Tritium/ Helium-3 Analysis

In cooperation with the University of Miami’s Noble Gas Laboratory, the Tritium Laboratory now offers the measurement of both tritium and its radioactive decay product, helium-3. The tritium/helium-3 ratio can be used to determine the “age” of a water sample with a resolution of 0.1 years for young (< 40 years old) water. Water “age” is defined as the elapsed time that the water has been isolated from the atmosphere. In a groundwater sample the “age” is equivalent to how long ago the sample was recharged to the aquifer.

tritium The Noble Gas Laboratory measures the amount of helium-3 in a water sample using mass spectrometry. Tritium is determined from an additional sample collected at the same time by the helium in-growth method. The water sample for tritium analysis is first degassed to remove any helium-3 and then sealed in a glass container. After the sample is sealed, helium-3 begins to accumulate as tritium decays. After an appropriate time for helium-3 to accumulate (1 week to 1 year depending on the initial tritium concentration) the in-grown helium-3 is measured using mass spectrometry. The tritium concentration in the sample is then determined from the amount of in-grown helium-3, the length of time the sampled was sealed, and the radioactive decay rate (12.32 years) of tritium. Accuracy of the helium in-growth method is 0.01 TU.

The mass spectrometer system used to measure helium is currently undergoing a major renovation. Please contact the Tritium Lab for additional information.