JP7624891B2 - Steam generator reinforcement method and steam generator - Google Patents

Description

This disclosure relates to a method for reinforcing a steam generator and a steam generator.

In a steam generator used in a pressurized water reactor (PWR) or the like, a heat exchanger is provided in a lower part of a cylindrical body for cooling high-temperature primary cooling water from the reactor by heat exchange between the primary cooling water and the secondary cooling water. A water supply part for supplying secondary cooling water to the heat exchanger and a steam-water separator for separating the secondary cooling water heated by the primary cooling water and rising in the heat exchanger into steam and hot water are provided in an upper part of the body. The water supply part discharges the secondary cooling water from the upper part of the heat exchanger in the body. At this time, a part of the secondary cooling water hits a target area on the outer surface of the steam-water separator. If the secondary cooling water hits the target area on the outer surface of the steam-water separator for a long period of time, the target area is thinned due to erosion or corrosion.
Patent Document 1 discloses a repair method for the case where the main body shell of a moisture separator through which steam flows is thinned by the steam flow, in which a coating of a corrosion-resistant alloy is formed by thermal spraying on the thinned portion.

JP 2011-219850 A

However, the space in which the target area of the outer surface of the steam-water separator that the secondary cooling water hits is located is narrow. For this reason, thermal spraying of the target area of the outer surface of the steam-water separator is difficult to perform, and it takes a long time to repair or reinforce the target area of the steam-water separator.

The present disclosure has been made to solve the above problems, and aims to provide a steam generator reinforcement method and steam generator that can improve the workability of reinforcement and efficiently reinforce the target area of the outer surface of the steam-water separator.

In order to solve the above problems, the method of reinforcing a steam generator according to the present disclosure includes a cylindrical body portion extending in the vertical direction, a heat exchange section provided in the lower part of the body portion for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool it, a water supply section provided above the heat exchange section within the body portion for supplying the secondary cooling water to the heat exchange section, and a steam-water separator provided above the heat exchange section within the body portion for separating the secondary cooling water, which is heated by the primary cooling water and rises in the heat exchange section, into steam and hot water. In a steam generator having a steam generator, a method for reinforcing a target area of the outer surface of the steam separator that is hit by the secondary cooling water supplied from the water supply unit includes a preparation step of preparing a plurality of backing plates processed into a shape that conforms to the target area of the outer surface outside the body, a carrying step of carrying the plurality of backing plates into the body, and a welding step of overlapping and welding the plurality of backing plates carried into the body to the target area of the outer surface and arranging them along the target area of the outer surface.

The steam generator according to the present disclosure comprises a cylindrical body extending in the vertical direction, a heat exchange section provided in the lower part of the body for cooling by heat exchange between high-temperature primary cooling water and secondary cooling water, a water supply section provided in the body above the heat exchange section for supplying the secondary cooling water to the heat exchange section, a steam-water separator provided in the body above the heat exchange section for separating the secondary cooling water that is heated by the primary cooling water and rises in the heat exchange section into steam and hot water, and a plurality of backing plates welded to a target area of the outer surface of the steam-water separator that is hit by the secondary cooling water supplied from the water supply section and aligned along the target area of the outer surface.

According to the present disclosure, it is possible to improve the workability of reinforcing the steam generator and efficiently reinforce the target area of the outer surface of the steam-water separator.

FIG. 1 is a schematic configuration diagram showing a steam generator according to an embodiment of the present disclosure. 2 is a diagram showing the relative positional relationship between the water supply section and a riser pipe of a steam-water separator in FIG. 1 as viewed from above the water supply section. FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2 . FIG. 4 is a perspective view showing the riser pipe and the backing plate attached to the outer peripheral surface of the riser pipe shown in FIGS. FIG. 5 is a perspective view showing a first example of the backing plate of FIG. 4 . FIG. 5 is a perspective view showing a second example of the backing plate of FIG. 4 . 10A to 10C are diagrams showing a process of attaching a backing plate to an outer circumferential surface of a riser pipe in a method for reinforcing a steam generator according to an embodiment of the present disclosure. 10A and 10B are diagrams showing an example of a method for pressing a backing plate against an outer circumferential surface of a riser pipe in the process of attaching the backing plate to the outer circumferential surface of the riser pipe.

<Embodiment>
(Configuration of steam generator)
The steam generator 1 of this embodiment shown in Fig. 1 is applied to, for example, a nuclear power plant. In the steam generator 1, heat is exchanged between high-temperature primary cooling water heated in a nuclear reactor (not shown) and secondary cooling water supplied from the outside, and steam is generated from the secondary cooling water by heat exchange with the primary cooling water. The generated steam can be sent from the steam generator 1 to a turbine generator (not shown) to generate electricity.
1 to 4, the steam generator 1 includes a body section 2, a heat exchange section 3, a water supply section 4, a steam-water separator 5, and a plurality of backing plates 9. Moreover, as shown in FIG. 1, the steam generator 1 further includes a water chamber head 6 and a moisture separator 7.

