China 
Africa 
Explore chapters and articles related to this topic
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Uranium compounds are primarily used in the nuclear industry. It has been used over the years for a number of commercial ventures, some successful and others not. Uranium dioxide was employed as a filament in series with tungsten filaments for large incandescent lamps used in photography and motion pictures. It has a tendency to eliminate the sudden surge of current through the bulbs when the light is turned on, which extends the life of the bulbs. Some alloys of uranium were used in the production of steel; however, they never proved commercially valuable. Sodium and ammonium diuranates have been used to produce colored glazes in the production of ceramics. Uranium carbide has been suggested as a good catalyst for the production of synthetic ammonia. Uranium salts in small quantities are claimed to stimulate plant growth; however, large quantities are clearly poisonous to plants.
Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
The fissioning process for the nuclear fuels takes place within the core of a reactor. This is the main event of the nuclear power. There are, however, a number of other important events that take place for the nuclear fuels, both before and after their sojourn in the core. All these events combined constitute the nuclear fuel cycle. The cycle covers all activities involved in obtaining and irradiating fuel in nuclear reactors, as well as spent fuel processing and dispersing of the fission product wastes produced during irradiation in these reactors. The cycle does not leave out the interim storage and transport that links the pathways through which fuels transverse. Taking, for example, the case of uranium, the key steps that constitute the fuel cycle are Uranium ore miningUranium ore millingConversion into uranium compoundEnrichment (for certain types of nuclear fuel)Fuel manufacture and assemblyFuel irradiation in the reactor coreFuel discharge from the reactor for coolingSpent fuel processing (extraction of unused uranium and of newly created plutonium)Recycling of uranium and plutoniumManagement and disposal of radioactive waste
Nuclear Power
Published in Sheila Devasahayam, Kim Dowling, Manoj K. Mahapatra, Sustainability in the Mineral and Energy Sectors, 2016
Uranium ores first undergo an initial refining process in which they are crushed to produce a powder, processed to leach out and concentrate uranium compounds, and dried. The process is called milling and the resulting product is called yellowcake and is approximately 85% U3O8 (Figure 22.1).
Redox potential and uranium sorption onto sediments: kinetic and thermodynamic characteristics
Published in Chemistry and Ecology, 2020
Rong Liao, Zeming Shi, Yuejiao Chen, Xinyu Wang
Sediments are the ‘source’ and ‘sink’ of heavy metals. The sediments can absorb under certain conditions, but heavy metals may be released from the sediments once the conditions are changed [9]. Uranium is highly toxic, both chemically as a heavy metal and radiologically [10]. The ion strength, pH, Eh, uranium concentration, contact time, temperature, and other factors affect the uranium sorption onto sediments [11–13]. The uranium species are influenced by these factors. U (VI) and U (IV) are the most common oxidised states of uranium in nature. Hexavalent uranium compounds exist mainly as UO22+ and easily form coordination compounds with OH-, CO32-, SO24-, and PO34-. UO2 is the main species for tetravalent uranium. The hexavalent uranium compounds are more soluble, migratory, and toxic than the tetravalent uranium compounds [14]. Owing to the strong complexation between uranium and phosphorus, the Chinese phosphate rock is distributed mainly in various marine sedimentary types and has a high uranium-rich capacity. In phosphate mining and processing, U(VI) can easily migrate through the water system and thus affect the environment [15,16]. Various factors such as the composition of the aqueous solution, U content, Eh, and pH affect the migration of uranium. The redox potential (Eh) is one of the most important factors in the characterisation of the depositional environment. It is also an important parameter for the analysis of the migration and transformation characteristics of uranium in the epigenetic environment and remediation of radioactive contamination [17–19]. Theoretically, the reduction of U (VI) to U (IV) and its fixing in the form of insoluble UO2 are an ideal method to remove U (VI) from pollutants [20]. In the natural environment, owing to the long-term water coverage, aquifer sediments usually exhibit a wide range of redox states. Eh affects the sorption of uranium on sediments. However, it is difficult to evaluate the sorption characteristics of uranium on sediments under natural conditions. An experimental simulation of the flooding environment can be used to easily study the sorption characteristics of uranium on sediments. Therefore, in this study, the effects of the flooding time and Eh on the sorptions of uranium onto sediments were studied by flooding and static experiments. The conversion of uranium species according to Eh, characteristics of the kinetics, and thermodynamics of the sorptions of uranium onto sediments were also investigated.