A method for treating radioactively contaminated graphite

Abstract

This application provides a method for treating radioactively contaminated graphite. The method includes the following steps: separating the radioactive contamination layer of the graphite to obtain a graphite powder sample formed from the separated contamination layer; mixing the graphite powder sample with hydrophilic inorganic nanoparticles to form a modified graphite sample; and mixing the modified graphite sample with cement to prepare a cementitious body. This method for treating radioactively contaminated graphite can reduce the amount of radioactively contaminated graphite to be treated.

Description

Technical Field

[0001] This application relates to the field of radioactive contaminant treatment technology, and in particular to a method for treating radioactive contaminated graphite. Background Technology

[0002] Graphite is resistant to high temperatures and radiation, possesses high mechanical strength, good chemical stability, and excellent thermal conductivity. It is commonly used in reactors as a neutron moderator and neutron reflector. In Generation IV reactors, high-temperature gas-cooled reactors and molten salt reactors also employ graphite as a moderator. It is estimated that reactor decommissioning worldwide will generate tens of millions of tons of waste graphite. Therefore, the treatment and disposal of large quantities of waste graphite is one of the challenges facing reactor decommissioning projects.

[0003] In related technologies, radioactive contaminated graphite is treated using incineration technologies (laser incineration, fluidized bed incineration, steam pyrolysis incineration, etc.), fixation / solidification technologies (asphalt / epoxy resin mixtures, epoxy resin, asphalt impregnation technology, cement curing, glass curing, graphite self-propagating ceramic curing, etc.), and isotope separation technologies. However, the fixation / solidification technologies in these technologies directly solidify radioactive contaminated graphite with cement, which greatly increases the amount of radioactive contaminated graphite to be treated, thereby significantly increasing the treatment cost. Summary of the Invention

[0004] In view of this, the main objective of the embodiments of this application is to provide a method for treating radioactively contaminated graphite that can reduce the amount of radioactively contaminated graphite to be treated.

[0005] To achieve the above objectives, the technical solution of this application embodiment is implemented as follows:

[0006] This application provides a method for treating radioactively contaminated graphite, the method comprising:

[0007] The radioactive contamination layer of the radioactive contamination graphite is separated to obtain a graphite powder sample formed from the separated radioactive contamination layer.

[0008] The graphite powder sample was mixed with hydrophilic inorganic nanoparticles to form a modified graphite sample.

[0009] The modified graphite sample was mixed with cement to prepare a cement-cured body.

[0010] In one embodiment, separating the radioactive contamination layer from the radioactive contaminated graphite specifically includes the following steps:

[0011] Determine the thickness of the radioactive contamination layer;

[0012] The outer surface layer of the radioactive contaminated graphite with the measured thickness was separated.

[0013] In one embodiment, separating the outer surface layer of the radioactive contaminated graphite with the measured thickness includes the following steps:

[0014] The thickness was measured by grinding and polishing the outer surface layer of the radioactive contaminated graphite using a polishing machine.

[0015] In one embodiment, determining the thickness of the radioactive contamination layer specifically includes the following steps:

[0016] Obtain a measurement sample of the radioactively contaminated graphite;

[0017] The thickness of the radioactive contamination layer is determined by laser-induced spectral stripping and analysis of the elemental content in the measured sample, based on the elemental content.

[0018] In one embodiment, the element content includes the content of at least one of Cs, Co, Sr and Cl.

[0019] In one embodiment, determining the thickness of the radioactive contamination layer based on the element content specifically includes the following steps:

[0020] When the element content in the measured sample after stripping reaches the set value, the thickness of the radioactive contamination layer is determined by weighing and thickness measurement.

[0021] In one embodiment, the hydrophilic inorganic nanoparticles are hydrophilic inorganic nanoparticles of silicon dioxide.

[0022] In one embodiment, the hydrophilic inorganic nanoparticle silica in the modified graphite sample has a mass ratio greater than or equal to 0.5% and less than or equal to 8%.

[0023] In one embodiment, the hydrophilic inorganic nanoparticles are introduced into the surface of graphite particles in the graphite powder sample by physical mixing to form the modified graphite sample.

[0024] In one embodiment, the processing method includes:

[0025] The radioactive contaminated graphite is cut to obtain multiple measurement samples of the same shape;

[0026] Laser-induced spectral stripping and analysis were performed to determine the elemental content in some of the measured samples.

[0027] The thickness of each of the measured samples is determined by polishing with a polishing machine.

