Structures, systems and components that are important to nuclear safety are designed, manufactured, constructed, installed, commissioned, quality assured, maintained, tested and inspected to the appropriate standards. The codes and standards need to be evaluated to determine their applicability, adequacy and sufficiency.

The consideration of a conservative design is one important element of the Safety Case. This is generally used together with high manufacturing quality, the use of proven materials, inspection, functional testing and defect tolerability. In a UK Safety Case, the assessment of fracture risk of those mechanical components whose likelihood of gross failure is so low that can be discounted requires the determination of the actual critical defect size in order to compare it with the detectable defect size used for inspections.

For the UK EPR™ the 2007 Edition of the RCC-M Code including Addenda 2008, 2009 and 2010 will be the design code of reference and the RSE-M Code version 2010 Appendix 5 will form the basis of the methodology used for standard fracture mechanics assessments of the UK EPR™. Previously, the UK nuclear structural integrity community has used the ASME Code Section III for the UK previous PWR and the R6 procedure for fracture mechanics assessments.

This paper explains the choice of these two codes for the UK EPR™ and the work carried out to date by EDF Energy to demonstrate its compliance with the UK expectations for components critical to safety.

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