Detection and modeling of magnetite buildup in steam generators

A major problem in nuclear power plant steam generators is the denting of tubes due to the corrosion of the tube support plate in the crevice gap adjacent to the tube, resulting from the attack of concentrated aggressive chemical impurities on the materials of the steam generator. An early detection of accumulation of this corrosion product (magnetite) in the crevice gap would help avoid squeezing and denting of tubes by chemically flushing the unit. The main objectives of the research reported here were to determine theoretically the feasibility of using a simple variable reluctance magnetic probe to detect the presence of magnetite in the crevice gap, and to develop a finite element model for predicting probe signals.