JPS6332393A - Nuclear reactor stop device - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear reactor shutdown device applied to, for example, a back-up reactor shutdown device for a gas-cooled nuclear reactor.

(Conventional technology) A conventional example will be explained with reference to FIGS. 3 and 4.

Figure 3 shows a gas-cooled nuclear reactor! ! ! ! It is a vertical cross-sectional view showing a roughly 14-dimensional structure, and the reference numeral 1 in the figure indicates a reactor vessel.

A reactor core 2 is provided within this reactor vessel 1 .

This reactor core 2 is constructed by loading fuel rods 3 into a pile of graphite blocks serving as a moderator. Further, an inlet pipe 4 is connected to the bottom of the reactor vessel 1 into which a coolant such as helium gas flows, and an outlet pipe 5 passes through the inlet pipe 4. The coolant that has flowed into the reactor vessel 1 passes through the reactor core 2 from above to below, is heated by the nuclear reaction heat of the reactor core 2, and then flows out from the outlet pipe 5. On the other hand, reactor vessel 1
A heat exchanger 6 is provided outside the outlet pipe 5, and after the high temperature coolant flowing out from the outlet pipe 5 is heat exchanged with the secondary coolant in the heat exchanger 6, the inlet pipe 4 is transferred by a circulation pump 7. The reactor is then returned to the reactor vessel 1 through the reactor vessel 1. In addition, a purification system 8 is provided to purify the coolant in order to prevent high-temperature oxidation of metal materials and graphite. Further, a control rod guide tube 9 is inserted into the reactor core 2 from above, and a control rod 10 is housed in the control rod guide tube 9 so as to be movable up and down. By inserting and pulling the control rods 10 into the reactor core 2, the output of the reactor core 2 is controlled.

The control rods 10 are driven by a control rod drive mechanism 11 provided at the upper end of the reactor vessel 1, and the control rod drive mechanism 11 consists of a wire rope 12 welded to the control rod 9 and The wire rope 12 is wound around a drum 13, and the tram 13 is driven by a motor.
The control rod 1Q is moved up and down by retracting or letting out.

On the other hand, in anticipation of an emergency situation in which insertion of the control rods 10 becomes impossible, a backup reactor shutdown device 14 is provided. Although a plurality of the fuel rods 3, control rods 10, and back-up reactor shutdown device 14 are provided, the figure shows one each for simplicity.

FIG. 4 t shows the nuclear reactor shutdown device] 4, and the reference numeral 15 in the figure is a guide tube.

This guide tube 15 is inserted into the reactor core 2 from above, and its upper end is open. A neutron absorption element storage hopper (hereinafter referred to as hopper) 16 is installed above the guide tube 15. The hopper 16 stores a large number of neutron absorbing elements 17 in which neutron absorbing materials, such as 84C/C made by hardening carbon carbide with graphite, are shaped into spheres with a diameter of about 10 tm or pellets with a diameter and height of about 10 tm. has been done.

The lower end of the hopper 16 has a conical cylindrical shape with a smaller diameter at the bottom, and the lower end opening serves as a neutron absorption element drop port 18,
This neutron absorption element drop port 18 is located above the guide tube 15. Further, the neutron absorption element drop port 18 is closed by fitting a columnar plug 19 from the inside.

The plug 19 is connected via a drive shaft 20 to a plug drive mechanism 21 provided above the hopper 16.

As shown in FIG. 4, the plug drive mechanism 21 transmits the rotational force of the drive motor 22 to the hole screw 25 via gears 23 and 24, and converts the rotation of the ball screw 25 into the vertical movement of the ball nut 25. Convert this ball nut 26
The vertical movement of is transmitted to the drive@20 via the connecting plate 27.

By the way, the symbols 28 and 29 in the figure are the connecting plates 20, respectively.
These are an upper limit switch and a lower limit switch that detect the upper and lower limit positions of . In addition, the hopper 1
A housing tube 30 is provided inside the housing tube 6, and the plug 19 is moved up and down along the inside of the housing tube 3O. Further, the drive shaft 20 passes through a drive shaft through hole 31A of the shield 31 and is connected to the plug drive mechanism 21.

