Patent Number: 
Section: claims

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; andgastight cladding tubes inserted into said skeleton, each of said gastight cladding tubes being filled with a column of fuel pellets, at least some of said gastight cladding tubes each having a multilayer wall, said multilayer including:a mechanically stable matrix formed of a first zirconium alloy of a given thickness, alloyed to a given extent, and disposed in a middle of said multilayer wall, said first zirconium alloy being formed of 0.8 to 2.8% niobium and zirconium of industrial purity and at most 2.7% of further additives; anda protective layer of a second zirconium alloy thinner than said given thickness and alloyed to a lesser extent than said given extent of said first zirconium alloy, said protective layer bound metallurgically to said matrix and disposed on an inside of said matrix facing said fuel pellets, said second zirconium alloy containing from 0.2% 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 said 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 in said first zirconium alloy, a quantity of said further additives is smaller than a quantity of the niobium. 3. The fuel element according to claim 1, wherein said first zirconium alloy contains 1.0±0.2% niobium, 0.14±0.02% oxygen, a remainder being the zirconium of industrial purity. 4. The fuel element according to claim 1, wherein said first zirconium alloy has precipitations of secondary phases, and a size of said precipitations of secondary phases corresponds to a standardized annealing duration of lower than 0.5×10−18 h.