KR101513806B1 - Ultrasonic Cleaning System and Method for Irradiated Nulcear Fuel Assemblies - Google Patents

Abstract

Disclosed are an ultrasonic cleaning system and a method for irradiating a nuclear fuel assembly. An ultrasonic cleaning system according to the present invention generates an ultrasonic wave while a nuclear fuel assembly stored in a nuclear fuel storage unit in a nuclear fuel storage tank is left, and can clean it. Moreover, because an ultrasonic cleaning process is performed between nuclear fuel assemblies, various nuclear fuel assemblies can be cleaned at the same time.

Description

[0001] Ultrasonic Cleaning System and Method for Irradiated Nulcear Fuel Assemblies [

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning apparatus used for operation and maintenance of a nuclear power plant, and more particularly, to an ultrasonic cleaning apparatus and method for ultrasonically cleaning an irradiated nuclear fuel assembly.

Nuclear power plants are equipped with nuclear fuel assemblies inside their nuclear reactors, and generate nuclear energy by causing nuclear materials in nuclear fuel assemblies to fission. Generally, fuel assemblies are composed of a plurality of fuel rods in the form of a square bundle, and fuel materials are charged into the fuel rods. During operation of the reactor, the surface of the fuel rod of the nuclear fuel is at a high temperature of about 1000 ° C., so that the impurities contained in the coolant in the reactor and the substances contained in the coolant are deposited on the surface of the fuel rod. have. For example, changes in nuclear performance due to changes in neutron irradiation characteristics of fuel rods, damage due to a rise in the surface temperature of fuel rods, increase in worker exposure due to deposition and impurities circulating in the system, increase in worker exposure, And increased opacity of the cooling water.

<Correlation between the axial power distribution abnormality and the surface deposition of nuclear fuel>

In some pressurized water reactor type nuclear power plants, the axial power distribution abnormality of nuclear fuel has been reported. This phenomenon occurs when impurities or coolant-containing substances are deposited on the surface of the fuel rod of the nuclear fuel and the characteristics of the nuclear fuel are changed. When the phenomenon becomes worse, the power of the nuclear power plant should be lowered and operated. Therefore, it is necessary to clean the irradiated fuel to mitigate or eliminate such axial power distribution abnormal phenomenon.

<Axial Dispersion Distribution of Nuclear Fuel and the Relationship Between Zinc>

Recently, a technique of injecting zinc into a reactor coolant to reduce the stress corrosion cracking of the steam generator heat transfer tube and reduce the radiation dose of the worker is utilized. However, while zinc infusion technology has such a positive effect, research has shown that zinc is deposited on the surface of nuclear fuel and contributes to axial power distribution abnormalities.

<Original technology related to ultrasonic cleaning of nuclear fuel>

Conventionally, there has been developed a technique of cleaning the nuclear fuel by ultrasonic waves in order to remove the deposits on the surface of the nuclear fuel to solve the abnormal distribution of the axial power distribution of the nuclear fuel.

Korean Patent No. 10-724819 (name: nuclear fuel ultrasonic cleaning apparatus and method) discloses a method of positioning one fuel assembly at a time in a housing, followed by cleaning with ultrasonic waves. However, this method can not only clean one fuel assemblage at a time but also takes a long time to install or remove all cleaning equipment, which is inefficient. In addition, since the fuel assembly is poured into a separate housing in which the ultrasonic transducer is installed, the fuel is taken out from the fuel reservoir, and the spent fuel is transferred to the fuel housing, .

It is an object of the present invention to provide a nuclear fuel ultrasonic cleaning apparatus and method in which a plurality of irradiated nuclear fuel assemblies can be simultaneously cleaned by installing a plurality of nuclear fuel assemblies on empty portions of a nuclear fuel storage reservoir .

In order to accomplish the above object, a nuclear fuel ultrasonic cleaning apparatus according to the present invention includes an ultrasonic cleaning unit, an impurity suction unit, and a control unit.

