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Zhang, T.*; Morita, Koji*; Liu, X.*; Liu, W.*; Kamiyama, Kenji
Annals of Nuclear Energy, 179, p.109389_1 - 109389_10, 2022/12
Times Cited Count：1 Percentile：31.61(Nuclear Science & Technology)Zhang, T.*; Morita, Koji*; Liu, X.*; Liu, W.*; Kamiyama, Kenji
Extended abstracts of the 2nd Asian Conference on Thermal Sciences (Internet), 2 Pages, 2021/10
For the Japanese sodium cooled fast reactor, a fuel subassembly with an inner duct structure (FAIDUS) was designed to avoid the re-criticality by preventing the large-scale pool formation. In the present study, using the finite volume particle method, the EAGLE ID1 test which was an in-pile test performed to demonstrate the effectiveness of FAIDUS was numerically simulated and the thermal-hydraulic mechanisms underlying the heat transfer process were analyzed.
Zhang, T.*; Funakoshi, Kanji*; Liu, X.*; Liu, W.*; Morita, Koji*; Kamiyama, Kenji
Annals of Nuclear Energy, 150, p.107856_1 - 107856_10, 2021/01
Times Cited Count：5 Percentile：65.59(Nuclear Science & Technology)Yoshida, Hiroyuki; Uesawa, Shinichiro
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08
Hashimoto, Shintaro; Sato, Tatsuhiko
Journal of Nuclear Science and Technology, 56(4), p.345 - 354, 2019/04
Times Cited Count：5 Percentile：48.99(Nuclear Science & Technology)Particle transport simulations based on the Monte Carlo method have been applied to shielding calculations. Estimation of not only statistical uncertainty related to the number of trials but also systematic one induced by unclear physical quantities is required to confirm the reliability of calculated results. In this study, we applied a method based on analysis of variance to shielding calculations. We proposed random- and three-condition methods. The first one determines randomly the value of the unclear quantity, while the second one uses only three values: the default value, upper and lower limits. The systematic uncertainty can be estimated adequately by the random-condition method, though it needs the large computational cost. The three-condition method can provide almost the same estimate as the random-condition method when the effect of the variation is monotonic. We found criterion to confirm convergence of the systematic uncertainty as the number of trials increases.
Morita, Koji*; Ogawa, Ryusei*; Tokioka, Hiromi*; Liu, X.*; Liu, W.*; Kamiyama, Kenji
Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 11 Pages, 2018/10
The EAGLE in-pile ID1 test has been performed by Japan Atomic Energy Agency to demonstrate early fuel discharge from a fuel subassembly with an inner duct structure, which is named FAIDUS. It was deduced that early duct wall failure observed in the test was initiated by high heat flux from the molten pool of fuel and steel mixture. The posttest analyses suggest that molten pool-to-duct wall heat transfer might be enhanced effectively by the molten steel with large thermal conductivity in the pool without the presence of fuel crust on the duct wall. In this study, mechanisms of heat transfer from the molten pool to the duct wall was analyzed using a fully Lagrangian approach based on the finite volume particle method for multi-component, multi-phase flows. A series of pin disruption, molten pool formation and duct wall failure behaviors was simulated to investigate mixing and separation behavior of molten steel and fuel in the pool, and their effect on molten pool-to-duct wall heat transfer. The present 2D particle-based simulations demonstrated that large thermal load beyond 10 MW/m
on the duct wall was caused by effective heat transfer due to direct contact of liquid fuel with nuclear heat to the duct wall.
Li, X.; Sato, Ikken; Yamaji, Akifumi*; Duan, G.*
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07
Molten corium-concrete interaction (MCCI) is an important ex-vessel phenomenon that could happen during the late phase of a hypothetical severe accident in a light water reactor. In the present study, a three-dimensional (3-D) numerical study has been performed to simulate COMET-L3 test carried out by KIT with a stratified molten pool configuration of simulant materials with improved MPS method. The heat transfer between corium/crust/concrete was modeled with heat conduction between particles. Moreover, the potential influence of the siliceous aggregates was also investigated by setting up two different case studies since there was previous study indicating that siliceous aggregates in siliceous concrete might contribute to different axial and radial concrete ablation rates. The simulation results have indicated that metal melt as corium in MCCI can have completely different characteristics regarding concrete ablation pattern from that of oxidic corium, which needs to be taken into consideration when assessing the containment melt-through time in severe accident management.
