System for utilizing unused heat-exchange water of passive auxiliary feedwater system, and reactor cooling control method utilizing unused heat-exchange water of passive auxiliary feedwater system

A system for utilizing unused heat-exchange water of a passive auxiliary feedwater system, the system comprising:

• a steam generator to generate steam by heat from a nuclear reactor;
• a passive condensation tank in which heat-exchange water is stored;
• a condenser arranged inside the passive condensation tank and spaced apart from a bottom part of the passive condensation tank;
• a steam supply line arranged between the steam generator and an inlet of the condenser inside the passive condensation tank and providing a pipeline for cutting off steam supply to a turbine side and branching the steam off to the condenser when an operation of the nuclear reactor is stopped;
• and
• a condensate water recovery line arranged between an outlet of the condenser and the steam generator and providing a pipeline for recovering condensate water through the condenser to the steam generator,
• wherein a residual water discharge flow path is arranged between the passive condensation tank and the condensate water recovery line and discharges remaining water remaining between the condenser and the bottom part of the passive condensation tank to the condensate water recovery line.