JP3263266B2 - Steam separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam-water separator for separating a gas-liquid two-phase flow into a liquid and a gas. To a steam-water separator that separates the steam and water.

[0002]

2. Description of the Related Art In a boiling water reactor (BWR),
A reactor core loaded with a number of fuel assemblies is housed in a reactor pressure vessel, and a steam separator is installed above the reactor core.
The steam separator is provided in a forested state on the shroud head that covers the core shroud, and separates the gas-liquid two-phase flow from the core into water and steam, and the separated steam is guided to a steam dryer. Moisture is removed. The water separated from the steam is guided to a downcomer around the core.

FIG. 5 shows a conventional example of a steam-water separator.

A core shroud 2 is provided in a reactor pressure vessel 1 of a boiling water reactor, and a fuel (not shown) is loaded in the core shroud 2 to form a core 3.
A large number of steam separators 5 are provided on a shroud head 4 attached to the upper end of the core shroud 2 in a stand state.

Each steam separator 5 has a tubular shape having three stages of steam separators 5a, 5b, 5c, which are upper and lower stages, and is disposed below the lowermost stage (first stage) 5a. An extending stand pipe 6 is connected to the shroud head 4. Drainage outlets (first-stage drainage, second-stage drainage, and third-stage drainage) 7a, 7b, and 7c are opened at the lower end positions of the separation stages 5a, 5b, and 5c, respectively. . The lower end of the stand pipe 6 serves as the air / water inlet 8 and is located at the uppermost stage (third stage).
The upper end of the separation stage 5a is a steam outlet 9.

As described above, most of the conventional steam-water separators are of two-stage or three-stage type.
Are connected to a stand pipe 6. The gas-liquid two-phase flow flowing from the stand pipe 6 is separated into gas and liquid, and the water separated in the first separation stage 5a exits from the first stage drain port 7a above the shroud head 4. The water not separated in the first separation stage 5a is separated in the second separation stage 5b and the third separation stage 5c, and the water around the steam separator 5 is discharged from the second and third drain outlets 7a and 7b, respectively. Go to

The discharged water passes around the stand pipe 6 in the radial direction and flows from the lower end of the steam dryer skirt 12 to the downcomer 13.

[0008] The performance of steam separators is often expressed in terms of carryover and carryunder and the operating water width affected by them. The carryover is the weight fraction of water in the steam separated by the steam separator, and the carry under is the weight fraction of steam in the water separated by the steam separator. The lower the respective, the better the performance.

[0009] Carry over and carry under are affected by the water level H around the steam separator. In general, when the water level is high, carry-over increases and carry under decreases. Conversely, low water levels reduce carryover,
Carry under increases. The water level at which the carryover is at the design limit is determined as the upper water level, and the water level at which the carry under is at the design limit is determined as the lower water level.

FIGS. 6 (a), 6 (b) and 6 (c) show the carryover measured in the performance test of the steam separator (ASME Paper 73-WA / Pwr-4).
Quote). In the figure, L indicates the water level around the steam separator.

It can be seen that when L is large, carry-over increases. From FIG. 6 showing the components, it can be seen that the main component of the carryover when the water level is high is from the periphery of the steam separator. This is because droplets generated when the steam flow discharged together with the water from the second and third stages collide with the water surface formed around the steam separator at a high speed, and the droplets of the steam separator are generated. It is considered that they were carried in the direction of the steam outlet.

When the water around the standpipe flows into the downcomer, the water level around the steam-water separator rises due to the resistance due to the narrow flow passage area corresponding to the curvature of the standpipe or shroud head that stands. I have. A typical BWR shroud head has a curvature of about 5-6 meters. As a result, the water level around the steam separator becomes higher toward the center of the shroud head, and this is called a water surface inclination. That is, the upper limit of the water level determined by the carry-over of the steam separator is determined by the highest part around the steam separator.

[0013] Normally, the reactor has a water level around the steam separator,
The reactor is operated so as to be between the upper limit and the lower limit of the water level, and the range is called an operating water width, and the reactor is stopped when the range deviates from the range.

[0014]

However, since there is a great demand on the control equipment to keep the water level of the reactor within the above-mentioned range and a great deal of strain on the operators, it is desirable to make the operating water level width as large as possible. ing.

An object of the present invention is to provide a steam-water separator which can increase the operating water level width by increasing the upper limit of the operating water level width of the reactor, thereby improving the operating performance.

[0016]

In order to achieve the above object, a first aspect of the present invention is to provide a plurality of boiler water reactors which are provided above a core of a reactor pressure vessel in a standing manner, each of which is a multi-stage type. In the cylindrical water / water separator having the water / water separation stage and the drain port, the gap between each adjacent water / water separator is covered above the drain port of the second separation stage counted from the bottom. A droplet capture ring is provided.

According to a second aspect of the present invention, in the steam-water separator according to the first aspect, the droplet capturing ring is formed of a net-like material, a perforated plate, or another permeable material.

