JPH08277428A - Separation of technetium and device therefor - Google Patents

Abstract

PURPOSE: To reduce the generation of a secondary radioactive waste resulting from the separation of technetium. CONSTITUTION: A salt-free reagent as a reducing agent and a catalyst are added to a radioactive waste liq. contg. technetium in a waste liq. treating tank 5. The reduction of technetium is promoted by the action of the reagent and catalyst, and the technetium is converted to metallic technetium. The metallic technetium and catalyst are removed from the radioactive waste liq. by a filter part 33. Since the salt-free reagent is decomposed into gas by the reduction reaction, the technetium is not contained in the secondary radioactive waste. Consequently, the generation of the secondary radioactive waste is reduced as the technetium is separated. Further, since the technetium is efficiently reduced to metallic technetium, the technetium concn. in the radioactive waste is remarkably decreased after the metallic technetium is removed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for separating and removing technetium from a solution containing a radionuclide.
Solutions containing radionuclides are used in nuclear power plants, reprocessing plants,
This is a radioactive liquid waste generated from radioactive isotope handling facilities and other nuclear facilities.

[0002]

2. Description of the Related Art Conventional technetium separation methods include:
As described in JP-A-54-96412, JP-A-62-3694, JP-A-5-188188, or JP-A-4-204293, the technetium in the waste liquid is subjected to a solvent extraction method or a molten salt. It was separated and removed by the extraction method. As described in JP-A-60-194399, JP-A-5-66289, JP-A-1-215727 or JP-A-2-54732, an ion exchange method or an adsorption method has been adopted.

Further, JP-A-5-52995 discloses an oxidation volatilization method, JP-A-5-100085 discloses a combined use of an anion exchange method and a reduction precipitation method to an oxide, and JP-A-5-209998 discloses. The combined use of the reduction method to the oxide and the electrolytic deposition method of the coexisting metal for the purpose of removing from the metal is described respectively.

Further, JP-A-62-93320 describes a method of recovering Tc by heating in the presence of a reducing agent and a platinum group element. Japanese Unexamined Patent Publication No. 215895/1993 describes a method of adding SiC and alcohol as a reducing agent and a reducing aid, respectively, as one of the methods for recovering Ru and Tc at the same time.

[0005]

In the conventional method, a relatively large amount of solvent, molten salt, ion exchanger (resin) and adsorbent (activated carbon) were required. Further, the volatilization method requires an oxidizing agent and sulfuric acid, and when two types of methods are used together, complicated operations and processes are required. Further, it is necessary that a platinum group element such as Ru coexists, and a heating operation, a solid reducing agent,
A reduction aid was needed.

[0006] It is an object of the present invention to provide a technetium separation method and apparatus capable of reducing the amount of radioactive secondary waste generated in the technetium separation treatment.

Another object of the present invention is to provide a technetium separation method and an apparatus therefor capable of further promoting the reduction reaction.

Another object of the present invention is to provide a technetium separation method which can simplify the apparatus structure.

Another object of the present invention is to provide a technetium separation method capable of reducing the amount of reducing agent used.

Another object of the present invention is to provide a technetium separation method which can improve the recovery efficiency of solid technetium.

Another object of the present invention is to provide a technetium separation method which can reduce the consumption of catalyst.

Another object of the present invention is to provide a technetium separation method which does not require the installation of a new device for returning the removed catalyst into the container.

[0013]

The feature of the invention of claim 1 that achieves the above object is that a reducing agent, a salt-free reagent, is added to radioactive waste liquid to reduce technetium in the presence of a catalyst and a salt-free reagent. To make it a solid state and separate it from the radioactive liquid waste.

The technetium in the radioactive liquid waste is efficiently reduced to metal technetium by the action of the catalyst and the salt-free reagent. Therefore, the concentration of technetium in the radioactive liquid waste after the metal technetium removal is significantly reduced.

Although the salt-free reagent is a weak reducing agent, it can promote the reduction reaction of technetium due to the promoting effect of the catalyst. The catalyst promotes the reduction of technetium to the solid state. The effect of promoting reduction by the catalyst is exerted by adsorbing hydrogen on the catalyst surface and reacting it with technetium. The salt-free reagent is decomposed into gas components such as nitrogen and carbon dioxide by the reaction with technetium or the reaction with holes. Therefore, the salt-free reagent does not become radioactive secondary waste, but the amount of radioactive secondary waste that accompanies the technetium separation treatment is reduced.

