2004, Volume 7, Issue 13+14
Low-Level Tritium Concentration Measurements by Liquid Scintillation Counting in Environmental Water Samples
National Institute of Cryogenic and Isotopic Technologies, Rm. Valcea
Despite the relatively low toxicity of tritium, monitoring of tritium activity concentrations in the environment is necessary in order to follow its circulation in the hydrosphere and biosphere. There are two standard recommendation [1, 2] that specify a method for determining tritium concentration in water by liquid scintillation counting. Basically, the principle is the same with small differences between the two chemical treatments of water samples. In the present work, a low background liquid scintillation system detector Quantulus 1220, is used to determine tritium concentration in different types of water: drinking water, precipitation, surface water and wastewater. All samples were measured according to the two studied standards, but we observed several parameters that were important for good scintillation measurement, pH, conductivity, and holding time of sample: scintillant mixture. There is some interference in the measurement process that leads to different results for the same water sample prepared by the two methods. Establishing the most appropriate routine procedure for tritium measurement in water sample, was the main goal of our study. The results obtained to the Sixth IAEA Inter-comparison of Low-level Tritium Measurements in Water (TRIC2000) confirm the settled procedure. Even if the uncertainty of the method is high, and even if tritium levels in the environment continue to decrease, the direct measurement of tritium concentration in water sample can still be a more rapid and cheaper measurement method for environment.
Liquid scintilation, tritium.
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