JP2011226990A - Steam generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam generator that can prevent any damage on a connecting part between an inner shell and an inner pipe when trouble occurs.SOLUTION: A steam generator 1 comprises an inner shell 2 and an outer shell 3 constituting a primary coolant passage, and a primary coolant outlet/inlet pipe 6 for distributing the primary coolant into the passage. And the primary coolant outlet/inlet pipe 6 has a double-pipe structure consisting of an inner pipe 61 and an outer pipe 62, which the inner pipe 61 is connected to the inner shell 2 and the outer pipe 62 is connected to the outer shell 3. And the inner shell 2 is connected through a thermal sleeve 10 to the inner pipe 61.

Description

  The present invention relates to a steam generator, and more particularly, to a steam generator that can prevent damage to a connection portion between an inner cylinder and an inner pipe when an abnormality occurs.

  A typical steam generator includes an inner cylinder and an outer cylinder that constitute a flow path for the primary coolant, and a primary coolant inlet / outlet pipe for allowing the primary coolant to flow through the flow path. In addition, the primary coolant inlet / outlet pipe has a double pipe structure including an inner pipe and an outer pipe, and the inner pipe is connected to the inner cylinder and the outer pipe is connected to the outer cylinder. As a conventional steam generator having such a configuration, a technique described in Patent Document 1 is known.

Japanese Patent Laid-Open No. 08-278397

  Here, when an abnormality occurs in the steam generator and the flow of the primary coolant is interrupted, the inner pipe of the primary coolant inlet / outlet pipe becomes hotter than the outer pipe and greatly expands. Then, due to the difference in thermal expansion between the inner tube and the outer tube, thermal stress is generated at the connecting portion between the inner cylinder and the inner tube, and this connecting portion may be damaged.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a steam generator capable of preventing damage to a connection portion between an inner cylinder and an inner tube when an abnormality occurs.

  In order to achieve the above object, a steam generator according to the present invention includes an inner cylinder and an outer cylinder constituting a flow path of a primary coolant, and a primary coolant inlet / outlet pipe for circulating the primary coolant through the flow path. And the primary coolant inlet / outlet pipe has a double pipe structure including an inner pipe and an outer pipe, and the inner pipe is connected to the inner cylinder and the outer pipe is connected to the outer cylinder. A steam generator having a structure, wherein the inner cylinder and the inner tube are connected via a thermal sleeve.

  In this steam generator, the inner cylinder and the inner tube are connected via a thermal sleeve. Therefore, when a difference in thermal expansion occurs between the inner tube and the outer tube, the thermal sleeve made of a high thermal expansion material is large. Thermal expansion reduces the difference in thermal expansion between the inner cylinder and the inner tube. Then, compared with the structure without the thermal sleeve, the thermal stress acting on the connection portion between the inner cylinder and the inner tube is relieved. Thereby, there exists an advantage by which the failure | damage of the connection part of an inner cylinder and an inner pipe at the time of abnormality occurrence is prevented.

  In the steam generator according to the present invention, the thermal sleeve is made of a material having a higher linear expansion coefficient than the inner pipe.

  In this steam generator, the thermal sleeve can appropriately follow the thermal expansion of the inner pipe when the inner pipe is thermally expanded. Thereby, there exists an advantage by which the failure | damage of the connection part of an inner cylinder at the time of abnormality occurrence and an inner pipe is prevented effectively.

  According to this steam generator, since the inner cylinder and the inner tube are connected via the thermal sleeve, when a thermal expansion difference occurs between the inner tube and the outer tube, the thermal sleeve made of a high thermal expansion material Greatly expands and relaxes the difference in thermal expansion between the inner cylinder and the inner tube. Then, compared with the structure without the thermal sleeve, the thermal stress acting on the connection portion between the inner cylinder and the inner tube is relieved. Thereby, there exists an advantage by which the failure | damage of the connection part of an inner cylinder and an inner pipe at the time of abnormality occurrence is prevented.

FIG. 1 is an axial sectional view showing a steam generator according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view showing a thermal sleeve of the steam generator shown in FIG. FIG. 3 is a graph showing the relationship between the thermal sleeve length and the difference in thermal expansion. FIG. 4 is an explanatory view showing a modification of the steam generator described in FIG. 1. FIG. 5 is an explanatory view showing a modification of the steam generator described in FIG. 1. FIG. 6 is an explanatory view showing a general HTGR.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[High temperature gas furnace]
FIG. 6 is an explanatory view showing a general HTGR.

