核动力工程

Mathematical Adjoint Equation of Interface Current Method for Neutron Transport Calculation

ZHANG Ying, CHEN Wei, CHEN Li-xin

2005, 26(2): 97-101.

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This paper derives the mathematical adjoint equation of neutron transport equation, which is solved in hexagonal geometry by interface current method in the condition that the neutron source in cell adopts constant assumption. The calculation method of mathematical equation and the progress of inner and outer iteration are introduced. Based on the TPHEX code for forward equation calculation, the TPHEX_J0 code to calculate the mathematical equation is encoded. The calculation checkout proves that the keff of system calculated by TPHEX_J0 and TPHEX code are all in good agreement, and the calculation results of TPHEX_J0 code are reliable.

Information Flow Model Based on Network Security of Nuclear Power Plant

LIU Yi-he

2005, 26(2): 102-104,120.

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In order to precisely describe the information flow from 1E degree to non 1E degree subsets of the network in the Nuclear Power Plant network, a new security information flow mathematics model based on this network is given in this paper. This model incorporated the new concept of the planar-classification function, which combined the classification of the sub-network and the classification of object. Safety classification of the objects was divided based on the function values and the information flow policy is described with the function values of two objects. Strict mathematic verification showed that this information flow model is reasonable and safe, which can reflect the safety requirements of the Nuclear Power Plant network.

3-Dimensional Numerical Simulation of Sodium Spray Fire Accidents in LMFBRs

ZHANG Bin, ZHU Ji-zhou, HAN Lang

2005, 26(2): 105-109.

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In order to estimate and foresee the sequence of sodium spray fires that may occur in the liquid metal cooled fast breeder reactors (LMFBRs), this paper develops a program to analyze such sodium fire accidents. The present study gives a 3-dimensional numerical analysis code for sodium spray fires. The spatial distributions of gas temperature and chemical species concentrations in the cell that sodium spray fires happened are given. This paper gives detailed explanation of combustion models and heat transfer models that applied in the program. And the calculation procedure and method in solving the fluid field are narrated in detail. Good agreements of an overall transient behavior are obtained in a sodium spray combustion test analysis. The comparison between the analytical and experimental results shows that the program presented in this paper is creditable and reasonable for simulating the sodium spray fires.

Analysis of Improvement Plan for Miniature Neutron Source Reactor

ZHAO Hai-ge, GUO Cheng-zhan, SUN Hui-bin, GAO Yong-chun, ZHENG Wu-qin, GAO Ji-jin, WANG De-liang

2005, 26(2): 110-113.

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This paper analyzes some improvement plans to prolong the single operation time of the Miniature Neutron Source Reactor (MNSR). Test results shows that after adding proper quantity of Be plates on the top Be plates box, the single operation time of MNSR can be greatly prolonged by installing the compensation Cd-plate outside the flank Be-reflector and making the plate and central control rod move together, without any change of central control rod and the original structure of the reactor core. The operation performance of MNSR can be improved.

Study on Spray Model during Severe Accidents

LIN Ji-ming, JIA Bao-shan, LIU Bao-ting

2005, 26(2): 114-120.

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In case of severe accident of PWR, large amount of hydrogen may accumulate in the containment. Unsuitable action of containment spray system will change the inert environment of containment, and cause hydrogen challenge or detonation that may challenge the integrity of containment. The condition of the containment pressure for avoiding hydrogen combustion, at different amount of hydrogen, is concluded based on reasonable assumptions and experimental correlations of hydrogen detonation. One conservative spraying mode, upon which spraying pump is manually turned on or off with containment pressure, is proposed in this paper. The analysis results aiming at DAYA Bay Nuclear Power Plant by using MELCOR show that the operation mode is feasible. The impact of pit flooding, spontaneous hydrogen combustion and containment basement compositions on the spraying mode is also analyzed in this paper.

Study on Grey Model in ONB of Nature Circulation

ZHOU Tao, YANG Rui-chang, TAN Shi-wei

2005, 26(2): 121-124,157.

