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Yamashita, Naoki; Irisawa, Eriko; Kato, Chiaki; Sano, Naruto; Tagami, Susumu
JAEA-Technology 2022-035, 29 Pages, 2023/03
JAEA-Technology-2022-035.pdf:2.54MB
In the treatment process of the current commercial reprocessing plant (Rokkasho Reprocessing Plant), the high-level liquid waste concentrator is the equipment that treats the most corrosive solution. In the high-level liquid waste concentrator, the extracted liquid waste after separation of uranium and plutonium is heated, concentrated, and reduced in volume. Therefore, the amount of gamma- rays emitted from fission products and the concentration of corrosive metal ion species such as neptunium-237 (
Np) are the highest in the reprocessing process, and the amount of corrosion in the high-level liquid waste concentrate canner is expected to be large. In this study, in order to clarify the effect of gamma-rays on the corrosion reaction of stainless steel in nitric acid solutions containing Np from the electrochemical viewpoint, the corrosion test apparatus for heat transfer surfaces in an airtight concrete cell at the Waste Safety TEsting Facility (WASTEF) of Nuclear Science Research Institute was modified to enable electrochemical measurements under gamma-ray irradiation. The effect of gamma-rays on the corrosion reaction taking place on the stainless steel surface was discussed from the electrochemical test results obtained. As a result, changes in the immersion potentials of stainless steel and the polarization curves due to chemical species caused by radiolysis of gamma-ray irradiation were confirmed.
Sano, Naruto; Yamashita, Naoki; Hishino, Kazutoyo*; Tsukada, Manabu*; Sawauchi, Fumiya*; Otake, Yoshinori*; Ichise, Kenichi; Tagami, Susumu
JAEA-Technology 2022-034, 47 Pages, 2023/03
JAEA-Technology-2022-034.pdf:2.81MB
The Waste Safety Testing Facility (WASTEF) was established in 1982 as an experimental facility for long-term storage of solidified high-level radioactive waste generated in the reprocessing of spent light water reactor fuel and the subsequent safety assessment of geological disposal. It is a historic facility that started operation in 1982. This facility consists of 5 concrete cells, 1 lead cell, 6 glove boxes, and 7 hoods, and is a large-scale facility that can use nuclear fuel materials including uranium and plutonium and radioactive isotopes including TRU. In this facility, research and development requested by the research department is carried out in the Hot Material Examination Section. In addition, patrol inspections, self-inspections, etc. are also carried out as maintenance management based on safety regulations. This report summarizes the overview of WASTEF facilities, the results of operation, maintenance and management work in FY2021, and the future outlook.
Sugihara, Kenta; Onodera, Naoyuki; Idomura, Yasuhiro; Yamashita, Susumu
Dai-36-Kai Suchi Ryutai Rikigaku Shimpojiumu Koen Rombunshu (Internet), 5 Pages, 2022/12
The conventional Allen-Cahn type multi-phase field method was modified to conserve not only the sum of the masses of all phases but also the mass of each phase. The interface advection calculations within a two-dimensional rotational velocity field were performed as a verification problem, and the conservation was successfully achieved. The proposed method was used to calculate the horizontally aligned pair of bubbles rising, and it was found that the bouncing phenomenon between bubbles can be calculated at 1/50 resolution of the high-resolution calculation by Zhang et al. using the volume of fluid method.
Uesawa, Shinichiro; Yamashita, Susumu; Shibata, Mitsuhiko; Yoshida, Hiroyuki
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 8 Pages, 2022/10
Ono, Ayako; Yamashita, Susumu; Sakashita, Hiroto*; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09
Japan Atomic Energy Agency is developing the computational fluid dynamics code, JUPITER, based on the volume of fluid (VOF) method to analyze detailed thermal-hydraulics in a reactor. The detailed numerical simulation of boiling from a heating surface needs a substantial computational cost to resolve the microscale thermal-hydraulic phenomena such as the bubble generation from a cavity and evaporation of a micro-layer. This study developed the simplified boiling model from the heating surface to reduce the computational cost, which will apply to the detailed simulation code based on the surface tracking method such as JUPITER. We applied the simplified boiling model to JUPITER, and compared the simulation results with the experimental data of the vertical heating surface in the forced convection. We confirmed the degree of their reproducibility, and the issues to be modified were extracted.
