JP2012145284A - Steam generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam generator which can make it hard to cause a recess or a flaw in the heat conductive pipe and prevent a drop in the reliability and the durability of a heat conductive pipe.SOLUTION: The steam generator 10 includes an outer cylinder 11, an inner cylinder 21, which is arranged inside the outer cylinder and is supported by a support 28, many heat conductive pipes 22, which are arranged inside the inner cylinder and are shaped like reverse U's, a pipe plate 17, which is fixed to the lower part in the inner cylinder to support the ends of many heat conductive pipes, a plurality of pipe supporting plates 24A-24G, which are supported by a stay rod 25 extended upward from the pipe plate to support the direct pipe parts of many heat conductive pipes, a water supply pipe 16, which is provided in the outer cylinder to send supply water, and a steam separator 26, which is provided at the upper part inside the inner cylinder to separate steam and heat water that are generated in heat exchange between primary cooling water, flowing in many heat conductive pipes, and the supply water. The support 28 is arranged between the outer cylinder and the inner cylinder and also is arranged in the middle part excluding both ends of the lower barrel 21a of the inner cylinder.

Description

  The present invention relates to a steam generator, for example, a steam generator used as a heat exchanger in a nuclear power generation facility.

  As a nuclear power generation facility, for example, in a pressurized water nuclear power plant, primary cooling water heated in a nuclear reactor is supplied to a steam generator.

  In the steam generator described above, an inner cylinder (tube group outer cylinder) is arranged in the hollow sealed outer cylinder with a predetermined distance from the inner wall surface, and an inverted U-shape is formed in the inner cylinder. A number of heat transfer tubes are arranged. Tube plates that support both end portions of the multiple heat transfer tubes are disposed at the lower portion of the outer cylinder. Tube support plates are arranged at a plurality of locations along the height direction of the inner cylinder. The straight tube portion of the heat transfer tube is inserted through the tube hole of the tube support plate and supported by the tube support plate. The tube support plate is supported at a plurality of locations by a number of stay rods, and the peripheral edge thereof is fixed to the inner peripheral surface of the inner cylinder. Between the inner cylinder and the outer cylinder, a plurality of supports (axial restraints) are arranged at the lower end of the inner cylinder and at a position spaced apart by a predetermined distance in the circumferential direction of the inner cylinder. The inner cylinder is supported by the outer cylinder by a plurality of support tools.

  Therefore, the primary cooling water heated in the nuclear reactor is supplied to a large number of heat transfer tubes through a water chamber formed in the lower part of the outer cylinder, while the secondary cooling water is supplied to the upper part of the outer cylinder. When supplied from the pipe to the inner cylinder through the outer cylinder, the secondary cooling water is heated by the primary cooling water to generate secondary steam. The secondary steam is supplied to the steam turbine through a main steam pipe provided at the upper end of the outer cylinder, and the steam turbine is rotated to drive the generator.

  In Patent Documents 1 and 2 below, a plurality of jack assemblies (positions spaced at predetermined intervals in the longitudinal direction of the tube group outer cylinder (wrapper portion) and at predetermined intervals in the circumferential direction ( A steam generator is described which is positioned and supported on the barrel by radial support means).

JP 2007-147138 A (see, for example, paragraphs [0027], [FIG. 1], [FIG. 2], [FIG. 4], etc. of the specification) Japanese Patent Publication No. 7-18522 (see, for example, [FIG. 1], [FIG. 2], etc.)

  By the way, manufacture of the steam generator of the structure mentioned above is performed in the state which has arrange | positioned the longitudinal direction of an outer cylinder in the horizontal direction. After assembling the inner tube, support, tube plate, tube support plate, stay rod, and heat transfer tube inside the outer tube, post-weld heat treatment (PWHT) is performed to ensure the soundness of the welded portion after the welding process. It goes to the water chamber formed in the lower part of.

