Nuclear power plant

Abstract

Provided is a nuclear power plant that prevents the pressure in an external well from rising beyond a design pressure of the external well even if process piping is broken between a dry well penetration and an external well penetration in a double-shell reinforced concrete reactor containment vessel. A nuclear power plant according to an embodiment is characterized in that process piping passing between a dry well penetration (15) and an external well penetration (24) of a double-shell reactor containment vessel (20) is surrounded by an external well protection means (27) and isolated from an external well (32).

Description

nuclear power plants

[0001] The present invention relates to a nuclear power plant having a double-shell reactor containment vessel made of reinforced concrete.

[0002] A conventional reinforced concrete reactor containment vessel for a nuclear power plant will be outlined with reference to FIGS. 11 to 17. FIG.

[0003] (FIG. 11: Explanation of a conventional first nuclear power plant) FIG. 11 is an elevational cross-sectional view showing an example of the configuration around the reactor containment vessel of a conventional first nuclear power plant. In FIG. 11 , a reactor core 1 is housed inside a reactor pressure vessel (RPV) 2. The reactor pressure vessel 2 is housed inside a reactor containment vessel 3. The reactor containment vessel 3 has a cylindrical shape (see FIG. 12 ). This reactor containment vessel 3 is used in advanced boiling water reactors (ABWRs). The reactor containment vessel 3 is made of reinforced concrete and is also called a reinforced concrete reactor containment vessel (RCCV) 12. A steel liner (not shown) is lined on the inner surface of the RCCV 12. A reinforced concrete foundation slab 13 is provided at the bottom of the reactor containment vessel 3 (RCCV 12). The foundation slab 13 forms part of the reactor containment vessel 3. A steel liner (not shown) is lined on the top surface of the foundation slab 13.

[0004] The interior of the containment vessel 3 is divided into a dry well 4 that houses the reactor pressure vessel 2 and a wet well 5, and the dry well 4 and wet well 5 form part of the containment vessel 3. The wet well 5 defines a pressure suppression pool 6 within it. A wet well gas phase 7 is formed above the pressure suppression pool 6. The outer wall of the dry well 4 is a cylindrical wall and is called the dry well wall 4a. The outer wall of the wet well 5 is also a cylindrical wall and is called the wet well wall 5a. The dry well wall 4a and the wet well wall 5a are integrated to form the outer wall (cylindrical wall) 3a of the containment vessel 3 (see Figure 12). The inner diameter of the cylindrical wall 3a is approximately 29 m. However, the inner diameter of the cylindrical wall 3a is not limited to 29 m. The thickness of the cylindrical wall 3a is approximately 2 m. However, the thickness of the cylindrical wall 3a is not limited to 2 m. The ceiling of the dry well 4 is a flat plate, and this portion is called the top slab 4b of the dry well 4.

[0005] The reactor pressure vessel 2 is supported by a cylindrical pedestal 61 via an RPV skirt 62 and an RPV support 63. The pedestal 61 is a composite structure of steel plates and concrete. The space inside the pedestal 61, which is below the reactor pressure vessel 2 in the dry well 4 and is surrounded by the cylindrical wall of the pedestal 61, is called the pedestal cavity 61a. In the case of the RCCV 12 of the ABWR, the cylindrical wall of the pedestal 61 forms the boundary wall between the wet well 5 and the dry well 4, and this space in particular is called the lower dry well 4d.

[0006] In the case of the RCCV 12 of the ABWR, the space above the RPV support 62 of the dry well 4 is called the upper dry well 4c. The ceiling of the wet well 5 is a flat plate that forms the boundary with the upper dry well 4c. This part forms the floor of the upper dry well 4c and is called the diaphragm floor 5b.

[0007] A reactor containment vessel head 10 is disposed above the reactor pressure vessel 2. The reactor containment vessel head 10 is made of steel and has a structure that allows it to be removed during refueling.

[0008] The dry well 4 and the suppression pool 6 are connected by a LOCA vent pipe 8. LOCA is an abbreviation for loss of coolant accident. Multiple LOCA vent pipes 8 are installed, for example, ten, but only two are shown in Figure 9 (see Figure 12). The LOCA vent pipe 8 has a horizontal vent pipe 8a that opens into the pool water in the submerged portion of the suppression pool 6. In the case of the RCCV 12, three horizontal vent pipes 8a are installed vertically on one LOCA vent pipe 8. In the case of the RCCV 12, the LOCA vent pipe 8 is installed inside the cylindrical wall of the pedestal 61. Therefore, in the case of the RCCV 12, this cylindrical wall of the pedestal 61 is also referred to as the vent wall. The vent wall is made of steel plate concrete with a thickness of approximately 1.7 m, with steel inner and outer surfaces. The LOCA vent pipe 8 and the pedestal 61 constitute part of the reactor containment vessel 3. If a pipe rupture occurs in the dry well 4 and a LOCA occurs, steam generated from the rupture flow is guided through the LOCA vent pipe 8 into the pressure suppression pool 6 and condenses, thereby suppressing the pressure in the reactor pressure vessel 3. The design pressure of the reactor containment vessel 3 is approximately 3.16 kg / cm2 (gauge pressure). However, the design pressure of the reactor containment vessel 3 is not limited to 3.16 kg / cm2 (gauge pressure).

[0009] As shown in FIG. 11 , process piping 14 connected to the reactor pressure vessel 2 is installed within the upper dry well 4c. The process piping 14 is forged from carbon steel for pressure vessels. The process piping 14 passes through a dry well penetration 15 and extends to the outside of the containment vessel 3. The process piping 14 is used for normal operation and shutdown of the nuclear power plant. Typical examples of process piping 14 include the main steam pipe and the feedwater pipe. The main steam pipe and the feedwater pipe extend to a turbine building (not shown) outside the reactor building (not shown). Other examples include, but are not limited to, the suction pipe for the shutdown cooling mode of the residual heat removal system and the suction pipe for the reactor water purification system. While the process piping 14 will not actually rupture, regulatory requirements require that the nuclear power plant be designed to maintain safety even if the process piping 14 ruptures. Therefore, the process piping 14 is generally provided with an inner isolation valve 16 inside the dry well 4 and an outer isolation valve 17 outside the dry well 4, near the dry well penetration 15. The inner isolation valve 16 and outer isolation valve 17 are normally open and close automatically in the event of an accident. In the event of an accident involving the release of radioactive materials inside the reactor pressure vessel 2 or the dry well 4, the inner isolation valve 16 and outer isolation valve 17 automatically close to prevent radioactive materials inside the reactor pressure vessel 2 and the dry well 4 from leaking outside the dry well 4 through the inside of the process piping 14. In addition, if it is assumed that the process piping 14 outside the dry well 4 breaks, the inner isolation valve 16 and outer isolation valve 17 automatically close to prevent reactor water and radioactive materials inside the reactor pressure vessel 2 from leaking outside the dry well 4.

[0010] 13 and 14 , the configuration of a drywell penetration 15 in a reinforced concrete reactor containment vessel (RCCV) 12, which is the reactor containment vessel 3 of a conventional first nuclear power plant, is described below. (FIG. 13: Detailed View of Drywell Penetration) FIG. 13 is a cross-sectional view showing an example of the configuration of a drywell penetration 15 in a reinforced concrete reactor containment vessel (RCCV) 12 of a conventional first nuclear power plant (ABWR). In FIG. 13 , a drywell wall protection sleeve 18 is provided that penetrates the drywell wall 4a. The drywell wall protection sleeve 18 is a cylindrical pipe. The drywell wall protection sleeve 18 is made of steel. The drywell wall protection sleeve 18 forms a passage through which the process pipe 14 passes through the drywell wall 4a (sleeve function). The drywell wall protection sleeve 18 also has sufficient strength to withstand piping collisions and jets that may occur if the process pipe 14 ruptures inside the drywell wall protection sleeve 18. This provides a function of protecting the drywell wall 4a from damage (protective function). The drywell wall protection sleeve 18 is generally simply called a sleeve, but for clarity, it will be referred to as the drywell wall protection sleeve 18 below. The end of the drywell wall protection sleeve 18 outside the drywell wall 4a is airtightly closed by a drywell wall penetration end plate 19a.

[0011] The drywell wall protection sleeve 18 is fixed to the upper drywell wall 4a by an inner flange plate 64 on the inside and an outer flange plate 65 on the outside. The inner flange plate 64 and the outer flange plate 65 are made of steel. The inner flange plate 64 and the outer flange plate 65 are fixed to the drywell wall protection sleeve 18 by an inner gusset plate 66 and an outer gusset plate 67. The inner gusset plate 66 and the outer gusset plate 67 are also made of steel. A number of the inner gusset plates 66 and the outer gusset plates 67 are arranged circumferentially and embedded in the concrete of the drywell wall 4a. This firmly fixes the drywell wall protection sleeve 18 to the drywell wall 4a, preventing it from moving vertically, horizontally, or circumferentially. The inner flange plate 64, the outer flange plate 65, the inner gusset plate 66, and the outer gusset plate 67 are collectively referred to as the sleeve fastener 68.

[0012] (FIG. 14: Illustrative Diagram of Drywell Penetration) FIG. 14 is an explanatory diagram showing an example of the cross-sectional configuration of a drywell penetration 15 in a reinforced concrete reactor containment vessel (RCCV) 12 of a conventional first nuclear power plant (ABWR). The diameter and thickness of the drywell wall protection sleeve 18 are enlarged for clarity. The diameter and thickness of the process piping 14 are also enlarged for clarity. Although a sleeve fastener 68 is provided, it is not shown for clarity (see FIG. 13). This method of depicting the penetration for clarity will be used consistently in the following penetration illustrations for clarity. In FIG. 14, the drywell wall 4a is made of reinforced concrete with a thickness of approximately 2 m. However, the thickness of the drywell wall 4a is not limited to 2 m. A steel liner (not shown) with a thickness of approximately 0.0064 m is laid on the inner surface. However, the thickness of the steel liner is not limited to 0.0064 m. In Figure 12, the drywell penetration 15 is composed of a drywell wall protection sleeve 18 that penetrates the drywell wall 4a, a portion 14a of the process piping 14 that passes through it, and a drywell penetration end plate 19a. The drywell wall protection sleeve 18 forms a passage for the process piping 14 within the drywell wall 4a. The drywell wall protection sleeve 18 is a cylindrical pipe. The drywell wall protection sleeve 18 is made of steel.

