JP2994084B2 - Riser tube holding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a riser tube holding device for stably holding a riser tube of a jet pump in a boiling water reactor, and more particularly to a riser tube for exchanging a riser brace and a mixing nozzle. The present invention relates to a riser pipe holding device used for restraining a riser pipe in the work according to (1).

[0002]

2. Description of the Related Art This type of riser tube holding apparatus is provided in a reactor pressure vessel of a boiling water reactor. FIG. 6 is a longitudinal sectional view showing a schematic configuration of a conventional boiling water reactor (hereinafter, referred to as BWR), and reference numeral 1 in the drawing denotes a BWR reactor pressure vessel. In the reactor pressure vessel 1, a coolant 2 also serving as a moderator and a reactor core 3 are accommodated. The core 3 includes a plurality of fuel assemblies (not shown), control rods, and the like, and is housed in a shroud 4.

[0003] The coolant 2 flows upward from the bottom of the reactor pressure vessel 1 through the reactor core 3, and when passing through the reactor core 3, its temperature rises due to the nuclear reaction heat of the reactor core 3, and the water and steam are vaporized. It becomes a liquid two-phase flow state. The coolant 2 in the two-phase flow state flows into the steam separator 4 installed above the reactor core 3, where it is separated into water and steam. The internal steam is introduced into a steam dryer 5 installed above the steam separator 4, and is dried to become dry steam.

[0004] The dry steam is transferred to a steam turbine (not shown) via, for example, four main steam pipes 6 connected to the reactor pressure vessel 1 and is used for power generation. On the other hand, the water separated by the steam separator 4 flows below the reactor core 3 via the downcomer 7 between the shroud 8 and the reactor pressure vessel 1.

[0006] As shown in FIG. 6, a control rod guide tube 9 is provided below the core 3, and control rods are inserted into and removed from the core 3 through the control rod guide tube 9. I will A control rod drive mechanism 10 is provided below the control rod guide tube 9.
The control rod driving mechanism 10 controls the insertion and withdrawal of the control rod into and out of the reactor core 3.

On the other hand, as shown in FIG. 6, a plurality of jet pumps 11 are installed at equal intervals in the circumferential direction in the downcomer section 7, while a recirculation pump (not shown) is provided outside the reactor pressure vessel 1. Will be installed. The recirculation pump, the jet pump 11 and the recirculation pipe constitute a reactor recirculation system. The reactor recirculation system supplies driving water to the jet pump 11 by a recirculation pump, and the coolant 2 is drawn into the lower part of the core by the action of the jet pump 11, and is forcedly circulated into the core 3 from the lower part of the core. I have.

The jet pump 11 has a configuration as shown in FIG. The jet pump 11 has a riser pipe 12 connected to a recirculation pipe. The riser pipe 12 is connected to a recirculation inlet nozzle 13 fixed to the reactor pressure vessel 1 and supplied from the recirculation pump. The coolant 2 is introduced into the riser tube 12. A pair of elbows 1 is provided above the riser pipe 12 via a transition piece 14.
5A and 15B are connected. The pair of elbows 15A and 15B have mixing nozzles 16A and 1B, respectively.
A pair of inlet throats 17A and 17B are connected via 6B. The paired inlet throats 17A and 17B have a pair of diffusers 18A.
And 18B are connected. When jetting the coolant 2 from the mixing nozzles 16A and 16B, the jet pump 11 draws in reactor water from the surroundings. The injected coolant 2 and the entrained reactor water are mixed in the inlet throats 17A and 17B. Thereafter, the hydrostatic head is restored by the diffusers 18A and 18B.

[0008] In this BWR, fluid vibration is generated by the flow of the coolant fed from the recirculation pump. Therefore, the riser pipe 12 has its lower end welded to the recirculation inlet nozzle 13, and the upper part of the riser pipe 12 is fixed to the reactor pressure vessel 1 via the riser brace 20. The inlet throats 17A and 17B of the jet pump 11 have mixing nozzles 16A,
The lower end is mechanically connected to the transition piece 14 via the upper end 16B and the elbows 15A, 15B, while the lower end is inserted into the upper end of the diffusers 18A, 18B, and the middle is fixed to the riser tube 12 as shown in FIG. It is attached to the bracket 21. The diffusers 18A and 18B of the jet pump 11 are fixed to a shroud support 22 welded to the reactor pressure vessel 1.

