JPH11295484A - Transport vessel of radioactive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transport vessel capable of safely housing radioactive material even in case of fall of a canister. SOLUTION: The transport vessel of radioactive material comprises a canister housing the radioactive material in the inside, and a cylinder housing the canister 16 in the inside. A liquid chamber 7 is formed between the inner peripheral face of the inner cylinder 2 and the outer peripheral face of the canister 16, and in the case where the hanging canister falls, buffing liquid in the liquid chamber absorbs impact. In addition, it is preferable that a liquid chamber 6 is formed between the inner face of an inner cylinder bottom part 2a and the outer face of a canister bottom part 16a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transport container suitable for transporting radioactive materials such as spent fuel assemblies, for example, spent fuel assemblies in nuclear power plants.

[0002]

2. Description of the Related Art Spent fuel is strongly activated by being irradiated with radiation in a nuclear reactor. Therefore, a transport container used for transporting the spent fuel (generally referred to as a cask, hereinafter referred to as such). Has been meticulously designed to clear strict standards. FIG. 3A shows an example of such a cask in the related art.
And an outer cylinder 12, a gamma ray shielding material 13 filled therebetween, and a neutron shielding material 14 that covers the outer cylinder 12 from outside.

[0003] Inside the inner cylinder 11, a canister 16 in which a used fuel assembly is hermetically stored is accommodated and sealed with a lid 17. Such a cask 10 is called a dry cask. FIG. 3B shows the canister 16.
This shows an example of the arrangement of the spent fuel assemblies 15 in the inside. In this conventional example, eleven spent fuel assemblies 15 are housed separately from each other. In addition, assuming a fall accident during transportation of the cask 10, a shock absorber for reducing the impact at the time of the fall is provided in the cask 10,
This is not illustrated.

[0004]

This conventional cask 1
0 is carried into a fuel processing facility (not shown) and delivered to a predetermined place, and the above-mentioned shock absorber is removed. Thereafter, in the fuel processing facility, the lid 17 is removed, and the canister 16 is lifted by a crane (not shown) via a lifting device (not shown). In this case, if the canister 16 falls into the cask 10 due to the accident of the lifting device or the crane described above, the canister 16 itself is not designed as a strength member, so that damage including the stored spent fuel assembly 15 occurs. there is a possibility. Therefore,
It is an object of the present invention to provide a transport container that can safely store radioactive materials even when a canister falls.

[0005]

In order to achieve this object, the present invention according to claim 1 provides a radioactive device having a canister for storing a radioactive substance therein, and a container body accommodating the canister therein. In a substance transporting container, a liquid chamber is formed between an inner peripheral surface of the container main body and an outer peripheral surface of the canister. The invention according to claim 2 is characterized in that a liquid chamber is further formed between an inner bottom surface of the container body and an outer bottom surface of the canister.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The same reference numerals indicate the same or corresponding parts. In FIG. 1 showing a preferred embodiment of a cask (transport container) according to the present invention, a cask indicated by reference numeral 1 is an inner cylinder 2 and an outer cylinder 3 and a gamma ray shielding material filled therebetween. 4 and a neutron shielding member 5 that covers the outer cylinder 3 from the outside in a known manner.

In this embodiment, a notch 2b is formed in the upper surface or the inner surface of the solid disk-shaped solid bottom portion 2a of the inner cylinder (container main body) 2, and the lower end of the outer cylinder 3 is formed therein. Are fitted and welded. On the upper surface of the bottom portion 2a of the inner cylinder, an annular flange portion 2d extending upward is formed at a portion radially inward of the annular portion at which the lower end of the inner cylinder main body 2c extends upward. I have. On the other hand, a notch 2f is formed in the outer peripheral edge of the lower surface of the sturdy annular top 2e of the inner cylinder 2, and the upper end of the outer cylinder 3 is fixed thereto by welding as shown. At least a part of the inner peripheral surface of the top 2e is formed with an annular flange portion 2g extending radially inward from the inner peripheral surface of the inner cylinder main body 2c.

A canister 16 containing a spent fuel assembly (see FIG. 3), which is a radioactive substance, is housed inside the inner cylinder 2 having such a structure, and is sealed with a lid 17.
The lid 17 is firmly attached to the top 2e of the inner cylinder 2 by means such as a bolt. Canister 16 with inner cylinder 2
In the state where the canister 16 is housed inside, the bottom of the canister 16 is placed on the flange 2d of the inner cylinder bottom 2a to form a disc-shaped liquid chamber 6 between the two bottoms and the inner cylinder top 2e. The canister 16 is formed by the flange portion 2g formed on the inner peripheral surface.
And a cylindrical liquid chamber 7 is formed between the outer peripheral surface of the inner cylinder 2 and the inner peripheral surface of the inner cylinder 2.

