Inspection of Circumferential IGA/SCC in Bruce Unit 4 SGS

Abstract

Circumferential IGA/SCC has been detected in the roll-transition zone of tubes in Bruce A SGs for over a decade, but recently became more pronounced in Unit 4 BO4 in 2006 and the spring of 2007. A number of ET probes have been developed to detect and characterize this degradation, including C-3/8, +Point and X-Probe. Comparisons of the inspection results from these probes and metallurgical results from removed tubes have provided insight into the strengths and limitations of each probe and how the probes can complement each other. This paper will discuss the evolution of the ET inspection approach for circumferential IGA/SCC and how the results have been used in recent FFS assessments in the Bruce Unit 4 SGs.