Capability Development for Probing AGR Fuel Cladding Performance - Implementing In-situ Observations to Access the Effect of Strain and Corrosion

这个博士项目的重点是开发能力，以探测AGR燃料包壳的性能受到施加的应变和暴露于水环境，以支持英国核退役管理局（NDA）的战略，实施扩展的湿/干存储乏先进气冷堆（AGR）燃料。总体目标是提供一种新的方法和信心，探测微型AGR燃料包壳样品，可以转移到热室工作条件下的辐照退役材料。沃金顿现场提供了Deben 5KN微型拉伸试验台和独特的设置，以模拟在这项工作所必需的热室条件下处理材料。也可以使用在曼彻斯特开发的一套手动应变钻机和类似的微型Deben钻机（NNL）。这些钻机将与一系列表征技术相结合（例如拉曼），从而可以进行模拟不同燃料储存情况的实验。（i）AGR包壳的原位应变、腐蚀和应力腐蚀破裂（SCC）测试的新能力，（ii）评估拉曼光谱作为AGR燃料包壳检查的潜在工具，（iii）提供可转移的知识/技能，这些知识/技能对于在热室装置中探测AGR包层至关重要，以满足NDA战略。本项目将解决以下关键里程碑：（i）─顶部光学成像系统将与这些钻机接口，以在应变期间观察覆层表面，以进行图像相关技术.这将提供有关表面应变分布的信息。(ii)将探讨拉曼光谱的应用，以评估NbC/NbCN沉淀物的存在，以及它们在施加应变过程中的行为和钝化膜特性。后者将包括在表面腐蚀之前/之后探测覆层表面，以暴露和溶解这些沉淀物。NbC已经被实施为在包层退化过程中发挥关键作用。(iii0原位电化学电池（在并行NDA资助的项目中开发）将用于电化学控制下的原位（应力）腐蚀测试，以模拟湿池储存条件。(iv)将使用统计方法探索最少数据对数据质量的影响。

This PhD project is centred on developing capability for probing the performance of AGR fuel cladding subjected to applied strain and exposure to aqueous environment to support the UK Nuclear Decommissioning Authority (NDA) strategy for implementing extended wet/dry storage of spent advanced gas-cooled reactor (AGR) fuel. The overarching goal is to provide a new methodology and confidence in probing miniature AGR fuel cladding samples, that can be transferred to hot cell working conditions on irradiated ex-service material. The Workington site provides access to a Deben 5KN miniature tensile rig and the unique set-up to simulate handling materials under hot cell conditions essential for this work. A set of manual straining rigs developed at Manchester and a similar miniature Deben rig (NNL) may also be accessed. The rigs will be interfaced with a range of characterisation techniques (e.g. Raman), allowing experiments to be carried out simulating different fuel storage scenarios.This project provides: (i) new capability for in-situ straining, corrosion, and stress corrosion cracking (SCC) testing of AGR cladding, (ii) assess Raman spectroscopy as a potential tool for AGR fuel cladding inspection, (iii) provide transferable knowledge/skills critical for probing AGR cladding in a hot-cell set-up to meet NDA strategy.The following key milestones will be addressed in this project: (i) A bench-top optical imaging system will be interfaced with these rigs to observe the cladding surface during straining for carrying out image correlation techniques. This will provide information about the distribution of surface strain. (ii) Application of Raman spectroscopy will be explored to assess the presence of NbC/NbCN precipitates, and their behaviour during the application of strain, and passive film characteristics. The latter will include probing the cladding surface before/after surface corrosion for exposing and dissolving these precipitates. NbC have been implemented to play a key role in the cladding degradation process. (iii0 A in-situ electrochemical cell (developed in a parallel NDA funded project) will be used for in-situ (stress) corrosion tests under electrochemical control to mimic wet pond storage conditions. (iv) The effect of minimal data on data quality will be explored with statistical means.