Method for producing low-radioactive background metal material by using vacuum electroslag furnace and its application

Abstract

The present invention provides a method for producing low-radioactive background metal materials by using a vacuum electroslag furnace and its application, comprising: selecting raw materials, wherein the radioactivity of key radioactive nuclides in the raw materials is respectively less than or equal to 50 mBq / kg, and the raw materials include: metal raw materials to be smelted and electroslag raw materials; using the electroslag raw materials to prepare low-radioactive background electroslag; using an organic solvent to clean the inner wall of the vacuum electroslag furnace, the organic solvent used needs to pass the radioactivity detection and the detection result is qualified, and the residual organic solvent is removed; in the cleaned vacuum electroslag furnace, the metal raw materials to be smelted are made into electrodes, the low-radioactive background electroslag and the electrodes are placed, and the metal is obtained after smelting; wherein the low-radioactive background electroslag extracts the key radioactive nuclides in the metal raw materials to be smelted.

Description

Technical Field

[0001] The present invention relates to the fields of metal smelting and particle physics rare event detection, and in particular to a method for producing low-radioactive background metal materials using a vacuum electric slag furnace, in particular to a method for removing extremely trace radioactive impurities in metals, which is used to reduce the radioactive background of metals and provide material support for rare event detection experiments. Background Art

[0002] In rare high-energy physics experiments such as neutrino detection and dark matter detection, the radioactive background requirements of the materials used are extremely stringent. The radioactive specific activity of the main nuclides must not exceed the order of 1mBq / kg (Bq is becquerel, which is the international unit of radioactive activity; mBq corresponds to millibecquerel). Neutrinoless double beta decay even pursues a specific activity of 1μBq (microbecquerel) / kg, which means that the mass fraction of U (uranium) and Th (thorium) must be controlled at the order of 1ppb (part per billion, when expressing the content of components in solids, 1ppb corresponds to 0.001μg / g) or even 1ppt (part per trillion). The mass fraction of U and Th in stainless steel is generally in the order of 1 to 100ppb, and the current common metallurgical processes generally do not consider elements with a content of 1ppm (part per million, when expressing the content of components in solids, 1ppm is 1μg / g) or lower.

[0003] In the past, the low-background materials required for rare-event high-energy physics experiments, except for oxygen-free copper and low-background stainless steel, were largely obtained by uncontrollable random selection, and their quality and quantity were difficult to guarantee. Researching the production method of low-background metal materials is a technical problem that needs to be solved in this field. Rare-event high-energy physics experiments have endless requirements for the background radioactivity level of materials, so it is also a technical pain point in this field.

[0004] At present, the metal material with the lowest radioactive background that is easily available in this field is oxygen-free copper, and the main radioactive nuclide content is at the order of 1μBq / kg. However, oxygen-free copper has poor mechanical properties and chemical stability, and is difficult to weld, which is subject to many restrictions in application. Compared with oxygen-free copper, stainless steel has better mechanical properties and corrosion resistance, but the radioactive background is about 1mBq / kg, which is about a thousand times higher than oxygen-free copper. This brings a lot of noise signals to physical detectors and also seriously limits its application. The production process of low-background stainless steel mainly relies on strict control of the source of materials, using only raw materials instead of recycled scrap steel, thereby reducing the pollution of artificial nuclides, but there is no effective control method for U, Th and their decay products. In addition, stainless steel has more alloying elements, and the uneven ablation during the smelting process also limits the choice of smelting process.

[0005] ESR (Electroslag Remelting) is a process in which electroslag is used as a resistor and purifying agent. The metal to be smelted is melted under the action of resistance heat, washed with slag, and solidified into high-quality electroslag ingots. The metal-electroslag reaction interface of electroslag remelting is extremely large, reaching 32 square centimeters / g, and the slag washing effect is very good. Through the precisely controlled solidification process, the metal structure is complete.

