Induction heating start-up method for nuclear waste cold crucible glassification

Abstract

The application discloses an inductive heating starting method for nuclear waste cold crucible glass solidification, which comprises a bubble tube arranged in a stepped mode, starting glass filled with two particle sizes, a high-conductivity consumable light starting medium with proper volume density, thickness and weight, and a high-frequency power source power setting program. The application is applicable to the starting heating of phosphate glass and borosilicate glass, improves the melting efficiency of the glass, shortens the consumption time of the light starting medium after floating, realizes rapid and efficient starting, and has the advantages of simple operation, controllable process, no pollution and high safety.

Description

Technical Field

[0001] This invention relates to the field of nuclear waste cold crucible glass curing technology, specifically to an induction heating start-up method for nuclear waste cold crucible glass curing. Background Technology

[0002] The wall 2 of the cold crucible is typically segmented, with cooling water flowing through the segmented metal tubes or curved metal plates. Since the crucible wall temperature generally does not exceed 200℃, the glass in contact with the cold wall solidifies, forming a "cold shell," which is typically about 1 cm thick. The bottom 4 of the crucible is also a water-cooled metal structure, with the glass completely enclosed within this solid glass "cold shell." A high-frequency coil 3 surrounds the crucible, providing a high-frequency magnetic field that induces a current in the molten glass. This current heats the melt inside the crucible through the Joule heating effect, thus achieving the induction melting process of the glass.

[0003] Currently, there are two main types of glass matrices used for nuclear waste solidification: borosilicate and phosphate. Both borosilicate and phosphate glasses are poor conductors at room temperature; they can only be effectively heated by high-frequency induction when the temperature reaches approximately 1100℃ and the resistivity reaches 1–10 Ω·cm. Therefore, an auxiliary heating medium, such as graphite, SiC, or highly conductive metals, needs to be added during cold crucible start-up. For cold crucible start-up heating of nuclear waste glass solidification, graphite rings are typically used as a consumable lightweight start-up medium. The melting temperature of borosilicates is between 1100 and 1200℃, while the optimal melting temperature of phosphate glass is between 950 and 1100℃. At these temperatures, graphite has strong reducing properties, easily reducing elemental phosphorus, altering the properties of the glass during start-up, and causing some corrosion to the crucible lid and exhaust gas system. Therefore, when performing cold crucible induction heating start-up of phosphate glass, the start-up process should be strictly controlled, and the start-up time should be shortened. It is necessary to develop a cold crucible start-up heating method applicable to, but not limited to, phosphate glass curing, to provide technical support for future engineering applications.

[0004] Ruiwei Electronic Materials (Tianjin) Co., Ltd. disclosed a starting melting device and method for preparing high-purity metal oxides in cold crucibles (CN102997661A). The device includes a graphite rod, an alumina ceramic tube, and a lifting system. The alumina ceramic tube is connected to the lifting system, and the graphite rod is inserted into the alumina ceramic tube. This device has a complex design, the graphite rod is not easily consumed, and it is not suitable for starting the glass solidification process in cold crucibles.

[0005] Kunming Bosheng Metal Materials Processing Co., Ltd. disclosed a starting melting device and method for high-frequency cold crucible melting of metal oxides (CN106643147A). This method involves assembling graphite petals into polygonal or annular shapes and placing them in metal oxide powder to initiate melting. This provides a large contact area, significantly reducing melting time while ensuring that impurities are not introduced into the metal oxide. However, the graphite petals are connected by graphite rods, resulting in a complex design and the graphite petals are not easily consumed, making it unsuitable for starting cold crucible glass solidification.

