Simultaneous Determination of 238U, 234U, 230Th, 226Ra, and 210Pb in Uranium Ores, Dusts, and Mill Tailings
1977; Lippincott Williams & Wilkins; Volume: 33; Issue: 5 Linguagem: Inglês
10.1097/00004032-197711000-00004
ISSN1538-5159
Autores Tópico(s)Radioactive element chemistry and processing
ResumoA procedure is described for determination of the five most important radionuclides of the 238U series in the same sample. This procedure helps to eliminate apparent changes in the isotopic composition caused by sample inhomogeneity and to maximize sensitivity and precision on air dusts when only small samples are available. The sample is decomposed with hydrofluoric acid and pyrosulfate fusion to guarantee complete conversion of refractory compounds to the ionic state before chemical separations are attempted. Thorium and radium are separated from the hydrochloric acid solution of the pyrosulfate cake by precipitation on barium sulfate. Thorium is then extracted into bis(2-ethylhexy)phosphoric acid, electrodeposited, and analyzed by alpha spectrometry. Radium is determined by the emanation procedure. Lead and bismuth are extracted into diethyldithiocarbamate from the filtrate of the barium sulfate separation, and 210Pb is determined by beta counting its 210Bi daughter. Uranium is extracted into Aliquat-336, after prior concentration on barium sulfate when the quantity of uranium present is small, electrodeposited, and analyzed by alpha spectrometry. Isotopic tracers for thorium and uranium are used and chemical yields for all four elements are higher than 85%. On the ores and dusts analyzed, the uranium was generally depleted in 234U by as much as 15–20% compared to the 238U parent, although one sample was depleted by 56%. Thorium-230 varied from slight depletion to substantial enrichment up to 75%. Radium-226 varied from much lower to much higher than its 230Th precursor, depending on the particular ore. Lead-210 was depleted significantly compared to its 226Ra precursor in every case except a single pitchblende standard known to be in equilibrium. No great differences in the isotopic composition were observed either among ores and dusts from the same mill or as a function of particle size.
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