#zircaloy

Alloys: Zircaloy

Not a specific alloy name, Zircaloy is a trademarked name for a common subgroup of zirconium alloys. Usually at least 95% zirconium by weight, these alloys often contain other metals such as tin, iron, chromium, nickel, and niobium, among other elements, to improve zirconium’s mechanical properties and corrosion resistance. Compositions of three zirconium alloys are shown in the top figure above. 

Zirconium as a pure metal has superior thermal properties and a very low absorption cross-section of thermal neutrons, and the main use of zirconium alloys is as cladding for fuel rods for nuclear reactors, especially water reactors. Aside from being corrosion resistant, zirconium alloys are also typically biocompatible and used for body implants such as knees or hips.

One difficultly that arises in using zirconium alloys such as Zircaloy is that the metal is difficult to find without hafnium, and therefore the hafnium must be separated from the zirconium, especially before it can be used in nuclear reactions. Another thing to watch for in zirconium alloys is hydrogen embrittlement, as the oxidation of zirconium in water releases hydrogen gas. 

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