Computational Analysis of Signatures of Highly Enriched Uranium Produced by Centrifuge and Gaseous Diffusion

Different enrichment processes have been used historically to produce highly enriched uranium (HEU) for weapon purposes. The most relevant ones are the gaseous diffusion process and the gas centrifuge. The two exploit different physical principles to separate isotopes of different molecular weight. It could therefore be expected that HEU might carry an isotopic signature that is unique to the enrichment process used to produce the material. Multi-isotope enrichment cascades are generally modeled using the matched-abundance-ratio approach. In this paper, we will present comparisons of the isotopic signatures predicted in gas centrifuge cascades with those predicted in gaseous diffusion cascades by using a modified version of the matchedabundance- ratio cascade code, MSTAR, which accounts for the physical differences in the stage separation factors in the two processes. Additionally, we will present the methodology used by the modified code and discuss representative results for HEU produced from both natural and reprocessed uranium. We find that essentially complete knowledge of the enrichment technologies employed, of the cascade design, and of the mode of operation is required in order to make meaningful (quantitative) statements about expected HEU signatures.