Method for manufacturing a nuclear fuel rod cladding and corresponding nuclear fuel rod cladding

Abstract

The manufacturing method is intended for the manufacture of a nuclear fuel rod cladding (4) comprising a substrate (14) covered with a protective coating (16). The manufacturing method comprises providing the substrate (14) and applying the protective coating (16) to the substrate (14) by physical vapour deposition by sputtering, simultaneously employing two or more mutually different techniques of physical vapour deposition by sputtering.

Description

[0001] DESCRIPTION

[0002] Method of manufacturing a nuclear fuel rod cladding and corresponding nuclear fuel rod cladding

[0003] The present invention relates to the field of nuclear fuel rod claddings (hereinafter also referred to as "claddings") intended to contain nuclear fuel.

[0004] Nuclear fuel including fissile material is generally contained in a cladding which prevents the dispersion of the nuclear fuel.

[0005] Nuclear fuel assemblies used in light water or heavy water reactors generally comprise a bundle of nuclear fuel rods, each nuclear fuel rod comprising a tubular cladding containing nuclear fuel, the cladding being sealed at each of its two ends by a plug.

[0006] Nuclear fuel rod claddings are made, for example, from zirconium-based alloys. Such zirconium-based alloys exhibit high performance under normal operating conditions in nuclear reactors.

[0007] However, they can reach their limits, particularly in terms of temperature, during severe accident conditions, such as a Loss Of Coolant Accident (LOCA).

[0008] During such an event, the temperature in the core of the nuclear reactor can reach more than 800°C, and the coolant is then mainly in the form of water vapor.

[0009] This can cause rapid degradation of the cladding of a nuclear fuel rod, including the release of hydrogen and rapid oxidation of the cladding, leading to its embrittlement or even its bursting, and therefore to the release of nuclear fuel from the cladding.

[0010] It is possible to provide a sheath comprising a substrate made of a zirconium-based alloy and covered with a protective coating made, for example, of a chromium-based material.

[0011] Such a protective coating generally allows to increase the tolerance of the sheath under normal and accident conditions. It is possible to manufacture such a sheath by depositing the protective coating on the substrate by physical vapor deposition.

[0012] However, such a technique for depositing the protective coating is relatively slow, especially for large coating thicknesses.

[0013] The widespread use of protective coatings on nuclear fuel cladding at the industrial level requires the ability to deposit the protective coating sufficiently quickly.

[0014] One of the aims of the invention is to propose a method for manufacturing a nuclear fuel cladding having a substrate coated with a protective coating, which can be implemented quickly.

[0015] To this end, the invention proposes a method for manufacturing a nuclear fuel rod cladding comprising a substrate covered with a protective coating, the manufacturing method comprising providing the substrate, and depositing the protective coating on the substrate by physical vapor deposition by cathode sputtering, by simultaneously implementing several physical vapor deposition techniques by cathode sputtering, different from each other.

[0016] The simultaneous implementation of several different physical vapor deposition techniques by sputtering allows for rapid deposition of the protective coating, obtaining a protective coating with good resistance to the external environment and good adhesion to the substrate.

[0017] “Simultaneous” implementation means that the different physical vapor deposition techniques are implemented together and at the same time, i.e. over the same period of time.

[0018] The different sputtering physical vapor deposition techniques implemented simultaneously may be implemented by using at least one cathode common to at least two of the different sputtering physical vapor deposition techniques that are implemented simultaneously and / or at least one cathode dedicated to only one of the different sputtering physical vapor deposition techniques that are implemented simultaneously.

[0019] Each physical vapor deposition technique is implemented by applying an excitation signal to the associated cathode, the excitation signal having a periodic pattern, the pattern being for example a plateau, a pulse or a pulse train.

[0020] The joint implementation of several different physical vapor deposition techniques using a single common cathode is, for example, achieved by combining the excitation signals emitted simultaneously and synchronously in such a way that their respective patterns are applied sequentially to the common cathode.

[0021] According to particular embodiments, the manufacturing method comprises one or more of the following optional features, taken individually or in all technically possible combinations:

[0022] - at least two of the different physical vapor deposition techniques by sputtering are implemented simultaneously using a common cathode;

[0023] - the manufacturing method comprises applying to each common cathode a combined excitation signal corresponding to the superposition of at least two elementary excitation signals, each elementary excitation signal being formed of a periodic pattern corresponding to a respective sputtering physical vapor deposition technique among the sputtering physical vapor deposition techniques implemented simultaneously using said common cathode, the elementary excitation signals being synchronized in such a way that their respective patterns are present sequentially in the combined excitation signal;

[0024] - each elementary excitation signal is generated by a respective excitation signal generator, the elementary excitation signals being synchronized and superimposed to form the combined excitation signal applied to said common cathode;

[0025] - at least one of the simultaneously implemented physical vapor deposition techniques by cathode sputtering is implemented using a dedicated cathode, by applying to this dedicated cathode an excitation signal for the implementation of this physical vapor deposition technique;

[0026] - each of the simultaneously implemented physical vapor deposition techniques by cathode sputtering is implemented using a dedicated cathode, by applying to this dedicated cathode an excitation signal for the implementation of this physical vapor deposition technique;

[0027] - the excitation signal of each dedicated cathode is generated by a respective excitation signal generator;

[0028] - the physical vapor deposition techniques implemented simultaneously are chosen from: unipolar or bipolar high-power pulsed magnetron sputtering (HiPIMS), unipolar or bipolar direct current (DC) magnetron sputtering, unipolar or bipolar pulsed direct current (pulsed-DC) magnetron sputtering, unipolar or bipolar medium frequency (MF) magnetron sputtering and unipolar or bipolar radio frequency (RF) magnetron sputtering;

[0029] - the substrate is made of a zirconium-based material and / or the protective coating is made of a chromium-based material;

[0030] - the thickness of the protective coating at the end of the deposition step is between 5 pm and 30 pm, in particular between 10 pm and 20 pm;

[0031] - the substrate has a shape of revolution around a central axis, the manufacturing method comprising rotating the substrate around the central axis during the deposition step;

[0032] - the manufacturing process includes polarization of the substrate during coating deposition.

