Development of a Digital Radiographic System for Power Plant Components

Corrosion-fatigue, a cracking mechanism in fossil-fueled generating plants, predominately occurs in the water walls and economizers of sub-critical plants. Cracking attributed to corrosion-fatigue has occurred in water wall tubing of both membrane and tangential designs. The occurrence (particularly in membrane water wall tubing) presents a challenge for nondestructive evaluation (NDE) because the mechanism manifests itself as multiple cracks which initiate and grow on the inside surface of the tubes on the casing side of the tubes, locations which are not typically accessible for conventional NDE techniques. To address detection of such cracking, EPRI is developing a radiographic system based on complementary metal oxide semiconductor (CMOS) technology. The system includes a CMOS real-time digital detector, portable X-Ray device, data acquisition and display software, and remotely operated robotic devices for positioning the X-Ray device and the detector throughout the boiler regions susceptible to corrosionfatigue cracking. The capabilities of the CMOS system for detection of corrosion-fatigue cracking in boiler water wall tubing are discussed in this paper.