We have studied the transport and chemical speciation of radiotoxic and toxic species for an event of water ingress in the vacuum vessel of experimental fusion facility ITER with the ASTEC code. In particular our evaluation takes into account an assessed thermodynamic data for the beryllium gaseous species. This study shows that deposited beryllium dusts of atomic Be and Be(OH)2 are formed. It also shows that Be(OT)2 could exist in some conditions in the drain tank.