Seismic isolation building and nuclear power facility

Abstract

To provide a seismic isolation building and a nuclear power facility that may secure safety in an earthquake by improving earthquake proof.SOLUTION: A retaining wall 20 is provided to cover an inner side surface of a digging space. A bottom surface member 21 is provided to cover an inner bottom surface of the digging space. A nuclear reactor building 10 receives buoyant force due to fluid 31 poured into a space formed by the retaining wall 20 and the bottom surface member 21 and floats from the bottom surface member 21, and is stored in the space with a clearance 30 filled with fluid between itself and the retaining wall 20. A lower pedestal 12 is fixed to the nuclear reactor building 10 and extends from the nuclear reactor building 10 toward the retaining wall. An upper pedestal 22 is fixed to the retaining wall 20 and extends toward the nuclear reactor building 10 so as to oppose to the lower pedestal 12 at a position of an opposite side to the bottom surface member 21 relative to the lower pedestal 12. A side surface seismic isolation bearing 101 is arranged between the lower pedestal 12 and the upper pedestal 22 and is fixed to each of the lower pedestal 12 and the upper pedestal 22.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a seismically isolated building and a nuclear facility. [Background technology]

[0002] Horizontal seismic isolation structures, which support the entire building with seismic isolation materials such as laminated rubber, have been put into practical use to reduce horizontal loads during earthquakes. In particular, a horizontal seismic isolation structure in which the entire building is supported from under the floor by seismic isolation materials is called a base isolation structure. Base isolation structures are called "base isolation" in English. In a base isolation structure, multiple seismic isolation materials are placed in the seismic isolation layer between the ground and the bottom of the building.

[0003] Since buildings normally support their own weight, they are strong against forces applied in the vertical direction, but weak against forces applied in the horizontal direction. For this reason, horizontal seismic isolation structures such as base isolation structures are required to reduce horizontal earthquake motion while supporting the building's own weight. Therefore, seismic isolation materials such as laminated rubber used in horizontal seismic isolation structures such as base isolation structures are hard in the vertical direction and soft in the horizontal direction, in other words, they have high rigidity in the vertical direction and low rigidity in the horizontal direction. In horizontal seismic isolation structures such as base isolation structures, seismic isolation materials are structured in this way to reduce earthquake damage to buildings.

[0004] In addition, nuclear facilities require strong earthquake safety measures to prevent the loss of safety-critical facilities and radiation exposure to surrounding areas due to earthquakes, and the introduction of seismic isolation structures is being considered for nuclear facilities.

[0005] For example, a technology has been proposed to provide a horizontal seismic isolation structure for the reactor building by installing a seismic isolation support device called a seismic isolation bearing between the upper foundation located at the bottom of the reactor building and the support frame connected to the lower foundation formed on the foundation bedrock. Also, a technology has been proposed to provide three-dimensional seismic isolation for the reactor vessel by combining a foundation seismic isolation structure with a vertical seismic isolation structure using a machine seismic isolation method. Furthermore, while the seismic isolation layer in a horizontal seismic isolation structure is usually an air layer in most cases, a technology has been proposed to reduce the number of seismic isolation members by injecting liquid such as water into the seismic isolation layer, utilizing buoyancy.

[0006] Furthermore, a recent trend in the location of next-generation reactor buildings is the increasing number of proposals for "underground reactor buildings" in which the main part of the reactor is located underground. Underground reactor buildings are structures that take into consideration nuclear security, such as the layout of equipment around the reactor, effective use of the site, and the risk of aircraft collisions. In terms of earthquake countermeasures, nuclear facilities often consider earthquake-resistant structures rather than seismic isolation structures, in the hope that earthquake motion will be smaller the further underground they are located. However, it is expected that the safety of nuclear facilities will be improved by adding seismic isolation structures rather than simply burying them underground. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 56-022833 [Patent Document 2] JP 2010-037789 A [Patent Document 3] JP 2004-027732 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, if a conventional base isolation structure is simply introduced to a next-generation underground reactor building with an underground buried site, a displacement difference occurs between the upper building above the seismic isolation layer on the underside of the building where seismic isolation materials such as laminated rubber are placed and the surrounding ground during an earthquake. The displacement difference here means that the surrounding ground, which is a non-seismic isolation area, displaces during an earthquake, but the upper building, which is a seismic isolation area, does not displace. Therefore, it is required to provide a clearance between the upper building and the surrounding ground because the displacement difference may become large at the boundary between the non-seismic isolation area and the seismic isolation area. If a clearance is provided, earth pressure acts on the inner wall of the surrounding ground, so a retaining wall must be installed to prevent the inner wall from collapsing inward. Since the retaining wall becomes higher in an underground buried site, the wall thickness of the retaining wall must be increased in order to ensure the stability of the excavated space, which may increase costs and cause the structure to become unstable.

[0009] In addition, in the behavior of horizontal seismic isolation structures including base isolation structures during earthquakes, the positions of the lines of action of the "inertial force acting on the center of gravity of the upper building" and the "restoring force acting on the seismic isolation layer" are different in the height direction and do not match, so the upper building rotates. This rotation generates tensile loads on the end seismic isolation members arranged on the underside of the building. When laminated rubber is used as the seismic isolation member, the laminated rubber is strong in compression but weak in tension, so rocking rotation and tensile loads are weak points of the seismic isolation structure. This effect becomes more noticeable the higher the shape of the upper building and the more slender the cross-sectional shape. If the upper building becomes more likely to rotate, the laminated rubber becomes more likely to be subjected to tension, which may cause it to break. Thus, if a base isolation structure is simply introduced to an underground reactor building, it is difficult to improve earthquake resistance and ensure safety during an earthquake.

