Preparation method of high-stability strontium-cesium ceramic solidified body

Abstract

The invention discloses a preparation method of a high-stability strontium-cesium ceramic solidified body, and belongs to the technical field of nuclear waste industrial treatment and application. According to the invention, an aluminum-silicon molecular sieve is used as a base material, the aluminum-silicon molecular sieve and strontium-cesium wastes are mixed and pressed, and the strontium-cesium ceramic solidified body with good chemical stability is prepared through three times of calcination and glaze spraying. According to the invention, the problem of volatilization of Cs under a high-temperature condition is solved; meanwhile, the strontium-cesium ceramic solidified body with good chemical stability is obtained, and a foundation is laid for research and development of solidification of 137Cs and 90Sr separated from high-level liquid waste.

Description

Technical Field

[0001] The invention relates to the technical field of industrial treatment and application of nuclear waste, and in particular to a method for preparing a high-stability strontium-cesium ceramic solidified body. Background Art

[0002] High-level waste (HLW) is one of the most difficult forms of nuclear waste to handle, and it mainly exists in the form of waste liquid (wastewater). Although the volume of HLW is less than 1% of the volume of nuclear waste produced by the nuclear fuel cycle, the radioactivity it contains exceeds 99% of the total radioactivity of the nuclear fuel cycle. Due to the complex composition and high volatility of HLW, it puts forward more stringent requirements on the adaptability (multi-nuclide, multi-component), inclusiveness (high solid solubility) and stability (mechanical, thermal and irradiation stability, etc.) of its solidification matrix.

[0003] Due to its inherent spatial pore structure, cesium garnet is considered to be the best carrier for permanent consolidation of radioactive cesium ions. Since cesium and strontium are both alkali metals, they can be solidified synergistically. The traditional method of solidifying cesium and strontium is to grind and press into shape by adding rocks, alkali manganese ore, etc., and calcine in the air at high temperatures of 1100℃-1300℃; however, cesium is generally easy to volatilize at temperatures above 1000℃, causing nuclide leakage. Summary of the invention

[0004] In view of the problems of fixation, volatilization and loss of cesium in the prior art, the present invention provides a method for preparing a highly stable strontium-cesium ceramic solid body, which can be applied to the preparation of cesium source cores, improve the recycling of nuclear waste, and also provide a new solidification method for the permanent disposal of strontium-cesium nuclear waste.

[0005] The present invention first provides a method for preparing a strontium-cesium ceramic solid body, comprising the following steps:

[0006] (1) mixing aluminum silicon molecular sieve and high-radiation strontium-cesium waste uniformly, pressing and molding, and calcining to obtain primary cesium garnet;

[0007] (2) crushing and grinding the primary cesium garnet, pressing and molding, and calcining to obtain secondary cesium garnet;

[0008] (3) Spraying glaze on the secondary cesium garnet, and then calcining to obtain the strontium-cesium ceramic solid body.

[0009] In the above preparation method, the aluminum silicon molecular sieve is a NaY molecular sieve; specifically, the molar ratio of SiO2 / Al2O3 in the NaY molecular sieve may be 4.8-5.6:1;

[0010] The mass percentage of the high-radiation strontium-cesium waste is 10%-30% based on the total mass of the aluminum silicon molecular sieve and the high-radiation strontium-cesium waste;

[0011] The glaze is composed of glaze and nickel nitrate solution; specifically, the volume ratio of the glaze to the nickel nitrate solution can be 100:(1-2); the concentration of the nickel nitrate solution can be 0.5-1g / L.

[0012] In the above-mentioned preparation method, in step (1), the pressure of the pressing molding is 5-10 MPa;

[0013] The calcination is carried out in an air atmosphere;

[0014] The calcination temperature is 700-800°C;

[0015] The calcination time is 1-2h;

[0016] The heating rate of the calcination is 5-10°C / min.

[0017] In the above-mentioned preparation method, in step (2), the pressure of the pressing molding is 8-10 MPa;

[0018] The calcination is carried out in an inert atmosphere;

[0019] The calcination temperature is 800-1000°C;

[0020] The calcination time is 1-2h;

[0021] The heating rate of the calcination is 5-10°C / min.

[0022] In the above-mentioned preparation method, in step (3), the number of times of spraying the glaze is 3-5 times;

[0023] The calcination is carried out in an air atmosphere;

[0024] The calcination temperature is 700-1000°C;

[0025] The calcination time is 1-2h;

[0026] The heating rate of the calcination is 5-10°C / min.

