Actinide isotopes

Preparation and handling of actinides are very difficult, because of their scarcity, radioactivity, toxicity and reactivity. The actinides isotopes are unstable and they transform spontaneously into other elements by a and (3 decay or by fission. The chemical toxicity of the actinides is similar to the toxicity of other heavy elements. The radio toxicity is extremely high giving radiation damage in cells. The safe handling of actinides samples needs hermetically closed containments (glove boxes) maintained under low pressure with respect to the laboratory to avoid the risk of dispersion and inhalation of the particles if a break of containment occurs. 

A primary goal of chemical separation processes in the nuclear industry is to recover actinide isotopes contained in mixtures of fission products. To separate the actinide cations, advantage can be taken of their general chemical properties [18]. The different oxidation states of the actinide ions lead to ions of charges from +1 (e.g., NpOj) to +4 (e.g., Pu" " ) (see Fig. 12.1), which allows the design of processes based on oxidation reduction reactions. In the Purex process, for example, uranium is separated from plutonium by reducing extractable Pu(IV) to nonextractable Pu(III). Under these conditions, U(VI) (as U02 ) and also U(IV) (as if present, remain in the... 

Often the products of nuclear reactions have very short half-lives. This is especially true for the heaviest elements obtained by bombardment of heavy targets with heavy ions. To identify and characterize such short-lived nuclides, fast separations are required solvent extraction techniques are well suited to provide the required fast separations. For example, the SISAK method [68] has been successfully used in conjunction with in-line gas jet separators at heavy ion accelerators to identify short half-life actinide isotopes produced by collision of heavy atoms. The Sisak method involves use of centrifugal contactors, with phase residence times as low as tenths of a second, in conjunction with in-line radiometric detection equipment. 

Table 1. Decay properties and availability of actinide isotopes for solid state studies ...

Fig. 3. Graphical illustration of a mixing relationship between two end-member components in a three-isotope normalization diagram (241Am/239+240Pu vs. 23SPu/239+240Pu). It is indicated that the measured anthropogenic actinide isotope ratios are, within uncertainty, identical to the atomic weapon component, therefore clearly indicating that actinide fallout from the Chernobyl accident was insignificant in western Europe.

Actinide isotope analysis method development using FI technique for column separation and preconcentration ICP-MS 138... 

Crain, J. S. and Alvarado, J., Hydride interference on the determination of minor actinide isotopes by inductively coupled plasma mass spectrometry,. /. Anal. At. Spectrom., 9, 1223-1227, 1994. 

Table 20-2 Principal Actinide Isotopes Available in Macroscopic Amounts 1...

Actinides found as environmental contamination in mosses collected from a bog in the eastern Italian Alps were analyzed after their chemical separation by extraction chromatography (deposited on steel targets) with respect to isotope ratios and their concentration was determined by LA-ICP-MS. Moss samples were contaminated with a variety of actinide isotopes. The detection limits for actinides were determined as 3.6-7.2 x 10 gg for " Am and respectively. The Pu/ Pu isotope ratio (0.212 0.003) was almost constant within experimental error for all samples investigated. Pu contamination in moss samples was mainly the result of global fallout after nuclear weapons tests. " Am was found at the 2x 10 " gg level. This example demonstrates that mosses can be used as bioindicators for environmental contamination. ... 

Information from Russia is limited and is based on personal communications. The address below is of interest for the many radioisotopes they produce, but especially highly enriched actinide isotopes as shown in Table 4.20 (see Vesnovskii and Polynov, 1992 Vesnovskii et al., 1992 Vesnovskii et al., 1993) ... 

Vesnovskii, S.P., Polynov, V.N., Nikitin, E.A. and Vjachin, U.N., Quality and availability of actinide isotopes from All-Russian Scientific Research Institute of Experimental Physics in Arzamas-16. Nucl. Instrum. Meth. Phys. Res. A334 (1993) 37. 

In actinide series, the elements of greatest interest as environmental contaminants are neptunium, plutonium, americium, and curium, because their presence at relatively high concentrations in ecosystems would represent potential health problems (Katz et al., 1986). Nuclear data for actinide isotopes are presented in Table 5.11. 

Eyal Y and Kaufman A (1982) Alpha-recoil damage in monazite preferential dissolution of the radiogenic actinide isotopes. Nuclear Technology 58 77-83... 

In contrast to the above, low energy fission of nuclei in the radium region results in mass yield curves with three peaks symmetric around AH. Furthermore, low energy or spontaneous fission of some heavy actinide isotopes, e.g. produces symmetric mass... 

FIG. 16.2. Production of higher actinide isotopes by irradiation of mixed oxide fiiel (3% Pu, rest depleted U) at constant power in a boiling water reactor. 

Actinide isotope Half-life/year Kg/year in spent fuel... 

The isotope enrichment process does not only lead to an increase in the concentration in the fuel, but also in a more than proportional increase in the concentration, as can be seen from Table 3.1., where the mass concentrations of the actinide isotopes in different types of fresh nuclear fuel are compared. As a... 

Table 3.1. Mass concentrations of actinide isotopes (in g/kg HM) in nuclear fuel (By courtesy of Siemens/KWU) different types of fresh...

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