JP5586213B2 - Emergency core cooling system - Google Patents

Description

  The present invention relates to an emergency core cooling apparatus, and more particularly, to an emergency core cooling apparatus suitable for application to a boiling water reactor.

  A nuclear power plant such as a boiling water nuclear power plant includes a multiple safety system having an emergency power supply such as an emergency core cooling system and an emergency diesel generator (hereinafter referred to as an emergency DG). Due to this safety system multiplexing, when a loss of coolant accident (LOCA) occurs due to a pipe break connected to the reactor pressure vessel, even if a failure occurs in equipment included in one safety system, it remains. It is possible to safely cool and shut down the nuclear power plant with this safety system. For example, in the advanced boiling water reactor (ABWR), there are three types of safety systems with a high-pressure water injection system, a low-pressure water injection system with a residual heat removal system, and their emergency DGs. It has been. By providing a safety system of three sections, one emergency DG fails and the cooling system in the safety system of one section including this emergency DG becomes inoperative, and among the remaining two sections, Even if the piping breaks in either the high pressure injection system or the low pressure injection system of the emergency core cooling system included in the safety system of one category, the reactor core can be cooled with the remaining sound safety system it can. An example of an emergency core cooling apparatus having a safety system of three sections is described in Japanese Patent Application Laid-Open No. 62-217193 (see FIG. 2).

  In order to improve the operation rate of the nuclear power plant, inspection and maintenance of the equipment provided in the safety system of the emergency core cooling system is performed during operation of the nuclear power plant, and the periodic inspection period to be performed while the nuclear power plant is shut down is shortened Applying online maintenance is being considered. In the emergency core cooling device, it is necessary to keep the safety system necessary for cooling the core and the containment vessel in a standby state so that the safety system can be operated when LOCA occurs. Even when online maintenance is performed for a safety system of one category in the emergency core cooling device, at least one safety system must be operated when LOCA occurs during online maintenance. For this reason, an emergency core cooling apparatus has been proposed that has one more safety system and four safety systems.

  In an emergency core cooling system with a 4-section safety system, the emergency DG fails in the 1-section safety system, the pipe breaks in the other 1-section safety system, and the other 1-section safety system Even if online maintenance is performed and the three-section safety system is in an inoperable state, the reactor core can be cooled by the remaining one-section safety system when LOCA occurs.

  An example of an emergency core cooling apparatus that is provided with a 4-section safety system and enables on-line maintenance is proposed in Japanese Patent Laid-Open No. 2008-281426. The emergency core cooling device described in Japanese Patent Application Laid-Open No. 2008-281426 includes a three-section dynamic safety system and a one-section static safety system.

  In a boiling water nuclear power plant, it has been proposed to use a normal reactor purification system as an emergency cooling system for injecting cooling water into the reactor core during LOCA (Japanese Patent Laid-Open No. 6-160586). JP-A-7-318687 and JP-A-8-62373). In Japanese Patent Laid-Open No. 6-160586, a pressure suppression pool is connected to a purification system pipe between a non-regenerative heat exchanger of a nuclear reactor purification system and a filtration demineralizer to diversify water sources. When LOCA occurs, cooling water in the pressure suppression pool is supplied to the reactor core through the purification system piping of the reactor purification system.

  In JP-A-7-318687 and JP-A-8-62373, when LOCA occurs, the cooling water in the pressure suppression pool is cooled by the non-regenerative heat exchanger of the reactor purification system, and then the reactor Supplied to the reactor core through the purification system piping.

JP 62-217193 A JP 2008-281426 A JP-A-6-160586 JP-A-7-318687 JP-A-8-62373

  The emergency core cooling device described in Japanese Patent Application Laid-Open No. 2008-281426 has four sections of safety systems, and it is necessary to increase one section of safety systems (static safety systems) in order to perform online maintenance. is there. For this reason, the system configuration of the nuclear power plant is increasing in size. In addition, Japanese Patent Laid-Open Nos. 6-160586, 7-318687, and 8-62373 do not mention online maintenance of the emergency core cooling device.

  The objective of this invention is providing the emergency core cooling device which can simplify the system configuration | structure of a nuclear power plant and can implement on-line maintenance.

In order to achieve the above-described object, the present invention is characterized by a three-section safety system having a high-pressure core water injection system, a low-pressure water injection system, and an emergency power supply device,
A purification system pipe connected to the reactor pressure vessel, a cooling device provided in the purification system pipe, a second pump and a purification device, and a first on-off valve are installed to connect the pressure suppression pool and the purification system piping to the cooling system. The cooling water pipe connected upstream, the second on-off valve provided in the purification system pipe upstream of the connection point between the purification system pipe and the cooling water pipe, and both ends connected to the purification system pipe bypassing the purification device A reactor purification system having a bypass pipe;
A first switching device having a first terminal and a second terminal connected to the service bus and connecting the second pump to either the first terminal or the second terminal, and the emergency of each of the three safety systems An emergency power supply device having three third terminals separately connected to the power supply device, and connecting the second terminal to one of the third terminals and connecting the second terminal to the second terminal A power switching device having a second switching device for switching between,
And a control device that performs switching control of the first switching device and the second switching device.

  Since the reactor purification system and the power supply switching device are provided, when a coolant loss accident occurs while online maintenance is being performed for one safety system among the three safety systems, etc. Even if the safety system of the two categories does not work for some reason, the reactor cleaning system is used as one safety system, and the second pump provided in the reactor cleaning system is subjected to online maintenance. The cooling water in the pressure suppression pool can be cooled and poured into the reactor pressure vessel by the cooling device provided in the reactor purification system, driven by the power from the emergency power supply device in the section. Since the nuclear reactor purification system is also used as one safety system, it is not necessary to provide a new safety system in preparation for online maintenance, so the system configuration of the nuclear power plant can be simplified. In addition, assuming that the safety system of the two categories does not operate for some reason in the event of a coolant loss accident, it is equipped with a safety system of one category that is also used as a reactor purification system. Online maintenance for safety systems can be performed. This contributes to improving the operating rate of the nuclear power plant.

