JPS61194393A - Drive for control rod of nuclear reactor - Google Patents

Abstract

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

Description

TECHNICAL FIELD The present invention relates to a device for driving a shaft-shaped object in its axial direction, and more particularly to a device for driving a control rod of a nuclear reactor.

(Prior Art) Currently, light water reactors are widely used nuclear reactors for power generation, and control rods are used to start, stop, and adjust the output of the light water reactors.

Control rods are inserted into a reactor core mainly made of nuclear fuel from above or below, or are pulled out from above or below to control nuclear reactions within the reactor core.
A control rod drive is used for pulling out.

Furthermore, during the operation of a nuclear reactor, in the event of an emergency such as a loss of external power or the occurrence of a LOCA, it is necessary to completely insert the control rods into the reactor core instantly, and the functions of the control rod drive device are designed to meet this need.

The following structure is often adopted to drive control rods that are inserted into the reactor core from above and pulled out upwards. That is, a large number of circumferential grooves are cut on the outer surface of the drive shaft connected to the control rod. At least one of a pair of latch mechanisms arranged apart from each other along the longitudinal direction of the drive shaft moves in the axial direction by a predetermined stroke, and the latches alternately engage the circumferential grooves to drive the drive shaft. The shaft is moved in its axial direction, eventually driving the control rod up and down.

In an emergency, both of the pair of latch mechanisms will automatically separate from the drive shaft, and the drive shaft will fall with the control rod and be inserted into the reactor core.

Figure 1 is an enlarged view of a part of the drive shaft 0.
There are many circumferential grooves (hereinafter abbreviated as grooves) on the outer surface of 1.
1 is formed over the entire stroke.

A latch support tube 08 is provided on the outside of the guide tube 013 which surrounds the drive shaft 01, and supports the latch mechanism I.

As mentioned above, there are two sets of latch machines PT, and the illustrated one is one of them.

The latch arm 02 supported via the latch pin 05 pivots by three legs at equal circumferential intervals as the plunger 07 rises.

That is, the plunger 07 and the latch arm 02 are linked together by the link pin 04 and the latch link 06, and as the plunger o7 rises, the latch arm 02 pivots counterclockwise. For this purpose, latch arm 02
One pawl 021 of engages with one of the grooves 011.

The spring 019 biases the plunger 07 downward, and the plunger 07 is raised by exciting a coil (not shown).

(Problems to be Solved by the Invention) Nuclear power generation has been put into practical operation in recent years, and since its proportion in the total amount of power generation is small, base load operation has conventionally been carried out. In other words, the output was kept constant, and the control rods were driven less frequently to adjust the output.

However, as is well known, the demand for electric power varies greatly depending on the season or the time of day, and as the proportion of nuclear power generation increases, the need for load following operation becomes stronger. However, if the number of repetitions of engagement between the claw 021 of the latch arm 02 and the groove 011 becomes too large, the amount of wear on both increases, and there is a possibility that smooth driving over the entire life of the nuclear reactor cannot be achieved.

(Means and effects for solving the problems) The present invention has been made in view of the above-mentioned circumstances. That is, the present invention has a drive shaft in which a large number of circumferential grooves are formed adjacent to each other in the axial direction on the outer peripheral surface, and the drive shaft is moved in the axial direction by a latch mechanism to control the control rod connected to the drive shaft. In a drive device, at least two pawls of the latch arm that engage with the circumferential groove of the drive shaft are arranged side by side, and this reduces the friction force and contact force that acts between the groove and the pawl. The aim is to reduce the amount of wear on these parts.

(Example) The present invention will be described below based on illustrated embodiments.

2 and 3, the drive shaft 1, the upper latch arm 2, the lower latch arm 3, and the two claws 2a provided on the latch arm 2.3.

2b% 3a% 3b% Link pin 4, latch pin 5, latch links 6a, 6b, movable latch plungers 7a, 7b, latch support tube 8a.

8b, fixed magnetic pole 9, movable magnetic pole 1o, gripping coil ll
a % 11 b, set screw 12, guide tube 13, upper flange 14, scissor plate 15 a, 15 b,
15 c.

