Hironori Onoe

An Application of Hydraulic Tomography to a Large-Scale Fractured Granite Site, Mizunami, Japan

While hydraulic tomography (HT) is a mature aquifer characterization technology, its applications to characterize hydrogeology of kilometer-scale fault and fracture zones are rare. This paper sequentially analyzes datasets from two new pumping tests as well as those from two previous pumping tests analyzed by Illman et al. (2009) at a fractured granite site in Mizunami, Japan. Results of this analysis show that datasets from two previous pumping tests at one side of a fault zone as used in the previous study led to inaccurate mapping of fracture and fault zones. Inclusion of the datasets from the two new pumping tests (one of which was conducted on the other side of the fault) yields locations of the fault zone consistent with those based on geological mapping. The new datasets also produce a detailed image of the irregular fault zone, which is not available from geological investigation alone and the previous study. As a result, we conclude that if prior knowledge about geological structures at a field site is considered during the design of HT surveys, valuable non-redundant datasets about the fracture and fault zones can be collected. Only with these non-redundant data sets, can HT then be a viable and robust tool for delineating fracture and fault distributions over kilometer scales, even when only a limited number of boreholes are available. In essence, this paper proves that HT is a new tool for geologists, geophysicists, and engineers for mapping large-scale fracture and fault zone distributions.

Incorporating geologic information into hydraulic tomography: A general framework based on geostatistical approach

U.S. Environmental Security Technology Certification Program (ESTCP) [ER-201212]; NSF EAR [1014594]; National Natural Science Foundation of China [51609173]; Key Laboratory for Groundwater and Ecology in Arid and Semi-Arid Areas, CGS [KLGEAS201601]; Outstanding Overseas Professorship award through Jilin University by the Department of Education, China; Global Expert award through Tianjin Normal University from the Thousand Talents Plan of Tianjin City; Natural Sciences & Engineering Research Council of Canada; [MOST 103-2221-E-224-054]; [MOST 104-2221-E-224-039]; [MOST 105-2625-M-224-002]

Deposition of radiocesium on the river flood plains around Fukushima

The environment in the area around Fukushima Daiichi Nuclear Power Plant has been contaminated by widely deposited significant amount of radioactive materials, which were released to the atmosphere caused by the Fukushima Daiichi Nuclear Power Plant accident due to the Great East Japan Earthquake, which occurred on March 11, 2011. The radiocesium released in the accident mainly affects radiation dose in the environment. Decontamination work in the contaminated area except a mountain forests has been conducted to decrease the radiation dose. However, there are concerns that the redistribution of this radiation due to water discharge will occur due to the resulting transport of radiocesium. In particular, the deposition of soil particles containing radiocesium on the flood plains in the downstream areas of Fukushimas rivers can potentially increase the local radiation dose. Therefore, it is important to understand the influence of the deposition behavior of radiocesium on the radiation dose. Investigations of rivers have been performed to enhance the understanding of the mechanisms by which radiocesium is deposited on these flood plains. It was found that the spatial distribution of the radiocesium concentration on the flood plain along the river is heterogeneous with a dependence on the depositional condition and that the number of points with high air dose rates is limited. In detail, the radiocesium concentration and air dose rates in flood channels are higher than those at the edges of the river channels. Based on these heterogeneity and hydrological events, the deposition and transport mechanisms of the radiocesium due to water discharge at rivers were also interpreted, and a conceptual model was constructed.

Hydrogeological Characterization on Surface-Based Investigation Phase in the Mizunami Underground Research Laboratory Project, in Japan

The Mizunami Underground Research Laboratory (MIU) project is being carried out by Japan Atomic Energy Agency in the Cretaceous Toki granite in the Tono area, central Japan. The MIU project is a purpose-built generic underground research laboratory project that is planned for a broad scientific study of the deep geological environment as a basis of research and development for geological disposal of nuclear wastes. One of the main goals of the MIU project is to establish comprehensive techniques for investigation, analysis, and assessment of the deep geological environment. The MIU project has three overlapping phases: Surface-based Investigation (Phase I), Construction (Phase II) and Operation (Phase III). Hydrogeological investigations using a stepwise process in Phase I have been carried out in order to obtain information on important properties such as, location of water conducting features, hydraulic conductivity and so on. Hydrogeological modeling and groundwater flow simulations in Phase I have been carried out in order to synthesize these investigation results, to evaluate the uncertainty of the hydrogeological model and to identify the main issues for further investigations. Using the stepwise hydrogeological characterization approach and combining the investigation with modeling and simulation, understanding of the hydrogeological environment has been progressively improved.Copyright

TECHNICAL KNOW-HOW OF SITE DESCRIPTIVE MODELING FOR SITE CHARACTERIZATION

The site descriptive model covering the current status of characteristics of geological environment and the site evolution model for estimation of the long-term evolution of site conditions are used to integrate multi-disciplinary investigation results. It is important to evaluate uncertainties in the models, to specify issues regarding the uncertainties and to prioritize the resolution of specified issues, for the planning of site characterization. There is a large quantity of technical know-how in the modeling process. It is important to record the technical know-how with transparency and traceability, since site characterization projects generally need long duration. The transfer of the technical know-how accumulated in the research and development (R&D) phase to the implementation phase is equally important. The aim of this study is to support the planning of initial surface-based site characterizations based on the technical know-how accumulated from the underground research laboratory projects. These projects are broad scientific studies of the deep geological environment and provide a technical basis for the geological disposal of high-level radioactive wastes. In this study, a comprehensive task flow from acquisition of existing data to planning of field investigations through the modeling has been specified. Specific task flow and decision-making process to perform the tasks have been specified.Copyright