Design and Development of an Automated Pellet Inspection System for Nuclear Fuel Pellets

A prototype for inline, non-destructive inspection of uranium dioxide (UO2) fuel pellets at production speeds of two pellets per second is presented. The system tests the surface of each cylindrical ceramic pellet using three different methods: laser 2D profile, laser surface roughness, and machine vision camera. The arrangement of these sensors allows for complete cylindrical and end surface inspection of every pellet, which are judged against manufacturing visual inspection criteria. Sensor selection and inspection arrangement have already been developed in past work, the present advancements are in the area of system refinement and automation. Internal non-destructive testing techniques of the dense ceramic pellets are explored, but ultimately efforts are placed on the completion and testing of the inspection prototype. A simple yet effective TRIZ-based pellet handling system using gravity feed is designed and integrated, along with real-time control software developed in LabVIEW. The machine vision algorithm and illumination setup are adapted to overcome challenges identified with actual UO2 pellets. Testing is performed to optimize the system's false positive and defect detection results, from which the more common defect types are tested and system statistical false detection rates are calculated. With relatively low error rates and successful detection of all sample defects, the automated system is validated for inspection of UO2 pellets.