JP2003344586A - Disposal container and disposal method for radioactive waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a radioactive waste disposal container hardly corroded compared with conventional steel vessel and capable of retaining nuclides for a long time and obtain a disposal method for preventing contamination from the outer surface of the disposal container during a series of works for disposal. <P>SOLUTION: The radioactive waste disposal container for the burial disposal of radioactive waste in the underground is constituted of Zircaloy. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disposal container used for burying radioactive waste generated from a nuclear facility and a disposal method thereof.

[0002]

2. Description of the Related Art Generally, radioactive waste generated from a nuclear facility is stored in a disposal container and buried underground in order to prevent radiation exposure. By the way, as a radioactive waste disposal container currently used or being examined, a steel container is generally used from the viewpoints of material strength, material availability, workability, and shielding performance.

As a conventional low-level radioactive waste disposal container, a drum 1 as shown in FIG. 5 is used.
In this case, when the radioactive waste having a high dose is stored in the drum can, the drum can 1 may be provided with a shielding function from the viewpoint of reducing the exposure of workers, but in that case, the inside of the drum can 1 is made of concrete. It is common to apply lining.

Further, in the case of disposing of radioactive waste having a relatively high radioactivity concentration than conventional low-level radioactive waste, a steel disposal container 2 larger than a drum can as shown in FIG. 6 is considered. The disposal container has been used overseas. In general, a concrete shield or a steel shield with a thickness of several cm to several tens of cm is considered for this container depending on the dose of radioactive waste to be stored.

[0005]

However, in the conventional steel container as described above, the disposal container is gradually corroded by groundwater after being buried in the ground, and groundwater enters the disposal container. , It is assumed that the nuclide in the radioactive waste in the disposal container will come into contact with the groundwater, and the nuclide will move to the outside of the disposal site as the groundwater flows out. Therefore, there is a problem in that the disposal site must be designed on the safe side so that there will be no problem with radiation exposure even if nuclide migration occurs due to corrosion of the container in the future.

In view of the above, the present invention provides a radioactive waste disposal container that is less corrosive than conventional steel containers and can retain a nuclide in the disposal container for a long time, and the outer surface of the disposal container. The purpose is to obtain a disposal method that prevents the contamination of

[0007]

The invention according to claim 1 is
In a disposal container for burying radioactive waste in the ground, the disposal container is formed of Zircaloy. The invention according to claim 2 is a disposal container for burying radioactive waste in the ground, wherein an inner layer of zircaloy is provided on the inner surface of the steel container.

According to a third aspect of the invention, in a disposal container for burying radioactive waste in the ground, an intermediate layer made of zircaloy is provided between an outer layer made of steel and an inner layer made of steel. It is characterized by

The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the zircaloy container, the inner layer of zircaloy, or the middle layer of zircaloy is:
It is characterized in that it is manufactured by using recycled products from waste or radioactive waste made of Zircaloy.

Further, the invention according to claim 5 is a method for disposing radioactive waste, wherein after disposing the radioactive waste in the disposal container according to any one of claims 1 to 3, the radioactive waste is stored. The feature is that the container is stored in a container for burial disposal and buried in the ground.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a first embodiment of the present invention. A radioactive waste disposal container 10 for burying radioactive waste in the ground is itself formed of a zircaloy material. . The container shape may be either rectangular (cubic) or cylindrical, and the rolled material may be assembled into the container by welding, or may be manufactured by casting. It is possible to select a rational method from the viewpoint of container manufacturing cost and requirements for a series of operations for waste production, transportation, and disposal, depending on the disposal case.

As shown in Table 1, since the zircaloy material has a higher corrosion resistance than carbon steel and stainless steel and a slower corrosion rate, it is possible to secure the soundness of the disposal container for a longer period than the steel container. It is possible to trap the nuclide in the disposal container. In addition, the longer the retention period of radioactive waste in the disposal container, the more the decay of nuclides is expected.
It is also possible to rationalize the facility scale of radioactive waste disposal sites.

[0013]

[Table 1]

FIG. 2 is a diagram showing a second embodiment of the present invention, in which the radioactive waste disposal container 20 is a steel container 21.
Is provided with an inner layer 22 of Zircaloy. A handling mechanism 23 such as a trunnion is provided on the outer surface of the steel container 21.

The radioactive waste disposal container 20 may be manufactured by manufacturing a zircaloy container as in the first embodiment and coating the outside with a steel plate, or a steel container. It is also possible to insert a container made of Zircaloy into the assembly.

By the way, the radioactive waste disposal container is required to have a function for a series of handling operations such as storage of radioactive waste, solidification, closing of a lid, transportation, or placement in a disposal site. For example, various processing including welding, such as hanging ears for handling the disposal container, holes and threads for the lid bolt portion, installation of a mortar filling port, and the like are required. However, Zircaloy has excellent corrosion resistance, but on the other hand, it has a problem that it is more difficult to process than steel.

