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Tanai, Kenji; Kikuchi, Hirohito; Nakamura, Kunihiko*; Tanaka, Yukihisa*; Hironaga, Michihiko*
JAEA-Research 2010-025, 186 Pages, 2010/08
JAEA-Research-2010-025.pdf:9.01MB
Bentonite-based material is used as one of the components of the LLW, TRU and HLW disposal facilities. Required characteristics of bentonite-based material are low permeability, swelling property, etc. Those are evaluated in many cases by laboratory test results. However the uncertainty exists in the evaluation of those characteristics in construction. Because even if the index of the dry density etc is the same, laboratory test results have variability. In addition, the uncertainty in construction has the possibility to increase the uncertainty of long-term evaluation of characteristics. On the other hand, several of laboratory test methods of bentonite are not standardized. So, this is a possibility that is one of the uncertain causes of the evaluation of characteristics of the bentonite. Therefore, it is hoped that the laboratory tests of bentonite are standardized. Therefore, this study analysis the uncertainty on the physical properties by laboratory tests and put together the problem and ponts of concern in the tests.
Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.
JAEA-Research 2009-013, 70 Pages, 2009/06
JAEA-Research-2009-013.pdf:8.85MB
Cementitious materials will be used to ensure construction and operational safety and work efficiency in a deep geological repository. The low alkaline cement has been developed to reduce uncertainties due to hyper alkaline for the long-term safety performance of the repository system. Functions of cementitious material required in each phase of repository construction, operation and closure were summarized in a separate report entitled "Application Study on Low Alkaline Cementitious Materials for Deep Geological Repository of High Level Radioactive Wastes (Phase I) "In this report, properties of low alkaline cement/concrete which have been developed both at home and abroad, and recipes of the low alkaline concrete taken account of application to the repository component have been investigated. Fresh and hardened properties of the low alkaline cement are equivalent to the OPC and the low alkaline cement has an advantage over OPC in terms of leaching resistance. The HFSC developed by JAEA, which belongs to a pozzolanic type low alkaline cement will be able to apply to the shotcrete and the lining concrete by choosing an adequate recipe. Clarification of influences of the chemical composition of groundwater on leachate properties of the hydrates, examination of pH measurement of cement leachate, evaluation of corrosion behavior of rebar embedded in the HFSC concrete are raised as open questions for future activities.
Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.
JAEA-Research 2008-112, 43 Pages, 2009/03
JAEA-Research-2008-112.pdf:4.58MB
In deep geological repository, use of cementitious material for rock support, lining, and grouting is essential for construction and operation and possibly raises in groundwater pH due to leachate from the cements. Since this hyperalkaline condition may lead to degradation of barriers, there is concern that it gives significant impact on long-term safety performance of the repository system. Because of these backgrounds, developments of low alkaline cement have been conducted both at home and abroad. JAEA is now planning to conduct an in-situ test for shotcreting using low alkaline cement at the Horonobe URL. On the other hand, CRIEPI has studied and developed cementitious materials for disposal of radioactive wastes. This joint research report summarizes requirements and expected performance of cementitious materials in repository taking account of surrounding conditions in each stage of the repository program so as to reflect them to further development of the low alkaline cement.