JPH0462039B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention provides a steam turbine-driven water injection system for a nuclear reactor that can be used in a boiling water nuclear power plant, both in the event of a loss of coolant accident and in the event of a total loss of AC power. Regarding.

(Technical background and problems of the invention) In boiling water nuclear power plants, in view of past failures of nuclear power generation equipment, the importance of the ability to maintain the reactor water level in the event of a loss of coolant accident or in the event of a loss of all AC power is important. However, it has recently received a lot of attention.

Equipment to deal with these events includes:
There is a steam turbine-driven high-pressure water injection system that uses reactor steam as a direct power source, and a reactor isolation cooling system.
The former is designed to operate independently in the event of a loss of coolant accident, and the latter in the event of a total AC power loss.

These steam turbine-driven make-up water systems are
The steam generated by the nuclear reaction inside the reactor is used as a direct driving source, and even in the event of a loss of coolant accident or loss of all AC power, the pump can be driven without using any AC power. Supply cooling water into the reactor. Therefore, in combination with a separately installed electrically driven make-up water system, this contributes to increasing the diversity of drive sources and improves the reliability of the reactor water replenishment ability in the event of an abnormal event at a nuclear power plant.

However, since the makeup water systems mentioned above use furnace steam as a direct driving source, if these makeup water systems operate, there is a risk of furnace steam leaking from the turbine shaft seal, turbine stop valve, or turbine control valve. be. If this is left unattended, there is a risk that workers will be exposed to radioactivity contained in the reactor steam.To avoid such a situation, the above-mentioned make-up water system should be equipped with valves and turbine shaft seals included in each system. A leakage steam treatment device is installed to treat the leakage steam from each section.

Next, referring to FIGS. 2 and 3, a leakage steam treatment device for a reactor isolation cooling system and a high pressure water injection system will be described.

Figure 2 shows an example of a leakage steam treatment device for a reactor isolation cooling system. Steam in the reactor is led to a steam turbine 3 through a turbine stop valve 1 and a turbine control valve 2, and after doing work here, the steam is It is introduced into the pool water in the suppression pool 4. A pump 5 driven by the steam turbine 3 sends cooling water into the reactor during reactor isolation.

The leakage steam treatment device of the reactor isolation cooling system includes a turbine stop valve 1, a turbine control valve 2, and piping 6, 7, 8 for guiding leakage steam from the turbine shaft sealing part of the steam turbine 3, and a barometric pipe for condensing the leakage steam. - A condenser 9, a vacuum tank 10 connected to this barometric condenser, and a vacuum pump 1 that maintains the degree of vacuum in this vacuum tank 10.
1, a pipe 12 that guides the exhaust gas from the vacuum pump into the pool water in the pressure control pool 4, and a check valve 13 and an isolation valve 14 inserted into this pipe.

In the reactor isolation cooling system configured as described above, the turbine stop valve 1 other than the steam turbine 3,
All dynamic devices such as the turbine control valve 2 and the vacuum pump 11 are driven by a DC power source (battery).

In this plant, when a total AC power loss event occurs, all make-up water systems driven by the AC power supply stop functioning, causing the water level in the reactor to drop.
When this generates a low water level signal, the turbine stop valve 1 and the turbine control valve 2 are automatically opened, and the furnace steam is introduced into the steam turbine 3 to drive it. The pump 5 is started by this steam turbine and supplies cooling water into the reactor.

At the same time, the vacuum pump 11 is automatically started, and the furnace steam leaking from the turbine stop valve 1, the turbine control valve 2, the shaft seal of the steam turbine 3, etc. is forcibly absorbed into the barometric condenser 9, and from this condenser. The gas transferred to the vacuum tank 10 is forcibly discharged to the liquid phase portion of the pressure suppression pool 4 through the piping 12, the check valve 13, and the isolation valve 14.

In this way, in the conventional atomic isolation cooling system, when all AC power is lost, the reactor steam leaking from the valves and turbine shaft seals is discharged to the liquid phase part of the pressure control pool 4, thereby preventing it from leaving the system. It is designed so that there is almost no leakage.

However, if a loss of coolant accident occurs in the above-mentioned nuclear power plant, the situation will be completely different from the case of a total AC power loss accident.

In other words, in the event of a loss of coolant accident, high-energy fluid within the reactor passes through the vent pipe to the pressure suppression pool 4.
Therefore, the non-condensable gas discharged from the reactor containment vessel is transferred to the gas phase within the pressure suppression pool 4, and the pressure within the pressure suppression pool 4 rises rapidly.