[0013] The end of the drywell wall protection sleeve 18 on the upper drywell 4c side opens to the upper drywell 4c. Meanwhile, the end of the drywell wall protection sleeve 18 outside the drywell wall 4a is hermetically closed by a drywell penetration end plate 19a. The drywell penetration end plate 19a extends circumferentially around the process piping 14 and is welded to the drywell wall protection sleeve 18 at weld points 70. In principle, the drywell penetration end plate 19a is manufactured by integral forging with the process piping 14. However, in exceptional cases where it is difficult to manufacture the drywell penetration end plate 19a by integral forging, the drywell penetration end plate 19a may be welded to the process piping 14. The drywell penetration end plate 19a and the drywell wall protection sleeve 18 are welded to the weld points 70. This firmly secures the process piping 14 to the drywell wall protection sleeve 18.

[0014] The drywell wall protection sleeve 18, the portion 14a of the process piping 14, and the drywell penetration end plate 19a form a drywell penetration space 15a. The drywell penetration space 15a is connected to the upper drywell 4c and constitutes part of the drywell 4c. Therefore, even if the process piping 14 ruptures inside the drywell penetration space 15a, the rupture flow is released into the upper drywell 4c, and the steam generated from the rupture flow is guided through the LOCA vent pipe 8 into the pressure suppression pool 6 and condenses there (see Figure 11). This allows the pressure inside the containment vessel 3 to be kept below the design pressure of the containment vessel 3. Thermal insulation (not shown) is provided around the outer periphery of the process piping 14. The thickness of the insulation is approximately half the gap between the drywell wall protection sleeve 18 and the process piping 14. However, the thickness of the insulation is not limited to half the gap between the drywell wall protection sleeve 18 and the process piping 14.

[0015] (FIG. 15: Description of the Conventional Second Nuclear Power Plant) The conventional second nuclear power plant will be described with reference to FIGS. 15 to 17. FIG. 15 is a cross-sectional elevation view showing an example of the configuration of the reactor containment vessel and its surroundings in the conventional second nuclear power plant. This conventional example is shown in FIGS. 1 and 2 of Patent Document 1. It is also shown in FIG. 1 of Patent Document 2. This conventional example is adopted in the Severe Accident Tolerant and Optimized Reactor (SATOR, ICONE19-43342). In FIG. 15, a reactor core 1 is housed inside a reactor pressure vessel 2. The reactor pressure vessel 2 is housed inside a reactor containment vessel 3. The reactor containment vessel 3 has a cylindrical shape (see FIG. 16). In FIG. 15, the configurations of the reactor core 1, reactor pressure vessel 2, and reactor containment vessel 3 are the same as those of the conventional first nuclear power plant shown in FIG. 11. In the following, to avoid redundancy, only the configurations of the conventional second nuclear power plant that are different from the conventional first nuclear power plant will be described.

[0016] (Explanation of the External Well) In the conventional second nuclear plant, an external well 32 is further provided outside the dry well 4 and the wet well 5. The external well 32 is adjacent to the containment vessel 3 via the outer wall 3a of the containment vessel 3. That is, the external well 32 is adjacent to the dry well 4 via the dry well common wall (dry well wall) 4a, and is adjacent to the wet well 5 via the wet well common wall (wet well wall) 5a. The outer wall 3a of the containment vessel 3 consists of the dry well common wall (dry well wall) 4a and the wet well common wall (wet well wall) 5a. The outer wall of the external well 32 is called the external well wall (external wall) 32a. The ceiling portion of the external well 32 is a flat plate, and this portion is called the top slab 32b of the external well 32. The external well wall 32a and the top slab 32b are made of reinforced concrete. The top slab 32b of the external well 32 airtightly connects the upper end of the outer wall 3a of the containment vessel 3 to the upper end of the external well wall 32a. The external well 32 has the same pressure resistance and airtightness as the dry well 4 and the wet well 5. The design pressure of the external well 32 is approximately 3.16 kg / cm2 (gauge pressure). However, the design pressure of the external well 32 is not limited to 3.16 kg / cm2 (gauge pressure). A pressure gauge (not shown) and a thermometer (not shown) are provided within the external well 32.

[0017] The external well 32 is also made of reinforced concrete. Like the containment vessel 3, a steel liner (not shown) is lined on the inner surface. The thickness of the steel liner is, for example, 0.0064 m. However, the thickness of the steel liner is not limited to 0.0064 m. In this conventional example, the external well wall (outer wall) 32 a of the external well 32 is configured to surround the outer wall 3 a of the containment vessel 3 (see FIG. 16 ). The outer wall 3 a of the containment vessel 3 and the outer wall 32 a of the external well 32 form a double wall. The containment vessel 3 and the external well 32 are integrated to form the double-shell containment vessel 20. The outer wall 3 a of the containment vessel 3 is called the first shell (inner shell) 21 of the double-shell containment vessel 20, and the outer wall 32 a of the external well 32 is called the second shell (outer shell) 22 of the double-shell containment vessel 20. The inner shell 21 is made of reinforced concrete and is cylindrical. The outer shell 22 is not limited to a cylindrical shape and may have a rectangular or elliptical planar shape, but in FIG. 14 , the outer shell 22 is depicted as a cylindrical wall. The inner diameter of the inner shell 21 is approximately 29 m. However, the inner diameter of the inner shell 21 is not limited to 29 m. The thickness of the inner shell 21 is approximately 2 m. However, the thickness of the inner shell 21 is not limited to 2 m. The inner diameter of the outer shell 22 is, for example, approximately 41 m. However, the inner diameter of the outer shell 22 is not limited to 41 m. The thickness of the outer shell 22 is approximately 2 m. However, the thickness of the outer shell is not limited to 2 m. In particular, the thickness of the outer shell 22 below the diaphragm floor 5 b may be an appropriate thickness, such as 2.5 m, 2.6 m, or 3.0 m, to increase seismic strength. The distance between the inner shell 21 and the outer shell 22 is, for example, 4 m. However, the distance between the inner shell 21 and the outer shell 22 is not limited to 4 m. A reinforced concrete foundation slab 23 is provided at the bottom of the double-shell containment vessel 20. The foundation slab 23 constitutes part of the double-shell containment vessel 20. A steel liner (not shown) is attached to the top surface of the foundation slab 23. When the outer shell 22 is cylindrical, the double-shell containment vessel 20 is also called a double-cylindrical containment vessel. The outer shell 22 is also called an outer well wall 32a.One of the advantages of the double-shell reactor containment vessel 20 is that, in the event of a core meltdown accident and the release of radioactive material into the reactor containment vessel 3, even if the radioactive material leaks from the inner shell 21, the radioactive material is contained within the outer well 32, and the outer shell 22 can significantly reduce the amount of radioactive material leaking outside the double-shell reactor containment vessel 20. This function is called the double containment function of the double-shell reactor containment vessel 20. There is no pressure suppression pool inside the outer well 32, and no LOCA vent pipe is provided.

[0018] 15 and 16, in the second conventional nuclear plant, the process piping 14 passes through the dry well penetration 15, passes inside the external well 32, and further passes through the external well penetration 24 to reach the outside of the external well 32. In this conventional example, the process piping penetration 26 is composed of the dry well penetration 15, the external well penetration 24, and a portion 14c of the process piping 14 therebetween. The inner isolation valve 16 is provided inside the upper dry well 4c. The external isolation valve 17 is provided outside the external well 32. The structure of the dry well penetration 15 is the same as the structure of the dry well penetration 15 of the first conventional nuclear plant shown in FIG.

[0019] (Figure 17. Explanation of process piping penetration) Figure 17 will be used to explain the process piping penetration 26 of the double-shell reactor containment vessel 20. The process piping penetration 26 is composed of the dry well penetration 15, the outer well penetration 24, and the portion 14c of the process piping 14 therebetween. The structure of the dry well penetration 15 is the same as the structure of the dry well penetration 15 of the conventional first nuclear plant (see Figure 14). The outer well wall 32a is made of reinforced concrete with a thickness of approximately 2m. However, the thickness of the outer well wall 32a is not limited to 2m. A steel liner (not shown) with a thickness of approximately 0.0064m is laid on the inner surface of the outer well wall 32a. However, the thickness of the steel liner is not limited to 0.0064m.

[0020] In Figure 17, the external well penetration 24 is composed of an external well wall protection sleeve 25 that penetrates the external well wall 32a, a portion 14b of the process piping 14 that passes through it, and an external well penetration end plate 19b. The external well wall protection sleeve 25 is a cylindrical pipe. The external well wall protection sleeve 25 forms a passage for the process piping 14 to pass through the external well wall 32a (sleeve function). The external well wall protection sleeve 25 also has the strength to withstand piping collisions and jets that may occur if the process piping 14 breaks inside the external well wall protection sleeve 25. This provides a function to protect the external well wall 32a from damage (protection function). The external well wall protection sleeve 25 is generally simply referred to as a sleeve, but for clarity, it will be referred to as the external well wall protection sleeve 25 below. The inner diameter and thickness of the external well wall protection sleeve 25 are the same as those of the drywell wall protection sleeve 18. The outer well wall protection sleeve 25 is also provided with a sleeve fastener 68 (not shown) and is fixed to the outer well wall 32a (see FIG. 13), similar to the dry well wall protection sleeve 18. Therefore, the outer well wall protection sleeve 25 is firmly fixed to the outer well wall 32a and cannot move up and down, left and right, or circumferentially.

