Oxidation behaviour of steels in advanced gas cooled reactors

EDF Energy operates 14 advanced gas cooled reactors (AGRs) in the UK to generate electricity.CO2 gas is used as the primary coolant in the AGRs, and a range of steels are used as for the structural components: e.g. 9Cr-1Mo ferritic steels and stainless steels. These steels are susceptible to both oxidation and carburisation in CO2 dominated primary coolant gas under high pressure between 300 and 650 degrees C. Material degradation is a key concern for lifetime extension of the power stations, and EDF Energy and its predecessors have carried out a series of research programmes to better understand steel oxidation behaviour in AGRs and to develop more realistic lifetime prediction methodologies. These are used to secure safe and reliable operation of the AGRs. In this paper, an overview of oxidation behaviour of steels used in AGRs and some examples from the above programmes are described.