  According to the present invention, the system configuration of a nuclear power plant can be simplified, and online maintenance of an emergency core cooling device can be performed.

1 is a configuration diagram of one safety system that is also used as a reactor purification system of an emergency core cooling apparatus according to embodiment 1, which is a preferred embodiment of the present invention. FIG. It is a block diagram of each safety system of other 3 divisions in the emergency core cooling device of Example 1. FIG. It is explanatory drawing which shows the outline | summary of the four safety systems in the emergency core cooling device of Example 1. FIG. When a coolant loss accident occurs when one section of the high pressure water injection system is broken and online maintenance is being performed on the other one section of the low pressure water injection system, the elapsed time after the coolant loss accident and the It is a characteristic view which shows a water level and a relationship. When a coolant loss accident occurs when one section of the low-pressure water injection system breaks down and online maintenance is performed in the other one section of the low-pressure water injection system, the elapsed time after the coolant loss accident and the It is a characteristic view which shows a water level and a relationship. It is a block diagram of one safety system used also as a nuclear reactor purification | cleaning system of the emergency core cooling device of Example 2 which is another Example of this invention. It is a block diagram of one safety system used also as a nuclear reactor purification | cleaning system of the emergency core cooling device of Example 3 which is another Example of this invention.

  Examples of the present invention will be described below.

  An emergency core cooling apparatus according to embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS. First, the configuration of a boiling water nuclear power plant to which the emergency core cooling apparatus 14 of the present embodiment is applied will be described with reference to FIGS. 1 and 2.

  In the boiling water nuclear power plant, the nuclear reactor is disposed in the reactor containment vessel 6. As shown in FIG. 2, the nuclear reactor includes a reactor pressure vessel 1, a core 2, a core shroud 3, and a plurality of internal pumps 5. A reactor core 2 loaded with a plurality of fuel assemblies (not shown) is disposed in the reactor pressure vessel 1. The core 2 is surrounded by a core shroud 3 installed in the reactor pressure vessel 1. An annular downcomer 4 is formed between the reactor pressure vessel 1 and the core shroud 3. A plurality of internal pumps 5 are installed at the bottom of the reactor pressure vessel 1, and an impeller (not shown) of each internal pump 5 is arranged in the downcomer 4.

  The reactor pressure vessel 1 is disposed in a dry well 7 in the reactor containment vessel 6 and supported by a pedestal (not shown) installed in the reactor containment vessel 6. An annular pressure suppression chamber 8 which is a wet well is disposed surrounding the pedestal. A pressure suppression pool 9 filled with cooling water is formed in the pressure suppression chamber 8. The dry well 7 and the pressure suppression chamber 8 are isolated from each other. The upper ends of the plurality of vent passages 32 provided in the reactor containment vessel 6 are opened to the dry well 7, and the lower ends of the vent passages 32 are opened to the water in the pressure suppression pool 9.

  A main steam pipe 10 provided with isolation valves 11 </ b> A and 11 </ b> B is connected to the reactor pressure vessel 1. A water supply pipe 12A provided with isolation valves 13A and 13B and a water supply pipe 12B provided with isolation valves 13C and 13D are connected to the reactor pressure vessel 1, respectively. Isolation valves 11 </ b> A, 13 </ b> A, and 13 </ b> C are disposed outside the reactor containment vessel 6, and isolation valves 11 </ b> B, 13 </ b> B, and 13 </ b> D are disposed in the dry well 7 in the reactor containment vessel 6.

  The boiling water nuclear power plant includes a nuclear reactor purification system 15. The reactor purification system 15 includes a purification system pipe (first pipe) 16, a regenerative heat exchanger 17, non-regenerative heat exchangers 17A and 17B, purification system pumps 19A and 19B, and filtration desalters (purification devices) 20A and 20B. Have A regenerative heat exchanger 17, non-regenerative heat exchangers 17 A and 17 B, purification system pumps 19 A and 19 B, and filtration demineralizers (purification devices) 20 A and 20 B are provided in the purification system pipe 16. The purification system pipe 16 has one end connected to the reactor pressure vessel 1 and the other end connected to the water supply pipe 12A. An isolation valve 21A disposed in the dry well 7 and an isolation valve 21B disposed outside the reactor containment vessel 6 are provided in the purification system pipe 16. A regenerative heat exchanger 17 is disposed downstream of the isolation valve 21B. The non-regenerative heat exchanger 17A connected to the auxiliary machine cooling system 18A and the non-regenerative heat exchanger 17B connected to the auxiliary machine cooling system 18B are provided in the purification system pipe 16 so as to be parallel to each other. And it arrange | positions downstream of the regenerative heat exchanger 17.

  The purification system pumps 19A and 19B located downstream of the non-regenerative heat exchangers 17A and 17B are also provided in the purification system pipe 16 so as to be parallel to each other. Filtration demineralizers 20A and 20B located downstream of the purification system pumps 19A and 19B are provided in the purification system pipe 16 so as to be parallel to each other. An on-off valve 26 is provided in the purification system pipe 16 between the purification system pumps 19A and 19B and the filtration demineralizers 20A and 20B. Both ends of a bypass pipe 27 that bypasses the on-off valve 26 and the filtration demineralizers 20 </ b> A and 20 </ b> B are connected to the purification system pipe 16. An on-off valve 28 is provided in the bypass pipe 27.

  A purification system pipe 16 on the downstream side of the filtration desalters 20 </ b> A and 20 </ b> B is connected to the regenerative heat exchanger 17. An on-off valve 29 is provided in the purification system pipe 16 between the connection point of the bypass pipe 27 and the purification system pipe 16 and the regenerative heat exchanger 17 on the downstream side of the filtration desalters 20A and 20B. A bypass pipe 30 that bypasses the on-off valve 29 and the regenerative heat exchanger 17 downstream of the filtration desalters 20A and 20B is connected to the purification system pipe 16. An on-off valve 31 is provided in the bypass pipe 30.