[0010] The problems related to rocking rotation and tensile load are common to horizontal isolation structures using base isolation structures. That is, even in the technology that combines base isolation structures and vertical isolation structures using mechanical isolation methods, it is assumed that clearances must be provided, and there is a risk of increased costs and structural instability due to the installation of retaining walls. In addition, in the technology that reduces the number of isolation members by utilizing buoyancy by injecting liquid such as water into the isolation layer, a condition is introduced that sets the height at which the liquid is injected low. Specifically, the draft depth is limited to a height at which the fixed load and buoyancy of the floating structure body are the same or the buoyancy is smaller than the fixed load when the floating structure is inserted. Since the draft depth is limited low in this way, it is difficult to reduce the earth pressure on the inner wall from the surrounding ground, and there is a risk of increased costs and structural instability due to the installation of retaining walls. Furthermore, in both technologies, rocking rotation and tensile loads are not reduced, and there is a risk of damage to the isolation members. Therefore, it is difficult to improve earthquake resistance and ensure safety during earthquakes.

[0011] The disclosed technology has been made in consideration of the above, and aims to provide a seismically isolated building and nuclear facility that improves earthquake resistance and ensures safety during earthquakes. [Means for solving the problem]

[0012] In one embodiment of the seismically isolated building and nuclear facility disclosed in the present application, an excavation space is formed by excavating the ground. A retaining wall is provided to cover the inner side surface of the excavation space. A bottom member is provided to cover the inner bottom surface of the excavation space. A building is stored in the space in a state in which the building floats from the bottom member due to buoyancy caused by liquid injected into the space formed by the retaining wall and the bottom member and has a gap filled with the liquid between the building and the retaining wall. A first pedestal is fixed to the building and extends from the building toward the retaining wall. A second pedestal is fixed to the retaining wall and extends from the retaining wall toward the building at a position opposite the bottom member with respect to the first pedestal. A first seismic isolation member is disposed between the first pedestal and the second pedestal and is fixed to each of them. Effect of the Invention

[0013] In one aspect, the present invention can improve earthquake resistance and ensure safety during earthquakes. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a nuclear facility according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the AA cross section of the base-isolated building according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing the forces acting on a reactor building when no sudden external force such as an earthquake acts and only the effect of gravity acts. [Figure 4] FIG. 4 is a diagram showing an example of the relationship between the draft and the static acting force. [Diagram 5] FIG. 5 is a diagram showing an example of the arrangement of side seismic isolation bearings when the lower pedestal is annular. [Figure 6] FIG. 6 is a plan view showing an example of the arrangement of side seismic isolation bearings when the lower pedestal is rectangular. [Figure 7] FIG. 7 is a diagram showing the balance of horizontal earthquake loads in a seismically isolated building. [Figure 8] FIG. 8 is a diagram showing the rocking rotational motion that occurs in a cylindrical building placed in an excavated space and equipped with a conventional base isolation structure. [Figure 9] FIG. 9 is a diagram showing an example of the arrangement of seismic isolation members when a conventional base isolation system is provided for a cylindrical building placed in an excavated space. [Figure 10] FIG. 10 is a diagram showing an example of the arrangement of seismic isolation members when a conventional base isolation system is provided for a building with a rectangular plan that is placed in an excavated space. [Figure 11] Figure 11 shows the risks caused by deformation of the surrounding ground. [Figure 12] FIG. 12 is a diagram illustrating a structure of a retaining wall in a nuclear facility according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, examples of the seismic isolated building and nuclear facility disclosed in the present application will be described in detail with reference to the drawings. Note that the seismic isolated building and nuclear facility disclosed in the present application are not limited to the following examples. EXAMPLES

[0016] (Structure of nuclear facilities and seismically isolated buildings) 1 is a perspective view of a nuclear facility according to an embodiment. The nuclear facility 1 has a reactor building 10 and a retaining wall 20. Although not shown, the nuclear facility 1 is also provided with an auxiliary building in which a cooler that cools steam and turns it back into water is disposed. If the nuclear facility 1 is a power generation facility, a turbine or a generator may be disposed in the auxiliary building. The reactor building 10 and the auxiliary building are connected by a connecting pipe that transports steam and water.

[0017] As shown in Fig. 1, the reactor building 10 is installed in an excavated space obtained by excavating the ground including the location where the reactor building 10 is to be placed. The surrounding ground 2 is the ground surrounding the excavated space obtained by excavating the ground. Furthermore, a retaining wall 20 is provided on the inner wall of the excavated space. A clearance 30 exists between the reactor building 10 and the retaining wall 20. A liquid such as water is injected into the clearance 30.

[0018] Fig. 2 is a schematic diagram of the AA cross section in Fig. 1. Next, the details of the installation state of the reactor building 10 will be described with reference to Fig. 2. The building having a seismic isolation structure including the reactor building 10, the retaining wall 20, the bottom member 21, and the clearance 30 shown in Fig. 2 is a "seismically isolated building."