[0009] The jet pump 11 is used in a severe situation to circulate a coolant as compared with other devices. For this reason, a large load acts on each member of the jet pump 11, and severe stress acts on the riser brace 20, which supports the riser pipe 12 in the middle thereof.

The riser brace 20 has a structure as shown in FIG. That is, the pad 23 is integrally formed on the inner wall of the reactor pressure vessel 1,
Then, the four thin plates 24 are welded. These four thin plates 2
The thin plate 4 has a thickness of, for example, about 10 mm, and the leading ends of the thin plates 24 are connected via a block 25 to be integrated. The riser pipe 12 is welded inside the block 25 (on the side of the reactor pressure vessel 1).

The riser brace 20 is provided on the riser tube 1.
2 suppresses fluid vibrations during the operation of the reactor during the operation of the reactor, and absorbs a difference in thermal expansion between the reactor pressure vessel 1 made of carbon steel and the riser pipe 12 made of austenitic stainless steel. Therefore, during the operation of the reactor, the riser brace 20 is in a deformed state while absorbing the difference in thermal expansion.

In the BWR having the above structure, for example, when an excessive load is applied due to the breakage of the external pipe or the riser brace 20 is damaged, the riser brace 20 has a stress corrosion crack (hereinafter referred to as "Stress Corrosion Crack"). It is assumed that SCC will occur and be damaged. When the riser brace 20 is damaged as described above, the riser brace 20 needs to be replaced.

As a method of replacing the damaged riser brace 20, a method of cutting and removing the riser brace 20 and reattaching a replacement riser brace shown in the specification and drawings of Japanese Patent Application No. 61-283896, for example, is used. Conceivable.

[0014]

By the way, when the riser brace 20 is removed, the riser pipe 12 of the jet pump 11 is supported only by the recirculation inlet nozzle 13, and the nozzle support position is the riser pipe 12. The riser tube 12 is tilted unless the riser tube 12 is held, thereby causing an excessive bending moment to be applied to the nozzle support portion, which may damage the nozzle support portion.

If the replacement riser brace is mounted while the riser pipe 12 is moved, the transition piece 14 and the elbows 15A and 15B will be displaced from each other, thereby causing the jet pump flow. The characteristics may be affected, and if the misalignment increases, the inlet throats 17A and 17B may not be able to be reattached.

For this reason, it is necessary to restrain the displacement of the riser tube 12 during the replacement work of the riser brace 20. As shown in FIGS. 6 and 7, the riser tube 12 and the riser brace 20 need to be restrained. The annular space (downcomer portion) between the furnace pressure vessel 1 and the shroud 8 is an extremely narrow place, and the riser pipe 12, the inlet throats 17A, 17B, and the like are in a forested state. Further, the device for holding the riser pipe 12 may be configured such that the riser pipe 12 is not displaced from the initial position and is locally deformed or damaged at the support position of the riser pipe 12 from the time of installation and restraint to the completion of construction. It is required by design to be able to hold without. Therefore, the operation of restraining the displacement of the riser tube 12 is extremely difficult.

The present invention has been made in consideration of the above-described circumstances, and can stably hold the riser pipe from the initial position without displacing the riser pipe from the initial position, from the time of installation and restraint to the completion of the work. It is an object of the present invention to provide a riser tube holding device that is easy to perform and that does not cause local deformation or damage to the riser tube.

[0018]

According to the present invention, as a means for achieving the above-mentioned object, a riser pipe is installed between a reactor pressure vessel and a shroud, and the rise and fall of the riser pipe is caused by a projecting force on the reactor pressure vessel and the shroud. A base pedestal installed at an arbitrary position in the direction; a pair of divided blocks mounted on the base pedestal and enclosing the riser pipe from both sides; a reactor pressure vessel or shroud installed outside each of these divided blocks And a plurality of support mechanisms for pressing and supporting each of the divided blocks against the riser tube by the reaction force.

[0019]

In the riser tube holding device according to the present invention, after the base gantry is installed at an arbitrary position in the vertical direction of the riser tube,
On this base stand, a pair of divided blocks and a plurality of support mechanisms are installed. Then, by pressing the reactor pressure vessel or the shroud with each support mechanism, each divided block is pressed against the riser pipe by the reaction force. This allows
A riser tube is supported. For this reason, it is possible to stably hold the riser tube with a large holding force without displacing it. Further, since the division block and the support mechanism form a division structure, it can be easily installed by remote control even in a limited narrow space.

