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A fuel element for a pressurized water reactor is described. The fuel element contains a laterally open skeleton having control-rod guide tubes each with a first end and a second end, spacers fastened to the control-rod guide tubes, a fuel element head disposed at the first end of the control-rod gu

A fuel element for a pressurized water reactor is described. The fuel element contains a laterally open skeleton having control-rod guide tubes each with a first end and a second end, spacers fastened to the control-rod guide tubes, a fuel element head disposed at the first end of the control-rod guide tubes, and a fuel element foot disposed at the second end of the control-rod guide tubes. Gastight cladding tubes are inserted into the skeleton and each is filled with a column of fuel pellets. At least some of the gastight cladding tubes have a multilayer wall. The multilayer wall is formed of a mechanically stable matrix containing a first zirconium alloy disposed in a middle of the multiplayer wall; and a thinner protective layer of a second zirconium alloy alloyed to a lesser extent than the first zirconium alloy. The thinner protective layer is bound metallurgically to the matrix and is disposed on an inside of the matrix facing the fuel pellets.

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1. A fuel element for a pressurized water reactor, comprising:a laterally open skeleton having control-rod guide tubes each with a first end and a second end, spacers fastened to said control-rod guide tubes, a fuel element head disposed at said first end of said control-rod guide tubes, and a fuel

1. A fuel element for a pressurized water reactor, comprising:a laterally open skeleton having control-rod guide tubes each with a first end and a second end, spacers fastened to said control-rod guide tubes, a fuel element head disposed at said first end of said control-rod guide tubes, and a fuel element foot disposed at said second end of said control-rod guide tubes; and gastight cladding tubes inserted into said skeleton and each filled with a column of fuel pellets, at least one of said gastight cladding tubes having a multilayer wall, said multilayer wall including: a mechanically stable matrix formed of a first zirconium alloy disposed in a middle of said multilayer wall, said first zirconium alloy containing 1.0 to 1.8% Sn, 0.2 to 0.6% Fe, and up to 0.3% Cr, a remainder being zirconium of industry purity, said first zirconium alloy having precipitations of secondary phases, a size of the precipitations corresponding to a standardized annealing duration of 2 to 80×10??h; and a thinner protective layer of a second zirconium alloy alloyed to a lesser extent than said first zirconium alloy, said thinner protective layer bound metallurgically to said matrix and disposed on an inside of said matrix facing said fuel pellets, said second zirconium alloy containing at least 0.2% and up to 0.8% by weight of iron, a remainder being zirconium of industrial purity, said second zirconium alloy having precipitations of secondary phases, a size of the precipitations corresponding to a standardized annealing duration of about 0.1 to 3×10?18 h. 2. The fuel element according to claim 1, wherein an iron content of said second zirconium alloy is 0.40±0.04% by weight.3. The fuel element according to claim 1, wherein said first zirconium alloy contains 1.3±0.1% Sn; 0.28±0.04% Fe; 0.16±0.03% Cr; 0.01±0.002% Si and 0.14±0.02% O.4. The fuel element according to claim 1, including flow guide blades being carried by at least said spacers in an upper part of said fuel element, on a side facing away from a flow of pressurized water, for intermixing the pressurized water.5. The fuel element according to claim 1, including a further protective layer of a third zirconium alloy which is thinner than said matrix and is bonded metallurgically to an outside of said multilayer wall.6. The fuel element according to claim 1, wherein said second zirconium alloy contains at least 0.30% by weight of iron, a remainder being zirconium of industrial purity.7. The fuel element according to claim 1, wherein said second zirconium alloy contains at most 0.6% by weight, of iron, a remainder being zirconium of industrial purity.8. The fuel element according to claim 1, wherein said first zirconium alloy contains at least 1.2% Sn, at least 0.24% Fe and at least 0.10% Cr, a remainder being zirconium of industrial purity.9. The fuel element according to claim 1, wherein said first zirconium alloy contains at most 1.5% Sn, at most 0.5% Fe and at most 0.25% Cr, a remainder being zirconium of industrial purity.10. The fuel element according to claim 1, wherein the size of the precipitations in said first zirconium alloy corresponds to a standardized annealing duration of 30±10·10?18 h.11. A method for producing a cladding tube for a fuel rod of a pressurized water reactor, which comprises the steps of:providing a first zirconium alloy containing 1.0 to 1.8% Sn, 0.2 to 0.6% Fe, and up to 0.3% Cr, a remainder being zirconium of industry purity; providing a second zirconium alloy containing at least 0.2% and up to 0.8% by weight of iron, a remainder being zirconium of industrial purity; thermally treating the first zirconium alloy and the second zirconium alloy differently and independent of one another, in each case solution annealing, with subsequent-different standardized annealing durations of 2 to 80×10?18 h and 0.1 to 3×10?18 h, respectively; producing from the first zirconium alloy and at least the second zirconium alloy a multilayer composite tube, a wall of the multilayer composite tube containing, in a middle region, as a matrix, a thick layer of the first zirconium alloy, and to an inside of the thick layer of the first zirconium alloy a protective layer formed of the second zirconium alloy, the protective layer being bonded to the matrix metallurgically; and processing the multilayer composite tube further into a finished cladding tube, in such a way that the protective layer and the thick layer are subjected to substantial equivalent thermal conditions, without the solution annealing. 12. The method according to claim 11, which comprises forming the second zirconium alloy to contain 0.2 to 0.5% by weight of iron, a remainder being zirconium of industrial purity, and, before the production of the multilayer composite tube, the second zirconium alloy is treated at most with a standardized annealing duration of below 2×10?18 h.13. The method according to claim 11 which comprises forming the second zirconium alloy to contain 0.4±0.04% by weight of iron.14. The method according to claim 11, which comprises further processing the multilayer composite tube into the finished cladding tube with a standardized annealing duration of below 3×10?18 h.15. The method according to claim 11, which comprises during the production of the multilayer composite tube, a third zirconium alloy is bonded metallurgically to the first zirconium alloy.16. The method according to claim 11, which comprises subjecting the second zirconium alloy to a standardized annealing duration of about 1±0.5×10?18 h before a production of the multilayer composite tube.17. The method according to claim 11, which comprises forming the second zirconium alloy to contain 0.3 to 0.5% by weight of iron, a remainder being zirconium of industrial purity, and, before the production of the multilayer composite tube, the second zirconium alloy is treated at most with a standardized annealing duration of below 2×10?18 h.18. The method according to claim 11, which comprises further processing the multilayer composite tube into the finished cladding tube with a standardized annealing duration of below 2×10?18 h.19. A cladding tube for a fuel rod of a pressurized water reactor, in combination with a column of fuel pellets filled therein, comprising:a multilayer wall, including: a mechanically stable matrix formed of a first zirconium alloy disposed in a middle of said multilayer wall, said first zirconium alloy containing 1.0 to 1.8% Sn, 0.2 to 0.6% Fe, and up to 0.3% Cr, a remainder being zirconium of industry purity, said first zirconium alloy having precipitations of secondary phases, a size of the precipitations corresponding to a standardized annealing duration of 2 to 80×10?18 h; and a thinner protective layer of a second zirconium alloy alloyed to a lesser extent than said first zirconium alloy, said thinner protective layer bound metallurgically to said matrix and disposed on an inside of said matrix facing said fuel pellets, said second zirconium alloy containing at least 0.2% and up to 0.8% by weight of iron, a remainder being zirconium of industrial purity, said second zirconium alloy having precipitations of secondary phases, a size of the precipitations corresponding to a standardized annealing duration of about 0.1 to 3×10?18 h.