JP2013231696A - Immobilizing agent and immobilizing method for radioactive waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immobilizing agent and an immobilizing method for safely and securely coating and immobilizing the residual body after decontamination processing on incineration ashes including radioactive wastes and radioactive contaminants, dust, sewage sludge, and other objects to be decontaminated so as to secure safety in the future.SOLUTION: There is provided an immobilizing agent for radioactive substance which is a mixed liquid body of (A) 60-80 wt.% of a substance prepared by mixing and stirring (a) 60-80 wt.% of water glass, (b) 10-25 wt.% of apatite, (c) 5-15 wt.% of powdery magnesium, and (d) 5 wt.% of barium, (B) 10-30 wt.% of cellulose, and (C) 5-15 wt.% of cation.

Description

  In the present invention, in order to separate and remove radioactive pollutants from incinerated ash, dust, sediment, etc. contaminated by radioactive materials, particularly uranium-based radioactive materials, they were separated or captured from the object when decontamination was performed. The present invention relates to a radioactive substance immobilizing agent and an immobilizing method for carrying out immobilization treatment so that the radioactive substance does not exert the influence of radiation on the outside again.

  Processing and use of so-called radioactive materials with radioactivity such as various nuclear application equipment typified by nuclear power plants, factories that separate, concentrate, and process nuclear fuel, storage and processing plants for radioactive waste, etc. In facilities and storage facilities where processing is performed, and in the vicinity thereof, the radioactive material itself and radioactive pollutants with high radioactivity are scattered, released, or leaked due to, for example, inadequate handling, equipment failures, accidents, natural disasters, etc. , Exposed to dangers such as diffusion. Radiation causes irreparable damage to human skin, various organs, cells, etc., and in the worst case, there is no denying the concern of having a fatal effect. In particular, regarding the exposure to the human body, the influence of strontium 90 (Sr90) that is easily deposited on bone and cesium 137 (Cs137) that is easily deposited on the whole body has been pointed out. When processing radioactive materials themselves or radioactive waste, it is required not to cause scattering, runoff, diffusion, etc. of the materials in the processing process. How to do it is extremely important.

  As described above, since radioactive substances remain in the incinerated ash, the radioactive material is naturally not solved by final treatment such as incineration, dilution, embedding, ocean dumping, etc. like general waste and waste liquid. Therefore, since it is theoretically difficult to completely solve the problem of residual radioactivity, it is possible to maintain a sealed state semi-permanently in the case of a processing means that maintains safety in the future, for example, a solid. Immobilization is essential. Such treatment requires a permanent treatment that does not return to nature in any form such as once decontaminated radioactive materials and radioactive solids, liquids and gases.

  Patent document 1 is disclosing the manufacturing method of the solidification material which calcinates and solidifies what mixed the garbage incineration ash after removing heavy metal with the powder of animal bone powder, lime, and siliceous limestone. Patent Document 2 discloses a solidifying agent containing sodium silicate, slaked lime and alum and a method of solidifying with the solidifying agent in order to suppress elution of heavy metals, fluoride compounds, boron compounds and the like. ing.

JP-A-4-61978

JP 2011-26151 A

An object of the present invention is to decontaminate radioactive waste and dust containing radioactive contaminants, waste, sewage sludge, and other decontamination objects in order to ensure safety at present and in the future. Another object of the present invention is to provide a radioactive substance immobilizing agent and an immobilizing method for safely and reliably coating and immobilizing a residual object after the operation. As the immobilizing agent to be used in the present invention, the physical and chemical characteristics are stable, the property of surrounding and immobilizing the object relatively easily is required, and the physical properties are also stable. Sodium silicate or sodium silicate is suitable. These sodium silicate and sodium silicate are also called “water glass” and are liquids in which anhydrous silicic acid (SiO ₂ ) and sodium oxide (Na ₂ O) are mixed in various ratios.

  In Japanese Patent Application No. 2012-104707, the applicant discloses a decontamination agent and a decontamination method used for separating and removing radioactive pollutants from soil, incineration ash, dust and the like contaminated by radioactive materials. The present invention provides a radioactive substance immobilizing agent and an immobilizing method that allow the incinerated ash treated by the decontaminating agent and the decontaminating method to maintain a sealed state.

