JP5663324B2 - Steam separator and boiling water reactor using the same - Google Patents

Description

  The present invention relates to a steam separator used in a boiling water reactor.

  In a general boiling water reactor, a steam separator is installed at the upper part of the core in order to separate water and steam generated in the core. In the steam separator, a swirler (swirl blade) gives a swirl speed to the gas-liquid two-phase flow of water and steam, and the water and steam are separated by utilizing the gas-liquid density difference by centrifugal force. The separated water is drained from below the steam separator, returns to the downcomer, and is sent again to the core by the recirculation pump. The separated steam is further dehumidified through a steam dryer and then sent to the turbine. Power generation efficiency is improved by removing moisture as much as possible from the steam generated in the core.

  The performance of the steam separator is expressed by the steam separation efficiency that removes the moisture contained in the steam. The steam-water separation efficiency is expressed as a carry-over expressed by the weight ratio of moisture contained in the steam after passing through the steam-water separator, and a weight ratio of the amount of steam contained in the moisture separated from the steam. Evaluated by carry-under.

  Among these, the carry-over of the steam separator is limited by the inlet condition of the steam dryer provided in the subsequent stage and must be suppressed to 10% or less.

  FIG. 2 is an enlarged view of the periphery of the swirler, which is the main part of the steam separator. In this figure, 6 is an inner wall surface of the first-stage inner cylinder 64, in which a swirl vane 81 is installed to constitute a swirler 63. The gas-liquid two-phase flow W of water and steam from the core enters from the lower part of the first stage inner cylinder, and when the upward flow of the gas-liquid two-phase flow W reaches the swirler 63, the curved surface of the swirl blade 81 in FIG. Collide with 2. Then, it is confirmed from the analysis result that a collision between water and steam occurs and a liquid film is formed on the curved surface 2 where the collision occurs. The formed liquid film moves in the radial direction by the centrifugal force obtained from the twisted structure of the swirl vane while rising on the curved surface 2 of the swirl vane 81 because of the upward velocity component originally possessed. In this figure, 5 is a horizontal plane that cuts a portion including the swirler 63 of the steam separator.

  Due to the swirler structure of the steam separator shown in FIG. 2, the liquid film formed on the curved surface 2 then rises in two paths. The first path is a path (8 in FIG. 3) that moves in the radial direction on the curved surface 2 of the swirl vane 81 and reaches the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser. In this case, as shown in FIG. 3, the liquid film rises while drawing the locus of the arrow 8 in the state of the liquid film on the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser. The rising liquid film reaches the top of the inner wall surface 6 of the first stage inner cylinder 64, is drained from the lower side of the steam separator as separated water, and returns to the downcomer.

  The second path is a path that rises on the curved surface 2 of the swirl vane 81 and reaches the upper end portion 3 of the swirl vane 81. The liquid film that could not reach the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser in the radial direction when it reached the upper end 3 of the swirl vane 81 as shown by the locus of the arrow 7 in FIG. Loses the wall surface in contact with the upper end 3 of the swirl vane 81 and becomes a droplet 4. This droplet 4 increases the moisture in the vapor, resulting in a worse carry-over.

  Therefore, in order to improve carry-over, the same liquid film is applied to the first inner cylinder 64 before the liquid film formed on the curved surface 2 of the swirl vane 81 reaches the upper end 3 of the swirl swirl 81 of the swirler. What is necessary is just to move to radial direction to the inner wall surface 6 of this or the inner wall surface of a diffuser.

  Patent Document 1 offsets carry-over, which increases due to reduction of pressure loss, by newly providing a swirler inside the hub to increase the swirling speed of the gas-liquid two-phase flow and improve the gas-liquid separation efficiency.

JP 2010-43969 A

  FIG. 4 shows a horizontal cross section (for example, horizontal cross section 5 in FIG. 2) of the portion including the swirler of the steam separator proposed in Patent Document 1. In FIG. In FIG. 4, reference numeral 26 denotes a hub located at the center of the swirler 63, and a plurality of swirl vanes 81 (in the example shown in the figure) from the hub 26 toward the inner wall 6 of the first-stage inner cylinder 64 in the circumferential direction or the inner wall side of the diffuser. 8).

