JP2012093284A - Radioactive effluent treatment method and treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid corrosion of facility equipment by conveniently removing halogen-based ions from effluents containing halogen-based ions (compounds) such as effluents from scrubber treatment of off-gas generated by nuclear facilities.SOLUTION: An adsorbate and a radioactive effluent containing halogen-based ions are brought into contact for absorption of the halogen-based ions into the adsorbate to remove the halogen-based ions from the radioactive effluent. Then, the adsorbate is brought into contact with a solution containing carbonate ions to desorb and collect the halogen-based ions from the adsorbate.

Description

  The present invention relates to a method for treating radioactive liquid waste.

  Off-gas generated from nuclear facilities is usually treated with a scrubber or the like to prevent leakage of radionuclides to the environment. Processing waste liquid is generated by scrubber treatment. In addition to radioactive nuclides, scrubber treatment waste liquid is caused by off-gas etc. incinerated flammables and flame retardants (halogens such as fluorine, chlorine, bromine and iodine) May also be included. These halogens (system compounds) are generally present as ions in the treatment waste liquid.

  On the other hand, the treatment waste liquid is generally concentrated and reduced in volume to be used for cement solidification. However, when it contains halogen as described above, it is difficult to concentrate from the viewpoint of preventing corrosion of facility equipment. In addition, from the viewpoint of environmental standards and emission standards, it is difficult to concentrate waste liquids containing halogen.

  Therefore, when the radioactive liquid waste contains halogen as described above, it is necessary to remove the halogen from the liquid waste. On the other hand, in the general industry, in the waste liquid containing halogen, it is necessary to remove the halogen from the waste liquid.

  Patent Document 1 discloses the removal of halogens such as chlorine and bromine from waste liquid, after the waste liquid is spray-combusted, and then the generated combustion gas is subjected to a ferritization treatment to remove it. Has been. However, since this method is a treatment method for experimental waste liquid, a pre-treatment system for each waste liquid is required, and if a large amount of waste liquid is to be processed, the apparatus configuration becomes large and unrealistic.

  Patent Document 2 discloses a concentration in which fluorine-containing wastewater is desalted by electrodialysis, and this desalination treatment liquid is regenerated as make-up water to the source of fluorine-containing wastewater, and a hydrofluoric acid concentrate can be used. It has been disclosed to reduce to However, since such a method using electrodialysis is costly, there is a problem that the cost increases when a large amount of waste liquid is processed.

JP 2008-49225 A JP 2004-174439 A

  An object of the present invention is to easily remove halogen from waste liquid containing halogen (system compound), such as off-gas scrubber treatment waste liquid generated from a nuclear facility, and avoid corrosion of facility equipment.

  One aspect of the present invention is to contact a radioactive waste liquid containing a halogen ion with an adsorbing substance, adsorb the halogen ion to the adsorbing substance, and remove the halogen ion from the radioactive waste liquid. And a step of contacting an adsorbing substance with a solution containing carbonate ions, and separating and recovering the halogen-based ions from the adsorbing substance.

  According to the present invention, halogen ions can be easily removed from waste liquids containing halogen ions (halogen compounds), such as off-gas scrubber treatment waste liquid generated from nuclear facilities, and corrosion of facility equipment can be avoided. .

It is a schematic block diagram which shows the processing apparatus of the waste liquid of embodiment.

  Embodiments of a waste liquid treatment method and a treatment apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the radioactive waste liquid treatment apparatus of the present embodiment.
In the processing apparatus 10 shown in FIG. 1, a scrubber processing apparatus 11, an adsorption tank 12, and a concentration tank 13 are sequentially arranged from the waste liquid introduction side to the downstream side. Further, a carbonate ion-containing solution storage tank 14 and a pH adjustment chemical liquid tank 15 are arranged above the adsorption tank 12. Further, a solution recovery tank 16 is disposed below the adsorption tank 12.

  The scrubber treatment device 11 and the adsorption tank 12 are connected by a pipe 24, and the adsorption tank 12 and the concentration tank 13 are connected by a pipe 27. The carbonate ion-containing solution storage tank 14 and the adsorption tank 12 are connected by a pipe 25, and the solution recovery tank 16 and the adsorption tank 12 are connected by a pipe 26. Further, a pipe 28 is connected between the pH adjusting chemical solution tank 15 and the carbonate ion-containing solution storage tank 14. As a result, the processing apparatus 10 shown in FIG. 1 constitutes a batch type processing apparatus.

