JP6477160B2 - Method and apparatus for eluting spent ion exchange resin - Google Patents

Description

  The present invention relates to an elution method and apparatus for efficiently removing metal ions and cladding from a used ion exchange resin that adsorbs metal ions and is mixed with cladding (iron rust) containing iron oxide as a main component. In particular, the present invention is a technique for efficiently removing a radioactive substance from a used ion exchange resin containing a clad mainly composed of iron oxide while adsorbing the radioactive substance used in a nuclear power plant or the like. Useful.

  In nuclear power plants, the ion exchange resin used to purify the cooling water system containing radioactive materials by directly touching the fuel rods such as the reactor water purification system (CUW) and the fuel storage pool water purification system (FPC) Because it is adsorbed in large quantities, it is stored in a resin tank inside the power plant as radioactive waste with a high dose rate. At nuclear power plants, ion-exchange resins are also used to remove radioactive substances from primary cooling system equipment and piping contaminated with radioactive substances and the surfaces of metal parts of systems containing them by chemical cleaning. The spent ion exchange resin is also stored in the resin tank as high dose rate radioactive waste. Waste containing these radioactive substances is finally kneaded with a solidification aid such as cement and stabilized, and then buried.

  If the waste ion exchange resin can be disposed of by incineration, the volume of radioactive waste can be significantly reduced. In this case, the radioactive material is concentrated in the incineration ash, so that the incineration ash has a high dose. If the radioactive material can be completely removed from the waste ion exchange resin, it is possible to prevent the incineration ash from becoming a high dose, and the volume can be reduced by incineration. Various studies have been made.

  Conventionally, as a technique for removing a radioactive substance from a waste ion exchange resin, Patent Document 1 discloses that sulfuric acid is passed through an elution device filled with a waste resin to elute an ionic radioactive substance, and diffusion dialysis is performed from the eluent. A technique for separating radioactive materials and recycling sulfuric acid is disclosed. Patent Document 2 discloses a waste resin treatment method in which waste resin is immersed in an oxalic acid aqueous solution.

JP 2004-28697 A JP 2013-44588 A

The high-dose waste resin used in the reactor water purification system and the fuel storage pool water purification system adsorbs radioactive material ions and is mixed with clad mainly composed of iron oxide. Since the clad also contains a radioactive substance, it is necessary to remove the clad from the waste resin at the same time in order to completely remove the radioactive substance from the waste resin. The chemical form of the clad contained in the waste resin is mainly magnetite (Fe ₃ O ₄ ) and hematite (α-Fe ₂ O ₃ ).

As described in Patent Document 1, it is difficult to dissolve hardly-soluble hematite (α-Fe ₂ O ₃ ) in a method in which normal temperature sulfuric acid that has not been heated is passed through a waste resin. Since the clad cannot be removed from the resin, there is a problem that radioactive materials remain.
In Patent Document 2, it is said that metal ions adsorbed on the waste resin are eluted and removed by using an oxalic acid aqueous solution having a predetermined concentration or more. However, only the immersion treatment adsorbs on the waste resin. It is not possible to elute and remove metal ions below the equilibrium concentration.

  It is an object of the present invention to provide an elution method and apparatus for efficiently eluting and removing metal ions such as ionic radioactive substances adsorbed in a waste ion exchange resin to an extremely low level and dissolving and removing a clad. To do.

  In the Japanese Patent Application No. 2013-221321, the present inventors use an acid heated to a predetermined temperature to efficiently elute and remove ionic radioactive substances in the waste ion exchange resin and dissolve the cladding. A technology to remove was proposed. As a result of intensive studies to further improve this technique, the present inventors stir spent ion exchange resin in a heated acid eluent to dissolve and remove the clad from the adsorbed metal. Batch treatment to elute most of the ions, and then pass the unheated acid eluent through the used ion exchange resin to continuously remove the adsorbed metal ions to a very low level. It has been found that by performing the treatment in a single elution tank, metal ions and cladding can be efficiently removed from the used ion exchange resin with a compact apparatus.

  That is, the gist of the present invention is as follows.

[1] A powdered or granular used ion exchange resin adsorbed with metal ions and mixed with a clad composed mainly of iron oxide and an acid eluent are filled in an elution tank, and the used ion exchange resin and The acid eluent is stirred while warming in the elution tank to elute the metal ions from the spent ion exchange resin and dissolve the clad, and then the upward flow or A method for elution of a used ion exchange resin, comprising a step of passing an acid eluent in a downward flow.

[2] The used ion exchange resin elution method according to [1], wherein the acid eluent is heated to 60 ° C. or higher in the stirring step.

[3] The used ion exchange resin elution method according to [1] or [2], wherein in the stirring step, gas is introduced from the lower part of the elution tank and stirred.

[4] The method for eluting used ion exchange resins according to any one of [1] to [3], wherein the acid eluent is a sulfuric acid and / or oxalic acid solution.

[5] The method for eluting used ion exchange resins according to any one of [1] to [4], wherein the metal ion is Co-60.

[6] A powdered or granular used ion exchange resin adsorbed with metal ions and mixed with a clad composed mainly of iron oxide is brought into contact with an acid eluent to remove the metal ions from the used ion exchange resin. And an elution tank filled with the used ion exchange resin and acid eluent, and the used ion exchange resin and acid elution filled in the elution tank. A stirring means for stirring the liquid, a heating means for heating the acid eluent in the elution tank, and a liquid passing means for passing the acid eluent upward or downward through the elution tank. The used ion exchange resin and the acid eluent are stirred while being heated in the elution tank, and then the acid eluent is passed through the elution tank. Elution device.

[7] The used ion exchange resin elution apparatus according to [6], wherein the heating means is a means for heating the acid eluent so as to be 60 ° C. or higher.

[8] The used ion exchange resin elution apparatus according to [6] or [7], wherein the stirring means is means for introducing gas from the lower part of the elution tank and stirring the gas.

[9] The used ion exchange resin elution apparatus according to any one of [6] to [8], wherein the acid eluent is a sulfuric acid and / or oxalic acid solution.

[10] The used ion exchange resin elution apparatus according to any one of [6] to [9], wherein the metal ion is Co-60.

In the present invention, the used ion exchange resin is stirred in a heated acid eluent, so that the metal ions adsorbed on the used ion exchange resin are ion-exchanged with H ⁺ ions and most of them are eluted and removed. At the same time, the clad mainly composed of iron oxide such as hematite mixed in the used ion exchange resin can be efficiently dissolved and removed. In addition, by performing a continuous liquid passing treatment in which an acid eluent that has not been heated is passed after the stirring step, metal ions that could not be removed by the stirring step can be further eluted and removed to an extremely low level. . In addition, since the above-described stirring process and liquid passing process are performed in a single elution tank, the process can be efficiently performed with a compact apparatus without causing the problem of upsizing of the apparatus by performing two steps. It can be carried out.

