JPH09257980A - Internal pump system - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: An ATW which is an abnormal transient phenomenon accompanied by RPT such as load shedding or a scrum non-operation.
It is to ensure the safety of the nuclear power plant when S occurs and the integrity of the fuel. SOLUTION: MG set 200 with one fluid coupling
Multiple internal pumps 1-1 to 1 in A and 200B
-5, 1-6 to 1-10, in an internal pump system of a nuclear power plant, when a signal 7 of a transient event accompanied by a recirculation pump trip (RPT) such as load shedding occurs, or a nuclear reactor When the pressure 20 or the reactor water level 21 reaches a specified value and ATWS occurs, which is an abnormal transient phenomenon accompanied by a scram non-operation, when the reactor output is in the operating condition 18 of a percentage or more, the transient event or the Optimum number of internal pumps that differs based on ATWS and reactor operating conditions 1-1
~ 1-7 trip at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal pump system for a boiling water nuclear power plant which employs an internal pump as a recirculation pump for a nuclear reactor.

[0002]

2. Description of the Related Art Among improved boiling water nuclear power plants, in order to improve the controllability of the pump speed and to minimize the influence of external power system disturbance, the coolant recirculation in the reactor pressure vessel is recirculated. In an internal pump system provided with 10 internal pumps for use in a vehicle, a variable frequency power supply device including an AC motor mechanically connected as a power supply device and a control device for the internal pump, a fluid coupling, and an AC generator. It is considered optimal to apply two units. Five internal pumps are connected to each AC generator, and the AC generator supplies electric power to each pump. Also, by changing the position of the rake pipe of the fluid coupling and adjusting the amount of oil in the fluid coupling, the torque transmitted from the AC motor to the AC generator is changed, and as a result, the AC generator speed and its connection It controls the speed of 5 internal pumps. The recirculation pump trip (RPT) method in this system is
In the case of load shedding, for example, the characteristic that the rotational speed of the remaining internal pumps temporarily rises when a partial number of the five internal pumps connected to the same AC generator is tripped when the load is shed. As a result, it is based on the simultaneous trip of five internal pumps. In addition, since a rapid core flow reduction is required to reduce the output when the load is cut off, an internal pump trip circuit breaker is provided downstream of the AC generator to allow five units to trip at the same time. . 5 trips of this internal pump can be performed at the same time except when the load is cut off.
ATWS (A) which is an abnormal transient phenomenon with RPT such as turbine trip, total feed water loss, feed water heating loss and main steam isolation valve closure, or with scram inactivation.
nicipated Transients Wit
hout Scram: A phenomenon that is expected when a scrum fails at the time of an event that should scram the reactor).

[0003]

By the way, the optimal number of pump trips at the time of occurrence of ATWS which is a transient event involving RPT such as load shedding or an abnormal transient phenomenon involving non-operation of the scrum is the transient event, or It depends on the operating conditions of the ATWS and the reactor. But,
In the conventional system, the optimum number of trips is selected based on the operating conditions of ATWS and the reactor, which are transient events involving RPT such as load shedding, or abnormal transient events involving scram non-operation, and the internal pump is selected. The operation method of tripping is not considered. Therefore, when a reactor with various core characteristics is considered when a transient event with RPT such as load shedding or an abnormal transient phenomenon with scram non-operation occurs, an appropriate pump trip is not always required. This is not always done, and there is a problem that the safety of the nuclear power plant and the integrity of the fuel cannot be ensured.

In view of the above problems, an object of the present invention is to ensure the safety of a nuclear power plant at the time of occurrence of ATWS, which is a transient event accompanied by RPT such as load shedding, or an abnormal transient phenomenon accompanied by scram inactivation, and fuel consumption. An object is to provide an internal pump system suitable for ensuring soundness.

