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

Abstract
The radiation shielding performance of bentonite clay as the main component of the landfill liners is investigated using
hematite powder as an additive. For this, theoretical and experimental methods have been used to examine different mixtures
of hematite powder and bentonite clay, including pure bentonite, and bentonite with 15, 30, and 45% of hematite powder.
Energy-dispersive X-ray (EDS) and scanning electron microscopy (SEM) experiments are undertaken to better understand
and analyze bentonite and hematite from a chemical perspective. To evaluate the radiation shielding performance of the
mixtures, the linear attenuation coefficient is calculated and simulated employing the XCOM database and MCNP code,
respectively. The results are then compared with the experimental approach of radiation permeation by a NaI (Tl) detector
which were in good agreement. The hydraulic permeability tests have been also conducted to ensure that the mixtures meet the
requirement according to the EPA standard. The results revealed that with increasing the additive percentage the attenuation
coefficient grows linearly; however, the hydraulic permeability increases simultaneously. The bentonite with 45% hematite
powder outperformed other compounds in providing 30 and 50% improvement in gamma-ray radiation shielding and a 25%
and 17% decrease in both TVL and HVL values, at the energy levels of 1173 and 1332 keV, respectively.

Keywords Sodium bentonite · Hematite · Radiation shielding · Nuclear waste management · Hydraulic permeability