  According to the present invention, the radioactive substance is efficiently removed from the used ion exchange resin including the clad (iron rust) mainly composed of iron oxide while adsorbing the ionic radioactive substance, and the radiation dose is extremely low. The waste ion exchange resin reduced to the level can be obtained, and the waste ion exchange resin after the treatment can be incinerated. Since the waste ion exchange resin after the treatment has the iron rust dissolved and removed, the iron rust does not remain in the incineration ash. Therefore, in the incineration treatment, for example, about 1/100 to 1/200 before the incineration treatment. A large volume reduction effect can be obtained.

It is a systematic diagram which shows an example of embodiment of the elution apparatus of the used ion exchange resin of this invention. It is a systematic diagram which shows an example of the apparatus which decontaminates a radioactive waste ion exchange resin according to this invention, and reproduces | regenerates and reuses the obtained acid waste liquid. It is a systematic diagram which shows the other example of the apparatus which decontaminates a radioactive waste ion exchange resin according to this invention, and reproduces | regenerates and reuses the obtained acid waste liquid.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system diagram showing an example of an embodiment of an elution apparatus for used ion exchange resin of the present invention.

In FIG. 1, reference numeral 1 denotes an elution tank, which is filled with a used ion exchange resin (hereinafter sometimes referred to as “waste ion exchange resin”) 10. Reference numeral 2 denotes a liquid-permeable (breathable) separation plate for preventing the waste ion exchange resin 10 from flowing out of the elution tank 1. Reference numeral 3 denotes a heater for heating the acid eluent 10 in the elution tank 1. 4 is an acid eluent storage tank, acid eluate of the acid eluent storage tank 4 is fed from the pipe 11 having a pump P and a valve V ₁ for elution tank 1, waste ion exchange resin eluting tank 1 10 acid eluent used in the process (acid waste liquid) is discharged from the pipe 12 having a valve V _2. 5 is an acid waste liquid storage tank for storing the discharged acid waste liquid. Reference numeral 13 denotes an introduction pipe for stirring air in the elution tank 1 and has a valve V ₃ . 14 is an exhaust pipe having a valve _{V 4.}

In order to treat the waste ion exchange resin according to the present invention, first, after the waste ion exchange resin 10 is filled in the elution tank 1, the valves V ₁ and V ₄ are opened, the valves V ₂ and V ₃ are closed, and the pump P Is operated to supply a predetermined amount of the acid eluent in the acid eluent storage tank 4 to the elution tank 1 from the pipe 11. At this time, the acid eluent may be preheated or at room temperature. Then, the pump P is stopped, the valve V ₁ is closed. Then, under warming by a heater 3, the air introduced from the bottom of the elution vessel 1 a valve V ₃ is opened, mixing the waste ion-exchange resin 10 and the acid eluate in the elution vessel 1 with stirring Gas (stirring Process).

After the waste ion exchange resin 10 and the acid eluent are stirred and mixed for a predetermined time, the valves V ₃ and V ₄ are closed to stop the introduction of air and the heater heating. Thereafter, the valve V ₂ is opened to discharge the acid eluent in the elution tank 1 from the pipe 12 to the acid waste liquid storage tank 5, and the valve V ₁ is opened and the pump P is operated to turn the acid eluent storage tank 4 from the pipe 11. The acid eluent contained therein is passed through the elution tank 1 in a downward flow (liquid passing step). After passing the acid eluent for a predetermined time, the valves V ₁ and V ₂ are closed, the pump P is stopped, the acid eluent is stopped, and the treatment of the waste ion exchange resin 10 is finished.

  By performing the agitation step, 90% or more of the metal ions adsorbed on the waste ion exchange resin 10 can be eluted and removed, and the cladding can also be dissolved and removed, but adsorbed on the waste ion exchange resin. The metal ions that are present can only be removed to the equilibrium concentration of the acid eluent in this stirring step. In the agitation step, after roughly removing most of the metal ions adsorbed on the waste ion exchange resin 10, the metal ion adsorbed on the waste ion exchange resin 10 is obtained by performing a liquid passing step. Elution can be eliminated to an extremely low level.

<Waste ion exchange resin>
The waste ion exchange resin to be treated according to the present invention adsorbs metal ions and is a clad containing iron oxide as a main component (herein, iron oxide as a main component contains 50 wt% or more of iron oxide in the clad). ) In the form of a powder (average particle size distribution determined by laser diffraction / scattering method, particle size at an integrated value of 50% is about 10 to 200 μm in the swollen state) or granular (diamond) Ion Ion Exchange Resin / Synthetic Adsorbent Manual [1] Revised 4th edition, Chapter III, Section 7 (4) “Used ion exchange resin with an average diameter of about 300 to 1180 μm (about 50 to 14 mesh)” Any cation exchange resin or anion exchange resin can be used as long as it adsorbs metal ions that elute as cations in contact with an acid eluent. It may be fat. In particular, the present invention touches direct fuel rods such as spent ion exchange resins (reactor water purification system (CUW), fuel storage pool water purification system (FPC)) in nuclear power plants, and purifies cooling water systems containing radioactive substances. Radioactive metal ions are removed from the acid waste solution in which the radioactive material is dissolved in acid from the used ion exchange resin, primary cooling system equipment and piping contaminated with radioactive material in nuclear power plants, and the surface of the metal members of the system including these. is suitable for ion exchange resin) of cobalt -60 (60 ^Co) and nickel -63 (63 ^Ni) waste ion exchange resin having adsorbed radioactive metal components such as the processing used to. In CUW and FPC, a powdered mixed resin of a cation exchange resin and an anion exchange resin is mainly applied, and it contains a fibrous filter aid made of cellulose or acrylic material to prevent an increase in the fluid flow differential pressure. Many. A waste ion exchange resin containing a fibrous filter aid is suitable because the pressure difference in the flow rate of the acid eluent in the present invention is less likely to increase. In addition, there is no restriction | limiting in particular in the adsorption amount of the radioactive substance of a waste ion exchange resin, and content of a clad.

<Acid eluent>
As the acid eluent, an aqueous solution of an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid, or an organic acid such as formic acid, acetic acid or oxalic acid can be used. These acids may be used singly or in combination of two or more. However, when stirring under heating at a temperature described later, sulfuric acid and / or Or it is preferable to use oxalic acid.

The acid concentration in the acid eluent has a suitable concentration depending on the acid used. For example, the sulfuric acid concentration is preferably 3 to 40% by weight, more preferably 5 to 30% by weight. The oxalic acid concentration is preferably 0.1 to 40% by weight, more preferably 1 to 20% by weight. When the acid concentration is lower than the above range, the dissolution efficiency of hematite (α-Fe ₂ O ₃ ), which is the main component of the cladding, is lowered. That is, the clad is present in a form mixed with or entering the waste ion exchange resin, the main component of which is hardly soluble hematite, and it is difficult to dissolve with a low concentration of acid. If the acid concentration in the eluent is high, the amount of hydrogen generated in the regeneration treatment of the acid waste liquid described later becomes excessive, and the electrodeposition efficiency decreases.

