Radiation stability and durability of magnesium phosphate cement for radioactive reactive metals encapsulation

The encapsulation of Radioactive Reactive Metallic Waste (RRMW) in ordinary Portland cement poses significant challenges due to its incompatibility with the alkaline environment of the matrix. To address this issue, magnesium phosphate cements (MPC) emerge as potential solutions for the safe and effective immobilisation of RRMWs. The radiation stability and durability of an optimised formulation have been examined for samples irradiated up to 1000 kGy, in particular concerning the leaching behaviour of the three main constituents of the cement hydration products, and on four artificially added elements used to simulate radionuclides commonly found in radioactive waste (caesium, strontium, europium, and cobalt). The mortars exhibited excellent leaching behaviour and a high mechanical resistance, even after irradiation, freeze-thaw cycles, and water immersion. No significant radiation-induced effects were observed in the mineralogical and microstructural properties of the mortars, thus supporting their stability at the examined doses. Having verified the compliance with the main Italian waste acceptance criteria, the results of this research represent an encouraging step for the future implementation of MPCs for RRMWs conditioning.