JPS6363878B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reducing the volume of radioactive miscellaneous combustible waste generated in nuclear facilities.

Nuclear equipment such as nuclear power plants generate large amounts of combustible miscellaneous solid waste. The amount generated during periodic inspections is particularly large, and the annual amount generated reaches about 1,000 drums (200 drums) at a 1,000 MWe twin unit light water reactor nuclear power plant. In Japan, until recently, this waste has been canned in drums and stored on-site. However,
Due to the large number of drums generated, it became clear that the time would come sooner than expected when they would no longer be able to store them on-site due to space constraints, and incineration treatment with a large volume reduction ratio of approximately 80 was judged to be promising. As a result, incineration of these flammable miscellaneous solids has actually begun.

Currently, radioactive combustible miscellaneous solids that are considered to be incinerated include paper, paper waste, clothing, cloth waste, polyethylene, wood, and flammable air conditioning filters.

Among these, wood is mostly used as scaffolding during periodic inspections, but recently metal has been replaced, and this occurrence is rare. Furthermore, although flammable air conditioning filters have recently been developed, the number of facilities that have adopted them is small, and the incineration process is still on a trial basis. Therefore, it is found that in order to reduce the number of drums of flammable miscellaneous solids currently generated in radiation handling facilities, it is effective to reduce the volume by incinerating paper, paper waste, clothing, cloth waste, and polyethylene. .

These flammable miscellaneous solids are also included in municipal waste.
As it belongs to a category of municipal waste that is relatively easy to incinerate, we have developed a radioactive combustible miscellaneous solids incinerator using the method used in municipal waste incineration facilities with some improvements from the standpoint of radiation protection. The reality is that it is being misappropriated. Therefore, the method of supplying radioactive combustible miscellaneous solids to the incinerator is also similar to municipal waste. Essentially nothing has changed.

There are various incineration methods such as bed combustion method, grate combustion method, packed bed combustion method, moving bed combustion method, moving grate combustion method, rotary kiln combustion method, and fluidized bed combustion method. Supply methods can be broadly divided into two types: batch type and continuous type. From the perspective of stable operation of the incinerator,
Although the continuous type is superior, each of the conventional types has the drawbacks described below, and it is difficult to say that they are sufficient for application to radioactive waste treatment.

In the conventional batch system shown in FIG. 1, combustible miscellaneous solids generated in facilities handling radioactive materials are usually collected in a waste storage site 1 in a state packed in polyethylene bags. The bags are opened manually and the non-combustibles are separated.
After repacking the appropriate amount into a small bag, it is intermittently poured into the incinerator 2 from the top. This has the following drawbacks.

(b) All work is done manually, requiring a great deal of labor and leading to an increase in radiation exposure.

(b) Due to intermittent feeding, the amount of material to be burned in the furnace, furnace temperature, heat load, amount of combustion gas, combustion conditions, etc. fluctuate, which tends to cause incomplete combustion.

(c) For this purpose, it is necessary to adjust the supply while monitoring the combustion state, but it is difficult to automate this process.

(d) Due to incomplete combustion, volume reduction is reduced and exhaust gas after-treatment becomes troublesome.

(e) Since waste is separated without being crushed, accurate separation is difficult, and non-combustible materials are likely to get mixed in, causing problems.

In addition, in the conventional continuous system shown in Fig. 2, bagged waste at a temporary waste storage site is crushed as is in a crusher 3, placed in a storage hopper 4, and then transported to an incinerator 2.
, and is continuously fed to the incinerator 2 by a feeder 6 at the bottom of the feed hopper 5 . Although this method of crushing has the advantage that it is relatively easy to separate and recover metals, etc., the conventional method has the following drawbacks.

(b) The amount of combustible miscellaneous solids that must be treated in radioactive handling facilities is extremely small compared to that in municipal waste incinerators. For this reason, the supply amount becomes very small, and the following problems arise in the crushed state, and it is necessary to solve these problems.

(i) Dry cloth has a very small apparent density after being crushed, so it is very difficult to take out a quantitative amount, and it is easy to form brittleness even in a container.

(ii) Wet paper rags tend to adhere to the vessel walls, etc., making it difficult to cut out a fixed amount and also difficult to transport.

(b) There is a high risk that fine powder or cotton lint produced by crushing will be carried out of the furnace without being incinerated by air currents.

