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JAEA Reports

Prediction of RPV lower structure failure and core material relocation behavior with MPS method (Contract research)

Yoshikawa, Shinji; Yamaji, Akifumi*

JAEA-Research 2021-006, 52 Pages, 2021/09

JAEA-Research-2021-006.pdf:3.89MB

In Fukushima Daiichi Nuclear Power Station (referred to as "FDNPS" hereafter) unit2 and unit3, failure of the reactor pressure vessel (RPV) and relocation of some core materials (CRD piping elements and upper tie plate, etc.) to the pedestal region have been confirmed. In boiling water reactors (BWRs), complicated core support structures and control rod drive mechanisms are installed in the RPV lower head and its upper and lower regions, so that the relocation behavior of core materials to pedestal region is expected to be also complicated. The Moving Particle Semi-implicit (MPS) method is expected to be effective in overviewing the relocation behavior of core materials in complicated RPV lower structure of BWRs, because of its Lagrangian nature in tracking complex interfaces. In this study, for the purpose of RPV ablation analysis of FDNPS unit2 and unit3, rigid body model, parallelization method and improved calculation time step control method were developed in FY 2019 and improvement of pressure boundary condition treatment, stabilization of rigid body model, and calculation cost reduction of debris bed melting simulation were achieved in FY2020. These improvements enabled sensitivity analyses of melting, relocation and re-distribution behavior of deposited solid debris in RPV lower head on various cases, within practical calculation cost. As a result of the analyses of FDNPS unit2 and unit3, it was revealed that aspect (particles/ingots) and distribution (degree of stratification) of solidified debris in lower plenum have a great impact on the elapsed time of the following debris reheat and partial melting and on molten pool formation process, further influencing RPV lower head failure behavior and fuel debris discharging behavior.

Journal Articles

Chapter 18, Moving particle semi-implicit method

Wang, Z.; Duan, G.*; Koshizuka, Seiichi*; Yamaji, Akifumi*

Nuclear Power Plant Design and Analysis Codes, p.439 - 461, 2021/00

Journal Articles

Consistent robin boundary enforcement of particle method for heat transfer problem with arbitrary geometry

Wang, Z.; Duan, G.*; Matsunaga, Takuya*; Sugiyama, Tomoyuki

International Journal of Heat and Mass Transfer, 157, p.119919_1 - 119919_20, 2020/08

 Times Cited Count:3 Percentile:65.8(Thermodynamics)

Journal Articles

Development of a multiphase particle method for melt-jet breakup behavior of molten core in severe accident

Wang, Z.; Iwasawa, Yuzuru; Sugiyama, Tomoyuki

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 12 Pages, 2020/08

JAEA Reports

Development of technology to prevent scattering of radioactive materials in fuel debris retrieval (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*

JAEA-Review 2019-037, 90 Pages, 2020/03

JAEA-Review-2019-037.pdf:7.0MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Technology to Prevent Scattering of Radioactive Materials in Fuel Debris Retrieval". The objective of the present study is to clarify the behavior of microparticles in gas and liquid phases in order to steadily confine radioactive microparticles at the time of debris retrieval in Fukushima Daiichi Nuclear Power Station. In addition, as measures to prevent scattering, we will evaluate and develop methods by experiments and simulation as to; (1) a method to suppress the scattering with minimum amount of water utilizing water spray etc., and (2) a method to suppress the scattering by solidifying fuel debris.

Journal Articles

Estimation method of systematic uncertainties in Monte Carlo particle transport simulation based on analysis of variance

Hashimoto, Shintaro; Sato, Tatsuhiko

Journal of Nuclear Science and Technology, 56(4), p.345 - 354, 2019/04

 Times Cited Count:1 Percentile:23.13(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.

Journal Articles

Development of numerical simulation method for small particles behavior in two-phase flow by combining interface and Lagrangian particle tracking methods

Yoshida, Hiroyuki; Uesawa, Shinichiro; Horiguchi, Naoki; Miyahara, Naoya; Ose, Yasuo*

Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 6 Pages, 2018/11

Journal Articles

Particle-based simulation of heat transfer behavior in EAGLE ID1 in-pile test

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$$^{2}$$ on the duct wall was caused by effective heat transfer due to direct contact of liquid fuel with nuclear heat to the duct wall.

Journal Articles

Three-dimensional numerical study on pool stratification behavior in molten corium-concrete interaction (MCCI) with MPS method

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.

