JPH09222488A - Asymmetry fuel assembly for boiling water reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To equalize the thermal margin of the whole body of a fuel rod and improve the limit output performance of it by extending a piece for redirecting and introducing a coolant to an appropriate place in a fuel assembly for a boiling water reactor where a water channel is located biasedly toward a corner from a diagonal as to a fuel-rod holding spacer which is configured like a tetragonal lattice. SOLUTION: A square water channel 14A is placed biasedly toward a corner 12a on a diagonal from the axial center of a spacer 12, so that the thermal margin of a fuel rod 13 is large on the corner 12a side and small in an area E. As a result, the limit output property deteriorates. In this invention, a piece 21 for introducing the reorientation of a coolant equalizes the thermal margin by meandering the coolant toward the fuel rod 13 on the area E side to improve the limit output performance. The piece 21 is extended outwardly and diagonally upward from side plates 14a and 14b on the side of a coolant passage G1 which is placed on the control rod side in an inside frame board 14B where the water channel 14A is inserted and supported.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear fuel assembly which is used by being loaded in a core of a boiling water nuclear reactor, and which includes a large number of fuel rods arranged in a square lattice, and a diagonal line in the square lattice. Regarding an asymmetric fuel assembly in which square or round water channels are biasedly arranged near one corner above, an inner frame body for inserting and supporting the water channel in the spacer, Appropriately extend the coolant deflection introduction piece, increase the size of only the flow vanes at the specified locations of the known flow vanes provided on the outer frame of the spacer, or increase the bending angle of the flow vanes. By doing so, it is intended to improve the limit output performance of the fuel rod.

[0002]

2. Description of the Related Art As is known, in order to load a nuclear fuel assembly a into a core of a boiling water reactor, a core support plate disposed below the core 1 as disclosed in FIG. 2, the lower tie plates 10 of the set of four nuclear fuel assemblies a are seated on the fuel support fittings 3 provided therein, and thereby the nuclear fuel assembly is in a standing state. Each upper side of the body a is inserted into the lattice frame 4a of the upper lattice plate 4 arranged above the core 1.

Here, in FIG. 7 of the above, reference numeral 5 shows a known control rod formed in a cross shape, which is erected from below the core 1 through the fuel support fitting 3 and is formed in a cross shape. It is configured such that it can be inserted into or withdrawn from the coolant passage G separated from each other among the four nuclear fuel assemblies a,
In this case, the structure of the coolant channel G is as shown in FIG.
As clearly shown in (A) and (B), types called C lattice and D lattice are known. Then, in the above-mentioned C lattice, as shown in the same figure (A), the control rods 5 are formed between _four sets of nuclear fuel assemblies a ₁ , a ₂ , a ₃ and a ₄ into which the control rods 5 are inserted and are separated from each other. Control rod side coolant flow path g ₁ separation width w
₁ and the separation width of the non-control rod side coolant flow passage g ₂ that is formed between 1 and the set of four nuclear fuel assemblies a ₄ , a ₃ , a ₂ , a ₁ in which the control rod 5 is not inserted. w ₂ is equal to w ₂ .

On the other hand, in the so-called D grid, as shown in FIG. 6B, the separation width W ₁ of the control rod side coolant passage G _{1 and} the separation width of the non-control rod side coolant passage G ₂ are separated. The width W ₂ is
It is set such that W ₁ > W ₂ . Here, the above-mentioned nuclear fuel assembly a is held by a plurality of spacers 12 between the upper tie plate 11 and the lower tie plate 10 as understood from FIGS. 8 and 9. In addition, a fuel main body 15 in which a large number of fuel rods 13 and a small number of water channels 14 are vertically installed at a predetermined interval, and the upper tie plate 11 and the lower type that are fitted on the fuel main body 15 And a channel box 16 fixed at rate 10.

