JPS60216295A - Driving mechanism of control rod - 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 a control rod drive mechanism that is installed in a fast breeder reactor (hereinafter referred to as a nuclear reactor) and changes the insertion depth of a control rod into a 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.

A cylindrical upper guide tube 3 having the same outer diameter as the casing 2 is concentrically connected to the lower end of the cylindrical casing 2 with an upper lid of the control rod drive mechanism 1 . The casing 2 and the upper guide tube 3 are supported by the upper lid part of the reactor vessel (not shown), and the upper guide tube 3 is suspended at a predetermined position above the reactor core (not shown) inside the reactor vessel. A long bar-shaped gripper rod 4 is inserted into the center of the upper guide tube 3 so as to be movable up and down, and a long gripper tube 5 is fitted into the outer periphery of the gripper rod 4 inside the upper guide tube 3 so as to be movable up and down. .

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. The gripper 6 is expanded when the expanding mandrel 7 is pushed into it from below, and when the expanding mandrel 7 is not pushed in, it is elastically restored to a small diameter. Inside the casing 2 are a drive motor 8, a feed screw mechanism 9 driven by the drive motor 8, an electromagnet 10, a gripper rod gripping mechanism 11 that is operated by the electromagnet 10 and releasably grips the upper end of the gripper rod 4, and a gripper tube. 5 is provided with a gripper tube gripping mechanism 12 that grips and releases the upper end of the tube. An acceleration tube 13 is fitted into the upper guide tube 3 and on the outer periphery of the gripper tube 5 so as to be vertically movable, and the upper end surface of the acceleration tube 13 and the inner peripheral protruding ring of the upper guide tube 3 form a handling head, which will be described later, at its lower end surface. It is pressed against the upper end surface of 21. casing 2,
The control rod drive mechanism 1 is connected to the upper guide tube 3 to the acceleration tube 13 and the acceleration spring 14, respectively.

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. Inside the lower guide tube 20 is a handling head 21 whose upper end is integrated.
A control rod 22 is inserted so as to be vertically movable. At the center of the upper end of the handling rod 21, a retaining hole 23 is provided which is a tapered hole with the upper end facing downward, and the lower end of the gripper 6 has a bulging outer periphery at the lower end of the gripper rod 4. The control rod 22 is gripped by the gripper 6 via the handling head 21 by being expanded and pressed by the mandrel 7 .

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

When making an emergency shutdown of the nuclear reactor, the control rods 22 are rapidly lowered and inserted deepest into the reactor core as described below.

'By demagnetizing the electromagnet IO, the gripper rod gripping mechanism 11 is opened and the gripper rod 4 is released from its upper end grip and falls. If the gripper rod 4 falls,
The expanding mandrel 7 forming the lower end is pulled out from the position shown in FIG. 1 with respect to the gripper 6 and falls to the position shown in FIG.
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, so that the falling speed of the handling head 21 and therefore the control rod 22 integrated therewith is reduced by the extension force of the acceleration spring 14. is accelerated through the acceleration tube 13, and the control rods 22 rapidly fall 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 therewith 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. Because the upper guide tube 3 moves vertically, the upper guide tube 3 is on the same vertical line under normal conditions.
Even if the central axis position of the lower guide tube 20 shifts horizontally due to an earthquake, the handling head 21 and the acceleration tube 13
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 inside the upper guide tube 3. The outer diameter of the lower end portion 13 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, even if there is a slight misalignment between the upper guide tube 3 and the lower guide tube 20, including a tilt of 1 degree, the upper guide tube The inner diameter of acceleration tube 3 is approximately equal to the outer diameter of acceleration tube 1.
3. Since it is larger than the sum of the outer diameters of the handling head 21, there is no problem with the acceleration effect by the acceleration tube 13 and the rapid fall of the handling head 21 and control rod 22. However, if the misalignment is large, As shown in Figure 2,
There is a risk that the lower end of the accelerating tube 13 will fall between the outer periphery of the upper end of the handling head 21 and the inner periphery of the upper guide tube 3, making it impossible for the handling head 21 and therefore the control rods 22 to fall quickly, and preventing an emergency shutdown of the reactor. Ta.

[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 in the horizontal direction with the outer periphery of the upper end of a handling head.

[Summary of the invention]

This invention improves the accelerating tube in the conventional control rod drive mechanism, so that 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 at the upper end of the control rod is larger than the inner diameter of the upper guide tube. The above object is achieved by forming the lower end surface of the acceleration tube in contact with the upper end surface of the handling head into a convex curved surface that is relatively movable laterally.

[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 replaces the acceleration tube 13 in the conventional control rod drive mechanism 1fs1 with an acceleration tube 11 different from that in the conventional control rod drive mechanism 1fs1.
3 and the other parts have exactly the same structure as the control rod drive mechanism 1, so only this different part ζ will be explained, and the same structural parts will be referred to as the parts shown in FIG. 3. The same reference numerals as in FIG. 1 are used, and the explanation given above for FIG. 1 will be used instead of the same reference numerals as in FIG.

The shape of the upper part of the acceleration tube 113 is exactly the same as that of the acceleration pipe 13, and the lower part thereof has a tapered sleeve shape with an outer diameter gradually increasing 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 rod 21 is pressed into contact with the upper end surface of the rod 21 to the upper handling of the control rod 22. The outer diameter of the acceleration tube 113 is set to such an extent that the acceleration tube 113 can freely move up and down in the upper guide tube 3 even if the acceleration tube 113 is tilted or misaligned to some extent with respect to the upper guide tube 3, including the bulged portion at its lower end. 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 outer diameters of the two is smaller than the inner diameter of the upper guide tube 3. Further, the lower end surface of the acceleration tube 113 is formed into a spherical surface having a center on the central axis of the acceleration tube 113, which is movable laterally relative to the upper end surface of the handling head 21 in contact with the lower end surface of the acceleration tube 113. ing.

