JPS61233397A - Plastic solidifying treating method of radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a method for solidifying powdery or granular radioactive waste discharged from nuclear facilities using a thermosetting resin. [Prior art] [and its problems] As a method for processing radioactive powder or granular waste such as dried concentrated waste liquid and used ion exchange resin discharged from nuclear facilities such as nuclear power plants,
For example, as disclosed in Japanese Unexamined Patent Publication No. 48-44700, 1 a method of solidifying these radioactive wastes using a thermosetting resin, particularly an unsaturated polyester resin, is different from the conventional solidifying method using asphalt or cement. It is known as an advantageous treatment method because it has a greater volume reduction effect, has better water resistance, and can solidify in a shorter time than the solidification method.

To provide an overview of the structure and operation of a plastic solidification processing device that uses unsaturated polyester resin as a thermosetting resin (hereinafter referred to as assimilation material) to solidify radioactive waste at room temperature. The system diagram is shown in Fig. 5 @ In Fig. 5, powdered or granular radioactive waste is charged into the hopper IK2. Liquid unsaturated polyester resin as a solidification material charged into the first tank 3 4. After weighing appropriate amounts of the polymerization initiator 6 charged into the second tank 5 and the polymerization accelerator 8 charged into the third tank 7, they are sequentially charged into the mixing tank 9, and the stirrer 10 A liquid mixture 11 is obtained by stirring and mixing for a predetermined period of time using a mixing tank 9, and the mixture 11 is dropped from the mixing tank 9 into a container 12 such as a drum placed below it. Next, the container 12 containing the liquid mixture 11 is moved to a predetermined location and left at room temperature to cure the liquid mixture 11 at room temperature, thereby forming a plastic solidified body 13 in the container 12.

In the above process, the unsaturated polyester resin is used as the assimilation material 4 by appropriately selecting a polymerization initiator 6 and a polymerization accelerator 8 and adding them to the unsaturated polyester resin to allow the curing reaction to occur at room temperature. Since it has quick curing properties, it is easy to obtain a solidified body containing the radioactive waste 2 without the need for incidental equipment such as heating, and it can be hardened as a large solidified body 13 using a drum container 12 or the like. This is because it is possible and suitable for imparting the required strength to the solidified material 13.However, even when unsaturated polyester resin is used as the solidified material 4, it is possible to drop it into the container 12. Due to the large difference in specific gravity between the solidifying material 4 and the radioactive waste 2, the radioactive waste 2 settles in the liquid mixture 11, and the radioactive waste 2 is uniformly dispersed in the liquid mixture 11. The resulting solidified material 13 is cured in areas where the radioactive waste 2 and the solidifying material 4 are separated from each other. There are various drawbacks such as: In order to solve this phenomenon of settling of the radioactive waste 2, the amounts of the solidifying material 4 and the polymerization accelerator 8 are adjusted to complete the hardening of the liquid mixture 11 before the radioactive waste 2 settles. A short-time curing method is also possible, but if the curing time is accelerated as in (a) and (b), the liquid mixture 11 will harden in the pipe that flows out of the liquid mixture 11, blocking the pipe and solidifying the radioactive waste. This is not a preferred method because the process itself becomes impossible.

Therefore, a method is desired in which the radioactive waste 2 is maintained in a uniformly dispersed state until the liquid mixture 11 is completely hardened within the container 12. [Object of the Invention] The present invention has been made in view of the above points. The purpose is to solidify radioactive waste into plastic.
It is an object of the present invention to provide a treatment method capable of uniformly dispersing radioactive waste in a solidified body without causing the radioactive waste to settle during the treatment process.

[Key points of the invention]

In the present invention, radioactive waste having a particle size distribution of 200 μm or less is used, and the amount of radioactive waste added to the unsaturated polyester resin used as an assimilation material is 5%.
By setting the amount to 5% to 75% by weight, it is possible to prevent the radioactive waste from settling during the solidification process and to obtain a solidified body in which the radioactive waste is uniformly dispersed.

[Embodiments of the invention]

The present invention will be explained below based on examples.

In carrying out the present invention, the present inventors carried out experiments using sodium sulfate powder, which is commonly used in experiments on this food, as a simulated waste (hereinafter referred to as waste) instead of radioactive waste. However, since the experimental equipment used was the same as that shown in FIG. 5, the explanation of the equipment configuration and solidification procedure will be omitted.

