JPS5946900A - Method of burning 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 The present invention relates to a method of incinerating spent ion exchange resin and filter sludge containing radioactive materials generated in nuclear power facilities using microwaves as a heating source.

Radioactive waste generated from nuclear facilities is increasing year by year. Furthermore, since storage and dumping locations for these wastes are extremely limited, there is an urgent need to develop a treatment method that has a large volume reduction effect and reduces the amount of waste generated.

Conventionally, radioactive waste has been treated by cement solidification method or asphalt solidification method. However, filter sludge and used ion exchange resin are hardly treated by these methods, and at present, they are simply stored in a '=1 trench. The main reason for this is that large volume reductions cannot be expected with the cement solidification method or asphalt solidification method. In particular, with the cement solidification method, 4 volumes of solidified material are generated for every 1 volume of filter sludge or used ion exchange resin. This results in four times as much solidified material as waste. Incineration has generally been adopted as the treatment method with the greatest volume reduction effect, but the waste to be incinerated is limited to combustible miscellaneous solids such as paper and cloth, and filter sludge/filter sludge, etc. At present, this method has hardly been applied to used ion exchange resins due to technical difficulties.

The present invention focuses on an incineration method that has a large volume reduction effect, uses microwaves as a heating source, and provides a method for incinerating used ion exchange containers and filter sludge containing radioactive waste. The purpose is to

The purpose of using microwaves as a heating source is that microwaves can heat substances from within, resulting in a fast temperature rise rate, making them suitable for heating substances with poor thermal conductivity, and that microwave output can be controlled easily. Because it is easy, heating 1iIJ
This is because it makes it easier to control.

The used ion exchange resin and filter sludge are in the form of powder or particles, and most of them have a diameter of 1 mm or less. Although some wastes, such as cellulosic sludge, are relatively combustible, most are nonflammable. Because of its small size, even if it is thrown into a regular incinerator, it will pass through the grate and fall to the bottom of the furnace. Furthermore, even if the waste is simply heated in a state where it is deposited on the hearth, in addition to its flame retardant nature, it is powdery or small-grained, making it difficult to incinerate the waste unless a sufficient supply of combustion air reaches the waste. Therefore, in order to incinerate materials in this form, the incinerator must be constructed in a manner that prevents combustible materials from falling through the grate, such as a fluid flow method, and that also provides a sufficient supply of air.

The present invention prevents powder and small-particle combustible materials from falling from a fire grate (referring to a holder that holds waste, hereinafter referred to as waste holder) without using a flow method, and also Air or oxygen is injected into the waste, and a special waste holder described below is provided so that a sufficient amount of gas with an oxygen content of 50% or more is supplied, and combustion air or oxygen is injected into the waste. However, the method for supplying gas with an oxygen content of 50 g or more is a) A method in which the gas is introduced from below the waste holder. It is possible to use a feeding method that suits the situation, such as switching to method (a) when an inconvenience occurs, such as when the ventilation resistance increases due to clogging, etc., and the waste is irradiated with microwaves from above and incinerated. This provides a method to do so. The method b) will be explained based on FIG.

The waste 2 is fed into the incinerator l from the feeder 7. Combustion air or oxygen is introduced into it, and the gas 8 with an oxygen content of 50% or more is guided into the lower part 9 of the incinerator through a hole drilled in the lower part of the incinerator, passes through the waste holding body 3, and becomes waste 2. Supplied. The waste holder 3 is made of a porous heat-resistant material or a heat-resistant packed layer, and preferably has a heat-resistant temperature of 800°C or higher.

Ceramics or sintered metals are suitable for porous heat-resistant materials, and are limited to those that have excellent breathability, heat resistance, and strength. It should not be limited. Processed ceramics and silica gel as heat-resistant fillers? Alumina etc. are suitable, but they are breathable like porous heat-resistant materials.

The material is not limited to the above materials as long as the heat resistance 7 strong inflection conditions are satisfied. These fillers are held by gilt copper or perforated plates (dispersion plates), and the packed layer should maintain an appropriate packing density and layer height for breathability and prevention of waste falling. The decomposition gas and combustion gas of the waste are discharged from the exhaust duct 10 and are separately processed and purified. The microwave 11 serving as a heating source is irradiated from above the waste 2 . The entire incinerator 1 is a metal container 5
The outer periphery is further covered with a heat insulating material to prevent heat radiation. The entire furnace is mounted on a fixed incinerator lid by means of a moving mechanism 12. 4 is a heat insulating container main body, and 6 is its lid.

