JP2012150064A - Treatment system of spent iron-exchange resin and filter sludge in nuclear power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method and a treatment system which effectively and stably store radioactive waste such as spent iron-exchange resin and filter sludge generated in a nuclear power plant with a simple system for a long period of time.SOLUTION: The present invention is a treatment method of spent iron-exchange resin and filter sludge generated in a nuclear power plant. The treatment method dries resin by low-temperature heating by irradiating the resin with microwave under reduced pressure and stores the dried resin.

Description

  The present invention relates to a treatment system for radioactive waste such as used ion exchange resin and filter sludge generated in a nuclear power plant.

  Ion exchange resin and filter sludge (powder ion exchange resin, cellulose filter aid, etc.) used for nuclear reactor coolant purification systems and fuel pool cooling and purification systems are stored as radioactive waste after use. It has been stored in the tank for a long time. These used ion exchange resins and filter sludges are constantly generated as the nuclear power plant is operated. Therefore, it is considered necessary to have a volume reduction technology that efficiently reduces the volume of these wastes.

  The ion exchange resin is based on styrene-divinylbenzene and is chemically stable. Cellulosic filter sludge is also stable. These volume reductions usually require high temperature pyrolysis.

  As a volume reduction treatment technique for waste resin, there are JP-A-59-44699 (Patent Document 1) and JP-A-59-44698 (Patent Document 2). These patent documents describe a method of reducing the volume by adding an oxidation catalyst to a waste ion exchange resin and then irradiating it with microwaves to evaporate and remove moisture and perform heat melting, combustion or thermal decomposition. JP 59-46899 A (Patent Document 3) uses a microwave to dry and heat incinerate used ion-exchange resin, and adds a solidifying material to the volume-reduced waste container. In addition, a method for treating exhaust gas generated during thermal decomposition with plasma is described.

JP 59-44699 A JP 59-44698 A JP 59-46899 A

  In the case of the thermal decomposition methods of Patent Documents 1 and 2, since the thermal decomposition is performed by adding an oxidation catalyst and irradiating with microwaves, the ionic resin can be efficiently decomposed. However, there is a need for a treatment system for waste gas generated with combustion, in which the volume reduction rate is slightly reduced by adding the catalyst. Since the method of Patent Document 3 involves remote control by a manipulator and operation of a plasma generator, the processing system is complicated. These technologies have been studied for over 20 years, but have not been installed in existing nuclear power plants.

  Water coexists in a tank that stores used ion exchange resin and filter sludge. Water is decomposed by radiation from radioactive substances contained in used ion exchange resins and filter sludges to generate hydrogen gas. In addition, there is a possibility that the ion exchange resin is partially decomposed by radiation and the water quality in the storage tank is changed, leading to deterioration or corrosion of the inner wall of the storage tank.

  An object of the present invention is to provide a treatment method and a treatment system for efficiently stabilizing radioactive waste such as used ion exchange resin and filter sludge and storing them for a long period of time.

  The treatment system of the present invention is a system in which used ion exchange resin or filter sludge is irradiated with microwaves, heated and dried at a temperature as low as the boiling point of water, and then stored.

  Usually, in order to dry ion exchange resin and filter sludge, a method of heating from the outside with a heater or the like is used. In the external heating system, the surface of the object to be heated rises in temperature, and heat is transferred to the inside of the object to be heated by the heat conduction of the object to be heated. I need. In the case of rapid heating, if the temperature of the heat source is increased, the temperature gradient between the surface of the object to be heated and the inside becomes large, and the surface layer part may be thermally decomposed even though the internal temperature does not rise sufficiently.

  The microwave heating under reduced pressure conditions of the present invention is an internal heating method in which the object to be heated itself becomes a heating element, and can be efficiently and uniformly dried. In addition, it is possible to promptly respond to temperature adjustment during start-up and stop of the apparatus or during drying.

  In a test conducted by the inventors, it was confirmed that the ion exchange resin can be dried by irradiating the ion exchange resin with 700 W microwave for about 5 minutes. It is possible to further improve efficiency by setting the pressure reduction condition.

  According to the present invention, radioactive waste such as used ion exchange resin and filter sludge generated at a nuclear power plant can be stabilized efficiently and stored for a long period of time.