<Separation plate>
As described above, the ion exchange resin used in the reactor water purification system and the fuel storage pool water purification system is often a powdered resin having an average particle size in the swollen state of about 10 to 200 μm. When processing such a powdery resin, it is difficult to stop leakage of the ion exchange resin with a slit-like separation plate used in a normal ion exchange tower. For this reason, a porous plastic plate such as a plastic sintered plate can be suitably used as the separation plate 2. Such a separation plate 2 can also serve as a diffuser plate in gas stirring.

  Separation plate 2 must have acid resistance, heat resistance, and radiation resistance, and the materials thereof include radiation-resistant fluororesin (such as ETFE), high-density polyethylene, ultrahigh molecular weight polyethylene, and polypropylene. The resin material is mentioned. The separator plate 2 preferably has an average pore diameter of 1 to 20 μm and more preferably 2 to 10 μm from the viewpoint of preventing leakage of the powdery resin and preventing an excessive increase in the differential pressure during air diffusion.

  In FIG. 1, a separation plate 2 is provided in the lower part of the elution tank 1 in order to pass a downward flow in the liquid passing process. Is provided.

<Stirring step>
The amount of the acid eluent used in the stirring step is the natural sedimentation volume of the waste ion exchange resin 10 filled in the elution tank 1 (the mixture of the waste ion exchange resin and the eluent is set in a measuring cylinder and settled when left for 12 hours. 1.5 to 20 times the volume of the waste ion exchange resin, if the waste ion exchange resin contains foreign materials such as filter aids, etc. Is preferable, and the amount is more preferably 2 to 10 times. If the amount of the acid eluent in the stirring step is too small, metal ions may not be sufficiently eluted and the clad may not be dissolved sufficiently. Absent.

  In the present invention, the stirring in the stirring step is preferably performed by gas introduction by gas introduction. This is because trouble is likely to occur in mechanical stirring because the viscosity of the mixed slurry of the waste ion exchange resin 10 and the acid eluent when the waste ion exchange resin 10 is stirred and mixed with the acid eluent is high. Since the elution tank 1 has a high dose, it is necessary to reduce the maintenance as much as possible. From this viewpoint, gas agitation is preferable. The amount of gas for gas stirring is not limited so long as the waste ion exchange resin 10 and the acid eluent can be sufficiently stirred and mixed in the elution tank 1. Usually, the gas amount per minute (NL) is preferably 0.2 to 5 times the natural sedimentation volume (L-resin) of the waste ion exchange resin 10, although it varies depending on factors such as 0.5 to More preferably, it is doubled. That is, 0.2 to 5 NL / (min · LR) is preferable, and 0.5 to 2 NL / (min · LR) is more preferable.

  As described above, when the separation plate is a plastic porous plate, it can also function as a diffuser plate that diffuses gas into the elution tank.

  The heating temperature in the stirring step is preferably such that the acid eluent in the elution tank 1 is 60 ° C. or higher, particularly 70 to 120 ° C., particularly 80 to 100 ° C. If the heating temperature is too low, the cladding dissolution efficiency is poor. If the heating temperature is too high, water evaporation and acid volatilization become excessive, which is not preferable in terms of work.

  The treatment time of the stirring step is preferably about 0.5 to 24 hours, and particularly preferably about 2 to 12 hours. If the treatment time is too short, the metal ions may not be sufficiently eluted and the clad may not be dissolved. If the treatment time is too long, the effect corresponding to the elution cannot be obtained, and the treatment time becomes long.

  In the agitation process, a predetermined amount of acid eluent is supplied to an elution tank filled with waste ion exchange resin and stirred under heating under predetermined conditions, and then the acid eluent in the elution tank is once discharged. Then, it may be performed twice or more, such as supplying a predetermined amount of the acid eluent again and stirring under heating under predetermined conditions. In that case, the amount of acid eluent per one time and the stirring time are made smaller than the above-mentioned preferable conditions, and the total amount of acid eluent and the stirring time of a plurality of stirring steps should be the above-mentioned preferable conditions. It is preferable.

<Liquid passing process>
In the liquid passing step after the stirring step, the acid eluent passed through the elution tank 1 may be at room temperature (about 10 to 30 ° C.). By passing the acid eluent at room temperature in this way, deterioration of the cation exchange membrane can be prevented in the regeneration treatment of the acid waste liquid described later. That is, as will be described later, when the acid waste liquid discharged by the elution treatment of the waste ion exchange resin is regenerated using metal ion permeation through the cation exchange membrane, the cation exchange membrane is brought into contact with a high-temperature acid waste liquid. There is a problem that the exchange membrane is thermally deteriorated. For this reason, in Japanese Patent Application No. 2013-221321, the high-temperature acid waste liquid is cooled by a heat exchanger and then subjected to a regeneration treatment. In the present invention, in the liquid passing process, a normal temperature acid eluent is passed, By storing the high temperature acid waste liquid and the normal temperature acid waste liquid in the flow-through process in the acid waste liquid storage tank 5, the temperature of the acid waste liquid in the acid waste liquid storage tank 5 is 50 ° C. or less, preferably the cation exchange membrane does not deteriorate, preferably The temperature can be set to 40 ° C. or less, and a heat exchanger for cooling the acid waste liquid is not required or the cooling load can be reduced.

  The amount and time of the acid eluent to be passed in the liquid passing process are not particularly limited as long as the metal ions adsorbed on the waste ion exchange resin 10 can be sufficiently eluted and removed. For example, the liquid flow rate can be 5 to 20 times the natural sedimentation volume of the waste ion exchange resin 10 filled in the elution tank 1, but is not limited to this range.

When the acid elution liquid flow SV is too slow, the processing efficiency is poor, and when it is too fast, the elution efficiency is poor. Therefore, the acid elution liquid passage SV is 0.2 with respect to the natural sedimentation volume of the waste ion exchange resin 10 filled in the elution tank 1. ˜30 hr ⁻¹ is preferable, and ¹ to 10 hr ⁻¹ is more preferable.

  It should be noted that the acid eluent used in the stirring step and the liquid passing step, particularly the acid eluent used in the liquid passing step, has a metal ion concentration to be eluted and removed of 20 μg / L or less. It is preferable for efficiently eluting and removing the metal ions adsorbed on the metal.

<Decontamination / regeneration treatment of waste ion exchange resin>
The acid waste liquid containing the anode and the cathode, which is obtained in the above stirring step and the liquid passing step, elutes the metal ions adsorbed on the waste ion exchange resin and dissolves the clad mixed in the waste ion exchange resin. When introduced into the electrodeposition tank and energized between the anode and cathode of the electrodeposition tank, the cationic radioactive material in the acid waste liquid and the iron ions derived from the cladding are electrodeposited on the cathode and removed from the acid waste liquid. It is preferable to reuse the obtained treatment liquid as an acid eluent.

