Consequences of deuterium retention and release from Be-containing mixed materials for ITER Tritium Inventory Control

In order to assess the tritium removal procedure currently suggested for ITER (wall baking at 513 K (240 deg. C) for the main chamber, at 623 K (350 deg. C) for the divertor), deuterium (D) retention and release behaviour of beryllium (Be)-containing materials are investigated. In pure Be, D is predominantly released around 470 K with a relatively sharp desorption peak. Mixing of tungsten (W) or carbon (C) into Be changes the D desorption behaviour causing less efficiency D removal by the baking procedure. Especially, high C concentrations in Be affect the D release behaviour significantly and prevents removal of the retained D by baking at 623 K. As a consequence, the baking operation in ITER would work for tritium removal from the first wall and Be-rich deposited layers formed at low temperature areas, while it does not work for C-rich codeposited layers and/or plasma-facing surfaces heated above 623 K during a discharge.