JP5463196B2 - Nuclear power plant with reactor containment cooling equipment - Google Patents

Description

  The present invention relates to a nuclear power plant equipped with a containment vessel cooling facility.

  Boiling water nuclear power plants (nuclear power plants) are equipped with facilities for removing decay heat generated during a coolant loss accident and suppressing pressure rise in the reactor containment vessel. In the event of loss of coolant such as main steam pipe breakage, the steam released from the reactor pressure vessel into the containment vessel and the noncondensable gas in the containment vessel flow into the pressure suppression pool in the pressure suppression chamber through the vent pipe. To do. At this time, the non-condensable gas flowing into the pressure suppression pool moves to the upper space (wet well) of the pressure suppression pool. Moreover, the vapor | steam which flowed into the pressure suppression pool condenses, and discharge | releases thermal energy in a pressure suppression pool. Therefore, the pressure suppression pool can suppress a rapid pressure increase in the reactor containment vessel.

  As an example of reactor containment cooling equipment, Patent Document 1 discloses a technique of installing a dry well cooler containing a heat transfer tube in a dry well. In this dry well cooler, when non-condensable gas exists around the heat transfer tube, the heat removal performance (condensation performance) by the heat transfer tube is deteriorated. Then, the dry well cooler of patent document 1 makes the casing internal pressure in a dry well cooler low using an air blower so that a non-condensable gas may not accumulate in a heat transfer pipe periphery part. And an airflow is produced | generated using the pressure difference inside and outside a casing, and non-condensable gas is discharged | emitted from a dry well cooler. In addition, an opening / closing part is provided at the lower part of the dry well cooler. The opening / closing part has a mechanism for opening upon detection of a coolant loss accident.

JP 2007-51929 A

  However, the dry well cooler of Patent Document 1 uses dynamic devices such as a blower and an opening / closing part. Therefore, in order to improve the reliability of the reactor containment cooling equipment, it is desirable not to use dynamic equipment.

  Then, an object of this invention is to improve the reliability of the reactor containment vessel cooling equipment.

  The present invention provides a communication portion that communicates with the dry well in the partition wall, and includes an opening portion facing the space in the partition wall and an opening portion provided below the surface of the pressure suppression pool below the diaphragm floor. 1 piping is provided.

  According to the present invention, the reliability of the reactor containment cooling equipment can be improved.

1 is a diagram of a reactor containment cooling system according to Embodiment 1. FIG. It is the figure which showed the modification of the nuclear reactor containment vessel cooling equipment of Example 1. FIG. It is the figure which showed another modification of the nuclear reactor containment vessel cooling equipment of Example 1. FIG. The enlarged view of a heat exchanger is shown. The top view of a heat exchanger is shown. 3 is a diagram of a reactor containment cooling system according to Embodiment 2. FIG.

  Examples of the present invention will be described below.

  FIG. 1 shows an overview of a nuclear power plant. The nuclear power plant is installed so as to surround the reactor pressure vessel 2 in the reactor containment vessel 8, a reactor containment vessel 8 containing the reactor core 1, a reactor containment vessel 8 containing the reactor pressure vessel 2. The dry well 3, the pressure suppression chamber 5 that holds the pressure suppression pool 4, and the vent pipe 6 that communicates the dry well 3 and the pressure suppression pool 4. The diaphragm floor 40 partitions the dry well 3 and the pressure suppression chamber 5. Further, the reactor containment vessel cooling facility includes a heat exchanger 9 and a cooling water pool 13. The heat exchanger 9 includes a heat transfer tube 10, an upper header 11, and a lower header 12. The cooling water pool 13 is provided on the outer upper part of the reactor containment vessel 8. The heat exchanger 9 and the cooling water pool 13 are connected by piping, and constitute a cooling water circulation system. The gas phase space of the cooling water pool 13 is connected to the atmosphere by an exhaust pipe 14. For example, the cooling water pool may be an equipment pool that is used for temporary placement of the in-furnace structure by filling water during periodic inspection. In the present embodiment, the upper header 11 and the lower header 12 of the heat exchanger 9 and the cooling water pool 13 are communicated to supply cooling water to the heat transfer tube 10.

  The heat exchanger 9 is provided on the upper surface of the diaphragm floor 40. The partition wall 17 is formed so as to cover the heat exchanger 9, and a communication portion 18 that communicates with the dry well 3 is formed. This communication part 18 is formed by piping or a hole. The diaphragm floor 40 facing the space in the partition wall is provided with an opening, and a pipe 19 is provided so that fluid flowing out from the opening flows into the pressure suppression pool 4. That is, the pipe 19 includes an opening facing the space in the partition wall and an opening provided below the water surface of the pressure suppression pool below the diaphragm floor.

