Wall Thining Management at EDF France

Topic :

Wall thining management

ABSTRACT :

Among the various degradation modes that causes pipe wall thinning in the secondary system of Nuclear Power Plants (Flow Accelerated Corrosion, Cavitation, Droplet impigement), FAC is the one that is the more widespread in the installation and that requires the strongest efforts to fight. The wall thickness loss due to FAC can effectively occur in any carbon steel piping containing hot water or wet steam and can lead to pipe ruptures with dramatic consequences.

Electricité de France operates 58 Pressurized Water Reactors that were put in service between 1977 and 1997. The degradations and leaks due to FAC that EDF has experienced and the numerous accidents that have been reported abroad, lead EDF to develop a global strategy to control FAC on piping. This strategy has been written by the corporate engineering level of EDF in a National Maintenance Rule called "RNM" and is applied by every Nuclear Power Plant operator of the EDF fleet. The RNM is mainly based on the use of the FAC prediction software "BRT-CICERO^TM" as well as on specific actions for the lines or elements that are not modeled in the software.