[0021] The end of the external well wall protection sleeve 25 on the external well 32 side opens into the external well 32. Meanwhile, the end of the external well protection sleeve 25 outside the external well wall 32a is airtightly closed by the external well penetration end plate 19b. The external well penetration end plate 19b extends in the circumferential direction of the process piping 14 and is welded to the external well wall protection sleeve 25 at weld points 72. The external well penetration end plate 19b is manufactured by integral forging with the process piping 14. However, in exceptional cases where it is difficult to manufacture by integral forging, the external well penetration end plate 19b may be welded to the process piping 14. The external well penetration end plate 19b and the external well wall protection sleeve 25 are welded to the weld points 72. This firmly fixes the process piping 14 to the external well wall protection sleeve 25. The outer well wall protection sleeve 25, the portion 14b of the process piping 14 passing through it, and the outer well penetration end plate 19b constitute the outer well penetration 24. The portion 14c of the process piping 14 between the dry well penetration 15 and the external well penetration 24 passes through the outer well 32. Thermal insulation (not shown) is provided on the outer periphery of the process piping 14. The thickness of the thermal insulation is approximately half the gap between the outer well wall protection sleeve 25 and the process piping 14. However, the thickness of the thermal insulation is not limited to half the gap between the outer well wall protection sleeve 25 and the process piping 14. In the conventional second nuclear power plant, the dry well penetration 15 and the outer well penetration 24 are provided, and the process piping 14 passes through the dry well wall 4a and the outer well wall 32a and into the outer well 32.

[0022] 17, the process piping 14 is field-welded at weld point 71. The process piping passing through the dry well penetration 15 across weld point 71 is referred to as dry well wall-side process piping 14d. The process piping passing through the outer well penetration 24 is referred to as outer well wall-side process piping 14e. The outer well wall protective sleeve 25, the outer well penetration end plate 19b, and the outer well wall-side process piping 14e form the outer well penetration space 24a. The outer well penetration space 24a is connected to the outer well 32 and forms part of the outer well 32. Therefore, if the outer well wall-side process piping 14e ruptures inside the outer well penetration space 24a, the rupture flow will be released into the outer well 32, and steam generated from the rupture flow will be released into the outer well 32. There is no pressure suppression pool or LOCA vent pipe installed in the outer well 32 (see FIG. 15). Therefore, if the outer well wall side process pipe 14e breaks inside the outer well penetration space 24a, the pressure inside the outer well 32 will rise above the design pressure of the outer well 32.

[0023] In Figure 17, the drywell wall-side process piping 14d and the external well wall-side process piping 14e are field-welded at weld point 71. The process of field-welding the drywell wall-side process piping 14d and the external well wall-side process piping 14e at weld point 71 is described below. First, the drywell wall 4a and the drywell wall protective sleeve 18 are constructed. Next, the drywell wall-side process piping 14d and the drywell penetration end plate 19a are inserted into the drywell wall protective sleeve 18 from the external well 32 side of the drywell wall protective sleeve 18 and field-welded at weld point 70. After that, the external well wall 32a and the external well wall protective sleeve 25 are constructed. Next, the external well wall-side process piping 14e and the external well penetration end plate 19b are inserted into the external well wall protective sleeve 25 from the outside of the external well wall 32a of the external well wall protective sleeve 25 and field-welded to the external well wall protective sleeve 25 at weld point 72. Finally, the drywell wall-side process piping 14d and the external well wall-side process piping 14e are welded on-site at weld point 71. This increases the risk of the process piping 14 breaking at weld point 71. Weld point 71 is located within the external well 32. This increases the risk of the process piping 14 breaking within the external well 32. Furthermore, the construction period for the above construction process is prolonged because parallel construction of the drywell wall 4a and the external well wall 32a is not possible. Furthermore, the drywell penetration 15 and the external well penetration 24 are firmly fixed by the process piping 14. Therefore, if an accident or earthquake that increases the pressure inside the containment vessel 3 causes the drywell wall 4a and the external well wall 32a to behave differently, the piping reaction force from the process piping 14 may act on the drywell penetration 15 and the external well penetration 24, potentially damaging the walls surrounding the drywell penetration 15 and the external well penetration 24.

[0024] JP 2021-67509 A (US 2023 / 0070817 A1) JP 2012-117821 A (US 2013 / 0259184 A1)

[0025] When a double-shell reactor containment vessel 20 is constructed by providing a second shell (outer shell) 22 outside the outer wall (cylindrical wall) 3a of the reactor containment vessel 3 as a first shell (inner shell) 21, if the process piping 14 ruptures inside the external well 32, there is a problem that the pressure inside the external well 32 will rise above the design pressure of the external well 32. Furthermore, if an accident or earthquake that causes an increase in pressure inside the reactor containment vessel 3 causes the dry well wall 4a and the external well wall 32a to behave differently, the piping reaction force of the process piping 14 that is firmly fixed to both the dry well penetration 15 and the external well penetration 24 may damage the walls around the dry well penetration 15 and the external well penetration 24.

[0026] An external well protection means is provided to isolate the process piping 14 from the external well 32 so that a rupture flow does not flow into the external well 32 when the process piping 14 is ruptured. An expandable bellows is also provided at the penetration portion of the process piping.

[0027] According to an embodiment of the present invention, even if the process piping 14 breaks between the dry well penetration 15 and the outer well penetration 24 of the double-shell reactor containment vessel 20, the outer well protection means 27 can suppress a pressure increase in the outer well 32. Furthermore, even if the dry well wall 4a and the outer well wall 32a behave differently due to an accident or earthquake that causes a pressure increase inside the reactor containment vessel 3, damage to the walls around the dry well penetration 15 and the outer well penetration 24 can be prevented.

[0028] FIG. 1 is an elevational cross-sectional view showing the configuration around a double-shell reactor containment vessel of a nuclear power plant according to a first embodiment of the present invention. FIG. 2 is a plan view showing the configuration around a double-shell reactor containment vessel of a nuclear power plant according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to the first embodiment of the present invention. FIG. 4a is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to a second embodiment of the present invention. FIG. 4b is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to the second embodiment of the present invention. FIG. 4c is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to the second embodiment of the present invention. FIG. 5a is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to a third embodiment of the present invention. FIG. 5b is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to a fourth embodiment of the present invention. FIG. 5c is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to a fifth embodiment of the present invention. FIG. 6a is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a sixth embodiment of the present invention. FIG. 6b is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a seventh embodiment of the present invention. FIG. 7a is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to an eighth embodiment of the present invention. FIG. 7b is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a ninth embodiment of the present invention. FIG. 8a is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a tenth embodiment of the present invention. FIG. 8b is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to an eleventh embodiment of the present invention. FIG. 9a is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a twelfth embodiment of the present invention. FIG. 9b is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a thirteenth embodiment of the present invention. 9c is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a fourteenth embodiment of the present invention. Fig. 10a is an explanatory diagram showing the configuration of a process piping penetration for a double-shell reactor containment vessel according to a fifteenth embodiment of the present invention.FIG. 10b is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to a sixteenth embodiment of the present invention. FIG. 10c is an explanatory diagram showing the configuration of a process piping penetration in a double-shell reactor containment vessel according to a seventeenth embodiment of the present invention. FIG. 11 is a cross-sectional elevation view showing the configuration around the containment vessel of the first conventional nuclear power plant (ABWR). FIG. 12 is a plan view showing the configuration around the containment vessel of the first conventional nuclear power plant (ABWR). FIG. 13 is a cross-sectional view showing the configuration of a drywell penetration in the first conventional nuclear power plant (ABWR). FIG. 14 is an explanatory diagram showing the configuration of a drywell penetration in the first conventional nuclear power plant (ABWR). FIG. 15 is a cross-sectional elevation view showing the configuration around the double-shell reactor containment vessel of the second conventional nuclear power plant (SATOR). FIG. 16 is a plan view showing the configuration around the containment vessel of the second conventional nuclear power plant (SATOR). FIG. 17 is an explanatory diagram showing the configuration of a process piping penetration in the second conventional nuclear power plant (SATOR).

[0029] The configuration of a process piping penetration 26 of a reinforced concrete double-shell containment vessel 20 according to an embodiment of the present invention will be described below with reference to Figures 1 to 10c. Here, parts that are the same as or similar to those in the prior art described above, and parts that are the same as or similar to those in the following embodiments, will be given the same reference numerals, and only the essential parts will be described without redundant explanation.

[0030] (Explanation of FIG. 1) FIG. 1 is an elevational view showing the configuration of a double-shell reactor containment vessel 20 according to a first embodiment of the present invention. The configuration of the double-shell reactor containment vessel 20 is the same as that of the double-shell reactor containment vessel 20 of a conventional second nuclear power plant. In this embodiment, a second shell (outer shell) 22 is provided on the outside of a first shell (inner shell) 21. The inner shell 21 is a cylindrical wall made of reinforced concrete. The outer shell 22 is also made of reinforced concrete. FIG. 2 is a plan view showing the configuration of the double-shell reactor containment vessel 20 according to the first embodiment of the present invention. The shape of the outer shell 22 is not limited to a cylinder, but may be rectangular or elliptical, and in FIG. 2, the outer shell 22 is depicted as a cylindrical wall. One of the advantages of the double-shell reactor containment vessel 20 is that, in the event of a core meltdown accident and the release of radioactive material into the reactor containment vessel 3, even if the radioactive material leaks from the inner shell 21, the radioactive material is contained within the outer well 32, and the outer shell 22 can significantly reduce the amount of radioactive material leaking outside the double-shell reactor containment vessel 20. This function is called the double containment function of the double-shell reactor containment vessel 20. There is no pressure suppression pool inside the outer well 32, and no LOCA vent pipe is provided.

[0031] 1 and 2, this embodiment differs from the conventional second nuclear plant in that an outer well protection means 27 is provided between the dry well penetration 15 and the outer well penetration 24. The outer well protection means 27 completely surrounds the portion 14c of the process piping 14 passing between the dry well penetration 15 and the outer well penetration 24, isolating it from the outer well 32 (see FIG. 3). The outer well protection means 27 has a strength sufficient to withstand jets, pressure increases, and temperature increases resulting from piping collisions and rupture flows that may occur if the process piping 14 breaks inside. If possible, the outer well protection means 27 may be outer well protection piping 30 (see FIG. 3).

