JPS63229400A - Processing 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] [Field of Industrial Application] The present invention relates to a volume reduction treatment system for radioactive waste generated from nuclear power plants, and is particularly applicable to waste containing thermoplastic resin as a component. The present invention relates to a suitable volume reduction solidification treatment method.

[Conventional technology]

In the conventional treatment method, the waste to be solidified and the cement used as the solidifying agent were mixed and solidified, but the amount of waste to be filled was low due to the mixing characteristics with cement and the physical properties of the solidified material. (Unexamined Japanese Patent Publication No. 48-82300) [Problems to be solved by the invention] Among the above-mentioned conventional technologies, regarding the cement solidification method, the crosstalk characteristics between the waste to be solidified and the cement used as the solidification material and the physical properties of the solidified body are There are restrictions on the amount of waste to be filled due to
Approximately 20 kgL of filter sludge, which is the target waste, on a dry weight basis could not be mixed into the 200Q drum.

In addition, methods have been developed and put into practical use, such as drying and pulverizing radioactive waste and then compression-molding it into pellets, and kneading it with solidifying materials such as plastic to solidify it, but these methods are currently not being used in power plants. Among filter auxiliary materials currently used, Demifiner and the like, which contain thermoplastic resin as a constituent component, have problems such as being easily affected by heat during the drying process and difficult to powderize.

An object of the present invention is to provide a method for treating radioactive waste that utilizes the physical properties of the waste itself and can achieve a high volume reduction ratio for waste that is difficult to process using other methods.

[Means for solving problems]

In order to solve these problems, in the present invention, waste having a thermoplastic resin such as the target demifiner as a constituent component is degassed under reduced pressure conditions, and 2
The waste is directly solidified by processing it at a temperature below the decomposition temperature of about 20°C.

[Effect]

The waste volume reduction and solidification treatment method according to the present invention has two primary characteristics and can satisfy the conditions required for this method.

The first feature is that the waste is dried and solidified without using a known centrifugal thin film dryer, and the temperature is above the softening temperature of the thermoplastic components contained in the target waste and under the decomposition temperature of the constituent components. By passing the waste under vacuum degassing between screw feeders housed in a casing that is heated to a high temperature, the moisture in the waste is blown away and the thermoplastic components in the waste are removed. Since it exerts its effect as a binder, it can be molded and assimilated.

The second feature is that the exit shape of the casing that houses the screw feeder that supplies and transports waste is square, so that solidified waste with a square cross section is continuously extruded. Therefore, by winding up the waste into a roll and placing it in a container that stores the waste, it is possible to increase the volume reduction effect compared to the conventional method of reducing the volume by turning it into powder or pellets. be. However, the second feature is not an essential requirement of the present invention, and although the volume reduction ratio will be slightly worse, the outlet shape of the casing is not limited to a rectangular shape, and it can also be used at the front wall or for continuously forming waste. Instead of winding the solidified material into a roll, it can also be cut into appropriate lengths and handled as pellets.

Therefore, regarding the processing temperature, which is an important point in the present invention,
It is necessary to keep the temperature below the decomposition temperature, but for example, in the case of waste filter aid material whose product name is Demifiner,
In this case, the thermoplastic resin containing 0% is acrylonitrile fiber.

Its thermal softening temperature is about 130'C, and its decomposition temperature is about 2
It is 80'C. Therefore, the demifiner can be solidified within that temperature range. In fact, by selecting 220°C as the processing temperature, which is within the solidification temperature range,
It has been confirmed that a solidified substance is produced.

In addition, during processing, it is necessary to remove the water content of approximately 50% of the waste, so it is necessary to forcibly degas the steam generated under solidification processing conditions.
When actually carrying out the solidification treatment, good results could be obtained by reducing the pressure inside the heating jacket to about 100 rrrn Hg.

In other words, one feature of the present invention is that by solidifying a substance with thermoplastic properties by utilizing its properties, a suitable solidified body is provided, and a significant volume reduction effect can be obtained compared to the conventional technology. .

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1, 2, and 3.

FIG. 1 is a system configuration diagram of a method for treating radioactive waste according to the present invention.

The filter sludge storage tank 1 stores filter sludge generated as waste after being used in condensate treatment, waste liquid treatment, etc. in a nuclear power plant. The present invention is a method for assimilating filter sludge, such as Demifiner, which contains a thermoplastic resin as a constituent component.

An example of the component composition of Demifiner is 33% of cationic powder resin based on the dry weight of waste, 17% of anionic powder resin based on dry weight of waste, and 50% of thermoplastic acrylonitrile fiber based on the dry weight of waste. has been done. The cationic powder resin and the anionic powder resin are thermosetting ion exchange resins. That is, Demifiner is a material containing 50% thermoplastic material on a waste dry weight basis and 50% thermosetting material on a waste dry weight basis.

