Analysis method for element content in waste incineration ash of nuclear power plant

Abstract

The invention provides a method for analyzing the content of elements in waste incineration ash of a nuclear power plant. The method comprises the following steps: preparing incineration ash into ash powder; performing heat treatment on the ash powder; dissolving the ash powder subjected to heat treatment to obtain a solution of elements to be detected; measuring the content of the to-be-measured element in the solution of the to-be-measured element; wherein the to-be-detected elements comprise metal elements and non-metal elements at the same time. The method disclosed by the invention can be used for simultaneously measuring the contents of various elements in the waste incineration ash of the nuclear power plant.

Description

Technical Field

[0001] The invention belongs to the research field of waste treatment technology, and in particular relates to a method for analyzing the element content in nuclear power plant waste incineration ash. Background Art

[0002] According to the Chinese Radioactive Waste Classification Method (GB 9133-1995), low- and medium-level radioactive solid waste refers to solid waste containing or contaminated with radionuclides with a specific activity of ≤4×10 10 Bq / kg (5a≤ half-life≤30a) or 4×10 9 Bq / kg (half-life>30a) of solid waste. This type of waste contains no or only a very small amount of long-lived transuranic nuclides. Since low- and intermediate-level solid waste accounts for 90% of the total volume of radioactive solid waste, the effective treatment method for low- and intermediate-level solid waste is volume reduction to achieve the principle of minimizing nuclear waste.

[0003] Incineration volume reduction is a better volume reduction treatment method. The ash has good thermal stability, but since most of the radioactive nuclides in the waste are retained in the ash (95% to 99%), the ash needs to be solidified.

[0004] Therefore, in order to advantageously carry out the above-mentioned solidification process, it is necessary to analyze the element content in the incineration ash. Summary of the invention

[0005] In view of this, the main purpose of the present invention is to provide a method for analyzing the element content in incineration ash, especially in nuclear power plant waste incineration ash, and more especially in nuclear power plant combustible solid waste incineration ash. The method can realize the simultaneous measurement of multiple elements in nuclear power plant waste incineration ash, the measurement results are accurate, and the reagent consumption is small, the operation is simple, and it is relatively friendly to the environment.

[0006] To achieve the above object, the present invention provides a method for analyzing the element content in the ash from the incineration of nuclear power plant waste. The method comprises the following operations:

[0007] preparing the incineration ash into ash powder;

[0008] thermally treating the ash powder;

[0009] dissolving the heat-treated ash powder to obtain a solution to be tested; and

[0010] Measuring the content of the element to be tested in the solution to be tested;

[0011] The elements to be detected include both metal elements and non-metal elements.

[0012] In some embodiments, heat treating the ash powder comprises: performing the heat treatment in the presence of an alkali flux under temperature program control. In some specific embodiments, the alkali flux comprises one or more of sodium hydroxide, potassium hydroxide or lithium hydroxide.

[0013] In some embodiments, the temperature raising program is: from room temperature to 300°C: 2h; from 300°C to the first temperature: 0.5h; keeping at the first temperature for 0.5h-1h;

[0014] The first temperature is a temperature at which the ash powder is incinerated and the alkali flux is completely melted.

[0015] In some embodiments, the first temperature is 500°C to 550°C.

[0016] In some embodiments, the mass ratio of the ash powder to the alkali flux is 1:5 to 1:10. In a specific embodiment, the mass ratio of the ash powder to the alkali flux is 1:10.

[0017] In some embodiments, preparing the incineration ash into ash powder includes: grinding the incineration ash at 1000 rpm to 1500 rpm, then drying at a temperature of 100° C. to 105° C., and then sieving through a 100-200 mesh sieve.

[0018] In some embodiments, the dissolving comprises: for every 0.10 g of ash powder, first adding 2 mL to 10 mL of deionized water to soak for more than 3 hours, and then adding 2 mL to 5 mL of 30 v / v% to 50 v / v% hydrochloric acid.