Latch housing 16, fill housing 17.7"/x! J link 18 a % 18 b % 1
8 C% Honey 19a 119 b, 19C1 Raised magnetic pole 2
1, a presser spring 22, a spring presser 23, a latch 24, a screw 25, a raising coil 26, and a drive shaft housing 27 are shown.

A control rod (not shown) is connected to the lower end of the drive shaft 1, and a circumferential groove 101 is formed on the outer peripheral surface.

Note that FIG. 3 shows an enlarged view of the latch arm 2.3 in FIG. 2. Although only one latch arm 2.3 is shown in FIG. 2, three latch arms 2.3 are provided around the drive shaft 1 with an arcuate spacing of 120 degrees. The pawls 2a, 2b or 3a, 3b of the latch arm 2.3 swing around the upper latch arm 2 or the lower latch arm 3 and the latch pin 5.
By engaging the groove 101, the drive shaft 1 is held in a predetermined position. The latch arm 2.3 swings, the link pin 4, the latch pin 5, the latch link (3a, 5b,
A latching mechanism t, aq-t, formed by movable latching plungers 7a, 7b and latch arms 2a, 2b,
b, the latch support tubes 8a, Bb, the fixed magnetic pole 9, the movable magnetic pole 10, and the coils Ila, llb.

That is, when one of the gripping coils lla, llb, for example 11a, is energized, the movable latching plunger 7
a, the movable magnetic pole 10 forms an electromagnetic circuit, and the plunger 7a moves upward against the spring 19a. This results in
The latch arm 2 pivots so that the pawls 2a, 2b approach the drive shaft 1, and the pawls 2a, 2b move toward the groove 10 as shown in FIG.
1. When the current is cut off, the elastic restoring force of the spring 19a pushes down the plunger 7a, causing the latch arm 2 to pivot in the opposite direction and the claws 2a, 2b to separate. Each magnetic pole 9.10 is connected to the guide tube 13'' by means of a set screw 12!
! It is fixed to the bamboo latch support tube 8a.

The swinging operation of the latch arm 3 is also performed in the same procedure as the latch arm 2. Note that scissor plates 15a and 15b15C are attached to each magnetic pole to protect the joint surfaces. Each coil 113111b, 26 is connected to a coil housing 17 fixed to the outer periphery of the latch housing 16.
Near both ends of each coil lla, llb, 26 are seven lux rings 18 for stabilizing the magnetic field.
A to 18C are installed. Other components include a raising coil 26, a raising magnetic pole 21, and a magnetic pole fixing screw 1 for moving the upper latch mechanism La in the axial direction.
2. There are a scissor plate 15c1, a spring 19C, and a flux ring 18d, and a drive shaft housing 27 is coupled to the upper part of the latch housing 16. Also, the lower latch mechanism 1. b Tech, coil 11 b K energized,
After the latch arm 3 pivots in the engagement direction, a presser spring 22 and a spring presser 23 are provided, which are adjusted to raise the latch arm 3 by about 1 to 2 fi, and the latch stop 24
is fixed to the lower end of the guide tube 13 with a screw 25.

Next, the movement of the drive shaft 1 will be explained. Normally, the drive shaft 1 is held only by the lower latch arm 3. Second
The figure shows the situation. To raise the drive shaft 1, the upper latch arm 2 is first pivoted in the engagement direction.

