JPH07218693A - Decontamination hood device for dry ice blast - Google Patents

Abstract

PURPOSE:To provide a decontamination hood device capable of preventing scattering of removed decontamination matter to the periphery during decontamination of dry ice blast and preventing secondary contamination by effectively recovering and purifying the radioactive removed matter in the exhaust air. CONSTITUTION:A decontamination hood 10, a dust collector 30 and an exhaust blower 50 are connected with hoses 51 and 52. An object to be decontaminated is put in the decontamination hood 10 and dry ice particles are ejected from a nozzle at high pressure for decontamination processing. The atmosphere in the decontamination hood is sucked and exhausted to send to the dust collector 30 where solid, liquid and gas are separated with a cyclone. The solid and liquid are fallen to recover in a recovery vessel placed in the lower part of the dust collector. The gas passes the demister and HEPA filter arranged in the upper part of the dust collector where the mist in the gas is removed and contaminated matter is filtered and the purified gas is sucked and exhausted out of the dust collector top to the exhaust blower 50. As the demisted gas is filtered with the filter, mist freezing in the filter at very low temperature is avoided. The spent demister and filter are contained in a collection vessel and pressed by compression, which enables reducing volume by compression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry ice blast decontamination technique for decontaminating by ejecting dry ice particles to a decontamination target at high pressure to remove radioactive contaminants from the decontamination target, More specifically, the present invention relates to a hood device for effectively preventing secondary peeling caused by the exfoliation of dry ice blast decontamination scattered around.

[0002]

2. Description of the Related Art Since radioactive waste generated from facilities using nuclear fuel is contaminated with transuranium nuclides, etc., management standards have been established for the amount of pollution and the radiation equivalent rate, and the management standards have been adopted. It has been dyed.

In the decontamination process of contaminants, in order to prevent the diffusion of contamination, the interior of equipment such as a decontamination cell which has a high sealing property and is shielded so as to minimize the exposure of workers. It is performed by using a remote device such as a manipulator. One of these decontamination treatments is a low-level treatment by dry ice blast decontamination shown in FIG. For dry ice blast decontamination, dry ice particles in tank 1 are mixed with compressed air (about 6 kg / cm ² ) in feeder 2.
By accelerating and emitting from the tip of the blast nozzle 4 held by the manipulator 3 to the decontamination target 6 temporarily placed on the turntable 5, the contaminants adhering to the surface of the decontamination target 6 are peeled off. Remove. The decontamination object 6 that has been decontaminated in this way and has a reduced contamination level is then miniaturized by cutting or the like, highly filled in a storage container, and hermetically stored / discarded.

As the blast material used for decontamination, in addition to the above-mentioned dry ice particles, a metal polishing material or the like is generally used. Although the metal abrasive has a high grinding power, a high decontamination effect can be obtained, but on the other hand, after being used as a blasting material, it is easily crushed and the polishing effect is deteriorated, so that it is discarded as a secondary waste. On the other hand, dry ice grain blast material sublimes to carbon dioxide after use,
It is advantageous in that it does not remain as secondary waste unlike metal abrasives.

[0005]

However, in the dry ice blast decontamination as shown in FIG. 9, exfoliated substances due to decontamination scatter after blasting and move to the inside of the decontamination cell or to the ventilation system of the decontamination cell. Therefore, secondary pollution may occur.

Therefore, it is also attempted to prevent scattered matters from scattering after blasting by using a local exhaust system as shown in FIG. This device is configured such that one end of a bendable pipe 7 is connected to an inlet of a filter chamber 8 and an exhaust blower 9 is connected to an outlet of the filter chamber 8. A HEPA filter 8a is arranged in the filter chamber 8. ing. By installing the tip of the pipe 7 in the vicinity of the decontamination target 6, the peeled substance after blasting is sucked into the pipe 7 together with carbon dioxide gas in which dry ice particles have sublimated, and the peeled substance is filtered by the filter 8a, and the exhaust blower The exhaust gas from 9 is sent to a decontamination cell ventilation system (not shown). However, since dry ice particles are used and the environment is extremely low, there is a problem that water in the air is solidified and dew condensation occurs on the surface of the filter 8a, and the filter is easily clogged. As a result, the amount of filters to be discarded increases, and it is possible that not only time and effort are required for the processing work such as shredding when discarding the filters after use, but also secondary waste is increased.

