JPH10132999A - Device and method for removing deposit uranium by washing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove uranium by washing in a short time, and reduce the production of a secondary waste by providing an oxalic acid supplying device and a hydrogen peroxide adding device on an acid washing tank, and providing oxalic acid distilling devices on the acid washing tank and a water washing tank. SOLUTION: A matter to be treated through an acetone tank 1 is ultrasonically vibrated in an acid washing tank 2, and uranium is removed by oxalic acid and hydrogen peroxide. Thereafter, the matter to be treated is washed in a water washing tank 3 and dried in a drying tank 4. The acid washing tank 2 is provided with an oxalic acid tank (supplying device) and a H2 O2 tank (hydrogen peroxide adding device) so as to regularly keep the hydrogen peroxide concentration and oxalic acid concentration in the washing solution constant. Since the activity of the acid is thus kept constant, the removing efficiency of uranium can be satisfactorily kept. Further, the acid washing tank 2 and the water washing tank 3 are provided with oxalic acid distilling devices, so that the washing solution in the acid washing tank 2. and the washing solution in the water washing tank are recovered and distilled, respectively, to recover oxalic acid, and the resulting water is returned to the water washing tank 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for removing and removing uranium from an object to be treated having uranium dioxide (UO ₂ : hereinafter referred to as uranium) adhered to the surface. is there.

[0002]

2. Description of the Related Art Pipes and mechanical parts to which uranium is attached are produced as radioactive waste from nuclear fuel production facilities and the like. Generally, such radioactive waste is collectively airtight such as a 200L drum. It is packed in highly radioactive shielding containers and stored in dedicated facilities such as storage facilities.

[0003] The demand for storage space is increasing because the amount of such radioactive waste is increasing year by year. However, it is difficult to secure a storage space due to the nature of radioactive waste. Has become an important issue.

Generally, as a method of reducing the volume of radioactive waste to which uranium is attached, there is a method of diverting an ultrasonic cleaning apparatus used for cleaning metal parts, semiconductors, and the like.

[0005]

However, the volume reduction of radioactive waste has the following problems. That is, an aqueous solution of oxalic acid is an example of a cleaning solution effective for cleaning uranium. Oxalic acid has the advantage of reacting selectively with uranium without reacting with the object itself, but the reaction rate between oxalic acid and uranium is slow, and the surface of the object There is also a disadvantage that it takes a lot of time to completely remove uranium adhering to the surface using oxalic acid.

[0006] Another problem is that a large amount of cleaning liquid used for cleaning uranium is generated as secondary waste. These cleaning solutions can be subjected to volume reduction by precipitation and separation by chemical treatment. However, the generation of these secondary wastes not only lowers the volume reduction rate, but also requires another treatment for the treatment of these secondary wastes. It requires a process and is costly.

[0007] Further, as another problem, radioactive waste is not always of a fixed material and shape, and may have various shapes such as a cylindrical shape such as a pipe or a complicated shape such as a mechanical part. There are many things to have. Since the conventional ultrasonic cleaning apparatus used for cleaning metal parts and semiconductors is configured to irradiate ultrasonic waves in a fixed direction with a constant intensity,
When such an ultrasonic cleaning device is used for cleaning and removing uranium, cleaning unevenness occurs depending on the shape of the radioactive waste, and uranium cannot be completely removed.

In view of the above, the present invention provides an apparatus for cleaning and removing adhered uranium which can efficiently and efficiently remove uranium in a short time when an oxalic acid aqueous solution is used as a cleaning solution for removing uranium from the surface of radioactive waste. It is intended to provide a cleaning removal method.

Another object of the present invention is to provide an apparatus and a method for cleaning and removing adhered uranium in which the amount of secondary waste generated in the uranium cleaning and removal operation of radioactive waste is as small as possible.

It is a further object of the present invention to provide an apparatus and a method for cleaning and removing adhered uranium which can always stably wash radioactive waste of any shape without causing uneven cleaning. I have.

