Depressurization system for reactor vessel of nuclear power plant

Abstract

The present invention relates to a depressurization system for a containment vessel of a nuclear power plant, the system comprising: a reactor vessel for accommodating a reactor core, a steam generator and a primary coolant; a containment vessel which has a free space and which accommodates the reactor vessel in the free space; a steam discharge part which is disposed at the upper portion of the reactor vessel and which discharges the steam of the primary coolant; a storage vessel which is connected to the steam discharge part and which stores a secondary coolant; and a spray part connected to the storage container so as to spray the secondary coolant into the free space.

Description

Depressurization system of nuclear power plant reactor vessel

[0001] The present invention relates to a depressurization system for a nuclear power plant reactor vessel.

[0002] The safety depressurization system applied to low-power small reactors releases the high-temperature, high-pressure primary coolant inside the reactor vessel into the sealed containment vessel surrounding the reactor vessel to quickly depressurize the reactor vessel in the event of an accident such as complete loss of feedwater.

[0003] However, recently, the containment vessel surrounding low-power small reactors has been significantly reduced in volume compared to the reactor building in conventional commercial nuclear power plants, so in the event of an accident, the coolant released outside the reactor vessel can be pressurized more quickly to a higher pressure.

[0004] This generates very high peak pressures compared to commercial furnaces.

[0005] For this reason, the containment vessels of small reactors are designed to have a very thick thickness of more than 60 mm to withstand high peak pressures.

[0006] Ultimately, the thicker thickness reduces thermal conductivity, slowing down the rate at which heat energy inside the containment vessel is transferred to the external heat sink.

[0007] To overcome this, the conventional method of increasing the heat transfer area of ​​a small reactor containment vessel has low economic feasibility due to increased manufacturing cost, transportation cost, and manufacturing difficulty, and causes the problem of space constraints.

[0008] The purpose of the present invention is to provide a depressurization system for a nuclear power plant reactor vessel.

[0009] The object of the present invention is achieved by a depressurization system for a containment vessel of a nuclear power plant, comprising: a reactor vessel accommodating a reactor core, a steam generator, and primary coolant; a containment vessel forming a free space and accommodating the reactor vessel within the free space; a steam discharge unit positioned at an upper portion of the reactor vessel and discharging steam of the primary coolant; a storage vessel connected to the steam discharge unit and storing secondary coolant; and a spray unit connected to the storage vessel and spraying the secondary coolant into the free space.

[0010] The above steam discharge unit discharges some of the steam of the primary coolant into the free space and supplies the remainder to the storage container.

[0011] The above steam discharge unit includes a discharge valve that opens due to a pressure difference between the reactor vessel and the free space.

[0012] The steam discharge unit further includes a first pipe section connected to the reactor vessel and discharging a portion of the steam of the primary coolant into the free space; and a second pipe section connecting the reactor vessel and the storage container and supplying the remainder of the steam of the primary coolant to the storage container; wherein the second pipe section branches from the first pipe section.

[0013] The vapor of the primary coolant supplied through the second pipe section pressurizes the secondary coolant.

[0014] The above storage container is located outside the above containment vessel.

[0015] The second pipe section includes a first rupture plate that is ruptured by the pressure of steam supplied to the storage container.

[0016] The first rupture plate normally blocks the movement of the vapor, and when the vapor reaches the first pressure, it ruptures to move the vapor into the storage container.

[0017] The above spray unit comprises a spray nozzle that discharges the secondary coolant into the free space; and

[0018] It includes a third pipe part, one end of which is connected to the spray nozzle and the other end is located inside the secondary coolant.

[0019] The third pipe section includes a second rupture plate that is ruptured by the pressure of the storage container.

[0020] The above second rupture plate normally blocks the movement of the secondary coolant, and when the pressure of the storage container reaches the second pressure, it ruptures and moves the secondary coolant to the spray nozzle.

[0021] It includes an injection unit for injecting coolant condensed in the free space into the interior of the reactor vessel.

[0022] The above injection unit includes an injection valve that opens due to a pressure difference between the reactor vessel and the free space.

[0023] According to the present invention, a depressurization system for a nuclear power plant reactor vessel is provided.

[0024] FIG. 1 is a drawing showing a depressurization system of a nuclear power plant reactor vessel according to a first embodiment of the present invention.

[0025] Figure 2 is a drawing showing a depressurization system of a nuclear power plant reactor vessel according to a second embodiment of the present invention.

[0026] Figure 3 is a flowchart showing a method for depressurizing a nuclear power plant reactor vessel according to the first embodiment of the present invention.