  The scrubber treatment device 11 is a method of collecting dust by passing exhaust gas in the stored water (reservoir type), a method of injecting pressurized water into the flow of exhaust gas (pressurized water type), and a cleaning liquid sprayed on a filling material such as plastic or porcelain. General methods such as a method of collecting exhaust gas in contact with the water film (packed layer type) and a method of contacting the exhaust gas by dispersing the cleaning liquid with a rotating body (rotary type) can be used.

  The adsorption tank 12, the concentration tank 13, the carbonate ion-containing solution storage tank 14, the pH adjustment chemical solution tank 15, and the solution recovery tank 16 are made of materials having excellent corrosion resistance such as stainless steel (SUS) and polytetrafluoroethylene. To do.

  The adsorbing tank 12 is filled with a predetermined adsorbing substance, preferably a hydrotalcite-like substance, Schwertmannite, ettringite, and monosulfate. It should be noted that the adsorbed substance needs to be packed densely in the adsorption tank 12 so that the effect can be obtained. However, by providing a partition plate or the like, only the lower part of the adsorption tank 12 is packed densely. You can also do it.

  However, the ratio of the adsorbed substance and the waste liquid in the adsorption tank 12 is preferably 1: 100 to 1: 1 by weight ratio. As a result, the adsorption efficiency of the halogen-based ions in the radioactive liquid waste by the adsorbent can be improved.

The hydrotalcite-like substance means a substance that contains a hydrotalcite structure in at least a part of the substance and functions as an adsorbing substance. The hydrotalcite is represented by, for example, the general formula [Mg ₃ Al (OH) ₈ ] 1 / 2CO ₃ ² · 2H ₂ O, and is an octahedron (brucite layer) centered on magnesium ions. Are two-dimensionally connected, and a layer in which a part of magnesium ions is replaced with aluminum ions is laminated to form a layered structure.

_Supermanite is represented by the general formula (Fe ₈ O ₈ (OH) _8-2x (SO ₄ ) _x ), and is particularly excellent in ion adsorptivity. Ettlingite is represented by a general formula of 3CaO.Al ₂ O ₃ .3CaSO ₄ .32H ₂ O, and has excellent adsorptivity for ions and the like. Monosulfate usually exists as a hydrate, is represented by the general formula 3CaO.Al ₂ O ₃ .CaSO ₄ .12H ₂ O, and has excellent adsorptivity for ions and the like.

  In addition, halogen ions in the present embodiment include halide ions (fluoride ions, chloride ions, bromide ions, etc.), halide ions, perhalogens in addition to so-called halogen ions such as fluorine ions, chlorine ions, bromine ions, and the like. It also contains acid ions, hypohalite ions and the like.

Next, a processing method using the processing apparatus shown in FIG. 1 will be described.
First, for example, off-gas generated from a nuclear facility or the like is introduced into the scrubber processing apparatus 11 through the pipe 21, and the cleaning liquid is introduced into the scrubber processing apparatus 11 through the pipe 22 and cleaned. As the cleaning liquid, water or the like, sodium hydroxide solution or the like can be used. The treated gas is released out of the system through the pipe 23.

  The processing waste liquid obtained through the cleaning in the scrubber processing apparatus 11 may contain volatile radionuclides. In addition, halides such as chlorine and bromine generated due to incineration of combustibles and flame retardants are included.

  The components as described above are ionized in the waste liquid, and chlorine and bromine generated due to incineration of combustibles and flame retardants are also present by dissociating chloride ions and bromide ions, respectively. Become.

  In addition, the scrubber processing apparatus 11 can be omitted, and the off-gas can be directly introduced into the adsorption tank 12, or can be provided in a separate pre-processing apparatus separated from the processing apparatus 10 of the present embodiment. . However, by incorporating the scrubber treatment device 11 in the treatment device 10, a circulation line is provided between the scrubber treatment device 11 and the adsorption tank 12, and the waste liquid from which the halogen-based ions have been removed by the adsorbent in the adsorption tank 12 is scrubber. The operation can be returned to the treatment apparatus and washed again, and the operation of returning the waste liquid to the adsorption tank 12 and bringing it into contact with the adsorbent can be repeated a plurality of times.

