JP3315572B2 - Fuel assembly and debris filter and lower tie plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel assembly used, for example, in a core of a boiling water reactor, and more particularly to a fuel assembly and a debris filter provided with means for preventing foreign matter from entering the inside. As well as the lower tie plate.

[0002]

2. Description of the Related Art In general, a fuel assembly for a boiling water reactor generally includes a plurality of nuclear fuel rods having a large number of nuclear fuel pellets therein and an upper end of a water rod in which a neutron moderator flows inside by an upper tie plate. While holding, these lower ends are supported by the lower tie plate. These fuel rods and water rods are held at regular intervals by a plurality of spacers arranged in the axial direction.Water, which is a neutron moderator and coolant, flows in from the opening at the lower end of the lower tie plate, and It is supplied inside the aggregate.

[0003] In the periodic inspection of the reactor, operations such as replacement of a fuel assembly by opening the upper lid of the reactor pressure vessel are performed. Therefore, it cannot be said that there is no possibility that any foreign matter falls into the reactor during the regular inspection work. In addition to periodic inspections, when repairing reactors or pipes, metal wires and pieces of metal may enter the coolant loop, and other causes may cause microstructure damage in the reactor and debris. It cannot be said that there is no possibility of remaining in the reactor.

[0004] It is conceivable that the foreign matter mixed in the reactor flows in the reactor together with the coolant during the operation of the reactor, enters the fuel assembly, and causes fretting damage to the fuel assembly members. .

Therefore, the following two types have been proposed as known technologies provided with a foreign matter catching mechanism for preventing fretting damage to a fuel rod, a spacer, or the like due to such foreign matter.

The lower tie plate has a foreign matter capturing function, that is, the lower tie plate itself, which is the inlet of the coolant to the fuel assembly, has a function of capturing foreign matter.

A device provided with a debris filter as a foreign matter capturing mechanism In order to more effectively capture foreign matter, instead of having the lower tie plate also serve as a capturing function as described in JP-A-63-91591. And a separate debris filter.

[0008]

However, the above-mentioned known technology has the following problems. That is,
When foreign matter that has entered from the lower tie plate coolant inlet is captured by the debris filter (the foreign matter capturing portion of the lower tie plate in the above-described type), the captured foreign material hinders the flow of the coolant into the fuel assembly. You. Therefore,
As the amount of foreign matter to be captured increases, clogging occurs in this portion and pressure loss increases, and there is a possibility that sufficient coolant may not be supplied between the fuel rods, which is not preferable in terms of fuel integrity.

An object of the present invention is to provide a fuel assembly, a debris filter, and a lower tie plate which can reduce a decrease in the amount of coolant flowing into the fuel assembly when foreign matter is captured and improve fuel integrity. It is to be.

[0010]

To achieve the above object, according to the solution to ## to hold by the present invention lever, a plurality of fuel rods fissile material is filled therein, the upper end portion of the plurality of fuel rods An upper tie plate, a lower tie plate that holds lower end portions of the plurality of fuel rods and guides a coolant supplied from below between the upper fuel rods, and the lower portion as a substrate member
Upper wall of tie plate, cooling provided on this upper wall
A number of coolant supply holes for guiding material between the fuel rods;
Each coolant supply hole located at the lower end of the upper wall surface and next to it
Cooling connecting at least one coolant supply hole in contact
A material passage, at least one foreign matter capturing mechanism that captures and removes foreign matter mixed in the coolant flowing into the lower tie plate by the plurality of coolant supply holes ,
Is provided.

That is, the coolant supplied into the lower tie plate from below in the reactor is provided with at least one foreign matter trapping mechanism, for example, a debris filter or a foreign matter trapping function provided in the internal space of the lower tie plate. Substrate such as lower tie plate upper wall surface
It passes through the timber, the coolant supply of the lower tie plate upper wall surface
Foreign matter mixed in by a large number of holes formed in the substrate member such as a supply hole is captured and removed. This reduces the possibility of fretting damage due to foreign matter. Thereafter, the coolant is guided between the plurality of fuel rods, the lower end of which is held by the lower tie plate and located above the lower tie plate,
The fuel rods, which are filled with fissile material, are heated.

