Preparation method of Li72Pb28 alloy for fusion reactor solid cladding

Abstract

The invention belongs to the technical field of nuclear power, and particularly relates to a preparation method of a Li72Pb28 alloy for a fusion reactor solid cladding. According to the invention, the smelting atmosphere of filling helium after vacuumizing is adopted, so that the purpose of filling helium can reduce the volatilization of the lithium element on one hand, and can take away part of reaction heat and prevent the lithium element from being oxidized on the other hand due to the strong heat conduction capability of helium on the other hand; a lithium material is put into a porous material frame and is added step by step, so that lead and lithium are mixed to form alloying, and the lithium element is more uniform; the aluminum oxide crucible is used for smelting the Li72Pb28 alloy, so that the problem of chemical reaction with metal lithium when a graphite crucible is adopted can be avoided, lithium element loss and pollution of crucible impurities to the alloy are effectively prevented, current is not generated in the smelting process, and the electromagnetic stirring effect can more effectively act on the Li72Pb28 alloy. The technical problem in smelting preparation of the Li72Pb28 alloy is solved. A Li72Pb28 alloy smelting process method and parameters are established, and the problems of lithium element content control, cast ingot alloying and the like are solved.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power technology, and in particular relates to a solid blanket Li 72 Pb 28 Alloy preparation method. Background Art

[0002] Blanket material is an important component of fusion reactor, responsible for tritium breeding, neutron and energy conversion. Blanket material is divided into solid blanket and liquid blanket. Lead-lithium alloy is an important candidate material for fusion reactor blanket. At present, the relatively mature technology is liquid blanket Li 17 Pb 83 Alloy (17 atomic ratio), Li 17 Pb 83 It is the eutectic component in the lithium-lead system (also known as the lithium-lead eutectic alloy Lead-Lithium Eutectic, LEE), and has the lowest melting point in the system (about 235°C, such as Figure 2 As shown), domestic and foreign research on low melting point Li 17 Pb 83 Eutectic alloy preparation has been extensively developed, although Li 17 Pb 83 Alloy preparation technology has been developed relatively maturely, but the use of liquid cladding Li 17 Pb 83 Alloys used as fusion reactor blanket materials also have the problem of high-temperature corrosion. According to the latest research results on the conceptual design of the neutron breeder blanket for the Chinese Nuclear Fusion Demonstration Reactor in 2023 by the Chinese Academy of Sciences Science Island, solid Li 72 Pb 28 Alloy is expected to become the first choice, Li 72 Pb 28 The alloy has the highest melting point in the system (about 235°C, such as Figure 2 ), as a solid cladding can avoid the problem of high temperature corrosion, it is urgent to develop Li 72 Pb 28 Preparation of alloys. Summary of the invention

[0003] In order to overcome the problems existing in the related art, a method for solid blanket Li for fusion reactor is provided. 72 Pb 28 Alloy preparation method.

[0004] According to one aspect of the embodiments of the present disclosure, there is provided a solid blanket Li for a fusion reactor. 72 Pb 28 A method for preparing an alloy, the method comprising:

[0005] Step 1: Follow Li 72 Pb28 The designed components of the alloy are weighed so that the lithium element exceeds the preset proportion;

[0006] Step 2, putting lead into an alumina crucible, and loading lithium into a plurality of porous material frames and locking them, each of which is installed under a freely liftable stirring rod in the equipment;

[0007] Step 3, after the induction furnace is evacuated, it is filled with helium of a preset pressure value;

[0008] Step 4, start heating to melt the lead, raise the temperature to a preset temperature and keep it warm;

[0009] Step 5, inserting each porous material frame into the bottom of the solution in turn and stirring up and down continuously until all the lithium materials in each material frame are melted;

[0010] Step 6: After all the lithium materials in the multiple material boxes are added, the heating is stopped after the preset insulation time, and the alloy liquid is cooled to room temperature and then taken out of the furnace.

[0011] In a possible implementation, in step 1, the lithium element is in excess of 10%-15%.

[0012] In a possible implementation, in step 2, the material frame is a mesh structure.

[0013] In a possible implementation, the material frame is made of 304 stainless steel, and the mesh diameter is 400-600 μm.

[0014] In a possible implementation, in step 3, the induction furnace is evacuated to below 0.01 Pa, filled with 0.05-0.08 MPa helium, evacuated again to below 0.01 Pa, and filled with 0.07-0.08 MPa helium.

[0015] In a possible implementation, in step 4, heating is started to melt the lead, and the temperature is raised to 720-760° C. and maintained.

