Abstract:
The present invention discloses a passive cooling system of a containment building, to which a plate-type heat exchanger is applied. A passive cooling system of a containment building comprises: a containment building; a plate-type heat exchanger provided to at least one of the inside and the outside of the containment building and comprising channels respectively provided to the both sides of a plate so as to be arranged dividedly from each other such that the plate-type heat exchanger carries out mutual heat exchange between the internal atmosphere of the containment building and a heat exchange fluid while maintaining a pressure boundary; and a pipe connected to the plate-type heat exchanger by penetrating the containment building so as to form the path of the internal atmosphere of the containment building or the heat exchange fluid.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present disclosure relates to a passive cooling system of a containment building to which a plate-type heat exchanger is applied and a nuclear power plant including the same. 
         [0003]    2. Description of the Related Art 
         [0004]    Reactors are divided into active reactors using active power such as a pump and passive reactors using passive power such as gravity force, gas pressure according to the configuration method of a safety system. Furthermore, reactors are divided into loop type reactors (for example, Korean pressurized water reactor) in which a main component (a steam generator, a pressurizer, a pump impeller, etc.) is installed at an outside of the reactor vessel and integrated type reactors (for example, SMART reactor) in which the main component is installed at an inside of the reactor vessel according to the installation location of the main component. 
         [0005]    In the nuclear power plant industry, a passive containment building cooling system (or containment building cooling system) has been mostly used as a system for condensing steam and cooling internal atmosphere in order to maintain the integrity of the containment building when coolant or steam is discharged to increase a pressure within the containment building (or reactor building, containment vessel, safety guard vessel) due to the occurrence of a loss of coolant accident or steam line break accident in various reactors including an integrated type reactor. 
         [0006]    For a method of being used with the purpose similar to that of the passive containment building cooling system, a method of using a suppression tank for guiding steam discharged to a containment building to the suppression tank (commercial BWR, CAREM: Argentina, IRIS: Westinghouse Company), a method of applying a steel containment to cool (spray, air) an external vessel (AP1000: Westinghouse), and a method of using a heat exchanger (SWR1000: France Framatome ANP, AHWR: India, SBWR: GE), and the like are used. For a heat exchanger of the containment building cooling system, a shell and tube type heat exchanger or condenser (SBWR: U.S. GE Company) is mostly applied thereto. In general, a containment structure for protecting an outside of the reactor vessel (or reactor coolant system of a loop type reactor) is referred to as a containment building (or reactor building) when fabricated and constructed using reinforced concrete, and referred to as a containment vessel (safety guard vessel in case of a small size) when fabricated and constructed using steel. 
         [0007]    The performance of a heat exchanger in a containment building cooling system mainly depends on a condensation phenomenon of steam. When atmosphere is not efficiently circulated, steam may not be efficiently supplied thereto, thereby reducing the performance of the heat exchanger. Furthermore, a lot of devices and structures may be disposed within a containment building in a nuclear power plant in which a containment building cooling heat exchanger is disposed within a containment building, and thus there is a difficulty in the layout, and thus reduction in size and weight is required. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the present disclosure is to provide a passive containment building cooling system for overcoming the defect of a plate type heat exchanger and solving a problem such as flow instability or the like occurring in applying the plate type heat exchanger, and a nuclear power plant including the same. 
         [0009]    Another object of the present disclosure is to propose a passive containment building cooling system for providing an intermediate flow path to a fluid flow path at a lower heat exchange performance side in applying the plate type heat exchanger to enhance the heat exchange performance, and a nuclear power plant including the same. 
         [0010]    Still another object of the present disclosure is to propose a passive containment building cooling system for cooling the containment building in a passive manner, and safely injecting condensate collected during the cooling process into a reactor coolant system, and a nuclear power plant including the same. 
         [0011]    In order to accomplish an object of the foregoing aspects, a passive containment building cooling system according to an embodiment of the present disclosure may include a containment building, a plate type heat exchanger installed on at least one place of an inside and an outside of the containment building, and provided with channels arranged to be distinguished from one another at both sides of a plate to exchange heat between atmosphere within the containment building and heat exchange fluid from each other while maintaining a pressure boundary, and a line connected to the plate type heat exchanger through the containment building to form a flow path of the atmosphere within the containment building or the heat exchange fluid. 
         [0012]    According to the present disclosure having the foregoing configuration, various structures and methods for increasing a flow resistance of an inlet region may be proposed to solve a flow instability problem or the like of the plate type heat exchanger, thereby applying the plate type heat exchanger to the passive containment building cooling system. 
         [0013]    Furthermore, according to the present disclosure, an open type flow path may be provided or a plurality of open type flow paths may be installed together to mitigate a bottleneck phenomenon of an inlet of the plate type heat exchanger, thereby applying the plate type heat exchanger to a passive containment building. 
         [0014]    When the plate type heat exchanger is applied to the passive containment building cooling system, it may have durability to a high-temperature, high-pressure environment, thereby facilitating the maintenance of a pressure boundary between a primary fluid and a secondary fluid, allowing reduction in size with a high heat exchange performance to comply with a strict design standard on an earthquake load or the like, and overcoming an environmental condition of the containment building during an accident. 
