JP2001183490A - Reactor core flow control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor core flow control system in a boiling water nuclear power plant having internal pumps, avoiding lowering of the output during the disturbance of a power supply due to system-shutdown and suitably maintaining soundness of the fuel. SOLUTION: The boiling water nuclear power plant, having a plurality of internal pumps 3-1 to 3-10 uses a MG set with a fluid joint consisting of a MG set drive motor 403, a fluid joint 404 and a variable frequency generator 405, as a variable frequency power supply for the internal pumps, with all of the plurality of internal pumps connected to the MG set with the fluid joint. The plurality of internal pumps are divided into plural groups 3-1 to 3-5 and 3-6 to 3-10, each group of which is connected with the MG sets with fluid joints 403A, 404A, 405A and 403B, 404B and 405B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a core flow control system for a boiling water nuclear power plant employing an internal pump (recirculation pump).

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional core flow control system for a boiling water nuclear power plant having an internal pump has ten internal pumps 3-1 to 3-1.
3-10, 10 variable frequency power supply devices (inverter devices) 423A-1 to 423A-5, 423B-6 to 42
3B-10, four input transformers 421A, 422A, 4
21B, 422B and two MG sets (Moter
-Generator) (403A-405A, 403)
B-405B) Two in-house transformers 20-1 and 20-
2. It is composed of circuit breakers 412A, 424A, 412B, 424B. The voltage from the generator 7 is transformed by the on-site transformers 20-1 and 20-2,
A, 424A, 412B, and 424B, are directly input to the MG set (403A-405A, 403B-405B) and the input transformers 422A and 421B, and
The output of the set is input to input transformers 421A and 422B. Input transformers 421A, 422A, 421
B, 422B transform the voltage, inverter devices 423A-1 to 423A-5, 423B-6 to 423B
-10 is input. Inverter devices 423A-1 to 423A-4
23A-5, 423B-6 to 423B-10 convert and output the power supply frequency to the internal pumps 3-1 to 3-10, and directly control the conversion of the rotation speed of the pumps. Here, the MG set (403A-405A, 403B-40
5B) is to maintain the power supply to the inverter device for a certain period of time even when a power supply disturbance such as a system accident occurs due to mechanical inertia and to maintain the required core cooling. 403A-405A, 403
B-405B) itself with internal pumps 3-1 to 3-
3 and 3-8 to 3-10 do not have the function of converting the power supply frequency. The conversion of the power supply frequency is performed by the inverter 423A.
-1 to 423A-3 and 423B-8 to 423B-10. The inverter devices 423A-1 to 423A-42
3A-5, 423B-6 to 423B-10 have little electrical inertia. In addition, the circuit breakers 412A, 424A, 4
12B and 424B are installed from the viewpoint of device protection.

[0003]

In a conventional core flow control system of a boiling water nuclear power plant having an internal pump, a bus voltage is reduced for a short time (= about several hundred milliseconds) due to a system accident or the like. When an event of returning to the original bus voltage after 100 milliseconds (hereinafter, abbreviated as “instantaneous stop”) occurs, six internal pumps 3-1 to 3-3, 3- Regarding 8 to 3-10, since the mechanical inertia of the MG set is large, the inverter devices 423A-1 to 423A are generated by the mechanical inertia.
The input voltages of −3, 423B-8 to 423B-10 do not decrease. Therefore, it is possible to continue the operation while supplying a constant flow rate from the pump to the core without lowering the internal pump speed. Meanwhile, MG
For the four internal pumps 3-4 to 3-5 and 3-6 to 3-7 connected to two systems without a set, MG
Since mechanical inertia due to the set cannot be expected, inverter devices 423A-4 to 423A-5 and 423B-6 to 4
The input voltage of the 23B-7 drops directly under the influence of the bus voltage drop. For this reason, the pump speed decreases, and the flow rate supplied to the core by the internal pump also decreases. As a result, the total core flow decreases,
The reactor power will be reduced by an amount corresponding to the decrease in the total core flow rate (for example, a decrease of about 20%). This is not preferable from the viewpoint of stable power supply, and is a problem.

