A RAPID METHOD FOR THE SIMULTANEOUS DETERMINATION OF GROSS ALPHA-ACTIVITIES AND BETA-ACTIVITIES IN WATER SAMPLES USING A LOW-BACKGROUND LIQUID SCINTILLATION-COUNTER

The radiological examination of water requires a rapid screening techn ique that permits the determination of the gross alpha and beta activi ties of each sample in order to decide if further radiological analyse s are necessary. In this work, the use of a low background liquid scin tillation system (Quantulus 1220) is proposed to simultaneously determ ine the gross activities in water samples. Liquid scintillation is com pared to more conventional techniques used in most monitoring laborato ries. In order to determine the best counting configuration of the sys tem, pulse shape discrimination was optimized for 6 scintillant/vial c ombinations. It was concluded that the best counting configuration was obtained with the scintillation cocktail Optiphase Hisafe 3 in Zinsse r low diffusion vials. The detection limits achieved were 0.012 Bq L(- 1) and 0.14 Bq L(-1) for gross alpha and beta activity respectively, a fter a 1:10 concentration process by simple evaporation and for a coun ting time of only 360 min. The proposed technique is rapid, gives spec tral information, and is adequate to determine gross activities accord ing to the World Health Organization (WHO) guideline values.