Re: Re: Built in the first place
You quote from http://www.chernobyl.info/index.php?navID=10 when saying the reactor power level dropped to less that one percent "for unknown reasons".
I believe the current consensus is that the experiment protocol called for a reduction in power output to ~20%. However, this was only supposed to take place after the output had already been reduced to 50%. This had not been possible due to an earlier shortfall in grid supply caused by the failure of a power station elsewhere. The reactor was therefore running at normal output when the experiment began.
Reducing the power from 100% to 20% resulted in an increase in the fission poison product xenon-135, which absorbs neutrons. The resulting unexpected drop in reactor output was counteracted by withdrawing the control rods beyond recommended limits.
Additional increases in coolant flow, as called for by the experiment protocol, further reduced the reactor's output, since water also absorbs neutrons. The technicians responded by removing manual control rods. Although the reactor's output was now restored to its expected level, fission was to a large degree controlled by factors outside the technicians' control, i.e. xenon-135, which was eventually expended, and water, which was removed from the core by the design of the experiment itself.
The disaster, from the start of the experiment, to the steam explosion and resulting ignition of the graphite moderator, took approximately 43 seconds.