The ultrasonic cleaning unit is inserted into the empty storage reservoir among the plurality of fuel storage reservoirs stored in the nuclear fuel storage tank filled with the cooling water to generate ultrasonic waves to clean impurities on the surface of the fuel assembly stored in the surrounding fuel storage reservoir.

The impurity suction unit sucks the cooling water to filter the impurities, and the control unit controls operations of the ultrasonic cleaning unit and the impurity suction unit.

According to an embodiment, the ultrasonic cleaning unit may include at least one ultrasonic transducer in the form of a longitudinally elongated shape so as to generate a constant ultrasonic wave and be inserted into the fuel reservoir; And at least one support member for supporting the at least one ultrasonic transducer in the elongated shape in the longitudinal direction.

In this case, it is preferable that the at least one support member is a tube filled with a gas and having a constant buoyancy to propagate ultrasonic waves generated by the ultrasonic transducer outwardly.

According to an embodiment, the ultrasonic cleaning apparatus includes a base plate for supporting the ultrasonic cleaning unit and the impurity suction unit, and a buoyancy adjusting unit. The buoyancy adjusting portion is provided on one side of the base plate to generate buoyancy to lighten the weight of the whole water.

For example, the buoyancy control unit may include: a lower case fixed to the base plate; An upper case forming an inner space portion having a variable size together with the lower case; An intake pipe for supplying a gas to fill the internal space portion from the outside; A pressure regulating valve for controlling the size of the buoyancy by regulating the volume of the internal space by controlling the air pressure of the internal space by opening and closing the intake pipe; And an exhaust valve for exhausting the gas filled in the internal space portion.

Further, the buoyancy control unit may include: a first pressure gauge for measuring the water pressure of the cooling water in the fuel storage tank; And a second pressure gauge for measuring the air pressure of the internal space portion. In this case, the controller may control the air pressure to be higher than the water pressure to raise the base plate, or may control the air pressure to be lower than the water pressure to lower the base plate.

According to an embodiment, the impurity suction unit includes a suction pump for sucking cooling water in the fuel storage tank; And a filter for filtering and filtering the impurities in the cooling water sucked by the suction pump.

Further, when the ultrasonic cleaning apparatus of the present invention further includes a radiation detector for detecting the intensity of radiation of the impurities collected in the filter and providing the radiation detector to the control unit, It can be judged that the cleaning has been completed.

In another aspect of the present invention, there is provided a method of cleaning an ultrasonic cleaning apparatus, comprising the steps of: (a) inserting an ultrasonic cleaning unit of an ultrasonic cleaning apparatus into an empty storage tank among a plurality of nuclear fuel storage tanks stored in a nuclear fuel storage tank filled with cooling water ; (b) washing the impurities on the surface of the fuel assembly stored in the surrounding fuel storage space by ultrasonic waves generated by the ultrasonic scales; And (c) the impurity suction unit of the ultrasonic cleaning apparatus sucks the cooling water using a suction pump, and filters and filters the impurities floating in the cooling water using a filter.

The fuel ultrasonic cleaning apparatus of the present invention does not need to take out the nuclear fuel assembly stored in the nuclear fuel storage compartment for the purpose of cleaning because the nuclear fuel assembly stored in the nuclear fuel storage compartment is left without being taken out.

The ultrasonic cleaning apparatus of the present invention is inserted into an empty storage reservoir in a nuclear fuel storage reservoir to generate ultrasonic waves inside the nuclear fuel storage reservoir and deliver the ultrasonic waves to the surrounding nuclear storage reservoir to clean the plurality of nuclear fuel assemblies It can be cleaned at the same time.

The ultrasonic cleaning apparatus of the present invention generates buoyancy to reduce weight in water to facilitate transport in the water and minimizes the risk of accidents where the cleaning device falls onto the nuclear fuel assembly during transport.

