JP6913652B2 - Boiling water reactor - Google Patents

Description

The present invention relates to a boiling water reactor in which a steam dryer is installed inside a reactor pressure vessel.

As a background technique in this technical field, there is Japanese Patent Application Laid-Open No. 2013-113754 (Patent Document 1). This publication describes a structure in which a steam dryer formed in a boiling water reactor has a support ring, and a seismic block is welded to the outer surface of the support ring.

Then, it is described that the support bracket is fitted into the seismic block, and the support bracket supports the support ring and the seismic block, and it is described that the support structure of the steam dryer is improved in seismic resistance.

Japanese Unexamined Patent Publication No. 2013-113754

Patent Document 1 describes a boiling water reactor in which a steam dryer is installed inside a reactor pressure vessel. However, Patent Document 1 does not describe a case where an external force in the vertical direction generated at the time of an earthquake or the like acts on a steam dryer formed in a boiling water reactor.

In such a boiling water reactor, for example, when an earthquake occurs, the steam dryer may float when a vertically upward external force exceeding its own weight acts on the steam dryer. When such a floating steam dryer is lifted by a certain amount, it is supported by a holddown bracket so that it cannot be lifted any more. After that, when the vertical upward external force acting on the steam dryer disappears, the steam dryer re-seats on the support bracket, but there is a concern that an impact load may be applied to the steam dryer and the support bracket at this time. NS.

Therefore, the present invention provides a boiling water reactor in which the influence of an external force in the vertical direction is mitigated even when an external force in the vertical direction acts on the steam dryer installed inside the reactor pressure vessel. For example, the present invention provides a boiling water reactor that reduces floating even when a vertically upward external force acts on the steam dryer in the event of an earthquake or the like.

In order to solve the above problems, the boiling water reactor of the present invention is contained in a reactor pressure vessel and is hardened so as to extend horizontally to a steam dryer for drying steam and an outer circumference of the steam dryer. A support ring to be installed, a support bracket that supports the support ring and is installed horizontally on the inner peripheral surface of the reactor pressure vessel, a spacer block that is fixed to both sides and the upper side of the support bracket in the circumferential direction, and a spacer. A seismic block that has a structure that opens outward in the radial direction of the support ring so as to suppress the horizontal movement of the support ring on both sides and the upper side in the circumferential direction of the block, and is fixed to the support ring. It is installed in a seismic block and has two clamps that approach from both sides in the circumferential direction of the spacer block, contact the lower side of the spacer block, and release the contact by inserting a pin from between the upper sides thereof.

According to the present invention, it is possible to provide a boiling water reactor in which the influence of an external force in the vertical direction is mitigated even when an external force in the vertical direction acts on the steam dryer installed inside the reactor pressure vessel. .. That is, it is possible to provide a boiling water reactor that reduces floating even when a vertically upward external force acts on the steam dryer in the event of an earthquake or the like.

It is a vertical cross-sectional view which shows roughly the structure of the boiling water reactor. It is a perspective view which shows the peripheral structure of a steam dryer schematicly. It is a perspective view which shows the peripheral structure of a seismic block roughly. It is a top view which shows the peripheral structure of the seismic block which concerns on embodiment of this invention, and shows the state in the operation period of a nuclear reactor. It is a top view which shows the peripheral structure of the seismic block which concerns on embodiment of this invention, and shows the state in the periodic inspection period of a nuclear reactor. It is a top view which shows the peripheral structure of the seismic block which concerns on 2nd Embodiment of this invention, and shows the state in the operation period of a nuclear reactor. It is a top view which shows the peripheral structure of the hole down pole which concerns on 3rd Embodiment of this invention.

Hereinafter, examples of the present invention will be described with reference to the drawings.

In this embodiment, an example of a boiling water reactor that reduces floating even when a vertically upward external force acts on the steam dryer in the event of an earthquake or the like will be described.

FIG. 1 is a vertical cross-sectional view schematically showing the configuration of a boiling water reactor.

