JPH06174886A - Support structure for stand pipe in nuclear reactor - Google Patents

Abstract

PURPOSE:To reduce loads applied to stand pipes and a shroud head due to vibration by operating a reactor pressure vessel supporting portion with a spring made of shape memory alloy and a bias spring. CONSTITUTION:A spring made of shape memory alloy and a bias spring are used as pressure contact members 20, 23, respectively, and the set temperature for the shape memory function is adjusted to the plant operating temperature. At the startup of the plant the temperature inside a pressure vessel 1 rises to the operating temperature and then the spring made of shape memory alloy is allowed to return to its memory shape by the shape memory function against the resistance of the bias spring so that the members 20, 23 are pressed into contact with the individual stand pipes 7 and the vessel 1 to horizontally support the pipes and the vessel. A stand pipe supporting portion 16 and a pressure vessel supporting portion 17, which support the pipes 7 and the vessel 1 by means of this support pressure, are rigidly connected to each other by a connecting rod 18. Therefore, each of the pipes 7 can be rigidly secured to the vessel 1. At room temperature the shape memory function does not work and the pipes 7 become free. Therefore, vibration of the pipes 7 at an earthquake during normal operation can be reduced, thus reducing loads applied to the pipes 7 and a shroud head 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support structure for a stand pipe in a nuclear reactor for reinforcing a stand pipe erected in a boiling water reactor having an enhanced natural circulation force.

[0002]

2. Description of the Related Art An outline of a conventional boiling water reactor will be described with reference to FIGS. In the figure, reference numeral 1 is a reactor pressure vessel, a reactor core 2 is arranged in the reactor pressure vessel 1, and the reactor core 2 is surrounded by a shroud 3. The shroud 3 holds the core support plate 4 and the upper lattice plate 5, and the shroud head 6 is provided at the upper end portion.

A large number of stand pipes 7 are erected on the upper end of the shroud head 6 as shown in an enlarged view in FIG.
A steam separator 8 is attached to the stand pipe 7. A steam dryer 9 is installed above the steam separator 8. A plurality of internal pumps 10 are attached to the lower part of the reactor pressure vessel 1, and a main steam nozzle is attached to the upper side surface.
11 and the water supply nozzle 12 are attached.

The cooling water flowing from the water supply nozzle 12 into the reactor pressure vessel 1 is guided to the internal pump 10 through the gap with the shroud 3. The cooling water that has passed through the internal pump 10 changes its direction from the lower part of the reactor pressure vessel 1 and becomes an upward flow and flows into the core 2.

The cooling water heated in the core 2 flows into the stand pipe 7 as a gas-liquid two-phase flow, the moisture is removed by the steam separator 8 and the steam is dried by the steam dryer 9 to be the main component. It is discharged from the steam nozzle 11 into the reactor pressure vessel 1.

The above is the main mechanism of steam generation,
Of these, the stand pipe 7 is directly welded 13 to the upper portion of the shroud 3 as shown in FIG. 15, and has a role of drying the steam flow having a high humidity to some extent together with the steam separator 8.

A detailed structure near the stand pipe 7 is shown in FIG.
Starting from FIG. 16, description will be made. The shroud 3 has a cylindrical structure, and a dish-shaped lid called a shroud head 6 is mounted on the shroud 3.

In the shroud head 6, more than 200 circular openings are cut in a 1100 MWe class nuclear reactor, and stand pipes 7 are welded 13 to each of the openings. Therefore, the space between the stand pipes 7 is narrow.

A nuclear power plant located in an area where a relatively large earthquake is expected to occur has a sufficient seismic design for its equipment. The standpipe 7 is no exception, as shown in Fig. 16, the standpipe reinforcement plate.
14 is installed to improve the rigidity of the stand pipe 7. The method of fixing the stand pipe 7 and the stand pipe reinforcing plate 14 is welding as shown in FIG.

Further, as shown in FIG. 15, a stand pipe 7 used in a boiling water reactor having an increased natural circulation force is welded 13 to the shroud head 6 to increase the length of each stand pipe 7 which is conventionally raised. Since it is set longer than this, the weight increases and the load applied during an earthquake etc. also increases. On the other hand, the strength is about the same as the conventional stand pipe.

[0011]

The long stand pipe 7 used in a boiling water reactor having an increased natural circulation force has a free standing structure in which the lower end is directly welded to the shroud head 6 and the upper end is unsupported. . Therefore, during normal operation and during an earthquake, the standpipe 7
An excessive load is applied to the main body and shroud head 3.

