JPH07260969A - Fuel cladding pipe for nuclear reactor - Google Patents

Abstract

PURPOSE:To obtain a fuel cladding pipe for nuclear reactor which improves the corrosion resistance, and maintains a suppressing force against a sudden oxidization of the inner surface. CONSTITUTION:As a lining layer made of zirconium provided on the inner surface of a cladding pipe basic member made of a zirconium alloy, a minute amount of additive of either one or more of Co, Rh, and Pd is included in a high purity of zirconium, and furthermore, less than 1200ppm of oxygen, and less than 2000ppm totally of other unavoidable impurities are also included.

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 in a nuclear reactor fuel rod.

[0002]

2. Description of the Related Art FIG. 2 is an explanatory view showing the structure of a vertical cross section of a fuel rod. FIG. 3 is an explanatory diagram showing the configuration of the cross section of FIG. As shown in the figure, a fuel cladding for a light water or heavy water cooled reactor is usually equipped with a fuel cladding tube (2) made of a zirconium alloy, and contains a large number of fuel pellets (1) and plenum springs (3) inside. It is loaded and sealed with upper and lower end plugs (4) to form a fuel rod.

[0003] Usually, a zirconium alloy cladding tube is irradiated with neutrons to become brittle, and stress corrosion cracking is likely to occur. Therefore, as shown in FIG. 2, in order to prevent stress corrosion cracking, it is known to line the inner surface of the cladding tube 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.
Below, the oxygen content is below 1200ppm. Such zirconium is a so-called "commercial reactor grade sponge zirconium", and other impurities and their amounts are as shown in Table 1. The fuel cladding tube has an outer diameter of 8 to
20 mm, wall thickness 0.4 to 1.5 mm, and the above-mentioned lining thickness is 0.03 to
0.2 mm.

[0005]

[Table 1]

[0006]

However, in such a fuel clad tube, when water enters the clad tube due to manufacturing defects of the clad tube or fretting with foreign matter, the zirconium layer having a low corrosion resistance on the inner surface abruptly. Since the zirconium layer is oxidized and the zirconium layer expands in volume due to the oxidation, the damage to the fuel is expanded, and a large amount of radioactivity in the fuel rod may be released into the reactor water.

According to the present invention, a fuel cladding for a nuclear reactor having improved corrosion resistance, a fuel cladding for a nuclear reactor which maintains a suppressing force against rapid oxidation of the inner surface, and resistance to stress corrosion cracking are retained. It is an object of the present invention to obtain a fuel cladding for a nuclear reactor and a highly reliable fuel cladding for a nuclear reactor.

[0008]

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,
In a fuel cladding tube having a zirconium lining layer metallurgically bonded to the cladding substrate, as the lining layer, one of cobalt (Co), rhodium (Rh), and palladium (Pd) in high-purity zirconium is used. It contains any one or more trace additives, and further contains 1200 ppm or less of oxygen and other inevitable impurities of 2000 ppm or less in total.

According to a second aspect of the present invention, there is provided a fuel cladding tube for a nuclear reactor according to the first aspect, wherein the lining layer is cobalt (Co) or rhodium (Rh). , Palladium (Pd), and the total amount of one or more trace additives is 0.05% or more and 1% or less.

In the fuel cladding tube for a nuclear reactor according to the present invention as defined in claim 3, a fuel cladding tube base material for a nuclear reactor made of a zirconium alloy for containing a nuclear fuel therein, and the cladding tube base metallurgically In a fuel cladding having a bonded zirconium lining layer, the zirconium lining layer comprises cobalt (Co), rhodium (R) in high purity zirconium.
h) and palladium (Pd), the total of one or more trace additives is 0.05% to 1%, oxygen of 600 ppm or less, and other unavoidable impurities of 1000 ppm or less in total.

[0011]

In the present invention, as the zirconium lining layer provided inside the zirconium alloy cladding tube base material, one of cobalt (Co), rhodium (Rh) and palladium (Pd) is contained in high-purity zirconium. Since it contains one or more trace additives and further contains 1200ppm or less of oxygen and other unavoidable impurities of 2000ppm or less in total, the corrosion resistance is improved depending on the addition amount of the trace additive and the internal surface sharply changes. The ability to suppress oxidation can be maintained.

That is, when water enters the inside of the cladding due to manufacturing defects of the cladding or fretting with foreign matter, the zirconium layer having low corrosion resistance on the inner surface is rapidly oxidized, and the zirconium layer causes volume expansion due to the oxidation. However, the damage to the fuel has spread, and a large amount of radioactivity in the fuel rods may be released into the reactor water.

Therefore, in order to prevent the damage from spreading due to oxidation of the fuel cladding tube, a small amount of Co, Rh, and Pd additives are added to pure zirconium forming the zirconium lining layer on the inner surface. It was found that the rapid oxidation of the zirconium layer on the inner surface was suppressed by increasing the element content.

