After 75 years or so of nuclear power, we already have tens of thousands of years of nuclear waste to deal with (it'll be deadly that long), not to mention nuclear isotopes in the ocean, in the soil, and in the air (from bomb testing, mining, processing; from use of DU weaponry, and from numerous other sources. From Chernobyl, from Fukushima, from Love Canal -- yes, despite the denial). Rivers and shorelines where nuclear plants are sited are typically heavily polluted with radioactive material. Etc.

Nuclear energy is "clean" in the same sense that electric cars are "clean" -- meaning the pollution (lithium mining and processing, for just a start, in the case of EVs) is out of sight for most people and both the public and the politicians can pretend it doesn't exist.