Coolant tank, and passive containment cooling system comprising same

A nuclear reactor building passive cooling system disposed adjacent to an outer wall of a nuclear reactor building and capable of passively cooling the nuclear reactor building, the system comprising:

• a storage tank storing cooling water;
• a partition part arranged within the storage tank and dividing an inside of the storage tank into a first storage tank and a second storage tank to separate the cooling water;
• a first heat exchanger extending from the storage tank to the nuclear reactor building and cooling the nuclear reactor building on the basis of the cooling water;
• a unidirectional valve provided on the partition part and allowing the cooling water of the second storage tank to be introduced into the first storage tank when a water level of the first storage tank is reduced;
• and
• wherein the first heat exchanger comprises an inlet pipe into which the cooling water is introduced from the second storage tank, an outlet pipe along which the cooling water provided from the inlet pipe returns back into the first storage tank;
• and a heat exchange unit disposed between the inlet pipe and the outlet pipe.