  In such a horizontal section, the liquid film 21 formed on the curved surface 2 of the swirl vane 81 moves (arrow A) from the hub 26 side to the inner wall 6 of the first stage inner cylinder 64 or the inner wall side of the diffuser. The contour of the horizontal section of the curved surface 2 is a straight line, the angle with the inner wall 6 surface of the first stage inner cylinder 64 or the inner wall surface of the diffuser is small, and the liquid film 21 does not flow smoothly on the curved surface 2 of the swirl blade 81. Stay.

  Thereby, in the structure of Patent Document 1, many droplets 4 are generated at the upper end portion 3 of the swirl blade 81.

  Therefore, the present invention suppresses the amount of droplets 4 generated at the upper end 3 of the swirl vane 81, thereby reducing carryover and improving the steam-water separation efficiency, and boiling using the steam-water separator. The purpose is to obtain a water reactor.

  In order to achieve the above object, in the present invention, a stand pipe that guides a gas-liquid two-phase flow from below to above, a flow path that communicates with the upper end face of the stand pipe, and a flow path on the upper end face is formed. A diffuser that expands the cross-sectional area of the flow path upward from the cross-sectional area, a first stage inner cylinder that communicates with the upper end surface of the diffuser to form a flow path, and a concentric spacing between the first stage inner cylinders A first-stage outer cylinder that surrounds and forms an annular flow path, and a first hole that closes the inner peripheral edge of the upper end surface of the first-stage outer cylinder and that has a circular hole with a smaller diameter than the first-stage inner cylinder A first stage in which a circular hole is formed as a flow path to a second stage inner cylinder by standing up in a cylindrical shape downward from an inner peripheral edge forming a circular hole of the first stage annular plate and a circular hole of the first stage annular plate Radiation around the hub and the hub passing through the axial center of the pick-off ring and the gas-liquid two-phase flow path The inner edge of the swirl vane is fixed to the hub, and the outer edge is fixed to the inner wall of the diffuser or the inner wall of the first stage inner cylinder in the radial direction. In the section of the horizontal plane of the portion including the swirler of the steam separator, a part or all of the contour from the hub to the diffuser or from the hub to the inner wall of the first stage inner cylinder is a curve.

  Further, the curved directions of the curved surfaces on both the front side and the back side of the swirl vane are the same.

  A plurality of the reactor pressure vessels are arranged in parallel above the core provided on the lower side inside the reactor pressure vessel.

  In order to achieve the above object, in the present invention, a hub provided at the axial center of a cylindrical body that forms a gas-liquid two-phase flow path from below to above, and a cylindrical body centered on the hub. A swirler including a plurality of swirling blades radially attached toward the inner surface, the inner edge of the swirling blade being fixed to the hub in the radial direction, and the outer edge being fixed to the inner wall of the cylindrical body in the radial direction In the steam-water separator, the plurality of swirl vanes are given the same direction twist in the height direction, and the horizontal section is also given the same direction twist.

  According to this configuration, the liquid film that is formed on the curved surface of the swirl vane and moves in the radial direction due to centrifugal force is smooth without staying at the junction between the swirl vane and the inner wall surface of the first stage inner cylinder or the inner wall surface of the diffuser. It becomes possible to move to the inner wall surface of the first stage inner cylinder or the inner wall surface of the diffuser.

  By doing so, more of the liquid film formed on the curved surface of the swirl vane moves to the inner wall surface of the first stage inner cylinder or the inner wall surface of the diffuser, and becomes droplets at the upper end of the swirl vane. Therefore, the carryover is reduced and the steam-water separation efficiency can be improved.

  According to the present invention, carry-over can be reduced and the steam-water separation efficiency can be improved.

