THE NOx SYSTEM IN HOMOGENEOUS AND HETEROGENEOUS NUCLEAR WASTE

This report summarizes advances of the above-mentioned EMSP project during the period July 1, 2001-June 30, 2002. The project focuses on the effects of organic chemicals in stored nuclear waste and their impact on pretreatment and tank closure issues. Managing the tank wastes and site cleanup activities requires understanding of the chemistry of organics in aqueous basic solutions that contain high nitrate and nitrite concentrations under the field of g and b irradiation. The goal of this EMSP project is to quantitatively characterize the important chemical processes that are induced by radiolysis of the organic complexants, and their degradation products, during the storage in tanks. Furthermore, concerns that arise from pretreatment and tank closure issues, e.g., Tc speciation, can be rationalized with the mechanistic knowledge provided here. Recognizing that experiments cannot reproduce every conceivable realistic scenario, the project emphasizes computational methodologies . None of the Hanford tanks is currently on a watch list, partially due to the predictive understanding of the tanks' chemistry that was developed by these projects and their predecessor activities. The project is closely coupled to another EMSP project (81883) and exchange of information between the two related studies is frequent