EP4189706A1 - Nuclear fuel cladding element and method for manufacturing said cladding element - Google Patents

Nuclear fuel cladding element and method for manufacturing said cladding element

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Publication number
EP4189706A1
EP4189706A1 EP21752046.9A EP21752046A EP4189706A1 EP 4189706 A1 EP4189706 A1 EP 4189706A1 EP 21752046 A EP21752046 A EP 21752046A EP 4189706 A1 EP4189706 A1 EP 4189706A1
Authority
EP
European Patent Office
Prior art keywords
deposition
protective coating
substrate
target
carried out
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21752046.9A
Other languages
German (de)
French (fr)
Inventor
Pierre Barberis
Jeremy BISCHOFF
Karl Buchanan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Areva NP SAS
Original Assignee
Framatome SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Framatome SA filed Critical Framatome SA
Publication of EP4189706A1 publication Critical patent/EP4189706A1/en
Pending legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/02—Fuel elements
    • G21C3/04—Constructional details
    • G21C3/06—Casings; Jackets
    • G21C3/07—Casings; Jackets characterised by their material, e.g. alloys
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/0021—Reactive sputtering or evaporation
    • C23C14/0036—Reactive sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/04—Coating on selected surface areas, e.g. using masks
    • C23C14/046—Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon
    • C23C14/16—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon
    • C23C14/165—Metallic material, boron or silicon on metallic substrates or on substrates of boron or silicon by cathodic sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3435—Applying energy to the substrate during sputtering
    • C23C14/345—Applying energy to the substrate during sputtering using substrate bias
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/3485—Sputtering using pulsed power to the target
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • C23C14/351—Sputtering by application of a magnetic field, e.g. magnetron sputtering using a magnetic field in close vicinity to the substrate
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
    • G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/02—Fuel elements
    • G21C3/04—Constructional details
    • G21C3/045—Pellets
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
    • G21C3/02—Fuel elements
    • G21C3/04—Constructional details
    • G21C3/16—Details of the construction within the casing
    • G21C3/20—Details of the construction within the casing with coating on fuel or on inside of casing; with non-active interlayer between casing and active material with multiple casings or multiple active layers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • Nuclear fuel cladding element and method of manufacturing such a cladding element
  • the present invention relates to the field of nuclear fuel cladding, in particular nuclear fuel rod cladding, and their method of manufacture.
  • the nuclear fuel including the fissile material is generally contained in a sealed sheath which prevents the dispersion of the nuclear fuel.
  • the nuclear fuel assemblies used in light water reactors generally comprise a bundle of nuclear fuel rods, each nuclear fuel rod comprising a sheath containing nuclear fuel, the sheath being formed of a sheath tube closed at each of its both ends by a plug.
  • the cladding tubes of the nuclear fuel assemblies are made, for example, of zirconium or of a zirconium-based alloy. Such alloys exhibit high performance under normal conditions of use in nuclear reactors. However, they can reach their limits, particularly in terms of temperature during severe accident conditions, such as during a loss of cooling fluid accident (or LOCA for "Loss Of Coolant Accident").
  • the temperature can reach more than 800°C and the cooling fluid is essentially in the form of water vapour.
  • This can cause rapid degradation of the cladding tube, with in particular the release of hydrogen and rapid oxidation of the cladding tube leading to its embrittlement or even to its bursting, and therefore to the release of nuclear fuel from the cladding.
  • part of the hydrogen produced is absorbed (hydriding) by the sheath, leading to its embrittlement.
  • WO2016/042262A1 proposes a nuclear fuel cladding comprising a substrate made of zirconium or zirconium alloy and covered with a protective coating made of chromium or chromium alloy, the protective coating having a columnar microstructure.
  • One of the aims of the invention is to provide a nuclear fuel cladding element which has satisfactory resistance to hydriding and/or oxidation.
  • the invention proposes a nuclear fuel cladding element, the cladding element comprising a substrate made of a material based on zirconium and a protective coating externally covering the substrate, the protective coating being made of a chromium-based material, in which the protective coating has a columnar microstructure composed of columnar grains and has on its outer surface a density of microdroplets lower than 100 per mm 2 .
  • the columnar microstructure provides a ductile protective coating that can resist deformation, which limits the risk of cracks appearing in the event of deformation of the cladding element.
  • the appearance of a crack would be likely to expose the substrate to the external environment, which could cause its degradation and weakening, and ultimately lead to an opening of the cladding element.
  • microdroplets Limiting the density of the microdroplets present on the surface of the protective coating makes it possible to further improve the resistance of the sheathing element. Indeed, the presence of microdroplets limits the protection conferred by the protective coating by allowing the infiltration of cooling fluid along the borders of the microdroplets, reducing the resistance to corrosion and oxidation of the cladding element, especially at high temperature.
  • the microdroplets constitute discontinuities in the microstructure of the protective coating, which form points of weakness and which are likely to initiate cracks in the protective coating.
  • the presence of microdroplets affects at least locally the microstructure of the protective coating, the columnar grains generally having a larger average diameter under the microdroplets.
  • the sheathing element comprises one or more of the following optional characteristics, taken individually or according to all technically possible combinations:
  • the columnar grains have an average diameter equal to or less than 1 mhi, preferably equal to or less than 0.5 mhi;
  • the columnar grains have an average diameter between 0.05 mhi and 5 mhi, preferably between 0.1 mhi and 2 mhi;
  • the microdroplets have a diameter equal to or less than 20 mhi;
  • the protective coating has a thickness of between 5 mhi and 25 mhi.
  • the protective coating is made of a chromium-based material, for example pure chromium or a chromium-based alloy, for example a binary chromium alloy, in particular a binary chromium-aluminum alloy, a binary chromium alloy - nitrogen or a chromium-titanium binary alloy;
  • the sheathing element is a sheathing tube, in particular a nuclear fuel rod sheathing tube.
  • the invention also relates to a nuclear fuel element comprising nuclear fuel placed inside a cladding formed by at least one cladding element as defined above.
  • the invention also relates to a nuclear fuel rod comprising nuclear fuel disposed inside a sheath formed of a tubular sheathing element as defined above, closed at its ends by plugs.
  • the invention also relates to a method of manufacturing a sheathing element as defined above, comprising obtaining the substrate and then depositing the protective coating on the substrate by physical vapor deposition by cathodic sputtering of a target or by physical deposition by cold spraying.
  • the deposition of the protective coating by physical vapor deposition or by physical deposition by cold spraying, in particular by magnetron sputtering, makes it possible to obtain the columnar microstructure while limiting the density of microdroplets on the surface of the protective coating. .
  • the manufacturing method comprises one or more of the following optional characteristics, taken individually or according to all technically possible combinations:
  • the deposition is carried out by physical vapor deposition by magnetron sputtering
  • the substrate is in the form of a plate and the deposition step is carried out in such a way that the rate of deposition of the protective coating on the substrate is between 1 pm/h and 30 pm/h;
  • the substrate is a tube having a central axis
  • the deposition step is carried out by driving the substrate in rotation around its central axis and in such a way that the rate of deposition of the protective coating on the substrate is between 1 /p pm/h and 30/p pm/h;
  • the deposition is carried out by physical vapor deposition by supplying the target with direct current so as to obtain a current density of between 0.0005 A/cm 2 and 0.1 A/cm 2 on the target or with pulsed current with current peaks so as to obtain a current density of between 0.01 A/cm 2 and 5 A/cm 2 on the target during current peaks;
  • the deposition is carried out by physical vapor deposition with an electrical bias voltage of the substrate relative to the target during the physical vapor deposition, which is negative and between - 10 V and - 200 V.
  • FIG. 1 is a schematic view in longitudinal section of a nuclear fuel rod
  • FIG. 2 is a schematic cross-sectional view of a cladding tube of a nuclear fuel rod
  • FIG. 3 is a micrograph of a section of a protective coating deposited on a substrate
  • FIG. 4 is a schematic view of a region of the surface of a protective coating, illustrating the presence of microdroplets
  • FIG. 5 is a schematic view of an assembly for depositing a coating on a substrate by physical vapor deposition
  • FIG. 8 is a photograph taken under a microscope of the surface of a protective coating deposited on a substrate by physical vapor deposition by cathodic evaporation by arc with heating of the substrate.
  • Figure 1 illustrates a nuclear fuel rod 2 intended for example to be used in a light water reactor, in particular a pressurized water reactor (or PWR for "Pressurized Water Reactor”) or a boiling water reactor (or BWR for “Boiling Water Reactor”), a reactor of the “VVER” type, a reactor of the “RBMK” type, or a heavy water reactor, for example of the “CANDU” type.
  • a pressurized water reactor or PWR for "Pressurized Water Reactor”
  • BWR Boiling Water Reactor
  • the nuclear fuel rod 2 has the shape of an elongated rod along a rod axis A.
  • the nuclear fuel rod 2 comprises a sheath 4 containing nuclear fuel.
  • the sheath 4 comprises a tubular sheathing element 6 (or “sheathing tube”), extending along the pencil axis A and closed at each of its ends by a plug 8.
  • the nuclear fuel is in the form of a stack of pellets 10 stacked axially inside the cladding element 6, each pellet 10 containing fissile material.
  • the stack of pellets 10 is also called "fissile column”.
  • the nuclear fuel rod 2 comprises a spring 12 arranged inside the sheathing element 6, between the stack of pellets 10 and one of the plugs 8, to push the stack of pellets 10 towards the other cap 8.
  • a void or plenum 14 and present between the stack of pellets 10 is the plug on which the spring 12 bears.
  • FIG. 2 which shows a cross-sectional view of the sheathing element 6, the latter comprises a substrate 16 covered on the outside with a protective coating 18.
  • Substrate 16 has an inner surface 16A facing the inside of sheath 4, and an outer surface 16B facing outside of sheath 4.
  • Protective coating 18 covers outer surface 16B of substrate 16 to protect it of the external environment.
  • the sheathing element 6 is here a tube, and, correspondingly, the substrate 16 here has a tubular shape.
  • the substrate 16 is for example made of a material based on zirconium.
  • a zirconium-based material means a pure zirconium or zirconium-based alloy material.
  • a pure zirconium material is a material comprising at least 99% by weight of zirconium.
  • a zirconium-based alloy is an alloy comprising at least 95% by weight of zirconium.
  • the zirconium-based alloy is for example chosen from one of the known alloys such as M5, ZIRLO, E110, HANA and N36.
  • the substrate 16 has for example a thickness of between 0.4 mm and 1 mm.
  • the thickness of the substrate 16 is the distance between the internal surface 16A and the external surface 16B of the substrate 16.
  • the protective coating 18 is a thin layer having for example a thickness strictly less than that of the substrate 16.
  • the protective coating 18 has for example a thickness comprised between 5 ⁇ m and 25 ⁇ m, in particular a thickness comprised between 10 ⁇ m and 20 ⁇ m.
  • the thickness of the protective coating 18 is taken perpendicular to the surface on which the protective coating 18 is deposited, here the outer surface 16B of the substrate 16.
  • the protective coating 18 is the outermost layer of the sheath element 6.
  • the protective coating 18 is in contact with the external environment.
  • the protective coating 18 is made of a chromium-based material.
  • a chromium-based material means a pure chromium material or a chromium-based alloy.
  • a pure chromium material is a material comprising at least 99% by weight of chromium.
  • a chromium-based alloy is an alloy comprising at least 85% by weight of chromium.
  • the chromium-based material is a chromium-based alloy chosen from: a binary chromium-aluminum alloy (CrAI), a binary chromium-nitrogen alloy (CrN) and a binary chromium-titanium alloy (CrTi ).
  • the protective coating 18 comprises a single layer made of chromium-based material or several superimposed layers made of chromium-based material, preferably with the same chromium-based material.
  • the structure of the protective coating 18 in several superimposed layers results for example from the deposition process used to deposit the protective coating 18 on the substrate 16.
  • the protective coating 18 has a columnar microstructure.
  • the microstructure of the protective coating 18 has columnar grains 20, ie grains which have the general shape of an elongated cylinder in a direction of extension DE perpendicular to the surface on which the protective coating 18 is deposited. , here the outer surface 16B of the substrate 16.
