Method for inhibiting crystallization of high-level waste glass solidified body

Abstract

The invention relates to the technical field of radioactive waste solidification treatment, in particular to a method for inhibiting crystallization of a high-level waste glass solidified body, which comprises the following steps: S1, uniformly mixing glass raw materials, heating, melting and cooling to obtain base glass; s2, mixing the base glass with high-level waste, heating, melting and cooling to obtain a glass solidified body; wherein the glass curing body comprises a network changing body and a network forming body; and the molar ratio of the network altering body ions to the network forming body ions is 0.4-0.5. By limiting the ratio of the content of the network changing body to the content of the network forming body in the glass solidified body, high-efficiency solidification of the simulated high-level waste is achieved, meanwhile, crystals in the waste glass melt and the solidified body are prevented from being separated out, good technological performance and solidified body performance are maintained, and the method has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of solidification treatment of radioactive waste, and particularly to a method for inhibiting crystallization of high-level radioactive waste glass solidified body. Background Art

[0002] Glass solidification is a widely accepted and most widely used method for treating high-level radioactive liquid waste worldwide. It fixes radionuclides in a flexible glass network structure to achieve atomic-scale solidification of various toxic elements and prevent them from migrating to the external environment. Due to the complex composition of high-level radioactive liquid waste, it has the characteristics of high content of transition metal elements (such as molybdenum, iron, and nickel), high content of rare earth elements (such as neodymium, cerium, and lanthanum), and high content of corrosion activation products (such as zirconium). For example, in high-level radioactive liquid waste generated during the reprocessing of spent fuel with a burnup of 45000 MWd / tU or more, the contents of molybdenum, neodymium, and zirconium (calculated as oxides) in the waste oxides are generally greater than 10 wt%. Therefore, high-level radioactive waste glass needs to have a high containment capacity for the above-mentioned various waste elements.

[0003] Due to the excellent physical and chemical stability and relatively low melting temperature of borosilicate glass, it has become the preferred base material for glass solidification. However, the relatively low containment capacity of borosilicate for molybdenum trioxide limits the improvement of the waste loading. Since molybdenum exists as molybdate in the depolymerized region of the glass network, currently, mainly by adding high contents of boron, alkali / alkaline earth metals to the glass to increase the flexibility of the glass network, thereby enhancing the solidification ability for molybdenum. For example, Chinese patents CN 115057618 B and CN 115583796A disclose solidification formulations of silicate glass with high boron content, by introducing high contents of boron oxide and sufficient alkali metal / alkaline earth metals to provide sufficient network voids for the dissolution of molybdate.

[0004] However, the relatively high degree of network depolymerization, while enhancing the waste containment capacity, reduces the anti-crystallization ability of the glass by lowering the crystallization activation energy. During melting and heat preservation, the precipitation and deposition of crystals may increase the melt viscosity, resulting in difficult discharging, and in severe cases, blocking the discharge port. The precipitation of some crystal types may cause the composition of the waste glass to deviate from the target value, leading to a decline in properties such as leaching resistance.

[0005] It is necessary to develop a method for inhibiting the crystallization problem of high-level radioactive waste glass to achieve efficient solidification of high-level radioactive liquid waste while avoiding the precipitation of crystals in the glass melt and the solidified body, and maintaining good process performance and solidified body performance. Therefore, how to balance the waste element containment capacity of high-level radioactive waste glass and the anti-crystallization performance of the glass has become an urgent technical problem to be solved. Summary of the Invention

[0006] In view of this, the present invention provides a method for suppressing the crystallization of high-level radioactive waste glass, which controls the degree of network polymerization of the glass, avoids the crystallization of the waste glass melt and the solidified body, ensures the safe operation of the furnace and the stable performance of the solidified body, realizes the efficient solidification of simulated high-level radioactive waste, and maintains the good anti-crystallization performance of the glass.

