JP3191813B2 - Fuel channel box, fuel assembly and method of use - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel fuel channel box and a fuel assembly, a method of use and a method of operating a nuclear reactor.

[0002]

2. Description of the Related Art Zirconium alloys have been used in reactor fuel assemblies because they are materials having excellent corrosion resistance and a small neutron absorption cross section. Zr-Sn-Fe-C called Zircaloy-2 or Zircaloy-4 is used for the above-mentioned applications.
An r-Ni alloy is mainly used. When these alloys are used in a nuclear reactor for a long period of time, the (0001) plane is oriented in the plate thickness direction as shown in FIG. 2, so that elongation and bending deformation occur in a specific direction. If bending deformation occurs in the fuel channel box, the operation of the reactor is hindered because the gap for driving the control rod is closed. When bending deformation occurs, the interval between the fuel and the cladding tube changes, and the ratio of water to uranium locally increases or decreases, so that the fission reactivity changes. As a result, corrosion of the fuel cladding tube may be accelerated due to abnormal heat generation, and the fuel may be damaged. In order to prevent bending deformation of the fuel channel box due to such non-uniformity of neutron irradiation, it has been studied to make the neutron irradiation uniform by replacing the fuel assembly loading position in the reactor core. However, the reduction of the control rod driving gap and the change of fission reactivity due to the bending deformation are the main factors that limit the life of the fuel channel box.

[0003] Corrosion of the fuel channel box is also a factor that limits its life. As a method for improving the corrosion resistance, heat treatment for rapidly cooling the Zr alloy from the α + β phase temperature range or the β phase temperature range is disclosed in Japanese Patent Publication Nos. 56-12310 and 60-44387. However, since the bending deformation due to irradiation growth cannot be reduced for the reasons described below, it cannot be a technique for suppressing irradiation growth of a zirconium alloy member.

[0004]

In the above prior art, the grain size, orientation, mechanical properties, etc. of the zirconium alloy member are not changed by heat treatment, and only the corrosion resistance is improved. As a result, the α + β temperature range (800 to 98 ° C.) is more than the β phase temperature range (≧ 980 ° C.) in which the crystal grains are coarsened.
(0 ° C.), and the crystal orientation, which is an important factor in suppressing irradiation growth, is not changed by this heat treatment.
It did not become a technique for suppressing irradiation growth of zirconium alloy members. Published Patent Application No. 59-229475 discloses that the Fl value is 0.1.
A method for orienting to 5-0.5 is disclosed. However, this method is not an irradiation growth suppression technique for the reason described later, but rather promotes irradiation growth.

[0005] An object of the present invention is to provide a fuel channel box and a fuel assembly using a zirconium-based alloy rectangular cylindrical member having little elongation and bending deformation due to the above-mentioned irradiation growth, and a method of use and a method of operating a nuclear reactor. It is in.

[0006]

The present invention is based on irradiation growth if the <0001> crystal orientation of the hexagonal Zr metal of the zirconium-based alloy prismatic cylindrical member is almost completely randomized as shown in FIG. Bending deformation can be suppressed.

[0007] The present invention relates to a method for producing a steel sheet, comprising:
b using a zirconium-based alloy plate containing 5% by weight or less and having a balance of 90% by weight or more of Zr,
The orientation ratio (Fr value) of r in the direction perpendicular to the plate surface in the <0001> crystal orientation is set to 0.20 to 0.50.

In particular, the present invention relates to a hexagonal Z
The orientation ratio (Fr value) of r in the direction perpendicular to the surface of the cylindrical member with respect to the <0001> crystal orientation (Fr value), the orientation ratio in the longitudinal direction of the cylindrical member (Ft), and the orientation ratio in the circumferential direction (Fl) are as follows. Is preferably 0.20 to 0.50.

In the present invention, it is preferable that the alloy plate has an α phase and a crystal grain size is 50 to 500 μm.

According to the present invention, the above alloy plate has an α phase, and the <0001> crystal orientation of the hexagonal Zr of the alloy is substantially randomly oriented, and 3 × 10 ²² n / cm ² fast neutrons The strain due to irradiation growth is preferably 3 × 10 ⁻⁴ or less.

According to the present invention, the β ratio is set so that the hexagonal Zr of the above-mentioned alloy plate has an orientation ratio (Fr value) of the <0001> crystal orientation in the direction perpendicular to the plate surface to be 0.26 to 0.40.
It is preferable to adjust the heating holding time in the single-phase temperature range.

[0012] The present invention relates to a method for producing a steel sheet, comprising: 5% by weight or less of Sn and / or 5% by weight of Nb formed by cold rolling and annealing;
After processing a zirconium-based alloy plate having 90% by weight or more of Zr into a desired shape, a rectangular tubular member formed by welding is heated and held in a β-phase single-phase temperature region, and then quenched by forced cooling with a refrigerant. A fuel channel box that has been annealed thereafter, wherein the heating and holding during the quenching is performed in a direction perpendicular to the surface of the cylindrical member with the <0001> crystal orientation of hexagonal Zr of the alloy at a temperature in the β-phase single-phase temperature region. Has an orientation ratio (Fr value) of 0.20 to 0.50.
The time is adjusted so that

[0013] The present invention relates to a method for producing a steel sheet, comprising: 5% by weight or less of Sn and / or 5% by weight of Nb formed by cold rolling and annealing;
A rectangular tubular member formed by welding a zirconium-based alloy plate having a Zr of 90% by weight or more into a desired shape and then locally welding to a β-phase single-phase temperature region while relatively moving to each other by an induction heating coil. Continuously heated and held,
Then, a quenched fuel channel box which is forcibly quenched by a refrigerant and then annealed, wherein the heating and holding in the quenching is performed at a temperature in the β-phase single-phase temperature region at a <0001> crystal orientation of hexagonal Zr of the alloy. The orientation ratio (Fr value) in the direction perpendicular to the surface of the cylindrical member is 0.2.
The time is adjusted so as to be 0 to 0.50.

