JP2008157972A - Inlet structure for coolant core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make proper the passage pressure loss factor in an inlet orifice or the like disposed in a portion surrounded by a reinforcing beam and uniform the flow rate in fuel assemblies, thereby improving cooling capability. <P>SOLUTION: An inlet structure for coolant core includes: a core support plate 6; a reinforcing beam 7 supporting the core support plate 16 from a lower portion thereof; a plurality of control rod guide pipes 10 standing perpendicularly upward from a bottom side of a reactor pressure vessel and having upper end portions fitted respectively to fuel support holes formed to the core support plate 6; a fuel support member 16 inserted into upper end portions of the control rod guide pipes and supported by the core support plate 6 vertically in a core so as to support lower end portions of fuel assemblies 15 arranged in the core; an inlet orifice 19 formed to the fuel support member 16 so as to adjust the flow rate of a coolant flowing into the fuel assemblies 15; and vortex control means for controlling vortex of the coolant flowing into the inlet orifice 19 formed to the fuel support member 16, the vortex control means being provided at a portion on a coolant upstream side of the inlet orifice 19. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for equalizing the flow rate of a coolant flowing in a fuel assembly loaded in a core of a boiling water nuclear reactor, and in particular, a coolant for a fuel support fitting serving as a coolant inlet into the fuel assembly. The present invention relates to a coolant core inlet structure in which a flow rate pressure loss coefficient at an inlet portion is reduced to achieve a uniform flow rate.

  The prior art will be described with reference to FIGS. FIG. 32 is an overall configuration diagram showing a configuration of a reactor pressure vessel of an improved boiling water reactor (ABWR) as an example of a boiling water reactor. In this ABWR, a steam dryer 2, a steam separator 3, an upper lattice plate 4, a core shroud 5, a core support plate 6 and the like are arranged in the reactor pressure vessel 1 from the top. Inside the core shroud 5, several hundred fuel assemblies 17 are vertically arranged in a lattice arrangement, thereby forming a core. Further, a control rod 18 having a function of controlling the reactor power and stopping the reactor in an emergency is introduced from the lower part of the core to the core inlet via the control rod guide tube 10. Further, a plurality of recirculation pumps 8 for circulating the coolant are arranged in the lower part of the reactor pressure vessel 1.

  In such a configuration, during operation, the coolant circulation to the core is performed by the recirculation pump 8 disposed at the lower part of the reactor pressure vessel 1. That is, the coolant rises from the bottom of the core and flows into the fuel assembly 17, is heated in the fuel assembly 17 and rises as a gas-liquid two-phase flow, and the steam / water separator 3 Separated. The steam further rises, moisture is separated by the steam dryer 2, is guided to the main steam pipe 9, and is guided to a turbine (not shown). On the other hand, the water separated from the steam separator 3 and the steam dryer 2 into a single-phase state descends, is led to the recirculation pump 8 via the outside of the core shroud 5, and rises again toward the core. And circulates in the fuel assembly 17.

  FIG. 33 is an enlarged sectional view showing the fuel assembly 17 and its support structure. In the fuel assembly 17, a plurality of fuel rods 12 containing fissile material are arranged in parallel in a vertically long rectangular tube channel box 11 whose upper and lower ends are open, and these fuel rods 12 are placed in the channel box 11. The fuel spacer 13 is supported at a plurality of locations in the vertical direction, and the upper and lower ends of the fuel rod 12 are fixed by an upper tie plate 14 and a lower tie plate 15 through which a coolant can flow. The upper and lower ends of the fuel assemblies 17 are supported by the horizontal upper lattice plate 4 and the core support plate 6, respectively. The coolant flows from the lower tie plate 15, rises in the channel box 11, is heated while passing through the fuel rods 12, and is discharged from the upper tie plate 14 as a gas-liquid two-layer flow.

  The lower end portion of the fuel assembly 17 is supported on the core support plate 6 via the fuel support fitting 16. As fuel support fittings, although not shown, a peripheral fuel support fitting for supporting the fuel assembly 17 alone at the periphery of the core, and four fuel assemblies at the center of the core as shown in FIG. A central fuel support bracket 16 that supports 17 as a set is applied. The former peripheral fuel support fitting has a vertical cylindrical configuration, and the coolant is introduced directly upward from the downward opening, so the structure of the coolant flow path becomes a relatively simple and smooth flow, The flow path pressure loss coefficient and the like are not particularly problematic. On the other hand, in the case of the latter center part fuel support bracket 16 shown in FIG. 33, the four fuel assemblies 17 are supported in a lattice arrangement, and the control rod 18 is inserted into the center part. Therefore, the center fuel support fitting 16 is disposed in the upper end portion of the control rod guide tube 10, and a coolant inlet for introducing the coolant to the outer peripheral surface side of the control rod guide tube 10. 41 opens sideways, and an inlet orifice 19 is provided in the coolant inlet 41. Further, a coolant channel 42 for guiding the coolant flowing in from the coolant inlet 41 to each fuel assembly 17 is formed in the center portion fuel support bracket 16 upward. Therefore, in the case of this center part fuel support bracket 16, after the coolant rises from the lower part of the core, the coolant is introduced to the coolant inlet 41 in a lateral direction and then further vertically upward in the coolant channel 42. It has a structure having a complicated route of changing the direction and flowing to the fuel assembly 17. Hereinafter, in the description of the present invention, the “fuel support fitting” means the central fuel support fitting 16.

  Around the fuel support 16, a vertical plate-like beam plate 7 a that is a beam material of a reinforcing beam 7 that reinforces the core support plate 6 from below is disposed. For this reason, in the fuel assembly 17 supported by the central fuel support bracket 16, the coolant rising by the recirculation pump 8 provided at the lower part of the reactor pressure vessel 1 is applied to the lower surface of the core support plate 6 together. Since it flows in through the gap between the reinforcing beam 7 and the control rod guide tube 10 that are in contact with each other, the streamline has a more complicated structure.

  This point will be described in detail with reference to FIGS. FIG. 34 is an overall view showing the configuration of the core support plate 6 and the reinforcing beam 7.

  FIG. 34A shows a core support plate 6 and a cross beam which is a structural example of the reinforcing beam 7. The core support plate 6 has a horizontal disk shape and has a large number of holes 6 a for mounting the fuel support fittings 16. The reinforcing beam 7 which is a cross beam has a configuration in which a beam plate 7 a made of a vertical plate combined in a square lattice shape is provided as a beam material in a circular frame 20. The upper edge of each beam plate 7a of the cross beam is joined to the lower surface of the core support plate 6 for reinforcement. FIG. 34B shows a reinforcing beam 7 called a single beam as another configuration example. This single beam has a structure in which a circular frame 20 has parallel vertical beam plates 7a and connecting rods 21 orthogonal thereto as beam materials, which are arranged in a square lattice pattern. In the following description, a cross beam excellent in mechanical strength will be representatively described, but the content of a single beam is substantially the same.

