CN115477474A - Iron phosphate glass bead for radioactive nuclear waste solidification treatment and preparation method thereof - Google Patents

Abstract

An iron phosphate glass bead for curing radioactive nuclear waste and a preparation method thereof, firstly, the mass percentage of oxide is P ₂ O ₅ 40～70，Fe ₂ O ₃ 5～15，Al ₂ O ₃ 10～30,SiO ₂ 0.5～2，Bi ₂ O ₃ 0.5～2,Cr ₂ O ₃ 0.5～2,M ₂ 0 to 15 of O, (M is one or more of Li, na and K), and 0 to 15 of MeO (Me is one or more of Mg, ca, sr and Ba). Secondly, weighing and uniformly mixing the raw materials, melting and homogenizing the raw materials in a smelting furnace, pouring the molten liquid on a hollow stainless steel roller with cooling water introduced, pressing the molten liquid into glass sheets, and crushing the glass sheets by a machine to obtain small glass blocks. Sieving, mixing the glass pieces with graphite powder, placing into a rocking furnace, rapidly sintering into balls, cooling,and screening out graphite powder. Putting glass balls into Na ₂ CO ₃ And/or treating in NaOH mixed solution, and cleaning the surface to obtain the iron phosphate glass beads which can be used for curing high-radioactive nuclear wastes.

Description

Iron phosphate glass beads used for solidification treatment of radioactive nuclear waste and preparation method thereof

technical field

The invention relates to an iron phosphate glass bead, a preparation method and an application thereof, which are used for solidification treatment of radioactive nuclear waste, and are especially suitable for solidification treatment of high radioactive nuclear waste discharged in fields such as the nuclear industry.

Background technique

Nuclear energy, as a clean energy with no pollution and almost zero emissions, has been widely developed. However, the use of nuclear energy will generate a large amount of radioactive waste, and the problem of its treatment and disposal has become increasingly apparent, which has become a problem of worldwide concern. In order to firmly incorporate radionuclides into a stable inert substrate and meet the requirements for safe disposal, the waste is generally immobilized. As the first generation of solidification technology for high-level radioactive waste, vitrification is currently the only solidification treatment method that has realized industrial operation, and it is also one of the forms that are generally accepted by people and satisfy safe disposal. Vitrification specifically refers to the melting of inorganic components in waste at high temperature, and after cooling, glass or glass-like substances are formed, so that radionuclides are fixed in the glass network to achieve stabilization. Its advantage is that it has no selectivity to radionuclides, can solidify almost all components in high-level waste liquid, and has a low leaching rate of the glass solidified body, a large volume reduction ratio, and good radiation and thermal conductivity. With the world's first vitrification facility put into operation in Marcourt AVM, France, countries such as the United Kingdom, the United States, Belgium, Russia, and Japan have also gradually realized the industrialization of vitrification.

Generally speaking, the nuclear waste vitrification process is directly in the highly radioactive waste liquid or in the calcined material after it is calcined, and puts the matrix glass beads used to contain the nuclear waste in proportion, in a Joule ceramic heating furnace or a high frequency induction furnace It is melted, homogenized, leaked, and then solidified into glass, and the radioactive nuclear waste is fixed in the glass. In order to facilitate melting and increase curing efficiency, the matrix glass is usually melted first and pre-treated to prepare glass beads that facilitate the smooth realization of the process. Glass beads are selected, because the glass beads have good rolling properties and the production process is convenient, and can be easily mixed with nuclear waste and added to the furnace for rapid melting.

The glass bead material used for vitrification treatment, first of all, the matrix glass has good tolerance and can contain a certain amount of nuclear waste. It can quickly react with the nuclear waste in the furnace to form a uniform high-temperature glass melt, and then solidify it through the discharging process. It is a vitrified body with good performance; secondly, it has good vitrification property, which is very important for the preparation of glass beads, and it is difficult to quickly form a ball into a glass matrix that is easy to devitrify. Qualified matrix glass beads are transparent, not easy to bond, and quickly roll into the melter during solidification treatment, increasing the efficiency of continuous melting of nuclear waste solidified glass.