[0006] Ruiwei Electronic Materials (Tianjin) Co., Ltd. disclosed a process (CN107502951A) for preparing high-purity alumina polycrystalline using a graphite suspension cold crucible. This method uses a high-purity graphite ring to initiate melting and prepare the high-purity alumina polycrystalline, ensuring the graphite ring remains at the top of the molten pool and is continuously oxidized into carbon dioxide gas by air, thus preventing contamination of the alumina polycrystalline. During startup, only a small amount of alumina powder (1 cm high) is added above the graphite ring, which is quickly exposed and consumed. Although new alumina powder is continuously added above the graphite ring, a sufficient molten zone still needs a considerable amount of time to form to ensure proper startup of the cold crucible. Therefore, this method requires a relatively large graphite ring mass. As new alumina powder is continuously added, the graphite ring floating on the surface of the melt is prone to shifting to the vicinity of the crucible wall, causing arcing and posing a safety hazard during startup.

[0007] The China Institute of Atomic Energy has disclosed a start-up method (CN106910545B) for the solidification treatment of radioactive waste liquid in a cold crucible. This method boasts advantages such as simple material placement and no pollution during start-up. However, the 1cm layer of start-up glass covering the start-up material (graphite ring) causes the graphite ring to quickly become exposed and consumed after the start-up process begins. This can easily lead to the start-up glass failing to melt for an extended period in the area from the top of the crucible bottom to below the graphite ring.

[0008] The China Institute of Atomic Energy has disclosed a start-up method (CN108305700B) for the cold crucible solidification treatment of radioactive waste. This method boasts advantages such as simple material placement and no radioactivity during start-up. However, the use of titanium wire as the start-up medium can easily contaminate the molten glass. During start-up, as the molten glass gradually expands, the density of the titanium wire, exceeding that of the molten glass, causes it to gradually sink to the bottom of the crucible, potentially leading to sparking at the tip and posing a safety hazard.

[0009] The China Institute of Atomic Energy disclosed a bubbling-stirring cold crucible and bubbling stirring method for glass curing (CN110316940A). The bubbling tubes are evenly arranged at the bottom of the crucible and divided into two groups, resulting in a more uniform temperature distribution within the melt and eliminating significant stirring dead zones. However, this method sets all bubbling tubes to the same height (extending 3cm into the bottom of the crucible), which cannot effectively solve the problem of excessively long melting time of the solid glass at the bottom of the crucible during startup. After the melt in the cold crucible melts (startup complete), pulsed bubbling is performed by introducing gas pulses into the melt through each bubbling tube. This intermittent bubbling is prone to risks; for example, after bubbling stops, the gas outlet of the bubbling tube may become adhered to by solid glass, easily causing blockage of one or more bubbling tubes and affecting the bubbling effect.

[0010] When using a graphite ring for startup, as the starting glass beads are continuously heated and melted, the amount of molten glass above the graphite ring gradually increases, causing the graphite ring to slowly float until it is completely floating above the surface of the molten glass. At this point, there are still a large number of unmelted glass beads and a softened layer between the glass beads and the melt at the bottom of the crucible, which need to be gradually melted to the bottom of the crucible through heat transfer from the molten glass. If there are no bubbles at the bottom of the crucible or the bubble heights are set uniformly, the melting process is very slow and inefficient.

[0011] In addition, the input power of the high-frequency power supply should be adjusted to match the different stages of the cold crucible's start-up heating; otherwise, it may cause insufficient heating efficiency of the graphite ring or violent combustion, affecting the normal start-up of the cold crucible and making the process uncontrollable. Summary of the Invention

[0012] To overcome the shortcomings of existing cold crucible start-up heating technologies, this invention provides an induction heating start-up method for the glass solidification of nuclear waste cold crucibles. The application fields include, but are not limited to, the start-up heating of phosphate glass and borosilicate glass. It can achieve rapid and efficient start-up. The method is simple to operate, the process is controllable, pollution-free, and highly safe.

[0013] The technical solution adopted by this invention to solve its technical problem is:

[0014] An induction heating initiation method for glass solidification of nuclear waste in a cold crucible, characterized by comprising:

[0015] No fewer than three bubbling tubes are passed through the bottom of the cold crucible and extended into the interior of the cold crucible, with the height of each bubbling tube inside the cold crucible arranged in a stepped manner from high to low.