Guo, L.*; Morita, Koji*; Tobita, Yoshiharu
Journal of Nuclear Science and Technology, 53(2), p.271 - 280, 2016/02
Times Cited Count：7 Percentile：55.03(Nuclear Science & Technology)
n waves in tokamaksBierwage, A.; Shinohara, Koji
Physics of Plasmas, 21(11), p.112116_1 - 112116_21, 2014/11
Times Cited Count：23 Percentile：72.13(Physics, Fluids & Plasmas)Takizuka, Tomonori; Hosokawa, Masanari*
Contributions to Plasma Physics, 46(7-9), p.698 - 703, 2006/09
Times Cited Count：14 Percentile：43.86(Physics, Fluids & Plasmas)Enhanced heat and particle fluxes to the divertor plates after an ELM crash in H-mode plasmas are the crucial issues for the tokamak reactor operation. Kinetic effect in the transient behaviour of SOL-divertor plasmas for this case is not yet well known. We investigate above problems with an advanced particle simulation code, PARASOL. Dependence of the particle and heat propagations on the collisionality is studied systematically. Effect of the particle recycling is also studied.
Matsumoto, Taro; Naito, Hiroshi*; Tokuda, Shinji; Kishimoto, Yasuaki*
Nuclear Fusion, 45(11), p.1264 - 1270, 2005/11
Times Cited Count：14 Percentile：43.63(Physics, Fluids & Plasmas)A gyrokinetic particle simulation is executed to clarify the effect of the electron inertia on the MHD phenomena in the reversed shear configuration (RSC) of a cylindrical tokamak plasma. It is found that the collisionless (kinetic) double tearing modes grow up at the Alfvn time scale, and nonlinearly induce the internal collapse when the helical flux at the magnetic axis is less than that at the outer resonant surface. After the internal collapse, the secondary reconnection is induced by the current concentration due to the 
convective flow. It is also clarified that a nonlinear dynamics accompanied with the elementary processes caused by the flow can generate a new RSC with resonant surfaces. In the presence of the density gradient, after the full reconnection induced by the mode, the radial electric field is found to be generated due to the difference of the 
motion between ions and electrons. However, the intensity of the radial field is not so large as that induced by the collisionless kink mode.
Terada, Hiroaki; Chino, Masamichi
Proceedings of 2nd International Conference on Radioactivity in the Environment, p.15 - 18, 2005/10
The previous version of Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) has been composed of mass-consistent wind field model WSYNOP and particle dispersion model GEARN. Because WSYNOP has no capability to predict meteorological fields, its accuracy and resolution depends on meteorological input data, and it is impossible to treat physical processes realistically. To improve these problems, an atmospheric dynamic model MM5 is introduced and applied to the Chernobyl accident for the verification. Two calculation cases are conducted, CASE-1 a calculation for European region Domain-1, and CASE-2 a domain nesting calculation for Domain-1 and the region around Chernobyl Domain-2. The air concentration and surface deposition of 
Cs calculated by CASE-1 agree well with the measurements by statistical analysis and comparison for the horizontal distribution. In the result of CASE-2, the detailed distribution of surface Cs deposition around Chernobyl which was impossible to calculate in CASE-1 is predicted with high accuracy.
Matsumoto, Taro; Naito, Hiroshi*; Tokuda, Shinji; Kishimoto, Yasuaki
Physics of Plasmas, 12(9), p.092505_1 - 092505_7, 2005/09
Times Cited Count：2 Percentile：6.86(Physics, Fluids & Plasmas)The behavior of the collisionless magnetohydrodynamics modes is investigated by the gyro-kinetic particle simulation in a cylindrical tokamak plasma in the parameter region where the effects of electron inertia and electron parallel compressibility are competitive for magnetic reconnection. Although the linear growth of the 
internal kink-tearing mode is dominated by the electron inertia, it is found that the growth rate can be nonlinearly accelerated due to the electron parallel compressibility proportional to the ion sound Larmor radius 
. It is also found that, as decreasing the electron skin depth 
, the maximum growth rate before the internal collapse saturates independently of the microscopic scales such as and . The acceleration of growth rate is also observed in the nonlinear phase of the double tearing mode.
simulations of microturbulenceIdomura, Yasuhiro
Purazuma, Kaku Yugo Gakkai-Shi, 81(8), p.581 - 592, 2005/08
A gyrokinetic particle simulation is a powerful tool in studying tokamak microturbulence. A method, which is a standard method in recent gyrokinetic particle simulations, dramatically improved an efficiency of a particle simulation by reducing a particle noise, and full torus turbulence simulations are enabled. In this paper, the method is reviewed, and issues in full torus gyrokinetic particle simulations are discussed.
