An investigation of metallic uranium corrosion in a Geological Disposal Facility (GDF) setting.

地质处置是国际公认的最安全的高活性放射性废物的长期解决方案，联合王国的遗留废物，包括那些含有铀金属的废物，打算以这种方式管理。目前的博士项目将调查未受辐照的Magnox铀金属的腐蚀行为，在类似于地质处置设施（GDF）的条件下（一）关闭前和（二）关闭后。该项目还将设法对反应堆辐照铀的微量样品进行分析，以确定腐蚀速度是否与未辐照金属的腐蚀速度具有密切的可比性。预计任何存在于中间水平废物（ILW）包中的残余铀金属将被包裹在水泥浆或污泥中，但有可能将未加工废物储存在自屏蔽箱中;这意味着已部分腐蚀的未加工废物中的“遗留”铀可能直接接触GDF中的地下水。因此，本研究将研究在高pH值和碳酸盐含量的水中铀的腐蚀行为，同时（i）裸露和部分腐蚀，并与（ii）U包裹在水泥浆中和（iii）包裹在Mg（OH）2污泥中进行比较。主要重点将是未封装的铀在类似于GDF环境的水化学中的腐蚀，并将包括在这些条件下的气体释放速率的研究，以及从池塘水化学到GDF水化学的pH值过渡。这是一个有待详细研究的研究领域。

Geological disposal is internationally recognised as the safest long-term solution for higher activity radioactive wastes and the UK's legacy wastes, including those containing uranium metal, are intended to be managed in this way. The current PhD project will investigate the corrosion behaviour of unirradiated Magnox uranium metal, under conditions analogous to a Geological Disposal Facility (GDF) both (i) pre-closure and (ii) post-closure. The project will also seek to conduct analysis of micro-samples of reactor-irradiated uranium to determine if corrosion rates are closely comparable to those derived from unirradiated metal.This study aims to better underpin the expected behaviour of metallic uranium following disposal in a GDF. It is expected that any residual uranium metal present in an Intermediate Level Waste (ILW) package will be encased in either grout or sludge but there is the potential for raw waste storage in self-shielded boxes; which would mean that 'carry-over' uranium in the raw waste, which is already part-corroded, could directly contact groundwaters in a GDF. Accordingly the study will examine the corrosion behaviour of uranium under water at high pH and carbonate content whilst (i) naked and part-corroded, and in comparison to (ii) U encased in grout and (iii) entrapped in Mg(OH)2 sludge. The primary focus would be on unencapsulated uranium corrosion in water chemistries analogous to a GDF environment and would include studies of gas release rates under these conditions as well as the pH transition from pond-water chemistry to GDF water chemistry. This is an area of research yet to be studied in any detail.