[0004] Further, as an event in which the bus voltage is instantaneously lost due to a system accident or the like and it takes a long time to recover to the original voltage (hereinafter, abbreviated as "all stop"), there is a loss of an external power supply. . If the external power supply is lost, four internal pumps without the MG set will trip at the same time as the power loss, and six with the MG set will trip instantly due to the mechanical inertia of the MG set. However, it trips, for example, three seconds after the power is lost. In this case, since the inertia of the internal pump itself is small, the core flow rate sharply decreases. A sharp decrease in the core flow rate causes transition boiling of the fuel, which is a very severe event from the viewpoint of ensuring fuel integrity and is a problem.

When the bus voltage gradually decreases due to system fluctuation or the like, the input voltages of all the inverter devices also gradually decrease regardless of the presence or absence of the MG set. On the other hand, the inverter device has a function of stopping the inverter device itself from the viewpoint of protecting its own equipment when the voltage drop reaches a certain set value. As a result, all of the inverter devices may trip at the same time, and in this case, too, for the same reason as the loss of the external power supply, it becomes a very severe event from the viewpoint of ensuring fuel integrity.

[0006] The inverter system used in the conventional core flow control system is complicated and expensive as a device. Particularly, when the generator load is cut off, when the reactor pressure is high and the reactor water level is low, the inverter system is used. The interlock that trips the internal pump using the inverter system required a complicated mechanism.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, an object of the present invention is to provide a boiling water nuclear power plant having an internal pump, which is suitable for avoiding a decrease in output during a power supply disturbance due to a system accident and ensuring fuel integrity. To provide a simple core flow control system.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a variable frequency power supply for an internal pump is used.
An MG set with a fluid coupling comprising a G set drive motor, a fluid coupling and a variable frequency generator is used, and all of the plurality of internal pumps are connected to the MG set with a fluid coupling. Here, an MG set with a fluid coupling is connected to each of the plurality of internal pumps divided into a plurality of groups. Also, an MG set with a fluid coupling is connected to each group of ten internal pumps divided into two groups of five.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration of a core flow control system in a boiling water nuclear power plant showing an embodiment of the present invention. In FIG. 1, the reactor core 2
, The cooling water in the reactor pressure vessel 1 is sent by the internal pumps 3-1 to 3-10 to secure the core flow rate. The cooling water is heated in the reactor core 2 and is generated as steam in the reactor pressure vessel 1. The generated steam enters the turbine 6 through the main steam pipe 4, and rotates the turbine 6. The steam used for rotating the turbine 6 is cooled by the condenser 10 and returned to the cooling water. This cooling water is supplied again into the reactor using the water supply pump 11. Further, the generator 7 is driven by the rotation of the turbine 6, and supplies power to the system from the generator 7.

First, an embodiment of the present invention in which an MG set system with a fluid coupling is applied to a core flow rate control system will be described with reference to FIG. The core flow control system includes a turbine electrohydraulic control device 200, a recirculation flow control circuit 300, and an MG set system 400A, 4 with a fluid coupling.
00B. A load setting signal 425 is input from a load setting device (not shown) to the turbine electro-hydraulic control circuit 200, and the reactor pressure signal 17 detected by the pressure detector 13 and the turbine speed signal 16 from the turbine 6 To calculate the load / speed deviation signal 201 corresponding to the output. The recirculation flow control circuit 300 receives the load / speed deviation signal 201 and the variable frequency generator speed signals 402A and 402B that are fed back from the MG set systems 400A and 400B with a fluid coupling. The recirculation flow control circuit 300 outputs the load / speed deviation signal 201
And rake pipe position control signals 301A and 301B are calculated from the variable frequency generator speed signals 402A and 402B. MG set system with fluid coupling 400A, 400
B, the rake pipe position control signals 301A and 301B are inputted, and the generators 7 transmit the rake pipe position control signals 301A and 301B.
Supply power through. The MG set systems 400A and 400B with a fluid coupling are provided with a rake pipe position control signal 30.
1A, 301B, the internal pump 3-1 to
For 3-10, variable frequency generator rotation speeds 401A and 401B for changing the pump rotation speed are output. The MG set system with fluid coupling 400A drives the internal pumps 3-1 to 3-5, and the MG set system with fluid coupling 400B drives the internal pumps 3-6 to 3-10, respectively. The internal pump speed is synchronized with the variable frequency generator speeds 401A and 401B, and is fed back to the recirculation flow control circuit 300 as variable frequency generator speed signals 402A and 402B.