Cs deposition due to the Chernobyl nuclear accidentTerada, Hiroaki; Chino, Masamichi
Journal of Nuclear Science and Technology, 42(7), p.651 - 660, 2005/07
Times Cited Count：18 Percentile：74.92(Nuclear Science & Technology)The prediction performance of WSPEEDI (Worldwide version of System for Prediction of Environmental Emergency Dose Information), which consists of the atmospheric dynamic model MM5 and the Lagrangian particle dispersion model GEARN-new, is evaluated by measurements of precipitation and surface deposition of Cs over Europe during the Chernobyl accident. It is concluded that MM5/GEARN-new can predict Cs deposition distribution with good accuracy when accurate precipitation is predicted by using a explicit scheme on cloud microphysics with ice phase processes. High-resolutional calculation is also conducted for the area surrounding Chernobyl by a nesting method. MM5/GEARN-new can predict quite a realistic distribution of Cs deposition around Chernobyl which was not calculated by the previous version.
Villard, L.*; Angelino, P.*; Bottino, A.*; Allfrey, S. J.*; Hatzky, R.*; Idomura, Yasuhiro; Sauter, O.*; Tran, T. M.*
Plasma Physics and Controlled Fusion, 46(12B), p.B51 - B62, 2004/12
Times Cited Count：29 Percentile：67.01(Physics, Fluids & Plasmas)This paper reviews the present status of recent first principles based plasma turbulence simulations, and gives quantitative discussions on influences of the v// nonlinearlity and the geometry effects in the gyrokinetic Poisson equaiton, which are ignored in the conventional approximations, on simulations results. Careful treatments of these effects enable turbulence simulations satisfying the conservation of the energy and the particle number. The new simulation disclosed new phenomena, and it is found that (1) turbulence spreading is induced by avalanche like phnemena consisting of bursty heat transport and local flattening of pressure profiles, and (2) nonlinearly driven E
B flows become global shear flows with scale lengths of about 30 ion gyro radii.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Journal of Plasma and Fusion Research SERIES, Vol.6, p.17 - 72, 2004/00
A global gyrokinetic toroidal particle code for a 3D nonlinear simulation (GT3D) has been developed for a comprehensive study of the ion and electron anomalous transport arising from the ion temperature gradient driven - trapped electron mode (ITG-TEM) turbulence in tokamak plasmas. In the preliminary linear ITG-TEM calculations, basic properties of ITG-TEM modes are confirmed. Adding trapped electrons not only increases the growth rate of the ITG mode, but also produces another unstable electron mode, the TEM mode, which is unstable even at 
. The dominant mode changes from the ITG mode to the TEM mode depending on 
and 
. In linear benchmark calculations using Cyclone base case parameters, eigenfrequencies obtained from GT3D, GTC(PPPL-UCI) and FULL(PPPL) show reasonable quantitative agreement.
O
Mo, S.-K.*; Denlinger, J. D.*; Kim, H.-D.*; Park, J.-H.*; Allen, J. W.*; Sekiyama, Akira*; Yamasaki, Atsushi*; Kadono, Koji*; Suga, Shigemasa*; Saito, Yuji; et al.
Physical Review Letters, 90(18), p.186403_1 - 186403_4, 2003/05
Times Cited Count：143 Percentile：95.5(Physics, Multidisciplinary)no abstracts in English
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 43(4), p.234 - 243, 2003/04
Times Cited Count：119 Percentile：94.91(Physics, Fluids & Plasmas)no abstracts in English
Kida, Takashi; Umeda, Miki; Sugikawa, Susumu
JAERI-Data/Code 2003-001, 29 Pages, 2003/03
JAERI-Data-Code-2003-001.pdf:6.34MB
MOX dissolution using silver-mediated electrochemical method will be employed for the preparation of plutonium nitrate solution in the criticality safety experiments in NUCEF. A simulation code for the MOX dissolution has been developed for the operating support. In this report an outline of the simulation code is proposed and a comparison with the experimental data and a parameter study on the MOX dissolution rate are described.The principle of this code is based on Zundelevich's model for PuO dissolution using Ag
. The influence of nitrous acid on the material balance of Ag and the surface area of MOX powder on the basis of particle size distribution are taken into consideration in this model. A comparison with experimental data was carried out to confirm a validity of this model. It was confirmed that the behavior of MOX dissolution could adequately be simulated using the appropriate MOX dissolution rate constant. The parameters affecting the dissolution rate were studied, it was found that MOX particle size was major governing factor on the dissolution rate.
