APPLICATION OF THE POTENTIAL DROP METHOD FOR INSERVICEMONITORING OF INDICATIONS FOR CRACK INITIATIONOR CRACK PROPAGATIONFUNDAMENTALPRINCIPLES AND PRACTICAL APPLICATION

摘要

Developed by TUEV Anlagentechnik, Cologne, for monitoring material areas such as, e.g. welds, for crackformation or crack growth, the potential drop method was put through theoretical examinations, simulations using anelectrolytic tank, 5 trials in 4 nuclear power plants and one calibration test. At that time it had reached a stage ofdevelopment which enabled it to be used for practical applications.The method was then used so far in 4 power plants for a period of up to 3,5 years in on-line monitoring ofindications/findings obtained earlier and has thus been instrumental in ensuring safe continued operation.Like other established NDT methods, this one is suitable for monitoring also welds for crack formation and crackgrowth during recurrent inspections (off-line reading with a mobile measuring system) but compared with theconventional methods it saves operations on site and reduces the time required for measuring to a mimimum. Prior tothe installation of the area of measurement an initial check for defects needs to be made.