JP7564076B2 - Radioactive material storage container - Google Patents

Description

This disclosure relates to a radioactive material storage container.

Radioactive material storage containers are known for storing radioactive material generated in nuclear reactors of nuclear power plants and the like. In this type of radioactive material storage container, for example, radioactive material is stored in a basket provided in the internal space of the main body, but the temperature rises due to decay heat from the stored radioactive material. For example, Patent Document 1 discloses a radioactive material storage container in which a heat pipe is embedded in the basket in which the radioactive material is stored, thereby improving heat removal performance.

Japanese Patent Application Publication No. 1-259299

Decay heat from the radioactive material stored in the basket forms a thermal distribution with a maximum temperature at a specific location in the radioactive material storage container through heat transfer and radiation, depending on the structural layout of the radioactive material storage container and the storage layout of the radioactive material. The number, amount, or amount of heat of radioactive material that can be stored in the radioactive material storage container is set within a range in which the maximum temperature in such a thermal distribution satisfies the required reference temperature. For this reason, in designing a radioactive material storage container, it is important to provide a margin for the maximum temperature in the thermal distribution when the radioactive material is stored. In the above-mentioned Patent Document 1, heat pipes are embedded in the basket to improve heat removal performance, but the effective range is limited to the vicinity of the heat pipes, and no margin for the maximum temperature in the thermal distribution when the radioactive material is stored is provided.

At least one embodiment of the present disclosure has been made in consideration of the above circumstances, and aims to provide a radioactive material storage container that can ensure a tolerance to the required reference temperature by suppressing the maximum temperature of each component in the temperature distribution caused by decay heat from the stored radioactive material.

In order to solve the above problems, a radioactive material storage container according to at least one embodiment of the present disclosure comprises:
A radioactive material storage container for storing radioactive material,
At least a portion of the surface is covered with an anisotropic heat transfer material having a first thermal conductivity along an in-plane direction that differs from a second thermal conductivity along an out-of-plane direction.

According to at least one embodiment of the present disclosure, it is possible to provide a radioactive material storage container that can ensure a tolerance to the required reference temperature by suppressing the maximum temperature of each component in the temperature distribution due to decay heat from the stored radioactive material.

FIG. 1 is a perspective view showing a basic configuration of a radioactive material storage container according to some embodiments. FIG. 2 is a cross-sectional view in the axial direction of the radioactive substance storage container shown in FIG. 1 . 2 is a radial cross-sectional view of the radioactive substance storage container shown in FIG. 1 . 3 is a schematic diagram showing anisotropy of heat conduction in a first anisotropic heat transfer material and a second anisotropic heat transfer material. FIG. 1 is a schematic diagram showing a cross-sectional structure along an axial direction of a radioactive substance storage container according to one embodiment. FIG. 6 is an analysis result of the temperature distribution in the radioactive material storage container shown in FIG. 5. FIG. 13 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive substance storage container according to another embodiment. FIG. 13 is a schematic diagram showing a cross-sectional structure along a radial direction of a radioactive substance storage container according to another embodiment. FIG. 13 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive substance storage container according to another embodiment. 13 is an enlarged cross-sectional view of the vicinity of a recess for inserting a gasket provided in a lid of a radioactive material storage container according to another embodiment. FIG. FIG. 13 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive substance storage container according to another embodiment. FIG. 2 is a perspective view of pieces constituting a basket provided in the radioactive material storage container 1. 13 is a diagram showing a schematic diagram of heat conduction in a radioactive material storage container having a basket composed of the pieces of FIG. 12. FIG. 11A and 11B are diagrams illustrating another example of heat conduction in a radioactive material storage container.

Below, several embodiments will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the invention and are merely illustrative examples.

Figure 1 is a perspective view showing the basic configuration of a radioactive material storage container 1 according to some embodiments, Figure 2 is an axial cross-sectional view of the radioactive material storage container 1 shown in Figure 1, and Figure 3 is a radial cross-sectional view of the radioactive material storage container 1 shown in Figure 1.

