Supporting structure of pressure vessel

Abstract

A supporting structure of a pressure vessel is disclosed in which a footing formed integral with the lower edge of the side wall of the pressure vessel is placed within an annular recess formed in the concrete foundation and securely held in position by anchor bolts and concerete blocks are disposed in the annular recess inside the pressure vessel thereby holding firmly the footing in position. Intermediate members are interposed between the concrete foundation and the concrete blocks. When the side wall and hence the footing of the pressure vessel is raised as the internal pressure is increased, only the concrete blocks are raised while the concrete foundation, that is the concrete floor remains in the same position. Therefore no excessive forces are exerted to the concrete foundation or floor so that cracking thereof may be prevented. A portion of a liner support, which is embedded in the concrete foundation within the pressure vessel for supporting thereupon a lining plate, adjacent to the inner wall of the pressure vessel is cut off and is not welded to the lining plate so that the deformation of the lining plate is permitted when the footing is raised. Thus the stress concentration at the joint between the pressure vessel and the lining plate can be prevented, whereby the lining plate may be prevented from being damaged.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a supporting structure of a pressure vessel and especially of a nuclear reactor containment vessel.

In general a nuclear reactor such as a boiling-water type reactor is placed within a reactor containment vessel in order to prevent the release of significant radioactivity to the environment due to the breakdown of the coolant circulation system. Therefore careful consideration has been given in design of a nuclear reactor containment vessel and its supporting structure in order to give the special assurance to the safety of a reactor. However the conventional supporting structure of a reactor containment vessel is not satisfactory to give the maximum assurance to the safety of a nuclear reactor as will be described hereinafter.

The footing of the conventional reactor containment vessel is embedded into a concrete foundation and is securely held in position by means of anchor bolts. Thereafter concrete is placed to embed the anchor belts in the concrete foundation. The edge of a lining plate which is placed upon the concrete floor within the containment vessel is welded to the inner wall of the containment vessel to provide a bottom thereof. Thus, the lining plate provides the air- and water-tightness to prevent the release of radioactivity to the environment. In order to prevent the deformation of the lining plate due to its thermal expansion, it is welded to upper ends of liner supports embedded in the concrete floor within the containment vessel.

When the internal pressure is increased within the containment vessel due to the breakdown of the coolant circulation system of a nuclear reactor contained or in case of an earthquake, the side of the containment vessel is subjected to the tensile forces which act upwardly so that the anchor bolts are forced to elongate with the result of the rise of the footing of the containment vessel. As a result many cracks are propagated in the concrete floor with the result of the dangerous decrease in load bearing capability thereof. The concrete floor or foundation cannot contain the internal pressure or cannot withstand the forces exerted thereto in case of an earthquake once cracks are propagated in the concrete floor or foundation. If the initial tightening loads of the anchor bolts are increased, the elongation of the anchor bolts in case of the increase in internal pressure or in case of an earthquake may be prevented to some extent. However this method cannot overcome the fundamental defects of the conventional supporting structure of a reactor containment vessel because of the creep in the concrete foundation, relaxation of the anchor bolts and the retightening of the anchor bolts which must be carried out periodically.

Furthermore when the footing is raised or floated, the lining plate welded to the inner wall of a containment vessel is subjected to deformation. As a result considerably great stress concentrations are induced in the joint between the lining plate and the inner wall of the containment vessel, and in the worst case the lining will be seriously damaged. The lining plate which is generally thin and is provided for the purpose of preventing the release of radioactivity to the environment must be free from the stress concentration due to the deformation thereof. The internal pressure acting upon the lining plate is received by the concrete foundation below the lining plate.

SUMMARY OF THE INVENTION

In view of the above, one of the objects of the present invention is to provide an improved supporting structure of a pressure vessel capable of giving the maximum safety assurance.

Another object of the present invention is to provide an improved supporting structure of a pressure vessel which may effectively prevent the cracking of a concrete foundation even when a footing of the pressure vessel is somewhat raised.

A further object of the present invention is to provide an improved supporting structure of a pressure vessel capable of preventing the deformation of a lining plate, which forms the bottom of the pressure vessel, and the resulting stress concentration.