In order to achieve the above-mentioned other object, the feature of the invention of claim 2 is that a photocatalyst is used as a catalyst, and a radioactive waste liquid containing a salt-free reagent and a photocatalyst is irradiated with electromagnetic waves to reduce technetium to a solid state. It is in.

Since the photocatalyst is used, the reduction reaction of technetium is promoted as compared with the case where the photocatalyst is not used.
Further, technetium solidified by the reduction reaction is adsorbed on the photocatalyst in a short time. This effectively removes technetium in the radioactive liquid waste.

The photocatalyst emits electrons to accelerate the reduction reaction of technetium upon irradiation with electromagnetic waves. Further, the photocatalyst adsorbs hydrogen (atoms) on the surface and reacts with technetium to accelerate the reduction reaction. Electromagnetic waves serve to release electrons and holes from the photocatalyst. Electrons directly and indirectly reduce technetium, and holes are consumed by salt-free reagents or electron donors.

A feature of the invention of claim 3 for achieving the above-mentioned other object is to supply a radioactive liquid waste containing a salt-free reagent into a column packed with a catalyst.

As a result, the device structure can be remarkably simplified. Further, technetium in the radioactive liquid waste can be reduced and removed more continuously by a relatively simple operation.

A feature of the invention of claim 4 to achieve the above-mentioned other object is to use a salt-free reagent containing nitrogen and hydrogen as the salt-free reagent.

Since the salt-free reagent contains nitrogen and hydrogen, the reducing action of technetium is large. Therefore, technetium can be efficiently reduced with a relatively small amount of salt-free reagent.

Salt-free reagents containing nitrogen and hydrogen include ammonium salts, hydrazine salts and hydroxylamine salts.

A feature of the invention of claim 6 for attaining the above-mentioned other object is to adsorb the solid technetium to the catalyst.

Since the technetium solid produced by the reduction reaction is adsorbed on the catalyst, the efficiency of recovering the technetium solid from the radioactive waste liquid is improved.

The feature of the invention of claim 7 that achieves the above-mentioned other object is that a radioactive waste liquid containing a catalyst and a salt-free reagent is present in a container, and technetium contained in the radioactive waste liquid is reduced to a solid state. , The catalyst and solid technetium are removed from the radioactive liquid waste discharged from the container, a new radioactive liquid waste is supplied into the container, and this new radioactive liquid waste is to contain the removed catalyst and solid technetium. .

The catalyst removed from the discharged radioactive waste liquid can be used for new radioactive waste liquid, and the consumption amount of the catalyst can be reduced. As a result, the amount of catalyst that becomes radioactive waste can be significantly reduced, so the amount of radioactive secondary waste generated by the technetium separation treatment is reduced.

In order to achieve the above-mentioned other object, the feature of the invention of claim 8 is that the catalyst and solid-state technetium are removed by a filter from the radioactive waste liquid from which the catalyst and solid-state technetium are discharged. It is to be carried into the container by the new radioactive waste liquid that has passed through and is supplied to the container.

The catalyst removed by the filter is carried into the container by using the new radioactive waste liquid which has passed through the filter and is supplied into the container, so that the removed catalyst can be easily returned into the container. be able to. It is not necessary to install a new device to return the removed catalyst into the container.

A feature of the invention of claim 9 that achieves the above-mentioned other object is that the catalyst and solid technetium are removed from the discharged radioactive waste liquid by a filter provided near the waste liquid discharge part at the bottom of the container, After the new radioactive waste liquid is supplied into the container, the catalyst and solid technetium removed by the filter are mixed with the new radioactive waste liquid by agitating the new radioactive waste liquid.

As in the case where the catalyst removed by the filter using the new radioactive waste liquid is carried into the container, the removed catalyst can be easily returned to the container. It is not necessary to install a new device to return the removed catalyst into the container.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(Example 1) The first example of the present invention is a method for separating technetium from a high-level waste liquid generated by reprocessing of nuclear fuel, which will be described with reference to FIG.

