If you roll a billiard ball at a bowling ball, the smaller ball rebounds, barely slowed. But roll it at another billiard ball and it stops dead, transferring its energy. Radiation shielding follows a similar principle: different types of radiation require materials suited to the way they interact with matter.
With their high penetrating power, gamma rays are best absorbed by dense, heavy elements like lead. Neutrons lose the most energy to light atoms of similar mass, such as hydrogen. Nuclear reactors, spacecraft and radiotherapy facilities can involve multiple types of radiation, creating a special challenge. “These radiation-intensive environments increasingly require materials that are not simply good shields, but are also lightweight, mechanically robust, processable and multifunctional,” said Ice Tee, a Senior Scientist at the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE).
Polymers could offer a way forward, according to Tee and colleagues at the A*STAR Institute of Advanced Intelligence and Computing (A*STAR IAIC), A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE²) and Massachusetts Institute of Technology (MIT), US. These materials are low-density, hydrogen-rich and tuneable to achieve highly specific functions. Led by Tee, A*STAR IMRE Principal Scientist Warintorn Thitsartarn and A*STAR ISCE² Senior Principal Scientist Jianwei Xu, the researchers reviewed the scientific literature to identify design principles that could guide engineering of radiation-resistant polymer systems.
“Effective mixed-radiation shielding requires a combination of complementary materials, each tailored to a specific radiation interaction,” Tee said. In such hybrid or multilayer structures, a hydrogen-rich matrix could slow fast neutrons, while boron or gadolinium could capture them once slowed. Heavy fillers could then weaken gamma rays, including secondary photons released during neutron capture.
The team’s review also highlighted the value of uniform filler distribution at the atomic scale. When shielding elements cluster together, radiation can readily pass through other regions left unprotected. Indeed, the team found published simulations showing that uniform dispersion improved shielding performance in polymer composites. Moreover, fine-tuning the molecular architecture, including the density of linkages, can help scatter radiation and promote recovery from damage without sacrificing structural integrity.
The review also revealed an increasing focus on predictive materials design, with computational modelling becoming increasingly prominent. Looking towards real-world deployment, meanwhile, Tee and colleagues cautioned that industry-standard tests “may significantly underestimate the structural degradation a polymer will experience over a 60-year service life.”
Even when higher radiation doses are used, the accelerated timeline—mere weeks instead of decades—means oxygen mainly reacts at the polymer surface and damage is restricted to the outer shell. Under real service conditions, however, exposure occurs much more slowly. Continuous low-dose radiation allows oxygen to diffuse further into the material, potentially weakening the polymer more broadly and gradually shortening its lifespan.
The team is now applying these insights to engineer lightweight, durable materials that can maintain high shielding and damage recovery performance in radiation-intensive environments, in collaboration with Michael Short at MIT and researchers at the Thailand Institute of Nuclear Technology.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Materials Research and Engineering (A*STAR IMRE), the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE²) and the A*STAR Institute of Advanced Intelligence and Computing (A*STAR IAIC).
