JPS6340900A - Method of processing radioactive ion exchange resin - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for treating radioactive spent ion exchange resins generated in nuclear facilities.

[Conventional technology]

Research and development of various methods for processing radioactive used ion exchange resins is being carried out in various fields.

Typical tabulation methods and their drawbacks are as follows.

(1) Incineration method: This is a method of incinerating radioactive used ion exchange resin, but if the radioactivity level contained is high, maintenance of the furnace becomes difficult and excessive performance is required of the exhaust gas treatment equipment. There are drawbacks such as

(2) Pyrolysis method: This is a method in which the supply of oxygen is cut off and decomposition is performed at high temperatures, and then the decomposed gas is combusted. Compared to the incineration method, it generates a little more soot and dust, but it requires an extra pyrolysis plant. It is necessary and only slightly reduces the disadvantages of incineration.

(3) Chemical decomposition method: This is a method of oxidative decomposition through a chemical reaction with chemicals, and requires strict control and the use of expensive equipment materials because it handles strong oxidizers and radionuclides at high temperatures. There is.

(4) Direct solidification method: This is a method of surface solidification of radioactive ion-based resin with cement, asphalt, polymer, etc. However, since the ion exchange resin is an organic substance, consideration must be given to long-term storage of the solidified material. be.

[Problem that the invention seeks to solve]

The present invention mainly has the following points: (1) The surface radioactivity of the used resin, which has a relatively high radioactivity level, is reduced to facilitate incineration and chemical decomposition (2) The radionuclides are transferred to inorganic substances. The above-mentioned two points are intended to solve the above-mentioned problems by providing a disposal form that is characterized by long-term stability.

[Means for solving problems]

The present invention (1) In the method for treating radioactive ion exchange resin,
A process of eluting radionuclides from radioactive used ion exchange resin using an acid solution ■ A process of solidifying the resin from which the radionuclides have been eluted after inorganizing it by incineration or chemical decomposition ■ An eluent containing radionuclides is a process in which two iron ions and an alkali are added, stirred at 65 to 70°C, oxidized to produce ferrite particles, and radioactive nuclides are incorporated into the ferrite particles. Ferrite particles are removed from the liquid by magnetic separation or filtration. (2) A method for treating a radioactive ion exchange resin, which is characterized by comprising a step of separating the ferrite particles into an inorganic solidified body. The liquid from which the ferrite particles have been separated is solidified after evaporation and concentration or as it is. ,■
A process of eluting radionuclides from radioactive used ion exchange resin using an acid solution ■ A process of solidifying the resin from which the radionuclides have been eluted after inorganizing it by incineration or chemical decomposition ■ An eluent containing radionuclides K, Step of adding stable nuclides or radionuclides with short half-lives that are isotopes of the contained radionuclides ■ Further, divalent iron ions and alkali are added to this solution 6
After stirring at 5 to 70°C, oxidation is performed to generate ferrite particles, and the radioactive nuclide is incorporated into the ferrite particles together with the added nuclide. Ferrite particles are separated from the liquid by magnetic separation or filtration, and an inorganic solidified body (( (3) A method for treating a radioactive ion exchange resin, which comprises a step of solidifying the liquid from which the ferrite particles have been separated, either after evaporation and concentration or as it is;
A process in which radionuclides are contained in a radioactive used ion exchange resin using an acid solution ■ A process in which the resin from which the radionuclides have been eluted is mineralized by incineration or chemical decomposition, and then solidified ■ The acid solution containing the radionuclides is diffused treated with a dialysis membrane, and the acid solution separated by this treatment (g of the radionuclide)
On the other hand, divalent iron ions and alkali are added to the radionuclide-containing waste liquid obtained by separating the acid solution by treatment with a diffusion dialysis membrane, and the mixture is oxidized after stirring at 65 to 70°C. A process in which ferrite particles are generated and radionuclides are incorporated into the ferrite particles ■ A process in which the ferrite particles are separated from the liquid by magnetic separation or filtration to form an inorganic solidified body ■ The liquid from which the ferrite particles have been separated is solidified after M concentration or as it is (4) A method for treating a radioactive ion exchange resin, the method comprising:
A process in which radionuclides are eluted from radioactive used ion exchange resin using an acid solution ■ A process in which the resin from which radionuclides have been eluted is mineralized by incineration or chemical decomposition and then solidified ■ An acid solution containing radionuclides is The waste liquid containing radionuclides obtained by treating with a diffusion dialysis membrane and separating the acid solution. Adding a stable nuclide or a radionuclide with a short half-life, which is an isotope of the radionuclide contained in the liquid ■ Further, divalent iron ions and an alkali are added to this solution.
A process in which ferrite particles are produced by stirring at 5 to 70°C and then oxidized to incorporate radionuclides into the ferrite particles together with added nuclides ■ A process in which ferrite particles are separated from the liquid by magnetic separation or filtration to form an inorganic solidified body ■ This method of treating a radioactive ion exchange resin is characterized by comprising a step of solidifying the liquid from which the ferrite particles have been separated, either after evaporation and condensation or as it is.