Journal Articles

Numerical simulations of gas-liquid-particle three-phase flows using a hybrid method

Guo, L.*; Morita, Koji*; Tobita, Yoshiharu

Journal of Nuclear Science and Technology, 53(2), p.271 - 280, 2016/02

 Times Cited Count:6 Percentile:61.4(Nuclear Science & Technology)

Journal Articles

Study of SOL/divertor plasmas in JFT-2M

Kawashima, Hisato; Sengoku, Seio; Uehara, Kazuya; Tamai, Hiroshi; Shoji, Teruaki*; Ogawa, Hiroaki; Shibata, Takatoshi; Yamamoto, Masahiro*; Miura, Yukitoshi; Kusama, Yoshinori; et al.

Fusion Science and Technology, 49(2), p.168 - 186, 2006/02

 Times Cited Count:2 Percentile:18.25(Nuclear Science & Technology)

Experimental efforts on JFT-2M have been devoted to understand SOL/Divertor plasmas and to investigate power and particle controllability. Open divertor configuration was used for the first decade of JFT-2M started in 1984. We found out the SOL/Divertor plasma properties such as in/out asymmetry, heat and particle diffusivities, and SOL current at ELMs. Handling of power and particle was demonstrated by active control methods such as local pumping, edge ergodization, divertor biasing, and edge heating. For improvement of power and particle control capability of divertor, it was modified to closed configuration in 1995, which demonstrated the baffling effects with narrower divertor throat. Dense and cold divertor state (n$$_{e}$$$$^{div}$$ = 4$$times$$10$$^{19}$$ m$$^{-3}$$ and T$$_{e}$$$$^{div}$$ = 4 eV), compatible with the improved confinement modes (e.g. H-mode), was realized by strong gas puffing. Being related with the core confinement at H-mode, the edge plasma fluctuations were identified by an electrostatic probe. These are reviewed in this paper.

Journal Articles

$$delta f$$ simulations of microturbulence

Idomura, 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 $$delta f$$ 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 $$delta f$$ method is reviewed, and issues in full torus gyrokinetic particle simulations are discussed.

Journal Articles

Reprocessing technologies of the High Temperature Gas-cooled Reactor (HTGR) fuel

Sumita, Junya; Ueta, Shohei; Kunitomi, Kazuhiko; Yoshimuta, Shigeharu*; Sawa, Kazuhiro

Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(4), p.546 - 554, 2003/12

A High Temperature Gas-Cooled Reactor (HTGR) is particularly attractive due to capability of producing high temperature helium gas and its inherent safety characteristic. Research and development of high temperature gas turbine plant and high temperature heat utilizing technology are now undergoing. The High Temperature Engineering Test Reactor (HTTR) is a research facility constructed by the Japan Atomic Energy Research Institute. This paper describes reprocessing technology of HTGR fuels. Coated fuel particles, consisted of a microsphere of low enriched UO$$_{2}$$ with TRISO particles, are used as the HTGR fuels. In order to reprocess HTGR fuels, a head-end process is needed and JAERI had confirmed jet-grind method as basic technologies of the head-end process. Since Purex method can be used after the head-end process, a reprocessing system for the HTGR fuels could be established. Also the preliminary study on the methodology for disposing graphite blocks in a HTGR was carried out, and its evaluation results were briefly presented.

Journal Articles

Dynamic load balancing algorithm for particle transport Monte Carlo simulation code

Takemiya, Hiroshi*; Higuchi, Kenji; *

Modeling and Simulation Based Engineering, p.497 - 502, 1998/00

no abstracts in English

JAEA Reports

The Parallel processing of EGS4 code on distributed memory scalar parallel computer: Intel Paragon XP/S15-256

Takemiya, Hiroshi*; *; *

JAERI-Data/Code 96-010, 52 Pages, 1996/03

JAERI-Data-Code-96-010.pdf:2.28MB

no abstracts in English

Journal Articles

Development of Monte Carlo machine for particle transport problem

Higuchi, Kenji; ;

Journal of Nuclear Science and Technology, 32(10), p.953 - 964, 1995/10

 Times Cited Count:1 Percentile:18.1(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Application study of parallel processing to the particle transport simulation

*; Nakakawa, Masayuki; Mori, Takamasa

Comput. Assist. Mech. Eng. Sci., 1, p.177 - 189, 1994/00

no abstracts in English

Journal Articles

Development of JAERI Monte Carlo machine and its effective performance

Higuchi, Kenji; ; ; ; Tokuda, Shinji; *; *; *

Comput. Assist. Mech. Eng. Sci., 1, p.191 - 204, 1994/00

no abstracts in English

Journal Articles

Computer simulation of two-dimensional continuum flows by the direct simulation Monte Carlo method

; Yokokawa, Mitsuo

Molecular Simulation, 12(3-6), p.441 - 444, 1994/00

 Times Cited Count:3 Percentile:27.55(Chemistry, Physical)

no abstracts in English

31 (Records 1-20 displayed on this page)