  FIG. 35 is an enlarged view showing the arrangement relationship of the fuel support bracket 16, the fuel assembly 17, the control rod 18, and the like arranged inside one lattice space formed by the beam plate 7 a of the reinforcing beam 7 in a plan view. It is. 36 is a detailed view (a cross-sectional view taken along the line A0-A0 in FIG. 33) showing a part of FIG. 35 (the upper right ¼ part divided by the imaginary line A in FIG. 35). FIG. 37 is a sectional view taken along line BB in FIG. 36.

  As shown in FIG. 36, four control rod guide tubes 10 and four fuel support fittings 16 are arranged in a square lattice pattern in one square area C surrounded by the reinforcing beam plate 7a. ing. Each fuel support bracket 16 supports four fuel assemblies 17 at equal intervals in the circumferential direction. Thus, 16 fuel assemblies 17 are arranged in one region surrounded by the reinforcing beam 7a.

  The fuel support bracket 16 has a coolant channel extending from a portion of each fuel assembly 17 that supports the lower tie plate 15 to a position below the core support plate 6, and is used for introducing coolant into the coolant channel. The coolant inlet 41 opens on the side surface of the fuel support fitting 16, and the inlet orifice 19 is provided at the coolant inlet 41. The coolant rises through a gap between the beam 7 a of the reinforcing beam 7 and the control rod guide tube 10 and then flows laterally into the inlet orifice 19.

  When the cross beam shown in FIG. 34 (A) is adopted as the reinforcing beam 7 of the core support plate 6, the reinforcing beam plate 7a is positioned at a corner intersecting at right angles and surrounded by both surfaces. The channel area is narrower, and the channel pressure loss coefficient is larger than the positions other than the corners. For this reason, as it is, the flow rate flowing into the fuel assemblies 17 located at the corners intersecting the reinforcing beam plate 7a at a right angle decreases.

  Therefore, in order to appropriately distribute the flow rate flowing into each fuel assembly 17, adjustment is made by the inlet orifice 19.

The flow rate of the coolant flowing through each fuel assembly 17 is determined based on the flow path pressure loss coefficient determined by the diameter of the inlet orifice 19 near the core support plate 6 and the reinforcing beam plate 7, the structure of the fuel assembly 17, and the like. Is done. Here, the channel pressure loss coefficient is the pressure difference ΔP and flow rate Q in a certain section.

It is a value defined by. Note that the flow rate Q may be a volume flow rate or a mass flow rate.

  Depending on the magnitude of the output generated in the fuel assembly 17, the bubbles generated inside the fuel assembly 17 are also different. As a result, the flow path pressure loss coefficient in the fuel assembly 17 is also different. In the design of a water-type nuclear power plant, the diameter of the inlet orifice 19 is adjusted so that the distribution of the flow rate is uniform when the outputs of the fuel assemblies are the same.

  As described above, the flow rate flowing into each fuel assembly 17 is adjusted by the inlet orifice 19, and the inlet orifice 19 located at the corner that intersects the reinforcing beam plate 7a at a right angle has a flow passage cross-sectional area of Since every corner should be the same, it should be adjusted to the same shape. However, it has been observed that when the inlet orifice 19 having the same shape is installed at the corner portion, the flow rate of the coolant flowing into the fuel assembly 17 adjusted by the inlet orifice 19 is not the same.

  The present invention has been made in view of such circumstances, and has clarified the cause of the non-uniform flow rate of the coolant in the inlet orifice portion of the fuel assembly and the countermeasures, and the flow path pressure loss coefficient in the coolant core inlet structure. An object of the present invention is to provide a coolant core inlet structure capable of optimizing the flow rate and appropriately adjusting the flow rate in the fuel assembly.

  The inventor has observed in detail the coolant flow at the coolant inlet of the fuel support fitting disposed in the portion surrounded by the reinforcing beam plate using the test equipment. As a result, the distance between the beam plate 7a in the horizontal center position of the inlet orifice shown by C in FIG. 36 and the control rod guide tube 10 is controlled with the beam plate 7a in the horizontal peripheral position of the inlet orifice shown in FIG. It is wider than the interval between the rod guide tubes 10. For this reason, the flow path pressure loss coefficient at the position indicated by C is smaller than the flow path pressure loss coefficient at the position indicated by D, and the flow rate of the coolant that rises at the position indicated by C is greater than the flow rate at the position indicated by D. For this reason, the coolant that has risen in the position indicated by C collides with the lower surface of the core support plate 6, resulting in a flow that descends the position indicated by D, which has a small flow velocity. I understood that.

  This phenomenon will be described with reference to FIGS. 38 and 39. FIG. 38 is a schematic cross-sectional view taken along the line B-B of FIG. 36 described above, that is, the inflow state of the coolant in the inlet orifice 19 that opens opposite to the diagonal direction of the beam plate 7a of the reinforcing beam 7 arranged in a square lattice pattern. FIG. 39 is a view showing the flow of the coolant in the front direction of the inlet orifice 19, that is, in the DD section of FIG. 38.

  As indicated by the flow lines 25 in these drawings, the coolant rising from below in the reactor pressure vessel 1 flows as an upward flow into the gap between the beam plate 7 a of the reinforcing beam 7 and the control rod guide tube 10. When a part of the coolant rising along the vicinity of the outer surface of the control rod guide tube 10 reaches the position of the inlet orifice 19, the coolant flows sideways and flows directly into the inlet orifice 19. However, most of the coolant that rises along the beam plate 7a side of the reinforcing beam 7 rises as an upward flow 25a, collides with the lower surface of the core support plate 6, and then downwards at the horizontal peripheral position of the inlet orifice. It becomes the downward flow 25b.

  In the narrow region 22 facing the corners of the two beam plates 7a intersecting at right angles, the positional relationship between the beam plate 7a and the control rod guide tube 10 is symmetric with respect to the horizontal direction. Then, a downward flow 25b descends in the horizontal peripheral position of the inlet orifice, and two vortices 25c are generated toward the inlet orifice 19 to form a so-called twin vortex. At this time, a strong vortex is generated when the difference in flow path pressure loss coefficient between the horizontal center position and the peripheral position of the inlet orifice 19 of the coolant rising between the beam plate 7a and the control rod guide tube 10 is large. . Such formation of the vortex 25c was clearly observed under a flow test simulating an actual shape, for example, under conditions of a pressure of about 7 MPa, a temperature of about 280 ° C., and a flow rate of about 2 m / s.

