核动力工程

Mixing Preformance Analysis for Advanced Fuel Assembly Grid

CHEN Wei-hong, ZHANG Hong, ZHANG Feng-lin, HU Hai-xiang, HU De-yong, CHEN Ping, LEI Tao

2008, 29(3): 1-4,27.

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Fuel assembly grids of pressurized water reactor strengthen the coolant mixing around fuel rod through mixing structure.The size and shape of mixing vane affects the mixing performance and flow resistance.This paper introduces the process and result of grid mixing performance optimizing design.Using CFD software,three dimensional flow field of three grid design schemes are analyzed and compared.The results show that the mixing performance of scheme 3 is better than that of scheme 1 and 2 in terms of the highest fluid temperature and the most difference in temperature.And mixing performance of scheme 1 and 2 is better than that of scheme 3 in terms of typical channel average temperature.

Effect of Aspect Ratio on Temperature Distribution of Fluid in Narrow Rectangular Channels

ZENG He-yi, QIU Sui-zheng, SU Guang-hui, JIA Dou-nan

2008, 29(3): 5-8.

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3D numerical simulation were performed on forced convection heat transfer in narrow rectangular channel with large aspect ratio under uniformly heating fluxes on the wide surfaces,while the narrow surfaces were kept under adiabatic condition.The simulation results agreed well with the experimental data.By using the 3D numerical simulation,effects of aspect ratio on temperature distribution of fluid in narrow rectangular channels were studied,and the results showed that for the narrow rectangular channels with large aspect ratio,heat concentration phenomena existed both in the corner regions and the center regions on the heating surfaces;The heat concentration at the center region of heating surfaces is weaker than that near the corner regions and will vanish with the decrease of the aspect ratio of the rectangular channel.In addition,due to false diffusion,low order interpolation scheme such as power scheme failed to predict the heat concentration at the center region of the heating surfaces.

Flow and Heat Transfer Mechanism and Key Issues in a Narrow Channel

XU Jian-jun, CHEN Bing-de, WANG Xiao-jun

2008, 29(3): 9-13.

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The compact heat transfer device is widely applied in the engineering technology,which contributed to the development of flow and heat transfer mechanism in a narrow channel.The development of flow and heat transfer mechanism and its related key issues are presented,including measurement methods and related issues on flow and temperature field,nucleate phenomenon and flow pattern,pressure drop,heat transfer characteristic and critical heat flux which is very concerned in the engineering.Aiming at the research actuality and issues on the flow and heat transfer mechanism in a narrow channel at present,the research directions on the flow and heat transfer mechanism in a narrow channel are suggested.

Numerical Simulation of Hydrodynamic Mixing in Narrow Rectangular Multi-Channel

XU Jian-jun, CHEN Bing-de, XIONG Wan-yu, WANG Xiao-jun, WANG Fei

2008, 29(3): 14-17.

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With the help of the Computational Fluid Dynamics code,hydrodynamic mixing in the narrow rectangular multichannel is numerical simulated.The results show that the water flow rate in two side channels is lower than that in the mean main channel after passing through the whole axial mixing sections.Under the different ratios of the water flow rate at the inlet,the water flow rate in the mean main channels is consistent after passing through the whole axial mixing sections.Hydrodynamic mixing in former 4 mixing sections is obvious,and hydrodynamic mixing decreases with the increasing of the number of the axial mixing section.During the process of the mixing,the part of water in the mean main channel of the high flow rate at the inlet enters into the channel of the lower flow rate,and the secondary flow forms in the mixing section,but the secondary flow decreases with the increasing of the number of the axial mixing section.

Transitional Reactivity Variation from Natural to Forced Circulation

YAO Qing-sheng, WANG Zhang-li, HAN Wei-shi, HE Ke-yu

2008, 29(3): 18-22,55.

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In order to study the disciplinarian of reactivity variation in the transient state from natural to forced circulation,a calculation model was established for the reactor and primary coolant system based on MATLAB.The calculation results indicate that the coolant flux changes in conformity to hyperbolic tangent curve in the transient state.The coefficient k and flux rising multiple,W∞/W0,determine the flux grads and time for flux to steady.It can effectively improve the minimum reactor period to choose appropriate value of coefficient k in reactor design.And reducing the flux grads of transient state can decrease the peak value of reactivity and increase the security of reactor.