[0027] In the above method, the glaze is a ceramic glaze, which can be a fusible glaze (below 1100°C), a medium-temperature glaze (1100-1250°C) or a high-temperature glaze (above 1250°C); it is a product purchased on the market, generally composed of feldspar, kaolin and quartz.

[0028] In the above preparation method, the high-level strontium-cesium waste is solid.

[0029] In the above preparation method, the inert atmosphere is argon or nitrogen atmosphere.

[0030] The present invention also provides a method for solidifying and treating high-level radioactive waste strontium and cesium, comprising the following steps:

[0031] (1) mixing aluminum silicon molecular sieve and high-radiation strontium-cesium waste uniformly, pressing and molding, and calcining to obtain primary cesium garnet;

[0032] (2) crushing and grinding the primary cesium garnet, pressing and molding, and calcining to obtain secondary cesium garnet;

[0033] (3) Spraying glaze on the secondary cesium garnet, and then calcining to obtain the strontium-cesium ceramic solid body.

[0034] In the above method, the aluminum silicon molecular sieve is a NaY molecular sieve; specifically, the molar ratio of SiO2 / Al2O3 in the NaY molecular sieve may be 4.8-5.6:1;

[0035] The mass percentage of the high-radioactive strontium-cesium waste is 10%-30% based on the total mass of the aluminum silicon molecular sieve and the high-radioactive strontium-cesium waste;

[0036] The glaze is composed of glaze and nickel nitrate solution; specifically, the volume ratio of the glaze to the nickel nitrate solution may be 100:1-2; the concentration of the nickel nitrate solution may be 0.5-1 g / L.

[0037] In the above method, the glaze is a ceramic glaze, which can be a fusible glaze (below 1100°C), a medium-temperature glaze (1100-1250°C) or a high-temperature glaze (above 1250°C); it is a product purchased on the market, generally composed of feldspar, kaolin and quartz.

[0038] In the above method, in step (1), the pressure of the pressing molding is 5-10 MPa;

[0039] The calcination is carried out in an air atmosphere;

[0040] The calcination temperature is 700-800°C;

[0041] The calcination time is 1-2h;

[0042] The heating rate of the calcination is 5-10°C / min.

[0043] In the above method, in step (2), the pressure of the pressing molding is 8-10 MPa;

[0044] The calcination is carried out in an inert atmosphere;

[0045] The calcination temperature is 800-1000°C;

[0046] The calcination time is 1-2h;

[0047] The heating rate of the calcination is 5-10°C / min.

[0048] In the above-mentioned preparation method, in step (3), the number of times of spraying the glaze is 3-5 times;

[0049] The calcination is carried out in an air atmosphere;

[0050] The calcination temperature is 700-1000°C;

[0051] The calcination time is 1-2h;

[0052] The heating rate of the calcination is 5-10°C / min.

[0053] In the above method, the high-level strontium-cesium waste is solid.

[0054] In the above preparation method, the inert atmosphere is argon or nitrogen atmosphere.

[0055] The present invention has the following advantages and outstanding technical effects: the method provided by the present invention is to prepare a strontium-cesium ceramic solid body under relatively mild conditions by using a glaze spraying and three-time calcination method; the present invention solves the problem of Cs volatilization under high temperature conditions; at the same time, a strontium-cesium ceramic solid body with good chemical stability is obtained, which is a good method for the research and development of separation of high-level radioactive liquid waste. 137 Cs, 90 Sr solidification laid the foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 1 is the X-ray diffraction pattern of the strontium-cesium ceramic solid body prepared in Example 1-3. DETAILED DESCRIPTION

[0057] The present invention provides a method for preparing a strontium-cesium ceramic solidified body or a method for solidifying and treating high-level radioactive waste strontium-cesium, comprising the following steps:

[0058] (1) mixing aluminum silicon molecular sieve and high-radiation strontium-cesium waste uniformly, pressing and molding, and calcining to obtain primary cesium garnet;

[0059] (2) crushing and grinding the primary cesium garnet, pressing and molding, and calcining to obtain secondary cesium garnet;

[0060] (3) Spraying glaze on the secondary cesium garnet, and then calcining to obtain the strontium-cesium ceramic solid body.