The radioactive material storage container 1 is a cask for transporting and storing radioactive material such as spent fuel, and includes a basket 2 for storing the radioactive material, a main body 4 surrounding the basket 2, a lid 6 for closing the main body 4, and an outer cylinder 8 surrounding the main body 4. The basket 2 has a storage space for radioactive material arranged in a lattice (matrix) shape as viewed from the axial direction by combining a plurality of pieces (see FIG. 12 ). The main body 4 has a substantially cylindrical shape with an internal space 10 for storing the basket 2, an opening 12 on one end side, and a bottomed shape closed by a bottom 14 on the other end side.
The basket 2 is made of a metal material such as carbon steel, stainless steel, boron-added stainless steel, aluminum alloy, or boron-added aluminum alloy.

The lid part 6 isolates the radioactive material stored in the basket 2 disposed in the internal space 10 from the outside by closing the opening 12 of the main body trunk 4. In this embodiment, the lid part 6 has a double structure including a first lid part 6a facing the internal space 10 and a second lid part 6b provided outside the first lid part 6a. The first lid part 6a and the second lid part 6b have flange shapes corresponding to the first step part 12a and the second step part 12b, respectively, provided in the opening 12 of the main body trunk 4, and are detachably fixed to the main body trunk 4 by being fastened by bolts 18 inserted into bolt holes 16 (see FIG. 2 ).
The bolt holes 16 and the bolts 18 are provided in a plurality of positions at predetermined intervals in the circumferential direction in each of the first cover portion 6a and the second cover portion 6b.

A recess 20 (gasket groove) is provided on the surface of the first lid portion 6a and the second lid portion 6b facing the first step portion 12a and the second step portion 12b. The recess 20 extends in the circumferential direction, and a gasket 22 is disposed therein to improve the airtightness between the main body 4 and the lid portion 6 at the opening 12.

An outer cylinder 8 is provided on the outer periphery of the main body barrel 4 so as to cover the outer periphery of the main body barrel 4. The outer cylinder 8 has a roughly cylindrical shape like the main body barrel 4, and is provided coaxially with the main body barrel 4. A plurality of heat transfer fins 24 are provided at intervals in the circumferential direction between the outer surface of the main body barrel 4 and the inner surface of the outer cylinder 8. These heat transfer fins 24 are provided to connect the main body barrel 4 and the outer cylinder 8, and have the function of dissipating heat generated inside the main body barrel 4 to the outer surface of the radioactive material storage container 1 via the heat transfer fins 24.

The radioactive material storage container 1 also includes a neutron shielding material 26 for shielding neutrons from the radioactive material stored in the basket 2. The neutron shielding material 26 is, for example, a resin material. In this embodiment, a first neutron shielding material 26a, a second neutron shielding material 26b, and a third neutron shielding material 26c are provided as the neutron shielding material 26. The first neutron shielding material 26a is provided on the side of the radioactive material storage container 1 by filling a space in which the heat transfer fins 24 are provided between the outer surface of the main body trunk 4 and the inner surface of the outer cylinder 8. The second neutron shielding material 26b is provided on the lid portion 6, and more specifically, is built in between the first lid portion 6a and the second lid portion 6b. The third neutron shielding material 26c is built in the bottom portion 14 of the main body trunk 4.
Incidentally, the radioactive material storage container 1 having the above-mentioned configuration is stored in a vertical position on the floor surface via the stand 50, but the present invention may also be applied to the case where it is stored in a horizontal position.

As described below with reference to Figs. 5 to 14, at least a portion of the surface of the radioactive material storage container 1 having the above-mentioned basic configuration is covered with an anisotropic heat transfer material 30. The anisotropic heat transfer material 30 is a component in which a first thermal conductivity σ1 in the in-plane direction is different from a second thermal conductivity σ2 along the out-of-plane direction, and is a laminated material of graphene such as a graphene sheet. This allows the decay heat from the radioactive material stored in the radioactive material storage container 1 to be dispersed over a wide area of the radioactive material storage container by the anisotropic heat transfer material 30, preventing a specific location from becoming too hot. As a result, the maximum temperature in the radioactive material storage container 1 can be reduced and the tolerance for the required reference temperature can be improved, and the improved tolerance makes it possible to increase the number of radioactive materials stored and to store high burnup fuel.