Further, the above-mentioned nuclear fuel assembly a is at a corner upper end which is one corner of the channel box 16, and a channel fastener 17 is attached as shown in FIG. Leaf spring 17
a and 17b are one side wall 16a in the channel box 16 and the other side wall 1 which is continuously provided orthogonally thereto.
6b and 6b, respectively. The nuclear fuel assembly a as described above has the nuclear fuel assemblies a ₁ and a ₂ , a ₃ as shown in FIG. 8 and FIG.
And a ₄ , a ₁ and a ₃ , and a ₂ and a ₄ are the respective leaf springs 1 of the channel fastener 17 described above.
By bringing the 7a and 17b into contact with each other, the elastic force based on this makes the four nuclear fuel assemblies a ₁ , a ₂ , a
The pair of side walls of each channel box 16 in ₃ and a ₄ are loaded so as to be in elastic contact with the upper lattice plate 4 in the core 1.

[0006] Now, when loaded with such nuclear fuel assemblies a above the core 1, in the case of C gratings the by FIG. 6 (A) is the control rod side coolant passage g ₁ and uncontrolled Since the separation widths w ₁ and w ₂ of the rod-side coolant flow path g ₂ are formed to have the same width length, the flow rate distribution of the coolant becomes uniform, and therefore the concentration distribution of the fuel element is biased. Even if there is not, the output of the nuclear fuel assembly a becomes flat over the entire surface.

However, in the D grid shown in FIG. 6B, the separation width W _{1 of the} control rod side coolant passage G ₁ is as described above.
However, since it is set to be larger than the separation width W ₂ of the non-control rod side coolant passage G ₂ , the control rod side coolant passage G ₁ is more likely to react because the flow rate of the coolant is larger. The output of the fuel rods increases, whereas in the non-control rod side coolant flow passage G ₂ , the flow rate of the coolant is the same as in the above, and the reaction is less likely to occur, so the output tends to decrease. Therefore, there is a latent problem that the local peaking coefficient increases. For this reason, as a means for suppressing the local peaking coefficient, at present, for the fuel near the control rod side coolant flow passage G ₁ which is wide in the nuclear fuel assembly a, the enrichment degree is set to a low level in advance. As for the fuel near the non-control rod side coolant passage G ₂ which is narrow, the output is flattened by increasing the concentration of the fuel.

However, when the countermeasures based on the enrichment distribution as described above are taken, the local peaking coefficient is reduced, so that the overall reactivity is also reduced. Therefore, from the viewpoint of improving the neutron utilization rate, If this is the case, it will not be the optimal measure.

On the other hand, in order to increase the burnup of the nuclear fuel assembly, there is a lattice type as shown in FIG. 9 or a spacer 12 in which the fuel rods are arranged in a square lattice by the ring element type. The fuel rod 13 at its axial center
It is known that the water channel 14A having a thick rectangular shape or a round shape is vertically installed in the space occupied by a plurality of the above-mentioned fuel cells. For the purpose of suppressing the local peaking coefficient, as already shown by the phantom line in FIG.
An asymmetric fuel assembly has been proposed in which the arrangement of the water channels 14A is displaced to the biased position 18.

As can be seen from FIG. 9, this asymmetric fuel assembly is located on the diagonal line 19 of the spacer 12 and is closer to one corner 12a.
It is a deviation of A. According to this structure, prismatic water channel 14A to the non-control rod side coolant passage G ₂ closer with a narrow width is offset, this result, in a state in which the asymmetric fuel assemblies loaded in the core 1 , The control rod side coolant passage G ₁ , the non-control rod side coolant passage G ₂ , and the inside of the channel box 16, the moderator distribution is made uniform in the radial direction, and the local peaking coefficient is obtained. It is effective in suppressing

As is also known, in the asymmetric fuel assembly, as shown in FIG. 10, both the lattice type and ring element type spacers 12 have a square outer frame 12A. An inner frame plate 14 for inserting and supporting the water channel 14A at the biased position inside
B is fixed to the outer frame body 12A. Further, the outer frame body 12A has four outer peripheral surface plates 12b, 12c, 12d, and 12e which are upwardly flowed over the entire circumference of the outer frame body 12A. A large number of flow vanes (FLOW VANE) 20 inwardly and obliquely upward from the plate upper ends of the side plates 12b to 12e so as to allow a curved flow toward the inside of the support 12.
Are extended in a uniform form. The extension positions of the flow vanes 20 are selected so as to be directed to the mutual gaps that serve as the coolant flow passages of the vertically mounted fuel rods 13.

