γ-shielding performance and irradiation-induced changes of CeO₂-barite concrete

With the development of Generation-IV nuclear reactors, the demand for radiation shielding materials in nuclear power plants and nuclear waste storage facilities is notably increasing. In this study, ordinary barite concrete was chosen as the reference, and the effects of four mix designs, namely, 0%%, 10%, and 20% CeO₂ (by volume fraction of cementitious material) and 20% CeO₂ + 5% silica fume, on the γ-shielding performance and mechanical properties of barite concrete were systematically investigated. Long-term ⁶⁰Co γ irradiation tests lasting 100 h (cumulative dose ≈730 kGy) were conducted, combined with the application of multiple microstructural characterization techniques to systematically elucidate the mechanism. The results revealed that (1) 20% CeO₂ resulted in an increase in the linear attenuation coefficient by ~ 2.8% with limited overall shielding gain; (2) CeO₂ acted as a nucleation accelerator, promoting calcium (aluminate) silicate hydrate (C-(A)-S-H) gel formation but introducing interfacial pores, which were effectively mitigated by 5% silica fume coaddition; (3) γ irradiation resulted in the densification of the microstructure through sub-100-nm pore filling, reducing the cumulative porosity by 6-18% and increasing the C-(A)-S-H content by 6-34%; and (4) no key phase decomposition was detected at 730 kGy, confirming long-term structural stability. These findings provide a theoretical basis for optimizing high-performance nuclear shielding concrete.