JPS61226684A - In-pile 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 the internal structure of a nuclear reactor, and in particular, to an internal structure of a nuclear reactor in which a fastening method for fastening a shroud head and an upper lattice plate to a shroud is improved. Regarding structure.

[Technical background of the invention and its problems]

As shown in FIG. 7, the nuclear reactor includes a shroud 12 that surrounds the outer periphery of a reactor core 11 housed in a reactor pressure vessel.
and a shroud head 13 forming a brenum above the core 11. The core 11 in the center of the Sierra Loud 12 is supported by a core support plate 14 at its lower part and by an upper lattice plate 15 at its upper part. Further, the shroud head 13 has a steam/water separator 16 assembled thereon.

The shroud 12 and shroud head 13 are connected to 36 shrouds shown in FIGS. 8 and 9 in order to support the internal pressure generated because the reactor is operated at 286°C and the overturning load during an earthquake. It is fastened with Radbolt 17.

This shroud head bolt 17 has an inner rod 23 inserted into a cylindrical outer pipe 24. A tipper 25 is provided at the lower end of the inner rod 23 projecting downward from the lower end of the outer pipe 24, and is hooked onto the lower end of a shroud bolt lug 26 protruding from the shroud 12. Inner rod 23
The upper stud 29 is fixed to the outer pipe 24 by a nut 19 and restricts movement of the inner rod 23 in the axial direction. A base 27 fixed to the lower end of the outer pipe 24 is placed on the shroud head bolt lug 28 of the shroud head 13. In addition, in FIG. 8 and FIG. 9, 18 is a support ring that supports the steam/water separator 16, 20 is a spring, 21 is a head, and 22 is a spacer.

Further, the inner rod 23 is made of Inconel 600, while the shroud 12 and the shroud head 13 are made of stainless steel. Therefore, since the former has a smaller coefficient of thermal expansion than the latter, the shroud 12 and the shroud head 13 are tightly tightened when the reactor reaches a high temperature.

However, such a shroud head bolt 17,
Before reactor operation, it is necessary to fix the upper end of the inner rod 23 and the upper end of the outer pipe 24 with nuts 19, and in addition, there are 36 Rad bolts 1 to the shroud arranged around the shroud head 13, and each The nut 19 had to be loosened and tightened by remote underwater operation, which was very time consuming and troublesome.

Further, when the reactor is shut down or when changing fuel during periodic inspections, it is necessary to remove the shroud head 13, and at that time, the nut 19 also requires work to be removed and installed, and the workability is not necessarily good.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it reduces the time required to remove and install nuts as in the past, and allows the shroud head etc. to be easily and reliably fastened to the shroud, thereby shortening the periodic inspection period. The purpose is to provide an internal structure of a nuclear reactor that can achieve the following.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention includes an engagement lug on either one of a shroud assembled in the core of a nuclear reactor and a reactor internal structure such as a shroud head placed on this shroud. , and an engagement block is provided on the other side of the engagement block so as to be engageable with the engagement lug.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to FIGS. 1 to 6. Note that in FIGS. 1 to 6, the same reference numerals indicate the same parts, and a description of the overlapping parts will be omitted.

FIG. 1 is a main part configuration diagram showing the configuration around a shroud head in an embodiment of the present invention, and in the figure, reference numeral 1 indicates a shroud. In this embodiment, when the shroud head 2 forming the upper brenum is fastened to the shroud 1 surrounding the outer periphery of the reactor core, the shroud head 2 positioned on the shroud 1 is rotated in the circumferential direction, and the shroud 1
This is accomplished by engaging the engagement blocks 3 and engagement lugs 4 provided on the shroud head 2 with each other.

That is, as shown in the figure, a protruding engagement lug 4 is provided on the upper part of the shroud 1, and the shroud head 2
An L-shaped protruding engagement block 3 that engages with the engagement lug 4 is provided on the outer periphery of the flange portion at the lower part.
They are placed in corresponding positions, e.g. 4 at 90 degree intervals around the circumference of shroud 1 or shroud head 2.
Each is provided.

The engagement block 3 itself is rotated in the direction in which the shroud head 2 is to be fastened to the shroud 1, for example, when rotated clockwise when viewed from a plane as shown in the figure.
The front ball portion on the rotating side has a notched single-shape shape, and is designed to mesh with the engagement lug 4 at this notched portion.

Therefore, in order to connect the shroud head 2 where these engaging blocks 3 are provided and the shroud 1 where the engaging lugs 4 are provided, the engaging lugs 4 and the engaging blocks 3 are connected to the shroud 1. The shroud head 2 is lowered so as not to interfere with each other, and stops slightly above the flange surface of the shroud 1. Next, the shroud head 2 is rotated in the circumferential direction using a jig, and the flange portions are gradually brought into alignment from the time when the bottom surface of the engagement lug 4 and the notched inner surface of the engagement block 3 come into contact. Then, the engagement lug 4 and the engagement block 3 are brought into sufficient contact,
Further, the rotation of the shroud head 2 is stopped when the flange portion surfaces are in sufficient contact with each other. Thereby, the shroud head 2 is fastened to the shroud 1.

At this time, the engaging surfaces of the engaging block 3 and the engaging lug 4 are each provided with an inclined surface that attracts each other with respect to the fastening rotation direction.

