Tritium measurement by use of Ready CapTM

Liquid scintillators have been widely used in the research and development of safe handling techniques of a large amount of tritium for thermonuclear fusion reactors. This gives rise to bothersome problems such as waste handling. To avoid the problem of waste handling, several solid scintillators have been developed. Among those, Ready CapTM developed by Beckman Instruments appears to have great potential for tritium measurement. Its applicability for tritium, however, has not been investigate so far. We examined, therefore, its reliability for tritium measurements by using tritiated water as a model system. The count rates were kept constant irrespective to the amount of tritiated water above 0.03 cm3. This is due to the fact that the maximum range of the tritium β-rays is only 6 μm in water. This observation indicates that the apparent counting efficiency is inversely proportional to the amount of the sample water. It was revealed that it is possible to determine the tritium activity of tritiated water with Ready CapTM by taking the inverse proportionality of the efficiency into account. In addition, the present examination showed that accuracy and reproducibility are quite good. They are comparable to the measurements using liquid scintillators, although its detection limit of tritium is estimated as about 1 x 10-9 Ci/cm3. On the basis of those results, it was concluded that Ready CapTM is quite helpful for the tritium measurements in the research and development of tritium handling techniques. (author)