[0016] In a possible implementation, in step 6, the preset duration is 20 minutes.

[0017] The beneficial effects of the present disclosure are as follows: The present disclosure designs the following technical solutions: (1) A smelting atmosphere is adopted which is filled with helium after vacuuming. The purpose of filling with helium is to reduce the volatilization of lithium elements on the one hand, and to take away part of the reaction heat due to the strong thermal conductivity of helium, and to prevent the oxidation of lithium elements at the same time; (2) The lithium material is placed in a porous material frame and added step by step. Compared with the traditional hopper, the material frame can be inserted below the liquid surface of the molten pool to effectively prevent the lithium material from floating up. At the same time, the material frame is used to continuously mechanically stir the molten pool, promote the mixing of lead and lithium to form an alloy, and make the lithium element more uniform; (3) An alumina crucible is used for Li72 Pb 28 Alloy smelting can avoid the problem of chemical reaction with metallic lithium when using graphite crucible, effectively preventing lithium loss and crucible impurities from contaminating the alloy. On the other hand, since alumina is a non-conductor, no current is generated during the smelting process, and the electromagnetic stirring effect can act more effectively on Li 72 Pb 28 Alloy. Solved Li 72 Pb 28 Technical issues in alloy smelting and preparation. 72 Pb 28 The alloy smelting process method and parameters solve the problems of lithium content control and ingot alloying. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is used for fusion reactor solid blanket Li 72 Pb 28 Flowchart of the alloy preparation method.

[0019] Figure 2 It is the phase diagram of lead-lithium alloy in the related art. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 It is used for fusion reactor solid blanket Li 72 Pb 28 Flow chart of the alloy preparation method, such as Figure 1 As shown, the method comprises the following steps:

[0022] Step 1: Follow Li 72 Pb 28 The designed composition of the alloy is weighed and the lithium element is in excess of 10-15%.

[0023] Step 2: Put lead into an alumina crucible, and put lithium into three porous material frames and lock them. The material frames are mesh structures made of 304 stainless steel with a mesh diameter of 400-600 μm. The three material frames are respectively installed under three freely liftable stirring rods in the equipment.

[0024] Step 3, evacuate the induction furnace to below 0.01Pa, fill it with 0.05-0.08MPa high-purity helium, evacuate it again to below 0.01Pa, and fill it with 0.07-0.08MPa high-purity helium.

[0025] Step 4, start heating to melt the lead, raise the temperature to 720-760°C and keep it warm.

[0026] Step 5, insert each porous material frame into the bottom of the solution in turn and stir up and down continuously until the lithium material in each material frame is completely melted.

[0027] Step 6: After all the lithium materials in the multiple material frames are added, the heating is stopped after the heat preservation is continued for 20 minutes, and the alloy liquid is cooled to room temperature and then taken out of the furnace.

[0028] Through the smelting process method and parameter design, high melting point Li 72 Pb 28 Preparation of alloys, Li 72 Pb 28 Alloying fully forms a high melting point compound, the alloy melting point is greater than 650°C, and the total impurity content is less than 200μg / g.

[0029] In the related art, Li 72 Pb 28 The alloy preparation process has the following difficulties: (1) Lithium has a low melting point and is very volatile, especially when it is combined with Li 17 Pb 83 In comparison, Li 72 Pb 28 The higher the alloy melting temperature, the greater the amount of lithium volatilization, making it difficult to control the lithium content. (2) Lithium metal is very easy to oxidize. (3) The lead-lithium alloying process releases a large amount of heat, and the melt temperature is difficult to control. Excessive temperature is more likely to cause lithium volatilization loss. (4) The large difference in lead and lithium density can easily lead to insufficient alloying reaction. (5) The impurity content of the smelted ingot is difficult to control.

[0030] Among the above problems, excessive lithium volatilization and oxidation will cause insufficient lithium content in the alloy, insufficient alloying, and large difference in lead and lithium density. Insufficient stirring will also cause insufficient alloy contact and insufficient alloying. Insufficient alloying will cause the alloy to fail to completely form a high-melting-point compound, and the melting point will be low.

