Abstract: This paper studies a liquid scintillation counter measurement method for radium-226 in water. The method extracts radon-222, a daughter of radium-226, from water sample and enters into scintillation solution by means of insoluble scintillation liquid, thus realizes the separation of radon-222 from other interfering nuclides in water. After a period of time, when radium-226 and its daughter reached equilibrium, alpha/beta discrimination measurement was carried out by liquid scintillation counter to separate radon-222 and its alpha emmision daughters polonium-218 and polonium-214 from the beta emmision daughters bismuth-214 and lead-210, and indirectly obtains the activity concentration of radium-226 in the aqueous phase through the measurement of total alpha counts of radon-222, polonium-218 and polonium-214. The results indicated that the quench of liquid scintillation on the measurement of radium-226 in water is very low, and the Quantulus 1220 liquid scintillation counter has a measurement background of 0.02 cpm for this method, with a measurement efficiency of 2.52-2.60 and a minimum detection level of less than 2 mBq/L, which can meet the requirement for the measurement of radium in environmental samples.

Key words: LSC, radium-226, alpha/beta discrimination measurement