  The high temperature gas reactor 100 includes a nuclear reactor vessel 110 and a steam generator 120, which are installed adjacent to each other (side-by-side type high temperature gas reactor). Further, the primary coolant inlet / outlet port 111 of the reactor vessel 110 and the primary coolant inlet / outlet port 121 of the steam generator 120 are connected via a connecting pipe 130. Further, the connecting pipe 130 has a double pipe structure including an inner pipe and an outer pipe (not shown).

  In the high temperature gas reactor 100, the primary coolant (for example, helium gas) heated in the reactor vessel 110 is introduced into the primary cooling system of the steam generator 120 through the inner tube of the connecting tube 130. And heat exchange is performed between this primary coolant and the secondary coolant (for example, water vapor | steam) which distribute | circulates to the secondary cooling system of the steam generator 120, and a secondary coolant is heated. And this secondary coolant is used as a working fluid of a steam turbine, for example. Further, the primary coolant cooled by the heat exchange is recovered to the primary cooling system of the reactor vessel 110 through the outer tube (an annular portion of the inner tube and the outer tube) of the connecting tube 130. The primary coolant circulates between the reactor vessel 110 and the steam generator 120, whereby the secondary coolant of the steam generator 120 is continuously heated.

[Steam generator]
FIG. 1 is an axial sectional view showing a steam generator according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view showing a thermal sleeve of the steam generator shown in FIG.

  The steam generator 1 is applied to, for example, the high temperature gas furnace 100 described above. The steam generator 1 includes an inner cylinder 2 and an outer cylinder 3, a center pipe 4, a heat transfer tube group 5, a primary coolant inlet / outlet pipe 6, a secondary coolant inlet pipe 71, and a secondary coolant outlet pipe 72. Provide (see FIG. 1). The inner cylinder 2 and the outer cylinder 3 have a long container shape, and the inner cylinder 2 is inserted and installed inside the outer cylinder 3 with its axial direction set up in the vertical direction (double cylinder structure). Thereby, the flow path of the primary coolant is formed in the inner cylinder 2 and the annular portions of the inner cylinder 2 and the outer cylinder 3. Moreover, the inner cylinder 2 has the upper side opening part 21 in the top part. Further, an inner cylinder 22 having a bottomed structure is disposed inside the inner cylinder 2 with its bottom facing the upper opening 21 of the inner cylinder 2 and with its opening facing the bottom of the inner cylinder 2. . At this time, a gap is formed between the outer peripheral surface of the inner cylinder 22 and the inner peripheral surface of the inner cylinder 2 to form a flow path for the primary coolant. The center pipe 4 is a long cylindrical member that is inserted from the bottom of the inner cylinder 2 and opens upward inside the inner cylinder 22. At this time, the inner cylinder 2 (the insertion opening of the center pipe 4) and the outer periphery of the center pipe 4 are connected, and the gap between the inner cylinder 2 and the center pipe 4 is sealed. The heat transfer tube group 5 is formed of a helical coil or the like, and is disposed between the inner peripheral surface of the inner cylinder 22 and the outer peripheral surface of the center pipe 4 and extends in the axial direction of the inner cylinder 2.

  The primary coolant inlet / outlet pipe 6 has a double pipe structure including an inner pipe 61 and an outer pipe 62 and serves as an inlet / outlet for the primary coolant from the reactor vessel 110 side. The inner pipe 61 is a part obtained by extending the center pipe 4 downward, and is formed by welding a pipe material to the lower end of the center pipe 4. A heat insulating material covered with a liner is disposed on the inner peripheral surfaces of the inner pipe 61 and the center pipe 4. The outer tube 62 is a nozzle formed at the bottom of the outer body 3, and is welded to the outer body 3 to open inside the outer body 3. The secondary coolant inlet pipe 71 and the secondary coolant outlet pipe 72 serve as inlets and outlets for circulating the secondary coolant to the heat transfer tube group 5. The secondary coolant inlet pipe 71 passes through the inner cylinder 2 and the outer cylinder 3 from the lower side and is connected to the lower end of the heat transfer tube group 5. The secondary coolant outlet pipe 72 penetrates the inner cylinder 2, the inner cylinder 22 and the outer cylinder 3 from the upper side and is connected to the upper end portion of the heat transfer tube group 5. As a result, a flow path for the secondary coolant that passes from the secondary coolant inlet tube 71 through the heat transfer tube group 5 to the secondary coolant outlet tube 72 is formed.

