Comprehensive model of eddy current based pressure tube to calandria tube gap measurement

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This project will focus on generating a comprehensive theoretical model of the eddy current (EC) response that arises during pressure tube (PT) to calandria tube (CT) gap measurement, which is used in prediction of time-to-contact between PT and CT in CANDU fuel channels. While a gap measurement capability is presently being qualified by fuel channel inspection service providers, no comprehensive physical model of the electromagnetic processes, which incorporates the effects of the most significant essential parameters on gap measurement, exists. Two dimensional (2D) analytical models, simulating EC gap coils above a flat plane, have been developed, but these models do not accurately reproduce many of the factors that affect gap measurement accuracy. For example, the curved PT and CT geometry, a key parameter for the accurate measurement of gap in the range of 6-10 mm, is not easily modeled in 2D. A three dimensional (3D) model of the eddy current response to PT to CT gap variation is required to adequately address these curved geometry features. A validated 3D eddy current model of response to variation in PT to CT gap can be used as part of an inspection qualification program, by inexpensively supplementing laboratory and field measurements and assisting in the quantification of the effect of essential parameters such as pressure tube resistivity and wall thickness variations on gap measurement accuracy.