JPH06230165A - Anti-drop unit for drive shaft - Google Patents

Abstract

PURPOSE:To allow holding of a control rod, not partaking in emergency stop of nuclear reactor, at an arbitrary position. CONSTITUTION:The anti-drop unit for drive shaft comprises a hold latch 57 for securing a drive shaft 1 in the axial direction by engaging in a groove 1a of the drive shaft 1 while being urged by a spring 56, and a mechanism for releasing the drive shaft 1 by exciting a release coil 53 and moving a hold plunger 55 while resisting against the spring 56. The drive shaft 1 is secured by the hold latch 57 under power interrupted state and the drive shaft 1 is prevented from falling without supplying any power thus allowing a control rod, not partaking in the emergency stop of nuclear reactor, at an arbitrary position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive shaft drop prevention device for holding a long member, for example, a control rod used in a nuclear reactor, and inserting or withdrawing the control rod into or from a reactor core.

[0002]

2. Description of the Related Art In order to control the combustion output of a fuel assembly inside a reactor core, control rods are inserted into and removed from the reactor core. The control rods are driven to be inserted and withdrawn by a control rod driving device installed on the upper lid of the reactor vessel.

The control rod drive device has a drive shaft which holds a fuel rod at one end and vertically drives the fuel rod, and the drive shaft is driven by, for example, a magnetic jack type drive device. The magnetic jack type drive device vertically moves the drive shaft up and down by exciting an armature having a latch that meshes with the drive shaft with an external coil.

On the other hand, when the reactor is to be brought to an emergency stop due to some cause, for example, loss of power, it is necessary to insert control rods into the reactor core to safely stop the reactor. For this reason, in the magnetic jack type drive device, the drive shaft is held and driven when energized, and when the power source is lost, the drive shaft is released from holding and the control rod is dropped by its own weight, and the control rod is inserted into the reactor core. To safely shut down the reactor.

[0005]

The conventional control rod drive device has a function of dropping the control rods into the reactor core to shut down the reactor safely when power is lost. Control rods that were not involved in the emergency shutdown were also inserted in the core.

As an example of the control rod that is not involved in the emergency stop of the reactor, a control rod (moderator adjustment control rod: Water Di) for changing the internal volume of the moderator (light water in a light water reactor: H ₂ O) is used.
splacer Rod: WDR). This WDR is located at two positions: the full insertion position where it is fully inserted into the core to eliminate the specified light water in the core, and the full extraction position where it is completely withdrawn from the core to allow the existence of light water in the core. Selectively retained. Although this WDR is provided with a fall prevention mechanism at all extraction positions, it does not have a fall prevention function during insertion and extraction.

[0007]

SUMMARY OF THE INVENTION The structure of the present invention for solving the above-mentioned problems is, in a drive device provided with a drive shaft for holding an elongated member at one end and vertically driving the elongated member, From a stopper that locks the drive shaft in the axial direction by locking it to the drive shaft by an urging force, and a release mechanism that releases the locking of the stopper to the drive shaft against the urging force of the elastic member when excited. It is characterized by

[0008]

When the drive shaft is driven, the release mechanism is actuated by the excitation, and the stopper is released from the lock on the drive shaft so that the drive shaft can be moved up and down. When the power is lost, the stopper is locked to the drive shaft by the elastic member to prevent the drive shaft from falling.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cross section of a drive device equipped with a fall prevention device according to an embodiment of the present invention, and FIG. 2 shows a detailed situation of the fall prevention device. The drive device shown in FIG. 1 is installed on the upper part of the upper lid of the reactor vessel, and the control rod is inserted into the reactor core.
It is to be pulled out. In this example, a drive device for a moderator adjustment control rod (WDR) will be described as an example of the control rod.

As shown in FIG. 1, a circumferential groove 1a is provided on the outer circumference of a drive shaft 1 having a WDR (not shown) connected to the lower portion thereof. A latch housing 2 is arranged outside the drive shaft 1, and a coil housing 4 is arranged outside the latch housing 2 via a flux ring 3.
The coil housing 4 is provided with a lifting coil 5, a movable gripping coil 6 and a fixed gripping coil 7 from above. A raising magnetic pole 8 and a movable holding magnetic pole 9 are arranged between the raising coil 5 and the drive shaft 1, and a movable holding magnetic pole 9 and a movable holding plunger 10 are arranged between the movable holding coil 6 and the drive shaft 1. The fixed gripping pole 11 and the plunger 1 are provided between the fixed gripping coil 7 and the drive shaft 1.
2 is arranged, and further below the plunger 12, a fixed gripping plunger 13 is arranged.

