JPH0342398Y2 - - Google Patents

Description

[Detailed explanation of the invention] Conventional transport containers (casks) that transport radioactive and heat-generating materials such as spent nuclear fuel are
As shown in Figure 1, a large number of fins 2 for heat dissipation are installed on the outer surface of the container body 1, and a neutron shielding layer 3 (range) is attached to the base of the fins to cover them. When storing nuclear fuel, in order to prevent the scattering of radioactivity, a transport container is submerged in water in a spent nuclear fuel storage pool, and the spent nuclear fuel is stored underwater in the transport container and sealed.

Therefore, when the transport container containing and sealed spent nuclear fuel is taken out from the pool, the outer surface of the transport container, which is covered with the neutron shielding layer 3 and in which a large number of fins 2 are implanted, is contaminated with a small amount of radioactive material. It is extremely difficult to clean and decontaminate the complex-shaped outer surface as described above because of pool water adhering to it.

The present invention relates to a device that solves the above-mentioned difficulties in conventional transport containers for radioactive materials. It is characterized in that it has a truncated conical inner surface that fits together, has fins implanted on the outer surface, and is covered with a neutron shielding layer, and that the outer tube is detachably attached to the container body. However, its purpose is to
The fins and neutron shielding layer provided on the outer surface of the transport container can be separated from the container body,
An object of the present invention is to provide a radioactive material transport container that can be decontaminated by removing contaminated water very easily.

The present invention has the above-mentioned configuration, and includes a container body for enclosing a pyrogenic radioactive substance having a conical outer surface, a frusto-conical inner surface closely fitted to the conical outer surface, and an outer surface. The container has a structure in which fins are embedded in the container and an outer cylinder covered with a neutron shielding layer is detachably attached, so that only the main body of the container, with the outer cylinder removed, can be submerged in water to contain and seal radioactive materials. Contaminated water adhering to the conical outer surface of the container body can be easily and cleanly removed by washing, making it possible to perform decontamination work extremely easily and completely.

Furthermore, according to the present invention, the truncated conical inner surface of the outer cylinder can be fitted to the conical outer surface of the container body after decontamination, making it easy to install, and the outer cylinder can be tightly fitted to the outside of the container body. Because the fins and neutron shielding layer provided on the outside of the outer cylinder are integrated, the heat dissipation effect and shielding effect of the fins and neutron shielding layer provided on the outside of the outer cylinder can be obtained almost the same as conventional ones. This has the advantage of exhibiting a heat insulating function between the container body and the inner and outer surfaces of the outer cylinder, thereby preventing a rise in temperature inside the container body.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
An embodiment of the present invention is shown in FIGS. 2A and 2B. Reference numeral 11 shown in FIG. 2A is a container body, which includes a conical outer surface 11 ₁ , a storage chamber 11 ₂ for radioactive material a, that is, spent nuclear fuel, It is equipped with a sealing lid 12 that is removably attached to the upper part with bolts 15, and a lead layer ₁₁₃ for shielding gamma rays emitted from the radioactive substance a is buried inside the container body 11. A sealing O-ring 13 is attached to the upper part, and furthermore,
Push bolts 14, ₁₄ , which can move upwardly and retractably, are screwed onto both sides of the lower part of the conical outer surface 111, and the heat is transferred to the outside around the radioactive material a stored in the storage chamber ₁₁₂ . It is filled with water, helium gas, etc. for release.

Next, FIG. 2B shows an outer tube 20 that is detachably attached to the outside of the container body 11, and the outer tube 20 is closely fitted to the conical outer surface ₁₁₁ of the container body 11. It has a truncated conical inner surface ₂₀₁ which has a shape corresponding to the shape shown in FIG. It has a structure in which the outer surface is covered with a neutron shielding layer 23 that shields neutrons emitted from the formed radioactive substance a.

Note that the container body 11 and the outer tube 20 are made of stainless steel or the like.