Ono, Ayako; Yamashita, Susumu; Sakashita, Hiroto*; Suzuki, Takayuki*; Yoshida, Hiroyuki
Dai-26-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2022/07
JAEA is implementing a simulation of a two-phase flow in the reactor core by TPFIT and JUPITER which are developed by JAEA based on the surface tracking method. However, it is impossible to simulate a boiling on the heating surface in the large-scale domain by this type of simulation method since the simulation of boiling based on the surface tracking method needs the fine mesh which sufficiently resolves the initiation of boiling. Therefore, JAEA started to develop the simplified boiling model applied for the two-phase flow in the fuel assemblies. In this study, the simulation results of the convection boiling on a vertical heating surface and the comparison between the simulation results and experimental results are shown.
Sugihara, Kenta; Onodera, Naoyuki; Idomura, Yasuhiro; Yamashita, Susumu
Keisan Kogaku Koenkai Rombunshu (CD-ROM), 27, 5 Pages, 2022/06
The phase-field method has been successfully applied to various multi-phase flow problems as an interface tracking method for gas-liquid interfaces. However, the accuracy of the phase-field method depends on hyper-parameters, which are empirically adjusted for each problem. The phase-field method sustains sharp interfaces by the balance between the numerical viscosity of the advection term and the interface modification by the diffusion and anti-diffusion terms. Based on this fact, we propose a method for deriving the optimal hyper-parameters in a non-empirical manner by performing a basic error analysis of the interface advection.
Ono, Ayako; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03
JAEA is developing the methodology to predict the critical heat flux based on a mechanism in order to reduce the cost for full mock-up test. The evaluation method based on a mechanism is expected to be able to predict in the wide range of parameter under the unexpected conditions including the severe accident. In this study, the JUPITER code developed by JAEA is examined to apply for the two-phase flow simulation of LWR fuel assembly with the spacer grid. The benchmark data of single-phase flow in the bundle with the spacers by KAERI were used to validate the simulation result by JUPITER. Moreover, the single-phase flow simulation was conducted by another simulation method, STAR-CCM+, as a supplemental analysis to consider the effect of the different simulation methods. Finally, the two-phase flow simulation for the bundle with the spacer was conducted by JUPITER. The effect of the spacer with a vane on the bubble behavior is discussed.
pellet in molten Zr claddingIto, Ayumi*; Yamashita, Susumu; Tasaki, Yudai; Kakiuchi, Kazuo; Kobayashi, Yoshinao*
Journal of Nuclear Science and Technology, 10 Pages, 2022/00
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)Ina, Takuya*; Idomura, Yasuhiro; Imamura, Toshiyuki*; Yamashita, Susumu; Onodera, Naoyuki
Proceedings of 12th Workshop on Latest Advances in Scalable Algorithms for Large-Scale Systems ScalA21) (Internet) , 8 Pages, 2021/11
Times Cited Count：0 Percentile：0.02A new mixed-precision preconditioner based on the iterative refinement (IR) method is developed for preconditioned conjugate gradient (P-CG) and multigrid preconditioned conjugate gradient (MGCG) solvers in a multi-phase thermal-hydraulic CFD code JUPITER. In the IR preconditioner, all data is stored in FP16 to reduce memory access, while all computation is performed in FP32. The hybrid FP16/32 implementation keeps the similar convergence property as FP32, while the computational performance is close to FP16. The developed solvers are optimized on Fugaku (A64FX), and applied to ill-conditioned matrices in JUPITER. The P-CG and MGCG solvers with the new IR preconditioner show excellent strong scaling up to 8,000 nodes, and at 8,000 nodes, they are respectively accelerated up to 4.86
and 2.39 from the conventional ones on Oakforest-PACS (KNL).
Koyama, Shinichi; Nakagiri, Toshio; Osaka, Masahiko; Yoshida, Hiroyuki; Kurata, Masaki; Ikeuchi, Hirotomo; Maeda, Koji; Sasaki, Shinji; Onishi, Takashi; Takano, Masahide; et al.
Hairo, Osensui Taisaku jigyo jimukyoku Homu Peji (Internet), 144 Pages, 2021/08
JAEA performed the subsidy program for the "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris (Development of Technologies for Enhanced Analysis Accuracy and Thermal Behavior Estimation of Fuel Debris))" in 2020JFY. This presentation summarized briefly the results of the project, which will be available shortly on the website of Management Office for the Project of Decommissioning and Contaminated Water Management.
