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Journal Articles

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950$$^{circ}$$C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Journal Articles

Corrosion property of container using hybrid material for thermal decomposition process of sulfuric acid

Ioka, Ikuo; Kuriki, Yoshiro*; Iwatsuki, Jin; Kawai, Daisuke*; Yokota, Hiroki*; Inagaki, Yoshiyuki; Kubo, Shinji

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 5 Pages, 2020/08

A thermochemical water-splitting iodine-sulfur processes (IS process) is one of candidates for the large-scale production of hydrogen using heat from solar power. Severe corrosive environment which is thermal decomposition of sulfuric acid exists in the IS process. A hybrid material with the corrosion-resistance and the ductility was made by a plasma spraying and laser treatment. The specimen had excellent corrosion resistance in the condition of 95 mass% boiling sulfuric acid. This was attributed to the formation of SiO$$_{2}$$ on the surface. The container using the hybrid material was experimentally made. The pre-oxidized container using hybrid technique was prepared for the corrosion test in boiling sulfuric acid to evaluate the corrosion characteristics of the container. There was no detaching of the surface with the weld part and the R processing. We proposed the calculation method of corrosion rate from the ions dissolved in the sulfuric acid solution after the corrosion test.

Journal Articles

Study of container using hybrid technique for sulfuric acid decomposition of thermochemical water-splitting iodine-sulfur process

Ioka, Ikuo; Iwatsuki, Jin; Kuriki, Yoshiro*; Kawai, Daisuke*; Yokota, Hiroki*; Kubo, Shinji; Inagaki, Yoshiyuki; Sakaba, Nariaki

Mechanical Engineering Journal (Internet), 7(3), p.19-00377_1 - 19-00377_11, 2020/06

A thermochemical water-splitting iodine-sulfur processes (IS process) is one of candidates for the large-scale production of hydrogen with high cost performance. Severe corrosive environment which is thermal decomposition of sulfuric acid exists in the IS process. A hybrid material with the corrosion-resistance and the ductility was made by a plasma spraying and laser treatment. The specimen had excellent corrosion resistance in the condition of 95 mass% boiling sulfuric acid. This was attributed to the formation of SiO$$_2$$ on the surface. To confirm the production characteristics of a container using the hybrid material, the container which has a welded part, a chamfer, a curved surface was experimentally made. There was no detachment in the plasma spraying and laser treated layer of the container after the laser treatment. It was confirmed that the construction of the container with high corrosion resistance in sulfuric acid was possible in the hybrid technique.

JAEA Reports

Study on the applicability of the fiber-optic crack detection sensor as a safety technology (Joint research)

Hiraiwa, Kenichi*; Hirai, Kazuhide*; Sano, Tadashi*; Osawa, Hideaki; Sato, Toshinori; Aoyagi, Yoshiaki; Fujita, Tomo; Aoyagi, Kazuhei; Inagaki, Daisuke*

JAEA-Technology 2015-033, 50 Pages, 2015/11

JAEA-Technology-2015-033.pdf:12.6MB

Japan Atomic Energy Agency (hereinafter referred to as JAEA) has been conducted a geoscientific research and development project at the Mizunami Underground Research Laboratory and the Horonobe Underground Research Laboratory in order to construct scientific and technological basis for geological disposal. As a collaborative research between JAEA and Tokyo Sokki Kenkyujo Co., Ltd. (hereinafter referred to as TML), we focused on the fiber-optic crack detection sensor developed by TML as a method to detect cracks in the support system that may affect the stability of rock cavern during the operation. To verify long-term safety performance of the sensor for decades, "Evaluation test of long-term durability of fiber-optic crack detection sensor and the support system" at the Mizunami Underground Research Laboratory and "Performance evaluation test of fiber-optic crack detection sensor for in-situ crack detection" at the Horonobe Underground Laboratory Research Laboratory were conducted. As the result, we understand that fiber-optic crack detection sensor is applicable measurement method to promptly detect the cracks in the support system.

