JPH04120498A - Device for preventing ejection of control rod of reactor - Google Patents

Abstract

PURPOSE:To attain core safety by preventing the rise of drive shaft in case of pressure part rupture the action of stopper lutch without preventing the rise of gear pitch P(1+alpha) and a fall of gear pitch alphaP on the shaft during normal drawing up. CONSTITUTION:In normal insertion of a control rod or scram, the gear 2a on a drive shaft 2 moves from top to bottom, and therefore, the stopper lutch 4 does not prevent the downward movement of the shaft 2. And in normal shaft withdrawal operation for one time, the shaft is raised by P(1+alpha) which is larger than the pitch P of the gear 2a, and then lowered by alphaP. During rising, the lutch 4 engages with a gearing groove 3 and holds up the stopper 5 together with the shaft 2, and thus a pin 13 engages with a step 12. Next, during lowering the shaft 2 for alphaP, a link arm 9 touches the pin 14 and then, the engagement between the pin 13 and the step 12 is released. Thus the shaft 2 can be drawn. If the pressure part breaks and the shaft tends to move upward, however, the lutch 4 retains the engagement with the shaft 2 and thus prevents upward movement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a control rod ejection prevention device in a control rod drive mechanism of a PWR nuclear reactor.

[Prior Art] As shown in FIG. 3, in a conventional PWR reactor, a magnetic jack control rod drive device 41 drives a drive shaft 2 up and down, and a control rod cluster 43 is engaged with the lower end of the drive shaft. The structure is such that the drive shaft 2 and the drive device drive part 42 are located in a pressure-resistant part 40 that protrudes from the reactor lid 44. When the control rods are pulled out and inserted during reactor operation, the cam 47 of the drive part of the control rod drive device 41 engages the drive shaft 2, and in this state, the control rods are moved upwardly or downwardly by the magnetic jack 50, and the control rods are moved downwardly. This is carried out by repeatedly holding the drive shaft 2 by the cam 48 of the holding section and then releasing the drive section cam 47. In addition, during a scram, the power to the magnetic jack 50 is turned off, so that the drive part cam 47 and the holding part cam 48 are separated from the drive shaft 2, and the drive shaft 2 and the control rod cluster 43 engaged with the lower end of the drive shaft are naturally moved. It falls and is inserted into the reactor core 45.

[Problems to be Solved by the Invention] However, as described above, in the conventional nuclear reactor, the drive shaft 2 and the drive device drive part 42 are located in the pressure-resistant part 40 that protrudes from the reactor lid 44. , when the protruding pressure-resistant part 40 is assumed to break, a state in which the drive shaft 2 and the control rod cluster 43 engaged with the lower end of the drive shaft 2 are suddenly pulled upward from the reactor due to the pressure difference between the reactor internal pressure and the outside pressure. , an event called a control rod ejection accident occurs.

Current plants are designed to safely shut down the reactor even if such a control rod ejection accident is assumed, but if a control rod ejection prevention device is provided, it will be even safer.

In view of these points, it is an object of the present invention to provide a control rod ejecting prevention device that prevents control rod ejecting accidents.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a drive in which the pitch of the chevron-shaped teeth is P, and the engagement groove has an axial depth shallower than αP on the upper inclined surface of the tooth. a shaft, a stopper having an inclined surface on the side thereof, fixedly installed in the nuclear reactor and disposed on the side of the drive shaft,
a stopper casing that houses the stopper and has an inclined surface on the upper part of which the inclined surface of the stopper side contacts and slides, and a bumper part that prevents the stopper from rising; a stop latch that engages with the engagement groove of the drive shaft and is resiliently biased into a substantially horizontal state by a lower spring; a link arm having a stepped portion; and a release pin and a support pin implanted in a lower part of the stopper and along an inclined surface of the stopper casing; A stepped portion is provided at a position that engages the support pin of the stopper casing from above when P(1+α) of P (1+α) rises, and in a state where the stepped portion engages the support pin from above, the link arm tilts outward until it abuts the release pin, and the support pin and the stepped portion are disengaged, and the drive shaft engages with a stopper casing fixedly installed in the reactor on the side of the drive shaft. a first gear block housed in the stopper casing; a second gear block that meshes with the first gear block and rotates in the opposite direction to the first gear block and is housed in the casing;
a stopper rack that engages with the second gear block and moves up and down; a box in which the stopper rack is slidably housed, a lower end of which is pivoted to a lower part of the casing and is tiltable outward relative to the drive shaft; a release latch that contacts the inside of the upper part of the box on the drive shaft side and tilts the box outward as the second gear block rotates in one direction to release the engagement between the second gear block and the stopper rack; Equipped with
As the second gear block rotates in the other direction, the second gear block rotates in the other direction.
The stopper rack that engages with the gear block is raised, and the upper end of the stopper rack comes into contact with a bumper portion in the stopper casing.