(Torso)
The body 2 is formed in a cylindrical shape extending in the vertical direction and has a lower body 2a forming a lower half, an upper body 2b forming an upper half, a conical body 2c connecting the lower body 2a and the upper body 2b, and an upper mirror 2d provided at the upper end of the upper body 2b.
The upper body 2b has a manhole 21 (entrance/exit) for entering and exiting the inside of the body 2. The manhole 21 is located at the top of the upper body 2b, but is not limited thereto. The size of the manhole 21 is, for example, large enough for a person to pass through. The upper body 2b is provided with a lid 23 for opening and closing the manhole 21. The upper body 2b has a slightly smaller diameter than the lower body 2a. The conical body 2c is formed in a substantially truncated cone shape so that the lower body 2a and the upper body 2b can be connected. The upper mirror 2d is formed with a steam exhaust port 22. A pipe (not shown) is connected to the steam exhaust port 22 for sending steam exhausted from the body 2 to a turbine generator.

A tube sheet 8 is disposed at the lower end of the lower body 2a. The tube sheet 8 covers the opening at the lower end of the lower body 2a. The tube sheet 8 has multiple tube holes 8a that penetrate in the vertical direction.

(Heat exchange section)
The heat exchange unit 3 is provided inside the lower body 2a (the lower part of the body 2) and cools the high-temperature primary cooling water by heat exchange between the primary cooling water and the secondary cooling water. The heat exchange unit 3 has a tube bundle outer cylinder 31 (wrapper tube), a heat transfer tube bundle 32A, a tube support plate 33, and an anti-vibration member 34.
The tube bank outer cylinder 31 is formed in a cylindrical shape extending in the vertical direction. The tube bank outer cylinder 31 is disposed at a predetermined interval from the inner peripheral surface of the lower body 2a. The lower end of the tube bank outer cylinder 31 is located near the tube sheet 8 disposed at the lower end of the lower body 2a. The upper end of the tube bank outer cylinder 31 is connected to the lower end of the riser pipe 51 of the steam-water separator 5.

The heat transfer tube group 32A is provided inside the tube group outer cylinder 31. The heat transfer tube group 32A has a plurality of heat transfer tubes 32 that are in an inverted U-shape and extend in the vertical direction. Each heat transfer tube 32 is arranged so that it extends from the upper end to the lower end of the lower body 2a with the arc portion of the U-shape facing upward. Both ends of each heat transfer tube 32 located on the lower end side of the lower body 2a are inserted and fixed into the tube holes 8a of the tube plate 8. As a result, both ends of each heat transfer tube 32 open below the tube plate 8.

The tube support plate 33 is attached to the tube bundle outer cylinder 31 so that its plate thickness direction faces the up-down direction of the tube bundle outer cylinder 31. Multiple tube support plates 33 are arranged at intervals in the up-down direction. The multiple tube support plates 33 support the heat transfer tubes 32 at their mid-length portions. Specifically, the tube support plate 33 has multiple heat transfer tube insertion holes 33a formed therein that penetrate in the plate thickness direction. The tube support plate 33 supports the heat transfer tubes 32 by inserting the heat transfer tubes 32 into the heat transfer tube insertion holes 33a.

The vibration-proof member 34 is inserted between the overlapping arc portions of the heat transfer tube 32. The vibration-proof member 34 suppresses fluid-induced vibrations that may occur in the U-shaped arc portions of the heat transfer tube 32 when the primary cooling water passes through the heat transfer tube 32.

The heat exchange section 3 configured as above is formed with a flow passage 35. The flow passage 35 is formed so that the secondary cooling water supplied from the water supply section 4 into the lower body 2a flows down between the inside of the lower body 2a and the outside of the tube group outer cylinder 31, turns around at the tube plate 8, and rises along the heat transfer tube group 32A inside the tube group outer cylinder 31.

(Mizumikagami)
The water chamber head 6 is provided below the tube plate 8. The inside of the water chamber head 6 is divided into an inlet side water chamber 6A and an outlet side water chamber 6B. One end of each of the heat transfer tubes 32 is connected to the inlet side water chamber 6A. Meanwhile, the other end of each of the heat transfer tubes 32 is connected to the outlet side water chamber 6B.

The water chamber mirror 6 is formed with an inlet nozzle 6Aa that opens the inlet side water chamber 6A to the outside of the water chamber mirror 6, and an outlet nozzle 6Ba that opens the outlet side water chamber 6B to the outside of the water chamber mirror 6. A piping (not shown) is connected to the inlet nozzle 6Aa for sending the primary cooling water from the reactor to the heat exchange section 3. A piping (not shown) is connected to the outlet nozzle 6Ba for returning the primary cooling water after heat exchange in the heat exchange section 3 to the reactor.