  It has been found that when the coolant flows into the inlet orifice 19 with such a vortex 25c, the flow path pressure loss coefficient at the inlet orifice 19 increases. Further, the amount of increase in the channel pressure loss coefficient at the inlet orifice 19 varies depending on the state of the vortex. Further, in the case of a twin vortex having symmetry such as the entrance orifice 19 positioned at the corner of the two beam plates 7a intersecting at right angles, the state of the vortex generated by a slight difference in shape within the manufacturing accuracy range. And the amount of vortex fluctuation over time is large. For this reason, the twin vortex state generated by a slight difference in shape at the entrance orifice 19 located at the corner of the two beam plates 7a intersecting at right angles that should produce the same flow path pressure loss coefficient. Changed, and it was found that there was a difference in the channel pressure loss coefficient.

  On the other hand, the inlet orifice 19 at a position not facing the beam plate 7a, that is, the inlet located at the corner of the two beam plates 7a intersecting at right angles on the opposite side of the inlet orifice 19 at the fuel support bracket 16 is provided. In the orifice 19, the control rod guide tube 10 and the flow path width formed by the control rod guide tube 10 at the peripheral position in the horizontal direction of the inlet orifice 19 are not narrow. There is no significant difference in the flow rate of the coolant rising up. For this reason, there is no flow of coolant that collides with the core support plate 6 and descends at the peripheral position in the horizontal direction of the inlet orifice 19, or even if it occurs, it does not flow at a high flow rate. Therefore, strong vortices such as the corners of the two beam plates 7a intersecting at right angles do not occur. Therefore, the increase amount of the channel pressure loss coefficient due to the vortex at the inlet orifice 19 is also reduced.

  In addition, in the inlet orifice 19 at a position rotated by 90 ° about the center of the fuel support fitting from the position of the corner of the two beam plates 7a intersecting at right angles, only one of the horizontal peripheral positions of the inlet orifice 19 is present. A narrow flow path is formed by the beam plate 7a and the control rod guide tube 10, and the other is a relatively wide flow channel formed by the control rod guide tube 10 and the control rod guide tube 10. The coolant flow paths are not symmetrical in the 19 horizontal directions. For this reason, the descending flow of the coolant at the peripheral position in the horizontal direction of the inlet orifice 19 where the flow path is formed by the beam plate 7a and the control rod guide tube 10 becomes faster, and the generated vortex becomes one, Even if one occurs, it becomes a vortex without symmetry. In the case of the vortex having no symmetry as described above, it was found that the change in the state of the vortex due to a slight flow path shape is smaller than that of the symmetric vortex. Therefore, when the coolant flows into the inlet orifice 19 with a vortex, the change in the flow pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path before the inlet orifice 19 intersects at a right angle. It is smaller than the entrance orifice 19 at the corner of the two beam plates 7a.

  Therefore, the inventor stabilizes the flow path pressure loss coefficient generated at the inlet orifice 19 at the corner portion of the two beam plates 7a intersecting at right angles and adjusts the flow rate in the fuel assembly based on the above observation results. In order to be appropriate, it is necessary to control the twin vortex generated at this position. Specifically, (1) the vortex flowing into the inlet orifice 19 is reduced. (2) The present inventors have found that it is effective to suppress the generated vortex, (3) stabilize the generated vortex, and the like.

  The present invention has been made based on the above knowledge, and in the invention according to claim 1, a core support plate provided in a reactor pressure vessel of a boiling water reactor and having a plurality of fuel support holes; A reinforcing beam that reinforces the core support plate from the lower surface side, and a plurality of control rod guide tubes that stand vertically from the bottom side of the reactor pressure vessel and whose upper ends are combined with the fuel support hole portions of the core support plate; A fuel support fitting inserted into the upper end of each control rod guide tube, supported by the core support plate and supporting the lower ends of a plurality of fuel assemblies arranged vertically in the core, and provided in the fuel support fitting In the coolant core inlet structure comprising an inlet orifice for adjusting the flow rate of the coolant flowing into the fuel assembly, vortex control means for controlling the vortex of the coolant flowing into the inlet orifice provided in the fuel support fitting The entrance orif Provided on the upstream side of the scan or the inlet orifice, the vortex control means, the center of the inlet orifice to provide a coolant core inlet structure is disposed structure above the lower end of the reinforcing beam.

  According to a second aspect of the present invention, the vortex control means includes a beam plate asymmetrically with respect to a line connecting the center of the fuel support fitting and the intersection of the beam plates of the reinforcing beam facing the inlet orifice of the fuel support fitting. The coolant core inlet structure according to claim 1, wherein a through hole is formed in a part of the coolant core inlet structure.

  According to the present invention, it is possible to optimize pressure loss at the inlet orifice and the like, and to appropriately adjust the flow rate in the fuel assembly.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. Note that the same or corresponding components as those shown in the conventional example will be described with reference to FIGS. 32 to 39 using the same reference numerals as those shown in these drawings. In the following embodiment, a case where the cross beam shown in FIG. 32A is applied as the reinforcing beam will be described, but the same applies to the single beam shown in FIG.

[First Embodiment (FIGS. 1 to 3)]
FIG. 1 is a side sectional view of a flow path portion showing a coolant core inlet structure according to a first embodiment of the present invention, and FIG. 2 is a perspective view of a core support fitting applied in the present embodiment. 3 (A) and 3 (B) are explanatory diagrams of operation.

  As shown in FIGS. 1 and 2, the coolant core inlet structure of the present embodiment includes a core support plate 6 provided in a reactor pressure vessel of a boiling water reactor and having a plurality of fuel support holes, and the core. A reinforcing beam 7 that reinforces the support plate 16 from the lower surface side, and a plurality of control rod guide tubes 10 that stand vertically from the bottom side of the reactor pressure vessel and whose upper ends are combined with the fuel support hole portions of the core support plate 6. A fuel support bracket 16 inserted into the upper end of each control rod guide tube, supported by the core support plate 6 and supporting the lower ends of a plurality of fuel assemblies 15 arranged vertically in the core, and the fuel support bracket 16 And an inlet orifice 19 for adjusting the flow rate of the coolant flowing into the fuel assembly 15.

  The fuel support bracket 16 includes a fuel support portion 16a that supports the four fuel assemblies 15, and a control rod insertion hole 16b that is located at the center thereof. In such a configuration, the vortex control means for controlling the vortex of the coolant flowing into the inlet orifice 19 provided in the fuel support fitting 16 is provided on the upstream side of the inlet orifice 19. This vortex control means weakens the downward flow of the coolant from the core support plate 6 to the inlet orifice 19, thereby weakening the swirling flow around the substantially horizontal axis toward the inlet orifice 19 to suppress the generation of vortices. To do.

