JP2000275391A - Spent fuel storage cask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spent fuel storage cask which is improving heat removal efficiency for decay heat generated by spent fuel and is superior in storage efficiency. SOLUTION: For the structure of a dry storage cask, non-organic materials are used for the material of neutron shield 23 and is placed inside a γ shielding body 22 being the cask body, and cooling fins are eliminated from the cask body in the structure. Since high temperature resistivity is improved compared with conventional neutron shield body, the number of storage body of spent fuel can be increased. The structure can be simplified by eliminating the cooling fins, and so inexpensive spent fuel storage cask is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a spent fuel storage cask for storing or storing and transporting spent fuel,
In particular, it relates to metal casks that manage and store spent fuel in a dry state.

[0002]

2. Description of the Related Art Fuel used for a certain period in a core of a nuclear power plant is taken out of the core and temporarily stored in a spent fuel pool or the like. The fuel after the completion of the predetermined cooling period is finally carried out to a reprocessing plant, where it is reprocessed, and uranium and plutonium are taken out as resources and reused.

At present, the amount of spent fuel generated in a nuclear power plant is increasing along with the demand for power generation. Therefore, even if a reprocessing plant operates, the amount of spent fuel generated in Japan exceeds the processing capacity of the reprocessing plant. This means that they need to be properly managed and stored until they are reprocessed. The required storage capacity is 6000 tU in 2010 and 15 in 2020.
000 tU scale.

[0004] As methods for stable storage at or outside the premises of a nuclear power plant, there are dry storage systems such as cask storage, vault storage, silo storage, and concrete cask storage, and wet storage systems for water pools. ,
In consideration of cost and long-term stable storage, dry storage is attracting attention.

[0005] Of the dry storage systems, the cask storage system currently in practical use in Japan has a main body thickness such that the storage cask main body 20 can shield γ-rays generated by spent fuel as shown in FIG. The neutrons generated by the spent fuel are taken into consideration and shielded by a neutron shielding material provided outside the γ-ray shield. A basket 6 made of a neutron absorbing material is arranged in the storage cask.
The spent fuel 7 is arranged in a lattice in this basket, and is designed to prevent the criticality of the spent fuel 7 body in any case. In addition, for the purpose of efficiently removing the decay heat generated by the spent fuel, the cask body 2 is used.
Cooling fins 19 are mounted outside the zero. still,
The storage cask main body lid has a double structure of the primary lid 8 and the secondary lid 5, and has a structure for securely enclosing the radioactivity stored in the storage cask main body. A trunnion 4 is attached to the outside of the storage cask for use in handling such as hanging.

Next, when loading spent fuel into an empty storage cask, the spent fuel is first transported to a cask pit provided in a spent fuel pool for loading spent fuel.
Spent fuel to be stored is stored in a storage cask. The storage cask containing a predetermined number of the spent fuels is moved to a decontamination pit, and after checking the contamination state of the surface of the cask main body, the primary lid 8 is attached and the water inside the storage cask is discharged. After the discharge, the inside of the storage cask is vacuum-dried and filled with an inert gas such as helium gas. After confirming the sealing of the primary lid, the storage cask
It is loaded on a transport vehicle such as a trailer and transported to a storage building. The storage cask carried into the storage building is transferred to the storage area and stored after confirmation of acceptance.

[0007]

SUMMARY OF THE INVENTION In the case of storing spent fuel in a dry storage cask in a spent fuel storage facility, in order to provide a dry storage cask with improved economy, it is necessary to store spent fuel. It is desirable to increase the number of bodies and simplify the structure. At the same time, the weight of the dry storage cask is about 100 tons in a state in which the spent fuel is stored, and the work of unloading from the reactor building requires careful and large-scale work, and at the same time, a large unloading cost is required. Therefore, it is better to increase the number of spent fuels stored in the storage cask in order to reduce the number of times of carrying out.

[0008] However, the dry storage cask is
A polymer compound is used to shield neutron rays generated from spent fuel stored inside. The neutron shielding material is limited to about 150 ° C. as a limit temperature at which the shielding function is ensured in consideration of shape change and weight reduction. Therefore, when trying to store spent fuel having a short cooling period, spent fuel having high burnup, and spent fuel having a large calorific value, such as MOX fuel, it is difficult to increase the number of storage bodies. there were.