(Water Supply Department)
1 and 2, the water supply section 4 is provided inside the upper body 2b (above the heat exchange section 3 within the body section 2). The water supply section 4 introduces secondary cooling water from the outside of the body section 2 and supplies it to the heat exchange section 3. The water supply section 4 has an annular water supply pipe 41 and a plurality of discharge pipes 42 (J tubes).
The ring-shaped water supply pipe 41 is formed in a ring shape along the inner circumference of the cylindrical upper body 2b. An introduction pipe 43 is connected to the ring-shaped water supply pipe 41, which passes through the upper body 2b and introduces secondary cooling water from the outside into the ring-shaped water supply pipe 41.

2 , the multiple discharge pipes 42 are provided on the annular water supply pipe 41 so as to be arranged at intervals from each other in the circumferential direction of the annular water supply pipe 41. Each discharge pipe 42 discharges the secondary cooling water flowing in the annular water supply pipe 41 downward toward the heat exchange section 3.
As shown in Fig. 3, one longitudinal end of each discharge pipe 42 is connected to the annular water supply pipe 41. The other longitudinal end of each discharge pipe 42 is a discharge port 42b through which the secondary cooling water is discharged, and faces downward. Specifically, each discharge pipe 42 is curved in a J shape so as to extend upward from the upper end of the annular water supply pipe 41 and then turn back downward. The discharge port 42b of each discharge pipe 42 is located radially inside the annular water supply pipe 41.

(Steam/water separator)
1, the steam-water separator 5 is provided inside the upper body 2b (above the heat exchange section 3 within the body 2). The steam-water separator 5 separates the secondary cooling water, which is heated by the primary cooling water in the heat exchange section 3 and rises, into steam and hot water.

The steam-water separator 5 has a cylindrical riser pipe 51 that extends in the vertical direction. The lower end of the riser pipe 51 is connected to the upper end of the tube group outer cylinder 31 of the heat exchange section 3. As a result, the secondary cooling water rising inside the tube group outer cylinder 31 of the heat exchange section 3 passes inside the riser pipe 51. As shown in Figures 1 and 2, the diameter of the riser pipe 51 viewed from the vertical direction is smaller than the diameter of the annular water supply pipe 41 of the water supply section 4. The riser pipe 51 is arranged to pass inside the annular water supply pipe 41 in the vertical direction.

When viewed from the top and bottom, the riser pipe 51 is located close to the inner edge of the annular water supply pipe 41. For this reason, as shown in Figures 2 and 3, a portion of the circumferential area of the outer peripheral surface 51a (outer surface) of the riser pipe 51 is located close to the discharge port 42b of the discharge pipe 42 of the water supply section 4, and serves as a target area 51aA that is hit by the secondary cooling water discharged from the discharge port 42b. The angular range of the target area 51aA of the riser pipe 51 in the circumferential direction may be, for example, 170 degrees to 180 degrees, but is not limited to this.

(Backing plate)
As shown in FIGS. 2 to 4, the backing plates 9 are overlapped and welded to the target area 51aA of the riser pipe 51. Each backing plate 9 is formed in a shape that conforms to the outer peripheral surface 51a of the cylindrical riser pipe 51 so as to be in close contact (surface contact) with the target area 51aA of the riser pipe 51. As shown in FIGS. 4 to 6, the backing plate 9 is formed in a shape that is curved in an arc shape in one direction along the surface of the backing plate 9. Specifically, each backing plate 9 is formed in a curved rectangular shape having a pair of horizontal sides 9a extending along the circumferential direction of the riser pipe 51 and a pair of vertical sides 9b extending along the longitudinal direction (up-down direction) of the riser pipe 51. The size of each backing plate 9 is smaller than the entire area of the target area 51aA of the riser pipe 51. In this embodiment, each backing plate 9 is formed in a shape and size that can pass through the manhole 21 (see FIG. 1) of the body 2.

As shown in FIG. 4, the multiple backing plates 9 are arranged along the outer peripheral surface 51a (outer surface) of the riser pipe 51 so as to cover the entire target area 51aA of the riser pipe 51. Here, the length of the vertical side 9b of the backing plate 9 is set to be equal to or greater than the length of the target area 51aA in the longitudinal direction of the riser pipe 51. In addition, the length of the horizontal side 9a of the backing plate 9 is smaller than the length of the target area 51aA in the circumferential direction of the riser pipe 51. Therefore, the multiple backing plates 9 are arranged only in the circumferential direction of the riser pipe 51. Note that if the length of the vertical side 9b of the backing plate 9 is smaller than the length of the target area 51aA in the longitudinal direction of the riser pipe 51, the multiple backing plates 9 may also be arranged in the longitudinal direction (up and down direction) of the riser pipe 51.

