Partial-defect detection using a digital Cerenkov viewing device and image processing

Fuel assemblies with substituted Zircaloy rods, water rods, missing fuel rods and substituted uranium rods were measured using a digital Cherenkov viewing device. Substituted Zircaloy rods can be detected visually from the DCVD image if they are located in the periphery of the assembly but are more difficult to detect when located in the central area of fuel assemblies. Empty positions can be detected from the DCVD image because of the higher light intensity in adjacent water gaps. For GE12S and Atrium 10B fuel assemblies, the missing fuel rod area is much brighter than the light above the partial-length fuel rods. The light intensity can be 88 percent higher and is easily detected. The light intensity is slightly lower than the partial-rod area when the missing rod is in the periphery of the assembly where fewer near-neighbour rods are present to generate the Cherenkov light. Data from the substituted uranium rods are still being analyzed. (author)