Data of radon measurement in underground facilities of Mizunami Underground Research Laboratory

Aoki, Katsunori; Yamanaka, Hiroki*; Watanabe, Kazuhiko*; Sugihara, Kozo

JAEA-Data/Code 2020-018, 45 Pages, 2021/02

JAEA-Data-Code-2020-018.pdf:4.54MB
JAEA-Data-Code-2020-018-appendix(DVD-ROM).zip:6.8MB

Mizunami Underground Research Laboratory (MIU) Project is pursued by Japan Atomic Energy Agency (JAEA) in the crystalline host rock (granite) as a part of geoscientific study of JAEA, and underground facilities of MIU are constructed down to 500m blow the ground surface. As small amount of Uranium is normally contained in granite, high concentration of radon is sometimes detected in the air of the underground facilities constructed in granitic rocks depending on their ventilation conditions. Radon concentrations in underground facilities of MIU have been measured according to the excavation progress of underground facilities or the change of ventilation system. It is recognized that the data obtained by the actual measurement of radon concentration in such underground facilities are rare and valuable. This repot summarizes the measured data from fiscal 2010 to fiscal 2020, together with the information of ventilation conditions and air temperature which affect radon concentrations in underground facilities. The variation of the equilibrium factors of radon is also examined with the actually measured data. As a result, it has been found that radon concentration in the drift is high in summer and low in winter according to the natural ventilation caused by the seasonal temperature difference between in and out of the underground facilities. Furthermore, the temporary increase in the equilibrium factor of radon in the drift at the start of ventilation is supposed to be due to the aerosol increase by the ventilation flow, such as the dust blown up.

Proceedings of Information and Opinion Exchange Conference on Geoscientific Study, 2019

Nishio, Kazuhisa*; Shimizu, Mayuko; Iyatomi, Yosuke; Hama, Katsuhiro

JAEA-Review 2020-013, 59 Pages, 2020/08

JAEA-Review-2020-013.pdf:19.64MB

The Tono Geoscience Center (TGC) of Japan Atomic Energy Agency (JAEA) has been conducting geoscientific study in order to establish a scientific and technological basis for the geological disposal of HLW. Technical information of the result on the geoscientific study conducted at TGC is provided at the annual Information and Opinion Exchange Conference on Geoscientific Study of TGC for exchanging opinions among researchers and engineers from universities, research organizations and private companies. This document compiles the research presentations and posters of the conference in Mizunami on November 20, 2019.

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami group and the Toki granite (fiscal year 2017)

Fukuda, Kenji; Watanabe, Yusuke; Murakami, Hiroaki; Amano, Yuki; Hayashida, Kazuki*; Aosai, Daisuke*; Kumamoto, Yoshiharu*; Iwatsuki, Teruki

JAEA-Data/Code 2018-021, 76 Pages, 2019/03

JAEA-Data-Code-2018-021.pdf:3.78MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the influence of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2017. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Study on engineering technologies in the Mizunami Underground Research Laboratory (FY 2015); Development of recovery and mitigation technology on excavation damage (Contract research)

Fukaya, Masaaki*; Takeda, Nobufumi*; Miura, Norihiko*; Ishida, Tomoko*; Hata, Koji*; Uyama, Masao*; Sato, Shin*; Okuma, Fumiko*; Hayagane, Sayaka*; Matsui, Hiroya; et al.

JAEA-Technology 2016-035, 153 Pages, 2017/02

JAEA-Technology-2016-035.pdf:37.6MB

The researches on engineering technology in the Mizunami Underground Research Laboratory (MIU) project in FY2016, detailed investigations of the (mechanical) behaviors of the plug and the rock mass around the reflood tunnel through ongoing reflood test were performed as part of (5) development of technologies for restoration and/or reduction of the excavation damage. As the result, particularly for the temperature change of the plug, its analytical results agree fairly well agree with the measurement ones. This means cracks induced by temperature stress can be prevented by the cooling countermeasure works reviewed in designing stage. In addition, for the behaviors of the plug and the bedrock boundary after reflooding the reflood tunnel, comparison between the results obtained by coupled hydro-mechanical analysis (stress-fluid coupled analysis) with the ones by several measurements, concluded that the model established based on the analysis results is generally appropriated.

