Mechanical and radiation shielding assessment of high-density/magnetite-cementitious plaster for repair and retrofit of nuclear power plant structures.

Concrete plays a critical role in nuclear power plants (NPPs) as structural material and radiation shielding. Severe defects during construction of NPP concrete could lead to catastrophic leakages. Therefore, cement plaster propably with acceptable radiation protection could be a good solution as a repairing technique. Thus, this study investigates the mechanical and radiation shielding properties of non-conventional cementitious plaster incorporating magnetite powder as a partial/full replacement for traditional sand. ​Five cement plaster mixtures were proposed with varying proportions of magnetite powder and sand, in which their mechanical and radiation attenuation properties were analyzed. Experimental evaluations including workability, density, compressive strength, and gamma-ray attenuation were investigated. Furthermore, γ-ray and fast neutron shielding has been evaluated using software programs such as EpiXS, NXCom, and MRCsC. Results showed that incorporating magnetite powder in cement plaster production lowers the compactness of the matrix by up to 46.2%. Consequently, the compressive strength was generally decreased by up to 65.4% with increased magnetite content. However, the density of the plaster was increased by up to 48.7% compared to traditional cement plaster. Furthermore, owing to increased density, the radiation shielding efficiency of magnetite cement plaster was generally enhanced. Cement plaster with 100% magnetite content achieved superior linear attenuation coefficient (LAC) for gamma rays with 264% increase at 0.01 MeV and 43% increase at 10 MeV compared to the traditional sand plaster. Also it acquired better fast neutron shielding performance, with a macroscopic removal cross-section (Σ