Direct contact condensation (DCC) of a steam jet discharged into a subcooled water pool is an efficient way to condensate a large quantities of water at high pressure and temperature without introducing any complex device. This phenomenon is used in many nuclear engineering fields, such as pressure suppression pool in Boiling Water Reactors (BWRs), condensing pool in Pressurized Water Reactors (PWRs) and suppression tank in International Thermonuclear Experimental Reactor (ITER). Safety in nuclear facilities, like Nuclear Power Plant (NPP), is very important because of the past occurrence of nuclear accidents such as Fukushima or Chernobyl. The constructors of nuclear facilities, the operating energy companies in NPP and national regulators are well aware of the importance of the safety aspect. DCC is applied to improve the safety in a BWR on off-normal conditions and accident transients, such as a Loss of Coolant Accident (LOCA). This study will focus not only on the suppression pool in a Boiling Water Reactor (BWR) but also on the suppression tank in the Vacuum Vessel Pressure Suppression System (VVPSS) in ITER.