Development of ultrasonic inspection technique for epoxy liner in nuclear fuel interim storage

Epoxy coating in nuclear fuel storage degrades with aging and hazardous radiation. In order to evaluate the deterioration of the epoxy, the dependence of acoustic impedance on mechanical properties is studied. Unlike metals, the epoxy is hard to measure the acoustic velocity because the surface of epoxy coating applied on a concrete wall is wavy and highly attenuative for the ultrasound. In this paper, simulated annealing (SA) algorithm is used to calculate the acoustic impedance using a multiple reflection waves from the rough epoxy surface. Epoxy films coated on small concrete cubes are subjected to the accelerated aging conditions and tested by SA method to calculate acoustic impedance of the epoxy film. The experimental results show that the acoustic impedance has a good correlation with the degradation of epoxy coating and the method developed in this study can be applied effectively to monitor the aging of the epoxy coating in the nuclear fuel storage. (orig.)