Abstract:
Determinations of low level Rn-222 concentration in water was carried out by ultra low level liquid scintillation counter (Wallac Quantulus 1220) with pulse shape analysis (PSA). However, beta ray was found to be the major interference in alpha ray measurement from Rn-222 in Uranium-238 decay series. Optimum setting pulse shape analysis could minimize this interference. Moreover, the alpha measurement was also interfered from other radionuclide in water sample. Toluene was selected as the most effective solvent for Rn-222 extraction. By this method, Rn-222 was extracted from 500-ml water sample by using 20-ml toluene. Then 10 ml of the extracted toluene was mixed with 10 ml cocktail in a glass scintillation vial before measuring (alpha ray) by liquid scintillation counter. This method can also be used to measure the cocentration of Rn-222 in environmental water samples such as underground, surface, tab, mineral, rain and hot spring water. The detection limit of Rn-222 was found to be 4.49X10 -3 Bq/liter at 240 minutes counting time.