[0019] In some embodiments, the measurement includes using ICP-MS, taking indium as the internal standard element, sequentially measuring a series of standard substances to draw a working standard curve, then measuring a blank control and a solution of the element to be measured, and determining the concentration of each element to be measured using a standard curve method.

[0020] In some embodiments, the concentrations of the series of standard solutions are 0, 0.02 ng / mL, 0.1 ng / mL, 0.5 ng / mL, 2 ng / mL, 5 ng / mL, and 10 ng / mL, respectively, the concentration of indium is 1 ng / mL, and a working standard curve is drawn with the concentration of the element to be measured as the horizontal axis and the ratio of the ion current intensity of the element to be measured to indium as the vertical axis.

[0021] In some embodiments, the elements to be detected include two or more of cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium, chromium, and iodine, preferably all of the elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of an implementation method of the present application.

[0023] Figure 2 It is a comparison chart of the measured value and the theoretical value of the element to be measured in Example 1 of the present invention.

[0024] Figure 3 This is a comparison chart of the measured value and the theoretical value of the element to be measured in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] The following specific embodiments are discussed in conjunction with the accompanying drawings to exemplary embodiments. The specific embodiments included herein should not be construed as limitations of the present invention. Further, although specific language may be used to describe features, actions and / or structures in the embodiments described herein, the claims are not limited to the described features, actions and / or structures. It will be appreciated by those skilled in the art that other embodiments including improvements are within the spirit and scope of the present invention.

[0026] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0027] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the invention belongs.

[0028] In practice, there are many types of low- and medium-level solid wastes, of which about 40% are combustible wastes, including various fiber materials (such as cotton fabrics such as work clothes, wood, paper, etc.), rubber and plastic products, and ion exchange resins, etc. During incineration and volume reduction, combustible wastes are converted into inorganic residues (ash) and waste gas after incineration treatment, which has a high waste volume reduction ratio. The ash produced by incineration has good thermal stability, but the bottom slag and fly ash generated by incineration are still secondary hazardous wastes. Most of the radioactive nuclides in the waste (95% to 99%) will remain in the ash, so the ash needs to be solidified.

[0029] The elements of nuclear power plant solid waste incineration ash that are of key concern involve fission nuclides, radionuclides produced by neutron activation, and heavy metal elements, and it is difficult to achieve complete combustion during the incineration of nuclear power plant waste, so its incineration ash matrix is ​​complex, including inorganic components, some unburned organic matter, and more incompletely burned carbon black, and the elements that usually need to be detected also include metal elements and non-metal elements. This makes it not only complicated in the method of acid dissolution (such as CN114878672A, HJ781-2016, HJ786-2016, HJ999-2018), but also difficult to control experimental parameters, time-consuming and labor-intensive, and also consumes a large amount of various concentrated acids, and non-metal elements that are volatile under acidic conditions cannot be effectively measured. Therefore, a method for analyzing the content of elements in nuclear power plant waste incineration ash is needed, which can effectively solve the problem that organic matter and a large amount of carbon black in incineration ash are difficult to digest and metal elements and non-metal elements are difficult to effectively measure at the same time.

[0030] Based on this, the present application provides a method for analyzing the element content in the ash from the incineration of nuclear power plant waste. Through the method of ashing digestion + alkali fusion, the elements to be tested are fixed in the fixing agent, which avoids the loss of volatile elements and helps to recover all the elements to be tested (including both metal elements and non-metal elements, such as cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium, chromium, and iodine), solving the problems of the difficulty in digesting organic matter and a large amount of carbon black in the existing methods and the simultaneous effective measurement of metal elements and non-metal elements.

[0031] In this application, "metallic elements" and "non-metallic elements" have the conventional meanings in the art. Metallic elements include, but are not limited to, cobalt, strontium, cesium, manganese, zirconium, niobium, silver and chromium; non-metallic elements include, but are not limited to, tellurium and iodine.

