Abstract: The invention is directed to an apparatus and method for inspecting spring hold down bolts of an upper tie plate of a fuel rod assembly in a nuclear reactor and includes an inspection fixture adapted to be aligned with the upper tie plate of the nuclear reactor fuel rod assembly for placement into a position for rapid and easy insitu inspection of the hold down bolts of the upper tie plate. The fixture is provided with a plurality of ultrasonic transducers which are positioned on the fixture so that when the fixture is placed into the inspection position each transducer will be located proximate to one of the hold down bolts for conducting effective ultrasonic scanning of the bolt while the bolt is in place. A multi-channel ultrasonic flaw detector is connected to each of the transducers for indicating whether there are any flaws in each of the hold down bolts when the fixture is placed into the inspection position and the ultrasonic transducers are activated.

Abstract: A fuel assembly mechanical flow restriction apparatus for detecting failure in situ of nuclear fuel rods in a fuel assembly during reactor shutdown.

Abstract: A method for measuring the thickness of a layer of crud containing ferromagnetic material deposited on nuclear fuel rods using eddy current lift-off (coil-to-conductor spacing) measurement by exciting a probe coil at predetermined frequency which penetrates only into the layer of crud containing the ferromagnetic material.

Abstract: A method for measuring the thickness of an oxide layer formed on the cladding surface of nuclear fuel rods and underlying a crud layer containing ferromagnetic material using eddy current lift-off measurements by exciting a probe coil at a first frequency which penetrates only into the crud layer and by exciting a probe coil at a second frequency which penetrates the crud layer, the oxide layer and into the cladding of a nuclear fuel rod. By subtracting vectorally the complex impedance resulting from exciting the probe coil at the first frequency from the complex impedance resulting from exciting the probe coil at the second frequency, the thickness of the oxide layer formed on the cladding is measured.

Abstract: A fuel assembly mechanical flow restriction apparatus for detecting failure in situ of nuclear fuel rods in a fuel assembly during reactor shutdown.

Abstract: An ultrasonic inspection system for ultrasonic inspection of the guide structure of a reactor pressure vessel having two shear wave transducers, one positioned to face in a first direction about 30.degree. from normal to a top edge of the grid members of the top guide structure and a second one positioned to face in a second direction about 30.degree. from normal to a top edge of the grid members of the top guide.

Abstract: A system and method of the present invention measures the relative stress in the cladding of a nuclear fuel rod caused by the internal gas pressure of the rod. This is done by determining the attenuation ratio of two specific frequencies from a broadband low frequency acoustic energy spectrum. Relative pressure differentials are measurable and therefore any loss of fuel rod gas pressure is a direct indication of fuel rod cladding failure.

Abstract: A reactor pressure vessel top guide structure inspection and transport system comprising a remotely operable and positionable underwater vehicle for traversing the top guide structure of a reactor pressure vessel and for positioning an inspection system for detecting defects in the top guide structure.

Abstract: An apparatus for measuring fuel assembly bow and twist comprising a fixturing apparatus, a reference device and an ultrasonic measuring device.

Abstract: A method and apparatus for eliminating erroneous test readings during ultrasonic testing of nuclear fuel rods is disclosed. The method and apparatus employ the use of an alignment guide to effect temporary alignment of the fuel rods during testing in order to overcome mechanical deviations of the rods. The alignment guide includes elongated, parallel guide bars for insertion into an array prior to ultrasonic testing. The bars are mounted on a base which, in turn, is movably mounted on a support element. A fixed guide maintains the relative position of the guide bars with respect to one another. A hydraulic element causes the guide bars to be inserted and removed from the fuel array. In a preferred arrangement, the alignment guide may be removably mounted on a frame containing the ultrasonic testing equipment.