[0005]

In the internal pump system of a nuclear power plant in which a plurality of internal pumps are installed in one MG set with a fluid coupling, recirculation pump trips such as load shedding ( RP
It is solved by simultaneously tripping different optimal internal pump numbers in response to ATWS which is a transient event with T) or an abnormal transient event with scram non-operation. In addition, when a signal of a transient event such as a generator load cutoff, turbine trip, loss of all feed water, loss of feed water heating or closure of the main steam isolation valve is generated, and the reactor is in an operating state of reactor output a percent or more, By simultaneously tripping different optimal numbers of internal pumps in response to transients and reactor operating conditions,
Will be resolved. In addition, when the reactor pressure or reactor water level reaches a specified value and ATWS occurs, the reactor output a
When the operating state is more than the percentage, it is solved by simultaneously tripping different optimal internal pump numbers corresponding to the operating states of the ATWS and the reactor. Here, the optimum number of internal pumps described above is determined by taking into consideration the influence of the void reactivity coefficient determined by the capacity of the turbine bypass valve and the fuel characteristics.

The present invention provides an optimum number of pump trips that varies depending on the ATWS and reactor operating conditions, which is a transient event involving a recirculation pump trip (RPT) such as load shedding, or an abnormal transient phenomenon involving a scrum inoperability. Recirculation pump trip (R
The optimum number of internal pumps is tripped at the same time when a transient event involving PT) occurs or when an abnormal transient phenomenon involving a scram inaction occurs, ATWS. As a result, when a transient event with RPT such as load shedding occurs or an abnormal transient phenomenon with a scrum inoperative occurs, ATWS
It is possible to secure the safety of the nuclear power plant at the time of occurrence and the soundness of the fuel.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration of an internal pump system in a boiling water nuclear power plant showing an embodiment of the present invention. In FIG. 1, in a boiling water nuclear power plant, in order to secure a core flow rate of cooling water, the cooling water is cooled by the internal pumps 1-1 to 1-10 (1
(Only 1 and 1-6 are shown) are sent to the reactor core 12. The cooling water is heated in the reactor core 12 and is generated as steam in the reactor pressure vessel 11. The generated steam enters the turbine 1 through the main steam pipe 13 and the regulator valve 6. The steam used for the turbine 1 is cooled by the condenser 10 and returned to cooling water. Further, steam that escapes through the bypass pipe 9 and the bypass valve 8 is also cooled by the condenser 10 and returned to the cooling water. The returned cooling water is supplied to the inside of the nuclear reactor again by using the water supply pump 14. Generator 3
Are driven by the turbine 1 to generate electric power. In addition, the internal pump system is a MG set system with a fluid coupling in which a voltage transformed by the generators 3 by the on-site transformers 50-1 and 50-2 is applied to control rotation of the internal pumps 1-1 to 1-10. 200A and 20
0B. Further, the MG set system 200A with a fluid coupling includes a control valve rapid closing signal 7 corresponding to the rapid closing of the control valve 6, a reactor output signal 16 obtained by converting a neutron flux signal detected by the neutron flux detection device 15, and a reactor pressure. Signal 20 and reactor water level signal 21 are input, and internal pump 1-1 to
Trip control of 1-5. Where reactor output signal 1
6 represents the operating state of the nuclear reactor. Then, the MG set system with fluid coupling 200B receives the pump trip signal 19 from the MG set system with fluid coupling 200A, and trip-controls the internal pumps 1-6 to 1-10. Here, the power load unbalance relay circuit 4 compares the turbine rotation speed signal 2 from the turbine 1 with the generator output signal from the generator 3, and determines the turbine rotation speed as when the generator load cutoff occurs. When the difference between the signal 2 and the generator output signal from the generator 3 becomes equal to or greater than the set value, the control valve rapid closing request signal 5 is output.