The boiling water reactor 1 includes a reactor pressure vessel 2, a core 4, a core shroud 6, a steam separator 14, and a steam dryer 15. A top lid 3 is detachably installed at the upper end of the reactor pressure vessel 2, and a core 4, a core shroud 6, a steam separator 14 and a steam dryer 15 are installed inside the reactor pressure vessel 2. There is. The steam dryer 15 is included in the reactor pressure vessel 2 to dry the steam.

The core shroud 6 is installed so as to surround the core 4 in which a plurality of fuel assemblies 5 are formed. A core support plate 7 attached to the core shroud 6 is installed at the lower end of the core 4, and an upper lattice plate 8 attached to the core shroud 6 is installed at the upper end of the core 4. The upper end of each fuel assembly 5 is supported by the upper grid plate 8.

A plurality of control rod drive mechanism housings 13 are installed at the bottom of the reactor pressure vessel 2. A plurality of control rods 11 that are taken in and out of the fuel assembly 5 are connected to control rod drive mechanisms (not shown) installed inside each control rod drive mechanism housing 13. A plurality of control rod guide pipes 12 are installed below the core 4 inside the reactor pressure vessel 2, and the control rods 11 pulled out from the core 4 are housed inside the control rod guide pipes 12.

A plurality of reactor coolant recirculation pumps 9 are installed inside the downcomer 44, which is an annular region formed between the reactor pressure vessel 2 and the core shroud 6. A shroud head 10 is installed at the upper end of the core shroud 6, and a steam separator 14 is installed above the shroud head 10. Further, a steam dryer 15 is installed above the steam separator 14.

In the boiling water reactor 1, a part of the reactor cooling water is heated by a nuclear reaction in the core 4 composed of a plurality of fuel assemblies 5 arranged inside the reactor pressure vessel 2. The gas-liquid two-phase flow of the reactor cooling water and steam is separated into the reactor cooling water and steam by the steam separator 14 installed above the core 4. The steam separated by the steam separator 14 is guided to a steam dryer 15 installed above the steam separator 14 to remove water contained in the steam.

A plurality of steam dryer units 45, a support ring 16 and a cylindrical skirt 17 arranged in parallel are installed in and around the steam dryer 15. The support ring 16 is installed in the steam dryer 15 to support the load of the steam dryer 15, and is installed below the steam dryer 15 so as to surround the steam dryer 15.

Further, the upper end of the skirt 17 is installed on the support ring 16 and is installed so as to extend downward from the support ring 16.

A plurality of holddown brackets 18 are installed inside the upper lid 3 of the reactor pressure vessel. The holddown pole 19 and the lifting eye 20 are installed in the steam dryer 15 while forming a gap so as to be located directly below the holddown bracket 18.

A certain gap is formed between the lifting eye 20 and the holddown pole 19 formed on the upper part of the steam dryer 15 and the holddown bracket 18 provided inside the upper lid 3 of the reactor pressure vessel 2. It is installed so that it can be done.

FIG. 2 is a perspective view schematically showing the peripheral configuration of the steam dryer.

The support ring 16 is installed in the steam dryer 15 and supports the load of the steam dryer 15. The support ring 16 installed below the steam dryer 15 so as to surround the steam dryer 15 is fixedly installed so as to extend horizontally on the outer periphery of the steam dryer 15. A steam dryer unit 45, a skirt 17, a holddown pole 19, and a lifting eye 20 are installed in and around the steam dryer 15.

The seismic block 21 has a structure that is open toward the outside in the radial direction of the support ring 16 so as to suppress the horizontal movement of the support ring 16. The seismic block 21 is welded to the support ring 16 and fixed.

FIG. 3 is a perspective view schematically showing the peripheral configuration of the seismic block.

By installing the seismic block 21, the support ring 16 can withstand the horizontal load acting on the steam dryer 15. The seismic block 21 is welded to the support ring 16 and fixed. Further, the seismic block 21 is installed on both sides and the upper side in the circumferential direction of the spacer block 23.

The support bracket 22 supports the support ring 16 and is installed horizontally on the inner peripheral surface of the reactor pressure vessel 2. Spacer blocks 23 are welded and fixed to both sides and the upper side of the support bracket 22 in the circumferential direction. The spacer block 23 is installed so as to project several centimeters from the seismic block 21.

