Lightweight enhanced-attenuation shielding for high-energy gamma-rays based on nanostructured composite materials

If civilian and military equipment and personnel are to be effectively protected in a high-radiation environment – such as that found in space, in a nuclear-powered naval vessel, or in a nuclear-active battlefield environment – then shielding against high-energy photons must be enhanced to a degree well beyond that afforded by traditional shielding materials. Materials that are highly-effective in stopping nuclear by-products before they encounter the warfighter or sensitive electronics can mitigate the need to develop radiation-hard components or to use biological countermeasures following personnel radiation exposure. Unfortunately, the current shielding modality, in which one adds more material-depth in order to increase the attenuation of any damaging quanta, is unattractive for deployed missions because the weight and volume of high-Z materials for photon shielding becomes operationally cumbersome. This is especially true for aerospace missions, where enabling significant radiation protection is currently unfeasible with existing shielding materials. To enable truly transformational improvements in shielding performance, the small interfacial scattering losses at material interfaces can be exploited in a material with multitudinous interfaces, such as a nanoparticle composite material with high-Z (e.g. Pb) nanoparticles surrounded by lower-Z media, such that these effects dominate and significantly enhance the overall attenuation. In addition to enhanced gamma-ray attenuation, our material has: (1) a mass-density reduction of 50 – 90 % of the equivalent bulk material, (2) high thermal and mechanical strength, (3) low-cost synthesis, (4) mechanical flexibility, and (5) readily scalable production methods. In Phase I, we demonstrated the feasibility of forming nanostructured gamma-ray shields using a variety of nanoparticle compositions and manufacturing methods. These include a “bottom-up” chemical synthesis as well as a “top-down” mechanical milling approach – both of which are scalable to large volumes at low manufacturing costs that are comparable on a per-volume basis to traditional shielding materials. Nanostructured solids produced via these processes demonstrated significantly higher linear attenuation coefficients than comparable bulk materials, in some cases several times (> 5x) higher. Customized modeling guided the material design, including the use of lower-Z nanoparticles, agreeing with attenuation measurements. During Phase II, our goal is to transition the proof-of-concept material systems and manufacturing methods into scalable methods capable of producing large-area, large-volume lightweight nanostructured shields that are potentially flexible and comparable in cost to existing materials. The successful completion of Phase II will realize transformational improvements in radiation protection materials, enabling the protection of infantry, light vehicle, and aerospace missions and personnel in high-energy radiation environments.