The radioactive used ion exchange resin to be treated in the present invention is generated at nuclear power plants and the like. This ion exchange resin is, for example, one in which a quaternary ammonium group is added to a styrene/divinylbenzene-based polymer compound (anion exchange resin), or one in which a sulfonic acid group is added to the same polymer compound (cation exchange resin). ) etc. Specifically, for example, Mitsubishi Chemical Industries ■Cracked product name Diaion 5AN-1, 5UN-1.

There are 5KN-5, 5MN-1, 5MN-3, etc.

Spent ion-exchange resins generated at nuclear power plants are usually stored after being put into service, so the short half-life nuclides have decayed after long-term storage, so the main radionuclides they contain have long half-lives. Co-60, Cs-137, and Sr-90. Their half-lives are 5.3 years, 30.2 years, and 2a8 years, respectively.

This kind of used ion exchange resin is used to elute radionuclides with a solution. As the eluent, any of acid solutions, alkaline solutions, and neutral salt solutions can be used, but acid solutions are preferred from the viewpoint of radionuclide elution performance, and strong acid solutions are particularly preferred. Strong acids hydrochloric acid, nitric acid, fffl
There is no difference in elution performance between any of the acids, but sulfuric acid has the highest J when considering use within a nuclear power plant. If the acid concentration is too low, the radionuclides in the spent ion exchange resin cannot be eluted due to the selectivity coefficient between the acid in the ion exchange resin and the adsorbed radionuclide. Meet economically. Therefore, in the present invention, the N1 concentration is 1 to
It is good to set it as 5N (regulation), desirably 2-3N.

In addition, the larger the amount of acid solution passed through, the better the elution will be, but too much acid solution is not economical.

Therefore, in the present invention, when resin 1 is applied, 5X to 50xL (x
is preferably the specified concentration of acid).

For example, according to experimental results using 2N sulfuric acid, it was found that the liquid flow fi10. It has been confirmed that the decontamination coefficient is 10 or more for a (that is, 5x for X of 2 standards) and 101 or more for 100t.

Here, the decontamination coefficient is a value defined by (the amount of radioactivity possessed by the ion exchange resin before passing through the solution)/(the amount of radioactivity possessed by the ion exchange resin after passing through the solution).

The ion exchange resin from which radioactive nuclides have been eluted in this manner and has become a shell, so to speak, is turned into inorganic residue by ion exchange resin mineralization equipment such as incineration equipment or chemical decomposition equipment.

This inorganic residue is prepared for final disposal either as it is or as an inorganic solid.

The eluate that eluted radionuclides from the radioactive ion exchange resin is treated as follows.

(1) Divalent iron ions and an alkali are added to the eluent containing the radionuclide and stirred at 65 to 70°C, and then oxidized to generate ferrite particles and incorporate the radionuclide into the ferrite particles. (First invention) (2) A stable nuclide or a radionuclide with a short half-life, which is an isotope of the contained radionuclide, is added to the eluent containing the radionuclide, and then two strokes of iron ions and an alkali are added. addition 65
After stirring at ~70°C, it is oxidized to form ferrite particles and the radionuclides are incorporated into the ferrite particles together with the added nuclide. (Second invention) (3) The lta solution containing the radionuclides is treated with a diffusion dialysis membrane, and the acid solution separated by the treatment is used to elute the radionuclides from the radioactive ion exchange resin in the pretreatment step. In addition, 2 m of iron ions and alkali were added to the radionuclide-containing waste liquid obtained by separating the acid solution through the diffusion dialysis membrane, and the mixture was stirred at 65 to 70°C, and then oxidized to form ferrite particles. is generated and the radioactive nuclide is incorporated into the ferrite particles. (Third invention) (4) The eluate containing the radionuclide is treated with a diffusion dialysis membrane, and the acid solution separated by the treatment is reused to separate the radionuclide from the radioactive ion exchange resin in the pretreatment step. At the same time, a stable nuclide or a radionuclide with a short half-life that is an isotope of the contained radioactive waste liquid nuclide is added to the radionuclide-containing waste liquid obtained by treating it with the diffusion dialysis membrane and separating the acid solution, and then After divalent iron ions and alkali are added and stirred at 65 to 70°C, oxidation is performed to generate ferrite particles, and the radioactive nuclide is incorporated into the ferrite particles together with the added nuclide.

