Investigation of the Dynamic Characteristics of CANDU Fuel Bundle

CANDU堆燃料棒束故障和燃料棒束端板长期开裂的历史由来已久。这些故障中的大多数是由于一次系统热输送泵产生的声压脉动。例如，在1990年，达林顿核电站中的一个燃料棒束由于燃料元件的过度振动而损坏。发现燃料棒束端板断裂，随后的检查在1号和2号机组的一些燃料通道中发现了严重的磨损痕迹。燃料棒束端板中的裂纹是由燃料棒束的轴向响应引起的，燃料棒束的轴向响应是由在主热传输（PHT）叶片通过频率下产生的声压脉动触发的。最近，在布鲁斯电力核电站的一些燃料棒束中观察到端板开裂。如果外部激励频率（例如由PHT泵产生的激励频率）与燃料棒束的固有振动频率之一匹配，则导致端板开裂的燃料棒束振动问题恶化。因此，燃料棒束的动态特性的精确知识对于设计可以实施以缓解该问题的有效缓解技术至关重要。到目前为止，很少有知识，如果有的话，燃料棒束的动态特性和辐射对其响应的影响。因此，本项目的主要目标是实验和数值研究CANDU燃料的动态特性，包括辐射对燃料棒束动力学的影响。该项目的输出将提供急需的有关燃料棒束特性的信息，以帮助现有的CANDU运营商管理和缓解燃料棒束的振动问题和端板开裂问题。这不仅有助于提高CANDU堆燃料棒束的安全性和可靠性，从而直接有利于加拿大经济，而且还可用于未来的CANDU堆，以避免燃料棒束故障。

There has been a history of failures in CANDU fuel bundles and chronic cracking of fuel bundle end-plates. Most of these failures were attributed to the acoustic pressure pulsations generated by the primary system heat transport pumps. For example, in 1990, one of the fuel bundles in the Darlington nuclear power plant was damaged as a result of excessive vibration of the fuel elements. The fuel bundle endplates were found broken and subsequent inspections found severe wear marks in a few fuel channels in Units 1 and 2. The cracks in the fuel bundle endplates were caused by axial response of the fuel bundle, which was triggered by acoustic pressure pulsations generated at the primary heat transport (PHT) vane-passing frequency. More recently, endplates cracking in some fuel bundles has been observed at Bruce Power Nuclear Generating plant. The fuel bundle vibration problem that results in end plate cracking is exasperated if an external excitation frequency, such as that generated by the PHT pumps, matches one of the natural vibration frequencies of the fuel bundle. As such, the precise knowledge of the dynamic characteristics of the fuel bundle is of paramount importance to devise effective mitigation techniques that can be implemented to alleviate this issue. Up to date there is little knowledge, if any, about the dynamic characteristics of fuel bundles and the effect of radiation on their response. Therefore, the main objective of this project is to experimentally and numerically investigate the dynamic characteristics of CANDU fuel including the effect of radiation on the fuel bundles dynamics. The output of this project will provide a much needed information about the fuel bundle characteristics to aid existing CANDU operators to manage and mitigate the vibration problems and the end plate cracking issue of fuel bundles. This will not only support the increased safety and reliability of CANDU fuel bundles, which will directly benefit the Canadian economy, but could also be used in future CANDU reactors to avoid fuel bundle failures.