The backing plates 9 arranged in the circumferential direction of the riser pipe 51 are fixed to the riser pipe 51 by welding. At least one pair of horizontal sides 9a of each backing plate 9 is joined to the riser pipe 51 by fillet welding. In addition, the vertical sides 9b of the backing plates 9 forming both ends of the backing plates 9 in the circumferential direction of the riser pipe 51 are also joined to the riser pipe 51 by fillet welding. However, when all of the four sides 9a, 9b are joined by welding, a part of the sides is left unwelded in order to release air remaining inside.
The vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction of the riser pipe 51 may be joined to the riser pipe 51 by, for example, fillet welding. Note that the vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction of the riser pipe 51 may not be welded, for example, by simply fitting these vertical sides 9b to each other. In this case, the vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction may be formed, for example, in an uneven shape that fits into each other.

Each backing plate 9 is preferably made of a material that has high corrosion resistance to the secondary cooling water. Examples of materials that have high corrosion resistance to the secondary cooling water include Cr-Mo low alloys and Ni-based alloys.

Figure 5 shows a backing plate 9C formed from a Cr-Mo low alloy. The backing plate 9C shown in Figure 5 has a main body plate portion 91 made of a Cr-Mo low alloy, and an edge portion 92 made of carbon steel and welded to at least a part of the periphery of the main body plate portion 91. The edge portion 92 made of carbon steel may be provided at the portion of the backing plate 9C that is to be welded to the riser pipe 51. In the backing plate 9C shown in Figure 5, only the portions of the backing plate 9C that form a pair of horizontal sides 9a (the upper and lower portions of the backing plate 9C) are formed from the edge portion 92 made of carbon steel. Note that the portions that form the pair of horizontal sides 9a and the pair of vertical sides 9b (i.e., the entire periphery of the backing plate 9C) may be formed from the edge portion 92 made of carbon steel.

Figure 6 shows the backing plate 9N when it is made of a Ni-based alloy. The backing plate 9 made of a Ni-based alloy is made of a single material (i.e., only the Ni-based alloy).

(Moisture separator)
1, the moisture separator 7 is disposed inside the upper body 2b and above the steam-water separator 5. The moisture separator 7 removes moisture from the steam separated in the steam-water separator 5 to produce a state close to dry steam.

In the steam generator 1 shown in FIG. 1, the primary cooling water heated by the reactor is sent to the inlet water chamber 6A, circulates through the heat transfer tubes 32 of the heat exchange section 3, and reaches the outlet water chamber 6B. Meanwhile, the secondary cooling water is supplied to the heat exchange section 3 from the water supply section 4, passes through the flow passage 35 of the heat exchange section 3, and rises along the heat transfer tube group 32A. At this time, in the heat exchange section 3, heat exchange occurs between the high-temperature primary cooling water and the secondary cooling water, and the cooled primary cooling water is returned to the reactor from the outlet water chamber 6B. Meanwhile, the secondary cooling water heated by the primary cooling water rises inside the tube group outer cylinder 31 and is separated into steam and hot water in the steam separator 5. Then, the separated steam is discharged to the outside of the body 2 through the steam outlet 22 after moisture is removed in the moisture separator 7, and is sent to the turbine generator.

(Method of reinforcing steam generator)
Next, a method for reinforcing a steam generator according to this embodiment will be described.
The configuration of the steam generator before reinforcement is the same as the configuration of the steam generator 1 shown in Figures 1 to 4 except for a plurality of backing plates 9. The target to be reinforced in the steam generator reinforcement method is a target area 51aA of the outer circumferential surface 51a of the riser pipe 51 (the outer surface of the steam-water separator 5) with which the secondary cooling water supplied from the water supply section 4 hits.

To reinforce the outer peripheral surface 51a of the riser pipe 51, first, a preparation step is performed in which multiple backing plates 9 as illustrated in Figures 5 and 6 are prepared outside the torso 2 (for example, in another factory away from the steam generator). In the preparation step, each backing plate 9 is processed into a shape that conforms to the target area 51aA of the outer peripheral surface 51a of the riser pipe 51. Also, in the preparation step, each backing plate 9 is formed into a shape and size that allows it to pass through the manhole 21 (see Figure 1) of the torso 2. In this embodiment, the length of the vertical side 9b of the backing plate 9 prepared in the preparation step is equal to or greater than the length of the target area 51aA in the longitudinal direction of the riser pipe 51. Also, the length of the horizontal side 9a of the backing plate 9 is smaller than the length of the target area 51aA in the circumferential direction of the riser pipe 51.

In the preparation step, a backing plate 9C (see FIG. 5) made of a Cr-Mo low alloy or a backing plate 9N (see FIG. 6) made of a Ni-based alloy is prepared. When preparing a backing plate 9C made of a Cr-Mo low alloy in the preparation step, as shown in FIG. 5, a rim portion 92 made of carbon steel is joined to the periphery of a main body plate portion 91 made of a Cr-Mo low alloy by welding (e.g., buttering welding). When welding the main body plate portion 91 and the rim portion 92, a post-heat treatment is performed depending on the composition of the members.

