Study on rapid measurement of α and β activity in radioactive wastewater by liquid scintillation spectrometer

The discharge of radioactive wastewater from nuclear facilities is an important source of radionuclides entering and polluting the environment. Rapid and accurate acquisition of radioactivity in water is the premise of radiation protection and important data of environmental monitoring. Using liquid scintillation spectrometers to measure the radioactivity of α and β in water has the outstanding advantages of quicker sample pretreatment, simpler measurement method and higher detection efficiency. In this paper, based on the vehicle low background liquid scintillation spectrometer (SIM-MAX LSA3000B), 14C、40K、90Sr-90Y and 241Am are selected as the typical nuclides to study the measurement influence of standing time, liquid scintillation cocktail, sample bottle, volume ratio of sample/ liquid scintillation cocktail and PH value of systems on liquid scintillation measurement. The experimental results show that the composite counting method adopted by SIM-MAX LSA3000B has low requirements for standing time, the detection efficiency of low potassium glass bottle and polyethylene bottle is similar, and the detection efficiency of acid system is high. Among commercial liquid scintillation cocktails, LLT liquid scintillation cocktail has slightly higher background and detection efficiency. Under the same total volume of liquid scintillation samples, for βnuclide samples, the detection efficiency decreases with the increase of sample proportion, but the reduction range is within 8%, for αnuclide samples, the detection efficiency is basically unchanged. According to the measurement method established based on the above experimental results, the total measurement time shall not exceed 100 minutes. Under the specific activity of 0.1Bq/mL, the detection efficiency of α and β is not less than 70%. Under the specific activity of 1Bq/ mL and above, the detection efficiency of α is not less than 95%, and the detection efficiency of β is not less than 80%.