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Terasaka, Yuta; Iimoto, Takeshi*; Saso, Michitaka*; Fujita, Reiko*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 66(4), p.203 - 207, 2024/04
no abstracts in English
Hironaka, Kota; Lee, J.; Koizumi, Mitsuo; Ito, Fumiaki*; Hori, Junichi*; Terada, Kazushi*; Sano, Tadafumi*
Nuclear Instruments and Methods in Physics Research A, 1054, p.168467_1 - 168467_5, 2023/09
Times Cited Count：0 Percentile：0.02(Instruments & Instrumentation)Koide, Kaoru
JAEA-Research 2023-003, 101 Pages, 2023/06
JAEA-Research-2023-003.pdf:14.08MB
This study developed a geobotanical remote sensing method for estimating high water table areas such as groundwater discharge points using differences in the growth conditions of forest trees induced by moisture supply from groundwater in a humid warm-temperate forest area. A new vegetation index (VI) termed AgbNDVI (Added green band NDVI) was proposed to discriminate the differences. The AgbNDVI proved to be more sensitive to water stress on green vegetation than existing VIs: SAVI and EVI2, and possessed a strong linear correlation with the vegetation fraction. To validate the proposed method, a 23 km
study area was selected in the Tono region of Gifu Prefecture, central Japan. The AgbNDVI values were calculated from atmospheric corrected SPOT HRV data. To correctly detect high VI points, the influence factors on tree growth were identified using the AgbNDVI values, DEM and forest type data; the study area was then divided into 555 segments according to combinations of the influence factors: elevation, slope gradient, slope aspect and forest type. Thresholds for detecting high VI points were defined for each segment based on a histogram of AgbNDVI values. By superimposing the high VI points on topographic and geologic maps, most of the high VI points are clearly located on the concave/convex slopes and near the geologic boundaries prone to groundwater runoff. In addition, field investigations support the correctness of the high VI points, because the growth increments and biomass of trees (
) are greater than at points other than the high VI points, and they are located around known groundwater seeps and in a high water table area. Consequently, the proposed method can be expected to provide useful information for characterizing hydrogeological structures by combining with conventional photo-geological interpretation.
-ray discrimination based on the property and thickness controls of scintillators using Li glass and LiCAF(Ce) in a -ray fieldKaburagi, Masaaki; Shimazoe, Kenji*; Terasaka, Yuta; Tomita, Hideki*; Yoshihashi, Sachiko*; Yamazaki, Atsushi*; Uritani, Akira*; Takahashi, Hiroyuki*
Nuclear Instruments and Methods in Physics Research A, 1046, p.167636_1 - 167636_8, 2023/01
Times Cited Count：3 Percentile：94.27(Instruments & Instrumentation)We focus on the thickness and property controls of inorganic scintillators used for thermal neutron detection in intense -ray fields without considering pulse shape discrimination techniques. GS20
(a lithium glass) and LiCaAlF
:Ce(LiCAF:Ce) cintillators with thicknesses of 0.5 and 1.0 mm, respectively, have been employed. Pulse signals generated by photomultiplier tubes, to which the scintillators were coupled, were inserted into a digital pulse processing unit with 1 Gsps, and the areas of waveforms were integrated for 360 ns. In a 
Co -ray field, the neutron detection for GS20 with a 0.5-mm thickness was possible at dose rates of up to 0.919 Gy/h; however, for LiCAF:Ce, neutron detection was possible at 0.473 Gy/h, and it failed at 0.709 Gy/h. Threfore, in a Co -ray field, the neutron/-ray discrimination of GS20 was better than that of LiCAF:Ce due to its better energy resolution and higher detection efficiency.
