JP2013228316A - Fuel spacer, fuel assembly, and method for manufacturing fuel spacer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spacer excellent in mechanical strength and productivity while considering improvement of limit output and suppression of increase of pressure loss, and to provide a fuel assembly including the spacer.SOLUTION: A fuel spacer 1 of one embodiment includes: a spacer body part 2 including a fuel rod support part 3 having a plurality of insertion areas A for inserting fuel rods thereinto and holding the fuel rods inserted into the insertion areas A at a predetermined interval and a band part 5 surrounding the outer periphery of the fuel rod support part 3; a base part 7 fixed on upper ends of cells 4 constituting the fuel rod support part 3; and a cooling material agitation part 6 located on the base part 7 in sub-channel areas S to be gap areas between adjacent fuel rods held by the fuel rod support part 3 and having blade parts 8 inclined from an axial direction of the fuel rods at a predetermined angle.

Description

  The present invention relates to a fuel spacer and a fuel assembly, and more particularly to a fuel spacer used in a fuel assembly for a boiling water reactor, a fuel assembly using the fuel spacer, and a method for manufacturing the fuel spacer.

  FIG. 6 shows a schematic configuration of a fuel assembly 21 that is generally used. Here, an example of a fuel assembly used in a boiling water reactor is shown. As shown in FIG. 6, a water rod 22 serving as a coolant flow path is disposed at the center, and a plurality of fuel rods 23 having nuclear fuel therein are arranged in a square lattice pattern around the water rod 22. The water rod 22 and the fuel rod 23 are fixed at the upper and lower ends by a lower tie plate 24 and an upper tie plate 25, respectively, and are disposed at appropriate intervals between the lower tie plate 24 and the upper tie plate 25 (see FIG. The fuel spacer 26 is held at a predetermined interval. The channel box 27 is attached to the upper tie plate 25 and surrounds the outer periphery of the water rod 22 and the fuel rod 23 (fuel bundle) bundled by the spacer 26.

  In nuclear power generation, in order to improve the economics of power generation, it is desired to increase the burnup of fuel assemblies and increase the power density. One way to meet these demands is to increase the effective length of the fuel rods by increasing the number of fuel rods contained in one fuel assembly, thereby increasing the margin for the limit value of the linear power density. is there. The fuel assemblies loaded in the boiling water reactor (BWR) currently used in Japan are mainly 9-row 9-column fuel assemblies. On the other hand, the 10-row 10-column type has been widely introduced overseas, and the development of an 11-row 11-column fuel assembly has been promoted with the aim of further increasing the burnup (Patent Document 1, etc.).

  In addition, in order to meet the above requirements, improvement of each member constituting the fuel assembly has been promoted. Speaking of spacers, considering that the spacer has a role of preventing turbulent flow in the coolant flowing through the fuel assembly and preventing boiling transition, and that the ratio of the spacer to the flow resistance in the fuel assembly is large. The structure and shape have been improved.

  Here, the structure of a conventional spacer will be described with reference to FIG. FIG. 7A is a top view of an example of a conventional lattice-type spacer 100, and FIG. 7B is a side view of the lattice-type spacer 100. FIG. 7C shows an example of the divider 110 that is one of the constituent members of the lattice type spacer 100.

  As shown in FIG. 7A, a rectangular insertion region A for inserting a fuel rod is formed by crossing the divider 110 in a lattice shape inside a substantially rectangular band portion 120.

  Further, as shown in FIGS. 7A and 7B, a tab 122 is provided on the side surface of the band portion 120 for the purpose of positioning the fuel rod and the spacer in the channel box. Furthermore, a flow tab 121 is provided at the upper end of the band portion 120 for the purpose of stirring the coolant on the upper side of the spacer (that is, downstream of the coolant).

  As shown in FIG. 7C, the divider 110 is provided with a spring 111 for the purpose of positioning the fuel rod in the insertion region A. A flow wing 112 is provided for the purpose of stirring the coolant on the upper side of the spacer. The divider 110 is manufactured by pressing a plate material having a predetermined thickness. The thicknesses of the divider 110 and the band portion 120 are determined in consideration of the distance between the fuel rods 23 and the characteristics of the spring 111, for example.

  By the way, when designing a spacer, (1) improvement of thermal limit output, (2) ensuring sufficient mechanical strength, (3) minimization of neutron absorption, (4) suppression of increase in pressure loss. , (5) Manufacturability, and (6) Easiness of assembly when assembling the fuel assembly must be taken into consideration. Among these viewpoints, many conventional spacers have been developed for the purpose of (1) improvement of limit output and (4) suppression of increase in pressure loss.

  As an example of the spacer for the purpose of improving the limit output, by providing a swirl vane in the subchannel region that is a gap region between adjacent fuel rods, a swirl flow is generated on the upper side of the spacer, and the coolant There has been proposed one in which a liquid phase is attached to the surface of a fuel rod (Patent Document 2).

  In addition, the shape of the spacer cell or lattice can be changed like a swirl vane to create a turbulent flow in the coolant, or the swirl vane or swirl vane can be incorporated in the upper part of the spacer to What produces a swirl flow is proposed (patent documents 3 and 4 grades). When the swirl vanes and swirl vanes are provided on the upper side of the spacer, the horizontal cross-sectional area of the spacer is suppressed from abruptly decreasing compared to the case where these are disposed within the height of the spacer. It is known that the increase is also effective.

  Next, as an example of the spacer for the purpose of suppressing the increase in pressure loss, the curvature of the round cell is reduced for the purpose of suppressing the flow resistance by reducing the cross-sectional area in the horizontal direction (Patent Document 5). Alternatively, a structure has been proposed in which two rectangular lattice spacers are joined by being shifted by 90 degrees to form a single spacer that supports a water rod and a fuel rod (Patent Document 6).

