JP2874995B2 - Radioactive waste decontamination equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for decontaminating radioactive waste comprising abrasives and dust after blast decontamination.

(Prior Art) FIG. 3 is a diagram showing an example of a conventional radioactive waste decontamination apparatus. In the example shown in FIG. 3, radioactive metal waste
31 is blast decontaminated in the blast chamber 32 by the abrasive discharged from the blast robot 33. The abrasive and the grinding dust after the blast are simultaneously sucked by the exhaust blower 34, separated into air containing the abrasive and the grinding dust in the cyclone classifier 35, and the separated abrasive is reused and separated. The air containing the grinding dust was guided to an exhaust treatment system consisting of a bag filter 36 and a HEPA filter 37 and was treated.

In the above-described decontamination apparatus, when radioactive metal waste is blasted with an abrasive, most of the radioactive substance attached to the metal surface becomes grinding dust and is separated from the metal surface. Therefore, when the abrasive is recirculated and used as in the decontamination apparatus described above, it is necessary to completely separate the abrasive and the grinding dust.

(Problems to be Solved by the Invention) However, in the classification method using a cyclone as in the above-described conventional decontamination apparatus, the ratio of the abrasive transferred to the air side is small, but conversely, the abrasive is not included in the abrasive. There is a problem that the ratio of dust is large. There is also a classifier using a cyclone that improves this point, but there is a problem that the structure is complicated and radioactive substances are easily deposited. Furthermore, there is a problem that classification in a blast chamber cannot be performed because air in which abrasives, grinding dust, and fine dust are mixed is sent to a classifier through a single pipe.

Due to the above problems, if the number of circulations is increased by recirculating the abrasive, the contamination of the abrasive itself progresses quickly, the decontamination effect is reduced, and the abrasive cannot be used, and the amount of secondary waste generated is reduced. There was a problem that it would increase.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a radioactive waste decontamination apparatus capable of more completely separating abrasive and grinding dust.

(Means for Solving the Problems) The decontamination apparatus for radioactive waste of the present invention, in a closed state, transfers a blast decontamination apparatus for blast decontamination of radioactive metal waste and a radioactive waste after blast treatment. A transfer device and a plurality of classifiers are provided at a certain angle to have a gravity classification function of horizontal flow classification and vertical flow classification to classify the radioactive waste transferred by the transfer device into abrasives and grinding dust. A radioactive waste classification device installed at an angle,
An exhaust treatment device for treating exhaust gas containing classified dust and exhaust gas from a blast decontamination device.

(Operation) In the above-described configuration, since a plurality of classifying plates are provided in the classifying device at a predetermined angle with a step difference, the abrasive material and the grinding dust are classified by the number of stages by passing through the device once. Classification can be performed with higher accuracy. Also, at this time, since the classifying plate is configured to be inclined by a certain angle, the functions of both horizontal flow classification and vertical flow classification can be achieved at the same time.

In addition, the blast decontamination apparatus of the present invention includes the above-described classification apparatus, and connects the hermetically sealed blast decontamination apparatus and the exhaust gas treatment apparatus via a pipe to first classify the suspended grinding dust in the blast chamber in advance. As a result, the contamination of the abrasive can be minimized, and the decontamination of radioactive waste can be performed more completely.

(Embodiment) FIG. 1 is a diagram showing a configuration of an example of a classification device used in the radioactive waste decontamination device of the present invention. In the example shown in FIG. 1, 1 is an inlet for radioactive waste consisting of abrasives and grinding dust, 2 is a supply port for clean air used for classification, 3
Is a regulating damper for regulating the amount of clean air supplied, 4 is a sieve for removing large waste in radioactive waste,
Classification plates 5-1 to 5-4 are provided at a fixed angle, and 6-1 to 6-4 are provided at lower ends of the respective classification plates 5-1 to 5-4 at fixed intervals. Collision plates for radioactive waste, 7a and 7b are introduction plates for guiding the radioactive waste after passing through the sieve 4 to the classification plates 5-1 to 5-4, 8 is an outlet for discharging the abrasive after classification, 9 is a collection port for collecting the grinding dust after classification, 10 is an exhaust nozzle for exhausting dust floating in fine powder and generating a flow of clean air in the apparatus, and 11 is a clean nozzle for exhaust air to the exhaust nozzle 10. And a partition plate 12 for guiding the grinding duct to the collection port 9, and 12 is grinding dust deposited on the collection port 9.

In the classifier described above, radioactive waste consisting of abrasives and grinding dust to be classified is introduced into the apparatus through the inlet 1, and large waste is first removed by the sieve 4.
The radioactive waste from which the large waste has been removed descends along the introduction plates 7a and 7b, and falls from the tip of the introduction plate 7b toward the classification plate 5-1. During this fall, the clean air supply port 2 is directed toward the exhaust nozzle 10 through the lower opening of the partition plate 11.
The flow of clean air supplied from
The light grinding dust is carried along the flow of clean air through the lower opening of the partition plate 11 toward the exhaust nozzle 10, and along the way, some of the light grinding dust sediments by gravity and the grinding dust collection port 9, the heavy abrasive drops down along the classifying plate 5-1 and contacts the collision plate 6-1 before dropping toward the classifying plate 5-2. A similar gravity classification operation including horizontal flow classification and vertical flow classification is performed by the classification plate 5-2.
After that, the abrasive is discharged from the abrasive outlet 8 to the outside of the apparatus.

