AbstractAn integrated Ingress-of-Coolant Event (ICE) test facility was constructed to investigate quantitatively effectiveness and functional performance of a vacuum vessel pressure suppression system (VVPSS) during the ICE in International Thermonuclear Experimental Reactor (ITER). The integrated ICE test facility simulated structural components of the ITER VVPSS with a scaling factor of 1/1600. From the present study it was clarified experimentally that the ITER VVPSS is very effective to reduce the pressurization during the ICE because the condensation of vapor within a suppression tank is enhanced and the pressure rise characteristics strongly depend on the cross-sectional area of the relief piping, and then the pressure rise rate in ITER is expected between 100 and 200 kPa s−1.