JP2011145140A - Chemical decontamination liquid processing method and processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of shortening time for decomposition in a method of decomposing a reducing agent such as organic acid in a solution after chemical decontamination. <P>SOLUTION: In the method, organic acid in a chemical decontamination liquid is decomposed in a first organic acid decomposition step, then the organic acid is decomposed into an allowable discharge concentration by adding an oxidizing agent of chemical equivalent or more to the undecomposed organic acid in a second organic acid decomposition step, the oxidizing agent is decomposed by adding a reducing agent of chemical equivalent or more to the unreacted oxidizing agent in an oxidizing agent decomposition step, and it is purified by a filter and a mixed bed resin in a purification step. The chemical decontamination liquid flows each step once through. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for treating a chemical decontamination solution containing an organic acid, and in particular, treats an aqueous solution containing an organic acid that is generated when the surface of a member contaminated by radiation in a nuclear power plant is chemically decontaminated. Regarding the method.

In a nuclear power plant, an oxide film containing a radionuclide is attached to or generated on the surface of a component that comes into contact with reactor water containing a radioactive substance during operation of the nuclear power plant. For this reason, since the radiation dose increases around the piping and equipment of the nuclear power plant, it is necessary to reduce the exposure dose of the workers during the periodic inspection work of the nuclear power plant or the dismantling work at the time of decommissioning the facility.
For this reason, chemical decontamination is carried out in nuclear power plants.

  A chemical decontamination method for a nuclear power plant includes an oxidative decontamination step of oxidizing and dissolving a chromium-based oxide contained in an oxide film formed on the surface of a component using an aqueous solution containing an oxidizing decontamination agent. And a reductive decontamination step of reductively dissolving the iron-based oxide, which is a main component of the oxide film, using an aqueous solution containing a reductive decontaminant.

  There is a method using an organic acid as the reductive decontamination agent. For example, in the chemical decontamination method described in Patent Document 1, a dicarboxylic acid such as oxalic acid is used as a reducing decontamination agent.

  As a method for treating an organic acid associated with the invention described in Patent Document 1, Patent Document 2 proposes a method of decomposing using an iron complex and ultraviolet rays. The organic acid treatment method described in Patent Document 2 decomposes oxalic acid, which is a reducing decontamination agent, into water and carbon dioxide by the catalytic action of an iron complex, hydrogen peroxide, and ultraviolet irradiation. In the method for decomposing dicarboxylic acids such as oxalic acid described in Patent Document 3, oxalic acid is decomposed into water and carbon dioxide by the catalytic action of an iron complex and irradiation with visible light.

  Patent Document 4 describes a method for decomposing a reductive decontaminant using a catalyst impregnated with a noble metal such as platinum, ruthenium, vanadium and palladium and hydrogen peroxide.

Japanese Patent Publication No. 3-10919 JP-T 9-510784 JP 2006-162277 A JP 2000-105295 A

  In the conventional chemical decontamination liquid processing method, the method of decomposing by irradiating with ultraviolet rays or visible light has low decomposition efficiency of the reductive decontamination agent, so it is necessary to circulate the decontamination liquid to the decomposition equipment multiple times. The time for decomposing and eliminating the decontaminating agent becomes longer. Moreover, when it is going to shorten decomposition | disassembly time, it is necessary to enlarge decomposition | disassembly equipment, and installation cost increases.

  On the other hand, the decomposition method using a noble metal catalyst has higher decomposition efficiency of the reducing decontaminating agent than the method of irradiating with ultraviolet rays or visible light, and can shorten the decomposition time, but decomposes the decontaminating agent to a dischargeable concentration. In order to achieve this, it is necessary to pass the decontamination solution through the catalyst a plurality of times. Therefore, the ratio of the time for decomposing the reducing decontaminant in the decontamination process is large, and further reduction of the decomposition time is desired.

  The objective of this invention is providing the processing method of the chemical decontamination liquid which can shorten the time required for decomposition | disassembly of a reductive decontamination agent.

  The feature of the present invention that achieves the above-described object is that a first organic acid decomposition step that decomposes a chemical decontamination solution containing an organic acid, and an oxidant is added to the remaining organic acid that is not decomposed in the first organic acid decomposition step The second organic acid decomposition step decomposed by the above and the oxidant decomposition step of decomposing the oxidant remaining in the second organic acid decomposition step by adding a reducing agent. It is to be.

  According to the present invention, the time required for processing a chemical decontamination solution containing an organic acid can be shortened.

It is a flowchart which shows the process sequence in the processing method of the chemical decontamination liquid concerning embodiment of this invention. It is a block diagram of the processing apparatus used with the processing method of the chemical decontamination liquid concerning the 1st Embodiment of this invention. It is a block diagram of the processing apparatus used with the processing method of the chemical decontamination liquid concerning the 2nd Embodiment of this invention. It is a block diagram of the processing apparatus used with the processing method of the chemical decontamination liquid concerning another embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to these embodiments.

Example 1
FIG. 1 is a flowchart showing a processing procedure in the chemical decontamination liquid processing method of this embodiment, and FIG. 1 is a schematic diagram of the configuration of the chemical decontamination apparatus used in the chemical decontamination liquid processing method according to this embodiment. It is shown in 2.

  First, the structure of the processing apparatus which processes chemical decontamination liquid is demonstrated using the processing apparatus 1 of chemical decontamination liquid shown in FIG. In the present embodiment, oxalic acid will be described as an example of the reducing decontamination solution contained in the chemical decontamination solution.

