Tritium decontamination from various materials (experiment with used tritium gas cylinder)

It has been reported by the present authors that introduction of water vapor to the purge gas can give quick decontamination of tritium from the surface of various materials through the isotope exchange reaction between water vapor in the gas phase and tritium on the surface, At collection of contaminated wastes with tritium, it is required by regulation to know the amount of tritium trapped to surface and bulk of disposal materials. However, it is difficult to measure the amount of tritium on the surface of materials such as tritium gas cylinder or pipes and reaction vessels in a tritium handling system. In this study, several experiments were performed applying the isotope exchange reaction between water vapor in the gas phase and tritium in the surface water to estimate the amount of tritium on the inner surface of used tritium gas cylinder made of aluminum alloy, and the results obtained from these experiments were compared with result of the smear method. Observed value for the amount of tritium on the surface of the aluminum alloy was similar to the value estimated using the trapping capacity of water on aluminum obtained by our previous experimental results. It is confirmed that injection of a little amount of water to the system makes it possible to extract whole tritium trapped on the inner surface of gas cylinder, though the smear method could not give quantitatively reliable results for measure the amount of tritium on the surface.