[0061] The method of the present invention uses a glaze spraying and three-time calcination method to prepare a strontium-cesium ceramic solid body, which solves the problem of Cs volatilization under high temperature conditions; at the same time, a strontium-cesium ceramic solid body with good chemical stability is obtained. After leaching for 21 days at 70°C, the normalized leaching rates of strontium and cesium in the solid body are very low, which provides a basis for the research and development of separation of high-level radioactive waste. 137 Cs, 90 Sr solidification laid the foundation.

[0062] The present invention is further described in detail below in conjunction with specific embodiments. The given examples are only for illustrating the present invention, rather than for limiting the scope of the present invention.

[0063] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0064] The quantitative tests in the following examples were all repeated three times, and the results were averaged.

[0065] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0066] The aluminum silicon molecular sieve used in the following examples and comparative examples is NaY molecular sieve with a SiO2 / Al2O3 molar ratio of 5.2:1, purchased from Tianjin Nanhua Catalyst Co., Ltd.

[0067] The composition of the simulated strontium-cesium high-level waste liquid used in the following examples and comparative examples is shown in Table 1 below.

[0068] Table 1 Simulated strontium-cesium high-level waste liquid (anion is NO3 - )

[0069] element Simulated liquid mg / L <![CDATA[Ba 2+ ]]> 379 <![CDATA[Cs + ]]> 449 <![CDATA[Fe 3+ ]]> 0.19 <![CDATA[Mo 6+ ]]> 27 <![CDATA[Na + ]]> 11.4 <![CDATA[Pd 2+ ]]> 0.606 <![CDATA[Rb 2+ ]]> 69 <![CDATA[Sr 2+ ]]> 142 <![CDATA[HNO3]]> 0.3mol / L

[0070] 5 liters of simulated strontium-cesium high-level waste liquid was prepared according to the contents in Table 1, and then evaporated to dryness, and dried at 100° C. for 6 hours to obtain simulated strontium-cesium nitrate.

[0071] The glaze used in the following examples is a water meteor transparent glaze medium temperature glaze produced by Jingdezhen Water Meteorite Ceramics Museum.

[0072] Example 1

[0073] Weigh 1.4 g of dry aluminum silicate molecular sieve and 0.6 g of simulated strontium cesium nitrate, and mix them evenly; press the mixture into a φ10 cylindrical core block at 5 MPa; heat the cylindrical core block to 700°C at a rate of 5°C / min in an air atmosphere, keep it warm for 1 hour, and naturally cool it to room temperature to obtain a primary cesium garnet; crush and grind the primary cesium garnet, press it into shape at 10 MPa, heat it to 1000°C at a rate of 5°C / min in an inert atmosphere (argon), and keep it warm for 1 hour; naturally cool it to room temperature to obtain a secondary cesium garnet.

[0074] Take 50 mL of glaze, add 0.5 mL of 1 g / L nickel nitrate, mix well, spray onto the secondary cesium garnet, and repeat the spraying 5 times to obtain a sprayed glaze block.

[0075] The glaze block is heated to 1000°C at a rate of 5°C / min in an air atmosphere, kept at this temperature for 1 hour, and naturally cooled to room temperature to obtain a highly stable strontium-cesium ceramic solid body, the crystal structure of which is as follows: Figure 1 shown.

[0076] The strontium-cesium ceramic solid body prepared in this embodiment was leached according to the MCC-1 international leaching method, using deionized water as the leaching agent at 70°C for 21 days, and the normalized leaching rate of strontium was 2.05×10 -4 gm -2 .d -1 ; The normalized leaching rate of Cs is 5.23×10 - 4 gm -2 .d -1 .

[0077] Example 2

[0078] Weigh 1.6 g of dry aluminum silicate molecular sieve and 0.4 g of simulated strontium cesium nitrate, and mix them evenly; press them into φ10 cylindrical core blocks at 10 MPa; heat the cylindrical core blocks to 800°C at a rate of 5°C / min in an air atmosphere, keep them warm for 1 hour, and naturally cool them to room temperature to obtain primary cesium garnet; crush and grind the primary cesium garnet, press them into shape at 8 MPa, heat them to 1000°C at a rate of 5°C / min in an inert atmosphere (argon), and keep them warm for 1 hour; naturally cool them to room temperature to obtain secondary cesium garnet.