[0011]

According to the first aspect of the present invention, in order to solve the above-mentioned problem, pickling of uranium dioxide adhering to an object to be processed is pickled with a cleaning liquid comprising an aqueous oxalic acid solution to which hydrogen peroxide has been added. An apparatus for cleaning and removing adhered uranium having an apparatus and a washing apparatus having a washing tank for washing the pickled object with washing water, wherein the pickling apparatus includes:
An pickling tank containing the cleaning liquid, an oxalic acid supply device for supplying oxalic acid into the pickling tank, a hydrogen peroxide addition device for adding hydrogen peroxide into the pickling tank, and the pickling tank An ultrasonic generating means for applying ultrasonic vibration to the inside, and a heating means for heating the cleaning liquid in the pickling tank to a predetermined temperature, wherein the pickling tank and the water washing tank include the cleaning liquid. Alternatively, an oxalic acid distillation apparatus for recovering oxalic acid and uranyl oxalate by distilling the washing water and returning the obtained water to the washing tank is provided.

In the present invention, uranium adhering to an object to be treated is pickled by using a cleaning solution obtained by adding hydrogen peroxide to an oxalic acid aqueous solution. At this time, uranium is oxidized by hydrogen peroxide to a hexavalent state which is most likely to react with oxalic acid, and the oxidized uranium reacts with oxalic acid to produce uranyl oxalate. The reaction formula at this time is shown below.

[0013] _{UO 2 + H 2 O 2 →} UO 2 2+ + H 2 O + O 2- ···· (1) the formula ^{_{UO 2 2+ + 3H 2 C 2}} O 4 + O 2- → H 4 UO 2 (C 2 O ₄ ) ₃ + H ₂ O (2)

The reaction proceeds most when an aqueous solution containing 5 to 10% of oxalic acid and 1 to 3% of hydrogen peroxide is used as a washing solution, and is preferably 5 to 10%.
An aqueous solution containing oxalic acid and 1-3% hydrogen peroxide is used as a cleaning solution.

Further, in the present invention, the pickling tank containing the cleaning liquid includes an oxalic acid supply device for supplying oxalic acid, and a hydrogen peroxide addition device for adding hydrogen peroxide to the pickling tank.
Ultrasonic generation means for applying ultrasonic vibration in the pickling tank,
And heating means for heating the cleaning liquid in the pickling tank to a predetermined temperature.

That is, hydrogen peroxide and oxalic acid react with uranium adhering to the object as shown in the above formulas (1) and (2), respectively. The amount of hydrogen peroxide and oxalic acid in the pickling tank decreased,
Uranium removal efficiency is reduced. Therefore, in the present invention, an oxalic acid supply device and a hydrogen peroxide addition device are attached to the pickling tank, and the hydrogen peroxide and oxalic acid are constantly maintained at a constant hydrogen peroxide concentration and oxalic acid concentration in the cleaning solution. Has been added. This keeps the activity of the acid constant,
Uranium removal efficiency can always be kept good.

The pickling tank also includes an ultrasonic wave generating means and a heating means. The ultrasonic wave generating means applies ultrasonic waves to the object in the pickling tank to physically remove uranium from the object. The cleaning liquid is heated by a heating means to a predetermined temperature, preferably 90 to 100 ° C., which is the optimum temperature for the reaction with uranium, and the uranium is also chemically treated. It is easy to withdraw from.

Further, in the present invention, an oxalic acid distillation apparatus is attached to both the pickling tank and the water washing tank, and the cleaning liquid in the pickling tank and the cleaning water in the water washing tank are respectively collected and distilled to obtain oxalic acid and water. It is configured to recover uranyl oxalate and return the obtained water to the washing tank.

Thus, uranyl oxalate generated by the reaction between uranium and oxalic acid on the surface of the object can be taken out of the cleaning solution. Therefore, the storage space can be significantly reduced as compared with the conventional case where pipes, mechanical parts, and the like are directly housed in a highly airtight radioactive shielding container such as a 200 L drum. Of course, by drying the uranyl oxalate taken out, the volume can be further reduced, so that the amount as radioactive waste is much smaller than before.

The object to be treated after the treatment in the pickling tank is washed with water in the washing tank. At this time, the cleaning liquid adhering to the surface of the object to be treated is produced by the reaction between uranium and oxalic acid. Uranyl oxalate will remain in the washing tank. In the present invention, by providing the oxalic acid distillation apparatus also in the washing tank, the washing liquid and uranyl oxalate in the washing tank are removed, and the object to be treated can always be washed with normal water.