In the following embodiments, the anisotropic heat transfer material 30 includes at least one of a first anisotropic heat transfer material 30a in which the first thermal conductivity σ1 is greater than the second thermal conductivity σ2, and a first anisotropic heat transfer material 30b in which the second thermal conductivity σ2 is greater than the first thermal conductivity σ1. FIG. 4 is a schematic diagram showing the anisotropy of heat conduction in the first anisotropic heat transfer material 30a and the second anisotropic heat transfer material 30b. FIG. 4 shows a schematic diagram of the anisotropic heat transfer material 30 installed on the installation member 1' (for example, at least a part of the radioactive material storage container 1 described above). The first anisotropic heat transfer material 30a has excellent heat transfer along the in-plane direction because the first thermal conductivity σ1 is greater than the second thermal conductivity σ2. On the other hand, the second anisotropic heat transfer material 30b has excellent heat transfer along the out-of-plane direction because the second thermal conductivity σ2 is greater than the first thermal conductivity σ1. Such a first anisotropic heat transfer material 30a and a second anisotropic heat transfer material 30b can be realized as appropriate by adjusting the stacking direction of a material with anisotropic thermal conductivity, such as a graphene sheet.

In addition, in the anisotropic heat transfer material 30 formed by stacking graphene, the thermal conductivity in the direction of high thermal conductivity (first thermal conductivity σ1 in the first anisotropic heat transfer material 30a and second thermal conductivity σ2 in the second anisotropic heat transfer material 30b) is, for example, 700 to 1950 [W/m·K], and the thermal conductivity in the direction of low thermal conductivity (second thermal conductivity σ2 in the first anisotropic heat transfer material 30a and first thermal conductivity σ1 in the second anisotropic heat transfer material 30b) is, for example, 10 to 20 [W/m·K].

Figure 5 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive material storage container 1 according to one embodiment, and Figure 6 shows the analysis results of the temperature distribution in the radioactive material storage container 1 shown in Figure 5 (Figure 6 shows a simplified version of the configuration in Figure 5). In this embodiment, the first anisotropic heat transfer material 30a is provided on at least one of the inner and outer surfaces of the main body trunk 4 (Figure 5 illustrates an example in which the first anisotropic heat transfer material 30a is provided on both the inner and outer surfaces of the main body trunk 4, but it may be provided on only one of them).

According to this embodiment, if the first anisotropic heat transfer material 30a is not provided, the decay heat from the radioactive material stored in the basket 2 is transferred to the surroundings from the basket 2, as shown on the left side of FIG. 6, resulting in a high-temperature spot near the axial center of the radioactive material storage container 1. In contrast, by providing the first anisotropic heat transfer material 30a on at least one of the inner and outer surfaces of the main body trunk 4, the decay heat from the basket 2 is transferred along the in-plane direction (axial direction) and dispersed over a wide range of the main body trunk 4, as shown on the right side of FIG. 6. As a result, the maximum temperature of the basket 2 is reduced, and a tolerance to the reference temperature can be ensured.

Although not shown in FIG. 5, as described above with reference to FIG. 2, a first neutron shielding material 26a is provided between the outer surface of the main body barrel 4 and the inner surface of the outer cylinder 8. Therefore, the first anisotropic heat transfer material 30a in FIG. 5 is arranged along the first neutron shielding material 26a. Generally, neutron shielding materials have a relatively small tolerance to the reference temperature among the components of the radioactive material storage container 1, but by providing the first anisotropic heat transfer material 30a along the first neutron shielding material 26a in this manner, the temperature of the first neutron shielding material 26a, which has a small tolerance, can be suitably reduced.

Figure 7 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive material storage container 1 according to another embodiment. In this embodiment, the first anisotropic heat transfer material 30a is provided on at least one of the inner surface or the outer surface of the outer cylinder 8 (Figure 7 illustrates a case in which the first anisotropic heat transfer material 30a is provided on both the inner surface and the outer surface of the outer cylinder 8, but it may be provided on only one of them).

According to this embodiment, by providing the first anisotropic heat transfer material 30a on at least one of the inner surface or the outer surface of the outer cylinder 8, the decay heat from the basket 2 is transferred along the in-plane direction (axial direction) and dispersed over a wide range of the outer cylinder 8, as in the embodiment described above with reference to FIG. 5. As a result, the maximum temperature of the outer cylinder 8 is reduced, and a tolerance to the reference temperature can be ensured.

Figure 8 is a schematic diagram showing the radial cross-sectional structure of a radioactive material storage container 1 according to another embodiment.

In this embodiment, the first anisotropic heat transfer material 30a is provided so as to cover the surfaces of the multiple heat transfer fins 24 provided between the main body 4 and the outer cylinder 8. This allows the decay heat from the radioactive material stored in the basket 2 to be dispersed over a wide area without concentrating at a specific point on the heat transfer fins 24, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container 1.

