JPS5895296A - Joint for reactor coolant system - 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 joint for a reactor cooling system, and particularly to a joint for a reactor water injection system installed in a reactor pressure vessel such as a low-pressure injection system or a high-pressure injection system, and a joint installed in a reactor pressure vessel. This invention relates to a joint for a nuclear reactor cooling system used for connection with a nozzle.

Conventionally, slip joints have been common as joints in nuclear reactor cooling systems, and other methods have been to make the joints rigid.

In response, there are demands for joints to be featured in order to counteract loads during earthquakes, and there is a desire for joints that are simple and have a high degree of freedom.

An object of the present invention is to provide a joint that can meet the above requirements.

In order to meet this objective, the joint of the present invention has a bellows structure, and is made of metal in which the bellows are formed in multiple layers. It has been known that metal bellows have been used in nuclear reactors in order to protect against high temperatures or to prevent deterioration caused by the atmosphere. The present invention aims at extending the life of such metal bellows by making them multi-layered. This is because, by making the metal plate multi-layered, the thickness of the metal plate in each layer becomes one-half to one-several fraction of 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 bellows, this bending stress becomes small in inverse proportion to the thickness.

The inventors confirmed that the cause of damage to metal bellows is due to repeated bending stress, and decided to adopt a multilayer metal bellows. It has been experimentally confirmed that this can maintain a useful life of 30 years.

Hereinafter, one embodiment of the present invention will be described based on the drawings. In Figure 1, reactor pressure vessel (hereinafter abbreviated as RPV)■
There is a shroud 2 welded inside. That R, PV 1
Three low-pressure injection type LPCI couplings 3 are arranged around the entire circumference to connect the very narrow annulus portion (see FIG. 2) of the tunnel loud 2. This LPCI coupling 3
This is to perform low-pressure core water injection cooling in the event of a loss of reactor coolant accident. Also, this LPCI coupling 3 is R, P
Excessive relative displacement occurs because the thermal expansion coefficients of VI (material: low-alloy steel) and Nyuroud 2 (stainless steel) are different.In order to absorb this excessive relative displacement and displacement during earthquakes, L
A bellows 4 is used within the PCI coupling 3. (See Figure 3) The bellows 4 has an overall structure as shown in Figure 4. This bellows 4 has an R welded to the RPVl side, a PV side flange 5, and a flange welded to the shroud side. 6 through a clamp 7 as shown in FIG. A sleeve 8 is inserted inside the bellows 4 to prevent sudden temperature differences (the third
(see figure). Furthermore, there is a cover 4 divided into two on the outside in the same way.
8 is for installation. In order for the bellows 4 to absorb excessive relative displacement due to thermal expansion and displacement during an earthquake, the plate thickness of the bellows 4 should be made extremely thin. For this purpose, as shown in FIG. 5, three extremely thin plates were stacked to form three layers, and the welded portions of the three plates were arranged equally. By making the bellows 4 three-layered (as confirmed by strength calculations and prototype production), it became possible to absorb excessive relative displacement due to thermal expansion and displacement during earthquakes.

Furthermore, when on-site modification is required, the work will be extremely difficult as it will be remotely controlled from the top of the RPV1. In order to make this difficult work easier, the bellows 4 is provided with jig insertion holes 4b and 4C as shown in FIGS. 4, 7 and 8, and the bellows 4 is attached and detached using these holes. Figure 9 shows bellows 4 and end fitting 4
This is the connection part with d. The bellows 4 has a backing ring 4h that covers it from the outside to receive internal pressure,
A welding groove (tapered shape) is provided at the end of the three layers of the bellows 4 and the end fitting 4d to form a sufficient weld 4f.

Note that the end fitting 4d and the cover 43 are connected by welding 4g.