According to the present invention, a metal member having a larger coefficient of thermal expansion than the alloy is formed in a rectangular cylindrical member formed by welding a zirconium-based alloy plate formed by cold rolling and annealing into a desired shape and then welding. A mandrel is inserted, and at least both ends of the rectangular cylindrical member are fixed to the mandrel and continuously heated and held while being relatively moved to each other by an induction heating coil locally in a β-phase single-phase temperature region, and then A quenching forcedly quenched by a refrigerant, more preferably a fuel channel box annealed more preferably, wherein the heating and holding during the quenching is performed at a temperature in the β-phase temperature region and the hexagonal Zr of the alloy is <0.
001> The time is adjusted so that the orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is 0.20 to 0.50.

According to the present invention, a zirconium-based alloy plate formed by cold rolling and annealing is formed into a U-shape,
Next, the rectangular cylindrical member formed by welding is heated and held in the β-phase temperature range, and then quenched by forcibly quenching with a refrigerant, followed by annealing and, after the annealing, an oxide film formed on the entire surface of the cylindrical member by autoclave treatment. Wherein the heating and holding in the quenching is performed in such a manner that the <0001> crystal orientation of the hexagonal Zr of the alloy in a direction perpendicular to the surface of the cylindrical member at a temperature in the β phase temperature region. Rate (Fr value) from 0.20 to 0.5
The time is adjusted to be 0.

According to the present invention, there is provided a fuel rod containing a fuel pellet in a fuel cladding tube, a channel box for accommodating a plurality of the fuel rods, a spacer for partitioning the fuel rods in the channel box, an upper portion of the channel box, In a fuel assembly including an upper lattice plate and a lower lattice plate provided at a lower part, the channel box is formed by cold rolling and annealing to form Sn of 5% by weight or less and / or Nb of 5% by weight or less, and 90% by weight or more. After processing a zirconium-based alloy plate having a Zr into a desired shape, a rectangular cylindrical member formed by welding is heated and held in a β-phase temperature region,
Then, the quenching is forcibly quenched by a refrigerant and then annealed, and the heating and holding in the quenching is performed at a temperature in the β-phase temperature region of the hexagonal Zr of the alloy.
<0001> The time is adjusted so that the orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is set to 0.20 to 0.50.

According to the present invention, a single operation of the nuclear fuel can be carried out at a removal burnup of 32 GWd / t or more, or at least one operation.
A method of using a fuel channel box for replacing and operating the nuclear fuel, wherein the channel box is a rectangular cylinder formed by welding a zirconium alloy plate formed by cold rolling and annealing into a desired shape and then welding. The quenched member is heated and held in the β-phase temperature region, and then quenched by forcibly quenching with a refrigerant, more preferably annealed thereafter, and the holding time in the quenching is a temperature in the β-phase temperature region. <00 of the hexagonal Zr of the alloy
<01> The time is adjusted so that the orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is set to 0.20 to 0.50.

According to the present invention, an operation with an extraction burnup of 32 GWd / t or more or at least one
A method of using a fuel channel box for operating by exchanging nuclear fuel, wherein the channel box is a rectangular cylinder formed by welding a zirconium alloy plate formed by cold rolling and annealing into a desired shape and then welding. Is β
In the phase temperature region, the hexagonal Zr of the alloy is heated and held for a period of time in which the orientation ratio (Fr value) of the <0001> crystal orientation in the direction perpendicular to the surface of the tubular member (Fr value) is 0.20 to 0.50. After the quenching forcibly quenched by the quenching process, and more preferably, after the subsequent annealing, an oxide film is formed on the entire surface of the tubular member by an autoclave treatment.

According to the present invention, there is provided a fuel rod containing a fuel pellet in a fuel cladding tube, a channel box for accommodating a plurality of the fuel rods, a spacer separating the fuel rods in the channel box, an upper portion of the channel box, A method of using a fuel assembly, comprising an upper grid plate and a lower grid plate provided at a lower portion, and operated at a removal burnup of 32 GWd / t or more by one loading of nuclear fuel or at least once by replacing nuclear fuel. The channel box may be formed by welding a zirconium-based alloy plate having a Zr of 5% by weight or less of Sn and / or 5% by weight or less of Nb and 90% by weight or more into a desired shape by cold rolling and annealing. The formed rectangular cylindrical member is heated and held in the β-phase temperature range, and then quenched by forcibly quenching with a refrigerant. Ku is a one produced by the subsequent annealing, the holding time in the quenching of hexagonal Zr of the alloy at a temperature of at the β-phase temperature region <000
1> The time is adjusted so that the orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is set to 0.20 to 0.50.

The present invention relates to a method of using a fuel channel box which operates at a neutron irradiation dose of 10 ²² n / cm or more by a single loading of nuclear fuel, wherein the channel box is formed by cold rolling and annealing. After the formed zirconium alloy plate is processed into a desired shape, a rectangular cylindrical member formed by welding is heated and held in a β-phase temperature region, and then quenched by forcibly quenching with a refrigerant, more preferably manufactured by subsequent annealing. And the holding time in the quenching is the orientation ratio (Fr value) of the <0001> crystal orientation of the hexagonal Zr of the alloy in the direction perpendicular to the surface of the cylindrical member at the temperature in the β phase temperature region. 0.20 to 0.2.
The time is adjusted to be 50.

