JP2002116292A - Storage cask of spent nuclear fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new storage cask of spent nuclear fuel, capable of effectively reducing the stress added to the cask body made of concrete. SOLUTION: The storage cask of spent nuclear fuel is provided with a cylindrical steel liner 7 along the inner wall of the cask body 1, made of concrete having a cylinder shape with a bottom for containing spent nuclear fuel. The steel liner 7 consists of a plurality of liners 8a, 8b and 8c which are separated in the axial direction. This configuration allows axial thermal expansion generated in the steel liner 7, so that stresses added to the cask body made of concrete are reduced drastically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In general, since such spent nuclear fuel generates a high level of radiation and high decay heat, the spent nuclear fuel is sealed in a canister which is a cylindrical stainless steel container having excellent corrosion resistance and heat resistance. After being stored in a large-sized concrete cylindrical container (height: about 6 m × outer diameter: about 4 m, wall thickness: about 800 mm) called storage cask, stored and cooled at a predetermined place for a certain period of time, it is sequentially re-used. It is sent to a processing plant for reprocessing.

[0003] Conventionally, this storage cask is composed of a concrete cask main body 1 having a cylindrical shape with a bottom as shown in FIG. The cask lid 3 is attached to the upper opening 2 side by a fastening bolt 4 so that the canister C
Is stored while heat and radiation generated from the canister C side are reliably shielded.

[0004] As shown in FIG.
Are formed at the bottom and the top, respectively, and a plurality of exhaust ports 6, 5,... Are formed. After the outside air is introduced from the bottom intake port 6 to cool the canister C therein, By discharging the heated air from the upper exhaust port 7, natural air cooling is performed simultaneously with storage of the canister C.

[0005]

Incidentally, in the conventional storage cask having such a structure, a thick (about 50 mm) steel liner 7 having a cylindrical shape is further integrated along the inner wall thereof. Canister C
The heat and radiation (mainly γ-rays and neutron rays) are more reliably shielded.

However, since the steel liner 7 is constantly exposed to a high temperature due to the heat from the canister C that emits high decay heat, the steel liner 7 expands thermally and exerts a large tensile force on the surrounding cask body 1. A disadvantage such as application of a stress such as a shearing force may be considered.

Therefore, it is conceivable to reduce the thickness of the steel liner 7 to reduce the stress applied to the cask body 1. However, if the thickness is simply reduced, sufficient heat and heat will not be obtained.
This causes inconvenience that a radiation shielding effect cannot be obtained.

Accordingly, the present invention has been devised to effectively solve such a problem, and an object of the present invention is to maintain a superior heat and radiation shielding effect while maintaining a stress applied to a concrete cask body. The present invention provides a new storage cask for spent nuclear fuel that can effectively reduce fuel consumption.

[0009]

According to the present invention, a tubular steel liner is formed along the inner wall of a concrete cask body having a bottomed cylindrical shape. Wherein the steel liner comprises a plurality of divided liners divided in the axial direction.

That is, since the steel liner is constituted by a plurality of divided liners divided in the axial direction, thermal expansion in the axial direction is allowed, so that the stress applied to the concrete cask body 1 is greatly reduced. can do.

More specifically, as set forth in claim 2,
Each of the split liners is supported on the inner wall side of the cask main body by a ring-shaped shear connector provided along the outer peripheral portion, and each split liner is independently formed by forming a gap between the split liners. Since it is supported in the cask body and the thermal expansion can be effectively allowed by the gap between them, the axial tensile stress applied to the cask body can be reduced more effectively.

Further, as described in the third aspect, by providing a shielding member along the gap between each of the divided liners, the gap is surely shielded, and the heat and radiation leak from the gap are effectively prevented. Can be shielded.

Further, as described above, by forming each of the divided liners with a thinner steel plate than in the prior art, it is possible to reduce the radial stress due to thermal expansion and to further reduce the stress inside. By providing the shielding plate with a certain gap, a heat / radiation shielding effect equal to or higher than that of the related art can be exhibited.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a storage cask for spent nuclear fuel according to the present invention.

As shown in the drawing, the storage cask according to the present invention differs from the conventional integrated type in that a cylindrical steel liner 7 provided inside a concrete cask body 1 having a bottomed cylindrical shape is provided. , A plurality (three in this embodiment) of divided liners 8a, 8 divided in the axial direction (up and down)
b, 8c.

