Preparation method of UC powder

Abstract

The invention belongs to the technical field of UC powder preparation, solves the problem that only one uranium source and one carbon source can be used, and discloses a UC powder preparation method which comprises the following steps: carrying out acid dissolution on uranium oxide by using nitric acid to obtain a uranyl acid solution, or directly dissolving uranyl nitrate or uranyl fluoride by using deionized water to obtain a uranyl solution, adding a carbon source into the uranyl acid solution, and stirring to obtain a UC powder solution; the method comprises the following steps: dissolving uranyl acid into an acid solution, dispersing a carbon source in the acid solution, adding ammonia water into the uranyl acid solution in which the carbon source is dispersed under a stirring condition to obtain a carbon-containing ADU precipitate, filtering the carbon-containing ADU slurry obtained by precipitation, drying the filtered carbon-containing ADU filter cake, and heating and calcining the dried carbon-containing ADU powder in an inert atmosphere to obtain UC powder. According to the method, the carbon source and uranium are mixed by adopting a wet method-dry method combined process, so that the mixing uniformity is ensured, and the uranium oxide is not only limited to uranium dioxide.

Description

Technical Field

[0001] The present application belongs to the technical field of UC powder preparation, and in particular, relates to a method for preparing UC powder. Background Art

[0002] The new ceramic fuel or dispersed fuel made of UC has the advantages of traditional UO2 ceramic fuel and unique characteristics, namely high thermal conductivity, high uranium content and high density, which can provide guarantee for improving the operating parameters of the reactor. Therefore, this fuel has attracted wide attention and great interest and is considered to be a very potential and advanced nuclear fuel.

[0003] At present, the traditional method for preparing UC powder is to first fully mix uranium dioxide powder and carbon black and press them into blocks, then sinter the pressed uranium oxide-carbon black blocks at high temperature to produce a carbon thermal reduction reaction, thereby generating uranium carbide blocks, and then crush and grind the sintered uranium carbide blocks to obtain uranium carbide powder. This method is limited by the fact that it can only use UO2 with a near stoichiometric ratio as a uranium source and carbon black as a carbon source, and it also needs to be pressed and formed before high-temperature carbon thermal reduction. It is limited in terms of raw materials and is relatively demanding in terms of process. Summary of the invention

[0004] The purpose of the present application is to provide a method for preparing UC powder, which solves the problem that only one uranium source and one carbon source can be used. At the same time, the preparation process of the method is simple and the required equipment is generally available.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] In a first aspect, the present application provides a method for preparing UC powder, comprising:

[0007] Step 1: dissolving uranium oxide with nitric acid to obtain a uranyl acid solution, or directly dissolving uranyl nitrate or uranyl fluoride with deionized water to obtain a uranyl solution;

[0008] Step 2: adding a carbon source to the uranyl acid solution to disperse the carbon source in the acid solution;

[0009] Step 3: Under stirring conditions, adding ammonia water to the uranyl acid solution dispersed with the carbon source to obtain a carbon-containing ADU precipitate;

[0010] Step 4: filtering the carbon-containing ADU slurry obtained by precipitation, and drying the filtered carbon-containing ADU filter cake;

[0011] Step 5: The dried carbon-containing ADU powder is subjected to a temperature-raising calcination treatment under an inert atmosphere to obtain UC powder.

[0012] In some embodiments, the uranium oxide is one or more of UO2, U3O8, and UO3.

[0013] In some embodiments, the concentration of nitric acid is 2 mol / L to 12 mol / L, the amount of nitric acid added is controlled so that the molar ratio of nitric acid to uranium in uranium oxide is 3:1 to 5:1, and the temperature of the dissolution process is controlled at 45°C to 95°C.

[0014] In some embodiments, the carbon source is an inorganic carbon source or an organic carbon source. The inorganic carbon source includes carbon black, graphite, and graphene. The organic carbon source includes glucose, fructose, and lactose.

