JPH0777590A - Fuel cladding pipe for nuclear reactor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a fuel cladding tube for nuclear reactor, and a manufacturing method therefor, in which the stress corrosion crack resistance is enhanced while maintaining restraint against abrupt oxidation of the inner surface. CONSTITUTION:A zirconium inner lining layer provided on the inside of a zirconium alloy cladding tube is composed of high purity zirconium containing at least one trace additive out of tin, iron, chromium, nickel, niobium, vanadium or molybdenum, 1200ppm or less of oxygen, and total 2000ppm or less of other inevitable impurities, wherein the trace additive is deposited as an intermetallic compound having average particle size in the range of 0.07 to 0.3mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear reactor fuel cladding tube used for a nuclear reactor fuel rod and a method for producing the same.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view showing the structure of a vertical cross section of a fuel rod. FIG. 4 is an explanatory view showing the configuration of the cross section of FIG. As shown in the figure, a fuel cladding tube 2 usually made of a zirconium alloy is used for a fuel rod for a light water or heavy water cooling type reactor, and a large number of fuel pellets 1 and a plenum spring 3 are loaded in the fuel cladding tube. The fuel rod is sealed with the stopper 4 to form a fuel rod.

When a cladding tube made of a zirconium alloy is irradiated with neutrons, it becomes embrittled by irradiation and is easily damaged by stress corrosion cracking. Therefore, as shown in FIG. 4, in order to prevent stress corrosion cracking, it is known to line the inner surface of the cladding tube 2 with zirconium 5, which is softer and has a higher purity than zircaloy alloy.

According to US Pat. No. 4,300,492, the total impurity content of pure zirconium is 1000 ppm or more and 5000 ppm or more.
The oxygen content is 1200 ppm or less. Such zirconium is a so-called "commercial reactor-grade sponge", and the amounts of other impurities are as shown in Table 1. The fuel cladding tube has an outer diameter of 8 to 20 mm and a wall thickness of 0.4 to 1.5 m.
The above-mentioned lining thickness in m is 0.03 to 0.2 mm.

[0005]

[Table 1]

By the way, in such a fuel clad tube, due to manufacturing defects of the clad tube and fretting with foreign matter, when water enters the clad tube, the zirconium layer on the inner surface is rapidly oxidized and the damage to the fuel is expanded, A large amount of radioactivity in the fuel rods could be released into the reactor water.

In order to prevent the damage from spreading due to the oxidation of the fuel cladding tube, it is considered to add tin, iron, chromium, nickel, niobium or the like to pure zirconium of the zirconium layer on the inner surface. It is expected that the rapid oxidation of the lining will be suppressed by increasing the amount of such elemental components.

[0008]

However, when a trace amount of additives such as tin, iron, chromium, nickel and niobium is added to pure zirconium as the zirconium layer, the resistance to stress corrosion cracking is relatively lowered. New drawbacks will arise.

[0009] The present invention provides a highly reliable fuel cladding tube for a nuclear reactor, which has improved resistance to stress corrosion cracking while maintaining the ability to suppress rapid oxidation of the inner surface, and a method for manufacturing the same.

[0010]

In a fuel cladding for a nuclear reactor according to the present invention, a zirconium alloy fuel cladding for a nuclear reactor containing a nuclear fuel therein and the cladding substrate. In a fuel cladding tube having a zirconium lining layer metallurgically bonded to the zirconium alloy inside the material, the lining layer comprises tin, iron, chromium, nickel, niobium, vanadium, molybdenum in high-purity zirconium. One or more of the trace additives and oxygen
1200ppm or less and 2000ppm total of other unavoidable impurities
The following small amount of additive is deposited as an intermetallic compound having an average particle size of 0.07 μm or more and 0.3 μm or less.

Further, in the fuel cladding for a nuclear reactor according to the invention described in claim 2, in the fuel cladding for a nuclear reactor according to claim 1, the cladding tube base material has a wall thickness of 0.4 mm or more.
1.5mm or less, the thickness of the lining layer is 0.03mm or more 0.
It is 2 mm or less.

Further, in the fuel cladding for a nuclear reactor according to the invention described in claim 3, in the fuel cladding for a nuclear reactor according to claim 1, the tin, iron, chromium, nickel, niobium, vanadium, It contains 0.2% or more and 1% or less of the total of one or more trace additives of molybdenum.

Further, in the fuel cladding for a nuclear reactor according to the invention described in claim 4, in the fuel cladding for a nuclear reactor according to claim 1, only 0.2% of iron is contained as the trace additive.
It is included above 1% or less.