FIG. 2 shows a detailed configuration of the recirculation flow control circuit 300 according to the present embodiment. Recirculation flow control circuit 300
Is composed of a main controller 408, speed controllers 409A and 409B, and rake tube drive motors 410A and 410B. The main controller 408 in the recirculation flow control circuit 300 includes:
Load calculated by the turbine electro-hydraulic control circuit 200 /
The speed request signal 411 is calculated using the speed deviation signal 201. The speed request signal 411 is separated into two at the output side of the main controller 408, and each of the variable frequency
After taking the deviation from 02A or 402B, it is input to the speed controller 409A or 409B. Speed controller 4
The speed request signal calculated in 09A or 409B is input to rake tube drive motors 410A and 410B, respectively. Rake tube position control signals 301A and 301B are output from the rake tube drive motors 410A and 410B to control the positions of the rake tubes 406A and 406B.

FIG. 3 shows a detailed configuration of MG set systems 400A and 400B with a fluid coupling. In FIG.
The voltage from the generator 7 is applied to the on-site transformers 20-1 and 20-
After changing the pressure in step 2, breaker 412 for MG set trip
A and 412B are input to MG set systems 400A and 400B with fluid coupling. Since the functions of MG set systems with fluid coupling 400A and 400B are equivalent, the following description will be made for MG set system with fluid coupling 400A. The MG set system 400A with a fluid coupling transmits the torque from the MG set drive motor 403A that moves at a constant rotation speed by the alternating current through the in-house transformer 20-1 and the torque from the MG set drive motor 403A to the variable frequency generator 405A. And a variable frequency generator 405A for changing the internal pump rotation speed by the torque from the fluid coupling 404A. Fluid coupling 404A
Is filled with oil, and by changing the oil level position in the fluid coupling 404A, the MG set driving motor 40
The torque transmitted from 3A to variable frequency generator 405A is changed, and the rotation speed of variable frequency generator 405A is changed. Changing the oil level of the fluid coupling 404A
This is performed by changing the position of the rake tube 406A inserted in A. The position of the rake pipe 406A is determined by the rake pipe position request signal 301A from the recirculation flow control circuit 300.
Will be changed by The output of the variable frequency generator 405A is divided into five, and the breakers 407A-1 to 407A-
5, and is supplied to the internal pumps 3-1 to 3-5 to control the pump rotation speed. Now, if the load / speed deviation signal 201 shown in FIG. 1 changes and the rake pipe position request signal 301A from the recirculation flow control circuit 300 changes, the position of the rake pipe 406A changes, and the fluid coupling 40 changes.
Change the oil level of 4A. This change in the oil level changes the torque transmitted from the MG set drive motor 403A to the variable frequency generator 405A, and changes the rotation speed of the variable frequency generator 405A. By changing the rotation speed of the variable frequency generator 405A, the rotation speeds of the internal pumps 3-1 to 3-5 are controlled. Here, the circuit breakers 407A-1 to 407A-5 are internal pump trip circuit breakers provided on the input side of the internal pump, and stop the drive of the downstream internal pump.
Alternatively, when an abnormality occurs in the internal pump, the internal pump has a function of disconnecting the pump from the system. In the present embodiment, ten internal pumps and two MG set systems with fluid coupling have been described. However, it goes without saying that the number and the number of systems may be arbitrarily determined as necessary.

FIG. 5 shows a comparison between the instant embodiment employing the MG set systems 400A and 400B with a fluid coupling as the internal pump drive mechanism and the conventional example shown in FIG. Instantaneous blackout is generated by system fault or the like, when the bus voltage drops within the time tt ₁ as (a), in the case of the conventional example (shown by a dotted line), four internal pump having no MG set, The pump speed is reduced as shown in (b) because it is directly affected by the bus voltage drop. However, the pump speeds of the six internal pumps having the MG set maintain the current state. However, the total core flow rate decreases as shown in (c), and the generator output eventually decreases as shown in (d). On the other hand, in the case of the present embodiment (shown by a solid line), both systems have fluid coupling M
Since the G set systems 400A and 400B have mechanical inertia, the output voltage to each internal pump does not decrease even if the bus voltage decreases for a short time. For this reason, the pump speed is maintained at the present level as shown in (b), and since all the internal pumps are driven, the total core flow rate is kept constant as shown in (c). As a result,
As shown in (d), there is no decrease in the generator output at the moment of an instantaneous stop. As described above, according to the present embodiment, the operation at the momentary stop can be continued, and the stable supply of electric power is possible.

