Solvent extraction nuclear fuel reprocessing

Uses Plasticizer for lacquers, plastics, cellulose esters, and vinyl resins heat-exchange liquid carbonless copy paper systems in aircraft hydraulic fluids solvent extraction of metal ions from solution of reactor products uranium extraction and nuclear fuel reprocessing pigment grinding assistant antifoaming agent solvent for nitrocellulose and cellulose acetate. 

Solvent extraction separates heavy metals (in particular, the actinides) from lighter metals and from each other and has been an important tool for nuclear chemistry over the last 60 years. As seen in the other chapters of this book, solvent-extraction chemistry remains of vital interest for nuclear fuel reprocessing and for the cleanup and segregation of nuclear waste. 

Despite the demonstrated effectiveness of solvent-extraction (SX) processes employing conventional organic diluents in nuclear-fuel reprocessing and... 

Solvent extraction In hydrometallurgy to recover metals from ores In nuclear fuel reprocessing In waste water treatment To recover natural products from plants or from fermentation liquors In organic synthesis and analytical chemistry As a degreaser and cleaning agent... 

The simplicity, speed, and versatility of solvent extraction make it an excellent radiochemical separation method. Even simple equipment like a test tube or a separation funnel allows radiochemists to perform elaborate studies within a few minutes. The method works for a wide concentration range, from the rather concentrated solutions in uranium production or nuclear fuel reprocessing to one-atom-at-a-time separations of the heaviest elements. 

Used in extraction of lanthanide and actinide elements and in nuclear fuel reprocessing. Plasticiser for cellulose esters, lacquers, plastics and vinyl resins. Used neat or as a soln. in CHCI3, hexane or CCI4 as an extraction solvent for the coordinatively solvated salts (NO3 , Cl ) e.g. U02(N03)2 (TBP)2- Odourless liq. Mod. sol. H2O, misc. org. solvs. df 0.98. Mp < —80°. Bp 289° dec.. 

In addition, solvent extraction is appHed to the processing of other metals for the nuclear industry and to the reprocessing of spent fuels (see Nuclearreactors). It is commercially used for the cobalt—nickel separation prior to electrowinning in chloride electrolyte. Both extraction columns and mixer-settlers are in use. 

Nuclear Waste. NRC defines high level radioactive waste to include (/) irradiated (spent) reactor fuel (2) Hquid waste resulting from the operation of the first cycle solvent extraction system, and the concentrated wastes from subsequent extraction cycles, in a faciHty for reprocessing irradiated reactor fuel and (3) soHds into which such Hquid wastes have been converted. Approximately 23,000 metric tons of spent nuclear fuel has been stored at commercial nuclear reactors as of 1991. This amount is expected to double by the year 2001. 

In 1942, the Mallinckrodt Chemical Company adapted a diethylether extraction process to purify tons of uranium for the U.S. Manhattan Project [2] later, after an explosion, the process was switched to less volatile extractants. For simultaneous large-scale recovery of the plutonium in the spent fuel elements from the production reactors at Hanford, United States, methyl isobutyl ketone (MIBK) was originally chosen as extractant/solvent in the so-called Redox solvent extraction process. In the British Windscale plant, now Sellafield, another extractant/solvent, dibutylcarbitol (DBC or Butex), was preferred for reprocessing spent nuclear reactor fuels. These early extractants have now been replaced by tributylphosphate [TBP], diluted in an aliphatic hydrocarbon or mixture of such hydrocarbons, following the discovery of Warf [9] in 1945 that TBP separates tetravalent cerium from... 

The solvent extraction process that uses TBP solutions to recover plutonium and uranium from irradiated nuclear fuels is called Purex (plutonium uranium extraction). The Purex process provides recovery of more than 99% of both uranium and plutonium with excellent decontamination of both elements from fission products. The Purex process is used worldwide to reprocess spent reactor fuel. During the last several decades, many variations of the Purex process have been developed and demonstrated on a plant scale. 

High-grade pitchblende ores are leached with nitric acid to recover uranium. Extraction of uranium from nitrate solutions is usually performed with TBP. TBP-based solvents are used in several areas of the nuclear industry, especially for reprocessing of spent nuclear fuels and for refining the uranium product of the Amex and Dapex processes. Extraction of uranium by TBP solvents is described in sections 12.3.4 and 12.5. 

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