Radiochemical rare earths

This useful technique has made many contributions to radio- and nuclear chemistry, although primarily for investigational purposes rather than those of separation for its own ends. Thode and his co-workers have made many investigations into the inert gases produced in fission and it was by these means that the fine structure of fission was first discovered (79), (121). Since then several other elements, the rare-earths, strontium, caesium, zirconium, and molybdenum (35), (50), (132) have been investigated, and the isotopic ratios obtained provide relative values of fission-yields which are more accurate than can be obtained by standard radiochemical means. The latter technique, however, requires rather less heavily irradiated material than the former. 

The data of Table I are derived from early time radiochemical data reported by Stevenson (5). The linearity of the radionuclide ratios was first pointed out in that report. The aerial filter samples were taken at successively later times, 1 and 2, below the reported cloud base, and 3, 4, and 5 in the cloud. The tabulated values of rA correspond to atom ratio of isotope A to an arbitrary refractory isotope normalized by dividing by the atom ratio in which the two species were formed. Refractory species include the isotopes of the rare earths Eu and Tb as well as 45Ca, 89Zr, Sc, and others produced by neutron reactions on stable isotopes. The tabulation has been limited to fission product species. However, the... 

Although this method can give very good decontamination factors and also a high yield, the speed of the separation as It Is ordinarily used Is rather slow. This technique, however, occupies a prominent position In the radiochemical separation of the rare earth elements (258) and the actinide elements (119) ... 

Radiochemical group separation has a major advantage over individual element separation in that it is far less time consuming, yet it can permit suflBcient separation to allow precise analysis. For example, by simply separating the rare earth elements (REE) as a group after neutron activation, it is possible to measure most of the rare earth spectra by direct counting and thus determine their distribution. 

Later, many fast radiochemical separations and ingenious automatic chemical separation methods were developed (Herrmann and Denschlag 1969,1982 Rengan and Meyer 1993) and were applied to the determination of independent fission yields (Denschlag 1986, 1997). Summarily, one can say that the methods developed allow isolating any element formed from the complex mixture of fission products within the time span of a few seconds (exception rare earth elements that require a time span of minutes). 

In the comprehensive studies of the radioactive species produced in the fission of uranium it has been found that over thirty are members of the rare earth family (isotopes of yttrium and the group lanthanum through europium). The chemical and physical identification of these was an important part of the research program of the Manhattan Project. Standard oxidative separations and fractional precipitations and the use of radiochemical methods based on chain relations served to distinguish the activities of yttrium, lanthanum, cerium, and some of praseodymium, and those of samarium and europium. The characterization of the sequence praseodymium, neodymium, and element 61 presented very difficult problems that were solved only with the intensification of ion exchange methods originally developed by Boyd and co-workers and applied to the rare earth field by Cohn and co-workers. (Marinsky et al. 1947)... 

Rare Earth Elements (REE). Several radiochemical procedures are based on the chemical similarities of the rare earth elements, especially those of lanthanides. 

In a two-cycle Purex procedure, the recoveries of both Pu and U are on the order of 99.9% the Pu/U separation factor is 10 . The literature reports that plutonium decontamination factors from the fission products are 10 , and that the only long-lived impurities detected in the final product are Zr, Tc, and ° Ru. However, the authors experience has been that the light rare earths (mainly La and Ce), thorium, neptunium, and the trivalent actinides (Am and Cm), which exhibit some degree of complexation in nitrate media (Guseva and Tikhomirova 1979), are present in a gram-sized plutonium sample at concentrations that are detectable by radiochemical means. 

The /-block consists of the 4/ metals, La-Lu, and the 5/ metals, Ac-Lr. The common terms lanthanide and actinide derive from the names of the first elements of each series, and the symbol Ln, not assigned to any particular element, is a useful way to designate the lanthanides as a class. The older term for lanthanides, rare earths, is sometimes encountered. The actinides are radioactive, and only Th and U are sufficiently stable to be readily handled outside high-level radiochemical facilities t /2 = 4.5 x 10 years Th, ti/2 = 1.4 x 10 years). Even though they have no / electrons, scandium (Sc) and yttrium (Y) in group 3 are also typically considered with the /-block elements because of their rather similar chemistry. 

Radiochemical purity assessment, 342 Radioscanners, 350 Raman spectroscopy, 222-223,230 combination of TLC and, 147 surface-enhanced, 34,223,836 Rare earth elements (REE), detection and identification of, 520... 

Baker, J.D., Meikrantz, D.H., Gehrke, R.J., Greenwood, R.C. Nuclear decay studies of rare-earth fission-product nuclides using fast radiochemical separation techniques. J. Radioanal. Nucl. Chem. Art. 142, 159-171 (1990)... 

Geochemists were some of the first researchers to realize the enormous benefits of ICP-MS for the determination of trace elements in digested rock samples. Until then, they had been using a number of different techniques, including neutron activation analysis (NAA), thermal ionization mass spectrometry (TIMS), ICP-OES, x-ray techniques, and GFAA. Unfortunately, they all had certain limitations, which meant that no one technique was suitable for all types of geochemical samples. For example, NAA was very sensitive, but when combined with radiochemical separation techniques for the determination of rare earth elements, it was extranely slow and expensive to run. TIMS was the technique of choice for carrying out isotope ratio studies because it offered excellent precision, but unfortunately was painfully slow. Plasma... 

SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis REE, rare earth element exclusion chromatography IT, isotopic tracing RNAA, radiochemical neutron activation analysis. 

Shinotsuka, K., and Ebihara, M. (1997). Precise determination of rare earth elements, thorium and uranium in chondritic meteorites by inductively coupled plasma mass spectrometry—A comparative study with radiochemical neutron activation analysis. Anal. Chim. Acta 338(3), 237. 

Schuhmacher, J. and Maler-Dorst, N. A Radiochemical Separation Scheme for the Quantitative Determination of 45 Elements and of the Rare Earths in Biological Specimens by Means of Nputron Activation. Kerntechnik 1 , No. 4, 165 (1972). (In German and English). 26 35775... 

Bril, K.J., 1964, Mass Extraction and Separation, in Eyring, L., ed.. Progress in the Science and Technology of the Rare Earths, Vol. 1 (Pergamon Press, Oxford) pp. 30-61. Briicher, E. and I. Toth, 1972, Radiochem. Radioanal. Lett. 12, 53,... 

The magnitude of effort required is illustrated by the classic work on zone-refined aluminum by Albert of the CNRS Laboratory in Paris. Samples were analyzed for over 60 elements plus the rare earths by high-sensitivity neutron activation using detailed radiochemical procedures. Elements such as carbon, oxygen, and nitrogen were determined by photonuclear or charged-particle activation. This procedure required the efforts of a four-man team for 12 hr, an additional person for nine days, and another person for two weeks to analyze the rare earths. After the amounts of individual contaminants were totaled (for many there were only experimental upper limits of 1-10 ng), it was possible to establish that a particular sample of aluminum contained less than 2 ppm total impurities (i.e., it was not quite 6-9 s pure). 

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