[0015] In some embodiments, the amount of carbon source added is such that the ratio of C in the carbon source to U in the uranyl acid solution is C:U=3:1-5:1.

[0016] In some embodiments, during the ADU precipitation process, the rate of adding ammonia water is 200 mL / min to 400 mL / min, and the stirring speed during the precipitation process is 100 rpm to 300 rpm.

[0017] In some embodiments, the drying process adopts segmented drying, and the temperatures are set at 50, 80, and 100° C., respectively, and the drying time under each temperature segment is maintained at 3 h to 8 h.

[0018] In some embodiments, the calcination process is carried out by a programmed temperature rising method, and there are multiple temperature rising sections and insulation sections. The temperature of the first insulation section is 400°C to 550°C, and the insulation time of this section is 2h-4h. The heating rate from room temperature to the first insulation section is controlled at 4°C / min to 8°C / min.

[0019] In some embodiments, during the calcination process, the temperature of the second insulation section of the calcination process is 900°C to 1200°C, the insulation time of this section is 3h to 6h, and the heating rate from the first insulation section to the second insulation section is controlled at 4°C / min to 8°C / min.

[0020] In some embodiments, during the calcination process, the temperature of the third insulation section of the calcination process is 1800°C to 2000°C, the insulation time of this section is 4h to 8h, and the heating rate from the second insulation section to the third insulation section is controlled at 8°C / min to 12°C / min.

[0021] Compared with the prior art, the preparation method of UC powder provided in this application has the following beneficial effects:

[0022] The present application adopts a wet-dry process to mix the carbon source and uranium, which not only ensures the uniformity of the mixing, but also makes the uranium oxide not limited to uranium dioxide.

[0023] The present application adopts a carbon-containing ADU precipitation process, so that the carbon source and uranium are more closely combined, and the carbon and uranium are more evenly distributed, and the properties of the UC obtained after high-temperature calcination are more consistent.

[0024] When preparing UC, the present application does not require the core block pressing, thereby reducing the pressing and molding process after mixing UO2 powder and carbon black powder, as well as the subsequent crushing process after the carbon thermal reduction is completed.

[0025] The UC powder prepared by the present application has a uranium content of 93.6% after analysis and characterization, and the proportion of UC phase in the powder can reach 94.6% after XRD detection.

[0026] By adopting the technical solution of the present application, the raw materials for preparing UC are more extensive, which can be UO2, U3O8, or UO3.

[0027] In addition, when preparing UC, the type of carbon source is not limited to carbon black, but can be an inorganic carbon source, such as carbon black, graphite, graphene, etc., or an organic carbon source, such as glucose, fructose, lactose, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for the technical description.

[0029] Figure 1 A flow chart of the method for preparing UC powder provided in this application;

[0030] Figure 2 Schematic diagram of the preparation process of UC powder provided in this application. DETAILED DESCRIPTION

[0031] The following is further explained in detail through specific implementation methods.

[0032] like Figure 1 As shown, the present application provides a method for preparing UC powder, and the specific steps are as follows:

[0033] Step 1: Use a certain concentration of nitric acid to acid dissolve the uranium oxide to obtain a uranyl acid solution. If there is insoluble residue, it can be filtered;

[0034] Step 2: Add an appropriate amount of carbon source to the uranyl acid solution under mechanical stirring. To ensure that the carbon source is more evenly dispersed in the acid solution, ultrasonic waves can be used at the same time.

[0035] Step 3: Under stirring conditions, adding an appropriate amount of ammonia water at a certain speed to the uranyl acid solution containing the carbon source dispersed therein to obtain a carbon-containing ADU precipitate;

[0036] Step 4: filtering the carbon-containing ADU slurry obtained by the above precipitation, and drying the filtered carbon-containing ADU filter cake;

[0037] Step 5: The dried carbon-containing ADU powder is subjected to a temperature-raising calcination treatment under an inert atmosphere to obtain UC powder.

