JPH0358680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a safety system for a nuclear reactor.

[Background of the invention]

In current boiling water nuclear power plants, a test closed circuit is installed to confirm the integrity of the main steam isolation valve for isolating the main steam piping. In order to isolate the valve from the safety system, considering the generation of a valve closing signal such as a reactor scram signal, an event may occur in which the main steam isolation valve does not close quickly when the valve closing signal is generated.

A conventional example will be explained with reference to FIGS. 4 to 10.

Figure 4 shows a schematic diagram of the main steam system of a boiling water nuclear power plant. The main steam isolation valve 1 is attached to the main steam pipe 21 that connects the nuclear reactor 20 and the turbine,
Used to isolate nuclear reactors and turbines.

Figure 5 shows a schematic diagram of the main steam isolation valve opening/closing operation system. The main steam isolation valve 1 is opened and closed by supplying air to the air cylinder 2 from a compressed air system. The valves are operated by a main steam isolation valve quick-closing logic circuit 5 and a surveillance test logic circuit 6 installed in the central control room.
This is done by During plant operation, the main steam isolation valve quick-closing logic circuit 5 is in a normal state, and the electromagnetic valves 8 and 9 are energized to supply air to the lower part of the air cylinder 5 and the valve is open.

Figure 6 shows the rapid closing of the valve. When the reactor scram signal 14 enters the main steam isolation valve rapid closing logic circuit 5, the circuit is released, and the solenoid valves 8 and 9 are de-energized, so that air is supplied to the upper part of the air cylinder 2, and the air cylinder 2 The air from the lower part is exhausted from the two exhaust ports 18 and 19, and the valve is approximately 5
Closes quickly in seconds.

Figure 7 shows the valve surveillance test. When the main steam isolation valve rapid closing logic circuit 5 is in the normal state, the surveillance test logic circuit 6 is activated by the manual switch 4.
When electricity is applied, the solenoid valve 7 is energized and the pilot valve 11 is operated, thereby cutting off the air that was being supplied to the lower part of the air cylinder 2, and the air at the lower part of the air cylinder is slowly discharged into the atmosphere through the throttle valve 13. be done. As the cylinder pressure decreases, the valve slowly closes due to the force of the spring 3.

However, in FIG. 8, while the surveillance test logic circuit 6 is energized, the reactor scram signal 1 is
4 or when a main steam pipe rupture signal occurs. The main steam isolation valve quick-close logic circuit 5 is released, and the solenoid valve 7 remains energized, but the solenoid valve 8,
9 is de-energized, and the pilot valves 10 and 12 operate. Air is supplied to the upper part of the air cylinder 2, and the air at the lower part of the air cylinder 2 is supplied to the exhaust port 1.
8 and throttle valve 13, but the main exhaust is:
As shown in FIG. 9, the rapid closing time 22 during the surveillance test is closed only from the exhaust port 18.
is later than the normal rapid closing time 23 mentioned above,
It takes about 5.5 seconds.

The main steam isolation valve 1 is designed to close within 5 seconds from a fully open state to a fully closed state based on safety analysis. Therefore, if this valve is closed for 5.5 seconds, the steam and reactor water flowing out from the broken part of the main steam pipe will be
As shown in the figure, it will increase by about 20%24.

It is undesirable for the amount of highly radioactive reactor water to increase in this way. Therefore, it is necessary to close the main steam isolation valve at a high speed in the event of an accident such as when the main steam pipe ruptures during a surveillance test. Examples of patents that describe in detail how to operate a main steam isolation valve include JP-A No. 51-321924 and JP-A No. 50-45323.

[Purpose of the invention]

An object of the present invention is to provide a nuclear reactor safety system that can prevent abnormal outflow of reactor water due to a main steam pipe rupture accident that occurs during a main steam isolation valve surveillance test.

[Summary of the invention]

The present invention prevents abnormal leakage of reactor water by detecting a main steam pipe rupture signal that occurs during a main steam isolation valve surveillance test and simultaneously issuing a main steam isolation valve closing signal and a surveillance test cancellation signal. It is configured so that it can be done.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the main steam shutoff method for a boiling water nuclear reactor according to the present invention is shown in accordance with the accompanying drawings.

