SR-90 IN NATURAL-WATERS DETERMINED ON LIQUID SCINTILLATION SPECTROMETERS USING VAVILOV-CHERENKOV RADIATION

The problem of direct determination of Sr-90 in natural waters using t he radiation from Y-90 and a liquid scintillation spectrometer is exam ined. In contrast with the classical method of liquid scintillation sp ectrometry, the beta-particles emitted by the water sample are detecte d using not the luminescence of a liquid scintillator but the Vavilov- Cherenkov radiation from the sample itself. The method is tested on fr esh water samples from reservoirs of the Chernobyl NPP exclusion zone by comparing direct measurements using the proposed method with those made after radiochemical separation of Sr-90 from the same samples by traditional methods. Good agreement is seen for Sr-90 concentrations g reater than 50 pCi/liter. The contribution from natural radionuclides present in the water must be taken into account in order to measure lo wer Sr-90 concentrations.