[0012]

As described above as the prior art, when an asymmetric fuel assembly is used, it can be effective in suppressing the local peaking coefficient, but it is effective in removing heat from the fuel rods 13. Channel Box 1 to contribute
Considering the distribution of the coolant within the fuel cell 6, the fuel rods are clearly arranged asymmetrically. Therefore, the thermal margin of the fuel rods 13 in the target fuel assembly surrounded by the channel box 16 is shown in FIG. As can be understood from FIG. 10, the non-control rod side coolant flow passage G ₂ side becomes large, and the thermal margin on the control rod side coolant flow passage G ₁ side becomes smaller compared to this, so that there is a space between the two. A difference in thermal margin occurs, and as a result, the marginal output performance deteriorates.

Further, considering the asymmetric fuel assembly, as is known, generally, the steam generated by the heat generation of the fuel rods 13 is cross-sectional direction, that is, in the radial direction of the asymmetric fuel assembly described above. It is known that there is a tendency to shift to the side with a larger flow passage cross-sectional area. Therefore, as illustrated by FIG. 1 according to the present invention, the separation width W ₁ is clearly shown by an imaginary line on the control rod side coolant flow passage G ₁ side which is wider than the non-control rod side coolant flow passage G ₂ . Steam tends to collect on the side of the fuel rods 13 existing in the region E, and as a result, the vapor density in the region E increases and the heat removal property for the fuel rods 13 decreases, so that the thermal margin tends to decrease. However, it is expected to become even larger.

In the present invention, based on the above consideration, in the asymmetric fuel assembly of this type, the flow rate of the coolant flowing through the coolant passage near the control rod side coolant passage in the channel box However, considering that it is effective to increase this as much as possible in order to improve the limit output of the asymmetric fuel assembly, it is possible to focus on providing the following configuration. did it.

The present invention is based on the above-mentioned attention, and in the asymmetrical fuel assembly for a boiling water reactor according to claim 1, the inner frame body for inserting and supporting the water channel in the spacer is controlled. From the face plate end of the side wall facing the rod-side coolant flow path, a coolant turning-introducing piece bent outward and obliquely upward is extended, whereby the coolant is heated. The fuel rod located near the flow path of the coolant on the control rod side, where there is a concern that the operating margin will be reduced, will be able to provide sufficient inflow to equalize the flow distribution of the coolant in the channel box and The purpose is to make it possible to avoid the deterioration of the marginal output performance due to the thermal margin difference of the rods.

Further, according to the second aspect of the present invention, instead of providing a new coolant turning-introducing piece, attention is paid to a flow vane in a spacer that has been provided up to now, and the control rod is described above. The flow vane near the side coolant passage is formed to have a larger size than the flow vane near the non-control rod side coolant passage. To increase the output power of the fuel rod, thereby avoiding the deterioration of the limit output performance due to the imbalance of the thermal margin of the fuel rod as described in claim 1.

In the third aspect of the present invention, the surface area of the flow vanes is set to have a large or small difference as in the second aspect, so that the coolant is introduced toward the fuel rod at a desired position. On the other hand, the bending angle of the flow vanes is set to have a large or small difference, whereby a larger amount of the coolant is directed to the fuel rods near the control rod side coolant passage, and thereby, the above-mentioned claim I am trying to achieve the same purpose as in 2.

[0018]

In order to achieve the above object, the present invention provides a plurality of square lattice arrays vertically arranged between an upper tie plate and a lower tie plate. A large number of fuel rods held by a certain spacer and one water channel arranged on a diagonal line of the spacer and biased toward one corner,
A fuel main body vertically mounted at a predetermined interval, and a channel box fitted to the fuel main body and fixed to the upper tie plate and the lower tie plate,
In the asymmetric fuel assembly in which the water channel is inserted in and supported by the inner frame plate of the spacer, when the water channel is loaded on the core of the boiling water reactor on the side wall of the inner frame plate, Wide control rod side into which a control rod that is a letter is inserted.A pair of side plates facing the coolant flow path side has the above-mentioned control for the coolant that flows upward from one or both face plate upper ends. An asymmetric fuel assembly for a boiling water reactor, characterized in that a coolant turning-introducing piece capable of bending to a fuel rod on a rod-side coolant flow path side is extended outward and obliquely upward. Trying to provide.

