JP3095485B2 - Full capacity turbine bypass nuclear power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear power plant equipped with a recirculation pump having a built-in nuclear reactor. The present invention relates to a full-capacity turbine bypass nuclear power plant capable of shifting to islanding operation.

[0002]

2. Description of the Related Art In the conventional water level control of a nuclear power plant, when the reactor water level rises and reaches a high water level set point, the steam turbine is immediately stopped and the reactor is controlled. The operation is stopped by urgently inserting a rod.

That is, steam generated in a nuclear reactor is guided to a steam turbine through a turbine steam control valve, and a generator is coaxially connected to the steam turbine. The steam that has worked in the steam turbine is led to the main condenser, which is connected to a bypass pipe that leads the steam from the main steam pipe directly through a bypass valve without passing through the steam turbine. And
Normally, the bypass valve is closed.

If the load on the generator is cut off due to an accident in the power transmission system or the like, the turbine steam control valve is quickly closed to protect the steam turbine and the generator, and the supply of steam to the steam turbine is stopped. At the same time, the bypass valve is suddenly opened and the steam generated in the reactor is led directly to the condenser.

However, in a partial-capacity bypass plant in which a part of the steam generated by the reactor is bypassed, the capacity of the bypass valve and the condenser can handle only a part of the steam of the rated capacity, so that the load of the generator is reduced. During shutdown, the reactor pressure increases. For this reason, in the partial capacity bypass plant, the reactor is scrammed at the same time as the load is cut off, so that the reactor power and the reactor pressure are reduced.

On the other hand, in a full-capacity bypass plant, the bypass valve has a capability of processing 100% of the steam flow during the rated operation. It is intended to be designed to be able to shift to islanding operation.

However, when the operation shifts to the in-house independent operation, there is a time difference between the closing of the turbine steam control valve and the opening of the bypass valve.
Because of the possibility that the neutron flux rises and the reactor shuts down, several of the recirculation pumps were shut down to avoid this and shift to low-power in-house isolated operation. In this way, it is designed to suppress the furnace output.

[0008]

When several recirculation pumps are tripped by a load rejection signal, the core flow rate decreases, voids increase, and the reactor power is suppressed. At this time, the reactor water level increases. As a result, turbine trip occurs due to high reactor water level. Here, when the steam turbine is tripped, the turbine stop valve provided in the main steam pipe is closed, and a reactor scram is generated, leading to a plant shutdown.

That is, despite the fact that the bypass valve is opened and the continuous operation is possible, the plant is stopped due to another factor such as a rise in the reactor water level. Therefore, as a full capacity bypass plant, even if the capacity of the bypass valve or the like is simply increased, the function cannot be sufficiently performed.

In a nuclear power plant, a main steam pipe for connecting a nuclear reactor and a steam turbine is closed by a turbine steam control valve which is closed by a load shedding signal and a steam turbine is shut by being closed by an abnormal signal such as a high reactor water level. A turbine stop valve is installed for the purpose. The purpose of this turbine trip based on the reactor water level is to prevent steam with high moisture from flowing into the steam turbine via the main steam pipe and damaging turbine blades when the reactor water level rises. .

Even in such a case, since the steam turbine and the nuclear reactor are shut down from the viewpoint of preventing damage to the blades of the turbine, there is a problem that it may not be possible to shift to the site alone operation.

An object of the present invention is to provide an interlock for preventing the output of a turbine trip signal when a reactor water level high signal is generated and a load shedding signal is input to the turbine trip circuit. It is an object of the present invention to provide a full-capacity turbine bypass nuclear power plant that shifts to on-site independent operation while avoiding a turbine trip due to a temporary high reactor water level at the time of occurrence.

[0013]

According to the first aspect of the present invention,
Recirculation to stop the supply of steam to the steam turbine by the load shedding signal of the generator and guide the main steam from the reactor to the condenser by the turbine bypass valve to prevent the reactor pressure from rising and reduce the core flow rate At a full-capacity bypass nuclear plant with a pump trip,
Reactor water load shedding signal and the reactor water level to be output is output at a reached the water level height setting value when load shedding occurs
An interlock is provided to avoid shutting down the steam turbine and the reactor when both of the height signals are output .

[0014]

When a load shedding signal is issued, the turbine steam control valve is rapidly closed, the steam supply to the steam turbine is temporarily stopped, and the turbine bypass valve is quickly opened to directly transfer steam generated in the reactor. It leads to the condenser to suppress the reactor pressure rise.

Further, several of the recirculation pumps are tripped in response to the load shedding signal, so that the reactor power is reduced, but the voids are increased and the reactor water level is temporarily increased.

However, the water level once increased by the selective insertion of the control rod concurrently with the recirculation pump trip decreases again. Here, the turbine steam control valve generally opens again shortly after the load shedding occurs and sends the steam necessary for the in-house independent operation to the steam turbine.Therefore, in the interlock circuit in the turbine trip circuit, the load shedding signal and the atomic By stopping the output of the turbine trip signal when the high reactor water level signal is input to prevent the shut-off valve of the turbine from shutting down, it is possible to avoid the shutdown of the steam turbine and the reactor, and to facilitate the transition to the on-site isolated operation. .

[0017]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram of a full-capacity bypass nuclear power plant. A reactor core 2 is accommodated in a reactor pressure vessel 1, and a coolant 3 is circulated by a recirculation pump 4.

The heat generated by the nuclear reaction in the reactor core 2 is efficiently absorbed by the coolant 3, and is relocated to the lower part of the reactor pressure vessel 1 in order to control the output of the reactor by changing the flow rate of the coolant 3. Ten circulation pumps 4 are provided. The steam generated in the reactor core 2 is guided to a steam turbine 6 through a main steam pipe 5 connected to the upper part of the reactor pressure vessel 1. The torque generated by the steam turbine 6 is transmitted by a turbine main shaft 7 to a generator (not shown) to generate power.

