JP2016080508A - Decontamination treatment system and decomposition method for decontamination waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decontamination treatment system and a decomposition method for decontamination waste water, for reducing an amount of secondary waste when treating a decontamination waste liquid.SOLUTION: A decontamination treatment system is provided with: a decontamination device 15 that uses decontamination treatment water obtained by sequentially adding an oxidizing agent 13a and a reducing agent 14a in a decontamination tank 12 in which a decontamination object 11 is immersed to perform circulation treatment through a primary line Lboth ends of which are connected to the decontamination tank 12 while generating primary treated water Wwhich is treated by the oxidizing agent 13a, and a secondary treated water Wwhich is treated by the oxidizing agent 14a; a secondary line Lthat branches from the primary line Lfor introducing the secondary treated water Wand returns to the primary line Lagain; a cation resin tower 31 that is disposed in the secondary line L, removes a metal ion and a radio active nuclide eluted in the secondary treated water Wbeing the decontamination waste water, and obtains a tertiary treated water W; a permanganic acid supply part that supplies a permanganic acid to the tertiary treated water Win which the reducing agent after a removing treatment remains; and a separation part 41 that separates a manganese dioxide of a decomposition product in the tertiary treated water Wto which the permanganic acid is supplied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a decontamination processing system and a decontamination wastewater decomposition method.

  In radiation handling facilities such as nuclear power plants and spent fuel reprocessing plants, structural parts such as pipes that come into contact with radioactive liquid waste containing radioactive materials are associated with the operation of nuclear power plants and reprocessing plants in radiation handling facilities. A film of oxide or salt containing radioactive material adheres to or forms on the inner surface. If the operation period of the facility becomes longer, the radiation dose around pipes and equipment will increase, and there is a risk that the radiation dose to workers will increase during periodic inspections, maintenance work, and waste demolition work. In order to reduce the exposure of workers, it is necessary to remove (decontaminate) radioactive substances attached to piping and equipment.

  A typical reactor to be decontaminated is a reactor primary cooling system (primary cooling system). A scale called a clad containing a radioactive substance is attached to the primary cooling system. This cladding serves as a radiation source for workers to receive radiation exposure around the primary cooling system piping and equipment. In order to reduce radiation exposure and improve the working environment, it is necessary to remove the cladding and decontaminate piping and equipment. For decontamination of piping and equipment, for example, a chemical decontamination method in which chemical treatment is performed using a chemical is used.

  In addition, decontamination waste liquid generated by decontamination of equipment in such a radiation handling facility uses, for example, ion exchange resins such as cation resins and anion resins to chemically radiate radioactive substances such as metal ions contained in the decontamination solution. A method of performing an adsorption process has been proposed (see, for example, Patent Documents 1 and 2).

JP 2004-45371 A Japanese Patent No. 2509654

  In the waste liquid treatment method for decontamination waste liquid, ion exchange resins such as cation resin and mixed bed resin (mixture of cation resin and anion resin) used for treatment of metal ions in decontamination waste liquid are used as secondary waste. Although used, the used ion exchange resin has a high dose, so that incineration is difficult. In addition, since the cation resin is an organic substance and the mixed bed resin is an organic substance and contains a chelate compound (metal chelate), it is possible to solidify the ion exchange resin into a solid substance and bury it in a disposal site. Have difficulty.

  High-dose organic matter causes hydrogen gas to be generated by radioactive decomposition. In addition, the chelate compound promotes nuclide migration and causes the barrier performance of the disposal site to deteriorate. For these reasons, the ion exchange resin and the chelate compound used for the treatment of the decontamination waste liquid are not allowed to be buried. Therefore, the ion exchange resin generated as secondary waste cannot be disposed of and must be stored in the nuclear power plant.

  In particular, organic acid and permanganic acid are used as decontamination agents, and by repetitive decontamination with organic acid and oxidation treatment with permanganic acid alternately, multiple metal oxides on the waste surface are dissolved. In the case of removing the surface contamination, metal ions such as manganese (Mn), iron (Fe), nickel (Ni), chromium (Cr) and cobalt (Co) are contained in the decontamination waste liquid after the decontamination treatment. Since the content is increased, there is a problem that the ratio of the amount of the cation resin that adsorbs metal ions is larger than that of the anion resin, and the amount of used resin that is a secondary waste is increased.

  Also, the waste of chemical decontamination treatment is about 11% of the cladding, about 11% of permanganic acid as the oxidizing agent, and the rest such as oxalic acid and citric acid as the reducing agents. There is a problem that the organic acid is about 79% and the load of the reducing agent is overwhelmingly large.

  When the organic acid in the decontamination waste liquid of this chemical decontamination treatment is treated with, for example, an ion exchange resin, the waste ion exchange resin becomes waste, and the storage amount of the used resin that is the secondary waste further increases. There's a problem.

  Therefore, in order to reduce the amount of used ion exchange resin that is difficult to be buried, the emergence of a technique for further improvement is desired.

  In view of the above problems, the present invention provides a decontamination treatment system and a decontamination wastewater decomposition method for reducing the amount of secondary waste without treating an organic acid with an ion exchange resin when treating a decontamination waste liquid. The task is to do.

