JP2011191080A - Steam separator for nuclear reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steam separator capable of suppressing increase in pressure loss as much as possible, and realizing low carryover even in the case of high steam quality. <P>SOLUTION: Since droplets formation around the steam separator is suppressed by disposing a drainage collision member 2 having a droplet capturing guide 3 on the outside of an outer tube 15 of the steam separator, and allowing drainage from the steam separator to enter below water along the drainage collision member 2 with less collision, and the droplet capturing guide 3 suppresses discharge of tiny droplets and the like generated by collision of the drainage with the drainage collision member 2 to a steam drier, the carryover of the surrounding of the steam separator does not increase even in the case of high steam quality. In addition, the drainage collision member 2 and the droplet capturing guide 3 are disposed at only a limited part of a path around the steam separator to suppress the increase in pressure loss. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a steam separator for separating steam generated in a boiling water reactor from cooling water.

  In a nuclear power plant, high-temperature and high-pressure steam generated in a reactor pressure vessel is supplied to a steam turbine that drives a generator and used as driving steam for the generator.

  In order to suppress the occurrence of erosion and corrosion in the turbine blade portion of the steam turbine that receives the supply of the steam, the steam generated in the reactor pressure vessel is divided into a plurality of steam separators in the reactor pressure vessel. The steam is separated from the cooling water in the reactor pressure vessel by the steam-water separation facility, and the droplets in the steam are removed, and then the steam is passed through the steam dryer in the reactor pressure vessel. Droplets are removed below a certain value required by the steam turbine to produce dry steam.

  The steam separator and the steam dryer are installed in the reactor pressure vessel and, as described above, perform the action of removing droplets from the steam in two stages to produce dry steam. The steam turbine described above is supplied and consumed as driving steam for the generator. Such a reactor is known as a boiling water reactor (hereinafter referred to as BWR) or an improved boiling water reactor (hereinafter referred to as ABWR).

  A conventional air / water separator has a multi-stage structure with drainage channels between the inner and outer cylinders, and the inner cylinder and drainage channels communicate with each other between the upper and lower multistages via a pick-off ring. And a centrifugal mechanism in which the steam / water separation unit is configured in multiple stages (for example, see Patent Document 1). As a result, the steam and the cooling water are centrifuged in multiple stages in the inner cylinder, and the separated cooling water is returned from the drainage channel to the lower cooling water as drainage. On the other hand, the separated steam flows into the steam dryer and further receives droplets to be supplied to the steam turbine side.

  One of the performance indicators of the steam separator is carryover. Carryover represents the weight ratio of cooling water to steam discharged as droplets from the steam separator to the steam dryer. For carry-over, the gas-liquid separation inside the steam-water separator is insufficient, and a part of the cooling water is in the form of droplets that are mixed into the steam and discharged from the steam-water separator to the steam dryer. The droplets generated by carryover from the inside of the separator and collision of the drainage and steam discharged from the steam separator against the water surface around the steam separator are discharged to the steam dryer by the rising steam. There is carry-over from around the water separator.

  If these carry-overs are large, wet steam will be discharged to the steam dryer. If the droplets are not sufficiently removed by the steam dryer, the turbine blades may be damaged. In order to ensure the reliability of the steam turbine, a design limit value is provided for overload, and existing steam-water separators in the reactor have room for the required value of the design limit value.

  As a means for suppressing carryover from around the steam separator as much as possible, a structure (for example, refer to Patent Document 2) provided with a droplet trap ring that covers the flow path around the steam separator, A structure (for example, refer to Patent Document 3) in which a demister is filled between an inner cylinder and an outer cylinder each provided with a configured through hole is known.

  Further, as a gas-liquid separation means, it is known to remove droplets from the vapor by using a vibration preventing plate that connects the steam-water separators or collision with the outer wall of the facing steam-water separator (for example, (See Patent Document 4).

  Furthermore, the drain outlet from the separation region of the second stage of the steam / water separator is covered with a pipe that surrounds the outer cylinder of the steam / water separator, and the upper end of the pipe is closed, so that the inside of the reactor starts from the lower end of the pipe. It is known that the drainage of the steam separator is induced in the cooling water (see, for example, Patent Document 5).

JP-A-10-197678 Japanese Patent Laid-Open No. 8-179077 JP 2004-245656 A JP 2000-153118 A JP 2000-199797 A

  In the future, the output of existing boiling water reactors planned in Japan will be improved, and the output will be higher than that of ABWR, a highly economical simplified boiling water reactor (hereinafter referred to as ESBWR) that is planned to be built in the United States. In the increased next-generation nuclear reactor (hereinafter referred to as the next-generation BWR), the steam quality (ratio of the steam mass flow rate to the total mass flow rate) at the inlet of the steam separator becomes larger than the current ABWR.