The steam that has worked in the steam turbine 6 is cooled again in the condenser 8 to become a liquid phase. Further, the condenser 8 is provided with a bypass pipe 9 for guiding steam directly from the main steam pipe 5 without passing through the steam turbine 6. The main steam pipe 5 has a turbine steam control valve 10 and a turbine stop valve 11,
The bypass pipe 9 is provided with a turbine bypass valve 12. The turbine steam control valve 10 is normally controlled by a predetermined signal to control the reactor pressure, while the turbine bypass valve 12 remains closed.

On the other hand, a motor 13 for applying a driving force to the recirculation pump 4 is connected thereto.
Is rotating by receiving power from the power supply device 14. Further, a control rod 15 for power control is installed below the reactor pressure vessel 1, and the control rod drive mechanism 16 performs an insertion / extraction operation.

A signal from a reactor water level detector 17 provided in the reactor pressure vessel 1 and a signal from a generator load cutoff detection circuit 18 are input to a turbine trip circuit 19. A signal is output to the turbine steam control valve 10 and a turbine bypass valve 12 from the generator load cutoff detection circuit 18.

In the turbine trip circuit 19,
As shown in the example interlock logic diagram of FIG.
An interlock circuit 20 for stopping the turbine trip signal S20 for the turbine stop valve 11 when the load shedding signal S18 and the high reactor water level signal S17 are input. Next, the operation of the above configuration will be described.

When the load on the generator is cut off due to a power transmission system accident or the like in the reactor plant, the generator load cutoff detecting circuit 18 detects this and outputs a load cutoff signal, and the turbine steam control valve 10. Is quickly closed to temporarily stop the supply of steam to the steam turbine 6, to suppress the increase in the rotation speed of the steam turbine 6, and to suppress the turbine bypass valve 12.
Also, a rapid opening signal is given to direct the steam generated in the reactor to the condenser 8 so that the reactor pressure does not increase. Further, the trip signal for the recirculation pumps is issued to the pump power supply device 14 by the load rejection signal for several of the recirculation pumps.

Conventionally, when a turbine trip occurs due to a high reactor water level when the generator load is cut off, the two valves of the turbine steam control valve 10 and the turbine stop valve 11 are double-closed, Here, the turbine steam control valve 10 is generally reopened about one minute after the occurrence of load shedding, so that steam necessary for in-plant operation alone is sent to the steam turbine 8. In addition, when load shedding occurs, control rod 15 is used to reduce the furnace power in parallel with the recirculation pump trip.
However, the water level that has risen once due to this effect usually drops after a few seconds.

That is, the generation of high-humidity steam, which is concerned by the rise in the reactor water level, is limited to the first few seconds, during which time the turbine steam control valve 10 is closed. Even if the stop valve 11 is not closed, there is no fear of damaging the turbine blade. After that, the generation of steam having a high moisture content is eliminated by the decrease in the reactor water level.

Considering these facts, when the generator load is cut off, the turbine steam control valve 10 is closed for about 1 minute, so that the reactor water level rises for a short time and the water level rises to the set water level. Even so, it is unlikely that a turbine trip is necessary.

Therefore, at this time, in the interlock circuit 20 shown in FIG. 2 in the turbine trip circuit 19 to which the load shedding signal S18 from the generator load shedding detection circuit 18 is inputted, the load shedding signal S18 is inputted. In addition, even if the reactor water level high signal S17 at the water level high set value due to the reactor water level rise is input due to the increase in the void and the reactor power decrease due to the trip of the recirculation pump, the turbine stop valve 11 By stopping the turbine trip signal S20 which closes quickly to avoid shutting down the steam turbine 6 and the reactor, it is easy to shift to the in-house isolated operation at the low furnace power.

In the turbine trip circuit 19, if necessary due to factors other than the above, for example, due to input of a turbine failure signal or the like, the turbine stop valve 11 is closed to stop the steam turbine 6, and the steam turbine 6 A signal is transmitted to the control rod drive mechanism 16 by another interlock circuit (not shown) due to the stop of the control rod, and the control rod 15 is
Emergency insertion into the reactor to safely shut down the reactor is the same as before.

[0030]

As described above, according to the present invention, it is possible to avoid a turbine trip caused by a rise in the reactor water level caused by a recirculation pump trip at the time of load shedding. By facilitating the transition to the islanding operation, there is an effect of improving the reliability and safety of the operation of the full capacity turbine bypass nuclear power plant.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a full-capacity bypass nuclear power plant according to the present invention.

FIG. 2 is a logic diagram showing an example of an interlock in the turbine trip circuit of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Reactor core, 3 ... Recirculation pump, 4
... Main steam pipe, 5 ... Steam turbine, 6 ... Turbine main shaft, 7
... condenser, 8 ... bypass pipe, 9 ... turbine steam control valve,
10: turbine stop valve, 11: turbine bypass valve, 12: motor, 13: power supply, 14: control rod, 15: control rod drive mechanism, 16: reactor water level detector, 17: generator load cutoff detection circuit, 18… turbine trip circuit.

Claims (1)

(57) [Claims] 1. A steam supply to a steam turbine is stopped by a load shedding signal of a generator, and main steam from a reactor is guided to a condenser by a turbine bypass valve to prevent a rise in reactor pressure and to reduce a core flow rate. in total volume bypass nuclear power plant having a recirculating pump trip of reducing the sometimes load shedding signal and the reactor water level is output when load shedding occurs of the generator has reached the water level height setting value output
And a steam turbine and an interlock for avoiding shutdown of the reactor when both of the high reactor water level signals are output .