Thorium from ores

There are a number of minerals in which thorium is found. Thus a number of basic process flow sheets exist for the recovery of thorium from ores (10). The extraction of mona ite from sands is accompHshed via the digestion of sand using hot base, which converts the oxide to the hydroxide form. The hydroxide is then dissolved in hydrochloric acid and the pH adjusted to between 5 and 6, affording the separation of thorium from the less acidic lanthanides. Thorium hydroxide is dissolved in nitric acid and extracted using methyl isobutyl ketone or tributyl phosphate in kerosene to yield Th(N02)4,... 

The Recovery of Uranium and Thorium from Ores 65.2.2.1 Uranium... 

Th and Th. The members of the decay chain, Th (UX-1) and Th (ionium). Table 5.2, are found in natural thorium when uranium is present in thorium ores. Because of the short half-life of Th, its concentration in thorium is inconsequential, and it soon decays from separated thorium. Eighty-thousand-year Th, on the other hand, is a significant constituent of thorium from ores containing uranium. The Th/ Th atom ratio is given by... 

Head, A. J. et al. The Extraction and Concentration of Thorium from Ores. Part V. Further Studies on the Recovery from Monazite with the aid of Cellulose Phosphate following Sulphuric Acid Attack. D.S.I.R. Report, CRL/AE 166 (1958). 

Suppl. Vol. Part A The Element A 1 Thorium Deposits. Geochemistry (in preparation) A 2 History. Isotopes. Recovery of Thorium from Ores - 1986... 

Thorium has a wide distribution in nature and is present as a tetravalent oxide in a large number of minerals in minor or trace amounts. Thorium is significantly more common in nature than uranium, having an average content in the earth s cmst of approximately 10 ppm. By comparison, Pb is approximately 16 ppm. Thorium has a seawater concentration of <0.5 x 10 . Thorium refined from ores free of uranium would be almost... 

Fig. 12.4 Simplified flow sheet used in the recovery of thorium from its ores.

Figure 21 An outline flowsheet for the alkaline extraction of thorium from its ore...

It should be noted that breeders would not reduce the demand for uranium ore for many decades because several LWR and/or HWR converters (which produce fissionable material, but less than consumption) are required during the run-in of a breeder cycle to equilibrium. The doubling time of a breeder (the time required for the breeder to produce sufficient fissionable material to start up a second breeder reactor) might be a significant part of its operating life. Furthermore, natural uranium will be required for the thorium cycle, if it is used, and for startup of the fusion cycle. The tritium for the fusion cycle will be made in nuclear reactors, as it now is for nuclear weapons. The nuclear industry will always be dependent on a continuing supply of uranium from ore. 

Burners vs. breeders Burners depend on uranium from ore but may recycle the residual fissionable material from the spent fuel to reduce the ore requirement. Breeders produce more fissionable material than they consume by converting either uranium-238 into plutonium-239 or thorium-232 into uranium-233. The breeders depend on the plutonium-239 or uranium-233 from the burners to bring them into equilibrium, and this may take 30 years. 

Two engineering system demonstrations were performed to reduce the uranium-from-ore requirements of LWRs recycle of the plutonium and conversion to the thorium-uranium cycle to achieve thermal breeding. The demonstration phase of the plutonium recycle development was carried out in seven power reactors. Several LWRs originally were started up on the thorium-uranium cycle, and a light... 

Typical ores are monazite and xenotime which are lanthanide orthophosphates that also contain much thorium and bastnasite, which is, approximately, LnF(C03). The relative amounts of the elements vary widely from ore to ore. The Chinese ores and concentrates, relatively new to the market, tend to be richer in some elements (Dy, Sm, Nd, Pr) than those previously in commerce. 

The chemistry of the early actinide metals has been most extensively studied for many reasons. Chief among these is the availability of materials for study. Thorium and uranium obtained from ores as described above have been available for chemical investigations for well over 100 years. In fact, all early actinide elements may be found in nature, although only thorium, protactinium, and uranium are present in sufficient quantities to justify extraction. The remaining early actinide elements, neptunium and plutonium, are produced in large quantities in nuclear reactors. 

A puzzling observation that led to the discovery of isotopes was the fact that lead obtained from uranium-containing ores had an atomic mass lower by two full atomic mass units than lead obtained from thorium-containing ores. Explain this result, using the fact that decay of radioactive uranium and thorium to stable lead occurs via alpha and beta emission. 

Separation of thorium and uranium from ore samples using anion-exchange column (Dowex 1-X8) has been investigated [1]. Thorium was eluted with 6 M HCl. 

Thorium has been recovered as a by-product of uranium production from ores of the Blind River district in Ontario in which the uranium thorium ratio is 6 1 [C5], In such thorium the Th activity is 3.1 X 6 = 18.6 times the activity of the Th. 

The principal steps in producing refined thorium compounds from thorium-bearing ores are concentration of thorium minerals, extraction of thorium from concentrates, purification or refining of thorium, and conversion to metal or the thorium compound finally wanted. This section describes the concentration of monazite, the principal source of thorium in the past the extraction of thorium from monazite and the recovery of thorium from leach liquors by solvent extraction. Purification of thorium is described in Sec. 9 and conversion in Sec. 10. 

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