Investigation on gamma-ray shielding and permeability of clay-steel slag mixture

Radiation shielding around low-level radioactive waste disposals is one of the most important issues in environmental protection and sustainable development. Using a suitable cover layer to surround and cap these waste disposals for isolation is essential. Clay is usually used for covering these disposals because it is relatively impermeable and a natural and eco-friendly material. In this research, the effect of adding steel slag to bentonite clay as an industrial waste, relatively cheap and available material, is investigated to improve its radiation shielding performance. In addition, the effect of increasing the steel slag to bentonite on the hydraulic permeability coefficient has been examined. Energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) tests have been conducted for chemical and microstructure analyses. This study has been carried out using both experimental and simulation methods. In the experimental part, the linear attenuation coefficient is measured for pure bentonite clay and bentonite clay mixed with 10, 20, 30 and 40% of steel slag. The permeability coefficient has been measured for target mixtures of bentonite clay and steel slag. Results show that adding steel slag to bentonite clay can improve the radiation shielding performance, whereas the mixture will be more permeable. The results also indicate that by adding 40% steel slag, radiation shielding coefficient will considerably improve compared to bentonite clay, while the permeability factor remains under the maximum allowable value for the landfill cover layer. Respecting the environmental and economic considerations, employing the mixture of bentonite clay and 40% steel slag can be a suitable alternative as a radiation shielding material for capping the low-level radioactive waste disposal.