ACCURATE DETERMINATION OF LOW-LEVEL RADON CONCENTRATION IN WATER BY MEANS OF GAMMA-RAY SPECTROMETRY

A solvent extraction method combined with gamma-ray spectrometry has b een applied to the measurement of low-level radon concentration in wat er. Radon in 900 mL of water was extracted into 120 mL of organic solv ent. The radon content was derived from gamma-ray spectrometry of daug hter nuclides Pb-214 and Bi-214. Extraction rates defined by the ratio of the extracted radon amount to that in the original sample of water were experimentally determined to be 0.758 +/- 0.020 for xylene and 0 .671 +/- 0.018 for toluene. The detection limit of the radon concentra tion measurement was 0.082 Bq L-1 using the xylene extraction method. This method has been applied to the measurement of the radon concentra tion in tap water.