WO2022213545A1 - Zirconium alloy and preparation method therefor, cladding tube, and fuel assembly - Google Patents

Abstract

Disclosed are a zirconium alloy and a preparation method therefor, a cladding tube, and a fuel assembly. The zirconium alloy comprises the following components in percentages by mass: 0.48% to 0.95% of niobium, 0.37% to 0.75% of tin, 0.03% to 0.15% of iron, and 0 to 0.15% of vanadium, and further comprises 1100 ppm to 1600 ppm of oxygen and the balance of Zr, wherein the contents of niobium, iron and vanadium satisfy the following relationship: (Nb-0.45％)≥Fe+V and Fe+V≤0.2%. Due to the proportion of each component, the zirconium alloy of the present invention has a more excellent corrosion resistance and creep resistance compared with an existing Zr-4 alloy, and is suitable for cladding, grillwork and a guide tube of a fuel assembly of a nuclear power plant reactor and improves the service performance and safety performance of the fuel assembly.

Description

Zirconium alloy and preparation method thereof, cladding tube and fuel assembly technical field

The invention relates to the technical field of nuclear fuel, in particular to a zirconium alloy and a preparation method thereof, a cladding tube and a fuel assembly.

Background technique

Zirconium alloys are widely used as structural materials for nuclear fuel assemblies because of their small thermal neutron absorption cross-section, excellent corrosion resistance, radiation resistance and mechanical properties. Studies have shown that the existing zirconium alloys have strong creep resistance, but also have shortcomings in corrosion resistance.

In order to meet the ever-increasing demand for fuels, it is not possible to excel only in corrosion resistance or creep resistance. It is necessary to optimize the composition ratio and add other elements. Zirconium alloy with excellent properties.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a zirconium alloy with excellent corrosion resistance and creep resistance and a preparation method thereof, a cladding tube made of the zirconium alloy, and a fuel assembly having the cladding tube .

The technical scheme adopted by the present invention to solve the technical problem is: to provide a zirconium alloy, comprising the following components by mass percentage: niobium 0.48%-0.95%, tin 0.37%-0.75%, iron 0.03%-0.15%, vanadium 0-0. 0.15%, also including oxygen 1100ppm-1600ppm, the balance is Zr;

Wherein, the contents of niobium, iron and vanadium satisfy the following relationships: (Nb-0.45%)≥Fe+V, Fe+V≤0.2%.

Preferably, in the zirconium alloy, C≤100ppm, N≤45ppm.

The present invention also provides a preparation method of the above-mentioned zirconium alloy, comprising the following steps:

S1. Provide raw materials containing zirconium, niobium, tin, iron and vanadium components respectively, and weigh the raw materials according to the mass percentage of each component in the zirconium alloy;

S2, smelting the raw material to obtain an alloy ingot;

S3, forging the alloy ingot into a billet;

S4, the blank is subjected to beta quenching;

S5. The billet after β quenching is subjected to multiple cold rolling, and intermediate annealing is carried out between cold rolling;

S6. Final annealing is performed on the cold-rolled billet to obtain a zirconium alloy.

Preferably, in step S3, the temperature of the forging is 800°C-1100°C.

Preferably, in step S4, the temperature of the beta quenching is 950°C-1100°C.

Preferably, in step S5, the temperature of the intermediate annealing is 550°C-600°C.

Preferably, in step S5, the billet is extruded or hot rolled before cold rolling.

Preferably, in step S6, the temperature of the final annealing is 440°C-600°C.

Preferably, the preparation method further comprises the following steps:

S7, processing the zirconium alloy into a cladding tube, a lattice or a guide tube.

The present invention also provides a cladding tube, which is made of the zirconium alloy described in any one of the above.

The present invention also provides a fuel assembly comprising the cladding tube described above.

Compared with the existing Zr-4 alloy, the zirconium alloy of the present invention has more excellent corrosion resistance performance and creep resistance performance through the ratio of each component, and is suitable for the cladding, lattice and other components of the nuclear power plant reactor fuel assembly. Guide tube to improve the service performance and safety of the fuel assembly.

Detailed ways

The zirconium alloy of the present invention is a zirconium-tin-niobium alloy with a low content of transition metals, which comprises the following composition in mass percentage:

Nb (niobium) 0.48%-0.95%, Sn (tin) 0.37%-0.75%, Fe (iron) 0.03%-0.15% and V (vanadium) 0-0.15%, also including O (oxygen) 1100-1600ppm, the remainder The amount is Zr (zirconium).

Wherein, the contents of niobium, iron and vanadium satisfy the following relationships: (Nb-0.45%)≥Fe+V, Fe+V≤0.2%.

The zirconium alloy also includes: C (carbon)≤100ppm, N (nitrogen)≤45ppm. Understandably, some inevitable and small amounts of impurities are also included.