After the preparation step, a carrying step is performed in which multiple backing plates 9 are carried into the interior of the torso 2. In the carrying step, multiple backing plates 9 are carried into the torso 2 through the manhole 21 of the torso 2. Here, each backing plate 9 is formed in a shape and size that allows it to pass through the manhole 21, so that each backing plate 9 can be carried into the interior of the torso 2 easily and reliably.

After the carrying step, a welding step is performed in which the multiple backing plates 9 carried into the body 2 are overlapped and welded to the target area 51aA of the outer circumferential surface 51a of the riser pipe 51, and aligned along the target area 51aA. The welding step will be described in detail below.

In the welding step, first, as shown in FIG. 7, the area (hereinafter referred to as the welding area 51aB) of the outer circumferential surface of the riser pipe 51 to which the backing plate 9 is to be welded is polished so that the backing plate 9 can be well welded to the riser pipe 51. The welding area 51aB in FIG. 7 is a band-shaped area extending in the circumferential direction of the riser pipe 51, and two are formed at an interval in the longitudinal direction (up and down direction) of the riser pipe 51. These two welding areas 51aB are located on both sides of the target area 51aA in the longitudinal direction of the riser pipe 51. The positions of the two welding areas 51aB correspond to a pair of horizontal sides 9a of the backing plate 9. When the vertical sides 9b of the backing plate 9 are welded to the riser pipe 51, a band-shaped welding area (not shown) extending in the longitudinal direction of the riser pipe 51 and corresponding to the vertical sides 9b of the backing plate 9 may be formed on the riser pipe 51.

Next, as shown in FIG. 8, the backing plate 9 is placed over the target area 51aA of the outer circumferential surface 51a of the riser pipe 51, and it is confirmed whether the backing plate 9 is in close contact (surface contact) with the outer circumferential surface 51a of the riser pipe 51 without any gaps. If there is a gap between the backing plate 9 and the outer circumferential surface 51a of the riser pipe 51, the backing plate 9 is pressed against the outer circumferential surface 51a of the riser pipe 51, for example, using the pressing tool 10 shown in FIG. 8.

The pressing tool 10 has a base member 101 and a wedge member 102. The base member 101 is formed in an L-shape and has an opposing portion 103 that faces the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 with a gap therebetween when the base member 101 is attached to the riser pipe 51 by welding. The wedge member 102 is sandwiched between the backing plate 9 arranged to overlap the target area 51aA of the riser pipe 51 and the opposing portion 103 of the base member 101. By sandwiching the wedge member 102 between the backing plate 9 and the opposing portion 103 of the base member 101, the backing plate 9 can be pressed against the outer circumferential surface 51a of the riser pipe 51. This allows the backing plate 9 to be in close contact with the outer circumferential surface 51a of the riser pipe 51 without any gaps. The pressing tool 10 is removed from the riser pipe 51 after the backing plate 9 is welded.

After it is confirmed that the backing plate 9 is in close contact with the outer circumferential surface 51a of the riser pipe 51 without any gaps, the backing plate 9 is temporarily attached to the riser pipe 51 by welding. The backing plate 9 is temporarily attached to the riser pipe 51 by TIG welding or the like so that short weld beads (spot-shaped weld beads) are spaced apart. The backing plate 9 is temporarily attached at least between a pair of horizontal sides 9a of the backing plate 9 and the welded area 51aB of the riser pipe 51 (see FIG. 7). The backing plate 9 may also be temporarily attached, for example, between the vertical sides 9b of the backing plate 9 and the corresponding welded area (not shown) of the riser pipe 51.

After the temporary attachment of the backing plate 9, the backing plate 9 is permanently welded. In the permanent welding of the backing plate 9, the backing plate 9 is welded to the riser pipe 51 by fillet welding or the like so that the weld bead is longer than when the backing plate 9 was temporarily attached. In the permanent welding, for example, the backing plate 9 may be welded to the riser pipe 51 by continuous welding in which the entire horizontal side 9a or vertical side 9b of the backing plate 9 is welded. In the permanent welding, for example, the backing plate 9 may be welded to the riser pipe 51 by intermittent welding (tap welding) in which multiple linear weld beads are arranged at intervals along the horizontal side 9a or vertical side 9b of the backing plate 9.

In this embodiment, the upper horizontal side 9a of the backing plate 9 and the vertical sides 9b of the backing plates 9 forming both ends of the multiple backing plates 9 in the circumferential direction of the riser pipe 51 are welded to the riser pipe 51 by continuous welding. The lower horizontal side 9a of the backing plate 9 is welded to the riser pipe 51 by intermittent welding. Note that the vertical sides 9b of the backing plates 9 adjacent to each other in the circumferential direction of the riser pipe 51 do not have to be welded to the riser pipe 51 by, for example, fitting together, or may be welded to the riser pipe 51 by, for example, continuous welding.
By joining the upper horizontal edges 9a and vertical edges 9b of the backing plate 9 to the riser pipe 51 by continuous welding, the secondary cooling water discharged from the water supply section 4 can be prevented from entering between the riser pipe 51 and the backing plate 9 even if it flows downward from above the backing plate 9.