  The upper header 11 and the lower header 12 of the heat exchanger 9 are connected to a pipe 16 and a pipe 15 that communicate with each other on the bottom surface of the cooling water pool 13 outside the reactor containment vessel 8. In this embodiment, the heat exchanger 9 including the vertical heat transfer tube 10 and the upper header 11 and the lower header 12 is provided. However, even if a horizontal heat transfer tube or an inclined heat transfer tube is used, the heat transfer is performed. There is no problem because the same effect as in the present embodiment can be obtained by communicating the header portions installed on both sides of the heat pipe with the cooling water pool.

  Here, when a coolant loss accident (for example, breakage of the main steam pipe 20) occurs, a large amount of steam flows out from the main steam pipe 20 into the dry well 3 at the initial stage of the accident, and the temperature in the dry well 3 And the pressure increases. Steam and non-condensable gas (including nitrogen gas sealed inside the reactor containment vessel 8 during normal operation of the reactor) reach the opening 7 of the vent pipe 6 provided in the water of the pressure suppression pool 4. It overcomes the water head due to the water depth and flows into the pressure suppression pool 4. The steam condenses and suppresses an excessive pressure increase in the reactor containment vessel 8. At that time, the water temperature of the pressure suppression pool 4 rises due to vapor condensation. The non-condensable gas moves to the wet well 21 above the pressure suppression pool 4.

  Further, the vapor and the non-condensable gas flow into the partition wall 17 through the communication part 18. Steam exchanges heat with the cooling water in the heat transfer tubes 10 on the outer wall of the heat transfer tubes 10, and condenses on the outer walls of the heat transfer tubes 10. The condensed water flows down along the outer wall of the heat transfer tube 10, collects in the lower part of the space defined by the partition wall 17, and flows down to the pressure suppression pool 4 through the pipe 19 together with the non-condensable gas. The noncondensable gas present in the periphery of the heat transfer tube 10 deteriorates the condensation performance of the heat transfer tube 10. However, when steam is generated in the dry well 3, the pressure in the dry well becomes higher than the pressure in the wet well. Due to this pressure difference, the non-condensable gas flows out to the pressure suppression pool 4 through the pipe 19 and moves to the wet well 21. Therefore, the heat removal performance of the heat transfer tube 10 can be maintained. In addition, nitrogen gas sealed during normal operation of the reactor does not increase during an accident. Therefore, if the non-condensable gas can be continuously discharged to the pressure suppression pool 4, the concentration (existence ratio) of the non-condensable gas in the dry well 3 decreases, so that the heat removal performance by the heat transfer tube 10 can be improved. it can.

  In this way, most of the vapor and non-condensable gas in the partition wall overcome the water head due to the water depth up to the opening of the pipe 19 that opens in the water of the pressure suppression pool 4 and flow into the water of the pressure suppression pool 4. Thereafter, the steam condenses and suppresses an excessive pressure increase in the reactor containment vessel 8. The water temperature of the pressure suppression pool 4 rises due to the steam condensation in the pool water and the condensed water flowing in from the interior of the partition wall 17. Further, the non-condensable gas discharged from the pipe 19 moves to the wet well 21 above the pressure suppression pool 4.

  In the reactor containment vessel cooling system of this embodiment, the partition wall 17 is provided with a communication portion 18 that communicates with the dry well, and an opening facing the space in the partition wall and the pressure suppression pool 4 provided below the diaphragm floor. A pipe 19 having an opening provided below the water surface is provided. By providing this pipe 19, when a coolant loss accident occurs, it is possible to discharge noncondensable gas together with steam to the pressure suppression pool. Therefore, the noncondensable gas can be discharged through the pipe 19 even if the reactor containment vessel cooling facility does not have dynamic equipment. Therefore, the reliability of the reactor containment cooling equipment can be improved.

  In the present embodiment, the opening of the pipe 19 located below the water surface of the pressure suppression pool 4 is provided above the uppermost opening 7 of the vent pipe 6. After the coolant loss accident occurs, the pressure in the dry well 3 decreases with time. The opening of the pipe provided below the water surface of the pressure suppression pool is located above the uppermost outlet of the vent pipe (the uppermost outlet of the vent pipe is formed at a deeper position. Therefore, the amount of steam and non-condensable gas flowing into the pressure suppression pool 4 from the vent pipe 6 is reduced, and the inflow first stops. On the other hand, the vapor | steam and noncondensable gas which flow in into the pressure suppression pool 4 from the piping 19 continue flowing continuously. For this reason, while suppressing the pressure rise in a reactor containment vessel, cooling in the reactor containment vessel 8 can be continued.

