JPS6088206A - Flow fluctuation supplessing method and construction of branch pipes in recycling piping system in bwr plant - Google Patents

Abstract

PURPOSE:To prevent fluctuation of branched fluid flow rate in a piping system in which a header has branch pipes provided with fluid outlets at least in three directions, by providing a swirlling flow inducing device on at least a side of the branch pipes or the vicinity. CONSTITUTION:In a piping system in which a cross branch pipe 5 connected to a header 4 has connection of horizontal branch pipes 6, 6 and a vertical riser pipe 8, the longitudinal section cofiguration of a reducer 11 connected right above the cross branch pipe 5 is manufactured to have a steep slanting surface on a side and a vertical surface on the opposite side in the same manner as the inner surface of the branch pipe 5. By this configuration, the outlet center point C1 and the inlet center point C2 are made eccentric and the eccentric reducer 11 comes to have a function of swirlling flow inducing device. Thus, on the vicinity of the cross branch pipe 5 a stable counterclockwise swirlling flow is produced and smooth branching of the flow to the horizontal branch pipe 6, 6 is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piping system for a nuclear power plant, and in particular to a piping system for a nuclear reactor recirculation system, which is a system that adjusts the flow rate of coolant supplied to the reactor core in a boiling water reactor. The present invention provides a method for suppressing flow rate fluctuations related to the internal flow of the recirculation system piping (hereinafter referred to as recirculation system piping) and the internal flow of the piping system.

A recirculation system piping according to the prior art is shown in FIG.

1 indicates the reactor pressure vessel. Below, reactor pressure vessel 1
The recirculation system piping installed in the recirculation system has the following configuration. Return bent pipe section 8, return bent pipe section 9 with 1,100-character pipe, inlet valve 13, pump 11 for forced circulation of cooling water in the reactor pressure vessel 1, motor 12 for driving the pump 11, discharge Pipe 2, outlet valve 14, main pipe 3, cross branch pipe (hereinafter referred to as cross) 4, header bent pipe 5, reducer 15,
It is constructed as shown in FIG. 1 from a 1,000-character branch 6 and a riser pipe 7. When operating a boiling water reactor,
Cooling water in the reactor pressure vessel 1 flows through the recirculation system piping.

That is, the pump 11 is driven, and the cooling water in the reactor pressure vessel is pumped through the bent pipe section 8, the bent pipe section 9 with a 101-ji pipe, and the inlet valve 13.
, the suction pipe 10, the pump 11, the discharge pipe 2, the outlet valve 14, and the main pipe 3, and then flow into the cloth 4. The flow path of the cooling water is divided by the cross portion 4, and a portion of the cooling water is directly discharged from the cross portion 4 through the reducer 15 and the riser pipe 7 into a jut pump (not shown) in the reactor pressure vessel 1.

The remaining cooling water, which is the majority, is branched from the cross 4 by a plurality of 100-1-shaped pipe branches 6 disposed in the header curved pipe 5, and is discharged into the jut pump via the riser pipe 7.

FIG. 2 shows details of the cross section 4.

FIG. 3 is a side and plan view thereof. The flow fo from the main pipe 3 is the cross section 4, and the flow f in the direction of the header curved pipe 5.
1, f2, and a branched flow of f3 toward the reducer 75 direction. As shown in Figures 4 and 5, the flow in this branch pipe is divided into two types: a flow with a swirl in which the vortex center passes through the header curved pipes on both sides (Figure 4), and a flow with a large swirl in the center of the branch pipe. In some cases, the flow exhibits a highly irregular flow within the reducer section 15 (FIG. 5), with no flow accompanied by alternating barbs. In other words, the flow inside the cross section is a swirling flow (
The vortices that cause vortices (Fig. 4) occur and disappear, and the flow in the pipe including the cross section becomes unstable, and the flow resistance in the f1, f2, and f3 directions (Fig. 2) at the branch section increases. As a result, the liquid volume distribution and pressure loss to each riser pipe may fluctuate irregularly. When such a flow fluctuation phenomenon occurs, the amount of cooling water flowing into the reactor fluctuates, which may lead to fluctuations in the output of the BWR, which is a problem.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, and to effectively suppress flow fluctuations in a BWR recirculation piping system with a simple structure; It is an object of the present invention to provide a boiling water nuclear power plant that can operate more stably without system flow rate fluctuations.

