Theoretical expressions for removing tritium from exhaust gas

A tritium cleanup system for application to exhaust gases discharged from a large helical device has been developed. It is constructed of five main components and is able to remove tritium in the chemical form of hydrogen molecules. In a previous study, a decomposition-processing vessel was developed, which is one of the five main components, and the system's performance installed in this vessel was tested based on computer simulations. In the simulations, the process gas was assumed to be made up of hydrogen, methane and helium, where part of the hydrogen and methane had been tritiated, and helium had been added to maintain a proper flow rate in the cleanup system. Several assumptions about the gas component fraction and tritium ratio in the gas to be processed were made. Two fundamental equations were used to express the removal of tritium in both chemical forms of hydrogen molecules and methane in the simulations. However, detailed descriptions of the assumptions and equations were not given. In the present paper, both the assumptions and equations are theoretically explained.