JP2013174461A - Pressurized-water reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a flow rate allocation by suppressing a supply reduction in a coolant to a fuel assembly of a peripheral part in the vicinity of a positioning key due to flow going around the positioning key.SOLUTION: In a pressurized-water reactor, a cylindrical porous plate 20 arranged so as to partition a lower plenum 8 and a bottom part of an annular flow channel 6 and having a plurality of inward flow channels for constituting a flow channel to the lower plenum 8 formed is provided in a reactor vessel 3 having a positioning key 12 for mutually positioning a lower core support plate 9 and the reactor vessel 3, and flow resistance of the cylindrical porous plate 20 in this area is reduced in order to suppress a decrease in flow flowing into the lower plenum 8 from a downcomer 6 being an annular flow channel between a reactor core tank 5 and the reactor vessel 3 in a lower portion of the positioning key 12 due to the existence of the positioning key 12.

Description

  Embodiments of the present invention relate to a pressurized water reactor.

  In general, in a pressurized water reactor, the coolant flows into the reactor vessel from the inlet nozzle of the reactor vessel, and is an annular flow path portion configured between the inner surface of the reactor vessel and the outer surface of the reactor core. Lower the downcomer. The coolant that descends the downcomer and reaches the lower end of the downcomer, that is, the lower plenum inlet, turns into an upward flow in the lower plenum, which is an almost hemispherical region, and passes through a number of vertical holes opened in the lower core support plate. And reach the core where the fuel assemblies are installed.

  The flow path from the inlet nozzle to the core is designed so that the factors that cause vortices and flow collisions are eliminated as much as possible, and the flow rate of the coolant entering each fuel assembly is stable and uniform. .

  For example, Patent Document 1 discloses a technique for installing a vortex suppression plate in a lower plenum.

  FIG. 12 is a vertical sectional view showing a flow in the vicinity of the lower plenum in an example of a conventional pressurized water reactor. The flow descending the downcomer 6 passes through the lower plenum inlet 7 and flows into the lower plenum 8. When the flow path of the lower plenum inlet 7 becomes narrower, the flow velocity of the inflow into the lower plenum 8 increases and the inertia increases.

  Due to this inertia, the flow in the lower plenum 8 is a fast flow descending along the inner surface of the bottom of the reactor vessel 3 toward the center of the bottom of the reactor vessel 3, and the flow from the periphery toward the center is the center of the bottom. There is a tendency to change direction and rise. Due to this flow tendency, a distribution in which the coolant flow rate passing through the upward flow holes of the lower core support plate 9 increases at the center of the lower core support plate 9 appears. That is, when the flow path of the lower plenum inlet 7 is narrowed, the tendency of increasing the coolant flow rate supplied to the central fuel assembly tends to appear.

JP 2007-163477 A

  FIG. 13 is an elevational sectional view showing a flow in the vicinity of the lower plenum when a cylindrical perforated plate is provided in an example of a conventional pressurized water reactor. In order to alleviate the non-uniformity of the core flow rate distribution, a cylindrical perforated plate 301 having a large number of radial through holes may be installed at the lower plenum inlet 7 as shown in FIG.

  When this cylindrical perforated plate 301 is used, the downcomer downward flow changes the direction of the flow radially inward at the lower plenum inlet 7, passes through the cylindrical perforated plate 301, and is directed substantially radially inward with respect to the lower plenum 8. Inflow as a flow of. Since the flow diffuses when passing through the cylindrical perforated plate 301, and the flow flows near the lower surface of the lower core support plate 9, it becomes difficult for the flow to converge at the central portion, and the central fuel assembly The aforementioned tendency of increasing the flow rate of flowing coolant is alleviated.

  FIG. 14 is an elevational sectional view of the vicinity of the lower plenum including the positioning key. In the downcomer 6 that is an annular channel, usually, several positioning keys 12 for positioning the lower part of the reactor core 5 and the reactor vessel 3 in the radial direction are installed in the circumferential direction.

  15 is a view taken along the line XV-XV in FIG. 14 showing the flow in the vicinity of the lower plenum in an example of a conventional pressurized water reactor. The broken line in FIG. 15 shows the flow of the coolant. As shown in the drawing, when the downcomer downward flow reaches near the positioning key 12, there is a flow around the positioning key 12. This flowing-around flow has a higher flow velocity than a downcomer descending flow that is substantially uniform in the circumferential direction on the upstream side.

