Neptunium-239, extraction

These reaction rates are too low to explain the appreciable extraction of neptunium obtained in the short-residence-time HA contactors used at Hanford and elsewhere. Swanson [S24] reported that radiolysis reaction products of TBP and nitric acid present in Purex solutions increased the neptunium oxidation rate and provided a possible explanation. He found that the oxidation rate could be increased several orders of magnitude by adding a synthetic rate-accelerating material (RAM) produced by reacting the aciform of nitropropane, CjHs(CH)(NO)(OH), with nitric and nitrous acids, and recommended addition of such a catalyst to Purex feed if increased neptunium extraction were desired. 

The wastes from uranium and plutonium processing of the reactor fuel usually contain the neptunium. Precipitation, solvent extraction, ion exchange, and volatihty procedures (see Diffusion separation methods) can be used to isolate and purify the neptunium. 

Holm et al. [74] used a spectrometry for the determination of 237neptunium in seawater. The actinides are preconcentrated from a large seawater sample by hydroxide precipitation. The neptunium was isolated by ion exchange, fluoride precipitation, and extraction with TTA. 238Neptunium or 235neptunium was used to determine the radiochemical yield. 

Subsequently, solvent extraction was applied to recover the fission product technetium from the residue remaining after the fluorination of irradiated uranium fuel elements . The residue was leached with concentrated aluminum nitrate solution, which was extracted by 0.3 M trilaurylamine in a hydrocarbon diluent. After separation of uranium, neptunium, and aluminum nitrate, technetium was back extracted into a 4 N sodium hydroxide solution. 

Route all neptunium as Np(V) to the high-level waste in the first extraction cycle... 

Neptunium is not found in nature in any extractable quantities. However, it occurs in uranium ores in exceedingly small concentrations resulting from neutron capture of uranium isotopes. No major application is known for this element. Its isotope, Np-237, is used in neutron detection instruments. 

Neptunium-237 is obtained as a by-product of making plutonium from uranium isotopes in nuclear reactors. Significant amounts of this element may be recovered from plutonium plant nuclear wastes. Both the recovery and purification of neptunium can be carried out by various chemical processes, including precipitation, solvent extraction and ion exchange. 

Uranium. Perricos and Belkas (25) have determined uranium in six coals by neutron activation followed by separation of the uranium daughter neptunium-239 by carrier-free extraction chromatography. The coals, from mines in northern Greece, had very high uranium concentrations (0.012-0.037%). However, uranium at the few parts per million level found in most coals could no doubt be determined by a modification of this method. 

The most widely used neutral extractants, however, are the organophosphoms compounds, of which the ester, TBP, is the most important. TBP forms complexes with the actinide elements thorium, uranium, neptunium, and plutonium by bonding to the central metal atom via the phosphoryl oxygen in the structure... 

The formation of complex compounds of neptunium with cupferron and a number of other complexing agents has been studied.95 More recently, the extraction of neptunium(IV and VI) from HC1, HBr and HN03 media has been investigated.96... 

Birkett, J.E., Carrott, M.J., Fox, O.D. et al. 2007. Controlling neptunium and plutonium within single cycle solvent extraction flowsheets for advanced fuel cycles. J. Nucl. Sci. Technol. 44 (3) 337-343. 

Tochiyama, O., Nakamura, Y., Hirota, M., Inoue, Y. 1995. Kinetics of nitrous acid-catalyzed oxidation of neptunium in nitric acid - TBP extraction system. J. Nucl. Sci. Technol. 32 118-124. 

Taylor, R.J., Sinkov, S.I., Choppin, G.R., May, I. 2008. Solvent extraction behavior of neptunium(rV) ions between nitric acid and diluted 30 % tri-butyl phosphate in the presence of simple hydroxamic acids. Solvent Extr. Ion Exch. 26 (1) 41-61. 

Zhu, Y., Song, C. 1992. Recovery of neptunium, plutonium and americium from highly active waste. Tri-alkyl phosphine oxide extraction. In Transuranium Elements A Half Century. Morss, L.R. Fuger, J., Eds. ACS, Washington, DC, pp. 318-330. 

Banerjee, S. Mohapatra, P.K. Bhattacharyya, A. Basu, S. Manchanda, V.K. Extraction of tetravalent neptunium isoxazolonates as their TOPO adducts, Radiochim. Acta 92 (2004) 95-99. 

Madic, C. Kertesz, C. Sontag, R. Koehly, G. Application of extraction chromatography to the recovery of neptunium, plutonium and americium from an industrial waste, Sep. Sci. Technol. 15 (1980) 745-762. 

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