According to the above configuration, upon receiving the actuation signal, the drive motor 2
2 rotates forward, and the connection plate 27 rises until it comes into contact with the upper limit switch. The actuation of the upper limit switch 28 causes the drive motor 22 to stop. Connection plate 2
One of the interlocking plugs 7 rises to open the neutron absorption element drop port 18, and the neutron absorption element 17 naturally falls into the reactor core 2 through the guide tube 15 due to its own weight, causing an emergency shutdown of the reactor.

(Problems to be solved by the invention) High-temperature gas-cooled nuclear reactors contain H20, Co, H2, Co2
．． In order to keep the reaction of chemical impurities such as 02 with hot graphite and hot metals to a minimum, purification systems are used to remove these impurities in the helium gas coolant.

Possible sources of chemical impurities in helium gas coolant include:

■ Air contamination during maintenance and refueling, ■ Gas release from graphite and components, ■ Contamination of water from steam generators, ■ Contamination of lubricants from helium gas circulators, ■ Core components and impurity gases Among the above-mentioned items 1 to 2, the problem to be solved by the present invention is to prevent air from getting mixed in during maintenance and fuel exchange in item 0. There are several possible situations in which air may be mixed in during maintenance and fuel changes. In the case of backup reactor shutdown equipment, the hopper is filled with a large number of neutron absorption elements, and air that has entered the gap has a large resistance and is difficult to escape to the outside.

When replacing gas together with a nuclear reactor system, complete gas replacement cannot be performed. Therefore, a lot of time is required to purify the helium coolant.

The present invention has been made based on the above points, and its purpose is to replace the air in the reactor vessel by replacing the gas in the hopper alone and incorporating helium gas into the reactor vessel in a sealed state. An object of the present invention is to provide a nuclear reactor shutdown device that can reduce contamination.

[Structure of the Invention] (Means for Solving the Problems) As a means for solving the above problems, the backup nuclear reactor shutdown system of the present invention is constructed as shown in FIGS. 1 and 2.

That is, the guide tube 15 inserted into the reactor core from above,
It is installed above the guide tube 15 to store the neutron absorbing element 17 therein, and is provided with a neutron absorbing element drop port 101 at its lower end for dropping the neutron absorbing element 17 into the reactor core through the guide tube 15. a neutron absorption element storage hopper 16, a plug 19 for closing the neutron absorption element drop port 101, a plug drive mechanism 21 for raising the plug 19 and opening the neutron absorption element drop port 101, and this plug drive mechanism. 21 and the plug 19, and a compression spring 102 provided in the middle of the drive shaft 20.

Further, the neutron absorption element drop port 101 is composed of an upper part 101A larger than the outer diameter of the plug 19, and a lower part 101B smaller than the outer diameter of the plug 19. Roughly, the tip of the plug 19 is brought into contact with the stepped part of the neutron absorption element drop port 101 and is strongly pressed by the force of the compression spring 102, thereby closing the gap between the fitting part of the plug 19 and the neutron absorption element drop port 101. and the drive shaft 2
By making the diameter of the upper end of the drive shaft 20 larger than the drive shaft through hole 31A of the shield 31 and bringing the stepped portion 2OA of the drive shaft 20 into contact with the shield upper surface 31B, the gap between the drive shaft through hole 31A and the drive shaft 20 is reduced. and the plug drive mechanism 21
It has a spring-close type electromagnetic brake 104 that provides a braking force when the power is not energized, and a valve 105 for gas replacement is installed in the hopper 16.

(Function) In other words, a compression spring 102 is provided in the middle of the drive shaft 20, and the upper part of the diameter of the neutron absorption element drop port 101 is connected to the plug 19.
By making the larger portion 101A and the lower portion smaller than the plug 19, the plug 19 is fitted into the portion 101A larger than the plug 19. As a result, the neutron absorbing element 17 can be stored in the neutron absorbing element storage hopper 16 without being dropped, and one plug can be easily inserted and used.

On the other hand, when the tip of the plug 19 is applied to a portion 101B having a smaller diameter than the plug 19 and the compression spring 102 is compressed, the restoring force of the compression spring 102 allows the tip of the plug 19 to be strongly pressed against the portion 101B.

