阅读说明：本技术 一步法制备烧绿石相硼硅酸盐玻璃陶瓷固化基材的方法 (Method for preparing pyrochlore phase borosilicate glass ceramic cured substrate by one-step method ) 是由 廖其龙 吴康明 竹含真 王辅 于 2019-09-03 设计创作，主要内容包括：本发明公开了一步法制备烧绿石相硼硅酸盐玻璃陶瓷固化基材的方法,其特征是：按Na<Sub>2</Sub>SiO<Sub>3</Sub> 30～40份、CaF<Sub>2</Sub> 7～9.5份、H<Sub>3</Sub>BO<Sub>3</Sub> 6～8.5份、Nb<Sub>2</Sub>O<Sub>5</Sub> 15～25份、TiO<Sub>2</Sub> 3.5～6份、Nd<Sub>2</Sub>O<Sub>3</Sub> 12～18.5份、Al(OH)<Sub>3</Sub> 2～4.5份、SiO<Sub>2</Sub> 3.5～6.5份的重量份配比取各原料；以无水乙醇或/和水为介质,将原料放入球磨设备中球磨；干燥；1200℃～1400℃保温1～3小时；转移到保温炉中,降温到450～500℃保温1～4小时,冷却即制得。本发明制备的烧绿石相硼硅酸盐玻璃陶瓷固化基材结构稳定性好、化学稳定性好,可靠性高,可用于高放核废物的固化处理。(The invention discloses a method for preparing pyrochlore phase borosilicate glass ceramic curing substrate by one step, which is characterized by comprising the following steps: according to Na 2 SiO 3 30-40 parts of CaF 2 7 to 9.5 parts of H 3 BO 3 6 to 8.5 parts of Nb 2 O 5 15 to 25 parts of TiO 2 3.5-6 parts of Nd 2 O 3 12 to 18.5 parts of Al (OH) 3 2 to 4.5 parts of SiO 2 3.5-6.5 parts of the raw materials; using absolute ethyl alcohol or/and water as a medium, and putting the raw materials into ball milling equipment for ball milling; drying; preserving heat for 1-3 hours at 1200-1400 ℃; transferring the mixture into a heat preservation furnace, cooling to 450-500 ℃, preserving heat for 1-4 hours, and cooling to obtain the product. The pyrochlore phase borosilicate glass ceramic curing substrate prepared by the method has the advantages of good structural stability, good chemical stability and high reliability, and can be used for curing high radioactive nuclear waste.)

1. The one-step method for preparing pyrochlore phase borosilicate glass ceramic cured substrate is characterized by comprising the following steps of:

a. preparing materials: with Na₂SiO₃、CaF₂、H₃BO₃、Nb₂O₅、TiO₂、Nd₂O₃、Al(OH)₃、SiO₂As a raw material, according to Na₂SiO₃30 to 40 parts by weight of CaF₂7 to 9.5 parts by weight of H₃BO₃6 to 8.5 parts by weight of Nb₂O₅15 to 25 parts by weight of TiO₂3.5 to 6 parts by weight of Nd₂O₃12 to 18.5 parts by weight of Al (OH)₃2 to 4.5 parts by weight of SiO₂Taking raw materials of each component in a proportion of 3.5-6.5 parts by weight;

b. mixing: taking absolute ethyl alcohol or/and water as a medium, putting the raw materials into ball milling equipment, and carrying out ball milling and mixing for 4-6 hours to prepare uniformly mixed batch slurry;

c. and (3) drying: drying the batch slurry in a constant-temperature drying oven for 24-36 hours to obtain batch;

d. melting: heating the batch mixture to 1200-1400 ℃ at the speed of 2.5-10 ℃/min in a high-temperature furnace, and preserving the temperature for 1-3 hours to prepare a silicate melt;

e. cooling and annealing: and transferring the silicate melt into a heat preservation furnace with the temperature of 900-1100 ℃, cooling to the annealing temperature of 450-500 ℃ at the cooling rate of 5-15 ℃/min, preserving the heat for 1-4 hours, and cooling to the normal temperature along with the furnace to obtain the pyrochlore phase borosilicate glass ceramic solidified substrate.

2. The one-step process for preparing a pyrochlore phase borosilicate glass ceramic cured substrate according to claim 1 wherein: in the step b, the anhydrous ethanol or/and water is/are used as a medium, and the raw materials are put into ball milling equipment, wherein the method comprises the following steps: the raw materials, the grinding balls and the absolute ethyl alcohol or/and water are put into ball milling equipment according to the weight percentage of 6-30% of the total weight of the raw materials, 20-60% of the grinding balls and 30-70% of the absolute ethyl alcohol or/and water.

3. The one-step process for preparing a pyrochlore phase borosilicate glass ceramic cured substrate according to claim 1 wherein: and c, drying the batch slurry in a constant-temperature drying oven for 24-36 hours, wherein the drying time is as follows: and drying the batch slurry in a constant-temperature drying oven at the temperature of 60-80 ℃ for 24-36 hours.

