Diffusion of corrosion agents through an engineered barrier system

许多国家正在研究安全储存用过的核燃料的长期解决办法。加拿大核废物管理组织选择的一种解决办法是使用位于地面以下几百米处的深层地质处置库。DGRs将储存用过的燃料罐（UFC），周围环绕着一个工程屏障系统（EBS），由铜涂层组成，阿萨腐蚀屏障和高度压实的膨润土（HCB），围绕着UFC。六氯代苯遇水膨胀，因此可以密封储存库内的缝隙，并提供适度的导热介质。它还可以减缓地下水渗透，并在aUFC破裂时延缓放射性核素的移动。此外，六氯苯可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，硫化物的扩散可导致微生物影响的腐蚀（MIC），可能导致屏障的早期失效。本研究将探讨影响硫化物扩散至UFC表面的因素。该项目将包括根据加拿大目前的设计规格和对DGR条件的预测，在一系列潜在处置库条件下进行的扩散实验。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ofparametric研究，以完善和优化加拿大DGR的设计。这项研究的结果将确定可能导致更高腐蚀率的关键参数，从而改进NWMO的EBSdesign，并为加拿大人提供一种安全和可持续的废核燃料处置方法。这项研究将解决有关腐蚀性物质通过地下环境中的工程屏障系统扩散的重要科学问题，还将提高预测建模能力，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 geologicalrepositories (DGRs) that would be located several hundred metres below ground level. DGRs would store usedfuel canisters (UFCs) surrounded by an engineered barrier system (EBS), composed of copper coatings to act asa corrosion barrier and highly compacted bentonite (HCB) that surrounds the UFC. HCB swells upon contactwith water and can therefore seal gaps within the repository and provide a moderately thermally conductivemedium. It can also slow groundwater infiltration and retard the movement of radionuclides in the event of aUFC breach. In addition, the HCB can suppress microbial activity near the container by restricting space andwater availability to microbes that may be present. However, diffusion of sulphide can result in microbiallyinfluenced corrosion (MIC), potentially causing early failure of the barrier. The proposed research willinvestigate the factors that can affect sulfide diffusion to the UFC surface. The project will include diffusionexperiments performed under a range of potential repository conditions, based on current Canadian designspecifications and predictions for DGR conditions. The results of the experimental studies will be used tofurther expand and validate a three-dimensional computer model. The resulting model will be capable ofparametric studies to refine and optimize the design of the Canadian DGR. The results of this study willidentify key parameters that may result in higher corrosion rates, leading to a refinement of NWMO's EBSdesign and providing Canadians with a safe and sustainable method of used nuclear fuel disposal. This studywill address significant scientific questions regarding diffusion of corrosive species through the engineeredbarrier system in sub-surface environments, and will also enhance predictive modelling capabilities tostrengthen the sponsoring agency's long-term DGR design/performance criteria.