         [0015]    In addition, according to the present disclosure, it may be possible to have an excellent heat exchange performance due to a high integration of the plate type heat exchanger, thereby allowing reduction in weight, allowing reduction in size to greatly mitigate a layout problem within the containment building or the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
           [0017]    In the drawings: 
           [0018]      FIG. 1  is a conceptual view illustrating a passive containment building cooling system and a nuclear power plant including the same associated with an embodiment of the present disclosure; 
           [0019]      FIG. 2  is a conceptual view illustrating a passive containment building cooling system and a nuclear power plant including the same associated with another embodiment of the present disclosure; 
           [0020]      FIG. 3  is a conceptual view illustrating a passive containment building cooling system and a nuclear power plant including the same associated with still another embodiment of the present disclosure; 
           [0021]      FIG. 4  is a conceptual view illustrating a passive containment building cooling system and a nuclear power plant including the same associated with yet still another embodiment of the present disclosure; 
           [0022]      FIGS. 5 through 16  are flow path conceptual views illustrating a plate type heat exchanger selectively applicable to the passive containment building cooling system in  FIGS. 1 through 4 ; 
           [0023]      FIG. 17  is a conceptual view illustrating a passive containment building cooling system and a nuclear power plant including the same associated with still yet another embodiment of the present disclosure; 
           [0024]      FIG. 18  is a conceptual view illustrating a passive containment building cooling system and a nuclear power plant including the same associated with yet still another embodiment of the present disclosure; 
           [0025]      FIG. 19  is a conceptual view illustrating a plurality of plate type heat exchangers selectively applicable to the passive containment building cooling system in  FIGS. 17 and 18 ; and 
           [0026]      FIG. 20  is a layout conceptual view illustrating a plurality of plate type heat exchangers illustrated in  FIG. 19 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Hereinafter, a passive containment building cooling system associated with the present disclosure will be described in more detail with reference to the accompanying drawings. Even in different embodiments according to the present disclosure, the same or similar reference numerals are designated to the same or similar configurations, and the description thereof will be substituted by the earlier description. Unless clearly used otherwise, expressions in the singular number used in the present disclosure may include a plural meaning. 
         [0028]    A plate type heat exchanger in the present disclosure may refer to all plate type heat exchangers when there is any difference in the processing method or bonding method of a plate thereof as well as a typical plate type heat exchanger and a printed circuit type heat exchanger, unless otherwise specified in particular. Furthermore, a containment building in the present disclosure may collectively refer to a containment building, a reactor building, a containment vessel, a safety guard vessel, and the like, unless otherwise specified in particular. 
         [0029]      FIG. 1  is a conceptual view illustrating a passive containment building cooling system  100  and a nuclear power plant  10  including the same associated with an embodiment of the present disclosure. 
         [0030]    Referring to  FIG. 1 , for the sake of convenience of explanation, the passive containment building cooling system  100  and the nuclear power plant  10  including the same disclosed in the present disclosure are symmetrically illustrated around a reactor coolant system  12 , wherein a normal operation of the nuclear power plant  10  is illustrated on the right, and the occurrence of an accident at the nuclear power plant  10  is illustrated on the left. It is likewise in the other drawings illustrated to be symmetrical to each other. 
         [0031]    The nuclear power plant  10  may include a containment building  11  for surrounding an outside of the reactor coolant system  12  to prevent the leakage of radioactive materials. The containment building  11  is a constituent element commonly referring to a containment vessel, a safety guard vessel and a reactor building. 
         [0032]    During a normal operation of the nuclear power plant  10 , when feedwater is supplied from a feedwater system  13  to a steam generator  12   b  through a feedwater line  13   a , steam is generated by the steam generator  12   b  using heat transferred from a reactor core  12   a . The steam is supplied to a turbine system  14  through a steam line  14   a , and the turbine system  14  produces electricity using the supplied steam. Isolation valves  13   b ,  14   b  are open during a normal operation of the nuclear power plant  10 , but closed by an actuation signal during the occurrence of an event. 
         [0033]    Various safety systems for maintaining the integrity of the nuclear power plant  10  during the occurrence of an accident exist in the nuclear power plant  10 , and a safety injection system  15 , and the passive containment building cooling system  100  are systems included in the safety systems. 
         [0034]    Among them, the passive containment building cooling system  100  is a system for cooling atmosphere within the containment building  11  and condensing steam to reduce a pressure when coolant or steam is discharged to increase a pressure within the containment building  11  due to the occurrence of a loss of coolant accident, a break accident of the steam line  14   a , or the like, thereby maintaining the structural integrity of the containment building  11 . 
         [0035]    The passive containment building cooling system  100  proposed by the present disclosure may include a plate type heat exchanger  120 , and may further include an emergency fluid storage section  110  or coolant storage section  130  according to the characteristics of the nuclear power plant  10 . 
         [0036]    The emergency fluid storage section  110  is formed to store heat exchange fluid therein, and installed at an outside of the containment building  11 . The emergency fluid storage section  110  may include an opening portion  111  at an upper portion thereof to discharge heat transferred from atmosphere within the containment building  11  to an outside. 
         [0037]    When heat is transferred to the heat exchange fluid of the emergency fluid storage section  110  through heat exchange from atmosphere within the containment building  11 , the temperature of the heat exchange fluid increases. Furthermore, the temperature of the heat exchange fluid continuously increases while the heat transfer continues, and the heat exchange fluid evaporates. Steam formed by evaporating the heat exchange fluid is discharged to an outside through the opening portion  111  at an upper portion of the emergency fluid storage section  110 , and heat transferred from atmosphere within the containment building  11  by the evaporation of the heat exchange fluid is discharged to an outside by evaporation heat. 
         [0038]    The atmosphere within the containment building  11  transfers heat to the heat exchange fluid of the emergency fluid storage section  110 , and is cooled and compensated. Accordingly, a pressure increase within the containment building  11  may be suppressed. 
         [0039]    The plate type heat exchanger  120  exchanges heat between atmosphere within the containment building  11  and the heat exchange fluid of the emergency fluid storage section  110 . The plate type heat exchanger  120  may be installed at least one place of an inside and an outside of the containment building  11 , and it is illustrated in  FIG. 1  that the plate type heat exchanger  120  is installed in an atmosphere region within the containment building  11 . 
