压水堆核电站蒸汽发生器二次侧化学清洗工艺中型试验研究

报道了PWR核电站蒸汽发生器(SG)二次侧腐蚀产物(Fe_3O_4)化学清洗工艺中型试验研究。试验在中型化学清洗试验回路上进行。在实验室研究和小回路试验的基础上,中型规模的试验研究评定了以EDTA(乙二胺四乙酸)为主的化学清洗工艺(温度、流量、时间、清洗方式)、腐蚀产物沉积形式对腐蚀产物清洗的有效性和验证SG二次侧结构材料在化学清洗过程中的安全性。用电化学线性极化法优化化学清洗剂的缓蚀剂组分,并在中型试验回路     

压水堆核电站蒸汽发生器二次侧化学清洗工艺中型试验研究

报道了PWR核电站蒸汽发生器(SG)二次侧腐蚀产物(Fe_3O_4)化学清洗工艺中型试验研究。试验在中型化学清洗试验回路上进行。在实验室研究和小回路试验的基础上,中型规模的试验研究评定了以EDTA(乙二胺四乙酸)为主的化学清洗工艺(温度、流量、时间、清洗方式)、腐蚀产物沉积形式对腐蚀产物清洗的有效性和验证SG二次侧结构材料在化学清洗过程中的安全性。用电化学线性极化法优化化学清洗剂的缓蚀剂组分,并在中型试验回路上得到验证,得出以EDTA为主的最佳化学清洗剂组分。电化学法监测清洗过程中材料腐蚀的实验室初步研究已基本完成。中型化学清洗试验研究得出了核电站SG二次侧腐蚀产物化学清洗的最佳工艺,工艺由清洗、漂洗、钝化三个步骤组成。     

压水堆核电厂二回路ETA水化学处理研究

秦山核电厂320 MW核电机组使用乙醇胺(ETA)替换氨作为二回路系统p H调节剂后,在给水p H相同的条件下,汽-水分离再热器(MSR)疏水、蒸汽发生器(SG)排污水的p H明显升高;汽-水两相中水相区域设备的腐蚀产物铁含量明显降低,流动加速腐蚀得到抑制,有效改善二回路系统的腐蚀状况;腐蚀产物向蒸汽发生器二次侧的转移得以降低;同时进一步提高凝水混床的周期制水量,减少了凝水混床树脂的再生次数及再生酸、碱的用量和耗水量,从而减轻运行人员的工作负担和再生废液对环境的污染。     

ETA对PWR二回路设备材料抗蚀作用研究

世界上已有60％的核电厂采用新型碱化剂ETA(Ethanolamine乙醇胺)作为二回路水化学pH控制剂。美国有80％的核电厂采用ETA。ETA作为二回路水化学pH控制剂,能够显著抑制蒸汽发生器(SG)传热管和二回路系统材料的各种类型腐蚀,延长SG使用寿命,提高在役核电厂的经济性。     

吗啉对PWR蒸汽发生器二次侧材料的防蚀作用

氨/联氨全挥发处理(AVT)不能克服压水堆(PWR)核电厂蒸汽发生器(SG)二次侧汽水两相流区域的材料磨蚀和腐蚀问题。有报道:低挥发性的化学添加剂吗啉(Morpholine)能改善SG二相流区域材料的抗蚀性能,吗啉全挥发处理已用于PWRs上。文中研究了吗啉在PWR核电厂SG二次侧停堆湿保养时和正常运行工况时最佳使用浓度,并用表面分析技术初步探讨了吗啉对材料(碳钢A3、低合金钢S271)的防蚀作用。     

吗啉对PWR蒸汽发生器二次侧材料的防蚀作用

氨/联氨全挥发处理(AVT)不能克服压水堆(PWR)核电厂蒸汽发生器(SG)二次侧汽水两相流区域的材料磨蚀和腐蚀问题。有报道:低挥发性的化学添加剂吗啉(Morpholine)能改善SG二相流区域材料的抗蚀性能,吗啉全挥发处理已用于PWRs上。文中研究了吗啉在PWR核电厂SG二次侧停堆湿保养时和正常运行工况时最佳使用浓度,并用表面分析技术初步探讨了吗啉对材料(碳钢A3、低合金钢S271)的防蚀作用。     