According to a third aspect of the present invention, in the steam-water separator according to the first aspect, the droplet capturing ring is formed in a polygonal plate shape or a disk shape made of a non-permeable material, and the peripheral portions are vertically overlapped with each other. And a lateral gap is formed in an overlapping portion of each of the droplet capturing rings.

According to a fourth aspect of the present invention, in place of the droplet capturing ring according to the first aspect, a droplet capturing plate made of a corrugated plate or another curved plate is provided vertically.

According to a fifth aspect of the present invention, in the steam-water separator according to any one of the first to fourth aspects, a gutter for receiving water is provided below the droplet catching ring or the droplet catcher plate, and the gutter is vertically elongated. And a drain pipe whose lower end outlet is opened at a height between the drain port of the lowermost separation stage and the shroud head is provided.

According to a sixth aspect of the present invention, in the steam / water separator according to the first aspect, the height of the first drain port opened at the lowermost portion is formed above the shroud head by adjusting the length of the stand pipe. It is characterized by being arranged parallel to the water surface inclination.

[0022]

According to the configuration of the present invention described above, the carry-over component generated around the steam separator is reduced, and the water level around the steam separator is relatively reduced. The rise of surrounding water level is reduced. This reduces carryover. As a result, the upper limit of the operating water level determined by carry-over is increased, so that the operating water level width is widened and the operability of the BWR is improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a steam separator according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention.

A core shroud 22 is provided in a reactor pressure vessel 21 of a boiling water reactor.
A fuel core (not shown) is loaded in 2 to form a reactor core 23. A large number of steam separators 25 are provided on a shroud head 24 attached to the upper end of the core shroud 22 in a standing state.

Each of the steam separators 25 has a tubular shape having three stages of steam separators 25a, 25b, and 25c, and is disposed below the lowermost stage (first stage) 25a. An extending standpipe 26 is connected to the shroud head 24. Drain outlets (first-stage drain, second-stage drain, third-stage drain) 27a, 27b, 2 at the lower end positions of the separation stages 25a, 25b, 25c, respectively.
7c has been established. The lower end of the stand pipe 26 is a steam-water inlet 28, and the upper end of the uppermost stage (third separation stage) 25 a is a steam outlet 29.

In the steam-water separator 25 configured as described above, a hexagonal column-shaped droplet capture ring 30 made of a mesh material is provided on the upper outer peripheral side of the intermediate second separation stage 25b and the upper third separation stage. The gaps 31 between the steam separators 25 are provided by the droplet capturing rings 30. Note that the droplet capture ring 30 may be formed of a perforated plate having small holes to be a flow path of vapor, or other air-permeable material. In the figure, reference numeral 32 denotes a steam dryer skirt, and a downcomer 33 is formed on the outer peripheral side thereof.

The shroud head 24 has a curvature of about 10 m or more so as to be substantially flat.

In the steam / water separator 25 according to this embodiment having such a configuration, when the water level H around the steam / water separator 25 is high, the water is discharged from the second separation stage 25b or the third separation stage 25c together with water. Drops on the water surface caused by the steam flow
The droplet is captured by the droplet capture ring 30.

Since the droplet capturing ring 30 has an air-permeable structure such as a mesh structure, the vapor passes therethrough, but the droplet collides with a fine wire or the like and is accumulated in the droplet capturing ring 30. Thereafter, the amount of water in the droplet capture ring 30 increases, and the droplet falls due to its weight. As a result, the amount of water flowing into the steam dryer 25, that is, the carryover is reduced.

Further, in the shroud head 24, the area of the flow path through which the water discharged from the steam separator 25 flows into the downcomer 33 in the area where the stand pipes 26 stand up there, especially in the central part of the shroud head 24, Be wider than the ones. For example, when the radius of curvature of the shroud head 24 is changed from the conventional value of about 6 m to 10 m, the height of the center of the shroud head 24 is reduced by about 0.4 m.
Therefore, the flow resistance becomes smaller than that of the conventional one, so that the inclination of the water surface around the steam separator 25 becomes smaller. this is,
In particular, it means that the water level around the steam-water separator 25 located at the center of the shroud head 24 is lower than that of the conventional one, thereby reducing carryover.

FIG. 2 schematically shows another embodiment of the present invention. The second separation stage 2 from below the steam separator 25
After 5b, a circular or polygonal droplet capture ring 40 made of a non-breathable material is provided. The droplet capture rings 40 of the adjacent water / water separators 25 are arranged such that their peripheral edges overlap each other in the vertical direction, and a lateral gap is formed in the overlapping portion. Also, the height of the first stage drain 27a of the steam separator 25 is determined by adjusting the length of the stand pipe 26 so as to be parallel to the water surface inclination formed above the shroud head 24. I have.

The steam-water separator 2 of FIG.
At 5, the carryover component generated from around the steam separator 25 flows to the steam dryer while the flow direction is changed by the droplet capture ring 40. When the moisture-containing steam changes the direction of flow, the water and the steam are separated by the density difference between the steam and the water, so that the moisture flowing into the steam dryer is reduced, and the carryover is reduced.