[0016] The first batch of fine-particle starting glass beads is filled into the cold crucible as the bottom glass bead layer, and the filling height h1 is 1 / 4 to 1 / 2 of the height H of the outer coil of the cold crucible;

[0017] A consumable lightweight starting medium is placed on the bottom glass beads and located at the center of the cold crucible;

[0018] Continue to fill the cold crucible with a second batch of coarse-grained starting glass beads as the upper glass bead layer, with a filling height of h2, and the total height of the glass bead layer h1+h2 is 1 to 1.1 of the height H of the outer coil of the cold crucible;

[0019] Cover the cold crucible with its lid, turn on the exhaust gas system, and introduce compressed air or oxygen. Set the flow rate of a single bubble tube to 100–300 L / h. Set the high-frequency power supply to constant power and remote control mode to expand the molten glass zone inside the cold crucible. The consumable lightweight starting medium floats above the molten glass and begins to burn until it is completely burned out. Specifically:

[0020] A staged, stepped heating method is adopted, assuming the maximum working power of the melt is set to P. max When the power is between (0 and 1 / 2)P max When the power is between 1 / 2 and 3 / 4 of its rated power, increase the power every 5 to 10 minutes, with the increase not exceeding 15 kW; when the power is between 1 / 2 and 3 / 4 of its rated power... max When the power is between 10 and 20 minutes, the power is increased every 10 to 20 minutes, with the increase not exceeding 10 kW; when the power is between (3 / 4 to 1) P max During operation, the power should be increased every 20-30 minutes, with the increase not exceeding 5kW. Increasing the power too quickly can cause the consumable lightweight starting medium to overheat and melt, preventing the glass melt zone from reaching high-frequency resonance and resulting in startup failure. Increasing the power too slowly will prolong the startup time and affect heating efficiency. After the consumable lightweight starting medium is depleted, adjust the power supply based on the glass melt temperature.

[0021] Once all the bubbles appear in the bubbling tubes, set the flow rate of compressed air to 50-100 L / h and stabilize for 10-20 minutes. Then, the induction heating of the cold crucible will be completed, and the feeding, glass replacement, homogenization, and material discharge processes can begin.

[0022] Preferably, the height of the bubbling tube inside the cold crucible ranges from 10mm to 60mm, specifically:

[0023] When the diameter of the crucible bottom is less than 400mm, the bubbling tubes are located on the circumference of 2 / 3 of the crucible bottom diameter, with a total of 3 tubes. The included angle between the positions of the 3 bubbling tubes is 120°, and the height is between 10 and 40mm, decreasing sequentially in either a counterclockwise or clockwise direction.

[0024] When the crucible diameter is small, the crucible height is also relatively small. Therefore, setting three circumferential bubbling tubes located at 2 / 3 of the diameter of the bottom of the crucible can achieve a good overall homogenization effect of the glass melt. The height of the bubbling tubes is between 10 and 40 mm to ensure that the bubbles can pass through the cold shell layer, and the glass melt surface will not churn violently due to the bubbling tubes being set too high.

[0025] When the diameter of the bottom of the crucible is between 400 and 600 mm, one central bubbling tube and four bubbling tubes located on the circumference of two-thirds of the diameter of the bottom of the crucible are set. The height of the central bubbling tube is between 10 and 20 mm. Except for the central bubbling tube, the included angle of the four bubbling tubes is 90°, and the height is between 20 and 50 mm. They are lowered in a counterclockwise or clockwise direction.

[0026] When the crucible diameter is moderate, the crucible height is also relatively moderate. Therefore, setting four bubble tubes located at 2 / 3 of the circumference of the crucible bottom and one central bubble tube can achieve a good overall homogenization effect of the glass melt. The height of the bubble tubes is between 10 and 50 mm to ensure that the bubbles can penetrate the cold shell layer without causing violent turbulence on the glass surface due to the bubble tubes being set too high. Due to the increased surface area of ​​the crucible, setting a central bubble tube, and having the lowest central bubble height, can achieve a good homogenization effect of the melt in the central area of ​​the crucible.

