核动力工程

Hybrid Low-Order Harmonics and Linear Perturbation Expansion Method for Fast Loading Pattern Evaluation-Ⅱ:Numerical Verification

FU Xue-feng, LU Dong, ZHANG Shao-hong, ZHAO Rong-an

2009, 30(5): 1-4,39.

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Abstract:
In order to address [U2] the issue of large computational workload in the process of optimum loading pattern search for commercial PWR NPP, a new method--Hybrid Harmonics and Linear Perturbation （HHLP） is proposed to perform the fast loading pattern evaluation. While another accompanying paper introduces the theory of HHLP method, this paper summarizes the extensive test results for various test problems, including a depletion problem, large and extremely large perturbation problems and two exhaustive enumeration problems and enumerated LPs. Numerical results demonstrate that all these results are consistently good and HHLP method is very promising.

Correction Method for Critical Extrapolation of ControlRods-Rising during Physical Start-Up of Reactor with Spatial Effect

SHANG Xue-li, ZHANG Fan, CHEN Wen-zhen

2009, 30(5): 5-7.

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Reasons why the extrapolated critical curve obtained by lifting control rods is cambered during the physical start-up of a reactor are analyzed. Spatial flux deformation factor is introduced, and a new method, by which influences of spatial effect in the reactor are avoided additionally, is proposed based on what is achieved by removing source neutrons. The new method is employed to a real example. Comparing the new results with those of real physical start-up and achieved only by removing source neutrons, it is shown that the new method avoids cambering phenomenon of the extrapolated curve much better, and obtains more precise critical position of control rods, so the reactor will reach the criticality more safely.

Application of Coarse-Mesh Finite Difference Acceleration in Transportation Calculation by Method of Characteristics

TANG Chun-tao, ZHANG Shao-hong

2009, 30(5): 8-12.

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In order to address the low convergence issue of the method of characteristics, the coarse-mesh finite difference （CMFD） formulation, which is a widely recognized acceleration technique for coarse mesh diffusion calculation, is studied to speedup the MOC transport calculation. Numerical tests on C5G7 MOX benchmark problem and a 69 group test problem defined based on C5 demonstrate that CMFD acceleration is quite efficient in reducing the number of MOC iterations and the computing time. It also shows that the larger scale of the problem, the better effect of the CMFD acceleration.

Real-Time Simulation Model of PWR Core by Time-Space Separation Method

DUAN Xin-hui, JIANG Ping

2009, 30(5): 13-17.

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The method of simulation and modeling is studied for PWR core. Based on the method of separating the Time and Space variables, the neutron flux distributions are calculated from the 3D diffusion equations of two energy groups and six delayed neutron precursors, taking account of the following parameters effects on reactivity such as moderator density, boron concentration, xenon and samarium poisoning, control rod positions, moderator and fuel temperature, and fuel burn-up. The simulation algorithms and models are built on the STAR-90 simulation platform. The simulation results show that the computing speed is rapid and the model parameters are easy to adjust with time-space separation method.

Application of Flexible Model in Neutron Dynamics Equations

LIU Cheng, ZHAO Fu-yu, FU Xian-gang

2009, 30(5): 18-21,66.

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Big errors will occur in the modeling by multimode methodology when the available core physical parameter sets are insufficient. In this paper, the fuzzy logic membership function is introduced to figure out the values of these parameters on any point of lifetime through limited several sets of values, and thus to obtain the neutron dynamics equations on any point of lifetime. In order to overcome the effect ofsubjectivity in the membership function selection on the parameter calculation, quadratic optimization is carried out to the membership function by genetic algorithm, to result in a more accurate neutron kinetics equation on any point of lifetime.

Experimental Research on Mixing Coefficient of Fuel Assembly in Single-Phase

CAO Nian, LANG Xue-mei, LU Dong-hua, MA Jie-liang, KANG Ji-wei, ZHANG Xing-wu

2009, 30(5): 22-25,47.

