COG fitness for service fatigue program

As the population of nuclear power plants ages, new defects are appearing in Steam Generators (SG) subjected to particularly sever operational stresses, among them pitting, support plate denting, stress corrosion cracking, fatigue induced cracking, and fretting. Utilities are requiring additional data to characterize defects after their detection, i.e., their depth, length and orientation, in order to optimize any tube plugging decision. In this paper, progress report on CANDU development of FFSG (fitness for service) requirements are provided. Currently, the FFSG program has launched projects into three main fields; viz. specimen testing simulating CANDU SG environment especially regarding fatigue crack initiation, propagation and stress corrosion cracking of I-600, I-800 and M-400 alloys, data compilation and evaluations, criteria document preparation for SG tubing degradation evaluations based on deterministic and probabilistic risk assessment methods. The paper as well discusses the database that is currently being prepared for the PVRC. In the PVRC database information is collected from different worldwide sources in Japan Europe, the US and Canada