JPS6134120B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a nuclear reactor fuel cleaning apparatus for removing adhering contaminants such as crud adhering to the fuel of a boiling water nuclear reactor or the like.

Background technology and its problems In nuclear reactors that use water as a coolant, activated metal impurities contained in the coolant adhere to the surface of the fuel during reactor operation, forming so-called cruds and emitting radiation. Becomes a source of pollution. Therefore, it is important to remove crud from spent fuel or fuel in use in order to remove sources of radioactive contamination.

Conventionally, in order to remove such adhered contaminants, measures such as having a worker scrub the fuel in the fuel pool with a brush or spraying jet under water have been taken. However, these methods have the problem that workers are exposed to a large amount of radiation, and the contaminants peeled off from the fuel diffuse into the water, making recovery difficult and causing the contaminants to spread.

On the other hand, recently, cleaning devices using ultrasonic cleaners have also been considered. However, conventional ultrasonic cleaning equipment uses a method in which an ultrasonic vibrator is installed in water and moved.
Not only does inspection and maintenance of the ultrasonic transducer become troublesome, but it also requires a large-scale drive mechanism, which makes the entire device complicated.Furthermore, it takes a long time to inspect and maintain the system that ultimately collects the attached contaminants. There were some issues, such as:

Purpose of the Invention The present invention has been made based on the above circumstances, and its purpose is to be able to sufficiently remove contaminants attached to fuel without dispersing them into water, without requiring manual labor, and to have a simple structure. The object of the present invention is to provide a reactor fuel cleaning device that is easy to inspect and maintain and is very effective in reducing radiation exposure.

Summary of the Invention That is, the present invention selects an internal container that is installed underwater in a fuel pool or the like with its opening facing upward and accommodates water and reactor fuel as an object to be cleaned, and the opening of the internal container. a cleaning container consisting of a lid mechanism that covers the interior of the cleaning container, and an outer container that is placed outside the inner container and forms a closed annular space between the inner container and the inner container; a plurality of ultrasonic transducers that are attached in the vertical and vertical directions and send ultrasonic waves to the reactor fuel through the wall of the inner container; an oscillator that drives these ultrasonic transducers; and an oscillator that is installed outside the water a water feeding mechanism that selectively introduces water into the internal container from an upper position of the internal container via a pump; and a suction port at the bottom of the internal container; A reactor fuel cleaning device is comprised of a collection mechanism that collects adhering contaminants peeled off from the surface of the fuel by flushing it out of the container.

Embodiment of the Invention An embodiment of the present invention will be described below with reference to the drawings. In the figure, 1 is a cleaning container. This cleaning container 1 is designed to be placed in water 2 of a fuel pool of a boiling water reactor, for example, and has a double structure with an outer container 4 provided outside an inner container 3. The inside of the inner container 3 is filled with water 2a, and the reactor fuel 5 as an object to be cleaned is supported by support structures 6a and 6b. The fuel 5 is, for example, a fuel assembly for a boiling water nuclear reactor.

Further, the upper end openings of the inner container 3 and the outer container 4 can be sealed by an upper lid 7a and an air chamber lid 7b, respectively. Moreover, the upper lid 7a is
An automatic opening/closing device 8 enables opening/closing by remote control from the outside.

In addition, an air chamber 1 is provided between the inner container 3 and the outer container 4.
0, and a plurality of ultrasonic transducers 11... are housed in this air chamber 10. These ultrasonic transducers 11...
As shown in FIG.
The fuel is arranged in several places, towards the fuel 5 above.
It is designed to oscillate ultrasonic waves of 20KHz to 50KHz. Further, the signal cable 12 of each ultrasonic transducer 11 is led out of the cleaning container 1 and connected to an ultrasonic oscillator 13.

Furthermore, a collection mechanism 15 is connected to the cleaning container 1 . This collection mechanism 15 includes a water supply section 15a that sends water into the internal container 3, and a recovery section 15b that drains the water in the internal container 3 and collects pollutants. That is, the recovery section 15b is composed of a drain pipe 16, a gate valve 17, a filter 18, etc., and the suction port 16a of the drain pipe 16 is opened at the bottom of the inner container 3 so that water inside the inner container 3 can be sucked. It's summery. Further, the filter 18 has a function of capturing attached contaminants separated from the fuel 5, and the filtered water after passing through the filter is returned to the pool water 2. The filter 18 is a removable cartridge type filter so that the captured contaminants can be easily collected.