  The chemical decontamination liquid processing apparatus 1 of this embodiment includes a valve 3, a liquid passage pipe 2 through which the chemical decontamination liquid after chemical decontamination passes, and an oxidizing agent (peroxidation in this embodiment) in the liquid passage pipe 2. A first oxidant injection system 11 for injecting hydrogen), a valve 31 for adjusting the injection amount of the oxidant injected from the first oxidant injection system 11, and a first for controlling opening and closing of the valve 31 Control device 32, decomposition device 4 for firstly decomposing organic acid (oxalic acid in this embodiment) contained in the reductive decontamination solution after chemical decontamination, and measuring the concentration of organic acid in the chemical decontamination solution that passes through Measuring instrument 9, a second oxidant injection system 12 for injecting an oxidant (permanganic acid in the present embodiment) into the liquid passage 2, and an oxidant injection from the second oxidant injection system 12. A valve 33 for adjusting the amount, a second control device 34 for controlling the opening and closing of the valve 33, and a chemical decontamination passing through the liquid passage 2 And the peroxidic acid injected from the second oxidant injection system 12, the measuring instrument 10 for measuring the concentration of the oxidant contained in the chemical decontamination liquid that has passed through the mixer 5, and the flow pipe 2, a reducing agent injection system 13 for injecting a reducing agent (hydrogen peroxide in this embodiment), a valve 35 for adjusting the amount of reducing agent injected from the reducing agent injection system 13, and opening and closing of the valve 35 A third control device 36 that controls the chemical decontamination solution that has passed through the liquid flow pipe 2 and the hydrogen peroxide that has been injected from the reducing agent injection system 13, and the chemical removal that has been discharged from the mixer 6. A filter 7 that passes the dye solution and a mixed bed resin tower 8 that removes ions from the chemical decontamination solution that has passed through the filter 7 are provided. In order from the upstream side of the path of the liquid passing pipe 2 through which the chemical decontamination liquid passes, there are a valve 3, a decomposition device 4, a measuring device 9, a mixer 5, a measuring device 10, a mixer 6, a filter 7, and a mixed bed resin tower 8. Be placed. The first control device 32 is connected to the water quality monitor 16 and the valve 31. The second control device 34 is connected to the measuring instrument 9 and the valve 33. The third control device 36 is connected to the measuring instrument 10 and the valve 35.

  In the present embodiment, a catalyst tower packed with a noble metal catalyst is used as the decomposition device 4, a conductivity meter is used as the measuring device 9, a static mixer is used as the mixers 5 and 6, and a spectrophotometer is used as the measuring device 10.

  The first oxidant injection system 11 is arranged to inject an oxidant into the liquid flow pipe 2 downstream of the valve 3 and upstream of the decomposition apparatus 4. The first oxidant injection system 11 includes, for example, a chemical tank filled with hydrogen peroxide, a liquid feed pump, and a valve.

  The second oxidant injection system 12 is arranged so as to inject an oxidant into the liquid flow pipe 2 on the downstream side of the measuring instrument 9 and on the upstream side of the mixer 5. The second oxidant injection system 12 includes, for example, a chemical tank filled with permanganic acid, a liquid feed pump, and a valve.

  The reducing agent injection system 13 is arranged so as to inject the reducing agent into the liquid flow pipe 2 downstream of the measuring instrument 10 and upstream of the mixer 6. The reducing agent injection system 13 includes, for example, a chemical tank filled with hydrogen peroxide, a liquid feed pump, and a valve.

Next, a method for treating a chemical decontamination solution will be described with reference to FIGS. In the reduction decontamination process in chemical decontamination for nuclear power plants, chemical decontamination is performed by passing a decontamination solution containing an organic acid on the surface of the components constituting the nuclear power plant and in contact with the reactor water. To implement. The reductive decontamination liquid, which is a chemical decontamination liquid, passes through the decontamination target site 14, system piping 15, water quality monitor 16, liquid feed pump 17, valve 19, cation exchange resin tower 21, valve 20, valve 22 in FIG. 2. Circulates to the decontamination site 14. The concentration of the reducing agent in the reductive decontamination liquid is measured by, for example, the water quality monitor 16, and the measurement result is output to a reductive decontamination control device (not shown).
The reduction decontamination control device adjusts the amount of oxalic acid injected from the reducing agent injection system 27 based on the measured reducing agent concentration.

  After completion of the reduction decontamination process, the decomposition treatment of the reduction decontamination liquid is started. The processing procedure of the reductive decontamination solution of this embodiment includes a first organic acid decomposition step S1, a second organic acid decomposition step S2, an oxidant decomposition step S3, and a purification step S4, as shown in FIG. . The processing procedure shown in FIG. 1 uses the chemical decontamination liquid processing apparatus 1 shown in FIG. 2 and supplies the reduced decontamination liquid after chemical decontamination to the liquid passing pipe 2 via the valve 3 for processing. Do.

  First, the valve 3 in the processing apparatus 1 is opened, the valve 20 is closed, and the chemical decontamination solution is distributed to the processing apparatus 1.

  The first organic acid decomposing step S1 is a step of first decomposing an organic acid (oxalic acid in this embodiment) contained in the reductive decontamination solution after chemical decontamination. The apparatus comprising the oxidant injection system 11, the valve 31 and the first control device 32 is used. As the decomposition apparatus 4, an apparatus that decomposes an organic acid once through, for example, a noble metal catalyst tower or an ultraviolet irradiation apparatus can be used. Although hydrogen peroxide is used as the oxidant injected from the first oxidant injection system 11, ozone or the like may be used. The injection amount of the oxidizing agent injected from the first oxidizing agent injection system 11 is determined based on the concentration of the reducing agent measured by the water quality monitor 16. When the oxalic acid concentration information measured by the water quality monitor 16 is transmitted to the first control device 32, the first control device 32 adjusts the opening and closing of the valve 31 based on the oxalic acid concentration, and injects hydrogen peroxide. Control the amount. The reducing decontamination liquid after chemical decontamination is supplied to the decomposing apparatus 4 together with the oxidant injected from the first oxidant injection system 11 in the first organic acid decomposition step S1. As described above, the first control device 32 controls the injection amount of the oxidant injected from the first oxidant injection system 11 based on the measurement result of the water quality monitor 16, so that about 90% of the oxidant is injected in the decomposition device 4. Decomposes acid. Oxalic acid contained in the chemical decontamination solution is decomposed into carbon dioxide and water by reaction with an oxidizing agent.

