JP2001074872A - Method for manufacturing zirconium alloy for nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a zirconium alloy with improved nodular resistance and uniform corrosion resistance even if a fuel is set to highly combustible. SOLUTION: The method is used to manufacture a zirconium alloy that is made of 3.00 wt.% or less tin, 0.30 wt.% or less iron, 0.15 wt.% or less chrome, 0.20 wt.% or less nickel, and 0.1-0.5 wt.% or less vanadium while the remainder is essentially made of zirconium. In specific heat-treatment conditions after the zirconium alloy is heated and cooled to 830 deg.C or higher (α+β quenching or β quenching), the heat-treatment conditions are set so that an accumulation annealing parameter ΣAi that has been determined by an expression, ΣAi=Σti.exp(-40000/Ti) (ti; retention time at a temperature of Ti, Ti; heat-treatment time (K)), reaches 1×10-17 h or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a zirconium alloy used in a nuclear reactor.

[0002]

2. Description of the Related Art At present, zirconium alloys are widely used as fuel cladding tubes and core structural materials in boiling water reactors, pressurized water reactors and the like. The zirconium alloys that have been most commonly used so far are Zircaloy-2 and Zircaloy-4. Table 1 shows their chemical compositions in weight%.
Is shown in units of In addition, Zr-2.5% by weight Nb,
Alloys such as Zr-1.0 wt% Nb have also been applied to nuclear reactors.

[0003]

[Table 1]

[0004] The above-mentioned alloys are alloys developed mainly in consideration of neutron economy, corrosion resistance and strength. Neutron economics describes the extent to which neutrons escape leakage and wasteful absorption and are effectively used for fission reactions.

[0005] With these alloys used in boiling water light water reactors, there has been a problem that lens-shaped local corrosion called nodular corrosion occurs during operation of the reactor. Nodular corrosion grows with an increase in the service life, and may become exfoliated when the corrosion layer becomes thicker. Therefore, the occurrence of nodular corrosion not only reduces the thickness of structural materials, but also increases the exposure of workers during periodic inspections due to the fact that the corroded layer activated by neutron irradiation peels off and is present in the reactor water. May cause

As a technique for preventing the occurrence of such nodular corrosion, for example, the following is known. (1) A method for suppressing nodular corrosion by adding a small amount of vanadium to a conventional zirconium alloy described in JP-A-3-31438, (2) Changing the alloy composition described in JP-A-483838, (3) -213437
No. 3 or less by weight of a rare earth element described in Japanese Patent Application Laid-Open Publication No. H11-209, and (4) a heat treatment method in which a zirconium alloy is heated to a temperature range of α + β phase or β phase for a short time and then quenched (Reference 1). Can be

In the vanadium-added zircaloy-2 according to the above (1), the first heat treatment according to the above (4) and cold rolling are performed so as to form an α + β phase or a β phase in which Fe, Cr, Ni, etc. are dissolved. A second heat treatment is performed to remove distortion due to. These heat treatments are performed for the same purpose as Zircaloy-2. By the above-described method, nodular corrosion is suppressed under the current operating conditions of the actual furnace, and the corrosion mode is changing to uniform corrosion in which an oxide film as a corrosion product grows uniformly. Literature 1 “Extreme Fuel Technology” Research Subcommittee, Nuclear Fuel Engineering Current Status and Prospects, (1993)
110.

[0008]

The vanadium-doped zirconium alloy with improved resistance to noji error corrode sufficiently fulfills its function under current LWR operating conditions. However, at present, a high burnup of the reactor fuel is planned to improve the economic efficiency of the nuclear power plant, and in this case, the reactor fuel cladding stays in the reactor for a long time. Therefore, the amount of corrosion increases and the environment becomes more severe for the material. Under such an environment, there is a concern that a uniform corrosion acceleration phenomenon in which the corrosion rate increases at a high burnup will occur. Therefore, there is a demand for a material which does not generate nodular corrosion in the furnace and has excellent uniform corrosion resistance, which does not cause uniform corrosion acceleration.