An embodiment of a nuclear reactor safety system according to the present invention is shown in FIG. This safety system is permitted when the operating conditions of the surveillance test logic circuit 6, the operation of the manual switch 4, and the operating state of the main steam isolation valve rapid closing logic circuit 5 are satisfied at the same time. Both logic circuits are in co-operation state, and the pilot valves 10, 11, and 12 are operated by the excitation of the solenoid valves 7, 8, and 9, and the pressure at the bottom of the air cylinder 2 of the valve is slowly discharged to the atmosphere through the throttle valve 13. As a result, the valve is slowly closed by the force of the spring 3.

FIG. 2 also shows a circuit when the reactor scram signal 14 is generated while the valve is undergoing a surveillance test by actuation of the manual switch 4. Occurrence of the reactor scram signal 14 disables the main steam isolation valve quick-close logic circuit 5. A release signal from the main steam isolation valve quick-close logic circuit 5 releases the surveillance test logic circuit 6. Therefore, the solenoid valves 7, 8, and 9 are all in a non-energized state, and the spring 15
The pilot valve 10, 1 changes depending on the
1 and 12 are activated to exhaust air from the exhaust port 16. Therefore, the pilot valve is switched by the force of the spring 17, and the air in the lower part of the air cylinder 2 is exhausted from the two exhausts 18 and 19, and the air is supplied to the upper part of the air cylinder 2 through the pilot valve 12, and the air is switched by the force of the spring 3. The combined valve can be closed quickly.

According to the present invention, it is possible to create the same condition as the normal quick-closing condition 23 of the valve shown in FIG. 9 described above, so that the valve quickly closes in about 5 seconds. Therefore, it is possible to prevent the increase 24 in the amount of steam and reactor water flowing out when the main steam pipe breaks as shown in FIG. 10 described above.

FIG. 3 shows another embodiment. In this embodiment, the reactor scram signal 14 is directly used as the release condition for the surveillance test logic circuit 6.

〔Effect of the invention〕

Adopting the present invention provides the following effects.

1. In a safety system that quickly closes a main steam isolation valve due to a reactor scram signal generated during a surveillance test of the main steam isolation valve, the valve can be closed at high speed by canceling the surveillance test logic circuit.

2. Rapid closure of the main steam isolation valve can prevent abnormal leakage of reactor water that occurs when the main steam piping is ruptured.

[Brief explanation of drawings]

Figure 1 is a logic circuit diagram of one embodiment of the present invention, Figure 2 is a logic circuit diagram of an embodiment of the present invention.
The figure is a valve closing circuit diagram when a reactor scram signal is generated after implementing the present invention, Figure 3 is another embodiment of the present invention, Figure 4 is a schematic system diagram of a boiling water nuclear power plant, and Figure 5 is a schematic diagram of a boiling water nuclear power plant. Main steam isolation valve opening/closing operation diagram, Figure 6 is a valve operation diagram when a reactor scram occurs, Figure 7 is a valve operation diagram during a surveillance test, and Figure 8 is a valve operation diagram when a reactor scram signal occurs during a surveillance test. Operation diagram, Figure 9 is the main steam isolation valve closing characteristic diagram, Figure 10.
is a diagram showing the amount of reactor water flowing out when the main steam pipe breaks. 1... Main steam isolation valve, 2... Air cylinder, 3... Spring, 4... Manual switch, 5, 6...
...Logic circuit, 7-9...Solenoid valve, 10-12...
Pilot valve, 13... Throttle valve, 14... Signal, 15, 17... Spring, 16, 18, 19...
Exhaust port, 20... Reactor containment vessel, 21... Main steam pipe, 22, 23... Valve closing characteristics, 24... Abnormal outflow reactor water amount.

Claims (1)

[Claims] 1. In a device for adjusting a main steam isolation valve that moves a valve body up and down using an air cylinder, there is a means for switching the supply of air into the air cylinder, and a main steam isolation valve quick-closing device that outputs a main steam isolation valve closing signal. a first solenoid valve that is opened when the main steam isolation valve close signal is input and supplies operating air to the air supply switching means; a manual switch that outputs a test signal; Surveillance for outputting an activation signal when the closing means is in one of a state in which the main steam isolation valve closing signal is not outputted and a scram signal is not inputted, and at the same time, the closing means is in a state in which the test signal is outputted. A main steam isolation valve control device comprising test logic means and a second solenoid valve that is opened upon input of said actuation signal and supplies actuation air to said air supply switching means.