Separation of Radionuclides

The exigencies of research current around that time in the chemistry and separation of radionuclides led Calvin and his associates (1950) to introduce trifluorothenoylacetone (TTA), a reagent systematically and specifically designed for the solvent extraction of highly charged cations which had to be carried out from acidic solutions in order to avoid hydrolysis. 

Law, J.D., Herbst, R.S., Todd, T.A. 2002. Integrated AMP-PAN, TRUEX, and SREX testing. II. Flowsheet testing for separation of radionuclides from actual acidic radioactive waste. Sep. Sci. Technol. 37 (6) 1353-1373. 

Shaibu, B.S. Reddy, M.L.P. Prabhu, D.R. Kanekar, A.S. Manchanda, V.K. N, N -dimethyl-N, N -dibutyl tetradecyl malonamide impregnated magnetic particles for the extraction and separation of radionuclides from nuclear waste streams, Radiochim. Acta 94 (2006) 267-273. 

Egorov, O., O Hara, M. J., Grate, J. W., and Ruzicka, J., Sequential injection renewable separation column instrument for automated sorbent extraction separations of radionuclides, Anal. Chem., 71, 345-352, 1999. 

Kremliakova, N. Y., Novikov, A. P, and Myasoedov, B. F., Extraction chromatographic separation of radionuclides of strontium, cesium, and barium with the use of tvex-dchl8c6, J. Radioanal. Nucl. Chem. Lett., 145, 23-28, 1990. 

Separation of radionuclides by distillation is applicable if volatile compounds arc formed. Separation of from irradiated Tc has already been mentioned in section 12.1. Other examples are separation of Ru as R11O4 under oxidizing conditions, and volatilization of Tc as TC2O7 from concentrated H2SO4 at 150-250 C. -P may be purified by volatilization as PCI5 in a stream of CE. 

Solvent extraction is widely used for separation of radionuclides, because this technique is simple, fast and applicable in the range of low concentrations. Addition of a carrier is not required. Some examples of separation of radionuclides by solvent extraction are given in Table 12,8, As already mentioned in section 11,6, solvent extraction plays an important role in reprocessing. Tributyl phosphate (TBP), methyl isobutyl ketone (Hexon) and trilaurylamine (TLA) are preferred complexing agents for separation and purification of U and Pu,... 

Heterogeneous exchange of radionuclides on carbonates has already been mentioned. Exchange on other sparingly soluble minerals (e.g. halides, sulfates, phosphates) may lead to rather selective separation of radionuclides. Following the exchange at the surface, ions may be incorporated into the solids in the course of recrystallization, which is a very slow but continuous process. Anomalous solid solutions with radioactive ions of different charges may also be formed. 

The Szilard-Chalmers effect permits separation of radionuclides at high specific activity and purity from the matrix in which they are produced. Preparation of the pure product is an empirical process because of the complex interaction of the three sequential steps producing the free radioactive ion or atom, maintaining the product in its new form in the sample matrix, and separating the product from the matrix. Success of the process is evaluated empirically in terms of the specific activity of the product relative to the matrix or, alternately, the fractional yield of the product. 

One of the main differences between radiochemical analytical procedures and classical analytical methods is that the element (and particularly its radioisotope) to be determined is present in the sample in minor to trace amounts. Separation of radionuclides is performed with the aid of a suitable carrier. Generally, the carrier is a stable isotope (or a suitable compound) that is added to the radioactive compound in a small but detectable amount and has identical chemical properties. An isotopic carrier, i.e., a stable isotope of the element in question, is most frequently used. Both the radioactive isotope and the carrier must be in the same chemical form. The isotopic carrier is irreversibly mixed with the radioactive compound and cannot be separated from it again by chemical means. Such a carrier can therefore be used only when a lower specific activity is sufficient for the subsequent operations. For example, barium or lead can serve as carriers when... 

Essentially all the separation methods known from classical analytical chemistry can be applied to chemical separations of radionuclides and labeled compounds from samples to be analyzed precipitation, electrolytic deposition, extraction, ion exchange, distillation, chromatography, etc. 

Complexation can be used to separate metallic ions on an industrial scale. Fig. 2 illustrates the process in the case of the separation of nickel and cobalt ions. A chelating agent (e.g., diethyl hexyl phosphoric acid) is added to a heptane stationary phase. A large volume (up to 20 times the CCC machine volume Vc) of the ionic solution is introduced into the CCC column. The nickel ions are displaced in the aqueous phase, and the cobalt ions can be collected in the stationary phase. More than two ions can be separated in bands of increasing complexation constants order. Because no ions can stay trapped inside the CCC machine, it could be a very potent tool in the separation of radionuclides in the processing of nuclear wastes. 

The schemes adopted for the treatment of waste by various countries may differ in respect of processes and engineering, however all have the same objective i.e. volume reduction and separation of radionuclides in a concentrated fraction leaving the bulk of waste depleted in radioactivity. 

Gas proportional counters for alpha and beta emitters also require previous separation of radionuclides due to their low capacity to discriminate between particles with different energies. 

There are many examples using these approaches for SPE of trace metals using atomic spectrometry detection (Miro and Hansen, 2013 Ruzicka, 2014), column separations of radionuclides and affinity chromatography (Ruzicka, 2014), the determination of organic molecules in food or clinical samples (Chen and Wang, 2007 Miro et al., 2011 Ruzicka, 2014) and for DNA assays, bioligand interaction assays and cellular studies (Ruzicka, 2014). Over the last few years, BIA has been combined with the LOV platform (Chen and Wang, 2007 Miro and Hansen, 2012 Ruzicka, 2014). 

Eichler, B. Preparative thermo gas chromatographic separation of radionuclides in hydrogen and air carrier gas stream. Radiochem. Radioanal. Lett. 22, 147-155 (1975)... 

Eichler, B., Domanov, V.P. Reactive desorption techniques and adsorption at various temperatures-used for the separation of radionuclides. J. Radioanal. Chem. 28, 143-152... 

---