JPH0789157B2 - Control rod drive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control rod drive device, and particularly to a control rod drive device suitable for application to a boiling water reactor.

[Prior Art] In a boiling water reactor, a control rod drive device is installed in a control rod drive device housing provided in a lower portion of a reactor pressure vessel.

The control rod drive device has an annular space formed between a main cylinder and a piston tube provided in the main cylinder,
A drive piston is provided that moves axially within the annular space. An indexing tube provided on the drive piston is connected at its upper end to the control rod.

Such a control rod driving device is disclosed in Japanese Patent Laid-Open No. 219492/1983. The control rod drive device disclosed in this publication has a groove inside the main cylinder at a portion where the annular seal of the drive piston is located at the end of the control rod emergency insertion.

[Problems to be solved by the invention]

The control rod drive receives the high pressure driving water pressure from the accumulator until the quick opening valve in the water pressure control unit is artificially closed even after the control rod is decelerated / braked by the buffer mechanism during the emergency insertion of the control rod. In order to continue to withstand the high stresses that occur, a large amount of strength is needed.

Reducing stress in a control rod drive device is a problem for improving reliability. As a solution to this problem, for example, the above-mentioned Japanese Patent Laid-Open No.
There is a control rod drive device shown in Japanese Patent Publication No. 219492. this is,
Unnecessary high-pressure drive water is released by the groove provided inside the main cylinder.

However, in this technique, there was much leakage of driving water applied to the drive piston at the beginning of the normal drive withdrawal operation after the control rod emergency insertion operation was completed, and no consideration was given to the influence on the withdrawal operation.

An object of the present invention is to provide a control rod drive device capable of reducing internal stress generated during a control rod emergency insertion operation without affecting normal drive operation.

[Means for solving problems]

The above-mentioned object is to provide an external cylinder installed in a housing attached to a reactor vessel and a hollow internal cylinder installed in this external cylinder with a clearance between the cylinder and the internal cylinder. This can be achieved by providing an opening / closing means that allows the discharge of the fluid to the outside and prevents the fluid from flowing into the gap from the outside.

[Action]

When the opening / closing means is opened, the high-pressure drive fluid, which is the drive source of the drive piston, can be released to the outside from the gap formed between the outer cylinder and the inner cylinder, thereby reducing the pressure in the gap. it can.

〔Example〕

A control rod drive apparatus which is a preferred embodiment of the present invention used in a boiling water reactor will be described with reference to FIGS.

The control rod drive device of the present embodiment supplies drive water to the control rod drive device main body 3 and the control rod drive device main body 3 installed in the control rod drive mechanism housing 2 provided in the lower portion of the reactor pressure vessel 1. The pump 4 and the hydraulic control unit 5 having the functions of controlling the drive water supplied from the pump 4 and having the function of providing the high-pressure drive water to be supplied to the control rod drive device main body 3 during the control rod emergency insertion operation. The control rod drive device main body 3 is
The lower flange portion 7 of the main cylinder 6 (which is an external cylinder) is attached to the control rod drive mechanism housing 2 by being connected to the flange portion 2A of the control rod drive mechanism housing 2 while maintaining liquid tightness. A fixed piston 8 is attached to a lower portion of the main cylinder 6, and a piston tube 9 extending above the fixed piston 8 in the main cylinder 6 forms an internal cylinder. A vertically movable drive piston 10 is housed in an annular gap formed between the main cylinder 6 and the piston tube 9. An annular seal material is provided on the inner and outer peripheral surfaces of the drive piston 10 at the portions in contact with the piston tube 9 and the main cylinder 6, respectively. Drive piston 10
The index tube 13 extending upward is connected to a control rod 15 via a coupling 14 at the upper end of the index tube 13. Above the piston tube 9 is a buffer
16 is provided, and a fixed piston 17 is fixed to the upper end of the fixed piston 17 by a nut 18. The outer circumference of the fixed piston 17 is in contact with the inner surface of the index tube 13, an annular seal member 19 is provided between the fixed piston 17 and the index tube 13, and the inside of the fixed piston 17 is as shown in FIG. It has a cylindrical shape, and a buffer piston 20 that is vertically movable is provided on the outer periphery of the buffer shaft 16. The buffer piston 20 moves up and down in the fixed piston 17. The buffer piston 20 is limited in the vertical movement range by the lower end 17A of the fixed piston 17 and the shoulder portion 16A of the buffer shaft 16. The buffer piston 20 is urged downward by a compression spring 21 installed in the outer surface of the buffer shaft 16, the inner surface of the fixed piston 17, and the space surrounded by the buffer piston 20, and is pressed against the shoulder portion 16A of the buffer shaft 16. ing. The buffer shaft 16 has a plurality of orifice holes 22 provided in the horizontal direction. Each orifice hole 22 is connected to a communication hole 23 provided in the center of the buffer shaft 16 and extending in the longitudinal direction. Each orifice hole 22 is sequentially closed from below by the rise of the buffer piston 20. The buffer mechanism 16, the fixed piston 17, the buffer piston 20, and the compression spring 21 constitute a buffer mechanism. Space 24 formed by the main cylinder 6, fixed piston 8, picaton tube 9, and drive piston 10.
Is a first flange provided on the lower flange portion 7 of the main cylinder 6.
It communicates with the flow path 25 and the insertion port 26. A deep hole channel 27 is provided in the piston tube 9 in the axial direction, and a deep hole channel 27 is provided in the lower flange portion 7 of the main cylinder 6 via a channel 28 provided in the horizontal direction of the fixed piston 8. The two flow paths 29 and the extraction port 30 are connected. Further, the deep hole flow path 27 is formed by being surrounded by the piston tube 9, the drive piston 10, the index tube 13, and the fixed piston 17 by a plurality of communication holes 31 provided in the buffer shaft 16 in the horizontal direction. Space 32 will be contacted.

