JPS60161593A - Piping structure of recirculation system, etc. for 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 a piping structure such as a nuclear reactor recirculation system, and in particular, to a piping structure in which three branch pipes of different diameters are connected to a main pipe to form a cross shape. This article relates to piping structures such as nuclear reactor recirculation systems with improved parts.

[Technical background of the invention and its problems]

Generally, a nuclear power plant has a reactor system such as a reactor recirculation system, and is equipped with various piping equipment.

For example, a nuclear reactor recirculation system forcibly circulates coolant to the reactor core to extract the heat generated in the reactor core, effectively generating steam, and changing the flow rate of the reactor core coolant as appropriate. Heat output (steam generated ft) t-controlled. For this purpose, the reactor recirculation system is provided with two independent circulation piping systems for forced circulation of the coolant.

This circulation pipe uses a recirculation pump to raise the pressure of reactor water taken out from the reactor pressure vessel to a predetermined pressure, and then supplies the reactor water as pump driving water to the numerous generators installed inside the reactor pressure vessel. It is supposed to be done. In order to evenly distribute drive water to half of all jet pumps using one system of circulation piping, headers are provided in the circulation piping to distribute drive water in appropriate directions.

The header has a plurality of live pipes, for example, five live pipes that distribute the fluid from the circulation pipe in an appropriate direction, and the tip of each of these riser pipes branches into two, and each of these branch ends is connected to the suction port of the jet pump. connected to each side. Therefore, one live pipe supplies driving water to 92 jet pumps, and five live pipes supply driving water to half of all the jet pumps, for example, 10 jet pumps.

Incidentally, the piping branch portion of the header is formed in a cross shape as shown in FIG. That is, a horizontal branch pipe 2 is connected to the tip of the main header pipe 1 connected to the discharge port of the circulation pipe so as to be perpendicular thereto, and #1 of this horizontal branch pipe 2
A central riser pipe 3A rises from approximately the middle portion, and this central live pipe 3A is disposed opposite to the head main pipe 1. Therefore, the area around the piping branch portion of the head main pipe 1 to which the horizontal branch pipe 2 and the central two-seater pipe 3A are respectively connected forms a cross shape as shown in FIG. Each eccentric part of this cross-shaped pipe branch is formed with a curved part 4 that bulges toward the center of the pipe branch, and a cone whose diameter gradually decreases as it goes in the fluid flow direction of the central live pipe 3A. A central live pipe 3A is connected to the tip of the header main pipe 1 via a table-shaped reducer 5 to smooth the flow of fluid at the pipe branch. The inner diameters of these horizontal branch pipes 2 and the central riser pipe 3A are both formed to be smaller than the inner diameter of the main header pipe 1, and are connected concentrically to the main header pipe 1 as shown in the central riser pipe 3AFi@2 figure. The pipe centerline OA of the central riser pipe 3A coincides with the pipe centerline OB of the header main pipe 1. On the other hand, the horizontal branch pipe 2 has its pipe center line 0C-OD connected to the header main pipe 1 at a required angle with the pipe center OB of the header main pipe 1 as the center, and both left and right horizontal branch pipes 2A and 2B are formed so that the expansion angle A is 180°.

In this way, since the pipe center line OA of the central riser pipe 3A coincides with the pipe center line OB of the header main pipe 1, if there is no turbulence in the fluid flow in the header main pipe 1, the central riser 13A and the horizontal branch pipe 2 can maintain a constant value.

However, in general, turbulence occurs in the fluid flow within the header main pipe 1 and at piping branch parts due to the curved portion 4 etc. The water does not always coincide with the road center line OB and is divided into each branch pipe. In particular, when the left and right horizontal branch pipes 24, 24 are connected to the header main pipe 1 at a required angle of expansion, a swirling flow is generated in the fluid flow in the left and right horizontal branch pipes 2A and 2i. For this purpose, the center of fluid flow in the header main pipe 1 is
There was a problem in that W was deviated to the lower ID side of the inner circumferential wall in the header main pipe 1, and the flow rate distribution ratio to the horizontal branch pipe 2, central riser pipe 3A, etc. fluctuated, making it impossible to maintain a constant value. . Therefore, in a nuclear reactor recirculation system provided with a header having such a conventional piping structure, there has been a frequent problem that it is not possible to stably supply equal driving water to each of a large number of jet pumps.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is a piping structure for a nuclear reactor recirculation system, etc. that stabilizes the fluid flow in the main pipe and always maintains the distribution ratio of the flow rate to each branch pipe at the piping branch. The purpose is to provide

[Overview of the invention]

In order to achieve the above-mentioned object, the present invention is configured as follows.

