JP6049262B2 - Radioactive liquid processing equipment - Google Patents

Description

  The present invention relates to a radioactive liquid waste treatment apparatus that can be applied to the entire waste liquid treatment containing a high level of radioactive material.

Conventionally, urgent treatment is performed on contaminated water (radioactive waste liquid) in which high-level radioactive substances generated in nuclear power plants are dissolved (see, for example, Patent Document 1).
Specifically, it is a method of reducing the dose in the waste liquid by removing radioactive substances by adsorption or precipitation, and then further purifying by desalting. In this case, the purified treated water can be reused as fuel cooling water to suppress an increase in the total amount of high-level waste liquid.

  By the way, as a general processing flow of general radioactive waste liquid, first, the radioactive waste liquid is sent to the oil separation device, and after removing the oil, the cesium adsorption device uses an adsorbent such as zeolite to adsorb cesium, In the decontamination equipment, nuclides other than cesium are adsorbed and coagulated. In addition, when seawater is mixed with radioactive waste liquid, the chlorine is removed by reverse osmosis membrane (RO) treatment in the desalination unit, reused as cooling water through the treated water receiving tank, and the removed chlorine is The amount is reduced by evaporation.

Special table 2009-189798

However, the conventional waste liquid treatment method has the following problems.
That is, in each processing step described above, a large amount of secondary waste contaminated with radioactivity is generated. Specifically, waste adsorbent (zeolite or the like) that adsorbs radioactive substances in the cesium adsorption device, sludge concentrated by precipitation treatment, concentrated water separated by desalting treatment, and the like are generated. These secondary wastes are further processed appropriately and moved to the final disposal site. Until the final disposal method is determined, they are stored in a predetermined temporary storage site for a long time. May be required.

  On the other hand, seawater may be used as cooling water during emergency processing. In such a case, concentrated high-concentration chlorine is also contained in the secondary waste generated from the radioactive liquid waste. Therefore, since storage facilities for storing secondary waste for a long period of time are corroded by chlorine, it is required to remove as much chlorine as possible, and there is room for improvement in that respect.

  The present invention has been made in view of the above-mentioned problems, and by reducing the high concentration chlorine in the waste liquid evaporated and concentrated, the corrosion of the peripheral equipment of the secondary waste is prevented, and the secondary waste An object of the present invention is to provide a radioactive liquid waste treatment apparatus capable of long-term storage.

In order to achieve the above object, in the radioactive liquid waste treatment apparatus according to the present invention, an evaporative concentration part for evaporating and condensing a radioactive liquid waste containing chlorine ions, and a high concentration radioactive liquid waste concentrated by the evaporative concentration part, An electrolytic treatment unit that performs an electrolytic treatment so that gas and hypochlorite ions are generated, and a high-concentration radioactive liquid waste after the electrolytic treatment are contained in an acid-added state, and chlorine gas is released from the high-concentration radioactive liquid waste. A chlorine gas diffusing unit, and the evaporating and concentrating unit and the electrolytic processing unit are operated in a neutral state.

  In the present invention, in the evaporating and concentrating portion, it can be separated into concentrated water (high radiation, high salt concentration) and condensed water (low radiation, low salt concentration), and the condensed water is led to the outside as dischargeable water. After generating hydrogen gas and hypochlorite ions by electrolytic treatment of the high-concentration radioactive liquid waste generated from the evaporation and concentration section, the high-concentration radioactive liquid waste after the electrolytic treatment is added with acid in the chlorine gas diffusion section. By storing and dissipating chlorine gas from the high-concentration radioactive liquid waste, chlorine ions can be discharged out of the system as chlorine gas. As a result, the concentration of chlorine ions in the concentrated waste liquid (secondary waste) can be reduced, and it is possible to operate near neutrality except for the chlorine gas diffusion part. In addition to increasing the durability of materials due to corrosion in the equipment installed, it is possible to reduce the amount of expensive materials (metals) used in the equipment, enabling long-term storage of secondary waste, The overall processing cost can be reduced.

