Igarashi, Kai*; Onuki, Ryoji*; Sakai, Takaaki*; Kato, Shinya; Matsuba, Kenichi; Kamiyama, Kenji
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 6 Pages, 2020/08
Watanabe, So; Ogi, Hiromichi*; Arai, Yoichi; Aihara, Haruka; Takahatake, Yoko; Shibata, Atsuhiro; Nomura, Kazunori; Kamiya, Yuichi*; Asanuma, Noriko*; Matsuura, Haruaki*; et al.
Progress in Nuclear Energy, 117, p.103090_1 - 103090_8, 2019/11
Hirakawa, Moe*; Kikuchi, Yuichiro*; Sakai, Takaaki*; Tanaka, Masaaki; Ohshima, Hiroyuki
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07
Gas entrainment (GE) from cover gas is one of key issue for Sodium-cooled fast reactors to prevent unexpected effects to core reactivity. By using a computational fluid dynamics (CFD) code, analyses have been conducted to estimate the drifting vortexes on water experiments which were generated as wake vortexes behind a plate obstacle in the circulating water channel. In this paper, the results of comparison between experiments and analyses were discussed and the gas core lengths from the surface vortexes were evaluated by using the evaluation tool named StreamViewer developed by Japan Atomic Energy Agency.
Abe, Hiroshi; Tokuhira, Shinnosuke*; Uchida, Hirohisa*; Oshima, Takeshi
Nuclear Instruments and Methods in Physics Research B, 365(Part A), p.214 - 217, 2015/12
no abstracts in English
Abe, Hiroshi; Shimomura, Takuya; Tokuhira, Shinnosuke*; Shimada, Yukihiro*; Takenaka, Yusuke*; Furuyama, Yuta*; Nishimura, Akihiko; Uchida, Hirohisa*; Daido, Hiroyuki; Oshima, Takeshi
Proceedings of 7th International Congress on Laser Advanced Materials Processing (LAMP 2015) (Internet), 4 Pages, 2015/08
A short pulse laser (the nanosecond and femtosecond) was applied to hydrogen absorbing alloys surface layer, and a surface modification experiment was put into effective to aim at improvement of hydrogen adsorption functionally. It was investigated about correlation between an initial hydrogen absorption reaction rate of hydrogen alloys and a laser irradiation in this research. The laser irradiation condition was done with pulse width 100 fsec and energy 0.2 - 3.4 mJ/pulse. It blazed down on hydrogen absorbing alloys (LaNiAl) and changed local order in the surface. As a result, the initial hydrogen absorption reaction rate was 1.5 - 3.0 times as fast as a irradiated sample, and the result and laser irradiated sample found out that a hydrogen absorption function improves. A laser irradiation can conclude to be effective in surface modification of the hydrogen storage materials.
Kitabatake, Satomi*; Ushiroda, Tota*; Hirayama, Ryoichi*; Furusawa, Yoshiya*; Funayama, Tomoo; Yokota, Yuichiro; Okahata, Yoshio*; Ito, Atsushi*
JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 86, 2015/03
Biological effects of high-LET radiation could be understood in terms of the ion track structure. Therefore the evaluation of the contribution of both core and penumbra regions to biological effects is an important issue for the study of high-LET effects. In the present study, we developed a protocol to make a uniform DNA sheet with insoluble nature in aqueous solution, and explored the applicability to the detection of 8-OHdG distributions after heavy-ion irradiation. Water-insoluble DNA sheet was irradiated with proton and neon ion beams at JAEA-Takasaki. After irradiation DNA samples were incubated with an 8-OHdG antibody followed by with a second antibody containing a fluorescence probe. The preliminary results indicated that upon ion irradiation randomly distributed dot-like fluorescence was observed, suggesting that these dots may be from incident ions.
Otosaka, Shigeyoshi; Nakanishi, Takahiro; Suzuki, Takashi; Sato, Yuhi; Narita, Hisashi*
Environmental Science & Technology, 48(21), p.12595 - 12602, 2014/11
From August 2011 to July 2013, a sediment trap was deployed at 100 km east of the Fukushima Daiichi Nuclear Power Plant and sinking particles were collected. Sinking flux of Cs decreased over time with seasonal fluctuation. The Cs fluxes were mainly affected by two principal modes. One was a rapid sinking of radiocesium-bound particles (moderate mode). This mode was dominant especially in the early post-accident stage, and was presumed to establish the distribution of radiocesium in the offshore seabed. Another was the secondary transport of particles attributed to turbulence near the seabed and was observed in winter (turbulence mode). Although the latter process would not drastically change the distribution of sedimentary radiocesium, attention should be paid as this key process redistributing the accident-derived radiocesium may cumulatively affect the long-term distribution.