浅论核电厂蒸汽发生器传热管破裂事故与SG二次侧水质控制

蒸汽发生器(SG)是核电厂关键设备之一，是一、二回路共用设备。发生蒸汽发生器传热管破裂(SGTR)事故时，一回路冷却剂通过SG流入二回路而造成一回路冷却剂丧失。SGTR可能导致堆芯损坏，并造成放射性向环境释放。控制SG二次侧水质是确保SG传热管完好性、防止SGTR事故发生的有效措施，也是涉及到SG使用寿命的问题。本文旨在通过探讨SGTR发生的主要原因，强调SG二次侧水质控制的重要性，以及核电厂应提高SG水质监测标准、加大水处理力度的必要性。     

压水堆核电站蒸汽发生器二次侧淤渣化学清洗

研究以EDTA为主的化学清洗剂的组分、pH、温度、时间、流量对PWR SG二次侧淤渣主要成分Fe_3O_4溶解量的影响和对材料(低合金钢;S 271、碳钢A3,800合金)在清洗过程中抗腐蚀性能影响。建立了化学清洗试验小回路(30L)。用化学清洗试验小回路进行扩大清洗工艺试验研究。模拟PWR SG二次侧正常运行工况,研究化学清洗剂残余量对材料的抗腐蚀性能影响。结果认为以EDTA为主的化学清洗剂(pH=7,10％EDTA、1％助溶剂、0.25％缓蚀剂A),在934±5℃,8h,112r/min或1.8～2.0t/h清洗过程中,能溶解18～23g/L Fe_3O_4。在整个清洗过程中,材料腐蚀在允许范围内。化学清洗剂残余量低于0.01％EDTA时,不影响材料在PWR SG二次侧正常运行工部(260±5℃)时的抗腐蚀性能。     

压水堆核电站蒸汽发生器二次侧淤渣化学清洗

研究以EDTA为主的化学清洗剂的组分、pH、温度、时间、流量对PWR SG二次侧淤渣主要成分Fe_3O_4溶解量的影响和对材料(低合金钢:S 271、碳钢A3,800合金)在清洗过程中抗腐蚀性能影响。建立了化学清洗试验小回路(30L)。用化学清洗试验小回路进行扩大清洗工艺试验研究。模拟PWR SG二次侧正常运行工况,研究化学清洗剂残余量对材料的抗腐蚀性能影响。结果认为以EDTA为主的化学清洗剂(pH=7,10％EDTA、1％助溶剂、0.25％缓蚀剂A),在93±5℃,8h,112r/min或1.8～2.0t/h清洗过程中,能溶解18～23g/L Fe_3O_4。在整个清洗过程中,材料腐蚀在允许范围内。化学清洗剂残余量低于0.01％EDTA时,不影响材料在PWR SG二次侧正常运行工况(260±5℃)时的抗腐蚀性能。     

压水堆核电厂二回路水质泥渣沉积分析与控制优化

核电厂蒸汽发生器相当于一个巨大的垃圾收集器,二回路系统的杂质及异物等均进入蒸汽发生器后,容易发生杂质沉积,并导致蒸汽发生器传热管传热效率降低,严重时甚至会引起蒸汽发生器传热管腐蚀破损。因此,本文从核电厂二回路各系统管道和容器的材质、二回路水质控制以及二回路腐蚀等方面出发,分析核电厂蒸汽发生器的泥渣含量高的原因,并提出合理的技术改进。最终达到降低蒸汽发生器泥渣量的沉积,提高蒸汽发生器的安全使用寿命的目的。     

