JPH0666984A - Annular arrangement type drier - Google Patents

Abstract

PURPOSE:To improve steam/water separation performance, simplify components and make maintenance easy by annularly arranging steam/water separators and steam driers in the upper space of reactor pressure vessel and locating in the center, upper insertion type control rods. CONSTITUTION:A multitude of stand pipes 14 and steam/water separators 11 arranged annularly in upper pressure vessel 1 and also above them, steam driers 12 are annularly arranged. The steam/water two-phase flow B generated by nuclear reaction in fuel rods 8 flows upward in the flow path between the fuel rods 8 in fuel channels, merges once in the space constituting of a core shroud 7 and a shroud head 10 and is separated again in a multitude of pipes 14 and separators 11 into hot water A and steam C. Then, the steam C including mist water droplets passes steam inflow pipes 12b and a few dryer elements placed in the drier 12 where the liquid component carried over is cut off, passes steam outflow pipes 12c and main steam nozzle 13 and flows out to a steam turbine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor internal structure, and more particularly to a steam separation mechanism suitable for improving two-phase flow separation performance and facilitating maintenance.

[0002]

2. Description of the Related Art A conventional reactor pressure vessel is shown in FIG. Compared with FIG. 1, which is an embodiment of the present invention, the steam separator 11
The steam dryer 12 is independently installed in the center of the pressure vessel 1. Originally, the steam separator 11 actively separates the hot water / steam system two-phase flow B generated in the fuel rods 8 on the free liquid surface, and further includes steam contained in the hot water A returning to the downcomer. It is for suppressing carry under. 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.
In the case of a boiling water reactor, the control rod 4 and the control rod drive mechanism 3 are installed below the pressure vessel 1. Therefore, it is a valid concept as an early reactor, and great care has been taken with respect to various types of reliability of this type of actual equipment. There are issues to consider. For example, as a publicly known example, an invention relating to an upper insertion type control rod is disclosed in
-7588, JP-A-59-84192, JP-A-61-230078,
There are JP-A-62-197794 and JP-A-1-113696. All of these are inventions relating to the upper insertion type control rod, but there is no specific structure presented regarding the dryer structure and arrangement necessary for constructing the upper insertion type control rod system.
That is, the conventional steam dryer 12 separates mist droplets due to the difference between the inertial force of the vapor stream and the gravity of the mist liquid mass or droplets contained in the vapor. Therefore, the steam dryer 12 having a thin corrugated plate structure has a large pressure loss of the two-phase flow, and it is also necessary to study vibration due to fluid force based on the differential pressure.

Therefore, it is necessary to solve the technical problems relating to the improvement of the separation performance of the steam dryer and the reduction of the pressure loss, and at the same time, it is necessary to have a relatively simple structure for facilitating the maintenance of the equipment during the regular inspection of the reactor. .

[0004]

SUMMARY OF THE INVENTION The above-mentioned prior art is a steam-water separator for phase-separating a gas-liquid two-phase flow generated by a fuel rod on a free liquid surface, and moist water contained in a steam flow in the upper part of the device. And a steam dryer for removing the gas are installed as separate elements in the upper space of the reactor pressure vessel. The internal structure of the nuclear reactor is complicated by the structure of the support part to ensure the reliability of the device structure because each device receives the hydrodynamic force of the hot water flow or steam flow, and the maintenance at the time of regular inspection is also complicated. It is possible that Further, in the case of the conventional boiling water reactor, the control rod is inserted from the lower part, so that the structure of the lower part of the pressure vessel becomes complicated, resulting in complicated maintenance and various problems from the viewpoint of safety. An object of the present invention is to arrange a steam separator and a steam dryer annularly in the upper space of the furnace so that the control rod is inserted from the upper part to the central part of the furnace to improve the steam separation performance. The purpose is to facilitate maintenance by simplifying the equipment as a furnace internal structure.

[0005]

In order to achieve the above object, the present invention arranges a conventional steam separator and a steam dryer in an annular shape in the upper space of a reactor pressure vessel, and inserts the upper part in the central portion. By installing the type control rod, the liquid components in the hot water / steam system two-phase flow generated in the fuel rod can be removed efficiently, and the steam-water separation performance is improved and maintenance is facilitated.

[0006]

[Operation] When the steam separator and the steam dryer are annularly arranged in the upper space of the furnace, and the upper insertion type control rod is installed in the center, the structure of the conventional steam separator and steam dryer Compared with the arrangement, in the case of the steam dryer, since the steam flow path flows in the dryer element arranged annularly in the circumferential direction,
Centrifugal force acts on the vapor flow to cause centrifugal separation of mist droplets in the vapor, which can reduce the number of conventional dryer corrugated plate elements, which reduces pressure loss on the vapor side and gas-liquid separation efficiency. Is improved. Further, by arranging the dryer in an annular shape, fluctuations in the differential pressure of the flow do not occur in the dryer channel or the like, so that the dryer structure is less susceptible to flow vibration and the reliability is improved. Further, carry under of steam contained in the hot water descending in the downcomer flowing into the internal pump is also suppressed.
Further, by arranging the steam separator and the steam dryer annularly in the furnace, a space in the central space of the pressure vessel is secured. Therefore, it becomes possible to insert the control rod into the central space from above. As a result, compared with the conventional lower insertion type control rod system, the lower structure of the pressure vessel is simplified and the maintenance becomes very easy.

By the above three mechanisms of the annularly arranged steam / water separator, the steam dryer and the upper insertion type control rod system, the separation efficiency of the steam / water separator and the steam dryer, which is the reactor internal structure, is improved. The structure has advantages such as improvement, reduction of pressure loss, suppression of fluid vibration, and easy maintenance. By these actions, the internal structure of the reactor, especially the dryer, is made compact, and the safety and reliability of the reactor pressure vessel are secured.

