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 degreesC with 933 Pa O(2)) 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 mum/h near the surface and 0.9 mum/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 degreesC with 933 Pa O(2) 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 degreesC in pure Ar, and a rapid increase of tritium release was observed when the purging gas was shifted from pure Ar to Ar-1%O(2). When a whole TFTR tile was baked in air at 350 degreesC for 1 h and then at 500 degreesC 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. (C) 2002 Elsevier Science B.V. All rights reserved.