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Grey system theory is applied to analyze the experimental data of onset of nuclear boiling in Freon natural circulation. The magnitude sequence of the factors that have effects on ONB (Onset of Nucleate Boiling) of nature circulation are confirmed as the heating power, inlet quality, liquid temperature, mass flow and pressure. Based on the experimental results, Grey model GM(1,1) and GM(1,4) are established by using the grey theory. The effects of the heating power, inlet quality, liquid inlet temperature and flow on the position of ONB are analyzed by using GM(1,1). Both models can be used to predict the development trend of the experimental data.

Renovation of RELAP5 as Thermal-Hydraulic System Code for Simulator in Nuclear Power Plant

LIN Meng, YANG Yan-hua, HU Rui, SU Yun, ZHANG Rong-hua

2005, 26(2): 125-129,139.

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Original RELAP5 is a non-real-time code, and has limitation on the data communication and calculation process control, so it is not very suitable for simulator. A new thermal-hydraulic system code for simulator, RELAPSIM, has been developed by employing RELAP5 at NSSE. The course of development consists of three major parts. Firstly, the time control function has been added into the code to meet the requirement of real-time calculation. Secondly, the function of controlled dynamic data communication was improved, thus thermal-hydraulic parameters can be exported from the code and can be input and modified by commands. Finally, the function of calculation process control was embedded in RELAP5 code, which provides the full ability to fulfill the multiple operations, such as starting up, shutting down, freezing, running, snapshoting, and resetting. This paper presents the development activities and the results of assessment by using RELAP5 and RELAPSIM.

Experimental Investigation on Instabilities of Steam-Water Two-Phase Flow in Large L/d Inclined Parallel Upward Smooth Pipes

GAO Feng, CHEN Ting-kuan, LUO Yu-shan, YIN Fei

2005, 26(2): 130-134.

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Experiments on instabilities of steam-water two-phase flow in inclined upward internally bare pipes have been performed on a high-pressure steam-water test loop. Different types of two-phase flow instabilities including pressure drop oscillation (PDO) and density wave oscillation(DWO) were observed. Experiments indicated that PDO happened without upstream compressible volume supplied by a surge tank when the rate of test pipe length and test pipe inner diameter L/d >1200. The effects of system parameters such as system pressure, mass flow rate, heat flux and inlet sub-cooling are significant on both DWO and PWO. The analytical results showed that PDO happened at a lower exit quality and in the positive portion of the ΔP-G curves with both channel flow rates oscillation in phase, DWO happened at higher exit quality and in the negative portion of the ΔP-G curves with both channel flow rates oscillating out of phase. The investigation results indicated that the oscillation characteristics in inclined parallel upward smooth pipes were similar with in vertical parallel upward pipes.

Numerical Analysis On Flows in Jet Pumps

HE Pei-jie, LU Jun-xian, LONG Xin-ping, LU Hong-qi

2005, 26(2): 135-139.

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Numerical calculation and a more detailed flow analysis are presented, based on the body-fitted coordinate system, hybrid finite analytical method and k -ε turbulence model that are applied to predict the flows in jet pump for boiling water reactor. Predictions have been made and compared with experimental data pertaining to the centerline velocity decay and wall static-state pressure variation. The theoretical predictions compare well with the experimental data. The flow analysis results show that the jet potential core length and the appearance of the re-circulation in jet pump flows depend strongly on the flow ratio.

Overlapped Flow of Flow Oscillation Caused by Rolling Motion and Density Wave Oscillation of Natural Circulation

TAN Si-chao, PANG Feng-ge

2005, 26(2): 140-143.

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The characteristic of nuclear plant natural circulation flow instability under rolling motion condition was carried out experimentally. The results showed that the flow oscillation caused by rolling motion and the density wave oscillation made the system oscillate with overlapped effect, which made the system more instable. Based on the frequency chart analysis, the effect of overlapped was analyzed.

Study on Brazability of Low-melting-point Ag-AI-Sn Brazing Filler

YANG Jing, QIU Shao-yu, ZHU Jin-xia, WANG Fei, LIU Xiao-rong

2005, 26(2): 144-147.

