Temperature Sensitivity Study of Eddy Current and Digital Gauge Probes for Oxide Measurement

Novel fuels are part of the nationwide effort to reduce the enrichment of Uranium for energy production. Fuel performance is determined by irradiating tfuel plates. The plate checker used in this experiment at Idaho National Lab (INL) performs nondestructive testing on fuel rod and plate geometries with two different types of sensors: eddy current and digital thickness gauges. The sensors measure oxide growth and sample thickness on research fuels, respectively. Sensor measurement accuracy is crucial because even microns of error is significant when determining the viability of an experimental fuel. One parameter known to affect the eddy current and digital gauge sensors is temperature. Since both sensor accuracies depend on the ambient temperature of the system, the plate checker has been characterized for these sensitivities. Additionally, the manufacturer of the digital gauge probes has noted a rather large coefficient of thermal expansion for their linear scale. In this work, the effect of temperature on the eddy current and digital gauge probes is evaluated, and thickness measurements are provided as empirical functions of temperature. Additionally, an experimental coefficient of thermal expansion for the probe material has been reported and compared with the manufacturer’s specifications.