Journal Articles

Washout of clay-rich gouge in a pregrouted fault zone and increase of groundwater inflow during tunnel excavation in Neogene siliceous mudstone (Horonobe, Japan)

Ishii, Eiichi; Hashimoto, Yuta; Inagaki, Daisuke*

Proceedings of 10th Asian Regional Conference of International Association for Engineering Geology and the Environment (IAEG ARS 2015) (USB Flash Drive), 4 Pages, 2015/09

This manuscript describes unpredicted inflow which occurred during tunnel excavation for a permeable fault zone with clay-rich gouge although the fault zone was pregrouted. Some observational evidence indicates that the gouge was increasingly washed out into the tunnel through the rockbolts penetrating the gouge and the boundary between the shotcrete and the gouge on the excavation side wall during excavation. The resultant piping/erosion of the gouge probably accelerated groundwater flow from the outer aquifer of the pregrouted zone to the tunnel. After an excavation outcrop exposing the fault zone was temporarily shotcreted, major inflow occurred from the nucleated flow channel in the fault zone, breaking the shotcrete. When a fault zone including such clay-rich gouge is pregrouted, washout of the gouge during tunnel excavation should be fully cared because the gouge itself is not cemented by pre-grouting due to its low-porosity.

Journal Articles

Effective 3D data visualization in deep shaft construction

Inagaki, Daisuke*; Tsusaka, Kimikazu*; Aoyagi, Kazuhei; Nago, Makito*; Ijiri, Yuji*; Shigehiro, Michiko*

Proceedings of ITA-AITES World Tunnel Congress 2015 (WTC 2015)/41st General Assembly, 10 Pages, 2015/05

Journal Articles

Investigations for av change of an excavation damaged zone with time at the 250 m gallery in the Horonobe Underground Research Laboratory

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.

Journal Articles

Hydrogeomechanical investigation of an excavation damaged zone in the Horonobe Underground Research Laboratory

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

Journal Articles

A Study of mechanical stability of support elements and surrounding rock mass during shaft sinking through a fault

Tsusaka, Kimikazu*; Inagaki, Daisuke*; Nago, Makito*; Ijiri, Yuji*

Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 9 Pages, 2014/10

Journal Articles

An Investigation on mechanical properties of in-situ rock mass at the Horonobe Underground Research Laboratory

Tsusaka, Kimikazu*; Inagaki, Daisuke*; Niunoya, Sumio*; Jo, Mayumi*

Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 9 Pages, 2014/10

Journal Articles

Quantitative assessment of an Excavation Damaged Zone from variations in seismic velocity and fracture distribution around a gallery in the Horonobe Underground Research Laboratory

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.

JAEA Reports

Collection of measurement data in 2012 fiscal year at the Horonobe Underground Research Laboratory Project

Inagaki, Daisuke

JAEA-Data/Code 2013-022, 116 Pages, 2014/03

JAEA-Data-Code-2013-022.pdf:8.83MB
JAEA-Data-Code-2013-022-appendix(DVD-ROM)-1.zip:4112.42MB
JAEA-Data-Code-2013-022-appendix(DVD-ROM)-2.zip:4186.23MB
JAEA-Data-Code-2013-022-appendix(DVD-ROM)-3.zip:3175.59MB
JAEA-Data-Code-2013-022-appendix(DVD-ROM)-4.zip:3945.48MB
JAEA-Data-Code-2013-022-appendix(DVD-ROM)-5.zip:1257.91MB

In the Horonobe Underground Research Laboratory (URL) Project, construction of the Ventilation Shaft, the East and West Access Shafts and the drifts has been conducted as a phase II research. In the research, observation of the lithofacies and fractures, and in-situ tests are conducted in each face. In addition, measuring instruments such as tunnel lining concrete stress meter and extensometer are installed in particular face for the purpose of the validation of the results of predictive analysis, conducted in phase I. This report summarizes the measurements data acquired at the East shaft and the 350 m Gallery.

