Initiatives to Reduce Feeder Wall Thinning

Abstract

It was recognised in 1996 that outlet feeder pipes in the Heat Transport System (HTS) of CANDU reactors are corroding at a higher than expected rate. This degradation has been ascribed to Flow Accelerated Corrosion (FAC). a phenomenon known to affect carbon steel components exposed to turbulent flows of de-oxygenated water. A number of actions have been devised to reduce the FAC rate of CANDU outlet feeders. One option being implemented in existing plants is the operation of the HTS coolant in the 10.2 0.20 wt% has been recommended. In this paper, the correlation of plant feeder wall thinning measurements and life-time operating pH, of the stations will be described along with a discussion of issues associated with operational measurement and control of pH, in the HTS. The development of chemical treatments to reduce the FAC rate will be discussed. Finally. results of tests to demonstrate the reduction of the FAC rate through increasing the chromium content of the carbon steel will be summarised.