Preparation method of pollucite-induced radioactive tracing strontium-cesium glass solidified body

Abstract

The invention discloses a preparation method of a pollucite-induced radioactive tracing strontium cesium glass solidified body, and belongs to the technical field of nuclear waste industrial treatment and application. The preparation method of the radioactive strontium cesium glass solidified body provided by the invention comprises the following steps: (1) uniformly mixing pollucite, granite glass powder, radioactive strontium, radioactive cesium and a mixed grinding solvent, and carrying out compression molding to obtain a solidified precursor block; and (2) calcining the solidified precursor block in an inert atmosphere to obtain the radioactive strontium cesium glass solidified body. According to the method disclosed by the invention, radioactive strontium-cesium nuclides are induced by utilizing pollucite, so that the radioactive strontium-cesium nuclides easily enter a glass grid, the volatilization of strontium and cesium is reduced, the method can be applied to the preparation of a cesium source core and the reutilization of nuclear wastes, and a new curing method is also provided for permanent treatment of the strontium-cesium nuclear wastes.

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 cesium garnet-induced radioactive tracer strontium-cesium glass solidified body. Background Art

[0002] High-level waste (HLW) is one of the most difficult forms of nuclear waste to handle. It mainly exists in the form of waste liquid (wastewater). Although the volume of high-level waste 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 high-level waste, 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 strontium is to grind and press it into shape by adding rocks, alkali manganese ore, etc., and calcine it in the air at a high temperature of 1100℃-1300℃; however, cesium is generally easy to volatilize above 1000℃, causing nuclides to leak; glass solidification has a wide range of tolerance for different elements and can achieve atomic-scale solidification of nuclides. Glass solidification technology is an inorganic volume reduction process. The waste volume reduction ratio can reach 20 to 30 times, which helps to reduce the volume of waste. The glass solidification process is simple and easy to operate remotely. It is currently the only industrially applied and most mature high-level waste liquid treatment technology in the world. Glass solidification has excellent thermal stability and mechanical stability, can resist external shock and vibration, has good radiation resistance, and is suitable for radioactive strontium and cesium solidification. However, how to achieve the glass solidification of radioactive strontium and cesium and solve the problem of cesium volatilization loss is an urgent problem to be solved. Summary of the invention

[0004] The invention provides a method for preparing a cesium garnet-induced radioactive tracer strontium-cesium glass solidified body. The method utilizes cesium garnet to induce radioactive strontium-cesium nuclides to make them easily enter the glass grid, thereby reducing the volatilization of strontium-cesium. The method 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] In order to solve the above technical problems, the present invention first provides a method for preparing a radioactive strontium-cesium glass solidified body, comprising the following steps:

[0006] (1) mixing cesium garnet, granite glass powder, radioactive strontium, radioactive cesium and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block;

[0007] (2) calcining the solidified precursor block under an inert atmosphere to obtain the radioactive strontium-cesium glass solidified body.

[0008] In the above-mentioned preparation method, in step (1), the mass percentage of the cesium garnet is 10%-20% based on the total mass of the cesium garnet and the granite glass powder;

[0009] Calculated by radiation dose, the dose of radioactive strontium in each gram of the radioactive strontium-cesium glass solidified body is 2×10 6 -2×10 7 Bq;

[0010] Calculated by radiation dose, the dose of radioactive cesium in each gram of the radioactive strontium-cesium glass solidified body is 10 6 -10 7 Bq;

[0011] The volume ratio of the mixed grinding solvent to the mass ratio of the solid is (1.5-3) mL:1 g, wherein the mass of the solid is based on the total mass of the cesium garnet and the granite glass powder;

[0012] The mixed grinding solvent is anhydrous ethanol.

[0013] In the above-mentioned preparation method, in step (1), the particle size of the granite glass powder is less than 200 mesh;

[0014] The granite glass powder is obtained by calcining granite and boron oxide.

[0015] In the above preparation method, based on the total mass of the granite and boron oxide, the mass percentage of the granite is 75%-85%, specifically 80%.

[0016] In the above-mentioned preparation method, the calcination temperature in the preparation process of the granite glass powder is 1000-1100° C., and the calcination time is 1-2 hours.

[0017] In the above-mentioned preparation method, in step (1), the pressure of the compression molding is 8-10 MPa and the time is 5-10 min;

[0018] In step (2), the calcination temperature is 1100-1200°C, the time is 1-2h, and the calcination heating rate is 5-10°C / min.

[0019] The present invention also provides a method for solidifying radioactive strontium and cesium, comprising the following steps:

[0020] (1) mixing cesium garnet, granite glass powder, radioactive strontium, radioactive cesium and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block;

[0021] (2) calcining the solidified precursor block under an inert atmosphere to complete the solidification treatment of the radioactive strontium and cesium.