  In addition, by providing angled protrusions with a gradually decreasing cross-sectional area at the top and bottom of the spacer, it is possible to suppress a rapid decrease in the cross-sectional area in the horizontal direction and to reduce the pressure loss of fluid upstream and downstream of the spacer. The thing is proposed (patent document 7).

  However, by improving the structure and shape of the spacers, many of the spacers have a large horizontal cross-sectional area and a large pressure loss on the downstream side of the coolant. For this reason, the pressure loss in the whole fuel assembly tends to increase. On the other hand, a fuel assembly has been proposed in which a spacer having a high coolant agitation effect is applied only to a spacer in the vicinity of a region where boiling transition is likely to occur, and a spacer having a low pressure loss is applied to other spacers (patents). Reference 8).

JP 2010-151640 A JP-A-5-150074 Japanese Patent No. 3267967 JP-A-6-273559 Japanese Patent Laid-Open No. 6-214073 Japanese Patent Laid-Open No. 7-287088 JP-A-1-217294 JP 2001-318182 A Japanese Patent No. 3356498

  As described above, various proposals for improving the spacers have been proposed in order to increase the burnup of the fuel assembly and increase the power density. By applying these, a certain effect can be expected. However, the adoption of these improvements suggests new challenges.

  The subject is ensuring of manufacturability and mechanical strength. As the number of fuel rods included in one fuel assembly increases, the diameters of the water rods and fuel rods become smaller, and the gap between the fuel rods and the gap between the fuel rods and the channel box narrow. There is a tendency. Therefore, in order to properly position the water rod and the fuel rod and maintain an appropriate distance, a more precise design and manufacture of the spacer is required. Thus, ensuring the manufacturability of the spacer is one of the problems.

  Further, in order to narrow the gap and minimize the neutron economy, it is necessary to reduce the thickness of the constituent members (divider, cell, band, etc.) of the spacer as much as possible. Therefore, securing the mechanical strength of the spacer is also an issue. Ensuring the mechanical strength of the spacer is extremely important in order to ensure the integrity of the fuel assembly not only during normal operation of the reactor but also during abnormalities such as earthquakes.

  However, the improvement of the spacers found in the prior art tends to be complicated in shape and structure in order to achieve an increase in the limit output and a suppression of an increase in pressure loss. In many cases, no consideration is given to ensuring strength.

  For example, when the torsion plates for creating the swirl flow are attached to the spacer one by one as in Patent Document 9, considering the number of torsion plates required for manufacturing one spacer, it is necessary for the manufacture and attachment of the torsion plates. It is hard to say that man-hours are large and manufacturability is excellent.

  The present invention has been made on the basis of the above technical recognition, and its object is to provide a spacer having excellent mechanical strength and manufacturability, while taking into consideration the improvement of the limit output and the suppression of the increase in pressure loss. A fuel assembly comprising a spacer is provided.

A fuel spacer according to an aspect of the present invention includes:
A spacer having a plurality of insertion regions through which fuel rods are inserted, a fuel rod support portion that holds the fuel rods inserted through the insertion regions at a predetermined interval, and a band portion that surrounds the outer periphery of the fuel rod support portion The main body,
A base portion fixed on the upper side of the partition member constituting the fuel rod support portion and a position above the base portion in a subchannel region which is a gap region between adjacent fuel rods held by the fuel rod support portion. A coolant agitation part having a blade part inclined at a predetermined angle with respect to the axial direction of the fuel rod;
It is characterized by providing.

In the fuel spacer,
The fuel rod support portion is configured as a cylindrical cell connected as a partition member in a square lattice shape,
The base portion may be configured in a cross shape so that the intersection point is located substantially at the center of the subchannel region and the end portion is fixed to the upper end of the cell.

In the fuel spacer,
An end portion of the base portion may extend to the band portion, and the base portion may connect the fuel rod support portion and the band.

In the fuel spacer,
The fuel rod support portion is configured as a cylindrical cell connected as a partition member in a square lattice shape,
The base portion is configured in a frame shape along the boundary of the gap region defined by the four cells,
The coolant agitation part may be held at a predetermined gap from the upper end of the cell by a claw part attached to a side surface of the base part so as to protrude from the lower end of the base part.

In the fuel spacer,
The fuel rod support portion is configured as a cylindrical cell connected as a partition member in a square lattice shape,
The base may be configured in a frame shape along a boundary of a gap region defined by the four cells, and may be fixed to the upper end of the cell without a gap.

In the fuel spacer,
The fuel rod support part is configured as a crossing of a divider as the partition member in a lattice shape,
The base may be configured in a lattice shape along an upper end of the divider so as to include a plurality of intersections of the divider.

In the fuel spacer,
The fuel rod support part is configured as a crossing of a divider as the partition member in a lattice shape,
The base may be formed in a cross shape along the upper end of the divider, and the intersection may be located above the divider intersection.

In the fuel spacer,
An end portion of the base portion may extend to the band portion, and the base portion may connect the fuel rod support portion and the band.

In the fuel spacer,
The fuel rod support part is configured as a crossing of a divider as the partition member in a lattice shape,
The base portion may be configured in a lattice shape along the upper ends of all the dividers and the upper ends of the band portions constituting the fuel rod support portion.

In the fuel spacer,
A blade portion that is inclined at a predetermined angle with respect to the axial direction of the fuel rod held by the fuel rod support portion may be provided on the base portion positioned at the upper end of the band portion.

In the fuel spacer,
The horizontal width of the base portion may be larger than the thickness of the partition member.