A switching valve 6 is provided in the pipe 30. The pipe 31 connected to the switching valve 6 is inserted into the waste liquid treatment tank 5. Valve 7 with filter is pipe 3
1 is provided. The valve with filter 7 includes a valve section 32 and a filter section 33 located on the waste liquid treatment tank 5 side of the valve section 32.
Is provided. The pump 40 is provided in the pipe 30 downstream of the switching valve 6. The reducing agent tank 37 filled with the reducing agent 2 is connected to the waste liquid processing tank 5 through a pipe 38. A valve 39 is provided in the pipe 38. The catalyst tank 34 filled with the catalyst 3 is connected to the waste liquid treatment tank 5 by a pipe 35. A valve 36 is provided in the pipe 35.

The high-level liquid waste 1 generated from the nuclear fuel reprocessing unit (not shown) is ⁹⁰ Sr, ⁹⁹ Tc of fission products,
¹³⁷ Cs, ¹⁴⁴ Ce and transuranium element ²³⁷ Np, ²⁴¹ Am
And other radionuclides are included. The high-level waste liquid 1 is introduced into the waste liquid treatment tank 5 by switching the switching valve 6 to the waste liquid treatment tank 5 side (introduction side). The reducing agent 2 and the catalyst 3 are added into the waste liquid treatment tank 5 by opening the valves 39 and 36. Further, ethanol, which is a reduction aid, is also added to the waste liquid treatment tank 5. After that, the waste liquid in the waste liquid treatment tank 5 is stirred by the stirrer 19. For example,
As the reducing agent 2, ammonium carbonate or the like which is a salt-free reagent is used, and as the catalyst 3, platinum black or the like is used. Ammonium carbonate is present in solution, i.e. in the high level waste liquor 1 in the form of carbonate and ammonium ions.
One to two hours after stirring, the technetium in the high-level waste liquid 1 was changed from tetravalent or zero valent from a state of 7-valent ion (a state of 4 oxygen atoms coordinated and -1 anion as a whole). It is reduced to the solid (oxide or metal) state. The nitric acid concentration of the high-level waste liquid 1 is about 3 mol / liter. Generally, it is difficult to reduce technetium in a solution having such a high acid concentration, but the inventors have discovered that technetium can be sufficiently reduced by the above reducing agent in the presence of a catalyst. The reducing agent is also a salt-free reagent and is decomposed into a gas component after the reaction. The reducing agent is a substance that itself has a function of releasing hydrogen or electrons to reduce the target substance. The reduction aid is a substance having a function of blocking the reverse reaction of the reduction reaction, that is, the oxidation reaction.

After the technetium has been reduced, with the valve section 32 open, the switching valve 6 is switched to connect the filter valve 7 with the pump 40 and the pump 4
0 is driven. The treated waste liquid 4 in the waste liquid treatment tank 5 passes through the valve 7 with a filter and the switching valve 6 and is discharged. The filter portion 33 of the valve 7 with a filter captures the catalyst and solid technetium and prevents them from being discharged to the outside together with the treated waste liquid 4. As a filter for solid-liquid separation used in the filter section 33, a filtration mechanism such as a sintered metal filter or a hollow membrane is effective.
The catalyst and solid technetium attached on the filter (on the side of the waste liquid treatment tank) are backwashed when the next high-level waste liquid 1 is supplied to the waste liquid treatment tank 5, and returned to the waste liquid treatment tank 5. The catalyst is repeatedly used in this way, and finally it is backwashed with a cleaning liquid (pure water or the like) and recovered together with solid technetium. Separation of catalyst and technetium is achieved by redissolving technetium. After the technetium separation, the catalyst can be reused again in the technetium reduction and separation process from the high-level waste liquid 1, or for other purposes.

