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Li, C.-Y.; Wang, K.*; Uchibori, Akihiro; Okano, Yasushi; Pellegrini, M.*; Erkan, N.*; Takata, Takashi*; Okamoto, Koji*
Applied Sciences (Internet), 13(13), p.7705_1 - 7705_29, 2023/07
Times Cited Count:1 Percentile:56.82(Chemistry, Multidisciplinary)Yuan, X.*; Hu, Q.*; Lin, X.*; Zhao, C.*; Wang, Q.*; Tachi, Yukio; Fukatsu, Yuta; Hamamoto, Shoichiro*; Siitari-Kauppi, M.*; Li, X.*
Journal of Hydrology, 618, p.129172_1 - 129172_15, 2023/03
Times Cited Count:0 Percentile:0(Engineering, Civil)Wang, Q.*; Hu, Q.*; Zhao, C.*; Yang, X.*; Zhang, T.*; Ilavsky, J.*; Kuzmenko, I.*; Ma, B.*; Tachi, Yukio
International Journal of Coal Geology, 261, p.104093_1 - 104093_15, 2022/09
Times Cited Count:5 Percentile:66.48(Energy & Fuels)Yanagisawa, Hiroshi
JAEA-Technology 2021-023, 190 Pages, 2021/11
Computational analyses on nuclear criticality characteristics were carried out for heterogeneous lattice systems composed of water moderator and fuel rods utilized in low-power research and test reactors, in which the depletion of fuel due to burnup is relatively small, by using the continuous-energy Monte Carlo code MVP Version 2 with the evaluated nuclear data library JENDL-4.0. In the analyses, the minimum critical number of fuel rods was evaluated using calculated neutron multiplication factors for the heterogeneous systems of the uranium dioxide fuel rod in the Static Experiments Critical Facility (STACY) and the Tank-type Critical Assembly (TCA), and the uranium-zirconium hydride fuel rod in the Nuclear Safety Research Reactor (NSRR). In addition, six sorts of the ratio of reaction rates, which are components of neutron multiplication factors, were calculated in the analyses to explain the variation of neutron multiplication factors with the ratio of water moderator to fuel volume in a unit fuel rod cell. Those results of analyses are considered to be useful for the confirmation of reasonableness and validity of criticality safety measures as data showing criticality characteristics for water-moderated heterogeneous lattice systems composed of the existing fuel rods in research and test reactors, of which criticality data are not sufficiently provided by the Criticality Safety Handbook.
Tachi, Yukio; Ito, Tsuyoshi*; Gylling, B.*
Water Resources Research, 57(11), p.e2020WR029335_1 - e2020WR029335_20, 2021/11
Times Cited Count:2 Percentile:17.12(Environmental Sciences)This paper focuses on the scaling approach for sorption and diffusion parameters from laboratory to in-situ conditions using the dataset of LTDE-SD experiment performed at the sp HRL. The near-surface heterogeneities at both fracture surface and rock matrix could be evaluated by conceptual model with high porosity and diffusivity, and sorption capacity, and their gradual change at the near-surface zones. The modelling results for non-sorbing Cl-36 and weak-sorbing Na-22 could validate the model concept and the parameter estimation of porosity and diffusivity, by considering the disturbed zone of 5 mm thickness with gradual parameter changes. The De values of these cationic and anionic tracers showed typical cation excess and anion exclusion effects. The modelling results for high sorbing tracers (Cs-137, Ra-226, Ni-63 and Np-237) with different sorption mechanism could confirm the validity of the scaling approaches of Kd values as a function of particle size and their relation to the near-surface disturbances.
Kobayashi, Masaki*; Anh, L. D.*; Suzuki, Masahiro*; Kaneta-Takada, Shingo*; Takeda, Yukiharu; Fujimori, Shinichi; Shibata, Goro*; Tanaka, Arata*; Tanaka, Masaaki*; Oya, Shinobu*; et al.
Physical Review Applied (Internet), 15(6), p.064019_1 - 064019_10, 2021/06
Times Cited Count:5 Percentile:35.58(Physics, Applied)Kimoto, Kazushi*; Okano, Aoi*; Saito, Takayasu*; Sato, Tadanobu*; Matsui, Hiroya
Doboku Gakkai Rombunshu, A2 (Oyo Rikigaku) (Internet), 76(2), p.I_97 - I_108, 2020/00
This study investigates the propagation characteristics of surface wave traveling in a random heterogeneous medium. For this purpose, ultrasonic measurements are performed on a granite block as a typical randomly heterogeneous medium. In this measurement, a line-focus transducer is used to excite ultrasonic waves, whereas a laser Doppler vibrometer is used to pickup the ultrasonic motion on the surface of the granite block. The measured waveforms are analysed in the frequency domain to evaluate the travel-time for each measurement point based on the Fermat's principle. From the ensemble of travel-times, the probability distribution is established as a function of travel-distance. The uncertainty of the travel-time and its spatial evolution are then investigated using the standard deviation of the travel-time as a measure of the uncertainty. As a result, it was found that the uncertainty is approximately proportional to the mean travel-time divided by the square root travel-distance.
