JP5629446B2 - REACTOR CONTROL RODS COMPOSITE, PROCESS FOR PRODUCING THE COMPOSITE AND REACTOR CONTROL RODS USING THE COMPOSITE - Google Patents

Description

The present invention relates to a composite material for a reactor control rod used in a light water reactor, a method for producing the composite material, and a nuclear reactor control rod using the composite material.

In general, a nuclear reactor control rod 1 applied to a boiling water reactor or the like includes, as shown in FIG. 7, for example, a front end structural member 4 having a handle 3 formed at a front end portion and provided with a guide roller 4a and an endless structural member. A tie rod 6 that joins the tie rod 5, a cooling hole 9 that protrudes radially from the tie rod 6, and into which a coolant is introduced. A wing 2 that is formed by a sheath 7 having a deep U-shaped cross section, and a sheath 7 has a plurality of neutron absorbing elements (hereinafter referred to as hafnium metal plates) 10 arranged in parallel with the axis of the tie rod 6.

Conventionally, such a reactor control rod 1 is called a flux-strap hafnium control rod as a long-life control rod, and this reactor control rod 1 is made of hafnium or a hafnium alloy as shown in FIGS. A pair of hafnium metal plates 10 made of these are opposed to each other, and these hafnium metal plates 10 are housed in a metal sheath 7 as neutron absorbing elements. That is, in this flux strap type hafnium control rod, the neutron absorbing element is divided in the longitudinal axis direction 11 of the wing 2 and the thickness of the hafnium metal plate 10 in each divided section is determined according to the neutron absorption amount in each section. Thus, the nuclear lifetime of the neutron absorber is made uniform over the entire control rod. That is, as shown in FIGS. 8 and 9, each wing 2 has a configuration in which the hafnium metal plate 10 is welded and fixed in an opposed state using a plurality of tops 12 on the inner surface of the sheath 7 that forms the outer shell of the wing 2. ing.

In such a conventional nuclear reactor control rod 1, when each frame 12 and the sheath 7 are fixed by welding, the sheath 7 slightly shrinks in a concave shape with respect to the hafnium metal plate 10 due to welding deformation. In addition to eliminating the gap between the sheath 7 and the hafnium metal plate 10, there is a possibility of being strongly restrained. In such a state, not only the absorption margin of the corrosion product to be formed in the gap between the sheath 7 and the hafnium metal plate 10 disappears, but also the thermal expansion between the sheath 7 and the hafnium metal plate 10. Further, since the structure does not allow relative displacement due to differences in irradiation growth, there is a possibility that excessive stress is generated in the thin plate-like sheath 7. In addition, the conventional control rod has a structure in which the hafnium metal plate 10 and the sheath 7 are held by welding through a plurality of tops 12, and various comparisons during operation including the load at the time of scram are performed by this welded portion. A large load is carried. When the top 12 is fixed by welding in this manner, a tensile residual stress is generated in the vicinity of the welded portion, which may cause stress corrosion cracking in the sheath 7 in the vicinity of the welded portion. It may threaten the safety of the furnace.

Although such a nuclear reactor control rod has a welded structure as in Patent Document 1, there is no description of measures for reducing residual stress caused by welding.

JP-A-9-113644 JP 59-17192 A JP 2008-203196 A

In the control rod for a reactor applied to the above-described boiling water reactor or the like, in the conventional flux strap type hafnium control rod, the opposed hafnium metal plate is sandwiched between sheaths, and the interval is maintained by the top, but the top end of the top By welding the sheath, the sheath is deformed and the thin plate of the sheath falls to the hafnium side, generating a tensile residual stress on the sheath plate. When used in such a state, stress corrosion cracking may occur in the sheath due to the residual stress of tension and high-temperature water due to the water environment. In addition, there is a problem that the gap between the sheath and hafnium disappears due to deformation of the sheath due to welding, which may cause crevice corrosion, leading to a decrease in the reliability of the reactor control rod.

