基于应变与加速度响应的核电厂小支管振动评价

核电厂存在大量的仪表管、取样管、排气管等小支管,其机械振动疲劳断裂是商业运行核电厂经常出现的问题。本文以阳江核电站二号机组GRE023管线的实测振动应力对其振动疲劳寿命进行了评价,采用有限元方法以加速度时程二次积分获得的位移时程为输入对其振动疲劳寿命进行了分析,获得了小支管振动疲劳瞬态动力分析关键参数设置方法,同时也为类似结构的减振改造设计积累了经验,为核电厂小支管振动治理提供了参考。     

核电厂小支管的模态与振动响应分析

随着核电机组运行年限的增加,小支管的振动疲劳缺陷变得越来越突出,给核电厂的安全、经济运行带来了威胁。因此,为了保障核电厂的安全运行,需要对敏感管的约束结构进行改造和优化。本文以国内某核电厂小支管为研究对象,通过现场实测与理论分析相结合的手段,获得了小支管的模态特性,结合现场实测数据,用谱分析的方法计算得到小支管在运行工况下的振动响应,计算结果表明,该小支管疲劳应力超过了疲劳许用交变应力,即该小支管为敏感管。通过本文的计算分析,不仅准确地判断出了敏感管,更为后续小支管的约束结构改造和优化提供了理论依据。     

核电厂小支管振动初始筛选原则与应用举例

根据国内外核电厂运行经验,在高振动条件下小支管（管径小于2英寸的连接支管）与母管连接处的焊缝容易疲劳失效,增大管内的放射性液体泄漏风险。岭澳核电厂十年定期安全审查（PSR）项目对反应堆冷却剂系统的一些辅助系统和专设安全系统的小支管振动疲劳情况进行普查,对振动过高的小支管进行了安全评估,对未通过评估的小支管采取相应的减振措施,以确保核电厂的安全运行。本文在调研分析主要核电国家初始筛选标准的基础上,确定了PSR项目的初始筛选原则,并举例介绍其应用。     

核电厂小支管振动评定方法与减振技术研究

根据ASME OM-S/G-2007 Part3,借鉴国内外核电厂在小支管振动评定方法与减振技术方面的反馈,本文系统地介绍了核电厂小支管振动的评定方法:振动位移评定、振动速度评定和振动交变应力评定。然后以岭澳核电厂L1ASG952VD所在小支管为研究对象,进行振动评定和减振技术研究,提出了优选减振措施和其他减振措施。这些评定方法和减振技术可为小支管的振动处理提供参考。     

两环路核电厂试验支管振动疲劳研究

针对国内二代改进型的两环路核电厂试验用支管中存在的振动疲劳问题,文章提出了一种确定疲劳振动的测量和计算分析方法,并运用该方法对国内某两环路核电厂小支管进行了工况分析、振动测量和最大有效振动速度计算,同时采用结构力学有限元程序ANSYS软件对小支管的振动疲劳应力进行了分析。结果表明,该方法能够很好地诊断出小支管中存在的第一类敏感管和第二类敏感管,从而为判断在两环路核电厂试验中支管是否为敏感管提供了理论依据。     

大亚湾核电站小支管振动测量结果分析评定

大亚湾核电站在运行中,有部分辅助系统的小支管(管径不大于5.08cm)的振动较大,并有少数小支管出现振裂的情况,给核电站的安全运行带来不利影响.在大亚湾核电站十年安全审评时对辅助给水系统、安全壳喷淋系统、反应堆换料水池和乏燃料水池冷却和处理系统、化学和容积控制系统、反应堆硼和水补给系统、余热排出系统、安全注入系统和设备冷却水系统的潜在敏感管进行了现场振动测量.本文按相关要求对测量结果进行了分析评定,给出敏感管清单及改造建议.     