Hereinafter, referring to FIG. 2, an example of an apparatus for decontaminating radioactive waste ion exchange resin according to the present invention and regenerating and reusing the acid waste liquid obtained by decontamination treatment by electrodeposition treatment will be described. explain. In FIG. 2, members having the same functions as those in FIG. In FIG. 2, the valves V _{1 to} V ₄ are not shown.

  The apparatus of FIG. 2 includes an acid eluent storage tank 4 for storing an acid eluent, and an elution tank 1 which is a packed tower filled with a waste ion exchange resin 10 (a separation plate 2 is provided in the lower part of the elution tank 1). And a heater 3 is provided on the outer periphery.), An acid waste liquid storage tank 5 for storing the acid waste liquid discharged from the elution tank 1, and an electrodeposition in which the acid waste liquid from the acid waste liquid storage tank 5 is introduced. A tank 6 and a catholyte storage tank 7 for storing the catholyte supplied to the electrodeposition tank 6 are provided. The electrodeposition tank 6 has a structure in which an anode chamber 6A having an anode 6a and a cathode chamber 6B having a cathode 6b are separated by a cation exchange membrane 8, and the acid waste liquid is passed through the anode chamber 6A, and the catholyte Is passed through the cathode chamber 6B.

  The decontamination process of the waste ion exchange resin 10 in the elution tank 1 is performed in the above-described stirring process and liquid passing process, and the acid waste liquid discharged in the stirring process and the acid waste liquid discharged in the liquid passing process are acid waste liquid storage tanks. 5 is stored.

Acid waste liquid in the acid waste liquid tank 5 is introduced into the anode compartment 6A of the pump P _A through a pipe 15 through electrodeposition bath 6, the treated acid effluent electrodeposition is circulated to the acid eluent storage tank 4 via piping 16, Reused as acid eluent.
On the other hand, in the cathode chamber 6B of the electrodeposition tank 6, the catholyte catholyte storage tank 7 is introduced through the pipe 17 by the pump P _B, it is returned to the catholyte reservoir 7 via a pipe 18.
The acid eluent storage tank 1 is appropriately replenished with acid from the pipe 19, and the catholyte storage tank 7 is appropriately replenished with the catholyte from the pipe 20.

By supplying electricity to the anode 6a and the cathode 6b of the electrodeposition tank 6, radioactive metal ions in the acid waste liquid introduced from the acid waste liquid storage tank 5 into the anode chamber 6A of the electrodeposition tank 6 and iron ions derived from the clad are exchanged. It passes through the membrane 8 and moves to the cathode chamber 6B, where it is electrodeposited on the cathode 6b. The acid waste liquid treatment liquid from which radioactive metal ions and iron ions have been removed in the electrodeposition tank 6 is returned to the acid eluent storage tank 4 and recycled.
The catholyte in the cathode chamber 6 </ _b > _B is circulated between the catholyte storage tank 7 by the pump PB, and the reduced amount of the catholyte is added to the catholyte storage tank 7 for circulation and reuse.

  The catholyte is preferably a liquid having a pH of 1 to 9, particularly 2 to 8. When the pH of the catholyte is too low, re-dissolution of the electrodeposited metal occurs on the cathode, which may reduce the electrodeposition rate. On the other hand, when the pH of the catholyte is too high, metal hydroxide is likely to be generated as a suspended substance in the liquid. For this reason, when the pH of the catholyte is out of the above range, it is preferable to appropriately adjust the pH with an alkali or an acid.

  The catholyte preferably contains a ligand capable of forming a complex with a metal ion that has permeated the cation exchange membrane, and in order to make such a ligand exist, a complex that forms a complex with the metal ion. It is preferable to add an agent.

The complexing agent includes a dicarboxylic acid having two carboxyl groups in the molecule and a salt thereof (hereinafter sometimes referred to as “dicarboxylic acid (salt)”), and a tricarboxylic acid having three carboxyl groups in the molecule. Those selected from acids and salts thereof (hereinafter sometimes referred to as “tricarboxylic acid (salt)”) are preferred. These may use only 1 type and may mix and use 2 or more types. Dicarboxylic acids (salts) and tricarboxylic acids (salts) suppress the generation of suspended substances during electrodeposition due to their chelating effects, and have an excellent effect in improving the electrodeposition effect.
In contrast, a monocarboxylic acid having one carboxyl group in the molecule has a weak binding force with metal ions, and a suspended substance composed of a metal hydroxide is generated in the liquid. Problems such as not wearing. Further, when a carboxylic acid having four or more carboxyl groups in the molecule is used, there is a problem that the binding force with metal ions is too strong, the metal is retained in the liquid, and the electrodeposition rate is significantly reduced. .

  As the dicarboxylic acid (salt) and tricarboxylic acid (salt), those represented by the following formula (1) are particularly preferable in that suspended substances are hardly generated and electrodeposition proceeds rapidly. The dicarboxylic acid (salt) or tricarboxylic acid (salt) represented by the following formula (1) has 1 to 3 carbon atoms between the carboxyl groups in the molecule, and is derived from its shape. Thus, it is estimated that an appropriate binding force can be obtained with the metal ion.

^{_{M 1 OOC- (CHX 1) a}} - (NH) b - (CX 2 X 4) c -CX 3 X 5 -COOM 2
... (1)
(In the formula (1), X ¹ , X ² and X ³ each independently represent H or OH, X ⁴ and X ⁵ each independently represent H, OH or COOM ³ , M ¹ , M ² , M ³ each independently represent H, monovalent alkali metal or ammonium ion, and a, b, and c each independently represent an integer of 0 or 1. However, in Formula (1), X ⁴ and X ⁵ are simultaneously COOM ³ will never be reached.)

Suitable dicarboxylic acids in the present invention, for example, oxalic acid (ethanedioic acid, HOOC-COOH), malonic acid (propanedioic acid, _HOOC-CH 2 -COOH), succinic acid (butanedioic acid, HOOC-CH ₂ -CH ₂ -COOH), glutaric acid (pentanedioic _{acid, HOOC-CH 2 -CH 2 -CH} 2 -COOH), malic acid (2-hydroxybutanedioic _{acid, HOOC-CH 2 -CH (OH} ) -COOH) , Tartaric acid (2,3-dihydroxybutanedioic acid, HOOC—CH (OH) —CH (OH) —COOH), iminodiacetic acid (HOOC—CH ₂ —NH—CH ₂ —COOH), etc. Acid, succinic acid, malic acid, tartaric acid and iminodiacetic acid are particularly preferred. Examples of the tricarboxylic acid include citric acid (HOOC—CH ₂ —COH (COOH) —CH ₂ —COOH), 1,2,3-propanetricarboxylic acid, and citric acid is particularly preferable. In addition, examples of salts of these dicarboxylic acids and tricarboxylic acids include alkali metal salts such as sodium salts and potassium salts, and ammonium salts.