[Function] The drive shaft can be lowered without being restricted by the control rod protrusion prevention device of the present invention. Therefore, during normal control rod insertion operations and scramming, the drive shaft can be lowered unimpeded.

The rise of the drive shaft is caused by the drive of the magnetic jack during one step of normal withdrawal.
When +α) rises, the stopper (stop latch, stopper rack) of the control rod protrusion prevention device rises together with the drive shaft, and the control rod protrusion prevention device is released by the fall of aP of the drive shaft, and the control rod protrusion prevention device is released by one step of the drive shaft. does not prevent the raising of

In the event of a control rod ejection accident, the control rod ejection prevention device operates to prevent the drive shaft from rising.

[Example 1] A detailed explanation of the present invention will be given below with regard to the illustrated embodiment.
The present invention is to install the upper core structure 1, for example, at a position where the control rod guide tube 51 engages with the drive shaft 2, as shown by reference numeral l in FIG. Explain.

FIG. 1 is a longitudinal sectional view showing the first embodiment, and FIG.
In this case, the drive shaft 2 is a drive shaft as shown in FIG. 3 of the nuclear reactor, and has a magnetic jack type control rod drive device 41 on its upper part, similar to the conventional example explained in FIG. 3 above. It acts on The drive shaft 2 is provided with an engagement groove 3 on the upper inclined surface of the tooth 2a, in which a stop latch 4 engages.

The depth β of this engagement groove 3 is set to be shallower than αP (where P is the pitch of the teeth 2a of the drive shaft 2).

The stop latch 4 is rotatably connected to a stopper 5 which is slidably inserted into a stopper casing 6 by means of a pin 7. This stopper latch 4 is attached to approximately the center of the stopper 5 in the horizontal direction, as shown in the cross section of a part of the stopper 5, and is prevented from rotating above the horizontal direction by contacting the part of the stopper 5. Normally, it is always pressed upward by a spring 8 to maintain a horizontal position.

Further, the stopper 5 is formed with an inclined surface 5a and is slidable on the inclined surface 6c of the stopper casing 6.

Further, a link arm 9 is pivotably attached to the stopper 5 by a pin 10. This link arm 9 has
A long hole 11 is bored, and a stepped portion 12 is provided in the long hole 11. A support pin 13 is provided in the elongated hole 11 so as to protrude from the stopper casing 6 . The step part 12 and the support pin 13 in the elongated hole 11 are arranged so that when the drive shaft 2 rises by the distance P between the peaks of the teeth 2a, that is, the link arm 9 moves along with the stopper 5 on the drive shaft 2 by P(1+α). The support pin 13 is provided at a position where it engages with the stepped portion 12 when the support pin 13 is lifted up. Further, the stopper 5 is set such that its center of gravity is farther from the support pin 13 than the drive shaft 2 is. Therefore, when the drive shaft 2 rises by P (1+α), the step 12 of the long hole 11 of the link arm 9 engages with the engagement pin 13, and then the link arm 9 moves down together with the stopper 5 even a little ( When the link arm 9 moves downward (downward movement), the support pin 13 is engaged with the stepped portion 12 of the link arm 9, so that the link arm 9 acts to move the stopper 5 away from the drive shaft 2. Furthermore,
A release pin 14 is provided on the stopper box 6 in a protruding manner. This release pin 14 releases the engagement between the step 12 of the elongated hole 11 of the link arm 9 and the engagement pin 13. When the link arm 9 rotates, it hits the release pin 14 and releases the release pin 14. It is designed to be released by levering it as a fulcrum. In addition, 6a is the breadth part of the stopper box 6, and 6b is the window hole of the stopper casing 6.

