JPH0587971A - Emergency core cooling system of nuclear reactor - Google Patents

Abstract

PURPOSE:To enable highly reliable water injection into a reactor core during reactor accident for a high pressure range to a low pressure range thereof, without any additional dynamic equipments which require very high reliability. CONSTITUTION:At a position higher than a reactor core 14 in a nuclear reactor pressure vessel 13, a gravity falling type core cooling system pool 17 is installed in a nuclear reactor containment vessel 1. Beneath the cooling system pool 17, a pressure suppression pool 15 is also installed and a steam injector 2 is installed in a dry well of the nuclear reactor containment vessel 1, as well. This steam injector 2 is connected to a steam feed line 4 which is connected to the nuclear rotor pressure vessel 13, a steam discharge line 5, a feed water line 3 which is connected to the gravity falling type core cooling system pool 17, and a drain line 36 which is connected to the pressure suppression pool 15, and also both a reducing valve 20 of the steam feed line 4 and a control valve 6 of the feed water line 4 are connected to a controller 38 through signal leads 39 and 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear reactor emergency core cooling system, and more particularly to a nuclear reactor emergency core cooling system using a steam injector suitable as an emergency high pressure core water injection system for light water reactors.

[0002]

2. Description of the Related Art In a nuclear power plant, an emergency core cooling system facility (ECCS) is provided in case of a coolant outflow due to a break of a reactor system piping. This equipment consists of multiple independent systems, and is configured to start automatically in the event of an accident. 2. Description of the Related Art Conventionally, it is known that a steam injector is incorporated into an emergency cooling system of a nuclear reactor in an emergency core cooling facility.

That is, as shown in FIG. 4, a steam injector 2 is installed in a reactor containment vessel 1, and a water supply line 3, a steam line 4 and a cooling water discharge line 5 are connected to the steam injector 2. The water supply line 3 is connected to a cooling water supply tank 8 installed outside the reactor containment vessel 1 through a water supply check valve 6 and a water supply control valve 7, and a steam line 4 is connected via a steam supply control valve 9. Connected to the main steam line 10,
The cooling water discharge line 5 is connected to the main water supply pipe through the discharge check valve 11.
12 and the reactor containment vessel 1 via this main water supply pipe 12.
It is connected to the reactor pressure vessel 12 housed inside. In addition,
In the figure, reference numeral 14 is the core, 15 is the pressure suppression pool, and 16 is the isolated cooling pool. The steam injector 2 has a structure as shown in FIG. 5, for example.

That is, in the steam injector shown in FIG. 5, a casing 22 having a steam supply port 21 is provided with a steam jet nozzle 24 having a needle valve 23, and the steam jet nozzle 24 is provided.
Adjacent to the water suction port 25. A steam / water mixing nozzle 26 and a pressurizing dephasor are provided downstream of the steam jetting nozzle 24.
27 is provided and communicates with the discharge port 29 via the check valve 28. The throat portion 30 of the steam / water mixing nozzle 26 has an overflow drainage port 32 communicating with an overflow water distribution pipe 31.

Then, for example, the needle valve 23 is attached to the handle 33.
When the steam supplied from the steam supply port 21 is discharged from the steam discharge nozzle 24 by the steam discharge nozzle 24,
The steam is condensed by the supply water (about 70 ° C. lower than the saturation temperature of the supply steam) sucked from the water suction port 25, flows into the steam / water mixing nozzle 26, and becomes a high-speed water flow in the throat section 30. That is, the throat portion 30 has a structure in which the cooling water flows out from the cooling water discharge port as a high-speed water flow whose pressure is higher than the driving steam pressure.

As described above, the steam injector 2 has an advantage that its structure is not so complicated and that it itself does not require a dynamic device such as a motor. A check valve for overflow (not shown) is provided in the casing 22, and the drain line connected from the check valve causes the steam / water mixing nozzle 24 to have a negative pressure when the steam injector operates. ,
The check valve has the advantage that it automatically closes and does not require negative pressure. In an emergency core cooling system for a nuclear reactor using this steam injector, when emergency core cooling is required due to loss of coolant, etc., the water supply control valve opens and water is supplied to the steam injector, and steam supplied from the steam line is After condensing, the feed water is pressurized and injected into the core to cool the core.