[0006] In view of this, it is necessary to propose a method for producing low-radioactive background metal materials using a vacuum electroslag furnace, which can effectively remove radioactive nuclides and reduce the level of radioactive background of metal materials. Summary of the invention

[0007] In response to the above technical problems, the present invention provides a method for producing low-radioactive background metal materials using a vacuum electric slag furnace. By utilizing the extraction effect of low-radioactive background electric slag, it can be used to effectively remove radioactive nuclides in metal raw materials directly derived from ores, thereby reducing the radioactive background of the metal after smelting.

[0008] The present invention provides a method for producing low-radioactive background metal materials by using a vacuum electroslag furnace, the method comprising:

[0009] (a) selecting raw materials, wherein the radioactivity of key radionuclides in the raw materials is less than or equal to 50 mBq / kg, and the raw materials include: metal raw materials to be smelted and electroslag raw materials;

[0010] (b) using the electroslag raw material to produce low-radioactive background electroslag;

[0011] (c) using an organic solvent to clean the inner wall of the vacuum electroslag furnace, the organic solvent used needs to pass the radioactivity test and the test result is qualified, and the residual organic solvent is removed;

[0012] (d) in the cleaned vacuum electroslag furnace, making the metal raw material to be smelted into an electrode, placing the low-radioactive background electroslag and the electrode, and obtaining the metal after smelting;

[0013] Among them, in (d), the low-radioactive background electroslag extracts key radioactive nuclides in the metal raw materials to be smelted.

[0014] As an optional technical solution, in (a), the metal raw material to be smelted is directly obtained from ore, the ore is selected from natural ore, and no recycled materials shall be used in the production process of the metal raw material.

[0015] As an optional technical solution, in (a), the electroslag raw material includes at least electroslag metals, the electroslag metals are directly produced from ore, and the ore is selected from natural ore, and no recycled materials shall be used in the production process of the electroslag metals.

[0016] As an optional technical solution, the electroslag metal is selected from one or a combination of metal calcium, metal magnesium and metal aluminum; wherein the purity of metal calcium, metal magnesium and metal aluminum is not less than 99.9% respectively.

[0017] As an optional technical solution, in (a), the electroslag raw material also includes silicon dioxide, and the silicon dioxide is synthetic high-purity quartz.

[0018] As an optional technical solution, in (b), preparing the low-radioactive background electroslag includes:

[0019] Producing calcium oxide and calcium fluoride from the metallic calcium; producing aluminum oxide from the metallic aluminum; producing magnesium oxide from the metallic magnesium; and

[0020] Any two or more of the calcium oxide, the calcium fluoride, the aluminum oxide, the magnesium oxide and the silicon dioxide are mixed to form a mixture, and the mixture is smelted to prepare the low-radioactive background electroslag.

[0021] As an optional technical solution, the method (a) further includes:

[0022] Using trace detection equipment to detect key radionuclides in the raw materials, the key radionuclides include artificial nuclides 60 Co. 137 Cs and natural nuclides 238 U. 232 Th, 40 K. 226 Ra, 228 Ra, 228 Ac, 210 One or more of Pb.

[0023] As an optional technical solution, 60 Co. 137 Cs content is less than or equal to 10mBq / kg, 40 K content is less than or equal to 50mBq / kg, 238 U content is less than or equal to 50mBq / kg, 232 Th content is less than or equal to 15mBq / kg.

[0024] As an optional technical solution, the metal raw material with a mass greater than 1 kg is selected to perform radioactive trace detection of the key radioactive nuclides.

[0025] The present invention also provides an application of the above method, which is applied to extract key radioactive nuclides in the electroslag remelting process.