[0033] The invention also relates to a nuclear fuel rod cladding comprising a substrate covered with a protective coating deposited on the substrate by physical vapor deposition by simultaneously implementing a plurality of different physical vapor deposition techniques by cathodic sputtering.

[0034] The invention also relates to a physical vapor deposition installation, the installation comprising a chamber, at least one atmosphere control device for generating a rarefied atmosphere in the chamber, at least one cathode and an excitation device, the installation being configured for the deposition of a protective coating on a substrate introduced into the chamber by simultaneously implementing several different physical vapor deposition techniques by cathode sputtering using the cathode(s).

[0035] According to particular embodiments, the installation comprises one or more of the following optional features, taken individually or in all technically possible combinations:

[0036] - the installation comprises at least one common cathode for the simultaneous implementation of at least two of the physical vapor deposition techniques by cathode sputtering implemented simultaneously, the excitation device being configured to generate a combined excitation signal of the common cathode which corresponds to the superposition of several elementary excitation signals, each elementary excitation signal having a periodic pattern corresponding to a respective one of the physical vapor deposition techniques by cathode sputtering implemented simultaneously using said common cathode, the elementary excitation signals being combined in such a way that their respective patterns are present sequentially in the combined excitation signal;- the installation comprises at least one dedicated cathode for implementing one of the physical vapor deposition techniques by cathode sputtering implemented simultaneously, the excitation device being configured to generate a respective excitation signal for each dedicated cathode, the excitation signal corresponding to the physical vapor deposition technique by cathode sputtering associated with this dedicated cathode.;

[0037] - the installation is configured for substrate polarization during coating deposition.

[0038] The invention and its advantages will be better understood upon studying the description which follows, given solely as a non-limiting example, and made with reference to the appended drawings, in which:

[0039] - Figure 1 is a schematic longitudinal sectional view of a nuclear fuel rod having a cladding;

[0040] - Figure 2 is a schematic cross-sectional view of the cladding of the nuclear fuel rod of Figure 1;

[0041] - Figure 3 is a schematic view of an installation for depositing a coating on a substrate by physical vapor deposition by cathodic sputtering, comprising a cathode common to two physical vapor deposition techniques by cathodic sputtering implemented simultaneously.

[0042] - Figure 4 contains graphs illustrating the realization of a combined excitation signal for the excitation of a cathode for the implementation of physical vapor deposition by cathodic sputtering;

[0043] - Figure 5 contains graphs illustrating the realization of a combined excitation signal for the excitation of a cathode for the implementation of physical vapor deposition by cathodic sputtering;

[0044] - Figure 6 is a schematic view of another installation for depositing a coating on a substrate by physical vapor deposition by cathodic sputtering, the installation comprising two dedicated cathodes, each intended for the implementation of a respective physical vapor deposition technique by cathodic sputtering.

[0045] Figure 1 illustrates a nuclear fuel rod 2 intended for use 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 "VVER" type reactor, a "RBMK" type reactor, or a heavy water reactor, for example of the "CANDU" type. The nuclear fuel rod 2 has an elongated shape along a longitudinal axis A.

[0046] Nuclear fuel rod 2 includes a cladding 4 containing nuclear fuel.

[0047] The sheath 4 is tubular and extends along the longitudinal axis A.

[0048] The sheath 4 is sealed at each of its ends by a respective cap 6.

[0049] The nuclear fuel is for example in the form of a stack of pellets 8 stacked axially inside the cladding 4, each pellet 8 containing fissile material. The stack of pellets 8 is also called a “fissile column”.

[0050] The nuclear fuel rod 2 comprises a spring 10 arranged inside the cladding 4, between the stack of pellets 8 and one of the plugs 6, to push the stack of pellets 8 towards the other plug 6. A vacuum or plenum 12 is preferably present between the stack of pellets 8 and the plug 6 on which the spring 10 bears.

[0051] Figure 2 shows a cross-sectional view of the sheath 4.

[0052] The sheath 4 comprises a substrate 14 provided with a protective coating 16.

[0053] The substrate 14 is tubular and extends along the longitudinal axis A. In other words, the substrate 14 is a rectilinear tube whose central axis is the longitudinal axis A.

[0054] The substrate 14 has, for example, an external diameter of 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.

[0055] The substrate 14 is made of pure zirconium or a zirconium-based alloy.

[0056] The term "pure zirconium" means a material containing at least 99% by weight of zirconium and the term "zirconium-based alloy" means an alloy containing at least 95% by weight of zirconium.

[0057] The zirconium-based alloy is, for example, chosen from one of the known alloys such as M5, ZIRLO, E1 10, HANA, N36, Zircaloy-2 and Zircaloy-4.