  The second organic acid decomposing step S2 is a step of decomposing the undecomposed organic acid contained in the chemical decontamination liquid that has passed through the first organic acid decomposing step S1 to a concentration capable of draining, and is subsequent to the measuring instrument 9 shown in FIG. In addition, an apparatus having a configuration in which the second oxidant injection system 12, the mixer 5, the valve 33, and the second control device 34 are installed is used. As the measuring device 9, a measuring device (conductivity meter in this embodiment) that can determine the concentration of the organic acid by passing the chemical decontamination solution is used. As the mixer 5, the chemical decontamination liquid is allowed to pass through to sufficiently mix the oxidant supplied from the second oxidant injection system 12 and the chemical decontamination liquid, and the organic acid decomposition reaction is completed ( In this embodiment, a static mixer) is used. In this embodiment, permanganic acid is used as the oxidant supplied from the second oxidant injection system 12, but an aqueous solution of permanganate, ozone, hydrogen peroxide, or the like may be used. The oxidant supplied from the second oxidant injection system 12 is selected in consideration of the reaction rate with oxalic acid, the decomposability in the subsequent oxidant decomposition step S3, the removability in the purification step S4, and the like. The amount of undegraded oxalic acid contained in the chemical decontamination solution that has passed through the decomposition apparatus 4 is quantified by the measuring instrument 9 installed in the second organic acid decomposition step S2. The amount of oxidant injected from the second oxidant injection system 12 is determined based on the concentration of oxalic acid measured by the measuring instrument 9. When the concentration information of the oxalic acid measured by the measuring instrument 9 is transmitted to the second control device 34, the second control device 34 adjusts the opening and closing of the valve 33 based on the oxalic acid concentration, and injects permanganic acid. Control the amount. The amount of permanganic acid injected from the second oxidant injection system 12 is based on the quantitative result in the measuring instrument 9 and is 1 to 1. 1 times the chemical equivalent with respect to the amount of oxalic acid contained in the chemical decontamination solution. It is set to double. When a set amount of permanganic acid is injected into the liquid flow pipe 2, a mixed liquid of chemical decontamination liquid and permanganic acid enters the mixer 5. The mixer 5 sufficiently mixes the chemical decontamination solution and permanganic acid, and reacts oxalic acid contained in the chemical decontamination solution with permanganic acid, which is an oxidizing agent, to decompose oxalic acid into carbon dioxide and water. . Oxalic acid and permanganic acid react quantitatively, and the reaction rate of oxalic acid and permanganic acid is high at the process temperature (80 ° C to 90 ° C) often used in the reduction decontamination process of chemical decontamination. It is known that oxalic acid can be decomposed to a dischargeable concentration, for example, 10 ppm or less, by adding permanganic acid in an amount equal to or greater than the chemical equivalent. Here, the injection amount of the oxidizing agent injected from the second oxidizing agent injection system 12 is not less than the chemical equivalent of the oxidizing agent used in the decomposition reaction of oxalic acid by the oxidizing agent, preferably 1 to 1 times the chemical equivalent. . Double the amount. By injecting an oxidizing agent having a chemical equivalent or more, oxalic acid in the chemical decontamination solution is decomposed to a concentration capable of being discharged. The residence time of the chemical decontamination liquid in the mixer 5 is set so as to be equal to or longer than the time when the oxalic acid contained in the chemical decontamination liquid becomes less than the concentration that can be discharged by the reaction with the oxidizing agent.

  The oxidant decomposition step S3 is a step of decomposing the oxidant contained in the chemical decontamination liquid that has passed through the second organic acid decomposition step S2, and is provided at the rear stage of the measuring instrument 10 shown in FIG. 6, the apparatus of the structure which installed the valve | bulb 35 and the 3rd control apparatus 36 is used. As the measuring device 10, a measuring device (a spectrophotometer in this embodiment) capable of quantifying the concentration of the oxidizing agent by passing the chemical decontamination solution is used. The mixer 6 is the same as the mixer 5, in which the chemical decontamination liquid is sufficiently mixed with the reducing agent supplied from the reducing agent injection system 13 by passing the chemical decontamination liquid, and the decomposition reaction of the oxidizing agent is completed. Use one. As the reducing agent supplied from the reducing agent injection system 13, hydrogen peroxide is used in this embodiment, but an inorganic reducing agent other than hydrogen peroxide, or an organic reducing agent such as ascorbic acid or hydrazine is used. You can also. The reducing agent supplied from the reducing agent injection system 13 is selected in consideration of the reaction rate with the oxidizing agent and the removability in the subsequent purification step S4. When an oxidizing agent having a chemical equivalent or more is injected in the second organic acid decomposition step S2, the chemical decontamination liquid that has passed through the second organic acid decomposition step contains an unreacted oxidizing agent (permanganic acid). The unreacted permanganic acid concentration contained in the chemical decontamination liquid that has passed through the mixer 5 is quantified by measuring, for example, absorbance at 525 nm in the measuring instrument 10. When the measuring device 10 quantifies the concentration of unreacted permanganic acid, the amount of reducing agent injected from the reducing agent injection system 13 is determined based on the determination result. When the concentration information of the permanganic acid measured by the measuring instrument 10 is transmitted to the third control device 36, the third control device 36 adjusts the opening and closing of the valve 35 based on the concentration of the permanganic acid, and performs the peroxidation. Control the amount of hydrogen injection. The amount of hydrogen peroxide injected from the reducing agent injection system 13 is 1 to 1.2 times the chemical equivalent with respect to the amount of permanganate contained in the chemical decontamination solution based on the quantitative result in the measuring device 10. Set. A mixed liquid of the chemical decontamination liquid and hydrogen peroxide injected from the reducing agent injection system 13 is injected into the mixer 6. The mixer 6 mixes the chemical decontamination solution and hydrogen peroxide as a reducing agent, and decomposes the oxidizing agent by a reaction between the oxidizing agent and the reducing agent. That is, the chemical decontamination solution and hydrogen peroxide are mixed by the mixer 6, and the permanganate is decomposed into manganese ions and / or manganese dioxide. Permanganic acid and hydrogen peroxide react quantitatively, and the reaction rate of permanganic acid and hydrogen peroxide at the process temperature (80 ° C to 90 ° C) often used in the reduction decontamination process of chemical decontamination. Is known to be large, and almost all of permanganic acid can be decomposed by adding more than an equivalent amount of hydrogen peroxide. The amount of reducing agent injected is at least the chemical equivalent of the reducing agent used in the decomposition reaction of the oxidizing agent by the reducing agent, preferably 1 to 1.2 times the chemical equivalent.