[0027] Figure 4 is a flowchart showing a method for depressurizing a nuclear power plant reactor vessel according to a second embodiment of the present invention.

[0028] The present invention will be described in more detail with reference to the accompanying drawings. The attached drawings are merely examples provided to further illustrate the technical concepts of the present invention, and therefore, the scope of the present invention is not limited to the attached drawings.

[0029] A depressurization system of a nuclear power plant reactor vessel is described with reference to FIGS. 1 and 2.

[0030] FIG. 1 is a drawing showing a depressurization system of a nuclear power plant reactor vessel according to a first embodiment of the present invention, and FIG. 2 is a drawing showing a depressurization system of a nuclear power plant reactor vessel according to a second embodiment of the present invention.

[0031] The depressurization system (1) according to the first embodiment includes a containment vessel (10), a reactor vessel (20), a storage vessel (30), a steam discharge unit (40), a spray unit (50), and an injection unit (60).

[0032] The containment vessel (10) accommodates a reactor vessel (20), a storage vessel (30), a steam discharge section (40), a spray section (50), and an injection section (60), and forms a free space.

[0033] The reactor vessel (20) includes a reactor core (210), a steam generator (not shown), and primary coolant.

[0034] The reactor core (210) is located at the bottom of the reactor vessel (20) and is surrounded by primary coolant.

[0035] Although not shown in Fig. 1, the steam generator is located at the mid-height of the reactor vessel (20) and generates steam from the primary coolant using heat generated in the reactor core (210).

[0036] The storage container (30) is located within the containment vessel (10) and contains secondary coolant.

[0037] The primary coolant and secondary coolant of the present invention may be in a liquid and / or gaseous state, and may be coolant, coolant fluid, or coolant steam.

[0038] The steam discharge unit (40) is located at the top of the reactor vessel (20) and discharges the steam of the primary coolant outside the reactor vessel (20).

[0039] The steam discharge unit (40) includes a first pipe unit (410), a second pipe unit (420), and a discharge valve (430).

[0040] The first piping section (410) is connected to the reactor vessel (20) and discharges some of the vapor of the primary coolant into free space.

[0041] The second piping section (420) connects the reactor vessel (20) and the storage vessel (30) to supply the remainder of the vapor of the primary coolant to the storage vessel (30).

[0042] The discharge valve (430) is located in the first pipe section (410). However, it is not limited thereto, and in other embodiments, it may be installed in the second pipe section (420).

[0043] The discharge valve (430) is opened and closed due to the difference in pressure between the internal pressure of the reactor vessel (20) and the pressure of the free space.

[0044] In Fig. 1, the first pipe section (410) and the second pipe section (420) are in the form of branch pipes, and there is one discharge valve (430).

[0045] However, in other embodiments, the first pipe section (410) and the second pipe section (420) may be formed independently, and a discharge valve (430) is installed in each pipe.

[0046] The spray unit (50) is connected to the storage container (30) and sprays the secondary coolant into the free space.

[0047] The sprinkler unit (50) includes a third pipe unit (510) and a spray nozzle (520).

[0048] One end of the third pipe section (510) is connected to the spray nozzle (520), and the other end is located inside the secondary coolant.

[0049] The other end (A) of the third pipe section (510) illustrated in FIG. 1 may be located at 1% to 10%, 1% to 20%, or 1% to 30% of the height (L) of the storage container (30).

[0050] The spray nozzle (520) is located at the top of the storage container (30) and sprays the secondary coolant that has moved through the third pipe section (510) into the free space of the containment container (10).

[0051] Finally, the injection unit (60) injects the coolant condensed in the free space of the containment vessel (10) into the reactor vessel (20).

[0052] The injection unit (60) is installed at a higher position than the reactor core (210).

[0053] The injection unit (60) includes an injection valve (610), and the injection valve (610) is opened and closed due to the difference between the internal pressure of the reactor vessel (20) and the pressure of the free space.

[0054] Next, a second embodiment of a depressurization system of a nuclear power plant reactor vessel will be described with reference to FIG. 2.

[0055] The second embodiment is identical to the first embodiment except for the differences described below.

[0056] The depressurization system (1) according to the second embodiment includes a containment vessel (10), a reactor vessel (20), a storage vessel (30), a steam discharge unit (40), and a spray unit (50).

[0057] The containment vessel (10) accommodates the reactor vessel (20) and a portion of the steam discharge section (40) and the spray section (50).

[0058] The storage container (30) is located outside the containment vessel (10) and contains secondary coolant.

[0059] The second pipe section (420) includes a first rupture plate (421), and at least a portion of the second pipe section (420) is located outside the containment vessel (10).

