Diffusion of corrosion agents through an engineered barrier system

许多国家正在研究安全储存用过核燃料的长期解决办法。加拿大核废料管理组织（NWMO）选择的其中一个解决方案是使用位于地面以下数百米的深层地质储存库（dgr）。DGRs将使用过的燃料罐（UFC）储存在工程屏障系统（EBS）周围，该系统由铜涂层（作为腐蚀屏障）和包裹在UFC周围的高压实膨润土（HCB）组成。HCB与水接触后膨胀，因此可以密封储存库内的空隙，并提供适度的导热介质。它还可以减缓地下水渗透，并在UFC决口的情况下延缓放射性核素的移动。此外，HCB可以通过限制可能存在的微生物的空间和水的可用性来抑制容器附近的微生物活动。然而，硫化物的扩散会导致微生物影响腐蚀（MIC），可能导致屏障的早期失效。拟进行的研究将研究影响硫化物向UFC表面扩散的因素。该项目将包括在一系列潜在的储存库条件下进行扩散实验，这些条件基于当前加拿大的设计规范和对DGR条件的预测。实验研究的结果将用于进一步扩展和验证三维计算机模型。由此产生的模型将能够进行参数化研究，以改进和优化加拿大DGR的设计。这项研究的结果将确定可能导致更高腐蚀速率的关键参数，从而改进NWMO的EBS设计，并为加拿大人提供一种安全和可持续的乏燃料处置方法。这项研究**将解决有关腐蚀物质在地下环境中通过工程屏障系统扩散的重要科学问题，并将增强预测建模能力，以**加强赞助机构的长期DGR设计/性能标准。

Many countries are studying long-term solutions for safe storage of used nuclear fuel. One such solution,**selected by the Canadian Nuclear Waste Management Organization (NWMO), is the use of deep geological**repositories (DGRs) that would be located several hundred metres below ground level. DGRs would store used**fuel canisters (UFCs) surrounded by an engineered barrier system (EBS), composed of copper coatings to act as**a corrosion barrier and highly compacted bentonite (HCB) that surrounds the UFC. HCB swells upon contact**with water and can therefore seal gaps within the repository and provide a moderately thermally conductive**medium. It can also slow groundwater infiltration and retard the movement of radionuclides in the event of a**UFC breach. In addition, the HCB can suppress microbial activity near the container by restricting space and**water availability to microbes that may be present. However, diffusion of sulphide can result in microbially**influenced corrosion (MIC), potentially causing early failure of the barrier. The proposed research will**investigate the factors that can affect sulfide diffusion to the UFC surface. The project will include diffusion**experiments performed under a range of potential repository conditions, based on current Canadian design**specifications and predictions for DGR conditions. The results of the experimental studies will be used to**further expand and validate a three-dimensional computer model. The resulting model will be capable of**parametric studies to refine and optimize the design of the Canadian DGR. The results of this study will**identify key parameters that may result in higher corrosion rates, leading to a refinement of NWMO's EBS**design and providing Canadians with a safe and sustainable method of used nuclear fuel disposal. This study**will address significant scientific questions regarding diffusion of corrosive species through the engineered**barrier system in sub-surface environments, and will also enhance predictive modelling capabilities to**strengthen the sponsoring agency's long-term DGR design/performance criteria.