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Journal Articles

Characteristics and formation process of fractures in crystalline rocks in northern Kyushu

Murakami, Hiroaki; Ashizawa, Masaomi*; Tanaka, Kazuhiro*

Oyo Chishitsu, 59(1), p.2 - 12, 2018/04

This study describes the features of fractures and their fillings along with the long-term behavior of their hydrogeological structures in an underground environment based on the results of a geological investigation conducted at an underground facility in northern Kyushu. Fractures were classified into five groups on the basis of fracture orientation: A, B, C, D, and low-angle groups. The genesis of all fractures is the cooling process of granodiorite pluton. Almost all of the water-conducting fractures are included in the B group. Because a number of fracture fillings in the B group are filled by prehnite and crushed fragments of epidote and quartz, the fractures in this group alternated sealing and re-opening. The fracture characteristics in the B group are follow as: accompanying many alteration halos, long trace length, and cutting off other fractures. These results indicate that fractures in the B group have possibly functioned as pathways for groundwater flow in the long term.

JAEA Reports

Synthesized research report in the second mid-term research phase, Mizunami Underground Research Laboratory Project, Horonobe Underground Research Laboratory Project and Geo-stability Project (Translated document)

Hama, Katsuhiro; Sasao, Eiji; Iwatsuki, Teruki; Onoe, Hironori; Sato, Toshinori; Fujita, Tomo; Sasamoto, Hiroshi; Matsuoka, Toshiyuki; Takeda, Masaki; Aoyagi, Kazuhei; et al.

JAEA-Review 2016-014, 274 Pages, 2016/08

JAEA-Review-2016-014.pdf:44.45MB

We synthesized the research results from the Mizunami/Horonobe Underground Research Laboratories (URLs) and geo-stability projects in the second midterm research phase. This report can be used as a technical basis for the Nuclear Waste Management Organization of Japan/Regulator at each decision point from siting to beginning of disposal (Principal Investigation to Detailed Investigation Phase).

JAEA Reports

Studies on the reconstruction of the concept of rock mass around the tunnel; Japanese fiscal year, 2014 (Contract research)

Kojima, Keiji*; Onishi, Yuzo*; Aoki, Kenji*; Tochiyama, Osamu*; Nishigaki, Makoto*; Tosaka, Hiroyuki*; Yoshida, Hidekazu*; Murakami, Hiroaki; Sasao, Eiji

JAEA-Research 2015-017, 54 Pages, 2015/12

JAEA-Research-2015-017.pdf:17.3MB

This report is concerned with research to reconstruct more realistic near-field (NF) concept for the geological disposal of radioactive waste. This year is the final year of this committee activities. So we have carried out the summary on Re-thinking of NF concept and its technical basis. Cooperation between the study fields and combination of various science and technology and evaluation methods are one of the important technical bases of NF concept. In addition, since the "Great East Japan Earthquake 2011", the safety paradigm has shifted dramatically. In the reconstruction of realistic NF concept, it is necessary to analyze what security matters whether society has become unacceptable for geological disposal. Committee, we also exchange views on such matters and presented the direction of future research and development for geological disposal.

Journal Articles

Stability of geological environment from the perspective of uranium deposit

Sasao, Eiji

ESI-News, 32(4), p.155 - 162, 2014/08

This report compiled the information on distribution and mode of occurrence of uranium deposit was compiled from the published data. Distribution of uranium deposit suggests that geological environments suitable for geological isolation are widely distributed in the Japanese Islands, despite their location in a geologically active area. The mode of occurrence of the uranium deposits indicates that formation of uranium-bearing mineral as well as sorption is expected in both sedimentary and crystalline rocks. The functioning of the natural barrier would be expected in various geological environments in the Japanese Islands, because mineralization and sorption are regarded as a barrier function to retard the migration of radionuclides in HLW, and because of the uranium deposits in the various rock types.

JAEA Reports

Activation energy of diffusivities for deuterated water in compacted sodium-bentonite; Through-diffusion experiment and molecular dynamics simulation

; Sato, Haruo; Ishidera, Takamitsu; Fujii, Naoki*; Kawamura, Katsuyuki*

JNC-TN8400 2001-031, 44 Pages, 2002/05

JNC-TN8400-2001-031.pdf:1.58MB

In order to quantify effect of temperature on diffusivity of deuterated water (HDO) in compacted sodium-bentonite, through-diffusion experiments were conducted at elevated tempemture from 298 to 333 K. Kunipia F (Na-montmorillonite content $$>$$ 98 wt. %; Kunimine Industly Co.) was compacted to a dry density of 0.9 and l.35 Mg/m$$^{3}$$. Since smectite flakes were perpendicularly oriented to a direction of compaction, anisotropy of diffusivity was investigated parallel and normal to the preferred orientation of smectite. Effective diffusion coeficient D$$_{e}$$ of HDO was larger for a diffusional direction parallel to the preferred orientation than normal to that for both dry densities. These results well agreed to the previously reported ones for tritiated water. Activation energies of D$$_{e}$$ in compacted bentonite increased with increasing dry density in the range of 19 - 25 kJ/mol which was slightly larger than that in bulk water (18 kJ/mol). This relationship can be considered to be due to both the pore structure development and high activation energy of water (18-23 kJ/mol) in the vicinity of smectite surface (within 2 nm) on the basis of molecular dynamics simulations.