Patent ZL201010190038.1 discloses a production method for glass beads used to solidify high-radioactive nuclear waste, and the selected glass substrate is borosilicate glass. Borosilicate glass can contain a variety of oxides and wastes, and its cured body has good chemical stability and radiation stability. However, for high-level waste liquid containing higher concentrations of sulfur, molybdenum, etc., the solidification ability of borosilicate glass is limited, and it will separate to produce a second phase (yellow phase), which floats above the glass melt and cannot be uniformly Included in the glass matrix, can not play the role of curing. Moreover, the melting temperature of borosilicate glass is too high, and the solidification rate of volatile radioactive isotopes such as strontium and cesium is low. The network structure of phosphate glass is phosphorus-oxygen tetrahedron, which can be connected by bridge oxygen to form different phosphate structures, and has a high tolerance for molybdenum, sulfur and other elements. In the mid-1990s, researchers in the United States developed a new type of phosphate glass with good chemical and thermal stability—iron phosphate glass. The study found that Fe ³⁺ can enter the network structure of phosphate glass to form a stable Fe-OP bond to replace the unstable POP covalent bond, thereby improving the chemical stability of phosphate glass. Compared with borosilicate glass, phosphate vitrified body also has lower melting temperature, glass softening temperature and transition temperature, and has a small viscosity and a wide range of glass formation, and has the potential to become a solidified substrate for nuclear waste treatment.

Contents of the invention

The present invention firstly provides the basic formula of iron phosphate glass used for preparing glass beads, which has good glass-forming performance and strong ability to contain waste; secondly, it provides a preparation method of iron phosphate glass beads used in the solidification process of nuclear waste .

Concrete technical scheme of the present invention is as follows:

A preparation method of iron phosphate glass beads is characterized in that: the composition mass percentage of the glass is:

Wherein M is one or more of alkali metals Li, Na and K, and Me is one or more of alkaline earth metals Mg, Ca, Sr and Ba.

The present invention also provides a kind of preparation method of above-mentioned iron phosphate glass beads, comprising the following steps:

(1), calculate formula according to glass component and mass percentage, and take raw material, mix uniformly, obtain compound;

(2) Put the mixed material into the crucible and melt it in an electric melting furnace at 1000-1200°C, then feed oxygen for 2-4 hours, with a gas volume of 100-120 liters/hour, to obtain a clear and uniform glass melt;

(3), pour the clarified and uniform glass melt on the hollow stainless steel roller that feeds cooling water, press it into a glass sheet with a thickness of 3 mm, and then crush it by machine to obtain a glass block with an outer diameter of 1-3 mm;

(4) Mix glass pieces and graphite powder according to the mass ratio of 1:1, transfer them to a swing electric melting furnace, set the temperature to 850-950°C, swing frequency to 30 rpm, and swing angle to 120° °, depending on the amount of glass, shake quickly for 15 to 45 minutes to soften the surface of the glass block rapidly, and shrink the edges and corners under the action of surface tension, and form glass balls with the swing of the furnace. Transfer the mixture of glass balls and graphite powder to an annealing furnace at 400-500°C, and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter of 1-3mm.

(5) Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3 mol/L, and stir for 10 to 15 minutes to make the lye react with the surface of the glass beads to quickly remove the impurities on the surface of the glass beads. Graphite powder, then wash the lye on the surface of the glass beads with clear water, absolute ethanol, and deionized water in sequence, and finally transfer to a 90°C oven for drying to obtain iron phosphate glass beads.

The beneficial effect of the present invention is that: the composition of spent fuel reprocessing waste is very complex, and at the same time contains more zirconium, molybdenum, rare earth, actinides and the like which are easy to produce crystal phases. Compared with borosilicate glass, the advantage of choosing phosphate glass is that the oxyphosphorus tetrahedron has a large space and a more open structure, which can accommodate more rare earth, actinide and heavy metal ions. Adding a small amount of silicon dioxide, bismuth trioxide and chromium trioxide to the glass composition can adjust the viscosity and improve the glass network. Crystallization. The iron phosphate glass beads prepared by the invention have good anti-crystallization ability and strong ability to contain waste, and because the glass has good glass-forming properties, the leftover material of the beading process can be returned to the furnace for remelting, and can be reprocessed and recycled.

