KR20160002296A - Flow control system of gravity injection system to steam generator for nuclear power plants - Google Patents

Abstract

The present invention relates to a gravity injection flow control system for a steam generator used in a nuclear power plant. More specifically, valves and pipes related to one or more water supply storage tanks are installed on the outside of a storage building in a pressurized water reactor (PWR) nuclear power plant in order to control the flow amount from the water supply storage tanks to a system even in the case of plant outages with no electrical power, thereby removing the remaining heat in the reactor core by directly injecting the water supply to the steam generator. The present invention installs the water supply storage tanks on the outside of the storage tanks in order to provide sufficient water easily and design a simple passive safety system operation by using the tanks in the nuclear power plant generating electricity even when a conventional secondary water supply system does not work due to a design criterion accident or a power loss accident, thereby sufficiently removing the remaining heat to prevent the reactor core from melting. Accordingly, the present invention can ensure the reliability of the nuclear power plant and keep the public safe.

Description

TECHNICAL FIELD [0001] The present invention relates to a gravity flow control system for a nuclear power plant,

The present invention relates to a gravity flow control system for a steam generator of a nuclear power plant, and more particularly, to a system for controlling gravity flow rate of a nuclear power plant steam generator, The present invention relates to a steam generator gravity feed flow control system for a nuclear power plant capable of removing residual heat of a core by injecting water directly into a steam generator.

As demand for electricity production worldwide has surged, nuclear power plants have played a major role in electricity production so far. Nuclear power has greatly benefited from the economic benefits from low electricity production costs. Nuclear power generation uses electricity generated from the process of artificially fissuring fissile material such as uranium to generate electricity. It is very important to consider the safety of the risk of radioactive materials and radiation due to fission. Conventional nuclear power plants also provide reasonable safety with an engineering safety system, but research and development on safety systems for safety improvement have been continuing.

The secondary side condensation system of the pressurized light water reactor disclosed in Korean Patent No. 10-2010-0134277 is a system in which the heat generated in the core is transferred to the steam generator and heat generated in the condenser, After condensing, it is configured to rejoin the steam generator. In this connection, Korean Patent Registration No. 10-2014-0040518 discloses an emergency water sucking device for a steam generator for failing the secondary side condensing system of the driven side described in the above patent.

1 is a block diagram of a conventional loop-type PWR reactor coolant system and a safety system. The conventional safety system uses water in the nuclear fuel reloading water tank 20 as a coolant. First, the water enters the reactor vessel 40 to lower the core temperature by the safety injection pump 30 from the nuclear fuel reloading tank 20 in the containment building 10 in the event of a coolant loss in the reactor coolant system. Secondly, at the time of increasing the temperature and pressure in the reactor containment building 10, the coolant is sprinkled in the containment building sprinkler 60 by the reactor building sprinkling pump 50 from the fuel reloading water tank 20. Thirdly, in the case of a core melt accident in the reactor vessel 40, from the nuclear fuel recharging tank 20 to the center of the reactor vessel 40 from the cavity 80 at the lower end of the reactor by the static cooling pump 70, Water is filled for preservation.

2 is a configuration diagram showing a conventional loop type pressurized light water reactor auxiliary water supply system and an emergency water supply system. The auxiliary water supply system for removing the conventional residual heat is classified into two types. First, the main steam isolation valve of the main steam pipe connected by the high pressure and low pressure turbines is closed, the valve installed in the pipe connected to the auxiliary water turbine is opened to supply steam to the auxiliary water turbine, To inject the feed water into the steam generator (90). Secondly, when an AC power or an off-site power from an emergency diesel generator installed in a nuclear power plant is available, electric power is supplied to the motor drive pump to feed water to the steam generator 90 and then to the steam generator 90 The residual heat is removed indirectly. In case of failure of the operation of the auxiliary water supply system, the water is injected into the steam generator by the piping of the emergency water supply system composed of the fire truck and the fire line.

Since the conventional safety system currently used is operated by the pumps driven by the AC power source, it is impossible to cope with accidents in the case where power is not supplied, and since it is impossible to enter the containment building at the time of an accident, It is difficult to repair the broken system. Also, the driven secondary side condensation system involves the complexity and instability of operation and operation because it utilizes the natural circulation of water. In the case of the steam generator injection system using the fire truck described above, the response time is slow and the response time is also very short considering the accident coping and the amount of the fire truck coolant.