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The mixing coefficient test of the fuel assembly with French X type space grids was performed in the Large Scale Thermo-Hydraulic Experiment Facility. The special temperature measurement element was designed and exit temperatures of subchannels were measured accurately. The mixing coefficient obtained from the test, in conjunction with FLICAⅢF subchannel analysis code, is 0.065, which is closed to French designed data 0.066. The experimental results also show that the mixing coefficient is affected by the structure of fuel assembly rather than by thermal parameters.

Development and Validation of Thermal-Hydraulic Analysis Code for Plate Type Fuel Research Reactors

LU Qing, ZHANG Zhi-jian, QIU Sui-zheng, SU Guang-hui, TIAN Wen-xi

2009, 30(5): 26-29,43.

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Abstract:
A thermal-hydraulic analysis code has been developed with Visual Fortran 6.5 for the investigation of plate type fuel reactors, based on the fundamental conservation of mass, momentum and energy, and some proper constitutive correlations of flow friction factor, heat transfer and property. The Reactivity Insertion Accident（RIA） and Loss Of Flow Accident （LOFA）, which have been defined in the IAEA 10 MW MTR Benchmark transients, were analyzed with this developed program. The comparison of some key parameters, such as the core power at scram, the maximum fuel temperature, the maximum clad temperature and the maximum outlet coolant temperature demonstrated that the results were consistent with that in the literature, which indicated that the model of this developed code is proper for thermal-hydraulic analysis of plate type research reactors.

Condensation Heat Transfer Coefficient at Vapour-Liquid Interface of Subcooled Flow Boiling in Vertical Narrow Rectangular Channel

YUAN De-wen, PAN Liang-ming, CHEN De-qi, WANG Xiao-jun

2009, 30(5): 30-34.

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High speed camera visualized subcooled flow boiling bubble condensation experiments at 5 000 fps were conducted. Combined with the theoretic analysis, and considering the effect of convective heat transfer and the thickness of thermal boundary layer on condensation heat transfer, the relationship between dimensionless bubble diameter β and interface condensation heat transfer Nusselt number Nu Compared with experimental results, the error of the prediction is ranged within ± 25%.

Stability Analysis of a Simplified Model of Supercritical Water-Cooled System

XUE Ai-jun, CHENG Xu

2009, 30(5): 35-39.

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This paper presents the stability analysis of a simplified model of supercritical water-cooled system. Based on the perturbation linearization and Laplace transformation, transfer function of the simplified system model is established. A stability map is generated using both dimensionless parameters, i.e. sub-pseudo-critical number and trans-pseudo-critical number. An unstable region nearby the pseudo-critical point is determined. The effect of some important parameters on the stability behavior is investigated. It is found that the system is stabilized with a higher hydraulic resistance of the inlet, fluid inlet velocity. It is also found that a longer heating zone or a bigger acceleration of gravity leads to a larger stability margin of the system.

Resistance Characteristics of Single-Phase Flow through Porous Media

LIU Xue-qiang, YAN Xiao, XIAO Ze-jun

2009, 30(5): 40-43.

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In the present paper, the resistance characteristics of single-phase flow under the high Re number is studied.. By modifying the inertia factor with Re, the resistance correlation of single-phase flow in porous media has been obtained. The chief factors which affect the resistance characteristics of single-phase flow in porous media have been discussed. The experiment indicates that the inertia factor is affected by permeability and porosity of porous media, as well as Re.

Study on Characterization of Interaction Layer between U-10wt%Mo Alloy and LT24 Al

CHEN Jian-gang, YIN Chang-geng, SUN Zhang-long, PANG Xiao-xuan, LIU Yun-ming

2009, 30(5): 44-47.

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Abstract:
The characterization of interaction layer（IL） between U-10wt%Mo alloy and LT24 Al was studied in detail in this paper. Sandwich structured U-Mo/LT24 Al diffusion couples were hot pressed at different temperature and pressure for different time. Then they were analyzed by Optical Microscope （OM） and Scanning Electron Microscope （SEM） to observe the width of the IL. The distribution of the diffusion elements and the phases in the IL were determined by Energy Dispersive Spectroscopy （EDS） and X Ray Diffraction （XRD）. Analysis results are as follows: the diffusion manner was reaction diffusion, and diffusion direction mainly was that Al atoms diffused to U-Mo alloy; diffusion mechanism was vacancy diffusion and growth kinetics showed reaction was controlled by the diffusion speed; the IL containing single phase was constituted mainly by （U, Mo） Al₃; the IL containing two phases or more was constituted mainly by （U, Mo） Al₃ and （U, Mo） Al₄ and Al₂₀Mo₂U; and Si impurity in the LT24 Al was easy to enrich in the IL which showed Si added to Al could play positive role on improve compatibility between U-Mo and Al.