(Fourth Invention) The effects of adding divalent iron and alkali in the first to fourth inventions will be explained below.

When divalent iron and alkali are added and heated and stirred, the amount of divalent iron to be added is, for example, the following formula (1), +
As shown in 21, a certain amount or more is required depending on the amount of metal ions other than iron (excluding sodium, potassium, etc.), but too much is not economical or from the perspective of volume reduction. is also not a good idea. Therefore, in the present invention, the equivalent ratio is preferably 1 to 10 times, preferably 1.5 to 3 times, the amount of metal ions other than iron.

Also, the pH of the alkali is 10-12, preferably 115-12.
11.5 and more preferably in steps of about 11.

The heating temperature is preferably 60 to 75°C, preferably 65 to 70°C, and one hour is sufficient for stirring time.

It is then oxidized by aeration with air or oxygen. If it is not preferable to exhaust the air, it is preferable to use oxygen instead of air and use it for circulation. A mixed hydroxide of divalent iron and other metals is created by heating and stirring, and when this mixed hydroxide is oxidized by aeration, it is redissolved, and through the process of complex formation, it finally becomes ferrite particles. is generated.

For example, the reaction formula for divalent metal ion 1+ is as follows.

Formation of mixed hydroxide〉 f+ (S −Y )F”e” + 6 (OH)−M
yFe m−y (OH)s”・(1) Production of ferrite> MyFei−a(oH)′+3(ox→MyFes−,
o4+5 H2O... 12) In this way, the radionuclide, together with the added divalent iron, becomes MyF□ in formula (2).
It is incorporated into ferrite particles such as those shown by -704.

In the second and fourth inventions, the stable nuclide or the radionuclide with a short half-life, which is an isotope of the contained radionuclide, is, for example, Co-
59, if the radionuclide contained is (, +-157), it is C8-135, etc.

Furthermore, in the third and fourth inventions, the treatment of the eluent from which the radioactive ion exchange resin has been eluted with a diffusion dialysis membrane includes concentrating the radionuclide-containing waste liquid through a diffusion dialysis membrane such as a semipermeable membrane; Eluent containing almost no radionuclides (
This is to separate the acid solution).

Hereinafter, the present invention will be explained in detail with reference to Examples.

Embodiment 1 FIG. 1 is a flowchart showing an embodiment of the first method of the present invention.

A predetermined amount of used ion exchange resin 11 is received into elution chamber 1. After receiving the resin, an eluent (for example, an aqueous sulfuric acid solution) 13 is passed through the resin to elute the radioactive nuclide. Eluent 18 containing radionuclides is received in reaction tank 2 .

The ion exchange resin 12 from which radioactive nuclides have been eluted in this way and has been de-shelled is turned into an inorganic body 61 by an ion exchange resin mineralization equipment 6 such as an incineration equipment or a chemical decomposition equipment.

The eluent 14 sent to the reaction tank 2 contains u, as described above.
Divalent iron 21 in the form of ferrous ions, preferably ferrous sulfate, and an alkali, preferably caustic soda 22, are added while maintaining the pH and temperature ranges, and heated (heater not shown).
, stirring is performed using a stirrer 26.

Aerate with air 23 in the missing number. As mentioned above, if it is not desirable to exhaust air 24, oxygen may be used for circulation instead of air.

In reaction a2, a mixed hydroxide of divalent iron and other metals is first formed, and when this mixed hydroxide is oxidized by Uyo aeration, it redissolves as shown in the above formula (1) # t21 , through the process of complex formation, ferrite particles are finally generated, and together with divalent iron added with a radioactive nucleus, ferrite particles (as shown by MyFo 5-yO4 in formula (2)) are incorporated. .

The liquid 25 containing the ferrite particles is sent to the solid-liquid separator 3 and separated into liquid and ferrite particles.

Ferrite particles are ferromagnetic, so magnetic separation is effective, but filtration is also possible. It is also possible to incorporate the separation function of the solid-liquid separator 30 into the reaction tank 2.