Further, the ultrasonic cleaning apparatus of the present invention can automatically detect the completion time of the ultrasonic cleaning in water by checking the intensity change of the radioactivity increased as the impurities are collected.

1 is a perspective view of a nuclear fuel ultrasonic cleaning apparatus of the present invention,
FIG. 2 is a perspective view of the nuclear fuel ultrasonic cleaning apparatus of FIG. 1,
3 is a view showing a nuclear fuel ultrasonic cleaning apparatus inserted into a nuclear fuel storage vessel,
4 is a conceptual diagram of a buoyancy control unit according to an embodiment of the present invention, and
5 is a flowchart provided in the description of the cleaning method of the nuclear fuel ultrasonic cleaning apparatus of the present invention.
<Description of Symbols>
10. Nuclear fuel storage tank 30. Nuclear fuel storage tank
31. Empty fuel storage tank 31. Cooling water inlet
110. Ultrasonic cleaning unit 111. Ultrasonic wave converter
113. Tube 130. Impurity suction
150. Buoyancy control unit 151. Lower case
153. Internal space 155. Upper case
157. Sealing ring 159. Intake piping
161. Pressure regulating valve 163. Exhaust valve
165. First pressure gauge 167. Second pressure gauge
171. Base plate 171a. Absorber
171b. Observation opening 173. Hook fixing ring

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the drawings.

Referring to FIGS. 1 to 4, the nuclear fuel ultrasonic cleaning apparatus 100 of the present invention cleans the nuclear fuel assembly in a nuclear fuel storage tank 10 filled with cooling water. Here, the fuel assemblies are used at least once to release the radioactivity, and have a shape of a square fuel rod bundle as described above.

A nuclear fuel storage tank (10) is a device for cooling and storing at least one (Irradiated) nuclear fuel in a nuclear power plant for storage before reuse or disposal. A plurality of fuel assemblies are stored in the nuclear fuel storage tank 10 while being inserted into a plurality of fuel storage bases 30, respectively. The nuclear fuel storage tank 10 is filled with cooling water so that a plurality of nuclear fuel storage tanks 30 can be stored in the water and cooling water in the nuclear fuel storage tank 10 can be introduced into the lower portion of each nuclear fuel storage tank 30 The inlet 30a is filled with the cooling water inside the fuel storage bases 30.

The nuclear fuel ultrasonic cleaning apparatus 100 basically includes an ultrasonic cleaning unit 110, a impurity suction unit 130, a buoyancy control unit 150, and a base plate 171 for supporting them. The nuclear fuel ultrasonic cleaning apparatus 100 further includes a control unit (not shown) for controlling the operation of the ultrasonic cleaning unit 110, the impurity suction unit 130, and the buoyancy control unit 150 operating in the nuclear fuel storage tank 10, . In the following description, the operations of the ultrasonic cleaning unit 110, the impurity suction unit 130, and the buoyancy control unit 150 are controlled by the control unit unless otherwise described.

The ultrasonic cleaning unit 110 includes at least one ultrasonic transducer 111 for generating ultrasonic waves using external electric energy to clean the surface of the nuclear fuel assembly. 31).

Therefore, the ultrasound transducer 111 may be any type including a Push Pull type, a Piezo type, or a Magnetostriction Vibration type, as long as it has a size and shape that can be inserted into the fuel reservoir 30. It may be of the type. The push-pull element has the characteristic that the ultrasonic waves are spread out in the direction of 360 degrees from the surface of the circular rod shape, and the piezoelectric element emits ultrasound energy only in one direction, and the characteristic that can generate a relatively large output in the case of the magnetostrictive element Therefore, select the appropriate one according to the application.

In the embodiment of Fig. 1, the ultrasonic transducer 111 has a shape elongated in the longitudinal direction. It is preferable that the longitudinal length of the ultrasonic transducer 111 is smaller than the length of the fuel reservoir 30. In this case, the ultrasonic cleaning unit 110 may further include a support member for supporting the ultrasonic transducer 111 extended in the vertical direction and allowing the ultrasonic wave transducer 111 to be easily inserted into the nuclear fuel reservoir 30. Likewise, It is preferable to have a shape extending in the longitudinal direction so as to be inserted into the fuel reservoir 30 together with the fuel electrode 111.