  A cooling water pipe (second pipe) 22 provided with an on-off valve 25 is connected to a water intake 23 arranged in the cooling water in the pressure suppression pool 3, and further between the isolation valve 21 </ b> B and the regenerative heat exchanger 17. To the purification system pipe 16. A pipe 24 provided with the on-off valve 25B is juxtaposed with the on-off valve 25A and connected to the cooling water pipe 22.

  As shown in FIG. 3, the emergency core cooling device 14 of the present embodiment includes a safety system 33 of section I, a safety system 49 of section II, a safety system 67 of section III, and a safety system 95 of section IV. . The safety system 95 of Category IV includes the cooling water pipe 22, the purification system pipe 16, the non-regenerative heat exchangers 17A and 17B, the purification system pumps 19A and 19B, and the bypass pipe 27 of the reactor purification system 15 shown in FIG. , 30. Specific configurations of the safety systems 33, 49, and 67 will be described below with reference to FIG.

  The safety system 33 is a dynamic safety system, an isolation cooling system (hereinafter referred to as RCIC) 34, which is a high pressure core water injection system, a low pressure water injection system (hereinafter referred to as LPFL) 41, and an emergency DG (emergency power supply device). 48. The RCIC 34 has a water injection pump 36 and an RCIC pipe 35. The RCIC pipe 35 connects the water intake 38 disposed in the cooling water of the pressure suppression pool 9 and the water supply pipe 12A. A water injection pump 36 is provided in the RCIC pipe 35, and a rotation shaft of the turbine 37 is connected to a rotation shaft of the water injection pump 36. A valve 39 is provided in the RCIC pipe 35 upstream of the water injection pump 36, and a valve 40 is provided in the RCIC pipe 35 downstream of the water injection pump 36.

  The LPFL 41 includes an LPFL pipe 42, a motor-driven water injection pump 43, and a heat exchanger (cooling device) 44. An LPFL pipe 42 connects the water intake 27 disposed in the cooling water of the pressure suppression pool 9 and the water supply pipe 12B. A heat exchanger 44 connected to the water injection pump 43 and the auxiliary machine cooling system 45 is provided in the LPFL pipe 42, and the heat exchanger 44 is disposed downstream of the water injection pump 43. A valve 46 is provided in the LPFL pipe 42 upstream of the water injection pump 43, and a valve 47 is provided in the LPFL pipe 42 downstream of the heat exchanger 44.

  An emergency DG 48 is connected to each motor (not shown) of the water injection pump 43 and the pump (not shown) of the auxiliary machine cooling system 45.

  The safety system 49 is a dynamic safety system, and includes a high-pressure core water injection system (hereinafter referred to as HPCF) 50, LPFL 57, and emergency DG 66. The HPCF 50 includes a motor-driven water injection pump 52 and an HPCF pipe 51. The HPCF pipe 51 is connected to a water intake 53 arranged in the cooling water of the pressure suppression pool 9. The HPCF pipe 51 penetrates the reactor pressure vessel 1, and the water outlet 56 of the HPCF pipe 51 is disposed above the core 2 and inside the core shroud 3. A water injection pump 52 is provided in the HPCF pipe 51. The valve 54 is provided in the HPCF piping 51 upstream of the water injection pump 52, and the valves 55 </ b> A and 55 </ b> B are provided in the HPCF piping 51 downstream of the water injection pump 52. The valve 55 </ b> A is disposed outside the reactor containment vessel 6, and the valve 55 </ b> B is disposed in the dry well 7.

  The LPFL 57 includes an LPFL pipe 58, a motor-driven water injection pump 59, and a heat exchanger (cooling device) 60. An LPFL pipe 58 is connected to a water intake 62 disposed in the cooling water of the pressure suppression pool 9. An LPFL pipe 58 passes through the reactor pressure vessel 1, and a water outlet 65 of the LPFL pipe 58 is disposed in the downcomer 4. A heat exchanger 60 connected to the water injection pump 59 and the auxiliary machine cooling system 61 is provided in the LPFL pipe 58, and the heat exchanger 60 is disposed downstream of the water injection pump 59. A valve 63 is provided in the LPFL pipe 58 upstream of the water injection pump 59, and valves 64 A and 64 B are provided in the LPFL pipe 58 downstream of the heat exchanger 60. The valve 64 </ b> A is disposed outside the reactor containment vessel 6, and the valve 64 </ b> B is disposed in the dry well 7.

  An emergency DG 66 is connected to each motor (not shown) of the water injection pumps 52 and 59 and the pump (not shown) of the auxiliary machine cooling system 61.

  The safety system 67 is a dynamic safety system and includes HPCF 68, LPFL 75, and emergency DG84. The HPCF 68 includes a motor-driven water injection pump 70 and an HPCF pipe 69. An HPCF pipe 69 is connected to a water intake 71 disposed in the cooling water of the pressure suppression pool 9. The HPCF pipe 69 penetrates the reactor pressure vessel 1, and the water outlet 74 of the HPCF pipe 69 is disposed above the core 2 and inside the core shroud 3. A water injection pump 70 is provided in the HPCF pipe 69. The valve 72 is provided in the HPCF pipe 69 upstream of the water injection pump 70, and the valves 73 </ b> A and 73 </ b> B are provided in the HPCF pipe 69 downstream of the water injection pump 70. The valve 73 </ b> A is disposed outside the reactor containment vessel 6, and the valve 73 </ b> B is disposed in the dry well 7.

