JPH04110799A - Disposal method for radioactive waste - Google Patents

Abstract

PURPOSE:To allow a compressed body to have a confining property of radioactive nuclides by packing fine grained adsorbents having good performance of adsorbing radioactive nuclides around miscellaneous solid wastes thrown into a metallic vessel, thereafter compressively molding the metallic vessel. CONSTITUTION:Radioactive, miscellaneous solid wastes 1 are packed in a metallic vessel 2 such as a drum can. At this time, fine-grained adsorbents 3 having good performance of adsorbing radioactive nuclides are packed around the waste 1. Besides, the quantity of packed adsorbents 3 is set by the type of radioactive nuclide, the type of adsorbent 3, expected distribution coefficient, etc. Then, the waste 1 packed in the vessel 2 are compressively molded by the force, for example, of 1,000 to 2,000 tons to obtain a compressed body 4. The compressed body 4 contains fine-grained adsorbents 3 having good adsorptivity for radioactive nuclides inside, and has a confining property of radioactive nuclides in itself. The compressed body 4 can be directly buried in a concrete pit, but when it is put in a metallic vessel such as a drum can, and packed with solidifiers around itself to be solidified, confining property of the compressed body can be more improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for treating non-flammable radioactive waste.

(Prior art) Conventionally, as a treatment method for non-combustible radioactive miscellaneous solid waste such as metal, radioactive waste is compressed as it is or placed in a metal container such as a drum, and the resulting compressed body is compressed. Furthermore, a method of storing the waste in a metal container, solidifying the surrounding area with cement mortar, etc., and burying the waste in a concrete pit is being considered.

However, in terms of safety evaluation, it is assumed that after a long period of about 300 years, the condition of such waste bodies and the surrounding concrete bits will be reduced to the level of sand, and their physical containment properties cannot be expected. I take it as a thing.

Therefore, the ``partition coefficient'' is being considered as a standard for evaluating the radioactivity confinement in such waste bodies. 20 "Partition coefficient" quantitatively represents the adsorption/adsorption equilibrium between the surface phase in which the radionuclide constitutes the solidifying agent and the liquid phase such as groundwater, and is the ratio between radioactivity in the solid phase per unit weight and per unit volume. It is defined as the ratio of radioactivity in the liquid phase of

Since it is thought that the conventional compacted body itself does not have the ability to trap radioactivity, the ability of the waste body to trap radioactivity is evaluated by the distribution coefficient of the solidifying material.

(Problem H to be solved by the invention) The present invention solves these conventional problems and makes it possible to confine radioactivity in the waste body as a whole by giving the compressed body itself the ability to confine radioactivity. It was completed to provide a method for disposing of radioactive waste with improved containment properties.

(Means for Solving the Problems) The first invention of the present application made to solve the above problems has excellent adsorption performance of radionuclides around radioactive miscellaneous solid waste placed in a metal container. This method is characterized in that a metal container is compressed and molded after being filled with a powder adsorbent to obtain a compressed body, thereby giving the compressed body the ability to confine radionuclides.

Further, the second invention is characterized in that the compressed body obtained according to the first invention is placed in a metal container, and the surrounding area is filled with a solidifying material.

In the following, the invention will be explained in more detail with reference to illustrated embodiments.

(Example) First, as shown in Figure 1, radioactive miscellaneous solid waste (1) is filled into a metal container (2) such as a drum.
At this time, the surrounding area of the miscellaneous solid waste (1) is filled with a powdery adsorbent (3) that has excellent adsorption performance for radionuclides.

The typical adsorbent (3) is hentonite, but other adsorbents include perminulite, activated carbon, silica gel, activated alumina, synthetic zeolite, and activated clay other than hentonite (allophane, pisite, akbarjai). 1 to Seviolite). In particular, it is preferable to fill miscellaneous solid waste (1) such as pipes with an adsorbent (3). The filling amount of adsorbent (3) depends on the type of radionuclide and adsorbent (3).
It shall be set based on the type of data, expected distribution coefficient, etc.

Next, the miscellaneous solid waste (1) filled in the metal container (2) is compression-molded with a force of, for example, 1,000 to 2,000 tons to obtain a compressed body (4) as shown in FIG. This compressed body (4) contains powder-like adsorbent (
3), which itself has the ability to confine radionuclides.

This compressed body (4) can be buried in a concrete bit as it is, but according to the second invention, the compressed body (4) is further buried in a metal container such as a drum as shown in FIG.
5), and the solidifying material (6) is preferably filled around the solidifying material (6) for solidifying. Cement mortar is generally used as the solidifying material (6) for this purpose;
It goes without saying that it is preferable to use a material that has excellent adsorption performance for radionuclides.

(Effects of the Invention) As explained above, according to the radioactive waste solidification treatment method of the present invention, a powdery adsorbent having excellent adsorption performance for radionuclides is placed in a metal container together with miscellaneous solid waste and compressed. Since it is molded, the compressed body itself can also have the ability to confine radionuclides.

For this reason, in waste bodies obtained by conventional disposal methods, the compressed body itself was considered to have no ability to trap radionuclides, whereas in the waste bodies obtained by the method of the present invention, the compressed body also does not contain radionuclides. Even if it is assumed that in the future concrete pits will be reduced to the level of sand and physical radioactivity containment properties cannot be expected, chemical containment properties can be expected to improve radioactivity containment properties. It is possible to delay the migration of nuclides underground. Furthermore, since the radionuclide confinement properties of waste bodies have been improved, the load on artificial barriers such as concrete pits in buried disposal sites can be reduced, making it possible to construct buried disposal sites at low cost.

It goes without saying that if the compressed body is further placed in a metal container and solidified with cement mortar having excellent adsorption properties according to the second aspect of the invention, the radionuclide confinement property of the waste body can be further improved.

As explained above, the present invention improves the radioactivity confinement properties of the waste body as a whole, so it contributes to the development of industry as a radioactive waste disposal method that solves the conventional problems. There are some things that are extremely large.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the state in which miscellaneous solid waste is packed together with an adsorbent into a metal container, Figure 2 is a cross-sectional view showing a compressed body formed by compression molding, and Figure 3 is a cross-sectional view showing the compressed body further packed into a metal container. FIG. 3 is a sectional view showing a filled and solidified waste body. (1): Miscellaneous solid waste, (2): Metal container, (3): Adsorbent, (4): Compressed body, (5): Metal container, (6):
Solidifying material.

Claims (1)

[Claims] 1. After filling the surrounding area of radioactive miscellaneous solid waste put into a metal container with a powdery adsorbent that has excellent adsorption performance for radionuclides, the metal container is compression molded and compressed. A method for disposing of radioactive waste, characterized in that the compressed body has the ability to confine radionuclides by obtaining a body. 2. A method for treating radioactive waste, which comprises placing the compressed body obtained by the method according to claim 1 in a metal container, and filling the surrounding area with a solidifying material to solidify it.