At this time, the plurality of holes formed in the substrate member of the above-described foreign matter capturing mechanism have a coolant passage connecting each hole and at least one hole adjacent to the hole, for example, a lower coolant passage.
Grooves formed on the inflow side surface of the substrate member, such as the lower end portion of the upper wall of the part tie plate, are also provided. Therefore, at the time of capturing by the foreign material capturing mechanism, for example, even when the coolant inflow side of one hole is completely blocked by the captured foreign material, the coolant flowing from the adjacent hole that is not blocked by the foreign material, It flows through the coolant passage connecting the two holes into the closed hole. Therefore, unlike the conventional structure, the coolant does not flow at all toward the coolant outlet side of the closed hole, so that the amount of coolant flowing into the fuel assembly is locally and entirely reduced. Can be reduced. Also, for example, the lower end of the upper wall of the lower tie plate
If a groove is formed as a coolant passage in
The mold used to manufacture the tie plate
Just change it so that a groove is formed in the upper wall
Saves machining and welding processes for forming grooves.
The number of manufacturing steps can be reduced and cost can be reduced.

In order to achieve the above object, the present invention provides
According to the report, several fuel rods with fissile material inside
And an upper type that holds the upper ends of these fuel rods
And the lower end of the plurality of fuel rods, and
A lower tap for guiding the supplied coolant between the upper fuel rods.
Plate, a substrate member and the substrate member.
With a large number of holes, the cold flowing into the lower tie plate
Foreign matter mixed in the waste material is captured by the large number of holes.
At least one foreign matter capturing mechanism for removing
Board member of the serial extraneous matter catching mechanism is formed on the surface of the coolant inlet side of the substrate member, and each of holes formed in the substrate member thereof
Provided with a groove for coupling the at least one hole adjacent to the hole
Fuel assembly, characterized in Tei Rukoto is provided.

In order to achieve the above object, the present invention provides
According to the report, several fuel rods with fissile material inside
And an upper type that holds the upper ends of these fuel rods
And the lower end of the plurality of fuel rods, and
A lower tap for guiding the supplied coolant between the upper fuel rods.
Plate and a substrate member and a number of holes formed in the substrate member provided in the internal space of the lower tie plate.
In the coolant flowing into the lower tie plate
The contaminants are trapped and removed by the large number of holes.
At least one debris filter ,
The substrate member of the yellow filter was formed on the substrate member.
Connecting each hole with at least one hole adjacent to the hole
Fuel assembly is provided which is characterized that you have provided the that coolant passages.

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

According to the present invention, in order to achieve the above-mentioned object, according to the present invention, a plurality of fuel rods filled with fissile material, an upper tie plate holding upper ends of the plurality of fuel rods, holding the lower ends of the plurality of fuel rods, extending the coolant supplied from below the lower tie plate for guiding between above the fuel rods, in a substantially horizontal direction in the upper or in the lower tie plate of the lower tie plate A first perforated plate or a mesh structure plate provided with a large number of first through-holes in a substantially vertical direction, and foreign matter mixed in the coolant flowing into the lower tie plate is removed by the first through-holes. A first foreign matter capturing mechanism for capturing and removing, and a plurality of second foreign substances extending substantially horizontally below the first perforated plate or the mesh structure plate in the lower tie plate and having a larger diameter than the first through hole. Through holes are provided almost vertically Having a second perforated plate or a mesh structure plate, having a second foreign matter capturing mechanism for capturing and removing foreign matter mixed in the coolant flowing into the lower tie plate by the second through-hole, The first perforated plate or the mesh structure plate of the first foreign matter capturing mechanism, or the second perforated plate or the mesh structure plate of the second foreign substance capturing mechanism, each hole formed in the perforated plate or the mesh structured plate and the holes thereof And a coolant passage connecting at least one hole adjacent to the fuel assembly.

[0024] To achieve the above object, according <br/> to the onset bright, the coolant supplied from below, fissile material therein guided between a plurality of fuel rods of the upper filled At least one is disposed in the inner space of the lower tie plate, and includes a substrate member and a plurality of holes formed in the substrate member, the foreign matter mixed in the coolant flowing into the lower tie plate being removed by the plurality of holes. A debris filter for capturing and removing the debris by a hole provided with a coolant passage connecting each hole and at least one hole adjacent to the hole.

Preferably, in the debris filter, there is provided a debris filter, wherein the coolant passage is a groove formed on a surface of the substrate member on a coolant inflow side.

