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JAEA Reports

Study on crystalline rock aiming at evaluation method of long-term behavior of rock mass (Joint research)

Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya

JAEA-Research 2017-010, 61 Pages, 2017/11

JAEA-Research-2017-010.pdf:16.86MB

JAEA has started this study as a collaboration study with Tokyo University from 2016. In the fiscal year of 2016, creep testing on Tage tuff was continuously conducted. Existing theory of rate process and stochastic process was modified to be applied to evaluate effects of water, and then the modified theory was validated based on the results of strength and creep tests performed under dry and wet conditions. Furthermore, effects of water contents on stress-strain curves were examined by uniaxial compression testing under various water content conditions.

JAEA Reports

Study on crystalline rock aiming at evaluation method of long-term behavior of rock mass; FY2015 (Contract research)

Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya; Kuwabara, Kazumichi; Ozaki, Yusuke

JAEA-Research 2016-014, 52 Pages, 2016/09

JAEA-Research-2016-014.pdf:7.19MB

With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock is required, not only during construction and operation but also over a period of thousands of years after closure. On the other hand, it is known that rock and the rock mass surrounding the disposal gallery shows time dependent behavior such as creep or the stress-relaxation. It becomes the issue in the stability evaluation of the disposal gallery to grasp the behavior. In order to solve this issue, we pushed forward research development. we pushed forward research development. In the fiscal year of 2015, the creep testing machine for Tage tuff was moved to the new building. The creep test was continuously conducted and the total testing time exceeded 17 years. The testing equipment and procedure were examined to investigate the deformation, failure and time-dependency of rock under wet conditions and between room temperature and 100 $^{circ}$ C. The long-term strength of rock under triaxle stress state was researched with the aid of laboratory testing results and in situ stress measurement.

Journal Articles

Assessment of irradiation temperature stability of the first irradiation testi rig in the HTTR

Shibata, Taiju; Kikuchi, Takayuki; Miyamoto, Satoshi*; Ogura, Kazutomo*

Nuclear Engineering and Design, 223(2), p.133 - 143, 2003/08

https://doi.org/10.1016/S0029-5493(03)00041-4

Times Cited Count：1 Percentile：10.87(Nuclear Science & Technology)

The High Temperature Engineering Test Reactor (HTTR) can provide very large spaces at high temperatures for irradiation tests. The I-I type irradiation equipment was developed as the first irradiation rig. It will be served for an in-pile creep test on a stainless steel with large standard size specimens. It uses the ambient high temperature of the core for the irradiation temperature control. The target irradiation temperatures are 550 and 600 $^{circ}$ C with the target temperature deviation of 3 $^{circ}$ C. In this study, the irradiation temperature changes at transient conditions were analyzed by an FEM code and the temperature controllability of the equipment was examined by a mockup test. The controllability was evaluated with the measured temperature transient data at the core graphite components in the Rise-to-Power tests of the HTTR. The result indicates that the temperature control method of the equipment is effective to keep the irradiation temperature stable in the irradiation test.