Complexes separation from used nuclear fuels

Cyanex 301 One of the solvent extraction processes, used together with UREX, for separating the components of used nuclear fuel. This process uses a complex phosphinic acid, [bis(2,4,4-trimethylpentyl)dithiophosphinic acid], made by Cytec Industries, Canada. Its purpose is to separate americium, curium, and lanthanide fission products from the other components. 

Tridentate N-donor ligands are efficient in separating actinides from lanthanides selectively by solvent extraction, an area of potential great importance in treatment of used nuclear fuel rods. The tridentate ligand 2,2 6 ,2 -terpyridyl (terpy) forms a range of complexes. The perchlorate complexes [Ln(terpy)3] ( 104)3 contain nine-coordinate cations with near- )3 symmetry, a structure initially deduced from the fluorescence spectrum of the europium compound (Section 5.4) and subsequently confirmed by X-ray diffraction smdies (Figure 4.7)... 

Nuclear fuel reprocessing was first undertaken with the sole purpose of recovering plutonium, for weapons use, from uranium irradiated in nuclear reactors. These reactors, called the production reactors, were dedicated to transmuting as much of the uranium as possible to plutonium. From its original scope of recovering exclusively plutonium, with no attempts to either recover or recycle uranium, nuclear fuel reprocessing has since grown into a much more sophisticated and complex operation with expanded scope. It is now called upon to separate uranium and plutonium from the fission products, and to purify these elements to levels at which these fissile materials can be conveniently recycled for reuse. The present scope also extends to fission products separation and concentration. 

The development of solvent-impregnated resins and extraction-chromatographic procedures has enabled the automation of radiochemical separations for analytical radionuclide determinations. These separations provide preconcentration from simple matrices like groundwater and separation from complex matrixes such as dissolved sediments, dissolved spent fuel, or nuclear-waste materials. Most of the published work has been carried out using fluidic systems to couple column-based separations to on-line detection, but robotic methods also appear to be very promising. Many approaches to fluidic automation have been used, from individual FI and SI systems to commercial FI sample-introduction systems for atomic spectroscopies. 

The different redox stability of U and Pu is important in nuclear fuel reprocessing, one function of which is to separate unused uranium from 239Pu, which is itself used as a nuclear fuel. Dissolving the spent fuel elements in aqueous HN03 gives Pu(VI) and U(VI). Subsequent separation steps then depend on differences in complexing power and solubility of these ions. 

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