  The LPFL 75 includes an LPFL pipe 76, a water pump 77 driven by a motor, and a heat exchanger (cooling device) 78. An LPFL pipe 76 is connected to a water intake 80 disposed in the cooling water of the pressure suppression pool 9. An LPFL pipe 76 penetrates the reactor pressure vessel 1, and a water outlet 83 of the LPFL pipe 76 is disposed in the downcomer 4. A heat exchanger 78 connected to the water injection pump 77 and the auxiliary machine cooling system 79 is provided in the LPFL pipe 76, and the heat exchanger 78 is arranged downstream of the water injection pump 77. A valve 81 is provided in the LPFL pipe 76 upstream of the water injection pump 77, and valves 82 A and 82 B are provided in the LPFL pipe 76 downstream of the heat exchanger 78. The valve 82 </ b> A is disposed outside the reactor containment vessel 6, and the valve 82 </ b> B is disposed in the dry well 7.

  An emergency DG 84 is connected to each motor (not shown) of the water injection pumps 70 and 77 and the pump (not shown) of the auxiliary machine cooling system 79.

  The emergency core cooling device 14 is provided with a power supply switching device 96. The power switching device 96 includes a first switching device 86 and a second switching device 90. The first switching device 86 has a movable terminal 87 and fixed terminals 88 and 89. The second switching device 90 has a movable terminal 91 and fixed terminals 92, 93, 94. The movable terminal 87 is connected to the service bus 85 of the in-house power source. The fixed terminal 88 is connected to the service bus 85 of the in-house power supply, and the fixed terminal 89 is connected to the movable terminal 91 of the second switching device 90. Fixed terminal 92 is connected to emergency DG 48, fixed terminal 93 is connected to emergency DG 66, and fixed terminal 94 is connected to emergency DG 84.

  During normal operation of the boiling water nuclear power plant, the valves 40, 47, 55A, 55B, 64A, 64B, 73A, 73B, 82A and 82B of the safety systems 33, 49 and 67 are closed and the valves 39, 46 and 54 are closed. 63, 72, and 81 are open. The on-off valves 25A, 25B, 28, 31 of the reactor purification system 15 and the safety system 95 are closed, and the isolation valves 11A, 11B of the main steam pipe 10 and the isolation valves 13A, 13B, 13C, 13D of the water supply pipe are opened. Yes. Isolation valves 21A and 21B and valves 26 and 29 of the reactor purification system 15 are open.

  By driving the internal pump 5, the cooling water of the downcomer 4 is boosted and supplied to the reactor core 2. The cooling water flowing into the core 2 is heated by the heat generated by the nuclear fission of the nuclear fuel material in the fuel assembly, and a part thereof becomes steam. A gas-liquid two-phase flow containing steam and cooling water is guided to a steam / water separator (not shown) disposed above the core 2 to separate the steam and cooling water. Moisture is removed from the separated steam by a steam dryer (not shown) installed in the reactor pressure vessel 1 above the steam separator, and the turbine is passed through the main steam pipe 10 (not shown). ). The turbine is rotated by steam, and a generator (not shown) connected to the turbine is also rotated to generate power.

  The steam exhausted from the turbine is condensed into water by a condenser (not shown). This water is supplied into the reactor pressure vessel 1 through the water supply pipes 12A and 12B as water supply. The cooling water separated by the steam separator is lowered together with the water supply in the downcomer 4 and is pressurized by the internal pump 5.

  During normal operation of the boiling water nuclear power plant, the cooling water in the reactor pressure vessel 1 is purified by the filtration demineralizers 20A and 20B of the reactor purification system 15. Both (or one) of the purification system pumps 19A and 19B are driven. Since the purification system pump is driven, the cooling water in the reactor pressure vessel 1 flows into the purification system pipe 16. This cooling water is cooled by the regenerative heat exchanger 17 and further cooled by both (or one) of the non-regenerative heat exchangers 17A and 17B.

  Cooling water whose pressure is increased by the purification system pump 19A and having a temperature of 100 ° C. or less is supplied to the filtration desalters 20A and 20B. The filtration desalters 20A and 20B remove solids such as cladding and ions such as cations contained in the cooling water. The cooling water purified by the filtration demineralizers 20A and 20B is heated by the high-temperature cooling water that has passed through the isolation valves 21A and 21B in the regenerative heat exchanger 17, and the temperature rises. The cooling water whose temperature has increased in the regenerative heat exchanger 17 is returned into the reactor pressure vessel 1 through the purification system pipe 16 and the water supply pipe 12A.

  During normal operation of the boiling water nuclear power plant, as shown in FIG. 3, on-line maintenance is performed on the LPFL 75 of the safety system 67 in Section III. It is assumed that during this online maintenance, the main steam pipe 10 is broken in the reactor containment vessel 6 upstream of the isolation valve 11B (or a crack penetrating the main steam pipe 10 is generated), and LOCA is generated. The high-temperature steam discharged from the breakage point of the main steam pipe 10 to the dry well 7 is discharged into the cooling water of the pressure suppression pool 9 through the plurality of vent passages 32 and condensed. As a result, the pressure increase in the dry well 7 is suppressed.

  However, the cooling water in the reactor pressure vessel 1 becomes steam and is discharged into the dry well 7 from the broken portion of the main steam pipe 10. For this reason, the level of the cooling water in the reactor pressure vessel 1 may be lowered, and the fuel assembly in the core 2 may be exposed. In order to avoid this situation, the emergency core cooling device 14 is operated, and the cooling water in the pressure suppression pool 9 is supplied into the reactor pressure vessel 1 to flood the core 2.