Latch support tubes 14a and 14b are provided between the movable grip plunger 10 and the drive shaft 1 and between the fixed grip plunger 13 and the drive shaft 1, and the movable grip latch 15 is provided on the latch support tubes 14a and 14b. A fixed grip latch 16 is rotatably supported via latch pins 15a and 16a, respectively. As the movable grip latch 15 and the fixed grip latch 16 rotate, the claws are locked in the groove 1a of the drive shaft 1.

A latch link 17 is provided between the movable grip plunger 10 and the movable grip latch 15, and a fixed grip plunger 13 and a fixed grip latch 16 are provided.
A latch link 18 is provided across That is,
Axial movement of the movable grip plunger 10 rotates the movable grip latch 15 via the latch link 17, and axial movement of the fixed grip plunger 13 rotates the fixed grip latch 16 via the latch link 18. .

The movable grip magnetic pole 9, the movable grip plunger 10 and the plunger 12 are biased downward by springs 19, respectively. By sequentially energizing the lifting coil 5, the movable grip coil 6, and the fixed grip coil 7, the movable grip magnetic pole 9, the movable grip plunger 10, and the plunger 12 move in the axial direction against the biasing force of the spring 19. The movable grip latch 15 and the fixed grip latch 16 are provided three on the same circumference.

When the movable gripping coil 6 and the fixed gripping coil 7 are energized, the movable gripping plunger 10 and the plunger 12 are joined to the movable gripping magnetic pole 9 and the fixed gripping magnetic pole 11 by electromagnetic force, and the movable gripping latch 15 and the fixed gripping latch 16 are connected. Rotate to engage with the drive shaft 1. When the currents of the movable grip coil 6 and the fixed grip coil 7 are cut off, the joint surface is opened by the urging force of the spring 19 and the movable grip latch 15 and the fixed grip latch 16 rotate in opposite directions. After the fixed grip latch 16 is engaged with the drive shaft 1, the fixed grip latch 16 is lifted by the pressing spring 20 by about 1 to 2 mm.

Next, the operation of the drive shaft 1 will be described. Normal,
The drive shaft 1 is held only by the fixed grip latch 16. To raise the drive shaft 1, first, the movable grip latch 15 is rotated in the engaging direction. At this time, since the drive shaft 1 is lifted by the fixed grip latch 16 by about 1 to 2 mm, the movable grip latch 15 does not engage with the groove 1a of the drive shaft 1. Next, fixed grip latch 1
When 6 is rotated in the anti-engagement direction, the drive shaft 1 descends by about 1 to 2 mm, and the load of the drive shaft 1 system is applied to the movable grip latch 15 (load movement). When the raising coil 5 is energized in this state, the drive shaft 1 rises by about 16 mm by the gap between the raising magnetic pole 8 and the movable gripping magnetic pole 9. After that, the fixed grip latch 16 is rotated in the engaging direction to move the load to the fixed grip latch 16, the movable grip latch 15 is rotated in the anti-engagement direction, and the energization to the lifting coil 5 is cut off. Complete one cycle of climbing exercise. By repeating such an operation or the reverse operation, the drive shaft 1 is raised or lowered to selectively hold the WDR at two positions of the full insertion position and the full withdrawal position.

Since the WDR does not participate in the emergency shutdown of the nuclear reactor, a fall prevention device 51 is provided so that the drive shaft 1 does not fall due to its own weight even if the power source is lost. The fall prevention device 51 will be described with reference to FIGS. 1 and 2.

A latch housing 2 is extended below the fixed grip coil 7, and a lower coil housing 52 is arranged outside the latch housing 2 via a flux ring 3. A release coil 53 is provided in the lower coil housing 52. A release magnetic pole 54 and a hold plunger 55 are arranged between the release coil 53 and the drive shaft 1, and the hold plunger 55 is biased downward with respect to the release magnetic pole 54 by a spring 56 as an elastic member. A latch support tube 61 is provided between the hold plunger 55 and the drive shaft 1, and the latch support tube 61 is provided.
A hold latch 57 as a stopper is rotatably supported by a latch pin 57a. When the hold latch 57 rotates, the claw is locked in the groove 1a of the drive shaft 1.

A hold link 58 is provided between the hold plunger 55 and the hold latch 57, and the hold link 5 is moved by the axial movement of the hold plunger 55.
The hold latch 57 is rotated via 8. When the release coil 53 is not energized, the spring force of the spring 56 urges the hold plunger 55 downward so that the hold link 58 becomes substantially horizontal and the hold latch 5
The claw 7 is locked in the groove 1 a of the drive shaft 1. When the release coil 53 is energized, the hold plunger 55 is joined to the release magnetic pole 54 against the spring force of the spring 56, and the hold link 57 causes the hold latch 57 to rotate in the opposite engagement direction. That is, the release coil 53 and the release magnetic pole 5
4 and the hold plunger 55 constitute a release mechanism.

