Event Timeslots (1)

Day 1 – June 20
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In the UK, Advanced Gas-Cooled Reactors (AGRs) use a variation of 316 stainless steel as the fuel cladding due to its high temperature and corrosion resistance. The operating lives of all of the UK AGRs have been extended over recent years. As the older AGR stations reach the point where further extensions are not viable, preparation for removing the fuel and decommissioning is the next step. As a result of these extensions, and necessary lifetime management of irreplaceable core components, the UO2 fuel may have experienced increased burn-up and time in reactor, potentially impacting the cladding end of life properties (and therefore performance) during post-discharge and storage activities. Therefore, it is paramount to investigate and establish any physical and mechanical properties changes, in order to mitigate any potential future handling issues.

The aim of this PhD is to gain a fundamental understanding of the effects of radiation damage on the AGR fuel cladding material, stainless steel, by extrapolating data to predict damage for higher burn up nuclear fuel. The current focus of the project is to use a novel X-ray Diffraction (XRD) technique, Convolutional Multiple Whole Profile (CMWP) analysis, in order to determine the dislocation density and defect type within a material. This is done by analysing diffractograms, specifically parameters such as peak broadening. In order to fully understand the applicability of this technique to AGR material, a metallic zirconium system will first be investigated to establish CMWP fitting parameters. This is because zirconium alloys have been thoroughly investigated with this technique and has proven to work, therefore analysing elemental zirconium, which has less complex diffraction pattern, will be a good foundation.

In this contribution, the analysis of zirconium will be presented. Two investigations will be undertaken, the first being the zirconium as-received (Zr-AR) compared to a Zr-AR that has been heat treated (Zr-AR+HT) in order to anneal and recrystallise the sample. The second investigation was the comparison of Zr-AR+HT against zirconium that has been cold-worked to varying degrees. Future work packages, which include comparison with stainless steel materials and microscopy data will also be described.