The opening / closing mechanism for opening / closing the flow path for releasing high-pressure drive water at the end and the end of the control rod emergency insertion operation is a piston tube 9
At the upper end of the control rod, when the control rod is inserted suddenly, the drive piston 10 comes into contact with the buffer piston 20 of the buffer mechanism and slightly below the lower surface of the drive piston 10 immediately before the deceleration of the control rod 15 is started. Has a flow passage 47 that is horizontally provided on the piston tube 9 and communicates with the deep hole flow passage 27, and is an elastic opening / closing plate 49 provided at an opening portion on the deep hole flow passage 27 side.
have. Opening and closing of the flow path 47 is done with this elastic plate.
49, the reaction force of the opening / closing plate 49 does not operate with the pressure of the drive water supplied during normal drive, but operates with the pressure of the high-pressure drive water supplied to the control rod drive mechanism during emergency insertion of the control rod. Set. The opening / closing plate 49 is restricted in angle during its operation by the restriction plate 48, and damage is prevented.

The control rod drive device main body 3 has roughly two types of required drive functions.

The first function is to insert or pull out control rods stepwise by a pitch between fuel assemblies in the reactor core (hereinafter, this function is referred to as normal drive operation). This is a function required when starting up and shutting down the reactor, compensating for the deterioration of the reactivity of the fuel during rated power operation, adjusting the power distribution in the core, and the like.

The second function is a function of rapidly inserting all the control rods simultaneously between the fuel assemblies of the reactor core (hereinafter, this function is referred to as a control rod emergency insertion operation). This is a function required when an emergency shutdown of a nuclear reactor occurs due to some abnormality,
Exceptionally high reliability is required from the standpoint of reactor safety.

Hereinafter, the operations of the pump 4 and the water pressure control unit 5 will be described for the normal drive and control rod emergency insertion operations related to the present embodiment.

There are two normal drive operations, an insertion operation and a withdrawal operation.
For the insertion operation, the drive water pressurized by the pump 4 is piped through the pipe 33 and the switching valve 34 in the water pressure control unit 5.
And further through the insertion port 26 and the first flow path 25 into the space 24 below the drive piston 10. On the other hand, the water in the space 32 above the drive piston 10 is guided from the communication hole 31 to the deep hole flow passage 27, the flow passage 28, the second flow passage 29, and the extraction port 30, and further through the pipe 36. It reaches the inside of the pipe 37 in the water pressure control unit 5, and is discharged from the switching valve 38 to the low pressure side from the pipe 39 connected to another water pressure control unit (not shown). As a result, a differential pressure is generated between the space 24 below the drive piston 10 and the space 32 above it, and an upward force is applied to the drive piston 10. Therefore, the drive piston
10 is moved upward, and an index tube 13 extending above the drive piston 10 and a control rod 15 connected by a coupling 14 are inserted between fuel assemblies of a reactor core (not shown). Then, by a known means (not shown), the control rod
15 is held in the selected position.

