Year
2007
Abstract
Containment verification techniques play an important role in IAEA verification in order to maintain continuity of knowledge. In this paper, we address containment verification for MOX fuel transportation flasks and propose an approach based on three-dimensional laser scanning. Comprehensive containment verification needs to include the flask seals, but also the integrity of the entire flask surface as well as any welds because an aggressor might choose to directly penetrate the flask shell, leaving the seals intact. Our approach is based on the assumption that any attempt to cut the flask open and to remodel its surface will leave changes either to the reflow pattern of the welds or to the exact three-dimensional structure of the flask surface. Initially, a three-dimensional reference model of the entire flask surface and the welds is created by acquiring a number of scans and patching them together into a single model. The flask surface is sampled at a point density of approximately 500 micrometers while the welds need to be scanned at a higher density of approximately 50 micrometers in order to grasp the details of the reflow patterns. For subsequent verification, random parts of the flask surface and/or the welds are scanned and compared to the reference model. We demonstrate in a number of examples that tampering both with the welds - e.g. by cutting and rewelding a weld seam - and with the flask surface itself - e.g. by cutting a hole into the surface, welding it back into place and grinding the welds smooth - can be detected using this approach.