JPH09197087A - Pressurized water nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressurized water reactor provided with control rod cluster guide tubes of which control rods contained are never vibrated by the separated flow of coolant. SOLUTION: In a continuous part of control rod cluster guide tube 30, a plurality of coolant discharge windows 40a, 40b, 40c aligned in straight line are provided, which are arranged dispersively as much as possible in the region between the lower end 9a elevation of an outlet nozzle 9 and the lower end elevation 6a' of upper core support columns 6a. Coolant passes through the first and second path holes 11b and 11a punched in the upper core plate 11, flows into the upper plenum 2 and the control rod cluster guide tube 30, and eventually flows out of the outlet nozzle 9. As the discharge windows are arranged dispersively as mentioned above, the coolant, without flowing back in the discharge window, is discharged directly and immediately to the outside as separated flow through each discharge window. The continuous part has a dispersion promotor plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized water reactor having a control rod cluster guide tube provided in a reactor internal structure in a reactor vessel.

[0002]

2. Description of the Related Art FIG. 4 shows a reactor internal structure in a general pressurized water nuclear power plant and a flow of a primary coolant in the reactor container. A control rod cluster 5 held by a drive shaft 4 of a control rod driving device (not shown) at the top of the reactor vessel 1 is guided above the nuclear fuel assembly 2 loaded in the reactor vessel 1. To support, a plurality of control rod cluster guide tubes 6 forming the upper internals are provided. Details of the upper core internal structure composed of these control rod cluster guide tubes 6, upper core support columns 6a, etc. are shown in FIG. 5 (a), and one of the control rod cluster guide tubes is shown in FIG. 6 has been removed and is shown enlarged in FIG.

The control rod cluster 5 shown in FIG. 4 because it is well known is a cluster of control rods in which neutron absorbers are coated with stainless steel pipes and the upper ends of the control rods are clustered by joints called spiders. The control rod is inserted into the control rod guide tube (not shown) in the fuel assembly 2 from above the corresponding fuel assembly 2, and the control rod is pulled out from the control rod guide tube. In the normal operation of the nuclear reactor, the control rod cluster 5 is held above the fuel assembly 2 at the extraction position. Since the main flow 7 of the primary coolant flows at a high speed near the drawing position, the control rod is exposed to this flow. The control rod cluster guide tube 6 plays a role of protecting the control rod from the high-speed mainstream 7 so that the control rod can be accurately positioned and inserted into and pulled out from the fuel assembly 2.

As can be understood from FIGS. 5 and 6, the control rod cluster guide pipe 6 erected on the upper core plate 11 having the flow passage holes 11a has a substantially cylindrical upper portion and a substantially square lower portion. It consists of side parts. The lower part is a tubular member having a substantially quadrangular horizontal section for enclosing the control rod cluster, strictly speaking, an octagonal tubular member, and is reinforced by a multi-stage guide plate 8 which is axially separated and is attached in the transverse direction. There is. The upper part is also reinforced by the same guide plate 8. Each guide plate 8
As shown in FIG. 6 (a), a plurality of holes 10a and slits 10b are provided in order to enable the insertion and withdrawal of control rods, and the number and arrangement of a plurality of control rods and spiders (not shown). It is drilled according to the pattern. These holes 10a and slits 10b serve as guides for positioning the control rod.

Referring again to FIGS. 4 and 5, the inlet nozzle 3
The primary coolant flowing from the reactor vessel 1 into the reactor vessel 1 is reversed in the lower plenum of the reactor vessel 1 and then passes through the fuel assembly 2,
The high-speed mainstream 7 passes through the upper core plate 11 and finally leaves the reactor vessel 1 through the outlet nozzle 9. Upper core plate 11
At the time of passing, the main flow 7 becomes a branch flow 13 and is provided at the lower end of the control rod cluster guide pipe 6 for screwing the control rod cluster guide pipe 6 to the upper core plate 11 at a high speed. The control rod cluster guide pipe 6 flows in through the passage hole for the primary coolant, which is formed in the lower flange 12 with the screw hole. In order to allow the branched flow 13 to escape to the outside of the control rod cluster guide pipe 5, as shown best in FIG. 6B, a fluid discharge window is formed on the side wall of the continuous portion 14 of the control rod cluster guide pipe. 15 is provided, but some of the branch flows 13 pass through the fluid discharge window 15 according to its inertia, are inverted by the lowermost guide plate 8 of the control rod cluster guide tube 6, and then are arranged close to each other. It will flow out through the fluid discharge window 15 provided.

Further, in order to protect each control rod from the branch flow 13 in the area usually called the continuous portion 14 from the upper surface of the lower flange 12 to the vicinity of the lowermost guide plate 8, In order to continuously guide the control rod, a sheath plate 16 usually called a sheath and a lower guide cylinder 17 called a C tube are provided in the continuous portion 14.
Are provided.