The neutron shield is housed inside a fin for transferring decay heat generated from spent fuel to the atmosphere outside the gamma ray shield which also serves as the main structure of the dry storage cask. . For this reason, since the structure is complicated, many man-hours are required at the time of manufacturing a dry storage cask, which causes a cost increase.

[0010] At the same time, the trunnion of the dry storage cask has a structure in which it is directly supported by the main body also serving as a gamma ray shield, so that the neutron shield is discontinuous at the trunnion portion.

[0011]

Therefore, as a structure of a dry storage cask, a neutron shield is made of an inorganic material, and the neutron shield is installed inside a gamma ray shield which also serves as a cask body. A dry storage cask which has a structure in which a main body has no fin and which solves the above-mentioned problem is provided.

Furthermore, in the conventional dry storage cask, the cask cavity is filled with an inert gas such as helium gas, but according to the present invention, the cavity is not inferior in heat conductivity to gas. Since the neutron shield composed of an inorganic material is filled, it is possible to use the fuel at a higher temperature without deteriorating the heat removal performance of the spent fuel due to the heat conduction of the dry storage cask.

[0013]

(First Embodiment) FIG. 1 shows an embodiment of the present invention. FIG. 1 is a vertical sectional view of a spent fuel storage cask according to the present invention. Regarding the shielding of neutron rays among the radiation emitted by the spent fuel, the upper lid has a structure in which the shielding body 22 provided inside is made of a material made of an inorganic substance. On the side, the shield 22 provided inside the gamma shield 23 having structural strength is configured to be made of a material made of an inorganic substance with respect to the shielding of neutron rays among the radiation emitted by the spent fuel. . The bottom also has a structure in which a shield 22 provided inside a gamma shield 23 having structural strength is configured of a material made of an inorganic substance with respect to shielding of neutron rays among radiation emitted by spent fuel. FIG. 2 is a horizontal sectional view of a spent fuel storage cask in a case where the basket 6 for storing spent fuel according to the present invention has a lattice shape. Regarding the shielding of neutrons among the radiation emitted by spent fuel,
The shielding body 22 provided inside the γ shielding body 23 having structural strength is configured to be made of a material made of an inorganic substance.

In the spent fuel storage cask having the above structure, when the basket 6 for storing the spent fuel is formed in a lattice shape, the basket 6 and the shielding member 23 for γ-rays emitted from the spent fuel are used. A neutron shield 2 in the gap between the spent fuel storage cask structure and the body
2, the structure is filled with an inorganic material which is durable even at a high temperature of about 400 ° C. and has a high-temperature neutron absorption effect, thereby effectively shielding radiation emitted from spent fuel. In this case, B, Cd, and H, which are substances having a high neutron absorption effect, are used as materials for the neutron shield.
It is composed of a simple substance or a compound containing f, Ir, Hg and RE (rare earth element). For example, since B ₄ C has been used as a material for a control rod of a BWR core, it is suitable as a material for a neutron shield used in the present invention. The shape of the substance when B ₄ C is used may be either a powder or a sintered body. In addition, for example, B alone or as a compound of B,
BN, FeB, AlB ₂ , BaB ₆ , CeB ₆ , CrB,
CrB ₂ , HfB ₂ , LaB ₆ , MgB ₂ , MnB, Mo
B, NbB ₂ , NiB, SiB ₄ , TaB, TaB ₂ , TiB
_{2, VB 2, WB, ZrB} 2, B 2 O 3, BPO 4, BP, B
₂ S ₃ and H ₃ BO ₃ are applicable.

