JPH0675082A - Multiple steam water separator - Google Patents

Abstract

PURPOSE:To improve the steam/water separator capability for high temperature water steam system two-phase flow and reduce pressure loss by multiplying the steam/water separator, making the bottommost swirl vane angle small, upper one's angle large and the topmost swirl vane angle largest. CONSTITUTION:A steam/water separator is in three steps. Since ascending steam/water two-phase flow from a stand pipe 14 is slug flow with small void fraction, the angle of swirl vane 15a is made small to mainly separate liquid block in this separator 11a and pressure loss is medium grade. Since the above is anular flow with large void fraction, the angle of swirl vane 15b is made slightly large to mainly separate liquid film in this separator 11b and pressure loss is medium grade. Since the topmost is mist flow with large void fraction, the angle of swirl vane 15c is made largest to mainly separate liquid drops in this separator 11c and pressure loss is small. In this manner, the arrangement of the separators 11a to 11c and the angles of the swirl vanes 15a to 15c are determined accordingly to the flow regime of steam/water two-phase flow and the total pressure loss is reduced and the separation capability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal structure of a nuclear reactor, and more particularly to a multi-stage steam-water separator for improving two-phase flow separation performance and reducing two-phase flow pressure loss. The present invention relates to a suitable air / water separation mechanism.

[0002]

2. Description of the Related Art A conventional reactor pressure vessel is shown in FIG. 5, and an outline of a conventional steam-water separator is shown in FIG. Compared with FIG. 1 and FIG. 2 which are one embodiment of the present invention, the steam separator 11 is installed only one stage in the ascending two-phase flow direction. Originally, steam separator 11
Applies the hot water / steam system two-phase flow B generated in the fuel rod 8 to the hot water A flow against the inner wall of the body 17 by the centrifugal force of the swirl vanes 15 to separate the steam C into steam and water. This is for suppressing carry under of steam contained in the hot water A returning to the downcomer. Further, the steam dryer 12 is for suppressing carry-over of the moisture mist liquid contained in the steam C phase-separated by the steam separator 11 to the steam turbine.

Therefore, the early reactors are appropriate for the type of the one-stage steam-water separator 11 and the one-stage steam dryer 12, and are meticulous to pay attention to the various reliability of the actual equipment of this type. However, there are many issues to be considered in order to further improve performance. For example, as a publicly known example, in JP-A-62-35291, the flow resistance of the liquid discharge passage of the steam-water separator arranged in the radial direction of the furnace is adjusted to improve the steam-water separation performance. Further, in Japanese Patent Laid-Open No. 62-64989, the pressure loss is reduced by not changing the inner diameter of the flow passage along the flow direction.

However, the pressure loss in the conventional one-stage steam-water separator is the largest in the two-phase flow pressure loss due to the sharp bending of the two-phase flow as a swirl flow by the swirl vanes.

Therefore, the technical problems of both improvement of separation performance and reduction of pressure loss in the steam separator are solved, and further, a relatively simple structure for facilitating maintenance of the equipment at the time of regular inspection of the reactor. Need to

[0006]

In the above-mentioned conventional technique, the swirl vane angle in the water-water separator is increased in order to phase-separate the gas-liquid two-phase flow generated by the fuel rod on the free liquid surface, and the two-phase flow is increased. It is designed to utilize the centrifugal force to improve the water-water separation efficiency by forming the swirling flow of. Therefore, the flow in the steam separator has a large pressure loss due to abrupt two-phase flow bending loss in the swirl vanes. Also,
Since the flow transition of the two-phase flow is rapidly performed in the one-stage steam-water separator, the steam-water separation efficiency is not so good, and there is room for further improvement.

An object of the present invention is to improve the steam-water separation performance and reduce the two-phase flow pressure loss by using a multi-stage steam-water separator.

[0008]

In order to achieve the above object, the present invention divides a conventional steam separator into several stages, in which the swirl vane angle is small in the low void fraction region and swirl is in the high void fraction region. A multi-stage steam-water separator was used to increase the blade angle and facilitate the improvement of steam-water separation performance and reduction of pressure loss for each flow mode in the hot water / steam system two-phase flow generated in the fuel rod. It is a thing.