Furthermore, in the fuel cladding for a nuclear reactor according to the present invention as defined in claim 5, in the fuel cladding for a nuclear reactor according to claim 1, the zirconium lining layer contains less than 600 ppm of oxygen. , The total of other unavoidable impurities is 1000
It contains less than ppm.

Further, in the fuel cladding for a nuclear reactor according to the invention described in claim 6, in the fuel cladding for a nuclear reactor according to claim 1, the intermetallic compound is 0.1 μm or more and 0.2 μm or more.
The average particle size is less than μm.

Further, in the method for producing a nuclear reactor fuel cladding tube according to the present invention, a step of molding a zirconium alloy cladding tube base portion for loading nuclear fuel,
A step of molding a zirconium lining portion integrally provided on the inner surface of the base material portion, and a double layer in which the base material portion is arranged on the outer surface side and the inner lining portion is arranged on the inner surface side by combining the base material portion and the inner lining portion. In the method for producing a fuel cladding tube, which comprises a step of forming a tubular body and a step of metallurgically bonding the base material portion and the lining portion of the double tubular body, in the zirconium lining portion, high-purity zirconium is used. In addition, a material containing a trace additive of at least one of tin, iron, chromium, nickel, niobium, vanadium, and molybdenum is prepared.
After heating to 00 ° C or higher and cooling, heat treatment such as annealing or hot extrusion sets the parameter ΣA defined by the following formula based on temperature and time to 1 × 10 ^-18 or more and 1 × 10 ^-16 or less. Heat treatment is performed.

ΣA = t · exp (-Q / RT) t; holding time at temperature T (hours) T; annealing temperature (K) Q; activation energy R; gas constant Q / R; 40000

According to the eighth aspect of the present invention, there is provided a method for producing a fuel clad tube for a nuclear reactor, wherein in the method for producing a fuel clad tube according to the seventh aspect, the lining portion and the base material portion are provided. After performing the hot extrusion in combination, the cold working treatment and the annealing treatment are repeated once or more.

Further, in the method for producing a fuel cladding tube for a nuclear reactor according to the present invention of claim 9, in the method for producing a fuel cladding tube according to claim 7, the base material portion and the lining portion are metallurgical. In the step of mechanically bonding, after the base material portion and the lining portion are molded into a double pipe body by hot extrusion, only the base material portion is cooled while cooling the inner surface of the double pipe body to 100 ° C or less.
After heating to 900 ° C or higher, cold working and annealing at 650 ° C or lower are repeated once or more.

According to a tenth aspect of the present invention, there is provided a method for producing a fuel clad tube for a nuclear reactor, wherein in the method for producing a fuel clad tube according to the eighth aspect, the fuel clad tube is a boiling water atom. A cladding tube for a fuel rod for a furnace, wherein the heat treatment of the outer surface of the fuel cladding tube sets the parameter ΣA to 1 × 10.
It is performed in the range of ^-19 to 5 × 10 ^-18 .

[0021]

In the present invention, the zirconium lining layer provided inside the zirconium alloy cladding tube substrate is one of tin, iron, chromium, nickel, niobium, vanadium and molybdenum in high-purity zirconium. One or more trace additives, oxygen of 1200 ppm or less, and total of other unavoidable impurities of 2000 ppm or less, and the trace additives are deposited as an intermetallic compound having an average particle size of 0.07 μm or more and 0.3 μm or less. Therefore, it is possible to obtain a fuel clad tube having improved resistance to stress corrosion cracking while maintaining the suppressing force against rapid oxidation of the inner surface.

That is, generally, when a small amount of additives such as tin, iron, chromium, nickel, niobium, vanadium, and molybdenum is added to high-purity zirconium, resistance to rapid oxidation is improved, while such small amounts of additives are added. As a result, zirconium becomes hard and the resistance to stress corrosion cracking decreases.

However, in the present invention, the content of oxygen in zirconium is 1200 ppm or less, preferably 6 ppm or less.
00ppm or less, total content of other unavoidable impurities is 2000
When the amount of trace additives is 0.07 μm or more and 0.3 μm or less, preferably 0.1 μm or more and 0.2 μm or less in the case of ppm or less, preferably 1000 ppm or less, the intermetallic compound is precipitated to have resistance to stress corrosion cracking. It has been found that does not decrease.

The content of oxygen, the total content of other unavoidable impurities, and the particle size of the intermetallic compound are heated to 1000 ° C. or higher in the manufacturing process of the cladding tube shown in FIG. 1 or 2 described later.・ Process for rapid cooling (ie β process) or 900 ℃
The parameter ΣA given by the following formula based on temperature and time is 1 × 10 ^-18 or more and 1 × 1
It can be obtained by setting it to 0 ^-16 or less.