By the way, as a zirconium lining layer, pure zirconium is added to cobalt (Co) and rhodium (R).
When a small amount of additives such as h) and palladium (Pd) is added, the corrosion resistance is improved according to the added amount, but on the contrary, the hardness is increased, the ductility is decreased, and the stress corrosion cracking resistance is decreased. Is expected.

That is, in the present invention, when cobalt (Co), rhodium (Rh), palladium (Pd) or the like is added to high-purity zirconium, the corrosion resistance and the stress corrosion cracking resistance that suppress rapid oxidation are To satisfy both,
The total amount of any one or more trace additives of cobalt (Co), rhodium (Rh), and palladium (Pd) is
It is desirable to be 0.05% or more and 1% or less. If the total amount of the above trace additives is less than 0.05%, the corrosion resistance will be poor, and 1%
If it exceeds, the hardness increases, the ductility decreases, and the stress corrosion cracking resistance deteriorates.

That is, in order to improve resistance to rapid oxidation, trace amounts of cobalt (Co), rhodium (Rh) and palladium (Pd) are added to high-purity zirconium. When 0.05% or more and 1% or less is added, zirconium does not harden and resistance to stress corrosion cracking does not decrease. Therefore, it is possible to obtain the fuel clad tube which maintains the resistance to the stress corrosion cracking while maintaining the suppressing force against the rapid oxidation of the inner surface.

Generally, the addition of a different kind of metal hinders the migration of oxygen and metal atoms in the mother layer metal and improves the corrosion resistance. This is because the additive element is replaced with a part of the lattice in the mother layer metal, and the concentration of lattice defects involved in the movement of oxygen and metal atoms is reduced. Such actions are caused by electrical interactions at the atomic level. Cobalt (C
o), rhodium (Rh), palladium (Pd), and other minor additives are all elements of the third and fourth periods of the genus 8 of fiber metal, and have similar chemical properties and electronic arrangements. It is presumed that similar effects appeared.

In addition, it is generally known that pure metal has poor corrosion resistance and stress corrosion cracking resistance and high ductility, but the trace amount additive of the present invention is effective in improving corrosion resistance at the atomic level. Since it has little effect on mechanical properties such as ductility, it exhibits excellent ductility. Therefore, the stress is relaxed by the lining layer, and the stress corrosion cracking property of Zry-2 can be reduced.

In the present invention, high purity zirconium is added to cobalt (Co), rhodium (Rh), palladium (P
It contains the trace amount additive of d), oxygen of 1200 ppm or less, and other inevitable impurities. This is because if the oxygen contained in the lining layer exceeds 1200 ppm, the metal becomes hard and the workability is lowered, and the ductility required as the lining material is lowered. Therefore, oxygen contained in the zirconium lining layer is set to 1200 ppm or less. Further, more preferably, if the content of oxygen is 600 ppm or less, the ductility is further improved.

Further, as the other unavoidable impurities contained in the lining layer, there are concretely those shown in the above-mentioned Table 1, and when the total amount exceeds 2000 ppm, hardness increases and ductility deteriorates. More preferably, if the content is 1000 ppm or less, the ductility becomes better.

As described above, the present invention has a zirconium alloy fuel cladding tube base material for a nuclear reactor that contains a nuclear fuel therein, and a zirconium lining layer metallurgically bonded to the cladding tube base material. In the fuel cladding tube, the zirconium lining layer contains cobalt (Co), rhodium (R) in high-purity zirconium in a total amount of 0.05% or more and 1% or less.
h), palladium (Pd), one or more trace additives, 600ppm or less of oxygen, and 1000ppm or less of other unavoidable impurities in total, so the ability to suppress rapid oxidation of the inner surface is maintained. At the same time, it is possible to obtain a fuel clad tube that retains resistance to stress corrosion cracking, and further a fuel clad tube that is more excellent in ductility and workability.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process drawing showing the manufacturing process of an embodiment of the coating tube of the present invention. In the present invention, regarding the manufacturing process shown in FIG. 1, in this embodiment, the element added to the zirconium lining layer lining the inner surface of the cladding tube is used as a parameter,
A trial lining material was manufactured by the manufacturing process shown in FIG.

The corrosion resistance and the stress corrosion cracking resistance (SCC resistance) of each of various examples (Examples 1 to 12) in which the concentrations of the trace additives and the trace additives were different were examined. The results are shown in Table 2 below. Incidentally, Comparative Example No. 13 in the table
Zircaloy 2 (one of zirconium alloys) which is a conventional cladding tube base material, and Comparative Example No. 14 is pure zirconium which is a conventional lining material.

