Year
2006
Abstract
Identification of highly enriched uranium (HEU) is a primary objective of taking Safeguards environmental samples. Additionally, the isotopic characteristics of the HEU may be useful in verifying the enrichment process used to produce the enriched uranium. The isotopic characteristics of the HEU are the result of a number of factors such as the feed material and enrichment cascade configuration. This paper will show that the environmental signature of HEU produced from a single cascade is distinguishable from similarly enriched uranium produced from a series of four cascades. For both cases, the feed material is assumed to be recycled natural uranium (NU) and the product is HEU with 90% 235U. The MStar model (also known as the matched abundance ratio cascade model) is used to determine the isotopic content of the uranium enrichment streams in two possible enrichment scenarios. The first case models a single cascade that enriches the NU feed to 90% 235U in a single pass. The second enrichment case achieves the same final enrichment but through a four-step cascade process, where the product from the lower cascade is used as the feed for the next enrichment cascade. In this manner, the NU feed is enriched to 4%, 20%, 65% and 90% 235U sequentially. Although in both cases the resulting product is 90% HEU, the isotopic content of the two products are distinctive and could be used to identify different sources of enriched uranium.