Development and Characterization of Extractive Scintillating Resins for Determination of Ultra-Low-Level Plutonium in Aqueous Systems

Extractive scintillating resins (ESRs) simplify quantification of radionuclides from aqueous solutions by reducing the number of steps required and by reducing waste. Two formulations of plutonium ESRs were developed and characterized: (1) by attaching scintillating polymer chains to the surface of a commercially available Pu extraction resin and (2) by impregnating a scintillating resin bead with an organic ligand shown to extract Pu at circumneutral pH. In the first formulation, plastic scintillating polymer was attached to the surface of Pu-02 Analig®, a proprietary silica-based molecular recognition resin developed by IBC Advanced Technologies® for selective aqueous Pu uptake. Batch uptake of the modified resin tests indicated high affinity for 242Pu(IV) from a pH 1 solution (uptake \u3e90%). This resin subsequently was loaded into a perfluoroalkoxy alkane column, and detection efficiency was quantified with a liquid scintillation counter without the introduction of cocktail. On-line measurement with the resin was conducted utilizing a flow-cell radiation detector to quantify the plutonium accumulated on the resin as it was loading on the column. Plutonium quantification with the resins was successful with uptake efficiencies values of \u3e99% and 97% and detection efficiency values of 36.4% and 28.5% for batch and on-line measurements, respectively. Further optimization studies demonstrated that shorter modification times with particles \u3c63μm demonstrated the greatest efficiency for Pu detection and that high concentrations of Fe(III) will interfere with Pu uptake. In the second formulation, dibenzoylmethane (DBM) was investigated for Pu uptake through a series of batch uptake studies and liquid-liquid extractions. Pu(IV) was the primary form to result in uptake with DBM, however extraction was relatively poor due to hydrolysis and adsorption effects of Pu(IV) at low to circumneutral pH. This was demonstrated when Pu(IV) would adsorb to non-functionalized resin surface to the same extent as a DBM coated surface. When incorporated with a scintillating resin, the DBM significantly quenched light due to absorption of UV wavelengths that are required for fluorophores. Pu selective ESRs are a nuclear forensics tool capable of monitoring water systems for unforeseen releases of plutonium. Given a sufficient counting time of 15 minutes and approximately 300 mL of solution volume, a minimum detection limit capable of meeting the EPA limit for gross alpha activity in drinking water can be achieved with the modified Analig® Pu02 resin