Tailored bifunctional polymer for plutonium monitoring

High Sorption and Selective Extraction of Actinides from Aqueous Solutions

The selective elimination of long-lived radioactive actinides from complicated solutions is crucial for pollution management of the environment. Knowledge about the species, structures and interaction mechanism of actinides at solid–water interfaces is helpful to understand and to evaluate physicochemical behavior in the natural environment. In this review, we summarize recent works about the sorption and interaction mechanism of actinides (using U, Np, Pu, Cm and Am as representative actinides) on natural clay minerals and man-made nanomaterials. The species and microstructures of actinides on solid particles were investigated by advanced spectroscopy techniques and computational theoretical calculations. The reduction and solidification of actinides on solid particles is the most effective way to immobilize actinides in the natural environment. The contents of this review may be helpful in evaluating the migration of actinides in near-field nuclear waste repositories and the mobilization properties of radionuclides in the environment.

Task-Specific Supported Liquid Membrane for Actinide Assay in Aqueous Streams by Thermal Ionization Mass Spectrometry

Thermal ionization mass spectrometry is the most commonly used technique for the determination of Pu isotopic composition and concentration in complex matrices but involves multiple steps including sample pretreatment, removal of matrix, preconcentration of Pu, and loading on a rhenium filament for TIMS analysis. The present work reports the synthesis of the N,N'-dioctyl-α-hydroxyacetamide (DOHA) functionalized supported liquid membrane that offered dual functions: (i) matrix elimination and/or preconcentration of actinides from complex aqueous samples and (ii) served as a loading substrate for TIMS analysis. The ligand composition in the membrane can be tuned aiming either for selective preconcentration of Pu from an aqueous matrix or for bulk removal of actinides. The membrane, impregnated with 0.2 M DOHA in dodecane, showed very high selectivity for Pu^IV in acidic medium, in the presence of other competing actinides, viz., Am^III, U^VI, and Np^V. The membrane based loading in TIMS improved the sample utilization efficiency and ionization efficiency compared to the conventional solution loading technique, offering Pu analysis from a single Re filament, that served as both vaporization and ionization filament and direct determination of ²³⁸Pu in the presence of ²³⁸U, eliminating the requirement of alpha spectrometry. It was possible to achieve >80% reduction in analysis time and >95% reduction in secondary waste generation by the SLM-TIMS method, compared to conventional TIMS involving Pu purification by anion exchange resin. Pu concentrations in seawater and groundwater samples, synthetic urine, and dissolver solution of irradiated fuel were determined by SLM-TIMS, employing the isotope dilution (ID) technique, with very good accuracy and precision. The membrane, impregnated with 2 M DOHA in dodecane, showed strong affinity for actinides and was successfully employed for the removal of bulk actinides from aqueous samples with more than 96% recovery.

Pore-Filled Scintillating Membrane as Sensing Matrix for α-Emitting Actinides

Pore-filled membranes with scintillating properties have been synthesized for sensing α-emitting radionuclides. The membranes have been prepared by in situ UV-initiator-induced polymerization of monomer bis[2-(methacryloxy)ethyl] phosphate in pores of the host membranes, poly(propylene) and poly(ethersulfone). The polymerization has been carried out in the presence of scintillating molecules, 2,5-diphenyloxazole. These scintillating molecules are physically trapped in the thus formed microgel in the membrane. Much higher α-scintillation efficiency has been obtained for the (241)Am-loaded poly(ethersulfone)-based grafted membrane compared to poly(propylene)-based membrane. This was attributed to the aromatic backbone of the poly(ethersulfone) membrane. The scintillation response of poly(ethersulfone)-based membranes has been found to be linear over the range of (241)Am activity studied. The pore-filled scintillating membranes have been found to be selective toward Pu(4+) ions at higher HNO3 concentration compared to Am(3+). The analytical performance of the pore-filled scintillating membranes has been evaluated. The membranes have been found to be stable and reusable. The scintillating membrane with optimized composition has been applied for quantification of Pu in a soil sample.

Superparamagnetic bi-functional composite bead for the thermal ionization mass spectrometry of plutonium(iv) ions

Single resin bead-based thermal ionization mass spectrometry (TIMS) offers numerous advantages for Pu(iv) determinations in complex aqueous samples.

Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu

Quantification of actinides in the complex environmental, biological, process and waste streams samples requires multiple steps like selective preconcentration and matrix elimination, solid source preparations generally by evaporation or electrodeposition, and finally alpha spectrometry. To minimize the sample manipulation steps, a membrane based isotope dilution alpha spectrometry method was developed for the determination of plutonium concentrations in the complex aqueous solutions. The advantages of this method are that it is Pu(IV) selective at 3M HNO3, high preconcentration factor can be achieved, and obviates the need of solid source preparation. For this, a thin phosphate-sulfate bifunctional polymer layer was anchored on the surface of microporous poly(ethersulfone) membrane by UV induced surface grafting. The thickness of the bifunctional layer on one surface of the poly(ethersulfone) membrane was optimized. The thickness, physical and chemical structures of the bifunctional layer were studied by secondary ionization mass spectrometry (SIMS), scanning electron microscopy (SEM) and SEM-EDS (energy-dispersive spectroscopy). The optimized membrane was used for preconcentration of Pu(IV) from aqueous solutions having 3-4M HNO3, followed by direct quantification of the preconcentrated Pu(IV) by isotope dilution alpha spectrometry using (238)Pu spike. The chemical recovery efficiency of Pu(IV) was found to be 86±3% below Pu(IV) loading capacity (1.08 μg in 2×1 cm(2)) of the membrane sample. The experiments with single representative actinides indicated that Am(III) did not sorb to significant extent (7%) but U(VI) sorbed with 78±3% efficiency from the solutions having 3M HNO3 concentration. However, Pu(IV) chemical recovery in the membrane remained unaffected from the solution containing 1:1000 wt. proportion of Pu(IV) to U(VI). Pu concentrations in the (U, Pu)C samples and in the irradiated fuel dissolver solutions were determined. The results thus obtained were found to be in good agreement with those obtained by conventional alpha spectrometry, biamperometry and thermal ionization mass spectrometry.