Therefore, finally, the technetium in the high-level waste liquid 1 is recovered as a small amount of solution. In this example, the reducing agent is a salt-free reagent and the catalyst is repeatedly used, so that the amount of secondary waste generated can be minimized. That is, the volume of the high level waste liquid does not change and the volume of technetium removed is very small. Ammonium carbonate, which is the reducing agent used in this example, contains hydrogen and nitrogen and therefore has a large reducing action. Therefore, in the present embodiment, since the technetium in the high-level waste liquid 1 can be efficiently reduced with a small amount of ammonium carbonate, the amount of solid technetium removed by the filter unit 33 also increases and the amount of secondary waste generated. Decrease. The radioactivity level of the treated waste liquid 4 is reduced.

The effect of this embodiment will be described with reference to FIG. Figure 2 shows the technetium concentration (relative value) remaining in the solution when technetium ions were present in a 3 mol / liter nitric acid solution equivalent to the high-level waste liquid 1 and the above method and other methods for comparison were carried out. It is the figure which showed change. After the catalyst was added to the technetium solution, the effects of various reagents were examined, and the following was revealed. Besides the catalyst,
The technetium concentration in the solution did not change when no reagent was added or when only ethanol was added.
That is, in these cases, the reduction reaction of technetium does not proceed, and technetium is stably dissolved as an ion in the solution. Although it was necessary to add some reagent (reducing agent), it was found that ethanol alone was not sufficient. When potassium carbonate is added as a reducing agent,
The technetium concentration in the solution gradually decreased, but slowly. It was found that technetium was gradually separated and recovered as a solid from the solution by adding the catalyst and potassium carbonate. If ammonium carbonate is added,
As shown in FIG. 2, the technetium concentration in the solution decreased relatively quickly. It was found that technetium can be effectively recovered from the nitric acid solution by adding a catalyst and ammonium carbonate.

The recovery mechanism of technetium will be considered from the experimental results shown in FIG. Since the recovery (reduction) of technetium is progressing in the presence of ammonium salt, it is considered that the reducing action of ammonium ion (ammonia) itself or the reducing action of hydrogen in ammonium ion controls the reaction. . In particular, it is known that hydrogen is adsorbed on a catalyst such as platinum in an atomic state and has a function of reducing a dissolved substance, and has a sufficient ability to reduce technetium. Since similar effects were observed with hydroxylamine nitrate, it was found that a substance (reagent) having a reducing ability or having hydrogen contributes to the reduction, solidification, and recovery of technetium from the solution. The presence of these substances and catalysts is an essential requirement for the reduction and recovery of technetium.

The high-level waste liquid 1 contains various nuclides. Most nuclides do not interfere with the technetium reduction and recovery reaction. Some nuclides consume the reducing agent (competing with the reduction reaction of technetium), but adding an additional reducing agent causes no problem.

As described above, according to the present embodiment, it is a very simple method and is highly toxic with a long half-life (210,000 years) from reprocessing high-level waste liquid, and from the disposal site due to infiltration of groundwater after waste disposal. It is possible to separate and remove technetium that easily migrates to other places. From this, it is possible to eliminate the toxicity and danger of the waste caused by technetium. Further, the volume of radioactive waste liquid or radioactive waste that requires long-term management can be reduced. Further, there is an effect that the management period of a large amount of radioactive waste liquid can be significantly shortened and the harm can be rendered harmless in a short time.

Further, technetium, which is a useful element used as a catalyst and an agent for preventing the adhesion of shellfish etc. to the hull, can be recovered and reused. If ruthenium, rhodium, and palladium coexist, they are recovered at the same time and reused as a catalyst or the like. These useful metals include the method utilizing the difference in redox potential, the method utilizing the difference in chemical properties, etc.
They can be separated from each other by a commonly used method.

In this embodiment, since the nitric acid concentration is not lowered, the amount of waste liquid to be treated and the amount of waste liquid after treatment are hardly increased. In this embodiment, the same pipe is used for supplying the waste liquid to the treatment tank and discharging the treated waste liquid from the treatment tank, and a filter is provided in the middle of this pipe to backwash the filter with the waste liquid supply. Therefore, the technetium separation method and the procedure can be simplified, and the separation device can be simplified and downsized.

The salt-free reagent does not become a radioactive secondary waste because it becomes a gas by the reducing action as described above. Therefore, the present embodiment can reduce the amount of radioactive secondary waste generated by the technetium separation treatment.