         [0040]    The plate type heat exchanger  120  may include channels arranged to be distinguished from one another at both sides of a plate between two fluids within the containment building  11  and emergency fluid storage section  110  from each other while maintaining a pressure boundary between an inside and an outside of the containment building  11  to allow the atmosphere of the containment building  11  to pass through a channel at one side and allow the heat exchange fluid of the emergency fluid storage section  110  to pass through a channel at the other side. The plate type heat exchanger  120  may be coupled to a casing  126  surrounding at least part of the plate type heat exchanger  120 . 
         [0041]    The plate type heat exchanger  120  should induce heat exchange without mixing two fluids to maintain a pressure boundary during the process of exchanging heat between the atmosphere of the containment building  11  and the heat exchange fluid of the emergency fluid storage section  110 . To this end, the channels of the plate type heat exchanger  120  may include an atmosphere flow path allowing atmosphere within the containment building  11  to pass therethrough and a fluid flow path for allowing the heat exchange fluid of the emergency fluid storage section  110  to pass therethrough. 
         [0042]    When the plate type heat exchanger  120  is installed within the containment building  11 , an inlet guide flow path section  121   a  for guiding the entrainment of atmosphere existing within the plate type heat exchanger  120  to the plate type heat exchanger  120  may be installed in an inlet region of the atmosphere flow path, and an outlet guide flow path section  121   b  for discharging atmosphere or condensate from the plate type heat exchanger  120  to an inside of the containment building  11  may be installed in an outlet region of the atmosphere flow path. The atmosphere within the containment building  11  is introduced into the plate type heat exchanger  120  through the inlet guide flow path section  121   a , and discharged to an inside of the containment building  11  again through the outlet guide flow path section  121   b.    
         [0043]    The emergency fluid storage section  110  requires a flow path that flows from an outside of the containment building  11  to an inside thereof to pass through the plate type heat exchanger  120 . Accordingly, the plate type heat exchanger  120  is connected to the emergency fluid storage section  110  by lines  123   a ,  123   b  passing through the containment building  11 . The lines  123   a ,  123   b  form a flow path for connecting the emergency fluid storage section  110  to the plate type heat exchanger  120 . 
         [0044]    Since the heat exchange fluid of the emergency fluid storage section  110  is collected to the emergency fluid storage section  110  again subsequent to passing through the channels of the plate type heat exchanger  120 , the plate type heat exchanger  120  may include an inlet header  122   a  and an outlet header  122   b  for this purpose. 
         [0045]    The inlet header  122   a  is installed in an inlet region of the fluid flow path to distribute heat exchange fluid supplied from the emergency fluid storage section  110  to each fluid flow path. Furthermore, the outlet header  122   b  is formed in an outlet region of the fluid flow path to collect heat exchange fluid that has passed through the fluid flow path to return to the emergency fluid storage section  110 . 
         [0046]    The atmosphere within the containment building  11  passing through the plate type heat exchanger  120  is introduced into an inlet of an upper end section of the plate type heat exchanger  120  and discharged to an outlet of a lower end section thereof, and the heat exchange fluid of the emergency fluid storage section  110  passing through the plate type heat exchanger  120  is introduced into an inlet of a lower end section of the plate type heat exchanger  120  and discharged to an outlet of an upper end section thereof. The atmosphere within the containment building  11  transfers heat to the heat exchange fluid of the emergency fluid storage section  110  while passing through the plate type heat exchanger  120 , and cools and condenses to descend, and the heat exchange fluid of the emergency fluid storage section  110  receives heat from the atmosphere to ascend while passing through the plate type heat exchanger  120 , and returns again to the emergency fluid storage section  110 . 
         [0047]    The temperature of the heat exchange fluid of the emergency fluid storage section  110  gradually increases by the heat exchange fluid returned to the emergency fluid storage section  110  from the plate type heat exchanger  120 , and the heat exchange fluid evaporates during a continuous temperature increase to discharge the transferred heat to an outside using evaporation heat. 
         [0048]    The plate type heat exchanger  120  is a passive facility in which a density difference induced from a temperature difference of the fluid is used as actuating power. Accordingly, as long as there exists actuating power due to an increase of atmosphere temperature and pressure within the containment building  11  during the occurrence of an accident, fluid circulation and heat transfer in the plate type heat exchanger  120  is continuously carried out. 
         [0049]    The lines  123   a ,  123   b  connected between the plate type heat exchanger  120  and emergency fluid storage section  110  pass through the containment building  11 , and isolation valves  124   a ,  124   b  are installed on the lines  123   a ,  123   b . The isolation valves  124   a ,  124   b  may maintain an open state both during a normal operation or the occurrence of an accident of the nuclear power plant  10 . However, when a pressure boundary of the containment building  11  is damaged while performing a maintenance work or when the passive containment building cooling system  100  is damaged due to the occurrence of an accident, the isolation valves  124   a ,  124   b  are closed by an actuating signal. The check valve  125  may be installed and is open due to a flow during the operation of the passive containment building cooling system  100  to prevent a reverse flow. 
         [0050]    The coolant storage section  130  is installed in a downward direction that is advantageous to collecting condensate formed by condensing atmosphere passing trough the plate type heat exchanger  120 . The coolant storage section  130  may maintain a state in which at least part of an upper section thereof is open. 
         [0051]    The coolant storage section  130  is connected to a safety injection line  15   a  to use the collected condensate for safety injection to the reactor coolant system  12 . The safety injection system  15  is a system for injection coolant into the reactor coolant system  12  to maintain a water level when a loss of coolant accident of the reactor coolant system  12  has occurred, and the safety injection line  15   a  is connected between the safety injection system  15  and the reactor coolant system  12 . 
