JPH0151955B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a method for solidifying radioactive waste using a thermosetting resin.

[Technical background of the invention and its problems] In recent years, it has been considered to dry and powder radioactive waste fluid generated from nuclear power plants and other nuclear facilities, and to treat this powder by solidifying it with thermosetting resin, etc. It is being

However, radioactive waste may contain substances that inhibit the polymerization reaction of thermosetting resins.
For example, the main component of concentrated waste fluid generated at boiling water nuclear power plants is sodium sulfate (Na ₂ SO ₄ ), but other minor components include Ca, Si, Fe, Co,
Often contains elements such as Ni and Cu,
In particular, it was found that the presence of Cu hydroxide significantly inhibits the polymerization reaction of thermosetting resins.

This is because copper hydroxide has amphoteric properties and dissociates as shown in the following formula, Cu(OH) ₂ Cu ⁺⁺ +2OH ^- Cu(OH) ₂ CuO ₂ ^-- +2H ^{+ H + generated} here This is thought to be due to the reaction with primary radicals generated by the polymerization initiator and polymerization accelerator, and the radicals in the subsequent chain reaction, thereby inactivating the radicals.

Thermosetting resins that harden through radical polymerization are difficult to cure in the presence of sources of H ⁺ that react with radicals, such as copper hydroxide, and mixtures of radioactive waste and thermosetting resins are difficult to cure when they are not polymerized. Otherwise, it will be stored in a storage container with insufficient hardening. . If this mixture remains unpolymerized, it can hardly be expected to have any radioactivity trapping ability, and the unpolymerized solidifying agent is classified as a dangerous substance under the Fire Service Act, making radioactive waste even more dangerous. There was a problem.

[Object of the Invention] The present invention was made to solve these problems, and is capable of sufficiently curing even if the radioactive waste contains substances that interfere with the curing reaction, such as copper hydroxide. The purpose is to provide a method for solidifying radioactive waste.

[Summary of the Invention] That is, the method of the present invention involves mixing a thermosetting resin, a polymerization initiator, and a polymerization accelerator into a radioactive waste liquid containing copper hydroxide or other amphoteric substances, and solidifying the mixture. It is characterized in that a mixture of alkaline substances is used during the polymerization reaction.

Examples of the thermosetting resin used in the present invention include those obtained by mixing a monomer such as styrene with an unsaturated polyester obtained by condensing maleic anhydride and phthalic anhydride with propylene glycol. It will be done. This mixture exhibits a curing reaction at room temperature when a polymerization initiator such as methyl ethyl ketone peroxide and a polymerization accelerator such as cobalt naphthenate are added. Note that polymerization accelerators such as cobalt naphthenate are usually commercially available after being diluted with a solvent such as toluene or mineral spirits.

The alkaline substance used in the present invention may react with the polymerization accelerator, cause thickening after mixing with the polymerization accelerator, or contain a large amount of polymerization accelerator or diluent to achieve a viscosity that can be transferred by a pump. What you have to use is not appropriate. For example, calcium hydroxide is not preferred because it reacts with cobalt naphthenate, which is a polymerization accelerator, and thickens, making it difficult to supply. Magnesium oxide has the property of thickening, becoming 10 times as viscous after being left for 10 days as it was immediately after mixing, so such products are good for immediate use, but have the disadvantage that they cannot be stored for long periods of time. In any case, once the alkaline substance is added to the polymerization accelerator, it is necessary to constantly stir it.

In the present invention, a diluent may be added to obtain a transportable viscosity within a range that does not reduce the strength of the solidified product.

As a diluent, it is desirable that it has low volatility, is stable for a long period without deterioration, has an appropriate viscosity, and can be added in a small amount. Examples include unsaturated polyester resin, styrene, mineral spirits, toluene, dioctyl phthalate, and the like.

However, if the polymerization accelerator is to be stored for a long period of time, unsaturated polyester resins are unsuitable because they may react with the polymerization accelerator and harden.

In the present invention, a thermosetting resin is added to and mixed with dried and powdered radioactive waste, and then a polymerization promoter and a polymerization promoter mixed with an alkaline substance are added using a pump or the like, and the mixture is allowed to stand at room temperature.

[Embodiments of the invention] Next, examples of the present invention will be described.

Example 1 Magnesium oxide was added to a polymerization accelerator at a ratio of 1:1 and mixed, and this mixture was mixed with sodium sulfate.
59% by weight and 1% by weight of a polymerization initiator (methyl ethyl ketone peroxide) in a mixed solution of 40% by weight of a thermosetting resin whose main component is an unsaturated polyester resin and 1% by weight of copper hydroxide based on the resin content. The alkaline substance was added and mixed to a concentration of 1% by weight. After standing for a day and night, a strong solidified plastic was obtained.

The surface hardness (Shore D) of this solidified plastic was approximately 82 to 89, which was comparable to that of radioactive waste not containing copper hydroxide.

Example 2 A plastic solidified product was obtained in the same manner as in Example 1, except that a 1:2:2 mixture of the polymerization accelerator, highly active industrial magnesium oxide (Kiyowa Mag #150), and mineral spirits was used. The surface hardness of this plastic solidified body was comparable to that in the absence of copper hydroxide.

[Effects of the Invention] As explained above, according to the method of the present invention, even if there is a substance that inhibits the polymerization curing reaction, such as copper hydroxide, curing is carried out sufficiently, and a strong solidified plastic product can be obtained. . Moreover, when adding an alkaline substance, it is only necessary to slightly modify the polymerization accelerator injection piping by installing a stirrer in the polymerization accelerator tank or installing a pump for high viscosity.
Furthermore, since the alkaline substance is added as a liquid mixture, it has the advantage of good dispersion and good miscibility with thermosetting resins and radioactive waste.

Claims (1)

[Claims] 1. When a thermosetting resin, a polymerization initiator, and a polymerization accelerator are mixed and solidified with radioactive waste containing copper hydroxide or a substance that dissociates to generate H ⁺ , a polymerization accelerator is used. A method for solidifying radioactive waste characterized by using a mixture of alkaline substances and an alkaline substance during a polymerization reaction. 2 Claim 1 in which the polymerization accelerator is in liquid form
Solidification treatment method for radioactive waste as described in section.