Moreover, in the radioactive waste liquid processing apparatus which concerns on this invention, the diffusion tower which has an air aeration mechanism and an off-gas discharge port may be provided in the chlorine gas diffusion part. Furthermore, the stripping tower may be operated at pH2 .

In this case, the pH of the stripping tower is adjusted to around 2, and the chlorine in the liquid moves into the gas phase so that the chlorine gas generated by this pH adjustment is in equilibrium with the chlorine concentration in the air coexisting in the tower. . Since the chlorine concentration in the air is 0, the chlorine gas actively moves into the gas phase until the equilibrium state is reached, thereby promoting the emission. By aeration of the stripping tower in this way, the pH of the stripping tower can be operated at around 2, and as the operating pH increases, the amount of acid added decreases, so the pH is adjusted to around 1 as described above. The amount of acid added to the stripping tower can be reduced as compared with the case of doing so.
Further, since the diffusion rate of chlorine gas is increased by aeration of the diffusion tower, the reaction time is shortened, and the apparatus can be simplified and downsized.

  Moreover, in the radioactive waste liquid processing apparatus which concerns on this invention, it is preferable to provide in the front | former stage part of the electrolytic cell which electrolyzes the Cl concentration adjustment part which adjusts the chloride ion density | concentration of high concentration radioactive waste liquid to 5000-6000 mg / L. .

  In this case, since almost all of the chloride ion (Cl-) concentration in the raw water can be converted into hypochlorite ion (ClO-) and dissipated, the chloride ion removal rate can be increased.

  According to the radioactive liquid waste processing apparatus of the present invention, it is possible to prevent corrosion of peripheral facilities of secondary waste by reducing high-concentration chlorine in the waste liquid evaporated and concentrated. Therefore, secondary waste can be stored for a long time.

It is a flowchart which shows typically the process of the radioactive waste liquid processing apparatus by the 1st Embodiment of this invention. It is a flowchart which shows typically the process of a dechlorination apparatus. It is a figure which shows the pH dependence of chlorine. It is a flowchart which shows typically the process of the dechlorination apparatus by 2nd Embodiment. It is a figure which shows a chlorine dissipation test result. It is a flowchart which shows typically the process of the dechlorination apparatus by 3rd Embodiment. It is a figure which shows the relationship between the chloride ion density | concentration and residual chlorine density | concentration in an electrolysis process.

  Hereinafter, a radioactive liquid waste processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention.

(First embodiment)
As shown in FIG. 1, the radioactive liquid waste treatment apparatus 1 according to the present embodiment includes a radioactive substance from a waste liquid containing a radioactive substance such as cesium or a cleaning liquid generated by washing contaminated soil containing a radioactive substance such as cesium. It is related with the method of isolate | separating and removing.

  That is, the radioactive liquid waste treatment apparatus 1 includes a plurality of (in this case, two stages) evaporative concentration apparatus 2 (2A, 2B) (evaporation concentration section) for sequentially evaporating and condensing the radioactive liquid waste W. In the process of becoming the concentrated waste liquid W2, the oil removal equipment 3, the filtration equipment 4, the first evaporative concentration apparatus 2A, and the second evaporative concentration apparatus 2B are connected and arranged in that order from the upstream side toward the downstream side. It has become. The radioactive liquid waste treatment apparatus 1 includes a condensed water lead-out path 21 that guides the first condensed water G1 generated from the first stage first evaporative concentration apparatus 2A to the outside of the radioactive liquid waste treatment apparatus 1, and a second stage second evaporative concentration apparatus. A condensed water reflux path 22 for introducing the second condensed water G2 generated from 2B (evaporating and concentrating apparatus other than the first evaporating and concentrating apparatus 2A) to the first evaporating and concentrating apparatus 2A. In addition, a dechlorination device 6 (dechlorination unit) is provided between the first evaporative concentration device 2A and the second evaporative concentration device 2B to reduce the chloride ion concentration in the concentrated waste liquid.