Next, in the case of the asymmetric fuel assembly for a boiling water reactor according to claim 2, the coolant flowing upward in the outer frame plate of the spacer according to claim 1,
In the asymmetric fuel assembly in which the flow vanes are extended inward and obliquely upward from the upper end of the plate so that this can be bent toward the inside of the spacer, when loaded into the core of a boiling water reactor. , A wide control rod side into which a control rod having a cross shape is inserted, and a large flow vane extending from one or both of the outer peripheral plates facing the coolant channel side, the control rod being inserted. The content is that the surface area to which the coolant is applied is formed larger than that of the flow vanes extending from the pair of outer peripheral surface plates directed to the narrow control rod side coolant flow path side which is not controlled.

Further, according to a third aspect of the present invention, in comparison with the second aspect, when the control rod having a cross shape is inserted into the core of the boiling water reactor, the wide control rod side is inserted. In the pair of perimeter plates facing the coolant channel side, the large curved flow vanes extending from one or both of them are the pair of outer faces directed to the narrow control rod side coolant channel side in which the control rod is not inserted. The difference is that the inward bending angle with respect to the outer frame plate is formed larger than that of the flow vanes extending from the side plate.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION First of all, the present application relates to claim 1.
The case of using the lattice type spacer in FIG. 1 and the asymmetric fuel assembly for a boiling water reactor using the ring element type spacer of FIG. 4 will be described in detail below. The basic structure thereof is the same as the structure already described in detail with reference to FIGS. 8 and 9, and the same constituent members are the nuclear fuel assemblies and asymmetric fuel assemblies in the conventional example, and the members in the core explicitly shown in FIG. The same reference numeral is adopted.
That is, the fuel main body 15 and the channel box 16 fitted and fixed to the fuel main body 15 are provided, and the fuel main body 15 is provided between the upper tie plate 11 and the lower tie plate 10 and is provided with a plurality of spacers arranged vertically. A large number of fuel rods 13 held by 12 and a rectangular water channel 14A are vertically mounted and held while being separated from each other by a predetermined distance.

Further, similarly to the above-mentioned conventional example, at the corner upper end which is one corner of the channel box 16,
A pair of leaf springs 17a, 17b branched from the channel fastener 17 are attached to the core 1 of the boiling water reactor, and the control rod 5 is inserted into each of the wide widths. The control rod side coolant passage G ₁ is projected toward the side of the coolant passage G, and of course, the adjacent nuclear fuel assembly a is mounted.
_As described above, the leaf springs 17a and 17b of the channel fasteners 17 of ₁ and a ₂ are loaded in the core 1 in the elastically contacting state with each other.

As described above, in FIGS. 1 to 4,
14B is an inner frame plate fixed to the spacer 12 for inserting the water channel 14A and supporting it.
A is a square outer frame plate, 12f of FIGS. 1 to 3 are vertical and horizontal lattice plates internally fixed to the outer frame plate 12A, and
4 and 5, in the outer frame plate 12A, a large number of ring elements 12g are fixedly installed in an circumscribed state.

According to a first aspect of the present invention, in such an asymmetric fuel assembly for a boiling water reactor, as shown in FIGS. 1 and 4, the core 1 of the boiling water reactor is loaded. At this time, the four side plates 1 on the side walls of the inner frame plate 14B
4a, 14b, 14c, 14d, one of which is _one of the pair of side plates 14a, 14b oriented toward the wide control rod side coolant flow passage G ₁ side into which the above-mentioned cruciform control rod 5 is inserted. Alternatively, the coolant deflection introduction piece 2 from the upper end of both face plates
1 is extended. Here, in the above figure, the inner frame plate 14
Although the rectangular water channel 14A is fitted to B, the round water channel 14A is fitted to the inner frame plate 14B so as to be inscribed.