[0020]

1 to 4 show a first embodiment of the present invention.
This will be described with reference to FIG.

FIG. 1 shows an example of a riser tube holding device according to the present invention. The same members as those of the conventional riser tube shown in FIGS. In the drawing, reference numeral 12 denotes a riser pipe of the jet pump 11, and this riser pipe 1
2 is disposed in an annular space (downcomer section 7) between the reactor pressure vessel 1 and the shroud 3, and the riser brace 2
0 is supported by the reactor pressure vessel 1. The riser pipe holding device 30 according to the present embodiment is installed at a position below the riser brace 20 and holds the riser pipe 12.

As shown in FIG. 1, the riser pipe holding device 30 includes a base frame 31 and a pair of divided blocks 32A, 32A.
2B, and a pair of support mechanisms 33A, 33B for pressing the divided blocks 32A, 32B against the riser tube 12.

As shown in FIG. 2, the base mount 31 has a base plate 31 having a notch 34 in which the riser tube 12 is disposed.
a and the base plate 31 abutted against the base plate 31a
and the base plates 31a and 31b are formed in two halves from the base plate 31b.
5 are fitted into grooves 36 provided in the base plate 31a, so that the upper surfaces are combined in a state of being flush with each other.

As shown in FIG. 2, two air cylinders 37 are provided on the lower surface side of each of the base plates 31a and 31b so as to face each other. By pressing the pressure vessel 1 and the shroud 8, the base stand 31
2 is fixed at an arbitrary position in the vertical direction. Thus, the load of the riser pipe holding device 30 is supported, and the installation work can be performed smoothly.

A pair of divided blocks 32A, 32B
As shown in FIGS. 1 and 3, each of the divided blocks 32 is formed into a hat-shaped section having a concave surface 38 having the same or similar curvature as the outer diameter of the riser tube 12.
After holding the riser tube 12 from both sides with A and 32B, each divided block 32A and 32B is connected to a pair of support mechanisms 33A and 33A.
The riser pipe 12 is restrained and held by pressing from the outside with 33B.

As shown in FIGS. 1 and 4, each of the support mechanisms 33A and 33B includes a cylinder block 39 disposed outside each of the divided blocks 32A and 32B, and a cylinder (not shown) built in the cylinder block 39. ), And a high-pressure pipe 41 for supplying a working fluid such as water to the cylinder is installed in the cylinder block 39. The high-pressure pipe 41
It is connected to a single fluid pressure source (not shown) via a high pressure hose 42. Then, each of these support mechanisms 33A, 33
B presses each of the divided blocks 32A and 32B against the riser tube 12 by the reaction force by pressing the reactor pressure vessel 1 and the schnaud 8 by extending the pressing piston 40, thereby restraining and supporting the riser tube 12. It has become.

Next, the operation of the present embodiment will be described.

When installing the riser tube holding device 30,
Prior to this installation work, the structure above the shroud 8, which is an item to be carried out in a regular periodic inspection of the reactor, is removed, and a work platform is installed on the reactor pressure vessel 1 and equipment installation space is provided. To secure
The inlet throats 17A and 17B are removed. After that, the riser pipe holding device 30 is installed.

At the time of this installation, first, each of the base plates 31a and 31b having the divided structure is individually suspended in a furnace.
The base plates 31a and 31b are combined with the riser tube 12 arranged in the notch 34. Then, as shown in FIG. 2, the ridge 35 is fitted into the groove 36 and the two base plates 31
The upper surfaces of the a and 31b are combined in a flush state. Therefore, the air cylinder 37 on the lower surface of each base plate 31a, 31b
1 and 3, the air cylinder 37 presses the reactor pressure vessel 1 and the shroud 8 as shown in FIGS. Thus, the base gantry 31 is fixed at an arbitrary position in the vertical direction of the riser tube 12.

Next, as shown in FIG. 3, the divided blocks 32A and 32B are separately suspended and mounted on the base stand 31, and are opposed to both sides thereof via the riser tube 12.

Next, the support mechanisms 33A and 33B are suspended outside the divided blocks 32A and 32B via, for example, an operation rope 43 as shown in FIG. On this occasion,
If the pressing piston 40 is contracted, the support mechanism 3
3A can be suspended as it is, but the support mechanism 33B cannot be suspended as it is because the riser brace 20 is an obstacle. Therefore, in this case, the two operating ropes 43
One of them is suspended from beneath the riser brace 20 to be suspended and operated from both sides of the riser brace 20.

