JPH11218596A - Storage for spent nuclear fuel - Google Patents

Abstract

(57) [Summary] [Problem] To simplify the structure of a storage, reduce the amount of radiation shielding material used for construction, reduce the construction cost, shorten the construction period, and reduce the storage amount per site area. Provide a storage for spent nuclear fuel that can be increased. A chamber (4) constructed of a radiation shielding material and configured to allow air to flow therethrough and to be discharged from an air outlet (15), and a storage pipe (5) inside the chamber (4). 5. The intake duct 10, and the exhaust duct 14 are transportable parts, and these parts are assembled to form a storage module. A plurality of the storage modules are vertically stacked underground to form a storage group, and the radiation is shielded by covering the storage group with soil 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage for spent nuclear fuel for storing spent nuclear fuel generated from a nuclear power plant or the like and radioactive waste generated in a reprocessing step thereof.

[0002]

2. Description of the Related Art Spent nuclear fuel discharged from nuclear power plants located in various locations in Japan is stored in storage facilities adjacent to power generation facilities. At present, nuclear power plants in Japan
Spent nuclear fuel assemblies removed from the reactor are stored underwater in storage pools within the power plant. This method has a large calorific value at the stage of being taken out even if it is a spent nuclear fuel, and has a high radiation level.
It was conceived as a storage measure until the radiation level attenuated for easy handling. However, in this pool storage method, a great deal of cost is required for circulating the cooling water in the pool. For the purpose of cost reduction, as a storage for radioactive materials (for example, solidified radioactive waste and spent nuclear fuel assemblies), for example, Japanese Patent Laid-Open No.
Dry storage, such as that disclosed in US Pat. No. 175,294, has been developed.

FIG. 4 shows an outline of the structure of this storage. The storage is composed of a chamber 41, a handling facility 47, an intake duct 45 for cooling air, and an exhaust duct 44. The handling equipment 47 in the radiation control area is constructed of a heavy radiation shielding material such as concrete for radiation shielding. Further, the chamber 41 and the foundation are also heavy structures to support this. The spent nuclear fuel is stored in a storage container, and stored in a storage pipe 42 regularly installed on the floor in the chamber 41. Cooling of the inside of the chamber 41 is performed by natural ventilation, in which cooling air (atmosphere) is introduced into the chamber from the air introduction port 51 and is ventilated, and is discharged from the air discharge port 46. This conventional dry storage integrates the chamber and the handling equipment. Handling equipment is equipped with cranes and loading equipment, so a large space is required. In order to support it, the walls and floors supporting the base of the storage and the handling equipment are made thick using radiation shielding materials. Therefore, the entire building is large for the storage capacity of the storage. Further, it is common that storage pipes are installed in a plane at predetermined intervals on the floor surface in the chamber.

[0004]

As described above, in the prior art, the chamber of the storage and the handling equipment are integrated with each other and are constructed of a radiation shielding material. Therefore, the exhaust duct must be provided high, and the walls, floors, building ceilings, and the like that support the handling equipment must be thick, so that a large amount of radiation shielding material such as reinforced concrete must be used. For that purpose, a long construction period is required, and the construction cost is high. Further, since the storage pipe is installed on the floor in the chamber in a planar manner, the storage amount per site area is small. The present invention has been made to solve the above problems,
Spent nuclear fuel that can simplify the structure of storage, reduce the amount of radiation shielding materials used in construction, reduce construction costs, shorten the construction period, and increase the storage capacity per site area The purpose is to provide storage.

[0005]

In order to solve the above-mentioned problems, a storage for spent nuclear fuel according to the present invention is constructed of a radiation shielding material, and is configured such that air flows through the inside and is discharged from an air outlet. Chamber and a storage pipe inside the chamber, a chamber, a storage pipe, an intake duct,
In addition, in a spent nuclear fuel storage in which the exhaust duct is made to be a transportable part and these parts are assembled to form a storage module, a plurality of storage modules are vertically stacked underground to form a storage group. , And the radiation is shielded by covering the periphery of the storage group with soil.

