Plutonium separation process

When the Plutonium Project was established early in 1942, for the purpose of producing plutonium via the nuclear chain reaction in uranium in sufficient quantities for its use as a nuclear explosive, we were given the challenge of developing a chemical method for separating and isolating it from the uranium and fission products. We had already conceived the principle of the oxidation-reduction cycle, which became the basis for such a separations process. This principle applied to any process involving the use of a substance which carried plutonium in one of its oxidation states but not in another. By use of this... 

Although the outline of a chemical separation process could be obtained by tracer-scale investigations, the process could not be defined with certainty until study of it was possible at the actual separation plants. Therefore, the question in the summer of 1942, was as follows How could any separations process be tested at the concentration of plutonium that would exist several years later in the production plants when, at this time, there was not even a microgram of plutonium available This problem was solved through an unprecedented series of experiments encompassing two major objectives. First, it was decided to attempt the production... 

Other reasons for investigating plutonium photochemistry in the mid-seventies included the widely known uranyl photochemistry and the similarities of the actinyl species, the exciting possibilities of isotope separation or enrichment, the potential for chemical separation or interference in separation processes for nuclear fuel reprocessing, the possible photoredox effects on plutonium in the environment, and the desire to expand the fundamental knowledge of plutonium chemistry. 

Large-scale plutonium recovery/processing facilities originated at Los Alamos and Hanford as part of the Manhattan Project in 1943. Hanford Operations separated plutonium from irradiated reactor fuel, whereas Los Alamos purified plutonium, as well as recovered the plutonium from scrap and residues. In the 1950 s, similar processing facilities were constructed at Rocky Flats and Savannah River. 

Plutonium Scrap Processing. In addition to recovering plutonium from irradiated reactor fuel, a Plutonium Reclamation Facility (PRF)( 7,8) is operated at the Hanford site to recover, separate, and purTfy kilogram amounts of plutonium from a wide range of unirradiated scrap materials. A 20 percent TBP-CC1 k solution is used to extract Pu(IV) from HN03-HF-A1(N03)3 solutions of dissolved scrap. 

Other Pyrochemical Processes. The chemistry of pyrochemi-cal separation processes is another fertile area of research e.g., new molten salt systems, scrub alloys, etc. and the behavior of plutonium in these systems. Studies of liquid plutonium metal processes should also be explored, such as filtration methods to remove impurities. Since Rocky Flats uses plutonium in the metal form, methods to convert plutonium compounds to metal and purify the metal directly are high-priority research projects. 

Early experimental work in electrorefining at Los Alamos by Mullins et-all ) demonstrated that americium could be partitioned between molten plutonium and a molten NaCl-KCl salt containing Pu+3 ions, and Knighton et-al(8), working at ANL on molten salt separation processes for fuel reprocessing, demonstrated that americium could be extracted from Mg-Zn-Pu-Am alloys with immiscible molten magnesium chloride salts. Work... 

In some countries, the main purpose of reprocessing is to recover plutonium for weapons use. The main separation process in all known reprocessing plants is solvent extraction. 

A primary goal of chemical separation processes in the nuclear industry is to recover actinide isotopes contained in mixtures of fission products. To separate the actinide cations, advantage can be taken of their general chemical properties [18]. The different oxidation states of the actinide ions lead to ions of charges from +1 (e.g., NpOj) to +4 (e.g., Pu" " ) (see Fig. 12.1), which allows the design of processes based on oxidation reduction reactions. In the Purex process, for example, uranium is separated from plutonium by reducing extractable Pu(IV) to nonextractable Pu(III). Under these conditions, U(VI) (as U02 ) and also U(IV) (as if present, remain in the... 

Birkett, J.E. Carrott, M.J. Fox, O.D. Jones, C.J. Maher, C.J. Roube, C.V. Raylor, R.J. Woodhead, D.A. Recent developments in the Purex process for nuclear fuel reprocessing Complexant based stripping for uranium/plutonium separation, Chimia 59 (2005) 898-904. 

Process monitoring, with on-line instruments that operate autonomously for extended periods of time, presents significant challenges and opportunities. The requirements for monitors will vary with the application they support. Where the monitor is set up to support a particular separation process, the analytical objectives may be to determine a single species. The technetium monitor described above, designed to support a technetium removal process, is such an example. On the other hand, some processes may seek to determine multiple actinides in a process stream. These actinides could be a selected group of the transuranic (TRU) elements, or the multiple isotopes of a particular actinide like plutonium. 

Plutonium Finishing. The separated plutonium was processed to Pu02 by conventional cation resin exchange, oxalate precipitation, and calcination methods. 

Feed for the second plutonium cycle was prepared by first oxidizing the Pu(lll) to Pu(lV) and the sulfamate ion to nitrogen gas and sulfate ion with sodium nitrite. The plutonium was diluted to about 0.5 g/L to meet the nuclear safety requirements of the second plutonium cycle. Nitric acid was adjusted to 3.8 to 4.0M to meet the salting requirements of the solvent extraction separation process. 

Plutonium is manufactured in megagram quantities neptunium, americium, and curium in kilogram quantities californium in gram amounts berkelium in 100-milligram amounts and einsteinium in milligram quantities. Chemical separations play a key role in the manufacture of actinide elements, as well as in their recovery, and analysis in the nuclear fuel cycle. This collection of timely and state-of-the-art topics emphasizes the continuing importance of actinide separations processes. 

Irradiation also affects the course of more conventional separation processes. Visible and ultraviolet light have been found to affect plutonium solvent extraction by photochemical reduction of the plutonium (12). Although the results vary somewhat with the conditions, generally plutonium(VI) can be reduced to pluto-nium(IV), and plutonium(IV) to plutonium(III). The reduction appears to take place more readily if the uranyl ion is also present, possibly as a result of photochemical reduction of the uranyl ion and subsequent reduction of plutonium by uranium(IV). Light has also been found to break up the unextractable plutonium polymer that forms in solvent extraction systems (7b,c). The effect of vibrational excitation resulting from infrared laser irradiation has been studied for a number of heterogeneous processes, including solvent extraction (13). 

The 2.54-cm diameter Electropulse Column shown in Figure 1, after completion of uranium runs, was installed at Battelle Memorial Institute (Columbus, Ohio) for uranium-plutonium partition tests. Six electrolytic runs were made under conditions corresponding to partitioning in the first process cycle to determine the effect of uranium reduction efficiency R(u) on t le separation process. The organic feed contained 80 to 83 grams/L of uranium and 0.71 to 0.82 grams/L of plutonium. The nitric acid concentration in the aqueous feed was 2.5 to 2.8 M and in the organic feed 0.2 to 0.3 M. 

Effective purification of plutonium hexafluoride is proved through the selective adsorption of FPs on NaAlFi. A rather high decontamination factor (more than 5 x 103) is attained for ruthenium fluoride (36). A new separation process of PuF6 from UF6 by the selective adsorption onto UO2F2 is proposed (37). 

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