Neptunium dioxide

Purex process, 6, 951 Neptunium complexes, 3, 1131-1215 cupferron, 2, 510 Neptunium dioxide ions disproportionation Purex process, 6, 950... 

Neptunium (TV) didioxide Np + 2CV —> NpO. Neptunium dioxide is a powder used to form metal targets that are to be radiated by plutonium. 

Neptunium forms a number of halides in various oxidation states. These include tri-, tetra- and hexafluorides of compositions NpFs, NpF4, and NpFe, respectively trichloride, NpCF and tetrachloride, NpCh tribromide, NpBrs and the triiodide NpN. Neptunium fluorides are formed by heating neptunium dioxide at elevated temperatures with fluorine in the presence of hydrogen fluoride. The tetrachloride, NpCh is obtained similarly by heating the dioxide with carbon tetrachloride vapor at temperatures above 500°C. Neptunium tribromide and triiodide are prepared by heating the dioxide in a sealed vessel at 400°C with aluminum bromide and aluminum iodide, respectively. 

Neptunium is fairly reactive and forms some interesting compounds. Examples include neptunium dialuminide (NpAl2) and neptunium beryllide (NpBc3). These compounds are unusual because they consist of two metals joined to each other. Normally, two metals do not react with each other very easily. Neptunium also forms a number of more traditional compounds, such as neptunium dioxide (Np02), neptunium trifluoride (Npp3), and neptunium nitrite (NPNO2). 

Np02 Np02, neptunium dioxide Np02+, dioxidoneptunium(l+) [not neptunyl(l+)] Np022+, dioxidoneptunium(2+) [not neptunyl(2+)] ... 

Derivation Neptunium oxalate is precipitated from solutions containing nitric acid and neptunium. The neptunium oxalate is calcined at 500-550C, producing neptunium dioxide. 

Neptunium dioxide, Np03, is the most stable of the neptunium oxides. It crystallizes with the fluorite structure of all the actinide dioxides, with a crystalline density of 11.14 g/cm . It can be formed from the thermal decomposition of other neptunium compounds, such as the hydroxide, the nitrate, or the oxalate, in the temperature range of 600 to 1000°C. High-fired NpOj can be dissolved in hot concentrated nitric acid containing small amounts of fluoride. 

Np02 NEPTUNIUM DIOXIDE 1236 PbCI2[g] LEAD DICHLORIDE (GAS) 1282... 

Purex process, 951 Neptunium(VI) reduction Purex process, 951 Neptunium dioxide ions disproportionation rex process, 950 Nerve growth factor snake venoms zinc, 613... 

BFS-1 critical facility was used to continue studies on the characteristics of fast reactor cores designed for the weapons grade plutonium utilization and minor actinides burning, for instance, the effect of neptunium introduction into fuel. The first stage of these studies made on the insert of the BN-800-Superphenix reactor fuel with up to 14% of depleted uranium dioxide replaced by neptunium dioxide was accomplished in 1995 (BFS-67 critical assemblies set). 

On the further stage, about 13% of depleted uranium dioxide in the central area of the insert were replaced by neptunium dioxide (BFS-69-2), and the same set of measurements was conducted. 

In early 1994 about 250 pellets of neptunium dioxide were manufactured in each of which 40 g of neptunium was enclosed within a thin-walled stainless steel can of 5 cm in diameter and 1 cm thick. 

Such amount allowed to replace some part of depleted uranium dioxide by neptunium dioxide in the central zone of 30 1 volume, neptunium content being 13.5 % heavy nuclei. Deliberately increased neptunium content allowed to sharpen its effect upon the parameters under investigation. 

The condensed oxides of Np have had only limited characterization, especially as compared to the uranium system. Early studies suggested that neptunium dioxide did not form superstoichiometric compositions, in contrast to the uranium system. The... 

Neptunium dioxide crystallizes in the cubic fluorite structure and magnetic measurements have been reported from 4 to 300 K [16,74,75]. There is a magnetic transition at 2S.4K. Above 60 K, the susceptibility follows the Curie-Weiss law pgn = 2.95-3.00/ig, 0 = —22 K). Below 10-12 K, the magnetic susceptibility becomes independent of temperature (xm = ... 

Osborne, D.W. and Westrum, E.E. (1953) The heat capacity of thorium dioxide from 10 to 305 K. The heat capacity anomalies in uranium dioxide and neptunium dioxide. 

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