4. The one-step process for preparing a pyrochlore phase borosilicate glass ceramic cured substrate according to claim 1 wherein: said Nd in the compounding of step a₂O₃For simulating high-level nuclide Nd³⁺The raw material components of (1).

5. The one-step process for preparing a pyrochlore phase borosilicate glass ceramic cured substrate according to claim 1 wherein: and the ball milling equipment in the step b is a planetary ball mill.

6. The one-step process for preparing a pyrochlore phase borosilicate glass ceramic cured substrate according to claim 1 wherein: and e, the heat preservation furnace in the step e is a high-temperature box type resistance furnace.

7. The one-step process for preparing a pyrochlore phase borosilicate glass ceramic cured substrate according to claim 1 wherein: and the water in the step b is distilled water or deionized water.

Technical Field

The invention belongs to preparation of a glass ceramic curing substrate of high radioactive nuclear waste, and relates to a method for preparing a pyrochlore phase borosilicate glass ceramic curing substrate by a one-step method. The invention relates to a radioactive nuclear waste curing method taking pyrochlore phase borosilicate glass ceramics as a curing substrate, which is suitable for curing high-level radioactive nuclear waste discharged in the fields of nuclear industry and the like.

Background

The nuclear energy is an efficient and clean energy source, and peaceful utilization of the nuclear energy has profound influence on national regulation of energy structure, promotion of energy conservation and emission reduction and response to climate change. Since nearly half a century, with the development of nuclear power plants and the retirement of military nuclear weapons, more and more high-level nuclear wastes (HLW for short) are generated, and how to safely and effectively dispose the high-level nuclear wastes, particularly plutonium with long half-life and high radioactivity and a small amount of actinides, has become a main problem of disposing the high-level nuclear wastes, isolates the high-level nuclear wastes from the environment where human beings live, and has an important influence on the cycle development of nuclear fuel.

To date, the safest method for disposing high radioactive nuclear waste internationally acknowledged is to bury the high radioactive nuclear waste in a permanent disposal warehouse underground, and the method for separating and solidifying the high radioactive nuclear waste in a stable matrix such as glass, glass ceramic and ceramic is generally accepted, but the glass solidification has the defects of non-ideal nuclear waste packing capacity and strong element selectivity in ceramic solidification, so that the glass ceramic solidification is a potentially industrialized and ideal solidification treatment technology, and borosilicate glass is the most mature matrix in the HLW solidification matrix at present, but the low content of actinides and the instability at high temperature bring troubles to the treatment of the high radioactive nuclear waste. The complex oxide with the pyrochlore structure has potential application prospect in the field of curing high radioactive nuclear waste, and has attracted extensive attention in recent decades. Pyrochlore-type oxides are generally represented by the formula A₂B₂O₇Wherein the A and B sites are generally 8 and 6 coordinated respectively, with one eighth of their anionic sites being vacant, since they are so uniqueThe pyrochlore can contain various actinides due to the special structure, and has the advantages of stable structural performance, strong nuclide containing capability, low leaching rate, strong irradiation resistance and the like. Therefore, the pyrochlore-structure-containing crystalline phase is compounded with the borosilicate glass to prepare the pyrochlore-phase-enriched borosilicate glass ceramic serving as a curing substrate of high radioactive nuclear waste, and the pyrochlore-structure-containing borosilicate glass ceramic has wide application prospect and great industrial value. However, in the prior art, pyrochlore-rich borosilicate glass ceramic cured substrates are difficult to synthesize, and the mainstream methods for preparing glass ceramic cured bodies remain the fusion-crystallization method and the sintering method. The melting-crystallization method requires high-temperature heat treatment, which is not favorable for controlling crystal phase and components; the sintering method is similar to a ceramic curing process, and has a complex process and high equipment requirement. Research and practice history in the field indicates that the two processes are not compact enough and engineering of high radioactive nuclear waste solidification treatment is not easy to realize.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for preparing a pyrochlore phase borosilicate glass ceramic cured substrate by a one-step method. According to the invention, through component and process parameter design, pyrochlore phase borosilicate glass ceramic solidified base materials are prepared by adopting the process flows of high-temperature melting, rapid cooling, slow cooling and annealing, and the prepared pyrochlore phase borosilicate glass ceramic solidified body has the advantages of various borosilicate glass material containing wastes, large component adjustability, strong pyrochlore phase ceramic phase nuclide containing capability, low leaching rate and the like; therefore, the invention provides a new simple and effective preparation process method of the pyrochlore-phase borosilicate glass ceramic solidified body, which takes the pyrochlore-phase borosilicate glass ceramic material as the solidified substrate of the high radioactive nuclear waste and also provides a new simple and effective preparation process method of the pyrochlore-phase borosilicate glass ceramic solidified body for the solidification treatment of the high radioactive nuclear waste.

