Synergistic Effects of Surface Reaction and Radiation Defects on Tritium Release Behavior from Solid Breeding Materisla of Fusion Reactor Blanket

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(1) Hydroxyl groups on the surface of Li_2O were studied by using diffuse reflectance method with Fourier transform infrared spectroscopy at high temperature up to 1073K under controlled D_2O or D_2 partial pressure. Multiple peaks due to stretching vibration of O-D were observed at 2748,2717,2660,2620,2540,2520,2490cm^<-1> showing different behavior with temperature and atrnosphere. Multiple peaks mean that surface is not homogeneous for D_2O adsorption. When D_2 was added to sweep gas, peak intensities of 2540cm^<-1> and 2490 cm^<-1> increased. This indicates that the surface is influenced by oxygen potential. Assignment of the observed peaks to the surface bonding structure was conducted.(2) In-siru observation system of luminescence and tritium release at high temperature under controlled atmosphere under reactor irradiation was constructed. In-situ luminescence studies were also conducted under reactor irradiation at 77K,ion irradiation up to 800K and gamma-ray irradiation at 77-300K.Luminescence spectra were found to be consisted of several emission bands at 235nm, 305nm, 340nm, 375nm, 430nm and 510nm, which were assigned to self-trapped exiton (sigma-and pi-polarized transitions.), F^0, F^+, F_2, and F_2 center affected by a hydroxide group, respectively. Effects of temperature, irradiation species and atmosphere were studied. Mechanism of defect formation and luminescence emission was elucidated from them. Correlation was also found between luminescence emission from the defects and tritium release behavior, indicating synerism between surface reaction and radiation defects.(3) From these results, tritium release model was constructed which includes surface reaction and the effect of defect.