Some Recent Observations on Steam Generator Tubing Degradation

Abstract

The steam generator tubing materials at the Pickering, Bruce, and Darlington stations are manufactured from Monel 400, Inconel 600, and Incoloy 800 respectively. These materials are subjected to different operating conditions. This paper presents a summary of the recent damage mechanisms observed on the inside and outside surfaces of the tubes. These mechanisms include underdeposit pitting and intergranular attack. In addition, the morphology of the flaws and, where possible, the likely causative factors are discussed. The information is based on the metallurgical examination of removed tubes.