[0032] Reference Figure 1 , the method of the present invention comprises the following operations:

[0033] S1: preparing incineration ash into ash powder;

[0034] S2: heat treating the ash powder;

[0035] S3: dissolving the heat-treated ash powder to obtain a solution to be tested; and

[0036] S4: Measure the content of the element to be tested in the solution to be tested.

[0037] In the present invention, "nuclear power plant waste incineration ash" refers to the combustible solid waste incineration ash of a nuclear power plant, which is the residual material formed after the combustible solid waste generated during the operation of the nuclear power plant is incinerated.

[0038] In the present invention, preparing the incineration ash into ash powder S1 includes grinding, drying and sieving the incineration ash to make the particles of the sample to be tested finer, more uniform, and convenient for subsequent processing, while removing moisture from the sample. In the present invention, preparing the incineration ash into ash powder includes: grinding the incineration ash at 1000 rpm to 1500 rpm for 2 to 3 minutes. Exemplarily, the incineration ash can be ground at grinding rates such as 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, and 1500 rpm. In the present invention, preparing the incineration ash into ash powder also includes drying the ground incineration ash at a drying temperature of 100°C to 105°C. Exemplarily, the ground incineration ash can be heated by a heating device at 105°C for 1 hour to dry the sample. In the present invention, preparing the incineration ash into ash powder also includes, for example, sieving the dried ash powder through a 100-200 mesh sieve to obtain a uniform and fine ash powder.

[0039] In the present invention, heat treatment S2 of the ash powder includes: heat treatment of the ash powder under the control of a temperature rising program in the presence of an alkali flux. In this way, the organic matter and carbon black in the ash powder are ashed by "ashing digestion + alkali flux". At the same time, the addition of the alkali flux can improve the ashing effect on the one hand, and on the other hand, during the heat treatment process, the alkali flux can react with the elements to be measured in the sample to be measured to form a stable compound, and fix the elements to be measured in the molten solvent, thereby reducing the loss of the elements to be measured, especially the volatile elements, and helping to recover all the elements to be measured, thereby improving the measurement accuracy of the analytical method. The term "ashing" refers to the process of thermally decomposing or converting the organic matter and carbon black in the ash powder into carbides, carbon dioxide, water, etc. The term "alkali flux" refers to a chemical substance that can react with the sample under high temperature conditions to convert the elements to be measured in the sample into a soluble form.

[0040] In some embodiments, the alkaline flux includes one or more of sodium hydroxide, potassium hydroxide, or lithium hydroxide, wherein the melting point of sodium hydroxide is 318.4°C, the melting point of lithium hydroxide is 462°C, and the melting point of potassium hydroxide is 380°C.

[0041] In some embodiments, the mass ratio of ash powder to alkali flux is 1:5 to 1:10. Thus, less alkali flux can not only effectively fix the element to be measured in the ash powder, but also reduce the amount of subsequent dissolving acid, thereby ensuring the accuracy of the measurement result. Exemplarily, the mass ratio of ash powder to alkali flux is 1:10.

[0042] In the present invention, the temperature rise program is: from room temperature to 300°C: 2h; from 300°C to the first temperature: 0.5h; keep warm at the first temperature for 0.5h-1h, and the first temperature is the temperature at which the ash powder is ashed and the alkali flux is completely melted. In the present invention, the temperature at which the incineration ash is ashed and the alkali flux is completely melted is 500°C to 550°C. Thus, heat treatment under the control of the temperature rise program can simultaneously achieve the complete ashing of organic matter and carbon black in the incineration ash and the melting of the alkali flux, so that the elements to be measured in the incineration ash can be retained to the greatest extent, which is beneficial to improve the measurement accuracy of the analytical method. Exemplarily, the temperature rise program is: from room temperature to 300°C in 2 hours; from 300°C to 500°C in 0.5 hours; and keep warm at 500°C for 1 hour. Alternatively, the temperature program is: from room temperature to 300°C in 2 hours; from 300°C to 550°C in 0.5 hours; and maintaining at 550°C for 0.5 hours.

