1. A method for scanning shipping containers for nuclear material comprising: scanning a shipping container with a rotating CT-based x-ray device producing CT scan data as said shipping container moves through a scan area; slicing said scan data into a sequence of 2-dimensional slices; locating nuclear weapon component target shapes in said 2-dimensional slices including spheres, cylinders, cannon barrels or pellets, using pattern classification techniques; re-slicing said scan data along at least two different axes to verify said possible shapes; outputting scan recognition signals to an artificial intelligence processor relating to detection of any of said nuclear weapon component target shapes in a particular container; comparing at said artificial intelligence processor said scan recognition signals with data such as a bill of lading container content lists, port of origin data or container weight to produce an event probability number; quantifying a total metal content for said container; raising said event probability number when a contents list for said container does not show a total metal content compatible with the total metal content for the container; outputting a risk alarm from any container having an event probability greater than a predetermined value.