[0019] In the seismically isolated building, the retaining wall 20, the bottom member 21, and the upper pedestal 22 have an earthquake response similar to that of the surrounding ground 2. On the other hand, the lower pedestal 12, the bottom seismic isolation bearing 102, the reactor building 10, and the reactor pressure vessel 11 are seismically isolated areas that are structurally insulated from the surrounding ground 2 by the side seismic isolation bearing 101 and the clearance 30, which are the boundary areas.

[0020] In the following, the direction of gravity, i.e. the direction perpendicular to the Earth's surface toward the center of the Earth, will be referred to as "down." The opposite direction to the direction of gravity, i.e. the direction perpendicular to the Earth's surface from the center of the Earth toward the Earth's surface, will be referred to as "up." The direction parallel to the horizontal plane perpendicular to the direction of gravity will be referred to as "horizontal."

[0021] As described above, the ground including the location where the reactor building 10 is to be placed is excavated downward to a size large enough to accommodate the reactor building 10, forming an excavated space. For example, if the reactor building 10 is cylindrical, the ground is excavated so that the excavated space becomes a cylinder having a diameter larger than the diameter of the reactor building 10. However, as long as the reactor building 10 can be accommodated in the excavated space, the shape does not have to match the horizontal cross section of the reactor building 10.

[0022] Furthermore, in order to float the reactor building 10 in the excavated space by liquid, the excavated space has a depth sufficient to store liquid that provides buoyancy for floating the reactor building 10. For example, if the specific gravity of the entire reactor building 10 relative to water is 0.8, it is preferable that the excavated space has a depth sufficient to allow 80% or more of the reactor building 10 to be submerged.

[0023] The retaining wall 20 is arranged so as to cover the inner wall of the excavation space. The retaining wall 20 arranged on the inner wall is subjected to earth pressure from the surrounding ground 2 toward the excavation space. The retaining wall 20 holds down the surrounding ground 2 from the excavation space toward the surrounding ground 2 so as not to collapse into the excavation space in which the reactor building 10 is arranged due to the earth pressure. Here, since the excavation space becomes deeper according to the size of the reactor building 10, the retaining wall 20 receives greater earth pressure from the surrounding ground 2 as the height of the reactor building 10 increases. Therefore, the retaining wall 20 is provided with a thickness to prevent it from collapsing into the excavation space. However, as described later, the retaining wall 20 receives pressure from the excavated space toward the surrounding ground 2 due to water pressure, so it does not need to be thick enough to withstand the entire earth pressure of the surrounding ground 2.

[0024] A bottom surface member 21 is disposed so as to cover the bottom surface, which is the lowest surface of the excavated space. The bottom surface member 21 is joined to the retaining wall 20 so as to prevent the liquid 31 stored inside from leaking out.

[0025] However, the watertightness of the retaining wall 20 and the bottom member 21 does not need to be so high, and cracks may be tolerated. This is because it is believed that groundwater often exists in the surrounding ground 2, and even if cracks occur in the retaining wall 20 or the bottom member 21, the internal and external water pressures will be steadily balanced and stable.

[0026] The upper pedestal 22 is a flat plate-like member extending horizontally from the retaining wall 20 toward the space formed by the retaining wall 20 and the bottom member 21. In other words, the upper pedestal 22 extends horizontally toward the reactor building 10 when the reactor building 10 is disposed in the space formed by the retaining wall 20 and the reactor building 10. The upper pedestal 22 is joined and fixed to the retaining wall 20. The upper pedestal 22 has a length extending toward the reactor building 10 that does not reach the reactor building 10.

[0027] The upper pedestal 22 in this embodiment is provided all around so as to surround the entire periphery of the inner wall of the retaining wall 20. In this embodiment, the upper pedestal 22 is formed to have an inner periphery having the same shape as the horizontal cross section of the space formed by the retaining wall 20. For example, when the retaining wall 20 forms a cylindrical space, the upper pedestal 22 has an annular shape with an opening facing in the vertical direction, and the outer periphery is joined to the inner wall of the retaining wall 20. Furthermore, multiple upper pedestals 22 are arranged at different positions in the vertical direction to form multiple layers. This upper pedestal 22 is an example of a "second pedestal."

[0028] The reactor building 10 is disposed in a space formed by a retaining wall 20 and a bottom member 21. Moreover, the reactor building 10 is disposed so that a clearance 30 exists between the retaining wall 20 and the reactor building 10. The reactor building 10 houses, for example, a reactor pressure vessel 11 and the like therein.

[0029] The lower pedestal 12 is provided on the side surface of the reactor building 10 that faces the retaining wall 20, and is a flat plate-like member extending toward the retaining wall 20. The lower pedestal 12 is joined and fixed to the side surface of the reactor building 10. The lower pedestal 12 has a length that extends toward the retaining wall 20 but does not reach the retaining wall 20.

[0030] The lower pedestal 12 according to this embodiment is provided all around the side of the reactor building 10 so as to surround the entire periphery. In addition, in this embodiment, the lower pedestal 12 is formed in the same shape as the upper pedestal 22. For example, when the upper pedestal 22 has a circular ring shape, the lower pedestal 12 also has a circular ring shape with an opening facing the vertical direction, and the inner periphery is joined to the side of the reactor building 10. Furthermore, a plurality of lower pedestals 12 are also arranged at different positions in the vertical direction to form multiple layers. Specifically, the lower pedestals 12 are provided in the same number as the upper pedestals 22, at positions facing upward. The lower pedestals 12 are an example of a "first pedestal."

