Emergency core cooling system

Abstract

To prevent the leakage of radioactive steam to the outside in an emergency. [Solution] An emergency core cooling system comprising a steam turbine 1 driven by radioactive steam 3 generated in the reactor during an emergency, a cooling pump 2 connected to the steam turbine and supplying cooling water to the reactor, a seal section 15 consisting of a barometric condenser 4, a vacuum tank 5, a condensate pump 6, and a vacuum pump 8, and a reactor cooling pump room 12 housing these devices, wherein a discharge pipe 10 that discharges non-condensable gas from the vacuum tank to the suppression pool 9 is provided with a branch pipe 11 that discharges the non-condensable gas to the reactor cooling pump room when the pressure in the suppression pool exceeds a specified value.

Description

Technical Field

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[0001] Embodiments of the present invention relate to an emergency core cooling device during reactor isolation in a boiling water reactor.

Background Art

[0002] In a boiling water reactor, for example, when the reactor is isolated due to a power loss accident or the like and the feed water to the reactor stops, an emergency core cooling device for supplying cooling water into the reactor to cool the core is provided.

[0003] As shown in FIG. 7, this emergency core cooling device supplies cooling water 29 from a condensate storage tank or the like to the reactor by a cooling pump 2 connected to a steam turbine 1 using the emergency steam turbine 1 as a driving source. The steam turbine 1 includes a seal portion 15 composed of a barometric condenser 4, a vacuum tank 5, a condensate pump 6, a vacuum pump 8, and the like.

[0004] The steam that drives the emergency steam turbine 1 is radioactive steam 3 generated by the decay heat of the reactor, and there is a possibility that the radioactive steam 3 may leak from the gap portions along the axle portion and valve rod directly connected to the cooling pump 2. Therefore, the radioactive steam 3 is condensed by directly contacting the cooling water by the barometric condenser 4 and collected in the vacuum tank 5. The condensed water is discharged from the condensate pump 6 to the cooling pump 2 through the suction pipe 7, and the non-condensable gas is discharged to the suppression pool 9 through the check valve 27 by maintaining the negative pressure of the vacuum tank 5 by the vacuum pump 8.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the conventional emergency core cooling system shown in Figure 7, when the pressure in the vacuum tank 5 drops, non-condensable gas is returned to the vacuum tank 5 from the discharge side of the vacuum pump 8 to lower the pressure in the suppression pool 9.

[0007] However, in emergencies such as power outages, the pressure in the suppression pool 9 rises, increasing the pressure on the discharge side of the vacuum pump 8. This can cause the vacuum pump 8 to malfunction, potentially leading to radioactive steam 3 leaking to the outside and preventing the seal section 15 from functioning properly.

[0008] The present invention was made to solve the above problems, and aims to provide an emergency core cooling system that can prevent the leakage of radioactive steam to the outside in an emergency. [Means for solving the problem]

[0009] To solve the above problems, the emergency core cooling system according to this embodiment comprises a steam turbine driven by radioactive steam generated in the reactor during an emergency, a cooling pump connected to the steam turbine and supplying cooling water to the reactor, a seal section consisting of a barometric condenser, a vacuum tank, a condensate pump, and a vacuum pump, and a reactor cooling pump room in which these devices are housed, wherein the discharge pipe that discharges non-condensable gas from the vacuum tank to the suppression pool is provided with a branch pipe that discharges the non-condensable gas to the reactor cooling pump room when the pressure in the suppression pool exceeds a specified value. [Effects of the Invention]

[0010] According to this embodiment, the safety of the reactor and the external environment can be improved by preventing the leakage of radioactive steam to the outside in the event of an emergency. [Brief explanation of the drawing]

[0011] [Figure 1] A diagram illustrating the configuration of an emergency core cooling system according to the first embodiment. [Figure 2] A diagram showing the configuration of an emergency core cooling system according to a modified example 1 of the first embodiment. [Figure 3] A diagram illustrating the configuration of an emergency core cooling system according to a second embodiment. [Figure 4] A diagram showing the configuration of an emergency core cooling system according to a modified example 2 of the second embodiment. [Figure 5] A diagram illustrating the configuration of an emergency core cooling system according to a third embodiment. [Figure 6] A diagram illustrating the configuration of an emergency core cooling system according to the fourth embodiment. [Figure 7] Diagram of a conventional emergency core cooling system. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the emergency core cooling system according to the present invention will be described with reference to the drawings.