Briefly stated, the most important feature of the present invention resides in the fact that the footing of a pressure vessel is placed within a recess formed in a concrete foundation and is securely held in position by means of anchor bolts embedded in the concrete foundation and concrete blocks with intermediate members being interposed between the concrete blocks and the concrete foundation.

Another important feature of the present invention is provision of the stress relieving means which are disposed adjacent to the joint between the edge of the lining plate and the inner wall of the pressure vessel.

The above and other objects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a vertical sectional view of a first embodiment of the present invention applied to a nuclear reactor containment vessel;

FIG. 2 is a fragmentary sectional view, on enlarged scale, illustrating a portion indicated by II in FIG. 1;

FIG. 3 is a cross sectional view taken along the line III--III of FIG. 1;

FIG. 4 is a cross sectional view taken along the line IV--IV of FIG. 3;

FIG. 5 is a cross sectional view taken along the line V--V of FIG. 4; and

FIGS. 6 and 7 are sectional views of second and third embodiments, respectively, of the present invention.

Same reference numerals are used to designate similar parts throughout the figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment, FIGS. 1 - 5

In the embodiments to be described hereinafter, the present invention will be explained as being applied to a boiling-water type nuclear reactor. FIG. 1 shows the supporting structure of a reactor containment vessel generally indicated by numeral 1. The containment vessel 1 has a footing generally indicated by 2 and extended from the lower end of a side wall and anchored securely to a concrete floor or foundation 4 by anchor bolts 5. Between the containment vessel 1 and a concrete shield 7 and close to the concrete floor or foundation 4 is formed a pit 9 into which is filled sand. The pit 9 may be formed between the containment vessel 1 and the concrete foundation 4. Within the containment vessel 1 and upon the concrete floor or foundation 4 is laid a lining plate 11 whose edge is welded to the inner wall of the containment vessel 1. The lining plate 11 is also securely joined to liner supports 13 embedded into the concrete foundation 4. The liner supports are securely fixed to the concrete foundation by anchor bolts 14. The anchor bolts 5 and 14 are anchored to a concrete foundation mat 15 below the concrete floor or foundation 4.

FIG. 2 is a fragmentary sectional view, on enlarged scale, of the containment vessel 1 shown in FIG. 1. The footing 2 of the containment vessel 1 comprises a flange 22 joined to the inner wall of the containment vessel 1, a base or foot plate 20, outer stays 24 joined by welding to the outer wall of the containment vessel 1 and its base plate 20 and inner stays 21 joined by welding to the inner wall of the containment vessel 1, its flange 22 and base plate 20. The flange 22 is connected by a suitable weld joint as at 23 to the inner wall of the containment vessel 1. The base plate 20 is fixed to the lower edge of the side wall of the containment vessel 1 by welding. The footing 2 of the containment vessel 1 is placed in an annular groove 26 in the concrete foundation or floor 4. Alternatively, the footing 2 may be divided into a plurality of sections which may be placed in a plurality of arcuate recesses formed in the concrete floor 4 along the same circle. The base plate 20 is securely held in position by the anchor bolts 5 embedded in the foundation mat 15. After the nuts 6 of the anchor bolts 5 are securely tightened, they are welded to the base plate 20 to prevent the loosening of the nuts 6. The upper surface of the flange 22 substantially flushes with the surface of the concrete floor 4 within the containment vessel 1 when the containment vessel 1 is installed. The anchor bolts 5 are interconnected with each other by an anchor plate 28.

The liner suports 13 are embedded within the concrete floor 4 in the form of a grill as best shown in FIG. 3, and are securely held in position by the anchor bolts 14. Upon the lining supports 13 is laid the lining plate 11 and welded thereto. The edge of the lining plate 11 is welded to the flange 22 jointed to the inner wall of the containment vessel 1. The welded portion between the lining plate 11 and the flange 22 is designated by numeral 25. Because the diameter of the bottom of the containment vessel 1 and hence the diameter of the inner plate 11 is generally large, the lining plate 11 is divided into a plurality of sections in order to facilitate the fabrication and transportation, and the component parts of the lining plate 11 are assembled by welding on the field.

