Research and Application of Maintenance Decision Method of Complex Equipment in Nuclear Power Plant

The determination of maintenance mode of complex equipment in nuclear power plant is an essential work for reliability analysis and maintenance decision. Currently, the main decision method of maintenance mode is reliability centered maintenance( RCM) logic decision-making process, but the process is a qualitative analysis process. Based on a comprehensive analysis of factors affecting equipment reliability and maintenance work, it adopts a fuzzy synthesis decision method to establish a maintenance decision model,which uses the maximum subordination principle and expert assessment method to determine the maintenance mode of complex equipment. Combined with a concrete example of generators in nuclear power plant,a description of maintenance decision method was proposed in the application of complex equipment. The research shows that the method is feasible and reliable.

Research on Monitoring and Earlywarning System of Marine Organisms for the Intake of Nuclear PowerPlants

An monitoring and early-warning system is proposed for marine organisms and the cause of water intake blockage is analyzed. Based on the intelligent sensing technology, computer software and hardware technology and digital signal processing technology, the buoy monitoring platform system is developed by internet of things technology, cloud computing and the application of large data. Remote real-time monitoring of aquatic organisms and foreign bodies is realized based on underwater acoustic detection and low light imaging technology. Data processing center is estab-lished to store, analyze and process monitoring information and display it in real time, and provide emergency decision support. Through develop-ment and test of relevant key equipments, the reliability of cold source system of nuclear power plants is improved, which effectively reduces the influence of marine biological invasion on security and economic operation of the units.

Development and Application of Maintenance Template in Pressurized Water Reactor Nuclear Power Plant

Good practices of maintenance optimization in nuclear power field need to be effectively consolidated and inherited,and maintenance optimization can provide technology support to create a long-term reliable and economic operation for nuclear power plants( NPPs) especially for a large number of nuclear powers under construction. Based on the development and application of maintenance template in developed countries,and combining with reliability-centered maintenance( RCM) analysis results and maintenance experience data over the past ten years in domestic NPPs, the development process of maintenance template was presented for Chinese pressurized water reactor( PWR) NPP,and the application of maintenance template to maintenance program development and maintenance optimization combined with cases were demonstrated. A shortcut was provided for improving the efficiency of maintenance optimization in domestic PWR NPP,and help to realize a safe,reliable,and economic operation for domestic NPPs.

Reliability-Centered Maintenance-Based Maintenance Decision in New Nuclear Power Plants

Taking the project of introducing reliability-centered maintenance( RCM) into maintenance decision in an AP1000 nuclear power plant( NPP) under construction as the research object,an improved RCM methodology was proposed, and the application software and an RCM-based maintenance strategies management system were designed. In the pilot project,the RCMbased maintenance decision methodology had been applied to determining the maintenance strategies for two systems. Both the decision process and the results were described in this paper. The achievements of this project promoted the introduction and routinization of an advanced and effective maintenance decision mode in nuclear power field,which could provide valuable reference for new NPPs in China.

Analysis on SH-CCT curves of HD15Ni1MnMoNbCu steel for nuclear power station

The microstructural evolution and Vickers hardness measurement in the welding heat-affected zone(HAZ) of HD15Ni1 MnMoNbCu steel for nuclear power station were investigated by Gleeble-3180 thermal mechanical simulator,and the simulated HAZ continuous cooling transformation curves(SH-CCT) were measured simultaneously.With t_(8/5) increasing from3.75 s to 15 000 s,the product was obtained martensite,bainite,ferrite and pearlite,successively.The result of microstructure and Vickers hardness in the heat-affected zone was in good agreement with those measured by SH-CCT diagram with the heat input 16.2 kJ/cm as an example to weld the HD15Ni1 MnMoNbCu steel pipe using TIG/SMAW/SAW welding methods.

Risk Assessment,Management and Application in Nuclear Power Plant Operation

To introduce the basic concepts of technical specification of nuclear power plant,a risk assessment and management technique based on the probabilistic safety analysis( PSA) method was proposed. The risk-informed method was used,and an example was given to show how to use some specific risk metrics like CDF / LERF /ICDP / ILERP to analyze and manage the risk associated with activities in nuclear power plant operation. The advantage of this technique can be concluded from this paper,and this technique should be used more widely and deeply in nuclear industry.

Type Selection for Present Nuclear Power Development in China

With rapid development of nuclear power in China, in view of reactor type selection, this paper analyzes the current situation that faces nuclear power industry, the technical characteristics of optional reactors and the tendency of nuclear power technology development in the future. The proposals put forward in this paper include choosing and introducing GW-class advanced PWR as main reactors, carrying out self-supporting projects and technical transfer negotiations, in addition, promoting the design of the advanced generation-II PWR and initiating small-scaled construction. The ultimate target is to catch up with the world advanced level by means of technical upgrading and recreation based on technology importation and assimilation.