In the welding step, the plurality of backing plates 9 are welded together to cover the entire target area 51aA of the outer circumferential surface 51a of the riser pipe 51. In the welding step, when welding the plurality of backing plates 9, for example, a given backing plate 9 may be temporarily attached and then permanently welded, and then another backing plate 9 may be temporarily attached and then permanently welded, or, for example, the plurality of backing plates 9 may be temporarily attached and then permanently welded.
When the above-mentioned welding steps are completed, the method for reinforcing the steam generator is completed.

This method of reinforcing a steam generator can be applied to both steam generators that are already in use and steam generators that have not yet been used (before use). In a steam generator that has already been used, the above-mentioned method of reinforcing a steam generator can be applied to repair the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 that has been thinned by contact with the secondary cooling water with multiple backing plates 9. Also, in a steam generator that has not yet been used (before use), the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 can be reinforced with backing plates 9 to prevent the target area 51aA from being thinned by the secondary cooling water.

According to the steam generator 1 and the reinforcing method for a steam generator of this embodiment, the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 (the outer surface of the steam-water separator 5) is covered by the backing plate 9. This makes it possible to suppress or prevent the secondary cooling water supplied from the water supply section 4 from hitting the target area 51aA of the outer circumferential surface 51a of the riser pipe 51. In other words, the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 can be protected from the secondary cooling water. This makes it possible to suppress or prevent the outer circumferential surface 51a of the riser pipe 51 from being thinned due to erosion or corrosion.

In addition, by providing a plurality of backing plates 9 corresponding to the target area 51aA of the outer circumferential surface 51a of the riser pipe 51, the size of each backing plate 9 can be made smaller than the target area 51aA. This makes it easy to carry the backing plate 9 into the body 2. In addition, by making each backing plate 9 small, even if the distance between the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 and the water supply section 4 (particularly the annular water supply pipe 41 and the discharge pipe 42) is narrow, each backing plate 9 can be easily welded to the outer circumferential surface 51a of the riser pipe 51. In other words, the workability of the reinforcement can be improved, and the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 can be reinforced efficiently.

In addition, in the steam generator 1 and the method for reinforcing a steam generator of this embodiment, the backing plate 9 is formed of a Cr-Mo low alloy or Ni-based alloy that has high corrosion resistance to secondary cooling water. This makes it possible to effectively prevent the backing plate 9 from being thinned due to erosion or corrosion, even if the secondary cooling water supplied from the water supply section 4 hits the backing plate 9 covering the target area 51aA of the outer circumferential surface 51a of the riser pipe 51 for a long period of time.

Furthermore, according to the steam generator 1 and the steam generator reinforcing method of this embodiment, the backing plate 9 made of a Cr-Mo low alloy is configured by welding an edge portion 92 made of carbon steel to at least a part of the periphery of a main body plate portion 91 made of a Cr-Mo based low alloy. As a result, even if the main portion of the backing plate 9 is made of a Cr-Mo low alloy, when welding the backing plate 9 to the outer circumferential surface 51a of the riser pipe 51 in the trunk portion 2, no post-heat treatment is required for the welded portion of the backing plate 9. This point will be described below.
In order to weld the Cr-Mo low alloy to the riser pipe 51, it is necessary to perform a pre-heat treatment of the welded portion in the torso section 2, which makes it difficult to work inside the torso section 2 and to apply the backing plate 9. On the other hand, the above-mentioned pre-heat treatment is not required when welding carbon steel to the riser pipe 51. As a result, when welding the edge portions 92 of the backing plate 9, which are made of carbon steel and form the horizontal sides 9a and vertical sides 9b of the backing plate 9, to the outer circumferential surface 51a of the riser pipe 51, no pre-heat treatment is required, which improves workability inside the torso section 2 and makes it easy to apply the backing plate 9 to the outer circumferential surface 51a of the riser pipe 51.

In addition, in the steam generator 1 and the method for reinforcing a steam generator of this embodiment, when the backing plate 9 is formed of a Ni-based alloy, pre-heat treatment of the welded portion of the backing plate 9 is not required when welding the backing plate 9 to the outer peripheral surface 51a of the riser pipe 51. This is because pre-heat treatment is not required when welding Ni-based alloys. As a result, workability within the body portion 2 is improved when welding the backing plate 9 to the outer peripheral surface 51a of the riser pipe 51 within the body portion 2, and the application of the backing plate 9 to the outer peripheral surface 51a of the riser pipe 51 can be easily performed.

Although each embodiment of the present disclosure has been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like that do not depart from the gist of the present disclosure are also included.

<Additional Notes>
The reinforcing method for a steam generator and the steam generator described in each embodiment can be understood, for example, as follows.