According to the present invention, the position of the channel box at the time of operation after the operation with the removal burn-up of 32 GWd / t or more is arranged at the same position as that at the time of the previous operation at least once by loading the nuclear fuel once. A method of operating a nuclear reactor that operates by replacing fuel, wherein the channel box is formed by processing a zirconium-based alloy plate formed by cold rolling and annealing into a desired shape, and then forming a rectangular tubular member by welding. Quenched by heating and holding in the β-phase temperature range, then forcibly quenched by a refrigerant, and more preferably manufactured by subsequent annealing, and the holding time in the quenching is a temperature in the β-phase temperature range. The time was adjusted so that the orientation ratio (Fr value) of the <0001> crystal orientation of the hexagonal Zr of the alloy in the direction perpendicular to the surface of the cylindrical member was 0.20 to 0.50. Characterized in that it is a shall.

In particular, the removal burnup is 38 GWd / t
It can be used on the high burn-up side of 45 GWd / t or more, and the effect becomes more remarkable.

[0023]

The aforementioned deformation occurs because the <0001> crystal orientation of the hexagonal Zr metal is oriented perpendicular to the zirconium alloy surface as shown in FIG. When the hexagonal Zr metal receives neutron irradiation, the crystal shrinks in the <0001> direction and
01> direction. More precisely, the atomic plane perpendicular to the (0001) plane by neutron irradiation
(Dislocations) are introduced, and the crystal shrinks and expands. As a result, in the fuel channel box in which the <0001> crystal orientation is oriented perpendicular to the surface, irradiation growth occurs in the longitudinal direction and the width direction. The closer to the center of the reactor core, the greater the neutron irradiation dose. If the neutron irradiation dose is different, the irradiation growth amount will differ, causing bending deformation. Randomization of <0001> crystal orientation is effective for suppressing irradiation growth. Irradiation growth is a deformation that does not involve a change in volume. Therefore, even if individual crystal grains of a polycrystal are deformed in a specific direction, the direction is random, and therefore, it is equivalent to no deformation as a whole.

In order to quantitatively evaluate the orientation of the crystal orientation, the X-ray of a specific crystal plane is usually determined by a combination of reflection and transmission X-ray diffraction methods.
X-ray diffraction intensity was measured, and from the measured X-ray diffraction intensity,
Is generally used to calculate the F-number.

In equation (1), φ represents a specific direction (for example,
Specific crystal orientation (for example, <000
2> crystal orientation), and V (φ) is the volume fraction of the crystal oriented in the φ direction. The r-direction, t-direction, and l-direction are defined as normal directions (F
r), the longitudinal direction (Ft) of the plate (tube), and the plate width (pipe circumference) direction (Fl), there is a relationship of Fr + Ft + Fl = 1.0, and if the crystal orientation is completely randomized, Fr = Ft = Fl = 1/3.

Each of Fr, Ft and Fl is 0.20 to
0.50, Fr 0.25 to 0.5
It is preferable to set it to 0.2, Fl 0.25 to 0.36, Ft 0.25 to 0.36, and particularly to 0.31 to 0.35.

(000) of plates and tubes manufactured according to the normal cold working and repeated annealing process.
2) The Fr value of the crystal plane (equivalent to the: 0001) plane is 0.6.
Before and after, the <0001> crystal orientation is mainly oriented in the surface normal direction of the plate (tube). Such a state in which the <0001> crystal orientation is oriented in the surface normal direction is called texture. FIG. 3 shows the relationship between the neutron irradiation amount and the irradiation elongation using the Fr value as a parameter. Fr value is 0.5
When it is 0 or less, preferably 0.45 or less, the irradiation elongation is remarkably reduced, and by setting the Fr value to 0.333 to 0.350, the elongation can be increased even in a high irradiation range of neutron irradiation ≧ 10 ²² (n / cm ² ). It turns out that it becomes substantially 0 (zero).

As one means for obtaining a texture that satisfies the Fr value ≦ 0.50, the zirconium alloy member is heated to a β-phase temperature range (a temperature exceeding 980 ° C. for a zircaloy alloy),
In addition, this is a method in which βZr crystal grains are sufficiently grown and then rapidly cooled by spraying with water during cooling. By performing this treatment, the hexagonal αZr crystal is transformed into a cubic βZr crystal, and is transformed again into a hexagonal αZr crystal during the cooling process. In this heat treatment, βZr crystal grains should grow to at least 100 μm or more in order to obtain a texture having a Fr value of 0.333 to 0.350, and βZr should be obtained in order to obtain a texture having a Fr value ≦ 0.50. The crystal grain is at least 50 μm or more and 500
μm or less, preferably 150 μm or more and 300 μm or less. The heating time at the β-phase temperature is higher in the β-phase temperature range (preferably 1100 to 1350 ° C., more preferably 1 to 1350 ° C.).
(100-1200 ° C) can be heated in a short time.
The holding time at the maximum heating temperature can be performed in a very short time, for example, 1.5 to 600 seconds, preferably 5 to 1 second.
00 seconds. In particular, it is preferable to perform the processing in the range indicated by the mark in FIG.

The α is not transformed by heating in the α + β phase temperature range.
Since Zr crystals remain, a favorable texture cannot be obtained. In addition, even if heating is performed in the β-phase temperature range, if the holding time is short and the heating temperature is low, a favorable texture cannot be obtained. The reason is that in the transformation from αZr to βZr (heating process) and the transformation from βZr to αZr (cooling process), the (0001) crystal plane of αZr and (11
0) The transformation proceeds while maintaining the crystal orientation relationship in which the crystal plane is parallel to the crystal plane, so that no change in the crystal orientation occurs after the completion of heating and cooling. In order to obtain a texture having a random crystal orientation, β having various crystal orientations should be used.
It is necessary to grow Zr crystal grains. For this purpose, a temperature and a holding time (P value of 0.8 or more) sufficient for βZr crystal grains to grow to at least 50 μm or more are adjusted.

