 , more than 60 reactors have received 20-year extensions to their licensed lifetimes.The average capacity factor for all US reactors has improved from below 60% in the 1970s and 1980s, to 92% in 2007.After the Three Mile Island accident, NRC-issued reactor construction permits, which had averaged more than 12 per year from 1967 through 1978, came to an abrupt halt; no permits were issued between 1979 and 2012 (in 2012, four planned new reactors received construction permits).