Lithium isotopes enrichment

Figure 2. Lithium isotope enrichment by extraction chromatography, Li DBM 2 TOPO vs. LiOH...

Figure 3. Lithium isotope data for a range of commercially-available synthetic concentration standards (Qi et al. 1997a). The inset expands the c. 60%o range of reported natural samples. Although most anthropogenically-processed Li retains a broadly terrestrial value, nearly 20% of the samples examined show enormous isotopic enrichment in the heavy isotope.

Lithium is enriched in high temperature (c. 350°C) vent fluids by a factor of 20-50 relative to seawater (Edmond et al. 1979 Von Damm 1995). The Li isotopic compositions of marine hydrothermal vent fluids ranged from MORB-like to heavier compositions (see... 

Turning now to lithium, we have two nuclides available for NMR measurements Li and Li. Both are quadrupolar nuclei with spin quantum number / of 1 and 3/2, respectively. The natural abundance of Li (92.6%) provides enough NMR sensitivity for direct measurements, but also Li (7.4%) can easily be observed without enrichment. However, isotopic enrichment poses no practical problem and is advantageous if sensitivity is important, as for measurements of spin-spin coupling constants in solution and of quadrupole coupling constants in the sohd state. 

A series of investigations was performed on the structure of the complexes formed by unsaturated hydrocarbons with lithium dissolved in a solid argon matrix. The structures proposed for these complexes are based on assignment of the perturbations observed in the IR spectra of the free hydrocarbons and their isotopically enriched species. 

Germanium metal is also used in specially prepared Ge single crystals for y-ray detectors (54). Both the older lithium-drifted detectors and the newer intrinsic detectors, which do not have to be stored in liquid nitrogen, do an excellent job of spectral analysis of y-radiation and are important analytical tools. Even more sensitive Ge detectors have been made using isotopically enriched Ge crystals. Most of these have been made from enriched 7<5Ge and have been used in neutrino studies (55—57). 

More frequently the absorption line profiles overlap partially and, additionally, to obtain isotopically pure sources is difficult. Thus, part of the absorption observed will be due to the other isotope. Using a natural lithium hollow cathode lamp and a lamp made from enriched (93%) lithium-6, Chapman and Dale [236] were able to determine lithium isotopic... 

The Li nucleus can absorb a fast (above 3 MeV) neutron to produce a tritium nucleus, an alpha particle, and a slower neutron. A moderated neutron can be absorbed by a Li nucleus to produce a tritium and an alpha. Neutronic calculations indicate that a thick sphere of natural lithium could breed about 1.8 tritium atoms for each tritium atom burned in a fusion reaction (1 ). Structure and portions of the volume left open for fueling or driver beams reduce the 1.8 tritium breeding ratio. If the ratio falls below 1.0, it may be increased by addition of a neutron multiplier such as Be or Pb, and by isotopically enriching the Li in °Li. 

The alkali elution curves of the displacement chromatography are shown in Fig. 17, the ratio Li/ Li dependent on the effluent volume is given in Fig. 18. As one can see from Fig. 18, an increase of the Li/ Li ratio from 0.07 to 0.09 is found within the lithium elution band which corresponds to a column length of 91 cm. The relative enrichment of the heavy lithium isotope Li in the first fractions — that is in the methanolic phase — agrees with isotopic separations of calcium using a condensation resin with dibenzo(18]crown-6 and [2b.2.2], respectively (Chap. 4.3.2.3 and Chap. 4.3.2.4). Fujine and coworkers have also carried out one breakthrough experiment with methanolic solutions of cesium chloride and lithium acetate The evaluation of the front analysis with Spedding and coworkers method resulted in an isotopic separation factor of a = 1.014. 

From a breakthrough experiment in the system [2. 2.1] resin/0.116 M methanolic LiCl solution (column height = 22 cm, diameter = 0.9cm), Nishizawa and co-workerswere able to calculate the following isotopic fractionation factors a = 1.047 (0 °C), a = 1.037 (30 °C). From the results of the batch and breakthrough experiments it follows that there is a promising possibility for an enrichment of lithium isotopes on a technical scale with the use of the [2b.2.1] cryptand resin exchanger. 

Lithium aluminates have a potentially important role in the development of new types of nuclear reactors [78-81], This role is a result of the nuclear reaction between the 6Li isotope and neutrons 6Li(n,a), which results in a tritium (3H) ion. The natural abundance of 6Li is 7.5%, so ceramics can be made without any need for isotopic enrichment. The 3H ions are the plasma fuel for fusion devices. The design of the... 

SI. Saito, E., and G. Dirian Procesa for the Isotopic Enrichment of Lithium by Chemical Exchange, British Patent 902,755, Aug. 9, 1962. 

Trauser and co-workers investigated the application of molecular or short-path distiUation in the enrichment of the lithium isotopes. They developed single and multi-stage apparatus and found separation factors between 1.052 and 1.064 for one stage in the temperature range from 535 to 627 °C. In a similar way the mercury isotopes were separated. 

The pH control chemical is lithium hydroxide, enriched in the lithium-7 isotope to 99.9%. This chemical is chosen for its compatibility with the materials and water... 

In the majority of operating PWR plants, LiOH is used to compensate for the acidity of boric acid in order to attain an optimum coolant pH the lithium constituent of this compound consists of isotopically enriched Li (>99.99%) in order to minimize production. In the primary coolant, the total Li concentration ranges between 0.5 and 2 ppm depending on the current boric acid concentration and on the chemistry regime employed (see Section 1.3). 

By using isotopic enrichment, the contributions of Li" " and Na mobility to the total conductivity have been decoupled. " Despite the difference in cation size and typical coordination environments lithium and sodium show similar activation energies of ca 0.64 eV and make similar contributions to the overall conductivity of the phase. This observation is incompatible with the simple view of a positive cation migrating through a static window and indeed it has been shown that the sulfate anions in LiNaS04 are dynamic in the P phase. There is an energy barrier to anion... 

Lithium has two NMR active isotopes Li (7.4%) and (92.6%), of which is the isotope of choice due to its higher magnetogyric ratio and natural abundance. Both isotopes are available in isotopically enriched form making NMR tracer studies relatively easy. 

Large-scale production has been applied to enrich U-235, deuterium, and lithium-6. Gaseous diffusion is the principal technology for U-235 and is discussed further as part of the fuel cycle. Dual-temperature chemical exchange processes are used to enrich hydrogen and lithium isotopes. 

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