[0032] (Explanation of FIG. 3) FIG. 3 is an explanatory diagram showing the configuration of a process piping penetration 26 of a double-shell reactor containment vessel 20 according to a first embodiment of the present invention. In FIG. 3, the dry well penetration 15 is composed of a dry well wall protection sleeve 18 and a portion 14a of the process piping 14 within the dry well wall protection sleeve 18. A dry well penetration end plate 19a (see FIG. 17) is not provided. The outer well penetration 24 is composed of an outer well wall protection sleeve 25, a portion 14b of the process piping 14 within the outer well wall protection sleeve 25, and an outer well penetration end plate 19b. In this embodiment, the process piping penetration 26 is composed of the dry well penetration 15, the outer well penetration 24, an outer well protection means 27, and a portion 14c of the process piping 14 within the protection means 27. In this embodiment, an outer well protection piping 30 is provided as the outer well protection means 27. The outer well protection piping 30 is made of steel. The external well protection piping 30 has the strength to withstand jets, pressure increases, and temperature increases resulting from piping collisions and rupture flows that may occur if the process piping 14 inside it ruptures. The external well protection piping 30 is installed between the dry well penetration 15 and the external well penetration 24. The external well protection piping 30 is welded to the dry well wall protection sleeve 18 on-site at weld points 90. The external well protection piping 30 is welded to the external well wall protection sleeve 25 on-site at weld points 91. The external well wall protection sleeve 25 is welded to the external well penetration end plate 19b on-site at weld points 72. A test tap piece (not shown) may be installed between the external well protection sleeve 25 and the external well penetration end plate 19b. In this case, the test tap piece (not shown) also becomes part of the external well penetration 24. The external well penetration end plate 19b airtightly closes the outer end of the external well wall 32a of the external well penetration 24. The outer well protection piping 30 surrounds the portion 14c of the process piping 14 between the dry well penetration 15 and the outer well penetration 24, completely isolating it from the outer well 32. The dry well wall protection sleeve 18, the outer well protection piping 30, the outer well wall protection sleeve 25, the outer well penetration end plate 19b, and the process piping 14 form a communication space 31. The communication space 31 opens into the upper dry well 4c.If the process piping 14 breaks inside the communication space 31, the break flow will be released into the upper dry well 4c. Steam generated from the break flow is led to the pressure suppression pool 6 by the LOCA vent pipe 8 and condenses there (see Figure 1). Therefore, the pressure inside the containment vessel 3 will not exceed the design pressure. The outer well protection piping 30 prevents the break flow from being released into the outer well 32, so the pressure inside the outer well 32 will not exceed the design pressure of the outer well 32.

[0033] 3, in this embodiment, the process piping 14 is not welded inside the communication space 31. Inside the communication space 31, the process piping 14 is a single continuous pipe. This reduces the probability of the process piping 14 breaking inside the communication space 31. The process piping 14 can be a continuous pipe because, in this embodiment, a dry well penetration end plate 19a (see FIG. 17) is not provided.

[0034] The construction process of this embodiment is as follows. In this embodiment, the construction of the drywell wall 4a and the drywell wall protection sleeve 18 and the construction of the external well wall 32a and the external well wall protection sleeve 25 can be performed in parallel. After both constructions are completed, the protective piping 30 is welded. Furthermore, the process piping 14 is inserted into the external well wall protection sleeve 25 from the outside of the external well wall 32a, and the external well wall protection sleeve 25 is welded to the external well penetration end plate 19b at the weld point 72. If a test tap piece (not shown) is provided on the outside of the external well wall protection sleeve 25, the test tap piece (not shown) is inserted between the external well wall protection sleeve 25 and the external well penetration end plate 19b and welded to the external well penetration end plate 19b. The process piping 14 can be inserted from the outside of the external well wall protection sleeve 25 because the drywell wall end plate 19a (see FIG. 17 ) is not provided.

[0035] Although this embodiment (Figure 3) has the above-mentioned excellent features, there are some concerns. In the event of an accident in which radioactive material is released into the upper dry well 4c, the radioactive material in the upper dry well 4c may also infiltrate the communication space 31. The communication space 31 is part of the upper dry well 4c, but it passes through the outer well wall 32a and reaches the outer well penetration end plate 19b. The outer well penetration end plate 19b is located outside the outer well wall 32a. With this configuration, the double containment function of the double-shell reactor containment vessel 20 according to the present invention is not achieved. However, because the communication space 31 is formed as a vessel by welding steel piping, radioactive material inside it will not leak outside the outer well wall 32a. This can be confirmed by conducting a leakage test after the plant is constructed. Leakage of radioactive material from the process piping penetration 26 does not occur through the communication space 31, but rather through the inside of the process piping 14 due to leakage from the inner isolation valve 16 and the outer isolation valve 17 (see Figure 1). Because the isolation valves are not welded, leakage cannot be completely prevented. This is called a bypass leak. Radioactive materials in the upper dry well 4c may bypass the reactor building (not shown), which functions as a secondary containment vessel, and leak outside the reactor building (not shown) through the process piping 14. Countermeasures against this bypass leak are required by installing a leak suppression system (not shown). However, some countries ignore the risk of bypass leakage and implement regulations based on the unphysical idea that radioactive materials will leak into the reactor building (not shown) through the steel wall or steel liner of the reactor containment vessel. As a result, the need for a leak suppression system (not shown) may be overlooked. Without this correct understanding, the need for bypass leakage countermeasures may be overlooked, and regulatory authorities may assume that radioactive materials will also leak from the communication space 31. As a result, countermeasures may not be implemented in necessary areas, and unnecessary countermeasures may be required.

[0036] (Explanation of Figures 4a to 4c) Figures 4a to 4c are explanatory diagrams showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a second embodiment of the present invention. Using Figures 4a to 4c, a method for ensuring double containment of radioactive materials in the communication space 31 will be described. In Figure 4a, a cover plate 33 is provided on the process piping 14. The cover plate 33 is made of steel and is attached to the process piping 14, for example, by integral forging. The cover plate 33 is provided within the communication space 31 at the boundary with the upper dry well 4c. Furthermore, a dry well wall protection sleeve 18 and a cover 34 are provided in contact with the cover plate 33. Heat-resistant sealants (not shown) are provided at the contact surfaces of the cover 34, the dry well wall protection sleeve 18, and the cover plate 33. The cover 34 can be opened and closed (see Figure 4c). The cover 34 is normally closed. The cover 34 isolates the communication space 31 from the upper dry well 4c. As a result, the communication space 31 has a double containment function for radioactive materials even in the event of an accident in which radioactive materials are released into the reactor containment vessel 3. The lid 34 serves as a first barrier for radioactive materials, and the communication space 31 constitutes a second barrier. Even if radioactive materials leak from the lid 34 and enter the inside of the communication space 31, the communication space 31 serves as a second barrier, thereby achieving a double containment function.

[0037] FIG. 4b is an explanatory diagram of the lid 34 of this embodiment, viewed from the upper drywell 4c side. The lid 34 is divided into two halves, left and right, with hinges 35 on the left and right sides to allow it to be opened and closed. One end of the hinge 35 is connected to the drywell wall protection sleeve 18 via a base (not shown). The hinge 35 is equipped with a spring (not shown) that presses the lid 34 against the backing plate 33 and the drywell wall protection sleeve 18, thereby crimping it into place. The contact surfaces of the left and right lids are uneven, similar to a door, so that they overlap without any gaps. The diameter of the inner circular portion of the lid 34 is larger than the outer diameter of the process piping 14 because thermal insulation (not shown) is installed between them. The backing plate 33 is necessary to ensure that the lid is tightly attached while avoiding the thermal insulation (not shown).

[0038] FIG. 4c is an explanatory diagram showing the lid 34 in an open state in this embodiment. If the process piping 14 breaks inside the communication space 31, the pressure of the break flow overcomes the force of the spring (not shown) of the hinge 35 and opens the lid 34. This allows the break flow to flow into the upper dry well 4c. Steam generated from the break flow is vented through the LOCA vent pipe 8 into the pressure suppression pool 6 and condenses (see FIG. 1). This limits the pressure inside the containment vessel 3 to below the design pressure of the containment vessel 3. The lid 34 functions as a check valve. In the event of an accident that increases the pressure inside the containment vessel 3, the lid 34 remains closed. As the pressure inside the containment vessel 3 increases, the lid 34 is tightly pressed against the dry well wall protection sleeve 18 and the backing plate 33, maintaining the closed state. On the other hand, in the event of an accident that increases the pressure inside the communication space 31, the lid 34 opens.

[0039] This embodiment has the excellent feature of having no welds in the process piping 14, allowing for parallel construction of the dry well wall 4a and the outer well wall 32a. However, the dry well wall protection sleeve 18 and the outer well sleeve 25 are firmly connected by the outer well protection piping 30. Therefore, if the dry well wall 4a and the outer well wall 32a behave differently due to an accident or earthquake that causes a rise in pressure inside the containment vessel 3, a large piping reaction force may act on the dry well penetration 15 and the outer well penetration 24, causing damage to the walls around each penetration. This problem is also present in Example 1 (FIG. 3).

[0040] (Explanation of FIG. 5a) FIG. 5a is an explanatory diagram showing the configuration of a process piping penetration 26 in a double-shell containment vessel 20 according to a third embodiment of the present invention. The basic configuration of this embodiment is similar to that of Example 1 (FIG. 3), but differs in the following respects. In this embodiment, the dry well wall protection sleeve 18, the external well protection piping 30, and the external well wall protection sleeve 25 are provided as a single continuous pipe or as a pre-welded, integrated process piping penetration protection sleeve 26a. In this case, on-site welding work at weld points 90 and 91 can be omitted (see FIG. 3). However, in this case, the construction process of the dry well wall 4a and the construction process of the external well wall 32a must be synchronized. This requires complete synchronization for all process piping penetrations. Furthermore, in this embodiment, the dry well wall 4a and the external well wall 32a are firmly connected by the process piping penetration protection sleeve 26a. Therefore, if an accident or earthquake causes the pressure inside the reactor containment vessel 3 to rise and the dry well wall 4a and the external well wall 32a behave differently, a large piping reaction force will act on the dry well penetration 15 and the external well penetration 24, which could damage the walls around each penetration.