Moreover, there are Patent Documents 2 and 3 as examples in which the sheath is not used. This nuclear reactor control rod is welded with a hafnium plate and a zirconium thin plate at the joint, and extruded to improve adhesion. However, this nuclear reactor control rod has various problems such as a problem of residual stress due to extrusion processing and a point that the corrosion resistance is not particularly problematic.

The present invention has been made to solve the above-mentioned problems of the prior art, and can reduce the residual stress in each part of the reactor control rod, suppress the irradiation growth, and improve the corrosion resistance, thereby realizing a long life. An object of the present invention is to provide a composite material for a nuclear reactor control rod, a method for producing the composite material, and a nuclear reactor control rod using the composite material.

A method for manufacturing a composite material for a nuclear reactor control rod according to the present invention includes a composite material forming step in which a hafnium plate material surface is coated with a zirconium alloy to form a composite material, and an α-β transformation of the zirconium alloy with respect to the composite material. A quenching process in which quenching is performed at a temperature equal to or higher than a temperature, and a molding process in which cold working or hot working is performed without being exposed to 625 ° C. or higher after the quenching process. The hot working is performed in a range where the cumulative annealing parameter ΣAi does not exceed 2 × 10 ⁻¹⁹ hours according to the following formula .
ΣAi = Σti × exp (−Q / RTi)
Here, ti: treatment time (hour) in the i-th heat treatment step after β quenching.
Ti: Processing temperature (K) in step i.
Q: Activation energy.
R: Gas constant.
Q / R = 40000.

  Further, in the nuclear reactor control rod composite material according to the present invention, the zirconium alloy is Sn; 1.2 to 1.7 mass%, Fe; 0.07 to 0.20 mass%, Cr; 0.05 to 0.00. 15% by mass, Ni: 0.03 to 0.08% by mass, the balance being a composition comprising Zr and unavoidable impurities, manufactured by the above method for manufacturing a nuclear reactor control rod composite To do.

Furthermore, a nuclear reactor control rod according to the present invention is characterized by being constituted by the above-described method for manufacturing a nuclear reactor control rod composite or a nuclear reactor control rod composite.

In a nuclear reactor control rod composite material according to the present invention, a method of manufacturing the composite material, and a nuclear reactor control rod using the composite material, the residual stress in each part of the nuclear reactor control rod is reduced and irradiation growth is suppressed. In addition, since the corrosion resistance is improved, a long life can be realized. For this reason, the reliability of the reactor control rod can be improved, and a high-quality reactor control rod can be provided.

The principal part sectional drawing of the control rod material which shows 1st Embodiment of this invention. The principal part sectional drawing of the control rod material which shows the modification of 1st Embodiment of this invention. The flowchart which shows the manufacturing method of the composite material for nuclear reactor control rods which shows the 1st Embodiment of this invention. 1 is a cross-sectional view of a nuclear reactor control rod showing a first embodiment of the present invention. Sectional drawing of the control rod material which shows 2nd Embodiment of this invention. The perspective view which shows 6th Embodiment of this invention. The partially cut perspective view which shows the conventional nuclear reactor control rod. The front view which notched and showed a part of wing of the conventional control rod. The side view of the conventional control rod.

Hereinafter, embodiments of a composite material for a nuclear reactor control rod according to the present invention, a method for producing the composite material, and a nuclear reactor control rod using the composite material will be described with reference to the drawings.

(First embodiment)
FIG. 1 and FIG. 2 are main part sectional views showing an enlarged main part of a neutron absorber of a nuclear reactor control rod showing a first embodiment of the present invention and its modification, and FIG. FIG. 4 is a cross-sectional view of the nuclear reactor control rod showing the first embodiment of the present invention. FIG. In the present embodiment, the same parts as those in the conventional example are denoted by the same reference numerals, and description of the structure of those parts is omitted.

