Politics! Every time nuclear power is mentioned Chernobyl, Fukushima and/or Three Mile Island are almost obligatorily mentioned. No matter that they were all older designs with much more risk than more recent designs, or that the US Navy has operated nuclear reactors safely for 70 years, or their ecological advantages, or....pick a reason. POLITICS!
And to be frank given the history of corporations and governments cutting costs coupled with human behavior I really wouldn't past someone, somewhere, somehow fucking something up with even one of the newer designs.