In order to ensure safety, it is necessary to inspect the inside of the reactor on a regular basis. Also, when changing fuel, it is necessary to work inside the reactor. The steam dryer 15 needs to be removed and installed when inspecting the inside of these reactors or when changing fuel.

As described above, since the seismic block 21 and the spacer block 23 are not fixed by welding or the like, and because the seismic block 21 and the spacer block 23 are in contact with each other on both sides and the upper side in the circumferential direction, the steam dryer 15 Can be removed from above and installed from above.

FIG. 4 is a plan view showing the peripheral configuration of the seismic block according to the embodiment of the present invention, and shows the state during the operation period of the nuclear reactor.

FIG. 4 shows a seismic block 21, a support ring 16, a support bracket 22, a spacer block 23, and a skirt 17.

The support ring 16 is fixed so as to extend horizontally on the outer periphery of the steam dryer 15, and a skirt 17 is installed below the support ring 16. Spacer blocks 23 are welded to the support bracket 22 that supports the support ring 16 on both sides and the upper side in the circumferential direction. Seismic blocks 21 that suppress the movement of the support ring 16 with respect to the support bracket 22 are installed on both sides and the upper side of the spacer block 23 in the circumferential direction. The seismic block 21 is welded to the support ring 16, and the seismic block 21 has a notch structure that is open outward in the radial direction of the support ring 16.

Two clamps 31 are installed in the seismic block 21. The clamp 31 is rotatably installed on the seismic block 21. A torsion spring 32 is installed on the rotating shaft 37 between the seismic block 21 and the clamp 31 so that a force is applied so that the lower ends of the two clamps 31 rotate in an approaching direction.

Since the clamp 31 installed in the seismic block 21 has a structure in which the spacer block 23 protrudes several centimeters from the seismic block 21, a part of the lower ends (inner tip portion) of the two clamps 31 is the spacer block 23. The support block 22 is supported via the spacer block 23 in contact with a part (outer portion) of the lower end of the.

That is, the clamp 31 installed in the seismic block 21 utilizes the fact that the spacer block 23 has a structure that protrudes several centimeters from the seismic block 21. Therefore, the thickness of the clamp 31 is preferably equal to or less than the length of the spacer block 23 protruding from the seismic block 21. As a result, it is not necessary to supplement the extra space and the like, and the spacer block 23 can be easily supported by the clamp 31.

During the operation period of the nuclear reactor, a state in which a part of the lower end of the clamp 31 is in contact with a part of the lower surface of the spacer block 23 is maintained by the force of the torsion spring 32. When an earthquake or the like occurs, an upward force acts on the steam dryer 15, and at this time, the clamp 31 receives a downward force from the spacer block 23. This downward force is transmitted to the steam dryer 15 via the seismic block 21 and the support ring 16, and can prevent the steam dryer 15 from floating.

Further, the installation position of the rotating shaft 37 is preferably inside the position where the clamp 31 contacts a part of the lower end of the spacer block 37. As a result, when the clamp 31 receives a downward force from the spacer block 37, the clamp 37 can act inward (in the direction in which the lower ends of the two clamps 31 approach each other).

Further, the clamp 31 (clamp 31 on the right side in the drawing) has a substantially "ko" shape, and is from the lower part of the clamp 31 (the side below the "ko") to the upper part of the clamp 31 (the side above the "ko"). ) Is preferably a long shape. This is to prevent the steam dryer 15 from floating and to realize a structure that enables the steam dryer 15 to be removed from above and attached from above.

The clamp 31 on the left side of the drawing has an inverted shape of the clamp 31 on the right side of the drawing, and has a substantially “U” shape with the right side open.

FIG. 5 is a plan view showing the peripheral configuration of the seismic block according to the embodiment of the present invention, and shows the state of the nuclear reactor during the periodic inspection period.

Similar to FIG. 4, FIG. 5 shows a seismic block 21, a support ring 16, a support bracket 22, a spacer block 23, and a skirt 17. Further, FIG. 5 also shows a clamp 31, a torsion spring 32, and a rotating shaft 37, as in FIG.