When an earthquake occurs and the control rods 22 are inserted deep into the reactor core via this control rod drive mechanism equipped with the accelerator tube 113 to bring about an emergency shutdown of the reactor, the grip on the handling head 21 by the gripper 6 is released. , the handling head 21, and the control rod 22 integrated below these fall, and this falling speed is caused by the rapid descent of the acceleration tube 113, which is urged downward by the acceleration spring 14, due to the tension of the acceleration spring 14. The speed will be increased. When an incorrect tilt occurs between the upper guide tube 3 and the lower guide tube 20 due to vibrations during an earthquake, etc., the acceleration tube 113, which is indirectly guided to the upper guide tube 3 via the gripper tube 5, and the lower Although a misaligned tilt occurs between the control rod 22 guided by the guide tube 20 and the integrated handling head 21, when the acceleration tube 113 descends, the lower end outer diameter of the acceleration tube 113 and the handling head 21
Since the sum of the outer diameter of the upper end is larger than the inner diameter of the upper guide tube 3, the lower end of the acceleration tube 113 falls between the outer circumference of the handling head 21 and the inner circumference of the upper guide tube 3. There is no interference between the outer periphery of the handling head 21 and the rapid descent of the rad 21 into the handling of the acceleration tube 113, and the lower end surface of the acceleration tube 113 is spherical and relative to the upper end surface of the handling head 21. Since the acceleration tube 113 is movable laterally, even if the lower end surface of the acceleration tube 113 and the upper end surface of the handling head 21 come into contact with each other in a tilted manner, the horizontal force generated by this contact will not be applied to the acceleration tube 113.
This is absorbed by the relative lateral movement between the lower end surface and the upper end surface of the handling head 21, causing distortion between the outer periphery of the acceleration tube 113 and the handling head 21 and the inner periphery of the upper guide tube 3, and the control rod 2.
2 and the inner part of the lower guide tube 3, and therefore, there is no problem in rapidly lowering the acceleration tube 113, handling head 21, and control rod 22.

〔Effect of the invention〕

The control rod drive mechanism according to the present invention includes a handling rod provided at the upper end of the control rod, which is supported by the upper lid of the reactor vessel and is vertically movable within a lower guide tube fixed vertically above the core in the reactor vessel. A gripper tube that engages with the head and lifts the control rod, a gripper rod that is inserted into the gripper tube so as to be able to move up and down to maintain and release the gripper tube from the handling head; The control rod drive mechanism is equipped with an acceleration tube that is movably fitted and biased downward by a spring, and whose 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 When the grip is released and the control rod integrated with the handling head is inserted deep into the core into the lower guide tube for an emergency shutdown of the reactor, in this control rod drive mechanism, the acceleration tube moves up and down. The inner diameter of the upper guide tube of the range is smaller than 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, and the lower end surface of the accelerating tube is relative to the upper end surface of the handling head, which dissipates into this lower end surface. It is formed into a convex curved surface that can be moved laterally, so even if vibrations caused by an earthquake cause an inclination misalignment between the upper guide tube, the acceleration tube therein, the lower guide tube, and the handling head guided by the inner periphery. , there is an effect that there is no possibility that the acceleration tube falls between the inner circumference of the upper guide tube and the outer circumference of the handling head and obstructs the fall of the acceleration tube, the handling head, and therefore the control rod;
Furthermore, the horizontal force that acts between the lower end surface of the accelerator tube and the upper end surface of the handling head due to the above-mentioned tilt misalignment is absorbed by the free relative lateral movement of the two. This has the effect of preventing twisting between the control rod and the lower guide tube, and therefore, the control rod that is released from the control rod drive mechanism and falls is spring-biased downward. The control rods are accelerated by the accelerator tube whose lower end surface is pressed against the upper end surface of the control rod handling head, and regardless of the above-mentioned inclination misalignment, the rods fall reliably and rapidly deep into the reactor core within the lower guide tube, which causes an emergency reactor shutdown. This has the effect of maintaining certainty.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional control rod drive mechanism, and Figure 2 is a
FIG. 1 is an enlarged sectional view of the main part of the control rod drive mechanism in the operating state □, and FIG. 3 is an enlarged sectional view of the main part of the control rod drive mechanism according to the present invention. 3... Upper guide tube, 4... Gripper rod, 5...
・Gripper tube, 13,113...Acceleration tube, 14...
Acceleration spring, 20... Lower guide tube, 21... No. 1 handling head, 22... Control rod. (7317) Agent Patent attorney Kensuke Norichika (and 1 other person) Figure 1

Claims (1)

[Claims] An upper guide tube that is supported by the upper lid of the reactor vessel and hangs down above the core in 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 the fixed lower guide tube; A gripper and a collar rod that hold and release the handling head in a fixed state are vertically movably fitted into the outer periphery of the gripper tube within the upper guide tube and are biased downward by a spring so that the lower end surface thereof is attached to the upper end surface of the handling head. In the control rod drive mechanism, the outer diameter of the lower end of the accelerating tube and the outer diameter of the upper end of the handling head is the upper part of 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 acceleration tube is formed into a convex curved surface that is larger than the inner diameter of the guide tube and is movable laterally relative to the upper end surface of the handling head that is still in contact with the lower end surface.