Okazaki, Yasuyuki*; Hayashi, Hisashi*; Aoyagi, Kazuhei; Morimoto, Shingo*; Shinji, Masato*
Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12
In the design of tunnel support, the behavior of the rock mass around a tunnel and the stress acting on the tunnel support may be predicted using a numerical analysis. However, in such a numerical analysis, it is common to assume that each stratum comprises a homogeneous material, ignoring the heterogeneity of the geomechanical properties inherent to the rock mass. For this reason, it is not unusual for the results of the numerical analysis to differ from the actual behavior. We performed a tunnel excavation analysis considering the heterogeneity of the geomechanical properties in the rock mass to investigate the local increase in the tunnel support stress obtained in the 350 m gallery at the Horonobe Underground Research Laboratory. The results revealed that, in order to predict the locally increased support stress in advance, it is necessary to carry out a tunneling excavation analysis considering the heterogeneity of the geomechanical properties. It was also revealed that the scale at which the geomechanical properties fluctuate is an important factor.
Tachi, Yukio; Ito, Tsuyoshi*; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*
Water Resources Research, 54(11), p.9287 - 9305, 2018/11
Times Cited Count:5 Percentile:26.11(Environmental Sciences)Effects of fine-scale surface alterations on radionuclide migration in fractured crystalline rocks were investigated by a comprehensive approach coupling a series of laboratory tests, microscopic observations and modelling, using a single fractured granodiorite sample from the Grimsel Test Site, Switzerland. Laboratory tests including through-diffusion, batch sorption and flow-through tests using five tracers indicated that tracer retention was consistently in the sequence of HDO, Se, Cs, Ni, Eu, and as well as showing the existence of a diffusion-resistance layer near the fracture surface, cation excess and anion exclusion effects for diffusion. Microscale heterogeneities in structural properties around the fracture were clarified quantitatively by coupling X-ray CT and EPMA. A three layer model including weathered vermiculite, foliated mica and undisturbed matrix layers, and their properties such as porosity, sorption and diffusion parameters, could provide a reasonable interpretation for breakthrough curves and concentration distributions near fracture surface of all tracers, measured in flow-through tests.
Kamemura, Katsumi*; Aoyagi, Kazuhei; Nago, Makito*; Sugawara, Kentaro*
Dai-45-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.43 - 48, 2018/01
In situ stress state is very important for the design of deep underground facility of high-level radioactive waste disposal repository. This study establishes a practical and effective method for estimating in situ stress state based on the measured convergence and detailed geological observations during gallery excavation. The convergence was measured in various directions of the loop gallery at 350m depth of the Horonobe URL; this allows determination of the stress state corresponding to the rock mass behavior in 120m 200m area. In situ stress state estimated by the back analysis considering existing faults and fractures showed a good agreement with that of estimated from hydraulic fracturing method.
Miyabe, Masabumi; Oba, Masaki; Kato, Masaaki; Wakaida, Ikuo; Watanabe, Kazuo
JAERI-Tech 2005-043, 27 Pages, 2005/08
Multi-step resonance ionization spectrometry for long-lived nuclei in nuclear waste materials requires laser sources having high frequency stability and tunability. In this study we have developed a novel frequency control system consisting of digital circuitry and computer to improve the frequency tunability of the developed laser stabilization system using dichroic atomic vapor laser lock (DAVLL) and fringe offset lock (FOL) techniques. Based on the heterodyne experiment and multi-step laser induced fluorescence spectroscopy of atomic Ca, the frequency stability and tunability of the developed system were evaluated.
Watanabe, Shoichi; Yamamoto, Toshihiro; Miyoshi, Yoshinori
Transactions of the American Nuclear Society, 91, p.431 - 432, 2004/11
Temperature effect is a main factor which affects the transient characteristics at a criticality accident. A series of reactivity effects due to changes in fuel temperatures were measured for two kinds of STACY heterogeneous lattice configurations. The core was composed of LWR-type fuel rod array and low-enriched uranyl-nitrate-solution concerning the dissolver of the reprocessing facility for LWR spent fuel. The critical solution heights at various solution temperatures were measured. From the change of the critical water height with fuel temperature, the reactivity effect was evaluated by a critical-solution-level worth method. The temperature effect was also calculated by using SRAC and the transport calculation code TWODANT. The experimental value was estimated to be -2.0 cent/C for the case "2.1cm-pitch", and -2.5 cent/C for the case "1.5cm-pitch". The calculated results gave agreement with the experiments within 10%.
Nojiri, Naoki; Fujimoto, Nozomu; Mori, Tomoaki; Obata, Hiroyuki*
JAERI-Data/Code 2004-012, 65 Pages, 2004/10
DELIGHT code is a fuel cell burnup analysis code which can produce the group constants necessary for High Temperature Gas-cooled Reactors (HTGR) core analyses. Collision probability method is used to the lattice calculation. The lattice calculation model is a cylinder type fuel or a ball type fuel of the HTGR. This code characterizes the burnup calculation considering the double heterogeneity caused by coated fuel particles of the HTGR fuel. DELIGHT code has updated its nuclear data library to the latest JENDL-3.3 data, and included new burnup chain models in order to calculate high burnup HTGR cores. The material regions of the periphery burnable poisons (BPs) were divided into details in order to improve calculation accuracy of the BP lattice calculation. This report presents the revised points of the DELIGHT-8 and can be used as user's manual.
