Neptunium reprocessing

Uranium-239 [13982-01 -9] has a half-life of 23.5 min neptunium-239 [13968-59-7] has a half-life of 2.355 d. Recycling or reprocessing of spent fuel involves separation of plutonium from uranium and from bulk fission product isotopes (see Nuclearreactors, chemical reprocessing). 

Neptunium has been recovered during the reprocessing of defense-related fuels. The is recycled back to a reactor where it is transmuted to... 

Nagasaki, S., Wisnubroto, D.S., Enokida, Y., Suzuki, A. 1994. Neptunium separation from nitric acid solutions with CMPO. 4th Int. Conf. Nuclear Fuel Reprocessing and Waste Management, RECOD 94 Proceedings Vol. 3, London, UK, April 24-28. 

The sucessful experiments for the retention of plutonium onto alumina from TTN0 -HF solution gave enough confidence to recomend the proposed method to separate traces of plutonium from waste solutions in the presence of macroamounts of uranium (VI). Of course, only macroamounts of thorium, uranium (IV) and rare earths are serious interfering ions, since they precipitate with HF. The behavior expected for neptunium in the same system should be similar to plutonium, thorium and rare earths. The retention of neptunium from HNO - HF solutions is in progress. The sorption yield for Pu was around 95%. The sorption mechanism is not well established. Figure 3 shows the proposed flowsheet for recovery of Pu traces from reprocessing waste solutions. 

Neptunium, like its plutonium neighbor, can exist in oxidation states that vary from +3 to +6 (disregarding the +7 state which is not pertinent to reprocessing-related solutions). In... 

The long-term radioactivities of neptunium, americium, and curium in the high-level reprocessing wastes from the uranium-fueled water reactor are shown in Fig. 8.7. Except for Am and Np, these curves are also applicable to unprocessed discharge fuel. The curves Am and Np have been calculated for 0.5 percent of the plutonium in discharge fuel to appear in the wastes, so that there is not sufficient Pu to significantly increase the amounts of Am and... 

Figure 8.7 Radioactivity in curium, americium, and neptunium as a function of decay time. (Amount in the wastes produced annually by reprocessing fuel discharged from a 1000-MWe uranium-fueled PWR.)...

Early Work. The irradiated fuel, upon discharge from the reactor, comprises the residual unbumt fuel, its protective cladding of magnesium alloy, zirconium or stainless steels, and fission products. The fission process yields over 70 fission product elements, while some of the excess neutrons produced from the fission reaction are captured by the uranium isotopes to yield a range of hew elements—neptunium, plutonium, americium, and curium. Neutrons are captured also by the cladding materials and yield a further variety of radioactive isotopes. To utilize the residual uranium and plutonium in further reactor cycles, it is necessary to remove the fission products and transuranic elements and it is usual to separate the uranium and plutonium this is the reprocessing operation. 

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