KR 10-0584835 B1

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a nuclear power plant steam generator capable of achieving removal of residual heat from a steam generator by supplying water by gravity from a water supply reservoir, System.

It is also an object of the present invention to provide a steam generator gravity injection flow control system for a nuclear power plant capable of solving the complexity of the complex safety system and the complexity of operation from the existing tank and injection piping installation.

In addition, there is provided a nuclear power plant steam generator including a porous feedwater injection piping system and a passive air injection prevention piping system for controlling the flow rate by a drop in water level at the inlet of each injection pipe and preventing the entry of air into the pipe due to contact with air, And a gravity injection flow rate control system.

In order to achieve the above object, the present invention provides a system for controlling gravity flow rate of a steam generator for a nuclear power plant, comprising: a water supply reservoir connected to each steam generator outside a containment building having a plurality of steam generators; A plurality of gravity injection pipes disposed in the water supply reservoir such that the inlet of each pipe has a different height according to a water level of the water supply; And a steam generator installed in the steam generator pipeline for connecting the gravity injection pipe to the steam generator. In case that the main water supply system is disconnected in the event of a power loss accident, an atmospheric release valve opened to reduce the pressure of the steam generator system to the atmospheric pressure level And a gravity injection valve which is opened after the pressure of the steam generator system is reduced to an atmospheric pressure level by opening the gravity injection valve, wherein the gravity injection pipe is connected to the steam generator gravity injection system pipe And supplies the water in the water storage tank to the steam generator by gravity.

According to the present invention, by installing the water supply reservoir outside the containment building, even if the existing auxiliary water supply system does not operate at the time of design basis accident and power plant loss accident using one or more tanks to the nuclear power plant producing electricity, The operation design of the passive safety system and the easy addition of outside are possible, so that the residual heat is sufficiently removed to prevent the melting of the core, thereby maintaining the health of the nuclear power plant and ensuring public safety.

In addition, it is possible to solve the problem that the steam generator is broken due to a rise in the water level in the steam generator by installing the water injection pipe at the water level in the water supply reservoir, and long term cooling can be achieved efficiently by using the limited water supply.

In addition, it is possible to install the feed water supply piping as the inflow water supply inflow pipe or the inflow air inflow prevention piping system at the inlet of the water supply inflow pipe, so that it is possible to inject the designed water supply flow rate without supplying the power supply and without human intervention, The performance degradation can be prevented.

In addition, since the steam generator gravity injection flow control system of a nuclear power plant does not have to be complicated about technical and applicability, it is very licensable, so that unlike the existing safety systems, Or to a nuclear power plant currently in operation.

In addition, since the water supply reservoir exists outside the containment building in case of an accident at the nuclear power plant where access to the inside of the containment building is impossible, it is very easy to supply water from the outside when the water supply reservoir is drained, .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a conventional loop type PWR safety system. FIG.
2 is a view showing a conventional loop type pressurized light water reactor auxiliary water supply system and an emergency water supply system.
3 is a view showing a pressurized light water reactor to which a steam generator gravity injection flow rate regulating system for removing passive residual heat according to the present invention is applied.
FIG. 4 is a view showing a steam generator gravity injection flow rate regulating system according to the present invention. FIG.
5 is a view showing a porous water supply injection piping system in which water is injected through a plurality of holes in a side surface area of the piping according to the present invention.
6 is a view showing a system for preventing passive air injection with a floating disk according to the present invention.
Fig. 7 is a view showing a piping system for a passive air injection preventing system having a floating stopper according to the present invention; Fig.
8 is a configuration diagram showing an open state of a passive air injection preventing piping system having a buoyancy valve according to the present invention.
9 is a configuration diagram showing a closed state of a passive air injection preventing piping system having a buoyancy valve according to the present invention;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

