上海科技大学知识管理系统

When nuclear fuel assemblies operate in a reactor, oxide films will form on the surface of the fuel cladding, which reduces the thermal conductivity of the cladding and increases the risk of corrosion and degradation. Therefore, measuring the thickness of the oxide film is crucial for maintain the nuclear power plant safety. The thickness of the oxide film on nuclear fuel assemblies usually ranges from a few micrometers to several tens of micrometers, which requires high-precision systems to measure it. Eddy current testing (ECT) is widely used for pool side inspections due to its simplicity and ease of on-site implementation. ECT method relies on the lift-off effect of the induction coil under sinusoidal excitation to measure the thickness of the oxide film. This paper presents an ECT probe with two coils and a temperature sensor for oxide film thickness measurement. The probe is connected to the instrumentation with a coaxial cable with length over 10 m. The output of the probe is calculated based on the transmission line model of the cable, resulting in well match of the experimental and the numerical calculation. A prototype probe is developed and tested experimentally. The results indicate that the probe can accurately measure the thickness of oxide films at the micrometer level.