The pulling-out operation is performed after the indexing tube 13 is slightly lifted by the above-mentioned inserting operation in order to release the position holding by the above-mentioned known means not shown. That is, the driving water pressurized by the pump 4 is guided to the pipes 37 and 36 by the pipe 33 through the switching valve 40 in the water pressure control unit 5,
It is supplied from the drawing port 30 through the second flow path 29, the flow path 28, and the deep hole flow path 27 to the space 32 above the drive piston 10 from the communication hole 31. The water in the space 24 below the drive piston 10
Through the flow path 25, the insertion port 26 and the pipe 35, the changeover valve 41 in the water pressure control unit 5 discharges it to the low pressure side from the pipe 39 connected to another water pressure control unit (not shown). As a result, the space 24 below the drive piston 10 and the space above
A differential pressure is generated between the drive piston 10 and the drive shaft 32, and a downward force is applied to the drive piston 10. Accordingly, the drive piston moves downward, and the control rod 15 connected by the index tube 13 and the coupling 14 is pulled out from the fuel assembly in the reactor core (not shown).

In the normal driving operation, if the amount of leakage of driving water that applies pressure to the driving piston 10 increases, the operation of the driving piston 10 is hindered.

The emergency insertion of the control rod is performed by the quick opening valve 42,4 in the water pressure control unit 5.
It is done by opening 3 at the same time. As a result, the high-pressure drive water stored in the accumulator 44 is supplied to the space 24 below the drive piston 10 through the rapid opening valve 42 through the same route as the insertion operation of the normal drive operation. The water in the space 32 above the drive piston 10 passes through the same route as in the insertion operation of the normal drive operation, and the rapid opening valve in the water pressure control unit.
It is discharged from the pipe 45 to the atmosphere side via 43. This creates a differential pressure between the spaces 24 and 32, which causes the drive piston 10
An upward force is applied to the drive piston 10, the drive piston 10 rapidly moves upward, and the control rod 15 is rapidly inserted between the fuel assemblies in the reactor core.

At this time, the above-mentioned opening / closing mechanism operates. That is, after the lower surface of the drive piston 10 passes through the position of the flow passage 47 provided in the piston tube 9 at the end of the control rod emergency insertion operation (when the lower surface of the drive piston 10 is located above the flow passage 47).
Alternatively, the pressure of the high-pressure drive water that drives the drive piston 10 while passing is applied to the opening / closing plate 49, and the opening / closing plate 49 is pushed toward the limiting plate 48 side by the pressure to open the flow path 47. For this reason,
The deep hole flow passage 27 and the space 24 are connected to each other, and the high-pressure drive water that has driven the drive piston 10 flows from the space 24 to the deep hole flow passage 27 through the flow passage 47, which is the same as the control rod emergency insertion operation. Is released to the atmosphere side.

The deceleration / braking of the drive piston 10 having an upward inertial force is performed by a buffer mechanism including a buffer shaft 16, a fixed piston 17, a buffer piston 20, and a compression spring 21 provided at the upper end of the piston tube 9 as described later. Will be done at.
That is, at the end of the control rod emergency insertion operation, the drive piston 10
Collides with the lower end of the buffer piston 20. The buffer piston 20 sequentially closes the orifice hole 22 provided in the buffer shaft 16 from the bottom as the drive piston 10 rises.
Therefore, the water in the space 46 is pressurized by the rise of the buffer piston 20 and flows from the orifice hole 22 into the communication hole 23. The drive piston 10 is decelerated by the fluid damper effect and the liquid damper effect of the pressure increase in the space 46 due to the decrease of the orifice hole 22 at this time, and further, via the buffer piston 20, the drive piston 10 contacts the lower end 17A of the upper fixed piston 17 of the piston tube 9. Contact and stop. Drive piston for emergency insertion of control rod
The pressure of the high-pressure drive water that is the drive source of 10 is automatically lowered by the opening / closing mechanism having the opening / closing plate 49 described above, and the control rod 15
When the control rod 15 falls due to its own weight overcoming the above-mentioned pressure, the control rod 15 is held at the maximum insertion position by a known means (not shown), and the control rod emergency insertion operation ends. Due to the pressure drop, the opening / closing plate 49 closes the return channel 47 to a fixed position and closes the deep hole channel 27.
And disconnect from space 24 and space 32.

