Neptunium diagram

A system particularly studied from a thermodynamic point of view is the monocarbide (AnCi x) system. A range of stability for carbon deficient compositions in the monocarbides is present in many metal-carbon phase diagrams. Table 6 shows the composition range at room temperature for actinide monocarbides. The non-stoichiometry range is very limited for uranium monocarbide for neptunium and plutonium monocarbides, the stoichiometric AmCj oo composition is not stable. 

Cope, R. G., D. G. Hughes, R. G. Loasby, and D. C. Miller The Plutonium-Ruthenium and Plutonium-Neptunium binary Phase Diagrams. In E. Grison, W. B. H. Lord, and R. D. Fowler (Eds.), Plutonium 1960. Proc. of the 2nd Int. Conf. on Plutonium Metallurgy, Grenoble (1960). London Cleaver-Hume Press Ltd. 1961. 

Fig. 3 Potential-pH diagram of the neptunium-water system at 298 K with SnC>2 conduction band edge overlaid. Dissolved neptunium activity= 0.01...

The uranium-neptunium and uranium-plutonium alloys show a total miscibility in the liquid phase and in the A2-solid solution, moreover they exhibit phases with structures different from those of the pure components in a rather large range of composition in the middle of the phase diagram. 

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