  • Each columnar grain 20 has a height, taken along the direction of extension DE of the columnar grain 20.
  • Each columnar grain 20 has a diameter.
  • the diameter of a columnar grain 20 is for example measured on a micrograph by measuring the width of the columnar grain 20, i.e. its dimension perpendicular to its direction of extension.
  • each columnar grain 20 is not perfectly cylindrical and has a diameter that can vary along the columnar grain 20.
  • columnar grains 20 do not all have the same diameter.
  • an average diameter of the columnar grains 20 of the protective coating 18 near the outer surface 18B is also possible to determine an average diameter of the columnar grains 20 of the protective coating 18 near the outer surface 18B, as the sum of the diameters of the columnar grains 20 visible on a micrograph of the coating of protection 18 near the outer surface 18B, divided by the number of columnar grains 20 considered.
  • the columnar grains 20 have an average diameter equal to or less than 1 ⁇ m, in particular an average diameter equal to or less than 0.5 ⁇ m.
  • the very fine columnar grains 2 at the interface between the substrate 16 and the protective coating 18 allow good cohesion of the protective coating 18 on the substrate 16.
  • the diameter of the columnar grains 20 tends to increase.
  • the columnar grains 20 Preferably, near the outer surface 18B of the protective coating 18, the columnar grains 20 have an average diameter of between 0.05 ⁇ m and 5 ⁇ m, preferably between 0.1 ⁇ m and 2 ⁇ m.
  • the relatively fine columnar grains 20 on the outer surface 18B of the protective coating 18 limit the fragility and the risk of flaking of the protective coating 18.
  • microdroplets 22 may appear on the outer surface 18B of the protective coating 18.
  • the density of microdroplets 22 on the outer surface 18B of the coating 18 is equal to or less than 100 per mm 2 , in particular equal to or less than 10 per mm 2 .
  • the density of microdroplets 22 on the outer surface 18B of the protective coating 18 is for example determined by observation under an optical or electron microscope of a given reference region of the outer surface 18B, preferably on which represents a sample representative of the homogeneity of the outer surface 18B.
  • the density of microdroplets 22 on the outer surface 18B of the protective coating 18 is for example determined as the number of microdroplets 22 present in the reference region of the outer surface 18B of the protective coating 18, divided by the area of the region reference.
  • the reference region represents for example a fraction of the outer surface 18B of the protective coating 18.
  • the area of the reference region is large enough for the measurement carried out to be representative.
  • the area of the reference region is equal to or greater than 10 mm 2 .
  • the microdroplets 22 present on the external surface 18B have a diameter equal to or less than 20 ⁇ m.
  • the outer surface 18B is devoid of microdroplets having a diameter greater than 20 ⁇ m.
  • Each microdroplet 22 present on the outer surface 18B of the protective coating 18 promotes in operation the infiltration of cooling fluid (typically water) along the boundaries between the microdroplet 22 with the columnar grains 22, which reduces the resistance corrosion of the cladding element and the resistance to oxidation of the cladding element, in particular at high temperature (typically 280°C to 350°C in normal operation and between 800°C and 1200°C in accident conditions, in a pressurized water reactor).
  • cooling fluid typically water
  • each microdroplet 22 defines a discontinuity in the microstructure of the protective coating 18, which weakens the protective coating 18 by constituting a point of weakness and by being liable to initiate cracks in the protective coating 18.
  • each microdroplet 22 locally affects the formation of the microstructure of the protective coating 18, generally by causing the growth of grains of larger diameter under the microdroplet 22.
  • microdroplets can be the source of crack creation.
  • the absence of microdroplets with a diameter greater than 20 mhi limits this risk.
  • the deposition of the protective coating 18 is carried out in such a way as to avoid the formation of microdroplets with a diameter greater than 20 mhi.
  • the sheathing element 6 described above is a sheathing tube for the production of a nuclear fuel rod 2 comprising nuclear fuel disposed inside the sheathing element 6 closed in leaktight manner at each of its ends. by a cap.
  • the cladding element 6 is in the form of a plate, for example to form a nuclear fuel element 2 in the form of a plate comprising a layer of nuclear fuel interposed (ie sandwiched) between two elements of sheathing 6 in the form of a plate.
  • Such a sheathing element 6 in the form of a plate is produced analogously to what has been described above, in particular as regards the material of the substrate 16, the material of the protective coating 18, the thickness of the substrate 16 , the thickness of the protective coating 18, the microstructure of the protective coating 18 and the droplet limitation on the outer surface 18B of the protective coating 18.
  • the manufacturing method includes a step for obtaining the substrate 16.
  • the substrate 16 is a tube, which has for example an external diameter between 8 mm and 15 mm, in particular between 9 mm and 13 mm, and/or a length of between 1 m and 5 m, in particular between 2 m and 5 m.
  • Such a tube is for example obtained in a known manner by crawl step rolling, from a tubular blank of larger diameter and shorter length than the tube.
  • the manufacturing method then comprises a step of depositing the coating on the outer surface 16B of the substrate 16, for example by physical vapor deposition by cathodic sputtering.
  • the substrate 16 and a target 24, which is made of a suitable material to form the protective coating 18, are placed in a rarefied atmosphere, formed for example of an inert gas, such as argon, and an electrical potential difference is generated between target 24 and substrate 16, target 24 defining a cathode and substrate 16 defining an anode (target 24 is brought to an electrical potential higher than that of substrate 16) .
  • a rarefied atmosphere formed for example of an inert gas, such as argon
  • the target 24 is for example made of pure chromium.
  • the target 24 is for example made of a chromium alloy having different proportions, but allowing the deposition of a protective coating with the targeted proportions (for example a target in chromium-aluminum alloy with 15% by weight of aluminum in order to obtain a protective coating in chromium-aluminum alloy with 10% by weight of aluminum).
  • the deposition step is carried out using a physical vapor deposition installation 26, comprising a chamber 28, the target 24 disposed inside the chamber 28, and a pump 30 whose inlet is fluidically connected to chamber 28 to generate a rarefied atmosphere in chamber 26, and an electric circuit 32 to generate a potential difference between the target 24 and the substrate 16 introduced inside the chamber 28.
  • the substrate 16 is introduced into the chamber 28, a rarefied atmosphere is created in the chamber 28 using the pump 30, and the potential difference between the target 24 and the substrate 14 is generated by the electric circuit 32, which makes it possible to carry out the physical vapor deposition.
  • the physical vapor deposition is carried out by magnetron sputtering.
  • a magnetic field is generated, preferably at least close to the target 24.
  • the magnetic field is generated for example by one or more permanent magnets 34, as illustrated in Figure 4, and/or one or more electromagnets.
  • the substrate 16 has the shape of a tube, in particular a tube having a symmetry of revolution around a central axis, as is the case for a substrate 16 for a sheathing tube of a pencil of nuclear fuel, during the deposition step, the substrate 16 is rotated around its central axis.
  • the protective coating 18 is preferably deposited on the tube-shaped substrate having a central axis by causing the substrate 16 to rotate around this central axis and in such a way that the deposition speed of the protective coating 18 on the substrate 16 is between 1/p prn/h and 30/p prn/h.
  • a sheathing element 6 in the form of a plate, so that the outer surface 16B of the substrate 16 is substantially planar.
  • a cladding element 6 makes it possible to form a nuclear fuel element in the general shape of a plate, comprising nuclear fuel interposed (or sandwiched) between two cladding elements 6 in the form of a plate.
  • the deposition step is carried out without rotation of the substrate 16.
  • the deposition of the protective coating 18 on a plate-shaped substrate is carried out in such a way that the rate of deposition of the protective coating 18 on the substrate 16 is between 1 ⁇ m/h and 30 ⁇ m/h.
  • the deposition rate of the protective coating 18 conditions the microstructure of the protective coating 18 which will be obtained.
  • the deposition rates proposed above make it possible to obtain a desired microstructure, ie a columnar microstructure with columnar grains having a small diameter at the interface between the substrate 18 and the protective coating 18, and a diameter not too large at the outer surface 18B of the protective coating, as indicated above.
  • the deposition rate of the protective coating 18 by physical vapor deposition by cathode sputtering, in particular by magnetron cathode sputtering, is a function in particular of the current density passing through the target 24 and of the polarization of the substrate, ie of the difference le electrical potential of substrate 16 and the electrical potential of target 24 during deposition.
  • physical vapor deposition can be performed with continuous current density (i.e. applying a continuous electric current to target 24) or pulsed current density (i.e. applying a pulsed electric current comprising pulses).
  • the current density of the target is the intensity of the current passing through the target divided by the area of the active surface of the target, ie the surface of the target which is turned towards the substrate 16 and which receives the charged particles of the plasma projected onto target 24.
  • the deposition of the protective coating 18 is carried out by supplying the target 24 with a direct current so as to obtain for the target 24 a current density of between 0.0005 A/cm 2 and 0.1 A /cm 2 , preferably between 0.0005 A/cm 2 and 0.05 A/cm 2 , or by supplying the target 24 with a pulsed current with current peaks so as to obtain for the target 24 a density of current of between 0.01 A/cm 2 and 5 A/cm 2 during current peaks (ie peak current density), preferably of between 0.01 A/cm 2 and 0.5 A/cm 2 .
  • the target power density is the electrical power passing through the target divided by the active surface area of the target.
  • the deposition of the protective coating 18 is carried out by supplying the target 24 with a direct current so as to obtain for the target 24 a power density of between 0.5 W/cm2 and 100 W/cm 2 , preferably a density of power between 0.5 W/cm2 and 50 W/cm 2 , or by supplying the target 24 with a pulsed current with current peaks so as to obtain for the target 24 a power density of between 10 W/cm2 and 50,000 W/cm 2 (ie the peak power density), preferably a power density of between 10 W/cm 2 and 5,000 W/cm 2 .
  • the electrical bias voltage of substrate 16 relative to target 24 during physical vapor deposition is negative and between -10 V and -200 V, more preferably between -50 V and -150 V.
  • the deposition is carried out with a pulsed current with one or more of the following parameters:
  • the average power density (the average over time of the electrical power density passing through the target 24) is between 1 W/cm 2 and 5 W/cm 2 ;
  • the peak power density (the electrical power passing through the target 24 at each current pulse per unit area of the target 24) is between 30 W/cm2 and 100 W/cm2;
  • the frequency of the current pulses is between 50 Hz and 5000 Hz;
  • the duration of the current pulses is between 10 ps and 50 ps;
  • the pressure residing inside the chamber in which the physical vapor deposition is carried out is between 0.1 Pa and 0.4 Pa;
  • the distance between the substrate 16 and the target 24 is between 50 mm and 200 mm, more preferably between 80 mm and 140 mm.
  • the physical vapor deposition is carried out on the substrate 16 without any heat input other than that resulting from the bombardment of the substrate 16 by the particles (atoms, ions, etc.) torn from the target 24 due to the setting in implementation of physical vapor deposition.
  • the substrate 16 is not heated using a heating device. This makes it possible to limit the risk of exceeding the phase transition temperature of the material of the substrate 16.
  • Physical vapor deposition by magnetron cathode sputtering can be carried out using one of the following techniques or a combination of at least two of the following techniques: DC magnetron cathode sputtering, cathode sputtering magnetron in pulsed direct current (in English "Pulsed Direct Current” or “DC pulsed"), sputtering High Power Impulse Magnetron Sputtering (HiPIMS or HPMS), Bipolar Magnetron Sputtering (MSB), Dual Magnetron Sputtering Magnetron Sputtering” (DMS)), unbalanced magnetron sputtering (in English “Unbalanced Magnetron Sputtering” (UBM)).
  • DC magnetron cathode sputtering cathode sputtering magnetron in pulsed direct current (in English "Pulsed Direct Current” or “DC pulsed")
  • HiPIMS or HPMS sputtering High Power Impulse Magnetron Sputtering
  • MSB Bipolar Magnetr
  • Figures 6 to 8 are photographs taken under a microscope of the surface of protective coatings 18 deposited on a substrate 16 by physical vapor deposition by magnetron sputtering with pulsed current, under an argon atmosphere, with different sets of parameters, shown in Table 1 below:
  • Example 1 and Example 2 are carried out respecting the physical vapor deposition parameters indicated above, while Example 3 is not carried out respecting all these parameters.
