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Journal Articles

Thundercloud project; Exploring high-energy phenomena in thundercloud and lightning

Yuasa, Takayuki*; Wada, Yuki*; Enoto, Teruaki*; Furuta, Yoshihiro; Tsuchiya, Harufumi; Hisadomi, Shohei*; Tsuji, Yuna*; Okuda, Kazufumi*; Matsumoto, Takahiro*; Nakazawa, Kazuhiro*; et al.

Progress of Theoretical and Experimental Physics (Internet), 2020(10), p.103H01_1 - 103H01_27, 2020/10

Journal Articles

Downward terrestrial gamma-ray flash observed in a winter thunderstorm

Wada, Yuki*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Matsumoto, Takahiro*; Makishima, Kazuo*; Tsuchiya, Harufumi

Physical Review Letters, 123(6), p.061103_1 - 061103_6, 2019/08

 Times Cited Count:7 Percentile:20.02(Physics, Multidisciplinary)

Journal Articles

Gamma-ray glow preceding downward terrestrial gamma-ray flash

Wada, Yuki*; Enoto, Teruaki*; Nakamura, Yoshitaka*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakazawa, Kazuhiro*; Morimoto, Takeshi*; Sato, Mitsuteru*; Matsumoto, Takahiro*; Yonetoku, Daisuke*; et al.

Communications Physics (Internet), 2(1), p.67_1 - 67_9, 2019/06

 Times Cited Count:6 Percentile:25.43(Physics, Multidisciplinary)

Journal Articles

Hydrogen removal from hydrogenated diamond-like carbon films by exposure to photon and energetic atomic oxygen beams

Yokota, Kumiko*; Tagawa, Masahito*; Matsumoto, Koji*; Furuyama, Yuichi*; Kitamura, Akira*; Kanda, Kazuhiro*; Tode, Mayumi; Yoshigoe, Akitaka; Teraoka, Yuden

Protection of Materials and Structures from the Space Environment; Astrophysics and Space Science Proceedings, Vol.32, p.531 - 539, 2012/08

Journal Articles

Survivability of silicon-doped diamond-like carbon films in energetic atomic/molecular oxygen beam environments

Tagawa, Masahito*; Kishida, Kazuhiro*; Yokota, Kumiko*; Matsumoto, Koji*; Yoshigoe, Akitaka; Teraoka, Yuden; Zhang, J.*; Minton, T. K.*

Protection of Materials and Structures from the Space Environment; Astrophysics and Space Science Proceedings, Vol.32, p.547 - 555, 2012/08

JAEA Reports

Extrusion and erosion of bentonite buffer, 3

Matsumoto, Kazuhiro; Fujita, Tomoo

JAEA-Research 2011-014, 26 Pages, 2011/06

JAEA-Research-2011-014.pdf:1.98MB

The extrusion of bentonite buffer is one of the important issues on the physical stability in the geological disposal of the high level radiation waste. In this report, the long-term extrusion experiment of the bentonite buffer material to an imitation crack was carried out, and the behavior was observed. Moreover, in consideration of the evaluation subject of the closing performance of a disposal site, the extrusion experiment with material with a large sand combination rate was carried out.

JAEA Reports

Study of the applicability of the diffusion model of bentonite buffer material, 2

Matsumoto, Kazuhiro; Fujita, Tomoo

JAEA-Research 2010-058, 56 Pages, 2011/03

JAEA-Research-2010-058.pdf:1.73MB

Bentonite buffer material is envisaged as a component of the engineered barrier system for high-level radioactive waste disposal. As a result of its swelling property, the buffer may extrude into the surrounding host rock through open fractures. If this persists for extremely long periods of time, the buffer extrusion could lead to a reduction of buffer density, which may in turn degrade the expected performance. In this report, verification of the solid phase diffusion theory of the past was performed and future problems were extracted based on expertise.