In view of the above, the present invention prevents the decontaminated debris from scattering around during dry ice blast decontamination, and also effectively collects and purifies the debris in the exhaust before the exhaust gas is discharged. It is made for the purpose of providing a decontamination hood device that enables the decontamination.

[0008]

A decontamination hood apparatus for dry ice blasting according to the present invention will be described below with reference to the reference numerals in the drawings showing an embodiment. As shown in FIG. 1, the hood device of the present invention comprises a decontamination hood 10, a dust collector 30, and an exhaust blower 50.

As shown in FIG. 2, the decontamination hood 10 has a turntable 1 on which a decontamination object 12 is placed inside a container having an openable / closable lid 11, an exhaust pipe 19 and a drain pipe 20.
3, a decontamination target fixing means 17 for holding and fixing the decontamination target on the turntable, and a blast nozzle 15 for ejecting dry ice particles at a high pressure toward the decontamination target placed on the turntable. Is provided.

As shown in FIG. 4, the dust collector 30 includes a cyclone 33 for separating solid / liquid and gas, and an inlet pipe 34 for tangentially introducing exhaust gas and waste water from the decontamination hood 10 into the cyclone. An outlet pipe 35 disposed at the center of the cyclone top for discharging the gas separated by the cyclone to the outside of the dust collector, a cylindrical HEPA filter 36 detachably disposed below the outlet pipe, and an HE
A cylindrical demister 37 concentrically and removably arranged on the outer periphery of the PA filter, a discharge pipe 39 arranged at the center of the bottom of the cyclone for collecting the solid and liquid separated by the cyclone, and a discharge pipe 39 attached below the discharge pipe. It has the collection container 40 arrange | positioned freely.

The exhaust pipe 19 and drain pipe 20 of the decontamination hood 10 and the inlet pipe 34 of the dust collector 30 are connected to the hose 5.
1, and the outlet pipe 35 of the dust collector 30 and the exhaust blower 50 are connected by a hose 52.

[0012]

In the apparatus of the present invention described above, the lid 11 of the container of the decontamination hood 10 is opened, the decontamination object 12 is placed on the turntable 13 inside the container, and the decontamination object fixing means 17 is used. After holding and fixing, by ejecting dry ice particles from the blast nozzle 15 at high pressure, the radioactive contaminants adhering to the decontamination target can be peeled off. The atmosphere in the decontamination hood containing carbon dioxide gas due to sublimation of the peeled material and dry ice particles is sucked from the exhaust pipe 19 connected to the exhaust blower 50 through the dust collector 30 and sent to the dust collector 30. Does not scatter the peeled material to the surrounding area. Condensation water generated in the decontamination hood in a cryogenic environment collects at the bottom of the decontamination hood, so drain pipe 2
Suction and discharge with 0.

Exhaust gas and waste water from the decontamination hood are sent into the cyclone 33 through the inlet pipe 34 of the dust collector 30, where the solid / liquid and the gas are separated by cyclone separation. The separated solid / liquid is recovered in the recovery container 40 below the cyclone through the discharge pipe 39. on the other hand,
The gas rises along the inner peripheral wall of the cyclone 33, and the mist contained in the gas is removed by passing through the demister 37, and then the trace amount of contaminants is further removed by passing through the HEPA filter 36, and thus filtered. The purified gas is sucked and discharged from the outlet pipe 35 connected to the exhaust blower 50.

The mist removed by the demister 37 drops as water drops and is collected in the collection container 40 together with the cyclone-separated solid / liquid. When the predetermined amount is collected, the collection container 40 is removed from the dust collector 30 and treated as radioactive waste. In addition, the used demister 37 and HEPA filter 36 are also used in the recovery container 4
It can be collected within 0 and processed. If the recovery container 40 is a pail that can be compressed and reduced in volume, the used demister 37
By compressing together with the HEPA filter 36 and the HEPA filter 36, the compression volume reduction process can be performed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing preferred embodiments. FIG. 1 shows the overall concept of a decontamination hood device for dry ice blast according to the present invention, which is constituted by connecting a decontamination hood 10, a dust collector 30 and an exhaust blower 50 with hoses 51 and 52. . Exhaust gas and drainage in the decontamination hood 10, and further discharge of the solid and liquid separated by the dust collector 30 are performed by suction by the exhaust blower 50. The entire hood device is installed inside a shielded decontamination cell and is remotely operated by a manipulator from outside the decontamination cell.