Otosaka, Shigeyoshi; Kato, Yoshihisa*
Environmental Science; Processes & Impacts, 16(5), p.978 - 990, 2014/05
Since the accident of Fukushima Daiichi Nuclear Power Plant (1FNPP), significant levels of anthropogenic radionuclides have been detected from seabed sediments off the east coast of Japan. In this paper, the approximate amount of accident-derived radiocesium in seabed sediments off Fukushima, Miyagi and Ibaraki prefectures was estimated. As of October 2011, the total amount of sedimentary Cs was 0.200.05 PBq (decay corrected to March 11, 2011) and about 95% of the radiocesium was accumulated in the regions shallower than 200 m depths. The large inventory in the coastal sediments was attributed to effective adsorption of dissolved radiocesium onto sediments. Although rivers are also an important source to supply radiocesium to the coastal regions, the potential was relatively lower than that of the above-mentioned process at least in the early stage, within half a year, after the accident.
Abe, Hiroshi; Aone, Shigeo*; Morimoto, Ryo*; Uchida, Hirohisa*
Journal of Alloys and Compounds, 580(Suppl.1), p.S219 - S221, 2013/12
no abstracts in English
Abe, Hiroshi; Orimo, Satoshi; Kishimoto, Masahiko*; Aone, Shigeo*; Uchida, Hirohisa*; Daido, Hiroyuki; Oshima, Takeshi
Nuclear Instruments and Methods in Physics Research B, 307, p.218 - 220, 2013/07
We investigated the structure changes of a hydrogen storage alloy by ion irradiations, and its absorption property in order to obtain basic data and to elucidate relevant mechanisms of hydrogen absorption by the influence of the irradiation. In previous studies, the induction of vacancies in a hydrogen absorption alloy was found to be effective to increase in the hydrogen absorption rate. As well known, the rate of hydrogen absorption strongly depends upon the surface state of a hydrogen storage alloy because the dissociation of hydrogen molecules or water molecules needs electron change with the surface in the H gas or electrochemical reaction process. In this study, ion irradiations were made at a room temperature using the laser driven proton beam method, at Kansai Photon Science Institute, Japan Atomic Energy Agency. The beam treatment has several unique properties such as short pulse duration, high peak current, low transverse emittance, and wide energy range from KeV to MeV. The irradiation was used to modify the alloy surface using this equipment. From obtained results, the initial hydrogen absorption rate was found improved by the laser driven proton beam rather more effectively than a mono-energetic proton beam. Discussion is made on the correlation among proton irradiation (laser driven proton or mono-energetic proton) and the initial hydrogen absorption rate of the alloy. We argue about the usefulness of an energy spread beam.
Abe, Hiroshi; Aone, Shigeo*; Morimoto, Ryo*; Uchida, Hirohisa*; Oshima, Takeshi
Transactions of the Materials Research Society of Japan, 36(1), p.133 - 135, 2011/03
The introduction of vacancies in Pd was found to be effective for an increase in the initial hydrogen absorption rate in a previous study. Also, it was reported that the initial hydrogen absorption rate depends strongly on the surface conditions of metals. Heavy ions with keV ranges can create severe damage and high densities of vacancy near the surface of materials. As well known, the formation of hydride phases can be facilitated by the presence of vacancy because vacancy acts as hydrogen trapping site to form hydrides. Thus, the hydrogen absorption characteristics of Pd may be improved by the irradiation of heavy ions. As a result, the initial hydrogen absorption rate increased due to ion irradiation, and the value became 310 times higher than un-irradiated Pd.
Ohashi, Yusuke; Asanuma, Noriko*; Harada, Masayuki*; Wada, Yukio*; Matsubara, Tatsuo; Ikeda, Yasuhisa*
Journal of Nuclear Science and Technology, 46(8), p.771 - 775, 2009/08
Most of the metal or bed material wastes generated from uranium enrichment facilities or uranium refining and conversion plants are contaminated by uranium fluoride compounds such as UF. The UF powder was completely dissolved in BMICl(1-buthyl-3-methylimidazolium chloride). The uranium concentrations of metal waste dropped below the temporary proposed clearance level (1.0 Bq/g) using BMICl. In the cyclic voltammogram of BMICl solution when dissolving UF, uncoupled reduction and oxidation peaks were observed and the reduction peak was considered to correspond to the reduction of uranyl(VI) + e uranyl(V) followed by further reduction to UO.
Abe, Hiroshi; Morimoto, Ryo*; Sato, Fumiatsu*; Azuma, Yorito*; Uchida, Hirohisa*
Journal of Alloys and Compounds, 408-412, p.348 - 350, 2006/02
Mm(misch metal) based hydrogen storage alloys are applied to the negative electrode of the Ni-H battery and other hydrogen storage systems. In such pratical applications, various surface processes of hydrogen molecules often become rate contolling. Therefore, the improvement of the alloy surface is of great importance to promote the initial activation and hydriding rate. We have reported that the alkaline pretreatment of an alloy surfece exhibits a high durability against CO attack. Since low energy ion irradiation is quite useful for surface modification of materials, the hydriding proerties of a Mm is expected on electrochemical hydriding rate of the alloy. As a result, the ion irradiation Mm was found to induce a higher hydriding rate than that of the un-irradiation one.
