Californium separation

Stary (1966) discusses the results of Oak Ridge National Laboratory studies of americium/californium separation factors in HDEHP extraction as a function of the organic diluent, As presented in table 6, while the change in diluent from normal paraffin hydrocarbons to aromatic hydrocarbons to chlorinated solvents results in an order of magnitude variation in the overall extraction of Am and Cf, the Am/Cf separation factors remain constant at 110( 8). 

The targets were then removed for chemical separation of the einsteinium from californium. 

The Multi-Purpose Processing Facility was installed in F Canyon (reprocessing plant) at SRP for separation of Californium and trans-californium elements using newly developed, high-pressure, chromatographic cation exchange processes. 

Californium is separated from other elements by fractionation and precipitation, and further purified by solvent extraction or ion exchange. 

This collection of the state-of-the-art papers emphasizes the continuing importance of industrial-scale production, separation, and recovery of transplutonium elements. Americium (At. No. 95) and curium (At. No. 96) were first isolated in weighable amounts during and immediately after World War II. Berkelium and californium were isolated in 1958 and einsteinium in 1961. These five man-made elements, in each case, subsequently became available in increasing quantities. 

Benker, D. E. Chattin, F. R. Collins, E. D. Knauer, J. B. Orr, P. B. Ross, R. G. Wiggins, J. T. "Chromatographic Cation Exchange Separation of Decigram Quantities of Californium and Other Transplutonium Elements", paper presented at Symposium on Industrial Scale Production-Separation-Recovery of Transplutonium Elements, 2nd Chem. Congr. North American Continent, Las Vegas, NV, 1980. 

Chromatographic Cation Exchange Separation of Decigram Quantities of Californium and Other Transplutonium Elements... 

At this rate, the pressure drop through the two columns is 2 to 5 MPa. The eluent solutions used ares 220 mL of 0.25 M AHIB— pH 3.9 (to elute the actinides from the loading column onto the separation column), about 1.5 L of 0.25 M AHIB—pH 4.2 (to elute all the fermium, einsteinium, and californium), 700 mL of... 

The separation column effluent is divided into about 15 fractions that are collected in small (250-mL) polyethylene bottles. The volume collected in each bottle is determined by the appearance of the alpha-emitting elements in the column effluent solution as indicated by the response from the flowthrough alpha detector a typical response curve is shown in Fig. 2. Normally/ two einsteinium fractions/ two intermediate fractions/ and three californium fractions are collected. The intermediate fractions are taken when the valley between the einsteinium and californium peaks occurs on the response curve and usually contain less than 5% of each element. Sometimes the alpha trace will show a small fermium peak just ahead of the einsteinium/ but usually there is not enough fermium alpha to make a response and the fermium is assumed to be in one or both of the two fractions taken just prior to the einsteinium. The berkelium is primarily a beta emitter and is not detected by either the alpha or neutron detectors thus, three fractions are usually taken after the californium alpha peak to isolate the berkelium. If there is a significant amount of 244Cm he feed (milligram quantities)/ the alpha trace will show a third major peak when americium and curium are eluted at the end of the run. 

The einsteinium-fermium and californium fractions collected during the initial separation described above are processed by means of a second cycle of high-pressure chromatographic cation exchange for additional partitioning of the actinide elements. The equipment and processing steps are similar to those described above. 

Californium-252 production was especially challenging, as it involved the sequential capture of 14 neutrons along with the intermediate separation and fabrication of two intermediate targets (americium and curium isotopes) when starting with Pu-23 9.27 This production campaign lasted ten years, produced about 10 g of Cf-252, and then was terminated. The product was evaluated as a neutron source but had insufficient value to justify continuing production. 

Modifications to this process can be made to effect recovery of neptunium, americium, curium, californium, strontium, cesium, technetium, and other nuclides. The efficient production of specific transuranic products requires consideration of the irradiation cycle in the reactor and separation of intermediate products for further irradiation. 

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. 

Plutonium is manufactured in megagram quantities neptunium, americium, and curium in kilogram quantities californium in gram amounts berkelium in 100-milligram amounts and einsteinium in milligram quantities. Chemical separations play a key role in the manufacture of actinide elements, as well as in their recovery, and analysis in the nuclear fuel cycle. This collection of timely and state-of-the-art topics emphasizes the continuing importance of actinide separations processes. 

Curium, berkelium, californium and einsteinium were separated from the americium samples irradiated by neutrons. For preliminary separation the anion exchange in hydrochloric acid and lithium chloride solutions was used as well as the HDEHP extraction. Mutual separation of the transamericium elements was made by using DIAION CK08Y cation exchange resin. Nuclides prepared and separation methods adopted are summarized in Table 1 (1-15). 

The actinides, such as californium or berkelium, can be separated by a method which had been used successfully to separate the rare earth elements. It is known as the ion exchange absorption-elution method, a complicated name for something very simple. It can be demonstrated with other... 

The actual apparatus used to separate berkelium from californium, for example, is a dark column of resin surrounded by a glass jacket which serves merely to contain a vapor that warms the column so the process will go on faster at a high temperature. 

Ion-exchange chromatography is generally used for the separation of the transplutonium elements (americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawren-cium). Determinations are usually made directly by a-spectrometry with solid-state detectors. Some elements (americium, curium, berkelium, californium) also have long-lived isotopes and can be determined by chemical methods such ultraviolet-visible spectrophotometry. 

Some basic chemical properties of the first transuranium elements became already evident in the discovery experiments, in which chemical separations played a crudal role. With time, a vast amount of information has been amassed on the chemistry of the elements available in macro quantities, i.e., all the elements through californium and, to a lesser degree, einsteinium (see, e.g., Katz et al. 1986). 

The identification of element 98 was accomplished with a total of only 5,000 atoms (Thompson et al. 1950b). The ion-exchange techniques were also used in the separation and identification of californium. Element 98 was eluted in the expected fraction, and the observed half-life and ot-particle energy of the radioactivity were also in agreement with predictions. It was named after the state of its discovery, although the chemical analog of element 98 was dysprosium (Dy). 

Modolo, G., P. Kluxen, and A. Geist. 2009. Selective separation of americium (III) from curium (El), californium (111) and lanthanides (IE) by the LUCA process. Proceedings of Global 2009, Paris, France, Sept. 6-11, Pap>er 9336. 

For basic studies on weighable quantities of californium, the Cf isotope is used. Its alpha half-life of 351 4 years [2,3] makes it suitable for chemical/physical experiments, where weighable quantities of californium are required. The Cf isotope is available as an isotopically pure material from the decay of Bk (beta emitter, half-life of 320 days), the latter being the major berkelium isotope obtained from reactors ( Bk is also formed, but it has a 3.5 h half-life). To obtain Cf free of other californium isotopes, it is first necessary to separate berkelium chemically from the californium produced in a reactor, and then permit the Bk to decay to Cf, which can subsequently be chemically separated from the berkelium. Currently, up to 60 mg per year of Bk are produced in the HFIR at ORNL, which is sufBdent to provide multi-milligram amounts of Cf [4]. The only other known production of Bk, and hence isotopically pure Cf (excluding the use of a mass separator), is in the USSR. The quantity of these materials available in the USSR is believed to be less than that produced by the HFIR. 

The choice of a separation and purification scheme depends on the nature of the californium source, the particular isotopes of californium involved, the amount of material, the impurities present, as well as several other factors. In short, the procedure should be customized to the particular needs at hand. Usually ion exchange is involved either as the main separative technique or in some secondary... 

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