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Two kinds of low-melting-point filler metals(Ag-8Al-6Sn and Ag-8Al-6Sn-1Ni) have been prepared. Based on the concerned national standards, the melting characteristic, the spreadability and the clearance fillabitity on and between the titanium alloy and stainless steel,and the strength of the joints between titanium alloy and stainless steel had been evaluated.. The results indicated that the Ag-8Al-6Sn-1Ni brazing filler has better brazing technological performance than the Ag-8Al-6Sn filler. The seam of the titanism and stainless steel joints was analyzed by metallographic examination and SEM. The results indicated that the brazed joints using the Ag-8Al-6Sn filler were reliable,and its organic property was favorable.

Effects of Mean Strain on the Random Cyclic Stress-Strain Relations of 0Cr18Ni10Ti Pipe Steel

ZHAO Yong-xiang, YANG Bing, LI Peng-zhou

2005, 26(2): 148-152,178.

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Experimental study is performed for the effects of the mean strain on the random cyclic stress-strain relations of the new nuclear material, 0Cr18Ni10Ti pipe steel. From saving the size of specimens, an improved maximum likelihood fatigue test method is proposed to operate the present strain-controlled fatigue tests. Six straining ratios, -1, -0.52, -0.22, 0.029, 0.18, and 0.48, respectively, are applied to study the effects. Fatigue test has been carried out on totally 104 specimens. The test results reveal that the material exhibits a Masing behaviour and the saturation hysteresis loops under the six ratios hold an entirely relaxation effect of mean stress. There is no effectively method for the description of the mean straining effects under this case. Previous Zhao's random stress-strain relations are therefore applied to characterizing effectively the scattering test data under the six ratios on a basis of Ramberg-Osgood equation. Then the effects of the ratios are analyzed respectively on the average stress amplitudes, the standard deviations of the stress amplitudes, and the stress amplitudes under different survival probabilities and confidences. The results reveal that the ratios act a relatively decreasing effect to the stress amplitudes under higher survival probabilities and confidences. The strongest effect appears at the ratio of 0.029, and a weaker effect acts as the distance increase of the ratio from the zero. In addition, it is indicated that the effects from the sense of average fatigue lives might result in a wrong conclusion. The effects can be appropriately assessed from a probabilistic sense to take into account the scattering regularity of test data and the size of sampling.

Mean Strain Effects on the Random Cyclic Strain-Life Relations of 0Cr18Ni10Ti Pipe Steel

ZHAO Yong-xiang, YANG Bing, LI Peng-zhou

2005, 26(2): 153-157.

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Experimental study is performed on the mean strain effects on the random cyclic strain-life relations of the new nuclear material, 0Cr18Ni10Ti pipe steel. In order to save costs of specimens and tests, an improved maximum likelihood fatigue test method is applied to manage the present strain-controlled fatigue tests. Six straining ratios, respectively, -1,-0.52, 0.22, 0.029, 0.18, and 0.48, are applied to study the effects. Total 104 specimens are fatigued.Since the material exhibits an entirely relaxation effect of mean stress under the six ratios and, in addition, there is no effectively method for the description of the mean straining effects under this case, previous Zhao's random strain-life relations are therefore applied for effective characterization of the scattering test data under the six ratios on a basis of Coffin-Manson equation. Then the effects of the ratios are analyzed respectively on the average fatigue lives, the standard deviations of the logarithms of fatigue lives, and the fatigue lives under different survival probabilities and confidences. The results reveal that the ratios greater than zero exhibit a positive effect of about 1.3 to 1.6 times under the survival probability of 0.999 and the confidence of 95%. A negative effect is exhibited for the case of the ratios less than zero. In addition, the assessment of the effects from the sense of average fatigue lives might result in a wrong conclusion for the practice of higher reliabilities. The effects can be appropriately assessed from a probabilistic sense to take into account the average lives, the scattering regularity of test data, and the size of sampling.

Effects of Thermo-mechanical Processing on Microstructure of Zr-Sn-Nb Alloy

LIU Yan-zhang, ZHAO Wen-jin, PENG Qian, SUN Zhang-long

2005, 26(2): 158-162.