As shown in FIGS. 1 and 3, the composite material forming step A is made of a zirconium alloy on one surface of the hafnium metal plate 21 constituting the wing 2 of the reactor control rod 20 or on both opposing surfaces as shown in FIG. The protective materials 22 and 23 are covered (joined). Thereafter, by performing quenching at a temperature equal to or higher than the α-β transformation temperature in the quenching step B, the reactor control rod composite plates 24 and 25 having excellent corrosion resistance can be obtained.

The reactor control rod composite plates 24 and 25 are constructed by forming the cross 30 shown in FIG. 4 so that the protective plates 22 and 23 are on the outer side (the side facing the fuel assembly). Is formed into a cross-shaped control rod shape having a space 31 through which water as a moderator can flow. Thereafter, the handle 3 as the tip structural member 4 is attached to the upper side by welding. Further, the end structure 4 is also attached to the lower portion by welding to form the control rod 20.

In the present embodiment, an example of mold processing of the cross 30 is shown, but the plate members 24 and 25 are one or two so that the protective plates 22 and 23 are on the outer side (side facing the fuel assembly). Of course, the wings 2 may be formed in the form of a cross-shaped control rod formed by pasting the plates together.

In this case, it is possible to obtain a nuclear reactor control rod with improved reliability by covering the outer plate material portion with a protective plate.

The operation of the nuclear reactor control rod composite plates 24 and 25 thus configured will be described.

In the conventional structure, stainless steel is used for the U-shaped sheath, support piece, etc., and these are joined by TIG welding. In the state where high residual stress on the tensile side is generated on the sheath plate by welding, When exposed to high-temperature reactor water environments, stress corrosion cracking occurs in stainless steel, impairing the function of the control rod. Therefore, in the present invention, the surface of the hafnium metal plate 21 is coated (attached) with the protective materials 22 and 23 made of a zirconium alloy to form a composite material having a layer structure, and a hexagonal close-packed structure (α Quenching is carried out at or above the α-β transformation temperature at which the phase changes from a phase) to a body-centered cubic structure (β phase).

Further, in the present embodiment, the molding step C may be performed after the quenching step B in producing the nuclear reactor control rod composite plates 24 and 25. In this forming step C, the cumulative annealing parameter ΣAi obtained by the following equation 1 indicated by the sum of functions of the heat treatment temperature and time after β quenching is processed within a range not exceeding 2 × 10 ⁻¹⁹ hours. Irradiation resistance is improved by maintaining excellent corrosion resistance and further controlling the crystal orientation.

(ΣAi = Σti × exp (−Q / RTi) (1)
Here, ti: treatment time (hour) in the i-th heat treatment step after β quenching, Ti: treatment temperature (K) of step i, Q: activation energy, R: gas constant, Q / R = 40000.

A nuclear reactor control rod is constituted by a neutron absorber made into a composite material through such processes. For this reason, since the outstanding corrosion characteristic of the member which contacts high temperature water can be maintained, corrosion can be prevented.

  With the above configuration and operation, according to the present invention, in the nuclear reactor control rod, the residual stress in each part of the nuclear reactor control rod is reduced by forming a cross-shaped structure with a synthetic material of hafnium and a zirconium alloy, and irradiation is performed. Since growth is suppressed and corrosion resistance is improved, a longer life can be realized. For this reason, the reliability of the control rod can be improved, and a high-quality reactor control rod can be provided.

(Second Embodiment)
Next, a second embodiment of a reactor control rod composite material according to the present invention, a method for manufacturing the composite material, and a reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the second embodiment, in the reactor control rod composite materials 24 and 25 of the first embodiment, in the quenching process B after the composite material forming process A, the β region (body-centered cubic structure) of the zirconium alloy is used. Quenching is performed in the (β phase) region). β quenching is usually performed by heating to between approximately 1173K and 1373K.