The first anisotropic heat transfer material 30a covering the surface of the heat transfer fin 24 may extend to at least one of the main body trunk 4 or the outer tube 8 adjacent to the heat transfer fin 24. In the example of FIG. 8, the first anisotropic heat transfer material 30a covering the surface of the heat transfer fin 24 extends to the surface of the other adjacent heat transfer fin 24 via the outer surface of the main body trunk 4. This allows the heat of the main body trunk 4 to be efficiently released to the outer tube 8 through the heat transfer fin 24 by the first anisotropic heat transfer material 30a, so that the decay heat from the radioactive material stored in the basket 2 can be dispersed over a wider range. In particular, in this embodiment, the first anisotropic heat transfer material 30a covering the surface of the heat transfer fin 24 is provided so as to reach another adjacent heat transfer fin 24 via the outer surface of the main body trunk 4, so that the heat is dispersed by the first anisotropic heat transfer material 30a over the entire circumferential direction of the main body trunk 4.

Figure 9 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive material storage container 1 according to another embodiment. In this embodiment, the first anisotropic heat transfer material 30a is provided on at least one of the inner surface or outer surface of the lid portion 6 (Figure 9 illustrates a case in which the first anisotropic heat transfer material 30a is provided on the inner surface (the surface facing the basket 2 located in the internal space 10) of the lid portion 6 (first lid portion 6a), but it may be provided on the outer surface of the lid portion 6). This allows the decay heat from the radioactive material stored in the basket 2 to be dispersed over a wide range without concentrating at a specific point on the lid portion 6, thereby reducing the maximum temperature of the lid portion 6 and ensuring a tolerance to the reference temperature.

Although not shown in FIG. 9, as described above with reference to FIG. 2, a second neutron shielding material 26b is provided on the lid portion 6 (between the first lid portion 6a and the second lid portion 6b). Therefore, the first anisotropic heat transfer material 30a in FIG. 9 is arranged along the second neutron shielding material 26b. Generally, neutron shielding materials have a relatively small tolerance to the reference temperature among the components of the radioactive material storage container 1, but by providing the first anisotropic heat transfer material 30a along the second neutron shielding material 26b in this manner, the temperature of the second neutron shielding material 26b, which has a small tolerance, can be suitably reduced.

Figure 10 is an enlarged cross-sectional view of the vicinity of the recess 20 into which the gasket 22 provided on the lid 6 of the radioactive material storage container 1 according to another embodiment is inserted. The first anisotropic heat transfer material 30a provided on the lid 6 may be provided so as to cover the recess 20 in at least one of the first lid 6a or the second lid 6b. In Figure 10, the first anisotropic heat transfer material 30a covers the recess 20 along the recess 20 provided on the first lid 6a or the second lid 6b so as to reach the surrounding surface. The gasket 22 placed in the recess 20 has a relatively small tolerance to the reference temperature among the components of the radioactive material storage container 1, but by covering the recess 20 in which the gasket 22 is placed with the first anisotropic heat transfer material 30a, the concentration of decay heat from the radioactive material in the recess 20 can be suppressed, and the temperature of the gasket 22 placed in the recess 20 can be suitably reduced.

In addition, since the first lid portion 6a is located closer to the basket 2 than the second lid portion, it is susceptible to the effects of decay heat from the radioactive material storage container 1 stored in the basket 2. Therefore, only the recess 20 provided in the first lid portion 6a may be covered with the first anisotropic heat transfer material 30a. In this case, by limiting the application range of the first anisotropic heat transfer material 30a to the recess 20 of the first lid portion 6a, which is susceptible to the effects of decay heat, it is possible to reduce costs while also suitably reducing the temperature of the gasket 22 placed in the recess 20.

Figure 11 is a schematic diagram showing a cross-sectional structure along the axial direction of a radioactive material storage container 1 according to another embodiment. In this embodiment, the first anisotropic heat transfer material 30a is provided on at least one of the inner surface or outer surface of the bottom 14 of the main body trunk 4 (Figure 11 illustrates a case in which the first anisotropic heat transfer material 30a is provided on the inner surface of the bottom 14 (the surface facing the basket 2 located in the internal space 10), but it may be provided on the outer surface of the bottom 14). This allows the decay heat from the radioactive material stored in the basket 2 to be dispersed over a wide range without concentrating at a specific point on the bottom 14 of the main body trunk 4, thereby reducing the maximum temperature of the bottom 14 of the main body trunk 4 and ensuring a tolerance to the reference temperature.