  When the acid waste liquid contains a plurality of types of metal ions, it is preferable that an ammonium salt coexists with a dicarboxylic acid (salt) and / or a tricarboxylic acid (salt). For example, when an acid waste solution containing Co and Fe is regenerated, if no ammonium salt is added, the electrodeposition rate of Co is usually higher than that of Fe, and the electrodeposition of Fe on the Co electrodeposition layer is performed. A layer is formed, but by adding an ammonium salt, the electrodeposition rates of Co and Fe become substantially equal, and Co and Fe are electrodeposited in an alloy form. When the electrodeposition rates of Co and Fe are different and electrodeposition is performed by separating the Co layer and the Fe layer, the electrodeposition tends to float or peel off due to the difference in the physical properties of Co and Fe, and continuous electrodeposition processing is performed. There is a risk that it will not be possible.

  Any ammonium salt may be used as long as it produces ammonium ions in the liquid. For example, ammonium chloride, ammonium sulfate, ammonium oxalate, and ammonium citrate are preferable. These ammonium salts may be used alone or in combination of two or more. In particular, when ammonium dicarboxylate such as ammonium oxalate or ammonium tricarboxylate such as ammonium citrate is used, the ammonium salt and the complexing agent of the present invention can be used, and suspension due to the chelating effect of dicarboxylic acid or tricarboxylic acid It is possible to obtain the effect of suppressing the generation of substances and the effect of adjusting the electrodeposition rate of Co and Fe with one agent.

  The concentration of the complexing agent in the catholyte is not particularly limited, but the complex in the catholyte introduced into the cathode chamber with respect to the total molar concentration of metal ions in the acid waste solution introduced into the anode chamber. The molar concentration of the agent is preferably 0.1 to 50 times, particularly preferably 0.5 to 10 times. As the catholyte, for example, the above-mentioned complexing agent is 0.01 to 20% by weight, preferably 0 An aqueous solution containing 1 to 5% by weight of pH 1 to 9, preferably pH 2 to 8 is used. If the amount of complexing agent in the catholyte is too small, the effect of inhibiting suspended substances due to the use of the complexing agent cannot be obtained sufficiently, and if too much, the chelating effect becomes too great and the electrodeposition rate Decreases.

  The complexing agent is oxidatively decomposed when it comes into contact with the anode of the electrodeposition tank, but the catholyte containing the complexing agent is in direct contact with the anode by separating the anode chamber and the cathode chamber by a cation exchange membrane. Therefore, the complexing agent is not oxidized and consumed wastefully. Therefore, in the present invention, the amount of complexing agent to be replenished in the catholyte may be small, and the amount of chemicals used can be reduced.

  When an ammonium salt is used, the ammonium salt is preferably used in an amount such that the concentration in the catholyte is 0.01 to 20% by weight, preferably 0.1 to 5% by weight. If the concentration of the ammonium salt is too low, the above effect due to the use of the ammonium salt cannot be sufficiently obtained, and if it is too high, the effect is not improved and the amount of chemicals used increases.

The electrodeposition conditions (current value, current density, temperature, etc.) are not particularly limited, but the current density is preferably 5 to 600 mA / cm ² with respect to the cathode area in terms of electrodeposition efficiency.

  In the apparatus of FIG. 2, the radioactive substance is highly concentrated by electrodepositing what becomes a metal cation upon dissolution, such as cobalt-60 and nickel-63 contained in the radioactive waste ion exchange resin. can do. On the other hand, it is possible to obtain a waste ion exchange resin whose radiation dose is reduced to an extremely low level, and the treated waste ion exchange resin can be incinerated. Then, the amount of waste can be reduced to a capacity of 1/100 to 1/200 by incinerating the waste ion exchange resin into incineration ash.

  In the apparatus of FIG. 2, the electrodeposition tank 6 is a closed system. However, since hydrogen gas is generated from the cathode, it is preferable to use an open system with the upper part opened. In addition, when replacing the cathode electrodeposited with metal, the replacement is easier if the upper part of the electrodeposition tank is open. In the electrodeposition tank 6, the acid waste liquid and the catholyte may be passed through the cation exchange membrane 8 in the opposite directions.

FIG. 3 is a system diagram showing an example of another embodiment of a decontamination / regeneration treatment apparatus for radioactive waste ion exchange resin.
The decontamination / regeneration treatment apparatus of FIG. 2 performs the permeation of the cation exchange membrane of metal ions and the electrodeposition of metal ions in one tank of the electrodeposition tank 6, but the decontamination / regeneration treatment apparatus of FIG. The electrodialysis tank 50 and the electrodeposition tank 60 are provided separately, the cation exchange membrane of metal ions is permeated in the electrodialysis tank 50, the electrodeposition of metal ions is performed in the electrodeposition tank 60, and a plurality of sheets This cation exchange membrane is provided in the electrodialysis tank 50 to improve the processing efficiency. Further, in the decontamination / regeneration processing apparatus of FIG. 3, a first acid eluent storage tank 30A and a second acid eluent storage tank 30B are provided as acid eluent storage tanks, and two acid eluent storage tanks are provided. And the acid waste liquid storage tank are alternately subjected to continuous processing so as to bear the function alternately.
In FIG. 3, members having the same functions as those in FIG.

  The decontamination treatment of the waste ion exchange resin 10 in the elution tank 1 is performed in the above-described stirring process and liquid passing process. As described below, the first acid eluent storage tank 30A and the second acid eluent storage tank 30B are separated. Switch over alternately and continue processing.

First, the acid eluent is filled into the first acid eluent reservoir 30A (the second acid eluent reservoir 30B is empty). Then, the valve V ₁₅ is opened, the pump P is operated, the pipe only of acid eluate amount necessary stirring step from the first acid eluate reservoir 30A 21,11A, supplies the elution vessel 1 through 11. After supplying a predetermined amount of acid eluent to the elution tank 1, the pump P is stopped, the valve V ₁₅ is closed, air is introduced from the pipe 13, and the heater 3 is heated to perform the above-described stirring step. Do. After completion of the stirring process, the valves V ₁₁ and V ₁₅ are opened, the pump P is operated, the acid waste liquid is discharged from the elution tank 1 through the pipes 12 and 12B to the second acid eluent storage tank 30B, and the first acid elution is performed. The acid eluent in the liquid storage tank 30A is passed through the elution tank 1 to perform a liquid passing process. When substantially the entire amount of the acid eluent in the first acid eluent storage tank 30A is discharged, the liquid passing process is terminated. However, a small amount of the acid eluent is left in the first acid eluent storage tank 30A so that the pump P does not engage with air.

