Deuterium trapping in deep traps of differently oriented pyrolytic graphite exposed to D2 gas at 1473 K |
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| Affiliation: | 1. Institute of Physical Chemistry of the Russian Academy of Sciences, Leninsky pr., 31, 117915 Moscow, Russian Federation;2. MS 1056, Sandia National Laboratories, Albuquerque, NM 87185-1056, USA;1. Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, 3190 Gofuku, Toyama City, Toyama 930-8555, Japan;2. Electronics and Computer Engineering, National Institute of Technology, Toyama College, 1-2 Ebie-neriya, Imizu City, Toyama 933-0293, Japan;3. KAKEN Company Limited, 1044 Horimachi, Mito City, Ibaraki 310-0903, Japan;1. National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan;2. Shimane University, Matsue, Shimane 690-8504, Japan;3. Shizuoka University, Shizuoka 422-8529, Japan;4. University of Toyama, Toyama 930-8555, Japan;5. Kindai University, Higashi-Osaka, Osaka, 577-8502, Japan;6. QST, Rokkasho, Aomori 039-3212, Japan;7. EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK;8. University of Helsinki, PO Box 64, FI-00560 Helsinki, Finland;9. Royal Institute of Technology (KTH), 100 44 Stockholm, Sweden;1. Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan;2. Department of Chemistry, Graduate School of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan;3. Nuclear Professional School, School of Engineering, The University of Tokyo, 2-22, Shirakata-shirane, Tokai, Naka 319-1188, Ibaraki, Japan;4. The University Museum, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan;1. Consorzio C.r.e.a.t.e, Via Claudio, 21 Napoli 80125, Italy;2. Institut de Radioprotection et de SÛreté Nucléaire (IRSN), PSN-RES, SAG, Cadarache, Saint-Paul-Lez-Durance 13115, France;3. ENEA, Nuclear Fusion Tecnologies, Via Enrico Fermi 45, I-00044 Frascati, Rome, Italy |
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| Abstract: | Due to their importance for tritium inventories in future DT fueled fusion machines, experimental data on H isotope diffusion, absorption and retention in deep traps (Eb ≅ 4.3 eV) of graphites exposed to hydrogen at elevated temperatures have been reviewed. Deuterium retention was studied in edge- and basal-oriented pyrolytic graphite (PG) and polycrystalline RG-Ti-91 damaged by irradiation with 200 keV carbon ions. Deuterium loading was done by soaking in D2 gas at 1473 K, and the resulting D retention was measured by nuclear reaction analysis. The microstructure was studied by cross-sectional TEM, SEM and microprofilometry. The concentration of strong traps created by irradiation and estimated by the amount of accumulated deuterium was shown to saturate with the damage above ≈1 dpa at about 1000 appm. In non-damaged and damaged graphites deuterium diffuses via porous grain boundaries and along basal planes within crystallites, while its migration through the graphite lattice along the c direction was found to be negligible. Radiation modifications of PG retard deuterium diffusion and decrease the rate of its chemical erosion by a factor of five. The amount of deuterium accumulated in strong traps in graphites is mainly influenced by their macro- and microstructure, while the degree of graphitization seems to be less important. Derivations are made of the susceptibility of damaged graphites, in particular, CFCs to the retention of hydrogen isotopes in deep traps. |
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