Protactinium-233, separation from

Protactinium (of mass number 231) is found in nature iu all uranium ores, since it is a long-lived member of the uranium series. It occurs in such ores to the extent of about part per million parts of uranium. An efficient method for the separation of protactinium is by a carrier technique using zirconium phosphate which, when precipitated from strongly acid solutions, coprecipitates protactinium nearly quantitatively. Then the protactinium is separated from the carrier by fractional crystallization of zirconium oxychloride. 

Quantitative methods of obtaining protactinium start from the carbonate precipitate from the treatment of the acid extract of certain uranium ores. After this carbonate precipitate is dissolved, the protactinium remains 111 the silica gel residue, from the solution of which it is obtained on a manganese dioxide carrier. An alternate method effects final separation... 

Protactinium can be separated from natural ore concentrates by cycles consisting of adsorption on Mn02 precipitates followed by solvent extraction of the cupferron complex with pentyl acetate.94... 

In one significant respect, U-233 is better than uranium-235 and plutonium-239 its higher neutron yield per neutron absorbed. Given a start with some other fissile material (U-235 or Pu-239), a breeding cycle similar to but more efficient than that with U-238 and plutonium (in slow-neutron reactors) can be set up. The Th-232 absorbs a neutron to become Th-233, which normally decays to protactinium-233 and then U-233. The irradiated fuel can then be unloaded from the reactor, the U-233 separated from the thorium, and fed back into another reactor as part of a closed fuel cycle. 

The product actinium can be separated from the precursor radium by solvent extraction or ion exchange, and gram amounts of actinium have been obtained by this procedure. This is not at all an easy task, considering the highly radioactive substances involved, but is preferable by far to extraction from natural sources. Protactinium can be produced by the nuclear reactions ... 

Other elements that show strong adsorption from dilute HCl include many of the transition metals, tin, tellurium, and polonlum. 3 Kraus and Moore have effected the separation of protactinium and uranium by adsorbing them from 8M HCl on a column of Dowex A-1 resin and developing the column with 3.8m HCl. Protactinium appeared first In the eluent, separated from uranium. The uranium fraction contained, however, a fair amount of protactinium tailing. ... 

An additional material based on the extractant octyl-phenyl-N,N-diisobutyl-carbamoylmethylphosphine oxide, or CMPO, (marketed under the name TRU-Spec) has also been widely utilized for separations of transuranic actinides (Horwitz et al. 1993a) but is also useful for uranium-series separations (e.g., Burnett and Yeh 1995 Luo et al. 1997 Bourdon et al. 1999 Layne and Sims 2000). This material has even greater distribution coefficients for the uranium-series elements U (>1000), Th (>10000), and Pa. As shown in Figure 1, use of this material allows for sequential separations of Ra, Th, U, and Pa from a single aliquot on a single column. Separations of protactinium using this material (Bourdon et al. 1999) provide an alternative to liquid-liquid extractions documented in Pickett et al. (1994). 

Figure 1. Schematic diagram showing a TRU-spec extraction chromatography method for separation of uranium, thorium, protactinium, and radium from a single rock aliquot. Further purification for each element is normally necessary for mass spectrometric analysis. Analysis of a single aliquot reduces sample size requirements and facilitates evaluation of uranium-series dating concordance for volcanic rocks and carbonates. For TIMS work where ionization is negatively influenced by the presence of residual extractant, inert beads are used to help remove dissolved extractant from the eluant.

Burnett WC, Yeh CC (1995) Separation of protactinium from geochemical materials via extraction chromatography. Radioact Radiochem 6 22-32... 

To remove radium and other radioactive constituents from pitchblende, Hahn and Meitner treated pulverized pitchblende repeatedly and for long periods of time with hot concentrated nitric acid. From the insoluble siliceous residue they separated a new radioactive substance, which they called protoactinium. This name has subsequently been shortened to protactinium. When they added a little tantalum salt to a solution containing protactinium, the reactions of the new substance so closely resembled those of tantalum that Hahn and Meitner were unable to separate the two substances (118). Since tantalum is not radioactive, the protactinium could thus be obtained free from other radioelements. Since protactinium is not an isotope of tantalum, it should be possible to separate them from each other (119). By working up large quantities of rich pitchblende residues from the Quinine Works at Braunschweig, Hahn and Meitner were able to extract more active preparations of the new element (49). 