  Therefore, since the cleaning by the scrubber treatment device 11 and the adsorption operation by the adsorbing substance can be performed a plurality of times, the concentration of the halogen-based ions in the waste liquid can be reduced to a predetermined concentration and then concentrated. It becomes like this. As a result, the corrosion of facility equipment or the like can be avoided more effectively during the volume reduction process.

  Next, the waste liquid obtained in the scrubber treatment apparatus 11 is opened to the valve 31, transferred to the adsorption tank 12 through the pipe 24, and brought into contact with the adsorbed substance filled therein, whereby the halogen-based ions in the above-described waste liquid are obtained. To adsorb. The adsorption of the halogen ions is performed by ion exchange between an anion substance such as a hydrotalcite-like substance and an anion such as a hydroxide ion contained therein and a halogen ion.

  Next, the waste liquid is supplied into the concentration tank 13 through the pipe 27 with the valve 34 opened. At this time, since most of the halogen ions contained in the waste liquid are removed in the adsorption tank 12, the halogen liquid ions are hardly contained in the waste liquid transferred to the concentration tank 13. Therefore, even when the waste liquid is concentrated in the concentration tank 13, it is possible to prevent corrosion of the facility equipment, specifically, the concentration tank 13. Moreover, since the halogen-type ion is hardly contained in the waste liquid in the concentration tank 13, it is preferable also from the viewpoint of environmental standards and discharge standards.

  The waste liquid after the concentration treatment is transferred to the waste liquid treatment system through the pipe 29. The concentration operation in the concentration tank 13 is performed, for example, by heating the waste liquid and evaporating the solvent or the like.

  As described above, according to the present embodiment, the halogen-based ions in the waste liquid are adsorbed on the predetermined adsorbent and removed from the waste liquid. Therefore, for each processing system as described in the prior art, There is no need to prepare a pretreatment system and no complicated treatment such as electrodialysis is performed. Therefore, it is possible to remove halogen-based ions from the waste liquid very easily and inexpensively.

  In addition, Preferably, the pH value of a waste liquid shall be 6 or more. If the acidity of the waste liquid becomes too strong, the adsorbed material may be deteriorated, and the adsorption ability for halogen ions may be deteriorated. The upper limit of the pH value of the waste liquid is 10. If this is exceeded, the adsorbed material may be deteriorated.

  The concentration tank 13 can be omitted in the same manner as the scrubber processing apparatus 11, or can be incorporated in a separately provided post-processing apparatus.

  Although not specifically shown in FIG. 1, the transfer of the waste liquid from the scrubber processing apparatus 11 to the adsorption tank 12 and the transfer of the waste liquid from the adsorption tank 12 to the concentration tank 13 are performed using a predetermined pump (not shown).

  As described above, when a halogen ion is adsorbed to an adsorbing substance in the adsorbing tank 12, the amount of adsorption of the halogen ion of the adsorbing substance increases with time, and the adsorption of the halogen ion of the adsorbing substance is increased. Performance may be reduced. Therefore, in the present embodiment, the following operation is performed to regenerate the adsorbed material.

  First, the valve 31 and the valve 34 positioned at the front stage and the rear stage of the adsorption tank 12 are closed, the valve 32 and the valve 33 are opened, and the carbonate ion-containing solution is supplied into the adsorption tank 12 from the carbonate ion-containing solution storage tank 14. To do. As a result, the halogen-based ions adsorbed by the adsorbing substance are separated from the adsorbing substance and stored in the solution recovery tank 16 together with the supplied carbonate ion-containing solution. The solution containing the halogen ions stored in the solution recovery tank 16 is appropriately transferred to a halogen treatment system.

  The contact between the adsorbing substance and the carbonate ion-containing solution is preferably performed for several hours to several tens of hours.

  The solution recovery tank 16 is not an essential constituent element in the present embodiment, and can be omitted, and the solution containing the halogen ion can be directly transferred to the halogen treatment system.

  In addition, when the carbonate ion-containing solution is brought into contact with the adsorbent that has adsorbed the halogen ions, the halogen ions are separated from the adsorbent as described above, for example, in the adsorbent such as a hydrotalcite-like substance. Since ions have a higher adsorptivity than halogen ions, ion exchange between carbonate ions and halogen ions occurs, and as a result, halogen ions adsorbed on adsorbents such as hydrotalcite-like substances are released. It is.

