JPS6225288A - Upper structure in reactor for 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 The present invention relates to a pressurized water nuclear reactor, and particularly to an improvement of the upper structure inside the reactor.

BACKGROUND OF THE INVENTION Among the various pressurized water reactors there are so-called improved reactors whose longitudinal dimensions are considerably longer than conventional reactors. In this case, the length of the control rod drive shaft exposed to the coolant flow within the top of the reactor vessel will naturally become longer.
To protect the control rod drive shaft from vibrations excited by the coolant flow, the control rod drive shaft must be surrounded by a protective tube.

In addition, this protection tube must be provided with a passage means for passing the coolant from the top of the reactor vessel into the core during an emergency.

However, in the conventional flow path means, a flow path hole is provided at the root of the protective tube, whose shell is weak against bending moments, and a complicatedly shaped flow dividing device is provided as a separate component.

[Problems to be Solved by the Invention] Accordingly, in the conventional technology, the strength of the protective tube is weak. An object of the present invention is to provide an internal upper structure of a nuclear reactor that can quickly solve these problems.

[Means for Solving the Problems]] For this purpose, the present invention provides a nuclear reactor vessel that is suspended and supported within a reactor vessel,
The present invention relates to an in-core superstructure of a nuclear reactor having a core barrel surrounding an inner lower core, the in-core superstructure according to the present invention having an upper structure located directly above the reactor core and having a control rod assembly guide tube. a calandria structure located above the superstructure; and a control rod assembly having control rods that are movable up and down within the core and control rod assembly guide tubes. The calandria structure has a bottom plate and a top plate that are parallel to each other, and these drawing plates are rigidly connected by a number of protection tubes that individually surround the control rod drive shaft, and the protection tubes pass through the top plate. A passage hole having a small inclination with respect to the protection tube axis is formed in this upper plate penetrating portion in fluid communication with the top of the reactor vessel above the upper plate and the inside of the protection tube.

The upper plate penetration part of the protection tube has a larger radial dimension than the thickness of the protection tube, and can also be made thicker in the axial direction. It becomes possible to form flow passage holes for fluid communication between the top of the reactor vessel and the inside of the protection tube.

Therefore, there is no need to form a flow passage hole at the base of the protection tube, and weaknesses in the strength of the protection tube are eliminated.

Moreover, since the degree of inclination of the flow passage hole formed in this way with respect to the protection tube axis is reduced, the jet axis of the coolant flowing inside the flow passage hole toward the inside of the protection tube is away from the protection tube axis. Also, a Coanda effect occurs in which the coolant tends to flow along the inner wall of the protective tube.

Therefore, the coolant jet does not collide with the control rod drive shaft in the protection tube, and the control rod drive shaft is no longer excited.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows a longitudinal section of a nuclear reactor according to the present invention, and FIG. 2 is a detailed sectional view of the part circled in FIG.
FIG. 3 is a sectional view taken along line I-1 in FIG. 2. In FIG. 1, a reactor vessel 1 has a cylindrical main body 1a and an upper lid 1b detachably attached to a flange portion of the main body 1a. 18 and an outlet nozzle 19 are integrally formed. In the main body la of the container 1, there is an annular downward flow path I cooperating with the inner wall surface of the container 1.
C, the core barrel 2 is suspended from the flange of the main body 1a at the upper part, and is welded to the lower core plate 4 at the lower part.

Inside and below the core barrel 2, a core A consisting of a large number of fuel assemblies 3 (only four are shown in the figure) is supported between a lower core plate 4 and an upper core plate 6.

Further, inside the core barrel 2, there are an upper structure 5 located directly above the core A and a calandria structure 7 located above the upper structure 5.

The upper structure 5 is attached to the flange portion of the vessel body 1a at the upper part in the same way as the core tank, and at the lower part the upper core plate is attached to a large number of control rod assembly guide tubes 16 and 17 (only two are representatively shown in the figure). ). In this embodiment, a guide tube 16 guides the control rods 11 assembled into an assembly, and a guide tube 17 guides the water removal rod 12.

The calandria structure 7 has a top plate 8 and a bottom plate 9 parallel to each other.
The top plate 8 and bottom plate 9 are rigidly connected to each other by a number of hollow protection tubes 10. This protection tube 1
0 surrounds the control rod drive shaft 13 connected to the aforementioned control rod 11 or water exclusion rod 12, and mechanically its lower part protects the drive shaft 13 from the lateral flow in the calandria tM 3e body 7. , the northern part protects the drive shaft 13 from the bypass flow at the reactor vessel top 1e. Control rod drive shaft 1
3, the one connected to the control rod 11 is the upper lid body 1b.
The drive device 14 attached to the water removal rod 12 is shown as being connected to the drive device 15 similarly attached to the lid body 1b. Therefore, within the fuel assembly 3, there are control rods 1 for controlling the thermal output.
1-1 The water removal rods 12 that control the reaction chamber are movable back and forth, and these rods are inserted into and withdrawn from the fuel assembly 3 by the drive device 14.15 via the drive shaft 13. By doing so, the output and reactivity are controlled.

As is clear from FIG. 2, which shows details of the portion where the protective tube 10 penetrates the upper plate 8 of the calandria structure 7, that is, the portion surrounded by a circle in FIG.
It is divided into an upper protection tube 10a and a lower protection tube 10a, and these protection tube parts each have a penetration part 2.
2, for example, by welding 23, and the penetrating portion 2
2 is also fixed to the upper plate 8, for example, by welding 24.

