JPS61265598A - Stop device for nuclear reactor - 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 [Technical Field of the Invention] The present invention relates to an improvement in a nuclear reactor shutdown device for emergency shutdown of a nuclear reactor by dropping a neutron absorption element into a reactor core.

[Technical background of invention! ] A conventional example will be explained with reference to FIGS. 5 and 6. Fifth
The figure is a vertical cross-sectional view showing a schematic configuration of a gas-cooled nuclear reactor, and reference numeral 1 in the figure indicates a reactor vessel.

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

The reactor core 2 is constructed by loading fuel rods 3 into stacked graphite blocks serving as a moderator. Also, reactor vessel 1
An inlet pipe 4 through which a coolant such as helium gas flows is connected to the bottom of the inlet pipe 4, and an outlet pipe 5 is inserted into 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 passes through the exit pipe 5. flows out from.

On the other hand, a heat exchanger 6 is provided outside the reactor vessel 1, 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 circulation pump 7, it is returned into the reactor vessel 1 via the inlet pipe 4.

Further, a tlIlIll rod guide tube 8 is inserted into the core 2 from above, and a control rod 9 is housed in the control rod guide tube 8 so as to be able to move up and down. By inserting and withdrawing the control rods 9 into and out of the reactor core 2, the output of the reactor core 2 is controlled. Note that the control rods 9 are driven by a control rod drive mechanism 10 provided at the upper end of the reactor vessel 1, and the IJtll rod drive mechanism 10 connects a wire lobe 11 to the control rod 9.
11 is wound around a drum 12, and the drum 12 is driven by a motor to wind in or let out the wire lobes 11, thereby raising and lowering the control rod 9.

On the other hand, a back-up reactor shutdown device 14 is provided in anticipation of an emergency situation in which it becomes impossible to insert the control rod 9 the next day. Although a plurality of the fuel rods 3, the control rods 9, the control rod drive mechanism 10, and the backup reactor shutdown device 14 are each provided, the figure shows one each for simplification.

By the way, the backup reactor shutdown device 14 has the same structure and operating principle as the control rod drive mechanism 10 in order to avoid redundant failures due to common causes with the control rod drive mechanism 10.
It is different from.

Figure 6 shows the reactor shutdown device 14, and the reference numeral 1 in the figure shows the reactor shutdown device 14.
5 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. Inside the hopper 16, 10 m+ of neutron absorbing material such as boron carbide (84C) is placed.
A large number of neutron absorbing elements 17 are stored, each having a spherical shape with a diameter of about 10a1, or a pellet shape with a diameter and height of about 10a1.

The lower end of the hopper 16 has a conical cylindrical shape with a smaller diameter at the bottom, and the lower end opening is used as a neutron absorption element drop port,
The said guide i! of said fall opening 1B! It is located above 15. Further, the neutron absorption element drop 018 is closed by fitting a columnar plug 19 from the inside.

The plug 19 is connected to a plug drive mechanism m provided above the hopper 16 via a connecting rod 2Q.

As shown in FIG. 6, the plug drive mechanism 21 transmits the rotational force of the drive motor 22 to the ball screw 25 via gears 23 and 24, and converts the rotation of the ball screw 25 into vertical movement of the ball nut 26. The vertical movement of the pole nut 26 is transmitted to the connecting rod 20 via the connecting plate 27. Reference numerals 28I3 and 29 in the figure are an upper limit switch and a lower limit switch that detect the upper and lower limit positions of the connecting plate 20, respectively, and 30 is a bearing that supports the lower end of the ball screw 25 and the upper part of the connecting rod 2Q. ,3
1 is a drive box. Further, a storage cylinder 33 is provided in the hopper 16, and the plug 19 is inserted into the storage cylinder 33.
It moves up and down along the inner peripheral surface of 3.

According to the above configuration, when a reactor emergency stop signal is output from the reactor safety protection system (not shown), the drive motor 22 rotates forward and the connection plate 27 rises until it comes into contact with the upper limit switch 28 . The actuation of the upper limit switch 28 causes the drive motor 22 to stop. During this time, the plug 19 rises to open the neutron absorption element drop port 18, and the neutron absorption element 17 falls naturally into the reactor core 2 through the guide tube 15 due to its own weight, causing an emergency shutdown of the reactor.

[Problems with Background Art] According to the above configuration, the neutron absorption element 17 is connected to the hopper 16.
If the neutron absorbing element 1 is stored in a stable state within the neutron absorbing element 1, even if the plug 19 is raised to release the neutron absorbing element falling 018, the neutron absorbing element 1
7 was suppressed from falling and the reactor was not shut down.
There was a problem in that it took a long time for the reactor to shut down.