核电厂仪表管道振动疲劳耐久性能改进研究

针对役前及初始运行期间核电厂出现较多的仪表管道振动疲劳断裂问题,设计了两套不同规格及焊接方式的、端部带有集中质量的悬臂管道试验件。对试验件开展了宽带随机耐久试验,分析了试样振动交变应力幅、频率响应特征及疲劳寿命,结果表明,通过采取增大管道外径和壁厚、改变焊接形式等措施,能够显著改进结构低频共振、试样振动疲劳寿命分散性较大等问题,显著提升管道结构的振动疲劳耐久性能。     

核级不锈钢管座焊接区与母材区疲劳裂纹扩展性能对比研究

焊接接头广泛应用于核电站管座处,而疲劳裂纹扩展是导致焊接接头失效的重要原因之一。因此,研究焊接区材料的疲劳裂纹扩展和寿命预测方法对准确预测焊接接头的寿命具有重要意义。本文以核电厂常用的304L不锈钢焊缝材料为对象,研究不同载荷比、不同取样方向对疲劳裂纹扩展速率的影响;基于试验数据建立焊缝材料的疲劳裂纹扩展速率模型,并与美国机械工程师协会（ASME）标准中奥氏体钢进行对比。结果表明:不同取样方向对焊缝疲劳裂纹扩展速率的影响不大,但载荷比对其有较大影响,较低载荷比下,焊缝的疲劳裂纹扩展速率在某个应力强度因子幅值（?K）前高于母材的疲劳裂纹扩展速率,在其之后则低于母材,而较高载荷比下则恰恰相反。      

某核电厂低压安注泵小流量管线振动原因研究

由于小支管振动超标的敏感管问题是困扰所有核电站的难题。国内外投入了大量的人力和物力来解决敏感管问题。分析判断振动原因是解决敏感管问题的首要因素。本文用综合的技术手段对某核电厂安注系统低压安注泵小流量管线中的敏感管振动原因进行了分析研究。通过在管线上布置加速度计进行现场振动实测获得了管线的振动分布,通过振动加速度的时程的RMS值分布获得了节流孔板后方是振动最大的位置,通过对节流孔板后方的加速度进行频谱分析初步判断为节流孔板过分节流导致通过孔板的流体汽化而出现了汽蚀现象。通过对节流孔板的理论分析获得了节流孔板前后的压差并与阻塞压差进行比较进一步验证了节流孔板的过分节流现象。最后用CFD进行了三维流场分析获得了整个管线的详细流场分布,并得到了经过节流孔板后出现了流场中低于流体饱和蒸汽压的区域,该区域是流体汽化区。通过综合的手段最后确定导致该小流量管线振动高的主要原因是节流孔板的汽蚀。本文所用的方法对其他具有类似的振动现象的振动原因分析具有借鉴的意义。     

钴靶组件流致振动试验研究

采用数值分析与试验研究相结合的方法,通过模拟反应堆内真实边界与流速,获得了钴靶组件的振动频率、振型等振动特性参数以及0.75～2 kg/s不同冷却剂流速下的响应试验数据;利用综合数值计算与试验测试结果对结构进行了疲劳评价。分析结果表明,靶件在0.75～2 kg/s流速下的各种响应有效值较小,可满足10 a寿命期限。     

Vibration testing of full-scale structures

Vibration testing of nuclear reactor plant systems is discussed as a part of the determination of the response of such systems to earthquakes. The methods of ambient, harmonic excitation, and impulse testing are compared. Harmonic excitation tests provide a method of obtaining the complete dynamic characteristics of a system and of selectively studying each of the components of the system, e.g. containment, pressure vessel, steam generator. Generally, both ambient and impulse testing studies do not provide as much detailed information. Problems in interpreting test results are discussed, in particular the problems of differing frequency spectrum excitation level of the exciting force from strong-motion earthquakes and extrapolation of responses in the presence of non-linearities in the system behavior. The equipment, performance and evaluation of steady-state forced vibration tests and of impulse tests by detonating explosives are described.     