  Further, a region immediately downstream of the positioning key 12 that is an obstacle to the flow, that is, a region immediately below the positioning key is called a wake region, and the pressure is reduced in this region. On the other hand, the pressure rises in the region located under the wraparound flow as compared with the wake region.

  In FIG. 14, the upper outer region of the cylindrical porous plate 301 represented by point A is the wake portion of the positioning key, and the pressure is lower than that of the lower outer region of the cylindrical porous plate 301 represented by B. To do. In such a case, since the differential pressure between A and C is usually smaller than the differential pressure between B and D, the flow rate of the coolant flowing through the upper portion of the cylindrical porous plate 301 and flowing into the lower plenum is Less than the bottom and other areas.

  Thus, in the region immediately below the positioning key, the flow rate of the coolant flowing through the upper part of the cylindrical porous plate 301 and flowing into the lower plenum is reduced, so that it can be easily inferred from the flow shown in FIG. The problem was that the flow rate of the coolant flowing into the peripheral portion of the upward circulation holes of the lower core support plate 9 was reduced.

  Due to such pressure distribution due to the flow around the positioning key 12, there is a problem that the supply of coolant to the peripheral fuel assembly near the positioning key 12 is reduced.

  The present invention has been made to solve the above problems, and is a pressurized water atom capable of improving the flow rate distribution by suppressing the decrease in the supply of coolant to the peripheral fuel assembly adjacent to the positioning key. The purpose is to obtain a furnace.

  In order to achieve the above-described object, an embodiment of a pressurized water reactor according to the present invention includes a cylindrical reactor vessel having a vertical axis as an axis, and a reactor vessel provided in the reactor vessel. A cylindrical core tank that forms an annular flow path portion with the side surface; a core disposed in the core tank; and a lower part of the core that is in contact with the lower part of the core tank and spreads horizontally A lower core support plate provided with a plurality of upward flow passage holes to the core and forming a lower plenum together with the bottom of the reactor vessel; and positioning the lower portion of the core vessel and the reactor vessel relative to each other For positioning, a plurality of coolant inlet nozzles formed horizontally and spaced apart from each other on the side wall of the reactor vessel, and a side by side horizontally spaced from the side wall of the reactor vessel Formed and connected directly to the top of the core. A plurality of coolant outlet nozzles, a lower plenum in contact with the bottom of the reactor vessel, and a bottom of the annular channel, and a channel from the bottom of the annular channel to the lower plenum. A plurality of inward flow path holes are formed, and the flow resistance of the portion belonging to the lower part of the positioning key is reduced in order to suppress a decrease in the flow rate of the coolant flowing into the lower plenum from the lower part of the positioning key. And a cylindrical perforated plate.

  According to the embodiment of the present invention, it is possible to obtain a pressurized water reactor capable of suppressing a decrease in the supply of coolant to the peripheral fuel assembly adjacent to the positioning key and improving the flow distribution.

1 is an elevational sectional view in the vicinity of a lower plenum of a first embodiment of a pressurized water reactor according to the present invention. 1 is an overall vertical sectional view of a first embodiment of a pressurized water reactor according to the present invention. FIG. 3 is a view taken along the line III-III in FIG. 1 in the vicinity of the lower plenum of the first embodiment of the pressurized water reactor according to the present invention. It is an elevational sectional view of the vicinity of the lower plenum of the second embodiment of the pressurized water reactor according to the present invention. FIG. 5 is a view taken along the line VV in FIG. 4 near the lower plenum of the second embodiment of the pressurized water reactor according to the present invention. It is an elevation sectional view near the lower plenum of the third embodiment of the pressurized water reactor according to the present invention. FIG. 7 is a view taken along the line VII-VII in FIG. 6 near the lower plenum of the third embodiment of the pressurized water reactor according to the present invention. It is a bird's-eye view of the cylindrical porous board of 3rd Embodiment of the pressurized water reactor which concerns on this invention. It is an elevational sectional view of the vicinity of the lower plenum of the fourth embodiment of the pressurized water reactor according to the present invention. It is a bird's-eye view of the cylindrical porous board of 4th Embodiment of the pressurized water reactor which concerns on this invention. It is a bird's-eye view of the cylindrical porous board of 5th Embodiment of the pressurized water reactor which concerns on this invention. It is an elevation sectional view showing the flow near the lower plenum in the example of the conventional pressurized water reactor. It is an elevational sectional view showing a flow in the vicinity of the lower plenum when a cylindrical perforated plate is provided in an example of a conventional pressurized water reactor. It is an elevational sectional view near the lower plenum including a positioning key in an example of a conventional pressurized water reactor. It is the XV-XV arrow directional view of FIG. 14 which shows the flow of the lower plenum vicinity in the example of the conventional pressurized water reactor.

