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Eight samples of F82H ferritic/martensitic steel were irradiated at 300 K with 20 MeV W ions to the damage level of 0.54 displacements per atom at the damage peak. Three samples were afterwards annealed in vacuum at 423 K for 72 h and then at 373 K for 106 h. Three other samples were annealed in H 2 atmosphere at 100 kPa at the same annealing temperatures and durations. All samples were exposed at room temperature to D 2 O vapor at the partial pressures in the range from 3 to 6 kPa for 365 to 1181 days. After termination of the D 2 O vapor exposure, the surfaces of the samples were partly covered by small (≤1 mm in diameter) drops of D 2 O water. Thus, the damaged samples were exposed to a mixture of D 2 O vapor and water. Trapping of deuterium at the ion-induced defects in the damage zone was examined by the D( 3 He, p) 4 He nuclear reaction. It has been found that the W-ion-induced defects generated in the F82H samples are decorated by deuterium diffusing from the surface. [ABSTRACT FROM AUTHOR]

Surface topography and deuterium retention in polycrystalline hot-rolled W and W–5%Re have been examined after exposure to a low-energy (76 eV), high flux (around 10 22 D/m 2 s) deuterium plasma to an ion fluence of 10 26 D/m 2 at various temperatures. The methods used were confocal laser scanning microscopy and the D( 3 He, p) 4 He nuclear reaction at 3 He energies varied from 0.69 to 4.0 MeV. During exposure to the D plasma at temperatures in the range from 348 to 673 K, small blisters of size in the range from about 1 to about 15 μm, depending on the exposure temperature, are formed on the W and W–5%Re surfaces. In the W–5%Re, the deuterium retention demonstrates its maximum at exposure temperature of 463 K, while in the W this maximum is shifted to 523 K. A difference in the temperature dependence of the D retention for the W and W–5%Re is explained, as a rough approximation, by temperature dependences of the ductility of these materials. [ABSTRACT FROM AUTHOR]

Abstract: Surface topography and deuterium retention in tungsten have been examined after exposure to a low-energy (38eV/D), high-flux (1022 D/m2s) deuterium plasma at ion fluences of 1026 and 1027 D/m2 and various temperatures. The methods used were scanning electron microscopy equipped with focused ion beam, thermal desorption spectroscopy, and the D(3He,p)4He nuclear reaction at 3He energies varied from 0.69 to 4.0MeV. During exposure to the D plasma, blisters with various shapes and sizes depending on the exposure temperature are formed on the W surface. At the temperatures above 700K no blisters appear. The deuterium retention increases with the exposure temperature, reaching its maximum value of about 1022 D/m2 at 480–530K, and then decreases to about 1019 D/m2 at 800K. [Copyright &y& Elsevier]

Abstract: Depth profiles of deuterium trapped in single crystal Mo, polycrystalline Mo, and molybdenum trioxide film on polycrystalline Mo irradiated with 200eV D ions have been measured up to a depth of 8μm using the D(3He,p)4He nuclear reaction at a 3He energy varied from 0.69 to 4.0MeV. For the D ion irradiation at 323K to the highest ion fluence of 5×1024 D/m2, the D concentration decreases from several at.% in the near-surface layer to bulk values below 10−4 at.% for single crystal Mo and about 10−2 at.% for polycrystalline Mo. The maximum D concentration in molybdenum trioxide film differs little in value from that for polycrystalline Mo. Blister formation at high fluences is observed for polycrystalline Mo and molybdenum trioxide film, but not for single crystal Mo. As the irradiation temperature increases from 323 to 493K, the D retention in the polycrystalline Mo decreases from about 3×1021 down to about 2×1018 D/m2. [Copyright &y& Elsevier]

Abstract: Depth profiles of deuterium up to a depth of 10μm have been measured using the D(3He,p)4He nuclear reaction in a resonance-like technique after exposure of sintered boron carbide, B4C, at elevated temperatures to a low energy (≈200eV/D) and high ion flux (≈1021 m−2 s−1) D plasma. The proton yield was measured as a function of incident 3He energy and the D depth profile was obtained by deconvolution of the measured proton yields using the program SIMNRA. D atoms diffuse into the bulk at temperatures above 553K, and accumulate up to a maximum concentration of about 0.2at.%. At high fluences (⩾1024 D/m2), the accumulation in the bulk plays a major role in the D retention. With increasing exposure temperature, the amount of D retained in B4C increases and exceeds a value of 2×1021 D/m2 at 923K. The deuterium diffusivity in the sintered boron carbide is estimated to be D =2.6×10−6exp{−(107±10)kJmol−1/RT}m2 s−1. [Copyright &y& Elsevier]