As described above with reference to FIG. 2, the third neutron shielding material 26c is provided at the bottom 14 of the main body trunk 4. Therefore, the first anisotropic heat transfer material 30a in FIG. 11 is arranged along the third neutron shielding material 26c. Generally, neutron shielding materials have a relatively small tolerance to the reference temperature among the components of the radioactive material storage container 1, but by providing the first anisotropic heat transfer material 30a along the third neutron shielding material 26c in this way, the temperature of the third neutron shielding material 26c, which has a small tolerance, can be suitably reduced.

Figure 12 is a perspective view of pieces 35 that make up the basket 2 of the radioactive material storage container 1, and Figure 13 is a schematic diagram showing the state of heat conduction in a radioactive material storage container 1 having a basket 2 made up of the pieces 35 of Figure 12. As shown in Figure 12, the pieces 35 are configured as hollow bodies basically having a roughly plate shape, and have at least one concave engaging portion 36 on the edge along the longitudinal direction. The basket 2 is configured from multiple pieces 35 by combining such engaging portions 36.

In this embodiment, an anisotropic heat transfer material 30 is provided on at least a part of the inner surface or outer surface of each piece 35 constituting the basket 2 (FIG. 12 shows, as an example, an anisotropic heat transfer material 30 provided to cover the outer surface of the piece 35). This anisotropic heat transfer material 30 may be the first anisotropic heat transfer material 30a or the second anisotropic heat transfer material 30b. In addition, both the first anisotropic heat transfer material 30a and the second anisotropic heat transfer material 30b may be used in combination. These anisotropic heat transfer materials 30 can be provided according to the heat distribution of the radioactive material stored in the basket 2. In this way, by providing two types of anisotropic heat transfer materials 30 with different anisotropies of thermal conductivity to the pieces 35 constituting the basket 2 according to the heat distribution, the maximum temperature in the radioactive material storage container 1 can be suitably reduced while suppressing structural changes to the radioactive material storage container 1.

A heat transfer support member made of a heat conductive material such as an aluminum alloy may be provided between the basket 2 and the inner surface of the main body 4, and an anisotropic heat transfer material 30 may be provided on at least a portion of the surface of such a heat transfer support member.

Figure 13 shows how decay heat from radioactive material stored in the basket 2 is transferred from the center, where the radioactive material is concentrated, to the ends, and then dissipated radially toward the surrounding main body shell 4. To achieve this type of heat transfer, for example, a first anisotropic heat transfer material 30a is placed in the center of the basket 2, where the temperature is higher, to disperse the heat toward the ends of the basket 2 and reduce the maximum temperature, and a second anisotropic heat transfer material 30b is placed on the end side (upper or lower) of the basket 2 to promote heat dissipation from the basket 2 to the surrounding main body shell 4.

Figure 14 is a diagram showing another example of heat conduction in a radioactive material storage container 1. In this example, an anisotropic heat transfer material 30 is provided on the outer surface of the outer cylinder 8 so that the amount of heat dissipation at the lower part is larger than that at the upper part in the radioactive material storage container 1 installed on the stand 50. In order to realize such heat conduction, in Figure 14, a second anisotropic heat transfer material 30b is provided on the upper part of the outer surface of the outer cylinder 8, and a first anisotropic heat transfer material 30a is provided on the lower part of the outer surface of the outer cylinder 8. As a result, in the basket 2, the temperature difference between the lower part where the first anisotropic heat transfer material 30a is provided and the upper part where the second anisotropic heat transfer material 30b is provided becomes large, thereby realizing the heat transfer shown in Figure 14. Such a temperature difference along the vertical direction of the outer cylinder 8 generates an upward air current around the radioactive material storage container 1, which promotes heat exchange between the radioactive material storage container 1 and the outside air, thereby improving heat removal.

As explained above, according to each of the above-mentioned embodiments, it is possible to provide a radioactive material storage container 1 that can ensure a margin for the required reference temperature by suppressing the maximum temperature in the temperature distribution due to decay heat from the stored radioactive material.