As an emergency core cooling system for injecting at a low pressure, a gravity-drop type core cooling system having a structure shown in FIG. 6 is known. The gravity-drop core cooling system pool 17 is installed at a position higher than the core 14 in the reactor containment vessel 1, and is connected to the reactor pressure vessel 13 with a cooling line 19 having a check valve 18 to form a reactor pressure vessel 13. Is equipped with a plurality of pressure reducing valves 20. A pressure equalizing line 34 is connected between the pressure suppression pool 15 and the check valve 18,
The pressure equalizing line 34 is provided with a pressure equalizing line control valve 35. Since this gravity drop type core cooling system uses gravity as a driving force, it does not require a dynamic device such as a pump and has a simple structure. In this gravity drop type emergency core cooling system, when an accident such as pipe breakage occurs, the pressure reducing valve 20 opens to reduce the pressure in the reactor pressure vessel 13, and cooling water due to gravity drop flows into the core for cooling. ..

[0008]

However, in the emergency core cooling system of a nuclear reactor using the steam injector 2, in order for the steam injector 2 to start, an interface at which the inflowing steam comes into contact and condensation occurs is required. is there. Since cooling water must be supplied to the steam injector 2 to form the interface, a separate drive system such as a pump is required. In a reactor cooling system using a steam injector, when emergency core cooling is required due to loss of coolant or the like, the steam supply control valve 9 and the water supply control valve 7 that drive the steam injector 2 are reliably opened to supply water. The water in the tank 8 must flow in. Therefore, there is a problem that the steam injector does not operate unless a system necessary for starting these is prepared.

In the gravity drop type emergency core cooling system, the pressure inside the reactor pressure vessel 13 is rapidly reduced to the atmospheric pressure by opening the depressurization 20 so that the cooling water due to the gravity drop is not injected into the core. Therefore, it is a problem that a large number of highly reliable pressure reducing valves that open at the time of an accident must be used in an amount of about twice the number of conventional BWRs.

The present invention has been made to solve the above problems, and provides an emergency core cooling system for a nuclear reactor which has a steam injector start-up system and which can highly reliably inject water into the core in the event of an accident from high pressure to low pressure. It is in.

[0011]

A first aspect of the present invention is to provide a reactor pressure vessel housed in a reactor containment vessel, and a reactor containment vessel at a position higher than a reactor core arranged in the reactor pressure vessel. A gravity drop core cooling system pool installed in the vessel, a pressure suppression pool installed under the gravity drop cooling system pool, and a steam injector installed in the dry well of the reactor containment vessel. , A steam supply line connecting the steam inlet of the steam injector and the reactor pressure vessel, a water supply line connecting the water supply port of the steam injector and the gravity drop core cooling system pool, and cooling water of the steam injector A cooling water discharge line connecting the discharge port and the reactor pressure vessel, a drain line connecting the drain port of the steam injector and the pressure suppression pool,
A control device for controlling the pressure reducing valve of the steam supply line and the control valve of the water supply line are provided.

The second invention is installed in the reactor containment vessel at a position higher than the reactor pressure vessel housed in the reactor containment vessel and the reactor core arranged in the reactor pressure vessel. Gravity drop type core cooling system pool, pressure suppression pool installed below this gravity drop type cooling system pool,
A steam injector installed in the dry well of the reactor containment vessel, a steam supply line connecting the steam inlet of the steam injector and the reactor pressure vessel, a water inlet of the steam injector, and the gravity drop type. A water supply line connecting the core cooling system pool, a cooling water discharge line connecting the cooling water discharge port of the steam injector and the reactor pressure vessel, and a drain line connecting the drain port of the steam injector and the pressure suppression pool And a water supply circulation pump installed in the pressure suppression pool, and a water supply circulation line having the water supply pump and a check valve for water supply circulation and connecting the gravity drop type cooling pool. ..

