JPS61262699A - Method and device for treating radioactive waste ion exchange resin - 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 method and apparatus for safely and easily processing radioactive waste ion exchange resin generated in nuclear power plants and the like.

[Conventional technology]

Nuclear power plants discharge large amounts of used waste ion exchange resin that is tinged with radioactivity. This kind of waste resin is the largest type of radioactive waste generated during regular operation of nuclear power plants, and since no effective treatment method has been established for it, it is actually stored in drums as is. . In addition, attempts have been made to reduce the volume of these waste resins, including dry incineration and oxidative decomposition using chemicals.

[Problem that the invention seeks to solve]

Among the above-mentioned conventional disposal methods, the method of packing and storing waste in drums has the problem that it requires a vast storage area and is subject to space constraints because the amount of waste increases over time. Therefore, it is desired to establish a technology for reducing the volume of waste resin. Although it is possible to reduce the volume of waste with the incineration method.

There was a problem in that a large amount of radioactive gas and dust were generated during incineration, and large-scale equipment and costs were required to dispose of them.

This invention was made in view of the current situation as described above.
It is an object of the present invention to provide a method and apparatus for processing radioactive waste ion exchange resin that can safely and easily reduce the volume by carbonizing and incinerating the radioactive waste ion exchange resin.

[Means for solving problems]

The present invention provides the following method and apparatus for treating radioactive waste ion exchange resin.

(1) A method for treating radioactive waste ion exchange resin, which includes the steps of drying the radioactive waste ion exchange resin, thermally decomposing and carbonizing the dried resin, and incinerating the char produced by carbonization.

(2) A mixing section that mixes radioactive waste ion exchange resin with carbon, a drying section that heats and dries the mixture supplied from this mixing section by placing it between electrodes, and drying that is supplied from this drying section. A treatment device for radioactive waste ion exchange resin, comprising a thermal decomposition section that heats and carbonizes materials by placing them between electrodes, and an incineration section that incinerates the char supplied from the thermal decomposition section.

[For production]

In the method for treating radioactive waste ion exchange resin of the present invention, the radioactive waste ion exchange resin is dried, then thermally decomposed and carbonized, and the generated char is incinerated. The ash produced by incineration can be made into lumps by compression molding, sintering, etc., thereby making it possible to reduce the volume of waste. Also the steam generated,
Although cracked gas and combustion gas are processed separately, they are small in amount and do not involve dust, so they can be easily processed.

In addition, in the radioactive waste ion exchange resin treatment apparatus of the present invention, the radioactive waste ion exchange resin is mixed with carbon components such as waste activated carbon and returned char in the mixing section, and this mixture is interposed between the electrodes of the drying section and energized. It is heated and dried, and the dried product is placed between electrodes in a thermal decomposition section and heated with electricity to carbonize it by thermal decomposition, and the generated char is incinerated in an incineration section. This makes it possible to safely and easily process and reduce the volume of radioactive waste ion exchange resin.

〔Example〕

Hereinafter, the present invention will be explained with reference to embodiments of the drawings.

The drawing is a system diagram of the embodiment. In the drawing, 1 is a mixer, with which a waste resin tank 2 is connected via a pump 3 and a dehydrator 4, and an activated carbon tank 5 and a recycled carbon tank 6 are directly connected. The dehydrator 4 is preferably a centrifugal machine, but may be a trommel type dehydrator or other dehydrators.

7 is a decomposition device, which has a drying section 8 at the top and a thermal decomposition section 9 at the bottom, a cylindrical passage 10 passing through these, and a mixer 1 communicating with the top thereof. Drying section 8
The thermal decomposition section 9 has almost the same configuration, and porous electrodes 11a, llb..., and 12a are provided in multiple stages facing each other so as to constitute a part of the cylindrical wall of the passage 10, respectively. .

12b..., agitators 13a, 13b provided in the passage 10 between these electrodes, and casings 14a, 14b covering these from the outside of the passage 10 for each drying section 8 and pyrolysis section 9. There is.

Although the passage 10 may be cylindrical or rectangular, a vertical passage is preferable because the resin can be transferred by gravity, and a membrane-shaped passage is provided with a piston or the like to transfer the resin. Porous electrode 11a
..., 12a... can be made of sintered stainless steel powder, etc. If the passage 10 is cylindrical, it is formed into a curved plate shape, and when it is a rectangular cylinder, it is formed into a flat plate shape. every 9
They are arranged in an insulated state, facing each other with a phase difference of 0°, and the facing parts are connected to the power supply device 15 in parallel. The power supply device 15 may be an alternating current or a direct current, but an alternating current is preferable.

The agitators 13a and 13b are used to agitate the mixture flowing down the passage 1o so as to uniformly heat the mixture by applying electricity, and may be a known static mixer, for example, one in which twisted plates are arranged in series in a pipe at an angle of 90°. etc. are available. A rotary valve 16 is provided at the bottom of the passage 1o.

