JPH05134090A - Full capacity turbine bypass nuclear plant - Google Patents

Abstract

PURPOSE:To make a shift easy to station isolated operation by providing an interlock circuit for avoiding the stoppages of a stem turbine and a nuclear reaction in the case where a reactor water level is high due to the load cut-off of a generator. CONSTITUTION:When the load of a generator is cut off due to an accident or the like of a transmission system, a load cutoff signal is output within a load cutoff detection circuit 18, with a governing valve 10 quickly closed the steam supply for a steam turbine 6 is stopped temporarily, and with a quickly opening signal transmitted to a bypass valve 12 steam sent from a nuclear reactor 1 is led to a steam condenser 8. In addition, the trip of a recirculation pump 4 is performed within a pump power source device 14. Even if within an interlock circuit 20 of a turbine trip circuit 19 a load cutoff signal is input and a reactor water level high signal from a water level detector 17 is input due to the trip of a pump 4, a turbine trip signal is prevented and the stoppages of the turbine 6 and the reactor 1 are avoided. Thereby the shift to isolated in site operation in low reactor output becomes easy.

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 with a built-in nuclear reactor, and avoids stopping the steam turbine and the reactor even when the load on the generator is cut off. The present invention relates to a full-capacity turbine bypass nuclear power plant capable of shifting to an independent operation.

[0002]

2. Description of the Related Art In conventional reactor water level control in a nuclear power plant, when the reactor water level rises and reaches a high water level set value, the steam turbine is immediately stopped and the reactor is controlled. It is configured to insert the rod in an emergency and stop the operation.

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 guided to the main condenser, and this main condenser is connected to a bypass pipe that guides the steam directly from the main steam pipe through the bypass valve without passing through the steam turbine. And
Normally, the bypass valve is closed.

When the load on the generator is cut off due to an accident in the power transmission system, the turbine steam control valve is rapidly closed to protect the steam turbine and the generator, and the steam is supplied to the steam turbine. At the same time as the shutdown, the bypass valve is opened suddenly and the steam generated in the reactor is directly led to the condenser.

However, in a partial capacity bypass plant in which a part of the steam generated by the nuclear reactor is bypassed, the capacity of the bypass valve and the condenser can process only part of the steam having a rated capacity, so that the load of the generator is reduced. When shut off, the reactor pressure rises. For this reason, in the partial capacity bypass plant, the reactor is scrammed at the same time as the load is cut off to mitigate the increase in reactor output and reactor pressure.

On the other hand, in the full capacity bypass plant, the bypass valve has the ability to process 100% of the steam flow rate during the rated operation, so that even if the load is cut off, the reactor will not be stopped and the generator will not be shut down. The purpose is to have a design that allows the operation to shift to islanding.

However, at the time of shifting 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, so the reactor pressure rises during this time.
Since there is a possibility that the neutron flux will rise and lead to reactor shutdown, to avoid this and to shift to in-house isolated operation with low output, shut down several of the many recirculation pumps. It is designed to suppress the furnace output.

[0008]

When several recirculation pumps are tripped by the load cutoff signal, the core flow rate decreases, voids increase and the reactor power is suppressed. At this time, the reactor water level is reduced. Turbine trip due to reactor water level rise to rise. When the steam turbine is tripped here, the turbine stop valve provided in the main steam pipe is closed, and at the same time, the reactor scram is generated and the plant is stopped.

That is, even if the bypass valve is opened and the continuous operation is enabled, the plant is stopped due to another factor such as the rise of 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, its function cannot be sufficiently fulfilled.

In a nuclear power plant, a main steam pipe connecting a reactor and a steam turbine is closed by a turbine steam control valve that is closed by a load cutoff signal and an abnormal signal such as reactor water level high, and the steam turbine is stopped. A turbine stop valve is installed to do so. The purpose of this turbine trip due to the high reactor water level is to prevent steam with high humidity from flowing into the steam turbine via the main steam pipe and damaging the turbine blades when the reactor water level rises. ..

Even in such a case, since the steam turbine and the nuclear reactor were stopped from the viewpoint of preventing blade damage of the turbine, there was a possibility that the operation could not be switched to the independent operation in the plant.

It is an object of the present invention to provide an interlock for blocking the output of the turbine trip signal when the load trip signal is input to the turbine trip circuit when the reactor water level high signal is generated, and the load trip It is to provide a full-capacity turbine bypass nuclear plant that avoids a temporary turbine trip due to a high reactor water level at the time of occurrence and shifts to island operation.

[0013]

[Means for Solving the Problems] The steam supply to a steam turbine is stopped by a load cutoff signal of a generator and main steam from a reactor is guided to a condenser by a turbine bypass valve to prevent an increase in reactor pressure. In a full-capacity bypass nuclear plant equipped with a recirculation pump trip circuit that reduces the core flow rate, when the reactor water level reaches the high water level setting value due to the load cutoff signal of the generator, steam turbine and reactor Equipped with an interlock to avoid stoppage.

[0014]

[Function] When the load cutoff 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 rapidly opened to directly remove the steam generated in the reactor. It leads to a condenser and suppresses the pressure rise in the reactor.

Further, due to the load cutoff signal, several of the many recirculation pumps are tripped, so that the reactor output decreases but voids increase and the reactor water level temporarily rises.

