AbstractThe safety analysis for of loss-of-vacuum accident (LOVA) as well as ingress-of-coolant event (ICE) is among the last task left in ITER R&D. On the assumption of LOVA after occurring ICE, it is corollary that activated dusts are under the wet condition. Transport behavior of in-vessel activated dusts under wet condition is not known well in comparison with dry case. In this study, the wetted particles transport behavior is investigated experimentally by using a vacuum vessel that serves as a steam generator. The relations among the relative humidity, the entrainment of particles in the exhaust gas flow and the adhesion rate of dust particles on the confined wall have been cleared. The entrainment ratio decreases as the relative humidity increases and increases as the initial pressure difference increases.