ADVANTAGES OF LOW-BACKGROUND LIQUID SCINTILLATION ALPHA-SPECTROMETRY AND PULSE-SHAPE ANALYSIS IN MEASURING RN-222, URANIUM AND RA-226 IN GROUNDWATER SAMPLES

Liquid scintillation counting (LSC) and pulse shape analysis (PSA) was used in measuring radon and gross alpha-and beta-activities in ground water. We used conventional LSC counters for the measurement of radon in water, but low-background LSC spectrometers for the gross activity measurements. The lower limit of detection (LLD) for radon in water is 0.6 Bq/l for a 60 min count with a conventional counter, but 0.1 or 0 .2 Bq/l, with the two types of low-background LSC spectrometers equipp ed with a pulse shape analyser (PSA). The gross alpha and beta activit y measurements are made using a simple sample preparation method, PSA of a low background LSC and spectrum analysis. The LLD recorded for gr oss alpha and beta with the two spectrometers are 0.02 and 0.03 Bq/l a nd 0.2 and 0.4 Bq/l, respectively, for a 180 minutes count and a 38 ml sample volume. The method also enable the calculation of the U and Ra -226 contents in water and indicates the presence of some other long-l ived radionuclides, (Pb-210, Ra-228 or K-40). The LLD for U recorded w ith both spectrometers is 0.02 Bq(-1) and for Ra-226 0.01 Bq.l(-1). Th e LLDs attained by this LSC method are two orders of magnitude lower t han the maximum permissible concentrations set for U and Ra-226.