JPS6263894A - 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 [Industrial Application Field] The present invention relates to a nuclear reactor, and in particular to a boiling water nuclear reactor having a reactor cooling system (a low pressure injection system (LPCI) and a high pressure injection system (HPCI)). This invention relates to a nuclear reactor suitable for use as a nuclear reactor.

[Conventional technology]

Boiling water reactors are caused by pipe breaks, etc. For example, an LPCI is provided as an emergency reactor cooling system that supplies cooling water to the reactor core in the event of a loss of coolant accident. This LPC
As shown in Japanese Unexamined Patent Publication No. 55-136997, cooling water is introduced from the outside of the reactor pressure vessel to the reactor core in the reactor shroud through a reactor cooling system nozzle. This conventional LPCI has a structure in which a reactor cooling nozzle and cooling system piping provided on the core shroud side are connected by a flexible bellows structure. What is the use of this bellows?

This is also preferable from the viewpoint of load countermeasures during earthquakes.

[Problem that the invention seeks to solve]

Bellows, which serve as joints used in conventional nuclear reactor cooling systems, are made of metal and are subjected to repeated bending stress as they expand and contract in the axial direction due to repeated startup and shutdown of the nuclear reactor. The bellows may be damaged by this bending stress, and a bellows that has undergone repeated bending stress a predetermined number of times is replaced with a new bellows.

An object of the present invention is to provide a nuclear reactor having a reactor cooling system with a low risk of damage and a long life.

[Means for solving problems]

The purpose of the above is to provide a cylindrical joint that connects the reactor cooling system nozzle provided in the reactor pressure vessel and the cooling system piping provided in the shroud containing the reactor core. This can be achieved by using metal bellows with mutually different seam positions.

Furthermore, the cylindrical joint has an end fitting part extending in the axial direction, a bucking ring part formed at the upper part of one end of the end fitting part and protruding on the side opposite to the end fitting part, and an external part of the buckling ring part. A pair of coupling rings each having a convex portion formed in the backing ring, and both ends of each of these coupling rings being fitted into and fixed to the backing ring portion, are formed by a plurality of layers, and the joint positions of each of the plurality of layers are mutually aligned. By providing different metal bellows and a pair of covers that cover the metal bellows and have one end fixed to the convex portion of each coupling link, the life of the reactor cooling system can be further extended.

[Effect]

By making the metal bellows multi-layered, the thickness of the metal material in each layer is at least 1/2 or less compared to a single layer.
Even if bending stress is applied to the metal bellows, this bending stress decreases in inverse proportion to the thickness of the metal layer. Furthermore, since the joint positions of the plurality of layers are different from each other, the decrease in strength of the bellows due to the joints is minimized. This effect significantly reduces the probability of bellows breakage and significantly extends the life of the reactor cooling system compared to conventional systems.

Furthermore, according to the second feature, the end of the bellows made of multiple layers is inserted into the backing ring part of the coupling ring, so that even if the bellows is subjected to a large internal pressure, the bellows are pressed against the backing ring part, and the bellows Peeling of multiple layers from each other can be prevented. Therefore, compared to the first feature described above, the probability of breakage of the bellows is reduced and the life of the reactor cooling system is extended.

〔Example〕

Conventionally, it is known that metal bellows have been used as bellows used in nuclear reactors due to the need to counter high temperatures or prevent deterioration due to the atmosphere.The present invention makes such metal bellows multi-layered. This is intended to extend the life of the metal bellows. This is because by applying multiple layers, the thickness of the metal material in each layer becomes 1/2 to several times smaller than that of a single layer. Therefore, even if bending stress is applied to each part of the bellows due to expansion and contraction of the metal bellows, this bending stress will be small in inverse proportion to the thickness of the metal layer. We confirmed that the cause was due to repeated bending stress,
We came up with the idea of using multilayer metal bellows. It has been experimentally confirmed that this can ensure a service life of 30 years.

A preferred embodiment of the present invention based on the above considerations will be described below.

FIG. 1 shows a longitudinal section of a boiling water nuclear reactor equipped with a joint, which is an embodiment of the present invention. One embodiment will be explained based on FIGS. 1 to 3.

