Abstract
Investigations into potentially extending the lives of UK advanced gas-cooled reactors have highlighted the need for improved understanding of the long-term oxidation and carburisation of 9Cr ferritic steels. These steels were used in evaporators and primary superheaters and as these are to be used beyond their original design lives, it is necessary to ensure that these degradation routes remain within acceptable levels. A dimensional metrology technique has been applied to archived autoclave samples to measure such damage. These samples had previously been exposed to a range of temperatures, pressures and gas chemistries representative of those experienced by 9Cr steels in CO2-rich AGR gases. Earlier sample assessments had focused on weight change measurements, but the dimensional technique enables measurement of duplex oxide thicknesses around samples and the extraction of related data from longer exposure times. These data also support estimation of the extent of both carbon and oxygen uptake.
Highlights
IntroductionThe potential to extend the operational lives of UK-based AGR (advanced gas-cooled reactor) plants is being considered
The potential to extend the operational lives of UK-based AGR plants is being considered
Earlier sample assessments had focused on weight change measurements, but the dimensional technique enables measurement of duplex oxide thicknesses around samples and the extraction of related data from longer exposure times
Summary
The potential to extend the operational lives of UK-based AGR (advanced gas-cooled reactor) plants is being considered The case for such an extension depends upon the remnant life of a number of key components within the reactors, including the evaporators and primary superheaters, which were constructed using 9Cr-1Mo ferritic steels [1,2,3,4]. These steels were chosen due to their good resistance to oxidation/carburisation and stress corrosion during their design lifetimes, as well as having reasonable mechanical and welding properties [1,2,3]. For plant life extension cases, the impact of oxidation/carburisation on these steels at longer exposure times must be considered
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