JPH04132999A - Decontamination of radioactive waste - Google Patents

Abstract

PURPOSE:To make a screw conveyer and the like, unnecessary, and to enable stable contamination treatment for long time by providing a cascading sorter and the like just below a blasting decontamination device, and by constituting the system so that the cascade sorting may be conducted right after the blasting treatment. CONSTITUTION:First of all, abrasives are supplied to a blasting device 10 and an exhaust blower 14 is actuated. After that, radioactive metallic waste 2 is transported into a blasting room 1 and the abrasives are spouted from a nozzle 3 to conduct the blasting treatment. During the treatment, floating dusts in the blasting room 1 are exhausted via a pipe route 13 and is initially sorted by a bag filter 11, as well. The abrasives after the blasting treatment fall down to a lower part and fed to a cascade sorter 4 to be fed from a feed hole 5 and to be sorted by clean air. Also during this treatment, floating fine dusts in the sorter 4 are fed to the bag filter 11 via the pipe route 13. The abrasives sorted by the sorter 4 are tentatively stored in a hopper 7 and then supplied to a cyclone sorter 8. The sorted grinding dusts are stored in a collecting container 6 of the grinding dusts.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to blast decontamination of radioactive metal waste, and in particular to a method for decontaminating radioactive waste using an improved classification device for classifying abrasive material and grinding dust. This relates to dyeing equipment.

(Prior Art) FIG. 3(a) is a diagram showing an example of a conventional radioactive waste decontamination apparatus. In the example shown in FIG. 3(a), radioactive metal waste 41 is blast decontaminated in a blast chamber 42 by an abrasive material discharged from a blast nozzle 43. The abrasive material and grinding dust after blasting are removed by exhaust blower 4.
4 and separated into air containing abrasive material and grinding dust in a cyclone classifier 45. The separated abrasive material is recycled and used, and the separated air containing grinding dust is passed through a bag filter 46 and HEPA. It was led to an exhaust treatment system consisting of a filter 47 for treatment.

In the above-described decontamination apparatus, when radioactive metal waste is blasted using an abrasive material, most of the radioactive substances adhering to the metal surface become grinding dust and are separated from the metal surface. Therefore, when the abrasive material is recycled and used as in the decontamination device described above, it is necessary to completely separate the abrasive material from the grinding dust.

(Problem to be solved by the invention) However, in the classification method using a cyclone as in the conventional decontamination equipment described above, the proportion of abrasive material transferred to the air side is small, but conversely, there are some abrasive particles in the abrasive material. There was a problem that a large proportion of dust was mixed in. There is also a classifier that uses a cyclone that has improved this point, but it has a problem that the structure is complicated and radioactive substances tend to accumulate. Furthermore, since the air mixed with the abrasive material, grinding dust, and fine powder dust is sent to the classifier through two pipes, there is also the problem that classification cannot be performed in the blast chamber.

On the other hand, the problems of the cyclone classifier mentioned above are solved,
In order to improve the classification accuracy of radioactive waste, Fig. 3 (b)
As shown in FIG. 3A, an example is known in which a cascade classifier 48 is provided in place of the cyclone classifier 45 with the same configuration as in FIG. 3(a).

However, even in the example using the cascade classifier shown in FIG.
etc., there was a problem that grinding dust was likely to accumulate. As a result, the abrasive material is contaminated by contact with the grinding duct in the vicinity of the screw conveyor, and maintenance of these devices becomes complicated.

Furthermore, there is a problem in that the abrasive material comes into frequent contact with the grinding dust, and the abrasive material is easily contaminated.

An object of the present invention is to solve the above-mentioned problems and provide a radioactive waste decontamination device that can more completely separate abrasive material and grinding dust and achieve highly accurate decontamination. .

(Means for Solving the Problems) The radioactive waste decontamination device of the present invention includes a blast decontamination device that blasts and decontaminates radioactive metal waste in a sealed state;
A radioactive waste decontamination device comprising a classification device that classifies radioactive waste after blast decontamination into abrasive material and grinding dust, and an exhaust treatment device that processes exhaust gas containing the classified dust, wherein the classification device is characterized by comprising a cascade-type first classification device installed directly below the blast decontamination device, and a cyclone-type second classification device installed downstream of the first classification device. It is something to do.