  The invention described in claim 1 includes: (A) (a) 60 to 80% by weight of water glass, preferably about 70% by weight; (b) 10 to 25% by weight of apatite, preferably about 15% by weight; c) Powdered magnesium of 5 to 15% by weight, preferably about 10% by weight, and (d) Barium 3 to 7% by weight, preferably about 5% by weight, of 90 ° C. to 110 ° C., preferably about 100 ° C. (B) Cellulose is 10 to 30% by weight, preferably 20% with respect to 60 to 80% by weight, preferably about 70% by weight of the substance mixed and stirred while heating at a temperature of 20 to 70 minutes, preferably 30 to 60 minutes. About 50% by weight and (C) cation 5 to 15% by weight, preferably about 10% by weight, with mixing at 50 to 90 ° C., preferably 60 to 80 ° C., preferably 20 to 40 minutes, preferably 3 Fixing agent of radioactive material, characterized in that stirring-mulled for partial extent.

  The invention according to claim 2 includes (A) (a) 60 to 80% by weight of water glass, preferably about 70% by weight, and (b) 10 to 25% by weight of apatite, preferably about 15% by weight, c) Powdered magnesium 5 to 15% by weight, preferably about 10% by weight, and (d) Barium 3 to 7% by weight, preferably about 5% by weight, 60 to 80% by weight, preferably It is a mixed liquid of about 70% by weight, (B) cellulose 10 to 30% by weight, preferably about 20% by weight, and (C) cation 5 to 15% by weight, preferably about 10% by weight. Characterized radioactive material immobilization agent.

  The invention according to claim 3 is a method of adding 20 to 10%, preferably 7 to 9% of the fixing agent according to claim 1 to the radioactively contaminated incineration ash while mixing at room temperature while mixing. It is a method for immobilizing a radioactive substance in which the radioactive substance is surrounded and fixed with water glass by stirring and kneading for -40 minutes.

  The invention described in claim 4 includes 50 wt% suspension in which apatite is dissolved in sulfamic acid, 30 wt% liquid in which aluminum, titanium and zinc are dissolved in sulfuric acid, barium and nitric acid. A mixture of the decontamination agent and the incineration ash settled at the bottom after the decontamination treatment of the radioactively contaminated incineration ash with the decontamination agent that is a mixed liquid of 20% by weight of the magnesium-dissolved liquid. The mixture is dried to a moisture content of about 3% and then stirred for 20 to 40 minutes at room temperature while mixing the dried mixture with 6 to 10%, preferably 7 to 9%, of the fixing agent according to claim 1. -It is a method for immobilizing a radioactive substance in which the radioactive substance is surrounded and fixed with water glass by kneading.

  The invention according to claim 5 is a method for immobilizing a radioactive substance, wherein the immobilized radioactively contaminated incineration ash and a mixture of the decontamination agent and the incineration ash are granulated in a pellet form. The invention described in 6 is a method for immobilizing a radioactive substance, wherein the radioactively contaminated incineration ash is incineration ash of sewage sludge.

  The radioactive substance immobilizing agent and the immobilizing method according to the present invention are used to incinerate various organic substances contaminated by radioactivity such as cesium 137 (Ce137) and strontium 90 (Sr90) in the primary treatment. The incinerated ash is radioactive and cannot be discarded as it is. In the present invention, the incinerated ash having radioactivity is immobilized as a glass-covered granular material confined with the above-mentioned water glass.

  In Japanese Patent Application No. 2012-104707, the applicant discloses a decontamination agent and a decontamination method used for separating and removing radioactive pollutants from soil, incineration ash, dust and the like contaminated by radioactive materials. . The decontamination agent and the decontamination method disclosed herein are obtained by immersing and dissolving radioactive incineration ash in the decontamination agent, and adsorbing the radioactive substance mainly on cow bone meal or apatite components in the decontamination agent. Thus, the remaining radioactivity is decontaminated until it reaches a level that does not hinder human life.

Since the radioactive substance remains naturally in the precipitate after the decontamination process (mixture of the decontamination agent and the incinerated ash settled on the bottom after the decontamination process), the residue Things cannot be discarded as they are. In the present invention, the radioactive residue is immobilized as a glass-coated granule encapsulated by the water glass described above. Therefore, it can be granulated as glass-coated pellets fixed so as not to be easily released by re-separation, scattering, dissolution, etc. over a long period of time, and can be stored in a state where there is no danger to the surroundings. Become.

It is explanatory drawing which shows the component ratio and structural example of the fixing agent which concern on this invention. It is a conceptual diagram which shows the usage example (immobilization process example) of the fixing agent which concerns on this invention, a figure (A) shows the process with respect to the incineration ash which was radioactively contaminated, and the figure (B) was radioactively contaminated. It is a figure which shows the process with respect to the incineration ash which decontaminated the incineration ash with the decontamination agent.

