Uranium extraction efficiency

It has recently been discovered that the roasting of carnotite ore at 850°C in the presence of a few per cent of calcium sulphate, prior to carbonate leaching, enhances both the vanadium and uranium extraction efficiencies. A convenient way of achieving the desired conditions is to blend the ore with another carnotite ore with a high natural calcium sulphate content, when available, rather than waste the beneficial effect of the latter by treating it alone. 

In order to make use of thorium as a nuclear resource for power generation, development of efficient separation processes are necessary to recover 233U from irradiated thorium and fission products. The THORium uranium Extraction (THOREX) process has not been commercially used as much as the PUREX process due to lack of exploitation of thorium as an energy resource (157,180). Extensive work carried out at ORNL during the fifties and sixties led to the development of various versions of the THOREX process given in Table 2.6. The stable nature of thorium dioxide poses difficulties in its dissolution in nitric acid. A small amount of fluoride addition to nitric acid is required for the dissolution of more inert thorium (181). 

Moreover, under a particular set of conditions, the extraction efficiencies for the SC-C02 system were typically found to be very similar to the corresponding values in dodecane. The strong correlation between the SFE and conventional SX results for the two ions suggests that the solvation behavior of SC-C02 is similar to that of dodecane for the TBP system. Substitution of a stronger Lewis base, such as triph-enyl- (TPPO), tributyl- (TBPO), or trioctylphosphine oxide (TOPO) for TBP, generally yielded higher extraction efficiencies for both uranium and thorium. For both TBPO and TOPO, in fact, extraction was nearly quantitative over the entire range of... 

In-situ leaching in the seams themselves proceeds with sulfuric acid or carbonate solutions. The leaching agent is fed in via injection tubes into the rock seam and brought to the surface via a central tube. In situ uranium leaching efficiency is 60 to 85%. Currently ca. 5000 t of uranium are extracted in this way. 

Furthermore when the effect of diluent on the extraction efficiency of TOPO for uranium(VI) is examined in the extraction of aqueous solutions containing 5 g/1 of uranyl salts in nitric and sulphuric acids, it is found from some representative data (Table 3) that hydrocarbons such as alkane or cycloalkane enhance the extraction efficiencies in all systems, while halogen-substituted hydrocarbon such as chloroform reduces them. 

By calcnlating the residence times of the various solids in the tank and relating them to their corresponding extraction curves, the total uranium extraction for the entire train of mixers was estimated. The cost of the various mixer options, the prodnction efficiency net resnlt, and the cost of the installation and tank design conld be combined to yield the economic optimum for the plant. 

The effect of temperature deserves special mention since it represents a major ndvanlage for the liquid-membrane process.9 9 Figure 19.4-5 compares the influence or temperature on extraction of uranium by the SX and LM techniques. In the case of liquid membraues. extraction efficiency increases with tempemiure... 

Unlike the results found by Loyland et al (30) for uranium, we observed no repartitioning of either plutonium or americium amongst the various operational soil fractions after SFE. In all SFE experiments conducted in this work a net reduction of both plutonium and americium activity was observed across all soil fractions. Additionally, as the ligand system was changed from the less acidic beta-diketone TTA to the more acidic beta-diketone HFA the extraction efficiency of plutonium from the sesquioxide and residual fractions increased dramatically. Thus, it is likely that a more effective, and possibly complete, extraction could be performed if a reagent were added in small quantities to the extraction mixture to specifically attack the sesquioxide fraction. 

The increase in D between 33 and 25 suggests that subcritical CO2 is more effective at uranium extraction than the ScF phase. A similar increase in extraction efficiency for liquid CO2 over ScF CO2 has also been observed in the extraction of and Zxi with P-diketone modified CO2. (44) It is difficult to explain the increase in extraction efficiency in terms of increased solubility, since the density diffnence between liquid and ScF CO2 is snuill (0.86 - 0.83 g/mL at ISO atm). Further study is nee to asc tain if, and why. liquid CO2 could have higher D values and extraction rates. If real, the increase of D, and subsequently the extraction efficiency, is very significant to metal extraction with compressed CO2. Liquid CO2 is preferable to ScF CO2, since lower pressures are safer, energetically more favorable, and do not require expensive high pressure equipment. 

Extraction Efficiency of Uranium in X50 Liqui-Cel Extra-Flow, Celgard, Module... 

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