JPH10170694A - Method for disposing of radioactive waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for disposing of radioactive wastes, by which radioactive nuclides contained in a used ion-exchange resin and filter aid can be fully and easily separated at low cost. SOLUTION: A slurry 101 of an ion-exchange resin containing radioactive nuclides and/or a filter aid is prepared, and heating and pressurization are performed to allow water contained in the slurry 101 to enter a supercritical state. Further, oxygen 102 is supplied to the slurry 101 to cause oxidation decomposition of organic matter, with a gaseous-phase component generated after the oxidation decomposition being introduced into a gas waste disposal system, and the residual liquid-phase and solid-phase components being formed into inorganic stable solids after enrichment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating radioactive waste generated from a nuclear facility, and more particularly to a used desalter or a filter desalter of a nuclear power plant. The present invention relates to a method for treating an ion exchange resin and a filter aid. The present invention is equally applicable to the treatment of radioactive organic waste generated from nuclear fuel reprocessing plants and nuclear research facilities, especially filter sludge such as used ion exchange resins and filter aids.

[0002]

2. Description of the Related Art Japanese Patent No. 1944918 and Japanese Patent Application Laid-Open No. 4-1021 are currently in practical use as a method for treating radioactive spent ion exchange resin generated from nuclear facilities.
No. 00 publication and the like. That is, the former method is a method of eluting a medium / long half-life radionuclide adsorbed on a radioactive spent ion exchange resin using an acid solution, and the latter is a method of dividing the concentration of the radionuclide into three stages, and In this method, the storage and disposal method is determined according to the concentration, and the volume of the used ion exchange resin is reduced and stabilized.

[0003] The above-mentioned method is used for a spent ion-exchange resin generated from a PWR-type nuclear power plant containing almost no radioactive cladding or a used ion-exchange resin for a distilled water desalination tower in a waste liquid evaporator even in a BWR-type nuclear power plant. This is a very good method.

[0004] However, the spent ion exchange resin and filter aid generated from the drainage purification system and the fuel pool water purification system of the BWR type nuclear power plant capture a large amount of radioactive cladding. However, the radionuclide cannot be sufficiently eluted by passing an acid solution. This is because the clad does not easily separate from the ion exchange resin or the filter aid and dissolves in a normal acid solution.

Japanese Patent Application Laid-Open No. 6-186397 discloses that
As a method of separating the radioactive cladding attached to the surface of the used ion exchange resin, mechanical operation such as ultrasonic irradiation or stirring is performed while neutralizing the surface charge of either the ion exchange resin or the cladding, or both. A method of adding has been proposed.

Further, Japanese Patent Application Laid-Open No. 56-132599 proposes a method in which a used ion-exchange resin having a radioactive clad attached thereto is rapidly cooled, frozen, thawed, and vibrated at a high frequency to separate the ion-exchange resin from the clad. I have.

A method of wet catalytic oxidation of an organic resin using aqueous hydrogen peroxide instead of separating the cladding or radioactive nuclides as described above is also known. JP-A-53-88500,
JP-A-57-1446, JP-A-59-98740
And JP-A-59-141049.

[0008] Clads trapped by ion exchange resins and filter aids are described in literatures (eg, Takeshi Izumi, FAPIG [13]
9] 41-43 (1995))
According to the trapping state, it is classified into three types: intergranular iron trapped between resin particles, surface iron adsorbed on the resin surface, and intragranular iron taken into the particles from the resin surface.

Most of the intergranular iron can be removed by backwashing, and the surface iron is exfoliated by ultrasonic cleaning, but the intragranular iron is partially dissolved and finally exfoliated with hot hydrochloric acid. To dissolve the clad almost completely, it is necessary to treat it with hot aqua regia.

Therefore, in the method of separating intergranular iron and surface iron as disclosed in JP-A-6-186397 and JP-A-56-132599, intragranular iron cannot be separated and remains in the resin. And radionuclides cannot be separated sufficiently. In Japanese Patent No. 1944918, only the intergranular iron peels off during the resin transfer process.