(1) The method for reinforcing a steam generator according to the first aspect comprises a cylindrical body extending in the vertical direction, a heat exchange section provided in the lower part of the body for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool it, a water supply section provided above the heat exchange section within the body for supplying the secondary cooling water to the heat exchange section, and a steam-water separator provided above the heat exchange section within the body for separating the secondary cooling water, which is heated by the primary cooling water and rises in the heat exchange section, into steam and hot water. A method for reinforcing a steam generator, which reinforces a target area of the outer surface of the steam-water separator that is hit by the secondary cooling water supplied from the water supply unit, includes a preparation step of preparing a plurality of backing plates that are processed into a shape that conforms to the target area of the outer surface outside the body, a carrying step of carrying the plurality of backing plates into the body, and a welding step of overlapping and welding the plurality of backing plates carried into the body to the target area of the outer surface and arranging them along the target area of the outer surface.

According to the above configuration, the target area of the outer surface of the steam-water separator is covered by multiple backing plates, which can suppress or prevent the secondary cooling water supplied from the water supply unit from hitting the target area of the outer surface of the steam-water separator. In other words, the target area of the outer surface of the steam-water separator can be protected from the secondary cooling water. This can suppress or prevent the outer surface of the steam-water separator from being thinned due to erosion or corrosion.

In addition, by providing a plurality of backing plates corresponding to the target area on the outer surface of the steam-water separator, the size of each backing plate can be made smaller than the target area. This makes it easier to carry the backing plates into the body. Furthermore, by making each backing plate small, even if the distance between the target area on the outer surface of the steam-water separator and the water supply section is narrow, each backing plate can be easily welded to the outer surface of the steam-water separator. In other words, the workability of the reinforcement is improved, and the target area on the outer surface of the steam-water separator can be efficiently reinforced.

(2) In the method for reinforcing a steam generator according to the second aspect, the backing plate is formed from at least a Cr-Mo based low alloy.

The Cr-Mo low alloy that forms the backing plate has high corrosion resistance against secondary cooling water. Therefore, even if the secondary cooling water supplied from the water supply unit hits the backing plate that covers the target area on the outer surface of the steam-water separator for a long period of time, it is possible to effectively prevent the backing plate from being thinned due to erosion or corrosion.

(3) In the method for reinforcing a steam generator according to the third aspect, the backing plate has a main body plate portion made of a Cr-Mo low alloy and an edge portion made of carbon steel and welded to at least a portion of the periphery of the main body plate portion.

According to the above configuration, by welding the edge of the backing plate made of carbon steel to the outer surface of the steam-water separator, it is possible to attach the backing plate to the target area on the outer surface of the steam-water separator. Here, when welding Cr-Mo low alloys, pre-heat treatment is required for the welded part, but when welding carbon steel, pre-heat treatment is not required for the welded part. As a result, pre-heat treatment is not required when welding the backing plate to the outer surface of the steam-water separator inside the body, which improves workability inside the body and simplifies the application of the backing plate to the outer surface of the steam-water separator.

(4) In the method for reinforcing a steam generator according to the fourth aspect, the backing plate is made of a Ni-based alloy.

The Ni-based alloy forming the backing plate has high corrosion resistance against the secondary cooling water, and therefore, even if the secondary cooling water supplied from the water supply unit hits the backing plate covering the target area on the outer surface of the steam-water separator for a long period of time, it is possible to suppress thinning of the backing plate.
Furthermore, by welding a backing plate made of a Ni-based alloy to the outer surface of the steam-water separator, the backing plate can be attached to the target area of the outer surface of the steam-water separator. Here, when welding the Ni-based alloy, no pre-heat treatment is required for the welded portion. As a result, when welding the backing plate to the outer surface of the steam-water separator inside the body, the pre-heat treatment is not required, improving workability inside the body and facilitating the application of the backing plate to the outer surface of the steam-water separator.

(5) In the method for reinforcing a steam generator according to the fifth aspect, the body portion has a manhole for entering and exiting the body portion, and the backing plate is formed in a shape and size that allows it to pass through the manhole.

The backing plate is shaped and sized to pass through the manhole, so it can be easily and reliably brought into the body.

(6) The steam generator according to the sixth aspect comprises a cylindrical body extending in the vertical direction, a heat exchange section provided in the lower part of the body for cooling by heat exchange between high-temperature primary cooling water and secondary cooling water, a water supply section provided in the body above the heat exchange section for supplying the secondary cooling water to the heat exchange section, a steam-water separator provided in the body above the heat exchange section for separating the secondary cooling water that is heated by the primary cooling water and rises in the heat exchange section into steam and hot water, and a plurality of backing plates welded to a target area of the outer surface of the steam-water separator that is hit by the secondary cooling water supplied from the water supply section and aligned along the target area of the outer surface.