[0079] Take 50 mL of glaze, add 0.5 mL of 0.5 g / L nickel nitrate, mix well, spray onto the secondary cesium garnet, and repeat the spraying 5 times to obtain a sprayed glaze block.

[0080] The glaze block was heated to 800°C at a rate of 5°C / min in an air atmosphere, kept at that temperature for 1 hour, and naturally cooled to room temperature to obtain a highly stable strontium-cesium ceramic solid body with a crystal structure such as Figure 1 shown.

[0081] The strontium-cesium ceramic solid body prepared in this embodiment was leached according to the MCC-1 international leaching method, using deionized water as the leaching agent at 70°C for 21 days. The normalized leaching rate of strontium was 6.23×10 -4 gm -2 .d -1 ; The normalized leaching rate of Cs is 3.67×10 - 4 gm -2 .d -1 .

[0082] Example 3

[0083] Weigh 1.8 g of dry aluminum silicate molecular sieve and 0.2 g of simulated strontium cesium nitrate, and mix them evenly; press them into φ10 cylindrical core blocks at 5 MPa; heat the cylindrical core blocks to 700°C at a rate of 5°C / min in an air atmosphere, keep them warm for 1 hour, and naturally cool them to room temperature to obtain primary cesium garnet; crush and grind the primary cesium garnet, press them into shape at 8 MPa, heat them to 1000°C at a rate of 5°C / min in an inert atmosphere (argon), and keep them warm for 1 hour; naturally cool them to room temperature to obtain secondary cesium garnet.

[0084] Take 50 mL of glaze, add 0.5 mL of 0.5 g / L nickel nitrate, mix well, spray on the secondary cesium garnet, repeat spraying 3 times; obtain a sprayed glaze block.

[0085] The glaze block was heated to 700°C at a rate of 5°C / min in an air atmosphere, kept at this temperature for 1 hour, and naturally cooled to room temperature to obtain a highly stable strontium-cesium ceramic solid body with a crystal structure such as Figure 1 shown.

[0086] The solidified body was leached according to the MCC-1 international leaching method, using deionized water as the leaching agent at 70°C for 21 days. The normalized leaching rate of strontium was 4.06×10 -4 gm -2 .d -1 ; The normalized leaching rate of Cs is 1.29×10 -4 gm -2 .d -1 .

[0087] Comparative Example 1

[0088] 1.4 g of dry aluminum silicon molecular sieve and 0.6 g of simulated strontium cesium nitrate were weighed and mixed evenly; the mixture was pressed into a φ10 cylindrical core block at 5 MPa; the cylindrical core block was heated to 1000°C at a rate of 5°C / min in an air atmosphere, kept warm for 1 hour, and naturally cooled to room temperature to obtain a solid body; the solid body was leached at 70°C for 21 days according to the MCC-1 international leaching method with deionized water as the leaching agent, and the normalized leaching rate of strontium was 3.82×10 -2 gm -2 .d -1 ; Normalized leaching rate of Cs 6.25×10 -2 gm -2 .d -1 .

[0089] Comparative Example 2

[0090] 1.6 g of dried aluminum silicon molecular sieve and 0.4 g of simulated strontium cesium nitrate were weighed and mixed evenly; the mixture was pressed into a φ10 cylindrical core block at 10 MPa; the cylindrical core block was heated to 800°C at a rate of 5°C / min in an air atmosphere, kept at this temperature for 1 h, and naturally cooled to room temperature to obtain a solid body; the solid body was leached at 70°C for 21 days using deionized water as the leaching agent according to the MCC-1 international leaching method, and the normalized leaching rate of strontium was 4.78×10 -2 gm -2 .d -1 ; The normalized leaching rate of Cs is 3.29×10 - 2 gm -2 .d -1 .

[0091] Comparative Example 3

[0092] 1.6 g of dry ZSM-5 molecular sieve and 0.4 g of simulated strontium cesium nitrate were weighed and mixed evenly; the mixture was pressed into a φ10 cylindrical core block at 10 MPa; the cylindrical core block was heated to 800°C at a rate of 5°C / min in an air atmosphere, kept at this temperature for 1 h, and naturally cooled to room temperature to obtain a solid body; the solid body was leached at 70°C for 21 days using deionized water as the leaching agent according to the MCC-1 international leaching method, and the normalized leaching rate of strontium was 3.78×10 -1 gm -2 .d -1 ; The normalized leaching rate of Cs is 7.89×10 -1 gm -2 .d -1 .