That is, each of these divided liners 8a, 8
The b and 8c are provided with a ring-shaped shear connector 9 integrally therearound as shown in FIG. 2, and the portion of the shear connector 9 is a concrete base material inside the cask main body 1 as shown in FIG. The divided liners 8a, 8b, 8c are supported independently so as to be embedded in the space, and are independently supported with fixed gaps S, S therebetween.

As a result, each of the divided liners 8a, 8b, 8 is dissipated by decay heat from the canister C accommodated therein.
Even when c is heated to a high temperature and expands in the axial direction (up and down), the gaps S and S effectively allow this thermal expansion, so that the axial stress applied to the canister body 1 is reduced. It can be greatly reduced or reduced to almost nothing. In addition, since the lower edge of the divided liner 8c located at the lowermost portion is placed on the bottom liner 8d, the support by the shear connector 9 may be omitted.

As shown in FIGS. 2 and 3, each of the divided liners 8a, 8b and 8c has a plate thickness much smaller than that of the prior art, for example, about 1/2 (about 25 mm). I have. Therefore, the amount of radial thermal expansion generated not only in the axial direction but also in each of the divided liners 8a, 8b, 8c is reduced, and the radial stress applied to the canister body 1 is greatly reduced. Further, as shown in the drawing, a shielding plate 10 made of stainless steel or the like is provided at a fixed distance inside the divided liners 8a, 8b, 8c via the support member 12 and the guide rail 11. It can exhibit excellent heat and radiation shielding effect.

That is, the divided liners 8a, 8b, 8
By making c thinner, the amount of thermal expansion in the radial direction can be reduced, but simply making it thinner greatly reduces its heat and radiation shielding effect. for that reason,
According to the present invention, the original heat and radiation shielding effect is exerted by providing a shielding plate 10 corresponding to another liner at a predetermined distance inside the divided liners 8a, 8b, 8c. Things. Even if the shielding plate 10 is further provided in this manner, the size of the cask main body 1, that is, the inner diameter is almost the same as that of the conventional one because the plate thickness of each of the divided liners 8 a, 8 b, and 8 c is correspondingly thin. Therefore, there is no possibility that the heat and radiation shielding effect of the cask body 1 itself is adversely affected. In addition, this shielding plate 1
Although 0 may have a flush surface, if a plurality of folds 12 are formed as shown in the figure, expansion and contraction in the radial direction becomes free, and the radial direction applied to the divided liners 8a, 8b and 8c is increased. Thermal expansion can be reduced more effectively.

Further, as shown in FIGS. 1 and 2, gaps S, S between these divided liners 8a, 8b, 8c are
Since the ring-shaped shielding members 13, 13 are provided so as to be embedded in the concrete base material inside the cask main body 1, the shielding effects of the gaps S, S can be sufficiently exhibited.

In this embodiment, the steel liner 7 has been described as an example in which the steel liner 7 is composed of three divided liners 8a, 8b, 8c. However, the present invention is not limited to these.
It is a matter of course that the same operation and effect can be obtained even if the number is divided into three or more or less.

[0023]

In summary, according to the present invention, since the steel liner formed inside the cask main body is formed by a plurality of divided liners divided in the axial direction, the stress applied to the concrete cask main body is reduced. It is possible to greatly reduce the amount, and to provide an excellent effect such as providing a new storage cask with higher reliability.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing an embodiment of a spent fuel storage cask according to the present invention.

FIG. 2 is a perspective view showing a split liner according to the present invention.

FIG. 3 is a partial plan view showing a split liner according to the present invention.

FIG. 4 is a partially cutaway perspective view showing an example of a conventional storage cask.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cask main body 7 Steel liner 8a, 8b, 8c Split liner 9 Shear connector 10 Shielding plate 13 Shielding member C Canister S Clearance

Claims (4)

[Claims] 1. A spent nuclear fuel storage cask having a cylindrical steel liner along the inner wall of a concrete cask body having a bottomed cylindrical shape, wherein the steel liner is divided in the axial direction. A storage cask for spent nuclear fuel, comprising a plurality of split liners. 2. Each of the divided liners is supported on the inner wall side of the cask main body by a ring-shaped shear connector provided along an outer peripheral portion thereof, and allows thermal expansion between the divided liners. The storage cask for spent nuclear fuel according to claim 1, wherein a gap is formed. 3. The storage cask for spent nuclear fuel according to claim 2, wherein a shielding member is provided along each gap between the divided liners. 4. The used waste according to claim 1, wherein each of the divided liners is formed of a thin steel plate, and a shielding plate is provided inside the divided liner with a predetermined gap therebetween. Storage cask for nuclear fuel.