On the left, the Ishioka horizontal branch pipe connects multiple branch pipes with different diameters to the main pipe and diverts the fluid from the main pipe to the side in the flow direction, and the straight branch is placed opposite the main pipe and directs the fluid forward. In a piping structure such as a pipe and a non-pipe system, the pipe center of the straight branch pipe is eccentric in the radial direction with respect to the pipe center of the main pipe.

[Embodiments of the invention]

Hereinafter, a case in which an embodiment of the present invention is applied to a nuclear reactor recirculation system will be described with reference to FIGS. 3 to 6.

FIG. 3 is a schematic front view showing the overall configuration of the reactor recirculation system, and reference numeral 10 in the figure indicates a reactor pressure vessel. A reactor core 11 is housed within the reactor pressure vessel 10 and is submerged with reactor water 12 . In the down cam part (annular part) between the cylindrical core shroud that surrounds the outer periphery of the reactor core 11 and the inner circumferential wall of the reactor pressure vessel 10, a large number of jet pumps 13, for example, several jet pumps 13, are arranged annularly at equal intervals. It is set up. On the other hand, the circulation piping 14 that once takes out the reactor water 12 to the outside of the reactor pressure vessel 10 and returns it to the inside is connected to two systems in the reactor containment vessel (not shown) that houses the reactor pressure vessel 10. are provided independently from each other. A recirculation pump 15 is interposed in the middle of the circulation pipe 14, and this circulation pipe 1
The end of the suction port 4 is connected to the lower part of the reactor pressure vessel 10, and reactor water 12 is forcibly taken out to the outside. On the other hand, the discharge port end of the circulation pipe 14 is connected to the suction port side of the jet pump 13 via a header 16, and gate valves 17 are interposed before and after the recirculation pump 150, respectively. Therefore, the reactor water taken out from the lower part of the reactor pressure vessel 10 is guided through the circulation pipe 14 to the recirculation pump 15, where it is pressurized, and then diverted to branch pipes as appropriate at the header 16. The water is supplied to each jet pump 13 as pump driving water. The flow rate control of this pump driving water is performed by changing the pump flow rate of the recirculation pump 15.

The header 16 is configured as shown in FIG.
It has a header main pipe 18 to which four discharge port ends are connected.

A horizontal branch pipe is connected to the tip of the header main pipe 18 so as to be perpendicular thereto, and a plurality of live pipes 19, for example, five live pipes 19, are respectively erected from the upper surface of the horizontal branch pipe rib. The inner diameters of the live pipes 19 and the horizontal branch pipes are smaller than the inner diameter of the header main pipe 18, so that the fluid flow rate from the header main pipe 18 is evenly distributed to each branch pipe. The horizontal branch pipe is curved in the direction of its pipe axis, and is bent into a semi-annular shape so as to surround half the outer periphery of a core shroud (not shown). The tip of the live tube 19 further branches into two branches, and each branch end is connected to the suction port side of the jet pump 13, respectively. That is, one system of circulation piping 14 includes five live pipes 19.
Drive water is evenly supplied to half of all the jet pumps 13, for example, 10, through the headers 16t which are branched into the headers 16t.

Among the live pipes 19, the pipe branch s rises from the middle part in the axial direction of the horizontal branch pipe connection, and the central live pipe 19A, which is disposed facing the header main pipe 18, is connected to the header main pipe 18.
As shown in FIG. 5, B is formed in a substantially cross shape and is configured to divide the fluid from the header main pipe 18 into three directions: left, right sides, and front. The corners of this cross-shaped piping branch B form curved parts 21 each having a sieving surface so as to bulge toward the center of this branch B, and the diameter thereof gradually decreases as it goes in the fluid flow direction. Central live pipe 19A via a truncated conical reducer n
is connected to the tip of the header main pipe 18 to facilitate fluid division within the pipe branch B.

As shown in FIG. 5, the horizontal branch pipe has a left horizontal branch pipe 2OA and a right horizontal branch pipe 20B that extend from the outer circumferential surface of the tip end of the header main pipe 18 to the left and right sides (radial direction), respectively. Canal center line QC, O of both limb canals 20A', 2t)B
D intersects the pipe center line OB of the header main pipe 18 in the vertical direction.

Also, the rain center line OC of both horizontal branch pipes 2OA and 20B.

The expansion angle of the OD is 180° as shown in FIG.