  When the steam quality increases (the steam speed increases), the waste water and steam discharged from the second and third stage drainage channels of the steam separator collide with the water surface around the steam separator. The amount of droplets generated increases and the droplets are discharged to the steam dryer by the rising steam, thereby increasing the carry-over from around the steam-water separator.

  Providing a droplet trap ring that completely covers the flow path around the steam-water separator to prevent carryover from around the steam-water separator increases pressure loss in the flow path around the steam-water separator. In addition, even in an air / water separator in which a through-hole is provided in the inner cylinder and the outer cylinder constituting the air / water separator and the demister is filled between them, the gas-liquid two-phase flow passes through the demister section, so that the pressure loss is reduced. To increase.

  In order to promote gas-liquid separation, when a vapor containing droplets from the inside of the steam / water separator collides with the outer wall of the facing steam / water separator, droplets having a small diameter are generated around the steam / water separator. there is a possibility. Since the droplet having a small diameter is discharged to the steam dryer even if the rising speed of the steam is small, there is a possibility that carry-over from around the steam-water separator increases.

  In the configuration in which the drainage of the steam separator is covered with piping to force the drainage to the lower cooling water side, the steam discharged from the second-stage drainage port cannot escape to the upper space. It is feared that it will be contained in recirculated water. When the amount of steam contained in the recirculated water increases, the BWR or ABWR may reduce the pump performance of the jet pump or the internal pump that circulates the recirculated water.

  An object of the present invention is to provide a steam-water separation facility that can suppress an increase in pressure loss as much as possible and realize low carry-over even in high steam quality.

  A means for solving the problems of the present invention is a plurality of steam separators arranged in parallel in a reactor pressure vessel, wherein the steam water is separated from cooling water in the reactor pressure vessel. This is a steam-water separation facility having a droplet capturing guide having a shape that is arranged limited to a part of the space existing on the outer periphery of the separator and is open on the lower side.

  According to the steam-water separation facility of the present invention, an increase in pressure loss can be suppressed as much as possible, carry-over from around the steam-water separator can be kept low, and the reliability of a plant employing a boiling water reactor can be improved. Can contribute.

It is a longitudinal cross-sectional view of the steam-water separator group which provided the drainage collision member with a droplet capture guide of this invention. It is explanatory drawing which showed the structure of the drainage collision member with a droplet capture guide by Example 1 of this invention, and arrangement | positioning to a steam-water separator group. It is explanatory drawing which showed the structure of the drainage collision member with a droplet capture guide by Example 2 of this invention, and arrangement | positioning to a steam-water separator group. It is explanatory drawing which showed the structure of the droplet capture guide by Example 3 of this invention, and arrangement | positioning to a steam-water separator group. 1 is a longitudinal sectional view of an improved boiling water reactor in which a steam separator according to the present invention is employed.

  Hereinafter, embodiments of the present invention will be described in detail.

  The configuration of an ABWR to which each embodiment of the present invention is applied will be described with reference to FIG. As shown in FIG. 5, the ABWR includes a core 21 that generates heat, a shroud 22 and a shroud head 23 that surround the core 21, a plurality of steam-water separators 1 that are attached to the shroud head 23 and arranged in parallel, And an internal pump 26 for circulating the cooling water in the pressure vessel 25.

  The cooling water sent to the core 21 by the internal pump 26 is heated and boiled in the core 21 and becomes a gas-liquid two-phase flow of steam and water. This gas-liquid two-phase flow is separated into steam and water by the steam separator 1 in the pressure vessel 25.

  Since the separated steam is a wet steam containing a lot of moisture, the steam is further removed by the steam dryer 24 in the pressure vessel 25 to obtain a dry steam. It is sent through a main steam pipe 27 to a steam turbine that drives a generator (not shown).

  Further, the cooling water separated by the steam separator 1 is mixed with the feed water supplied from the feed water nozzle 28 in the pressure vessel 25, flows into the downcomer 29, and is recirculated to the core 21 by the internal pump 26.

