Tritium Management for LHD Deuterium Plasma Experiments

Abstract

In high-temperature plasma experiments using deuterium gas in large fusion devices, tritium is produced by the deuterium fusion reaction. Although the amount of tritium produced is not large, it is a radioactive material, so it is essential to develop safe handling systems and obtain public acceptance. Here, we summarize tritium safety management and tritium behavior in the facility, and have monitored the results of six years of deuterium plasma experiments in the Large Helical Device (LHD). More than 95% of the tritium exhausted from the LHD vacuum vessel was recovered by a tritium removal system. The extremely low concentrations of tritium discharged from the stack into the environment were monitored for each chemical form of tritiated water vapor, tritiated molecular hydrogen, and tritiated hydrocarbons, and were verified to be well below the levels specified by management at the National Institute for Fusion Science (NIFS). Although the tritium handled in the LHD deuterium experiment was a small amount, the operational experience and the instruments thereby developed would likely be useful for tritium safety management in future fusion reactors.