3 is a view showing a pressurized light water reactor to which a steam generator gravity injection flow rate regulating system for removing residual heat according to the present invention is applied. The heat generated by the fission is first transferred to the coolant from the core. The heated coolant flows to the steam generator (90) at a higher position and transfers heat from the steam generator (90) serving as a heat exchanger to the water supply of the secondary side system. The water in the secondary side system at the time of normal operation is heated in the steam generator 90 to become steam, and the steam operates the turbine to produce electricity. Since the pressure in the coolant system at the time of a power loss accident is so high that injection is impossible and the system connected to the steam generator 90 can not operate the turbine, the steam is supplied to the steam generator 90 by a pump to remove residual heat . However, when a power loss accident occurs, it is impossible to supply AC power to the pump, and when the pump driven by the turbine connected to the secondary side fails, heat can not be removed from the steam generator 90. In order to efficiently remove the residual heat in such an accident, the main steam isolation valve 110 and the main feedwater isolation valve 120 connected to the normal turbine are first closed to isolate a portion connected to the turbine and the condenser. Thereafter, in order to reduce the pressure of the steam generator system, the atmosphere discharge valve 130 installed in the secondary system is opened to reduce the pressure of the steam generator system to the atmospheric pressure level. After the pressure of the steam generator system is reduced, the gravity injection valve 140 installed in the steam generator gravity feed system piping connected to the steam generator 90 is opened from the inside of the water supply reservoir 100 to secure the flow channel. Accordingly, even if the water level difference of the water supply from the water supply reservoir 100 to the steam generator 90 is generated and the pressure of the steam generator 90 is maintained at a pressure slightly higher than the atmospheric pressure, The feedwater can be injected according to the force of gravity. The injected feedwater is indirectly removed from the reactor coolant system in the steam generator 90, and is vaporized. The steam generated by removing the residual heat can be discharged without increasing the pressure of the steam generator 90 due to the continuous opening of the atmospheric release valve 130 provided in the present design of the nuclear power plant. Steam generation in the secondary system of a nuclear power plant is used to remove heat through phase changes from feed water to steam by heat transfer, unlike the coolant of the primary system, which is not directly radiated to neutrons.

FIG. 4 is a view illustrating a gravity injection flow rate control system capable of passively controlling a flow rate according to the present invention. As shown in the drawing, a pipe installed for injecting the steam generator gravity is connected into the water supply reservoir 100. According to this system, the water supply in the water storage tank 100 can be injected into the steam generator 90 by the gravity due to the water level difference. Each inlet pipe inlet in the water supply reservoir 100 is designed in multiple for each water level, as shown. This is because, due to the inherent characteristics of nuclear power plants, the residual heat immediately after the reactor shutdown is initially very large, but the amount of residual heat is greatly reduced over time. In order to inject the amount of water corresponding to the residual heat, the inlet level of the gravity injection pipe 150 may be varied to passively change the main adoption over time. This effectively utilizes the amount of water in the external water supply reservoir 100 installed outside the containment, so that the residual heat of the reactor can be cooled for a long period of time when access to the nuclear power plant from outside and external filling are impossible. In addition, since an excessive supply of water to the steam generator causes an abnormality in the steam generator from the high water level in the event of an accident, the flow control system of the gravity injection, whose flow rate is adjusted, prevents the fault due to excessive rise of the steam generator can do.

The basic design of the steam generator gravity injection flow control system for removing residual heat of the nuclear power plant is such that the entrance of the pipe is installed at each water level in the water storage tank 100 as described above with reference to FIG. In this design, after the reactor shutdown, the flow rate required to be injected into the steam generator 90 is proportional to the amount of residual heat of the reactor core. The required flow rate is determined by the number of inlet piping and the level of each piping inlet associated with the opening and closing of the inlet to the piping due to the lowering of the water level. As the number of injection pipes increases, the injection area changes to a smaller value depending on the water level difference. Therefore, the injection amount can be continuously changed by reducing the difference in the actual injection flow rate with respect to the flow rate to be injected. The flow control according to the injection area is further elaborated by an application design which constitutes a plurality of holes in the lateral area of the pipe as described above in FIG. In the basic design, the inlet water level of each pipe can be opened and closed to the inlet water supply due to the drop in the water supply water level. Therefore, the water supply amount injected into the steam generator over time is correlated with the design value . 4, when the water level of the water supply is lower than the water level of the pipe inlet, the inlet of the pipe is opened and brought into contact with the air in the water supply reservoir 100. [ This can close the inlet of the piping to prevent piping of the air due to the lowering of the level into the passive air injection preventing piping system, which will be described later.