In the fuel spacer,
The vertical width of the base portion may be larger than the horizontal width of the base portion.

In the fuel spacer,
A plurality of the blade portions may be arranged symmetrically with respect to the center of the subchannel region.

In the fuel spacer,
You may make it the number of the said blade | wing parts on the said base part increase so that a subchannel area | region with a small thermal margin.

In the fuel spacer,
The coolant stirring unit may be provided only in a predetermined subchannel region.

A fuel assembly according to an aspect of the present invention includes:
Multiple fuel rods,
An upper tie plate for fixing upper ends of the plurality of fuel rods;
A lower tie plate for fixing lower ends of the plurality of fuel rods;
Bundling the plurality of fuel rods at a predetermined interval, and having a plurality of fuel spacers spaced in the axial direction,
At least one of the plurality of fuel spacers is a fuel spacer according to the present invention.

A fuel assembly according to an aspect of the present invention includes:
Multiple fuel rods,
An upper tie plate for fixing upper ends of the plurality of fuel rods;
A lower tie plate for fixing lower ends of the plurality of fuel rods;
Bundling the plurality of fuel rods at a predetermined interval, and having a plurality of fuel spacers spaced in the axial direction,
The fuel spacer according to the present invention is provided only in an axial region closer to the upper tie plate than the lower tie plate.

A fuel assembly according to an aspect of the present invention includes:
Multiple fuel rods,
An upper tie plate for fixing upper ends of the plurality of fuel rods;
A lower tie plate for fixing lower ends of the plurality of fuel rods;
Bundling the plurality of fuel rods at a predetermined interval, and having a plurality of fuel spacers spaced in the axial direction,
At least two of the plurality of fuel spacers are fuel spacers according to the present invention, and the number of the blade portions is larger as the fuel spacer is disposed closer to the upper tie plate of the fuel assembly. .

A method for manufacturing a fuel spacer according to an aspect of the present invention includes:
By connecting cylindrical cells in a square lattice shape, a fuel rod support portion having a plurality of insertion regions through which fuel rods are inserted and holding the fuel rods inserted through the insertion regions at a predetermined interval is manufactured. And a process of
Producing a coolant agitation part having a base part and a blade part located on the base part for stirring the coolant;
The blade portion is positioned in a subchannel region that is a gap region between adjacent fuel rods held by the fuel rod support portion, and the base portion straddles the plurality of cells along the upper end of the cell. Fixing the coolant stirring part to the fuel rod support part;
It is characterized by providing.

In the method for manufacturing the fuel spacer,
In the manufacturing process of the coolant stirring part, the base part and the blade part may be integrally formed by press molding of a metal plate.

In the method for manufacturing the fuel spacer,
As the base, a base having a horizontal width larger than the thickness of the cell may be used.

In the method for manufacturing the fuel spacer,
The base of the coolant agitation unit may have a vertical width larger than a horizontal width.

A method for manufacturing a fuel spacer according to an aspect of the present invention includes:
By crossing the plate-like dividers in a lattice shape, a fuel rod support portion having a plurality of insertion regions through which the fuel rods are inserted and holding the fuel rods inserted through the insertion regions at a predetermined interval is produced. Process,
Producing a coolant agitation part having a base part and a blade part located on the base part for stirring the coolant;
The blade portion is positioned in a subchannel region which is a gap region between adjacent fuel rods held by the fuel rod support portion, and the base portion straddles a plurality of the dividers along the upper end of the divider. Fixing the coolant stirring part to the fuel rod support part;
It is characterized by providing.

In the method for manufacturing the fuel spacer,
In the manufacturing process of the coolant stirring part, the base part and the blade part may be integrally formed by press molding of a metal plate.

In the method for manufacturing the fuel spacer,
As the base portion, a base portion whose horizontal width is larger than the thickness of the divider may be used.

In the method for manufacturing the fuel spacer,
The base of the coolant agitation unit may have a vertical width larger than a horizontal width.

  According to the present invention, it is possible to provide a spacer excellent in mechanical strength and manufacturability, and a fuel assembly including the spacer, while taking into consideration improvement of limit output and suppression of increase in pressure loss.

(A) is a perspective view of a part of the spacer according to the first embodiment of the present invention, (b) is a top view of a part of the spacer, and (c) and (d) are cooling of the spacer. It is a perspective view of a material stirring part. (A) is a perspective view of a part of the spacer according to the second embodiment of the present invention, (b) is a top view of a part of the spacer, and (c) is a coolant agitating part of the spacer. It is a perspective view, (d) is a side view of a part of the spacer. (A) is a perspective view of a part of a spacer according to a modification of the second embodiment of the present invention, (b) is a top view of a part of the spacer, and (c) is a coolant for the spacer. It is a perspective view of a stirring part. (A) is a perspective view of a part of a spacer according to a third embodiment of the present invention, (b) is a top view of a part of the spacer, and (c) is a coolant agitating part of the spacer. It is a perspective view. (A) is a perspective view of a part of a spacer according to a modification of the third embodiment of the present invention, (b) is a top view of a part of the spacer, and (c) is a coolant for the spacer. It is a one part perspective view of a stirring part. It is a longitudinal cross-sectional view of the conventional general fuel assembly. (A) is a top view of an example of a conventional lattice-type spacer, (b) is a side view of the spacer, and (c) shows an example of a divider constituting the spacer.

  Hereinafter, three embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the component which has an equivalent function is attached | subjected the same code | symbol, and detailed description of the component of the same code | symbol is not repeated.