[0007]

The branched flow 13 reversed by the lowermost guide plate 8 flows out from the fluid discharge windows 15 arranged close to each other as described above, but When the guide plate 8 is reversed, a large turbulent flow or vortex flow is generated. The positioning function of each control rod is satisfied by the guide plate 8. However, due to the influence of this turbulent flow, the control rod passing through the hole of the guide plate 8 is vibrated and repeatedly contacted with the guide plate 8.
For this reason, the cladding of the control rod may be worn due to long-term operation. As a result, there is a concern that the usage time of the control rod is limited.

Therefore, the main object of the present invention is to provide a pressurized water reactor equipped with a control rod cluster guide tube in which the contained control rods are not excited by the branched flow of the coolant. is there. Another object of the present invention is to provide a pressurized water reactor capable of promoting re-branching of the coolant branch flow in the control rod cluster guide pipe.

[0009]

In order to achieve the above-mentioned object, the present invention provides a reactor vessel having a coolant outlet nozzle, which is suspended in the reactor vessel and through which the coolant outlet nozzle is inserted. A core basin, an upper core support plate disposed above the coolant outlet nozzle in the core basin, disposed below the coolant outlet nozzle in the core basin, and having a first flow An upper core plate having a passage hole and a second passage hole, and a plurality of upper core supports extending between the upper core support plate and the upper core plate with a lower end nozzle facing the first passage hole. A control rod cluster guide tube, comprising: a column; and a plurality of control rod cluster guide tubes that extend through the upper core support plate and extend upward with the lower end opening facing the second flow path hole. A continuous portion having the lower end opening of Is provided with a plurality of coolant discharge windows aligned in a straight line, the plurality of coolant discharge windows being the height of the lower end of the coolant outlet nozzle and the height of the lower end nozzle of the upper core support column. It is characterized in that it is arranged as dispersed as possible in the region between.

The coolant is the first and the first holes formed in the upper core plate.
It flows into the upper plenum between the upper core plate and the upper core support plate and the control rod cluster guide pipe through the second flow path hole, and finally becomes a lateral flow and flows out from the coolant outlet nozzle. . The plurality of coolant discharge windows provided in the control rod cluster guide tube are distributed as much as possible in the region between the height of the lower end of the coolant outlet nozzle and the height of the lower end nozzle of the upper core support column. Since the coolant flows in the lateral direction toward the outlet nozzle of the coolant, it flows backward from the coolant discharge window into the control rod cluster guide tube, and the lateral flow generated in the lower nozzle of the upper core support column is generated. The flow of the coolant in the control rod cluster guide pipes is re-diverged from each coolant discharge window to the outside directly and early without the flow from the coolant discharge window back to the inside. It as a result,
The flow rate of the coolant passing through the continuous portion is greatly reduced, and the flow velocity of the coolant in the direction traversing the control rod is also significantly reduced.

In the continuous portion of the control rod cluster guide tube, a dispersion promoting plate that defines the upper edge of each of the coolant discharge windows is disposed so as to cross the lower end portion. Is preferred. In this case, since the dispersion promoting plate exists on the upper edge of the coolant discharge window, the coolant flow rising in the continuous portion collides with these dispersion promoting plates and a part of them is forcibly stopped. The coolant is sequentially discharged from the coolant discharge windows along the lower surface of the dispersion promoting plate to promote the dispersion of the flow. With such dispersion of the outflow rate, the flow velocity of the coolant across each control rod is further reduced, the fluid force on each control rod is weakened, and the exciting force is further reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments of the present invention, that is, embodiments will be described in detail with reference to FIG. 1 to FIG. Indicate the same or corresponding portions.

FIG. 1 shows a part of an upper internal structure of a pressurized water reactor in which an embodiment of the present invention is embodied, and FIG.
1 is an enlarged perspective view of one of the control rod cluster guide tubes constituting the upper furnace internal structure of FIG. 1, and FIG.
The area indicated by is enlarged. In the upper reactor internal structure shown in FIG. 1, reference numeral 1 represents a reactor vessel in which a coolant outlet nozzle 9 is integrally formed,
On the flange portion 1a, a core tank 20 surrounding a core composed of a fuel assembly (not shown) and an upper core support located above an upper core plate 11 with which an upper end of the fuel assembly is engaged. The board 21 is hung.