That is, FIG. 5 shows a state in which the pin 32 is inserted between the two clamps 31 from the upper part of the two clamps 31.

During the periodic inspection period of the reactor, after the upper lid 3 of the reactor pressure vessel 2 is removed, the pin 33 is between the two clamps 31 from above the reactor pressure vessel 2 (that is, above the clamp 31). It is plugged in. As a result, the clamp 31 rotates about the rotation shaft 37 as a fulcrum so that the lower ends of the two clamps 31 are separated from each other, the contact between the spacer block 23 and the clamp 31 is released, and the steam dryer 15 can be removed upward. It will be possible.

Further, the bent portion 46 of the clamp 31 is formed at an obtuse angle. As a result, when the pin 32 is inserted between the two clamps 31 from the upper part of the two clamps 31, the lower ends of the two clamps 31 rotate in directions away from each other, and the spacer block 23 and the clamp 31 can easily come into contact with each other. It will be released.

The two clamps 31 at the positions where the pins 32 are inserted are formed so as to face each other so that the upper side is wider than the lower side during the operation period of the reactor. As a result, when the pin 32 is inserted from above the two clamps 31 during the periodic inspection period of the nuclear reactor, the lower ends of the two clamps 31 rotate in directions away from each other, and the spacer block 23 and the clamp 31 can be easily separated from each other. The contact is released.

That is, the two clamps 31 are installed on the seismic block 21, approach from both sides in the circumferential direction of the spacer block 23, come into contact with the lower side of the spacer block 23, and insert the pin 33 from between the upper side thereof. The contact is released.

FIG. 6 is a plan view showing the peripheral configuration of the seismic block according to the second embodiment of the present invention, and shows the state during the operation period of the nuclear reactor.

Similar to FIG. 5, FIG. 6 shows a seismic block 21, a support ring 16, a support bracket 22, a spacer block 23, and a skirt 17. Note that, in FIG. 6, instead of the clamp 31, the torsion spring 32, and the rotating shaft 37 shown in FIG. 4, a nut 35, a stopper 36, and an L-shaped bolt 34 are shown.

As shown in FIG. 6, the seismic block 21 is provided with two through holes for passing bolts 34. Two stoppers 36 are welded and fixed to the lower surface of the seismic block 21 in the vicinity of each through hole. The bolt 34 has a bent portion bent by 90 ° from the axial direction. In other words, it has an L shape.

The bolt 34 has a structure in which the bolt 34 is tightened by the nut 35 while being passed through the through hole of the seismic block 21, and at this time, the bent portion comes into contact with the stopper 36, so that the rotation of the bolt 34 when the nut 35 is tightened is caused. It is suppressed and the bent portion can be kept in the lower position of the spacer block 23. In this state, by further tightening the nut 35, it is possible to bring a part of the bolt 34 into contact with the lower surface of the spacer block 23.

During the operation period of the nuclear reactor, it is used in a state where a part of the bolt 34 and the lower surface of the spacer block 23 are kept in contact with each other, so that the steam dryer 15 can be lifted even in the event of an earthquake or the like. On the other hand, a downward force is applied from the spacer block 23 to the bolt 34, and this force is transmitted to the steam dryer 15 via the seismic block 21 and the support ring 16 to prevent the steam dryer 15 from floating.

Further, during the periodic inspection period of the reactor, the contact between a part of the bolt 34 and the lower surface of the spacer block 23 is released by loosening the nut 35 after the upper lid 3 of the reactor pressure vessel 2 is removed. Further, by rotating the bolt 34 by 90 ° so that the tip of the bent portion faces the center side of the reactor pressure vessel 2, the bent portion of the bolt 34 comes off from the lower side of the spacer block 23, so that the steam dryer 15 is moved. It can be taken out upward.

In this embodiment, since the bolt 34 is passed through the through hole formed in the seismic block 21, the spacer block 23 does not necessarily have to have a structure protruding several centimeters from the seismic block 21.

FIG. 7 is a plan view showing a peripheral configuration of a hole-down pole according to a third embodiment of the present invention.

This embodiment relates to a holddown pole 19 formed on the steam dryer 15.