[0009]

[Operation] By making the steam separator multi-stage and gradually increasing the swirl vane angle from bottom to top, pressure loss in the lower low void fraction region is reduced compared to the conventional one-stage steam separator. Moreover, even if a high void fraction region is formed along the upper portion, the fluid density becomes small, so that the pressure loss per stage can be reduced. Moreover, as compared with the case where the centrifugal separation is performed rapidly in the one-stage system, the water-water separation performance, particularly the carryover can be rapidly reduced when the centrifugal separation is gradually performed in the multi-stage system. Of course, with respect to the carry under, if it is adjusted by reducing the flow resistance of the hot water outlet, the structure becomes effective with respect to both carry over and carry under.

As described above, there are advantages that the separation efficiency of the steam-water separator, which is the internal structure of the nuclear reactor, is improved, the pressure loss is reduced, and the maintenance is easy. By these actions, the structure in the upper part of the reactor, especially the separator, is made compact, and further the safety and reliability of the reactor pressure vessel are secured.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1, 2 and 3. FIG. 1 shows a vertical sectional view of a reactor pressure vessel. First, the structure of the reactor pressure vessel will be described.
In this basic structure, a fuel rod 8 for causing a nuclear reaction in a reactor pressure vessel 1 is installed inside a core shroud 7 in the lower part of the vessel, and a control rod guide tube 4 and a control rod guide are provided under the fuel rod 8. A tube drive mechanism 3 is installed. And these devices are being fixed by the core support plate 5, the fuel support metal fitting 6, etc. Further, the uppermost portion of the fuel rod 8 is the upper support plate 9
It is fixed by. On the other hand, several internal pumps 2 for circulating hot water A are installed in the circumferential direction between the reactor pressure vessel 1 and the core shroud 7. Next, in order to take out steam from the gas-liquid two-phase flow generated by boiling in the fuel rods 8, a shroud head 10 is provided above the core shroud 7.
There are a number of stand pipes 14 and a multi-stage steam separator 11 on top of this. Further, a steam dryer 12 for removing mist droplets at the outlet of the steam separator 11 is installed above the steam dryer 12. Further, a main steam nozzle 13 for letting out steam generated in the reactor is provided at an upper portion of the reactor pressure vessel 1.

Next, the operation inside the reactor pressure vessel 1 will be described. First, the gas-liquid two-phase flow B generated by the nuclear reaction in the fuel rod 8 rises in the flow path between the fuel rods 8 in the fuel channel,
These gas-liquid two-phase flows are once gathered in the space formed by the core shroud 7 and the shroud head 10, and again, in the many stand pipes 14 and the multistage steam-water separator 11 above them, the hot water liquid A And steam C are separated. Then, the vapor stream C containing mist droplets has the liquid component carried over in the vapor dryer 12 cut off, and the main vapor nozzle 13
To the steam turbine. On the other hand, the hot water A separated in the steam separator 11 descends through the downcomer portion composed of the reactor interior 1 and the core shroud 7, and is sucked into the internal pump 2. Then, the hot water discharged from the internal pump 2 flows into the reactor from the leg portion opened at the lower part of the core shroud 7, flows in a cross flow between the control rod guide tube drive mechanisms 3 and again to the fuel rods 8. Return.

The features of the present invention will now be described with reference to FIG. First, FIG. 2 shows an example in which the steam separator 11 is of a three-stage type. Since the gas-liquid two-phase flow rising from the stand pipe 14 is a slag flow region having a small void ratio, the swirling blade 15a
The angle is made small, and the main separator 11a mainly separates liquid lumps, and the pressure loss here is medium. further,
Since it is an annular flow region with a large void fraction, the swirl vane 1
5b has a slightly larger blade angle, the main separator 11b is mainly for liquid film separation, and the pressure loss here is also moderate. Then, the swirl vane 15c has the largest angle because it becomes a spray flow region having a larger void rate at the uppermost portion,
The main separator 11c mainly separates droplets. Here, the flow velocity of the two-phase flow is high, but since the void ratio is high and the fluid density is low, the pressure loss is small. Therefore, according to the flow mode of the gas-liquid two-phase flow flowing in the separator along the upper separator from the lowermost separator 11a, the point of the separation efficiency for separating and cutting the liquid component in each area, and each area. The optimum separator arrangement and the swirl vane angle may be set from both of the viewpoints of reducing the pressure loss in the above. FIG. 3 is an explanatory diagram showing the performance of the three-stage steam separator of FIG.

