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Sugita, Yutaka; Aoyagi, Kazuhei; Kubota, Kenji*; Nakata, Eiji*; Oyama, Takahiro*
JAEA-Research 2018-002, 72 Pages, 2018/06
JAEA-Research-2018-002.pdf:6.16MB
In a excavation of shafts and galleries in the deep underground for disposing radioactive waste, an excavation damaged zone (EDZ) is developed around the galleries and shafts owing to the stress redistribution. Since the characteristic changes of the rock mass in the EDZ affects the radionuclides migration behavior, it is important to understand the long-term behavior of the EDZ. Thus, we performed the in situ experiment to investigate the long-term behavior of EDZ as part of the collaborative research between Japan Atomic Energy Agency and Central Research Institute of Electric Power Industry in the 140m gallery in the Horonobe Underground Research Laboratory. In this research, we investigated the extent, mechanism of the change of hydro-mechanical characteristic, and long-term behavior of the EDZ on the basis of the comprehensive estimation of the results of the observation of the drift wall and the various investigations using boreholes such as geological investigation, the seismic and resistivity tomography, hydraulic test, water content monitoring, borehole loading test, convergence measurement, and so on. In addition, we clarified applicability and future tasks of the testing method used in this research for the investigation of the long-term behavior of the EDZ.
Aoyagi, Kazuhei; Kubota, Kenji*; Nakata, Eiji*; Suenaga, Hiroshi*; Nohara, Shintaro*
JAEA-Research 2017-004, 91 Pages, 2017/06
JAEA-Research-2017-004.pdf:6.07MB
In this study, we performed seismic tomography, seismic refraction survey, resistivity tomography, and hydraulic tests to investigate the hydro-mechanical property of the excavation damaged zone (EDZ) in the 250 m gallery of the Horonobe Underground Research Laboratory. As a result of seismic tomography, seismic velocity is significantly decreased within 1 m from the gallery wall. The decrease of seismic velocity is related to the density of fracture induced around the gallery wall as a result of the gallery excavation. Thus the extent of the fractures induced by gallery excavation, i.e., EDZ fractures is clarified to be within 1.0 m from the gallery wall. The enhanced hydraulic conductivity was detected within 0.5 to 1.0 m from the gallery wall on the basis of the result of hydraulic tests. This is almost consistent with the extent of the region that seismic velocity is significantly decreased. Therefore, it is estimated that EDZ fractures induced around the gallery leads to the increase of hydraulic conductivity. In addition, the desaturation zone around the gallery is not induced as a result of resistivity tomography. From these results, the hydro-mechanical property of the EDZ is clarified in detail. Also, the in situ tests and evaluation method applied in this study are appropriate to investigate the EDZ in detail.
Hama, Katsuhiro; Sasao, Eiji; Iwatsuki, Teruki; Onoe, Hironori; Sato, Toshinori; Fujita, Tomoo; 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).
Hama, Katsuhiro; Mizuno, Takashi; Sasao, Eiji; Iwatsuki, Teruki; Saegusa, Hiromitsu; Sato, Toshinori; Fujita, Tomoo; Sasamoto, Hiroshi; Matsuoka, Toshiyuki; Yokota, Hideharu; et al.
JAEA-Research 2015-007, 269 Pages, 2015/08
JAEA-Research-2015-007.pdf:68.65MBJAEA-Research-2015-007(errata).pdf:0.07MB
We have synthesised the research results from Mizunami/Horonobe URLs and geo-stability projects in the second mid-term research phase. It could be used as technical bases for NUMO/Regulator in each decision point from sitting to beginning of disposal (Principal Investigation to Detailed Investigation Phase). High quality construction techniques and field investigation methods have been developed and implemented and these will be directly applicable to the National Disposal Program (along with general assessments of hazardous natural events and processes). It will be crucial to acquire technical knowledge on decisions of partial backfilling and final closure by actual field experiments in Mizunami/Horonobe URLs as main themes for the next phases.
Aoyagi, Kazuhei; Ishii, Eiichi; Kondo, Keiji*; Tsusaka, Kimikazu*; Fujita, Tomoo
JAEA-Research 2015-001, 46 Pages, 2015/03
JAEA-Research-2015-001.pdf:4.92MB
JAEA-Research-2015-001-appendix(CD-ROM).zip:67.95MB
Japan Atomic Energy Agency (JAEA) has been conducting R&D activities at the off-site URL at Horonobe, Hokkaido, Japan in order to enhance reliability of technology related to deep geological disposal of HLW in sedimentary rocks. In this report, strength properties (cohesion and frictional angle) of rock masses in the Koetoi and Wakkanai formations are investigated on the basis of triaxial tests conducted in the Horonobe URL considering the relative depths to the formation. Strength properties investigated in this report are compared with the properties obtained in the designing phase. The cohesion in the Koetoi Formation increased with increasing depth. On the other hand, in the transition zone of the Wakkanai Formation, the cohesion increased significantly in the shallow Wakkanai formation (transition zone). Below the transition zone, the cohesion does not significantly depend on the depth. Thus the strength properties between two formations were found to be different. Comparing the cohesions and frictional angles determined from triaxial tests with the values determined in the designing phase, there was no agreement between these values in almost all the depth. Thus it is essential to determine cohesion and frictional angle considering the relative depths to the formation for detailed understanding of strength properties of rock mass.
