摘要Objective:To assess the detection efficiencies of liquid radioisotopes in a well-type Nal(Tl)gamma spectrometer,focusing on the short-lived isotopes 99Tcm,131I,and 18F.Methods:The detection efficiencies of liquid 99Tcm,1311,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 de-viation 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.