  The higher the concentration of the carbonate ion-containing solution, the more effectively the halogen ions can be separated from the adsorbent. Specifically, the lower limit value of the concentration of the carbonate ion-containing solution is preferably 0.5 mol / L. If it is smaller than this, there may be a case where the halogen-based ions cannot be sufficiently separated from the adsorbent by the carbonate ion-containing solution. On the other hand, for the reasons described above, the upper limit of the concentration of the carbonate ion-containing solution is the saturated concentration. This saturation concentration depends on the type of solvent and the temperature of the solution.

  In addition, the solvent which comprises a carbonate ion containing solution employ | adopts water in consideration of melt | dissolution of a hydrosite. Examples of the solute that generates carbonate ions include sodium carbonate, potassium carbonate, rubidium carbonate, and cesium carbonate. By dissolving such a solute in the solvent, the solute becomes carbonate ions, and the carbonate ion-containing solution described above is obtained.

  Further, the contact of the solution containing carbonate ions with the adsorbent is preferably performed so that the amount of the carbonate ion-containing solution per 1 g of the adsorbent is 1 to 10 mL. If the concentration of the carbonate ion-containing solution is less than 1 mL, the halogen ions may not be sufficiently detached from the adsorbent by the carbonate ion-containing solution. On the other hand, when the concentration of the carbonate ion-containing solution exceeds 10 mL, it is no longer possible to improve the release of halogen ions from the adsorbent by the carbonate ion-containing solution, and the carbonate ion-containing solution to be used is wasted. It may happen.

  Furthermore, the carbonate ion-containing solution is preferably contacted with the adsorbing substance at 10 to 60 ° C. Thereby, the detachment of the halogen-based ions from the adsorbing substance can be performed more effectively and efficiently. This is based on the principle of separation of halogen ions from the adsorbent when the carbonate ion-containing solution is used.

  Moreover, it is preferable to perform the contact with the adsorbent of the solution containing carbonate ions at a pH of 7 or more and 12 or less. Thereby, the detachment of the halogen-based ions from the adsorbing substance can be performed more effectively and efficiently. This is also based on the principle of detachment of halogen ions from the adsorbent when the carbonate ion-containing solution is used.

  In addition, when the pH of the carbonate ion-containing solution stored in the carbonate ion-containing solution storage tank 14 is outside the above range, that is, when the carbonate ion-containing solution is acidic, a pH adjuster such as water is added from the pH adjusting chemical solution tank 15. Sodium oxide, potassium hydroxide, calcium hydroxide, or the like is supplied to the carbonate ion-containing solution storage tank 14 via the pipe 28.

  By performing the operation as described above, the halogen-based ions can be released from the adsorbing material and regenerated, so that the adsorbing material can be again used for the adsorption of the halogen-based ions.

  Moreover, it is preferable to heat-treat for several hours with respect to the adsorption substance after halogen ion detachment | leave, for example in the range of 400-500 degreeC which is the temperature which an adsorption substance does not deteriorate. In this case, since the carbonate ions adsorbed on the adsorbing material can be effectively removed, the adsorbing material can be regenerated more completely, and the adsorbing material is higher when it is again subjected to the adsorption of halogen-based ions. Reproducibility is exhibited, and the adsorption of halogen ions can be performed more effectively and efficiently.

Example 1
In this example, a solution (waste liquid) containing 5 mmol / L of fluoride ion, chloride ion, sulfate ion, and borate ion was passed through an adsorption tank filled with hydrotalcite, and the room temperature was 4 weeks. After placement, solid-liquid separation was performed, and the concentrations of fluoride ion, chloride ion, sulfate ion and borate ion in the liquid phase were measured. The ratio of hydrotalcite to solution was 1:10 by weight.

  As a result, it was found that the concentration decreased from the initial concentration of 5 mmol / L to 0.45 mmol / L, 0.45 mmol, 50.95 mmol / L, and 2.35 mmol / L, respectively. That is, it was found that the concentration of fluoride ions and chloride ions, which are corrosive substances, was reduced to about 0.08 times by the hydrotalcite.