According to a third aspect of the present invention, the reactor pressure vessel stored in the reactor containment vessel and the reactor pressure vessel installed at a position higher than the reactor core arranged in the reactor pressure vessel. Gravity drop type core cooling system pool, pressure suppression pool installed below this gravity drop type cooling system pool,
A steam injector installed in the dry well of the reactor containment vessel, a steam supply line connecting the steam inlet of the steam injector and the reactor pressure vessel, a water inlet of the steam injector, and the gravity drop type. A water supply line connecting the core cooling system pool, a cooling water discharge line connecting the cooling water discharge port of the steam injector and the reactor pressure vessel, and a drain line connecting the drain port of the steam injector and the pressure suppression pool An accumulator water supply tank installed in the dry well of the reactor containment vessel, and an accumulator line having a start-up control valve connecting the accumulator water supply tank and the water supply port of the steam injector, the pressure reducing valve and the start-up valve. And a control device for controlling the control valve for use.

[0014]

In the first aspect of the invention, in an emergency, for example, first, the gravity drop type core cooling system pool supplies water to the steam injector for startup, and then the steam released from the pressure reducing valve is introduced into the steam injector to start the steam injector. To do. Water in the core cooling system pool is pressurized and injected into the core to cool the core. Thereby, the cooling water can be injected in a wide pressure range from high pressure to low pressure.

In the second aspect of the present invention, during normal operation, the gravity drop type cooling core system pool is pumped up from the pressure suppression pool to the gravity drop core cooling system pool by the amount of water flowing into the pressure suppression pool through the drain line of the steam injector. In an emergency, the steam released from the pressure reducing valve is introduced into the steam injector to activate the steam injector. Gravity drop type core cooling system pool water is pressurized and injected into the core. Therefore, by constantly supplying water to the steam injector by gravity, it is possible to omit a dynamic device such as a water supply pump for driving the steam injector and a control valve that operates in an emergency. Other functions are similar to those of the first invention.

In the third aspect of the invention, in an emergency, the starting water is first supplied from the accumulator water supply tank to the steam injector,
Next, the steam released from the pressure reducing valve is introduced into the steam injector, and the steam injector is activated. By this start-up, the water in the cooling system pool is pressurized and injected into the core.
In addition, for emergency cooling, by supplying steam injectors from a gravity-drop type core cooling system pool above the core, it is possible to omit dynamic equipment such as the water pump for driving the steam injectors. Other functions are similar to those of the first invention.

[0017]

EXAMPLE A first example of the emergency core cooling system for a nuclear reactor according to the present invention will be described with reference to FIG. In the figure, the same parts as those in FIG. 4 and FIG.

That is, in FIG. 1, a water supply line 3 connected to a water supply port, a steam supply line 4 connected to a steam inlet, a cooling water discharge line 5 connected to a cooling water discharge port, and a drain line 36 are connected to the steam injector 2. ing. The water supply line 3 passes through a water supply control valve 6 and is a gravity-drop type cooling system pool.
17, the steam line 4 is passed through the pressure reducing valve 20 to the reactor pressure vessel.
13, the cooling water discharge line 5 is connected to the reactor pressure vessel 13 via the discharge check valve 11, and the drain line 36 is connected to the pressure suppression pool 15 via the drain check valve 37. The water supply control valve 6 and the pressure reducing valve 20 are connected to the control device 37 via signal lines 38 and 39, respectively.