Journal Articles

A Study of the regional stress and the stress state in the galleries of the Horonobe Underground Research Laboratory

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.

Journal Articles

Rock spalling and countermeasures in shaft sinking at the Horonobe Underground Research Laboratory

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Aoki, Tomoyuki*; Shigehiro, Michiko*

Proceedings of 6th International Symposium on In-situ Rock Stress (RS 2013) (CD-ROM), p.339 - 346, 2013/08

The Horonobe Underground Research Laboratory is planned to consist of the Ventilation Shaft (4.5 m in diameter), the East and West Access Shafts (6.5 m in diameter). The host rock of the URL site comprises Neogene sedimentary rocks. The unconfined compressive strength of the rocks is less than 20 MPa on average. Anisotropic stress distribution around the URL is also confirmed. Because several highly permeable fractures (hydraulic transmissivity: approximately 10$$^{-5}$$m$$^{2}$$/s) with the size greater than the shaft diameter develop under the condition of around 2 in competence factor (i.e., the ratio of the unconfined compressive strength of rock to the initial stress) below a depth of 250 m, shaft sinking is a challenging issue from the viewpoint of tunnel engineering in the Horonobe URL Project. In this paper, the construction of the Ventilation Shaft below a depth of 250 m at the Horonobe URL is reported. During shaft sinking, fracture mapping of the shaft wall was performed. The geometry of the shaft wall was also measured using a three-dimensional laser scanner in order to investigate the shape and volume of rock spalling in the shaft wall resulting from the excavation work. Rock spalling was predominantly observed on the south and north wall rock corresponding to the direction of the minimum horizontal initial stress. A large amount of rock spalling also developed along a large-scale fault. With respect to the lining span and the layout of rockbolts, several support patterns were designed and installed as the countermeasures to prevent the development of excessive rock spalling. A flowchart for selecting the optimum support design was then developed.

Journal Articles

Relationship between rock mass properties and damage of a concrete lining during shaft sinking in the Horonobe Underground Research Laboratory Project

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Kamemura, Katsumi*; Matsubara, Makoto*; Shigehiro, Michiko*

Proceedings of ITA-AITES World Tunnel Congress 2013 (WTC 2013)/39th General Assembly, p.2014 - 2021, 2013/05

Japan Atomic Energy Agency (JAEA) has been constructing three shafts to a depth of 500 m in the Horonobe Underground Research Laboratory Project. In this study, in consideration of support patterns installed, a relationship between the rock mass properties and mechanical response to excavation was investigated in detail during the construction of the East Access Shaft below a depth of 250 m. Since the shaft has intersected several faults with the size greater than the shaft diameter, some amounts of rock spalling have occurred and cracks have severely developed in a concrete lining in highly fractured zones. The results of pre-excavation grouting were compared with the results of fracture mapping in the shaft wall obtained during the shaft sinking. Applicability of several support patterns installed to control massive spalling during the shaft sinking was also analysed using the results of geometry profiling of shaft wall using a three-dimensional laser scanner and convergence measurements. As a result, based the empirical relationships among the characteristics of rocks, dimension of spalling, damage of a concrete lining and support patterns, a flow chart for selection of span of a concrete lining was proposed to control its severe damage prior to shaft excavation.

JAEA Reports

Collection of URL measurement data in 2011 fiscal year at the Horonobe Underground Research Laboratory Project

Inagaki, Daisuke; Tokiwa, Tetsuya; Murakami, Hiroaki

JAEA-Data/Code 2012-029, 132 Pages, 2013/02

JAEA-Data-Code-2012-029.pdf:8.0MB
JAEA-Data-Code-2012-029-appendix(DVD-ROM)-1.zip:5339.82MB
JAEA-Data-Code-2012-029-appendix(DVD-ROM)-2.zip:4415.05MB
JAEA-Data-Code-2012-029-appendix(DVD-ROM)-3.zip:127.72MB