The penetrating portion 22 includes a flange-shaped protrusion 25 extending radially outward beyond the outer circumferential surface of the protective tube, and has a counterbored through hole 2 so that the drive shaft 13 can move up and down.
6 in the center. The inner diameter and outer diameter of the penetrating portion 22 are selected such that the wall thickness in the radial direction is sufficiently larger than the wall thickness of the protection tube 10. In addition, the protruding portion 25 has a plurality of flow passage holes 21 (eight in the embodiment as shown in FIG. 3) spaced apart in the circumferential direction. A diagonal hole is formed for fluid communication with the inside of the protection tube 10. It is preferable that the inclination θ of each channel hole 21 with respect to the longitudinal axis of the protective tube 10 is as small as possible, and as understood from FIG.
The outlet side opening of the flow path hole 21 is arranged so that the coolant flowing into the protection tube from the inside of the protection tube 10 follows the inner wall of the protection tube 10 as much as possible.

During operation of the reactor having the above-described structure, the coolant flowing from the inlet nozzle 18 descends through the annular downward passage 1c between the vessel body 1a and the reactor core fff2, as shown by the arrow, and reaches the bottom of the body. The flow reverses at the blemish part 1d, becomes an upward flow, enters the core region through a large number of flow passage holes 4a (only a few are shown in FIG. 1 as a representative) in the lower core plate 4, and is heated there. , flows into the upper structure 5 through the passage holes 6a of the upper core plate 6.

The coolant rises inside and outside the control rod assembly guide tubes 16, 17 into the calandria structure 7 where it is laterally redirected and exits through the outlet nozzle 19 into a steam generator (not shown). flowing towards.

On the other hand, a small portion of the coolant that has entered the calandria structure 7 is transferred to the spray nozzle 20 located at the position shown in FIG.
It flows as a bypass flow from there, cools the top part 1e of the reactor vessel 1, and then flows from the upper part of the protection tube 10 and the flow passage hole 21 (the part circled in FIG. The coolant enters the protection tube 10 from the coolant main flow (Fig. 2), merges with the main flow of the coolant, and flows out from the outlet nozzle 19.

In the event of a hypothetical loss of coolant accident, the water retained in the top 1e of the reactor vessel 1 will descend through the aforementioned flow passage holes 21 into the protective tube 10, and then the control rod assembly guide. tube 1
6.17 and flows directly into the core region to cool it.

[Effects of the Invention] According to the inner reactor upper side passage of the nuclear reactor of the present invention having the above-described configuration and operation, the following special effects can be achieved.

(1) By providing the channel hole Z1 in the penetration part 2z, the cross-sectional moment of inertia 1- of the root part of the protection tube 10 can be increased in this part so that it is more resistant to bending moment. The weakness in the strength of the protection tube 10 is eliminated.

(2) By appropriately setting the wall thickness of the penetration part 22,
Since the inclination angle θ of the flow passage hole 21 with respect to the protection tube axis can be made small, a Coanda effect occurs in which the sill follows the protection tube inner wall from the flow passage hole 21 into the protection tube 10, and the drive that penetrates the inside of the protection tube 10 is generated. Drive shaft 13 due to impact of coolant jet on shaft 13
excitation is relaxed.

(3) Although the penetrating portion 22 has a porous structure similar to that of the flow path hole 21, the thickness of the penetrating portion 22 in the axial direction can be increased. An improvement in effectiveness can be expected, and concerns about fluid vibration of the drive shaft 13 can be further alleviated.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a nuclear reactor with an internal reactor upper structure according to the present invention, Fig. 2 is a detailed cross-sectional view of the part surrounded by a circle) I in Fig. 1, and Fig. 3 is a - It is an m-line sectional view. 1. Reactor vessel 21. Core tank 3...Fuel ↑-
1 assembly 5... Upper horizontal body 7... Calandria structural wood 8... Top plate 9... Bottom plate
10...Protection tube 11...Control rod
13... Control rod drive shaft 16... Control rod assembly guide tube 21... Channel hole 17... Control rod assembly guide tube 2
2... Penetration part 1e... Reactor vessel top A...
・Continued from page 91 of Figure 2 of the reactor core Inventor: Katsutoshi Shimizu Inside the Otemachi-style company, Chiyoda-ku, Tokyo Inventor: Eiji Yoshikawa Inside the Kobe Shipyard & Machinery Works, Wadazakichosha, Hyogo-ku, Kobe City

Claims (1)

[Claims] An in-core upper structure of a nuclear reactor having a core barrel suspended in a reactor vessel and surrounding an inner lower core, the upper structure being located directly above the reactor core and having a control rod assembly guide tube; The calandria structure includes a calandria structure located above the superstructure, and a control rod assembly having control rods that are movable up and down in the core and control rod assembly guide tubes, and the calandria structures are arranged parallel to each other. It has a bottom plate and a top plate, both of which are rigidly connected by a number of protection tubes that individually surround the control rod drive shaft, the protection tubes extending through the top plate, and the protection tubes extending through the top plate. An internal upper structure of a nuclear reactor in which a passage hole with a small inclination with respect to the axis of the protection tube is formed in the upper part of the reactor in fluid communication with the top of the reactor vessel above the upper plate and the inside of the protection tube.