[0026] In order to achieve the above object, the present invention
O lever, an upper wall, it is formed on the upper wall, and a plurality of coolant supply holes for guiding the coolant supplied from below between upwardly fissile material therein is filled in the plurality of fuel rods, before
Each coolant supply hole is located at the lower end of the upper wall.
To at least one coolant supply hole adjacent to
A coolant passage, which holds lower end portions of the plurality of fuel rods, and traps and removes foreign matters mixed in the coolant supplied from below by the plurality of coolant supply holes. lower tie is provided, wherein the br /> to Turkey.

Further, in order to achieve the above object, the present invention
According to the upper wall and the upper wall,
The supplied coolant is filled with fissile material
A number of coolant supply holes leading between the upper plurality of fuel rods;
Holding the lower end portions of the plurality of fuel rods, and
Foreign matter mixed in the coolant supplied from the
In the lower tie plate is removed by catching the coolant supply hole number, are formed on the coolant inlet side of the front SL upper wall, little adjacent to each coolant supply hole to the coolant supply hole
Lower tie plate, wherein that you have provided with a groove for coupling the Kutomo one coolant supply hole is provided.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. This embodiment is an embodiment of a fuel assembly including a debris filter for capturing foreign matter in a lower tie plate.

FIG. 2 is a longitudinal sectional view showing the entire structure of the fuel assembly according to this embodiment. In FIG. 2, a fuel assembly 20 includes a fuel rod 21 filled with fissile material and an upper tie plate 2 holding upper and lower ends of the fuel rod 21, respectively.
3 and a lower tie plate 1, a plurality of fuel spacers 24 arranged in the axial direction of the fuel assembly 20, a fuel spacer 24 for appropriately maintaining a gap between adjacent fuel rods 21, and a water rod for holding the fuel spacer 24. 22 and upper tie plate 2
3 and a channel box 25 surrounding the outer circumference of the bundle of fuel rods 21 held by the fuel spacer 24.

FIG. 3 is a longitudinal sectional view showing the detailed structure of the lower tie plate 1. As shown in FIG. In FIG. 3, the lower tie plate 1
Has a coolant inlet 2 at the lower end, and a hole 3 in the upper wall surface 1A into which the lower end plug of the fuel rod 21 is inserted and supported.
And a coolant introduction hole 4 for guiding a coolant into the fuel assembly 20. FIG. 4 is an enlarged vertical sectional view showing a detailed structure of the hole 3 and the coolant introduction hole 4.

A debris filter 10 for trapping foreign matter in the coolant is disposed between the coolant inlet 2 and the upper wall 1A in the internal space of the lower tie plate 1. In addition,
The position of the debris filter 10 may be any position between the coolant inlet 2 and the upper wall surface 1A.

The detailed structure of the debris filter 10 will be described with reference to FIGS. FIG. 5 is a longitudinal sectional view of the debris filter 10, and FIG. 1 is a bottom view of the debris filter 10 viewed from the coolant inlet side (from the direction A in FIGS. 3 and 5). 5 and 1, the debris filter 10
Has a large number of holes 11 formed in a plate-shaped substrate member 10A,
Further, a large number of grooves 12 are formed on the coolant inlet 2 side of the substrate member 10A so as to connect adjacent holes 11 to each other. At this time, the hole 11 is smaller than the coolant introduction hole 4 provided in the fuel rod support 3 of the lower tie plate 1. In addition, some grooves 12 among many grooves 12 are the surface (upper surface) on the opposite side of the debris filter 10.
It may penetrate up to.

Further, the lower tie plate 1 having the above structure
6, the debris filter 10 is sandwiched between a lower tie plate lower member 1a having a coolant inlet 2 and a lower tie plate upper member 1b having a fuel rod support structure, as shown in FIG. Later, it is manufactured by performing full circumference welding.

In the fuel assembly 20 according to the present embodiment, the coolant supplied from the coolant inlet 2 into the lower tie plate 1 is mixed by the large number of holes 11 when passing through the debris filter 10. Foreign matter is captured and removed, thereby reducing the potential for fretting damage due to foreign matter. Thereafter, the coolant is guided between the plurality of fuel rods 21 whose lower ends are held by the lower tie plate 1 and located above the lower tie plate 1, and the plurality of fuel rods 21 filled with fissile material therein. Heated.