The Caching and Pricing Strategy for Information-Centric Networking with Advertisers’Participation

As users’access to the network has evolved into the acquisition of mass contents instead of IP addresses,the IP network architecture based on end-to-end communication cannot meet users’needs.Therefore,the Information-Centric Networking(ICN)came into being.From a technical point of view,ICN is a promising future network architecture.Researching and customizing a reasonable pricing mechanism plays a positive role in promoting the deployment of ICN.The current research on ICN pricing mechanism is focused on paid content.Therefore,we study an ICN pricing model for free content,which uses game theory based on Nash equilibrium to analysis.In this work,advertisers are considered,and an advertiser model is established to describe the economic interaction between advertisers and ICN entities.This solution can formulate the best pricing strategy for all ICN entities and maximize the benefits of each entity.Our extensive analysis and numerical results show that the proposed pricing framework is significantly better than existing solutions when it comes to free content.

Nonlinear Impact Damage Evolution of Charpy Type and Analysis of Its Key Influencing Factors

The current research of Charpy impact mainly focuses on obtaining the ductile brittle transition temperature of materials by experiments.Compared with experiments,numerical simulation can study many problems with harsh conditions.However,there are still few studies on the influence of geometric factors such as side grooves.In this paper,the geometry of standard Charpy impact test is designed.Specimens with different widths and side grooves are tested.The finite element model of Charpy impact was established by ABAQUS software.Use test results and simulation results to verify each other.The effects of sample width,side groove depth and side groove bottom fillet on the impact fracture resistance of the sample were studied.The results show that the specimen width is positively correlated with the impact toughness of the specimen.The side groove greatly reduces the impact toughness of the material;the toughness of side groove decreases with the increase of depth;the fracture toughness of side groove decreases with the increase of fillet at the bottom of side groove.The proportion of toughness energy to impact energy of samples was analyzed.The results show that the toughness energy accounts for about 70%of the impact energy of the sample,which has little to do with the geometric characteristics of the sample.This study presents a reliable method for studying Charpy impact tests.The influence of geometric parameters is obtained,which provides a reference method for the study of impact toughness of high toughness materials.

Efects of thermal aging temperature and Cr content on phase separ-ation kinetics in Fe-Cr alloys simulated by the phase feld method

Phase feld simulations of phase separation in Fe-Cr binary alloys were performed by using the Cahn-Hilliard difusion function.A new mobility model in relation to aging temperature and Cr content was used in the simulations.Two alloys of Fe-30at%Cr and Fe-35at%Cr were investigated at two diferent aging temperatures of 573 and 673 K.The phase separation kinetics was found to consist of three stages:wavelength modulation,amplitude increase,and coarsening of Cr-enriched regions.A higher thermal aging temperature accelerated the phase separation and increased the wavelength of concentration fluctuation.While the efect of Cr content on the phase separation kinetics was slight,Fe-Cr alloys with a higher Cr content were found to generate a larger number and a fner size of Cr-enriched regions.The simulation results provide consultation for design and safe operation of duplex stainless steel pipes in nuclear power plants.

Effects of pulse energy ratios on plasma characteristics of dual-pulse fiber-optic laser-induced breakdown spectroscopy

Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two laser pulses is independently adjusted within 0–30 m J with the total energy fixed at 30 m J.The inter-pulse delay remains 450 ns constantly.As the energy share of the first pulse increases,a similar bimodal variation trend of line intensities is observed.The two peaks are obtained at the point where the first pulse is half or twice of the second one,and the maximum spectral enhancement is at the first peak.The bimodal variation trend is induced by the change in the dominated mechanism of dual-pulse excitation with the trough between the two peaks caused by the weak coupling between the two mechanisms.By increasing the first pulse energy,there is a transition from the ablation enhancement dominance near the first peak to the plasma reheating dominance near the second peak.The calculations of plasma temperature and electron number density are consistent with the bimodal trend,which have the values of 17024.47 K,2.75×10^(17)cm;and 12215.93 K,1.17×10^(17)cm;at a time delay of 550 ns.In addition,the difference between the two peaks decreases with time delay.With the increase in the first pulse energy share,the plasma morphology undergoes a transformation from hemispherical to shiny-dot and to oblate-cylinder structure during the second laser irradiation from the recorded images by using an intensified charge-coupled device(ICCD)camera.Correspondingly,the peak expansion distance of the plasma front first decreases significantly from 1.99 mm in the single-pulse case to 1.34 mm at 12/18(dominated by ablation enhancement)and then increases slightly with increasing the plasma reheating effect.The variations in plasma dynamics verify that the change of pulse energy ratios leads to a transformation in the dual-pulse excitation mechanism.

The Condenser Performance Test and Thermal Performance Analysis of Variable Conditions in TQNPC

Condenser is one of the important auxiliary equipments in nuclear power plants. The thermal efficiency of the entire unit was depended on the condenser performance. Cleanliness factor and condenser corrected pressure are the two most important evaluation indexes. The definition and derivation of these two evaluation indexes were elaborated and clarified in this paper. And the condenser performance at variable conditions was analyzed. The seawater temperature, pipe plugging rate and seawater volume rate effect on unit output was calculated. The calculation method was simple, which can provide reference guidance for similar power plant.

