JPH0366635B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the inside of a nuclear reactor, and particularly to a nuclear reactor cooling system (low pressure injection system (LPCI) and high pressure injection system (HPCI)).
The present invention relates to a nuclear reactor suitable for use as a boiling water reactor.

[Conventional technology]

A boiling water reactor is equipped with, for example, an LPCI as an emergency reactor cooling system that supplies cooling water to the reactor core in the event of a loss of coolant accident caused by a pipe rupture or the like. This LPCI, as shown in Japanese Patent Application Laid-open No. 136997/1983, guides cooling water from the outside of the reactor pressure vessel to the reactor core in the reactor shroud through a reactor cooling system nozzle. This traditional LPCI is
It has a structure in which the reactor cooling nozzle and the cooling system piping provided on the core shroud side are connected by a flexible bellows structure. The use of this bellows 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. There is a possibility that 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.

The first object of the present invention is to provide a joint between pipe ports in a reactor that is easy to handle in a nuclear reactor, and the second object of the present invention is to provide a joint between pipe ports in a reactor that has a long life. A third 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]

A first means for achieving the first object of the present invention is to connect both a pipe port on the reactor pressure vessel side and a pipe port on the shroud side installed in the reactor pressure vessel. Moreover, the joint is axially deformable, and the joint includes a pair of coupling rings fixed to both ends of a metal bellows, and a pair of coupling rings coupled to each of the coupling rings so as to surround the metal bellows. A joint between pipe ports in a nuclear reactor, characterized by comprising a cover and a jig insertion hole provided in the cover, and a second object for achieving the second object of the present invention.
The means is a joint that connects a pipe port on the reactor pressure vessel side and a pipe port on the shroud side arranged in the reactor pressure vessel and is deformable in the axial direction, The joint includes a pair of coupling rings fixed to both ends of a metal bellows, and a pair of covers coupled to each of the coupling rings so as to surround the metal bellows, and the ends of the metal bellows are A joint between pipe ports in a nuclear reactor, characterized in that both ends of the metal bellows are fixed to a pair of coupling rings while being fitted into the coupling rings, and the third object of the present invention is achieved. A third means for this purpose is a reactor pressure vessel having a reactor cooling system nozzle, a shroud installed in the reactor pressure vessel and containing the reactor core, and a shroud installed in the shroud and opening on the side of the reactor core. It consists of a cooling system pipe, and a cylindrical joint that connects the reactor cooling system nozzle, the cooling system nozzle, and the cooling system pipe and is deformable in the axial direction, and the cylindrical joint extends in the axial direction. It has an end fitting part, a buckling 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 a convex part formed on the outside of the buckling ring part. a pair of coupling rings, and a metal bellows formed of a plurality of layers with both ends fitted and fixed to the buckling ring portions of each of the coupling rings, and each of the plurality of layers has a different joint position; The nuclear reactor is characterized by comprising a pair of covers having one end fixed to the convex portion of each of the coupling rings and covering the metal bellows.

[Effect]

According to the first means, a coupling ring is attached to both ends of the metal bellows, a cover is fixed to the coupling ring, and a jig insertion hole is used to attach the coupling ring to the cover. By engaging the jig and handling the joint inside the reactor, it is possible to avoid applying the load of the cover or excessive force during handling to the metal bellows, which has low rigidity, and to avoid applying force to the bellows. It has the advantage of being easy to handle even in the furnace.

According to the second means, the cover protects the metal bellows from thermal or other physical forces from the outside, and the external force applied to the cover is received by the coupling ring and is not applied to the metal bellows.
In addition, since the end of the metal bellows is fixed inside the coupling ring, even if pressure inside the pipe increases and force is applied from the inside, the fixed part will be pressed against the fixed ring and will not be easily peeled off, which will shorten the service life. Produces a longer effect.

According to the third means, in addition to protecting the bellows with a cover attached to the coupling ring, the bellows is made of a flexible thin multi-layered material, so that stress is not unreasonable, and furthermore, each layer of the bellows is The joints are offset from each other to disperse the strength change caused by the joints, resulting in flexibility and excellent strength, and even when the internal pressure increases, the end of the bellows is pressed against the inside of the coupling ring, and the end of the bellows is pressed in the direction of peeling action. Because pressure doesn't work. Due to these synergistic effects, the reactor cooling system has no risk of damage and has a long lifespan.