For example, as shown in FIG. 5, when the post-weld heat treatment is performed on the vicinity of the tube plate 102 in the outer cylinder 101, the heat 110 by this process is generated on the lower side (right direction in the figure) and the upper side of the outer cylinder 101. Conducted in the left direction. As described above, since the heat treatment is performed after welding with the steam generator placed horizontally, the gas (air) in the outer cylinder is warmed by this heat treatment, and the warmed gas stays in the upper part in the outer cylinder. is doing. In response to the heat of the gas, the inner cylinder 103 disposed in the outer cylinder 101 and the plurality of stay rods 104 disposed in the inner cylinder 103 are heated. The upper gas between the outer cylinder and the inner cylinder has a higher temperature than the gas in the inner cylinder. That is, a temperature distribution is generated in the outer cylinder. Therefore, the thermal elongation amount ΔL ₁₁ of the portion disposed above the inner cylinder 103 is larger than the thermal elongation amount ΔL ₁₂ of the stay rod 104 disposed on the upper side. Since the tube plate 102 is a thick plate-like member, the heat 110 hardly conducts to the multiple stay rods 104 through the tube plate 102.

  In the stay rod 104, the lower end portion is fixed to the tube plate 102, and heat-extends upward. In the inner cylinder 103, the lower end portion thereof is supported by the outer cylinder 101 by the support tool 105, and heat expands upward. Due to these thermal elongations, a distortion that curves in a direction away from the tube plate 102 occurs at a portion of the tube support plate 106 supported by the inner cylinder 103 and the stay rod 104 arranged on the upper side. In particular, in the tube support plate 106 disposed at the uppermost position in the inner cylinder, the distortion due to the thermal expansion of the inner cylinder 103 is large.

  When distortion occurs in the tube support plate 106, the inner surface of the tube hole of the tube support plate 106 is inclined with respect to the heat transfer tube inserted through the tube hole, and the open end of the tube hole is pressed against the heat transfer tube. That is, a large load is applied to the heat transfer tube. For this reason, a dent and a damage | wound may be produced in a heat exchanger tube.

  As described above, when the heat transfer tube is dented or scratched, the reliability and durability of the heat transfer tube are impaired.

  In view of the above, the present invention has been made to solve the above-described problems, and is a steam that is unlikely to cause dents and scratches on the heat transfer tube and can prevent deterioration of the reliability and durability of the heat transfer tube. It aims to provide a generator.

The steam generator according to the first invention for solving the above-described problem is:
An outer cylinder having a hollow sealed shape, a tube group outer cylinder disposed in the outer cylinder and supported by a support, and a number of heat transfer tubes having an inverted U shape disposed in the tube group outer cylinder A plurality of heat transfer tube groups, a tube plate fixed to a lower portion of the outer cylinder and supporting end portions of the plurality of heat transfer tubes, and a plurality of support rods supported by stay rods extending upward from the tube plate. A plurality of pipe support plates that support the straight pipe portion of the heat transfer pipe, a water supply pipe that is provided in the outer cylinder and feeds water into the outer cylinder, and is provided at an upper portion in the outer cylinder, and the multiple heat transfer tubes A steam generator comprising a steam generated by heat exchange between the heat medium flowing in the pipe and the feed water and a steam separator separating hot water;
The support is disposed between the outer tube and the tube group outer tube, and is disposed in an intermediate portion excluding both ends of the straight tube portion of the tube group outer tube.

ただし、Ｌ１が管群外筒内にて一番上方に配置される管支持板と管板の距離を示し、Ｌ２が管群外筒内にて一番上方に配置される管支持板と支持具の距離を示し、Ｔ１が外筒下部へ溶接後熱処理をしたときにおける外筒と管群外筒の間の空間の温度を示し、Ｔ２がそのときの管群外筒内の温度を示し、Ｔ３がそのときの管板よりも上方部分の外筒の温度を示し、α１がステーロッドの線膨張係数を示し、α２が管群外筒の線膨張係数を示し、α３が外筒の線膨張係数を示す。 The steam generator according to the second invention for solving the above-described problem is
A steam generator according to the first invention,
The support is arranged at a position satisfying the following expression (1).