The longitudinal cross-sectional view of a steam-water separator. The swirler enlarged view of a steam separator. FIG. 3 is a horizontal sectional view of a swirl blade 81. The figure which expanded and showed the circumference | surroundings of the swirler which is the principal part of a steam-water separator. The figure which showed the locus | trajectory of the liquid film of the inner wall face of a 1st step | paragraph inner cylinder. The horizontal sectional view in the part containing the swirler of the steam separator. The longitudinal cross-sectional view of a boiling water reactor. The longitudinal cross-sectional view of a steam-water separator. The figure which showed the curvature direction of the swirl | wing blade of the steam-water separator by this invention. The figure which showed the curvature direction of the swirl | wing blade of the conventional steam-water separator. The longitudinal cross-sectional view of a steam-water separator. The swirler enlarged view of a steam separator. FIG. 3 is a horizontal sectional view of a swirl blade 81. The figure which showed the creation method of a Bezier curve.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Before describing the structure of the steam separator of the present embodiment, the schematic structure of a boiling water reactor to which the steam separator is applied will be described with reference to FIGS. 5 and 6.

  FIG. 5 is a longitudinal sectional view of an improved boiling water reactor (hereinafter abbreviated as ABWR). The ABWR has a reactor pressure vessel 32, and a core shroud 31 is installed inside the reactor pressure vessel 32. The core 34 loaded with a plurality of fuel assemblies (not shown) is disposed in the core shroud 31. The steam separator 35 and the steam dryer 36 are disposed above the core 34 in the reactor pressure vessel 32.

  An internal pump 38 (recirculation pump) for supplying water to the core is disposed below an annular downcomer 33 formed between the reactor pressure vessel 32 and the core shroud 31. By operating the internal pump 38, the cooling water in the downcomer 33 is supplied to the core. In the core, the cooling water boils with the heat generated by the fission, resulting in a two-phase state of steam and water.

  The gas-liquid two-phase flow generated in the core 34 flows into the steam separator 35, and a swirl speed is given by the swirler in the steam separator 35. Centrifugal force acts on the two-phase flow due to the swirling speed, and water and steam are separated by the difference in density between water and steam.

  The two-phase flow that has passed through the steam-water separator 35 flows into the steam dryer 36, and moisture is further removed. In this way, steam with a moisture content reduced to 0.1 weight percent or less is sent to a turbine (not shown) through the main steam pipe 37 to generate electricity.

  The structure of the steam separator will be described in more detail with reference to FIG. FIG. 6 is a longitudinal sectional view of a steam separator used in ABWR. In the steam-water separator 35 of FIG. 6, the gas-liquid two-phase flow W generated in the core 34 enters from the stand pipe 61 and reaches the swirler 63 installed in the diffuser 62 portion. In the swirler 63, the gas-liquid two-phase flow W is gas-liquid separated as described with reference to FIGS.

  Further, in the steam separator 35, the water and gas separated by the swirler 63 are returned to the downcomer 33, and a path for guiding the steam to the turbine is formed by three stages of inner and outer cylinders.

  The first stage is formed by a first stage inner cylinder 64, a first stage pick-off ring 65, a first stage outer cylinder 66, and a first stage annular plate 67. A gap is formed between the top of the first stage inner cylinder 64 and the first stage annular plate 67, and the space between the first stage inner cylinder 64 and the first stage outer cylinder 66 forms a drainage channel. To do. For this reason, the first path described in FIG. 3 (the path that travels radially on the curved surface 2 of the swirl vane 1 and reaches the inner wall surface 6 of the first stage inner cylinder or the inner wall surface of the diffuser) 8 is raised. The liquid film reaches the top of the first stage inner cylinder 64 and passes through the gap between the first stage annular plate 67 and the drainage channel between the first stage inner cylinder 64 and the first stage outer cylinder 66. Returned to downcomer 33.