JAEA Reports

Long-term immersion tests of engineered materials in the Tono mine; Results for glass material

; ; *; Hirose, Ikuro

JNC-TN7430 2000-001, 47 Pages, 2000/12

JNC-TN7430-2000-001.pdf:4.09MB

Long-term immersion tests of glass material at ambient temperature (about 18 $$^{circ}$$C) for 10 years were performed in a gallery at the Tono mine in Japan, in order to assess durability of glass matelial contacted with natural groundwater. The gallery was constructed at a depth of 130 m below ground surface in the Toki Granite. Monolithic glass blocks with dimensions of 10 $$times$$ 10 $$times$$ 10 mm (cubic type) and of 25 mm in diameter and 8 mm in thickness (disk type: The wall of sample was covered by stainless steel of 1 mm thick.) were used for the tests. Both type of samples with and without clay were put in Teflon vessels, which have small holes on the wall, and inserted into boreholes excavated at the gallery floor. In addition to the immersion tests, static leaching test with cubic type glass and ground water was also performed at the gallery. The samples of each test were collected in time intervals of 6 months, 1 year, 2 years, 3 years and 10 years and were subjected to weight loss measurement and several surface analyses. The results were as follows: (1)Weight losses of each sample were proportional to time intervals. This result is attributable to constant dissolved silica concentration in the ground water during tests. (2)The weight losses of disk type glass were slightly larger than those of cubic type glass. This result is attributable to elemental release from internal cracks of disk type glass, instead of effect of stainless steel on the glass dissolution. (3)The weight losses for the tests with clay were slightly smaller than those for tests without clay. This result is attributable to higher concentration of dissolved silica in pore water of clay.

JAEA Reports

The Primary evaluation of the impacts of naturaI phenomena on the safety functions of the geological disposal system; An Example study on site generic phase

Makino, Hitoshi; ; Miyahara, Kaname

JNC-TN8400 2000-033, 74 Pages, 2000/11

JNC-TN8400-2000-033.pdf:3.13MB

Natural phenomena is one of the potential factors perturbing the long-term stability of the geological environment, and for natural phenomena, it is necessary to consider uncertainties relevant to time, frequency and effect. Therefore it will be important to have information about the potential impacts of natural phenomena on the safety functions of geological disposal system in the future by assuming that natural phenomena perturbs the safety functions of the geological disposal system. In this report, we have considered 4 natural phenomena, 'uplift, subsidence and denudation', 'climatic and sea-level changes', 'earthquakes and fault movement' and 'volcanism', which had been extracted by investigation in foreign countries and by considering the characteristics of Japan as natural phenomena which may perturb the long-term stability of the geological environment. And we have considered mainly typical effects of naturaI phenomena on geological environment and investigated the typical impacts of those natural phenomena on the safety functions of the geological disposal system. On perturbation scenarios, the maximum of total doses have been less than regulatory guidelines in foreign countries in all situations except the cases assuming that a new fault, which causes significant pathway of groundwater flow and nuclide migration, intersects the waste packages. In the case, the maximum of total doses may reach the same level as regulatory guidelines in foreign countries or natural radiation exposure in Japan depending on fault generation time or grandwater flow rate through the fault. And, on isolation failure scenarios, it has been implied that nuclide mass/flux originated from geological disposal is comparable level with nuclide mass/flux in natural environment. These results could give useful information about the potential impacts of natural phenomena on the safety functions of geological disposal system, and also could show the potential importance of ...

JAEA Reports

None

Takeda, Seietsu; ; ; Nakatsuka, Noboru; ; ;

JNC-TN7410 2000-003, 65 Pages, 2000/11

JNC-TN7410-2000-003.pdf:5.09MB

JAEA Reports

Regional hydrogeological study project; Results from 1992-1999 period

Koide, Kaoru; ; Takeuchi, Shinji; ; ; ;