[0028] This application provides a method for treating radioactively contaminated graphite. On one hand, the radioactive contamination layer of the graphite is separated to obtain a graphite powder sample formed from the separated contamination layer. That is, in this method, the entire radioactively contaminated graphite is not directly mixed and cured with cement; instead, only the radioactive contamination layer is peeled off for mixing and curing with cement. This significantly reduces the amount of radioactively contaminated graphite to be treated, thereby lowering the treatment cost. On the other hand, the graphite powder sample is mixed with hydrophilic inorganic nanoparticles to form a modified graphite sample, and the modified graphite sample is mixed with cement to prepare a cement-cured body. Since hydrophilic inorganic nanoparticles themselves have abundant surface hydroxyl groups and good hydrophilic properties, the addition of hydrophilic inorganic nanoparticles modifies the graphite powder sample, greatly enhancing its hydrophilicity and improving the mixing and curing effect with cement. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating a method for treating radioactively contaminated graphite according to an embodiment of this application. Detailed Implementation

[0030] In the description of the embodiments of this application, technical terms such as "first," "second," and "third" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] One embodiment of this application provides a method for treating radioactively contaminated graphite. Please refer to [link to relevant documentation]. Figure 1 The processing method includes the following steps;

[0033] Step S1: Separate the radioactive contamination layer from the radioactive contamination graphite to obtain a graphite powder sample formed from the separated radioactive contamination layer.

[0034] Step S2: Mix the graphite powder sample with hydrophilic inorganic nanoparticles to form a modified graphite sample.

[0035] Step S3: Mix the modified graphite sample with cement to prepare a cement-cured body.

[0036] Specifically, radioactive contaminated graphite is graphite that has been contaminated by radioactivity. For example, for low-radioactive contaminated graphite, a radioactive contamination layer has formed on its surface, while the interior is less contaminated or uncontaminated.

[0037] Therefore, after the radioactive contamination layer of the radioactive contamination graphite is separated, it forms a powdered graphite sample. On the one hand, by making the separated radioactive contamination layer into a powder, it is easier to mix the graphite powder sample with hydrophilic inorganic nanoparticles, which can improve the mixing uniformity of the two. On the other hand, it is easier for the mixed modified graphite sample to fully mix and react with cement, thereby improving the preparation effect of cement solidified body.

[0038] Hydrophilic inorganic nanoparticles possess abundant surface hydroxyl groups, thus exhibiting good hydrophilic properties. Mixing hydrophilic inorganic nanoparticles with graphite powder samples can enhance the hydrophilicity of graphite, thereby improving the mixing and preparation effect of modified graphite samples and cement.

[0039] The specific type of hydrophilic inorganic nanoparticles can be determined according to the actual situation. For example, hydrophilic inorganic nanoparticles are hydrophilic inorganic nanoparticles of silicon dioxide.

[0040] It should be noted that the content of hydrophilic inorganic nanoparticle silica in the modified graphite sample can be set according to the actual situation.

[0041] For example, the mass ratio of hydrophilic inorganic nanoparticles (silica) in the modified graphite sample is greater than or equal to 0.5% and less than or equal to 8%, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. This can effectively improve the hydrophilicity of the modified graphite sample.

[0042] In fact, the method for treating radioactively contaminated graphite in this application is a combined physical-chemical treatment method. That is, the radioactive contamination layer of radioactively contaminated graphite is separated to form a powdered graphite sample, and then the graphite powder sample is chemically modified with hydrophilic inorganic nanoparticles to form a modified graphite sample, thereby improving its hydrophilicity, and then mixed with cement to prepare a cement solidified body.

[0043] In the method for treating radioactively contaminated graphite of this application, on the one hand, the radioactive contamination layer of the radioactively contaminated graphite is separated to obtain a graphite powder sample formed from the separated radioactive contamination layer. That is, in the method for treating radioactively contaminated graphite of this application, the entire radioactively contaminated graphite is not directly mixed with cement and cured; instead, only the radioactive contamination layer of the radioactively contaminated graphite is peeled off for mixing and curing with cement. This significantly reduces the amount of radioactively contaminated graphite to be treated, thereby reducing the treatment cost. On the other hand, the graphite powder sample is mixed with hydrophilic inorganic nanoparticles to form a modified graphite sample, and the modified graphite sample is mixed with cement to prepare a cement-cured body. Thus, since hydrophilic inorganic nanoparticles themselves have abundant surface hydroxyl groups and good hydrophilic properties, by adding hydrophilic inorganic nanoparticles to modify the graphite powder sample, the hydrophilic properties of the graphite powder sample are greatly enhanced, thereby improving the mixing and curing effect with cement.

