JPS5832356B2 - Water sealing device in nuclear reactor system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear power plant, and particularly to a water sealing device in a nuclear reactor system for sealing main piping of an emergency core cooling system.

The water sealing system in a nuclear power plant is the emergency core cooling system (
When the T'ECC8 (hereinafter referred to as T'ECC8) is started or stopped, prevent significant deterioration of pump performance due to the presence of air pockets in the main piping on the suction side and discharge side of the main pump. The purpose is to prevent the water hammer phenomenon in the system due to valve opening and closing operations, and to shorten the time for coolant to flow into the reactor pressure vessel by enclosing three pipes.

Figure 1 shows the high-pressure core spray system, which is part of the ECC8 system in a conventional plant, and its water sealing system is
By driving the sealing pump 3 whose water source is the condensate storage tank 1 or the pressure suppression chamber 2, the check valve 4. The main pump discharge side piping 1 is sealed by supplying water from the water sealing pipe 6 provided with l=- and the global check valve 5, and the orifice 9 is similarly supplied by a branch pipe 8 from the water sealing pipe 6. , is configured to seal the suction pipe 11 from the pressure suppression chamber 2 through the globe valve 10.

In this way, conventional plant water sealing devices operate continuously for a long period of time during plant operation (however,
A sealing pump is used as a dynamic device (stopped when the main pump 12 of the ECC5 system is in operation).

For this reason, it has become a problem to ensure sufficient reliability of the water sealing system, which has a water sealing pump as a dynamic device, including securing power supply, and the layout of the reactor building has made it difficult to ensure that the water sealing pump and peripheral equipment In addition to securing the installation location,
It is necessary to consider safety measures to protect against plant accidents.

The purpose of the present invention is to eliminate the water seal pump as a dynamic device, install a tank that is supplied with water from the condensate make-up water system, etc. at the top of each system of the ECC 8, and install water seal piping led from the tank. The purpose is to seal the suction side piping and the discharge side piping of the ECC 8 by pressurizing it with a pump of the condensate make-up water system or by pressurizing it with the gravity of the water held in the tank.

Another object of the present invention is to detect leakage and outflow of the water held in the ECC8 main pipe after the water sealing as described above, using a water level gauge provided in the tank.

Another object of the present invention is to prevent the water hammer phenomenon that may occur when the injection valve of the ECC 8 is opened or closed by absorbing energy by the free space above the water surface of the tank.

Still another object of the present invention is to provide the possibility of constructing a system test line using a tank as a water source by adding or changing some piping routes to the above system.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows an example of a water sealing device according to the present invention.
At the top of the main pump 12 and coolant injection line 13 of each system of the CC 5, one or more tanks 14 are installed, as shown in FIGS. 3a and 3b, respectively.

Water is supplied to the tank 14 through a condensate make-up water system (hereinafter referred to as M
UWC) 15.

The water sealing pipe 6 from the tank 14 is provided with an electric isolation valve 16, and is connected to the downstream side of the check valve 17 of the main pump discharge side pipe 7 of each system of the ECC 8.

The main pump suction side pipe 18 is branched from a water sealing pipe 20 having an electric isolation valve 19, and has a globe valve 21 and a check valve 2.
Furthermore, a water sealing pipe 24 branching from the water sealing pipe 20 is connected to the main pump discharge side pipe 27 via a globe valve 25 and a check valve 26, and a water sealing pipe 23 having a tank The efficiency of water sealing by gravity pressurization of the retained water 28 of 14 is improved.

A water level gauge 29 is provided in the tank 14, and MUW is detected at a high water level.
Stopping the water supply from Cl 5 and E at low water level.
It is configured to detect leakage from isolation valves 30, 31 and 32 located below the CC8.

A vent pipe 33 is provided at the top of the tank 14 to vent air when the tank 14 is filled with water.

Next, the effect will be explained.

During normal times, the retained water 28 of the water tank 14 flows into the main pump suction side piping 18 and the main pump discharge side piping 7, 27 due to the action of gravity, and the system is water-sealed.

The air inside the pipe 7.18.27
4 and is discharged from the system through the vent pipe 33.