Due to this pressure increase, the exhaust pressure of the vacuum pump 11 increases and its exhaust efficiency decreases, so the barometric condenser 9 and the vacuum tank 1
The degree of vacuum inside 0 is reduced, and the effect of condensing leaked steam is reduced.

As a result, if the reactor isolation cooling system continues to operate during a loss of coolant accident, the leakage steam treatment device will not be able to function and reactor steam will leak out of the system.
In particular, the reactor steam at the time of the accident may contain extremely high concentrations of radioactivity, which would be suppressed during normal operation, so it is not practical to activate the reactor isolation cooling system in the event of a loss of coolant accident. It is impossible.

On the other hand, as shown in FIG. 3, the high-pressure water injection system includes a steam turbine 2 rotated by furnace steam introduced through a turbine stop valve 20 and a turbine control valve 21.
2, and a pressure suppression pool 23 into which this exhaust gas is introduced.
and a pump 24 that is driven by the steam turbine 22 and sends high-pressure water into the furnace. Pipes 26, 27, 28 that guide steam to the barometric condenser 25, and a vacuum tank 29 connected to the barometric condenser 25.
and a vacuum pump 30 that evacuates the inside of this vacuum tank, and the exhaust gas from the vacuum pump 30 is supplied to a pipe 31 and a globe valve 32 inserted therein.
is led to the emergency gas treatment system for treatment.

In this way, the high-pressure water injection system and the reactor isolation cooling system have similar system configurations, but the capacity of the high-pressure water injection system is generally several times larger than that of the reactor isolation cooling system. , is also different in that the exhaust gas of the vacuum pump 30 is configured to be introduced into the emergency gas treatment system.

This emergency gas treatment system uses a high-performance charcoal filter to efficiently remove the radioactivity that leaked into the reactor building during a loss of coolant accident, while also directing exhaust gas into the exhaust pipe using a fan driven by an AC power source. and release into the atmosphere at high altitudes.

In this way, in the event of a loss of coolant accident, the high-pressure injection system decontaminates the exhaust gas released from the vacuum pump 30 using the emergency gas treatment system, and prevents exposure to radioactivity contained in the reactor steam leaking from the system. control the dangers of

However, as described above, the high-pressure water injection system has the drawback that, since the emergency gas treatment system uses an AC power source as a driving source, it becomes inoperable when all AC power is lost, and the exhaust gas from the vacuum pump 30 cannot be discharged.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks in the prior art, and provides a steam turbine-driven water injection system for a nuclear reactor that is operable in both a loss of coolant accident and a loss of all AC power supply event. The purpose is to

[Summary of the invention]

In order to achieve the above object, the steam turbine-driven water injection device for a nuclear reactor of the present invention is inserted into the turbine shaft seal and its piping system of a steam turbine that drives makeup water pumps of the reactor isolation cooling system and high-pressure water injection system. A barometric condenser that condenses leaked steam from the valve, a vacuum tank connected to this barometric condenser, a vacuum pump that evacuates the inside of this vacuum tank, and piping that connects the discharge side of this vacuum pump and the pressure suppression pool. It is characterized by comprising an inserted check valve and an electric valve that is inserted in a pipe branching from the upstream side of the check valve and leading to the emergency gas treatment system, and opens in the event of a loss of coolant accident. It is something.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. 3 described above are given the same reference numerals.

In FIG. 1, the reactor isolation cooling system and the high-pressure water injection system have the same configuration, each including a turbine stop valve 20, a turbine control valve 21, a steam turbine 22, a pump 24, a barometric condenser 25, a vacuum tank 29, and a high-pressure water injection system. A vacuum pump 30 is provided.

A check valve 4 is provided on the discharge side piping 40 of the vacuum pump 30.
1 and an isolation valve 42 are inserted, the tip of which is immersed in the liquid phase of the pressure suppression pool 23. Further, an electric valve 44 driven by an AC power source is inserted in a pipe 43 branched to the pipe 40 between the vacuum pump 30 and the check valve 41, and its tip is connected to the pipe 40 as shown in FIG. It is connected to an emergency gas treatment system with the same configuration as described.

A pressure switch 45 is installed in the pressure suppression pool 23 to detect the pressure of the gas phase portion.
When the detected pressure rises above a preset value, the pressure switch 45 sends a signal to the electric valve 44 to open it.

