Cooling System of the emergency cooling tank and nuclear power plant equipped latter

The invention relates to a cooling system for an emergency cooling tank includes a tank configured to store cooling water receiving heat transferred from a nuclear reactor or containment. A heat exchange device exposed to the outside of the reservoir to operate in air, and configured to exchange heat between the fluid in the reservoir and air and an opening and closing unit installed at the level of an upper portion of the tank configured to be opened by a flow of fluid generated by evaporation of cooling water, following a pressure difference from the outside air upper setpoint.