Curium purification

Curium purification was effected via the reaction of the Cm oxalate with aqueous KOH the pure Cm(OH)3 was obtained quantitatively using an 0.5M-OH- excess. A high-temperature form of Cm metal was prepared by reducting CmOj with Th and volatilizing the curium at 1650 °C. This form of the metal is face-centred cubic, with a metallic radius and valence of 1.78 A and + 3.0, respectively. 

Large Scale Method for the Production and Purification of Curium. 

This article presents a general discussion of actinide metallurgy, including advanced methods such as levitation melting and chemical vapor-phase reactions. A section on purification of actinide metals by a variety of techniques is included. Finally, an element-by-element discussion is given of the most satisfactory metallurgical preparation for each individual element actinium (included for completeness even though not an actinide element), thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, and einsteinium. 

A research and development program on the recovery and purification of potentially useful by-product actinides from the nuclear fuel cycle was carried out some years ago in the Federal Republic of Germany as part of the "Actinides Project" (PACT). In the course of this program, procedures for the recovery of neptunium, americium and curium isotopes from power reactor fuels, as well as procedures for the processing of irradiated targets of neptunium and americium to produce heat-source isotopes, have been developed. The history of the PACT Program has been reviewed previously (1). Most of the PACT activities were terminated towards the end of 1973, when it became evident that no major commercial market for the products in question was likely to develop. 

Bigelow, J. E. Collins, E. D. King, L. J. "The "Cleanex" Process A Versatile Solvent Extraction Process for Recovery and Purification of Lanthanides, Americium, and Curium," Actinide Separations, ACS Symp. Series, No. 117, 1980, 147-155. 

Plutonium Purification. The same purification approach is used for plutonium separated from sediments or seawater. In case reduction may have occurred, the plutonium is oxidized to the quadrivalent state with either hydrogen peroxide or sodium nitrite and adsorbed on an anion exchange resin from 8M nitric acid as the nitrate complex. Americium, curium, transcurium elements, and lanthanides pass through this column unadsorbed and are collected for subsequent radiochemical purification. Thorium is also adsorbed on this column and is eluted with 12M hydrochloric acid. Plutonium is then eluted from the column with 12M hydrochloric acid containing ammonium iodide to reduce plutonium to the non-adsorbed tervalent state. For seawater samples, adequate cleanup from natural-series isotopes is obtained with this single column step so the plutonium fraction is electroplated on a stainless steel plate and stored for a-spectrometry measurement. Further purification, especially from thorium, is usually needed for sediment samples. Two additional column cycles of this type using fresh resin are usually required to reduce the thorium content of the separated plutonium fraction to insignificant levels. 

Americium, Curium, and Californium Purification. These elements, together with any lanthanides in the sample or added as carriers, pass through the anion exchange column used to remove plutonium. This fraction is purified to remove natural-series radionuclides which interfere with americium, curium, or californium measurements as well as stable elements which plate with the transuranics and produce spectral degradation. This latter consideration is especially important for lanthanides as neodymium is used as a carrier. Two lanthanide/actinide separation cycles immediately before electroplating are essential for acceptable plate quality. 

The Cleanex Process A Versatile Solvent Extraction Process for Recovery and Purification of Lanthanides, Americium, and Curium... 

HD(DIBM)P (Experiment 4) permits the best purification of americium (DF Am/Cm 18,750) while DF Cm/Am remains close to 7. An aqeaous acidity decrease, which was expected to increase DF Cm/Am, has no effect, but causes a drop in DF Am/Cm, probably due to higher curium extraction. 

Separation of Actinides from the Samples of Irradiated Nuclear Fuels. For the purpose of chemical measurements of burnup and other parameters such as accumulation of transuranium nuclides in irradiated nuclear fuels, an ion-exchange method has been developed to separate systematically the transuranium elements and some fission products selected for burnup monitors (16) Anion exchange was used in hydrochloric acid media to separate the groups of uranium, of neptunium and plutonium, and of the transplutonium elements. Then, cation and anion exchange are combined and applied to each of those groups for further separation and purification. Uranium, neptunium, plutonium, americium and curium can be separated quantitatively and systematically from a spent fuel specimen, as well as cesium and neodymium fission products. 

Large-scale purification of americium, curium, and californium with pressurized cation exchange has been planned at SRP for many years (1). Initial work involved SRP batch extractions to isolate a crude actinide-lanthanide fraction followed by solvent extraction and ion exchange in the SRL high level caves (1J. For large-scale purification, a single step was substituted for batch extraction and solvent extraction. Plant Purex solvent (30 vol % tri-n-butyl phosphate in n-paraffin) was used to minimize flush time and cross-contamination of solvent. 

Cm is recovered from irradiated Pu/Al alloys and Am02(Pu02)/Al cermets by dissolution, extraction of plutonium with TBP in n-dodecane, extraction of americium and curium from the aqueous raffinate with 50 percent TBP in kerosene, purification of the americium and curium fraction by extraction with tertiary amines, and separation of americium by precipitation of the double carbonate K5 Am02 (003)3 A high-pressure ion-exchange system for the separation... 

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. 

It is proposed to use non-aqueous methods of fuel reprocessing. Non-aqueous technologies developed in Russia and related to the processing of fuel from fast reactors with incomplete purification from fission products (about 1% of them remain in refabricated fuel) and with the release of only curium from the fuel (neptunium and americium and 1% of curium remain) allow the production of such fresh fuel for fast reactors that cannot be directly used to create nuclear weapons [XVI-9]. 

Isotopes of curium are also found in waste streams from plutonium-239 production, but in amounts smaller than those of americium. Curium is produced by the beta decay of Am and Am formed by neutron capture in Am and Am. The amount of curium-244 accumulated in process wastes and in unprocessed irradiated fuel elements as of 1985 is estimated at more than 100 kg [5]. Separation and purification of curium and americium is best carried out by the ion-exchange procedures described below (see Section 14.3.5). 

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