Method for removing fluoride residues on zirconium alloy surface after acid pickling

Abstract

The invention relates to the field of nuclear fuel manufacturing, in particular to a method for removing fluoride residues on the surface of zirconium alloy after acid pickling. The method comprises the following steps: putting the zirconium alloy subjected to acid pickling into a complexing solution, and carrying out bubbling treatment on the complexing solution by adopting ultrasonic waves; the complexing solution is an aluminum nitrate solution with the concentration of 25-30 g / L; taking out the zirconium alloy treated by the complexing solution, and soaking and cleaning the zirconium alloy with deionized water at 50-70 DEG C; soaking with deionized water; and drying. The surface quality of the zirconium alloy subjected to acid pickling is improved, the corrosion resistance of the zirconium alloy is facilitated, and generation of acid pickle is reduced.

Description

Technical Field

[0001] The present invention relates to the field of nuclear fuel manufacturing, and particularly to a method for removing fluoride residues on the surface of zirconium alloy after pickling. Background Art

[0002] During the production of zirconium alloy tubes, rods, plates, strips and other products, pickling is an important surface treatment step, which is used to remove scale, impurities, rolling oil stains, etc. formed on the surface during the production processes such as hot rolling and cold rolling of zirconium alloy, and to improve the surface state of zirconium alloy. In the pickling process, pickling solution is usually prepared by mixing nitric acid, hydrofluoric acid and deionized water in a certain proportion. After the pickling of zirconium alloy is completed and taken out from the pickling tank, there is still a large amount of pickling solution remaining on its surface. The pickling solution will continue to chemically react with the zirconium alloy. The hydrofluoric acid in the pickling solution reacts with the zirconium alloy to form complexes such as zirconium fluoride and remains on the surface of the zirconium alloy, which is likely to cause the fluoride ion to exceed the standard and affect the corrosion resistance of the zirconium alloy, bringing potential safety hazards to the safe operation in the nuclear fuel reactor.

[0003] During the pickling of zirconium alloy, a large amount of flowing water is often used to wash the surface of the pickled zirconium alloy to quickly remove the pickling solution remaining on the surface of the zirconium alloy, prevent the reaction between hydrofluoric acid and the zirconium alloy, and achieve the purpose of removing the fluorine residue on the surface of the pickled zirconium alloy. However, a large amount of flowing water flushing generates a large amount of waste acid solution containing nitrogen and fluorine, and the treatment of the waste acid solution is difficult and costly. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: to provide a method for removing fluoride residues on the surface of zirconium alloy after pickling, which improves the surface quality of the zirconium alloy after pickling, is beneficial to the corrosion resistance of the zirconium alloy, and reduces the generation of waste acid solution.

[0005] The present invention provides a method for removing fluoride residues on the surface of zirconium alloy after pickling, including the following steps:

[0006] Step S1: Place the pickled zirconium alloy in a complexing solution, and perform bubbling treatment on the complexing solution by ultrasonic waves; the complexing solution is prepared with deionized water, and the quality requirements for deionized water are: the maximum values of fluoride ions and chloride ions are 0.15 μg / g; at 25 °C, the conductivity ≤ 2.0 μS / cm; at 25 °C, the pH value is 6.0 - 8.0;

[0007] The complexing solution is an aluminum nitrate solution with a concentration of 25 - 30 g / L;

[0008] During the treatment, through chelation, termination, and complexation, fluorides that are easily soluble in water are generated;

[0009] Step S2: Take out the zirconium alloy treated by the complexing solution, and soak and clean it with deionized water at 50 - 70 °C;

[0010] Step S3: Soak in deionized water;

[0011] Step S4: Drying treatment.

[0012] In a specific embodiment of the present invention, the preparation method of the complexing solution is as follows:

[0013] Mix analytical pure 99.9% aluminum nitrate with deionized water.

[0014] In a specific embodiment of the present invention, in step 1, the soaking time in the complexing solution is not less than 180 seconds.

[0015] In a specific embodiment of the present invention, in step 2, the soaking time in deionized water at 50 - 70 °C is not less than 300 seconds.

[0016] In a specific embodiment of the present invention, in step 3, the soaking time in deionized water is not less than 300 seconds.

