JPH076018B2 - Zr alloy with excellent corrosion resistance for reactor fuel cladding - Google Patents

Description

TECHNICAL FIELD The present invention relates to a Zr alloy exhibiting excellent corrosion resistance particularly when used for producing a reactor fuel cladding tube exposed to high-temperature high-pressure water or high-temperature high-pressure steam. Is.

[Prior Art] Conventionally, generally, there is a pressurized water type (PWR) reactor in a nuclear power plant, and a Zr alloy is used for a fuel cladding tube of this reactor. Zircaloy 4 containing Sn: 1.2 to 1.7%, Fe: 0.18 to 0.24%, Cr: 0.07 to 0.13%, and the balance Zr and unavoidable impurities. It is well known that is used.

[Problems to be solved by the invention]

On the other hand, in recent years, along with the increase in burnup of fuel for improving the economical efficiency of nuclear power plants, the residence time of the fuel cladding tube in the reactor tends to be prolonged. However, it is the current situation that it is not possible to deal with this due to insufficient corrosion resistance.

[Means for solving problems]

Therefore, the inventors of the present invention, from the viewpoints described above, in order to develop a Zr alloy exhibiting superior corrosion resistance when used as a fuel cladding tube of a nuclear reactor, particularly pay attention to the conventional Zr alloy described above As a result, when the Sn content is relatively low, Nb is contained as an alloy component, and the content of nitrogen as an unavoidable impurity is 60 ppm or less, the corrosion resistance is further improved, and When used for fuel cladding,
We have obtained the knowledge that it can be used for a long period of time.

Therefore, the present invention has been made based on the above findings, and contains Sn: 0.2 to 1.15%, Fe: 0.18 to 0.24%, Cr: 0.07 to 0.13%, Nb: 0.05 to 1%, The Zr alloy for a reactor fuel cladding tube is characterized by the balance consisting of Zr and inevitable impurities, and having a composition in which the nitrogen content as inevitable impurities is 60 ppm or less.

In the Zr alloy of the present invention, the Sn, Fe, and Cr components have the effect of improving the corrosion resistance in the coexisting state, and therefore, the content of any of these three components is If the content is less than the lower limit, it is not possible to ensure the desired excellent corrosion resistance,
On the other hand, if the content of any one of the above three components exceeds the above upper limit, the corrosion resistance will be reduced again.
It was determined that Sn: 0.2 to 1.15%, Fe: 0.18 to 0.24%, Cr: 0.07 to 0.13%.

Further, the Nb component also has an effect of further improving the corrosion resistance of the alloy, but if the content is less than 0.05%, the desired corrosion resistance improving effect cannot be obtained, while if the content exceeds 1%,
Not only is the workability deteriorated due to the excessive amount of precipitates in the alloy, but it is also undesirable because it increases the neutron attracting action, so its content is 0.05 to 1%.
I decided.

Further, if the content of nitrogen as an unavoidable impurity exceeds 60 ppm, it is not possible to ensure excellent corrosion resistance even if the contents of Sn, Fe, Cr, and Nb are limited as described above. Was determined to be 60 ppm or less.

〔Example〕

Next, the Zr alloy of the present invention will be specifically described by way of Examples.

As raw materials, various kinds of products with a purity within the range of 99.8% or more
Zr sponge, Sn powder with 99.9% purity, Fe
Powder, Cr powder, and Nb powder are prepared, and these raw materials are mixed in predetermined compounding compositions, mixed, and then pressed into a green compact, and the green compact is melted in an arc furnace to produce a button material. Then, after hot forging under the conditions of temperature: 600 ° C, reduction rate: 50%, heating to temperature: 1080 ° C, water quenching treatment, and then salt bath pickling Cold rolling at a rolling rate of 50%, and then at a temperature of 630 ℃
After carrying out recrystallization annealing under the condition of holding time, cold rolling was performed again at a reduction rate of 50%, and subsequently at a temperature of 450 ° C, 2
By performing strain relief annealing under the condition of holding time, and finally subjecting to pickling and polishing, the components have the composition shown in Table 1 and width: 20 mm x length: 40 mm x thickness: Specimens of invention Zr alloys 1-8 and comparative Zr alloys 1-7 having a dimension of 0.5 mm were produced respectively.

The comparative Zr alloys 1 to 7 all have compositions in which the content of any of the constituent components (marked with * in Table 1) is outside the range of the present invention.

Then, using the test pieces of the invention Zr alloys 1 to 8 and the comparative Zr alloys 1 to 7 obtained as a result, using a static autoclave tester which is usually used, in steam, temperature: 450
72 ° C, pressure: 105kg / cm ²
The corrosion weight gain after the 0 hour test was measured. The results of these measurements are shown in Table 1.

〔The invention's effect〕 From the results shown in Table 1, all of the Zr alloys 1 to 8 of the present invention show excellent corrosion resistance, while the comparative Zr alloy 1
As can be seen from Nos. 7 to 7, it is clear that if the content of any one of the constituents deviates from the scope of the present invention, the corrosion resistance will decrease.

As described above, the Zr alloy of the present invention exhibits excellent corrosion resistance especially under the condition where the fuel cladding of a nuclear reactor is exposed, and therefore, when it is put to practical use, it can be used for a significantly long period of time. It has industrially useful properties such as

Claims (1)

[Claims] 1. A composition comprising Sn: 0.2 to 1.15%, Fe: 0.18 to 0.24%, Cr: 0.07 to 0.13%, Nb: 0.05 to 1%, the balance being Zr and inevitable impurities, and as an inevitable impurity. A Zr alloy for a nuclear reactor fuel cladding tube having excellent corrosion resistance, characterized in that the nitrogen content of the composition is 60 ppm or less (above weight%).