[0093] From the comparison between the above-mentioned comparative examples 1 and 2 and the embodiments 1 and 2, it can be seen that the solidified body obtained by directly using aluminum silicon molecular sieve to solidify the simulated strontium cesium nitrate without spraying treatment has a high strontium cesium leaching rate, which is not conducive to the permanent disposal of the radioactive solidified body; from the comparison between comparative example 3 and embodiment 2, it can be seen that the solidified body leaching rate of the simulated strontium cesium nitrate solidified by ZSM-5 molecular sieve is relatively high.

Claims

1. A method for preparing a strontium-cesium ceramic solid body, comprising the following steps: (1) mixing aluminum silicon molecular sieve and high-radiation strontium-cesium waste uniformly, pressing and molding, and calcining to obtain primary cesium garnet; (2) crushing and grinding the primary cesium garnet, pressing and molding, and calcining to obtain secondary cesium garnet; (3) Spraying glaze on the secondary cesium garnet, and then calcining to obtain the strontium-cesium ceramic solid body.

2. The preparation method according to claim 1, characterized in that: The aluminum silicon molecular sieve is a NaY molecular sieve; specifically, the molar ratio of SiO2 / Al2O3 in the NaY molecular sieve may be 4.8-5.6:1; The mass percentage of the high-radioactive strontium-cesium waste is 10%-30% based on the total mass of the aluminum silicon molecular sieve and the high-radioactive strontium-cesium waste; The glaze is composed of glaze and nickel nitrate solution; specifically, the volume ratio of the glaze to the nickel nitrate solution may be 100:1-2; the concentration of the nickel nitrate solution may be 0.5-1 g / L.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the compression molding pressure is 5-10 MPa; The calcination is carried out in an air atmosphere; The calcination temperature is 700-800°C; The calcination time is 1-2h; The heating rate of the calcination is 5-10°C / min.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In step (2), the pressure of the compression molding is 8-10 MPa; The calcination is carried out in an inert atmosphere; The calcination temperature is 800-1000°C; The calcination time is 1-2h; The heating rate of the calcination is 5-10°C / min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step (3), the glaze is sprayed 3-5 times; The calcination is carried out in an air atmosphere; The calcination temperature is 700-1000°C; The calcination time is 1-2h; The heating rate of the calcination is 5-10°C / min.

6. A method for solidifying high-level radioactive waste strontium and cesium, comprising the following steps: (1) mixing aluminum silicon molecular sieve and high-radiation strontium-cesium waste uniformly, pressing and molding, and calcining to obtain primary cesium garnet; (2) crushing and grinding the primary cesium garnet, pressing and molding, and calcining to obtain secondary cesium garnet; (3) Spraying glaze on the secondary cesium garnet, and then calcining to obtain the strontium-cesium ceramic solid body.

7. The method according to claim 6, characterized in that: The aluminum silicon molecular sieve is a NaY molecular sieve; specifically, the molar ratio of SiO2 / Al2O3 in the NaY molecular sieve may be 4.8-5.6:1; The mass percentage of the high-radioactive strontium-cesium waste is 10%-30% based on the total mass of the aluminum silicon molecular sieve and the high-radioactive strontium-cesium waste; The glaze is composed of glaze and nickel nitrate solution; specifically, the volume ratio of the glaze to the nickel nitrate solution may be 100:1-2; the concentration of the nickel nitrate solution may be 0.5-1 g / L.

8. The method according to claim 6 or 7, characterized in that: In step (1), the pressure of the compression molding is 5-10 MPa; The calcination is carried out in an air atmosphere; The calcination temperature is 700-800°C; The calcination time is 1-2h; The heating rate of the calcination is 5-10°C / min.

9. The method according to any one of claims 6 to 8, characterized in that: In step (2), the pressure of the compression molding is 8-10 MPa; The calcination is carried out in an inert atmosphere; The calcination temperature is 800-1000°C; The calcination time is 1-2h; The heating rate of the calcination is 5-10°C / min.

10. The preparation method according to any one of claims 6 to 9, characterized in that: In step (3), the glaze is sprayed 3-5 times; The calcination is carried out in an air atmosphere; The calcination temperature is 700-1000°C; The calcination time is 1-2h; The heating rate of the calcination is 5-10°C / min.

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