The supporting members exemplarily shown in FIGS. 1 and 4 are realized by arranging four tubes 113 having a rectangular cross section in a longitudinal direction, and the ultrasonic transducer 111 is fixed to the outer surface of the tube 113.

The inside of the tube 113 is filled with air or a gas such as argon or nitrogen so that the tube 113 itself and the ultrasonic transducer 111 can receive buoyancy in water. The buoyancy by the tube 113 is reduced by the buoyant force generated by the buoyancy regulator 150 described below and the water weight of the nuclear fuel ultrasonic cleaning apparatus 100 is reduced so that the nuclear fuel ultra- 10 to prevent the fuel from falling onto the fuel assembly during transport. In addition, gases such as air, argon, and nitrogen, which fill the inside of the tube 113, minimize the disappearance of ultrasonic energy due to the substances in the tube 113 without propagating.

The ultrasonic cleaning unit 110 operates in a state where the ultrasonic cleaning unit 110 is inserted into the empty storage unit 31 of the plurality of fuel storage units 30 during storage in the fuel storage tank 10 to generate ultrasonic waves. The ultrasonic waves generated by the ultrasonic cleaning unit 110 are transmitted to the fuel assemblies (i.e., the fuel rods) housed in the neighboring nuclear fuel storage bases 30 because the ultrasonic waves can pass through the wall surface of the fuel reservoir 30 made of metal. And is concentratedly transferred to the nearby cooling water to generate cavitation near the nuclear fuel and remove impurities on the surface of the nuclear fuel assembly.

1, the ultrasonic cleaning unit 110, the impurity suction unit 130, and the buoyancy control unit 150 are supported by a base plate 171. The impurity suction unit 130 sucks floating impurities from the fuel assembly during the nuclear fuel cleaning process of the ultrasonic cleaning unit 110 and collects the impurities. The buoyancy regulator (150) regulates buoyancy of the entire nuclear fuel ultrasonic cleaning apparatus (100).

The impurity suction unit 130 may have any structure for sucking and collecting floating impurities from the nuclear fuel assembly in the nuclear fuel cleaning process of the ultrasonic cleaning unit 110 in water.

For example, the impurity suction unit 130 may include a suction pump and a filter. The inlet of the suction pump is brought into contact with the upper portion of the base plate 171 to suck impurities floating inside and outside the nuclear fuel storage vessel 30 through the plurality of absorption openings 171a provided in the base plate 171, ), And the filter removes the solid matter.

The impurity suction unit 130 is positioned above the fuel storage unit 30 and is required to suck impurities that float in the plurality of fuel storage units 30. 1, the upper end of the ultrasonic cleaning part 110 is attached to the lower center of the base plate 171 so that the lower surface of the base plate 171 when the ultrasonic cleaning part 110 is inserted into the fuel storage part 31 The absorbing port 171a of the base plate 171 comes into contact with the upper portion of the nuclear fuel storage basin 30. As a result,

In addition to the absorption port 171a connected to the suction pump, a drain port is formed in the base plate 171 for discharging the purified cooling water while being sucked through the absorption port 171a and passing through the suction pump and the filter. In addition, an observation opening 171b is formed at the center of the base plate 171 so that the upper fuel reservoir 30 can be visually observed.

As described below, if the cleaning range of the ultrasonic cleaning unit 110 is limited to the extent of 'the reservoir abutting the storage unit 31 in which the ultrasonic cleaning unit 110 is inserted', as in the example shown in FIG. 1, And the impurity suction unit 130 is provided on the upper surface of the base plate 171 so that the impurity suction unit 130 is opposed to the abutting storage unit. The impurities 110 are disposed on the lower surface of the base plate 171, It is preferable that the suction portion 130 be disposed. However, the position and arrangement of the impurity suction unit 130 are not necessarily limited thereto.

