Hyperspectral Imaging Based Corrosion Detection in Nuclear Packages

In the Sellafield nuclear site, Cumbria, U.K., intermediate-level waste and special nuclear material are stored above ground in stainless steel packages or containers, with thousands expected to be stored for several decades before permanent disposal in a geological disposal facility. During this intermediate storage, the packages are susceptible to corrosion, which can potentially undermine their structural integrity. Therefore, long-term monitoring is required. In this work, hyperspectral imaging (HSI) was evaluated as a nondestructive tool for detecting corrosion on stainless steel surfaces. Real samples from Sellafield, including stainless steel 1.4404 (known as 316L) and 2205 plates from the Sellafield atmospheric testing corrosion site, were imaged in the experiments, measuring the spectral responses for corrosion in the visible near-infrared (VNIR, 400-1000 nm) and short-wave-infrared (SWIR, 900-2500 nm) regions. Based on the spectral responses observed, a new concept denoted as corrosion index (CI) was introduced and evaluated to estimate corrosion maps. With the CI, every pixel in the hyperspectral image is given a value between zero and one, aimed at representing corrosion intensity for a given location of the sample. Results suggest that HSI, combined with our proposed CI analysis techniques, could be used for effective automated detection of corrosion in nuclear packages.