Waste such as demifiner made of the above substances is stored in the filter sludge storage tank 1. The demifiner in the storage tank is sent to a centrifugal dehydrator 3 at a constant flow rate by a transfer pump 2. About 50% of the moisture in the demifiner fed at a constant flow rate is removed by the dehydration action of the centrifugal dehydrator 3.

The demi-finer whose water content has been reduced to about 50% by the centrifugal dehydrator 3 is supplied to a supply feeder 4 driven by a motor 5. The demifiner supplied to the supply feeder 4 is quantitatively supplied to the heating jacket feeder 6. The heating jacket feeder 6 has a casing 8 heated by a heater 7.
A feeder 9 for the purpose of kneading and transferring is housed inside, and the feeder 9 is driven by a drive motor 10. Furthermore, the inside of the casing 8 is vacuum degassed by a vacuum pump 11, and after the vacuum degassing, the gaseous waste enters a vent treatment bag @12 and is treated. A certain amount of waste solidified by the heating jacket feeder 6 is wound up by a waste winding device 23 and then stored in a waste storage container 32.

FIG. 2 shows an embodiment of the control system for the main parts of the radioactive waste treatment method of the present invention.

The demi-finer supplied in a constant quantity from the filter sludge storage tank 1 by the transfer pump 2 is sent to the supply feeder 4 and further sent to the heating jacket feeder 6. When the demifiner is kneaded and transferred in the heating jacket feeder 6, the ammeter 20 reads the current value of the motor 10 driving the heating jacket feeder 6. Ammeter 20
is connected to a control circuit 21, and the control circuit 21 controls the rotation speed of the motor 5 driving the supply feeder 4 while monitoring the current value of the heating jacket feeder 6, so that the current value is constant, that is, the load is constant. control.

When the waste mixed in the heating jacket feeder 6 is injected from inside the casing, the speed detector 22 detects the injection speed. The signal from the speed detector 22 is input to the control circuit 21 . The control circuit 21 controls the winding speed of the waste winding device 23 to keep the thickness of the easily deformable waste in the winding device constant.

A position detector 24 detects the state in which the waste material is wound on the waste material winding device 23, that is, the thickness of the roll. The position detector 24 is connected to the control circuit 21, and when the roll thickness reaches a certain value, the motor 10 driving the heating jacket feeder 6 and the motor 5 driving the supply feeder 4 are connected to the control circuit 21. Transfer pump 2 stops. When the motor stops, the lot is replaced and the assimilation process begins again.

Figure 3 shows the second step in the radioactive waste treatment method of the present invention.
An example other than the winding method shown in the figure will be described.

After the waste mixed in the heating jacket feeder 6 is injected from the inside of the casing, it is passed through a water bath 30. The waste material rapidly cooled in the water bath 30 loses its viscosity and becomes completely solidified. The solidified waste is cut into pellets by a cutter 31. The pelleted waste 40 is stored in a waste storage container 32 such as a drum can.

In addition, here, after the waste material kneaded in the heating jacket feeder 6 is injected from the casing, it is rapidly cooled and solidified through the water bath 30 and then cut into pellets by the cutter 31, but the waste material is not passed through the water bath 30. It is also possible to cut the waste in its softened state into pellets, cool them in the atmosphere, and then store them.

According to this example, when the conventional method of cement solidification was applied when disposing of waste by filling it into drums, the amount of waste to be filled in the drum was about 20 kg, whereas the amount of waste filled in the drum was 1. In the case of the power type, the amount of waste drum filled is approximately 1
The weight is 20 kg, and high volume reduction performance can be achieved.

〔Effect of the invention〕

According to the present invention, target waste can be assimilated by utilizing the characteristics of thermoplastic substances, so even substances with physical properties that are difficult to pulverize using a centrifugal thin film dryer can be solidified.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a radioactive waste treatment method according to an embodiment of the present invention, FIG. 2 is a control system diagram of the main parts of the radioactive waste treatment method of the present invention, and FIG. 3 is a system diagram of a radioactive waste treatment method according to an embodiment of the present invention. It is a system diagram when applied to pelletization. 1... Filter sludge storage tank, 2... Transfer pump, 3... Centrifugal dehydrator.

Claims (1)

[Claims] 1. Among the filter sludge generated after being used in condensate treatment, waste liquid treatment, etc. at nuclear power plants, waste containing thermoplastic resin as a constituent component is treated at a temperature equal to or higher than the softening temperature of the thermoplastic component, and A radioactive waste disposal method characterized by drying and solidifying by utilizing the property of forming and solidifying at a temperature below the decomposition temperature of the components.