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Understanding the speciation and redox behavior of technetium in high ionic strength complex media


EMSL Project ID
48902

Abstract

One of the DOE-EM current challenges is to meet regulatory requirements for near term disposal of technetium-99 (Tc), one of the most important performance assessment risk contributors during long-term waste storage. The long half-life, complex chemical behavior, limited incorporation in mid- to high-temperature immobilization processes, and high mobility in subsurface environments make Tc one of the most difficult contaminants to dispose of and/or remediate. In the multicomponent liquid matrices such as those related to the contaminated groundwater found in the Hanford area vadose zone, liquid nuclear tank waste, and solution generated during used nuclear fuel reprocessing, Tc exists in multiple oxidation states and chemical forms, and a thorough understanding of its behavior and speciation is lacking. The lack of the scientific information on Tc redox speciation, stability of its oxidation states, and inter-conversion among species in the complex liquid solutions results in inability to design technically defensible approaches for the overall Tc management including separation and immobilization strategies. The objective of this work is to address the scientific and technical uncertainties limiting accurate prediction of Tc behavior and design of effective mitigatation strategies. This project will gain a fundamental understanding of the most prominent Tc oxidation states and chemical species in the complex liquid matrices typical for the liquid tank waste solutions and contaminated subsurface environment.

Project Details

Project type
Large-Scale EMSL Research
Start Date
2015-10-01
End Date
2016-09-30
Status
Closed

Team

Principal Investigator

Tatiana Levitskaia
Institution
Pacific Northwest National Laboratory

Co-Investigator(s)

Sayandev Chatterjee
Institution
Pacific Northwest National Laboratory

Team Members

Vanessa Holfeltz
Institution
Pacific Northwest National Laboratory

Gabriel Hall
Institution
Pacific Northwest National Laboratory