         [0052]    The coolant storage section  130  is connected to the safety injection line  15   a  to perform a function of the safety injection system  15  during the second-half stage (the latter stage) of an accident in which coolant and condensate stored therein is injected into the reactor coolant system  12  during an accident. When an isolation valve  131  that is opened by an actuating signal during the occurrence of an accident and a check valve  132  that is opened by a flow are opened, and a pressure of the reactor coolant system  12  decreases lower than a water head of the coolant storage section  130  a check valve  132  is opened by a flow, the coolant stored in the coolant storage section  130  and the collected condensate can be injected into the reactor coolant system  12  through the safety injection line  15   a , similarly to other safety injection systems  15 . 
         [0053]    Steam discharged from the reactor coolant system  12  to an inside of the containment building  11  due to the occurrence of an accident is cooled and condensed through heat exchange in the plate type heat exchanger  120 , and collected into the coolant storage section  130 , and safely injected again into the reactor coolant system  12 . Accordingly, when the passive containment building cooling system  100  proposed by the present disclosure is used even though an accident such as a loss of coolant accident or the like occurs at the nuclear power plant  10 , it may be possible to suppress an increase of the temperature and pressure of the containment building  11  as well as continuously circulate coolant during the second-half stage (the latter stage) of the accident thereby maintaining a water level of the reactor coolant system  12  for a long period of time. 
         [0054]    The process of collecting condensate into the coolant storage section  130  may collect condensate freely falling from the plate type heat exchanger  120 , but as illustrated in the drawing, a condensate return line  140  may be installed in the plate type heat exchanger  120 . The condensate return line  140  is extended from the plate type heat exchanger  120  to the coolant storage section  130  to allow atmosphere within the containment building  11  to transfer heat from the plate type heat exchanger  120  to the heat exchange fluid and induce condensate formed by condensation to the coolant storage section  130 . 
         [0055]    The atmosphere that has passed the plate type heat exchanger  120  is condensed to form condensate, and the condensate may be collected into the coolant storage section  130  through the condensate return line  140 . 
         [0056]    According to the characteristics of the nuclear power plant  10 , it may be configured with a hybrid type plate type heat exchanger  220  operated in an air cooling manner during the second-half stage (the latter stage) in which the emergency fluid storage section  110  is exhausted. Furthermore, according to the characteristics of the nuclear power plant  10 , it may be configured with an air cooling type plate type heat exchanger  120  operated in an air cooling manner using atmosphere outside the containment building  11  when the emergency fluid storage section  110  is not installed in  FIG. 1 . In this case, the heat exchange fluid may include atmosphere outside the containment building  11 . The lines  123   a ,  123   b  may be extended to a space outside the containment building  11  through the containment building  11  to circulate atmosphere outside the containment building. 
         [0057]    Hereinafter, a passive containment building cooling system and a nuclear power plant including the same according to another embodiment will be described. 
         [0058]      FIG. 2  is a conceptual view illustrating a passive containment building cooling system  200  and a nuclear power plant  20  including the same associated with another embodiment of the present disclosure. 
         [0059]    The passive containment building cooling system  200  may include a plate type heat exchanger  220 , and may include an emergency fluid storage section  210  and a cooling water storage section  230  according to the characteristics of the nuclear power plant  20 . 
         [0060]    Contrary to the passive containment building cooling system  100  illustrated in  FIG. 1 , the plate type heat exchanger  220  of the passive containment building cooling system  200  illustrated in  FIG. 2  is installed within the emergency fluid storage section  210 . Atmosphere within a containment building  21  uses lines  223   a ,  223   b  connected between the containment building  21  and the plate type heat exchanger  220  through the containment building  21  and the emergency fluid storage section  210  as flow paths. 
         [0061]    When an accident occurs, atmosphere within the containment building  21  is introduced into the plate type heat exchanger  220  within the emergency fluid storage section  210  through the lines  223   a ,  223   b . In the plate type heat exchanger  220 , the atmosphere (specifically, steam contained in the atmosphere) that has transferred heat to heat exchange fluid is condensed to form condensate, and air is cooled and introduced again into the containment building  21  through the lines. Then, the air is discharged into the atmosphere within the containment building  21 , and the condensate freely falls down or is collected into a cooling water storage section  230  through a condensate return line  240 . 
         [0062]    An inlet guide flow path  221   a  is installed in an inlet region of the fluid flow path to induce heat exchange fluid within the emergency fluid storage section  210  to the plate type heat exchanger  220 . An outlet guide flow path  221   b  is installed in an outlet region of the fluid flow path to induce the discharge of heat exchange fluid from the plate type heat exchanger  220  to the emergency fluid storage section  210 . 
         [0063]    An inlet header  222   a  is installed in an inlet region of the atmosphere flow path to distribute atmosphere introduced from the containment building  21  to each channel, and an outlet header  222   b  is installed in an outlet region of the atmosphere flow path to collect the atmosphere or condensate that has passed through each channel to return to an inside of the containment building  21 . 
         [0064]    The inlet region of the fluid flow path and the outlet region of the atmosphere flow path may be a lower section of the plate type heat exchanger  220 , and the outlet region of the fluid flow path and the inlet region of the atmosphere flow path may be an upper section of the plate type heat exchanger  220 . 
         [0065]    The condensate return line  240  is branched from the line  223   b  passing through the containment building  21  and extended to the cooling water storage section  230 . 
         [0066]    According to the characteristics of the nuclear power plant  20 , it may be configured with a hybrid type plate type heat exchanger  220  operated in an air cooling manner during the second-half stage (the latter stage) in which the emergency fluid storage section  210  is exhausted. Furthermore, according to the characteristics of the nuclear power plant  20 , it may be configured with an air cooling type plate type heat exchanger  220  operated in an air cooling manner using atmosphere outside the containment building  21  when the emergency fluid storage section  210  is not installed in  FIG. 2 . 
