発表論文 2022

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[2022_01]

An overview of tritium retention in dust particles from the JET-ILW divertor

T Otsuka1, S Masuzaki2, N Ashikawa2,3, Y Torikai4, Y Hatano5, M Tokitani2,3, Y Oya6, N Asakura7, T Hayashi7, H Tanigawa7, Y Iwai7, A Widdowson8, M Rubel9 and JET Contributors10

1 Department of Electric and Electronic Engineering, Kindai University, Higashi-Osaka, Japan
2 National Institute for Fusion Science, Toki, Japan
3 The Graduate University for Advanced Studies, SOKENDAI, Toki, Japan
4 Graduate School of Science and Engineering, Ibaraki University, Mito, Japan
5 Hydrogen Isotope Research Center, University of Toyama, Toyama, Japan
6 College of Science, Shizuoka University, Shizuoka, Japan
7 National Institutes for Quantum and Radiological Science and Technology, Rokkasho, Japan
8 Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, United Kingdom
9 KTH Royal Institute of Technology, Stockholm, Sweden
Author note
10 See author list: J. Mailloux et al 28th IAEA Fusion Energy Conference, 2021.

Abstract
Tritium (T) retention characteristics in dust collected from the divertor in JET with ITER-like wall (JET-ILW) after the third campaign in 2015–2016 (ILW-3) have been examined in individual dust particles by combining radiography (tritium imaging plate technique) and electron probe micro-analysis. The results are summarized and compared with the data obtained after the first campaign in 2011–2012 (ILW-1). The dominant component in ILW-1 dust was carbon (C) originating from tungsten-coated carbon fibre composite (CFC) tiles in JET-ILW divertor and/or legacy of C dust after the JET operation with carbon wall. Around 85% of the total tritium retention in ILW-1 dust was attributed to the C dust. The retention in tungsten (W) and beryllium (Be) dominated particles was 100 times smaller than the highest T retention in carbon-based particles. After ILW-3 the main component contributing to the T retention was W. The number of small W particles with T increased, in comparison to ILW-1, most probably by the exfoliation and fragmentation of W coatings on CFC tiles though T retention in individual W particles was smaller than in C particles. The detection of only very few Be-dominated dust particles found after ILW-1 and ILW-3 could imply stable Be deposits on the divertor tiles.

Keywords:
Accepted:17 December 2021

[2022_02]

Suppression of vacancyformation and hydrogen isotope retention in irradiated tungsten by addition of chromium

Jing Wanga, Yuji Hatanoa, Takeshi Toyamab, Tomoaki Suzudob,c, Tatsuya Hinokid, Vladimir Kh.Alimove, Thomas Schwarz-Selingerf

a Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, Toyama 930-8555, Japan
b Institute for Materials Research, Tohoku University, Oarai 311-1313, Japan
c Center for Computational Science and e-Systems, Japan Atomic Energy Agency, Tokai Mura 319-1195, Japan
d Open Innovation Institute, Kyoto University, Uji 611-0011, Japan
e Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow 119071, Russia
f Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, Garching D-85748, Germany

Abstract
To study the effect of the content of chromium (Cr) in the tungsten (W) matrix on the vacancy formation and retention of hydrogen isotopes, the samples of the W-0.3 at.% Cr alloy were irradiated with 6.4 MeV Fe ions in the temperature range of 523–1273 K to a damage level of 0.26 displacement per atom (dpa). These displacement-damaged samples were exposed to D2 gas at a temperature of 673 K and a pressure of 100 kPa to decorate ion-induced defects with deuterium. The addition of 0.3 at.% Cr into the W matrix resulted in a significant decrease in the retention of deuterium compared to pure W after irradiation especially at high temperature (≥773 K). Positron lifetime in W-0.3 at.% Cr alloy irradiated at 1073 K was almost similar to that for non-irradiated one. These facts indicate the suppression of the formation of vacancy-type defects (monovacancies and vacancy clusters) by 0.3 at.% Cr addition, which leads to the significant reduction in deuterium retention in W-0.3 at.% Cr alloy.

Keywords:Tungsten, Chromium, Deuterium retention, Ion irradiation
Accepted:30 November 2021

[2022_03]

Refractive index measurements of solid deuterium-tritium

Keisuke Iwano1, Jiaqi Zhang1, Akifumi Iwamoto1,2, Yuki Iwasa3, Keisuke Shigemori1, Masanori Hara4, Yuji Hatano4, Takayoshi Norimatsu1 & Kohei Yamanoi1

1 Institute of Laser Engineering, Osaka University, 2‑6 Yamadaoka, Suita, Osaka 565‑0871, Japan.
2 National Institute for Fusion Science, 322‑6 Oroshi, Toki, Gifu 509‑5292, Japan.
3 National Metrology Institute of Japan(NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1‑1‑1 Central 3, Umezono,Tsukuba, Ibaraki 305‑8563, Japan.
4 Faculty of Science, Academic Assembly, University of Toyama, 3190 Gofuku, Toyama 930‑8555, Japan.

Abstract
Physical properties of tritium (T) and deuterium (D) have been of great interest as a fuel for nuclear fusion. However, several kinds of the physical properties in a cryogenic environment have not been reported. Optical properties in liquid and solid phases are indispensable for the quality control of the DT fuel. We study the dependence of the refractive index of solid DT on temperature. A dedicated cryogenic system has been developed and forms a transparent solid DT in a prism cell. Refractive index measurements based on Snell’s law were conducted. The refractive indexes of solid DT are from 1.1618 ± 0.0002 to 1.1628 ± 0.0002 in the temperature range of 19.40 K to 17.89 K.