(A) is a water-water separation efficiency η characteristic, and the middle diagram is a pressure loss ΔP characteristic diagram. Further, (b) is a diagram of a three-stage separator. Separator placement Top to bottom, 1st stage, 2nd
The stage, the uppermost part is the third stage, and the swirl vane angle α gradually increases along the upward direction. On the other hand, the conventional example shows a case in which only one stage with a large swirl vane angle α is installed in the third stage of this figure. From this, comparing the characteristics of the air-water separation efficiency η and the pressure loss ΔP of the conventional example and the present invention,
In the case of the present invention, the water-water separation characteristic is large and the pressure loss is small. In this way, by making the steam-water separator multi-stage, the swirl vane angle α is adjusted according to the flow pattern of the two-phase flow to optimize the steam-water separation efficiency and reduce the pressure loss in each stage. A separation mechanism can be configured. Therefore,
The multi-stage steam separator can improve steam separation efficiency, reduce pressure loss, and facilitate maintenance during regular inspection.

Another embodiment of the present invention will be described with reference to FIG. In contrast to the invention shown in FIG. 2, the present invention uses an outer cylinder 1 for each stage.
8 has the same diameter, and the annular flow path width 19 is larger at the lower level. This is because the void ratio is small and the liquid component is large in the lower part, so that the hot water discharge port is made large and the return flow loss of the hot water is made small. On the other hand, since the amount of return of hot water becomes smaller toward the upper stage, the flow loss becomes small even in the narrow annular flow passage 19c as it is.

Therefore, as in this structure, the steam separator 1
By making 1 a multi-stage type, it is possible to provide a separation mechanism in which the pressure loss is reduced and the steam-water separation efficiency is further improved by changing the swirl vane angle for each stage with respect to each void fraction region. In addition, maintenance at the time of regular inspection becomes easy, and the internal structure of the reactor is highly safe and reliable.

[0017]

EFFECTS OF THE INVENTION According to the present invention, the steam-water separator is of a multi-stage type, whereby the number of steam-water separators is divided according to the two-phase flow mode in the steam-water separator, and the void fraction in the lower part is In a small region, the swirl vane angle is made small to reduce the two-phase flow bending loss, and in the region with a large void fraction in the upper part, the swirl vane angle is made large to reduce the two-phase flow bending loss, and the pressure of the steam separator It is possible to reduce the loss and improve the steam-water separation performance.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a reactor pressure vessel according to an embodiment of the present invention.

FIG. 2 is a sectional view of the multistage steam-water separator of FIG.

FIG. 3 is an explanatory view of steam-water separation performance and pressure loss characteristics of the present invention.

FIG. 4 is a sectional view of a multi-stage steam separator according to another embodiment of the present invention.

FIG. 5 is a vertical sectional view of a conventional reactor pressure vessel.

FIG. 6 is a sectional view of a conventional one-stage steam-water separator.

[Explanation of symbols]

11 ... Steam separator, 14 ... Stand pipe, 15 ... Swirl vane, 16 ... Riser, 17 ... Trunk, 18 ... Outer cylinder, 19 ... Annular flow path, 20 ... Discharge port, 21 ... Steam discharge port, 22 ... Steam Discharge pipe, 23 ... Hot water discharge port.

Claims (3)

[Claims] 1. A multistage steam-water separator characterized in that a steam-water separator installed in an upper portion of a shroud head is provided with a plurality of stages in an axial direction in a nuclear reactor. 2. The multi-stage steam separator according to claim 1, wherein the angle of swirl vanes in the steam separator for each stage is changed for each two-phase flow mode in the steam separator. 3. The multi-stage steam separator according to claim 1, wherein the swirl vanes in the steam / water separator have a small angle in the low void fraction region and the swirl vanes have a large angle in the high void fraction region.