[0011] In the BWR nuclear power plant, it is considered that hydrogen is injected into the reactor water to keep the reactor water in a reducing atmosphere from the viewpoint of reducing exposure, but in this case, the cladding is made of a PWR type nuclear power plant. It becomes nickel ferrite having a spinel structure in the same manner as described above, so that it becomes more difficult to dissolve in a normal acid solution.

Further, JP-A-53-88500, JP-A-57-1446, and JP-A-59-987, in which an organic resin is subjected to wet catalytic oxidation using aqueous hydrogen peroxide.
No. 40, JP-A-59-141049 and the like disclose that the resin is not completely decomposed and the organic matter remains in the liquid, which makes the treatment of the liquid difficult and that the method is chemically unstable. Since a large amount of hydrogen oxide water is used, there are safety problems, and facilities for storage and maintenance are difficult. For this reason, this technology has not been put to practical use.

[0013]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems. For example, radioactive nuclides contained in used ion exchange resins and filter aids can be sufficiently, at low cost, and easily. It is an object of the present invention to provide a method for treating radioactive waste that can be separated.

[0014]

Means for Solving the Problems As a result of intensive studies, the present inventors were able to solve the above-mentioned conventional problems. That is, in the present invention, a slurry of an ion exchange resin containing a radionuclide and / or a filter aid is prepared, and heated and pressurized so that water contained in the slurry is in a supercritical state. Oxygen is supplied to oxidatively decompose organic substances, the gas phase components generated after the oxidative decomposition are introduced into the gas waste treatment system, and the remaining liquid and solid phase components are concentrated to inorganic stable solids. And a method for treating radioactive waste.

The present invention also provides a method for treating radioactive waste, wherein an alkaline aqueous solution is introduced to neutralize acidic components generated after oxidative decomposition, and a liquid phase component is adjusted to a desired pH.

Further, the present invention provides an ion exchange resin and / or
Alternatively, the slurry is stirred in a waste supply tank containing a slurry of a filter aid, and the slurry is introduced into an oxidative decomposition device that performs oxidative decomposition of organic substances by a waste supply pump. Is detected and the
An object of the present invention is to provide a method for treating the above-mentioned radioactive waste, in which the amount of an alkaline aqueous solution added is controlled so that H becomes a set value.

Further, the present invention provides an aqueous alkaline solution
An object of the present invention is to provide a method for treating the radioactive waste introduced into one or more of an oxidative decomposition device, a waste supply tank, or a waste supply tank and a waste supply pump.

Further, according to the present invention, there is provided a method for detecting the temperature of an oxidative decomposer by controlling the supply amount of an ion-exchange resin and / or a filter aid to the oxidative decomposer to maintain the temperature of the oxidative decomposer appropriately. It is intended to provide a waste disposal method.

Further, the present invention provides an ion exchange resin and / or
Another object of the present invention is to provide a method for treating the above-mentioned radioactive waste in which the supply amount of a filter aid is detected and oxygen is supplied at a stoichiometric ratio or more necessary for oxidative decomposition.

Further, the present invention provides a method for treating radioactive waste, wherein a waste supply tank having a stirring function is provided, and an ion exchange resin and / or a filter aid is supplied to the oxidative decomposition apparatus therefrom. It is.

Further, the present invention provides the above-mentioned method for treating radioactive waste, wherein distilled water as a decomposition product is reused for adjusting the concentration of a slurry of an ion exchange resin and / or a filter aid or for transporting the slurry. It is.

Further, the present invention provides a method for treating radioactive waste as described above, wherein the temperature of the oxidative decomposition apparatus is detected, the amount of distilled water used for recirculation is adjusted, and the temperature of the oxidative decomposition apparatus is appropriately maintained. is there.

Japanese Unexamined Patent Publications Nos. 61-16569 and 61-16598 disclose a method for treating radioactive waste using water in a supercritical state. In addition, using supercritical water and oxygen together,
The technical idea of completely oxidatively decomposing the ion exchange resin and / or the filter aid is not disclosed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. Embodiment 1 FIG. 1 is a flowchart of a processing process according to an embodiment of the present invention. In FIG. 1, 1 is an oxidative decomposition device using supercritical water, 2 is a decomposition gas treatment device, 3 is a decomposition product liquid concentrating device containing solids after the decomposition product gas has escaped, and 4 is an evaporation and concentration device. This is a solidifying device that converts the concentrated liquid into a stable solidified body.