Journal Articles

Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure study on oxidative etching of diamond-like carbon films by hyperthermal atomic oxygen

Tagawa, Masahito*; Yokota, Kumiko*; Kitamura, Akira*; Matsumoto, Koji*; Yoshigoe, Akitaka; Teraoka, Yuden; Kanda, Kazuhiro*; Niibe, Masahito*

Applied Surface Science, 256(24), p.7678 - 7683, 2010/10

 Times Cited Count:10 Percentile:52.34(Chemistry, Physical)

Surface structural changes of a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS), synchrotron radiation photoelectron spectroscopy (SR-PES), and near-edge X-ray absorption fine structure (NEXAFS). It was confirmed that the DLC surface was oxidized and etched by high-energy collisions of atomic oxygen. RBS and real-time mass-loss data showed a linear relationship between etching and atomic oxygen fluence. SR-PES data suggested that the oxide layer was restricted to the topmost surface of the DLC film. NEXAFS data were interpreted to mean that the sp$$^{2}$$ structure at the DLC surface was selectively etched by collisions with hyperthermal atomic oxygen, and an sp$$^{3}$$-rich region remained at the topmost DLC surface. The formation of an sp$$^{3}$$-rich layer at the DLC surface led to surface roughening and a reduced erosion yield relative to the pristine DLC surface.

JAEA Reports

Study of the applicability of the diffusion model of bentonite buffer material

Matsumoto, Kazuhiro; Tanai, Kenji

JAEA-Research 2009-070, 47 Pages, 2010/03

JAEA-Research-2009-070.pdf:21.27MB

The buffer that will be used as a component of the engineered barriers system swells when saturated by groundwater. As a result of this swelling, buffer may penetrate into the surrounding rock zone through open fractures. It sustained for extremely long periods of time, the buffer extrusion could lead to reduction of buffer density, which may in turn degrade the assumed performance. In this report, the viscosity of bentonite was measured as one of the parameter of diffusion model. In addition, the simulation analysis was carried out to confirm the applicability of diffusion model.

JAEA Reports

Erosion phenomenon evaluation of bentonite buffer material; Generation behavior of bentonite colloid

Matsumoto, Kazuhiro; Iijima, Kazuki; Tanai, Kenji

JAEA-Research 2008-097, 64 Pages, 2009/02

JAEA-Research-2008-097.pdf:9.27MB

In the geological disposal of High Level Radioactive Waste (HLW), buffer material composed of engineered barriers system is expected to play important roles for the post-closure safety, for example, retardation of radionuclide migration. After overpack is breached, vitrified waste is considered to be dissolved by groundwater, followed by radionuclide dissolution into the groundwater and migration through the buffer material, as a reference scenario of safety assessment. It is also concerned about that bentonite colloids generated from the buffer may sorb radionuclides released from the buffer and consequently facilitate the radionuclide migration due to forming stable pseudo-colloids. In this study, erosion experiments of bentonite were carried out under the flow condition simulating groundwater flow and the generation rate of bentonite colloid from buffer materials is also discussed.

Journal Articles

The Measurement of density distribution of bentonite buffer extruded into fractures by using X-ray CT scanner

Matsumoto, Kazuhiro*; Tanai, Kenji

Genshiryoku Bakkuendo Kenkyu, 15(1), p.27 - 35, 2008/09

For the geological disposal of the high-level radioactive waste, it is important to develop the model to evaluate the long-term stability of the engineered barrier system. The increase in the reliability of the evaluation model may reduce the uncertainty of the safety assessment. In this study, the density distribution of the bentonite buffer extruded into the artificial fractures was measured by using a X-ray CT scanner to promote understanding of the extrusion phenomenon of the bentonite into fractures.