In the spent fuel storage cask having the above structure, a polymer compound is conventionally used as a neutron shield. However, the limit temperature at which the shielding function is maintained in consideration of a shape change and weight reduction is about 150 ° C. Although only a temperature up to a certain level is allowed, the use of the above-mentioned inorganic material as a neutron shield enables use at a high temperature of about 400 ° C., and significantly improves the high-temperature durability. At the same time, the spent fuel storage cask of the conventional structure has a basket for storing the spent fuel and γ generated from the spent fuel.
He gas is filled in the gap between the body and the spent fuel storage cask structure which also serves as a wire shield, and the decay heat generated by the spent fuel due to the radiation and heat transfer effect of the He gas is used for the spent fuel. Although the spent fuel is removed by being discharged to the outer surface of the storage cask, according to the present invention, for example, B ₄ C is used as a neutron shielding body instead of He filled in the conventional spent fuel cask. Filling the sintered body does not reduce the heat removal effect because the thermal conductivity of B ₄ C is about 100 times higher than that of He. In the spent fuel storage cask of the present invention, γ having structural strength
Since the neutron shield 22 is located inside the shield 23, the neutron shield 22 can be used even in the case of a fall.
Has a structure that is difficult to lose. As another effect, the neutron shielding body can be evenly filled in the trunnion portion. Further, since the conventional spent fuel storage cask has a structure without heat transfer fins, the manufacture of the cask is simplified and an inexpensive storage cask can be provided.

However, the neutron shield of the inorganic material has a higher specific gravity than the conventional neutron shield of the polymer compound, so that the whole storage cask may become heavier. It is more effective to optimize the amount of necessary and sufficient neutron shielding material.

(Second Embodiment) FIG. 3 shows another embodiment of the present invention.
Shown in FIG. 3 is a horizontal sectional view of the spent fuel storage cask when the basket 6 for storing spent fuel according to the present invention has a lattice shape. Γ, which has structural strength, for shielding neutrons from radiation emitted by spent fuel
The shield 22 provided inside the shield 23 has a structure made of a material made of an inorganic substance.

In the spent fuel storage cask having the above structure, when the basket 6 for storing the spent fuel is formed in a lattice shape, the spent fuel which also serves as a shield 23 for the gamma rays emitted from the basket and the spent fuel is used. The entire space between the fuel storage cask structure and the body is filled with an inorganic material that is durable even at a high temperature of about 400 ° C. and has a high temperature neutron absorption effect as a neutron shield 22. It has a structure that effectively blocks radiation emitted from fuel. In this case, B, Cd, and H, which are substances having a high neutron absorption effect, are used as materials for the neutron shield.
It is composed of a simple substance or a compound containing f, Ir, Hg and RE (rare earth element). For example, since B ₄ C has been used as a material for a control rod of a BWR core, it is suitable as a material for a neutron shield used in the present invention. The shape of the substance when B ₄ C is used may be either a powder or a sintered body. In addition, for example, B, BN, FeB, AlB ₂ , BaB ₆ , CeB ₆ , Cr
B, CrB ₂ , HfB ₂ , LaB ₆ , MgB ₂ , MnB, Mo
B, NbB ₂ , NiB, SiB ₄ , TaB, TaB ₂ , T
iB ₂ , VB ₂ , WB, ZrB ₂ , B ₂ O ₃ , BPO ₄ , B
P, B ₂ S ₃ and H ₃ BO ₃ can be applied.

In the spent fuel storage cask having the above structure, a polymer compound is conventionally used as a neutron shield. However, in consideration of shape change and weight reduction, a limit temperature at which the shielding function is maintained is about 150 ° C. Although only a temperature up to a certain level is allowed, the use of the above-mentioned inorganic material as a neutron shield enables use at a high temperature of about 400 ° C., and significantly improves the high-temperature durability. At the same time, the spent fuel storage cask of the conventional structure has a basket for storing the spent fuel and γ generated from the spent fuel.
He gas is filled in the gap between the body and the spent fuel storage cask structure which also serves as a wire shield, and the decay heat generated by the spent fuel due to the radiation and heat transfer effect of the He gas is used for the spent fuel. Although the spent fuel is removed by being discharged to the outer surface of the storage cask, according to the present invention, for example, B ₄ C is used as a neutron shielding body instead of He filled in the conventional spent fuel cask. The thermal conductivity of B ₄ C is reduced to He by filling the sintered body into the entire gap between the basket and the body as a spent fuel storage cask structure that also serves as a shield for γ-rays emitted from spent fuel. About 1
Because it is about 00 times higher, the heat removal effect can be greatly improved.
In the spent fuel storage cask of the present invention, the neutron shield 22 is provided inside the γ shield 23 having structural strength, so that the neutron shield is hardly lost even in the case of a fall. Having. As another effect, the neutron shielding body can be evenly filled in the trunnion portion. Further, since the conventional spent fuel storage cask has a structure without heat transfer fins, the manufacture of the cask is simplified and an inexpensive storage cask can be provided.