A feature of the present invention is that the flow within the recirculation piping system becomes unstable due to the generation and disappearance of vortices inside the cross-branch pipe, which is the intersection of the main pipe, header bend pipe, and riser pipe. As a means to eliminate this unstable flow, we created a stable swirling flow in the cross-branched pipe to stabilize the flow in the recirculation piping system. .

Examples of the present invention will be specifically described below. FIG. 6 is a schematic diagram of a cross portion of a recirculation piping system according to a preferred embodiment of the present invention. Components that are the same as those of the conventional example (FIG. 3) are designated by the same reference numerals. The reducer 15 connected to the opening facing the main pipe 3 has an upstream opening center C1 and a downstream opening center C.
This is an eccentric retainer in which the straight line connecting 2 is inclined with respect to the bottom surface.

Since this embodiment is configured as described above, a stable swirling flow can be provided by the flow branching to the header curved pipe rather than the flow deflection passing from the main pipe to the reducer section. This makes it possible to maintain the flow within the cross section in a hydrodynamically stable state, with no fluctuations in the flow resistance to each direction at the cross branch, and no fluctuations in the flow distribution to each riser pipe. It becomes constant, and fluctuations in the BWR output are prevented. Since the flow inside the reactor is also stabilized, it becomes possible to provide a BWR plant with high reliability in terms of structure and strength.

FIG. 7 is a schematic diagram of a recirculation system branch piping in which the reducer section is a cross-branched pipe. In the case of this embodiment, since the opening that branches into the header curved pipe is created in the eccentric resistor part,
Since the vortex core passing through the header curved pipe is less likely to shift in the downstream direction (in the direction of the riser pipe), a more stable swirling flow can be provided, so that exactly the same effect as above can be achieved.

Fig. 8 shows an example in which the axial center C3 of the header bent pipe and the axial center C4 of the main pipe are shifted from each other in the cross section 4, and the swirling flow at the branch section can be stabilized to rotate in one direction. Therefore, the same effect as above can be obtained.

FIG. 9 shows the above example in which the reducer is further changed to an eccentric reducer.

FIG. 10 is a schematic diagram of a recirculation system piping structure in which the pipe axis center C5 of the riser pipe 7 and the pipe axis center C6 of the main pipe 3 intersect, and the vortex is centered in the pipe axis direction of the header curved pipe 5. This is an example of a flow path configuration that is likely to generate a swirling flow.

FIG. 11 is a schematic diagram of recirculation system piping having a structure in which guide vanes 16 are provided to generate a swirling flow in the cross section flow path. In this embodiment, the guide vanes also provide a swirling flow with a constant swirling direction. can be generated stably, so the same effect as above can be achieved.

As described above, according to the present invention, it is possible to stabilize the generation of swirling flow at the cross branch with an extremely simple structure without significantly changing the structure of the conventional BWR recirculation system piping. , it is possible to eliminate flow rate fluctuations in the recirculation system and provide a stable BWR plant with no output fluctuations.

[Brief explanation of the drawing]

Figure 1 is a structural diagram of the conventional recirculation system piping for a boiling water reactor.
Fig. 2 is a structural diagram of the cross-branched pipe shown in Fig. 1, Fig. 3 is a side view of the cross-branched pipe shown in Fig. 2, and Fig. 4 is an explanatory diagram of the swirling flow generated in the cross-branched pipe section. , FIG. 5 is an explanatory diagram showing the internal flow situation when the swirling flow in the cross-branched pipe disappears, and FIG. 6 is a structural diagram of the cross-branched pipe in the recirculation system piping according to a preferred embodiment of the present invention. , FIG. 7 is a structural diagram of a cross branch pipe showing another embodiment of the present invention shown in FIG. 6, FIGS. 8 and 9 are structural diagrams of a cross branch pipe showing other embodiments of the present invention, FIG. 10 is an explanatory diagram of another embodiment, and FIG. 11 is another embodiment of the present invention, which is a structural diagram of a cross branch section in which a swirling flow generating device is disposed in the pipe. 1...Reactor pressure vessel, 3...Main pipe, 4...Cross branch pipe, 5...
Header bent pipe, 7... riser pipe, 11... pump, 12...
Motor, 15...Register, 16...Guide vane. Agent Patent Attorney Akio Takahashi