JAEA Reports

A Study on extrusion behavior of buffer material into fractures using X-ray CT method

Tanai, Kenji; Matsumoto, Kazuhiro*

JAEA-Research 2007-094, 11 Pages, 2008/02

JAEA-Research-2007-094.pdf:5.34MB

The buffer that will be used as a component of the engineered barriers system for geological disposal of high-level radioactive waste is designed to swell when it becomes saturated by groundwater. As a result of the swelling, bentonite buffer material may penetrate through open fractures into the surrounding host rock. If it is sustained for extremely long periods of time, the bentonite extrusion could lead to reduction of the buffer density, which may in turn degrade the expected performance (e.g. low permeability, diffusion control, colloid filtration, load-bearing capacity, etc). In this study, extrusion test with X-ray CT measurement was carried out to clarify the mechanical behavior of bentonite extrusion through fractures in the surrounding rock. In the extrusion test, the out flow distance into fracture is affected by bentonite content ratio and ionic strength of ground water. X-ray CT measurement is available to evaluate the density distribution of bentonite into the fractures. The X-ray CT measurement will play an important role for study of extrusion behavior of buffer material, particularly for development of extrusion models for compacted bentonite.

Journal Articles

A Study of extrusion behaviour of buffer material into fractures

Tanai, Kenji; Matsumoto, Kazuhiro*

Proceedings of 3rd International Meeting on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, p.57 - 64, 2008/00

As a candidate buffer material for geological disposal of high level radioactive waste, densely compacted bentonite has a number of favourable properties, such as its low permeability and high capacity for radionuclide sorption. Furthermore, as the bentonite will be resaturated and swelled gradually after repository closure, not only will any gaps within the bentonite be sealed, but the bentonite may also be excluded into fractures in the surrounding rock, diverting a part of the water flow away from the repository. This situation is potentially advantageous to repository safety. However, if loss of bentonite into fractures due to extrusion and subsequent erosion of the extruding front by flowing groundwater is too pronounced, then the decrease in density of the bentonite within the repository may lead to reduce its favourable properties. Therefore, the extrusion and erosion of bentonite buffer from the disposal pit or tunnel should be quantitatively understood to ensure long-term performance of the engineered barriers for the geological disposal system. In this study, an attempt was made to use X-ray CT technique to measure, non-destructively, the density distribution of bentonite buffer extruded into the artificial fractures.

JAEA Reports

Status of assessment tools on the performance guarantee contents of buffer material

Tanai, Kenji; Jintoku, Takashi*; Kikuchi, Hirohito*; Nishimura, Mayuka; Matsumoto, Kazuhiro*; Aoyanagi, Shigeo; Yui, Mikazu

JAEA-Research 2006-035, 32 Pages, 2006/06

JAEA-Research-2006-035.pdf:3.46MB

In order to contribute to the safety standards and guidelines which a regulator decides, state-of the art assessment method is investigated and summarized in the table about performance guarantee contents of buffer material related to the mechanical support and protection of the overpack and rock matrix, and the retardation of radionuclide. In addition, examples of the assessment tool are described. In this report, summary of (1) basic properties of bentonite, including swelling properties, mechanical properties and hydraulic properties, (2) long-term behavior of bentonite, including creep deformation, penetration into host rock, erosion and alteration, (3) gas permeability, (4) colloid filtration and (5) mechanical stability of the near-field is described. Check points, assessment methods (based on the data obtained from the experimental results, the estimation value obtained from empirical equations and database, and the modeling calculations) and latest results of these R&D programs were also summarized.

JAEA Reports

The Study plan on applicability to actual geological environment conditions of the engineering technology for geological disposal of high level nuclear-waste through the second phases in Horonobe Underground Research Project

Aoyanagi, Shigeo; Yui, Mikazu; Tanai, Kenji; Kawakami, Susumu; Fujita, Tomoo; Taniguchi, Naoki; Shibata, Masahiro; Konishi, Kazuhiro; Nishimura, Mayuka; Kikuchi, Hirohito*; et al.

JAEA-Review 2006-014, 61 Pages, 2006/03

JAEA-Review-2006-014.pdf:5.03MB

no abstracts in English

Journal Articles

Study of long-term behavior of engineered and geological barrier system

Aoyanagi, Shigeo; Oda, Yoshihiro; Sasamoto, Hiroshi; Shibata, Masahiro; Tanai, Kenji; Taniguchi, Naoki; Nishimura, Mayuka; Fujisaki, Kiyoshi; Kikuchi, Hirohito*; Matsumoto, Kazuhiro*

