PNNL

Abstract

Here, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to 60Co gamma radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures. Specifically, the temperature-dependent dissolution rates of irradiated 20 nm boehmite versus pristine material in 3M NaOH solutions were several times lower (e.g., rate constant of 0.026 ·h-1 versus 0.075 ·h-1 at 60 oC), with an apparent activation energy 40 kJ·mol–1 higher. Although various imaging techniques and X-ray diffraction measurements consistently revealed no obvious differences between pristine and irradiated samples, detectable shifts were observed in the X-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, along with a lower O/Al ratio after irradiation. This suggests that ?-irradiation may be to stabilize boehmite particle surfaces by driving their chemistry and structure toward more stable aluminum oxide forms. These findings have the potential to enhance our understanding of related reactions in nuclear waste and may be useful for the development of more robust predictive models and effective strategies for waste cleanup.