FIGS. 2A and 2B schematically show the cask 1 shown in FIG. 1. FIG. 2A shows a state immediately before the stored canister 16 is lifted, and FIG. 2B shows a state in which the canister 16 is lifted. In FIG. 2A, the liquid chambers 6 and 7
Is filled with water 8 as a buffer solution. Therefore, when the canister 16 is lifted in the direction of the arrow by a crane or the like (not shown), as shown in FIG.
Water 8 remains at the level H above the flange 2d.

Therefore, even if the lifted canister 16 falls, the water 8 at the level H absorbs the water.
Damage to the canister 16 and the fuel assembly contained therein is minimized.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this, and various modifications can be made, for example, as listed below. 1) In the embodiment, water is used as the buffer solution to be filled in the liquid chambers 6 and 7. However, a liquid other than pure water is used if the desired buffer action is obtained and the transport container has no adverse chemical effect. Can. 2) To form the liquid chamber 6, an annular flange portion 2d is formed on the upper surface or the inner surface of the inner cylinder bottom portion 2a, but the flange portion is not annular but a protrusion of any shape extending in the axial direction. Can be. In addition, the protrusion is also provided on the inner cylinder bottom 2a.
Instead, it may be formed on the lower surface or the outer surface of the bottom 16a of the canister 16, or may be provided on both the inner cylinder bottom and the canister bottom. 3) Also, since the most important thing is to prevent the lifted canister 16 from being damaged when it falls, the buffer liquid has accumulated to a level above the bottom 2a of the inner cylinder 2 in the lifted state. If the volume of the liquid chamber 7 is sufficient to secure such a level, the above-described flange portion 2d or the projection is not necessarily required. 4) Further, in the embodiment, in order to form the liquid chamber 7, a flange 2g is formed on the inner peripheral surface of the inner cylinder top 2e,
Although this is brought into contact with the outer peripheral surface of the canister 16, it is not necessary to provide such a flange portion 2g, and a predetermined diameter difference may be simply provided between the outer diameter of the canister and the inner diameter of the inner cylinder. 5) The liquid chamber 6 has a simple disk shape, but may be divided into a plurality of sections in an arbitrary manner. Further, the liquid chamber 7 is also a simple cylindrical body, but may be similarly divided into a plurality. 6) Although both the canister 16 and the cask 1 have been described as having a cylindrical shape, this is not always necessary, and the cross section may be a rectangular tube shape such as a square.

[0012]

According to the first aspect of the present invention, since the liquid chamber is formed at least between the inner peripheral surface of the container body and the outer peripheral surface of the canister, when the canister is lifted,
The buffer exists to a certain level inside the container body.
Therefore, even if the canister falls, damage to the canister including the radioactive substance inside can be minimized by this buffer solution. According to the second aspect of the present invention, in addition to the liquid chamber, the liquid chamber is formed between the bottom inner surface of the container body and the bottom outer surface of the canister.
Almost the entire surface of the canister, including the bottom surface, is surrounded by the buffer solution.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a radioactive substance transport container according to the present invention.

FIGS. 2A and 2B are diagrams schematically showing the transport container shown in FIG. 1, wherein FIG. 2A is a diagram showing a state immediately before lifting of the canister, and FIG. 2B is a diagram showing a lifting state of the canister.

FIG. 3A is a longitudinal sectional view of a conventional transport container, and FIG.
FIG. 3 is a cross-sectional view showing an arrangement of fuel assemblies in a canister.

[Explanation of symbols]

1. Cask (transport container), 2. Inner cylinder (container body), 2.
a: bottom of inner cylinder (bottom of container body), 6: liquid chamber, 7: liquid chamber, 16: canister, 16a: bottom of canister.

Claims (2)

[Claims] 1. A radioactive substance transport container comprising: a canister accommodating a radioactive substance therein; and a container body accommodating the canister therein, wherein at least an inner peripheral surface of the container main body and an outer peripheral surface of the canister. A transport container for radioactive substances, wherein a liquid chamber is formed between the container and the container. 2. The transport container according to claim 1, wherein a liquid chamber is also formed between an inner bottom surface of the container body and an outer bottom surface of the canister.