In that figure, if you look at the median (the black line), it's quite small.
There is this one very anti-nuclear Stanford professor, who has managed to publish some estimates where the carbon footprint of nuclear power is way larger than in other estimates. These numbers are probably now forever part of the literature, and they make the range of published numbers quite large in every literature survey.
Sometimes this activist professor also sues people for libel, if they publish results disagreeing with his.
https://en.wikipedia.org/wiki/Mark_Z._Jacobson
