Fuel cladding tube reactor water

Cladding tube reactor fuel water (4) for a pressurized water reactor, comprising said tube coating an outer layer (6) of a first zirconium alloy and having metallurgically bonded thereto an inner layer (7) of a the second zirconium alloy, adapted to protect said inner layer (7) to the casing (4) against stress corrosion cracking, in which the thickness of the inner layer (7) is 5-40% of the thickness of cladding tube reactor fuel (4), wherein the second zirconium alloy comprising tin as alloy material, and wherein each of the zirconium alloy comprises at least 96 weight percent zirconium, characterized that the first zirconium alloy comprises 500-2000 ppm by weight of oxygen, and because the main materials of the first alloy zirconium alloy are niobium, iron and tin, wherein the content of Cua lquier additional substance is below 0.05 percent by weight, and that the first zirconium alloy comprises at least 0.1 weight percent niobium.