Zirconium alloy

With Zircaloy, also zircaloy, zircaloy or Zircaloy are metal alloys that consist of more than 90 % of zirconium, respectively. Zirconium has a very important role in the chemical process equipment (nozzles, pumps, pipes or valves), because the element has a very high corrosion resistance. Furthermore, the alloy contains a small amount of tin (about 1.5 %) and most other metals, such as iron, nickel, chromium or niobium.

Because of its low capture cross section for neutrons, i.e. neutrons its high permeability, Zircaloy cladding tubes of the fuel rods for nuclear reactors is used. In these sheaths, the nuclear fuel, usually uranium dioxide or uranium- plutonium mixed oxide is (MOX ), in the form of tablets ( pins ) ( pellets). To achieve the highest possible thermal conductivity, the remaining gap between the cladding tube of Zircaloy and the nuclear fuel, helium gas is compressed therein.

Generally, a corrosion of the Zirkalloyoberflächen is inevitable in a reactor. The corrosion, and therefore the thickness of the oxide layer, increasing steadily over time. Its magnitude is mainly determined by the nature of the material, the cladding tube, and the chemical composition of the surrounding coolant. The ever- present radiation in the reactor also influences the structure of the cladding material. Corrosion is therefore one of the processes which limit the operating time of the fuel in a reactor to about three to five years.