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Ebihara, Kenichi; Yamaguchi, Masatake; Kaburaki, Hideo; Nishiyama, Yutaka
Materials Research Society Symposium Proceedings, Vol.1125, p.133 - 138, 2009/07
We report the simulation result of phosphorus segregation under ion irradiation using the rate theory model incorporating the results of first principles calculations. According to our recent results of first principles calculations, we found that the vacancy mechanism dominates phosphorus transport in ion-irradiated nickel rather than the interstitial mechanism and that atomic kinetics of the interstitial mechanism differs from that previously reported. By modifying the rate theory model of Murphy and Perks according to these considerations and adjusting the simulation parameters, we can obtain the phosphorus distribution that is much closer to experimental results rather than their report.
Oi, Takao; Inagaki, Manabu; Kawamura, Makoto; Ebashi, Takeshi
Materials Research Society Symposium Proceedings, Vol.1124, p.407 - 412, 2009/00
In the safety assessment of geological disposal system of radioactive waste, diverse apprehensions have been extracted from the viewpoint of the impact on the safety and the researches relating to those have been carried out strenuously. However, systematical investigation for presenting the relative importance of those has so far scarcely been conducted. The demonstration of the importance is critical issue to contribute the improvement of reliability of safety assessment. In this study, the following investigations were carried out with the goal of developing the systematic approach which can present the relative importance of the apprehensions: (1) Establishment of Total Assessment Work Frame [TAWF], (2) Establishment of the organaization procedure for evaluating the relative importance.
Tachi, Yukio; Seida, Yoshimi; Doi, Reisuke; Xia, X.*; Yui, Mikazu
Materials Research Society Symposium Proceedings, Vol.1124, p.573 - 579, 2009/00
Honda, Akira; Masuda, Kenta; Nakanishi, Hiroshi*; Fujita, Hideki*; Negishi, Kumi*
Materials Research Society Symposium Proceedings, Vol.1124, p.365 - 372, 2009/00
Yoshida, Yasushi*; Yoshikawa, Hideki
Materials Research Society Symposium Proceedings, Vol.1124, p.413 - 420, 2009/00
Ra is one of the important radionuclide for performance assessment of HLW. Concentration of Ra in groundwater is limited by an interaction with calcite. Incorporation of Ra can be evaluated by partition coefficient. In addition to this parameter, a number of surface layers which contribute ion substitution reaction is also necessary for calculation. Therefore experiments were carried out. As a result, a number of surface layers of calcite is estimated as 15to 44. Those values are consistent with estimated value in literature. With this number of layers, the migration analysis of 4n+2 series radionuclides were performed with reaction of calcite. This effect can be evaluated with partition coefficient. As a result, release rates of Ra was largest in their series on an outer surface of engineered barrier and about one order magnitude lower than that for radionuclide of highest release rate at the point of 100 m in rock.
Igarashi, Takahiro; Nakazawa, Tetsuya; Tsuru, Tomohito; Kaji, Yoshiyuki
no journal, ,
Aging of nuclear power plants is one of the important issues for a safe long term operation of light water reactors. Stress corrosion cracking (SCC) is one of the problems of the aging of nuclear reactors. Many studies on SCC have been carried out with macroscopic and microscopic viewpoints. It was experimentally clear that cracks propagate mainly along random grain boundaries (GBs). In this study, an extended semi-empirical molecular orbital method was developed. This method enables us to estimate structural parameters, electronic structures, and bond energies for various large systems, which have more than 10000 atoms. Using the developed method, the bond energies of Fe atoms in 
3 and random GBs in bulk body center cubic iron were estimated. Consequently it was confirmed that the bond strength of iron atoms in random GB became weaker than that in 3 GB.
/SiC interface defect structure generated with first-principles molecular dynamics simulationMiyashita, Atsumi; Onuma, Toshiharu*; Iwasawa, Misako*; Tsuchida, Hidekazu*; Yoshikawa, Masahito
no journal, ,
no abstracts in English
-Co thin films studied by XPS and X-ray magnetic circular dichroismMatsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Hirao, Norie; Baba, Yuji; Maeda, Yoshihito
no journal, ,
-Co hybrid filmsSakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Naramoto, Hiroshi*; Maeda, Yoshihito
no journal, ,
In the present study, the V and T dependences of the TMR effect are investigated intensively for the co-deposited C-Co films with different compositions. The mechanism of the giant TMR effect is discussed taking our recent results for the microstructures of the granular films (i.e., a hybrid structure of the covalent C-Co compound and Co nanoparticles dispersed therein) and the electronic and spin states of the C-Co compound studied by XPS and X-ray magnetic circular dichroism (XMCD) spectroscopy into account.