The joint between the liner supports 13 and the lining plate 11 is best shown in FIG. 4. The sections of the lining plate 11 are welded together along the liner support 13 at 33 and also welded thereto. The upper portion of the web of the liner support 13 adjacent to the lining plate is cut off as indicated by 34 (See FIG. 2) a predetermined length at the end of the liner support 13 adjacent to the inner wall of the containment vessel 1. The section of the cut off portion 34 is shown in FIG. 5, in detail.

Referring back to FIG. 2, concrete blocks 36 are disposed between the inner wall of the containment vessel 1 and the inner wall of the annular recess 26 in the concrete floor 4 and between the flange 22 and the base plate 20. An intermediate member 38 made of paper, a thin wooden or metal plate is interposed between the concrete block 36 and the inner wall of the annular recess 26.

The upper surface of the concrete block 36 is made into contact with under surfaces of the flange 22 and the lining plate 11. Alternatively, the length of the flange 22 may be so determined as to cover the whole upper surface of the concrete block 36.

The portion of the annular recess 26 outside of the footing 2 of the containment vessel 1 defines the bottom of the pit portion 9 into which is filled sand. Sand is also filled in the space above the footing 2. Instead of sand, gravel may be used.

When the internal pressure inside the containment vessel 1 increases or in case of an earthquake, the supporting structure of the containment vessel in accordance with the present invention can absorb the external forces. The mode of absorbing the external shocks produced when the internal pressure is increased due to the breakdown of the coolant circulation system (not shown) will be described hereinafter. The pressurized and high temperature steam fills the containment vessel 1 so that the upward forces are exerted to the footing 2. The anchor bolts 5 are exerted with the tension so that they are elongated. Then the footing 2 is moved upwardly as indicated by the two-dot lines in FIG. 2. That is, the undersurface of the base plate 20 is raised to the level indicated by the two-dot lines A so that the concrete blocks 36 are also raised. Since the concrete blocks 36 are separated from the concrete floor 4 by the intermediate members 38, no crack is produced or propagated in the concrete floor 4 even when the concrete blocks 36 are raised. Furthermore sand is filled in the annular recess 26 outside of the containment vessel 1 so that even when the footing 2 is raised no cracking is produced in the concrete floor 4 outside of the containment vessel 1. Sand in the pit portion 9 serves to prevent the stress concentrations upon the wall of the containment vessel 1 close to the footing 2 thereof.

When the footing 2 is raised or floated, the lining plate 11 is subjected to deformation. Since the cut off portions 34 are provided in the liner supports 13, the stress produced in the lining plate 11 may be sufficiently relieved. That is, at the cut off portions 34, the lining plate 11 is free to bend itself. Therefore the lining plate 11 may be prevented from being damaged, and the joint between the lining plate 11 and the flange 22 may be also prevented from being damaged. Thus the air- and water-tightness of the containment vessel 1 may be maintained.

As described hereinbefore, according to the present invention, cracking of the concrete foundation as well as breaking of the lining plate may be prevented so that the safety of the containment vessel may be much improved. Furthermore the step of tightening the anchor bolts may be eliminated.

Second Embodiment, FIG. 6

The second embodiment shown in FIG. 6 is substantially similar in construction to the first embodiment described hereinbefore except additional concrete blocks 40 are placed upon the base plate 20 in the annular recess 26 outside of the containment vessel 1 to prevent the nuts of the anchor bolts 5 from loosening. The concrete blocks 40 are spaced apart from the outer side wall of the annular recess 26 so that sand in the pit portion 9 may fill the space therebetween. The height of the concrete block 40 is selected so as to be greater than the depth of the annular recess 26 to extend into the pit portion 9.

Third Embodiment, FIG. 7

The third embodiment shown in FIG. 7 is substantially similar to the second embodiment shown in FIG. 5 except that the concrete blocks 40 fill the annular recess 26 outside of the containment vessel 1 upon the base plate 20 thereof, thereby forming the bottom of the pit portion 9. Between the outer side wall of the annular recess 26 and the concrete blocks 40 are interposed intermediate members 42 similar to the intermediate members 38 between the inner wall of the annular recess 26 and the inner concrete block 36 inside the containment vessel 1.