In a study of the long-lived protactinium isotopes produced from thorium bombarded by high energy deuterons or helium ions (175), pieces of thorium metal of 25 mil thickness were used to increase the total yield of the protactinium. On the other hand, when the time for chemical separations had to be shortened in order to study the short-lived protactinium Isotopes, thinner pieces of thorium, 5 mils or less in thickness, were used to ensure rapid dissolution. In some cases, thorium nitrate powders wrapped in aluminum were used as the target in order to reduce further the time for dissolution of the target. 

At the time, Soddy was seeking evidence that lead from thorium ores had different atomic weights from normal lead. When Soddy announced the discovery of a sample of lead of atomic mass 207.74, he acknowledged the contribution of Hitchins for the separation and analysis work. Thus, Hitchins precise and accurate measurements on the atomic masses of lead from different sources were among the first evidence for the existence of isotopes.51 In addition, Hitchins took over the research on protactinium from Cranston when the latter was drafted for the First World War. 

Regelous et al have reported ou the use of the isotope dilutiou techuique (using a Pa spike with a half-life of 26.97 days) for the quantitative measurement of 20 fg of protactinium in silicate rocks after chemical separation of the actinide from the rock matrix by MC-ICP-MS (Neptune, Thermo Fisher Scientific, Bremen - equipped with uiue Faraday detectors, oue secondary electron multiplier and a retarding potential quadrupole for high abundance sensitivity measurements). 

Tn reviewing the chemistry of the actinides as a group, the simplest approach is to consider each valence state separately. In the tervalent state, and such examples of the divalent state as are known, the actinides show similar chemical behavior to the lanthanides. Experimental diflB-culties with the terpositive actinides up to plutonium are considerable because of the ready oxidation of this state. Some correlation exists with the actinides in studies of the lanthanide tetrafluorides and fluoro complexes. For other compounds of the 4-valent actinides, protactinium shows almost as many similarities as dijSerences between thorium and the uranium-americium set thus investigating the complex forming properties of their halides has attracted attention. In the 5- and 6-valent states, the elements from uranium to americium show a considerable degree of chemical similarity. Protactinium (V) behaves in much the same way as these elements in the 5-valent state except for water, where its hydrolytic behavior is more reminiscent of niobium and tantalum. 

After Abelson returned to Washington, McMillan pressed on. Unstable neptunium decayed by beta emission with a 2.3-day half-life he suspected it decayed to element 94. By analogy with uranium, which emits alpha particles naturally, element 94 should also be a natural alpha emitter. McMillan therefore looked for alphas with ranges different from the uranium alphas coming off his mixed luranium-neptunium samples. By autumn he had identified them. He tried some chemical separations, finding that the alpha-activity did not belong to an isotope of protactinium, uranium or neptunium. He was that close. 

If fuel salt is withdrawn from the core and protactinium (Pa) separation is done in a... 

To obtain significant quantities of protactinium, a separation procedure was developed for extracting protactinium from the sludge that was left after the ether extraction of uranium at the Springfields refinery. The process yielded 127 g of pure Pa from 60 tons of sludge. Protactinium metal can be obtained by reducing Pap4 with... 

Discovery Protactinium was identified by Fajans and Gohring in Karlsruhe in 1913, who named the new element brevium. They had discovered the isotope Pa with a half-life of 5.70 h. Lise Meitner at the Kaiser-Wilhelm Institute for Chemistry in Berlin separated the oxide of a more long-lived isotope from pitchblende (mixed with tantalum oxide). She published the news in 1918 together with Otto Hahn. The new element was discovered independently in the same year by F. Soddy, J. A. Cranston and A. Fleck in Glasgow. The name protactinium was selected because it was recognized as the prototype for actinium. The element was first isolated by Aristid V. Crosse in 1934. He prepared 2 mg of the metal. 

Protactinium. No efforts have been made to achieve high solubilities of protactinium in order to use it as a component of reactor fuel solutions. Rather, the chemistry of protactinium has been examined in order to devise processes for removing Pa continuously from thorium breeder blanket systems. A project was undertaken by the Mound Laboratories [28] to separate gram quantities of the longer-lived Pa which could be used in studies of the chemistry of protactinium. 

The head end process transfers bred uranium, protactinium, and fission products out of the solid pha.se portion of the slurry and into the liquid phase. After this step the two phases are partially. separated. A liquid portion transferred to the volatility plant carries bred uranium, protactinium, and fission products with it for stripping with HF. The stripped liquid bismuth is returned to the head end plant for mixing with fresh slurry feed. The head end process is not 100% efficient i.e., the uranium and protactinium are not completely removed from the slurry before reconstitution and return to the blanket region. This problem has been examined ill some detail and was taken into account in determining economics. 

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