For Nb (niobium), studies have shown that the solid solution niobium in the zirconium alloy is beneficial to the corrosion resistance and creep resistance of the zirconium alloy, but the high content of niobium will be sensitive to heat treatment. Therefore, in the present invention, in order to ensure the zirconium alloy The alloy has excellent corrosion resistance and creep resistance. The content of Nb is controlled at 0.48wt% to 0.95wt%, and the content of Nb, Fe, V is required to satisfy the relationship (Nb-0.45%) ≥ Fe+ V, can ensure that enough niobium atoms are dissolved in the matrix, so as to ensure that the zirconium alloy has excellent corrosion resistance and creep resistance.

Tin (Sn) has a large solid solubility in zirconium. After a certain amount of tin is incorporated, the strength and creep resistance of zirconium alloys will be improved, but the addition of tin will reduce the uniform corrosion resistance of zirconium alloys. On the other hand, the addition of tin can improve the corrosion resistance of zirconium alloys in high Li concentration environments. In the present invention, after comprehensively considering corrosion resistance and creep resistance, the content of tin is controlled at 0.37wt% to 0.75wt%.

Iron (Fe) and vanadium (V) are transition metal elements, which can be added to the zirconium alloy to increase the corrosion resistance of the zirconium alloy. The addition of vanadium can improve the hydrogen absorption resistance of the zirconium alloy. Such transition metal elements such as iron and vanadium need to be added in an appropriate amount in zirconium alloys, and if they are added too much (over 0.2%), the corrosion resistance of zirconium alloys will decrease. Therefore, in the present invention, the content of elements such as Fe and V is strictly controlled, the Fe content is controlled at 0.03wt% to 0.15wt%, the V content is controlled at 0 to 0.15wt%, and the total amount of Fe and V in the zirconium alloy is controlled ≤ 0.2wt%, to ensure that the zirconium alloy has sufficient corrosion resistance and sufficient oxidation resistance when serving in the stack.

In the zirconium alloy of the present invention, the content of niobium, iron and vanadium satisfies (Nb-0.45%)≥Fe+V, so as to ensure that enough Nb element is dissolved in the zirconium alloy, and tin is mixed, so that the zirconium alloy matrix is solid-dissolved in the zirconium alloy. Sufficient solid solution atoms, so that the alloy maintains excellent creep resistance.

In the zirconium alloy of the present invention, the addition of oxygen (O) can improve the strength and creep resistance of the zirconium alloy, but as the oxygen content increases, the machinability of the zirconium alloy will decrease, especially the punching resistance. Therefore, the oxygen content is controlled at 1100ppm-1600ppm.

The preparation method of the zirconium alloy of the present invention may comprise the following steps:

S1. Provide raw materials containing zirconium, niobium, tin, iron and vanadium respectively, and weigh the raw materials according to the mass percentage of each component in the zirconium alloy (calculation of ingredients).

Among them, the zirconium raw material uses nuclear grade sponge zirconium. Niobium, tin, iron and vanadium elements are added in the form of pure metals or master alloys.

S2, smelting the raw material to obtain an alloy ingot.

Put all the raw materials into a vacuum melting furnace for melting, adjust the content of O, C and N, and finally obtain an alloy ingot.

S3, the alloy ingot is forged into a billet at a temperature of 800°C-1100°C.

S4, the blank is subjected to beta quenching.

Among them, the temperature of β quenching is 950℃-1100℃, and the temperature is kept for a long enough time to make the whole billet reach the quenching temperature.

S5. The billet after β quenching is subjected to multiple cold rolling, and intermediate annealing is performed between cold rolling.

Wherein, according to the shape of the zirconium alloy to be formed (such as pipes, etc.), before cold rolling, the billet is extruded or hot rolled, and then the billet is subjected to at least 4 passes of cold rolling. The temperature of the intermediate annealing is 550°C-600°C.

S6. Final annealing is performed on the cold-rolled billet at 440° C.-600° C. to obtain a zirconium alloy.

When zirconium alloy is used as the cladding tube material, stress relief annealing or recrystallization annealing is preferred, and the annealing temperature is 440-600°C, and the prepared cladding has excellent corrosion resistance and sufficient creep resistance.

When zirconium alloy is used as the guide tube material, recrystallization annealing is preferred, and the annealing temperature is 540-600° C. The prepared guide tube has excellent creep resistance and sufficient corrosion resistance.

When a zirconium alloy is used as a lattice strip, recrystallization annealing is preferred. The lattice strip prepared at an annealing temperature of 540-600°C has excellent creep resistance, radiation growth resistance and sufficient corrosion resistance.

In order to facilitate the processing of zirconium alloys into cladding tubes, guide tubes or grid strips, etc., the zirconium alloy profiles are prepared through the above steps S1-S6.

Zirconium alloys can also be made into sheets or tubes according to the needs of the application.

Further, the preparation method of the present invention may further comprise the following steps:

S7. The zirconium alloy obtained in step S6 is processed into a cladding tube, a grid or a guide tube for use in a fuel assembly.

In an application embodiment, the above-mentioned zirconium alloy is made into a cladding tube of a fuel assembly.

