What could happen if the rods began to melt?
Just like at the Three Mile Island nuclear disaster in Dauphin County, Pa., pieces of the rods could crack and crumble to the bottom of the reactor. As their temperature rises, the fuel rods made of zircaloy cladding and cement with ceramic fuel pellets inside would expand like a balloon, said Arthur Motta, chair of nuclear engineering program at Penn State University. In a really severe accident such as Chernobyl, “it becomes like molten metal with ceramic, a blob. This [in Japan] is all inside the pressure vessel, a cylindrical containment under pressure which is very thick.” Should the rods melt, they would eventually make their way down to the bottom of the reactor and could react with the metal there. Worst-case scenario, the blob pierces through that and into the bottom of the containment. Part of the melted rods fell to the bottom of containment at Three Mile Island, said Prof. Luxat, but luckily water there had formed a solid protective surface to prevent piercing. As Prof. Hol
