Columbia International Affairs Online: Working Papers

CIAO DATE: 04/2012

Why Fukushima Was Preventable

James M. Acton, Mark Hibbs

March 2012

Carnegie Endowment for International Peace


Public sentiment in many states has turned against nuclear energy following the March 2011 accident at Japan’s Fukushima Daiichi Nuclear Power Station. The large quantity of radioactive material released has caused significant human suffering and rendered large stretches of land uninhabitable. The cleanup operation will take decades and may cost hundreds of billions of dollars. The Fukushima accident was, however, preventable. Had the plant’s owner, Tokyo Electric Power Company (TEPCO), and Japan’s regulator, the Nuclear and Industrial Safety Agency (NISA), followed international best practices and standards, it is conceivable that they would have predicted the possibility of the plant being struck by a massive tsunami. The plant would have withstood the tsunami had its design previously been upgraded in accordance with state-of-the-art safety approaches. The methods used by TEPCO and NISA to assess the risk from tsunamis lagged behind international standards in at least three important respects: * Insufficient attention was paid to evidence of large tsunamis inundating the region surrounding the plant about once every thousand years. * Computer modeling of the tsunami threat was inadequate. Most importantly, preliminary simulations conducted in 2008 that suggested the tsunami risk to the plant had been seriously underestimated were not followed up and were only reported to NISA on March 7, 2011. * NISA failed to review simulations conducted by TEPCO and to foster the development of appropriate computer modeling tools.