If this method requires time to seal the water, the tank 14 is filled with water and pressurized by the condensate make-up water system to quickly seal the pipes 7, 18, 27.

After the water sealing is completed, adjust the water level of the tank 14 to the normal water level,
The electric isolation valve 34 stops the water supply from the MUWCl 5 and isolates it from the MUWCl 5.

Here, isolation valves 30°31. which are located at the lower level and should be fully closed.
32 is leaking, the water level in the tank 14 will drop, and the leakage can be detected by the water level gauge 29.

When the ECC 8 starts and stops during a coolant loss accident, the electric isolation valve 19 is closed based on the flow rate signal from the flow meter 35, and the electric isolation valve 16 is controlled to be in the open state as shown in FIG. 4. Create a system configuration like this.

When the injection valve 36 is rapidly opened and closed, the injection valve 3
The main pump 12 and piping caused by the sudden change from the gas phase to the liquid phase at the 6th end? , 18°27.13 pressure fluctuations due to the water hammer phenomenon are absorbed by the free space 37 of the tank 14.

Pipes 38, 39 and valves 40 are used to return water discharged from the main pump 12 to the pressure suppression chamber 2 during system tests, and the outer pipes 42, 43, and 44 are similarly used to return water to the condensate storage tank 1. .

Further, the pipes 46 and 47 having the decompression orifice 45 are minimum O-lines for preventing the main pump 12 from shutting down.

FIG. 5 shows a simplified system configuration when the capacity of the water sealing tank and water sealing piping is increased.
is a globe valve provided in the pipe 48.

By using this system and opening and closing the valves shown in Table 1 below, it is possible to replace the system configuration with a tank 14 as a water source in addition to the conventional condensate storage tank.

As explained above, the water sealing device according to the present invention is composed of only a small-capacity tank, piping, and instrumentation, so it operates continuously during plant operation, such as a water sealing pump, for a long period of time. There is no need to install dynamic equipment that requires sufficient reliability and maintenance.
There were 5 cars in 8, but all of them are gone.

), reliability as a water sealing device and EC using it
The health of each system of C8 will improve.

Conventionally, a pressure gauge installed on the downstream side of the check valve on the discharge side of the pump was used to detect whether or not the water seal was sufficient. There is no risk of any residue remaining, and the reliability of detection is increased.

By using the free space in the tank to absorb water hammer energy when opening and closing the injection valve, piping and system equipment can be protected.

[Brief explanation of drawings]

Figure 1 is a system diagram of an emergency core cooling system with a conventional water sealing pump, Figure 2 is a system diagram showing an example of the water sealing device according to the present invention, and Figure 3 is the height difference between the tank and the system. This figure shows the positional relationship when considering the following: Fig. a shows a system diagram when each system is sealed with one tank, and Fig. 1 shows a system diagram when each system is sealed with multiple tanks. System diagram, FIG. 4 is an explanatory diagram showing an example of the case where the tank is used to prevent water hammer, and FIG. 5 is a system diagram showing an example of the case where the tank is also considered as a water source for system tests. 1... Condensate storage tank, 2... Pressure suppression chamber, 7, 2
7... Main pump discharge side piping, 14... Tank, 15
...Condensate make-up water system, 18...Main pump suction side piping,
20゜23.24... Water sealing piping, 29... Water level gauge,
48...Sakakokan, 49...Tamagataben.

Claims (1)

[Scope of Claims] 1. In each system of the emergency core cooling system, water is supplied from the condensate make-up water system, which is installed at the top of the systems, and water is supplied from the water system to the emergency core cooling system. A water sealing device for a nuclear reactor system, comprising a water sealing pipe connected to a main pump suction side pipe and a discharge side pipe, and a valve provided on the pipe. 2. A water sealing device in a nuclear reactor system according to claim 1, wherein the tank is provided with a water level gauge capable of measuring the water level. 3. Claim 1, characterized in that piping is provided to connect the tank and the main pump discharge side piping, and this piping is provided with an isolation valve that closes in response to a signal indicating a high flow rate on the main pump discharge side. A water sealing device in a nuclear reactor system according to item 1 or 2.