Claims (7)

[Claims] 1. In the cross branch having openings on all sides, the first opening is connected to a main pipe connected to a recirculation pump outlet;
The opening facing the first opening has a reducer portion in which the cross-sectional area of the flow path gradually decreases, and a riser pipe is formed integrally with the reducer at a portion of the reducer portion where the cross-sectional area of the flow path is the smallest; In addition, in a recirculation piping system of a boiling water nuclear power plant (hereinafter referred to as BWR), a header bent pipe is connected to two openings of the cross branching part to which the main pipe and the reducer are not connected. , the flow at the cross branch always exhibits a stable swirling flow in a fixed direction, and the vortex center passes through the header curved pipes arranged symmetrically on both sides of the main pipe, thereby stabilizing the recirculated cooling water. A method for suppressing flow rate fluctuations in BWR recirculation piping and piping systems, characterized by causing the flow to flow. 2. In the cross branch having openings on all sides, the first opening is connected to a main pipe connected to a recirculation pump outlet;
The opening facing the first opening has a reducer portion in which the cross-sectional area of the flow path gradually decreases, and a riser pipe is formed integrally with the reducer at a portion of the reducer portion where the cross-sectional area of the flow path is the smallest; In addition, in a recirculation piping system of a boiling water nuclear power plant (hereinafter referred to as BWR), a header bent pipe is connected to each of the two openings of the cross branch part to which the main pipe and the reducer are not connected. , a BWR characterized in that the resistor of the cross-branched pipe portion is constituted by an eccentric resistor that is eccentric with respect to the axis of the main pipe.
Recirculation piping system. 3. 3. The BWR recirculation piping system according to claim 2, wherein said cross-branched pipe section is configured by disposing two openings connected to said header bent pipe in said eccentric reducer section. 4. In the cross branch having openings on all sides, the first opening is connected to a main pipe connected to a recirculation pump outlet;
The opening facing the first opening has a reducer portion in which the cross-sectional area of the flow path gradually decreases, and a riser pipe is formed integrally with the reducer at a portion of the reducer portion where the cross-sectional area of the flow path is the smallest; In addition, in a recirculation piping system of a boiling water nuclear power plant (hereinafter referred to as BWR), a header bent pipe is connected to each of the two openings of the cross branch part to which the main pipe and the reducer are not connected. . A recirculation piping system for a BWR, characterized in that the axis of the header bent pipe of the cross-branched pipe section and the axis of the main pipe are shifted from each other. 5. 5. The BWR recirculation piping system according to claim 4, wherein in the cross branch pipe section, the reducer is an eccentric reducer. 6. In the cross branch having openings on all sides, the first opening is connected to a main pipe connected to a recirculation pump outlet;
The opening facing the first opening has a reducer portion in which the cross-sectional area of the flow path gradually decreases, and a riser pipe is formed integrally with the reducer at a portion of the reducer portion where the cross-sectional area of the flow path is the smallest; In addition, in a recirculation piping system of a boiling water nuclear power plant (hereinafter referred to as BWR), a header bent pipe is connected to each of the two openings of the cross branch part to which the main pipe and the reducer are not connected. B, characterized in that the axial center of the riser pipe connected to the cross branch pipe section is configured to intersect with the axial center of the main pipe.
WR recirculation piping system. 7. In the cross branch having openings on all sides, the first opening is connected to a main pipe connected to a recirculation pump outlet;
The opening facing the first opening has a reducer portion in which the cross-sectional area of the flow path gradually decreases, and a riser pipe is formed integrally with the reducer at a portion where the cross-sectional area of the flow path of the reducer portion is the minimum, In addition, in a recirculation piping system of a boiling water nuclear power plant (hereinafter referred to as BWR), a header bent pipe is connected to each of the two openings of the cross branch part to which the main pipe and the reducer are not connected. . A BWR recirculation piping system, characterized in that a swirling flow generator is disposed inside the cross-branched pipe flow path.