         [0067]      FIG. 3  is a conceptual view illustrating a passive containment building cooling system  300  and a nuclear power plant  30  including the same associated with still another embodiment of the present disclosure. 
         [0068]    For the passive containment building cooling system  300  illustrated in  FIG. 3 , another plate type heat exchanger  320   a  is added to the passive containment building cooling system  100  illustrated in  FIG. 1 , and the configuration of lines  323   a ,  323   b ,  323   c  for circulating atmosphere and heat exchange fluid is different therefrom. 
         [0069]    A plate type heat exchanger  320  may include a first plate type heat exchanger  320   a  installed within a cooling water storage section  330  and a second plate type heat exchanger  320   b  installed in an atmospheric region within a containment building  31 . 
         [0070]    The first plate type heat exchanger  320   a  is formed in such a manner that at least part thereof is immersed in cooling water accommodated in the cooling water storage section  330 , and an inlet thereof is connected to the emergency fluid storage section  310  by the line  323   a  to receive heat exchange fluid from the emergency fluid storage section  310 . 
         [0071]    The second plate type heat exchanger  320   b  is formed in such a manner that an inlet thereof is connected to an outlet of the first plate type heat exchanger  320   a  by the line  323   b  to form a closed loop for circulating the heat exchange fluid of the emergency fluid storage section  310 , and an outlet thereof is connected to the emergency fluid storage section  310  by the line  323   c.    
         [0072]    The heat exchange fluid of the emergency fluid storage section  310  is introduced into the first plate type heat exchanger  320   a  from the emergency fluid storage section  310  to primarily exchange heat with condensate stored in the cooling water storage section  330 . At least part of an upper section of the cooling water storage section  330  is open, and therefore, the condensate stored in the cooling water storage section  330  is in a high-temperature state due to receiving heat from the atmosphere of the containment building  31  or introducing coolant at high temperature discharged from a reactor coolant system  32  when the temperature of the containment building  31  increases. Accordingly, the condensate stored in the cooling water storage section  330  is introduced to an upper section of the first plate type heat exchanger  320   a  and discharged to a lower section thereof to transfer heat to the heat exchange fluid supplied from the emergency fluid storage section  310 . 
         [0073]    The heat exchange fluid that has received heat from the first plate type heat exchanger  320   a  is introduced to the second plate type heat exchanger  320   b  through the line  323   b  connected between the first plate type heat exchanger  320   a  and the second plate type heat exchanger  320   b . The heat exchange fluid exchanges heat with the atmosphere of the containment building  31  passing through another channel from the second plate type heat exchanger  320   b  to receive heat, and is discharged to an upper section of the second plate type heat exchanger  320   b  and returned to the emergency fluid storage section  310  through the line  323   c  to continue circulation. 
         [0074]    According to the characteristics of the nuclear power plant  30 , it may be configured with a hybrid type plate type heat exchanger  320  operated in an air cooling manner during the second-half stage (the latter stage) in which the emergency fluid storage section  310  is exhausted. Furthermore, according to the characteristics of the nuclear power plant  30 , it may be configured with an air cooling type plate type heat exchanger  320  operated in an air cooling manner using atmosphere outside the containment building  31  when the emergency fluid storage section  310  is not installed in  FIG. 3 . 
         [0075]      FIG. 4  is a conceptual view illustrating a passive containment building cooling system  400  and a nuclear power plant  40  including the same associated with yet still another embodiment of the present disclosure. 
         [0076]    A plate type heat exchanger  420  is formed with a longer length than the height of the cooling water storage section  430  to be partially immersed in the cooling water storage section  430 . As illustrated in the drawing, a part of the plate type heat exchanger  420  is immersed in cooling water, and another part thereof is exposed to the atmosphere of a containment building  41 . 
         [0077]    The channels of the plate type heat exchanger  420  may include a cooling water flow path, a fluid flow path and an atmosphere flow path. The cooling water flow path is arranged at one side of a plate (a boundary surface) to allow the cooling water of the cooling water storage section  430  to pass therethrough, and the fluid flow path is arranged at the other side of the plate to allow the heat exchange fluid of the emergency fluid storage section  410 . The atmosphere flow path is started from an outlet region of the cooling water flow path subsequent to the cooling water flow path to allow atmosphere continuously transferring heat to the heat exchange fluid passing through the fluid flow path to pass therethrough. 
         [0078]    The heat exchange fluid introduced into the plate type heat exchanger  420  from the emergency fluid storage section  410  is primarily heated by the cooling water of the cooling water storage section  430  and secondarily heated by the atmosphere of the containment building  41 . 
         [0079]    In the above, the operation of the passive containment building cooling system due to natural circulation has been described, but in actuality when the plate type heat exchanger is applied to the passive containment building cooling system, problems such as flow instability in a two phase flow region, bottleneck phenomenon at a heat exchanger inlet, and the like may occur, and thus it is required to enhance them. Hereinafter, a structure of the plate type heat exchanger proposed by the present disclosure to enhance the problems will be described. 
         [0080]    The following description will be described without distinguishing a atmosphere flow path from a fluid flow path, and unless the description thereof is only limited to either one of the atmosphere flow path and the fluid flow path, the description of the atmosphere flow path will be also applicable to that of the fluid flow path, and the description of the fluid flow path will be also applicable to that of the atmosphere flow path. 
         [0081]      FIGS. 5 through 17  are flow path conceptual views illustrating a plate type heat exchanger  520  selectively applicable to the passive containment building cooling system  100 ,  200 ,  300 ,  400  in  FIGS. 1 through 4 . 
         [0082]    First, it is illustrated that channels  527  in  FIGS. 5 and 6  correspond to fluid flow paths and atmosphere flow paths, respectively, and the fluid flow path and atmosphere flow paths are both formed with closed flow paths. 