Tonoike, Kotaro; Yamamoto, Toshihiro; Watanabe, Shoichi; Miyoshi, Yoshinori
Journal of Nuclear Science and Technology, 41(2), p.177 - 182, 2004/02
Times Cited Count:14 Percentile:66.01(Nuclear Science & Technology)As a part of the development of a subcriticality monitoring system, a system which has a time series data acquisition function of detector signals and a real time evaluation function of alpha value with the Feynman- method was established, with which the kinetic parameter (alpha value) was measured at the STACY heterogeneous core. The Hashimoto's difference filter was implemented in the system, which enables the measurement at a critical condition. The measurement result of the new system agreed with the pulsed neutron method.
Takada, Tomoyuki; Miyoshi, Yoshinori; Katakura, Junichi
JAERI-Tech 2003-036, 80 Pages, 2003/03
In order to perform accuracy evaluation of the critical calculation by the combination of multi-group constant library MGCL and 3-dimensional Monte Carlo code KENO-IV among critical safety evaluation code system JACS, benchmark calculation was carried out from 1980 in 1982. Some cases where the neutron multiplication factor calculated in the heterogeneous system in it was less than 0.95 were seen. In this report, it re-calculated by considering the cause about the heterogeneous system of the U+Pu nitric acid solution systems containing the neutron poison shown in JAERI-M 9859. The present study has shown that the keff value less than 0.95 given in JAERI-M 9859 is caused by the fact that the water reflector below a cylindrical container was not taken into consideration in the KENO-IV calculation model. By taking into the water reflector, the KENO-IV calculation gives a keff value greater than 0.95 and a good agreement with the experiment.
Kondoh, Takashi; Miura, Yukitoshi; Lee, S.*; Richards, R. K.*; Hutchinson, D. P.*; Bennett, C. A.*
Review of Scientific Instruments, 74(3), p.1642 - 1645, 2003/03
Times Cited Count:20 Percentile:68.13(Instruments & Instrumentation)Measurements of energy spectrum and density profile of confined alpha-particles are required for ITER. Several methods have been proposed, however, a measurement technique hasn't been established yet. A collective Thomson scattering (CTS) system based on a pulsed CO laser is being developed to demonstrate feasibility of alpha-particle diagnostics for ITER. The pulse laser (15J, 1m, 0.6 m) and a wide band (~ 8GHz) heterodyne receiver with a quantum-well infrared photodetector (QWIP) have been developed and installed in the JT-60U tokamak. Stray light is reduced by a notch filter with hot CO gas. Heterodyne receiver is absolutely calibrated using large area blackbody radiation source. Scattered signal from JT-60U plasma has not detected because of electrical noise originated from discharge of the pulsed laser and stray signal caused by impurity of the spectrum of the pulsed laser.
Kugo, Teruhiko
Journal of Nuclear Science and Technology, 39(3), p.256 - 263, 2002/03
Times Cited Count:3 Percentile:23.39(Nuclear Science & Technology)Two vector computation algorithms; an odd-even sweep (OES) method and an independent sequential sweep (ISS) method, have been developed for the characteristics method to solve the neutron transport equation in a heterogeneous geometry. They realize long vector lengths without recursive operations for effective use of vector computers. Their efficiency has been investigated to a realistic fuel assembly calculation. For both methods, a vector computation is 15 times faster than a scalar computation. From a viewpoint of a comparison between the OES and ISS methods, the ISS method is superior to the OES method because the ISS method shows a faster convergence and saves a computer memory without reducing a computation speed.
Kugo, Teruhiko
JAERI-Research 2001-051, 39 Pages, 2001/11
Fast computation of the characteristics method to solve the neutron transport equation in a heterogeneous geometry has been studied. Two vector computation algorithms; an odd-even sweep (OES) method and an independent sequential sweep (ISS) method have been developed and their efficiency to a typical fuel assembly calculation has been investigated. For both methods, a vector computation is 15 times faster than a scalar computation. From a viewpoint of comparison between the OES and ISS methods, the ISS method is superior to the OES method because the ISS method shows a faster convergence and saves a computer memory without reducing a computation speed. In the vector computation, a table-look-up method to reduce computation time of an exponential function saves only 20% of a whole computation time. Both the coarse mesh rebalance method and the Aitken acceleration method are effective as acceleration methods for the characteristics method, a combination of them saves 70-80% of outer iterations compared with a free iteration.
Kondoh, Takashi; Lee, S.; Miura, Yukitoshi
Purazuma, Kaku Yugo Gakkai-Shi, 76(9), p.883 - 887, 2000/09
no abstracts in English
Mori, Takamasa; Okumura, Keisuke; Nagaya, Yasunobu; Ando, Hiroei
Transactions of the American Nuclear Society, 83, p.283 - 284, 2000/00
no abstracts in English