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Tokiwa, Tetsuya; Sawada, Sumiyuki; Ochiai, Shoji; Miyakawa, Kazuya
Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.1021 - 1025, 2013/01
In the Horonobe area of Japan, underground facilities have been excavated in soft sedimentary rocks in order to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste in Japan. Pre-excavation grouting was carried out at 250 to 380 m depth at the location of the planned Ventilation Shaft. After the grouting, the shaft was excavated from 250 to 350 m depth, and fracture mapping was carried out to understand the characteristics of water conductive fractures by focusing on the occurrence of injected grout. Fractures consist mainly of shear fractures, and extension fractures and faults are observed in the shaft. The faults are associated with fault rocks and high continuity. Grout was mainly observed in fractures located on the branching part from faults rather than the fault itself, and therefore high-permeability fractures are not the fault itself (fault core) but fractures located on the branching part in the damage zone of the fault.
Sato, Koichi*; Inoue, Kazuya*; Yoshiie, Toshimasa*; Xu, Q.*; Wakai, Eiichi; Kutsukake, Chuzo; Ochiai, Kentaro
Journal of Nuclear Materials, 386-388, p.203 - 205, 2009/04
Times Cited Count：2 Percentile：16.97(Materials Science, Multidisciplinary)V-4Cr-4Ti F82H, Ni and Cu were irradiated with fission and fusion neutrons at room temperature and 473 K. Defect structures were analyzed and compared using positron annihilation lifetime measurement, and microstructural evolution was discussed. The mean lifetime of positrons (the total amount of residual defects) increased with the irradiation dose. The effect of cascade impact was detected in Ni at room temperature. The size and the number of vacancy clusters were not affected by the displacement rate in the fission neutron irradiation at 473 K for the metals studied. The vacancy clusters were not formed in V Cr Ti irradiated at 473 K in the range of 10
-10
dpa. In F82H irradiated at 473 K, the defect evolution was prevented by pre-existing defects. The mean lifetime of positrons in fission neutron irradiation was longer than that in fusion neutron irradiation in V Cr Ti at 473 K. It was interpreted that more closely situated subcascades were formed in the fusion neutron irradiation and subcascades interacted with each other, and consequently the vacancy clusters did not grow larger.
; Ogata, Yoshiaki; Ochiai, Kazuya; ;
PNC TN8410 91-276, 76 Pages, 1991/11
None
; Ogata, Yoshiaki; ; ; Ochiai, Kazuya; ;
PNC TN8410 91-275, 126 Pages, 1991/11
None
Takeda, Korehiro; Kaneko, Hiromitsu; Watanabe, Kazuyoshi; Ochiai, Kazuya
PNC TN841 84-63, 10 Pages, 1984/10
This study was started in 1982 as the part of BEFAST programme. In this year (1984), periodical measurements of the concentrations of micro-element (Fe,Ni,Cr)in the pool water continuously perform and the results were statistically compared with the results of 1983. It seems that nosignifi
Ochiai, Kazuya; Takeda, Korehiro; Watanabe, Kazuyoshi; Komaki, Jun*
PNC TN841 84-62, 22 Pages, 1983/09
As a part of the IAEA coordinated programme on BEFAST, behavior of spent fuel assemblies during extended storage, corrosion of pool components has been investigated. In this study the concentrations of micro-elements of corrosion products (Fe, Cr, Ni) in pool water have been periodically measured and the evaluation of corrosion has been made from the results of analysis. The concentration of micro-elements of corrosion products (Fe, Cr, Ni) was almost constant during this study. Corrosion rate was estimated to be only a little as compared with the pool lining in thickness of 3 mm (the side) or 4 mm (the base).
Abe, Tomohisa; Yoshimura, Kazuya; Funaki, Hironori; Sanada, Yukihisa; Ochiai, Shinya*; Nagao, Seiya*
no journal, ,
The results of long-term monitoring in the difficult-to-return zone, which has been conducted continuously since the accident at the Fukushima Daiichi Nuclear Power Plant, were analyzed in order to identify trends in the variation of atmospheric radiocesium concentration and resuspension factor. In addition, an analytical case study is presented in which the results of atmospheric radiocesium concentrations are used to evaluate the activity median aerodynamic diameter and internal dose rate.
Abe, Tomohisa; Yoshimura, Kazuya; Funaki, Hironori; Nakanishi, Takahiro; Ochiai, Shinya*; Nagao, Seiya*
no journal, ,
no abstracts in English
Abe, Tomohisa; Yoshimura, Kazuya; Funaki, Hironori; Nakanishi, Takahiro; Ochiai, Shinya*; Nagao, Seiya*
no journal, ,
no abstracts in English
Abe, Tomohisa; Yoshimura, Kazuya; Funaki, Hironori; Nakanishi, Takahiro; Ochiai, Shinya*; Nagao, Seiya*
no journal, ,