After passing liquid step of upper respiratory, the valve _{V 18, V 14} open, the pump _{P A} is operated (together with the pump _P 2, _{P 3} also actuates, energizing the electrodialysis cell 50 and the electrodeposition tank 60.) , an acid waste liquid in the first acid eluate reservoir 30A piping 22 and 25, through the L ₁ feeds sent to electrodialysis cell 50, the pipe a liquid metal ion is removed by electrodialysis in the electrodialysis cell 50 L ₂ , 26 to return to the second acid eluent storage tank 30B. This step may be started after the above-described liquid passing step is completed, but in the liquid passing step using the acid eluent in the first acid eluent reservoir 30A, the acid eluent is added to the second acid eluent reservoir 30B. May accumulate in parallel with the above-described liquid passing process before the acid eluent in the first acid eluent storage tank 30A runs out.

After the acid waste solution in the second acid eluent storage tank 30B is regenerated for a predetermined time, the electrodialysis tank 50 and the electrodeposition tank 60 are de-energized, the valves V ₁₈ and V ₁₄ are closed, and the pumps P _A , P ₂ and P ₃ are stopped, and the regeneration process of the liquid in the second acid eluent storage tank 30B is completed. The regeneration time is set to a time until the metal ion concentration in the solution is reduced to such an extent that the acid waste solution can be reused as an acid eluent (as described above, this metal ion concentration is 20 μg / L or less). .
In the electrodeposition tank 60, metal is electrodeposited on the cathode 62A, but if the cathode chamber 62 is filled with the electrodeposition liquid when the energization of the electrodeposition tank 60 is stopped, the electrodeposit is dissolved. It is preferable to stop the energization after draining the liquid from the electrodeposition tank 60 (at least the cathode chamber 62 of the electrodeposition tank 60).

  Moreover, after completion | finish of the above-mentioned liquid passing process, the deionized ion exchange resin in the elution tank 1 is taken out, and an untreated waste ion exchange resin is filled. However, when the ion exchange resin in the elution tank 1 is not sufficiently decontaminated, the decontamination process using the acid eluent in the second acid eluent storage tank 30B is performed without replacing the ion exchange resin. You may go.

Thereafter, the regenerated acid eluent in the second acid eluent storage tank 30B is fed to the elution tank 1, and the stirring process and the liquid passing process are performed in the same manner as described above. It is fed to the liquid storage tank 30A, and the acid waste liquid in the first acid eluent storage tank 30A is regenerated by electrodeposition.
That is, the valve V ₁₇ is opened, the pump P is operated, and an amount of the acid eluent necessary for the stirring process is supplied from the second acid eluent storage tank 30B to the elution tank 1 through the pipes 22, 11B, and 11. After supplying a predetermined amount of the acid eluent elution tank 1, a pump P is stopped, the valve V ₁₇ is closed, and performs stirring step performs heating by the heater 3 with from the pipe 13 to introduce air. After completion of the stirring process, the valves V ₁₂ and V ₁₇ are opened, the pump P is operated, the acid waste liquid is discharged from the elution tank 1 to the first acid eluent storage tank 30A through the pipes 12 and 12A, and the second acid elution is performed. The acid eluent in the liquid storage tank 30B is passed through the elution tank 1 to perform a liquid passing process. When substantially the entire amount of the acid eluent in the second acid eluent storage tank 30B is discharged, the liquid passing process is terminated. However, a small amount of the acid eluent is left in the second acid eluent reservoir 30B so that the pump P does not engage with air.

After passing liquid step of upper respiratory, the valve _{V 16, V 13} open, the pump _{P A} is operated (together with the pump _P 2, _{P 3} also actuates, energizing the electrodialysis cell 50 and the electrodeposition tank 60.) , an acid waste liquid in the first acid eluate reservoir 30A piping 21 and 23, through the L ₁ feeds sent to electrodialysis cell 50, the pipe a liquid metal ion is removed by electrodialysis in the electrodialysis cell 50 L ₂ , 24, and returned to the first acid eluent storage tank 30A. This step may be started after the above-described liquid passing step is completed, but in the liquid passing step using the acid eluent in the second acid eluent storage tank 30B, the acid eluent stored in the first acid eluent storage tank 30A. May accumulate in parallel with the above-described liquid passing step before the acid eluent in the second acid eluent reservoir 30B runs out.

After the acid waste solution in the first acid eluent storage tank 30A is regenerated for a predetermined time, the electrodialysis tank 50 and the electrodeposition tank 60 are de-energized, the valves V ₁₆ and V ₁₃ are closed, and the pumps P _A , P ₂ and P ₃ are stopped, and the regeneration process of the liquid in the second acid eluent storage tank 30B is completed.

  At the end of the liquid passing step using the acid eluent in the first acid eluent reservoir 30A or the second acid eluent reservoir 30B, the eluent in each acid eluent reservoir and the eluent in the elution tank 1 are air or the like. The total amount of the acid waste liquid may be sent to the second acid eluent storage tank 30B or the first acid eluent storage tank 30A. By doing so, when the deionized ion exchange resin is replaced, the consumption of the acid eluent accompanying the resin discharge can be minimized.

  40 is a heat exchanger for cooling the acid waste liquid fed to the electrodialysis tank 50. In the present invention, the acid eluent at normal temperature is passed through after the stirring step with the heated acid eluent. Since the acid waste liquid temperature can be lowered by performing the liquid passing step, this heat exchanger is not necessarily required.

Next, the electrodialysis tank 50 will be described. In the electrodialysis tank 50, the bipolar membrane BP and the cation exchange membrane CM are alternately arranged between the anode 51A and the cathode 52A.
A bipolar film (first bipolar film) BP is disposed to face the anode 51A, and an anode chamber 51 is formed between the anode 51A and the first bipolar film BP.
A bipolar film BP (second bipolar film) BP is disposed opposite the cathode 52A, and a cathode chamber 52 is formed between the cathode 52A and the second bipolar film BP.

  A plurality of (three in FIG. 3) cations are provided at predetermined intervals between the first bipolar film BP that partitions the anode chamber 51 and the second bipolar film BP that partitions the cathode chamber 52. The exchange membrane CM is arranged, and the bipolar membrane (third bipolar membrane) BP is arranged at a further interval between the cation exchange membranes CM, whereby a liquid passage chamber is formed.

  The chamber on the anode 51A side of the cation exchange membrane CM is a deionization chamber 53 through which the acid waste liquid is passed, and the chamber on the cathode 52A side of the cation exchange membrane CM is a concentration chamber 54 through which the electrodeposition solution is passed. is there.

  The bipolar membrane BP is an ion exchange membrane having a structure in which a cation exchange membrane layer and an anion exchange membrane layer are laminated, and the anion exchange membrane layer is disposed on the anode 51A side and the cation exchange membrane layer is disposed on the cathode 52A side. Is done. Even if a voltage is applied, the bipolar membrane BP does not transmit cations or anions, and is energized by dissociating water into hydrogen ions and hydroxide ions in the bipolar membrane BP.