The present invention has been made in view of the above, and an object of the present invention is to provide a fuel cell having a high burnup,
An object of the present invention is to provide a method for producing a zirconium alloy having excellent nodular corrosion resistance and uniform corrosion resistance.

[0010]

That is, according to the present invention, tin is less than 3.00% by weight, iron is less than 0.30% by weight, chromium is less than 0.3% by weight.
In a method for producing a zirconium alloy comprising 15% by weight or less, 0.2% by weight or less of nickel, 0.1% to 0.5% by weight of vanadium and the balance substantially consisting of zirconium, the zirconium alloy is heated to 830 ° C. or more. Cooling (α + β
Cumulative annealing parameters (ΣAi) quantifying the heat treatment conditions under predetermined heat treatment conditions after quenching or β quenching)

[0011]

Equation 3] _{ΣAi = Σt i · exp (-40000} / T i) t i; temperature T _i hold time at T _i; heat-treating temperature (K) is none of the intended so that l × 10 ~ ¹⁷ h or more This is to achieve the purpose.

Further, the present invention is to produce a zirconium alloy in the following steps. That is,
(A) a step of adding 0.1 to 0.5% by weight of vanadium to the raw material of the zirconium alloy by weighing the raw material, (b) a first heat treatment step of converting the zirconium alloy into an α + β phase or β phase metal structure, and then quenching it, c) Cumulative annealing parameter ΣAi quantifying the heat treatment conditions

[0013]

The second heat treatment for annealing at a heat treatment temperature (K) is not less than l × 10 ~ ¹⁷ h condition; Equation 4] _{ΣAi = Σt i · exp (-40000} / T i) t i; temperature T _i hold time at T _i Process.

That is, with such a manufacturing method,
As means for suppressing nodular corrosion, steps (a) and (b) are provided. A vanadium-added zircaloy-2 prepared by adding vanadium to zircaloy-2 was subjected to a nodular corrosion test (4 hours at 410 ° C. + 16 hours at 520 ° C., 123 atm steam) outside the furnace, and vanadium related to weight increase due to corrosion. FIG. 2 shows the results of the investigation on the effect of the amount of addition. In this figure, ΔAi of the process A
Is 1.62 × 10 to ¹⁸ h, Step B is 6.48 × 10 to ¹⁷ h
It is.

From this, it can be seen that the weight increase is minimized when the amount of vanadium added is about 0.3% by weight, and the nodular corrosion resistance is superior to that of the non-added material. But,
Since the addition of 0.1% by weight is inferior in nodular corrosion resistance to the additive-free material, the amount of vanadium added to Zircaloy-2 is preferably in the range of more than 0.1% by weight and 0.5% by weight or less.

The means of the present invention further comprises a step (c) for suppressing uniform corrosion. FIG. 3 shows the results of a uniform corrosion test of two kinds of zircaloy-2 and zircaloy-2 added with 0.3% by weight of vanadium produced by changing ΔAi.

In this figure, ΔAi in the step A is 1.62 × 1
0 to ¹⁸ h, Step B is 6.48 × 10 to ¹⁷ h. Also, in this figure, the vertical axis indicates the amount of increase in alloy weight due to oxidation, and the horizontal axis indicates the time of the corrosion test. The slope of the graph indicates the rate of progress of corrosion. Although these two types are alloys having exactly the same composition, the progress speed of corrosion is greatly different.
This is a zirconium alloy that is much slower than the process, has excellent uniform corrosion resistance, and has excellent uniform corrosion resistance without generating nodular corrosion.

This is considered to be due to the following reasons. Vanadium-doped Zircaloy-2 has Zr, Fe,
There are intermetallic compound precipitates composed of Cr, Ni and V, whose structure is probably Zr (Fe, Cr, Ni,
V) ₂ . Alloy Table 2 shows V / (Fe + Cr + Ni +) obtained by analyzing 200 precipitates of the alloys prepared in Steps A and B by energy dispersive X-ray analysis.
V), Fe (Fe + Cr + Ni + V), Cr / (Fe +
Cr + Ni + V) and Ni / (Fe + Cr + Ni +)
The average value of the characteristic X-ray count ratio V) is shown.

