CN116813197A - A kind of borosilicate glass curing aid for the treatment of medium and low radioactive waste liquid and its use method - Google Patents

Abstract

A borosilicate glass curing aid for the treatment of medium and low radioactive waste liquids and its use method. Its composition range is: SiO ₂ 45～65, B ₂ O ₃ 12～25, Al ₂ O ₃ 0.6～ 20. ZnO 0.6～6.5, ZrO ₂ 0.6～2.5, RE ₂ O ₃ 0.6～6.5, MO 0.6～12, among which, RE ₂ O ₃ (RE is one or more of La, Nd, Y), M is One or more of Mg, Ca, Sr and Ba. The mass percentage of Na ₂ O in the prepared cured glass can reach 20-30%, and the cured glass product satisfies the molar ratio of O/(Si+B+Al) of 2.0-2.5, (2ΣM+Na)/(Si+B +Al) molar ratio is 0.5 to 1.0. The method of use is to weigh and mix the raw materials of additives and sodium oxide according to the proportion of the formula, melt, pour, and anneal in an electric furnace to produce high-sodium solidified glass. This product meets the requirements of the solidified glass production process, and its viscosity and conductivity The process parameters such as rate are moderate, and it is suitable for the solidification treatment of high sodium, medium and low radioactive steam waste liquids.

Description

A borosilicate glass curing aid for the treatment of medium and low radioactive waste liquids and How to use it

Technical field

The invention belongs to a method for processing medium and low radioactive nuclear waste. It relates to a borosilicate curing glass additive with high sodium oxide containment rate and a method of using it. It is suitable for high sodium, medium and low radioactive materials discharged from the nuclear industry and other fields. Solidification of nuclear waste.

Background technique

Nuclear energy does not produce any air pollution during power generation and is efficient and practical as a clean energy source. However, the radioactive waste produced in the nuclear fuel cycle is extremely toxic and can cause great damage to the ecological environment. Its safe disposal has always been the focus of domestic and foreign attention. According to the different radioactivity levels of nuclear waste, nuclear waste is divided into high-level waste, intermediate-level waste and low-level waste. Among them, medium- and low-level radioactive nuclear waste liquids originate from the three stages of the nuclear fuel cycle (front-end, middle-end or operation, back-end), accounting for the largest proportion, reaching 97%. Vitrification technology is currently a feasible method widely used in the world to treat and dispose of medium and low radioactive nuclear waste liquid. By co-melting liquid low- and medium-level radioactive waste with basic glass raw materials into a glass body, atomic-scale solidification of low-level and medium-level radioactive waste can be achieved, thereby preventing the migration of radionuclides to the external environment within the disposal life of the solidified glass body.

At present, the United States, South Korea, Italy and Russia have all used glass solidification methods to treat low- and medium-level radioactive waste liquids and plan to conduct geological disposal. China's nuclear waste reprocessing plants urgently need to dispose of the solidified acidic low-medium radioactive vapor residue and alkaline medium-low radioactive vapor residue, which mainly contain source items such as UO ₂ (NO ₃ ) ₂ and NaNO _3. The mass of NaNO ₃ The proportion reaches more than 99%. The research on the formula of solidifying medium and low radioactive waste liquid is mainly reflected in solidifying high content mass percentage of sodium oxide. Sodium oxide is a highly reactive alkali metal oxide. If the solidified glass contains a large amount of sodium oxide, it will inevitably affect the chemical stability of the solidified body. The storage of solidified glassware of medium and low radioactive waste liquids needs to be maintained for more than hundreds of years. Therefore, higher requirements are placed on the chemical stability of cured glass formulations containing high mass percentages of sodium oxide.