Project report on the construction phase at the Mizunami Underground Research Laboratory Project

Nohara, Tsuyoshi; Saegusa, Hiromitsu*; Iwatsuki, Teruki; Hama, Katsuhiro; Matsui, Hiroya; Mikake, Shinichiro; Takeuchi, Ryuji; Onoe, Hironori; Sasao, Eiji

JAEA-Research 2015-026, 98 Pages, 2016/03

JAEA-Research-2015-026.pdf:32.97MB

Tono Geoscience Center (TGC) of Japan Atomic Energy Agency (JAEA) is being performed Mizunami Underground Research Laboratory (MIU) Project, which is a broad scientific study of the deep geological environment as a basis of research and development for geological disposal of nuclear wastes, in order to establish comprehensive techniques for the investigation, analysis and assessment of the deep geological environment in fractured crystalline rock. The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). The project goals of the MIU Project from Phase I through to Phase III are: (1) to establish techniques for investigation, analysis and assessment of the deep geological environment, and (2) to develop a range of engineering for deep underground application. This report summarizes the results of geoscientific study on Phase II to 500m depth. During Construction phase, we have evaluated of adequacy of techniques for investigation, analysis and assessment of the deep geological environment on Surface-based Investigation phase, and have established systematic methodology for stepwise investigation and evaluation of the geological environment on Construction phase. Further, with respect to design and construction of underground facilities, it was confirmed the validity of the engineering involved in the construction, maintenance and management of underground facilities.

Mizunami Underground Research Laboratory Project; Rock mechanical investigations at the -500m stage

Kuwabara, Kazumichi; Sato, Toshinori; Sanada, Hiroyuki; Takayama, Yusuke

JAEA-Research 2015-005, 378 Pages, 2015/07

JAEA-Research-2015-005.pdf:125.5MB
JAEA-Research-2015-005.zip:0.53MB

This report presents the results of following rock mechanical investigations conducted at the -500m Stage. (1) Laboratory tests using cores and block samples obtained at the -500m Stage. (2) In-situ stress measurement using Compact Conical-ended Borehole Overcoring (CCBO) method at the -500m Stage. (3) In-situ stress measurements using Differential Strain Curve Analysis(DSCA) method at the -500m Stage. (4) Development of rock mechanical model.

Hydrological and geological characterization of deep subsurface structures in and around the main shaft fault at the Mizunami Underground Research Laboratory

Nohara, Tsuyoshi; Sakai, Toshihiro; Murakami, Hiroaki; Ishibashi, Masayuki

no journal, , 

Existing data was analyzed in order to understand Hydrological and Geological Characterization of deep subsurface structures in and around the Main Shaft fault at the Mizunami Underground Research Laboratory. As a result, in response to the low permeability structure of the Main Shaft Fault, fault gouges and alteration parts are found to be continuously distributed in the wall of the Main Shaft. One of the most high-permeable structure was estimated to be constituted by low-angle fractures with a sheet-like calcite. Shear of low angle fractures showed relatively low permeability. It may be possible to understand the permeability structure of these features in a drilling survey of granitic rocks.

Study of permeable structure distribution and hydrogeological structure model of granitic rocks; Features of the permeable structures deduced from the wall surface geological data of the Mizunami Underground Research Laboratory

Nohara, Tsuyoshi; Takeuchi, Ryuji; Sakai, Toshihiro

no journal, , 

Focusing on the characteristics of the faults and fractures of the MIU, based on analysis of existing data and on geological investigations, we examined the geological and hydrological features of the deep underground granitic rocks in the site scale. As a result, main permeable structures of granitic rocks can be associated with the old structures formed with the faulting and/or hydrothermal activity in geological times. Furthermore, we examined the distribution of the major permeable structures, based on the distribution of the geological structures.

Development and validation of a fracture model for the granite rocks at Mizunami Underground Research Laboratory, Japan

Elena, K.*; Teklu, H.*; Wang, Y.*; Iwatsuki, Teruki; Ozaki, Yusuke

no journal, , 

In this study, Discrete Fracture Network Model (DFN) is built based on the fracture data observed in the Mizunami Underground Research Laboratory. 297 fractures data with discharge is analyzed for the estimation of stochastic quantity under the assumption that those fractures are permeable and have an great impact on the hydraulic conductivity field. Both models of fracture and hydraulic conductivity around the Closure Test Drift at the depth of 500m are generated from derived stochastic models. The hydraulic model is input into the numerical simulation. The matching of calculated and observed inflow into research tunnel indicates the validity of generated model and modeling approach for fractured rock. These results are a part of results in Task C of Decovalex2019.