In addition, the components in the above-described embodiments may be replaced with well-known components as appropriate without departing from the spirit of this disclosure, and the above-described embodiments may be combined as appropriate.

The contents described in each of the above embodiments can be understood, for example, as follows:

(1) A radioactive material storage container according to one embodiment comprises:
A radioactive material storage container (1) for storing radioactive material,
At least a portion of the surface is covered with an anisotropic heat transfer material (30) having a first thermal conductivity (σ1) in an in-plane direction and a second thermal conductivity (σ2) along an out-of-plane direction that differ from each other.

According to the above aspect (1), at least a portion of the surface of the radioactive material storage container for storing radioactive material is covered with an anisotropic heat transfer material. This allows the decay heat from the radioactive material stored in the radioactive material storage container to be dispersed over a wide area of the radioactive material storage container by the anisotropic heat transfer material, preventing specific locations from becoming too hot. As a result, the maximum temperature of each member in the radioactive material storage container can be reduced, and the tolerance for the reference temperature required for each member can be improved. The improved tolerance makes it possible to increase the number of radioactive materials stored and to store high burnup fuel.

(2) In another embodiment, in the above embodiment (1),
The radioactive material storage container comprises:
a basket (2) for containing said radioactive material;
A main body (4) surrounding the basket;
A lid portion (6) for closing the end of the main body;
An outer cylinder (8) surrounding the main body;
A radioactive material storage container comprising:
The anisotropic heat transfer material is provided on at least a portion of the basket, the main body, the lid, and the outer cylinder.

According to the above aspect (2), anisotropic heat transfer material is provided for at least a part of the main components of the radioactive material storage container, namely the basket, main body, lid, and outer cylinder. This disperses the decay heat transferred to these components, and effectively reduces the maximum temperature in the radioactive material storage container.

(3) In another aspect, in the above (1) or (2),
The anisotropic heat transfer material includes a first anisotropic heat transfer material (30a) having the first thermal conductivity greater than the second thermal conductivity.

According to the above aspect (3), at least a portion of the radioactive material storage container is covered with a first anisotropic heat transfer material having a first thermal conductivity along an in-plane direction that is greater than a second thermal conductivity along an out-of-plane direction. This allows the decay heat from the radioactive material to be dispersed along the in-plane direction without concentrating at a specific location, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(4) In another embodiment, in the above embodiment (3),
The radioactive material storage device includes a main body (4) surrounding a basket (2) for storing the radioactive material;
The first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of the main body barrel.

According to the above aspect (4), a first anisotropic heat transfer material is provided on at least one of the inner surface or the outer surface of the main body of the radioactive material storage container. This allows the decay heat from the radioactive material to be dispersed over a wide area without concentrating at a specific location on the main body, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(5) In another aspect, in the above (3) or (4),
a main body (4) surrounding the basket (2) for storing the radioactive material;
and an outer cylinder (8) surrounding the main body.
The first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of the outer cylinder.

According to the above aspect (5), a first anisotropic heat transfer material is provided on at least one of the inner surface or the outer surface of the outer tube of the radioactive material storage container. This allows the decay heat from the radioactive material to be dispersed over a wide area without concentrating at a specific location on the outer tube, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(6) In another aspect, in any one of the above (3) to (5),
a main body (4) surrounding a basket (2) for storing the radioactive material;
An outer cylinder (8) surrounding the main body;
The heater further includes a plurality of heat transfer fins (24) spaced apart in a circumferential direction between the outer surface of the main body barrel and the inner surface of the outer cylinder,
The first anisotropic heat transfer material is provided so as to cover surfaces of the plurality of heat transfer fins.

According to the above aspect (6), the first anisotropic heat transfer material is provided on the heat transfer fins of the radioactive material storage container. This allows the decay heat from the radioactive material to be dispersed over a wide area without concentrating at a specific point on the heat transfer fins, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(7) In another aspect, in any one of the above (3) to (6),
a main body (4) surrounding the basket (2) for storing the radioactive material;
A lid portion (6) that closes one end of the main body,
The first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of the lid portion.

According to the above aspect (7), a first anisotropic heat transfer material is provided on at least one of the inner surface or the outer surface of the lid of the radioactive material storage container. This allows the decay heat from the radioactive material to be dispersed over a wide area without concentrating at a specific point on the lid, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(8) In another aspect, in any one of the above (3) to (7),
a main body (4) surrounding the basket (2) for storing the radioactive material;
a lid portion (6) that closes one end of the main body barrel and has a recess (20) between the lid portion and the main body barrel, and a gasket (22) is disposed between the lid portion and the main body barrel;
The first anisotropic heat transfer material is provided so as to cover the recess.