Abstract: Samples of polycrystalline ITER-grade W and recrystallized W were irradiated at room temperature with 20MeV W ions to displacement damage up to 0.5dpa. The damaged W samples were then exposed to (i) D neutrals at 403–573K and (ii) D2 gas at 673–1073K and pressures of 1.2 and 100kPa. Trapping of deuterium in the damage zone was examined by the D(3He, p)4He nuclear reaction with 3He energies between 0.69 and 4.0MeV allowing determination of the D concentration up to a depth of 6μm. It has been found that generation of the W-ion-induced displacement damage leads to accumulation of deuterium in the damage zone up to concentration depending on the exposure temperature and, at temperatures ⩾673K, on the D2 gas pressure. Thermal desorption spectra allowed a conclusion that deuterium is mainly accumulated in the form of D atoms bound to inner walls of vacancy clusters. [Copyright &y& Elsevier]

Abstract: Deuterium retention in porous vacuum plasma-sprayed tungsten coating has been examined after exposure to low-energy, high-flux (1022 D/m2 s) pure D and helium-seeded D plasmas to ion fluences in the range from 1026 to 1027 D/m2 at various temperatures. The methods used were thermal desorption spectroscopy and the D(3He,p)4He nuclear reaction, allowing determination of the D concentration at depths up to 7μm. Under exposure to pure D plasma (76eV ) at 340–560K, the D concentration reaches 0.1–0.2at.% at depths of several micrometers, while at temperatures above 700K the D concentration is below 10−2 at.% and deuterium is retained over the whole thickness of the coating. Seeding of 76eV He+ into the D plasma reduces the D retention at temperatures of 400–600K. However, at temperatures above 700K, the D retention becomes comparable to that for pure D plasma exposure. [Copyright &y& Elsevier]

Abstract: Hydrogen isotope exchange in re-crystallized polycrystalline tungsten was investigated at 320 and 450K. In a first step the tungsten samples were loaded with deuterium to a fluence of 1024 D/m2 from a low-temperature plasma at 200eV/D particle energy. In a second step, H was implanted at the same particle energy and similar target temperature with a mass-separated ion beam at different ion fluences ranging from 2×1020 to 7.5×1023 H/m2. The analytic methods used were nuclear reaction analysis with D(3He,p)α reaction and elastic recoil detection analysis with 4He. In order to determine the D concentration at depths of up to 7.4μm the 3He energy was varied from 0.5 to 4.5MeV. It was found that already at an H fluence of 2×1020 H/m2, i.e. at 1/5000 of the initial D fluence, about 30% of the retained D was released. Depth profiling of D without and with subsequent H implantation shows strong replacement close to the surface at 320K, but extending to all analyzable depths at 450K especially at high fluences, leading to higher release efficiency. The reverse sequence of hydrogen isotopes allowed the analysis of the replacing isotope and showed that the release of D is balanced by the uptake of H. It also shows that hydrogen does not diffuse through a region of filled traps into a region were unfilled traps can be encounter but transport is rather a dynamic process of trapping and de-trapping even at 320K. Initial D retention in H loaded W is an order of magnitude higher than in pristine W, indicating that every H-containing trap is a potential trap for D. In consequence, hydrogen isotope exchange is not a viable method to significantly enhance the operation time before the tritium inventory limit is reached but should be considered an option to reduce the tritium inventory in ITER before major interventions at the end of an operation period. [Copyright &y& Elsevier]

Abstract: Deuterium depth profiles in graphite tiles of JT-60U have been determined by means of the D(3He,p)4He nuclear reaction. Tiles with net carbon deposition showed high deuterium retention. A D/C ratio of 0.07 was found in the outer dome wing tile. In the inner divertor tile covered with a thick deposition layer, the depth profile shows a broad peak in a deep region. This indicates that deuterium trapped in the shallow region can be replaced by hydrogen with hydrogen discharges due to isotope exchange, while deuterium trapped in the deeper region can not. Deuterium in the redeposited layers can be more easily removed than that in the substrate. The deuterium concentration in the outer divertor target tile was very low (D/C<0.003). The highest D/C ratio, 0.09, was found in the upper region of the first wall. [Copyright &y& Elsevier]