Design and development of an automated pellet inspection system for nuclear fuel pellets
Abstract
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 Lab VIEW. 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.