[0026] Compared with the prior art, the method and application of the present invention for producing low-radioactive background metal materials by using a vacuum electroslag furnace, using low-radioactive background electroslag and metal raw materials to be smelted for electroslag remelting, effectively absorbing the radioactive background in the metal raw materials to be smelted. 238 U. 232 Th, 40 K. 226 Ra, 228 Ra, 228 Ac, 210 Pb and other radioactive nuclides, thereby achieving the purpose of further reducing the radioactive background of metal raw materials. Furthermore, the method for producing low-radioactive background metal materials using a vacuum electric slag furnace provided by the present invention can significantly reduce the radioactive background of metal raw materials, and at the same time has the advantage of good process repeatability, and can change the method of obtaining low-radioactive background metals from uncontrollable random selection to production according to demand, and can better guarantee the quality and time schedule of production, thereby meeting the demand for low-radioactive background metals in rare case high-energy physics experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] none. DETAILED DESCRIPTION

[0028] In order to provide a further understanding of the purpose, structure, features, and functions of the present invention, the following detailed description is given in conjunction with the embodiments.

[0029] Electroslag remelting metallurgy uses electroslag as a resistor and purifying agent. The metal to be smelted melts under the action of resistance heat, and after slag washing, it solidifies into high-quality electroslag ingots. The metal-electroslag reaction interface of electroslag remelting is extremely large, up to 32 square centimeters / g, and the slag washing effect is very good. In addition, the electromagnetic force causes the slag pool to move strongly, which strengthens the reaction of the steel-slag interface.

[0030] At present, the first step in steel production is blast furnace ironmaking. The raw materials used include iron ore, coke, limestone, etc. The process of smelting iron into steel also requires calcium oxide, etc. As listed in Table 1, the main radioactive nuclide content of these raw materials is in the order of 10 to 100 Bq / kg. The slag produced by steel metallurgy can generally be considered to be composed of six oxides, namely SiO2, Al2O3, CaO, MgO, MnO, and FeO. The radioactivity of these slags is also relatively high. However, the radioactivity of the pure iron, stainless steel and other materials produced is much lower than that of ore, coke, and limestone. These data show that the slag material is 238 U series, 232 Th series, 40 Radioactive nuclides such as K have an extraction and enrichment effect, with an enrichment factor of about 1000-10000 times. Several slag systems of the electroslag used in vacuum electroslag remelting of liquid crystals have a large overlap with six oxides such as SiO2, Al2O3, CaO, MgO, MnO, and FeO. Therefore, the research on low-background metal materials can be transformed into the research on low-background slag or slag-making materials.

[0031] Table 1 shows the background radioactivity levels of metallurgical materials and products (slag), mainly for key radionuclides. 137 Cs, 60 Co. 238 U. 232 Th, 40 The radioactivity level of K was detected.

[0032] <![CDATA[ 137 Cs]]> <![CDATA[ 60 Co]]> <![CDATA[ 238 In]]> <![CDATA[ 232 Th]]> <![CDATA[ 40 K]]> China's iron ore average 270 68 China's coal average 383 51 Average value of copper mines in China 142 34 Blast furnace slag 3.0±0.1 2.1±0.1 19.5 32 59.6 Slag-making material-fluorite <0.004 <0.15 389±11 73±15 140±6 Slag-making material - light burning <0.005 0.11±0.07 42±3 34±1 64±3 VOD furnace steelmaking slag <0.1 0.11±0.06 99±4 36±1 <1 K-OBM-S Converter Steelmaking Slag 0.052±0.04 <0.2 270±19 37±6 <4 Steelmaking refining slag <0.004 0.12±0.1 222±9 54±3 <1.5 Stainless steel <0.001 <0.0006 <0.0002 <0.0003 <0.011 Pure Iron <0.002 <0.001 <0.0005 <0.001 <0.002

[0033] Table 1 Radioactive background data of metallurgical related materials and products (Bq / kg)

[0034] Among them, VOD furnace (vacuum oxygen decarburization); K-OBM (oxygen bottom-blown converter steelmaking) -S converter stainless steel smelting.

[0035] Research has found that in the process of smelting raw metals using electroslag remelting, since the various components and impurities of the raw metals have been well controlled, the main smelting purpose at this time is to use electroslag to absorb the impurities in the liquid metal. 238 U. 232 Th, 40 K. 226 Ra, 228 Ra, 228 Ac, 210 Pb and other radionuclides.