[0022] In the above method, in step (1), the mass percentage of the cesium garnet is 10%-20% based on the total mass of the cesium garnet and the granite glass powder;

[0023] Calculated by radiation dose, the dose of radioactive strontium in each gram of the glass solidified body obtained after calcination is 2×10 6 -2×10 7 Bq;

[0024] Calculated by radiation dose, the dose of radioactive cesium in each gram of the glass solidified body obtained after calcination is 10 6 -10 7 Bq;

[0025] The volume ratio of the mixed grinding solvent to the mass ratio of the solid is (1.5-3) mL:1 g, wherein the mass of the solid is based on the total mass of the cesium garnet and the granite glass powder;

[0026] The mixed grinding solvent is anhydrous ethanol.

[0027] In the above method, in step (1), the particle size of the granite glass powder is less than 200 mesh;

[0028] The granite glass powder is obtained by calcining granite and boron oxide.

[0029] In the above preparation method, based on the total mass of the granite and boron oxide, the mass percentage of the granite is 75%-85%, specifically 80%.

[0030] In the above method, the calcination temperature in the preparation process of the granite glass powder is 1000-1100° C., and the calcination time is 1-2 hours.

[0031] In the above method, in step (1), the pressing pressure is 8-10 MPa and the pressing time is 5-10 min;

[0032] In step (2), the calcination temperature is 1100-1200°C, the time is 1-2h, and the calcination heating rate is 5-10°C / min.

[0033] The cesium garnet used in the present invention is obtained by calcining aluminum silicon molecular sieve and strontium cesium nitrate solid in air atmosphere;

[0034] Specifically, the aluminum silicon molecular sieve is a NaY molecular sieve, and the SiO2 / Al2O3 molar ratio in the molecular sieve is 4.8-5.6:1;

[0035] The mass ratio of the aluminum silicate molecular sieve to the strontium cesium nitrate solid may be (60-80):(20:40);

[0036] The calcination temperature may be 700-800° C.; the calcination time may be 1 hour.

[0037] The present invention has the following advantages and outstanding technical effects: the method provided by the present invention is to use cesium garnet and granite as a base material to glass-solidify strontium-cesium radioactive materials under relatively mild conditions; the present invention solves the problem of volatilization of radioactive cesium under high temperature conditions of 1100-1200°C; at the same time, a radioactive strontium-cesium glass solidified body with easy separation of the crucible and the glass body and good chemical stability is obtained, which is a good method for the research and development of separation of high-level waste liquid 137 Cs, 90 Sr solidification laid the foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the X-ray diffraction pattern of the radioactive strontium-cesium glass solidified body in Example 1. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below in conjunction with specific embodiments. The given examples are only for illustrating the present invention, but not for limiting the scope of the present invention.

[0040] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0041] The quantitative tests in the following examples were all repeated three times, and the results were averaged.

[0042] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0043] The present invention provides a method for preparing a radioactive strontium-cesium glass solidification body or a method for solidifying radioactive strontium-cesium, comprising the following steps:

[0044] (1) mixing cesium garnet, granite glass powder, radioactive strontium, radioactive cesium and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block;

[0045] (2) calcining the solidified precursor block under an inert atmosphere to obtain the radioactive strontium-cesium glass solidified body.

[0046] The method of the present invention uses cesium garnet to induce radioactive strontium cesium nuclides, so that the nuclides can easily enter the glass grid, thereby reducing the volatilization of strontium cesium and improving the recycling of nuclear waste. The method of the present invention uses cesium garnet and granite as a base material to glass-solidify strontium cesium radioactive materials under relatively mild conditions, solves the problem of volatilization of radioactive cesium under high temperature conditions of 1100-1200°C, and at the same time, obtains a radioactive strontium cesium glass solidified body with good chemical stability and easy separation of the crucible and the glass body, which is useful for the research and development of separation of high-level waste liquid. 137 Cs, 90 The preparation method of the cesium garnet used in the following examples is as follows: Aluminum silicon molecular sieve (NaY molecular sieve, SiO2 / Al2O3 molar ratio of 5.2:1, purchased from Tianjin Nanhua Catalyst Co., Ltd.) and simulated strontium cesium nitrate solid are mixed uniformly according to a mass ratio of 70:30, heated to 700°C at a heating rate of 5°C / min in an air atmosphere, kept warm for 1h, and naturally cooled to room temperature to obtain cesium garnet.

[0047] The preparation method of the simulated strontium cesium nitrate solid is as follows: 5 liters of simulated strontium cesium high-level waste liquid is prepared according to the content in Table 1, and then evaporated to dryness, and dried at 100° C. for 6 hours to obtain simulated strontium cesium nitrate solid.

