Laboratory Tests of an Ultrasonic Inspection Technique to Identify Defective CANDU Fuel Elements

In the rare occurrence of a fuel failure during normal operation, the primary coolant can enter the element. Visual techniques are normally used for the postirradiation inspection of discharged CANadian Deuterium Uranium (CANDU) fuel bundles to help identify such failures. In this work, a more sensitive method, based on underwater angled-beam ultrasonic inspection, is investigated under laboratory conditions. Only nonirradiated fuel elements were tested. Identification is possible with the introduction of water into the fuel element, which acts as a couplant for sound waves, thereby providing for a clear demarcation of the fuel pellets within the element in observed scans. This study therefore demonstrates that the inspection of the outer-ring (i.e., higher-powered) elements in the complex fuel bundle structure is possible.