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Improvement of solidification model and analysis of 3D channel blockage with MPS method

Frontiers in energy 2021年第4期15卷 946-958页

作者： Reo KAWAKAMI Xin LI Guangtao DUAN Akifumi YAMAJI Isamu SATO Tohru SUZUKI cooperative major in nuclear energy Graduate School and Advanced Science and EngineeringFaculty of Science and EngineeringWaseda University3-4-1 OkuboShinjuku-kuTokyo169-8555Japan Department of nuclear Engineering and Management The University of Tokyo7-3-1 HongoBunkyo-kuTokyo113-8656Japan Department of nuclear Safety Engineering Faculty of EngineeringTokyo City University1-28-1 TamazutsumiSetagaya-kuTokyo158-0087Japan

In a severe accident of a nuclear power reactor,coolant channel blockage by solidified molten core debris may significantly influence the core degradations that *** moving particle semi-implicit(MPS)method is one of the Lagrangian-based particle methods for analyzing incompressible *** the study described in this paper,a novel solidification model for analyzing melt flowing channel blockage with the MPS method has been developed,which is suitable to attain a sufficient numerical accuracy with a reasonable calculation *** prompt velocity diffusion by viscosity is prioritized over the prompt velocity correction by the pressure term(for assuring incompressibility)within each time step over the“mushy zone”(between the solidus and liquidus temperature)for accurate modeling of solidification before fixing the coordinates of the completely solidified *** sustain the numerical accuracy and stability,the corrective matrix and particle shifting techniques have been applied to correct the discretization errors from irregular particle arrangements and to recover the regular particle arrangements,*** validate the newly developed algorithm,2-D benchmark analyses are conducted for steady-state freezing of the water in a laminar flow between two parallel ***,3-D channel blockage analyses of a boiling water reactor(BWR)fuel support piece have been *** results show that a partial channel blockage develops from the vicinity of the speed limiter,which does not fully develop into a complete channel blockage,but still diverts the incoming melt flow that follows to the orifice region.

关键词： boiling water reactor(BWR) severe accident channel blockage moving particle semi-implicit(MPS)method solidification*

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Broadband FIR absorption spectra of lowdensity polyethylene sheets containing six different antioxidants and estimation of their contents by chemometric analysis

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High Voltage 2019年第3期4卷 161-166页

作者： Takaaki Ogishima Chiaki Kuroda Naoshi Hirai Yoshimichi Ohki Department of Electrical Engineering and Bioscience Waseda UniversityShinjuku-kuTokyo 169-8555Japan Research Institute for Materials Science and Technology Waseda UniversityShinjuku-kuTokyo 169-8555Japan cooperative major in nuclear energy Waseda UniversityShinjuku-kuTokyo169-8555Japan

Antioxidants are usually added to polymeric insulating materials to suppress oxidative ***,the details of antioxidant added to a polymer are often not *** the other hand,compared to mid-infrared absorption spectroscopy,terahertz(THz)absorption spectroscopy,and far-infrared(FIR)absorption spectroscopy have not been performed so *** on the above backgrounds,six different kinds of antioxidants were added into low-density polyethylene sheets with four different contents,and their THz and FIR absorption spectra were *** a result,it has become clear that each antioxidant shows its specific absorption peaks,by which the antioxidants can be ***,the antioxidant content can be estimated by the absorption intensity of the specific peak.A chemometric analysis can make the estimation more accurately than a simple comparison of absorption intensity.

关键词： FIR absorption estimation

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Analysis of OECD/NEA medium 1000 MWth sodium-cooled fast reactor using the Monte Carlo serpent code and ENDF/B-VIII.0 nuclear data library

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nuclear Science and Techniques 2020年第12期31卷 77-87页

作者： Fatima IAl-Hamadi Bassam AKhuwaileh Peng Hong Liem Donny Hartanto Department of Mechanical and nuclear Engineering University of SharjahP.O.BOX 27272SharjahUnited Arab Emirates Graduate School of Engineering Cooperative Major in Nuclear EnergyTokyo City University(TCU)1-28-1 TamazutsumiSetagayaTokyoJapan Scientific Computational Division Nippon Advanced Information Service(NAIS Co.Inc.)416 MuramatsuTokaimuraIbarakiJapan

This study presents a benchmark evaluation of the new ENDF/B-VIII.0 nuclear data library for the Organization for Economic Co-operation and Development/nuclear energy Agency Medium 1000 MWth sodium-cooled fast reactor(SFR).The study presented herein covers both SFR core types,i.e.,metallic fueled(MET-1000)and oxide fueled(MOX-1000),simulated using the continuous-energy Monte Carlo Serpent2 *** neutronics performances of the ENDF/B-VIII.0-based simulations were compared mainly to two libraries:ENDF/B-VII.1 and *** comparison includes several neutronics parameters evaluated for the beginning and end of the cycle *** parameters include the effective multiplication factor keff,total effective delayed neutron fraction beff,sodium void reactivity(DqNa),Doppler constant(DqDoppler),and control rod worth(DqCR).In addition,a sensitivity study was used to reveal the major isotope/reaction pairs contributing to the discrepancy observed in the performance of the three libraries using 33 and 44-energy-group structures.