Vibration of nuclear fuel bundles

Several mathematical models have been proposed for calculating fuel rod responses in axial flows based on a single rod consideration. The spacing between fuel rods in liquid metal fast breeder reactors (LMFBRs) is small; hence fuel rods will interact with one another due to fluid coupling. The objective of this paper is to study the coupled vibration of fuel bundles. To account for the fluid coupling, a computer code (AMASS) is developed to calculate added mass coefficients for a group of circular cylinders based on the potential flow theory. The equations of motion for rod bundles are then derived including hydrodynamic forces, drag forces, fluid pressure, gravity effect, axial tension and damping. Based on the equations, a method of analysis is presented to study the free and forced vibrations of rod bundles. Finally, the method is applied to a typical LMFBR fuel bundle consisting of seven rods.     

Vibration Compacted UO2 Fuel,(III) Effects of Random Wave Vibration on Compacted Density

Random wave motion of characteristics and intensities measured in terms of frequency and normalized acceleration has been applied to vibratory compaction of UO₂ powder in a metal tube, and the results are compared with those obtained by other methods of vibration.

Densification proceeds rather slowly but steadily with random wave compaction, which moreover does not appear to produce the particle segregation on the top layers of the UO₂ powder experienced with sinusoidal and other forms of wave. Consequently, the densities obtained are consistently higher than by other methods of vibration at the same normalized acceleration level.

Acceleration peaks, and not average values, appear to be the predominant factor determining the efficacy of vibration in particle compaction, while displacement peaks contribute little either to compaction or to particle segregation.     

Vibration Compacted UO2 Fuel, (I) Effects of Sinusoidal Vibration on Compacted Density

A systematic study has been made on the effect of differences in conditions of applied vibration on the density obtained with a ternary grained powder of arc-fused and crushed UO₂ powder packed in a stainless steel cladding tube.

Comprehensive analysis is made of the relationships between densities obtained and vibration conditions, defined by combinations of two factors among four-i.e., frequency, displacement, velocity and acceleration. The highest density has been found to be obtained at the highest acceleration, provided that displacement is in the range of 10~30 μm, and this range is found to be the optimum condition for all levels of acceleration.

The process of vibratory compaction is discussed on the basis of the combination of different factors conducive to the compaction, segregation and disintegration of the powder particles.     

Vibration and stability of prestressed shells

Thin shells are widely used structural elements and are sometimes subjected to time-dependent loads after they have already acquired some prestress. The response of such a shell can be very different from that when the prestress is absent. The general methods of calculation of the response of the shell are discussed. The stability limit of the shell is viewed as a special result obtained in the free vibration analysis. An example of a typical containment shell of a nuclear power plant, housing the reactor, is worked out in detail.     

通风机叶片振动安全性分析

针对传统的叶片振动安全性调频分析方法的4种局限性,提出了一种叶片振动安全性动应力分析法.该方法可在实际动载荷未知的情况下,进行叶片动应力及叶片振动安全性分析.本文介绍了叶片振动安全性动应力分析法的特点,并通过实例说明了该方法的可行性.     

基于压力容器振动信号分析的堆芯吊篮壳型振动特性研究

核反应堆堆芯吊篮的振动状态直接关系到堆芯的安全运行,但堆芯吊篮处于高温和强辐照环境下,无法直接在吊篮上布置传感器测量其振动。本文利用安装在压力容器上的加速度计间接监测吊篮的振动,通过对多核电机组压力容器振动信号相干谱、自功率谱和互功率谱进行分析,获得吊篮壳型振动频率和振幅,并将分析结果与秦山核电厂二期1号机组试验实测值进行比较,分析结果与试验结果相近。研究表明通过对压力容器振动信号的监测与分析,能够有效识别堆芯吊篮壳型振动特性,为吊篮状态评价提供基础。      

秦山核电厂化容系统振动测量

本文简要地介绍了秦山核电厂化容系统在调试期间的振动测量。测量与调试同步进行；主要使用便携式测振仪对事先确定的测点进行现场实测。测量结果表明，泵的振动级别大部分达到Ａ级，管道的振动满足振动鉴定准则的要求。