  Each steam separator 1 has the configuration shown in FIG. That is, the steam / water separator 1 shown in FIG. 1 is a steam / water separator that utilizes a centrifugal action of a three-stage configuration. The steam / water separator 1 has a stand pipe 11 fixed to the shroud head 23 so as to communicate with the upper part of the shroud head 23, fixed to the upper end of the stand pipe 11 and connected to the stand pipe 11, and has a small flow area. A diffuser 12 that connects a stand pipe 11 and an inner cylinder 14 (which will be described later) having a large flow area, a swirler 13 that is fixed in the diffuser 12 and applies a turning force to a two-phase flow of steam and water, and fixed to the upper end of the diffuser 12 The inner cylinder 14 connected to the diffuser 12 and connected to the diffuser 12, the outer cylinder 15 disposed so as to surround the outer periphery of the inner cylinder 14 with a gap, a plate for closing the upper end of the outer cylinder, and a short provided at the center portion thereof Pickoff ring 16 made of a pipe, drainage flow path used as a flow path that is set in a gap between the inner cylinder and the outer cylinder and guides drainage from the inner upper end of the inner cylinder 14 downward 7. A drainage channel outlet 18 formed as a drainage port of the drainage channel with a gap between the outer cylinder and the stand pipe 11, in detail, a droplet capture guide 3 described later is provided on the outer cylinder 15. The drainage collision member 2 is supported. In FIG. 1, the same numerals are marked on the equivalent functional parts of each stage of the steam separator 1 as symbols, and the symbols a, b, and c are added to the numerals to identify the equivalent functional parts for each stage. To distinguish.

  The lower end of the first stage outer cylinder 15a is opened downward in the first stage drainage channel outlet 18a, and an opening exists below the water surface 30 formed around the steam-water separator. The second-stage drainage channel outlet 18b and the third-stage drainage channel outlet 18c are formed around the steam-water separator, with the lower ends of the second-stage outer cylinder 15b and the third-stage outer cylinder 15c opening in the horizontal direction. An opening exists above the water surface 30 to be formed.

  The drainage collision member 2 provided with the droplet capturing guide 3 is provided on the outer side of the outer cylinder 15 from above the second stage drainage channel outlet 18b to below the water surface 30 formed around the steam-water separator.

  The structure of the drainage collision member 2 provided with the droplet capturing guide 3 according to the first embodiment is shown in FIG. FIG. 2A is a cross-sectional view taken along the line AA in FIG. A plurality of steam-water separators 1 are arranged in a lattice pattern, and the second-stage drainage channel outlet 18b faces the drainage collision member 2 that is fixedly provided outside the outer cylinder 15 of the adjacent steam-water separator 1. Be placed.

  FIG. 2B is a perspective view of the drainage collision member 2, and a droplet capturing guide 3 is provided at the upper end of the drainage collision member 2. Although the droplet capture guide 3 has an L-shaped cross section or in other embodiments, it is U-shaped as shown in FIG. 3B, and both of them are opened to the lower side where the opening surface is vertically downward. Have a different shape.

  FIG. 2 (c) is a modification of the drainage collision member 2 according to the first embodiment shown in FIG. 2 (b), and has a shape opened to the lower side as in FIG. 2 (b). A drainage guide groove 4 is provided on the vertical surface of the drainage collision member 2.

  Next, the operation of the steam / water separator 1 according to the first embodiment configured as described above will be described below. The gas-liquid two-phase flow that flows in from the stand pipe 11 is given a swirling force by the swirler 13, and the water having a high density is pushed out by the centrifugal separation action, and the steam having a low density collects in the center.

  The water pushed outward is the cooling water in the reactor pressure vessel from the drainage channel outlet 18 through the drainage channel 17 formed by the inner cylinder 14 and the outer cylinder 15 from the gap between the inner cylinder 14 and the pickoff ring 16. Returned to some reactor water. The steam separator 1 of this embodiment is provided with three stages of mechanisms for draining the liquid film in this way.

  Of these, the drainage discharged from the second-stage drainage channel outlet 18b collides with the drainage collision member 2 provided so as to face the second-stage drainage channel outlet 18b, and on the vertical surface of the drainage collision member 2. Then, a liquid film is formed, and the liquid is discharged below the water surface around the steam separator 1 by flowing down.

  It is suppressed that the drainage from the second drainage channel outlet 18b collides with the steam water surface formed around the steam separator 1 together with steam having a high speed, and droplets are generated around the steam separator 1. Is suppressed.

  Moreover, if the drainage guide groove 4 is provided in the drainage collision member 2, drainage along the drainage collision member 2 is promoted. Further, when the droplets around the steam separator 1 are carried by the rising vapor, the droplets are discharged to the vapor dryer 24 by the droplet capture guide 3 provided at the upper end of the drainage collision member 2. Can be suppressed.

