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. ************

核燃料组件在操作过程中主要暴露于高速轴向流。在轴向流条件下，燃料组件会经历流动湍流引起的随机振动。所产生的湍流激发已得到充分了解，并在燃料组件的设计阶段被解释，从而确保了燃料机械完整性。对于某些设计和/或操作条件，燃料组件可以暴露于更复杂的流动条件下，这导致了更高的振动，在某些情况下，燃料杆螺纹磨损和故障。最严重的是，燃料组件会横向（部分）跨流到燃料组件的纵轴（部分）交叉流。例如，横向流量可能是由较老植物中的核心挡板板分离引起的。结果是强大的局部跨流，特别是对于束外围的燃油棒。由于植物继续运作40年的阈值，因此由局部跨流引起的网格杆折射磨损引起了重大关注。对于某些植物，特定的设计特征还可能在燃油束中引入跨流。为了减轻冷却液事故损失（LOCA）的极端压力（LOCA），策略性地位于LOCA孔或插槽中已纳入反应堆芯，该芯将高速射流流横向引入燃油棒。目前的项目解决了由轴向/横向流组合引起的燃料束振动的问题。该项目的主要目的是对圆形横截面横射流流以及平面喷气机的燃油束动力学发展，并通过正常的燃油捆绑插槽。从更广泛的角度来看，该项目旨在发现这些复杂的轴向/横向流动的燃料振动和不稳定性的基本机制。预期基本结果的重要性超出了核场。高速复杂的流动在从能源产生到化学工业的各种工业环境中遇到。因此，预计该研究结果将在更广泛的应用中为加拿大行业做出重大贡献。 ************