The ferrite particles 31 containing radionuclides thus separated are sent to an inorganic solidification facility 4 such as a cement solidification facility, where they become a solidified body 42 and are ready for final disposal. Of course, instead of assimilation, it may be stored in a high integrity container (not shown).

On the other hand, 32 liquids from which radioactive nuclides have been removed are sent as they are or, if necessary, after neutralization and evaporation concentration, to an assimilation facility 5 such as a cement assimilation facility or an asphalt solidification facility, where they are solidified (41).
Prepare for final disposition.

Decontamination coefficient by removing radionuclides as ferrite from eluent 14 containing radionuclides (amount of radioactivity in eluent 14, /amount of radioactivity in liquid 32 after ferrite separation)
102 or more is obtained.

[Example 2] FIG. 2 is a flowchart showing an embodiment of the second method of the present invention.

Dissolve a predetermined amount of used ion exchange resin 11! , accepted at t11. After acceptance, an eluent (for example, an aqueous sulfuric acid solution) 15 is passed through the resin to elute the radioactive nuclide from the resin. Eluent 14 containing the radionuclide is received into reaction 12.

The ion exchange resin 12 from which radioactive nuclides have been eluted in this manner and has been de-shelled is turned into an inorganic body 61 by an ion exchange resin mineralization equipment 6 such as sale equipment or chemical decomposition equipment.

Stable nuclides or radionuclides with a short half-life 27 that are isotopes of the contained radionuclides are added to the eluent 14 sent to the reaction tank 2.
was added, and the treatment was then carried out in the same manner as in Example 1 in reaction tank 2.

The decontamination coefficient obtained by removing radionuclides from an eluent containing radionuclides by weiring them into ferrite particles can be obtained at 101 or higher even without the addition of radionuclide isotopes, but it is further improved by adding them. In other words, the concentration of each gold ion in the liquid 32 after ferrite separation remains constant regardless of the concentration of metal ions in the eluent 14. If added, the amount can be reduced by that amount. For example, if Co-60 originally exists in the eluent 14, the stable nuclide Co -59
If the total Co concentration is made to be 10 η/l by adding 10 η/l, the decontamination coefficient will increase by 102 to 2×10′ times.

[Embodiment 3] FIG. 5 is a flowchart showing an embodiment of the third method of the present invention.

A predetermined amount of used ion exchange resin 110 is received into elution tank 1. After acceptance, an eluent (for example, sulfuric acid aqueous solution 13) is passed through the resin to elute radionuclides from the resin.

The ion exchange resin 12, which has been stripped of its radioactive nuclides and has been de-shelled, is processed by an ion exchange resin mineralization equipment 6 such as an incineration equipment or a chemical decomposition equipment to remove the inorganic residue 61.
shall be.

On the other hand, most of the eluent (#) containing the radionuclide is recovered by a diffusion dialysis device 28 having a diffusion dialysis membrane A and reused for elution of the radionuclide.

The eluent (acid) is recovered by the diffusion dialysis device, and the waste acid containing most of the radionuclides with a low acid concentration (some of which is contained in the recovered acid solution) is sent to the reaction tank 2 and treated as follows. Processing is performed in the same manner as in Example 1.

This embodiment provides a decontamination coefficient of 103 or more.

[Example 4] A predetermined amount of used ion exchange resin 11 is received into elution tank 1. After acceptance, an eluent (acid solution) 13 is passed through to elute the radioactive nuclide.

The ion exchange resin 12 from which the radioactive nuclides have been eluted and whose shells have been removed is removed by an ion exchange resin mineralization membrane such as incineration equipment or chemical decomposition equipment, and the inorganic residue 6
1 = On the other hand, most of the eluent (acid) of the eluent 14 containing the radionuclide is recovered by the diffusion dialysis membrane #2B having the diffusion dialysis membrane A and reused for elution of the radionuclide.

The eluent was collected using a diffusion dialysis membrane, and the acid concentration was reduced.The waste containing most of the radionuclides (some of which were contained in the recovered acid solution) was then recovered. Add a stable isotopic nuclide or a radionuclide with a short half-life 27.For example, if the radionuclide contained is Co-60, Co-59, and if the radionuclide contained is Cs-157, add Cs-133. Add each.

The eluent (a) is recovered by the diffusion dialysis device 28, the acid concentration is reduced, and the waste acid is added with a stable nuclide or a radionuclide with a short half-life 27, which is an isotope of the contained radionuclide.
It is sent to reaction tank 2 and treated in the same manner as in Example 1.