[0027] When the diameter of the crucible bottom is between 600 and 1000 mm, one central bubbling tube and six bubbling tubes located on the circumference of two-thirds of the crucible bottom diameter are set. The height of the central bubbling tube is between 10 and 20 mm. Except for the central bubbling tube, the included angle of the six bubbling tubes is 60°, and the height is between 20 and 60 mm. The height decreases sequentially in either a counterclockwise or clockwise direction.

[0028] When the crucible diameter is large, the crucible height is also relatively high. Therefore, setting up six bubble tubes located at 2 / 3 of the circumference of the crucible bottom and one central bubble tube can achieve a good overall homogenization effect of the glass melt. The height of the bubble tubes is between 10 and 60 mm to ensure that the bubbles can penetrate the cold shell layer without causing violent turbulence on the glass surface due to the bubble tubes being set too high. Because the surface area of ​​the crucible is increased and the central bubble height is the lowest, setting up a central bubble tube can effectively achieve a homogenization effect of the melt in the central area of ​​the crucible.

[0029] Preferably, the particle size of the first batch of fine-particle starting glass beads is 2-4 mm, and the particle size of the second batch of fine-particle starting glass beads is 4-8 mm.

[0030] Preferably, the consumable lightweight starting medium has a bulk density greater than 1.8 g / cm³. 3 Purified graphite rings with a thickness of 1-3 mm, a weight of 30-100 g, an impurity content of ≤0.03 wt.% and an ash content of ≤0.1 wt.%.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1) Two types of glass beads are used for loading the starting glass. The bottom of the crucible is filled with finer-grained glass beads, while the top of the consumable lightweight starting medium (graphite rings) is filled with larger-grained glass beads. This allows the graphite rings to be immersed in the molten glass for a longer period. The weight of the unmelted glass above the graphite rings slows their ascent, resulting in a larger high-temperature molten glass zone within the same timeframe, thus improving the melting efficiency before the graphite rings float. This prevents the graphite rings from rising too quickly, which could lead to a thicker unmelted glass layer at the bottom of the crucible.

[0033] 2) Several bubbling tubes are set at the bottom of the crucible. The height of the bubbling tubes extending into the crucible is set in a stepped manner. When the cold crucible is heated, the bubbling effect is manifested when the glass melt reaches the vicinity of the bubbling tube at the maximum height. The disturbance effect of the glass melt is enhanced, and the heat transfer effect is enhanced. This can quickly improve the melting efficiency of solid glass beads or softened layer 10mm to 60mm away from the bottom of the crucible. It is also beneficial to improve the expansion efficiency of solid glass beads at the bottom of the crucible after the graphite ring is completely floated.

[0034] 3) Using purified graphite rings with specific volume density, thickness and weight can improve the melting efficiency of glass beads, shorten the consumption time after the graphite rings float to the surface, and thus shorten the start-up time.

[0035] 4) The high-frequency power supply setting program is adopted. The graphite ring will not overheat and melt before it floats up. After the graphite ring floats up, it can be consumed quickly. The operation is simple and the startup process is safe and controllable. Attached Figure Description

[0036] Figure 1 This is a cross-sectional view of the crucible during the start-up of the cold crucible of the present invention;

[0037] In the diagram: 1—Crucible lid; 2—Water-cooled crucible wall; 3—High-frequency coil; 4—Water-cooled crucible bottom; 5, 6, 7—Bubble tube; 8—Second batch of starting glass beads; 9—High-conductivity consumable starting medium; 10—First batch of starting glass beads.

