Application of damage mechanism-specific NDE methods in support of risk-informed inspections

Risk-informed inservice inspection (RISI) programs effectively concentrate limited and costly examination resources on systems and locations most relevant to plant safety. The thought process used in the selection of nondestructive evaluation (NDE) methods and procedures in a RISI program is expected to change toward integrating NDE into integrity management, with a concentration on understanding failure mechanisms. Identifying which damage mechanisms may be operative in specific locations and applying appropriate NDE methods to detect the presence of these damage mechanisms is fundamental to effective RISI application. Considerable information is already available on inspection for damage mechanisms such as intergranular stress corrosion cracking (IGSCC), thermal fatigue, and erosion-corrosion. Similar procedures are under development for other damage mechanisms that may occur individually or in combination with other mechanisms. Guidance is provided on application of NDE procedures in an RISI framework to facilitate implementation by utility staff (Gosselin, 1996)