Effect of red mud additive on the performance of clay barriers for radioactive waste disposals: an experimental study

Abstract
Extensive use of radioactive materials has led to the production of low-level nuclear waste that emits dangerous gamma rays which pollute the environment. Low-level nuclear waste is usually disposed in landfills to prevent damage from organisms exposed to gamma rays. These landfills are usually covered and capped with bentonite clay due to their desirable properties such as long-term chemical stability, low hydraulic permeability, easy access, and low price. This clay cover is responsible for controlling the emission of gamma rays and preventing hydraulic permeability. In this study, red mud powder additive as a waste product of steel industry with high specific gravity has been added to the bentonite clay in 0, 15, 30, and 45 percentages, to improve the performance of radiation protection and hydraulic conductivity prevention. For this, the effect of red mud and bentonite mixtures are investigated on the improvement of linear attenuation coefficient (μ) and hydraulic permeability coefficient (K) using experimental, theoretical, and simulation methods. Nal(Tl) detector with Cobalt60 source for the experimental procedure, XCOM database for theoretical approach, and MCNP code for simulation methods have been used, in two energy levels of 1173 keV and 1332 keV. Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) analyses are performed to identify fine particles and chemically analyze bentonite and red mud. The results show that bentonite with 45% red mud with a linear attenuation coefficient of 10.32 m-1 had the best performance at the two energy levels.
Keywords Bentonite clay · Red mud powder · Radiation shielding · Radioactive waste management · Hydraulic
permeability