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Hot-rolling, cold-rolling and quenching tests of Zr-Sn-Nb alloy were carried out at 750℃, 780℃, 800℃ and 820℃, respectively. The microstructures of different heat-treated Zr-Sn-Nb alloy and the characteristics of β-Zr and second precipitate particles were studied and analyzed using transmission electron microscope (TEM) and optical microscope (OM). The results showed that N18 contained α+β phases while heating at 780℃ and above, and the higher the heating temperature, the more the β-Zr phases produced. The majority of second phase particles (SPPs) in Zr-Sn-Nb alloy were h.c.p Zr(Fe, Cr)₂ Laves phases with the lattice parameter a=0.502nm, c=0.818nm, which was similar to that of Zr-4 alloy. In addition, there were a few f.c.c. Zr(Fe、Cr)₂ Laves phases with lattice parameter a=0.716nm. The results have been discussed extensively.

Comprehensive Control of PWR Pressurizer Using Typical Fuzzy Controllers

JU Xiao-long, ZHANG Nai-yao, JIA Bao-shan, CUI Zhen-hua

2005, 26(2): 163-166,178.

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A comprehensive fuzzy control scheme for pressure and water level of PWR pressurizer is presented in this paper, where three typical fuzzy controllers are used to control the electrical heater, spray and relief valves, as well as feed valve, respectively. An integral-separated method is adopted in pressure control system. Computer simulation results in steam load step change, linear change and load-rejection operating conditions have shown that static and dynamic control performance of pressure and water level have been improved greatly, and the TFC based comprehensive fuzzy control scheme is effective and much better than the GA-FC and PID control schemes.

Development of Control System for SG Cleaning Device in Nuclear Power Plant

LI Bi-cheng, DAI Bing, SHENG Sai-bin, LIU Yu-long, WANG Xian-yuan

2005, 26(2): 167-170,178.

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With the development of the operation and management technology in the nuclear power plant, people pay more attention to the maintenance of SG second-side. The SG cleaning device developed in this paper is a high-precise motion control system composed of PLC controller and AC servomotor. The human-machine interface incorporates the on-site operator station and the remote touch-sensitive screen, which reduces the total radiation for the operators. Moreover, this control system also has such functions as the emergency shutdown under fault condition, sludge collection and video monitor for operation status. Finally, this paper puts forward an artificial nerve network model, which compensates the nonlinear effects of the control system caused by the static friction resulted from the deflection of the mechanical armand system motion. It can further improve the control precision. The operation of the control system is stable and simple.

Establishment of Rule Base for PWR Pressurizer Fuzzy Controller by Genetic Algorithm

LIU Sheng-zhi, CUI Zhen-hua, ZHANG Nai-yao

2005, 26(2): 171-174.

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A method to establish the fuzzy rule base automatically is described in this paper. According to the data produced by PID control system, a genetic algorithm is used to establish the fuzzy rule base automatically. This method is applied to the PWR pressurizer fuzzy control system. The simulation result shows that this fuzzy control system is with good performances:less overshoot, faster response and more stable transient.

A Method for Early Failure Detection and Monitoring of On-line Condition of Nuclear Reactor

SHENG Huan-xing, LI Hong-xia

2005, 26(2): 175-178.

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Monitoring of Vibration of Reactor Internal Structures in Nuclear Power Plant(referred to as the standard hereafter), which will be issued by nuclear industry, concludes a new methods for a new type of nuclear power plant instrumentation and control system. This new system differs from the traditional monitoring systems, as it aims primarily at early failure detection. Useful information is provided to plant operators, but in particular to the inspection/maintenance personnel. The standard is used as an example for early failure detection and on-line condition monitoring methods based on signature analysis and feature vector monitoring in general.

Improvement of MJTR Detector Layout

LI Zheng-yi, HUANG Yong

2005, 26(2): 179-181,186.

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The life of Mimjiang Test Reactor (MJTR) detectors and its control system will be shortened due to the nearby strong neutron and γ irradiation in the core. With the enlarging of the diameter of the irradiation channel in the reactor, the changing of the center location of the channel and the increasing of the volume of irradiation sample, the disturbance to the neutron signal received by the detectors will be increased, which is harmful to the safe operation of the reactor. Thus the layout of MJTR detectors is improved. This paper introduces the measures, design principle and methods and result for the improvement of the layout of the detectors. Debugging results indicate that the layout of the detector channels and function assignment in the improved design are reasonable, and can meet the design requirements.

Improvement of Indication Signal Evaluation in Control Rods In-service Inspection

LI Su-jia, YUAN Li, QIAO Wei

2005, 26(2): 182-186.