Numerical Simulation of Flow-Accelerated-Corrosion of Carbon Steel in Single Liquid Phase Flow

LIU Zhong, LIU Chunbo, ZHENG Yugui

2009, 30(5): 48-53.

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Flow-Accelerated Corrosion（FAC） is a phenomenon that induces carbon steel to degrade, which usually occurs in the secondary pipes in nuclear power plant. Many accidents have happened because of FAC in many countries in the word. A computational model for FAC of the carbon steel in single flows is developed with reasonable assumptions. The solubility of Fe₃O₄ in high temperature is calculated. Mass transfer coefficients are calculated with method of CFD（Computational Fluid Dynamics）, and the results are successfully used in the computational model. FAC rate in straight pipe predicted by the model agrees with results in experiment. The results show that FAC is influenced by temperature, pH and velocity greatly, which is very significant in preventing FAC-induced accidents from happening.

Effect of Heat Treatment on Mutual Diffusion of U-Mo Alloy with Nb

PANG Xiao-xuan, YIN Chang-geng, CHEN Jian-gang, SUN Zhang-long, LIU Yun-ming, SUN Xu-dong, LIU Ting-ting

2009, 30(5): 54-57.

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Abstract:
Solid bonding diffusion couples of U-Mo/Nb have been made by Covering and Hot rolling. The diffusion couples were heat-treated at 760℃ and 790℃. The thickness of diffusion layers were measured by Energy Dispersive Spectrometer （EDS） and the relationships between annealing time and thickness of the diffusion layers were also studied by the Non-linear curve fitting. The results indicated that it has biggish difference between the simulation equations under the two temperatures.

Corrosion Behavior of New Type Zirconium Alloys in Superheated Steam

WANG Jun, LONG Chong-sheng, XIONG Ji, MIAO Zhi, FAN Hong-yuan, HUANG Zhao-hua, YING Shi-hao

2009, 30(5): 58-61.

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The microstructure and corrosion behaviors of Zr-xFe-yCr alloys have been investigated in the superheated steam of 500℃/10.3 MPa. The results show that the composition of Zr-Fe-Cr alloy after vacuum melting, β quenching, vacuum covered hot and cold rolling, and vacuum annealing are α-Zr base and dispersed Zr（Cr, Fe）2 particles. A nodular corrosion takes place on the Zr-4 and Zr-0.2Fe-0.1Cr specimens, but uniform corrosions occur on the Zr-Fe-Cr alloys with appropriate Fe and Cr, in the 500℃ and 10.3 MPa superheated steam. The Zr-1.0Fe-0.6Cr specimens have the best corrosion resistance, and its corrosion resistance in the superheated steam is better than that of N18 and Zr-4 alloys. The alloy specimens with different contents of Fe and Cr are with quite different corrosion resistances, which indicates that the composition of zirconium alloys is the key factor to improve the corrosion resistance in 500℃/10.3 MPa.

Corrosion Behaviors of Candidate Materials for Supercritical-Cooled Water Reactor

ZHU Fa-wen, ZHANG Le-fu, QIAO Pei-peng, LIU Rui-qin, BAO Yi-chen, CHEN Yu-qing

2009, 30(5): 62-66.

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Abstract:
The corrosion behaviors of ferritic-martensitic steel P92, austenitic stainless steel type 316L and nickel-based alloy 690 have been investigated in supercritical water （SCW） at 600℃ and 23 MPa. After exposed to SCW for 625 h, the weight gain of alloy 690, 316L and P92 are 0.001 02 g/（m²·h）, 0.060 6 g/（m²·h） and 0.101 27g/（m²·h）, respectively. SEM observation shows that a three-layer oxide film is formed on P92, a single-layer oxide film is formed on 316L and a very thin oxide film with some pitting is formed on alloy 690.