  • the protective coating 18 has few droplets G on its outer surface 18B.
  • the protective coating 18 has on its outer surface 18B a density of microdroplets of 50 per mm 2 .
  • Example 1 gave a result similar to that of example 2, the protective coating 18 having on its outer surface 18B a density of microdroplets of 50 per mm 2 .
  • the protective coating 18 of example 3 illustrated by FIG. 7 was also produced by physical vapor deposition by magnetron sputtering but outside the recommended ranges, in particular for the pressure and the peak power density.
  • the density of microdroplets is in this case approximately 2500 microdroplets per mm 2 , which is much higher than the desired maximum density of microdroplets which is 100 microdroplets per mm 2 .
  • the protective coating 18 of the example in Figure 8 was fabricated by physical vapor deposition by sputtering by arc with heating of the substrate and parameters different from those of magnetron sputtering.
  • the protective coating 18 has on its outer surface 18B a density of microdroplets greater than 10,000 per mm 2 .
  • the deposition of the protective coating can be carried out according to another technique, for example by physical deposition by cold spraying.
  • the invention it is possible to obtain a nuclear fuel cladding element which has good resistance to oxidation and to hydriding, in normal operation of the nuclear reactor and in accident conditions, for example during a loss of coolant accident.

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Abstract

The nuclear fuel cladding element comprises a substrate (16) made of a material based on zirconium and a protective coating (18) externally covering the substrate (16), the protective coating (18) being made of a material based on chromium, and having a columnar microstructure composed of columnar grains (20) and having on its outer surface (18B) a microdroplet density of less than 100 per mm2.

Description

DESCRIPTION DESCRIPTION
Elément de gainage de combustible nucléaire et procédé de fabrication d’un tel élément de gainage Nuclear fuel cladding element and method of manufacturing such a cladding element
La présente invention concerne le domaine des gaines de combustible nucléaire, en particulier des gaines de crayon de combustible nucléaire, et leur procédé de fabrication. The present invention relates to the field of nuclear fuel cladding, in particular nuclear fuel rod cladding, and their method of manufacture.
Le combustible nucléaire incluant la matière fissile est généralement contenu dans une gaine étanche qui évite la dispersion du combustible nucléaire. The nuclear fuel including the fissile material is generally contained in a sealed sheath which prevents the dispersion of the nuclear fuel.
Les assemblages de combustible nucléaire utilisés dans les réacteurs à eau légère comprennent généralement un faisceau de crayons de combustible nucléaire, chaque crayon de combustible nucléaire comprenant une gaine contenant du combustible nucléaire, la gaine étant formée d’un tube de gainage fermé à chacune de ses deux extrémités par un bouchon. The nuclear fuel assemblies used in light water reactors generally comprise a bundle of nuclear fuel rods, each nuclear fuel rod comprising a sheath containing nuclear fuel, the sheath being formed of a sheath tube closed at each of its both ends by a plug.
Les tubes de gainage des assemblages de combustible nucléaire sont réalisés par exemple en zirconium ou en alliage à base de zirconium. De tels alliages présentent des performances élevées en conditions normales d’utilisation dans les réacteurs nucléaires. Cependant, ils peuvent atteindre leurs limites notamment en terme de température lors de conditions accidentelles sévères, comme par exemple lors d’un accident de perte de fluide de refroidissement (ou LOCA pour « Loss Of Coolant Accident » en anglais). The cladding tubes of the nuclear fuel assemblies are made, for example, of zirconium or of a zirconium-based alloy. Such alloys exhibit high performance under normal conditions of use in nuclear reactors. However, they can reach their limits, particularly in terms of temperature during severe accident conditions, such as during a loss of cooling fluid accident (or LOCA for "Loss Of Coolant Accident").
Lors d’un tel évènement, la température peut atteindre plus de 800°C et le fluide de refroidissement se présente essentiellement sous forme de vapeur d’eau. Ceci peut causer une dégradation rapide du tube de gainage, avec notamment un dégagement d’hydrogène et une oxydation rapide du tube de gainage conduisant à sa fragilisation voire à son éclatement, et donc au relâchement de combustible nucléaire hors de la gaine. Lors de l’oxydation, une partie de l’hydrogène produit est absorbée (hydruration) par la gaine entraînant une fragilisation de cette dernière. During such an event, the temperature can reach more than 800°C and the cooling fluid is essentially in the form of water vapour. This can cause rapid degradation of the cladding tube, with in particular the release of hydrogen and rapid oxidation of the cladding tube leading to its embrittlement or even to its bursting, and therefore to the release of nuclear fuel from the cladding. During oxidation, part of the hydrogen produced is absorbed (hydriding) by the sheath, leading to its embrittlement.
WO2016/042262A1 propose une gaine de combustible nucléaire comprenant un substrat réalisé en zirconium ou en alliage de zirconium et recouvert d’un revêtement de protection réalisé en chrome ou en alliage de chrome, le revêtement de protection présentant une microstructure colonnaire. WO2016/042262A1 proposes a nuclear fuel cladding comprising a substrate made of zirconium or zirconium alloy and covered with a protective coating made of chromium or chromium alloy, the protective coating having a columnar microstructure.
Un des buts de l’invention est de proposer un élément de gainage de combustible nucléaire qui présente une résistance satisfaisante à l’hydruration et/ou à l’oxydation. One of the aims of the invention is to provide a nuclear fuel cladding element which has satisfactory resistance to hydriding and/or oxidation.
A cet effet, l’invention propose un élément de gainage de combustible nucléaire, l’élément de gainage comprenant un substrat réalisé dans un matériau à base de zirconium et un revêtement de protection recouvrant extérieurement le substrat, le revêtement de protection étant réalisé dans un matériau à base de chrome, dans lequel le revêtement de protection présente une microstructure colonnaire composée de grains colonnaires et présente sur sa surface externe une densité de microgouttelettes inférieure à 100 par mm2. To this end, the invention proposes a nuclear fuel cladding element, the cladding element comprising a substrate made of a material based on zirconium and a protective coating externally covering the substrate, the protective coating being made of a chromium-based material, in which the protective coating has a columnar microstructure composed of columnar grains and has on its outer surface a density of microdroplets lower than 100 per mm 2 .
La microstructure colonnaire permet d’obtenir un revêtement de protection ductile pouvant résister à la déformation, ce qui limite les risque d’apparition de fissures en cas de déformation de l’élément de gainage. L’apparition d’une fissure serait susceptible d’exposer le substrat à l’environnement extérieur, ce qui pourrait provoquer sa dégradation et son affaiblissement, et conduire in fine à une ouverture de l’élément de gainage. The columnar microstructure provides a ductile protective coating that can resist deformation, which limits the risk of cracks appearing in the event of deformation of the cladding element. The appearance of a crack would be likely to expose the substrate to the external environment, which could cause its degradation and weakening, and ultimately lead to an opening of the cladding element.
La limitation de la densité des microgouttelettes présentes à la surface du revêtement de protection permet d’améliorer encore la résistance de l’élément de gainage. En effet, la présence de microgouttelettes limite la protection conférée par le revêtement de protection en permettant l’infiltration de fluide de refroidissement le long des frontières des microgouttelettes, réduisant la résistance à la corrosion et à l’oxydation de l’élément de gainage, en particulier à haute température. Les microgouttelettes constituent des discontinuités dans la microstructure du revêtement de protection, qui forment des points de faiblesse et qui sont susceptibles d’initier des fissures dans le revêtement de protection. En outre, la présence de microgouttelettes affecte au moins localement la microstructure du revêtement de protection, les grains colonnaires présentant généralement un diamètre moyen plus élevé sous les microgouttelettes. Limiting the density of the microdroplets present on the surface of the protective coating makes it possible to further improve the resistance of the sheathing element. Indeed, the presence of microdroplets limits the protection conferred by the protective coating by allowing the infiltration of cooling fluid along the borders of the microdroplets, reducing the resistance to corrosion and oxidation of the cladding element, especially at high temperature. The microdroplets constitute discontinuities in the microstructure of the protective coating, which form points of weakness and which are likely to initiate cracks in the protective coating. In addition, the presence of microdroplets affects at least locally the microstructure of the protective coating, the columnar grains generally having a larger average diameter under the microdroplets.
Selon des modes de réalisation particuliers, l’élément de gainage comprend une ou plusieurs des caractéristiques optionnelles suivantes, prises individuellement ou selon toutes les combinaisons techniquement possibles : According to particular embodiments, the sheathing element comprises one or more of the following optional characteristics, taken individually or according to all technically possible combinations:
- à proximité de et/ou à l’interface entre l’élément de gainage et le revêtement de protection, les grains colonnaires présentent un diamètre moyen égal ou inférieur à 1 mhi, de préférence égal ou inférieur à 0,5 mhi ; - near and/or at the interface between the cladding element and the protective coating, the columnar grains have an average diameter equal to or less than 1 mhi, preferably equal to or less than 0.5 mhi;
- à proximité de et/ou sur la surface externe du revêtement de protection, les grains colonnaires présentent un diamètre moyen entre 0,05 mhi et 5 mhi, de préférence entre 0,1 mhi et 2 mhi ; - Near and / or on the outer surface of the protective coating, the columnar grains have an average diameter between 0.05 mhi and 5 mhi, preferably between 0.1 mhi and 2 mhi;
- les microgouttelettes possèdent un diamètre égal ou inférieur à 20 mhi ; - the microdroplets have a diameter equal to or less than 20 mhi;
- le revêtement de protection présente une épaisseur comprise entre 5 mhi et 25 mhi.- the protective coating has a thickness of between 5 mhi and 25 mhi.
- le revêtement de protection est réalisé en un matériau à base de chrome, par exemple en chrome pur ou en un alliage à base de chrome, par exemple un alliage binaire de chrome, en particulier un alliage binaire chrome-aluminium, un alliage binaire chrome- azote ou un alliage binaire chrome-titane ; - l’élément de gainage est un tube de gainage, en particulier un tube de gainage de crayon de combustible nucléaire. - the protective coating is made of a chromium-based material, for example pure chromium or a chromium-based alloy, for example a binary chromium alloy, in particular a binary chromium-aluminum alloy, a binary chromium alloy - nitrogen or a chromium-titanium binary alloy; - the sheathing element is a sheathing tube, in particular a nuclear fuel rod sheathing tube.
L’invention concerne aussi un élément de combustible nucléaire comprenant du combustible nucléaire disposé à l’intérieur d’une gaine formée par au moins un élément de gainage tel que défini ci-dessus. The invention also relates to a nuclear fuel element comprising nuclear fuel placed inside a cladding formed by at least one cladding element as defined above.
L’invention concerne aussi un crayon de combustible nucléaire comprenant du combustible nucléaire disposé à l’intérieur d’une gaine formée d’un élément de gainage tubulaire tel que défini ci-dessus, fermé à ses extrémités par des bouchons. The invention also relates to a nuclear fuel rod comprising nuclear fuel disposed inside a sheath formed of a tubular sheathing element as defined above, closed at its ends by plugs.
L’invention concerne également un procédé de fabrication d’un élément de gainage tel que défini ci-dessus, comprenant l’obtention du substrat puis le dépôt du revêtement de protection sur le substrat par dépôt physique en phase vapeur par pulvérisation cathodique d’une cible ou par dépôt physique par projection à froid. The invention also relates to a method of manufacturing a sheathing element as defined above, comprising obtaining the substrate and then depositing the protective coating on the substrate by physical vapor deposition by cathodic sputtering of a target or by physical deposition by cold spraying.
Le dépôt du revêtement de protection par un dépôt physique en phase vapeur ou par dépôt physique par projection à froid, en particulier par pulvérisation cathodique magnétron, permet d’obtenir la microstructure colonnaire tout en limitant la densité de microgouttelettes à la surface du revêtement de protection. The deposition of the protective coating by physical vapor deposition or by physical deposition by cold spraying, in particular by magnetron sputtering, makes it possible to obtain the columnar microstructure while limiting the density of microdroplets on the surface of the protective coating. .