  The first invention of the present invention for solving the above-described problem is based on an oxidizing agent using decontamination water in which an oxidizing agent and a reducing agent are sequentially added to a decontamination tank in which an object to be decontaminated is immersed. A decontamination device that circulates through a primary line having both ends connected to the decontamination tank while generating secondary treatment water using a primary treatment water and a reducing agent, and the secondary treatment is branched from the primary line. A secondary line that introduces water and returns to the primary line again, and a removal device that is interposed in the secondary line and that removes metal ions and radionuclides eluted in the secondary treated water to obtain tertiary treated water Separating the permanganic acid supply unit for supplying permanganic acid to the tertiary treated water in which the reducing agent remains after passing through the removing device, and the decomposition product in the tertiary treated water to which the permanganic acid is supplied; And a separation unit as a next treated water, In the decontamination processing system that.

  A second invention is the decontamination processing system according to the first invention, further comprising a hydrogen peroxide supply unit that supplies hydrogen peroxide to the quaternary treated water.

  A third invention is the decontamination processing system according to the first or second invention, further comprising an oxalic acid supply unit that supplies oxalic acid to the quaternary treated water.

  A fourth invention is the decontamination treatment system according to the third invention, further comprising an oxalic acid removal tower for removing residual oxalic acid in the quaternary treated water supplied with the oxalic acid.

  According to a fifth aspect of the present invention, in the decontamination processing system according to any one of the first to fourth aspects, the separation unit is a collection member that collects solid matter or a precipitation device that precipitates. .

  According to a sixth aspect of the present invention, the decontamination target is subjected to decontamination treatment by using a decontamination treatment water to which an oxidizing agent and a reducing agent are sequentially added, followed by a second decontamination treatment. The reducing agent remaining in the tertiary treated water from which the metal ions and radionuclides eluted in the secondary treated water are removed is decomposed by permanganic acid, and the decomposition products in the tertiary treated water supplied with the permanganic acid are separated, It is in the decomposition method of the decontamination wastewater characterized by making it a quaternary treated water.

  A seventh invention is the method for decomposing decontamination waste water according to the sixth invention, wherein hydrogen peroxide is supplied to the quaternary treated water.

  An eighth invention is the method for decomposing decontamination wastewater according to the sixth or seventh invention, wherein oxalic acid is supplied to the quaternary treated water.

  A ninth invention is the method for decomposing decontamination waste water according to the eighth invention, wherein residual oxalic acid in the quaternary treated water supplied with the oxalic acid is removed.

  According to the present invention, the organic acid in the treated water that is the decontamination waste liquid after the decontamination treatment is decomposed with permanganic acid, and the manganese ions of the decomposition products are recovered as a solid, thereby greatly reducing the amount of waste. be able to.

FIG. 1 is a schematic diagram of a decontamination processing system according to the first embodiment. FIG. 2 is a process diagram of the decontamination processing method according to the first embodiment. FIG. 3A is a liquid flow diagram for executing the oxidation step S11. FIG. 3-2 is a liquid flow diagram for executing the reduction step S12. FIG. 3-3 is a liquid flow diagram for performing the removal step S13. FIG. 3-4 is a liquid flow diagram for executing the decontamination water decomposition step S14. FIG. 4A is a schematic diagram of the decontamination processing system according to the second embodiment. FIG. 4B is a process diagram of the decontamination processing method according to the second embodiment. FIG. 5A is a schematic diagram of a decontamination processing system according to the third embodiment. FIG. 5-2 is a schematic diagram of the decontamination processing system according to the third embodiment. FIG. 5C is a process diagram of the decontamination processing method according to the third embodiment. FIG. 6A is a schematic diagram of a decontamination processing system according to a fourth embodiment. FIG. 6B is a process diagram of the decontamination processing method according to the fourth embodiment. FIG. 7 is a schematic diagram of a separation unit installed in the decontamination processing system according to the first embodiment. FIG. 8 is a schematic configuration diagram schematically illustrating an example of a nuclear power plant to which the waste liquid treatment system according to the embodiment of the present invention is applied.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

<Nuclear power plant>
A case where the waste liquid treatment system according to the embodiment of the present invention is applied to a nuclear power plant will be described with reference to the drawings. The nuclear power plant nuclear reactor uses light water as the reactor coolant and neutron moderator, and converts it into high-temperature and high-pressure water that does not boil throughout the primary system. This is a pressurized water reactor (PWR) that generates steam by exchanging it and sends the steam to a turbine generator to generate electricity. The present embodiment is not limited to PWR but can be applied to an improved pressurized water reactor (APWR) or a boiling water reactor (BWR) which is an improvement of the PWR. It can also be applied to radiation handling facilities.

  FIG. 8 is a schematic configuration diagram schematically illustrating an example of a nuclear power plant to which the waste liquid treatment system according to the embodiment of the present invention is applied. As shown in FIG. 8, a nuclear power plant 100 includes a reactor cooling system (hereinafter also referred to as a primary system) 112 including a nuclear reactor 111, and a turbine system (hereinafter referred to as a secondary system) that exchanges heat with the reactor cooling system 112. 113). A reactor coolant (primary cooling water) flows through the reactor cooling system 112, and a secondary coolant (secondary cooling water) flows through the turbine system 113.

  The reactor cooling system (primary system) 112 includes a nuclear reactor 111 and a steam generator 116 connected to the nuclear reactor 111 via a cold leg 115a and a hot leg 115b. In addition, a pressurizer 117 is interposed in the hot leg 115b, and a reactor coolant pump 118 is interposed in the cold leg 115a. The reactor 111, the cold leg 115 a, the hot leg 115 b, the steam generator 116, the pressurizer 117, and the reactor coolant pump 118 are accommodated in the reactor containment vessel 119.

