Episode 2 continues the discussion of our current energy mix and their associated benefits and challenges. Nuclear energy now supplies 70% of our low-carbon electricity. There have been no major accidents in the United States since Three Mile Island, but some close calls: corrosion detected in 2002 at the Davis-Besse plant could have caused a meltdown if uncorrected. All of the current U.S. nuclear plants are to be retired in the next 40 years, but cost overruns and the continuing problem of nuclear waste disposal cast doubt on the long-term viability of nuclear power.