Conversion of Tritium Gas to Tritiated Water in Air

The conversion reaction of tritium gas to tritiated water in dry air has been studied using low–concentration tritium gases which have three different hydrogen isotope compositions. The conversion was directly proportional to a ratio of radioactivity of T₂ to that of total tritium. This demonstrates that the T₂ decay process is predominant for the conversion reaction at low initial tritium concentrations. First-order rate constants for the reaction in dry air are found to be independent of initial tritium concentration. A model to predict the rate constant of the production of tritiated water from T₂ in dry air has been developed. The modeling results show that the T₂ decay process is predominant at low concentrations, while O⁺ and N₂⁺ ions formed through tritium beta-ray induced reactions play important roles at high concentrations.