  That is, in the coolant core inlet structure of the present embodiment, the vortex control means sets the length from the lower end of the core support plate 6 to the center position of the inlet orifice 19 of the fuel support fitting 16 as L1, and FIG. ), The quarter arc length c of the outer surface of the control rod guide tube 10 assumed to form a coolant ascending flow path for one inlet orifice 19 and the reinforcing beam 7 surrounding the quarter arc length portion. When the value obtained by dividing the cross-sectional area S of the ascending flow path by the sum (a + b + c) of the horizontal lengths a and b of the beam plate 7a is the inlet flow path representative diameter D1, L1 / D1 is set to 1.7 or more. In addition, the center of the inlet orifice 19 is arranged above the lower end of the reinforcing beam.

  This point will be described with reference to FIG. In FIG. 3B, L1 / D1 is taken on the horizontal axis, and the ratio of flow path pressure loss coefficients of the inlet orifice 19 is taken on the vertical axis, and these relationships are obtained from experimental results. The experiment was performed under conditions of a coolant pressure of about 7 MPa, a temperature of about 280 ° C., and a flow rate of about 2 m / s.

  As a result, as shown in FIG. 3 (B), when L1 / D1 was increased, the ratio of the channel pressure loss coefficient tended to decrease gradually. Then, when L1 / D1 is gradually increased with respect to the current core orifice position where L1 / D1 is about 1.4, that is, the center position of the inlet orifice 19 is set below the core support plate 6, the flow path pressure loss coefficient It can be seen that when the ratio of λ is gradually decreased and L1 / D1 = about 1.7 or more, the rate of decrease in the ratio of the channel pressure loss coefficient becomes gradual and stabilized.

  L1 / D1 is about 1.7, where D1 is 4, the length L1 from the lower end of the core support plate 6 to the center position of the inlet orifice 19 of the fuel support bracket 16 is about 7 cm. From this, it is understood that the ratio of the flow path pressure loss coefficient can be optimized by setting the height of the inlet orifice to a position exceeding about 7 cm below the core support plate 6.

  Therefore, in this embodiment, L1 / D1 is set to 1.7 or more, that is, the length about L1 from the lower end of the core support plate 6 to the center position of the inlet orifice 19 of the fuel support fitting 16 is set to a value exceeding about 7 cm.

  As a result, as shown by the flow lines in FIG. 1, the coolant rising by the recirculation pump becomes the rising flow 25 a rising through the gap between the reinforcing beam 7 and the control rod guide tube 10, and the core support plate 6. After colliding with the lower surface, the downward flow 25b, which is a downward flow, becomes longer than in the prior art. Due to such a long distance movement, the downward flow 25b is attenuated, whereby the swirl flow around the substantially horizontal axis toward the inlet orifice 19 is attenuated, and the generation of vortices is suppressed.

  In a normal design, the height position of the inlet orifice 19 is set to about 7 cm below the core support plate 6 under conditions of a coolant pressure of about 7 MPa, a temperature of about 280 ° C., and a flow rate of about 2 m / s. In contrast, the above-described vortex is generated, but in the case of the present embodiment having the above-described configuration, the generation of the vortex can be suppressed.

  In order to suppress the generation of vortices, it is more effective that the height position of the inlet orifice 19 is lower than the height of the core support plate 6. However, if the inlet orifice 19 is made too low, the height of the fuel support fitting 16 increases, and the material necessary for manufacturing the fuel support fitting 16 increases, or the manufacturability deteriorates. In addition, it is desirable that the center of the inlet orifice is not lower than the lower end of the reinforcing beam 7.

  According to the present embodiment, the swirl flow after colliding with the core support plate 6 by changing the structure of the fuel support bracket 16 and the control rod guide tube 10 and disposing the inlet orifice 19 lower than the normal design. Mitigates the influence of the coolant on the coolant flow in the vicinity of the inlet orifice 19, suppresses the generation of vortices, reduces the increase in the flow pressure loss coefficient due to the vortices at the inlet orifice 19, Can be suppressed. For this reason, the flow rate of the coolant flowing into the fuel assembly 17 can be appropriately adjusted, and the cooling performance can be improved.

[Second Embodiment (FIG. 4)]
FIG. 4 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the second embodiment of the present invention.

  In the present embodiment, one or a plurality of through holes 26 are formed in a part of one of the two beam plates 7 a that intersects the reinforcing beam 7 at a right angle. If the through-holes 26 drilled in the two beam plates 7a intersecting at right angles are asymmetric in the horizontal direction with respect to the inlet orifices 19 arranged at the corners of the two beam plates 7a intersecting at right angles The through holes 26 may be formed in both of the two beam plates 7a intersecting at right angles.

  According to such a configuration, the flow path area is equivalently enlarged at the position of the through hole 26, or the coolant flow lines colliding with the core support plate 6 are disturbed due to the entry / exit of the coolant from the through hole 26, The horizontal symmetry of the coolant flow with respect to the inlet orifice 19 is broken. As a result, the generated vortex is also asymmetrical, and a change in the flow path pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path can be suppressed. As a result, the flow rate of the coolant flowing into the fuel assembly 17 can be adjusted appropriately.

  According to this embodiment, by suppressing the generation of vortices, the coolant flow rate flowing into the fuel assembly can be appropriately adjusted by the inlet orifice.

[Third Embodiment (FIGS. 5 and 6)]
FIG. 5 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the third embodiment of the present invention, and FIGS. 6A and 6B are enlarged cross-sectional views of the E portion of FIG. Different examples are shown.

  In the present embodiment, the ascending flow of the coolant before colliding with the core support plate 6 is disturbed in advance to raise the horizontal central position of the inlet orifice 19 and suppress the flow descending at the horizontal peripheral position. It is.

  That is, in this embodiment, as shown by E and F in FIG. 5, the surface of the control rod guide tube 10 or the beam plate 7a of the reinforcing beam 7 is subjected to surface processing as vortex control means in the middle of the flow path. It is.

  As the surface processing, for example, as shown in FIG. 6A, minute roughness 31 is formed on at least one surface of the reinforcing beam plate 7a and the control rod guide tube 10 to increase the surface roughness. It is. Further, as shown in FIG. 6B, a groove 32 is formed on at least one surface of the reinforcing beam plate 7a and the control rod guide tube 10. With such a configuration, the surface roughness of the reinforcing beam plate 7a and the control rod guide tube 10 is finished to a surface roughness of, for example, 25 μm or more.

  According to such a configuration, it is possible to weaken the swirling flow toward the inlet orifice 19 and suppress the generation of vortices. That is, in the conventional normal design, the surface roughness of the beam plate 7a of the reinforcing beam 7 of the core support plate or the control rod guide tube 10 is about 12.5 μm, and the generation of vortices due to the generation of the swirl flow described above. However, according to the present embodiment, the generation of such vortices can be suppressed.

