Uranium isotopes and

A number of special processes have been developed for difficult separations, such as the separation of the stable isotopes of uranium and those of other elements (see Nuclear reactors Uraniumand uranium compounds). Two of these processes, gaseous diffusion and gas centrifugation, are used by several nations on a multibillion doUar scale to separate partially the uranium isotopes and to produce a much more valuable fuel for nuclear power reactors. Because separation in these special processes depends upon the different rates of diffusion of the components, the processes are often referred to collectively as diffusion separation methods. There is also a thermal diffusion process used on a modest scale for the separation of heflum-group gases (qv) and on a laboratory scale for the separation of various other materials. Thermal diffusion is not discussed herein. 

Th and 231Pa are ubiquitous components of recently deposited deep-sea sediments because they are produced uniformly throughout the ocean from the decay of dissolved uranium isotopes and they are actively collected onto sinking particles. The distribution with depth of these nuclides in deep-sea sediments may be modeled to estimate rates of sedimentation extending over the past 200 to 300 thousand years. These techniques complement 14C dating methods that only extend to about 40 thousand years before the present. 

If you know the half-lives of uranium isotopes and the percentage of lead isotopes in some uranium-bearing rock, you can calculate the date the rock was formed. Rocks dated in this way have been found to be as much as 3.7 billion years old. Samples from the moon have been dated at 4.2 billion years, which is close to the estimated age of our solar system 4.6 billion years. 

Determine counting efficiency of the proportional detector in Step 5 for three 3,000-s periods to measure alpha particles and beta particles. Record in Data Table 7.2. Also perform overnight count (50,000 s) for alpha-particle spectral analysis of the planchet to identify the uranium isotopes and any other radionuclides and to determine their relative amounts from their alpha-particle energy spectra and record results in Data Table 7.2. Count alpha- and beta-particle background in proportional counter and alpha-particle spectral background in spectrometer for at least the same periods. 

The abundance sensitivity can also be considered for ions beams with a mass difference of two mass units. For example, the ultrasensitive measurement of is limited by peak tailing from the major uranium isotope and °Sr detection at the ultratrace level is difficult due to peak... 

Uranium hexafluoride is the key compound in the separation of the uranium isotopes and In its manufacture uranium(lV) oxide is first reacted with hydrogen fluoride to uranium tetrafluoride, which is then reacted with elemental fluorine to uranium hexalluoride ... 

URANIUM ISOTOPES AND CONTENT IN THE DEEP GROUNDWATERS OF THE TRI-STATE REGION, U.S.A. 

Cowart, J.B., 1981. Uranium isotopes and Ra content in the deep groundwaters of the... 

In addition to these elemental fractionations, separation between the two long lived uranium isotopes, and U, occurs commonly in ground-waters (Cherdyntsev, 1971). Thus, although the ultimate parent of radium is 2 U, the local source for a radium anomaly may be comprised mostly of 230rpj little uranium, or U and in-grown little U... 

A study of the kinetics of the separation of the uranium isotopes and by uranium(iv)-uranium(vi) chemical exchange on cationic exchange resins in sulphuric acid has demonstrated that large-scale uranium enrichment by this method would be uneconomical. The sorption of uranium from highly concentrated nitric acid solutions on AMP resins has been shown to be variable and dependent on concentration. 

Pu. The isotope Pu is the longest-lived of the plutonium- isotopes, with a half-life of 8 X 10 years. It can be produced by neutron absorption in Pu, but because of the short half-life and low concentration of Pu only minute quantities of Pu, of the order of 10" percent, are present in reactor-produced plutonium [K2]. Small quantities of Pu, as well as Pu and Pu, are present in the residues from nuclear explosions, resulting from the decay of the neutron-rich uranium isotopes and formed by multiple neutron capture in the high neutron... 

Oose-sepaiation case. In many multistage isotope separation processes a — 1 < 1, so that / — 1 1 and 7 — 1 < 1. The gaseous diffusion process for separating uranium isotopes and the water distillation process for enriching deuterium are examples. 

Nuclei differ in their stability, and some are so unstable that they undergo radioactive decay. The ratio of the number of neutrons to number of protons (N/Z) in a nucleus correlates with its stability. Calculate the N/Z ratio for (a) Sm (b) Fe (c) °Ne (d) ° Ag. (e) The radioactive isotope decays in a series of nuclear reactions that includes another uranium isotope, and three lead isotopes, Pb, °Pb, and ° Pb. How many neutrons, protons, and electrons are in each of these fi ve isotopes ... 

Lawrence s 184-inch cyclotron was soon modified to separate uranium isotopes and became the prototype for the calutrons used for similar purposes in the Manhattan Project. Both during and after the war, Lawrence was one of the most politically influential American scientists he served on many key committees, including the Scientific Panel that advised on the first use of the atomic bomb. 

The long-lived uranium isotopes and are both chemotoxic and radio toxic (Fisher 1988, Metivier 1988), vhereas all other isotopes and decay products vith their much shorter half-lives are only critical due to the ionizing radiation emitted during their radioactive decay. This is the result of the inverse relationship between the specific radioactivity (Bqkg ) and the halflife of a radionuclide. 

Since the lifetimes of the uranium isotopes and are difrerent, the isotopic ratio between their end products Pb and Pb can also be used for age determination. One can derive the relationship... 

The table below shows the percentage of natural abundance of each natural uranium isotope, and their respective half-lives. 

General mention should be made of the a-emitters radium 226, polonium 210, radon (radioactive inert gas) 220 and 222, uranium isotopes and thorium isotopes. 

The main task in the monitoring of radionuclides in fission products (nuclides produced by primary and secondary processes associated with fission, generally of the uranium isotopes and U), transuranium nuclides, and transplutonium elements is the identification of nuclides and the determination of yield. A... 

Elemental fluorine is an important chemical in the nuclear industry for separation of uranium isotopes and also for the manufacture of SFg, fluorinated organics, and polymers. The only source of fluorine is electrolysis usually carried out in the eutectic KF 2HF at a temperature of 355-383K and using a current density of 70-200 mAcm" [4, 17-19]. The selection of cell components and cell design is again determined by stability of materials to the very aggressive electrolysis... 

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