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Iwamoto, Osamu; Iwamoto, Nobuyuki; Kunieda, Satoshi; Minato, Futoshi; Nakayama, Shinsuke; Abe, Yutaka*; Tsubakihara, Kosuke*; Okumura, Shin*; Ishizuka, Chikako*; Yoshida, Tadashi*; et al.
Journal of Nuclear Science and Technology, 60(1), p.1 - 60, 2023/01
Times Cited Count：75 Percentile：99.99(Nuclear Science & Technology)Sako, Hiroyuki; Harada, Hiroyuki; Sakaguchi, Takao*; Chujo, Tatsuya*; Esumi, Shinichi*; Gunji, Taku*; Hasegawa, Shoichi; Hwang, S.; Ichikawa, Yudai; Imai, Kenichi; et al.
Nuclear Physics A, 956, p.850 - 853, 2016/12
Times Cited Count：13 Percentile：65.38(Physics, Nuclear)Sato, Toshinori; Tanno, Takeo; Sanada, Hiroyuki; Yokoyama, Tatsuya*; Shimoyama, Masahiro*
Heisei-25 Nendo (2013 Nen) Shigen, Sozai Gakkai Shuki Taikai Koenshu, p.257 - 258, 2013/09
Japan Atomic Energy Agency is operating underground research laboratory projects in order to establish a firm scientific basis for safe geological disposal of HLW. One of these is the Mizunami Underground Research Laboratory (MIU) project focused on crystalline rock. In situ stress measurement by Compact Conical-ended Borehole Overcoring (CCBO) are conducted to understand in situ stress state at 300 m depth.
Tanno, Takeo; Sato, Toshinori; Sanada, Hiroyuki; Hikima, Ryoichi*; Yokoyama, Tatsuya*; Shimoyama, Masahiro*
Heisei-25 Nendo (2013 Nen) Shigen, Sozai Gakkai Shuki Taikai Koenshu, p.255 - 256, 2013/09
rock stresses were measured by Compact Conical-ended Borehole Overcoring (CCBO) technique in the 300m depth gallery at the Mizunami Underground Research Laboratory and the measurement results were evaluated using a conventional method and a new test of strain sensitivity method. To compare the 
rock stress evaluated by both methods, the new test of strain sensitivity method resulted in more accurate evaluation than the conventional method, because of its improved stress deviations.
Yokoyama, Tatsuya*; Shimoyama, Masahiro*; Sato, Toshinori; Sanada, Hiroyuki; Tanno, Takeo; Hikima, Ryoichi
no journal, ,
In order to obtain the in-situ stress state around the Mizunami Underground Research Laboratory, we have measured the initial stress state by using the Compact Conical-ended Borehole Overcoring (CCBO) technique in the 300m depth gallery. We newly tried to correct the strain sensitivity with biaxial loading test using the recovered core in the CCBO technique. In this case, we were able to confirm the effectiveness of the correction method in comparison with the results of this analysis newly introduced and the conventional methods.
Sumita, Junya; Shibata, Taiju; Muto, Takenori*; Mihashi, Masahiko*; Sato, Masahiro*; Yamashita, Ryo*; Sakaba, Nariaki
no journal, ,
Since graphite is porous material containing 20% of porosity, the characteristics of graphite strongly depends on shape and volume distribution of pore. It is essential to establish the production method for further reducing the characteristic variation of graphite to produce high quality graphite. Therefore, it is necessary to establish the simple method for prediction of the characteristics of graphite. Although they have been characterized as a function of porosity, it is necessary to characterize them as a function of some detailed factors in order to further reduce the characteristic variation and to characterize them with high accuracy. The authors have been developing the method for predicting the characteristics of graphite by analysis of shape and volume distribution of open pore and closed pore using two and three dimensional images in order to characterize graphite with high accuracy. In the present study, quantity of open pore and closed pore analyzed by a digital image analysis was compared with that measured by a mercury porosimeter. Both results indicated that open pore increased with increasing porosity and closed pore showed almost constant value. However, the volume of closed pore by the mercury porosimeter was measured up to 5% larger than that by the digital image analysis. It is necessary to clarify the correlation between the volume of closed pore analyzed by the digital image analysis and that measured by the mercury porosimeter to measure closed pore with high accuracy by the mercury porosimeter in the next step.
Sumita, Junya; Shibata, Taiju; Muto, Takenori*; Mihashi, Masahiko*; Sato, Masahiro*; Yamashita, Ryo*; Sakaba, Nariaki
no journal, ,
Graphite materials are used for the in-core components of High Temperature Gas-cooled Reactor (HTGR) which is a graphite-moderated and helium gas-cooled reactor. The HTGR is particularly attractive due to capability of producing high temperature helium gas, and its passive and inherent safety features. The Very High Temperature Reactor (VHTR) is one of the most promising candidates as the Generation-IV nuclear reactor systems. Since the thermal conductivity of graphite is one of important properties to evaluate the maximum core temperature of the VHTR, many researchers investigated and reported it. Graphite material is porous material containing 20% of porosity and the thermal conductivity strongly depends on shape and volume distribution of pore. It is important to evaluate the thermal conductivity as a function of them. In the presentation, the evaluation results of the thermal conductivity for fine-grain isotropic graphite as a function of open pores and closed pores measured by a mercury porosimeter were reported. Moreover, the prediction method for the thermal conductivity considering the amount of open and closed pore was discussed.
Sumita, Junya; Shibata, Taiju; Mihashi, Masahiko*; Muto, Takenori*; Sato, Masahiro*; Yamashita, Ryo*; Sakaba, Nariaki
no journal, ,
The characteristics of graphite have been characterized as a function of porosity. In order to further reduce the characteristic variation and to characterize them with high accuracy, it is necessary to characterize them as a function of some detailed factors. Therefore, we focused on the open and closed pore of graphite and analyzed them based on two and three dimensional images to develop the prediction method for thermal conductivity of graphite. In the present study, it was reported analytical results of pore distribution and comparison result of predicted thermal conductivity to the experimental one.
Mihashi, Masahiko*; Muto, Takenori*; Sato, Masahiro*; Sumita, Junya; Shibata, Taiju; Sakaba, Nariaki; Yamashita, Ryo*
no journal, ,
The large size isotropic graphite is required to have small characteristic variation. Since characteristics of graphite are affected by porosity, in the first stage of improvement of large size graphite, porosity of large size isotropic graphite has been examined using mercury porosimeter.