When the generator load is cut off and the difference between the turbine speed signal 2 and the generator output signal from the generator 3 exceeds the set value, the power load unbalance relay circuit 4 is adjusted. The sudden valve closing request signal 5 is output, and the regulator valve 6 is rapidly closed in order to suppress the increase in the rotational speed of the turbine. The bypass valve 8 is rapidly opened by the control valve abrupt closing signal 7 output based on the abrupt closing of the control valve 6, and the bypass pipe 9 is opened.
The main steam is allowed to escape to the condenser 10 through the passage to suppress the rise in the reactor pressure due to the closing of the regulator valve 6. At this time, the control valve rapid closing signal 7 and the reactor output signal 16 are input to the MG set system with fluid coupling, and the MG trip system with fluid coupling has a pump trip signal from the MG set system with fluid coupling 200A. 19 is input, and the optimum number of pumps out of the internal pumps 1-1 to 1-5 and the internal pumps 1-6 to 1-10 is tripped based on the control valve rapid closing signal 7 and the reactor output signal 16. To be done. On the other hand, to the MG set system 200A with a fluid coupling, the pressure or water level of the reactor is input as the reactor pressure signal 20 or the reactor water level signal 21, and the operating state of the reactor is input as the reactor output signal 16. A pump trip signal 19 is input to the MG set system 200A with a fluid coupling from the MG set system 200 with a fluid coupling, and an internal pump is generated based on the reactor pressure signal 20 or the reactor water level signal 21 and the reactor output signal 16. 1-1 to 1-5, internal pump 1
Among -6 to 1-10, the optimum number of pumps is tripped. In this case, the optimum value is determined based on the transient event associated with the load shedding of the generator, or the abnormal transient event (ATWS) associated with the water level or pressure of the reactor exceeding a specified value, and the operating state (conditions) of the reactor. Calculate the number of pump trips in advance by analysis. The capacity of the bypass valve 8 differs depending on the plant. Therefore, when the capacity of the bypass valve 8 is less than the rated value of the main steam, from the viewpoint of ensuring the soundness of the fuel, the reactor is scrammed by the control valve rapid closing signal 7 and the reactor is stopped. On the other hand, when the capacity of the bypass valve 8 is equal to or larger than the rated value of the main steam, the reactor output is appropriately reduced to continue the operation without performing the reactor scram. However, in any of the bypass valve capacities, it becomes necessary to trip some of the internal pumps 1-1 to 1-10 as a reactor output reducing means. Therefore, the capacity of the bypass valve 8 is taken into consideration when the optimum number of pump trips is obtained in advance by analysis. Further, since the optimum number of pump trips described above is also influenced by the factor of the void reactivity coefficient determined by the fuel characteristics, the void reactivity coefficient is also taken into consideration.

FIG. 2 shows an M with fluid coupling according to this embodiment.
The detailed structure of the G set system 200A and the MG set system 200B with a fluid coupling is shown. In FIG.
The MG set system with fluid coupling 200A includes internal pumps 1-1 to 1-5, an MG set trip breaker with fluid coupling 100A, and an MG set drive motor 101.
A, variable frequency generator 102A, fluid coupling 103A, rake pipe 104A, internal pump trip circuit breaker 105A, circuit breaker (device protection) 106A-1 to 106
A-5, reactor output monitor relay 150, AND circuit 1
51, OR circuit 152, pressure monitor relay 153, water level monitor relay 154, and OR circuit 155. MG set system 200B with fluid coupling includes internal pumps 1-6 to 1-10, circuit breaker 100B for MG set trip with fluid coupling, MG set drive motor 101B,
Variable frequency generator 102B, fluid coupling 103B, rake pipe 104B, circuit breaker (for equipment protection) 106B-1 to 10
6B-5, circuit breaker 106 for internal pump trip
It consists of C-1 and 106C-2.

The detailed operation of tripping the optimum number of internal pumps will be described with reference to FIG. here,
The optimum number of trips of the internal pump when the generator load is cut off or when ATWS occurs is 7 when the operating condition of the reactor, that is, the reactor output a percentage or more is operating.
It is assumed that the number of units is 5 and the reactor output is less than a percentage when operating. Since the functions of the MG set system with fluid coupling 200A and 200B are equivalent, the following description will be made on the MG set system with fluid coupling 200A.
(However, since the configuration of the circuit breaker for the internal pump trip differs between 200A and 200B, it will be described later.) Normally, the MG set system 200A with a fluid coupling is supplied from the generator 3 via the in-house transformer 50-1. The MG set driving motor 101A is driven at a constant rotation speed by the alternating current, and the torque from the MG set driving motor 101A is supplied to the variable frequency generator 10 via the fluid coupling 103A.
2A to control the rotation speed of the variable frequency generator 102A. Here, the fluid coupling 103A is filled with oil, and by changing the oil level position in the fluid coupling 103A, the torque transmitted to the variable frequency generator 102A is changed, and the variable frequency generator 102A Change the rotation speed. The oil surface of the fluid coupling 103A is changed by changing the fluid coupling 10
This is done by changing the position of the rake tube 104A inserted in 3A. The output from the variable frequency generator 102A is divided into five parts, which are an internal pump trip circuit breaker 105A provided on the output side of the variable frequency generator 102A and an internal pump trip circuit breaker 105A. Is output to the internal pumps 1-1 to 1-5 via the circuit breakers 106A-1 to 106A-5 to variably control the rotation speed of the internal pumps. The device protection circuit breakers 106A-1 to 106A-5 are provided for the purpose of protecting the device by disconnecting the pump from the system when an abnormality occurs in the downstream internal pump. Further, in the MG set system 200B with a fluid coupling, the five internal pumps 1 whose rotation speed is controlled by the output of the variable frequency generator 102B.
-6 to 1-10, two of them are device protection circuit breakers 106B installed for the purpose of device protection.
1, 106B-2, 106B-1, 106B-2
106C-1 and 106C-2 are provided as an internal pump trip circuit breaker on the input side of. Here, the internal pump trip circuit breaker is a circuit breaker for control that operates in an emergency.The provision of an internal pump trip circuit breaker device and a protective circuit breaker is responsible for control and protection of the same device. The reason for this is that the function separation is not preferable.

