JP3017316B2 - Fuel storage container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-walled fuel storage system in a sodium-cooled fast breeder reactor, in which spent fuel taken out of the reactor by a refueling machine or the like is stored until it is carried out of the reactor facility. For containers.

[0002]

2. Description of the Related Art When removing spent fuel from the core of a nuclear reactor, the spent fuel is accompanied by high heat generation due to the decay heat generated by fission products. Then, the heat is transferred from the outer surface of the pot to the fuel storage facility outside the furnace, and the pot is loaded into the fuel storage container filled with sodium. FIG. 4 shows a state where the fuel pot 2 containing the spent fuel 1 is placed on the storage rack 4 in the fuel storage container 3. The heat generated by the spent fuel 1 loaded in this manner is converted into sodium, which is a coolant in a cooling pipe 6 provided in the fuel storage container 3 by convection and heat conduction of the sodium 5 charged in the fuel storage container 3. Tell
The coolant is circulated to the cooling system 7 outside the fuel storage container 3 and radiated to the outside air by the air-cooled cooler 8 of the cooling system 7, and the spent fuel 1
Cooling.

[0003] By the way, the conventional fuel storage container 3 comprises an inner container 9 and an outer container 10 from the viewpoint of safety so that sodium 5 does not flow out to the outside when broken.
The cooling of the spent fuel 1 employs a method of transferring heat to the outside as described above, so that there is a large amount of cooling equipment.
In addition, it is not preferable in terms of layout in reducing the size of the fuel handling equipment.

Therefore, cooling from the outer surface of the fuel storage container 3 has been considered in order to rationalize the cooling equipment and reduce the size of the fuel handling equipment. In this case, the inner container 9 and the outer container 10
In order to promote heat transfer, it is effective to make the inner container 9 and the outer container 10 in close contact with each other, but a void is provided between the inner container and the outer container to check the soundness of the container. In addition, it is necessary to detect sodium leaking into the void.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a system for cooling a fuel storage container from the outer surface, which has a gap between the inner container and the outer container for detecting sodium leakage and has a high heat conductivity. It is intended to provide a heavy wall fuel storage container.

[0006]

According to the present invention, there is provided a double-walled fuel storage container comprising an inner container in contact with sodium and an outer container in contact with air. Are filled with a heat transfer promoting material.

As the heat transfer promoting material to be filled in the gap between the inner container and the outer container, metal powder having high heat conductivity and good fluidity is used.

[0008]

According to the double-walled fuel storage container of the present invention configured as described above, the heat generated by the decay heat of the spent fuel in the fuel pot placed on the storage rack in the fuel storage container is:
The sodium filled in the fuel storage container is transmitted to the inner container by convection and heat conduction, is efficiently transmitted from the inner container to the outer container via the heat transfer promoting material, and is radiated from the outer container to air. When the fuel pot containing the spent fuel, which is a heating element, is loaded in the storage rack, a thermal expansion difference occurs between the inner container and the outer container, and the body of the inner container gradually expands downward. The heat transfer promoting material between the inner container and the outer container rises, the gap between the inner container and the outer container is filled, and the heat transfer promoting material adheres to the inner container and the outer container. The obtained fuel can be efficiently cooled. If the fuel pot containing the spent fuel, which is a heating element, is taken out of the double-walled fuel storage container (or before loading), a difference in heat shrinkage occurs between the inner container and the outer container, and the The body of the container returns to the original state, the heat transfer promoting material between the inner container and the outer container descends, the gap between the inner container and the outer container is filled, and the heat transfer promoting material is removed from the inner container and the outer container. Since it is in close contact with the container, high heat transfer efficiency is obtained and high-temperature sodium can be efficiently cooled. Also, since the heat transfer promoting material between the inner container and the outer container is a powder, sodium leaking from the inner container is detected by monitoring ambient gas in the gap between the inner container and the outer container. It is possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the double-walled fuel storage container of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a double-walled fuel storage container 11 outside a furnace. 11
Is suspended in a recess 13 of the reactor building 12 and
An outside air introduction path 14 is opened at the bottom of the bottom 3, and an outside air outlet path 15 leading to a stack (not shown) is provided above the recess 13. The double-walled fuel storage container 11 includes an inner container 16 and an outer container 17, and a gap is provided between the inner container 16 and the outer container 17, and the gap is filled with the heat transfer promoting material 18. Have been. The heat transfer promoting material 18 is preferably a metal powder or the like having a high thermal conductivity and a good fluidity. In this example, Al powder is used. Note that graphite powder may be used instead of Al powder. A storage rack 19 is provided in the double-walled fuel storage container 11, and is filled with sodium 20. Above the sodium 20, an inert gas, in this example, argon gas 21 is filled. 22
Is a shielding lid, and a door valve 24 is provided at the spent fuel entrance / exit 23.