The catalyst removed from the radioactive waste liquid discharged by the filter unit 33 can be used for new radioactive waste liquid, and the consumption amount of the catalyst can be reduced. Reduction in catalyst consumption also leads to reduction in the amount of radioactive secondary waste generated by the technetium separation process. Further, in the present embodiment, the catalyst removed by the filter unit 33 is carried into the catalyst tank 34 by using the new radioactive waste liquid that has passed through the filter unit 33 and is supplied into the catalyst tank 34. The removed catalyst can be easily returned to the catalyst tank 34. It is not necessary to install a new device to return the removed catalyst into the catalyst tank 34.

Although platinum is used as the catalyst in the above embodiments, the same effect can be obtained by using other catalysts (metal ruthenium, metal rhodium, metal palladium, etc.). Further, if separate pipes are used for supplying the high-level waste liquid 1 to the waste liquid treatment tank 5 and discharging the processed waste liquid 4 from the waste liquid treatment tank 5, a slightly complicated device configuration is obtained, but It is possible to completely avoid contamination by the waste liquid before treatment. In this case, the solids remaining on the filter must be backwashed with a cleaning liquid other than the waste liquid to remove, or mechanically removed. In the case of mechanical removal, it is possible to avoid addition of the cleaning liquid and increase of the waste liquid volume, reduce the amount of water in the solid, or omit water removal from the solid. Although the present embodiment has been described for the case of being applied to the reprocessing high-level waste liquid, the same effect can be obtained even if it is applied to another nitric acid (acidic) waste liquid.

(Embodiment 2) Next, a second embodiment of the present invention will be described.
The case of application to a low acid concentration or neutral low level radioactive waste liquid will be described with reference to FIG.

The low-level radioactive waste liquid 8 is supplied from the waste liquid filling tank 9 to the waste liquid processing tank 12 by opening the valve 41. Next, hydrazine nitrate (HN) containing hydrogen and nitrogen
Valve 4 is a very weak reducing agent that is a salt-free reagent such as
2, a catalyst such as titanium oxide is supplied to the waste liquid treatment tank 12 from the reducing agent tank 10, a catalyst such as titanium oxide is opened from the catalyst tank 11 by opening the valve 43, and a reducing auxiliary agent such as ethanol is supplied to the waste liquid treatment tank 12 respectively. To be done. It is sufficient to add a very small amount of HN. By rotating the rotary blades 14 directly connected to the motor 13, the contact between the technetium in the low level radioactive waste liquid 8 and the reducing agent, the catalyst or the like is promoted. The reduction reaction of technetium ions and the adsorption reaction to the catalyst proceed. After these reactions sufficiently proceed, the valve portion of the valve with filter 15 is opened. The valve with filter 15 has a filter portion and a valve portion, like the valve with filter 7. The filter portion is located closer to the waste liquid treatment tank 12 than the valve portion. Treated waste liquid is a solid component (technetium-adsorbed catalyst)
Is left on the filter surface and transferred to the treated waste liquid receiving tank 16. Technetium is separated from the low-level radioactive waste liquid 8 by the above process. This embodiment is the same as the first embodiment.
Unlike the above, since the acid concentration is low, even a very weak reducing agent such as HN can reduce technetium ions in the presence of a catalyst to convert them into a solid state. HN is decomposed into a gas component and water after the reaction.

Catalyst attached to the filter (waste liquid treatment tank side) or technetium solid (catalyst adsorbing technetium)
Is a low-level radioactive waste liquid 8 (and reducing agent) for the next treatment.
Is supplied to the waste liquid treatment tank 12 and the liquid is stirred,
It diffuses again into the waste liquid in the waste liquid processing tank 12. The catalyst can also be used repeatedly. Finally, the catalyst is recovered together with technetium by the cleaning liquid (pure water or the like) supplied into the waste liquid treatment tank 12. A solid-liquid separation filter such as a sintered metal filter used in the filter portion is installed on the same surface as the bottom surface of the waste liquid treatment tank 12. The rotary blades 14 are installed near the bottom surface or have a structure that can be moved near the bottom surface. With these structures, the catalyst trapped by the filter can be effectively diffused into the waste liquid.
Separation of catalyst and technetium is achieved by redissolving technetium. After the technetium separation of the catalyst,
Once again, it can be reused in the technetium reduction, separation process from the low-level radioactive waste, or for other purposes.