Borosilicate glass curing substrate has the advantages of good thermodynamic stability, good chemical stability, low radionuclide leaching rate, and small thermal expansion coefficient. Therefore, borosilicate glass is preferred as the curing material in large foreign glass curing facilities. base material. Chinese patent 200980153530.7 discloses an aluminoborosilicate solidified glass for treating moderately radioactive waste liquids. The maximum mass content of sodium oxide in the prepared glass solidified body is only 15%. Literature Liu Lijun et al., Nuclear Chemistry and Radiochemistry, 2014, Vol. 36, No3: 163-168. published a high-sulfur and high-sodium borosilicate cured glass formula, in which the sodium oxide content in the base glass is 5.21% , the content of sodium oxide in the source term is 45.103%. Calculated based on the containment rate of the source term of 16%, the total sodium oxide content of this cured glass formula is only 12.37%.

In view of the extremely high cost of disposal of low-quality solidified glass, it is necessary to increase the containment rate of sodium oxide. Therefore, it is necessary to develop a method that has a high containment rate of sodium oxide, and the chemical stability of the solidified product meets the requirements of geological disposal conditions, and is suitable for continuous melting production. Curing glass additives.

Contents of the invention

In view of the above requirements that the solidification and disposal of existing medium and low radioactive waste liquids need to contain higher sodium oxide content, a borosilicate curing glass additive with high sodium oxide containment rate and its use method are proposed. The prepared high-sodium solidified glass has good glass-forming properties and high chemical stability, and is suitable for the continuous solidification treatment of medium and low-level radioactive waste.

The technical solution of the present invention is as follows:

The oxide mass percentage component range of borosilicate curing glass additives used to cure Na ₂ O is:

Among them, RE ₂ O ₃ (RE is one or more of La, Nd, Y), and M is one or more of Mg, Ca, Sr, and Ba.

Using the above curing glass additives to cure cured glass products with high sodium oxide content, the mass percentage based on the total mass of the cured glass is:

Among them, RE ₂ O ₃ (RE is one or more of La, Nd, Y), M is one or more of Mg, Ca, Sr, Ba, and satisfies O/(Si+B+Al) The molar ratio of (2ΣM+Na)/(Si+B+Al) is 0.5-1.0.

The invention also provides a method for using the above-mentioned borosilicate curing glass additive to contain high sodium oxide, which includes the following steps:

(1) Weigh the raw materials according to the mass percentage of glass additives and sodium oxide, and mix them evenly to obtain a mixture;

(2) Put the mixture into a crucible, put it into a furnace with a temperature ranging from 1150 to 1200°C, melt it, and clarify it for 1 to 3 hours to obtain a clear and uniform glass melt;

(3) Pour the clear and uniform glass melt into a stainless steel mold preheated to 350-450°C, and then transfer it to an annealing furnace preheated to 450-500°C;

(4) Keep the temperature in the annealing furnace for 1 to 5 hours, and then lower to room temperature to obtain high borosilicate solidified glass.

In the above preparation method, when the raw materials are weighed according to the glass composition and mass percentage as described in step (1), B ₂ O ₃ comes from one or more of B ₂ O ₃ and boric acid; Al ₂ O ₃ comes from Al( OH) ₃ , one or more of aluminum carbonate, aluminum nitrate; Na ₂ O comes from one or more of sodium carbonate, nitrate; the MO comes from the carbon of alkaline earth metal One or more of acid salts and nitrates.

The present invention will be further described below. The present invention requires that the molar ratio of O/(Si+B+Al) be controlled at 2.0-2.5, and the molar ratio of (2ΣM+Na)/(Si+B+Al) be controlled at 0.5-1.0. The prepared solidified glass takes on the amorphous form of glass after casting and annealing. The main network bodies in glass are silicon, boron, and aluminum. When the molar ratios of O/(Si+B+Al) and (2ΣM+Na)/(Si+B+Al) are high, the glass network body is insufficient and it is easy to analyze. crystallization, and will reduce the chemical stability of the glass; when it is lower, the glass modifier is insufficient, which will also lead to phase separation and crystallization.