  Hereinafter, an embodiment of a pressurized water reactor according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First embodiment]
FIG. 1 is an elevational sectional view of the vicinity of a lower plenum of a first embodiment of a pressurized water reactor according to the present invention. FIG. 2 is an overall vertical sectional view of the present embodiment. 3 is a view taken along the line III-III in FIG. 1 in the vicinity of the lower plenum of the present embodiment.

  The core 1 is surrounded by a core tank 5. A cylindrical nuclear reactor vessel 3 with the vertical direction as an axis encloses a reactor core tank 5, and the side portion of the reactor vessel 3 and the reactor core tank 5 form a downcomer 6 that is an annular flow path.

  A plurality of coolant inlet nozzles 4 are formed on the side wall of the reactor vessel 3 so as to be horizontally aligned with a space between them, and a plurality of coolant outlet nozzles are formed to be horizontally aligned with a space between each other. 11 is provided. The coolant outlet nozzle 11 is directly connected to the upper plenum 10 constituting the upper part of the core.

  A lower core support plate 9 is provided below the core 1 so as to extend in the horizontal direction in contact with the lower portion of the core tank 5. The lower core support plate 9 has a plurality of upward flow passage holes, and the coolant that has passed through each flow passage hole flows into each fuel assembly (not shown) of the core 1.

  The upper part of the reactor vessel 3 is a removable lid, and the lower part is a bottom plate 3a for constituting a sealed state. A lower plenum 8 is configured in a space surrounded by the bottom plate 3 a in the space in the reactor vessel 3.

  The flow path from the coolant inlet nozzle 4 to the core 1 eliminates factors that cause vortices and flow collisions as much as possible, so that the flow rate of the coolant entering each fuel assembly is stable and uniform. Designed to. For this purpose, a vortex suppression plate 13 is provided in the lower plenum 8.

  Further, the lower plenum inlet 7 is provided with a cylindrical perforated plate 20 disposed so as to partition the downcomer 6 that is an annular flow path portion and the lower plenum 8 that is a bottom space in the reactor vessel 3. . A plurality of inward flow path holes 21 are formed in the cylindrical perforated plate 20, and these form a flow path from the bottom of the downcomer 6 to the lower plenum 8.

  When the cylindrical perforated plate 20 is not provided, the coolant flowing into the lower plenum 8 from the downcomer 6 via the lower plenum inlet 7 flows toward the center of the lower plenum 8 as shown in FIG. When 7 is narrow, the coolant flow rate supplied to the peripheral fuel assemblies tends to be lower than the coolant flow rate supplied to the fuel assemblies in the central portion of the core 1. The reason why the cylindrical perforated plate 20 is provided is to alleviate such non-uniformity of the flow distribution in the core 1.

  In addition, a positioning key 12 for positioning the lower core support plate 9 and the reactor vessel 3 between the lower core support plate 9 and the reactor vessel 3 below the reactor core 5 below the downcomer 6. Is provided.

  The lower portion of the cylindrical porous plate 20 is connected to and supported by the reactor vessel 3 by a support member 31. The connection by the support member 31 may be a connection by simple welding.

  A cylindrical porous plate 20 is provided in the lower part of the core tank 5, and there is a gap 32 between the upper end of the cylindrical porous plate 20 and the core tank 5 to form a flow path.

  The broken line in the figure indicates the state of the flow in the vicinity of the positioning key 12 provided at the lower end of the reactor core 5. When the downward flow of the downcomer 6 reaches near the positioning key 12, there is a flow around the positioning key 12. This flowing-around flow has a larger flow velocity than the downcomer downflow that is substantially uniform in the circumferential direction on the upstream side, and the pressure in the region immediately below the positioning key 12 decreases.