[0058] The substrate 14 has an inner surface 14A facing the inside of the substrate 14 and an outer surface 14B facing the outside of the substrate 14. The inner surface 14A delimits the space for receiving the nuclear fuel. The outer surface 14B is opposite the inner surface 14A.

[0059] The protective coating 16 covers the outer surface 14B of the substrate 14.

[0060] The protective coating 16 serves to protect the outer surface 14B of the substrate 14 from the external environment. In the absence of the protective coating 16, the outer surface 14B of the sheath 14 would be exposed to the external environment. The protective coating 16 is made, for example, of a chromium-based material.

[0061] The term "chromium-based material" means a pure chromium material or a chromium-based alloy. A pure chromium material herein means a material comprising at least 99% by weight of chromium. A chromium-based alloy herein means an alloy comprising at least 80% by weight of chromium.

[0062] The thickness of the protective coating 16 is preferably between 5 μm and 30 μm, in particular between 10 μm and 20 μm.

[0063] A method of manufacturing the sheath 4 comprises providing the substrate 14 and depositing the protective coating 16 on the substrate 14 by physical vapor deposition by simultaneously implementing several physical vapor deposition techniques by cathode sputtering, different from each other.

[0064] Physical vapor deposition by sputtering of a coating on a substrate is carried out by generating an electric field using a cathode (or "target") placed in a chamber containing a rarefied atmosphere formed for example by a neutral gas, such as argon, the electric field causing the appearance in the chamber of a plasma containing atoms and electrically charged particles (electrons, ions, etc.) which are precipitated on the cathode under the effect of the electric field and detach atoms from the cathode (i.e. the cathode is sputtered, hence the expression sputtering), these atoms detached from the cathode then going to be deposited on the substrate. Optionally, a reactive gas, such as nitrogen or oxygen, is present in the rarefied atmosphere.

[0065] Advantageously, physical vapor deposition by sputtering is carried out by magnetron sputtering.

[0066] Physical vapor deposition by magnetron sputtering of a coating on a substrate is carried out by generating an electric field and a magnetic field using a cathode (composed of a "target" and a "magnetron") arranged in a chamber containing a rarefied atmosphere formed for example of a neutral gas, such as argon, the electromagnetic field causing the appearance in the chamber of a plasma containing atoms and electrically charged particles (electrons, ions, etc.) which are precipitated on the cathode under the effect of the electromagnetic field and detach atoms from the cathode (i.e. the cathode is sputtered, hence the expression cathode sputtering), these atoms detached from the cathode then going to be deposited on the substrate.

[0067] The magnetron comprises, for example, one or more permanent magnets and / or one or more electromagnets. The provision of a magnetic field allows for better control of the trajectory of electrically charged particles reaching the cathode, which allows for better control of a coating deposition rate, in particular for obtaining a higher coating deposition rate.

[0068] In the following, unless otherwise stipulated, the expressions “deposition technique” and “physical vapor deposition technique” designate physical vapor deposition techniques by cathodic sputtering, possibly magnetron.

[0069] The method of manufacturing the sheath 4 thus comprises the simultaneous implementation of several different physical vapor deposition techniques by cathodic sputtering to deposit the protective coating 16 on the substrate 14.

[0070] The physical vapor deposition techniques are implemented simultaneously using at least one cathode common to at least two of the physical vapor deposition techniques implemented simultaneously and / or at least one dedicated cathode, each dedicated cathode being used for the implementation of only one of the physical vapor deposition techniques implemented simultaneously.

[0071] Preferably, when several cathodes are used for the simultaneous implementation of different physical vapor deposition techniques, these cathodes are made of the same material.

[0072] In an exemplary embodiment, at least two of the different physical vapor deposition techniques are implemented simultaneously using a common cathode, by applying to this common electrode a combined excitation signal corresponding to the superposition of several elementary excitation signals, each elementary excitation signal corresponding to one of the physical vapor deposition techniques implemented simultaneously using said common electrode.

[0073] Each elementary excitation signal has, for example, a periodic pattern, the pattern being, for example, a plateau, a pulse, or a pulse train.

[0074] The combined excitation signal is obtained for example by emitting the elementary excitation signals simultaneously and synchronously such that the respective patterns of the elementary excitation signals are present sequentially in the combined excitation signal, the respective patterns of the elementary excitation signals being applied sequentially to the common cathode.

[0075] In the combined excitation signal, the pattern of each elementary excitation signal is present in time windows distinct from those of the pattern of each other elementary excitation signal forming the combined excitation signal. The pattern of each elementary excitation signal is present in time windows dedicated to this elementary excitation signal, to the exclusion of the patterns of the other elementary excitation signals.

[0076] Patterns of different elementary excitation signals are not present at the same time in the combined excitation signal.

[0077] In an exemplary embodiment, a first physical vapor deposition technique and a second physical vapor deposition technique are implemented simultaneously using a common cathode by applying to this common cathode a combined excitation signal corresponding to the superposition of a first elementary excitation signal and a second elementary excitation signal, the first elementary excitation signal corresponding to the first physical vapor deposition technique and the second elementary excitation signal corresponding to the second physical vapor deposition technique, the first elementary excitation signal and the second elementary excitation signal being synchronized such that their respective elementary patterns are alternated in the combined excitation signal.

