JP2006266967A - Processing method for waste ion exchange resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent disperse of radioactive Cs outside a system and obtain a large weight reduction and volume reduction without requiring any special equipment and special oxidation decomposition process. <P>SOLUTION: The processing method for waste ion exchange resin essentially requires the following processes (1) to (3). Heat treatment process (1): Waste ion exchange resin including radioactive Cs is heat-treated. The temperature range of 400°C to 1,000°C commonly used is proper. Cooling process (2): Exhaust gas generated by the heat treatment is cooled and the radioactive Cs is condensed in the condition that tar does not adhere to filters. The exhaust gas is cooled to 400°C or higher and less than 600°C, more desirably 500°C or higher and less than 600°C. Dust removing process (3): The cooled exhaust gas is passed through a dust-preventing device to trap condensed radioactive Cs. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in a method for treating a waste ion exchange resin containing radioactive Cs.

  Conventionally, radioactive liquid waste generated from radioactive facilities such as nuclear power plants is usually vaporized and concentrated, and solids are solidified, etc., but the vaporized water is condensed and liquefied, and then the concentration of radioactive substances is reduced by ion exchange treatment. In general, it is reused as various treated water. And waste ion exchange resin containing the used radioactive Cs which generate | occur | produces with this waste water reuse needed to be mineralized and to reduce weight and volume.

  As a method for weight reduction and volume reduction, there is a decomposition method by heat treatment such as dry distillation, incineration, etc. However, if the resin decomposition rate or the resin decomposition rate is increased, the exhaust gas temperature increases due to combustion heat generation, and radioactive Cs is vaporized. In the dust filter, Cs cannot be collected, and even the exhaust gas treatment system is scattered and contaminated, so that the exhaust gas treatment system cannot be maintained. In addition, when exhaust gas cooling is performed excessively in order to prevent Cs from volatilizing, there is an inconvenience that tar content adheres to the filter and the filter is clogged.

In order to cope with such a problem, the following oxidative decomposition method has been proposed. (See Patent Document 1)
That is, waste ion exchange resin is loaded into an oxidative decomposition tank provided with a vacuum pump, and after reducing the pressure to 1 to 20 torr vacuum, an oxidizing gas such as oxygen gas activated in an ionic state is supplied thereto. The waste ion exchange resin is oxidatively decomposed at a low temperature of 200 ° C. or lower by stirring.

According to this method, since the processing temperature is a low temperature of 200 ° C. or lower, nuclides such as radioactive Cs are not vaporized, and thus an advantage is obtained that they are not released out of the system. However, this method requires a special oxidative decomposition tank equipped with a high-frequency heating mechanism for activating the oxidizing gas, and it must be operated under reduced pressure by a vacuum pump. However, special oxidative decomposition treatment is required, equipment costs and operating costs increase, and the oxidative decomposition reaction rate is not large, so the effect of weight reduction and volume reduction is not as expected as compared to the processing time. The problem remained.
Japanese Patent Laid-Open No. 6-34796: “Resin Oxidation Decomposition Apparatus” paragraphs (0013), (0018) (0033), etc.

  The present invention has been made to solve the above-described problems, does not require special equipment or special oxidative decomposition treatment, can reliably prevent radioactive Cs from being scattered outside the system, and greatly reduces the weight. Provided is a method for treating a waste ion exchange resin containing radioactive Cs capable of obtaining a volume reduction effect.

  The above problem is that when the exhaust gas generated by heat treatment of the waste ion exchange resin containing radioactive Cs is removed, the exhaust gas is cooled and controlled to a temperature of 400 ° C. to 600 ° C., so that the dust removal means can remove the radioactive material in the exhaust gas. This can be solved by the method for treating a waste ion exchange resin of the present invention characterized by collecting Cs.

  The present invention also relates to a case where the waste ion exchange resin containing radioactive Cs is based on a styrene divinylbenzene copolymer, or a thermal decomposition treatment or an incineration treatment in which the heat treatment is performed at a temperature of 400 ° C to 1000 ° C. It is preferable that a certain form, and further, the dust removing means is a dust removing device using a heat-resistant filter made of ceramic or metal.

  The waste ion exchange resin treatment method of the present invention can utilize a normal thermal decomposition treatment or incineration treatment performed at a temperature of 400 ° C. to 1000 ° C. when heat treating the waste ion exchange resin containing radioactive Cs. And no special equipment is required. Also, as the dust removing means at the subsequent stage, a dust removing device using a heat-resistant filter made of ceramic or metal is suitable, but this can also be an ordinary device.