As described above, the Fr value changes depending on the heat treatment, but the temperature and the holding time are important factors. Accordingly, in order to keep the Fr value at 0.50 or less in the β-phase temperature region, it is preferable that the parameter P obtained by the above equation is 1.5 or more (βZr crystal grain is 60 μm or more).

Further, the parameter P is between 2.5 and 5 (βZr
Crystal grains 70 to 500 μm) are preferred, and especially 3.2 to 5 μm.
(ΒZr crystal grains 100 to 500 μm) is preferred.

As a zirconium-based alloy, Sn 5% by weight
And / or Nb of 5% by weight or less, and a balance of 90% by weight or more (preferably 95 to 98.5% by weight) of a zirconium-based alloy having Zr. Sn and Nb are necessary to increase the strength of Zr, and the former needs 3% and the latter needs 5% or less. The lower limits are each preferably 0.1%.
As a zircaloy-based alloy, Sn is preferably 1 to 2%,
In particular, it is preferably from 1.2 to 1.7%. This alloy has Fe0.
5% or less, Cr 0.5% or less, or this Cr and Ni 0.2
% Or less, or Fe and Ni thereof, especially Fe 0.1 to 0.38%, Cr 0.05 to 0.15%, N
i containing 0.03 to 1.25%, Fe 0.22 to 0.2
38%, Cr 0.05-0.15% and Ni 0.09-0.1.
The one containing 15%, the latter Fe and Ni may be used alone, but a composite is preferable, and the (Fe / Ni) ratio is preferably 1.3 to 10.

As an alloy containing Nb, Zr-0.5-2
% Nb, Zr-2 to 5% Sn-0.5 to 1.5% Nb-
0.5-1.5% Mo, Zr-0.5-0.15% Sn-
0.5 to 1.5% Nb-0.1 to 1.0% Fe, Zr-0.5.
Fe of 5 to 5.0% Nb-0 to 3.0% Sn-2% or less,
An alloy containing one or more of Ni, Cr, Ta, Pd, Mo, and W is used.

According to the production method of the present invention, heating in the β-phase temperature range involves heating the sheet material continuously for a desired holding time with an induction coil while moving the sheet material and simultaneously forcibly cooling after the heating. <0001>
The orientation becomes random and a material having high corrosion resistance to high-temperature and high-pressure pure water is obtained. The cooling is preferably performed by a fountain, and is preferably performed at a cooling rate of 100 ° C./sec or more, particularly 150 ° C./sec or more. Infrared and electric furnaces are also used as heating means.

When heating in the β-phase temperature region, it is preferable to fix and restrain the member by using a member having a higher thermal expansion coefficient than that of the Zr-based alloy. Particularly, in the case of a tubular member, heat is applied so that the entire surface does not contact the inner surface of the member. It is preferable to insert a metal member that is partially in contact with each other and to fix both ends to each other to perform heating and cooling so that the tubular member is not deformed during heating and cooling. By providing such a restraining member, heating and cooling can be easily performed. SUS304,316, as a restraining member
Austenitic stainless steel having a larger coefficient of thermal expansion than a Zr-based alloy such as 347 is preferable.

In the present invention, after the β-phase heat treatment, annealing for uniformly heating the whole is performed. Annealing is 500-650 ° C
(Preferably 550-640 ° C.). It is preferable that the annealing is also performed by restraining by the above-described restraining member, so that the tubular member can be shaped. These heat treatments are performed in a non-oxidizing range atmosphere, particularly preferably in Ar.

After the final heat treatment, the oxide film on the surface is removed by sandblasting and pickling. After the oxide film is removed, the surface is oxidized by an autoclave, and a stable oxide film is formed on the surface to obtain a final product. In addition, the ends such as the screw holes for fixing at the both ends described above are used after being removed.

The channel box of the present invention is used by flattening the welded portion after two U-shaped members are butted and plasma-welded to form a square tube. It is preferable that the heat treatment of the rectangular tube is performed by inserting an X-shaped restraining member.

[0039]

EXAMPLES As zirconium composite sheet materials, three kinds of zircaloys having the alloy compositions shown in Table 1 were used and subjected to the heat treatment shown in Table 2.

[0040]

[Table 1]

[0041]

[Table 2]

Each of the alloys is a plate having a thickness of 2 mm, and is repeatedly subjected to cold rolling and annealing at 650 ° C. for 2 hours before receiving. Heat treatment Nos. 2 to 4 shown in Table 2
A test piece having a width of 40 mm and a length of 40 mm was cut out of a receiving material, heated in an electric furnace, and cooled in water. The parameter P is obtained by the above equation. No. 1 and No. 2 are comparative, No. 3
Nos. To 6 relate to the present invention.

Table 3 shows (0002) of No. 1 to 6 heat-treated materials.
Plane (: parallel to the (0001) plane) and (1010) plane (:
The F-number measurement result of (perpendicular to (0001) plane) is shown. The F value is measured by a combination of the reflection and transmission X-ray diffraction methods described above. Fr is the orientation ratio in the direction perpendicular to the surface of the tubular member, Ft is the orientation ratio in the longitudinal direction, F
l is the orientation ratio in the circumferential direction.

