Bend points of hydrogen partial pressure curves obtained by tritium removal simulation tests

A tritium cleanup system has been developed for exhaust gases containing tritium in various chemical forms. This system is distinguished from conventional procedures in that tritium is removed as tritiated hydrogen molecules. Basically, the system consists of five main components, including a hydrogen separator and a decomposition-processing vessel. A previous study assumed that the gas for processing consisted of hydrogen, methane, and helium, with some proportion of tritiated hydrogen and methane. The performance of this tritium cleanup system was examined using a computer-based simulation. To monitor the removal of tritium from the exhaust gas, the partial pressures of the respective components were examined during processing. The curve for the partial pressure of hydrogen contains two clear bends. In the present study, the correspondence between these bend points and their time width and simulation condition was examined in relation to the hydrogen partial pressure curves obtained under 28 conditions, differing in component proportion and process gas volume. It was found that two bend points moved, depending on the process gas condition, and three patterns appeared for the hydrogen partial pressure curves. A mechanism was proposed for explaining the movement of the bend points and the three patterns.