PNNL

The Science                                

Boehmite is an aluminum-based mineral commonly found in the Earth’s crust, industrial byproducts, and legacy radioactive tank waste. Understanding how boehmite behaves after irradiation is important for processing the legacy radioactive tank waste. Researchers found that irradiated boehmite nanoplatelets have significantly rougher surface textures than non-irradiated nanoplatelets, leading to different surface chemistry. The rougher surface texture is likely due to the breakup of surface groups by radiation and affects how the boehmite interacts with charged species in solution.

The Impact

Mineral aggregates can cause challenges in processing waste. Legacy radioactive tank waste contains significant amounts of aluminum-based solids, like boehmite, in slurries that are radioactive with high salt concentrations. Developing an understanding of how radiation affects aggregation, particularly when coupled with high concentrations of salts, is important for effectively managing this type of waste. By identifying the effects of radiation-induced surface changes, this work provides insight into the likely behavior of boehmite within legacy radioactive tank waste.

Summary

Legacy radioactive tank waste is a complex mixture of irradiated chemical species at high concentrations. While the waste is in solution, it includes substantial amounts of solids such as boehmite. The boehmite particles tend to form aggregates, altering the material’s properties and affecting the viscosity of the overall solution. Researchers explored the aggregation behavior of boehmite nanoplatelets with and without irradiation under a range of salt concentrations and pH values. They found that irradiated boehmite nanoplatelets formed smaller, rod-shaped aggregates while pristine boehmite aggregated into larger spheres. Close examination showed that the surface of the irradiated materials was significantly rougher in texture, with a disruption of surface hydroxide groups the likely cause. The rougher surface texture affects how the boehmite interacts with ions in solution, causing irradiated boehmite to behave differently than pristine boehmite. This set of experiments provides insight into boehmite behavior at conditions relevant for understanding and processing legacy radioactive tank waste.

PNNL Contact

Jay LaVerne, University of Notre Dame, laverne.1@nd.edu

Carolyn Pearce, Pacific Northwest National Laboratory, carolyn.pearce@pnnl.gov

Funding

This work was supported as a part of IDREAM, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. The authors acknowledge the support of the National Institute of Standards and Technology, Center for Neutron Research, Department of Commerce in providing the research neutron facilities used in this work. Access to both NBG30 SANS and BT5 USANS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. A.I.K. acknowledges the support of the Scientific User Facilities Division, Office of Basic Energy Sciences, Department of Energy. The authors acknowledge the Notre Dame Radiation Laboratory, which is supported by the Division of Chemical Sciences, Geosciences and Biosciences, Basic Energy Sciences, Office of Science, United States Department of Energy through grant number DE-FC02-04ER15533.