Onodera, Naoyuki; Idomura, Yasuhiro; Hasegawa, Yuta; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*
Proceedings of International Conference on High Performance Computing in Asia-Pacific Region (HPC Asia 2021) (Internet), p.120 - 128, 2021/01
Times Cited Count：0 Percentile：0.01We develop a multigrid preconditioned conjugate gradient (MG-CG) solver for the pressure Poisson equation in a two-phase flow CFD code JUPITER. The MG preconditioner is constructed based on the geometric MG method with a three-stage V-cycle, and a RB-SOR smoother and its variant with cache-reuse optimization (CR-SOR) are applied at each stage. The numerical experiments are conducted for two-phase flows in a fuel bundle of a nuclear reactor. The MG-CG solvers with the RB-SOR and CR-SOR smoothers reduce the number of iterations to less than 15% and 9% of the original preconditioned CG method, leading to 3.1- and 5.9-times speedups, respectively. The obtained performance indicates that the MG-CG solver designed for the block-structured grid is highly efficient and enables large-scale simulations of two-phase flows on GPU based supercomputers.
Onodera, Naoyuki; Idomura, Yasuhiro; Ali, Y.*; Yamashita, Susumu; Shimokawabe, Takashi*; Aoki, Takayuki*
Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.210 - 215, 2020/10
This paper presents a GPU-based Poisson solver on a block-based adaptive mesh refinement (block-AMR) framework. The block-AMR method is essential for GPU computation and efficient description of the nuclear reactor. In this paper, we successfully implement a conjugate gradient method with a state-of-the-art multi-grid preconditioner (MG-CG) on the block-AMR framework. GPU kernel performance was measured on the GPU-based supercomputer TSUBAME3.0. The bandwidth of a vector-vector sum, a matrix-vector product, and a dot product in the CG kernel gave good performance at about 60% of the peak performance. In the MG kernel, the smoothers in a three-stage V-cycle MG method are implemented using a mixed precision RB-SOR method, which also gave good performance. For a large-scale Poisson problem with 
cells, the developed MG-CG method reduced the number of iterations to less than 30% and achieved 2.5 speedup compared with the original preconditioned CG method.
Chai, P.; Yamashita, Susumu; Yoshida, Hiroyuki
Annals of Nuclear Energy, 145, p.107606_1 - 107606_13, 2020/09
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The eutectic reaction model in JUPITER code was validated against two series of experimental tests that performed by JAEA. An experiment that aimed to evaluate the eutectic reaction between Zircaloy and Stainless steel, was simulated by JUPITER code to validate its reliability on predicting the binary eutectic reaction phenomenon. A comparison of the simulation and experimental results demonstrates good agreement on the increase rate of the solution depth at various temperature environments. Another series of tests which aimed to predict the eutectic reaction between the control rod blade and channel box in BWR, were simulated by JUPITER code to test its applicability on predicting the eutectic reaction between multiple mixture components. Although the deviation could not be completely eliminated, the reaction performance in the experiment was reasonably reproduced. As a result, it could be concluded that JUPITER code is feasible to predict the eutectic reaction behavior in nuclear severe accident.
Idomura, Yasuhiro; Onodera, Naoyuki; Yamada, Susumu; Yamashita, Susumu; Ina, Takuya*; Imamura, Toshiyuki*
Supa Kompyuteingu Nyusu, 22(5), p.18 - 29, 2020/09
A communication avoiding multigrid preconditioned conjugate gradient method (CAMGCG) is applied to the pressure Poisson equation in a multiphase CFD code JUPITER, and its computational performance and convergence property are compared against the conventional Krylov methods. The CAMGCG solver has robust convergence properties regardless of the problem size, and shows both communication reduction and convergence improvement, leading to higher performance gain than CA Krylov solvers, which achieve only the former. The CAMGCG solver is applied to extreme scale multiphase CFD simulations with 90 billion DOFs, and its performance is compared against the preconditioned CG solver. In this benchmark, the number of iterations is reduced to 
, and 
speedup is achieved with keeping excellent strong scaling up to 8,000 nodes on the Oakforest-PACS.
