JP2001318187A - Cask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat conduction efficiency of a cask. SOLUTION: A plate member 201 is attached around a shell body 101 and on the part of the plate member 201 coming outside the cask, mountains are provided. Inside a space 206 formed with the plate member 201, an aluminum honeycomb member 210 combined with resin 106 is installed. The decay heat conducted to the shell body 101 is conducted to the plate member 201 constituting the cask outer surface via the plate member 201 and the honeycomb member 210 and radiated. At this time, by providing mountains 207 to the plate member 201 and spreading the radiation area, radiation efficiency is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cask for accommodating and storing spent fuel assemblies after combustion, and capable of efficiently discharging the decay heat of the spent fuel assemblies to the outside.

[0002]

2. Description of the Related Art A nuclear fuel assembly that has been burned at the end of a nuclear fuel cycle and has become unusable is called a spent nuclear fuel assembly. Spent nuclear fuel contains a highly radioactive material such as FP and needs to be thermally cooled. Therefore, the spent nuclear fuel is cooled for a predetermined period in a cooling pit of a nuclear power plant. Then, it is stored in a cask which is a shielding container, transported to a reprocessing facility by a truck or the like, and stored.

FIG. 10 is a configuration diagram showing an example of a conventional cask. FIG. 11 is an axial sectional view of the cask shown in FIG. In the cask 500, the spent fuel assembly is accommodated in a stainless steel body 501 that blocks γ-rays (not shown). Body 501
A plurality of strips 502 are radially welded to the outer periphery of the. This strip 502 is bent into a substantially U-shaped cross section, its side edge 521 is welded to the trunk body 501, and the other side edge 522 is formed at the corner of the adjacent strip 502. It is welded at the folding line 523. The strip 502 is made of a material having good thermal conductivity, for example, a copper plate or the like, in order to release decay heat propagated from the trunk body 501 to the outside. The space formed by the strip 502 is filled with a resin 503 for absorbing neutrons.

A fin 504 for heat radiation is welded to the outside of each strip 502. The fin 504 has a comb shape and a curved tooth surface. The decay heat of the spent fuel assembly is first transmitted to the trunk body 501.
Since the strip 502 is welded to the body 501,
The decay heat propagates from the trunk body 501 to the strip 502 and is released to the outside through the externally exposed surface of the strip 502 and the fins 504.

[0005]

However, in the above-mentioned conventional cask 500, the plate-like fins 5
Because of the welded structure of No. 04, there is a problem that a temperature distribution occurs on the outer surface and uniform heat dissipation cannot be performed. In other words, the temperature of the junction with the fin 504 is high, and the temperature of the strip 502 between the fin 504 and the fin 504 is low, which is not preferable in terms of heat radiation efficiency. Then, this invention was made in view of the above, and an object of this invention is to provide the cask which can improve heat dissipation efficiency.

[0006]

In order to achieve the above-mentioned object, in this cask, a trunk body in which a basket for storing a radioactive material such as a spent fuel assembly is disposed, and a periphery of the trunk body is provided. And a plurality of plate-shaped members provided on the body, a part of the plate-shaped member is in contact with the trunk body, and the other part constitutes an outer surface of the cask and one or more chevron portions or valley portions Was bent and the other part was joined to an adjacent plate-like member, and the space defined by this plate-like member was filled with a neutron absorbing material. Decay heat from the spent fuel assembly is transmitted from the trunk body to the plate-like member, and is radiated from the outer surface of the cask. Since a chevron or a trough is formed on the outer surface of the cask, the heat dissipation area is increased as compared with a conventional cask having a simple cylindrical outer shape, and heat is efficiently dissipated. In addition,
This plate-shaped member may be manufactured by bending a plate material or may be manufactured by extrusion.

In particular, by combining the neutron absorbing material and the honeycomb material so that the honeycomb material is at least in contact with the trunk body, the neutron absorbing material is interposed through the honeycomb material even when the thermal conductivity of the neutron absorbing material is low. Heat can be conducted. The thermal conductivity can also be improved by combining a neutron absorber and a plurality of thermal conductors.

Next, the honeycomb material or the heat conductor is made of aluminum or copper, and the plate-like member is made of iron.
By using copper or aluminum, the honeycomb member or the heat conductor can have a main heat transfer function, and the plate-like member can have strength. In order to further improve the thermal conductivity, a copper plate, an aluminum plate, or a graphite sheet can be attached to one or both surfaces of the plate-like member. In this case, the use of a honeycomb material or a heat conductor is not essential. It is also possible to improve the thermal conductivity by bringing a part of the plate-shaped member in contact with the trunk body or a part of a copper plate or an aluminum plate into surface contact with the trunk body.