[0041] (Explanation of FIG. 5b) FIG. 5b is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a fourth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 3 (FIG. 5a). This embodiment is further characterized by the provision of a bellows 36 on the process piping penetration protective sleeve 26a to mitigate piping reaction forces in the event of an accident or earthquake that causes a pressure increase inside the reactor containment vessel 3. The bellows 36 is made of steel. The bellows 36 is expandable and contractible. The bellows 36 is welded to the process piping penetration protective sleeve 26a at welds 37 and 38. The bellows 36 has the same airtightness and pressure resistance as the reactor containment vessel 3. However, it does not have resistance to piping collisions or jets that may occur if the process piping 14 ruptures. Therefore, there is a risk that the original safety function of the process piping penetration protective sleeve 26a may be impaired. In this embodiment, even if the dry well wall 4a and the external well wall 32a behave differently in an accident or earthquake that causes a pressure rise inside the containment vessel 3, the bellows 36 absorbs the piping reaction force, preventing damage to the walls surrounding the dry well penetration 15 and the external well penetration 24. While only one bellows 36 is shown in Figure 5b for simplicity, multiple bellows 36 may be provided to improve flexibility. In this embodiment, the communication space 31 opens to the upper dry well 4c. Therefore, in the event of an accident in which radioactive material is released into the upper dry well 4c, the radioactive material in the upper dry well 4c will also penetrate into the communication space 31. Because the communication space 31 is highly airtight due to welding, radioactive material will not actually leak from the communication space 31 even in the event of an accident in which radioactive material is released into the containment vessel 3. However, the communication space 31 passes through the external well wall 32a and reaches the external well penetration end plate 19b. The outer well penetration end plate 19b is provided on the outside of the outer well wall 32a. In such a configuration, the double-shell reactor containment vessel 20 according to the present invention does not achieve the double containment function for radioactive materials.

[0042] (Explanation of FIG. 5c) FIG. 5c is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a fifth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 4 (FIG. 5b). This embodiment further includes a cover plate 33, a lid 34, and a hinge 35. The configuration, action, and function thereof are the same as those described in Example 2 (see FIGS. 4a to 4c). The lid 34 is openable and closable (see FIG. 4c). The lid 34 is normally closed. The lid 34 isolates the communication space 31 from the upper dry well 4c. This allows the communication space 31 to function as a double containment for radioactive materials even in the event of an accident in which radioactive materials are released into the reactor containment vessel 3. The cover plate 33, the lid 34, and the hinge 35 can also be provided in Example 3 (FIG. 5a). This allows the double containment for radioactive materials to be achieved even in the case of Example 3 (FIG. 5a).

[0043] (Explanation of FIG. 6a) FIG. 6a is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a sixth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 1 (FIG. 3). This embodiment is further characterized by the provision of a bellows 40a at the drywell penetration 15 to mitigate the piping reaction force in the event of an accident or earthquake that causes a rise in pressure inside the reactor containment vessel 3. The bellows 40a is made of steel. The bellows 40a is expandable and contractible. In FIG. 6a, a drywell wall secondary sleeve 41 is provided around the drywell wall protection sleeve 18. No sleeve fastener is provided on the drywell wall protection sleeve 18. A sleeve fastener 68 (not shown; see FIG. 13) is provided on the drywell wall secondary sleeve 41. The drywell wall secondary sleeve 41 is made of steel. The inner diameter of the drywell wall secondary sleeve 41 is larger than the outer diameter of the drywell wall protection sleeve 18. The bellows 40a is welded to the drywell wall secondary sleeve 41 at weld 75 inside the outer well 32. The bellows 40a is further welded to the drywell wall secondary sleeve end plate 44 at weld 76. In this embodiment, the drywell wall secondary sleeve end plate 44 is welded to the drywell wall protective sleeve 18 at weld 92. The bellows 40a has the same airtightness and pressure resistance as the containment vessel 3. However, it is not resistant to piping collisions or jets that may occur if the process piping 14 ruptures inside the drywell penetration 15. Even in this case, however, the drywell wall protective sleeve 18 blocks the piping collisions and jets, preventing damage to the bellows 40a. In other words, the drywell wall protective sleeve 18 serves as protective piping for the bellows 40a. For this reason, in this embodiment, the drywell wall protective sleeve 18 may be referred to as protective piping for simplicity. However, for clarity, the term drywell wall protective sleeve 18 will be used hereinafter. Furthermore, a jet deflector 42a is provided on the upper dry well 4c side of the dry well wall secondary sleeve 41. The jet deflector 42a is provided to prevent the jet from entering the dry well wall secondary sleeve 41 and damaging the bellows 40a in the event of a piping rupture accident in another process piping in the upper dry well 4c.The jet deflector 42a is welded to the drywell wall protection sleeve 18 at weld point 77, leaving a gap between it and the drywell wall secondary sleeve 41. The gap is provided to accommodate the expansion of the bellows 40a. The jet deflector 42a may also be connected to the drywell wall secondary sleeve 41. In this case, a gap is provided between the jet deflector 42a and the drywell wall protection sleeve 18. The bellows 40a could also be installed on the upper drywell 4c side, but this is not advisable due to the narrowness of the upper drywell 4c. In this embodiment, even if the drywell wall 4a and the external well wall 32a behave differently in an accident or earthquake that increases pressure inside the containment vessel 3, the bellows 40a absorbs the piping reaction force, thereby preventing damage to the walls surrounding the drywell penetration 15 and the external well penetration 24. While only one bellows 40a is shown in Figure 4a for simplicity, multiple bellows 40a may be installed to improve expansion and contraction. Furthermore, in this embodiment, the bellows 40a are provided in the dry well penetration 15, and therefore their installation work can be carried out in parallel with the construction work of the outer well wall 32a, thereby shortening the construction period. Note that, since the communication space 31 is highly airtight due to welding, even if an accident occurs in which radioactive material is released into the containment vessel 3, radioactive material will not actually leak from the communication space 31. However, because the communication space 31 opens to the upper dry well 4c and the outer well penetration end plate 19b is provided outside the outer well wall 32a, the double containment function of the double shell containment vessel 20 is not achieved at the process piping penetration 26.

[0044] (Explanation of FIG. 6b) FIG. 6b is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a seventh embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 6 (FIG. 6a). This embodiment further includes a backing plate 33, a lid 34, and a hinge 35. The configuration, action, and function thereof are the same as those described in Example 2 (see FIGS. 4a to 4c). The lid 34 is openable and closable (see FIG. 4c). The lid 34 is normally closed. The lid 34 isolates the communication space 31 from the upper dry well 4c. This allows the communication space 31 to function as a double containment for radioactive materials even in the event of an accident in which radioactive materials are released into the containment vessel 3. The configuration of this embodiment is the same as that of Example 2 (FIG. 4a), except that a drywell wall secondary sleeve 41, a bellows 40a, a drywell wall secondary sleeve end plate 44, and a jet deflector plate 42a are further provided around the outer periphery of the drywell wall protection sleeve 18.

[0045] (Explanation of Figure 7a) Figure 7a is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to an eighth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 1 (Figure 3). This embodiment is further characterized by the provision of a bellows 40b at the outer well penetration 24 to mitigate piping reaction forces due to accidents or earthquakes that cause pressure increases inside the reactor containment vessel 3. The bellows 40b are made of steel. The bellows 40b are expandable and contractible. In Figure 7a, an outer well wall secondary sleeve 43 is provided around the outer well wall protective sleeve 25. No sleeve fastener is provided on the outer well wall protective sleeve 25. A sleeve fastener 68 (not shown; see Figure 13) is provided on the outer well wall secondary sleeve 43. The outer well wall secondary sleeve 43 is made of steel. The inner diameter of the outer well wall secondary sleeve 43 is larger than the outer diameter of the outer well wall protective sleeve 25. The bellows 40b is welded to the outer well wall secondary sleeve 43 at weld point 78 outside the outer well wall 32a. The bellows 40b is further welded to the outer well wall secondary sleeve end plate 45 at weld point 79. In this embodiment, the outer well wall secondary sleeve end plate 45 is integrally forged with the outer well penetration end plate 19b and the process piping 14. The outer well wall secondary sleeve end plate 45 and the outer well penetration end plate 19b are sometimes collectively referred to as end plates. The bellows 40b has the same airtightness and pressure resistance as the outer well 32. However, it is not resistant to piping collisions or jets that may occur if the process piping 14 breaks inside the outer well penetration 24. However, even in such a case, the outer well wall protective sleeve 25 blocks the piping collisions and jets, preventing damage to the bellows 40b. In other words, the outer well wall protective sleeve 25 serves as protective piping for the bellows 40b. For this reason, in this embodiment, the external well wall protection sleeve 25 may be simply referred to as protection piping. However, for clarity, the name external well wall protection sleeve 25 will be used below. In this embodiment, the external well protection piping 30 is provided by extending the external well wall protection sleeve 25 into the external well 32 and integrating it into the external well 32. This eliminates the need to weld the external well protection piping 30 and the external well protection sleeve 25 on-site. However, welding on-site may also be performed.Furthermore, a jet deflector plate 42b is provided on the external well protection piping 30. The jet deflector plate 42b is provided to prevent the jet from penetrating into the external well wall secondary sleeve 43 and damaging the bellows 40b in the event of a piping rupture accident in another process piping within the external well 32. The jet deflector plate 42b is welded to the external well protection piping 30 at weld points 80, leaving a gap between the jet deflector plate 42b and the external well wall secondary sleeve 43. The gap is provided to accommodate expansion of the bellows 40b. The jet deflector plate 42b may also be provided connected to the external well wall secondary sleeve 43. In that case, the gap is provided between the jet deflector plate 42b and the external well protection piping 30. In this embodiment, even if the dry well wall 4a and the external well wall 32a behave differently due to an accident or earthquake that increases the pressure inside the containment vessel 3, the bellows 40b absorbs the piping reaction force, preventing damage to the walls surrounding the dry well penetration 15 and the external well penetration 24. While only one bellows 40b is shown in FIG. 7a for simplicity, multiple bellows 40b may be provided to improve flexibility. Because the communication space 31 is highly airtight due to welding, radioactive material will not actually leak from the communication space 31 even if an accident occurs in which radioactive material is released into the containment vessel 3. However, because the communication space 31 opens to the upper dry well 4c and the external well penetration end plate 19b is located outside the external well wall 32a, the double containment function of the double-shell containment vessel 20 is not achieved at the process piping penetration 26.

