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Costantini, J.-M.*; Guillaumet, M.*; Lelong, G.*; Ishikawa, Norito; Seo, P.*; Yasuda, Kazuhiro*
Nuclear Instruments and Methods in Physics Research B, 558, p.165567_1 - 165567_6, 2025/01
Times Cited Count：0 Percentile：0.00(Instruments & Instrumentation)Radiation damage is studied in ion-irradiated sintered CeO
and (Ce, Gd)O
samples. Near Infra-red (NIR) spectra measurements were carried out by using the diffuse reflectivity mode for all of these sintered samples. Samples were irradiated with 100-MeV Kr, 200-MeV Xe, and 36-MeV W ions. Four broad absorption bands centered at 3700, 4100, 6000, and 7600 cm
(i.e. 0.46, 0.51, 0.74, and 0.94 eV) are deduced from fits of the FTIR spectra for the ion-irradiated CeO and (Ce, Gd)O samples accompanied by a change in color from ivory to green. No such bands are recorded for the virgin (Ce, Gd)O samples with 5, 10, and 15 mol GdO
with an increasing amount of oxygen vacancies. Absorption bands are tentatively assigned to electronic transitions involving cerium vacancy levels in the band gap, which has been also observed under high-energy electron irradiation.
Constantini, J.-M.*; Seo, P.*; Yasuda, Kazuhiro*; Bhuian, AKM S. I.*; Ogawa, Tatsuhiko; Gourier, D.*
Journal of Luminescence, 226, p.117379_1 - 117379_10, 2020/10
Times Cited Count：15 Percentile：61.96(Optics)Cathodo-luminescence is used for detection of lattice defects, in particular oxygen vacancies in ceramics induced by electrons. However, how oxygen vacancy production efficiency depends on sample temperature, incoming electron flux, and electron energy was not clear. In this study, oxygen vacancies were made in the specimens of CeO by irradiation of 400-1250 keV electrons and the cathodoluminescence from thus induced vacancies were observed by photo-fiber probe combined with CCD. As the result, the dependence of luminescence intensity on specimen temperature depends on the carrier trapping frequency and luminescence efficiency while luminescence center production/annihilation speed determines the dependency on the incoming electron flux. Moreover, radiation transport calculation conducted by the particle transport simulation code PHITS indicates that the number of electrons above the defect production threshold energy is vital to explain incoming electron energy dependence.
Yui, Mikazu; Ishikawa, Hirohisa; Watanabe, Atsuo*; Yoshino, Kyoji*; Umeki, Hiroyuki; Hioki, Kazumasa; Naito, Morimasa; Seo, Toshihiro; Makino, Hitoshi; Oda, Chie; et al.
JAEA-Research 2010-015, 106 Pages, 2010/05
JAEA-Research-2010-015.pdf:13.58MB
This report summarizes the activity of Phase I of Waste Management Working Group of the United States - Japan Joint Nuclear Energy Action Plan started in 2007. The working group focused on consolidation of the existing technical basis between the U.S. and Japan and the joint development of a plan for future collaborative activities. Firstly, the political/regulatory frameworks related to nuclear fuel cycles in both countries were reviewed. The various advanced fuel cycle scenarios in both countries were surveyed and summarized. Secondly, the waste management/disposal system optimization was discussed. Repository system concepts for the various classifications of nuclear waste were reviewed and summarized, then disposal system optimization processes and techniques were reviewed, and factors to consider in future repository design optimization activities were also discussed. Finally the potential collaboration areas and activities related to the optimization problem were extracted.
Kim, W. J.*; Seo, M.-R.*; Park, J. Y.*; Sumita, Junya; Shibata, Taiju; Sawa, Kazuhiro
no journal, ,
Carbon-carbon (C/C) composites have been widely used for high-temperature structural applications because they possess excellent mechanical properties such as high specific strength and thermal shock resistance. In the nuclear industry, the composites have also been considered for plasma facing materials in fusion reactors and high-temperature structural parts in gas cooled reactors. In the high-temperature gas cooled reactor, the composites are being considered for the application of various high-temperature structural parts such as control rod components, core restraint belts, tie rods, upper plenum shroud, hot duct insulation cover sheets, and floor blocks. However, the carbon based materials are susceptible to oxidation at temperatures above 400 
C. Therefore, the oxidation behavior and property degradation at high temperature under impure He or in air in case of accidental air ingress should be evaluated before the deployment of composites. In this study, the oxidation behavior of several nuclear-grade C/C composites was evaluated at various temperatures. Thermal and mechanical properties of the composites were also measured before and after oxidation. The oxidation experiments were performed in range of 500 to 1100 C under air or Ar atmosphere. Thermal diffusivity, flexural strength, tensile strength, and interlaminar shear strength of as-received and oxidized specimens were evaluated.
