Evaluation of flaw indication - an extension of fast fracture assessment into the post yield regime

The limitations of the ASME Pressure Vessel and Boiler Code Section XI increase when attempts are made to apply Appendix A to the evaluation of flaws in thinner sections than those of the LWR pressure vessels. The most important point is that Appendix A is restricted to the principles of linear elastic fracture mechanics and these are not applicable to the fast fracture analysis of many of the structures in systems other than water reactors. Attention has been given to the development of a route for the evaluation of flaws in ferritic steels at temperatures below those at which time dependent effects have to be considered. The route can make use of simple calculations in which inherent pessimism is acceptable and can be guaranteed. Where a more rigorous examination is required more sophisticated calculations can be used. The recommended analysis route is based on recent work within the Central Electricity Generating Board based on the two criteria fracture analysis method. The steps in the procedure are essentially those of ASME Section XI extended into the post yield regime. This format has been adopted as it is one familiar to engineers dealing with fracture mechanics. The remaining limitations will be discussed and the associated experimental validation work identified. (author)