  When LOCA occurs, all control rods (not shown) provided in the reactor pressure vessel 1 are fully inserted into the reactor core 2 and the reactor is scrammed. Thereby, the operation of the boiling water nuclear plant is stopped. The isolation valves 11A, 11B, 13A, 13B, 13C, and 13D are closed by the occurrence of LOCA. Power generation by this boiling water nuclear power plant is stopped. When LOCA occurs, the RCIC 34 is first activated. High-pressure steam in the reactor pressure vessel 1 is supplied to the turbine 37 through a pipe (not shown). The turbine 37 is driven by steam and rotates the water injection pump 36. The valve 40 is opened simultaneously with the start of supply of steam to the turbine 37. Cooling water in the pressure suppression pool 9 flows into the RCIC pipe 35 from the water intake 38 and is pressurized by the water injection pump 36. High-pressure cooling water discharged from the water injection pump 36 is supplied into the reactor pressure vessel 1 through the RCIC pipe 35 and the water supply pipe 12A. In the RCIC 34, the water injection pump 36 is rotated not by the electric power generated by driving the emergency DG but by the turbine 37 driven by the high-pressure steam in the reactor pressure vessel 1, so that the high-pressure cooling is performed simultaneously with the generation of LOCA. Water can be supplied into the reactor pressure vessel 1 having a high pressure, and the flooding of the core 2 is maintained.

  Furthermore, simultaneously with the occurrence of LOCA, the power supply of an electric water injection pump or the like provided in the safety system is switched to the emergency DG, and an activation signal is transmitted to the safety water injection pump. Thereby, the water injection from the sound safety system to the core is continued, and the flooding of the core 2 is maintained for a long time.

  The boiling water nuclear power plant is provided with an automatic decompression system (ADS). The ADS is configured by providing a relief safety valve in each main steam pipe (for example, four main steam pipes) 10 and connecting a steam exhaust pipe extending into the cooling water of the pressure suppression pool 9 to each relief safety valve. When LOCA occurs and the isolation valves 11A and 11B are closed and the pressure in the reactor pressure vessel 1 rises to the set pressure, the relief safety valve opens, and the steam in the reactor pressure vessel 1 becomes the relief safety valve and steam exhaust. It is discharged into the cooling water of the pressure suppression pool 9 through the pipe and condensed. Thereby, the pressure rise in the reactor pressure vessel 1 is suppressed.

  When the LOCA occurs in the state where the online maintenance is being performed on the LPFL 75 of the safety system 67 of the category III, the emergency DG 66 of the safety system 49 of the category II has failed, and the LPFL 41 of the safety system 33 of the category I has failed. Suppose that the LPFL pipe 42 of this is broken. For this reason, when the LOCA occurs, the safety systems 33, 49, and 67 cannot sufficiently function, so that the cooling water is poured into the reactor pressure vessel 1 by the safety system 95. The cooling water is poured into the reactor pressure vessel 1 by the safety system 95 as follows.

  When performing online maintenance on the LPFL 75 of the safety system 67 of Section III, the electrical load such as the water injection pump of the safety system is disconnected from the emergency DG 84, and the second switching device 90 is manually operated. Switch to the emergency DG 84 side that covers the safety system 67. As a result, during online maintenance, the safety system 95 that is also used as the purification system shown in the section IV is covered with the emergency DG 84. This switching is performed manually before online maintenance. The other emergency DG is in a state before the second switching device 90 is switched, that is, in a state where it is connected only to a water injection pump or the like of each exclusive section.

  The control device 97 activates the emergency DGs 48, 66, 84 based on the LOCA signal input when the LOCA is generated, and disconnects the movable terminal 87 from the fixed terminal 88 and connects it to the fixed terminal 86. The first switching device 86 switches from the in-house power supply 85 side to the emergency DG 84 side. By this operation, at the time of LOCA, the safety system 95 shared with the section IV purification system can be activated simultaneously with other safety systems as an alternative to the system that is performing online maintenance. For example, even if online maintenance is performed on the LPFL 75 of the safety system 67, the alternative water injection and cooling functions can be maintained by the safety system 95. It is assumed that when the LOCA occurs, online maintenance is performed on the LPFL 75 in the safety system 67 of section III, the emergency DG 66 fails in the safety system 49, and the LPFL pipe 42 is broken in the safety system 33. . In this state, when LOCA occurs, the safety system 95 is driven by the emergency DG 84 as an alternative to the safety system 67 performing online maintenance, and there is no reduction in the number of systems that can be operated.

  During LOCA, the in-house power supply cannot be used due to the shutdown of the boiling water nuclear power plant, but the electric power generated by driving the emergency DG 84 by the switching operation of the first switching device 86 by the control device 97 described above is purified. The pumps 19A and 19B and auxiliary motor cooling systems 18A and 18B are supplied to respective motors that drive the pumps. These pumps are driven. When starting the switching operation of the first switching device 86, the control device 97 closes the isolation valves 21A and 21B and the valves 26 and 29 and opens the valves 25A, 25B, 28 and 31.

  When the storage battery is connected to the control device 97 via a switch and the in-house power supply cannot be used due to the occurrence of LOCA, the switch is closed and current is supplied from the storage battery to the control device 97. Therefore, control by the control device 97 becomes possible. After the storage battery is connected, current is supplied to the control device 97 from, for example, an external power supply that supplies power generated at another power plant or the above-described emergency DG that is driven. For this reason, the supply of current to the control device 97 is not interrupted by the occurrence of LOCA.

  The cooling water in the pressure suppression pool 9 flows into the purification system pipe 16 through the valves 25A and 25B and the cooling water pipe 22 by driving the purification system pumps 19A and 19B. The non-regenerative heat exchanger 17A is supplied with cooling water from the auxiliary machine cooling system 18A, and the non-regenerative heat exchanger 17B is supplied with cooling water from the auxiliary machine cooling system 18B. The cooling water that has flowed into the purification system pipe 16 is cooled by the non-regenerative heat exchangers 17A and 17B, and the pressure is increased by the purification system pumps 19A and 19B. Thereafter, the pressurized cooling water passes through the bypass pipes 27 and 30, and is supplied to the reactor pressure vessel 1 through the purification system pipe 16 and the feed water pipe 12A downstream of the bypass pipe 30. The injection of the cooling water into the reactor pressure vessel 1 by the safety system 95 is continuously performed after the injection of the cooling water into the reactor pressure vessel 1 by the RCIC 34 is completed.