The ion exchange resin and the filter aid are stored in a slurry state in a storage tank of a nuclear power plant. These wastes 101 are supplied to the oxidative decomposition device 1 which can maintain a supercritical water state as a slurry. The slurry is, for example, 1 to ion exchange resin or filter aid.
It can have three times (by weight) water. The oxidative decomposition device 1 may be either a continuous type or a batch type.

In the case of the continuous type, the oxidative decomposition apparatus 1 is maintained in a supercritical water state, and is supplied in a slurry state in which the waste 101 is stored. Oxygen is supplied thereto to oxidatively decompose the waste 101.

In the case of the batch type, after the waste 101 is supplied to the oxidative decomposition apparatus 1, the temperature and the pressure are brought to a supercritical water state. Oxygen 102 is supplied thereto to oxidize and decompose the waste 101 in the same manner as in the case of the continuous type.

The processing conditions in the oxidative decomposition apparatus 1 will be described in Embodiment 2 below.

Decomposition gas 1 generated by the oxidative decomposition apparatus 1
11 is guided to the decomposition product gas treatment device 2 and processed.
The main components of the decomposition product gas 111 are CO ₂ and H ₂ O, N ₂ and a very small amount of NOx, and basically do not contain radionuclides, but they are installed in a nuclear power plant just in case. Via the exhaust gas treatment system 50.

Here, in order to prevent dew condensation in the duct to the exhaust gas treatment equipment and the exhaust gas treatment equipment itself, the decomposition product gas treatment apparatus 2 cools the gas once, dehumidifies it, reheats it, and then sends it to the exhaust gas treatment system 50. send.

FIG. 2 is a flow chart of a processing process of the decomposition product gas processing apparatus. In FIG. 2, the decomposition product gas 1
11 is a reheater 2 for reducing the relative humidity after the moisture is condensed in the cooler 21 and the moisture is removed in the moisture separator 22.
Heated at 3. Waste gas 11 whose humidity has been reduced in this way
2 is sent to a nuclear power plant waste gas treatment system 50. Distilled water 113 generated by dehumidification does not basically contain radionuclides, but is passed through the desalter 24 or sent directly to the waste liquid treatment system 60 for treatment, or released as it is. Is done.

After the decomposition product gas 111 is released, the remaining decomposition product liquid 121 is evaporated in the decomposition product liquid concentrating device 3 to become a concentrated solution 124, and is transferred to the solidifying device 4, where it is moved to the solidifying device 4, where an inorganic matrix (for example, cement) is used. And solidified into an inorganic stable solidified body. Here, the radioactive nuclide that was present in the waste 101 is contained in the decomposition product liquid 121 in a liquid phase or a solid phase, which means that the radioactive waste could be turned into an inorganic stable solid.

FIG. 3 is a flow chart of a processing process of the decomposition product liquid concentrating apparatus. In FIG. 3, except that the concentrated liquid 124 is processed, the configuration and function are the same as those of the decomposition product gas processing apparatus 2 in FIG. 2, and the same processing is performed. This device also has a function similar to that used for concentrating waste liquid in a nuclear power plant.

(Embodiment 2) 50% of ion exchange resin
The slurry is put into an oxidative decomposition apparatus, and the amount of oxygen required to oxidize and decompose the ion exchange resin (stoichiometric ratio) is 1.2 times the amount of oxygen. A supercritical water state of 873K and 25MP exceeding the point of 647.3K and 22MP was maintained for 10 minutes. As a result, the ion exchange resin was completely oxidized and decomposed, and no organic matter was detected as well as the solid matter. As the ion exchange resin, a granular resin and a powder resin were tested, and all of the results were as described above. In general, in order to oxidatively decompose an ion exchange resin or a filter aid, oxygen having a stoichiometric ratio of 1 to 3 times is used. The temperature and pressure applied to bring water to a supercritical state may be any conditions sufficient to oxidatively decompose the ion exchange resin or filter aid, but are usually 650 to 900K and 25 to 40M.
P is employed, and the oxidative decomposition time also depends on the amount and type of the ion exchange resin or filter aid to be treated, but is usually about 3 to 60 minutes.