  This is because by increasing the surface roughness of the reinforcing beam plate 7a and the control rod guide tube 10, the turbulent flow state is promoted, and the flow of the coolant descending the horizontal peripheral position of the inlet orifice 19 is weakened. As a result, the generation of vortices is suppressed, the increase of the flow pressure loss coefficient due to the vortex of the inlet orifice 19 is reduced, and a stable flow pressure loss coefficient can be obtained.

  According to this embodiment, by suppressing the generation of vortices, the coolant flow rate flowing into the fuel assembly can be appropriately adjusted by the inlet orifice.

[Fourth Embodiment (FIG. 7)]
FIG. 7 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the fourth embodiment of the present invention.

  In the present embodiment, the rising flow of the coolant before colliding with the core support plate 6 is disturbed in advance to suppress the generation of vortices. That is, as the vortex control means, the projection 27 is formed on at least one surface of the reinforcing beam plate 7a and the control rod guide tube 10, thereby promoting turbulent flow and weakening the swirl flow toward the inlet orifice 19. It is what.

  According to such a configuration, the flow of the coolant rising in the flow path is agitated, and the turbulent flow is promoted and the generation of vortices can be suppressed as in the third embodiment. As a result, the flow path pressure loss coefficient due to the vortex at the inlet orifice 19 is reduced.

  According to this embodiment, by suppressing the generation of vortices, the coolant flow rate flowing into the fuel assembly can be appropriately adjusted by the inlet orifice.

[Fifth Embodiment (FIG. 8)]
FIG. 8 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the fifth embodiment of the present invention.

  In the present embodiment, the vortex is suppressed by smoothly flowing the coolant upward flow 25 a into the inlet orifice 19.

  That is, as a vortex control means, a rectifying member 28 having a curved surface facing the inlet orifice 19 is provided at the lower surface position of the core support plate 6 facing the inlet orifice 19, thereby facilitating the flow of the coolant. In this configuration, the flow of the coolant descending at the peripheral position in the horizontal direction of the orifice 19 is weakened and the generated vortex is suppressed.

  According to this embodiment, by suppressing the generation of vortices, the coolant flow rate flowing into the fuel assembly can be appropriately adjusted by the inlet orifice.

  In the illustrated example, the surface of the rectifying member 28 is an arcuate curved surface, but it may be constituted by a plurality of surfaces.

[Sixth Embodiment (FIG. 9)]
FIG. 9 is a cross-sectional plan view of the flow path portion showing the coolant flow to the inlet orifice according to the sixth embodiment of the present invention.

  In the present embodiment, as the vortex control means, a rectifying member 30 having a curved surface facing the inlet orifice 19 is provided at the corners of the two beam plates 7a that intersect the reinforcing beam 7 at a right angle. is there.

  By providing the rectifying member 30, the width of the flow path formed by the bar guide tube 10 and the beam plate 7 a around the horizontal direction of the inlet orifice 19, and the bar guide tube 10 at the horizontal center position of the inlet orifice 19 The difference in the flow path width formed by the rectifying member 30 is reduced. For this reason, the difference in the flow velocity of the coolant that rises at each position is reduced, the flow of the coolant that descends the peripheral position in the horizontal direction of the inlet orifice 19 is weakened, and the generation of vortices is suppressed.

  According to this embodiment, by suppressing the generation of vortices, the coolant flow rate flowing into the fuel assembly can be appropriately adjusted by the inlet orifice.

  In the example shown in the figure, the surface of the rectifying member 30 is an arcuate curved surface, but may be a flat surface as long as the difference in flow path width is reduced.

[Seventh Embodiment (FIG. 10)]
FIG. 10 is a cross-sectional plan view of the flow path portion showing the coolant flow to the inlet orifice according to the seventh embodiment of the present invention.

  In the present embodiment, the direction of the opening surface of the inlet orifice 19 is asymmetric with respect to the diagonal direction at the corners of the beam plate 7a orthogonal to each other, thereby making the generated vortex asymmetric. .

  In the above-described conventional example, the direction of the opening surface of the inlet orifice 19 is symmetric with respect to the diagonal direction at the corners of the beam plate 7a that are orthogonal to each other, so that a symmetric twin vortex is likely to occur. The state of the symmetrical twin vortex is greatly changed by a slight change in the shape of the flow path, and the flow pressure loss coefficient due to the vortex at the inlet orifice 19 is easily changed.

  According to this embodiment, the direction of the opening surface of the inlet orifice at the position of the corner portion of the orthogonal beam plate 7a is asymmetric with respect to the diagonal direction in the corner portion of the orthogonal beam plate 7a. The flow vortex pressure loss coefficient at the inlet orifice 19 is not changed by a slight change in the shape of the flow path.

  According to this embodiment, the generated vortex is made asymmetric so that the flow path pressure loss coefficient at the inlet orifice 19 does not change due to a slight change in the shape of the flow path, and flows into the fuel assembly through the inlet orifice. The coolant flow rate to be adjusted can be adjusted appropriately.

[Eighth Embodiment (FIGS. 11 and 12)]
FIG. 11 is a side sectional view of a flow path portion showing a coolant flow to an inlet orifice according to an eighth embodiment of the present invention, and FIG. 12 is an enlarged side view showing the inlet orifice portion shown in FIG. It is.

  In the present embodiment, a flow distribution member 29 having a mesh shape or a perforated plate shape is disposed in the opening of the inlet orifice 19.

  Since the coolant flows into the flow dispersion member 29 in a dispersed manner, it cannot flow in a large vortex state. And since the swirl | vortex of a big vortex does not continue to the flow dispersion | distribution member 29, the vortex produced upstream of the flow dispersion | distribution member 29 also becomes weak. For this reason, the swirling energy of the vortex flowing into the flow dispersion member 29 is reduced, and as a result, the increase amount of the flow path pressure loss coefficient due to the vortex in the flow dispersion member 29 is reduced.

  According to this embodiment, the swirling energy of the vortex flowing into the flow dispersion member is reduced, so that the change in the flow path pressure loss coefficient in the flow dispersion member due to the vortex is reduced, and the flow dispersion member flows into the fuel assembly. The coolant flow rate can be adjusted appropriately.

  The shape of the flow dispersion member 29 is not limited to that shown in the figure, and various changes can be made.

[Ninth Embodiment (FIG. 13)]
FIG. 13 shows a ninth embodiment of the present invention, and is a configuration diagram showing a modification of the flow dispersion member 29 shown in the eighth embodiment. The structure for attaching the flow dispersion member 29 to the fuel support fitting 16 is basically the same as the overall structure shown in FIG.