As described in FIG. 7, the holddown pole 19 has a pole 41 fixed so as to extend above the steam dryer 15 and a cylinder capable of sliding in the vertical direction with respect to the pole 41. 42 is installed.

A push spring 43 is installed inside the cylinder 42.

The cylinder 42 is installed so as to maintain contact with the lower side of a plurality of holddown brackets 18 installed on the upper lid 3 fixed to the reactor pressure vessel 2.

During the operation period of the nuclear reactor, the holddown pole 19 receives a downward force due to the action of the push spring 43, so that the force that the steam dryer 15 tries to lift in the event of an earthquake is alleviated, and the steam dryer The 15 does not separate from the support bracket 22, and it is possible to avoid applying an impact load to the steam dryer 15 and the support bracket 22.

The present invention is not limited to the above-described embodiments, and includes various modifications. Further, in the present invention, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the described configurations. For example, it is possible to delete a part of the configuration of each embodiment.

Further, in each of the above-described embodiments, the advanced boiling water reactor (ABWR) is exemplified as the reactor, but the same applies to the boiling water reactor (BWR).

1 Boiling water reactor 2 Reactor pressure vessel 3 Top lid 4 Core 5 Fuel assembly 6 Core shroud 7 Core support plate 8 Upper lattice plate 9 Reactor coolant recirculation pump 10 Shroud head 11 Control rod 12 Control rod guide tube 13 Control Rod Drive Mechanism Housing 14 Air-Water Separator 15 Steam Dryer 16 Support Ring 17 Skirt 18 Holddown Bracket 19 Holddown Pole 20 Lifting Eye 21 Seismic Block 22 Support Bracket 23 Spacer Block 31 Clamp 32 Twist Spring 33 Pin 34 Bolt 35 Nut 36 Stopper 41 Pole 42 Cylinder 43 Push spring

Claims (6)

A steam dryer that is contained in a reactor pressure vessel and dries steam,
A support ring fixed so as to extend horizontally on the outer circumference of the steam dryer,
A support bracket that supports the support ring and is installed horizontally on the inner peripheral surface of the reactor pressure vessel.
Spacer blocks fixed to both sides and the upper side of the support bracket in the circumferential direction,
The spacer block has a structure that is open outward in the radial direction of the support ring so as to suppress the horizontal movement of the support ring on both sides and the upper side in the circumferential direction, and is fixed to the support ring. Seismic block and
Two clamps installed on the seismic block, approaching from both sides in the circumferential direction of the spacer block, contacting the lower side of the spacer block, and releasing the contact by inserting a pin from between the upper sides thereof.
A boiling water reactor characterized by having. The boiling water reactor according to claim 1, wherein the thickness of the clamp is not more than or equal to a length of the spacer block protruding from the seismic block. The clamp is supported by a rotating shaft formed on the seismic block, and the installation position of the rotating shaft is inside a position where the clamp contacts a part of the lower end of the spacer block. Item 2. The boiling water reactor according to item 1. The boiling water reactor according to claim 1, wherein the clamp has a bent portion, and the bent portion is formed at an obtuse angle. The boiling water according to claim 1, wherein the two clamps at the positions where the pins are inserted are formed so as to face each other so that the upper side is wider than the lower side during the operation period of the reactor. Type reactor. A steam dryer that is contained in a reactor pressure vessel and dries steam,
A support ring fixed so as to extend horizontally on the outer circumference of the steam dryer,
A support bracket that supports the support ring and is installed horizontally on the inner peripheral surface of the reactor pressure vessel.
Spacer blocks fixed to both sides and the upper side of the support bracket in the circumferential direction,
The spacer block has a structure that is open outward in the radial direction of the support ring so as to suppress the horizontal movement of the support ring on both sides and the upper side in the circumferential direction, and is fixed to the support ring. Seismic block and
The seismic block has
Two through holes are installed, and two bolts that can be passed through the through holes and contact a position adjacent to the lower side of the support bracket, and
Two nuts for tightening the bolts and
A boiling water reactor that is installed under the seismic block and has two stoppers that suppress the rotation of the bolts.

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