Chemical cleaning of PWR steam generators with a low temperature process

Corrosion products generated in the steam, feedwater and condensate systems of a PWR will be transferred by the feedwater into the secondary side of the steam generators (SG). Up to several hundred kilograms of deposits may collect on the surfaces of the SG. These deposits not only reduce the efficiency of the SG by deterioration of the heat transfer, but also cause an acceleration of the corrosion of the SG tubes and blockage of support plate passages.The chemical removal of the corrosion products opens the possibility to eliminate causes of defects on heat transfer tubes by removing the corrosion products and trapped impurities.A low temperature cleaning process, based on the EPRI developed SGOG iron and copper solvents, was applied in November 1990 to remove the hard deposits from the tube sheets of a two-loop plant. The sludge containing over 60% copper was removed with the application of one iron removal step and several copper removal steps. Over 95% of the available sludge was removed. The corrosion of the unalloyed and low alloy materials was extremely low. The Incoloy 600 tubes showed no corrosion.In addition aspects of crevice cleaning at elevated temperatures are mentioned.     

Numerical model for estimation of corrosion location in nuclear power plant steam generators

Deposition of dissolved impurities and corrosion in steam generators is a significant problem in the operation of nuclear power plants. Impurities and corrosion products usually accumulate in the secondary sides of steam generators (SG) and form deposits on the SG surfaces. A high level of impurity concentration close to the SG heating surface causes the corrosion process to occur with more intensity. The aim of this study is to estimate the most probable locations of impurity concentration and deposition in a SG. Equations representing the convection and diffusion in the liquid phase close to the heated surface (the viscous sub layer) are derived. Based on the mass balance of impurities in the viscous sub layer as the boundary condition, the derived differential equations are solved by the finite volume (upwind) methods. The distribution of impurities, sediment formation rate and the location of the depositions in the viscous sub layer at different heat flux values are studied in steady and unsteady states.     

核电站蒸汽发生器冲洗装置控制系统的开发

随着核电站运行和管理水平的提高,蒸汽发生器(SG)二次侧维护越来越受到重视。笔者开发的SG冲洗装置的主要部份是以PLC控制器和交流伺服电机核心组成的高精度运动控制系统。人-机操作界面采用现场操作站和遥控触摸屏相结合的方式,减少操作人员整体辐射水平。同时,该系统还具有事故工况下急停、泥渣收集和运行状态视频监视等功能。最后,提出了利用人工神经网络模型补偿冲洗手臂挠曲和系统运动控制中静摩擦力等造成的非线性影响,进一步提高系统控制精度。系统运行稳定、操作简单。     

Thermal hydraulic behaviors during loss of RHR system at mid-loop operation of Chinese 300 MWe PWR NPP

Thermal hydraulic behavior of nuclear power plant (NPP) is analyzed by using mechanistic computer code for loss of residual heat removal (RHR) system during mid-loop operation of Chinese 300 MWe two-loop pressurized water reactor is presented. In the absence of recovery of RHR or other accident management measures, the reactor core will be uncovered for a long term resulting in core heat-up, degradation and relocation to the lower plenum. The effectiveness of available mitigate measures, such as safety injection system, gravity feed from refueling water storage tank (RWST) and steam generator (SG) reflux-condensation, are investigated. Coolant injection is highly effective in halting the accident progression and make the core recovered. The cooling capability of SG reflux-condensation has a relationship with different availabilities of steam generators and decay heat power. 6 days after shutdown, 2SG operation can keep the water level at mid-line of hot leg. 12 days after shutdown, both 2SG operation and 1SG operation can keep the water level at mid-line of hot leg. The analyses also indicate that the cooling mechanism of safety injection system is more effective than gravity feed from RWST and SG reflux-condensation. Through confirming the success criteria of SG reflux-condensation, time windows can be devided. Then, event trees for loss of RHR system under mid-loop operation are built with considering the analysis results and abnormal procedure.     

Applicability of Chemical Cleaning Process to Steam Generator Secondary Side, (IV)

The application of chemical cleaning for dissolving and removing scale and sludge is being planned in the Japanese pressurized water reactor (PWR) plant in order to maintain high heat transfer performance and to prevent steam generator (SG) tube degradation. In this paper, the effectiveness of the Electric Power Research Institute (EPRI) and German Kraftwerk Union (KWU) processes on the integrity of structural materials other than SG tubes and the comprehensive applicability of chemical cleaning are discussed. The integrity of structural materials such as carbon steel, low-alloy steel and stainless steel was maintained after the EPRI and KWU processes. KWU chemical cleaning tailored for crevice cleaning has been studied to improve its cleaning effectiveness in crevices and to control the corrosion depth of structural materials less than the criterion for corrosion depth.     

