Impacts of gamma ray emissions of materials containing 232U on safety, security, and safeguards

Abstract

The introduction of 232U to uranium materials is a possible technique to reduce the material attractive of the material for weapons purposes. In order to implement 232U in civilian nuclear fuel cycles, its impacts on safety, security, and safeguards must be considered. This study will utilize an initial mixture of 0.03 at.% 232U with natural uranium, enriched to approximately 3, 5, 20, and 90 at.% 235U. The mixture with natural uranium, 3, 5, and 20 at.% 235U represent uranium isotopic vectors that would be commonly found within civilian nuclear fuel cycles. The 90 at.% 235U isotopic vector represents weapons grade uranium. The security and safeguards results from each isotopic vector will be compared to results from a corresponding isotopic vector that does not contain 232U, but has the same 235U/238U ratio. Considering 232U’s daughter products contribute significantly to the gamma ray emissions over time, the isotopic vectors will be evaluated at three time intervals: fresh, 0.5 year, and 10 years. When compared to standards put in place by U.S. Nuclear Regulatory Commission, the dose rates produced by the uranium isotopic vectors containing 232U indicate the need for additional safety protocol to shield workers from this increased dose rate. These gamma ray emissions produce a significant increase in detectability in the weapons grade uranium isotopic vector with 232U even in the presence of lead shielding. A common safeguards technique used to verify 235U enrichment was shown to be useless in the presence of 232U and its daughter products. This would require the use of a different technique in order to verify the 235U enrichment.