  For this reason, in the electrodialysis tank 50 of FIG. 3, when a voltage is applied between the anode 51A and the cathode 52A, the metal ions in the acid waste liquid flowing through the deionization chamber 53 permeate the cation exchange membrane CM. Then, it moves into the electrodeposition liquid flowing through the concentration chamber 54. Thereby, the metal ion in an acid waste liquid is removed. Although acid group anions (for example, sulfate ions and hydrogen sulfate ions) in the acid waste liquid are electrically attracted to the anode 51A side, the bipolar membrane BP does not permeate the acid ions, so that it remains in the acid waste liquid. The later liquid can be reused as an acid eluent.

In FIG. 3, the acid waste liquid introduced into the deionization chamber 53 of the electrodialysis tank 50 through the pipes L ₁ , L _1A , L _1B and the pipe L _1C has metal ions removed by electrodialysis in the electrodialysis tank 50. Then, it is returned to the first acid eluent storage tank 30A or the second acid eluent storage tank 30B via the pipes L _2A , L _2B , L _2C and the pipe L ₂ and reused.

On the other hand, the electrodeposition liquid from the electrodeposition solution storage tank 80 by a pump _{P 1,} pipe _{L 3} and the pipe _{L 3A,} L _3B, is introduced through the _{L 3C} to concentrating compartment 54 of the electrodialysis cell 50. Electrodeposition liquid containing metal ions that have permeated the cation exchange membrane CM from the deionization chamber 53 and moved to the concentration chamber 54 by electrodialysis in the electrodialysis tank 50 is connected to the pipes L _4A , L _4B , L _4C and the pipe L ₄ . After that, it is returned to the electrodeposition liquid storage tank 80. As described later, since the metal ions in the electrodeposition liquid storage tank 80 are removed in the electrodeposition tank 60, the electrodeposition liquid from which the metal ions have been removed is supplied to the electrodialysis tank 50. Is done.
As the electrodeposition liquid, the same one as the catholyte in FIG. 2 described above is used.

  An electrode solution containing an electrolyte is circulated in the anode chamber 51 and the cathode chamber 52 of the electrodialysis tank 50. It is necessary to select an electrolyte that does not cause oxidation at the anode 51A, reduction at the cathode 52A, or precipitation at the cathode 52A, and sulfuric acid or an alkali metal salt of sulfuric acid is preferable.

In Figure 3, electrodeposition tank common electrodeposition solution storage tank 70 is provided with anolyte 60, the electrode solution of the electrodeposition liquid storage tank 70 to the anode chamber 51 of the electrodialysis cell 50 through a pipe L ₅ by the pump P ₂ After the introduction, it is introduced into the cathode chamber 52 through the pipe L ₆ and returned to the electrodeposition liquid storage tank 70 through the pipe L _7, and the electrode liquid in the electrodeposition liquid storage tank 70 is supplied to the pipe L ₈ by the pump P _3. introduced into the anode chamber 61 of the electrodeposition tank 60 through, but to form a circulation passage for returning the through pipe L ₉ electrodeposition solution storage tank 70 is not intended to be limited to this embodiment, the electrodes An electrode solution storage tank may be provided for each chamber.

  In the electrodialysis tank 50 shown in FIG. 3, three cation exchange membranes CM are provided and three deionization chambers 53 are formed. However, the number of cation exchange membranes CM is not limited to three, and even two can be used. Four or more may be used. The larger the number of cation exchange membranes in the electrodialysis tank, the larger the cation exchange membrane area and the shorter the migration distance of metal ions and the faster the permeation rate of metal ions. The resistance of the entire tank increases, power consumption increases, and the temperature in the electrodialysis tank increases. If the temperature of the electrodialysis tank becomes 40 ° C. or higher, the ion exchange membrane, particularly the bipolar membrane BP may be deteriorated. Therefore, when the temperature of the electrodialysis tank tends to rise, the temperature in the electrodialysis tank is 40 ° C. or higher. It is preferable to cool the acid waste liquid, the electrodeposition liquid or the electrode liquid as necessary so as not to become.

  In FIG. 3, the acid waste liquid in the deionization chamber 53 and the electrodeposition liquid in the concentration chamber 54 are passed in the same direction, but they may be passed in opposite directions. Moreover, there is no restriction | limiting in particular also about the flowing direction of the electrode liquid of the anode chamber 51 and the cathode chamber 52. FIG.

  In addition, it is preferable to provide an appropriate spacer between the cation exchange membrane CM and the bipolar membrane BP of the electrodialysis tank 50 so that the membranes are in close contact with each other due to membrane deflection or the like and the flow path is not blocked. The shape of the spacer is not particularly limited as long as the flow path is secured, and any shape such as a net shape, a honeycomb shape, or a ball shape can be adopted. The material of the spacer is preferably selected according to the properties of the liquid to be passed, and when the acid waste liquid is treated, a material having acid resistance is selected.

Next, the electrodeposition tank 60 will be described.
As the electrodeposition tank, as shown in FIG. 3, a two-chamber electrodeposition tank 60 in which an anode chamber 61 in which an anode 61A is disposed and a cathode chamber 62 in which a cathode 62A is disposed is partitioned by a cation exchange membrane CM. Is preferably used. It electrodeposition solution which contains metal ions sent to the electrodialysis cell 50 color electrodeposition solution storage tank 80 is introduced to the cathode chamber 62 of the pipe L ₁₀ a through electrodeposition tank 60 by the pump P _4. By applying a voltage between the anode 61A and the cathode 62A of the electrodeposition tank 60, the metal ions in the electrodeposition liquid are deposited as metal on the cathode 62A and are electrodeposited and immobilized.

  As in the electrodialysis tank 50, an electrolyte solution that does not oxidize at the anode 61A is used as the anolyte in the electrodeposition tank 60. In FIG. 3, the anolyte in the electrodeposition tank 60 and the electrode liquid in the electrodialysis tank 50 are shared, but these may be separated.

  As in the electrodialysis tank 50, the flow direction of the anolyte in the anode chamber 61 and the flow direction of the electrodeposition liquid in the cathode chamber 62 may be the same as shown in FIG. May be.

  In the electrodialysis tank 50, the ion exchange membrane disposed between the cation exchange membranes does not transmit metal ions (if a membrane that allows metal ions to pass through is used, the ion exchange membrane passes through the cation exchange membrane and moves to the electrodeposition solution. Metal ions permeate through the membrane and return to the acid waste liquid) and do not permeate the acid group anion (when a membrane through which the acid group anion permeates is used, the acid group anion penetrates the membrane, It is a condition that the electrode solution is transferred to the electrodeposition solution or the electrode solution in the anode chamber, and the acid waste solution cannot be reused as the acid solution). From such a point, not only a bipolar membrane but also a hydrogen selective cation exchange membrane can be used. The hydrogen selective permeation type cation exchange membrane is a cation exchange membrane having a high hydrogen ion transport number (ratio in which the movement of hydrogen ions contributes to the current) and satisfies the above-mentioned required characteristics. As a hydrogen selective permeation type cation exchange membrane, AGC Engineering's Selemion CMF or the like can be adopted as a commercial product.

