Patent Number: 
Section: claims

1. A passive residual heat removal system, comprising:a reactor pressure vessel;a reactor core placed in the reactor pressure vessel;a primary containment vessel including a drywell to surround the reactor pressure vessel, and a suppression chamber internally provided with a suppression pool;a vent line connecting the drywell and the suppression pool, the vent line being fitted with a plurality of openings in the suppression pool;a coolant pool filled with a coolant and provided above the primary containment vessel;a heat exchanger placed under the coolant in the coolant pool;a steam suction line connecting the drywell and the heat exchanger;a condensate storage tank disposed below the heat exchanger and above an upper end of the reactor core;a first condensate discharge line connecting the condensate storage tank and the heat exchanger;a non-condensate gas discharge line connected at a first end thereof to an upper section of the condensate storage tank and at a second end thereof to the suppression pool, the second end of the non-condensate gas discharge line being open at a position higher than a highest opening of the vent line in the suppression pool;a second condensate discharge line connected at a first end thereof to a position below that section of the condensate storage tank to which the first end of the non-condensate gas discharge line is connected, and at a second end thereof to the suppression pool, the second end of the second condensate gas discharge line being open at a position lower than a lowest opening of the vent line in the suppression pool; anda condensate return line connected at a first end thereof to a position below that section of the condensate storage tank to which the first end of the second condensate discharge line is connected, and at a second end thereof to a side portion of the reactor pressure vessel, the side portion being above the upper end of the core;wherein the open end of the second condensate discharged line, positioned in the suppression pool, is branched into a plurality of horizontal lines, with condensate discharge ports being formed at distal ends of the branched horizontal lines. 2. A passive residual heat removal system, comprising:a reactor pressure vessel;a reactor core placed in the reactor pressure vessel;a primary containment vessel including a drywell to surround the reactor pressure vessel, a suppression chamber internally provided with a suppression pool, and a pedestal formed directly under the reactor pressure vessel, as space that is demarcated atop from the drywell;a vent line connecting the drywell and the suppression pool, the vent line being fitted with a plurality of openings in the suppression pool;a coolant pool filled with a coolant and provided above the primary containment vessel;a heat exchanger placed under the coolant in the coolant pool;a steam suction line connecting the drywell and the heat exchanger;a condensate storage tank disposed below the heat exchanger and above an upper end of the reactor core;a first condensate discharge line connecting the condensate storage tank and the heat exchanger;a non-condensate gas discharge line connected at a first end thereof to an upper section of the condensate storage tank and at a second end thereof to the suppression pool, the second end of the non-condensate gas discharge line being open at a position higher than a highest opening of the vent line in the suppression pool;a second condensate discharge line connected at a first end thereof to a position below that section of the condensate storage tank to which the first end of the non-condensate gas discharge line is connected, and at a second end thereof to the pedestal; anda condensate return line connected at a first end thereof to a position below that section of the condensate storage tank to which the first end of the second condensate discharge line is connected, and at a second end thereof to a side portion of the reactor pressure vessel, the side portion being above the upper end of the core;wherein parallel branches are provided on part of the condensate return line, a squib valve is provided as a condensate return valve on one of the parallel branch lines, and an air-operated valve is provided as another condensate return valve on the other branch line. 3. The passive residual heat removal system according to claim 1, further comprising:a depressurization line connecting the reactor pressure vessel and the primary containment vessel, and a depressurization valve opening/closing the depressurization line. 4. The passive residual heat removal system according to claim 1, wherein:a ratio of V/Q between the amount of coolant, V (m3), in the condensate storage tank, and thermal output power Q (GW) of the core under rated operation, is at least 20. 5. A nuclear power plant facility, comprising the passive residual heat removal system according to claim 1.