This can prevent gas leakage from the neutron absorption element drop port. On the other hand, the upper end of the drive shaft 20 is made larger than the drive shaft through hole 31A of the shield, and the stepped portion 2OA of the drive shaft is
is pressed against the upper surface 31B of the shield. This allows the gap between the drive shaft through hole 31A and the drive shaft 20 to be closed. Further, the pressing force is applied by first energizing the electromagnetic brake '104 of the plug drive groove 21 to eliminate the braking force and applying rotational torque to the pole screw 25.

If the electricity to the electromagnetic brake 104 is turned off after the rotational torque is applied, the braking force of the electromagnetic brake 104 moves and the pressing force can be maintained. When replacing the inside of the hopper 16 with gas, a vacuum pump 108 and a helium gas supply device 109 are connected outside the reactor vessel via piping and valves 106 and 107 beyond the valve 105, as shown in FIG. In addition, a vacuum pump is placed at the tip of the neutron absorption element drop port 101 to prevent external pressure from being applied to one plug during gas replacement and pushing the plug upward.]
] Connect 0 and exhaust. After evacuating the inside of the hopper, fill it with helium gas to the extent of 0.1 to 8/cjG, close the valve 105, connect the piping from the end of the valve 105, valves 106 and 107, and the vacuum pump 108 to the helium gas supply device 109 and the vacuum pump. 110 can be removed and assembled into the reactor vessel in a state where the hemicombus gas is contained.

(Example) Hereinafter, an example of a nuclear reactor shutdown device according to the present invention will be described with reference to FIGS. 1 and 2.

Note that parts that are the same as those in the prior art are denoted by the same reference numerals, and their explanations will be omitted.

FIG. 1 is a longitudinal sectional view of a nuclear reactor shutdown device according to this embodiment. FIG. 2 is a longitudinal cross-sectional view of a nuclear reactor shutdown device explaining the present invention in detail. Reference numeral 101 in the drawing indicates a neutron absorption element drop port, which is provided at the lower end of the neutron absorption element storage hopper 16, and is normally closed by a plug 19.

The neutron absorbing element drop port 101 has an upper part with a diameter 101A larger than the plug 19, and a lower part with a diameter 101B smaller than the plug 19. Further, a compression spring 102 is provided in the middle of a drive shaft 20 that connects the plug 19 and the plug drive mechanism 21. Both ends of the compression spring 102 are fixed to the drive shaft 20, and the tip of the plug 19 comes into contact with the caliber stepped portion of the neutron absorption element drop port 101 and is pressed by the force of the compression spring 102.

Further, the hopper 16 is fixed to the lower surface of the shield 31. The drive shaft 20 passes through the drive shaft through hole 31A of the shield 31 and is connected to the plug drive mechanism 21. Further, the drive shaft 20 has a diameter larger than that of the drive shaft through hole 31A at the point where it exits the drive shaft through hole 31A.
is in contact with B. Further, the plug drive mechanism 21 has a spring close type electromagnetic brake 104 that has a braking force when not energized, and a valve 105 for gas replacement is installed in the hopper 16.

The operation will be explained based on the above configuration.

By providing a compression spring 102 in the middle of the drive shaft 20 and making the upper part of the diameter of the neutron absorption element drop port 101 a part 101A larger than the plug 19, the plug 19 can be fitted into this part. The plug 19 can be stored in the hopper 16 without being dropped, and the plug 19 can be inserted and removed easily. On the other hand, by making the diameter of the lower part of the neutron absorption element drop port 101 smaller than that of the plug 19, when the tip of one plug is applied to this stepped part and the compression spring 102 is compressed, the restoring force of the compression spring 1.02 This allows the tip of the plug to be strongly pressed against the plug, thereby preventing debris from leaking from the neutron absorption element drop port. On the other hand, by making the upper end of the drive shaft 20 larger than the drive shaft through hole 31A of the shield and pressing the stepped portion 2OA of the drive shaft against the upper surface 31B of the shield, the gap between the drive shaft through hole 31A and the drive shaft 20 is reduced. Since it can be closed, gas leakage from the drive shaft through hole 31A can be prevented. The pressing force is applied by first energizing the electromagnetic brake 104 of the plug drive mechanism 21 to eliminate the braking force, and then applying rotational torque to the pole screw 25. If the electricity to the electromagnetic brake 104 is turned off when the rotational torque is applied, the braking force of the electromagnetic brake 104 is activated and the pressing force can be maintained.