Fretting Wear Behavior of Alloy-800 Tube Materials

ZHANG Xiao-yu, REN Ping-di, LI Zhang-xiang, CAI Zhen-bing, ZHU Min-hao

2009, 30(5): 67-70,74.

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Investigation of Alloy-800 under the column-against-column contact with various normal loads of 80 N and 50 N and displacement amplitudes from 2 μm to 40μm in ambient environment is demonstrated in this paper. Experimental results show that the fretting regime of Alloy-800 is transformed from the partial slip regime into the mixed fretting regime and gross slip regime by its fretting behavior with increaseing displacement amplitude under the same normal load. The coefficient of friction in the partial slip regime is lower than that in the mixed fretting regime and gross slip regime .Three different fretting regimes can be observed under fretting condition. In partial slip regime, micro-slipping occurs at the edge of the contact with slight damage and small crack, the wear scar area and fretting wear volume in gross slip regime are large, and in mixed fretting regime, aggregation of debris is obvious. Abrasive wear and friction oxidation are main fretting wear mechanisms of Alloy-800.

FE-Meshfree Coupled Method for Calculating Stress Intensity Factor of Circumferential Through-Wall Crack on Pipes

JIANG Nai-bin, ZHAO Hua, LIU Jun, LIU Cheng, LU Yue-chuan

2009, 30(5): 71-74.

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Based on a transition matrix used to couple the finite element method and meshfree method, a coupled method was developed, in which the part with high gradient stress was set as the meshfree domain, and the remainder part was finite element domain. With this method, the stress intensity factors in one cracked through-wall pipe with circumferential crack were calculated, and the result was consistent with those calculated with ABAQUS code, which proved the feasibility and validity of the current method.

Effect of Different Distribution Condition of Fatigue Loads on Fatigue Life

LIU Qing-gang, YU Xin-qi, SHEN Shi-ming

2009, 30(5): 75-78,104.

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In this article, 3 distribution styles, i.e, normal distribution, log-normal distribution and Gamma distribution, are used to simulate the variety of fatigue loads S. Same average value of fatigue loads variety S and different coefficient of variation C are adopted in every distribution style, and corresponding fatigue life N_rand and the average fatigue life Navg in the condition of S=S are calculated. By comparing the fatigue life N_rand and N_avg, a rule can be found that when the average value of fatigue loads variety is small, the fatigue life will first increase and decrease later with the increasing of the coefficient of variation, and when the average value of the fatigue loads variety is large, the fatigue life will always decrease while the coefficient of variation increases.

ALE Finite Element Formulation for Fluid-Structure Problems

WEI Yong-tao, LIU Li-ling, Philippe H. Geubelle

2009, 30(5): 79-83,88.

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Based on the arbitrary Lagrange-Euler description the prediction–correction algorithm is presented for analyzing the fluid–structure interaction problems. The Galerkin/Least squares finite element method in ALE form is employed to simulate the incompressible viscous flow with large boundary motions, and the pseudo–elasticity method on the basis of the updated Lagrangian formulation is proposed to calculate the mesh motion. The coupling condition is established by applying Dirichlet and Neumann boundary conditions to the fluid and solid domains, respectively. Then the coupling process of a cantilever beam perpendicular to the flow in a channel is analyzed numerically, and the numerical results demonstrate the validity of the method proposed.

Analysis of Fission Product Behavior in Bypass Containment Severe Accident Induced by SGTR of AP1000

HUANG Gao-feng, TONG Li-li, CAO Xue-wu

2009, 30(5): 84-88.

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The accident analysis model of AP1000 was established by using the integrated safety analysis code. On the basis of analyzing the progression of bypass containment accident initiated by SGTR, the characteristics including fission products release and transport were analyzed and computed, with focus on the distribution of inert gases, volatile fission products and nonvolatile fission products, and the status of fission products in primary system and environment. The source terms released to the environment are calculated.