         [0083]    When a fabrication technique of a printed circuit type heat exchanger is applied to the plate type heat exchanger  520 , it has a structure capable of allowing a dense flow path arrangement by a photochemical etching technology and removing a welding between the plates of the heat exchanger using a diffusion bonding technology, and allows a typical plate type heat exchanger to have a dense flow path arrangement. The plate type heat exchanger  520  may include channels  527  distinguished from each other at both sides of a plate since heat exchange should be induced while exchanging heat between the atmosphere of the containment building and the heat exchange fluid of the emergency fluid storage section and maintaining a pressure boundary between an inside (atmosphere) and an outside (heat exchange fluid) of the containment building. Here, the atmosphere of the containment building may denote atmosphere within the containment building. 
         [0084]    The channels  527  may include an atmosphere flow path allowing atmosphere to pass therethrough and a fluid flow path allowing a heat exchange fluid to pass therethrough, and each channel  527  corresponds to either one of the atmosphere flow path and the fluid flow path. The atmosphere flow path is arranged at one side of a plate to allow atmosphere within the containment building to pass therethrough, and the fluid flow path is arranged at the other side of the plate to allow the heat exchange fluid of the emergency fluid storage section pass therethrough while maintaining a pressure boundary to the atmosphere flow path. 
         [0085]    The shape of the atmosphere flow path and fluid flow path may be a closed flow path in the shape of allowing atmosphere to pass therethrough only in one direction and allowing heat exchange fluid to pass therethrough only in a direction opposite to the one direction. Furthermore, the shape of the atmosphere flow path and fluid flow path may be also an open flow path in the shape of allowing atmosphere or heat exchange fluid to pass therethrough even in a direction crossing the one direction. 
         [0086]    The shape of the atmosphere flow path and fluid flow path may vary according to the installation location of the plate type heat exchanger  520 . The plate type heat exchanger  520  may be installed at least one place of an inside and an outside of the containment building. In particular, the closed flow path may be applicable regardless of the installation location of the plate type heat exchanger  520 , but the open flow path may be applicable in a restrictive manner to prevent the damage of a pressure boundary. 
         [0087]    When the plate type heat exchanger  520  is installed at an inside of the containment building, an open flow path may be applicable to the atmosphere flow path, but the open flow path may not be applicable to the fluid flow path due to the damage of a pressure boundary. On the contrary, when the plate type heat exchanger  520  is installed at an outside of the containment building such as the emergency fluid storage section, an open flow path may be applicable to the fluid flow path, but the open flow path may not be applicable to the atmosphere flow path due to the damage of a pressure boundary. 
         [0088]    Referring to  FIGS. 5 and 6 , all the flow paths of the plate type heat exchanger  520  illustrated in the drawings correspond to closed flow paths, wherein a conceptual view of  FIG. 5  illustrates a fluid flow path, and a conceptual view of  FIG. 6  illustrates an atmosphere flow path. The fluid flow path and atmosphere flow path are arranged at both sides of a plate on the basis thereof. Accordingly, a fluid flow path illustrated in  FIG. 5  corresponds to an opposite surface of an atmosphere flow path illustrated in  FIG. 6 . 
         [0089]    The plate type heat exchanger  520  may include an inlet region  528   a , an outlet region  528   b  and a main heat transfer region  528   c . The inlet region  528   a  is a region for distributing atmosphere or heat exchange fluid supplied to the plate type heat exchanger  520  to channels  527 , respectively, and the main heat transfer region  528   c  is a region for carrying out substantial heat exchange between atmosphere and heat exchange fluid, and the outlet region  528   b  is a region for collecting and discharging atmosphere or heat exchange fluid that has completed heat exchange from the channels  527 , respectively. The main heat transfer region  528   c  is connected between the inlet region  528   a  and the outlet region  528   b , and formed between the inlet region  528   a  and the outlet region  528   b.    
         [0090]    Referring to  FIG. 5 , since a temperature of the heat exchange fluid is lower than that of the atmosphere, the temperature thereof increases due to heat transferred from the atmosphere while the heat exchange fluid passes through the plate type heat exchanger  520 . On the contrary, referring to  FIG. 6 , since a temperature of the heat exchange fluid is higher than that of the atmosphere, the temperature thereof decreases due to cooling during which heat is transferred to the heat exchange fluid while the atmosphere passes through the plate type heat exchanger  520 . 
         [0091]      FIG. 7  is a conceptual view illustrating a fluid flow path of the plate type heat exchanger  520  including headers  522 ,  522   b  at an inlet and an outlet thereof. 
         [0092]    The plate type heat exchanger  520  may further include an inlet header  522   a  and an outlet header  522   b , and the channel  527  corresponds to a fluid flow path. 
         [0093]    The inlet header  522   a  is installed in an inlet region of a fluid flow path and connected to each fluid flow path to distribute heat exchange fluid supplied from the emergency fluid storage section. The outlet header  522   b  is installed in an outlet region of a fluid flow path and connected to each fluid flow path to collect heat exchange fluid that has passed through the fluid flow path and return to the emergency fluid storage section. 
         [0094]    When the plate type heat exchanger  520  is installed within the containment building, the heat exchange fluid of the emergency fluid storage section is supplied to the fluid flow path and supplied to the channels  527 , respectively, through the inlet header inlet header  522   a . Furthermore, the heat exchange fluid, the temperature of which is increased due to heat transferred from the main heat transfer region  528   c , is collected again through the outlet header  522   b  and moved to the emergency fluid storage section. 
         [0095]      FIGS. 8 and 9  are modified examples illustrating a fluid flow path of the plate type heat exchanger  520  having headers at an inlet and an outlet thereof. 
