A novel two-phase mixture optimization framework for radiation shielding UHPC: Advancing ultra-high-performance shielding materials for improved nuclear safety and security

By leveraging the exceptional mechanical strength and durability merits of ultra-high-performance concrete (UHPC) to fulfill nuclear safety and security requirements, radiation shielding UHPC (RS-UHPC) promises to advance the safe deployment of nuclear energy. This study presents a novel, two-phase (mortar-to-composite) mixture design optimization framework for RS-UHPC by coupling dry- and wet-particle-packing with Optimal Custom Mixture Design (OCMD). The framework was then implemented to develop new RS-UHPCs incorporating various combinations of magnetite, ferroboron, and ilmenite. To this end, thirty RS-UHPC mixtures were developed and evaluated for workability, density, and compressive strength (f’ c ) and radiation shielding measured in terms of linear attenuation coefficient (µ), thermal neutron absorption cross-section (∑ abs ), and fast neutron removal cross-section (∑ R ). RS-UHPCs with up to 170 MPa f’ c —with improvement in f’ c by up to 33 %, ∑ R by over 120 %, µ by 57 %, and ∑ abs by nearly 700 %—were achieved. These findings demonstrate the efficiency of the proposed RS-UHPC mixture design framework to deliver a promising ultra-high-performance shielding material for revolutionizing the safety and security of nuclear infrastructure.