Uranium rays

Uran-saure, /. uranic acid, -strahlen, m.pl. uranium rays, -tonbad, n. (Photog.) uranium toning bath, -tonung, /. uranium toning, uranuranig, a. uranoso-uranic, uranium(IV,VI). Uran-verbindung, /. uranium compound, -ver-starker, m. uranium intensifier. -vitriol, n. (Aftn.) johannite. 

Curie chose for her dissertation research the new topic of uranium rays, a phenomenon that had only recently been observed by Henri Becqiierel. The mystery was the source of the energy that allowed uranium salts to expose even covered photographic plates. Curie s first efforts in the field were systematic examinations of numerous salts to determine which salts might emit rays similar to those of Becquerel s uranium. After discovering that both thorium and uranium were sources of this radiation. Curie proposed the term radioactive to replace uranium rays. She also discovered that the intensity of the emissions depended not on the chemical... 

As one can see from the laboratory log-book of Marie and Pierre Curie they started to study the Becquerel rays, or uranium rays, on December 16, 1897. First the work was conducted by Marie alone and then Pierre joined her on February 5,1898. He performed measurements and processed the results. They mainly measured the radiation intensities of various uranium minerals and salts as well as metallic uranium. The results of extensive experiments suggested that uranium compounds had the lowest radioactivity, the metallic uranium exhibited a higher radioactivity, and the uranium ore known as pitchblende had the highest radioactivity. These results indicated that pitchblende, probably, contained an element whose activity was much higher than that of uranium. 

The many possible oxidation states of the actinides up to americium make the chemistry of their compounds rather extensive and complicated. Taking plutonium as an example, it exhibits oxidation states of -E 3, -E 4, +5 and -E 6, four being the most stable oxidation state. These states are all known in solution, for example Pu" as Pu ", and Pu as PuOj. PuOl" is analogous to UO , which is the stable uranium ion in solution. Each oxidation state is characterised by a different colour, for example PuOj is pink, but change of oxidation state and disproportionation can occur very readily between the various states. The chemistry in solution is also complicated by the ease of complex formation. However, plutonium can also form compounds such as oxides, carbides, nitrides and anhydrous halides which do not involve reactions in solution. Hence for example, it forms a violet fluoride, PuFj. and a brown fluoride. Pup4 a monoxide, PuO (probably an interstitial compound), and a stable dioxide, PUO2. The dioxide was the first compound of an artificial element to be separated in a weighable amount and the first to be identified by X-ray diffraction methods. 

Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees G. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. 

Oxygen and nitrogen also are deterrnined by conductivity or chromatographic techniques following a hot vacuum extraction or inert-gas fusion of hafnium with a noble metal (25,26). Nitrogen also may be deterrnined by the Kjeldahl technique (19). Phosphoms is determined by phosphine evolution and flame-emission detection. Chloride is determined indirecdy by atomic absorption or x-ray spectroscopy, or at higher levels by a selective-ion electrode. Fluoride can be determined similarly (27,28). Uranium and U-235 have been determined by inductively coupled plasma mass spectroscopy (29). 

Radiometric ore sorting has been used successfully for some uranium ores because uranium minerals emit gamma rays which may be detected by a scintillation counter (2). In this appHcation, the distribution of uranium is such that a large fraction of the ore containing less than some specified cut-off grade can be discarded with tittle loss of uranium values. Radioactivity can also be induced in certain minerals, eg, boron and beryllium ores, by bombarding with neutrons or gamma rays. 

Radioactivity occurs naturally in earth minerals containing uranium and thorium. It also results from two principal processes arising from bombardment of atomic nuclei by particles such as neutrons, ie, activation and fission. Activation involves the absorption of a neutron by a stable nucleus to form an unstable nucleus. An example is the neutron reaction of a neutron and cobalt-59 to yield cobalt-60 [10198 0-0] Co, a 5.26-yr half-life gamma-ray emitter. Another is the absorption of a neutron by uranium-238 [24678-82-8] to produce plutonium-239 [15117 8-5], Pu, as occurs in the fuel of a nuclear... 

