The estimate is that nuclear kills 0.04 people per TWh produced. This includes mining, refining, and the construction and operation of nuclear power plants. Natural gas kills about 4 people per TWh produced, making it far more lethal than nuclear all considered.
Fascinating in a grim way, rooftop solar is actually more lethal than nuclear, at 0.44 per TWh. Quite literally more people have died falling off roofs installing solar panels than died at Chernobyl. With rooftop being such a minuscule percentage of global production, expect that number to change.
By and far the most lethal is coal. The world average is 161 per TWh. But that average is hiding a lot of nastiness, because the true range is between 15 (US) and 278 (China). Quite literally millions of people die each year due to pollution, most of them because of coal.
This is a classic case of how people don’t calculate risk correctly. Nuclear accidents are scary, rare things and so people focus in on them. But in trying to get rid of nuclear we’ve ended up shifting primarily to coal and natural gas, energy sources that kill multiple orders of magnitude more people than nuclear does. But because these people die one at a time in hospitals, we end up missing the scale of the tragedy as a society.