FIG. 5 is a view showing a porous water supply injection pipe system to which water is injected through a surface area of a pipe according to the present invention. A plurality of water supply inlets 210 of a small size may be formed in each gravity injection pipe 150 of the gravity injection flow rate regulating system installed in the water supply reservoir 100 of FIG. The water is gravity injected into the steam generator (90). As the water supply level in the water supply tank 100 decreases, the number of the water supply inlets 210 in the surface area of the piping contacting the water decreases, so that the flow rate of the water supply supplied to the steam generator 90 continuously decreases . The flow rate can be adjusted to design the size and number of the water inlet 210 in proportion to the residual heat generated in the core of the reactor. In this system, the upper surface of the pipe is in a closed state, and the sum of the areas of the opened water inlet 210 of the side area is smaller than the area of the upper surface. It is possible to prevent the air in the water storage tank 100 from being injected into the injection pipe 100 when the water level drops below the entrance height in the gravity injection flow rate control system described above with reference to FIG. have.

FIG. 6 is a configuration diagram showing a passive air injection preventing piping system having a floating disk 310 according to the present invention. As shown, each inlet of the steam generator flow control gravity feed pipe 150 is provided with a floating disk 310 made of a material heavier than water beneath the float 320 capable of floating in water made at a density lower than that of water And a string-shaped disk support line 330 connecting the inside of the inlet pipe and the center of the floating disk 310 is provided. When the level of the water supply is higher than the inlet of the pipe, the float 320 is positioned higher by buoyancy and the floating disk 310 is supported by the disk support line 330 and is positioned above the pipe, The disk support string 330 descends into the inlet of the piping and eventually the floating disk 310 closes the inlet of the gravity feed system piping. In order to close the inlet of the pipe accurately, a disk guide 340 exists at the center of the lower end of the floating disk 310 in the direction of pipe inlet, and a protrusion protrudes at the edge of the lower end of the floating disk 310. Accordingly, it is possible to prevent the infusion of air in the pipe when the water level becomes lower than the inlet height of the pipe.

7 is a configuration diagram showing a passive air injection preventing piping system having a floating cap 410 according to the present invention. As shown, each inlet of the steam generator flow control gravity injection pipe 150 is provided with a floating cap 410 made of a material heavier than water beneath the float 420 capable of float made at a density lower than that of water, And a cord-like stopper string 430 for connecting the inside of the inlet of the injection pipe and the center of the flap 410 is provided. When the water level of the water is higher than the inlet of the pipe, the floating cap 410 is supported by the cap support line 430 and is positioned at the upper portion of the pipe. As the water level is similar to or lower than the inlet of the pipe, The string 430 descends in the direction of the inlet of the piping, and finally the closure cap 410 closes the inlet of the gravity feed system piping. In order to close the inlet of the pipe accurately, a cap guide 440 exists in the center of the lower end of the floating cap 410 in the direction of the pipe inlet, and the inlet portion of the gravity injection flow rate control system exists in the form of a funnel. Accordingly, it is possible to prevent the infusion of air in the pipe when the water level becomes lower than the inlet height of the pipe.

Figs. 8 and 9 are block diagrams showing the open and closed states of the passive air injection preventing piping system having the buoyancy valve according to the present invention. As shown, the float 520 has a floatable float 520 made of a lighter density than water at the periphery of each inlet of the steam generator flow control gravity feed line 150, And is connected to the support string 530. The support strap 530 is connected to the support 540 and the float valve body 510 is at the end of the support 540. The support base 540 is fixed and only the center of the support base is fixed so as to be rotatable. The supporter 530 is urged in the direction of the float 520 so that the supporter 540 is urged toward the fixed pulley 550 in the direction of the fixed pulley 550, So that the floating valve body 510 is located far from the inlet of the pipe, and the inlet of the pipe is maintained in the open state. The float 520 exists at the water level of the water supply and the force in the direction of the float 520 becomes smaller than the force due to the weight of the float valve body 510. As a result, The body 510 is lowered to close the inlet of the pipe. Accordingly, it is possible to prevent the injection of air into the pipe when the water level becomes lower than the inlet height.

The steam generator gravity injection flow rate control system for removing residual heat according to the present invention is provided with a water supply reservoir 100 installed on the roof of a first or second auxiliary building or turbine building outside a nuclear power plant containment building, 2 and 3, the above-described safety concept can be achieved.

