Development of a sustainable solution for the elimination of helium in copper cold spray process for used nuclear fuel containers

在过去的几十年里，加拿大的核反应堆已经生产了近260万个使用过的燃料棒。预计这一数字在未来40年内将翻一番。加拿大只是在最近才通过一项行动方针，** 处理长期封闭乏核燃料的问题，由核废物管理组织 ** 负责设计和执行加拿大的计划。对长期 ** 安全可靠的管理备选方案进行评估后，开发了一种将 ** 加拿大的废燃料集中封闭和隔离在一个深层地质处置库中的办法。加拿大设计与其他设计的不同之处 ** 在于所提出的耐腐蚀外部铜涂层。与现有的双壳外包装 ** 设计（钢壳上的厚铜套管）相反，耐腐蚀铜涂层更薄（3 mm厚），并与钢壳一体化。这种设计大大减少了每个UFC** 所需的铜量和钢壳上的机械应力。西北气象组织选择电沉积在钢容器上产生铜 ** 涂层，然后将其装载用过的核燃料棒束并用铜涂层盖端封闭。选择冷气动力喷涂（CGDS或冷喷涂）作为首选 ** 技术，以完成安全壳和盖端接头（封闭焊接区）的铜涂层。**西北气象组织仍在寻求一种新的创新方法，以减少在CGDS过程中使用氦气。增强CGDS涂层附着力的另一种方法是在颗粒撞击之前控制基材温度。该提案旨在建立在少数有限的研究基础上，这些研究强调了基材 ** 预热作为CGDS之前的表面制备方法的潜力。可以预见，在通过CGDS在钢上涂覆铜涂层之前 **，适当的基材加热可以提高涂层的附着强度（从 ** 增加的机械和冶金结合），并允许仅使用氮气作为工艺气体。该 ** 将代表用于封闭焊接区的CGDS涂层的安全、高效和具有成本效益的解决方案。

Canadas nuclear reactors have produced almost 2.6 million used fuel bundles over the last decades. This**number is expected to double over the next 40 years. Only very recently has Canada adopted a course of action**to deal with the long-term containment of the spent nuclear fuel, with the Nuclear Waste Management**Organization (NWMO) responsible for designing and implementing Canada's plan. Assessment of long-term**safe and secure management options has led to the development of a centralized containment and isolation of**Canada's used fuel in a deep geological repository (DGR). What differentiates the Canadian design from others**is the corrosion-resistant outer copper coating that is proposed. As opposed to existing dual-shell overpack**designs (thick copper sleeve on steel shell), the corrosion resistant copper coating is thinner (3 mm thick) and**integrally bonded to the steel shell. This design reduces drastically the amount of copper required for each UFC**and mechanical stresses on the steel shell. NWMO has selected electrodeposition to produce the copper**coatings on the steel vessels prior to loading them with used nuclear fuel bundles and closing them with a**copper coated cap end. Cold Gas Dynamic Spraying (CGDS or cold spray) was selected as the preferred**technique to complete the copper coating at the containment vessel and cap end junction (closure weld zone).**NWMO is still seeking a new innovative way to alleviate the use of helium in the CGDS process. An**alternative approach to enhance CGDS coating adhesion is the control of substrate temperature prior to particle**impact. This proposal aims to build on few limited studies that have highlighted the potential of substrate**preheating as a surface preparation method prior to CGDS. It is envisioned that proper substrate heating prior**to applying copper coating on steel by CGDS could result in enhanced coating adhesion strength (from**increased mechanical and metallurgical bonds) and allow the use of nitrogen only as the process gas. This**would represent a safe, highly efficient and cost-effective solution for the CGDS coating of the closure weld zone.