JPH0519674B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a fast breeder reactor (hereinafter referred to as a nuclear reactor).
This invention relates to a control rod drive mechanism that is attached to a control rod and changes the insertion depth of the control rod into the reactor core.

[Technical background of the invention]

A plurality of control rod drive mechanisms are installed in a nuclear reactor, grip each of the plurality of control rods inserted into the reactor core, change the depth of insertion into the reactor core, and control the output of the reactor. In addition, in the event of an emergency, the control rods are quickly inserted to the deepest position in the reactor core, and the reactor is brought to an emergency shutdown to ensure its safety.

A conventional control rod drive mechanism will be explained with reference to FIGS. 1 and 2.

Cylindrical casing 2 with upper lid of control rod drive mechanism 1
A cylindrical upper guide tube 3 having the same outer diameter as the casing 2 is concentrically connected to the lower end of the casing 2 . The casing 2 and the upper guide tube 3 are supported by an upper lid part of a reactor vessel (not shown), and the upper guide tube 3 is suspended at a predetermined position in the reactor vessel above the reactor core (not shown). A long rod-shaped gripper rod 4 is inserted into the center of the upper guide tube 3 so as to be vertically movable, and a long tubular gripper tube 5 is fitted into the outer periphery of the gripper rod 4 within the upper guide tube 3 so as to be vertically movable.
The lower end of the gripper tube 5 forms a cylindrical collet-shaped gripper 6 having a plurality of slots in the axial direction. The lower end of the gripper rod 4 bulges out to form a spindle-shaped expanding mandrel 7. Gritspa 6 is
When the expanding mandrel 7 is pushed into it from below, it is expanded, and when the expanding mandrel 7 is not pushed in, it is elastically restored and has a small diameter. Inside the casing 2, a drive motor 8,
A feed screw mechanism 9 driven by a drive motor 8, an electromagnet 10, a gripper rod gripping mechanism 11 operated by the electromagnet 10 to grip and release the upper end of the gripper rod 4, and a gripper rod gripping mechanism 11 that grips and releases the upper end of the gripper tube 5. Gripping pipe gripping mechanism 1
It is equipped with 2. Inside the upper guide tube 3, gripper tube 5
An acceleration tube 13 is fitted into the outer periphery of the accelerator tube 13 so as to be vertically movable, and between the upper end surface of the acceleration tube 13 and the inner periphery protruding ring seat of the upper guide tube 3, and between the outer periphery of the gripper tube 5, there is a compression coil spring forming an acceleration spring 14. is fitted into the acceleration tube 1
3 is urged downward and its lower end surface is pressed against the upper end surface of a handling head 21, which will be described later. The casing 2, the upper guide tube 3 to the acceleration tube 13, and the acceleration spring 14 constitute the control rod drive mechanism 1.

Below the upper guide tube 3, within the reactor core (not shown), a lower guide tube 20 is vertically placed with its central axis substantially extending from the central axis of the upper guide tube 3. A control rod 22 whose upper end forms a handling head 21 is inserted into the lower guide tube 20 so as to be vertically movable. At the center of the upper end of the handling head 21, an engaging hole 23 is provided which is a tapered hole whose upper end widens downward, and the lower end of the gripper 6 has a bulging outer periphery on the wall of this tapered hole. The control rod 22 is gripped by the gripper via the handling head 21 by being expanded and pressed by the grippers 7.

When the handling head 21 is gripped by the gripper 6 and the gripper rod gripping mechanism 11 and the gripper tube gripper mechanism 12 grip the gripper rod 4 and gripper tube 5, respectively, and the drive motor 8 is operated in the forward or reverse direction, the feed screw mechanism is activated. 9, the electromagnet 10, the gripper rod 4, the gripper tube 5, the acceleration tube 13, and the handling head 21 move upward or downward together, and the control rod 22, which is integrated with the handling head 21, also moves upward or downward through the lower guide tube 20.
The insertion depth into the reactor core (not shown) is changed by moving upward or downward, thereby controlling the output of the reactor.

When making an emergency shutdown of the reactor, the control rods 22
As described below, it descends rapidly and is inserted into the deepest part of the reactor core.

By demagnetizing the electromagnet 10, the gripper rod gripping mechanism 11 opens and the gripper rod 4 is released from its upper end grip and falls. When the gripper rod 4 falls, the expanding mandrel 7 forming its lower end falls off from the position shown in FIG. 1 to the position shown in FIG. 2 relative to the gripper 6, and the gripper 6 contracts in diameter due to its own elasticity. Due to this diameter reduction, the handling head 21 is released from the gripper 6, and the control rod 22 falls. At this time, the acceleration tube 13 is urged downward by the acceleration spring 14 and its lower end surface is pressed against the upper end surface of the handling head 21. Therefore, due to the tension force of the acceleration spring 14, the handling head 21 The falling speed of the control rod 22 is accelerated through the acceleration tube 13, and the control rod 22 rapidly falls deep into the reactor core (not shown), thereby causing an emergency shutdown of the reactor.