[0044]

[Table 3]

In a sheet material (heat treatment No. 1) manufactured by repeating ordinary cold rolling and annealing, the Fr on the (0002) plane
The value is as high as about 0.7, and the Fr value of the (1010) plane (about 0.1
5) is lower than the Fl and Ft values,
2) It can be seen from the results in Table 3 that the plane is oriented substantially parallel to the plate surface. The F value of the heating / cooling plate material (heat treatment No. 2) within the α + β phase temperature range is the receiving material (heat treatment No. 1)
From the above, it is understood that the texture does not change by heating and cooling to the α + β phase temperature range. When cooled after holding for 1 minute and 5 seconds in the β-phase temperature range (1000 ° C.) (heat treatment No. 3, 6), (000
2) Decrease of Fr value of surface, increase of Fl and Ft values, and (10
10) An increase in the Fr value of the plane and a decrease in the Fl and Ft values are recognized, and the crystal orientation is randomized. However, it does not satisfy Fr value ≦ 0.35 which is a target value for being usable even in a high irradiation range of neutron irradiation amount ≧ 10 ²² (n / cm ² ). 1
When the temperature is kept at 000 ° C. for 10 minutes (heat treatment No. 4) and when the heating temperature is increased to 1200 ° C. (heat treatment No. 5),
The F value of both the (0002) and (1010) surfaces is about 0.33, indicating that the crystal orientation is almost completely randomized. As described above, the No. 4 and 5 heat-treated materials do not bend or elongate even in a high irradiation range and even when the neutron irradiation amount is uneven in the member.

FIG. 3 is a diagram showing the relationship between the fast neutron irradiation dose and the irradiation growth strain. As shown in the figure, when the Fr value exceeds 0.4, the strain increases rapidly with an increase in the neutron irradiation dose, but when the Fr value is less than 0.4, the strain saturates even after irradiation, and does not increase. In particular, Fr = 0.
In the case of No. 35, since the <0001> crystal orientation is substantially randomly oriented, the strain in the normal direction, the longitudinal direction, and the thickness direction is canceled out among the respective crystals, so that 0.5 × 10 ^-4. The following does not occur at all. In the case of Fr = 0.4, the amount of strain is small up to the irradiation dose of 3 × 10 ²² n / cm ² , but the strain gradually increases with the neutron irradiation dose higher than that. However, when Fr = 0.35, the strain does not increase even if the neutron irradiation dose increases.

FIG. 4 shows Fr values and fast neutrons 3 × 10 ²² n
FIG. 2 is a diagram showing a relationship between irradiation and irradiation growth strain caused by irradiation at / cm ² . The strain increases sharply as the Fr value increases. In particular, the irradiation growth strain at Fr = 0.35 is about 0.3.
2 × 10 ^-4 , about 1.5 × 10 ^-4 of Fr = 0.4 about 7
Significantly less than 1 /. Also, Fr = 0.4 is equivalent to Fr = 0.
It is remarkably small, about 1/3 of 5. However, Fr = 0.5
Is about half of Fr = 0.6, and Fr = 0.6 is about half of Fr = 0.7. If Fr exceeds 0.4, no great effect can be obtained.

The rounded crystal grains observed in the metal structure of each of the heat-treated materials of Nos. 1, 3, and 4 were αZr, and no βZr crystal grains were present. The polygonal crystal grains observed in FIGS. 4B and 4C are βZr crystal grains formed during heating and holding in the β phase temperature range, and as the holding time at 1000 ° C. increases from 1 minute to 10 minutes, It can be seen that the βZr crystal grain size grows large. The layered or acicular structure found in the βZr crystal grain size is formed when βZr is transformed again into αZr during the cooling process.
Not r grain boundaries.

FIG. 5 shows the relationship between the βZr crystal grain size and the Fr value of the (0002) plane. Β with a crystal grain size of 200 μm or more
By growing the Zr crystal grains, the Fr value ≦ 0.35
It can be seen that the texture of is formed.

By growing the grains (000
2) Although the crystal orientation of the plane can be randomized, the degree of randomization of the orientation is about 7 at a Fr value of 0.40.
5%, at which time the particle size is about 100 μm. 1
With a crystal grain size of 50 μm or more, about 8
It is randomized to 0% or more, and the Fr value becomes 0.385. Further, the random ratio at an Fr value of 0.35 is about 90% or more, and the crystal grain size at that time is about 250 μm or more.

FIG. 6 is a graph showing the relationship between the βZr crystal grain size and the irradiation growth strain. As shown in the figure, when the particle size is 90 μm or more, the strain amount is remarkably low at about 1.5 × 10 ⁻⁴ , but when the particle size is 150 μm or more, the strain becomes extremely small, 0.5 × 10 ⁻⁴ or less. In particular, when the thickness is 200 μm or more, it is about 0.3 × 10 ⁻⁴ .

FIG. 7 shows a parameter P = (3.55 + logt).
It is a diagram which shows the relationship between xlog (T + 980) and irradiation growth strain. As shown in the figure, the irradiation growth strain is greatly affected by a parameter P determined by the relationship between the temperature and the holding time in the heat treatment. The parameter P is an important factor that determines the orientation ratio of the <0001> crystal orientation of Zr. In the heat treatment at 1000 ° C., the irradiation growth strain sharply decreases when P is 0.5 or more, further gradually decreases from 0.5 to 3.5, becomes almost constant at 3.5 or more, and approaches zero. Irradiation growth occurs when P is less than 3.5, but hardly occurs above P.

In particular, the effect is great at 1.5 or more, and 3.2
5 to 5 are preferred.

FIG. 8 is a diagram showing the relationship between the Fl value of the (0002) plane of the alloys shown in Tables 1 and 4 at each temperature and holding time. As shown in the drawing, when the temperature is lower than 980 ° C., the Fl value becomes 0.20 or less, and it is difficult to obtain a crystal having a random <0002> crystal orientation. However, at 980 ° C, 11
Seconds, preferably at 1000 ° C for more than 10.5 seconds or 1
By heating above 240 ° C. and above the line connecting these points for 1.1 seconds or more, an Fl value exceeding 0.25 can be obtained and a higher randomness can be obtained. Also, 9
Heating at 80 ° C. or more for 6 seconds or more and 1240 ° C. or more for 6 seconds or more, and above the line connecting these points, yields an Fl value greater than 0.20 and 0.25 or less. Those lower than this line have an Fl value of 0.20 or less, have a low degree of randomness, and have a small effect on elongation.