Further, in FIG. 1, between the upper core plate 11 and the upper core support plate 21, as described with reference to FIG. 4, a plurality of upper core support columns 6a are arranged in appropriate places in a scattered manner. The lower end of the coolant passage hole (second passage hole) 11a.
The control rod cluster guide tube 30 supported by the upper core plate 11 as desired, extends upward through the upper core support plate 21. The inner end of the outlet nozzle 9 described above extends inward in the radial direction and penetrates the side wall of the core tub 20, and is defined between the upper core plate 11 and the upper core support plate 21.
It opens at almost the center of the vertical direction. Since this is a well-known structure, only a brief description will be given, but the lower end nozzles 6a ′ of each upper core support column 6a have a coolant passage hole (first flow path hole) 11b formed in the upper core plate 11. Located at the top, the lower end nozzle 6a 'is composed of a plate member 6a "having an obliquely inclined edge as shown.

Referring now to FIG. 2, one of the control rod cluster guide tubes 30 shown in FIG. 1 is shown enlarged in perspective view. 2 and FIG. 3 showing an enlarged view of a portion A of the control rod cluster guide tube 30, the control rod cluster guide tube 30 includes a guide plate 32 located at the uppermost position of the continuous portion 31, and the guide plate 32. Plate 32 and lower flange 33
Between the two dispersion promoting plates 34, 34, and the sheath plate 3 extending between the guide plate 32 and the lower flange 33.
5 and a lower guide tube 36, which are surrounded by a substantially quadrangular, strictly octagonal enclosing plate 37 having a cross-sectional shape substantially comparable to the outer shapes of the guide plate 32 and the dispersion promoting plate 34. There is. The sheath plate 35 is a plate body having a horizontal U-shaped cross section, and a guide plate 32 and a dispersion promotion plate 3 are provided on the back surface of the plate body in order from the top along the axial direction thereof.
4, 34 and the lower flange 33 are provided with notches or recesses (not shown) for fitting, and at an appropriate side surface position in the axial direction, an appropriate number, an appropriate size, an appropriate shape (implementation). It has an opening 38 that is oval in shape. Further, the sheath plate 35 is formed with two recesses 35e having a substantially circular cross section for accommodating the control rod. On the other hand, in the substantially cylindrical lower guide tube 36, in addition to the opening 36a, a slit 36b extending from one end to the other is formed.

A plurality of (three in the present embodiment) coolant discharge windows 40a, 40b, 40c are provided on the long side of the side wall of the enclosing plate 37 in the portion forming the continuous portion 31. As can be understood from FIG. 3, each coolant discharge window is formed in a rectangular shape having an upper edge, a lower edge and two side edges, and the upper edge of the uppermost discharge window 40 a has a shroud 37.
Is defined by a guide plate 32 that extends outwardly through the plate, and the upper edges of the other two emission windows 40b and 40c similarly extend outwardly through the shroud 37 and the dispersion promoting plates 34 and 34.
Is defined by

Furthermore, the emission windows 40a, 40b, 40 described above are used.
c are linearly aligned in the axial direction of the control rod cluster guide tube 30 and are arranged as dispersed as possible. That is, FIG.
In, these emission windows are
It is distributed and arranged in the area sandwiched between 1 and 42. As can be seen from FIG. 1, the chain line 41 corresponds to the height of the lower end portion 9a of the coolant outlet nozzle 9, and the chain line 42 constitutes the lower end nozzle 6a ′ of the upper core support column 6a. Is a line extending in the horizontal direction from the upper end of the member 6a ″ having the above-described diagonal line.

As shown in FIG. 3, during the operation of the reactor, the branch flow 13 of the coolant rises and flows into the inside from the control rod cluster guide pipe 30 and flows at a high speed. Since the coolant discharge windows 40a, 40b, 40c are dispersedly arranged as described above, the branch flow 13 is directly discharged from the discharge windows 40a, 40b, 40c into the branch flows 13c, 13b, 13a. . As a result, the flow rate of the coolant passing through the continuous portion 31 is significantly reduced, and the flow velocity of the coolant in the direction traversing the control rod (not shown) is also significantly reduced. Otherwise, for example, the dashed line 41 (Fig. 1)
In the upper plenum 22 there is a lateral flow of the coolant towards the outlet nozzle 9 when the discharge window is above, so that this flow is from the discharge window into the control rod cluster guide tube. When the backflow occurs and the discharge window exists below the chain line 42, the lateral flow generated in the lower end nozzle 6a ′ of the upper core support column 6a also similarly flows back inside from the discharge window.

Further, when each of the branched flows 13c, 13b, 13a flows out from the discharge windows 40a, 40b, 40c, the guide plate 32 and the dispersion promoting plates 34, 34 are present at the upper edge of the discharge windows. The coolant flow rising in the nuisance portion 31 collides with the guide plates 32 and the dispersion promoting plates 34, 34, and a part of the coolant flow is forcibly stopped, and the coolant flows from the discharge windows along the lower surface of the plate. It flows out sequentially, and the dispersion of the flow is promoted.

