Preparation method of cerium-neodymium oxide induced super-uranium nuclide ceramic solidified body

Abstract

The invention discloses a preparation method of a cerium-neodymium oxide induced super-uranium nuclide ceramic solidified body, and belongs to the technical field of nuclear waste industrial treatment and application. The preparation method comprises the following steps: by taking cerium oxide and neodymium oxide synergistic gadolinium-zirconium pyrochlore as a base material, adding a super-uranium nuclide, carrying out compression molding, and calcining in an air atmosphere at 1400-1700 DEG C for 3-5 hours to obtain a super-uranium nuclide ceramic solidified body. According to the method, the cerium-neodymium oxide and the gadolinium-zirconium pyrochlore base material ceramic are used for solidifying the super-uranium nuclide radioactive substance under the mild condition, the super-uranium nuclide radioactive solidified body with good chemical stability is obtained, and the disposal problem of the super-uranium nuclide for more than ten thousands of years is solved.

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 cerium-neodymium oxide-induced transuranic nuclide ceramic solidified body. Background Art

[0002] High-level radioactive waste 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 radioactive 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 radioactive 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] Solidification is an important step in ensuring the safe use of nuclear energy. High-level radioactive waste contains highly radioactive nuclides, such as neptunium, plutonium, americium, and technetium. These nuclides are highly toxic and have long half-lives. Once leaked, they will have long-term effects on the environment and human health. Solidification technology can stably seal these nuclides in the solidified body to reduce nuclear safety risks. The ceramic solidified body has excellent thermal conductivity, thermal stability, corrosion resistance, and radiation stability, and can remain stable in various environments; it achieves a good volume reduction effect, reduces the volume of waste, and reduces the processing cost by optimizing the process and improving efficiency, achieving good economic benefits.

[0004] The effective treatment of high-level radioactive waste is the key to the sustainable development of nuclear energy. Through solidification treatment, the impact of nuclear waste on the environment can be reduced, the public's acceptance of nuclear energy utilization can be improved, and support can be provided for the long-term development of nuclear energy. Summary of the invention

[0005] The purpose of the present invention is to solve the solidification of transuranic nuclides after separation of high-level radioactive waste in the prior art, provide a method for preparing a cerium-neodymium oxide-induced transuranic nuclide ceramic solidified body, and provide a new solidification method for permanent disposal of transuranic nuclide waste.

[0006] The present invention first provides a method for preparing a transuranium nuclide ceramic solid body, comprising the following steps:

[0007] (1) mixing gadolinium zirconium pyrochlore powder, cerium oxide, neodymium oxide, transuranic nuclides and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block;

[0008] (2) calcining the solidified precursor block to obtain the transuranic nuclide ceramic solidified body.

[0009] In the above preparation method, the mass percentage of the cerium oxide is 30%-75% based on the total mass of the cerium oxide and the neodymium oxide;

[0010] The mass percentage of the gadolinium zirconium pyrochlore powder is 70%-90% based on the total mass of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide;

[0011] Calculated by radiation dose, the total dose per 1g of the transuranic nuclide ceramic solid body is 10 6 -10 7 Bq;

[0012] The liquid-to-solid ratio of the mixed grinding solvent and the solid is (1.5-3) mL:1 g, wherein the mass of the solid is the sum of the masses of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide.

[0013] In the above-mentioned preparation method, in step (1), the pressing pressure is 8-15 MPa and the time is 5-10 min.

[0014] In the above-mentioned preparation method, in step (2), the calcination is carried out in air;

[0015] The calcination temperature is 1400-1700°C; the calcination time is 3-5h; and the calcination heating rate is 5-10°C / min.

[0016] In the above preparation method, the transuranic nuclides include Am, Np and Pu; specifically, the transuranic nuclides may be Am, Np and Pu, wherein Am accounts for 90%, and Np and Pu each account for 5%.

[0017] The particle size of the gadolinium zirconium pyrochlore powder is less than 200 mesh;

[0018] The mixed grinding solvent is anhydrous ethanol.