(Embodiment 3) A 50% water slurry obtained by adding 100 mg / liter of hematite as a simulation of cladding to an ion exchange resin is put into an oxidative decomposition apparatus, and the amount (quantity) required for oxidative decomposition of the ion exchange resin is obtained. Oxygen of 1.2 times the theoretical ratio was sealed, and the temperature and pressure were kept as they were in a supercritical water state of 873K and 25MP exceeding the critical points of water, 647.3K and 22MP, and maintained for 10 minutes. As a result, the ion exchange resin was completely oxidatively decomposed, and no organic matter was detected. As the ion exchange resin, a granular resin and a powder resin were tested, and all of the results were as described above.

As described above, according to Embodiments 1 to 3, oxygen is supplied to the ion exchange resin or the filter aid in the supercritical water, and these are completely oxidatively decomposed. The decomposition products are oxides of these constituent elements, specifically, CO ₂ and H ₂ O
Is the main component, and is N ₂ , a very small amount of NOx, and sulfate from other elements contained in the functional groups of the ion exchange resin. The trapped clad components, adsorbed radionuclides, and the like are in a liquid phase or solid phase, although there are some changes in state, and become inorganic stable solids. Therefore, according to the first to third embodiments, the following effects are achieved. (1) Since the used ion exchange resin and filter aid can be treated as a slurry, no special pretreatment is required; (2) Only oxygen is added for oxidative decomposition, and hydrogen peroxide solution is used. No special maintenance such as is required. Also, no special equipment such as a tank for its storage is required; (3) The main decomposition products are non-radioactive CO ₂ and H ₂ O
Therefore, the radionuclide can be easily separated from the radionuclide; and (4) The radionuclide can be made into an inorganic stable solidified product, which is suitable for long-term storage and disposal as well as volume reduction.

(Embodiment 4) Next, an example of neutralization by adding an alkaline aqueous solution to an acidic substance will be described. As described in Embodiment 1, the waste 101 of the slurry of the ion-exchange resin and the filter aid is supplied to the oxidative decomposition device 1 that can maintain the supercritical water state as the slurry. The oxidative decomposition device 1 may be either a continuous type or a batch type.

FIG. 4 is a flow chart for explaining a case where the oxidative decomposition is of a batch type in an embodiment in which an alkaline aqueous solution is added. In FIG. 4, used ion exchange resin is supplied as slurry 101 to the oxidative decomposition apparatus 1 in a slurry state. An alkaline aqueous solution (generally, a caustic soda aqueous solution) having an amount equivalent to 1.1 to 1.5 times the amount of sulfur previously determined by chemical analysis of a sample of the waste 101 is added to the oxidative decomposition apparatus. deep. Hereinafter, Embodiments 1 to
As described in 3, the oxidative decomposition apparatus 1 is kept in a supercritical water state, and oxygen 102 is supplied. As a result, p
H became about 8.

(Embodiment 5) FIG. 5 is a flow chart for explaining a case where oxidative decomposition is of a continuous type in an embodiment in which an alkaline aqueous solution is added. In FIG. 5, waste 1
01 is supplied from the waste supply tank 11 having a stirring function to the oxidative decomposition apparatus 1 by the waste supply pump 12 in a water slurry state. The oxidative decomposition apparatus 1 is maintained in a supercritical water state, and is supplied in a slurry state in which the waste 101 is stored. Oxygen 102 is supplied there to oxidize and decompose the waste 101. Decomposition liquid 121
In order to adjust the temperature and pressure conditions of the cooling / pressure reducing device 15 so that a normal pH meter can be used, the pH of the decomposition product solution 121 is detected by the pH meter 16, and the calculation controller 17 adjusts the pH to the set value. The required amount of the alkaline aqueous solution is calculated, the discharge amount of the alkaline aqueous solution supply pump 14 is controlled, the alkaline aqueous solution is supplied from the alkaline aqueous solution supply tank 13 to the oxidative decomposition device 1, and the pH of the decomposition product liquid 121 is set to about 7. .
In this case, since the alkali aqueous solution supply pump 14 needs to be directly press-fitted into the high-pressure portion of the oxidative decomposition device 1, a high-pressure flow variable metering pump is used.