[Objective of the Invention] The present invention has been made based on the above points, and its object is to ensure that the neutron absorption elements are quickly and reliably moved into the reactor core when the plug is raised to open the drop port. An object of the present invention is to provide a nuclear reactor shutdown device that can be dropped onto the ground and bring the reactor to an emergency shutdown.

[Summary of the Invention] That is, the nuclear reactor shutdown device according to the present invention has a double wall body consisting of a guide tube inserted into the reactor core from above, and an inner wall body and an outer wall body installed above the guide tube. A neutron absorbing element storage hopper that accommodates a neutron absorbing element between the double walls and has a neutron absorbing element drop port at the lower end for allowing the neutron absorbing element to fall into the reactor core via a guide tube; a plug that is installed to be movable up and down to open and close the neutron absorption element drop port; a plurality of recesses formed on the lower end side of the plug; When the drop port is closed, the plug is pushed into the recess by the inner wall of the neutron absorbing element drop port, when the plug is in the intermediate position, a part of the plug is projected from the recess, and when the plug is at the upper limit position, the inner wall body is pushed into the recess. The present invention is characterized by comprising a protrusion that is pushed into the recess by a protrusion, a drive mechanism that moves the plug up and down, and a rotation mechanism that rotates the plug when it moves up and down.

In other words, when making an emergency shutdown of a nuclear reactor, the plug is raised while rotating, and at that time, a portion of the protrusion protrudes from the recess, and this protruding portion destroys the stability of the neutron absorption element packed layer all around. , try to drop the neutron absorption element quickly.

[Embodiment of the Invention] An embodiment of the present invention will be described with reference to FIGS. 1 to 4. 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 sectional view showing a part of the nuclear reactor shutdown device according to this embodiment. The plug 101 is a thick-walled cylindrical body, and a connecting rod 20 is connected to its upper end via two thrust bearings 102 and 103.

A spiral groove 104 is formed within a predetermined range from the lower end on the inner circumferential surface of the housing tube (inner wall body) 33 that accommodates the plug 101. The above-mentioned plug 101 is in this spiral groove 104.
An engaging protrusion 105 protruding from the cylindrical surface of the upper end is engaged. Further, the spiral groove 104 is formed at a predetermined angle of inclination so that the frictional resistance at the contact portion with the engagement protrusion 105 does not prevent the rotation of the plug 101.

A plurality of recesses 106 are formed at equal intervals in the circumferential direction on the lower end cylindrical surface of the plug 101.
A protrusion 108 is accommodated within the protrusion 6 via a spiral spring 107. This protrusion 108 is urged radially outward by the spiral spring 107. Further, the outlet portion 106A of the recessed portion 106 is slightly narrowed, so that the protrusion 10
8 does not protrude beyond the recess 106.

The operation will be explained based on the above configuration. First, we will explain what happens when a nuclear reactor is in normal operation. In this case, the reactor shutdown device is not operating and is in the state shown in FIG. 1. The plug 101 closes the neutron absorption element drop opening 1, and at this time the projection 108 comes into contact with the inner wall of the neutron absorption element drop 018 and is housed in the recess 106 against the biasing force of the spiral spring 107. ing. Therefore, the neutron absorption element 17 will not fall.

Next, a case will be described in which a reactor emergency stop signal is output from a reactor safety protection system (not shown).

First, the drive motor 22 rotates forward. Positive rotation of the drive motor 22 causes the plug 101 to rise via the gears 23, 24, the ball screw 25, the pole nut 26, the connecting plate 27 and the connecting rod 20. When the plug 101 rises, the engagement protrusion 105 comes into contact with the spiral groove 104'm, and the plug 101 rises while rotating. Then, the plug 101 rises, and the plug 101
As shown in FIG.
08 is pushed outward in the radial direction by the spring force of the spiral spring 107, and a portion of the protrusion 108 protrudes from the recess 106.

The portion protruding from the recess 106 pushes the neutron absorbing element filling layer, and as a result, the stability of the neutron absorbing element filling layer is destroyed, and the neutron absorbing element 17 begins to fall as shown in FIG. The fallen neutron absorption element 17 then falls into the reactor core 2 via the guide tube 15. Also the third
Since the plug 101 is rotating in the process of rising from the state shown in the figure to the state shown in FIG.
The stability of the neutron absorption element filling layer is effectively destroyed, and the neutron absorption elements 17 quickly fall. Then, as the plug 101 rises and the lower end of the plug 101 is located above the lower end of the housing 1!
It is urged inward in the radial direction by A, and is forcibly housed in the recess 106 against the urging force of the spiral spring 107. This state is the state shown in FIG.

