JPH0731276B2 - Transport container for nuclear fuel materials, etc. - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transportation container for safely transporting a nuclear fuel material or the like (a nuclear fuel material and a material polluted by a nuclear fuel material; the same applies hereinafter), and particularly to a small-sized transportation. It concerns a container.

[0002]

2. Description of the Related Art There is a strong demand for safety in the transportation of nuclear fuel materials, and there is a law concerning the regulation of nuclear source materials, nuclear fuel materials and nuclear reactors (Law No. 166 of 1957), and the enforcement order of the same law (Showa 32). Year Cabinet Order No. 324), regulations concerning the transportation of nuclear fuel materials, etc. outside factories or business establishments (Prime Minister's Office Ordinance No. 57 of 1978), vehicle transportation regulations of nuclear fuel materials (Prime Minister's Office Ordinance No. 72 of 1978), ships Safety Law (Showa 8
Year Law No. 11), Hazardous Material Ship Transportation and Storage Regulations (Ministry of Transportation Ordinance No. 33 of 1957), Aviation Law (Law No. 231 of 1952), Aviation Law Enforcement Regulations (Ministry of Transportation Ordinance No. 5 of 1952)
It is strictly regulated by laws such as No. 6). The regulations vary depending on the type and quantity of nuclear fuel materials to be transported, but for the strictest B (U) -type fissile packages, strength tests (from 9m height Tests for dropping packages, etc., Fire tests (800
It is said that the soundness must be maintained even under conditions such as a test in which a package is placed in an environment of ° C for 30 minutes).

[0003] Conventionally, among containers for transporting nuclear fuel materials and the like, which have a large weight such as spent fuel, the outer container and the lid constitute a sealed boundary, and the contents are arranged. Designed so that the basket contacts the outer container,
It is said that a shock absorber of wood (balsa wood, teak wood) is attached to the head and bottom of the head to provide a shock absorbing function. Further, since such a shipping container has a large amount of heat generation, a special fan or other device for heat dissipation has been added.

On the other hand, a sample having a relatively small weight and a small calorific value, such as a sample for test and research, has the following structure. That is, the outer container and the inner container holder that stores the inner container that forms the sealed boundary are filled with wood or metal fiber (a kind of stainless steel wire mesh is rolled up), and these are fixed. The method that is not performed is general. The filling material has a function of a cushioning material, and also has a function of removing heat generation of the stored material when the metal fiber is filled. Some unused fuel element transportation containers have an inner container directly fixed to an outer container, but they do not have a function of removing the contents because they do not generate heat.

[0005]

In the conventional example, in the event of a fire, the heat outside the transportation container is transferred to the inside by conduction, radiation, etc., causing a phenomenon such as an increase in temperature and pressure inside the transportation container. There is a risk. Further, the wood-based shock absorber may cause a heat generation phenomenon due to its own fuel in a high temperature environment, and the metal fiber does not have a heat insulating function because the heat conduction is good. That is, the conventional technology has not been fully functional in heat resistance during a fire. The present invention has in mind a relatively small shipping container, for example, a shipping container of 5 t or less. In a small shipping container,
In order to improve the handleability, it is advantageous to fill the cushioning / insulating material between the outer container and the inner container. It is desirable that the filler not only has a buffer function during normal times but also does not burn even during a fire, and that it also has a heat insulating property assuming a fire. For that purpose, it is necessary to select an appropriate cushioning / insulating material. If the cushioning material has a heat insulating property, the heat outside the transportation container is difficult to transfer to the inner container, but on the other hand, the heat generated from the nuclear fuel material etc. stored in the inner container is transferred to the outside. Need to be removed. Although these two requirements are basically contradictory, measures are taken to remove the heat generated from the stored items during normal times and to sufficiently reduce the amount of heat transferred from the outside to the inner container during a fire. There is a need.
Further, in the conventional small-sized transport container, a cushioning material is filled between the inner container holder and the outer container without being fixed to the outer container. Therefore, the inner container is not always located at the center of the outer container. As a result, the dose equivalent rate at the surface of the outer container or at a certain distance from it will vary depending on the location, and the inner container must be shielded assuming that it is in the most biased position in each direction. As a result, the weight of the shipping container is increased. Therefore, it is desirable that the inner container is in a fixed position in the outer container. For that purpose, the inner container is fixed to the outer container, but its structure is required to reduce the shock to the inner container when a strong shock is applied from the outside.

