CASE STUDIES OF PULSED EDDY CURRENT TO MEASURE WALL LOSS IN FEEDWATER HEATER SHELLS

摘要

There have been several feedwater heater shell failures in nuclear power plants caused by flow-accelerated corrosion (FAC). This failure mechanism may be one of the most important types of damage to mitigate because FAC damage has occasionally resulted in catastrophic failures and human fatalities. Predicting, detecting, and eliminating significant FAC damage can significantly reduce future forced outages and increase personnel safety. This paper describes the implementation of recent developments to perform cost-effective examinations. These advances include the use of specialized pulsed eddy current (PEC) hardware and software to scan for wall thinning without removing insulation. APTECH has performed more than 50 nuclear power plant projects on hundreds of feedwater shells, as well as numerous pipe examination projects, using the PEC equipment as a cost-effective screening tool for the detection of areas with significant wall loss. Results of shell wall loss measurements using ultrasonic examination (UT), the PEC average wall thickness (AWT) estimate, and the PEC evaluated Defect Algorithm are compared in this study.