Water quality — Actinium-227 — Test method using alpha-spectrometry

This document specifies a test method to determine the activity concentration of 227Ac in all types of waters by alpha spectrometry.

The test method is applicable to test samples of supply/drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling and handling and test sample preparation (see ISO 5667-1, ISO 5667-3, ISO 5667-10). Filtration of the test sample is necessary.

The detection limit depends on the sample volume, the instrument used, the background count rate, the detection efficiency, the counting time, the chemical yield, and the progeny ingrowth. The method described in this document, using currently available alpha spectrometry apparatus, has a detection limit of approximately 0,03 Bq·l 1, when directly measuring the alpha peak of 227Ac. This detection limit is lower than the WHO criteria for safe consumption of drinking water for any actinide alpha emitter (0,1 Bq·l 1).[4] This value can be achieved with a counting time of 48 h for a sample volume of 1 l.

Only a small fraction of 227Ac decays through alpha emissions (~1,42 %). An option to lower the detecti