Feeders pipes can face an unacceptable wall thinning, due to flow accelerated corrosion for this reason periodic measurements of the wall thickness are necessary.

The chemistry control, as for the steam generators, can mitigate the degradation process and extend their service life.

• For the two-inch outlet tubes, this trend was not noticed clearly. This group, of two inches of diameter, had not shown any significant change of wall thinning rate between 2000 and 2002. Maybe this was due to the low amount of tubes inspected up to 2002 of this group that were not enough to calculate a reliable value for the average of the mentioned wall thinning rate.

• Of the 379 outlet feeder bends (first ones) inspected until the last programmed outage (May 2004), all they would reach the Design Life of 30 years (24 EFPY, keeping in mind a gross capacity factor of 80%). However, some outlet feeders (around 39) have minimum wall thickness which are near to the minimum allowed values and need to be re-visited during next outages for assuring that all they are fit for service, or to discover some of them that could need a substitution before the end of the Plant’s Design Life. Figure 5 shows thickness evolution.

A. V.2.1.3. Secondary side piping

CNEA development a code to determine the areas of the secondary piping circuit that could be susceptible of FAC, being determined 40 new inspection points for the next programmed outages.