Thermo-Hydraulic Characteristics of Melt Jet for Premixing

LI Tian-shu, YANG Yan-hua, YUAN Ming-hao, HU Zhi-hua

2008, 29(3): 23-27.

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In order to investigate the coarse mixing stage mechanism of the vapor explosion,an observable experiment equipment facility for low-temperature molten materials to be dropped into water was designed in this study.In the experiment,molten material jet was injected into water to experimentally obtain the visualized information.The effects of metal temperature,coolant temperature and jet diameter were investigated.The experimental results show that jet dimensionless length L/ D agrees well with the correlation.The jet diameter and coolant temperature have effects on the falling of the jet front while metal temperature hasn’t.

Application of LES in Simulation of Fluid Buffet on Core Barrel Excited by FIV

XI Zhi-de, CHEN Bing-de, LI Peng-zhou

2008, 29(3): 28-31.

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The fluid field in down comer between reactor vessel and core barrel of Qingshan II phase 1:5 model test is simulated with LES,and the pulse pressure distribution on the surface of the core barrel is obtained.The effect of Smagorinsky coefficient in Smagorinsky sub-grid model is studied and the result shows that the pressure RMS decreases with the increase of the Smagorinsky coefficient.The comparison with the experiment shows that when the Smagorinsky coefficient equals 0.18,it is suitable for the model test.The pulse pressure RMS of LES agrees with the experiment,and the difference of the pulse pressure PSD between LES and the experiment is discussed.The effect on the pressure by fluid velocity is studied and the distribution of pressure in space is obtained.

Analysis Method by Fracture Finite Element for Tee with Longitudinal Through-Wall Crack

LU Yue-chuan, ZANG Feng-gang

2008, 29(3): 32-34,40.

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This paper presents how to use finite element procedure ABAQUS to conduct the fracture finite element analysis for tee with longitudinal through-wall crack,and focuses on the establishment of computation model and calculation method of J-integral.The finite element computation results are compared with the therotical results for the straight pipe,which showes that the two results are almost the same.This indicates that the method,input and singular element which used to calculate J-integral are correct.The methods and processes can be used to analyze J-integral of tee with longitudinal through-wall crack by ABAQUS.

Time-Domain Superposition Method for Fitting Multi-Damping Response Spectra

ZHAO Feng-xin, ZHANG Yu-shan

2008, 29(3): 35-40.

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In this paper,a method of superposing narrow-band time history in time domain is proposed,which can be utilized to enhance the fitting precisions of design ground shaking time history to multi-damping specified single-damping target response spectrum;and then by superposing narrowband time histories in time domain,the initial acceleration time history is further modulated,to improve its fitting precision to the multi-damping target response spectra.The numerical examples demonstrated that the design ground motions generated by the proposed method possess very high fitting precisions to the multi-damping target spectra.

Capability Design for Pressurizer Relief Tank

ZHONG Fa-jie, LI Hai-ying, ZHANG Yu-long

2008, 29(3): 41-43,51.

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Based on the state equation of ideal gas,the laws of conservation of mass and energy,and the thermophysical properties of water and steam,and assuming that the process of medium change is adiathermal,the design principal and method for capability of the Pressurizer Relief Tank is proposed,and its validity is verified against the parameters of the Pressurizer Relief Tank in operating plants,which shows a good agreement.

Optimization Method Applied in Development of Spacer Grid of PWR Fuel Assembly

TANG Yu, HU Hai-xiang, CHEN Ping, WANG Kai-ming

2008, 29(3): 44-47.

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This paper introduces an optimization method based on the CFD（Computational Fluid Dynamics） technology.The method combined the CFD code with the 3D CAD code and the CAO（Computational Aided Optimization） code,and performed the structural design of the mixing vanes to improve the thermal-hydraulic performance of grids,and verified the results of the optimization through the CFD analysis on 5×5 grid.The results show that it is feasible to adopt the optimization technology to optimize the design of the spacer grid.

Development and Manufacture of New-Style Hafnium Control Rod

HUANG Hong-wen, YE Lin, QIAN Da-zhi, XU Xian-qi, ZHANG Zhi-hua

2008, 29(3): 48-51.

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Metallic hafnium possesses a combination of properties that makes it the preferred material for control rods of nuclear reactors.To prevent the irradiation deformation and the mechanical property degrade of hafnium plates,and to increase the service life of the control rods,a new-style square-tube control rod is developed.The elemental composition,mechanical property,the corrosion resistance and the physical charac-teristics of hafnium are studied during the development.Some verification tests of the control rod are carried out after the manufacture,which prove that the design and manufacture of the new-style control rod meet the requirement of the technical conditions.The control rod has an approved mechanical property,and the service life can be increased effectively.