In view of the above circumstances, it is an object of the present invention to provide a transportation container for a nuclear fuel material or the like, which is resistant to impacts, shields heat from the outside, and can release the heat inside.

[0007]

SUMMARY OF THE INVENTION According to the present invention, an inorganic fiber is filled between an outer container for protecting contents and an inner container holder for storing the inner container, and the inner container holder is gusseted to form the outer container. The present invention is intended to achieve the above object by a transportation container for a nuclear fuel substance or the like, which is characterized by being fixed to.

[0008]

Since the inner container holder is fixed to the outer container by the gusset, the position of the inner container stored in the holder does not change with respect to the outer container. As a result, the dose equivalent rate at the surface of the outer container or at a point at a certain distance from the surface can be made uniform. In normal times, the heat generated from nuclear fuel material is
It is released to the outside through the inner container, gusset and outer container.
In this case, the gusset also serves as a conductor for removing heat generated internally. In the event of a fire, heat is transferred from the outside to the inside of the shipping container (inner container), and the gusset becomes a heat conductor at that time. Therefore, from the viewpoint of heat conduction, the cross-sectional area of the gusset is sufficient to remove the heat generated from the stored items under normal conditions, and the amount of heat transfer should be below a certain value during a fire. Must be decided. By doing so, it is possible to suppress the temperature rise in the inner container even in the event of a fire. Since the inorganic fiber has a low thermal conductivity, it blocks the transfer of external heat to the inside in case of fire. The inorganic fibers do not burn even at high temperatures, and since some of them do not change in chemical change and physical properties, the aforementioned heat transfer is prevented even during a fire and after the end of the fire. It does not lose the shock absorbing function described below. Since the inorganic fiber has a large porosity, it has a shock absorbing function when the molded fiber is closely packed. By filling both sides of the gusset, the gusset will deform when impacted, but will not break under the legal test conditions. Therefore, it plays a role of supplementing the above-mentioned fixing and holding functions.

[0009]

EXAMPLES Examples of the present invention will be described with reference to the accompanying drawings. Here, a container for transporting a sample such as a nuclear fuel material used for testing and research, for example, a small transport container A of 5 t or less will be described. The outline of this transport container and the nuclear fuel materials contained in it are as follows. Type of package: B (U) type fissile package, transport index: 10 or less, total weight of package: maximum 180 kg, outer dimension of transport container: outer diameter of about 560 mm, height of 715 mm, dimension of inner container: Outer diameter Φ135 mm, inner diameter Φ115 mm, height 409 mm, calorific value of stored items: 14.7 W or less The small transport container A stores the stored items and an inner container B that constitutes a sealed boundary, and an outer container C that protects this. It is roughly divided into.
The outer container C is composed of a stainless steel outer container outer plate 1 having a thickness of 3 mm and an outer container lid 2. The outer container outer plate 1 is composed of a body plate 3, a bottom plate 4 and a mirror plate 5, and the bottom plate 4 and the mirror plate 5 are welded to the body plate 3. The body plate 3 is provided with a body melting plug 6 for releasing the gas filled between the outer container C and the inner container B when the gas expands at an abnormally high temperature. The outer container lid 2 is covered with a rubber pad 7 to prevent liquid from entering. The outer container lid 2 is composed of a stainless steel outer container lid bottom plate 8 having a thickness of 3 mm, an outer container lid body plate 9 and an outer container lid upper plate 10. The bottom plate 8 and the upper plate 10 are the body plate 9 described above.
Be welded to. In order to reduce the impact on the lid part, in the peripheral part of the outer container lid 2, there are eight penetration tubes 11 which are made of stainless steel and have a thickness of 1.65 mm and which are sealed and welded to each other. It is attached, and the upper part thereof is projected from the upper plate 10 of the outer container lid by 5 mm. When the container A falls and receives an impact, the tubes 11a and 11b separate from the welded portion and slide. The outer container lid mounting bolt 12 is inserted into the bottom of the tube and fixed to the inner container holder flange 13.
Further, since the expanded gas in the outer container lid 2 is released at an abnormally high temperature, the lid melting plug 14 is attached to the upper portion thereof.

