Toshiaki MANAKA,^1)* Goroh ITOH,²⁾ Junya KOBAYASHI,²⁾ Shigeru KURAMOTO²⁾ and Yuji HATANO³⁾

1) Department of Environmental Materials Engineering, NationalInstitute of Technology (KOSEN), Niihama College
2) Major in Mechanical Systems Engineering, Graduate School of Science and Engineering, Ibaraki University
3) Hydrogen Isotope Center, Organization for Promotion of Research, University of Toyama

Abstract
To understand the process and mechanism for hydrogen embrittlement in steels, visualization of the location of hydrogen is essential. In the present study, two visualization techniques, hydrogen microprint technique (HMT) and tritium autoradiography (TAR), were applied to a pure iron sheet 20% tensile-deformed with cathodic hydrogen charging. When the specimen was covered with photographic emulsion shortly (40 min) after the deformation, HMT showed that the charged hydrogen atoms diffused out at majorly grain boundaries and minorly in the grain interiors. The TAR, conducted on the same sample but completely de-hydrogenated and then charged with tritium, revealed that hydrogen enhances the formation of vacancies or vacancy clusters with plastic deformation, which are located along grain boundaries and deformation bands and act as relatively stable trapping sites for tritium.

https://doi.org/10.2355/isijinternational.ISIJINT-2023-279
Accepted:October 26, 2023

M. Yajima², M. Tokitani², Y. Oya⁵, S.E. Lee⁶, Y. Hatano⁶, N. Asakura⁷, T. Hayashi⁸,M. Oyaidzu⁸, J. Likonen⁹, A. Widdowson¹⁰, M. Rubel11,12 and JET Contributors

1 Ibaraki University Graduate School of Science and Engineering, Mito, Japan
2 National Institute for Fusion Science, Toki, Japan
3 Kindai University, Higashi-Osaka, Japan
4 SOKENDAI, Toki, Japan
5 Shizuoka University, Shizuoka, Japan
6 Hydrogen Isotope Research Center, University of Toyama, Toyama, Japan
7 National Institute for Quantum and Radiological Science and Technology, Naka, Japan
8 National Institute for Quantum and Radiological Science and Technology, Rokkasho, Japan
9 VTT Technical Research Centre of Finland, Otakaari 3J, 02150 Espoo, Finland
10 Culham Centre for Fusion Energy, United Kingdom Atomic Energy Authority, Culham Science Center, Abingdon OX14 3DB, United Kingdom of Great Britain and Northern Ireland
11 KTH Royal Institute of Technology, 100 44 Stockholm, Sweden
12 Uppsala University, Box 516, 751 20 Uppsala, Sweden

Abstract
Divertor tiles after Joint European Torus-ITER like wall (JET-ILW) campaigns and dust collected after JET-C and JET-ILW operation were examined by a set of complementary techniques (full combustion and radiography) to determine the total, specific and areal tritium activities, poloidal tritium distribution in the divertor and the presence of that isotope in individual dust particles. In the divertor tiles, the majority of tritium is detected in the surface region and, the areal activities in the ILW divertor are in the 0.5–12 kBq cm⁻² range. The activity in the ILW dust is associated mainly with the presence of carbon particles being a legacy from the JET-C operation. The total tritium activities show significant differences between the JET operation with ILW and the earlier phase with the carbon wall (JET-C) indicating that tritium retention has been significantly decreased in the operation with ILW.

https://doi.org/10.1088/1741-4326/ad0c08
Accepted:13 November 2023

M. Hatakeyama ^a, Y. Asai ^b, D. Nakato ^b, M. Nishimura ^b, Y. Hatano ^c, S. Sunada ^a K. Sato ^d

a Graduate School of Science and Engineering for Research, University of Toyama
b Graduate School of Science and Engineering for Education, University of Toyama
c Hydrogen Isotope Research Center, University of Toyama
d Graduate School of Science and Engineering, Kagoshima University

Abstract
Precipitation-hardened Cu–Cr–Zr alloy is proposed as a heat sink material for various components of the ITER owing to its high strength, high conductivity, and superior resistance against neutron irradiation. Oxidedispersion- strengthened copper (ODS-Cu) was selected as the candidate material. Hydrogen embrittlement of Cu–Cr–Zr, Cu–Cr, and ODS-Cu (GlidCop® CuAl60) alloys was evaluated using the slow strain rate technique (SSRT) in 0.1 M sodium sulfate (Na₂SO₄) solutions under cathodic hydrogen charging or after D₂ gas exposure. Thermal desorption spectroscopy (TDS) measurements were performed to estimate the differences in the hydrogen-trapping sites using hydrogen charging methods. According to the TDS results, the quantity of hydrogen retained in ODS-Cu exceeded that in the other alloys by an order of magnitude because of hydrogen trapping at the grain boundaries and the particle/matrix interface. Cu–Cr–Zr alloys tend to trap more hydrogen than Cu–Cr alloys because of the addition of Zr. As a result of the SSRT, no hydrogen embrittlement was observed in any alloy, regardless of the hydrogen charging method. All alloys exhibited excellent hydrogen embrittlement resistance under the conditions adopted in this study.

https://doi.org/10.1016/j.nme.2024.101580
Accepted:3 January 2024