[0019] The present invention also provides a method for solidification treatment of transuranic nuclides, comprising the following steps:

[0020] (1) mixing gadolinium zirconium pyrochlore powder, cerium oxide, neodymium oxide, transuranic nuclides and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block;

[0021] (2) calcining the solidified precursor block to complete the solidification treatment of the transuranic nuclides.

[0022] In the above-mentioned solidification treatment method, the mass percentage of the cerium oxide is 30%-75% based on the total mass of the cerium oxide and the neodymium oxide;

[0023] The mass percentage of the gadolinium zirconium pyrochlore powder is 70%-90% based on the total mass of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide;

[0024] Calculated by radiation dose, the total dose per 1g of solidified body obtained after calcination is 10 6 -10 7 Bq;

[0025] The liquid-to-solid ratio of the mixed grinding solvent and the solid is (1.5-3) mL:1 g, wherein the mass of the solid is the sum of the masses of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide.

[0026] In the above-mentioned solidification treatment method, in step (1), the pressing pressure is 8-15 MPa and the pressing time is 5-10 min.

[0027] In the above-mentioned solidification treatment method, in step (2), the calcination is carried out in air;

[0028] The calcination temperature is 1400-1700° C.; the calcination time is 3-5 hours; and the calcination heating rate is 5-10° C. / min.

[0029] In the above solidification treatment method, the transuranic nuclides include Am, Np and Pu; specifically, the transuranic nuclides may be Am, Np and Pu, wherein Am accounts for 90%, and Np and Pu each account for 5%.

[0030] The particle size of the gadolinium zirconium pyrochlore powder is less than 200 mesh;

[0031] The mixed grinding solvent is anhydrous ethanol.

[0032] In the present invention, the gadolinium zirconium pyrochlore powder is obtained by grinding gadolinium oxide and zirconium oxide after calcination.

[0033] The present invention has the following advantages and outstanding technical effects: the method provided by the present invention is to use cerium-neodymium oxide in conjunction with gadolinium-zirconium pyrochlore-based ceramic to solidify transuranic radioactive materials under relatively mild conditions; the present invention solves the disposal problem of transuranic nuclides that has lasted for tens of thousands of years, obtains a transuranic radioactive solidified body with good chemical stability, and lays a foundation for the research and development of transuranic solidification separated from high-level waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The X-ray diffraction patterns of the transuranium nuclide ceramic solid bodies prepared in Examples 1 and 2 are shown in FIG. DETAILED DESCRIPTION

[0035] 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.

[0036] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0037] The quantitative tests in the following examples were all repeated three times, and the results were averaged.

[0038] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0039] The present invention uses cerium oxide and neodymium oxide in conjunction with gadolinium zirconium pyrochlore as the base material, adds a certain amount of radioactive tracer transuranic nuclides americium neptunium plutonium, presses and shapes, and calcines for 3-5 hours at 1400-1700°C in an air atmosphere to obtain a transuranic nuclide ceramic solidified body. The present invention solves the problem of permanent disposal of transuranic nuclides, realizes the radioactive transuranic nuclide solidification verification experiment in domestic and foreign laboratories for the first time, improves the public's acceptance of nuclear energy utilization, and provides support for the long-term development of nuclear energy, which is of great significance.

[0040] Several specific embodiments are given below to further understand and implement the present invention.

[0041] The preparation method of the gadolinium zirconium pyrochlore powder used in the following examples is as follows: gadolinium oxide and zirconium oxide are uniformly mixed in a molar ratio of 1:1, and calcined at 1400° C. for 5 hours in an air atmosphere to prepare a gadolinium zirconium pyrochlore solid; alcohol is added to the prepared gadolinium zirconium pyrochlore solid stone and ball-milled for 3 hours, and sieved to obtain a gadolinium zirconium pyrochlore powder with a mesh size of less than 200.

