JPS60224768A - Production of zirconium-base alloy having high corrosion resistance for nuclear reactor - Google Patents

Abstract

PURPOSE:To obtain a fuel clad pipe having high corrosion resistance for a nuclear reactor without generation of a crack by specifying the reduction in area in the first cold working to be executed to a Zr-base alloy, more particulary a blank pipe thereof to be executed after the hardening treatment thereof to a specific value or below. CONSTITUTION:The reduction in area in the first cold working to be executed after the (alpha+beta) or beta phase hardening treatment is specified to <=75%, by which the decrease in the ductility of the above-mentioned alloy by the above-mentioned hardening treatment and the generation of a crack with an increase in the hardness thereof can be prevented. The similar effect is also obtd. by executing the first warm plastic working to be executed after the above-mentioned hardening treatment, at 100-550 deg.C then executing the succeeding cold plastic working if necessary. The alloy is more preferably subjected to >=2 passes of cold working and >=3 passes of annealing treatments after the first cold or warm plastic working to be executed after the hardening treatment. The Zr-base alloy having high corrosion resistance and excellent resistance to nodular cracking is obtd. without cracking by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing a highly corrosion-resistant zirconium alloy for nuclear reactors, and particularly relates to a method for producing highly corrosion-resistant fuel cladding for nuclear reactors [Background of the Invention] Zirconium Base alloys are used for fuel jacket tubes, fuel channel boxes, etc. of atomic couplants because of their corrosion resistance and extremely small neutron absorption cross sections. These wooden structures are irradiated with neutrons for a long period of time in a furnace, and at the same time exposed to high-temperature, high-pressure water or steam, oxidation progresses, and white spots in the form of white oxides, sometimes called nodular corrosion, are formed on their surfaces. This white spotted oxide becomes coarser as the corrosion reaction progresses, and may even peel off in some cases. Thinning of the core due to such abnormal corrosion causes a decrease in the strength of the reactor internal structural members, which is a concern from the safety and reliability point of view of the reactor internal structural members. , methods to prevent this abnormal corrosion, that is, nodular corrosion, are being investigated. Among these, the well-known ones are zirconia l, which has corrosion resistance through heat treatment, especially induction hardening VC, and ``Zirconyl'', which is a typical material for alloys (main component: about 15% ZI group). Sn.

(0.1% pc, 0.1% Cr and 0.05% Ni added)
and "Zircaloy-4" (main component: about 1.5% in Zr group)
Addition of Sn, 0.21Fe, and 0.1% Cr) is known.

The conventional manufacturing method of highly corrosion-resistant fuel cladding for nuclear reactors is α+β,
Alternatively, there are no particular regulations regarding the processing method for the first cold plastic working performed after the β-quenching treatment.

(As a method for manufacturing highly corrosion-resistant fuel cladding tubes,
No. 22364 is publicly known. ) If the conventional manufacturing method for nuclear reactor fuel cladding tubes is applied to the process after the above α/β or β quenching treatment, the quenching process will decrease due to the decrease in ductility and increase in hardness of the zirconium-based alloy due to the quenching process. The disadvantage was that cracks often appeared during the subsequent initial cold rolling.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a highly corrosion-resistant fuel cladding tube for a nuclear reactor.

[Summary of the invention]

The present invention is based on the knowledge that the hardness and ductility of an α+β or β quenched material depend on the temperature at which the quenched material is held during hardness tests and tensile tests. By applying the above knowledge to the first cold plastic working after α+β or β quenching treatment, it is possible to roll the above-mentioned quenched material with the working degree of conventional cold plastic working.1. c.
, i7+.

[Embodiments of the invention]

The present invention will be explained in detail below.

(The zirconium alloy for blue is Zircaloy-2 (main component: about 1.5% Sn in Zr group).

Approximately 01 chips p6. approx. o, 1 scr and approx. 0,05% Ni
Attached by Jon). α+7? The quenching process is usually carried out on the above-mentioned cylindrical tube, which is generally referred to as a cylindrical tube and has an outer diameter of about 64 tsrq, a wall thickness of about 11 tones, and a length of about 4000 mm. When cold plastic working was performed with a cross-section reduction rate of 75%, the cold plastic working caused shearing during cutting. The above cold plastic working is
It is by Pilger Mill. In other words, the critical area reduction rate of the first cold plastic working after α+β quenching is approximately 75
%It turns out that. In other words, by making the cross-section reduction rate i of the first cold plastic working after heating and cold treatment 75% or more, the water tube that has been subjected to the above quenching treatment can be reduced to the current fuel-infiltrated tube size (outer diameter approximately 123 mm) in 3 passes. , wall thickness approximately 0.9 rtr
However, if the cold rolling limit is 75% ('17 surface reduction rate il/L).
During mass production, considering the safety factor in the above 17+j reduction rate, the area reduction rate of about 60 to 65 inches or the cold rolling that satisfies the area reduction of 60% or less and 15. In this example, the quenched wood-if is cold-rolled three times in total, with GOfi being the area reduction rate in one area due to the first cold-rolling, so that the outer diameter is approximately 12, 1211 processed with highly corrosion-resistant fuel cladding tube t having a thickness of about 3 m+++I and a thickness n of about 0.9 is shown. The outer diameter is about 64 blood, the thickness is about 117cm, and the length is about 4000+im.
The base tube for the fuel cladding tube is heated to Takaoka 7) l +'M conduction heating 1 to about 90 CI', and then cooled with hair oil,
Cold treatment was performed (-1 quenched raw tube was produced.