[0078] As illustrated in Figure 3, a sputtering physical vapor deposition installation 20 configured for the simultaneous implementation of several different physical vapor deposition techniques using a common cathode, and in particular for the simultaneous implementation of a first physical vapor deposition technique and a second physical vapor deposition technique are implemented simultaneously using a common cathode.

[0079] The installation 20 comprises a chamber 22 for receiving one or more substrates 14, an atmosphere control device 24 for generating a rarefied atmosphere in the chamber 22, a common cathode 26 and an excitation device 28 connected to the common cathode 26.

[0080] The atmosphere control device 24 comprises for example a pumping device 30 connected to the chamber 22 to generate a rarefied atmosphere in the chamber 22 and a gas supply device 32 fluidly connected to the chamber 22 to supply a neutral gas, e.g. argon and / or a reactive gas, e.g. nitrogen or oxygen.

[0081] The excitation device 28 is configured to generate a combined excitation signal applied to the common cathode 26 and corresponding to the superposition of elementary excitation signals for the implementation of physical vapor deposition techniques.

[0082] Each physical vapor deposition technique is implemented by applying an elementary excitation signal to the associated cathode, the elementary excitation signal having a periodically repeated pattern, the pattern being for example a plateau, a pulse or a pulse train.

[0083] The superposition of periodic excitation signals is carried out in a synchronized manner such that the respective patterns of the excitation signals are applied sequentially to the cathode.

[0084] The excitation device 28 is here configured for the simultaneous implementation of a first physical vapor deposition technique and a second physical vapor deposition technique using the common cathode 26.

[0085] The excitation device 28 comprises for example a first electrical generator 34 and a second electrical generator 36 connected in parallel to the common cathode 26, the first electrical generator 34 and the second electrical generator 36 being configured to respectively generate a first electrical signal for the implementation of the first physical vapor deposition technique and the second electrical signal for the implementation of the second physical vapor deposition technique, in a synchronized manner.

[0086] The installation 20 optionally comprises a magnetic field generator 38 (or magnetron) configured to generate a magnetic field in the vicinity of the common cathode 26, for implementing vapor deposition techniques by cathode sputtering known as “magnetron” using the common cathode 26.

[0087] The magnetic field generator 38 comprises one or more permanent magnets and / or one or more electromagnets.

[0088] When the magnetic field generator 38 is active, the first physical vapor deposition technique and the second physical vapor deposition technique implemented simultaneously are magnetron sputtering physical vapor deposition techniques.

[0089] In operation, the atmosphere control device 24 generates a rarefied atmosphere in the chamber 22 and the excitation device 28 generates the combined excitation signal and applies it to the common cathode 26, such that the physical vapor deposition techniques are carried out simultaneously using the common cathode 26.

[0090] In particular, in the illustrated example, the first electrical generator 34 and the second electrical generator 36 generate the first elementary excitation signal and the second elementary excitation signal simultaneously, the first elementary excitation signal and the second elementary excitation signal being combined by superposition to generate the combined excitation signal. Where appropriate, the magnetic field generator 38 generates a magnetic field in the vicinity of the common cathode 26.

[0091] Each of the physical vapor deposition techniques implemented simultaneously can be carried out in unipolar or bipolar mode.

[0092] Subsequently, in the absence of precision, each physical vapor deposition technique can be used in unipolar mode or in bipolar mode.

[0093] Physical vapor deposition techniques implemented simultaneously are, for example, chosen from: unipolar or bipolar high-power pulsed magnetron sputtering (HiPIMS), unipolar or bipolar direct current (DC) magnetron sputtering, unipolar or bipolar pulsed direct current (pulsed-DC) magnetron sputtering, unipolar or bipolar medium frequency (MF) magnetron sputtering and unipolar or bipolar radio frequency (RF) magnetron sputtering.

[0094] In one exemplary embodiment, the common cathode 26 is used for the simultaneous implementation of unipolar or bipolar high-power pulsed magnetron sputtering (HiPIMS) physical vapor deposition and unipolar or bipolar medium-frequency (MF) magnetron sputtering physical vapor deposition.

[0095] Optionally, the installation 20 is configured to polarize the substrate 14 during the implementation of the physical vapor deposition. The polarization of the substrate 14 makes it possible to improve the deposition, in particular the quality and density of the deposited coating. The polarization of the substrate 14 is carried out for example using a dedicated substrate polarization generator 14. The substrate polarization generator 14 is for example configured to apply a constant voltage to the substrate, for example a voltage of the order of 100V.

[0096] Figure 4 comprises three graphs representing a first elementary excitation signal S1, a second elementary excitation signal S2 and a combined excitation signal SC resulting from the combination, and more particularly from the superposition of the first elementary excitation signal S1 and the second elementary excitation signal S2, each graph indicating an instantaneous power of the corresponding excitation signal as a function of time.

[0097] The first elementary excitation signal S1 is configured for the realization of a physical vapor deposition technique by high power pulsed magnetron sputtering.

[0098] The first elementary excitation signal S1 is periodic and based on a first pattern formed of a first pulse. The first elementary excitation signal S1 thus comprises first repeated pulses with a first frequency F1 and a first power P1.

[0099] The second elementary excitation signal S2 is configured for carrying out a medium power magnetron sputtering vapor deposition technique.

