Structural integrity assessments of power plant components: the R5 and R6 procedures

Failures of power generating plant have serious economic and safety implications. The availability of validated assessment methods enables routine structural integrity assessments to be performed as aids to: (i) safety case acceptance; (ii) planning of outages and repair and inspection strategies; and (iii) plant life extension arguments. The requirement to regularly perform such assessments within Nuclear Electric and the former Central Electricity Generating Board (CEGB) has led to the development of the assessment procedures R5 and R6. These procedures are described and recent advances highlighted. An example of the use of R5 to analyse the failure of a welded steel pressure vessel is given. The conservatism of the assessment procedure is emphasised