Addressing self-irradiation damage and its impact on the long-term behaviour of nuclear waste matrices

核裂变提供了一种可靠的低碳能源，但是，由于核反应堆运行产生的核废料需要适当的处理和密封在耐用的材料中，以确保生物圈在近期和长期的将来不受放射性元素的污染。地质处置（GD）——包括将宿主材料限制在一个安全屏障（通常是一个金属罐）内，然后将这些废物包装永久沉积在一个预先选定的地质地点——现在是包括英国在内的一种国际公认的方法。然而，几千年后，外层的安全屏障会被腐蚀，宿主物质会暴露在周围的地质条件下。当与水/湿气接触时，放射性元素可能从宿主基质释放到周围的地质环境中，从那里它们可以被运送到生物圈中。了解废物包装的长期变化——从其制造之日开始——是解决放射性同位素最终释放问题的关键因素。除了腐蚀外，在地质处理条件下，废物包装会发生变化的一个原因是，受限制的放射性同位素的放射性衰变会在原子水平上破坏宿主基质，称为自辐照损伤。这种损害在数十万到数百万年的积累可能会改变废物包装的化学和机械耐久性。这些辐照引起的修饰对放射性同位素的最终释放有重大影响。因此，解决废物包装的辐射稳定性问题是证明地质处置长期安全性的重要组成部分。这项研究计划将利用哈德斯菲尔德大学的迈阿密辐照设施来研究自辐照损伤的影响和He在各种类型的废物包装中的积累，从玻璃到玻璃陶瓷复合材料。采用原位双离子束辐照的透射电子显微镜，对辐照引起的改性进行实时监测。双离子束辐照是核废料形式中最接近自辐照损伤的方法，可产生可靠和现实的结果。这些离子辐照效应将与与核工业伙伴合作进行的锕系元素掺杂研究进行比较，从而可以确定模拟自辐照损伤所需的辐照条件。将对浸出（凝胶）和未浸出的材料进行研究，以了解辐照引起的废物包装演变，并解决辐射损害对浸出的影响，反之亦然。通过与外部合作伙伴合作，如澳大利亚ANSTO、法国CEA Marcoule、剑桥大学和英国国家核实验室，该提案将汇集国际公认的研究人员的经验和专业知识，以更好地了解在地质处置条件下，包括浸出在内的自辐射损害所导致的废物形态演变。

Nuclear fission offers a reliable low carbon source of energy, but, the nuclear waste generated as a result of nuclear reactor operation needs proper treatment and confinement in a durable material to ensure that the biosphere is not contaminated with radioactive elements in the near and long-term future. Geological disposal (GD) - which involves confining the host material inside a safety barrier (usually a metal canister) and then permanent deposition of such wastepackages in a pre-selected geological site - is now an internationally accepted methodology including the UK. Nonetheless, after thousands of years, the outer safety barrier will get corroded and the host material will be exposed to the surrounding geological conditions. When in contact with water/moisture, the radioelements may be released from the host matrix into the surrounding geology from where they can be transported into the biosphere. Understanding long-term changes in the wastepackages -starting from the day of their fabrication - is a key element in addressing the eventual release of the radioisotopes. Besides corrosion, one of the reasons why the wastepackages will change under geological disposal conditions is the fact that radioactive decay of the confined radioisotopes will damage the host matrix at atomic level called as self-irradiation damage. This damage accumulation over hundreds of thousands to millions of years can potentially alter the chemical and mechanical durability of the wastepackages. These irradiation induced modifications can have a significant effect on the eventual release of the radioisotopes. Thus, addressing radiation stability of the wastepackages is an essential part of demonstrating long-term safety of the geological disposal.This research proposal will utilize MIAMI irradiation facility at the University of Huddersfield to study the effects of self-irradiation damage and He accumulation in various types of waste packages ranging from glasses to glass-ceramic composites. Using a transmission electron microscope with in-situ dual-ion-beam irradiation, the irradiation induced modifications will be monitored in real time. The dual-ion-beam irradiation represents the closest analogue to self-irradiation damage in nuclear wasteforms yielding reliable and realistic results. These ion irradiation effects will be compared with actinide doping studies to be undertaken in collaboration with nuclear industry partners, thereby, allowing establishing the irradiation conditions necessary to simulate the self-irradiation damage. The research will be undertaken on leached (gels) and non-leached materials to understand the irradiation induced evolution of the wastepackages and address the effect of radiation damage on the leaching and vice versa. By collaborating with external partners such as ANSTO Australia, CEA Marcoule France, University of Cambridge and, National Nuclear Lab UK, this proposal will bring together the experience and expertise of internationally recognised researchers to develop a better understanding of the wasteform evolution due to self-irradiation damage under geological disposal conditions including leaching.