On the other hand, when the pitch of the teeth 2a of the drive shaft 2 is P, (1) During normal extraction, in one step of extraction, after a rise of P (1+α) due to the drive by the magnetic jack, a fall of aP; ■During normal insertion, P is lowered by the drive by the magnetic jack in one step of insertion. ■During emergency insertion (scram), it is continuously lowered by turning off the power to the magnetic jack. ■In the event of an ejection accident, the Continuously rises and moves due to the differential pressure load inside and outside. To explain in more detail, when the control rods are withdrawn and inserted during reactor operation, as shown in FIG.
In this state, the magnetic jack 50 moves the drive shaft 2 upward or downward, the drive shaft 2 is held by the cam 48 of the holding section disposed below, and then the drive section cam 47 is released, which is repeated.

In addition, at the time of scram, the power of the magnetic jack 50 is turned off, so that the drive part cam 47 and the holding part cam 48 are separated from the drive shaft 2, and the drive shaft 2 and the control rod cluster 43 engaged with the lower end of the drive shaft 2 are removed. It falls naturally and is inserted into the reactor core 45.

Therefore, when the stop latch 4 moves the drive shaft 2 upward by engaging the engagement groove 3 formed on the tooth surface of the drive shaft 2 with its tip 4a, the stop latch 4 moves the stopper 5 to the drive shaft 2. It works together to lift it upward.

Further, when the drive shaft 2 moves from above to below, the stop latch 4 has a tip 4a that is connected to the drive shaft 2.
The drive shaft 2 is separated from the engagement groove 3 by the action of the spring 8.
When the teeth of the stop latch 4 contact from above, the stop latch 4 rotates downward around the pin 7 and does not inhibit the downward movement of the drive shaft 2. Therefore, the normal insertion operation of the control rod and the scram During the insertion operation, the teeth of the drive shaft 2 move from the top to the bottom, so the stop latch 4 is inserted into the drive shaft 2.
does not impede movement.

In addition, the normal drawing operation is driven by the magnetic jack as described above, and the drive shaft 2 is
Although the pitch of the teeth of the drive shaft 2 rises, it is first pulled upward by P (1 + α), which is larger than P, and then αP
It exhibits so-called overshoot behavior. Therefore, during normal extraction, the stop latch 4 engages with the engagement groove 3 of the drive shaft 2 and lifts the stopper 5 in conjunction with the drive shaft 2, while the stop latch 4 is pulled up by P (1+α). The link arm 9, which is pivotally connected by a pin 10, is also pulled up together with the stopper 5. When the link arm 9 is lifted by P(1+α), the step 12 of the long hole 11 provided in the link arm 9 engages with the support pin 13, so when the drive shaft 2 is lowered by αP from this point, As shown in FIG. 1(8), the link arm 9 is supported by the support pin 13, and the stopper 5 is also supported by the link arm 9. Then, since the center of gravity of the stopper 5 is set to be farther from the support pin 13 than the drive shaft 2, the stopper 5 receives a rotational moment about the support pin 13 in a direction away from the drive shaft 2, and rotates. , drive shaft 2
and the stop latch 4 are separated, and the engagement between the drive shaft 2 and the stop latch 4 is first released while the drive shaft 2 is lowered by αP, and as it rotates further, the link arm 9 is
At the release pin 14, the engagement between the engagement pin 13 and the stepped portion 12 of the link arm 9 is released by levering the release pin 14 as a fulcrum, and the stopper 5 is moved along the inclined surface 6c of the stopper casing 6 due to its own weight. It descends and returns to the position shown in FIG. 1(A) before being lifted up. Therefore, during normal extraction, the drive shaft 2 is raised by P(1+α) and lowered by 02 minutes, and the above-mentioned raising and lowering of the stopper 5 is repeated, and the drive shaft 2 can be withdrawn.

However, the pressure-resistant part 4 protruding from the reactor vessel M44
When a break occurs in the stop latch 4 and the drive shaft 2 attempts to move upward, the stop latch 4 moves only upward.
remains engaged with the drive shaft 2, and as shown in FIG. 1(C), the stopper 5 lifted by the stop latch 4 collides with the bumper portion 6a, thereby inhibiting the upward movement of the drive shaft 2. It acts on This prevents control rod ejection accidents.8 [Embodiment 2] The second embodiment will be explained with reference to FIG. 2. FIG. 2 is a longitudinal sectional view showing the second embodiment. In the figure, a gear 21 is meshed with the drive shaft 2, and a gear 22 is fixed coaxially with the gear 21. Gear 2 meshing with the gear 22
A gear 24 and a latch gear 25 are fixed coaxially to the gear 3. The gears 21, 22 are connected to the first gear block, the gears 23, 24 . The latch gear 25 is referred to as a second gear block. A stopper rack 30 is engaged with the gear 24, and a release latch 26 is detachably engaged with the latch gear 25. The release latch 26 is always pressed by a spring 34 so as to be restored to its original state, and has a claw piece pivotably attached to one end thereof so as to be rotatable, and is pressed by a spring 28 so as to always maintain the initial position. 27 are provided.