[0031] Here, the number of layers formed by the upper pedestal 22 and the lower pedestal 12 is preferably determined according to the number of side seismic isolation bearings 101 used to provide a seismic isolation structure to the reactor building 10. Moreover, the upper pedestal 22 and the lower pedestal 12 only need to be located at opposing positions capable of sandwiching the side seismic isolation bearings 101, and may be placed above and below the side seismic isolation bearings 101 as members having a width capable of sandwiching the side seismic isolation bearings 101 if they have sufficient strength.

[0032] The side seismic isolation bearing 101 is disposed between the lower pedestal 12 and the upper pedestal 22, with its lower surface joined to the lower pedestal 12 and its upper surface joined to the upper pedestal 22. The side seismic isolation bearing 101 is a seismic isolation member that absorbs the horizontal force generated by the difference in displacement between the lower pedestal 12 and the upper pedestal 22 when an earthquake occurs, thereby making it difficult for the earthquake vibrations to be transmitted to the reactor building 10.

[0033] The target for arranging the side seismic isolation bearing 101 is preferably a facility such as a power plant where it is not necessary to provide windows in the outer wall, called the outer wall, of the reactor building 10. In general buildings, it is normal to provide windows for residential use in the outer wall, and it is difficult to apply the seismic isolation structure in which the side seismic isolation bearing 101 according to this embodiment is arranged. Therefore, the seismic isolation structure according to this embodiment is suitable mainly as a seismic isolation structure for non-residential buildings such as the nuclear facility 1.

[0034] Furthermore, the combinations of the lower pedestal 12, the upper pedestal 22, and the side seismic isolation bearings 101 are arranged in multiple layers at different positions in the vertical direction. The vertical positions of each of these combinations are determined so that the center of gravity of the reactor building 10 and the center of rigidity of the reactor building 10 coincide with each other when an earthquake occurs. This makes it possible to suppress the rotational rocking motion of the entire reactor building 10.

[0035] A plurality of bottom seismic isolation bearings 102 are provided on the bottom surface facing the bottom member 21 of the reactor building 10. The bottom seismic isolation bearings 102 support the reactor building 10 on the bottom member 21 when the reactor building 10 is installed in a seismically isolated building. In this embodiment, the bottom seismic isolation bearings 102 are seismic isolation members, but may be simply a foundation without a seismic isolation function.

[0036] The bottom seismic isolation bearings 102 may be removed because the liquid 31 is injected into the clearance 30 and the reactor building 10 is held in the liquid 31 in a state where it is raised above the bottom member 21 due to buoyancy. However, by attaching the bottom seismic isolation bearings 102 to the bottom of the reactor building 10, in cases where the liquid 31 decreases and sufficient buoyancy cannot be secured, etc., the bottom seismic isolation bearings 102 can provide support and improve the seismic isolation performance.

[0037] The construction sequence up to this point is, for example, as follows: The reactor building 10 with the bottom seismic isolation bearings 102 arranged on its bottom surface is inserted into the space formed by the retaining wall 20 and the bottom member 21, and is placed in a state in which it is supported by the bottom member 21 via the bottom seismic isolation bearings 102. Next, starting from the bottom layer, the lower pedestal 12 is joined to the reactor building 10, then the side seismic isolation bearings 101 are joined to the lower pedestal 12, and then the upper pedestal 22 is joined to the side seismic isolation bearings 101 and to the retaining wall 20. The combination of the lower pedestal 12, the side seismic isolation bearings 101, and the upper pedestal 22 is placed to form a predetermined number of layers.

[0038] The clearance 30 is a gap provided so that if a displacement difference occurs between the reactor building 10 and the retaining wall 20 due to the seismic isolation structure during an earthquake, the reactor building 10 will not collide with the retaining wall 20 due to the displacement difference.

[0039] During an earthquake, the reactor building 10 moves horizontally within the range of extension of the side isolation bearings 101 due to the displacement difference with respect to the surrounding ground 2. In other words, the clearance 30 should be a distance that ensures that the lower pedestal 12 does not come into contact with the inner wall of the retaining wall 20 and that the upper pedestal 22 does not come into contact with the side of the reactor building 10 when the side isolation bearings 101 are fully extended.

[0040] A liquid 31 such as water is injected into the clearance 30. The liquid 31 may be something other than water, for example, heavy muddy water. The liquid 31 injected into the clearance 30 exerts buoyancy on the reactor building 10, causing the reactor building 10 to float up from the bottom member 21. That is, the reactor building 10 receives a force from below due to the buoyancy of the liquid 31, and the side seismic isolation bearing 101 receives a force pushing the lower pedestal 12 downward from above, and stops in a state where it floats up from the bottom member 21 in the water.

[0041] FIG. 3 is a diagram showing the force that the reactor building receives when only the effect of gravity acts without the action of a sudden external force such as an earthquake. The reactor building 10 receives its own weight P0 downward due to gravity. The reactor building 10 receives bottom buoyancy P1 from the liquid 31 from the bottom to the top. The bottom buoyancy P1 is a force larger than the own weight P0 of the reactor building 10. Therefore, the reactor building 10 moves upward due to the bottom buoyancy P1. As the reactor building 10 moves upward, the lower pedestal 12 joined to the reactor building 10 also moves upward. Since the upper pedestal 22 is fixed by being joined to the retaining wall 20, when the lower pedestal 12 moves upward, it receives interference from the side seismic isolation bearing 101 provided between the lower pedestal 22 and the upper pedestal 22. The side seismic isolation bearing 101 receives an upward load from the lower pedestal 12 and a compressive force acts on the side seismic isolation bearing 101. The lower pedestal 12 receives a side reaction force P2 corresponding to the compressive force from the side isolation bearings 101. All lower pedestals 12 on which the side isolation bearings 101 are arranged receive the side reaction force P2. Then, the sum of the self-weight P0 and the total of the side reaction forces P2 balances the bottom buoyancy P1, so that the reactor building 10 comes to rest in the liquid 31, floating above the bottom member 21.

