One-dimensional experiments of a natural circulation two-phase flow under an external reactor vessel cooling

During a severe accident in a nuclear power plant, a decay heat from a molten corium should be removed to maintain an integrity of the reactor vessel. This feasible strategy can be achieved by a External Reactor Vessel Cooling (ERVC) which requires a coolant to be circulated sufficiently between the reactor vessel and its insulation. For this reason, one-dimensional experiments were conducted to estimate the natural circulation flow under the ERVC condition of the APR1400. The experimental facility is one-dimensional and scaled down to be a half height and a 1/238 channel area of the APR1400 reactor vessel. The natural circulation mass flow rates were measured with the various coolant inlet/outlet areas, heights of the supplied water level and the coolant outlet, and steam generation rates. In results, the natural circulation mass flow rates mainly depended on the inlet/outlet area, and the natural circulation mass flow rate increased, as the outlet height as well as the supplied water level increased.