A distributor 17 is provided opposite to the lower part of the passage 10, and a char cooling tank 18 is disposed at one outlet thereof and communicates with the recycled char tank 6.

An incinerator 19 is arranged at the other outlet of the distributor 17, a combustion table 21 having a heater 2o inside is supported by a vibrator 22, and an air supply port 23, an exhaust port 24 and an ash discharge port 25 are provided on the outside. It is provided.

The casing 14a of the drying section 8 is connected to a cooler 26, and the casing 14b of the pyrolysis section 9 is connected to a cracked gas incinerator 27. In addition, the cracked gas incinerator 27 and the incinerator 19
The exhaust port 24 of the incinerator 19 is connected to a dust removal device 28, and the ash discharge port 25 of the incinerator 19 (also connected to a sintering device 30 via a pressure forming device 29).

The method for treating radioactive waste ion exchange resin using the radioactive waste ion exchange resin treatment apparatus configured as described above is as follows. First, the waste resin 31 is transferred to the waste resin tank 2 in the form of a slurry containing a large amount of water, sent to the dehydrator 4 by the pump 3 to be dehydrated, and then supplied to the mixer 1.

On the other hand, waste activated carbon 32 is supplied from the waste activated carbon tank 5 to the mixer 1 and mixed with waste resin. Here, the waste activated carbon is mixed as a carbon component, and if there is no waste activated carbon, fresh activated carbon or other carbon components may be used. Since char is generated after the start of operation, the recycled char 33 can be mixed as a carbon component, and there is no need to mix waste activated carbon or the like. The reason why carbon is mixed here is to lower the electrical resistivity of the waste resin and make it easier to heat it with electricity, and the mixing of carbon physically destroys the pure water film around the waste resin. At the same time, the voids are filled and the electrical resistivity is reduced. The mixing ratio of carbon content is 0.1 per part by weight of waste resin.
-1.5 parts by weight, preferably 0.3 to 0.7 parts by weight.

The mixture 34 of the mixer 1 is supplied to the upper part of the passage 1° of the decomposition device 7, and flows down the passage 10 through the drying section 8 and the thermal decomposition section 9 in sequence while being stirred by the agitators J113a and 13b. In the drying section 8 and the pyrolysis section 9, the porous electrode 11a
A voltage is applied from the power supply device 15 to... and 12a..., and electrical heating is performed through the mixture between the electrodes.

The electrical heating is based on Joule heat, whereby the mixture is dried in the drying section 8 and carbonized in the thermal decomposition section 9 to become char 35.

The ability of electrical heating is determined by the electrical resistivity of the mixture within passageway 10 and the applied voltage. Electrical resistivity is determined by the mixing ratio of carbon to waste resin and the pressure and temperature of the mixture, but it is generally 200 to 2 at around 100°C.
000Ωl, preferably about 400 to 500Ω1. Also, the pressure of the mixture indicates the degree of compression of the mixture, 1
0~200g/a! , preferably 20 to 50 g/ffl
That's about it. The applied voltage varies depending on the spacing between the electrodes, but is about 10 to 200V, preferably about 40 to 100V.

The mixture in the passage 1o is supported by the rotary valve 16, so in the case of a vertical type, the pressure from the top becomes the pressure necessary for energization heating, but if further pressure is required, the mixture at the top of 1 passage 1o is A screw feeder or the like may be provided to apply pressure.

In the drying section 8, water in the mixture is evaporated by electrical heating, and steam 36 is produced through the porous electrodes 11a..., 12a...
The casing 14a is taken out to the cooler 26, and the condensate 38 generated by cooling with the cooling water 37 is sent to the water treatment line together with the waste water 39 of the dehydrator 4 and treated.

The dried material 4o flowing down from the drying section 8 is further heated with electricity in the thermal decomposition section 9 to raise its temperature, and is carbonized by thermal decomposition to become char 35. The gas generated here passes through the porous electrodes 11c..., 12c... to the casing 1.
4b is taken out as cracked gas 41 and incinerated in a cracked gas incinerator 27.

The char 35 is intermittently taken out by the rotary valve 16, and the decomposition device 7 is also operated intermittently.

Continuous operation may be performed by taking out the char continuously.

The taken out char is distributed by a char distributor 17, a part of which is cooled in a char cooling tank 18, and returned to the recycled char tank 6 as a recycled char 33.