Further, the stopper rack 30 is slidably and loosely fitted into a stopper gear box 29 which is swingable about a pivot 33, and comes into contact with and separates from the gear 24 through a window hole 29b. The box 29 of the stopper rack is always pressed toward the gear 24 by a spring 31. In addition, 32 is a bumper part.

A stopper casing 35 is fixed at a predetermined location within the reactor.

Therefore, as the drive shaft 2 moves up and down, the drive shaft 2
Gear 21 meshing with gear 21 causes clockwise and counterclockwise rotation, and gear 23 . through gear 22 coaxial with gear 21 .
24.25 also causes counterclockwise 0 clockwise rotation. When the latch gear 25 rotates clockwise, the release latch 26 is pushed and moved in the direction away from the drive shaft 2, and as a result, the release latch 26 moves the stopper rack box 29 in the direction away from the drive shaft 2. , the stopper rack 30 is released and separated from the gear 24. On the other hand, when the latch gear 25 rotates counterclockwise, the release latch 26 prevents the movement of the gear 25 by the action of the spring 28 which allows the release latch 26 to rotate in only one direction. First, since it can freely rotate, the stopper rack 30 in mesh with the gear 24 moves upward in response to the counterclockwise rotation of the gear 24.

Therefore, in the event of a control rod ejection accident, the drive shaft 2 moves only upward, so the gear 24 and the latch gear 25 rotate counterclockwise, and the stopper gear 30 is also lifted upward, as shown in FIG. As shown in (B), it protrudes from the window hole 29a of the stopper gear box 29 and hits the bumper portion 32 of the stopper casing 35, thereby preventing the drive shaft 2 from moving upward. This will prevent control rod ejection accidents.

The stopper casing 35 is fixed at a predetermined location in the reactor, and is moved upward by P(1+α), which is larger than the pitch P of the teeth of the drive shaft 2, and then by repeatedly moving downward by aP. When normally pulling out the drive shaft 2,
When the drive shaft 2 rises by P(1+α), the latch gear 25 rotates counterclockwise, and the stopper rack 30 meshing with the gear 24 is lifted upward by P(1+α), but as αP falls Sometimes, the latch gear 25 rotates clockwise as shown in FIG. 2(C), and by pressing the release latch 26, the stopper gear box 29 is also pressed.
The stopper rack 3o is released from the gear 24 and returns to its original position (the position shown in FIG. 2(A)) due to its own weight. Therefore, during normal extraction, the drive shaft 2 is raised by P(1+α), and as αP is repeatedly lowered, the stopper gear 3° is repeatedly raised and lowered, and the drive shaft 2 can be withdrawn.

Also, when the drive shaft 2 is normally inserted or scrammed, the latch gear 25 is rotated clockwise and the release latch 26 is pushed in the direction away from the drive shaft 2, pressing the stopper gear box 29. As a result, the stopper gear 3° is turned into a gear. Released from 24,
The downward movement of the drive shaft 2 is not inhibited.

As described above, this embodiment has the same effect as the first embodiment.

[Effects of the Invention] As explained above, according to the present invention, control rod ejection can be prevented, so even if a pressure-resistant part is assumed to break, a control rod ejection accident will not occur. The safety and reliability of the plant can be improved.

[Brief explanation of drawings]