In this way, each of the support mechanisms 33A, 33A
If B is suspended outside each of the divided blocks 32A and 32B, each pressing piston 40 is extended at a low pressure as shown in FIG. Then, the tip of each pressing piston 40 comes into contact with the reactor pressure vessel 1 or the shroud 8,
The divided blocks 32A and 32B are pressed by the reaction force,
The play of each member is absorbed.

When the backlash is absorbed, the pressure of the working fluid is gradually increased, and the riser pipe 12 is pressed uniformly from the reactor pressure vessel 1 side and the shroud 8 side. Thus, the riser tube 12 is restrained and held.

When the work related to the riser pipe 12 is completed, the pressure of the pressing piston 40 is released, and the riser pipe holding device 30 is removed by a procedure reverse to the installation.

Since the base frame 31, the divided blocks 32A and 32B, and the support mechanisms 33A and 33B all have a divided structure, even in a narrow space between the reactor pressure vessel 1 and the shroud 8, It can be suspended and installed by remote control.

Further, since the base frame 31 is supported by the reactor pressure vessel 1 and the shroud 8, a large supporting force is obtained, and the divided blocks 3 mounted on two sides thereof are provided.
2A, 32B and the weight of the support mechanisms 33A, 33B can be stably supported. Therefore, the work of installing the divided blocks 32A and 32B and the support mechanisms 33A and 33B becomes extremely easy.

FIG. 5 shows a second embodiment of the present invention, in which a pair of support mechanisms 33A, 33B in the first embodiment are shown.
Instead of four support mechanisms 53A, 53B, 53C, 53
D, each divided block 32A, 32B is supported by two support mechanisms 53A, 53B and 53C, 53D.

In other respects, the configuration is the same as that of the first embodiment, and the operation is the same.

Thus, each divided block 32A, 32B
To two support mechanisms 53A, 53B and 53C, 53
D, each supporting mechanism 53A,
53B, 53C, 53D, shroud 8 and riser tube 1
It is no longer necessary to mount on the base gantry 31 through the minimum gap between the reactor pressure vessel 2 or the reactor pressure vessel 1 and the riser pipe 12. For this reason, not only a 1,000,000 kW or higher output BWR but also a shroud 8
The present invention can be applied to a small output in which the reactor and the reactor pressure vessel 1 are extremely close, for example, a 500,000 kW type BWR without any trouble.

[0040]

As described above, according to the present invention, the riser pipe can be rigidly and stably restrained and supported during the construction work on the riser pipe, and the riser pipe may be deformed or damaged. Nor. For this reason, construction related to the riser pipe can be performed smoothly and reliably.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a riser pipe holding device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a structure of a base gantry of FIG. 1;

FIG. 3 is a configuration diagram showing a structure of a divided block mounted on a base gantry.

FIG. 4 is a configuration diagram showing a structure of a support mechanism disposed outside each divided block.

FIG. 5 is a configuration diagram showing a riser pipe holding device according to a second embodiment of the present invention.

FIG. 6 is a longitudinal sectional view schematically showing a configuration of a BWR.

FIG. 7 is a configuration diagram showing a structure of a jet pump.

FIG. 8 is a configuration diagram showing a relationship between a riser pipe and a riser brace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 8 Shroud 11 Jet pump 12 Riser pipe 20 Riser brace 30 Riser pipe holding device 31 Base gantry 31a, 31b Base plate 32A, 32B Division block 33A, 33B, 53A, 53B, 53C, 53D Support mechanism 37 Air cylinder 38 Concave surface 39 Cylinder block 40 Pressing piston

Claims (1)

(57) [Claims] 1. A base pedestal installed between a reactor pressure vessel and a shroud, and mounted on an arbitrary position in a vertical direction of a riser pipe by a pressing force on the reactor pressure vessel and the shroud, and mounted on the base pedestal. And a pair of divided blocks that hold the riser pipe from both sides, and are installed outside of each of these divided blocks.By pressing the reactor pressure vessel or shroud, each divided block is moved to the riser pipe by the reaction force. A riser tube holding device, comprising: a plurality of support mechanisms for pressing and supporting.