A method of examining iron oxides speciation and transport to steam generators during nuclear power reactor startups

Secondary side corrosion products (sludge) collected during one of CANDU1¹ reactor startups from wet layup have been examined by X-ray fluorescence and Mössbauer spectroscopy. The transport and chemical form of iron oxides and oxyhydroxides were determined in condensate, feedwater and preheater outlet as a function of temperature and time. The sludge burst and oxidation states of iron oxides were correlated with the rise of reactor power and corresponding changes in temperature, condensate vacuum and water flow rate. In particular, a sharp γ-FeOOH to Fe₃O₄ switch was observed that coincided in time with the onset of condensate vacuum. Also, it was found that the startup after wet layup is characterized by only brief and fairly small sludge burst at about 30% reactor power and which contributes only a small amount of undesirable α-Fe₂O₃ to total iron transport to steam generator. Thus, sludge burden to steam generators can be minimized with proper layup and startup practices.     

Shutdown dose rate calculation code system and its application to EAST tokamak

For safe operation and maintenance of nuclear devices, it is very important to predict the dose rate distribution after shutdown. Based on the rigorous two-step (R2S) method, a new shutdown dose rate calculation code system was developed for nuclear devices with large dimension and complex geometries. By coupling the Monte Carlo particle transport calculation code MCNP with the activation simulation code FISPACT, the dose rate calculation codes integrate the functions of neutron transport calculation, activation calculation and decay gamma transport calculation. This code system was applied to the shutdown dose analysis for experimental advanced superconducting tokamak (EAST). Three-dimensional dose rate distributions of the EAST for different cooling times and spatial locations were obtained. The results can be used to assist radiation protection in EAST.     

压水堆一回路冷却剂活化腐蚀产物钴银锑

介绍了压水堆核电厂一回路冷却剂中主要活化腐蚀产物钴、银、锑源项的产生和对于停堆机组剂量大幅增加的影响。研究这些核素在反应堆运行和停堆期间的行为并尽早探知这些污染物的出现,以便确定相应的解决办法。它包括：从源头做起,与一回路冷却剂系统接触的设备和部件尽量不采用含有钴、银、锑的材料;制定严格的水化学和停堆程序,使得对这些核素污染的净化能力最佳化和对过度污染最小化;根据具体情况改进净化工艺,限制污染带来的影响。实践证明,这些措施对减少或限制钴、银、锑的污染是行之有效的。     

核聚变装置停机剂量率分析计算的严格两步(R2S)法

在三维蒙特卡罗粒子输运程序MCNP的基础上，发展了一种用于几何结构复杂的核聚变装置如托卡马克装置停机剂量率的精确计算方法——严格两步法(R2S)。首先对R2S方法进行描述，然后在ITER停机剂量率实验T426的基础上进行校核计算，并与“直接一步法”(DIS)进行了比较分析，结果显示，R2S方法与实验吻合得非常好，最大误差大约为15％，而且，相对于DIS方法(最大误差为25％)而言更准确。     

On the speed of response of an FPGA-based shutdown system in CANDU nuclear power plants

Several issues in an FPGA based implementation of shutdown systems in CANDU nuclear power plants have been investigated in this paper. A particular attention is on the response time of an FPGA implementation of safety shutdown systems in comparison with operating system based software solutions as in existing CANDU plants. The trip decision logic under “steam generator (SG) level low” condition has been examined in detail. The design and implementation of this logic on an FPGA platform have been carried out. The functionality tests are performed in a hardware-in-the-loop (HIL) environment by connecting the FPGA based system to an NPP simulator, and replacing one channel of Shutdown System Number 1 (SDS1) in the simulator by the FPGA implementation. The response time of the designed system is also measured through multiple tests under different conditions, and statistical data analysis has been performed. The results of the response time tests are compared against those of a software-based implementation of the same trip logic.