JP2002311193A - Decontamination device for radioactive contaminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decontaminate decontamination objects without damaging and decontaminating the surface of parts adhered by radioactive materials by the contact of reactor water in a nuclear power plant, reduce radioactive waste liquid and drastically reduce the dose of workers. SOLUTION: The device is constituted of a decontaminating mechanism combining a device for bubbling water to a decontamination object and a discharge nozzle of high pressure water, a mechanism for recovering and separating removed radioactive waste liquid and a mechanism for monitoring and controlling decontamination state. The outlet water separated from the waste liquid is reused as high-pressure water. Consequently, decontamination is automatically and efficiently done without changing the steps of the decontamination device and the dose of workers can be drastically reduced. Also, decontamination waste liquid is drastically reduced by reusing outlet water for decontamination which is separated from decontamination waste liquid with a filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for decontaminating radioactive contaminants which can be used for decontamination of radioactive substances attached to the surface of articles in contact with reactor water of a nuclear power plant.

[0002]

2. Description of the Related Art There is a decontamination apparatus for radioactively contaminated metal waste (JP-A-5-34498) for decontaminating contaminated portions of metal waste that has been contaminated by radioactive substances. This apparatus is a wet blast method using a non-magnetic material or a weak magnetic material as an abrasive.

[0003] In addition, a high-pressure jet method in which high-pressure water is sprayed on a contaminated surface, a wet blast method in which a stainless steel or carbon steel ball is mixed with water and an abrasive and then jetted are used.

[0004]

The apparatus for decontaminating radioactively contaminated metal waste repeatedly uses abrasives, but the abrasives that have been damaged and the final used abrasives must be treated as radioactive waste. . It is a method of decontaminating metal waste, and decontamination is performed without considering the influence of the base material. Therefore, it is difficult to control fine decontamination, and it is not suitable for decontamination of parts to be reused and used.

In the case of the high-pressure water jet method, a large amount of high-pressure water is used to enhance the decontamination effect. However, a large amount of liquid is generated as secondary waste, and this waste treatment facility is enlarged. There is a problem to do. In addition, in the wet blast method, a large amount of liquid secondary waste is not generated because the abrasive can be repeatedly used by using a low-pressure liquid. However, if the processing liquid obtained by mixing the same abrasive and liquid is repeatedly used, contaminated metal particles containing radioactive substances accumulate in the system, increasing the radioactivity in the decontamination equipment, and causing radiation exposure of workers. There is an obstacle to increasing the dose. Furthermore, the contaminated metal particles generated by the decontamination process and the crushed abrasive were collected by a cartridge type filter,
This filter cartridge is generated in large quantities as secondary waste.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to remove radioactive substances adhering to the surface of a part to be reused without damaging the base material of the part by periodic inspection.
Another object of the present invention is to provide a decontamination apparatus capable of reducing a large amount of radioactive waste liquid and reducing the exposure dose to workers. The device in the present invention is as follows.

[0007] The outer surfaces of parts, tools and the like in contact with reactor water of a nuclear power plant are contaminated with oxides containing radioactive substances, and water used for decontamination in an apparatus for mechanically removing the oxides. , A pressurized air is injected into the water stored in the cleaning tank, and a radioactive contaminated article to be decontaminated placed on the cleaning tank. And a plurality of discharge nozzles that are decontaminated with a structure that integrates bubbling and jetting high-pressure water, and radioactive substances removed in the water settle at the lower part of the washing tank and have a radiation equivalent. A filter incorporated in a shielded drum that collects the same in order to increase the rate, a pump for transferring the pump and outlet water separated by the filter, a valve for supplying high-pressure water from the discharge nozzle, and the shielded drum. Surface and the washing tank Radioactive contaminant decontamination equipment, comprising: a radiation measuring device for measuring the dose equivalent rate of the decontaminated symmetrical object, a water level meter for monitoring the water level in the cleaning tank, and a controller receiving this signal. Is achieved by

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration in which a plurality of discharge nozzles 3 are set in a cleaning tank 1, a switching valve 4 connected to a hydraulic valve 5 connected to a hydraulic pressure supply system is set to a water side, and an air-water introduction pipe is used. Water 12 is injected from the discharge nozzle into the washing tank 1 up to the set value of the water level gauge 6. The radioactively contaminated article 2 whose surface to be decontaminated is contaminated is fixed on the table 15. In this state, the air pressure valve 6 of the air pressure supply system is opened to the set opening, the switching valve 4 is set to the air side, and the air 13 is jetted into the water 12 from the discharge nozzle 3 through the air water introduction pipe 2 to generate bubbles 14. Bubbling the water 12
The radioactive substance 8 attached to the surface of the contaminated object is removed. The bubbles 14 in the bubbling pass through an exhaust duct 24 provided in the upper lid 23 to collect radioactive substances attached to the bubbles 14 by a local exhaust fan 25, and the bubbles 14 exit to an exhaust line. The removed radioactive material 8 precipitates and accumulates in the lower portion of the cleaning tank 1 and raises the dose equivalent rate in the work place.