So far the present invention has been described as being applied to the nuclear reactor containment vessel, but it is understood that the present invention may be also applied to pressure vessels for storing therein semi-finished products or the like which may produce heat and/or gas, whereby the internal pressure may be increased. It is also understood that various modifications can be effected without departing from the true spirit of the present invention.

Claims

What is claimed is:

1. A supporting structure of a pressure vessel comprising:

footing means secured to a lower edge of a side wall of said pressure vessel for installing the vessel on a concrete foundation,

said footing means including a base plate fixed on the lower edge of the side wall of said pressure vessel and a lining plate support member joined to the inner surface of said side wall so as to project therefrom,

liner support means installed in the concrete foundation inside the side wall of said pressure vessel,

a lining plate mounted on the liner support means and fixed to the lining plate support member at the edge thereof to form the bottom surface of the pressure vessel,

said lining plate and said lining plate support member having thereunder concrete for reinforcing them, and

a first means disposed adjacent to an inner edge of the base plate at an end thereof and to an under surface of the lining plate at the other opposite end thereof for permitting the concrete on the base plate inside the side wall of the vessel to be moved with the base plate, when an unusual pressure increase occurs in the pressure vessel,

said liner support means having means for relieving the stress produced in the lining plate when an unusual pressure increase occurs in the pressure vessel said relieving means being disposed at ends thereof facing said first means.

2. A supporting structure of a pressure vessel as set forth in claim 1, further comprising an annular recess provided on the concrete foundation which reinforces the lining plate for disposing therein said footing means, said first means being disposed on the inner side wall of said annular recess for separating the concrete on the base plate inside the side wall of said pressure vessel from the inner side wall of said annular recess, thereby permitting said concrete to be moved when an unusual pressure increase occurs in the pressure vessel.

3. A supporting structure of a pressure vessel as set forth in claim 2, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.

4. A supporting structure of a pressure vessel as set forth in claim 2 further comprising a pit portion formed between the outer surface of the side wall of said pressure vessel and a concrete structure provided on the concrete foundation outside of the side wall of the pressure vessel in communication with the annular recess outside of the pressure vessel, said pit portion containing filler.

5. A supporting structure of a pressure vessel as set forth in claim 4, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.

6. A supporting structure of a pressure vessel as set forth in claim 4 further comprising concrete blocks fixed on the base plate outside of the pressure vessel and a space formed between said concrete blocks and the outer side wall of the annular recess, said space containing the filler in the pit portion.

7. A supporting structure of a pressure vessel as set forth in claim 6, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.

8. A supporting structure of a pressure vessel as set forth in claim 1 further comprising a pit portion formed between the outer surface of the side wall of said pressure vessel and a concrete structure provided on the concrete foundation outside of the side wall of the pressure vessel, said pit portion containing filler.

9. A supporting structure of a pressure vessel as set forth in claim 8 further comprising concrete blocks fixed on the base plate outside of the pressure vessel and a space formed between the concrete blocks and the inner side wall of the pit portion, said space containing the filler in the pit portion.

10. A supporting structure of a pressure vessel as set forth in claim 9, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.

11. A supporting structure of a pressure vessel as set forth in claim 8, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.

12. A supporting structure of a pressure vessel as set forth in claim 1 further comprising a pit portion formed between the outer surface of the side wall of said pressure vessel and a concrete structure provided on the concrete foundation outside of the side wall of the pressure vessel, and a second means disposed on an inner side surface of the pit portion and adjacent to an outer edge of the base plate at an end thereof, for separating concrete placed on the base plate outside of the pressure vessel from the inner side surface of the pit portion, thereby permitting the concrete to be moved when an unusual pressure increase occurs in the pressure vessel.

13. A supporting structure of a pressure vessel as set forth in claim 12, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.

14. A supporting structure of a pressure vessel as set forth in claim 2 further comprising a second means disposed on an outer side surface of the annular recess and adjacent to an outer edge of the base plate at an end thereof for separating concrete placed on the base plate outside of the pressure vessel from the outer side surface of the annular recess, thereby permitting the concrete to be moved when an unusual presure increase occurs in the pressure vessel.

15. A supporting structure of a pressure vessel as set forth in claim 14, wherein said liner support means are provided with cut off portions at ends thereof facing said first means.