According to the present invention, thermal expansion and excessive relative displacement during earthquakes can be easily absorbed, and furthermore, it can be easily attached and detached during on-site modification.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the reactor core, and Figure 2 is A in Figure 1.
-A sectional view, FIG. 3 is a detailed view of part B in FIG. 1 (LPCI coupling), FIG. 4 is an overall view of the bellow according to the present invention, FIG. The figure is a detailed view of part D in Figure 5, Figure 7 is a sectional view from E to E in Figure 4, Figure 8 is a view from F-F in Figure 4, and Figure 9 is a detailed view of part G in Figure 4. It is a diagram. 1...Reactor pressure vessel (RPV), 2.../NIRAUD, 3...LPCI coupling, 4...Bello, 5
...RPV side flange, 6...Nyuroud side flange, 7...Clamp, 8...Sleeve, 4a...
Cover, 4b... Jig insertion hole, 4c... Jig insertion hole, 4d... End fitting, 4e... Bellow welded part, 4f... Welded part of bellow and end fitting 8, 4 g...Welded part of Kahart end fitting, 4h...Backing ring. Figure 2 9 Sugar 4 - is Y551! ] Fig. 6 Fig. 7 ￥58 Kuni No. 9 Procedural Amendment (m”t3) 1977., 2+1 1+9 ・1・1i′1 table reference Sho+11ri 6f1-11f, 1゛1 Application No. 1927δ ,3
No. - Name of the invention Name 1.+1 for making a joint supplementary 11 for a nuclear reactor cooling system! -'Jun-i? Patent applicant 11 pieces Marunouchi-5-1, Chiyo 111-ku, Tokyo PI +j, l', +l (l・Co., Ltd. II F+
, 'ξ Manufacturing Representative ゛ 3 1) Shigeru Katsu Address: 2-41-8 Kameido, Koto-ku, Tokyo Name:
Zensha Co., Ltd. Okuda Sokape 1-・Mushi Marunouchi, Chiyotn-ku, Tokyo-'T'V
- Full text of the specification subject to amendment No. 15 No. 1 and the corrected drawing specification Title of the invention Reactor cooling system joint Claim 1, Reactor cooling system nozzle provided in a reactor pressure vessel and the interior of the reactor pressure vessel A joint for a nuclear reactor cooling system that connects cooling system piping provided in a reactor cooling system, the joint comprising a metal bellows formed in multiple layers and a cover that surrounds the bellows and is divided into two in the direction of expansion and contraction. . 2. The joint for a nuclear reactor cooling system according to claim 1, wherein the joint positions of the plurality of layers forming the bellows are different from each other. A A joint that connects a reactor cooling system nozzle provided in a reactor pressure vessel and a cooling system piping provided in the reactor pressure vessel, and is a joint that connects an end fitting part extending in the axial direction and the end fitting part of this end fitting part. A pair of coupling rings having a backing 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 at the upper part of the packing ring part, and a backing ring part of each of these coupling rings. The bellows is formed of a plurality of layers and has both ends fitted and fixed thereto, and a pair of covers having jig insertion holes and having one end fixed to the convex portion of each of the coupling rings and covering the bellows. Reactor cooling system joints. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a joint for a nuclear reactor cooling system, and in particular to a joint for a reactor water injection system installed in a reactor pressure vessel such as a low-pressure injection system or a high-pressure injection system, and a nozzle installed in the reactor pressure vessel. Relating to joints for reactor cooling systems used to connect with. Conventionally, slip joints have been common as joints in nuclear reactor cooling systems, and other methods have been to make the joints rigid. In response, there are demands for joints to be featured in order to counteract loads during earthquakes, and there is a desire for joints that are simple and have a high degree of freedom. An object of the present invention is to provide a joint that can meet the above requirements. In order to meet this objective, the joint of the present invention has a bellows structure, and the bellows is made of metal formed in multiple layers. It has been known that metal bellows have been used in nuclear reactors in order to protect against high temperatures or to prevent deterioration caused by the atmosphere. The present invention aims at extending the life of such metal bellows by making them multi-layered. This is because, by making the metal plate multi-layered, the thickness of the metal plate in each layer becomes one-half to one-several fraction of 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 bellows, this bending stress becomes small in inverse proportion to the thickness. The inventors confirmed that a cause of damage to metal bellows is due to repeated bending stress, and came up with the idea of using a multilayer metal bellows. It has been experimentally confirmed that this can ensure a service life of 30 years. Preferred embodiments of the joint according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a sectional view of a reactor pressure vessel equipped with a joint according to an embodiment of the present invention, and the second cause is a plane sectional view of the reactor pressure vessel along the line Yes, Figure 3 is the first
It is a partially notched enlarged view of the recessed part of a figure. In FIG. 1, a reactor pressure vessel 10 is provided with a large number of nozzles such as a steam nozzle 14 and a differential nozzle 16 in addition to an LPCI nozzle 12. And reactor pressure vessel 1
0 contains a reactor core 20 surrounded by a shroud 18. Inside this core 20, an upper lattice plate 22 is provided.
, a core support plate 24 , and a number of fuel assemblies 28 supported by stubs 26 are arranged, and low-pressure water can be injected by LPCI through a joint 28 provided at the upper end of the shroud 18 . As shown in FIG. 2, the reactor pressure vessel 10 and the shroud 18 have circular cross sections and are arranged concentrically. Further, the LPCI nozzle 12 is generally provided on three sides,
