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

地质处置被国际公认为高活度放射性废物最安全的长期解决方案，英国的遗留废物，包括那些含有铀金属的废物，打算以这种方式进行管理。目前的PHD项目将研究未辐照的Magnox铀金属在类似于地质处置设施(GDF)的条件下的腐蚀行为，包括(I)关闭前和(Ii)关闭后。该项目还将寻求对反应堆辐照的铀的微量样本进行分析，以确定腐蚀率是否与未辐照的金属的腐蚀率非常接近。这项研究旨在更好地支持金属铀在GDF中处置后的预期行为。预计中级废物(ILW)包装中存在的任何残余铀金属都将被包裹在灌浆或污泥中，但有可能将原始废物储存在自我屏蔽盒中；这将意味着已经部分被腐蚀的原始废物中的“残留”铀可能直接接触GDF中的地下水。因此，这项研究将考察铀在高pH值和碳酸盐含量高的水中的腐蚀行为，同时(I)裸露和部分腐蚀，并与(Ii)包裹在灌浆中的铀和(Iii)包裹在Mg(OH)2污泥中的铀进行比较。重点将主要放在类似于GDF环境的水化学中的无包封铀腐蚀，并将包括研究在这些条件下的气体释放速率以及从池塘-水化学到GDF水化学的pH转变。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.