Sensitivity of a specially designed calorimeter for absolute evaluation of tritium concentration in water

Applicability of a specially designed high-sensitivity conduction calorimeter has been examined to determine the absolute amount of tritium in tritiated water. A given concentration of tritiated water was prepared for examinations. Prior to measurements by the calorimeter, the concentration of tritium was measured by a liquid scintillation counter, and it was determined as 46.0 ± 0.5 MBq/cm3. This tritiated water, 20 cm3, was loaded into a sample cell of the calorimeter. The concentration of tritium determined by the calorimeter was 45.2 ± 2.0 MBq/cm3, and it agreed with that by the liquid scintillation counter within a few percent. In addition, detection limit of the present calorimeter was evaluated to be 40 MBq, considering the standard deviation of background level measured without tritiated water. It was concluded, therefore, that the present calorimeter can be utilized as a standard device for determination of the absolute amount of tritium in tritiated water.