JP3605247B2 - Method of changing coolant flow path in pressurized water reactor and upper core structure in pressurized water reactor vessel - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internal structure of a nuclear reactor, and more particularly to an upper core structure of a pressurized water reactor.
[0002]
[Prior art]
An example of a typical internal structure of a conventional pressurized water reactor is shown in FIG. In general, the structure and its function are as follows. A coolant 5 flows into the reactor vessel 1 from an inlet nozzle 3 formed integrally with the reactor vessel 1, flows down the downcomer 7, and reaches the bottom plenum 9. The coolant 5 inverted in the bottom plenum 9 flows upward through the core 11 composed of a large number of fuel assemblies, and is heated to a high temperature, passes through the upper core plate 15 of the upper core structure 13 and passes through the upper plenum 17. Leads to. The upper plenum 17 is defined by an upper core plate 15 and an upper core support plate 21 for suspending and supporting the upper core plate 15 via an upper core support column 19, and an outlet nozzle formed integrally with the reactor vessel 1. The coolant 5 flows out through 23. The upper opening of the reactor vessel 1 is closed by a detachable upper lid 25, and the control rod cluster guide tube 29 corresponds to the control rod driving device 27 provided above the upper lid 25. Is provided so as to pass through.
The plurality of control rods inserted one by one into the hollow guide tube of the fuel assembly are assembled in a cluster by a spider member, and are called a control rod assembly or a control rod cluster. When driven in the vertical direction by 27, it is guided by the control rod cluster guide tube 29. The structure of the control rod cluster guide tube 29 is shown in FIGS.
[0003]
As shown in FIGS. 8 and 9, the control rod cluster guide tube 29 includes an upper tube 29a and a lower tube 29b having a substantially rectangular cross section, and is fixed to the upper core support plate 21 by a middle flange 29c. A lower flange 29d of the lower cylinder 29b forms a narrow gap 31 adjacent to the upper core plate 15, and a flow window 29e is formed in the lower side of the lower cylinder 29b. Therefore, the coolant 5 flows as indicated by the arrow, and flows out into the upper plenum 17 through the gap 31 and the flow window 29e.
[0004]
[Problems to be solved by the invention]
In the above-described upper core structure, the gap 31 is relatively small as compared with the flow window 29e. Therefore, a considerable part of the coolant flows through the flow window 29e as the main flow. Since this main flow changes its flow direction in the lower cylinder 29b, it flows across the narrow control rods of the control rod cluster, thereby giving fluid-excited vibration to this. For this reason, there has been a problem that the control rod comes into contact with the horizontal guide support plate of the control rod cluster guide tube to increase wear.
Therefore, an object of the present invention is to provide an upper core structure of a pressurized water reactor that can suppress fluid-induced vibration of a control rod, or to provide an upper core structure of an already installed pressurized water reactor. An object of the present invention is to provide a remodeling method for changing a flow path of a reactor coolant so as to suppress fluid-induced vibration of a control rod.
[0005]
[Means for Solving the Problems]
To solve the problems According to the process 30, according to the present invention, the upper core plate to press the fuel assembly group constituting the core, a control rod cluster guide tubes for guiding the control rod clusters are inserted into and removed from the reactor core, the An upper core support plate supporting the control rod cluster guide tube above the upper core plate, and, in a pressurized water reactor having an upper part in a reactor vessel, a remodeling method for changing a flow path of a coolant includes: Before remodeling between the lower end of the control rod cluster guide tube and the upper core plate upper surface by additionally interposing a shim plate structure between the middle flange of the control rod cluster guide tube and the upper surface of the upper core support plate Is formed by adding a gap relatively larger than the gap.
Further, according to the present invention, an upper core plate for holding a fuel assembly group constituting a core, a control rod cluster guide tube for guiding a control rod cluster to be inserted into and removed from the core, and the control unit above the upper core plate. An upper core structure in a pressurized water reactor vessel having an upper core support plate supported through a rod cluster guide tube comprises a shim plate structure between a middle flange of the control rod cluster guide tube and an upper surface of the upper core support plate. A gap corresponding to the thickness of the shim plate structure is formed between the lower end of the control rod cluster guide tube and the upper surface of the upper core plate so that a considerable portion of the reactor coolant flows through the gap. It is characterized by becoming.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals throughout the drawings including the above-described drawings.
In FIG. 1, a shim plate 33 is sandwiched between a middle flange 29 c of the control rod cluster guide tube 29 and the upper core support plate 21. The attached state of the shim plate 33 is shown in an enlarged manner in FIG. The details of the shim plate 33 are shown in FIGS. 3 (a) and 3 (b), but the mounting thickness is T, and the control rod has a thickness T as compared with the conventional state (a) without the shim plate 33. The height of the cluster guide tube 29 is raised. Since the control rod cluster guide tube 29 is mainly supported by the upper core support plate 21, a lower flange 29d of the control rod cluster guide tube 29 positioned by a support pin or the like of the upper core plate 15 is shown in FIG. As a result, the upper core plate 15 is separated from the upper core plate 15 by a corresponding amount, and the shape is raised. FIG. 4A shows the relationship between the lower flange 29d and the upper core plate 15 when the shim plate 33 is not attached. The gap 31 in FIG. 4A is clearly smaller by the thickness T than the gap 35 in FIG.
Further, as shown in FIG. 5 which is an enlarged view of a part of FIG. 2 (b), the middle flange 29c has an annular projection 29f forming an in-row type fitting structure. The plate 21 has an annular recess 21a. Furthermore, the shim plate 33 has an inner peripheral end 33a that receives the annular projection 29f and enters the annular recess 21a, and as shown, is combined with each other to obtain a predetermined positioning accuracy. Then, as shown in FIG. 2, the middle flange 29 c of the control rod cluster guide tube 29 is securely fixed to the upper core support plate 21 by the fixing bolt 37.
[0007]
The control rod cluster guide tubes 29 fixed to the upper core support plate 21 via the shim plates 33 as described above are arranged side by side as shown in FIG. 6, and the upper core support columns 19 arranged at appropriate positions. Thereby, the upper core support plate 21 and the upper core plate 15 are connected to each other to form the upper core structure 113. In order to convert the already installed upper core structure 13 of the reactor into the above-described upper core structure 113, the fixing bolt 37 is loosened and removed from each control rod cluster guide tube 29, and each control rod cluster guide tube is removed. 29, the shim plate 33 is fitted therein, the control rod cluster guide tubes 29 are inserted again into the upper core support plate 21 as shown in FIG. 1, and the fixing bolts 37 as shown in FIG. Tighten and fix with. When a large gap 35 is formed between the lower flange 29d and the upper core plate 15 in this manner, a large amount of coolant flows therethrough in relation to fluid resistance. That is, the flow path of the coolant is changed, the amount of the coolant passing through the flow window 29e is reduced, and the fluid oscillating force of the control rod is reduced, so that the fluid-induced vibration of the control rod and the wear due to the vibration are reduced.
[0008]
【The invention's effect】
As described above, according to the present invention, the control rod cluster guide tube included in the upper core structure of the existing pressurized water reactor is simply provided with the shim plate structure, and the control rod cluster guide tube and the upper The gap between the core plate and the core plate is enlarged to change the coolant flow path, so that the fluid-induced vibration of the control rod and the wear caused by the vibration can be reduced.
[Brief description of the drawings]
FIG. 1 is a partial side view showing a main part of an embodiment according to the present invention.
FIG. 2 is an explanatory diagram showing an enlarged main part of FIG. 1;
FIG. 3 is an explanatory diagram showing a main part of FIG. 1 in an enlarged manner.
FIG. 4 is an explanatory diagram showing an enlarged main part of FIG. 1;
FIG. 5 is a partial cross-sectional view showing a part of FIG. 2B in an enlarged manner.
FIG. 6 is an elevational sectional view showing the upper core structure after the modification according to the embodiment.
FIG. 7 is a conceptual vertical sectional view showing an example of the internal structure of a conventional pressurized water reactor.
FIG. 8 is an enlarged partial elevation view showing a portion VIII of FIG. 7;
FIG. 9 is an enlarged partial elevation view showing a part of FIG. 8;
[Explanation of symbols]
Reference Signs List 1 reactor vessel 5 coolant 11 core 15 upper core plate 19 upper core support column 21 upper core support plate 29 control rod cluster guide tube 29a upper cylinder 29b lower cylinder 29c middle flange 29d lower flange 29e flow window 31 gap 33 shim plate 35 Gap 37 Fixing bolt

