A COMPARISON OF DIFFERENT OPTICAL TECHNIQUES FOR COPPER
CANISTER AUTHENTICATION AND APPLIED FORENSICS

One of the challenges of nuclear safeguards for spent fuel storage in long-term geological repositories is the continuity of knowledge of the fuel assemblies from the encapsulation facility to the repository, which requires containment and surveillance measures. Following the proposal of the Swedish Nuclear Fuel and Waste Management Company (SKB), spent fuel is encapsulated in copper canisters with a cast iron insert in an encapsulation facility, transported by ship approximately 300 nautical miles and then emplaced underground. These canisters will be marked with an engraved identification tag on the lid that includes the country of origin, serial number and a control digit. Ideally, this identifier is unique and cannot be falsified. In a previous work, we presented coherent scanning interferometry (CSI) as a non-invasive optical measurement technique to identify the naturally occurring manufacturing artefacts of the engraving process at the bottom of the identification characters as unique fingerprint for canister authentication. In this work, we introduce two alternative techniques for copper canister authentication, namely laser triangulation (LT) and direct feature comparison in microscope images. We will discuss their advantages and drawbacks with respect to CSI. Laser triangulation is a non-contact optical surface metrology technique that allows 3D reconstruction of surfaces based on the geometrical arrangement between a line laser, the target and a range camera. Both techniques, LT and microscope image processing, could be easily implemented as compact detection instruments for the field and allow fast data acquisition and results. By comparing different copper samples with the same engraved identification tag for cross-sample analysis, we evaluate the performance of both techniques for authentication purposes. Our work underpins a potential pathway to nuclear safeguards of spent fuel containers and has implications for cross-disciplinary areas, such as general surface authentication or forensic analysis.