On the other hand, the foreign matter collected in the filter radiates radioactivity. Therefore, when the amount of foreign matter collected increases, the amount of radiation detected by the filter is also proportionally increased. Then, the intensity of the radiation detected in the filter is also stagnated if the cleaning is completed and the amount of foreign matter collected is no longer increased. Therefore, according to the embodiment of the present invention, the nuclear fuel ultrasonic cleaning apparatus 100 is provided with a radiation detector near the filter, and when the increase in the radiation intensity is stalled based on the output of the radiation detector, It can be judged that the ultrasonic cleaning has been completed.

The buoyancy control unit 150 has a container shape and is installed on the upper surface of the base plate 171 to generate a constant buoyancy force, thereby reducing the weight of the nuclear fuel ultrasonic cleaning apparatus 100 in water. Accordingly, the ultrasonic cleaning apparatus 100 is accidentally moved to the upper part of the nuclear fuel assembly in the nuclear fuel storage tank 10 so that the nuclear fuel assembly is not damaged by the impact.

The tube 113 and the ultrasonic transducer 111 are stretched downward on the empty fuel reservoir 31 in an empty state and the fuel reservoir 31).

&Lt; Embodiment of buoyancy control part &

The buoyancy regulator 150 according to another embodiment of the present invention can control the size of buoyancy.

4, the buoyancy control unit 150 includes a lower case 151 fixed to the base plate 171, an upper case 155 forming an inner space 153 together with the lower case 151, And a sealing ring 157 that seals between the upper case 155 and the lower case to seal the inner space 153.

The buoyancy control unit 150 includes an intake pipe 159 for introducing the buoyancy adjusting gas supplied from the outside (for example, a compressed gas supply source) into the internal space 153, A pressure regulating valve 161 for controlling the flow and an exhaust valve 163 for exhausting the gas in the internal space 153 to the outside. The buoyancy control unit 150 includes a first pressure gauge 165 for measuring the water pressure of the cooling water and a second pressure gauge 167 for measuring the air pressure in the internal space 153. [ The buoyancy controlling gas filling the inner space portion 153 may be air, argon, nitrogen, helium, or the like.

The volume of the internal space 153 is adjusted by adjusting the size of the internal space 153 by vertically conveying the upper case 155 while maintaining the airtightness with the lower case 151 according to the size of the internal air pressure. The control unit automatically controls the size of the internal space 153 of the buoyancy control unit 150, that is, the buoyancy force, by controlling the pressure control valve 161 and the exhaust valve 163.

When the pressure control valve 161 is opened and the gas outside the nuclear fuel storage tank 10 flows into the internal space portion 153 through the intake pipe 159, the internal air pressure of the buoyancy control portion 150 becomes large, . On the contrary, when the exhaust valve 163 is opened and the gas filled in the internal space 153 through the intake pipe 159 is discharged to the outside, the internal air pressure of the buoyancy regulating part 150 becomes small, the volume becomes small, Loses.

Particularly, the buoyancy control unit 150 may measure the water pressure of the cooling water with the first pressure gauge 165, increase the internal air pressure to be higher than the water pressure of the cooling water, raise the fuel ultrasonic cleaning apparatus 100 (i.e., The fuel pressure ultrasonic cleaning apparatus 100 may be lowered by adjusting the internal air pressure to be smaller than the water pressure. With this adjustment, the buoyancy regulator 150 can control the adhesion between the absorption port 171a and the fuel reservoir 30.

Referring to FIG. 1, the nuclear fuel ultrasonic cleaning apparatus 100 of the present invention includes a hook fixing ring 173. The manager can connect the hook of the crane to the hook fixing hook 173 to support the hook when the fuel ultrasonic cleaning apparatus 100 of the present invention is moved to the cleaning position by a separate crane or the like.