The oil removal equipment 3 has a general configuration in which oil and dust (floating suspension) are separated from the supplied radioactive waste liquid W and recovered and removed. Hereinafter, the separated oil and the like are simply referred to as “oil K”. That is, the oil K that has floated is removed, and water (the radioactive waste liquid W from which the oil K has been removed) is extracted from the tank bottom and sent to the filtration equipment 4. In addition, the oil component K separated and recovered here becomes a secondary waste containing a radioactive substance.
Specific examples of the oil removal equipment 3 include a CIP separator and a pressure levitation separator.

  The filtration equipment 4 can adopt, for example, a membrane separation type or a sand filtration type, and separates and removes sand and dust (garbage that cannot be removed by the oil removal equipment 3), and water (filtered radioactive waste liquid). W) is sent to the first evaporative concentration apparatus 2A. Note that the solid matter M (sand, dust, etc.) recovered by filtration becomes secondary waste containing radioactive substances.

The evaporative concentrator 2 (2A, 2B) can employ, for example, a vacuum vapor compression type, concentrates the radioactive waste liquid W, concentrates the concentrated water N (highly radioactive, high salt concentration) and condensed water G (low radioactive, low Salt concentration).
In the first evaporative concentration apparatus 2A arranged in the preceding stage, the first concentrated water N1 is sent to the second evaporative concentration apparatus 2B, and the first condensed water G1 passes through the condensed water outlet path 21 and is used as cooling water. Or they are released. On the other hand, in the second evaporative concentration apparatus 2B arranged in the subsequent stage, the second concentrated water N2 is extracted as the concentrated waste water, and the second condensed water G2 passes through the condensed water reflux path 22 as described above and is concentrated in the first evaporation. Returned to device 2A. The second condensed water G2 returned to the first evaporating and concentrating device 2A is mixed with the radioactive waste liquid W before concentration, and is again subjected to the concentrating step by the first evaporating and concentrating device 2A.

  The condensed water outlet 21 for extracting the first condensed water G1 generated by the first evaporative concentrator 2A includes a first conduit 23 that is reused as cooling water, and a second conduit 24 that is discharged as a surplus. , Have been branched. The second conduit 24 adsorbs radioactive material contained in the first condensed water G1 to reduce the radiation dose to a set discharge standard value or less (approximately 0.01 to 0.001 or less). Equipment 5 is provided.

  Adsorption equipment 5 adsorbs cesium and strontium, adsorbs residual cesium, strontium and other nuclides, reduces the radioactivity, adsorbs all ions, and generates secondary waste By using an ion exchange resin or the like that reduces the amount, the salt concentration and radiation dose in the first condensed water G1 can be reduced to the discharge water level with the minimum amount of secondary waste generated.

  As shown in FIG. 2, the dechlorination apparatus 6 removes chlorine ions from the high-concentration radioactive waste liquid W2 concentrated by the first evaporative concentration unit 2A that evaporates and condenses the radioactive waste liquid W containing chlorine ions. The dechlorination device 6 includes an electrolytic processing unit 61 that performs electrolytic processing on the high-concentration radioactive waste liquid concentrated by the first evaporative concentration device 2A so that hydrogen gas and hypochlorite ions (ClO-) are generated. The high-concentration radioactive waste liquid after the electrolytic treatment is accommodated with a pH adjusting agent (acid) added, and a chlorine gas-dissipating part 62 for dissipating chlorine gas from the high-concentration radioactive waste liquid and a silver chloride precipitate are generated and solidified. And a precipitation processing unit 63 that is removed as a phase.

  The electrolytic treatment unit 61 is provided with an electrolytic bath 64. The chlorine gas diffusion unit 62 is supplied with the waste liquid electrolyzed in the electrolytic bath 64 and the diffusion tower 65 to which the pH adjuster (acid) is added, and the chlorine gas diffused in the diffusion tower 65. And a chlorine recovery device 66 (chlorine recovery unit) for recovery.