[0042] Example 1

[0043] Cerium oxide (30 wt%) and neodymium oxide (70 wt%) were mixed evenly to obtain a cerium-neodymium mixed oxide; 0.1 g of dry cerium-neodymium oxide and 0.9 g of gadolinium-zirconium pyrochlore powder were weighed; an activity of 1×10 6 Bq transuranium nuclides Am / Np / Pu (Am activity accounts for 90%, Np and Pu account for 5% each), add 1.5mL of anhydrous ethanol, mix well, and then press at 8MPa for 10min to obtain a solidified precursor block; the solidified precursor block is placed in a ceramic crucible, heated to 1400°C at a rate of 5°C / min in an air atmosphere, kept warm for 4h, and naturally cooled to room temperature to obtain a transuranium nuclide ceramic solidified body; then the transuranium nuclide ceramic solidified body is 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 investigate the chemical stability, and the normalized leaching rate of radioactive nuclides is 3.13×10 -4 g / m 2 .d.

[0044] Example 2

[0045] Cerium oxide (50 wt%) and neodymium oxide (50 wt%) were mixed evenly to obtain a cerium-neodymium mixed oxide; 0.2 g of dry cerium-neodymium oxide and 0.8 g of gadolinium-zirconium pyrochlore powder were weighed; 5×10 6 Bq transuranium nuclides Am / Np / Pu (Am accounts for 90%, Np and Pu each account for 5%), add 2mL of anhydrous ethanol, mix well, and then press at 12MPa for 8min to obtain a solidified precursor block; the solidified precursor block is placed in a ceramic crucible, heated to 1500°C at a rate of 5°C / min in an air atmosphere, kept warm for 5h, and naturally cooled to room temperature to obtain a transuranium nuclide ceramic solidified body; then the transuranium nuclide ceramic solidified body is 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 investigate the chemical stability, and the normalized leaching rate of radioactive nuclides is 7.45×10 -5 g / m 2 .d.

[0046] Example 3

[0047] Cerium oxide (70 wt%) and neodymium oxide (30 wt%) were mixed evenly to obtain a cerium-neodymium mixed oxide; 0.3 g of the dried cerium-neodymium mixed oxide and 0.7 g of gadolinium-zirconium pyrochlore powder were weighed; 1×10 6 Bq transuranium nuclides Am / Np / Pu (Am accounts for 90%, Np and Pu each account for 5%), add 3mL of anhydrous ethanol, mix well, and then press at 15MPa for 5 minutes to obtain a solidified precursor block; the solidified precursor block is placed in a ceramic crucible, heated to 1700°C at a rate of 5°C / min in an air atmosphere, kept warm for 3h, and naturally cooled to room temperature to obtain a transuranium nuclide ceramic solidified body; then the transuranium nuclide ceramic solidified body is 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 investigate the chemical stability, and the normalized leaching rate of radioactive nuclides is 3.25×10 -4 g / m 2 .d.

[0048] Example 4

[0049] Cerium oxide (70 wt%) and neodymium oxide (30 wt%) were mixed evenly to obtain a cerium-neodymium mixed oxide; 0.3 g of the dried cerium-neodymium mixed oxide and 0.7 g of gadolinium-zirconium pyrochlore powder were weighed; 1×10 7Bq transuranium nuclides Am / Np / Pu (Am accounts for 90%, Np and Pu each account for 5%), add 2mL of anhydrous ethanol, mix well, and then press at 10MPa for 5 minutes to obtain a solidified precursor block; the solidified precursor block is placed in a ceramic crucible, heated to 1500°C at a rate of 10°C / min in an air atmosphere, kept warm for 3h, and naturally cooled to room temperature to obtain a transuranium nuclide ceramic solidified body; then the transuranium nuclide ceramic solidified body is 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 investigate the chemical stability, and the normalized leaching rate of radioactive nuclides is 4.08×10 -4 g / m 2 .d.

