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• Alleviation of impurities levels in Li for IFMIF-type neutron source are suggested. • No fatal problems are found by applying the alleviation of impurities levels. • Level of Be-7 in Li under process can be diminished by the alleviation. The alleviated limits of impurities of nitrogen and hydrogen isotopes in lithium are suggested to be 400wppm and 550appm, respectively for early realization of Advanced Fusion Neutron Source planned in Japan. The applicability of the suggestion is discussed by comparing to that of IFMIF. As the results, not less than 4-year buffer for R&D of nitrogen trap are brought in, which is thought as one of bottle neck. Additionally, the application of this suggestion would diminish the beryllium (a radioactive isotope will generate in A-FNS process) concentration in processing lithium, as well. On the other hand, it is indicated that there would be no fatal problems by application of the present suggestion. [ABSTRACT FROM AUTHOR]

The annihilation behavior of irradiation defects induced in neutron-irradiated Li2TiO3 and Li2ZrO3 were investigated with the tritium release behavior. It was revealed that the common characteristics in both samples were that the annihilation process of irradiation defects consisted of two first-order processes and E’-center could act as tritium trapping site, and otherwise was the way how the E’-center annihilated. The difference was suggested to attribute to the mobility of M as M4+ (or M3+, etc.). [ABSTRACT FROM AUTHOR]

The annihilation behavior of irradiation defects induced in neutron-irradiated Li2TiO3 and Li2ZrO3 were investigated with the tritium release behavior. It was revealed that the common characteristics in both samples were that the annihilation process of irradiation defects consisted of two first-order processes and E’-center could act as tritium trapping site, and otherwise was the way how the E’-center annihilated. The difference was suggested to attribute to the mobility of M as M4+ (or M3+, etc.). [ABSTRACT FROM AUTHOR]

Abstract: Retention of hydrogen isotopes in the carbon (isotropic graphite) first wall tiles of JT-60U was studied by secondary ion mass spectrometry and thermal desorption spectroscopy. The surface morphology and erosion/deposition profiles of the tiles were characterized using scanning electron microscope and X-ray photoelectron spectroscopy. The upper area is mainly eroded, while the bottom area of the inboard wall is dominated by deposition. In contrast to the divertor area, hydrogen isotope retention in the eroded wall area was generally larger than that in the deposition dominated area. Measured near surface concentrations of hydrogen isotopes in the wall tiles, as well as the D/H ratios, were a little higher than those in the divertor area. This indicates direct implantation of high-energy D from NBI into the first wall. The lower temperature of the first wall relative to the divertor tiles would reduce desorption and/or replacement of implanted D by subsequent D or H impingement. [Copyright &y& Elsevier]

The behavior of hydrogen isotopes in boron was studied by XPS and TDS. The samples used were boron polycrystals and boron thin films produced by plasma CVD using decaborane (B10H14) diluted by He gas. The 1.0 keV deuterium ions were implanted into the samples up to fluence of 5.4 × 1021 D m-2 at various temperatures. It was found that deuterium retention at 573 K was decreased less than 35% compared to that at room temperature. The activation energies for B–D–B and B–D bonds were estimated to be 1.11 ± 0.21 and 2.17 ± 0.36 eV for the boron thin film, and 1.36 ± 0.20 and 2.27 ± 0.45 eV for the boron polycrystal, respectively. The B–H distance and the activation energy for the B–H bond were also calculated by the Gaussian 03 code and these were consistent with the experimental values. [Copyright &y& Elsevier]

Abstract: Distribution of deuterium and hydrogen retained in graphite tiles placed in the divertor region of JT-60U with the dual side pumping geometry was investigated by thermal desorption spectroscopy. The retention of hydrogen isotopes was nearly proportional to the thickness of the carbon redeposited layers, though their concentration changes with the poloidal location and orientation of the surface tiles. The least concentration of (H+D)/C (∼0.02) was found in the redeposited layers on the inner divertor tile. Rather high hydrogen concentration was found in the redeposited layers on plasma shadowed area. In particular, the redeposited layers on the bottom side of the outer dome wing tile shadowed from plasma and facing to the pumping slot showed the highest concentration of 0.13 in (H+D)/C. In JT-60U, however, the carbon deposition in the shadowed area is very small, resulting in a smaller total retention in the divertor area compared to other large tokamaks. [Copyright &y& Elsevier]

Abstract: The chemical behavior of energetic deuterium implanted into tungsten carbide (WC) samples has been investigated by XPS and TDS. The TDS experiments showed that almost of all deuterium retained in WC was desorbed in the temperature region from 300 to 700K and the residue at around 1000K. The deuterium (D2) desorption peak at around 1000K was found to originate from the desorption of deuterium atom (D) trapped by carbon (C). Its retention was considerably small and was saturated at low deuterium ion (D2 +) fluence. The area of the large D2 desorption peaks, which corresponds to the D retention in WC, increased as D2 + fluence increased. The D2 desorption in the temperature range of 300–700K takes place in three stages, the lower two peaks were attributed to the desorption of D retained in two interstitial sites, and the highest peak corresponds to D trapped by carbon vacancies induced by chemical sputtering of C by energetic D2 +. From these experimental results, the D trapping and detrapping behaviors are discussed and it is concluded that the hydrogen isotope retention is governed by the amount of interstitial sites and carbon vacancies in WC. The hydrogen isotope retention could be lowered if the surface temperature of WC were above 700K. [Copyright &y& Elsevier]

Abstract: In the present study, the thermal desorption behavior of deuterium implanted into diamond was investigated by means of TDS and XPS. From the results of TDS experiments, the most of all implanted deuterium was desorbed by forming D2 mainly, and two desorption peaks were observed in the temperature range from 700 to 1100K and from 1100 to 1300K. The lower temperature deuterium desorption from the diamond was similar to that from HOPG. However, the D/C value of the diamond was approximately 0.2, which was almost half the value of the HOPG. The C1s XPS spectra of diamond were shifted towards lower energy with increasing heating temperature above 773K. In addition, the π–π∗ transition peak appeared above this temperature. These meant that the disordered diamond structure were reconstructed through the desorption of deuterium, and stabilized by formation of a graphite network. [Copyright &y& Elsevier]