these pipes are not zirconium but it s sort of like the same idea of rusting. it is not rusting, it is ox di says. when something gets rusty, it starts to degrade and breaks down. if the bottom of your car looks like this, like mine does right now, you start to worry about whether you have to replace it, whether you need framework done, or whether you just need a new car. rust. zirconium doesn t rust but it does oxidize when it is exposed to air so the combination of the heat and the oxidization, it is like super fast rusting on steroids. between that, the metal starts to break an and allows the our rain to get exposed and it s so hot it begins to melt. it s true for spent fuel rods.