Nuclear fission neptunium from

Separation of Actinides from the Samples of Irradiated Nuclear Fuels. For the purpose of chemical measurements of burnup and other parameters such as accumulation of transuranium nuclides in irradiated nuclear fuels, an ion-exchange method has been developed to separate systematically the transuranium elements and some fission products selected for burnup monitors (16) Anion exchange was used in hydrochloric acid media to separate the groups of uranium, of neptunium and plutonium, and of the transplutonium elements. Then, cation and anion exchange are combined and applied to each of those groups for further separation and purification. Uranium, neptunium, plutonium, americium and curium can be separated quantitatively and systematically from a spent fuel specimen, as well as cesium and neodymium fission products. 

Liquid HLW is the concentrated aqueous raffinate from the hquid-Uquid extraction process. It contains practically aU fission products, neptunium and transplutonium elements as well as 0.5 to 1.0 percent of the uranium and plutonium fed to the extraction process. It represents a very small fraction of the total radioactive waste volume produced in nuclear installations. 

The first transuranium elements, neptunium and plutonium, were obtained in tracer amounts from bombardments of uranium by McMillan and Abelson and by Seaborg, McMillan, Kennedy, and Wahl, respectively, in 1940. Both elements are obtained in substantial quantities from the uranium fuel elements of nuclear reactors. Only plutonium is normally recovered and is used as a nuclear fuel since, like 235U, it undergoes fission its nuclear properties apparently preclude its use in hydrogen bombs. Certain isotopes of the heavier elements are made by successive neutron capture in 239Pu in high-flux nuclear reactors (> 1015 neutrons cm-2 sec- ). Others are made by the action of accelerated heavy ions of B, C, N, O or Ne on Pu, Am or Cm. 

The a-emitting product was identified as a new element fi-om the study of chemical behavior of this isotope. It was distinctly different from both uranium and neptunium in its redox properties the 3+ and 4+ valence states were more stable. A second isotope of element 94, Pu, with a half-life of24,000 years was synthesized immediately as a daughter of P decay of Np, which confirmed the presence of element 94. The isotope Pu produced in appreciable amounts in nuclear reactors is of major importance, because of its large fission cross section with thermal neutrons. It was named after the planet Pluto in analogy to uranium and neptunium. 

Each of these elements may be used for production of nuclear fuel or other purposes. The recovery efficiency for uranium is reported as 99.87% and for plutonium 99.36%-99.51% (NEA 2012). The extended PUREX includes separation of neptunium and technetium as well as recovery of americium and curium that are also separated from each other by additional extraction stages as given in detail in the flowsheet (NEA 2012). The advanced UREX-i-3 process generates six streams after separation uranium for re-enrichment Pu-U-Np for mixed oxide fuel c for managed disposal Am-Cm to be used as burnable poisons and for transmutation high-heat-generating products (Cs and Sr) and a composite vitrified waste with all other fission products. Some fuel types may require preliminary steps like grinding to enable their dissolution. 

It is proposed to use non-aqueous methods of fuel reprocessing. Non-aqueous technologies developed in Russia and related to the processing of fuel from fast reactors with incomplete purification from fission products (about 1% of them remain in refabricated fuel) and with the release of only curium from the fuel (neptunium and americium and 1% of curium remain) allow the production of such fresh fuel for fast reactors that cannot be directly used to create nuclear weapons [XVI-9]. 

In a nuclear reactor, different isotopes are produced by fission at varying rates, and each of these isotopes has their own specific half-life decay periods. Thus, identifying the different atomic species present inside a nuclear reactor at a given time is very complicated. For instance, in a reactor of the starting mass of LP will decay into neptunium in 24 min. For a fixed mass, % of the starting mass of this same amount will have decayed into neptunium in 48 min. The additional complication comes from the continued and simultaneous production of IP via the neutron capture process. There are plenty of neutrons in an operating reactor, so additional IP is continually produced from the large number of IP present. 

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