ΣA = t · exp (-Q / RT) t; holding time at temperature T (hours) T; annealing temperature (K) Q; activation energy R; gas constant Q / R; 40000

In this case, the trace additives of tin, iron, chromium, nickel, niobium, vanadium, molybdenum and the like added to zirconium for improving the resistance may be used alone or in combination. However, in order to sufficiently suppress rapid oxidation, the total amount of these trace additives should be 0.2% (2
000 ppm) or more and 1% (10000 ppm) or less is desirable, and as shown in the examples described later, the most excellent properties are those containing only 2000 ppm or more and 10000 ppm or less of iron.

That is, in order to improve resistance to rapid oxidation, trace amounts of additives such as tin, iron, chromium, nickel, niobium, vanadium and molybdenum are added to high-purity zirconium. When heating a layer, set the ΣA parameter to 1 × 10 ^-18 or more and 1 × 1
When heat is applied so as to be 0 ^-16 or less, a trace amount of additive is precipitated as an intermetallic compound having an average particle size of 0.07 µm or more and 0.3 µm or less, zirconium is softened again, and resistance to stress corrosion cracking is improved.

That is, when the ΣA parameter is heated to 1 × 10 ^-18 or less, the grain size of the intermetallic compound in the lining layer becomes 0.
When it is less than 07 μm, zirconium becomes hard and resistance to stress corrosion cracking becomes low. On the other hand, if heat is applied to the ΣA parameter of 1 × 10 ⁻¹⁶ or more, the intermetallic compound is 0.00
In addition to coarsening to more than 03 mm (0.3 μm), it was revealed that as a result, not only the corrosion resistance of zirconium deteriorates, but also the resistance to stress corrosion cracking deteriorates.

Further, after the base material portion and the lining portion are metallurgically bonded, that is, after the lining portion and the base material portion are combined and hot extrusion is performed, cold working treatment and annealing treatment, etc. Another heat treatment may be repeated once or more. In this case, the ΣA parameters of the temperature and time of the heat treatment related to the lining portion are naturally within the above range.

Further, the above-mentioned ΣA parameter is set to 1 × 10.
^{Since the} application of heat so as to be not less than ^{-18 and not} more than 1 × 10 ^-16 is limited to at least the lining portion, in the step of metallurgically bonding the base portion and the lining portion to the base portion, After forming the double tubing with the lining part by hot extrusion, while cooling the inner surface of the double tubing to 100 ° C or lower, heat only the base material to 900 ° C or higher, then cold work as well as
It is also possible to obtain a desired structure of the base material portion by repeating annealing at 650 ° C. or less once or more.

In order to suppress the oxidation of the outer surface of the zirconium alloy coated tube provided with the lining layer, which is generated by the reaction with cooling water when used in a boiling water reactor, Japanese Patent Application No. As described in -73123, it is desirable that the ΣA parameter is 1 × 10 ⁻¹⁹ or more and 5 × 10 ⁻¹⁸ or less.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process drawing showing a manufacturing process of an embodiment of a covering pipe, and FIG. 2 is a process drawing showing a manufacturing process of another embodiment of a covering pipe. In the present invention, in the manufacturing process shown in FIG. 1 or 2, β treatment or α + heating at 1000 ° C. or 900 ° C. or higher
In the heating process after the β treatment process, the parameter ΣA given by the following formula based on temperature and time is set to 1 × 10 ⁻¹⁸ or more 1
It was set to × 10 ^-16 or less. The specific parameter ΣA was set at the temperature and time shown in Table 2 below.

ΣA = t · exp (-Q / RT) t; holding time at temperature T (hours) T; annealing temperature (K) Q; activation energy R; gas constant Q / R; 40000

[0034]

[Table 2]

In this embodiment, an inner lining material was manufactured by the manufacturing process shown in FIG. 1 and the conventional technique using the element added to the zirconium layer (lining layer) lining the inner surface of the cladding tube as a parameter, and the corrosion resistance and the stress corrosion resistance were evaluated. Cracking resistance (SCC resistance
The following table 3 shows the results of examination of (sex).

A specific method for manufacturing a cladding tube is as follows. The lining part is formed into a predetermined shape by hot working from arc melting and then subjected to β treatment at 1050 ° C. for 30 minutes, and then at 720 ° C. for 5 minutes.
Anneal for time. It should be noted that the conventional technique does not have this annealing step. Further, the base material is formed into a predetermined shape by hot working from arc melting, and then subjected to β treatment at 1050 ° C. for 30 minutes.