Aoyagi, Kazuhei; Tsusaka, Kimikazu; Kubota, Kenji*; Tokiwa, Tetsuya; Kondo, Keiji; Inagaki, Daisuke
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 70(4), p.412 - 423, 2014/12
The authors have been conducting seismic and resistivity tomography surveys in a gallery of the Horonobe Underground Research Laboratory in order to investigate an extent of an excavation damaged zone (EDZ) along time. The objective of this paper is to discuss an influence of fracture distribution and water saturation of a rock mass on variations in seismic velocity and the value of apparent resistivity in an EDZ. Based on the result of seismic tomography survey, the extent of a layer which has low seismic velocity was about 1.0 m from the gallery wall after excavation of the tomography area. From the results of resistivity tomography survey, the value of apparent resistivity has not changed remarkably along time. To investigate a relationship between variations in seismic velocity and density of fracture in the survey area, the authors built a three dimensional fracture model around the tomography area. From the comparison of seismic velocity with density of fracture, seismic velocity decreased almost linearly as the density of fracture increased. Also, it was found that density of fracture in the layer of low seismic velocity could be estimated using a simple numeric model. From this result, seismic tomography survey and investigation of density of fracture are suitable method for evaluation of an EDZ.
Aoyagi, Kazuhei; Tsusaka, Kimikazu*; Nohara, Shintaro*; Kubota, Kenji*; Tokiwa, Tetsuya*; Kondo, Keiji*; Inagaki, Daisuke*
Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 8 Pages, 2014/10
Aoyagi, Kazuhei; Tsusaka, Kimikazu; Kondo, Keiji; Inagaki, Daisuke
Rock Engineering and Rock Mechanics; Structures in and on Rock Masses, p.487 - 492, 2014/05
In a high-level radioactive waste (HLW) disposal project, it will be important to evaluate an Excavation Damaged Zone (EDZ). In particular, in an EDZ, new fractures are expected to develop in response to excavation. These fractures can cause increase in permeability of rock mass around the gallery. In order to investigate density of these fractures in an EDZ, the authors integrated information of fracture mapping of a gallery into a result of seismic tomography survey conducted in the Horonobe underground Research Laboratory. As a result, seismic velocity decreased almost linearly as the density of fracture increased. Also, it was found that density of fracture in an EDZ is expected to be evaluated by the trend which is calculated from simple numeric model. This analysis provides useful data for HLW disposal from a viewpoint that one can evaluate condition of fractures in an EDZ using the result of seismic tomography survey.
Aoyagi, Kazuhei; Tsusaka, Kimikazu; Tokiwa, Tetsuya; Kondo, Keiji; Inagaki, Daisuke; Kato, Harumi*
Proceedings of 6th International Symposium on In-situ Rock Stress (RS 2013) (CD-ROM), p.331 - 338, 2013/08
In a high-level radioactive waste disposal, initial stress state is important for designing support and layout of repository. Based on the background, objectives of this paper is to investigate the state of regional stress in detail and change of initial stress state along construction of the Underground Research Laboratory (URL). Hydraulic fracturing tests and observation of the borehole breakouts through borehole televiewer logging have been conducted in the boreholes around the Horonobe URL and in the galleries of the URL. As a result, the values of the stress measured in the boreholes around the URL increased along depth and the orientations of the maximum horizontal stress were different between a map scale fault. In addition, values of initial stresses measured in the galleries were less than those of boreholes around the URL and orientation of the maximum horizontal stress were different in each depth of the gallery. These results suggest that measurements of the stress in the galleries are important for modification of the layout designed before construction of the URL.