However, the neutron shield of the inorganic material has a higher specific gravity than the conventional neutron shield of the polymer compound, so that the whole storage cask may become heavier. It is more effective to optimize the amount of necessary and sufficient neutron shielding material.

(Third Embodiment) FIG. 4 shows another embodiment of the present invention.
Shown in FIG. 4 is a horizontal sectional view of a spent fuel storage cask when the basket 6 for storing spent fuel according to the present invention has a square tube shape. Γ, which has structural strength, for shielding neutrons from radiation emitted by spent fuel
The shield 22 provided inside the shield 23 has a structure made of a material made of an inorganic substance.

In the spent fuel storage cask having the above structure, when the basket 6 for storing the spent fuel is formed in a square tube shape, the basket 6 also serves as a shield 23 for gamma rays emitted from the spent fuel. A neutron shield 2 is provided in the gap between the spent fuel storage cask structure and the body.
2, the structure is filled with an inorganic material which is durable even at a high temperature of about 400 ° C. and has a high-temperature neutron absorption effect, thereby effectively shielding radiation emitted from spent fuel. In this case, B, Cd, and H, which are substances having a high neutron absorption effect, are used as materials for the neutron shield.
It is composed of a simple substance or a compound containing f, Ir, Hg and RE (rare earth element). For example, B ₄ C has been used as a material for control rods in BWR cores, and is therefore suitable as a material for the neutron shield used in the present invention. The shape of the substance when B ₄ C is used may be either a powder or a sintered body. In addition, for example, B alone or as a compound of B,
BN, FeB, AlB ₂ , BaB ₆ , CeB ₆ , CrB,
CrB ₂ , HfB ₂ , LaB ₆ , MgB ₂ , MnB, Mo
B, NbB ₂ , NiB, SiB ₄ , TaB, TaB ₂ , TiB
_{2, VB 2, WB, ZrB} 2, B 2 O 3, BPO 4, BP, B
₂ S ₃ and H ₃ BO ₃ are applicable.

In the spent fuel storage cask having the above structure, a polymer compound is conventionally used as a neutron shield. However, in consideration of shape change and weight reduction, a limit temperature at which the shielding function is maintained is about 150 ° C. Although only a temperature up to a certain level is allowed, the use of the above-mentioned inorganic material as a neutron shield enables use at a high temperature of about 400 ° C., and significantly improves the high-temperature durability. At the same time, the spent fuel storage cask of the conventional structure has a basket for storing the spent fuel and γ generated from the spent fuel.
He gas is filled in the gap between the body and the spent fuel storage cask structure which also serves as a wire shield, and the decay heat generated by the spent fuel due to the radiation and heat transfer effect of the He gas is used for the spent fuel. Although the spent fuel is removed by being discharged to the outer surface of the storage cask, according to the present invention, for example, B ₄ C is used as a neutron shielding body instead of He filled in the conventional spent fuel cask. Filling the sintered body does not reduce the heat removal effect because the thermal conductivity of B ₄ C is about 100 times higher than that of He. In the spent fuel storage cask of the present invention, γ having structural strength
Since the neutron shield 22 is provided inside the shield 23, the neutron shield has a structure that makes it difficult for the neutron shield to be lost even in the case of a fall. As another effect, the neutron shielding body can be evenly filled in the trunnion portion. Further, since the conventional spent fuel storage cask has a structure without heat transfer fins, it is possible to provide an inexpensive storage cask that is easy to manufacture.

However, the neutron shield of the inorganic material has a higher specific gravity than the conventional neutron shield of the polymer compound, so that the weight of the entire storage cask may be heavy. It is more effective to optimize the amount of necessary and sufficient neutron shielding material. Further, when the basket for storing the spent fuel is in the shape of a square tube, the weight of the basket is increased but the strength is increased as compared with the case where the basket is used in the form of a lattice.