[0038] Figure 2 The following are the arrangement diagrams of the bubble tubes in embodiments 1 and 2 of the present invention for cold crucibles with a bottom diameter of less than 400 mm;

[0039] Figure 3 This is a diagram showing the arrangement of the bubble tubes in a cold crucible with a bottom diameter between 400 and 600 mm, according to the present invention.

[0040] Figure 4 This is a diagram showing the arrangement of the bubble tubes in the cold crucible of the present invention, where the bottom diameter is between 600 and 1000 mm.

[0041] In the diagram: 11, 13, 15—bubbling tubes located on the circumference of 2 / 3 of the bottom diameter of the crucible; 12, 14—central bubbling tubes. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The terms "first," "second," "third," "fourth," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may include steps or units not listed.

[0044] Please refer to Figure 1 As shown in the figure, the cold crucible includes a crucible lid 1, a water-cooled crucible wall 2, a high-frequency coil 3, and a water-cooled crucible bottom 4; bubble tubes 5, 6, and 7 are set at the bottom of the crucible, with no less than 3 of them, and the height of the bubble tubes extending into the crucible is set in a stepped manner, with the lowest not less than 10 mm and the highest not more than 60 mm; the first batch of starting glass beads 10 is filled into the bottom of the crucible; a purified graphite ring 9 is placed above the first batch of starting glass beads 10; and the second batch of starting glass beads 8 is continued to be filled into the crucible. Figure 2 The layout of the bubbling tubes is as follows when the bottom diameter of the crucible is less than 400mm. In this case, the bubbling tube 11 is located on the circumference of 2 / 3 of the bottom diameter of the crucible. There are 3 bubbling tubes in total. The included angle of the 3 bubbling tubes is 120° and the height is between 10 and 40mm. They are lowered in a counterclockwise or clockwise direction. Figure 3 The layout of the bubble tubes is such that the diameter of the bottom of the crucible is between 400 and 600 mm. At this time, one central bubble tube (12) and four bubble tubes (13) located on the circumference of 2 / 3 of the diameter of the bottom of the crucible are set. The height of the central bubble tube is between 10 and 20 mm. Except for the central bubble tube, the included angle of the four bubble tubes is 90° and the height is between 20 and 50 mm. They are lowered in a counterclockwise or clockwise direction. Figure 4The layout of the bubble tubes is such that the diameter of the bottom of the crucible is between 600 and 1000 mm. At this time, one central bubble tube 14 and six bubble tubes (15) located on the circumference of 2 / 3 of the diameter of the bottom of the crucible are set. The height of the central bubble tube is between 10 and 20 mm. Except for the central bubble tube, the included angle of the six bubble tubes is 60° and the height is between 20 and 60 mm. The height decreases in a counterclockwise or clockwise direction.

[0045] Example 1

[0046] The inner diameter of the cold crucible is 350mm, and the crucible wall is made of water-cooled stainless steel; the bottom of the crucible has a water-cooled stainless steel segmented structure with 6 segments and 3 bubble tubes, located as shown in the figure. Figure 2 As shown, the heights of the upper surface extending out of the water-cooling box are 15mm, 25mm, and 35mm respectively; the height of the high-frequency coil is 350mm.

[0047] The start-up method for induction heating of a cold crucible is as follows:

[0048] (1) Turn on all bubble tubes to ventilate. The gas is compressed air, and the flow rate is set to 180L / h.

[0049] (2) The first batch of phosphate glass starting glass beads 1 (fine particles) with a particle size of 2-4 mm is loaded into the bottom of the crucible. The loading weight is 18 kg and the height from the lower edge of the high frequency coil is 140 mm.

[0050] (3) Place a purification graphite ring above the starting glass bead 1. The volume density of the purification graphite ring is 1.83 g / cm³. 3 It has a thickness of 3mm and a weight of 60g;

[0051] (4) Continue to fill the crucible with the second batch of phosphate glass starting glass beads 2 (coarse particles), with a particle size of 4-8 mm and a filling weight of 32 kg. The total filling height is basically the same as the height H of the high-frequency coil.

