The U(VI) silicate minerals such as uranophane (Ura) Ca[(UO2)(SiO3OH)]2·5H2O, sklodowskite (Sklo) Mg[(UO2)(SiO3OH)]2·6H2O, and Na-boltwoodite (NaB) Na(H3O)[(UO2)SiO4] are common in nature, and also observed as corrosion products in studies of long-term aging of spent nuclear fuel. These solids can control the dissolved concentrations of uranium in groundwater, and also influence the dissolved concentrations of other actinides such as pentavalent neptunium (Np(V)) associated with them. Mineral dissolution and metal ion desorption were tested by equilibrating mineral suspensions containing tracer levels of 233U or 237Np for 7 days at pH 11. Changes in dissolved U concentrations with time indicate initial mineral dissolution, followed by re-precipitation; this observation for dissolved U was consistent whether the system included traces of Np(V) or not. Interestingly, for studies involving U(VI) silicates containing traces of 237Np, the Np was continuously released from the solid, even during re-precipitation of the dissolved U. These studies will be described and discussed in the context of direct disposal of spent nuclear fuel.

Behavior of U(VI) silicate minerals and Np(V)-doped U(VI) silicates

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.