Liquid scintillation counting is used to determine the quantity of tritium (³H) present in water. Calibration for tritium counting is accomplished using tritium solutions traceable to NIST.

Analysis of Water, Precipitation, and Atmospheric Moisture

Water and precipitation samples are prepared by distillation of a 100-mL sample. After discarding the first 10-mL of distillate, a 20-mL water fraction is collected for analysis. Blanks are prepared from distilled low tritium water. Atmospheric moisture samples are prepared a priori by the S.M. Stoller Corporation. Nine milliliters of the distilled fraction is mixed with 11-mL of liquid scintillation cocktail (Packard Ultima Gold LLT) in a plastic liquid scintillation vial. Samples are analyzed on a Beckman LS5000TA liquid scintillation counter. Samples are analyzed for six 70-minute cycles. The average net cpm within the H-3 energy window are then determined and recorded.

Analysis of Milk Samples

A 100-mL aliquot of milk is split into four equal parts. The fats and heavy cream are removed and discarded from the milk sample through the use of a high speed centrifuge. Concentrated nitric acid is then added to the remaining liquid to precipitate soluble tritiated proteins. Precipitated solids are then removed from the liquid sample via the high speed centrifuge and discarded. Sodium hydroxide pellets are added to the remaining liquid to precipitate the remaining soluble tritiated proteins. These precipitated solids are removed from the liquid sample via separation using the high speed centrifuge and discarded. The remaining liquid is then distilled at low heat. After discarding the first 20-mL of distillate, a 20-mL water fraction is collected for analysis. Nine milliliters of the distilled fraction is mixed with 11-mL of liquid scintillation cocktail (Packard Ultima Gold LLT) in a plastic liquid scintillation vial. Samples are analyzed on a Beckman LS5000TA liquid scintillation counter. Samples are analyzed for six 70-minute cycles. The average net cpm within the H-3 energy window are then determined and recorded.

EAL staff run two tritium spiked milk tracers along with the milk samples being analyzed for tritium. At least two tracers are processed using two different milk samples to verify the accuracy and yield of tritium from the milk samples.

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Last modified: June 26, 2001