Helium blanketing and gas circulation effect of hydriding reaction with ZrCo

Abstract

The tritium storage bed receives and supplies tritium gas for fusion facilities. Inert gases, such as helium-3, which is produced by tritium beta decay, disturb the absorption behavior of tritium in the bed and this is called the Helium Blanketing Effect (HBE). This study focused on the HBE and gas circulation as a way of breaking the HBE for the hydriding reaction with ZrCo. The hydriding reaction with the application of 100 % hydrogen without helium-4 was completed within five minutes under 120 kPa initial hydrogen partial pressure and 20 °C reactor temperature. With 5% helium-4 in the hydrogen, it took more than 1000 min for the hydriding reaction to be completed under the same conditions. The HBE was broken with the application of a gas-circulation process. Even with 50 % helium-4 in the hydrogen, the hydriding reaction was completed in five minutes under the same conditions. In an experiment conducted at various flow rates of gas circulation, breaking the HBE was observed even at a small flow rate. The gas circulation process can efficiently break the HBE and separate the helium-3 produced in the tritium storage bed.