As a result of incinerating ion exchange resin and filter sludge in this incinerator, the amount of incineration residue is 50% of the original amount of waste.
100 or less, a good result was obtained. Examples are shown below.

Examples Representative brands of ion exchange resins and filter sludge used in nuclear facilities were selected and tested. The results are shown in Table 1.

Table 1 (Note) Microwave frequency for heating source: 2450 MH
2I Dekaniyu KW was used.

1) Method A method in which air for combustion of waste or oxygen is introduced into it and a gas having an oxygen content of 50% or more is introduced from above the waste will be explained based on FIG.

Figure 1 is based on method (a), but the gist of method (a) is to inject combustion air or oxygen into it, lead a gas with an oxygen content of 50% or more from 10, and supply it to waste 2. , the waste gas holder 3, and the exhaust gas passes through the lower part 9 of the furnace and is discharged from the furnace 8.

The biggest disadvantage of the method of (a) supplying a gas with an oxygen content of 50% or more by injecting combustion air or oxygen from the bottom of the waste holder is that the waste or incineration residue injects oxygen into the supply air or There is a risk that it will be scattered by gases with an oxygen content of 50 or more and carried away into the exhaust gas. Some types of filter sludge have a low specific gravity and are easily scattered. If waste is scattered in an unburned state, there is a risk of increased load on the waste gas treatment system and ignition in the unburned material collection section, and if it is incineration residue, radioactivity from the waste gas treatment increases. The method shown in (2) is a method in which a load is added to the feedstock and a gas having an oxygen content of 50 parts or more is introduced from above the waste. In this method, the flame is directed downward, so the thermal efficiency is lower than that in the method (a), and there is a drawback that the waste holding body 3 is required to have higher heat resistance strength. ``i, Not at all, and the effect of scattering is great because it is prevented by the waste holder and the filter effect of the waste layer itself is taken into account.

Method c) When the combustion air or oxygen is added to the waste and the oxygen content is 50% or more, the gas is normally introduced from above the waste, but there is no ventilation resistance in the waste holding body. If the amount of waste and incineration residue increases, the method described in Method 1 below the holder can prevent scattering of waste and incineration residue, but conversely the waste holder may become clogged with them. There are cases. In such a case, the ventilation direction is reversed, i.e., by the method (a) mentioned above, the opposite air is sent to clean the waste holding body.
It may be necessary to perform a This is the ventilation force θ that can deal with such problems.

As mentioned above, when incinerating waste using microwaves as a heating source, it is necessary to diversify the method of supplying combustion air or oxygen to it, and supplying gas with an oxygen content of 50% or more. Another major factor is that the A ψ class of is becoming more 4'j*. New products are increasingly being adopted as filter aids and ion exchange resins for purifying waste liquids, and combinations of different aids are still being used in hopes of synergistic effects of the advantages of conventional products. Moreover, the impurities captured by them are also diverse. In addition, the nature of waste that is illegally incinerated becomes extremely complex, as it may undergo changes over time while being stored. From this point of view, the present invention aims to provide a method that can deal with the incineration of waste that can be considered at present.

Next, we will discuss the method of mixing incineration residue of radioactive waste with radioactive waste in advance and then incinerating it, and the method of supplying the incineration residue of radioactive waste to the lower layer and the radioactive waste to the upper layer and then incinerating it.

Microwave heating is called 7iL heat, and heat is generated by consuming microwave star energy within a dielectric body, and the condition is that the object to be heated is a dielectric body.

The magnitude of the dielectric loss determines whether the material is easily heated or heated. The present invention focuses on the fact that radioactive waste incineration residue exhibits a large loss of 7L, and aims to speed up heating by mixing it with radioactive waste that is to be incinerated in advance. It is something.

The main constituents of radioactive waste such as filter sludge and used ion exchange resin are organic substances. Therefore, when it is incinerated, a residue called 19 [subcarbide] rich in carbonaceous substances remains as an incineration residue.

