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Suzuki, Seiya; Nemoto, Yoshihiro*; Shiiki, Natsumi*; Nakayama, Yoshiko*; Takeguchi, Masaki*
Annalen der Physik, 535(9), p.2300122_1 - 2300122_12, 2023/09
Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)Sumita, Takehiro; Sudo, Ayako; Takano, Masahide; Ikeda, Atsushi
Science and Technology of Advanced Materials; Methods (Internet), 2(1), p.50 - 54, 2022/02
Mikami, Satoshi; Tanaka, Hiroyuki*; Matsuda, Hideo*; Sato, Shoji*; Hoshide, Yoshifumi*; Okuda, Naotoshi*; Suzuki, Takeo*; Sakamoto, Ryuichi*; Ando, Masaki; Saito, Kimiaki
Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12
Times Cited Count:22 Percentile:66.33(Environmental Sciences)The deposition densities of radiocesium and the air dose rates were repeatedly measured in a large number of undisturbed fields within the 80km zone that surrounds the Fukushima Dai-ichi Nuclear Power Plant site between 2011 and 2016, and features of their temporal changes were clarified. The average air dose rate excluding background radiation in this zone decreased to about 20% of the initial value during the period from June 2011 to August 2016, which was essentially a result of the radioactive decay of Cs with a half-life of 2.06y. The air dose rate reduction was faster than that expected from the decay of radiocesium by a factor of about two, with most of this reduction being attributed to the penetration of radiocesium into the soil. The average deposition densities of Cs and Cs in fields that were not decontaminated were found to have decreased nearly according to their expected radioactive decay, which indicated that the movement of radiocesium in the horizontal direction was relatively small. The effect of decontamination was apparently observed in the measurements of air dose rates and deposition densities. Nominally, the average air dose rates in the measurement locations were reduced by about 20% by decontamination and other human activities, of which accurate quantitative analysis is and continue to be a challenge.
Sanada, Yukihisa; Miyamoto, Kenji*; Ochi, Kotaro; Matsuzaki, Koji*; Ogawa, Toshihiro*; Senga, Yasuhiro*
Kaiyo Riko Gakkai-Shi, 24(2), p.9 - 18, 2018/12
Seven years passed since Fukushima Dai-ichi Nuclear Power Station accident which was caused large amount of radionuclide release to the sea. Elucidation of behavior mechanism of radiocesium in the seabed is required for restarting fishing industry. We developed radiation detection system using the unmanned surface vehicle for in-situ measurement of radiocesium concentration in seabed sediment. This system is able to automatically navigate to measurement point and obtain the radiation data on the bottom sediment. The detector was calibrated by comparing the actual sediment samples. The periodical measurement off-shore the Fukushima Prefecture was performed using developed this system. As these results, distribution of radiocesium concentration was changed due to oceanographic condition. However, radiocesium inventory was tendency to decrease according to radiocesium half-life in measurement area. This system is effective for elucidation of behavior mechanism of radiocesium because it can easily measure the radiocesium concentration in the bottom sediment.
Sakurai, Akitaka; Aoyagi, Kazuhei; Fujita, Tomoo; Motoshima, Takayuki*
JAEA-Data/Code 2015-023, 46 Pages, 2016/02
In a high level radioactive waste (HLW) disposal project, it is necessary to investigate the long-term behavior of thermos-hydro-mechanical-chemical of the rock mass around the engineered barrier system of the HLW waste for the safety assessment of the disposal system. In addition, long-term stability of the rock mass around the galleries are required for the disposal facility. Considering these backgrounds, the authors measure the deformation behavior of the vertical pit drilled on the floor of the 350 m gallery in the Horonobe Underground Research Laboratory. In situ measurements of the deformation of the pit and rock mass around the pit was conducted to apply to the assessment of the long-term deformation behavior. The authors describe the drilling of the vertical pit, geological observation, specification of the measurement instrument, measurement method, and result of the measurement in this report.
Niunoya, Sumio*; Aoyagi, Kazuhei; Fujita, Tomoo; Shirase, Mitsuyasu*
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.336 - 341, 2016/01
In the Horonobe Underground Research Laboratory, rock mass classification and determination of mechanical properties of rock mass was conducted considering the effect of the density of fractures in the rock mass. In this paper, the authors report the mechanical properties of rock mass detected by plate loading tests and in situ shear tests in the 250 m and 350 m galleries. As a result, the failure criteria based on the result of in situ shear tests provides the most conservative value for the design of support pattern and assessment of stability of the gallery.
Aoyagi, Kazuhei; Sakurai, Akitaka; Niunoya, Sumio*
JAEA-Data/Code 2015-012, 171 Pages, 2015/09
The objective of this report is to investigate the three dimensional stress state in the 250 m Niche off the West Shaft No.1 at the Horonobe Underground Research Laboratory. For the measurement, three 20.0m long boreholes were drilled. Hydraulic fracturing was applied as a stress measurement method. For the analysis, shut-in pressure of a transverse fractures, reopening pressure of longitudinal fractures and stress condition causing borehole breakouts were integrated into the equation; then stress state was calculated by inversion technique. As a result of the in situ stress state measurement around the experimental area, the orientation of the maximum principal stress was estimated to be ESE-WNW, dipping 70 from the vertical axis. The orientation of the minimum principal stress was NEN-SWS, dipping 60 from vertical axis. The orientation of the principal stresses is almost coincided with the direction of borehole breakouts and longitudinal crack induced in the boreholes. The values of the maximum and minimum principal stresses were 2.6 MPa and 2.1 MPa, respectively.