Further, according to the present invention, the oxalic acid distillation apparatus is configured to return the washing liquid in the pickling tank and the water obtained by distilling the washing water in the washing tank to the washing tank as washing water. The amount of liquid to be disposed of can be reduced.

According to a second aspect of the present invention, in the apparatus for cleaning and removing adhered uranium according to the first aspect, the pickling tank includes a concentration detector for detecting a concentration of hydrogen peroxide and a concentration of oxalic acid in the cleaning solution. Means, and adjusting means for adjusting the amount of hydrogen peroxide added to the hydrogen peroxide adding apparatus and / or the amount of oxalic acid supplied to the oxalic acid supplying apparatus based on the detection result of the detecting means. And

The rate of reaction between uranium and oxalic acid changes according to the oxalic acid concentration and the concentration of hydrogen peroxide. When uranium and oxalic acid react, the amount of oxalic acid decreases, and the reaction rate decreases. That is, in order to always react uranium with oxalic acid at a constant rate, it is necessary to add a reduced amount of oxalic acid to the cleaning solution as needed by reacting with uranium.

Therefore, in the present invention, the oxalic acid amount and the hydrogen peroxide amount in the cleaning solution are detected by the concentration detecting means so that the oxalic acid amount and the hydrogen peroxide amount in the cleaning solution become constant. It is adjusted by adjusting means.

For example, the reaction between uranium and oxalic acid progresses most when the cleaning solution contains 5 to 10% oxalic acid and 1 to 3% hydrogen peroxide. Detects the concentration of oxalic acid or the concentration of hydrogen peroxide in the pickling tank, and the values detected at this time are:
When the respective values become smaller than the predetermined values, the adjusting means adds or supplies hydrogen peroxide and / or oxalic acid until the respective values become the predetermined values, thereby adjusting the acid activity to be constant. .

Further, in the invention according to claim 3, in the apparatus for cleaning and removing adhered uranium according to claim 1, a degreasing tank using a degreasing bath containing an organic solvent is provided before the pickling tank.
The degreasing tank is provided with an organic solvent distillation apparatus for recovering the organic solvent from the tank by distillation and returning it to the degreasing tank.

That is, in many cases, oil such as mechanical oil is attached to the object to be treated, in addition to uranium, and this oil interferes with the above-described equations (1) and (2), and Removal efficiency may be reduced. Therefore, in the present invention, a degreasing tank is provided in front of the pickling tank, and degreasing is performed in the degreasing tank before pickling the object to be processed, so that oil such as mechanical oil adhering to the surface of the object to be processed is removed. It removes the uranium in the pickling tank so that it can be effectively cleaned and removed.

Further, the degreasing tank is provided with an organic solvent distillation apparatus. This apparatus separates the oil dissolved in the organic solvent from the organic solvent by distillation, collects the organic solvent, and removes the organic solvent from the degreasing tank. , It is possible to reduce the amount of liquid to be disposed of as a waste liquid as a whole.

According to a fourth aspect of the present invention, in the apparatus for cleaning and removing adhered uranium according to the first aspect, the heating means includes a closed circulation system for heating an outer wall surface of the pickling tank with a heating liquid medium. And

That is, since the cleaning liquid is an acid solution, if a heating means such as a thermostat is directly introduced into the cleaning liquid and the cleaning liquid is directly heated, the heating means is damaged by corrosion.
Therefore, in the present invention, a heating means such as a thermostat is put into a heating liquid medium such as water to heat the pickling tank indirectly from the outer wall surface of the pickling tank.

Further, since such a heating liquid medium is circulated, the temperature of the heating liquid medium itself is always made uniform,
The entire pickling tank can always be maintained at the optimum temperature.

For the same reason, the ultrasonic wave generating means for applying ultrasonic vibration to the pickling tank does not directly apply ultrasonic vibration to the pickling tank, but applies the ultrasonic vibration to the cleaning liquid via a heating liquid medium. It is preferable to use a configuration in which ultrasonic vibration is applied indirectly, such as by applying ultrasonic waves. However, as described above, the optimal temperature of the reaction with uranium is 90 to 100 ° C. Depending on the type of heating liquid medium such as
Many bubbles may be generated.

Since the bubbles absorb the ultrasonic vibration, the ultrasonic vibration is not transmitted to the pickling tank. Therefore, by employing a configuration in which the heating liquid medium is circulated, bubbles generated in the heating liquid medium can be removed, so that ultrasonic vibration can always be transmitted to the cleaning liquid satisfactorily.