[0060] The first rupture plate (421) is located outside the containment vessel (10), but is not limited thereto, and in another embodiment of the present invention, it may be located inside the containment vessel (10).

[0061] The first rupture plate (421) normally blocks the movement of steam supplied to the storage container (30), and when the steam pressure supplied to the storage container (30) reaches the first pressure, it ruptures to move the steam to the storage container (30).

[0062] The first pressure may be 101% to 150%, 105% to 130%, or 110% to 120% of the design reference pressure.

[0063] The third pipe section (510) includes a second rupture plate (511), and at least a portion of the third pipe section (510) is located outside the containment vessel (10).

[0064] The second rupture plate (511) is located outside the containment vessel (10), but is not limited thereto, and in another embodiment of the present invention, it may be located inside the containment vessel (10).

[0065] The second rupture plate (511) normally blocks the movement of the secondary coolant supplied to the spray nozzle (520), and when the pressure of the storage container (30) reaches the second pressure, it ruptures to move the secondary coolant to the spray nozzle (520).

[0066] The second pressure may be 101% to 150%, 105% to 130%, or 110% to 120% of the design reference pressure.

[0067] Although the second embodiment does not include an injection unit (60), in another embodiment of the present invention, the configuration of the second embodiment may include an injection unit (60).

[0068] Below, the operation of the depressurization system of a nuclear power plant reactor vessel in the event of an accident is described with reference to FIGS. 3 and 4.

[0069] FIG. 3 is a flowchart showing a method for depressurizing a nuclear power plant reactor vessel according to a first embodiment of the present invention, and FIG. 4 is a flowchart showing a method for depressurizing a nuclear power plant reactor vessel according to a second embodiment of the present invention.

[0070] The operation of the depressurization system (1) of the reactor vessel (20) according to the first embodiment is described in detail through Fig. 3.

[0071] In the event of an accident, a large amount of primary coolant inside the reactor vessel (20) is generated in the form of steam, and the pressure inside the reactor vessel (20) becomes higher than the pressure of the free space, so the release valve (430) opens and the steam inside the reactor vessel (20) is released (S10).

[0072] After the steam of the primary coolant in the reactor vessel (20) passes through the discharge valve (430), some of the steam is discharged into the free space through the first pipe section (410) (S21), and some of the remaining steam is supplied to the upper part of the storage vessel (30) through the second pipe section (420) (S22).

[0073] As the internal pressure of the storage container (30) increases due to the steam supplied to the storage container (30), the secondary coolant is pressurized and moves through the third pipe section (510).

[0074] The secondary coolant is sprayed into the free space through a spray nozzle (520) connected to the other end of the third pipe section (510) (S30).

[0075] The steam released into the free space through the first pipe section (410) meets the secondary coolant sprayed into the free space through the spray nozzle (520) and transfers condensation heat to be condensed (S40).

[0076] The coolant that has been condensed and turned into a liquid moves to the bottom of the containment vessel (10) by gravity.

[0077] When the lower water level of the containment vessel (10) increases and reaches the height of the injection portion (60), the injection valve (610) is opened and the condensed coolant is injected into the reactor vessel (20) (S50), thereby filling the reactor core (210) (S60).

[0078] Finally, the operation of the depressurization system (1) of the reactor vessel (20) according to the second embodiment is described in detail through Fig. 4.

[0079] When an accident occurs in which a large amount of primary coolant inside the reactor vessel (20) is generated in the form of vapor and the pressure inside the reactor vessel (20) becomes higher than the pressure of the free space, the operator detects this and operates the release valve (430) (S100).

[0080] According to the instructions of the nuclear power plant, the release valve (430) is opened and the steam inside the reactor vessel (20) is released (S110).

[0081] Some of the vapor of the primary coolant inside the reactor vessel (20) is discharged into free space through the first pipe section (410) (S210).

[0082] A portion of the remaining steam moves to the second pipe section (420) and ruptures the first rupture plate (421) when the pressure of the steam reaches the first pressure (S220).

[0083] It is supplied to the upper part of the storage container (30) through the broken first rupture plate (421) (S230).

[0084] As the internal pressure of the storage container (30) increases due to the steam supplied to the storage container (30), the secondary coolant is pressurized and moves through the third pipe section (510).

[0085] When the pressure of the secondary coolant that has moved to the third pipe section (510) reaches the second pressure, the second rupture plate (521) is ruptured (S310).

[0086] The secondary coolant is sprayed into the free space through the spray nozzle (520) connected to the other end of the third pipe section (510) through the ruptured second rupture plate (521) (S320).

