['The', 'main', 'drawback', 'of', 'thermo', '-', 'oxidation', 'in', 'most', 'actual', 'devices', 'and', 'ITER', 'is', 'its', 'limitation', 'to', 'maintenance', 'periods', ',', 'when', 'the', 'vessel', 'walls', 'can', 'be', 'heated', 'up', 'around', '300–400', '\xa0', '°', 'C', 'by', 'hot', 'helium', 'injection', 'through', 'the', 'cooling', 'system', '[', '19,20', ']', ',', 'and', 'also', 'because', 'of', 'the', 'required', 'reconditioning', 'of', 'the', 'walls', 'before', 'plasma', 'operation', 'to', 'remove', 'the', 'absorbed', 'oxygen', '[', '10', ']', '.']