[0017] In a specific embodiment of the present invention, step 4 is specifically as follows:

[0018] Use heated compressed air at 80 °C - 100 °C to dry the zirconium alloy, removing the residual water stains on the surface of the zirconium alloy.

[0019] In a specific embodiment of the present invention, after step S4, it further includes:

[0020] Take a sample to detect the fluorine residue on the surface of the zirconium alloy. After passing the inspection, the zirconium alloy is registered and stored in the warehouse.

[0021] Compared with the prior art, the method for removing fluoride residues on the surface of zirconium alloy after pickling in the present invention has the following beneficial effects:

[0022] 1) The steps such as using aluminum nitrate complexing treatment for the pickling solution remaining on the surface of the zirconium alloy, soaking in hot water and deionized water are simple and easy to implement, convenient to operate, and easy to realize industrial production.

[0023] 2) It can effectively remove the fluoride residues on the surface of the zirconium alloy, reduce the fluoride ion residue amount, and improve the surface quality of the zirconium alloy.

[0024] 3) Reducing the fluoride residues on the surface of the zirconium alloy improves the surface quality of the zirconium alloy after pickling, is beneficial to the corrosion resistance of the zirconium alloy, and extends the service life of the zirconium alloy.

[0025] 4) It meets the high - standard requirements for zirconium alloys in high - end applications such as nuclear power, improves the production technology level of zirconium alloys in China, and increases the use safety of nuclear materials.

[0026] 5) Reducing the usage amount of deionized water, reducing the generation of nitrogen - and fluorine - containing waste acid solution, reducing the production cost of zirconium alloy, and improving its economy.

[0027] In summary, the method for removing fluoride residues on the surface of zirconium alloy after pickling of the present invention has important practical value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow diagram showing the method for removing fluoride residues on the surface of zirconium alloy after pickling. DETAILED DESCRIPTION OF THE INVENTION

[0029] To further understand the present invention, the implementation solutions of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the present invention.

[0030] An embodiment of the present invention discloses a method for removing fluoride residues on the surface of zirconium alloy after pickling, as Figure 1 shown, including the following steps:

[0031] Step S1: Place the pickled zirconium alloy in a complexing solution, and use ultrasonic waves to bubble the complexing solution;

[0032] The complexing solution is an aluminum nitrate solution with a concentration of 25 - 30 g / L;

[0033] The preparation method of the complexing solution is:

[0034] Mix analytical pure aluminum nitrate of 99.9% with deionized water;

[0035] The quality requirements for the deionized water are: the maximum values of fluoride ions and chloride ions are 0.15 μg / g; at 25°C, the conductivity ≤ 2.0 μS / cm; at 25°C, the pH value is 6.0 - 8.0.

[0036] The soaking time in the complexing solution is not less than 180 seconds.

[0037] In this step, the aluminum nitrate complexing solution reacts with the fluoride residues on the surface of the zirconium alloy to produce neutralization, termination, and complexation reactions, generating fluorides that are easily soluble in water.

[0038] (1) Neutralization reaction

[0039] The Al(NO3)3 complexing solution can neutralize HF in the pickling solution. Al(NO3)3 hydrolyzes to form Al(OH)3, and Al(OH)3 reacts with HF in the pickling solution as follows:

[0040] Al(OH)3 + 3HF = AlF3 + 3H2O

[0041] The HF brought out from the pickling solution by the zirconium material reacts with Al(OH)3 in the complexing solution to produce a neutralization reaction, generating AlF3 and H2O.

[0042] (2) Neutralization effect

[0043] The HF carried out from the pickling solution by zirconium material reacts with the Al(OH)3 in the complexing solution, and the pickling reaction is completely ended. The Al(NO3)3 complexing solution plays a neutralization role in the pickling process.

[0044] (3) Complexing effect

[0045] Aluminum is the best complexing agent for fluoride ions. The Al in the complexing solution 3+ quickly generates various complexes with zirconium and fluoride ions on the surface of the zirconium alloy and dissolves in the Al(NO3)3 complexing solution. The fluoride ions are separated from the surface of the zirconium alloy, avoiding or reducing the formation of acid spots. The complex formation reaction is as follows:

[0046] [AlF n (n-3) , that is, Al 3+ +nF - =[AlF n (n-3)

[0047] [Al(ZrOF4) n (2n-3) , that is, Al 3+ +n(ZrOF4) 2- =[Al(ZrOF4) n (2n-3)

[0048] Step S2: Take out the zirconium alloy after being treated by the complexing solution, soak and wash it with deionized water at 50 - 70°C for no less than 300 seconds;

[0049] Step S3: Soak in deionized water for no less than 300 seconds;

[0050] Step S4: Drying treatment.