However, L1 indicates the distance between the tube support plate disposed at the uppermost position in the outer tube of the tube group and the tube plate, and L2 indicates support between the tube support plate disposed at the uppermost position in the outer tube of the tube group. Indicates the distance of the tool, T1 indicates the temperature of the space between the outer cylinder and the tube group outer cylinder when heat treatment after welding to the lower part of the outer cylinder, T2 indicates the temperature in the tube group outer cylinder at that time, T3 indicates the temperature of the outer cylinder above the tube plate at that time, α1 indicates the linear expansion coefficient of the stay rod, α2 indicates the linear expansion coefficient of the tube group outer cylinder, and α3 indicates the linear expansion of the outer cylinder. Indicates the coefficient.

  According to the steam generator according to the present invention, the support is disposed between the outer tube and the tube group outer tube, and is disposed in an intermediate portion excluding both ends of the straight tube portion of the tube group outer tube. Even if the steam generator is placed horizontally and the post-weld heat treatment is performed on the water chamber provided at the lower part of the outer cylinder, the upper side of the outer tube of the tube group compared to the conventional steam generator The amount of thermal elongation to the tube is small, and the difference in thermal elongation between the tube group outer cylinder and the stay rod is small. Thereby, the distortion which arises in a pipe support plate becomes small, it becomes difficult to produce a dent and a damage | wound in a heat exchanger tube, and the fall of the reliability and durability of a heat exchanger tube can be prevented.

1 is a schematic configuration diagram of a steam generator according to a first embodiment of the present invention. It is explanatory drawing when manufacturing a steam generator. It is explanatory drawing when heat processing after welding is performed with respect to the water chamber of a steam generator. It is explanatory drawing in case distortion does not arise in a pipe support plate, when post-weld heat processing is performed with respect to the water chamber of a steam generator. It is explanatory drawing when heat processing after welding is performed with respect to the water chamber of the conventional steam generator.

  The steam generator according to the present invention will be specifically described in Examples.

  A steam generator according to a first embodiment of the present invention will be described with reference to FIGS.

  The steam generator according to the present embodiment is a steam generator used in a pressurized water nuclear power plant. As shown in FIG. 1, the steam generator 10 is connected to a substantially cylindrical lower barrel 12, a cone barrel 13 that is connected to the upper end of the lower barrel 12 and expands in diameter toward the upper side, and is connected to the upper end of the cone barrel 13. And an outer cylinder (container) 11 composed of a substantially cylindrical upper body 14.

  A tube plate 17 is integrally connected to the lower portion of the lower body 12 and is disposed so as to close the lower portion of the outer cylinder 11. The tube plate 17 is a plate-like member having a large thickness, and has a large number of holes.

  The lower side of the tube plate 17 is partitioned by a partition plate 18 into a high temperature side water chamber 19 and a low temperature side water chamber 20.

  Inside the outer cylinder 11, an inner cylinder (tube group outer cylinder) 21 is arranged with a predetermined distance from the inner wall surface 11 a. The inner cylinder 21 is a substantially cylindrical member, and includes a lower cylinder 21a having a straight tube shape, and an upper cylinder 21b that is connected to the upper end of the lower cylinder 21a and has a portion that expands in diameter. The lower end portion of the lower body 21 a of the inner cylinder 21 extends to the vicinity of the tube plate 17.

  A large number of inverted U-shaped heat transfer tubes 22 are arranged inside the inner cylinder 21. A large number of heat transfer tubes 22 constitute a heat transfer tube group 23. The straight pipe portions of all the heat transfer tubes 22 are surrounded by the lower body 21 a of the inner cylinder 21. A portion of each heat transfer tube 22 curved in an inverted U shape is disposed on the upper side. Both ends on the lower side of each heat transfer tube 22 are inserted into a large number of holes formed in the tube plate 17 and fixed by expansion, and are connected to the high temperature side water chamber 19 and the low temperature side water chamber 20, respectively. The straight tube portion of the heat transfer tube 22 is a tube support having a substantially disk shape arranged at a plurality of locations (seven locations in the illustrated example) with a predetermined interval in the vertical direction (the height direction of the inner cylinder 21). It is supported by the plates 24A to 24G. Specifically, tube holes for inserting a large number of heat transfer tubes 22 are formed in the tube support plates 24A to 24G, and the straight tube portion of the heat transfer tubes 22 is formed in the tube holes of the tube support plates 24A to 24G. It is inserted and supported by the tube support plates 24A-24G.