The content of the invention is as follows: the one-step method for preparing pyrochlore phase borosilicate glass ceramic cured substrate is characterized by comprising the following steps of:

a. preparing materials: with Na₂SiO₃、CaF₂、H₃BO₃、Nb₂O₅、TiO₂、Nd₂O₃、Al(OH)₃、SiO₂As a raw material, according to Na₂SiO₃30 to 40 parts by weight of CaF₂7 to 9.5 parts by weight of H₃BO₃6 to 8.5 parts by weight of Nb₂O₅15 to 25 parts by weight of TiO₂3.5 to 6 parts by weight of Nd₂O₃12 to 18.5 parts by weight of Al (OH)₃2 to 4.5 parts by weight of SiO₂Taking raw materials of each component in a proportion of 3.5-6.5 parts by weight;

b. mixing: putting the raw materials into ball milling equipment to be ball milled and mixed for 4-6 hours by taking absolute ethyl alcohol or/and water as a medium to prepare uniformly mixed batch slurry;

c. and (3) drying: drying the batch slurry in a constant-temperature drying oven for 24-36 hours, and discharging absolute ethyl alcohol or/and water in the raw materials to obtain a batch;

d. melting: heating the batch mixture to 1200-1400 ℃ at the speed of 2.5-10 ℃/min in a high-temperature furnace, and preserving the temperature for 1-3 hours to prepare a silicate melt;

e. cooling and annealing: and (3) quickly transferring the silicate melt to a heat preservation furnace with the temperature of 900-1100 ℃, then cooling to the annealing temperature of 450-500 ℃ at the cooling rate of 5-15 ℃/min, preserving the heat for 1-4 hours, and cooling to the normal temperature along with the furnace to obtain the pyrochlore phase borosilicate glass ceramic solidified substrate.

The invention comprises the following steps: in the step b, the anhydrous ethanol or/and water is/are used as a medium, and the raw materials are put into ball milling equipment, preferably: the raw materials, the grinding balls and the absolute ethyl alcohol or/and water are put into ball milling equipment according to the weight percentage of 6-30% of the total weight of the raw materials, 20-60% of the grinding balls and 30-70% of the absolute ethyl alcohol or/and water.

The invention comprises the following steps: in the step c, the batch slurry is dried in a constant-temperature drying oven for 24 to 36 hours, preferably: and drying the batch slurry in a constant-temperature drying oven at the temperature of 60-80 ℃ for 24-36 hours.

The invention comprises the following steps: said Nd in the compounding of step a₂O₃For simulating high-level nuclide Nd³⁺The raw material components of (1).

The invention comprises the following steps: the ball milling equipment in the step b is preferably a planetary ball mill, and the high-speed ball milling is carried out by taking absolute ethyl alcohol or/and water as a medium.

The invention comprises the following steps: the holding furnace in the step e is preferably a high-temperature box type resistance furnace.

The invention comprises the following steps: and the water in the step b is distilled water or deionized water.

Compared with the prior art, the invention has the following characteristics and beneficial effects:

(1) in the pyrochlore phase borosilicate glass ceramic, the pyrochlore can stably confine monovalent metal and divalent alkaline earth metal elements in high radioactive nuclear waste to A site in a crystal structure, confine high radioactive nuclide or high valent metal elements to A site or/and B site in the crystal structure, other elements can enter into a glass phase, and the glass ceramic solidified body prepared by the invention has the advantages of uniform crystal phase size, single structure and high crystallinity;

(2) by adopting the method, the pyrochlore phase in the pyrochlore phase borosilicate glass ceramic solidified body prepared by the method regularly and orderly grows in the glass phase, the pyrochlore is a ceramic material with excellent chemical stability, and the chemical leaching rate of elements in the crystal phase is lower, so that the glass ceramic solidified body prepared by the method has good chemical stability;

(3) the pyrochlore-phase borosilicate glass ceramic solidified substrate is prepared by adopting the process flows of high-temperature melting, rapid cooling, slow cooling and annealing, and the prepared pyrochlore-phase borosilicate glass ceramic solidified body has the advantages of various types of borosilicate glass material containing wastes, large component adjustability, strong pyrochlore-phase ceramic phase nuclide containing capability, low leaching rate and the like;

(4) according to the invention, the pyrochlore phase borosilicate ceramic solidified body is synthesized in one step after ball milling and mixing of the raw materials, the process of secondary heating crystallization is avoided, the one-step synthesis process technology of the glass ceramic material is adopted, the production efficiency is high, the prepared pyrochlore phase borosilicate glass ceramic solidified body has good structural stability, excellent chemical stability, simple process technology, no secondary heating crystallization process, high reliability, suitability for industrial production, easiness for engineering application and wide application in the solidification treatment of high radioactive nuclear waste;

(5) the preparation method has the advantages of simple preparation process, easy operation, simple and convenient process, low cost and strong practicability.

Drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of a pyrochlore-phase borosilicate glass ceramic cured body obtained in example 4, example 13 or example 21;

FIG. 2 is a Scanning Electron Microscope (SEM) photograph of a pyrochlore-phase borosilicate glass-ceramic cured product obtained in example 4, example 13, example 16 or example 21, wherein the surface of the sample was etched with 10% hydrofluoric acid for about 15 seconds.

Detailed Description

The following examples are intended to further illustrate the present invention and should not be construed as limiting the scope of the invention, which is intended to be covered by the claims appended hereto.