[0013] [First Embodiment] An emergency core cooling system according to the first embodiment will be described with reference to Figure 1.

[0014] (composition) In this embodiment, as shown in Figure 1, inside the reactor cooling pump room 12, a branch pipe 11 is provided upstream of the check valve 27 installed in the discharge pipe 10 from the vacuum pump 8 to the suppression pool 9, with a pressure regulating valve 13 installed along the branch pipe.

[0015] (action) In the event of a power outage or similar accident, the cooling pump 2 is driven by the steam turbine 1. If the pressure in the suppression pool 9 rises over time and exceeds a specified value, the non-condensable gas discharged from the vacuum tank 5 is switched to the branch pipe 11 when the check valve 27 is closed, and the pressure regulating valve 13 installed in the branch pipe 11 opens, allowing the gas to be discharged into the reactor cooling pump room 12 outside the system.

[0016] While the pressure in the suppression pool 9 increases over time, most of the non-condensable gases such as noble gases generated by decay heat decay because their half-lives are very short. Substances with long half-lives such as iodine remain, but since they condense in the barometric condenser 4, the influence of radioactive substances is small, and even if they are discharged into the reactor coolant pump chamber 12, the influence is small.

[0017] (Effect) According to the present embodiment, even when the pressure in the suppression pool 9 increases, the sealing function of the seal portion 15 is maintained, and external leakage of the radioactive steam 3 generated from the reactor into or outside the building can be prevented. As a result, it is possible to improve the influence on the indoor and external environments by radioactive substances during subsequent recovery and manual startup of the cooling pump 2 in an emergency such as a power loss accident.

[0018] Furthermore, even when the oxygen concentration in the suppression pool 9 increases, it is possible to avoid an increase in the oxygen concentration in the suppression pool 9 by switching the discharge destination to the branch pipe 11.

[0019] (Modification 1) In the above embodiment, the non-condensable gas is discharged into the reactor coolant pump chamber 12 through the branch pipe 11. However, as shown in FIG. 2, it may be discharged from the condensate storage tank pipe 23 or the main condenser pipe 24 to the condensate storage tank or the main condenser through the pressure regulating valve 13. Thereby, the retention of radioactive substances in the reactor coolant pump chamber 12 can be suppressed, and the function of the seal portion 15 can be maintained.

[0020] [Second Embodiment] The emergency core cooling device according to the second embodiment relates to a device for removing radioactive substances contained in non-condensable gases.

[0021] (Configuration) As shown in FIG. 3, this emergency core cooling device includes a tank 14 containing water, a branch pipe 11 whose tip is submerged in the water in the tank 14, and a tank vent pipe 16 for discharging non-condensable gas in the tank 14.

[0022] (Effect, Action) Since the non-condensable gas contains condensable radioactive material, the water in tank 14 captures the condensable radioactive material contained in branch pipe 11, and the non-condensable gas is discharged into the reactor cooling pump room 12 through tank vent pipe 16. This makes it possible to remove radioactive material that could not be recovered as condensed water in the barometric condenser 4.

[0023] (Modification 2) In the modified example 2, as shown in Figure 4, a scrubbing device 17 for atomizing non-condensable gas is attached to the tip of the branch pipe 11 shown in Figure 3.

[0024] This process increases the contact area between the non-condensable gas and water by scrubbing (foaming) the non-condensable gas, thereby improving the effectiveness of removing radioactive materials contained in the non-condensable gas.