  The tube support plates 24A to 24G are supported at a plurality of locations by a plurality of stay rods 25 (only one is shown in FIG. 1) extending upward from the tube plate 17. The peripheral portions of the tube support plates 24 </ b> A to 24 </ b> G are fixed to the inner peripheral surface of the inner cylinder 21. Therefore, the tube support plates 24 </ b> A to 24 </ b> G prevent the heat transfer tube 22 from vibrating, and the intervals between the multiple heat transfer tubes 22 are maintained. Furthermore, when a lateral load acts on the heat transfer tube 22 due to an earthquake or the like, the lateral load can be supported by the tube support plates 24A to 24G.

  An air / water separator 26 that separates the feed water into steam and hot water is provided at the upper portion of the inner cylinder 21 inside the upper body 14. A steam dryer 27 that removes moisture from the separated steam and brings it into a state close to dry steam is provided in the upper part of the upper body 14.

  A water supply pipe 16 for sending secondary cooling water (water supply) into the lower body is inserted into the upper body 14 between the heat transfer tube group 23 and the steam separator 26. A main steam pipe (not shown) for exhausting steam is inserted into the ceiling portion of the upper body 14.

  In the steam generator 10 described above, the primary cooling water (heat medium) heated in the nuclear reactor (not shown) is supplied to the high temperature side water chamber 19 and then circulates in the heat transfer tube 22, so that the low temperature side The water chamber 20 is configured to return to the nuclear reactor.

  On the other hand, the secondary cooling water is supplied into the space (downcomer) between the outer cylinder 11 and the inner cylinder 21 via the water supply pipe 16 and descends in the downcomer. Enters the cylinder and ascends the inner cylinder. When the secondary cooling water flows while rising in the inner cylinder, it is heated by receiving heat from the primary cooling water via the heat transfer pipe 22. Thereby, steam is generated, and the steam is sent to the steam turbine (not shown) through the steam separator 26, the steam dryer 27, and the main steam pipe.

  In the steam generator 10 described above, at a position of distance d1 (<length in the longitudinal direction of the lower barrel 21a of the inner cylinder 21) from the upper end of the lower barrel 21a (straight pipe portion) of the inner cylinder 21, and A support tool (axial restraint tool) 28 is disposed at a position spaced apart by a predetermined distance in the circumferential direction of the lower barrel 21 a of the inner cylinder 21. The inner cylinder 21 is supported by the outer cylinder 11 by the support tool 28.

  That is, the above-described support 28 is disposed at a location other than the end portion of the lower barrel 21a (straight tube portion) of the inner cylinder 21, that is, an intermediate portion excluding the upper end portion and the lower end portion of the lower barrel 21a of the inner cylinder 21. The Thereby, compared with the case where the conventional steam generator 100 described above, specifically, the support 105 is provided at the lower end portion of the inner cylinder 103, the upper end of the lower barrel 21a of the inner cylinder 21 by heat treatment after welding is higher. The amount of thermal elongation to the side can be reduced. This is because both ends of the lower barrel 21a of the inner cylinder 21 are free ends, and the upper barrel 21a of the inner cylinder 21 can be thermally extended at the upper end and the lower end. Therefore, the pipe support plate fixed in the vicinity of the end portion, that is, the uppermost pipe support plate 24A arranged in the inner cylinder and the lowermost arrangement in the inner cylinder. The distortion at the tube support plate 24G (at the bottom) is reduced. As a result, the load applied to the heat transfer tube 22 is reduced, and the possibility of impairing the reliability and durability of the heat transfer tube 22 is reduced.

  The manufacture of the steam generator 10 described above is performed in a state where the longitudinal direction of the outer cylinder 11 is arranged in the horizontal direction, as in the conventional steam generator 100. Specifically, as shown in FIG. 2, the longitudinal direction of the outer cylinder 11 is arranged in the horizontal direction, and in this state, the inner cylinder 21 in the lower part from the enlarged diameter portion, the support tool, and the inside of the outer cylinder 11. 28, the tube plate 17, the tube support plate 24, the stay rod 25, the heat transfer tube 22, the partition plate, and the like are assembled, and then a post-weld heat treatment (PWHT) is performed on the water chambers 19 and 20. The outer cylinder 11 includes a lower body 12 and a conical cylinder 13 connected to the upper end of the lower body 12.