  In the electrolytic treatment unit 61, the electrolytic cell 64 is operated while being in the liquid state (substantially neutral) of the raw water, and chloride ions (Cl−) in the solution are converted into hypochlorite ions (ClO−) by electrolytic reaction. To do. At this time, since ClO- accumulates in the liquid, only hydrogen gas is generated in the electrolytic cell 64. Hydrogen generated in the electrolytic cell 64 is diluted to a concentration below the explosion limit by mixing air and then diffused into the atmosphere.

In the chlorine gas dissipater 62, the solution after the electrolysis is introduced into stripping column 65, by lowering the pH by adding pH adjusting agents (acids, sulfuric acid or nitric acid), was converted to ClO- to Cl _2, in the gas phase To dissipate. In order to increase the removal rate of chlorine gas, it is preferable to adjust the liquid pH to around 1 as shown in FIG.
Chlorine ions (chlorine gas) generated in the stripping tower 65 are collected by being introduced into a chlorine recovery device 66 and are made harmless by being absorbed by an alkaline material such as sodium hydroxide (NaOH).
Further, the off-gas is diffused into the atmosphere, and the recovered liquid recovered by the chlorine recovery device 66 is discharged after performing a process for satisfying the discharge regulation value.

Next, the operation of the radioactive liquid waste treatment apparatus 1 will be specifically described based on the drawings.
As shown in FIG. 1, in the radioactive liquid waste treatment apparatus 1 of the present embodiment, the first concentrated water N1 (high radiation, high salt concentration) and the first condensed water G1 (low radiation, low concentration) in the first evaporative concentration apparatus 2A. Salt concentration), and only the first condensed water G1 generated from the first evaporating and concentrating device 2A passes through the condensed water deriving channel 21 and is discharged to the outside as the first evaporating and concentrating device. The first radioactive water N1 having a low radioactive concentration and a low salt concentration evaporated by 2A is introduced into the second evaporation concentrator 2B. Then, in the second evaporative concentration apparatus 2B, the treated second condensed water G2 is not led out to the outside, but is introduced into the first evaporative concentration apparatus 2A via the condensed water recirculation path 22, and again the first evaporative concentration apparatus 2B. The second concentrated water N2 treated with 2A and further evaporated and concentrated can be disposed of as a concentrated waste liquid (secondary waste).
As described above, in the radioactive liquid waste treatment apparatus 1, since it is possible to concentrate at a high salt concentration and a high radiation dose in the evaporation concentration treatment compared to the reverse osmosis membrane treatment, the evaporation concentration portions 2 </ b> A and 2 </ b> B in a plurality of stages (two stages). As a result, it is possible to reduce the amount of concentrated waste liquid (second concentrated water N2) that is finally generated with high radioactivity and high salt concentration, and to reduce the volume.

Further, by providing the two-stage evaporative concentration apparatus 2A, 2B, the concentration rate of the evaporative concentration process in the first evaporative concentration apparatus 2A can be suppressed, and the first condensation derived from the first evaporative concentration apparatus 2A. It is possible to prevent impurities mixed with radioactivity from being mixed into the water G1. For example, by suppressing the concentration rate by the first evaporative concentration apparatus 2A to about 10 times, the concentration of impurities contained in the droplets at the time of evaporation can be suppressed to about 10 times. It can be kept low.
If radioactivity is mixed in the first condensate G1 generated in the first evaporative concentrator 2A, the first condensate G1 has a low radioactivity and a low salt concentration. After that, it can be discharged out of the system as effluent water, and the amount of adsorbent used for reducing to a level that can be discharged at this time can be reduced.

Further, hydrogen gas and hypochlorite ions (ClO-) are generated by electrolytic treatment by the dechlorination device 6 with respect to the high concentration radioactive waste liquid generated from the first evaporative concentration device 2A, and then electrolyzed in the chlorine gas diffusion unit 62. By storing the high-concentration radioactive liquid waste after the treatment with acid added, and dissipating chlorine gas from the high-concentration radioactive liquid waste, chlorine ions (Cl-) can be discharged out of the system as chlorine gas.
As a result, the concentration of chlorine ions in the concentrated waste liquid (secondary waste) can be reduced, and the durability of the material due to corrosion can be increased in the equipment provided around the secondary waste, and it can be used in equipment. Therefore, it is possible to reduce the amount of expensive material (metal) to be used, so that the secondary waste can be stored for a long period of time, and the overall processing cost can be reduced.