[0038] In step 1, the uranium oxide is, for example, UO2, U3O8 or UO3.

[0039] In step 1, during the nitric acid dissolution process, the nitric acid concentration is (2-12) mol / L, the amount of nitric acid added is controlled so that the molar ratio of nitric acid to uranium in uranium oxide is 3:1-5:1, and the temperature of the dissolution process is controlled at (45-95)°C.

[0040] In step 1, during the nitric acid dissolution process, the uranium concentration in the acid solution after dissolution is preferably (60-150) g / L.

[0041] In step 2, the carbon source is, for example, an inorganic carbon source (such as carbon black, graphite, graphene, etc.), or, for example, an organic carbon source (such as glucose, fructose, lactose, etc.).

[0042] In step 2, mechanical stirring is used, and the stirring speed is preferably (100-300) rpm. In order to ensure that the inorganic carbon source is evenly dispersed in the acid solution, it can be carried out in an ultrasonic cleaning instrument.

[0043] In step 2, the amount of carbon source added is such that the ratio of C in the carbon source to U in the uranyl acid solution is C:U=(3:1-5:1).

[0044] In step 3, the amount of ammonia water added during the ADU precipitation process is related to the acidity of the acid solution, and the amount added is preferably such that the pH of the final precipitation mother liquor is 8 to 11.

[0045] In step 3, the rate of adding ammonia water during the ADU precipitation process is (200-400) mL / min.

[0046] In step 3, mechanical stirring is used in the precipitation process, and the stirring speed is controlled at (100-300) rpm.

[0047] In step 4, the carbon-containing ADU slurry obtained in step 3 can be filtered by centrifugation, vacuum filtration, etc.

[0048] In step 4, the drying process is carried out in an oven. The drying process adopts a segmented drying method. The temperatures are set at 50, 80, and 100° C., respectively. The drying time under each temperature segment is maintained at (3 to 8) hours to ensure that the ADU is completely dried.

[0049] In step 5, the calcination process is carried out in an atmosphere protection furnace. The calcination process is protected by an inert gas, which can be argon or helium.

[0050] In step 5, the calcination process is carried out by programmed heating, and there are multiple heating sections and insulation sections. The temperature of the first insulation section is (400-550)°C, and the insulation time of this section is (2-4)h. The heating rate from room temperature to the first insulation section is controlled at (4-8)°C / min.

[0051] In step 5, the temperature of the second insulation section of the calcination process is (900-1200)°C, the insulation time of this section is (3-6) hours, and the heating rate from the first insulation section to the second insulation section is controlled at (4-8)°C / min.

[0052] In step 5, the temperature of the third insulation section of the calcination process is (1800-2000)°C, the insulation time of this section is (4-8)h, and the heating rate from the second insulation section to the third insulation section is controlled at (8-12)°C / min.

[0053] In step 5, after the third heat preservation stage of the calcination process is completed, the temperature can be naturally cooled. The entire cooling process also needs to be protected by inert gas to prevent the generated UC powder from being oxidized by oxygen in the air.

[0054] Example 1

[0055] Example 1: Using U3O8 as raw material and graphite as carbon source, UC powder is prepared by acid dissolution, graphite dispersion, ADU precipitation, filtration and drying, and high-temperature calcination. The specific process includes the following:

[0056] Step 1: Weigh 1000g of U3O8 powder for standby use, add 3L of deionized water into a 5L container, then add 1L of concentrated nitric acid (mass percentage 68%), the concentration of nitric acid is 3.5mol / L, turn on the heating, when the temperature is 60℃, add U3O8 powder, the temperature of the whole dissolution process is controlled not to exceed 95℃, and it is completely dissolved after about 3h, transfer it into a 10L container, add appropriate amount of deionized water, so that the uranium concentration in the acid solution is 120g / L.