The illustrated embodiment has the above-described structure, and when storing radioactive material a, that is, spent nuclear fuel, in the container body 11 at a power plant or the like, the outer cylinder 2
0 and the lid 12 are submerged in water in a pool for storing spent nuclear fuel, and after storing the spent nuclear fuel in the storage chamber ₁₁₂ using appropriate equipment (not shown), In the same water, the lid 12 is applied with bolts 15, and the O-ring 13 is compressed and sealed.

Thereafter, the sealed container body 11 is taken out into the atmosphere, and the radioactive contaminated water adhering to the conical outer surface 11 ₁ is washed and decontaminated, and then the conical outer surface 11 ₁ of the container body 1 is cleaned and decontaminated. The truncated conical inner surface 20 ₁ of the outer cylinder 20 is fitted into the outer cylinder 20 and brought into close contact.

The transportation container containing the spent nuclear fuel, sealed and with the outer cylinder 20 tightly fitted to the outside of the container body 11 is transported to, for example, a reprocessing plant, where the spent nuclear fuel is discharged, and the push bolt 14 , 14 upward, the outer cylinder 20 is pushed up and comes off easily, making it easy to separate. Wash it with clean pool water or the like to remove radioactivity from the container body and outer cylinder. dye.

Therefore, according to the embodiment, the outer cylinder 20 does not need to be submerged in a pool contaminated with radioactivity, and the gap that is disposed on the outer cylinder 20 side, which has a complicated shape and is difficult to clean, can be saved. The fins 22 and the neutron shielding layer 23 disposed at the base of the fins 22 are not contaminated with minute amounts of radioactive substances in the pool water, and the difficult decontamination work required in the past becomes unnecessary.

On the other hand, since the conical outer surface 11 ₁ of the container body 11 to which pool water contaminated with radioactivity adheres is a smooth metal surface, it can be easily and completely cleaned, and the conical outer surface 11 Even if the truncated conical inner surface 20 _{1 of} the outer cylinder 20 that is in contact with the outer cylinder 20 becomes contaminated, it can be similarly easily and completely decontaminated.

In addition, in this embodiment, the conical outer surface 111 of the container body 11 and the outer cylinder 20 in contact with the conical outer surface ₁₁₁ of the container body 11 are
An extremely fine gap is created between the truncated conical inner surface 20 ₁ , and the existence of this gap causes heat dissipation,
The influence of heat shielding is shown in FIGS. 3 and 4.

FIG. 3 shows the temperature distribution of each part of the transport container in normal use. In contrast to the temperature distribution A in the conventional transport container shown in FIG. As shown, the temperature increases only by about 10°C in the storage chamber 11 ₂ , container body 11 , and lead layer 11 ₃ .
1. There is no effect on the material used or the function of the lead layer ₁₁₃ , and it is possible to obtain substantially the same heat dissipation effect as the conventional method.

Figure 4 shows the temperature distribution of each part of the transport container in the event of a fire.In the event of a fire, that is, if the outside becomes abnormally high temperature, the temperature distribution in the conventional transport container shown in Figure 1 is On the other hand, the temperature distribution in the present embodiment is low, and the extremely fine gaps exhibit a heat insulating function, and the container body 11 and the lead layer 11
_3. The temperature distribution in the storage chamber 11 ₂ and the radioactive material a portion is approximately the same as in the conventional case, and the heat shielding effect is also sufficient.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a conventional radioactive material transport container, FIG. 2A is a longitudinal sectional view showing the container body of the embodiment of the present invention, FIG. FIG. 3 is a temperature distribution diagram in normal use, and FIG. 4 is a temperature distribution diagram in the event of a fire. 11: Container body, 11 ₁ : Conical outer surface, 11
₂ : Containment chamber, 11 ₃ : Lead layer, 12: Lid, 13: O-ring, 14: Push bolt, 15: Bolt, 20:
Outer cylinder, 20 ₁ : frustoconical inner surface, 22: fin,
23: Neutron shielding layer.

Claims (1)

[Scope of utility model registration request] The container body has a conical outer surface for enclosing an exothermic radioactive substance, a truncated conical inner surface that is closely fitted to the conical outer surface, and has fins implanted on the outer surface, and a neutron shielding layer. 1. A radioactive substance transport container comprising a covered outer cylinder, the outer cylinder being detachably attached to the container body.