[0007] The technical solution of the present invention is realized as follows:

[0008] In a first aspect, the present invention provides a method for suppressing the crystallization of a high-level radioactive waste glass solidified body, comprising the steps of:

[0009] S1. Mix the glass raw materials evenly, heat and melt them, and then cool to obtain a base glass;

[0010] S2. Mix the base glass with high-level radioactive waste, heat and melt them, and then cool to obtain a glass solidified body;

[0011] Wherein, the oxide composition in the glass solidified body includes network modifiers and network formers;

[0012] The molar ratio of the ions of the network modifier to the network former is 0.4 to 0.5.

[0013] On the basis of the above technical solution, further, the ions of the network modifier include one or more of Li + , Na + , Ca 2+ , K + , Cs + , Rb + , Mg 2+ , Ba 2+ and Sr 2+ . It can destroy the glass network structure, provide more sites for the dissolution of waste components such as molybdenum in the glass, and at the same time improve the glass-forming ability.

[0014] On the basis of the above technical solution, further, the network former ions include multiple of Si 4+ , B 3+ and Al 3+ . Their high content can form a complete network and enhance the thermal stability of the glass.

[0015] Specifically, by controlling the molar ratio of the ions of the network modifier to the network former in the high-level radioactive waste vitrified body, the purpose of balancing the waste containment capacity and anti-crystallization performance of the glass is achieved. When the ratio is less than 0.4, the content of alkali / alkaline earth metals as network modifiers in the glass is too low, the degree of polymerization of the glass network is relatively high, and it is difficult to homogenize due to insufficient glass-forming ability and insufficient containment capacity for waste components such as molybdenum. When the ratio is greater than 0.5, the content of alkali / alkaline earth metals as network modifiers in the glass is relatively high, the glass network is damaged by the network modifier, resulting in a decrease in the degree of polymerization. At the same time, the increase in network flexibility will significantly increase the diffusion rate of easily precipitated components in the glass melt, leading to an increase in the crystallization tendency of the glass. When the ratio is between 0.4 and 0.5, the glass has both high waste solidification ability and good anti-crystallization performance.

[0016] Based on the above technical solutions, further, the chemical composition of the vitrified body includes SiO 2 , B 2 O 3 , Al 2 O 3 , CaO, MgO, BaO, Li 2 O, Na 2 O, MoO 3 , ZrO 2 , Nd 2 O 3 , La 2 O 3 , CeO 2 , Y 2 O 3 , Fe 2 O 3 , Cr 2 O 3 , NiO, TeO 2 , SnO 2 , BaO, SrO, Cs 2 O, Rb 2 O, K 2 O, MnO, etc.

[0017] Based on the above technical solutions, further, the molar ratio of the network modifier to the network former is 0.42 to 0.46.

[0018] Based on the above technical solutions, further, the heating and melting temperature in steps S1 and S2 is 1100 - 1300 °C, and the heating and melting time in steps S1 and S2 is 1 - 24 h.

[0019] On the basis of the above technical solutions, further, the cooling method is to pour the glass liquid obtained by heating and melting and then naturally cool it in the air.

[0020] In a second aspect, the present invention provides a high-level radioactive waste vitrified body, which is prepared by using the method described in the first aspect.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) By restricting the lower limit of the ratio of the network modifier to the network former in the waste glass, there are enough gaps in the network to ensure the effective solidification of the waste components by the glass;

[0023] (2) By restricting the upper limit of the ratio of the network modifier to the network former in the waste glass, the integrity of the glass network is ensured, and then the crystallization is inhibited by increasing the activation energy for crystal precipitation;

[0024] (3) The method provided by the present invention is easy to achieve the efficient solidification of simulated high-level radioactive waste liquid while avoiding crystal precipitation in the glass melt and the vitrified body, maintaining good process performance and vitrified body performance, and having good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is the XRD pattern of the high-level radioactive waste liquid vitrified body prepared in Examples 1-5 and Comparative Example 1 of the present invention after heat treatment at 800 °C for 24 h. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a method for suppressing the crystallization of high-level radioactive waste vitrified body, and a simulated high-level radioactive waste vitrified body is prepared. Its designed composition is shown in Table 1, where the molar ratio of network modifier ions to network former ions is 0.40. The specific steps are as follows:

[0030] (1) Calculate the basic glass components, weigh the borosilicate glass raw materials and mix them evenly, heat and melt them in a muffle furnace at 1200 °C for 1 h, and after the glass melt is naturally cooled in the air, break it to obtain borosilicate basic glass with a particle size of 2 mm;

[0031] (2) Mix the basic glass particles and the simulated high-level radioactive waste according to the calculated ratio, heat and melt them in a muffle furnace at 1150 °C for 3 h, and after the glass melt is naturally cooled in the air, obtain the simulated glass solidified body.

[0032] Break the obtained simulated glass solidified body into glass particles with a particle size of about 1 mm, wash and dry them thoroughly, weigh 3 g of glass powder sample, put it into a covered corundum crucible, and heat-treat it at 800 °C for 24 h. Through semi-quantitative analysis of the X-ray diffraction pattern, the crystal content precipitated in the glass is measured to be about 0.1 wt%.

[0033] Table 1

[0034]

[0035]

[0036] Example 2

[0037] This embodiment provides a method for suppressing the crystallization of high-level radioactive waste vitrified body, and a simulated high-level radioactive waste vitrified body is prepared. Compared with Example 1, the main difference is that on the premise of keeping the contents of the remaining components unchanged, the following components are adjusted, which are 47.5% SiO in terms of mass percentage of oxides 2 , 14.5% B 2 O 3 , 10.5% Na 2 O, 2.5% Li 2 O, 4.5% Al 2 O 3 , 5.0% CaO, and its designed composition is shown in Table 2, where the molar ratio of network modifier ions to network former ions is 0.47. The specific steps are as follows:

[0038] (1) Calculate the basic glass components, weigh the borosilicate glass raw materials and mix them evenly, heat and melt them in a muffle furnace at 1100 °C for 24 h, and after the glass melt is naturally cooled in the air, break it to obtain borosilicate basic glass with a particle size of 2 mm;

[0039] (2) Mix the basic glass particles and the simulated high-level radioactive waste according to the calculated ratio, heat and melt them in a muffle furnace at 1100 °C for 24 h, and obtain the simulated glass solidified body after the glass liquid is naturally cooled in the air.

[0040] Carry out the same sample pretreatment and heat treatment as in Example 1, and measure that the crystal content precipitated in the glass is about 0.2 wt%.

[0041] Table 2

[0042]

[0043]

[0044] Example 3

[0045] This example provides a method for suppressing crystallization of a high-level radioactive waste glass solidified body, and obtains a simulated high-level radioactive waste glass solidified body. The main difference compared with Example 1 is that, on the premise of keeping the contents of the remaining components unchanged, the following components are adjusted, and the mass percentage of oxides is 46% SiO 2 , 14.5% B 2 O 3 , 11.0% Na 2 O, 2.5% Li 2 O, 5% Al 2 O 3 , 5.5% CaO, and its designed composition is shown in Table 3. The molar ratio of network modifier ions to network former ions is 0.50. The specific steps are as follows:

[0046] (1) Calculate the basic glass components, weigh the borosilicate glass raw materials and mix them evenly, heat and melt them in a muffle furnace at 1300 °C for 3 h, and obtain borosilicate basic glass with a particle size of 2 mm after the glass liquid is naturally cooled in the air and broken.

[0047] (2) Mix the basic glass particles and the simulated high-level radioactive waste according to the calculated ratio, heat and melt them in a muffle furnace at 1300 °C for 1 h, and obtain the simulated glass solidified body after the glass liquid is naturally cooled in the air.