[0046] (Explanation of FIG. 7b) FIG. 7b is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a ninth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 8 (FIG. 7a). This embodiment further includes a backing plate 33, a lid 34, and a hinge 35. The configuration, action, and function thereof are the same as those described in Example 2 (see FIGS. 4a to 4c). The lid 34 is openable and closable (see FIG. 4c). The lid 34 is normally closed. The lid 34 isolates the communication space 31 from the upper dry well 4c. This allows the communication space 31 to function as a double containment for radioactive materials even in the event of an accident in which radioactive materials are released into the containment vessel 3. The configuration of this embodiment is the same as that of Example 2 (FIG. 4a), except that an outer well wall secondary sleeve 43, a bellows 40b, an outer well wall secondary sleeve end plate 45, and a jet deflector 42b are further provided around the outer well wall protection sleeve 25.

[0047] (Explanation of FIG. 8a) FIG. 8a is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a tenth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 1 (FIG. 3). This embodiment is further characterized by the provision of a bellows 40c at the outer well penetration 24 to mitigate piping reaction forces due to accidents or earthquakes that cause pressure increases inside the containment vessel 3. This embodiment is similar to Example 8 (FIG. 7a), except that the bellows 40c is provided inside the outer well 32. In FIG. 8a, the bellows 40c is welded to the outer well wall secondary sleeve 43 inside the outer well 32 at weld point 78. The bellows 40c is further welded to the outer well wall secondary sleeve end plate 45a at weld point 85. The outer well wall secondary sleeve end plate 45a is welded to the outer well protection piping 30 at weld point 86. The bellows 40c has the same airtightness and pressure resistance as the outer well 32. However, the bellows 40c is not resistant to piping collisions or jets that may occur if the process piping 14 breaks inside the external well penetration 24. However, even in such cases, the external well wall protection sleeve 25 blocks the piping collisions and jets, preventing damage to the bellows 40c. In other words, the external well wall protection sleeve 25 serves as protective piping for the bellows 40c. For this reason, in this embodiment, the external well wall protection sleeve 25 may be simply referred to as protective piping. However, for clarity, the term "external well wall protection sleeve 25" will be used below. In this embodiment, the external well protection piping 30 is integrated with the external well wall protection sleeve 25 by extending it into the external well 32. This eliminates the need for on-site welding of the external well protection piping 30 and the external well protection sleeve 25. However, on-site welding may be performed. Furthermore, a jet deflector 42c is provided on the outer side of the external well wall 32a of the external well wall secondary sleeve 43. Jet deflector 42c is provided to prevent a jet from penetrating into outer well wall secondary sleeve 43 and damaging bellows 40c in the event of a piping rupture accident in another process piping outside outer well wall 32a. Jet deflector 42c is welded to outer well wall protective sleeve 25 at weld point 87, with a gap between it and outer well wall secondary sleeve 43.The gap is provided to accommodate the expansion of the bellows 40c. The jet deflector 42c may be connected to the outer well wall secondary sleeve 43. In this case, the gap is provided between the jet deflector 42c and the outer well wall protection sleeve 25. In this embodiment, even if the dry well wall 4a and the outer well wall 32a behave differently due to an accident or earthquake that causes a rise in pressure inside the containment vessel 3, the bellows 40c absorbs the piping reaction force, thereby preventing damage to the walls surrounding the dry well penetration 15 and the outer well penetration 24. Note that while only one bellows 40c is shown in Figure 8a for simplicity, multiple bellows 40c may be provided to improve expansion and contraction. Note that because the communication space 31 is highly airtight due to welding, radioactive materials will not actually leak from the communication space 31 even if an accident occurs in which radioactive materials are released into the containment vessel 3. However, since the communication space 31 opens to the upper dry well 4c and the external well penetration end plate 19b is located outside the external well wall 32a, the double containment function of the double-shell reactor containment vessel 20 is not achieved at the process piping penetration 26.

[0048] (Explanation of FIG. 8b) FIG. 8b is a cross-sectional view showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to an eleventh embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 10 (FIG. 8a). This embodiment further includes a backing plate 33, a lid 34, and a hinge 35. The configuration, action, and function thereof are the same as those described in Example 2 (see FIGS. 4a to 4c). The lid 34 is openable and closable (see FIG. 4c). The lid 34 is normally closed. The lid 34 isolates the communication space 31 from the upper dry well 4c. This allows the communication space 31 to function as a double containment for radioactive materials even in the event of an accident in which radioactive materials are released into the containment vessel 3. The configuration of this embodiment is the same as that of Example 2 (FIG. 4a), except that an outer well wall secondary sleeve 43, a bellows 40c, an outer well wall secondary sleeve end plate 45a, and a jet deflector plate 42c are further provided around the outer well wall protection sleeve 25.

[0049] (Explanation of FIG. 9a) FIG. 9a is a cross-sectional view showing the configuration of a process piping penetration 26 of a double-shell reactor containment vessel 20 according to a twelfth embodiment of the present invention. In this embodiment, a drywell penetration end plate 19a is further provided at the outer end of the upper drywell wall 4a of the drywell wall protection sleeve 18. The drywell penetration end plate 19a is welded to the drywell wall protection sleeve 18 at a welding point 70. The drywell penetration end plate 19a constitutes the drywell penetration 15. The basic configuration of this embodiment is the same as that of the process piping penetration 26 of the conventional second nuclear plant (see FIG. 17). The drywell wall-side process piping 14d and the outer well wall-side process piping 14e are field-welded at a welding point 71. In FIG. 9a, an outer well protection means 27 is provided between the drywell penetration 15 and the outer well penetration 24. The outer well protection means 27 is welded to the drywell penetration end plate 19a at a welding point 73. The outer well protection means 27 is welded to the outer well wall protection sleeve 25 at weld points 74. The outer well protection means 27 completely surrounds the portion 14c of the process piping 14 that passes between the dry well penetration 15 and the outer well penetration 24, isolating it from the outer well 32. The outer well protection means 27, the dry well penetration end plate 19a, the process piping 14, the outer well penetration end plate 19b, and the outer well wall protection sleeve 25 form a sealed space 28. Even if the process piping 14 breaks inside the sealed space 28, the break flow is contained inside the sealed space 28. Therefore, even if the process piping 14 breaks inside the sealed space 28, a pressure increase inside the outer well 32 can be suppressed. On the other hand, if the process piping 14 breaks inside the sealed space 28, the break cannot be detected by a pressure gauge (not shown) inside the outer well 32. To detect the break, a pressure gauge or the like must be provided for the sealed space 28. Furthermore, after the dry well wall side process piping 14d and the external well side process piping 14e are welded on-site at welding point 71, the external well protection means 27 must be welded on-site at welding points 73 and 74. For this reason, the external well protection means 27 must be split horizontally into two parts with semicircular cross sections, and welded on-site into a piping shape.Furthermore, the external well protection means 27 must be designed to withstand the pressure that would be generated if the process piping 14 inside it were to rupture, and must be designed to withstand high pressures similar to those of the process piping 14. The external well wall protection sleeve 25 must also be designed to withstand high pressures similar to those of the process piping 14.

[0050] In Figure 9a, the drywell wall protection sleeve 18, the drywell penetration end plate 19a, and the portion 14a of the process piping 14 within the drywell wall protection sleeve 18 constitute the drywell penetration space 15a. The drywell penetration space 15a is connected to the upper drywell 4c and constitutes part of the drywell 4c. Therefore, in the event of an accident in which radioactive material is released into the containment vessel 3, the radioactive material will enter the drywell penetration space 15a. The drywell penetration end plate 19a is integrally forged with the process piping 14 and welded to the drywell wall protection sleeve 18. Therefore, in reality, radioactive material will not leak outside the drywell penetration space 15a. However, even if radioactive material does leak outside the drywell penetration space 15a, any radioactive material leaked into the external well 32 will be contained within the external well 32. Furthermore, any radioactive material leaked into the sealed space 28 will be contained within the sealed space 28. Therefore, in this embodiment, the process piping penetration 26 has a double containment function for radioactive materials.

[0051] In this embodiment ( Figure 9a ), the drywell penetration end plate 19a is provided, and construction space is required for inserting and installing the drywell wall-side process piping 14d into the drywell wall protection sleeve 18 from the outside of the drywell wall 4a. Therefore, installation of the outer well wall 32a, the outer well wall protection sleeve 25, and the outer well wall-side process piping 14e cannot be performed until installation of the drywell wall 4a, the drywell wall protection sleeve 18, and the drywell wall-side process piping 14d is complete. In other words, parallel construction on the drywell wall 4a side and the outer well wall 32a side is not possible. Furthermore, welding of the outer well protection means 27 cannot be performed until welding of the drywell wall-side process piping 14d and the outer well wall-side process piping 14e is completed. This significantly lengthens the construction period in this embodiment. Furthermore, in this embodiment, the drywell penetration 15 and the outer well penetration 24 are firmly connected by the outer well protection means 27. Therefore, if the dry well wall 4a and the external well wall 32a behave differently due to an accident or earthquake that causes the pressure inside the reactor containment vessel 3 to rise, a large piping reaction force will act on the dry well penetration 15 and the external well penetration 24, which could cause damage to the walls around the dry well penetration 15 and the external well penetration 24.