[0050] Example 5

[0051] Cerium oxide (75 wt%) and neodymium oxide (25 wt%) were mixed evenly to obtain a cerium-neodymium mixed oxide; 0.25 g of the dried cerium-neodymium mixed oxide and 0.75 g of gadolinium-zirconium pyrochlore powder were weighed; 5×10 6 Bq transuranium nuclides Am / Np / Pu (Am accounts for 90%, Np and Pu each account for 5%), add 2mL of anhydrous ethanol, mix well, and then press at 10MPa for 5 minutes to obtain a solidified precursor block; the solidified precursor block is placed in a ceramic crucible, heated to 1500°C at a rate of 5°C / min in an air atmosphere, kept warm for 4 hours, and naturally cooled to room temperature to obtain a transuranium nuclide ceramic solidified body; then the transuranium nuclide ceramic solidified body is 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 investigate the chemical stability, and the normalized leaching rate of radioactive nuclides is 7.86×10 -5 g / m 2 .d.

[0052] Figure 1 The X-ray diffraction patterns of the transuranium nuclide ceramic solid bodies prepared in Examples 1 and 2 are shown in FIG. Figure 1 It can be seen that the structure of the transuranium nuclide ceramic solid body prepared in Examples 1 and 2 is a typical crystalline phase structure.

Claims

1. A method for preparing a transuranium nuclide ceramic solid body, comprising the following steps: (1) mixing gadolinium zirconium pyrochlore powder, cerium oxide, neodymium oxide, transuranic nuclides and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block; (2) calcining the solidified precursor block to obtain the transuranic nuclide ceramic solidified body.

2. The preparation method according to claim 1, characterized in that: The mass percentage of the cerium oxide is 30%-75% based on the total mass of the cerium oxide and the neodymium oxide; The mass percentage of the gadolinium zirconium pyrochlore powder is 70%-90% based on the total mass of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide; Calculated by radiation dose, the total dose per 1g of the transuranic nuclide ceramic solid body is 10 6 -10 7 Bq; The liquid-to-solid ratio of the mixed grinding solvent and the solid is (1.5-3) mL:1 g, wherein the mass of the solid is the sum of the masses of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the compression molding pressure is 8-15 MPa and the time is 5-10 min.

4. The preparation method according to any one of claims 1 to 3, characterized in that: In step (2), the calcination is carried out in air; The calcination temperature is 1400-1700°C; the calcination time is 3-5h; and the calcination heating rate is 5-10°C / min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The transuranic nuclides include Am, Np and Pu; The particle size of the gadolinium zirconium pyrochlore powder is less than 200 mesh; The mixed grinding solvent is anhydrous ethanol.

6. A method for solidification of transuranic nuclides, comprising the following steps: (1) mixing gadolinium zirconium pyrochlore powder, cerium oxide, neodymium oxide, transuranic nuclides and a mixed grinding solvent uniformly, and pressing and molding to obtain a solidified precursor block; (2) calcining the solidified precursor block to complete the solidification treatment of the transuranic nuclides.

7. The curing method according to claim 6, characterized in that: The mass percentage of the cerium oxide is 30%-75% based on the total mass of the cerium oxide and the neodymium oxide; The mass percentage of the gadolinium zirconium pyrochlore powder is 70%-90% based on the total mass of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide; Calculated by radiation dose, the total dose per 1g of solidified body obtained after calcination is 10 6 -10 7 Bq; The liquid-to-solid ratio of the mixed grinding solvent and the solid is (1.5-3) mL:1 g, wherein the mass of the solid is the sum of the masses of the gadolinium zirconium pyrochlore powder, cerium oxide and neodymium oxide.

8. The curing method according to claim 6 or 7, characterized in that: In step (1), the compression molding pressure is 8-15 MPa and the time is 5-10 min.

9. The curing method according to any one of claims 6 to 8, characterized in that: In step (2), the calcination is carried out in air; The calcination temperature is 1400-1700°C; the calcination time is 3-5h; and the calcination heating rate is 5-10°C / min.

10. The curing method according to any one of claims 6 to 9, characterized in that: The transuranic nuclides include Am, Np and Pu; The particle size of the gadolinium zirconium pyrochlore powder is less than 200 mesh; The mixed grinding solvent is anhydrous ethanol.

Images