Steam generator maintenance in EDF nuclear power plant

Steam generator tubing takes a very special place in the maintenance strategy of a nuclear steam supply system. Indeed, tube walls may be degraded through various mechanisms, ranging from corrosion and stress corrosion to vibration and wear. These different types of defect may initiate and develop in quite a short time so that a particular surveillance and maintenance program is necessary to maintain an acceptable level of safety and availability. Moreover, the size of the EDF steam generator population is such that inspection and repair strategy needs to be optimized. As for the objectives ascribed to S.G. tubing maintenance, they can be stated as follows: . with respect to safety, to maintain the tube rupture probability at a sufficiently low level. This means to define proper actions to compensate the risk increase associated with tube degradations, . with respect to availability, to limit the number of shutdowns due to out of specification primary to secondary leakage. On the other hand, corresponding actions should not shorten steam generator life time in an unacceptable way