[0052] (Explanation of Figure 9b) Figure 9b is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a thirteenth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 12 (Figure 9a). This embodiment is characterized by the addition of a bellows 40a to the drywell penetration 15 to mitigate the piping reaction force caused by an accident or earthquake that increases the pressure inside the reactor containment vessel 3. The bellows 40a is made of steel. The bellows 40a is expandable and contractible. In Figure 9b, a drywell wall secondary sleeve 41 is provided around the drywell wall protection sleeve 18. No sleeve fastener is provided on the drywell wall protection sleeve 18. A sleeve fastener (not shown; see Figure 13) is provided on the drywell wall secondary sleeve 41. The drywell wall secondary sleeve 41 is made of steel. The inner diameter of the drywell wall secondary sleeve 41 is larger than the outer diameter of the drywell wall protection sleeve 18. The bellows 40a is welded to the drywell wall secondary sleeve 41 at weld 75 inside the outer well 32. The bellows 40a is further welded to the drywell wall secondary sleeve end plate 44 at weld 76. In this embodiment, the drywell wall secondary sleeve end plate 44 is integrally forged with the drywell penetration end plate 19a and the drywell wall-side process piping 14d. The drywell wall secondary sleeve end plate 44 and the drywell penetration end plate 19a are sometimes collectively referred to as the end plate. The bellows 40a has the same airtightness and pressure resistance as the containment vessel 3. However, it is not resistant to piping collisions or jets that could occur if the process piping 14 ruptures inside the drywell penetration 15. However, even in such a case, the drywell wall protective sleeve 18 blocks the piping collisions and jets, preventing damage to the bellows 40a. In other words, the drywell wall protective sleeve 18 serves as a protective piping for the bellows 40a. For this reason, in this embodiment, the drywell wall protection sleeve 18 may be simply referred to as protection piping. However, for clarity, the term drywell wall protection sleeve 18 will be used below. Furthermore, a jet deflector 42a is provided on the upper drywell 4c side of the drywell wall secondary sleeve 41.The jet deflector 42a is provided to prevent the jet from penetrating the drywell wall secondary sleeve 41 and damaging the bellows 40a in the event of a piping rupture in another process piping within the upper drywell 4c. The jet deflector 42a is welded to the drywell wall protection sleeve 18 at weld points 77, leaving a gap between it and the drywell wall secondary sleeve 41. The gap is provided to accommodate expansion of the bellows 40a. The jet deflector 42a may also be connected to the drywell wall secondary sleeve 41. In that case, the gap is provided between the jet deflector 42a and the drywell wall protection sleeve 18. Note that the bellows 40a could also be provided on the upper drywell 4c side, but this is not advisable due to the narrowness of the upper drywell 4c. In this embodiment, even if the dry well wall 4a and the external well wall 32a behave differently due to an accident or earthquake that causes a rise in pressure inside the containment vessel 3, the bellows 40a absorbs the piping reaction force, preventing damage to the walls around the dry well penetration 15 and the external well penetration 24. Note that while only one bellows 40a is shown in Figure 9b for simplicity, multiple bellows 40a may be provided to improve flexibility. In this embodiment, the double containment function for radioactive materials at the process piping penetration 26 is ensured, as in Example 12 (Figure 9a).

[0053] In this embodiment (Figure 9b), the drywell penetration end plate 19a and secondary sleeve end plate 44 are provided, and construction space is required to insert and install the drywell wall-side process piping 14d into the drywell wall protection sleeve 18 from the outside of the drywell wall 4a. Therefore, construction of the outer well wall 32a and outer well penetration 24 cannot begin until construction of the drywell wall 4a and drywell penetration 15 is complete. In other words, parallel construction on the drywell wall 4a side and the outer well wall 32a side is not possible. Furthermore, welding of the outer well protection means 27 cannot begin until welding of the drywell wall-side process piping 14d and the outer well wall-side process piping 14e is completed. This significantly lengthens the construction period for this embodiment.

[0054] (Explanation of FIG. 9c) FIG. 9c is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a fourteenth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 12 (FIG. 9a). This embodiment is characterized by the addition of a bellows 40b to the external well penetration 24 to mitigate piping reaction forces due to accidents or earthquakes that cause pressure increases inside the containment vessel 3. The configurations of the external well penetration 24 and the bellows 40b are the same as those of Example 8 (FIG. 7a), and therefore a description thereof will be omitted. Note that while the bellows 40b could also be provided on the external well 32 side, this would be inadvisable because it would overlap with the external well protection means 27. In this embodiment, even if the dry well wall 4a and the external well wall 32a behave differently due to an accident or earthquake that causes pressure increases inside the containment vessel 3, the bellows 40b absorbs the piping reaction forces, thereby preventing damage to the walls surrounding the dry well penetration 15 and the external well penetration 24. 9c shows only one bellows 40b for simplicity, but multiple bellows 40b may be provided to improve flexibility. In this embodiment, the double containment function of radioactive materials at the process piping penetration 26 is ensured, as in Example 12 (FIG. 9a).

[0055] (Explanation of FIG. 10a) FIG. 10a is an explanatory diagram showing the configuration of a process piping penetration 26 of a double-shell reactor containment vessel 20 according to a fifteenth embodiment of the present invention. In this embodiment, the drywell penetration end plate 19a is provided connected to the outer well wall protection sleeve 25. The drywell penetration end plate 19a is welded to the outer well wall protection sleeve 25 at weld points 81. The drywell penetration end plate 19a constitutes the outer well penetration 24. The drywell penetration end plate 19a is not integrally forged with the process piping 14, but is welded to the process piping 14 at weld points 82. The drywell penetration end plate 19a is separated from the drywell penetration 15 and does not constitute the drywell penetration 15. However, since it also functions as the end plate for the drywell penetration 15, it is referred to as the drywell penetration end plate 19a. The outer well protection means 27 is provided between the drywell wall protection sleeve 18 and the drywell penetration end plate 19a. The outer well protection means 27 is welded to the dry well wall protection sleeve 18 at weld points 83. The outer well protection means 27 is welded to the dry well penetration end plate 19a at weld points 84.

[0056] In this embodiment ( FIG. 10 a ), the construction process is as follows: The drywell wall 4 a and the drywell wall protection sleeve 18 are constructed first. Concurrently, the outer well wall 32 a and the outer well wall protection sleeve 25 are constructed. The drywell penetration end plate 19 a is welded to the outer well wall protection sleeve 25 at weld point 81. The process piping 14 and the outer well penetration end plate 19 b, manufactured by integral forging, are passed from the outside of the outer well wall 32 a through the outer well wall protection sleeve 25, the drywell penetration end plate 19 a, and the drywell wall protection sleeve 18. The outer well penetration end plate 19 b and the outer well wall protection sleeve 25 are welded to weld point 72. Next, the drywell penetration end plate 19 a is welded to the process piping 14 at weld point 82. Finally, the outer well protection means 27 is welded to the drywell wall protection sleeve 18 and the drywell penetration end plate 19 a at weld points 83 and 84. The outer well protection means 27 must be installed after welding of the weld points 82 has been completed. For this reason, the outer well protection means 27 must be divided horizontally into two semicircular sections, which must be welded on-site to form a pipe. The process pipe 14 is not welded along the way. The process pipe 14 is a single, continuous pipe inside the process pipe penetration 26. This is possible because the dry well penetration end plate 19a is not manufactured by integral forging with the process pipe 14, but is welded to the process pipe 14 after it has been installed.

[0057] In this embodiment ( FIG. 10 a), the outer well protection means 27 completely surrounds the portion 14 c of the process piping 14 between the dry well penetration 15 and the outer well penetration 24, isolating it from the outer well 32. Therefore, even if the process piping 14 breaks inside the outer well protection means 27, the break flow is not released into the outer well 32, and the pressure inside the outer well 32 does not rise above the design pressure of the outer well 32. If the process piping 14 breaks inside the outer well protection means 27, the break flow passes through the dry well wall protection sleeve 18 and is released into the upper dry well 4 c. Steam generated from the break flow passes through the LOCA vent pipe 8 and is vented into the pressure suppression pool 6 where it condenses (see FIG. 1 ). Therefore, the pressure inside the containment vessel 3 does not exceed the design pressure.

[0058] In this embodiment ( FIG. 10 a), the drywell penetration end plate 19 a, the process piping 14, the outer well penetration end plate 19 b, and the outer well wall protection sleeve 25 form a sealed space 29. If the process piping 14 breaks inside the sealed space 29, the breakage flow is contained within the sealed space 29. Therefore, no pressure rise occurs in the outer well 32. However, to detect a process piping break inside the sealed space 29, a pressure gauge or the like must be provided for the sealed space 29. In addition, although the drywell penetration end plate 19 a needs to be welded to the process piping 14 at weld point 82, this is not generally implemented but is implemented only in exceptional cases. In other words, this embodiment can only be implemented exceptionally.

[0059] In this embodiment ( FIG. 10 a), the drywell wall protection sleeve 18, the outer well protection means 27, the drywell penetration end plate 19a, and the process piping 14 form a drywell penetration space 15a. The drywell penetration space 15a is connected to the upper drywell 4c and forms part of the drywell 4c. Therefore, in the event of an accident in which radioactive material is released into the containment vessel 3, the radioactive material will enter the drywell penetration space 15a. The drywell wall protection sleeve 18 is welded to the outer well protection means 27. The outer well wall protection means 27 is welded to the drywell penetration end plate 19a. The drywell end plate 19a is welded to the process piping 14. Therefore, in reality, radioactive material will not leak outside the drywell penetration space 15a. However, even if radioactive material were to leak outside the drywell penetration space 15a, any radioactive material leaked into the outer well 32 would be contained within the outer well 32. Furthermore, radioactive materials leaking into the sealed space 29 are confined within the sealed space 29. Therefore, in this embodiment, the process piping penetration 26 has a double containment function for radioactive materials.

[0060] In this embodiment ( FIG. 10 a ), the dry well penetration 15 and the external well penetration 24 are firmly connected by an external well protection means 27. Therefore, if the dry well wall 4 a and the external well wall 32 a behave differently due to an accident or earthquake that causes a rise in pressure inside the containment vessel 3, a large piping reaction force will act on the dry well penetration 15 and the external well wall penetration 24, which could damage the walls around the dry well penetration 15 and the external well penetration 24.

[0061] (Explanation of FIG. 10b) FIG. 10b is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a sixteenth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 15 (FIG. 10a). This embodiment is further characterized by the provision of a bellows 40a at the drywell penetration 15 to mitigate piping reaction forces due to accidents or earthquakes that cause pressure increases inside the containment vessel 3. The configurations of the drywell penetration 15 and the bellows 40a are the same as those of Example 6 (FIG. 6a), and therefore a description thereof will be omitted. Note that while the bellows 40a could also be provided on the upper drywell 4c side, this is not advisable due to the narrowness of the upper drywell 4c. In this embodiment, even if the drywell wall 4a and the outer well wall 32a behave differently due to an accident or earthquake that causes pressure increases inside the containment vessel 3, the bellows 40a absorbs the piping reaction forces, thereby preventing damage to the walls surrounding the drywell penetration 15 and the outer well penetration 24. In Figure 10b, only one bellows 40a is shown for simplicity, but multiple bellows 40a may be provided to improve flexibility. In this embodiment, the bellows 40a are provided at the dry well penetration 15, so their installation work can be carried out in parallel with the construction work of the outer well wall 32a, thereby shortening the construction period. In this embodiment, the double containment function of radioactive materials at the process piping penetration 26 is ensured, as in Example 15 (Figure 10a).

