JPH01188643A - Zr alloy for covering tube of atomic reactor fuel having excellent corrosion resistance - Google Patents

Abstract

PURPOSE:To furthermore improve the corrosion resistance of the subject Zr alloy by relatively reducing the Sn contents, limiting the N contents as inevitable impurities and providing it with specific compsn. CONSTITUTION:The Zr alloy contains, by weight, 0.2-1.15% Sn, 0.18-0.6% Fe and 0.07-0.4% Cr, contains at need one or two kinds of 0.05-1% Nb and 0.01-0.2% Ta and the balance constituted of Zr with inevitable impurities; it furthermore has the compsn. of <=60ppm N contents as the inevitable impurities. In this compsn., at the time of <0.2% Sn contents, prescribed strength can not be obtd., and on the other hand, at the time of >1.15%, the drastical lowering of the corrosion resistance is induced. For the lower limit or less of each contents of Fe and Cr, the desired effect on the improvement of corrosion resistance and strength can not be obtd., and on the other hand, for the upper limit or more of each contents, the corrosion resistance is drastically reduced. At the time of >60ppm N contents, its corrosion resistance is rapidly deteriorated.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a Zr alloy that exhibits excellent corrosion resistance particularly when used in the manufacture of nuclear reactor fuel cladding tubes exposed to high-temperature, high-pressure water or high-temperature, high-pressure steam. It is.

[Conventional technology]

Conventionally, pressurized water type (PWR) reactors have been used in nuclear power plants, and Zr alloys have been used to manufacture fuel cladding tubes for these reactors. (hereinafter % indicates weight %), Sn: 1.2 to 1.7%.

Fe: 0.18-0.24%.

Cr: 0.07-0.13%.

It is well known that Zircaloy-4 is used, which has a composition of Zr and unavoidable impurities.

[Problem to be solved by the invention]

On the other hand, in recent years, with the increase in fuel burnup to improve the economic efficiency of nuclear power plants, the residence time of fuel cladding tubes in the reactor has tended to become longer. Currently, however, it is not possible to deal with this problem due to insufficient corrosion resistance.

[Failure to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors focused particularly on the above-mentioned conventional Zr alloy in order to develop a Zr alloy that exhibits much better corrosion resistance when used as a fuel cladding tube for a nuclear reactor. As a result of research, it was found that in the above conventional Zr alloy, when the Sn content is kept relatively low and the nitrogen content as an unavoidable impurity is reduced to below eoppm,
- Corrosion resistance has been significantly improved, and when Nb and Ta are included as alloy components, further corrosion resistance improvement effects can be obtained, allowing long-term use when used as combustion cladding in nuclear reactors. We have obtained the knowledge that

Therefore, this invention was made based on the above findings, and includes Sn: 0.2-1.15%, Fe: 0.1
8-0.8%.

Cr: 0.07-0.4%.

and, if necessary, Nb: 0.05~1%, Ta: 0.01~
0.2%.

A corrosion-resistant Zr alloy for nuclear reactor fuel cladding tubes containing one or two of the above, the remainder consisting of Zr and unavoidable impurities, and having a nitrogen content as an unavoidable impurity of [i0 ppm or less] It has the following characteristics.

Next, the reason why the composition range of the Zr alloy of the present invention is limited as described above will be explained.

(a) The 5n Sn component has the effect of improving the strength of the alloy, but
If the content is less than 0.2%, the specified strength cannot be secured, while if the content exceeds 1.15%,
Since it causes a significant decrease in corrosion resistance, its content is set at 0.2 to 1.15%.

(b) Fe and Cr These components have the effect of improving the corrosion resistance and strength of the alloy when coexisting, but their content
Cr: less than 0.1896 and Cr: less than 0.07%, the desired effect cannot be obtained;
If the content exceeds 0.6% and 0.4%, the corrosion resistance will be significantly reduced, so the content is reduced to Fe: 0.18-0.6% and Cr: 0.0
It was set at 7-0.4%.

(c) Nb and Ta These components have the effect of further improving the corrosion resistance of the alloy, so they are included as necessary, but the content is less than 0.05% for Nb and 0.0% for Ta. 01
If the content is less than 1% Nb, the desired effect of improving corrosion resistance cannot be obtained, while if the content exceeds 1% Nb and 0.2% Ta, it causes deterioration of corrosion resistance. .05-1%.

Ta: Set at 0.01-0.2%.

(d) N as an unavoidable impurity The N component is a component harmful to the corrosion resistance of the alloy, and if its content exceeds 60 ppm, the corrosion resistance will rapidly deteriorate, so the upper limit was set at 80 ppm. .

〔Example〕

Next, the Zr alloy of the present invention will be specifically explained using examples.

As a raw material for dissolution, 2 with various purity levels of 998% or more
“Sponge, all of which have a purity of 99.9% or more.
N powder, Fe powder, Cr powder, Nb powder, and Ta powder are prepared, these raw materials are blended into a predetermined composition, mixed, and then melted in an arc furnace to make a button material. After holding the temperature at 1010°C for 15 minutes, hot forging, heating again at 1010°C, water quenching, and removing oxide scale by machining, temperature 2600°C, rolling ratio = Hot rolling was carried out under conditions of 50%, followed by pickling to remove oxide scale, cold rolling was carried out at a rolling reduction of 50%, and then the temperature was maintained at 2630°C for 2 hours. By performing crystal annealing and cold rolling again at a rolling rate of 50%, Zr alloy sheets 1 to 1 of the present invention having the compositions shown in Table 1 and each having a thickness of 0.5 fins were obtained. No. 17 and comparative Zr alloy plates) r) J1 to J6 were manufactured, respectively.

Note that all of the comparative Zr alloy plates 1 to 6 have compositions in which the content of one of the constituent components (marked with * in Table 1) is outside the scope of the present invention.

Next, from the various plate materials obtained as a result, 20mII
x 25mm, and 51 mm from one side in the longitudinal direction
A test piece with a small hole of 23 mm in diameter was cut out at point 1I11, and using a normal static autoclave device,
In steam, temperature: 400℃, pressure crab 105kg/
An out-of-core corrosion test was conducted under conditions similar to those to which the fuel cladding of the nuclear reactor is exposed, and the corrosion increase after 120 days was measured. The measurement results are shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, it can be seen that the Zr alloy plate of the present invention
- Materials 1 to 17 all exhibit excellent corrosion resistance, but as seen in Comparative Zr alloy sheets 1 to 6, the content of any of the constituent components falls outside the scope of the present invention. It is clear that the corrosion resistance is reduced.

As mentioned above, the Zr alloy of the present invention exhibits excellent corrosion resistance particularly under the conditions to which the combustion cladding of a nuclear reactor is exposed, so if it is put into practical use, it can be used for an extremely long period of time. It has industrially useful properties such as.

Claims (2)

[Claims] (1) Sn: 0.2-1.15%, Fe: 0.18-0
．． 6%, Cr: 0.07-0.4%, the remainder consists of Zr and unavoidable impurities, and the nitrogen content as an unavoidable impurity is 60 ppm or less (wt%). A Zr alloy for nuclear reactor fuel cladding tubes with excellent corrosion resistance. (2) Sn: 0.2-1.15%, Fe: 0.18-0
．． 6%, Cr: 0.07 to 0.4%, and further contains one or two of Nb: 0.05 to 1%, Ta: 0.01 to 0.2%. A Zr alloy for nuclear reactor fuel cladding tubes having excellent corrosion resistance, characterized in that the remainder is Zr and unavoidable impurities, and the content of nitrogen as an unavoidable impurity is 60 ppm or less (weight %).