According to the above aspect (8), the first anisotropic heat transfer material is provided so as to cover the recess provided in the flange portion of the lid portion of the radioactive material storage container. The gasket placed in the recess has a relatively small tolerance to the reference temperature among the components of the radioactive material storage container, but by covering the recess in which the gasket is placed with the first anisotropic heat transfer material in this manner, it is possible to suppress the decay heat from the radioactive material from concentrating in the recess, and to suitably reduce the temperature of the gasket placed in the recess.

(9) In another aspect, in any one of the above (3) to (8),
The radioactive material storage device includes a main body (4) surrounding a basket (2) for storing the radioactive material;
The first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of a bottom portion (14) of the main body barrel.

According to the above aspect (9), a first anisotropic heat transfer material is provided on at least one of the inner surface or the outer surface of the bottom of the main body that constitutes the radioactive material storage container. This allows the decay heat from the radioactive material to be dispersed over a wide area without concentrating at a specific point on the bottom, so that the maximum temperature in the radioactive material storage container can be suitably reduced.

(10) In another aspect, in any one of the above (3) to (9),
a neutron shielding material (26) for shielding neutrons from the radioactive material;
The first anisotropic heat transfer material is provided along the neutron shielding material.

According to the above aspect (10), the first anisotropic heat transfer material is provided along the neutron shielding material provided in the radioactive material storage container. Among the components of the radioactive material storage container, the neutron shielding material has a relatively small tolerance to the reference temperature, but by providing the first anisotropic heat transfer material along the neutron shielding material in this manner, the temperature of the neutron shielding material, which has a small tolerance, can be suitably reduced.

(11) In another aspect, in any one of the above (1) to (10),
The anisotropic heat transfer material includes a second anisotropic heat transfer material (30b) having the second thermal conductivity greater than the first thermal conductivity.

According to the above aspect (11), at least a portion of the radioactive material storage container is covered with a second anisotropic heat transfer material in which the second thermal conductivity along the out-of-plane direction is greater than the first thermal conductivity along the in-plane direction. This allows the decay heat from the radioactive material to be dispersed along the out-of-plane direction without concentrating at a specific location, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(12) In another embodiment, in the above embodiment (11),
A basket (2) for containing the radioactive material,
The second anisotropic heat conductive material is provided on at least a portion of the inner surface or the outer surface of a piece (35) that constitutes the basket.

According to the above aspect (12), a second anisotropic heat transfer material is provided on at least one of the inner surface or the outer surface of the component piece of the basket of the radioactive material storage container. This allows the decay heat from the radioactive material to be dispersed over a wide area without concentrating at a specific point of the basket, thereby making it possible to suitably reduce the maximum temperature in the radioactive material storage container.

(13) In another aspect, in any one of the above (1) to (12),
The anisotropic heat transfer material is
A first anisotropic heat transfer material (30a) having a thermal conductivity in the in-plane direction greater than a thermal conductivity in the out-of-plane direction;
A second anisotropic heat transfer material (30b) having a thermal conductivity in the out-of-plane direction greater than a thermal conductivity in the in-plane direction;
Including,
The first anisotropic heat transfer material and the second anisotropic heat transfer material are provided in accordance with the heat distribution of the radioactive material.

According to the above aspect (13), by providing two types of anisotropic heat transfer materials with different thermal conductivity anisotropy in the radioactive material storage container according to the heat distribution, it is possible to suitably reduce the maximum temperature in the radioactive material storage container while minimizing structural changes to the radioactive material storage container.

(14) In another embodiment, in the above embodiment (13),
When the radioactive material storage container is installed, the first anisotropic heat transfer material is provided below the second anisotropic heat transfer material.

According to the above aspect (14), in the radioactive material storage container in the installed state, the first anisotropic heat transfer material is provided below the second anisotropic heat transfer material. This increases the amount of heat dissipation at the lower part of the radioactive material storage container compared to the upper part, and generates a temperature difference in the vertical direction in the radioactive material storage container. This temperature difference generates an air current that flows upward around the radioactive material storage container, promoting heat exchange in the radioactive material storage container and improving heat removal performance.