Thereafter, cold rolling was performed three times with a cross-sectional reduction rate of 60%, 80%, and 80% to produce a highly corrosion-resistant fuel cladding tube. After the cold rolling, air annealing was performed for about 2 hours at fjoOC17, and then the next step of cold rolling was performed. After the final separation rolling, final annealing was performed for about 580 tl for 2 hours. in this way,
By setting the cross-section reduction rate of the initial cold rolling to 60%,
A highly corrosion-resistant fuel cladding tube could be manufactured by cold rolling three times.

Next, an example will be shown in which the warm Caloe method of the present invention is applied to the first cold plastic working after the same quenching treatment as above. Figure 2 shows the relationship between the holding temperature and hardness of the α+β quenched material and the α annealed material during the hardness test. As shown in this figure, by setting the holding temperature of the α/β-quenched material to approximately 10 Orl, the temperature of the quenched material is 6. ! ! It can be confirmed that the field strength is equal to or lower than that of α-annealed material with a sufficient recrystallized structure. Under the above temperature conditions, it becomes possible to give the quenched material the workability of the α-annealed material) 112.

FIG. 1 shows an example in which the hot working method of the present invention is applied to the initial cold plastic working of a blank tube that has been subjected to α/β quenching treatment. In the figure, [1]Q is the raw pipe that has been subjected to α/10β quenching treatment, and [2]
" indicates the die, "3" indicates the mandrel, "4" indicates the inside of the pipe-shaped mandrel support, "5" indicates the mandrel lubricating oil supplied through the mandrel support, and "6" indicates the die lubricating oil.

The mandrel lubricating oil and the die lubricating oil were maintained at 200C, and the former was allowed to flow into (circulate) the inside of the raw tube, and the latter was injected onto the outer surface of the raw tube and the die.

Although the raw tube generates processing heat during plastic working, the temperature of the lubricating oil is set so that the maximum temperature of the raw tube is lower than the crystallization temperature of Zircaloy (approximately 550 C), that is, the temperature of the present invention. When the interworking method was applied to the initial plastic working of a blank tube that had been subjected to α/β quenching treatment, the cross-sectional area reduction rate was 75%.
After the warm plastic working of the present invention, annealing at about 600C,
Cold plastic working, annealing at about 600C, cold plastic working, about 5
A highly corrosion-resistant fuel cladding tube having an outer diameter of about 12.3yo+ and a wall thickness of about 0.9 tart was manufactured by sequentially annealing the tube.

The above two types of highly corrosion resistant fuel cladding tubes to 500tl'150? / cm" was subjected to a corrosion test in which it was held in high-temperature, high-pressure steam for 25 hours. These conditions were such that the corrosion inside the furnace was 70%. A normal fuel cladding tube was also used as a reference for the corrosion test. Corrosion resistance was evaluated based on the occupancy rate of nodular generated on the outer surface of the tube.The outer surface of the fuel clad tube ULJ manufactured by the processing method of the present invention exhibited a black, glossy appearance, and no nodular corrosion occurred at all. ., On the other hand, conventionally, the outer surface of the fuzzy tube is
Significant corrosion had occurred on each layer. As described above, the fuel cladding tube manufactured by the method of the present invention has excellent nodular corrosion resistance.

As described above, according to the present invention, it was possible to form a hardened raw tube into a corrosion-resistant fuel cladding tube for a nuclear reactor by three times of plastic working. 7'c In order to prevent cracks from occurring due to plastic working, do you use hardened steel? , :~550
It is also effective to maintain the area at about C and keep the area reduction rate to 75% or less. Basic'l! Since f can be processed into a fuel intake pipe for nuclear reactors and fuels by three times of plastic working or three times of cold plastic working, the effect is that all the hardened raw pipes can be processed using the conventional pass schedule. be,

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram 1, J2, showing a preferred embodiment of the present invention.
Figure C is a characteristic diagram showing the relationship between the holding temperature and hardness measurement of 'try-2'. ...Inside the mandrel support, 5...Fig. 1 Fig. 52 −Hitachi City Koda company

Claims (1)

[Scope of Claims] 1. After the final hot working of the zirconium-based alloy, the alloy is heated to a temperature range including the α phase and β phase or to the temperature range of the β phase, and then subjected to multiple cold workings. A highly corrosion-resistant zirconium base for a nuclear reactor, characterized in that the cross-section reduction rate in the first cold working performed after the heating and quenching treatment is 75 inches or less, in a method of performing plastic working and multiple annealing treatments. Alloy manufacturing method. 2. After the final hot working, heating to a temperature range including α phase and β phase and rapid cooling is performed, followed by cold working with a reduction in area of 75% or less, and then cold working two or more times. A method for producing a highly corrosion-resistant zirconium-based alloy for nuclear reactors according to claim 1, which comprises processing and annealing three or more times. 3. After the final hot working of the zirconium-based alloy, it is heated to a temperature range that includes the α phase and β phase of the alloy, or to the temperature range of the β phase, and then rapidly cooled, and then subjected to multiple times of plastic working and multiple times of annealing. A highly corrosion-resistant zirconium base for a nuclear reactor, wherein the first plastic working after the heating and quenching treatment is carried out at a warm temperature of 100C or more and 550C or less, and subsequent plastic working is carried out cold. Alloy manufacturing method. 4. After the final hot working, heating to a temperature range including α phase and β phase, rapid cooling, and then further heating to 550°C at 100C or higher.
4. The method for producing a highly corrosion-resistant zirconium-based alloy according to claim 3, wherein plastic working is performed at a temperature of C or lower, followed by cold working two or more times and annealing three or more times.