According to this embodiment, the following effects can be achieved. That is, a plurality of recesses 1 are provided at the lower end of the plug 101.
06 are formed at equal intervals in the circumferential direction, and a protrusion 108 is accommodated in the recess 106 via a spiral spring 107. When the reactor emergency stop signal is output, the protrusion 17 partially protrudes radially outward, and in this state, the plug 101
rises as it rotates. Therefore, the protruding portion of the protrusion 108 can thrust the neutron absorbing element filling layer all around, effectively destroying its stable state, and as a result, the neutron absorbing element 17 causes a so-called bridging phenomenon. It quickly falls into the reactor core 2 through the guide tube 15 without any problems. Therefore, the reactor can be stopped within a very short time after the reactor emergency stop signal is output.

In particular, since the plug 101 is rotated, the projection of the protrusion 108 from the recess 106 can move the neutron absorbing element filling layer around the entire circumference, destroying its stability. Yes, and extremely effective. When the plug 101 is located above the end of the storage tube 33, the protrusion 108 is inserted into the lower end tapered portion 33 of the storage tube 33.
A allows it to be accommodated smoothly in the recess 106, and its operation is smooth. Moreover, at that time, the neutron absorption elements 17 have fallen one after another from the lower layer, and do not return to a stable state again, making it possible to stop the nuclear reactor reliably and quickly. As described above, according to the nuclear reactor shutdown device according to this embodiment, the reliability of the device is significantly increased, and the safety of the nuclear reactor can be significantly improved.

Although a sphere was used as the protrusion in the above example, the protrusion is not limited to this, and various shapes can be considered.In short, a part of the protrusion protrudes from the recess to effectively create a stable earthen floor for the neutron absorption element packed layer. It is only necessary to destroy it, and then return it to the recessed part by smooth movement. Further, the rotation mechanism is not limited to the spiral groove and the engagement protrusion, and various configurations can be considered.

[Effects of the Invention] As detailed above, according to the nuclear reactor shutdown device according to the present invention, when the reactor emergency shutdown signal is output, the stable state of the neutron absorption element packed bed is effectively destroyed and the neutron absorption element can be dropped into the reactor core within an instant, greatly improving the reliability of the device as well as the safety of the reactor.

[Brief explanation of the drawing]

Figures 1 to 41i! ! 1 is a diagram showing an embodiment of the present invention; FIG. 1 is a partial sectional view of a nuclear reactor shutdown system; FIG. 2 is a partial sectional view taken along ■-■ of FIG. Figures 5 and 6 are diagrams used for conventional explanations, Figure 5 is a diagram showing the configuration of a gas-cooled reactor, and Figure 6 is a diagram showing the configuration of a reactor. FIG. 3 is a longitudinal cross-sectional view of the stopping device. DESCRIPTION OF SYMBOLS 1... Reactor vessel, 2... Reactor core, 15... Guide tube, 17... Neutron absorption element, 18... Neutron absorption element fall port, 1-... Drive mechanism, 101... ·plug,
104... Spiral groove, 105... Engaging protrusion, 106...
... Groove, 107... Spiral spring, 108... Protrusion. Applicant's representative Patent attorney Takehiko Suzue Figure 3 Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) A double-walled body consisting of a guide tube inserted from above into the core and an inner wall and an outer wall installed above the guide tube, and a neutron absorption element is housed between the double-walled bodies. At the same time, a neutron absorbing element storage hopper is provided at the lower end with a neutron absorbing element dropping port through which the neutron absorbing element is dropped into the reactor core via a guide tube, and a neutron absorbing element storage hopper is installed in the inner wall so as to be movable up and down, and the neutron absorbing element is dropped into the reactor core through a guide tube. A plug whose mouth opens and closes, a plurality of recesses formed on the side of the lower end of the plug, and a neutron absorption element accommodated in the recesses via an elastic body when the plug closes the drop port of the neutron absorption element. a protrusion that is pushed into the recess by the inner wall of the drop opening, a part of which protrudes from the recess when the plug is at the intermediate position, and is pushed into the recess by the inner wall when the plug is at the upper limit position; A nuclear reactor shutdown device comprising: a drive mechanism that moves the plug up and down; and a rotation mechanism that rotates the plug when the plug moves up and down. (2) The rotating mechanism comprises a spiral groove formed on the inner circumferential surface of the inner wall, and an engaging protrusion that projects from the plug and slides into the spiral groove. Nuclear reactor shutdown device according to item 1.