According to a fifth aspect of the present invention, in the apparatus for cleaning and removing adhered uranium according to the first aspect, the object to be treated is moved into the pickling tank and / or the water washing tank to change its arrangement. Means.

That is, in the present invention, even if the moving means moves the object and changes the arrangement, the ultrasonic wave generating means irradiates ultrasonic waves in a certain direction with a constant intensity on the object. On the other hand, since ultrasonic waves are emitted from various angles, it is possible to prevent the occurrence of uneven cleaning.
As such moving means, there are elevating means for elevating and lowering the object to be processed in each tank with a constant torque, and rotating means for rotating the object to be processed by changing the number of rotations at a certain rotation speed or at a certain time interval. No.

Further, the invention according to claim 6 is a pickling step of pickling uranium dioxide adhering from the object to be treated with a cleaning liquid comprising an aqueous oxalic acid solution to which hydrogen peroxide has been added,
A washing step of washing the pickled object with washing water, wherein the pickling step includes immersing the object in a cleaning solution heated to a predetermined temperature. By applying ultrasonic vibration, the uranium dioxide on the surface of the object is washed and removed, and in the water washing step, the object to be pickled in the pickling step is immersed in cleaning water to generate ultrasonic vibration. By giving, the cleaning liquid on the surface of the object to be treated is removed, uranyl oxalate in the cleaning liquid and oxalic acid and uranyl oxalate in the cleaning water are respectively recovered by distillation, and the obtained water is returned to the water cleaning tank. A method for cleaning and removing adhered uranium, further comprising a reprocessing step.

According to the present invention, when pickling uranium adhering to an object to be treated with a cleaning solution comprising an aqueous oxalic acid solution to which hydrogen peroxide has been added, the cleaning solution is heated to a predetermined temperature,
In addition, ultrasonic vibration is given.

That is, the cleaning solution comprising an aqueous solution of oxalic acid to which hydrogen peroxide has been added provides a hexavalent state in which hydrogen peroxide is most likely to react with oxalic acid and a uranium in which oxalic acid is in a hexavalent state. To produce uranyl oxalate, which proceeds in different ways depending on the temperature of the cleaning solution. Therefore, in the present invention, the reaction efficiency of oxalic acid and uranium is improved by heating the cleaning liquid to a predetermined temperature, that is, a temperature at which the reaction proceeds most favorably.

At this time, by applying ultrasonic vibration to the cleaning liquid, uranium adhering to the surface of the object to be processed is separated from the surface of the object to be processed, and is easily affected by the cleaning liquid. Improves reaction efficiency.

After the pickling step, the object to be treated is immersed in washing water and washed with water by applying ultrasonic vibration to complete the washing and removal of the attached uranium of the present invention. In the present invention, the washing liquid and the washing water are re-treated. And a reprocessing step.

That is, as the treatment of the object proceeds, the amount of uranyl oxalate generated by the reaction between oxalic acid and uranium in the cleaning liquid adheres to the surface of the object in the cleaning water. The amount of oxalic acid and uranyl oxalate increases. In particular, in the case of performing a batch type cleaning, the reaction efficiency is reduced when a large amount of uranyl oxalate is present in the cleaning solution, and when a large amount of oxalic acid and uranyl oxalate is present in the cleaning water, when the object to be treated is lifted, This is not preferable because there is a possibility of adhering.

Accordingly, in the present invention, the oxalic acid and uranyl oxalate contained in each of the cleaning liquid and the cleaning water are distilled to recover the uranyl oxalate content in the cleaning liquid and the cleaning water. Further, since the water obtained at this time is reused as washing water, the amount of liquid to be disposed of as waste liquid can be reduced.

Therefore, the storage space can be significantly reduced as compared with the conventional case where pipes, mechanical parts, and the like are directly housed in a highly airtight radioactive shielding container such as a 200 L drum. Of course, by drying the uranyl oxalate taken out, the volume can be further reduced, so that the amount as radioactive waste is much smaller than before.

In the invention according to claim 7, in the method for cleaning and removing adhered uranium according to claim 6, the cleaning solution is an aqueous solution containing 5 to 10% oxalic acid and 1 to 3% hydrogen peroxide. Wherein the heating is performed so that the temperature is 90 to 100 ° C.