On the other hand, the water supply section 15a includes a water supply pipe 20, gate valves 21 and 22, a water supply pump 23, etc., and the water intake port 20a of the water supply pipe 20 is connected to the pool water 2
It is installed inside and is designed to take in pool water.

To clean the fuel 5 using the reactor fuel cleaning device configured as described above, first, the automatic opening/closing device 8 is used to open the top cover 7a, and the fuel 5 is accommodated in the internal container 3. Next, the ultrasonic oscillators 11 are driven by the ultrasonic oscillator 13 to oscillate ultrasonic waves toward the fuel 5. Adhesive contaminants such as crud adhering to the fuel 5 are removed by ultrasonic vibration energy, so-called ultrasonic cleaning is performed, and the removed adhering contaminants accumulate at the bottom of the inner container 3. After cleaning for a predetermined period of time, the water pump 23 is driven and the gate valves 17, 21, and 22 are opened. This operation causes some of the pool water to flow into the water pipe 2.
0 and sent to the internal container 3,
Water 2a in the inner container 3 is sent to the filter 18 through the drain pipe 16. Therefore, the contaminants in the inner container 3 are transferred together with the water to the filter 18 and captured by the filter 18. The filtered water that has passed through the filter 18 is returned to the pool water 2 again.

That is, according to the above embodiment, since cleaning is performed using ultrasonic vibration energy, crud and the like adhering to the fuel 5 can be thoroughly removed, resulting in a high decontamination effect. In addition, contaminants such as crud separated from the fuel 5 are captured by the filter 18 by taking a portion of the pool water 2 into the inner container 3 and distributing it, so that the contaminants can be captured reliably without being spread. Moreover, filter 1
Since it is only necessary to take out 8 and treat the contaminated material, measures against radioactive waste are easy. In addition, since the cleaning process is performed in pool water, the radiation shielding effect is high, which is very advantageous in terms of radiation exposure countermeasures.

Furthermore, by housing the ultrasonic transducers 11 in the air chamber 10 between the inner container 3 and the outer container 4, these transducers 11... are prevented from being submerged in water, so maintenance of the transducers 11... - Easy handling such as inspection, ie maintenance.

Further, since water containing attached contaminants does not flow through the pump 23, the pump 23 can be exposed to the atmosphere as in the embodiment, and as a result, maintenance of the pump 23 can be facilitated.

Note that the cleaning device of the present invention is not limited to a fuel pool, and may be installed in a pool in other nuclear reactor equipment.

Effects of the Invention According to the cleaning device of the present invention, it is possible to reliably remove and recover radioactive contaminants without dispersing them into the water, and work can be done in a shielded state underwater by remote control, thereby preventing radiation exposure. The ultrasonic vibrator, which is the vibration source, is attached to the outer surface of the inner container, and this attached part is isolated from water, so inspection and maintenance of the ultrasonic vibrator is easy. Because it uses a fixed method, the configuration can be simplified, and water containing adhered contaminants does not flow through the water supply pump used for the final collection of adhered contaminants.
The pump can be installed in the atmosphere, and the pump can be easily inspected and maintained.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a vertical cross-sectional view schematically showing a cleaning device, and FIG. 2 is a cross-sectional view taken along the - line in FIG. 1. 1...Cleaning container, 2...Pool water, 2a...
Water, 5...Reactor fuel, 11...Ultrasonic vibrator,
13... Ultrasonic oscillator, 15... Collection mechanism, 16
a...Inhalation port.

Claims (1)

[Claims] 1. An inner container that is installed underwater with its opening facing upward and contains water and reactor fuel as an object to be cleaned, a lid mechanism that selectively covers the opening of the inner container, and a cover mechanism of the inner container that selectively covers the opening of the inner container. a cleaning container consisting of an external container disposed on the outside and forming a closed annular space between it and the internal container; and a plurality of internal containers attached to the outer surface of the internal container of the cleaning container in the circumferential direction and in the vertical direction. an ultrasonic vibrator that sends ultrasonic waves to the reactor fuel through the wall of the reactor;
an oscillator that drives these ultrasonic transducers; a water supply mechanism that selectively introduces water into the internal container from an upper position of the internal container via a pump provided outside the water; and a collection mechanism having an inlet at the bottom and collecting contaminants peeled off from the surface of the fuel by flushing water sent by the water supply mechanism out of the inner container. A nuclear reactor fuel cleaning device characterized by: