Defects in the fuel rods of nuclear fuel assemblies are ascertained and located by ultrasonic means. The fuel assemblies are subjected to ultrasonic waves. Differences in fuel rod resonance is indicative of defective rods.

Apparatus and method for detecting defective fuel rods

A method of repairing partly burnt-off fuel elements in a fuel-element pit of a pressurized-water reactor which includes placing a fuel element previously detected as being defective into a holding cage in substantially upright position with the aid of remotely controlled tools, and tipping it over through 180°; removing the then upwardly disposed fuel-element foot from the fuel element so as to expose the ends of the fuel rods received in the fuel element; inspecting the fuel rods, the ends of which are then freely accessible for defects; removing with a fuel-rod exchanging tool those fuel rods at least which are determined to be defective and depositing them in a storage container; and raising replacement rods with the fuel-rod exchanging tool and inserting them into the fuel element without bending stress in exchange for the removed fuel rods.

Method of repairing partly burnt-off fuel elements in the fuel-element pit pressurized water reactors and device therefor

Method and apparatus for detecting defective fuel elements in a nuclear reactor assembly. The assembly (20) is kept entirely immersed in a liquid such as water, ultrasonic waves are propagated successively in each of the fuel elements of the assembly or rods (21), an ultrasonic sensor (25) is disposed near the assembly (20) and the waves which may be scattered into the protective liquid by the defects in the fuel rod are picked up to determine the presence of a defective assembly and locate the defective rod in the assembly. The invention is particularly applicable to fuel assemblies of a pressurized water nuclear reactor.

Method and device for detecting defective fuel elements in a nuclear reactor fuel assembly

The invention relates to a method for testing fuel element tubes by ultrasonic energy. For testing, each tube becomes disposed in the space between a transmit transducer and a receive transducer. The echo signals falling within a predetermined time interval are evaluated. Since the distance between the transducers may vary as the transducers move through the space between fuel element tubes, the transmitted signal reaching the receive transducer without passing through the tube may be confused with the revolving echo signal. Therefore, this invention discloses an arrangement for cyclically controlling the setting of the time gate before each such tube is in position between the transducers. To this end, the ultrasonic transit time of signals between the transmit transducer and the receive transducer is measured in the gap between the last tested tube and the next to be tested tube. A constant value is subtracted from the measured transit time value and this constant value is selected so that the transmitted signal received during the transit time measurement falls just outside the gated time interval.

Method of testing fuel element tubes for defects

An ultrasonic search unit for locating defective fuel elements within a fuel assembly used in a water cooled nuclear reactor is presented. The unit is capable of freely traversing the restricted spaces between the fuel elements.

Heiko Ing Grad Foerch

Papers

Verfahren und einrichtung zum lokalisieren defekter brennstaebe eines reaktor- brennelements