The R5 procedures have been developed within the UK power generation industry to assess the integrity of nuclear and conventional plant operating at high temperatures. Within R5, there are specific procedures for assessing creep-fatigue crack initiation in initially defect-free components (Volume 2/3), components containing defects (Volume 4/5), dissimilar metal weldments (Volume 6) and similar metal ferritic weldments under steady loading (Volume 7).

A key driver for continued developments in the R5 Procedure is the operational feedback from thirty years of operation of the UK Advanced Gas-Cooled Reactor (AGR) fleet. This experience from operation of the UK AGR fleet can be used to inform the design and operation of future high temperature reactors. Some of the lessons learnt from long-term operation of austenitic stainless steels at high temperatures are detailed briefly within this paper.

Further, this paper briefly outlines the current R5 procedures and then focuses on two significant recent developments in these procedures: treatment of carburisation and its impact on creep-fatigue crack initiation and improved methods for predicting creep-fatigue crack growth under combined primary and secondary loads.

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