This embodiment improves the recovery of the eluent and the decontamination coefficient.

〔Effect of the invention〕

(1) Since most of the radioactivity has been removed from the ion exchange resin supplied to the incineration equipment or chemical decomposition equipment, subsequent processing is facilitated.

In other words, maintenance of these facilities, treatment of exhaust gas,
It will be easier to handle the remaining balance.

(2) Radionuclides are incorporated into ferrite particles, so
Its separation is easy.

(3) Since the radionuclide is incorporated into the ferrite particles, it has excellent long-term stability whether it is used as it is or solidified.

(4) Adding isotopes improves the decontamination coefficient.

(5) Since the acid is recovered and reused, the amount of acid consumed and the amount of secondary waste generated are reduced.

[Brief explanation of drawings]

1 to 4 are flowcharts showing embodiments of the present invention. Sub-Agents 1) Meifuku Agent Ryo Hagiwara - Sub-Agent Atsuo Anzai Figure 3

Claims (4)

[Claims] (1) In the method for treating radioactive ion exchange resin, [1
] A step of eluting radioactive nuclides from a radioactive used ion exchange resin using an acid solution, [2] A step of solidifying the resin from which the radioactive nuclides have been eluted after being mineralized by incineration or chemical decomposition, [3 [4] Ferrite A process for separating particles from a liquid by magnetic separation or filtration to form an inorganic solidified body; [5] a process for solidifying the liquid from which the ferrite particles have been separated after evaporation and concentration or as it is; Method. (2) In the method for treating radioactive ion exchange resin, [1
] Step of eluting radionuclides from radioactive used ion exchange resin using an acid solution [2] Step of solidifying the resin from which radionuclides have been eluted after inorganizing it by incineration or chemical decomposition [3] Step of solidifying radionuclides Step of adding a stable nuclide or a radionuclide with a short half-life, which is an isotope of the contained radionuclide, to the eluent containing the contained radionuclide [4] Further, divalent iron ions and an alkali are added to this solution, and the mixture is heated at 65 to 70°C. After stirring, oxidation is performed to generate ferrite particles, and the radionuclide is incorporated into the ferrite particles together with the added nuclide [5] The ferrite particles are separated from the liquid by magnetic separation or filtration to form an inorganic solidified body [6] ] A method for treating a radioactive ion exchange resin, comprising a step of evaporating and concentrating the liquid from which ferrite particles have been separated or solidifying the liquid as it is. (3) In the method for treating radioactive ion exchange resin, [1
] Step of eluting radionuclides from radioactive used ion exchange resin using an acid solution. [2] Step of solidifying the resin after incineration or chemical decomposition of the resin from which radionuclides have been eluted. [3] Step of solidifying radionuclides. The containing acid solution is treated with a diffusion dialysis membrane,
The acid solution separated by this treatment is reused for elution of the radionuclide [4] On the other hand, the radionuclide-containing waste liquid obtained by separating the acid solution by treatment with a diffusion dialysis membrane contains divalent iron. Step of adding ions and alkali and stirring at 65 to 70°C, oxidizing to generate ferrite particles and incorporating radionuclides into the ferrite particles [5] Ferrite particles are separated from the liquid by magnetic separation or filtration to form an inorganic solid. Step [6] A method for treating a radioactive ion exchange resin, which comprises a step of solidifying the liquid from which the ferrite particles have been separated after evaporation and concentration or as it is. (4) In the method for treating radioactive ion exchange resin, [1
] Process of dissolving radionuclides from radioactive used ion exchange resin using an acid solution [2] Process of solidifying the resin after eluting radionuclides after inorganicizing it by incineration or chemical decomposition [3] Process of solidifying radionuclides The acid solution containing is treated with a diffusion dialysis membrane,
The acid solution separated by this treatment is reused for elution of the radionuclide [4] On the other hand, the radionuclide-containing waste liquid obtained by separating the acid solution by treatment with a diffusion dialysis membrane contains isotopes of the radionuclide contained in it. Step of adding stable nuclides or radionuclides with short half-lives [5] Further, divalent iron ions and alkali are added to this solution, stirred at 65 to 70°C, and then oxidized to produce ferrite particles. Step of incorporating radionuclides into ferrite particles together with added nuclides [6] Separating the ferrite particles from the liquid by magnetic separation or filtration to form an inorganic solidified body [7] The liquid from which the ferrite particles have been separated is evaporated and concentrated or as it is. 1. A method for treating radioactive ion exchange resin, comprising a step of solidifying it.