A small amount of ZrO ₂ also participates in the glass network, which is beneficial to improving the chemical stability of the glass, but if it exceeds 2%, it is easy to produce crystal nuclei, leading to crystallization and reducing the glass-forming properties of the glass. Rare earth oxides such as lanthanum oxide, neodymium oxide and yttrium oxide can increase the thermal transition temperature of glass, improve the glass-forming properties of glass, and increase the viscosity of glass. As a modification of glass, alkaline earth metals can adjust the coordination number, conductivity, and viscosity of glass.

The beneficial effects of the present invention are:

The glass additive provided by the invention can contain sodium oxide with a high-quality percentage content, and the cured glass prepared is transparent without crystallization and has excellent chemical stability, meeting the requirements for the chemical stability of the solidified body in the nuclear industry standard EJ1186-2005. The viscosity and conductivity of the solidified glass are suitable for the solidification production process of the Joule ceramic electric furnace of the continuous furnace, and are suitable for the solidification treatment of medium and low-level radioactive waste liquids with high sodium content.

Description of the drawings

Figure 1 is a graph of elemental leaching rates of 28-day chemical stability of six embodiments of the present invention.

Detailed ways

The component mass percentage of the high-sodium borosilicate cured glass product provided in the embodiment for the treatment of medium and low radioactive waste liquids is:

Among them, RE ₂ O ₃ (RE is one or more of La, Nd, Y), M is one or more of Mg, Ca, Sr, Ba, and O/(Si+B+Al) The molar ratio is 2.0 to 2.5, and the molar ratio of (2ΣM+Na)/(Si+B+Al) is 0.5 to 1.0.

In the embodiment, the method of using the above-mentioned glass additive to contain high content of sodium oxide includes the following steps:

(1) Weigh the raw materials according to the glass components and mass percentage, and mix them evenly to obtain a mixture;

(2) Put the mixture into a crucible, put it into a furnace with a temperature ranging from 1150 to 1200°C according to the composition and mass percentage, and melt it, and then clarify it for 1 to 3 hours to obtain a clear and uniform glass melt;

(3) Pour the clear and uniform glass melt into a stainless steel mold preheated to 350-450°C and then quickly transfer it to an annealing furnace preheated to 450-500°C;

(4) Keep the temperature in an annealing furnace for 1 to 5 hours, and then lower it to room temperature at a rate of 1°C/minute to obtain the borosilicate solidified glass.

The present invention will be further described below in conjunction with specific examples.

Table 1 shows the composition of cured glass products, the molar ratios of O/(Si+B+Al) and (2ΣM+Na)/(Si+B+Al) of six embodiments of the present invention:

Table 1

Example 1:

According to the mass percentage composition of the oxides in the formula of Example 1 in Table 1: weigh 44 grams of sodium carbonate, 42 grams of silicon dioxide, 17.7 grams of diboron trioxide, 4 grams of aluminum oxide, 3 grams of zinc oxide, and 1 gram of zirconium oxide. g, 1 g of lanthanum oxide, 1 g of neodymium oxide, 2 g of yttrium oxide, 4 g of light magnesium oxide, and 1.29 g of barium carbonate, mix evenly to obtain a mixture, put the mixture into a silica crucible, and heat it at 1200°C Melt in the furnace and clarify for 1 hour to obtain a clear and uniform glass melt; pour the clear and uniform glass melt into a stainless steel mold preheated to 390°C and then quickly transfer it to an annealing furnace preheated to 500°C; Keep the temperature in the annealing furnace for 2.5 hours to eliminate stress, and then lower it to room temperature at a rate of 1°C/minute to obtain high-sodium borosilicate glass for solidification treatment of medium and low radioactive waste liquids. The high-temperature viscosity of glass at 1150°C was measured to be 23 Poise using Orton's RSV-16RT high-temperature rotational viscometer. The resistivity was measured according to the method provided in GB/T 10581-2006 "Test Plan for Resistance and Resistivity of Insulator Materials at High Temperatures" and the conductivity at 1150°C was calculated to be 0.56S/cm. According to the standard EJ 1186-2005 "Characterization of Radioactive Waste Bodies and Waste Packages", the normalized element leaching rate of static immersion in deionized water at 90℃±1℃ for 28 days is shown in the figure. The leaching rates of single elements are less than 0.2g/m ² . The chemical stability, viscosity, conductivity and other process parameters are suitable for the continuous smelting and geological storage of solidified glass for medium and low radioactive waste liquids.