  From the above, even if the steam quality increases (the steam speed increases), the carry-over from the surroundings of the steam separator 1 does not increase.

  1 and 2 show the drainage impingement member 2 provided so as to face the second-stage drainage channel outlet 18b. The drainage channel outlet 18 is horizontally disposed around the steam-water separator. A similar effect can be obtained by providing the drainage collision member 2 so as to face the outlet of the drainage channel in the third and subsequent stages where the opening exists above the water surface 30 to be formed.

  The steam separator 1 according to the second embodiment is shown in FIG. In this second embodiment, adjacent steam-water separators 1 are connected by a drainage collision member 2 in which the droplet capturing guide 3 in the first embodiment described above is provided on both sides. Other configurations are the same as those of the first embodiment.

  In the second embodiment, the drainage collision member 2 is arranged in such a manner that the adjacent steam-water separators 1 are connected to each other. Unlike the first embodiment, the drainage collision member 2 is connected to the steam-water separator group. By utilizing as a support structure, the structure which suppressed the vibration of the steam-water separator 1 can be provided, without newly employ | adopting the coupling tool of steam-water separators. Other operations are the same as those of the first embodiment.

  The steam separator 1 according to the third embodiment is shown in FIG. In the third embodiment, the target on which the droplet capturing guide 3 in the first embodiment described above is provided is replaced with the outer wall of the outer cylinder 15 of the steam separator 1 adjacent to the drainage collision member 2. is there.

  In the structure of the steam / water separator 1 according to the third embodiment, the drainage channel outlet 18 is disposed so as to face the outer wall of the outer cylinder 15 of the adjacent steam / water separator 1, and above the facing position, As shown in FIG. 4B, the droplet capturing guide 3 is installed at a portion of the outer wall of the cylinder 15. The droplet trapping guide 3 has an L-shaped cross section, and has a shape opened to the lower side where the opening surface is vertically downward as shown in FIG. 4B.

  In the third embodiment, the outer wall of the outer cylinder 15 of the adjacent steam / water separator 1 is also used as the drainage collision member 2 ', so that when the drainage collides with the outer wall of the outer cylinder 15, a minute droplet is generated and rises. Although there is a possibility of being accompanied by the air flow, the discharge to the steam dryer can be suppressed by capturing with the droplet capturing guide 3. Other operations are the same as those of the first embodiment.

  As described above, in each embodiment of the present invention, the swirler 13 that imparts a swirling force to the gas-liquid two-phase flow, the inner cylinder 14 through which the gas-liquid two-phase flow passes, and the outside of the inner cylinder 14 are surrounded. To the outer cylinder 15 for forming the drainage channel 17 for discharging the liquid film separated on the inner wall surface side of the inner cylinder 14 to the outside, the pick-off ring 16 provided at the inlet of the drainage channel 17, and the inner cylinder 14 A stand pipe 11 for guiding a gas-liquid two-phase flow; a diffuser 12 for connecting the stand pipe 11 having a small flow path area and the inner cylinder 14 having a large flow path area; and the inner cylinder 14, the outer cylinder 15, and the pickoff A steam-water separator 1 in which a plurality of drainage channels 17 and drainage channel outlets 18 are formed by a ring 16, and a drainage collision member 2 having a normal direction of a collision surface in a horizontal direction outside the outer cylinder 15. The drainage flow path outlet 18b in the second stage from the bottom A droplet trapping guide 3 having an L-shaped or U-shaped cross section and an opening surface vertically downward is provided at a portion of the drainage collision member 2 or the outer wall 15 (drainage collision member 2 ') higher than the position. Yes.

  In the second embodiment, the drainage collision member 2 is disposed between the adjacent steam-water separators 1, and the adjacent steam-water separators 1 are connected to each other by the drainage-impact member 2. The strength of vibration resistance of the group has been increased.

  Further, in the first embodiment and the second embodiment, when the drainage guide groove 4 is provided to meander on the surface where the drainage of the drainage collision member 2 flows down, the droplets adhering to the drainage collision member 2 are removed. It can be collected and collected in a wide range of drainage guide grooves 4 and quickly returned to the reactor water.

  Moreover, since the lower end of the drainage collision member 2 is below the level of the reactor water formed in the outer space of the outer cylinder 15 in any of the embodiments, the drainage flowing down in contact with the surface of the drainage collision member 2 Compared to falling directly on the water surface, the water enters with less impact, so that the bubbles of fine droplets are scattered in the upper space on the water surface and are not accompanied by the rising airflow.