Yamamoto, Kazami; Hatakeyama, Shuichiro; Otsu, Satoru*; Matsumoto, Tetsuro*; Yoshimoto, Masahiro
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.494 - 498, 2021/10
J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) provides more than 700 kW proton beam to the neutron target. In order to investigate the influence of the radiation, we intend to evaluate the radiations such as the neutron and gamma-rays, which are generated due to the proton beam loss. If the amount of beam loss is excessive, it becomes difficult to identify the individual neutron and gamma ray. Therefore, we investigated the signal rate of the extraction point of RCS. Preliminary result indicated that we can enough distinguish the neutron and gamma-ray by the liquid scintillator.
Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei*; Haga, Katsuhiro; Shimada, Tsubasa*; Kanomata, Kenichi*
Materials Science Forum, 1024, p.145 - 150, 2021/03
To realize a high beam power operation at the J-PARC, a mercury target vessel covered with water shroud was developed. In the first step, to realize an operation at 500 kW, the basic structure of the initial design was followed and the connection method between the mercury vessel and the water shroud was changed. Additionally, the operation at a beam power of 500 kW was realized in approximately eight months. In the second step, to realize the operation at 1 MW, the new structure in which only rear ends of vessels were connected was investigated. Cooling of the mercury vessel is used to reduce thermal stress and thick vessels of the water shroud are used to increase stiffness for the internal pressure; therefore, it was adopted. The stress in each vessel was lower than the allowable stress based on the pressure vessel code criteria prescribed in the Japan Industrial Standard, and confirmation was obtained that the operation with a beam power of 1 MW could be conducted.
Sheikh, M. A. R.*; Liu, X.*; Matsumoto, Tatsuya*; Morita, Koji*; Guo, L.*; Suzuki, Toru*; Kamiyama, Kenji
Energies (Internet), 13(19), p.5018_1 - 5018_15, 2020/10
Times Cited Count：7 Percentile：26.21(Energy & Fuels)Sugino, Kazuteru; Takino, Kazuo
JAEA-Data/Code 2019-011, 110 Pages, 2020/01
JAEA-Data-Code-2019-011.pdf:3.37MB
A deterministic discrete ordinates method (SN method) transport calculation code for three-dimensional hexagonal geometry has been developed as the MINISTRI code (Ver. 7.0). MINISTRI is based on the triangle-mesh finite difference method, which can perform neutron transport calculations with high accuracy for cores of fast power reactors and assemblies of the Russian BFS critical facility. The present study has derived a proper scheme for remarkably improving the convergence of MINISTRI by investigating the issue of previous MINISTRI (Ver. 1.1), which sometimes plays a poor convergence performance in calculations for large-scale power reactor cores. The verification test of improved MINISTRI has been carried out for various cores by setting the reference result as the multi-group Monte-Carlo calculation with the same cross-sections as used in MINISTRI. As a result, it is found that the agreements are within 0.1% for eigenvalues and within 0.7% for power distributions. Thus, the satisfying accuracy of MINISTRI has been confirmed. In order to reduce the calculation time, the initial diffusion calculation scheme and the parallel processing have been implemented. As a result, the calculation time is reduced to the approximately one tenth compared with previous MINISTRI. Furthermore, adoption of the treatment of the anisotropic cell streaming effect, preparation of the perturbation calculation tool, implementation of the function for specification of the triangle-mesh-wise material and merging of the hexagonal-mesh calculation code MINIHEX have been carried out. Thus, the versatility of MINISTRI has been enhanced.
Matsuura, Yuto*; Hayano, Akira; Itakura, Kenichi*; Suzuki, Yukinori*
Applied Soft Computing, 84, p.105737_1 - 105737_9, 2019/11
Times Cited Count：2 Percentile：14.62(Computer Science, Artificial Intelligence)LiDAR (laser imaging detection and ranging) has been developed to obtain a high-resolution point cloud data indicating the detailed 3D shapes of an object. To identify discontinuities in a rock mass of a tunnel gallery wall, it is necessary to approximate the rock mass surface with small planes. Normal vectors of the planes are important to identify discontinuities. We developed an algorithm for estimation of planes based on multi-dimensional particle swarm optimization (MD PSO) from point cloud data. Point cloud data were segmented into bounding boxes and grouped into clusters by MD PSO. Planes were estimated using the least squares method for point cloud data in the respective clusters. The newly developed MD PSO algorithm was evaluated using point cloud data obtained from a gallery wall. Evaluation was carried out in comparison with the previous developed variable-box segmentation (VBS) algorithm. The MD PSO-based algorithm showed a 7% higher accuracy than that of the VBS algorithm.