[0036] At present, the commonly used slag systems in electroslag remelting metallurgy include CaF2, Al2O3, CaO, MgO, SiO2, etc. Other components exist in small amounts. Several combinations are selected according to actual conditions, and there have been many studies. The selection of electroslag slag system is a very important task in electroslag metallurgy. In addition to considering electrical conductivity, melting point, boiling point, chemical stability, viscosity, and surface tension, the background radioactivity of the electroslag slag system needs to be considered in order to obtain metals with low radioactive background levels according to the research objectives. At present, Al2O3 with a background level of 0.1 to 1Bq / kg and synthetic SiO2 with a level of 1mBq / kg have been found. In the past, CaF2 and CaO came from ores, so the background radioactivity was extremely high, at the level of 100Bq / kg, which was difficult to meet the requirements of low radioactive background electroslag. Preliminary exploration has found that CaF2 and CaO in the electroslag slag system can be made by burning metal calcium at a level of no more than 10mBq / kg in fluorine gas and oxygen, and Al2O3 and MgO can be obtained by burning the corresponding pure metals in oxygen. Alternatively, CaF2, CaO, Al2O3, and MgO can also be prepared by other chemical reactions, which can be selected independently according to the type of raw materials selected. For example, metal Ca that has been tested for radioactivity reacts with high-purity water to produce Ca(OH)2, and then Ca(OH)2 reacts with hydrofluoric acid that has been tested for radioactivity and calcined to obtain CaF2. CaO can also be obtained by high-temperature calcination of Ca(OH)2. Metal Al that has been tested for radioactivity reacts with hydrochloric acid that has been tested for radioactivity to produce AlCl3, and then high-purity NH3 is introduced to produce Al(OH)3, which is then calcined to produce Al2O3.

[0037] Based on the above analysis, the problem that urgently needs to be overcome is how to reduce the radioactive background level of the electroslag in the electroslag remelting metallurgical process, optimize the electroslag's ability to adsorb, extract and enrich radioactive impurities, and at the same time ensure that the mechanical properties of the metal during smelting remain unchanged, so as to meet the low-radioactive target metal required for rare event high-energy physics experiments.

[0038] Specifically, the present invention provides a method for producing low-radioactive background metal materials using a vacuum electroslag furnace, comprising:

[0039] (a) selecting raw materials, wherein the radioactivity of key radionuclides in the raw materials is less than or equal to 50 mBq / kg, and the raw materials include: metal raw materials to be smelted and electroslag raw materials;

[0040] (b) using the electroslag raw material to produce low-radioactive background electroslag;

[0041] (c) using an organic solvent to clean the inner wall of the vacuum electroslag furnace, the organic solvent used needs to pass the radioactivity test and the test result is qualified, and the residual organic solvent is removed;

[0042] (d) in the cleaned vacuum electroslag furnace, making the metal raw material to be smelted into an electrode, placing the low-radioactive background electroslag and the electrode, and obtaining the metal after smelting;

[0043] Among them, in (d), the low-radioactive background electroslag extracts key radioactive nuclides in the metal raw materials to be smelted.

[0044] In the above-mentioned method of producing low-radioactive background metal materials using a vacuum electroslag furnace of the present invention, raw materials are selected, and the electroslag produced by using low-radioactive raw materials has a low radioactive background level, and the electroslag with low radioactive background further extracts key radioactive nuclides in the metal during the smelting process with the metal to be smelted, thereby reducing the radioactive background level of the metal. The low-radioactive background metal produced by the electroslag remelting method can meet the demand for low-radioactive background metals in rare case high-energy physics experiments.

[0045] In an optional embodiment, the metal raw materials to be smelted are directly obtained from ore, the ore is selected from natural ore, and no recycled materials shall be used in the production process of the metal raw materials to be smelted; the electroslag raw materials at least include electroslag metals, the electroslag metals are directly obtained from ore, the ore is selected from natural ore, and no recycled materials shall be used in the production process of the electroslag metals.