On the other hand, when considering the conventional stand pipe reinforcing method, the space between the stand pipes 7 is very narrow, and it is difficult to fix the stand pipe reinforcing plate 14 to the space by welding 13. .

In addition to this, since flaw detection inspection is also required for these welds 13, there is a problem that it becomes more difficult to construct the stand pipe reinforcing plate 14 for the stand pipe 7.

The present invention has been made to solve the above problems, and has a simple structure, is excellent in workability, and is capable of reducing the load due to the vibration applied to the stand pipe and the shroud head. To provide a support structure.

[0015]

According to the present invention, a stand pipe support portion and a reactor pressure vessel support portion are connected by a connecting member, and the stand pipe support portion is arranged in an arrangement state of stand pipes in the reactor pressure vessel. The reactor pressure vessel support comprises: a plurality of tubular support members arranged so as to match; and a pressure contact member that holds the bias spring and the shape memory alloy spring provided on the tubular support member. The section is characterized by comprising a pressure contact member holding a bias spring and a shape memory alloy spring held in pressure contact with the inner surface of the reactor pressure vessel, or an operating member operated by the pressure contact member.

[0016]

The shape memory alloy spring and the bias spring reversibly operate in two directions, that is, a direction close to and a direction away from the stand pipe and the reactor pressure vessel due to the shape memory effect and the spring force.

As a result, when the plant is in operation, the press contact member presses the individual stand pipes and the reactor pressure vessel in a horizontal direction to rigidly support the stand pipe with respect to the reactor pressure vessel. Then, the displacement of the stand pipe at the time of normal operation and at the time of an earthquake is reduced, thereby reducing the load applied to the stand pipe and the shroud head.

On the other hand, when the plant is out of operation, the support force of the stand pipes of the stand pipe support portion and the reactor pressure vessel is released by the spring force of the bias spring, and the stand pipe is placed in the reactor pressure vessel together with the shroud head. It can be easily installed and removed.

[0019]

EXAMPLE A first example of a support structure for a stand pipe in a reactor according to the present invention will be described with reference to FIGS. 1 to 7. 1 shows a boiling water reactor to which the present embodiment is applied, FIG. 2 shows a state in which the present embodiment is attached to the stand pipe in FIG. 1, and FIG. 3 shows a support structure according to the present embodiment. FIG. 4 to FIG. 7 are for explaining the operation of the support structure.

That is, in FIG. 1, reference numeral 1 is a reactor pressure vessel, a reactor core 2 is arranged in the reactor pressure vessel 1, and the reactor core 2 is surrounded by a shroud 3. The shroud 3 includes a core support plate 4 and an upper lattice plate 5
And a shroud head 6 is provided at the upper end. A large number of stand pipes 7 are erected on the upper end of the shroud head 6 as shown in an enlarged view in FIG. 2, and a steam separator 8 is attached to the stand pipes 7.

A steam dryer 9 is installed above the steam separator 8. A plurality of internal pumps 10 are attached to the lower part of the reactor pressure vessel 1, and a main steam nozzle 11 and a water supply nozzle 12 are attached to the upper side surface.

The standpipe support structure 15 shown in FIG. 3 is attached to the standpipe 7. The stand pipe support structure 15 has a stand pipe support 16 and a reactor pressure vessel support 17 in contact with the inner surface of the reactor pressure vessel 1. The stand pipe support 16 and the reactor pressure vessel support 17 are connected by a connecting rod 18 as a connecting member.

The stand pipe supporting portion 16 is composed of a plurality of cylindrical supporting members 19 connected to a connecting rod 18 as a connecting member, and a pressure contact member 20 provided on the side surface of the cylindrical supporting member 19. . The arrangement relationship of the plurality of cylindrical support members 19 connected to the connecting rod 18 is maintained at an interval that matches the arrangement state of the stand pipes 7 standing in the reactor pressure vessel 1.

The pressure contact member 20 provided on the tubular support member 19 is formed by holding a plate-shaped bias spring 21 and a plate-shaped shape memory alloy spring 22.

On the other hand, the reactor pressure vessel supporting portion 17 is connected to the connecting rod 18.
A plate member 24 having a pressure contact member 23 connected to the tip of the plate is attached. The plate member 24 contacts the inner surface of the reactor pressure vessel 1. The press contact member 23 is formed by being held by a bias spring 21 and a shape memory alloy spring 22.