As described above, the progress of the reaction between oxalic acid and uranium depends on the concentration of oxalic acid contained in the cleaning solution and the temperature of the cleaning solution. Here, the optimum concentration of oxalic acid contained in the cleaning solution, that is, the concentration at which uranium was most removed was examined.

An aqueous solution containing 3% of oxalic acid as a washing solution;
An aqueous solution containing 5%, an aqueous solution containing 10%, and an aqueous solution containing 15% were prepared, and changes in the surface contamination density after cleaning for a certain period of time were examined. FIG. 4 shows the results.
The vertical axis indicates the surface contamination density (Bq / cm ² ), and the horizontal axis indicates the cleaning time (minute).

At the same time, hydrogen peroxide was added to each of these four concentrations of oxalic acid aqueous solution at 0% and 0.5%, respectively.
%, 1%, and 3%, the change in surface contamination density after cleaning for a certain period of time was examined. The result is shown in FIG. The vertical axis indicates the surface contamination density (Bq / cm ² ), and the horizontal axis indicates the cleaning time (minute).

From the above, it was found that an aqueous solution containing 5 to 10% of oxalic acid and 1 to 3% of hydrogen peroxide has the lowest surface contamination density, and the reaction between oxalic acid and uranium proceeds.

Further, using the cleaning liquid which has most advanced reaction with uranium, the uranium cleaning / removing ability depending on the material of the object to be treated and the uranium cleaning / removing ability depending on the temperature of the cleaning liquid were examined. FIG. 6 shows the uranium cleaning / removing ability when the temperature of the cleaning liquid is 25 ° C. (normal temperature), FIG. 7 shows the uranium cleaning / removing ability when the cleaning liquid is 60 ° C., and FIG. 8 shows the uranium cleaning / removing ability when the cleaning liquid is 90 ° C.

From these results, it can be seen that the temperature at which the reaction proceeds most is 90 ° C. or higher. When the oxalic acid solution has a concentration of 5%, the oxalic acid solution boils at 100 to 105 [deg.] C. However, boiling causes bubbles in the solution, and the bubbles reduce the ultrasonic action. An aqueous solution containing 10% of oxalic acid and 1 to 2% of hydrogen peroxide is heated as a temperature of 90 to 100 ° C. and used as a cleaning liquid.

In the invention according to claim 8, in the method for cleaning and removing adhered uranium according to claim 6, an ultrasonic vibration is applied to the cleaning liquid via an ultrasonic transmission medium. And how to do it.

That is, in the present invention, in order to promote the reaction between oxalic acid and uranium, in addition to adjusting the optimal temperature conditions and chemical conditions such as oxalic acid concentration and hydrogen peroxide concentration,
By physically applying ultrasonic vibration, the reaction between oxalic acid and uranium is further facilitated, and the reaction time is further shortened.

According to a ninth aspect of the present invention, in the method for cleaning and removing adhered uranium according to the sixth aspect, the object is moved and changed in the pickling tank and / or the water washing tank. The method is characterized in that the traveling direction of the ultrasonic wave applied to the object is relatively changed.

Generally, an ultrasonic vibrator for generating ultrasonic waves is provided at one place. Although it is also possible to provide a plurality of transducers to the pickling tank or the washing tank so as to apply ultrasonic waves to the object to be treated from a plurality of directions, in the present invention, in the pickling tank and the washing tank, By moving the object, the traveling direction of the ultrasonic wave applied to the object is relatively changed.

As a result, even if the ultrasonic waves in the pickling tank and the water washing tank are irradiated with a fixed intensity and a fixed direction, the object to be processed is irradiated with the ultrasonic waves from various angles.
The occurrence of uneven cleaning can be prevented. Further, there is an advantage that the mechanism is simple and the cost is not required because a plurality of transducers are not required.

[0056]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIG. 1, but it is needless to say that the present invention is not limited to this embodiment.

In FIG. 1, this apparatus comprises an acetone tank 1 containing acetone as a degreasing bath, and an acetone tank 5 containing a cleaning liquid.
Pickling tank 2 containing an aqueous solution containing 1% oxalic acid and 1% hydrogen peroxide, and washing tank 3 containing pure water for washing.
And a drying tank 4 for blowing hot air at a constant temperature. Acetone tank 1 and pickling tank 2 each have a thickness of 5 to 10 mm
Are provided with inner tanks 1a and 2a made of heat-resistant glass.
Acetone or the cleaning liquid is contained in the inner tanks 1a and 2a, respectively.

