Investigation of the 230Th(p,2n)229Pa reaction as a route to 225Ac
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Chemistry - Radiation chemistry, radiochemistry, a↗
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Separation of thorium from uranium ore
Thorium-230 has many research applications, but there is not a commercial source of this isotope. However, since 230 Th is part of the 238 U decay chain, it can be separated from naturally occurring uranium. In this work, a novel procedure was developed to separate thorium from uranium ore, consisting of leaching, liquid–liquid extraction, precipitations and ion exchange chromatography. Here, the final product was 91.32 ± 0.77 mg of thorium with a purity of 99.5 ± 1.2 wt%. Of that, 7.65 ± 0.10 mg was 230 Th and the remainder 232 Th. The total yield of 230 Th was 71.1 ± 5.4%. Ways to improve the yield by further processing the back-extraction solution are suggested.
230Th↗
Temperature dependence of uranium and thorium partitioning in igneous zircons
Zircon is a key mineral in geochronology because of its chemical and physical durability and tendency to incorporate radioactive trace elements such as U and Th. Quantifying the partitioning of the actinide elements is critical to constrain initial non-secular equilibrium amounts of 230 Th in zircon. An excess or deficit of 206 Pb will be produced from such an initial excess/deficit of 230 Th from the secular equilibrium condition, which influences the calculated 206 Pb/ 238 U age (Schärer, 1984, Mattinson, 1973). However, there is no standard way to calculate Th/U partitioning ratios when applying age corrections to young igneous zircon, making uncertainties hard to estimate. To better understand U and Th partitioning of zircon/melt that is the cornerstone of the secular disequilibrium correction, zircon was synthesized in one-atmosphere experiments using basaltic andesite, andesite, and rhyolite starting materials, doped with Zr, U, and Th. Different experimental temperatures and oxygen fugacity conditions (ΔQFM−4 to ΔQFM+4) were explored to examine their effects on U and Th partitioning. In addition, we specifically quantify the effects of sector zoning, fractional crystallization, and melt composition on U and Th partitioning. By combining experimental and natural zircon data, we find that temperature has the primary control on the partitioning of U and Th in the zircon and calibrate an inverse relationship between these partition coefficients and crystallization temperatures. The calibrated equation can be applied to the 230 Th correction for an improvement in the accuracy of Th-corrected 206 Pb/ 238 U dates when the zircon crystallization temperature is known.
206Pb/238U dating↗