Hoshasei Haikibutsu Anzen Kenkyu Nenji Keikaku (Heisei-13-Nendo$$sim$$Heisei-17-Nendo) Kenkyu Seika Hokokushu, p.179 - 203, 2006/03

no abstracts in English

JAEA Reports

Permeation Behavior of Organic Matter in the Compacted Bentonite under Saline Condition

Tobitsuka, Sachiko; Kikuchi, Hirohito*; Matsumoto, Kazuhiro*; Iijima, Kazuki; Sato, Haruo

JNC-TN8400 2005-019, 65 Pages, 2005/08

JNC-TN8400-2005-019.pdf:3.23MB

The permeation behavior of organic matter through a compacted bentonite was evaluated in low and high ionic strength condition. The concentration of organic matters eluting from bentonite was analyzed. Polyacrylic acid solutions (average molecular weight:15,000 or 450,000) were permeated during maximum 140 days to the compacted bentonite (Kunigel V1, 100%) at dry density 1.2 g/cm$$^{3}$$. In low ionc strength condition, polyacrylic acid sodium (MWave: 15,000) was detected after 70 days in the permeated solution. In high ionic strength condition, it was found after 52 days. Polyacrylic acid (MWave: 450,000) didn't permeate in the both of system. It indicates that organic matters less than MWave: 450,000 aren't filtrated by bentonite. It is supposed that the organic compound which can change its conformation to a chain-like structure, are not likely to be filtrated, even if its molecular weight is more than 15,000. In low ionic strength condition, the concentration of eluting organic carbon from bentonite is 7.4-12.5 mg /l. In high ionic strength condition it is 4.2-6.5 mg /l.

JAEA Reports

Analysis of Case with Change of Density of Buffer Material by Extrusion Behavior to Use Diffusion Model

Matsumoto, Kazuhiro*; Tanai, Kenji; Kanno, Takeshi*; Iwata, Yumiko*

JNC-TN8400 2005-009, 40 Pages, 2005/06

JNC-TN8400-2005-009.pdf:2.5MB

The buffer that will be used as a component of the engineered barriers system swells when saturated by groundwater. As a result of this swelling, buffer may penetrate into the peripheral rock zone surrounding the buffer through open fractures. It sustained for extremely long periods of time, the buffer extrusion could lead to reduction of buffer density, which may in turn degrade the assumed performance. In this report, the viscosity of bentonite was measured as one of the parameter of diffusion model. In addition, the simulation analysis was carried out to confirm the applicability of diffusion model. Moreover, an analytical evaluation on extrusion behavior of buffer into rock fractures was performed due to estimate the long-term stability of buffer as reduction of density.

JAEA Reports

Extrusion and Erosion of Bentonite Buffer (II) -Evaluation of Extrusion Process of Bentonite Buffer in Horonobe Groundwater(HDB-6)-

Matsumoto, Kazuhiro*; Tanai, Kenji

JNC-TN8400 2004-026, 41 Pages, 2005/02

JNC-TN8400-2004-026.pdf:0.81MB

The extrusion and erosion of bentonite buffer is one of the important issues on physical stability of bentonite buffer in the HLW geological disposal. This report provides the results of the measurement on the extrusion behave of bentonite buffer with Horonobe underground water (HDB-6) and on the applicability of X-ray CT to evaluate the extrusion behave of bentonite buffer. The erosion test was carried out will NaCl solution water control to Horonobe underground water and control to the artificial seawater.

JAEA Reports

Extrusion and Erosion of Bentonite Buffer

Matsumoto, Kazuhiro*; Tanai, Kenji

JNC-TN8400 2003-035, 53 Pages, 2004/02

JNC-TN8400-2003-035.pdf:0.78MB

The extrusion and erosion of bentonite buffer is one of the important issues on physical stability of bentonite buffer in the HLW geological disposal. This report provides the results of the measurement on the extrusion behave of bentonite buffer with artificial sea water and of the analysis of bentonite colloid with distilled water in order to understand the erosion behavior of bentonite buffer. The applicability of X-ray CT to evaluate the extrusion behave of bentonite buffer is presented.

51 (Records 1-20 displayed on this page)