevention Science and Technology Agency

Taniguchi, Wataru; Takachi, Kazuhiko; *; Mori, Koji*

JNC TN8400 99-055, 168 Pages, 1999/09

JNC-TN8400-99-055.pdf:4.14MB

In Japan, where many earthquakes have been occurring, it's very important to evaluate aseismatic mechanical stability of the engineered barrier system (EBS) of high-level radioactive waste (HLW) repository. In this study as a cooperative project of JNC with National Research Institute for Earth Science and Disaster Prevention Science and Technology Agency, that started from 1992, aseismatic mechanical stability of the EBS of HLW repository have been evaluated based on the engineering scale vibration test of the engineered barrier and the analytical methods. In this report, the results of the engineering scale vibration test of the engineered barrier and the development of the analytical computer code for seismic response of the engineered barriers are described, following Study of Vibration Behavior Deep Underground Cavity and Internal Structure (1). From this study, the following conclusions are obtained (1)Engineering scale vibration test of engineered barrier. From the results of sweep wave vibration tests conducted to examine the effect of natural frequency of the EBS, the natural frequency of the EBS tends to decrease as the acceleration increases. From the results of vibration tests with the actual seismic waves characteristics, both of the simulated overpack and the buffer have no significant response against seismic and then simulated engineered barriers behave dynamically as a rigid body. (2)Development of the analytical computer code for seismic response of the engineered barrier. The analytical computer code has been developed considering the non-linear dynamic properties of the buffer material between stress and strain. verification analysis results for the engineering scale vibration test of the engineered barrier mentioned above, using the analytical computer code, agree with vibration test of the engineered barrier.