In the double-walled fuel storage container 11 of the embodiment constructed as described above, the spent fuel 25 is transferred from the nuclear reactor in a state where the spent fuel 25 is put in the fuel pot 26 filled with sodium, and the door valve is provided. Spent fuel 25 is suspended from the opened spent fuel entrance 23 of the inside 24 and loaded into the storage rack 19 as shown in FIG.
The heat generated by the heat of decay is transmitted to the inner container 16 by convection and heat conduction of the sodium 20 filled in the double-walled fuel storage container 11, and the heat transfer promoting material 18 is transmitted from the inner container 16.
That is, the heat is efficiently transmitted to the outer container 17 via the Al powder, and is radiated from the outer container 17 to the air. The air that has been radiated and has become high temperature is led out of the outlet path 15 and sent to a stack (not shown), and the low-temperature air is introduced into the recess 13 of the reactor building 12 through the inlet path 14.

When the fuel pot 26 containing the spent fuel 25 as the heating element is loaded in the storage rack 19, a difference in thermal expansion between the inner container 16 and the outer container 17 occurs, and the body of the inner container 16 is heated. 2 gradually expands downward as shown in FIG. 2, and the heat transfer promoting material 1 between the inner container 16 and the outer container 17.
8 rises, the gap between the inner container 16 and the outer container 17 is filled, and the Al powder is removed from the inner container 16 and the outer container 1.
7, high heat transfer efficiency is obtained, and the heat of the spent fuel 25 is efficiently radiated from the outer container 17 to the air, so that the spent fuel can be efficiently cooled.

When the fuel pot 26 containing the spent fuel 25 as a heating element is taken out of the double-walled fuel storage container 11 (or before loading), the inner container 16 and the outer container 17 are connected. A heat shrinkage difference occurs, and as shown in FIG.
6 returns to its original state, the Al powder as the heat transfer promoting material 18 between the inner container 16 and the outer container 17 descends by its own weight, and the gap between the inner container 16 and the outer container 17 is filled. A
Since the powder is in close contact with the inner container 16 and the outer container 17, high heat transfer efficiency is obtained, and the heat of the high-temperature sodium 20 is efficiently radiated from the outer container to the air, so that the sodium can be efficiently cooled, and The cooling efficiency of the spent fuel 25 loaded in the storage rack 19 later can be increased.

Even if a crack enters the inner container 16 or the outer container 17, the particle size of the Al powder is larger than the crack. Does not leak.

By providing a fin on the outer surface of the outer container 17 or a plate for collecting heat radiated to the air side, the cooling efficiency of the spent fuel can be further improved.

[0015]

As described above, in the double-walled fuel storage container according to the present invention, the space between the inner container and the outer container is filled with the heat transfer promoting material, so that it is loaded on the storage rack in the container. When the heat generated by the decay heat of the spent fuel is transmitted to the inner container by convection and heat conduction of sodium, the heat transfer promoting material efficiently transmits the heat to the outer container and radiates heat to the air. Is high. In addition, when the inner container expands due to the temperature rise of sodium due to the heat generation of the spent fuel, and returns to the original state by taking out the spent fuel, the metal powder having a high heat conductivity and a high fluidity as a heat transfer promoting material is obtained. Since the gap between the inner container and the outer container is constantly filled and adhered ascending or descending, spent fuel or sodium can always be efficiently cooled.

[Brief description of the drawings]

FIG. 1 is a conceptual view of a double-walled fuel storage container according to the present invention.

FIG. 2 is an explanatory view of a state of an inner container and a heat transfer enhancing material when spent fuel is cooled in the double-walled fuel storage container of FIG. 1;

FIG. 3 is an explanatory view of a state of an inner container and a heat transfer promoting material after removal of spent fuel in a double-walled fuel storage container of FIG. 2;

FIG. 4 is a conceptual diagram of a conventional fuel storage container.

[Explanation of symbols]

 11 Double-walled fuel storage container 16 Inner container 17 Outer container 18 Heat transfer promoting material

Claims (2)

(57) [Claims] An outer fuel storage container of a sodium-cooled fast breeder reactor includes an inner container in contact with sodium and an outer container in contact with air, and a gap between the inner container and the outer container is filled with a heat transfer promoting material. A fuel storage container characterized in that: 2. A fuel storage container, wherein the heat transfer promoting material is a metal powder having a high thermal conductivity and a good fluidity.