Description of drawings

The X-ray diffraction figure after Fig. 1 glass bead pulverization;

Fig. 2 solidified glass with 22% containment rate;

The X-ray diffraction pattern after Fig. 3 solidified glass pulverization;

Figure 4. Elemental leaching data for 7-day chemical stability of cured glass.

detailed description

The component mass percentage of the iron phosphate glass beads provided in the embodiment is:

Wherein M is one or more of alkali metals Li, Na and K, and Me is one or more of alkaline earth metals Mg, Ca, Sr and Ba.

The preparation method of glass beads in the embodiment comprises the following steps:

(1), calculate formula according to glass component and mass percentage, and take raw material, mix uniformly, obtain compound;

(2) Put the mixed material into the crucible and melt it in an electric melting furnace at 1000-1200°C, then feed oxygen for 2-4 hours, with a gas volume of 100-120 liters/hour, to obtain a clear and uniform glass melt;

(3), pour the clarified and uniform glass melt on the hollow stainless steel roller that feeds cooling water, press it into a glass sheet with a thickness of 3 mm, and then crush it by machine to obtain a glass block with an outer diameter of 1-3 mm;

(4) Mix glass pieces and graphite powder according to the mass ratio of 1:1, transfer them to a swing electric melting furnace, set the temperature to 850-950°C, swing frequency to 30 rpm, and swing angle to 120° °, depending on the amount of glass, shake quickly for 15 to 45 minutes to soften the surface of the glass block rapidly, and shrink the edges and corners under the action of surface tension, and form glass balls with the swing of the furnace. Transfer the mixture of glass balls and graphite powder to an annealing furnace at 400-500°C, and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter of 1-3mm.

(5) Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3 mol/L, and stir for 10 to 15 minutes to make the lye react with the surface of the glass beads to quickly remove the impurities on the surface of the glass beads. Graphite powder, then wash the lye on the surface of the glass beads with clear water, absolute ethanol, and deionized water in sequence, and finally transfer to a 90°C oven for drying to obtain iron phosphate glass beads.

Table 1 provides the glass formulations of 5 embodiments of the present invention:

Table 1

Example 1:

According to Example 1 in Table 1, take by weighing 85.9 grams of ammonium dihydrogen phosphate, 8 grams of ferric oxide, 18 grams of aluminum oxide, 25.6 grams of sodium carbonate, 2.9 grams of barium carbonate, 1.5 grams of bismuth oxide, 1.5 grams of silicon oxide, chromium oxide 0.5 g, mixed evenly to obtain a mixture. After melting in an electric melting furnace at 1000°C, oxygen was introduced for 2 hours at a gas volume of 120 liters per hour to obtain a clear and uniform glass melt. The clarified and uniform glass melt is poured on a hollow stainless steel roller fed with cooling water, pressed into a 3mm thick glass sheet, and then crushed by a machine to obtain a glass block with an outer diameter of 1-3mm. Mix glass pieces and graphite powder in a mass ratio of 1:1, transfer to a swing-type electric melting furnace, set the temperature to 900°C, swing frequency to 30 rpm, swing angle to 120°, and swing quickly for 20 minutes , so that the surface of the glass block is softened rapidly, and the edges and corners shrink under the action of surface tension, and the glass ball is formed as the furnace swings and rolls. Transfer the mixture of glass spheres and graphite powder to an annealing furnace at 450° C., and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter less than 3 mm and greater than 1 mm. Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3mol/L, and stir for 10-15 minutes to make the lye react with the surface of the glass beads to quickly remove the graphite powder on the surface of the glass beads, and then Rinse the lye on the surface of the glass beads sequentially with water, alcohol, and deionized water, and finally transfer to an oven at 90°C for drying to obtain iron phosphate glass beads.