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Considering that an indication signal may not be evaluated certainly in Rod Cluster Control Assembly in-service eddy current test, the test specimen with artificial flaws were fabricated, the magnet core was installed in coil assembly to produce magnetic saturation coils in order to eliminate possible magnetic impact on the control rods, and 3-point centre aligned device was changed with 6-point center aligned device in coil assembly to improve the examination condition and enhance the inspection reliability. Test and examination results showed that the current inspection technique can detect the axial and circumferential flaws for both bobbin and pancake coils; for pancake coils, it can distinguish single or multiple flaws, but not for bobbin coils; and the eddy current signal was signified by axial flaws. However, structure signals sometimes were similar with circumferential flaw signals.

Analysis of Dynamical Response of Nuclear Power Plant Concrete Containment under Contact Blast Load

WANG Tian-yun, REN Hui-qi, WANG Yu-lan

2005, 26(2): 187-191,195.

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Nuclear power plant may be the target of the precision-guided bomb unit in the modern war and the attack of terrorists. Nuclear power plant containment shell is a large-volume pre-stressed reinforced concrete silo-shell structure to prevent radioactivity, and is the most important protected object in special condition. Based on the structure of nuclear power plant containment, this paper uses liquid-solid coupling arithmetic to analyze the concrete containment dynamical response under contact blast load. Detailed analysis reveals the law of structure damage and stress distribution of the containment shell in contact blast. These numerical values provide important technical parameters for the decision of safety measures for NPP in war.

Nonconformance Management During Site Construction of Nuclear Power Plant

LI Shi-chang

2005, 26(2): 192-195.

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The definition of terms "nonconformity" in HAF003(1991), ISO9001:2000 and IAEA50-C-Q(1996) are compared and connotations are expatiated respectively. Management measures such as classifying, grading and leveling nonconformance (nonconformities) are introduced for the implementing of IAEA50-C-Q(96), and issues requiring more attention in the nonconformity management are proposed.

3D Digital Dynamic Management of Maintenance Projects for Nuclear Power Plant

WANG Bai-zhong, LUO Ya-lin, FANG Hao, MA Li, ZHANG Jie, WANG Ruo-bing, XIE Min

2005, 26(2): 196-198,208.

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The whole process for the application of digital plant technique in the equipment transport in reactor building and the dynamic management of the spatial arrangement in Daya Bay Nuclear Power Station was introduced in the paper. The establishment of 3D digital Daya Bay plant, and the method and procedure to apply it in the nuclear power plant maintenance project have been discussed. This project utilizes the outer database to preserve the maintenance status of equipments, and avoids the damage or changing of the original 3D final model. Based on the maintenance procedure, the spatial arrangement and schedule for the maintenance of nuclear power station have simulated and optimized for the whole process. This technique can simulate and optimize the arrangement and spatial arrangement for maintenance in limited space. It has been applied successfully in the reactor vessel head replacement for Unit 2 of Daya Bay NPP to shorten the time for key routes and the total time of this project by 16 hours and 92.5 hours, respectively.

Application of Genetic Neural Network in Steam Generator Fault Diagnosing

LIN Xiao-gong, JIANG Xing-wei, LIU Tao, SHI Xiao-cheng

2005, 26(2): 199-202,208.

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In the paper, a new algorithm which neural network and genetic algorithm are mixed is adopted, aiming at the problems of slow convergence rate and easily falling into part minimums in network studying of traditional BP neural network, and used in the fault diagnosis of steam generator. The result shows that this algorithm can solve the convergence problem in the network trains effectively.

Estimation of Graphite Dust Quantity and Size Distribution of Graphite Particle in HTR-10

LUO Xiao-wei, YU Su-yuan, ZHANG Zhen-sheng, HE Shu-yan

2005, 26(2): 203-208.

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In 10MW High Temperature Gas-cooled Reactor (HTR-10), the wear of graphite components generates the graphite dust to influence the normal working of the reactor. The graphite dusts come from three parts:core, unload pipe and load pipe. Based on the graphite wear experiments, we here estimated that the graphite generation under normal working condition is about 2.74kg/a. By the mass-weighted average, the distribution function of volume, area and diameter for graphite particle were obtained.

2005 Vol. 26, No. 2