[0057] Step 2: Weigh 171.3 g of graphite. The molar ratio of graphite added to U in the uranyl acid solution is C:U=4:1. Slowly add graphite under mechanical stirring. The stirring speed is controlled at 250 rpm. To ensure that the graphite is evenly dispersed in the acid solution, the stirring time is continued for 5 hours.

[0058] Step 3: Under mechanical stirring, add ammonia water to the uranyl solution with graphite uniformly dispersed, and the stirring speed is controlled at 250rpm. Perform ADU precipitation, and the addition rate of ammonia water is controlled at 300mL / min. The amount of ammonia water added in this process is preferably such that the pH of the final precipitation mother solution is 9-10.

[0059] Step 4: Filter and dry the precipitated carbon-containing ADU slurry. The drying process is carried out in an oven, using a staged drying method, drying at 50, 80, and 100° C. for 4 hours, respectively, until the ADU is completely dried.

[0060] Step 5: Use a sintering furnace to calcine the dried carbon-containing ADU at high temperature, and argon is introduced throughout the calcination process for protection. The program temperature is used to prevent the ADU filter cake with a high moisture content from being sintered directly into blocks at high temperature, which is not convenient for obtaining powdered UC. The heating program is from room temperature to 500°C, the heating rate is controlled at 6°C / min, and the temperature is kept at this temperature for 4 hours. The temperature is continued to rise to 1000°C, the heating rate is controlled at 10°C / min, and the insulation time at this temperature is 5 hours. The temperature is continued to rise to 1900°C, the heating rate is controlled at 10°C / min, and the temperature is kept at this temperature for 7 hours. Finally, the power is turned off and the temperature is naturally cooled to room temperature. The entire cooling process also needs to be protected by argon to prevent the generated UC powder from oxidizing with oxygen in the air.

[0061] Step 6: The prepared UC powder was sampled and packaged in an argon-filled glove box, and sent for analysis. XRD analysis showed that the UC phase ratio was 92.8%.

[0062] Example 2

[0063] Example 2: Using UO2 as raw material and fructose as carbon source, UC powder is prepared through acid dissolution, fructose dissolution and dispersion, ADU precipitation, filtration and drying, and high-temperature calcination. The specific process includes the following:

[0064] Step 1: Weigh 1000g of UO2 powder for standby use, add 3L of deionized water into a 5L container, then add 1.2L of concentrated nitric acid (mass percentage 68%), the concentration of nitric acid is 4.0mol / L, turn on the heating, when the temperature is 60℃, add UO2 powder, the temperature of the whole dissolution process is controlled not to exceed 95℃, and it is completely dissolved after about 3h, transfer it into a 10L container, add appropriate amount of deionized water, so that the uranium concentration in the acid solution is 140g / L.

[0065] Step 2: Weigh 556.0 g of fructose. The molar ratio of fructose added to U in the uranyl acid solution is C:U=5:1. Slowly add fructose under mechanical stirring. The stirring speed is controlled at 280 rpm. To ensure that all fructose is dissolved in the acid solution and evenly dispersed, the stirring time is continued for 3 hours.

[0066] Step 3: Add ammonia water to the uranyl solution with uniformly dispersed fructose under mechanical stirring, and control the stirring speed at 240rpm. Perform ADU precipitation, and control the addition speed of ammonia water to 300mL / min. The amount of ammonia water added in this process is preferably such that the pH of the final precipitation mother solution is 8-9.

[0067] Step 4: Filter and dry the precipitated fructose-containing ADU slurry. The drying process is carried out in an oven, using a staged drying method, drying at 50, 80, and 100° C. for 4 hours, respectively, until the ADU is completely dried.

