2025 Volume 23 Issue 12 Pages 546-559
Cementation is the principal method for long-term conditioning of intermediate- and low-level nuclear waste (ILW/LLW). During hydration, cementitious matrices are exposed to ionizing radiation - primarily gamma rays - raising the question of the potential effect of irradiation on hydration reactions and, ultimately, on material properties. The available literature presents contradictory results, partly attributable to experimental biases related to temperature, drying, and carbonation under irradiation conditions.
This study aims to evaluate the impact of gamma irradiation on the hydration of C3S, CEM I, CEM III/A, and CEM III/C pastes under controlled experimental conditions (constant temperature, autogenous environment, sealed systems). The mineralogical and microstructural properties of irradiated materials were systematically compared to those of non-irradiated control samples and mature pastes irradiated under analogous conditions. The results show an absence of significant alteration in mineralogy at the mesoscale, and in mechanical properties, with the methodology considered. Only slight modifications in pore size distribution were observed.
These observations indicate the absence of a direct coupling between gamma irradiation and hydration. They confirm that cementitious matrices retain their properties under conditions representative of the immobilization process for ILW/LLW waste packages by cementation. Thus, the assumptions of safety studies, based on data obtained from mature materials, remain fully valid.