When emergency core cooling is required due to pipe breakage or the like, the water supply control valve 6 first opens to supply water to the steam injector 2 through the water supply line 3 due to a decrease in the water level in the pressure vessel 13. Next, when the pressure reducing valve 20 linked with the control valve 6 having the control system device 38 such as a timer is opened and the steam is supplied to the steam injector 2, the steam is condensed inside the steam injector 2 and the steam injector 2 is activated. The supply water is boosted to a pressure equal to or higher than the supply vapor pressure, that is, a pressure in the reactor pressure vessel 13 or higher. Check valve for discharge 11
Since it opens, water can be poured into the core 14. On the other hand, the steam / water mixing nozzle in the steam injector 2 in which the steam injector 2 operates has a negative pressure, and the drain check valve 37 closes the drain 36. Further, in the construction of an actual plant, in order to improve the starting characteristics of the steam injector, the steam injector 2
Is installed in the dry well as low as possible, and it is important to increase the water head difference from the gravity drop type core cooling system pool 17.

According to the first embodiment, the system has a system necessary for starting the steam injector as the emergency core cooling system, and has a pressure higher than that of the gravity drop type core cooling system and higher than the pressure in the reactor pressure vessel. Since it is possible to inject the boosted cooling water into the core, it is possible to inject water into the core in a wide pressure range from high pressure to low pressure, and it is possible to significantly reduce the number of pressure reducing valves that require high reliability. Increases safety. Further, the system configuration is simple, and the conventional technology can be used, so that the cost is excellent, and the system is suitable as an emergency cooling system for a nuclear reactor.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, the steam injector 2
A water supply line 3 connected to a water supply port, a steam supply line 4 connected to a steam inlet, a cooling water discharge line 5 connected to a cooling discharge port, and a drain line 36 are connected to the. The water supply line 3 is supplied through the water supply check valve 41 to the gravity drop cooling system pool 17, the steam supply line 4 is supplied through the pressure reducing valve 20 to the reactor pressure device 13, and the cooling water discharge line 5 is supplied through the discharge check valve 11. A drain line 36 is connected to the furnace pressure vessel 13 via a drain check valve 37 to the pressure suppression pool 15. A water supply circulation pump 42 is installed in the pressure suppression pool 15. The water supply circulation pump 42 is connected to the dynamic drop type core cooling system pool 17 by a water supply circulation line 43. Water supply circulation line 43
A check valve 44 for water supply circulation is connected to the. Further, during normal operation of the nuclear reactor, the cooling water supplied to the steam injector 7 is constantly fed from the drain line 36 to the pressure suppression pool.
Flowing from the pressure suppression pool 15 to the gravity-falling core cooling system pool 17 is circulated in a closed system in which a circulation pump 42 pumps up the pressure suppression pool water. The cooling water that circulates in this closed system does not require a large flow rate because it continuously forms a condensation interface with the steam at the injector when the steam injector 7 is started. Therefore, the circulation pump 42 needs only a small procedure, and since the lift is at most from the pressure suppression pool 15 to the isolated cooling pool 16, it is possible to use a small one with low power consumption. It does not need to be extremely reliable as it does not need to be activated when is needed.

When an emergency core cooling system is required due to pipe breakage or the like, the pressure reducing valve 8 is caused by a decrease in the water level in the reactor pressure vessel 13.
Is opened and steam is supplied to the steam injector 2. Since there is always a flow rate of supply water through the water supply line 3 due to gravity, steam condensation occurs, the steam injector 2 operates, and the supply water is boosted to a pressure higher than the supply steam pressure, that is, a pressure in the reactor pressure vessel 2 or higher. Therefore, since the discharge check valve 11 opens, water can be poured into the core 14. Meanwhile, the steam injector 2
Is activated, the steam / water mixing nozzle inside the steam injector becomes negative pressure, and the check valve 37 for drain drains the drain line.
36 closes. Further, in the construction of an actual plant, in order to improve the starting characteristics of the steam injector, the steam injector 7 is installed in the dry well at a position as low as possible to increase the water head difference from the gravity drop type core cooling system pool 17. This is very important.

According to the second embodiment, a dynamic device such as a steam injector feed pump, which requires high reliability for starting a steam injector as an emergency core cooling system, and an advanced control in an emergency. The control valve to operate can be omitted. On the other hand, since cooling water that has been pressurized to a pressure higher than that in the reactor pressure vessel at a pressure higher than that of the gravity drop type core cooling system can be injected into the core, core water injection is possible in a wide pressure range from high pressure to low pressure, and high reliability The number of pressure reducing valves required can also be significantly reduced.

Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 3, the steam injector 2
Is connected to a starting accumulator line 45 connected to the water supply port, a water supply line 3 also connected to the water supply port, a steam supply line 4 connected to the steam inlet, a cooling water discharge line 5 connected to the cooling water discharge port, and a drain line 36. There is. The accumulator line 45 passes through the control valve 46 for starting and the accumulator water supply tank 47, and the water supply line 3 passes through the check valve 41 for supplying water.
7. Reactor pressure vessel 13 through pressure reducing valve 20 for steam supply line 4, reactor pressure 13 through discharge check valve 11 for cooling water discharge line 5, and pressure control through drain check valve 37 for drain line 36. It is tied to pool 15. The pressure reducing valve 20 and the starting control 46 are connected to the control device 38 by signal lines 40 and 48, respectively.

However, when emergency core cooling is required due to pipe breakage or the like, the control valve 46 for starting the steam injector 2 is first opened due to the decrease in the water level in the reactor pressure vessel 13, and the steam injector 2 stores the accumulator water tank. 47 to accumulator line 45
Water is supplied to the steam injector 2, and then the pressure reducing valve 20 linked with the control valve 46 is opened by the control device 38 such as a timer, and the steam injector 2 is started when steam is supplied to the steam injector 2. Then, condensation of steam occurs inside the steam injector 2, the steam injector 2 operates, and the supply water from the gravity drop type core cooling system pool 17 is supplied steam pressure or more,
That is, since the discharge check valve 11 opens by increasing the pressure in the reactor pressure vessel 13 or more, water can be injected into the reactor core 14. On the other hand, the steam / water mixing nozzle inside the steam injector 2 in which the steam injector 2 operates becomes negative pressure, and the check line 37 for the steam injector drain closes the drain line 36. In order to improve the starting characteristics of the steam injector 2 in the construction of an actual plant, the steam injector 2 should be installed at the lowest possible position in the dry well to increase the water head difference from the gravity drop type core cooling system pool 17. is important.

According to the third embodiment, the emergency core cooling system has a system necessary for starting the steam injector, and the pressure is higher than that of the gravity drop core cooling system and is higher than the pressure in the reactor pressure vessel. Since boosted cooling water can be injected into the core, core water injection is possible in a wide pressure range from high pressure to low pressure, and reducing the number of pressure reducing valves that require high reliability further enhances reactor safety. .. Also,
Since the system configuration is simple and the existing technology is used, the cost is excellent and it is suitable as an emergency cooling system for a nuclear reactor.

[0027]

According to the present invention, by supplying water to the steam injector by gravity from the water supply line connected to the gravity drop type core cooling system pool, it is possible to omit the dynamic equipment such as the water supply pump for starting the steam injector. In addition, the steam released from the pressure reducing valve is introduced into the steam injector, and by activating the steam injector, the cooling water in the gravity drop type core cooling system pool can be boosted to a pressure higher than the pressure in the reactor pressure vessel and injected into the core. Therefore, cooling water can be injected in a wide pressure range from high pressure to low pressure, and rapid depressurization is not required, so the number of pressure reducing valves required to have high reliability can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of an emergency core cooling system for a nuclear reactor according to the present invention.

FIG. 2 is a system diagram showing a second embodiment of an emergency core cooling system for a nuclear reactor according to the present invention.

FIG. 3 is a system diagram showing a third embodiment of an emergency core cooling system for a nuclear reactor according to the present invention.

FIG. 4 is a system diagram showing a first example of a conventional emergency core cooling system for a nuclear reactor.

5 is a vertical sectional view showing an example of the steam injector in FIG.