  As described above, the nuclear reactor 111 is a pressurized water nuclear reactor, and the inside thereof is filled with a nuclear reactor coolant (primary cooling water). The reactor 111 accommodates a large number of fuel assemblies 121, and a large number of control rods 122 for controlling nuclear fuel fission in the fuel rods of the fuel assemblies 121 can be inserted into the fuel assemblies 121. Is provided.

  When the nuclear fuel in the fuel rod of the fuel assembly 121 is fissioned while controlling the fission reaction by the control rod 122, thermal energy is generated by this fission. The generated thermal energy heats the reactor coolant, and the heated reactor coolant is sent to the steam generator 116 via the hot leg 115b. On the other hand, the reactor coolant sent from each steam generator 116 via the cold leg 115 a flows into the reactor 111 and cools the reactor 111.

  The pressurizer 117 interposed in the hot leg 115b suppresses boiling of the reactor coolant by pressurizing the reactor coolant that has become high temperature. Further, the steam generator 116 evaporates the secondary coolant by causing the reactor coolant (primary coolant), which has become high temperature and high pressure, to exchange heat with the secondary coolant (secondary coolant), thereby generating steam. The reactor coolant generated and cooled to high temperature and pressure is cooled. The reactor coolant pump 118 circulates the reactor coolant in the reactor cooling system 112, and sends the reactor coolant from the steam generator 116 to the reactor 111 via the cold leg 115a, and also the reactor coolant. From the nuclear reactor 111 to the steam generator 116 through the hot leg 115b.

  The reactor coolant circulates between the reactor 111 and the steam generator 116. The reactor coolant is light water used as a coolant and a neutron moderator.

  The turbine system (secondary system) 113 includes a turbine 125 connected to each steam generator 116 via a steam pipe 124, a condenser 126 connected to the turbine 125, a condenser 126, and each steam generator. And a water supply pump 128 interposed in a water supply pipe 127 that connects to 116. A generator 129 is connected to the turbine 125.

  A series of operations in the turbine system 113 of the nuclear power plant 100 will be described. When steam flows from the steam generator 116 into the turbine 125 via the steam pipe 124, the turbine 125 rotates. When the turbine 125 rotates, the generator 129 connected to the turbine 125 generates power. Thereafter, the steam discharged from the turbine 125 flows into the condenser 126. The condenser 126 has a cooling pipe 130 disposed therein, and one of the cooling pipes 130 is connected to a water intake pipe 131 for supplying cooling water (for example, seawater). Is connected to a drain pipe 132 for draining the cooling water. The condenser 126 cools the steam flowing in from the turbine 125 through the cooling pipe 130, thereby returning the steam to a liquid. The secondary coolant that has become liquid is sent to the steam generator 116 via the feed water pipe 127 by the feed water pump 128. The secondary coolant sent to the steam generator 116 becomes steam again by exchanging heat with the reactor coolant in the steam generator 116.

  In such a nuclear power plant 100, members constituting the reactor equipment such as reactor equipment and various pipes are generally made of a steel material such as stainless steel or carbon steel. When these components that make up the nuclear reactor equipment are used, the surfaces of the components making up the nuclear reactor equipment such as nuclear reactor equipment and various pipes are corroded by contact with high-temperature water (primary cooling water). A film is formed. The coating is at least one kind of metal or oxide such as radioisotope (RI), chromium (Cr), iron (Fe), nickel (Ni).

Radioactivity in the reactor water is taken into the coating formed on the wetted parts of the reactor equipment and the inner surface of the piping exposed to high-temperature water (primary cooling water), and it becomes an exposure radiation source. Such decontamination objects of reactor equipment such as reactor equipment and various pipes are decontaminated using the waste liquid treatment system according to the embodiment of the present invention. In addition, decontamination means removing the radioactive material adhering to the decontamination object such as piping and equipment of the decontamination system of the nuclear reactor equipment.
In addition, since it is the same decontamination object also in the following Examples, these description is abbreviate | omitted.

<First decontamination system>
FIG. 1 is a schematic diagram of a decontamination processing system according to the first embodiment.
As shown in FIG. 1, the decontamination processing system 10A according to the present embodiment is a decontamination treatment water in which an oxidizing agent 13a and a reducing agent 14a are sequentially added to a decontamination tank 12 in which an object 11 to be decontaminated is immersed. Is used to generate the primary treated water W ₁ by the oxidant 13a and the secondary treated water W ₂ by the reducing agent 14a, and circulate through the primary line L ₁ having both ends connected to the decontamination tank 12. a dyeing apparatus 15 is branched from the primary line L _1, introducing a secondary treatment water W _2, is interposed between the secondary line L _2, the secondary line L ₂ which returns to the primary line L _1, the decontamination waste water The metal ion radionuclide eluted in the secondary treated water W ₂ is removed, and the cation resin tower 31 as a removing device for obtaining the tertiary treated water W ₃ and the reducing agent after passing through the cation resin tower 31 remain. Permanganic acid supply unit that supplies permanganic acid to tertiary treated water W ₃ The oxidizing agent supply unit 13 and a separation unit 41 that separates the solid product (manganese dioxide) of the decomposition product in the tertiary treated water W ₃ supplied with permanganic acid.

  A decontamination object 11 is disposed in the decontamination tank 12.

Oxidant supplier 13, for example, an oxidizing agent supply line L ₁₁ for supplying an oxidizing agent 13a such as permanganic acid solution, and a oxidant supply valve V ₁₁ provided in the oxidizing agent supply line L ₁₁ Yes.