The fuel assembly includes the above-mentioned cladding tube made of zirconium alloy, and also includes fuel pellets sealed in the cladding tube. Since the cladding tube is made of the above-mentioned zirconium alloy, the cladding tube has better corrosion resistance and creep resistance than the cladding tube made of the conventional Zr-4 alloy, thereby improving the service performance and safety of the fuel assembly.

The present invention will be further described below through specific embodiments.

According to the preparation method of the present invention, the zirconium alloys of Examples 1 to 4 were prepared. Table 1 shows the content of each component in the zirconium alloys of Examples 1 to 4 and Comparative Example 1.

Table 1

The zirconium alloys and Zr-4 alloys (Zr-1.30Sn-0.20Fe-0.10Cr-0.12O) prepared in Examples 1 to 4 and Comparative Example 1 were used as Comparative Example 2 to conduct corrosion tests. The corrosion test was carried out in an autoclave, the corrosion conditions were 360°C/18.6MPa/deionized water, and the test time was 130 days. The results are shown in Table 2 below.

Table 2

Example	Corrosion amount (mg/dm 2 )
1	45.88
2	42.29
3	44.12
4	45.42
Comparative Example 1	44.75
Comparative Example 2	63.30

From the data shown in Table 2, it can be seen that the zirconium alloys of Examples 1-4 and Comparative Example 1 have higher corrosion resistance (less weight gain) than the Zr-4 alloy of Comparative Example 2.

The zirconium alloys prepared in Examples 1 to 4 and Comparative Example 1 and the Zr-4 alloy (Zr-1.30Sn-0.20Fe-0.10Cr-0.12O) as Comparative Example 2 were subjected to internal pressure creep tests. The creep test was carried out on a professional creep machine, the temperature was 400°C, the hoop stress was 130MPa, and the test time was 240 hours. The results are shown in Table 3 below.

table 3

Example	Strain (mm/mm)
1	0.70
2	0.44
3	0.81
4	0.51
Comparative Example 1	0.91
Comparative Example 2	1.79

From the data shown in Table 3, it can be seen that the zirconium alloys of Examples 1-4 satisfy (Nb-0.45%)≥Fe+V, which is lower than that of Comparative Example 1 (Nb-0.45%)<Fe+V and Comparative Example The Zr-4 alloy of 2 shows higher creep resistance (less creep deformation).

It can be understood that, in the present invention, except for the above-mentioned embodiments, the zirconium alloys within the content range of each component of the present invention and satisfying the content relationship have excellent corrosion resistance performance and creep resistance performance, and are suitable for use as nuclear power plant reactor cladding materials. , lattice material and guide tube material.

The above descriptions are only the embodiments of the present invention, and do not limit the scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description of the present invention, or directly or indirectly applied in other related technical fields, will not limit the scope of the invention. Similarly, it is included in the scope of patent protection of the present invention.

Claims (11)

1. A zirconium alloy is characterized by comprising the following components by mass percentage: niobium 0.48%-0.95%, tin 0.37%-0.75%, iron 0.03%-0.15%, vanadium 0-0.15%, and oxygen 1100ppm-1600ppm, The balance is zirconium;

   Wherein, the contents of niobium, iron and vanadium satisfy the following relationships: (Nb-0.45%)≥Fe+V, Fe+V≤0.2%.
2. The zirconium alloy according to claim 1, wherein, in the zirconium alloy, C≤100ppm and N≤45ppm.
3. A preparation method of zirconium alloy described in claim 1 or 2, is characterized in that, comprises the following steps:

   S1. Provide raw materials containing zirconium, niobium, tin, iron and vanadium components respectively, and weigh the raw materials according to the mass percentage of each component in the zirconium alloy;

   S2, smelting the raw material to obtain an alloy ingot;

   S3, forging the alloy ingot into a billet;

   S4, the blank is subjected to beta quenching;

   S5. The billet after β quenching is subjected to multiple cold rolling, and intermediate annealing is carried out between cold rolling;

   S6. Final annealing is performed on the cold-rolled billet to obtain a zirconium alloy.
4. The method for preparing a zirconium alloy according to claim 3, wherein in step S3, the temperature of the forging is 800°C-1100°C.
5. The method for preparing a zirconium alloy according to claim 3, wherein in step S4, the temperature of the beta quenching is 950°C-1100°C.
6. The method for preparing a zirconium alloy according to claim 3, wherein in step S5, the temperature of the intermediate annealing is 550°C-600°C.
7. The method for preparing a zirconium alloy according to claim 3, wherein in step S5, the billet is extruded or hot rolled before cold rolling.
8. The method for preparing a zirconium alloy according to claim 3, wherein in step S6, the temperature of the final annealing is 440°C-600°C.
9. The preparation method of zirconium alloy according to any one of claims 3-8, is characterized in that, also comprises the following steps:

   S7, processing the zirconium alloy into a cladding tube, a lattice or a guide tube.
10. A cladding tube, characterized in that it is made of the zirconium alloy according to claim 1 or 2.
11. A fuel assembly is characterized by comprising the cladding tube of claim 10 .