Actinides nitrates

Table 4.18 Constants for Extraction of Actinide Nitrate Adducts with Phosphoric Acid Trialkylesters (Free Rotation of the P Substituents) and with A,A-Dialkylamides (Restricted Rotation Around the Amide Moiety)...

There are a great many actinide nitrate complexes, many of which are important in separation procedures whereby the elements are extracted from aqueous nitric acid into nonpolar solvents. Of these, the U02+ complexes are best characterized they are typically 8-coordinate with two bidentate N03" ions and two neutral ligands (H20, THF, DMSO, and R3PO) forming a distorted equatorial hexagon. 

MIBK is a poorer extractant of oxidation state (VI) actinide nitrates than Butex or TBP and is not an effective extractant for oxidation state (IV) actinides at acidities below ca. 1 M HNO3. However, MIBK will extract U02(N03)2 and Pu02(N03)2 from aqueous streams salted with nitrate and this provided the basis of the Redox process shown in outline in Figure 36. The salting... 

Figure 3. Actinide recycle occurs between the subsystems within the WTF. Wastes enter the subsystems in the left column. Actual recovery occurs in the central column subsystems. A mixture of actinide nitrates is sent from Actinide Product Concentration to the fuel reprocessing plant for codenitration.

In the present investigation we will use the DV-DFS method to armpare uranyl, neptunyl and plutonyl nitrate dihydrates from the viewpoint of their partial densities of states due to the An components. We discuss the similarity and difference in the electronic structures of these actinide nitrate dihydrates in order to estimate their stabilities. We also apply population analysis to confirm how far the An electrons contribute to the chemical bonding between the actinide and donor oxygen atoms. Finally, we compare the bonding nature between the... 

The first solvent to be adopted at Hanford was methylisobutylketone ("MIBK" or "Hexone"). This solvent forms adduct compounds with coordinatively unsaturated compounds like the actinide nitrates, e.g. Pu(N03)4 2, where S repres ts tihe adduct molecule... 

Fig. 21. The extraction of pentavalent and trivalent actinide nitrates by 10 v/o TOA in xylene. 219...

Ryan, J. L. (1960). Species Involved in the Anion-exchange Absorption of Quadrivalent Actinide Nitrates. The Journal of Physical Chemistry, Vol. 64, No. 10, (October 1960), pp. 1375-1385, ISSN 0022-3654... 

Highly selective transport of U(VI) (9) and Pu(IV) 10) over several fission-product contaminants has been achieved in both organic BLM and SLM systems employing TBP in dodecane as the mobile carrier. The source phase was an extremely dilute actinide nitrate solution (10" M) in 2 M nitric acid. Ascorbic acid was found to be the most efficient strippant for Pu(IV), whereas dilute ammonium carbonate was best for U(VI). 

The actinide nitrates whose structures are known are listed in Table 20.9, and a review of actinide complexes has been published by Casellato et al [413]. These are limited mainly to tetravalent Th and to uranyl complexes. In the Th(iv) and Pu(iv) compounds the NO3 ions are bidentate, which allows for large coordination numbers compared to the usual eight-fold coordination of these ions with monodentate ligands. In the uranyl complexes the two close actinyl oxygen atoms limit the available space for other bonded atoms, and the maximum number of equatorial oxygen atoms is six, even for bidentate NO3 ions. In Cs2lJ02(N03)4 all four NO3 ions are attached to the U atom even though space allows only two of them to be bidentate. 

Fig. 21.8 Extraction of (a) tetravalent and (b) hexavalent actinide nitrates at low concentrations (< 10 mm) by 19% tributyl phosphate in kerosene, at 25°C [174], The curves give the distribution ratios D = C (org) C (aq) as a function of the (initial) nitric acid concentration in the aqueous phase, C .

Plgiire 35. The partition coefficient of actinide nitrates between 19 6 TBP In kerosene and aqueous solution as a function of equilibrium nitric acid concentration. U (VI), Np (Vl), aNp (IV), APu (VI) at 20O-23OC., after K. Alcock, G. F.-Best, E. Hesford,... 

---