In this way, by quenching in the β region of the zirconium alloy, it is possible to maintain good corrosion resistance by dissolving the additive elements in the zirconium alloy, so that the reactor control can extend the life of the reactor control rod Bar composites 24 and 25 can be obtained.

(Third embodiment)
Next, a third embodiment of a reactor control rod composite material according to the present invention, a method for producing the composite material, and a reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the second embodiment, the reactor control rod composite materials 24 and 25 of the first embodiment are used in the α + β region (hexagonal close-packed structure) of the zirconium alloy in the quenching process B after the composite material forming process A. (Alpha phase) and body centered cubic structure (β phase)). In this way, by quenching in the α + β region of the zirconium alloy, it is possible to maintain good corrosion resistance by dissolving the additive element in the zirconium alloy, so that the reactor control rod life can be extended. Control rod composites 24 and 25 can be obtained.

(Fourth embodiment)
Next, a fourth embodiment of a reactor control rod composite material, a method of manufacturing the composite material, and a reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

The fourth embodiment according to the present invention shows a method for controlling the crystal orientation in the control rod plate having the features of the nuclear reactor control rod plates of the first to third embodiments.

The workpiece after the quenching step B is cold or hot within a range of 625 ° C. or lower in the forming step C and the cumulative annealing parameter (ΣAi) expressed by the above-described formula 1 is smaller than 2 × 10 ⁻¹⁹ hours. A plate material for a nuclear reactor control rod characterized by controlling the crystal orientation 33 of the hafnium-zirconium alloy crystal 32 constituting the composite plate materials 24, 25 by maintaining the corrosion resistance as shown in FIG. It is. Since the irradiation direction can be controlled by doing in this way, it can be set as the board | plate material for nuclear reactor control rods which can prolong the damage life of a control rod.

(Fifth embodiment)
Next, a fifth embodiment of a reactor control rod composite material, a method of manufacturing the composite material, and a reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

The fifth embodiment according to the present invention shows a method for depositing a zirconium alloy in a reactor control rod plate having the characteristics of the reactor control rod plates of the first to fourth embodiments.

  A reactor control rod plate material characterized in that a zirconium alloy serving as protective plates 22 and 23 is attached to at least one surface of a hafnium metal plate 21 as a neutron absorber by hot rolling. In this way, because the hafnium material does not come into contact with the high-temperature high-pressure water, corrosion of the neutron absorber can be prevented, so that the control rod plate material can extend the damage life of the control rod. Can do.

(Sixth embodiment)
Next, a composite material for a nuclear reactor control rod, a method for producing the composite material, and a sixth embodiment of a nuclear reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

The sixth embodiment according to the present invention shows a method for depositing a zirconium alloy in the reactor control rod plate having the features of the reactor control rod plates of the first to fourth embodiments.

  It is a nuclear reactor control rod plate material characterized in that a zirconium alloy to be protective plates 22 and 23 is adhered to at least one surface of a hafnium metal plate 21 which is a neutron absorber by diffusion bonding. In this way, because the hafnium material does not come into contact with the high-temperature high-pressure water, corrosion of the neutron absorber can be prevented, so that the control rod plate material can extend the damage life of the control rod. Can do.

(Seventh embodiment)
Next, a description will be given of a seventh embodiment of a reactor control rod composite material, a method of manufacturing the composite material, and a reactor control rod using the composite material. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

The seventh embodiment according to the present invention shows a method for depositing a zirconium alloy in a reactor control rod plate having the features of the reactor control rod plates of the first to fourth embodiments.

  This is a plate for a reactor control rod, characterized in that a zirconium alloy to be the protective plates 22 and 23 is adhered to at least one surface of a hafnium metal plate 21 which is a neutron absorber by explosion. In this way, because the hafnium material does not come into contact with the high-temperature high-pressure water, corrosion of the neutron absorber can be prevented, so that the control rod plate material can extend the damage life of the control rod. Can do.

