Diversity and potential activity of microorganisms present in natural clay and bentonite: Key components of deep geological repositories for used nuclear fuel

负责使用过的核燃料管理的机构选择在结晶岩层或沉积岩层的工程储存库中进行深层地下储存，作为应对不断增长的使用过的燃料库存的一种安全、长期的解决方案(10万至100万年)。在如此长的时间内，本地或引入的微生物的代谢活动可能会影响储存库的完整性(例如，通过生产硫化物腐蚀燃料罐，或通过产生可能对储存库加压并导致粘土屏障破裂的气体)。此外，最近对瑞士特雷山1.7亿年前的沉积沉积物作为寄主岩层的适宜性的研究表明，各种微生物的数量非常少，包括那些具有潜在硫酸盐还原能力的微生物，当提供电子供体来源时，这些数字显著增加。这些发现的意义尚不确定，但预计会有适用于加拿大深层地质储存库(DGR)概念的技术转让。拟议的研究将调查微生物可能影响使用过的核燃料的DGR关键成分的各种情况，包括古代粘土中蕴藏的微生物种群的应用和进化意义，以及储存库大气从氧化状态到还原状态的转变。模拟储存库条件的模型系统将有助于评估工程过程和条件在关键微生物的生长和活性方面的表现，特别是腐蚀性和代谢中间体的形成程度。各种工程屏障系统组件之间的接口为生物膜的形成提供避难所并增强代谢活性也是一个关键目标。这些知识对于确保加拿大DGR被设计成减轻预期储存库生命周期中可能发生的微生物影响，以及帮助开发预测计算机模型以加强加拿大DGR的长期设计和性能标准是重要的。

Agencies responsible for used nuclear fuel management have selected deep underground storage in engineered repositories in either crystalline or sedimentary rock formations as a safe, long-term solution (100,000 to 1,000,000 years) to the growing used fuel inventory. Over such long time frames, potential exists for the metabolic activities of either indigenous or introduced microbes to impact the repository integrity (e.g., by corroding fuel canisters via sulphide production, or by producing gases that could pressurize the repository and cause fractures in the clay barrier). As well, recent studies examining the suitability of 170 million year-old sedimentary deposits at Mont Terri, Switzerland, as a host rock formation revealed the presence of very low numbers of a variety of microbes, including those with potential sulphate reducing capabilities, and when a source of electron donors was provided, these numbers increased significantly. The significance of these findings is not yet certain; however, technology-transfers applicable to the Canadian deep geological repositories (DGR) concept are anticipated. The proposed research will investigate various scenarios whereby microorganisms may impact key components of DGR for used nuclear fuel, including the applied and evolutionary significance of microbial populations harboured in ancient clays like the Mont Terri formation, as well as transformation of the repository atmosphere from an oxidizing to reducing state. Model systems simulating repository conditions will help to evaluate the performance of engineered processes and conditions in terms of the growth and activity of key microorganisms, and in particular, the extent to which corrosive and metabolic intermediates are formed. The potential for interfaces between the various engineered barrier system components to provide refuges for biofilm formation with enhanced metabolic activity is also a key goal. Such knowledge is important to ensure that Canadian DGRs are engineered to mitigate microbial effects that may occur over the expected repository life cycle, and to aid in the development of predictive computer models that strengthen Canada's long-term DGR design and performance criteria.