BWXT provides a feeder replacement service to several clients. The feedwater piping carries feedwater to and from the fuel channel via an inlet and outlet header. This pressurized heavy (D2O) feedwater is heated by the fuel, the feeders carry the water to the outlet header where it is pumped through the primary heat transfer system to the steam generators where the heat is transferred to light water producing steam. This steam is used to drive the steam turbines.
During reactor operating cycles feeder pipes are subject to wear through flow assisted corrosion which results in thinning of the feeder wall. Over time this thinning reaches a critical point and the feeder pipe needs to be replaced.
BWXT in association with AECL has developed a process for the rapid removal and replacement of sections of feeder pipe. This process allows the replacement of a section of feeder pipe during a normal planned outage and avoids the need to replace the entire feeder pipe which would require a lengthier shutdown.
The replacement process requires the defueling of the fuel channel and isolation of the feeder. Once isolated, the feeder is identified through a correct component verification procedure.
The complexity of feeder replacement changes depending on the location of the feeder and the space constraints around the target feeder. BWXT has developed a process and tooling to gain access to all feeder configurations whether they are short or long reach.
Through our continuous improvement program BWXT has successfully shortened the schedule for feeder replacement and is now consistently achieving a replacement time of less than 24 hours.