(First embodiment)
The spacer (fuel spacer) according to the first embodiment will be described with reference to FIG. FIG. 1A shows a perspective view of a part of a spacer (fuel spacer) 1 according to the first embodiment, and FIG. 1B shows a top view of a part of the spacer 1. FIGS. 1C and 1D are perspective views of the coolant stirring unit 6 of the spacer 1. In FIG. 1B, the circular broken line indicates the fuel rod held by the spacer, and the portions corresponding to the aforementioned spring 111 and tab 122 are omitted (the same applies to the drawings described below). ).

  The spacer 1 according to this embodiment includes a spacer main body 2 and a coolant agitation unit 6, and the coolant agitation unit 6 is fixed to the upper side of the spacer main body 2 by welding or the like. The spacer 1 is a so-called cell type spacer in which a plurality of cells are connected to form a fuel rod support portion.

  The spacer main body 2 includes a fuel rod support 3 and a band 5 surrounding the outer periphery of the fuel rod support 3.

  The fuel rod support portion 3 has a plurality of insertion regions A through which the fuel rods are inserted, and holds the fuel rods inserted through the insertion regions A at a predetermined interval.

  In this embodiment, the fuel rod support portion 3 is configured by connecting cylindrical cells 4 (partition members) in a square lattice shape, as shown in FIGS. The cell 4 is not limited to an octagonal cell having an octagonal cross section, and may be a round cell having a circular cross section, for example.

  As shown in FIG. 1C, the coolant stirring unit 6 includes a base portion 7 fixed to the upper end of the cell 4 and a blade portion 8 positioned on the base portion 7. By providing the coolant agitation unit 6, the blade unit 8 generates a swirling flow on the upper side of the spacer 1. In this embodiment, since the blade portion 8 can be provided at the center of the subchannel region S where the flow rate of the coolant is relatively large, a large coolant agitation effect can be obtained and the limit output can be improved. .

  As shown in FIG. 1 (b), the base portion 7 is configured in a cross shape so that the intersection point is located substantially at the center of the subchannel region S and the end portion is fixed to the upper end of the cell 4. Here, the sub-channel region S is a gap region between adjacent fuel rods held by the fuel rod support 3. The base portion 7 has a function as a reinforcing material that reinforces the connection between the adjacent cells 4.

  Note that the end of the cross-shaped base portion 7 may extend to the band portion 5, and the base portion 7 may connect the fuel rod support portion 3 and the band 5. Thereby, when a load in the horizontal direction is applied to the fuel assembly, deformation of the entire spacer can be suppressed.

  The blade portion 8 is provided on the base portion 7 in the subchannel region S as shown in FIG. The blade portion 8 is inclined at a predetermined angle with respect to the axial direction of the fuel rod held by the fuel rod support portion 3. Since the coolant flowing from the lower side to the upper side in the subchannel region S is stirred by the blade portion 8 toward the periphery, the limit output can be efficiently improved.

  In addition, the blade | wing part 8 is integrally formed with the base part 7 by press molding of the metal plate of 1 sheet. In addition, the blade portion 8 may be formed as a separate component from the base portion 7 and may be fixed on the base portion 7 by welding or the like.

  As shown in FIG. 1 (c), four blade portions 8 are attached to the cross-shaped base portion 7, and these blade portions 8 are arranged symmetrically with respect to the center of the subchannel region S. Has been. As a result, a swirling flow is generated on the upper side of the spacer (downstream of the coolant), and the liquid coolant is attached to the surface of the fuel rod.

  In addition, the number of the blade | wing parts 8 provided in the base part 7 is not restricted to four sheets, You may be 1-3 sheets. An example of the coolant stirring unit 6 in the case where the number of the blade portions 8 is two is shown in FIG. The number of blade portions 8 is preferably changed as appropriate according to the thermal margin in the subchannel region where the coolant agitating portion 6 is provided. More generally speaking, it is preferable to increase the number of blade portions on the base portion as the subchannel region has a smaller thermal margin. Thereby, a limit output can be improved, suppressing the increase in the pressure loss by a blade | wing part as much as possible.

  Further, the coolant agitation unit 6 may be provided only in the subchannel region with a small thermal margin. That is, the coolant agitation unit 6 may be provided only in a predetermined subchannel region (a region where boiling transition is likely to occur). Even if it does in this way, a limit output can be improved, suppressing the increase in the pressure loss by a coolant stirring part as much as possible.

Here, the manufacturing method of the spacer 1 according to the present embodiment will be described.
(1) First, the fuel rod support portion 3 is manufactured by connecting the cylindrical cells 4 in a square lattice shape.
(2) Next, the coolant stirring part 6 which has the base part 7 and the blade | wing part 8 which is located on this base part 7 and stirs a coolant is produced. Preferably, the base portion 7 and the blade portion 8 are integrally formed by press molding a single metal plate. In addition, the blade portion 8 may be formed as a separate component from the base portion 7. In this case, the blade portion 8 is fixed on the base portion 7 by welding or the like.
(3) Next, the base part 7 of the coolant agitation part 6 is fueled so that the blade part 8 is located in the subchannel region S and the base part 7 straddles the plurality of cells 4 along the upper end of the cell 4. The rod support 3 is fixed to the upper end of the cell 4.

  The step of fixing the band portion 5 so as to surround the outer periphery of the fuel rod support portion 3 may be performed before or after the coolant agitating portion 6 is fixed to the fuel rod support portion 3. May be.

  As described above, in the present embodiment, since the base portion 7 functions as a reinforcing material that reinforces the connection between the adjacent cells 4, the mechanical strength of the spacer can be improved.