First, the case of a transient event accompanied by RPT when the generator load is cut off will be described. The operating status of the reactor is
A reactor output monitor relay 15 as a reactor output signal 16 obtained by converting the neutron flux signal of the neutron flux detection device 15 of FIG.
Input to 0. When the reactor output signal 16 has increased to a percentage or more and the reactor is in the operating state, the reactor output monitor relay 150 outputs the operating state signal 18 to the AND circuit 151 for the reactor output a percentage or more.
In such an operating state, when the generator load cutoff occurs, a control valve rapid close signal 7 due to the generator load cutoff is generated, and a trip signal for five pumps in the MG set system 200A with a fluid coupling is generated via the OR circuit 152. 17 is output to shut off the internal pump trip circuit breaker 105A, and at the same time, the device protection circuit breakers 106A-1 to 10A-10.
6A-5 shut off, internal pump 1-1 to 1-5
To trip. At the same time, the AND condition of the operating state signal 18 of the reactor output a percent or more and the control valve rapid closing signal 7 is satisfied, the two pump trip signal 19 in the MG set system 200B with fluid coupling is output, and the internal pump trip is performed. Circuit breakers 106C-1 and 106C-2, and device protection circuit breakers 106B-1 and 10B-1 and 10C-2.
6B-2 shut off, internal pump 1-6, 1-7
To trip. From this, in the operating state where the reactor output is a percentage or more, when the regulator valve rapid closing signal 7 is generated due to the load interruption of the generator, the internal pump 1-1
~ 1-5, 1-6, 1-7 will be tripped simultaneously. In addition, during the output operation of the reactor output less than a percentage, when the regulator valve rapid closing signal 7 due to the load interruption of the generator is generated, the MG set system 200 with the fluid coupling is provided.
The five pump trip signal 17 in A is output, and the two pump trip signal 19 is not output to the MG set system 200B with a fluid coupling. Therefore, the five internal pumps 1-1 to 1-5 are simultaneously tripped. Done. As described above, in the case of a transient event involving RPT when the generator load is cut off, under the operating condition of the reactor output a percentage or more,
When the control valve abrupt closing signal 7 due to generator load cutoff is generated, seven internal pumps are simultaneously tripped, and in operating conditions where the reactor output is less than a percent,
When the control valve abrupt closing signal 7 is generated due to the load interruption of the generator, the five internal pumps are simultaneously tripped.