关键词： Serpent ENDF/B-VIII.0 Sodium-cooled fast reactor Sensitivity analysis

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CFD-DEM simulation of high density particles fluidization behaviors in 3D conical spouted beds

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Particuology 2024年第5期88卷 266-281页

作者： Lin Jiang Mofan Qiu Rongzheng Liu Bing Liu Youlin Shao Malin Liu Institute of nuclear and New energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing 100084China

The spouted bed has been used in the coating process of high-density nuclear fuel *** particle fluidization behaviors in pseudo-2D and 3D spouted beds were simulated and *** effects of four independent variables(cone angle,particle density,inlet gas velocity,and particle loading)on particle fluidization behaviors in the 3D spouted bed were investigated *** cone angle effect on fluidization mechanism was studied quantitatively first time.A new fluidization quality index was proposed based on the particle entrainment principle,and an extreme value was obtained when the cone angle was 60°,considered to be the optimum value for the 3D conical spouted *** was indicated the gas–solid contact efficiency can be kept up if the gas velocity was proportional to ρ_(p)^(0.65) and N_(p)^(0.78) when the particle density or loading was *** results will be useful for geometry and operation parameters design of the 3D conical spouted bed and helpful for developing the fluidization mechanism of high-density particles.

关键词： Spouted bed High-density particle CFD-DEM Fluidization quality index Particle loading

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CFD-DEM simulation of fluorination reaction in fluidized beds with local grid and time refinement method

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Particuology 2024年第1期84卷 145-157页

作者： Mofan Qiu Lin Jiang Rongzhen Liu Yaping Tang Malin Liu Institute of nuclear and New energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing100084China

The gas-solid reaction process with wide particle size distribution is extensively used in the chemical engineering field,especially the particle reacts with the gas gradually,such as fluorination reactions in fluidized *** the computational fluid dynamics-discrete element method(CFD-DEM)is used for the coupling simulation of multiphase and polydisperse particle reaction system,the grid size directly affects the accuracy of flow field information and simulation of chemical ***,particle calculation time step will directly affect the efficiency of coupling *** this work,a local grid and time step refinement method is proposed to simulate multiphase and polydisperse particle fluid-ization reaction *** this method,the refined DEM grids are automatically generated in the computational domain around the fine particles,and the detailed fluid phase information is obtained with the interpolation *** the two-phase coupling process,particles are divided into different groups based on physical properties,each group has its own independent time *** multistage conical-cylindrical spouted bed is proposed for the fluorination reaction process;the operating gas ve-locity range of the polydisperse particle system is extended by the new design while the particle size distribution changes with the gas-solid reaction *** is demonstrated that the local grid and time step refinement method can improve the accuracy and efficiency of the traditional CFD-DEM method in the reaction process simulation,which describes a polydisperse particle system with wide particle size *** at improving the simulation accuracy and efficiency,this paper will be helpful for simulating the particle reaction process in the gas-solid fluidized bed and beneficial for the development of the CFD-DEM method.

关键词： CFD-DEM Polydisperse particle Two-phase flow Fluidized bed

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Numerical simulation of uranium tetrafluoride fluorination in a multistage spouted bed using the improved CFD-DEM chemical reaction model

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Particuology 2023年第4期75卷 119-136页

作者： Mofan Qiu Zhao Chen Lin Jiang Rongzhen Liu Yaping Tang Malin Liu Institute of nuclear and New energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua University.Beijing.100084China

A CFD-DEM reaction coupling model was established to simulate UF_(4) fluorination process,in which heat and mass transfer,heterogeneous chemical reaction,and particle shrinkage model were *** gas behavior was described by the conservation laws of mass,momentum,and *** solid phase is modeled with the discrete element method,considering the gas-solid interphase force,contact force,heat transfer,and chemical reaction models based on the discretized *** particle can be individually tracked and associated with specific physical *** proposed CFD-DEM reaction coupling model based on particle shrinking reaction model with discretized surface was validated by the experimental and literature results at *** a multistage conical spouted bed was proposed and the process of UF_(4) fluoridation reaction in it was *** fluidization characteristics and the con-centration distribution of gaseous products in the spouted bed with an extended gas velocity range were obtained and *** addition,the effects of different parameters,such as superficial gas velocity,temperature,fluorine concentration,on fluoridation rate and the fluorine conversion rate were inves-tigated based on the proposed CFD-DEM reaction coupling *** results obtained in this work are beneficial for method development of the chemical reaction simulation research in particle scale using the CFD-DEM model,and useful for operation and equipment parameters design of the uranium tetra-fluoride fluorinate industrial process in the future.

