Structural and thermal stability studies on irradiated magnesium potassium phosphates for back end nuclear fuel cycle applications

Magnesium potassium phosphate (MKP) cement has emerged as a potential eco-friendly alternative to Portland cement for nuclear waste encapsulation. Its superior resistance to sulfate attack, low permeability and mechanical strength makes it a promising material. This study investigates the thermal and radiation stability of MKP specimens prepared by gel crystallization, followed by heat treatment at 120, 400, 800 and 1000 °C and subsequent irradiation with 10 MeV electron beam to a dose of 20 MGy. MKP specimens prepared at room temperature (MgKPO4.6H2O) partially lose their structural water upon irradiation forming an amorphous phase which coexists with the untransformed MgKPO4.6H2O phase. MKP heat-treated at 1000 °C (KMgPO4 having monoclinic structure) exhibited high structural stability, minimal mass loss and negligible gas evolution under thermal and radiation conditions. A mechanism for radiation damage is proposed.