Selon des modes de mise en oeuvre particuliers, le procédé de fabrication comprend une ou plusieurs des caractéristiques optionnelles suivantes, prises individuellement ou selon toutes les combinaisons techniquement possibles : According to particular embodiments, the manufacturing method comprises one or more of the following optional characteristics, taken individually or according to all technically possible combinations:
- le dépôt est effectué par dépôt physique en phase vapeur par pulvérisation cathodique magnétron ; - the deposition is carried out by physical vapor deposition by magnetron sputtering;
- le substrat est en forme de plaque et l’étape dépôt est réalisé de telle manière que la vitesse de dépôt du revêtement de protection sur le substrat est comprise entre 1 pm/h et 30 pm/h ; - the substrate is in the form of a plate and the deposition step is carried out in such a way that the rate of deposition of the protective coating on the substrate is between 1 pm/h and 30 pm/h;
- le substrat est un tube présentant un axe central, et l’étape de dépôt est réalisée en entraînant le substrat en rotation autour de son axe central et de telle manière que la vitesse de dépôt du revêtement de protection sur le substrat est comprise entre 1/p pm/h et 30/p pm/h ; - the substrate is a tube having a central axis, and the deposition step is carried out by driving the substrate in rotation around its central axis and in such a way that the rate of deposition of the protective coating on the substrate is between 1 /p pm/h and 30/p pm/h;
- le dépôt est réalisé par dépôt physique en phase vapeur en alimentant la cible en courant continu de manière à obtenir une densité de courant comprise entre 0,0005 A/cm2 et 0,1 A/cm2 sur la cible ou en courant pulsé avec des pics de courant de manière à obtenir une densité de courant comprise entre 0,01 A/cm2 et 5 A/cm2 sur la cible lors des pics de courant ; - the deposition is carried out by physical vapor deposition by supplying the target with direct current so as to obtain a current density of between 0.0005 A/cm 2 and 0.1 A/cm 2 on the target or with pulsed current with current peaks so as to obtain a current density of between 0.01 A/cm 2 and 5 A/cm 2 on the target during current peaks;
- le dépôt est réalisé par dépôt physique en phase vapeur avec une tension de polarisation électrique du substrat par rapport à la cible durant le dépôt physique en phase vapeur, qui est négative et comprise entre - 10 V et - 200 V. L’invention et ses avantages seront mieux compris à la lecture de la description qui va suivre, donnée uniquement à titre d’exemple non limitatif, et faite en référence aux dessins annexés, sur lesquels : - the deposition is carried out by physical vapor deposition with an electrical bias voltage of the substrate relative to the target during the physical vapor deposition, which is negative and between - 10 V and - 200 V. The invention and its advantages will be better understood on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:
- la Figure 1 est une vue schématique en coupe longitudinale d’un crayon de combustible nucléaire ; - Figure 1 is a schematic view in longitudinal section of a nuclear fuel rod;
- la Figure 2 est une vue schématique en coupe transversale d’un tube de gainage d’un crayon de combustible nucléaire ; - Figure 2 is a schematic cross-sectional view of a cladding tube of a nuclear fuel rod;
- la Figure 3 est une micrographie d’une coupe d’un revêtement de protection déposé sur un substrat ; - Figure 3 is a micrograph of a section of a protective coating deposited on a substrate;
- la Figure 4 est une vue schématique d’une région de la surface d’un revêtement de protection, illustrant la présence de microgouttelettes ; - Figure 4 is a schematic view of a region of the surface of a protective coating, illustrating the presence of microdroplets;
- la Figure 5 est une vue schématique d’un ensemble de dépôt d’un revêtement sur un substrat par dépôt physique en phase vapeur, et - Figure 5 is a schematic view of an assembly for depositing a coating on a substrate by physical vapor deposition, and
- les Figures 6 et 7 sont des photographies prises au microscope de la surface de revêtements de protection déposés sur un substrat par dépôt physique en phase vapeur ; et- Figures 6 and 7 are photographs taken under a microscope of the surface of protective coatings deposited on a substrate by physical vapor deposition; and
- la Figure 8 est une photographie prise au microscope de la surface d’un revêtement de protection déposé sur un substrat par dépôt physique en phase vapeur par évaporation cathodique par arc avec chauffage du substrat. - Figure 8 is a photograph taken under a microscope of the surface of a protective coating deposited on a substrate by physical vapor deposition by cathodic evaporation by arc with heating of the substrate.
La Figure 1 illustre un crayon de combustible nucléaire 2 destiné par exemple à être utilisé dans un réacteur à eau légère, en particulier un réacteur à eau sous pression (ou PWR pour « Pressurized Water Reactor ») ou un réacteur à eau bouillante (ou BWR pour « Boiling Water Reactor »), un réacteur de type « VVER », un réacteur de type « RBMK », ou un réacteur à eau lourde, par exemple de type « CANDU ». Figure 1 illustrates a nuclear fuel rod 2 intended for example to be used in a light water reactor, in particular a pressurized water reactor (or PWR for "Pressurized Water Reactor") or a boiling water reactor (or BWR for “Boiling Water Reactor”), a reactor of the “VVER” type, a reactor of the “RBMK” type, or a heavy water reactor, for example of the “CANDU” type.
Le crayon de combustible nucléaire 2 présente la forme d’une tige allongée suivant un axe de crayon A. The nuclear fuel rod 2 has the shape of an elongated rod along a rod axis A.
Le crayon de combustible nucléaire 2 comprend une gaine 4 contenant du combustible nucléaire. The nuclear fuel rod 2 comprises a sheath 4 containing nuclear fuel.
La gaine 4 comprend un élément de gainage 6 tubulaire (ou « tube de gainage »), s’étendant suivant l’axe de crayon A et fermé à chacune de ses extrémités par un bouchon 8. The sheath 4 comprises a tubular sheathing element 6 (or "sheathing tube"), extending along the pencil axis A and closed at each of its ends by a plug 8.
Le combustible nucléaire se présente sous la forme d’un empilement de pastilles 10 empilées axialement à l’intérieur de l’élément de gainage 6, chaque pastille 10 contenant du matériau fissile. L’empilement de pastilles 10 est aussi appelée « colonne fissile ». The nuclear fuel is in the form of a stack of pellets 10 stacked axially inside the cladding element 6, each pellet 10 containing fissile material. The stack of pellets 10 is also called "fissile column".
Le crayon de combustible nucléaire 2 comprend un ressort 12 disposé à l’intérieur de l’élément de gainage 6, entre l’empilement de pastilles 10 et l’un des bouchons 8, pour pousser l’empilement de pastilles 10 vers l’autre bouchon 8. Un vide ou plénum 14 et présent entre l’empilement de pastilles 10 est le bouchon sur lequel le ressort 12 prend appui. The nuclear fuel rod 2 comprises a spring 12 arranged inside the sheathing element 6, between the stack of pellets 10 and one of the plugs 8, to push the stack of pellets 10 towards the other cap 8. A void or plenum 14 and present between the stack of pellets 10 is the plug on which the spring 12 bears.
Comme illustré sur la Figure 2 qui représente une vue en coupe transversale de l’élément de gainage 6, ce dernier comprend un substrat 16 recouvert extérieurement d’un revêtement de protection 18. As illustrated in Figure 2 which shows a cross-sectional view of the sheathing element 6, the latter comprises a substrate 16 covered on the outside with a protective coating 18.
Le substrat 16 présente une surface interne 16A, tournée vers l’intérieur de la gaine 4, et une surface externe 16B tournée vers l’extérieur de la gaine 4. Le revêtement de protection 18 recouvre la surface externe 16B du substrat 16 pour le protéger de l’environnement extérieur. Substrate 16 has an inner surface 16A facing the inside of sheath 4, and an outer surface 16B facing outside of sheath 4. Protective coating 18 covers outer surface 16B of substrate 16 to protect it of the external environment.
L’élément de gainage 6 est ici un tube, et, de manière correspondante, le substrat 16 présente ici une forme tubulaire. The sheathing element 6 is here a tube, and, correspondingly, the substrate 16 here has a tubular shape.
Le substrat 16 est par exemple réalisé dans un matériau à base de zirconium.The substrate 16 is for example made of a material based on zirconium.
Dans le contexte présent, un matériau à base de zirconium désigne un matériau en zirconium pure ou en alliage à base de zirconium. In the present context, a zirconium-based material means a pure zirconium or zirconium-based alloy material.
Un matériau en zirconium pur est un matériau comprenant au moins 99 % en poids de zirconium. A pure zirconium material is a material comprising at least 99% by weight of zirconium.
Un alliage à base de zirconium est un alliage comprenant au moins 95% en poids de zirconium. L’alliage à base de zirconium est par exemple choisi parmi un des alliages connus tels que M5, ZIRLO, E110, HANA et N36. A zirconium-based alloy is an alloy comprising at least 95% by weight of zirconium. The zirconium-based alloy is for example chosen from one of the known alloys such as M5, ZIRLO, E110, HANA and N36.
Le substrat 16 présente par exemple une épaisseur comprise entre 0,4 mm et 1 mm. L’épaisseur du substrat 16 est la distance entre la surface interne 16A et la surface externe 16B du substrat 16. The substrate 16 has for example a thickness of between 0.4 mm and 1 mm. The thickness of the substrate 16 is the distance between the internal surface 16A and the external surface 16B of the substrate 16.
Le revêtement de protection 18 est une couche mince présentant par exemple une épaisseur strictement inférieure à celle du substrat 16. The protective coating 18 is a thin layer having for example a thickness strictly less than that of the substrate 16.
Le revêtement de protection 18 présente par exemple une épaisseur comprise entre 5 pm et 25 pm, en particulier une épaisseur comprise entre 10 pm et 20 pm. L’épaisseur du revêtement de protection 18 est prise perpendiculairement à la surface sur laquelle le revêtement de protection 18 est déposé, ici la surface externe 16B du substrat 16. The protective coating 18 has for example a thickness comprised between 5 μm and 25 μm, in particular a thickness comprised between 10 μm and 20 μm. The thickness of the protective coating 18 is taken perpendicular to the surface on which the protective coating 18 is deposited, here the outer surface 16B of the substrate 16.
De préférence, le revêtement de protection 18 est la couche la plus externe de l’élément de gainage 6. Le revêtement de protection 18 est en contact avec l’environnement extérieur. Preferably, the protective coating 18 is the outermost layer of the sheath element 6. The protective coating 18 is in contact with the external environment.
Le revêtement de protection 18 est réalisé dans un matériau à base de chrome.The protective coating 18 is made of a chromium-based material.
Dans le contexte présent, un matériau à base de chrome désigne un matériau en chrome pure ou un alliage à base de chrome. Un matériau en chrome pur est un matériau comprenant au moins 99% en poids de chrome. In the present context, a chromium-based material means a pure chromium material or a chromium-based alloy. A pure chromium material is a material comprising at least 99% by weight of chromium.
Un alliage à base de chrome est un alliage comprenant au moins 85% en poids de chrome. A chromium-based alloy is an alloy comprising at least 85% by weight of chromium.
Dans un exemple de réalisation, le matériau à base de chrome est un alliage à base de chrome choisi parmi : un alliage binaire chrome-aluminium (CrAI), un alliage binaire chrome-azote (CrN) et un alliage binaire chrome-titane (CrTi). In an exemplary embodiment, the chromium-based material is a chromium-based alloy chosen from: a binary chromium-aluminum alloy (CrAI), a binary chromium-nitrogen alloy (CrN) and a binary chromium-titanium alloy (CrTi ).
Le revêtement de protection 18 comprend une seule couche réalisée en matériau à base de chrome ou plusieurs couches superposées réalisée en matériau à base de chrome, de préférence avec le même matériau à base de chrome. The protective coating 18 comprises a single layer made of chromium-based material or several superimposed layers made of chromium-based material, preferably with the same chromium-based material.
La structure du revêtement de protection 18 en plusieurs couches superposées résulte par exemple du procédé de dépôt utilisé pour déposer le revêtement de protection 18 sur le substrat 16. The structure of the protective coating 18 in several superimposed layers results for example from the deposition process used to deposit the protective coating 18 on the substrate 16.