The invention and its various advantages will be understood from the above description. Moreover, it is obvious that the form, structure and sequence can be modified without departing from the spirit and scope of the present invention or sacrificing the important effects of the present invention, and disclosed in this specification. The form is merely a preferred or exemplary embodiment of the present invention.

[0021]

As described above, according to the present invention as set forth in claim 1, the plurality of coolant discharge windows provided in the control rod cluster guide pipe have the height of the lower end of the coolant outlet nozzle, The lateral distribution of the coolant toward the outlet nozzles from the coolant discharge window through the control rod clusters is arranged as distributed as possible in the region between the upper core support column and the height of the lower end nozzles. The coolant flow in the control rod cluster guide pipe does not flow back into the guide pipe or the lateral flow generated at the lower end nozzle of the upper core support column does not flow backward from the coolant discharge window as well. Is re-branched from each coolant discharge window and discharged directly and early to the outside. As a result, the flow rate of the coolant passing through the continuous part is significantly reduced, and the flow velocity of the coolant in the direction traversing the control rods is also significantly reduced, so that the fluid vibration of the entire control rod cluster is reduced. It is possible to greatly reduce the wear and thickness reduction due to the vibration contact of the control rod with the guide plate of the control rod cluster guide tube.

According to the present invention described in claim 2,
In the continuous portion of the control rod cluster guide tube, the dispersion promoting plate that defines the upper edge of each of the coolant discharge windows is arranged so as to traverse the lower end portion. The coolant flow that rises up collides with these dispersion promoting plates, a part of which is forcibly dammed, and sequentially flows out from the respective coolant discharge windows along the lower surface of the dispersion promoting plate to disperse the flow. Therefore, with such dispersion of the outflow rate, the flow velocity of the coolant across each control rod is further reduced, the fluid force to each control rod is weakened, and the excitation force is further reduced. Therefore, it is possible to further contribute to the drastic reduction of the wear and thickness reduction due to the above-described vibrational contact.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a pressurized water reactor according to the present invention.

2 is a partially cutaway perspective view of a control rod cluster guide tube of the present invention used in the pressurized water nuclear reactor of FIG. 1. FIG.

FIG. 3 is an enlarged perspective view of a portion A in FIG.

FIG. 4 is a sectional view showing the structure of a general pressurized water reactor.

5 (a) is an enlarged cross-sectional view showing an upper internal structure of the pressurized water reactor of FIG. 4, and FIG. 5 (b) is an enlarged view showing a control rod cluster guide tube constituting the upper internal structure. It is a perspective view.

6 (a) is an enlarged sectional view showing a continuous part of the conventional control rod cluster guide pipe shown in FIG. 5 (b) by partially breaking it, and FIG. 6 (b) is the same continuum. It is an elevation view which shows a nuisance part by a partial cross section.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor vessel, 6a ... Upper core support pillar, 6a '... Lower end nozzle, 9 ... Coolant outlet nozzle, 9a ... Lower end of outlet nozzle, 11 ... Upper core plate, 11a ... Second flow passage hole, 11b
... 1st flow path hole, 13 ... Branch flow, 13a, 13b, 13c
... Re-branching flow, 20 ... Core tank, 21 ... Upper core support plate, 2
2 ... Upper plenum, 30 ... Control rod cluster guide tube, 31
... Continuous part, 32 ... Guide plate, 34 ... Dispersion promoting plate, 37 ... Enclosure plate for control rod cluster guide tube, 40a, 4
0b, 40c ... Coolant discharge window.

Claims (2)

[Claims] 1. A reactor vessel having a coolant outlet nozzle, a reactor core suspended from the reactor vessel, through which the coolant outlet nozzle is inserted, and a reactor core above the coolant outlet nozzle. An upper core support plate disposed in the core core, an upper core plate disposed below the coolant outlet nozzle in the core tank, and having a first flow path hole and a second flow path hole, A plurality of upper core support columns extending between the upper core support plate and the upper core support plate with a lower end nozzle facing the first flow path hole, and a lower end opening facing the second flow path hole. In a pressurized water reactor equipped with a plurality of control rod cluster guide tubes that extend upward through the upper core support plate, the control rod cluster guide tubes are linearly aligned in the continuous portion having the lower end opening. A plurality of coolant discharge windows are provided, The plurality of coolant discharge windows are arranged in a region between the height of the lower end of the coolant outlet nozzle and the height of the lower end nozzle of the upper core support column as dispersed as possible. A pressurized water reactor characterized by the above. 2. A dispersion promoting plate defining an upper edge of each of the coolant discharge windows is disposed in the continuous portion of the control rod cluster guide tube so as to traverse the lower end portion. The pressurized water nuclear reactor according to claim 1, wherein