[0042] The forces acting on the reactor building 10 are, because the bottom surface is completely raised, no force is transmitted from the bottom member 21 to the reactor building 10, and are the bottom buoyancy P1 due to the water, the weight P0 of the reactor building 10, and the side reaction force P2 from the side seismic isolation bearings 101. The buoyancy acting on the reactor building 10 acts not only on the bottom surface but also on the underside of the lower pedestal 12, but since the bottom buoyancy P1 is overwhelmingly large and the buoyancy of the lower pedestal 12 is expected to be negligibly small, it is ignored in this embodiment.

[0043] For example, the total weight of the reactor building 10 is 66,400 tf, and the volume is 41 m length x 41 m width x 49 m height = 82.369 m 3 Consider the case where the above-mentioned condition is satisfied. Figure 4 is a diagram showing an example of the relationship between the draft depth and the static acting forces. The static acting forces include the weight P0 of the reactor building 10, the bottom buoyancy P1, and the side reaction force P2. In Table 50, the total amount of the side reaction force P2 is simply represented as P2.

[0044] As shown in Table 50 in Fig. 4, when the draft is 39.5 m, the bottom buoyancy P1 balances with the weight of the reactor building 10, and the total amount of side reaction force P2 becomes zero. In other words, if the draft is made higher than 39.5 m, the reactor building 10 will have a seismic isolation structure in a floating state. However, if the draft cannot be set to 39.5 m or more, the total amount of side reaction force P2 will be a positive value, and the bottom seismic isolation bearing 102 will bear part of the weight of the reactor building 10. In other words, range 51 in Table 50 is the applicable range of the seismic isolation structure in a floating state of the reactor building 10 according to this embodiment.

[0045] In Table 50, the weight reaction force ratio P2 / P0 indicates the proportion of the weight of the reactor building 10 that the side seismic isolation bearing 101 bears. For example, when the draft is 39.5 m, the bottom buoyancy P1 is equal to the weight of the reactor building 10, so the side seismic isolation bearing 101 does not bear the weight of the reactor building 10, and the weight reaction force ratio is 0%. Also, for example, when the draft is 49.0 m, that is, when the liquid 31 is poured up to the building height, the bottom buoyancy P1 becomes larger than the weight P0, and the side seismic isolation bearing 101 supports an upward reaction force of P0-P1, that is, -15969tf. In this case, the weight reaction ratio is -24.0%, and considering that the bottom isolation bearings bear the entire weight because there is no bottom buoyancy in the base isolation structure, and the weight reaction ratio can be considered to be +100%, the total number of the base isolation bearings of the present invention can be said to be 24% of the number of the base isolation method, assuming that the same specifications of the base isolation bearings are used for the sake of simplicity. In other words, in contrast to the base isolation method, in which the total number of the bottom isolation bearings must be set to balance the weight, in the base isolation method of this embodiment, the total number of the side isolation bearings 101 is set to balance the difference between the buoyancy and the weight, and since the difference can be adjusted, the weight reaction ratio can be set smaller than that of the base isolation method. This makes it easier to plan the placement of the bottom isolation bearings 102, and thus increases the possibility of remodeling in case of an increase in the design load and the redundancy for changes in the earthquake load. Also, considering that bottom buoyancy does not have a horizontal restoring force, i.e., horizontal rigidity, reducing the total number of side seismic isolation bearings 101 leads to a reduction in the horizontal rigidity of the entire seismic isolation bearings, which makes it possible to lengthen the period of the seismic isolation structure and cut out more of the short-period components of seismic motion, thereby having the advantage of enhancing the seismic isolation effect.

[0046] Under these conditions, the reactor building 10 has an average density of 0.806 tf / m3 by simple calculation. 3 This average density is approximately the density of water, 1 tf / m 3is approximately 80% of the total. Therefore, the ratio of the acting forces is roughly estimated as follows. If the draft is set to 49 m, the same as the height of the reactor building 10, then the total of the upper building weight: bottom buoyancy P1: side reaction force P2 = 0.8:1:0.2. Therefore, in the nuclear facility 1 according to this embodiment, it is considered that the number of seismic isolation members can be reduced by up to approximately 24% compared to the conventional base isolation structure, in other words, the number can be reduced by 74%.

[0047] If the draft depth is set to approximately 80% of the height of the reactor building 10, i.e., 80.61285%, the volume of the reactor building 10 in the liquid 31 is 41m long x 41m wide x 39.5m high = 66.400m 3 In this case, the average density is 1.0 tf / m3 by simple calculation, which is equal to the density of water. Under this condition, the weight of the reactor building 10 and the bottom buoyancy P1 are balanced as described above, and the side reaction force P2 becomes zero.