The obtained iron phosphate glass beads are ground, passed through a 200-mesh sieve, and the X-ray diffraction pattern is tested, as shown in Figure 1, the spectral line is a typical amorphous peak package, indicating that there is no devitrification component in the glass, and the glass-forming performance is relatively good. it is good.

The common elements of the high-level radioactive waste liquid of power reactors include zirconium, molybdenum, rare earth and other components. The components of the simulated high-level radioactive waste liquid are ZrO ₂ , MoO ₃ , and La ₂ O ₃ . % simulated high-level radioactive waste liquid components (including Cs ₂ O 2%, SrO 3%, ZrO ₂ 4%, MoO ₃ 7%, La ₂ O ₃ 6%) were mixed evenly, and melted at a high temperature of 1200°C to obtain waste containment The solidified glass with an oxide mass percentage of 22%, as shown in Figure 2.

For the solidified glass, pass through a 200-mesh sieve and add α-Al ₂ O ₃ powder to test the X-ray diffraction pattern. As shown in Figure 3, the main body of the solidified glass is in an amorphous state, and there is a small amount of crystal phase. Compared with the standard pattern, The crystal phase obtained by analysis is called zirconium pyrophosphate. Quantitative analysis of the X-ray diffraction pattern shows that the calculated zirconium pyrophosphate crystal phase inside the solidified glass accounts for 1.6% of the volume of the glass solidified body, which is in line with the nuclear industry standard EJ1186-2005. , the crystallization rate of the glass solidified body after cooling to room temperature is lower than the standard of 5%.

Use the PCT method to evaluate the chemical stability of cured glass, referring to the standard ASTM C1285-14 issued by the American Society for Testing and Materials "Standard test method for determining chemical durability of nuclear, hazardous, and mixed waste glasses and multiphase glass ceramics: the product consistency test (PCT ) method specified in. The sample was pulverized and sieved to separate a powder with a particle size fraction of 100 to 200 mesh, which was washed and dried to constant weight. 1.5 g of each sample was placed in a teflon container filled with deionized water. After sealing, put it in an oven at 90°C for 7 days. Use ICP-OES to measure the concentration of various elements in the leach solution, and evaluate the chemical stability by calculating the normalized mass loss of each element. As shown in Figure 4, the normalized leaching rate of each element is far below 1 gram /( ^m2 ·day), which meets the requirements of performance evaluation of solidified nuclear waste and is suitable for long-term underground geological storage.

Example 2:

According to Example 2 in Table 1, take by weighing 64.8 grams of ammonium dihydrogen phosphate, 15 grams of ferric oxide, 14 grams of aluminum oxide, 2.5 grams of lithium carbonate, 1 gram of magnesium oxide, 16.5 grams of barium carbonate, 18.4 grams of potassium carbonate, bismuth oxide 2 grams, 0.5 grams of silicon oxide, and 1 gram of chromium oxide were uniformly mixed to obtain a mixture. After melting in an electric melting furnace at 1200°C, oxygen was introduced for 2 hours at a gas volume of 120 liters/hour to obtain a clear and uniform glass melt. The clarified and uniform glass melt is poured on a hollow stainless steel roller fed with cooling water, pressed into a 3mm thick glass sheet, and then crushed by a machine to obtain a glass block with an outer diameter of 1-3mm. Mix glass pieces and graphite powder according to the mass ratio of 1:1, transfer to a swing electric melting furnace, set the temperature at 950°C, swing frequency at 30 rpm, swing angle at 120°, and swing quickly for 20 minutes , so that the surface of the glass block is softened rapidly, and the edges and corners shrink under the action of surface tension, and the glass ball is formed as the furnace swings and rolls. Transfer the mixture of glass spheres and graphite powder to an annealing furnace at 480° C., and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter less than 3 mm and greater than 1 mm. Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3mol/L, and stir for 10-15 minutes to make the lye react with the surface of the glass beads to quickly remove the graphite powder on the surface of the glass beads, and then Rinse the lye on the surface of the glass beads sequentially with water, alcohol, and deionized water, and finally transfer to an oven at 90°C for drying to obtain iron phosphate glass beads.

