NEUTRON RADIOGRAPHIC TECHNIQUES AS A TOOL FOR NUCLEAR MATERIALS SAFEGUARDS

A few fuel samples have \"been neutron radiographed at the Transient Reactor Test Facility (TREAT) to explore the feasibility of using neutron radiography techniques for measuring the fissile content of reactor fuel elements. These preliminary measurements indicate that the U-235 content in flat-plate and pin-type elements with enrichments in the range of 10% can be determined, to an enrichment accuracy of about 0.5% if a standard of known enrichment is available for exposure with the unknown. For enrich- ments in the range between 30% and 90%, the accuracy is considerably less but should be better than 5%- Neutron radiography techniques could be used for enrichment analyses on spent reactor fuel elements or elements from fuel reprocessing systems which do not remove the majority of the fission products. Therefore, these techniques could be applied when gamma radiation levels prevent the use of gamma spectrometry for safe- guards inspections.