As this oxidizing agent 13a, in addition to using permanganic acid (HMnO ₄ ), for example, permanganate, perferrate, hydrogen peroxide (H ₂ O ₂ ), nitric hydrofluoric acid mixture of nitric acid and hydrofluoric acid. What contains any one or more of liquid etc. is used. Specific examples of the permanganate include potassium permanganate (KMnO ₄ ).

Further, the downstream side of the oxidant supply line L ₁₁ is connected to the merging line L ₁₀ . This confluence line L ₁₀ is provided with the merging line valves V _10, the downstream side of the confluence line L ₁₀ is connected to the primary line L _1.

For example, the oxidant supply unit 13 supplies the oxidant 13a of the permanganic acid aqueous solution to the decontamination tank 12 via the oxidant supply line L ₁₁ , the merging line L _10, and the primary line L _1. Chromium (Cr) adhering to the object 11 is oxidized and eluted to generate primary treated water W ₁ which is oxidizing agent treated water from which the chromium is oxidized and eluted.

The reducing agent supply unit 14 includes, for example, a reducing agent supply line L ₁₂ that supplies a reducing agent 14 a such as an organic acid, and a reducing agent supply valve V ₁₂ provided in the reducing agent supply line L ₁₂ .

As the reducing agent 14a, an organic acid having a reducing action and chelatingly bonded to a metal ion is used. Examples of the organic acid include oxalic acid (H ₂ C ₂ O ₄ ), citric acid (C ₆ H ₈ O ₇ ), and the like. Nitrofluoric acid mixed solution may be used. Also, oxalic acid and citric acid, or may be used those containing either one or more, such as oxalic acid and picolinic acid _{(C 6 H 5 NO 2)} .

The reducing agent supply unit 14 uses the reducing agent supply line L ₁₂ , the merging line L _10, and the primary line L ₁ as primary reducing water W ₁ filled in the decontamination tank 12 using, for example, an aqueous solution of oxalic acid as a reducing agent 14a. By supplying (adding) via, the iron adhering to the decontamination object 11 is reduced and eluted, and the secondary treated water W ₂ from which the iron is reduced and eluted is generated.

Both ends of the primary line L ₁ are connected to the decontamination tank 12, and the treated water (permanganic acid aqueous solution, primary treated water W ₁ or secondary treated water W ₂ ) in the decontamination tank 12 is circulated. . The primary line L ₁ is provided with a first valve V ₂₁ and a first pump P ₁ from the upstream side. Incidentally, a heater (not shown) provided on the primary line L _1, and heating the treated water circulating primary line L _1, may be the treated water to a high temperature state.

The first pump P ₁ circulates the treated water in the primary line L ₁ and can supply the treated water to the decontamination tank 12. Further, a merging line L ₁₀ is connected to the primary line L ₁ between the first pump P ₁ and the decontamination tank 12.

The secondary line L ₂ has both ends connected to the primary line L ₁ and is connected so as to partially bypass the primary line L _1, and treated water in the decontamination tank 12 (for example, secondary treated water W ₂ ). In the secondary line L ₂ , a second valve V ₂₂ and a second pump P ₂ are provided from the upstream side.

The secondary line L ₂ is provided with a cation resin tower 31 filled with a cation resin. From the secondary treated water W ₂ flowing through the secondary line L ₂ via a part of the primary line L ₁ , the above-mentioned and the chromium and radionuclides eluted with elution of metal ions such as iron removed by ion exchange, to produce a tertiary treated water W ₃ said radionuclide is removed.

The tertiary line L ₃ is connected to the secondary line L ₂ at both ends on the upstream side of the secondary line L _{2 in} which the cation resin tower 31 is arranged, and is connected so as to temporarily bypass the secondary line L _2. The treated water (for example, tertiary treated water W ₃ ) in the decontamination tank 12 is circulated. A fourth valve V ₂₄ is provided in the tertiary line L ₃ .

Further, a separation portion 41 is provided in the tertiary line L ₃ . The separation unit 41 removes manganese dioxide (MnO ₂ ), which is a precipitate generated when permanganic acid (HMnO ₄ ) is supplied as the oxidant 13a to the tertiary treated water W ₃ , and the precipitate is removed. The quaternary treated water W ₄ is produced.

Further, in the secondary line L ₂ , analysis units 32A and 32B for measuring the amount of Mn and the like in the secondary treated water W ₂ are arranged before and after the cation resin tower 31.

Next, a decontamination processing method using the decontamination processing system 10A configured as described above will be described.
FIG. 2 is a process diagram of the decontamination processing method according to the first embodiment.
FIGS. 3-1 to 3-4 are liquid flow diagrams of the decontamination processing systems 10A-1 to 10A-4 shown in FIG. 1 corresponding to each process.
As shown in FIG. 2, the decontamination processing method includes an oxidation step S11, a reduction step S12, a removal step S13, and a decontamination water decomposition step S14.

    First, as a preparation, the decontamination object 11 is disposed in the decontamination tank 12.

