JPS621239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for storing equipment and piping of a BWR type nuclear power plant, which aims to reduce radioactive debris generated from feed and condensate systems.

Conventionally, when periodically inspecting a BWR type nuclear power plant, if the plant is kept in a stopped state, rust will form on the parts of the equipment and piping that come into contact with water, and this rust will be carried into the reactor and emit radiation. Becomes a crud. For this reason, to prevent rust on equipment and piping, methods such as storing them full of water with a rust preventive agent added to them or drying them with a hot air blower after draining the water have been adopted.

When the above-mentioned storage is full of water, if construction is required, the water containing rust preventive agent in the equipment and piping must be drained, and the drained water must be reprocessed before being released. Also, dry storage has a better rust prevention effect than full water storage, but in this case as well, it is necessary to drain the water held in equipment and piping to the waste treatment system through the drain tray (Figure 2, 23). It takes a long time to drain the water after waiting for the temperature of the water to cool down to below the steam generation temperature. Furthermore, waste treatment systems cannot process large amounts of wastewater at once, so the amount of wastewater is limited and takes time. In the end, by the time the drainage is completed, the equipment,
The water in the pipes cools to around 20 degrees Celsius, making it difficult to dry them effectively naturally, so a hot air blower is used to dry them, but the problem is that the hot air does not reach the ends of the equipment and pipes. However, the current situation is that they are not stored sufficiently dry.

The present invention was made in consideration of the above-mentioned circumstances, and uses the high vacuum of the condenser to quickly extract hot water inside the equipment and piping into the condenser. Water droplets on the inner surface of the reactor are evaporated to allow it to dry naturally, thereby preventing the formation of rust, reducing the amount of crud brought into the reactor, and reducing radiation exposure.
Provides a storage method for BWR type nuclear power plant equipment and piping.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, steam generated from a nuclear reactor 1 is supplied to a turbine 2, which drives a generator 3. The steam that has done work in the turbine 2 is recovered in the condenser 4, where it is condensed and becomes condensed water. This condensate is sent out by a condensate pump 5, passes through an air extractor 6, a gland steam condenser 7, a condensate desalination device 8, and is further pressurized by a condensate boost pump 9. The condensate that has passed through the feedwater heater 10 and has been heated is then transferred to the feedwater heater 1 by the reactor feedwater pump 11.
2 to the reactor 1.

In the figure, 13 and 14 are vent valves and drain valves connected to appropriate places in the piping. Figure 2 is a conventional system diagram, in which there is a drain tray 2 downstream of the drain valves 14, 14.
3 and 23 were provided and connected to the waste treatment system 23.
When necessary, the vent valve 13 and the drain valve 14 are opened to discharge the water in the equipment and piping to the waste treatment system 24.

Returning to FIG. 1, in the present invention, the drain valves 14, 14
The downstream side of the drain pipe is connected to a drainage collecting pipe 17, and then connected to the condenser 4 via a water stand control tank 18, a drainage pipe 20, and an electric valve 21.

In the power generation equipment configured as described above, in the case of periodic plant inspections over a long period of time, etc., the water supply to the reactor 1 is stopped after the turbine generator is disconnected, and the water supply to the reactor 1 is stopped while the equipment and piping are still hot. Each vent valve 1
3, 13, open each drain valve 14, 14 and electric valve 21. Due to the vacuum of the condenser 4, the hot water in the equipment and piping is discharged to the condenser 4 via the drainage collecting pipe 17, the water level control tank 18, the drainage piping 20, and the electric valve 21. Water droplets remaining inside equipment and piping due to the rapid discharge of hot water are evaporated by the heat of the water droplets themselves and the residual heat of the equipment and piping, and the inside of the equipment and piping becomes naturally dry.

When the hot water in the equipment and piping finishes being extracted to the condenser, air flows into the condenser 4 and the condenser 4 is vacuum-broken, so a water level control tank 18 is provided as a vacuum-break prevention device. ing. The opening and closing of the electric valve 21 is controlled by a water level high or low water level signal from a level switch 19 installed in the tank 18. The orifice 22 is also used to prevent flashing.

As described above, the present invention is capable of quickly discharging hot water in the equipment and piping to the condenser without destroying the condenser vacuum when the turbine generator is disconnected while the equipment and piping are still hot. Let the equipment and piping dry naturally.
By preventing the occurrence of rust on the inner surfaces of equipment and piping, it is possible to reduce waste and reduce radiation exposure due to a reduction in the amount of crud flowing into the reactor. This is a highly efficient method for dry storage of BWR reactor plant equipment and piping.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a nuclear power plant showing one embodiment of the method of the present invention, and FIG. 2 is a conventional system diagram. 1... Nuclear reactor, 2... Turbine, 3... Turbine generator, 4... Condenser, 5... Condensate pump, 6
... Air extractor, 7 ... Gland steam condenser, 8
... Condensate desalination device, 9 ... Condensate boost pump, 10
...Feedwater heater group, 11...Reactor feedwater pump,
12... Feed water heater, 13... Vent valve, 14...
...Drain valve, 15... Condensate pipe, 16... Water supply pipe, 1
7...Drainage collecting pipe, 18...Water level control tank, 1
9... Level switch, 20... Drain piping, 21
...Electric valve, 22...Orifice.

Claims (1)

[Claims] 1. In a BWR type nuclear power generation facility consisting of a nuclear reactor, a turbine, a condenser, a feed water heater, etc.,
Connect the drain pipes connected to the bottom of the supply and condensate system equipment and piping to the condenser, and immediately after plant operation is stopped, use high vacuum in the condenser to quickly restore the hot water in the equipment and piping. A method for storing nuclear power plant equipment and piping, characterized in that water is extracted into a water container and water droplets remaining on the inner surface are evaporated by residual heat of the equipment and piping. 2. A method for storing nuclear power plant equipment and piping according to claim 1, characterized in that the drain pipe is connected to a condenser via a water level control tank.