The coolant turning-introducing piece 21 is shown in FIG.
Is curved so as to extend outwardly and obliquely upward with respect to the water channel 14A as indicated by the above, whereby the coolant flowing upward as shown by the arrow is When the coolant is applied to the introduction piece 21, it is deflected toward the fuel rod 13 side, so that the coolant is in the region E which has been clarified in the explanation of the conventional example.
It will be introduced toward the fuel rod 13 in which the heat removal property is lowered.

Here, of course, the coolant deflection introduction piece 21
It is better to extend from both of the pair of side plates 14a and 14b, and it is desirable to extend a plurality of tongue pieces from one side plate as shown in the drawing. At this time, in the case where the cooling medium turning / introducing piece 21 for one sheet is used, the pressure loss due to the cooling medium increases. Further, in the illustrated example, the cooling medium deflection introducing piece 21 formed in a tapered trapezoidal shape is extended toward the respective lattice plates 12f as shown in FIG. 1, and the deflected cooling medium is The fuel rods 13 are easily introduced toward the mutual gap.

As a result, according to the first aspect of the present invention, due to the presence of the coolant diverting / introducing piece 21, rather than the fuel rods 13 arranged on the non-control rod side coolant passage G ₂ side, The flow rate of the coolant supplied to the fuel rod 13 arranged on the control rod side coolant passage G ₁ side becomes large, and as a result, the water channel 14A of the asymmetrical fuel assembly is biased so that the fuel rod The imbalanced state related to the thermal margin is significantly corrected, which can solve the problem of the deterioration of the marginal output performance.

Next, the asymmetric fuel assembly for a boiling water nuclear reactor according to claim 2 will be described in detail with reference to FIGS. 2 and 5, and its basic structure will be the same as that of the conventional example described in claim 1. The same reference numerals are used for the same members, but in this embodiment, the round water channel 14A is used, and the outer side of the spacer 12 as in the conventional example. Frame plate 12A
2B, the flow vane 20 extends obliquely upward from the upper end portion of the plate toward the inside of the spacer 12 over the entire circumference, whereby the coolant that flows upward is formed as shown in FIG.
As described above, the music can flow toward the inside of the spacer 12.

The structure of claim 2 is different from the above-mentioned conventional example in that a pair of outer side face plates 12b, 12c oriented toward the control rod side coolant flow passage G ₁ side having the above-mentioned wide width,
Large flow vane 20A extending from one or both
However, the flow vane 2 extending from the pair of outer side face plates 12d and 12e directed toward the narrow non-control rod side coolant flow passage G ₂ side.
0 is that the surface area of the coolant that flows into the coolant is larger than 0. Therefore, in the illustrated example, the large flow vane 20A extends longer than the flow vane 20.

That is, the flow vanes 20 extending from the outer side face plates 12d and 12e are formed to have the same distribution surface area as conventional general-purpose flow vanes, but the outer side face plates 12b and
2c as one or both flow vanes of FIG.
The large flow vane 20A as specified in (A) and (B) is adopted. And these flow vanes 20,
It is desirable that the large flow vanes 20A have a tapered shape along the lattice plate 12f in FIG.

With this structure, as understood from the above explanations, the flow rate of the coolant supplied to the fuel rod 13 near the non-control rod side coolant passage G ₂ by the smaller flow vane 20. Rather than the control rod side coolant flow path G
_{Since the} flow rate supplied to the fuel rods 13 closer to _one side increases, the defect that the thermal margin of the fuel rods 13 decreases due to the deviation of the water channels 14A is caused by the large flow vanes 2.
It is canceled by the extension of 0A, whereby the above-mentioned claim 1
In the same manner as described above, the limit output performance can be improved.

In the third aspect, the basic configuration is the same as that of the second aspect, but the difference is that the flow vane in the spacer 12 in the second aspect is the same. Up to 20 small flow vanes,
The large-sized flow vanes 20A are arranged at appropriate positions, but the size of the flow vanes is not set to be different, but as clearly shown in FIG. Even if the flow vanes 20 of the same size are used, the difference is set in the bending angle toward the inside.

