Underscoring the seriousness of the situation, the Fukushima prefecture government Sunday widened its mandatory evacuation zone to 20 kilometers (12.4 miles) around both nuclear plants вЂ“ ordering an additional 80,000 people to leave, in addition to the 62,000 residents who had already left, Japanese press reports said. It is possible for that molten material to get so hot that it could melt through the primary steel confinement shell вЂ“ and then, even through the floor of the reactor building, US experts say. The rods are filled with uranium oxide ceramic pellets wrapped in zirconium cladding. 3 reactor based on the assumption that it is a possibility.'ДЄ nuclear reactor core meltdown occurs when fuel rods in the reactorвЂ™s core overheat and begin to melt. вЂњBut we are dealing with it under that assumption. вЂњWe cannot confirm this because it is in the reactor,вЂќ he continued. 1 reactor, he acknowledged 'there is that possibility.вЂќ Asked if fuel rods were partially melting in the No. 1 reactor, we ventilated and injected water at an early stage,' Edano said, according to wire reports of the press conference. 3 reactor dropped so that part of the fuel rods became exposed, Edano said. 1 reactor вЂ“ a previously unprecedented step that some US experts described as a desperate measure. Edano said the decision had been made far sooner to inject seawater directly into the No. 3 reactor at the Fukushima I plant, about 150 miles north of Tokyo, as well as at its No. A total of 11 of the nationвЂ™s 54 reactors shut down following the quake, knocking out about 30 percent of JapanвЂ™s power.ДЄt a Sunday morning press briefing, Chief Cabinet Secretary Yukio Edano said experts were 'assuming the possibility of a meltdown' at the No. Japanese authorities now list six reactors at two different nuclear power plants вЂ“ Fukushima I and nearby Fukushima II вЂ“ in a state of emergency following the massive earthquake and tsunami waves that hit Japan Friday. ItвЂ™s a last-ditch effort to cool them enough to avert Chernobyl- or Three Mile Island-like core meltdowns even as government officials admitted partial meltdowns are already assumed to have occurred in both units.

Japanese workers and nuclear experts raced against the clock to pump seawater into two damaged nuclear reactors.

Japan nuclear reactor meltdown 2011