That is, the bottom surface of the engagement lug 4 facing downward and the notched inner surface of the engagement flange 3 facing upward are gradually inclined downward in the rotational direction (clockwise). By doing so, when the engagement block 3 and the engagement lug 4 engage with each other, they are strongly engaged and are more firmly fastened.

In the illustrated example, the shroud head 2 is provided with the engagement block 3, and the shroud 1 is provided with the engagement lug 4. It is also possible to provide each engagement block 3 (not shown), and the same effect can be obtained in either case.

In addition, FIGS. 1 to 3 show cases in which an engagement block 3 or an engagement lug 4 is provided on the shroud 1 itself surrounding the outer periphery of the core, while FIGS. This is a case where an engagement block 3 or an engagement lug 4 is provided on the upper grid plate 5 placed on the upper end of the shroud 1 to support the upper part of the core. In either case, the shroud head 2 is securely fastened in a similar manner.

In addition, an engagement block 3 provided on the shroud head 2
Alternatively, the engagement lug 4 is compared to the constituent material of the shroud 1,
It is assumed that the coefficient of thermal expansion is small.

That is, since the shroud 1 and the shroud head 2 are usually made of stainless steel, the engagement block 3 or the engagement lug 4 is made of, for example, Inconel 600, which has a small coefficient of thermal expansion. Then, as the reactor starts operating and the temperature rises, the shroud 1 and shroud head 2 between l shown in FIG. 2 are made of stainless steel, and therefore try to expand due to thermal expansion. For the same length l, the engagement block 3 or the engagement lug 4 will not stretch as much. Therefore, the shroud 1 and the shroud head 2 are relatively tightened.

On the other hand, the tightening force F exerted by the engagement block and the engagement lug 4 is given by the following equation.

F-(α, -αi)・E-A・6 Here, α and αi are the coefficients of thermal expansion of stainless steel and Inconel 600, and E and A are each of Inconel 600.
The Young's modulus, cross-sectional area, and 6 pieces of the material respectively indicate that the temperature is rising.

For example, α -17, 6X 10-1/#II°C
, Ot--14, I X 10-1/JIl'C1E=
2゜06X10' illusion/-1ΔT-266℃, A=5X1
03-, the above-mentioned engagement block 3 and engagement lug 4
A mutual clamping force of about 96 tons can be obtained.

That is, a sufficient tightening force can be obtained by simply installing several engagement blocks 3 and engagement lugs 4 around the shroud 1 and shroud head 2.

(Effects of the Invention) As explained above, the present invention provides both a shroud that is assembled surrounding a core installed in a nuclear reactor and reactor internal structures such as a shroud head that are placed on this shroud. An engagement lug is provided on one side, and an engagement block is provided on the other side so as to be engageable with the engagement lug.

Therefore, according to this embodiment, the shroud head and the upper lattice plate can be securely fastened to the shroud with a large tightening force using a simple structure, and the nuts of the Radbolts can be remotely controlled underwater to a large number of shrouds, unlike the conventional method. This has the advantage that there is no need to rotate the shroud head, etc., and the shroud head etc. can be tightened very easily and quickly.

Therefore, it is possible to greatly shorten the work time for installing and removing the shroud head, etc., and therefore, the work process such as periodic inspection can be shortened, and the efficiency can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a main part configuration diagram showing the structure around the shroud head in an embodiment of the present invention, Fig. 2 is an enlarged view of part A in Fig. 1, and Fig. 3 is an enlarged view of part B in Fig. 1. Fig. 4 is a main part configuration diagram showing the structure around the shroud head in the embodiment of the present invention, Fig. 5 is an enlarged view of section C in Fig. 4, and Fig. 6 is an enlarged view of the section C in Fig. 4.
Figure 7 is a front view of the core of a conventional nuclear reactor, Figure 8 is a front view of a conventional shroud with the Rad bolts partially omitted, and Figure 9 is the same as Figure 8. It is a partial sectional view showing a part in cross section. 1... Shroud, 2... Shroud head, 3...
... Engagement block, 4... Engagement lug, 5... Upper grid plate, 11... Core, 12... Shroud, 13.
... Shroud head, 14... Core support plate, 15.
...Upper grid plate, 16...Steam water separator. Representative Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 4

Claims (1)

[Scope of Claims] 1. An engagement lug is provided on either a shroud that is assembled surrounding a core installed in a nuclear reactor or a reactor internal structure such as a shroud head that is placed on this shroud. 1. An internal reactor structure for a nuclear reactor, characterized in that an engagement block is provided on either one of the two so as to be engageable with the engagement lug. 2. The nuclear reactor according to claim 1, wherein the engagement lug and the engagement block have a smaller coefficient of thermal expansion than the constituent materials of reactor internal structures such as the shroud and the shroud head. Internal structure. 3. The internal reactor structure of a nuclear reactor according to claim 1, wherein the engagement block and the engagement lug have inclined surfaces on their mutual engagement surfaces. 4. The internal reactor structure of a nuclear reactor according to claim 1, wherein the engagement block is provided on the shroud head, and the engagement lug is provided on the shroud. 5. The internal reactor structure of a nuclear reactor according to claim 1 or 2, wherein the engagement block is provided on the shroud and the engagement lug is provided on the shroud head. 6. The internal reactor structure of a nuclear reactor according to claim 1, wherein the engaging block or the engaging lug is provided on the upper grid plate.