As mentioned above, when continuously incinerating combustible miscellaneous solids generated in conventional radioactive waste handling facilities, the amount to be processed (that is, the amount supplied to the incinerator) is very small, and a satisfactory quantitative cutting machine and transport method are required. There was no way. If this can be achieved, an incineration process suitable for incinerating radioactive waste, that is, capable of highly reliable and stable operation, will be possible.

The object of the present invention is to provide a processing method that satisfies this problem.

That is, the present invention crushes radioactive combustible waste using a crusher, compresses the crushed waste using a compressor to form pellets, and continuously feeds the compressed waste pellets into an incinerator. A method for disposing radioactive miscellaneous combustible waste, which is characterized by transporting and incinerating it to reduce its volume.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to preferred embodiments illustrated in FIG. 3 of the accompanying drawings.

According to one embodiment of the present invention shown in FIG. 3, radioactive miscellaneous combustible waste packed in polyethylene bags in the temporary waste storage site 1, such as paper, paper waste, clothing, cloth waste, etc., is shredded while still being packed in the bag. It is crushed by machine 3. The thus crushed waste is then separated, and after removing impurities such as metals, it is fed into a compression molding machine 7 and compression molded into pellets.

As this compression molding machine 7, a piston compression molding machine shown in FIG. 4 is suitable. i.e. axis 1
The crushed waste is put into a cylinder hole 8 formed in a disk 12 which rotates about 1, and is compressed and formed into pellets 10 by a piston 9.

This piston method is the simplest method, but the compression method is not limited to this.For example, it is also possible to compression mold the pellets into strings using an extruder or other extruder, and then cut them into appropriate sizes to make pellets. be.

The pellets compressed in this way are led to a hopper 5, and from there are transported to an incinerator 2 by a feeder 6.
It is continuously supplied to the factory and incinerated to reduce its volume.

According to the method of the present invention, the following effects can be achieved.

(1) By compressing the crushed material into pellets, the volume can be reduced, and the storage and supply hoppers can be made smaller. In some cases, one of the hoppers can be omitted as shown in FIG.

(2) The apparent density of the crushed material was very low, making it difficult to handle it, but compression molding dramatically improves handling properties.

(3) Related to this, it is possible to supply a fixed amount to the incinerator using a regular screw feeder, pneumatic transport, etc., which greatly contributes to the stable operation of the incinerator.

Experimental examples of the method of the present invention are shown below.

Paper, paper waste, clothing, cloth waste polyethylene sheets, etc. are crushed into 10 to 30 mm pieces using a cutter mill type crusher, and then crushed into φ (diameter) 20 mm x t (length) 5 mm pieces using a hydraulic press at a pressure of 100 kg/ ^cm2 . It was formed into cylindrical pellets of the same size.

As a result of the above, the physical properties of the crushed material were improved as shown below.

Γ Apparent density 0.001~0.1g/cm ³ ⇒0.4~0.9g/
cm ³ Γ Moisture content 30% or more⇒approximately 10% When the pellets obtained by the above operation were subjected to incineration treatment, the following effects were observed.

(1) Commonly used rotary leaf feeder,
The screw feeder allows easy quantitative cutting. Handling has also been dramatically improved.

(2) Bridge formation within the crushed material hopper has disappeared.

(3) The problem of incinerated materials being carried by the air current inside the furnace and being discharged outside the furnace in a non-flammable state has been completely eliminated.

(4) The combustion conditions inside the furnace were extremely stable, and operational controllability was improved.

[Brief explanation of drawings]

FIG. 1 is an elevational view explaining the conventional batch-type processing method, FIG. 2 is an elevational view explaining the conventional continuous-type processing method, FIG. 3 is an elevational view explaining the method of the present invention, and FIG. The figure is an elevational view of one example of a compression molding machine used in the method of the present invention. 1... Temporary waste storage site, 2... Incinerator, 3... Shredding machine, 4... Storage hopper, 5... Supply hopper, 6
... Supply feeder, 7 ... Compression molding machine, 8 ... Cylinder hole, 9 ... Piston, 10 ... Pellet,
11...axis, 12...disk.

Claims (1)

[Claims] 1 Radioactive miscellaneous combustible waste is crushed using a crusher, the crushed waste is compressed into pellets using a compressor, and the waste pellets thus compressed and formed are continuously sent to an incinerator. A method for disposing radioactive miscellaneous combustible waste, which is characterized by incinerating it and reducing its volume.