JPS61139792A - Core support structure of nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a core support structure for restraining horizontal movement of fuel installed in the core of a nuclear reactor.

[Technical background of the invention and its problems]

Generally, the core of a boiling water reactor is constructed as shown in FIG. That is, inside the reactor pressure vessel 1, a cylindrical shroud 2 is seated on a shroud support 1A concentrically with the reactor pressure vessel 1 and fixed by welding at a location 1B. A shroud head 3 is installed on this shroud 2. Furthermore, an upper lattice plate 4 having a large number of rectangular holes is installed at an upper position inside the shroud 2, and a core support plate 5 having a large number of circular holes is installed at a lower position thereof. Long fuel assemblies are arranged and mounted at the positions of the rectangular holes of the upper grid plate 4 and the circular holes of the core support plate 5, respectively, to constitute the reactor core. It is said to be constituent fuel 6. In addition, the upper grid plate 4 and the core support plate 5 are arranged so that the fuel 6
The horizontal movement of is restricted.

When assembling the core support structure formed in this way, first the shroud 2 is installed concentrically with the reactor pressure vessel 1, and after welding at the location 1B, the upper grid plate 4 and the core support plate 5 are welded together. is similarly installed concentrically with the reactor pressure vessel 1. In this case, the upper grid plate 4 is fixed to the shroud 2 by a large number of wedges 4A, and the core support plate 5 is fixed to the shroud 2 by a large number of stud bolts 5A.

However, installation of the upper grid plate 4 and the core support plate 6 requires strict installation precision, and the above-mentioned large number of wedges 4A r
3 and stud bolts 5A require a long installation schedule.

In addition, when a horizontal seismic force acts, the upper lattice plate 4
Although the core support plate 5 does not move in the horizontal direction because it is restrained by the wedges 4A, the core support plate 5 moves by the gap between the stud bolt 5A and the stud bolt hole of the core support plate 6, and as a result, the fuel There is a risk that the lower part of fuel 6 may move and tilt, which may obstruct insertion of a control rod installed between fuel 6 (not shown). In addition, since the shroud 2 is fixed to the reactor pressure vessel 1 by welding,
In the unlikely event that a malfunction occurs in the shroud 2, it will be difficult to remove or replace it, and it will also be difficult to repair the inside of the reactor pressure vessel 1 due to high radiation exposure, and the operation of the reactor will be interrupted. There was the inconvenience of being obstructed.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and is easy to manufacture, shortens the installation process in the reactor pressure vessel, and is easy to repair and replace, thereby improving the safety of the reactor. An object of the present invention is to provide a core support structure for a nuclear reactor that can improve performance and availability.

[Summary of the invention]

The core support structure of a nuclear reactor includes an upper lattice plate that arranges and supports the fuel installed in the core of the reactor while restraining horizontal movement at the upper part thereof, and restraining the horizontal movement of the fuel at the lower part thereof. The reactor core support plate arranged and supported by the reactor and the cylindrical shroud surrounding the outer periphery of the fuel are integrally formed in advance and are detachably attached to the shroud support in the reactor pressure vessel. .

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows an embodiment of the present invention, and reference numeral 7 in the figure indicates an integrated core support structure of this embodiment. This core support structure is not shown in FIG.
112a, intermediate section 2b, upper grid plate 4 and core support plate 5 are integrated into one piece. Further, the lower part 112c of the conventional shroud 2 is an integral structure with the shroud support 1A.

This core support structure 7 is manufactured in advance in a factory or the like by integrally or integrally with the upper shell 2a, intermediate shell 2b, upper lattice plate 4, and core support plate 5 of the shrou E2. Therefore, the large number of wedges 4A and stud bolts 5A, which are fixing parts between the upper grid plate 4 and the core support plate 5 shown in FIG. 5, are no longer required1, and manufacturing is extremely easy.

Then, the core support structure 7 which has been integrally manufactured in advance is placed on the shroud support 1A which also serves as the lower body of the shroud 2 of the reactor pressure vessel 1, and a large number of stud bolts 8 are mounted.
are tightly connected. In this case, core support + lr structure 7
A hollow cylindrical spacer 9 shown in FIG. 2 or a combination of double eccentric hollow cylindrical spacers 9A and 9B shown in FIG. The gap between the object 7 and the stud bolt 8 is eliminated.

In this way, the core support structure 7 of this embodiment can be easily installed into the reactor pressure vessel 1, and even if a horizontal seismic force acts on the core support structure 7, it will not move. At the same time, the movement of the fuel 6 is also restrained, and the insertion of the control rods installed between the fuels 6 is no longer inhibited.

Furthermore, since the core support structure is installed in the reactor pressure vessel using removable means such as bolted connections, welding is not required, and as a result, welding deformation does not occur and installation accuracy is improved.

Since the core support structure can be removed, repair or replacement becomes easy, and the inner wall of the reactor pressure vessel at the core location can be easily inspected or water refilled.

Furthermore, since the reactor core support structure of the present invention has a structure that does not move even when horizontal seismic force is applied, the movement of fuel is restricted and the insertion of control rods is not obstructed, thereby improving the safety and operation of the reactor. It is possible to improve the ratio.

Core support structure 7A of another embodiment of the present invention shown in FIG.
is the rim 11M3a of the shroud head 3, which is not shown in FIG.
The upper shell 2a of the shroud 2' is integrated with the upper body 2a of the shroud 2', thereby simplifying the structure of the core support structure 7 shown in FIG. 1 and making it easier to manufacture.

[Effects of the Invention] As described above, the reactor core support structure of the present invention has a shroud, a core support plate, and an upper lattice plate integrally formed, and has stronger rigidity and a greater margin in terms of strength. increase,
All the fixing parts of the upper grid plate and the core support plate are no longer required, which reduces the incidence of failure and improves reliability.

Further, the installation process of the upper grid plate and the core support plate is completely unnecessary, resulting in effects such as being able to shorten the construction process.

[Brief explanation of drawings]

1 to 3 show an embodiment of the core support structure of a nuclear reactor according to the present invention, FIG. 1 is a sectional view of the reactor, and FIGS. 2 and 3 show the core support structure and the reactor. 4 is a sectional view similar to the $1 figure showing another embodiment of the present invention; FIG. 5 is a sectional view showing the main parts of a conventional nuclear reactor. . 1...Reactor pressure vessel, 2...Shroud, 3...
・Shroud head, 4... Upper grid plate, 5... Core support plate, 6... Fuel, 7,7A... Integrated core support structure, 8... Stud bolt, 9.9A , 9B
···Spacer. Applicant's agent Hisashi Hatano Figure 1 Figure 2 Figure 3 Figure 4 Figure 5rI! J

Claims (1)

[Claims] 1. An upper lattice plate that arranges and supports fuel installed in the core of a nuclear reactor while restricting horizontal movement at the upper part thereof;
A core support plate that arranges and supports the fuel while restraining horizontal movement at its lower part, and a cylindrical shroud surrounding the outer periphery of the fuel are integrally formed in advance, and are mounted on the shroud support in the reactor pressure vessel. A nuclear reactor core support structure characterized by being installed in a detachable manner. 2. The core support structure for a nuclear reactor as set forth in claim 1, wherein the shroud support is tightened and fixed to the shroud support by stud bolts having spacers fitted thereon to restrain horizontal movement.