Study on the detection efficiencies of liquid 99Tcm, 131I, and 18F in a well-type NaI(Tl) gamma spectrometer

Abstract

Objective: To assess the detection efficiencies of liquid radioisotopes in a well-type NaI(Tl) gamma spectrometer, focusing on the short-lived isotopes 99Tcm, 131I, and 18F. Methods: The detection efficiencies of liquid 99Tcm, 131I, and 18F in a well-type NaI(Tl) gamma spectrometer were systematically investigated through calibration experiments and Monte Carlo simulations, and accounting for the coincidence-summing effect. Results: The results indicated that the detection efficiencies of 99Tcm, 131I, and 18F varied from 64.4% to 72.3%, 34.8%–43.1% and 27.3%–28.5% for different sample volumes ranging from 15 ​mL to 80 ​mL, respectively. The simulated detection efficiencies were highly consistent with the experimental results, with a largest relative deviation of 5% for the 3 radionuclides and 4 different sample volumes. Conclusion: The consistent results between the calibration experiments and Monte Carlo simulations reveal that this measuring device possesses high detection efficiencies of 99Tcm, 131I, and 18F, making it suitable for measuring low-level activity radioactive liquids, such as radioactive waste liquids to be discharged.

Keywords

• Well-type NaI(Tl) gamma spectrometer
• Liquid radioactive sample
• Detection efficiency
• Monte Carlo simulation
• Coincidence summing correction