The operation of the shape memory alloy spring 22 and the bias spring 21 will be described with reference to FIGS. 8 and 9. Figure 8
Shows the stress-strain characteristic of a normal metal material, and stainless steel is also included in this. That is, 0 in the figure
When the load is increased from point A to point A, the metallic material first undergoes elastic deformation. At this stage, the strain is reversible, and when the stress decreases, the strain is proportional to it, and the strain also decreases, and the relationship between the stress and the strain corresponds to one to one.

When the stress reaches the point A, the metallic material yields and starts plastic deformation. Although the strain increases with the increase of stress, if the load is decreased from this area toward point 0 (for example, point B in the figure), that is, the load is unloaded, the strain is no longer reversible, and points 0 and A are connected. It decreases parallel to the straight line and reaches point C.
That is, the strain at point C is accumulated inside the material as a permanent strain. In FIG. 8, the vertical axis represents external stress and the horizontal axis represents elongation.

On the other hand, in the shape memory alloy, as shown in FIG. 9, the process from the point A to the point B to the point C is similar to that of an ordinary metal material, but after reaching the point C, heating is performed. Then, the strain returns to 0, and the feature is that no deformation remains. It is sufficient that the heating temperature is about several tens of degrees, and it is possible to recover the shape by blowing hot air, for example, and the surrounding structures will not be adversely affected.

Although the shape memory effect is a one-way irreversible phenomenon, the bias spring 21 is installed in series with the shape memory alloy spring 22, and the bias spring 21 is set at a temperature away from the set temperature of the shape memory effect. It is possible to reversibly operate in two directions by setting the spring force to displace in the direction opposite to the operating direction of the shape memory effect.

A spring made of a shape memory alloy based on the above operating principle.
22 and the bias spring 21 are used as the pressure contact members 20 and 23 to set the shape memory effect set temperature to the operating temperature of the plant.

However, as shown in FIGS. 4 and 6, when the temperature inside the reactor pressure vessel 1 is a room temperature below the operating temperature of the plant when the plant is at rest, etc., the shape memory effect does not work, so the bias spring 21 The spring 22 made of the shape memory alloy is deformed by the spring force, and the pressure contact members 20, 23 are displaced in the direction away from the stand pipe 7 and the reactor pressure vessel 1.

Therefore, the stand pipes 7 are maintained in the state where the supporting action is released from the reactor pressure vessel 1, and the individual stand pipes 7 are in the free standing state. Also,
The stand pipe 7 which is separated from the reactor pressure vessel 1 and is in the free-standing state can be easily removed in the reactor pressure vessel 1 together with the shroud head 6, and can be easily installed on the contrary.

On the other hand, when the plant is operated, the temperature in the reactor pressure vessel 1 gradually rises to the plant operating temperature which is the set temperature of the shape memory effect. From this,
As shown in FIG. 7, the shape memory alloy spring 22 recovers to the memorized shape against the resistance of the bias spring 21 by the shape memory effect, and each stand pipe 7 and the reactor pressure vessel 1
Is supported by pressure contact members 20 and 23 in a horizontal direction. At this time, the horizontal supporting pressure of the pressure contact members 20 and 23 becomes the difference between the restoring force of the shape memory alloy spring 22 and the drag force of the bias spring 21 due to the shape memory effect.

The individual stand pipe support portions 16 and the reactor pressure vessel support portions 17 are connected to the stand pipe 7 by the above-mentioned support pressure.
Also, the standpipe 7 can be rigidly fixed to the reactor pressure vessel 1 by supporting the reactor pressure vessel 1 and rigidly connecting these support parts to each other by the connecting rods 18, and thus, during normal operation and It is possible to reduce the vibration of the stand pipe 7 during an earthquake and reduce the load applied to the stand pipe 7 and the shroud head 6.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 10 shows the reactor pressure vessel support portion, and the stand pipe support portion is the same as that of the first embodiment, so its explanation is omitted.

That is, in FIG. 10, a spring 22 made of a shape memory alloy, which is the same as the bias spring 21 wound in a coil shape, is inserted into the fixing member 25, and the springs 21 and 22 are interlocked by the spring force. The operating metal fitting 26 has been inserted. The fixing member 25 is placed and fixed on one end of the connecting rod 18 as shown in FIGS. 11 and 12. On the inner wall surface of the reactor pressure vessel 1 facing the operating fitting 26, a recess 27 into which one end of the operating fitting 26 projects is formed.

A coil-shaped shape memory alloy spring 22 and a bias spring 21 are used to determine the direction of the restoring force from the plastic region due to the shape memory effect of the shape memory alloy spring 22 and the spring reaction force of the bias spring 21. Match and install.