&Lt; Example: Sequential cleaning >

Hereinafter, a cleaning method of the nuclear fuel ultrasonic cleaning apparatus 100 of the present invention will be described with reference to FIG.

Since there is a certain limit to the transmission of ultrasonic energy, it is necessary to divide the entire fuel storage unit 30 into several unit groups and sequentially clean it. For example, if the ultrasound generated by a single ultrasound transducer 111 is such that it can clean the eight fuel assemblies surrounding it, the manager may group the entire fuel reservoir into nine (3 x 3) And can be sequentially cleaned in groups. At this time, it is preferable to empty the middle fuel reservoir of each group for insertion of the ultrasonic cleaning unit 110.

&Lt; Feeding and disposing step: S501 >

First, the nuclear fuel ultrasonic cleaning apparatus 100 is placed on the fuel reservoir 30 in the nuclear fuel storage tank 10. At this time, the crane hooks the hook of the crane to the hook fixing ring 173, and the crane transfers the nuclear fuel ultrasonic cleaning apparatus 100.

When the base plate 171 is positioned on the empty fuel storage unit 31 in the fuel storage unit 30, the ultrasonic cleaning unit 110 is inserted into the corresponding fuel storage unit 31 to prepare for cleaning.

&Lt; Ultrasonic cleaning step: S503 >

The control unit starts the ultrasonic cleaning by operating the ultrasonic transducer 111 and the suction pump of the impurity suction unit 130.

Ultrasonic cleaning is performed for a predetermined time. Ultrasonic waves generated by the ultrasonic transducer 111 are transmitted while passing through the fuel reservoir 30 to cause cavitation in the vicinity of the nuclear fuel, thereby cleaning the nuclear fuel assembly.

<Impurity collection step: S505>

The suction pump of the impurity suction unit 130 intensively sucks the cooling water of the eight fuel storage bins abutted to the empty fuel storage unit 31 through the absorption port 171a. As described above, since the base plate 171 is in close contact with the upper portion of the fuel reservoir 30 and the impurity suction unit 130 is opposed to the storage reservoir abutting the center of the absorption port 171a, the ultrasound transducer The cooling water in the eight fuel reservoirs abutted against the storage base 31 at which the fuel cell stack 111 is located is intensively sucked.

Floating impurities in the sucked cooling water are collected by the filter.

As described above, if the fuel reservoir is divided into groups of nine (3 × 3) units, each group is sequentially cleaned. In order to move the position of the nuclear fuel ultrasonic cleaning apparatus 100, the nuclear fuel ultrasonic cleaning apparatus 100 inserted in the specific nuclear fuel storage vessel 30 is pulled up to the next place, and then the empty fuel storage vessel 31). This series of processes can be performed by the buoyancy adjustment of the buoyancy regulator 150 and the external crane. In other words, the buoyancy control unit 150 increases the buoyancy by increasing the air pressure of the internal space 153 to a level higher than the water pressure, raising the nuclear fuel ultrasonic cleaning apparatus 100, reducing the air pressure to less than the water pressure, The ultrasonic transducer 111 is inserted into the empty fuel reservoir 31 and the absorption port 171a of the base plate 171 is brought into close contact with the fuel reservoir 30 while descending.

In this way, since the ultrasonic transducer 111 is inserted into the hollow portion of the fuel reservoir 30 in which the fuel is stored, the peripheral fuel is washed, and therefore, the fuel assembly is taken out from the fuel reservoir 30 Since there is no need to clean several fuel assemblies at the same time, the time required for cleaning is greatly reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

Claims (14)