[0100] The second elementary excitation signal S2 is periodic and based on a second pattern formed by a train of second identical pulses with a second frequency F2 and having a second power P2. The second elementary excitation signal S2 thus comprises a series of trains of second pulses, each train of second pulses comprising several successive identical pulses with a second frequency F2 and a second power P2.

[0101] A single train of second pulses is shown in Figure 4. The second elementary excitation signal S2 comprises several successive trains of second pulses.

[0102] Preferably, the first frequency F1 is strictly lower than the second frequency F2 and / or the first power P1 is strictly higher than the second power P2.

[0103] The duration of a train of second pulses of the second elementary excitation signal S2 preferably corresponds to the duration between a first pulse and the following first pulse of the first elementary excitation signal S1, and the interval between a train of second pulses of the second elementary excitation signal S2 and the following train of second pulses preferably corresponds to the duration of a first pulse of the first elementary excitation signal S1.

[0104] The first elementary excitation signal S1 and the second elementary excitation signal S2 are synchronized in such a way that the first pattern and the second pattern are alternated in the combined excitation signal SC.

[0105] The superposition of the first elementary excitation signal S1 and the second elementary excitation signal S2 results in a combined excitation signal SC comprising the first pulses at the first power P1 and, between each first pulse and the following first pulse, a train of second pulses at the second power P2.

[0106] In the combined excitation signal SC, the first pattern and the second pattern are formed sequentially, with the sequence being repeated periodically.

[0107] The combined excitation signal SC allows the first physical vapor deposition technique and the second physical vapor deposition technique to be implemented simultaneously. In particular, the first pulses at the first power P1 and with the first frequency F1 allow the first physical vapor deposition technique (high-power pulsed magnetron sputtering physical vapor deposition), the time intervals between the first pulses being used to implement the second physical vapor deposition technique (medium-frequency magnetron sputtering physical vapor deposition) which requires pulses at the second power P2 lower than the first power P1 with a second frequency F2 higher than the first frequency F1.

[0108] In one exemplary embodiment, the common cathode 26 is used for the simultaneous implementation of unipolar or bipolar high power magnetron sputtering (HiPIMS) physical vapor deposition and unipolar or bipolar direct current (DC) magnetron sputtering physical vapor deposition.

[0109] Figure 5 is analogous to Figure 4 and differs in that the second elementary excitation signal S2 is intended for carrying out a physical vapor deposition technique by direct current magnetron sputtering.

[0110] The second elementary excitation signal S2 is periodic and based on a second pattern in the form of a second plateau at a second power P2. The second elementary excitation signal S2 thus comprises plateaus at a second power P2, the plateaus being separated by intervals at zero power, the plateaus preferably having a duration longer than that of the intervals.

[0111] The spacing between the intervals corresponds to the duration between the first pulses of the first elementary excitation signal S1 and the duration of the intervals corresponding to the duration of the first pulses of the first elementary excitation signal S1.

[0112] Preferably, the first power P1 is strictly greater than the second power P2.

[0113] The superposition of the first elementary excitation signal S1 and the second elementary excitation signal S2 results in a combined excitation signal SC comprising the first pulses at the first power P1 with a plateau at the second power P2 between each first pulse and the following first pulse.

[0114] In the SC combined excitation signal, the first pattern and the second pattern are formed sequentially, with the sequence being repeated periodically. The SC combined excitation signal enables the first physical vapor deposition technique and the second physical vapor deposition technique to be implemented simultaneously.

[0115] In particular, the first pulses at the first power P1 and with the first frequency F1 make it possible to implement the first physical vapor deposition technique (high-power magnetron sputtering physical vapor deposition), the time intervals between the first pulses being used to implement the second physical vapor deposition technique (direct current magnetron sputtering physical vapor deposition) which requires a direct current at the second power P2 lower than the first power P1.

[0116] In an exemplary embodiment, at least one or each of the simultaneously implemented physical vapor deposition techniques is implemented using a dedicated cathode, by applying between this dedicated cathode and the substrate a specific excitation signal for the implementation of a single physical vapor deposition technique.

[0117] Each dedicated cathode is associated with a single physical vapor deposition technique and is distinct from each other cathode, dedicated or common.

[0118] In an exemplary embodiment, the excitation signal of each dedicated cathode is generated by a respective excitation signal generator.

[0119] An excitation device 28 in this case comprises a respective excitation signal generator associated with each dedicated cathode.

[0120] In an exemplary embodiment, a first physical vapor deposition technique is implemented using a first dedicated cathode, by applying to this first dedicated cathode a first specific excitation signal for the implementation of this first physical vapor deposition technique, and, simultaneously, a second physical vapor deposition technique is implemented using a second dedicated cathode, by applying to this second dedicated cathode a second specific excitation signal for the implementation of this first physical vapor deposition technique.

[0121] The installation 20 of Figure 6 differs from that of Figure 3, the numerical references associated with the similar elements of which are repeated, by the fact that the installation 20 comprises a first dedicated cathode 26A for the implementation of a first physical vapor deposition technique by cathodic sputtering and a second dedicated cathode 26B, distinct from the first dedicated cathode 26A, for the implementation of a second physical vapor deposition technique different from the first physical vapor deposition technique.

[0122] Preferably, the first dedicated cathode 26A and the second dedicated cathode 26B are made of the same material.

[0123] The excitation device 28 is configured to simultaneously generate a first specific excitation signal applied to the first dedicated cathode 26A and a second specific excitation signal applied to the second dedicated cathode 26B.

