Abstract: An apparatus for determining the depth of cracks in the surfaces of workpieces includes an ultrasonic transducer for sending ultrasonic signals to and receiving ultrasonic signals from the workpiece, an analyzer connected to the ultrasonic transducer for forming a frequency spectrum from the ultrasonic signals, an evaluating unit connected to the analyzer for determining an effective band width correlated with the depth of the cracks in the workpiece as the quotient of the integral of the frequency spectrum and the ordinate value of the center of concentration of the integrated surface of the frequency spectrum, and an indicator connected to the evaluating unit for indicating the depth of the cracks.

Abstract: Method for determining the contents of a fuel rod within a testing range extending in the longitudinal direction of the fuel rod, characterized by the features that(a) the position of a test coil concentrically surrounding the fuel rod is changed from the beginning to the end of the testing range, and(b) in the process, the impedance of the test coil is measured as a function of its position,(c) the test coil is fed with an a-c voltage,(d) the frequency of which is so low that the measurement value in the region of a fuel pellet of pure uranium dioxide is clearly distinguished from that which is measured in the region of a doped fuel pellet.

Abstract: Nuclear fuel rod ends of water-cooled reactor fuel rods, are heated in the region of the fission gas plenums and/or in the region of the upper or lower ends of the fuel columns. The moisture present in the case of damage to the fuel rods' casings, evaporates and is partly condensed at the end caps. In the case of a fuel rod completely filled with water, steam bubbles are generated. Both indications of casing leakage or damage are ascertained by ultrasonic reflection measurements and/or measurement of a temperature-vs-time curve, obtained at the end cap.