  Further, in the conventional spacer, as described with reference to FIG. 7, since the fuel rod support portion and the coolant agitating portion are integrally provided, the thicknesses of both must be the same. Considering the distance between the fuel rods, neutron economy, spring characteristics, etc., the thickness of the constituent members was limited. On the other hand, in this embodiment, the thickness of each structural member can be optimized by making the coolant stirring part 6 which has the blade | wing part 8 into a module separate from the spacer main-body part 2. FIG. For example, the thickness of the cell 4 is set to an optimum value for the characteristics of the spring to support the fuel rod, while the thickness of the base portion 7 of the coolant agitating portion 6 is increased to increase the rigidity of the base portion 7. Can be changed. For example, the horizontal width of the base portion 7 may be made larger than the thickness of the cell 4, or the vertical width (height) of the base portion 7 may be made larger than the horizontal width. Thus, the shape of the base portion 7 can be changed to an arbitrary shape without being affected by the cell 4 in order to increase the rigidity. According to this embodiment, the mechanical strength of the spacer can be further improved by increasing the rigidity of the base portion 7.

  It should be noted that the rigidity of the material may be changed without being limited to the case where the thickness is changed between the fuel rod support portion 3 and the coolant stirring portion 6. That is, the rigidity of the base portion 7 may be higher than the rigidity of the cell 4. Even in this case, the mechanical strength of the spacer can be further improved.

  In addition to the above effects, in the present embodiment, the coolant agitation unit 6 is a module separate from the spacer body 2. That is, the spacer is functionally separated into two modules, and each module is assigned a role. Thereby, the structure of each module can be simplified and productivity can be improved. In the case of a cell-type spacer, it is not easy in manufacturing to manufacture a cell integrated with a blade portion and assemble them by connecting them.

  On the other hand, according to the present embodiment, the coolant agitating unit 6 only needs to be fixed to a region having a small thermal margin, and therefore even when the blade portion is provided only in a region having a small thermal margin, the spacer Manufacturability can be maintained. That is, according to this embodiment, a spacer having a complicated structure can be obtained while maintaining manufacturability. Moreover, since one coolant stirring part 6 can have a plurality of blade parts 8, it is not necessary to attach the blade parts to the spacer body part one by one. Therefore, it is possible to reduce the number of man-hours for coupling the coolant stirring unit 6 to the fuel rod support unit 3 and to improve the manufacturability of the spacer.

(Second Embodiment)
Next, a spacer (fuel spacer) according to a second embodiment will be described with reference to FIG. 2A shows a perspective view of a part of a spacer (fuel spacer) 1A according to the second embodiment, and FIG. 2B shows a top view of a part of the spacer 1A. FIG. 2C is a perspective view of the coolant stirring unit 6A of the spacer 1A, and FIG. 2D is a side view of a part of the spacer 1A.

  One of the differences between the second embodiment and the first embodiment is the shape of the base of the coolant agitator. Hereinafter, the second embodiment will be described with a focus on differences from the first embodiment.

  The spacer 1A according to the present embodiment includes a spacer main body 2 and a coolant agitating unit 6A, and the coolant agitating unit 6A is fixed to the upper side of the spacer main body 2 by welding or the like.

  The coolant agitator 6 </ b> A generates a swirling flow on the upper side of the spacer 1 </ b> A, and includes a base 9 fixed to the upper end of the cell 4 and a blade 8 positioned on the base 9.

  As shown in FIG. 2C, the base portion 9 is configured in a frame shape along the boundary of the gap region defined by the four cells 4. For example, when the cell 4 is an octagonal cell, the gap region is a square columnar space having a square cross section, and the base portion 9 is a rectangular frame. The base 9 has a tab (claw part) 9 a attached to the side surface of the base 9 so as to protrude from the lower end of the base 9.

  By welding the tab 9 a to the cell 4, the coolant agitator 6 </ b> A is fixed to the fuel rod support 3. Further, as shown in FIG. 2D, the coolant agitating unit 6A is held by a tab 9a with a predetermined gap G from the upper end of the cell 4.

  As described above, in the present embodiment, since the base portion 9 having the tab 9a functions as a reinforcing material that reinforces the connection between the adjacent cells 4, the mechanical strength of the spacer can be improved.

  In the present embodiment, the coolant agitator 6A is a separate module from the spacer body 2. For this reason, the horizontal width of the base 9 of the coolant agitator 6A is made larger than the thickness of the cell 4, the vertical width (height) of the base 9 is made larger than the horizontal width, etc. By changing the shape of the base portion 9, the rigidity of the base portion 9 can be increased, and thereby the mechanical strength of the spacer can be further improved.

  Furthermore, according to the present embodiment, similarly to the first embodiment, it is possible to obtain a spacer having a complicated structure while maintaining manufacturability.

  Moreover, in this embodiment, the base part 9 is comprised by frame shape along the boundary of the gap | interval area | region defined by the cell. That is, the base 9 is provided so as to overlap the cell 4 when viewed from above the spacer. For this reason, according to this embodiment, the increase in the cross-sectional area of the spacer by the base part 9 can be suppressed, and the increase in pressure loss can be suppressed as much as possible.

  Here, the modification by this embodiment is demonstrated using FIG. FIG. 3A is a perspective view of a part of a spacer (fuel spacer) 1B according to this modification, FIG. 3B is a top view of a part of the spacer 1B, and FIG. 3C is a spacer. It is a perspective view of the coolant stirring part 6B of 1B.

  The coolant stirring unit 6 </ b> B has a base 10 fixed to the upper end of the cell 4 and a blade 8 positioned on the base 10.

  The base portion 10 is configured in a frame shape along the boundary of the gap region defined by the four cells, like the above-described base portion 9. However, as shown in FIG. 3C, the base portion 10 does not have a portion corresponding to the tab 9 a described above, and is fixed to the upper end of the cell 4 without a gap.