As an internal pump drive mechanism, MG set systems 400A and 400A with a fluid coupling are provided.
FIG. 6 shows a comparison of the behavior at the time of a full stoppage between the embodiment adopting 00B and the conventional example shown in FIG. When a total stoppage occurs due to the loss of the external power supply, the voltage to the transformers 20-1 and 20-2 instantaneously becomes zero as shown in FIG. In the case of the conventional example (indicated by the dotted line), all the four units without the MG set trip at the same time as the total stoppage, and the six units with the MG set trip with the mechanical inertia of the MG set but three seconds after the full stoppage. Therefore, the rotation of the internal pump is stopped as shown in FIG. The total core flow rate rapidly decreases as shown in (c), and it becomes difficult to secure the thermal integrity of the fuel. Eventually, the generator output will decrease as shown in (d). On the other hand, in the case of the present embodiment (shown by a solid line), even if the bus voltage is instantaneously lost, the pump speed is reduced because all the internal pumps are connected to the MG set system with a fluid coupling having large mechanical inertia. , Depending on the mechanical inertia of the MG set, and gradually decreases until time t ₁ as shown in FIG. As a result, the decrease in the total core flow rate is also moderated as shown in (c), and as shown in (d), the generator output at the time of a full stop is gradually decreased. As described above, according to the present embodiment, since the decrease in the total core flow rate at the time of the full stop is alleviated, the transition boiling of the fuel can be suppressed, and the thermal integrity of the fuel can be ensured. Regarding system fluctuations in which the bus voltage gradually decreases, in the case of the conventional example, the inverter device is used as the variable frequency power supply device. Stops its operation. For this reason, all the internal pumps are suddenly stopped at the time of system fluctuation. On the other hand, in the case of the present embodiment, an MG set with a fluid coupling having large mechanical inertia is adopted as the variable frequency power supply device, and the variable frequency generator does not stop even if a voltage drop is detected. In addition, it is possible to eliminate sudden stoppage of all the internal pumps at the time of system fluctuation. As a result, as in the case of a full stop, the decrease in the total core flow rate is alleviated, so that the thermal integrity of the fuel can be ensured.

Next, referring to FIG. 1, another embodiment of the present invention will be described as an interlock mechanism relating to a core flow control system in the case of a generator water load interruption in a boiling water nuclear power plant. The interlock mechanism according to the present embodiment includes a power load unbalance relay circuit 14, a control valve 5 installed in the main steam pipe 4, a bypass valve 9 installed in the bypass pipe 8, and an MG set system 400A with a fluid coupling. The power load unbalance relay circuit 14 receives the turbine speed signal 16 from the turbine 6 and the generator output signal from the generator 7, and the power load unbalance relay circuit 14 compares the two signals to generate power. When the machine load is interrupted, the difference between the two signals becomes equal to or larger than the set value, and the control valve suddenly closes and the bypass valve sudden open request signal 15 is output. The control valve rapid-closing bypass valve rapid-opening request signal 15 rapidly closes the control valve 5 and simultaneously opens the bypass valve 9 in order to suppress an increase in the rotation speed of the turbine. When the control valve 5 is rapidly closed and the bypass valve 9 is rapidly opened, the main steam is released to the condenser 10 through the bypass pipe 8 to suppress an increase in the reactor pressure due to the closing of the control valve 5. Further, when the control valve 5 is rapidly closed, the control valve quick-close signal 19 is transmitted, and the control valve quick-close signal 19 is input to the MG set system 400A with a fluid coupling. The capacity of the bypass valve 9 differs depending on the purpose. That is, when the capacity of the bypass valve 9 is less than the rated value of the main steam, the reactor is scrambled by the control valve rapid closing signal 19 from the viewpoint of ensuring the soundness of the fuel, and the reactor is stopped. On the other hand, when the capacity of the bypass valve 9 is equal to or larger than the rated value of the main steam, the reactor output is appropriately reduced, and the operation is continued without the reactor scram. Regardless of the bypass valve capacity, it is necessary to trip some of the internal pumps 3-1 to 3-10 as a reactor power reduction means.