Therefore, the outer portion, which requires strength and requires various processing including welding, such as hanging ears, is made of steel like the conventional disposal container, and the inner layer 22 of zircaloy is provided inside. The strength, shielding function and handling property of the conventional disposal container can be sufficiently ensured, and the radioactive substance in the disposal container can be retained by the inner zircaloy portion even after the outer steel is corroded. That is, by providing a handling mechanism 23 such as a trunnion on the steel portion outside the disposal container, the ease and strength of processing such as welding can be provided and the necessary shielding and corrosiveness at the inner zircaloy portion can be secured. You can

FIG. 3 is a diagram showing a third embodiment of the present invention, in which the radioactive waste disposal container 30 is made of a steel outer layer 3.
1 and a steel inner layer 32, a middle layer 33 made of zircaloy is provided, and a handling mechanism 34 is provided on the outer surface of the steel outer layer 31. This disposal container 3
0 can be manufactured by sandwiching a zircaloy material between steel materials before manufacturing the container to manufacture a container, or by casting zircaloy between steel double containers. Even in the radioactive waste disposal container 30, the steel outer layer 31 and the steel inner layer 32 can provide strength and workability, and the zircaloy intermediate layer 33 ensures shielding and corrosiveness. You can

By the way, in nuclear power generation facilities, the in-core structure to be discarded is a high-dose substance and is therefore stored in water. Even when the in-core structure to be discarded is stored in a disposal container, the disposal container It is conceivable to first submerge the waste in the water in which it is stored and then store the waste in a disposal container in the water. However, when the disposal container is submerged in water, the outer surface of the disposal container is contaminated.Therefore, it is necessary to decontaminate the disposal container and implement measures to prevent pollution so that the contamination does not spread during subsequent transportation or stationary operation at the disposal site. is there.

4 (a), (b), and (c) are views showing a disposal method in which the outer surface of the disposal container is prevented from being contaminated. First, as shown in (a), a shielding function is provided. Is sufficient, for example, the disposal container 10 is submerged in the water in the water pool 40, the high radiation dose waste 41 is stored therein, and the disposal container 10 is lifted from the water to the air as shown in FIG. The disposal container 10 is stored in the buried disposal container 42.

By further storing the disposal container 10 in which the high radiation dose waste 41 is stored in the buried disposal container 42 in the air as described above, the radioactive waste can be stored without contaminating the outer surface thereof. It is possible to store radioactive waste in a waste disposal container, and it is possible to reliably prevent the spread of pollution during subsequent transportation or stationary operation of the disposal site.

As the material of the zircaloy container in each of the above-mentioned embodiments, a new zircaloy material may be used, or a recycled product of the material of the zircaloy equipment to be buried and disposed.

That is, in the BWR type nuclear power generation facility,
Zircaloy is used as the channel box of the fuel assembly. The channel box will be used as radioactive material after being used in the nuclear reactor for a certain period of time. Therefore, by utilizing this used channel box as a material for a zircaloy disposal container, it is possible to reduce radioactive waste generated from a nuclear power generation facility and to effectively utilize zirconium resources. The zircaloy material of the channel box is activated by neutron irradiation in the nuclear reactor, but the radioactive nuclide can be separated and utilized as a recycled product by, for example, a decontamination method using a molten salt electrolysis method.

[0024]

As described above, since the present invention uses zircaloy as the material for the radioactive waste disposal container,
Due to the effect of improving the corrosion resistance, the nuclide can be stored in the disposal container for a long time. According to the above waste disposal method,
This has the effect of preventing the spread of pollution during transportation and stationary work at the disposal site.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a radioactive waste disposal container of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the radioactive waste disposal container of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the radioactive waste disposal container of the present invention.

4 (a), (b) and (c) are diagrams showing the radioactive waste disposal method of the present invention.

FIG. 5 is a perspective view showing an example of a conventional radioactive waste disposal container.

FIG. 6 is a perspective view showing another example of a conventional radioactive waste disposal container.

[Explanation of symbols]

10, 20, 30 Radioactive waste disposal container 21 steel container 22 Inner layer of Zircaloy 23 Handling mechanism 31 Steel outer layer 32 steel inner layer 33 Intermediate layer made of zircaloy 34 Handling mechanism 40 water pool 41 High radiation waste 42 Disposal container

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayuki Shibano             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Inventor Koichi Matsumoto             1-1 Shibaura, Minato-ku, Tokyo Co., Ltd.             Toshiba headquarters office (72) Inventor Reiko Fujita             2-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Ceremony Company Toshiba Hamakawasaki Factory (72) Inventor Yoshihisa Hayashi             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F-term (reference) 4D004 AA50 AB09 BB03 BB09

Claims (5)

[Claims] 1. A disposal container for burying and disposing of radioactive waste in the ground, wherein the disposal container is formed of Zircaloy. 2. A disposal container for burying radioactive waste in the ground, wherein a zircaloy inner layer is provided on the inner surface of the steel container. 3. A disposal container for burying radioactive waste in the ground, wherein an intermediate layer made of zircaloy is provided between an outer layer made of steel and an inner layer made of steel. Waste disposal container. 4. The zircaloy container, the zircaloy inner layer, or the zircaloy intermediate layer is manufactured by using a recycled product from zircaloy waste or radioactive waste. 4. The radioactive waste disposal container according to any one of 3 to 3. 5. The radioactive waste is stored in the disposal container according to any one of claims 1 to 3, and then the disposal container storing the radioactive waste is stored in a buried disposal container and buried underground. A method for disposing of radioactive waste, which is characterized in that