Yamashita, Susumu; Kino, Chiaki*; Yoshida, Hiroyuki
Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 7 Pages, 2020/08
In order to contribute the improvement of estimation accuracy for severe accident code such as SAMPSON, we have developed the chemical reaction model such as eutectic reaction and oxidation in micro scale, e.g., B
C-SUS in the control rod blade and UO-Zry in fuel rods, and implemented them to the computational fluid dynamics code named JUPITER. And we try to develop the coupled analysis frame work using SAMPSON and JUPITER to decrease uncertainty due to micro scale phenomena which cannot be calculate by severe accident analysis codes. From the preliminary analysis in fuel rod heating analysis by JUPITER using SAMPSON output data, it was revealed that the implemented chemical reaction models work stably and obtain reasonable results.
Onodera, Naoyuki; Idomura, Yasuhiro; Uesawa, Shinichiro; Yamashita, Susumu; Yoshida, Hiroyuki
Mechanical Engineering Journal (Internet), 7(3), p.19-00531_1 - 19-00531_10, 2020/06
A dry method is one of practical methods for decommissioning the TEPCO's Fukushima Daiichi Nuclear Power Station. Japan Atomic Energy Agency (JAEA) has been evaluating the air cooling performance of the fuel debris by using the JUPITER code based on an incompressible fluid model and the CityLBM code based on the lattice Boltzmann method (LBM). However, these codes were based on a uniform Cartesian grid system, and required large computational time and cost to capture complicated debris structures. We develop an adaptive mesh refinement (AMR) version of the CityLBM code on GPU based supercomputers and apply it to thermal-hydrodynamics problems. The proposed method is validated against free convective heat transfer experiments at JAEA. It is also shown that the AMR based CityLBM code on 4 NVIDIA TESLA V100GPUs gives 6.7x speedup of the time to solution compared with the JUPITER code on 36 Intel Xeon E5-2680v3 CPUs.
4 simulated bundleOno, Ayako; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Mechanical Engineering Journal (Internet), 7(3), p.19-00583_1 - 19-00583_12, 2020/06
JAEA is implementing the 3D detailed nuclear-thermal-coupled analysis code to analyze the transition state of the core and to reduce the likelihood of the design. In the development plan, the computational fluid dynamics code based on the VOF method, JUPITER, is applied for TH part of the 3D detailed nuclear-thermal-coupled analysis code.
Ono, Ayako; Yamashita, Susumu; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18) (USB Flash Drive), p.666 - 677, 2019/08
An evaluation methodology of critical heat fluxes (CHFs) based on a mechanism for fuel assemblies in light water reactors (LWRs) is needed in order to design and evaluate the safety for the fuel assemblies in LWRs. In our study, the numerical simulation with surface-tracking will be applied for the two-phase flow in fuel assemblies in order to obtain the detail data relating to the size and velocity of bubbles in the subchannel, which is needed to predict the CHF based on the mechanism. In this study, the numerical simulation of two-phase flow in 44 bundle was implemented by using JUPITER in order to establish the evaluation method of the size and velocity of bubbles by the numerical simulation, which is the multi-physics simulation code and enable to track the gas-liquid surface. The simulation results are validated by the curve of flow regime for air-water under the adiabatic condition. The bubble and velocity of bubbles obtained by simulation results are analyzed.
Onodera, Naoyuki; Idomura, Yasuhiro; Kawamura, Takuma; Uesawa, Shinichiro; Yamashita, Susumu; Yoshida, Hiroyuki
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05
A dry method is one of practical methods for decommissioning the TEPCO's Fukushima Daiichi Nuclear Power Station. Japan Atomic Energy Agency (JAEA) has been evaluating the air cooling performance by using the JUPITER code. However, the JUPITER code requires a large computational cost to capture debris' structures. To accelerate such CFD analyses, we use the CityLBM code, which is based on the lattice Boltzmann method (LBM) and is highly optimized for GPUs. The CityLBM code is validated against free convective heat transfer experiments at JAEA, and the similar accuracy as the JUPITER code is confirmed regarding the prediction capability of heat transfer and the resulting temperature distributions. It is also shown that the elapse time of a CityLBM simulation on GPUs is reduced to 1/6 compared with that of the corresponding JUPITER simulation on CPUs with the same number of GPUs and CPUs. The results show that the LBM is promising for accelerating thermal convective simulations.
