A thorough understanding of the chemistry of fission products is a crucial component to the safe storage and disposal of spent nuclear fuels; it also provides an effective tool for nuclear forensics. Tc-99 has a 6% cumulative fission yield and a 213,000 year half-life, making it a significant component of both the composition and radioactivity of spent nuclear fuels. Tc persists as either the highly mobile and water soluble Tc(VII) or the sparingly soluble Tc(IV) in the natural environment. Understanding the chemistry of the less mobile +4 oxidation state of Tc-99 will allow for improving technetium mobility modelling, therefore providing valuable data for successful site decontaminations and for nuclear forensics. This work seeks to determine stability constants for the complexation of Tc(IV) with the carboxylic ligands iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), hydroxyethyl ethylenediaminetriacetic acid (HEDTA) and diethylene triaminepentaacetic acid (DTPA), using liquid-liquid extraction methods. The stability constants for each Tc(IV) / ligand complex are then compared based on the number and type of coordination sites available for binding with each ligand. Additionally, the total dissolution of Tc(IV) in the presence of these ligand can be calculated using the determined stability constants. This research was funded by the Defense Threat Reduction Agency through grant # HDTRA1-12-0014.

Stability constant determinations for technetium (IV) complexation with selected carboxylic ligands in sodium nitrate

251st National Meeting (2016)

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