In the reactor isolation cooling system and high-pressure water injection system of the present invention configured as described above, the electric valve 44 is closed during normal operation of the reactor, and the discharge side of the vacuum pump 30 that is continuously operated is closed. Pressure suppression pool 2 through piping 40, check valve 41, and isolation valve 42
3 is evacuated into the liquid phase.

Here, when a coolant loss accident occurs and the internal pressure of the pressure suppression pool 23 rises above the set value, the electric valve 44 is opened by a signal from the pressure switch 45, and the discharge side of the vacuum pump 30 is connected through the pipe 43. Connected to the emergency gas treatment system. In this case, since the internal pressure on the emergency gas processing system side is lower than the internal pressure of the pressure suppression pool 23, the check valve 41 is automatically closed, and the exhaust gas from the vacuum pump 30 is introduced into the emergency gas processing system. After being processed in a manner similar to that described in connection with FIG. 3, it is released into the atmosphere.

On the other hand, when a total AC power loss event occurs, there is no significant pressure rise in the pressure suppression pool 23 and the pressure switch 45 does not operate, so the motor-operated valve 44 remains closed. Also, in this case,
Since no coolant loss accident signal is output, the electric valve 44 remains closed and the exhaust from the vacuum pump 30 is introduced into the pressure suppression pool 23.

In this way, in the present invention, the vacuum pump 30
The exhaust destination will be changed from the pressure suppression pool 23 to the emergency gas treatment system in the event of a loss of coolant accident, and will be connected to the pressure suppression pool 23 in other cases, including during a total AC power loss event, so the reactor isolation This allows the automatic cooling system and high-pressure water injection system to operate in response to both loss-of-coolant accidents and total AC power loss events. In the above description, an example has been described in which the exhaust destination of the vacuum pump 30 is changed using the pressure switch 45. This is pressure suppression pool 2
This is because we focused on the fact that a significant pressure increase in the internal combustion chamber 3 would only occur due to a loss of coolant accident. Therefore, the same effect can be expected by replacing the open signal of the electric valve 44 with the signal from the pressure switch 45 and the coolant loss accident occurrence signal. It is also possible to use it as a change signal.

〔Effect of the invention〕

As described above, according to the present invention, the reactor isolation cooling system and high pressure water injection system can be used to cope with both a loss of coolant accident and a total AC power loss event. Each system is configured so that when one system is originally supposed to handle an event, the other system backs up the event, greatly improving plant reliability in the event of loss of coolant or loss of all AC power. do.

In addition, even in plants where only the reactor isolation cooling system is installed as a turbine-driven make-up water system, this system can be used not only in the event of a loss of water supply or total AC power loss, but also in the event of a loss of coolant accident. This greatly improves safety.

[Brief explanation of the drawing]

Fig. 1 is a system schematic diagram showing an embodiment of the steam turbine-driven water injection system for a nuclear reactor according to the present invention, Fig. 2 is a system schematic diagram of a conventional reactor isolation cooling system, and Fig. 3 is a conventional high-pressure water injection system. FIG. 20...Turbine stop valve, 21...Turbine control valve, 22...Turbine, 23...Pressure suppression pool, 2
4...Steam turbine driven pump, 25...Barometric condenser, 29...Vacuum tank, 30...
Vacuum pump, 41... Check valve, 42... Isolation valve, 44
...Electric valve, 45...Pressure switch.

Claims (1)

[Scope of Claims] 1. A barometric condenser that condenses leaked steam from a valve inserted in the turbine shaft seal and piping system of a steam turbine that drives makeup water pumps of the reactor isolation cooling system and high-pressure water injection system. and,
A vacuum tank connected to this barometric condenser, a vacuum pump that evacuates the inside of this vacuum tank, a check valve inserted in the piping connecting the discharge side of this vacuum pump and the pressure suppression pool, and this check valve. A steam turbine-driven water injection device for a nuclear reactor, characterized in that it is equipped with an electric valve that is inserted in a pipe that branches from upstream and leads to an emergency gas treatment system, and that opens in the event of a loss of coolant accident. 2. The steam turbine-driven water injection device for a nuclear reactor according to claim 1, wherein the electric valve is configured to be operated by a signal from a pressure switch that detects the pressure in the pressure control pool. . 3. The steam turbine-driven water injection system for a nuclear reactor according to claim 1, wherein the electric valve is configured to be activated by a loss of coolant accident occurrence signal. 4. The steam turbine-driven water injection device for a nuclear reactor according to claim 1, wherein the electric valve is configured to be activated by a high exhaust pressure signal from a vacuum pump.