  The purification step S4 is a step of separating precipitates and ions contained in the chemical decontamination liquid that has passed through the oxidant decomposition step S3, and uses an apparatus constituted by the filter 7 and the mixed bed resin tower 8. The chemical decontamination liquid that has passed through the oxidant decomposition step S3 includes a decomposition product of the oxidant and an unreacted reducing agent. The chemical decontamination solution that has passed through the mixer 6 is sent to the filter 7. Particulate matter is removed in the filter 7, and ions are removed in the mixed bed resin tower 8. In this embodiment, in the filter 7, manganese dioxide is removed when manganese dioxide is generated. If the chemical decontamination solution contains unreacted hydrogen peroxide, it is decomposed by the filter 7. The chemical decontamination liquid that has passed through the filter 7 is sent to the mixed bed resin tower 8, and ions contained in the chemical decontamination liquid are removed. The chemical decontamination solution purified in the purification step S4 can be discharged as it is or supplied to a decontamination target site of another system and used as system water.

  According to the chemical decontamination liquid processing method and processing apparatus 1 of the present embodiment, oxalic acid that has not been decomposed by the decomposition apparatus 4 is reacted with an oxidizing agent (permanganic acid in the present embodiment) and is not reacted. Since oxidizer (permanganic acid in this embodiment) is decomposed by reaction with a reducing agent (hydrogen peroxide in this embodiment), oxalic acid can be decomposed once through. The time required for the decomposition of the acid can be shortened.

  In this embodiment, when the chemical decontamination solution is passed through the first organic acid decomposition step once, the chemical decontamination solution discharged from the step is applied to the organic acid decomposition method employed in the first organic acid decomposition step. A corresponding amount of undegraded organic acid is included. In the second organic acid decomposition step, an oxidizing agent having a chemical equivalent or more is added to the undecomposed organic acid, and the organic acid is decomposed to a concentration capable of being discharged by a chemical reaction. The chemical decontamination liquid that has passed through the second organic acid decomposition step contains an unreacted oxidant. In the oxidant decomposition step, a reducing agent equal to or more than the reaction equivalent is added to the oxidant to remove the oxidant. Decompose. In this embodiment, the oxidizing agent added in the second organic acid decomposition step has a high reaction rate with the organic acid, and the reducing agent added in the oxidizing agent decomposition step has a high reaction rate with the oxidizing agent. The one in which the decomposition reaction is completed in a time equivalent to or less than the water passage time in the acid decomposition step S1 is selected. Thus, in the conventional method, it was necessary to circulate the chemical decontamination solution a plurality of times in order to decompose the organic acid to a concentration capable of being discharged, whereas in this embodiment, the chemical decontamination solution is circulated once. Since the organic acid can be decomposed in a time equivalent to that described above, the time required for the decomposition of the reducing decontaminating agent can be shortened.

  Like the chemical decontamination solution processing method and processing apparatus 1 of the present embodiment, the second organic acid decomposition step S2 using permanganic acid is performed after the first organic acid decomposition step S1 using hydrogen peroxide. By doing so, the amount of waste can be reduced. That is, when the first organic acid decomposition step S1 using hydrogen peroxide is performed after the second organic acid decomposition step S2 using permanganic acid, the organic acid (oxalic acid in this embodiment) is decomposed. Therefore, the amount of permanganic acid required to do so increases as compared with the present embodiment, and the amount of resin for removing manganese ions after decomposition increases. As in this example, the amount of manganese ions can be reduced by performing the second organic acid decomposition step S2 using permanganic acid after the first organic acid decomposition step S1 using hydrogen peroxide, Thereby, the amount of waste can be reduced. The reaction rate for decomposing the organic acid is faster with permanganic acid than with hydrogen peroxide, but the method of decomposing using the hydrogen peroxide and catalyst in the first organic acid decomposing step S1 has a high concentration of organic acid. The efficiency of decomposition increases. For this reason, as in this embodiment, the first organic acid decomposition step S1 using hydrogen peroxide and the decomposition device 4 is performed before the second organic acid decomposition step S2, thereby requiring chemical decontamination liquid processing. You can save time. If the first organic acid decomposition step S1 is performed after the second organic acid decomposition step S2, the chemical decontamination solution obtained by partially decomposing the organic acid in the second organic acid decomposition step S2 is the first organic acid. Since it is injected into the decomposition step S1, a chemical decontamination solution having a low organic acid concentration is processed in the first organic acid decomposition step S1, and it is necessary to circulate the chemical decontamination solution through the decomposition device 4 a plurality of times. This may increase the processing time. By performing the first organic acid decomposition step S1 using hydrogen peroxide and the decomposition apparatus 4 before the second organic acid decomposition step S2 as in this embodiment, the one-through decomposition is possible.

(Example 2)
FIG. 3 schematically shows a configuration including the chemical decontamination liquid processing apparatus 1A used in the chemical decontamination liquid processing method according to the present embodiment. In the first embodiment, the measuring device 9 installed on the downstream side of the decomposition device 4, the second control device 34 connected to the measuring device 9 and the valve 33, the measuring device 10 installed on the downstream side of the mixer 5, The processing device 1 including the measuring device 10 and the third control device 36 connected to the valve 35 has been described, but the processing device 1A of the present embodiment is a measuring device 10A installed on the downstream side of the mixer 5, The first control device connected to the measuring device 10A and the valve 33, the measuring device 10B installed on the downstream side of the mixer 6, and the third control device 36A connected to the measuring device 10B and the valve 35 are provided. . Also in this embodiment, oxalic acid will be described as an example of the reducing decontamination solution contained in the chemical decontamination solution. In FIG. 3, the same reference numerals are given to the portions common to the first embodiment (FIG. 2), and the description overlapping with the first embodiment will be omitted below.

  The configuration of the chemical decontamination liquid processing apparatus 1A of the present embodiment will be described with reference to FIG. The processing apparatus 1A includes a valve 3, a disassembling apparatus 4, a mixer 5, a measuring instrument 10A, a mixer 6, a measuring instrument 10B, a filter 7 and a mixture in order from the upstream side of the path of the liquid passing pipe 2 through which the chemical decontamination liquid passes. A floor resin tower 8 is arranged. In this embodiment, a catalytic tower packed with a noble metal catalyst is used as the decomposition device 4, a static mixer is used as the mixers 5 and 6, a spectrophotometer is used as the measuring device 10A, and a hydrogen peroxide meter is used as the measuring device 10B. .

  The first oxidant injection system 11 is arranged so as to inject an oxidant (hydrogen peroxide in this embodiment) into the liquid flow pipe 2 downstream of the valve 3 and upstream of the decomposition apparatus 4. . The first oxidant injection system 11 includes, for example, a chemical tank filled with hydrogen peroxide, a liquid feed pump, and a valve.

