(09-04-2019, 07:48 PM)Black Aeronaut Wrote: It really is a shame. If not for this one rather esoteric safety flaw, the RBMK Reactor seems like the platonic ideal of fission reactors.
Esoteric?
There's a positive void coefficient in the reactor design. Which means it's not passively safe nor does it throttle itself down as it grows more active and starts to enter an uncontrollable state. That's not an esoteric design flaw, that's a disaster waiting to happen in any industrial process. That's why you shove as many safety systems onto it as you can fit to prevent it from exploding.
The use of graphite lead control rods only makes the problem worse. I get wanting to use a moderator to get a bit more reactivity going on start up, but it'd have been safer to use a neutron reflector (fast neutrons as you noted earlier are much less likely to split another atom compared to thermal neutrons, and RBMK reactors are thermal neutron based reactors) or another neutron absorbing material as the water displacing channel plug, even if that does mean you can't target specific channels with a bit of extra moderator to make it more reactive.
Part of the problem is that they designed a reactor where one of the safety systems also doubled as a reaction catalyst to make it go faster. And they did it deliberately. It's utter stupidity to give a safety system any other role other than being a safety system, as then it's no longer working or employed as a safety system.