Next, oxidation process S11 is performed. FIG. 3A is a liquid flow diagram for executing the oxidation step S11.
Here, in this example, a permanganic acid aqueous solution was used as the oxidizing agent 13a.
That is, a permanganic acid solution pooled in the oxidizing agent supply unit 13 as an oxidizing agent 13a, open the oxidant supply valve V _11, is introduced into the oxidant supply line L _11. Then, the merging line valve V ₁₀ is opened, and the oxidant 13a of the permanganic acid aqueous solution introduced into the oxidant supply line L ₁₁ is introduced into the primary line L ₁ through the merging line L ₁₀ .
Next, the primary line by opening the first valve V ₂₁ in L _1, the primary line L primary line L ₁ permanganic acid solution by driving the first pump P ₁ provided in ₁ and decontamination tank 12 Circulate between. At this time, the permanganic acid aqueous solution may be heated by a heater (not shown) and circulated as a high temperature state.

Here, in the decontamination tank 12, Cr exists as a Cr ₂ O ₃ , FeCr ₂ O _4, etc. in the oxide film adhering to the decontamination object 11 in the permanganate aqueous solution in which the decontamination object 11 is immersed. ³⁺ becomes Cr ⁶⁺ and elutes in the aqueous solution. That is, chromium (Cr) in the oxide film is oxidized and eluted, and primary treated water (including Cr ⁶⁺ ) W ₁ that is an aqueous solution of permanganate in which the chromium (Cr) is oxidized and eluted is generated.

Next, reduction process S12 is performed. FIG. 3-2 is a liquid flow diagram for executing the reduction step S12.
In this example, an oxalic acid aqueous solution was used as the reducing agent 14a.
That is, to close the oxidant supply valve V ₁₁ of the oxidant supply line L _11, and stopping the introduction of the oxidizing agent 13a, the oxalic acid aqueous solution of the reducing agent supply unit 14 opens the reducing agent supply valve V _12, the reducing agent supply It is introduced into the line L _12. Introducing the primary line L ₁ by merging line L ₁₀ a reducing agent 14a of oxalic acid aqueous solution introduced into the reducing agent supply line L _12.
Then, by driving the first pump P ₁ , an aqueous solution in which the oxalic acid aqueous solution and the permanganic acid aqueous solution are mixed (hereinafter referred to as “mixed aqueous solution”) is used as the primary line L ₁ and the decontamination tank 12. Circulate between. At this time, the mixed aqueous solution may be heated by a heater (not shown) and circulated as a high temperature state.

  Note that the oxalic acid concentration in the mixed aqueous solution is set to, for example, about 2000 ppm. The temperature of the oxalic acid aqueous solution is preferably from room temperature (20 ° C.) to less than 100 ° C. (temperature limit at which the aqueous solution does not boil).

Here, in the decontamination tank 12, Fe ²⁺ present as Fe ₃ O ₄ or the like in the oxide film attached to the decontamination target 11 in the mixed aqueous solution in which the decontamination target 11 is immersed becomes Fe ^3+. Elute in aqueous solution. That is, iron Fe in the oxide film is reduced and eluted to produce secondary treated water W ₂ that is a mixed aqueous solution in which the iron is reduced and eluted. Further, in the secondary treated water W ₂ , metal ions and radionuclides are eluted by the oxidation elution of chromium in the oxidation step S11 and the reduction elution of iron in the reduction step S12.

  Here, it is determined whether or not the oxide film attached to the decontamination object 11 is sufficiently removed in the reduction step S12. If the removal is insufficient, the oxidation step S11 and the reduction step S12 are set as “one decontamination cycle”, and the “one decontamination cycle” is executed a plurality of times. And if an oxide film is fully removed, it will progress to the removal process S13 which processes the following decontamination waste liquid.

Next, removal process S13 is performed. FIG. 3-3 is a liquid flow diagram for performing the removal step S13.
In removal step S13, first, by closing the first valve V ₂₁ of the merging line valves V ₁₀ and primary line L ₁ of the confluence line L _10, opening the second valve V ₂₂ of the secondary line L _2. Then, by driving the second pump P ₂ , the secondary treated water W ₂ that is the decontamination waste liquid derived from the decontamination tank 12 is transferred to the secondary line L ₂ via a part of the primary line L _1. It can be introduced and passed through the cation resin tower 31 and returned to the decontamination tank 12 again via the primary line L ₁ to enable circulation between the decontamination tank 12 and the secondary line L _2. .

Here, the cationic resin tower 31, to remove metal ions and radionuclides are eluted secondary treatment water W ₂ reduction step S12, it generates a tertiary treatment water W _3. Then, the tertiary treated water W ₃ is returned from the secondary line L ₂ to the decontamination tank 12 via the primary line L ₁ . Therefore, the secondary treated water W ₂ circulating between the secondary line L ₂ and the decontamination tank 12 by passing water through the cation resin tower 31 for a desired time is the tertiary treated water W from which metal ions have been removed. ₃

  The end of the removal step S13 for removing metal ions and radionuclides is determined by the analysis units 32A and 32B when the amount of metal ions (for example, Mn, Ni, etc.) in the treatment liquid is below a predetermined value.

Next, decontamination water decomposition process S14 is performed. FIG. 3-4 is a liquid flow diagram for executing the decontamination water decomposition step S14.
In decontamination hydrolysis step S14, opens the merging line valves V ₁₀ and oxidant supply valve V ₁₁ of the merging line L _10, oxidant supply the permanganate oxidizing agent 13a from the oxidant supply unit 13 to the primary line L ₁ supplied by the line L ₁₁ and the merging line L _10.
By supplying this permanganic acid, oxalic acid remaining in the tertiary treated water W ₃ in the decontamination solution is decomposed.