  On the other hand, the droplet 4 that has followed the second path 7 (path that rises on the curved surface 2 of the swirl vane 1 and reaches the upper end 3 of the swirl vane 1) 7 in FIG. And a part of them reaches the inner wall surface of the inner wall surface 6 of the first stage inner cylinder before reaching the top of the first stage, is captured, and is guided to the drainage channel. Further, the droplet 4 that has not reached the inner wall surface of the inner wall surface 6 of the first-stage inner cylinder and has not been captured passes through the first-stage pick-off ring 65 provided at the top of the first stage, and the second stage. Enter the inner and outer cylinders.

  The second stage and the third stage are basically configured similarly to the inner and outer cylinders of the first stage, with no swirler installed. Incidentally, the second stage includes a second stage inner cylinder 68, a second stage pick-off ring 69, a second stage outer cylinder 70, and a second stage annular plate 71, and the third stage includes a third stage inner cylinder 72, A third-stage pick-off ring 73, a third-stage outer cylinder 74, and a third-stage annular plate 75 are included.

  The swirler 63 is provided with a plurality of swirling blades 81 for giving a swirling speed to the two-phase flow in a cylindrical structure called the hub 26, and the outer edge of the swirling blade 81 is a first stage inner cylinder or a diffuser 62. It is fixed to. For this reason, the swirler 63 itself does not rotate, but the fluid that has passed through the swirler 63 rotates.

  The steam separator 35 is configured as shown in FIG. The gas-liquid two-phase flow W from the core 34 introduced into the steam separator 35 has a quality of about 14%. The two-phase flow W that has flowed into the stand pipe 61 forms a liquid film on the inner wall surface of the stand pipe 61 and is an annular spray flow in which steam flows in the center and droplets float in the steam. . When swirling speed is given to the gas-liquid two-phase flow W by the swirler 63, the steam mixed in the liquid film on the wall moves to the steam side in the center due to the difference in centrifugal force due to the gas-liquid density difference. The liquid droplet floating inside moves to the wall surface and is taken into the liquid film.

  The liquid film formed on the wall surface of the first stage inner cylinder 64 passes through the first stage drainage channel 50 formed by the first stage inner cylinder 64 and the first stage outer cylinder 66 by the first stage pick-off ring 65. It is discharged out of the steam separator 35. The water discharged from the first stage drainage channel 50 flows into the downcomer 33 again and is sent to the core 34 by the internal pump 38.

  The droplets in the vapor that have not reached the wall surface by the first stage inner cylinder 64 reach the inner cylinder wall surface by the second stage inner cylinder 68 or the third stage inner cylinder 72, and the second stage pick-off ring 69 or the third stage. The water is discharged from the stage pick-off ring 73 through the second stage drainage channel 51 or the third stage drainage channel 52 to the outside of the steam / water separator 35. The liquid droplets that have not reached the wall surface of the inner cylinder before passing through the third stage pick-off ring 73 flow out from the steam-water separator outlet 55 together with the steam.

One of the indicators of the separation efficiency of the steam separator is carryover, which is defined as the weight ratio of the liquid contained in the fluid flowing out of the steam separator. When the vapor mass flow rate is Wg (kg / s) and the liquid mass flow rate is Wl (kg / s), the carry-over CO is expressed by the following equation.
[Equation 1]
CO = Wl / (Wg + Wl) × 100 (%) (1)

The steam / water separator is configured as described above to achieve the steam / water separation function. In the first embodiment of the present invention, the steam / water separator 35 is configured as shown in FIG. FIG. 1 a shows the configuration of the steam separator 35, FIG. 1 b shows an enlarged view of the swirler 63, and FIG. 1 c shows a horizontal sectional view of the swirl vane 81.

  FIG. 1a is an embodiment of the present invention corresponding to FIG. 6, FIG. 1b is FIG. 2, and FIG. 1c is a portion corresponding to FIG. Although there are some differences in these figures (for example, where the swirler is installed), the present invention is valid regardless of this difference. The features of the present invention appear well in FIG. 1c. That is, in the horizontal cross section of the swirler 63 (FIG. 1c), the contour 91 of the swirl vane 81 is changed from the straight line 2 to the curve 91, and the surface 91 of the swirl vane 81 and the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser 62 are. It is connected smoothly.

