Uranium production methods

There are several hundred radionuclides that have been used as radiotracers. A partial list of the properties of these nuclides and their production methods are shown in Table 4.1. The three common production mechanisms for the primary radionuclides are (n,y) or (n,p) or (n,a) reactions in a nuclear reactor (R), charged-particle-induced reactions usually involving the use of a cyclotron (C), and fission product nuclei (F), typically obtained by chemical separation from irradiated uranium. The neutron-rich nuclei are generally made using reactors or... 

Although the fission products could be recovered as byproducts from the waste from spent nuclear reactor fuel, special-purpose neutron irradiation of highly enriched uranium (isotopically separated uranium-235) followed by chemical separation is the normal production method. The major products, molybdenum-99 and iodine-131 with fission yields of 6.1 and 6.7 percent, respectively, have important medical applications. Mo-99,... 

The thereby formed sulfuric acid is neutralized by adding magnesium hydroxide. Independently of the production method, the precipitated uranium concentrate is washed to remove adhering salt solution and then dried. The precipitates produced with ammonia are subsequently calcined in a multiple hearth kiln at 750°C, ammonia, sulfite and chloride being driven off and U3O8 being formed ... 

Because of its long half-life, potassium-40 can be used to date objects up to 1 million years old by determination of the ratio of to jgAr in the sample. The uranium-lead method is based on the natural uranium-238 decay series, which ends with the production of stable lead-206. This method is used for dating uranium-containing minerals several billion years old because this series has an even longer half-life. All the 2 6pb in such minerals is assumed to have come from Because of the very long half-life of 4.5 billion years, the amounts of intermediate nuclei can be neglected. A meteorite that was 4.6 billion years old fell in Mexico in 1969. Results of studies on such materials of extrater-... 

The diverse production methods for high-purity tungsten are summarized in Fig. 5.39. The raw material is always APT with different purity depending on the uranium and thorium content. It depends on the ore deposit whether these two elements are present or not. If the concentrations are unacceptably high after dissolution, a selective solvent extraction process removes the main portion of these two elements. 

Uranium ores differ widely in conqtosition, containing a variety of other elements which must be removed. As a result the production methods differ considerably depending on the particular ore to be processed although in every case very selective processes must be used. The following is a common scheme. 

Production of power from nuclear reactors involves uranium mining, fuel fabrication, the reactor operations, and storage of wastes. All of these processes may expose humans and the environment to radiation. Uranium production in the United States was 12,300 tons of U3O8 in 1977, primarily from western states, Texas, and Florida. Mining from deep shafts or open pits is the preferred method of uranium extraction, although in Florida it is produced as... 

Electrochemical reactors are usually batch operated. Obviously energy is supplied in the form of electricity. In some cases, such as uranium production, the product can be prepared by both electrochemical and other methods, but other methods may then prove to be more economic in practice. Uranium, for example, is manufactured by heating a mixture of magnesium and uranium tetrafluoride ... 

The simplicity, speed, and versatility of solvent extraction make it an excellent radiochemical separation method. Even simple equipment like a test tube or a separation funnel allows radiochemists to perform elaborate studies within a few minutes. The method works for a wide concentration range, from the rather concentrated solutions in uranium production or nuclear fuel reprocessing to one-atom-at-a-time separations of the heaviest elements. 

In nature thorium is commonly present as monazite, a lanthanide phosphate mineral that contains 1-15% ThOi and usually 0.1-1% UgOg. Thus, thorium is often produced as a byproduct together with rare earth metals and uranium. There are several production methods (see, e.g., Ritcey 2006). The choice of method depends not only on the composition of the ore but also on whether thorium is the main product or a by-product. 

Fluorine was first isolated in 1886 by the French chemist Moissan, after nearly 75 years of unsuccessful attempts by several others. For many years after its isolation, fluorine remained little more than a scientific curiosity, to be handled with extreme caution because of its toxicity. Commercial production of fluorine began during World War II, when large quantities were required in the fluorination of uranium tetrafluoride (UF4) to produce uranium hexafluoride (UF6), for the isotopic separation of U235 by gaseous diffusion in the development of the atomic bomb. Today, commercial production methods are essentially variations of the Moissan process, and safe techniques have been developed for the bulk handling of liquid fluorine. 

Initially, the only means of obtaining elements higher than uranium was by a-particle bombardment of uranium in the cyclotron, and it was by this means that the first, exceedingly minute amounts of neptunium and plutonium were obtained. The separation of these elements from other products and from uranium was difficult methods were devised involving co-precipitation of the minute amounts of their salts on a larger amount of a precipitate with a similar crystal structure (the carrier ). The properties were studied, using quantities of the order of 10 g in volumes of... 

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

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