[0031] In view of the above difficulties, the present invention has designed the following technical solutions: (1) adopting a smelting atmosphere that is filled with helium after evacuation. The purpose of filling with helium is to reduce the volatilization of lithium elements on the one hand, and to take away part of the reaction heat due to the strong thermal conductivity of helium, and to prevent the oxidation of lithium elements at the same time; (2) adopting a method of putting lithium materials into a porous material frame and adding them step by step. Compared with the traditional hopper, the material frame can be inserted below the liquid surface of the molten pool to effectively prevent the lithium materials from floating up. At the same time, the material frame can be used to continuously mechanically stir the molten pool, promote the mixing of lead and lithium to form an alloy, and make the lithium element more uniform; (3) using an alumina crucible for Li 72 Pb 28Alloy smelting can avoid the problem of chemical reaction with metallic lithium when using graphite crucible, effectively preventing lithium loss and crucible impurities from contaminating the alloy. On the other hand, since alumina is a non-conductor, no current is generated during the smelting process, and the electromagnetic stirring effect can act more effectively on Li 72 Pb 28 alloy.

[0032] In one application example, Li is prepared according to the following steps: 72 Pb 28 alloy.

[0033] In step 1, according to Li72Pb 28 The designed composition of the alloy is weighed and the lithium element is in excess of 12%.

[0034] In step 2, lead is placed in an alumina crucible, and lithium is placed in three porous material frames and locked. The material frames are mesh structures made of 304 stainless steel with a mesh diameter of 500 μm. The three material frames are respectively installed under three freely liftable stirring rods in the equipment.

[0035] In step 3, the induction furnace is evacuated to below 0.01 Pa, filled with 0.06 MPa high-purity helium, and then evacuated again to below 0.01 Pa, and filled with 0.07 MPa high-purity helium.

[0036] In step 4, heating is started to melt the lead, and the temperature is raised to 730°C and maintained.

[0037] In step 5, the stirring rod sequentially lowers the porous material frame into the bottom of the solution and continuously stirs up and down until all the lithium material in the material frame is melted.

[0038] In step 6, after all the lithium materials in the three material frames are added, the heating is stopped after the temperature is kept at room temperature for 20 minutes, and the alloy liquid is cooled to room temperature and then taken out of the furnace.

[0039] In another application example, Li 72 Pb 28 alloy.

[0040] In step 1, according to Li72Pb 28 The designed composition of the alloy was weighed and the lithium element was in excess of 13%.

[0041] In step 2, lead is placed in an alumina crucible, and lithium is placed in three porous material frames and locked. The material frames are mesh structures made of 304 stainless steel with a mesh diameter of 600 μm. The three material frames are respectively installed under three freely liftable stirring rods in the equipment.

[0042] In step 3, the induction furnace is evacuated to below 0.01 Pa, filled with 0.07 MPa high-purity helium, and then evacuated again to below 0.01 Pa, and filled with 0.08 MPa high-purity helium.

[0043] In step 4, heating is started to melt the lead, and the temperature is raised to 750°C and maintained.

[0044] In step 5, the porous material frame is inserted into the bottom of the solution in sequence and stirred up and down continuously until the lithium material in the material frame is completely melted.

[0045] In step 6, after all the lithium materials in the three material frames are added, the heating is stopped after the temperature is kept at room temperature for 20 minutes, and the alloy liquid is cooled to room temperature and then taken out of the furnace.

[0046] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A solid blanket Li for fusion reactor 72 Pb 28 The method for preparing the alloy is characterized in that: The method comprises: Step 1: Follow Li 72 Pb 28 The designed components of the alloy are weighed so that the lithium element exceeds the preset proportion; Step 2, putting lead into an alumina crucible, and loading lithium into a plurality of porous material frames and locking them, each of which is installed under a freely liftable stirring rod in the equipment; Step 3, after the induction furnace is evacuated, it is filled with helium of a preset pressure value; Step 4, start heating to melt the lead, raise the temperature to a preset temperature and keep it warm; Step 5, inserting each porous material frame into the bottom of the solution in turn and stirring up and down continuously until all the lithium materials in each material frame are melted; Step 6: After all the lithium materials in the multiple material boxes are added, the heating is stopped after the preset insulation time, and the alloy liquid is cooled to room temperature and then taken out of the furnace.

2. The method according to claim 1, characterized in that In step 1, the lithium element is in excess of 10%-15%.

3. The method according to claim 1, characterized in that In step 2, the material frame is a mesh structure.

4. The method according to claim 3, characterized in that The material of the material frame is 304 stainless steel, and the mesh diameter is 400-600μm.

5. The method according to claim 1, characterized in that In step 3, the induction furnace is evacuated to below 0.01 Pa, filled with 0.05-0.08 MPa helium, evacuated again to below 0.01 Pa, and filled with 0.07-0.08 MPa helium.

6. The method according to claim 1, characterized in that In step 4, heating is started to melt the lead, and the temperature is raised to 720-760°C and maintained.

7. The method according to claim 1, characterized in that In step 6, the preset duration is 20 minutes.

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