[0048] Furthermore, if the draft is lowered to 80% or less of the height of the reactor building 10, the side reaction force P2 will be directed upward, and a tensile load will act on the side seismic isolation bearing 101. Considering that seismic isolation members such as laminated rubber are weak against tensile loads, it is preferable not to lower the draft to a state where the weight and buoyancy are balanced. In order to prevent the side seismic isolation bearing 101 from being subjected to a tensile load, it is preferable to set the draft height in advance to a height at which the weight of the reactor building 10 and the bottom buoyancy P1 are balanced or higher. In the unlikely event that the draft is lowered and the buoyancy is insufficient, it is preferable that the side seismic isolation bearing 101 is not fixed to the lower pedestal 12 or the upper pedestal 22 in the vertical direction, but is joined to the side seismic isolation bearing 101 so as not to transmit a tensile force to the side seismic isolation bearing 101.

[0049] Fig. 5 is a diagram showing an example of the arrangement of seismic isolation side bearings when the lower pedestal is annular. In Fig. 5, the upper pedestal 22 is omitted so that the seismic isolation side bearing 101 can be seen. The dotted line 221 indicates the end of the upper pedestal 22. In order to stably support the reactor building 10, it is preferable to arrange at least three seismic isolation side bearings 101A to 101C in a balanced manner on the lower pedestal 12 on each floor so that they are evenly spaced around the circumference, as shown in Fig. 5.

[0050] Here, as the number of side seismic isolation bearings 101 per story increases, the load distribution and stress distribution of the lower pedestal 12 and the reactor building 10 approach a uniform spatial distribution, and local destruction due to stress concentration can be prevented. Therefore, from the viewpoint of local destruction due to stress concentration, the more the number of side seismic isolation bearings 101 per story, the better. Therefore, the number of side seismic isolation bearings 101 per story is preferably determined taking into consideration the size of the space to be provided and local destruction due to stress concentration.

[0051] Fig. 6 is a plan view showing an example of the arrangement of side seismic isolation bearings when the lower pedestal is rectangular. In this case as well, in order to stably support the reactor building 10, it is preferable to arrange at least four side seismic isolation bearings 101A to 101D on the lower pedestal 12 of each story, one at the center of each side of the rectangle, as shown in Fig. 6. In this case as well, from the viewpoint of localized destruction due to stress concentration, the more side seismic isolation bearings 101 per story, the better.

[0052] (effect) Next, some effects obtained by the nuclear facility 1 according to this embodiment will be described. The first effect is as follows. Comparing base isolation with the base isolation structure in the reactor building 10 according to this embodiment, when a conventional base isolation is provided for a building placed in an excavated space, the retaining wall 20 receives all of the earth pressure from the surrounding ground 2. In contrast, in the base isolation structure in the reactor building 10 according to this embodiment, water pressure is generated on the inside of the retaining wall 20 in the direction toward the surrounding ground 2, and this water pressure can offset the earth pressure received from the outside. Considering the density ratio as a simple estimate, the density of the ground is estimated to be 2.8 t / m at most.3 Since the above condition is satisfied, the earth pressure can be reduced to at least about 2 / 3. Therefore, the retaining wall 20 can be made thinner by the amount of the reduced earth pressure, which ensures ease of construction and reduces costs.

[0053] The second effect is as follows. Fig. 7 is a diagram showing the balance of horizontal earthquake loads in a seismically isolated building. Fig. 8 is a diagram showing the rocking rotation motion that occurs in a cylindrical building placed in an excavated space with a conventional base isolation structure.

[0054] In the seismic isolated building according to this embodiment, the horizontal load is balanced between the horizontal restoring force P3 caused by the horizontal deformation of the side seismic isolation bearings 101 and the inertial force acting on each part of the reactor building 10. The inertial force of the reactor building 10 is replaced with the sum P5 of the inertial forces acting on one point at the center of gravity. Meanwhile, each horizontal restoring force P3 caused by the horizontal deformation of each side seismic isolation bearing 101 is also replaced with the sum P4 of the restoring forces acting on one point at the center of rigidity.

[0055] In the seismic isolation building according to this embodiment, the height of the rigidity center can be changed by adjusting the position and rigidity of each of the side seismic isolation bearings 101. In the seismic isolation structure of the reactor building 10 according to this embodiment, the height of the rigidity center can be adjusted to the height of the center of gravity by adjusting the position and rigidity of each of the side seismic isolation bearings 101. If the positions of the rigidity center and the center of gravity are adjusted to coincide with each other, the positions of the sum of inertia forces P5 and the sum of restoring forces P4 will coincide with each other. As a result, in the seismic isolation building according to this embodiment, the rocking rotational motion that occurs in a base-isolated building can be suppressed, and the occurrence of tensile load on the side seismic isolation bearings 101 can be avoided.

[0056] In contrast, in a structure with a conventional base isolation, the vertical positions of the center of gravity and the center of rigidity are displaced during an earthquake. In that case, as shown in FIG. 8, the inertial force P11 of the center of gravity and the sum P12 of the restoring forces of the rigidity center are generated at different positions in the vertical direction. When such a force acts, a rocking rotational force P13 is generated around the center of gravity. The rocking rotational force P13 lifts the bottom end of the reactor building 10 on the opposite side to the direction of the inertial force P11 of the center of gravity. In this case, for example, the tensile force acting on the seismic isolation members 103C to 103F in FIG. 8 is smaller than the respective durability, so no rupture occurs, but the seismic isolation members 103A and 103B may be subjected to a large tensile force and may rupture. If the seismic isolation members 103A and 103B rupture, the appropriate seismic isolation structure cannot be maintained, resulting in a dangerous state. In this way, the seismic isolation building according to this embodiment can improve safety compared to a structure with a conventional base isolation.