Analysis of Common Cause Failure for Redundancy Pump Group in Nuclear Reactor

GUO Qiang, ZHAO Xin-wen, CAI Qi

2009, 30(5): 89-92.

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The paper applies the interrelated method of common cause failure to work out the parameters of common cause model with Bayesian estimate based on the classification and impact vector assessment of events involving component, and considering special function of check valve, and applies GO Methodology to work out the fault probabilities in start-up and operation process of the system. Its result shows that the common cause failure is very important in the reliability analysis for the redundancy system.

Analysis of Canned-Motor Pump Jamming Failure in Start Hot Standby Mode

MO Zheng-yu, WU Chao, LI Hai-feng, LIU Hua, YU Zhong-bin

2009, 30(5): 93-95,108.

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The reason of a canned-motor pump start failure is deduced in this paper. It is shown that the undersized gap of the lower guide bearing causes the start failure. By the stripping inspection data, the design value of the guide bearing gap, the cumulative departure of manufacturing assembly and the preloading of the bearing liner lead to the undersized gap. The test result shows that the improved canned-motor pump can start up successfully.

Analysis of Design Parameter Sensitivity of Direct Action Solenoid Valve

LIU Qian-feng, BO Han-liang, QIN Ben-ke

2009, 30(5): 96-100.

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The parameters of the direct action solenoid valve are analyzed using the ANSYS software and orthogonal experiment design. The result shows that the current influences the electromagnetic force of the direct action solenoid valve mostly. Further more, the design parameters of the direct action solenoid valve can be optimized by the analysis of the data of the orthogonal table.

Electron Beam Welding Technology for Butt Weld in Stainless Steel Tubes

LUO Xu-zhen, WANG Jian, YUAN Qunqi, LIU Xiao-rong, YUAN Jun, YANG Jun

2009, 30(5): 101-104.

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This paper presents an EBW （Electron Beam Welding） technology for butt weld in stainless steel （00Cr17Ni14Mo₂） tubes used in an electro-thermal component, which size is Φ22mm×2.5mm. By carrying out the EBW technology with a low current and a near-focusing manner, the inner convex of the weld is accurately controlled, the problem of external collapse is solved, and the One Side Welding Both Sides Formation technology is implemented. The specimen has passed all the tests required in Code RCC-M, including visual examination, liquid penetrate examination, X-ray inspection, tensile test, bending test, metallography detection, ferrite determination, and inter-granular corrosion test. Each quality above has reached the technological index grade I.

Piecewise H_∞ Control for Water Level of Steam Generator

WANG Wei, WANG Jun-ling, HAN Wei-shi

2009, 30(5): 105-108.

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Based on the linear parameter-varying （LPV） system, a system model is developed and the problem of state feedback piecewise H_∞ control is addressed for the level control of U-type steam generator in nuclear power plants. The sufficient conditions for the existence of controllers and the solved method of linear matrix inequalities are proposed in terms of Lyapunov stability theory approach. The feasibility is evaluated by numerical simulation and the results demonstrate that the proposed controllers can guarantee that the resulting closed-loop systems are quadratic stable and have desired H_∞ performance index in each operating region.

Ultrasonic Creeping Wave Test Technique for Dissimilar Metal Weld

YUAN Jian-zhong, YAN Zhi, YUAN Guang-hua, ZHANG Guo-feng, SHANG Jun-min

2009, 30(5): 109-112.

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To solve the problem encountered in the defect inspection of the surface and near-surface of dissimilar metal weld effectively, a new ultrasonic creeping wave test technique is developed. In this paper, the test technique and its experimental verification are mainly described. The verification results show that linear defect, which is similar to the defect found in liquid penetrant test, on the surface and near-surface of dissimilar metal weld can be detected effectively, by using ultrasonic creeping wave test technique. And the depth, length and height of the defect can be determined easily. The effective covering depth of ultrasonic creeping wave test technique will reach 0-9mm. Meanwhile, the planar defect, with equivalent area more than 3mm², existed in welds can be detected efficiently. So, accurate measurement, which self height dimension of planar defect is above 2mm, will be realized.

2009 Vol. 30, No. 5