The inner container holder 15 has a cylindrical shape made of stainless steel and has a thickness of 3 mm, and the inner container B is stored therein. From the upper part 3a and the lower part 3b of the outer container body plate 3, one cylindrical upper gusset 16 and one lower gusset 17 made of stainless steel having a thickness of 2 mm are formed at right angles and welded to each other to form the outer container body plate 3 And the inner container holder 15 are attached. Also, the lower gusset 17 has the same thickness 2
mm bottom stainless steel rectangular bottom gussets 18 are welded at right angles to each other and their lower ends are in contact with the bottom plate 4. The gussets 16, 17 and 18 are made of a material having a heat conductivity, for example, a metal, but they are sufficient to dissipate the heat generated in the inner container B to the outside in a normal time, and from the inside to the outside in case of a fire. The size of the cross-sectional area is adjusted so that the amount of heat transfer to the heat sink is below a certain value. Further, the gussets 16 to 18 are designed so as to be deformed but not broken when the transportation container A receives an impact, so that the gussets 16 can fulfill the impact mitigating function. The inner container holder 15 has a cylindrical shape made of a stainless steel plate having a thickness of 3 mm, and an upper container is welded to the outer container C by a lid plate inner container holder flange 15a. In order to reinforce the attachment of the inner container holder body portion 15b, a stainless steel inner container holder flange reinforcing plate 19 having a thickness of 3 mm is welded and attached to both of them. The inner container B is composed of an inner container body 20 made of stainless steel having a thickness of 10 mm and an inner container lid 21 made of stainless steel having a thickness of 23 mm. When the stored item is stored, the O-ring 22 is inserted and tightened by the eight inner container lid mounting bolts 23.

In this embodiment, the inorganic fiber is filled between the outer container outer plate 1 and the inner container holder 15 and inside the outer container lid 2. As this fiber, for example, a ceramic fiber 24 having particularly excellent heat resistance (heat insulating property) is used. It is, for example, a plate-like member obtained by molding polycrystalline alumina short fibers composed of the following components with a binder. SiO2: 49.9 w / o, AlO3: 51.8 w /
o, TiO: <0.1w / o MgO: <0.1w
The main characteristics of the ceramic fiber 24 are as follows. Mechanical properties: Bending strength 7.3 kg / cm2 Thermal properties:
Density 0.35kg / cm3, specific heat 0.25kcal / k
g ° C (100 ° C), thermal conductivity (fiber direction) 0.06k
cal / m · h · ° C (100 ° C), thermal conductivity (perpendicular to the fiber) 0.05 kcal / m · h · ° C (100 ° C),
Maximum operating temperature 1,300 ° C The filling form is thick in the lateral direction and thin in the vertical direction in consideration of energy absorption when the transportation container is dropped and the difference in thermal conductivity depending on the fiber direction. The method for filling this is as follows. An annular ceramic fiber plate 25 a is fitted into the inner container holder 15 to form the body protection layer 25. Next, after the lower gusset 17 is welded to the inside of the outer container body plate 3, the inner container holder bottom portion 15 c is fixed to the lower gusset 17 by the bolt 26. Next, a ceramic fiber plate 27a, which has been formed in advance, is tightly laminated between the bottom plate 4 and the lower gusset 17 to form the lower protective layer 27, and then the bottom plate 4 is welded to the body plate 3.
After that, the upper gusset 16 is welded to the inside of the body plate 3 similarly to the lower gusset 17. After the ceramic fiber plates 28a are tightly stacked on the upper gusset 16 to form the upper protective layer 28, the end plate 5 is put on the upper protective layer 28, and this is welded to the body plate 3. The filling of the ceramic fiber plate 29a into the outer container lid 2 is performed by welding the outer container lid bottom plate 8 and the body plate 9 and then closely stacking the ceramic fiber plates 28 to form an in-lid protective layer 29. Outer container top plate 10
And the body plate 9 is welded. The protective layer 2
5, 27-29 ceramic fiber plates 25a, 27
The direction of the fibers of a, 28a, and 29a is, as described above, the direction in which the heat transmission is blocked, that is, the direction perpendicular to the heat traveling direction.

