Even counting for the whole life cycle, nuclear is a very small greenhouse gas emitter. One plant lasts decades and a very small amount of ore needs to be mined, because uranium is very energy-dense.

I think your point is valid, but lacks generality. Almost nothing we do is carbon neutral. Our energy production certainly isn't. Playing devil's advocate, PV and wind turbines also need to be built, transported, installed, disassembled, and disposed of, all of which emits greenhouse gases.