In Situ Spectroscopic Analysis and Quantification of [Tc(CO)₃]⁺ in Hanford Tank Waste

The quantitative conversion of nonpertechnetate [Tc(CO)₃]⁺ species in nuclear waste storage tank 241-AN-102 at the Hanford Site is demonstrated. A waste sample containing the [Tc(CO)₃]⁺ species is added to a developer solution that rapidly converts the nonemissive species into a luminescent complex, which is detected spectroscopically. This method was first demonstrated using a [Tc(CO)₃]⁺ sample of nonwaste containing matrix to determine a detection limit (LOD), resulting in a [Tc(CO)₃]⁺ LOD of 2.20 × 10^-7 M, very near the LOD of the independently synthesized standard (2.10 × 10^-7 M). The method was then used to detect [Tc(CO)₃]⁺ in a simulated waste using the standard addition method, resulting in a [Tc(CO)₃]⁺ concentration of 1.89 × 10^-5 M (within 27.7% of the concentration determined by β liquid scintillation counting). Three samples from 241-AN-102 were tested by the standard addition method: (1) a 5 M Na adjusted fraction, (2) a fraction depleted of ¹³⁷Cs, and (3) an acid-stripped eluate. The concentrations of [Tc(CO)₃]⁺ in these fractions were determined to be 9.90 × 10^-6 M (1), 0 M (2), and 2.46 × 10^-6 M (3), respectively. The concentration of [Tc(CO)₃]⁺ in the as-received AN-102 tank waste supernatant was determined to be 1.84 × 10^-5 M.