U and Pu Isotopic Correlations to Check Consistency of Seized Nuclear Material Against a Known Inventory, Team Sweden Effort to Create and Use a Virtual National Nuclear Forensic Library (NNFL) in th

As a part of the Galaxy Serpent Tabletop Exercise, a rudimentarynotional national nuclear forensic library (NNFL) was created.The NNFL was based on irradiated fuel sample analysisdata provided by the exercise management. It was then usedto evaluate data from a notional seized material. Our effort wasconcentrated on a small number of uranium and plutonium isotopicratio correlations to draw conclusions on the consistencyof the seized material data against data in the NNFL to answerthe question if the seized material could have originated fromthe inventory described by the NNFL. The isotopic relationshipsused were selected based on several criteria, includingknown high discriminatory power in most cases involving irradiateduranium fuel, universality (data available for all materials inthe NNFL and for the seized material), constancy (no short halflivesinvolved) and low measurement uncertainty. Our analysisresulted in a clear negative conclusion: the unknown sampledata did not match any material in the notional NNFL. In addition,problems and possible strategies foreseen for setting upa real NNFL in a state with a comprehensive nuclear fuel cycleover many decades are discussed, stressing the central roleof operating and accountancy records in conjunction with fueldepletion modeling to make maximum use of costly samplingand analysis in mapping a complex nuclear material inventoryinto a useful NNFL.