[0044] In one embodiment, separating the radioactive contamination layer of radioactively contaminated graphite specifically includes the following steps:

[0045] Step S1: Determine the thickness of the radioactive contamination layer.

[0046] Step S2: Separate the outer surface layer of radioactive contaminated graphite with measured thickness.

[0047] In other words, the thickness of the radioactive contamination layer needs to be measured before it can be separated. After determining the thickness of the radioactive contamination layer, the outer surface layer of the radioactive contamination graphite can be processed to separate the outer surface layer of the radioactive contamination graphite of the measured thickness, i.e., the radioactive contamination layer.

[0048] This allows for more precise separation of the radioactive contamination layer, improving the treatment effect of radioactive contaminated graphite.

[0049] It should be noted that, in some embodiments, for the same radioactively contaminated graphite, that is, when the thickness of the radioactive contamination layer of the radioactively contaminated graphite is the same or close, a small number of samples can be taken for thickness measurement, and the radioactive contamination layer of all radioactively contaminated graphite can be separated according to the measured thickness, thereby greatly improving the processing efficiency.

[0050] Of course, in other embodiments, the thickness of different radioactive contaminated graphite can be measured separately to separate the respective radioactive contaminated layers based on their measured thicknesses.

[0051] It should be noted that the specific method for separating the outer surface layer of radioactive contaminated graphite for thickness measurement can be determined based on the actual situation.

[0052] For example, the thickness of the outer surface layer of radioactively contaminated graphite can be measured by grinding and polishing. This grinding and polishing method allows for more precise separation and thickness measurement of the radioactive contamination layer, enabling precision grinding and polishing. Simultaneously, the separated radioactive contamination layer can be ground into powdered graphite samples for subsequent processing.

[0053] In one embodiment, determining the thickness of the radioactive contamination layer specifically includes the following steps:

[0054] Step S1: Obtain a measurement sample of radioactively contaminated graphite.

[0055] Step S2: Laser-induced spectral stripping and elemental analysis are used to measure the elemental content in the sample, and the thickness of the radioactive contamination layer is determined based on the elemental content. This allows for a more accurate determination of the thickness of the radioactive contamination layer in radioactive graphite, reducing the amount of radioactive graphite to be treated while ensuring effective treatment.

[0056] Specifically, laser-induced breakdown spectroscopy (LIBS) uses an ultrashort pulse laser to focus on the sample surface to form plasma, and then analyzes the plasma emission spectrum to determine the material composition and content of the sample.

[0057] In step S2, by simultaneously peeling and analyzing the elemental content in the sample, the thickness of the radioactive contamination layer of the radioactive graphite can be determined more effectively.

[0058] The elemental content of the measured sample is analyzed, and the elemental content can be the content of one or more elements including Cs (cesium), Co (cobalt), Sr (strontium), and Cl (chlorine). This allows for a relatively accurate measurement of the thickness of the radioactive contamination layer.

[0059] It should be noted that, depending on the actual situation, the elemental content measurement can be performed on only a portion of the samples obtained from radioactively contaminated graphite, or it can be performed on all the samples obtained from radioactively contaminated graphite.

[0060] For example, a method for treating radioactively contaminated graphite includes the following steps:

[0061] Step S1: Cut the radioactive contaminated graphite to obtain multiple measurement samples of the same shape.

[0062] Step S2: Spectral stripping and analysis of the sample by laser-induced measurement of elemental content.

[0063] Step S3: The thickness of each sample is measured by grinding and polishing with a polishing machine. This greatly improves the efficiency of treating radioactively contaminated graphite. Furthermore, using samples of the same shape improves the accuracy of separating the radioactive contamination layer, thus enhancing the effectiveness of treating radioactively contaminated graphite.

[0064] It should be noted that the specific shape of the sample can be set according to the actual situation, such as square or round.

[0065] In one embodiment, determining the thickness of the radioactive contamination layer based on elemental content specifically includes the following steps:

[0066] Once the elemental content in the stripped sample reaches the set value, the thickness of the radioactive contamination layer is determined using a gravimetric method and a thickness measurement method. Therefore, by combining laser-induced emission spectroscopy, gravimetric analysis, and thickness measurement, the thickness of the radioactive contamination layer can be determined more accurately.

[0067] Specifically, the set value is used to determine the boundary between the radioactive contaminated layer and the uncontaminated layer within the radioactive contaminated graphite, and it can be determined according to the actual situation.

