I am a NW skeptic.
I'm a NW empiricist...
BTW on topic of radioactive contamination: in the event of any major disruption of society, most of the nuclear power plants can be expected to melt down, and their spent fuel pools can be expected to run dry. A spent fuel pool of a single reactor, that is maintained the way the reactors are ("i'll take the trash out tomorrow, honey!" approach), can release up to 10 Chernobyls of cs-137 or so (depending to the amount of fuel stored. Ten or more cores can be stored) . Even 1 Chernobyl corresponds to awful lot of nukes. Other fun fact is that the nuclear fuel uses zirconium cladding, which, if overheated, 'burns' even in absence of external oxygen, reacting with the uranium dioxide. When Chernobyl is discussed, it is commonly emphasised how unsafe was the design with combustible carbon inside the reactor. The combustible materials are a major deficiency, yes, and has likely helped the radioactive plume reach high altitudes, but all reactors have fuel that can and will burn if overheated via the decay heat. In the re-racked fuel pools that can result in combustion of even very old fuel after the fresh spent fuel ignites itself. the fuel pools of old reactors typically contain more spent fuel as per original design - once again the 'i'll just cram down trash and put this little bit on top' approach to trash we all know from our daily life.
Other interesting fact: It is a common assertion that fusion bombs are cleaner per yield, often asserted as dramatically so. Not very much in practice. Most of the 'fusion' bombs make half of their yield by fissioning the U-238 casing on the ultra fast fusion neutrons. Those neutrons do fission U-238, producing the fission products. In the testing, the substitute casing can be used; for example the Tzar Bomba had ~60 megaton yield, very clean, with afaik lead casing, but would have had 120 megaton yield, or more, with U238 casing, half of it from fission. So the contamination from nuclear testing is not directly comparable to that of nuclear war.
I wonder about the effect of a bomb (nuclear or otherwise) hitting or detonating at the worst possible distance from a nuclear power plant might be? I'm imagining if it was powerful enough it'd pull a lot of that radioactive material up and out...
Just a reminder that some of the old threats are still around (and hence that AI is not only something that can go hideously badly, but also some thing that could help us with the other existential risks as well):
http://blog.practicalethics.ox.ac.uk/2012/03/old-threats-never-die-they-fade-away-from-our-minds-nuclear-winter/
EDIT: as should have been made clear in that post (but wasn't!), the existential risks doesn't come from the full fledged nuclear winter directly, but from the collapse of human society and fragmentation of the species into small, vulnerable subgroups, with no guarantee that they'd survive or ever climb back to a technological society.