Americium reprocessing

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... 

Americium is released into surface water primarily from plutonium production reactors, nuclear fuel reprocessing facilities, or in nuclear accidents. It may also be released from radioactive waste storage facilities. Since 241Pu decays into 241 Am,241 Am is also released as a result of 241Pu releases. Water sampling data were used to estimate effluent releases from the SRS from the plant s start up in... 

Workers at plutonium reprocessing facilities, nuclear reactors, transuranium and low level waste storage facilities, or those engaged in the production or processing of243Am or241 Am may be occupationally exposed to americium. In addition, workers at sites where nuclear testing was conducted may also be exposed to americium. Workers in nuclear power stations may be exposed to airborne radionuclides. The... 

Environmental Fate. The environmental fate of americium has been extensively studied in relation to its introduction into the Irish Sea from the BNFL nuclear fuel reprocessing plant at Sellafield, United Kingdom (Belot et al. 1982 Bennett 1976 Bunzl et al. 1994, 1995 Malcolm et al. 1990 McCartney et al. 1994 McKay et al. 1994a Murray et al. 1978, 1979 Pattenden and McKay 1994 Walker et al. 1986). 

The isotopes are either produced by special irradiation of appropriate targets (plutonium 239/aluminum) in the case of americium 243 and curium 244, or, for americium 241, recovered from industrial wastes produced by reprocessing plants and plutonium oxide recycling. The annual production required to satisfy the various needs are respectively ... 

These two techniques are routinely used for the Am/Cm separations that we perform. However, they both have disadvantages. In the case of the precipitation of the double carbonate, the relatively high solubility of americium in solution (50 to 100 mg/L) requires reprocessing of the supernatant solution from the precipitation step which must be diluted considerably to avoid the precipitation of KN0 after acidification by HN0. For method (b), failure to oxidize the americium results in a loss to the CmF- precipitate. 

Americium and curium isotopes formed during irradiation of nuclear reactor fuels are diverted into the high-level waste (HLW) stream during fuel reprocessing. The HLW is thus the biggest... 

A full account of the problems considered in collecting, storing, and processing marine samples for transuranic analysis is given in the above-mentioned review (4). The specific methods discussed here were foimd effective at least for the transuranic analyses of seawater and sediments contaminated by global fallout, nuclear fuel reprocessing wastes, or nuclear power plant operation waste. In these cases, a preliminary acid treatment of the sample in the presence of suitable yield monitors seems to solubilize the transuranic elements and achieves isotopic equilibration between the yield monitor and sample. The yield monitors used were either Pu or sep qj. 238,239,240,24ip whereas Am was used for Am, 2 Cm, and by inference, Cf. In addition, it was convenient to use 50 mg of a lanthanide (neodymium) as a carrier for americium to purify the separated americium fraction. 

Separation of Actinides from High-level Waste (HLW). From the point of view of seeking a possible approach to the ultimate disposal of the HLW from the reprocessing of spent nuclear fuels, processes of solvent extraction and ion-exchange techniques have been studied to recover both americium and lanthanides from the HLW and to separate those subsequently. 

The americium and curium isotopes formed during irradiation of nuclear reactor fuels are diverted into the high-level waste (HLW) stream during fuel reprocessing. The HLW is thus the biggest potential source for these elements, and R+D activities to develop a process for the recovery of Am and Cm from HLW were started in 1967. A major condition was that the process to be developed must not essentially increase the waste amount to be processed further, must not use strongly corrosive reagents, and must be compatible with the final waste solidification procedure. 

Nuclear fuel reprocessing and partitioning allow recycling of useful fissionable materials such as uranium and plutonium, and remove harmful long-lived minor actinides (americium and curium). It is necessary also for safety storage of high-level liquid wastes(l). In order to improve efficiency of mutual separation between lanthanide and actinide elements, design of useful extractants are requisite. 

The long-term radioactivities of neptunium, americium, and curium in the high-level reprocessing wastes from the uranium-fueled water reactor are shown in Fig. 8.7. Except for Am and Np, these curves are also applicable to unprocessed discharge fuel. The curves Am and Np have been calculated for 0.5 percent of the plutonium in discharge fuel to appear in the wastes, so that there is not sufficient Pu to significantly increase the amounts of Am and... 

The radioactivities of the plutonium radionuclides in the high-level wastes from fuel reprocessing are shown as a function of storage time in Fig. 8.8 [PI], Because the initial plutonium quantities are due only to the small fraction, e.g., 0.5 percent, of the plutonium that is lost to these wastes in reprocessing, larger quantities appear after a few years due to the decay of americium and curium. The Pu increases with time because of the decay of " Am and Cm, Pu increases from the decay of Am and Cm, and Pu increases due to the decay of Cm. Therefore, even though the total actinide activity in these wastes is dominated by plutonium after the americium has decayed, the plutonium in the wastes at this time is due mainly to the earlier decay of americium and curium and not to the small fraction of plutonium lost to the wastes in fuel reprocessing. 

Figure 8.7 Radioactivity in curium, americium, and neptunium as a function of decay time. (Amount in the wastes produced annually by reprocessing fuel discharged from a 1000-MWe uranium-fueled PWR.)...

Early Work. The irradiated fuel, upon discharge from the reactor, comprises the residual unbumt fuel, its protective cladding of magnesium alloy, zirconium or stainless steels, and fission products. The fission process yields over 70 fission product elements, while some of the excess neutrons produced from the fission reaction are captured by the uranium isotopes to yield a range of hew elements—neptunium, plutonium, americium, and curium. Neutrons are captured also by the cladding materials and yield a further variety of radioactive isotopes. To utilize the residual uranium and plutonium in further reactor cycles, it is necessary to remove the fission products and transuranic elements and it is usual to separate the uranium and plutonium this is the reprocessing operation. 

There are two breeder reactor fuel cycles. One involves the irradiation of U/ Pu oxide fuel with fast neutrons and is at the prototype stage of development. The other involves the irradiation of Th/ U oxide fuel with thermal neutrons and is at the experimental stage. Fuel from the U/ Pu cycle may be reprocessed using Purex technology adapted to accommodate the significant proportion of plutonium present in the fuel. Increased americium and neptunium levels will also arise compared with thermal reactor fuel. The Th/ U fuel may also be reprocessed using solvent extraction with TBP in the Thorex (Thorium Recovery by Extraction) process. In this case the extraction chemistry must also take account of the presence of Pa arising as shown in Scheme 2. 

Aluminum(III) hydroxyfluorides minerals, 846 Alzheimer s disease aluminum removal, 770 Amberlite LA 2 solvent extraction palladium and platinum, 809 Americium breeder reactor fuels Purex process, 955 reprocessing, 954 Purex process, 946,950 sequestering agents, 962 Americium(III) complexes carbonates... 

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