〔Example〕

It is known that metal bellows are conventionally used in nuclear reactors because of the need to counter high temperatures or prevent deterioration due to the atmosphere. The present invention aims to extend the life of the metal bellows by making the metal bellows multi-layered. 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. The inventors of the present invention confirmed that one of the causes of damage to the metal bellows is due to repeated bending stress, and came up with the idea of adopting a multilayer metal bellows. This results in 30
It has been experimentally confirmed that it can secure a useful life of 20 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. This embodiment will be explained based on FIGS. 1 to 3.

A reactor pressure vessel 10 containing a reactor core 20 of a boiling water reactor is provided with a large number of nozzles such as a steam nozzle 14 and a circulation nozzle 16 in addition to an 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. This core 2
0, an upper grid plate 22, a core support plate 24, and a large number of fuel assemblies 27 are arranged. Additionally, an LPCI pipe port 32 is provided at the upper end of the shroud 18 . This LPCI pipe port 32 is connected to a joint 28, so that low pressure water can be injected into the reactor core 20 by the LPCI. Control rod guide tube 2
The stub 26 connected to the reactor pressure vessel 1
Provided at the bottom of 0.

As shown in FIG. 2, the reactor pressure vessel 10 and the shroud 18 have circular cross sections and are arranged concentrically. Further, three LPCI nozzles 12 are generally provided, each connected to a joint 28 and communicated within the shroud 18.

The joint 28 has a cylindrical shape, and as shown in FIG.
(connected to LPCI nozzle 12) and shroud 18 side.
It is connected to the LPCI pipe port 32. That is, the joint 28 consists of the bellows 34 and the pair of covers 36A and 36B covering the bellows 34.
is fixed at both ends to the outer peripheral surface of the mounting ring 38,
This mounting ring 38 is a clamp 4 with a half-split structure.
0,42 by LPCI port 30 and LPCI port 32
It is attached to. In addition, inside the joint 28,
A sleeve 44 has been inserted. This sleeve 4
4 is for preventing sudden temperature changes from being applied to the bellows 34. Smooth convex portions are formed on the outer peripheral surface of both ends, and these convex portions are attached to the mounting ring 38.
It is slidably inserted into the

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

Note that the coupling ring 46 has an end fitting portion 4 extending in the axial direction as shown in FIG.
8. A bucking ring part 50 protruding outside one end of the end fitting part 48 on the side opposite to the end fitting part 48, and a buckling ring part 50 formed on the outside of the buckling ring part 50 on the side of the end fitting part 48. It consists of a convex portion 52. This coupling ring 46 has a convex portion 5 on the outer periphery.
2, one end of the cover 36B (the same applies to the cover 36A) is welded to the welded portion 54, the bellows 34 is fitted into the buckling ring portion 50, and the bellows 34 is beveled at the welded portion 56.
The tips are welded together.

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 the bellows 34 are curved to form a cylinder and have a welded seam 64 along the longitudinal direction, as illustrated by the metal plate 58 in FIG. have. metal plate 5
8 welded and longitudinally extending seams 64;
The welded joints 66 of the metal plates 60 and the longitudinally extending joints 68 of the metal plates 62 are equally spaced at different positions in the circumferential direction of the bellows 34, as shown in FIG. They are arranged so that they are spaced apart.

Further, the jig insertion hole 47 of each cover 36 is
As shown in FIG. 7, they are provided at four locations, two in pairs, and each pair faces each other. Further, as shown in FIG. 8, recesses 70A and 70B are formed at opposite ends of the pair of covers 36A and 36B (the central portion of the joint 28). 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 caused by reactor pressure caused by the difference in coefficient of thermal expansion between the material of the reactor pressure vessel 10 (generally low alloy steel) and the material of the shroud 18 (generally stainless steel). Relative displacements between the container 10 and the shroud 18 can be accommodated. That is, the reactor pressure vessel 10
When the relative positions of the shroud 18 and the bellows 34 of the joint 28 expand and contract in the axial direction, the end of the sleeve 44 moves smoothly within the mounting ring 38, and the pair of covers 36A, 36B also changes in its mutual spacing to accommodate relative displacement between the reactor pressure vessel 10 and the shroud 18. 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 has a three-layer structure, which allows internal stress to be relatively reduced. Furthermore, since the bellows 34 is fitted into the bucking ring portion 50 of the coupling ring 46, when a large internal pressure is applied, the bellows 34 is pressed against the bucking ring portion 50, forming the bellows 34. It is possible to prevent the metal plates 58, 60 and 62 from peeling off. Then, the joints (64, 66, and 68) of the metal plates 58, 60, and 62 are arranged so as to be equally different, and the bellows 34 is formed by the joints.
The strength reduction is minimized.