Comme illustré sur la Figure 3, le revêtement de protection 18 présente une microstructure colonnaire. En d’autres termes, la microstructure du revêtement de protection 18 possède des grains colonnaires 20, i.e. des grains qui présentent une forme générale de cylindre allongé suivant une direction d’extension DE perpendiculaire à la surface sur laquelle le revêtement de protection 18 est déposé, ici la surface externe 16B du substrat 16. As illustrated in Figure 3, the protective coating 18 has a columnar microstructure. In other words, the microstructure of the protective coating 18 has columnar grains 20, ie grains which have the general shape of an elongated cylinder in a direction of extension DE perpendicular to the surface on which the protective coating 18 is deposited. , here the outer surface 16B of the substrate 16.
Chaque grain colonnaire 20 présente une hauteur, prise suivant la direction d’extension DE du grain colonnaire 20. Each columnar grain 20 has a height, taken along the direction of extension DE of the columnar grain 20.
Chaque grain colonnaire 20 présentent un diamètre. Le diamètre d’un grain colonnaires 20 est par exemple mesuré sur une micrographie en mesurant la largeur du grain colonnaire 20, i.e. sa dimension perpendiculairement à sa direction d’extension. Each columnar grain 20 has a diameter. The diameter of a columnar grain 20 is for example measured on a micrograph by measuring the width of the columnar grain 20, i.e. its dimension perpendicular to its direction of extension.
Bien entendu, chaque grain colonnaire 20 n’est pas parfaitement cylindrique et présente un diamètre pouvant varier le long du grain colonnaire 20. Of course, each columnar grain 20 is not perfectly cylindrical and has a diameter that can vary along the columnar grain 20.
En outre, les grains colonnaires 20 ne présentent pas tous le même diamètre.In addition, the columnar grains 20 do not all have the same diameter.
Il est possible de déterminer un diamètre moyen des grains colonnaires 20 du revêtement de protection 18 à l’interface entre le substrat 16 et le revêtement de protection 18 (i.e. à proximité de la surface interne 18A du revêtement de protection 18), comme la somme des diamètres de grains colonnaires 20 visibles sur une micrographie du revêtement de protection 18 à l’interface entre le substrat 16 et le revêtement de protection 18, divisée par le nombre de grains colonnaires 20 considérés. It is possible to determine an average diameter of the columnar grains 20 of the protective coating 18 at the interface between the substrate 16 and the protective coating 18 (ie close to the internal surface 18A of the protective coating 18), as the sum diameters of columnar grains 20 visible on a micrograph of the protective coating 18 at the interface between the substrate 16 and the protective coating 18, divided by the number of columnar grains 20 considered.
Il est aussi possible de déterminer un diamètre moyen des grains colonnaires 20 du revêtement de protection 18 à proximité de la surface externe 18B, comme la somme des diamètres de grains colonnaires 20 visibles sur une micrographie du revêtement de protection 18 à proximité de la surface externe 18B, divisée par le nombre de grains colonnaires 20 considérés. It is also possible to determine an average diameter of the columnar grains 20 of the protective coating 18 near the outer surface 18B, as the sum of the diameters of the columnar grains 20 visible on a micrograph of the coating of protection 18 near the outer surface 18B, divided by the number of columnar grains 20 considered.
De préférence, à l’interface entre le substrat 16 et le revêtement de protection 18, les grains colonnaires 20 présentent un diamètre moyen égal ou inférieur à 1 pm, en particulier un diamètre moyen égal ou inférieur à 0,5 pm. Preferably, at the interface between the substrate 16 and the protective coating 18, the columnar grains 20 have an average diameter equal to or less than 1 μm, in particular an average diameter equal to or less than 0.5 μm.
Les grains colonnaires 2 très fins à l’interface entre le substrat 16 et le revêtement de protection 18 permettent une bonne cohésion du revêtement de protection 18 sur le substrat 16. The very fine columnar grains 2 at the interface between the substrate 16 and the protective coating 18 allow good cohesion of the protective coating 18 on the substrate 16.
En s’éloignant de l’interface entre le substrat 16 et le revêtement de protection 18, le diamètre des grains colonnaires 20 a tendance à augmenter. Moving away from the interface between the substrate 16 and the protective coating 18, the diameter of the columnar grains 20 tends to increase.
De préférence, à proximité de la surface externe 18B du revêtement de protection 18, les grains colonnaires 20 présentent un diamètre moyen compris entre 0,05 pm et 5 pm, de préférence entre 0,1 pm et 2 pm. Preferably, near the outer surface 18B of the protective coating 18, the columnar grains 20 have an average diameter of between 0.05 μm and 5 μm, preferably between 0.1 μm and 2 μm.
Les grains colonnaires 20 relativement fins à la surface externe 18B du revêtement de protection 18 limitent la fragilité et le risque d’écaillage du revêtement de protection 18. The relatively fine columnar grains 20 on the outer surface 18B of the protective coating 18 limit the fragility and the risk of flaking of the protective coating 18.
Lors d’un dépôt du revêtement 18, en particulier un dépôt physique en phase vapeur, il peut apparaître des microgouttelettes 22 sur la surface externe 18B du revêtement de protection 18. During a deposition of the coating 18, in particular a physical vapor deposition, microdroplets 22 may appear on the outer surface 18B of the protective coating 18.
De préférence, la densité de microgouttelettes 22 sur la surface externe 18B du revêtement 18 est égale ou inférieure à 100 par mm2, en particulier égale ou inférieure à 10 par mm2. Preferably, the density of microdroplets 22 on the outer surface 18B of the coating 18 is equal to or less than 100 per mm 2 , in particular equal to or less than 10 per mm 2 .
La densité de microgouttelettes 22 à la surface externe 18B du revêtement de protection 18 est par exemple déterminée par observation au microscope optique ou électronique d’une région de référence donnée de la surface externe 18B, de préférence sur qui représente un échantillon représentatif de l’homogénéité de la surface externe 18B. The density of microdroplets 22 on the outer surface 18B of the protective coating 18 is for example determined by observation under an optical or electron microscope of a given reference region of the outer surface 18B, preferably on which represents a sample representative of the homogeneity of the outer surface 18B.
La densité de microgouttelettes 22 à la surface externe 18B du revêtement de protection 18 est par exemple déterminée comme le nombre de microgouttelettes 22 présentes dans la région de référence de la surface externe 18B du revêtement de protection 18, divisée par l’aire de la région de référence. The density of microdroplets 22 on the outer surface 18B of the protective coating 18 is for example determined as the number of microdroplets 22 present in the reference region of the outer surface 18B of the protective coating 18, divided by the area of the region reference.
La région de référence représente par exemple une fraction de la surface externe 18B du revêtement de protection 18. L’aire de la région de référence est suffisamment grande pour que la mesure effectuée soit représentative. De préférence, l’aire de la région de référence est égale ou supérieure 10 mm2. The reference region represents for example a fraction of the outer surface 18B of the protective coating 18. The area of the reference region is large enough for the measurement carried out to be representative. Preferably, the area of the reference region is equal to or greater than 10 mm 2 .
De préférence, les microgouttelettes 22 présentes sur la surface externe 18B possède un diamètre égal ou inférieur à 20 pm. En d’autres termes, la surface externe 18B est dépourvue de microgouttelette ayant un diamètre supérieur à 20 pm. Chaque microgouttelette 22 présente à la surface externe 18B du revêtement de protection 18 favorise en fonctionnement l’infiltration de fluide de refroidissement (typiquement de l’eau) le long des frontières entre la microgouttelette 22 avec les grains colonnaires 22, ce qui réduit la résistance à la corrosion de l’élément de gainage et la résistance à l’oxydation de l’élément de gainage, en particulier à haute température (typiquement 280 °C à 350 °C en fonctionnement normal et entre 800 °C et 1200 °C en conditions accidentelles, dans un réacteur à eau sous pression). Preferably, the microdroplets 22 present on the external surface 18B have a diameter equal to or less than 20 μm. In other words, the outer surface 18B is devoid of microdroplets having a diameter greater than 20 μm. Each microdroplet 22 present on the outer surface 18B of the protective coating 18 promotes in operation the infiltration of cooling fluid (typically water) along the boundaries between the microdroplet 22 with the columnar grains 22, which reduces the resistance corrosion of the cladding element and the resistance to oxidation of the cladding element, in particular at high temperature (typically 280°C to 350°C in normal operation and between 800°C and 1200°C in accident conditions, in a pressurized water reactor).
En outre, chaque microgouttelette 22 définit une discontinuité dans la microstructure du revêtement de protection 18, qui fragilise le revêtement de protection 18 en constituant un point de faiblesse et en étant susceptible d’initier des fissures dans le revêtement de protection 18. In addition, each microdroplet 22 defines a discontinuity in the microstructure of the protective coating 18, which weakens the protective coating 18 by constituting a point of weakness and by being liable to initiate cracks in the protective coating 18.
Au surplus, chaque microgouttelette 22 affecte localement la formation de la microstructure du revêtement de protection 18, généralement en provoquant la croissance de grains de plus gros diamètre sous la microgouttelette 22. Moreover, each microdroplet 22 locally affects the formation of the microstructure of the protective coating 18, generally by causing the growth of grains of larger diameter under the microdroplet 22.
La limitation de la densité des microgouttelettes 22 présentes à la surface externe 18B du revêtement de protection 18 permet donc d’améliorer la résistance de l’élément de gainage 6. Limiting the density of the microdroplets 22 present on the outer surface 18B of the protective coating 18 therefore makes it possible to improve the resistance of the sheathing element 6.
Par ailleurs, les grosses microgouttelettes peuvent être la source de création de fissure. L’absence de microgouttelette de diamètre supérieur à 20 mhi limite ce risque. Le dépôt du revêtement de protection 18 est effectué de manière à éviter la formation de microgouttelette de diamètre supérieur à 20 mhi. Furthermore, large microdroplets can be the source of crack creation. The absence of microdroplets with a diameter greater than 20 mhi limits this risk. The deposition of the protective coating 18 is carried out in such a way as to avoid the formation of microdroplets with a diameter greater than 20 mhi.
L’élément de gainage 6 décrit ci-dessus est un tube gainage pour la réalisation d’un crayon de combustible nucléaire 2 comprenant du combustible nucléaire disposé à l’intérieur de l’élément de gainage 6 fermé de manière étanche à chacune de ses extrémités par un bouchon. The sheathing element 6 described above is a sheathing tube for the production of a nuclear fuel rod 2 comprising nuclear fuel disposed inside the sheathing element 6 closed in leaktight manner at each of its ends. by a cap.
Dans un autre exemple de réalisation, l’élément de gainage 6 est en forme de plaque, par exemple pour former un élément de combustible nucléaire 2 en forme de plaque comprenant une couche de combustible nucléaire intercalée (i.e. prise en sandwich) entre deux éléments de gainage 6 en forme de plaque. In another exemplary embodiment, the cladding element 6 is in the form of a plate, for example to form a nuclear fuel element 2 in the form of a plate comprising a layer of nuclear fuel interposed (ie sandwiched) between two elements of sheathing 6 in the form of a plate.
Un tel élément de gainage 6 en forme de plaque est réalisé de manière analogue à ce qui a été décrit ci-dessus, notamment en ce qui concerne le matériau du substrat 16, le matériau du revêtement de protection 18, l’épaisseur du substrat 16, l’épaisseur du revêtement de protection 18, la microstructure du revêtement de protection 18 et la limitation des gouttelettes sur la surface externe 18B du revêtement de protection 18. Such a sheathing element 6 in the form of a plate is produced analogously to what has been described above, in particular as regards the material of the substrate 16, the material of the protective coating 18, the thickness of the substrate 16 , the thickness of the protective coating 18, the microstructure of the protective coating 18 and the droplet limitation on the outer surface 18B of the protective coating 18.