[0019]

[Table 2]

The alloy in the step B has a V / V
Since the (Fe + Cr + Ni + V) count ratio is small and the total content of Fe, Cr and Ni in the precipitate is high, it is considered that the amount of Fe, Cr and Ni dissolved in the alloy base material is small. The oxide film of zirconium alloy grows by the transfer of electrons from the metal / oxide film interface to the environment and the transfer of enzyme ions from the environment to the metal / oxide film interface. Then, the progress of corrosion becomes slow.

Fe, Cr and Ni dissolved in the oxide film contribute to the formation of oxygen vacancies. Since oxygen ions move by oxygen vacancies, Fe and C strongly contribute to the formation of oxygen vacancies.
It is considered that the progress of corrosion becomes slower for alloys with smaller solid solution amounts of r and Ni. It is considered that the corrosion progress of the alloy of the process B is slower than that of the alloy of the process A because the amount of solid solution of Fe, Cr and Ni in the alloy of the process B is smaller.

FIG. 6 shows the effect of ΔA on the increase in corrosion when Zircaloy-4 was subjected to a uniform corrosion test at 400 ° C. for 1200 hours.
The effect of i is shown. ΣAi about 2 times larger than the latter to the former from the comparison of the corrosion increment of 10 ~ ¹⁷ h and 10 ~ ¹⁸ h, Σ
The larger the Ai, the better the corrosion resistance. Also 1 × 10 ~
^No significant difference was observed in the corrosion increase over ¹⁷ hours, and it is considered that the vanadium-added zircaloy-2 produced by the present production method shows the same tendency.

Furthermore, 0.1 to 0.1.
Table 3 summarizes the corrosion rates obtained from the results of the uniform corrosion test of 5 wt% vanadium-added zircaloy-2.

[0024]

[Table 3]

In the range of the addition amount of 0.1 to 0.5% by weight, the smaller the amount of vanadium added, the better the uniform erosion resistance. Showed almost the same uniform corrosion rate. As shown in FIG.
Since the corrosion rate of uniform corrosion is the same between 0.3% by weight-added Zircaloy-2 and Zircaloy-2 produced in the step B, it shows the same or superior uniform corrosion resistance as Zircaloy-2. It is considered that vanadium addition of 0.5% by weight or less is effective.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows an embodiment applied to the actual production of nuclear reactor materials based on the production method of the present invention.
Is shown in the manufacturing process flow. In the present method for producing a plate material, basically, (1) a raw material weighing step, (2) a raw material dissolving step, (3) a β quenching step, (4) a hot rolling step, 5) pickling step, (6) vacuum annealing step, (7) cold rolling step, and the like.

In the step (1), tin is contained in an amount of 1.20 to 20% by weight.
1.70, iron 0.07-0.20, nickel 0.03-
0.08, chromium 0.05-0.15 (however, the total of iron, nickel and chromium is 0.18-0.38), and the specified amount of each element is set so that vanadium becomes 0.1-0.5. measure.

In the step (2), the raw material subjected to the step (1) is melted to form an alloy.

In the step (3), an antioxidant is applied to the zirconium alloy which has been subjected to the step (2), and air annealing is performed at 1050 ° C. for 1 hour, followed by water cooling.

In the steps (1) to (3), a zirconium alloy having excellent nodular corrosion resistance is obtained.

In the step (4), the zirconium alloy which has been subjected to the step (3) is heated to 800 ° C. and rolled.

In the step (5), pickling for dissolving the surface of the zirconium alloy oxidized in the steps (3) and (4) with an acid and edge care are performed.