Here, in this embodiment, in the decontamination apparatus 15, since permanganic acid is used as the oxidant 13a, permanganic acid is supplied from the oxidant supply unit 13, but permanganic acid is used as the oxidant. In the case of using an oxidizing agent other than the above, a manganic acid supply unit for supplying permanganic acid may be separately installed so that permanganic acid is supplied to the primary line L ₁ .

During the supply of the permanganic acid aqueous solution, the third valve V ₂₃ is closed, the fourth valve V ₂₄ and the fifth valve V ₂₅ are opened, and the tertiary treated water W ₃ to which the permanganic acid aqueous solution has been added is supplied to the tertiary line. It is introduced into the L _3.

Then, the tertiary treated water W ₃ to which permanganic acid has been added is passed through the separation unit 41 interposed in the tertiary line L _3, and decomposition generated when oxalic acid is decomposed by the addition of permanganic acid. A solid portion of manganese ions (for example, manganese dioxide (MnO ₂ ), manganese oxide (MnO), etc.) is separated and removed by the separation unit 41.
The treated water from which the oxalic acid has been decomposed and removed becomes the quaternary treated water W ₄ .

  Here, it is preferable to add permanganic acid in the same amount as residual oxalic acid and citric acid as reducing agents or in a small excess (about 1.1 equivalents).

In this decontamination water decomposition step S14, since oxalic acid is decomposed by supplying permanganic acid, manganese dioxide (MnO ₂ ) or manganese hydroxide (Mn (OH) is used as in the following formulas (1) and (2). ) As ₂ ), manganese ions are deposited as a solid (precipitate).
(COOH) ₂ → CO ₂ ; 2H ⁺ + 2e ⁻ (1)
HMnO ₄ + 3e ⁻ → MnO ₂ ↓ (2)

Here, the completion of the decomposition of oxalic acid in the decontamination water decomposition step S14 is performed by the analysis units 32A and 32B provided on the inlet side and the outlet side of the cation resin tower 31 of the secondary line L ₂ , respectively. Judgment is made by measuring the amount and not exceeding a predetermined value.

  Examples of the separation unit 41 that separates and removes the decomposition products include a collection separation method for collecting by a collection member such as a filter, and a sedimentation separation method for settling and separating the decomposition products. Moreover, the separation method by a liquid cyclone etc. can also be illustrated.

  Next, the advantage compared with the process by the conventional ion exchange resin at the time of using a filter as the separation part 41 is demonstrated.

  The organic acid (for example, oxalic acid and citric acid), which is the reducing agent 14a remaining in the decontaminated water after the decontamination process, is decomposed by permanganic acid, and the manganese ions of the decomposition products are separated from the solid by a filter. Since it is collected and separated, the amount of waste can be greatly reduced.

This is equivalent to 60 g of oxalic acid because 1 mol of manganese dioxide ((MnO ₂ ) = 86.94 g) is converted to oxalic acid and the reaction with oxalic acid is 1: 1.5.
Conventionally, when adsorbing oxalic acid using an anion resin, about 1 L of an anion adsorbing resin is required to treat 60 g of oxalic acid.

On the other hand, when oxalic acid is reacted with permanganic acid and precipitated as manganese dioxide as in this example, 1 mol of manganese dioxide is taken into consideration even if the moisture content of manganese dioxide and the weight of the filter used are taken into account. It will be about 350g. Here, since the density of manganese dioxide is 5.026 g / cm ³ , the precipitation treatment volume of manganese dioxide is about 69 mL.
Therefore, when 60 g of oxalic acid is to be treated by adsorption of an anion resin, 1 L of an anion resin is required. Therefore, when the precipitation treatment volume is compared, (69 mL / 1000 mL) = 0.06 (about 1/16) It becomes.

Thus, in the case of the present example, by reacting oxalic acid with permanganic acid and precipitating it as manganese dioxide, it becomes a solid treatment by adsorbing manganese dioxide with a filter, thereby reducing waste. The processing amount is about 1/16.
As a result, according to the present embodiment, compared with the case where the amount of waste is processed using the ion exchange resin, the amount of waste processed is greatly reduced.

<Second decontamination processing system>
FIG. 4A is a schematic diagram of the decontamination processing system according to the second embodiment. FIG. 4B is a process diagram of the decontamination processing method according to the second embodiment. The same members as those in the first embodiment are denoted by the same reference numerals, and a duplicate description is omitted.

As illustrated in FIG. 4A, the decontamination processing system 10B according to the present embodiment is a peroxide that supplies hydrogen peroxide 51a to the quaternary water W ₄ in the decontamination processing system 10A of the first embodiment. A hydrogen supply unit 51 is provided.
The hydrogen peroxide supply unit 51 includes a hydrogen peroxide supply line L ₂₁ for supplying hydrogen peroxide 51 a and a hydrogen peroxide supply valve V ₂₇ provided in the hydrogen peroxide supply line L ₂₁ . .

When permanganic acid is added in a small excess by the treatment method of Example 1, a small amount of permanganic acid may remain.
If the ion exchange resin purification is performed in the cation resin tower 31 for decontamination of the decontamination target 11 in the next cycle in a state where this permanganic acid remains, there is a concern that the cation exchange resin is deteriorated.

  Therefore, in this embodiment, in order to suppress degradation due to permanganic acid, hydrogen peroxide (liquid) is added in order to decompose and remove unreacted permanganic acid in the decontamination water decomposition step S14. Then, the permanganese decomposition step S15 for decomposing and removing permanganic acid is performed.

