Graphite Core Dismantling for Minimising Graphite Waste Volume

英国AGR和Magnox反应堆的当前基线策略包括在指定包中进行基本处理和灌浆后的整个砖回收。对于没有观察到裂纹的Magnox反应堆，可以进行整个砖的回收，但工程工具必须考虑堆芯结构中包含的金属部件。AGR堆芯预计会有大量的多重裂纹砖，因此需要开发额外的工程解决方案。即使整个砖回收是可以实现的，并随后进行一些破碎包装，这种选择不会导致最佳的包装废物体积。本项目的目标是探索回收芯石墨的蚕食和真空技术。虽然它是一种广泛使用的技术，并且以前曾被提议用于石墨，但TRL较低，并且仅限于基本概念研究;此外，Nibble和Vac尚未在核心石墨上进行过尝试。目的是确定最佳参数，与工程实施或安全情况相关的潜在问题。这种拆解方法的结果是破碎的石墨，然后可以很容易地用于废物最小化方法，如本体氧化或HIP。UoM已经完成了前者的重要工作，因此这项工作将侧重于后者，研究Nibble和真空方法，以实现工业规模。该研究将包括可行性研究，安全案例评估和HIP作为辐照石墨处理方法的优化。如果成功，将对辐照石墨进行HIP和后续浸出研究。在HIP之前，将对石墨及其性能进行表征，以了解其对HIP工艺的影响。将建立最佳可实现的体积最小化方法，然后对HIP石墨进行沥滤试验，以确定其作为固定方法的效率。

The current baseline strategy for the UK AGR and Magnox reactors includes whole brick retrieval followed by basic treatment and grouting inthe specified package. Whole brick retrieval is possible for Magnox reactors where no cracks have been observed but the engineering tools will have to take into consideration the metallic components that are included in the core structure. AGR cores are expected to have a significant number of multiply cracked bricks and hence development of additional engineering solutions will be required. Even if whole brick retrieval is achievable and it is followed by some crushing for packaging, this option does not result in the optimum packaged waste volume.The objective of this project is to explore the Nibble and Vacuum technique for retrieving the core graphite. Although it is a widely used technique and has been previously proposed for graphite, the TRL is low, and is limited to basic concept studies; in addition, Nibble and Vac has not been tried on core graphite. The aim will be to identify the optimum parameters, potential issues either related to the engineering implementation or to the safety case. The result of this dismantling method is crushed graphite that can then be readily used for waste minimisation methods, such as bulk oxidation or HIP. Significant work has been completed on the former by UoM so this work will focus on the latter with studies on the Nibble and Vacuum methodology to enable industrial scale up. The research will include a feasibility study, safety case assessment and optimisation of HIP as a treatment method for irradiated graphite. If successful, HIP and subsequent leaching studies will be performed on irradiated graphite. Characterisation of the graphite and its properties will be undertaken before HIPing in order to understand this effect on the HIP process. The optimum achievable volume minimisation method will be established followed by leaching tests on the HIPed graphite to determine its efficiency as an immobilisation method.