EDF'S ''OMF-structures'' RI-ISI process: overview of the methodology, applications and comparison with the other existing RI-ISI initiatives

The OMF-Structures process has been developed by EDF in order to optimise the maintenance of piping components. The principles of the OMF-Structures are consistent with the RCM concepts in EDF's OMF process (applied to active components). Several applications of this process have been performed. This paper also presents several applications which have been performed, notably on the AFW, RHR, and HPSI/LPSI systems of EDF's 900 MW PWR plants. These applications led to propose optimised preventive maintenance programs for these systems. These updated preventive maintenance programs confirmed and justified a large proportion of existing maintenance, despite some inspection tasks were suppressed and some inspection tasks were added. Globally, these new programs guarantee a better safety level, insuring that preventive maintenance is applied on piping segments where risks are concentrated. A comparative evaluation of the OMF-Structures process with the EPRI and WOG/ASME RI-ISI methodologies has been performed. This comparison demonstrated the consistence of the OMF-Structures principles and selection criteria with the other RI-ISI processes. (author)