The standard applies to all types of water with tritium activity concentrations from 5 to 1000 kBq/m3. Notes 1. Below activity concentrations of approximately 50 kBq/m3, an enrichment step can improve the accuracy of the determination and lower the lower analysis limit. However, enrichment means an extra step in the analysis process and therefore, apart from the greater analytical effort required, an additional source of error. There is a spread of approximately 3% due to the variability in the enrichment cells. This implies that for higher activity concentrations than approximately 50 kBq/m3, direct scintillation counting is preferable. However, for groundwater, for example, where low tritium levels are common, an additional enrichment step is necessary. 2. Water with activity concentrations greater than 103 kBq/m3 can be examined in accordance with the standard after dilution with background water (4.3). Another method for determining these levels is by increasing the volumetric tritium activity of the internal standard solution to be added (4.4). 3. Organically bound tritium is not determined with this method.
NEN 6420-1986 history
1986NEN 6420-1986 Water - Determination of tritiated water content by liquid scintillationcounting