关键词： CFD-DEM Particle shrinkage model Multistage spouted bed Uranium fluorination

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Derivation of lattice Boltzmann equation via analytical characteristic integral

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Chinese Physics B 2019年第1期28卷 431-441页

作者： Huanfeng Ye Bo Kuang Yanhua Yang School of nuclear Science and Engineering Shanghai Jiao Tong University National energy Key Laboratory of nuclear Power Software

A lattice Boltzmann(LB) theory, the analytical characteristic integral(ACI) LB theory, is proposed in this *** LB theory takes the Bhatnagar–Gross–Krook(BGK)-Boltzmann equation as the exact kinetic equation behind Navier–Stokes continuum and momentum equations and constructs an LB equation by rigorously integrating the BGK-Boltzmann equation along characteristics. It is a general theory, supporting most existing LB equations including the standard lattice BGK(LBGK) equation inherited from lattice-gas automata, whose theoretical foundation had been questioned. ACI LB theory also indicates that the characteristic parameter of an LB equation is collision number, depicting the particle-interaction intensity in the time span of the LB equation, instead of the traditionally assumed relaxation time, and the over-relaxation time problem is merely a manifestation of the temporal evolution of equilibrium distribution along characteristics under high collision number, irrelevant to particle kinetics. In ACI LB theory, the temporal evolution of equilibrium distribution along characteristics is the determinant of LB method accuracy and we numerically prove this.

关键词： lattice Boltzmann(LB) equation analytical characteristic integral characteristic parameter

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New friction factor and Nusselt number equations for laminar forced convection of liquid with variable properties

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Science China(Technological Sciences) 2018年第1期61卷 98-109页

作者： ZHAO HouJian LI XiaoWei WU XinXin Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Collaborative Innovation Center of Advanced Nuclear Energy Technology Institute of Nuclear and New Energy Technology Tsinghua University

Friction factor and heat transfer coefficient of liquid flow with variable properties can significantly differ from that with constant properties. Existing equations obtained by regression analysis of experimental data use correction factors to account for variable property effect. They are limited to specific kind of fluid and low or medium temperature differences. The correction factors of the equations for heating and cooling conditions are different. New explicit friction factor and Nusselt number equations for laminar forced convection of liquid with variable properties are derived with a first order approximation of dynamic viscosity-temperature variation. The new equations are applicable to all kinds of liquids and can be used for large temperature differences. Governing equations of laminar forced convection of water and ethanol are numerically solved using computational fluid dynamics(CFD)method and the results are used to verify the derived equations. The derived equations show good predictions of friction factors and Nusselt numbers for both heating and cooling conditions and show more accurate predictions than the existing equations. A dimensionless number is also introduced based on theoretical analysis to evaluate property variation effects on friction factors and heat transfer coefficients.

关键词： laminar convection friction factor heat transfer coefficient variable property

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First-principle studies of radioactive fission productions Cs/Sr/Ag/I adsorption on chrome-molybdenum steel in Chinese 200 MW HTR-PM

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nuclear Science and Techniques 2017年第6期28卷 123-132页

作者： Chuan Li Chao Fang Chen Yang Institute of nuclear and New energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua University

Chrome-molybdenum steel(2·1/4Cr1Mo) is one of the main products of steam *** adsorption behaviors of radioactive fission products on2·1/4Cr1Mo surface are critical in the analysis of ***,the adsorption behavior of cesium,strontium,silver and iodine on 2·1/4Cr1Mo was investigated with first-principle calculations that the Ag and I atoms prefer to be adsorbed at the square hollow site of the face-centered cubic iron cell with a binding energy of about 1 and 3 eV,*** contrast,Cs and Sr atoms are not adsorbed on the surface of the 2·1/*** results are again confirmed via analysis of charge density differences and the densities of ***,the adsorption rates of these fission products show that only I and Ag have significant adsorption on the metal *** adsorption results explain the amount of adsorbed radionuclides for an evaluation of nuclear safety in *** micro-pictures of the interaction between fission products and materials are a new and useful way to analyze the source term.

关键词： First-principle calculation Fission product Adsorption behavior HTR-PM

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Numerical simulation of particle sedimentation in 3D rectangular channel

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Applied Mathematics and Mechanics(English Edition) 2011年第9期32卷 1147-1158页

作者：刘马林 Institute of nuclear and New energy Technology Tsinghua University

The 3D lattice Boltzmann method is used to simulate particle sedimentation in a rectangular *** results of single particle sedimentation indicate that the last position of the particle is along the center line of the channel regardless of the initial position,the particle diameter,and the particle Reynolds *** wall effect on the terminal velocity is in good agreement with experimental results *** drafting,kissing,and tumbling （DKT） process is reproduced and analyzed by simulating two-particle cluster *** effects of the diameter ratio,initial position,and wall on the DKT process are *** the two particles have equal diameter sediment in the rectangular channel,a periodical DKT process and the spiraling trajectory are *** last equilibrium configuration is obtained from the simulation *** interesting regular sedimentation phenomena are found when 49 particles fall down under gravity.

关键词： sedimentation lattice Boltzmann method particle-particle interaction

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