In the step (6), the zirconium alloy which has been subjected to the step (5) is subjected to the steps (4), (6) and (10).
The cumulative annealing parameter (ΣAi) of the process is 1 × 1
0 ~ ^{1 7} h or more conditions vacuum annealing, carried out the subsequent furnace cooling.
In the step (6), a zirconium alloy having excellent uniform corrosion resistance is obtained.

In the step (7), the zirconium alloy subjected to the step (6) is rolled.

In the step (8), the edge of the zirconium alloy which has been subjected to the step (7) is treated. However, (6)-
Step (8) is repeated until the target thickness is reached.

In the step (9), the zirconium alloy which has been subjected to the step (8) is cut into a target size.

In the step (10), the zirconium alloy subjected to the step (9) is subjected to vacuum annealing at 577 ° C. for 2 hours.

[Example 2] In this method for producing a tube material, a raw material weighing step (1), a raw material dissolving step (2),
(3) hot forging process, (4) β quenching process,
(5) hot extrusion step, (6) tube processing step, (7)
(8), a cold rolling step (8), a bending correction step (12), and an inner / outer surface polishing step (13).

In the step (1), tin is contained in an amount of 1.20 to 20% by weight.
1.70, Tetsuya 0.07-0.20, Nickel 0.03
-0.08, chromium 0.05-0.15 (the sum of iron, nickel and chromium is 0.18-0.38), and the specified amount of each element so that vanadium becomes 0.1-0.5. Measure.

In the step (2), the raw material subjected to the step (1) is melted in vacuum to form an ingot.

In the step (3), the ingot after the step (2) is heated to a high temperature, hot forged, and extended into a long bar.

In the step (4), the long strip that has been subjected to the step (3) is β-hardened.

In the step (5), a hole is formed in the long rod which has been subjected to the step (4), surface cutting is performed, and pressing is performed at 600 to 700 ° C.

In the step (6), pickling for dissolving the surface oxidized in the step (5) with an acid and edge care are performed.

In the step (7), α + β quenching is performed on the zircaloy element tube after the step (6).

In the step (8), the zircaloy tube subjected to the step (7) is cold-rolled.

In the step (9), the steps (7) and (9)
Vacuum annealing is performed under the condition that the cumulative annealing parameter (ΣAi) in the step (11) and the step (11) is l × 10 to ¹⁷ h or more. In the step (9), a zirconium alloy having excellent uniform corrosion resistance is obtained.

The steps (8) and (9) are repeated to finish to the final dimensions.

In the step (10), the zircaloy tube subjected to the step (9) is subjected to finish cold rolling.

In the step (11), the zircaloy tube after the step (10) is washed and subjected to final vacuum annealing.

In the step (12), the bending of the zircaloy tube after the step (11) is corrected.

In the step (13), the inner and outer surfaces of the zircaloy tube subjected to the step (12) are polished.

In the step (14), the zircaloy tube subjected to the step (13) is cut to a specified length.

Next, an example in which the zirconium alloy manufactured by the present manufacturing method is applied to an actual reactor material will be described.
FIG. 5 is a perspective view of a fuel assembly loaded in a boiling water reactor, FIG. 4 (a) is a perspective view of a fuel rod, FIG. 4 (b) is a cross-sectional view of the fuel rod, and FIG. FIG. 3 is a vertical sectional view of a fuel rod.

In the fuel assembly 1 shown in FIG. 5, a predetermined number of fuel rods 6 and rod-like elements such as a warp rod 7 are generally arranged in a square in a channel box 2, and upper and lower ends thereof are connected to an upper type via end plugs. The spacers 5 are attached to the rate 3 and the lower tie plate 4, respectively, and the spacers 5 are arranged at predetermined intervals at a plurality of positions at intermediate height positions.

