Uranium separated

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

There are a number of industrial gas separation systems that use the selective permeability of plastics to separate the constituents. In design problems relating to such applications, the designer must consider the environmental conditions to determine whether the materials having the desired properties will withstand the temperatures and physical and chemical stresses of the application. Frequently the application will call for elevated temperatures and pressures. In the case of uranium separation, the extreme corrosivity of the fluorine compounds precluded the use of any material but PTFE. The PTFE... 

In any uranium separation process the work of enrichment increases rapidly with 235U content in the product. Because the price of natural uranium varies widely with time and location (and fluctuating government subsidies) it is useful to distinguish between the price of the feed and the value added by the separative process. For example, the purchaser himself might provide the feed and then pay only for the separative work required to make the desired product. Separative work is defined in Equation 8.7. 

S is the selectivity of photon absorption under the particular experimental conditions, and 8 is the relative abundance of the desired isotope. Equation 8.19 shows, for example, that S values on the order of 103 are required before more than about 10% of photons are used to excite D in natural abundance H/D mixtures (8 1.5 x 10-4). The selectivity required for uranium separation is less because > 8(D). 

Villani, S., 1979 Uranium Separation (Berlin, Springer-Verlag)... 

Karpas et al. reported on the determination of the 234U/238U isotope ratio (54.9 x 10-6) by MC-ICP-MS and ICP-QMS compared to a-spectrometry in hair, nail and water samples.46 A correlation of 0.99 was found between the two ICP-MS methods and of 0.98 with a-spectrometry for the water sample. The measurement time of the water sample after dilution for ICP-MS was 1 min and 1000 min (including uranium separation and counting time) for a-spectrometry.46... 

Step 3. Place a 50-mL beaker under the column to collect the eluent fractions. Add the uranium sample in 3 M HC1 from Step 1 to the top of the column with a transfer pipette. Open the stopcock to let the solution flow at a rate of about 1 mL/minute. Record the time of uranium separation. Rinse the beaker that contained the uranium sample twice with 5 mL of 3 M HC1 and pour it through the column. Pass an additional 10 mL of 3 M HC1 through the column. Then wash the column with 4 mL of concentrated HC1. Close the stopcock when the liquid just covers the resin. 

Efimova, Z.I., Smirnov, Yu.V. and Sokolova, I.D., Development of new methods of Uranium separation from non-tradition sources. (In Russian) At. Tekh. Rubezhom. 4 (1987) 3-9. 

Improvements in Thorium-Uranium Separation in the Acid-Thorex Process... 

Fluoride addition not only improves the thorium-uranium separation, but also minimizes the precipitation of thorium dibutyl phosphate in the uranium stripping column which has been a major problem in processing thorium based nuclear fuel materials using this process. ( 3,M... 

It is of interest to note that addition of 0.001 fluoride to the extraction scrub solution did not improve the zirconium-thorium separation significantly in the scrub section. A large improvement in zirconium-uranium separation has been observed by addition of fluoride to scrub streams in the Purex process. This difference is probably due to the thorium complexing the fluoride and lowering the free fluoride to a level which is ineffective in altering zirconium distribution. 

Several years ago, there was a lot of excitement concerning a method of using lasers to separate isotopes. A laser was adjusted to a very narrow wavelength that would excite only one of the uranium isotopes. With only one isotope excited it was projected that a near single stage separation method was possible. Little has been said about this method in recent years. The lack of the need for uranium separation has placed a damper on the developments. 

A similar sequence of operations in the uranium separation section separates uranium from rare earths. The difference here is use of triisoocytylamine as solvent because of its high selectivity for uranium. 

Finally, rare earths are extracted from the raffinate leaving the uranium separation section... 

If there were sufficient incentive to reduce the fuel-cycle inventory of plutonium, it would be possible to operate with shorter preprocessing cooling times and to take the remaining decay time after the plutonium-uranium separation. In the fast-breeder fuel cycle, where there is usually the greatest incentive to reduce fuel cycle fissile inventory and thereby to reduce the fissile doubling time, the content of the recovered uranium need not be as low as 10 disintegrations/(min-g), because the uranium is not to be recycled to isotope separation. 

In the Aquafluor process [G4] developed by the General Electric Company, most of the plutonium and fission products in irradiated light-water reactor (LWR) fuel are separated from uranium by aqueous solvent extraction and anion exchange. Final uranium separation and purification is by conversion of impure uranyl nitrate to UFg, followed by removal of small amounts of PuF , NpFg, and other volatile fluorides by adsorption on beds of NaF and Mgp2 and a final fractional distillation. A plant to process 1 MT/day of irradiated low-enriched uranium fuel was built at Morris, Illinois, but was never used for irradiated fuel because of inability to maintain on-stream, continuous operation even in runs on unirradiated fuel. The difficulties at the Morris plant are considered more the fault of design details than inherent in the process. They are attributed to the attempt to carry out aqueous primary decontamination, denitration, fluorination, and distillation of intensely radioactive materials in a close-coupled, continuous process, without adequate surge capacity between the different steps and without sufficient spare, readily maintainable equipment [G5, R8]. 

A cascade tiiat has the same number of units (i.e., the same capacity) in all stages of a group is known as a squared-off cascade. A cascade in which the number of units, or the capacity, in each stage decreases as the produce and waste ends of the cascade are approached is called a tapered cascade. A single multiplate distillation column is an example of a squared-off cascade a gaseous diffusion plant for uranium separation is an example of a tapered cascade. 

A gaseous diffusion plant is to be designed for a capacity of 10.8 million kg uranium separative work units per year with the following feed, product, and tails compositions (w/o = weight percent). 

Radium. Ra at. wt 226 (mass number of most stable isotope) at. no. 88 valence 2. A radioactive alkaline earth meta], Occurrence in earth s crust approx ]0-d% by wt. Natural isotopes 223, actinium X 224, thorium X 226 228, mesothorium 1. 22 Ra is a product of disintegration of uranium and is present in al] ores contg uranium. Separated in the form of a salt by P. and M. S. Curie from the pitchblende nf Joachimsthal, Bohemia Curie et at.. Compt. Rend. 127, 12]5 (1898). [soln of the element by electrolysis of an aq soln of radium chloride Curie, Debierne. ibid. 151, 523 (1910). 12 Ra iT, 6.7 years) produced by disintegration of thorium (I12Th) discovered in 1907 by O. Hahn in monazite residues from isolating thorium. Zaire (Congo) is the main producer of radium, Canada next. Clinical evaluation in... 

Radium Uraniums Separation Luminous paint i Cancer therapy ( oth decreasing)... 

Since all sources of thorium are associated with a certain amount of uranium, the first solvent-extraction cycle is designed solely to eliminate this element. The proportion of uranium to thorium can vary, but is often of the order of 5 per cent. The uranium distribution coefficient into tributyl phosphate is much higher than that of thorium under comparable conditions, e.g. 20 and 0-5 respectively for 40 per cent TBP/xylene or 6 and 0 04 respectively for 5 per cent TBP/xylene. The more highly diluted solvent is used for the uranium separation cycle in view of the higher ratio of the two distribution coefficients, or separation factor . Xylene is chosen in preference to, for example, odourless kerosene owing to the danger of formation of a third phase rich in thorium with the latter diluent. 

In fast reactors, the uranium-plutonium fuel of equilibrium composition is unfit for production of nuclear weapons. Its breeding properties are worse than those of uranium 20% enriched in (the IAEA limit). Absence of plutonium and uranium separation in all stages of the fuel cycle guarantees proliferation resistance. 

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