Nuclear PUREX process

Purex process, enthalpy change, 6, 952 hydroxides, 6, 887 irradiated nuclear fuel... 

Butex A process for separating the radioactive components of spent nuclear fuel by solvent extraction from nitric acid solution, using diethylene glycol dibutyl ether (also called Butex, or dibutyl carbitol) as the solvent. Developed by the Ministry of Supply (later the UK Atomic Energy Authority) in the late 1940s. Operated at Windscale from 1952 until 1964 when it was superseded by the Purex process. 

Redox [Reduction oxidation] A process for separating the components of used nuclear fuel by solvent extraction. It was the first process to be used and was brought into operation at Hanford, United States, in 1951, but was superseded in 1954 by the Purex process. The key to the process was the alternate reduction and oxidation of the plutonium, hence the name. The solvent was Hexone (4-methyl-2-pentanone, methyl isobutyl ketone), so the process was also known as the Hexone process. The aqueous phase contained a high... 

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. 

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... 

RADIATION EFFECTS IN SPENT NUCLEAR FUEL REPROCESSING 2.1. Purex Process... 

In tlie PUREX process, the spent fuel and blanket materials are dissolved in nitric acid to form nitrates of plutonium and uranium. These are separated chemically from the other fission products, including the highly radioactive actinides, and then the two nitrates are separated into tv/o streams of partially purified plutonium and uranium. Additional processing will yield whatever purity of the two elements is desired. The process yields purified plutonium, purified uranium, and high-level wastes. See also Radioactive Wastes in the entry1 on Nuclear Power Technology. Because of the yield of purified plutonium, the PUREX process is most undesirable from a nuclear weapons proliferation standpoint,... 

In a modified PUREX process (sometimes called coprocessing), the plutonium and uranium are not handled separately as their nitrates, but rather they are processed together, yielding plutonium diluted with uranium. The diluted product is useful for nuclear reactors, but not directly usable for nuclear weapons,... 

Although the PUREX process is regarded as a well-matured chemical technology in the nuclear industry, owing to its complex chemistry, high radiation field, evolution of the fuels to be processed (i.e., extended high burn-up and MOX fuel), safety and economical issues, and its principal position in establishing the nuclear fuel cycle, both fundamental and application studies have been continued. 

In order to make use of thorium as a nuclear resource for power generation, development of efficient separation processes are necessary to recover 233U from irradiated thorium and fission products. The THORium uranium Extraction (THOREX) process has not been commercially used as much as the PUREX process due to lack of exploitation of thorium as an energy resource (157,180). Extensive work carried out at ORNL during the fifties and sixties led to the development of various versions of the THOREX process given in Table 2.6. The stable nature of thorium dioxide poses difficulties in its dissolution in nitric acid. A small amount of fluoride addition to nitric acid is required for the dissolution of more inert thorium (181). 

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. 

The SETFICS process (Solvent Extraction for Trivalent /-elements Intragroup Separation in CMPO-Complexant System) was initially proposed by research teams of the former Japan Nuclear Cycle Development Institute (JNC, today JAEA) to separate An(III) from PUREX raffinates. It uses a TRUEX solvent (composed of CMPO and TBP, respectively dissolved at 0.2 and 1.2 M in -dodecane) to coextract trivalent actinides and lanthanides, and a sodium nitrate concentrated solution (4 M NaN03) containing DTPA (0.05 M) to selectively strip the TPEs at pH 2 and keep the Ln(III) extracted by the TRUEX solvent (239). However, the DFs for heavy Ln(III) are rather poor. An optimized version of the SETFICS process has recently been proposed as an alternative process to extraction chromatography for the recovery of Am(III) and Cm(III) in the New Extraction System for TRU Recovery (NEXT) process. NEXT basically consists of a front-end crystallization of uranium, a simplified PUREX process using TBP for the recovery of U, Np, and Pu, and a back-end Am(III) + Cm(III) recovery step (240, 241). 

Zhu, Y., Han, B., Wu, Q. 1999. Study on the integration of the PUREX process and the TRPO process in nuclear fuel cycle back end. Global 1999 Nuclear Technology -Bridging the Millennia, August-September, Jackson Hole, WY. 

Reprocessing is based on liquid-liquid extraction for the recovery of uranium and plutonium from used nuclear fuel (PUREX process). The spent fuel is first dissolved in nitric acid. After the dissolution step and the removal of fine insoluble solids, an organic solvent composed of 30% TriButyl Phosphate (TBP) in TetraPropylene Hydrogenated (TPH) or Isopar L is used to recover both uranium and plutonium the great majority of fission products remain in the aqueous nitric acid phase. Once separated from the fission products, back-extraction combined with a reduction of Pu(I V) to Pu(III) allows plutonium to be separated from uranium these two compounds can be recycled.2... 

Stieglitz, L., Becker, R. 1982. Chemical and radiolytic solvent degradation in the PUREX process, in Nukleare Entsorgung Nuclear Fuel Cycle-, Baumgartner, F., Ebert, K., Gelfort, E., Lieser, K.H. Eds. Verlag-Chemie Weinheim, Deerfield Beach, EL, Basel, 333-350. 

In fact, the first description of such a scheme, involving the application of SFE to spent nuclear fuel reprocessing, appeared shortly after publication of these results. Specifically, Smart et al.43 outlined two possible approaches to SC-C02-based reprocessing. In the first, dubbed the wet SF-PUREX process, SC-C02 merely serves as a replacement for the organic solvent (i.e., a normal paraffinic hydrocarbon) used in... 

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