  In any of the embodiments, the drainage flow so as to face the drainage collision member 2 provided in the adjacent steam separator 1 or the outer wall of the outer cylinder 15 (drainage collision member 2 ′) that is also used instead of the drainage collision member 2. The road outlet 18 is disposed, and the plurality of steam separators 1 are arranged in a triangular lattice pattern.

  In any of the embodiments, the droplet capturing guide 3 is not disposed so as to cover the entire outer periphery of the outer cylinder 15 of the steam / water separator 1, but rises in the outer space of the outer cylinder 15 of the steam / water separator 1. In order to suppress the ventilation resistance of fluid such as steam, as shown in FIG. 2, FIG. 3, FIG. 4, it is arranged limited to a part of the space existing on the outer periphery of the steam separator 1, and is caused by colliding drainage etc. While suppressing the entrainment of fine droplets to the steam dryer 24 side by the droplet capture guide 3, a significant increase in the ventilation resistance of the space existing on the outer periphery of the steam separator 1 was suppressed.

  As described above, a collision member in which the normal direction of the collision surface of the drainage from the steam separator is horizontal is provided, and the cross section perpendicular to the collision surface and parallel to the vertical direction is L at the upper end of the collision member. Dispose of the droplets from the steam separator to the drainage collision member by placing the droplet capture guide with a U-shape or U-shape and the opening face vertically downward limited to a part of the outer space of the steam-water separator. Along the water surface formed around the steam separator to suppress the generation of droplets around the steam separator, and the liquid catching guide provided at the upper end of the drainage collision member Since it is possible to suppress the droplets from being discharged to the steam dryer, the carry-over from around the steam / water separator does not increase even at high steam quality. Further, by providing a new structure such as a drainage collision member or a droplet capture guide only in a part of the flow path around the steam separator, an increase in pressure loss of the flow path can be suppressed.

  The present invention is applicable to a steam separator installed in a reactor pressure vessel of a boiling water reactor.

DESCRIPTION OF SYMBOLS 1 Air-water separator 2 Drainage collision member 2 'Outer cylinder 3 which also serves as a drainage collision member Droplet capture guide 4 Drainage guide groove 11 Stand pipe 12 Diffuser 13 Swirler 14 Inner cylinder 15 Outer cylinder 16 Pickoff ring 17 Drain flow path 18 Drain flow Road exit 21 Core 22 Shroud 23 Shroud head 24 Steam dryer 25 Pressure vessel 26 Internal pump 27 Main steam piping 28 Water supply nozzle 29 Downcomer 30 Water surface

Claims (9)

A plurality of steam separators arranged in parallel in the reactor pressure vessel, wherein the steam in the reactor pressure vessel separates the steam in the reactor pressure vessel from the cooling water in the reactor pressure vessel,
A steam-water separation facility comprising a droplet capturing guide having a shape that is disposed in a space existing on the outer periphery of the steam-water separator and limited to a part of the outer space and is open to the lower side.   2. The steam / water separation facility according to the item 1, wherein the droplet capturing guide is arranged in a horizontal radial direction outside the steam / water separator. In the above item 2, a drainage impingement member is provided toward the other steam-water separator side adjacent to the steam-water separator with a plate surface,
The drainage collision member is provided with the droplet capture guide,
A steam / water separation facility, wherein a lower portion of the drainage collision member is extended downward so as to be positioned below the surface of the cooling water.   4. The steam-water separation facility according to claim 3, wherein the plate surface of the drainage collision member and the droplet capturing guide are extended in the radial direction.   5. The steam / water separation facility according to the item 4, wherein the steam / water separators adjacent to each other are connected by the drainage collision member.   6. The steam / water separation facility according to any one of items 3 to 5, wherein the drainage collision member includes a drainage guide groove in the drainage collision member.   7. The steam-water separator according to any one of items 3 to 6, wherein the steam-water separators are arranged in a triangular lattice shape, and are adjacent to the drainage collision member provided on one of the adjacent steam-water separators. A steam / water separator, wherein a drainage channel outlet of the other steam / water separator is arranged so that drainage from a drainage channel outlet of the other steam / water separator is discharged.   3. The steam / water separation facility according to item 1 or 2, wherein the droplet capturing guide is installed on an outer wall of an outer cylinder of the steam / water separator.   9. In the item 8, the water / water separator is arranged in a triangular lattice shape, and the waste water is discharged in the direction of the outer wall so that waste water from the outlet of the other adjacent water / water separator is discharged. A steam / water separator, wherein a flow path outlet is disposed.

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