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$\text{\%}$ 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 ²⁵²Cf source and a fusion deuterium–tritium generator and to thermal neutrons using a moderated ²⁵²Cf source. The PE-based KGP were designed to reduce the neutron primary energy through neutron–hydrogen collisions, while ¹⁰B in B${}_4$C was exploited to capture and stop thermal neutrons. The fast-neutron shielding properties of 50 wt$\text{\%}$ 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$\text{\%}$ and 50 wt$\text{\%}$ 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$\text{\%}$ PE-KGP and 50 wt$\text{\%}$ 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.