[0008]

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 above the fuel rod 8. A tube drive mechanism 3 is installed. These devices are fixed by a core support plate, a fuel support fitting, and the like. Further, the uppermost portion of the fuel rod 8 is fixed by the upper support plate. 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, there is a shroud head 10 at the upper part of the core shroud 7, which is annularly arranged in the upper pressure vessel 1. Also, a large number of stand pipes 14 and steam separator 11 are installed. Further, a steam dryer 12 which is also annularly installed is installed above the steam separator 11 via a header or the like. 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 are again separated into hot water liquid A and steam C in the many stand pipes 14 and steam water separators 11. It Then, the steam flow C containing the mist droplets passes through the steam inflow pipe 12b, and the steam dryer 12
Liquid components that have passed through several dryer elements 12a installed therein and are carried over are cut, and flow out from the steam outflow pipe 12c through the main steam nozzle 13 to the steam turbine. In the case of a dryer that utilizes centrifugal separation as in the present invention, the number of corrugated plate structures that constitute the dryer element 12a can be reduced and sufficient separation performance can be obtained. Moreover, there is an advantage that the pressure loss in the dryer channel is also reduced. Further, even if the distance between the corrugated plate structures 12d constituting the dryer element 12a is widened, sufficient air-water separation performance can be ensured, so that the pressure loss can be further reduced. 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. And
The hot water discharged from the internal pump 2 flows into the reactor from the leg portion opened at the bottom of the core shroud 7 and returns to the fuel rods 8 again. Here, the features of the present invention will be described with reference to FIG. First, consider a state in the vicinity of the dryer element 12a portion of the dryer 12 arranged in an annular shape. A large number of corrugated plate structures 12d are installed in the dryer element 12a in the vapor flow C direction, and the mist droplets 15 in the vapor flow C pass through the corrugated plate flow passages. At this time, the inertial force of the mist droplet 15 acts on the mist droplet 15 in the flow direction, and the gravity of the mist droplet 15 acts on the downward direction. Further, centrifugal force acts in the radial direction. As described above, three fluid forces largely act on the mist droplets 15, and when the flow velocity of the vapor flow C is slow, gravity acts on the inertial force, so that the mist droplets 15 are generated in the dryer 12. To cut. On the other hand, when the flow velocity of the steam flow C is high, the action of the centrifugal force is large against the inertial force, so that the large mist droplets 15 are pressed against the outer peripheral portion of the dryer by the centrifugal separation and cut.

In this way, the steam C having a low mist moisture content passes through the steam dryer 12 to form steam having the originally required wetness and flow out from the reactor body through the main steam nozzle 13. To do. Therefore, the steam-water separator 11 and the steam dryer 12 are arranged in an annular shape, and the centrifugal separation of mist droplets by the swirling flow of steam is used in addition to the conventional gravity separation to improve the gas-liquid separation efficiency. Maintenance at the time of regular inspection can be facilitated.

Another embodiment of the present invention will be described with reference to FIG. The present invention differs from the invention of FIG. 2 in that the corrugated plate structure 12d is installed along the steam flow direction of the annularly arranged dryer 12, that is, along the circumferential direction of rotation. This allows
Each vapor channel is narrowed, and by distributing the vapor channels in the radial direction, the centrifugal separation action of the mist droplets 15 is enhanced. As a result, a centrifugal dryer is constructed,
The gas-liquid separation efficiency can be further improved.

Therefore, if this structure is installed, the steam separator 11 and the steam dryer 12 are annularly arranged in the upper space of the pressure vessel to sufficiently remove the hot water mist component contained on the steam side. Therefore, the gas-liquid separation efficiency is improved, and a separation mechanism that reduces pressure loss can be provided. On top of that, maintenance at the time of regular inspection becomes easy,
It becomes a highly safe internal structure.

[0014]

According to the present invention, by arranging the steam-water separator and the steam dryer annularly in the upper space of the reactor pressure vessel, an upper insertion type control rod is also possible and the steam-water separation performance is improved. It is possible to provide a reactor internal structure having improved performance, reduced pressure loss, simplified structure in terms of ease of maintenance during regular inspection, and high performance and safety.

[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 perspective view of the annular placement type dryer of FIG.

FIG. 3 is an explanatory view of the principle of FIG.

FIG. 4 is a cross-sectional view of an annular arrangement type dryer according to another embodiment of the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Internal pump, 3 ... Control rod guide tube drive mechanism, 4 ... Control rod guide tube, 7 ... Core shroud, 8 ... Fuel rod, 10 ... Shroud head, 11 ...
Steam separator, 12 ... Steam dryer, 12b ... Steam inlet pipe,
13 ... Main steam nozzle, 14 ... Stand pipe.

Claims (4)

[Claims] 1. A mist liquid in a steam flow, wherein a steam separator and a steam dryer separately installed above the steam separator are annularly arranged in an upper space of a pressure vessel in a nuclear reactor. An annular dryer that is characterized by improving the separation performance by centrifuging drops. 2. The dryer according to claim 1, wherein at least one dryer element having a corrugated plate structure is arranged perpendicularly to the steam flow in the dryer annularly arranged at arbitrary intervals along the steam flow circumferential direction flow. Circular arrangement type dryer. 3. The corrugated plate structure according to claim 1, wherein a plurality of corrugated plate structures are circumferentially arranged along the steam flow in the annularly arranged dryer so that steam flows between the corrugated plate passages. Annular type dryer. 4. The pressure vessel according to claim 1, wherein the steam separator and the steam dryer are annularly arranged, and a control rod which is inserted from above into a central space of the pressure vessel is installed. Annular type dryer with simplified structure.