Accounting for Recycled Uranium Produced from Reactor Irradiated Fuel

Recycled uranium generally contains trace amounts of reactor-produced isotopes, including plutonium, because it originates by chemical separation from irradiated fuel and target materials. Historically, the quantities of recycled uranium produced at Department of Energy (DOE) sites were not specifically documented, and production sites shipped both recycled uranium and natural uranium without type designation. Although, nuclear material accountability records for uranium do not show the path of production, they contain uranium enrichment and possibly chemical form information that may assist in determining the origin of the material. For an investigation of health concerns related to possible plutonium exposure from handling recycled uranium, DOE needed to have an accurate accounting of the quantities of recycled uranium produced and the quantities of reactor-produced contaminants in that recycled uranium. Prior to this investigation, there was no apparent need to know the origin of uranium used in agency processes. To assist in the investigation, the principal DOE sites that produced and utilized recycled uranium researched their records and published reports showing estimates of the production and use of recycled uranium, complete with concentrations of reactor-produced contaminants. Because the available records did not differentiate between recycled uranium and natural uranium, the sites developed their own specific operational definitions. These operational definitions caused differences between shipper and receiver data that could not be resolved prior to publication of the reports. Research conducted over the past year has clarified the production information, resulting in a uniform dataset that has been accepted by the production sites. This new accounting of recycled uranium production used a strategy of applying process knowledge and site material requirements to the analysis of the available records to distinguish between uranium types. Because the health issue primarily concerned exposure to plutonium in the recycled uranium, it was necessary to estimate the quantities of contaminants in the recycled uranium. The limited historical analysis data for recycled uranium was sufficient to allow conservative estimates of the contaminants contained in the recycled uranium produced. The methodology used for this research is discussed with specific examples.