JPS60222798A - Method of maintaining water level in nuclear reactor on tripof feed pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for maintaining reactor water level in a boiling water nuclear power plant, particularly when water is supplied only by a motor-driven water pump at low output. , relates to a preferred method for maintaining the water level in a Ryoko reactor when the pump trips.

[Background of the invention]

Previously, two motor-driven water supply bongs were installed, one of which was operated at low output, and the remaining one was used as a standby unit, but in order to reduce plant costs, only one motor-driven water supply pump was installed. I have a plan. At this time, it became necessary to establish a method for maintaining the reactor water level in the event that the pump trips. The present invention establishes that method.

[Purpose of the invention]

An object of the present invention is to provide a method for maintaining a good nuclear reactor water level when one motor-driven water pump trips while the plant is operating at low output.

[Summary of the invention]

The present invention provides a system for scrambling the reactor using the trip signal when the motor-driven water pump trips while the plant is in a low-output state and water is being supplied to the reactor by one motor-driven water pump. and activated the reactor isolation cooling system. By tripping the turbine, a large drop in the reactor water level is prevented,
It is designed to maintain the water level.

[Embodiments of the invention]

FIG. 1 shows a schematic configuration of a boiling water nuclear power plant to which the present invention is applied.

Cooling water heated in the reactor core 1 is boiled and becomes gas-liquid mixed water, which passes through an upper plenum 2 and is separated into saturated water and saturated steam by a steam separator 3. The saturated water descends, mixes with the water supplied from the water supply pipe 17, becomes subcooled water, and circulates back to the reactor core 1 again. The saturated steam is passed through the main steam isolation valve 6 along the main steam pipe 5;
It passes through the main stop valve 7 and the control valve 8 and enters the turbine 1o.
Mechanical work is performed here to generate electric power for a generator 11 directly connected to the turbine. The steam that has done work in the turbine is cooled by a 12K condenser and then becomes water.

This water is condensed water. Follow the pipes and reach the water supply pumps 14a and 14b.
Otherwise, the water is pressurized and returns to the pressure vessel 4 through the water supply pipe 17.

In the prior art, the water supply pumps include two turbine-driven water pumps 14a, 14b with a capacity of about 50%, and two motor-driven water pumps 15a, 15b with a capacity of 25%. Between 0% and 25% output when the plant is started, water is supplied only by the motor-driven water supply pump 15a, and 15b is on standby as a backup, and in the event that 15a trips, 15b will automatically start. Between 25% output and 50.1 output, the turbine-driven water supply pump 14a1
The motor-driven water supply pumps 15a and 15b are stopped to serve as backup for the motor-driven water supply pump 15a.

Between 50% output and 100% output, the two turbine-driven water supply pumps 14a and 14b are operated, and the motor-driven water supply pumps 15a and 15b are on standby as backup.

Now, in order to reduce Flint construction costs, there is a plan to remove one motor-driven water supply pump (the part surrounded by the dotted line in Figure 1).In this case, the problem is that the Motor-driven water supply pump 1 below Midekata
The problem with operating a 5AL unit is that in the unlikely event that it trips, there is no pump to automatically start it up as a backup. In other words, a stopped turbine-driven water pump cannot be automatically started due to its structure.
Even if it is manually started immediately, the bottle-driven water supply pump tends to become unstable in terms of control at low rotational speeds.

If no countermeasure is taken when the motor-driven water supply pump 15a is tripped, the following will occur.

First, the reactor water level gradually decreases to L3 level (
For example, when the water level reaches about 60 cm below the normal water level, the reactor is scrammed due to "reactor water level low" and the steel control rod 18 is suddenly inserted into the reactor core 1 by the sliding device 19 of the control bolt 1e.

Steam is gradually generated from the reactor's decay heat, so the reactor water level continues to fall, albeit at a slower rate. L2 level (for example, about 190m above normal water level)
When reaching the bottom, the main blocking valve 6 automatically closes, the reactor isolation cooling system 20 and the high-pressure core spray system 21 automatically start, and the water in the condensate storage tank 23 is discharged from the top of the pressure vessel 4. At the same time, water from the condensate storage tank 23 or water from the pressure suppression pool 24 is also sprayed from the upper part of the reactor core 1. This will restore the reactor water level.

The operational disadvantage of the above is that the high-pressure core spray system that is activated in the event of a pipe breakage accident is activated and applies unnecessary thermal shock to the reactor core 1.

Furthermore, the main steam isolation valve being closed also complicates the operation during restart.

The present invention solves the above-mentioned disadvantages.

That is, as shown in FIG. 2, if the turbine-driven water supply pumps 14a and 14b are stopped and only the motor-driven water supply pump 15a is in operation at the time of low output, and if the motor-driven water supply pump 15a trips, the atomic The nuclear reactor 1 is scrammed in order to suppress the amount of steam generated that causes a drop in the reactor water level.

Furthermore, in order to maintain the water level, the reactor isolation cooling system 2o is fully automatically activated. If the water is sprayed from the head of the pressure vessel 4, some of the water will enter the turbine 10 and damage the blades, so to prevent this, the turbine 10 is tripped and the main shutoff valve 7 is suddenly closed.

This prevents the operation of the high-pressure core system 21 and the automatic closing of the main steam isolation valve 6.

〔Effect of the invention〕

According to the present invention, automatic operation of the high-pressure core SGLEY system 21 and automatic closing of the main steam isolation valve 6 can be prevented, which is very convenient for plant operation.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a boiling water nuclear power plant to which the present invention is applied, and FIG. 2 is a functional block diagram showing the present invention. DESCRIPTION OF SYMBOLS 1... Reactor core, 4... Pressure vessel, 6... Main steam isolation valve, 7... Main blocking valve, 10... Turbine, 1
4a, b...Turbine-driven water supply pump, 15a, b...
...Motor-driven water supply pump, 18...Control rod, 19.
...Control rod drive device, 20...Reactor isolation cooling system,
21...High pressure core spray system.

Claims (1)

[Claims] 1. In a boiling water nuclear power plant equipped with multiple turbine-driven water pumps and one motor-driven water pump, all turbine-driven water pumps are stopped during low-output operation.
A water supply pump that automatically performs turbine tripping, reactor scram, and reactor isolation cooling system startup if the motor-driven water pump trips when one motor-driven water pump is in operation. How to maintain reactor water level during