Reactor pressure vessel 1 containing a reactor core 20 of a boiling water reactor
0 is provided with a large number of nozzles such as a steam nozzle 14 and a circulation nozzle 16 in addition to the %LPCI nozzle 12. A shroud 18 is installed within the reactor pressure vessel 10, and a reactor core 20 is housed within this shroud 18. In this core 20, an upper grid plate 22, a core support plate 24, and a large number of fuel assemblies 27 are arranged. Also.

An LPCI port 32 is provided at the upper end of the shroud 18 . This LPCI pipe port 32 is connected to the joint 28, so that low pressure water can be injected into the reactor core 20 by the LPCI. A stub 26 connected to the control rod guide tube 29 is provided at the bottom of the reactor pressure vessel 10.

As shown in FIG. 2, the reactor pressure vessel 10 and the shroud 18 have circular cross sections and are arranged concentrically. Moreover, the LPCI nozzle 12.

Generally, three of them are provided, each connected to a joint 28 and communicated with the inside of the shroud 18.

The joint 28 has a cylindrical shape, and as shown in FIG.
(connected to the nozzle 12) and the LPCI pipe port 32 on the shroud 18 side. That is, the bellows 34 and the pair of covers 36A, 36 covering the bellows 34
Both ends of the joint 28 consisting of B are fixed to the outer circumferential surface of a mounting ring 38, and this mounting ring 38 is attached to the LPCI pipe port 30 and the LPCI pipe port 32 with clamps 40 and 42 having a half-split structure. In addition, inside the joint 28,
A sleeve 44 has been inserted. This sleeve 44 is
This is to prevent sudden temperature changes to the bellows 34, and smooth convex portions are formed on the outer peripheral surface of both ends of the bellows 34.
This convex portion is slidably fitted into the mounting ring 38.

In the joint 28, as shown in FIG. 4, the bellows 34 and the covers 36A, 36B are fixed to a coupling ring 46. Covers 36A, 3 covering the bellows 34
6B reach near the longitudinal center of the bellows 34 and are separated from each other. The covers 36A and 36B each have a jig insertion hole 47 into which a jig for suspending the joint 28 is inserted.
is formed.

As shown in FIG. 9, the coupling ring 46 includes an end fitting portion 48 extending in the axial direction, and a backing ring portion 5 protruding outward from one end of the end fitting portion 48 on the opposite side from the end fitting portion 48.
0, a convex portion 52 formed on the outer side of the backing ring portion 50 on the end fitting portion 48 side.

This coupling ring 46 is attached to a convex portion 52 on the outer periphery of the cover 3.
6B (the same applies to the cover 36A) is welded and joined at the welding part 54, the bellows 34 is fitted into the backing ring part 50, and the tip of the bellows 34, which is beveled, is welded and joined at the welding part 56. are doing.

On the other hand, the bellows 34 has a three-layer structure composed of thin metal plates 58, 60, and 62 made of stainless steel or the like, as shown in FIG. The metal plates 58, 60 and 62 constituting this bellows 34 are shown in FIG.
As exemplified by , it is curved to form a cylinder and has a welded seam 64 along the longitudinal direction. a welded joint 64 of the metal plate 58 extending in the longitudinal direction;
A joint 66 of the metal plate 60 that is welded and extends in the longitudinal direction.
, a seam 6 which is welded to the metal plates 62 and extends in the longitudinal direction.
8 are arranged at equal intervals at different positions in the circumferential direction of the bellows 34, as shown in FIG.

Moreover, the jig insertion holes 47 of each cover 36 are as follows.

As shown in FIG. 7, they are provided at four locations, two in pairs, and each pair faces each other.

Furthermore, at the opposing ends of the pair of covers 36A and 36B (center part of the joint 28), a recess 70A is provided as shown in FIG.
, 70B are formed. The recesses 70A and 70B are formed at the upper and lower parts in FIG. 4, and have corresponding positions, forming a jig insertion hole 72.

The joint 28 of the embodiment configured as described above is a nuclear reactor due to the difference in thermal expansion coefficient due to the difference between the material of the reactor pressure vessel 10 (generally low alloy steel) and the material of the Siniroud 18 (generally stainless steel). Pressure vessel 10 and shroud 18
It is possible to absorb the relative displacement between the That is, when the positions of the reactor pressure vessel 10 and the shroud 18 change relative to each other, the bellows 34 of the joint 28 expands and contracts in the axial direction, and accordingly, the end of the sleeve 44 moves toward the mounting ring 3B.
A pair of covers 36A move smoothly inside.