At this time, a plurality of holes 11 of the debris filter 10 are provided with a groove 12 for connecting adjacent holes 11 together. Therefore, when foreign matter is captured, for example, even if the coolant inflow side of one hole 11 is completely blocked by the captured foreign matter, the coolant flowing in from the adjacent hole 11 that is not closed has a problem. Holes 11,
It flows into the closed hole 11 through the groove 12 connecting the holes 11. Therefore, unlike the conventional structure in which the groove 12 is not provided, the coolant does not flow at all to the coolant outflow side of the closed hole 11, so that the amount of coolant flowing into the fuel assembly 20 locally and The overall decrease can be reduced. That is, a decrease in the cooling capacity of the fuel rods 21 due to the coolant can be suppressed, so that the soundness of the fuel assembly 20 can be improved.

A second embodiment of the present invention will be described with reference to FIGS. The present embodiment is an embodiment of a fuel assembly in which the upper wall surface of the lower tie plate also has a foreign matter collecting function. Members equivalent to those in the first embodiment are denoted by the same reference numerals.

FIG. 7 is a longitudinal sectional view showing the entire structure of the fuel assembly 220 according to this embodiment. In FIG. 7, the main difference between the fuel assembly 220 and the fuel assembly 20 of the first embodiment is that the lower tie plate 201 in which the debris filter 10 is not provided and the upper wall surface also has a foreign matter collecting function is provided. It is a point provided.

FIG. 8 shows the detailed structure of the lower tie plate 201.
And FIG. Figure 8 shows the lower tie plate 20
9 is a longitudinal sectional view showing the entire structure of FIG.
It is IX horizontal sectional drawing. 8 and 9, the lower tie plate 201 is provided with a coolant inlet 2 at the lower end similarly to the lower tie plate 1 of the first embodiment, and the lower wall of the fuel rod 21 is provided on the upper wall surface 201A. A hole 3 into which an end plug is inserted and supported, and a coolant introduction hole 4 are provided. Further, unlike the lower tie plate 1 of the first embodiment, the coolant introduction hole 4 also has a foreign matter collecting function, and the coolant introduction hole 4 is provided on the coolant inflow side (the lower side in the figure) of the upper wall surface 201. A groove 212 is formed to connect the two.

Further, the lower tie plate 2 having the above structure
As shown in FIG. 10, the lower tie plate upper member 201b having a fuel rod support structure
After machining a groove 212 connecting the coolant introduction holes 4 from the inside of the lower tie plate, the lower tie plate upper member 201a having the coolant inlet 2 is formed into a lower tie plate upper member 201.
It is manufactured by welding all around b.

It should be noted that, as in the above manufacturing method, the upper member 20
Instead of being divided into the lower member 201a and the lower member 201a, the lower tie plate 201 may be integrally cast, and the casting mold may be changed so as to form the groove 212. According to this manufacturing method, machining for forming a groove and a welding process of the upper member 201b and the lower member 201a are eliminated, so that the number of manufacturing steps and cost can be reduced.

The other structure of the fuel assembly 220 is the first
It is almost the same as the fuel assembly 20 of the embodiment.

In the fuel assembly 220 according to this embodiment, the coolant supplied from the coolant inflow port 2 into the lower tie plate 201 passes through the upper wall surface 201A of the lower tie plate 201 when a large amount of coolant is supplied. Foreign matter mixed in by the introduction hole 4 is captured and removed, whereby the possibility of fretting damage due to the foreign matter is reduced.
Thereafter, the coolant is introduced between the plurality of fuel rods 21 whose lower ends are held by the lower tie plate 201 and located above the lower tie plate 201, and the plurality of fuel rods 21 are filled with fissile material. Heated.

At this time, the lower tie plate upper wall surface 201
A number of coolant introduction holes 4 of A are provided with grooves 212 for connecting adjacent coolant introduction holes 4 together. Therefore, when foreign matter is captured, for example, 1
Even when the coolant inflow side of the two coolant introduction holes 4 is completely closed, the coolant flowing from the adjacent coolant introduction holes 4 that are not closed is still in the two coolant introduction holes 4. The coolant flows into the closed coolant introduction hole 4 via the groove 212 connecting the coolant 4. Therefore, unlike the conventional structure in which the groove 212 is not provided, the coolant does not flow at all to the coolant outflow side of the closed coolant introduction hole 4, so that the amount of coolant flowing into the fuel assembly 220 is reduced. Local and global reductions can be reduced. That is, since the cooling ability of the fuel rods 21 due to the coolant can be prevented from lowering, the soundness of the fuel assembly 220 can be improved.

FIGS. 11 to 15 show a third embodiment of the present invention.
This will be described below. This embodiment is an embodiment of a fuel assembly in which two debris filters having different diameters are provided in a lower tie plate. Members equivalent to those of the first and second embodiments are denoted by the same reference numerals.