(Fourth Embodiment) FIG. 5 shows another embodiment of the present invention.
Shown in FIG. 5 is a horizontal sectional view of a spent fuel storage cask in a case where a basket 6 for storing spent fuel according to the present invention has a square tube shape. Γ, which has structural strength, for shielding neutrons from radiation emitted by spent fuel
The shield 22 provided inside the shield 23 has a structure made of a material made of an inorganic substance.

In the spent fuel storage cask having the above structure, when the basket 6 for storing the spent fuel has a square tube shape, the basket 6 also serves as a shield 23 for γ-rays emitted from the spent fuel. By filling the entire gap with the body as the spent fuel storage cask structure, as a neutron shield 22, is durable even at a high temperature of about 400 ° C., and is filled with an inorganic material having a high-temperature neutron absorption effect, It has a structure that effectively blocks radiation emitted from spent fuel. In this case, B, Cd, and H, which are substances having a high neutron absorption effect, are used as materials for the neutron shield.
f, Ir, Hg and R.I. E. FIG. (Rare earth elements) or other simple compounds or compounds. For example, since B ₄ C has been used as a material for a control rod of a BWR core, it is suitable as a material for a neutron shield used in the present invention. The shape of the substance when B ₄ C is used may be either a powder or a sintered body. In addition, for example, B, BN, FeB, AlB ₂ , BaB ₆ , CeB ₆ , Cr
B, CrB ₂ , HfB ₂ , LaB ₆ , MgB ₂ , MnB, Mo
B, NbB ₂ , NiB, SiB ₄ , TaB, TaB ₂ , T
iB ₂ , VB ₂ , WB, ZrB ₂ , B ₂ O ₃ , BPO ₄ , B
P, B ₂ S ₃ and H ₃ BO ₃ can be applied.

In the spent fuel storage cask having the above structure, a polymer compound is conventionally used as a neutron shield. However, a limit temperature at which the shielding function is maintained at about 150 ° C. in consideration of shape change and weight reduction is maintained. Although only a temperature up to a certain level is allowed, the use of the above-mentioned inorganic material as a neutron shield enables use at a high temperature of about 400 ° C., and significantly improves the high-temperature durability. At the same time, the spent fuel storage cask of the conventional structure has a basket for storing the spent fuel and γ generated from the spent fuel.
He gas is filled in the gap between the body and the spent fuel storage cask structure which also serves as a wire shield, and the decay heat generated by the spent fuel due to the radiation and heat transfer effect of the He gas is used for the spent fuel. Although the spent fuel is removed by being discharged to the outer surface of the storage cask, according to the present invention, for example, B ₄ C is used as a neutron shielding body instead of He filled in the conventional spent fuel cask. By filling the sintered body in the entire gap between the basket and the body as the spent fuel storage cask structure which also serves as a shield 23 for γ-rays emitted from spent fuel, the thermal conductivity of B ₄ C becomes He. Approximately 100 times higher than the above, it is possible to greatly improve the heat removal effect. In the spent fuel storage cask of the present invention, the neutron shield 22 is provided inside the gamma shield 23 having structural strength.
Therefore, the neutron shield has a structure that makes it difficult to lose the neutron shield even in the case of falling. As another effect, the neutron shielding body can be evenly filled in the trunnion portion. Further, since the conventional spent fuel storage cask has a structure without heat transfer fins, the manufacture of the cask is simplified and an inexpensive storage cask can be provided.

However, the neutron shield of the inorganic material has a higher specific gravity than the conventional neutron shield of the polymer compound, so that the weight of the entire storage cask may be heavy. It is more effective to optimize the amount of necessary and sufficient neutron shielding material. Further, when the basket for storing the spent fuel is in the shape of a square tube, the weight of the basket is increased but the strength is increased as compared with the case where the basket is used in the form of a lattice.

(Fifth Embodiment) FIG. 6 shows another embodiment of the present invention.
Shown in FIG. 6 is a horizontal sectional view of a spent fuel storage cask in the case where the basket 6 for storing spent fuel according to the present invention has a square tube shape. Γ, which has structural strength, for shielding neutrons from radiation emitted by spent fuel
The shield 22 provided inside the shield 23 has a structure made of a material made of an inorganic substance.

