In the aftermath of Fukushima, decisions to slow or stop the future use of nuclear power have not been based on rational economic analysis. We find that there are cost-effective technologies that would greatly mitigate future natural disasters. Even if the U.S. nuclear industry adopted new safety technologies and paid the full cost of insurance and borrowing, it is more efficient to continue to use existing nuclear plants than to replace them with new fossil fuel plants. However, new nuclear plant costs can exceed fossil fuel alternatives if the price of carbon emissions is below $118/ton. (JEL Q40, Q48, Q54)