  As described above, in this modification, since there is no tab 9a, the cross-sectional area of the spacer is small, and in addition, the lower end of the base portion 10 of the coolant agitating unit 6B and the upper end of the cell 4 of the fuel rod support unit 3 Are in contact with each other without any gaps, so the flow resistance is small. Therefore, according to the present modification, the same effect as that of the second embodiment can be obtained, and an increase in pressure loss can be further suppressed.

(Third embodiment)
Next, a spacer (fuel spacer) according to a third embodiment will be described with reference to FIG. FIG. 4A is a perspective view of a part of a spacer (fuel spacer) 1C according to the third embodiment, and FIG. 4B is a top view of a part of the spacer 1C. FIG. 6 is a perspective view of a coolant stirring part 6C of the spacer 1C.

  One of the differences between the third embodiment and the first embodiment is the configuration of the fuel rod support portion and the base portion. Hereinafter, the third embodiment will be described with a focus on differences from the first embodiment.

  The spacer 1C according to the present embodiment includes a spacer main body 2 and a coolant agitation unit 6C, and the coolant agitation unit 6C is fixed to the upper side of the spacer main body 2 by welding or the like. The spacer 1 </ b> C is a so-called divider type spacer in which a fuel rod support portion is configured by combining a plurality of dividers (partition members) parallel to the band portion 5 in a lattice shape.

  In the present embodiment, the fuel rod support portion 3 is configured by intersecting the dividers 11 in a lattice shape as shown in FIGS. 4 (a) and 4 (b).

  The base portion 12 of the coolant stirring unit 6C is configured in a lattice shape along the upper end of the divider 11 and includes a plurality of intersections of the divider 11. The size of the base portion 12 is not limited to the size of 3 × 4 shown in FIG. 4C, but can be arbitrarily selected in consideration of thermal margin, spacer manufacturability, and the like.

  As shown in FIG. 4C, the four blade portions 8 are arranged in a point-symmetric manner around the intersection of the base portion 12. As described in the first embodiment, it is preferable to appropriately determine the arrangement position and the number of the blade portions 8 according to the thermal margin of the subchannel region to be arranged. Therefore, not only when the same number of blade portions are arranged at all the intersections of the base as shown in FIG. 4C, the blade portions are arranged only at some intersections, or the number of blade portions at each intersection. May be changed.

Here, the manufacturing method of the spacer 1C according to the present embodiment will be described.
(1) First, the fuel rod support portion 3 is produced by crossing the plate-like dividers 11 in a lattice shape.
(2) Next, the coolant stirring part 6C which has the base part 12 and the blade | wing part 8 which is located on this base part 12 and stirs a coolant is produced. Preferably, the base portion 12 and the blade portion 8 are integrally formed by press molding a single metal plate. In addition, the blade portion 8 may be formed as a separate part from the base portion 12, and the blade portion 8 may be fixed on the base portion 12 by welding or the like.
(3) Next, the base portion 12 of the coolant agitator 6C is fueled so that the blade portion 8 is positioned in the subchannel region S and the base portion 12 straddles the plurality of dividers 11 along the upper end of the divider 11. It fixes to the upper end of the divider 11 of the rod support part 3.

  The step of fixing the band portion 5 so as to surround the outer periphery of the fuel rod support portion 3 may be performed before or after the coolant stirring portion 6C is fixed to the fuel rod support portion 3. May be.

  As described above, in the present embodiment, since the base portion 12 functions as a reinforcing material that reinforces the connection between the dividers 11 assembled in a lattice shape, the mechanical strength of the spacer 1C can be improved.

  Further, in the present embodiment, the coolant agitator 6C is a module separate from the spacer body 2. For this reason, the horizontal width of the base portion 12 of the coolant stirring section 6C is made thicker than the plate thickness of the divider 11, or the vertical width (height) of the base portion 12 is made larger than the horizontal width. The rigidity of the base part 12 can be increased by changing the shape of the base part 12, and the mechanical strength of the spacer can be further improved.

  Moreover, according to this embodiment, since the base part 12 is comprised by the grid | lattice form, the area | region which one coolant stirring part 6C covers is wide. Therefore, the man-hour for coupling the coolant agitator 6C to the fuel rod support 3 can be greatly reduced, and the productivity of the spacer can be further improved.

  Depending on the thermal margin or pressure loss and other factors, a plurality of types of spacers having different shapes may be manufactured. For example, this is a case where a fuel assembly configured to have a larger number of blade portions as a spacer arranged at a position closer to an upper tie plate described later is manufactured. In such a case, according to the present embodiment, since the coolant agitating portion whose shape is likely to be diversified can be manufactured separately from the fuel rod support portion, each of the coolant agitator portion and the fuel rod support portion can be manufactured. Excellent manufacturability. In addition, it is possible to flexibly change the performance of the spacer by changing the coolant agitating unit, and it is easy to deal with design and manufacturing. For example, when changing the number of blade parts, it is not necessary to make changes to the fuel rod support part, and the design and manufacturing process of the coolant agitation part may be changed. This is true not only for the present embodiment but also for the spacer according to the present invention.

  As in the first embodiment, the end of the base portion 12 may extend to the band portion 5, and the base portion 12 may connect the fuel rod support portion 3 and the band 5. Thereby, when a load in the horizontal direction is applied to the fuel assembly, deformation of the entire spacer can be suppressed.

