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A sample preparation sequence for actinide isotopic analysis by thermal ionization mass spectrometry (TIMS) is described that includes column-based extraction chromatography as the first separation step, followed by anion-exchange column separations. The sequence is designed to include a wet ashing step after the extraction chromatography to prevent any leached extractant or oxalic acid eluent reagents from interfering with subsequent separations, source preparation, or TIMS ionization. TEVA resin and DGA resin materials, containing extractants that consist only of C, N, O, and H atoms, were investigated for isolation of plutonium. Radiotracer level studies confirmed expected high yields from column-based separation procedures. Femtogram-level studies were carried out with TIMS detection, using multiple monoisotopic spikes applied sequentially throughout the separation sequence. Pu recoveries were 87% and 86% for TEVA and DGA resin separations, respectively. The Pu recoveries from 400 μL anion-exchange column separation sequences were 89% and 93% for trial sequences incorporating TEVA and DGA resin. Thus, a prior extraction chromatography step in the sequence did not interfere with the subsequent anion-exchange separation when a simple wet ash step was carried out in between these column separations. The average measurement efficiency for Pu, encompassing the chemical separation recoveries and the TIMS ionization efficiency, was 2.73% ± 0.77% (2σ) for the DGA resin trials and 2.67% ± 0.54% for the TEVA resin trials, compared to 3.41% and 2.37% (average 2.89%) for two control trials. These compare with an average measurement efficiency of 2.78% ± 1.70%, n = 33 from process benchmark analyses using Pu spikes processed through a sequence of oxalate precipitation, wet ash, iron hydroxide precipitation, and anion-exchange column separations. We conclude that extraction chromatography can be a viable separation procedure as part of a multistep sequence for TIMS sample preparation.

A method for chemically selective radiometric sensing of non-γ-emitting radionuclides in solution is described. Using scintillating microspheres with selective radionuclide uptake properties, radiochemical separation and radiometric detection steps are integrated within a sensor device. These microspheres are loaded into a renewable minicolumn that serves to capture, preconcentrate, and separate radionuclides. The preconcentrating minicolumn also localizes and retains radionuclides within a detector of well-defined geometry and emits a photometric signal. The sensor material in the column can either be regenerated with eluent chemistries or be renewed by fluidic replacement of the beads. The latter method allows the use of materials that bind analytes irreversibly or are unstable under regeneration conditions. Radionuclide-selective scintillating microspheres were prepared by coimmobilization of scintillating fluors and selective organic extractants within the pores of an inert polymeric support. Preparation and characterization of microspheres, and their use for selective quantitative sensing of (99)Tc(VII), is described in detail. A sensor-based procedure for (99)Tc(VII) analysis was developed and successfully applied toward the determination of (99)Tc(VII) in groundwater samples from the Hanford site, using standard addition techniques for quantification. Using a 50-mL sample volume and signal accumulation time of 30 min, the detection limit for (99)Tc(VII) was 0.37 dpm/mL (9.8 pg/mL).

A novel approach to the automation of sorbent extraction separations is described. An advanced sequential injection renewable separation column (SI-RSC) instrument was designed and optimized for automatically packing a separation column on-line, using it for a separation, and then disposing of the used separation material. Column packing/separation material disposal steps are accomplished fluidically using a frit restriction. Using a 250-μL renewable column, procedures were developed for the separation and analysis of 90Sr, 241 Am, and 99 Tc in aged nuclear waste samples employing Sr-resin, TRU-resin, and TEVA-resin sorbent extraction materials (Eichrom Industries). The separation performance of the RSC was identical to that of a freshly packed conventional column of similar size. With a renewable column, it is not necessary to elute all species from the column, carryover on the column from one separation to the next is eliminated, the same instrument can be used for multiple separations requiring different sorbent extraction media without physical changes to the instrument (sorbent extraction medium is selected in software), and the sorbent extraction material can be recovered for analysis of noneluted species.

An automated procedure for the determination of (99)Tc in aged nuclear waste has been developed. Using advanced sequential injection (SI) analysis instrumentation, (99)Tc(VII) is separated from radioactive and stable interferences using a TEVA resin column that selectively retains pertechnetate ion from dilute nitric acid solutions. The separated (99)Tc is eluted with 6 M nitric acid and quantified on-line with a flow-through liquid scintillation detector. A stopped-flow technique has been optimized that improves the analysis precision and detection limit compared to continuous-flow detection, reduces consumption of liquid scintillation cocktail, and increases sample throughput by separating the next sample while the present sample is being counted. The detection limit is 30 pCi, or 2 ng, of (99)Tc, using a 15-min stopped-flow period. The analysis time is 40 min for the first sample and is reduced to 20 min for each subsequent sample. Processed nuclear waste samples from the Hanford site were successfully analyzed by this new method.