In situ time-dependent characterisation of corrosion processes in nuclear waste storage and GDF environments

联合王国政府致力于通过长期地质处置和地面安全临时储存来管理放射性核废物。这些废物将储存在金属罐中，在地面储存、地质处置库在安放金属罐期间的运作以及最后关闭之后的整个过程中，腐蚀是对其完整性的一个关键的潜在威胁。我们计划研究一些可能的腐蚀过程的机制和速率，开发表征方法，这些方法将在未来研究类似的过程中普遍有用。金属的局部腐蚀发生在潮湿的环境中，通常发生在金属表面下的空腔中。评估腐蚀总速率或渗透深度的最常用方法是在腐蚀过程结束时制作金属的横截面，因此丢失了有关形状或化学性质随时间演变的任何信息。然而，通过使用来自同步加速器源的高强度X射线，现在可以在真实的时间内原位研究这些过程，因为X射线可以很容易地穿透水和金属表面。腐蚀部位的3D形状可以用X射线显微断层扫描来确定，化学可以用衍射和光谱来评估。所有这些技术都可以在钻石，英国的同步加速器设施。当这些技术与先进的基于实验室的技术相结合时，将出现腐蚀过程的机制和速率的全貌，从而能够开发和验证以可靠科学为基础的腐蚀预测模型，这对于支持核废料储存的政策决策是必要的。我们的项目是伯明翰大学、曼彻斯特大学、布里斯托大学和戴蒙德大学的研究人员之间的合作。位于哈韦尔研究中心（钻石旁边）的一名研究员将领导研究工作，协调每所大学的博士生的X射线实验，他们还将使用基于实验室的研究技术。每个人都将有一个独立的研究项目：其中包括：不锈钢在地面储存条件下的大气腐蚀和开裂行为;不同不锈钢在含硫物质的水泥中的腐蚀;铀和镁诺克斯在水泥废物中的腐蚀行为（所有这些都与中级放射性废物有关），以及碳钢在粘土中的行为，粘土可能是乏燃料储存的候选材料。在节目的最后，我们将探讨辐射损伤对这些腐蚀问题的影响。我们将与该领域的工业和国际专家密切合作开展研究，他们承诺在我们每三个月举行一次的会议上向我们提供非正式建议，以换取我们的研究结果。随着我们研究的进展，我们正在开发的X射线技术将变得更加常规，以至于为英国和国际废物管理计划进行合同工作的工业用户将采用这种技术。这些方法也可能有益于其他应用，如混凝土中钢筋的腐蚀和石油管道的腐蚀。我们计划在钻石举行一次关于核废料储存腐蚀问题的国际研讨会，分享我们的研究结果，并讨论建立“遗产”方案的可能性。腐蚀样品，这将允许监测腐蚀的发展，在典型的环境中，多年甚至几十年。有一个持续的需要熟练的研究人员与知识，在这方面面积：我们将培训一名研究员和三名博士生，内容涉及核废料储存、机制和腐蚀过程建模以及X射线技术的使用，他们将能够随着国家核废料战略的发展继续开展这项工作。

The UK Government is committed to managing radioactive nuclear waste through long-term geological disposal with safe interim storage above ground. The waste will be stored in metal canisters, and corrosion is a key potential threat to their integrity throughout the process of above-ground storage, operation of the geological repository during emplacement of the canisters, and following its final closure. We plan to investigate the mechanisms and rates of a number of the likely corrosion processes, developing characterisation methods that will be generically useful for studying similar processes in the future. Localised corrosion of metals takes place in wet environments, often in cavities under the metal surface. The commonest method for evaluating the total rate of corrosion or depth of penetration is to make a cross-section of the metal at the end of a corrosion process, so that any information on the time evolution of the shape or chemistry is lost. However, by using highly-intense X-rays from a synchrotron source, it is now possible to study these processes in situ in real time, since the X-rays can easily penetrate the water and metal surface. The 3D shape of the corrosion site can be determined with X-ray microtomography, and chemistry can be assessed with diffraction and spectroscopy. All of these techniques are available at Diamond, the UK's synchrotron facility. When these techniques are combined with advanced lab-based techniques, a full picture of the mechanisms and rates of corrosion processes will emerge, enabling the development and validation of corrosion prediction models underpinned with sound science that are necessary for underpinning policy decisions on nuclear waste storage. Our project is a collaboration between researchers at the Universities of Birmingham, Manchester and Bristol and Diamond. A Research Fellow based at the Research Complex at Harwell (next to Diamond) will lead the research effort, co-ordinating the X-ray experiments of the PhD students based at each University, who will also use lab-based research techniques. Each will have an individual research project: these include the atmospheric corrosion and cracking behaviour of stainless steels in above-ground storage conditions, the corrosion of different stainless steels in cement containing sulfur species, and the corrosion behaviour of uranium and Magnox in cement wasteforms (all related to intermediate-level waste), and the behaviour of carbon steel in clay, which may be a candidate for storage of spent fuel. Towards the end of the programme we will explore the influence of radiation damage on some of these corrosion problems. We will carry out the research in close collaboration with industrial and international experts in the field, who have committed to giving us informal advice in return for information on our findings at our three-monthly meetings. As our research progresses, the X-ray techniques that we are developing will become more routine, to the point where they will be taken up by industrial users who carry out contract work for both UK and international waste management programmes. The methods are also likely to be beneficial to other applications such as corrosion of reinforcing bars in concrete and corrosion of oil pipelinesWe plan to hold an international workshop at Diamond on corrosion issues in nuclear waste storage to share our findings and discuss the possibility of establishing a programme of "legacy" corrosion samples that will allow monitoring of the development of corrosion in typical environments over years or even decades.There is a continuing need for skilled researchers with knowledge in this area: we will train a research fellow and three PhD students in issues surrounding nuclear waste storage, mechanisms and modelling corrosion processes, and the use of X-ray techniques who will be able to continue this work as the country's nuclear waste strategy evolves.