Standards Development

Scope

This document specifies a method to measure gross alpha and gross beta activity concentration for alpha- and beta-emitting radionuclides using Liquid Scintillation Counting (LSC).

The method is applicable to all types of waters with a dry residue of less than 5 g·l-1and when no correction for colour quenching is necessary.

The method is applicable to test samples non-saline waters following proper sampling, handling and preparation.

Gross alpha and beta measurements do not provide the exact radioactive content of a sample but estimate activity based on standard calibration sources. These measurements, known as the alpha and beta index, serve as screening tools for an initial assessment of total radioactivity.

The method covers non-volatile radionuclides below 80 °C, since some gaseous or volatile radionuclides (e.g. radon and radioiodine) can be lost during the source preparation.

The method is applicable to test samples of drinking water, rain water, surface and ground water as well as cooling water, industrial water, domestic and industrial waste water after proper sampling and test sample preparation (filtration when necessary and taking into account the amount of dissolved material in the water).

The detection limit depends on the sample volume, the instrument used, the background count rate, the detection efficiency and the counting time. The detection limit of the method described in this document, using currently available liquid scintillation apparatus, is approximately 20 mBq·kg-1(α) and 100 mBq·kg-1(β), which is lower than the WHO criteria for safe consumption of drinking water 500 mBq·kg-1(α) and 1 000 mBq·kg-1(β).[4] This value can typically be achieved with a counting time of 500 min for a test sample volume of 0,08 l.

The method described in this document is applicable in the event of an emergency situation, because the results can be obtained in less than 4 h by directly measuring water test samples without any treatment.