Un procédé de fabrication de l’élément de gainage 6 va maintenant être décrit en référence à la Figure 4. Le procédé de fabrication comprend une étape d’obtention du substrat 16. Lorsque l’élément de gainage 6 est un tube de gainage d’un crayon de combustible nucléaire, le substrat 16 est un tube, qui présente par exemple un diamètre externe compris entre 8 mm et 15 mm, en particulier entre 9 mm et 13 mm, et/ou une longueur comprise entre 1 m et 5 m, en particulier entre 2 m et 5 m. Un tel tube est par exemple obtenu de manière connue par laminage à pas de pèlerin, à partir d’une ébauche tubulaire de diamètre plus grand et de longueur plus petite que le tube. A method of manufacturing the sheath element 6 will now be described with reference to Figure 4. The manufacturing method includes a step for obtaining the substrate 16. When the cladding element 6 is a cladding tube of a nuclear fuel rod, the substrate 16 is a tube, which has for example an external diameter between 8 mm and 15 mm, in particular between 9 mm and 13 mm, and/or a length of between 1 m and 5 m, in particular between 2 m and 5 m. Such a tube is for example obtained in a known manner by pilgrim step rolling, from a tubular blank of larger diameter and shorter length than the tube.
Le procédé de fabrication comprend ensuite une étape de dépôt du revêtement sur la surface externe 16B du substrat 16, par exemple par dépôt physique en phase vapeur par pulvérisation cathodique. The manufacturing method then comprises a step of depositing the coating on the outer surface 16B of the substrate 16, for example by physical vapor deposition by cathodic sputtering.
Au cour de l’étape de dépôt, le substrat 16 et une cible 24, qui est réalisée dans un matériau approprié pour former le revêtement de protection 18, sont placés dans une atmosphère raréfiée, formée par exemple d’un gaz neutre, tel l’argon, et une différence de potentiel électrique est générée entre la cible 24 et le substrat 16, la cible 24 définissant une cathode et le substrat 16 définissant une anode (la cible 24 est portée à un potentiel électrique supérieur à celui du substrat 16). During the deposition step, the substrate 16 and a target 24, which is made of a suitable material to form the protective coating 18, are placed in a rarefied atmosphere, formed for example of an inert gas, such as argon, and an electrical potential difference is generated between target 24 and substrate 16, target 24 defining a cathode and substrate 16 defining an anode (target 24 is brought to an electrical potential higher than that of substrate 16) .
Sous l’effet de la différence de potentiel entre le substrat 16 et la cible 24, un champ électrique apparaît entre le substrat 16 et la cible 24 dans l’atmosphère raréfiée, entraînant l’apparition d’un plasma contenant des particules chargées électriquement (électrons, ions...), qui sont précipitées sur la cible 24 sous l’effet du champ électrique et décrochent des atomes de la cible 24 (i.e. la cible 24 est pulvérisée, d’où le terme de pulvérisation cathodique), ces atomes détachés de la cible 24 allant ensuite se déposer sur le substrat 16. Under the effect of the potential difference between the substrate 16 and the target 24, an electric field appears between the substrate 16 and the target 24 in the rarefied atmosphere, resulting in the appearance of a plasma containing electrically charged particles ( electrons, ions, etc.), which are precipitated on the target 24 under the effect of the electric field and detach from the atoms of the target 24 (ie the target 24 is sputtered, hence the term sputtering), these atoms detached from the target 24 then going to be deposited on the substrate 16.
Dans le cas d’un revêtement de protection 18 en chrome pur, la cible 24 est par exemple réalisée en chrome pur. Dans le cas d’un revêtement de protection 18 réalisé dans un alliage de chrome, en particulier un alliage binaire de chrome comme indiqué précédemment, la cible 24 est par exemple réalisée dans un alliage de chrome possédant des proportions différentes, mais permettant le dépôt d’un revêtement de protection avec les proportions visées (par exemple une cible en alliage chrome-aluminium avec 15% en poids d’aluminium pour d’obtenir un revêtement de protection en alliage chrome-aluminium avec 10% en poids d’aluminium). In the case of a protective coating 18 of pure chromium, the target 24 is for example made of pure chromium. In the case of a protective coating 18 made of a chromium alloy, in particular a binary chromium alloy as indicated above, the target 24 is for example made of a chromium alloy having different proportions, but allowing the deposition of a protective coating with the targeted proportions (for example a target in chromium-aluminum alloy with 15% by weight of aluminum in order to obtain a protective coating in chromium-aluminum alloy with 10% by weight of aluminum).
Comme illustré sur la Figure 4, l’étape de dépôt est réalisée à l’aide d’une installation 26 de dépôt physique en phase vapeur, comprenant une chambre 28, la cible 24 disposée à l’intérieur de la chambre 28, et une pompe 30 dont l’entrée est reliée fluidiquement à la chambre 28 pour générer une atmosphère raréfiée dans la chambre 26, et un circuit électrique 32 pour générer une différence de potentiel entre la cible 24 et le substrat 16 introduit à l’intérieur de la chambre 28. As illustrated in Figure 4, the deposition step is carried out using a physical vapor deposition installation 26, comprising a chamber 28, the target 24 disposed inside the chamber 28, and a pump 30 whose inlet is fluidically connected to chamber 28 to generate a rarefied atmosphere in chamber 26, and an electric circuit 32 to generate a potential difference between the target 24 and the substrate 16 introduced inside the chamber 28.
Au cours de l’étape de dépôt, le substrat 16 est introduit dans la chambre 28, une atmosphère raréfiée est créée dans la chambre 28 à l’aide de la pompe 30, et la différence de potentiel entre la cible 24 et le substrat 14 est générée par le circuit électrique 32, ce qui permet de réaliser le dépôt physique en phase vapeur. During the deposition step, the substrate 16 is introduced into the chamber 28, a rarefied atmosphere is created in the chamber 28 using the pump 30, and the potential difference between the target 24 and the substrate 14 is generated by the electric circuit 32, which makes it possible to carry out the physical vapor deposition.
De préférence, le dépôt physique en phase vapeur est réalisée par pulvérisation cathodique magnétron. Preferably, the physical vapor deposition is carried out by magnetron sputtering.
Dans ce cas, un champ magnétique est généré, de préférence au moins à proximité de la cible 24. In this case, a magnetic field is generated, preferably at least close to the target 24.
La prévision d’un champ magnétique permet de mieux contrôler la trajectoire des particules chargées électriquement atteignant la cible 24, ce qui permet une vitesse de dépôt du revêtement de protection 18 mieux contrôlée, en particulier une vitesse dépôt du revêtement de protection 18 plus rapide. The provision of a magnetic field makes it possible to better control the trajectory of the electrically charged particles reaching the target 24, which allows a better controlled rate of deposition of the protective coating 18, in particular a faster rate of deposition of the protective coating 18.
Le champ magnétique est généré par exemple par un ou plusieurs aimants permanents 34, comme illustré sur la Figure 4, et/ou un ou plusieurs électroaimants. The magnetic field is generated for example by one or more permanent magnets 34, as illustrated in Figure 4, and/or one or more electromagnets.
En outre le dépôt physique en phase vapeur par pulvérisation, en particulier par pulvérisation cathodique magnétron, permet d’effectuer un dépôt présentant une uniformité satisfaisante, tout en limitant l’apparition de microgouttelettes 22 sur la surface externe 18B du revêtement de protection 18. In addition, physical vapor deposition by sputtering, in particular by magnetron cathode sputtering, makes it possible to perform a deposit having satisfactory uniformity, while limiting the appearance of microdroplets 22 on the outer surface 18B of the protective coating 18.
De préférence, lorsque le substrat 16 présente la forme d’un tube, en particulier un tube présentant une symétrie de révolution autour d’un axe central, comme c’est le cas pour un substrat 16 pour un tube de gainage d’un crayon de combustible nucléaire, pendant l’étape de dépôt, le substrat 16 est entraîné en rotation autour de son axe central. Preferably, when the substrate 16 has the shape of a tube, in particular a tube having a symmetry of revolution around a central axis, as is the case for a substrate 16 for a sheathing tube of a pencil of nuclear fuel, during the deposition step, the substrate 16 is rotated around its central axis.
Ceci permet d’effectuer un dépôt uniforme sur toute la circonférence de la surface externe 16B du substrat 16 en forme de tube. This makes it possible to perform a uniform deposit over the entire circumference of the outer surface 16B of the substrate 16 in the form of a tube.
Au cours de l’étape de dépôt, de préférence, le revêtement de protection 18 est déposé sur le substrat en forme de tube présentant un axe central en entraînant le substrat 16 rotation autour de cet axe central et de telle manière que la vitesse de dépôt du revêtement de protection 18 sur le substrat 16 est comprise entre 1/p prn/h et 30/p prn/h. During the deposition step, the protective coating 18 is preferably deposited on the tube-shaped substrate having a central axis by causing the substrate 16 to rotate around this central axis and in such a way that the deposition speed of the protective coating 18 on the substrate 16 is between 1/p prn/h and 30/p prn/h.
Il est possible de prévoir un élément de gainage 6 en forme de plaque, de sorte que la surface externe 16B du substrat 16 est sensiblement plane. Un tel élément de gainage 6 permet de former un élément de combustible nucléaire en forme générale de plaque, comprenant du combustible nucléaire interposé (ou pris en sandwich) entre deux éléments de gainage 6 en forme de plaque. Dans le cas d’un élément de gainage 6 en forme de plaque, l’étape de dépôt est effectuée sans rotation du substrat 16. It is possible to provide a sheathing element 6 in the form of a plate, so that the outer surface 16B of the substrate 16 is substantially planar. Such a cladding element 6 makes it possible to form a nuclear fuel element in the general shape of a plate, comprising nuclear fuel interposed (or sandwiched) between two cladding elements 6 in the form of a plate. In the case of a sheathing element 6 in the form of a plate, the deposition step is carried out without rotation of the substrate 16.
De préférence, le dépôt du revêtement de protection 18 sur un substrat en forme de plaque est réalisé de telle manière que la vitesse de dépôt du revêtement de protection 18 sur le substrat 16 est comprise entre 1 pm/h et 30 pm/h. Preferably, the deposition of the protective coating 18 on a plate-shaped substrate is carried out in such a way that the rate of deposition of the protective coating 18 on the substrate 16 is between 1 μm/h and 30 μm/h.
La vitesse de dépôt du revêtement de protection 18 conditionne la microstructure du revêtement de protection 18 qui sera obtenue. The deposition rate of the protective coating 18 conditions the microstructure of the protective coating 18 which will be obtained.
Les vitesses de dépôt proposées ci-dessus permettent d’obtenir une microstructure souhaitée, i.e. une microstructure colonnaire avec des grains colonnaires présentant un faible diamètre à l’interface entre le substrat 18 et le revêtement de protection 18, et un diamètre pas trop élevé à la surface externe 18B du revêtement de protection, comme indiqué plus haut. The deposition rates proposed above make it possible to obtain a desired microstructure, ie a columnar microstructure with columnar grains having a small diameter at the interface between the substrate 18 and the protective coating 18, and a diameter not too large at the outer surface 18B of the protective coating, as indicated above.
La vitesse de dépôt du revêtement de protection 18 par dépôt physique en phase vapeur par pulvérisation cathodique, en particulier par pulvérisation cathodique magnétron, est fonction notamment de la densité de courant traversant la cible 24 et de la polarisation du substrat, i.e. de la différence le potentiel électrique du substrat 16 et le potentiel électrique de la cible 24 au cours du dépôt. The deposition rate of the protective coating 18 by physical vapor deposition by cathode sputtering, in particular by magnetron cathode sputtering, is a function in particular of the current density passing through the target 24 and of the polarization of the substrate, ie of the difference le electrical potential of substrate 16 and the electrical potential of target 24 during deposition.
En outre, le dépôt physique en phase vapeur peut être réalisé avec une densité de courant continue (i.e. en appliquant un courant électrique continu à la cible 24) ou une densité de courant pulsée (i.e. en appliquant un courant électrique pulsé comprenant des impulsions). Further, physical vapor deposition can be performed with continuous current density (i.e. applying a continuous electric current to target 24) or pulsed current density (i.e. applying a pulsed electric current comprising pulses).
La densité de courant de la cible est l’intensité du courant traversant la cible divisée par l’aire de la surface active de la cible, i.e. la surface de la cible qui est tournée vers le substrat 16 et qui reçoit les particules chargées du plasma projetée sur la cible 24. The current density of the target is the intensity of the current passing through the target divided by the area of the active surface of the target, ie the surface of the target which is turned towards the substrate 16 and which receives the charged particles of the plasma projected onto target 24.
