Water quality — Gamma-ray emitting radionuclides — Test method using high resolution gamma-ray spectrometry

This document specifies a method for the physical pre-treatment and conditioning of water samples and the determination of the activity concentration of various radionuclides emitting gamma-rays with energies between 40 keV and 2 MeV, by gamma ray spectrometry according to the generic test method described in ISO 20042.

The method is applicable to test samples of drinking water, rainwater, surface and ground water as well as cooling water, industrial water, domestic and industrial wastewater after proper sampling, sample handling, and test sample preparation (filtration when necessary and taking into account the amount of dissolved material in the water). This method is only applicable to homogeneous samples or samples which are homogeneous via timely filtration.

The lowest limit that can be measured without concentration of the sample or by using only passive shield of the detection system is about 5·10-2 Bq/l for e.g. 137Cs.1 The upper limit of the activity corresponds to a dead time of 10 %. Higher dead times may be used but evidence of the accuracy of the dead-time correction is required.

Depending on different factors, such as the energy of the gamma-rays, the emission prob