More specifically, as disclosed in FIG. 3 above, there is a pair of outer side face plates 12b, 12c directed toward the wide control rod side coolant passage G ₁ side and extending from one or both of them. Bending angle of large curved flow vane 22 θ ₁
Of the flow vane 2 extending from the pair of outer side face plates 12d and 12e directed toward the narrow non-control rod side coolant flow path G ₂ side.
It is formed to be larger than the bending angle θ _{2 of} 0,
By doing so, substantially the same effect as that of the second aspect can be exhibited.

That is, for each bending angle, θ ₁ > θ ₂
If so, the coolant flowing upward is deflected by the existence of the flow vanes 20 as shown in FIG. 2B, and the presence of the large curved flow vanes 20A is larger than the flow amount introduced into the fuel rods 13. Since the flow rate that is changed by and is introduced into the fuel rod 13 is larger, a large amount of cooling water is supplied to the fuel rod 13 side closer to the control rod side coolant flow path G ₁ and the thermal margin is increased. At this point, the homogenization of all the fuel rods 13 is promoted, so that it is possible to expect an improvement in the limit output characteristic.

[0035]

Since the present invention is configured as described above, the first aspect of the present invention relates to the inner frame body for supporting the insertion of the water channel, and in the control rod side coolant passage side, Since the coolant turning-introducing piece was properly extended, the thermal margin of the fuel rod for the asymmetrical fuel assembly that can effectively suppress the local peaking coefficient,
The uniform distribution of water, which is the cooling medium, makes it possible to equalize the entire area inside the channel box.
The limit output performance can be improved.

Further, in the asymmetric fuel assembly according to claim 2, the flow vanes provided on the outer frame plate of the spacer, which has been adopted as the conventional example, are provided on the control rod side coolant passage side. By forming the flow vane in a large size, and not adopting the large size flow vane in claim 3, by adopting a large curved flow vane having a large bending angle with respect to the flow vane at a corresponding position, In either case, it is possible to ensure a sufficient supply of the coolant to the fuel rods on the control rod side coolant passage side, and it is possible to realize the improvement of the marginal output performance as in the first aspect.

[Brief description of drawings]

FIG. 1A is a plan explanatory view showing a square lattice type spacer portion in a core-loaded state of an asymmetric fuel assembly for a boiling water reactor according to the invention of claim 1;
(B) is a partially enlarged schematic view in which a part of the cross section taken along the line BB in (A) is cut away.

FIG. 2A is a plan view showing a square lattice type spacer portion in a core-loaded state of the asymmetric fuel assembly for a boiling water reactor according to claim 2; FIG.
FIG. 7 is a partially enlarged schematic view in which a part of a cross section taken along the line BB in FIG.

FIG. 3 is a partially enlarged schematic view of the asymmetric fuel assembly for a boiling water reactor according to claim 3 showing a square grid type spacer portion in a core-loaded state by a partial cutout of a vertical section. is there.

FIG. 4 is a plan view showing a square ring element type spacer portion in a core-loaded state of the asymmetric fuel assembly for a boiling water reactor according to claim 1;

FIG. 5 is a plan view showing a square ring element type spacer portion in a core-loaded state of an asymmetric fuel assembly for a boiling water reactor according to claim 2;

FIG. 6 is a plan view showing the arrangement positions of the nuclear fuel assemblies with respect to the upper lattice plate in the boiling water reactor core, (A) is a C lattice type, and (B) is a D lattice type.

FIG. 7 is a schematic perspective view of an essential part showing an installed state of a nuclear fuel assembly in a conventional boiling water reactor core.

FIG. 8 is a partially cutaway vertical front view showing a core-loaded state of a conventional boiling water nuclear reactor nuclear fuel assembly.

FIG. 9 is a schematic plan view showing a square lattice type spacer portion in a core loaded state of a nuclear fuel assembly in which conventional rectangular water channels are vertically installed at an axial center position and a biased position, respectively.