In the Horonobe Underground Research Laboratory (URL) Project, construction of the Ventilation Shaft, the East Shaft and the drifts has been conducted as a phase 2 research. In the research, observation of the lithofacies and fracture, and ${it in-situ}$ tests, simple elastic wave exploration, schmidt hammer test, equotip test, point load test are conducted in each face, and measuring instruments such as extensometer, rock-bolt axial force meter, shotcrete stress meter and tunnel lining concrete stress meter are installed in particular face. In addition, for the purpose of the validation of the results of predictive analysis, conducted in phase 1, about the amount of spring water during construction of underground facilities, data on the changes of amount of spring water and water quality is obtained. This report summarizes the measurements data acquired at the Ventilation Shaft, the East shaft and the 250 m Gallery.

Journal Articles

Initial stress measurement by hydraulic fracturing method in diatomaceous mudstone in the Horonobe Underground Research Laboratory

Kondo, Keiji; Tsusaka, Kimikazu; Inagaki, Daisuke; Sugita, Yutaka; Kato, Harumi*; Niunoya, Sumio*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.583 - 588, 2013/01

no abstracts in English

Journal Articles

Influence of rock spalling on concrete lining in shaft sinking at the Horonobe Underground Research Laboratory

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Koike, Masashi*; Matsubara, Makoto*; Sugawara, Kentaro*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.911 - 916, 2013/01

A repository for high-level radioactive waste in deep underground consists of several underground structures such as access and disposal drifts and shafts. In deep geological disposal project, a shaft is the first underground structure to be constructed and the last one to be backfilled. Therefore, the stability of shaft is one of key factors to steadily manage the project in the construction and operation phases. In this paper, the authors discuss influence of rock spalling on concrete lining in shaft sinking. Japan Atomic Energy Agency has been constructing three shafts (one is for ventilation and the others are for access use) up to a depth of 500 m in the Horonobe Underground Research Laboratory. During the construction of the Ventilation Shaft (4.5 m in diameter) below a depth of 250 m, rock spalling occurred at several depths and an open crack has developed in a concrete lining installed just above rock spalling. The authors have measured geometry of shaft wall by using three-dimensional laser scanner. They also conducted numerical analysis in order to calculate change in stress distribution and deformation induced by rock spalling in a concrete lining and the surrounding rock. As a result, it was clarified that rock spalling induced tensile stress in the vertical direction in a concrete lining. Especially, the tensile stress in a concrete lining was likely to exceed tensile strength of a concrete lining in the case that it developed more than 100 cm in depth.

Journal Articles

Geomechanical assessment of excavation damaged zone in the Horonobe Underground Research Laboratory, Japan

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.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation report for the 2011 fiscal year

Nakayama, Masashi; Amano, Kenji; Tokiwa, Tetsuya; Yamamoto, Yoichi; Oyama, Takuya; Amano, Yuki; Murakami, Hiroaki; Inagaki, Daisuke; Tsusaka, Kimikazu; Kondo, Keiji; et al.

JAEA-Review 2012-035, 63 Pages, 2012/09

JAEA-Review-2012-035.pdf:12.23MB

The Horonobe Underground Research Laboratory Project is planned to extend over a period 20 years. The investigations will be conducted in three phases, namely "Phase 1: Surface-based investigations", "Phase 2: Construction Phase" (investigations during construction of the underground facilities) and "Phase 3: Operation phase"(research in the underground facilities). This report summarizes the results of the investigations for the 2011 fiscal year (2011/2012). The investigations, which are composed of "Geoscientific research" and "R&D on geological disposal technology", were carried out according to "Horonobe Underground Research Laboratory Project Investigation Program for the 2011 Fiscal year". The results of these investigations, along with the results which were obtained in other departments of Japan Atomic Energy Agency (JAEA), are properly offered to the implementations and the safety regulations. For the sake of this, JAEA has proceeded with the project in collaboration with experts from domestic and overseas research organisations.

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