  Hereinafter, the configuration, usage example (an immobilization treatment example) and effects of the radioactive substance immobilizing agent according to the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the decontamination agent 1 according to the present invention comprises (a) about 70% by weight of water glass, (b) about 15% by weight of apatite, and (c) about 10% by weight of powdered magnesium, (D) A substance obtained by mixing and stirring about 5% by weight of barium (A) with about 70%, cellulose (B) 11 about 20% and cation (C) 12 about 10%.

  Although the production conditions of the fixing agent are slightly affected by the ambient temperature, in this example, the substance (A) is (a) 70% by weight of water glass, (b) 15% by weight of apatite, and (c). 10% by weight of powdered magnesium and 5% by weight of (d) barium are obtained by mixing and stirring while heating at a temperature of about 100 ° C. for 30 to 60 minutes. The mixture of (B) cellulose (20% by weight) and (C) cation (10% by weight) was mixed with 70% by weight of the substance (A) thus obtained over about 30 minutes at 60-80 ° C. Stir and knead to obtain the immobilizing agent.

  Here, the apatite used in the present invention is a calcined animal bone powder, and can be obtained by boiling live animal bone, for example, beef bone, calcining at a high temperature of about 900 ° C. to 1100 ° C., and crushing. Animal bone meal used in the present invention is bones that have been mostly discarded in conventional slaughterhouses and are usually regarded as troublesome, especially bones of animals such as cattle, horses, sheep, etc. What was obtained by processing the bone as follows was used. The raw bone is cut into a size that is easy to fire, boiled, and fired at around 900 ° C to 1100 ° C. If organic substances such as gelatin, fat, white matter, and glue other than bone components remain in the bone, they cause oxidative decay, so it is necessary to remove them reliably. By the boiling step, organic substances adhering not only to the outside of the bone but also to the pores are mostly separated and removed from the bone. Then, by performing the firing step, the remaining organic matter can be completely removed, and at the same time, the burned animal bone meal in which the humidity (moisture) in the bone is reduced to several percent or less, preferably to almost 0%. This is what is called apatite. According to the firing conditions, the bone is completely whitened and maintains an original tissue state having countless pores. After firing and cooling, the bone is crushed to form bone powder. In the case of raw bone, the bone powder thus obtained provides a yield of about 40% by weight compared to raw raw bone. The particles are mainly composed of calcium (about 33% by weight), phosphorus (about 16.7% by weight), barium (about 1.03% by weight), sodium (about 0.76% by weight), sulfur (about 0. 64% by weight) and other elements such as magnesium, potassium, chlorine, amine, iron, and the like, and innumerable micropores are continuously present inside and outside the particles, are alkaline, and exhibit an ion exchange effect. In the present invention, a mixture of the above apatite with a powder of silica, zeolite, or volcanic ejecta can be used. In the present invention, commercially available water glass can be used.

  Next, a usage example (an immobilization treatment example) of the immobilizing agent according to the present invention will be described. In the present invention, as shown in FIG. 2 (A), a normal temperature of about 10 to 15 ° C. is added to the incinerated ash 22 contaminated with radioactivity while adding and mixing the above-described fixing agent 6 to 10%. By stirring and kneading for 20 to 40 minutes below, the radioactive substance is surrounded by water glass and fixed.

  In the present invention, as shown in FIG. 2 (B), 50% by weight of a suspension in which apatite is dissolved in sulfamic acid, and 30% by weight of a liquid in which aluminum, titanium and zinc are dissolved in sulfuric acid, Incineration ash contaminated with radioactivity is removed by a decontamination agent (decontamination agent disclosed in Japanese Patent Application No. 2012-104707) which is a mixed liquid of 20% by weight of a liquid in which barium and magnesium are dissolved in nitric acid. The mixture of the decontamination agent and incineration ash that settled on the bottom after dyeing treatment (incineration ash after decontamination treatment) 23 is dried to a moisture content of about 3%, and then the dried mixture and the structure described above are used. By stirring and kneading for 20 to 40 minutes at room temperature while mixing with 6 to 10% of the fixing agent, the radioactive material is surrounded by water glass and fixed.

  In addition, the length of the stirring / kneading time in the above-described immobilization treatment and the amount of the fixing agent to be added should be handled while appropriately confirming depending on the weight of the radioactive contamination of the object to be treated, the treatment amount, and the like. Further, in the present invention, the radioactively contaminated incineration ash and the mixture of the decontaminating agent and the incineration ash that have been fixed can be collected as pellets in the form of granules, and the granulated granules can be used as roadbed materials, It can be used as an underlay or purification material for rivers and beaches. In the examples of the present invention, incineration ash of sewage sludge was used as incineration ash contaminated with radioactivity.

