On March 11th, 2011, an earthquake followed by a tsunami hit northern Japan. Within 2 days, three reactors at Fukushima Daiichi nuclear power plant melted down.The tubes of fuel in the reactors heated up, to maybe 3000 C, melted, and slumped to the bottom of the Reactor Pressure Vessel (RPV) that contained them. It then in all three cases burnt through the seals around the control rod entry holes in the bottom of this metal bottle, the RPV, and dribbled out in various amounts on to the concrete floor underneath, which it began to burn into and through.