Keywords:
Accepted:11 January 2022

[2022_04]

Characterization and qualification of neutron radiation effects
– Summary of Japan-USA Joint Projects for 40 years –

T. Murogaa, Y. Hatanob, D. Clarkc, Y. Katohd

a National Institute for Fusion Science, Toki, 509-5292 Japan
b University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
c U.S. Department of Energy, Germantown, 20874, MD, USA
d Oak Ridge National Laboratory, Oak Ridge, 37831, TN, USA

Abstract
The Joint Projects under the Japan-USA Fusion Cooperation Program started in 1981 and has continued for more than 40 years. In the Joint Projects, although a wide range of fusion materials and engineering issues were covered, neutron radiation effects on fusion reactor materials have always been the major research emphases, and the neutron irradiation facilities in the US were jointly used by Japanese and US researchers. Japanese test facilities including neutron and charged particle irradiation facilities were complementarily used. The initial focus of the Joint Projects was on fundamental fusion neutron radiation effects and irradiation correlation. Systematic comparison of fission and fusion radiation effects in comparable damage levels and the effects of transmutation-induced helium were investigated. The collaboration was then focused on the effect of dynamic irradiation effects in variable conditions. In addition to the relatively fundamental studies, the Joint Projects contributed largely to development of candidate materials such as RAFM steels, vanadium alloys, SiC/SiC composites, and tungsten alloys, through a mechanism-oriented approach. The Joint Projects also covered issues specific to materials application to fusion blankets and plasma-facing components, including neutron radiation effects such as tritium retention and permeation of neutron-irradiated plasma-facing materials. Various irradiation technologies were developed and applied to the irradiation experiments, including those for in-situ testing. Considering that high energy neutron sources, such as A-FNS and IFMIF-DONES, now have high viability, the research supporting the neutron source programs is essential. The knowledge obtained through the Joint Projects is valuable and should be advanced for this purpose. To this end, it is of urgent necessity to launch an international scientific program accumulating knowledge of fusion neutron radiation effects, including their fundamental aspects.

Keywords: Neutron radiation effects, Irradiation correlation, Low activation materials, Transmutation
Accepted: 20 December 2021

[2022_05]

Anomalous Hall effect of PdCo alloy thin films to detect low hydrogen concentration in air

Satoshi Akamarua, Haruya Yamamotob, Masanori Haraa

a Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
b Graduate School of Science and Engineering for Education, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract
The anomalous Hall effect of thin PdCo films (Pd0.8Co0.2 alloy films; 5, 15, and 30 nm thick) subjected to various hydrogen concentrations in the gas phase was investigated. The Hall voltage of the 15 and 30 nm thick PdCo films against an external magnetic field exhibited hysteresis, indicating the anomalous Hall effect of PdCo. The hydrogen absorption in the 5 nm PdCo film decreased the Hall voltage in all considered magnetic fields. Moreover, the slope of the Hall voltage around a zero magnetic field decreased. When N2 was used as the carrier gas, the slope was proportional to the logarithm of the hydrogen concentration. For dry air, the slope differed from and was similar to that for N2 below and above hydrogen concentrations of 0.5% and 1.0%, respectively. The adsorbed oxygen on the PdCo surface disturbed the dissolved hydrogen in PdCo at low hydrogen concentrations in dry air.

Keywords: PdCo thin film, Magnetism, Hydrogen sensor, Anomalous Hall effect, Adsorbed oxygen
Accepted: 8 December 2021

[2022_06]

Practical Application Study of Highly Active CO2 Methanation Catalysts Prepared Using the Polygonal Barrel-Sputtering Method: Immobilization of Catalyst Particles

Mitsuhiro Inoue1, Motohiko Sato2, Asuka Shima3, Hironori Nakajima4, Yoshitsugu Sone5,6, Takayuki Abe1

1Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, Gofuku 3190, Toyama, 930-8555, Japan 2Chemix Co. Ltd., Azamizodai 3481, Sagamihara, Kanagawa, 252-0328, Japan
3Japan Aerospace Exploration Agency (JAXA), Jindaiji-higashi-machi 7-44-1, Chofu, Tokyo, 182-8522, Japan
4Department of Hydrogen Energy Systems, Graduate School of Engineering, Kyushu University, Motooka 744, Nishiku, Fukuoka, 810-0395, Japan
5Japan Aerospace Exploration Agency (JAXA), Yoshinodai 3-1-1, Chuo-ku, Sagamihara, Kanagawa, 252-5210, Japan
6SOKENDAI, Yoshonodai 3-1-1, Chuo-ku, Sagamihara, Kanagawa, 252-5210, Japan

Abstract
This study investigated immobilization (without binders and high-temperature heating) of highly active CO2 methanation catalyst particles, prepared by the polygonal barrel-sputtering method, onto porous Al2O3 plates. The catalyst particles were fixed uniformly and firmly on the plates and retained their high CO2 methanation performance.

Keywords: Heterogeneous catalysis · Catalysis · CO2 valorization · Processes and Reactions, Hydrogenation · Processes and Reactions, CO2 methanation, Catalyst immobilization
Accepted: 05 April 2021