  In the ninth embodiment, as shown in FIG. 13, the flow dispersion member 29 is a coolant arranged asymmetrically with respect to the center position of the inlet orifice 19 provided in the coolant inlet 41 of the fuel support bracket 16. The structure has an inflow hole 43. That is, the center of the inlet orifice 19 is arranged on a line connecting the intersection of the orthogonal beam plates 7a and the center of the fuel support bracket 16, and the coolant is connected to the line connecting the intersection of the orthogonal beam plates 7a and the center of the fuel support bracket 16. The inflow hole 43 is a non-target structure. In the illustrated example, a group of coolant inflow holes 43 are unevenly distributed on one side on the left and right with respect to the center position of the inlet orifice 19 in a state in which the flow dispersion member 29 is vertically arranged.

  According to such a configuration, the position of the coolant inflow hole 43 is not bilaterally symmetric, and is unevenly distributed in either one of the left and right, thereby forming a single vortex instead of a twin vortex. Moreover, even if it becomes a twin vortex, it becomes asymmetric.

  The formation of such vortices has been observed by a flow test simulating an actual shape. As described above, the twin vortex generated under the conventional structure becomes one vortex in the present embodiment, so that the state of the vortex generated due to a slight difference in the shape of the flow path does not change, and the flow dispersion member The change in the flow path pressure loss coefficient at 29 is reduced.

  According to the present embodiment, the generated vortex is also asymmetrical, and a change in the flow pressure loss coefficient in the flow dispersion member due to a slight change in the flow path shape can be suppressed, so that the flow dispersion member flows into the fuel assembly. The coolant flow rate to be adjusted can be adjusted appropriately.

[Tenth Embodiment (FIG. 14)]
FIG. 14 shows the tenth embodiment of the present invention and is a configuration diagram showing another modification of the flow dispersion member 29 shown in the eighth embodiment. In this embodiment, the structure for attaching the flow dispersion member 29 to the fuel support bracket 16 is basically the same as the overall structure shown in FIG.

  In the ninth embodiment, as shown in FIG. 14, the coolant inflow hole 43 of the flow dispersion member 29 is located with respect to the center position of the inlet orifice 19 provided in the coolant inlet 41 of the fuel support fitting 16. Although the left and right coolant inflow holes 43 are arranged in a substantially symmetrical group, the interval between the groups of the left and right coolant inflow holes 43 is equal to the adjacent coolant inflow holes in the one coolant inflow hole 43 group. The configuration is larger than the interval between 43.

  According to such a configuration, twin vortices are generated as in the eighth embodiment, but because there is a gap between the groups of left and right coolant inflow holes 43, depending on slight changes in the shape of the flow path, The state of the generated twin vortex does not change. For this reason, the flow path pressure loss coefficient in the flow dispersion member 29 is not changed by a slight change in the shape of the flow path.

  According to this embodiment, since the state of the generated vortex is stabilized, the change in the flow path pressure loss coefficient in the flow dispersion member can be suppressed, so that the coolant flow rate flowing into the fuel assembly by the flow dispersion member Can be adjusted appropriately.

[Eleventh Embodiment (FIGS. 15 and 16)]
FIG. 15 is a side sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the eleventh embodiment of the present invention, and FIG. 16 is a side view showing the inlet orifice portion shown in FIG.

  In the present embodiment, the lower end of the coolant inlet 41 of the fuel support fitting 16 is arranged below the lower end of the reinforcing beam 7, and the inlet orifice is placed in the coolant channel 42 inside the fuel support fixture 16. 19 is provided. That is, one end of the inlet orifice 19 is supported on the inner surface of the coolant channel 42 in the fuel support bracket 16. When one end of the inlet orifice 19 is supported on the inner surface of the coolant channel 42 in the fuel support bracket 16 in this way, the other end of the inlet orifice 19 is supported by the coolant inlet 41 of the fuel support bracket 16. Substantially the inlet orifice 19 can be provided in the coolant channel 42 inside the fuel support 16.

  In the example shown in the drawing, the coolant inlet port 41 has an elongated shape in the vertical direction, and the lower end thereof is disposed below the lower end of the reinforcing beam 7. As shown in FIG. 16, the control rod guide tube 10 is also formed with a hole having the same shape as the coolant inlet 41.

  In addition, the inlet orifice 19 provided in the coolant channel 42 is constituted by a perforated plate having a large number of small-diameter orifice holes, or by superposing the perforated plate on a plate having a normal circular orifice hole. It has a porous orifice structure. Thereby, the inlet orifice 19 exhibits the same function as the flow dispersion member 29 described above.

  According to the configuration of this embodiment, the coolant inlet 41 has an elongated shape in the vertical direction, the lower end thereof is disposed below the lower end of the reinforcing beam 7, and the flow path at the coolant inlet 41. Since the cross-sectional area is also large, the coolant smoothly flows into the fuel support bracket 16, so that the above-described vortex generation is suppressed. Further, since the distance from the flow path formed by the control rod guide tube 10 where the vortex is generated and the beam plate 7a to the inlet orifice 19 is long, there is also an effect that the generated vortex attenuates before reaching the inlet orifice 19.

  According to this embodiment, since the vortex flowing into the inlet orifice 19 can be reduced, a change in the flow pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path can be suppressed. Thus, the coolant flow rate flowing into the fuel assembly can be adjusted appropriately.

  It should be noted that the effect of providing the inlet orifice 19 as a perforated plate, the effect of providing the inlet orifice 19 in the coolant channel 42 inside the fuel support fitting 16, and the fuel support fitting below the lower end of the reinforcing beam 7. The action of the 16 coolant inlets 41 arranged so that the lower ends thereof are arranged synergistically reduces vortices when flowing into the inlet orifice 19. It has the effect of reducing vortices when flowing in. Therefore, each configuration can be used independently, or a plurality of configurations can be used in appropriate combination.

  In addition, by installing the inlet orifice in the lower tie plate 15, the vortex generated by increasing the distance from the flow path formed by the control rod guide tube 10 and the beam plate 7a where the vortex is generated to the inlet orifice becomes the inlet orifice. However, since the lower tie plate 15 is exchanged together with the fuel assembly 17, an inlet orifice is required every time the fuel assembly 17 is exchanged, and its material and production are required. It is uneconomical. Further, the fuel assembly 17 may move a position in the core during operation, and the fuel assembly 17 is disposed at a position corresponding to a corner portion of the two beam plates 7a intersecting at a right angle. 17 is not disposed at a position corresponding to the corner portion of the two beam plates 7a intersecting at right angles even after the movement, so that the inlet orifice needs to be replaced even when the fuel assembly 17 moves in the core. It is inconvenient.