Further, the present invention preferably has a structure in which a plurality of storages are arranged in rows and columns according to the shape of the site.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a storage for spent nuclear fuel according to the present invention will be described below with reference to the drawings. FIG.
1 is a longitudinal sectional view showing the entire structure of one embodiment of a spent nuclear fuel storage according to the present invention, FIG. 2 is an enlarged cross-sectional view of the spent nuclear fuel storage according to the present embodiment, and FIG. It is a fragmentary sectional view which illustrates the assembled state of the storage for spent nuclear fuel. The spent nuclear fuel storage 1 according to the present embodiment is made of, for example, a radiation shielding material such as reinforced concrete. The storage is constructed by placing a plurality of storage modules vertically in the soil 3 under the base plate 2 which is capable of shielding radiation by hitting concrete or laying steel plates on the ground after the foundation work on the surface is completed. In the embodiment, five (5) are stacked and installed to form a storage group. Each storage module comprises a chamber 4a, a storage pipe 5, an intake duct, an exhaust duct, and a ventilation pipe connecting these ducts and the chamber. Specifically, the chamber 4a of each storage module is provided with a chamber inlet 4b for taking in cooling air and a chamber outlet 4c for exhausting the air after ventilating the inside of the chamber 4a. That is, an independent cooling air passage is provided for each storage module. The atmosphere is used for the cooling air, and the storage of the present embodiment guides the atmosphere from the air inlet 11 on the ground to the intake duct 10. This intake duct 11 and the chamber entrance 4 of each storage module
b is in communication with a vent pipe (entrance side) 13. Further, for each storage module, cooling air that has passed through the chamber 4a passes through the communication pipe (outlet side) 16 from the chamber outlet 4c, passes through the exhaust duct 14, and passes through the air outlet 1
5 to the ground. The spent nuclear fuel is filled in a nuclear fuel storage container (canister or cask 9) and stored in the storage pipe 5. In each storage module, no partition is provided between the modules in the module storage tube 5, and the canisters or casks 9 can be stacked in multiple stages.

The base plate 2 has an opening 7 for storing a canister or cask 9 in the storage tube 5. The storage tube 5 is provided below the opening 7 of the base plate 2, and the lower end thereof reaches the bedrock 8. Further, the upper end of the storage tube 5 is formed so that the shielding plug 6 having a thickness corresponding to the thickness of the base plate 2 can be fitted therein. It is shielded from radiation.

[0009] Intake duct 1 connecting storage modules
0 has an air inlet 11 that penetrates through the base plate 2 and opens on the ground. The intake duct 10 extends in the soil 3 near the chambers 4 of the storage group toward the bedrock 8 along the chambers 4 of the storage group, and introduces outside air from the air inlet 11 into the chambers 4a of the storage modules. It is designed to be sent.

Exhaust duct 1 connected to storage module
4 has an air discharge port 15 that penetrates through the base plate 2 and opens on the ground. The exhaust duct 14 approaches the chamber 4 of the storage group in the soil 3 and
From the ground to the ground.
The cooling air whose temperature has risen inside is discharged into the atmosphere.

In the storage for spent nuclear fuel according to the present embodiment, cooling air is individually circulated from the intake duct 10 into the chamber 4a of each storage module. By doing so, the inside of the chamber can be kept at a predetermined temperature or lower even in a vertically long chamber. Here, the predetermined temperature refers to a heat-resistant limit temperature of 65 ° C. of the concrete forming the chamber. In order to keep the temperature below this temperature, in the spent nuclear fuel storage of this embodiment, the diameter of the storage pipe 5, the chamber 4 a and the storage pipe 5
, The size of the diameter of the ventilation pipes 13 and 16, the dimensions of the members constituting the chamber 4a and the storage pipe 5, and the like. In this case, in order to keep the temperature of the cooling air at a predetermined temperature or less, the air flow path, the diameter of the ventilation pipes 13 and 16 or the length of the chamber 4a may be changed for each member. Good.

[0012] In the storage for spent nuclear fuel of the present embodiment,
The cooling air flows as shown by the arrow in FIG.
The temperature rises due to the decay heat generated by the spent nuclear fuel in the canister or cask 9 stored in the canister 9, and is discharged to the atmosphere through the exhaust duct 14. At this time, the cooling air can be circulated almost simultaneously to the chamber 4a of each storage module, so that an excessive rise in temperature of the storage tube in the chamber 4a can be prevented. Also,
If the sizes and lengths of the chambers and storage tubes of each storage module are previously selected so that the cooling air flowing in each air flow channel has a predetermined temperature, even if a plurality of canisters or casks are stacked, The temperature in the air flow path can be maintained below a predetermined temperature.

The chamber 4 of the spent nuclear fuel storage 1 according to the present embodiment does not need to be constructed with a heavy radiation shielding member, but may be made of a metal material. However, in the vicinity of the ground, it is preferable that the base plate be partially thickened with concrete or the like in consideration of the fact that the base plate has an opening. Further, the intake duct 10 and the exhaust duct 14 are preferably configured such that an appropriate duct diameter is selected for each storage module so that the amount of air passing through each flow path becomes equal. In addition, the number of stacked storage modules can be selected from one to several tens. Specifically, it is determined by the specifications of the spent nuclear fuel and the storage plan of the spent nuclear fuel. In addition, the length of the storage tube of each storage module can be determined regardless of the size of the cask or canister to be stored. It just needs to be able to be. In order to make the flow of the cooling air smooth, auxiliary air blowing means such as a blowing fan may be provided at the inlet of the intake duct 10 and the outlet of the exhaust duct 14 so as to suppress the temperature of the cooling air.