[0043] In the present invention, dissolving the heat-treated ash powder S3 includes adding deionized water to the heat-treated ash powder and adding hydrochloric acid to dissolve. In some embodiments, 2mL to 10mL is used for each treatment of 0.10g ash powder, such as 2mL, 2.5mL, 3mL, 3.5mL, 4mL, 4.5mL, 5mL, 6mL, 7mL, 8mL, 9mL, 10mL of deionized water for more than 3 hours, and then 2mL to 5mL is added, such as 2mL, 2.5mL, 3mL, 3.5mL, 4mL, 4.5mL, 5mL of 30v / v% to 50v / v%, such as 30v / v%, 35v / v%, 40v / v%, 45v / v%, 50v / v% of hydrochloric acid solution. Exemplarily, 5mL of deionized water is used for each treatment of 0.10g ash powder for 3 hours, and then 5mL of 30v / v% hydrochloric acid solution is added. Alternatively, 0.10 g of ash powder was soaked in 2.5 mL of deionized water for 4 hours, and then 2 mL of 40 v / v% hydrochloric acid solution was added.

[0044] In some embodiments, measuring the content of the element to be tested in the test solution S4 includes determining the content of each element using ICP-MS by a standard curve method.

[0045] Furthermore, the measurement S4 includes: a) drawing a standard working curve; and b) measuring the concentration of each element to be measured.

[0046] Further, a standard working curve of an element can be drawn by a method known in the art. Exemplarily, a series of standard solutions with concentrations of the element to be measured being 0, 0.02 ng / mL, 0.1 ng / mL, 0.5 ng / mL, 2 ng / mL, 5 ng / mL, and 10 ng / mL are prepared, and the series of standard solutions uses indium as the internal standard element, and the concentration of indium is 1.0 ng / mL. Then, the series of standard solutions are subjected to ICP-MS testing, and after the test results are obtained, a working standard curve is drawn with the concentration of the element to be measured as the abscissa and the ratio of the ion current intensity of the element to be measured to indium as the ordinate. "ICP-MS" is an analytical instrument that combines inductively coupled plasma (ICP) technology with mass spectrometry, and has high sensitivity.

[0047] Measuring the concentration of each element to be measured may include diluting the dissolved ash sample (for example, diluting with deionized water) so that the concentration of the element to be measured is 0.1 ng / mL to 10 ng / mL to obtain a solution to be measured. By diluting the content of the element to be measured to within the above concentration range, it is helpful to improve the measurement accuracy of the content of the element to be measured.

[0048] The present invention is described in more detail below by examples. It should be understood that the examples described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially. The chemical reagents and drugs used in the examples are all of premium grade purity.

[0049] Example 1: Analysis of the content of cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium and chromium in the ash from the simulated combustible waste incineration of a nuclear power plant

[0050] S1. Use a grinder (Beijing Xuxin Shengke Instrument Equipment Co., Ltd., ST-M200 high-throughput tissue grinder) to grind 5 g of incineration ash at a grinding rate of 1000 rpm for 3 minutes, then place the ground incineration ash in an oven at 105°C to dry for 1 hour, and then pass the dried sample through a 160-mesh sieve to obtain ash powder.

[0051] S2. Weigh 0.10 g of ash powder and 1.00 g of potassium hydroxide respectively, place them in a silver crucible, mix them evenly, and prepare a blank sample without adding ash powder; place the silver crucible in a muffle furnace, and set the heating program as follows: from room temperature to 300°C: 2 hours; from 300°C to 500°C: 0.5 hours, and keep warm at 500°C for 1 hour.

[0052] S3. Add 5 mL of deionized water to the silver crucible and soak for 3 hours, then add 5 mL of 30 v / v% HCl to dissolve.