Experiment 1 Based on the recognition that the particle size distribution of waste affects the sedimentation state in a liquid mixture, the present inventors crushed waste and produced samples consisting of relatively large particles and samples of this size. A sample was prepared from a large number of small particles. Figure 1 is a diagram showing the particle size distribution of these wastes, with straight line A representing a sample consisting of particles of 1000 μm or less (referred to as A waste), and straight line B representing a sample consisting of particles of 200 μm or less (B). These A and B wastes were weighed and blended so that the waste amount was 60% by weight and the solidifying material was 40% by weight, and then a polymerization initiator and a polymerization accelerator were added. The agent was added, stirred well, and polymerized and hardened in a drum container to form a solidified product. Figure 2 shows a diagram showing the relationship between the height of the obtained solidified material and the amount of waste contained therein, (a) is for A waste, and (b) is for B waste. This is the case. As is clear from Figure 2, in the case of waste A with large particles (&), there is no waste at the top of the solidified material, and the portion that retains the initial blended amount of 60% by weight is unevenly distributed. On the other hand, waste B consisting of small particles (B) maintains the initial blending amount of 60% by weight in the solidified material over almost the entire area. This means that in waste A, sedimentation occurs before the hardening of the assimilate is completed, but in waste B, waste A is almost uniformly dispersed without significant sedimentation. A solidified product with no waste at the top has a large amount of curing heat and shrinkage during the curing process, which causes problems such as cracks and gaps between the drum and the container, but solidification allows waste to be evenly distributed. The body does not show such defects and therefore the waste is 200 μm
It can be seen that particles having a particle size distribution within the following range are suitable.

Experiment 2 Next, since the content of waste in the solidified body is a factor that determines the strength of the solidified body, the present inventors determined the amount to be blended for the appropriate content of waste.

Since the evaluation standard performance is required to have a compressive strength of 500 kg/- for plastic solidified bodies containing radioactive waste, in this experiment, the compressive strength was 500 kg/-.
In order to find out the waste content that can obtain a compressive strength of d or more, the relationship between the two was determined using a solidified body of B waste, and the results are shown in Fig. 3. As can be seen from Fig. 3, the solidified material exhibits a compressive strength exceeding 500 k#/- at locations where the B waste content ranges from 50% to 75% by weight. In order to provide the above compressive strength, it is necessary to contain 50% to 75% by weight of waste.As mentioned above, the solidified material using OB waste has good dispersion of waste. In order to determine the blending amount that should give a waste content of 50% to 75% by weight that exhibits a compressive strength of 500 #/- in the upper 1005m of the solidified body, the blending amount of B waste is 40%. 50
, 55, 60. 65. 70° 75 each weight - mixed with unsaturated polyester resin as a solidifying agent to form a solidified body), content of B waste in the assimilate corresponding to each blending amount. A diagram representing the relationship with quantity was obtained and is shown in FIG.

As shown in Figure 4, the part of the solidified body from the upper end to 100 yen contains 50 to 75% by weight of B waste, that is,
To impart a compressive strength of k&/d or more, the blending amount should be 55%.
It can be seen that it is sufficient to set the content within the range of 75% by weight.

From the above experiments 1 and 2, when waste is mixed with solidification material and solidified, the waste does not settle in the solidified material, and the standard value of compressive strength of 500 kg/cj or more is imparted to the assimilated material. In order to
Using a substance with a diameter of 55 μm or less, the amount of solidifying agent added is 55 μm or less.
We have reached the conclusion that it is sufficient to decide between % by weight and 75 weight S.

In this experiment, we used sodium sulfate powder as a substitute for radioactive waste, but it is clear that similar results can be obtained when using radioactive waste. In order to treat it as radioactive waste, it can be easily achieved by charging it into the hot spring (-1) in Figure 5.

〔Effect of the invention〕

When solidifying radioactive waste into plastic using unsaturated polyester resin as a solidifying material, it is possible to prevent the radioactive waste from settling due to the difference in specific gravity between the radioactive waste and the solidifying material during the curing process. In order to obtain the desired compressive strength in the solidified material, according to the present invention, as explained in the examples, radioactive waste with a particle size distribution in which the maximum particle size is 200 μm or less is used, and radioactive waste is mixed with radioactive waste. Because the mixing ratio of radioactive waste with the solidifying material was determined to be in the range of 55% to 75% by weight, the radioactive waste did not settle until hardening, and the resulting solidified material contained uniformly radioactive waste over the entire area. It was possible to secure a compressive strength of 500 k#/cl/1, which is the strength evaluation standard for the solidified material, when the solidified material was dispersed.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the particle size distribution of waste, Figure 2 is a diagram showing the relationship between waste content and solidified body height, and Figure 3 is a diagram showing the relationship between waste content and solidified body compaction. Figure 4 is a diagram showing the relationship between the strength and the amount of waste added to the solidified body and the waste content. Figure 5 is the configuration of the radioactive waste plastic solidification processing equipment. Conceptual diagram showing the system 0 2...Radioactive waste, 4...Solidification material,
9...Mixing tank, 11...Liquid mixture,
12...Drum container. 13...Solidified body. ωi b4. Sakunuwap Figure 3

Claims (1)

[Claims] 1) A method in which a liquid mixture consisting of radioactive waste, an unsaturated polyester resin, a polymerization initiator, and a polymerization accelerator is injected into a drum container and left to solidify.
Using radioactive waste distributed with a particle size of less than μm,
A method for solidifying radioactive waste into plastic, characterized in that the radioactive waste and the unsaturated polyester resin are added at a mixing ratio of 55% to 75% by weight of the radioactive waste.