Understanding stability of strontium titanate crystalline matrix for β and γ radiation by employing γ-γ TDPAC spectroscopy

Strontium titanate perovskite plays a crucial role in the formation of the SYNROC phase assemblage, providing a favorable environment for the accommodation of ⁹⁰Sr from high level radioactive waste. The matrix experiences structural deterioration as a consequence of the radiations emanating from the immobilized radioactive waste. In an effort to comprehend the impact of β, γ radiation on the stability of the strontium titanate radioactive waste immobilization matrix, Time Differential Perturbed Angular Correlation (TDPAC) spectroscopy has been employed to analyze electric hyperfine interactions (HFI) in electron beam and γ irradiated strontium Titanate (STO). Previous research reported that TDPAC spectroscopy detected two distinct interaction sites, one associated with a static HFI and the other with dynamic HFI in the pristine STO sample. In the present work, STO was subjected to electron beam and γ radiation with doses ranging from 1 to 20 MGy to mimic the consequences of β and γ radiation in the immobilization matrix and HFIs are observed. The research findings show that there is no alteration in the static HFI which suggests radiation stability of the site with static electric field gradient (EFG). However, the dynamic HFI was observed to be sensitive to EB, γ irradiation. The relaxation of the dynamic EFG (τ) increased after irradiation but with dose its behaviour is contrasting. Due to the scarcity of literature on similar studies, it is not possible to offer any insights into the cause for change in dynamic HFI due to β, γ irradiation. Possibility of radiation induced defects creation and stability of STO matrix towards radiation damage is discussed.