         [0096]    The installation location of the inlet header  522   a  and outlet header  522   b  may vary according to the design of the plate type heat exchanger  520 . In particular, when a fabrication technique of a printed circuit type heat exchanger is applied to the plate type heat exchanger  520 , it may be fabricated by a photochemical etching technology to freely select the structure of channels  527 , and a typical plate type heat exchanger may adopt a flow path pattern without restraint, and thus the location of the inlet header  522   a  and outlet header  522   b  may also vary. 
         [0097]      FIGS. 8 and 9  illustrate an example in which in particular, the inlet header  522   a  and outlet header  522   b  are installed at a lateral surface of the plate type heat exchanger  520 , respectively, and each channels  527  is bent in at least one region thereof or formed to have a curved flow path and extended to the inlet header  522   a  or outlet header  522   b.    
         [0098]    An extension direction of the channel  527  in the inlet region  528   a  and an extension direction of the channel  527  in the outlet region  528   b  may be the same direction as illustrated in  FIG. 8 , or may be opposite directions to each other, and vary according to the design of the passive containment building cooling system. 
         [0099]    Referring to  FIG. 10 , it may be provided with a plurality of inlet headers  522   a ′,  522   a ″ and outlet headers  522   b ′,  522   h ″ to induce an efficient flow of the fluid flow path. The plurality of inlet headers  522   a ′,  522   a ″ may be connected to different fluid flow paths to supply heat exchange fluid to the different fluid flow paths, respectively, and the plurality of outlet headers  522   b ′,  522   h ″ may be connected to different fluid flow paths to collect heat exchange fluid from the different fluid flow paths, respectively. 
         [0100]    When there are provided with a plurality of inlet headers  522   a ′,  522   a ″ and outlet headers  522   b ′,  522   b ″, a size thereof may be reduced compared to a single header, thereby efficiently supplying heat exchange fluid to the fluid flow paths. Accordingly, as a whole, it may be possible to induce efficient flow to the fluid flow paths. 
         [0101]    Referring to  FIG. 11 , the channels may be formed in such a manner that a flow resistance of the inlet region  528   a  is relatively larger than that of the main heat transfer region  528   c  connected between the inlet region  528   a  and the outlet region  528   b  to mitigate flow instability due to two phase flow. 
         [0102]    There may be various methods of forming a relatively large flow resistance, but the plate type heat exchanger  520  illustrated in  FIG. 11  employs a structure in which a flow path in the inlet region  528   a  is formed with a smaller width than that of the main heat transfer region  528   c  and has a flow path  527   a  longer than a straight flow path. 
         [0103]    The flow path  527   a  of the inlet region  528   a  is formed in a zigzag shape to have a relatively larger flow resistance than that of straight flow path and connected to the main heat transfer region  528   c . Specifically, it is formed in a shape in which the flow path  727   a  of the inlet region  528   a  is alternatively and repetitively connected in a length direction and a width direction of the plate type heat exchanger  520 , and extended to the main heat transfer region  528   c . As a flow resistance of the inlet region  528   a  is formed to be larger than that of the main heat transfer region  528   c , it may be possible to reduce a flow instability occurrence probability in two phase flow. 
         [0104]    A flow expansion section  527   b  is formed between the inlet region  528   a  and the main heat transfer region  528   c , and formed in such a manner that a width of the flow path gradually increases toward an extension direction from a flow path size of the inlet region  528   a  to a flow path size of the main heat transfer region  528   c . The flow resistance relatively decreases while passing the flow expansion section  527   b , and the relatively small flow resistance is maintained on the flow path  527   c  of the subsequent main heat transfer region  528   c  and outlet region  528   b.    
         [0105]    Referring to  FIG. 12 , a common header  529  connected between the inlet header  522   a  disposed at a lateral surface of the plate type heat exchanger  520  and each channel  527  of the inlet region  528   a  may be installed at the plate type heat exchanger  520 . 
         [0106]    The common header  529  is extended from one side section of the plate type heat exchanger and connected between the inlet header  522   a  and flow path  527  to uniformly distribute heat exchange fluid supplied from the emergency fluid storage section to the flow paths  527 . The common header  529  may uniformly distribute heat exchange fluid to the fluid flow paths to prevent an flow rate from being concentrated on any one fluid flow path, and overcome a problem of inlet flow instability. 
         [0107]    Referring to  FIG. 13 , it is illustrated a modified example capable of changing a direction of forming the fluid flow path and a location of the outlet header  522   b  to a lateral surface section of the plate type heat exchanger  520 . 
         [0108]    Referring to  FIG. 14 , it is illustrated a modified example in which an inlet guide flow path  521   a  and an outlet guide flow path  521   b  are installed at an inlet and an outlet of the plate type heat exchanger  520 , respectively. 
         [0109]    The inlet guide flow path  521   a  is installed at an inlet of the plate type heat exchanger  520  and protruded in an entrainment direction of atmosphere to induce the atmosphere within the containment building to the plate type heat exchanger  520 . Furthermore, the outlet guide flow path  521   b  is installed at an outlet of the plate type heat exchanger  520  and protruded in a discharge direction of atmosphere to guide the atmosphere discharged from the plate type heat exchanger  520  to an inside of the containment building. 
         [0110]    Referring to  FIG. 15 , it is illustrated a modified example capable of changing a direction of forming the atmosphere flow path, and a location of the inlet guide flow path  521   a  and outlet guide flow path  521   b  to a lateral surface section of the plate type heat exchanger  520 . The atmosphere flow path is bent in at least once in the inlet region and outlet region, respectively, or formed to have a curved flow path and extended to a lateral surface section of the plate type heat exchanger  520 . 
         [0111]      FIG. 16  is a flow path conceptual view illustrating the plate type heat exchanger  520  having an open flow path. 