Next, the operation of this embodiment will be described. When an impact is applied to the transport container A during transportation, the impact is absorbed by the gussets 16, 17, 18 and the ceramic fiber plates 25, 27, 28, 29 of the protective layers 25, 27, 28, 29, and is transferred to the inner container holder. The contained inner container B is not impacted. The inner container B is gusset 16, 17, 1
Since it is fixed to the outer container C by 8, both containers B and C
The positional relationship of is always kept constant. for that reason,
The dose equivalent rate becomes uniform on the surface of the outer container C or at a place spaced a certain distance from it. Therefore, since it is sufficient to shield the radioactivity on the assumption that it is uniform, waste can be eliminated and the transport container can be lightened. Although heat is generated from the nuclear fuel material and the like in the inner container B, this heat is dissipated to the outside through the gussets 16, 17 and 18, so that the inside of the inner container B does not exceed the specified temperature. If the outside of the container gets hot due to a fire,
The transport container A is heated and the heat tends to be transferred to the inside of the container. However, since the protective layers 25, 27, 28, 29 in which the ceramic fiber plates 25a, 27a, 28a, 29a are laminated are formed between the outer container C and the inner container B,
The heat transfer to the inside is prevented. Therefore, even if a fire occurs, the inner container B does not reach an abnormally high temperature. The gusset has a function of deforming and absorbing the impact force when a strong impact is applied from the outside of the transportation container. From a structural point of view, it is desirable to design so that when an expected impact force is applied, it will not break and will deform. As a result, the gusset can play a role of protecting the transport container, particularly the inner container, even when it receives an impact.

[0013]

Since the present invention is constructed as described above, it has the following remarkable effects. (1) Since the inorganic fiber is filled between the outer container that protects the inner container and the inner container holder that houses the inner container, even if the outside temperature becomes abnormally high due to a fire or the like, the heat is transmitted to the inside of the container. Absent. Therefore, it is safe because the inside of the inner container does not become an abnormally high temperature due to the heat of the outside. Further, since this inorganic fiber has a buffering function, the impact is absorbed by the fiber when the impact is applied to the transport container, so that the inner container is not damaged. (2) The inner container is gusseted to the outer container. Since it is fixed, when heat is generated in the inner container, the heat is transmitted to the outside through the gusset. Therefore, it is safe because the inside of the inner container does not exceed the specified temperature. Also, since the positional relationship between the inner container and the outer container is regulated by the gusset,
A predetermined state is always maintained. Therefore, unlike the conventional example, in consideration of the dose equivalent rate, it is not necessary to shield the inner container on the assumption that it is in the most equipped position in each direction, so the weight of the transport container is lighter than that of the conventional example. can do.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 15 Inner container holder 16 Upper gusset 17 Lower gusset 18 Bottom gusset 24 Ceramic fiber A Transport container B Inner container C Outer container

Claims (4)

[Claims] 1. An inorganic fiber is filled between an outer container that protects the inner container and an inner container holder that stores the inner container, and the inner container holder is fixed to the outer container by a gusset. A container for transporting nuclear fuel materials. 2. An inorganic fiber is formed into a plate shape, and
The transport container for nuclear fuel material or the like according to claim 1, wherein the transport containers are closely stacked. 3. A transportation container for a nuclear fuel material or the like, wherein the fiber directions of the closely packed inorganic fibers are in different directions with respect to the heat entering the container. 4. The transport container for nuclear fuel material or the like according to claim 1, 2 or 3, wherein the inorganic fiber is a ceramic fiber.