Design of Eddy Current Testing Probe for Thickness Evaluation of Multilayers on Nuclear Fuel Claddings

Abstract

Nuclear fuel claddings are the first barrier against fission products in a primary circuit. Eddy current testing (ECT) is a commonly used nondestructive testing technique for measuring the thickness of chromium and oxide layers on claddings. Because of the lack of an analytical model for ECT probes above multilayer pipes, the design and optimization of the probe have not been reported. In this article, an analytical model for coils placed outside multilayer pipes involving arbitrary nonconductive and conductive layers is built based on second-order vector potential (SOVP). A model of nuclear fuel claddings is built, and the influence of probe parameters on signals is analyzed. According to the results, a design flowchart for the ECT probe is provided by considering resonance frequency and quality factors. Comparisons among the experiment, finite element model, and analytical model indicate that the built analytical model is validated and efficient. In addition, the performance of the new probe is better and more sensitive than that of the old probe; therefore, the proposed design flowchart is effective.