[0124] As illustrated in Figure 6, the excitation device 28 comprises for example a first electrical generator 34 configured to generate the first specific excitation signal and connected to the first dedicated cathode 26A and a second electrical generator 36 configured to generate the second specific excitation signal and connected to the second dedicated cathode 24B.

[0125] In operation, the atmosphere control device 24 generates a rarefied atmosphere in the chamber 22, the excitation device 28 simultaneously generates the first specific excitation signal applied to the first dedicated cathode 26A and the second specific excitation signal applied to the second dedicated cathode 26B, so as to simultaneously implement the first physical vapor deposition technique and the second physical vapor deposition technique.

[0126] In particular, the first electrical generator 34 and the second electrical generator 36 respectively generate the first specific excitation signal and the second specific excitation signal simultaneously, applied respectively to the first dedicated cathode 26A and to the second dedicated cathode 26B, so as to simultaneously implement the first physical vapor deposition technique and the second physical vapor deposition technique.

[0127] If applicable, the magnetic field generator 38 generates a magnetic field near the first dedicated cathode 26A and / or near the second dedicated cathode 26B.

[0128] Physical vapor deposition techniques implemented simultaneously are, for example, chosen from: unipolar or bipolar high-power pulsed magnetron sputtering (HiPIMS), unipolar or bipolar direct current (DC) magnetron sputtering and unipolar or bipolar medium frequency (MF) magnetron sputtering.

[0129] In an exemplary embodiment, the first dedicated cathode 26A is used for implementing unipolar or bipolar high power pulsed magnetron sputtering (HiPIMS) and the second dedicated cathode 26B is used for implementing unipolar or bipolar medium frequency (MF) magnetron sputtering.

[0130] In this case, the first specific excitation signal and the second specific excitation signal correspond respectively to the first elementary excitation signal S1 and the second elementary excitation signal S2 of Figure 3.

[0131] In an exemplary embodiment, the first dedicated cathode 26A is used for implementing unipolar or bipolar high power pulsed magnetron sputtering (HiPIMS) and the second dedicated cathode 26B is used for implementing unipolar or bipolar direct current (DC) magnetron sputtering.

[0132] In this case, the first specific excitation signal corresponds to the first elementary excitation signal S1 of Figure 3 and the second specific excitation signal is a constant continuous signal at the second power P2.

[0133] Preferably, during physical vapor deposition, the substrate 14, which is tubular along its longitudinal axis A, is rotated around its longitudinal axis A. This ensures uniform deposition around the circumference of the substrate 14.

[0134] To do this, the installation 20 is configured to rotate the substrate 14 around its longitudinal axis A during physical vapor deposition.

[0135] The invention is not limited to the exemplary embodiments and variant embodiments illustrated and described above.

[0136] It is possible to implement exactly two vapor deposition techniques simultaneously, using a common cathode or two dedicated cathodes, as illustrated in Figures 3 and 6.

[0137] More generally, the deposition of the protective coating 16 is carried out by simultaneously implementing one, two or more physical vapor deposition techniques by cathodic sputtering, using one or more common cathodes and / or one or more dedicated cathodes.

[0138] A physical vapor deposition installation 20 for carrying out the deposition of the protective coating 16 therefore comprises at least one common cathode 26 and / or at least one dedicated cathode 26A, 26B, the excitation device 28 being adapted to generate the combined excitation signal applied to each common cathode 26 and the specific excitation signal applied to each dedicated cathode 26A, 26B.

[0139] Each common cathode is used to implement a group of physical vapor deposition techniques comprising at least two physical vapor deposition techniques. Each group of physical vapor deposition techniques comprises, for example, two physical vapor deposition techniques (this is a pair or couple of physical vapor deposition techniques) or more than two physical vapor deposition techniques.

[0140] Each group of physical vapor deposition techniques is different from any other group(s) of physical vapor deposition techniques, while possibly containing at least one physical vapor deposition technique common to one or more other groups of physical vapor deposition techniques when several groups of physical vapor deposition techniques are implemented simultaneously, each using a respective common cathode.

[0141] Each dedicated cathode is associated with a respective physical vapor deposition technique, while possibly corresponding to a physical vapor deposition technique of one or more groups of physical vapor deposition techniques when at least one group of physical vapor deposition techniques is implemented simultaneously with the physical vapor deposition technique associated with the dedicated cathode.

[0142] In an exemplary embodiment, the deposition of the protective coating 16 is carried out by simultaneously implementing a first physical vapor deposition technique, a second physical vapor deposition technique and a third different physical vapor deposition technique, the first physical vapor deposition technique and the second physical vapor deposition technique being implemented using a common cathode, the third technique being implemented using a dedicated cathode separate from the common cathode.

[0143] In an exemplary embodiment, the deposition of the protective coating 16 is carried out by simultaneously implementing a first physical vapor deposition technique, a second physical vapor deposition technique and a third different physical vapor deposition technique, the first physical vapor deposition technique and the second physical vapor deposition technique being implemented using a first common cathode, the first physical vapor deposition technique and the third physical vapor deposition technique being implemented using a second common cathode distinct from the first common cathode.

[0144] In an exemplary embodiment, the deposition of the protective coating 16 is carried out by simultaneously implementing a first physical vapor deposition technique, a second physical vapor deposition technique and a third different physical vapor deposition technique, implemented respectively using a first dedicated cathode, a second dedicated cathode and a third dedicated cathode.

