Nuclear Meltdown of Fukushima Daiichi

Tsunami waves generated by the main shock of the Japan earthquake on March 11, 2011, damaged the backup generators at the Fukushima Daiichi plant. Although all three of the reactors that were operating were successfully shut down, the loss of power caused cooling systems to fail in each of them within the first few days of the disaster. Rising residual heat within each reactor’s core caused the fuel rods in reactors 1, 2, and 3 to overheat and partially melt down, leading at times to the release of radiation. Melted material fell to the bottom of the containment vessels in reactors 1 and 2 and bored sizable holes in the floor of each vessel—a fact that emerged in late May. Those holes partially exposed the nuclear material in the cores. Explosions resulting from the buildup of pressurized hydrogen gas occurred in the outer containment buildings enclosing reactors.