The entire clean energy argument depends on your classification of nuclear energy. Long term storage issues put it squarely in the unclean category for me so I'd argue that US energy is by and large pretty unclean. I'm also pricing in the expected value of meltdowns in my unclean rating. It's hard to quantify exactly but the black swan events have pretty catastrophic consequences for the environment. Since I've witnessed two very severe ones in my lifetime, one in what many people would call a technically very advanced country I don't think it's unreasonable. If you think that's tinfoilhat-crazy, fell free to talk to an insurance or reinsurance company about insuring nuclear plants fur a fon conversation.