When replacing gas in the hopper, as shown in Fig. 2, outside the reactor vessel, pipes are connected to the tip of valve 105, valve 106 and valve '10.
7 via vacuum pump 108 and helium gas supply device 1
Connect 09. External pressure is applied to the plug 19 when the hopper 16 is evacuated, and a vacuum pump 110 is connected to the tip of the neutron absorber drop port 101 to prevent the plug 19 from being pushed up.

After exhausting the inside of the hopper, remove helium scum at a rate of 0.1 kg/cm.
G, close the valve 105, remove the piping from the end of the valve 105, the valves 106 and 107, the vacuum pump, the helium gas supply device 109, and the vacuum pump 110, and enter the reactor vessel with the helium gas sealed. Incorporate.

As described above, according to this embodiment, the neutron absorption element drop port is provided with a part larger than the outer diameter of the plug and a smaller part, a compression spring is added to the drive shaft, and the upper part of the drive shaft is passed through the drive shaft of the shield. Simple modifications were made to the conventional technology, such as making it larger than the mouth, using a spring-close type solenoid valve that provides braking force when the plug drive mechanism is not energized, and installing a valve on the hopper. This prevents gas leakage inside the hopper. Therefore, gas replacement can be performed by the backup reactor shutdown equipment alone outside the reactor vessel, which prevents air from entering the reactor vessel from the backup reactor shutdown equipment, allowing gas replacement and gas purification in the reactor system. time can be shortened.

[Effects of the Invention] As detailed above, according to the reactor shutdown device according to the present invention, gas replacement and gas containment can be performed by the reactor shutdown device alone outside the reactor vessel with simple modification, making maintenance and maintenance easier. Air from the reactor shutdown equipment will not be mixed in during fuel exchange. Therefore, contamination with impurities during helium sludge cooling is reduced, and gas replacement and sludge purification of the reactor system are facilitated.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams for explaining one embodiment of the present invention. Figure 1 is a vertical cross-sectional view of the nuclear reactor shutdown equipment, and Figure 2 shows the state of the atomic rP shutdown equipment during gas replacement. A longitudinal cross-sectional view showing,
Figures 3 and 4 are diagrams for explaining conventional examples, where Figure 3 is a vertical cross-sectional view showing a schematic configuration of a gas-cooled nuclear reactor, and Figure 4 is a vertical cross-sectional view of a reactor shutdown device. . 1... Reactor vessel 2... Reactor core 16... Hopper 17... Neutron absorption element 19・・・・・・
...Plug 20... Drive shaft 2OA... Drive shaft step portion 101... Neutron absorption element drop port 101
A: Bore portion 101B larger than the outer diameter of the plug.
...Bore diameter portion 102 smaller than the outer diameter of the plug...
... Compression spring 104 ...... Electromagnetic brake with braking force when not energized Applicant Toshiba Corporation Representative Patent attorney Sa Suyama - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) A guide tube inserted into the reactor core from above, installed above the guide tube, stores a neutron absorption element inside, and inserts the neutron absorption element into the core through the guide tube at its lower end. a neutron absorbing element storage hopper equipped with a neutron absorbing element dropping port for dropping the neutron absorbing element into the neutron absorbing element; a plug for closing the neutron absorbing element dropping port; a drive mechanism for raising the plug and opening the neutron absorbing element dropping port; A drive shaft connecting the mechanism and the plug, a compression spring provided in the middle of the drive shaft, and a diameter of the upper part of the neutron absorption element drop port are made larger than the outer diameter of the plug, and a diameter of the lower part of the neutron absorption element drop port is made larger than the outer diameter of the plug. The tip of the plug is made smaller than the plug so that the tip of the plug comes into contact with the stepped portion of the neutron absorption element drop port and is strongly pressed by the force of the compression spring, and the upper end of the drive shaft is made smaller than the drive shaft through hole of the shield. Make it bigger
The nuclear reactor shutdown is characterized in that the stepped portion is brought into contact with the upper surface of the shield, a spring close type electromagnetic brake is provided which has a braking force when the drive is not energized, and a valve for gas replacement is installed in the hopper. Device.