[0046] Preferably, the electroslag metal is selected from one or a combination of calcium metal, magnesium metal, and aluminum metal, wherein the purity of calcium metal, magnesium metal, and aluminum metal is not less than 99.9%. In addition, the electroslag raw material also includes silicon dioxide, and the silicon dioxide is synthetic high-purity quartz.

[0047] Furthermore, the above also includes: using trace detection equipment to detect key radioactive nuclides in the metal raw materials, wherein the key radioactive nuclides include artificial nuclides 60 Co. 137 Cs and natural nuclides 238 U. 232 Th, 40 K. 226 Ra, 228 Ra, 228 Ac, 210 One or more of Pb.

[0048] Among them, preferably, 60 Co. 137 Cs content is less than 10mBq / kg, 40 K content is less than 50mBq / kg, 238 U content is less than 50mBq / kg, 232 The Th content is less than 15mBq / kg.

[0049] As an optional technical solution, (b) also includes:

[0050] Producing calcium oxide and calcium fluoride from the metallic calcium; producing aluminum oxide from the metallic aluminum; producing magnesium oxide from the metallic magnesium; and

[0051] Any two or more of the calcium oxide, the calcium fluoride, the aluminum oxide, the magnesium oxide and the silicon dioxide are mixed to form a mixture, and the mixture is smelted to prepare the low-radioactive background electroslag.

[0052] Specifically, optionally, the calcium, magnesium and aluminum are burned in high-purity oxygen to produce calcium oxide, magnesium oxide and aluminum oxide respectively; and the calcium is burned in high-purity fluorine gas to produce calcium fluoride.

[0053] In addition, metallic calcium may first react with high-purity water to produce calcium hydroxide, then the calcium hydroxide is calcined to obtain calcium oxide, and then hydrofluoric acid that has passed radioactivity testing and has a qualified test result is reacted with calcium hydroxide to produce calcium fluoride.

[0054] Metallic aluminum reacts with hydrochloric acid or aqua regia that has passed the radioactivity test and the test results are qualified to produce aluminum chloride, and then high-purity NH3 is introduced to produce Al(OH)3, and then calcined to produce Al2O3.

[0055] In an optional embodiment, the (d) further comprises:

[0056] The metal raw material to be smelted is prepared into an electrode, and the electrode is installed in the vacuum electroslag furnace;

[0057] The low-radioactive background electroslag is placed in the vacuum electroslag furnace, and the electrode is smelted with the low-radioactive background electroslag to produce the metal.

[0058] In an optional embodiment, the metal raw material to be smelted is steel, nickel and nickel-based alloys or titanium and titanium alloys or other metal materials suitable for electroslag remelting metallurgy.

[0059] In an optional embodiment, the metal raw material with a mass greater than 1 kg is selected to perform radioactive trace detection of the key radioactive nuclide. Preferably, the metal raw material with a mass greater than 5 kg is selected to perform radioactive trace detection of the key radioactive nuclide.

[0060] In an optional embodiment, the method further includes: cleaning the raw material, which includes: placing the metal raw material in a cleaning agent, ultrasonically cleaning the raw material to remove dust on the surface of the raw material, wherein the cleaning agent used needs to pass a radioactive test and the test result is qualified. The type of cleaning agent can be selected according to actual needs.

[0061] Preferably, the organic solvent is a volatile organic solvent, and the volatile organic solvent is selected from one or a combination of ethanol, acetone, ethyl acetate, and petroleum ether.

[0062] Example 1: Application of the method for producing low-radioactive background metal materials using a vacuum electroslag furnace to produce steel with low radioactive background

[0063] (a) Selection of raw materials. The selected raw materials must be traceable to their entire previous production process, and the previous production process is obtained from the corresponding ore smelting. It should be noted that the raw materials used in this application must not be made from recycled metal waste.