Further, combining this lining portion and the base material portion,
Processed by hot extrusion at 640 ° C for 10 minutes, then at 640 ° C, 2
After the time annealing step, after cold working, 620
Perform an annealing process at ℃ for 2 hours. Further, after cold working, the product becomes a product after another annealing step at 570 ° C. for 2 hours. The conventional example is the same as the present manufacturing method except that there is no annealing process for the lining portion.

[0038]

[Table 3]

As shown in Table 3, according to the present invention, tin, iron,
0.2% or more of any one of chromium, nickel, niobium, vanadium, and molybdenum, or a total of more than 1
% Or less lining material without degrading corrosion resistance,
Improved resistance to stress corrosion cracking (SCC resistance), especially iron
Lining material containing 0.2% or more and 1.0% or less (Example No. 5
7 (Fe alone), and Example No. 14-19 (Fe +
It was confirmed that the effect is large in α)).

In the table, Comparative Example No. 1 is Zircaloy 2 (one of zirconium alloy) which is a conventional cladding tube base material,
Comparative example No. 20 is pure zirconium (Zr) which is a conventional lining material. Example No. Nos. 2 to 19 are conventional Nos.
Compared with 20, the corrosion resistance is improved.

The manufacturing method according to the present invention (new)
When compared with the conventional (old), the example No. 2 to 19, in the method according to the present invention, the corrosion resistance is kept the same as the conventional one, and the SCC resistance is improved.

Further, among the steps shown in FIG. 1, the annealing step after the β-processing step of the lining portion may be hot working or a mixed step of annealing and hot working. Naturally, the parameter Σ given based on the temperature and time of this hot working
A is set to 1 × 10 ⁻¹⁸ or more and 1 × 10 ⁻¹⁶ or less. This makes it possible to adjust the size of the lining portion and make the lining portion from a large material.

Incidentally, as shown in FIG. 2, a predetermined annealing process may be performed after the lining portion and the base material portion are combined. FIG. 2 is a process drawing showing the manufacturing process of another embodiment of the cladding tube. In this step, the annealing step after the β treatment step of the lining portion is performed after the hot extrusion molding in combination with the base material portion. Naturally, the parameter ΣA of this annealing process is 1 × 1
It should be 0 ^-18 or more and 1 x 10 ^-16 or less.

Further, water was enclosed in this coating pipe to cool the inner surface of the double pipe body to 100 ° C. or lower, and only the base material portion was heated to 900 ° C. or higher without raising the temperature of the lining portion. It is also possible to carry out the α + β treatment step, and then repeat cold working and annealing at 650 ° C. or lower one or more times to obtain a desired base material structure.

Further, for example, the billet for the outer surface of the cladding tube base material is water-quenched in a shape having a hole in the center, and the lining portion is water-quenched (annealed) with a solid billet to obtain a cladding tube. The particle size of the intermetallic compound precipitated in the zirconium alloy of the base material can be made relatively smaller than the particle size of the intermetallic compound of the lining portion.

As described above, according to the present invention, the stress corrosion cracking resistance can be improved without deteriorating the corrosion resistance of the lining layer of the cladding tube, the stress corrosion cracking resistance is high, and by any chance. It is possible to supply a fuel cladding tube with high soundness, which does not cause the inner surface to be rapidly oxidized and the damage to spread even when the fuel cell is damaged.

[0047]

As described above, according to the present invention, the zirconium lining layer provided inside the cladding tube base material made of zirconium alloy contains tin, iron, chromium, nickel, niobium, vanadium and molybdenum in high purity zirconium. Any one or more of the trace additives, oxygen of 1200ppm or less, and the total of other unavoidable impurities of 2000ppm or less, and the trace additive is a metal having an average particle size of 0.07μm or more and 0.3μm or less. Since it is deposited as an intermetallic compound, while maintaining the ability to suppress rapid oxidation of the inner surface,
There is an effect that a fuel cladding tube having improved resistance to stress corrosion cracking can be obtained.

As the zirconium lining portion, a material containing high-purity zirconium and a trace additive of at least one of tin, iron, chromium, nickel, niobium, vanadium and molybdenum is prepared. After heating to 900 ° C or higher and cooling, heat treatment such as annealing or hot extrusion is a heat treatment in which the above-mentioned parameter ΣA defined based on temperature and time is set to 1 × 10 ^-18 or more and 1 × 10 ^-16 or less. By performing the above, the fuel cladding tube can be obtained.

