Abstract
Radionuclides may contaminate lubricant oils in nuclear power plants. In Brazil, this kind of waste has been stored in the generator’s facilities, awaiting treatment alternatives. This work intends to investigate a process to treat it for final deposition, using bentonite as sorbent material. This process will result in decontaminated oil, free from radiological control, and radioactive loaded sorbent, with considerable volume reduction of the radioactive waste. The study focuses in cobalt removal from a simulated oil waste (non-active). The production of the simulated waste is described. Benton-ite was used for equilibrium time determination, kinetic and adsorption studies. Cobalt adsorption equilibrium was rapidly attained after 30 minutes. The data was used for modelling the system’s kinetic, applying the pseudo first and pseudo second order equation models. Experimental data fitted to pseudo second order model, supporting the assump-tion that the adsorption is due to chemisorption. Batch sorption tests were conducted and the results fitted to Langmuir and Freundlich sorption models. Both isotherm models chosen for this work did not fit to the experimental data. Thus, these are preliminary results and the studies must be repeated to evaluate data variability and better statistical inference. Other isotherm models must be evaluated to choose the best fitted one and describe the sorption of cobalt on bentonite in oil matrix. Even though, bentonite has considerable potential as sorbent for the removal of cobalt from lubricant oil. Finally, the results might be extended to other kinds of radioactive oils and radioactive organic wastes.
Highlights
Nuclear applications in a wide range of areas, such as medicine, research activities, industries and power production generate radioactive waste
Two kinds of lubricant oils, Mobil Turbina 46 and Mobil SHC 624, the most used in the Brazilian Nuclear Power Plants (NPP), were mixed in equal proportions
It is not possible to conclude about the equilibrium time with the complete sorption of cobalt in few minutes, as occurred to these S/O ratios
Summary
Nuclear applications in a wide range of areas, such as medicine, research activities, industries and power production generate radioactive waste. The proper management of this waste is necessary to avoid possible negative impacts to human health and the environment. The biggest radioactive waste generators are the nuclear power plants. Their operational activities generate many types of radioactive waste, among them, contaminated lubricant oil. Lubricating oils are used in many areas of a nuclear power plant. They can be contaminated: the oil mixes with water and other contaminants from the nuclear reactor system and becomes contaminated with radioactive wastes, as well as dirt and moisture [1]
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