JP2020008541A - Cooling system of nuclear reactor during accident - Google Patents

Abstract

To solve the problems in which: at the time of an accident, temperature, pressure, and water level in a reactor are kept at a normal level and radiation is not emitted so a nuclear reactor can be continuously operated; a system is made light-weight, and inexpensive price with less amount of emergency power, and preliminary water; and operation stop and resumption of the nuclear reactor are performed by only one button for about 20 seconds so that personnel and their training are made unnecessary.SOLUTION: A cooling system comprises a cooler and a regulator in which water is always filled in the cooler up to its upper part, and 10 percent of water and 90 percent of air are filled in the regulator. In a stand-by state, the nuclear reactor has the same pressure as that of the cooling system, therefore each valve is opened and closed under the same pressure, and also a circulation pump performs water circulation under the same pressure so apparatuses can be miniaturized and required power can be smaller. Steam of the nuclear reactor is introduced into the cooler by releasing air from the regulator to cool the steam and change the steam into water to return to the nuclear reactor. It is determined which apparatuses control temperature of the nuclear reactor, pressure, and water level, so all of them are not attained only by cooling. In this case, since pressure of the cooling system is the same as that of the nuclear reactor, operation stop at the time of accident, and operation resumption after restoration of accident cause are done fully automatically in 20 seconds.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cooling device (hereinafter, the cooling device means the cooling device of the present invention) which is operated when a reactor is overheated in an accident and there is a danger of explosion.

In the event of a nuclear reactor accident, vents (hereinafter, vents mean releasing radioactive steam into the air) to prevent explosions caused serious damage to residents.
Many inventions that protect the reactor body in the event of a nuclear reactor accident have been devised on the premise of venting.

The conventional cooling system used only in the event of an accident is not specified as a condition that the steam valve and the water supply valve are closed to respond to the accident.If the cooling system is operated, the temperature, pressure, water level, etc. And was not separately controlled.
In the event of an accident, many maintenance personnel are required, training and cost are high, and simple observations and judgments cannot be made due to psychological fluctuations as can be seen from the course of the conventional accident.

Japanese Patent Application Laid-Open No. 2014-071054 Japanese Patent Application Publication No. 2014-085227 JP-A-2015-078847 JP 2015-194416 A

In the event of an accident, maintain the reactor temperature, pressure, and water level at normal levels without venting to avoid the danger of a reactor explosion.
To develop a cooling system that can be operated continuously with the water supply valve and the steam valve of the reactor closed in the event of an accident, reduce the power, water, and personnel used at this time, make the system smaller, lighter, cheaper, safer, and The challenge is to reduce the time for resuming operation after the completion of accident repair.

Although there are a pressurized reactor and a boiling water reactor, cooling of the reactor is the same, and therefore, the present invention describes a boiling water reactor.
If the reactor overheats in the event of an accident, the cooling system used only during the accident lowers the temperature of the reactor and returns steam to water to ensure safety.
In this case, in order to reduce the load on the valves of all the cooling devices, the internal pressure of the cooling devices and the pressure of the reactor are made the same, and the valves are made small, lightweight and inexpensive.

Normally, water is filled up to the top of the cooler of the cooling system, the regulator stores air at the same pressure as the reactor, and the entire system is kept at the same pressure as the reactor and waits for an accident.
In the event of an accident, the amount of air in the regulator is controlled by a pneumatic pump and an air valve to control the reactor water level with the cooler and reactor pressure equal.
The temperature of the reactor is controlled by the flow rate of the cooling water of the cooling device and the flow rate of the circulation pump.
If the reactor water level drops, supply water from the water inlet.
As described above, since equipment for controlling the target values of the temperature, the water level, and the pressure of the nuclear reactor is determined, it is not good because if the cooling is performed as in the conventional case, the temperature decreases.

At the time of the accident, the reactor is operated continuously with the reactor temperature, pressure and water level kept at specified values with the steam and water supply valves of the reactor closed and the generator and condenser stopped.
The cooling device of the present invention cools high-temperature, high-pressure steam with low-temperature cooling water at a pressure of 70 atm, 400 ° C water to 60 atm, 300 ° C. Since the pressure difference between the inlet and outlet is less than 1 atm, the emergency power supply is about 0.5% of the conventional reactor water supply and condenser.

The accident response equipment is small and inexpensive and operates automatically at the touch of a button, so there is no need for maintenance personnel, and the time until stabilization is about 20 seconds, and the temperature, water level, pressure, etc. Since there is no fluctuation and the control purpose and the device for controlling the control purpose are clearly linked, it is not an ambiguous control that can be solved by cooling all as conventionally.
The power and water used only in the event of an accident is about 0.5% of the conventional one, but it is good to have some reserve just in case.
After repairing the cause of the accident, operation can be resumed in about 20 seconds with the push of a button.

FIG. 3 is a principle view when the cooling device of the present invention is attached to a nuclear reactor.