In the spent fuel storage cask having the above structure, when the basket 6 for storing the spent fuel has a square tube shape, the basket 6 also serves as a shield 23 for γ-rays emitted from the spent fuel. The entire outer peripheral portion of the gap between the spent fuel storage cask structure and the body portion is filled with an inorganic material having high durability at a high temperature of about 400 ° C. and a high temperature neutron absorption effect as a neutron shield 22. As a result, a structure is provided that effectively blocks radiation emitted from spent fuel. In this case, B, which is a substance having a high neutron absorption effect,
Cd, Hf, Ir, Hg and R.C. E. FIG. (Rare earth element) or a compound containing the same. For example, B ₄ C is BW
Since it has been used as a material for a control rod of an R core, it is suitable as a material for a neutron shield used in the present invention. The shape of the substance when B ₄ C is used may be either a powder or a sintered body. In addition, for example, B, BN, FeB, AlB ₂ , BaB ₆ , Ce
B ₆ , CrB, CrB ₂ , HfB ₂ , LaB ₆ , MgB ₂ ,
_{MnB, MoB, NbB 2, NiB} , SiB 4, Ta
B, TaB ₂ , TiB ₂ , VB ₂ , WB, ZrB ₂ , B
₂ O ₃ , BPO ₄ , BP, B ₂ S ₃ , H ₃ BO ₃ can be applied.

In the spent fuel storage cask having the above structure, a polymer compound has been used as a neutron shielding body. However, in consideration of a shape change and weight reduction, a limit temperature at which the shielding function is maintained is about 150 ° C. Although only a temperature up to a certain level is allowed, the use of the above-mentioned inorganic material as a neutron shield enables use at a high temperature of about 400 ° C., and significantly improves the high-temperature durability. At the same time, the spent fuel storage cask of the conventional structure has a basket for storing the spent fuel and γ generated from the spent fuel.
He gas is filled in the gap between the body and the spent fuel storage cask structure which also serves as a wire shield, and the decay heat generated by the spent fuel due to the radiation and heat transfer effect of the He gas is used for the spent fuel. Although the spent fuel is removed by being discharged to the outer surface of the storage cask, according to the present invention, for example, B ₄ C is used as a neutron shielding body instead of He filled in the conventional spent fuel cask. By filling the sintered body in the outer periphery of the gap between the basket and the body as a spent fuel storage cask structure that also serves as a shield for gamma rays emitted from spent fuel, the thermal conductivity of B ₄ C is Although the heat removal effect is about 100 times higher than that of He, the heat removal effect can be greatly improved. However, since there is a gap between the square tubes of the basket, the heat removal effect is reduced by shielding gamma rays emitted from the basket and spent fuel. Use that also serves the body Inferior to when filled with all gap between the body of the fuel storage cask structure. In addition,
The spent fuel storage cask of the present invention has a structure in which the neutron shield 22 is hardly lost even in the case of a fall because the neutron shield 22 is provided inside the γ shield 23 having structural strength. . As another effect, the neutron shielding body can be evenly filled in the trunnion portion. Further, since the conventional spent fuel storage cask has a structure without heat transfer fins, the manufacture of the cask is simplified and an inexpensive storage cask can be provided.

However, the neutron shield of the inorganic material has a higher specific gravity than the conventional neutron shield of the polymer compound, so that the whole storage cask may become heavier. It is more effective to optimize the amount of necessary and sufficient neutron shielding material. Further, when the basket for storing the spent fuel is in the shape of a square tube, the weight of the basket is increased but the strength is increased as compared with the case where the basket is used in the form of a lattice.

(Sixth Embodiment) FIG. 7 shows an example of a method for loading a neutron shielding body according to the present invention. An aluminum alloy or stainless steel container 25 is filled with the inorganic material of the above-mentioned neutron shield, and a spent fuel storage cascade structure which also serves as a basket 6 for storing spent fuel and a shield for gamma rays emitted from spent fuel. It is inserted into the gap between the body and the body. The container is divided into a plurality of parts, and FIG. 7 shows an example in which the container is divided into four equal parts. The container 25 made of aluminum alloy or stainless steel does not need to be divided into equal parts as necessary. Further, a container 25 for filling the neutron shielding material.
Aluminum alloy is lighter than stainless steel,
It has high thermal conductivity and is suitable from the viewpoint of heat removal, but stainless steel is superior from the viewpoint of strength.