At this time, the lower latch arm 3 causes the drive shaft 1 to
■Since it is in a lifted state, the claws 2a, 2b of the upper latch arm 2,! : Does not engage with the groove 101 of the IIE moving shaft 1. The lower latch arm 3 is then pivoted in the anti-engagement direction. Then, the drive shaft 1 is lowered by about 1 to 2+III+, and the load of the drive shaft system is applied to the upper latch arm 2 (this action is hereinafter referred to as load movement). When the raising coil 26 is energized here, the drive shaft 1 is raised by about 16 fi (the gap between the raising magnetic pole 21 and the movable magnetic pole 10). Thereafter, the lower latch arm 3 is pivoted in the engagement direction to transfer the load to the lower latch arm 3, and then the dome latch arm 2
pivots in the anti-engagement direction, interrupting the current to the raising coil and completing the raising motion of the -cycle. This kind of behavior,
Alternatively, the reverse operation can be repeated to raise or lower the drive shaft 1, or in case of an emergency, the current to all coils can be cut off simultaneously and the latch arm 2.3 can be pivoted in the anti-engagement direction. Then, the drive shaft 1 is dropped. The reason for shifting the load is to prevent sliding contact between the claws 2a, 2b, 3a, 3b and the shaft 1 when the latch arm 2.3 swings. More specifically, latch arm 2.
3 is made of stainless steel, and has main claws 2a, 3a and sub-mold 2b.
, 3b are made of a cobalt-based alloy (for example, Stellite Kai 6, Stellite Yo 12, etc.). Either chromium carbide (Cr5C2)'i is adhered to this surface by explosive spraying or plasma spraying, or titanium nitride (TiN) is applied to the surface of the constituent material by ion-blating (by ionizing and accelerating metal particles, metal matrix is applied). It may also be brought into close contact by a surface treatment method in which the material is pierced into the surface of the material to bring it into close contact.

In this way, the wear of the main pawls 2a, 3a and the sub-dies 2b, 3b of the latch arm 2.3 can be further prolonged. Further, in the case of Cr3 C2 thermal spraying, it has been confirmed through tests that the wear of the groove 101 of the drive shaft 1 is reduced as well as the claw, and the wear life of both is extended as much as possible.

This proposal has the feature that it can be applied regardless of the material and shape of the latch arm pawl, and when using a cobalt-based alloy for the latch arm pawl part, the present proposal is suitable for cobalt-based alloys at the initial stage of operation.
It has the characteristics of preventing CO59) from being mixed into the primary coolant due to wear and elution, and suppressing the generation of 0060 in the secondary coolant.

In the embodiment described above, the latch arm 2.3 has two pawls.
Although the number of layers (2a, 2b, 3a, 3b) is formed, the number of layers may be further increased, and the grooves 101 in which the claws engage do not always have to be adjacent to each other.

Furthermore, in order to extend the life of the claws of the latch arm, as shown in FIG. It is. In this case, the width of the groove 101' of the drive shaft 1' is correspondingly wide, and the hatched portions in FIG.
This is the part that is wider than b.

If it is done as described above, it will be slightly affected by C and manufacturing errors, but once it is adjusted, the claws 2as2bs3a, 3b will come into equal contact with the slopes of the two grooves 101, hold the drive shaft 1, and move up or down. .

(Effects of the Invention) As described above, in the present invention, at least two pawls formed on the latch arm simultaneously engage with the circumferential groove of the drive shaft, thereby reducing the force acting on each pawl and the resulting wear. is greatly reduced and its lifespan is increased.

[Brief explanation of drawings]

Fig. 1 is a partial view of the conventional one, Fig. 2 is a partially cutaway plan view showing the embodiment of the present invention, Fig. 3 is a partially enlarged sectional view of Fig. 2, and Fig. 4 is a different one. FIG. 2 is a partial diagram of an embodiment. 1... Drive shaft, 2.3... Latch arm, 2as2
b, 3a, 3 b...claw, 101=circumferential groove,
La, lb...Latch mechanism

Claims (1)

[Claims] The drive shaft has a drive shaft in which a large number of circumferential grooves are formed adjacent to each other in the axial direction on the outer circumferential surface, and a latch mechanism having a latch arm that selectively engages the circumferential grooves allows the drive shaft to be moved through the drive shaft. In a device that drives a nuclear reactor control rod, at least two claws are formed protruding along the axial direction of the drive shaft on the surface of the latch arm facing the outer peripheral surface of the drive shaft, and the claws simultaneously A control rod drive device for a nuclear reactor, characterized in that each rod engages with the circumferential groove.