  As a result, the liquid film 93 that is formed on the curved surface 91 of the swirl vane 81 and moves in the radial direction due to centrifugal force is at the joint between the swirl vane 81 and the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser 62. It is possible to smoothly move to the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser 62 without staying.

  By doing so, more of the liquid film 93 formed on the curved surface 91 of the swirl vane 81 moves to the inner wall surface 6 of the first stage inner cylinder 64 or the inner wall surface of the diffuser 62, as shown in FIG. As shown by the locus of the arrow 8, the liquid film can be lifted even after passing through the swirler portion. At the same time, as shown by the locus of the arrow 7 in FIG. 2, the amount of liquid film that becomes droplets 4 at the upper end 3 of the swirling blade is reduced, so carry-over is reduced and steam-water separation efficiency is improved. The

  In FIG. 1 c, the back side contour 92 has a roundness that is approximately the same as the roundness of the contour 91 of the swirl vane 81. FIG. 7 is a horizontal cross section of a portion including a swirler of the steam separator according to the present invention. The swirler according to the present invention is characterized in that the curved surface 91 on the side where the liquid film is formed and the warp directions 94 and 95 of the curved surface 92 on the back side of the two curved surfaces of the swirl blade 81 are the same. For this reason, even if the warps 94 and 95 are increased, the cross-sectional area of the two-phase flow passage portion 96 can be kept constant, and an increase in pressure loss due to the reduction of the cross-sectional area can be prevented.

  On the other hand, FIG. 8 is a horizontal cross section of a portion including a swirler of a conventional steam separator. Since the swirler is manufactured by casting, curved portions 28 and 29 peculiar to the cast product are formed at the joint between the swirl blade 81 and the inner wall 6 of the first stage inner cylinder 64 or the inner wall of the diffuser 62. However, since the curved portions 28 and 29 have different warping directions on both sides of the swirl vane 81, the cross-sectional area of the passage portion 30 of the two-phase flow is reduced and the pressure loss of the steam / water separator is increased when the warpage increases. It becomes a cause.

  The swirler in FIG. 1 provides a rightward swirling flow, but this can be realized in the same manner even if it provides a leftward swirling flow as shown in FIG. In this case, of the two curved surfaces of the swirl blade 81, the direction of the curved surface 91 on the side where the liquid film is formed is different between FIG. 1c and FIG. 9c.

  As is apparent from the embodiment of FIGS. 1 and 9, the present invention is provided at the axial center of a cylindrical body (diffuser or first stage inner cylinder) that forms a gas-liquid two-phase flow path from below to above. And a plurality of swirling blades radially attached to the cylindrical body around the hub, and the inner edge of the swirling blade is fixed to the hub in the radial direction, and the inner wall of the tubular body In the steam-water separator including a swirler whose outer edge is fixed in the radial direction of the swirl vanes, the swirl vanes are twisted in the same direction in the height direction as shown in FIGS. 1b and 9b. In addition, it can be said that the steam-water separator has a structure in which the horizontal cross-section is also twisted in the same direction as shown in FIGS. 1c and 9c.

  FIG. 10 is a horizontal cross section of a swirler in which the curved surface 91 of the swirl vane 81 and the contour of the inner wall 6 of the first stage inner cylinder 64 are connected by a Bezier curve 107. An advantage of using the Bezier curve 107 as a curve is that the curved surface 91 of the swirl vane 81 and the inner wall surface 6 of the first stage inner cylinder 64 can be made continuous.

  A specific method for determining the Bezier curve 107 will be described below. First, in the horizontal section of FIG. 10, an auxiliary line 105 passing through the center 103 of the hub 26 and passing through the contour 91 of the swirl vane 81 and an auxiliary line 106 that passes through the hub center 103 and rotated counterclockwise, for example, 30 ° are drawn. The intersection 101 of the contour of the auxiliary line 105 and the hub 26 is the starting point, the intersection 102 of the auxiliary line 106 and the inner wall surface 6 of the first-stage inner cylinder is the end point, and the inside of the first-stage inner cylinder 64 at the intersection 102 and the intersection 102. For example, a quadratic Bezier curve that touches both tangents 108 of the wall surface 6 is determined.

