Plutonium solubility and speciation studies in a simulant of Air Intake Shaft water from the Culebra Dolomite at the Waste Isolation Pilot Plant

The aqueous concentration of a radionuclide is one factor that determines the rate at which the radionuclide might be transported away from a nuclear waste repository should a repository breach occur. This study documents research examining the solubility of plutonium in a brine composition of interest for performance assessment for the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico. Solutions starting with five different forms of plutonium, Pu(III), Pu(IV), Pu(IV)-polymer, Pu(V), and Pu(VI), were allowed to equilibrate in a brine with composition similar to that measured from the Culebra Member of the Rustler Formation in the Air Intake Shaft to the WIPP. Nearsteady-state conditions were reached within a year of reaction time. The resulting concentrations represent an upper bound on the amount of plutonium that can remain dissolved in solution under the experimental conditions (e.g., exclusive of colloids) and can thus be transported with the aqueous phase