FIG. 8 shows an example of a method of fixing the neutron shield. Inside the trunk as a spent fuel storage cask structure that also serves as a shield 23 for γ-rays emitted from spent fuel, the neutron shield 22 has a layered structure with the basket 6 and the fixture 26, and the neutron shield 22 is An inner side surface of a trunk as a spent fuel storage cask structure also serving as a shield 23 for γ-rays emitted from spent fuel and the basket 6 are fixed via fixing brackets 26. The fixing may be either by bolting or welding. At this time, the basket 6 is sandwiched between the fixing bracket 26 and the neutron shielding body 22 installed at the upper part thereof, so that the vertical connection is ensured. The structure of the portion of the neutron shielding body 22 fixed by the fixing bracket 26 is configured to be overlapped by the upper and lower neutron shielding bodies 22, so that the neutron shielding ability can be further enhanced.

[0035]

As described above, according to the present invention, it is possible to provide an inexpensive spent fuel storage cask in which the number of spent fuel storage units can be increased and the structure can be simplified.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a spent fuel storage cask according to a first embodiment of the present invention.

FIG. 2 is a horizontal sectional view of the spent fuel storage cask according to the first embodiment of the present invention.

FIG. 3 is a horizontal sectional view of a spent fuel storage cask according to a second embodiment of the present invention.

FIG. 4 is a horizontal sectional view of a spent fuel storage cask according to a third embodiment of the present invention.

FIG. 5 is a horizontal sectional view of a spent fuel storage cask according to a fourth embodiment of the present invention.

FIG. 6 is a horizontal sectional view of a spent fuel storage cask according to a fifth embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a neutron shielding body loading method according to the present invention.

FIG. 8 is a diagram illustrating an example of a method for fixing a neutron shield in the present invention.

FIG. 9 is a bird's-eye view showing a part of a conventional storage cask cut away.

[Explanation of symbols]

4 trunnion, 6 basket, 7 spent fuel assembly, 8 primary lid, 19 cooling fin, 20 cask body, 22 neutron shield, 23 gamma shield, 24
Body, 25: container, 26: fixing bracket.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Koyama 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Tadakazu Nakayama 3-1-1 Sachimachi, Hitachi-shi, Ibaraki No. 1 Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Jin Shimizu 7-2-1, Omika-cho, Hitachi City, Ibaraki Pref.

Claims (6)

[Claims] 1. A spent fuel cask for storing or transporting and storing spent fuel, comprising a basket for arranging and storing spent fuel in the cask, a gamma ray shielding member also serving as a cask body, and a neutron shielding member. A spent fuel storage cask comprising a neutron shield inside a gamma ray shield also serving as a cask body and outside a basket. 2. The spent fuel cask according to claim 1, wherein the neutron shield is made of an inorganic material, and B, Cd, Hf, Ir, H are substances having a high neutron absorption effect.
g and RE (rare earth element) or a simple substance or a compound. For example, B, BN, FeB, Al as a simple substance and a compound suitable for a material of a neutron shielding body
B ₂ , BaB ₆ , CeB ₆ , CrB, CrB ₂ , HfB ₂ ,
LaB ₆ , MgB ₂ , MnB, MoB, NbB ₂ , Ni
B, SiB ₄ , TaB, TaB ₂ , TiB ₂ , VB ₂ , WB,
A spent fuel storage cask comprising an inorganic material such as ZrB ₂ , B ₂ O ₃ , BPO ₄ , BP, B ₂ S ₃ , and H ₃ BO ₃ . 3. The spent fuel cask according to claim 1, wherein the spent fuel storage cask has a structure in which there is no fin outside the γ-ray shielding body also serving as the cask main body. 4. A spent fuel storage cask according to claim 1, wherein the neutron shield and the basket are fixed. 5. A spent fuel cask for storing or transporting and storing spent fuel, comprising a basket for arranging and storing spent fuel in the cask, a gamma ray shielding member also serving as a cask body, and a neutron shielding member. A spent fuel storage cask comprising a neutron shield made of an inorganic material outside a gamma ray shield also serving as a cask body. 6. A spent fuel storage cask according to claim 5, wherein the cask body has a structure in which there is no fin outside the γ-ray shielding body also serving as a cask main body.