This residue is heated from the outside, air or oxygen is injected into it, and by supplying enough gas with an r1!2 element content of hL of 50% or more, it burns slowly like a brick, and finally Leaves ash. The amount of carbide residue left after normal incineration is relatively large;! Approximately 115 to 1/1 of the stored waste
0, and when it is further burnt and becomes ash, it becomes less than 1/100. This ash-containing char has a much larger dielectric loss than the waste before combustion. Therefore, by mixing this in advance with waste having a small dielectric loss, it is possible to shorten the combustion time for charred waste. According to illegal examples, the moisture content of the waste shown in Table 1 is
/J Adjust to 50%. In advance, incineration residue of Sohachi waste (
A mixture of carbide) was prepared, and 20-50% of the waste fruit with a water removal rate of 50% was added to it and mixed uniformly. As a result of irradiating this mixed waste with microphone Lj waves, the following results were obtained. That is, when the amount of carbide mixed is 20%, the required combustion time is increased by about 20%, and when the amount of carbide mixed is 50%, it can be shortened to 1/2. From this, it was found that the time required for combustion is approximately proportional to the amount of carbide -hl- to be mixed. HL of the carbide to be mixed: f: If it is less than 20%, it will not be effective, and if it is more than 50%, the amount of waste to be treated will decrease, and the rapid acceleration of the combustion rate will cause problems with temperature rise and supply. Gas equipment with an oxygen content of 50 parts or more (+III or exhaust gas treatment equipment) by adding oxygen to the supplied air or to it with an increase in air volume, air waste, and -ri.
The amount of charred material to be mixed is preferably 0.4 to 1,000 to 1,000 yen per the drying standard of waste.

Next, as shown in Figure 2, incineration residue 13 is placed in the lower part,
A case in which radioactive waste is put into the container and heated and incinerated in a constant state will be described below. This method also involves incineration.
・Carbide, which is the main component of carbon dioxide, exhibits a large dielectric loss.
5'iii'i Since it is a microwave heating element, it further promotes the heat generation of the radioactive waste itself from the bottom, showing a remarkable effect.The results obtained were almost the same as the above-mentioned mixing. However, it has been confirmed that the heating acceleration effect reaches almost saturation when the amount of carbide residue is 1 weight or more per 1 weight of the dry standard amount of waste.From this, it can be seen that the amount of char residue is approximately 1 weight per 1 weight of the dry standard amount of waste. and shall be 0.4 or more.

The actual driving operation method according to the present invention can be easily contracted to the following three methods.

(1) Putting combustible radioactive waste into an incinerator (single heating method) (2) Putting a mixture of combustible radioactive waste and their incineration residue into the incinerator.

(Mixed heating method) (3) Put combustible radioactive waste on top of the incineration residue. (Two-layer heating method) After charging, irradiate with microwaves and incinerate. Waste is input according to the amount of incineration. The end point of incineration is determined by the radioactivity concentration of the incineration residue. That is, it should be incinerated at a radioactive concentration that does not exceed the surface dose rate of the final solidified material or the legal limit.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show examples of implementation according to the present invention. l...Incinerator, 2...Waste, 3...
...Waste holding body, 4...Insulating container body,
5...metal container, 6...lid, 7...
...Feeder, 8...Combustion air or oxygen is added to it, and gas with an oxygen content of 50 parts or more, 9...
...lower part of the furnace, 10...exhaust duct, Jl...
...Microwave, 12... Moving mechanism, 13...
...Incineration residue layer. Representative Patent Attorney Tadashi Shiozaki Hiroyasu / G Tsutomu 22 Procedural Amendment (Method) % Formula % 1. Indication of the case 1982 Patent Application No. 15'7733 2 Name of the invention Radioactive waste incineration method 3 Relationship with the case of the person making the amendment Patent applicant address 11-1 Haneda Asahi-cho, Ota-ku, Tokyo Name (
O2a) Ebara Corporation Representative Kiyoshi Akiyama 4 Agent Eng 101 5 Date of supplementary order

Claims (1)

[Scope of Claims] l In an incinerator that incinerates waste such as used ion exchange resin and filter sludge containing radioactive materials, a holder for holding the waste is provided in the furnace to prevent the waste from falling. An incineration method characterized by comprising a porous heat-resistant plate or a heat-resistant material-filled layer that provides air permeability, leads combustion air to the waste, and incinerates the waste using microwaves as a heating source. 2. The method according to claim 1, characterized in that combustion air or oxygen is introduced into it, and the gas having an oxygen content of 50q6 or more is introduced from below the holder when being supplied to the waste. 3. The method according to claim 1, characterized in that combustion air or oxygen is introduced into it, and when the gas having an oxygen content of 50 parts or more is supplied to the waste, it is introduced from above the waste. 4 When injecting combustion air or oxygen into it and supplying a gas with an oxygen content of 50 parts or more to the waste, it is usually introduced from above the waste, but this increases ventilation resistance in the waste holding body. In such a case, the method according to claim 1, wherein the method can be guided from below the holder. 5. The method as set forth in claim 1, wherein the incineration residue of radioactive waste is mixed with the radioactive waste in advance and then incinerated. 6. The method according to claim 2, in which incineration residue of radioactive waste is supplied to the lower layer and radioactive waste is supplied to the upper layer and then incinerated.