Patent Number: 
Section: claims

1. A process for the manufacture of a nuclear fuel cladding for a nuclear reactor, said fuel cladding comprising i) a substrate containing a zirconium-based internal layer coated or not coated with at least one interposed layer placed over said internal layer and ii) at least one external layer placed over the substrate and composed of a protective material chosen from chromium or a chromium-based alloy; the process comprising the following successive steps:a) providing a substrate containing a zirconium-based internal layer having an internal surface which delimits a closed volume for receiving the nuclear fuel and having an external surface opposite to said internal surface, said zirconium-based internal layer being coated or not coated with at least one interposed layer placed over said external face of the zirconium-based internal layer, said interposed layer having an internal face facing the external face of the zirconium-based internal layer, said interposed layer further comprising of at least one interposed material chosen from tantalum, molybdenum, tungsten, niobium, vanadium, hafnium or their alloys;b) ion etching of the external surface of the zirconium-based internal layer or, when present, of the external surface of the interposed layer; andc) deposition of said at least one external layer over the substrate and in contact with the external surface of the zirconium-based internal layer or, when present, with the external face of the interposed layer, said deposition being performed with a high power impulse magnetron sputtering (HiPIMS) process in which a magnetron cathode is composed of the protective material, said protective material being chosen from chromium or a chromium-based alloy,thereby producing a protected substrate suitable for use as a nuclear fuel cladding, wherein oxidation of the nuclear fuel cladding is inhibited on exposure of said cladding to a humid atmosphere at a temperature of 1200-1300° C. in the nuclear reactor. 2. A process for the manufacture of a nuclear fuel cladding according to claim 1, wherein the substrate provided in step (a) comprises an internal coating placed under said internal layer. 3. A process for the manufacture of a nuclear fuel cladding according to claim 1, wherein the zirconium-based internal layer is coated with at least one interposed layer placed over said internal layer. 4. A process for the manufacture of a nuclear fuel cladding according to claim 3, wherein said at least one interposed layer is placed over said internal layer by carrying out the following successive steps before the etching step a):a′) ion etching of the surface of said internal layer; andb′) production of a substrate by deposition of said at least one interposed layer over said internal layer with a high power impulse magnetron sputtering (HiPIMS) process in which the magnetron cathode is composed of the at least one interposed material. 5. A process for the manufacture of a nuclear fuel cladding according to claim 1, wherein deposition of said at least one external layer according to step (b) comprises depositing a first external layer with said HiPIMS sputtering process and depositing at least a part of an additional external layer or layers with a magnetron cathode sputtering process of a different type from the HiPIMS which is carried out simultaneously with said HiPIMS sputtering process. 6. The process according to claim 1, wherein each of said at least one external layer has a thickness of 1 μm to 50 μm. 7. The process according to claim 1, wherein each of said at least one external layer has a columnar structure. 8. The process according to claim 7, wherein constituent columnar grains of the columnar structure have a mean diameter of 100 nm to 10 μm.