JP2002328194A - Storage cask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the shielding thickness of a concrete lid body to effectively function by preventing radiation emitted from spent fuel, from passing through to an upper part from a clearance between the concrete lid body and an upper end opening part of a concrete cask body. SOLUTION: The concrete cask body 19 is provided with an annular step part 24 enlarged in diameter from a vertically middle position in the upper end opening part 4, with the upper part turned outward. The concrete lid body 20 is provided with an annular step part 27 fitted coinciding with the annular step part 24, integrally at the lower face of an upper face plate 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage cask used for storing spent fuel generated in a nuclear power plant or the like.

[0002]

2. Description of the Related Art In recent years, dry storage (air-cooled storage) of a spent fuel generated in a nuclear power plant or the like using a storage cask until the decay heat is removed has been studied.

[0003] As a transport cask used for transporting spent fuel, a transport cask generally made of a metal material is used, but a storage cask for long-term storage is used.
Considering its economy, it is considered to use a reinforced concrete structure.

As shown in FIG. 2, the storage cask includes a concrete cask main body 1 of a reinforced concrete structure having a storage space 3 into which a canister 2 containing used fuel is inserted from above, and a concrete cask main body. 1 and a concrete lid 5 that can be fitted into the upper end opening 4.

[0005] The concrete cask main body 1 is provided with a liner 6 made of carbon steel or stainless steel extending from the upper end opening 4 to the bottom so as to form a storage space 3 therein. It is formed by reinforced concrete 7 in which a large number of reinforcing bars (not shown) extending in the annular and vertical directions are arranged. The liner 6
The canister 2 is surrounded so that a gap is formed between the canister 2 and the outer peripheral surface of the canister 2.

As shown in FIG. 3, an annular shielding ring 8 made of carbon steel or stainless steel is integrally fixed to the upper end of the liner 6 at the position of the upper end opening 4 of the concrete cask main body 1 by welding. I have.

The concrete lid 5 is formed integrally with an upper surface plate 9 mounted on the upper surface of the shielding ring 8 and a lower surface of the upper surface plate 9 so as to be fitted inside the shielding ring 8. And a plug section 10. Plug part 10
Is composed of a metal plate 11 forming an outer shape and a reinforced concrete 12 in which a reinforcing bar is arranged inside the metal plate 11 and filled with concrete. Then, the outer peripheral flange portion of the upper surface plate 9 of the concrete lid 5 is
To the shielding ring 8. In FIG. 2, 1
4 is a bolt hole.

The concrete cask main body 1 shown in FIG. 2 has a bottom space 15 opening toward the bottom surface of the canister inserted into the storage space 3 and a concrete cask main body 1.
And a plurality of exhaust passages 17 penetrating from near the upper part of the storage space 3 to the upper part of the outer peripheral surface of the concrete cask body 1 from the lower periphery of the lower part of the bottom space 15. . The exhaust passage 17 is provided so that the radiation is transmitted from inside the concrete cask main body 1 to the exhaust passage 17.
The channel has a bent structure in order to prevent the water from being discharged outward linearly through the channel.

On the inner bottom surface of the concrete cask main body 1, a plurality of mounting tables 18 are provided radially around the bottom space 15 so as to be in contact with the bottom surface of the canister 2, and are inserted into the storage space 3. A gap is formed between the bottom surface of the canister 2 and the inner bottom surface of the concrete cask main body 1.

When the spent fuel is stored in the storage cask shown in FIG. 2, the spent fuel is sealed in the storage space 3 of the concrete cask main body 1 fixed in the storage facility so as not to contact the outside air. The canister 2 is inserted, the plug 10 of the concrete lid 5 is fitted into the shielding ring 8, and the outer peripheral flange of the upper plate 9 is fastened to the shielding ring 8 by bolts 13 shown in FIG.

According to the storage cask, the canister 2
Radiation such as γ-rays and neutrons emitted from spent fuel in the interior is shielded by the concrete cask body 1 and the concrete lid 5.

When the air in the storage space 3 is heated by the decay heat of the spent fuel sealed in the canister 2, the air flowing out of the storage space 3 to the outside of the concrete cask body 1 through the exhaust passage 17 is discharged. Flow A, the intake passage 16 from the outside of the concrete cask main body 1, the bottom space 1
5 flows into the storage space 3 through the storage space 3, and the air continuously flowing through the storage space 3 causes the canister 2.
The spent fuel inside is cooled.

[0013]

However, the conventional storage cask is provided with a shielding ring 8 provided at the upper end opening 4 of the concrete cask body 1 and a concrete lid 5 fitted inside the shielding ring 8. Inevitably, a gap S is generated between the plug portion 10 and the radiation, such as γ-rays and neutron rays, which go straight to the gap S, cannot be sufficiently shielded, and radiation passing (streaming) occurs. There has been a problem that the radiation dose on the upper part of the storage tank cask becomes high and the shielding thickness of the concrete lid 5 does not function effectively.

The present invention has been made in view of the above-mentioned circumstances, and prevents radiation emitted from spent fuel from passing through a gap between an upper end opening of a concrete cask main body and a concrete lid to an upper part to prevent the radiation. It is an object of the present invention to provide a storage cask in which the shielding thickness of the body can be effectively used.

[0015]

SUMMARY OF THE INVENTION The present invention provides a concrete cask main body having a storage space into which a canister filled with spent fuel can be inserted from an upper end opening, and an upper end fitted into the upper end opening of the concrete cask main body. A concrete lid closing the opening, and an intake passage communicating from a lower part of the outer peripheral surface of the concrete cask body to a lower part of the storage space, and an exhaust passage communicating from an upper part of the storage space to an upper part of the outer peripheral surface of the concrete cask body. Wherein the concrete cask body comprises:
The concrete lid body includes an annular stepped portion whose diameter is increased outward from the upper and lower intermediate positions in the upper end opening portion.
The storage cask according to claim 1, wherein an annular step portion that fits into and fits with the annular step portion is integrally provided on the lower surface of the upper surface plate.

