The effect of oxygen on the release of tritium during baking of TFTR D–T tiles

A series of tests involving 10 h baking under the current ITER design conditions (240 °C with 933 Pa O2) was performed using a cube of a carbon fiber composite tile that had been used in Tokamak Fusion Test Reactor (TFTR) during its deuterium–tritium burning operation. The removal rate of the codeposits was about 3 μm/h near the surface and 0.9 μm/h in the deeper region. Total amount of tritium released from the cube during 10 h baking was 202 MBq, while remaining tritium in the cube after baking was 403 MBq. Thus 10 h baking at 240 °C with 933 Pa O2 removed 1/3 of tritium from the cube. After 10 h baking, the tritium concentration on the cube surface also dropped by about 1/3. In addition, some tritium was released from another cube of the tile during baking at 240 °C in pure Ar, and a rapid increase of tritium release was observed when the purging gas was shifted from pure Ar to Ar–1%O2. When a whole TFTR tile was baked in air at 350 °C for 1 h and then at 500 °C for 1 h, the ratios of tritium released were 53 and 47%, respectively. Oxygen reacted with carbon to produce carbon monoxide during baking in air.