  In the steam generator 1, in the secondary cooling system, a secondary coolant from an external engine (for example, a steam turbine) is introduced into the heat transfer tube group 5 from the secondary coolant inlet pipe 71 and heated, and the secondary cooling is performed. The material is discharged from the material outlet pipe 72 to the outside and supplied to the external engine. On the other hand, in the primary cooling system, first, the high temperature primary coolant heated in the reactor vessel 110 flows into the inner pipe 61 of the primary coolant inlet / outlet pipe 6 through the inner pipe (not shown) of the connecting pipe 130. To do. Next, the primary coolant is introduced from the inner pipe 61 through the center pipe 4 to the inner cylinder 22 of the inner cylinder 2, and passes through the gap between the inner peripheral surface of the inner cylinder 22 and the outer peripheral surface of the center pipe 4. Descend inside. At this time, heat exchange is performed between the primary coolant and the secondary coolant in the heat transfer tube group 5, and the secondary coolant is heated.

  Next, the primary coolant that has passed through the heat transfer tube group 5 rises from the bottom of the inner cylinder 2 through the gap between the inner peripheral surface of the inner cylinder 2 and the outer peripheral surface of the inner cylinder 22, and the upper opening of the inner cylinder 2 is opened. It is discharged from the portion 21 and flows into the outer trunk 3. Next, the primary coolant descends through the annular portion between the outer peripheral surface of the inner cylinder 2 and the inner peripheral surface of the outer cylinder 3, and the outer pipe 62 (the inner pipe 61 and the outer pipe 62 of the primary coolant inlet / outlet pipe 6). And the outer tube (not shown) of the connecting pipe 130 is returned to the reactor vessel 110. The primary coolant is heated again in the reactor vessel 110 and supplied to the inner pipe 61 of the primary coolant inlet / outlet pipe 6. Thereby, a primary coolant circulates and a secondary coolant is heated continuously.

[Structure to suppress thermal expansion difference of primary coolant inlet / outlet pipe]
In the general steam generator 120, when the flow of the primary coolant is interrupted when an abnormality occurs, the inner pipe 1261 of the primary coolant inlet / outlet pipe 126 becomes hotter than the outer pipe 1262 and expands greatly (FIG. 6). reference). Then, due to the difference in thermal expansion between the inner tube 1261 and the outer tube 1262, thermal stress may occur in the connection portion A between the inner cylinder 122 and the inner tube 1261, and the connection portion A may be damaged.

  Therefore, in the steam generator 1, in order to reduce the influence of the thermal stress, the inner cylinder 2 and the inner pipe 61 and the center pipe 4 of the primary coolant inlet / outlet pipe 6 are connected via the thermal sleeve 10 (FIG. 1 and FIG. 2).

  For example, in this embodiment, the thermal sleeve 10 includes a sleeve main body 11 and sleeve end portions 12 and 12 constituting both ends of the sleeve main body 11, and has an annular structure (see FIG. 2). . The sleeve main body 11 has a cylindrical shape and is made of a material (high linear expansion coefficient material) having a higher linear expansion coefficient than the inner pipe 61 and the center pipe 4. As such a high linear expansion coefficient material, for example, austenitic stainless steel can be adopted. The sleeve end portion 12 has a flange shape and is made of a material (low linear expansion material) having the same linear expansion coefficient as the inner tube 61 and the center pipe 4. As such a low linear expansion coefficient material, for example, carbon steel, alloy steel, chromium molybdenum alloy steel, or the like can be adopted. The outer cylinder 3 and the outer pipe 62 of the primary coolant inlet / outlet pipe 6 are made of the same low linear expansion coefficient material as that of the inner cylinder 2. Further, the inner cylinder 2 and the outer cylinder 3 are connected via a support 9. Further, the center pipe 4 is fixed to the inner pipe 61 of the primary coolant inlet / outlet pipe 6 only at the lower end portion thereof, and is supported so as to be freely heat-extensible in the axial direction with respect to the inner cylinder 2.

  In the installation process of the thermal sleeve 10, one sleeve end portion 12 is inserted into a connection portion between the inner tube 61 and the center pipe 4 and welded to the inner tube 61 and the center pipe 4. The other sleeve end 12 is welded to the insertion port of the center pipe 4 at the bottom of the inner cylinder 2. The sleeve main body 11 is fitted between the sleeve end portions 12 and 12 and welded.

  In the installed state of the thermal sleeve 10, the sleeve body 11 is positioned coaxially with respect to the inner tube 61 and the center pipe 4, and the longitudinal direction thereof is disposed toward the longitudinal direction of the inner tube 61 and the center pipe 4. The sleeve body 11 has an axial length L, and the sleeve body 11 and the inner tube 61 are arranged at a distance D.