As shown in FIG. 3, by separately providing the electrodialysis tank and the electrodeposition tank, the metal ion dialysis speed in the electrodialysis tank and the metal ion electrodeposition speed in the electrodeposition tank are optimized. It is possible to set conditions such as current density.
The current density of the electrodialysis tank that performs dialysis of metal ions is 10 to 400 mA / mm with respect to the cathode area, regardless of whether a bipolar membrane or a hydrogen selective permeation cation exchange membrane is used. it is preferably cm ^2, and more preferably 20~200mA / cm ^2.
Moreover, it is preferable that it is 5-200 mA / cm < ² > with respect to a cathode area, and, as for the current density of an electrodeposition tank, it is more preferable that it is 10-150 mA / cm < ² >.

  In addition, as shown in FIG. 3, the electrodialysis tank and the electrodeposition tank are separately provided, so that the structure of the electrodeposition tank is simplified, and when the cathode deposited and deposited by the electrodeposition is replaced. Therefore, the replacement work can be easily performed without being hindered by complicated constituent members.

Hereinafter, the present invention will be described in more detail with reference to experimental examples instead of the examples. In the following, ⁶⁰ Co radiation dose was measured with a Ge semiconductor detector.

[Experimental Example 1]
<Preparation of simulated sample>
The following materials were mixed to prepare a sample simulating a used ⁶⁰ Co adsorption ion exchange resin.
<Simulation sample>
Fibrous filter aid: 38 g
⁶⁰ Co adsorption powdery cation exchange resin (average particle size 50 μm): 69 g
Powdered anion exchange resin (average particle size 48 μm): 50 g
Cladding (average particle size 1 μm, hematite / magnetite (weight ratio) = 7/3): 4.8 g

With respect to 5 g of this simulated sample, the ⁶⁰ Co radiation dose was measured and found to be 100 cps.

<Stirring step>
By stirring 8 g of a simulated sample 5 g in 400 mL of 5 wt% sulfuric acid aqueous solution heated to 90 ° C. (27 vol times of the simulated sample), the clad was dissolved and ⁶⁰ Co was eluted. After the stirring treatment, the radioactivity of the simulated sample was measured and found to be 5 cps.

<Liquid passing process>
Next, the simulated sample after the stirring treatment was packed in a small column having a diameter of 26 mm, and 200 mL of a 5 wt% sulfuric acid aqueous solution at room temperature (25 ° C.) was passed through at 1 mL / min (SV = 4 hr ⁻¹ ).
The ⁶⁰ Co radiation dose of the simulated sample after the liquid passing treatment was measured and found to be 0.03 cps.

<Result>
The results are summarized in Table 1. Decontamination factor (DF) is a ⁶⁰ Co radiation amount after treatment is a value obtained by dividing the ⁶⁰ Co radiation dose pretreatment (mock sample).

<Discussion>
From the above results, ⁶⁰ Co in the simulated sample reaches an equilibrium state only by the stirring process and cannot be reduced below the equilibrium adsorption amount, but then ⁶⁰ Co is highly removed by passing through the liquid passing process. It can be seen that a high decontamination factor (DF) can be achieved.

DESCRIPTION OF SYMBOLS 1 Elution tank 2 Separator plate 3 Heater 4 Acid eluent storage tank 5 Acid waste liquid storage tank 6 Electrodeposition tank 6A Anode chamber 6a Anode 6B Cathode chamber 6b Cathode 7 Catholyte storage tank 8 Cation exchange membrane 10 Waste ion exchange resin 50 Electrodialysis tank 51 Anode Chamber 51A Anode 52 Cathode Chamber 52A Cathode 53 Deionization Chamber 54 Concentration Chamber 60 Electrodeposition Tank 61 Anode Chamber 61A Anode 62 Cathode Chamber 62A Cathode 70 Electrode Liquid Storage Tank 80 Electrodeposition Liquid Storage CM Cation Exchange Membrane BP Bipolar Membrane

Claims (8)

A powder or granular used ion exchange resin adsorbing metal ions and mixed with a clad composed mainly of iron oxide and an acid eluent are filled in an elution tank, and the used ion exchange resin and acid eluent are filled. It is stirred while warming it eluant tank, together with eluting the metal ions from the spent ion-exchange resin, and stirred step of dissolving the cladding and subsequently acid eluent under countercurrent to the elution vessel A method for elution of a used ion exchange resin having a liquid passing step of passing the liquid ,
In the lower part of the elution tank, there is provided a liquid-permeable and breathable separation plate that prevents leakage of the used ion exchange resin and also serves as a diffuser plate in gas stirring,
In the stirring step, a gas is introduced from the lower part of the elution tank and stirred, and the used ion exchange resin is eluted.   The method of eluting used ion exchange resins according to claim 1, wherein in the stirring step, the acid eluent is heated so as to be 60 ° C or higher. The method for eluting used ion exchange resins according to claim 1 or 2 , wherein the acid eluent is a sulfuric acid and / or oxalic acid solution. The method for eluting spent ion exchange resin according to any one of claims 1 to 3 , wherein the metal ion is Co-60. A powdered or granular used ion exchange resin adsorbing metal ions and mixed with a clad composed mainly of iron oxide is brought into contact with an acid eluent to elute the metal ions from the used ion exchange resin. And an apparatus for dissolving and removing the clad,
An elution tank filled with the used ion exchange resin and an acid eluent;
A stirring means for stirring the used ion exchange resin and the acid eluent filled in the elution tank;
Heating means for heating the acid eluent in the elution tank;
The acid eluent eluant tank and a liquid passage means for passing fluid under countercurrent,
After stirring while warming it the spent ion exchange resin and acid eluent and the eluant vessel, acid eluate into the elution chamber is an elution apparatus of the used ion exchange resin liquid passage,
At the bottom of the elution tank, there is provided a liquid-permeable and breathable separation plate that prevents leakage of the used ion exchange resin and also serves as a diffuser plate in gas stirring,
The used ion exchange resin elution apparatus , wherein the stirring means is means for introducing gas from the lower part of the elution tank and stirring the gas . 6. The used ion exchange resin elution apparatus according to claim 5 , wherein the heating means is means for heating the acid eluent so as to be 60 ° C. or higher. 7. The spent ion exchange resin elution apparatus according to claim 5 , wherein the acid eluent is a sulfuric acid and / or oxalic acid solution. The used ion exchange resin elution apparatus according to any one of claims 5 to 7 , wherein the metal ion is Co-60.

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