Introduction of Design of Core Catcher for Tianwan Nuclear Power Station

CUI Fang-shui

2008, 29(3): 52-55.

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The design of core catcher of Tianwan nuclear power station comprehensively incorporates the exvessel containment facility,the cooling of the metallic surfaces of corium containment by passive water,reactor vessel melt-through and corium relocation into the core catcher is executed with the computer codes the improvement of corium properties by the sacrificial material and reducing density of heat flux.Analysis of the dynamic process of core degradation,debris relocation within the reactor vessel,molten pool formation,SCDAP/RELAP and MELCOR,and the reaction among the corium,the sacrificial material,and the metal material,as well as the thermal and hydraulic characteristic of heat exchanger is experimentally studied.

Calculation Error Analysis of Large-scale Flange of Pressure Vessel Based on Design Code GB150

TAN Zhong-wen, ZHANG Zheng-ming, HE Shu-yan

2008, 29(3): 56-58.

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If the large-scale flange of pressure vessel is designed as per the Chinese national code GB150,the stress of the flange obtained based on the code is always lower than the actual value.If the closure head of the vessel consists of the large-scale flange and the head cover with the two of them weld together directly,the stress calculation error obtained by GB150 will be even larger.This error is caused by the analysis method of the flange in GB150.Taken the containment vessel of 5 MW Nuclear Heating Reactor as an example,which was designed by Tsinghua University,the shortage of the large-scale flange design based on GB150 is introduced.

Accident Analysis of Station Blackout for China Advanced Research Reactor with Shutdown Failure

TIAN Wen-xi, QIU Sui-zheng, SU Guang-hui, JIA Dou-nan, ZHANG Jian-wei

2008, 29(3): 59-63,103.

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Based on the structural and operational characteristics of the China Advanced Research Reactor（CARR）,a thermal-hydraulic and safety analysis code was developed with the consideration of all possible coolant flow and heat transfer status.The code was adopted to analyze the severe station blackout accident（SBO） with the failure of both the control rod（CR） and the Emergency Core Cooling System（ECCS）.Some important thermal-hydraulic parameters,such as pressure,flow rate and temperature,in the mean channel and hot channel were obtained.The computational results indicated that the core power could decay to a very low level with the reactivity feedback of the coolant density,void fraction and fuel temperature,thus the integrality of the fuel assembly/element could be ensured under such sever accident condition.The results also showed the high inherent safety of the CARR.Furthermore,an interesting short-lived density wave flow instability phenomena occurred during the transient process.

Evaluation of Loss of Coolant Accident of MNPP with Medium and Small Break by Large Event Tree

XIN Shi-bao, SHAO Shi-wei, ZHANG Zhi-jian

2008, 29(3): 64-68.

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Loss of Coolant Accident（LOCA） with medium break and small break in the pipes directly joined to the primary coolant are analyzed in the case of MNPP is in full power operation condition.The requirements for safety functions in LOCA,the effects of the responses of mitigation systems and intervening behaviors of operators on core damage after initiating events are studied.During modeling accident sequences,the large event trees/small fault trees approach is adopted based on the simplification of support systems and front-line systems.By quantitative analysis,the dominative sequences and events led to core damage under initiating events are founded.Effective suggestions on system improvement and discussion on the application of large event tree/small event tree in MNPP PSA are also presented.

Prediction of Gas-Liquid Stratified Flow through Small Break at Bottom of Horizontal Pipe

LIANG Fa-chun, WANG Dong, LIN Zong-hu

2008, 29(3): 69-72.

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The leak of a small break located at the bottom of a horizontal pipe with gas-liquid stratified flow was investigated experimentally and theoretically.A specially designed leak measurement device was developed to measure the quality and mass flux.A 2.5mm id holes placed at the pipe wall was used to simulate the small break instead of using a branch for conventional break experimental apparatus.A radical basis function（RBF） neural network was constructed for prediction of outlet quality.The gas-liquid level and pres-sure difference between the main pipe and the break were identified as two input parameters of the RBF neural network.The mass flux was calculated using a modified two-phase orifice equation.It was found the predicted values of quality and mass flow rate agreed well with the experimental data.

