Containment Verification Using 3D Laser Technology

A novel system for detecting tampering on nuclear containers, in particular on MOX fuel transportation flasks, is described. As a complementary technique to seals and surveillance, it can be employed to maintain continuity of knowledge between inventories and physical inspections. The proposed system uses laser range imaging in order to create 3D surface maps of the entire container surface, at a lower resolution, as well as of any weld seams at higher resolution. Reference surface maps are created and securely stored, for example upon manufacturing and/or sealing a flask. For subsequent verifica-tion, random parts of the welds and of the surface are scanned, and the scans are compared to the reference. Both for the weld and for the surface verification, a key requirement is that no high-precision mechanical alignment or calibration of the instrument be necessary. The user needs to manually set up the instrument in front of the container and to immediately start acquiring scans. For the case of the weld verification, this is solved by first correcting for alignment imperfections and then extracting certain ¿feature functions¿, such as the weld width, height or cross-section along the scan. These feature functions create a unique ¿fingerprint¿ of the weld. The fingerprint of a verification scan can be efficiently matched against a database of reference fingerprints, regardless where along the weld the verification scan has been acquired. For the case of the surface verification, we propose an approach for automatic registration of two scans acquired from different scanner viewpoints. The ap-proach exploits the fact that the container surfaces are known to be cylindrical and does not require any user interaction such as marking corresponding point pairs. We present examples of both the weld and the surface verification and conclude that containment verification using 3D laser technology allows reliable detection of tampering.JRC.G.8-Nuclear safeguard