In the acetone tank 1 and the pickling tank 2, the space between the inner tanks 1a and 2a and the outer tanks 1b and 2b is filled with water, and ultrasonic vibration is applied to the water to apply ultrasonic waves. The child 6a, 6b is provided. The ultrasonic transducer 6a,
6b gives ultrasonic waves to water, and water applies ultrasonic waves to the inner tank 1;
Since it functions as an ultrasonic transmission medium for transmitting to the acetone or the cleaning liquid in a and 2a, the ultrasonic waves from the ultrasonic vibrators 6a and 6b are transmitted to the acetone or the cleaning liquid via water.

Each of the acetone tank 1, the pickling tank 2 and the water washing tank 3 is provided with an elevating device as shown in FIG. This lifting / lowering device includes a cleaning basket holding table 21 for holding a cleaning basket 20 and an air cylinder 22. The air cylinder 22 has a stroke of 15 cm.
Is raised and lowered (in the case of 28 KHz), whereby the cleaning basket 20 held on the cleaning basket holding table 21 is raised and lowered at a constant stroke in each tank. The material of the elevator is SUS31 considering corrosion resistance.
It is 6.

During the repetition of the cleaning operation, the impurities in the acetone increase and the acetone is contaminated.
Is provided with an acetone distillation apparatus. In this acetone distillation apparatus, acetone in the acetone tank 1 is distilled and collected, and returned to the tank again, and impurities in the acetone are collected as a residue. As a result, clean acetone is always stored in the acetone tank 1, so that not only the cleaning efficiency is improved but also the amount of acetone as waste liquid can be significantly reduced.

For the same reason, the pickling tank 2 is also provided with an oxalic acid distillation apparatus. That is, while the washing operation is repeated, uranyl oxalate generated in the washing solution increases and the washing solution is contaminated. Therefore, the oxalic acid distillation apparatus distills the washing solution in the pickling tank 2 to oxalic acid and uranyl oxalate. Is recovered as a residue. At this time, the obtained water is supplied into the washing tank 3 as rinsing water. Here, although not particularly shown, the radioactivity was measured at this time, and it was confirmed that the radioactivity was below the specified value.

As a result, the pickling tank 2 contains a cleaning liquid containing as little impurities as possible, so that not only the cleaning efficiency is improved but also the amount of cleaning liquid as waste liquid can be greatly reduced.

The pickling tank 2 has an inner tank 2a and an outer tank 2b.
In addition to the water and the ultrasonic vibrator 6b, a heater 5 with a thermostat, which is a heating means, and a circulation pump P constituting a closed circulation system are provided. The thermostat-equipped heater 5 adjusts the temperature of the water so as to be always 90 ° C., and the circulation pump P is driven by the inner tank 2 a and the outer tank 2 b
The generated water is circulated to remove air bubbles and to equalize the temperature of the water.

Further, a cleaning liquid is stored in the inner tank 2a of the pickling tank 2. The inner tank 2a is provided with a PH meter for measuring the pH of the cleaning liquid as a concentration detecting means, and a PH meter as an adjusting means. Pumps P1 and P2 with valves for opening and closing the valve based on the result are provided.

The pumps P1 and P2 with valves are respectively connected to an H ₂ O ₂ tank and an oxalic acid tank, and the valves are opened at a rate based on the detection result of the PH meter to open the H ₂ O ₂ amount or the oxalic acid tank. The amount of acid is adjusted to be always constant.

The water washing tank 3 is a tank for washing an object to be processed after being processed by the pickling tank 2 with ultrasonic vibration from the ultrasonic vibrator 6c and with a lifting device (not shown). Since the washing water contained in the tank is contaminated while repeating the above, a PH meter for measuring the acidity of the washing water and an oxalic acid distillation apparatus for removing oxalic acid and uranyl oxalate in the washing water are provided. Is provided.

