i think people are missing the point about nuclear power. they think it's a safety issue, or they're dealing with luddites that are afraid of technology.
the actual problem with nuclear is that the mining and shipping of uranium is so carbon-intensive as to defeat the point of using it. any issues you have with nuclear energy aside, it's just not an answer if you're trying to reduce carbon emissions.
further, we'll eventually run out of uranium, and then what? we'll need to shift to renewable energy, if we don't find ourselves back on coal in a pinch.
i'm not anti-nuclear; i think there's a place for nuclear power, and i think that research should continue to be funded around the potential use of fusion power. but, it's just simply not an answer to the climate crisis, and sanders is at least right to point that out.