FIG. 11 is a longitudinal sectional view showing the entire structure of the fuel assembly 320 according to this embodiment. In FIG.
The main difference between the fuel assembly 320 and the fuel assembly 20 of the first embodiment is that the fuel assembly 320 has a large number of holes 11 and grooves 12.
Instead of one debris filter 10, two debris filters 310 having only a large number of holes and no grooves
a, 310b are provided in the lower tie plate 301.

FIG. 12 is a longitudinal sectional view showing the detailed structure of the lower tie plate 301. In FIG. 12, the lower tie plate 301 has substantially the same wall structure as the lower tie plate 1 of the first embodiment except for the debris filter. The wall surface 301A is provided with a hole 3 into which the lower end plug of the fuel rod 21 is inserted and supported, and a coolant introduction hole 4 for guiding a coolant into the fuel assembly 320. Further, the detailed structures of the holes 3 and the coolant introduction holes 4 are the same as those in FIG. 4 shown in the first embodiment.

Further, between the coolant inlet 2 and the upper wall surface 301A in the inner space of the lower tie plate 301, two debris filters 310 for trapping foreign matter in the coolant are provided.
a, 310b are arranged.

The detailed structure of the debris filters 310a and 310b will be described with reference to FIGS. FIG. 13 is a bottom view of the debris filter 310a viewed from below (direction B in FIG. 12), and FIG. 14 is a bottom view of the debris filter 310b viewed from below (direction C in FIG. 12). 13 and 14, each of the debris filters 310a and 310b is constituted by a perforated plate. And coolant inlet 2
The hole diameter of the hole 311a of the debris filter 310a located on the side is larger than the hole diameter of the hole 311b of the debris filter 10b located on the upper wall surface 301A side.
The positions of the debris filters 310a and 310b are
As long as the debris filter 310a having a large hole diameter is disposed closer to the coolant inlet 2 than the debris filter 310b having a small hole diameter, the coolant inlet 2 to the upper wall surface 30 are provided.
Any position between 1A may be sufficient.

The lower tie plate 3 having the above structure
As shown in FIG. 15, in the manufacture of the lower tie plate lower member 301a having the coolant inlet port 2,
The entire circumference is welded with the debris filter 310a interposed between the lower tie plate intermediate member 301b and the lower tie plate upper member 301 having a fuel rod support structure.
c and the intermediate member 301b between the debris filter 310
The lower tie plate 301 is manufactured by performing the entire circumference welding with "b" therebetween.

In the fuel assembly 320 according to the present embodiment, the lower tie plate 30
The coolant supplied in 1 is composed of two debris filters 3
When passing through 10a and 10b, these debris filters 31
The foreign substances mixed in are captured and removed by the large number of holes 311a, 3b provided in the holes 0a, b. This reduces the possibility of fretting damage due to foreign matter. Thereafter, the coolant is guided between the plurality of fuel rods 21 whose lower ends are held by the lower tie plate 301 and is located above the lower tie plate 301, and the coolant is supplied by the plurality of fuel rods 21 filled with fissile material. Heated.

Here, the debris filter 310a,
In the case of a structure in which a foreign substance is captured by a large number of holes as in b, the basic performance is to capture a foreign substance larger than the hole diameter by catching it. Therefore, when the maximum size of the foreign matter that does not want to finally flow between the fuel rods is L (that is, the inflow of the foreign matter less than L is permitted), conventionally, the debris filter having the hole diameter of L passes through the debris filter in the flow direction 1. The hole diameter of the debris filter provided at the location or provided at a plurality of locations in the flow direction was all L. However, in this case, for example, a relatively large dimension L
₁ (> L) foreign matter, medium size L ₂ (> L) foreign matter, relatively small size L ₃ (where L> L ₃ ), etc. are mixed, and the holes having a hole diameter L remain in an irregular state. Therefore, when a foreign matter having a relatively large dimension L ₁ (>> L) is captured in one hole, a relatively small dimension L that should originally pass through the hole is provided in a gap between the captured foreign matter and the hole. There is a possibility that foreign matter of ₃ (however, L> L ₃ ) may be caught and clogged to completely close the hole.