[0048] Table 1 Simulated strontium-cesium high-level waste liquid (anion is NO3 - )

[0049] 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

[0050] The preparation method of the granite glass powder used in the following examples is as follows: 80% by mass of granite and 20% by mass of boron oxide are uniformly mixed, then calcined at 1000° C. for 2 hours, and after cooling, ball milled and sieved to obtain granite glass powder with a mesh size of less than 200.

[0051] Example 1

[0052] (1) Weigh 0.1 g of the dry cesium garnet prepared above and 0.9 g of granite glass powder, add 1×10 6 Bq Cs, 2×10 6 Bq Sr, add 1.5 mL of anhydrous ethanol, mix well, and then press at 8 MPa for 10 min to obtain a solidified precursor block;

[0053] (2) The solidified precursor block is placed in a graphite crucible and then in a quartz tube. In an inert atmosphere (argon atmosphere), the temperature is raised to 1100°C at a rate of 5°C / min, kept at this temperature for 1 hour, and naturally cooled to room temperature to obtain a radioactive strontium-cesium glass solid body. During the calcination process, the exhaust gas is absorbed with 0.5 mol / L nitric acid.

[0054] (3) The radioactive strontium-cesium glass solidified body was leached at 90°C for 14 days according to the American ASTM C1220-2017 standard (named "Standard Test Method for Static Leaching of Single Waste Body for Radioactive Waste Treatment") to examine the chemical stability. The normalized leaching rate of strontium was calculated to be 3.250×10 -3 g / m 2 .d, the normalized leaching rate of cesium is 2.508×10 - 3 g / m 2 .d; The quartz tube was cleaned three times with 0.5 mol / L nitric acid, a tail gas absorption liquid. The radioactivity of the cleaning liquid was tested, and the volatility of cesium was 0.25%, and the volatility of strontium was 0.02%.

[0055] Figure 1 is the X-ray diffraction pattern of the radioactive strontium-cesium glass solidified body in Example 1; Figure 1 It can be seen that the structure of the radioactive strontium-cesium glass solid body prepared in this embodiment is a typical amorphous crystal structure.

[0056] Example 2

[0057] (1) Weigh 0.2 g of dry cesium garnet and 0.8 g of granite glass powder; add 1×10 7 Bq Cs, 2×10 7 Bq Sr, add 2mL of anhydrous ethanol, mix well, and then press at 9MPa for 8min to obtain a solidified precursor block;

[0058] (2) placing the solidified precursor block into a graphite crucible, and then into a quartz tube, heating to 1150°C at a rate of 5°C / min under an inert atmosphere (argon atmosphere), keeping the temperature for 1 hour, and naturally cooling to room temperature to obtain a radioactive strontium-cesium glass solid body. During the calcination process, the tail gas was absorbed with 0.5 mol / L nitric acid;

[0059] (3) The radioactive strontium-cesium glass solidified body was leached at 90°C for 14 days according to the American ASTM C1220-2017 standard (named "Standard Test Method for Static Leaching of Single Waste Body for Radioactive Waste Treatment") to examine the chemical stability. The normalized leaching rate of strontium was calculated to be 1.868×10 -3 g / m 2 .d, the normalized leaching rate of cesium is 7.862×10 - 3 g / m 2 .d; The quartz tube was cleaned three times with 0.5 mol / L nitric acid, a tail gas absorption liquid. The radioactivity of the cleaning liquid was tested, and the volatility of cesium was 0.28%, and the volatility of strontium was 0.05%.

[0060] Example 3

[0061] (1) Weigh 0.15 g of dry cesium garnet and 0.85 g of granite glass powder; add 1×10 7 Bq Cs, 2×10 6 BqSr, add 3 mL of anhydrous ethanol, mix well, and then press at 10 MPa for 5 min to obtain a solidified precursor block;

[0062] (2) placing the solidified precursor block into a graphite crucible, and then into a quartz tube, heating to 1100°C at a rate of 5°C / min under an inert atmosphere (argon atmosphere), keeping the temperature for 2 hours, and naturally cooling to room temperature to obtain a radioactive strontium-cesium glass solid body. During the calcination process, the tail gas was absorbed with 0.5 mol / L nitric acid;

[0063] (3) The radioactive strontium-cesium glass solidified body was leached at 90°C for 14 days according to the American ASTM C1220-2017 standard (named "Standard Test Method for Static Leaching of Single Waste Body for Radioactive Waste Treatment") to examine the chemical stability. The normalized leaching rate of strontium was calculated to be 3.874×10 -3 g / m 2 .d, the normalized leaching rate of cesium is 9.987×10 - 3 g / m 2 .d; The quartz tube was cleaned three times with 0.5 mol / L nitric acid, a tail gas absorption liquid. The radioactivity of the cleaning liquid was tested, and the volatility of cesium was 0.28%, and the volatility of strontium was 0.03%.