(Eighth embodiment)
Next, an eighth embodiment of a nuclear reactor control rod composite, a method for producing the composite, and a nuclear reactor control rod using the composite will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

The eighth embodiment according to the present invention shows a method for attaching a zirconium alloy in a reactor control rod plate having the characteristics of the reactor control rod plates of the first to fourth embodiments.

A reactor control rod plate material, wherein a zirconium alloy to be protective plates 22 and 23 is adhered to at least one surface of a hafnium metal plate 21 as a neutron absorber by thermal spraying. In this way, because the hafnium material does not come into contact with the high-temperature high-pressure water, corrosion of the neutron absorber can be prevented, so that the control rod plate material can extend the damage life of the control rod. Can do.

(Ninth embodiment)
Next, a ninth embodiment of a nuclear reactor control rod composite material, a method for producing the composite material, and a nuclear reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

The ninth embodiment according to the present invention shows a method for depositing a zirconium alloy in a nuclear reactor control rod plate having the characteristics of the nuclear reactor control rod plates of the first to fourth embodiments.

A reactor control rod plate material characterized in that a zirconium alloy to be protective plates 22 and 23 is attached to at least one surface of a hafnium metal plate 21 as a neutron absorber by friction stir welding as shown in FIG. is there. In this way, because the hafnium material does not come into contact with the high-temperature high-pressure water, corrosion of the neutron absorber can be prevented, so that the control rod plate material can extend the damage life of the control rod. Can do.

(Tenth embodiment)
Next, a composite material for a nuclear reactor control rod, a method for producing the composite material, and a tenth embodiment of a nuclear reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the control rod plates 24 and 25 having the characteristics of the nuclear reactor control rod plates of the first to ninth embodiments, chemical components of the zirconium alloy to be attached as the protective plates 22 and 23 are shown.

The zirconium alloy adhered to the surface of the hafnium metal plate is Sn: 1.2 to 1.7% by mass, Fe; 0.07 to 0.20% by mass, Cr; 0.05 to 0.15% by mass, Ni; 0 A composite material for a nuclear reactor control rod comprising 0.03 to 0.08% by mass, the balance being Zr and inevitable impurities. By using such a zirconium alloy, it is possible to maintain good corrosion resistance even when used in the reactor, and therefore it is possible to provide a reactor control rod plate that can extend the life of the reactor control rod. .

(Eleventh embodiment)
Next, an eleventh embodiment of a nuclear reactor control rod composite material, a method for producing the composite material, and a nuclear reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the control rod plates 24 and 25 having the characteristics of the nuclear reactor control rod plates of the first to ninth embodiments, chemical components of the zirconium alloy to be adhered are shown.

The zirconium alloy to be adhered to the surface of the hafnium metal plate contains Sn: 1.2 to 1.7% by mass, Fe; 0.18 to 0.24% by mass, Cr; 0.07 to 0.13% by mass, A composite material for a nuclear reactor control rod, wherein the balance is a composition comprising Zr and inevitable impurities. By using such a zirconium alloy, good corrosion resistance can be maintained even when used in the furnace, so that it is possible to provide a control rod plate for a nuclear reactor that can extend the life of the control rod.

(Twelfth embodiment)
Next, a composite material for a nuclear reactor control rod, a method for producing the composite material, and a twelfth embodiment of a nuclear reactor control rod using the composite material will be described. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

In the control rod plates 24 and 25 having the characteristics of the nuclear reactor control rod plates of the first to ninth embodiments, chemical components of the zirconium alloy to be adhered are shown.

The zirconium alloy deposited on the surface of the hafnium plate is Nb; 0.2 to 1.5 mass%, Fe; 0.01 to 0.45 mass%, Sn; 0.02 to 0.45 mass% Sn, Cr; 0 0.05 to 0.5 mass%, Cu; 0.02 to 0.3 mass%, V; 0.1 to 0.3 mass%, and Ni; 0.01 to 0.1 mass% It is a composite material for a nuclear reactor control rod, characterized in that it has a composition composed of at least two additional elements and the balance of Zr and inevitable impurities. By using such a zirconium alloy, good corrosion resistance can be maintained even when used in the furnace, so that it is possible to provide a control rod plate for a nuclear reactor that can extend the life of the control rod.

