scope:

This International Standard describes the conditions for the determination of tritium activity concentration in samples of environmental water or of tritiated water ([3H]H2O) using liquid scintillation counting. The scintillation phenomenon results from interaction of ionizing radiation with solvents and compounds exhibiting fluorescence (scintillators). Both solvents and scintillators constitute the scintillation cocktail. The scintillation mixture is achieved by adding the scintillation cocktail to the test sample in order to obtain a homogeneous mixture. The choice of the analytical procedure (either with or without distillation of the water sample prior to determination), depends on the aim of the measurement and the sample characteristics [1], [2], [3]. Direct measurement of a raw water sample using liquid scintillation counting has to consider the potential presence of other beta emitter radionuclides. To avoid interference with these radionuclides when they are detected, the quantification of tritium will be performed following the sample treatment by distillation [4], [5], [6], [7]. The Annexes B, D and E describe three distillation procedures. NOTE 1 The method is not applicable to the analysis of organically bound tritium; its determination requires additional chemical processing (such as chemical oxidation or combustion). NOTE 2 Tritium activity concentrations below 106 Bq/l can be determined without any sample dilution. NOTE 3 A prior enrichment step can significantly lower the limit of detection [8], [9].