In addition, a base plate 2 is laid on the storage group over an area capable of sufficiently covering an area where the radiation of the spent nuclear fuel inside the storage tube reaches the ground.

Further, a spent nuclear fuel facility having a spent nuclear fuel storage 1 buried under the base plate 2 includes:
Handling facilities are provided. Handling equipment is equipped with cranes or loading machines. With this crane or loading machine, the cask or canister can be stored inside the storage pipe 5 through the storage pipe opening (not shown). FIG.
The canisters or casks 9 in the spent nuclear fuel storage 1 are stored one by one in the storage tube 5 by this handling equipment or the like, and a total of five stages are vertically stacked.

In the spent nuclear fuel storage 1 of this embodiment, the radiation that travels horizontally or downward in the soil 3 gradually attenuates and disappears as it travels through the soil 3. Also,
The radiation going to the ground is shielded by the base plate 2 and is attenuated and disappears. At this time, it is considered that the distance until the radiation disappears while traveling along the soil 3 is about several meters (for example, 2 m).

The storage module of the present embodiment is
The intake duct 10, the ventilation pipes 13, 16, the chamber 4a, the exhaust duct 14, and the like are transportable parts, and they are assembled or integrally formed, and the modules are sequentially stacked from the rock 8 as shown in FIG. If the module is installed, the standardization, productivity and transportability of the module are improved. It is also preferable because the construction work can be simplified.

Therefore, according to the spent nuclear fuel storage of the present embodiment, the following can be performed. (1) The temperature inside the chamber can be maintained at a predetermined temperature or less without providing the exhaust duct high above the ground. (2) Since the number of storage canisters or casks can be increased, the storage density per unit site area can be increased. (3) Radiation can be shielded by the base plate, shielding plug, and soil. (4) The chamber does not need to be constructed heavy, and the construction cost of the entire storage can be significantly reduced. (5) The construction period can be shortened by using components or modules.

The storage for spent nuclear fuel according to the present embodiment may have a configuration in which storages are arranged in a plurality of rows and columns in accordance with the shape of the site.

[0020]

According to the storage for spent nuclear fuel of the present invention, it is not necessary to use a thick shielding material and the structure of the storage can be simplified, so that the construction cost can be greatly reduced. Also,
The construction period can be shortened because it is modularized. Further, the storage density per unit area can be greatly increased. Therefore, according to the present invention, it is possible to reduce the building space on the ground as compared with the conventional storage for spent nuclear fuel, and to remarkably reduce the time, physical, and economical burden when building the storage. be able to.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the entire structure of one embodiment of a spent nuclear fuel storage according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the spent nuclear fuel storage according to the embodiment.

FIG. 3 is a partial cross-sectional view illustrating the assembled state of the spent nuclear fuel storage according to the embodiment;

FIG. 4 is a cross-sectional view showing one of the conventional examples of a spent nuclear fuel storage.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Storage for spent nuclear fuel 2 Base plate 3 Soil 4, 4a Chamber 4b Chamber inlet 4c Chamber outlet 5 Storage pipe 6 Shield plug 7 Opening 8 Rock bed 9 Canister and / or cask 10 Intake duct 11 Air inlet 13 Ventilation pipe (inlet) 14) Exhaust duct 15 Air outlet 16 Vent pipe (outlet side) 41 Chamber 42 Storage pipe 44 Exhaust duct 45 Intake duct 46 Air exhaust outlet 47 Handling equipment 48 Crane 49 Loading machine 50 Shielding plug 51 Air inlet

Claims (2)

[Claims] 1. A chamber constructed of a radiation shielding material and configured to allow air to flow therethrough and to be discharged from an air outlet, and a storage pipe inside the chamber, and further include a chamber, a storage pipe, and an intake duct. In the storage for spent nuclear fuel in which the exhaust duct is made to be a transportable part and the parts are assembled to constitute a storage module, a plurality of storage modules are vertically stacked underground to form a storage group. None, A storage for spent nuclear fuel, wherein radiation is shielded by covering the periphery of the storage group with soil. 2. The storage for spent nuclear fuel according to claim 1, wherein said storages are arranged in a plurality of rows and columns according to the shape of the site.