n=1, but my general takeaway from the show wasn't that nuclear is fundamentally flawed, it was that a series of pretty questionable choices by management and egregiously eschewing safety protocol lead to the accident. The graphite-tipped rods were also essential to the accident happening as well, but only after that series of bad choices had put the reactor in a such an extreme state. (Reading about the event on Wikipedia seems to confirm this take, but, of course I'm not pretending to have any more than the most basic layman's understanding of all this)