On the other hand, the pipe center line OA of the central riser pipe 19A is perpendicular to the plane including the pipe center lines QC and OD of the horizontal branch pipes and the pipe center line OB of the header main pipe 18 (see the fifth factor). It is eccentric upwards. That is, as shown in FIG. 6, the pipe center line OA of the central riser pipe 19A is vertically displaced upward with respect to the pipe center line OB of the header main pipe 18. As a result, when a secondary flow such as a swirling flow occurs in the fluid such as driving water in the header main pipe 18, since the center of the central riser pipe 19A is eccentric with respect to the center of the main header pipe V18, Center of fluid flow in header main pipe 18 OK
is displaced in the eccentric direction of the central live pipe 19A, and the fluid flow in the header main pipe 18 is maintained stably due to the wall anchoring effect of the flow by the inner circumferential wall portion 18U of the header main pipe 18. In addition, when a swirling flow occurs in the header main pipe 18 in water-splicing pipe addition, the lower part 18D of the inner circumferential wall of the header main pipe 18
Due to the swirling flow generated by the vortices, the curved part 21 of the piping connection part can maintain a stable "bending" without being affected by turbulent flow. Thereby, the fluid flow within the header main pipe 18 can be stabilized, and the flow rate distribution ratio between the central riser pipe 19A and the horizontal branch pipes can always be kept constant.

Therefore, if the piping branch B configured in this manner is applied to the header 16 of the reactor recirculation system, it is possible to stably supply drive water at an equal flow rate to each of the jet pumps 13.

In addition, although the above-mentioned embodiment described piping arranged in a nuclear reactor recirculation system, the present invention is not limited to this system, and can be used not only in other nuclear reactor systems but also in other industrial plants. It can also be applied to piping in.

〔Effect of the invention〕

As explained above, the reactor recirculation system piping according to the present invention has a cross-shaped branch pipe section in the circulation piping for forcibly circulating reactor water in the reactor pressure vessel. The live pipe has a riser pipe rising in substantially the same direction as the main pipe, and the center of the live pipe is eccentric in the radial direction with respect to the center of the main pipe. Therefore, in the present invention, even if the fluid generates a secondary flow such as a swirl flow in the main pipe, the fluid flow is stabilized in the main pipe due to the wall-clamping effect of the inner circumferential wall in the eccentric direction of the riser pipe, and each branch such as the live pipe The diversion of fluid into the tubes is kept constant. As a result, driving water can be evenly supplied to the jet pump.

[Brief explanation of the drawing]

Figure 1 is an enlarged front view of a piping branch in a conventional piping structure such as a reactor recirculation system, Figure 2 is an enlarged bottom view of a piping branch, and Figure 3 is an atom of a typical nuclear power plant. A schematic front view of the reactor recirculation system, Figure '4 is a front view of the reactor recirculation system piping with a part of the header omitted, and Figure 5 is a schematic front view of the reactor recirculation system piping related to this launch. Enlarged front view of main parts of structure,
Figure 6 is an enlarged bottom view of the support section. 1.18... to □ Ladder main pipe, '2.20... Horizontal branch pipe, 3.19... Riser pipe, 3A, 19A... Central riser pipe, 10... Reactor pressure vessel, Pipe 1...Reactor core, 12...Reactor water, 13...Jet pump, 14
...Circulation piping, 15...Recirculation pump, 16...
Header, 17... Gate valve, OA... Pipe center of central live pipe L on... Pipe center line of header main pipe, QC
, OD...Pipe center line of the horizontal branch pipe, OW...Center of fluid flow in the header main pipe. Representative Patent Attorney Kensuke Chika (and 1 other person) Figure 2 Figure 3 Figure 4 Figure 0, A) 8 Figure 6

Claims (1)

[Scope of Claims] 1. A horizontal branch pipe that connects a plurality of branch pipes with different diameters to the main pipe and separates the fluid from the main pipe to the sides in the flow direction, and a horizontal branch pipe that is disposed opposite to the main pipe and separates the fluid from the main pipe. In a piping structure such as a nuclear reactor recirculation system having a straight branch pipe that allows fluid to proceed straight forward in the flow direction, the pipe center of the straight branch pipe is made eccentric in the radial direction with respect to the pipe center of the main pipe. Features piping structure such as reactor recirculation system. 2. A piping structure such as a nuclear reactor recirculation system according to claim 1, wherein the inner diameter of the different diameter branch pipe is smaller than the inner diameter of the main pipe. 3. A piping structure for a nuclear reactor recirculation system or the like according to claim 1, wherein the center of the straight branch pipe is eccentric upward in the vertical direction with respect to the center of the main pipe.