Layout Design of Advanced Control Room of Pressurized Water Reactor NPP

SUN Yong-bin, JIANG Xiao-hua

2008, 29(3): 73-77.

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The design function of MCR is to guarantee the safety of NPP operation,reduce the operation pressure of operators.The diversity of DCS platform,digital HMI,back-up panels and the different control place for MCR/SCR should be carefully considered in the design of MCR.Due to the different standards and regulations are adopted by the Suppliers,the layout designs of control rooms are quite different.The Suppliers’ national standards and regulations also should be considered in the design and procurement of MCR,epecially the requirements in Chinese standards and regulations should be considered.

Study on Structure of Wide Energy Range Neutron Rem Counter

LIU Chun-yu, HAN Wei-shi, LI Jian-ping, CHEN Zhen-ping

2008, 29(3): 78-80,107.

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The energy response of the wide energy range neutron rem counter was calculated using the MCNP and FLUKA code,when the structure was changed.The result was compared with the standard curve of ICRP.The calculation results show that the energy response of conventional A-B neutron rem counter was improved greatly as a result of joining lead layer,which was affected by collocation and thickness of lead layer.The energy response of rem counter with single lead layer is better than the double layers.The energy response curve of rem counter agrees wellwith the standard curve of ICRP when the collocation of the lead layer is inside of rem counter and its thickness is 0.4cm.

Improvement of Fuel Handling Control System of HTR-10

HUANG Peng, HU Shou-yin, LIANG Xi-hua

2008, 29(3): 81-84,118.

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In order to meet the demand of long-term operation of 10MW High Temperature Gas-cooled Reactor（HTR-10）,some improvement had been made for the fuel handling control system.The design of automatic operation of the system had been finished by using the programmable ladder controller of OMRON C200HS.On the base of remaining the console and monitoring panel,the digital design of control and monitoring is completed by utilizing the configuration software of FIX6.15.The efficiency and safety of the fuel handling system are effectively enhanced by the improvement.

EMC Test and Design of I＆C System in Nuclear Power Plants

HUANG Wen-jun, YU Hao-yang, AO Chun-bo

2008, 29(3): 85-88,107.

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Based on wide application of digital Instrument and Control System（I＆C） in nuclear power plants,the paper presents how to verify the electromagnetic compatibility（EMC） of digital I＆C,and how to improve the EMC of digital I＆C.After analyzing the disturbance of I＆C in nuclear power plant environment,the paper firstly puts forward the correlative standards and test methods,and then based on the application in a NPP,it describes the synthetical methods to improve the EMC of digital I＆C during product and engineering design,such as electromagnetic protection,interference filter,electromagnetic shielding,fault isolation,fault-tolerance design,and environment reforming.

Numerical Simulation of Forced Convection Film Boiling on a Sphere

YUAN Ming-hao, YANG Yan-hua, LI Tian-shu, HU Zhi-hua

2008, 29(3): 89-93.

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A CFD code using improved Volume of Fluid（VOF） method to track liquid-vapor interface is developed to simulate forced convection film boiling on a sphere.The simulation results are compared with the experimental correlation,and the result show that the numerical method could simulate the physical process of forced convection film boiling on a sphere successfully.

Numerical Simulations of Particle Motion in a Two-Dimensional Pebble Bed Modular Reactor

LI Xiang, WANG Shu-yan, HE Yu-rong, ZHANG Ke, LU Hui-lin

2008, 29(3): 94-98.

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Motions of fuel and graphite pebbles in a two-dimensional pebble bed modular reactor（PBMR） have been numerically simulated by means of particle discrete element method（PDEM）.Velocity profiles,mixing and effect of frictional coefficient of pebbles and wall on flow behavior of particles was investigated.Results indicated that both fuel pebbles and graphite pebbles move down without radial movement,and uniform motion was formed in the column regime.While particles will be accelerated,some particles will attach to the walls at the taped part of reactor due to the reduction of sectional-area.The different residence time of fuel and graphite pebbles was found.The residence time of graphite pebbles is shorter than that of fuel pebbles.With the decrease of friction coefficient of pebbles and walls,the residence time of sphere particles were increased.

Application of CFD in Simulation of Enhancement of Two-Phase Heat Transfer by Longitudinal Vortex

HUANG Jun, WANG Hai-gang, HUANG Yan-ping, MA Jian, WANG Qiu-wang

2008, 29(3): 99-103.

