The micromechanics of fracture of hydrides in Zr-2.5Nb CANDU pressure tubes

CANDU反应堆在向安大略省和加拿大提供清洁能源方面作出了重大贡献。安大略省超过50%的电力是由CANDU反应堆产生的。大多数CANDU反应堆建于20世纪70年代和80年代，正在老化。为了继续运行这些反应堆，工程师必须向监管当局证明它们是安全的。决定CANDU反应堆寿命的主要部件之一是含有燃料束的锆合金压力管，它将热水冷却剂与冷慢化剂分开。在操作过程中，热水中的氢向管中产生的缺陷扩散，随着时间的推移，形成一种称为氢化锆的脆性相。为了确保管道的完整性和反应器的安全，重要的是要证明裂缝不会在这些氢化物中成核。该项目着重于利用先进的数值技术和基于衍射的实验来了解在缺陷附近形成的氢化物是如何破裂的，以及这种裂缝是如何导致失败的。有限元素模型将在西部大学开发和使用，并在研究生的帮助下，在加拿大核实验室进行实验，以研究纳米和中观尺度上裂缝的形成。这将有助于理解控制氢化物断裂的潜在机制。这项研究的结果有望帮助提高核工业中使用的模型的准确性，并提高CANDU反应堆堆芯中使用的压力管的寿命。

CANDU reactors have been contributing significantly in providing clean energy to Ontario and Canada. More than 50% of electricity in Ontario is generated by CANDU reactors. Most of CANDU reactors are built in 1970s and 1980s and are aging. In order to continue to operate these reactors, engineers are required to demonstrate to regulatory authorities that they are safe. One of the main components that determine the lifetime of CANDU reactors is the zirconium-alloy pressure tubes that contain fuel bundles and separate the hot water coolant from the cold moderator. During operation, hydrogen from hot water diffuses towards the flaws induced in the tube and with time, forms a brittle phase called zirconium hydrides. To ensure the integrity of the tubes and safety of the reactors, it is important to show that a crack will not nucleate in these hydrides. This project focuses on using advanced numerical techniques and diffraction-based experiments to understand how the hydrides that form in the vicinity of flaws will crack and how such cracks lead to failure. Finite element models will be developed and used at Western University, and with the help of graduate students, experiments will be done at Canadian Nuclear Laboratories to study formation of cracks at nano and meso-scales. This will help understand the underlying mechanisms that control fracture of hydrides.The results from this research are expected to help improve the accuracy of the models used in nuclear industry and improve the lifetime of the pressure tubes used in the core of CANDU reactors.