某核电厂MTU956应急柴油机在月度定期试验中,突发Al-B1缸动力单元组件损坏故障,造成多个组件损伤.其中,主润滑油管道被击穿引起柴油机润滑油压力低,致使保护停机,使电厂遭受巨大经济损失.本文主要通过对损坏组件的材料学全面检测分析,综合分析结论确定A1-B1缸动力单元组件事件发生的根本原因为曲轴制造阶段残留金属异物导致连杆大端轴瓦烧毁,并提出了监测建议,对核电厂应急柴油机运维具有重要意义.

核电厂某型凝汽器多次出现因钛管开裂导致海水泄漏问题,严重影响机组安全稳定运行.本文通过对历次事件规律统计分析和钛管金属学分析,确认钛管开裂问题均发生于单列运行或甩负荷工况下,钛管断口性质为疲劳开裂.通过研究该类型凝汽器设计准则,并与行业设计准则对比分析,发现该类型凝汽器在临界流速选取和实际流场不均匀性方面考虑不足,且当机组处于凝汽器单列运行工况下,机组运行功率过高,进一步促使钛管产生流体弹性激振问题.最后,通过加装防振条、预防性堵管以及单列运行机组功率控制等措施,有效降低了凝汽器海水泄漏风险.新设计的该型凝汽器也对此进行了改进,缩短了钛管跨距,从根本上提高了钛管产生流体弹性激振的安全裕度.

介绍了发电机内部短路故障的主要分类及产生原因.利用经典PARK方程法,进行了实例仿真计算.研究并掌握超大容量核电站用发电机短路故障原因和仿真计算,对发电机运维与设备管理技术人员具有指导作用.

The root cause for the fracture of upper valve seat of isolation valve of Containment Spray system (EAS) was investigated by residual stress testing, chemical analysis, metallographic analysis, hardness test and fracture analysis, combined with finite element analysis method. Through the laboratory analysis, the residual stress along the circumference direction was too low to cause the fracture and no corrosion phenomenon was found near crack origin. Also the metallographic structure and the hardness test were shown no abnormal phenomenon. The chemical element content was also qualified to the standard. Overload phenomenon was shown through the FEA analysis. The root cause of the fracture was shown to be overloading and corrective actions were adopted to prevent the incident reoccurring.

The limit switch plates of nuclear power plant unit 1 in the turbine bypass system valve are finding multiple fractures. On the basis of metallographic analysis and vibration analysis, the stress state of the pressure plate is simulated and calculated. The results show that there are some creases in the original plate of the limit switch and the installation error of the pressure plate is the main reason for the break.

某CPR1000核电厂汽轮机高压调阀动力油软管发生数次漏油，使机组被迫降功率进行故障处理。应用根本原因分析方法，对软管漏油事件可能存在的故障模式进行排查和论证，分析油压脉动与控制卡死区设置的关系，并对金属波纹管的疲劳寿命和可靠性进行评估。结果表明，软管漏油的原因是阀门开度控制不稳定导致软管油压脉冲波动大发生疲劳开裂，给出改进措施。

In the nuclear power station, the expansion joint of moisture separator re-heater (MSR for short) was founded locally folding deformation under the outage condition. Folding deformation increasing will lead expansion joint leak, it would cause emergency stop when leaking seriously. To solve these problems, this paper analysis mainly on three aspects: the material organization performance, the expansion joint installation and the stress characteristic of expansion joint. Both the verticality deviation in the process of installation and the material hardness value exceed standard are the root cause of these problems. At the end of the paper, the improvements have been put forward for this problem.

In this paper, the fracture analysis of the planet support, which was made of aluminium alloy and used in an electric actuator, was investigated. The laboratory analysis was conducted to find out whether there are defects generated during manufacturing process. Besides, the finite element analysis was carried out to calculate the maximum tensile stress and compared it with the material strength. The mechanism of the fracture was found to be low-cycle fatigue.

Equipment Failure Root Cause Analysis (ERCA) methodology is employed in this paper to investigate the root cause for charging pump’s pressure fluctuation of chemical and volume control system (RCV) in pressurized water reactor (PWR) nuclear power plant. RCA project task group has been set up at the beginning of the analysis process. The possible failure modes are listed according to the characteristics of charging pump’s actual pressure fluctuation and maintenance experience during the analysis process. And the failure modes are analysed in proper sequence by the evidence-collecting. It suggests that the gradually untightened and loosed shaft nut in service should be the root cause. And corresponding corrective actions are put forward in details.

The motor shaft rupture incident of Ling’ao nuclear power plant was analyzed by the international popular technique of root cause analysis.Firstly,all the probable failure modes of the motor rupture cause were analyzed with the efficient analytical techniques of Metallographic,Scanning Electron Microscope,Spectral Element Analysis,Stress Analysis and the Feedback of the Maintenance and Vibration test.And then the non-related failure modes were rejected,and the root cause and the contributor cause of the motor rupture were evidenced.Finally,the efficient maintenance and management advice are given to ensure the similar motor in a safe and reliable condition.

When all of bypass feedwater isolation valves of Daya Bay and Ling'ao NPPs were inspected under disassembled condition, it was found that the belt eyes were damaged in various degrees. The analysis on macro appearance, chemical composition, metallographic, Scanning Electron Microscope and fluid mechanics simulation were carried out on the damaged belt eyes. The results show that the flow rate of belt eye is well above the manufacturer's recommendation so that flow accelerated corrosion and cavitation erosion occur on the belt eyes. According to the damage causes of the belt eyes, corresponding corrective actions are proposed.