Neptunium americium reduced

Dissolution, described in Sec. 4.4, produces an aqueous solution of uranyl nitrate, plutonium(IV) nitrate, nitric acid, small concentrations of neptunium, americium, and curium nitrates, and almost all of the nonvolatile fission products in the fuel. With fuel cooled 150 days after bumup of 33,000 MWd/MT, the fission-product concentration is around 1700 Ci/liter. The fint step in the solvent extraction portion of the Purex process is primary decontamination, in which from 99 to 99.9 percent of these fission products are separated from the uranium and plutonium. Early removal of the fission products reduces the amount of required shielding, simplifies maintenance, and facilitates later process operations by reducing solvent degradation from radiolysis. 

Another benefit for the SFR fuel cycle system is the reduction of environmental burden by recycling all actinide nuclides and partitioning selected fission products (FPs). The spent fuel contains minor actinides (MAs ie, neptunium, americium, curium, etc.) as well as uranimn and plutonium. In the conventional nuclear fuel cycle, those MAs and FPs are disposed of in a deep geological repository as high-level radioactive wastes. Because of the long-lived radioactive MAs such as Am (half-life 433 years) and Np (half-life 2.1 million years), it takes several hundred thousand years to reduce the radiotoxicity of high-level radioactive waste to the level of natural uranium. 

Sorption isotherms were also measured for sorption of selenium, technetium, tin, radium, uranium, neptunium, plutonium, and americium on the reference Mabton Interbed solids. The GR-1A groundwater composition was used in these experiments. Two temperatures (23°C 2°C and 60°C 1°C) were used, and both oxidizing and reducing conditions were used for each radionuclide. 

Chemical components in the waste solutions potentially could affect radioelement solubility and sorption reactions, and thus enhance or reduce radionuclide transport. The effects of 12 chemical components on the solubility and sorption of cobalt, strontium, neptunium, plutonium, and americium were studied to... 

The actinides are base metals which require the reduction of a chloride or fluoride with sodium or barium for their isolation. Neptunium, for example, has been made by reducing its trifluoride with barium vapour at 1200°. The need for such drastic methods is understandable because the heats of formation of the ions are as much as three times greater than that of the Pt ion. The metals are silvery white and, except thorium and americium, have high densities. 

A tabulation of some of these results shows that only the + 3 state of neptunium is observed in frozen solutions, whereas in the pure solid a range of values from +3 to +5 is observed, which is independent of the charge state of the americium in the parent compound. An interesting comparison for K5[Am 02(C03)s]3 in the pure solid and in frozen solution indicates the existence of Np + alone in the pure solid and only Np in the frozen solution. This suggests that the presence of ice at low temperatures provides a reducing medium for neptunium. 

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