JP5558028B2 - Ion exchange resin treatment method and treatment apparatus - Google Patents

Description

  The present invention relates to a technology for treating an ion exchange resin used for reactor water purification in a nuclear power plant, and in particular, a treatment method for an ion exchange resin employing a wet method in which the ion exchange resin is oxidatively decomposed in water and the treatment thereof. Relates to the device.

  One of the waste generated at nuclear power plants is used ion exchange resin. This ion exchange resin supplements various ions drifting in the reactor water as well as iron oxides representing the clad (solid matter), all of which have radioactivity upon irradiation with neutrons. For this reason, the ion exchange resin processing technology requires measures to prevent radioactive exhaust gas and waste liquid generated in the processing process from leaking outside.

  2. Description of the Related Art Conventionally, as a representative technique for treating ion exchange resins, one that oxidatively decomposes ion exchange resins by either a dry method or a wet method has been proposed. In the dry method, a larger amount of a gaseous oxidant (for example, air) used for oxidative decomposition than in the wet method is produced, and a processed powder is generated. Therefore, strict handling of waste gas and powder is required as compared with the wet method, and the ion exchange resin processing apparatus tends to be large and complicated.

  On the other hand, in the wet method, the required amount of oxidant is suppressed and the product produced by oxidative decomposition is confined in water. Therefore, it becomes easier to handle the waste than the dry method, and the ion exchange resin processing apparatus can be downsized and simplified. Conventionally, as an ion exchange resin treatment technique based on a wet method, an ion exchange resin is reacted with hydrogen peroxide in the presence of a catalyst at 300 ° C. or higher (see Patent Document 1). In addition, there has also been proposed a method in which an oxygen-containing gas is injected and supplied in the presence of a catalyst for oxidative decomposition (see Patent Document 2).

JP 2000-65986 A JP 59-128499 A

  In the treatment and disposal of radioactive waste, it is important to increase the volume reduction rate and reduce the cost for storage and disposal. In any conventional ion exchange resin processing technology based on the wet method, a catalyst is used, so the volume reduction effect is reduced by the capacity of the catalyst. For example, in the treatment method described in Patent Document 1, 0.02 g or more of iron sulfate is required as a catalyst per 1 g of resin.

  Further, in the conventional ion exchange resin processing technology, organic carbon (TOC: Total Organic Carbon) such as acetic acid generated by oxidative decomposition of the ion exchange resin remains in the oxidative decomposition treatment liquid. The radioactive substance in the treatment liquid can be separated and recovered through, for example, a coprecipitation reaction with iron hydroxide, and the coprecipitation reaction is inhibited by the TOC remaining in the treatment liquid.

  The present invention has been made in view of the above circumstances, and it is possible to decompose the ion exchange resin without using a catalyst and also to decompose TOC in the treatment liquid well, thereby improving the volume reduction rate and good separation of radioactive substances. It is an object of the present invention to provide a treatment method of an ion exchange resin and a treatment apparatus thereof that can be recovered.

In order to achieve the above-described object, in the ion exchange resin treatment method according to the present invention, in the ion exchange resin treatment method used for reactor water purification in a nuclear power plant, the ion exchange resin is mixed with water to perform ion exchange. Hydrogen peroxide is added to the ion exchange resin slurry without using a catalyst, and the ion exchange resin slurry is treated at a treatment temperature of 100 ° C. or more and 175 ° C. or less and a treatment pressure of a saturated water vapor pressure or more of water. It is characterized by heating under.

Further, in the ion exchange resin treatment apparatus according to the present invention, in the ion exchange resin treatment apparatus used for reactor water purification in a nuclear power plant, the mixture of the ion exchange resin and water is stored as an ion exchange resin slurry. A reaction vessel configured to be able to be heated at a processing temperature of 100 ° C. or higher and 175 ° C. or lower and a processing pressure equal to or higher than the saturated water vapor pressure of water by adding hydrogen peroxide to the ion exchange resin slurry without using a catalyst. It is characterized by that.

  According to the present invention, the ion exchange resin can be decomposed without using a catalyst, and the TOC in the treatment liquid can be decomposed well, so that the volume reduction rate can be improved and the radioactive substance can be separated and recovered.

Explanatory drawing of the decomposition reaction of an ion exchange resin. The figure which shows the temperature dependence of a hydrogen peroxide decomposition rate. The figure which shows the verification test result of the processing method of the ion exchange resin which concerns on this invention. The figure which shows 1st Embodiment of the processing apparatus of the ion exchange resin which concerns on this invention.