The Research of Heat Transfer Area for 55/19 Steam Generator

A calculation method of heat transfer area for vertical natural circulated steam generator was introduced. According to the design requirements of steam generator 55/19 of CPR1000, its heat transfer area was calculated based on this method. The results show that the accuracy of partitional and overall calculation method is almost the same, but the result is different when using different calculation models. And the results are compared with the foreign companies for 55/19 steam generator.

Research and Application of New Threshold De-noising Algorithm for Monitoring Data Analysis in Nuclear Power Plant

Under the complex condition of nuclear power plant, all kinds of influence factors may cause distortion of on-line monitoring data. It is essential that on-line monitoring data should be de-noised in order to ensure the accuracy of diagnosis. Based on the research of wavelet analysis and threshold de-noising, a new threshold denoising method based on Mallat transform is proposed. This method adopts factor weighing method for threshold quantization. Through the specific case of nuclear power plant, it is verified that the algorithm is of validity and superiority.

Proton irradiation assisted localized corrosion and stress corrosion cracking in 304 nuclear grade stainless steel in simulated primary PWR water

Localized deformation and corrosion in irradiated 304 nuclear grade stainless steel in simulated primary water were investigated.The investigation was conducted by comparing the deformation structure,the oxide scale formed at the deformation structure,and their correlation with cracking.The results revealed that increasing the irradiation dose promoted localized corrosion at the slip step and grain boundary,which was primarily attributed to the strain concentration induced by enhanced localized deformation and depletion of Cr at grain boundary.Further,a synergic effect of the enhanced localized deformation and localized corrosion at the slip step and grain boundary caused a higher cracking susceptibility of the irradiated steel.

Effect of shrinkage porosity on mechanical properties of ferritic ductile iron

Casting defects could largely affect the mechanical properties of casting products. A number of test pieces made of ductile iron (EN-GJS-400-18-LT) with different levels of shrinkage porosity were prepared and then tensile and fatigue tests were performed to investigate the impact of shrinkage porosity on their mechanical properties. The results showed that the tensile strength decreases linearly with increasing of the shrinkage porosity. The tensile elongation decreases sharply with the increase of the shrinkage porosity mainly due to the non-uniform plastic deformation. The fatigue life also dramatically declines with increasing of the porosity and follows a power law relationship with the area percentage of porosity. The existence of the shrinkage porosity made the fatigue fracture complex. The shrinkage pores, especially those close to the surface usually became the crack initiation sites. For test pieces with less porosity, the fatigue fracture was clearly composed of crack initiation, propagation, and overloading. While for samples with high level of porosity, multiple crack initiation sites were observed.

Adsorption of NO and NH_3 over CuO/γ-Al_2O_3 catalyst

The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al2O3 catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350 °C. Comprehensive tests were carried out to study the adsorption behavior of NH3 and NO over the catalysts. The desorption experiments prove that NH3 and NO are adsorbed on CuO/γ-Al2O3 catalysts. The adsorption behaviors of NH3 and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH3 could be strongly adsorbed on the catalysts, resulting in coordinated NH3 and NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH3 and NO molecules with the Cu2+ present on the CuAl2O4 (100) surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu2+ site is energetically favorable, whereas NO bound is stronger than that of NH3 with the adsorption site, and key information about the structural and energetic properties was also addressed.

Oxygen Evolution Efficiency and Chlorine Evolution Efficiency for Electrocatalytic Properties of MnO_2-based Electrodes in Seawater

To improve both oxygen evolution efficiency and stability at high temperatures, Mn, Mn+Mo, Mn+Mo+V, and Mn+Fe+V oxide electrodes were prepared on a Ti substrate, with an intermediate layer of IrO_2, by an anodic deposition method. The crystal structure, surface morphology, pore size distribution, specific surface area, and voltammetric charge were then characterized for each electrode. The results demonstrated that for Mn-O electrodes, the preferential orientation of the(100) crystal plane and the mesopore structure played negative roles in the oxygen evolution reaction. On the basis of the electrocatalytic properties of MnO2-based electrodes in seawater, the outer surface voltammetric charge at a scan rate of 500 mV·s-1 was shown to effectively indicate whether oxygen evolution reactions were preferred over chlorine evolution reactions. The Mn-O electrode exhibited oxygen evolution efficiency of only 47.27%, whereas the Mn+Mo, Mn+Mo+V and Mn+Fe+V oxide electrodes displayed oxygen evolution efficiency of nearly 100%. This means that adding Mo, V, and Fe elements to the electrode can improve its crystal structure and morphology as well as further enhancing its oxygen evolution efficiency.

Corrosion Behavior and Mechanism of Irradiated 304 Nuclear Grade Stainless Steel in High-Temperature Water

Corrosion behavior and mechanism of irradiated 304 nuclear grade stainless steel were studied in simulated pressurized water reactor primary water.The microstructure of the oxide formed on the steel irradiated to different doses over an exposure period range of 25–1500 h was analyzed and compared.It was found that the general and intergranular corrosion rates of the steel were increased with irradiation dose,in correspondence with an evolution of the general oxide and the oxide formed at the grain boundary.Correlation of the oxide evolution with the corrosion kinetics and mechanism has been discussed in detail.