JPS59220685A - Pipeline for recirculation circulation of 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] [Field of Application of the Invention] The present invention relates to recirculation piping at a boiling water nuclear power plant, and in particular, to countermeasures against stress corrosion cracking, inspection performance, ease of installation, and use in limited spaces during modification. This invention relates to a piping structure suitable for dealing with.

[Background of the invention]

Conventional recirculation piping will be explained below with reference to FIGS. 1 and 2.

FIG. 1 shows an elevational view of the piping system, and FIG. 2 shows a plan view of FIG. 1.

In Fig. 1, l is the reactor pressure vessel (hereinafter abbreviated as RPV), 2 is the main pipe connected directly to the RI (RI) V1, 9 is the main pipe consisting of a straight pipe and an elbow tee, and 3 is the main pipe for carrying the coolant. A pump and motor for forced circulation; 4 is a main pipe that guides the coolant pressurized by the pump 3 to RP'V;5;
is a cross for branching from the main pipe 4, 6 is a distribution pipe distributed from the main pipe 4 and the cross 5, and 7 is a cross for the cross 5
The reducer 8 attached to the top of the pipe 6 indicates a riser pipe that leads the coolant (iRPVIK) from the distribution pipe 6.

The 6th part of the distribution pipe is connected to the nozzle holder 9 in order to branch to the riser pipe 8.
The structure requires

The cut riser pipe 8 and main pipes 2 and 4 have standard dimensions. It is a welded structure consisting of straight pipes and joints.

10 indicates the pump 3 inlet/outlet valve.

FIG. 2 shows the planar configuration of the vJ1 diagram.

The configuration of the main piping 2 and 4, pump 3, etc. is as shown in the figure, due to the ease of separation, installation, and assembly with the RP V 1.

The conventional technology has the structure and configuration as described above.
:9, There were the following drawbacks.

(1) From the perspective of stress corrosion cracking in domestic and overseas plants, the weld line has a standard size and structure.
There is a concern that the use of S304 is extremely likely to cause stress corrosion cracking due to the combination of three conditions: crystal tensile residual stress in the welded area, material, and environment.

(2) As a countermeasure against corrosion due to stress during low-speed operation, the adoption of low-carbon stainless steel is promoted, and as a result, the material is replaced at every inspection.

In this case, the installation space is different from the installation space at the time of construction, and the arrangement and settings of other equipment and equipment make it difficult to carry and install the replacement piping material into a very narrow and limited space. It is necessary to simplify the pipe piping route and improve installation ease.

[Object of the Invention] The present invention aims to eliminate the drawbacks of the prior art described above, and provides an arrangement #structure f: which is improved and aims to improve the reliability and workability of a piping system.

[Summary of the invention]

The characteristics of the present invention are that stress corrosion cracking-resistant materials are used to prevent stress corrosion cracking of pipe welds in existing plants, and that pipe parts are integrally forged and bent pipes are formed by high-frequency bending. By making improvements such as reducing the number of welded parts, and reducing the space required for delivery and installation of the piping system, the piping structure has been designed with consideration to workability such as periodic inspection and modification, and the usability of limited space. be.

[Embodiments of the invention]

An embodiment of the invention is shown in FIGS. 3 to 5.

Figure 3 shows a structure that improves the conventional distribution pipe structure, which has a complicated structure containing curved pipes with large diameter curvatures and is difficult to manufacture and install. The structure of the distribution pipe is shown.

The structure of this embodiment is that the conventional large-diameter curvature blood vessel is replaced by a high-frequency bent tube without large-diameter curvature, and the riser tube is also made of the high-frequency bent tube. It is an integrated system. In order to achieve the above structure, we made the structure of the cross section branching from the main pipe double to simplify the shape.

In FIG. 3, 11 is a double cross with a reducer, 1
2 shows a high frequency bent pipe for distributing p to the double cross 11 with a reducer.

The high-frequency bending pipe 12 is manufactured in advance by high-frequency bending so that the plate thickness on the outer periphery of the bending part does not decrease due to the bending process. Cooled by air cooling or rapid water cooling, and then subjected to solution heat treatment at a temperature around 1100C.

In addition, double crosses with reducers are manufactured by making a special original shape from the molten ingot, and then making it into the final shape by one-piece molding or casting that satisfies the standard dimensions and shape by drawing out the branches or by machine drilling. Similar in shape to the above-mentioned high-frequency bent pipe, it has been subjected to solution heat treatment.

FIG. 4 shows the detailed elevation view 1 of FIG. 3. The distribution pipe consists of an upper riser pipe and a lower riser pipe, and the reducer is directly connected to each branch of the motorcycle cross by welding. In this case, the relative spacing between the upper and lower riser pipes is such that it allows ultrasonic flaw detection during the service life of each welded portion.

FIG. 5 shows details of the double cloth with reducer according to the present invention.

The structure has dimensions and shape according to the standard, and T2 is installed at each end on the reducer side and at the cross distribution branch to allow for ultrasonic flaw detection during service life. This is a joint with a one-piece pipe section that has a dimension (equivalent to about 5 times the plate thickness).

゛In addition, the base of the branch has a thick structure that satisfies the reinforcement (strength) of the hole drilled in the plate.

In the distribution piping structure of the present invention, the length of the rising part of the horizontal portion of the distribution piping is changed, and the length of the riser pipe is changed by eliminating the welded portion of the riser pipe. (See Figure 6) In addition, in the distribution pipe structure of the horizontal part as shown in Figures 7 to 9, the 7'C structure (Figure 7), 9
Structure with a bending angle of 0° or more (Fig. 8) Furthermore, R
A structure (Fig. 9) in which the horizontal dimensions of each of the riser pipes from P to υ are connected by a double cross with a reducer can also be considered as a part of the application/modification of the present invention. In addition, when the cross section with a reducer of the present invention uses a reducer and a cloth each having a welded structure, or when the cross section with a reducer is welded to the cross section with a reducer as shown in FIG. 10 (the manufacturing method is the same as the cross section with a reducer), Even if the structure is substantially the same as that shown in the drawings, it shall be considered as part of the present invention.

〔Effect of the invention〕

Since the present invention has the above-described structure e configuration, the following effects can be achieved.

(1) By adopting a double cross with a reducer, the manufacturability of distribution piping, which was traditionally made internally, is greatly improved.

(2) By making the pipe diameter of the distribution pipe and the riser pipe the same, manufacturing man-hours and materials can be reduced by 41+lli.

(,3) Conventional grooves are also used when modifying plants in operation;'
Since the structure is Jl''-11!+ compared to the if ring header, the ease of transport and installation within a limited space can be greatly improved.

[Brief explanation of drawings]

Figure 1 is an elevation view of the circulation piping of the conventional structure, and Figure 2 is the
Fig. 3 is a plan view of the distribution pipe according to the embodiment of the present invention, Fig. 4 is an elevation view of Fig. 3, Fig. 5 is a sectional view of the 21h cross with reducer, Fig. 6 is a piping elevation view of an application example of the present invention, FIGS. 7 to 9 are plan views of the application example, and FIG.
Figure 0 is a sectional view of the cloth with a reducer. 1...■tP■, 5...Cross, 6...Large curvature curved pipe, 7...Reducer, 8...Riser pipe, 11...
・・Register wind-sa V, r; Leap V 60th δ Mouth 9 (2) Kaya 10 mouths

Claims (1)

[Claims] 1. For the reactor recirculation system piping in boiling water nuclear power plants, use all stress corrosion cracking resistant materials and adopt curved pipes made by integral forging of piping parts and high-frequency bending. Circulatory system piping.