On the other hand, in the present embodiment, the holes 3
Debris filter 310a having a relatively large hole diameter of 11a
Is disposed on the upstream side in the flow direction, and the debris filter 310b having a relatively small hole diameter of the hole 313b is disposed on the downstream side in the flow direction. Therefore, for example, according to the above dimension example, the hole diameter of the hole 311a of the upstream debris filter 310a is set to L _U (where L ₁ > L _U > L), and the hole diameter of the hole 311b of the downstream debris filter 310b is set to L. advance to capture the relatively large dimensions L ₁ foreign matter on the upstream side of the hole 311a. Those that pass through the upstream debris filter 310a in this way become foreign matter having a medium size L ₂ (where L _U > L ₂ > L) and foreign matter having a relatively small size L ₃ , which are compared with those of the downstream debris filter 310b. Very small hole 31
1b. Therefore, it is relatively eliminated large foreign matter dimension L ₁ is already to be captured neatly minute particle is relatively uniform. Therefore, that the design intention, only the dimensions of the medium L ₂ foreign matter become trapped, so less likely to be captured to a relatively foreign matter smaller dimension L _3, eyes as in the conventional structure The probability of causing clogging and completely closing the hole can be reduced. Therefore, it is possible to reduce a decrease in the amount of coolant flowing into the fuel assembly 320 locally and entirely. That is, since the cooling ability of the fuel rods 21 due to the coolant can be suppressed from decreasing, the soundness of the fuel assembly 320 can be improved.

In the third embodiment, 2
Although a single debris filter was used, the invention is not limited to this.
That is, three or more debris filters may be used as long as the diameter of the hole on the upstream side is larger. In this case, a similar effect is obtained.

In the third embodiment, a debris filter having a perforated plate structure is used, but the present invention is not limited to this. That is, a plurality of debris filters having a mesh structure such as a net may be used. Also in this case, the same effect can be obtained by arranging the debris filters with the coarser mesh sequentially from the lower tie plate coolant inlet side.

Further, as in the second embodiment, when the coolant introducing hole 4 provided in the lower tie plate upper wall surface 301A also has a function as a debris filter, the debris on the most downstream side in the flow direction is provided. The filter may be replaced with this. In this case, a similar effect is obtained.

FIGS. 16 to 18 show a fourth embodiment of the present invention.
This will be described below. This embodiment is an embodiment of a fuel assembly in which grooves similar to those of the first embodiment are formed in two debris filters provided in the lower tie plate in the second embodiment. Members equivalent to those in the first to third embodiments are denoted by the same reference numerals.

The fuel assembly according to the present embodiment is different from the third fuel assembly in the structure of two debris filters 410a and 410b provided in the lower tie plate.
FIG. 16 is a longitudinal sectional view showing the detailed structure of the lower tie plate. In FIG. 16, the lower tie plate 401 has substantially the same wall structure as that of the lower tie plate 301 of the third embodiment except for the debris filter.
A coolant inlet 2 is provided at the lower end, and an upper wall surface 40 is provided.
1A has a hole 3 into which the lower end plug of the fuel rod 21 is inserted and supported.
And a coolant introduction hole 4 for guiding a coolant into the fuel assembly. The detailed structure of the hole 3 and the coolant introduction hole 4 is also as follows.
Structure similar to that of the third embodiment (structure similar to FIG. 15)
It has become.

Further, between the coolant inlet 2 and the upper wall surface 401A in the inner space of the lower tie plate 401, two debris filters 410 for trapping foreign matter in the coolant are provided.
a, 410b are arranged.

The detailed structure of the debris filters 410a and 410b, which are the main parts of this embodiment, will be described with reference to FIGS. FIG. 17 is a bottom view of the debris filter 410a viewed from below (direction C in FIG. 16), and FIG. 18 is a bottom view of the debris filter 410b viewed from below (direction D in FIG. 16). 17 and 18, the difference between the debris filters 410a and 410b and the debris filters 310a and 310b of the third embodiment is that the grooves 412a connecting the adjacent holes 311a and the grooves 412b connecting the adjacent holes 311b are provided. Is provided. That is, the debris filter 310a of the third embodiment,
The configuration is such that the groove 12 of the first embodiment is applied to 310b.

The structure of the other fuel assemblies is substantially the same as that of the third embodiment.

In the fuel assembly according to the present embodiment,
Groove 412 similar to the effect of groove 12 of the first embodiment.
Since the effect of reducing the amount of coolant due to a and b and the effect of reducing and reducing the amount of coolant similar to the holes 311a and 3b of the third embodiment can be obtained together, the coolant flows into the fuel assembly. The decrease in the amount locally and globally can be more reliably reduced. That is, a decrease in the cooling capacity of the fuel rods due to the coolant can be more reliably suppressed, and the soundness of the fuel assembly can be more reliably improved.

