Speaker
Description
Technetium-99 (Tc-99) is a long-lived beta-emitting radionuclide of major concern in radioactive waste characterization, environmental monitoring, and nuclear facility decommissioning. Because Tc-99 is highly mobile in the environment and difficult to quantify at low activity levels, reliable radiochemical separation and accurate recovery correction are essential for precise determination. However, the direct use of an isotopic tracer such as Tc-99m is often impractical due to its short half-life and handling constraints, which limits routine application in laboratory and field analyses. Therefore, the development of an alternative and practical recovery monitoring strategy is required.
In this study, rhenium (Re), a group 7 transition metal with chemical properties analogous to technetium, was employed as a non-isotopic surrogate tracer to indirectly estimate chemical recovery. Selective isolation of Tc was achieved using Eichrom TEVA resin, which exhibits a high distribution coefficient and strong selectivity for pertechnetate under acidic conditions, enabling efficient separation and purification from interfering matrix elements. The overall performance of the radiochemical procedure was systematically validated through spike experiments and application to real waste samples.
Spike samples were processed through identical pretreatment, digestion, and separation steps. The experimental recovery of Re ranged from 94.2% to 97.5%, with a mean of 95.8% and a relative standard deviation of 1.5%, demonstrating stable chemical behavior and excellent reproducibility of the pretreatment process. After applying the recovery correction, the quantified Tc-99 analytical results showed good agreement with the reference values, yielding 104.9-109.2% of the expected activities (mean 106.9%, RSD 1.5%). These results confirm high analytical accuracy and precision and indicate that Re effectively mimics the chemical behavior of pertechnetate during separation.
To further evaluate practical applicability, the developed method was applied to real decommissioning waste matrices, including concrete, SUS-304 stainless steel, and Inconel samples. Although Tc separation and quantification were successfully achieved, the measured activities were systematically underestimated by approximately 20–40% compared with the reference values. This negative bias is presumed to result from incomplete dissolution of heterogeneous solid matrices, matrix interferences, or residual Tc retention during chemical processing. These findings highlight the need for further optimization of digestion and pretreatment conditions when analyzing complex decommissioning materials.
Overall, the combination of Re-based surrogate recovery correction and TEVA resin separation provides a practical, robust, and reproducible analytical strategy for Tc-99 determination without reliance on short-lived isotopic tracers. The proposed method offers reliable quantification for both controlled laboratory standards and real-world radioactive waste samples and is expected to be widely applicable to routine monitoring and decommissioning waste assessment.
ACKNOWLEDGMENTS
This work was supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Climate, Energy & Environment(MCEE) of the Republic of Korea (No. RS-2023-00239183).