[0055]

[Table 4]

FIG. 9 shows one embodiment of the fabrication of a channel box according to the present invention. The Zircaloy-C plate material described in Example 1 was cold-bent-shaped into a U-shape, and a 2 m 2
Two U-shaped members were formed, and these were plasma-welded to form a square tube 1. The unevenness of the weld is finished flat. A mandrel 2 made of SUS304 stainless steel is inserted into the inside of this square tube 1, fixed with screws 3, heated to a β-phase temperature range by high-frequency induction heating, and cooled by a nozzle 6 provided immediately below the high-frequency induction heating coil 4. Quenched with water. Hot water is also used as cooling water. The contact area of the mandrel 2 is reduced so as to reduce the influence of heat on the material to be heated. The entire heat treatment is completed by the rectangular tube 1 passing through the coil from above to below at a constant speed. Heating temperature is 1300 ℃, 1200 ℃, holding time is 20 seconds and 110
The feed speed of the rectangular cylinder 1 and the output of the high frequency power supply 5 were adjusted so that the holding time at 0 ° C. was 10 seconds. After heat treatment, width 4
A test piece having a length of 0 mm and a length of 40 mm was cut out and the F value was measured by an X-ray diffraction method. Table 5 shows the measurement results. The parameter P is 3.26 for 1300 ° C., 3.05 for 1200 ° C., and 2.07 for 110 ° C. Note that annealing is performed after the randomized heat treatment.

[0057]

[Table 5]

As shown in the table, (0002), (101)
0) On both surfaces, the F value is 1/3 in each case, indicating that the crystal orientation is completely random.

As a result of a high-speed neutron irradiation test, the strain at 3 × 10 ²² n / cm ² was about 0.3 × 10
It was extremely small, less than ^-4 . In addition, the crystal grain sizes of these were 100, 150 and 250 μm, respectively.

After the heat treatment, sandblasting and pickling are performed to remove an oxide film on the surface, and then autoclave treatment with steam is performed.

FIG. 10 is a partial sectional view of a BWR fuel assembly using the rectangular tube manufactured as described above.

As shown in the figure, the BWR fuel assembly is composed of a number of fuel rods 11, spacers 12 for holding them at predetermined intervals, a rectangular channel box 1 for accommodating them, and a fuel cladding tube. An upper tie plate 14 and a lower tie plate 15 for holding both ends of a fuel rod 11 containing fuel pellets therein, and a handle 13 for transporting the whole.

Further, the production of these fuel assemblies goes through complicated production steps, and each structure is assembled by welding.

The fuel channel box 1 is used in a state where the fuel rods 11 incorporated by the fuel spacers are accommodated therein, and the fuel rods are fixed by the upper tie plate 14 and the lower tie plate 15. As described above, the fuel channel box has a rectangular tube shape formed by joining two U-shaped plate-shaped workpieces by plasma welding. This member forcibly guides high-temperature water and steam generated from the fuel rods during operation of the plant to the upper portion, and is used for a long time in a state in which the stress that spreads the rectangular tube outward is constantly applied.

During use, the fuel assembly channel box is exposed to high-temperature and high-pressure reactor water and is subjected to neutron irradiation. Further, since the pressure inside the rectangular tube is higher than that outside, the rectangular tube receives an internal pressure. As a result, corrosion resistance under high temperature and high pressure environment and high creep deformation resistance under neutron irradiation are required.

A zirconium-based alloy generally has high corrosion resistance and a small neutron absorption cross section. These characteristics are suitable as a material for a fuel assembly for a nuclear reactor, and include a fuel cladding tube, a channel box 1, a spacer 1
2 and so on. As a specific zirconium-based alloy to be used, Zircaloy-2 (Sn 1.2 to 1.7 wt.
%, Fe 0.07 to 0.02 wt%, Cr 0.05 to 0.1
5 wt%, Ni 0.03-0.08 wt%, residual Zr),
Zircaloy-4 (Sn 1.2 to 1.7 wt%, Fe 0.1
8 to 0.24 wt%, Cr 0.05 to 0.15 wt%, remaining Zr), Zr-0.5 to 2 wt% Nb alloy, Zr-2 to 5
wt% Sn-0.5-1.5 wt% Nb-0.5-1.5 w
t% Mo alloy, Zr-0.5-1.5wt% Sn-0.5
-1.5 wt% Nb-0.1-1.0 wt% Fe alloy, Z
r-Nb (0.5-5.0 wt%)-Sn- (0-3.0
wt%)-Fe, Ni, Cr, Ta, Pd, Mo, W
(2% by weight or less), and it has been confirmed that the present invention is effective for any alloy plate.

The above-mentioned Zircaloy alloy is used for cladding channel boxes and spacers in a boiling water reactor. In particular, cladding tends to cause local oxidation (nodular corrosion). It is preferable to quench the α + β phase or β phase only on the outer surface either during the final hot working or after the final hot working. In particular, quenching is preferably performed before the first cold working. The heating temperature during quenching is 825 to 1
The temperature is preferably 100 ° C., and the heating time is preferably 1 minute to 3 to 30 seconds.

The heating is preferably performed continuously by an induction coil, and the cooling is preferably performed using a fountain following the heating. It is also possible to heat while flowing water in the tube. The cladding preferably has a <0001> orientation perpendicular to the tube surface having a Fr value of 0.66 or more. In the quenching, the temperature and time are controlled so that the crystal orientation does not become random. A zirconium-niobium alloy containing Nb has high strength, excellent creep characteristics, low hydrogen absorption rate, and does not cause local corrosion called nodular corrosion. These are preferable characteristics as a material for a fuel assembly member, but the corrosion of the welded portion and the heat-affected zone is accelerated, and a white oxide having a large peeling property is easily formed.

