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Shimada, Taro; Takeda, Seiji; Mukai, Masayuki; Munakata, Masahiro; Tanaka, Tadao
Materials Research Society Symposium Proceedings, Vol.1744, p.229 - 234, 2015/04
Integrated safety assessment methodology which analyzes radionuclide migration reflecting the spatial and temporal changes of disposal systems was developed for a geological disposal site with uplift and denudation, and then some case analyses for an assumed site with sedimentary rocks were carried out. The combination of uniform uplift and denudation has the most effect on the radionuclide migration because the groundwater flow velocity increases with decreasing the depth from the ground surface. In the case without denudation, tilted uplift has more effect than uniform uplift because flow velocity in tilted uplift increase with increasing hydraulic gradient. The long-term change of the geological structures including the uplift and denudation, the hydraulic conditions, and the recharge and outlet of the groundwater around a candidate site should be carefully investigated to determine the appropriate the place,depth and layout of the repository.
Teraoka, Yuden; Iwai, Yutaro*; Okada, Ryuta; Yoshigoe, Akitaka
no journal, ,
The decontamination of 
Cs is urgently necessary, especially in Fukushima prefecture, to make volume reduction of radioactive waste. In order to develop volume reduction techniques, chemical bonding states of Cs adsorbed in clay minerals, e.g. vermiculite, has been studied by using synchrotron radiation X-ray photoemission spectroscopy (SR-XPS). In this presentation, an interpretation of data obtained by surface charge modulation using an electron flood gun during SR-XPS and chemical bonding states of Cs in the vermiculite are discussed. SR-XPS experiments were conducted at the surface chemistry experimental station of BL23SU in SPring-8. The natural vermiculite was processed to adsorb Cs so that the Cs concentration was 2.1 wt%. The synchrotron radiation energy was 1486.6 eV, identical with the Al-K
line. The Auger parameter of Cs of CsClO
was closest to that of Cs-contained vermiculite, implying Cs in the vermiculite may interact with oxygen. In order to confirm it, chemical shift of Cs-3d core level was measured and four components were found. The highest binding energy component only shifted by using an electron flood gun may be originated from hydration in weathered wide crevices. The other three components not shifted as well as K atoms originally-contained between phyllosilicate layers are corresponding to covalent interaction with O and Si atoms in narrow phyllosilicate interlayers.
Ishikawa, Norito
no journal, ,
In this study, resistivity change as a function of ion-fluence has been measured in-situ for an oxide superconductor irradiated with high-energy heavy ions at low temperature in order to elucidate a mechanism of defect production due to high-density electronic excitation. The velocity effect appeared in the electronic stopping power (Se) dependence has been investigated in detail over a wide range of energy and mass of irradiating ions. Oxide superconductor EuBa2Cu3Oy (EBCO) thin films were irradiated at low temperature (100K) with various heavy ions in the energy range of 90 MeV-3.84 GeV, where defect production due to high-density electronic energy deposition is expected. The electrical resistivity were measured in-situ at 100 K. The shape of resistivity-fluence curves varies depending on the electronic stopping power. The resistivity-fluence curves can be reasonably interpreted by assuming the formation of columnar defects (ion-tracks). When Se is low, the resistivity increase as a function of ion-fluence exhibits a saturating behavior, suggesting that each columnar defect has the resistivity at saturation. When Se is high the resistivity increase as a function of ion-fluence shows an exponential increase, suggesting that each columnar defect has the resistivity much higher than that of the matrix. All these results can be consistently interpreted by assuming the accumulation of randomly distributed parallel columnar defects with relatively high resistivity and finite diameter (D).
c+a
dislocation in magnesiumKaburaki, Hideo; Itakura, Mitsuhiro; Yamaguchi, Masatake; Tsuru, Tomohito
no journal, ,
Kakurai, Kazuhisa
no journal, ,
Itakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake; Tsuru, Tomohito
no journal, ,
When dislocations dissociate, generalized stackingfault energy landscape determines the dissociation plane and thedissociation width. For the case of pyramidal dislocations in Mg, twoinequivalent slip planes are associated with one Burgers vector, andthe determination of the morphology of the split dislocation core ishighly non-trivial problem. Based on the first-principles calculationsof stacking fault energy of pyramidal planes and structural relaxationof dislocation core, we present unique properties of pyramidaldislocations in Mg.