Further, the cask has a plurality of cells, a basket for accommodating a spent fuel assembly in the cells and having an approximately octagonal outer shape, a basket for accommodating the basket inside, An inner shape is configured to fit the basket, and includes a trunk body that shields γ-rays, and a neutron shield provided outside the trunk body. With this configuration, the trunk body can have a sufficient thickness necessary for shielding γ rays, and the cask can be reduced in weight. Furthermore, by providing the neutron shield so as to be octagonal with respect to the trunk body, the number of neutron shields can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment. FIG. 1 is a perspective view showing a cask according to an embodiment of the present invention. FIG.
FIG. 2 is a radial sectional view of the cask shown in FIG. 1. In the cask 100, the trunk body 101 and the trunk body 1
The bottom plate 104 of No. 01 is a forged product made of carbon steel having a γ-ray shielding function. Note that stainless steel can be used instead of carbon steel. The trunk body 101 and the bottom plate 104
Are joined by welding. Further, a metal gasket is provided between the primary lid 110 and the body 101 in order to secure the sealing performance as a pressure-resistant container (not shown).

As shown in FIG. 3, a plurality of plate-like members 201 are attached to the outer periphery of the body 101. The plate-like member 201 is formed by bending and forming a rectangular iron plate, an aluminum plate, or a copper plate.
Is characterized in that a portion corresponding to the outer cylinder is formed in a mountain shape (angle shape portion 207). In addition, the edge 202 of the plate-like member 201 is a bent ridge portion 2 of the adjacent plate-like member 201.
03 (welded portion 202a). On the other hand, the plate-shaped member 201 is fixed by passing the wire 204 through the edge fixing hole 205 and winding the wire 204 around the trunk body 101. The plate-like member 201 may be formed by extrusion.

An aluminum or copper honeycomb material 210 having excellent thermal conductivity is provided in a space 206 formed by the plate member 201 and the outer surface of the body 101. The cells of the honeycomb material 210 are
Are formed in the axial direction, and the periphery thereof is the space 206
In contact with the inner surface 211. This is for improving the efficiency of heat conduction from the trunk main body 101. Further, a part of the honeycomb material 210 is filled with a resin 106 which is a polymer material containing a large amount of hydrogen and has a neutron shielding function. On the other hand, on the outer peripheral side of the honeycomb material 210, the resin 106
Is provided with a void layer 212 which is not filled. The honeycomb material 210 and the resin 106 are filled and compounded in different places,
It is inserted and fixed in the space 206. In addition, the space 20
In a state where the honeycomb material 210 is inserted in 6, the resin 106 in a flowing state may be injected and solidified by a thermosetting reaction or the like.

As the honeycomb material 210, various materials such as a roll core, a corrugated core and the like can be appropriately selected and used in addition to a hexagonal material having a normal cross section. A specific example is shown in FIG. FIG. 1A shows a honeycomb material 210a having a normal hexagonal cross section. FIG. 2B shows a honeycomb material 210b of a corrugated core type. Figure (c)
Shows a honeycomb material 210c having a structure in which dimple processing is performed on one surface and this is laminated. The honeycomb material 210d of FIG. 3D has a structure in which dimple processing is performed on both sides and the protrusion tips d1 are joined to each other. The honeycomb member 210e shown in FIG. 9E has a structure in which a plurality of holes e1 with a return e2 are provided in an aluminum plate and joined at the return portion e2.

Further, any material other than the honeycomb material can be used in combination with the resin 106 as long as it contributes to the improvement of the thermal conductivity. For example, a Raschig ring 210f, which is a heat conductor as shown in FIG.
And the resin 106 may be filled around the lahish ring 210f. Further, as shown in FIG.
g into the space 206, and the resin 106
May be filled. The cell size is
From the viewpoint of thermal conductivity, the smaller the better, the better, but it is not preferable to make the resin 106 difficult to fill.

The outer shape of the plate member 210 may be other than the above. For example, FIG.
As shown in (5), the outer surface of the plate-like member 220 may be formed into a valley shape (valley portion 221). Also, FIG.
As shown in FIG.
31 may be provided. Further, as shown in FIG. 13C, the cross section of the outer surface of the plate-like member 240 may be formed in an arc shape (arc portion 241). Other than this, various chevron portions or valley portions can be used as long as the heat radiation area can be increased.

Also, by providing the chevron 207 or the trough, a trough 208 formed on the outer surface of the cask.
(In the case of a chevron, it corresponds to the joint of the plate-like members, and in the case of a trough, it corresponds to the trough). In this way, the decontamination work of the cask 100 can be easily performed.

