Thorium results

The radioactive decay of uranium and thorium results in the formation of a series of isotopes that are radiogenic by themselves and keep disintegrating into stable lead isotopes. These radioactive disintegrations are accompanied by the emissions of 4He atoms. Three such radioactive series exist ... 

Tables 2 and 3 present the chemical analyses data. Table 4 shows the free water, and Table 5 shows the pH for increment samples. Table 6 gives size distribution data. Tables 7 through 10 address radium, uranium, and thorium results, and Table II lists emission spectrographic analyses.

It has been found in this connection that the 17 of or, in other words, the number of neutrons emitted per fission of a atom is about 2.37, thus providing a net 35 increase of 1.37 neutrons per fission. If all of these neutrons are absorbed in fertile material such as, fer example, thorium atoms, 1.37 atoms are produced for each atom consumed or destroyed by the chain reaction. However, it will be noted that the loss of as 0 much as 15 percent of the 2.37 neutrons by escape from the system or by parasitic absorption of other materials than the thorium results in a net increase of zero thus preventing the breeding of thermally fissionable material. An enumeration of the losses follows ... 

Effect of Fuel Processing on Actinide Decay Chains. Chemical separation of thorium results in material containing Th-232 and Th-228 only. Secular equilibrium of Pb-212 and Bi-212 from Th-228 takes 40 days governed by the half-life of Ra-224. Secular equilibrium of Ac-228 takes around 50 years, governed by the half-life of Ra-228. Chemical separation of uranium results in material containing U-234, U-235 and U-238 only. Subsequent enrichment for fuel increases the proportions of U-235 and inevitably of U-234. Th-234 and Pa-234m achieve secular equilibrium with U-238 within a year, but... 

Mona.Zlte, The commercial digestion process for m on a site uses caustic soda. The phosphate content of the ore is recovered as marketable trisodium phosphate and the rare earths as RE hydroxide (10). The usual industrial practice is to attack finely ground m on a site using a 50% sodium hydroxide solution at 150°C or a 70% sodium hydroxide solution at 180°C. The resultant mixed rare-earth and thorium hydroxide cake is dissolved in hydrochloric or nitric acid, then processed to remove thorium and other nonrare-earth elements, and processed to recover the individual rare earths (see... 

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... 

There is Httie known chemistry of tetrakis-Cp thorium complexes. Pseudotetrahedral molecules, (rj-ring) Tb (15), where ring = Cp [1298-75-5] or Ind [11133-17-6], have a measurable dipole, resulting from deviation of symmetry (88). Difference of coordination environments, eg, v] in the indenyl system and in the Cp system, appears to indicate great steric crowding about the thorium center, which probably limits the reactivity and synthetic derivatization of these complexes. 

Historically the use of mona2ite, a thorium-containing mineral, as the principal lanthanide resource led to confusion regarding the relation between radioactivity and the lanthanides. Inadequate separations produced Th-contaminated Ln products. Modem processing technology results in products that meet all regulatory requirements. 

With Acyl Halides, Hydrogen Halides, and Metallic Halides. Ethylene oxide reacts with acetyl chloride at slightly elevated temperatures in the presence of hydrogen chloride to give the acetate of ethylene chlorohydrin (70). Hydrogen haUdes react to form the corresponding halohydrins (71). Aqueous solutions of ethylene oxide and a metallic haUde can result in the precipitation of the metal hydroxide (72,73). The haUdes of aluminum, chromium, iron, thorium, and zinc in dilute solution react with ethylene oxide to form sols or gels of the metal oxide hydrates and ethylene halohydrin (74). 

Once the particle-reactive species have been scavenged, subsequent packaging and/or aggregation can result in the flux of particles and particle-reactive species from the water column. Thorium provides a unique way to study the environmental pathways and the biogeochemical processes that affect particle-reactive species. The four useful thorium isotopes are Th = A x yx), °Th... 

Surface water enrichment is the result of aeolian and fluvial inputs, which are thought to be the most important sources of Th to the ocean. Thorinm-232 has been proposed as a link between the radiogenic thorium isotopes and trace metals and anthropogenic pollutants. " While the pathways are very different for the radiogenic thorium isotopes, Th is delivered to the ocean in a fashion similar to many pollutants and trace metals. For example, Guo et found Th distributions in the Gulf of Mexico and off Cape Hatteras in the North Atlantic Ocean agreed well with the general distribution pattern of aluminum. 

The actinides ( actinons or actinoids ) are the fourteen elements from thorium to lawren-cium inclusive, which follow actinium in the periodic table. They are analogous to the lanthanides and result from the filling of the 5f orbitals, as the lanthanides result from the filling of the 4f. The position of actinium, like that of lanthanum, is somewhat equivocal and, although not itself an actinide, it is often included with them for comparative purposes. 

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. 

Diethyl oxalate is usually preferred because of its slower rate of hydrolysis. Satisfactory results are obtained in the precipitation of calcium, magnesium, and zinc thorium is precipitated using dimethyl oxalate. 

Glocker and Frohnmayer determined the characteristic constant c for nine elements (Reference 2, Table 4) ranging in atomic numbers from 42 (molybdenum) to 90 (thorium). They proved that identical results could be obtained with the sample in the primary (polychromatic) or in the diffracted (monochromatic) beam. The method was applied with good results to the determination of barium in glass of antimony in a silicate of hafnium in the mineral alvite and of molybdenum, antimony, barium, and lanthanum in a solution of their salts—for example, 5.45% barium was found on 90-minute exposure by the x-ray method for a glass that yielded 5.8% on being analyzed chemically. 

None of the products or experimental preparations is currently in clinical use or under development. Thorium oxide was not excreted at all furthermore it proved to be toxic because of long-lived a-radiation [4]. Other agents were not pursued because they displayed various types of toxicity or were less well tolerated than the extracellular contrast agents. Except thorium dioxide, none of them resulted in reliable and satisfactory contrast or provided important diagnostic information which could not have been obtained with a similar quality by more recently established imaging methods. In spite of an everlasting... 

Filaments are usually refractory metals such as tungsten or iridium, which can sustain high temperatures for a long time (T > 3000 K). The lifetime of filaments for electron sources can be prolonged substantially if an adsorbate can be introduced that lowers the work function on the surface so that it may be operated at lower temperature. Thorium fulfills this function by being partly ionized, donating electrons to the filament, which results in a dipole layer that reduces the work function of the tungsten. In catalysis, alkali metals are used to modify the effect of the work function of metals, as we will see later. 

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