[0064] The metal raw materials include two types of metal raw materials to be smelted and electroslag raw materials used to produce electroslag. The metal raw materials to be smelted are, for example, stainless steel; the electroslag metals used to produce electroslag are, for example, metal calcium, magnesium, and aluminum, with a purity of not less than 99.9%.

[0065] In addition, the raw materials for making electroslag also include high-purity synthetic quartz.

[0066] Randomly select corresponding metals (stainless steel, calcium, magnesium, aluminum) of about 5 kg each from batches of metal raw materials that meet the conditions, and measure the radioactivity of key radionuclides in them using high-purity germanium spectrometer, ICP-MS, neutron activation and other methods. 60 Co. 137 Cs content is less than 10mBq / kg, 40 K content is less than 50mBq / kg, 238 U content is less than 50mBq / kg, 232 The Th content is less than 15mBq / kg.

[0067] After sampling, this batch of raw materials will be sealed and awaiting the radioactivity test results. If the radioactivity is qualified, it will be ready to proceed to the next process. If it is not qualified, other batches will be sampled.

[0068] In addition, the sampling process of synthetic high-purity quartz refers to the sampling process of the above-mentioned metal raw materials.

[0069] (b) The metal calcium selected in (a) is used to prepare calcium oxide and calcium fluoride; the metal aluminum is used to prepare aluminum oxide; and the metal magnesium is used to prepare magnesium oxide.

[0070] The preparation method includes combustion in an oxygen or fluorine atmosphere, or chemical reactions such as hydrolysis and acid to form corresponding metal oxides or metal fluorides.

[0071] According to the steel smelting requirements, any two or more of calcium fluoride, calcium oxide, aluminum oxide, magnesium oxide and silicon dioxide are mixed in a certain proportion to form a mixture, and the mixture is smelted to form electroslag with low radioactive background.

[0072] (c) Cleaning of vacuum electroslag furnace: Before smelting, carefully clean the inner wall of the electroslag furnace, remove the attached matter and wipe it three times with a dust-free cloth dipped in ethanol, acetone or other organic solvents (which meet the requirements of radioactivity detection). The number of cleaning times can be adjusted appropriately according to the actual situation.

[0073] (d) Processing the qualified steel selected in (a) into electrodes that meet the requirements of the electric slag furnace, and placing the electric slag with low radioactive background obtained in (b) into the electric slag furnace to smelt the finished electrodes to obtain smelted steel.

[0074] According to actual smelting needs, the electrodes made of steel can be repeatedly smelted after replacing new low-radioactive background electroslag.

[0075] The method and application of the present invention for producing low-radioactive background metal materials by using a vacuum electroslag furnace are as follows: selecting raw materials, preparing electroslag with low radioactive background, and electroslag remelting with the electroslag with low radioactive background and the metal raw materials to be smelted, so as to effectively absorb the radioactive substances in the metal raw materials to be smelted. 238 U. 232 Th, 40 K. 226 Ra, 228 Ra, 228 Ac, 210 Pb and other radioactive nuclides, thereby achieving the purpose of further reducing the radioactive background of metal raw materials. Furthermore, the method for producing low-radioactive background metal materials using a vacuum electric slag furnace provided by the present invention can significantly reduce the radioactive background of metal raw materials, and at the same time has the advantage of good process repeatability, and can change the method of obtaining low-radioactive background metals from uncontrollable random selection to production according to demand, and can better guarantee the quality and time schedule of production, thereby meeting the demand for low-radioactive background metals in rare case high-energy physics experiments.

[0076] The present invention has been described by the above-mentioned relevant embodiments, but the above-mentioned embodiments are only examples for implementing the present invention. In addition, the technical features involved in the different embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. On the contrary, changes and modifications made without departing from the spirit and scope of the present invention are all within the scope of patent protection of the present invention.