In the handling head 21, a control rod 22 integrated therein is guided to the inner periphery of the lower guide tube 20, and an acceleration tube 13 is guided to the outer periphery of the gripper tube 5 inserted into the center of the upper guide tube 3. Since the upper guide tube 3 moves vertically in the upper guide tube 3, the upper guide tube 3 and the lower guide tube 2 are almost on the same vertical line under normal conditions.
Even if the central axis position of 0 shifts horizontally due to an earthquake, etc., the handling head 21,
The inner diameter of the upper guide tube 3 is sufficiently larger than the outer diameter of the handling head 21 and the acceleration tube 13 so that it can freely move up and down in the upper guide tube 3. The outer diameter of the lower end portion is made approximately equal, and the inner diameter of the upper guide tube 3 is made larger than the sum of the two outer diameters.

[Problems with background technology]

In the conventional control rod drive mechanism 1, in the case of an emergency shutdown of the nuclear reactor due to an earthquake or the like, even if there is a slight misalignment between the upper guide tube 3 and the lower guide tube 20, including the inclination, the upper guide tube 3 The inner diameter of the handlebar is larger than the sum of the outer diameters of the acceleration tube 13 and the handling head 21, which have approximately the same outer diameter.
1. Although there is no obstacle to the rapid fall of the control rod 22,
If the misalignment is large, as shown in FIG.
falls between the outer circumference of the upper end and the inner circumference of the upper guide tube 3,
The handling head 21 and therefore the control rod 22 could no longer be dropped rapidly, and there was a risk that emergency shutdown of the reactor would be hindered.

[Purpose of the invention]

This invention was made in order to solve the above-mentioned problems of the conventional control rod drive mechanism, and when an earthquake occurs, the control rods are accelerated downward through a spring-biased acceleration tube to rapidly accelerate the control rods into the reactor core. When making an emergency shutdown of a nuclear reactor by dropping it deeply, even if there is a tilt misalignment between the lower guide tube that guides the control rods and the upper guide tube that indirectly guides the accelerator tubes, the outer periphery of the lower end of the accelerator tubes and the control rods It is an object of the present invention to provide a control rod drive mechanism in which the control rod can rapidly fall without any trouble without contact interference with the upper end outer periphery of a handling head in the horizontal direction.

[Summary of the invention]

This invention improves the accelerator tube in the conventional control rod drive mechanism, so that the sum of the outer diameter of the lower end of the accelerator tube and the outer diameter of the upper end of the handling head at the upper end of the control rod is larger than the inner diameter of the upper guide tube. The above purpose is achieved by forming the lower end surface of the accelerator tube in contact with the upper end surface of the handling head into a convex curved surface capable of relative lateral sliding movement.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG. 3 and FIG. 1.

The control rod drive mechanism according to the present invention has a configuration in which the acceleration tube 13 in the conventional control rod drive mechanism 1 is replaced with a different acceleration tube 113, and the other parts have exactly the same structure as the control rod drive mechanism 1. Only these different parts will be explained, and for the same structural parts, the parts shown in FIG. 3 will be given the same reference numerals as in FIG. and replace it with that.

The shape of the upper part of the acceleration tube 113 is that of the acceleration tube 1.
In exactly the same way as No. 3, the lower part has a tapered sleeve shape with an outer diameter that gradually increases downward, and is thick. Like the acceleration tube 13, the acceleration tube 113 is fitted into the outer periphery of the gripper tube 5 in the upper guide tube 3 so as to be vertically movable, and is biased downward by an acceleration spring 14 fitted into its upper end surface and the outer periphery of the gripper tube 5. The lower end surface of the control rod 22 is pressed against the upper end surface of the upper handling head 21 of the control rod 22. The outer diameter of the acceleration tube 113 is such that the bulge at its lower end is such that even if the acceleration tube 113 is tilted or misaligned to some extent with respect to the upper guide tube 3, the acceleration tube 113 can freely move up and down in the upper guide tube 3. The outer diameter of the lower end of the acceleration tube 113 is larger than the outer diameter of the upper end of the handling head 21, and the sum of the two outer diameters is smaller than the inner diameter of the upper guide tube 3.
Furthermore, the lower end surface of the acceleration tube 113 is centered on the central axis of the acceleration tube 113, which is movable laterally relative to the upper end surface of the handling head 21 that is in contact with it. It is formed into a spherical surface.