DESCRIPTION OF SYMBOLS 1,20 ... Reactor control rod, 2 ... Wing, 3 ... Handle, 4 ... Tip structure material, 5 ... End structure material, 6 ... Tie rod, 7 ... Sheath, 9 ... Cooling hole, 10, 21 ... Neutron absorber ( Hafnium metal plate), 12 ... coma, 22, 23 ... protective plate (zirconium or zirconium alloy), 24, 25 ... composite plate material for nuclear reactor control rod, 30 ... cross, 31 ... space, 32 ... crystal, 33 ... crystal Orientation, A ... Composite material forming step, B ... Quenching step, C ... Molding step.

Claims (9)

A composite material forming step of forming a composite material by coating the surface of the hafnium plate with a zirconium alloy;
A quenching step of quenching the composite material at a temperature equal to or higher than the α-β transformation temperature of the zirconium alloy;
It consists of a molding process that performs cold working or hot working without being exposed to 625 ° C. or higher after this quenching process,
A method for producing a composite material for a nuclear reactor control rod, characterized in that the cold working or hot working in the forming step is performed in a range where the cumulative annealing parameter ΣAi does not exceed 2 × 10 ⁻¹⁹ hours according to the following formula .
ΣAi = Σti × exp (−Q / RTi)
Here, ti: treatment time (hour) in the i-th heat treatment step after β quenching.
Ti: Processing temperature (K) in step i.
Q: Activation energy.
R: Gas constant.
Q / R = 40000. The method for producing a composite material for a nuclear reactor control rod according to claim 1, wherein the quenching step is performed at a temperature in a β region or a (α + β) region of the zirconium alloy. 3. The crystal orientation of the composite material is controlled by cold working or hot working in the forming step after the quenching step. 4. Of manufacturing a composite material for a nuclear reactor control rod. In the composite material forming step, the composite material is formed by one means selected from hot rolling, diffusion bonding, explosion welding, thermal spraying, and friction stir welding for adhesion of the hafnium plate material and the zirconium alloy. A method for manufacturing a composite material for a nuclear reactor control rod according to any one of claims 1 to 3. The zirconium alloy is Sn; 1.2 to 1.7 mass%, Fe; 0.07 to 0.20 mass%, Cr; 0.05 to 0.15 mass%, Ni; 0.03 to 0.08 mass% A composite material for a nuclear reactor control rod, which is manufactured by the manufacturing method according to any one of claims 1 to 4, wherein the composite material is composed of Zr and the balance of Zr and inevitable impurities. The zirconium alloy contains Sn; 1.2 to 1.7 mass%, Fe; 0.18 to 0.24 mass%, Cr; 0.07 to 0.13 mass%, and the balance is Zr and inevitable impurities. A composite material for a nuclear reactor control rod, which is produced by the production method according to any one of claims 1 to 4, which has a composition comprising: The zirconium alloy is Nb; 0.2 to 1.5 mass%, Fe; 0.01 to 0.45 mass%, Sn; 0.02 to 0.45 mass% Sn, Cr; 0.05 to 0.5 At least two additions selected from the group consisting of wt%, Cu; 0.02-0.3 wt%, V; 0.1-0.3 wt%, and Ni; 0.01-0.1 wt% A composite material for a nuclear reactor control rod, which is produced by the production method according to any one of claims 1 to 4, wherein the composition is composed of the following elements and the balance is Zr and inevitable impurities. A control rod for a nuclear reactor manufactured by the manufacturing method according to any one of claims 1 to 4. A nuclear reactor control rod comprising the composite material for a nuclear reactor control rod according to any one of claims 5 to 7.

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