Characterisation and Decontamination of Radioactive Stainless Steel Waste

世界各地的核退役方案突出表明，必须更好地了解放射性核素如何相互作用并与材料表面结合。退役活动产生的废物预计数量巨大；因此，成本、安全和环境驱动因素都存在，以减少需要处置的所有类型的放射性废物的数量。受污染的金属占废物库存的很大比例，因为部件(如管道、船只和结构梁)在核作业期间受到污染。2016年，核退役管理局(NDA)报告称，仅英国就有大约3.2万吨受污染的中级废料(ILW)不锈钢。按照目前预计的约70,000 GB/立方米的垃圾处理速度，这一数量的垃圾加起来将是一项相当大的成本负债(约3亿GB)，需要由英国纳税人出资。如果考虑到其他形式的金属废物，以及来自英国以外的废物，这一价值将大大增加，挑战的规模也变得明显。彻底了解废物材料的性质对于核能部门降低退役成本至关重要。通过帮助利益攸关方了解他们面临的挑战，在规划退役作业和选择去污程序时，可以做出更明智的决定。该项目中提议的工作有助于选择最适当的退役战略，也有助于选择未来核设施的材料。因此，该项目最初的目标是利用最先进的设备和辅助工作来广泛表征一些真实的活跃植物样本，以建立对污染过程的机械理解。项目大纲该项目将包括两个关键阶段：第一阶段--这一阶段的重点是对从真实工厂获得的少量受污染的不锈钢样本进行充分鉴定。探索这些植物样本污染性质的辅助工作将在实验室规模受控条件下使用模拟污染溶液进行。像Sellafield的积极示范计划这样的举措将是学生学习“现实生活”活跃材料并为关键的核利益相关者创造新的知识储备的理想机会。这种合作的机会将通过塞拉菲尔德的综合项目团队进行安排。这项工作需要高分辨率的分析技术，因为预计这些材料上的放射性同位素浓度很低。这反过来又意味着需要获得NNL、钻石光源和曼彻斯特放射化学实验室等设施的专门设备。阶段2-在目标标本的特征确定之后，该项目的重点将转移到去污上。在核部门已经很好地认识到，将需要一个去污技术的‘工具箱’来使整个核不扩散区完全退役。然而，研究往往只关注一种技术，在没有直接比较的情况下，往往很难选择最合适的技术。通过对同一受污染的标本应用几种适当选择的去污方法，可以确定每种技术的利弊，并向业界提出建议。这项工作也将使去污技术研究进展到工业部署。EPSRC研究领域：核裂变(在能源主题下)

Nuclear decommissioning programmes across the world have highlighted the requirement for a greater understanding of how radionuclides interact and become bound to the surface of materials. The volume of waste arising from decommissioning activities is predicted to be substantial; therefore cost, safety and environmental drivers all exist to reduce the volume of all types of radioactive waste requiring disposal. Contaminated metals make up a significant proportion of the waste inventory as components (such as pipework, vessels and structural beams) become contaminated during nuclear operations. In 2016, the Nuclear Decommissioning Authority (NDA) reported that there is approximately 32,000 tonnes of contaminated intermediate level waste (ILW) stainless steel that exists in the UK alone. At a current predicted rate of ~£70,000/m3 to dispose of ILW, this volume of waste adds up to a considerable cost liability (~£300m) that will need to be funded by the UK taxpayer. When other forms of metallic waste are taken into account, as well as waste arising from outside the UK, this value becomes significantly larger and the size of the challenge apparent.A thorough understanding of the nature of waste materials is of vital importance for the nuclear sector in order to reduce the cost of decommissioning. Through helping stakeholders to understand their challenges, more informed decisions can be made when planning decommissioning operations and selecting decontamination procedures. The work proposed in this project supports the selection of the most appropriate decommissioning strategies and also feeds into the selection of materials in future nuclear facilities. Therefore, this project initially aims to extensively characterise a number of real active plant samples utilizing state-of-the-art facilities with supporting work to establish mechanistic understanding of contamination processes. This will inform decontamination strategies which will be tested in this work.Project OutlineThe project will involve two key stages:Stage 1 - The focus of this stage will be to fully characterize a small number of contaminated stainless steel specimens obtained from real plants. Supporting work exploring the nature of the contamination of these plant samples will be performed under lab scale controlled conditions using simulant contaminating solutions. Initiatives such as Sellafield's active demonstrator programme would be an ideal opportunity for the student to study 'real-life' active material and generate a new stock of knowledge for a key nuclear stakeholder. Opportunities for this collaboration will be arranged through Sellafield's Integrated Project Teams. High resolution analytical techniques will be required for this work due to the very low concentration of radioisotopes that are expected on these materials. This in turn means access to specialised equipment at facilities such as NNL, Diamond Light Source and Manchester's radiochemistry laboratories will be required.Stage 2 - Following the characterisation of the targeted specimens, the focus of this project will switch to the decontamination. It is well recognised in the nuclear sector that a 'toolbox' of decontamination technologies will be required to fully decommission the entire NDA estate. However, studies often only focus on one technology and it is often difficult to select the most appropriate technique without direct comparison. Through applying several appropriately selected decontamination processes to the same contaminated specimen the pros and cons of each techniques can be determined and recommendations made to the industry. This work will also enable the decontamination technologies studies to progress to industrial deployment. EPSRC Research Area: Nuclear Fission (under the Energy theme)