['Understanding', 'why', 'this', 'transition', 'behaviour', 'happens', 'is', 'critical', 'when', 'modelling', 'the', 'rate', 'of', 'growth', 'of', 'oxide', ',', 'and', 'therefore', 'to', 'the', 'lifetime', 'prediction', 'of', 'Zr', 'clads', ',', 'and', 'ultimately', 'to', 'the', 'safety', 'of', 'nuclear', 'power', 'reactors', '.']