In the event of an earthquake, etc., when the control rods 22 are inserted deep into the reactor core via this control rod drive mechanism equipped with the accelerating tube 113 to bring about an emergency shutdown of the reactor, the grip of the handling head 21 by the gripper 6 is released. The handling head 21 and the control rod 22 integrated below it fall, and this falling speed is caused by the acceleration tube 113 which is biased downward by the acceleration spring 14.
is rapidly lowered by the tension force of the acceleration spring 14, thereby increasing the speed. Due to vibrations during earthquakes, etc.
When an incorrect tilt occurs between the upper guide tube 3 and the lower guide tube 20, the acceleration tube 113, which is indirectly guided to the upper guide tube 3 via the gripper tube 5, and the lower guide tube 20, However, when the acceleration tube 113 descends, the acceleration tube 1
Since the sum of the outer diameter of the lower end of the acceleration pipe 113 and the outer diameter of the upper end of the handling head 21 is larger than the inner diameter of the upper guide tube 3, the acceleration pipe 113 is located between the outer circumference of the handling head 21 and the inner circumference of the upper guide tube 3. The lower end of the acceleration tube 113 does not fall down and the outer periphery of the acceleration tube 113 interferes with the outer periphery of the handling head 21, preventing the acceleration tube 113 from interfering with the handling head 21's rapid descent, and the lower end surface of the acceleration tube 113 has a spherical surface to facilitate handling. Since it can move laterally relative to the upper end surface of the head 21, even if the lower end surface of the accelerator tube 113 and the upper end surface of the handling head 21 come into contact with each other in an off-centered manner, the horizontal force generated by this contact will be It is absorbed by the relative lateral movement between the lower end surface of the acceleration tube 113 and the upper end surface of the handling head 21, and the acceleration tube 1
13. Without causing twisting between the outer circumference of the handling head 21 and the inner circumference of the upper guide tube 3, and between the outer circumference of the upper end of the control rod 22 and the inner circumference of the lower guide tube 3,
Therefore, the acceleration tube 113, the handling head 2
1. There is no problem with the rapid descent of the control rod 22.

〔Effect of the invention〕

The control rod drive mechanism according to the present invention includes an upper guide tube supported by the upper lid of the reactor vessel and hanging above the core inside the reactor vessel, and an upper guide tube disposed within the upper guide tube along its central axis. A gripper tube that lifts the control rod by engaging a handling head installed at the upper end of the control rod, which is movable up and down in a lower guide tube fixed vertically in the lower core; A gripper rod that maintains and releases the insertion state of the gripper pipe in engagement with the handling head, and a gripper rod that is fitted onto the outer periphery of the gripper pipe so as to be able to move up and down and is biased downward by a spring so that the lower end surface is pressed against the upper end surface of the handling head. In the event of an earthquake, etc., the handling head is released from the gripper tube of the control rod drive mechanism, and the control rods integrated with the handling head are inserted deep into the core in the lower guide tube. In this control rod drive mechanism, the inner diameter of the upper guide tube within the range in which the accelerator tube moves up and down is equal to the outer diameter of the lower end of the accelerator tube and the outer diameter of the upper end of the handling head. Moreover, since the lower end surface of the accelerator tube is formed into a convex curved surface that can move laterally relative to the upper end surface of the handling head that contacts this lower end surface, the upper guide tube and its Even if there is an inclination misalignment between the middle accelerator tube, the lower guide tube, and the handling head guided to its inner circumference, the accelerator tube will fall between the inner circumference of the upper guide tube and the outer circumference of the handling head, and the acceleration tube and handling head will be This has the effect of eliminating the possibility of obstructing the fall of the head and therefore the control rod, and furthermore, the horizontal force that acts between the lower end surface of the accelerating tube and the upper end surface of the handling head due to the above-mentioned tilt misalignment is reduced by the free relative lateral movement of both. This has the effect of preventing twisting of the acceleration tube against the upper guide tube, twisting of the handling head and the lower guide tube of the upper guide tube, and twisting of the control rod and the lower guide tube. The control rod, which is released from the grip of the rod drive mechanism and falls, is accelerated by an acceleration tube whose lower end surface is pressed against the upper end surface of the control rod handling head with a spring biased downward, and the control rod is accelerated by the acceleration tube whose lower end surface is pressed against the upper end surface of the control rod handling head. This has the effect of ensuring that the reactor rapidly falls deep into the core of the lower guide tube, thereby maintaining the certainty of an emergency shutdown of the reactor.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional control rod drive mechanism, FIG. 2 is an enlarged cross-sectional view of essential parts of the control rod drive mechanism in FIG. 1 in one operating state, and FIG. 3 is a control rod drive according to the present invention. FIG. 3 is an enlarged sectional view of the main part of the mechanism. 3... Upper guide pipe, 4... Gritsparod, 5
...Gripper tube, 13,113...Acceleration tube, 14
... Acceleration spring, 20 ... Lower guide tube, 21 ... Handling head, 22 ... Control rod.

Claims (1)

[Claims] 1. An upper guide tube supported by the upper lid of the reactor vessel and suspended above the core within the reactor vessel; A gripper tube that lifts the control rod by engaging a handling head provided at the upper end of the control rod that is movable up and down in a fixed lower guide tube, and a gripper tube that is inserted in the gripper tube so that it can be moved up and down. A gripper rod that maintains and releasably retains an engaged state with the head is fitted into the upper guide tube on the outer periphery of the gripper tube so as to be able to move up and down, and is biased downward by a spring so that its lower end surface is pressed against the upper end surface of the handling head. In the control rod drive mechanism, the sum of the outer diameter of the lower end of the accelerating tube and the outer diameter of the upper end of the handling head is within the range in which the lower end of the accelerating tube moves up and down. A control rod drive mechanism characterized in that the lower end surface of the accelerator tube is formed into a convex curved surface that is larger than the inner diameter and is capable of sliding laterally relative to the upper end surface of the handling head that abuts the lower end surface.