The permanganic acid decomposition step S15 after the completion of decontamination hydrolysis step S14, opens the hydrogen peroxide supply valve V _27, lines connecting the hydrogen peroxide 51a to the primary line L ₁ from the hydrogen peroxide supply unit 51 L ₂₁ is added to the quaternary treated water W ₄ circulating through the primary line L ₁ .

By adding hydrogen peroxide to the quaternary treated water W ₄ , decomposition reactions of the following formulas (3) and (4) occur.
H ₂ O ₂ → 2H ⁺ + O ₂ + 2e ⁻ (3)
MnO ₄ ⁻ + 3e ⁻ + 4H ⁺ + O ₂ → MnO ₂ ↓ + 2H ₂ O ↓ (4)

Thereby, permanganic acid that is a residue in the decontamination water decomposition step S14 can be removed as solid matter as manganese dioxide (MnO ₂ ) by the separation unit 41 (for example, collected in a filter).

  The addition of hydrogen peroxide 51a in the permanganic acid decomposition step S15 is performed by the analysis units 32A and 32B until the amount of permanganic acid (Mn) becomes a predetermined value or less.

  Hydrogen peroxide is added in this example, but hydrogen peroxide that does not contribute to this excessive reaction quickly self-decomposes and becomes oxygen, which may cause a load on the ion exchange resin of the cation resin tower 31, There is no deterioration of the ion exchange resin.

  According to the present embodiment, it is possible to decompose and remove excess permanganic acid, which is a residue in the decontamination water decomposition step S14, and thus suppress deterioration of the ion exchange resin during purification with the ion exchange resin. It is possible.

<Third decontamination system>
FIGS. 5A and 5B are schematic diagrams of the decontamination processing system according to the third embodiment. FIG. 5C is a process diagram of the decontamination processing method according to the third embodiment. The same members as those in the first embodiment are denoted by the same reference numerals, and a duplicate description is omitted.

As shown in Figure 5-1 and Figure 5-2, decontamination system 10C according to the present embodiment, the decontamination system 10A of the first embodiment, the more quartic treatment water W _4, oxalic acid 52a An oxalic acid supply unit 52 is provided.
The oxalic acid supply unit 52 includes an oxalic acid supply line L ₂₂ for supplying oxalic acid 52 a and an oxalic acid supply valve V ₂₈ provided in the oxalic acid supply line L ₂₂ .

  In Example 1, when permanganic acid is added to decompose the reducing agent, the decomposition product, manganese dioxide, may remain in the system (pipe, etc.).

  Therefore, in the present embodiment, for this measure, a cleaning step S16 is performed in which a small amount of oxalic acid (about several tens of ppm) is used for cleaning.

This wash step S16, after the end of the decontamination water decomposition step S14, open the oxalic acid supply valve V _28, via a line L ₂₂ connecting the oxalate 52a oxalic acid supply unit 52 to the primary line L _1, the primary It adds to the quaternary treated water W ₄ circulating through the line L ₁ .

Since manganese dioxide is dissolved in oxalic acid as shown in the following formula (5), manganese dioxide remaining in the system can be removed with oxalic acid.
MnO ₂ + (COOH) ₂ → (COO) ₂ Mn (5)

In-pipe cleaning with oxalic acid is performed while water is passed through the cationic resin tower 31.
This is because dissolved manganese ions are removed by passing water through the cationic resin.

After the washing process is completed, close the fourth valve V ₂₉ in the secondary line L _2, by opening the fifth valve V _30, and introduced into quaternary line L _4, interposed quaternary line L ₄ Oxalic acid is purified (removed) in the oxalic acid removal tower 61 filled with an anion resin, and the process proceeds to the next cycle.

  The oxalic acid removal tower 61 may use a mixed resin obtained by mixing an anion resin and a cation resin in addition to the anion resin.

  According to the present embodiment, it is possible to decompose and remove manganese dioxide, which is a residue in the decontamination water decomposition step S14, so that it can be prevented from remaining in the system (pipe, etc.). .

<Fourth decontamination system>
FIG. 6A is a schematic diagram of a decontamination processing system according to a fourth embodiment. FIG. 6B is a process diagram of the decontamination processing method according to the fourth embodiment. In addition, the same code | symbol is attached | subjected about the same member as the structure of Example 1 thru | or 3, and the overlapping description is abbreviate | omitted.

As shown in FIG. 6A, the decontamination processing system 10D according to the present embodiment is a peroxidation that supplies hydrogen peroxide 51a to the quaternary treated water W ₄ in the decontamination processing system 10A of the first embodiment. The hydrogen supply part 51 and the oxalic acid supply part 52 which supplies the oxalic acid 52a are provided.

  In Example 4, the operations of the permanganate decomposition step S15 and the cleaning step S16 of Example 2 and Example 3 are sequentially performed, and the residue is processed by the combined treatment of hydrogen peroxide 51a and oxalic acid 52a. is there.

That is, first, similarly to the operation of FIG. 4A in Example 2, the permanganate decomposition step S15 is executed, the hydrogen peroxide 51a is introduced into the quaternary treated water W ₄ , and the decontamination water decomposition step S14. The excess permanganic acid, which is a residue, is decomposed and removed.
Next, in the same manner as in the operations of FIGS. 5A and 5B of Example 3, the washing step S16 is performed, and the oxalic acid 52a is introduced into the quaternary treated water W ₄ to remove the manganese dioxide remaining in the system. Remove with oxalic acid.