FIG. 6 is a system diagram showing a second example of a conventional emergency core cooling system for a nuclear reactor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor containment vessel, 2 ... Steam injector, 3 ... Water supply line, 4 ... Steam supply line, 5 ... Cooling water discharge line,
6 ... Water supply control valve, 7 ... Water supply stop valve, 8 ... Cooling water supply tank, 9 ... Steam supply control valve, 10 ... Main steam line, 11
… Check valve for discharge, 12… Main water supply pipe, 13… Reactor pressure vessel,
14 ... Reactor core, 15 ... Pressure suppression pool, 16 ... Isolation cooling pool,
17 ... Gravity drop core cooling system pool, 18 ... Check valve, 19 ... Cooling line, 20 ... Pressure reducing valve, 21 ... Steam supply port, 22 ... Casing, 23 ... Needle valve, 24 ... Steam injection nozzle, 25 ... Water suction Mouth, 26 ... Steam ejection nozzle, 27 ... Booster diffuser, 28 ...
Check valve, 29 ... Discharge port, 30 ... Throat part, 31 ... Overflow water pipe, 32 ... Overflow drain port, 33 ... Handle, 34 ... Pressure equalizing line, 35 ... Pressure equalizing line control valve, 36 ... Drain line, 37 ... Check valve for drain, 38 ... Control device, 39,
40, 48 ... Signal lines, 41 ... Water supply check valve, 42 ... Water supply circulation pump, 43 ... Water supply circulation line, 44 ... Water supply circulation check valve, 45 ...
Accumulation line, 46 ... Control valve for start-up, 47 ... Accumulation water tank.

Claims (3)

[Claims] 1. A reactor pressure vessel housed in a reactor containment vessel, and a gravity drop type installed in the reactor containment vessel at a position higher than a reactor core arranged in the reactor pressure vessel. Core cooling system pool, pressure suppression pool installed below this gravity drop cooling system pool, steam injector installed in the dry well of the reactor containment vessel, and steam inlet of this steam injector A steam supply line connecting the reactor pressure vessel, a water supply line connecting the water supply port of the steam injector and the gravity drop core cooling system pool, a cooling water discharge port of the steam injector, and the reactor pressure vessel. Cooling water discharge line connecting
A drain line that connects the drain port of the steam injector and the pressure suppression pool, and a control device that controls a pressure reducing valve of the steam supply line and a control valve of the water supply line. Emergency core cooling system. 2. A reactor pressure vessel housed in a reactor containment vessel, and a gravity drop type installed in the reactor containment vessel at a position higher than a reactor core arranged in the reactor pressure vessel. Core cooling system pool, pressure suppression pool installed below this gravity drop cooling system pool, steam injector installed in the dry well of the reactor containment vessel, and steam inlet of this steam injector A steam supply line connecting the reactor pressure vessel, a water supply line connecting the water supply port of the steam injector and the gravity drop core cooling system pool, a cooling water discharge port of the steam injector, and the reactor pressure vessel. Cooling water discharge line connecting
A drain line that connects the drain port of the steam injector and the pressure suppression pool, a water supply circulation pump installed in the pressure suppression pool, the water supply pump and a check valve for water supply circulation, and the gravity drop type An emergency core cooling system for a nuclear reactor, comprising a water supply circulation line connecting with a cooling system pool. 3. A reactor pressure vessel stored in the reactor containment vessel, and a gravity drop type installed in the reactor containment vessel at a position higher than the reactor core arranged in the reactor pressure vessel. Core cooling system pool, pressure suppression pool installed below this gravity drop cooling system pool, steam injector installed in the dry well of the reactor containment vessel, and steam inlet of this steam injector A steam supply line connecting the reactor pressure vessel, a water supply line connecting the water supply port of the steam injector and the gravity drop core cooling system pool, a cooling water discharge port of the steam injector, and the reactor pressure vessel. Cooling water discharge line connecting
A drain line that connects the drain port of the steam injector and the pressure suppression pool, a pressure storage water supply tank installed in the dry well of the reactor containment vessel, and connects the pressure storage water supply tank and the water supply port of the steam injector. An emergency core cooling system for a nuclear reactor, comprising: a pressure accumulating line having a start-up control valve; and a control device for controlling the pressure reducing valve and the start-up control valve.