Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Curium Purex process

After a few years of storage, the main radioactive heat emitters in HLW are 90Sr and 137Cs. In addition, extremely long-lived actinides—neptunium, plutonium, americium, and curium—should be collected for transmutation in the future. Therefore, different flowsheets can be proposed for waste processing. It is possible to extract each radionuclide in the special extraction (sorption) cycle, for example, uranium and plutonium in the PUREX process, and after that, minor actinides (MAs) by the TRUEX process,4 strontium by the SREX process,5,6 and cesium by sorption7 or extraction.8... [Pg.360]

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. [Pg.484]

The P/T process will be coupled after an improved PUREX process that puts all technetimn, iodine, and neptunium into the waste fraction or into special fractions. Thus, the waste will contain fission products and minor actinides (americium and curium). The process will probably be a solvent extraction process although molten salt systems are also studied as an alternative. The main issue will be to obtain pure Am and Cm fractions for subsequent destruction, i.e., fractions that do not contain any lanthanides. Some of the lanthanides, which are chemically very similar to trivalent actinides, have very high neutron cross sections. Therefore, they must be removed to make actinide burning possible. In some cases, it may also be desirable to transmute some long-lived fission products, e.g., Tc and l, to more shortlived nuclides. [Pg.2424]

Over the past 10 years, modifications to the PUREX process have made it possible to more effectively separate neptunium. To effect the efficient separation of Np within the conventional PUREX process, Np is oxidized to VI state by nitrous add and is extracted in the first cycle along with U and Pu into the organic phase. The extracted Np( VI) follows the uranium stream and is later separated during the second purification cycle of uranium. In the RFC, the neptunium is sent to vitrification and disposed of as HLW but in an AFC option, the neptunium can be blended with MOX fuel or fabricated into special targets for later transmutation. The other minor actinides, ameridum and curium cannot be separated by reasonable modifications to the PUREX process. These elements will require the addition of special processing steps to separate them from the PUREX high-level waste stream. [Pg.2825]

In the AREVA version of the PUREX process, plutonium is removed from the uranium after the original extraction, converted to oxide and used in MOX fuel fabrication. Neptunium, americium, curium, and other remaining FPs (including lanthanides) are vitrified and incorporated in the HEW form (Richter et al., 2006). [Pg.399]

For future advanced nuclear systems, minor actinides are considered more as a resource to be recycled and transmuted than to be disposed of directly into a nuclear repository. A key feature of advanced fuel cycles technologies would be to separate M A and ultimately americium from curium. Several countries are investigating the separation of MA from a PUREX/COEX based process raffinate or a modified PUREX process raffinate using new extractant molecules with two potential options for actinide separations ... [Pg.437]

Americium and curium can be obtained from the aqueous waste of the Purex process. This americium is a mixture of Am and " Am. Isotopically pure Am, the decay product of " Pu, can be obtained from aged plutonium. Solvent extraction and ion-exchange procedures are used to recover americium from waste streams. Americium metal is produced by lanthanum reduction of the oxide, followed by vacuum distillation of the americium at 1400°C. [Pg.11]

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. [Pg.104]


See other pages where Curium Purex process is mentioned: [Pg.960]    [Pg.120]    [Pg.199]    [Pg.960]    [Pg.33]    [Pg.67]    [Pg.7105]   
See also in sourсe #XX -- [ Pg.946 ]

See also in sourсe #XX -- [ Pg.946 ]

See also in sourсe #XX -- [ Pg.6 , Pg.946 ]




SEARCH



Curium

Purex

© 2024 chempedia.info