The other part of the char distributed by the distributor 17 is sent to the incinerator 19.
While descending on the combustion platform 21 which is vibrated by the vibrator 22, it is ignited by the heater 20 and combusts. Heating by the heater 20 is only necessary at the beginning, and after ignition, spontaneous combustion occurs. Air 42 necessary for combustion is taken in from the air supply port 23, combustion gas 43 is discharged from the exhaust port 24,
Dust removal device 2 together with combustion gas 44 of cracked gas incinerator 27
At step 8, the dust is removed. Incineration ash 45 from the incinerator 19 is taken out from the ash outlet 25, pressure-formed in a pressure-forming device 29, and then sintered in a sintering device 30.

The condensate 38 and waste water 39 generated in the above treatment can be returned to the water treatment line and easily treated. Also, cracked gas 41
The amount of gas generated is smaller than the amount of combustion gas generated by the direct combustion method of waste resin, and since it is volatile and does not contain dust, 1 decomposition gas incinerator 27
can be easily and safely processed without auxiliary fuel. The combustion gas 44 is similarly small and does not contain dust, so dust removal is easy.

Since the combustion of char in the incinerator 19 is the combustion of carbon, no auxiliary fuel is required, no extra air is required, and the amount of combustion gas 43 generated is small. Also, combustion gas 4
Since the amount of dust in No. 3 is extremely small, it can be easily disposed of by the dust removal device 28. The incineration ash generated by combustion is mainly composed of inorganic substances captured by waste resin, and the amount thereof is small. This incinerated ash is further reduced in volume by pressure forming and sintering to form a shape suitable for handling and storage.

As described above, according to the above treatment method, radioactive waste ion exchange resin can be safely and easily reduced in volume, and the volume reduction rate is high. Furthermore, the processing equipment has a simple structure, can be operated at normal pressure, is highly safe, and can be automated and remotely operated.

In addition, in one or more processes, the waste heat generated can be recovered and used. In this case, the waste heat of the incinerator 19.27 can be used for drying, or the steam 36 can be cooled by using waste resin. You can also preheat it.

Next, the test results will be explained.

After dehydrating the waste resin with a water content of 30 to 40% by weight from simulated wastewater using a centrifugal dehydrator, the waste resin and activated carbon are mixed at a weight ratio of 4:1, and the mixture is supplied to the decomposition device 7 to generate an interelectrode voltage of 20V.
It was dried in a drying section 8 and carbonized in a thermal decomposition section 9. The generated char is incinerated in the incinerator 19, and the incinerated ash is 1156k
When pressure molded at g/cJ, the dry matter capacity was 10
The capacity was 4.50 compared to 0. The volume reduction rate at this time was 95.5% by volume. In addition, this molded product has a filling rate of 40
The volume reduction rate when stored in a container with a capacity of 88.
8% by volume. When the above molded product was sintered by heating at 1000°C for 90 minutes, the average value of fracture stress was 290.
kg/al.

〔Effect of the invention〕

According to the treatment method of the present invention, the radioactive waste ion exchange resin is carbonized and incinerated, so radioactive waste can be safely and easily reduced in volume, the volume reduction rate is high, and the waste gas generated , there is little wastewater, etc., and its treatment is easy.

Moreover, according to the treatment apparatus of the second invention, the structure and operation are simple, and radioactive waste ion exchange resin can be safely and efficiently treated to render it harmless.

[Brief explanation of the drawing]

The drawing is a system diagram showing an embodiment, and 1 is a mixer. 4 is a dehydrator, 7 is a decomposition device, 8 is a drying section, 9 is a thermal decomposition section, 11a..., 12a... are porous electrodes, 18 is a char cooling tank, 19 is an incinerator, 27 is a cracked gas incinerator,
28 is a dust removal device.

Claims (8)

[Claims] (1) A method for treating radioactive waste ion exchange resin, which includes the steps of drying the radioactive waste ion exchange resin, thermally decomposing and carbonizing the dried resin, and incinerating the char produced by carbonization. (2) The treatment method according to claim 1, wherein the drying and carbonization steps are carried out by electrical heating. (3) The treatment method according to claim 2, wherein the electrical heating is performed by mixing the resin with a carbon component. (4) The treatment method according to claim 3, wherein the carbon component is waste activated carbon or char produced in a subsequent process. (5) A mixing section that mixes radioactive waste ion exchange resin with carbon, a drying section that heats and dries the mixture supplied from this mixing section by interposing it between electrodes, and drying that is supplied from this drying section. A treatment device for radioactive waste ion exchange resin, comprising a thermal decomposition section that heats and carbonizes materials by placing them between electrodes, and an incineration section that incinerates the char supplied from the thermal decomposition section. (6) The processing apparatus according to claim 5, wherein the carbon content is char returned from the pyrolysis section. (7) The processing apparatus according to claim 5 or 6, wherein the electrodes of the drying section and the pyrolysis section are porous electrodes. (8) The processing apparatus according to any one of claims 5 to 7, wherein the drying section and the thermal decomposition section have stirring means between the electrodes.