Therefore, this embodiment also produces the same effect as that of the first embodiment.

Although titanium oxide is used as the catalyst in this embodiment, the same effect can be obtained by using another catalyst as in the first embodiment. In this embodiment, the solid remaining on the filter is finally removed from the filter by the cleaning liquid, but the cleaning liquid is not added, and the rotor is brought close enough to contact the filter surface to mechanically remove the solid. It is also possible. Such mechanical removal of solids has the effects of avoiding the addition of a cleaning liquid and increasing the volume of waste liquid, reducing the amount of water in the solid, or omitting the removal of water from the solid. This embodiment is an example originally applied to a low-level waste liquid having a low acid concentration or neutrality, but the same applies to the case where the present embodiment is applied after the acid concentration reduction treatment of nitric acid (acidic) waste liquid such as high-level waste liquid 1 Get the effect of. Examples of the acid concentration reduction treatment include denitration and dilution. Further, the same effect can be obtained by applying this embodiment to the alkaline waste liquid.

Since the technetium solid produced by the reduction reaction is adsorbed by titanium oxide which is a catalyst, the recovery efficiency of the technetium solid from the radioactive waste liquid is improved.

(Example 3) A third example of the present invention is to recover technetium from an acidic radioactive waste liquid by a method using light, which will be described with reference to FIG. In the device configuration of this embodiment, a light irradiation device (for example, a xenon lamp) 44 is provided in the device configuration of the first embodiment from which the valve with filter 7 is removed. The catalyst tank 34 has the photocatalyst 3 inside.
Fill with A.

The acidic radioactive waste liquid 17 containing technetium is supplied into the waste liquid treatment tank 5 through the pipes 30 and 31. Subsequently, the reducing agent 2, which is a salt-free reagent, and the photocatalyst 3A are also supplied into the waste liquid treatment tank 5. For example, reducing agent 2
Is ammonium carbonate, and the photocatalyst 3A is titanium dioxide having platinum supported on its surface. Ethanol, which is a reduction aid, is also supplied into the waste liquid treatment tank 5 from a tank (not shown). The acidic radioactive waste liquid to which the reducing agent 2, the photocatalyst 3A and the reduction aid have been added is irradiated with the light 18 emitted from the light irradiation device 44 while being stirred by the stirrer 19. The light 18 uses, for example, light emitted from a xenon lamp.

Irradiated light 18, reducing agent 2 and photocatalyst 3
By the action of A, the acidic radioactive waste liquid 17 in the waste liquid treatment tank 5
The technetium ion contained in is reduced and converted into a solid state, and is adsorbed by the photocatalyst 3A. After completion of the reduction and adsorption reactions, the stirrer 19 is stopped and the waste liquid is allowed to stand. Technetium together with the photocatalyst 3A settles at the bottom of the waste liquid treatment tank 5. Thereafter, the supernatant liquid in the waste liquid treatment tank 5, that is, the treated waste liquid 4 is driven from the waste liquid treatment tank 5 by driving the pump 40. The photocatalyst 3A remaining on the bottom of the waste liquid treatment tank 5 can be used as it is for the next treatment of the waste liquid 17. After separating technetium from the photocatalyst 3A recovered from the waste liquid treatment tank 5, this photocatalyst 3A may be reused in Example 3 or for other purposes.

This embodiment can obtain the same effect as that of the first embodiment. Since the light irradiation device 44 is not installed in the first embodiment, the configuration is simplified as compared with the present embodiment. However, in this embodiment, since the photocatalyst 3A is used and light is irradiated, the reduction reaction of technetium is accelerated as compared with the first embodiment. Therefore, the solid technetium contained in the acidic radioactive waste liquid 17 is adsorbed by the photocatalyst 3A in a short time.

Further, the recovered useful element technetium can be utilized in the industrial field or the research field.

