The low figure of CO2 usage often cited is based on an estimation you can read at https://onlinelibrary.wiley.com/doi/full/10.1111/j.1530-9290.... I don't remember it giving a clear estimate on how much it rises, but that is understandable, as already the current estimate is not a reliable figure.
But it's the wrong comparison. Nuclear energy is not to be replaced with fossil energy, but with renewables. So that "advantage" is completely irrelevant.
Not nearly even in the same ballpark as setting fossil fuels on fire, or do you have any sources that show otherwise?