Hagiwara, Hiroki; Iwatsuki, Teruki; Hasegawa, Takuma*; Nakata, Kotaro*; Tomioka, Yuichi*
Nihon Suimon Kagakkai-Shi, 45(2), p.21 - 38, 2015/07
This study evaluates a method to estimate shallow groundwater intrusion in and around a large underground research facility (Mizunami Underground Research Laboratory - MIU). Water chemistry, stable isotopes (D and O), tritium (H), chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF) in groundwater were monitored around the facility (from 20 m down to a depth of 500 m), for a period of 5 years. The results show that shallow groundwater inflows into deeper groundwater at depths of between 200-400 m. In addition, the content of shallow groundwater estimated using H and CFC-12 concentrations is up to a maximum of about 50%. This is interpreted as the impact on the groundwater environment caused by construction and operation of a large facility over several years. The concomitant use of H and CFCs is an effective method to determine the extent of shallow groundwater inflow caused by construction of an underground facility.
Hama, Katsuhiro; Metcalfe, R.*
Nihon Suimon Kagakkai-Shi, 44(1), p.39 - 64, 2014/02
Groundwater dating methods employed in projects aiming to develop deep geological repositories for radioactive wastes have been reviewed. The reviewed projects are being, or have been, undertaken in Japan, Finland, Sweden, Belgium, the UK, Germany, France, Switzerland, Canada and the U.S.A. A wide range of actual and potential repository host rock types are represented by these projects: fractured crystalline igneous and metamorphic rock (Japan, Finland and Sweden); fractured volcanic rock (U.K.); plastic argillaceous rock (Belgium); indurated argillaceous rock (Japan, France, Switzerland); salt (Germany and U.S.A); limestone (Canada); and tuff (U.S.A). Whatever the combinations of methods that have been used in a particular program their results have invariably been interpreted in combination with one another and in the context of other information that is available for the investigated site. That is, a particular groundwater dating method is never applied in isolation.
Ioka, Seiichiro; Iwatsuki, Teruki; Amano, Yuki; Furue, Ryoji*
Nihon Suimon Kagakkai-Shi, 37(1), p.3 - 8, 2007/02
For safety assessment of geological isolation, it is important to evaluate in situ redox buffer capacity in high-permeability zone as groundwater flow path. This study evaluated in situ sulfate reduction rate as redox buffer capacity in the conglomerate bedding in Toki Lignite-bearing Formation, which occurs at the lowest part of sedimentary rocks overlying basement granite. The bedding plays an important role as the main groundwater flow path. The result showed that in situ redox buffer capacity in the conglomerate bedding has been identified on first nine months, whereas in the following period the redox buffer capacity has not been identified for about fifteen months. This will be caused by the bedding became inappropriate for microbial survival as the organic matter which is needful for microbial activity was consumed. Thus, there will be limited redox buffer capacity in groundwater flow path even in formation including organic matter-bearing layer.
Ioka, Seiichiro; Furue, Ryoji*; Iwatsuki, Teruki
Nihon Suimon Kagakkai-Shi, 36(4), p.181 - 190, 2006/11
Hydrogeological and geochemical investigations are required when the deep underground environment is explored or when the water from these depths are to be used as a resource. This study demonstrates the methodology on geochemical sampling of groundwater to evaluate the redox condition in a deep borehole with large downward hydraulic gradient. In the case of losses of drilling fluids during drilling, groundwater was sampled using single and double packer equipment at the time of the fluid loss. When there was no loss of drilling fluids groundwater samples where successfully obtained using a long term multi-packer system.
Osawa, Hideaki; Sato, Tsutomu*; Sakai, Ryutaro; Osawa, Hideaki; Kodama, Toshio*
Nihon Suimon Kagakkai-Shi, 29(1), p.13 - 24, 1999/00
Lin, W.*; Hirahara, Noboru; Nishida, Kaoru*; Takahashi, Manabu*; Sakaki, Toshihiro
Nihon Suimon Kagakkai-Shi, 29(4), p.189 - 204, 1999/00