Radon concentration measurement in water by means of α liquid-scintillation spectrometry with a PERALS spectrometer

A high-resolution α liquid-scintillation spectrometer, PERALS, has been applied to the measurement of radon concentration in water. The efficiency calibration has been performed for the 5.49 MeV α-rays from 222Rn incorporated with a solvent extraction. Optimum conditions of the solvent extraction for radon have been investigated, and a volumetric ratio of 3 ml scintillator against 1 l sample water was adopted. The lower detection limit was estimated to be 0.68 Bq l−1 (3σ) in water. Applications of this method to ground and spring water samples have been given compared with those results by the γ-ray spectrometry method.