  DETAILED DESCRIPTION Embodiments of an ion exchange resin processing method and processing apparatus according to the present invention will be described with reference to the accompanying drawings.

  Ion exchange resins used for reactor water purification in nuclear power plants have a structure in which ion exchange groups are formed on a copolymer of styrene and divinylbenzene. Moreover, this ion exchange resin has a powder form (average particle diameter of 100 micrometers) and a granular form (average particle diameter of 600 micrometers).

  As shown in FIG. 1, the ion exchange resin processed based on the wet method includes a reaction process (A) in which an organic substance is eluted in a treatment liquid containing water and an oxidizing agent, and an organic substance eluted in the treatment liquid. Can be divided into a reaction process (B) in which is decomposed into carbon dioxide. The reaction process (A) proceeds more rapidly as the treatment temperature is higher, but the reaction process B is promoted by OH radicals using hydrogen peroxide as a generation source, and in addition to the treatment temperature, the hydrogen peroxide concentration is also increased. Affects the speed of progress.

  In the ion exchange resin treatment method of this embodiment, first, the ion exchange resin is mixed with water to form an ion exchange resin slurry, and hydrogen peroxide is added to the ion exchange resin slurry. The amount of hydrogen peroxide added is at least 1.15 times the minimum amount required for the total amount of ion exchange resin to generate and decompose carbon dioxide and water.

  Then, the mixture of the ion exchange resin slurry and hydrogen peroxide is heated at a treatment temperature of 100 ° C. to 175 ° C., preferably 140 ° C. to 175 ° C., and a pressure equal to or higher than the saturated vapor pressure of water.

  Hereinafter, the reason for setting this processing condition will be described.

  The ion exchange resin decomposes by reacting with hydrogen peroxide from the surface. Therefore, it is possible to know the correlation between the treatment temperature used in the oxidation treatment and the decomposition time until the oxidative decomposition is completed using the rate at which the ion exchange resin is decomposed (radius reduction rate).

  Here, “decomposition” of the ion exchange resin means that the radius of the ion exchange resin becomes half or less. Therefore, when the ion exchange resin is in a powder form (average particle size 100 μm), the radius is 50 μm or less, and when the ion exchange resin is granular (average particle size 600 μm), the radius is 300 μm or less. It is necessary to continue the oxidation treatment.

Table 1 shows the radius reduction rate of the ion exchange resin in the treatment liquid having a hydrogen peroxide concentration of 1.8 wt%. Table 2 shows the treatment temperature estimated from the radius reduction rate in Table 1 and the decomposition time of the ion exchange resin. Pressure conditions above the saturated water vapor pressure of water are used at any temperature.

  As shown in Table 2, when the processing temperature is 150 ° C., the powdered (average particle size 100 μm) ion exchange resin is decomposed in about 90 minutes, and the granular (average particle size 600 μm) ion exchange resin is 540 minutes to Decomposes in 570 minutes. When the treatment temperature is 200 ° C., the powdered ion exchange resin is decomposed in 30 minutes, and the granular ion exchange resin is decomposed in 150 to 180 minutes. That is, the higher the processing temperature, the faster the radius reduction rate of the ion exchange resin, and the time and cost required for decomposition can be reduced. However, considering the soundness of the ion exchange resin processing apparatus, it is preferable to suppress the processing temperature as much as possible.

  Based on such knowledge, first, the lower limit value of the treatment temperature used in the oxidation treatment of the ion exchange resin will be described.

  The time required for the granular ion exchange resin to decompose is a trial calculation of a processing temperature of 100 ° C. for 8 hours, 150 ° C. for 6 hours, 175 ° C. for 5 hours, and 200 ° C. for 4 hours. In addition, the time required until a powdery ion exchange resin is decomposed | disassembled is the trial calculation which will be less than 8 hours in the temperature range of 100 to 200 degreeC.

  Focusing only on the soundness of the ion exchange resin processing equipment, it is preferable that the processing temperature is low, but work can be done by completing the decomposition process of the ion exchange resin within 8 hours during the day (for example, 9:00 to 17:00). If attention is also paid to the fact that the burden on the user is reduced, the temperature used in the oxidation treatment of the ion exchange resin needs to be 100 ° C. or higher. In short, by setting the temperature used in the oxidation treatment of the ion exchange resin to 100 ° C., it is possible to reduce both the burden on the operator and maintain the soundness of the ion exchange resin treatment apparatus.