(15) In another aspect, in any one of the above (1) to (14),
The anisotropic heat conductive material comprises a graphene sheet.

According to the above aspect (15), the above-mentioned anisotropic heat transfer material may be realized by using a graphene sheet having an anisotropic heat transfer coefficient.

Reference Signs List 1 Radioactive material storage container 2 Basket 4 Main body 6 Lid 6a First lid 6b Second lid 8 Outer cylinder 10 Internal space 12 Opening 12a First step 12b Second step 14 Bottom 16 Bolt hole 18 Bolt 20 Recess 22 Gasket 24 Heat transfer fin 26 Neutron shielding material 26a First neutron shielding material 26b Second neutron shielding material 26c Third neutron shielding material 30 Anisotropic heat transfer material 30a First anisotropic heat transfer material 30b Second anisotropic heat transfer material 35 Piece 36 Engagement portion 50 Stand

Claims (13)

A radioactive material storage container for storing radioactive material,
At least a portion of the surface is covered with an anisotropic heat transfer material having a first thermal conductivity in an in-plane direction and a second thermal conductivity along an out-of-plane direction that are different from each other;
The anisotropic heat transfer material is
a first anisotropic heat transfer material having a thermal conductivity in an in-plane direction greater than a thermal conductivity in an out-of-plane direction;
A second anisotropic heat transfer material having a thermal conductivity in an out-of-plane direction greater than a thermal conductivity in an in-plane direction;
Including,
the first anisotropic heat transfer material is arranged so that decay heat from the radioactive material is transferred from a center of the radioactive material storage container toward an end of the container,
A radioactive material storage container, wherein the second anisotropic heat transfer material is arranged such that the decay heat transferred by the first anisotropic heat transfer material is transferred along a radial direction. The radioactive material storage container comprises:
a basket for containing the radioactive material;
A main body surrounding the basket;
A lid for closing an end of the main body;
An outer cylinder surrounding the main body;
A radioactive material storage container comprising:
The radioactive material storage container according to claim 1 , wherein the anisotropic heat transfer material is provided on at least a part of the basket, the main body, the lid, and the outer cylinder. a main body surrounding a basket for storing the radioactive material;
The radioactive material storage container according to claim 1 or 2, wherein the first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of the main body barrel. a main body surrounding a basket for storing the radioactive material;
and an outer cylinder surrounding the main body.
The radioactive material storage container according to claim 1 , wherein the first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of the outer cylinder. a main body surrounding a basket for storing the radioactive material;
An outer cylinder surrounding the main body;
The heater further includes a plurality of heat transfer fins spaced apart from one another in a circumferential direction between the outer surface of the main body and the inner surface of the outer cylinder,
The radioactive material storage container according to claim 1 , wherein the first anisotropic heat transfer material is provided so as to cover surfaces of the plurality of heat transfer fins. a main body surrounding a basket for storing the radioactive material;
a lid portion for closing one end of the main body,
The radioactive material storage container according to claim 1 , wherein the first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of the lid portion. a main body surrounding a basket for storing the radioactive material;
a lid portion that closes one end of the main body barrel and has a recess in which a gasket is disposed between the lid portion and the main body barrel,
The radioactive material storage container according to claim 1 , wherein the first anisotropic heat transfer material is provided so as to cover the recess. a main body surrounding a basket for storing the radioactive material;
The radioactive material storage container according to claim 1 , wherein the first anisotropic heat transfer material is provided on at least one of an inner surface and an outer surface of a bottom portion of the main body trunk. a neutron shielding material for shielding neutrons from the radioactive material;
The radioactive material storage container according to claim 1 , wherein the first anisotropic heat transfer material is provided along the neutron shielding material. a basket for containing the radioactive material;
The radioactive material storage container according to claim 1 , wherein the second anisotropic heat transfer material is provided on at least a part of an inner surface or an outer surface of a piece constituting the basket. The radioactive material storage container according to any one of claims 1 to 10, wherein the first anisotropic heat transfer material and the second anisotropic heat transfer material are provided according to the heat distribution of the radioactive material. A radioactive material storage container according to any one of claims 1 to 11, wherein, when the radioactive material storage container is installed, the first anisotropic heat transfer material is provided below the second anisotropic heat transfer material. The radioactive material storage container according to any one of claims 1 to 12, wherein the anisotropic heat transfer material comprises a graphene sheet.

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