Claims

1. A method for producing low-radioactive background metal materials using a vacuum electroslag furnace, characterized in that: The method comprises: (a) selecting raw materials, wherein the radioactivity of key radionuclides in the raw materials is less than or equal to 50 mBq / kg, the raw materials comprising: metal raw materials to be smelted and electroslag raw materials, wherein the metal raw materials to be smelted are steel, nickel and nickel-based alloys or titanium and titanium alloys; (b) using the electroslag raw material to produce low-radioactive background electroslag; (c) using an organic solvent to clean the inner wall of the vacuum electroslag furnace, the organic solvent used needs to pass the radioactivity test and the test result is qualified, and the residual organic solvent is removed; (d) in the cleaned vacuum electroslag furnace, making the metal raw material to be smelted into an electrode, placing the low-radioactive background electroslag and the electrode, and obtaining the metal after smelting; Wherein, in said (d), said low-radioactive background electroslag extracts key radionuclides in said metal raw material to be smelted, and said metal is a low-radioactive target metal required for rare event high-energy physics experiments; In (a), the electroslag raw material at least includes electroslag metals; the electroslag metals are selected from one or a combination of metal calcium, metal magnesium and metal aluminum with a radioactivity not higher than 10 mBq / kg; wherein the purity of metal calcium, metal magnesium and metal aluminum is not less than 99.9% respectively; the electroslag raw material also includes silicon dioxide, and the silicon dioxide is synthetic high-purity quartz; the metal raw material to be smelted is directly obtained from ore, the ore is selected from natural ore, and no recycled materials are used in the production process of the metal raw material to be smelted; the electroslag metals are directly obtained from ore, the ore is selected from natural ore, and no recycled materials are used in the production process of the electroslag metals; In the above (b), preparing the low-radioactive background electroslag comprises: Calcium oxide and calcium fluoride are prepared from the metal calcium having a radioactivity not higher than 10 mBq / kg; aluminum oxide is prepared from the metal aluminum; and magnesium oxide is prepared from the metal magnesium; wherein the calcium, magnesium and aluminum are burned in high-purity oxygen to prepare calcium oxide, magnesium oxide and aluminum oxide respectively; and the calcium is burned in high-purity fluorine gas to prepare calcium fluoride; or The preparation of the calcium oxide and the calcium fluoride includes: the metal calcium first reacts with high-purity water to prepare calcium hydroxide, then calcining the calcium hydroxide to obtain the calcium oxide, and then reacting hydrofluoric acid that has passed the radioactivity test and the test result is qualified with the calcium hydroxide to prepare the calcium fluoride; The preparation of the aluminum oxide includes: reacting the metal aluminum with hydrochloric acid that has passed the radioactivity test and the test result is qualified to prepare aluminum chloride, then introducing high-purity NH3 to prepare Al(OH)3, and then calcining to prepare the aluminum oxide; and Any two or more of the calcium oxide, the calcium fluoride, the aluminum oxide, the magnesium oxide and the silicon dioxide are mixed to form a mixture, and the mixture is smelted to prepare the low-radioactive background electroslag.

2. The method according to claim 1, characterized in that The above (a) also includes: Using trace detection equipment to detect key radionuclides in the raw materials, the key radionuclides include artificial nuclides 60 Co. 137 Cs and natural nuclides 238 U. 232 Th, 40 K. 226 Ra, 228 Ra, 228 Ac, 210 One or more of Pb.

3. The method according to claim 2, characterized in that 60 Co. 137 Cs content is less than or equal to 10mBq / kg, 40 K content is less than or equal to 50mBq / kg, 238 U content is less than or equal to 50mBq / kg, 232 Th content is less than or equal to 15mBq / kg.

4. The method according to claim 1, characterized in that The metal raw material with a mass greater than 1 kg is selected to carry out radioactive trace detection of the key radioactive nuclides.

5. An application of the method according to any one of claims 1 to 4, characterized in that: Used to extract key radioactive nuclides in the electroslag remelting process.