Modelling vibration of 37-element CANDU fuel string in an aged pressure tube

加拿大的几个核电站以及加拿大以外的所有CANDU 6反应堆都使用了含有37个元素的CANDU燃料束。随着国内外所有商用CANDU反应堆进入其第三或第四个十年的服务，这些反应堆的安全运行取决于我们评估老化如何导致燃料串微动和压力管磨损的能力。消除商业核电站因微动引起的磨损而导致的压力管过早失效，将减少不必要的反应堆关闭，为加拿大带来巨大的经济和环境效益。最终，这项研究将确保未来CANDU反应堆的设计满足与整个反应堆寿命和维护停机计划兼容所必需的磨损规格。这项研究的结果将有助于加拿大新成立的私营公司Candu在国内外核电行业的领导地位。来自核电站的状态报告表明，燃料串在运行过程中会振动，过度的振动会导致压力管的磨损，冷却剂中不希望出现的碎片数量，以及由于部件失效而导致燃料束完整性的损失。微动磨损损伤已成为核燃料设计工程师和分析人员关注的重要安全问题。与其他反应堆燃料一样，CANDU反应堆燃料在运行过程中暴露在恶劣的热、机械和辐射条件下，但CANDU反应堆组件老化的影响在很大程度上是未知的。到目前为止，还没有行业通用的工具来量化燃料管柱振动和压力管磨损。该项目将通过开发一种新的最先进的计算机程序来模拟运行条件下旧CANDU反应堆燃料通道中的微动磨损，从而解决这一知识差距。该计算机程序将用于评估实际操作条件下的微动磨损，并将假设许可机构在安全分析中经常要求的操作场景。长期目标是使计算机程序在核工业中得到充分验证和认证，用于量化燃料微动和压力管磨损。

The 37-element CANDU fuel bundles are used in several nuclear generating stations in Canada, and in all CANDU 6 reactors outside Canada. With all commercial CANDU reactors at home and abroad entering into their third or fourth decade of service, the safe operation of these reactors depends upon our ability to assess how aging results in fuel string fretting and pressure tube wear. Eliminating any premature failure of pressure tubes due to fretting-induced wear in commercial nuclear power plants will reduce unnecessary reactor shutdowns, resulting in significant economic and environmental benefits to Canada. Ultimately, this research will ensure that the design of future CANDU reactors meets the wear specifications necessary for compatibility with overall reactor life and maintenance outage schedules. The results of this research will help Candu, a new Canadian-owned private company, to secure its leadership position in the nuclear power industry at home and abroad. Condition reports from nuclear generating stations indicate that fuel strings vibrate during operations, and that excessive vibration causes wear of pressure tubes, undesired amounts of debris in the coolant, and loss of fuel bundle integrity due to the failure of components. Fretting-wear damage has become a significant safety concern for nuclear fuel design engineers and analysts. Like other reactor fuels, CANDU reactor fuel is exposed to harsh thermal, mechanical, and radiation conditions during operation, yet the effects of CANDU reactor component aging are largely unknown. To date, there is no industry-wide tool to quantify fuel string vibration and pressure tube wear. The project will address this knowledge gap by developing a new state-of-the-art computer program for simulating fretting wear in a fuel channel in an aged CANDU reactor under operating conditions. This computer program will be used to assess fretting wear for actual operating conditions and will also postulate operating scenarios often required by the licensing bodies in safety analysis. The long-term objective is to have the computer program fully validated and certified for use in the nuclear industry for quantifying fuel fretting and pressure tube wear.