36B also changes their mutual spacing, and the reactor cooling system @10
The relative displacement between the shroud 18 and the shroud 18 is absorbed. This effect also applies to relative displacement during earthquakes.

Further, the bellows 34 is not only protected from rapid thermal changes by the sleeve 44 and the cover 36, but also
By adopting a three-layer structure, internal stress can be made relatively small. Moreover, since the bellows 34 is fitted into the backing ring part 50 of the coupling ring 46, when a large internal pressure is applied, the bellows 34 is pressed against the backing ring part 50. It is possible to prevent the plates 58, 60 and 62 from peeling off. And the joint c of metal plates 58, 60 and 62
64. es and 68 are arranged so as to be equally different from each other, so that the decrease in the strength of the bellows 34 due to the seam is minimized.

Furthermore, by providing jig insertion holes 47° 72 in the cover 36, a jig for suspending the joint 28 can be inserted into the jig insertion holes 47, 72 during maintenance, inspection, etc. of the reactor pressure vessel 10. It can be hung easily. Therefore, the joint 28 can be easily removed and assembled during maintenance and inspection of the reactor pressure vessel 10.

In the above embodiment, the case where the bellows 34 has a three-layer structure has been described, but it goes without saying that the bellows 34 can have an arbitrary multi-layer structure with an arbitrary thickness depending on the internal pressure that the bellows 34 receives.

〔Effect of the invention〕

According to the first feature of the present invention, the bending stress generated in the bellows can be significantly reduced by the multi-layer structure, and a decrease in the strength of the bellows can be suppressed, thereby significantly reducing the risk of breakage of the bellows and extending the lifespan of the reactor cooling system. can be significantly lengthened.

According to the second feature of the present invention, it is possible to further prevent peeling between a plurality of layer tiles, the risk of bellows (7) M loss is lower than in the first feature, and the nuclear reactor Cooling system life is longer.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a boiling water reactor which is a preferred embodiment of the present invention, and No. 2I! I is the ■-■ cross-sectional view of Fig. 1, and the 3rd
The figure is an enlarged view of a portion of Figure 1, Figure 4 is a partially cutaway front view of the joint in Figure 3, Figure 5 is a cross-sectional view of the bellows in Figure 4, and Figure 6 is Figure 5. FIG. 7 is a cross-sectional view of the cover of the joint shown in FIG. 4, and FIG.
The figure is a view taken in the direction of the ■ arrow in FIG. 4, and FIG. 9 is an enlarged view of the ■ section in FIG. 4. DESCRIPTION OF SYMBOLS 10... Reactor pressure vessel, 12... LPCI nozzle, 18... Shroud, 20... Reactor core, 28...
Coupling, 30. 32... LPCI pipe port, 34... Bellows, 36A, 36B... Cover, 46... Coupling ring, 48... End fitting, 50... Backing ring, 52...・Convex part, 58, 60.62
...metal plate, 64,66.68...seam.

Claims (1)

[Claims] 1. A reactor pressure vessel having a reactor cooling system nozzle, a shroud installed in the reactor pressure vessel and containing a reactor core, and a shroud installed in the shroud and opening on the side of the reactor core. The reactor cooling system piping is composed of a cooling system piping and a cylindrical joint that connects the reactor cooling system nozzle and the cooling system piping and is deformable in the axial direction, and the cylindrical joint is formed of a plurality of layers. A nuclear reactor characterized in that it is a metal bellows in which the seam positions of these layers are mutually different. 2. A reactor pressure vessel having a reactor cooling system nozzle; a shroud installed in the reactor pressure vessel and containing the reactor core; cooling system piping provided in the shroud and opening on the core side; It consists of a cylindrical joint that connects the reactor cooling system nozzle and the cooling system piping and is deformable in the axial direction, and the cylindrical joint is connected to an end fitting part extending in the axial direction, and the end fitting part of the end fitting part. A pair of coupling rings having a bucking ring part formed at the upper end of one end and protruding on the opposite side from the end fitting part, and a convex part formed on the outside of the buckling ring part, and the backing ring part of each of these coupling rings. a metal bellow formed of a plurality of layers with both ends fitted and fixed to the metal bellows, each of which has a different seam position; and one end fixed to the convex portion of each of the coupling rings. and a pair of covers that cover the metal bellows.