[0087] The steam released into the free space through the first pipe section (410) meets the secondary coolant sprayed into the free space through the spray nozzle (520) and transfers condensation heat to be condensed (S400).

[0088] In another embodiment of the present invention, the following operation can be additionally performed after the operation of the decompression system (1) of the second embodiment.

[0089] The coolant that has condensed and become liquid moves to the bottom of the containment vessel (10) by gravity, and when the water level at the bottom of the containment vessel (10) increases and reaches the height of the injection part (60), the injection valve (610) is opened. Finally, the condensed coolant is injected back into the reactor vessel (20) to replenish the reactor core (210).

[0090] The amount of condensation of the coolant is proportional to the amount of heat transferred from the containment vessel to the heat sink outside the containment vessel. The amount of heat transfer is proportional to the temperature difference between the vapor inside the containment vessel and the external heat sink, the heat transfer area of ​​the containment vessel, and inversely proportional to the thickness of the solid material through which heat is conducted.

[0091] Therefore, in the present invention, the first coolant and the second coolant in vapor form are in direct contact, so that the heat energy of the first coolant is quickly transferred, thereby increasing the condensation amount and condensation speed of the first coolant, and also suppressing the pressure increase inside the containment vessel (10).

[0092] The present invention enhances safety by further enhancing the depressurization performance of a containment vessel through an indirect cooling method applied to conventional small nuclear reactors.

[0093] In addition, the enhanced decompression performance lowers the design pressure of the containment vessel and reduces the size of the containment vessel, making it superior in terms of manufacturability and economy.

[0094] Lastly, according to the present invention, the coolant discharged outside the reactor vessel (20) is condensed and injected back into the reactor vessel (20), thereby maintaining the reactor core in a passive state at all times, thereby maintaining the integrity of the nuclear fuel rods.

[0095] While specific aspects of the present invention have been described in detail above, it will be apparent to those skilled in the art that these specific descriptions merely represent preferred embodiments and are not intended to limit the scope of the present invention. Therefore, the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. In the depressurization system of a nuclear power plant containment vessel, Reactor vessel containing the reactor core, steam generators, and primary coolant; A containment vessel forming a free space and accommodating the reactor vessel within the free space; A steam discharge unit located at the upper part of the reactor vessel and for discharging steam of the primary coolant; A storage vessel connected to the above steam discharge unit and storing secondary coolant; and A depressurization system including a spray unit connected to the storage container and spraying the secondary coolant into the free space.

2. In paragraph 1, The above steam discharge unit, A depressurization system that discharges some of the vapor of the primary coolant to the free space and supplies the remainder to the storage container.

3. In paragraph 2, The above steam discharge unit, A depressurization system including a release valve that opens due to a pressure difference between the reactor vessel and the free space.

4. In paragraph 3, The above steam discharge unit, A first piping section connected to the reactor vessel and discharging a portion of the vapor of the primary coolant into the free space; and It further includes a second piping section connecting the reactor vessel and the storage vessel to supply the remainder of the vapor of the primary coolant to the storage vessel; The above second pipe section is a pressure reducing system branched from the above first pipe section.

5. In paragraph 4, A depressurization system in which the vapor of the primary coolant supplied through the second pipe section pressurizes the secondary coolant.

6. In paragraph 4, The above storage vessel is a depressurization system located outside the containment vessel.

7. In paragraph 6, The above second piping section, A depressurization system comprising a first rupture plate which is ruptured by the pressure of steam supplied to the storage container.

8. In paragraph 7, The above first rupture plate is, In normal times, the movement of the above vapor is blocked, A pressure reducing system that breaks down when the vapor reaches a first pressure and transfers the vapor to the storage vessel.

9. In paragraph 8, The above sprinkler system, A spray nozzle for discharging the secondary coolant into the free space; and A depressurization system including a third pipe section, one end of which is connected to the spray nozzle and the other end is located inside the secondary coolant.

10. In paragraph 9, The above third pipe section, A depressurization system including a second rupture plate that is ruptured by the pressure of the storage container.

11. In paragraph 10, The above second rupture plate is, In normal times, the movement of the above secondary coolant is blocked. A depressurization system that ruptures when the pressure of the storage container reaches the second pressure and moves the secondary coolant to the spray nozzle.

12. In paragraph 1, A depressurization system including an injection unit for injecting coolant condensed in the free space into the interior of the reactor vessel.

13. In paragraph 12, The above injection part, A depressurization system including an injection valve that opens due to a pressure difference between the reactor vessel and the free space.

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