2 and 3 show an embodiment of the decontamination hood 10, which is in the form of a box with a lid 11 which can be opened and closed. The lid 11 is opened at about 60 ° as shown by the alternate long and short dash line in FIG. 3, and its opening and closing can be facilitated by remote operation with a manipulator by using an air cylinder or the like (not shown). A turntable 13 on which the decontamination target 12 is placed is arranged inside the decontamination hood, and can be rotated at 0 to 20 rpm by the reduction motor 14. Blast nozzle 1 for dry ice particles
It is emitted from 5 toward the decontamination object 12 on the turntable, but since it is emitted at a high pressure (up to 22 kgf / cm ² ), the reaction force is large and it is difficult to hold it by the manipulator, so decontamination is performed. On the blast table 16 attached to the side wall of the lid 11 of the hood, the blast nozzle 15 is placed so that its angle can be freely changed.
The height of 6 can also be changed. Further, a fixing cylinder 17 is provided on the top of the lid 11 so that the decontamination object 12 on the turntable does not drop by the dry ice particles emitted at a high pressure.
The fixing arm 18 is extended from above to hold and fix the decontamination target. The decontamination hood is further provided with an exhaust pipe 19 for exhausting the atmosphere inside the decontamination hood to the side wall of the lid 11, and a drain pipe 20 for discharging water accumulated at the bottom of the decontamination hood. It is arranged on the lower side wall of the decontamination hood. A part of the lid 11 is a transparent window 21 made of, for example, an acrylic resin so that the inside of the decontamination hood can be checked.

When using the decontamination hood 10, first, the lid 11 is opened, the decontamination object 12 is placed on the turntable 13, and then the lid 11 is closed, and the fixing cylinder 17 is operated to fix the fixing arm 18. To extend downward to hold and fix the decontamination object on the turntable. Then turntable 13
While rotating, the dry ice particles are ejected from the blast nozzle 15 under high pressure to remove contaminants adhering to the decontamination target 12. Dry ice particles sublimate to carbon dioxide immediately after blasting. The atmosphere in the decontamination hood 10 containing the peeled material and carbon dioxide gas is sucked and discharged from the exhaust pipe 19 and sent to the dust collector 30. Further, since the inside of the decontamination hood 10 becomes an extremely low temperature environment due to the dry ice particles, dew condensation occurs, and the dew condensation water collects at the bottom of the decontamination hood. This condensed water is sucked and discharged by the drainage pipe 20 and the dust collector 3
Sent to 0. Thus, it is possible to effectively prevent the risk that the exfoliated substances and carbon dioxide gas scatter in the decontamination cell over a wide area to cause secondary pollution.

FIG. 4 shows an embodiment of the dust collector 30, and FIGS. 5 and 6 respectively show AA of FIG.
Figure 4 shows a cross-sectional view along the line B-B. The dust collector 30 has a cylindrical shape as a whole, and can be divided into a lid portion 30a, an upper portion 30b, and a lower portion 30c by a plurality of one-touch type clasps 31, 32. The inside of the upper part of the dust collector is composed of a cyclone 33 composed of a cone of about 30 °, and an inlet pipe 34 is tangentially attached to the lower part of the cyclone 33. The inlet pipe 34 is connected to the exhaust pipe 19 of the decontamination hood 10 by a hose 51 (FIG. 1). The top of the cyclone 33 is closed by a dust collector lid 30a, and a gas outlet pipe 35 is arranged upward in the center of the lid. Below the outlet pipe 35, a cylindrical HEPA filter 36 and a cylindrical demister 37 concentrically arranged on the outer periphery thereof are detachably arranged. The upper ends of the HEPA filter 36 and the demister 37 are closed by the lid portion 30a, and the lower ends thereof are closed by the bottom plate 38 including the central hollow portion. A discharge pipe 39 extends downward at the center of the bottom of the cyclone 33, and a recovery container 40 made of a press-compressible pail can is detachably arranged below the discharge pipe 39.