The operation of the above-described fall prevention device will be described.
While the drive shaft 1 is being raised or lowered, the release coil 53 is energized, the hold plunger 55 is joined to the release magnetic pole 54 against the spring force of the spring 53, and the hold latch 57 is rotated in the opposite engagement direction. Move.

When the power supply to the release coil 53 is cut off due to the loss of power source or the like, the hold plunger 55 moves downward due to the urging force of the spring 53, and the hold latch 57 rotates to engage with the drive shaft 1. As a result, the drive shaft 1 does not drop by its own weight. Hold latch 57
Since the claw of is rotated substantially perpendicular to the groove 1a of the drive shaft 1,
The link mechanism of the hold latch 57 will be attached at an appropriate angle close to vertical. As a result, the axial component force of the hold plunger 55 when the hold latch 53 is rotated in the opposite engagement direction is reduced.

The energization state when the control rod is inserted and withdrawn will be described with reference to FIGS. 3 and 4. FIG. 3 shows an oscillographic waveform at the time of pulling out, FIG. 4 shows an oscillographic waveform at the time of insertion, and the symbol at the time of insertion is attached with “′”.

The vertical axis of A is the current of the raising coil 5, the vertical axis of B is the current of the movable gripping coil 6, the vertical axis of C is the current of the fixed gripping coil 7, and the vertical axis of D is the current of the release coil 53.
The horizontal axis represents time.

At the point E when pulling out, the release coil 5
3 is a state in which the power supply is cut off, and the hold latch 57 is in a state of holding the drive shaft 1. At point F, the fixed grip coil 7 is excited, and the hold latch 57 moves the drive shaft 1
Is still being held. At point G, the current is reduced to suppress the amount of heat generated by the coil when the fixed grip latch 16 is completely engaged with the drive shaft 1.

At the point H, the current D of the release coil 53 is turned on, and the hold latch 57 rotates in the anti-engagement direction (open state). A normal extraction operation is performed between I and I, but during this time, the current D of the release coil 53 is kept open by the hold latch 57 due to the excitation by the reduced current, and there is no interference of the extraction operation.

At point J, the fixed grip coil 7 is kept energized after the normal extraction operation is completed, and the drive shaft 1 is held by the fixed grip latch 16. At point K, the current D of the release coil 53 is cut off, and the drive shaft 1 is held by the hold latch 57 in addition to being held by the fixed grip latch 16. At point L, the current A of the lifting coil 5, the current B of the movable gripping coil 6, the current C of the fixed gripping coil, and the current D of the release coil 53 are all disconnected. Therefore, the drive shaft 1 is pulled out and held in a state where the coil does not generate heat.

As shown in FIG. 4, the situation of the current A'of the lifting coil 5, the current B'of the movable gripping coil 6, the current C'of the fixed gripping coil and the current D'of the release coil 53 when the control rod is inserted. Shows a waveform similar to that at the time of extraction. Therefore, the drive shaft 1 is inserted and held in a state where the coil does not generate heat.

The above-mentioned fall prevention device 51 prevents the drive shaft 1 from falling even if the power supply is lost due to a failure of the electric system during the insertion or withdrawal of the control rod, and does not contribute to the emergency stop of the reactor. (WDR) can be held at any position without energization, and power consumption can be reduced and cooling device capacity can be reduced.

[0028]

The fall prevention device for a drive shaft according to the present invention comprises a stopper for fixing the drive shaft in the axial direction by urging an elastic member, and a release mechanism for releasing the fixation of the stopper by exciting the power supply. Since the drive shaft is fixed by the stopper in this state, the drive shaft can be prevented from falling without energizing. As a result, by applying the control rod drive device, it becomes possible to hold the control rod at an arbitrary position that is not involved in the emergency shutdown of the nuclear reactor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a drive device including a fall prevention device according to an embodiment of the present invention.

FIG. 2 is a detailed view of a fall prevention device.

FIG. 3 is a graph showing an energization state when a control rod is pulled out.

FIG. 4 is a graph showing the energization state when the control rod is inserted.

[Explanation of symbols]

 1 Drive Shaft 1a Groove 5 Lifting Coil 6 Movable Grip Coil 7 Fixed Grip Coil 15 Movable Grip Latch 16 Fixed Grip Latch 53 Release Coil 54 Release Magnetic Pole 55 Hold Plunger 56 Spring 57 Hold Latch 58 Hold Link

Claims (1)

[Claims] 1. A drive device having a drive shaft for holding an elongated member at one end and vertically driving the same in an axial direction, and fixing the drive shaft in the axial direction by locking the drive shaft by the urging force of an elastic member. A drive shaft fall prevention device, comprising: a stopper for releasing the drive shaft from the stopper and a release mechanism for releasing the locking of the stopper to the drive shaft against the biasing force of the elastic member when excited.