In the above means, the top plate of the concrete lid may be bolted to a fixing member provided at the upper end of the concrete cask main body.

In the storage cask of the present invention, since the concrete cask main body and the concrete lid are fitted to each other via the annular step at the upper end opening, radiation from the spent fuel is prevented from being emitted from the concrete cask main body. The radiation cannot pass through the annular step even if it goes straight to the gap between the concrete lid and the concrete lid, and the shielding thickness of the concrete lid effectively functions to enhance the radiation shielding effect. Can be.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of a storage cask according to the present invention. In the figure, the portions denoted by the same reference numerals as those in FIGS. 2 and 3 represent the same items, and detailed description thereof will be omitted. Only the features of the invention will be described.

The storage cask whose main part is shown in FIG. 1 is composed of a concrete cask main body 19 having a reinforced concrete structure into which a canister 2 (see FIG. 2) filled with spent fuel can be inserted from above, and the concrete cask And a concrete lid 20 having a reinforced concrete structure that can be fitted into the upper end opening 4 of the cask main body 19.

The concrete cask main body 19 has an enlarged diameter portion 21 formed by increasing the diameter of the upper part of the upper end opening 4 formed of the reinforced concrete 7 from the upper and lower middle positions toward the outside. 23 that annularly connects between the upper end opening 4 and the lower inner surface 22 of the upper end opening 4
To form the annular step portion 24. The step portion 23 of the annular step portion 24 may be a horizontal surface, or may be a surface having a downward slope from the outside to the inside as shown in FIG.

The upper end of the liner 6 provided on the inner surface of the concrete cask main body 19 is
The fixing member 25 provided at the upper end of the concrete cask main body 19 is fixed to the outer periphery of the upper end of the liner 6 by welding.

The concrete lid 20 has an upper surface plate 26 having a flange portion whose outer edge extends to the upper part of the fixing member 25, and a metal plate 11 provided on the lower surface of the upper surface plate 26.
And a plug portion 10 made of reinforced concrete 12,
An annular step 27 is formed on the peripheral portion of the plug 10 so as to fit with the annular step 24.

The outer peripheral flange portion of the upper surface plate 26 of the concrete lid 20 is fixed to a fixing member 25 provided at the upper end of the concrete cask main body 19 with bolts 28.

When the spent fuel is stored in the storage cask shown in FIG. 1, the concrete cask main body 19 fixed in the storage facility is opened from the open upper end opening 4.
The canister 2 (FIG. 2) in which the spent fuel is sealed so as not to contact the outside air is inserted into the storage space 3, and the annular step 27 of the concrete lid 20 is formed in the annular shape of the upper end opening 4 of the concrete cask body 19. The flange of the upper surface plate 26 is placed on the upper end of the concrete cask main body 19 by fitting so as to match the step portion 24, and the flange portion of the upper surface plate 26 is fixed to the upper end of the concrete cask main body 19 by bolts 25. To conclude.

By storing the storage cask in this state, radiation emitted from the spent fuel in the canister is shielded by the concrete cask main body 19 and the concrete lid 20.

At this time, since the concrete cask main body 19 and the concrete lid 20 have the annular steps 24 and 27 and are fitted to each other, the concrete cask main body 19 and the concrete lid 20 are discharged from the spent fuel contained in the canister. As shown in FIG. 1, even if the radiation goes straight to the gap S between the concrete cask main body 19 and the concrete lid 20, the radiation cannot pass through the gap, and accordingly, the shielding thickness of the concrete lid 20. Can function effectively to enhance the shielding effect.

It should be noted that the storage cask of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

[0029]

As described above, according to the storage cask of the present invention, the concrete cask main body and the concrete lid are structured so as to fit each other through the annular step at the upper end opening. Even if the radiation from the spent fuel is directed linearly to the gap between the concrete cask body and the concrete lid, the radiation cannot pass through the annular step, thus reducing the shielding thickness of the concrete lid. An excellent effect of effectively functioning to enhance the radiation shielding effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an example of an embodiment of a storage cask of the present invention.

FIG. 2 is a partially cutaway perspective view showing an example of a storage cask proposed in recent years.

FIG. 3 is a partial sectional view of the storage cask of FIG. 2;

[Explanation of symbols]

 2 Canister 3 Storage Space 4 Top Opening 16 Intake Channel 17 Exhaust Channel 19 Concrete Cask Body 20 Concrete Lid 24 Annular Step 25 Fixing Member 26 Top Plate 27 Annular Step 28 Bolt

Claims (2)

[Claims] 1. A concrete cask main body having a storage space into which a canister filled with spent fuel can be inserted from an upper end opening, and a concrete lid body that fits into the upper end opening of the concrete cask main body and closes the upper end opening. A storage cask having an intake passage communicating from a lower part of the outer peripheral surface of the concrete cask body to a lower part of the storage space, and an exhaust passage communicating from an upper part of the storage space to an upper part of the outer peripheral surface of the concrete cask main body. The concrete cask main body includes an annular step portion whose diameter is increased outward from an upper part of the upper end opening at an upper and lower intermediate position, and the concrete lid is fitted on the lower surface of an upper surface plate in conformity with the annular step part. A storage cask comprising an integrated annular step portion. 2. The storage cask according to claim 1, wherein the upper surface plate of the concrete lid is bolted to a fixing member provided at an upper end of the concrete cask main body.