[0064] Example 4

[0065] (1) Weigh 0.2 g of dry cesium garnet and 0.8 g of granite glass powder; add 1×10 6 Bq Cs, 2×10 6 Bq Sr, add 3 mL of anhydrous ethanol, mix well, and then press at 10 MPa for 5 min to obtain a solidified precursor block;

[0066] (2) placing the solidified precursor block into a graphite crucible, and then into a quartz tube, heating to 1100°C at a rate of 5°C / min under an inert atmosphere (argon atmosphere), keeping the temperature for 2 hours, and naturally cooling to room temperature to obtain a radioactive strontium-cesium glass solid body. During the calcination process, the tail gas was absorbed with 0.5 mol / L nitric acid;

[0067] (3) The radioactive strontium-cesium glass solidified body was leached at 90°C for 14 days according to the American ASTM C1220-2017 standard (named "Standard Test Method for Static Leaching of Single Waste Body for Radioactive Waste Treatment") to examine the chemical stability. The normalized leaching rate of strontium was calculated to be 7.896×10 -3 g / m 2 .d, the normalized leaching rate of cesium is 4.352×10 - 3 g / m 2 .d; The quartz tube was cleaned three times with 0.5 mol / L nitric acid, a tail gas absorption liquid. The radioactivity of the cleaning liquid was tested, and the volatility of cesium was 0.34% and that of strontium was 0.07%.

Claims

1. A method for preparing a radioactive strontium-cesium glass solidified body, comprising the following steps: (1) mixing cesium garnet, granite glass powder, radioactive strontium, radioactive cesium and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block; (2) calcining the solidified precursor block under an inert atmosphere to obtain the radioactive strontium-cesium glass solidified body.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass percentage of the cesium garnet is 10%-20% based on the total mass of the cesium garnet and the granite glass powder; Calculated by radiation dose, the dose of radioactive strontium in each gram of the radioactive strontium-cesium glass solidified body is 2×10 6 -2×10 7 Bq; Calculated by radiation dose, the dose of radioactive cesium in each gram of the radioactive strontium-cesium glass solidified body is 10 6 -10 7 Bq; The volume ratio of the mixed grinding solvent to the mass ratio of the solid is (1.5-3) mL:1 g, wherein the mass of the solid is based on the total mass of the cesium garnet and the granite glass powder; The mixed grinding solvent is anhydrous ethanol.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the particle size of the granite glass powder is less than 200 mesh; The granite glass powder is obtained by calcining granite and boron oxide.

4. The preparation method according to claim 3, characterized in that: The calcination temperature in the preparation process of the granite glass powder is 1000-1100° C. and the calcination time is 1-2 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step (1), the compression molding pressure is 8-10 MPa and the time is 5-10 min; In step (2), the calcination temperature is 1100-1200°C, the time is 1-2h, and the calcination heating rate is 5-10°C / min.

6. A method for solidifying radioactive strontium and cesium, comprising the following steps: (1) mixing cesium garnet, granite glass powder, radioactive strontium, radioactive cesium and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block; (2) calcining the solidified precursor block under an inert atmosphere to complete the solidification treatment of the radioactive strontium and cesium.

7. The method according to claim 6, characterized in that: In step (1), the mass percentage of the cesium garnet is 10%-20% based on the total mass of the cesium garnet and the granite glass powder; Calculated by radiation dose, the dose of radioactive strontium in each gram of the glass solidified body obtained after calcination is 2×10 6 -2×10 7 Bq; Calculated by radiation dose, the dose of radioactive cesium in each gram of the glass solidified body obtained after calcination is 10 6 -10 7 Bq; The volume ratio of the mixed grinding solvent to the mass ratio of the solid is (1.5-3) mL:1 g, wherein the mass of the solid is based on the total mass of the cesium garnet and the granite glass powder; The mixed grinding solvent is anhydrous ethanol.

8. The method according to claim 6 or 7, characterized in that: In step (1), the particle size of the granite glass powder is less than 200 mesh; The granite glass powder is obtained by calcining granite and boron oxide.

9. The method according to claim 8, characterized in that: The calcination temperature in the preparation process of the granite glass powder is 1000-1100° C. and the calcination time is 1-2 hours.

10. The method according to any one of claims 6 to 9, characterized in that: In step (1), the compression molding pressure is 8-10 MPa and the time is 5-10 min; In step (2), the calcination temperature is 1100-1200°C, the time is 1-2h, and the calcination heating rate is 5-10°C / min.

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