  Next, the upper limit value of the treatment temperature used in the oxidation treatment of the ion exchange resin will be described.

  FIG. 2 is a graph showing the temperature dependence of the oxygen production rate (hydrogen peroxide decomposition rate) due to the decomposition of hydrogen peroxide. This hydrogen peroxide decomposition rate is calculated using a well-known calculation formula, and is a calculation result when held at each temperature for 10 seconds. According to this calculation result, the decomposition rate of hydrogen peroxide increases as the temperature rises. For example, the decomposition rate of hydrogen peroxide of 15% or less at 175 ° C. or less is 30% or more at 200 ° C. or more.

  In general, when hydrogen peroxide is used as an oxidizing agent, it is preferable to adjust the hydrogen peroxide decomposition rate to be 15% or less in 10 seconds from the viewpoint of suppressing wasteful use of hydrogen peroxide. In order for the hydrogen peroxide decomposition rate to be 15% or less in 10 seconds, the treatment temperature of the oxidation treatment of the ion exchange resin needs to be 175 ° C. or less. This treatment temperature is the upper temperature limit in the oxidation treatment.

  However, considering that 15% of hydrogen peroxide is consumed for oxygen generation at 175 ° C., the amount of hydrogen peroxide added is the most necessary for the total amount of ion exchange resin to decompose by generating carbon dioxide and water. It is preferable to increase the amount by a small amount by 15% or more (1.15 times or more the necessary minimum amount).

  FIG. 3 is a diagram showing the results of a verification test of the ion exchange resin treatment method of the present embodiment. This demonstration test was conducted in order to confirm the correlation between the treatment temperature of the ion exchange resin and the decomposition rate of TOC.

<Test conditions>
Ion exchange resin slurry in which 16 g of ion exchange resin is mixed with 150 g of water (the ion exchange resin is a dry resin, and the weight ratio of the cation exchange resin to the anion exchange resin is 1) and the reactor water are floated. A mixed solution with iron oxide (5 wt% of the ion exchange resin) simulating the cladding was prepared.

  In addition, twice the amount of hydrogen peroxide necessary for the ion exchange resin to decompose into carbon dioxide was gradually and continuously supplied over 5 to 6 hours.

  And the processing temperature in the oxidative decomposition of the ion exchange resin is 100 ° C. and 140 ° C., and the processing pressure is 0.1 MPa in the case of 100 ° C. and 0.5 MPa in the case of 140 ° C. did.

<Test results>
As shown in FIG. 3, the ion exchange resin residue rate (see Formula 1) was 5% or less at 100 ° C. and 140 ° C. The residual ratio of TOC (see Formula 2) was 27% at 100 ° C. and 0.1% at 140 ° C. That is, it was shown that when the temperature used in the decomposition treatment of the ion exchange resin is 140 ° C. or higher, the TOC residue rate is significantly reduced as compared with the case of 100 ° C.
Residual rate of ion exchange resin (%) = (Wf−W _Fe ) / Wi × 100 (1)
Wf: Weight of all residues after participation treatment W _Fe : Weight of added iron oxide Wi: Weight of added ion exchange resin TOC remaining rate (%) = Cfc / Cic × 100 (2)
Cic: Carbon weight of ion exchange resin before oxidation treatment Cfc: TOC weight in treatment solution after oxidation treatment

  FIG. 4 is a diagram showing a first embodiment of the ion exchange resin processing apparatus according to the present invention.

  The ion exchange resin treatment apparatus 1 is an apparatus for decomposing used ion exchange resin by oxidation reaction using high-temperature and high-pressure water (water in a high-temperature and high-pressure state), and is used for the above-described ion-exchange resin treatment method. Used. The processing apparatus 1 includes a reaction vessel 3, a heater 4, a stirrer 5, a hydrogen peroxide tank 6, a hydrogen peroxide injection pipe 7, a pump 8, a heat exchanger 9, and a cooler 10 in a case 2 having a variable pressure. The gas extraction pipe 11, the gas-liquid separator 12, the expansion valve 13 and the measuring instrument 14 are stored.

  The reaction vessel 3 is configured such that the internal pressure changes in conjunction with the internal pressure adjustment of the case, and stores a mixture of ion exchange resin and water (ion exchange resin slurry). Moreover, this reaction container 3 is comprised so that attachment or detachment is possible.

  The heater 4 is provided so as to surround the reaction vessel 3 and is configured to be capable of being overheated so that the ion exchange resin slurry stored in the reaction vessel 3 has a required temperature (at least 100 ° C. to 175 ° C.). The stirrer 5 is immersed in the ion exchange resin slurry in the reaction vessel 3 to stir the ion exchange resin.