  According to the present embodiment, since the safety system 95 that is also used as the reactor cleaning system 15 is provided, when LOCA occurs, the safety system of one section (for example, Online maintenance is performed in the safety system 67), the emergency DG fails in the safety system (for example, the safety system 49) of the other one section, and the safety system (for example, the safety system 33) of the remaining one section Even when the LPFL pipe 42 is broken, the cooling water can be supplied into the reactor pressure vessel 1 by operating the safety system 95 that also serves as the reactor purification system 15. For this reason, it is possible to maintain the water injection / cooling function of the system under online maintenance, and even if LOCA occurs, the core 2 can be submerged in the reactor pressure vessel 1 and the fuel assembly can be cooled. become.

  Since the safety system 95 is also used as the nuclear reactor purification system 15, the system configuration of the boiling water nuclear power plant having the emergency core cooling device 14 of the present embodiment is able to perform online maintenance. The system configuration is simplified as compared with the system configuration of the boiling water nuclear power plant described in Japanese Patent Application Laid-Open No. 2008-281426, which does not include the purification system 15 and includes an emergency core cooling device having a safety system of four sections. The

  The cooling water in the pressure suppression pool 9 that has flowed into the purification system pipe 16 and cooled by the non-regenerative heat exchangers 17A and 17B of the safety system 95 and has fallen in temperature is supplied into the reactor pressure vessel 1 from the water supply pipe 12A. That is, it is supplied into the downcomer 4. The cooling water descends the downcomer 4 and is guided into the fuel assembly loaded in the core 2 and is heated by the decay heat of the nuclear fuel material in the fuel assembly. As the cooling water is heated by the decay heat, the fuel assembly is eventually cooled. The heated cooling water becomes steam and is discharged from the broken portion of the main steam pipe 10 to the dry well 7. This steam is discharged into the cooling water of the pressure suppression pool 9 through the vent passage 32 and condensed, and the decay heat of the nuclear fuel material generated in the core 2 is stored in the cooling water of the pressure suppression pool 9. Since the cooling water in the pressure suppression pool 9 is cooled by the non-regenerative heat exchangers 17A and 17B as described above, the decay heat generated in the core 2 is consequently removed by the non-regenerative heat exchangers 17A and 17B. Can do.

  When the LOCA occurs, the switching operation of the first switching device 86 is performed to drive the purification system pumps 19A and 19B of the safety system 95 and the auxiliary equipment cooling systems 18A and 18B by the emergency DG. be able to. For this reason, the cooling water of the pressure suppression pool 9 can be supplied into the reactor pressure vessel 1 by the safety system 95 when LOCA occurs.

  In the boiling water nuclear power plant to which the emergency core cooling device 14 of the present embodiment is applied, the reactor purification system 15 used during normal operation is connected to the pressure suppression pool 9 when LOCA occurs, and the first switching device 86 Since the power generated in the emergency DG by switching is supplied to the reactor purification system 15, the reactor purification system 15 can be used as a safety system 95 that is an alternative system for the low-pressure water injection system that is on-line maintained.

  In case of online maintenance of another safety system, the emergency DG of the section including the system for online maintenance of the second switching device 90 in order to operate the safety system 95 that is also used as the section IV purification system at the time of LOCA. Switch to the side. Thereby, the safety system 95 can be operated by the corresponding emergency DG by switching the first switching device 86 when LOCA occurs. For this reason, the online maintenance of the safety systems 33, 49, and 67 can be sequentially performed without newly providing a safety system of one section.

  When switching to the emergency DG, it is necessary to restart the pump. However, during normal operation of the boiling water nuclear power plant, in order to supply low-temperature cooling water to the filtration demineralizers 20A and 20B, the cooling water cooled to 100 ° C. or less by a non-regenerative heat exchanger is used as a purification system pump. Since it is supplied to 19A, there is no particular problem in restarting the purification system pump 19A. In addition, since the power supply capacity of the safety system 95 that is also used as the reactor purification system 15 is smaller than the power supply capacity of the system that is on-line maintained, there is no need to increase the power supply capacity of the emergency DG.

  The inventors evaluated the core cooling performance at the time of LOCA in the present embodiment in the first and second cases described below using the SAFER code, which is one of the license codes for boiling water reactors. It was. In the first case, the HPCF, which is an ABWR design standard accident, breaks, and online maintenance is performed for one LPFL. In the second case, one LPFL is broken and online maintenance is performed on the other LPFL. In the first case, the safety system is one isolated cooling system (RCIC) and one low-pressure water injection system (RCIC) because it is assumed that an emergency DG does not operate due to a single failure that needs to be considered for safety evaluation. LPFL) only operates, and in the second case, only one isolated cooling system (RCIC) and one high pressure core water injection system operate. In these analyses, the operation of the safety system 95 that is also used as the reactor purification system 15 is not considered.

  The evaluation results are shown in FIGS. In the first case shown in FIG. 4, the water level in the nuclear reactor falls after about 420 seconds have elapsed since the occurrence of LOCA. However, the water level begins to recover after about 450 seconds, and the minimum water level is maintained above the upper end of the heat generating part of the core. For this reason, the heat generating part of the fuel assembly loaded in the core is not exposed outside the cooling water. In the second case, the water level in the reactor after the LOCA is maintained above the lower end of the upper plenum. This means that the heat generating part of the fuel assembly loaded in the core is not exposed outside the cooling water, and there is no problem from the viewpoint of core cooling of the nuclear reactor.