FIG. 7 shows the MG with a fluid coupling described in FIG.
This is a detailed configuration in which the present embodiment is applied to a set system. In the MG set system 400A with fluid coupling,
An internal pump trip circuit breaker 413A is provided on the output side of the variable frequency generator 405A. As described with reference to FIG. 3, the input side of each internal pump is provided with an internal pump trip breaker 4 from the viewpoint of device protection.
07A-1 to 407A-5 are provided. When the control valve sudden close signal 19 is generated due to the generator load interruption, the control valve rapid close signal 19 is input to the MG set system 400A with a fluid coupling. The control valve sudden closing signal 19 is
The internal pump trip circuit breaker 413A is opened, and the internal pump trip circuit breakers 407A-1 to 407A-5 for device protection are also opened. As a result, the internal pumps 3-1 to 3-5 are tripped, the internal pumps 3-6 to 3-10 are continuously operated by the MG set system 400B with a fluid coupling, and the core flow rate is adjusted. According to the present embodiment, circuit breakers 413A and 407A-1 to 407A for the internal pump trip.
Since the interlock mechanism transmits the control valve sudden closing signal 19 to -5 and trips each circuit breaker, the structure and operation are simpler and cheaper than the conventional case where the inverter is stopped. is there. In the present embodiment, the control valve sudden closing signal 19 is input to the MG set system with fluid coupling 400A. However, the same applies when the control valve rapid closing signal 19 is input to the MG set system with fluid coupling 400B. Demonstrate function. In the present embodiment, the internal pump trip circuit breakers 413A are provided to provide the internal pump trip circuit breakers 413A to 407A.
Together with the internal pump 3-1A, the internal pump 3-1A only performs the internal pump trip using the internal pump trip circuit breaker 413A.
Even for trips 1 to 3-5, or without providing the circuit breaker 413A, the circuit breakers 407A-1 to 407A-
Needless to say, even if the internal pumps 3-1 to 3-5 are tripped by only 5, the same function is performed.

FIG. 8 shows an application configuration of FIG. In the MG set system 400A with the fluid coupling, the system is separated into two systems on the output side of the variable frequency generator 405A, and the internal pumps 3-1 to 3-2 are connected to one of these systems, and the other system is The internal pumps 3-3 to 3-5 are connected. Internal pump 3-1 to 3-
A circuit breaker 414A for an internal pump trip is provided on the system side connecting
5 is provided with a circuit breaker 413A for an internal pump trip via a timer 415 on the side of the system to which 5 is connected. MG set 40 with fluid coupling
When it is input to 0A, it is divided into two, one of which is direct breaker for internal pump trip 414A and 407A.
Enter -1 to 407A-2 and immediately release it. The other is input to the timer 415, and after a certain period of time, is output to the internal pump trip breakers 413A and 407A-3 to 407A-5.
The circuit breakers 413A and 407A-3 to 407A-5 are opened after a certain elapsed time while the series is interrupted. this is,
It is to trip an internal pump step by step. According to this application configuration example, it is possible to prevent a sharp decrease in the core flow rate and trip the internal pump as necessary. In this applied configuration example, the MG set system 400A with a fluid coupling is added to the control valve rapid closing signal 1
9 is input, but the same function is exerted even when the control valve rapid closing signal 19 is input to the MG set system 400B with a fluid coupling. In this application configuration example, an internal pump trip circuit breaker 414A and an internal pump trip circuit breaker 413A are provided, and the internal pump trip circuit breakers 414A and 407A-1 to 407A-4 are provided.
07A-2 allows internal pumps 3-1 to
3-2, and trips 413A and 407A-3 to 407A-5 for the internal pump trips.
Thus, the internal pumps 3-3 to 3-5 are caused to trip at the same time, but even if the internal pumps 3-1 to 3-5 are tripped only by the internal pump trip circuit breakers 414A and 413A. Alternatively, even if the internal pumps 3-1 to 3-5 are tripped only by the circuit breakers 407A-1 to 407A-5 without providing the circuit breakers 414A and 413A, the same function can be obtained. Nor.

