Capability for Volume Reduction of Concrete Contaminated by Radioactive Carbon Dioxide Using Rubbing

Abstract A large amount of concrete contaminated by 14CO2 will be discharged from decommissioning of aged nuclear power plants. Rubbing, which separates cements from concrete debris, would be one of manners which allows to reduce volume of the waste if most of the 14C presents in the cement inside the concrete. We confirmed that the 14CO2 adsorbs on the cements more than aggregates by a factor of approximately 2 orders. Rubbing was carried out to obtain the mass balance and decontamination factor using simulated concrete debris which was not contaminated by the 14CO2. The cements and fine aggregates were separated from the debris as fines by rubbing using a Los Angeles testing machine. Steel balls with different size and different amount were used to proceed rubbing more. In addition, production rates of the fines were investigated in the debris that the heat treatment was carried out or not. Residues in a mill of the Los Angeles testing machine were washed to remove deposits remained on the surface. We concluded that the volume reduction can be effectively achieved by rubbing the debris that applied the heat treatment using more steel balls with larger size. DF was not improved by washing the surface residues. However, washing can resolve the concerns regarding radiation protection due to scattering of fines contaminated with the 14CO2 in treatment of the residues after rubbing.