Test date: January 31, 2012 Test method: Gamma-ray spectrometry with germanium semiconductor detector (Ministry of Education, Culture, Sports, Science and Technology 1992)
Inspection device: GC2020 (CANBERRA)
“Non-detection” refers to less than 10 (Bq / l).
A mixture obtained by drying the mixture 23 of the decontamination agent and the incineration ash settled on the bottom of the container in the sewage sludge incineration ash decontaminated by the decontamination agent disclosed in Japanese Patent Application No. 2012-104707 until the water content becomes about 3%. (Result of the above test: cesium (Cs-137) is 1,510 (Bq / kg solid standard)) 20 kg at room temperature while mixing while adding 80 cc of the above-described fixing agent. The immobilization treatment was performed by stirring and kneading in the container 21 for 40 minutes, and the immobilization mixture was recovered as a granulated material in a pellet form. It was "not detected" when the said test | inspection was implemented about the collect | recovered granulated body. The suspension water separated from the mixture of the decontaminating agent and the incinerated ash is filtered using a specific filtering agent until no radiation dose is detected.

  According to the present invention, the high concentration radioactive material remaining after decontamination is further absorbed and captured by the apatite component (b), and the periphery of the radioactive material is covered and fixed by the water glass material. The influence of radiation on the surroundings will be greatly reduced. As a result of the addition of the cellulose component to the water glass component, the glass wall on which the water glass is solidified is not easily damaged, and can be safely maintained unless significant external pressure or impact is applied. In addition, since the coating with water glass is cracked if a strong impact from the outside is applied and may be crushed in extreme cases, a strong box-like body or It is desirable to take care not to damage human animals by storing them in barrels and locking them.

  The solidifying agent or immobilizing agent according to the present invention can be expected to be used not only for the radioactive substance itself released from the radioactive substance by decontamination but also for an object that is secondarily radioactive. It is necessary to pay careful attention to such radioactivity so as not to cause unnecessary exposure accidents. In the present invention, care must be taken so as to eliminate radiological accidents that may damage people who are not directly related but who simply enter the neighborhood, as well as those who handle radioactive materials.

1 Immobilizing Agent 10 Substance (A)
11 Cellulose (B)
12 Cation (C)
21 Container 22 Radioactive contaminated incineration ash 23 Decontaminant and decontaminated incineration ash mixture (decontaminated incineration ash)

Claims (6)

  (A) (a) 60-80% by weight of water glass, (b) 10-25% by weight of apatite, (c) 5-15% by weight of powdered magnesium, (d) 3-7% by weight of barium, To (B) 10 to 30% by weight of cellulose and (C) 5 to 15% by weight of cation, with respect to 60 to 80% by weight of the substance stirred and heated at a temperature of about 100 ° C. for 30 to 60 minutes, A radioactive substance immobilizing agent characterized by stirring and kneading for about 30 minutes under conditions of 60 to 80 ° C. with mixing.   (A) (a) 60 to 80% by weight of water glass, (b) 10 to 25% by weight of apatite, (c) 5 to 15% by weight of powdered magnesium, and (d) 5% by weight of barium A radioactive substance immobilizing agent, which is a mixed liquid of 60 to 80% by weight of a stirred substance, (B) 10 to 30% by weight of cellulose, and (C) 5 to 15% by weight of a cation.   The radioactive material is agitated and kneaded at room temperature for 20 to 40 minutes while adding and mixing 6 to 10% of the immobilizing agent according to claim 1 to the radioactively contaminated incineration ash. A method for immobilizing a radioactive substance, characterized in that it is surrounded and immobilized by water glass. 50% by weight of a suspension in which apatite is dissolved in sulfamic acid, 30% by weight of a liquid in which aluminum, titanium and zinc are dissolved in sulfuric acid, and 20% by weight in a liquid in which barium and magnesium are dissolved in nitric acid The mixture of the decontamination agent and the incineration ash that settled at the bottom after the decontamination treatment of the radioactively contaminated incineration ash is dried to a moisture content of about 3%,
The radioactive material is surrounded and fixed with water glass by stirring and kneading for 20 to 40 minutes at room temperature while mixing the dried mixture and 6 to 10% of the fixing agent according to claim 1. A method for immobilizing a radioactive substance characterized by comprising:   The fixed radioactive material according to claim 3 or 4, wherein the immobilized radioactively contaminated incineration ash and a mixture of the decontamination agent and the incineration ash are granulated into pellets. Method. 6. The radioactive substance immobilization method according to claim 3, wherein the radioactively contaminated incineration ash is incineration ash of sewage sludge.

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