Further, by adjusting the length of the stand pipe 26, the flow path area in the radial direction above the shroud head 24 becomes large, particularly at the center of the shroud head 24, so that the water surface inclination becomes small. This means that the water level around the steam separator 25, which is located particularly at the center of the shroud head 24, is lower than in the conventional case, and the carryover is also small.

FIG. 3 schematically shows another embodiment of the present invention. Dropping of a vertically long corrugated sheet as used in steam dryers of other BWRs in a gap between the second water separator 25 and the adjacent water / water separator 25 from below the water / water separator 2. A plate 50 is mounted. Further, the height of the first stage drain port 27a of the steam separator 25 is determined by adjusting the length of the stand pipe 26 so as to be parallel to the water surface inclination formed above the shroud head 24. .

In the steam-water separator 25 configured as described above, the Carry-O component generated from the periphery of the steam-water separator 25 is steam-dried while the flow direction is changed by the droplet capturing plate 50 composed of a corrugated plate. Flows into the vessel. When the moisture-containing steam changes the direction of the flow, the water and the steam are separated by the density difference between the steam and the water, so that the moisture flowing into the steam dryer is reduced, and the carryover is reduced.

Further, by adjusting the length of the stand pipe 26, the flow path area in the radial direction above the shroud head 24 is particularly large at the center of the shroud head 24, so that the water surface inclination is reduced. As a result, the water level around the steam separator 25 located at the center of the shroud head 24 becomes lower than that of the conventional one, and the carryover becomes smaller.

FIG. 4 schematically shows another embodiment of the present invention. That is, a gutter 60 is provided so as to surround the steam separator 25 after the second separation stage 25b of the steam separator 25, and the gutter 60 is provided with the first gutter of the steam separator 25.
A pipe 61 having an outlet portion is provided between the step drain 27 a and the shroud head 24. The gutter 60 and the pipe 61 prevent the droplets captured by the droplet capturing rings 30 and 40 and the corrugated droplet capturing plate 50 from returning to the vapor flow again, and ensure the shroud head 24 There is a function of flowing into the downcomer 33 through the upper part. As a result, carryover is further reduced.

[0039]

As described above, according to the present invention, it is possible to reduce carry-over caused by droplets generated around the steam separator, and it is provided at the center of the shroud head. Since the water level around the steam-water separator decreases, the upper limit of the operating water level width determined by the carryover of that portion increases. Therefore, since the operating water level width particularly in the BWR is widened, excellent effects such as improved operability are exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of a steam separator according to the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the present invention.

FIG. 3 is a schematic diagram showing still another embodiment of the present invention.

FIG. 4 is a schematic diagram showing still another embodiment of the present invention.

FIG. 5 is a schematic diagram showing a conventional steam separator.

FIGS. 6 (a), (b) and (c) are diagrams showing the performance of a conventional steam separator.

[Explanation of symbols]

 Reference Signs List 21 reactor pressure vessel 22 core shroud 23 core 24 shroud head 25 steam separator 25a first separation stage 25b second separation stage 25c third separation stage 26 stand pipe 27a first stage drain 27b second stage drain 27c Three-stage drain port 28 Air / water inlet 29 Steam outlet 30, 40 Droplet capturing ring 31 Gap 32 Steam dryer skirt 33 Downcomer 50 Droplet capturing plate 60 Gutter 61 Piping

Claims (6)

(57) [Claims] 1. A cylindrical steam-water separator provided in a large number above a reactor pressure vessel of a boiling water reactor and having a plurality of upper and lower multistage separation stages for steam-water separation and a drain port. A droplet capture ring provided above a drain port of a second separation stage counted from a lower portion, the droplet capture ring covering a gap between adjacent steam / water separators. 2. The steam-water separator according to claim 1, wherein the droplet capturing ring is formed of a mesh material, a perforated plate, or another permeable material. 3. The steam-water separator according to claim 1, wherein the droplet capturing ring is a polygonal plate or a disk made of a non-permeable material, and is arranged so that peripheral portions overlap in the vertical direction. A steam-water separator, wherein a horizontal gap is formed in an overlapping portion of each of the droplet capturing rings. 4. A droplet capturing ring according to claim 1,
A steam-water separator characterized in that a droplet capturing plate made of a corrugated plate or another curved plate is provided in a vertical direction. 5. The steam separator according to claim 1, wherein a gutter for receiving water is provided at a lower portion of the droplet capture ring or the droplet capture plate, and the gutter has a vertically elongated lower end outlet. A steam-water separator having a drainage pipe opened at a height between a drain port of a lowermost separation stage and a shroud head. 6. The steam-water separator according to claim 1, wherein the length of the stand pipe is adjusted to adjust the length of the first pipe.
A steam-water separator, wherein the height of the drain port is arranged in parallel with the water surface inclination formed above the shroud head.