  The second oxidant injection system 12 is disposed so as to inject an oxidant (permanganic acid in this embodiment) into the liquid flow pipe 2 downstream of the decomposition apparatus 4 and upstream of the mixer 5. The second oxidant injection system 12 includes, for example, a chemical tank filled with permanganic acid, a liquid feed pump, and a valve.

  The reducing agent injection system 13 is arranged so as to inject a reducing agent (hydrogen peroxide in this embodiment) into the liquid flow pipe 2 on the downstream side of the measuring instrument 10 </ b> A and on the upstream side of the mixer 6. The reducing agent injection system 13 includes, for example, a chemical tank filled with hydrogen peroxide, a liquid feed pump, and a valve.

  The first control device 32 is connected to the water quality monitor 16 and the valve 31, adjusts the opening / closing of the valve 31 based on the concentration of the reducing agent measured by the water quality monitor 16, and injects from the first oxidant injection system 11. Control the amount of oxidant injected. The second control device 34A is connected to the measuring instrument 10A and the valve 33, adjusts the opening and closing of the valve 33 based on the concentration of oxalic acid measured by the measuring instrument 10A, and injects from the second oxidant injection system 12 Control the amount of oxidant injected. The third controller 36A is connected to the measuring device 10B and the valve 35, controls the opening and closing of the valve 35 based on the concentration of hydrogen peroxide measured by the measuring device 10B, and reduces the amount injected from the reducing agent injection system 13. Control the dose of agent.

  Next, a method for treating a chemical decontamination solution using the treatment apparatus 1A of the present embodiment will be described.

  After completion of the reduction decontamination step, processing of the reduction decontamination solution is started. The processing procedure of the reductive decontamination solution of this example is a processing procedure in which the second organic acid decomposition step S2 and the oxidant decomposition step S3 of Example 1 are replaced with the second organic acid decomposition step S2a and the oxidant decomposition step S3a. It is.

  First, the valve 3 in the processing apparatus 1A is opened, the valve 20 is closed, and the chemical decontamination solution is distributed to the processing apparatus 1A.

  In the first organic acid decomposition step S1, as in Example 1, oxalic acid contained in the reductive decontamination liquid after chemical decontamination is decomposed into carbon dioxide and water. In the treatment apparatus 1A, hydrogen peroxide is injected from the first oxidant injection system 11 based on the measurement result of the oxalic acid concentration in the water quality monitor 16, and about 90% of the oxalic acid is decomposed in the decomposition apparatus 4. . Chemical decontamination containing undegraded oxalic acid is sent to the second organic acid decomposition step.

The second organic acid decomposing step S2a is a step of decomposing the undecomposed organic acid contained in the chemical decontamination solution that has passed through the first organic acid decomposing step S1 to a concentration capable of draining. The second oxidant injection system 12 injects permanganic acid into the liquid passing pipe 2 through which the chemical decontamination liquid discharged from the decomposition apparatus 4 passes.
The injection amount of permanganic acid supplied from the second oxidant injection system 12 is based on the design value of the decomposition rate of oxalic acid in the decomposition apparatus 4 immediately after the treatment of the chemical decontamination solution is started. Is set to a predetermined injection amount (for example, an injection amount that is 1 to 1.2 times the chemical equivalent of the amount of oxalic acid contained in the chemical decontamination solution). That is, the second control device 34A adjusts the opening and closing of the valve 33, and controls the injection amount of oxalic acid injected from the second oxidant injection system 12 so as to be the predetermined injection amount. The mixed liquid of the chemical decontamination liquid and permanganic acid that has passed through the liquid passage pipe 2 is mixed in the mixer 5. The chemical decontamination solution that has passed through the mixer 5 is sent to the measuring instrument 10A. The measuring device 10A measures the absorbance at 525 nm and measures the unreacted oxidant concentration. The measurement result measured by the measuring instrument 10A is sent to the second control device 34A. After the measurement of the permanganic acid is started by the measuring instrument 10A, the second controller 34A determines the permanganic acid injected from the second oxidant injection system 12 based on the measurement result of the measuring instrument 10A. Set the amount. The amount of permanganic acid to be injected is not less than the chemical equivalent in order to sufficiently decompose undecomposed oxalic acid. For this reason, it becomes possible to detect the oxidizing agent with the measuring instrument 10A, but the addition of an excessive oxidizing agent is not preferable because the processing load in the subsequent stage may increase. In the second organic acid decomposition step S2a, undecomposed oxalic acid is decomposed to a concentration that can be discharged.

  The oxidant decomposition step S3a is a step of decomposing the oxidant contained in the chemical decontamination liquid that has passed through the second organic acid decomposition step S2a. The chemical decontamination solution that has passed through the measuring instrument 10A is sent to the mixer 6 together with hydrogen peroxide injected from the reducing agent injection system 13 and mixed. The amount of hydrogen peroxide injected from the reducing agent injection system 13 is 1 equivalent to the chemical equivalent of the amount of permanganic acid injected from the second oxidant injection system 12 immediately after the treatment of the chemical decontamination solution is started. It is set to be double to 1.2 times. That is, the third control device 36A adjusts the opening and closing of the valve 35 and controls the injection amount of hydrogen peroxide injected from the reducing agent injection system 13 to be a set value. The chemical decontamination liquid that has passed through the mixer 6 is sent to the measuring device 10B, and unreacted hydrogen peroxide is quantified. The measuring instrument 10B measures the undecomposed oxidant concentration or the reducing agent concentration, and transmits the measurement result to the third controller 36A. After the measurement of the hydrogen peroxide by the measuring device 10B is started, the third controller 36A determines the amount of hydrogen peroxide injected from the reducing agent injection system 13 based on the result of the hydrogen peroxide determination by the measuring device 10B. Control the injection volume. The amount of the reducing agent to be injected is not less than the chemical equivalent in order to sufficiently decompose the oxidizing agent. In this oxidant decomposition step S3a, the unreacted oxidant contained in the chemical decontamination solution is decomposed.