[0048] Carry out the same sample pretreatment and heat treatment as in Example 1, and measure that the crystal content precipitated in the glass is about 0.4 wt%.

[0049] Table 3

[0050]

[0051]

[0052] Example 4

[0053] This example provides a method for suppressing crystallization of high-level radioactive waste vitrified body, and a simulated high-level radioactive waste vitrified body is prepared. The specific steps are different from those in Example 1 in that, while keeping the contents of the remaining components unchanged, the following components are adjusted, which are 49% SiO in terms of mass percentage of oxides 2 , 14.7% B 2 O 3 , 9.5% Na 2 O, 2% Li 2 O, 4% Al 2 O 3 , 5.3% CaO, and its designed composition is shown in Table 4, where the molar ratio of network modifier ions to network former ions is 0.42.

[0054] The same sample pretreatment and heat treatment as in Example 1 are adopted, and the content of precipitated crystals in the glass is measured to be less than 0.1 wt%.

[0055] The vitrified body prepared in this example has good uniformity, and the glass has both high waste solidification ability and good anti-crystallization performance.

[0056] Table 4

[0057]

[0058]

[0059] Example 5

[0060] This example provides a method for suppressing crystallization of high-level radioactive waste vitrified body, and a simulated high-level radioactive waste vitrified body is prepared. The specific steps are different from those in Example 1 in that, while keeping the contents of the remaining components unchanged, the following components are adjusted, which are 47.5% SiO in terms of mass percentage of oxides 2 , 15% B 2 O 3 , 10.3% Na 2 O, 2.2% Li 2 O, 4% Al 2 O 3 , 5.5% CaO, and its designed composition is shown in Table 5, where the molar ratio of network modifier ions to network former ions is 0.46.

[0061] The same sample pretreatment and heat treatment as in Example 1 are adopted, and no precipitated crystals other than the internal standard are detected in the glass.

[0062] The vitrified body prepared in this example has good uniformity, and the glass has both high waste solidification ability and good anti-crystallization performance.

[0063] Table 5

[0064]

[0065]

[0066] Comparative Example 1

[0067] This comparative example provides a method for suppressing the crystallization of high-level radioactive waste vitrified body, and a simulated high-level radioactive waste vitrified body is prepared. The specific steps are the same as those in Example 1, except that: the molar ratio of network modifier ions to network former ions is 0.56, and its designed composition is shown in Table 6.

[0068] The same sample pretreatment and heat treatment as in Example 1 were carried out, and the content of precipitated crystals in the glass was measured to be about 4.0 wt%.

[0069] Table 6

[0070] Component Content <![CDATA[SiO 2 > 45.5％ <![CDATA[B 2 O 3 > 13.5％ <![CDATA[Al 2 O 3 > 5.0％ <![CDATA[Sodium 2 O]]> 13％ <![CDATA[Li 2 O]]> 2.5％ CaO 5.0％ BaO 1.0％ SrO 0.5％ <![CDATA[Rb 2 O]]> 0.2％ <![CDATA[Cs 2 O]]> 1.0％ <![CDATA[ZrO 2 > 2.0％ <![CDATA[La 2 O 3 > 2.0％ <![CDATA[CeO 2 > 1.5％ <![CDATA[MoO 3 > 2.0％ <![CDATA[Cr 2 O 3 > 0.5％ <![CDATA[Fe 2 O 3 > 1.0％ NiO 0.5％ <![CDATA[Y 2 O 3 > 0.3％ <![CDATA[TeO 2 > 0.5％ <![CDATA[Nd 2 O 3 > 2.0％ MnO 0.5％ Total 100％

[0071] Comparative Example 2

[0072] This comparative example provides a method for suppressing the crystallization of high-level radioactive waste vitrified body, and a simulated high-level radioactive waste vitrified body is prepared. The specific steps are the same as those in Example 1, except that: the molar ratio of network modifier to network former content is 0.37, and its designed composition is shown in Table 7, and other steps are the same as those in Example 1.