  On the other hand, since the fuel support bracket is not replaced or changed in position when the fuel assembly 17 is replaced, when the inlet orifice is provided in the fuel support bracket, the fuel assembly 17 There is no need to replace the inlet orifice, such as by replacement.

[Twelfth Embodiment (FIGS. 17 to 19)]
FIG. 17 is a side sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the twelfth embodiment of the present invention, and FIG. 18 is an enlarged sectional view taken along line GG of FIG. FIG. 19 is a side view showing the inlet orifice portion shown in FIG.

  In this embodiment, in addition to the configuration substantially the same as that of the eleventh embodiment, vortex suppression including a plurality of parallel vertical plates from the coolant inlet 41 of the fuel support bracket 16 toward the inside of the coolant channel 42 is performed. A plate 46 is provided. Since other configurations are the same as those in the eleventh embodiment, description thereof will be omitted.

  For example, as shown in FIG. 17, the vortex suppression plate 46 has a configuration in which a plurality of vortex suppression plates 46 are arranged in parallel at equal intervals. For example, the inner surface of the coolant channel 42 facing the coolant inlet 41 of the fuel support bracket 16. It is integrally formed along the flow path direction by welding or the like.

  According to such a configuration of the twelfth embodiment, by providing the vortex suppression plate 46, the flow of the coolant flowing in from the coolant inlet 41 in the fuel support fitting 16 is parallel in one direction. And it will flow smoothly. For this reason, the vortex at the time of flowing into the inlet orifice 19 is further reduced, and a change in the flow path pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path can be reduced.

  According to the present embodiment, the change in the flow pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path can be further suppressed, so that the coolant flow rate flowing into the fuel assembly by the inlet orifice 19 can be appropriately set. Can be adjusted.

[Thirteenth Embodiment (FIGS. 20 to 23)]
FIG. 20 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the thirteenth embodiment of the present invention. FIG. 21 is a side view showing the inlet orifice portion shown in FIG. 20, and shows the control rod guide tube 10 and the combustion support fitting 16 in a state where they are separated from each other in the vertical direction.

  In the present embodiment, the lower end of the coolant inlet 41 of the fuel support bracket 16 is disposed above the lower end of the reinforcing beam 7, and the inlet orifice 19 is installed inside the fuel support bracket. In the example shown in FIGS. 20 and 21, the outer shape of the fuel support fitting 16 is substantially the same as the conventional example, but the inlet orifice 19 is disposed horizontally in the coolant channel 42. Similarly to the twelfth embodiment, the coolant channel 42 includes a vortex suppression plate formed of a plurality of parallel vertical plates from the coolant inlet 41 of the fuel support bracket 16 toward the inside of the coolant channel 42. 46 is provided.

  According to such a configuration, only the structure of the fuel support fitting 16 is changed, and the inlet orifice 19 of the multi-hole orifice structure is installed inside the fuel support fitting 16, so that it flows into the inlet orifice 19 of the multi-hole orifice structure. The action of reducing the vortex accompanied by the coolant, the action of reducing the vortex accompanied by the coolant flowing into the inlet orifice 19 due to the installation of the inlet orifice 19 inside the fuel support 16, and the inlet orifice 19 by the vortex suppression plate 46 The action of reducing the vortex accompanied by the inflowing coolant works, and the flow path pressure loss coefficient at the inlet orifice 19 can be stabilized.

  According to the present embodiment, the change in the flow pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path can be further suppressed, so that the coolant flow rate flowing into the fuel assembly by the inlet orifice 19 can be appropriately set. Can be adjusted. Moreover, in this Embodiment, the advantage that the change of the existing plant can be decreased is acquired.

  Further, as shown in FIGS. 22 and 23, even if the vortex suppression plate 46 is not provided, the flow path pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path due to the action of the multi-hole orifice structure or the like. Thus, the flow rate of the coolant flowing into the fuel assembly can be appropriately adjusted by the inlet orifice 19.

[Fourteenth Embodiment (FIGS. 24 and 25)]
FIG. 24 is a side sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the fourteenth embodiment of the present invention. FIG. 25 is a side view showing the inlet orifice portion shown in FIG. 24, in which the control rod guide tube 10 and the combustion support bracket 16 are shown in a state where they are separated from each other in the vertical direction.

  The present embodiment is a modification of the thirteenth embodiment, in which an inlet orifice 19 having a function as a porous orifice or a flow dispersion member is installed obliquely inside the fuel support bracket 16. Other configurations are substantially the same as those in the thirteenth embodiment, and include, for example, a vortex suppression plate 46.

  Due to the shape of the coolant flow path 42 of the fuel support bracket 16, the inlet orifice 19 can have a larger flow path cross-sectional area if it is arranged obliquely as in this embodiment.

  According to such a configuration of the fourteenth embodiment, the inlet orifice 19 having a function as a multi-hole orifice or a flow dispersion member is disposed obliquely inside the fuel support bracket 16 so that the flow area of the inlet orifice 19 is increased. The flow pressure loss coefficient at the inlet orifice 19 is changed by a slight change in the shape of the flow path by reducing the vortex of the coolant flowing into the inlet orifice 19 while ensuring the necessary flow rate. Thus, the flow rate of the coolant flowing into the fuel assembly can be appropriately adjusted by the inlet orifice 19.

[Fifteenth embodiment (FIGS. 26 and 27)]
FIG. 26 is a side sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the fifteenth embodiment of the present invention. FIG. 27 is a side view showing the inlet orifice portion shown in FIG. 26, in which the control rod guide tube 10 and the combustion support bracket 16 are shown in a state where they are separated from each other in the vertical direction.

  In the present embodiment, the vortex suppression plate 16 is omitted from the configuration of the fourteenth embodiment. An inlet orifice 19 having a function as a porous orifice or a flow dispersion member is provided.

  Also in the configuration of the fifteenth embodiment, the flow support area of the inlet orifice 19 can be increased by arranging the fuel support bracket 16 at an angle, and a multi-hole can be secured while ensuring a necessary flow rate. The vortex of the coolant flowing into the inlet orifice 19 is reduced by the action of the inlet orifice 19 as an orifice or a flow dispersion member, and a change in the flow pressure loss coefficient at the inlet orifice 19 due to a slight change in the shape of the flow path. Thus, the flow rate of the coolant flowing into the fuel assembly can be appropriately adjusted by the inlet orifice 19.

[Sixteenth Embodiment (FIGS. 28 and 29)]
FIG. 28 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the sixteenth embodiment of the present invention. FIG. 29 is a side view showing the inlet orifice portion shown in FIG. 28, and shows the control rod guide tube 10 and the combustion support bracket 16 in a state where they are separated from each other in the vertical direction.