(Function) In the above configuration, in order to avoid contact between the abrasive material and the grinding dust as much as possible during classification of radioactive waste, a cascade classifier is installed directly below the blast decontamination device, and the cascade classification is performed immediately after blasting. However, since the use of a screw conveyor etc. is eliminated, there is no place where grinding dust accumulates, and contamination of the abrasive material can be prevented.

In addition, a cyclone classifier was installed downstream of the cascade classifier, making it possible to classify radioactive waste twice.
In addition to improving the accuracy of classification, since a cyclone classifier is provided as the second classifier, there is no need to install a screw conveyor or the like between the cascade classifier and the cyclone classifier. Since there is no part where grinding dust accumulates, contamination of the abrasive material can be similarly prevented.

(Example) FIG. 1 is a diagram showing the configuration of an example of a radioactive waste decontamination apparatus of the present invention. In the example shown in Figure 1, 1 is a sealed blast chamber of a blast decontamination device, 2 is radioactive metal waste to be decontaminated, 3 is a nozzle for discharging abrasive material used for blasting, and 4 is a blast chamber. 1 is a cascade classifier installed directly below 1, 5 is a supply port for clean air used for classification in cascade classifier 4, 6 is a collection container for the grinding dust classified by cascade classifier 4, 7 is cascade classifier 4
8 is a cyclone classifier provided downstream of the cascade classifier 4, 9 is a pipe connecting the hopper 7 and the cyclone classifier 8, 10 is a hopper for storing the abrasives classified by the cyclone classifier 8. A blasting device for circulating the abrasive material into the blasting chamber, 11 a bag filter for separating the grinding dust classified by the cyclone classifier 8, 12
13 is a HEPA filter that further filters the grinding dust that has passed through the bag filter 11, and 13 is a blast chamber 1.
and the bag filter 11, between the cascade classifier 4 and the bag filter 11, and between the cyclone classifier 8 and the bag filter 11; 14 is a grinding dust and blast chamber in the cyclone classifier 8; 1 and the cascade separator 4 through a pipe line 13, a bag filter 11, and a HEPA filter 12.

The actual operation of the radioactive waste decontamination apparatus of the present invention described above is as follows. First, abrasive material used for blasting operation is supplied to the blasting device 10, and the exhaust blower 1
Next, the radioactive metal waste 2 is carried into the blast chamber 1, and abrasive material is ejected from the nozzle 3 to perform blasting.

At this time, the fine dust floating in the blasting chamber 1 is supplied to the bag filter 11 along with the exhaust through the pipe 13, and is primarily classified. The abrasive material after the blasting process falls to the bottom, is supplied to the cascade classifier 4, and is classified by clean air supplied from the supply port 5. Similarly, at this time, the fine dust floating in the cascade line splitter 4 is transferred to the pipe line 13.
The air is supplied to the bag filter 11 together with the exhaust air through the air.

The abrasive material classified in the cascade classifier 4 is temporarily stored in a hopper 7 and passed through a pipe 9 to a cyclone classifier 8.
supplied to Since the downstream classifier is the cyclone classifier 8, the abrasive material can be vacuum conveyed via the pipe line 9. Here, the pipe flow rate is preferably 20+e/s or more. The classified grinding dust is stored in a grinding dust collection container 6.

The abrasive material supplied to the cyclone classifier 8 is classified again in the cyclone classifier 8, and the fine dust after classification is guided to the exhaust system via the pipe 13, and the abrasive material after the classification is returned to the blasting device 10. , similar processing is performed.

FIG. 2 is a diagram showing the configuration of an example of a radioactive waste classification device used in the present invention. In the example shown in Figure 2, 2
1 is an input port for radioactive waste consisting of abrasive material and grinding dust, 22 is a supply port for clean air used for classification, 23 is an adjustment damper for adjusting the amount of clean air to be supplied, 2
4 is a sieve for removing large wastes from radioactive waste, 25
-1 to 25-4 are classification plates tilted at a certain angle, and 26-1 to 26-4 are classification plates 25-1 to 25.
Collision plates 27a and 27b for radioactive waste are provided at the lower end of -4 at a certain interval, and introduction plates 27a and 27b are used to guide the radioactive waste after passing through the sieve 24 to the classification plates 25-1 to 25-4. , 28 is a discharge port for discharging the abrasive material after classification, 29
30 is an exhaust nozzle for exhausting fine powder floating dust and generating a flow of clean air in the device; 31 is a collection port for collecting the grinding dust after classification; A partition plate 32 for guiding the grinding duct to the collection port 29 is the grinding dust accumulated in the collection port 29.