  Of the inward flow passage holes 21 provided in the cylindrical perforated plate 20, when an inward flow passage hole 21 similar to other regions is provided in a range corresponding to the region where the pressure decreases, a cylindrical shape in this region is formed. Since the pressure difference inside and outside the porous plate 20 is small, the flow flowing into the lower plenum is lowered.

  In order to avoid this and suppress a decrease in flow rate, a large inward flow passage hole 21a, which is a large-diameter inward flow passage hole with a small flow resistance, is provided in this region.

  In addition, in FIG. 3, although the large inward flow path hole 21a was circular, it is not limited to a circular shape and may have other shapes. In FIG. 3, the large inward flow passage hole 21 a is provided only in a region near the positioning key 12 in the cylindrical porous plate 20, but the cylindrical porous plate 20 is related to the flow around the positioning key 12. It may be provided up to the lower side.

  By providing the large inward flow passage hole 21a having a small flow resistance in this way, the flow from the region immediately below the positioning key 12 in which the pressure difference between the inside and outside of the cylindrical perforated plate 20 becomes small is reduced by the flow resistance. By compensating for the decrease, the inward flow rate equivalent to the area where the positioning key 12 is not provided can be secured. As a result, a local decrease in the circumferential distribution of the flow rate flowing into the lower plenum is suppressed.

  By being configured as described above, it is possible to suppress a decrease in the supply of coolant to the peripheral fuel assembly adjacent to the positioning key and improve the flow distribution.

[Second Embodiment]
FIG. 4 is an elevational sectional view of the vicinity of the lower plenum of the second embodiment of the pressurized water reactor according to the present invention. FIG. 5 is a view taken along the line V-V in FIG. 4 near the lower plenum of the present embodiment.

  In the present embodiment, a notch 22 is provided in a portion of the cylindrical perforated plate 20 facing a region where the pressure immediately below the positioning key 12 decreases. By providing the notch 22, the flow resistance of the flow passing from the outside to the inside of the cylindrical perforated plate 20 is reduced, and the local decrease in the pressure difference inside and outside this region is compensated, and the positioning key 12 is provided. An inward flow rate equivalent to that of the region that is not provided can be ensured.

  By being configured as described above, it is possible to suppress a decrease in the supply of coolant to the peripheral fuel assembly adjacent to the positioning key and improve the flow distribution.

[Third embodiment]
FIG. 6 is an elevational sectional view of the vicinity of the lower plenum of the third embodiment of the pressurized water reactor according to the present invention. FIG. 7 is a view taken along the line VII-VII of FIG. 6 near the lower plenum of the present embodiment. FIG. 8 is a bird's-eye view of the cylindrical porous plate of the present embodiment.

  This embodiment is a modification of the second embodiment, and a lower guide 23 and a side guide 24 are provided on the outlet side of the notch 22. These guides also have a function of compensating for a decrease in strength and rigidity of the cylindrical porous plate 20 due to the presence of the notch 22.

  By providing the lower guide 23 and the side guide 24 in this manner, the flow of the coolant flowing downward through the downcomer 6 passes through the cylindrical perforated plate 20 and flows into the lower plenum 8. The lower guide 23 having a substantially horizontal surface replaces the flow in a substantially horizontal plane directed radially inward. The flow that flows into the lower plenum 8 from the notch 22 is guided in the center direction, and the flow that flows into the lower plenum from the other inward flow passage holes 21 is prevented from being disturbed. It is suppressed.

  By being configured as described above, it is possible to suppress a decrease in the supply of coolant to the peripheral fuel assembly adjacent to the positioning key and improve the flow distribution.

[Fourth Embodiment]
FIG. 9 is an elevational sectional view of the vicinity of the lower plenum of the fourth embodiment of the pressurized water reactor according to the present invention. FIG. 10 is a bird's-eye view of the cylindrical porous plate of the present embodiment.

  In the lower region below the wake region of the positioning key 12, an opening 25 is provided in the lower portion of the cylindrical porous plate 20, and a deflection plate 26 is provided on the outlet side guided by the lower guide 23 and the side guide 24. It has been.