  In the present embodiment, in the oxidizing agent decomposition step S3a, the concentration of the oxidizing agent is measured using the measuring device 10B, and the reducing agent injected from the reducing agent injection system 13 is adjusted, but the measuring device 10A determines the concentration of the oxidizing agent. When measuring, it is good also as a structure which does not install the measuring device 10B. In this case, the third control device 36A is connected to the measuring device 10A and the valve 35, and adjusts the injection amount of the reducing agent injected from the reducing agent injection system 13 based on the concentration of the oxidizing agent measured by the measuring device 10A. To do.

  In this embodiment, the reducing agent injection system 13, the mixer 6, the valve 35, and the third control device 36 are used to decompose the oxidizing agent contained in the chemical decontamination solution that has passed through the two organic acid decomposition step S2a. (Oxidant decomposition step S3a), but the oxalic acid concentration and the oxidant concentration are measured with the measuring instrument 10A, and the oxalic acid concentration is below the concentration that can be discharged, and the oxidant concentration is the latter stage, particularly in the purification step S4. The amount of oxidant injected from the second oxidant injection system 12 may be adjusted so that the concentration does not affect the performance of the resin used. In this case, the oxidizing agent decomposition step S3a can be omitted.

The purification step S4 is a step of purifying the chemical decontamination liquid that has passed through the oxidant decomposition step S3a. The chemical decontamination solution that has passed through the mixer 6 is sent to the filter 7. The filter 7 removes particulate matter contained in the chemical decontamination solution and decomposes unreacted hydrogen peroxide. The chemical decontamination liquid discharged from the filter 7 is sent to the mixed bed resin tower 8 to remove ions contained in the chemical decontamination liquid.
The purified chemical decontamination solution is discharged or used as system water at a site to be decontaminated in another system.

  According to the chemical decontamination solution processing method and the processing apparatus 1A of the present embodiment, oxalic acid that has not been decomposed by the decomposition apparatus 4 is reacted with an oxidizing agent (permanganic acid in the present embodiment) and is not reacted. Since oxidizer (permanganic acid in this embodiment) is decomposed by reaction with a reducing agent (hydrogen peroxide in this embodiment), oxalic acid can be decomposed once through. The time required for the decomposition of the acid can be shortened.

  In this embodiment, when the chemical decontamination solution is passed through the first organic acid decomposition step once, the chemical decontamination solution discharged from the step is applied to the organic acid decomposition method employed in the first organic acid decomposition step. A corresponding amount of undegraded organic acid is included. In the second organic acid decomposition step, an oxidizing agent having a chemical equivalent or more is added to the undecomposed organic acid, and the organic acid is decomposed to a concentration capable of being discharged by a chemical reaction. The chemical decontamination liquid that has passed through the second organic acid decomposition step contains an unreacted oxidant. In the oxidant decomposition step, a reducing agent equal to or more than the reaction equivalent is added to the oxidant to remove the oxidant. Decompose. In this embodiment, the oxidizing agent added in the second organic acid decomposition step has a high reaction rate with the organic acid, and the reducing agent added in the oxidizing agent decomposition step has a high reaction rate with the oxidizing agent. The one in which the decomposition reaction is completed in a time equivalent to or less than the water passage time in the acid decomposition step S1 is selected. Thus, in the conventional method, it was necessary to circulate the chemical decontamination solution a plurality of times in order to decompose the organic acid to a concentration capable of being discharged, whereas in this embodiment, the chemical decontamination solution is circulated once. Since the organic acid can be decomposed in a time equivalent to that described above, the time required for the decomposition of the reducing decontaminating agent can be shortened.

  According to the chemical decontamination solution processing method and the processing apparatus 1A of the present embodiment, the second organic acid decomposition step S2a using permanganic acid is performed after the first organic acid decomposition step S1 using hydrogen peroxide. Therefore, as in Example 1, the amount of manganese ions can be reduced, and the amount of waste can be reduced. Further, in the present example, the first organic acid decomposition step S1 using hydrogen peroxide and the decomposition apparatus 4 is performed before the second organic acid decomposition step S2a. The time required for processing the dye solution can be shortened, and the one-through decomposition is possible.

(Example 3)
A configuration including the chemical decontamination liquid processing apparatus 1B used in the chemical decontamination liquid processing method according to the present embodiment is schematically shown in FIG. In the first embodiment, the measuring device 9 installed on the downstream side of the decomposition device 4, the second control device 34 connected to the measuring device 9 and the valve 33, the measuring device 10 installed on the downstream side of the mixer 5, Although the chemical decontamination liquid processing apparatus 1 including the measuring apparatus 10 and the third control apparatus 36 connected to the valve 35 has been described, the processing apparatus 1B of the present embodiment is a measurement installed on the downstream side of the mixer 5. 10C, the measuring instrument 10C, the valve 33, and the second control device 34B connected to the valve 35. Also in this embodiment, oxalic acid will be described as an example of the reducing decontamination solution contained in the chemical decontamination solution. In FIG. 4, the same reference numerals are given to portions common to the first embodiment (FIG. 2), and the description overlapping with the first embodiment will be omitted below.

  The structure of the chemical decontamination liquid processing apparatus 1B of the present embodiment will be described with reference to FIG. The processing apparatus 1B includes a valve 3, a decomposition apparatus 4, a mixer 5, a measuring instrument 10C, a mixer 6, a filter 7, and a mixed bed resin tower 8 in order from the upstream side of the path of the liquid passing pipe 2 through which the chemical decontamination liquid passes. Is placed. In this embodiment, a catalyst tower packed with a noble metal catalyst is used as the decomposition apparatus 4, a static mixer is used as the mixers 5 and 6, and a spectrophotometer is used as the measuring instrument 10C.

  The first oxidant injection system 11 is arranged so as to inject an oxidant (hydrogen peroxide in this embodiment) into the liquid flow pipe 2 downstream of the valve 3 and upstream of the decomposition apparatus 4. . The first oxidant injection system 11 includes, for example, a chemical tank filled with hydrogen peroxide, a liquid feed pump, and a valve.

  The second oxidant injection system 12 is disposed so as to inject an oxidant (permanganic acid in this embodiment) into the liquid flow pipe 2 downstream of the decomposition apparatus 4 and upstream of the mixer 5. The second oxidant injection system 12 includes, for example, a chemical tank filled with permanganic acid, a liquid feed pump, and a valve.