JNC-TN7400 2000-014, 83 Pages, 2000/11

JNC-TN7400-2000-014.pdf:4.84MB

The Japan Nuclear Cycle Development Institute (JNC) has been conducting a wide range of geoscientific research in order to build a firm scientific and technological basis for the research and development of geological disposal. One of the major components of the ongoing geoscientific research programme is the Regional Hydrogeological Study (RHS) project in the Tono region, central Japan. The main goal of the RHS project is to develop and demonstrate surface-based investigation methodologies to characterize geological environments at a regional scale in Japan. The RHS project was initiated in 1992. The first five years of the project were devoted mainly to develop methodologies and techniques for deep borehole investigations in crystalline rock in Japan. Investigations to verify the performance of new instruments and methods for borehole drilling, hydraulic testing and groundwater sampling were conducted. In the last four years, surface-based investigations and a stepwise development of models of the geological environment have been carried out. To date, remote sensing, geological mapping, airborne and ground geophysical investigations, and measurements in eleven deep boreholes have been carried out. Hydro monitorring is continuing in these boreholes. Important results that have been obtained from these investigations include multi-disciplinaly information about the heterogeneity of lithology and hydraulic, geochemical and rock mechanical properties of the granitic rock, and evolution of the groundwater geochemistry. Technical knowledge and experience have been accumulated, which allow application of the methodologies and techniques to characterize the geological environment in crystalline rock. The results from these R%D activities were used as prime inputs for the H12 report that JNC submitted to the Japanese Government in l999. Results from such R&D is also acknowledged by other geoscientific studies in general. JNC will synthesize the results from R&D ...

JAEA Reports

None

*

JNC-TN1440 2000-010, 145 Pages, 2000/11

JNC-TN1440-2000-010.pdf:6.19MB

no abstracts in English

JAEA Reports

None

*

JNC-TN1440 2000-009, 150 Pages, 2000/11

JNC-TN1440-2000-009.pdf:7.93MB

no abstracts in English

JAEA Reports

None

*

JNC-TJ7400 2000-015, 203 Pages, 2000/08

JNC-TJ7400-2000-015.pdf:6.07MB

no abstracts in English

JAEA Reports

None

; ; ; Saito, Hiroshi;

JNC-TN7410 2000-004, 16 Pages, 2000/04

JNC-TN7410-2000-004.pdf:0.5MB

JAEA Reports

None

Koide, Kaoru; ; ; ; ; Saito, Hiroshi

JNC-TN7410 2000-002, 31 Pages, 2000/04

JNC-TN7410-2000-002.pdf:1.55MB

JAEA Reports

None

Koide, Kaoru; ; ; ; ; Saito, Hiroshi; Takeuchi, Shinji

JNC-TN7410 2000-001, 56 Pages, 2000/04

JNC-TN7410-2000-001.pdf:2.6MB

JAEA Reports

None

Ezaki, Tetsuro*; Jinno, Kenji*; Mitani, Yasuhiro*; *; Uchida, Masahiro; *

JNC-TY8400 2000-004, 94 Pages, 2000/03

JNC-TY8400-2000-004.pdf:4.88MB

no abstracts in English

JAEA Reports

None

*; *

JNC-TJ7440 2000-004, 52 Pages, 2000/03

JNC-TJ7440-2000-004.pdf:12.62MB

no abstracts in English

JAEA Reports

None

*

JNC-TJ7420 2000-007, 28 Pages, 2000/03

JNC-TJ7420-2000-007.pdf:11.92MB

no abstracts in English

JAEA Reports

Investigation on sealing technique in geological disposal

*; Toida, Masaru*; Masumoto, Kazuhiko*

JNC-TJ8400 2000-021, 196 Pages, 2000/02

JNC-TJ8400-2000-021.pdf:8.23MB

For the geological disposal of high level radioactive wastes, after placement of tbe wastes, it is necessary to close off (to be called "sealing" hereafter) the underground potential passages (disposal pits, disposal tunnels, main and connecting tunnels and access tunnels) with an effective combination of engineered barriers such as buffers, backfilling materials, plugs and grout. It is necessary to ensure the long-term durability to isolate disposed wastes in the system. The results of the research works this year are as follows; (1)The objectives are to discuss the design of tunnel sealing experiments at URL site. The results of research were about (a)tracer experiment and numerical analysis (b)evaporation measurement (c)presentation at the coordination meeting (2)The discussion was about the equipment of inclined compaction methods and bearing capacity of rock against pressures for the concrete plugs.

JAEA Reports

Investigation on sealing technique in geological disposal

Toida, Masaru*; Masumoto, Kazuhiko*; *; Okutsu, Kazuo*; *

JNC-TJ8400 2000-020, 68 Pages, 2000/02

JNC-TJ8400-2000-020.pdf:5.87MB

For the geological disposal of high level radioactive wastes, after placement of the wastes, it is necessary to close off (to be called "sealing" hereafter) the underground potential passages (disposal pits, disposal tunnels, main and connecting tunnels and access tunnels) with an effective combination of engineered barriers such as buffers, backfiling materials, plugs and grout. It is necessary to ensure the long-term durability to isolate disposed wastes in the system. The results of the research works this year are as follows ; (1)The objectives are to discuss the design of tunnel sealing experiments at URL site. The results of research were about (a)tracer experiment and numerical analysis (b)evaporation measurement (c)presentation at the coordination meeting. (2)The discussion was about the equipment of inclined compaction methods and bearing capacity of rock against pressures for the concrete plugs.

67 (Records 1-20 displayed on this page)