In this embodiment, the oxalic acid distillation apparatus provided in the pickling tank 2 distills the washing water in the washing tank 3. The oxalic acid distillation apparatus and the washing tank 3 are connected via a switching valve. The switching valve is closed when the inside of the pickling tank 2 and the oxalic acid distillation apparatus are connected, and the inside of the pickling tank 2 is closed. When the connection between the oxalic acid distillation apparatus and the oxalic acid distillation apparatus is closed, the connection is opened to connect the inside of the washing tank 3 with the oxalic acid distillation apparatus.
The switching valve may be controlled such that the open / close state is automatically switched at regular intervals, or may be manually controlled.

In this embodiment, the oxalic acid distillation apparatus provided in the pickling tank 2 is configured to distill the washing water in the washing tank 3. The water in the washing tank 3 may be distilled by the oxalic acid distillation apparatus described above.

Further, the drying tank 4 is provided with a heater H and a blower 7, and the air heated to 100 ° C. by the heater H is sent out by the blower 7. Hot air is supplied.

In this embodiment, the distillation apparatus having the structure shown in FIG. 3 is used. That is, the liquid to be distilled is
The water is introduced into the distillation apparatus through the water injection pipe 31. The water injection pipe 31 is provided with a solenoid valve SV. The solenoid valve SV detects a water level A of a water level meter L provided in the distillation apparatus. The opening and closing of the valve is controlled so that the water level is constant.

This distillation apparatus is provided with a heater 32 inside, and the temperature of the heater 32 is controlled such that water is evaporated at a capacity of 10 L / h. A take-out valve 33 is provided at the bottom of the distillation apparatus so that uranyl oxalate accumulated at the bottom can be taken out from the take-out valve 33. The uranyl oxalate taken out is cooled to room temperature, dehydrated and dried to reduce the volume, and then discarded as solid waste.

The water evaporated from the surface is collected in the cooling tower 34 and cooled and liquefied as it rises. The liquefied water is guided to the outside through a water outlet 34a provided in the cooling tower 34. Is introduced into the washing tank 3 connected to the water outlet 34a.

In the case where the object to be treated having uranium adhered to the surface is washed and removed by using the apparatus having the above-described configuration, first, the object to be treated is immersed in an acetone tank, and the surface of the object is stained with ultrasonic waves by oil. Get rid of.

Although not particularly shown here, the object to be processed is placed in a cleaning basket so that a plurality of objects having various shapes can be cleaned at one time. The washing basket is set so as to pass through the acetone tank 1, the pickling tank 2, the washing tank 3, and the drying tank 4 by about 15 minutes by an automatic transport device. The acetone tank 1, the pickling tank 2, and the washing tank are used. Each of the tanks 3 is configured to be moved up and down by a 15 cm stroke by an elevating device.

The object to be processed after passing through the acetone tank 1 is put into the pickling tank 2, where it is subjected to a physical action by ultrasonic vibration and at the same time by the action of oxalic acid and hydrogen peroxide whose temperature has been adjusted to 90 ° C. Uranium attached to the surface of the object to be treated is converted into uranyl oxalate by a chemical action, and is removed from the object.

After a lapse of 15 minutes, the washing basket is transferred from the pickling tank 2 to the washing tank 3 and is washed well in the washing tank 3. At this time, oxalic acid and uranyl oxalate adhering to the surface of the workpiece are removed.

The washing basket washed well in the washing tank 3 is put into a drying tank 4 where it is dried by warm air heated to 100 ° C. Thereafter, the radioactivity is measured to confirm that the value is below the specified value, and the uranium washing and removal is completed.

[0078]

As described above, according to the present invention, even when an oxalic acid aqueous solution is used as a cleaning solution for removing uranium on the surface of radioactive waste, uranium can be efficiently removed in a short time. It is.

Further, impurities contained therein are removed by distillation of the washing liquid or washing water used for removing uranium,
The obtained water is reused as washing water, and the organic solvent is also recycled by distillation, so that the amount of secondary waste generated can be reduced.

Of course, the present invention also has an advantage that any type of radioactive waste can be stably washed without causing uneven cleaning.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an apparatus for cleaning and removing adhered uranium according to an example of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an elevating device used in the present embodiment.

FIG. 3 is a schematic configuration diagram of a distillation apparatus used in the present embodiment.

FIG. 4 is a graph showing changes in surface contamination density at different oxalic acid concentrations.

FIG. 5 is a diagram showing changes in surface contamination density at different hydrogen peroxide concentrations.