As the temperature in the reactor pressure vessel 1 fluctuates between the room temperature when the plant is at rest and the plant operating temperature,
The actuating metal fitting 26 is displaced due to the balance between the restoring force of the shape memory alloy spring 22 to the memory shape due to the shape memory effect and the spring force of the bias spring 21.

During operation of the plant, the operating metal fitting 26 is inserted into the recess 27 of the reactor pressure vessel 1 and the stand pipe 7 is fixed to the reactor pressure vessel 1 to reduce the amount of relative displacement in the horizontal direction. Therefore, the load applied to the stand pipe 7 and the shroud head 6 is reduced.

Further, when the plant is stopped, the spring 22 made of the shape memory alloy is deformed by the spring force of the bias spring 21, and the operating metal fitting is
26 is displaced and the stand pipe 7 and the reactor pressure vessel 1
Thus, the stand pipe 7 welded to the shroud head 6 can be easily attached to and detached from the reactor pressure vessel 1.

[0041]

According to the present invention, the stand pipe used in the boiling water reactor having an increased natural circulation force can be indirectly fixed to the reactor pressure vessel, so that the stand can be operated during normal operation and during an earthquake. It is possible to reduce an excessive load applied to the pipe and the shroud head. Further, along with this, it is possible to improve workability and work efficiency during plant construction and periodic inspection.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a reactor pressure vessel and a reactor internal structure of a boiling water reactor to which the present invention is applied.

FIG. 2 is an elevational view showing the first embodiment of the present invention in a state where it is attached to the stand pipe in FIG.

FIG. 3 is a perspective view showing a first embodiment of a stand pipe support structure according to the present invention.

FIG. 4 is a vertical cross-sectional view showing a state in which the stand pipe support portion of the stand pipe support structure in FIG. 3 releases the support of the stand pipe.

5 is a vertical cross-sectional view showing a state in which the stand pipe is supported by the stand pipe support portion of the stand pipe support structure in FIG.

FIG. 6 is a vertical cross-sectional view showing a state in which the support of the reactor pressure vessel is released by the reactor pressure vessel support portion of the stand pipe support structure of the present invention.

7 is a vertical cross-sectional view showing a state in which the reactor pressure vessel is supported by the reactor pressure vessel support portion of the stand pipe support structure in FIG.

FIG. 8 is a characteristic diagram showing a stress-strain relationship of a normal metal material.

FIG. 9 is a characteristic diagram showing a stress-strain relationship of a shape memory alloy.

FIG. 10 is a configuration diagram showing a reactor pressure vessel support portion in a second embodiment of the present invention.

11 is a vertical cross-sectional view showing a state in which the reactor pressure vessel support portion in FIG. 10 is fixed to a connecting rod and the support of the reactor pressure vessel is released.

FIG. 12 is a vertical cross-sectional view showing a state in which the reactor pressure vessel is supported by the reactor pressure vessel support portion in FIG.

FIG. 13 is a conceptual diagram showing a conventional boiling water reactor.

FIG. 14 is an elevation view showing the steam separator, the stand pipe and the shroud head in FIG.

FIG. 15 is an enlarged elevational view showing a joint portion between the stand pipe and the shroud head in FIG.

16 is a conceptual diagram showing a joint portion between a stand pipe and a stand pipe reinforcing plate in FIG.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Reactor core, 3 ... Shroud, 4 ...
Core support plate, 5 ... Upper lattice plate, 6 ... Shroud head,
7 ... Stand pipe, 8 ... Steam separator, 9 ... Steam dryer, 10 ... Internal pump, 11 ... Main steam nozzle, 12 ...
Water supply nozzle, 13… Welding, 14… Stand pipe reinforcement plate, 15
... Stand pipe support structure, 16 ... Stand pipe support, 17 ... Reactor pressure vessel support, 18 ... Connecting rod, 19 ... Cylindrical support member, 20, 23 ... Pressure contact member, 21 ... Bias spring, 22
… Shape memory alloy springs, 24… Plates, 25… Fixing members, 26…
Actuating bracket, 27 ... Recessed part.

Claims (1)

[Claims] 1. A stand pipe support portion and a reactor pressure vessel support portion are connected by a connecting member, and the stand pipe support portion is arranged so as to match the arrangement state of the stand pipes in the reactor pressure vessel. A plurality of tubular support members, and a pressure contact member holding a bias spring and a shape memory alloy spring provided on the tubular support member,
The reactor pressure vessel supporting portion is composed of a pressure contact member in which a bias spring and a shape memory alloy spring are held in pressure contact with the inner surface of the reactor pressure vessel, or an operating member operated by the pressure contact member. A support structure for a standpipe in a nuclear reactor.