Next, the case of the ATWS, which is an abnormal transient phenomenon accompanied by the scram not operating, will be described. ATWS responds by monitoring reactor water levels and pressures. The reactor pressure signal 20 and the reactor water level signal 21 are input to the MG set system with fluid coupling 200A. The reactor pressure signal 20 is input to the pressure monitor relay 153, and when the reactor pressure signal 20 rises above a certain value, the pressure monitor relay 153 outputs a signal to the OR circuit 155. Similarly, the reactor water level signal 21 is input to the water level monitor relay 154, and when the reactor water level signal 21 rises above a certain specified value, the water level monitor relay 154.
Outputs a signal from the OR circuit 155. Therefore,
As described above, from the reactor power monitor relay 150 to A
When the reactor pressure or the reactor water level reaches a specified value in the operating state of the reactor in which the operating state signal 18 is output to the ND circuit 151 at a reactor output a percentage or more, the OR circuit 155 causes the OR circuit 152 to operate. The five pump trip signal 17 in the MG set system 200A with a fluid coupling is output via the circuit breaker 105A for the internal pump trip, and the circuit breakers 106A-1 to 106A-5 for device protection are cut off. Trip the internal pumps 1-1 to 1-5. At the same time, the AND condition of the operation state signal 18 of the reactor output a percent or more and the signal from the pressure monitor relay 153 or the water level monitor relay 154 is satisfied, and the two pump trip signal 19 in the MG set system 200B with fluid coupling is output. Internal circuit trip breaker 106C-
1, 106C-2 are cut off, the device protection circuit breakers 106B-1, 106B-2 are cut off, and the internal pumps 1-6, 1-7 are tripped. From this, when the reactor pressure or the reactor water level reaches the specified value under the operating condition of the reactor output a percentage or more, seven internal pumps are simultaneously tripped. Further, when the reactor pressure or the reactor water level reaches the specified value during the output operation of the reactor output less than a percentage, the five pump trip signals 17 in the MG set system 200A with the fluid coupling are output, and the fluid coupling is output. Since the two-pump trip signal 19 is not output to the attached MG set system 200B, the internal pumps 1-1 to 1-5
No. 5 simultaneous trips will be conducted. In this way, in the case of ATWS, which is an abnormal transient phenomenon accompanied by a scram non-operation, seven internal pumps are installed when the reactor pressure or the reactor water level reaches the specified value under the operating condition of the reactor power a% or more. Are simultaneously tripped, and when the reactor pressure or the reactor water level reaches a specified value under the operating condition where the reactor power is less than a percent, the five internal pumps are simultaneously tripped.

FIG. 3 shows a comparison of the behavior when the generator load is cut off when the present embodiment is adopted as the internal pump trip system and when the conventional example is applied. When the generator load is cut off due to a system accident or the like, the regulator valve 6 is closed rapidly to suppress the increase in the rotational speed of the turbine, so that the void is crushed and the output (neutron flux) increases, but the internal pump By tripping
Since the core flow rate decreases, the voids increase, and the negative reactivity is injected, the increase in the output (neutron flux) can be suppressed. As shown in FIG. 3, when the generator load cutoff occurs at time t ₁ , when comparing 5 trips (dotted line) and 7 trips (solid line) of the internal pump, 7 trips are the core flow rate. Since the decrease of the output is large and the input of the negative reactivity becomes large, the increase of the output (neutron flux) is suppressed and the safety of the plant is secured. In addition, the minimum limit output ratio MCPR (Minimum Crit) at this time
When comparing 5 pump trips (dotted line) and 7 trips (solid line) of the internal pump for ical power Raito), the negative reactivity input is larger in 7 trips, so as shown in Fig. 3. And ΔMC
The value of PR can be kept low. Therefore, the seven-unit trip secures the thermal margin of the fuel when the load is cut off, and the fuel integrity is maintained. Further, in the plant where the capacity of the bypass valve 8 is equal to or higher than the rated value of the main steam, when the generator load is cut off, the reactor output is appropriately reduced and the operation is continued without the reactor scram. However, in order to continue the plant operation in this case, it is necessary to suppress the increase of the neutron flux due to the pressure increase immediately after the control valve 6 is rapidly closed. Even when this operation is performed, the increase in output can be suppressed 7
The pedestal trip is more effective in avoiding the scrum due to the high neutron flux signal.

It should be noted that in the present embodiment, transient events with RPT other than generator load shedding, such as turbine trip,
It is possible to replace the signal at the time of occurrence of these transient events with the control valve abrupt closing signal 7 even in the case of total feed water loss, feed water heating loss, main steam isolation valve closure, and the like. The same applies to transient events with RPT other than shutdown.