  The reducing agent injection system 13 is arranged so as to inject a reducing agent (hydrogen peroxide in this embodiment) into the liquid flow pipe 2 downstream of the measuring instrument 10C and upstream of the mixer 6. The reducing agent injection system 13 includes, for example, a chemical tank filled with hydrogen peroxide, a liquid feed pump, and a valve.

  The first control device 32 is connected to the water quality monitor 16 and the valve 31, adjusts the opening / closing of the valve 31 based on the concentration of the reducing agent measured by the water quality monitor 16, and injects from the first oxidant injection system 11. Control the amount of oxidant injected. The second control device 34B is connected to the measuring instrument 10C, the valve 33, and the valve 35. The second control device 34B adjusts the opening and closing of the valve 33 based on the concentration of permanganic acid measured by the measuring instrument 10C, and controls the inflow amount of the oxidant injected from the second oxidant injection system 12. . The second controller 34B adjusts the opening and closing of the valve 35 based on the concentration of permanganic acid measured by the measuring instrument 10C, and controls the injection amount of the reducing agent injected from the reducing agent injection system 13.

  Next, a method for treating the chemical decontamination liquid using the chemical decontamination liquid processing apparatus 1B of the present embodiment will be described.

  After completion of the reduction decontamination step, processing of the reduction decontamination solution is started. The processing procedure of the reductive decontamination solution of this example is a processing procedure in which the second organic acid decomposition step S2 and the oxidant decomposition step S3 of Example 1 are replaced with the second organic acid decomposition step S2b and the oxidant decomposition step S3b. It is.

  First, the valve 3 in the processing apparatus 1B is opened, the valve 20 is closed, and the chemical decontamination solution is distributed to the processing apparatus 1B.

  In the first organic acid decomposition step S1, as in Example 1, oxalic acid contained in the reductive decontamination liquid after chemical decontamination is decomposed into carbon dioxide and water. In the processing apparatus 1B, hydrogen peroxide is injected from the first oxidant injection system 11 based on the measurement result of the oxalic acid concentration in the water quality monitor 16, and about 90% of the oxalic acid is decomposed in the decomposition apparatus 4. . Chemical decontamination containing undegraded oxalic acid is sent to the second organic acid decomposition step.

  The second organic acid decomposing step S2b is a step of decomposing the undecomposed organic acid contained in the chemical decontamination solution that has passed through the first organic acid decomposing step S1 to a concentration that allows drainage. The second oxidant injection system 12 injects permanganic acid into the liquid passing pipe 2 through which the chemical decontamination liquid discharged from the decomposition apparatus 4 passes. The injection amount of permanganic acid supplied from the second oxidant injection system 12 is based on the design value of the decomposition rate of oxalic acid in the decomposition apparatus 4 immediately after the treatment of the chemical decontamination liquid is started. Is set to a predetermined injection amount (for example, an injection amount of 1 to 1.2 times the chemical equivalent of the amount of oxalic acid contained in the chemical decontamination solution). In other words, the second control device 34B adjusts the opening and closing of the valve 33 and controls the injection amount of permanganic acid from the second oxidant injection system 12 so that the predetermined injection amount is obtained. The mixed liquid of chemical decontamination liquid and permanganic acid that has passed through the decomposition apparatus 4 is mixed in the mixer 5. The chemical decontamination solution that has passed through the mixer 5 is sent to the measuring device 10C. The measuring instrument 10C measures the absorbance at 525 nm and quantifies unreacted permanganic acid contained in the chemical decontamination solution. The measurement result measured by the measuring instrument 10C is sent to the second control device 34B. After the measurement of the permanganic acid is started by the measuring device 10C, the second control device 34B performs the injection from the second oxidant injection system 12 based on the oxalic acid concentration measured by the measuring device 10C. Set the amount of manganic acid. The amount of permanganic acid to be injected is not less than the chemical equivalent in order to sufficiently decompose undecomposed oxalic acid. For this reason, the oxidant can be detected by the measuring instrument 10C. However, excessive addition of the oxidant is not preferable because the processing load in the subsequent stage may increase. In the second organic acid decomposition step S2b, undecomposed oxalic acid is decomposed to a concentration that can be discharged.

  The oxidant decomposition step S3b is a step of decomposing the oxidant contained in the chemical decontamination liquid that has passed through the second organic acid decomposition step S2b. The chemical decontamination liquid that has passed through the measuring device 10C is sent to the mixer 6 together with hydrogen peroxide injected from the reducing agent injection system 13, and mixed. The amount of hydrogen peroxide injected from the reducing agent injection system 13 is more than the chemical equivalent of the reaction with permanganic acid, for example, 1 to 1.2 times, based on the permanganate determination result in the measuring device 10C. Set to That is, the second control device 34B adjusts the opening and closing of the valve 35 based on the quantitative result of permanganic acid measured by the measuring instrument 10C, and controls the injection amount of hydrogen peroxide injected from the reducing agent injection system 13. To do.

  The purification step S4 is a step of purifying the chemical decontamination liquid that has passed through the oxidant decomposition step S3. The chemical decontamination solution that has passed through the mixer 6 is sent to the filter 7. The filter 7 removes particulate matter contained in the chemical decontamination solution and decomposes unreacted hydrogen peroxide. The chemical decontamination liquid discharged from the filter 7 is sent to the mixed bed resin tower 8 to remove ions contained in the chemical decontamination liquid. The purified chemical decontamination solution is discharged or used as system water at a site to be decontaminated in another system.

  According to the chemical decontamination liquid processing method and the processing apparatus 1B of the present embodiment, oxalic acid that has not been decomposed by the decomposition apparatus 4 is reacted with an oxidizing agent (permanganic acid in this embodiment), and is unreacted. Since oxidizer (permanganic acid in this embodiment) is decomposed by reaction with a reducing agent (hydrogen peroxide in this embodiment), oxalic acid can be decomposed once through. The time required for the decomposition of the acid can be shortened.