Aoyagi, Kazuhei; Sakurai, Akitaka; Niunoya, Sumio*
JAEA-Data/Code 2015-011, 182 Pages, 2015/09
The objective of this report is to investigate the three dimensional stress state in the 250 m Niche off the South Shaft No.1 at the Horonobe Underground Research Laboratory. For the measurement, three 20.0m long boreholes were drilled. Hydraulic fracturing was applied as a stress measurement method. For the analysis, shut-in pressure of a transverse fractures, reopening pressure of longitudinal fractures and stress condition causing borehole breakouts were integrated into the equation; then stress state was calculated by inversion technique. As a result of the in situ stress state measurement around the experimental area, the orientation of the maximum principal stress is estimated to be between E-W and ENE-WSW, dipping almost horizontal direction. This result agrees well with the estimated orientation of the main principal stress, the location of the borehole wall breakouts in 10-E250-M01 and the orientation of the generated crack in 10-E250-M03. The value of the maximum principal stress was 3.97 MPa.
Kuwabara, Kazumichi; Sato, Toshinori; Sanada, Hiroyuki; Takayama, Yusuke
JAEA-Research 2015-005, 378 Pages, 2015/07
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.
Takahashi, Masamitsu; Yoneda, Yasuhiro; Mizuki, Junichiro
Applied Surface Science, 237(1-4), p.219 - 223, 2004/10
Times Cited Count:5 Percentile:29.73(Chemistry, Physical)The GaAs(001)- reconstructed surface was investigated by in situ surface X-ray diffraction. The sample was subjected to measurements under molecular-beam epitaxy conditions without being transferred another chamber. Several X-ray diffraction patterns were measured with increasing the substrate temperature within the -phase of GaAs(001)- in a constant As flux of 510 Torr. At relatively low temperatures up to 545C, the observed X-ray diffraction patterns agree well to the 2(24) surface. However, a different X-ray diffraction pattern was obtained at 585C, while the periodicity still persited. This change is explained by partial As-dimer desorption which results in a mixture of the 2(24) and 2(24) structures.
Takahashi, Masamitsu; Yoneda, Yasuhiro; Inoue, Hirotane*; Yamamoto, Naomasa*; Mizuki, Junichiro
Japanese Journal of Applied Physics, Part 1, 41(10), p.6247 - 6251, 2002/10
Times Cited Count:55 Percentile:85.2(Physics, Applied)An X-ray diffractometer connected with a molecular-beam epitaxy (MBE) system has been constructed for in situ studies on the growing surfaces of III-V compound semiconductors. This diffractometer is based on the (4+2) type and equipped with an axis for rotating the receiving slit about the normal of the slit plane. This additional axis is used to align the resolution of the receiving slit properly for the surface X-ray diffraction measurement. For the alignment of the sample and the whole setup with respect to the X-ray beam, an XYZ-stage and an adjustable base plate are available. X-rays enter and leave the chamber through two cylindrical Be windows welded onto the MBE chamber. A graphite sheet which can be heated up to 250C is placed along the inside of the Be windows to protect the Be windows from being coated with evaporated materials. Preliminary data are presented to demonstrate the feasibility of static and dynamic measurements of growing surfaces using this instrument.
Yamada, Reiji; Snead, L. L.*; Kato, Yudai*
Proceedings of 4th International Energy Agency Workshop on SiCf/SiC Ceramic Composites for Fusion Structural Application, p.175 - 180, 2000/00
no abstracts in English
Suzuki, Motoe
JAERI-Research 94-022, 36 Pages, 1994/10
no abstracts in English
*;
JAERI-M 82-191, 72 Pages, 1982/12
no abstracts in English
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Journal of Nuclear Science and Technology, 17(4), p.281 - 290, 1980/00
Times Cited Count:12 Percentile:75.08(Nuclear Science & Technology)no abstracts in English
Hanawa, Satoshi; Hata, Kuniki; Uchida, Shunsuke; Nishiyama, Yutaka
no journal, ,
Water in the primary circuit of Nuclear Power Plants (NPPs) decomposes by radiolysis, then oxidants such as hydrogen peroxide and oxygen are generated as a result. Hydrogen peroxide is one of the major factor for initiation and propagation of stress corrosion cracking (SCC) in structural materials, hence in-situ monitoring of hydrogen peroxide at the point of interest in irradiation field is quite important to assure the integrity of NPPs. Concentration of hydrogen peroxide in irradiation field is governed by energy deposition by neutron and -ray in which the degree of energy is different in locations, while concentration in un-irradiation area decreases due to thermal decomposition. Quantitative evaluation of hydrogen peroxide is, however, available only by analyzing sampled water at present, and therefore in-situ monitoring of hydrogen peroxide at the point of interest becomes quite important. Frequency dependent complex impedance (FDCI) analysis gives characteristics of oxide film on the materials, and it becames clear by recent activities that the low frequency semicircles in Cole-Cole plots shows linear correlation to the concentration of hydrogen peroxide. JAEA is now developing a sensor for in-situ monitoring of hydrogen peroxide applicable to irradiation environment by applying FDCI. The outline and overall schedule of the sensor development will be reported in the presentation.
Shirase, Mitsuyasu*; Jo, Mayumi*; Motoshima, Takayuki*; Niunoya, Sumio*; Nakayama, Masashi; Tanai, Kenji
no journal, ,
no abstracts in English
Mikami, Satoshi; Saito, Kimiaki
no journal, ,
no abstracts in English
Morooka, Satoshi; Kawasaki, Takuro; Harjo, S.; Nakada, Nobuo*; Tsukada, Yuki*
no journal, ,
Kitagaki, Toru
no journal, ,
Zircon dissolution rates under flowing aqueous solutions of pH 0 (HCl), 7 (HO), 14 (NaOH aq) were in-situ measured from the zircon surface change by Phase-shift interferometric microscope.