Sample preparation system of ¹⁴C in the main materials of nuclear reactor

Background: The sample preparation system of ¹⁴C is necessary for measuring the radioactive contents of ¹⁴C and ³H for the decommissioning of nuclear reactor. Previous works were concentrated on the glass container and heating furnace which is not suitable for automatic sample process and exists safety risk. Purpose: In order to resolve the difficulty in main materials of nuclear reactor samples preparation of ¹⁴C, an intellectual preparation system of ¹⁴C samples was designed and developed. Methods: The system is designed to consist of buffer, decomposition chamber, catalysis bed, adsorption bed and absorbing bed. Samples were decomposed at high temperature in oxygen whilst the generated gas was translated to CO₂ by catalysis oxidation. The activity of ¹⁴C was measured by liquid scintillation counter using suspension method. Results: The radiochemical recovery rate of ¹⁴C was above 70%. The calculated detection limit for ¹⁴C was 0.0331 Bq·g^-1 for graphite and 0.021 8 Bq·g^-1 for concrete, respectively. Conclusion: This system was stable enough to be used for preparing graphite and concrete samples which contain low level or medium level radioactivity in nuclear reactor. (authors)