Ultrasonic defects measurements of fuel welded joints

Fuel elements welding joints of atomic power station should provide hermetic state of sheath in the course of exploitation period. The quality of welded joints is determined by non-destructive methods of control. Weld width and defects' evidence are determined by ultrasonic means in butt resistance welding joints of fuel elements. The boundary of a weld line is not structurally heterogeneous, so the reflection of waves with the frequency up to 50 MHz is not observed, that allows to obtain high sensitivity to small defects with opening of ∼ 0.4 x 10-3 mm. The best results could be achieved by means of supervision of two-dimensional images of defects. The program of data processing makes it possible to measure the width of the weld with the accuracy of ± 0.1 mm and sizes of defects. Fast generation (∼ 25 sec.) of weld images at C and B - scanning could be obtained as well. High sensitivity to small defects occurs through utilization of diffraction of spherical ultrasonic wave's effect. The proposed method of defects' measurements could be applied to different technical problems of atomic industry and mechanical engineering. (author)