Aoyagi, Kazuhei; Tsusaka, Kimikazu; Tokiwa, Tetsuya; Kondo, Keiji; Inagaki, Daisuke
Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.905 - 910, 2013/01
In a high-level radioactive waste (HLW) disposal project, quantitative evaluation of the extent of excavation damaged zone (EDZ), which is estimated to cause the mechanical, hydrological and geochemical effect to the rock. In Horonobe URL, P-wave tomography survey and rock core observation in the tomography area were conducted at the depth of 250 m to evaluate EDZ. In addition to these in-situ measurement and observation, the authors conducted numerical analysis to identify damaged zone. As a result of P-wave tomography, remarkable low velocity layer was extended about 0.6 m from the drift wall. From the result of rock core observation, the region which has several EDZ fractures developed to 0.3 m from the gallery wall. Furthermore, the numerical analysis showed that the failure zone was extended about 0.2 m from the drift wall. From these results, the authors concluded that the extension of remarkable low velocity layer matched with the extension of the region which has several EDZ fractures.
Okamura, Hiroyuki; Sakae, Hiroki*; Kidani, Keiji*; Hirayama, Naoki*; Aoyagi, Noboru; Saito, Takumi*; Shimojo, Kojiro; Naganawa, Hirochika; Imura, Hisanori*
Polyhedron, 31(1), p.748 - 753, 2012/01
Times Cited Count：28 Percentile：87.66(Chemistry, Inorganic & Nuclear)Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Ito, Shun*; Aoyagi, Eiji*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru
IEEE Transactions on Applied Superconductivity, 21(3), p.3192 - 3195, 2011/06
Times Cited Count：5 Percentile：33.75(Engineering, Electrical & Electronic)The flux pinning behaviors for the heavy ion irradiated Er123 films are investigated based on the detailed 
(
, 
, 
) properties. The double peaks of 
curves for //c appear in case of the matching field of 0.3 T along 
-axis and 1.7 T tilted from -axis. In addition, the peaks on () at = 0
(B//c), which originate from the columnar defects, decrease with increasing magnetic field but increase again near the irreversibility field. We found that the cooperation model of the -axis correlated and random pinning centers can describe the observed double peak behavior of (B) and the angular dependence of related to the correlated pinning.
Nagaishi, Ryuji; Yamada, Reiji; Aoyagi, Noboru; Sugo, Yumi
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 161, 2008/03
From the standpoints of utilization of radioactive wastes, and of sophistication of separation process of spent fuels, we have been investigating promotion or inhibition of radiation-induced reactions in immiscible heterogeneous systems: solutions coexisting/contacting with solid oxides, solvent system with aqueous and organic phases, etc.. We have recently report that the reactions of reduction of metal ions and of hydrogen production in aqueous solution were promoted by adding oxide particles to the solution, and that the radiolysis of amides in n-dodecane was dependent on aqueous solution contacting with the n-dodecane. In this report, we illustrate recover of platinum-group elements from aqueous solution, and non-toxic treatment of chrysotile asbestos using ionizing radiations as the experimental results found in fiscal 2006.
Aoyagi, Noboru; Nagaishi, Ryuji; Esaka, Fumitaka; Yamada, Reiji
Chemistry Letters, 36(7), p.890 - 891, 2007/07
Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)A high yield of H
gas was unprecedentedly produced due to the radiolysis of water containing asbestos while the morphology of them turned fibrous bundles into non-fibrous particles in 0.40 M HSO
solution over 2.0 MGy dose of irradiation. In conclusion, irradiation against asbestos in solutions can promote the hydrogen gas production and cause the morphological change of chrysotile without providing heat or chemicals.
Fukazawa, E.*; Tanaka, M.*; Yamamoto, H.*; Taira, K.*; Yamamoto, M.*; Okutsu, Kazuo*; Hane, Koji*; Aoyagi, Takayoshi*; Morikawa, Seiji*; Furuichi, Mitsuaki*
PNC TJ1100 98-007, 60 Pages, 1998/02
None
Fukazawa, E.*; Tanaka, M.*; Yamamoto, H.*; Taira, K.*; Yamamoto, M.*; Okutsu, Kazuo*; Hane, Koji*; Aoyagi, Takayoshi*; Morikawa, Seiji*; Furuichi, Mitsuaki*
PNC TJ1100 98-006, 434 Pages, 1998/02
None
Sakata, Shinya; *; *; *; Aoyagi, Tetsuo; Saito, Naoyuki; Harada, Hiro; Tani, Keiji
JAERI-M 94-050, 32 Pages, 1994/03
no abstracts in English
*; Aoyagi, Tetsuo; *; *; Tani, Keiji
JAERI-M 94-040, 90 Pages, 1994/03
no abstracts in English
Kikuchi, Mitsuru; *; Aoyagi, Tetsuo; Tani, Keiji
JAERI-M 91-057, 287 Pages, 1991/03
no abstracts in English
Aoyagi, Tetsuo; Tani, Keiji; *; *
JAERI-M 89-015, 90 Pages, 1989/02
no abstracts in English