  Here, refer to FIG. 3 for the amount of thermal expansion of the inner cylinder 21 and the stay rod 25 when the post-weld heat treatment is performed on the portion constituting the water chambers 19 and 20 in the outer cylinder 11 near the tube plate 17. This will be described in detail.

As shown in FIG. 3, when the post-weld heat treatment is performed on the outer cylinder 11 in the vicinity of the tube sheet, the heat 30 by this process is conducted to the lower side and the upper side of the outer cylinder 11. As described above, since the heat treatment after welding is performed in a state where the longitudinal direction of the outer cylinder 11 is arranged in the lateral direction, the gas in the outer cylinder is warmed by this heat treatment, and the warmed gas is heated in the outer cylinder. Stays up. In response to the heat of the gas, the inner cylinder 21 and the stay rod 25 are heated. The upper gas between the outer cylinder 11 and the inner cylinder 21 is at a higher temperature than the gas in the inner cylinder. That is, a temperature distribution is generated in the outer cylinder. Therefore, the thermal elongation amount ΔL ₁ of the portion disposed above the inner cylinder 21 is larger than the thermal elongation amount ΔL ₂ of the stay rod 25 disposed on the upper side. Since the tube plate 17 itself is a thick member, the heat 30 hardly conducts to the many stay rods 25 through the tube plate 17.

The lower end portion of the stay rod 25 is fixed to the tube plate 17 and thermally expands upward (left side in FIG. 3). The inner cylinder 21 is supported by the outer cylinder 11 by the support 28 at a distance d1 from the upper end of the lower barrel 21a, and is thermally expanded toward the upper side (left side in FIG. 3) and at the lower side (FIG. 3). Even if it is directed to the right), it will heat up. As a result, the heat expansion amount ΔL ₁ directed upward in the inner cylinder 21 is expressed as heat directed toward the upper side of the inner cylinder in the case of the conventional steam generator in which the lower end of the inner cylinder is supported by the outer cylinder by the support. It can be made smaller than the elongation amount ΔL ₁₁ . Thus, since the amount of thermal expansion ΔL ₁ directed upward of the inner cylinder 21 becomes small, the difference from the amount of thermal elongation ΔL ₂ of the stay rod 25 can be made smaller than in the case of the conventional steam generator. . Thereby, in the tube support plate 24 supported by the inner cylinder 21 and the stay rod 25, the distortion that curves in the direction away from the tube plate 17 is reduced compared to the conventional case. . In particular, in the tube support plate 24A disposed at the uppermost position in the inner cylinder, distortion due to thermal expansion of the inner cylinder is reduced.

  Since the distortion generated in the tube support plate 24A is thus reduced, the amount of inclination with which the inner surface of the tube hole of the tube support plate 24A is inclined with respect to the heat transfer tube 22 is reduced. Thereby, the open end of the tube hole is pressed against the heat transfer tube 22 and the load applied to the heat transfer tube 22 is reduced. As a result, dents and scratches are less likely to occur in the heat transfer tube 22, and a decrease in reliability and durability of the heat transfer tube 22 can be prevented as compared with the case of a conventional steam generator.

  Moreover, the fixing location in the longitudinal direction of the inner cylinder 21 of the support tool 28 described above depends on the design conditions such as the material and size of the outer cylinder 11, the inner cylinder 21, the tube support plates 24A to 24G, the stay rod 25, and the like. This value can be determined as appropriate. Assuming that the temperature of each member is uniform, it is possible to obtain the fixed portion of the support 28 described above using an approximate expression. Specifically, as shown in FIG. 4, when post-weld heat treatment is performed on the lower part of the outer cylinder, the temperature of the space between the outer cylinder 11 and the inner cylinder 21 is set to T1 ° C. The temperature of the space is T2 ° C., and the temperature of the outer cylinder 11 in the upper part of the tube sheet is T3 ° C. The initial temperature is T0 ° C. The distance between the uppermost (uppermost) tube support plate 24A and the tubeplate 17 in the inner cylinder is L1, and the uppermost (uppermost) pipe support is disposed in the inner cylinder. The distance between the plate 24A and the support 28 is L2. The linear expansion coefficient of the stay rod 25 is α1, the linear expansion coefficient of the inner cylinder 21 is α2, and the linear expansion coefficient of the outer cylinder 11 is α3.

