Investigating the effect of basalt fiber additive on the performance of clay barriers for radioactive waste disposals

Abstract
Radioactive materials are widely used in mining, manufacturing, medicine, and agricultural processes. The waste products from these materials are hazardous and should be appropriately dumped. As a result, a proper radiation shielding barrier is required to avoid the contamination of the surrounding environment. Clay soil is an efficient and eco-friendly radiation shielding material, which is commonly used to cap the hazardous and radioactive landfills. In this research, the effects of basalt fiber additive in four percentages, including 0.5, 1, 2, and 5 on the bentonite clay radiation shielding performance, were investigated using experimental and simulation methods. Also, the permeability of the mixtures is controlled to be in the acceptable range as a vital parameter for radioactive disposal barriers. Chemical and microstructure analyses were conducted on the utilized material, using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). Linear attenuation coefficient (μ), representing the material radiation shielding performance, was evaluated using the HPGe spectrometer detector, MCNP simulation code, and XCOM web program on the three commonly used gamma-ray energy levels of 137Cs (661.6 keV) and 60Co (1173.5 and 1332.5 keV). An acceptable agreement was observed between experimental and simulation results, revealing that adding basalt fiber improves the shielding performance due to a higher linear attenuation coefficient (μ), where 2% of basalt fiber leads to the highest values of 12.3 m-1, 10.14 m-1, and 8.5 m-1 obtained for 661.6 keV, 1173.2 keV, and 1332.5 keV energy levels, respectively. The results concluded that, due to radiation shielding performance, workability, and permeability limitations, the 2% basalt-bentonite mixture could be a new candidate covering low-level radioactive waste disposal.