  During abnormal operation of the steam generator 1, due to the difference in thermal expansion between the inner pipe 61 and the outer pipe 62, (a) the connecting portion between the inner cylinder 2, the inner pipe 61, and the center pipe 4 is axial with respect to the inner cylinder 2. Displace. Further, (b) in the configuration shown in FIG. 1, the inner tube 61 is thermally expanded in the horizontal direction (right direction in FIG. 1) with respect to the inner trunk 2.

  At this time, (a) the inner cylinder 2 and the inner pipe 61 and the center pipe 4 are connected via the thermal sleeve 10 made of a high thermal expansion material, so that the thermal sleeve 10 (sleeve body 11) is axially connected to the inner cylinder 2. Large thermal expansion. Then, the thermal sleeve 10 follows the thermal expansion of the inner tube 61 and the center pipe 4, and the thermal expansion difference in the axial direction between the inner cylinder 2, the inner tube 61 and the center pipe 4 is alleviated. Therefore, as compared with the structure having no thermal sleeve, the thermal stress acting on the connecting portion between the inner cylinder 2 and the inner pipe 61 and the center pipe 4 is relieved. (B) Since the thermal sleeve 10 has a distance D between the thermal sleeve 10 and the inner tube 61, the inner tube 61 and the center pipe 4 can be inclined with respect to the axial direction. Therefore, the inclination of the inner pipe 61 and the center pipe 4 absorbs the thermal expansion of the inner pipe 61 in the horizontal direction. Accordingly, breakage of the connecting portion between the inner cylinder 2 and the inner pipe 61 and the center pipe 4 is prevented.

[Thermal sleeve length]
FIG. 3 is a graph showing the relationship between the thermal sleeve length and the difference in thermal expansion. The figure shows the difference in thermal expansion between the inner and outer pipes of the primary coolant inlet / outlet pipe during steady operation (rated) and abnormal operation (abnormal) of the steam generator 1, and the length L of the thermal sleeve. Shows the relationship. During abnormal operation, the temperature difference between the inner pipe and the outer pipe rises to about 50 [° C.].

  As shown in FIG. 3, the difference in thermal expansion between the inner tube 61 and the outer tube 62 increases in proportion to the length L of the thermal sleeve 10 (sleeve body 11). Further, in the configuration in which the thermal sleeve is not installed (when L = 0), during the steady operation of the steam generator 1, the difference in thermal expansion between the inner pipe 61 and the outer pipe 62 becomes the reference value (0), which is abnormal. During operation, the difference in thermal expansion between the inner tube 61 and the outer tube 62 is the largest. Further, in both the steady operation and the abnormal operation, the difference in thermal expansion between the inner tube 61 and the outer tube 62 increases according to the length L of the thermal sleeve. The difference in thermal expansion is preferably close to the reference value when L = 0 in both steady operation and abnormal operation. On the other hand, the difference between the thermal expansion difference during steady operation and the thermal expansion difference during abnormal operation decreases as the length L of the thermal sleeve increases (the graph approaches). As the difference in thermal expansion difference is smaller, the gap between steady operation and abnormal operation is preferably smaller. However, if the length L of the thermal sleeve is too large, the difference in thermal expansion during rated operation is far from the reference value, which is not preferable.

  Therefore, in this steam generator 1, when the difference in thermal expansion between the inner tube and the outer tube during steady operation in a configuration without a thermal sleeve is used as a reference (0), the difference in thermal expansion during steady operation and an abnormality It is preferable to set the length L (= La) of the thermal sleeve 10 so that the difference in thermal expansion during operation is substantially equal (see FIG. 3). Thereby, the influence by the thermal expansion difference of the inner tube 61 and the outer tube 62 is effectively relieved.

  The relationship between the thermal expansion difference during steady operation and the thermal expansion difference during abnormal operation is not only the length L of the thermal sleeve 10 but also from the connection portion with the connecting pipe 130 to the connection portion with the thermal sleeve 10. It can also be adjusted by the length of the inner tube 61, the material of the high linear expansion material constituting the thermal sleeve 10, and the like.

[Modification]
4 and 5 are explanatory views showing a modification of the steam generator shown in FIG. In these drawings, the same components as those of the steam generator 1 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the steam generator 1 according to this modification, the outer pipe 62 of the primary coolant inlet / outlet pipe 6 is installed below the side of the outer body 3 (see FIGS. 4 and 5). Further, the inner pipe 61 is inserted into the inner cylinder 2 from the position of the outer pipe 62 and is bent vertically upward, and is welded to the bottom of the center pipe 4 installed inside the inner cylinder 2 at its upper end. It is connected.