  At this time, the displacement U-a due to thermal expansion at the connecting portion (the fixing portion of the uppermost tube support plate 24A to the inner tube 21) P1 of the inner tube 21 and the uppermost tube support plate 24A is the following (2). It is expressed by a formula.

  The displacement Ub due to thermal elongation at the connection point P2 between the uppermost tube support plate 24A and the stay rod 25 is expressed by the following equation (3).

  Here, L2 when the displacements of the position P1 and the position P2 are equal (L2 when the uppermost tube support plate 24A is not tilted) is equal to the above-described expression (2) and expression (3). (4).

  When this formula (4) is arranged by L2, the following formula (5) is obtained.

  Therefore, by disposing the support tool 28 at a position that satisfies the above-described expression (5), the amount of thermal expansion upward of the inner cylinder 21 and the amount of thermal expansion upward of the stay rod 25 become the same. . Therefore, even if the thermal treatment after thermal spraying is performed on the lower part of the outer cylinder, the uppermost tube support plate 24A is not distorted, so that the reliability and durability of the heat transfer tube can be prevented more reliably.

  According to the steam generator of the present invention, the difference in thermal expansion between the tube group outer cylinder and the stay rod is reduced, and digging of the heat transfer tube by the tube support plate can be prevented. It can be used beneficially in the furnace.

DESCRIPTION OF SYMBOLS 10 Steam generator 11 Outer cylinder 12 Lower cylinder 13 Conical cylinder 14 Upper trunk 16 Water supply pipe 18 Partition plate 19 High temperature side water chamber 20 Low temperature side water chamber 21 Inner cylinder 22 Heat transfer tube 23 Heat transfer tube group 24A-24G Tube support plate 25 Stay Rod 26 Steam / water separator 27 Steam dryer 28 Support tool 30 Heat

Claims (2)

An outer cylinder having a hollow sealed shape, a tube group outer cylinder disposed in the outer cylinder and supported by a support, and a number of heat transfer tubes having an inverted U shape disposed in the tube group outer cylinder A plurality of heat transfer tube groups, a tube plate fixed to a lower portion of the outer cylinder and supporting end portions of the plurality of heat transfer tubes, and a plurality of support rods supported by stay rods extending upward from the tube plate. A plurality of pipe support plates that support the straight pipe portion of the heat transfer pipe, a water supply pipe that is provided in the outer cylinder and feeds water into the outer cylinder, and is provided at an upper portion in the outer cylinder, and the multiple heat transfer tubes A steam generator comprising a steam generated by heat exchange between the heat medium flowing in the pipe and the feed water and a steam separator separating hot water;
The said generator is arrange | positioned between the said outer cylinder and the said tube group outer cylinder, and is arrange | positioned in the intermediate part except the both ends of the straight pipe part of the said tube group outer cylinder, The steam generator characterized by the above-mentioned. A steam generator according to claim 1,
The said steam generator is arrange | positioned in the position which satisfies the following (1) Formula, The steam generator characterized by the above-mentioned.

However, L1 indicates the distance between the tube support plate disposed at the uppermost position in the outer tube of the tube group and the tube plate, and L2 indicates support between the tube support plate disposed at the uppermost position in the outer tube of the tube group. Indicates the distance of the tool, T1 indicates the temperature of the space between the outer cylinder and the tube group outer cylinder when heat treatment after welding to the lower part of the outer cylinder, T2 indicates the temperature in the tube group outer cylinder at that time, T3 indicates the temperature of the outer cylinder above the tube plate at that time, α1 indicates the linear expansion coefficient of the stay rod, α2 indicates the linear expansion coefficient of the tube group outer cylinder, and α3 indicates the linear expansion of the outer cylinder. Indicates the coefficient.

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