FIGS. 1(A), (B), and (C) are vertical sectional views showing one embodiment of the present invention, and FIGS. 2(A), (B),
(C) is a longitudinal sectional view showing another embodiment, and FIG. 3 is an explanatory diagram of a conventional PWR reactor. 2... Drive shaft, 2a... Teeth, 3... Engagement groove, 4...
... Stopper latch, 5... Stopper, 5a... Inclined surface, 6... Stopper casing, 6a... Bumper portion, 6C... Inclined surface, 7.10... Pin, 8...・
Spring, 9... Link arm, 11... Long hole, 12... Step part, 13.14-... Pin, 21.22.23.24... Gear, 25... Latch gear, 26...Release latch, 27
...Claw piece, 28.31.34...Spring, 29...
Box, 30... Stopper rack, 32... Bumper portion, 35... Stopper casing, 4o... First
gear block, 41... second gear block. Procedural supplementary statement (spontaneous) October 11, 1990 Patent Application No. 241823, 1990 Representative Nakai Hata 5, date of amendment order Spontaneous 7, contents of amendment Claims (1) Mountain shape as attached a drive shaft having a tooth pitch of P and an engagement groove with an axial depth shallower than αP on the upper inclined surface of the teeth; a stopper having an inclined surface on the side; fixedly installed in a nuclear reactor; a stopper casing disposed on the side of the drive shaft, containing the stopper, having an inclined surface on which the inclined surface of the stopper side slides in contact with it, and a bumper portion on the upper part that prevents the stopper from rising; a stop latch whose upper end is pivotally supported by the stopper, whose tip engages with the engagement groove of the drive shaft, and whose upper end is pivotally supported by the stopper; a link arm having a longitudinal elongated hole in the lower part and a step part in the middle; a release pin and a support pin installed in the lower part of the stopper and installed along the inclined surface of the stopper casing; The long hole of the link arm has the stopper P(1+α
) is provided at a position that engages the support pin of the stopper casing from above when the link arm is raised, and in a state where the step engages the support pin from above, the link arm has a side surface that engages with the release pin. A control rod protrusion prevention device for a nuclear reactor, characterized in that the control rod is tilted outward until it comes into contact with the support pin, and the support pin disengages from the step. (2) A stopper casing that is fixed inside the reactor on the side of the drive shaft, and a first stopper casing that meshes with the drive shaft and is installed inside the stopper casing.
a gear block that meshes with the first gear block, rotates in the opposite direction to the first gear block, and is housed in the casing; and a second gear block that meshes with the second gear block and rotates in the opposite direction to the first gear block; A stopper rack that moves up and down, a box in which the stopper rack is slidably housed and whose lower end is pivoted to the lower part of the casing and can tilt outward with respect to the drive shaft; and a box that contacts the inner side of the upper part of the box on the drive shaft side. and a release latch that tilts the box outward as the second gear block rotates in one direction to release the engagement between the second gear block and the stopper rack, the second gear block With the rotation in the other direction, the second
A control rod protrusion prevention device for a nuclear reactor, characterized in that a stopper rack that engages with a gear block is raised, and the upper end of the stopper rack abuts a bumper portion in a stopper casing.

Claims (2)

[Claims] (1) A drive shaft with a pitch of chevron-shaped teeth P and an engagement groove with an axial depth shallower than αP on the upper inclined surface of the teeth, a stopper with an inclined surface on the side, and a nuclear reactor. fixed to the drive shaft, disposed on the side of the drive shaft, housing the stopper, and having an inclined surface on which the inclined surface of the stopper side contacts and slides, and a bumper portion on the top that prevents the stopper from rising. a stopper casing having an upper end pivotally supported by the stopper, a distal end engaging an engagement groove of a drive shaft, and resiliently biased in a substantially horizontal state by a lower spring; a link arm that is pivotally supported by the stopper and has a longitudinal elongated hole in the lower part and a stepped part in the middle thereof; and a release pin and support that are planted in the lower part of the stopper and planted along the slope of the stopper casing. A pin (1+α) of the stopper is provided in the elongated hole of the link arm.
A step is provided at a position that engages the support pin of the stopper casing from above when the link arm is raised, and in a state where the step engages the support pin from above, the link arm has its side surface contact the release pin. A control rod protrusion prevention device for a nuclear reactor, characterized by tilting outward until they abut, and then disengaging a support pin from a step. (2) A stopper casing that is fixed inside the reactor on the side of the drive shaft, and a first stopper casing that meshes with the drive shaft and is installed inside the stopper casing.
a gear block that meshes with the first gear block, rotates in the opposite direction to the first gear block, and is housed in the casing; and a second gear block that meshes with the second gear block and rotates in the opposite direction to the first gear block; A stopper rack that moves up and down, a box in which the stopper rack is slidably housed and whose lower end is pivoted to the lower part of the casing and can tilt outward with respect to the drive shaft; and a box that contacts the inner side of the upper part of the box on the drive shaft side. and a release latch that tilts the box outward as the second gear block rotates in one direction to release the engagement between the second gear block and the stopper rack, the second gear block With the rotation in the other direction, the second
A control rod protrusion prevention device for a nuclear reactor, characterized in that a stopper rack that engages with a gear block is raised, and the upper end of the stopper rack abuts a bumper portion in a stopper casing.