  Further, in this embodiment (see FIGS. 1 and 2), the water injection capacity to the core by the safety system 95 that is also used as the reactor purification system 15 used in the normal operation of the reactor, which is not considered in the above evaluation, is provided. Join. For this reason, the safety of the boiling water nuclear power plant to which the present embodiment is applied is further improved. In other words, from the viewpoint of reactor core cooling, by configuring a safety system 95 that also serves as the reactor purification system 15, in addition to the conventional safety systems 33, 49, and 67, Online maintenance is possible without installing a separate new safety system. However, from the viewpoint of reactor containment vessel cooling (residual heat removal), which is another safety objective, in order to cope with the second case, a low-pressure water injection system (LPFL) having a residual heat removal function is required. Since it does not work at all, an alternative safety system with a heat exchanger cooling function is required. As described above, the nuclear reactor purification system 15 includes the non-regenerative heat exchangers 17A and 17B cooled by the auxiliary machine cooling systems 18A and 18B. The safety system 95 including the non-regenerative heat exchangers 17A and 17B of the nuclear reactor purification system 15 and the purification system pumps 19A and 19B is provided with residual heat that is temporarily stored in the cooling water of the pressure suppression pool 9 when LOCA occurs. Can be removed. The residual heat is stored in the cooling water by condensing the steam released to the dry well 7 during LOCA through the vent passage 32 and the cooling water in the pressure suppression pool 9. The present embodiment having the safety system 95 can perform reactor containment vessel cooling (residual heat removal) even when an event in which the low-pressure water injection system does not operate at all during on-line maintenance is performed. Safety is improved.

  An emergency core cooling apparatus according to embodiment 2, which is another embodiment of the present invention, will be described with reference to FIG. The emergency core cooling device 14A of the present embodiment has a configuration in which the safety system 95 is replaced with a safety system 95A in the emergency core cooling device 14 of the first embodiment. Other configurations of the emergency core cooling device 14A are the same as those of the emergency core cooling device 14. The safety system 95A has a configuration in which the safety system 95 is further provided with a pipe 99, non-regenerative heat exchangers 100A and 100B, and pumps 102A and 102B. Other configurations of the safety system 95A are the same as those of the safety system 95. The emergency core cooling device 14A is provided in a boiling water nuclear power plant.

  The configuration different from the safety system 95 in the safety system 95A will be specifically described. One end of the pipe 99 is connected to the purification system pipe 16 between the connection point between the purification system pipe 16 and the cooling water pipe 22 and the regenerative heat exchanger 17, and the other end is a bypass pipe existing upstream from the on-off valve 26. 27 is connected to the purification system pipe 16 between a connection point between the purification system pipe 16 and the purification system pump 19A. A non-regenerative heat exchanger 100A connected to the auxiliary machine cooling system 101A and a non-regenerative heat exchanger 100B connected to the auxiliary machine cooling system 101B are provided in the pipe 99 so as to be parallel to each other. An on-off valve 103A is provided upstream of the non-regenerative heat exchanger 100A, and an on-off valve 103B is provided upstream of the non-regenerative heat exchanger 100B. Pumps 102A and 102B are provided in the pipe 99 downstream of the non-regenerative heat exchangers 100A and 100B so as to be parallel to each other. The motor of the pump 102A is connected to the movable terminal 87 of the first switching device 86 via a switch 104 provided on an operation panel (not shown). Although not shown, the motor of the pump 102B is also connected to the movable terminal 87 of the first switching device 86 via another switch 104.

  The non-regenerative heat exchangers 17 </ b> A and 17 </ b> B provided in the purification system pipe 16 are designed to satisfy the high pressure and high temperature conditions required for the reactor purification system 15. For this reason, in the non-regenerative heat exchangers 17A and 17B, the heat removal performance with respect to the cooling water in the pressure suppression pool 9 in which the object to be cooled is relatively low at the time of LOCA is lowered. Each of the non-regenerative heat exchangers 100A, 100B is non-removable from the heat removal performance of each of the heat exchangers 44, 60, 78 so as to compensate for the lack of heat removal performance of each of the non-regenerative heat exchangers 17A, 17B. The heat removal performance is obtained by subtracting the heat removal performance of each of the regenerative heat exchangers 17A and 17B. The capacity of each of the pumps 102A and 102B is a capacity obtained by subtracting the capacity of each of the pumps 19A and 19B from the capacity of each of the water injection pumps 43, 59, and 77.

  During normal operation of the boiling water nuclear power plant, as in the first embodiment, the second switching device 90 is connected to the emergency DG side included in the section to which the system undergoing online maintenance belongs. Further, the on-off valves 103A and 103B are closed, and the cooling water discharged from the reactor pressure vessel 1 to the purification system pipe 16 is not supplied to the non-regenerative heat exchangers 100A and 100B. Further, since each switch 104 is turned off, the pumps 102A and 102B are not driven.

  When LOCA occurs, all control rods (not shown) provided in the reactor pressure vessel 1 are fully inserted into the reactor core 2 and the reactor is scrammed. Thereby, the operation of the boiling water nuclear plant is stopped. At this time, when the same event illustrated in the first embodiment occurs in the emergency core cooling device 14A, first, the RCIC 34 operates in the same manner as the first embodiment, and the cooling water of the pressure suppression pool 9 is put into the reactor pressure vessel 1. Add water. The controller 97 drives an emergency DG that covers three sections. The control device 97 connects the movable terminal 87 to the fixed terminal 89 as in the first embodiment. A switch 104 connected to the pumps 102A and 102B is turned on by a LOCA signal generated at the time of LOCA.