Each is provided with a joint 28 and communicates with the interior of the shroud 18. The joint 28 is connected to the reactor pressure vessel 101 as shown in FIG.
The LPCI pipe port 30 of Iil and the pipe port 32 of the shroud 18111 are connected. That is, the joint 28 consisting of the bellows 34 and a pair of covers 36.36 covering the bellows 34 has both ends fixed to the outer peripheral surface of the mounting ring 38, and the mounting ring 38 is a clamp 40.4 having a half-split structure.
2 to the LPCI pipe ports 30 and 32. Note that a spring 44 is inserted into the joint 28. The purpose of this sleeve 44 is to prevent sudden temperature changes from occurring on the bellows 34. Smooth convex portions are formed on the outer peripheral surface of both ends, and these convex portions are slidably fitted into the mounting ring 38. ing. The joint 28, as shown in the partially cutaway front view of FIG.
Bellows 34 and cover 36 are secured to coupling ring 46. A cover 3 covering the bellows 34
6 is divided near the center in the longitudinal direction, and a jig insertion hole 47 into which a jig for suspending the joint 28 is inserted is formed in each part. Note that, as shown in FIG. 9, the coupling ring 46 includes an end fitting part 48 extending in the axial direction and a backing ring part 5 protruding at the upper end of one end of the end fitting part 48 on the opposite side from the end fitting part 48.
0 and a convex portion 52 formed on the upper end fitting portion 48 of this backing ring portion 50. This coupling ring 46 has one end of the cover 36 welded to a convex portion 52 on the outer periphery at a welding portion 54.
The bellows 34 is fitted into the backing ring portion 50, and the beveled end portion of the bellows 34 is welded and joined at a welding portion 56. 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, 62 constituting the bellows 34 are curved to form a cylinder and welded together at the ninth joint along the longitudinal direction, as illustrated by the metal plate 58 in FIG. The welded portion 64 of the metal plate 58, the welded portion 66 of the metal plate 60, and the welded portion 68 of the metal plate 62 are equally arranged at different positions, as shown in FIG. The jig insertion holes 47 of each cover 36 are provided at four locations as shown in FIG. 7, and six pairs of two holes are provided facing each other. Furthermore, a pair of covers 36.36 have mutually opposing ends (joint 2
8), there is a recess 70.70 as shown in FIG.
is formed. The recesses 70.degree. 70 are formed at the upper and lower portions in FIG. 4, and have corresponding positions, forming a jig insertion hole 72. In the joint of the embodiment configured as described above, the material of the reactor pressure vessel 10 (generally low alloy steel) and the material of the shroud 1 are
Reactor pressure vessel 10 and shroud 18 due to the difference in thermal expansion coefficient due to the difference in material (generally stainless steel)
It is possible to absorb the relative displacement between the That is, when the positions of the reactor pressure vessel 1o and the shroud 18 change relative to each other, the bellows 34 of the joint 28 expands and contracts in the axial direction,
Accordingly, the end of the sleeve 44 moves smoothly within the castle ring 38, and the distance between the pair of cups (-36° 36) also changes, causing the relative relationship between the reactor pressure vessel 10 and the shroud 18 to change. Absorbs displacement. This effect also applies to relative displacement during earthquakes. The bellows 34 is not only protected from rapid thermal changes by the sleeve 44 and cover 36, but also
By adopting a three-layer structure, internal stress can be kept relatively small. Furthermore, since the bellows 34 is fitted into the backing ring portion 50 of the coupling ring 46, when a large internal pressure is applied, the bellows 34 is pressed against the backing ring portion 50, forming the bellows 34. It is possible to prevent the metal plates 58, 60, 62 from peeling off. The joints (welded parts 64, 66, 68) of the metal plates 58, 60, 62 are arranged so as to be uniformly different from each other, so that the decrease in strength due to the joints is minimized. Furthermore, the cover 36 is provided with a jig hole 47.72, so that a jig for hanging the joint 28 can be inserted into the jig insertion hole 47.72 during maintenance, inspection, etc. of the reactor pressure vessel 10. Can be easily inserted and hung. 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. As explained above, according to the present invention, the low pressure water injection pipe (LPCI) provided in the reactor pressure vessel and the pipe port of the sheroud can be easily connected. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a reactor pressure vessel provided with an embodiment of the joint according to the present invention, and FIG. 2 is a cross-sectional view of the reactor pressure vessel along the line 3 is a partially cutaway enlarged view of part ■ in FIG. 1, FIG. 4 is a partially cutaway front view of the joint of the embodiment according to the present invention, and FIG. FIG. 6 is a diagram showing the joined state of the metal plates constituting the bellows, FIG. 7 is an explanatory diagram of the cover of the joint, FIG. 8 is a view taken in the direction of arrow ① in FIG. 4, Fig. 9 is an enlarged view of part ■ in Fig. 4 of the company. 2B...Joint, 34...Bellows, 36...Cover, 46...Coupling ring, 48...End fitting, J1!1 Item 2nd section 8 4th-hard 1ξ door]

Claims (1)

[Claims] 1. A joint that connects a reactor cooling system nozzle provided in a reactor pressure vessel and a cooling system piping provided in the reactor pressure vessel, which includes a metal bellows formed in multiple layers and a metal bellows surrounding this bellows. A joint for a reactor cooling system that has a cover that is divided into two in the expansion and contraction direction.