POSTED 28.06.18

R6, the first UK procedure for the assessment of the integrity of structures containing defects, was first published in 1976 by the UK Central Electricity Generating Board (CEGB). It was principally developed to facilitate the analysis of nuclear components and has influenced other nuclear standards and procedures such as ASME XI and the GE-EPRI procedure.
Fracture Mechanics 3
The R6 procedure has remained a cornerstone of structural integrity assessment procedures within the UK power industry and is recognised worldwide. The procedure is maintained and developed by a consortium of organisations which is led by EDF Energy. Experts from those organisations form the R6 Panel, who together manage and implement the R6 development programme.
The R6 Panel’s roles include: defining and prioritising development areas (based on industry needs) under a rolling 5-year plan, managing the implementation of that development work (specified via individual task sheets) through the associated participating organisations, and updating/revising the R6 procedure to ensure development findings are appropriately captured. Fundamental to this approach is ensuring that all areas of development are underpinned by thorough validation via both analytical and experimental techniques, and take account of the latest work available from the wider research community.

Engineering Analysis Services Limited (EASL) has long standing experience serving the nuclear industry and is a leading expert in structural integrity of high temperature plant.

cracked impeller

EASL has served the UK civil nuclear industry since the company’s inception in 1988, providing support to operation, outage and maintenance activities on plant, to improve plant availability and to support plant life extension. Over that period, EASL has maintained a strong relationship with EDF Energy Nuclear Generation (formerly British Energy, Nuclear Electric and CEGB), the owner/operators of the UKs civil nuclear reactor fleet and owners of the R6 procedure.

A formal member of the R6 Panel

Recognising its expertise in the application of structural integrity methods, we now made a formal member of the R6 Panel, providing an expert practitioner’s view point and focus. EASL is represented on EDF Energy R6 Panel by Paul Shard, EASL’s leading expert on structural integrity assessments and analysis.

EASL’s first contribution to the R6 development programme is a task seeking to provide validation of limit load solutions for plates containing semi-elliptical surface cracks under combined biaxial forces and cross-thickness bending moment.

Validation is being sought via systematic and detailed non-linear FEA considering semi-elliptical surface cracks in plates. A range of geometries and a range of biaxial and cross-thickness bending load combinations are being considered, and elastic and elastic-plastic Js determined. The FE analysis data will be used to investigate global limit load solutions, which were developed by Lei and Budden and published in 2015. Validation of these solutions will be sought principally via production of R6 Option 3 failure assessment lines and comparison with Option 1 and Option 2 failure assessment diagrams. Comparisons with other available local limit load solutions will also be carried out. Results will also be presented in the form of the geometry dependent plastic J calibration function h1 for use by the wider research community.



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