Example 3:

Take by weighing 41 grams of phosphorus pentoxide, 5 grams of ferric oxide, 20 grams of aluminum oxide, 25.6 grams of sodium carbonate, 21.4 grams of strontium carbonate, 1 gram of bismuth oxide, 2 grams of silicon oxide, and chromium oxide according to Example 3 in Table 1. 1 g, mixed evenly to obtain a mixture, which was melted in an electric melting furnace at 1200° C., and then fed with oxygen for 2 hours at a rate of 100 liters/hour to obtain a clear and uniform glass melt. The clarified and uniform glass melt is poured on a hollow stainless steel roller fed with cooling water, pressed into a 3mm thick glass sheet, and then crushed by a machine to obtain a glass block with an outer diameter of 1-3mm. Mix glass pieces and graphite powder in a mass ratio of 1:1, transfer to a swing-type electric melting furnace, set the temperature at 920°C, swing frequency at 30 rpm, swing angle at 120°, and swing quickly for 20 minutes , so that the surface of the glass block is softened rapidly, and the edges and corners shrink under the action of surface tension, and the glass ball is formed as the furnace swings and rolls. Transfer the mixture of glass spheres and graphite powder to an annealing furnace at 480° C., and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter less than 3 mm and greater than 1 mm. Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3mol/L, and stir for 10-15 minutes to make the lye react with the surface of the glass beads to quickly remove the graphite powder on the surface of the glass beads, and then Rinse the lye on the surface of the glass beads sequentially with water, alcohol, and deionized water, and finally transfer to an oven at 90°C for drying to obtain iron phosphate glass beads.

Example 4:

Take by weighing 70 grams of phosphorus pentoxide, 7 grams of ferric oxide, 10 grams of aluminum oxide, 13.7 grams of sodium carbonate, 2 grams of bismuth oxide, 2 grams of silicon oxide, and 1 gram of chromium oxide according to Example 4 in Table 1, and mix well , to obtain the mixture, which was melted in an electric melting furnace at 1100°C, and then fed with oxygen for 2 hours, with a gas volume of 100 liters/hour, to obtain a clear and uniform glass melt. The clarified and uniform glass melt is poured on a hollow stainless steel roller fed with cooling water, pressed into a 3mm thick glass sheet, and then crushed by a machine to obtain a glass block with an outer diameter of 1-3mm. Mix glass pieces and graphite powder in a mass ratio of 1:1, transfer to a swing electric furnace, set the temperature to 850°C, swing frequency to 30 rpm, swing angle to 120°, and swing quickly for 20 minutes , so that the surface of the glass block is softened rapidly, and the edges and corners shrink under the action of surface tension, and the glass ball is formed as the furnace swings and rolls. Transfer the mixture of glass spheres and graphite powder to an annealing furnace at 450° C., and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter less than 3 mm and greater than 1 mm. Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3mol/L, and stir for 10-15 minutes to make the lye react with the surface of the glass beads to quickly remove the graphite powder on the surface of the glass beads, and then Rinse the lye on the surface of the glass beads sequentially with water, alcohol, and deionized water, and finally transfer to an oven at 90°C for drying to obtain iron phosphate glass beads.

Example 5:

Take by weighing 78 grams of ammonium dihydrogen phosphate, 5 grams of ferric oxide, 30 grams of aluminum oxide, 17.1 grams of sodium carbonate, 6.25 grams of calcium carbonate, 0.5 grams of bismuth oxide, 1 gram of silicon oxide, and chromium oxide according to Example 5 in Table 1. 2 g, mixed uniformly to obtain a mixture, which was melted in an electric melting furnace at 1150° C., and fed with oxygen for 2 hours at a rate of 120 liters/hour to obtain a clear and uniform glass melt. The clarified and uniform glass melt is poured on a hollow stainless steel roller fed with cooling water, pressed into a 3mm thick glass sheet, and then crushed by a machine to obtain a glass block with an outer diameter of 1-3mm. Mix glass pieces and graphite powder in a mass ratio of 1:1, transfer to a swing-type electric melting furnace, set the temperature to 900°C, swing frequency to 30 rpm, swing angle to 120°, and swing quickly for 20 minutes , so that the surface of the glass block is softened rapidly, and the edges and corners shrink under the action of surface tension, and the glass ball is formed as the furnace swings and rolls. Transfer the mixture of glass spheres and graphite powder to an annealing furnace at 470° C., and anneal for 4 hours. Then cool down to room temperature with the furnace, sieve, and sieve out the graphite powder to obtain glass beads with a diameter less than 3 mm and greater than 1 mm. Put the sieved glass beads into the Na ₂ CO ₃ /NaOH solution with a concentration of 0.3mol/L, and stir for 10-15 minutes to make the lye react with the surface of the glass beads to quickly remove the graphite powder on the surface of the glass beads, and then Rinse the lye on the surface of the glass beads sequentially with water, alcohol, and deionized water, and finally transfer to an oven at 90°C for drying to obtain iron phosphate glass beads.

The iron phosphate glass beads prepared by the invention have strong tolerance and can contain volatile radioactive elements such as strontium and cesium, zirconium and rare earth elements that are easy to devitrify, and elements that are easy to produce yellow phases such as molybdenum and sulfur. The glass beads prepared by the method have a smooth surface and good rolling property, and can be conveniently rolled into a solidified glass Joule ceramic heating furnace or an electromagnetic induction furnace for continuous melting, and are suitable for solidification treatment of high-radioactive nuclear waste.

Claims (7)

1. an iron phosphate glass bead for radioactive nuclear waste solidification treatment, it is characterized in that: the composition mass percentage of described iron phosphate glass bead is:

Wherein, M is one or more of alkali metals Li, Na, and K, and Me is one or more of alkaline earth metals Mg, Ca, Sr, and Ba. 2. iron phosphate glass beads according to claim 1, is characterized in that: the composition mass percent of described iron phosphate glass beads is:

Wherein, M is one or more of alkali metals Li, Na, and K, and Me is one or more of alkaline earth metals Mg, Ca, Sr, and Ba. 3. iron phosphate glass beads according to claim 2, is characterized in that: the composition mass percent of described iron phosphate glass beads is:

. 4. a preparation method of the arbitrary described iron phosphate glass beads of claim 1-3, is characterized in that, comprises the following steps: ①. Calculate the formula according to the glass components and mass percentage, weigh the raw materials, and mix them evenly; ②. The mixture is melted at high temperature in a furnace to form a clear and uniform glass melt; ③. Pouring the melted glass on a hollow stainless steel roller fed with cooling water, pressing it into a glass sheet, and pulverizing it to obtain a glass block; 4. Mix the glass cullets and graphite powder according to the volume ratio of 1:3, and transfer them to swing in a swing furnace to form glass spheres; ⑤. Annealing, sieving and cleaning the glass spheres to obtain the iron phosphate glass beads. 5. the preparation method of iron phosphate glass beads as claimed in claim 4 is characterized in that, described annealing, sieving and cleaning treatment refer to that described glass spheres are transferred to an annealing furnace for annealing, and are cooled with the furnace to room temperature, then sieve, and sieve out the graphite powder to obtain glass beads; put the sieved glass beads into Na ₂ CO ₃ /NaOH solution, stir for 10-15 minutes, make the lye react with the surface of the glass beads, and remove the glass beads The graphite powder on the surface is washed with clear water, absolute ethanol, and deionized water in order to wash the lye on the surface of the glass beads, and finally transferred to an oven for drying to obtain iron phosphate glass beads. 6 . The method for preparing iron phosphate glass beads according to claim 5 , wherein the concentration of the Na ₂ CO ₃ /NaOH solution is 0.3 mol/L. 7. The application of the glass beads described in any one of claims 1-6 in the vitrification treatment of radioactive nuclear waste.

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