Dans un exemple de réalisation, le dépôt du revêtement de protection 18 est réalisé en alimentant la cible 24 avec un courant continu de manière à obtenir à la cible 24 une densité de courant comprise entre 0,0005 A/cm2 et 0,1 A/cm2, de préférence comprise entre 0,0005 A/cm2 et 0,05 A/cm2 , ou en alimentant la cible 24 avec un courant pulsé avec des pics de courant de manière à obtenir à la cible 24 une densité de courant comprise entre 0,01 A/cm2 et 5 A/cm2 lors de pics de courant (i.e. densité de courant pic), de préférence comprise entre 0,01 A/cm2 et 0,5 A/cm2. In an exemplary embodiment, the deposition of the protective coating 18 is carried out by supplying the target 24 with a direct current so as to obtain for the target 24 a current density of between 0.0005 A/cm 2 and 0.1 A /cm 2 , preferably between 0.0005 A/cm 2 and 0.05 A/cm 2 , or by supplying the target 24 with a pulsed current with current peaks so as to obtain for the target 24 a density of current of between 0.01 A/cm 2 and 5 A/cm 2 during current peaks (ie peak current density), preferably of between 0.01 A/cm 2 and 0.5 A/cm 2 .
La densité de puissance de la cible est la puissance électrique traversant la cible divisée par l’aire de la surface active de la cible. The target power density is the electrical power passing through the target divided by the active surface area of the target.
Dans un exemple de réalisation, le dépôt du revêtement de protection 18 est réalisé en alimentant la cible 24 avec un courant continu de manière à obtenir à la cible 24 une densité de puissance comprise entre 0,5 W/cm2 et 100 W/cm2, de préférence une densité de puissance comprise entre 0,5 W/cm2 et 50 W/cm2, ou en alimentant la cible 24 avec un courant pulsé avec des pics de courant de manière à obtenir à la cible 24 une densité de puissance comprise 10 W/cm2 et 50.000 W/cm2 (i.e. la densité de puissance pic), de préférence une densité de puissance comprise entre 10 W/cm2 et 5.000 W/cm2. In an exemplary embodiment, the deposition of the protective coating 18 is carried out by supplying the target 24 with a direct current so as to obtain for the target 24 a power density of between 0.5 W/cm2 and 100 W/cm 2 , preferably a density of power between 0.5 W/cm2 and 50 W/cm 2 , or by supplying the target 24 with a pulsed current with current peaks so as to obtain for the target 24 a power density of between 10 W/cm2 and 50,000 W/cm 2 (ie the peak power density), preferably a power density of between 10 W/cm 2 and 5,000 W/cm 2 .
De préférence, la tension de polarisation électrique du substrat 16 par rapport à la cible 24 durant le dépôt physique en phase vapeur est négative et comprise entre - 10 V et - 200 V, encore de préférence entre - 50V et - 150V. Preferably, the electrical bias voltage of substrate 16 relative to target 24 during physical vapor deposition is negative and between -10 V and -200 V, more preferably between -50 V and -150 V.
Dans un exemple de réalisation préféré, le dépôt est réalisé avec un courant pulsé avec un ou plusieurs des paramètres suivants : In a preferred exemplary embodiment, the deposition is carried out with a pulsed current with one or more of the following parameters:
- la densité de puissance moyenne (la moyenne dans le temps de la densité de puissance électrique traversant la cible 24) est comprise entre 1 W/cm2 et 5 W/cm2 ; - the average power density (the average over time of the electrical power density passing through the target 24) is between 1 W/cm 2 and 5 W/cm 2 ;
- la densité de puissance pic (la puissance électrique traversant la cible 24 à chaque impulsion de courant par unité de surface de la cible 24) est comprise entre 30 W/cm2 et 100 W/cm2 ; - the peak power density (the electrical power passing through the target 24 at each current pulse per unit area of the target 24) is between 30 W/cm2 and 100 W/cm2;
- la fréquence des impulsions de courant est comprise entre 50 Hz et 5000 Hz;- the frequency of the current pulses is between 50 Hz and 5000 Hz;
- la durée des impulsions de courant est comprise entre 10 ps et 50 ps; - the duration of the current pulses is between 10 ps and 50 ps;
- le dépôt physique en phase vapeur est réalisé dans une atmosphère constituée d’un gaz rare, en particulier une atmosphère constituée d’argon (Ar) ; - physical vapor deposition is carried out in an atmosphere made up of a rare gas, in particular an atmosphere made up of argon (Ar);
- la pression résidant à l’intérieur de la chambre dans laquelle est réalisé le dépôt physique en phase vapeur est comprise entre 0,1 Pa et 0,4 Pa ; et/ou - the pressure residing inside the chamber in which the physical vapor deposition is carried out is between 0.1 Pa and 0.4 Pa; and or
- la distance entre le substrat 16 et la cible 24 est comprise entre 50 mm et 200 mm, encore de préférence entre 80 mm et 140 mm. - the distance between the substrate 16 and the target 24 is between 50 mm and 200 mm, more preferably between 80 mm and 140 mm.
Le respect d’une ou plusieurs des plages de valeurs préférées indiquées ci-dessus permet d’obtenir la faible densité de gouttelettes. Meeting one or more of the preferred value ranges listed above achieves the low droplet density.
De préférence, le dépôt physique en phase vapeur est effectué sur le substrat 16 sans autre apport de chaleur que celui résultant du bombardement du substrat 16 par les particules (atomes, ions...) arrachées à la cible 24 du fait de la mise en oeuvre du dépôt physique en phase vapeur. Preferably, the physical vapor deposition is carried out on the substrate 16 without any heat input other than that resulting from the bombardment of the substrate 16 by the particles (atoms, ions, etc.) torn from the target 24 due to the setting in implementation of physical vapor deposition.
En particulier, le substrat 16 n’est pas chauffé à l’aide d’un dispositif de chauffage. Ceci permet de limiter le risque de dépasser la température de transition de phase du matériau du substrat 16. In particular, the substrate 16 is not heated using a heating device. This makes it possible to limit the risk of exceeding the phase transition temperature of the material of the substrate 16.
Le dépôt physique en phase vapeur par pulvérisation cathodique magnétron peut être réalisé selon une des techniques suivantes ou une combinaison d’au moins deux parmi les techniques suivantes : pulvérisation cathodique magnétron en courant continu (en anglais « Direct Current » ou « DC »), pulvérisation cathodique magnétron en courant continu pulsé (en anglais « Pulsed Direct Current » ou « DC pulsed »), pulvérisation cathodique magnétron pulsée à haute puissance (en anglais « High Power Impulse Magnetron Sputtering» (HiPIMS ou HPMS), pulvérisation cathodique magnétron bipolaire (en anglais « Magnetron Sputtering Bi-polar » (MSB)), pulvérisation cathodique dual magnétron (en anglais « Dual Magnetron Sputtering » (DMS)), pulvérisation cathodique magnétron déséquilibrée (en anglais “Unbalanced Magnetron Sputtering » (UBM)). Physical vapor deposition by magnetron cathode sputtering can be carried out using one of the following techniques or a combination of at least two of the following techniques: DC magnetron cathode sputtering, cathode sputtering magnetron in pulsed direct current (in English "Pulsed Direct Current" or "DC pulsed"), sputtering High Power Impulse Magnetron Sputtering (HiPIMS or HPMS), Bipolar Magnetron Sputtering (MSB), Dual Magnetron Sputtering Magnetron Sputtering” (DMS)), unbalanced magnetron sputtering (in English “Unbalanced Magnetron Sputtering” (UBM)).
Les Figures 6 à 8 sont des photographies prise au microscope de la surface de revêtements de protection 18 déposés sur un substrat 16 par dépôt physique en phase vapeur par pulvérisation cathodique magnétron avec courant pulsé, sous atmosphère d’argon, avec différents jeux de paramètres, indiqués dans le Tableau 1 ci-dessous : Figures 6 to 8 are photographs taken under a microscope of the surface of protective coatings 18 deposited on a substrate 16 by physical vapor deposition by magnetron sputtering with pulsed current, under an argon atmosphere, with different sets of parameters, shown in Table 1 below:
Tableau 1 Table 1
L’exemple 1 et l’exemple 2 sont réalisés en respectant les paramètres de dépôt physique en phase vapeur indiqué plus haut, tandis que l’exemple 3 n’est pas réalisé en respectant tous ces paramètres. Example 1 and Example 2 are carried out respecting the physical vapor deposition parameters indicated above, while Example 3 is not carried out respecting all these parameters.
Comme visible sur la Figure 6 qui représente un vue d’un échantillon réalisé selon l’exemple 2, le revêtement de protection 18 présente peu de gouttelettes G sur sa surface externe 18B. Dans cet exemple 2, le revêtement de protection 18 présente sur sa surface externe 18B une densité de microgouttelettes de 50 par mm2. As visible in Figure 6 which shows a view of a sample made according to Example 2, the protective coating 18 has few droplets G on its outer surface 18B. In this example 2, the protective coating 18 has on its outer surface 18B a density of microdroplets of 50 per mm 2 .
L’exemple 1 a donné un résultat similaire à celui de l’exemple 2, le revêtement de protection 18 présentant sur sa surface externe 18B une densité de microgouttelettes de 50 par mm2. Le revêtement de protection 18 de l’exemple 3 illustré par la Figure 7 a aussi été réalisé par dépôt physique en phase vapeur par pulvérisation cathodique magnétron mais hors des plages recommandées, en particulier pour la pression et la densité de puissance pic. La densité de microgouttelettes est dans ce cas d’environ 2500 microgouttelettes par mm2, ce qui est bien supérieure à la densité de microgouttelettes maximale recherchée qui est de 100 microgouttelettes par mm2. Example 1 gave a result similar to that of example 2, the protective coating 18 having on its outer surface 18B a density of microdroplets of 50 per mm 2 . The protective coating 18 of example 3 illustrated by FIG. 7 was also produced by physical vapor deposition by magnetron sputtering but outside the recommended ranges, in particular for the pressure and the peak power density. The density of microdroplets is in this case approximately 2500 microdroplets per mm 2 , which is much higher than the desired maximum density of microdroplets which is 100 microdroplets per mm 2 .
Le revêtement de protection 18 de l’exemple de la Figure 8 a été fabriqué par dépôt physique en phase vapeur par pulvérisation cathodique par arc avec chauffage du substrat et des paramètres différents de ceux de la pulvérisation cathodique magnétron. The protective coating 18 of the example in Figure 8 was fabricated by physical vapor deposition by sputtering by arc with heating of the substrate and parameters different from those of magnetron sputtering.
Comme visible sur la Figure 8, dans cet exemple, le revêtement de protection 18 présente sur sa surface externe 18B une densité de microgouttelettes supérieure à 10.000 par mm2. As visible in Figure 8, in this example, the protective coating 18 has on its outer surface 18B a density of microdroplets greater than 10,000 per mm 2 .
On notera que les échelles des photographies des Figures 6 à 8 sont différentes. Le dépôt du revêtement de protection par dépôt physique en phase vapeur par pulvérisation cathodique magnétron est préféré, mais l’invention n’est pas limitée à une telle technique de dépôt. It will be noted that the scales of the photographs of FIGS. 6 to 8 are different. The deposition of the protective coating by physical vapor deposition by magnetron sputtering is preferred, but the invention is not limited to such a deposition technique.
En variante, le dépôt du revêtement de protection peut être réalisé selon une autre technique, par exemple par dépôt physique par projection à froid (en anglais « Cold Spray »). As a variant, the deposition of the protective coating can be carried out according to another technique, for example by physical deposition by cold spraying.
Grâce à l’invention, il est possible d’obtenir un élément de gainage de combustible nucléaire qui présente une bonne résistance à l’oxydation et à l’hydruration, en fonctionnement normal du réacteur nucléaire et en condition accidentelle, par exemple lors d’un accident de perte de fluide de refroidissement. Thanks to the invention, it is possible to obtain a nuclear fuel cladding element which has good resistance to oxidation and to hydriding, in normal operation of the nuclear reactor and in accident conditions, for example during a loss of coolant accident.

