Neptunyl nitrate

In contrast to the neptunyl nitrate complex with Bipy, the structure of [Np02(N03)(Terpy)(H20)] (16) represents the monodentate coordination of the nitrate which provides one oxygen as donor in the equatorial plane of Np. The remaining equatorial positions are occupied by the nitrogen atoms of Terpy molecule and a water molecule (Fig. 16) [90]. The Np-N distances have moderate values, 2.580(5)-2.602(5) A. The largest atomic deviation from the least-squares equatorial plane is 0.360 A. 

KEYWORDS Dirac-Fock-Slater, DV-DFS, uranyl nitrate, neptunyl nitrate, plutonyl nitrate, stability, bonding nature... 

Neptunium. Np is in a class with Pa no efforts have been made to use it as a fuel solute, but consideration has been given to its formation in and removal from blanket solutions of [30a]. The chemistry of neptunium has been reviewed by Hindman et al. [30b], and the hydrolytic behavior has been reviewed by Kraus [30c]. Continuous separation of Np239 would provide a Pu product of high purity by radioactive decay, whereas plutonium recovered from long-term irradiation of usually contains appreciable amounts of Pu °. Spectrophotometric cells for use at elevated temperatures and pre.ssures in the study of the chemistry of neptunium (and other materials) have recently been developed by Wag-gener [30d] and have been used to measure the absorption spectra of dilute neptunium perchlorate in its six-, five-, four-, and three-valence states, using heavy w ater as the solvent. Dilute solutions of neptunyl nitrate in nitric acid have been so studied at temperatures up to 250°C the pentavalent state was found to be stable under the test conditions [30e]. 

UV-illuminated Np022+ is converted to Np(V), although this is primarily as a result of the photolysis of the nitrate anion (see Sect. 4.1.1). In perchloric acid, UV-illuminated neptunyl is reduced to Np(V) in this case, it has been assumed that the products of water photolysis act as a reductant [86]. 

Cesium plutonyl triacetate (pink) was prepared in the same manner as the neptunyl analog except the anion-exchange purified (18) Pu(IV) nitrate was oxidized to Pu( VI) nitrate by ozone at about 80°C. Analysis calculated for CsPu02(C2H302)3 Cs, 22.9 Pu, 41.2. Found Cs, 23.6 Pu, 41.3. 

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... 

In the upper part, the O 2p components of the ligands are dominant. Above 49gj which is occupied in the neptunyl and plutonyl nitrates. An 5f is the major component. The components and energies of each orbital are similar in all of the complexes. The electronic structures are also almost equivalent, with the exception of the number of electrons in 49g . ... 

Fig 3. Densities of 5f and 6d components for uranyl, neptunyl and plutonyl nitrates dihydrates. 

We have performed relativistic calculations on hexavalent uranyl, neptunyl and plutonyl nitrate dihydrates using the DV-DFS method. The valence energy level structures were similar to each other except for the HOMO level. The An 5f electrons of Np and Pu occupy the antibonding states and they contribute to the decrease in the bonding interaction between the actinide atoms and the oxygen atom of the water molecules. 

VI states occurs in water. Once the uranyl, neptunyl, and plutonyl ions are formed, the only practical way to remove the coordinated oxygen atoms is by reduction to the IV state. Although uranyl nitrate can be obtained as an anhydrous compound, in this form it is coordinatively unsaturated, and it is usually encountered as the hexahydrate or coordinated to equivalent ligands. 

Among the alkylammonium compounds, the tertiary amines are by far the most important actinide extractants, as has already been mentioned (Section 21.5.1). Extraction depends upon the nature and concentration of the anion in much the same manner as for neutral extractants (Section 21.5.2). A good example is the extraction of neptunyl(vi) by methyldioctylamine in chloroform from solutions containing increasing concentrations of sulfuric, hydrochloric, or nitric adds (Fig. 21.9) [178]. The value of D increases rapidly at low concentrations, and most rapidly for sulfuric add, as the complexes formed by the sulfate ion are much stronger than those formed by chloride or nitrate. Consequently, extractable... 

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