[Brief description of drawings]

FIG. 1 is a process drawing showing a manufacturing process of an embodiment of a cladding tube.

FIG. 2 is a process drawing showing a manufacturing process of another embodiment of the cladding tube.

FIG. 3 is an explanatory diagram showing a configuration of a vertical cross section of a fuel rod.

FIG. 4 is an explanatory diagram showing a configuration of a cross section of FIG.

Claims (10)

[Claims] 1. A fuel cladding tube base made of a zirconium alloy for containing nuclear fuel therein, and a zirconium lining layer metallurgically bonded to the zirconium alloy inside the cladding base. In the fuel cladding tube, the lining layer contains high-purity zirconium, a trace additive of at least one of tin, iron, chromium, nickel, niobium, vanadium, and molybdenum, oxygen of 1200 ppm or less, and other inevitable. A fuel cladding tube for a nuclear reactor, comprising a total amount of impurities of 2000 ppm or less, wherein the trace additive is deposited as an intermetallic compound having an average particle size of 0.07 μm or more and 0.3 μm or less. 2. The fuel cladding for a nuclear reactor according to claim 1, wherein the cladding tube base material has a wall thickness of 0.4 mm or more and 1.5 mm or less, and the lining layer has a wall thickness of 0.03 mm or more and 0.2 mm or more. A fuel cladding tube for a nuclear reactor, characterized in that: 3. The fuel cladding tube for a nuclear reactor according to claim 1, wherein the tin, iron, chromium, nickel, niobium, vanadium,
A fuel cladding tube for a nuclear reactor, which contains 0.2% or more and 1% or less of a total of one or more trace additives of molybdenum. 4. The fuel cladding for a nuclear reactor according to claim 1, wherein only 0.2% or more and 1% or less of iron is contained as the trace additive. 5. The reactor fuel cladding tube according to claim 1, wherein the zirconium lining layer contains 600 ppm of the oxygen.
Hereinafter, a fuel cladding for a nuclear reactor characterized by containing a total of 1000 ppm or less of other unavoidable impurities. 6. The fuel cladding for a nuclear reactor according to claim 1, wherein the intermetallic compound is deposited to have an average particle diameter of 0.1 μm or more and 0.2 μm or less. tube. 7. A step of molding a zirconium alloy cladding tube base material portion for loading nuclear fuel; a step of molding a zirconium lining portion integrally provided on an inner surface of the base material portion; A step of forming a double pipe body in which the base material portion is arranged on the outer surface side and the inner lining portion is arranged on the inner surface side by combining the inner pipe portion and the inner lining portion, and the base material portion and the lining portion of the double pipe body are metallurgically In the method for producing a fuel cladding tube, which comprises a step of bonding, as the zirconium lining portion, tin, iron, chromium, nickel, niobium, vanadium,
After preparing a material containing any one or more trace amounts of molybdenum and heating the material to 900 ° C or higher and cooling it, heat treatment such as annealing or hot extrusion is performed based on temperature and time. Parameter ΣA defined by the following formula is 1 × 10 ^-18 or more 1 × 1
A method of manufacturing a fuel cladding tube for a nuclear reactor, which comprises performing a heat treatment at 0 ^-16 or less. ΣA = t · exp (-Q / RT) t; retention time (time) at temperature T T; annealing temperature (K) Q; activation energy R; gas constant Q / R; 40000 8. The method for manufacturing a fuel clad tube according to claim 7, wherein after hot extrusion is performed by combining the lining portion and the base material portion, cold working treatment and annealing treatment are performed once. A method of manufacturing a fuel cladding tube for a nuclear reactor, characterized by repeating the above. 9. The method for producing a fuel clad tube according to claim 7, wherein the fuel clad tube is a clad tube for a boiling water reactor fuel rod, and the fuel clad tube has an outer surface with respect to an outer surface of the fuel clad tube. A method of manufacturing a fuel cladding tube for a nuclear reactor, characterized in that heat treatment is performed with the parameter ΣA in the range of 1 × 10 ⁻¹⁹ to 5 × 10 ⁻¹⁸ . 10. The method for manufacturing a fuel clad tube according to claim 7, wherein in the step of metallurgically bonding the base material portion and the lining portion, the base material portion and the lining portion are hot-extruded to form two pieces. After molding into a heavy pipe, only the base material is heated to 900 ° C or higher while cooling the inner surface of the double pipe to 100 ° C or less, and then cold working and annealing at 650 ° C or less are performed once. A method of manufacturing a fuel cladding tube for a nuclear reactor, characterized by repeating the above.