[0024]

[Table 2]

As shown in Table 2, the oxygen content in zirconium according to the present invention is 1200 ppm or less, preferably 600 ppm.
Below, when the total content of other unavoidable impurities is 2000 ppm or less, preferably 1000 ppm or less, cobalt (C
o), rhodium (Rh), and palladium (Pd), the lining material containing one or more of 0.05% or more and 1% or less in total improved corrosion resistance without deteriorating resistance to stress corrosion cracking. In addition, the following Table 3 is data of oxygen and other inevitable impurities in Examples 1 to 12 above.

[0026]

[Table 3]

Of the steps shown in FIG. 1, the annealing step after the β treatment step of the lining portion may be hot working or a mixed step of annealing and hot working. As a result, the size of the lining portion can be adjusted, and the lining portion can be manufactured from a large material.

As described above, according to the present invention, without deteriorating the stress corrosion cracking resistance of the lining layer of the cladding tube,
Supplying a highly sound fuel cladding tube that can improve corrosion resistance, has high resistance to stress corrosion cracking, and does not expand the damage due to rapid oxidation of the inner surface even if it should break. can do.

Further, the zirconium lining layer provided inside the zirconium alloy clad substrate is one of cobalt (Co), rhodium (Rh) and palladium (Pd) in high purity zirconium. The total amount of the above trace additives, oxygen 1200ppm or less, and other unavoidable impurities
Since it contains 2000 ppm or less, there is an effect that it is possible to obtain a fuel clad tube that retains resistance to stress corrosion cracking while maintaining the suppressing force against rapid oxidation of the inner surface.

[0030]

As described above, according to the present invention, as a zirconium lining layer provided on the inside of a zirconium alloy cladding tube base material, cobalt (Co), rhodium (Rh), palladium (Pd) is contained in high-purity zirconium. ), Which contains one or more trace additives,
Since it contains the following oxygen and other unavoidable impurities in a total amount of 2000 ppm or less, the corrosion resistance is improved according to the addition amount of the trace additive, and the suppressing power against the rapid oxidation of the inner surface can be maintained.

In the present invention, in order to improve resistance to rapid oxidation, trace amounts of cobalt (Co), rhodium (Rh) and palladium (Pd) are added to high-purity zirconium. When the total amount of the additives is 0.05% or more and 1% or less, zirconium is not hardened and the resistance to stress corrosion cracking does not decrease. Therefore, it is possible to obtain the fuel clad tube which maintains the resistance to the stress corrosion cracking while maintaining the suppressing force against the rapid oxidation of the inner surface.

Further, in the present invention, the present invention has a fuel cladding tube base material for a nuclear reactor made of a zirconium alloy that contains a nuclear fuel therein, and a zirconium lining layer metallurgically bonded to the cladding tube base material. In the fuel cladding tube described above, the zirconium lining layer contains cobalt (Co), rhodium (R) in high purity zirconium in a total amount of 0.05% or more and 1% or less.
h), palladium (Pd), one or more trace additives, 600ppm or less of oxygen, and 1000ppm or less of other unavoidable impurities in total, so the ability to suppress rapid oxidation of the inner surface is maintained. At the same time, it is possible to obtain a fuel clad tube that retains resistance to stress corrosion cracking, and further it is possible to obtain a fuel clad tube that is more excellent in ductility and workability.

[Brief description of drawings]

FIG. 1 is a process drawing showing a manufacturing process of an example of a coated tube of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a vertical cross section of a fuel rod.

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

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Claims (3)

[Claims] 1. A fuel cladding tube having a zirconium alloy fuel cladding tube base material for a nuclear reactor containing a nuclear fuel therein, and a zirconium lining layer metallurgically bonded to the cladding tube base material, As a layer, high-purity zirconium contains a trace additive of at least one of cobalt (Co), rhodium (Rh), and palladium (Pd), and further 1200 ppm
A fuel cladding tube for a nuclear reactor, comprising the following oxygen and other inevitable impurities of 2000 ppm or less in total. 2. The fuel cladding tube for a nuclear reactor according to claim 1, wherein the lining layer is cobalt (Co) or rhodium (R).
A fuel cladding tube for a nuclear reactor, characterized by containing 0.05% or more and 1% or less in total of a trace additive of at least one of h) and palladium (Pd). 3. A fuel cladding tube having a zirconium alloy fuel cladding tube base material for a nuclear reactor containing a nuclear fuel therein, and a zirconium lining layer metallurgically bonded to the cladding tube base material, wherein the zirconium The lining layer made of high-purity zirconium contains a total of at least one trace additive of cobalt (Co), rhodium (Rh), and palladium (Pd).
05% or more and 1% or less, and 600ppm or less of oxygen, totaling 10
A fuel cladding tube for a nuclear reactor, which contains 00 ppm or less of other unavoidable impurities.