  The hydrogen peroxide tank 6 stores hydrogen peroxide, and the hydrogen peroxide injection pipe 7 draws the hydrogen peroxide from the hydrogen peroxide tank 6 and guides it to the reaction vessel 3.

  The pump 8 is for injecting hydrogen peroxide against the internal pressure of the reaction vessel 3 and has a function of adjusting the amount of hydrogen peroxide charged into the reaction vessel 3. That is, the pump 8 continuously inputs hydrogen peroxide into the reaction vessel 3 at a required input amount. Note that oxygen generated by the decomposition of hydrogen peroxide has a lower oxidizing power than OH radicals generated in the same manner. For this reason, it is preferable to adjust the injection flow rate of hydrogen peroxide so that the interaction between the OH radical and the ion exchange resin can be performed efficiently without the hydrogen peroxide being decomposed to oxygen.

  The heat exchanger 9 is provided on the outlet side of the hydrogen peroxide injection pipe 7 and cools the hydrogen peroxide before being injected into the reaction vessel 3.

  The cooler 10 separates and removes moisture from the product generated by the decomposition reaction of the ion exchange resin that proceeds in the reaction vessel 3, and guides the product from which water has been separated and removed to the gas extraction pipe 11. The gas-liquid separator 12 separates the product guided to the gas extraction pipe 11 into a gas component (such as carbon dioxide) and a liquid. The gas component passes through the expansion valve 13 and is decompressed to atmospheric pressure, and then becomes an outlet fluid.

  The measuring instrument 14 measures the composition, concentration, temperature, and pressure of the fluid that is a decomposition component of the ion exchange resin and becomes the outlet fluid. For example, the pump 8 uses the carbon monoxide concentration measured by the measuring instrument 14 as an index, and supplies hydrogen peroxide so that the interaction between the ion exchange resin and OH radicals derived from hydrogen peroxide can be performed efficiently. Adjust the amount.

  Next, the effect of the processing method of the ion exchange resin which concerns on this embodiment, and its processing apparatus is demonstrated.

  (1) In the method for treating an ion exchange resin, the ion exchange resin is mixed with water to form an ion exchange resin slurry, hydrogen peroxide is added to the ion exchange resin slurry, and the ion exchange resin slurry is heated to 100 ° C. Heating is performed at the above treatment temperature and under a treatment pressure equal to or higher than the saturated water vapor pressure of water. For this reason, the ion exchange resin can be decomposed without using a catalyst, and the TOC in the treatment liquid can be decomposed well, so that the volume reduction rate can be improved and the radioactive substance can be separated and recovered. In addition, since the temperature condition is relatively mild, it is possible to maintain the soundness of the ion exchange resin processing apparatus and to expect the ion exchange resin to be decomposed within 8 hours. Mitigation is also possible.

  (2) Since the treatment temperature is 100 ° C. to 175 ° C., wasteful use of hydrogen peroxide can be suppressed, and the effect of (1) is enhanced.

  (3) Since the processing temperature is 140 ° C. to 175 ° C., in addition to the effect of (2), the decomposition of TOC can be remarkably enhanced.

  (4) By setting the treatment pressure to a pressure equal to or higher than the saturated water pressure of water (for example, 0.1 MPa to 0.5 MPa), the effects (1) to (3) can be easily obtained.

  (5) The amount of hydrogen peroxide added is at least 1.15 times the minimum amount required for the total amount of ion exchange resin to generate and decompose carbon dioxide and water. For this reason, even with a reaction process in which hydrogen peroxide is decomposed into oxygen, the ion exchange resin can be satisfactorily oxidized and decomposed.

  (6) In the ion exchange resin treatment apparatus 1, a mixture of the ion exchange resin and water is stored as an ion exchange resin slurry, and the ion exchange resin slurry is treated at a treatment temperature of 100 ° C. or higher and a saturated water vapor pressure of water. A reaction vessel 3 configured to be heatable under the above processing pressure is provided. For this reason, the ion exchange resin can be decomposed without using a catalyst, and the TOC in the treatment liquid can be decomposed well, so that the volume reduction rate can be improved and the radioactive substance can be separated and recovered. In addition, since the temperature condition is relatively mild, it is possible to maintain the soundness of the ion exchange resin processing apparatus and to expect the ion exchange resin to be decomposed within 8 hours. Mitigation is also possible.