[0025] [Third Embodiment] The third embodiment of the emergency core cooling system relates to a device for removing radioactive materials contained in non-condensable gas at the inlet 19 of a discharge pipe 10 connected to a vacuum tank 5, as shown in Figure 5.

[0026] In this embodiment, a venturi scrubber device 18, consisting of a spray nozzle 21 that sprays cleaning water 20, is installed at the inlet 19 of the discharge pipe 10 to remove radioactive materials. The recovered cleaning water and non-condensable gas are separated by a cyclone separator 22. This further improves the removal effect of radioactive materials contained in the non-condensable gas.

[0027] [Fourth Embodiment] The emergency core cooling system according to the fourth embodiment relates to a monitoring mechanism for appropriately discharging non-condensable gas from the branch piping 11.

[0028] As shown in Figure 6, this monitoring mechanism consists of a pressure detector 25 that detects the pressure in the suppression pool 9, an oxygen concentration meter 26 that detects the oxygen concentration, and a control valve 28 provided in the branch piping 11.

[0029] The pressure detector 25 monitors the pressure in the suppression pool 9 and prevents malfunctions such as the discharge of non-condensable gas from the branch pipe 11 even though it is available for discharge into the suppression pool 9. Furthermore, if the oxygen concentration in the suppression pool 9 exceeds a specified value, the oxygen concentration meter 26 opens the control valve 28 and discharges the non-condensable gas from the branch pipe 11.

[0030] This prevents malfunction of the branch pipe 11, thus preventing unnecessary discharge of radioactive materials. Furthermore, when the oxygen concentration in the suppression pool 9 becomes high, safety can be improved by switching the discharge destination to the branch pipe 11 to lower the oxygen concentration.

[0031] While embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0032] 1...Steam turbine, 2...Cooling pump, 3...Radioactive steam, 4...Barometric condenser, 5...Vacuum tank, 6...Condensate pump, 7...Suction piping, 8...Vacuum pump, 9...Suppression pool, 10...Discharge piping, 11...Branch piping, 12...Reactor cooling pump room, 13...Pressure regulating valve, 14...Tank, 15...Seal section, 16...Tank vent pipe, 17...Scrubbing device, 18...Venturi scrubber device, 19...Inlet section, 20...Wash water, 21...Spray nozzle, 22...Cyclone separator, 23...Condensate storage tank piping, 24...Main condenser piping, 25...Pressure detector, 26...Oxygen concentration meter, 27...Check valve, 28...Control valve, 29...Cooling water

Claims

1. An emergency core cooling system comprising a steam turbine driven by radioactive steam generated in the reactor during an emergency, a cooling pump connected to the steam turbine to supply cooling water to the reactor, a sealing section consisting of a barometric condenser, a vacuum tank, a condensate pump, and a vacuum pump, and a reactor cooling pump room housing these components, An emergency core cooling system characterized in that a discharge pipe for discharging non-condensable gas from the vacuum tank to the suppression pool is provided with a branch pipe that discharges the non-condensable gas to the reactor cooling pump room when the pressure in the suppression pool exceeds a specified value.

2. The emergency core cooling system according to claim 1, characterized in that a pressure control valve is provided in the branch piping, which opens when the pressure in the suppression pool exceeds a specified value.

3. The emergency core cooling device according to claim 1, characterized in that the tip of the branch pipe is submerged in water in the container to remove radioactive material contained in the non-condensable gas.

4. The emergency core cooling system according to claim 3, characterized in that a scrubbing device for atomizing the non-condensable gas is attached to the tip of the branch pipe.

5. The emergency core cooling system according to claim 1, characterized in that a spray nozzle for spraying cleaning water is provided at the inlet of the discharge pipe, and the discharged cleaning water and non-condensable gas are separated by a cyclone separator.

6. The emergency core cooling system according to claim 1, characterized in that it includes a pressure detector for monitoring the pressure in the suppression pool and an oxygen concentration meter for monitoring the oxygen concentration, and controls the opening and closing of a control valve provided in the branch piping based on the values ​​from the pressure detector and the oxygen concentration meter.

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