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) and procedures for assessing components containing defects (Volume 4/5).

Recent developments in the R5 Volume 2/3 procedure for assessing creep-fatigue initiation in defect-free components include improved methods for predicting creep damage and a new approach for assessing weldments. The improved methods for predicting creep damage include the option of using the stress-modified ductility exhaustion (SMDE) approach as an alternative to the existing ductility exhaustion approach, together with improved methods for assessing compressive dwells. The new approach for assessing weldments involves splitting the existing Fatigue Strength Reduction Factor (FSRF) into a Weldment Endurance Reduction (WER), which accounts for reduced fatigue endurance due to weld imperfections, and a Weldment Strain Enhancement Factor (WSEF), which accounts for material mismatch and local geometry effects.

This paper briefly outlines the current R5 Volume 2/3 procedures and then focuses on these two significant recent developments in the procedures.

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