The cover 109 includes a primary cover 110 and a secondary cover 11.
1. The primary lid 110 has a disk shape made of stainless steel or carbon steel that blocks γ rays. The secondary lid 111 also has a disk shape made of stainless steel or carbon steel, and a resin (not shown) is sealed on its upper surface as a neutron shield. Primary lid 110
And the secondary lid 111 is attached to the trunk main body 101 by a bolt made of stainless steel or carbon steel. Further, metal gaskets are provided between the primary lid 110 and the secondary lid 111 and the trunk main body 101, respectively, to maintain the internal sealing performance. On both sides of the cask main body, trunnions 117 for suspending the cask 100 are provided. When the cask 100 is transported, the shock absorbers 118 are attached to both sides thereof.

The inner surface of the torso main body 101 has a shape conforming to the outer shape of the basket 300 to be used, and the outer surface of the basket 300 is substantially in close contact with the torso main body 101. May occur). It is not necessary that the inner surface of the torso main body 101 be almost completely adjusted to the outer shape of the basket 300.
Can be formed so that a part of the outer surface thereof does not come into contact with them, and their ratio can be appropriately designed in consideration of the thermal conductivity.

The basket 300 contains Al or A
Aluminum alloy or aluminum alloy square pipe made by adding B (boron) or B compound powder with neutron absorption performance to alloy powder, bundled into a plurality of cells, and stacked with multiple cells A formed one (corresponding to the basket shown in FIG. 2), a rectangular plate made of an aluminum composite material or an aluminum alloy, which is orthogonally crossed by slits, and which are stacked in a confectionery shape can be used. In addition, cadmium can be used as a neutron absorber in addition to boron. The basket 300 according to the present embodiment can accommodate 33 spent fuel assemblies (for PWR), but the number of the fuel assemblies need not be 33. Needless to say, it can also be used as a cask for BWR.

Further, since the outer shape of the basket 300 has a shape close to an octagon, the inner surface of the torso main body 101 also has an octagonal shape when viewed roughly, and the torso main body 10 is opposed to each surface.
1 is formed in an octagonal outer surface. Thereby, the trunk body 10
1 is substantially uniform in thickness as a whole, and the weight can be reduced by eliminating the extra thickness. Further, the γ-ray shielding performance is secured in a necessary and sufficient range. Body 1
The inner surface and the outer surface of No. 01 are processed using a dedicated machining device. For details, refer to Japanese Patent Application No.
See the publication of No. 249314. In this embodiment, the shape of the trunk main body 101 is octagonal, but is not limited to this. That is, the basket 30
The shape of the torso main body 101 is adjusted to the
It can also be a square or the like (not shown).

When the spent fuel assemblies are stored in the cask 100, the cask 100 is submerged in the pool, and the spent fuel assemblies are stored in the water. For this reason, since a radioactive substance will adhere around the cask 100, it is necessary to decontaminate the radioactive substance when it is lifted from the pool. However, in the above-described conventional cask 500, the comb-shaped fins 504 are
Because it is a configuration welded to 2, it is difficult for decontamination brushes etc. to enter into the base part, and there is a shadowed part even when washing with spray water, etc., so it is necessary to wash it evenly, so decontamination is difficult There were serious problems.

On the other hand, in this embodiment, the basket 30 for storing the spent fuel assemblies therein is used.
0, and a plurality of plate-like members 201 provided around the trunk body 101. A part of the plate-like member 201 is in contact with the trunk body 101, and the other part is The outer surface of the cask 100 has one or more chevron portions 207 (or valley portions), and another part is joined to the adjacent plate member 201 to form the outer surface of the cask 100.
A cask characterized by filling the resin 206 into the space 206 formed by the space 01 and making the angle at the joint between the plate-like members 201 to be an obtuse angle θ.

As described above, by setting the angle at the joint to an obtuse angle θ, for example, about 120 degrees as shown in FIG.
The decontamination brushes and the like can reach every corner of the cask outer surface. For this reason, decontamination can be easily performed.

The spent fuel assemblies contained in the cask 100 include fissile materials and fission products, and the like.
Because it generates radiation and involves decay heat, the cask 1
It is necessary to ensure that the heat removal function, the shielding function and the criticality prevention function of 00 are maintained during the storage period. This cask 100
Here, a plurality of plate members 201 are provided around the body 101, and the honeycomb member 210 provided in the space 206 formed by the plate members 201 and the plate member 201 forming the outer surface of the cask 100 are formed into a mountain shape to radiate heat. By enlarging the area, the decay heat generated by the spent fuel assembly is efficiently transferred and released.