Next, referring to FIG. 1, an interlock mechanism relating to a core flow rate control system in a boiling water nuclear power plant when the reactor pressure is high and the water level is low will be described as another embodiment of the present invention. The interlock mechanism of the present embodiment converts the reactor pressure signal 17 and the reactor water level signal 18 into an MG set system 400A with a fluid coupling.
, While the MG set system with fluid coupling 40
OB is configured to receive a reactor water level signal 18. FIG. 9 is a detailed configuration in which the present embodiment is applied to the MG set system with a fluid coupling described in FIG. In the MG set system with fluid coupling 400A, an internal pump trip circuit breaker 413A is provided on the output side of the variable frequency generator 405A. As described in FIG. 3, the input side of each internal pump is provided with an internal pump trip circuit breaker 407A-1 from the viewpoint of device protection.
407A-5 are provided. On the other hand, the MG set tripping circuit breaker 4 is connected to the input side of the MG set drive motor 403B in the MG set system 400B with a fluid coupling.
A breaker 416B for MG set trip is provided in addition to 12B. Further, as described in FIG. 3, on the input side of each internal pump, the circuit breakers 407B-6 to 407B-10 for internal pump trip are provided from the viewpoint of device protection. Further, the MG set system 400A with a fluid coupling is provided with a pressure monitor relay 419A for inputting the reactor pressure signal 17, a water level monitor relay 418A for inputting the reactor water level signal 18, and an OR circuit 420A.
The MG set system 400B with a fluid coupling is provided with a water level monitor relay 417B for inputting the reactor water level signal 18. In the MG set system 400A with a fluid coupling, the reactor pressure signal 17 is transmitted to the pressure monitor relay 419A.
When the reactor pressure signal 17 rises above a predetermined value, a signal is output from the pressure monitor relay 419A to the OR circuit 420A. Further, when the type of the reactor water level signal 18 to the water level monitoring relays 418A, reached water level X ₁ of the specified value is reactor water level signal 18, OR circuit 4 from the level monitor relay 418A
A signal is output to 20A. When the reactor pressure or the reactor water level reaches a specified value, the OR circuit 420A supplies the internal pump trip circuit breakers 413A and 413A.
A signal is output to 07A-1 to 407A-5, and each breaker is simultaneously opened at the same time. On the other hand, in the MG set system 400B with a fluid coupling, the reactor water level signal 18 is input to the water level monitor relay 417B, and when the reactor water level signal 18 reaches a certain specified water level X ₂ (X ₁ > X ₂ ). , A signal is output from the water level monitor relay 417B to the MG set trip circuit breakers 412B and 416B, and each circuit breaker is simultaneously opened.

The reactor water level will be described with reference to FIG. Turned down reactor water level, when it reaches the water level X ₁ of the prescribed value as in (b), however, the fluid coupling with MG set system 400A, the water level monitor relay 418A is actuated, via the OR circuit 420A, the inter Null pump trip breakers 413A and 407A-1 to 40
7A-5 are simultaneously opened simultaneously. Circuit breakers 413A and 407A-1 to 407A for internal pump trip
Since -5 is provided on the output side of the MG set with a fluid coupling, the internal pumps 3-1 to 3-5 are immediately stopped, and the core flow rate rapidly decreases as shown in FIG. However, since the internal pumps 3-6 to 3-10 continue to be driven by the MG set system 400B with a fluid coupling, a predetermined core flow rate is maintained. Further, the reactor water level drops, and as shown in FIG.
_When it reaches ₂ , the water level monitor relay 417B in the MG set system 400B is activated, and the breakers 412B and 416B for MG set trip are simultaneously opened. In this case, MG set trip circuit breakers 412B and 41
6B is provided on the input side of the MG set with fluid coupling, so even if the power supply from the generator 7 is cut off, the MG set system with fluid coupling 400B has mechanical inertia. the mechanical inertia to continue driving the internal pump 3-6～3-10 reduces gradually until the core flow after the water level monitoring relay 417B operate time t _2. In the present embodiment, the reactor pressure signal 1
7 and the reactor water level signal 18, the circuit breakers provided on the input side and the output side of the MG set with a fluid coupling are tripped. Simple and inexpensive. In this embodiment, the MG with a fluid coupling is used.
It goes without saying that the same function is exhibited even if the configuration of the interlock system in the set system 400A or 400B is replaced with each other. Further, each of the internal pump trip circuit breakers and the MG set trip circuit breakers in the present embodiment may be configured in the same manner as the contents described in FIG. 7 and 8 described above.
A signal at the time of generator load interruption inputted to the internal pump trip circuit breaker of FIG. 9 and the reactor pressure high or the reactor inputted to the internal pump trip circuit breaker and MG set trip circuit breaker of FIG. The signals at the low water level are independent of each other, and the interlocks by those signals do not interfere with each other.