The niobium-zirconium multi-component alloy is composed of 0.5 to 2.0 wt% of Nb, up to 1.5 wt% of Sn, and Fe, Cr, Mo, V, Cu, Ni and W. Zirconium alloys containing up to 0.25 wt% of a third alloy element selected from the group have a special microstructure that is resistant to corrosion in high temperature steam environments.

As described above, the channel box of the present invention using these alloys is heated and held so that the F value on both sides of (0002) and (1010) is 1/3 each.
Obtained by quenching. As a result, the burnup 32
It can be used not only for GWd / t or more, but also for 45 GWd / t or more, and can be used for two cycles in which the clad attached to the surface is removed, fuel is replaced, and the fuel is used again, and there is little deformation. Therefore, it can be used at the same position as before in the core. The heat treatment and the orientation described above are preferably performed not only on the zircaloy alloy but also on the cladding tube made of the above-mentioned alloy.

By using a quenched tube for both the cladding tube and the channel box, an excellent tube as a whole can be obtained.

[0072]

As described above, according to the present invention, the neutron irradiation dose is 10 ²² (n / cm) because the crystal orientation of the channel box used for the fuel assembly is randomized.
Even when used in a high irradiation environment exceeding ² ), irradiation growth and bending deformation caused by irradiation growth do not occur. As a result, the fuel assembly channel box can be used for a long time, and can contribute to the reduction of spent fuel waste. Further, the corrosion resistance is also improved, which can contribute to the improvement of the reliability of the fuel assembly.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the orientation of the crystal orientation of a plate of the present invention.

FIG. 2 is a schematic diagram showing a mechanism of irradiation growth.

FIG. 3 is a diagram showing the effects of fast neutron irradiation dose and Fr value on irradiation growth strain.

FIG. 4 is a diagram showing the relationship between irradiation growth strain and Fr value.

FIG. 5 is a diagram showing a phase relationship between an Fr value and βZr crystal grains.

FIG. 6 is a diagram showing the relationship between irradiation growth strain and Zr crystal grain size.

FIG. 7 is a diagram showing a relationship between irradiation growth strain and a parameter P.

FIG. 8 is a diagram showing the relationship between the temperature and the holding time exerted on the Fr value.

FIG. 9 is a configuration diagram of an apparatus showing a method of manufacturing a channel box.

FIG. 10 is a partial cross-sectional view of the fuel assembly.

[Explanation of symbols]

1 ... channel box, 2 ... mandrel, 3 ... screw, 4
... high frequency induction heating coil, 5 ... high frequency power supply, 6 ... water spray nozzle, 7 ... welded part, 11 ... fuel rod, 12 ... spacer, 13 ... handle, 14 ... upper tie plate, 15 ...
Lower tie plate.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshitaka Kida 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Noriyuki Onaka 4026 Kuji-machi, Hitachi City, Ibaraki Hitachi, Ltd.Hitachi, Ltd. Inside the laboratory (72) Inventor Hideaki Ishizaki 3-1-1, Sachimachi, Hitachi, Ibaraki Pref.Hitachi, Ltd.Hitachi Plant (72) Inventor Hiromasa Hirakawa 3-1-1, Sachimachi, Hitachi, Ibaraki Co., Ltd. Hitachi, Ltd. Hitachi Plant (72) Inventor Hideo Maki 3-1-1, Sakaimachi, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Plant (56) References JP-A-59-229475 (JP, A) JP-A Sho 60-67648 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 3/06 G21C 3/30

Claims (10)