The uranium ores from which this new radiation was discovered were fluorescent, and x-ray tubes fluoresced thus, an early hypothesis was that the visible fluorescence and the new penetrating radiation were related and would occur together. Becquerel did a series of careful experiments showing that penetrating radiation also came from some materials that did not fluoresce. 

AT the path length, and P (A) the mass absorption coefficient at wavelength A. Between absorption edges, P (A) is proportional to Z A and is nearly independent of physical or chemical state. An absorption measurement on each side of an absorption edge is required for each element analyzed. X-ray absorption is especially useful in determining heavy elements in mixed materials of lower Z, such as lead in gasoline and uranium in aqueous solution. 

Cerous bromide [14457-87-5] CeBr, and praseodymium bromide [13536-53-3] PrBr, are claimed to be suitable for a molten salt bath used for the reduction of uranium oxide by magnesium (16). PrBr is claimed to be alight filter in a cathode ray tube (17). 

EXAFS is a nondestructive, element-specific spectroscopic technique with application to all elements from lithium to uranium. It is employed as a direct probe of the atomic environment of an X-ray absorbing element and provides chemical bonding information. Although EXAFS is primarily used to determine the local structure of bulk solids (e.g., crystalline and amorphous materials), solid surfaces, and interfaces, its use is not limited to the solid state. As a structural tool, EXAFS complements the familiar X-ray diffraction technique, which is applicable only to crystalline solids. EXAFS provides an atomic-scale perspective about the X-ray absorbing element in terms of the numbers, types, and interatomic distances of neighboring atoms. 

Gamma rays of various energy are emitted by potassium-40, thorium, uranium, and the daughter products of these two last elements contained in the earth formations surrounding the borehole. These elements occur primarily in shales. The gamma rays reaching the borehole form a spectrum typical of each formation extending from a few keV to several MeV. 

Spectral Gamma Ray Log. This log makes use of a very efficient tool that records the individual response to the different radioactive minerals. These minerals include potassium-40 and the elements in the uranium family as well as those in the thorium family. The GR spectrum emitted by each element is made up of easily identifiable lines. As the result of the Compton effect, the counter records a continuous spectrum. The presence of potassium, uranium and thorium can be quantitatively evaluated only with the help of a computer that calculates in real time the amounts present. The counter consists of a crystal optically coupled to a photomultiplier. The radiation level is measured in several energy windows. 

Figure 4-272 shows an example of a MWD spectral GR log. On the left track, SGR is the total GR count, and CGR is this total count minus the uranium count. On the right side of Figure 4-272 the wireline spectral gamma ray in the same interval is displayed. The curves are similar but some differences occur in the amplitude of the three curves. 

Fig 1-17 K, L, and M x ray energy-level diagram for a heavy element (uranium). The heaviest lines are those of major analytical interest. Lines of occasional analytical interest are of medium weight. The energy of a state is that which an atom has when an electron is missing from the level corresponding to that state. 

The examination and analysis of minerals have provided x-ray emission spectrography with a challenge and an opportunity. This situation has arisen because of a great growth of interest in uranium and thorium minerals in the rare-earth oxides and in metals such as tantalum and niobium, or hafnium and zirconium. On the whole, x-ray emission spectrography has met the challenge successfully, and the investigations that prove this also demonstrate the versatility and the value of the method.70"72... 

Thorium, determination by x-ray emission spectrography, 199, 329 together with that of uranium by radioactivity and x-ray emission spectrography, 209... 

Ultimate composition,.71 Ultraviolet spectrography compared with x-ray spectrography, 237-239 Unmodified scattering, 18, 20, 21 Uranium, determination, by x-ray emission spectrography, 187, 199, 203, 209, 234, 329... 

Uranium, in solution, determination by x-ray absorption-edge method, 142, 143... 

Yttrium, as internal standard in x-ray emission spectrography of uranium, 187, 203... 

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