Thorium-230, extraction

The separation of basic precipitates of hydrous Th02 from the lanthanides in monazite sands has been outlined in Fig. 30.1 (p. 1230). These precipitates may then be dissolved in nitric acid and the thorium extracted into tributyl phosphate, (Bu"0)3PO, diluted with kerosene. In the case of Canadian production, the uranium ores are leached with sulfuric acid and the anionic sulfato complex of U preferentially absorbed onto an anion exchange resin. The Th is separated from Fe, A1 and other metals in the liquor by solvent extraction. 

Thorex [Thorium extraction] A process for separating the products from the nuclear breeder reaction in which uranium-233 is produced by the neutron bombardment of thorium-232. It uses solvent extraction into tri-n-butyl phosphate. Developed at the Oak Ridge National Laboratory, TN, in the early 1960s. See also Butex, Purex, Redox. 

Siddall III, T.H. Trialkyl phosphates and dialkyl alkylphosphonates in uranium and thorium extraction, Ind. Eng. Chem. 51 (1959) 41 14. 

Renard, E.V., Pyatibratov, Y.P., Neumoev, N.V., Vhizhov, A.A., Kulikov, I.A., GoTdfarb, Y.Y., Sirotkina, I.G., Semenova, T.I. 1988. Isoparaffinic diluents for tri-n-butyl phosphate. Chemical, radiation-chemical stability, effect on tetravalent plutonium and thorium extraction. Soviet Radiochem. 30(6) 734-745. (Translated from Zhurnal Struktumoi khimii 30(6) 774-787.)... 

A typical nuclear industry may consist of mining and milling of uranium ore, thorium extraction, fuel fabrication, nuclear reactor operation, and production and application of radioactive isotopes for various industrial medical and research purposes. Almost, in all these steps, waste is generated that needs proper management. Radioactive wastes differ from other industrial wastes due to its radiation exposure and its radiological toxicity to human beings and their environment. Management of radioactive wastes is an important step in a nuclear industry and the objective is to effectively isolate radionuclides from the... 

Because of the complications introduced by ferric iron, Audsley et al. concluded that a solvent that would be selective for thorium in the presence of ferric iron and that would not be inhibited by phosphate would be preferable to the Dapex solvent. They concurred with the conclusion of Crouse and co-workers at Oak Ridge National Laboratory [CS], that long-chain primary amines selectively extract thorium in the presence of uranyl, ferric, and phosphate ions. Compounds of this type are now the preferred extractant for thorium in such systems. Application of this so-called Amex process to thorium extraction from monazite is described in Sec. 8.6. 

Table 6.18 summarizes distribution coefficients of hexavalent uranium, thorium, and trivalent cerium (representative of rare earths) for four different types of long-chain amines, in sulfate solution with phosphate ion absent. Primary amines have the highest coefficient for thorium and the lowest for uranium, with the converse true of tertiary amines such as were cited for uranium extraction in Chap. 5. Secondary amines extract both metals, with thorium extraction favored by branching distant from the nitrogen. Either primary or secondary amines provide good separation of thorium from cerium. 

The thorium extraction was performed under slightly different conditions In that NH11NO3 was substituted for U02(N03)2- An Ionium (Th SO) tracer was added to the solution and the distribution was measured by the determination of Ionium In each phase. 

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