When the process of this cleaning step S16 is completed, in the same manner as in Example 3, closing the fourth valve V ₂₉ in the secondary line L _2, by opening the fifth valve V _30, and introduced into quaternary line L _4, Oxalic acid is purified (removed) in the oxalic acid removing tower 61 filled with the anion resin interposed in the quaternary line L _4, and the process proceeds to the next cycle.

FIG. 7 is a schematic diagram of a separation unit installed in the decontamination processing system according to the first embodiment.
In the decontamination processing system 10A of the first embodiment, a filter is used as the separation unit 41. However, an embodiment in which a sedimentation tank is used instead of the filter will be described.
As shown in FIG. 7, the sedimentation tank 70 includes a treated water introduction port 71 a for introducing the tertiary treated water W ₃ to the side surface of the treatment tank main body 71 and a treated water drain for discharging the quaternary treated water W ₄ after the sedimentation process. An outlet 71b and a sediment discharge port 71c for discharging the sediment 72 settled in the treatment tank main body 71 to the outside of the system are provided.

  In Example 1, the collection is performed by a filter. However, since the particle diameter of manganese dioxide particles is very small, when the collection process is performed using the filter, the filter may be clogged or the pump pressure may increase. is there.

  For this reason, in this embodiment, instead of collecting with a filter, precipitation is collected using manganese dioxide as a precipitate 72 using a settling tank 70.

Here, since the precipitation rate of manganese dioxide precipitates on the order of about a minute, when the flow rate of the tertiary treated water W ₃ introduced into the settling tank 70 is, for example, 1.5 m ³ / Hr, the capacity of the settling tank 70 Is preferably about several tens of liters to 100 liters.

  The manganese dioxide precipitate 72 removed by the settling tank 70 is about several hundred grams when the decontamination process is performed for two cycles, and can be normally disposed of.

  According to the present embodiment, it is possible to improve the recoverability by the collection in the sedimentation tank 70 as compared with the separation by the filter of the first embodiment.

  That is, in the case of the first embodiment, the filter needs to be replaced due to clogging, but by installing the settling tank 70 as in the present embodiment, the precipitate 72 can be removed from the lower portion of the settling tank 70. And continuous processing is possible.

Further, by adding hydrogen peroxide 51a as in Example 2, the decomposition reactions of the following formulas (3) and (4) occur, and the sedimentation property of the precipitate is improved, which is more preferable.
H ₂ O ₂ → 2H ⁺ + O ₂ + 2e ⁻ (3)
MnO ₄ ⁻ + 3e ⁻ + 4H ⁺ + O ₂ → MnO ₂ ↓ + 2H ₂ O ↓ (4)

10A to 10D Decontamination treatment system 11 Decontamination object 12 Decontamination tank 13 Oxidizing agent supply unit 13a Oxidizing agent 14 Reducing agent supply unit 14a Reducing agent 15 Decontamination equipment 31 Cationic resin towers 32A, 32B Analysis unit 41 Separation unit 51 Over Hydrogen oxide supply unit 51a Hydrogen peroxide 52 Oxalic acid supply unit 52a Oxalic acid 61 Oxalic acid removal tower 70 Sedimentation tank 71a Treated water inlet 71b Treated water outlet 71c Sediment outlet 72 Sediment W ₁ Primary treated water W ₂ 2 Next treated water W ₃ Tertiary treated water W ₄ Fourth treated water

Claims (9)

While using decontamination water in which an oxidizing agent and a reducing agent are sequentially added to a decontamination tank in which an object to be decontaminated is immersed, the primary treatment water using an oxidizing agent and the secondary treatment water using a reducing agent are generated. A decontamination device that circulates through a primary line with both ends connected to a decontamination tank;
A secondary line branched from the primary line, introducing the secondary treated water, and returning to the primary line again;
A removal device that is interposed in the secondary line and removes metal ions and radionuclides eluted in the secondary treated water to obtain tertiary treated water;
A permanganic acid supply unit for supplying permanganic acid to the tertiary treated water in which the reducing agent remains after passing through the removing device;
A separation unit that separates a decomposition product in the tertiary treated water supplied with the permanganic acid to form a quaternary treated water;
A decontamination processing system comprising: In claim 1,
A decontamination treatment system comprising a hydrogen peroxide supply unit that supplies hydrogen peroxide to the quaternary treatment water. In claim 1 or 2,
The decontamination processing system provided with the oxalic acid supply part which supplies an oxalic acid to the said quaternary treated water. In claim 3,
A decontamination treatment system comprising an oxalic acid removal tower for removing residual oxalic acid in the quaternary treated water supplied with the oxalic acid. In any one of Claims 1 thru | or 4,
The decontamination processing system, wherein the separation unit is a collection member that collects solid matter or a precipitation device that precipitates. After decontaminating the decontamination object by performing primary treatment and secondary treatment using decontamination water in which an oxidizing agent and a reducing agent are sequentially added,
The reducing agent remaining in the tertiary treated water from which the metal ions and radionuclides eluted in the secondary treated water after the secondary treatment are removed is decomposed with permanganic acid,
A method for decomposing decontamination wastewater, wherein a decomposition product in tertiary treated water supplied with permanganic acid is separated into quaternary treated water. In claim 6,
A method for decomposing decontamination wastewater, wherein hydrogen peroxide is supplied to the quaternary treated water. In claim 6 or 7,
A method for decomposing decontamination wastewater, wherein oxalic acid is supplied to the quaternary treated water. In claim 8,
A method for decomposing decontamination wastewater, wherein residual oxalic acid in quaternary treated water supplied with oxalic acid is removed.

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