In FIG. 1, a reactor 1 is an existing boiling water reactor. (The same applies to pressurized type)
The steam valve 7 and the water supply valve 4 of the cooling device of the present invention are installed on the reactor side of the existing steam valve and the water supply valve, and the cooling device of the present invention is closed with the existing steam valve and the water supply valve closed at the time of an accident. drive.

In the normal standby state, water is supplied from the water supply port 15 to fill the upper part of the cooler 17 with water, the regulator 13 is filled with 10% of water 13 and about 90% of air 11, and the air valve 10 and the air pump 9 is operated to make the pressure of the air 11 equal to the internal pressure of the nuclear reactor 1.
Thereafter, the amount of air 11 is constantly controlled so as to be equal to the pressure of the reactor 1.
After that, the steam valve 7, the water supply valve 4, the water supply valve 16 and the air valve 10 are closed and the apparatus stands by until an accident occurs.
In the event of an accident, the steam valve 7, the water supply valve 4, the water supply valve 16, the air valve 10 is opened to release the air 11 of the regulator 5, the steam 2 of the reactor 1 is put into the cooler 17 and cooled, and the steam 21 of the cooler 17 is cooled with water. The water is supplied to the reactor 1 by the circulation pump 6 instead of 22.
The steam 21 is cooled by passing cooling water 19, 20 or air through a cooling pipe 18 of a cooler 17.

The separator 12 is attached to the regulator 5, and the water 13 and the air 11 of the regulator 5 are separated.
The air pump 9 sends air to the regulator 5 and controls the air valve 10 and the air pump 9 to adjust the water level of the reactor 1 while keeping the pressure of the air 11 of the regulator 5 equal to the pressure of the reactor 1. .
Thus, the water level of the reactor 1 is controlled by the air valve 10 and the air pump 9 of the regulator 5, the temperature is controlled by the amount of the cooling water 19, 20 of the cooler 17 and the output of the circulation pump 6, and the pressure is controlled by the temperature. The temperature can be controlled by controlling the temperature. However, if it is desired to lower only the pressure in a state where the temperature is high and the temperature is low, the air of the reactor 1 is evacuated and the steam of the reactor 1 is put into the cooler 17 and the circulation pump Increase the output of 6.

As a result, the temperature of the steam 2 in the reactor 1 is lower than the normal target value, but the pressure is also lower.
Although it is not usually possible, water is supplied from the water supply port 15 when the amount of water is low.
Although it is not usually possible, if there is too much water or steam, it is discharged from the water supply port 15.
Also in this case, the released water and steam are temporarily stored in a separate tank and cooled, and the steam and the like are not released to the atmosphere.

In the case of FIG. 1, the cooler 17 is a case where the steam is put outside and the cooling pipe 18 is put inside. However, the same operation is performed even if the cooling water is put outside and the steam pipe 18 is put inside.
In the event of an accident, the above equipment is operated automatically at the touch of a button, does not require maintenance personnel, and takes about 20 seconds to reach a stable state.

DESCRIPTION OF SYMBOLS 1 Nuclear reactor 2 Steam 3 Water 4 Water supply valve 5 Regulator 6 Circulation pump 7 Steam valve 8 Pipe 9 Air pump 10 Air valve 11 Air 12 Separator 13 Water 14 Pipe 15 Water supply port 16 Water supply valve 17 Cooler 18 Cooling pipe 19 Cooling water 20 cooling water 21 steam 22 water

Claims (2)

  It is characterized in that the cooling device of the present invention is installed separately in a conventional reactor and in the event of a nuclear reactor accident, the cooling device is operated even with the steam valve and the water supply valve of the conventional reactor closed. Reactor cooling system 1. The cooling device of the present invention has a steam valve and a water supply valve through which steam and water pass even when the steam valve and the water supply valve of the conventional reactor are closed.
2. The cooling device of the present invention has a cooler for cooling steam or water, and the cooler is always filled with water to the top.
3. The cooling device of the present invention has a regulator, and the regulator always contains about 10% of water and about 90% of air or nitrogen gas.
4. During normal operation, the pressure of the reactor and the internal pressure of the cooling device of the present invention should be equalized with all valves of the cooling device of the present invention closed.
5. In the event of an accident, with the existing steam valve and water supply valve of the reactor closed, control the amount of cooling water in the cooling system and the amount of water in the circulation pump with the temperature of the reactor as the control target, and control the pressure of the reactor. To control the amount of air or nitrogen gas in the regulator, and to control the water level in the reactor and control the flow of water in and out of the water inlet of the cooling system.
However, when the accident is minor, the existing steam valve and water supply valve of the reactor may be opened to operate the cooling device of the present invention in parallel.
Reactor cooling device using the above conditions 1, 2, 3, 4, 5 simultaneously The reactor cooling device using the above items 1, 2 simultaneously

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