Development of an eddy current testing technique for inspecting inner corrosion of cladding

Miyaji, Noriko ; Katsuyama, Kozo ; Nagamine, Tsuyoshi

An eddy current testing (ECT) technique was developed to check the soundness of irradiated fuel pins non-destructively. Here, the technique was applied to detect the decrease in wall thickness of the fuel pin cladding due to corrosion occurrence which had been irradiated in the experimental fast reactor Joyo. Dummy cladding provided with simulated inner corrosion was used to ascertain the technique applicability. This test confirmed that the decrease in wall thickness with simulated inner corrosion exceeding 30 m in depth could be detected. In the case of irradiated fuel pins, the decrease in wall thickness due to corrosion occurrence was not detected because the depth was too small; the maximum depth of the inner corrosion was 14 m. In addition, it should be noted that the physical changes on the cladding due to irradiation might have an influence on the signal.