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Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Uranium, U, is a radioactive metallic element. Uranium has three naturally occurring isotopes: uranium 234 (0.006%), uranium 235 (0.7%) and uranium 238 (99%). Uranium 234 has a half-life of 2.48 × 105 years, uranium 235 has a half-life of 7.13 × 108 years and uranium 238 has a half-life of 4.51 × 109 years. Uranium is a dense, silvery, solid material that is ductile and malleable; however, it is a poor conductor of electricity. As a powder, uranium is a dangerous fire risk and ignites spontaneously in air. It is highly toxic and a source of ionizing radiation. The TLV, including metals and all compounds, is 0.2 mg/m3 of air. The 4-digit identification number for uranium is 2979. Uranium is used in nuclear reactors to produce electricity and in the production of nuclear weapons systems.
Metals
Published in Ronald M. Scott, in the WORKPLACE, 2020
Uranium is primarily used to produce fuel for nuclear reactors and to produce weapons. Much of the mining of uranium ores in the United States occurs in western states. Early speculation in the hope of quick riches lead to the establishment of a large number of small uranium mining operations. As the industry matured, these small mines, often poorly ventilated, gave way to a relatively small number of much safer operations. The uranium is leached from ore using acidic ferric sulfate. In the process, the ferric ion is reduced to ferrous ion. Its reoxidation, allowing its reuse, is accomplished using a microorganism. The uranium is electrolytically reduced and precipitated as green cake (uranous fluoride) by the addition of hydrofluoric acid. Mining hazards include exposure to such radioactive species as uranium itself, radium, or radon gas. Inhalation of these radioactive species increases the risk of lung cancer. Chemical exposures are less important, and include exposures to such other metals found with the uranium as vanadium, lead, thorium, manganese, and arsenic. The silica rock of western mines adds the risk of silicosis. Because the ore is processed by wet techniques, the risks are relatively low. Uranium hexafluoride, a gas produced for isotopic separation in the gas centrifuge, is hazardous if a leak should occur in the apparatus handling this compound.
Occupational Health and Safety in Mines
Published in Debi Prasad Tripathy, Mine Safety Science and Engineering, 2019
Uranium is the used as a fuel for generating nuclear power. Uranium and its decay products emit alpha radiation and lower levels of beta and gamma radiation. The presence of a radioactive gas, called radon, in underground mines is a major concern. Many mine workers in the uranium mining industry have died due to excessive exposure to radon and its radioactive products. Along with uranium mines, radon exposure is observed in gold mines, particularly in South Africa, and coal mines in China. As uranium possesses both radioactivity and chemical toxicity, the mining and processing of uranium has well-known effects on humans and the environment. Due to exposure to radiation, lung cancer occurs commonly in uranium mine workers. A study of Czech and French uranium miners concluded that a substantial excess of lung cancer, reduced pulmonary function, and emphysema has been reported. The excess has been attributed primarily to irradiation of the tracheobronchial epithelium by alpha particles emitted during the radioactive decay of radon and its daughter products (Tomasek et al., 2008). One of the worst mining disasters occurred in Canadian uranium mines due to radiation exposure, in which around 400 uranium mine workers suffered lung cancer deaths due to excess radon exposure (Nolan, 2009).
Bifurcation Analysis of Xenon Oscillations in Large Pressurized Heavy Water Reactors with Spatial Control
Published in Nuclear Science and Engineering, 2022
Abhishek Chakraborty, Suneet Singh, M. P. S. Fernando
The safe operation of nuclear reactors is one of the most challenging aspects of the nuclear power industry. It involves a number of processes involving the generation of neutrons, their specific multiplications, their control, and the extraction of useful power out of the heat energy generated in the process. In most of the operating nuclear reactors, energy is produced by chain nuclear fission of 235U. In nuclear fission, a large nucleus like 235U is broken into multiple nuclei (fission products) with release of ~200 MeV of energy on absorption of a thermal/fast neutron(s). The heat which is produced in fission has to be removed by a coolant (generally H2O, D2O for thermal reactors and Na, Pb for fast reactors). This demands an efficient coupling between the neutronics and the thermal hydraulics to ensure a smooth, streamlined generation of power.
Spatial distribution and environmental risk assessment of heavy metals identified in soil of a decommissioned uranium mining area
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Qin Ling, Faqin Dong, Gang Yang, Ying Han, Xiaoqin Nie, Wei Zhang, Meirong Zong
Nowadays, nuclear energy has been utilized on a large scale. Uranium, as a main fuel of nuclear energy, has been extensively exploited. However, uranium mining has caused a great quantity of environmental problems, especially uranium ores associated with heavy metals often threaten ecosystems and human health (Liu et al.2017a; Štrok and Smodiš 2010; Tuovinen et al.2015). At the same time, mining activities, such as extraction, beneficiation, and smelting of metal ores, have become the main driving factors of the global biogeochemical cycle of heavy metals. These activities have produced a large number of mine wastes which contain numerous heavy metals (Štrok and Smodiš 2013). These mine wastes probably disperse more easily and rapidly into the environment than coarser ores. Thus, inappropriate disposal of these mine wastes would result in the diffusion of heavy metals into soil, river, sediments, or the whole ecosystems (Blake et al.2015; Elnaggar et al.2018). Soils, rivers, and sediments contaminated by heavy metals are of global concern, as the damage to the ecological environment may not be fully recovered (Singh and Kumar 2017; Wang et al.2017).
Uranium oxide catalysts: environmental applications for treatment of chlorinated organic waste from nuclear industry
Published in Environmental Technology, 2019
Svetlana Lazareva, Zinfer Ismagilov, Vadim Kuznetsov, Nadezhda Shikina, Mikhail Kerzhentsev
Compounds of depleted uranium can be employed as inexpensive and accessible materials (after the creation of the necessary infrastructure) in the development of efficient catalysts for various processes. Certainly, special attention should be paid to safety because of radioactivity and chemical toxicity of depleted uranium. Depleted uranium is weakly radioactive. Its radioactivity is determined mainly by alpha decay of U-238 isotope, with the radioactive half-life being about 4.5 billion years. External irradiation from depleted uranium is not a serious problem because alpha particles emitted by isotopes pass only several centimeters in air and can be stopped even by a sheet of paper. So they are unable to penetrate even into the superficial keratin layer of human skin [39,40]. The main radiation and toxic hazards of depleted uranium are related to its penetration as a dust into the body. Chemical toxicity of depleted uranium is less or comparable to that of transition metal compounds. As an example, the maximum permitted concentration limit of uranium in water is 0.075 mg/L, whereas the permitted limits of chromium, manganese and zinc are 0.26, 0.05 and 15 mg/L, respectively [41].