  In this embodiment, the porous orifice having the structure of the fourteenth embodiment is replaced with a normal one-hole orifice.

  Also in the configuration of the sixteenth embodiment, the inlet orifice 19 is disposed obliquely inside the fuel support bracket 16 so that the flow area of the inlet orifice 19 can be increased, and a necessary flow rate is ensured. On the other hand, the vortex of the coolant flowing into the inlet orifice 19 is reduced by the action of the vortex suppression plate 46, and the change of the flow pressure loss coefficient at the inlet orifice 19 due to the slight change in the shape of the flow path is further suppressed. Thus, the coolant flow rate flowing into the fuel assembly can be appropriately adjusted by the inlet orifice 19.

[Seventeenth Embodiment (FIGS. 30 and 31)]
FIG. 30 is a side sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the seventeenth embodiment of the present invention. FIG. 31 is a side view showing the inlet orifice portion shown in FIG. 30 and shows the control rod guide tube 10 and the combustion support bracket 16 in a state where they are separated from each other in the vertical direction.

  In the present embodiment, the multi-hole orifice of the configuration of the fifteenth embodiment is a normal one-hole orifice.

  Also in the configuration of the seventeenth embodiment, by arranging the inlet orifice 19 obliquely inside the fuel support bracket 16, the flow area of the inlet orifice 19 can be increased, and a necessary flow rate can be ensured. However, the vortex of the coolant flowing into the inlet orifice 19 is reduced by the action of being installed in the coolant channel 42 inside the fuel support bracket 16, and the inlet orifice 19 due to a slight change in the shape of the channel. Therefore, the flow rate of the coolant flowing into the fuel assembly can be adjusted appropriately by the inlet orifice 19.

[Other Embodiments]
The present invention is not limited to the case where the above-described embodiments are implemented alone, but may be implemented in various forms other than the above as a combined configuration such as arbitrarily combining elements of the embodiments. it can. Thereby, it is possible to obtain the effect in each embodiment in a synergistic form.

The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 1st Embodiment of this invention. The perspective view which shows the structure of the core support metal fitting applied to 1st Embodiment of this invention. (A) is an operation explanatory view according to the first embodiment of the present invention, (B) is a characteristic diagram for explaining the function according to the first embodiment of the present invention. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 2nd Embodiment of this invention. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 3rd Embodiment of this invention. (A), (B) is the E section expanded sectional view of FIG. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 4th Embodiment of this invention. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 5th Embodiment of this invention. The plane sectional view of the channel part which shows the coolant flow to the entrance orifice by a 6th embodiment of the present invention. The plane sectional view of the channel part which shows the coolant flow to the entrance orifice by a 7th embodiment of the present invention. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 8th Embodiment of this invention. The side view which expands and shows the inlet orifice part shown in FIG. The block diagram which shows 9th Embodiment of this invention. The block diagram which shows 10th Embodiment of this invention. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 11th Embodiment of this invention. The side view which shows the inlet orifice part shown in FIG. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 12th Embodiment of this invention. The expanded sectional view which follows the GG line of FIG. The side view which shows the inlet orifice part shown in FIG. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 13th Embodiment of this invention. The side view which shows the inlet orifice part shown in FIG. The sectional side view which shows the modification of the flow-path part by 13th Embodiment of this invention. The side view which shows the inlet orifice part shown in FIG. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 14th Embodiment of this invention. The side view which shows the inlet orifice part shown in FIG. The sectional side view of the flow-path part which shows the coolant flow to the inlet orifice by 15th Embodiment of this invention. The side view which shows the inlet orifice part shown in FIG. FIG. 28 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the sixteenth embodiment of the present invention. 29 is a side view showing the inlet orifice part shown in FIG. 28. FIG. FIG. 30 is a side cross-sectional view of the flow path portion showing the coolant flow to the inlet orifice according to the seventeenth embodiment of the present invention. 31 is a side view showing the inlet orifice portion shown in FIG. 30. FIG. 1 is a schematic cross-sectional view showing the overall configuration of a reactor pressure vessel. FIG. 33 is an enlarged cross-sectional view of the fuel assembly shown in FIG. 32. (A) is a perspective view which shows one structural example of a core support plate and a reinforcement beam, (B) is a perspective view which shows the other structural example of a reinforcement beam. The top view which shows the arrangement configuration of a fuel support metal fitting. The top view which expands and shows a part of FIG. FIG. 37 is a sectional view taken along line B-B in FIG. 36. Explanatory drawing which shows the generation | occurrence | production condition of a vortex by a side view. The DD arrow view of FIG. 38 which shows the generation | occurrence | production state of a vortex.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 2 Steam dryer 3 Steam-water separator 4 Upper lattice board 5 Core shroud 6 Core support plate 6a Many holes 7 Reinforcement beam 7a Beam plate 8 Recirculation pump 9 Main steam pipe 10 Control rod guide pipe 11 Channel Box 12 Fuel rod 13 Fuel spacer 14 Upper tie plate 15 Lower tie plate 16 Fuel support bracket 17 Fuel assembly 18 Control rod 19 Inlet orifice 20 Disc frame 21 Connecting rod 22 Region 1
23 Region 2
24 Area 3
25 Streamline 26 Through-hole 27 Protrusion 28 Rectification member 29 Flow dispersion member 30 Rectification member 31 Minute unevenness 32 Groove 41 Coolant inlet 42 Coolant flow path 46 Vortex suppression plate

Claims (2)

A core support plate provided in a reactor pressure vessel of a boiling water reactor and having a plurality of fuel support holes, a reinforcing beam formed by combining the beam support plate in a square lattice form by reinforcing the core support plate from the lower surface side; A plurality of control rod guide tubes that stand vertically from the bottom side of the reactor pressure vessel and whose upper ends are combined with the fuel support hole portions of the core support plate, and are inserted into the upper ends of the control rod guide tubes, A fuel support bracket that supports the lower ends of a plurality of fuel assemblies that are supported by the core support plate and are arranged vertically in the core, and a flow rate of a coolant that is provided on the fuel support bracket and flows into the fuel assemblies is adjusted. In the coolant core inlet structure comprising an inlet orifice, vortex control means for controlling the vortex of the coolant flowing into the inlet orifice provided in the fuel support fitting is provided upstream of the inlet orifice or the inlet orifice Provided, and coolant core inlet structure, characterized in that the center of the inlet orifice is a structure disposed above the lower end of the reinforcing beam. The vortex control means has a through hole in a part of the beam plate asymmetrically with respect to a line connecting the center of the fuel support bracket and the intersection of the beam plate of the reinforcing beam facing the inlet orifice of the fuel support bracket. The coolant core inlet structure according to claim 1, wherein the coolant core inlet structure is provided.

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