Claims

REVENDICATIONS
1. Elément de gainage de combustible nucléaire, l’élément de gainage comprenant un substrat (16) réalisé dans un matériau à base de zirconium et un revêtement de protection (18) recouvrant extérieurement le substrat (16), le revêtement de protection (18) étant réalisé dans un matériau à base de chrome, dans lequel le revêtement de protection (18) présente une microstructure colonnaire composée de grains colonnaires (20) et présente sur sa surface externe (18B) une densité de microgouttelettes inférieure à 100 par mm2. 1. Nuclear fuel cladding element, the cladding element comprising a substrate (16) made of a zirconium-based material and a protective coating (18) externally covering the substrate (16), the protective coating (18 ) being made of a chromium-based material, in which the protective coating (18) has a columnar microstructure composed of columnar grains (20) and has on its outer surface (18B) a density of microdroplets of less than 100 per mm 2 .
2. Elément de gainage selon la revendication 1 , dans lequel, à proximité de et/ou à l’interface entre l’élément de gainage et le revêtement de protection, les grains colonnaires présentent un diamètre moyen égal ou inférieur à 1 mhi, de préférence égal ou inférieur à 0,5 mhi. 2. Cladding element according to claim 1, in which, near and/or at the interface between the cladding element and the protective coating, the columnar grains have an average diameter equal to or less than 1 mhi, of preferably equal to or less than 0.5 mhi.
3. Elément de gainage selon la revendication 1 ou la revendication 2, dans lequel, à proximité de et/ou sur la surface externe (18B) du revêtement de protection, les grains colonnaires (20) présentent un diamètre moyen entre 0,05 mhi et 5 mhi, de préférence entre 0,1 mhi et 2 mhi. 3. Cladding element according to claim 1 or claim 2, in which, close to and/or on the external surface (18B) of the protective coating, the columnar grains (20) have an average diameter between 0.05 mhi and 5 mhi, preferably between 0.1 mhi and 2 mhi.
4. Elément de gainage selon l’une quelconque des revendications précédentes, dans lequel les microgouttelettes possèdent un diamètre égal ou inférieur à 20 mhi. 4. Cladding element according to any one of the preceding claims, in which the microdroplets have a diameter equal to or less than 20 mhi.
5. Elément de gainage selon l’une quelconque des revendications précédentes, dans lequel le revêtement de protection (18) présente une épaisseur comprise entre 5 mhi et 25 mhi. 5. Sheathing element according to any one of the preceding claims, in which the protective coating (18) has a thickness of between 5 mhi and 25 mhi.
6. Elément de gainage selon l’une quelconque des revendications précédentes dans lequel le revêtement de protection est réalisé en un matériau à base de chrome, par exemple en chrome pur ou un alliage à base de chrome, par exemple un alliage binaire de chrome, en particulier un alliage binaire chrome-aluminium, un alliage binaire chrome-azote ou un alliage binaire chrome-titane. 6. Cladding element according to any one of the preceding claims, in which the protective coating is made of a chromium-based material, for example pure chromium or a chromium-based alloy, for example a binary chromium alloy, in particular a binary chromium-aluminum alloy, a binary chromium-nitrogen alloy or a binary chromium-titanium alloy.
7. Elément de gainage selon l’une quelconque des revendications précédentes, l’élément de gainage étant un tube de gainage, en particulier un tube de gainage de crayon de combustible nucléaire. 7. Cladding element according to any one of the preceding claims, the cladding element being a cladding tube, in particular a nuclear fuel rod cladding tube.
8. Elément de combustible nucléaire comprenant du combustible nucléaire disposé à l’intérieur d’une gaine formée par au moins un élément de gainage selon l’une quelconque de revendications précédentes. 8. Nuclear fuel element comprising nuclear fuel disposed inside a sheath formed by at least one sheathing element according to any preceding claim.
9. Crayon de combustible nucléaire comprenant du combustible nucléaire disposé à l’intérieur d’une gaine formée d’un élément de gainage tubulaire selon l’une quelconque des revendications 1 à 7, fermé à ses extrémités par des bouchons. 9. Nuclear fuel rod comprising nuclear fuel disposed inside a sheath formed of a tubular sheathing element according to any one of claims 1 to 7, closed at its ends by plugs.
10. Procédé de fabrication d’un élément de gainage selon l’une quelconque des revendications 1 à 7, comprenant l’obtention du substrat (16) puis le dépôt du revêtement de protection (18) sur le substrat (16) par dépôt physique en phase vapeur par pulvérisation cathodique d’une cible (24) ou par dépôt physique par projection à froid. 10. A method of manufacturing a sheathing element according to any one of claims 1 to 7, comprising obtaining the substrate (16) then depositing the protective coating (18) on the substrate (16) by physical deposition in the vapor phase by sputtering a target (24) or by physical deposition by cold spraying.
11. Procédé de fabrication selon la revendication 10, dans lequel le dépôt est effectué par dépôt physique en phase vapeur par pulvérisation cathodique magnétron. 11. Manufacturing process according to claim 10, in which the deposition is carried out by physical vapor deposition by magnetron sputtering.
12. Procédé de fabrication selon la revendication 11 ou la revendication 12, dans lequel le substrat (16) est en forme de plaque et l’étape dépôt est réalisé de telle manière que la vitesse de dépôt du revêtement de protection (18) sur le substrat (16) est comprise entre 1 pm/h et 30 pm/h. 12. Manufacturing process according to claim 11 or claim 12, in which the substrate (16) is in the form of a plate and the deposition step is carried out in such a way that the rate of deposition of the protective coating (18) on the substrate (16) is between 1 pm/h and 30 pm/h.
13. Procédé de fabrication selon la revendication 11 ou la revendication 12, dans lequel le substrat (16) est un tube présentant un axe central, et l’étape de dépôt est réalisée en entraînant le substrat (16) en rotation autour de son axe central et de telle manière que la vitesse de dépôt du revêtement de protection (18) sur le substrat (16) est comprise entre 1/p pm/h et 30/p pm/h. 13. Manufacturing process according to claim 11 or claim 12, in which the substrate (16) is a tube having a central axis, and the deposition step is carried out by driving the substrate (16) in rotation around its axis. central and in such a way that the rate of deposition of the protective coating (18) on the substrate (16) is between 1/p pm/h and 30/p pm/h.
14. Procédé de fabrication selon l’une quelconque des revendications 10 à 13, dans lequel le dépôt est réalisé par dépôt physique en phase vapeur en alimentant la cible en courant pulsé avec des pics de courant. 14. Manufacturing process according to any one of claims 10 to 13, in which the deposition is carried out by physical vapor deposition by supplying the target with pulsed current with current peaks.
15. Procédé de fabrication selon la revendication 14, dans lequel le dépôt est réalisé avec une densité de puissance moyenne comprise entre 1 W/cm2et 5 W/cm2 ; 15. Manufacturing process according to claim 14, in which the deposition is carried out with an average power density of between 1 W/cm 2 and 5 W/cm 2 ;
16. Procédé de fabrication selon la revendication 14 ou 15, dans lequel le dépôt est réalisé avec une densité de puissance pic comprise entre 30 W/cm2 et 100 W/cm2 ; 16. Manufacturing process according to claim 14 or 15, in which the deposition is carried out with a peak power density of between 30 W/cm2 and 100 W/cm2;
17. Procédé de fabrication selon l’une quelconque des revendications 14 à 16, dans lequel le dépôt est réalisé avec une fréquence des impulsions de courant comprise entre 50 Hz et 5000 Hz; 17. Manufacturing process according to any one of claims 14 to 16, in which the deposition is carried out with a frequency of the current pulses of between 50 Hz and 5000 Hz;
18. Procédé de fabrication selon l’une quelconque des revendications 14 à 17, dans lequel le dépôt est réalisé avec une durée des impulsions de courant comprise entre 10 ps et 50 ps; 18. Manufacturing process according to any one of claims 14 to 17, in which the deposition is carried out with a duration of the current pulses of between 10 ps and 50 ps;
19. Procédé de fabrication selon l’une quelconque des revendications 14 à 18, dans lequel le dépôt est réalisé sous une pression comprise entre 0,1 Pa et 0,4 Pa. 19. Manufacturing process according to any one of claims 14 to 18, in which the deposition is carried out under a pressure of between 0.1 Pa and 0.4 Pa.
20. Procédé de fabrication selon l’une quelconque des revendications 14 à 19, dans lequel le dépôt est réalisé avec une distance entre le substrat (16) et la cible (24) comprise entre 50 mm et 200 mm, encore de préférence entre 80 mm et 140 mm. 20. Manufacturing process according to any one of claims 14 to 19, in which the deposition is carried out with a distance between the substrate (16) and the target (24) of between 50 mm and 200 mm, still preferably between 80 mm and 140 mm.
21. Procédé de fabrication selon l’une quelconque des revendications 10 à 20, dans lequel le dépôt est réalisé par dépôt physique en phase vapeur en alimentant la cible en courant continu de manière à obtenir une densité de courant comprise entre 0,0005 A/cm2 et 0,1 A/cm2 sur la cible (24), de préférence entre0,0005 A/cm2 et 0,05 A/cm2, ou en courant pulsé avec des pics de courant de manière à obtenir une densité de courant comprise entre 0,01 A/cm2 et 5 A/cm2 sur la cible (24) lors des pics de courant, de préférence entre 0,01 A/cm2 et 0,5 A/cm2. 21. Manufacturing process according to any one of claims 10 to 20, in which the deposition is carried out by physical vapor deposition by supplying the target with direct current so as to obtain a current density of between 0.0005 A/ cm 2 and 0.1 A/cm 2 on the target (24), preferably between 0.0005 A/cm 2 and 0.05 A/cm 2 , or in pulsed current with current peaks so as to obtain a density current of between 0.01 A/cm 2 and 5 A/cm 2 on the target (24) during current peaks, preferably between 0.01 A/cm 2 and 0.5 A/cm 2 .
22. Procédé de fabrication selon l’une quelconque des revendications 10 à 21 , dans lequel le dépôt du revêtement de protection 18 est réalisé en alimentant la cible 24 avec un courant continu de manière à obtenir à la cible une densité de puissance comprise entre 0,5 W/cm2 et 100 W/cm2, de préférence une densité de puissance comprise entre 0,5 W/cm2 et 50 W/cm2 ou avec un courant pulsé avec des pics de courant de manière à obtenir à la cible une densité de puissance comprise 10 W/cm2 50.000 W/cm2 (i.e. la densité de puissance pic), de préférence une densité de puissance comprise entre 10 W/cm2 et 5000 W/cm2. 22. Manufacturing process according to any one of claims 10 to 21, in which the deposition of the protective coating 18 is carried out by supplying the target 24 with a direct current so as to obtain for the target a power density of between 0 .5 W/cm2 and 100 W/cm 2 , preferably a power density between 0.5 W/cm2 and 50 W/cm 2 or with a pulsed current with current peaks so as to obtain at the target a power density between 10 W/cm 2 and 50,000 W/cm 2 (ie the peak power density), preferably a power density between 10 W/cm 2 and 5000 W/cm 2 .
23. Procédé de fabrication selon l’une quelconque des revendications 10 à 22, dans lequel le dépôt est réalisé par dépôt physique en phase vapeur avec une tension de polarisation électrique du substrat (16) par rapport à la cible (24) durant le dépôt physique en phase vapeur, qui est négative et comprise entre - 10 V et - 200 V. 23. Manufacturing process according to any one of claims 10 to 22, in which the deposition is carried out by physical vapor deposition with an electrical bias voltage of the substrate (16) relative to the target (24) during the deposition. physics in the vapor phase, which is negative and between - 10 V and - 200 V.
24. Procédé de fabrication selon l’une quelconque des revendications 10 à 23, dans lequel le dépôt est réalisé dans une atmosphère constituée d’un gaz rare. 24. Manufacturing process according to any one of claims 10 to 23, in which the deposition is carried out in an atmosphere consisting of a rare gas.
EP21752046.9A 2020-07-31 2021-07-29 Nuclear fuel cladding element and method for manufacturing said cladding element Pending EP4189706A1 (en)

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