Instead of light, electromagnetic waves such as radiation are used as the reducing agent 2.
Even when the acidic radioactive waste liquid 17 in the waste liquid treatment tank 5 in which the photocatalyst 3A and the photocatalyst 3A are mixed is irradiated, the same effect as in the present embodiment is obtained. The photocatalyst 3A having adsorbed technetium may be separated from the waste liquid by installing the valve 7 with a filter or by installing a centrifugal separator as in the first embodiment. Separation by a filter and centrifugal separation require extra equipment and operations, but solid-liquid separation can be performed efficiently.

(Embodiment 4) In the fourth embodiment of the present invention, the waste liquid treatment tank 5 is replaced with a column type processing apparatus. As shown in FIG. 5, the column 22 of the present embodiment is provided with a porous plate 21 at the lower end inside and is filled with a catalyst 3 (for example, palladium) above the porous plate 21. A pipe 3 for supplying the high-level waste liquid 1 is connected to the upper end of the column 22. The pipe 45 provided with the flow rate control valve 46 is the pipe 30.
Connected to.

The high-level waste liquid 1 flows through the pipe 30. A mixed liquid of a reducing agent (for example, ammonium nitrate) and a reducing auxiliary agent (for example, ethanol) is supplied from the pipe 45 into the pipe 30. The flow rate of the mixed solution is adjusted by the flow rate adjusting valve 46. The reducing agent and the reducing aid are mixed at a predetermined ratio and are filled in a tank (not shown). The mixed liquid of the high-level waste liquid 1, the reducing agent and the reducing aid is stored in the column 22.
Supplied within. While the high-level waste liquid 1 passes through the column 22, the technetium is reduced by the action of the reducing agent and the catalyst 3 in the same manner as in each of the above-described embodiments, and is adsorbed on the catalyst 3. The treated waste liquid 4 discharged from the column 22 contains almost no technetium and platinum group elements. The flow rate of the high-level waste liquid 1 in the column 22 needs to be controlled so that technetium does not flow out of the column 22. However, even if the discharged treated waste liquid 4 contains a desired amount of technetium or more, it is possible to remove the technetium by passing the waste liquid through the column 22 again.

The high-level waste liquid 1 can be continuously supplied until the adsorption amount of technetium or the like on the catalyst 3 becomes saturated or until the catalytic activity decreases. Further, by installing a plurality of columns 22 and switching (changing) these, it is possible to cope with continuous operation for a long time. Further, the same column 22 and catalyst 3 can be used for a long period of time by repeating reduction adsorption of technetium (waste liquid treatment) and redissolution desorption (technetium recovery). A column made of a transparent material such as quartz glass can be irradiated with light from the outside, and the efficiency of reducing and separating technetium can be improved.

This embodiment is also effective for general radioactive waste liquids other than the high level waste liquid 1. The acidity of the waste liquid is p
When in the H region, a very weak salt-free reagent is sufficient as the reducing agent.

This embodiment produces the effects obtained in the first embodiment. Furthermore, according to the present embodiment, the device configuration can be made more compact than in the first embodiment. In this example, technetium in the waste liquid can be efficiently separated and removed by a relatively simple operation procedure, and the toxicity of the waste liquid can be greatly reduced. In addition, the amount of highly toxic waste can be significantly reduced.

[0064]

According to the invention of claim 1, the concentration of technetium in the radioactive liquid waste after the removal of metal technetium is significantly reduced. Furthermore, since the salt-free reagent does not become radioactive secondary waste, the amount of radioactive secondary waste generated by the technetium separation treatment is reduced.

According to the second aspect of the invention, the reduction reaction of technetium is further promoted by the action of the photocatalyst. Also,
The technetium solidified by the reduction reaction is adsorbed by the photocatalyst in a short time, so that the technetium in the radioactive liquid waste can be efficiently removed. According to the invention of claim 3,
The device configuration can be remarkably simplified. In addition, technetium in radioactive liquid waste can be reduced more continuously with a relatively simple operation.
Can be removed.

According to the invention of claim 4, technetium can be efficiently reduced with a small amount of a salt-free reagent.

According to the invention of claim 6, the solid of technetium produced by the reduction reaction is adsorbed on the catalyst, so that the efficiency of recovery of the solid of technetium from the radioactive liquid waste is improved.

According to the invention of claim 7, the amount of consumption of the catalyst can be reduced. As a result, the amount of catalyst that becomes radioactive waste can be significantly reduced, so the amount of radioactive secondary waste generated by the technetium separation treatment is reduced.

