Novel geopolymer materials for fast and thermal neutron shielding

In this work, we developed novel geopolymer (GP) composites for neutron shielding applications by dispersing up to 50 wt % polyethylene (PE) and boron carbide (B 4 C) powders into a potassium-based GP (KGP) matrix. We measured their attenuation coefficients to fast neutrons using a spontaneous fission 252 Cf source and a fusion deuterium–tritium generator and to thermal neutrons using a moderated 252 Cf source. The PE-based KGP were designed to reduce the neutron primary energy through neutron–hydrogen collisions, while 10 B in B 4 C was exploited to capture and stop thermal neutrons. The fast-neutron shielding properties of 50 wt % PE-KGP were superior, with an attenuation coefficient to fission neutrons up to 30% higher than that of high-density concrete. The B 4 C-based KGP formulation with B 4 C at 25 wt % and 50 wt % outperforms commercial boron-loaded flexible materials by approximately 18% and 50%, respectively. In simulation, we combined KGP with PE and B 4 C dispersants. A prototypical material comprised of 50 wt % PE-KGP and 50 wt % B 4 C-KGP significantly outperformed barite in reducing the dose due to fission-based spectra, similar to those found at nuclear reactors. Additionally, KGP shows excellent adhesive properties, high-temperature resistance, and can be molded into any size or shape, as well as 3D or 4D printed. Therefore, PE and B 4 C-loaded KGP and associated manufacturing techniques can be effectively employed in nuclear power plants and other facilities that rely on intense neutron sources, significantly enhancing their safety and cost-effectiveness. • Developed and characterized novel potassium-based geopolymer (KGP) composites for fast and thermal neutron shielding. • Showed that B 4 C-loaded KGP outperforms commercial boron-loaded materials for thermal neutron shielding. • Emphasized the potential of 3D and 4D printing for manufacturing customized neutron shielding components. • Proposed KGP-based composites as cost-effective and efficient shielding solutions for nuclear power plants and fuel cycle facilities.