[0073] Table 7

[0074] Component Content <![CDATA[SiO 2 > 39.0％ <![CDATA[B 2 O 3 > 20.0％ <![CDATA[Al 2 O 3 > 8.0％ <![CDATA[Sodium 2 O]]> 12.5％ CaO 5.0％ <![CDATA[Li 2 O]]> 0％ BaO 1.0％ SrO 0.5％ <![CDATA[Rb 2 O]]> 0.2％ <![CDATA[Cs 2 O]]> 1.0％ <![CDATA[ZrO 2 > 2.0％ <![CDATA[La 2 O 3 > 2.0％ <![CDATA[CeO 2 > 1.5％ <![CDATA[MoO 3 > 2.0％ <![CDATA[Cr 2 O 3 > 0.5％ <![CDATA[Fe 2 O 3 > 1.0％ NiO 0.5％ <![CDATA[Y 2 O 3 > 0.3％ <![CDATA[TeO 2 > 0.5％ <![CDATA[Nd 2 O 3 > 2.0％ MnO 0.5％ Total 100％

[0075] Performance detection and analysis

[0076] The vitrified bodies prepared in Examples 1 to 5 and Comparative Example 1 were subjected to crystallization heat treatment and X-ray diffraction analysis, and the spectral results are as Figure 1 shown.

[0077] It can be seen from Figure 1 that the vitrified bodies prepared in Examples 1 to 5 have good uniformity, and no significant crystallization will occur even after long-term heat treatment at the crystallization temperature. The vitrified body glass has both a high waste solidification ability and good anti-crystallization performance.

[0078] The vitrified body prepared in Comparative Example 1 is uniform, but due to the low crystallization activation energy and the increased crystallization tendency, a large amount of crystals are precipitated after heat treatment at the crystallization temperature.

[0079] The vitrified body prepared in Comparative Example 2 has insufficient waste containment ability and poor glass-forming ability, and phase separation occurs during the glass melting process.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste, characterized in that: The following steps are involved: S1, mixing glass raw materials uniformly, heating and melting, and cooling to obtain basic glass; S2, mixing the base glass with high-level radioactive waste, heating and melting, and cooling to obtain a glass solidified body; Wherein, the oxide composition in the glass solidified body includes a network modifier and a network former; The molar ratio of the ions of the network modifier to the ions of the network former is 0.4 to 0.

5.

2. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste as claimed in claim 1, characterized in that: The network modifier ions include Li + 、Na + , Ca 2+ , K + , Cs + , Rb + Mg 2+ , Ba 2+ and Sr 2+ One or more of .

3. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste as claimed in claim 1, characterized in that: The ions of the network former include Si 4+ , B 3+ and Al 3+ In a variety of.

4. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste as claimed in claim 1, characterized in that: The chemical composition of the glass solid body includes multiple ones of SiO2, B2O3, Al2O3, CaO, MgO, BaO, Li2O, Na2O, MoO3, ZrO2, Nd2O3, La2O3, CeO2, Y2O3, Fe2O3, Cr2O3, NiO, TeO2, SnO2, BaO, SrO, Cs2O, Rb2O, K2O, and MnO.

5. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste as claimed in claim 1, characterized in that: The molar ratio of the ions of the network modifier to the ions of the network former is 0.42 to 0.

46.

6. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste as claimed in claim 1, characterized in that: The temperature of heating and melting in step S1 and step S2 is 1100-1300° C., and the time of heating and melting in step S1 and step S2 is 1-24 hours.

7. A method for inhibiting crystallization of a glass solidified body of high-level radioactive waste as claimed in claim 1, characterized in that: The cooling method comprises pouring the molten glass obtained by heating and melting and then cooling it naturally in the air.

8. A high-level radioactive waste glass solidification body, characterized in that: The method is prepared by the method according to any one of claims 1 to 7.

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