Furthermore, the cover 36 has jig insertion holes 47, 7.
2, the jig for suspending the joint 28 can be inserted into the jig insertion holes 47, 72 and easily suspended during maintenance, inspection, etc. of the reactor pressure vessel 10. Therefore, the joint 28 can be easily removed and assembled during maintenance and inspection of the reactor pressure vessel 10.

In addition, in the above embodiment, the bellows 34 is
Although the case where the bellows 34 has a layered structure has been described, it goes without saying that the bellows 34 can have any thickness and any multilayer structure depending on the internal pressure that the bellows 34 receives.

[Effects of the Invention] According to the first invention as set forth in claim 1, it is possible to provide a joint between pipe ports in a nuclear reactor that is easy to handle in a nuclear reactor.

According to the second invention described in claim 4, since the bellows can be protected from the inside and outside, the chance of breakage is reduced and the life of the joint between the pipe ports in the reactor is extended. This effect can be obtained.

According to the third invention described in claim 6, by making the bellows thinner and multilayered, and by shifting the joint position for each layer, bending stress is alleviated while suppressing a decrease in strength. can provide a nuclear reactor in which the life of the reactor cooling system can be extended due to the protection provided by the cover and the prevention of peeling action caused by internal pressure.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a boiling water reactor that is a preferred embodiment of the present invention, FIG. 2 is a cross-sectional view of FIG. Figure 4 is a partially cutaway front view of the joint in Figure 3, and Figure 5 is a partially cutaway front view of the joint in Figure 3.
Fig. 6 is a cross-sectional view of the bellows shown in Fig. 5, Fig. 7 is a cross-sectional view of the cover of the joint shown in Fig. 4, and Fig. 8 is a cross-sectional view of the part shown in Fig. 4. 9 is an enlarged view of the portion shown in FIG. 4. 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
... Batsking ring, 52 ... Convex portion, 58,
60, 62...metal plate, 64, 66, 68...seam.

Claims (1)

[Scope of Claims] 1. A joint that connects both the pipe port on the reactor pressure vessel side and the pipe port on the shroud side installed in the reactor pressure vessel in a continuous manner and is deformable in the axial direction. The joint includes a pair of coupling rings fixed to both ends of a metal bellows, a pair of covers coupled to each of the coupling rings so as to surround the metal bellows, and a fixing provided on the cover. A joint between pipe ports in a nuclear reactor, characterized by comprising a fitting insertion hole. 2. Claim 1 is characterized in that both ends of the metal bellows are fixed to the pair of coupling rings with the ends of the metal bellows being fitted into the coupling rings. Joint between pipe ports in a nuclear reactor. 3. Claim 2, characterized in that the metal bellows is a metal bellows formed of a plurality of metal plate layers, and in which the joint positions of these metal plate layers are different from each other. A joint between pipe ports in a nuclear reactor. 4. A joint that connects a pipe port on the reactor pressure vessel side and a pipe port on the shroud side installed in the reactor pressure vessel and is deformable in the axial direction, and the joint is , a pair of coupling rings fixed to both ends of a metal bellows, and a pair of covers coupled to each of the coupling rings so as to surround the metal bellows, wherein the end of the metal bellows is connected to the coupling ring. A joint between pipe ports in a nuclear reactor, characterized in that both ends of the metal bellows are fixed to the pair of coupling rings when the metal bellows is fitted into the pipe. 5. Claim 4, characterized in that the metal bellows is a metal bellows formed of a plurality of metal plate layers, and in which the joint positions of these metal plate layers are different from each other. A joint between pipe ports in a nuclear reactor. 6. 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 reactor core side, and An end fitting portion comprising a furnace cooling system nozzle and a cylindrical joint that connects the cooling system nozzle and the cooling system piping and is deformable in the axial direction, the cylindrical joint extending in the axial direction. , a pair of coupling rings having a buckling ring part formed at the top of one end of the end fitting part and protruding on the side opposite to the end fitting part, and a convex part formed on the outside of the buckling ring part; A metal bellows having both ends fitted and fixed into the buckling ring portion of each coupling ring and formed of a plurality of layers, each of which has a different joint position; A nuclear reactor comprising: a pair of covers having one end fixed to the shaped part and covering the metal bellows.