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

英国政府致力于通过在地面上安全临时储存的长期地质处置来管理放射性核废料。废物将储存在金属罐中，在地上储存、地质储存库在安置期间和最终关闭后的整个过程中，腐蚀是对其完整性的关键潜在威胁。我们计划研究一些可能的腐蚀过程的机制和速率，开发对未来研究类似过程普遍有用的表征方法。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洞中。评估总腐蚀速度或渗透深度的最常见方法是在腐蚀过程结束时制作金属的横截面，这样就会丢失有关形状或化学成分随时间演变的任何信息。然而，通过使用来自同步加速器的高强度X射线，现在可以实时原位研究这些过程，因为X射线可以很容易地穿透水和金属表面。腐蚀部位的三维形状可以用X射线显微断层成像来确定，化学成分可以用衍射和光谱分析来评估。所有这些技术都可以在英国的同步加速器设施戴蒙德获得。当这些技术与先进的实验室技术相结合时，将全面了解腐蚀过程的机制和速率，从而能够开发和验证有可靠科学支撑的腐蚀预测模型，这些模型是支持核废料储存政策决策所必需的。我们的项目是伯明翰大学、曼彻斯特大学、布里斯托尔大学和戴蒙德大学的研究人员合作完成的。哈威尔(戴蒙德旁边)研究中心的一名研究员将领导这项研究工作，协调每所大学博士生的X射线实验，这些博士生也将使用基于实验室的研究技术。每个项目都将有一个单独的研究项目：这些项目包括不锈钢在地面储存条件下的大气腐蚀和破裂行为，不同不锈钢在含硫水泥中的腐蚀行为，铀和Magnox在水泥废料中的腐蚀行为(所有这些都与中级废物有关)，以及碳钢在粘土中的行为，这可能是乏燃料储存的候选对象。在课程接近尾声时，我们将探讨辐射损害对其中一些腐蚀问题的影响。我们将与该领域的工业和国际专家密切合作进行研究，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，以换取我们的调查结果。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，以至于工业用户将使用这些技术，他们为英国和国际废物管理计划执行合同工作。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输油管道的腐蚀。我们计划在钻石举办一个关于核废料储存中的腐蚀问题的国际研讨会，分享我们的发现，并讨论建立一个“遗留”腐蚀样本计划的可能性，该计划将允许监测典型环境中几年甚至几十年的腐蚀发展。在这一领域，我们仍然需要有技能的研究人员：我们将培训一名研究员和三名博士生，了解围绕核废料储存、机制和腐蚀过程建模的问题。以及使用X射线技术，随着国家核废料战略的发展，谁将能够继续这项工作。

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.