  In this embodiment, when the chemical decontamination solution is passed through the first organic acid decomposition step once, the chemical decontamination solution discharged from the step is applied to the organic acid decomposition method employed in the first organic acid decomposition step. A corresponding amount of undegraded organic acid is included. In the second organic acid decomposition step, an oxidizing agent having a chemical equivalent or more is added to the undecomposed organic acid, and the organic acid is decomposed to a concentration capable of being discharged by a chemical reaction. The chemical decontamination liquid that has passed through the second organic acid decomposition step contains an unreacted oxidant. In the oxidant decomposition step, a reducing agent equal to or more than the reaction equivalent is added to the oxidant to remove the oxidant. Decompose. In this embodiment, the oxidizing agent added in the second organic acid decomposition step has a high reaction rate with the organic acid, and the reducing agent added in the oxidizing agent decomposition step has a high reaction rate with the oxidizing agent. The one in which the decomposition reaction is completed in a time equivalent to or less than the water passage time in the acid decomposition step S1 is selected. Thus, in the conventional method, it was necessary to circulate the chemical decontamination solution a plurality of times in order to decompose the organic acid to a concentration capable of being discharged, whereas in this embodiment, the chemical decontamination solution is circulated once. Since the organic acid can be decomposed in a time equivalent to that described above, the time required for the decomposition of the reducing decontaminating agent can be shortened.

  According to the chemical decontamination liquid processing method and processing apparatus 1B of the present embodiment, the second organic acid decomposition step S2b using permanganic acid is performed after the first organic acid decomposition step S1 using hydrogen peroxide. Therefore, as in Example 1, the amount of manganese ions can be reduced, and the amount of waste can be reduced. Further, in the present example, the first organic acid decomposition step S1 using hydrogen peroxide and the decomposition apparatus 4 is performed before the second organic acid decomposition step S2b. The time required for processing the dye solution can be shortened, and the one-through decomposition is possible.

  Furthermore, according to the chemical decontamination liquid processing method and the processing apparatus 1B of the present embodiment, the number of measuring instruments used in the processing apparatus can be reduced, and the apparatus can be rationalized.

  The present invention can be applied to treatment of a decontamination solution used for decontamination of piping and the like in nuclear facilities such as a boiling water nuclear plant, a pressurized water nuclear plant, and a nuclear fuel reprocessing plant.

1, 1A, 1B Chemical decontamination liquid treatment device 2 Fluid piping 4 Decomposition device 5, 6 Mixer 10, 10A, 10B, 10C Measuring instrument 11 First oxidant injection system 12 Second oxidant injection system 13, 27 Reducing agent injection system 26 Oxidant injection system 31, 33, 35 Valve 32 First controller 34, 34A, 34B Second controller 36, 36A Third controller

Claims (9)

A method for treating a chemical decontamination liquid, wherein the surface of a component constituting a nuclear power plant is chemically decontaminated using a decontamination liquid containing an organic acid, and the chemical decontamination liquid after the chemical decontamination is decomposed. ,
A first decomposition step for decomposing an organic acid contained in the chemical decontamination solution;
A second step of measuring an undecomposed organic acid in the first decomposing step, adding an oxidizing agent of a chemical equivalent or more to the undecomposed organic acid, and decomposing the organic acid contained in the chemical decontamination solution; And a concentration of an oxidizing agent contained in the chemical decontamination solution after the second decomposition step, a reducing agent having a chemical equivalent or more is added to the measured oxidizing agent, and the oxidizing agent A method for treating a chemical decontamination solution, comprising a third step of decomposing the composition.   The chemical decontamination solution according to claim 1, wherein the chemical decontamination liquid is decomposed by flowing once through in the order of the first decomposition step, the second decomposition step, and the third decomposition step. Processing method of decontamination liquid.   The method for treating a chemical decontamination solution according to claim 1 or 2, wherein the organic acid contained in the chemical decontamination solution is a dicarboxylic acid.   4. The oxidant added in the second step is any one or more of permanganic acid, permanganate, and ozone. The processing method of the chemical decontamination liquid as described.   The method for treating a chemical decontamination solution according to any one of claims 1 to 4, wherein the reducing agent added in the third step is hydrogen peroxide. A method for treating a chemical decontamination liquid, wherein the surface of a component constituting a nuclear power plant is chemically decontaminated using a decontamination liquid containing an organic acid, and the chemical decontamination liquid after the chemical decontamination is decomposed. ,
A first decomposition step for decomposing an organic acid contained in the chemical decontamination solution;
First, an oxidizing agent is added to the chemical decontamination solution after the first decomposing step to decompose the organic acid, and the concentration of the oxidizing agent and / or organic acid contained in the chemical decontamination solution thereafter is measured. Two steps;
A third reducing agent is added to the chemical decontamination solution after the second step to decompose the oxidizing agent, and the concentration of the oxidizing agent and / or the reducing agent contained in the subsequent chemical decontamination solution is measured. A method for treating a chemical decontamination solution, comprising a step. A method for treating a chemical decontamination liquid, wherein the surface of a component constituting a nuclear power plant is chemically decontaminated using a decontamination liquid containing an organic acid, and the chemical decontamination liquid after the chemical decontamination is decomposed. ,
A first decomposition step for decomposing an organic acid contained in the chemical decontamination solution;
A second step of adding an oxidant to the chemical decontamination solution after the first decomposition step to decompose the organic acid and measuring a concentration of the oxidant contained in the chemical decontamination solution thereafter;
A method for treating a chemical decontamination solution, comprising a third step of adding a reducing agent to the chemical decontamination solution after the second step to decompose the oxidizing agent.   The chemical decontamination solution according to claim 6 or 7, wherein the chemical decontamination solution is decomposed by flowing once through in the order of the first step, the second step, and the third step. Processing method of decontamination liquid. A chemical decontamination liquid processing apparatus that chemically decontaminates the surface of a component constituting a nuclear power plant using a decontamination liquid containing an organic acid, and decomposes the chemical decontamination liquid after the chemical decontamination. ,
A decomposition apparatus for decomposing an organic acid contained in the chemical decontamination solution;
A first measuring device for measuring a concentration of an organic acid and / or an oxidizing agent contained in the chemical decontamination liquid that has passed through the decomposition device;
An oxidant injection device for adding an oxidant to the chemical decontamination liquid that has passed through the decomposition device;
A solution mixing device for mixing the oxidant injected from the oxidant injection device and the chemical decontamination solution;
A second measuring device that measures the concentration of the oxidizing agent and / or reducing agent of the chemical decontamination solution that has passed through the solution mixing device;
A reducing agent injection device for adding a reducing agent to the chemical decontamination solution;
An apparatus for treating chemical decontamination liquid, comprising: a second solution mixing apparatus for mixing the reducing agent from the reducing agent injection apparatus and the chemical decontamination liquid.

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