In addition, according to the present invention, since simplification of the safety system design and use of the AC power source are not used, it is possible to achieve safety in case of human error reduction and power loss accident. This steam generator gravity injection flow rate regulating system is applicable to the conventional pressurized light water reactor as a supplement to the conventional safety system.

As described above, although the present invention has been described with reference to the limited embodiments and drawings of the loop type pressurized light water reactor, the present invention is not limited thereto, and the present invention may be applied to a pressurized heavy water reactor It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

10: Containment building
90: Steam generator
100: water storage tank
150: Gravity injection piping
210: Water inlet
310: floating disk
410: Floating plug
510: Floating valve body

Claims (8)

Nuclear Power Plant Steam Generator As gravity injection flow control system,
A water supply reservoir connected to each of the steam generators outside the containment building in which a plurality of steam generators are installed;
A plurality of gravity injection pipes disposed in the water supply reservoir such that the inlet of each pipe has a different height according to a water level of the water supply; And
And an opening of the atmospheric release valve that is opened in order to reduce the pressure of the steam generator system to the atmospheric pressure level when the main water supply system is shut off in the event of a power loss accident, provided in the steam generator gravity injection system pipe connecting the gravity injection pipe to the steam generator. And a gravity injection valve that is opened after the pressure of the steam generator system is depressurized to an atmospheric pressure level by the gravity injection valve,
Wherein the gravity injection pipe is a nuclear power plant that supplies water in the water supply reservoir to the steam generator through a gravity feed pipe through a steam generator gravity feed system pipeline secured by the opening of the gravity injection valve, system.
The method according to claim 1,
The feed water supplied to the steam generator through the gravity feed pipe indirectly removes residual heat from the reactor coolant system in the steam generator
Wherein the gravity feed flow control system comprises:
The method of claim 2,
The residual heat is removed by the water supplied to the steam generator through the gravity injection pipe, and the generated steam is discharged without increasing the pressure of the steam generator as the standby discharge valve is kept open
Wherein the gravity feed flow control system comprises:
The method according to claim 1,
The flow rate of the steam supplied to the steam generator through the gravity injection pipe is proportional to the amount of residual heat of the reactor core so that the flow rate of the gravity injection pipe and the flow rate of the gravity- Determined by
Wherein the gravity feed flow control system comprises:
The method according to claim 1,
Wherein a plurality of water inlet ports are formed in the gravity inlet pipe and each of the upper surfaces of the gravity inlet pipe is closed so that the flow rate of the water supplied into the water inlet is continuously controlled in accordance with the lowering of the water level, Not injected into the interior of the gravity feed line
Wherein the gravity feed flow control system comprises:
The method according to claim 1,
A float disk is disposed at each entrance of the gravity injection pipe, a floating disk is provided below the float, and a string-shaped disk support line connecting the inside of each entrance of the gravity injection pipe and the center of the floating disk is provided The floating disk has a disk guide formed at a center of a lower end of the gravity injection pipe, the entrance of the gravity injection pipe exposed above the water surface in the water supply reservoir as the water level in the water supply reservoir becomes lower than the inlet of the gravity injection pipe, Is closed by the floating disk to prevent the infusion of air
Wherein the gravity feed flow control system comprises:
The method according to claim 1,
Wherein each inlet of the gravity injection pipe has a funnel shape, a float is disposed at each inlet of the gravity injection pipe having the funnel shape, and a floating cap is provided below the float, and the inside of each inlet of the gravity injection pipe, And a stopper guide is formed in the center of the lower end of the floating stopper in the direction of the inlet of the gravity injection pipe so that the water level in the water supply reservoir is higher than the inlet of the gravity injection pipe The entrance of the gravity injection pipe exposed above the water surface in the water supply reservoir is closed by the floating stopper to prevent the inflow of air
Wherein the gravity feed flow control system comprises:
The method according to claim 1,
Wherein a floating member is disposed around each inlet of the gravity injection pipe and a fixed sheave is installed at a predetermined distance below the floating member and connected to the float to connect the supporting member to a supporting string passing through the fixed sheave, As the valve body is coupled and the water level in the water supply reservoir becomes lower than the inlet of the gravity injection pipe, the entrance of the gravity injection pipe exposed above the water surface in the water supply reservoir is closed by the floating valve body,
Wherein the gravity feed flow control system comprises:

Images