Date(s) - 11/19/2020
1:50 pm - 2:50 pm
Carolyn Pearce, Ph.D.
Pacific Northwest National Lab
The Hanford site in Washington State, which produced plutonium for the US weapons program, is the most contaminated nuclear site in the nation and is its largest environmental clean-up activity. During weapons production, 56 million gallons of liquid radioactive/chemical waste (sludge, salt cake, and supernate), with 170 million Curies of radioactivity and 240,000 tons of complex chemicals, were generated. This liquid waste is the primary environmental contamination risk, currently intended to be processed into a glass form for stabilization and to allow its radioactivity to safely dissipate over hundreds to thousands of years. Uncertainty associated with nuclear waste processing and disposal can be mitigated by: (i) characterizing waste chemistry; and (ii) understanding contaminant reactions both in the waste form and with environment.
A key issue of Hanford tank waste processing and disposal is that, although radionuclides such as technetium are the risk drivers, it is the ‘benign’ dominant elements such as aluminum (Al) that dictate the processing limits and uncertainties, given that tank waste is removed on a volume basis. Thus, safe, cost-effective, and efficient waste processing depends on a fundamental understanding of aluminum chemistry in these complex high ionic strength, highly alkaline solutions.
Research by the Interfacial Dynamics in Radioactive Environments and Materials (IDREAM) Energy Frontier Research Center (EFRC) has focused on leveraging national user facilities to unravel ion coordination, solvation, pairing with other ions, and cluster formation in these complex chemical environments. The goal of this research is to understand the mechanisms of speciation change that underpin solubility, nucleation and precipitation, using multiple spectroscopic techniques.