Thorium partition

Uranium and thorium partitioning into amphibole were also studied experimentally by Tiepolo et al. (2000a). Under the redox conditions of their experiments (FMQ-2 log units) U was dominantly tetravalent. They find no correlation between Aj, Djh and crystal composition, and, but again find a linear correlation with silica content ... 

Spinels. There are limited experimental data on uranium and thorium partitioning between magnetite and melt (Nielsen et al. 1994 Blundy and Brooker 2003). Both studies find U and Th to be moderately incompatible. Blundy and Brooker s results for a hydrous dacitic melt at 1 GPa and 1025°C give Du and D h. of approximately 0.004. The accuracy of these values is compromised by the very low concentrations in the crystals and the lack of suitable SIMS secondary standards for these elements in oxide minerals. Nonetheless, these values are within the range of Djh of magnetites at atmospheric pressure 0.003-0.025 (Nielsen et al. 1994). It is difficult to place these values within the context of the lattice strain model, firstly because there are so few systematic experimental studies of trace element partitioning into oxides and secondly because of the compositional diversity of the spinels and their complex intersite cation ordering. 

Another example of an important effect of bulk composition on partitioning behavior is provided by uranium and thorium partitioning into clinopyroxene. The decay series is frequently used as an indicator of the nature and timescales of magmatic processes (e.g., Condomines et aL, 1981 McKenzie, 1985). The parent isotope... 

Uranium/Plutonium/Thorium Partition. After the reduction step, the metals partition according to their solubility in the magnesium alloy. Magnesium is used as the focus metal because it provides a means of separating uranium from plutonium. 

The partition cycle columns were operated on flowsheet values and then a DBP solution was pumped to the extraction feed point in increasing amounts. The thorium content of the uranium product stream from the thorium partition column was monitored. The runs were then repeated using increasing increments of fluoride in the thorium partition solution and the thorium content again monitored in the uranium product from the partition column. 

Residual small amounts of thorium in the uranium stream after thorium partitioning were analyzed by ion exchange chromatography from a chloride medium followed by Thorin colorimetry. 

In the Acid-Thorex process, fluoride ion should be added to the thorium partitioning solution (1BX) to decrease thorium transfer to the uranium stripping column, particularly where highly radioactive feeds are used. This fluoride ion addition then decreases the precipitation of thorium-DBP in the uranium stripping column. Also, the partition cycle should be the first cycle in the Acid-Thorex process to allow separation of thorium from DBP. 

Rll. Ryon, A. D. McCabe-Thiele Graphical Solution of Uranium-Thorium Partitioning from 30% TBP-Amsco Solvent, Report ORNI 3045, JaiL 1961. 

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