I don't remember the complete list of events, but i don't see why putting a controll rod in too far would lead to an increase in fission, infact quite the opposite.. - I thought they tried to retract the fuel rods too fast or something and they ended up jamming... anyways amongst other controlls of which i don't know, apparently the controll rods are held by electromagnets, therefore a power failure means a stop to reactor activity.... Also the containment vessels are now built to withstand crazy stuff... there are many videos of tests of planes etc crashing into reactors, however ofcourse it is not about keeping stuff out, its about keeping stuff in...
- There also was not a nuclear explosion... the vessel just couldnt take the pressure...
what did you do?
If I can remember correctly, when perfrorming the tests, the coolant flow rate decreased, meaning the coolant flowed more slowly through the core, heating the water into steam thus creating a positive void coefficient (steam pockets in the core created and wiki puts it very well:
"The reactor had a dangerously large positive void coefficient. The void coefficient is a measurement of how a reactor responds to increased steam formation in the water coolant. Most other reactor designs have a negative coefficient, i.e. they attempt to decrease heat output when the vapor phase in the reactor increases, because if the coolant contains steam bubbles, fewer neutrons are slowed down. Faster neutrons are less likely to split uranium atoms, so the reactor produces less power (a negative feed-back). Chernobyl's RBMK reactor, however, used solid graphite as a neutron moderator to slow down the neutrons, and the water in it, on the contrary, acts like a harmful neutron absorber. Thus neutrons are slowed down even if steam bubbles form in the water. Furthermore, because steam absorbs neutrons much less readily than water, increasing the intensity of vaporization means that more neutrons are able to split uranium atoms, increasing the reactor's power output. This makes the RBMK design very unstable at low power levels, and prone to suddenly increasing energy production to a dangerous level. This behavior is counter-intuitive, and this property of the reactor was unknown to the crew."
At the moment of explosion, the rods were almost completely removed from the core, so as the power levels rose, the SCRAM was initiated but the lower section of the rods was made of graphite, which slowed the neutrons more than the steam it displaced, leading to more fission, a huge power spike which heated the steam further, and blew the core apart.
Contrary to what you might read about on wiki, it did NOT start a graphite fire! If you have ever tried to set graphite on fire, you will know that it is damned hard and completely impossible at the low temperatures of a reactor. The fire that you see in the photos is the building fabric, burning fuel and cladding.
I think that is more or less it, its quite complex to understand fully.
