becaususe you'u're going to let yoyour guard dowandd t that's t biggesesdanger. regulator can predidict ever possible c contingency thahat c affect the nuclear powower plan you haveve to be p prepared for anytything. but it is simply too expensive to prepare for everything. in the united states, most of our plants were designed, licensed and built decades ago. and -- in the 1960's, 1970's and 1980's and they were designed to a certrtain standar that was considered to be the best knowledge at the time, for instance, what's the most severere earthquake? and the historical record, what's the highest flood? that information was taken into account.t. but in some cases, the methods that were used for ananalyzing that datata were faulty. things were left out. for instance, the impact of an upstream d dam failure was not considered. but now we believe that to be a significant risk. the acony plalant in sosouth carolinana is one that's s been knowown for a long time to be ulnerable to a dam fale -- dam failure. owned by duke energy. a plant quadad cities in illino and riv