[0057] The third effect is as follows: At the nuclear facility 1, it is necessary to estimate the risk of an aircraft collision as a countermeasure against terrorism. As for this risk, it is desirable to consider not only the risk of the load at the time of an aircraft collision, but also the risk when aircraft fuel flows into the seismic isolation layer where the seismic isolation members are arranged.

[0058] In relation to this, if a conventional base isolation system is provided for a building to be placed in the excavated space, there is a concern that a fire may break out due to fuel flowing into the clearance 30. In contrast, in the nuclear facility 1 having the seismic isolation structure according to this embodiment, the clearance 30 is filled with liquid 31, so that the flow of aircraft fuel into the clearance 30 is suppressed. This makes it possible to prevent deterioration or damage caused by high heat being applied to the side isolation bearings 101, and to maintain earthquake resistance.

[0059] The fourth effect is as follows. The concept of "existing non-conformity" that is acceptable for general architecture does not apply to the nuclear facility 1 and the reactor building 10, and it is required to ensure a state that conforms to regulations and standards based on the latest knowledge. For example, if the seismic load is increased based on the latest knowledge, it is necessary to improve the structure of the nuclear facility 1 and the reactor building 10 to be compatible with the increased seismic load. For this reason, it is desirable to leave space in consideration of expandability when designing and constructing the nuclear facility 1.

[0060] When a conventional base isolation is provided for a building to be placed in an excavated space, a seismic isolation member such as laminated rubber is laid out in the base, and the seismic isolation member is placed directly below the vertical support member of the upper building. A large number of seismic isolation members are placed in order to support the entire weight of the building with the seismic isolation members placed in the base. For this reason, the seismic isolation members are already placed in most of the positions that meet the placement conditions for the seismic isolation members at the time of new construction. Even if the design earthquake motion is increased due to new findings, it is difficult to secure the space for adding the seismic isolation members or the space for installation work. In contrast, in the nuclear facility 1 having the seismic isolation structure according to this embodiment, the number of seismic isolation bearings can be suppressed to about 1 / 4 of the conventional base isolation method. Therefore, sufficient extra space can be secured for the placement space of the side seismic isolation bearings 101. If the design earthquake motion is updated and the building needs to be remodeled, the secured extra space can be used to consider adding or replacing new side seismic isolation bearings 101. In this way, in the nuclear facility 1 having the seismic isolation structure according to this embodiment, it is possible to provide redundancy in design and modification.

[0061] FIG. 9 is a diagram showing an example of the arrangement of seismic isolation members when a cylindrical building to be placed in an excavated space is provided with a conventional base isolation. Here, an explanation is given for a case where the annular lower pedestal 12 has five layers in the vertical direction. In the case of five layers, if four side seismic isolation bearings 101 are arranged in each layer, a total of 20 side seismic isolation bearings 101 are arranged. Here, the number of side seismic isolation bearings 101 arranged in each of the five layers, four per layer, is the number of side seismic isolation bearings 101 when the draft depth is 49 m. The number of seismic isolation members when a building to be placed in an excavated space equivalent to this case is provided with a conventional base isolation is 20 / 24%=84. When the base isolation structure has 84 seismic isolation members, for example, the seismic isolation members 103 are arranged as shown in FIG. 9.

[0062] Fig. 10 is a diagram showing an example of the arrangement of seismic isolation members when a conventional base isolation is provided for a building with a rectangular plane to be placed in an excavated space. Here, if the lower pedestal 12 has five layers and side seismic isolation bearings 101 are arranged as shown in Fig. 6, a total of 20 side seismic isolation bearings 101 will be arranged. Calculating in the same way as for the cylindrical case, the number of seismic isolation members required when a conventional base isolation is provided for a building to be placed in an excavated space equivalent to this case is 84. When the base isolation structure has 84 seismic isolation members, for example, seismic isolation members 103 are arranged as shown in Fig. 10.

[0063] Thus, when the lower pedestal 12 is annular, it is clear that there is more space when four side isolation bearings 101 are arranged on one floor than when the arrangement of the seismic isolation members 103 shown in Fig. 9. Also, when the lower pedestal 12 is rectangular, it is clear that there is more space when the side isolation bearings 101 are arranged as shown in Fig. 6 than when the arrangement of the seismic isolation members 103 shown in Fig. 10. Thus, regardless of the shape of the lower pedestal 12, the nuclear facility 1 according to this embodiment can reduce the number of seismic isolation members compared to when the conventional base isolation is provided in a square pillar building placed in an excavated space, and it becomes possible to provide redundancy in design and modification. EXAMPLES

[0064] Next, a description will be given of Example 2. The nuclear facility 1 according to this example differs from Example 1 in that the risk of deformation of the surrounding ground 2 is reduced. Fig. 11 is a diagram showing the risk caused by deformation of the surrounding ground.

[0065] In an underground-embedded seismic isolation building, earth pressure acts on the retaining wall 20 and the bottom member 21 from the surrounding ground 2. Depending on the condition of groundwater and cracks in the rock, the surrounding ground 2 may be displaced little by little. For example, as shown in FIG. 11, when the rock quality and physical properties of the upper ground 2A and the lower ground 2B of the surrounding ground 2 are different and the boundary layer is inclined, it is assumed that the upper ground 2A will move as shown by the arrow Q1, as shown in FIG. 11, and the retaining wall 20 will be cracked or deformed due to the action of the surrounding ground 2. In consideration of such events, in the design and construction of the reactor building 10, the strength of the building is ensured by increasing the wall thickness, but it is desirable to reduce such risks as much as possible.