  The Bezier curve to be used can be optimized by adjusting the angle between the auxiliary lines 105 and 106 and the order of the Bezier curve.

  The present invention is applicable to a boiling water reactor.

2: Curved surface of swirl vane 3: Upper end of swirl vane 4: Droplet 5: Horizontal plane cutting the portion including the swirler of the steam separator 6: Inner wall surface of the first stage inner cylinder 7: Liquid film on the swirl vane Movement locus 8: Movement locus of liquid film on the first stage inner cylinder 21: Liquid film 25: Curved surface on the side where the liquid film of the swirl vane is formed 26: Hub 27: Curved surface on the side where the liquid film of the swirl vane is not formed 28: Curvature direction of curved surface on the side where the liquid film of the swirl vane is formed 29: Warp direction of curved surface on the side where the liquid film of the swirl vane is not formed 30: Cross-sectional area of the passage part of the two-phase flow 31: Core shroud 32: Reactor pressure vessel 33: Downcomer 34: Core 35: Steam / water separator 36: Steam dryer 37: Main steam pipe 38: Internal pump 50: First stage drainage channel 51: Second stage drainage channel 52: First Three-stage drainage channel 55: Steam / water separator outlet 61: Stand pipe 62: Diffuser 3: Swirler 64: First stage inner cylinder 65: First stage pickoff ring 66: First stage outer cylinder 67: First stage annular plate 68: First stage inner cylinder 69: Second stage pickoff ring 70: Second stage Outer cylinder 71: Second stage annular plate 72: Third stage inner cylinder 73: Third stage pick-off ring 74: Third stage outer cylinder 75: Third stage annular plate 80: Hub 81: Swirling blade 91: Liquid of swirling blade Curved surface 92 on the side where the film is formed: Curved surface 93 on the side where the liquid film of the swirl vane is not formed 93: Liquid film 94: Warpage direction of the curved surface on the side where the liquid film of the swirl vane is formed 95: Liquid film on the swirl vane Curvature direction 96 of the curved surface on the non-formed side: sectional area of the passage part of the two-phase flow

Claims (2)

A stand pipe that guides the gas-liquid two-phase flow from below to above, and a flow path that communicates with the upper end face of the stand pipe to form a flow path, and the flow path breaks upward from the flow path cross-sectional area of the upper end face. A diffuser that expands the area, a first stage inner cylinder that communicates with the upper end surface of the diffuser to form a flow path, and an annular flow path is formed by concentrically surrounding the first stage inner cylinder at intervals. A first-stage outer cylinder, a first-stage annular plate that closes the inner peripheral edge of the upper end surface of the first-stage outer cylinder, and that has a circular hole having a smaller diameter than the first-stage inner cylinder, and the first-stage annular plate A first-stage pick-off ring in which the circular hole is formed as a flow path to the second-stage inner cylinder by standing downward in a cylindrical shape from the inner peripheral edge forming the circular hole of the plate, and a gas-liquid two-phase A hub passing through the axial center of the flow channel and a plurality of rotations mounted radially about the hub. The inner edge of the swirl vane is fixed to the hub, and the outer edge is fixed to the inner wall of the diffuser or the inner wall of the first stage inner cylinder in the radial direction. With a swirler,
In a cross section of the part including the swirler of the steam separator, the contour of the swirl blade from the hub to the diffuser or from the hub to the inner wall of the first stage inner cylinder is curved. And
The steam-water separator, wherein the curved directions of the curved surfaces on both the front side and the back side of the swirl vanes are the same . In the steam-water separator according to claim 1,
A boiling water reactor comprising a plurality of cores arranged in parallel above a core provided on a lower side inside a reactor pressure vessel.

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