Note that the dimensions of the classifying plates 5-1 to 5-4 vary depending on the size of the classifying device and cannot be unconditionally described. As an example, the length of the classifying plate is 100 mm or more, and the angle of the classifying plate is 15 mm.
It is preferable that the width of the classifier is 100 mm or more and the distance between the classifiers is 15 mm or more. Also,
The flow rate of the clean air between the classifying plates is desirably about 0.3 to 3 m / s, and 1 to 1.5 m / s is good when the particle size of the abrasive is 0.7 to 1 mm.

Using the classifier shown in FIG. 1 described above, a classification test of the abrasive and the grinding dust was performed under the conditions of a flow rate between the classification plates of 1.3 m / s and a supply speed of the abrasive of 2 kg / min. The results are shown in Table 1.

As can be seen from the test results in Table 1, grinding dust having a fine particle size was almost removed from the abrasive of the classification plate, and sufficient classification performance could be obtained.

FIG. 2 is a diagram showing an example of a radioactive waste decontamination device using the above-described classification device. In the example shown in FIG. 2, 13 is a radioactive metal waste to be decontaminated, 14 is a blast chamber of a blast decontamination apparatus for performing an actual blast decontamination operation, 15
Is a loading / unloading chamber for loading / unloading radioactive metal waste 13 to / from the blast chamber 14, 16 is a blast robot for discharging abrasives, 17
Is a classifier having the above-described configuration, 18 is a screw conveyor for supplying abrasives and grinding dust after blast decontamination to the classifier 17, 19 is a blast machine provided downstream of the classifier 17, and 20 is a classifier. A bag filter for separating the grinding dust classified by 17, 21 is a HEPA filter for further filtering the grinding dust that has passed through the bag filter 20, 22 is between the blast chamber 14 and the bag filter 20 and between the classification device 17 and the bag filter. An exhaust blower 23 sucks grinding dust in the classification device 17 and grinding dust floating in the blast chamber 14 through the pipeline 22, the bag filter 20, and the HEPA filter 21. It is.

In the decontamination apparatus for radioactive waste described above, the classification apparatus of the present invention using horizontal flow classification and vertical flow classification is used as a classification apparatus, and for directly sucking floating grinding dust in the blast chamber. Since the primary classification is made possible by providing the conduit 22, the classification of the abrasive and the grinding dust can be more completely performed, thereby minimizing the contamination of the abrasive,
The decontamination of radioactive metal waste can be more complete.

(Effects of the Invention) As described above in detail, according to the decontamination apparatus of the present invention, since the progress of radioactive contamination of the abrasive is slow, recirculation can be performed without reducing the decontamination performance for a long time, The classification of radioactive metal waste can be more complete.
Further, since the grinding dust floating in the blast chamber of the blast device is directly classified by the bag filter and the HEPA filter, it is possible to more effectively separate the abrasive and the grinding dust.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the configuration of a classification apparatus used in the radioactive waste decontamination apparatus of the present invention, and FIG. 2 is an example of a radioactive waste decontamination apparatus incorporating the classification apparatus shown in FIG. FIG. 3 is a diagram showing an example of a configuration of a conventional radioactive waste decontamination apparatus. DESCRIPTION OF SYMBOLS 1 ... Input port 2 ... Clean air supply port 3 ... Adjustment damper 4 ... Screen 5-1 to 5-4 ... Classification plate, 6-1 to 6-4 ... Impact plate 7a, 7b ... Introduction plate, 8 ... Exhaust port 9 ... Recovery port, 10 ... Exhaust nozzle 11 ... Partition plate, 12 ... Grit dust 13 ... Radioactive metal waste, 14 ... Blasting chamber 15 ... Carry-in / out chamber , 16… Blast robot 17… Classifier, 18… Screw conveyor 19… Blast machine, 20… Bag filter 21… HEPA filter, 22… Pipe line 23… Exhaust blower

Claims (1)

(57) [Claims] 1. A blast decontamination device for blast decontamination of radioactive metal waste in a sealed state, a transfer device for transferring the radioactive waste after blasting, and an abrasive for transferring the radioactive waste transferred by the transfer device A classification device for radioactive waste, in which a plurality of classification plates are provided at a certain angle to provide a horizontal classification and a vertical classification, and are classified into grinding dust. An apparatus for decontaminating radioactive waste, comprising: an exhaust treatment apparatus for treating exhaust gas containing dust and exhaust gas from a blast decontamination apparatus.