JPS6335750A - Zr alloy for nuclear reactor fuel clad pipe excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a Zr alloy for nuclear reactor fuel clad pipe excellent in corrosion resistance, by specifying a composition consisting of Sn, Fe, Cr, Nb, and Zr and also by limiting N content among inevitable impurities. CONSTITUTION:The Zr alloy has a composition which consists of, by weight, 0.2-1.15% Sn, 0.18-0.24% Fe, 0.07-0.13% Cr, 0.05-1% Nb, and the balance Zr with inevitable impurities and in which amount of N as an inevitable impurity is regulated to <=60ppm. This alloy shows superior corrosion resistance particularly under the conditions to which nuclear reactor fuel clad pipes are exposed, so that it enables long-period of use as the above clad pipes. In the above Zr alloy, corrosion resistance is deteriorated if any of the quantities of the above constituents deviates from the above compositional range.

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, there are pressurized water type (PWR) reactors in nuclear power plants, and Zr alloy is used for the fuel cladding of the reactor in parentheses. weight 1%).

Sn: 1.2-1.7%.

Fe: 0.18-0.24%, Cr: 0.07-0.13%.

It is well known that Zircaloy-4 having a composition of 'tD and the remainder consisting of Zr and unavoidable impurities is used.

[Problem that the invention seeks to solve]

On the other hand, in recent years, with the increase in burnup of fuel to improve the economic efficiency of nuclear power plants, The residence time of Jvtrl tubes in the furnace is becoming longer, but the above-mentioned conventional Zr alloy cladding tubes are unable to cope with this problem due to the insufficient edibility of 1lii'. is the current situation.

[Means for solving problems]

Therefore, the inventors of the present invention, etc., from the above-mentioned viewpoint.

In order to develop a Zr alloy that exhibits better corrosion resistance when used as a fuel cladding tube in a nuclear reactor, in particular
As a result of research focusing on r alloy, relatively 5nfi
Nb is included as one alloy acid component with a low content of l, and nitrogen is included as an unavoidable impurity! ”?60pp
If it is less than m, the corrosion resistance becomes even better, and it is suitable for use in fuel cladding tubes of nuclear reactors.

They found that it can be used for a long period of time.

Therefore, this invention has been made based on the above findings.

Sn: 0.2-1.15%.

Fe: 0.18-0.24%.

Cr: 0.07-0.13%.

Nb: 0.05-1%.

The Zr alloy for nuclear reactor fuel cladding tubes has a composition in which the remainder consists of Zr and unavoidable impurities, and the nitrogen content as an unavoidable impurity is 60 ppm or less.

In addition, in the Zr alloy of this invention, S t Fe ,
and Cr components have the effect of improving corrosion resistance when they coexist. Therefore, if the content of any of these three components is less than the above lower limit, the desired excellent corrosion resistance will not be achieved. On the other hand, if any of the above three components exceeds the above upper limit and becomes finite, the corrosion resistance will decrease again, so the content of these components is Wow.

Sn: 0.2 to 1.15%, Fe: 0.
The content was determined to be 18% to 0.24%, and Cr: 0.07% to 0.13%.

In addition, the Nb component also has the effect of further improving the corrosion resistance of the alloy, but if the content is less than 0.0596, the desired effect of improving corrosion resistance cannot be obtained;
If the content exceeds 0.05, the total number of precipitates in one alloy becomes too large, which not only deteriorates workability but also increases neutron absorption, which is undesirable. 196.

In addition, the nitrogen-containing acid as an unavoidable impurity is 60 ppm.
+ Sn r Fe + Cr * and N
Even if the content of b is limited to the above, it is not possible to ensure excellent corrosion resistance, so the nitrogen content is reduced to 60p.
pm or less.

〔Example〕

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

As raw materials, various Zr sponges with purity within the range of 99.8% or more, Sn powder, Fe powder, Cr powder, and Nb powder, all with purity of 99.9%, were prepared, and these raw materials were Each is blended into a predetermined composition,
After mixing, it is press-molded into a green compact.

This green compact is melted in an arc furnace to produce button material.

This was then hot forged at a temperature of 600°C and a rolling reduction of 50%, then heated to 1080°C, water quenched after forging, and then pickled in a salt bath. in,
Cold rolled at a rolling rate of 50%, and further prefecture degree 263
After recrystallization annealing at 0°C for 2 hours,
Cold rolling was performed again at a rolling reduction rate of 50%, followed by hot rolling.
i: The first
Test pieces consisting of Zr alloys 1 to 8 of the present invention and comparative Zr alloys 1 to 7 having the composition shown in the table and dimensions of width: 20 mm x length: 40 m x thickness: 0.5 m were prepared. manufactured respectively.

In addition, Comparative Zr Alloys 1 to 7 all have compositions in which any one of the constituent components (marked with * in Table 1) is outside the scope of the present invention, and Comparative Zr Alloy 1.
Using test pieces from 1 to 7, an out-of-furnace corrosion test was conducted in a commonly used stationary autoclave tester at a temperature of 450°C and a pressure of 105 Kg/crl in steam, and after 720 hours of testing. Corrosion increase Fi1 was measured. The results of these measurements are shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, Zr alloys 1 to 8 of the present invention are as follows:
Both exhibit excellent corrosion resistance.

As can be seen in Hi-Same Zr Alloys 1 to 7, it is clear that if the content of any one of the constituent components falls outside the scope of the present invention, the corrosion resistance will deteriorate.

As mentioned above, the Zr alloy of the present invention exhibits excellent corrosion resistance especially under conditions where the fuel 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 (1)

[Claims] Contains Sn: 0.2 to 1.15%, Fe: 0.18 to 0.24%, Cr: 0.07 to 0.13%, Nb: 0.05 to 1%. 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 nitrogen content as an unavoidable impurity is 60 ppm or less (weight %).