  In the above description, the coolant stirring unit 6C having the lattice-like base portion is applied to the divider-type spacer. However, the present invention is not limited to this, and the cross-shaped base portion described in the first embodiment is provided. The coolant stirring unit 6 may be applied to a divider type spacer. That is, a coolant stirrer that is configured in a cross shape so as to extend along the upper end of the divider 11 and has a base portion whose intersection is located above the intersection of the divider 11 may be applied instead of the coolant stirrer 6C. .

  Next, a modification according to the present embodiment will be described with reference to FIG. FIG. 5A is a perspective view of a part of a spacer (fuel spacer) 1D according to this modification, FIG. 5B is a top view of a part of the spacer 1D, and FIG. It is a one part perspective view of 1D coolant stirring part 6D. As can be seen from these drawings, in the present modification, the base portion is provided on all of the upper ends of the spacer main body portion 2 including the band portion 5. That is, the base portion 13 of the coolant agitating unit 6 </ b> D is configured in a lattice shape along the upper ends of all the dividers 11 constituting the fuel rod support unit 3 and the upper end of the band unit 5. Thereby, the connection strength between the fuel rod support portion 3 and the band portion 5 can be greatly improved, and the deformation of the entire spacer when a horizontal load is applied to the fuel assembly can be further suppressed.

  Moreover, according to this modification, when manufacturing a spacer, it is only necessary to fix one coolant stirring part 6D to the spacer main-body part 2, Therefore The productivity of a spacer can be improved markedly.

  In this modification, as shown in FIG. 5, a blade portion 8 a may be provided on the base portion 13 on the band portion 5. That is, on the base portion 13 positioned at the upper end of the band portion 5, a blade portion 8 a that is inclined at a predetermined angle with respect to the axial direction of the fuel rod held by the fuel rod support portion 3 may be provided. By changing the flow direction of the coolant that rises in the vicinity of the inner wall surface of the channel box and sending the coolant to the surface of the fuel rod by the blade portion 8a, the limit output can be further improved.

  The three embodiments and the modified spacers according to the present invention have been described above. Next, the fuel assembly provided with the spacer according to the present invention will be described.

(Fuel assembly)
The fuel assembly according to the present invention is the same as the fuel assembly described with reference to FIG. That is, a fuel assembly according to the present invention includes a plurality of fuel rods, an upper tie plate for fixing the upper ends of the plurality of fuel rods, a lower tie plate for fixing the lower ends of the plurality of fuel rods, A plurality of fuel rods are bundled at a predetermined interval, and a plurality of spacers spaced in the axial direction are provided. At least one of the plurality of spacers spaced in the axial direction of the fuel assembly is the spacer according to the present invention. According to such a fuel assembly, it is possible to improve the boiling transition performance and improve the thermal margin.

  Note that not all of the spacers included in the fuel assembly are spacers according to the present invention. The spacer according to the present invention may be provided in an axial region with a small thermal margin. Generally, in the fuel assembly, the thermal margin is high on the upstream side of the coolant (that is, the lower tie plate side), but the thermal margin is low on the downstream side of the coolant (that is, the upper tie plate side). Boiling transition is likely to occur. For this reason, it is effective to arrange the spacer according to the present invention above the fuel assembly. That is, it is preferable to provide the spacer according to the present invention only in the axial region closer to the upper tie plate than to the lower tie plate. Thereby, thermal margin can be improved, reducing the pressure loss of the whole fuel assembly.

  Further, from the same viewpoint as described above, a spacer having a larger number of blade portions may be disposed toward the downstream side of the coolant. That is, at least two of the plurality of fuel spacers included in the fuel assembly are the fuel spacers according to the present invention, and the fuel spacer arranged at a position closer to the upper tie plate may have a larger number of blade portions. Good. Even in this case, the thermal margin can be improved while reducing the pressure loss of the entire fuel assembly.

  Based on the above description, those skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. . You may combine suitably the component covering different embodiment. Various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

1, 1A, 1B, 1C, 1D Spacer 2 Spacer body 3 Fuel rod support 4 Cell 5 Band 6, 6 A, 6 B, 6 C, 6 D Coolant agitation 7, 9, 10, 12, 13 Base 9 a Tab (Nail part)
8,8a Blade 11 Divider 21 Fuel assembly 22 Water rod 23 Fuel rod 24 Lower tie plate 25 Upper tie plate 26 Spacer 27 Channel box 100 Grid type spacer 110 Divider 111 Spring 112 Flow wing 120 Band part 121 Flow tab 122 Tab A Insertion Region G Gap S Subchannel region

Claims (26)