According to the above configuration, the target area of the outer surface of the steam-water separator is covered by multiple backing plates, which can suppress or prevent the secondary cooling water supplied from the water supply unit from hitting the target area of the outer surface of the steam-water separator. In other words, the target area of the outer surface of the steam-water separator can be protected from the secondary cooling water. This can suppress or prevent the outer surface of the steam-water separator from being thinned due to erosion or corrosion.

In addition, by providing a plurality of backing plates corresponding to the target area on the outer surface of the steam-water separator, the size of each backing plate can be made smaller than the target area. This makes it easier to carry the backing plates into the body. Furthermore, by making each backing plate small, even if the distance between the target area on the outer surface of the steam-water separator and the water supply section is narrow, each backing plate can be easily welded to the outer surface of the steam-water separator. In other words, the workability of the reinforcement is improved, and the target area on the outer surface of the steam-water separator can be efficiently reinforced.

1 Steam generator 2 Body section 3 Heat exchange section 4 Water supply section 5 Steam-water separator 9 Backing plate 21 Manhole 51a Outer circumferential surface (outer surface)
51aA Target area 91 Body plate portion 92 Edge portion

Claims (7)

A cylindrical body portion extending in the vertical direction;
a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water;
a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section;
a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water;
A steam generator comprising:
A method for reinforcing a steam generator, comprising: reinforcing a target area of an outer surface of the steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, the method comprising:
A preparation step of preparing a plurality of backing plates on the outside of the body, the backing plates being shaped to conform to the target area of the outer surface;
A carrying step of carrying a plurality of the backing plates into the body portion;
a welding step of overlapping and welding the plurality of backing plates brought into the body to the target areas of the outer surface and arranging them along the target areas of the outer surface;
having
The method for reinforcing a steam generator includes forming the backing plate from at least a Cr-Mo based low alloy steel . A cylindrical body portion extending in the vertical direction;
a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water;
a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section;
a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water;
A steam generator comprising:
A method for reinforcing a steam generator, comprising: reinforcing a target area of an outer surface of the steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, the method comprising:
A preparation step of preparing a plurality of backing plates on the outside of the body, the backing plates being shaped to conform to the target area of the outer surface;
A carrying step of carrying a plurality of the backing plates into the body portion;
a welding step of overlapping and welding the plurality of backing plates brought into the body to the target areas of the outer surface and arranging them along the target areas of the outer surface;
having
The method for reinforcing a steam generator , wherein the backing plate has a main body plate portion made of Cr-Mo based low alloy steel and an edge portion made of carbon steel and welded to at least a portion of the periphery of the main body plate portion . A cylindrical body portion extending in the vertical direction;
a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water;
a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section;
a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water;
A steam generator comprising:
A method for reinforcing a steam generator, comprising: reinforcing a target area of an outer surface of the steam-water separator that is contacted by the secondary cooling water supplied from the water supply section, the method comprising:
A preparation step of preparing a plurality of backing plates on the outside of the body, the backing plates being shaped to conform to the target area of the outer surface;
A carrying step of carrying a plurality of the backing plates into the body portion;
a welding step of overlapping and welding the plurality of backing plates brought into the body to the target areas of the outer surface and arranging them along the target areas of the outer surface;
having
The method for reinforcing a steam generator , wherein the backing plate is made of a Ni-based alloy . The body portion has a manhole for accessing the body portion,
4. The method for reinforcing a steam generator according to claim 1 , wherein the backing plate is formed in a shape and size that allows it to pass through the manhole. A cylindrical body portion extending in the vertical direction;
a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water;
a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section;
a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water;
a plurality of backing plates that are overlapped and welded to a target area of an outer surface of the steam-water separator where the secondary cooling water supplied from the water supply section hits, and that are arranged along the target area of the outer surface;
Equipped with
The backing plate of the steam generator is made of at least a Cr-Mo based low alloy steel . A cylindrical body portion extending in the vertical direction;
a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water;
a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section;
a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water;
a plurality of backing plates that are overlapped and welded to a target area of an outer surface of the steam-water separator where the secondary cooling water supplied from the water supply section hits, and that are arranged along the target area of the outer surface;
Equipped with
The backing plate of the steam generator has a main body plate portion made of Cr-Mo based low alloy steel, and an edge portion made of carbon steel and welded to at least a part of the periphery of the main body plate portion . A cylindrical body portion extending in the vertical direction;
a heat exchange section provided in a lower portion of the body section for exchanging heat between high-temperature primary cooling water and secondary cooling water to cool the primary cooling water;
a water supply section provided in the body section above the heat exchange section and configured to supply the secondary cooling water to the heat exchange section;
a steam-water separator provided in the body portion above the heat exchange portion and configured to separate the secondary cooling water, which is heated by the primary cooling water in the heat exchange portion and rises, into steam and hot water;
a plurality of backing plates that are overlapped and welded to a target area of an outer surface of the steam-water separator where the secondary cooling water supplied from the water supply section hits, and that are arranged along the target area of the outer surface;
Equipped with
The steam generator , wherein the backing plate is formed of a Ni-based alloy .

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