The operation of the dust collector 30 is as follows. The exhaust gas sucked and discharged from the exhaust pipe 19 of the decontamination hood 10 is sent to the cyclone 33 from the inlet pipe 34, and is cyclone separated while swirling in the cyclone,
Separated into solid / liquid and gas. The separated solid / liquid is recovered by dropping from the discharge pipe 39 to the recovery container 40. On the other hand, the gas swirls up along the inner peripheral wall of the cyclone 33, and when passing through the demister 37, the mist contained in the gas is removed, and the removed mist becomes water droplets and drops from the demister 36, and then inside the cyclone 33. It is collected along the peripheral wall from the discharge pipe 39 to the collection container 40. When the gas dehumidified after passing through the demister 37 then passes through the HEPA filter 36, a trace amount of contaminants contained in the gas is further filtered, and the thus filtered and purified gas is sucked from the outlet pipe 35 to the exhaust blower 50. It is discharged and sent to a decontamination cell ventilation system (not shown). The demister 37 and H
Since the upper and lower ends of the EPA filter 36 are blocked, all the gas will pass through the demister 37 and the HEPA filter 36 in the radial direction as shown by the arrow (FIG. 4), which is effective by the demister and the HEPA filter. Dehumidification and filtration purification are performed. In addition, since the mist is removed by the demister 37 and then passed through the HEPA filter 36, the HEPA caused by the coagulation of the mist at an extremely low temperature is used.
The clogging of the filter 36 can be effectively reduced, and the life of the HEPA filter is improved.

The operation of the dust collector 30 has been described in the case where the inlet pipe 34 of the dust collector and the exhaust pipe 19 of the decontamination hood 10 are connected by the hose 51. However, a certain amount of dew condensation is formed on the bottom of the decontamination hood 10. When the water is collected, the hose 51 attached to the exhaust pipe 19 of the decontamination hood is removed and replaced with the drain pipe 20 to remove the decontamination hood 10.
Condensed water collected at the bottom is sucked and discharged together with the atmosphere inside the decontamination hood from the drain pipe 20, and this is collected by the dust collector 3
It is possible to separate the solid / liquid and the gas into the cyclone 33 by sending it into the zero cyclone 33 in the same manner as described above. The exhaust pipe 19 and the drain pipe 20 of the decontamination hood 10 are
If the hose is not attached, attach a blind cap (not shown) to close it. In some cases, hoses are attached to both the exhaust pipe 19 and the drain pipe 20 of the decontamination hood, and these hoses are joined at the inlet pipe 34 of the dust collector 30 so that the exhaust gas and the drainage in the decontamination hood 10 are simultaneously obtained. It is also possible to do so. The exhaust pipe 19 and the drain pipe 20 of the decontamination hood, and further, the attachment and connection of the hose to the inlet pipe 34 and the outlet pipe 35 of the dust collector 30 use various types of one-touch type couplers that have been conventionally used. Therefore, it can be easily performed by remote control using a manipulator.

Demister 37 and HEPA filter 36
If you replace after using the
Open and remove the dust collector lid 30a,
Take out the used demister and filter. Further, the clasp 32 is opened to take out the collection container 40, the used demister and the filter are stored in the collection container 40, and the collection container 40 is press-compressed in this state, whereby the volume can be reduced to about 1/3. it can. New demister and H
It can be reused by setting an EPA filter and a new recovery container at a predetermined position and assembling the dust collector 30 with the clasps 31 and 32.

The ice blast decontamination hood apparatus of the present invention comprising the decontamination hood 10 of FIG. 2, the dust collector 30 of FIG. 4 and the exhaust blower 50 is connected by hoses 51 and 52 (FIG. 1). Was installed in the decontamination cell as shown in FIG. 7 to perform ice blast decontamination. The graph in FIG. 8 shows the results of monitoring the surrounding contamination during decontamination. Monitoring points are X point (around decontamination hood 10), Y point (exhaust blower 50) and underground demister (Z point: not shown) for ventilation inside the decontamination cell in FIG.
Was monitored, and the dose equivalent of each treatment when 12 decontamination targets were decontaminated was measured. From the graph of FIG. 8, it can be confirmed that the exfoliated material exfoliated from the object to be decontaminated by the ice blast decontamination does not scatter in the decontamination cell and can prevent the secondary contamination from occurring. Decontamination hood 1
The increase in the dose equivalent at point A around 0 was observed due to the accumulation of contamination in the decontamination hood 10.