Moreover, since only hydrogen gas is generated in the electrolytic cell 64, explosiveness can be reduced as compared with hydrogen and chlorine mixed gas.
Furthermore, since only the chlorine gas is diffused in the diffusion tower 65, the amount of gas introduced into the chlorine recovery device 66 is reduced, and the device can be downsized.

  In the radioactive waste liquid processing apparatus according to the first embodiment described above, corrosion of peripheral facilities of secondary waste can be prevented by reducing high concentration chlorine in the evaporated and concentrated waste liquid. Therefore, secondary waste can be stored for a long time.

  Next, another embodiment of the radioactive liquid waste treatment apparatus of the present invention will be described with reference to the accompanying drawings. The same reference numerals are used for members and parts that are the same as or similar to those of the first embodiment described above. The description is omitted, and a configuration different from the embodiment will be described.

(Second Embodiment)
As shown in FIG. 4, the radioactive liquid waste treatment apparatus 1 according to the second embodiment includes an air aeration system in the stripping tower 65 of the chlorine gas stripping unit 62 in the dechlorination apparatus 6 of the above-described first embodiment. It has a mixing part 67 (air aeration mechanism) and an off-gas discharge port 68. In this case, the pH of the stripping tower 65 is adjusted to around 2, and the chlorine in the liquid moves into the gas phase so that the chlorine gas generated by this pH adjustment is in equilibrium with the chlorine concentration in the air coexisting in the tower. To do. Since the chlorine concentration in the air is 0, the chlorine gas actively moves into the gas phase until the equilibrium state is reached, thereby promoting the emission.

  In the second embodiment, by aeration of the stripping tower 65 with air, the pH of the stripping tower 65 can be set to around 2. For example, the pH is set to around 1 in the first embodiment described above. Compared with the case where it adjusts, the quantity of the acid added to the stripping tower 65 can be reduced. This is because when the pH increases by 1, the amount of acid added becomes approximately 1/10.

  Moreover, as shown in FIG. 5, the diffusion rate of the chlorine gas equivalent to the said 1st Embodiment is obtained by aeration of the diffusion tower 65. FIG. For example, in FIG. 5, when comparing the first case R1 with a pH of 1 and no aeration, and the fourth case R4 with a pH of 2 and aeration, the processing time until the residual chlorine concentration (mg / l) becomes 0 is obtained. (Min) is 10 minutes in the fourth case R4 and approximately 60 minutes in the first case R1. On the other hand, in the third case R3 having a pH of 2 and no aeration, the residual chlorine concentration is not 0 even after 60 minutes. From this, it is clear from the test results that even when PH is 2, the emission rate is increased by aeration. Since the reaction time is shortened by aeration in this way, the apparatus can be simplified and downsized.

(Third embodiment)
In the third embodiment shown in FIG. 6, in the dechlorination apparatus 6 of the first and second embodiments described above, after adjusting the chloride ion concentration of raw water to 5000 to 6000 mg / L, the electrolytic cell 64 To introduce. As shown in the test results of FIG. 7, the hypochlorite ion (ClO−) concentration generated in the electrolytic cell 64 is not limited to the chloride ion (Cl−) concentration of the raw water, and the residual chlorine concentration is 5000. This is because equilibrium is reached at ˜6000 mg / L. The adjustment of the chloride ion concentration is managed by appropriately changing the concentration rate in the first evaporative concentration apparatus 2A.
Further, in the present embodiment, a Cl concentration adjusting tank 69 (Cl concentration adjusting section) is provided at the front stage of the electrolytic cell 64, and the chloride ion concentration is adjusted by adding dilution water to the Cl concentration adjusting tank 69. It has become.
In this case, since almost all of the chloride ion (Cl-) concentration in the raw water can be converted into hypochlorite ion (ClO-) and dissipated, the chloride ion removal rate can be increased. For example, a removal rate of 90% or more can be expected.