  On the other hand, the temperature of the cooling water in the heat transfer tube 10 is increased by exchanging heat with steam, and the density of the cooling water is reduced. Furthermore, since the cooling water in the heat transfer tube 10 is boiled to generate steam, the density of the cooling water is reduced. Buoyancy occurs in the heat transfer tube 10 due to the difference in density of the cooling water. And cooling water flows into the cooling water pool 13 installed in the upper part of the reactor containment vessel 8, and the water temperature in the cooling water pool 13 rises. Since steam flows from the upper part of the space defined by the partition wall 17, the temperature of the cooling water in the heat transfer tube 10 on the upper header 11 side rises quickly. And in the piping 16 which connected the upper header 11 and the cooling water pool 13, the rising flow arises by the density difference of cooling water. Further, the low-temperature cooling water is supplied into the heat transfer tube 10 through a pipe 15 that connects the bottom of the cooling water pool 13 and the lower header 12 of the heat exchanger 9. In this way, a natural circulation flow is formed by the heat transfer tube 10, the upper header 11, the cooling water pool 13, and the lower header 12, and the cooling water is supplied to the heat transfer tube 10 for a long period of time.

  The cooling water pool 13 installed on the upper side outside the reactor containment vessel 8 is connected to the atmosphere by an exhaust pipe 14. Therefore, when the water temperature of the cooling water pool 13 reaches the boiling point, the pool water evaporates from the pool water surface and flows out of the cooling water pool 13 through the exhaust pipe 14. As described above, the cooling water circulation system in which the heat exchanger 9 and the cooling water pool 13 are connected by piping supplies the natural circulating water to the heat transfer pipe 10 and also statically evaporates the pool water in the cooling water pool 13. The decay heat can be dissipated outside the reactor containment vessel 8 based on the proper operating principle. Therefore, the reactor containment vessel 8 can be cooled and the pressure rise can be suppressed in the event of an accident.

  It is also possible to connect the cooling water pump and piping (not shown) used for the residual removal system to the upper header and the lower header of the heat exchanger to switch to the above-described cooling water circulation system. When the cooling water is supplied by the cooling water pump, the flow rate of the cooling water in the heat transfer tube increases, and the convective heat transfer coefficient in the heat transfer tube increases accordingly, so that the heat removal performance in the heat transfer tube is improved. Therefore, the pressure increase in the reactor containment vessel can be effectively suppressed as compared with the above-described cooling water circulation system.

  Moreover, if the height difference of the installation place of a heat exchanger and a cooling water pool is enlarged, the flow rate of the cooling water in a heat exchanger tube will increase according to the effect of gravity. Accordingly, the convective heat transfer coefficient in the heat transfer tube is increased, and the heat removal performance in the heat transfer tube can be improved.

  FIG. 2 shows a modification of the reactor containment cooling equipment. In FIG. 1, there is only one line 19 for connecting the space partitioned by the partition wall 17 and the pressure suppression pool 4, but it may be divided into a condensed water discharge pipe 25 and a non-condensable gas discharge pipe 26. . In this case, if the opening position of the non-condensable gas discharge pipe 26 is set higher than the opening position of the condensed water discharge pipe 25 in the internal space of the partition wall 17, the condensed water and the non-condensable gas are supplied. Can be easily separated.

  FIG. 3 shows a modification of the heat exchanger 9. FIG. 4A shows an enlarged view of the heat exchanger 9, and FIG. 4B shows a top view when FIG. 4A is viewed from the AA direction. The space partitioned by the partition wall 17 includes a space 22 where a communication portion 18 communicating with the dry well 3 exists, a space 23 where the heat exchanger 9 is installed, a pipe 25 for discharging condensed water communicating with the pressure suppression pool 4, and It is divided into a space 24 where a non-condensable gas discharge pipe 26 exists. Then, in the space 23, the clearance between the upper header 11 of the heat exchanger 9 and the ceiling and side walls of the space 23 and the clearance between the lower header 12 of the heat exchanger 9 and the floor and side walls of the space 23 are eliminated. It is possible to prevent 22 steam from flowing directly into the pressure suppression pool 4 without passing through the heat exchanger 9. Therefore, steam can be reliably supplied to the periphery of the heat transfer tube 10 and condensed.