Claims (3)

An upper core plate for holding the fuel assemblies constituting the core,
A control rod cluster guide tube for guiding a control rod cluster inserted into and removed from the core ,
An upper core support plate supporting the control rod cluster guide tube above the upper core plate, and a pressurized water reactor having an upper part in a reactor vessel,
A shim plate structure is additionally interposed between the middle flange of the control rod cluster guide tube and the upper surface of the upper core support plate to provide a shim plate structure between the lower end of the control rod cluster guide tube and the upper core plate upper surface. A method for changing a coolant flow path in a pressurized water reactor, characterized by adding a relatively large gap. An upper core plate for holding the fuel assemblies constituting the core,
A control rod cluster guide tube for guiding a control rod cluster inserted into and removed from the core,
An upper core support plate supporting the control rod cluster guide tube above the upper core plate , and an upper core structure of a pressurized water reactor vessel having:
A shim plate structure is interposed between a middle flange of the control rod cluster guide tube and an upper surface of the upper core support plate,
A gap corresponding to the thickness of the shim plate structure is formed between the lower end of the control rod cluster guide tube and the upper core plate upper surface,
An upper core structure in a pressurized water reactor vessel, wherein a significant portion of the reactor coolant flows through the gap. The upper part in the pressurized water reactor vessel according to claim 2, wherein there are a plurality of the control rod cluster guide tubes in which the middle flange is supported on the upper surface of the upper core support plate via the shim plate structure. Core structure.

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