Vibration of fuel bundles subjected to combined axial and localized cross-flow

轴向和局部横流组合作用下燃料棒束的振动

• 批准号: 529585-2018
• 负责人: Mureithi, Njuki
• 金额: $ 5.07万
• 依托单位: École Polytechnique de Montréal
• 依托单位国家: 加拿大
• 项目类别: Collaborative Research and Development Grants
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=660451
• 关键词: Vibration; fuel; bundles; subjected; combined

Nuclear fuel assemblies are exposed to primarily high speed axial flow during operation. Under axial flow conditions, the fuel assembly undergoes random vibration induced by the flow turbulence. The resulting turbulence excitation is well understood and has been accounted for at the design stage of the fuel assemblies thus ensuring fuel mechanical integrity. For certain design and/or operating conditions, the fuel assemblies can be exposed to more complex flow conditions which have led to significantly higher vibrations and in some cases fuel rod fretting wear and failure. Most serious is the case where the fuel assembly is subjected to (partial) cross-flow transverse to the longitudinal axis of the fuel assembly. Transverse flow may, for instance, result from core baffle plate separation in older plants. The result is strong localized cross-flow particularly for fuel rods in the bundle periphery. The grid-rod fretting wear induced by the localized cross-flow is of significant concern as plants continue to operate beyond their 40 year threshold. For some plants specific design features may also introduce cross-flow in the fuel bundles. To mitigate extreme pressures in the case of a Loss of Coolant Accident (LOCA), strategically located LOCA holes or slots have been incorporated in the reactor core, which introduces a high speed jet flow transverse to the fuel rods. The present project addresses the problem of fuel bundle vibration induced by combined axial/transverse flow. The primary goal of the project is to develop an understanding of the fuel bundle dynamics for transverse jet flows of circular cross-section as well as planar jets through slots normal to the fuel bundle. More broadly, the project aims to uncover the fundamental mechanisms underlying fuel vibration and instabilities for these complex axial/transverse flows. The importance of the expected fundamental results goes beyond the nuclear field. High speed complex flows are encountered in a wide range of industrial settings ranging from energy generation to chemical industries. The research results are therefore expected to significantly contribute to Canadian industries in this wider range of applications. ************

核燃料组件在运行过程中主要暴露在高速轴流中。在轴向流动条件下，燃料组件受流动湍流诱导的随机振动。由此产生的湍流激励是很好理解的，并在燃料组件的设计阶段考虑到了这一点，从而确保了燃料机械的完整性。对于某些设计和/或运行条件，燃料组件可能暴露在更复杂的流动条件下，这会导致更高的振动，在某些情况下，燃料棒微动磨损和故障。最严重的情况是燃料组件受到横跨燃料组件纵轴的(部分)横流。例如，在较老的工厂中，横向流动可能是由于堆芯挡板分离造成的。其结果是强烈的局部横流，特别是对于束状外围的燃料棒。局部横流引起的栅极微动磨损是一个令人担忧的问题，因为电厂的运行年限超过了40年。对于一些工厂，特殊的设计特点也可能在燃料束中引入横流。为了在发生冷却剂丢失事故(LOCA)的情况下缓解极端压力，反应堆堆芯中加入了位于战略位置的LOCA孔或槽，从而引入了横跨燃料棒的高速射流。本课题研究的是轴向/横向组合流动引起的燃料束振动问题。该项目的主要目标是了解圆形截面横向射流和平面射流通过垂直于燃料束的狭缝时的燃料束动力学。更广泛地说，该项目旨在揭示这些复杂的轴向/横向流动的燃料振动和不稳定性背后的基本机制。预期的基本结果的重要性超出了核领域。从能源生产到化学工业的各种工业环境中都会遇到高速复杂的流动。因此，预计研究结果将对加拿大工业在这一更广泛的应用领域做出重大贡献。************