This study develops an experimentally validated composition–thickness optimization approach for hydrogen–boron polymer composites. The thermal neutron shielding performance of high-molecular-weight polyethylene (HMWPE) composites loaded with borax pentahydrate is systematically investigated using an integrated experimental–computational approach, combining neutron radiography with MCNP5 Monte Carlo transport simulations to resolve the coupled roles of hydrogen-mediated neutron moderation, boron-driven thermal neutron absorption, and neutron buildup effects. A non-monotonic dependence of attenuation on both filler loading and composite thickness is observed, reflecting an intrinsic moderation–absorption trade-off in hydrogen–boron systems. An experimentally validated optimization window is established, with maximum attenuation achieved at approximately 40 wt% borax pentahydrate and a composite thickness of 1.5 cm. At higher boron loadings, attenuation exhibits saturation behavior due to reduced hydrogen atom density and diminished moderation efficiency prior to capture, while increasing thickness leads to neutron buildup and multiple scattering that limit further attenuation gains. The close agreement between neutron radiography measurements and MCNP5 predictions confirms the reliability of the proposed framework. These results establish transferable physics-based design rules for lightweight, cost-effective neutron shielding materials in reactor beamlines and neutron imaging systems, enabling more systematic optimization compared to conventional empirical selection of absorber content and thickness.
Aziz et al. (Thu,) studied this question.