         [0112]    The plate type heat exchanger  520  may include an open type flow path formed to introduce the atmosphere or the heat exchange fluid from a lateral surface to join atmosphere or heat exchange fluid passing through the channels so as to mitigate a bottleneck phenomenon at the inlet while maintaining a pressure boundary between the containment building and the emergency fluid storage section. 
         [0113]    The plate type heat exchanger  520  may include a first atmosphere flow path  527 ′ and a second atmosphere flow path  527 ″ for forming an open flow path. The first atmosphere flow path  527 ′ is connected between an inlet of an upper end section of the plate type heat exchanger  520  and an outlet of a lower end section thereof. The second atmosphere flow path  527 ″ is formed to flow the atmosphere in or out through an inlet and an outlet formed at both side sections of the plate type heat exchanger  520  and configured to form a count flow with the first atmosphere flow path  527 ′ so as to mitigate a bottleneck phenomenon of the inlet. 
         [0114]    Hereinafter, a structure of coupling a plurality of plate type heat exchangers as a scheme of mitigating a bottleneck phenomenon at an inlet of the plate type heat exchanger will be described. 
         [0115]      FIG. 17  is a conceptual view illustrating a passive containment building cooling system  600  and a nuclear power plant  60  including the same associated with still yet another embodiment of the present disclosure. 
         [0116]    A plurality of plate type heat exchangers  620  may be provided to mitigate a bottleneck phenomenon of the inlet. The plurality of plate type heat exchangers  620  may be arranged in parallel to an inside or outside of the containment building  61 . A bottleneck phenomenon that can occur due to a small inlet of the plate type heat exchanger  620  may be mitigated by increasing a number of plate type heat exchangers  620  and using an intermediate flow path between the plate type heat exchangers  620  as an atmosphere flow path at the same time. 
         [0117]    A casing  626  is formed to surround at least part of the plate type heat exchanger  620 , and a cooling fin  626 ′ is formed to surround at least part of the casing  626  to expand a heat transfer area thereof. The cooling fin  626 ′ may enhance a cooling efficiency of the atmosphere. 
         [0118]    An inlet connection line  623   a ′ is connected to the inlet headers  622   a  to distribute heat exchange fluid supplied from an emergency fluid storage section  610  to an inlet header  622   a  provided in each plate type heat exchanger  620 . An outlet connection line  623   b ′ is connected to an outlet header  622   b  for each outlet of the plate type heat exchanger  620  to collect the heat exchange fluid that has passed through each plate type heat exchanger  620  and return to the emergency fluid storage section  610 . 
         [0119]    Other configurations other than mitigating a bottleneck phenomenon of the inlet due to a plurality of plate type heat exchangers  620  provided therein have been described in  FIG. 1 . 
         [0120]      FIG. 18  is a conceptual view illustrating a passive containment building cooling system  700  and a nuclear power plant  70  including the same associated with yet still another embodiment of the present disclosure. 
         [0121]    The passive containment building cooling system  700  illustrated in  FIG. 18  is a modified exampled of the passive containment building cooling system  600  illustrated in  FIG. 17 . As illustrated in  FIG. 17 , the passive containment building cooling system  700  in  FIG. 18  is also provided with a plurality of plate type heat exchangers  720  to mitigate a bottleneck phenomenon at the inlet. 
         [0122]    The installation location of the plate type heat exchangers  720  may be an atmosphere region within the containment building  71 , and a cooling water storage section  730  for collecting condensate is installed at a lower section of the plurality of plate type heat exchangers  720 , respectively. 
         [0123]      FIG. 19  is a conceptual view illustrating a plurality of plate type heat exchangers  820  selectively applicable to the passive containment building cooling system  600 ,  700  in  FIGS. 17 and 18 . 
         [0124]      FIGS. 19A, 19B, 19C and 19D  illustrate a plan view, a left side view, a front view, and a right side view of the plurality of plate type heat exchangers  820 , respectively. The plate type heat exchangers  820  is surrounded by a casing  826 , respectively, and a cooling fin  826 ′ is installed at the casing  8826 . 
         [0125]    The heat exchange fluid supplied from the emergency fluid storage section is distributed to each plate type heat exchanger  820  through an inlet connection line  823   a ′, and the heat exchange fluids that have passed the plate type heat exchanger  820  is joined at an outlet connection line  823   b ′ and returned again to the emergency fluid storage section. The heat exchange fluid continuously cools atmosphere within the containment building and suppresses a pressure increase within the containment building while circulating the emergency fluid storage section and plate type heat exchanger  820 . 
         [0126]      FIG. 20  is a layout conceptual view illustrating a plurality of plate type heat exchangers  820  illustrated in  FIG. 19 . 
         [0127]    Referring to  FIG. 20A , a plurality of plate type heat exchangers  820  may be disposed to be separated from one another to correspond to a curved shape of the containment building  81 . 
         [0128]    Referring to  FIG. 20B , a plurality of plate type heat exchangers  820  may be formed in a rectangular shape and arranged in one column. 
         [0129]    Referring to  FIG. 20C , a plurality of plate type heat exchangers  820  may be formed in a cubic shape and arranged in vertical and horizontal directions. 
         [0130]    Referring to  FIG. 20D , a plurality of plate type heat exchangers  820  may be arranged in an inclined manner to a side wall of the containment building  81 . 
         [0131]    Referring to  FIG. 20E , a plurality of plate type heat exchangers  820  may be arranged in parallel to a side wall of the containment building  81 . 
         [0132]    The configurations and methods according to the above-described embodiments will not be applicable in a limited way to the foregoing passive containment building cooling system and a nuclear power plant including the same, and all or part of each embodiment may be selectively combined and configured to make various modifications thereto. 
         [0133]    The present disclosure may be used to enhance the performance of a passive containment building cooling system in the nuclear power plant industry.