Development of eddy current testing technique for irradiated fuel pins, 2; ECT results of irradiated fuel pins of high burn up

Miyaji, Noriko ; Nagamine, Tsuyoshi; Katsuyama, Kozo 

Eddy current testing (ECT) technique has been developed in order to check the soundness of irradiated fuel pins non-destructively. This paper describes the results that it was examined if corrosions were detected using an imitation fuel pin, made of 15Ni-15Cr-Ti and same type of the fuel pins irradiated in JOYO. As the results of experimental for an imitation pin, ECT detected the corrosions using frecquency 32kHz. And, the signal of eddy current became larger as the thickness of the cladding became smaller, because there was some correlation between the signal and thickness. As for the irradiated fuel pins, inner corrosions were not recognized from the signal because their sizes were too small. However, outside corrosions by sodium as coolant might have an influence on the signal. And, as well as a change of the electromagnetic characteristics of cladding by irradiation, inner pressure by FP gas and PCMI might have an influence on the signal.