Example 2:

According to the mass percentage composition of the oxide in the formula of Example 2 in Table 1: weigh 51.3 grams of sodium carbonate, 50 grams of silicon dioxide, 26.6 grams of boric acid, 0.5 grams of aluminum oxide, 2 grams of zinc oxide, 2 grams of zirconium oxide, 0.5 grams of lanthanum and 7.1 grams of strontium carbonate are mixed evenly to obtain a mixture. Put the mixture into a silica crucible, melt it in a furnace at 1200°C, and clarify it for 1 hour to obtain a clear and uniform glass melt; The glass melt is poured into a stainless steel mold preheated to 390°C and then quickly transferred to an annealing furnace preheated to 500°C. It is kept in the annealing furnace for 2.5 hours to eliminate stress, and then reduced to a temperature of 1°C/min at a rate of 1°C/min. At room temperature, high-sodium borosilicate glass for solidification treatment of medium and low radioactive waste liquids was obtained. The high-temperature viscosity of glass at 1150°C was measured to be 40 Poise using Orton's RSV-16RT high-temperature rotational viscometer. Test the resistivity according to the method provided in GB/T 10581-2006 "Test Plan for Resistance and Resistivity of Insulator Materials at High Temperatures", and calculate the conductivity at 1150°C to be 0.13S/cm. According to the standard EJ 1186-2005 "Characterization of Radioactive Waste Bodies and Waste Packages", the normalized element leaching rate of static immersion in deionized water at 90℃±1℃ for 28 days is shown in the figure. The leaching rates of single elements are less than 0.2g/m ² . The chemical stability, viscosity, conductivity and other process parameters are suitable for the continuous smelting and geological storage of solidified glass for medium and low radioactive waste liquids.

Example 3:

According to the mass percentage composition of the oxides in the formula of Example 3 in Table 1: weigh 34.2 grams of sodium carbonate, 55 grams of silicon dioxide, 23.1 grams of boric acid, 15.3 grams of aluminum hydroxide, 0.5 grams of zinc oxide, 2 grams of zirconium oxide, 1 gram of lanthanum oxide, 1 gram of neodymium oxide, 3 grams of yttrium oxide, 2 grams of light magnesium oxide, and 7 grams of calcium carbonate. Mix evenly to obtain a mixture, put the mixture into an alumina crucible, melt it in a furnace at 1200°C, and clarify it for 1 hour to obtain a clear and uniform glass melt; pour the clear and uniform glass melt into a furnace preheated to 390°C Formed in a stainless steel mold, and then quickly transferred to an annealing furnace preheated to 500°C; kept in the annealing furnace for 2.5 hours to eliminate stress, and then lowered to room temperature at a rate of 1°C/min to obtain medium and low radioactive waste liquid Cured high sodium borosilicate glass. The high-temperature viscosity of glass at 1150°C was measured to be 33 Poise using Orton's RSV-16RT high-temperature rotational viscometer. Test the resistivity according to the method provided in GB/T 10581-2006 "Test Plan for Resistance and Resistivity of Insulator Materials at High Temperatures", and calculate the conductivity at 1150°C to be 0.7S/cm. According to the standard EJ 1186-2005 "Characterization of Radioactive Waste Bodies and Waste Packages", the normalized element leaching rate of static immersion in deionized water at 90℃±1℃ for 28 days is shown in the figure. The leaching rates of single elements are less than 0.17g/m ² . The chemical stability, viscosity, conductivity and other process parameters are suitable for the continuous smelting and geological storage of solidified glass for medium and low radioactive waste liquids.