  (7) The processing apparatus 1 includes a stirrer 5 that stirs the ion exchange resin slurry stored in the reaction vessel 3. That is, hydrogen peroxide adheres sufficiently and efficiently to the surface of the ion exchange resin, dispersibility of the ion exchange resin in water is enhanced, and the heat treatment acts equally. For this reason, the effect of (6) is enhanced.

  (8) The processing apparatus 1 includes a measuring instrument 14 that measures the composition and concentration of the decomposition component, temperature, and pressure of the ion exchange resin slurry. For this reason, it is possible to automatically adjust the flow rate of hydrogen peroxide and the temperature and pressure which are conditions for the oxidation treatment of the ion exchange resin.

  (9) The processing apparatus 1 includes a case 2 configured to store the reaction vessel 3 and have a variable internal pressure, and is configured to change the internal pressure of the reaction vessel in conjunction with a change in the internal pressure of the case 2. For this reason, even if a radioactive substance leaks out of the reaction container 3, the dissipation of this radioactive substance into the environment is prevented. Further, through the internal pressure adjustment of the case 2, the internal pressure of the reaction vessel 3 that is an oxidation treatment condition of the ion exchange resin can be adjusted.

  (10) Since the reaction vessel 3 is configured to be detachable, the reaction vessel 3 can be easily cleaned, discarded and replaced.

  As mentioned above, although the processing method and the processing apparatus of the ion exchange resin which concern on this invention have been demonstrated based on one embodiment, about a specific structure, it is not restricted to this embodiment, In the claim Design changes and additions are allowed without departing from the spirit of the invention described.

  For example, since the decomposition component of ion exchange resin contains radioactive substances, this decomposition component is separated into a liquid component and a solid component, and the solid component is mixed with cement or glass to form a solidified body and added to the geological disposal it can.

  DESCRIPTION OF SYMBOLS 1 ... Processing apparatus of ion exchange resin, 2 ... Case, 3 ... Reaction container, 4 ... Heater, 5 ... Stirrer, 6 ... Hydrogen peroxide tank, 7 ... Hydrogen peroxide injection pipe, 8 ...... Pump, 9 ... Heat exchanger, 10 ... Cooler, 11 ... Gas extraction pipe, 12 ... Gas-liquid separator, 13 ... Expansion valve, 14 ... Measurement device.

Claims (9)

In the treatment method of ion exchange resin used for reactor water purification of nuclear power plant,
The ion exchange resin is mixed with water to form an ion exchange resin slurry,
Hydrogen peroxide is added to the ion exchange resin slurry without using a catalyst, and the ion exchange resin slurry is heated at a treatment temperature of 100 ° C. or more and 175 ° C. or less and a treatment pressure of a saturated water vapor pressure or more of water. A method for treating an ion-exchange resin. The treatment temperature is, 1 4 0 ° C. to processing method of the ion exchange resin according to claim 1, characterized in that a 175 ° C..   The method for treating an ion exchange resin according to claim 1 or 2, wherein the treatment pressure is 0.1 MPa to 0.5 MPa.   4. The hydrogen peroxide is added in an amount of 1.15 times or more of a minimum amount required for the total amount of ion exchange resin to generate and decompose carbon dioxide and water. The processing method of the ion-exchange resin of Claim 1.   The ion according to any one of claims 1 to 4, wherein a decomposition component of the ion exchange resin is separated into a liquid and a solid, and the solid is mixed with cement to form a solidified body. Treatment method for exchange resin. In the ion exchange resin treatment equipment used for reactor water purification in nuclear power plants,
A mixture of the ion exchange resin and water is stored as an ion exchange resin slurry , hydrogen peroxide is added to the ion exchange resin slurry without using a catalyst , and the water is saturated with water at a treatment temperature of 100 ° C. or more and 175 ° C. or less. An ion exchange resin processing apparatus comprising a reaction vessel configured to be heatable under a processing pressure equal to or higher than a pressure.   The processing apparatus of the ion exchange resin of Claim 6 provided with the stirrer which stirs the ion exchange resin slurry stored in the said reaction container.   The apparatus for treating an ion exchange resin according to claim 6 or 7, further comprising a measuring instrument for measuring a composition of a decomposition component of the ion exchange resin slurry or a concentration thereof.   7. A case in which the reaction vessel is stored and configured to be variable in internal pressure, and the internal pressure of the reaction vessel is configured to change in conjunction with a change in the internal pressure of the case. The processing apparatus of the ion exchange resin of any one of 8.

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