(Embodiment 6) FIG. 6 is a flow chart for explaining an embodiment in which the alkaline aqueous solution 103 is added to the waste supply tank 11. In this embodiment, since it is not necessary to directly inject the alkaline aqueous solution 103 into the high-pressure portion of the oxidative decomposition device 1, a low-pressure variable flow rate fixed-quantity pump or a centrifugal pump and a flow control valve can be used instead. In the sixth embodiment, the same parts as in the fifth embodiment have been omitted from description (the same applies hereinafter).

(Embodiment 7) FIG. 7 is a flow chart in which the supply location of the alkaline aqueous solution 103 is changed. In FIG. 7, the supply location of the alkaline aqueous solution 103 is set to a pipe between the waste supply tank 11 and the waste liquid supply pump 12. According to this aspect, since the pH of the decomposition product liquid 121 can be adjusted to about 7 by the same operation as in the fifth embodiment, it is possible to appropriately cope with the property change of the waste 101.

(Embodiment 8) In Embodiments 4 to 7,
The pH of the decomposition product 121 was adjusted to be around neutral (about 7). However, when the decomposition product liquid 121 becomes a cement solidified product as a final stable solidified product, the decomposition product liquid 12 is used.
The pH of 1 may be adjusted so as to be about 10 to 12 alkaline. In this case, it is not necessary to strictly control the addition amount of the alkaline aqueous solution 103.

In Embodiments 4 to 8, an alkaline aqueous solution is added to an acidic decomposition product generated after completely oxidatively decomposing an ion exchange resin or a filter aid to adjust the pH to about 7. . According to the fourth to eighth embodiments, the following effects can be obtained. (1) The pH of the oxidative decomposition product solution can be maintained at a set value, leading to a reduction in corrosion of constituent materials, and an improvement in safety and reliability of equipment. In addition, inexpensive materials can be used, and costs can be reduced. (2) By having a waste supply tank having a stirring mechanism, pH controllability of the generated decomposition solution is improved; and (3) alkali By placing the aqueous solution addition site upstream of the waste supply pump, the alkaline aqueous solution supply pump can have a low discharge pressure, or other means (for example, gravity drop) can be used, which contributes to cost reduction. be able to.

(Embodiment 9) Next, an embodiment for appropriately controlling the temperature of the oxidative decomposition apparatus will be described. FIG. 8 is a flowchart for that purpose. In FIG. 8, the oxidative decomposition device 1
Then, a waste ion supply resin 11 and / or a filter aid as waste 101 are supplied in a water slurry state by a waste supply pump 12 from a waste supply tank 11 having a stirring function. The oxidative decomposition apparatus 1 is maintained in a supercritical water state, and when oxygen 102 is supplied, the waste 101 is completely oxidatively decomposed. The oxidative decomposition device 1 is kept in a supercritical water state, and oxygen 102 is supplied. At this time, heat is generated due to the oxidation of the waste 101. This calorific value is equal to the heat of combustion of the waste 101, and if there is sufficient oxygen, the supplied waste 1
It is proportional to the amount of 01. Therefore, the temperature of the oxidative decomposition device 1 is detected by the thermometer 18, an appropriate amount of the waste 101 is calculated by the operation controller 19, and the supply amount according to the amount is adjusted by the waste supply pump 12, whereby the oxidation is performed. The amount of heat generated in the decomposition device 1 and thus the temperature of the oxidative decomposition device 1 can be controlled to be constant. Here, since the waste 101 has a uniform concentration in the waste supply tank 11 having the stirring function, the supply speed is stable.

The discharge amount of the waste supply pump is detected from the pump rotation speed and the current value, and the amount of oxygen necessary for the oxidative decomposition of the waste 101 is calculated by the operation controller 29. To control the amount of oxygen supplied.
By doing so, the temperature of the oxidative decomposition device 1 can be controlled more favorably, which leads to cost reduction. The amount of oxygen depends on the type and amount of the used ion exchange resin and the filter aid, but is, for example, 1 to 3 times the theoretical amount,
For example, about three times is exemplified. As the oxygen source, for example, aqueous hydrogen peroxide (30%) can be used. The supply amount of the waste 101 depends on the treatment capacity of the oxidative decomposition device 1 and the like, but is, for example, 0.1 to 100 g / min, for example, 0.1 g / min.
It can be 3 g / min. Under these conditions, for example, the oxidative decomposition apparatus 1 can be maintained at about 500 ° C.

