Automated Image Stitching of Down Channel Nuclear Reactor Fuel Channel Inspection Footage

Abstract

Routine inspection of the nuclear reactor core is fundamental to the continued safe operation of any nuclear power plant. Inspection methods vary but a common approach is visual inspection. Visual inspections are performed routinely on the UK's seven Advanced Gas-cooled Reactors (AGR) and in this paper, we focus on that design. The inspection footage recorded is in the form of video. A typical inspection consists of six scans of each cylindrical channel, each with a 70 degree field of view to guarantee the entire inner surface of the fuel channel is inspected. These scans are recorded with the camera field of view focused on the side walls but it is also possible to record a view looking straight down the channel. This type of forward facing footage is known as down channel footage.In this paper we demonstrate a novel framework for creating inspection images from down channel video footage. We demonstrate that it is possible to view both features of interest and defects in these images and compare them to inspection images stitched from regular footage. Down channel inspection images have a number of advantages compared with regular chanoramas including requiring only a single traversal of the fuel channel to record all the required footage and the illumination is much more uniform. While this paper focuses on unwrapping and stitching cylindrical nuclear inspection images from AGRs, the technique described could be adapted to stitch inspection data from other designs of reactor and industries where routine inspections are performed inside pipework.