However, in parallel with the recirculation pump trip, the water level once raised by the partial selective insertion of the control rod decreases again. Here, the turbine steam control valve generally opens again in a short time after the load is cut off and sends the steam required for island operation to the steam turbine.Therefore, in the interlock circuit in the turbine trip circuit, the load cutoff signal and the When the reactor water level high signal is input, the turbine trip signal output is stopped to prevent the turbine stop valve from closing, thus avoiding the shutdown of the steam turbine and the reactor and facilitating the transition to the island operation. ..

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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, in which a reactor core 2 is housed inside 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 core 2 is efficiently absorbed by the coolant 3, and in order to control the output of the reactor by changing the flow rate of this coolant 3, the heat is regenerated in the lower part of the reactor pressure vessel 1. Ten circulation pumps 4 are provided. The steam generated in the 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 rotational force generated in the steam turbine 6 is transmitted to a generator (not shown) by the turbine main shaft 7 to generate electric 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 directly guiding steam from the main steam pipe 5 without passing through the steam turbine 6. A turbine steam control valve 10 and a turbine stop valve 11 are installed in the main steam pipe 5.
Further, 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 provide pressure control of the reactor, while the turbine bypass valve 12 remains closed.

On the other hand, a motor 13 for giving a driving force to the recirculation pump 4 is connected to the recirculation pump 4.
Is powered by the power supply 14 and is rotating. Further, a control rod 15 for output control is installed in the lower portion of the reactor pressure vessel 1, and a control rod drive mechanism 16 performs an inserting / pulling operation.

Signals from a reactor water level detector 17 provided in the reactor pressure vessel 1 and a generator load cutoff detection circuit 18 are input to a turbine trip circuit 19, and the turbine trip circuit 19 outputs the turbine stop valve. A signal is sent to 11 and a signal is sent from the generator load cutoff detection circuit 18 to the turbine steam control valve 10 and the turbine bypass valve 12.

Further, in the turbine trip circuit 19,
As shown in the interlock logic diagram of FIG. 2, which is an example,
An interlock circuit 20 is configured to stop the turbine trip signal S20 to the turbine stop valve 11 when the load cutoff signal S18 and the reactor water level high signal S17 are input. Next, the operation of the above configuration will be described.

When the load of the generator is cut off due to an accident in the power transmission system in the nuclear reactor plant, the generator load cutoff detection circuit 18 detects this and outputs a load cutoff signal, and the turbine steam control valve 10 Is rapidly closed to temporarily stop the steam supply to the steam turbine 6 to suppress the increase in the rotation speed of the steam turbine 6, and to prevent the turbine bypass valve 12
Also, a rapid open signal is given to directly guide the steam generated in the reactor to the condenser 8 so that the pressure in the reactor does not rise. Further, the load shut-off signal causes the pump power supply device 14 to issue a trip signal to several of the many recirculation pumps to trip the recirculation pump 4.

Conventionally, when a turbine trip is reached due to the reactor water level being high when the generator load is cut off, the two valves of the turbine steam control valve 10 and the turbine stop valve 11 will be double closed. Here, the turbine steam control valve 10 is generally reopened about 1 minute after the load is cut off so that the steam required for in-house independent operation is sent to the steam turbine 8. Furthermore, in the event of load shedding, the control rod 15
However, the water level once increased by this effect usually decreases after a few seconds.

That is, as a result, the generation of high-moisture steam concerned by the rise in the reactor water level is limited to the first few seconds, and the turbine steam control valve 10 is closed during that time. Even if the stop valve 11 is not closed, there is no risk of damaging the turbine blade. Then, after that, generation of steam with high humidity disappears as the reactor water level decreases.

Considering these things, when the generator load is cut off, the turbine steam control valve 10 is closed for about 1 minute. Therefore, for a short period of time, the reactor water level rises to the water level high set value. Even if it arrives, it is not considered necessary to carry out a turbine trip.

Therefore, at this time, in the interlock circuit 20 shown in FIG. 2 in the turbine trip circuit 19 to which the load cutoff signal S18 from the generator load cutoff detection circuit 18 is input, the load cutoff signal S18 is input. Moreover, even if the reactor water level high signal S17 is input when the reactor water level reaches the set water level high value due to the increase in voids due to the trip of the recirculation pump and the decrease in reactor power, the turbine stop valve 11 Block the turbine trip signal S20 that closes rapidly to avoid shutting down the steam turbine 6 and the reactor, thereby facilitating the transition to in-house isolated operation at low reactor power.

In the turbine trip circuit 19, the turbine stop valve 11 is closed to stop the steam turbine 6 and the steam turbine 6 is shut down when it is necessary to input a turbine failure signal or the like due to factors other than the above. A signal is transmitted to the control rod drive mechanism 16 by another interlock circuit (not shown) when the control rod 15 is stopped,
It is the same as the conventional method to make an emergency insertion and to shut down the reactor safely.

[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 associated with a recirculation pump trip when a load cutoff occurs. Therefore, it is possible to avoid a stop of the steam turbine and the reactor. By facilitating the shift to the islanding operation, there is an effect that the reliability and safety of the full capacity turbine bypass nuclear power plant operation are improved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a full capacity bypass nuclear power plant of 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]

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 device, 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)

[Claims] 1. A generator load cutoff signal is used to stop the steam supply to the steam turbine, and main steam from the reactor is guided to a condenser by a turbine bypass valve to prevent an increase in reactor pressure and to prevent core flow. In a full-capacity bypass nuclear power plant equipped with a recirculation pump trip that reduces the Full-capacity turbine bypass nuclear power plant characterized by having a lock.