As mentioned above, although embodiment of the radioactive waste liquid processing apparatus by this invention was described, this invention is not limited to said embodiment, In the range which does not deviate from the meaning, it can change suitably.
For example, in the present embodiment, the number of stages of the evaporation concentrators 2A and 2B is two, but the number is not limited to this number, and a configuration in which three or more stages are provided is also possible. In the case of providing three or more stages of the evaporative concentrator, the condensed water reflux path 22 of the second and subsequent stages of the evaporative concentrator 2 is connected to the first evaporative concentrator 2A in the foremost stage, You may make it return to 1A evaporative concentration apparatus 2A, and you may make it return the condensed water recirculation path 22 of the evaporative concentration apparatus 2 of the 2nd stage or later to the evaporative concentration apparatus of the 1st previous stage.

  Moreover, although the dechlorination apparatus 6 by 2nd-4th embodiment mentioned above is provided between the 1st stage | paragraph and the 2nd stage | paragraph evaporative concentration apparatus 2A, 2B, the position is not limited. . For example, in the case where three or more multi-stage evaporative concentration apparatuses 2 are provided, the dechlorination apparatus 6 can be disposed between, for example, the second and third evaporative concentration apparatuses.

  Furthermore, the evaporation concentrating device 2 is not limited to the vacuum vapor compression type, and may be a decompression type or a scooping type concentrating device.

  In the present embodiment, the dechlorination apparatus 6 includes a precipitation processing unit 63, but the precipitation processing unit 63 may be omitted.

  In addition, it is possible to appropriately replace the constituent elements in the above-described embodiments with well-known constituent elements without departing from the spirit of the present invention, and the above-described embodiments may be appropriately combined.

1 Radioactive waste liquid treatment device 2 Evaporation concentration device (evaporation concentration unit)
2A 1st evaporation concentration apparatus (evaporation concentration part)
2B 1st evaporation concentration apparatus (evaporation concentration part)
3 Oil removal equipment 4 Filtration equipment 5 Adsorption equipment 5A-5G 1st-7th adsorption system 6 Dechlorination equipment (dechlorination part)
DESCRIPTION OF SYMBOLS 21 Condensate derivation | leading-out path 22 Condensed water return path 23 1st water path 24 2nd water path 61 Electrolytic process part 62 Chlorine gas diffusion part 63 Precipitation process part 64 Electrolysis tank 65 Stripping tower 66 Chlorine collection | recovery apparatus 67 Air aeration mixing part (air Aeration mechanism)
68 Off-gas outlet 69 Cl concentration adjusting tank (Cl concentration adjusting section)

Claims (4)

An evaporating and condensing part for evaporating and condensing radioactive liquid waste containing chlorine ions;
An electrolytic treatment section that performs electrolytic treatment on the high-concentration radioactive liquid waste concentrated by the evaporation and concentration section so that hydrogen gas and hypochlorite ions are generated;
A high-concentration radioactive liquid waste after the electrolytic treatment is accommodated in an acid-added state, and a chlorine gas diffusion unit that diffuses chlorine gas from the high-concentration radioactive liquid waste
With
Of the evaporative concentration unit, the electrolytic treatment unit, and the chlorine gas diffusion unit, the components other than the chlorine gas diffusion unit are operated in a neutral state .   The radioactive waste liquid treatment apparatus according to claim 1, wherein a diffusion tower having an air aeration mechanism and an off-gas discharge port is provided in the chlorine gas diffusion portion. The radioactive waste liquid treatment apparatus according to claim 2 , wherein the stripping tower is operated at a pH of 2.   4. The apparatus according to claim 1, wherein a Cl concentration adjusting unit that adjusts a chloride ion concentration of the high-concentration radioactive liquid waste to 5000 to 6000 mg / L is provided in a front stage of an electrolytic cell for electrolytic treatment. The radioactive waste liquid processing apparatus as described in the paragraph.

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