INTERNATIONAL ATOMIC ENERGY AGENCY USE OF FACILITY CALORIMETERS FOR SAFEGUARDS PURPOSES

The International Atomic Energy Agency is performing nuclear materials safeguards on an inventory of pure and scrap plutonium oxide powder materials held in Vault 3 of the Plutonium Finishing Plant, operated by the Westinghouse Hanford Company for the U. S. Department of Energy at the Hanford Site in Washington State. The International Atomic Energy Agency uses qualitative and quantitative techniques to verify the presence and quantity of the nuclear materials under safeguards. The Agency uses weighing, sampling, and destructive analyses to obtain the most accurate verification measurements of containers of plutonium powders. In contrast, the plant operator generally uses non-destructive plutonium assay based on gamma spectrometry and calorimetry for its most accurate plutonium powder container measurements. Recent results have shown that the operator’s calorimeter system achieves measurement variabilities comparable with, or better than, the destructive analyses, particularly for scrap. The results are achieved more quickly and economically, with less waste and lower radiation exposure and contamination hszud, by calorimetry than by classical destructive analyses. Techniques, including authentication methods, are being jointly developed to permit use of the operator’s calorimeter system for international safeguards purposes. The authentication is to ensure the independence of, and to substantiatethe validity of, calorimeter measurements for international safeguards. The authentication methods considered and being developed are discussed.