[0053] S4. Transfer the solution in the silver crucible into a 50 mL PFA volumetric flask, then rinse the silver crucible with deionized water three times, transfer the cleaning solution into the volumetric flask, and then dilute the volume to the mark on the volumetric flask with deionized water, dilute the element to be tested to a concentration in the range of 0.1 ng / mL to 10 ng / mL, and obtain a solution to be tested.

[0054] With indium as the internal standard element, a series of standard solutions of cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium and chromium were prepared, wherein the concentrations of cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium and chromium were 0, 0.02, 0.1, 0.5, 2.0, 5.0 and 10.0 ng / mL, respectively, and the concentration of indium was 1 ng / mL. The series of standard solutions were tested by ICP-MS, and after the test results were obtained, a working standard curve was plotted with the concentration of the element to be tested as the abscissa and the ratio of the ion current intensity of the element to be tested to indium as the ordinate.

[0055] The mass numbers of the elements to be tested in this embodiment are shown in Table 1. The content of each element in the solution to be tested was tested by ICP-MS. The test results were converted to obtain the content of each element to be tested in the ash sample. The test results are shown in Tables 2 and Figure 2 shown.

[0056] Table 1: Analytical mass numbers of each element to be measured in Example 1

[0057] element Analytical mass / amu element Analytical mass / amu element Analytical mass / amu Co 59 Mn 55 Nb 93 Sr 88 Ag 107、109 Cr 52 Zr 90 Te 128、130 Cs 133

[0058] Table 2: Measured and theoretical values ​​of each element in the simulated ash sample

[0059]

[0060] Through Table 2 and Figure 2 It can be seen that the method of the present invention can simultaneously measure multiple elements including metal elements and non-metal elements in the simulated combustible solid waste incineration ash of a nuclear power plant, and the test results are accurate.

[0061] Example 2: Analysis of the contents of cobalt, cesium, chromium, manganese, zirconium, niobium and iodine in the ash from the simulated combustible solid waste incineration of a nuclear power plant

[0062] S1. Use a grinder (Beijing Xuxin Shengke Instrument Equipment Co., Ltd., ST-M200 high-throughput tissue grinder) to grind 5 g of incineration ash at a grinding rate of 1500 rpm for 2 minutes, then place the ground incineration ash in an oven at 110°C and dry it for 0.5 hours, then pass the dried sample through a 160-mesh sieve to obtain ash powder.

[0063] S2. Weigh 0.20 g of ash powder, 1.00 g of sodium hydroxide and 10 ml of deionized water respectively and put them into a silver crucible and mix them evenly. At the same time, prepare a blank sample without adding ash powder; place the silver crucible in a muffle furnace and set the heating program as follows: from room temperature to 300°C: 2 hours; from 300°C to 550°C: 0.5 hour; keep warm at 550°C for 0.5 hour.

[0064] S3. Add 5 mL of deionized water to the silver crucible and soak for 4 hours, then add 4 mL of 40 v / v% HCl to dissolve.

[0065] The solution in the silver crucible was transferred to a 50 mL volumetric flask, and then the silver crucible was rinsed with deionized water for 3 times, and the cleaning solution was transferred to the volumetric flask. After that, the volume was fixed to the scale line of the volumetric flask with deionized water, and the element to be tested was diluted to a concentration in the range of 0.1 ng / mL to 10 ng / mL to obtain a solution to be tested.

[0066] With indium as the internal standard element, a series of standard solutions of cobalt, cesium, chromium, manganese, zirconium, niobium and iodine were prepared, wherein the concentrations of cobalt, cesium, chromium, manganese, zirconium, niobium and iodine were 0, 0.02, 0.1, 0.5, 2.0, 5.0 and 10.0 ng / mL, respectively, and the concentration of indium was 1 ng / mL. The series of standard solutions were tested by ICP-MS, and after the test results were obtained, a working standard curve was plotted with the concentration of the element to be tested as the abscissa and the ratio of the ion current intensity of the element to be tested to indium as the ordinate.