FIG. 10 (A) is a schematic explanatory view showing a square lattice type spacer portion in a core-loaded state of a nuclear fuel assembly, and FIG. 10 (B) shows a square ring element type spacer portion. It is a plane schematic explanatory view.

[Explanation of Codes] 1 core 5 control rod 10 lower tie plate 11 upper tie plate 12 spacer 12A outer frame plate 12a corner 12b outer face plate 12c outer face plate 12d outer face plate 12e outer face plate 13 fuel rod 14A water channel 14B Inner frame plate 14a Side plate 14b Side plate 15 Fuel main plate 16 Channel box 19 Diagonal line 20 Flow vane 20A Large flow vane 21 Coolant diverting introduction piece 22 Omagari flow vane G ₁ Control rod side Coolant flow passage G ₂ Non control rod side Coolant flow path θ ₁ Bending angle of large curved flow vanes θ ₂ Bending angle of flow vanes

Claims (3)

[Claims] 1. A large number of fuel rods held by a spacer, which is a plurality of square lattice arrays arranged vertically, between an upper tie plate and a lower tie plate, and a diagonal line of the spacer. There is a fuel main body in which one water channel, which is installed biased toward one corner, is vertically installed with a predetermined gap, and the upper tie plate fitted to the fuel main body. A channel box fixed to the lower tie plate, wherein the water channel is inserted into and supported by the inner frame plate of the spacer, and the water channel is provided on a side wall of the inner frame plate. When loaded in the core of a boiling water reactor, a pair of side plates facing the wide control rod side coolant channel side into which a control rod having a cross shape is inserted, and one or both face plate upper ends Upward from the department In the case of a flowing coolant, a coolant diverting / introducing piece capable of bending the coolant toward the fuel rod on the control rod side coolant passage side is extended outward and obliquely upward. Asymmetric fuel assembly for boiling water reactor. 2. A plurality of fuel rods held by a spacer, which is a plurality of square lattice arrangements arranged vertically, between an upper tie plate and a lower tie plate, and a diagonal line of the spacer. There is a fuel main body in which one water channel, which is installed biased toward one corner, is vertically installed with a predetermined gap, and the upper tie plate fitted to the fuel main body. A channel box fixed to the lower tie plate, and a coolant flowing upward in the outer frame plate of the above spacer,
In the asymmetric fuel assembly in which the flow vanes are extended inward and obliquely upward from the upper end of the plate so that this can be bent toward the inside of the spacer, when loaded into the core of a boiling water reactor. , A wide control rod side into which a control rod having a cross shape is inserted, and a large flow vane extending from one or both of the outer peripheral plates facing the coolant channel side, the control rod being inserted. The boiling water type is characterized in that the surface area to which the coolant is applied is formed larger than that of the flow vanes extending from the pair of peripheral plates facing the non-control rod side coolant flow passage side which is not narrowed. Asymmetric fuel assembly for nuclear reactors. 3. A plurality of fuel rods held by a spacer, which is a plurality of square lattice arrays arranged vertically, between an upper tie plate and a lower tie plate, and a diagonal line of the spacer. There is a fuel main body in which one water channel, which is installed biased toward one corner, is vertically installed with a predetermined gap, and the upper tie plate fitted to the fuel main body. A channel box fixed to the lower tie plate, and a coolant flowing upward in the outer frame plate of the above spacer,
In the asymmetric fuel assembly in which the flow vanes are extended inward and obliquely upward from the upper end of the plate so that this can be bent toward the inside of the spacer, when loaded into the core of a boiling water reactor. , A cross-shaped control rod is inserted into a wide control rod side into which the control rod side is inserted, and a large curved flow vane extending from one or both of the outer peripheral face plates is directed to the coolant flow path side, and the control rod is not inserted. The boiling water type is characterized in that the inward bending angle with respect to the outer frame plate is formed to be larger than that of the flow vanes extending from the pair of outer peripheral surface plates directed to the narrow non-control rod side coolant flow path side. Asymmetric fuel assembly for nuclear reactors.