(57) [Claims] 1. Sn formed by cold rolling and annealing.
5% by weight or less and / or 5% by weight or less of Nb, 90% by weight
After processing the zirconium-based alloy plate having the above-mentioned Zr into a desired shape, a rectangular cylindrical member formed by welding is heated and held in a β-phase single-phase temperature region, then quenched by forcibly quenching by a refrigerant and then annealed. A fuel channel box, wherein the heating and holding during the quenching is performed at a temperature in the β-phase single-phase temperature range, in which the <0001> crystal orientation of the hexagonal Zr of the alloy in the direction perpendicular to the surface of the cylindrical member with respect to the crystal orientation. A fuel channel box, wherein the time is adjusted so that (Fr value) is set to 0.20 to 0.50. 2. Sn formed by cold rolling and annealing.
5% by weight or less and / or 5% by weight or less of Nb, 90% by weight
After processing the above-mentioned zirconium-based alloy plate having Zr into a desired shape, a rectangular cylindrical member formed by welding is continuously moved relative to each other locally by an induction heating coil in a β-phase single-phase temperature region and continuously. A quenched and then annealed fuel channel box that is heated and held, and then forcibly quenched by a refrigerant, wherein the heat holding in the quenching is performed at a temperature in the β-phase single-phase temperature region, where the hexagonal Zr of the alloy is <0001> The orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is 0.20 to 0.50.
A fuel channel box characterized in that the time is adjusted to be: 3. A mandrel made of a metal member having a larger thermal expansion coefficient than that of the alloy in a rectangular cylindrical member formed by welding a zirconium-based alloy plate formed by cold rolling and annealing into a desired shape and then welding. Is inserted, and at least both ends of the rectangular cylindrical member are fixed to the mandrel and continuously heated and held while being relatively moved to each other by an induction heating coil in a β-phase single-phase temperature region, and then by a refrigerant. A quenched fuel channel box which is forcibly quenched, wherein the heating and holding during the quenching is performed at a temperature in the β-phase temperature region, where the <0001> crystal orientation of the hexagonal Zr of the alloy is perpendicular to the surface of the cylindrical member. A fuel channel box, wherein the time is adjusted so that the orientation ratio (Fr value) in the direction is set to 0.20 to 0.50. 4. A zirconium-based alloy plate formed by cold rolling and annealing is formed into a U-shape, and a rectangular cylindrical member formed by welding is heated and held in a β-phase temperature region. A quenching forcibly quenched by a refrigerant, followed by annealing and after the annealing, a fuel channel box in which an oxide film is formed on the entire surface of the tubular member by an autoclave treatment, wherein the heating and holding in the quenching is the β phase. At a temperature in the temperature range, the time is adjusted so that the orientation ratio (Fr value) of the <0001> crystal orientation of the hexagonal Zr of the alloy in the direction perpendicular to the surface of the cylindrical member is 0.20 to 0.50. A fuel channel box. 5. A fuel rod containing a fuel pellet in a fuel cladding tube, a channel box containing a plurality of the fuel rods,
In a fuel assembly including a spacer that partitions between the fuel rods in the channel box, an upper grid plate and a lower grid plate provided at upper and lower portions of the channel box, the channel box is subjected to cold rolling and annealing. 5% by weight of Sn and / or 5% by weight of Nb and 90% by weight or more of a zirconium-based alloy plate having a desired shape is processed into a desired shape, and then a rectangular cylindrical member is formed in a β-phase temperature region by welding. Quenching, followed by forcibly quenching with a refrigerant and then quenching by a coolant, and then annealing, wherein the heating and holding in the quenching is performed at a temperature in the β-phase temperature region and the hexagonal Zr of the alloy is <000
1) A fuel assembly, wherein the time is adjusted so that the orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is set to 0.20 to 0.50. 6. A method of using a fuel channel box which operates with a removal burn-up of 32 GWd / t or more by replacing the nuclear fuel with one charge of the nuclear fuel or at least once with replacement of the nuclear fuel. After processing a zirconium alloy plate formed by rolling and annealing into a desired shape, a rectangular cylindrical member formed by welding is heated and held in a β-phase temperature region, and then quenched to be forcibly quenched by a refrigerant. The holding ratio in the quenching is set at a temperature in the range of the β phase temperature so that the orientation ratio (Fr value) of the <0001> crystal orientation of the hexagonal Zr of the alloy in the direction perpendicular to the surface of the cylindrical member is 0.20. A method of using a fuel channel box, wherein the time is adjusted to 0.50. 7. A method of using a fuel channel box, which operates at a removal burnup of 32 GWd / t or more by one charge of nuclear fuel or exchanges nuclear fuel at least once, wherein the channel box is cold. After processing a zirconium alloy sheet formed by rolling and annealing into a desired shape, a rectangular cylindrical member formed by welding is a cylindrical member having a <0001> crystal orientation of hexagonal Zr of the alloy in a β phase temperature region. After heating and holding for a time in which the orientation ratio (Fr value) in the direction perpendicular to the surface is 0.20 to 0.50, and then quenching by forcible quenching with a refrigerant, an oxide film by autoclave treatment is applied to the entire surface of the tubular member. A method of using a nuclear fuel channel box, characterized in that it is formed. 8. A fuel rod containing fuel pellets in a fuel cladding tube, a channel box containing a plurality of the fuel rods,
A spacer for partitioning between the fuel rods in the channel box, an upper grid plate and a lower grid plate provided on the upper and lower portions of the channel box, and a removal burnup of 32 GWd / t or more by one loading of nuclear fuel Or a method of using a fuel assembly which is operated by replacing nuclear fuel at least once, wherein the channel box is formed by cold rolling and annealing to form 5% by weight or less of Sn and / or 5% by weight or less of Nb, 90% by weight or less. A rectangular cylindrical member formed by welding a zirconium-based alloy plate having a Zr of not less than% by weight into a desired shape, and then heating and holding the plate in a β-phase temperature region, and then forcibly quenching with a refrigerant to produce a quenched member. And the holding time in the quenching is a hexagonal Zr of the alloy at a temperature in the β phase temperature range.
Wherein the time is adjusted so that the <0001> crystal orientation in the direction perpendicular to the surface of the cylindrical member (Fr value) is 0.20 to 0.50. How to use 9. A method of using a fuel channel box which operates at a neutron irradiation dose of 10 ²² n / cm or more by a single loading of nuclear fuel, wherein the channel box is formed by cold rolling and annealing. A rectangular tubular member formed by welding a processed zirconium alloy plate into a desired shape and then heating and maintaining the β-phase temperature region in a β-phase temperature region, and then forcibly quenching with a refrigerant, and manufactured by quenching. The holding time at the temperature in the β phase temperature range, the orientation ratio (Fr value) of the <0001> crystal orientation of the hexagonal Zr of the alloy in the direction perpendicular to the surface of the cylindrical member (Fr value) is 0.20 to 0.50. The use of a fuel channel box, characterized in that the time is adjusted to perform. 10. The position of the channel box at the time of operation after the operation with an extraction burn-up of 32 GWd / t or more by the same loading of nuclear fuel is arranged at the same position as at the time of the previous operation, and fuel is supplied at least once. A method of operating a nuclear reactor that is replaced and operated, wherein the channel box is a β-phase tubular member formed by welding a zirconium-based alloy plate formed by cold rolling and annealing into a desired shape and then welding. It is manufactured by quenching that is heated and held in a temperature range and then forcibly quenched by a refrigerant, and the holding time in the quenching is <0001> of the hexagonal Zr of the alloy at a temperature in the β phase temperature range. The orientation ratio (Fr value) of the crystal orientation in the direction perpendicular to the surface of the cylindrical member is 0.20.
A method for operating a nuclear reactor, wherein the time is adjusted so as to be 0.50 to 0.50.