  FIG. 5 shows another embodiment of the reactor containment cooling equipment. Compared with FIG. 2, the present embodiment is different in that the condensed water discharge pipe 25 a connected to the bottom surface position of the space partitioned by the partition wall 17 is not inserted below the water surface of the pressure suppression pool 4. The condensed water discharge pipe 25 a extends downward in the dry well 3 and is connected to the reactor pressure vessel 2. A check valve 29 is provided in the pipe 25 a so that the fluid does not flow backward from the reactor pressure vessel 2. Further, the position where the condensed water discharge pipe 25 a is connected to the reactor pressure vessel 2 is above the upper end of the core 1.

  When the water level in the reactor pressure vessel 2 falls below the upper end of the reactor core 1 due to a coolant loss accident or the like, the reactor pressure vessel 2 is depressurized. Then, the condensed water condensed in the heat exchanger 9 is poured into the reactor pressure vessel 2 via the condensed water discharge pipe 25a to cool the core 1.

  Further, the non-condensable gas discharge pipe 26 is inserted into the pressure suppression pool 4 as in FIG. Therefore, the non-condensable gas flows from the dry well 3 into the partition wall 17 and is continuously discharged to the pressure suppression pool 4. The heat exchanger 9 condenses the steam without being affected by the non-condensable gas, and can suppress the pressure increase in the reactor containment vessel 8. In addition, since condensed water is poured into the reactor pressure vessel 2 through the piping 25a for discharging condensed water, the temperature rise of the pressure suppression pool 4 can be suppressed. Therefore, compared with the embodiment of FIG. 2, the temperature rise of the pressure suppression chamber 5 is suppressed, and the vapor partial pressure of the pressure suppression chamber 5 is suppressed. And the pressure in the reactor containment vessel 8 can be kept low.

DESCRIPTION OF SYMBOLS 1 Core 2 Reactor pressure vessel 3 Dry well 4 Pressure suppression pool 5 Pressure suppression chamber 6 Vent pipe 7 Opening part 8 Containment vessel 9 Heat exchanger 10 Heat transfer pipe 11 Upper header 12 Lower header 13 Cooling water pool 14 Exhaust pipe 15 , 16, 19 Piping 17 Bulkhead 18 Communication portion 20 Main steam pipe 21 Wet well 29 Check valve

Claims (5)

A reactor pressure vessel containing a reactor core, a reactor containment vessel for housing the reactor pressure vessel, a diaphragm floor for partitioning a dry well and a wet well in the reactor containment vessel, and provided on the diaphragm floor A heat exchanger composed of a plurality of heat transfer tubes, an upper header and a lower header, a partition wall covering the heat exchanger, a cooling water pool provided on the upper side outside the reactor containment vessel, and an upper portion of the heat exchanger In a nuclear power plant including a reactor containment vessel cooling facility in which a header and a lower header and the cooling water pool are connected by a cooling water circulation system,
The partition is provided with a communication portion that communicates with the dry well, and includes an opening facing the space in the partition and an opening provided below the water surface of the pressure suppression pool below the diaphragm floor. A nuclear power plant equipped with a reactor containment cooling system characterized by comprising one pipe.   2. The nuclear power plant having the reactor containment vessel cooling system according to claim 1, wherein, in addition to the first pipe, a second pipe that communicates the space in the partition and the space in the reactor pressure vessel is provided. A nuclear power plant equipped with a reactor containment cooling system.   The nuclear power plant provided with the containment vessel cooling system according to claim 1 or 2, wherein the opening of the first pipe below the surface of the pool is the uppermost outlet of the vent pipe provided in the pressure suppression pool. A nuclear power plant equipped with a reactor containment cooling system, characterized in that it is located above.   3. A nuclear power plant comprising the reactor containment vessel cooling system according to claim 2, wherein the opening on the space side of the second pipe is provided at a bottom surface position of the space, and the opening on the reactor pressure vessel side is the A nuclear power plant equipped with a reactor containment cooling facility, which is provided above the core.   In the nuclear power plant provided with the containment vessel cooling facility according to claim 1, the first pipe is constituted by a condensed water discharge pipe and a non-condensable gas discharge pipe, and the partition wall In the internal space, the reactor containment vessel cooling facility is provided, wherein an opening position of the non-condensable gas discharge pipe is provided at a position higher than an opening position of the condensed water discharge pipe. Nuclear plant.

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