  The area immediately below the positioning key 12 has a low pressure, while the lower area has a high pressure. Therefore, in this region, the pressure difference between the inside and outside of the cylindrical porous plate 20 is large. By providing a flow path with a small flow resistance and a large flow area on the cylindrical porous plate in this region, the flow of the coolant flowing into the lower plenum through this region is positively secured, and the deflection plate 26 By guiding obliquely upward, a decrease in the supply of coolant to the fuel assembly to the peripheral portion is to be prevented.

  In other words, in the present embodiment, the coolant supplied to the fuel assembly disposed on the outer peripheral portion of the flow flowing from the lower plenum inlet 7 to the lower plenum 8 is reduced at the lower portion of the positioning key. It is suppressed by guiding the flow directly from 7 to the outer periphery.

  By being configured as described above, it is possible to suppress a decrease in the supply of coolant to the peripheral fuel assembly adjacent to the positioning key and improve the flow distribution.

[Fifth Embodiment]
FIG. 11 is a bird's-eye view of a cylindrical porous plate of a fifth embodiment of a pressurized water reactor according to the present invention. The present embodiment is a modification of the fourth embodiment. In the fourth embodiment, a rectangular opening is used instead of the rectangular opening in the fourth embodiment.

  In the present embodiment, similarly to the fourth embodiment, it is possible to suppress a decrease in the supply of coolant to the fuel assemblies in the peripheral portion close to the positioning key and improve the flow rate distribution.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, in each embodiment, the case where the cylindrical perforated plate is supported from the reactor vessel at the lower portion thereof is shown. It may be. Moreover, you may combine the characteristic of each embodiment. Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Core 2 ... Fuel assembly 3 ... Reactor vessel 3a ... Bottom plate 4 ... Coolant inlet nozzle 5 ... Core tank 6 ... Downcomer (annular channel part)
7 ... Lower plenum inlet 8 ... Lower plenum 9 ... Lower core support plate 10 ... Upper plenum 11 ... Coolant outlet nozzle 12 ... Positioning key 13 ... Vortex suppression plate 20. ..Cylindrical perforated plate 21 ... inward flow passage hole 21a ... large inward flow passage hole 21b ... circular flow passage hole 22 ... notch 23 ... lower guide 24 ... Side guide 25 ... Opening 26 ... Deflection plate 31 ... Support member 32 ... Gap 301 ... Cylindrical perforated plate

Claims (5)

A cylindrical reactor vessel with the vertical axis as the axis;
A cylindrical reactor core tank that is provided in the reactor vessel and forms an annular channel portion with the inner surface of the reactor vessel;
A core disposed in the core tank;
A lower core support provided below the core and in contact with the lower part of the core tank so as to spread horizontally and having a plurality of upward flow passage holes to the core and forming a lower plenum together with the bottom of the reactor vessel The board,
A positioning key for mutual positioning of the lower part of the reactor core and the reactor vessel;
A plurality of coolant inlet nozzles formed horizontally on the side wall of the reactor vessel at intervals from each other;
A plurality of coolant outlet nozzles that are formed on the sidewalls of the reactor vessel and are arranged horizontally and spaced apart from each other and connected directly to the upper part of the core;
A plurality of inward flow paths that are disposed so as to partition a lower plenum in contact with a bottom of the reactor vessel and a bottom of the annular flow path and constitute a flow path from the bottom of the annular flow path to the lower plenum A cylindrical perforated plate in which a hole is formed and the flow resistance of the part belonging to the lower part of the positioning key is reduced in order to suppress a decrease in the flow rate of the coolant flowing into the lower plenum from the lower part of the positioning key;
A pressurized water reactor characterized by comprising:   The inward flow path hole includes at least one large inward flow path hole and a plurality of small flow path holes having a relatively smaller area than the large inward flow path hole. The pressurized water reactor according to claim 1, wherein the pressurized water reactor is disposed in a portion below the positioning key.   2. The pressurized water reactor according to claim 1, wherein the cylindrical perforated plate has a notch in at least a part of a portion below the positioning key.   The pressurized water reactor according to claim 3, further comprising a guide plate for guiding a coolant at an outlet of the notch.   The cylindrical perforated plate has an opening in at least a part of a lower portion of the positioning key, and has a deflecting plate for guiding a coolant inward and upward at an outlet of the opening. The pressurized water reactor according to any one of claims 1 to 4.

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