According to the ninth embodiment, it is possible to stably operate the temperature of the oxidative decomposition apparatus, to improve the stability of the apparatus, and to improve the safety and reliability of the equipment, and to reduce the consumption of oxygen. This has the effect of minimizing the running cost and suppressing running costs.

(Embodiment 10) Next, an embodiment in which distilled water generated in the treatment step is reused will be described. FIG.
It is a flowchart for that. In FIG. 9, an oxidative decomposition device 1 is provided with a waste supply tank 11 having a stirring function.
Spent ion exchange resin and / or a filter aid as the waste 101 are supplied by the waste supply pump 12 in a water slurry state. The oxidative decomposition apparatus 1 is maintained in a supercritical water state, and when oxygen 102 is supplied, the waste 101 is completely oxidatively decomposed. Among the oxidative decomposition products, distilled water 1
13 is separated by the decomposition product gas treatment device 2 and the decomposition product liquid concentrating device 3, transferred to the waste resin storage tank 70 installed in the nuclear power plant by the distilled water circulation device 5, and stored therein. The material 101 is reused as water necessary for transporting the slurry of the ion exchange resin and the filter aid to the waste storage tank 11. Further distilled water 1
13 is also used for adjusting the slurry concentration of the waste 101 supplied to the oxidative decomposition apparatus 1.

(Embodiment 11) FIG. 10 is a flowchart for explaining another embodiment. In FIG. 10, the amount of heat generated by the oxidative decomposition of the waste 101 in the oxidative decomposition device 1 is proportional to the slurry concentration of the waste 101, that is, the amount of the ion exchange resin and the amount of the filter aid. Therefore,
When the discharge capacity of the waste supply pump 12 is constant, the slurry concentration and, consequently, the calorific value can be kept within a certain range by adjusting the slurry concentration. For this,
The temperature of the oxidative decomposition device 1 is detected by a thermometer 51, and the amount of distilled water 113 to be reused is adjusted by controlling a distilled water supply amount adjuster 53 by an operation adjuster 52. The return point of the reused distilled water 113 is not the waste supply tank 11 shown in FIG.
Needless to say, a pipe between them may be used. The actual supply amount of distilled water depends on the amount and type of the used ion exchange resin and the like. For example, the supply amount of the waste water 101 is 0.3 g / min and the amount of distilled water is 1 g / min.
By setting it to 1 g / min, the temperature of the oxidative decomposition device 1 can be kept at about 500 ° C.

According to the tenth and eleventh embodiments, the following effects can be obtained. (1) As a utility, it is possible to reduce the guesswork necessary for transporting wastes in slurry and for adjusting the concentration of slurry supplied to the oxidative decomposition apparatus for stable operation of the oxidative decomposition apparatus, and running costs can be reduced. Decrease.
As a result, the amount of waste liquid generated from the present apparatus, that is, the amount of secondary waste is reduced, and the load on the waste liquid treatment apparatus of the nuclear power plant is reduced; and (2) the temperature of the oxidative decomposition apparatus is operated stably Therefore, the stability of the apparatus and the safety and reliability of the equipment can be improved.

Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to these embodiments. In particular, by combining the means described in the first to eleventh embodiments, a plurality of effects of each can be simultaneously exhibited. For example, the temperature control of the oxidative decomposition apparatus 1 can be combined with a mode in which distilled water generated in the treatment step is used again and a mode in which the amount of waste 101 is calculated and the supply amount is adjusted.

[0051]

According to the present invention, there is provided a method for treating radioactive waste, which is capable of separating radionuclides contained in, for example, used ion exchange resins and filter aids sufficiently, at low cost, and easily. Provided.

[Brief description of the drawings]

FIG. 1 is a flowchart of a processing process according to an embodiment of the present invention.

FIG. 2 is a flowchart of a processing process of the decomposition product gas processing apparatus.

