According to the 2009 update of an MIT study first published in 2003, nuclear power plants in the United States have become more reliable and significantly safer. For one thing, nuclear plant operators now receive better and more rigorous training. And, according to the report, new reactor designs meet strenuous safety standards. On the other hand, the MIT study also notes that since Three Mile Island and Chernobyl there have been some close calls. For example, in 2002 the Davis Besse reactor in Ohio avoided a serious accident when a hole in the reactor vessel was discovered during an inspection. The incident is all the more troubling for the fact that the plant owners apparently ignored early warning signs. So bottom line, the MIT report concludes that improved training and safety standards have made nuclear power relatively safer. But it’s not yet clear that all nuclear plants have embraced safety as their main priority.