[0020]

According to the present invention, since the MG set system with a fluid coupling having large mechanical inertia is used as a variable frequency power supply for all of a plurality of internal pumps, the power supply frequency of the internal pump is converted. At the same time, due to the mechanical inertia of the MG set with fluid coupling, it has the function of maintaining the power supply to the internal pump for a certain period of time even during a power disturbance due to a system accident and maintaining the required core cooling. It is possible to avoid a generator output decrease event, and at the time of a full stop, a decrease in the total core flow rate is alleviated, transition boiling of fuel is suppressed, and fuel integrity can be ensured and improved. In addition, since the MG set with a fluid coupling having large mechanical inertia is used as a variable frequency power supply for all of the plurality of internal pumps, the variable frequency generator does not stop when the system oscillates. It is possible to eliminate a sudden stop of all the internal pumps and improve the thermal soundness of the fuel.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a core flow control system in a boiling water nuclear power plant showing an embodiment of the present invention.

FIG. 2 is a detailed configuration diagram of a recirculation flow control circuit 300 of the present invention.

FIG. 3 is a detailed configuration diagram of an MG set system with a fluid coupling 400A, 400B showing an embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional core flow rate control system.

FIG. 5 is a diagram illustrating a comparison between the present invention and a conventional example at the time of a momentary stop

FIG. 6 is a diagram comparing the behavior of the present invention and the conventional example at the time of a complete stop.

FIG. 7 is a detailed configuration diagram of an interlock mechanism when a generator load is cut off according to another embodiment of the present invention.

8 is an application configuration diagram of FIG. 7;

FIG. 9 is a detailed configuration diagram of an interlock mechanism when a reactor pressure is high and a reactor water level is low according to another embodiment of the present invention.

FIG. 10 is a diagram showing a core flow rate characteristic according to a reactor water level.

[Explanation of symbols]

1: reactor pressure vessel, 2: reactor core, 3-1 to 3-1
0 internal pump, 4 main steam pipe, 5 regulator valve, 6 turbine, 7 generator, 9 bypass valve, 10
... condenser, 11 ... feed pump, 14 ... power load unbalance relay circuit, 200 ... turbine electro-hydraulic control device, 300 ... recirculation flow control circuit, 400A, 400
B: MG set system with fluid coupling, 403A: MG
Set drive motor, 404A: fluid coupling, 405A: variable frequency generator, 406A, 406B: rake tube, 40
7A-1 to 407A-5, 407B-6 to 407B-1
0: Circuit breaker for internal pump trip, 412A,
412B ... MG set trip circuit breaker, 413A, 4
14A: Circuit breaker for internal pump trip, 415
... Timer, 416B ... MG set trip circuit breaker,
417B, 418A ... water level monitor relay, 419A ...
Pressure monitor relay, 420A… OR circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Miyagawa 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Hitoshi Sakuma 3-2-2, Sachimachi, Hitachi-shi, Ibaraki No. 1 Inside Hitachi Engineering Co., Ltd. (72) Inventor: Unification Shida 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Kimiko Isono, Sachimachi, Hitachi City, Ibaraki Prefecture 3-1-1, Inside Hitachi, Ltd. Hitachi Plant

Claims (3)

[Claims] In a boiling water nuclear power plant having a plurality of internal pumps, an MG set drive motor is used as a variable frequency power supply for the internal pumps.
A core flow control system, characterized in that an MG set with a fluid coupling comprising a fluid coupling and a variable frequency generator is used, and all of the plurality of internal pumps are connected to the MG set with a fluid coupling. 2. In a boiling water nuclear power plant having a plurality of internal pumps, an MG set drive motor is used as a variable frequency power supply for the internal pumps.
An MG set with a fluid coupling comprising a fluid coupling and a variable frequency generator is used, and the MG set with a fluid coupling is connected to each of the plurality of internal pumps divided into a plurality of groups. Core flow control system. 3. In a boiling water nuclear power plant having 10 internal pumps, an MG set drive motor is used as a variable frequency power supply for the internal pumps.
Using the MG set with a fluid coupling composed of a fluid coupling and a variable frequency generator, the MG set with a fluid coupling is connected to each of the ten internal pumps divided into two groups of five each. A core flow control system.