[0145] In an exemplary embodiment, the deposition of the protective coating 16 is carried out by simultaneously implementing a first physical vapor deposition technique and a second physical vapor deposition technique, the first physical vapor deposition technique and the second physical vapor deposition technique being implemented using a common cathode, the first physical vapor deposition technique being implemented using a first dedicated cathode distinct from the common cathode, and, optionally, the second vapor deposition technique being implemented using a second dedicated cathode, distinct from the common cathode and the first dedicated cathode.

[0146] In the examples indicated above, the first physical vapor deposition technique, the second physical vapor deposition technique and the third physical vapor deposition technique implemented simultaneously are for example selected from unipolar or bipolar high power pulsed magnetron sputtering (HiPIMS), unipolar or bipolar direct current (DC) magnetron sputtering and unipolar or bipolar medium frequency (MF) magnetron sputtering.

[0147] The examples given above are combinable for the simultaneous implementation of the first physical vapor deposition technique, the second physical vapor deposition technique and the third physical vapor deposition technique implemented simultaneously.

[0148] Each of the first physical vapor deposition technique, the second physical vapor deposition technique, and the third physical vapor deposition technique can be implemented simultaneously using at least one common cathode and one dedicated cathode.

[0149] Furthermore, the invention can be applied to substrates other than nuclear fuel rod cladding substrates.

[0150] When the substrate is rotationally symmetrical about a longitudinal axis, preferably, physical vapor deposition is performed by rotating the substrate about its longitudinal axis to ensure uniform deposition around the circumference of the substrate.

[0151] By means of the invention, it is possible to carry out the deposition of a protective coating in a rapid manner, and better suited with the production of nuclear fuel rod cladding on an industrial scale. The deposition rate of the protective coating using a high-power pulsed magnetron sputtering physical vapor deposition (HiPIMS) technique and, simultaneously, another sputtering physical vapor deposition technique, such as direct current (DC) magnetron sputtering or medium frequency (MF) magnetron sputtering, can be two to four times higher than the deposition rate using only the high-power pulsed magnetron sputtering physical vapor deposition (HiPIMS) technique, while maintaining the same deposition quality.

[0152] In particular, the use of at least one common cathode 26 makes it possible to maximize the usage time of the common cathode 26.

[0153] In particular, a common cathode 26 used for implementing a high-power pulsed magnetron sputtering (HiPIMS) physical vapor deposition technique and, simultaneously, another sputtering physical vapor deposition technique such as direct current (DC) magnetron sputtering or medium frequency (MF) magnetron sputtering, can be used with a higher utilization rate than if it were used solely for implementing the high-power pulsed magnetron sputtering (HiPIMS) physical vapor deposition technique.

[0154] The time intervals between high-power pulses of the high-power pulsed magnetron sputtering (HiPIMS) physical vapor deposition technique are in fact used for the implementation of the said other sputtering physical vapor deposition technique.

[0155] The combination of several physical vapor deposition techniques by cathodic sputtering makes it possible to benefit from the advantages of the different techniques, in particular in terms of roughness of the protective coating 16, corrosion resistance of the protective coating 16, density of the protective coating 16 and / or adhesion of the protective coating 16 to the substrate 14.

[0156] Preferably, the deposition of the protective coating 16 is carried out in such a way that the sheath 4 has one or more of the following characteristics:

[0157] - the roughness of the protective coating is equal to or less than 2 pm, in particular equal to or less than 1 pm;

[0158] - the corrosion resistance of the protective coating 16 made of chromium-based material is such that the chromium oxide layer Cr2C>3 is less than 1 pm after five years of use in the core of a nuclear reactor in normal (non-accidental) operation; and / or

[0159] - the density of the protective coating is greater than 98%. Density here refers to the percentage of the theoretical density of the same compact material, or as the theoretical density minus the porosity rate. A density greater than 98% corresponds to a porosity rate of less than 2%)

[0160] The quality of the adhesion between the substrate 14 and the protective coating 16 is tested, for example, by implementing an expansion due to compression test known by the acronym EDC for “Expansion Due to Compression” in English.

[0161] Combining multiple sputtering physical vapor deposition techniques allows for a reduction in the overall size of a physical vapor deposition facility, due to the reduction in the number of cathodes required to achieve desired productivity.

[0162] The table below shows the results of three examples provided as non-limiting examples and one comparative example. [Table 1]

[0163] In the first example (Example 1), a single cathode is used to simultaneously implement high-power pulsed magnetron sputtering physical vapor deposition (HiPIMS) and direct current (DC) magnetron sputtering physical vapor deposition, by applying two superimposed signals to the cathode.

[0164] In the second example (Example 2), a single cathode is used to simultaneously implement high-power pulsed magnetron sputtering (HiPIMS) physical vapor deposition and medium-frequency (MF) magnetron sputtering physical vapor deposition, by applying two superimposed signals to the cathode.

[0165] In the third example (Example 3), two cathodes are used simultaneously, one to simultaneously implement high-power pulsed magnetron sputtering (HiPIMS) physical vapor deposition; and the other to implement direct current (DC) magnetron sputtering physical vapor deposition. Each cathode receives an excitation signal corresponding to the corresponding physical vapor deposition technique.

[0166] In the fourth example (Example 4) which is a comparative example, a single cathode is used to implement a single physical vapor deposition technique, more specifically high power pulsed magnetron sputtering (HiPIMS).