[0052] (5) Cover the crucible, turn on the exhaust gas system, and adjust the temperature measurement system, liquid level measurement system, and high-temperature camera system. Set the high-frequency power supply to constant power and remote control mode. The heating program is as follows:

[0053] ①0~50kW, power increases every 10 minutes, with an increase of 15kW;

[0054] ②50~75kW, power is increased every 15 minutes, with an increase of 10kW;

[0055] ③ >75kW, increase the power every 20-30 minutes, with the power increase not exceeding 5kW.

[0056] (6) After the graphite ring is completely exposed 1.4 hours after the power is increased, the graphite ring is completely consumed 2 hours after the power is increased.

[0057] (7) Lower the water-cooled temperature measurement system into the glass melt, closely observe the real-time temperature, and adjust the power supply to ensure that the temperature does not exceed 1100℃;

[0058] (8) After the power is increased for 2 hours, the three bottom bubbles will appear completely. The flow rate is set to 60L / h. After stabilizing for 15 minutes, the cold crucible heating is started and the feeding, glass replacement, homogenization and material leakage process begins.

[0059] Example 2

[0060] The inner diameter of the cold crucible is 350mm, and the crucible wall is made of water-cooled stainless steel; the bottom of the crucible has a water-cooled stainless steel segmented structure with 6 segments, and the number of bubbling devices is 3. The heights of the segments extending out of the upper surface of the water-cooled box are 15mm, 25mm, and 35mm, respectively; the height of the high-frequency coil is 350mm.

[0061] The start-up method for induction heating of a cold crucible is as follows:

[0062] (1) Turn on all bottom bubbling devices, the gas is compressed air, and the flow rate is set to 160L / h;

[0063] (2) The first batch of borosilicate starting glass beads 1 (fine particles) with a particle size of 2-4 mm and a loading weight of 14 kg are loaded into the bottom of the crucible and the height from the lower edge of the high frequency coil is 120 mm.

[0064] (3) Place a purified graphite ring on top of the first batch of starting glass beads. The volume density of the purified graphite ring is 1.83 g / cm³. 3 It has a thickness of 2mm and a weight of 40g;

[0065] (4) Continue to fill the crucible with the second batch of borosilicate starting glass beads 2 (coarse particles), with a particle size of 4-8 mm and a filling weight of 35 kg. The total filling height is basically the same as the height H of the high-frequency coil.

[0066] (5) Cover the crucible, turn on the exhaust gas system, and adjust the temperature measurement system, liquid level measurement system, and high-temperature camera system. Set the high-frequency power supply to constant power and remote control mode. The heating program is as follows:

[0067] ①0~50kW, power increases every 10min, with an increase of 10kW;

[0068] ②50~75kW, power is increased every 15 minutes, with an increase of 10kW;

[0069] ③ >75kW, increase the power every 20-30 minutes, with the power increase not exceeding 5kW.

[0070] (6) After the graphite ring is completely exposed 1.5 hours after the power is increased, the graphite ring is completely consumed 2 hours after the power is increased.

[0071] (7) Lower the water-cooled temperature measurement system into the glass melt, closely observe the real-time temperature, and adjust the power supply to ensure that the temperature does not exceed 1150℃;

[0072] (8) After the power is increased for 2 hours, the three bottom bubbles will appear completely. The flow rate is set to 60L / h. After stabilizing for 15 minutes, the cold crucible heating is started and the feeding, glass replacement, homogenization and material leakage process begins.