[0051] The specific content of the said step 4 is:

[0052] Use heated compressed air at 80°C - 100°C to conduct drying treatment on the zirconium alloy to remove the residual water stains on the surface of the zirconium alloy.

[0053] After the said step S4, it further includes:

[0054] Take samples to detect the fluorine residue on the surface of the zirconium alloy. After passing the inspection, the zirconium alloy is registered and stored in the warehouse.

[0055] ​​​​The present invention uses aluminum nitrate and deionized water to prepare a complexing solution, which reacts with the pickling solution remaining on the surface of the zirconium alloy to quickly remove the pickling solution on the surface of the zirconium alloy after pickling, prevent the reaction between hydrofluoric acid and the zirconium alloy to produce fluorides, improve the surface quality of the zirconium alloy after pickling, be beneficial to the corrosion resistance of the zirconium alloy, and reduce the generation of waste acid solution.

[0056] To further understand the present invention, the following examples are used to illustrate in detail the method for removing fluoride residues on the surface of the zirconium alloy after pickling provided by the present invention. The protection scope of the present invention is not limited by the following examples.

[0057] Example 1

[0058] 1) Pickling

[0059] Pickle zirconium alloy materials such as zirconium alloy tubes, rods, plates, and strips according to the established pickling system.

[0060] 2) Complexing

[0061] Add aluminum nitrate to deionized water to prepare a complexing solution with a complexing agent concentration of 25 g / L.

[0062] The complexing solution is prepared with deionized water. The quality requirements for deionized water are as follows: the maximum values of fluoride ions and chloride ions are 0.15 μg / g; at 25 °C, the conductivity ≤ 2.0 μS / cm; at 25 °C, the pH value is 6.0;

[0063] Quickly transfer the pickled zirconium alloy to the complexing tank and immerse it in the prepared complexing solution. During the complexing process, use an ultrasonic generator to bubble the solution, and the soaking time is 180 s.

[0064] 3) Hot water soaking

[0065] Take out the zirconium alloy treated with aluminum nitrate complexing, soak and clean it with deionized water at 50 °C. During the soaking process, bubble the deionized water, and the soaking time is 300 s.

[0066] 4) Deionized water soaking

[0067] Soak the zirconium alloy after hot water soaking in deionized water at room temperature. During the soaking process, bubble the deionized water, and the soaking time is 300 s.

[0068] 5) Drying

[0069] Use heated compressed air at 80 °C to dry the zirconium alloy to remove the water stains remaining on the surface of the zirconium alloy.

[0070] 6) Inspection and storage

[0071] Take samples to detect the fluorine residue on the surface of the zirconium alloy. After passing the inspection, the zirconium alloy is registered and stored in the warehouse.

[0072] Example 2

[0073] 1) Pickling

[0074] Pickle zirconium alloy materials such as zirconium alloy tubes, rods, plates, and strips according to the established pickling system.

[0075] 2) Complexation

[0076] Add aluminum nitrate to deionized water to prepare a complexing solution with a complexing agent concentration of 28 g / L.

[0077] The complexing solution is prepared with deionized water. The quality requirements for deionized water are as follows: the maximum values of fluoride ions and chloride ions are 0.15 μg / g; at 25°C, the conductivity ≤ 2.0 μS / cm; at 25°C, the pH value is 7.0.

[0078] Quickly transfer the pickled zirconium alloy to the complexing tank and immerse it in the prepared complexing solution. During the complexation process, use an ultrasonic generator to bubble the solution, and the soaking time is 200 s.

[0079] 3) Hot water soaking

[0080] Take out the zirconium alloy treated with aluminum nitrate complexation, soak and clean it with deionized water at 60°C. During the soaking process, bubble the deionized water, and the soaking time is 320 s.

[0081] 4) Deionized water soaking

[0082] Soak the zirconium alloy after hot water soaking in deionized water at room temperature. During the soaking process, bubble the deionized water, and the soaking time is 300 s.