The fuel rod shown in FIG. 4 includes a nuclear fuel material 9 which generates heat by generating a nuclear fission reaction, a fuel cladding tube 8 covering the nuclear fuel material 9, a plenum 12, an upper end plug 13 and a lower end plug 1.
4 The cladding channel box, water rod, upper end plug, lower end plug, and spacer in FIGS. 5 and 4 are in direct contact with the reactor water, and this part is currently made of Zircaloy-2 or Zircaloy-4, and has nodular corrosion. Uniform corrosion is a problem. By applying the zirconium alloy manufactured by the present manufacturing method to the zircaloy portion, a fuel excellent in nodular corrosion resistance as shown in FIG. 2 and also excellent in uniform corrosion resistance as shown in FIG. It can be an aggregate.

[0057]

As described above, according to the present invention, a zirconium alloy excellent in nodular corrosion resistance and uniform corrosion resistance even when a reactor fuel is burned up in a method for producing a zirconium alloy. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a production process of a zirconium alloy for a nuclear reactor.

FIG. 2 is a characteristic diagram showing the relationship between the amount of vanadium added to a zirconium alloy obtained by a nodular corrosion test and the weight increase of the alloy due to nodular corrosion.

FIG. 3 is a characteristic diagram showing a change over time of a uniform corrosion amount in steam at 400 ° C. of two kinds of vanadium-added zircaloy-2 and zircaloy-2 produced by changing ΔAi obtained by a uniform corrosion test.

FIG. 4 is a perspective view and a sectional view of a fuel rod using a zirconium alloy manufactured by the present manufacturing method.

FIG. 5 is a partially broken perspective view of a fuel assembly loaded in a boiling water reactor.

FIG. 6 is a characteristic diagram showing the effect of annealing parameters on the increase in corrosion of Zircaloy-4.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel assembly, 2 ... Channel box, 3 ... Upper tie plate, 4 ... Lower tie plate, S ... Spacer,
6: fuel rod, 7: water rod, 8: fuel cladding tube,
9 Nuclear fuel material, 10 Government, 11 Liner layer, 12
Prenem, 13: upper end plug, 14: lower end plug.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 640 C22F 1/00 641C 641 691C 691 691B 693A 693 693B G21C 3/06 GDPN (72) Inventor Yoshio Nonaka 2163, Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki Japan (72) Inventor Shuichi Nanagawa 2163, Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki Japan (72) Invention Person Yoshinori Eito 2163 Narita-cho, Oarai-machi, Higashiibaraki-gun, Ibaraki Japan (72) Inventor Yoshio Shimada Yoshinobu Shimada 2163, Narita-cho, Oarai-cho, Higashiibaraki-gun, Ibaraki Japan Nuclear fuel development Co., Ltd.

Claims (2)

[Claims] 1. Tin less than 3.00% by weight, iron 0.30% by weight
Hereinafter, in a method for manufacturing a zirconium alloy comprising 0.15% by weight or less of chromium, 0.20% by weight or less of nickel and 0.1 to 0.5% by weight of vanadium, and the balance substantially consisting of zirconium, in certain heat treatment conditions after ℃ heating and cooling to above (alpha + beta quenching or beta quenching), the cumulative annealing parameter quantifying the condition of the heat treatment (ShigumaAi) Equation 1] ΣAi = Σt _i · exp (-40000 / T _i) t _i; temperature T _i hold time at T _i; heat-treating temperature (K) is the manufacturing method of the reactor for a zirconium alloy, characterized in that at l × 10 ~ ¹⁷ h or more. 2. A step of adding 0.1 to 0.5% by weight of vanadium to a raw material of a zirconium alloy by weighing the raw material,
(B) a zirconium alloy and the alpha + beta phase or beta phase of the metal structure, then the first heat treatment step of quenching, (c) [2 Number Cumulative annealing parameter ShigumaAi quantifying the condition of the heat treatment ΣAi = Σt _i · exp ( -40000 / T _i) t _i; temperature T _i hold time at T _i; second heat treatment step of heat-treating temperature (K) is annealed under the above conditions l × 10 ~ ¹⁷ h, comprising the above steps Of producing a zirconium alloy for a nuclear reactor.