Technetium-99 Behavior in Savannah River Site High Level Waste Sludges During Waste Processing

This report presents results of an in-depth study of the behavior of technetium-99 (Tc-99) during waste processing operations at Savannah River Site. Tc-99 is a long lived (t1/2 equals 2.1E05 years) radioactive fission product of U-235. Its behavior during high level waste (HLW) processing is important to understand because Tc-99 can fractionate in the waste and appear in both the sludge and the salt tanks at Savannah River Site. Further it can also be soluble in groundwaters and thus is an important radionuclide that may dictate how much residual waste has to be removed from a waste tank to prepare it for permanent closure. Results are also presented for Pd-105, another important U-235 fission product. This fission product is stable, but it is important because it has a finite solubility in the sludge supernates in the HLW and is also used to calculate the concentration of the radionuclide Pd-107 that has to be reported in the Waste Acceptance Specifications to send HLW glass to a repository