[0023]

As can be seen from the above description, according to the decontamination hood device for ice blast of the present invention, the ice blast decontamination is performed in the decontamination hood, and the radioactive stripped material and dry ice particles are sublimated. All generated carbon dioxide gas was sent to the dust collector to collect the radioactive strips, so the radioactive strips did not scatter in the decontamination cell.
Secondary contamination can be effectively prevented.

Exhaust gas and waste water from the decontamination hood are cyclone-separated by a dust collector, and the separated solid and liquid are recovered in a recovery container, while the mist in the separated gas is removed by a demister and then a HEPA filter. Since a small amount of contaminants can be sent to the filter, mist coagulation in a cryogenic environment does not occur in the filter.
As a result, the filter is less likely to be clogged, the filter life can be extended, and a small amount of contaminants can be effectively filtered and purified by the filter and then discharged to the decontamination cell ventilation system.

Also, the used demister and HEPA filter can be housed in a recovery container for processing, and if the recovery container is a press-compressible pail, it can be pressed and compressed together with the used demister and HEPA filter. Also, the compression volume reduction processing can be performed to about 1/3.

Further, since the decontamination hood device of the present invention has a simple structure, it can be made compact and lightweight, and can be easily assembled, so that it can be handled by a remote device such as a manipulator in a narrow decontamination cell. Can be done easily.

[Brief description of drawings]

FIG. 1 is an explanatory view of the concept of a decontamination hood device for dry ice blast according to the present invention.

FIG. 2 is an explanatory view showing an embodiment of a decontamination hood which constitutes the decontamination hood device of the present invention.

FIG. 3 is a cross-sectional view showing a state in which an object to be decontaminated is placed in the decontamination hood of FIG.

FIG. 4 is a sectional view showing an embodiment of a dust collector that constitutes the decontamination hood device of the present invention.

5 is a cross-sectional view taken along the line AA of FIG.

6 is a cross-sectional view taken along the line BB of FIG.

FIG. 7 is an explanatory diagram showing a device layout in a decontamination cell when a peripheral contamination monitoring test at the time of decontamination by the decontamination hood device of the present invention is performed.

FIG. 8 is a graph showing the results of monitoring the surrounding pollution by the device layout of FIG.

FIG. 9 is an explanatory view showing a local exhaust device used in a conventional dry ice blast decontamination process.

[Explanation of symbols]

 10: Decontamination hood 11: Lid 12: Decontamination target 13: Turntable 15: Blast nozzle 17: Decontamination target fixing means 19: Exhaust pipe 20: Drainage pipe 30: Dust collector 33: Cyclone 34: Inlet pipe 35 : Outlet pipe 36: HEPA filter 37: Demister 39: Discharge pipe 40: Recovery container 50: Exhaust blower 51, 52: Hose

Claims (2)

[Claims] 1. A decontamination hood, a dust collector, and an exhaust blower; the decontamination hood mounts an object to be decontaminated inside a container having an openable / closable lid, an exhaust pipe, and a drain pipe. A turntable, a decontamination target fixing means for holding and fixing the decontamination target on the turntable, and a blast nozzle for ejecting dry ice particles at high pressure toward the decontamination target placed on the turntable. The dust collector is a cyclone that separates solid / liquid and gas, an inlet pipe that feeds exhaust gas and wastewater from the decontamination hood tangentially to the cyclone, and a gas that is separated by the cyclone as a dust collector. An outlet pipe disposed in the center of the cyclone top for discharging to the outside, a cylindrical HEPA filter detachably disposed below the outlet pipe, and concentrically removed on the outer periphery of the HEPA filter. It consists of a cylindrical demister arranged freely, a discharge pipe arranged in the center of the bottom of the cyclone to collect the solid and liquid separated by the cyclone, and a collection container detachably arranged below the discharge pipe. Decontamination for dry ice blast, characterized in that the exhaust pipe and drain pipe of the decontamination hood are connected to the inlet pipe of the dust collector with a hose, and the outlet pipe of the dust collector is connected to an exhaust blower with a hose. Hood device. 2. The decontamination hood device according to claim 1, wherein the recovery container is a pail that can be compressed and reduced.