Example 4:

According to the mass percentage composition of the oxides in the formula of Example 4 in Table 1: weigh 41 grams of sodium carbonate, 35 grams of silicon dioxide, 35.5 grams of boric acid, 18.3 grams of aluminum hydroxide, 5 grams of zinc oxide, 1.5 grams of zirconium oxide, 2 grams of yttrium and 3.7 grams of magnesium hydroxide are mixed evenly to obtain a mixture. Put the mixture into an alumina crucible, melt it in a furnace at 1200°C, and clarify it for 1 hour to obtain a clear and uniform glass melt; The glass melt is poured into a stainless steel mold preheated to 390°C and then quickly transferred to an annealing furnace preheated to 500°C. It is kept in the annealing furnace for 2.5 hours to eliminate stress, and then reduced to a temperature of 1°C/min at a rate of 1°C/min. At room temperature, high-sodium borosilicate glass for solidification treatment of medium and low radioactive waste liquids was obtained. The high-temperature viscosity of glass at 1150°C was measured to be 22 Poise using Orton's RSV-16RT high-temperature rotational viscometer. Test the resistivity according to the method provided in GB/T 10581-2006 "Test Plan for Resistance and Resistivity of Insulator Materials at High Temperatures", and calculate the conductivity at 1150°C to be 0.6S/cm. According to the standard EJ 1186-2005 "Characterization of Radioactive Waste Bodies and Waste Packages", the normalized element leaching rate of static immersion in deionized water at 90℃±1℃ for 28 days is shown in the figure. The leaching rates of single elements are less than 0.18g/m ² . The chemical stability, viscosity, conductivity and other process parameters are suitable for the continuous smelting and geological storage of solidified glass for medium and low radioactive waste liquids.

Example 5:

According to the mass percentage composition of the formula oxide in Example 5 in Table 1: weigh 34.2 g of sodium carbonate, 55 g of silica, 28.9 g of boric acid, 0.5 g of alumina, 1 g of zinc oxide, 0.5 g of zirconium oxide, and neodymium oxide. 2 grams, 4.3 grams of strontium carbonate, and 5.2 grams of barium carbonate, mix evenly to obtain a mixture, put the mixture into an alumina crucible, melt it in a furnace at 1200°C, and clarify it for 1 hour to obtain a clear and uniform glass melt; The clear and uniform glass melt is poured into a stainless steel mold preheated to 390°C and then quickly transferred to an annealing furnace preheated to 500°C. It is kept in the annealing furnace for 2.5 hours to eliminate stress, and then heated to 1°C/min. The rate is reduced to room temperature, and high-sodium borosilicate glass is obtained for solidification treatment of medium and low radioactive waste liquids. The high-temperature viscosity of glass at 1150°C was measured to be 75 Poise using Orton's RSV-16RT high-temperature rotational viscometer. Test the resistivity according to the method provided by GB/T10581-2006 "Test Plan for Resistance and Resistivity of Insulator Materials at High Temperatures", and calculate the conductivity at 1150°C to be 0.55S/cm. According to the standard EJ 1186-2005 "Characterization of Radioactive Waste Bodies and Waste Packages", the normalized element leaching rate of static immersion in deionized water at 90℃±1℃ for 28 days is shown in the figure. The leaching rates of single elements are less than 0.16g/m ² . The chemical stability, viscosity, conductivity and other process parameters are suitable for the continuous smelting and geological storage of solidified glass for medium and low radioactive waste liquids.