[0062]

According to the present invention, the porosity of the foreign matter trapping mechanism is improved.
Many holes formed in board members such as boards and mesh structure boards
(Through-hole, coolant supply hole) is provided with a coolant passage such as a groove connecting each hole and at least one hole adjacent to the hole. Even if the coolant inflow side is completely closed, no coolant flows to the coolant outflow side of the closed hole. Therefore, the amount of coolant flowing into the fuel assembly can be prevented from being locally and entirely reduced, and a decrease in the cooling capacity of the fuel rods caused by the coolant can be suppressed, so that the fuel integrity can be improved. .

[0063]

[Brief description of the drawings]

FIG. 1 is a bottom view of a debris filter provided in a fuel assembly according to a first embodiment of the present invention as viewed from a coolant inlet side.

FIG. 2 is a longitudinal sectional view illustrating an entire configuration of a fuel assembly including the debris filter illustrated in FIG.

FIG. 3 is a longitudinal sectional view showing a detailed structure of a lower tie plate provided with the debris filter shown in FIG.

FIG. 4 is an enlarged vertical sectional view showing a detailed structure of a hole and a coolant introduction hole in the lower tie plate shown in FIG. 3;

FIG. 5 is a longitudinal sectional view of the debris filter shown in FIG.

FIG. 6 is a longitudinal sectional view showing a procedure for manufacturing the lower tie plate shown in FIG.

FIG. 7 is a longitudinal sectional view illustrating an entire configuration of a fuel assembly according to a second embodiment of the present invention.

FIG. 8 is a longitudinal sectional view illustrating an entire structure of a lower tie plate illustrated in FIG. 7;

9 is a horizontal sectional view taken along the line IX-IX of FIG.

FIG. 10 is a longitudinal sectional view showing a procedure for manufacturing the lower tie plate shown in FIG.

FIG. 11 is a longitudinal sectional view illustrating an entire configuration of a fuel assembly according to a third embodiment of the present invention.

FIG. 12 is a longitudinal sectional view illustrating an entire structure of a lower tie plate illustrated in FIG. 11;

13 shows the debris filter shown in FIG.
It is a bottom view seen from the middle B direction.

FIG. 14 shows the debris filter shown in FIG.
It is a bottom view seen from the middle B direction.

FIG. 15 is a longitudinal sectional view illustrating a procedure for manufacturing the lower tie plate shown in FIG.

FIG. 16 is a longitudinal sectional view illustrating an entire structure of a lower tie plate provided in a fuel assembly according to a fourth embodiment of the present invention.

FIG. 17 shows the debris filter shown in FIG.
It is the bottom view seen from the middle C direction.

FIG. 18 shows the debris filter shown in FIG.
It is the bottom view seen from the middle D direction.

[Description of Signs] 1 Lower tie plate 1A Lower tie plate upper wall surface 1a Lower tie plate lower member 1b Lower tie plate upper member 2 Coolant inlet 3 Fuel rod lower end plug insertion hole 4 Coolant introduction hole 10 Debris filter 10A Debris Filter substrate member 11 Debris filter hole 12 Groove 20 Fuel assembly 21 Fuel rod 22 Water rod 23 Upper tie plate 24 Fuel spacer 25 Channel box 201 Lower tie plate 201A Lower tie plate upper wall surface 201a Lower tie plate lower member 201b Lower tie plate Upper member 212 Groove 220 Fuel assembly 301 Lower tie plate 301A Lower tie plate upper wall surface 301a Lower tie plate lower member 301b Lower tie plate intermediate member 301c Lower tie plate upper Material 310a, b debris filter 311a, b debris filter having a pore 320 fuel assembly 401 lower tie 401A lower tie plate upper wall surface 410a, b debris filter 412a, b groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-306280 (JP, A) JP-A-63-91591 (JP, A) JP-A-62-96891 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G21C 3/30 G21C 3/33

Claims (8)