  Next, in the present invention, the exhaust gas containing the vaporized radioactive Cs is cooled by an appropriate means, preferably at a temperature of 400 ° C. or higher and lower than 600 ° C., so that radioactive Cs is condensed while preventing tar condensation. Based on this, the radioactive Cs in the exhaust gas is collected by the dust removing means, so that it is possible to reliably prevent the radioactive Cs from being diffused outside the system while preventing the heat-resistant filter from being blocked by pyrolytic tar. Therefore, the present invention has a very great technical value as a treatment method of waste ion exchange resin which has solved the conventional problems.

Next, an embodiment according to the processing method of the waste ion exchange resin of the present invention will be described.
In the present invention, the following steps (1) to (3) are essential. That is, (1) Heat treatment step: A waste ion exchange resin containing radioactive Cs is heat treated. (2) Cooling step: The exhaust gas generated by the heat treatment is cooled to condense radioactive Cs. (3) Dust removal step: The cooled exhaust gas is passed through a dust removal device, and condensed radioactive Cs is collected.

(1) Heat treatment In the present invention, the waste ion exchange resin containing radioactive Cs to be treated is usually a resin structure based on a styrenedivinylbenzene copolymer. As mentioned above, it is a waste ion exchange resin used to reduce the concentration of radioactive substances by ion exchange treatment of the condensed liquid after concentration treatment of radioactive waste liquid generated from radioactive facilities, and is a radionuclide Contains radioactive Cs.

  The heat treatment of the waste ion exchange resin may be either a relatively low-temperature pyrolysis process (dry distillation process) or an incineration process that tends to be relatively high, and the temperature is usually 400 ° C. to 1000 ° C. The range is appropriate. If it is less than 400 ° C., the thermal decomposition efficiency is low and tar generation is remarkable, which is not preferable.

And in this invention, the incineration process of the combustion area | region of 600 to 1000 degreeC is more preferable from a viewpoint of weight reduction and volume reduction of a waste ion exchange resin. If the temperature is 600 ° C. or higher, the thermal decomposition rate is large and tar generation is considerably reduced.
As a device used for this purpose, a normally used fixed bed type combustion furnace and fluidized bed type combustion furnace capable of being decomposed into ash and combustion exhaust gas are suitable, and no special structure is required.

(2) Cooling step This is a step of cooling the heat treatment exhaust gas at the temperature generated by the heat treatment to condense the radioactive Cs vaporized by the heat treatment, and various types of cooling devices can be used. For example, it is possible to adopt a form such as natural cooling, forced air cooling, or forced water cooling in which the heat quantity of the high temperature exhaust gas is dissipated through the heat transfer wall. In this case, it is preferable from the viewpoint of thermal efficiency that a heat exchanger that performs heat exchange using the heating air for the heat treatment as a refrigerant is used. A cooling method in which cooling air is mixed and forcedly cooled is also preferable.

In the cooling step, the exhaust gas may be cooled to a temperature of 400 ° C. or higher and lower than 600 ° C., more preferably 500 ° C. or higher and lower than 600 ° C., and supplied to the next dust removing means.
This lower limit temperature is a condition for preventing tar in the exhaust gas from adhering to the filter, and the upper limit temperature is a condition for collecting the radioactive Cs without vaporizing the radioactive Cs.

(3) Dust removal step This is a step of removing dust containing radioactive Cs condensed by the cooling means from the exhaust gas. As the dust removal device, a ceramic or metal heat-resistant filter is used at a temperature of 400 ° C or higher. It is preferable from the point of processing gas. The heat-resistant filter preferably has a filtration particle size of 30 μm.

The following advantages can be obtained by the steps of the present invention described above.
(1) Since a normal thermal decomposition process or incineration process can be used as the heat treatment apparatus, the processing speed is high and no special equipment is required. Also, the cooling device and the dust removing device in the subsequent stage can be handled by a normal device, and this can be a very normal device.

  (2) Radioactive Cs is cooled and collected below the vaporization temperature, and it is possible to reliably prevent the radioactive Cs from being diffused out of the system, and the filter is not clogged with tar.

Claims (5)

  When removing exhaust gas generated by heat treating waste ion exchange resin containing radioactive Cs, the exhaust gas is cooled and controlled to a temperature of 400 ° C. to 600 ° C., and the radioactive Cs in the exhaust gas is collected by the dust removing means. A method for treating waste ion exchange resin.   The waste ion exchange resin treatment method according to claim 1, wherein the waste ion exchange resin containing radioactive Cs is based on a styrene divinylbenzene copolymer.   The method for treating a waste ion exchange resin according to claim 1 or 2, wherein the heat treatment is a thermal decomposition treatment or an incineration treatment performed at a temperature of 400 ° C to 1000 ° C.   The method for treating a waste ion exchange resin according to any one of claims 1 to 3, wherein the dust removing means is a dust removing device using a heat resistant filter made of ceramic or metal. The waste ion exchange resin treatment method according to claim 1, wherein the means for cooling the exhaust gas is a heat exchanger that exchanges heat with heating air used for the heat treatment.