By the above operation, the high-pressure drive water during the control rod emergency insertion operation can be discharged to the atmosphere side at the end of the control rod emergency insertion operation, and the stress inside the control rod drive device is greatly reduced by the decrease in the pressure. Reduce to. Further, by suppressing the change in the flow velocity of the high-pressure drive water, it is not necessary to absorb the inertial force of the high-pressure drive water inside the control rod drive device, and the generation of stress can be greatly reduced. Further, since the high-pressure drive water at the time of the control rod emergency insertion operation is discharged to the atmosphere side through the flow path 47, the deep hole flow path 27, and the pipe 45, the pressure of the high-pressure drive water is reduced, so that the opening / closing plate 49 is connected to the flow path 47. Close up. By blocking the communication between the deep hole flow path 27 and the space 24 in this way, the leakage of the driving water during the pulling out operation and the normal driving operation after the control rod emergency insertion operation is prevented, and the pressure of the driving water is reduced. It is possible to maintain the same normal driving characteristics as in the conventional case.

According to this embodiment, the following effects can be obtained.

(1) At the end of the control rod emergency insertion operation, the pressure of the high-pressure drive water automatically decreases, and the generation of stress in the control rod drive device due to the pressure of the drive water is reduced.

(2) The change in the flow velocity of the high-pressure drive water is suppressed, and the generation of stress due to the inertial force of the high-pressure drive water is reduced.

(3) Good normal drive characteristics can be obtained by maintaining the pressure of the drive water in normal drive.

(4) By reducing the stress generation, the strength margin is increased and the reliability is improved.

(5) By increasing the strength margin, the pressure of the high-pressure drive water for the control rod emergency insertion can be made higher than before, and the control rod emergency insertion can be shortened.

FIG. 4 shows another embodiment of the present invention. As shown in FIG. 4, a flow path 47 for releasing high-pressure drive water at the time of a control rod emergency insertion operation is provided so as to penetrate through the main cylinder 6, and an elastic opening / closing plate 49 and a limiting plate 48 are provided outside thereof. Is also good. In this case, the high-pressure drive water during the control rod emergency insertion operation passes between the control rod drive device housing 2 and the main cylinder 6, and the reactor pressure vessel 1
The operation is the same as that of the embodiment shown in FIG. 1 except that it is discharged to the side.

〔The invention's effect〕

According to the present invention, the stress generated in the control rod drive device at the time of emergency insertion of the control rod can be remarkably reduced, and the normal drive operation is not adversely affected.

[Brief description of drawings]

FIG. 1 is a detailed longitudinal sectional view of the vicinity of an upper end portion of a piston tube of a control rod drive device shown in FIG. 2 which is a preferred embodiment of the present invention, and FIG. 2 is a control rod of a preferred embodiment of the present invention. FIG. 3 is an overall structural view of the drive unit, FIG. 3 is a detailed vertical sectional view near the fixed piston in FIG. 2, and FIG. 4 is a vertical sectional view of another embodiment of the present invention. 4 ... Pump, 5 ... Water pressure control unit, 6 ... Main cylinder, 9 ... Piston tube, 10 ... Driving piston,
13 …… Indicative tube, 24,32 …… Space, 27 ……
Deep hole channel, 47 ... Channel, 49 ... Open / close plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiki Sukegawa 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (56) References JP-A-61-139793 (JP, A) ) JP-A-57-157185 (JP, A) JP-A-60-64298 (JP, A) JP-A-58-219492 (JP, A) Practical application JP-A-62-62290 (JP, U)

Claims (1)

[Claims] 1. An external cylinder installed in a housing attached to a reactor vessel, an internal cylinder installed in the external cylinder and having a space inside, and between the external cylinder and the internal cylinder. A drive piston that moves in the up-down direction in the annular space formed in the above, and allows the discharge of fluid from the annular space provided in any of the outer cylinder and the inner cylinder to the outside of the annular space. Moreover, a control rod drive device comprising an opening / closing means for preventing the inflow of fluid from the outside into the annular space.