First, the decay heat generated from the spent fuel assembly is transmitted to the body 101 through the basket 300 or the filled helium gas. Next, decay heat is transmitted to the outer surface of the cask 100 through the plate member 201 having a function as an internal fin and the honeycomb material 210. In particular, since the honeycomb material 210 is made of aluminum or copper having excellent heat conductivity, it efficiently absorbs heat from the body 101, transmits the heat to the plate-like member 201, and radiates heat from the outer surface of the cask to the outside. As described above, since the heat of the decay heat can be efficiently removed, the temperature in the cask can be kept lower than that of the conventional example if the decay heat is the same.

It should be noted that γ generated from the spent fuel assembly
The wire is a trunk body 10 made of carbon steel or stainless steel.
1, the plate-like member 201, the cover 109, and the like. Also, the neutrons are shielded by the resin 106 so as to eliminate the effects of radiation exposure on radiation workers. Specifically, the shielding function is designed so that the surface linear equivalent rate is 2 mSv / h or less, and the dose equivalent rate at 1 m from the surface is 100 μSv / h or less. Furthermore, since the basket 300 is made of a boron-containing aluminum alloy, it is possible to absorb neutrons and prevent the spent fuel assembly from reaching the criticality.

As described above, the cask 1 according to this embodiment
According to No. 00, a plurality of plate-like members 201 are attached to the trunk main body 101, a chevron portion 207 is provided in a portion of the plate-like member 201 forming an outer surface of a cask, and a space 206 formed by the plate-like member 201 is further provided. Since the aluminum honeycomb member 210 is put in the fin, the heat transfer efficiency of the decay heat can be improved. Further, according to the cask 100 according to this embodiment, a plurality of fins 5 are provided as in the related art.
Since there is no need to weld the 04 to the outer peripheral surface, there is an advantage that the production is not troublesome. The above cask 100
In the above, the spent fuel assemblies are accommodated, but it goes without saying that other radioactive materials can be accommodated.

FIG. 6 shows a modification of this embodiment.
In this cask, a plate member 201 made of carbon steel is provided around the body 101, and an aluminum plate 400 (or a copper plate or a graphite sheet) is provided on both surfaces of the plate member 201.
To paste. The space formed by the plate-like member 201 is filled with only the resin 106. An expansion margin 401 is formed between the outside of the resin 106 and the plate member 201 (not shown). In addition,
The aluminum plate 40 is provided only on one side of the plate-like member 201.
0 may be provided. Further, in order to increase the heat collection efficiency, as shown in FIG.
May be extended (extended portion 402) so as to make surface contact with the trunk body 101. In this case, the extension 40
2 to the aluminum plate 400, so that the temperature of the resin 106 can be kept low.
Quality deterioration of the resin 106 can be prevented.

In the above structure, the main heat transfer of the decay heat is performed by the aluminum plate 400 (in FIG. 7, the extension 402 of the aluminum plate is included). In addition,
Even when the honeycomb material 210 is used, the aluminum plate 400 (or copper plate) can be attached to the plate member 201. By doing so, the thermal conductivity of the cask can be further improved.

The shape of the plate member 201 is not limited to the shape shown in FIG. For example, as shown in FIG.
A Y-shaped plate-shaped member 250 may be used. This plate-like member 250 can be formed by bending or extrusion. This plate-like member 250
In the case of, the foot is welded to the trunk body 101, and both end edges are joined to the edge 251 of the adjacent plate-like member 250. Thus, the heat transfer fins and the outer surface of the cask 100 are formed by the plurality of plate members 250. In this case, the chevron 25
The welded portion 253 is located at the ridge line of No. 2. In addition,
If the strength of the weld 253 is low, the angle 252
The welding part 253 may be located in the middle of the center (not shown).

As shown in FIG. 9A, a cask having a valley 261 may be formed by using a plurality of umbrella-shaped plate members 260. Further, as shown in FIG. 3B, the outer surface of the plate-like member 270 having a T-shaped cross section is formed in a waveform (corrugated portion 271), and the edge 272 is connected to the edge of the adjacent plate-like member 270. Make sure to join. Even in this case, the same effect as described above can be obtained. Note that these plate members 260 and 270 may be formed by sheet metal processing or may be formed by extrusion processing.

[0032]

As described above, in the cask (claim 1) of the present invention, a trunk body in which a basket for storing a radioactive material such as a spent fuel assembly is disposed, and a periphery of the trunk body is provided. And a plurality of plate-shaped members provided on the body, a part of the plate-shaped member is in contact with the trunk body, and the other part constitutes an outer surface of the cask and one or more chevron portions or valley portions The other part is joined to the adjacent plate-like member, and the space formed by this plate-like member is filled with a neutron absorbing material, so that the decay heat generated inside is efficiently released to the outside can do.

