No one could have predicted on March 10, 2011, that the imminent Tōhoku earthquake, at magnitude 9.0, would be the greatest to hit Japan, or foreseen the giant tsunami that struck the Japanese coast minutes later. But that does not mean the subsequent meltdown of three reactors at the Fukushima Daiichi nuclear power station was unavoidable. The plant was built to withstand a big earthquake and survive a moderately sized tsunami, but a panoply of engineering errors—too-short sea walls, backup diesel generators installed in locations likely to flood, pools overcrowded with spent fuel rods, and a main control room insufficiently shielded against radiation—permitted the worst nuclear accident since Chernobyl. While Japanese nuclear regulators and TECPO, the utility that owns Fukushima Daiichi, knew that many of these vulnerabilities existed, the authorities’ sophisticated geophysical models considered such an intense earthquake to be impossible in the region.