  As a result of the switching operation of the first switching device 86 by the control device 97 described above, the electric power generated by driving the emergency DG included in the online maintenance section is converted into the purification system pumps 19A, 19B, the pumps 102A, 102B, The auxiliary motor cooling systems 18A, 18B, 101A, and 101B are supplied to respective motors that drive the pumps, and these pumps are driven. Since the isolation valves 21A and 21B are closed, the cooling water in the pressure suppression pool 9 passes through the cooling water pipe 22, is supplied to the non-regenerative heat exchangers 17A and 17B by the purification system pipe 16, and is further not supplied by the pipe 99. The regenerative heat exchangers 100A and 100B are supplied. The cooling water cooled by the non-regenerative heat exchangers 100A and 100B is increased in pressure by the pump 102A and merged with the cooling water discharged from the purification system pump 19A, and passes through the bypass pipes 27 and 30 and from the feed water pipe 12A to the reactor. Returned to the pressure vessel 1. This makes it possible to maintain a water injection and cooling function with a capacity equivalent to that of the safety system that is being maintained online.

  Also in this embodiment, online maintenance can be performed for any one of the systems included in the safety systems 33, 49, and 67, and each effect produced in the first embodiment can be obtained. Since the emergency core cooling device 14A of the present embodiment includes the non-regenerative heat exchangers 100A and 100B, the heat removal performance of the safety system 95A can be enhanced. In this embodiment, it is necessary to additionally install the non-regenerative heat exchangers 100A and 100B as compared to the first embodiment. 17B, the heat removal performance of each of the non-regenerative heat exchangers 17A and 17B can be subtracted from the heat removal performance of each of the heat exchangers 44, 60, and 78 so as to compensate for the shortage of the heat removal performance of each of the heat exchanges. Since the heat removal performance is achieved, for example, the system can be made more compact than installing a heat exchanger 78 of a system that is on-line maintained and a heat exchanger having a conductive capacity.

  An emergency core cooling apparatus according to embodiment 3, which is another embodiment of the present invention, will be described with reference to FIG. The emergency core cooling device 14B of the present embodiment has a configuration in which the control device 97 and the power switching device 96 are replaced with the control device 97A and the power switching device 96A in the emergency core cooling device 14A of the second embodiment. Other configurations of the emergency core cooling device 14B are the same as those of the emergency core cooling device 14A.

  The power switching device 96A has a configuration in which a third switching device 105 is added to the power switching device 96 used in the first and second embodiments. Other configurations of the power switching device 96A are the same as those of the power switching device 96. The third switching device 105 has a movable terminal 107 and a fixed terminal 106. The fixed terminal 106 is connected to the movable terminal 87 of the first switching device 86. The movable terminal 107 is connected to the opening / closing device 104 connected to the motor of the pump 102A. Another switching device 104 (not shown) connected to the motor of the pump 102B is also connected to the movable terminal 107.

  In the control device 97A, when the LOCA occurs when online maintenance is being performed in any of the safety systems 33, 49, 67, the movable terminal 107 of the third switching device 105 is connected to the fixed terminal 106.

  The purification system pumps 19A, 19B and the pumps 102A, 102B are driven, and the cooling water in the pressure suppression pool 9 is cooled by the non-regenerative heat exchangers 17A, 17B, 100A, 100B as in the second embodiment. The cooled cooling water is supplied to the reactor pressure vessel 1 through the water supply pipe 12A.

  In the present embodiment, each effect produced in the second embodiment can be obtained.

  The present invention can be applied to a boiling water nuclear power plant.

  DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Reactor core, 6 ... Reactor containment vessel, 7 ... Dry well, 8 ... Pressure suppression chamber, 9 ... Pressure suppression pool, 12A, 12B ... Water supply system, 14, 14A, 14B ... Emergency Core cooling device, 15 ... Reactor purification system, 16 ... Purification system piping, 17 ... Regenerative heat exchanger, 17A, 17B, 100A, 100B ... Non-regenerative heat exchanger, 19A, 19B ... Purification system pump, 20A, 20B ... Filtration demineralizer, 22 ... piping, 25A ... open / close valve, 27,30 ... bypass piping, 32 ... vent passage, 33, 49,67,95,95A ... safety system, 34 ... cooling system during isolation, 41,57, 75 ... Low pressure water injection system, 48, 66, 84 ... Emergency diesel generator, 50, 68 ... High pressure core water injection system, 86 ... First switching device, 90 ... Second switching device, 96, 96A ... Power switching device, 97 , 97A ... Control device 99 ... pipe, 105 ... third switching device.

Claims (3)

For each of the high pressure injection system and the low pressure injection system, and the high pressure injection system and the low pressure injection system that supply cooling water of the pressure suppression pool formed in the reactor containment vessel containing the reactor pressure vessel to the reactor pressure vessel. A three-part safety system having an emergency power supply for supplying power to each first pump provided;
A first piping connected to the reactor pressure vessel; a first cooling device provided in the first piping; a second pump and a purification device; and a first on-off valve, wherein the pressure suppression pool and the first piping are installed. A second on-off valve provided in the first pipe upstream of a first connection point of the first pipe and the second pipe, and the purification A reactor purification system having a bypass pipe bypassing the apparatus and having both ends connected to the first pipe;
A first switching device having a first terminal and a second terminal connected to a service bus, and connecting the second pump to either the first terminal or the second terminal, and the three-section safety system The third terminal is connected to each of the emergency power supply devices separately, and the second terminal is connected to the third terminal of one of the third terminals. A power switching device having a second switching device for switching the emergency power device connected to the power supply;
An emergency core cooling device comprising: a control device that performs switching control of the first switching device and the second switching device.   One end connected to the first pipe downstream from the first connection point and upstream from the first cooling device, the first pipe and the bypass pipe downstream from the second pump and upstream from the purification device Upstream of the second connection point, a third pipe having the other end connected to the first pipe, a second cooling device provided in the third pipe, and the third pipe provided in the third pipe. The emergency core cooling device according to claim 1, further comprising a third pump to which a current supplied from the first switching device to the second pump is supplied.   When performing online maintenance on any one of the opening / closing device for turning on / off the supply of the current supplied from the first switching device to the second pump to the third pump and the safety system of the three sections The emergency core cooling device according to claim 2, further comprising the control device that closes the switchgear.

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