  Further, the thermal sleeve 10 is installed at a connection portion between the inner body 2 and the inner tube 61. Specifically, one sleeve end portion 12 is inserted and welded to a boundary portion (connecting portion) between the straight portion and the curved portion of the inner tube 61. The other sleeve end 12 is welded to the insertion port of the inner tube 61 formed on the side of the inner body 2. The sleeve main body 11 is fitted and welded between the sleeve end portions 12 and 12. At this time, the sleeve main body 11 is coaxially positioned with respect to the inner tube 61 and is arranged with its longitudinal direction oriented in the horizontal direction.

  During abnormal operation of the steam generator 1, due to the difference in thermal expansion between the inner tube 61 and the outer tube 62, the connecting portion between the inner cylinder 2 and the inner tube 61 is axially connected to the inner cylinder 2 (horizontal direction ). At this time, since the inner body 2 and the inner tube 61 are connected via the thermal sleeve 10 made of a high thermal expansion material, the thermal sleeve 10 (sleeve body 11) can be largely thermally expanded in the axial direction of the inner tube 61. Then, the thermal sleeve 10 follows the thermal expansion of the inner tube 61, and the thermal expansion difference between the inner cylinder 2 and the inner tube 61 is alleviated. Therefore, the thermal stress acting on the connection portion between the inner cylinder 2 and the inner tube 61 is relieved as compared with a structure having no thermal sleeve. Thereby, damage to the connecting portion between the inner cylinder 2 and the inner pipe 61 and the center pipe 4 is prevented.

[effect]
As described above, the steam generator 1 includes the inner cylinder 2 and the outer cylinder 3 constituting the flow path of the primary coolant, and the primary coolant inlet / outlet pipe 6 for circulating the primary coolant through the flow path. (Refer to FIG. 1 and FIG. 4). The primary coolant inlet / outlet pipe 6 has a double pipe structure including an inner pipe 61 and an outer pipe 62, and the inner pipe 61 is connected to the inner trunk 2 and the outer pipe 62 is connected to the outer trunk 3. Have The inner cylinder 2 and the inner tube 61 are connected via the thermal sleeve 10 (see FIGS. 1, 2, 4, and 5).

  In such a configuration, when a difference in thermal expansion occurs between the inner tube 61 and the outer tube 62, the thermal sleeve 10 (sleeve body 11) made of a high thermal expansion material greatly expands, and the inner cylinder 2 and the inner tube are expanded. The thermal expansion difference from 61 is reduced (see FIGS. 2 and 5). Then, the thermal stress acting on the connecting portion between the inner cylinder 2 and the inner tube 61 is relieved as compared with the structure without the thermal sleeve. Thereby, there exists an advantage by which the failure | damage of the connection part of the inner cylinder 2 and the inner pipe | tube 61 at the time of abnormality generation | occurrence | production is prevented.

  In the above configuration, the thermal sleeve 10 (sleeve body 11) is preferably made of a material having a higher linear expansion coefficient than the inner tube 61. In such a configuration, the thermal sleeve 10 can appropriately follow the thermal expansion of the inner tube 61 when the inner tube 61 is thermally expanded. Thereby, there exists an advantage by which the damage of the connection part of the inner cylinder 2 and the inner pipe | tube 61 at the time of abnormality occurrence is prevented effectively.

  As described above, the steam generator according to the present invention is useful in that it can prevent damage to the connecting portion between the inner cylinder and the inner tube when an abnormality occurs.

DESCRIPTION OF SYMBOLS 1 Steam generator 2 Inner cylinder 21 Upper opening 22 Inner cylinder 3 Outer cylinder 4 Center pipe 5 Heat transfer tube group 6 Primary coolant inlet / outlet pipe 61 Inner pipe 62 Outer pipe 71 Secondary coolant inlet pipe 72 Secondary coolant outlet pipe 9 Support 10 Thermal sleeve 11 Sleeve body 12 Sleeve end 100 High-temperature gas reactor 110 Reactor vessel 120 Steam generator 130 Connecting pipe

Claims (2)

An inner cylinder and an outer cylinder constituting a flow path of the primary coolant, and a primary coolant inlet / outlet pipe for allowing the primary coolant to flow through the flow path, and the primary coolant inlet / outlet pipe is an inner pipe and an outer pipe. A steam generator having a double-pipe structure composed of tubes, wherein the inner tube is connected to the inner cylinder and the outer tube is connected to the outer cylinder;
The steam generator, wherein the inner cylinder and the inner pipe are connected via a thermal sleeve. The steam generator according to claim 1, wherein the thermal sleeve is made of a material having a higher linear expansion coefficient than the inner tube.

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