Further, in the cask of the present invention, the neutron absorbing material and the honeycomb material are combined, and the honeycomb material can contact at least the trunk body (Claim 2), and the neutron absorbing material and the plurality of heat conductors By combining (3), the thermal conductivity can be improved. Therefore, heat can be efficiently released.

Further, the honeycomb material or the heat conductor is made of aluminum or copper, and the plate-like member is made of iron (Claim 4). A copper plate or an aluminum plate is attached to one or both surfaces of the plate-like member. (Claim 5), making a part of the plate-shaped member in contact with the trunk body face-to-face contact with the trunk body (Claim 6), removing a part of a copper plate, an aluminum plate or a graphite sheet, By bringing the body into surface contact (claim 7), the thermal conductivity can be further improved, and heat can be efficiently released.

In the cask according to the present invention (claim 8), a basket having a plurality of cells for accommodating a spent fuel assembly in the cells and having a substantially polygonal outer shape, And the outer shape and inner shape are configured to fit the basket, and γ
Since it has a trunk main body that shields the radiation and a neutron shield provided outside the trunk main body, it is possible to secure a sufficient thickness of the trunk main body for shielding γ-rays and to reduce the weight of the cask. it can. Further, by providing the neutron shield so as to be polygonal with respect to the trunk body (claim 9), it is possible to reduce unnecessary neutron shields.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a cask according to a first embodiment of the present invention.

FIG. 2 is a radial sectional view of the cask shown in FIG.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is an explanatory view showing a honeycomb material and a heat conductive material.

FIG. 5 is an explanatory view showing a plate member.

FIG. 6 is an explanatory view showing a modified example of the cask.

FIG. 7 is an explanatory view showing a modified example of the cask shown in FIG. 6;

FIG. 8 is an explanatory view showing a modification of the plate member.

FIG. 9 is an explanatory view showing a modification of the plate member.

FIG. 10 is a configuration diagram showing an example of a conventional cask.

FIG. 11 is an axial sectional view of the cask shown in FIG. 10;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Cask 101 Trunk body 104 Bottom plate 106 Resin 109 Lid 110 Primary lid 111 Secondary lid 117 Trunnion 118 Buffer body 201 Plate member 204 Wire 206 Space 207 Angle section 210 Honeycomb material 212 Space (void layer) 300 Basket

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Hide Hide, 1-1-1, Wadazaki-cho, Hyogo-ku, Kobe-shi Inside the Kobe Shipyard, Rishi Heavy Industries Co., Ltd. (72) Shinji Ogame 5-chome, Komatsu-dori, Hyogo-ku, Kobe-shi No. 1-16 Inside Shinryo Hitec Co., Ltd.

Claims (9)

[Claims] 1. A trunk body in which a basket for storing a radioactive substance such as a spent fuel assembly is disposed,
A plurality of plate-like members provided around the trunk body, a part of the plate-like members being in contact with the trunk body, and another part constituting an outer surface of the cask, and a single or a plurality of chevron portions Alternatively, a cask characterized by having a valley-shaped portion, another portion of which is joined to an adjacent plate-shaped member, and a space formed by the plate-shaped member is filled with a neutron absorbing material. 2. The cask according to claim 1, wherein the neutron absorbing material and the honeycomb material are combined, and the honeycomb material contacts at least the trunk body. 3. The cask according to claim 1, wherein the neutron absorber and a plurality of heat conductors are combined. 4. The cask according to claim 2, wherein the honeycomb material or the heat conductor is made of aluminum or copper, and the plate-like member is made of iron, aluminum, or copper. 5. The cask according to claim 1, wherein an aluminum plate, a copper plate, or a graphite sheet is adhered to one or both surfaces of the plate-shaped member. 6. A part of the plate-like member that is in contact with a trunk body,
The cask according to any one of claims 1 to 5, wherein the cask is brought into surface contact with the trunk body. 7. The cask according to claim 5, wherein a part of said aluminum plate or copper plate is brought into surface contact with said trunk body. 8. A basket which has a plurality of cells and accommodates a spent fuel assembly in the cells and has a substantially polygonal outer shape, and a basket for accommodating the basket therein and having an outer shape and an inner shape. What is claimed is: 1. A cask comprising: a trunk main body configured to fit a basket and shielding gamma rays; and a neutron shield provided outside the trunk main body. 9. The cask according to claim 8, wherein the neutron shield is provided so as to be polygonal with respect to the trunk body.