An ultrasonic cleaner for inserting ultrasonic waves into an empty reservoir among a plurality of nuclear fuel storage reservoirs stored in the nuclear fuel storage reservoir filled with cooling water to clean impurities on the surface of the nuclear fuel assembly stored in the surrounding nuclear storage reservoir;
An impurity suction unit for sucking the cooling water to filter and filter the impurities; And
And a controller for controlling operations of the ultrasonic cleaner and the impurity suction unit,
The ultrasonic cleaning unit includes:
At least one ultrasonic transducer in the form of a longitudinally elongated shape for generating permanent ultrasonic waves and being inserted into the fuel reservoir; And
And at least one support member for supporting the at least one ultrasonic transducer in a longitudinally elongated form,
Wherein the at least one support member is a tube filled with a gas and having a predetermined buoyancy so that ultrasonic waves generated by the ultrasonic transducer are propagated outward.
delete delete The method according to claim 1,
A base plate for supporting the ultrasonic cleaning unit and the impurity suction unit; And
Further comprising a buoyancy regulator provided on one side of the base plate for generating a buoyancy to lighten the weight of the whole water.
5. The method of claim 4,
Wherein the buoyancy adjusting unit comprises:
A lower case fixed to the base plate;
An upper case forming an inner space portion having a variable size together with the lower case;
An intake pipe for supplying a gas to fill the internal space portion from the outside;
A pressure regulating valve for controlling the size of the buoyancy by regulating the volume of the internal space by controlling the air pressure of the internal space by opening and closing the intake pipe; And
And an exhaust valve for exhausting the gas filled in the internal space part.
6. The method of claim 5,
A first pressure gauge for measuring the water pressure of the cooling water in the fuel storage tank; And
And a second pressure gauge for measuring the air pressure of the internal space portion,
Wherein,
Wherein the controller controls the air pressure to be higher than the water pressure when the base plate is raised and controls the air pressure to be lower than the water pressure when the base plate is lowered.
5. The method of claim 4,
When the cleaning range of the ultrasonic cleaning unit is applied to the storage compartment in contact with the empty storage compartment,
Wherein the ultrasonic cleaning unit is provided at the center of a lower surface of the base plate and the impurity suction unit is provided on an upper surface of the base plate to suck the impurities.
The method according to claim 1,
The impurity-
A suction pump for sucking cooling water in the fuel storage tank; And
And a filter for filtering and filtering the impurities in the cooling water sucked by the suction pump.
9. The method of claim 8,
Further comprising a radiation detector for detecting the intensity of radioactivity of the impurities collected in the filter and providing the detected intensity to the control unit,
Wherein,
And when it is determined that the increase of the radiation intensity is stagnated, it is determined that the cleaning at the corresponding position is completed.
(a) inserting an ultrasonic cleaning part of an ultrasonic cleaning device into an empty storage space among a plurality of fuel storage containers stored in a nuclear fuel storage tank filled with cooling water;
(b) washing the impurities on the surface of the fuel assembly stored in the surrounding fuel storage space by ultrasonic waves generated by the ultrasonic scales; And
(c) the impurity suction portion of the ultrasonic cleaning device sucks the cooling water using a suction pump, and filters and filters the impurities floating in the cooling water using a filter,
The step (a)
Wherein the buoyancy regulating unit formed integrally with the ultrasonic cleaning unit and the impurity suction unit further comprises a buoyancy generating unit for regulating the size of the internal space.
delete 11. The method of claim 10,
The step of generating buoyancy comprises:
Wherein the control unit controls the air pressure of the internal space part to be larger than the water pressure of the cooling water in the fuel storage tank to raise the ultrasonic cleaning device and control the air pressure to be smaller than the water pressure so as to lower the ultrasonic cleaning device. Cleaning method.
11. The method of claim 10,
A plurality of fuel storage bases in the fuel storage tank are grouped in units of 3x3 when the cleaning range of the ultrasonic cleaning unit is in contact with the storage bases in contact with the empty storage bases, Leave the stand empty,
Wherein the steps (a) to (c) are sequentially repeated for each group.
11. The method of claim 10,
The step (c)
Detecting a radioactive intensity of an impurity trapped in the filter using a radiation detector, and determining that the cleaning at the position is completed when the increase in the radioactivity intensity is stalled.

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