Actually, it relied on two complimentary safeguard circuits to restrict the rod movements within its calculated performance envelope. They could not be overriden from the front panel, so electricians were dispatched to cut them off, in order to conduct an &quot;experiment&quot; in the wake of International Labour Day. How safe are the other reactor designs when malicious human intervention is considered is still a very open question.<p>I would also remark there was a deserved stream of criticism from the West both for the reactor design and the containment effort that followed. The overwhelming opinion throughout the 1990s-2000s was that the Western designs are safe and catastrophic scenarios like Chernobyl are implausible. Then Fukushima happens, the three reactors blow up and the only saving grace for Japan was the wind blowing oceanside. And the containment is done by low wage workers in sneakers, while Asimo and its advanced robot colleagues play robosoccer in Tokyo.<p>The narrative is now changed to other designs being &quot;inherently safe&quot;, although it&#x27;s not very plausible how <i>any</i> concentrated, massive release of energy can be made inherently safe. Yes you can reduce probabilities and exclude some catastrophic scenarios, but this is a thing with crises: they always come unexpected. I&#x27;m sure when the plug in a molten salt reactor fails for some reason (say tectonic shift from a quake), there will no doubt be another design touted as safe.<p>Now consider that fission power atm is what, 10-15% of compound world power generation? As of now it&#x27;s focused in a handful of nations, most of whom are known for safety culture. As it proliferates worldwide, the average quality of maintenance will decline and the number of stations would naturally multiply, so perhaps we&#x27;ll see a major nuclear accident every couple years instead of decades. And we haven&#x27;t even started with waste disposal and non-proliferation considerations here.<p>I&#x27;d really really rather wait for fusion.