Kawamura, Shunsuke; Naoe, Takashi; Ikeda, Tsubasa*; Tanaka, Nobuatsu*; Futakawa, Masatoshi
Advanced Experimental Mechanics, 4, p.33 - 37, 2019/08
A mercury enclosure vessel made of stainless steel is used as a spallation target in the pulsed spallation neutron source at J-PARC. It is severely damaged by the cavitation induced with pressure waves in association with the pulsed proton beam injection. A double-walled structure with a narrow mercury channel was adopted in the front end of the target vessel to reduce the cavitation damage. It has been experimentally demonstrated that the cavitation damage could be mitigated in the narrow channel but its mechanism has been unclarified yet. In this study, we investigated the cavitation from growing to collapsing through visualizing the spark-induced cavitation bubbles under flow field using a high-speed video camera. Furthermore, we measured the wall vibration due to the cavitation bubble collapse with changing flow velocity parametrically. It was found that the microjet collided perpendicular to the wall in the stagnant flow condition while it collided with an inclined angle from the perpendicular direction, suggesting that the collision pressure on the wall was reduced by flowing.
Asahina, Daisuke*; Aoyagi, Kazuhei; Kim, K.*; Birkholzer, J.*; Birkholzer, J. T.*; Bolander, J. E.*
Computers and Geotechnics, 81, p.195 - 206, 2017/01
Times Cited Count：33 Percentile：82.31(Computer Science, Interdisciplinary Applications)Novello, L.*; Cara, P.*; Coletti, A.*; Gaio, E.*; Maistrello, A.*; Matsukawa, Makoto; Philipps, G.*; Tomarchio, V.*; Yamauchi, Kunihito
IEEE Transactions on Applied Superconductivity, 26(2), p.4700507_1 - 4700507_7, 2016/03
Times Cited Count：7 Percentile：39.48(Engineering, Electrical & Electronic)Guo, L.*; Morita, Koji*; Tobita, Yoshiharu
Journal of Nuclear Science and Technology, 53(2), p.271 - 280, 2016/02
Times Cited Count：7 Percentile：54.81(Nuclear Science & Technology)Sasaki, Ichiro; Hanaoka, Hirofumi*; Yamada, Keiichi*; Watanabe, Shigeki; Sugo, Yumi; Ohshima, Yasuhiro; Suzuki, Hiroyuki; Ishioka, Noriko
Peptide Science 2014, p.257 - 260, 2015/03
Arifi, E.*; Ishimatsu, Koichi*; Iizasa, Shinya*; Namihira, Takao*; Sakamoto, Hiroyuki*; Tachi, Yukio; Kato, Hiroyasu*; Shigeishi, Mitsuhiro*
Construction and Building Materials, 67(Part B), p.192 - 196, 2014/09
Times Cited Count：5 Percentile：25.81(Construction & Building Technology)The Fukushima Dai-ichi Nuclear Plant accident has resulted in a large amount of radioactively contaminated concrete. The possible application of the pulsed power discharge to reduce the amount of contaminated concrete as radioactive waste was investigated. The contaminated concrete was decontaminated by separating contaminated matrix from uncontaminated coarse aggregate under pulsed power discharge process. In this study, a stable Cs isotope was used to simulate radioactively contaminated concrete. As a result, while the volume of reclaimed aggregate from contaminated concrete could be reproduced was up to 60%, nevertheless Cs detected in the reclaimed aggregate was only approximately 3%. Thus most of the Cs were dissolved in water during the discharge process. It is expected that the pulsed power could reduce the contaminated concrete waste by reusing aggregate. Further investigations are requested to test the applicability of this method under the realistic conditions close to the actual waste.
Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira; Yamaguchi, Yasuhiro
Journal of Nuclear Science and Technology, 42(9), p.768 - 778, 2005/09
Times Cited Count：17 Percentile：73.42(Nuclear Science & Technology)A new inventive radiation monitor, designated to DARWIN (Dose Assessment system applicable to various Radiations with WIde energy raNges), has been developed for monitoring doses at workspaces of high energy accelerator facilities and on ground. Characteristics of DARWIN were studied by both calculation and experiment. The calculated results indicate that DARWIN gives reasonable estimations of doses at most radiation fields. It was found from the experiment that DARWIN has an excellent property of measuring doses from all particles that significantly contribute to the background dose - photon, muon and neutron with wide energy ranges.
-ray detectionYamasoto, Kotaro; Tsutsumi, Masahiro; Oishi, Tetsuya*; Yoshizawa, Michio; Yoshida, Makoto
Nuclear Instruments and Methods in Physics Research A, 550(3), p.609 - 615, 2005/09
Times Cited Count：5 Percentile：41.01(Instruments & Instrumentation)A phoswich detector composed of a thin plate CsI(Tl) scintillator and a plastic scintillator (BC-400) has been designed and evaluated to improve the sensitivity in the low-energy region of large-area plastic scintillation detector. Applicability of the CsI(Tl)/Plastic phoswich detector was examined on radioactivity measurement of massive and large-area materials. The rise-time discrimination technique was applied in order to further improve the minimum detectable activity in the low-energy region. On the basis of the estimation of minimum detectable activity, it was made clear that the energy range of large-area plastic scintillation detector can be expanded down to a few tens of keV by adding a thin plate CsI(Tl) scintillator.
Yamauchi, Michinori*; Sato, Satoshi; Nishitani, Takeo; Kawasaki, Hiromitsu*
Proceedings of 21st IEEE/NPSS Symposium on Fusion Engineering (SOFE 2005) (CD-ROM), 4 Pages, 2005/09
no abstracts in English
Sakai, Mikio; Yamamoto, Toshihiro; Murazaki, Minoru; Miyoshi, Yoshinori
Nuclear Technology, 149(2), p.141 - 149, 2005/02
Times Cited Count：3 Percentile：24.17(Nuclear Science & Technology)In the conventional criticality evaluation of the nuclear powder system, the effects of particulate behavior have not been considered. In other words, it is difficult to reflect the particle behavior into the conventional criticality evaluation. We have developed a novel criticality evaluation code to resolve this issue. The criticality evaluation code, coupling a Discrete Element Method simulation code with a continuous-energy Monte Carlo transport code, makes it possible to study the effect of the particulate behavior on a criticality evaluation. The criticality evaluation code has been applied to the powder system of the MOX fuel powder agitation process. The criticality evaluations have been performed under mixing the MOX fuel powder in a stirred vessel to investigate the effects of the powder boundary deformation and particulate mixture conditions on the criticality evaluation. The evaluation results revealed that the powder uniformity mixture condition and the boundary deformation could make the neutron effective multiplication factor decrease.
Otsuki, Ryusei*; Nasu, Shoichi*; Ohashi, Kentaro*; Yamamoto, Ryoichi*; Fujii, Kimio; Okubo, Keisuke*
Funtai Oyobi Fummatsu Yakin, 51(8), p.626 - 629, 2004/08
The He, Ar and the Penning gas pressureeffects on the preparation yieldsof the fullerenes were investigated by means of the arc discharge method using graphite(PGX) anode buried in a tungsten rod and tungsten cathode for collector radii of 50mm. The maximum yield showed about 13-14 % at 67KPa in He gas. The yields in the mixtures of He and Ne gases (the Penning effect) were similar to those obtained in He gas. Weight ratios of C
to (C+C
) were about 20% in Ar gas, while those in He and Penning gas were about 60%. Ultra sonic vibration was effective to separate C from soot.
