Understanding neutron-shielding properties of self-healing poly(vinyl alcohol) hydrogels containing rare-earth oxides through simulations

Abstract

This work assessed the theoretical neutron-shielding capabilities of autonomously self-healing poly(vinyl alcohol) (PVA) hydrogels containing rare-earth oxides, namely samarium oxide (Sm2O3), europium oxide (Eu2O3), and gadolinium oxide (Gd2O3), through PHITS and GEANT4 simulations. The assessment covered a range of filler contents (from 0 to 20 %wt in 4 %wt increments) and neutron energies (0.025 eV, 1 MeV, and 4 MeV). The determination showed that there was good agreement between the results from both simulations (average percentage difference of 0.39 %), with the thermal neutron-shielding properties of the hydrogels improving as the filler content increased, evidenced by the hydrogels containing 20 %wt of the fillers, especially those with Gd2O3, exhibiting the highest overall shielding properties. On the other hand, the deviations in the ability to attenuate fast neutrons (1 MeV and 4 MeV) with respect to filler contents were less pronounced than those for thermal neutrons. Additionally, the recommended filler contents for actual production were also determined by comparing the results in this work with those obtained from two common 5 wt% borated hydrogels. The comparison revealed that the recommended contents for Sm2O3, Eu2O3, and Gd2O3 were 9.8, 12.3, and 1.6 %wt, respectively, of which the smallest recommended content of Gd2O3 confirmed the superiority of Gd2O3 in thermal neutron attenuation. Lastly, the overall outcomes from this work suggested that PVA hydrogels, with the addition of rare-earth oxides as fillers, could serve as promising, effective neutron-shielding materials, with the added benefit of being self-healable that prolonged the lifetime of the developed shielding hydrogels as well as enhancing the safety of personnel.