[0167] The deposition rates obtained in the first, second and third examples are 6 pm / h, 5.5 pm / h and 7 pm / h respectively, when the deposition rate achieved by implementing a single sputtering physical vapor deposition technique would be of the order of 2 to 3 pm / h, as illustrated in the fourth example in which the deposition rate is 2 pm / h.

Claims

CLAIMS 1. A method of manufacturing a nuclear fuel rod cladding (4) comprising a substrate (14) covered with a protective coating (16), the manufacturing method comprising providing the substrate (14); and depositing the protective coating (16) on the substrate (14) by physical vapor deposition by cathodic sputtering, by simultaneously implementing several physical vapor deposition techniques by cathodic sputtering, different from each other.

2. A manufacturing method according to claim 1, wherein at least two of the different sputtering physical vapor deposition techniques are carried out simultaneously using a common cathode (26).

3. Manufacturing method according to claim 2, comprising applying to each common cathode (26) a combined excitation signal (SC) corresponding to the superposition of at least two elementary excitation signals (S1, S2), each elementary excitation signal (S1, S2) being formed of a periodic pattern corresponding to a respective sputtering physical vapor deposition technique among the sputtering physical vapor deposition techniques implemented simultaneously using said common cathode (26), the elementary excitation signals (S1, S2) being synchronized in such a way that their respective patterns are present sequentially in the combined excitation signal (SC).

4. Manufacturing method according to claim 3, wherein each elementary excitation signal (S1, S2) is generated by a respective excitation signal generator, the elementary excitation signals (S1, S2) being synchronized and superimposed to form the combined excitation signal (SC) applied to said common cathode (26).

5. Manufacturing method according to any one of the preceding claims, wherein at least one of the simultaneously implemented physical vapor deposition techniques by cathodic sputtering is implemented using a dedicated cathode (26A, 26B), by applying to this dedicated cathode (26A, 26B) an excitation signal for the implementation of this physical vapor deposition technique.

6. The manufacturing method of claim 1, wherein each of the simultaneously implemented sputtering physical vapor deposition techniques is implemented using a dedicated cathode (26A, 26B), in applying to this dedicated cathode (26A, 26B) an excitation signal for the implementation of this physical vapor deposition technique.

7. Manufacturing method according to claim 5 or 6, wherein the excitation signal of each dedicated cathode (26A, 26B) is generated by a respective excitation signal generator (26A, 26B).

8. A manufacturing method according to any one of the preceding claims, wherein the simultaneously implemented physical vapor deposition techniques are selected from: unipolar or bipolar high-power pulsed magnetron sputtering (HiPIMS), unipolar or bipolar direct current (DC) magnetron sputtering, unipolar or bipolar pulsed direct current (pulsed-DC) magnetron sputtering, unipolar or bipolar medium frequency (MF) magnetron sputtering and unipolar or bipolar radio frequency (RF) magnetron sputtering.

9. Manufacturing method according to any one of the preceding claims, in which the substrate (14) is made of a zirconium-based material and / or the protective coating (16) is made of a chromium-based material.

10. Manufacturing method according to any one of the preceding claims, in which the thickness of the protective coating at the end of the deposition step is between 5 μm and 30 μm, in particular between 10 μm and 20 μm.

11. A manufacturing method according to any one of the preceding claims, wherein the substrate has a shape of revolution around a central axis, the manufacturing method comprising rotating the substrate (14) around the central axis during the deposition step.

12. A manufacturing method according to any preceding claim, comprising polarizing the substrate (14) during deposition of the coating.

13. Nuclear fuel rod cladding comprising a substrate (14) covered with a protective coating (16) deposited on the substrate by physical vapor deposition by simultaneously implementing a plurality of different physical vapor deposition techniques by cathodic sputtering.

14. Physical vapor deposition installation, comprising a chamber (22), at least one atmosphere control device (24) for generating a rarefied atmosphere in the chamber (22), at least one cathode (26, 26A, 26B) and an excitation device (28), the installation being configured for the deposition of a protective coating (16) on a substrate (14) introduced into the chamber (22) by simultaneously implementing several different physical vapor deposition techniques by cathodic sputtering using the cathode(s) (26, 26A, 26B).

15. Installation according to claim 14, comprising at least one common cathode (26) for the simultaneous implementation of at least two of the physical vapor deposition techniques by cathode sputtering implemented simultaneously, the excitation device (28) being configured to generate a combined excitation signal (SC) of the common cathode (26) which corresponds to the superposition of several elementary excitation signals (S1, S2), each elementary excitation signal (S1, S2) having a periodic pattern corresponding to a respective one of the physical vapor deposition techniques by cathode sputtering implemented simultaneously using said common cathode (26), the elementary excitation signals (S1, S2) being combined in such a way that their respective patterns are present sequentially in the combined excitation signal (SC).

16. Installation according to claim 14 or 15, comprising at least one dedicated cathode (26A, 26B) for implementing one of the physical vapor deposition techniques by cathode sputtering implemented simultaneously, the excitation device being configured to generate a respective excitation signal for each dedicated cathode (26A, 26B), the excitation signal corresponding to the physical vapor deposition technique by cathode sputtering associated with this dedicated cathode.

17. Installation according to any one of claims 14 to 16, configured for polarization of the substrate (14) during the deposition of the coating.

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