Abe, Hiroshi; Morimoto, Ryo*; Sato, Fumiatsu*; Azuma, Yorito*; Uchida, Hirohisa*
Journal of Alloys and Compounds, 404-406, p.288 - 292, 2005/12
The effect of ion irradiation on the rate of electrochemical hydriding rate of palladium (Pd) was investigated. In this study, ion irradiation onto the Pd surface was made with H, He, Ar and N in the acceleration energy range from 30 to 350 keV, and in the ion dose up to 1 10 cm. As the ion dose was increased, the initial rate of hydriding of Pd was increased. The ion irradiatiion treatment of the surface of a metal induces high concentrations of vacancy. The increased hydriding rate may be caused by the induction of high concentration of vacancy whichi traps hydrogen atoms, and this seems to accelerate the rates of hydride nucleation and growth in the surface. The ion irradiation was found as an effective way to enhance the rate of the initial activation of Pd in the electrochemical hydriding process.
Sakamoto, Shigeyasu*; Ishimori, Yuu; Maruo, Yoshihiro
JNC-TY6400 2004-001, 41 Pages, 2004/04
This report describes development of a radon standard source for establishing the traceability on radon concentration measurements.The radon that generates by babbling the radium solution was used for calibrations of radon measurement equipments. However, as for the radon source, which is reported here, the handling is easier because a solid phase radium source is used. Radioactivity of the radon, which is release in the vapor phase, was determined from a difference between the radioactivity of the radium and the radioactivity of the residual radon progeny in the source. Germanium detectors, which calibrated the detection efficiency with the gamma-ray reference sources, were used to those radioactivity measurements. As for the radioactivity of the radon, which is released from the radium source it was found that they are 988 Bqs. Sealing this source in the stainless steel container that is six liters in capacity, the standard radon source of density of 167.5 [Bq/l] was made.
JNC-TJ7400 2005-021, 75 Pages, 2004/02
Tono mine is one of the uranium mines of Japan and it has been the subject of extensive research regarding the nuclear waste disposal in rock. The top formation of the mine consists of sedimentary rocks ranging from sandstone to siltstone. An exploration adit was excavated by using the NATM, and this adit therefore was named as the NATM adit. At an extension of this adit, a series of horizontal boreholes were excavated for measuring in-situ stresses. The failure was observed in these boreholes, particularly at their crown and sidewalls. Following these observations some new boreholes were drilled into sedimentary rocks to investigate the causes and mechanism of failure of these non-supported boreholes. It is experimentally known that the rock exhibits some anomalous behaviour before the ultimate rupture, such as seismic electric signals, high acoustic emission activity. Furthermore, the behaviour of sedimentary rocks greatly depends upon their water content and some swelling, shrinkage, slaking may occur depending upon the environmental conditions. To investigate the coupled behaviour of sedimentary rocks in relation to clarifying the in-situ observations in the adit a research program was initiated, which consists of (1)Experiments (2)In-situ multi-parameter monitoring, and (3)Numerical studies. Experiments were concerned with, physical, electrical and mechanical properties of sedimentary rocks and their water-content migration characteristics. In-situ multi-parameter real-time monitoring involved electrical potential variations, acoustic emission activity, deformation, temperature and humidity variations in the boreholes and in the adit, which may be indicators for the possible failure around the boreholes. Numerical-studies were concerned with the conventional elasto-plastic stability analysis and also coupled analyses of water-content migration and stress field. The experimental studies clearly indicated that rocks around the boreholes exhibit time dependent ...
Takase, Yuichi*; JT-60 Team
AIP Conference Proceedings 694, p.235 - 242, 2003/05
A central electron temperature of 23 keV was obtained by EC wave injection. A highly localized current density profile was obtained by central ECCD, indicating an upper limit on the diffusion coefficient for resonant electrons of . The experimentally obtained current drive figure of merit was lower than theoretical prediction, possibly because of the negative loop voltage induced by overdrive. A comparison of HFS and LFS off-axis ECCD confirmed the theoretically expected trapped particle effect on the current drive efficiency. Offaxis LHCD was used to broaden the qmin radius and the ITB foot radius. N-NBCD was used to shrink the current hole radius. An integrated scenario consisting of (1) a novel plasma start-up method using RF plasma production and induction by vertical field and shaping coils, (2) a noninductive ramp-up stage, and (3) a transition to a high-density, bootstrap-dominated, highconfinement plasma, without the use of the OH solenoid, has been demonstrated. The plasma created by this technique had both internal and edge transport barriers, with (), , and at MA and .
Morita, Kenji*; Ishino, Shiori*; Tobita, Toru; Chimi, Yasuhiro; Ishikawa, Norito; Iwase, Akihiro
Journal of Nuclear Materials, 304(2-3), p.153 - 160, 2002/08
To study the mechanism of irradiation embrittlement in pressure vessel alloys, we performed high energy ion irradiation experiments using FeCu model alloys. The dependences of Vickers hardness change by irradiation on ion fluence, irradiation temperature and Cu content were discussed.
Ikezoe, Yasumasa; Suzuki, Kazuya; Nakashima, Mikio; Yokoyama, Atsushi; Shiraishi, Hirotsugu; Ono, Shinichi*
JAERI-Research 98-051, 43 Pages, 1998/09
no abstracts in English
Wakabayashi, Go*; Morimoto, Ryo*; Uchida, Hirohisa*; Abe, Hiroshi
no journal, ,
no abstracts in English