[0068] Step 5: The dried fructose-containing ADU is calcined at high temperature using a sintering furnace, and argon is introduced throughout the calcination process for protection. The temperature is programmed to rise from room temperature to 500°C, with a heating rate of 6°C / min, and the temperature is kept at this temperature for 4 hours. The temperature is then raised to 1000°C, with a heating rate of 10°C / min, and the temperature is kept at this temperature for 5 hours. The temperature is then raised to 1950°C, with a heating rate of 10°C / min, and the temperature is kept at this temperature for 7 hours. Finally, the power is turned off and the temperature is naturally cooled to room temperature. The entire cooling process also requires argon protection to prevent the generated UC powder from being oxidized by oxygen in the air.

[0069] Step 6: The prepared UC powder is sampled and packaged in an argon-filled glove box, and sent for analysis. Chemical analysis shows that the uranium content is 93.6%, and XRD analysis shows that the UC phase ratio is 94.2%.

[0070] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing UC powder, characterized in that: include: Step 1: dissolving uranium oxide with nitric acid to obtain a uranyl acid solution, or directly dissolving uranyl nitrate or uranyl fluoride with deionized water to obtain a uranyl solution; Step 2: adding a carbon source to the uranyl acid solution to disperse the carbon source in the acid solution; Step 3: Under stirring conditions, adding ammonia water to the uranyl acid solution dispersed with the carbon source to obtain a carbon-containing ADU precipitate; Step 4: filtering the carbon-containing ADU slurry obtained by precipitation, and drying the filtered carbon-containing ADU filter cake; Step 5: The dried carbon-containing ADU powder is subjected to a temperature-raising calcination treatment under an inert atmosphere to obtain UC powder.

2. The method for preparing UC powder according to claim 1, characterized in that: In step 1, the uranium oxide is one or more of UO2, U3O8, and UO3.

3. The method for preparing UC powder according to claim 1, characterized in that: In step 1, the concentration of nitric acid is 2 mol / L to 12 mol / L, the amount of nitric acid added is controlled so that the molar ratio of nitric acid to uranium in uranium oxide is 3:1 to 5:1, and the temperature of the dissolution process is controlled at 45° C. to 95° C.

4. The method for preparing UC powder according to claim 1, characterized in that: In step 2, the carbon source is an inorganic carbon source or an organic carbon source. The inorganic carbon source includes carbon black, graphite, and graphene. The organic carbon source includes glucose, fructose, and lactose.

5. The method for preparing UC powder according to claim 1 or 4, characterized in that: In step 2, the amount of carbon source added is such that the ratio of C in the carbon source to U in the uranyl acid solution is C:U=3:1-5:

1.

6. The method for preparing UC powder according to claim 1, characterized in that: In step 3, during the ADU precipitation process, the rate of adding ammonia water is 200 mL / min to 400 mL / min, and the stirring speed during the precipitation process is 100 rpm to 300 rpm.

7. The method for preparing UC powder according to claim 1, characterized in that: In step 4, the drying process adopts segmented drying, and the temperatures are set at 50, 80, and 100° C., respectively. The drying time under each temperature segment is maintained at 3 h to 8 h.

8. The method for preparing UC powder according to claim 1, characterized in that: During the calcination process, a programmed temperature rise method is adopted, and there are multiple temperature rise sections and insulation sections. The temperature of the first insulation section is 400℃~550℃, and the insulation time of this section is 2h-4h. The heating rate from room temperature to the first insulation section is controlled at 4℃ / min~8℃ / min.

9. The method for preparing UC powder according to claim 8, characterized in that: During the calcination process, the temperature of the second insulation section of the calcination process is 900°C to 1200°C, the insulation time of this section is 3h to 6h, and the heating rate from the first insulation section to the second insulation section is controlled at 4°C / min to 8°C / min.

10. The method for preparing UC powder according to claim 9, characterized in that: During the calcination process, the temperature of the third insulation section of the calcination process is 1800°C to 2000°C, the insulation time of this section is 4h to 8h, and the heating rate from the second insulation section to the third insulation section is controlled at 8°C / min to 12°C / min.

Images