Characterization of glass composite material by pressureless sintering of soil and its application to uranium contaminated soil as a waste form

Abstract

When operating and dismantling a nuclear facility that handles uranium, the surrounding soil may be contaminated, emphasizing the need for appropriate treatment and disposal methods for soil waste. This study assessed high-temperature sintering technology for uranium contaminated soil waste to overcome limitations in existing decontamination methods and the volume increase associated with current solidification technology. The sintering process was found to effectively vitrify and re-mineralize complex chemical components in the soil. Sintered bodies were produced under varying conditions, adjusting molding pressure, heating temperature, and time. Optimized conditions resulted in sintered bodies with a volume reduction rate exceeding 30 % and a compressive strength surpassing 10 MPa, indicating a significant impact on the phase conversion and re-mineralization of silt and clay minerals. The soil sintering mechanism was identified through comprehensive microscopic observations and mineral phase change analysis. Leaching evaluations of sintered bodies, made from simulated uranium-contaminated soil, demonstrated their applicability to contaminated soil wastes. Additionally, it was confirmed that the sintering temperature of the soil could be lowered by incorporating a small amount of B2O3, suggesting a means to enhance the economic feasibility of the treatment process. The findings of this study highlight the applicability of pressureless sintering technology, based on glass composite materials, capable of simultaneously reducing and stabilizing uranium-contaminated soil waste.