[0068] For example, the value is set to 0 or approximately 0.

[0069] The weighing method can be used to measure weight using a precision balance. The thickness measurement method can be used to measure thickness using a thickness gauge.

[0070] In one embodiment, the method for treating radioactively contaminated graphite specifically includes: introducing hydrophilic inorganic nanoparticles into the surface of graphite particles in a graphite powder sample through physical mixing to form a modified graphite sample. This allows the hydrophilic inorganic nanoparticles to accumulate on the surface of the graphite particles in the graphite powder sample, significantly enhancing the hydrophilic properties of the modified graphite sample.

[0071] In one specific embodiment, the method for treating radioactively contaminated graphite includes the following steps:

[0072] Step S1: Cut the radioactive contaminated graphite using an abrasive saw to obtain cut samples. Grind the edges of the cut samples with fine sandpaper to obtain several measurement samples of a certain shape (square or round). Place 2-3 samples in a sealed working chamber with a quartz glass window. Use LIBS (laser-induced emission spectroscopy) to analyze and measure the content of elements such as Cs, Co, Sr, and Cl in the samples while peeling them off, until the element content in the measurement samples is approximately 0. Remove the measurement samples and weigh and measure them using a precision balance and thickness gauge to determine the thickness of the radioactive contamination layer.

[0073] Step S2: Place the cut sample obtained in step S1 into a polishing machine, start the polishing machine to perform precision polishing on the cut sample, and precisely control the polishing thickness to the thickness of the radioactive contamination layer determined in step S1. Then collect all the polishing dust, i.e., the graphite powder sample.

[0074] Step S3: Introduce 0.5%-8% (by mass) of hydrophilic inorganic nanoparticle silica into the surface of graphite particles in the graphite powder sample through physical mixing to enhance the hydrophilicity of the modified graphite sample.

[0075] Step S4: Weigh a certain amount of modified graphite sample, mix it with ordinary silicate cement, water, additives, etc. in a certain proportion until it is uniform, prepare a cement solidified body sample and test the performance of the cement solidified body.

[0076] The cement solidified body obtained by this method has a inclusion capacity of 20% to 30% for modified graphite samples, which can well meet the process requirements for subsequent low-level waste cement solidification.

[0077] In the description of this application, the references to terms such as "in one embodiment," "in some embodiments," "in a specific embodiment," or "exemplary," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the embodiments of this application. In this application, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine the different embodiments or examples described in this application, as well as the features of the different embodiments or examples.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit the application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for treating radioactively contaminated graphite, characterized in that, The processing method includes: The radioactive contamination layer of the radioactive graphite is separated to obtain a graphite powder sample formed from the separated radioactive contamination layer; the thickness of the radioactive contamination layer is determined; a measurement sample of the radioactive graphite is obtained; the elemental content in the measurement sample is analyzed by laser-induced spectral stripping to determine the thickness of the radioactive contamination layer based on the elemental content; when the elemental content in the stripped measurement sample reaches a set value, the thickness of the radioactive contamination layer is determined by weighing and thickness measurement; the outer surface layer of the radioactive graphite with the determined thickness is separated; the outer surface layer of the radioactive graphite with the determined thickness is polished using a polishing machine. The graphite powder sample was mixed with hydrophilic inorganic nanoparticles to form a modified graphite sample. The modified graphite sample was mixed with cement to prepare a cement-cured body.

2. The method for treating radioactively contaminated graphite according to claim 1, characterized in that, The elemental content includes the content of at least one of Cs, Co, Sr and Cl.

3. The method for treating radioactively contaminated graphite according to claim 1 or 2, characterized in that, The hydrophilic inorganic nanoparticles are hydrophilic inorganic nanoparticles of silicon dioxide.

4. The method for treating radioactively contaminated graphite according to claim 3, characterized in that, The mass ratio of the hydrophilic inorganic nanoparticles silica in the modified graphite sample is greater than or equal to 0.5% and less than or equal to 8%.

5. The method for treating radioactively contaminated graphite according to claim 1 or 2, characterized in that, The hydrophilic inorganic nanoparticles are introduced into the surface of the graphite particles in the graphite powder sample through physical mixing to form the modified graphite sample.

6. The method for treating radioactively contaminated graphite according to claim 1 or 2, characterized in that, The processing method includes: The radioactive contaminated graphite is cut to obtain multiple measurement samples of the same shape; Laser-induced spectral stripping and analysis were performed to determine the elemental content in some of the measured samples. The thickness of each of the measured samples is determined by polishing with a polishing machine.

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