In the above-described classification apparatus of the present invention, radioactive waste consisting of abrasive material and grinding dust to be classified is input into the apparatus from the input port 21, and first! 124 to remove large waste. The radioactive waste from which large wastes have been removed descends along the introduction plates 27a and 27b, and falls from the tip of the introduction plate 27b toward the classification plate 25-1. During this falling, the radioactive waste comes into contact with the flow of clean air supplied from the clean air supply port 22 toward the exhaust nozzle 30 via the lower opening of the partition plate 31, and the light grinding dust is removed from the clean air. It is carried by the flow toward the exhaust nozzle 30 via the lower opening of the partition plate 31, and along the way, a part of the light grinding duct settles due to gravity and reaches the recovery port 29 of the grinding duct.
As the heavy abrasive material accumulates, the heavy abrasive material descends along the classification plate 25-1 and further comes into contact with the collision plate 26-1, and then falls toward the classification plate 25-2. Similar gravity classification operations consisting of horizontal flow classification and vertical flow classification are carried out on the classification plates 25-2 to 25-2.
5-4, and then the abrasive material is discharged from the abrasive material outlet 28 to the outside of the apparatus.

Note that the dimensions of the classification plates 25-1 to 25-4 vary depending on the size of the classification device, but cannot be said in part.
For example, the length of the classification plate is 100° or more, the angle of the classification plate is 15 to 60°, preferably 20 to 40°, the width of the classification plate is 100° or more, and the interval between the classification plates is 15cm or more. preferable. In addition, the flow rate of clean air between the classification plates is 0.3 to 3
m/s is desirable, and when the particle size of the abrasive is 0.7 to 1 square centimeter, 1 to 1.5 +/s is good.

The present invention is not limited only to the embodiments described above, and can be modified in many ways. For example, in the embodiments described above, an example of batch processing was shown as the blasting process, but the Control that keeps the amount constant (
For example, if the abrasive material is configured to be continuously supplied by weight and level control), continuous processing becomes possible.

(Effects of the Invention) As explained in detail above, according to the present invention, the cascade classifier is installed directly below the blast decontamination device, and the cascade classification is performed immediately after the blasting process, thereby eliminating the need for using a screw conveyor or the like. Therefore, it is possible to eliminate the accumulation of grinding dust, prevent contamination of the grinding material, and perform stable decontamination of radioactive waste over a long period of time.

In addition, a cyclone classifier was installed downstream of the cascade classifier, making it possible to classify radioactive waste twice.
In addition to improving the accuracy of classification, since a cyclone classifier is provided as the second classifier, there is no need to install a screw conveyor or the like between the cascade classifier and the cyclone classifier. Since there is no part where grinding dust accumulates, contamination of the abrasive material can be similarly prevented.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of an example of the radioactive waste decontamination device of the present invention, Fig. 2 is a diagram showing the configuration of an example of the radioactive waste classification device used in the present invention, and Fig. 3 (a ) and (b) are diagrams each showing the configuration of an example of a conventional radioactive waste decontamination device. 1...Blast room 2...Radioactive metal waste 3
...Nozzle 4...Cascade classifier 5.
...Supply port 6...Collection container 7...Hopper 8...Cyclone classifier 9...Pipe line 11...Bag filter 13...Pipe line 10...Blast device 12... HEPA filter 14...Exhaust blower

Claims (1)

[Scope of Claims] 1. A blast decontamination device for blasting and decontaminating radioactive metal waste in a sealed state, a classification device for classifying radioactive waste after blast decontamination into abrasive material and grinding dust, and a classified device for classifying radioactive waste into abrasive material and grinding dust. In a radioactive waste decontamination device comprising an exhaust treatment device for treating exhaust gas containing dust, the classification device
A radioactive substance characterized by comprising a cascade-type first classification device provided directly below the blast decontamination device, and a cyclone-type second classification device provided downstream of the first classification device. Waste decontamination equipment. 2. The radioactive waste removal method according to claim 1, wherein the blast decontamination device and the exhaust treatment device are connected through a pipe line, and the grinding dust floating in the blast decontamination device is directly subjected to primary classification. Dyeing equipment.