Chapter 12 - Reclamation of Sites Impacted by Mining Activities: Stabilization/Solidification of 232Th-Contaminated Soils

Abstract

The radioactive waste produced by mining activities contains a series of long-lived radionuclides, such as uranium (U), radium (Ra), and thorium (Th) isotopes. These radionuclides are considered to be TENORM (Technologically Enhanced Naturally Occurring Radioactive Materials) due to their high concentration in the mining byproducts. Their indiscriminate and improper disposal increases the risk of soil and groundwater contamination. According to the Environmental Protection Agency (EPA), among TENORM, 232thorium (232Th) is the primary source of contamination at the superfund sites, due to extraction activities. 232Th, as a soil pollutant, presents both a chemical and radiological hazard, and risks connected to 232Th exposure are increased by its γ-ray emission capacity. Very limited techniques are present in the literature to remediate 232Th-contaminated soils, but the cement-based stabilization/solidification (S/S) technique has been shown to be a perfect choice for this purpose. S/S has three main advantages: (i) it is well established as an efficient and cost-effective treatment, (ii) it has high versatility, and (iii) it produces no waste or contaminated wastewater that needs landfill disposal. In addition, employing of high-density binder/materials with γ-radiation shielding properties represents a key factor in remedial activities of radionuclide-polluted soils. In this work, we report the theoretical background including the S/S process and recent related scientific and technoeconomic development for the S/S application in reclamation activities of 232Th-contaminated soils from mining activities.