Uranium Hexafluoride UF

Elemental fluorine is used captively by most manufacturers for the production of various inorganic fluorides (Table 5). The market for gaseous fluorine is small, but growing. The main use of fluorine is in the manufacture of uranium hexafluoride, UF, by... 

Canada, are examples. These reactors do not use ordinai y water for the moderator. Most nuclear fission reactors use ordinaiy water for a moderator which requires that the fuel he about 3 percent and about 97 percent U. Achieving this enrichment requires that the solid uranium compounds in the yellow cake be converted to gaseous uranium hexafluoride (UF,). Following enrichment, gaseous UF is converted to solid uranium oxide (UO,) for fabrication of fuel elements for a nuclear reactor. 

Nuclear power is now the only substantial use for uranium. But before uranium can be used in a nuclear reactor, it must undergo several processes. After uranium is mined from geological mineral deposits, it is purified and converted into uranium hexafluoride (UF,). The UF, is next enriched, increasing the concentration of U-235 by separating out UF,5 made with U-238 atoms. The enriched UF, is then converted into uranium dioxide (UO,), and pressed into fuel pellets for use in the nuclear reactor. 

During the conversion process, the object is to create uranium hexafluoride (UF ), a highly corro-sh e substance that is gaseous at high temperatures, but is a white crystalline solid at lower temperatures. Uranium hexafluoride is easily transported in its ciystalline form to an enrichment facility (the step taken after conversion), but the gaseous form is well suited for the enrichment process, itself. First, the... 

For decades, fluorine was a laboratory curiosity and it was studied mainly by mineral chemists. As is often the case, it was coincidence and not planned research that gave rise to fluorine chemistry. The development of the organic chemistry of fluorine is a direct consequence of the Manhattan Project in order to build nuclear weapons, the isotopic enrichment of natural uranium into its radioactive isotope was needed. For this purpose, the chosen process involved gas diffusion, which required the conversion of uranium into gas uranium hexafluoride (UFs) was thus selected. In order to produce UFe gas on a large scale, fluorhydric acid and elemental fluorine were needed in industrial quantities. This was the birth of the fluorine industry. 

Highly developed centrifuges are used to enrich uranium for nuclear application (see Nuclear. REACTORS Uraniumand uranium compounds). Gaseous uranium hexafluoride, UF, is introduced into a very high speed tubular rotor, causing the lighter 235U-fraction to separate from that of the heavier 2 5U. 

Exxon Nuclear Company has conducted various development programs to support the design and licensing of a commercial nuclear fuel reprocessing plant. The uranium conversion portion of the reprocessing plant will use fluidized-bed processes for conversion of uranyl nitrate hexahydrate (UNH) to uranium hexafluoride (UF ). This paper describes the laboratory and pilot plant studies conducted at Oak Ridge National Laboratory (1) for Exxon Nuclear Company on the conversion of UNH to UF, and on the purification of UF. ... 

During the Manhattan Project, directed toward construction of the first nuclear weapons 4], a strong need arose for materials, lubricants, and cooling fluids resistant to attack by the extremely aggressive uranium hexafluoride (UF ) (Scheme 4.3). 

Concentrates are shipped from the uranium mill to a uranium refinery or conversion plant. Here chemical impurities are removed and the purified uranium is converted into the chemical form needed for the next step in the fuel cycle. Figure 1.14 shows concentrates being converted into uranium hexafluoride (UF ), the form used as process gas in the gaseous diffusion process for enriching U. Other possible products of a uranium refinery used in other fuel cycles are uranium metal, uranium dioxide, or uranium carbide. Uranium purification and conversion processes are also described in Chap. 5. 

This edition of the Regulations includes, for the first time, provisions regarding packaging requirements for uranium hexafluoride (UF ), based on both the relevant hazards, i.e. the radiological/criticality and the chanical hazards. Uranium hexafluoride is the only commodity for which such subsidiary hazards have been taken into account in the formulation of provisions in these Regulations (see para. 629). 

The load cell-based weighing system (LCBS) is used for weighing large uranium hexafluoride (UFs) product cylinders (Dermendjiev et al. 1983). Cylinders are weighed with the LCBS... 

The DU munitions supplied by the UK Starmet Corporation to BAe Systems (Royal Ordnance) contain a mixture of tads depleted DU, i.e. the residue following enrichment of uranium hexafluoride (UF, and reprocessed DU, which is extracted along with plutonium from irradiated fuel [32], Other impurities in DU (e.g. Tt, Zr, Al, and Cu) are introduced during product manufacture. Most measured values of the 235U/238U weight ratio in natural uranium show a constant figure of 0.00720 0.00006... 

This approach has been aiq >lied successfully in the analysis of the Barnwell Nuclear Fuel Plant s Uranium Hexafluoride (UF,) Facility, and should have applicabUity to other facilities. 

Uranium hexafluoride (UF ), also called hex, is probably the best known and most widely investigated compound of uranium mainly because it is the only uranium compound with significant vapor pressure at ambient temperatures and therefore an essential raw material for most commercial isotope enrichment processes. UFg is a white monoclinic crystalline solid that sublimes directly to a gas (reaches atmospheric pressure at 56.5°C), but when heated in a closed vessel will melt at 64.05°C, which is the triple point where the solid, liquid, and gas phases coexist, as shown in Figure 1.8. This is probably one of the most weU-recognized phase diagrams in the chemical literature. 

Test Methods for Subsampling, Chemical, Mass Spectrometric, Spectrochemical, Nuclear, and Radiochemical Analysis of Uranium Hexafluoride UF ... 

Packages designed to contain uranium hexafluoride shall meet the requirements prescribed elsewhere in these Regulations which pertain to the radioactive and fissile properties of the material. Except as allowed in para. 632, uranium hexafluoride in quantities of 0.1 kg or more shall also be packaged and transported in accordance with the provisions of the International Organization for Standardization document ISO 7195 Packaging of Uranium Hexafluoride (UF ) for Transport [10], and the requirements of paras 630-631. 

To increase the percentage of uranium-235 in a sample of uranium (a process called enrichment), one first prepares uranium hexafluoride, UF, a white, crystalline solid that is easily vaporized. Uranium hexafluoride vapor is allowed to pass through a series of porous membranes. Each membrane has many small holes through which the vapor can effuse. Because the UFe molecules with the lighter isotope of uranium travel about 0.4% faster than the UF molecules with the heavier isotope, the gas that passes through first is somewhat richer in uranium-235. When this vapor passes through another membrane, the uranium-235 vapor becomes further concentrated. It takes many effusion stages to reach the necessary enrichment. 

If the uranium is to be enriched in the isotope, it must be converted to the gaseous form, as uranium hexafluoride, UF, which is gaseous at around 60 C. This is achieved by reaction with fluorine gas ... 

Reactions carried out between uranium hexafluoride (UF ) and silane (SiH4) with 0.13 < UF5/SiH4 < 5.2 in the temperature range -196 to... 

A practical application of Graham s law arose during World War II, when scientists were studying the fission of uranium atoms as a source of energy. It became necessary to separate which is fissionable, from the more abundant isotope of uranium, which is not fissionable. Because the two isotopes have almost identical chemical properties, chemical separation was not feasible. Instead, an effusion process was worked out using uranium hexafluoride, UFs. This compound is a gas at room temperature and low pressures. Preliminary experiments indicated that could indeed be separated... 

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