[0066] FIG. 12 is a diagram showing the structure of a retaining wall in a nuclear facility according to the second embodiment. The retaining wall 20 according to the present embodiment is constructed by stacking a plurality of retaining wall blocks 23 in a row and joining adjacent retaining wall blocks 23 with joints 24. When a force of a predetermined value or more is applied from the surrounding ground 2, the joints 24 deform so as to move the retaining wall blocks 23 in the horizontal direction. This allows the retaining wall 20 to withstand both static and dynamic loads from the surrounding ground 2, and prevents the load from the surrounding ground 2 from being transmitted to the reactor building 10. In this case, it is preferable to use a shear key in the joints 24 to suppress excessive sliding deformation. The shear key is a joining method in which unevenness is provided at the joints of the retaining wall blocks 23 to suppress misalignment that occurs at the joints.

[0067] For example, a case will be described where the upper ground 2A is displaced in the direction of arrow Q1 as shown in Fig. 12. In this case, the joint 24 located at the boundary between the upper ground 2A and the lower ground 2B deforms, displacing the upper retaining wall block 23 in the direction pushed by arrow Q1, thereby absorbing the load caused by the deformation of the surrounding ground 2. In addition, as the retaining wall block 23 is displaced, the side seismic isolation bearing 101 connected to the upper pedestal 22 extending from the retaining wall block 23 also deforms, releasing the force. This allows the reactor building 10 to avoid being affected by the load caused by the deformation of the surrounding ground 2.

[0068] As explained above, in the seismically isolated building according to this embodiment, the retaining wall is divided into a number of retaining wall blocks, and adjacent retaining wall blocks are joined together with joints. This allows the retaining wall to deform and absorb the load even when a load is applied due to deformation of the surrounding ground, and protects the reactor building from the effects of the load due to deformation of the surrounding ground. This makes it possible to further improve the safety of the seismically isolated building and the nuclear facility that uses the seismically isolated building. [Explanation of symbols]

[0069] 1. Nuclear Facilities 2 Surrounding ground 2A Upper ground 2B Subsoil 10 Reactor Building 11 Reactor Pressure Vessel 12 Lower pedestal 20 Retaining Wall 21 Bottom member 22 Upper Pedestal 23 Retaining wall blocks 24 Joint 30 Clearance 31 liquid 101 Side seismic isolation bearing 102 Bottom seismic isolation bearing

Claims

1. An excavated space formed by excavating the ground; A retaining wall provided to cover the inner side surface of the excavation space; A bottom member provided to cover an inner bottom surface of the excavation space; a building that is stored in the space while floating above the bottom member due to buoyancy caused by a liquid injected into the space formed by the retaining wall and the bottom member and while having a gap filled with the liquid between the building and the retaining wall; A first base fixed to the building and extending from the building toward the retaining wall; a second pedestal that is fixed to the retaining wall and extends from the retaining wall toward the building so as to face the first pedestal at a position opposite the bottom member with respect to the first pedestal; a first seismic isolation member disposed between the first pedestal and the second pedestal and fixed thereto, the first seismic isolation member supporting the building floating in the liquid; A seismic isolation building comprising:

2. The first pedestal is provided at a plurality of different positions in a direction from the bottom member toward the building, The second pedestal is provided in a plurality of positions facing the first pedestals, The first seismic isolation member is disposed between the first base and the second base that face each other. The seismic isolation building according to claim 1 .

3. The seismically isolated building described in claim 2, characterized in that each of the multiple placement positions of the combination of the first pedestal, the second pedestal and the first seismic isolation member in a direction from the bottom member toward the building is determined so that the center of gravity of the building and the center of rigidity of the building coincide in the event of an earthquake.

4. The first base is provided around the entire periphery of the retaining wall, The second pedestal is provided around the entire periphery of the building at a position opposite to the first pedestal, The seismically isolated building according to claim 1 , wherein a plurality of the first seismic isolation members are arranged between a pair of the first base and the second base facing each other.

5. The seismic isolation building according to claim 1, further comprising a second seismic isolation member provided on the opposing surface between the building and the bottom member.

6. The retaining wall is A plurality of retaining wall blocks arranged in a row in a direction in which the building and the bottom member face each other; A connection portion that connects adjacent retaining wall blocks to each other so that the blocks can be relatively displaced in either a direction approaching or moving away from the building. The seismic isolation building according to claim 1, further comprising:

7. An excavated space formed by excavating the ground; A retaining wall provided to cover the inner side surface of the excavation space; A bottom member provided to cover an inner bottom surface of the excavation space; a reactor building that houses a reactor pressure vessel, floats from the bottom member due to buoyancy caused by liquid injected into a space formed by the retaining wall and the bottom member, and is housed in the space while having a gap filled with the liquid between the retaining wall and the bottom member; a first base fixed to the reactor building and extending from the reactor building toward the retaining wall; a second pedestal that is fixed to the retaining wall and extends from the retaining wall toward the building so as to face the first pedestal at a position opposite the bottom member with respect to the first pedestal; a first seismic isolation member disposed between the first base and the second base and fixed to each of them; A nuclear facility characterized by comprising:

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