[0067] The mass number of each element selected in this embodiment is shown in Table 3. The content of each element in the solution to be tested was tested by ICP-MS. The test results were converted to obtain the content of each element to be tested in the simulated ash sample. The test results are shown in Tables 4 and Figure 3 shown.

[0068] Table 3: Analytical mass numbers of each element to be measured in Example 2

[0069] element Analytical mass / amu element Analytical mass / amu element Analytical mass / amu Co 59 Cs 133 I 127 Cr 52 Zr 90 Mn 55 Nb 93

[0070] Table 4: Measured and theoretical values ​​of each element in the ash sample

[0071]

[0072] Through Table 4 and Figure 3 It can be seen that the method of the present invention can simultaneously measure multiple metal and non-metal elements in the simulated combustible solid waste incineration ash of a nuclear power plant, and the test results are accurate.

[0073] The analytical method of the present invention realizes the simultaneous and accurate measurement of the key elements cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium, chromium and iodine in the nuclear power plant waste incineration ash, and only a very small amount of alkaline fixative is used in the operation process, the reagent consumption is small, the operation is simple, and it is relatively friendly to the environment.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention.

Claims

1. A method for analyzing the element content in the ash from the incineration of nuclear power plant waste, comprising the following operations: preparing the incineration ash into ash powder; thermally treating the ash powder; dissolving the heat-treated ash powder to obtain a solution of the element to be measured; and Measuring the content of the element to be tested in the solution of the element to be tested; The elements to be detected include both metal elements and non-metal elements.

2. The method according to claim 1, wherein: The heat treatment of the ash powder includes: performing the heat treatment in the presence of an alkali flux under temperature program control. Optionally, the alkali flux includes one or more of sodium hydroxide, potassium hydroxide or lithium hydroxide.

3. The method according to claim 2, wherein: The heating program is: from room temperature to 300°C: 2h; from 300°C to the first temperature: 0.5h; keeping at the first temperature for 0.5h-1h; The first temperature is a temperature at which the ash powder is incinerated and the alkali flux is completely melted.

4. The method according to claim 3, wherein: The first temperature is 500°C to 550°C.

5. The method according to any one of claims 2 to 4, wherein: The mass ratio of the ash powder to the alkali flux is 1:5 to 1:

10. Optionally, the mass ratio of the ash powder to the alkali flux is 1:

10.

6. The method according to any one of claims 1 to 5, wherein: The method of preparing the incineration ash into ash powder comprises: grinding the incineration ash at 1000 rpm to 1500 rpm, drying at a temperature of 100° C. to 105° C., and then sieving through a 100-200 mesh sieve.

7. The method according to any one of claims 1 to 6, wherein: The dissolution comprises: for every 0.10 g of ash powder, firstly adding 2 mL to 10 mL of deionized water to soak for more than 3 hours, and then adding 2 mL to 5 mL of 30 v / v% to 50 v / v% hydrochloric acid.

8. The method according to any one of claims 1 to 7, wherein: The measurement includes using ICP-MS, taking indium as the internal standard element, sequentially measuring a series of standard substances to draw a working standard curve, then measuring a blank control and a solution of the element to be measured, and determining the concentration of each element to be measured using a standard curve method.

9. The method according to claim 8, wherein: The concentrations of the series of standard solutions are 0, 0.02 ng / mL, 0.1 ng / mL, 0.5 ng / mL, 2 ng / mL, 5 ng / mL, and 10 ng / mL, respectively; the concentration of indium is 1 ng / mL; and the working standard curve is plotted with the concentration of the element to be measured as the abscissa and the ratio of the ion current intensity of the element to be measured to indium as the ordinate.

10. The method according to any one of claims 1 to 9, wherein: The elements to be detected include two or more of cobalt, strontium, cesium, manganese, zirconium, niobium, silver, tellurium, chromium and iodine, preferably all of the elements.

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