Application of CT filter algorithms to digitized film data

The CT studies performed thus far in the RAS division have been based on neutron radiographs of two 7-pin reactor fuel bundles which were subjected to over-power accident simulations in the TREAT reactor. As a result of the tests, the pins were severely damaged, with molten fuel and steel spreading throughout the fuel assembly. The neutron radiographs are produced at the NRAD reactor facility at ANL-West in Idaho. The RAS reconstruction codes are based on the filtered back-projection technique, using standard fast Fourier transforms and filter algorithms. Because of the length of the fuel assemblies, and the fact that they are held only at the top by the rotation mechanism, it is nearly impossible to achieve a perfect vertical alignment, so a major part of the analysis time is spent in rotating and aligning the images. As part of this computerized alignment, each image is also normalized to a constant exposure time, based on the data in a neutron absorbing step wedge that is imaged along with the fuel pins. All computer codes were loosely developed from those given in the Donner Algorithms prepared for the National Cancer Institute and are currently run on a PDP-11/60 computer