FIG. 6 is a diagram showing the uranium cleaning and removing ability at 25 ° C. depending on the material of the object to be treated.

FIG. 7 is a diagram showing the uranium cleaning and removing ability at 60 ° C. depending on the material of the object to be treated.

FIG. 8 is a diagram showing the uranium cleaning and removing ability at 90 ° C. depending on the material of the object to be treated.

[Explanation of symbols]

 1: acetone tank 2: pickling tank 1a, 2a: inner tank 1b, 2b: outer tank 3: washing tank 4: drying tank 5: heater with thermostat 6a, 6b, 6c: ultrasonic vibrator 7: blower 20: cleaning Basket 21: Cleaning basket holder 22: Air cylinder 31: Water injection pipe 32, H: Heater 33: Take-out valve 34: Cooling tower SV: Solenoid valve L: Water level gauge P: Circulating pump P1, P2: Pump with valve

Claims (9)

[Claims] 1. A pickling apparatus for pickling uranium dioxide adhered to an object to be treated with a cleaning liquid comprising an aqueous oxalic acid solution to which hydrogen peroxide has been added, and a washing tank for washing the pickled object to be treated with washing water. An attached uranium washing and removing device having a water washing device comprising: a pickling tank containing the cleaning liquid; and an oxalic acid supply device that supplies oxalic acid into the pickling tank. A hydrogen peroxide adding device for adding hydrogen peroxide into the pickling tank, an ultrasonic generating means for applying ultrasonic vibration to the pickling tank, and a cleaning liquid in the pickling tank at a predetermined temperature. Heating means for heating, and in the pickling tank and the washing tank, the washing liquid or washing water is distilled to recover oxalic acid and uranyl oxalate, and the obtained water is placed in the washing tank. An oxalic acid distillation unit for returning to Adhering uranium washed away and wherein the. 2. A concentration detecting means for detecting a concentration of hydrogen peroxide and an oxalic acid concentration of the cleaning liquid in the pickling tank, and a peroxide of the hydrogen peroxide adding device based on a detection result of the detecting means. The apparatus for cleaning and removing adhered uranium according to claim 1, further comprising adjusting means for adjusting the amount of hydrogen added and / or the amount of oxalic acid supplied to the oxalic acid supply device. 3. A degreasing tank provided with a degreasing bath containing an organic solvent in front of the pickling tank, wherein the degreasing tank recovers an organic solvent from the tank by distillation and returns the organic solvent to the degreasing tank. The attached uranium cleaning / removing apparatus according to claim 1, further comprising: 4. The apparatus for cleaning and removing adhered uranium according to claim 1, wherein said heating means includes a closed circulation system for heating an outer wall surface of the pickling tank with a heating liquid medium. 5. The apparatus for cleaning and removing adhered uranium according to claim 1, further comprising a moving means for moving and moving an object to be treated in the pickling tank and / or the water washing tank. 6. A pickling step of pickling uranium dioxide adhered from an object to be treated with a cleaning liquid comprising an aqueous oxalic acid solution to which hydrogen peroxide has been added, and a water washing step of washing the pickled object to be treated with washing water. In the pickling step, the object to be treated is immersed in a cleaning solution heated to a predetermined temperature and subjected to ultrasonic vibration,
The uranium dioxide on the surface of the object is washed and removed, and in the water washing step, the object to be pickled in the pickling step is immersed in cleaning water and subjected to ultrasonic vibration to thereby remove the surface of the object. Removing the washing liquid, further comprising recovering uranyl oxalate in the washing liquid and oxalic acid and uranyl oxalate in the washing water by distillation, and returning the obtained water to the washing tank; A method for cleaning and removing adhered uranium. 7. The cleaning solution is an aqueous solution containing 5 to 10% of oxalic acid and 1 to 3% of hydrogen peroxide, and is heated to a temperature of 90 to 100 ° C. 7. The method for cleaning and removing adhered uranium according to claim 6, wherein: 8. The method for cleaning and removing adhered uranium according to claim 6, wherein ultrasonic vibration is applied to the cleaning liquid via an ultrasonic transmission medium. 9. The moving direction of the ultrasonic wave applied to the object to be processed is relatively changed by moving the object to be processed and changing the arrangement in the pickling tank and / or the water washing tank. The method for cleaning and removing adhered uranium according to claim 6.