Monitoring corrosion on-line with fiber optics.

Fiber-optic strain gages offer a novel way to measure the onset of intergranular attack (IGA) and the progression of stress corrosion cracking (SCC) on the outside surface of nuclear steam generator tubes at support plate crevices. An experimental on-line crack-monitoring system developed for EPRI by McDermott International Corporation's Babcock & Wilcox subsidiary uses light-emitting-diode sources and solid-state light detectors at each end of optical fibers to measure changes in strain in a tube. In laboratory tests, the fiber-optic gages proved more sensitive than standard foil strain gages in detecting strain changes caused by the onset of cracking.

Previous attempts …