Example 6:

According to the mass percentage composition of the oxide in Example 6 in Table 1: weigh 39.2 grams of sodium carbonate, 42 grams of silicon dioxide, 19.5 grams of boric acid, 15 grams of aluminum oxide, 3 grams of zinc oxide, 1 gram of zirconium oxide, and neodymium oxide. 3 grams, light magnesium oxide 2 grams, strontium carbonate 1.42 grams. Mix evenly to obtain a mixture, put the mixture into an alumina crucible, melt it in a furnace at 1200°C, and clarify it for 1 hour to obtain a clear and uniform glass melt; pour the clear and uniform glass melt into a furnace preheated to 390°C Formed in a stainless steel mold, and then quickly transferred to an annealing furnace preheated to 500°C; kept in the annealing furnace for 2.5 hours to eliminate stress, and then lowered to room temperature at a rate of 1°C/min to obtain medium and low radioactive waste liquid Cured high sodium borosilicate glass. The high-temperature viscosity of glass at 1150°C was measured to be 25 Poise using Orton's RSV-16RT high-temperature rotational viscometer. Test the resistivity according to the method provided by GB/T10581-2006 "Test Plan for Resistance and Resistivity of Insulator Materials at High Temperatures", and calculate the conductivity at 1150°C to be 0.45S/cm. According to the standard EJ 1186-2005 "Characterization of Radioactive Waste Bodies and Waste Packages", the normalized element leaching rate of static immersion in deionized water at 90℃±1℃ for 28 days is shown in the figure. The leaching rates of single elements are less than 0.18g/m ² . The chemical stability, viscosity, conductivity and other process parameters are suitable for the continuous smelting and geological storage of solidified glass for medium and low radioactive waste liquids.

Claims (9)

1. A borosilicate glass curing additive for the treatment of medium and low radioactive waste liquids, characterized in that the oxide mass percentage component range of the additive is: Among them, RE ₂ O ₃ (RE is one or more of La, Nd, Y), and M is one or more of Mg, Ca, Sr, and Ba. 2. The glass curing aid for treating medium and low radioactive waste liquid according to claim 1, characterized in that the B ₂ O ₃ comes from one or more of B ₂ O ₃ and boric acid; Al ₂ O ₃ comes from one or more of Al(OH) ₃ , aluminum carbonates, and nitrates; the MO comes from one or more of alkaline earth metal carbonates and nitrates. 3. According to claims 1 and 2, the glass curing aid for the treatment of medium and low radioactive waste liquids, the more preferred range of oxide mass percentage components is: 4. A method for solidifying medium and low radioactive waste liquids, characterized in that the glass curing aid for medium and low radioactive waste liquid treatment according to any one of claims 1 to 3 is used to solidify high-content Na ₂ O, the mass percentage of Na ₂ O in the prepared cured glass is 20 to 30%. 5. The solidification treatment method for medium and low radioactive waste liquid according to claim 4, characterized in that the solidification method includes the following steps: Step (1). Weigh the raw materials according to the following mass percentages and mix them evenly to obtain a mixture; Among them, RE is one or more of La, Nd, Y, M is one or more of Mg, Ca, Sr, Ba, and the molar ratio of O/(Si+B+Al) is 2.0~2.5 , the molar ratio of (2ΣM+Na)/(Si+B+Al) is 0.5~1.0; Step (2). Put the obtained mixture into a crucible, place it in a furnace to melt and clarify, and obtain a clear and uniform glass melt; Step (3). After the glass melt is cast and formed, it is annealed in a preheated annealing furnace to obtain high-sodium borosilicate solidified glass. 6. The solidification treatment method of medium and low radioactive waste liquid according to claim 5, characterized in that the high sodium borosilicate solidified glass is in the amorphous form of glass, and the network body in the glass is silicon, boron and aluminum. 7. The solidification treatment method of medium and low radioactive waste liquid according to claim 5 or 6, characterized in that the melting temperature is 1100-1200°C and the melting time is 13 hours. 8. The solidification treatment method of medium and low radioactive waste liquid according to claim 5 or 6, characterized in that the conductivity of the glass melt at 1150 degrees is 0.1~0.7S/cm, and the viscosity is 20~80Poise between. 9. The method for curing medium and low radioactive waste liquid according to any one of claims 5 to 8, characterized in that after the cured glass is statically soaked in deionized water at 90°C ± 1°C for 28 days, the single element The normalized leaching rates are all less than 1g/(day·m ² ).