FIG. 3 is a flowchart of a treatment process of the decomposition product liquid concentrating device.

FIG. 4 is a flow chart for explaining a case where oxidative decomposition is of a batch type in an embodiment in which an alkaline aqueous solution is added.

FIG. 5 is a flowchart for explaining a case where oxidative decomposition is of a continuous type in an embodiment in which an alkaline aqueous solution is added.

FIG. 6 is a flowchart for explaining an embodiment in which an alkaline aqueous solution is added to a waste supply tank.

FIG. 7 is a flow chart in which a supply location of an alkaline aqueous solution is changed.

FIG. 8 is a flowchart for explaining an aspect of appropriately controlling the temperature of the oxidative decomposition device.

FIG. 9 is a flowchart for explaining an embodiment in which distilled water generated in the processing step is reused.

FIG. 10 is a flowchart for explaining another mode of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oxidation decomposition apparatus 2 Decomposition gas processing apparatus 3 Decomposition liquid concentration apparatus 4 Solidification apparatus 5 Distilled water circulation apparatus 11 Waste supply tank 12 Waste supply pump 13 Alkaline aqueous solution supply tank 14 Alkaline aqueous solution supply pump 18, 51 Thermometer 29,52 Operation controller 28 Oxygen supply controller 53 Distilled water supply controller 70 Waste storage tank 101 Waste 102 Oxygen 103 Alkaline aqueous solution 111 Decomposition gas 112 Waste gas 113,123 Distilled water 121 Decomposition liquid 124 Concentration liquid

Continuation of front page (72) Inventor Wataru Kawamura 2-1-1, Shinhama, Arai-machi, Takasago-shi, Hyogo Inside the Mitsubishi Heavy Industries, Ltd. Takasago Research Laboratory

Claims (9)

[Claims] 1. A slurry of an ion exchange resin and / or a filter aid containing a radionuclide is prepared, and heated and pressurized so that water contained in the slurry becomes a supercritical state. Oxygen is supplied to oxidatively decompose organic substances, the gas phase components generated after the oxidative decomposition are introduced into the gas waste treatment system, and the remaining liquid and solid phase components are concentrated to inorganic stable solids. A method for treating radioactive waste. 2. The radioactive waste treatment method according to claim 1, wherein an alkaline aqueous solution is introduced to neutralize acidic components generated after the oxidative decomposition, and a liquid phase component is adjusted to a desired pH. 3. Agitating the slurry in a waste supply tank containing a slurry of an ion exchange resin and / or a filter aid, introducing the slurry into an oxidative decomposition apparatus for oxidatively decomposing organic substances by a waste supply pump, 3. The method for treating radioactive waste according to claim 2, wherein after the oxidative decomposition, the pH of the generated oxidative decomposition liquid is detected, and the amount of the aqueous alkali solution added is controlled so that the pH of the liquid becomes a set value. 4. The radioactive waste according to claim 3, wherein the aqueous alkali solution is introduced into one or more of an oxidative decomposition device, a waste supply tank, or a waste supply tank and a waste supply pump. Processing method. 5. The method according to claim 1, wherein the temperature of the oxidative decomposition device is detected and the supply amount of the ion exchange resin and / or the filter aid to the oxidative decomposition device is adjusted to maintain the temperature of the oxidative decomposition device appropriately.
The method for treating radioactive waste according to any one of claims 1 to 4. 6. The radioactive waste treatment method according to claim 5, wherein the supply amount of the ion exchange resin and / or the filter aid is detected, and oxygen is supplied at a stoichiometric ratio or more necessary for oxidative decomposition. 7. A waste supply tank having a stirring function is provided, and an ion exchange resin and / or
7. The method for treating a radioactive waste according to claim 5, wherein a filter aid is supplied. 8. The radioactive waste according to claim 1, wherein the distilled water as a decomposition product is reused for adjusting the concentration of the slurry of the ion exchange resin and / or the filter aid or for transporting the slurry. How to handle things. 9. The radioactive waste treatment method according to claim 8, wherein the temperature of the oxidative decomposition device is detected, and the temperature of the oxidative decomposition device is appropriately maintained by adjusting the amount of distilled water to be recycled.