(Example 2)
In Example 1, after fluoride ions and chloride ions were saturated and adsorbed on hydrotalcite, a 1 mol / L sodium carbonate solution (pH 11) was supplied at a rate of 4 ml per 1 g of hydrotalcite, Contact was made at 40 ° C. for 6 hours. As a result, it was found that when the amount of ions adsorbed on the hydrotalcite was 1, it was separated at a rate of about 0.7 for fluoride ions and about 0.99 for chloride ions.

(Example 3)
The hydrotalcite after releasing fluoride ions and chloride ions in Example 2 was heat-treated in the atmosphere at 500 ° C. for 3 hours, and then a solution containing chloride ions was obtained in the same manner as in Example 1. The solution was allowed to pass through and allowed to stand for 4 weeks, followed by solid-liquid separation, and the concentration of chloride ions in the liquid phase was measured.

  As a result, when the above heat treatment was performed, the amount of chloride ions adsorbed on hydrotalcite increased about 260 times. From this, it can be seen that the hydrotalcite can effectively remove the adsorbed carbonate ions by the heat treatment, and exhibits high regeneration ability.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Radioactive liquid processing apparatus 11 Scrubber processing apparatus 12 Adsorption tank 13 Concentration tank 14 Carbon ion containing solution storage layer 15 Chemical tank for pH adjustment 16 Solution recovery tank

Claims (13)

Contacting the radioactive waste liquid containing halogen-based ions with the adsorbing substance, adsorbing the halogen-based ions to the adsorbing substance, and removing the halogen-based ions from the radioactive waste liquid;
Contacting the adsorbent with a solution containing carbonate ions, separating the halogen-based ions from the adsorbent, and collecting;
A method for treating radioactive liquid waste, comprising:   The method for treating a radioactive liquid waste according to claim 1, further comprising a step of concentrating and reducing the volume of the radioactive liquid waste after removing the halogen-based ions.   The method for treating a radioactive liquid waste according to claim 1, further comprising a step of performing a heat treatment on the adsorbent after the halogen-based ions are released to regenerate the adsorbent.   The concentration method of the solution containing the said carbonate ion is 0.5 mol / L or more and a saturated concentration or less, The processing method of the radioactive waste liquid as described in any one of Claims 1-3 characterized by the above-mentioned.   The contact of the solution containing carbonate ions with the adsorbent is performed so that the amount of the solution containing carbonate ions per 1 g of the adsorbent is 1 to 10 ml. A method for treating a radioactive liquid waste according to any one of the above.   The method for treating a radioactive liquid waste according to any one of claims 1 to 5, wherein the solution containing the carbonate ion is brought into contact with the adsorbing substance at 10 to 60 ° C.   The method for treating a radioactive liquid waste according to any one of claims 1 to 6, wherein the solution containing the carbonate ion is brought into contact with the adsorbent at a pH of 7 or more and 12 or less.   The radioactive waste liquid according to any one of claims 1 to 7, wherein the adsorbing substance is at least one selected from the group consisting of a hydrotalcite-like substance, schwertmannite, ettringite, and monosulfate. Processing method.   The said radioactive waste liquid is a scrubber waste liquid, The processing method of the radioactive waste liquid as described in any one of Claims 1-8 characterized by the above-mentioned. An adsorbing tank for contacting the radioactive waste liquid containing halogen-based ions with the adsorbing substance, adsorbing the halogen-based ions to the adsorbing substance, and removing the halogen-based ions from the radioactive waste liquid;
A carbonate ion-containing solution storage tank for supplying and storing a solution containing carbonate ions for contacting the adsorbing substance in the adsorption tank, separating the halogen-based ions from the adsorbing substance, and collecting them;
An apparatus for treating radioactive liquid waste, comprising:   The apparatus for treating radioactive liquid waste according to claim 10, further comprising a concentration tank for concentrating and reducing the volume of the radioactive liquid waste after removing the halogen compound.   12. The radioactive waste liquid treatment apparatus according to claim 10, further comprising a scrubber treatment apparatus, wherein the radioactive waste liquid is a scrubber waste liquid.   The radioactive waste liquid according to any one of claims 10 to 12, wherein the adsorbing substance is at least one selected from the group consisting of a hydrotalcite-like substance, schwertmannite, ettringite, and monosulfate. Processing equipment.

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