[0083] 5) Drying

[0084] Dry the zirconium alloy with heated compressed air at 90°C to remove the remaining water traces on the surface of the zirconium alloy.

[0085] 6) Inspection and storage

[0086] Take samples to detect the fluorine residue on the surface of the zirconium alloy. After passing the inspection, the zirconium alloy is registered and stored in the warehouse.

[0087] Example 3

[0088] 1) Pickling

[0089] Pickle zirconium alloy materials such as zirconium alloy tubes, rods, plates, and strips according to the established pickling system.

[0090] 2) Complexation

[0091] Add aluminum nitrate to deionized water to prepare a complexing solution with a complexing agent concentration of 20 g / L.

[0092] The complex solution is prepared with deionized water, and the quality requirements for deionized water are as follows: the maximum values of fluoride ions and chloride ions are 0.15 μg / g; at 25 °C, the conductivity ≤ 2.0 μS / cm; at 25 °C, the pH value is 8.0;

[0093] Quickly transfer the pickled zirconium alloy to the complexing tank and immerse it in the prepared complex solution. During the complexing process, use an ultrasonic generator to bubble the solution, and the soaking time is 250 s.

[0094] 3) Hot water soaking

[0095] Take out the zirconium alloy treated by aluminum nitrate complexing, soak and clean it with deionized water at 50 °C to 70 °C. During the soaking process, bubble the deionized water, and the soaking time is 350 s.

[0096] 4) Deionized water soaking

[0097] Soak the zirconium alloy after hot water soaking in deionized water at room temperature. During the soaking process, bubble the deionized water, and the soaking time is 300 s.

[0098] 5) Drying

[0099] Use heated compressed air at 100 °C to dry the zirconium alloy and remove the residual water marks on the surface of the zirconium alloy.

[0100] 6) Inspection and storage

[0101] Take samples to detect the fluorine residue on the surface of the zirconium alloy. After passing the inspection, the zirconium alloy is registered and stored in the warehouse.

[0102] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0103] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for removing fluoride residues on the surface of zirconium alloy after pickling, characterized in that, It includes the following steps: Step S1: Place the pickled zirconium alloy in the complexing solution and perform bubbling treatment on the complexing solution by ultrasonic waves; the complexing solution is prepared with deionized water, and the quality requirements for deionized water are as follows: the maximum value of fluoride ions and chloride ions is 0.15 μg / g; at 25 °C, the conductivity ≤ 2.0 μS / cm; at 25 °C, the pH value is 6.0 - 8.0; The complexing solution is an aluminum nitrate solution with a concentration of 25 - 30 g / L; During the treatment, through nuclear, termination, and complexing effects, fluorides that are easily soluble in water are generated; Step S2: Take out the zirconium alloy treated with the complexing solution and soak and wash it with deionized water at 50 - 70 °C; Step S3: Soak in deionized water; Step S4: Perform drying treatment.

2. The method for removing fluoride residue on the surface of zirconium alloy after pickling according to claim 1, wherein The preparation method of the complexing solution is as follows: Mix analytical pure aluminum nitrate of 99.9% with deionized water.

3. The method for removing fluoride residues on the surface of zirconium alloy after pickling according to claim 1, characterized in that, In Step 1, the soaking time in the complexing solution is not less than 180 seconds.

4. The method for removing fluoride residue on the surface of zirconium alloy after pickling according to claim 1, characterized in that, In Step 2, the soaking time in deionized water at 50 - 70 °C is not less than 300 seconds.

5. The method for removing fluoride residue on the surface of zirconium alloy after pickling according to claim 1, characterized in that, In Step 3, the soaking time in deionized water is not less than 300 seconds.

6. The method for removing fluoride residue on the surface of zirconium alloy after pickling according to claim 1, wherein Step 4 is specifically: Use heated compressed air at 80 °C - 100 °C to perform drying treatment on the zirconium alloy to remove the residual water stains on the surface of the zirconium alloy.

7. The method for removing fluoride residues on the surface of zirconium alloy after pickling according to claim 1, characterized in that, After Step S4, it further includes: Take samples to detect the fluorine residue on the surface of the zirconium alloy. After passing the inspection, the zirconium alloy is registered and stored in the warehouse.

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