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Heat transfer can be improved by longitudinal vortex（LV） generated by longitudinal vortex generators（LVG） in narrow rectangular channel.The CFX10.0 is one kind of CFD commercial software,used to simulate vapor-liquid two-phase medium.The results show that the edge of narrow rectangular channel may be cooled by LV generated by LVG,and the flow velocity is improved in the center of channel,so the heat flux of hot plate can be improved obviously.At the same time,the mixing of cold and hot fluid may be enhanced by LV.Comparing with smooth channel,the efficiency of heat transfer is increased obviously with resistance of flow increases properly within the range of this paper.

Schedule Optimization for Nuclear Power Plant Periodic Maintenance

LU Qiang

2008, 29(3): 104-107.

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In order to improve the nuclear safety and equipment availability,this paper explores a way to gain maximum maintenance efficiency in terms of maintenance cost and capability factor.Firstly the plant system and equipment types are analyzed,and an optimal method for the control of risk,quality and cost are discussed A scheme to establish the optimization methodology and knowledge accumulation platform is put forward,considering the schedule optimization for periodic maintenances in Daya Bay nuclear power station and Ling’ao nuclear power station.

Research on Fault Diagnosis for RCP Rotor based on Wavelet Analysis

CHEN Zhi-hui, XIA Hong, WANG Tao-tao

2008, 29(3): 108-112.

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Wavelet analysis is with the characteristics of noise reduction and multiscale resolution,and can be used to effectively extract the fault features of the typical failures of the main pumps.Simulink is used to simulate the typical faults: Misalignment Fault,Crackle Fault of rotor,and Initial Bending Fault,then the Wavelet method is used to analyze the vibration signal.The result shows that the extracted fault feature from wavelet analysis can effectively identify the fault signals.The Wavelet analysis is a practical method for the diagnosis of main coolant pump failure,and is with certain value for application and significance.

Study and Application of Construction Technology of Shielding Concrete

WU Chong-ming, DING De-xin, CHEN Liang-zhu, ZHAO Jing-fa, LI Shi-long

2008, 29(3): 113-115,123.

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Process and techniques such as mixing,transportation and pouring have been studied.The construction technology for the shielding concrete with different densities has been summarized.The technology for the common concrete is quite different from that of shielding concrete,especially when its density is more than 4000 kg/m³.Application and practices have shown that different construction technologies shall be used for shielding concretes with different densities,and thus to ensure its uniformity and construction quality.

Fabrication of Titanium Sponge Hydride Powder

LI Chuan-feng, YIN Chang-geng, SUN Zhang-long

2008, 29(3): 116-118.

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The fabrication process for titanium sponge hydride powder was described in this paper.The titanium sponge was hydrided and then ground to 10mm with crushing mill under high-purity argon μm was about 98.9 %.The annual output of hydide powder product can reach 3t.

Numerical Image Processing of Shadowgraphs for Falling Film

LU Chuan, DUAN Ri-qiang, JIANG Sheng-yao

2008, 29(3): 119-123.

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Falling film is widely occurred in the safety system for the Advanced PWR Nuclear Power Plant（e.g.AP1000） and seawater desalination using nuclear energy.In this paper,the instability of falling film was experimentally studied by Shadowgraph technique.The disturbance wave pattern in a wide range of incline angle（β=0°～90°） were obtained in shadowgraph format.It is indicated that gravity is important for the development of disturbance waves.And moreover,the numerical image processing was applied to analyze the characteristics of disturbance waves on falling film,the development of disturbance waves was analyzed quantitatively and the importance of gravity for disturbance waves was proved again.The dependence of disturbance wave evolution on Reynolds number and flow distance in the main stream direction was obtained and meanwhile four distinctive regions were unveiled.It is indicated that Re has some influence on the regions distributing of disturbance waves.At last,the frequencies of disturbance waves were obtained by spectrum analysis,which accords with the experimental data.

Analysis Method for Relevance between Cost and Schedule in Construction Project Management

MA Ying

2008, 29(3): 124-128.

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Based on the mathematical models and experience drawn from the construction practice for the Chashma Nuclear Power Plant Project（Unit 2）,this paper probes into the basic principles for the analysis method for relevance between cost and schedule,and further put forward a set of reasonably achievable measures/approaches for the establishment of such cost-and-schedule relevance.

2008 Vol. 29, No. 3