Methodological features of monitoring the long-term dynamics of low levels of tritium in the environment

Abstract

The article considers the methodological features of long-term observations of the dynamics of changes in low levels of tritium in water bodies of the environment located in places of potential contamination by tritium. The еxperience of measurements of tritium on the low-background liquid scintillation alpha-, beta-radiometer “Quantulus 1220-003” has shown, that the accuracy of estimating the absolute values of the specific activity of tritium in the samples under study at its low levels is significantly related to the counting rate of the background sample. When planning long-term dynamic observations of changes in low levels of tritium in water bodies, it is necessary to foresee a number of factors that affect the accuracy of the estimates. One of the most significant factors is the presence of a background sample with a count rate of not more than 0.6 imp/ min, which makes it possible to measure the activity concentration of tritium at a level of 1 Bq/l for 12 hours. The stability and reproducibility of the results can be monitored using a reference solution, which must be used throughout the entire period of dynamic observation. Calibration of the device using the reference solution should be provided each time the scintillation cocktail is changed, since there may be differences in efficiency up to 10% when using the same type of scintillators with different shelf life. For the preparation of counting samples, rooms with minimal levels of tritium in air moisture and at a significant distance from rooms where work with elevated levels of tritium activity is carried out should be chosen. When reusing vials, it should be borne in mind that the efficiency of tritium detection may decrease, therefore, when using such vials, calibration measurements of standard solutions should also be carried out.