Actinides / Lanthanides / TALSPEAK / NPEX / Separation / Pu / NpSummary. Bench-scale studies to determine the extraction behavior of Pu, Np, Am and lanthanides with the organophosphorus extractants TBP, CMPO and HDEHP have been carried out. Based on the results obtained using actual spent nuclear fuel solutions, enhancements to the NPEX, TRUEX and TAL-SPEAK processes have been successful. In NPEX, > 99.94% of both Np and Pu were separated from the fission products. In TRUEX, essentially complete recovery of the actinides (An) and the lanthanides (Ln) was achieved. In TALSPEAK, the complete separation of Pu, Np and Am from the lanthanides was demonstrated several times under various process conditions. The recovery of transuranics (TRU), including Am and Cm, is nearly 100% (below detection limit in the Ln stream), while the total recovery of Ln in the product stream exceeded 99.97%.

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Polymeric-coated ferromagnetic particles with an absorbed layer of octyl(pheny1)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) diluted by tributyl phosphate (TBP) are being evaluated for application in the separation and the recovery of low concentrations of americium and plutonium from nuclear waste solutions. Due t o their chemical nature, these extractants selectively complex americium and plutonium contaminants onto the particles, which can be recovered from the waste solution using a magnet.The effectiveness of the extractant-absorbed particles at removing transuranics (TRU) from simulated solutions and various nitric acid solutions was measured by gamma and liquid scintillation counting of plutonium and americium. The HNOQ concentration range was 0.01M to 6U. The partition coefficients (Kd) for various actinides at 2M HNO3 were determined t o be between 3000 and 30,000. These values are larger than those projected for TRU recovery by traditional liquid/liquid extraction. Results from transmission electron microscopy indicated a large dependence of Kd on relative magnetite location within the polymer and the polymer surface area.Energy disperse spectroscopy demonstrated homogeneous metal complexation on the polymer surface with no metal clustering. The radiolytic stability of the particles was determined by using 6oCo gamma irradiation under various conditions. The results showed that I Q more strongly depends on the nitric acid dissolution rate of the magnetite than the gamma irradiation dose. Results of actinide separation from simulated high-level waste representative of that at various DOE sites are also discussed.

This article discusses the experimental program conducted at Argonne National Laboratory to study the performance of in situ formed mixed iron oxides (IS-MIO) for the removal of strontium (Sr), plutonium (Pu), neptunium (Np), uranium (U), and americium (Am) from the Savannah River Site (SRS) radioactive tank waste. The boundaries for the experimental work were defined in collaboration with SRS. IS-MIO was actually found to be a mixture of Fe(II) and Fe(III) oxides and hydroxides, including magnetite. Decontamination factor (DF) values were measured for both IS-MIO and monosodium titanate (MST), the baseline sorbent used by SRS. DF values for IS-MIO were found to be superior to MST for all isotopes studied. DF values for Pu, Np, and Sr, achieved within 30 min of IS-MIO formation were orders of magnitude larger than the needed values. DF values for U and Am were less than the former three but still acceptable, and greater than MST. V V C 2010 American Institute of Chemical Engineers AIChE J, 56: 3012-3020, 2010

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