Effect of burn-up on mechanical and chemical stability of spent fuel during wet and dry storage

在这十年内，目前在英国进行乏燃料后处理的两个工厂将关闭。由于先进气冷堆（AGR）和压水反应堆（PWR）仍在英国运行，预计将产生超过5000吨未经处理的AGR和PWR燃料。由于没有最终的处置解决方案，这些燃料将在池塘中冷却，然后在干桶中储存长达100年。由于乏核燃料的高度危险性，必须充分了解它们在这些贮存条件下的行为。一个突出的问题是贮存条件下燃耗对完整性SF的影响。高燃耗燃料具有更高的裂变产物积累，并且在反应堆内受到长时间的加热和辐照。因此，化学和机械性能预期会随着燃耗的变化而变化。比如：1.更多的裂变产物会导致燃料膨胀，这可能导致包壳破裂;2.长时间的加热会导致机械完整性的损失，例如通过开裂和晶粒生长;3.暴露于较长时间的辐照导致晶格损伤增强和进一步swelling.We的目标是合成和合成一系列的UO 2类似物乏AGR和PWR燃料，上述特征的代表，在不同的“燃耗”的范围。合成将使用常规固态方法进行，并且还通过热等静压进行，这将允许掺入挥发性裂变产物替代物，例如Cs、I。我们将进行一项研究，以了解在代表冷却池条件和失败的干桶情况的条件下，燃耗如何影响SF的腐蚀，以支持这些储存实践的安全评估。

Within this decade, the two plants currently reprocessing spent fuel (SF) in the UK will close. With Advanced Gas Cooled Reactors (AGR) and Pressurized Water Reactors (PWR) still operational in the UK, it is anticipated that in excess of 5000 tonnes of unprocessed AGR and PWR fuel will be generated. With no final disposal solution, these fuels will be cooled in ponds, prior to storage for up to 100 years in dry casks. Due to the highly hazardous nature of spent nuclear fuels, their behaviour under these storage conditions must be fully understood.One outstanding issue is the effect of burn-up on the integrity SF under storage conditions. High-burn up fuels have a higher accumulation of fission products and have been subject to prolonged heating and irradiation within the reactor. As such, the chemical and mechanical properties are expected to change, detrimentally, as a function of burn-up. For example:1. Higher incorporation of fission products could lead to swelling of the fuel which may cause the cladding to be breached;2. Prolonged heating can result in loss of mechanical integrity, e.g. through cracking and grain growth;3. Exposure to irradiation for longer time periods results in enhanced lattice damage and further swelling.We aim to synthesise and characterise a series of UO2 analogues for spent AGR & PWR fuel, representative of the characteristics described above, at a range of different "burn-up". Synthesis will be performed using conventional solid state methods, and also by hot isostatic pressing, which will allow the incorporation of volatile fission product surrogates, e.g. Cs, I. We will perform a study to understand how burn-up influences the corrosion of SF under conditions representative of cooling pond conditions and failed dry cask scenarios, to support safety assessment of these storage practices.