A spacer having a plurality of insertion regions through which fuel rods are inserted, a fuel rod support portion that holds the fuel rods inserted through the insertion regions at a predetermined interval, and a band portion that surrounds the outer periphery of the fuel rod support portion The main body,
A base portion fixed on the upper side of the partition member constituting the fuel rod support portion and a position above the base portion in a subchannel region which is a gap region between adjacent fuel rods held by the fuel rod support portion. A coolant agitation part having a blade part inclined at a predetermined angle with respect to the axial direction of the fuel rod;
A fuel spacer comprising: The fuel rod support portion is configured as a cylindrical cell connected as a partition member in a square lattice shape,
2. The base according to claim 1, wherein the base portion is configured in a cross shape so that an intersection point is located substantially at the center of the subchannel region and an end portion is fixed to an upper end of the cell. Fuel spacer.   The fuel spacer according to claim 2, wherein an end portion of the base portion extends to the band portion, and the base portion connects the fuel rod support portion and the band. The fuel rod support portion is configured as a cylindrical cell connected as a partition member in a square lattice shape,
The base portion is configured in a frame shape along the boundary of the gap region defined by the four cells,
The coolant agitation part is held at a predetermined gap from the upper end of the cell by a claw part attached to a side surface of the base part so as to protrude from the lower end of the base part. The fuel spacer according to claim 1. The fuel rod support portion is configured as a cylindrical cell connected as a partition member in a square lattice shape,
2. The base according to claim 1, wherein the base is configured in a frame shape along a boundary of a gap region defined by the four cells, and is fixed to the upper end of the cell without a gap. Fuel spacer. The fuel rod support part is configured as a crossing of a divider as the partition member in a lattice shape,
2. The fuel spacer according to claim 1, wherein the base portion is configured in a lattice shape along an upper end of the divider so as to include a plurality of intersections of the divider. The fuel rod support part is configured as a crossing of a divider as the partition member in a lattice shape,
2. The fuel spacer according to claim 1, wherein the base portion is formed in a cross shape so as to extend along an upper end of the divider, and an intersection thereof is located on an intersection of the divider.   The fuel spacer according to claim 6 or 7, wherein an end portion of the base portion extends to the band portion, and the base portion connects the fuel rod support portion and the band. The fuel rod support part is configured as a crossing of a divider as the partition member in a lattice shape,
2. The fuel spacer according to claim 1, wherein the base portion is configured in a lattice shape along the upper ends of all the dividers and the upper ends of the band portions constituting the fuel rod support portion.   The blade portion inclined at a predetermined angle with respect to the axial direction of the fuel rod held by the fuel rod support portion is provided on the base portion positioned at the upper end of the band portion. Item 10. The fuel spacer according to Item 9.   The fuel spacer according to claim 1, wherein a width of the base portion in a horizontal direction is larger than a thickness of the partition member.   The fuel spacer according to claim 1, wherein a width of the base portion in a vertical direction is larger than a width of the base portion in a horizontal direction.   The fuel spacer according to any one of claims 1 to 12, wherein a plurality of the blade portions are arranged point-symmetrically with respect to the center of the subchannel region.   The fuel spacer according to any one of claims 1 to 13, wherein the number of the blade portions on the base portion is larger in the subchannel region having a smaller thermal margin.   The fuel spacer according to any one of claims 1 to 13, wherein the coolant agitating portion is provided only in a predetermined subchannel region. Multiple fuel rods,
An upper tie plate for fixing upper ends of the plurality of fuel rods;
A lower tie plate for fixing lower ends of the plurality of fuel rods;
Bundling the plurality of fuel rods at a predetermined interval, and having a plurality of fuel spacers spaced in the axial direction,
The fuel assembly according to claim 1, wherein at least one of the plurality of fuel spacers is the fuel spacer according to claim 1. Multiple fuel rods,
An upper tie plate for fixing upper ends of the plurality of fuel rods;
A lower tie plate for fixing lower ends of the plurality of fuel rods;
Bundling the plurality of fuel rods at a predetermined interval, and having a plurality of fuel spacers spaced in the axial direction,
The fuel assembly according to any one of claims 1 to 15, wherein the fuel spacer according to any one of claims 1 to 15 is provided only in an axial region closer to the upper tie plate than to the lower tie plate. Multiple fuel rods,
An upper tie plate for fixing upper ends of the plurality of fuel rods;
A lower tie plate for fixing lower ends of the plurality of fuel rods;
Bundling the plurality of fuel rods at a predetermined interval, and having a plurality of fuel spacers spaced in the axial direction,
The fuel spacer according to any one of claims 1 to 15, wherein at least two of the plurality of fuel spacers are disposed closer to the upper tie plate of the fuel assembly. A fuel assembly characterized by a large number. By connecting cylindrical cells in a square lattice shape, a fuel rod support portion having a plurality of insertion regions through which fuel rods are inserted and holding the fuel rods inserted through the insertion regions at a predetermined interval is manufactured. And a process of
Producing a coolant agitation part having a base part and a blade part located on the base part for stirring the coolant;
The blade portion is positioned in a subchannel region that is a gap region between adjacent fuel rods held by the fuel rod support portion, and the base portion straddles the plurality of cells along the upper end of the cell. Fixing the coolant stirring part to the fuel rod support part;
A method for producing a fuel spacer, comprising:   20. The method of manufacturing a fuel spacer according to claim 19, wherein, in the manufacturing step of the coolant stirring part, the base part and the blade part are integrally formed by press forming a metal plate.   21. The method of manufacturing a fuel spacer according to claim 19, wherein the base of the coolant agitator has a horizontal width greater than the thickness of the cell.   The method for manufacturing a fuel spacer according to any one of claims 19 to 21, wherein the base of the coolant agitator has a width in a vertical direction larger than a width in a horizontal direction. By crossing the plate-like dividers in a lattice shape, a fuel rod support portion having a plurality of insertion regions through which the fuel rods are inserted and holding the fuel rods inserted through the insertion regions at a predetermined interval is produced. Process,
Producing a coolant agitation part having a base part and a blade part located on the base part for stirring the coolant;
The blade portion is positioned in a subchannel region which is a gap region between adjacent fuel rods held by the fuel rod support portion, and the base portion straddles a plurality of the dividers along the upper end of the divider. Fixing the coolant stirring part to the fuel rod support part;
A method for producing a fuel spacer, comprising:   24. The method of manufacturing a fuel spacer according to claim 23, wherein, in the manufacturing step of the coolant stirring part, the base part and the blade part are integrally formed by press forming a metal plate.   25. The method of manufacturing a fuel spacer according to claim 23, wherein the base of the coolant agitation unit has a horizontal width larger than a thickness of the divider.   26. The method of manufacturing a fuel spacer according to claim 23, wherein the base of the coolant agitating unit has a vertical width larger than a horizontal width.

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