According to the eighth aspect of the invention, the catalyst removed by using the new radioactive waste liquid supplied into the container can be easily returned to the container. It is not necessary to install a new device to return the removed catalyst into the container.

According to the ninth aspect of the invention, the catalyst removed by utilizing the stirring force of the new radioactive waste liquid can be easily returned into the container. It is not necessary to install a new device to return the removed catalyst into the container.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a Tc separation device that is an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the change over time in the amount of residual Tc in a nitric acid solution.

FIG. 3 is a configuration diagram of a Tc separation device that is another embodiment of the present invention.

FIG. 4 is a configuration diagram of a Tc separation device that is another embodiment of the present invention.

FIG. 5 is a configuration diagram of a Tc separation device that is another embodiment of the present invention.

[Explanation of symbols]

5, 12 ... Waste liquid treatment tank, 6 ... Switching valve, 7, 15
... Valve with filter, 10, 37 ... Reductant tank, 11, 34
... Catalyst tank, 16 ... Processed waste liquid receiving tank, 19 ... Stirrer, 22
... column, 32 ... valve part, 33 ... filter part.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mamoru Kamoshida 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Power & Electric Machinery Development Division

Claims (12)

[Claims] 1. A method for separating and removing technetium from a radioactive waste liquid containing technetium, wherein a salt-free reagent that is a reducing agent is added to the radioactive waste liquid, and the technetium is reduced in the presence of a catalyst and the salt-free reagent. A method of separating technetium, which comprises separating the radioactive waste liquid into a solid state. 2. The method for separating technetium according to claim 1, wherein the catalyst is a photocatalyst, and the radioactive waste liquid containing the salt-free reagent and the photocatalyst is irradiated with electromagnetic waves to reduce the technetium to a solid state. 3. The radioactive waste liquid containing the salt-free reagent is supplied into a column packed with the catalyst.
Technetium separation method. 4. The method for separating technetium according to claim 1, wherein the salt-free reagent is a salt-free reagent containing nitrogen and hydrogen. 5. The method for separating technetium according to claim 4, wherein the salt-free reagent is at least one substance selected from ammonium salt, hydrazine salt and hydroxylamine salt. 6. The method for separating technetium according to claim 1, wherein the solid of technetium is adsorbed on the catalyst. 7. The radioactive waste liquid containing the catalyst and the salt-free reagent is present in a container, and the technetium contained in the radioactive waste liquid is reduced to a solid state, and then the catalyst and the solid technetium are contained. Is removed from the radioactive waste liquid discharged from the container, new radioactive waste liquid is supplied into the container, and the new radioactive waste liquid contains the removed catalyst and solid technetium. 2. Method of separating technetium. 8. The catalyst and the solid technetium are removed from the discharged radioactive waste liquid by a filter, and the removed catalyst and solid technetium are
The method for separating technetium according to claim 7, wherein the new radioactive waste liquid that has passed through the filter and is supplied into the container is carried into the container. 9. The catalyst and the solid technetium are removed from the discharged radioactive waste liquid by a filter provided near the waste liquid discharge part at the bottom of the container,
After the new radioactive waste liquid is supplied into the container, the catalyst and the solid technetium removed by the filter are mixed with the new radioactive waste liquid by stirring the new radioactive waste liquid. The method for separating technetium according to claim 7, 10. The solid technetium-adsorbed catalyst is settled and separated in the container, and the radioactive waste liquid, which is the supernatant liquid in the container, is discharged from the container, and the new radioactive waste liquid is stored in the container. The method for separating technetium according to claim 7, wherein the technetium is supplied into the container in which a catalyst is present. 11. A container filled with a radioactive waste liquid, a first means for supplying a salt-free reagent into the container, a second means for supplying a catalyst into the container, and a container to be discharged from the container. An apparatus for separating technetium, comprising: a means for removing the catalyst and solid technetium contained in the radioactive waste liquid. 12. The technetium separation apparatus according to claim 11, wherein the second means is means for supplying a photocatalyst as the catalyst, and means for irradiating the radioactive liquid waste in the container with electromagnetic waves.