Study of Multi-parameters Separation for Oxide Film Thickness Measurement

The zirconium cladding is one of the most important safety barriers of a nuclear power plant. An oxide film may be formed on the outer surface of the cladding during the usage in the nuclear reactor, which seriously affects the safety and performance of the fuel assembly. How to measure the oxide film thickness with high-precision is still a problem to be studied. This paper proposes an oxide film thickness measurement method based on frequency-sweeping eddy current testing, which suppresses the effects of the interfering parameters by fusing the multi-frequency measurements. The influences of the excitation frequency, conductivity of the cladding tube and metal coating thickness on the oxide film measurement are analyzed. Then the algorithm of accurately calculation of the oxide film thickness is derived and verified. The results show that the calculation error of the oxide film thickness is less than 1 micron with different cladding conductivities.