[0015]

As described above, according to the present invention,
Based on the operating conditions of ATWS and the reactor, which is a transient event involving a recirculation pump trip (RPT) such as load shedding, or an abnormal transient phenomenon involving a scrum inoperability, the optimum number of pump trips is determined in advance by analysis. Optimal number of internal pumps can be tripped at the same time when a transient event such as a load cutoff or the like that involves a recirculation pump trip (RPT) occurs or when an abnormal transient phenomenon that causes a scrum inactivity occurs, ATWS. It is possible to ensure the safety of the nuclear power plant and the soundness of the fuel when a transient event involving RPT such as shutoff occurs or when an ATWS occurs, which is an abnormal transient phenomenon involving a scram inoperability.

[Brief description of drawings]

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

FIG. 2 is a detailed configuration diagram of an MG set system with a fluid coupling according to the present invention.

FIG. 3 is a behavior diagram when a generator load cutoff according to the present invention occurs.

[Explanation of symbols]

1 Turbine 3 Generator 4 Power load unbalance relay circuit 6 Adjusting valve 8 Bypass valve 10 Condenser 11 Reactor pressure vessel 12 Reactor core 15 Neutron flux detection device 150 Reactor output monitor relay 151 AND circuit 152 OR circuit 153 Pressure Monitor relay 154 Water level monitor relay 155 OR circuit 1-1 to 1-10 Internal pump 200A, 200B MG set system with fluid coupling 101A, 101B MG set drive motor 102A, 102B Variable frequency generator 103A, 103B Fluid coupling 104A, 104B Dip pipe 105A Circuit breaker for internal pump trip 106A-1 to 106A-5, 106B-1 to 106B
-5 Circuit breaker (for equipment protection) 106C-1, 106C-2 Internal pump trip circuit breaker

Claims (7)

[Claims] 1. A plurality of internal pumps are used as a recirculation pump of a nuclear reactor, a plurality of MG sets with fluid couplings are used as a variable frequency power source of the internal pumps, and one MG set with fluid couplings is used. In an internal pump system of a nuclear power plant where multiple internal pumps are installed in the ATWS, which is a transient event involving a recirculation pump trip (RPT) such as load shedding or an abnormal transient event involving a scram inoperability. Correspondingly, an internal pump system characterized by simultaneously tripping different optimal numbers of internal pumps. 2. A plurality of internal pumps are used as a recirculation pump of a nuclear reactor, a plurality of MG sets with fluid couplings are used as a variable frequency power source of the internal pumps, and one MG set with fluid couplings is used. In the internal pump system of a nuclear power plant with multiple internal pumps installed in the
When a transient event signal is generated due to a turbine trip, total feed water loss, feed water heating loss, or main steam isolation valve closure, etc., and when the reactor is in an operating state of reactor power a percent or more, the transient event and the reactor An internal pump system characterized by simultaneously tripping different optimal numbers of internal pumps according to operating conditions. 3. A plurality of internal pumps are adopted as a recirculation pump of a nuclear reactor, a plurality of MG sets with fluid couplings are used as a variable frequency power source of the internal pumps, and one MG set with fluid couplings is used. In the internal pump system of a nuclear power plant with multiple internal pumps installed in the reactor, when the reactor pressure or reactor water level reached a specified value and ATWS occurred, In some cases, an optimal internal pump system that trips different optimal numbers of internal pumps at the same time according to the operating states of the ATWS and the reactor. 4. The optimum number of internal pumps according to claim 1, wherein the optimum number of internal pumps is determined by taking into account the influence of a void reactivity coefficient determined by the capacity of the turbine bypass valve and fuel characteristics. And internal pump system. 5. The optimum number of internal pumps at the same time according to any one of claims 1 to 4,
An internal pump system that targets all internal pumps installed in one MG set with a fluid coupling and an arbitrary number of internal pumps installed in another MG set with a fluid coupling . 6. The circuit breaker for protecting equipment according to claim 5, wherein an internal pump trip circuit breaker for tripping all internal pumps installed in the MG set with fluid coupling is provided, and the circuit breakers are arranged in parallel. An internal pump system characterized by being arranged in series with. 7. The internal pump trip circuit breaker according to claim 5, which trips an arbitrary number of internal pumps installed in the MG set with a fluid coupling,
An internal pump system, wherein the circuit breaker is arranged in series with a device protection circuit breaker.