(57) [Claims] A plurality of fuel rods filled with fissile material therein; an upper tie plate for holding upper end portions of the plurality of fuel rods; and a lower end portion for holding lower end portions of the plurality of fuel rods. A lower tie plate for guiding the supplied coolant between the fuel rods above, an upper wall surface of the lower tie plate as a substrate member, and a number of coolants provided on the upper wall surface for guiding the coolant between the fuel rods A coolant passage provided at a lower end portion of the upper wall surface and connecting each coolant supply hole to at least one coolant supply hole adjacent to the coolant supply hole, wherein the coolant flows into the lower tie plate; A fuel assembly comprising: at least one foreign matter capturing mechanism for capturing and removing foreign matter mixed in the plurality of coolant supply holes. 2. A plurality of fuel rods filled with fissile material therein, an upper tie plate holding upper ends of the plurality of fuel rods, and a lower end holding lower ends of the plurality of fuel rods. A lower tie plate that guides the supplied coolant between the upper fuel rods; and a substrate member and a number of holes formed in the substrate member. The lower tie plate mixes with the coolant flowing into the lower tie plate. At least one foreign matter capturing mechanism that captures and removes foreign matter that is present by the plurality of holes, and a substrate member of the foreign matter capturing mechanism is formed on a surface of the substrate member on a coolant inflow side, and the substrate member A fuel assembly, comprising: a groove that connects each hole formed in the hole with at least one hole adjacent to the hole. 3. A plurality of fuel rods filled with fissile material therein, an upper tie plate holding upper ends of the plurality of fuel rods, and a lower end holding the plurality of fuel rods from below. A lower tie plate that guides the supplied coolant between the fuel rods above; a lower tie plate that is provided in an internal space of the lower tie plate and includes a substrate member and a number of holes formed in the substrate member. At least one of the plurality of holes captures and removes foreign matter mixed in the coolant flowing into the inside.
The substrate member of the debris filter includes a coolant passage that connects each hole formed in the substrate member and at least one hole adjacent to the hole. Fuel assembly. 4. A plurality of fuel rods filled with fissile material therein, an upper tie plate holding upper end portions of the plurality of fuel rods, and a lower end portion holding lower end portions of the plurality of fuel rods. a lower tie plate for guiding the supplied coolant between above the fuel rods, in the substantially vertical direction substantially horizontally extended in a number of first through-hole in the upper or the lower tie plate of the lower tie plate A first perforated plate or a mesh structure plate provided, a first foreign matter capturing mechanism for capturing and removing foreign matter mixed in the coolant flowing into the lower tie plate by the first through hole; A second second through hole extending in a substantially horizontal direction below the first perforated plate or the mesh structure plate in the lower tie plate and having a large number of second through holes having a diameter larger than the first through hole in a substantially vertical direction;
A perforated plate or a mesh structure plate, wherein foreign matter mixed in the coolant flowing into the lower tie plate is removed by the second
A second foreign matter capturing mechanism that captures and removes through a through-hole, wherein the first foreign matter capturing mechanism has a first perforated plate or a mesh structure plate, or the second foreign matter capturing mechanism has a second perforated plate or a mesh structured plate. A fuel assembly, comprising: a coolant passage connecting each hole formed in the perforated plate or the mesh structure plate with at least one hole adjacent to the hole. 5. A substrate member and at least one substrate disposed in an inner space of a lower tie plate for guiding a coolant supplied from below between a plurality of upper fuel rods filled with fissile material therein. In a debris filter having a number of holes formed in the member, foreign matter mixed in the coolant flowing into the lower tie plate is captured and removed by the number of holes, A debris filter comprising a coolant passage connecting at least one adjacent hole. 6. The debris filter according to claim 5, wherein said coolant passage is a groove formed on a surface of said substrate member on a coolant inflow side. 7. An upper wall surface, and a plurality of coolant supply holes formed in the upper wall surface for guiding a coolant supplied from below between a plurality of upper fuel rods filled with fissile material therein; A coolant passage provided at a lower end of the upper wall surface and connecting each coolant supply hole and at least one coolant supply hole adjacent thereto; holding a lower end of the plurality of fuel rods; and A lower tie plate, wherein foreign matters mixed in the coolant supplied from below are captured and removed by the plurality of coolant supply holes. 8. An upper wall surface and a plurality of coolant supply holes formed in the upper wall surface for guiding a coolant supplied from below between a plurality of upper fuel rods filled with fissile material therein. A lower tie plate that holds lower end portions of the plurality of fuel rods, and captures and removes foreign matter mixed in the coolant supplied from below by the plurality of coolant supply holes. A lower tie plate formed on a coolant inflow side of an upper wall surface and having a groove connecting each coolant supply hole and at least one coolant supply hole adjacent to the coolant supply hole.