[0062] (Explanation of Figure 10c) Figure 10c is an explanatory diagram showing the configuration of the process piping penetration 26 of the double-shell reactor containment vessel 20 according to a seventeenth embodiment of the present invention. The basic configuration of this embodiment is the same as that of Example 15 (Figure 10a). This embodiment is further characterized by the provision of a bellows 40b at the outer well penetration 24 to mitigate piping reaction forces due to accidents or earthquakes that cause pressure increases inside the containment vessel 3. The configurations of the bellows 40b, the outer well wall secondary sleeve 43, and the outer well wall secondary sleeve end plate 45 are the same as those of Example 8 (Figure 7a), and therefore will not be described here. Furthermore, a jet deflector 42b is provided on the dry well penetration end plate 19a. The jet deflector 42b is welded to the dry well penetration end plate 19a at weld points 94, with a gap between it and the outer well wall secondary sleeve 43. The gap is provided to accommodate expansion of the bellows 40b. The jet deflector 42b may be provided connected to the outer well wall secondary sleeve 43. In this case, the gap is provided between the jet deflector 42b and the dry well penetration end plate 19a. The bellows 40b could also be provided on the external dry well 32 side, but this would be inadvisable because it would overlap with the external well protection means 27. In this embodiment, even if the dry well wall 4a and the external well wall 32a behave differently due to an accident or earthquake that increases the pressure inside the containment vessel 3, the bellows 40b absorbs the piping reaction force, preventing damage to the walls surrounding the dry well penetration 15 and the external well penetration 24. While only one bellows 40b is shown in Figure 10c for simplicity, multiple bellows 40b may be provided to improve flexibility. In this embodiment, the double containment function of radioactive materials in the process piping penetration 26 is ensured, as in Example 15 (Figure 10a).

[0063] 1...core, 2...reactor pressure vessel (RPV), 3...reactor containment vessel, 3a...outer wall (cylindrical wall), 4...dry well, 4a...dry well wall (dry well common wall), 4b...top slab, 4c...upper dry well, 4d...lower dry well, 5...wet well, 5a...wet well wall (wet well common wall), 5b...diaphragm floor, 6...pressure suppression pool, 7...wet well gas phase, 8...LOCA vent pipe, 8a...horizontal vent pipe, 10...reactor containment vessel top lid, 12...reinforced concrete reactor containment vessel (RCCV), 13...foundation slab, 1 4...process piping, 14a...portion of process piping (portion within drywell wall protection sleeve 18), 14b...portion of process piping (portion within external well wall protection sleeve 25), 14c...portion of process piping (portion between drywell penetration 15 and external well penetration 24), 14d...drywell wall side process piping, 14e...external well wall side process piping, 15...drywell penetration, 15a...drywell penetration space, 16...inner isolation valve, 17...outer isolation valve, 18...drywell wall protection sleeve, 19a...drywell penetration end plate, 19b...external well Penetration end plate, 20...double shell reactor containment vessel, 21...first shell (inner shell), 22...second shell (outer shell), 23...foundation slab, 24...external well penetration, 24a...external well penetration space, 25...external well wall protection sleeve, 26...process piping penetration, 26a...process piping penetration protection sleeve, 27...external well protection means, 28...sealed space, 29...sealed space, 30...external well protection piping, 31...communication space, 32...external well, 32a...external well wall (outer wall), 32b...top slab, 33...back plate, 34...lid, 35...hinge, 36...bellows, 37...welded point , 38...welding point, 40a, b, c...bellows, 41...dry well wall secondary sleeve, 42a, b, c...jet deflector, 43...external well wall secondary sleeve, 44...dry well wall secondary sleeve end plate, 45, 45a...external well wall secondary sleeve end plate, 61...pedestal, 61a...pedestal cavity, 62...RPV skirt (vessel skirt), 63...RPV support (vessel support), 64...inner flange plate, 65...outer flange plate, 66...inner gusset plate, 67...outer gusset plate, 68...sleeve fixing device,70...welding point (dry well wall end plate 19a and dry well wall protection sleeve 18), 71...welding point (dry well wall side process piping 14d and outer well wall side process piping 14e), 72...welding point (external well penetration end plate 19b and outer well wall protection sleeve 25), 73...welding point (dry well penetration end plate 19a and outer well protection means 27), 74...welding point (external well protection means 27 and outer well wall protection sleeve 25), 75...welding point (bellows 40a and dry well 72...welding point (between the dry well wall secondary sleeve 41), 76...welding point (between the bellows 40a and the dry well wall secondary sleeve end plate 44), 77...welding point (between the jet deflector plate 42a and the dry well wall protection sleeve 18), 78...welding point (between the bellows 40b and the outer well wall secondary sleeve 43), 79...welding point (between the bellows 40b and the outer well wall secondary sleeve end plate 45), 80...welding point (between the jet deflector plate 42b and the outer well wall protection piping 30), 81...welding point (between the dry well penetration end plate 19a and the outer well wall protection sleeve 25), 82...welding point (dry well penetration end plate 19a and process piping 14), 83...welding point (external well protection means 27 and dry well wall protection sleeve 18), 84...welding point (external well protection means 27 and dry well penetration end plate 19a), 85...welding point (bellows 40b and external well secondary sleeve end plate 45), 86...welding point (external well wall secondary sleeve end plate 45 and external well protection piping 30), 87...welding point (jet deflector 42b and external well wall protection sleeve sleeve 25), 88...welding point (bellows 40b and external well wall secondary sleeve 44), 90...welding point (protection piping 30 and dry well wall protection sleeve 18), 91...welding point (protection piping 30 and external well wall protection sleeve 25), 92...welding point (dry well wall secondary sleeve end plate 44 and dry well wall protection sleeve 18), 93...welding point (jet deflection plate 42b and external well wall protection means 27), 94...welding point (jet deflection plate 42b and dry well penetration end plate 19a),

Claims

1. A reactor core, a reactor pressure vessel containing said core, a drywell containing said reactor pressure vessel, and a reinforced concrete reactor containment vessel having a wetwell containing a pressure suppression pool connected to said drywell via a LOCA vent pipe in the lower part and having a wetwell gas phase in the upper part, a pedestal supporting said reactor pressure vessel within said reactor containment vessel via an RPV skirt and an RPV support to form a pedestal cavity therein, an upper drywell which is the space above the RPV skirt of said drywell, a drywell wall constituting the outer wall of said upper drywell, a wetwell wall constituting the outer wall of said wetwell, an outer wall of the reactor containment vessel consisting of said drywell wall and said wetwell wall, an outer well made of reinforced concrete located outside said reactor containment vessel, adjacent to said outer wall of said reactor containment vessel, surrounding the outer wall of said reactor containment vessel and having the same pressure resistance and airtightness as said reactor containment vessel, and an outer well wall which is the outer wall of said outer well. a top slab of the external well airtightly connecting the upper end of the outer wall of the reactor containment vessel and the upper end of the external well wall; a double-shell reactor containment vessel made of reinforced concrete, consisting of the reactor containment vessel and the external well, with the outer wall of the reactor containment vessel as a first shell (inner shell) and the outer wall of the external well as a second shell (outer shell); process piping connected to the reactor pressure vessel, penetrating the drywell wall and the external well wall to reach the outside of the double-shell reactor containment vessel; a drywell wall protective sleeve penetrating the drywell wall to form a passage for the process piping within the drywell wall; a drywell penetration consisting of the drywell wall protective sleeve and a portion of the process piping passing through the interior of the drywell protective sleeve; an external well wall protective sleeve penetrating the external well wall to form a passage for the process piping within the external well wall; and an external well penetration consisting of the external well wall protective sleeve and a portion of the process piping passing through the interior of the external well wall protective sleeve.and an outer well protection means that is provided between the dry well penetration and the outer well penetration and surrounds the portion of the process piping that passes between the dry well penetration and the outer well penetration, isolating it from the outer well, wherein if the process piping breaks, a break flow will not flow into the outer well.

2. A nuclear power plant according to claim 1, wherein the external well protection means is an external well protection piping, and the external well protection piping is welded to the dry well wall protection sleeve and the external well wall protection sleeve.

3. A nuclear power plant according to claims 1 and 2, further comprising an openable and closable lid at the end of said dry well wall protection sleeve on the side of said upper dry well.

4. The nuclear power plant according to claim 1, wherein the dry well wall protection sleeve, the outer well protection means and the outer well protection sleeve constitute an integrated process piping penetration protection sleeve.

5. The nuclear power plant according to claim 4, wherein the process piping penetration protective sleeve is further provided with a bellows.

6. A nuclear power plant according to claims 4 and 5, further comprising an openable and closable cover at the end of the process piping penetration protection sleeve on the upper dry well side.

7. The nuclear power plant according to claim 1, further comprising a drywell penetration end plate extending from the process piping to the outer periphery outside the drywell wall and welded to the drywell wall protection sleeve, and the outer well protection means is welded to the drywell wall end plate and the outer well wall protection sleeve.

8. The nuclear power plant according to claim 1, further comprising a dry well penetration end plate connected to the outer well side end of the outer well wall protection sleeve and welded to the process piping, wherein the outer well protection means is welded to the dry well wall protection sleeve and the dry well penetration end plate.

9. A nuclear power plant according to any one of claims 1 to 8, further comprising a dry well wall secondary sleeve and a bellows provided on the outer periphery of the dry well wall protective sleeve.

10. A nuclear power plant according to any one of claims 1, 2, 3, 7 and 8, characterized in that an outer well wall secondary sleeve and a bellows are further provided on the outer periphery of the outer well wall protective sleeve.

Images