For this purpose, the lower part of the washing tank 1 is made funnel-shaped,
A filter 1 incorporated in a drum 11 that shields radioactive waste precipitated by a transfer pump 9 connected to a pipe 2.
The water at the outlet, which is sent to the filter 0 and the particles containing the radioactive substance are captured and separated by the filter 10, is discharged to the drain valve 7 and the outlet pipe 2.
1 and is returned to the hydraulic valve 5 and reused from the discharge nozzle 3 as high-pressure water.

The separated outlet water can be drained to the drain line by closing the drain valve 7, and the water level of the washing tank 1 can be adjusted to the set value of the water level gauge 16. In order to monitor the decontamination effect of the decontamination object 2 in the cleaning tank 1, the decontamination effect is performed by the cleaning tank radiation measuring device 17 a, this information is transmitted to the controller 18, the decontamination effect is determined, and the specified value is reached. For example, in response to the control signal 19, the hydraulic valve 5, the pneumatic valve 6, and the drain valve 7 are closed to stop the apparatus, thereby completing the decontamination work.

A surface radiation measuring device 17b for a drum with a shield is arranged for replacing a filter, and this information is transmitted to a controller 18, and when the filter replacement is determined and a specified value is reached, the device is stopped and the shielding is stopped. The filter 10 is replaced while being installed in the attached tram can 11. Exposure of the operator when replacing the filter 10 can be reduced.

Next, in order to inject high-pressure water from the discharge nozzle 3 of the radioactive contaminant 2 for decontamination, the setting of the water level gauge 16 is lowered to the position of the table 15 and the water pressure valve 5 is turned on by the water pressure supply system. The pressure is set to the set pressure, the switching valve 4 is set to the water side, and the high-pressure water 12 is injected from the discharge nozzle 3 through the air / water introduction pipe 22. The radioactive substance 8 adhering to the radioactive contaminant 2 is removed by the high-pressure water and settles at the lower part of the cleaning tank 1. Recovery of the precipitated radioactive waste is as described above. Since high-pressure water is circulated and reused, radioactive waste liquid can be significantly reduced.

Depending on the state of surface contamination of the object to be decontaminated, it is possible to select a bubbling method or a high-pressure water method to efficiently decontaminate the object.

According to the present invention, a bubbling of water is integrated with a nozzle for jetting high-pressure water for removing radioactive deposits, and decontamination can be performed without damaging a base material of a component to be decontaminated. The exit water separated and collected by the filter incorporated in the shielded drum with the removed radioactive deposits,
The equipment to be reused as a source of high-pressure water and used in this decontamination technology can be operated remotely, and can be applied to parts that come into contact with reactor water and have radioactive substances attached. Further, since the above-mentioned application is possible, it is possible to prevent an increase in the atmospheric dose equivalent rate in the work place, and it is possible to reduce the exposure of workers involved in decontamination.

[0015]

The present invention has the following effects.

It is possible to carry out decontamination efficiently without changing the decontamination apparatus and without damaging the parts to be decontaminated.
Exposure of workers can be significantly reduced.

The water used for decontamination is reused, and the treatment of contaminated waste liquid can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for decontaminating radioactive contaminants according to an embodiment of the present invention.

[Explanation of symbols]

1. Cleaning tank, 2. Radioactive contaminants, 3. Discharge nozzle, 4.
Switching valve, 5: hydraulic valve, 6: pneumatic valve, 7: drain valve,
8: radioactive substance adhering, 9: pump, 10: filter, 11: drum with shield, 12: water, 13: air,
14 ... bubbles, 15 ... stand, 16 ... water gauge, 17a ... radiation measuring device for washing tank, 17b ... radiation measuring device for drum with shield, 18 ... controller, 19 ... control signal, 20 ... piping, 21 ... outlet piping , 22 ... air water introduction pipe, 23 ...
Lid, 24 ... exhaust duct, 25: local exhaust fan.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsumi Hayashi 3-2-1, Sachimachi, Hitachi City, Ibaraki Prefecture Within Hitachi Engineering Co., Ltd. (72) Masayuki Makino 3-2-2 Sachimachi, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi Engineering Co., Ltd.

Claims (1)

[Claims] 1. The outer surfaces of components, tools, etc., in contact with reactor water of a nuclear power plant are contaminated with oxides containing radioactive substances, and are used for decontamination in a device for mechanically removing the oxides. A cleaning tank for storing water to be discharged, a table installed in the cleaning tank, and a radioactive contaminated object to be decontaminated placed on the table, and pressurized air to the water stored in the cleaning tank. Injecting, bubbling and jetting high-pressure water are integrated into a plurality of discharge nozzles for decontamination, and the radioactive material removed in the water precipitates at the lower part of the washing tank and the radiation equivalent A filter incorporated in a shielded drum that collects the liquid to increase the rate, a pump for transferring the water, a valve for supplying high-pressure water from the discharge nozzle to outlet water separated by the filter, and the shield. Drum surface and said A radiation measuring device that measures the dose equivalent rate of the object to be decontaminated in the cleaning tank, a water level meter that monitors the water level in the cleaning tank, and a controller that receives this signal. Decontamination equipment.