It is an irradiation test result using a microwave irradiation unit, and shows a correlation diagram between a microwave irradiation time and a drying rate. It is the schematic of the processing system of used ion exchange resin and filter sludge which is one suitable embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  The result of the microwave irradiation test to the ion exchange resin conducted by the present inventors is shown in FIG. In this test, microwave irradiation was performed on a sample simulating used ion exchange resin / filter sludge using a microwave irradiation unit. A sample simulating a used ion exchange resin / filter sludge is a sample prepared by mixing a granular cation exchange resin and an anion exchange resin in a dry weight ratio of 1: 1 and adjusting the water content to 60% by weight. The microwave irradiation unit repeatedly performed microwave irradiation for each sample for 5 minutes under atmospheric pressure under conditions of a microwave output of 700 W.

  The horizontal axis in FIG. 1 represents the cumulative time of microwave irradiation, and the vertical axis represents the weight change of the resin. When the sample resin is irradiated with microwaves, dehydration and partial thermal decomposition proceed, but an initial residue of about 40% by weight remains. On the other hand, when the microwave irradiation condition is about one-tenth of the atmospheric pressure, the boiling point of water drops to about 31 degrees, so that partial thermal decomposition does not occur. Therefore, the waste gas treatment system can be made very compact and the heating temperature can be low, so that it is expected that efficient dehydration and drying can be performed even with a small microwave irradiation amount. . Based on the above knowledge, the processing system of the used ion exchange resin and filter sludge of this example was constructed.

  FIG. 2 is a block diagram of a processing system in which the used ion-exchange resin / filter sludge is irradiated with microwaves to heat and dry the resin at a low temperature.

  The microwave irradiation processing system of the present embodiment includes a supply unit 100 that first quantifies a certain amount of resin by making a used ion exchange resin from a storage tank into a water slurry. The supply unit 100 adds pure water to transfer the resin from an existing used ion exchange resin storage tank to form a slurry and transfers it to a metering container, and the resin is quantified by the container. Excess free water is separated by a mesh provided in the metering container. In this case, it is possible to separate excess water with a filter press or the like, and in this case, a dehydration unit 110 is provided. The amount of resin received is quantified by a weight sensor, and is sent to the microwave irradiation unit 200 by a transfer unit 120 such as a bucket conveyor to a metering container that has received a certain amount of resin. The supply unit 100 includes a pure water supply tank unit 130, which is equipped with a tank mechanism for recovering excess water separated from the metering container. The recovered excess water is recycled and used for resin supply. .

  After receiving the metering container in the microwave oven 210, the microwave irradiation unit 200 adjusts the pressure condition in the microwave oven using the pressure control unit 220 that controls an appropriate decompression condition. Thereafter, the microwave generated from the microwave oscillator 230 is guided into the microwave oven from the waveguide 240, and microwave irradiation is performed. Since the microwave irradiation drying treatment system is low-temperature drying, the amount generated is smaller than the amount of waste gas generated by combustion decomposition by the conventional microwave irradiation heating combustion treatment, and most of the components in the waste gas are moisture. It can be easily removed. The exhaust gas component is purified and detoxified in the gas processing unit 300 and then released to the outside of the system.

  As an example of the exhaust gas unit, there is a treatment method using an alkali scrubber or a water scrubber. Further, a part of the water of the scrubber used here can be used with the water used in the supply unit to reduce waste.

  The container for which the microwave irradiation has been completed is transferred to the stabilization / storage unit 400 and stable and stored for a long time. An automatic processing system is formed by a control unit 500 that manages and controls each unit.

100 Supply Unit 110 Dehydration Unit 120 Transfer Unit 200 Microwave Irradiation Unit 210 Microwave Oven 220 Pressure Control Unit 230 Microwave Oscillator 240 Waveguide 300 Gas Processing Unit 400 Stabilization / Storage Unit 500 Control Unit

Claims (3)

  Used ion-exchange resin / filter sludge generated at nuclear power plants is stored by drying it at low temperature by microwave irradiation under reduced pressure. Processing method.   The used ion exchange resin / filter sludge treatment system according to claim 1, wherein a pressure condition in a microwave oven is adjusted during the microwave irradiation. In the processing system of used ion exchange resin and filter sludge generated at nuclear power plants,
A supply unit for supplying a certain amount of resin in a water slurry form of used ion exchange resin;
A microwave irradiation unit for irradiating the quantified used ion exchange resin with microwaves;
A pressure control unit that adjusts the pressure during microwave irradiation;
A stable storage unit for stabilizing and storing the residue of the used ion exchange resin after microwave irradiation;
An exhaust gas treatment unit for treating exhaust gas associated with low-temperature heat drying;
A spent ion exchange resin / filter sludge treatment system comprising a control unit for managing and controlling the supply unit, the microwave irradiation unit, the pressure control unit, and the stable storage unit.

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