[0073] Experiments show that the cold crucible start-up time is shortened to about 2 hours, and the graphite ring loss is reduced to less than 100g.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for induction heating to initiate the glass solidification of nuclear waste in a cold crucible, characterized in that: include: No fewer than three bubbling tubes are passed through the bottom of the cold crucible and extended into the interior of the cold crucible, arranged in a stepped manner from high to low inside the cold crucible. The first batch of fine-particle starting glass beads is filled into the cold crucible as the bottom glass bead layer, and the filling height h1 is 1 / 4 to 1 / 2 of the height H of the outer coil of the cold crucible. A consumable lightweight starting medium is placed on the bottom glass beads and located at the center of the cold crucible; Continue to fill the cold crucible with a second batch of coarse-grained starting glass beads as the upper glass bead layer, with a filling height of h2, and the total height of the glass bead layer h1+h2 is 1~1.1 of the height H of the outer coil of the cold crucible; Cover the cold crucible with the lid, turn on the exhaust gas system, and continuously introduce compressed air into the bubble tube. Set the flow rate of a single bubble tube to 100~300L / h. Set the high-frequency power supply to constant power and remote control mode to expand the glass melt melting zone in the cold crucible. After the consumable lightweight starting medium floats above the glass melt, it begins to burn rapidly until it is completely burned. When all the bubbling tubes start bubbling, the flow rate of compressed air into a single bubbling tube is set to 50~100L / h and stabilized for 10~20min, then the induction heating of the cold crucible ends. The bubbling tubes are arranged in a stepped pattern at the bottom of the crucible, specifically as follows: When the bottom diameter of the crucible is less than 400mm, the bubbling tubes are located on the circumference of 2 / 3 of the bottom diameter of the crucible, with a total of 3 tubes. The included angle between the positions of the 3 bubbling tubes is 120°, and the height is between 10 and 40mm. They are lowered in a counterclockwise or clockwise direction. When the diameter of the bottom of the crucible is between 400 and 600 mm, one bubble tube is set at the center of the bottom of the crucible and four bubble tubes are set at 2 / 3 of the diameter of the bottom of the crucible. The height of the central bubble tube is between 10 and 20 mm. The included angle of the four bubble tubes is 90° and the height is between 20 and 50 mm. They decrease in a counterclockwise or clockwise direction. When the diameter of the crucible bottom is between 600 and 1000 mm, one bubble tube is placed at the center of the crucible bottom, and six bubble tubes are placed around the circumference at two-thirds of the crucible bottom diameter. The height of the central bubble tube is between 10 and 20 mm. The included angle between the positions of the six bubble tubes is 60°, and their heights are between 20 and 60 mm, decreasing sequentially in either a clockwise or counterclockwise direction. The consumable lightweight starting medium has a bulk density greater than 1.8 g / cm³. 3 Purified graphite rings with a thickness of 1~3mm, a weight of 30~100g, an impurity content of ≤0.03wt.% and an ash content of ≤0.1wt.%.

2. The induction heating start-up method for glass solidification of nuclear waste cold crucibles according to claim 1, characterized in that: The first batch of fine-particle starting glass beads has a particle size of 2-4 mm, and the second batch of coarse-particle starting glass beads has a particle size of 4-8 mm.

3. The induction heating start-up method for glass curing of nuclear waste cold crucibles according to claim 1, wherein the power setting of the high-frequency power supply is specifically as follows: Assuming the maximum working power of the melt is set to P max , When the power is between (0~1 / 2)P max At that time, the power is increased every 5 to 10 minutes, and the power increase shall not exceed 15kW; When the power is between (1 / 2~3 / 4)P max At that time, the power is increased every 10 to 20 minutes, and the power increase shall not exceed 10kW; When the power is between (3 / 4~1)P max During this time, the power is increased every 20 to 30 minutes, with the power increase not exceeding 5 kW.

4. The induction heating start-up method for glass solidification of nuclear waste cold crucibles according to claim 1, characterized in that: It also includes real-time monitoring of the temperature of the molten glass and adjustment of the power supply. When the molten glass is phosphate glass, the temperature of the molten glass is ensured not to exceed 1100°C; when the molten glass is borosilicate glass, the temperature of the molten glass is ensured not to exceed 1150°C.

Images