Discussion of RBMK Reactor
I havent seen someone try to explain actually why, the reactor blew up, and why it was thought to be "impossible" or "unknown"
Full disclosure, I'm not a nuclear physicist, I'm an Astronomer who has read a crapload on the topic of Chernobyl because I always thought it was super interesting
Edit;
Read up on the post made by MCvarial, he kindly points out the errors below
And TraumaticTramAddict made a wonderful post further explaining the core reasons that caused the run away steam production that caused the explosion
Even when what I wrote below is wrong and mistaken, hopefully it will give context to those reading the messages I liked above to further understand the steps leading up to Chernobyl, further official documentation can be found in the posts to the thread for those curious of going deeper into the technicalities of RBMK reactors
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The Reactor was known to be problematic, and specifically inestable when it was intended to be producing low amounts of electricity, a situation that would actually cause the reactor to start producing more thermal energy. The key here is that at the time it wasnt known that the Reactor itself could explode, specially so when doing "the correct" by the book control of the reactor.
The accident happened because they were doing a low power test of the reactor, where one of the engineers in charge forced the reactor to go below the specified energy production for an extended period of time, this caused the reactor to overheat, but when the graphite bars (Moderators) with Boron tips (Absorbents) where lowered into the reactor, those bars actually pushed water away from the fuel that was boiling water around it, which meant that the excess neutrons werent getting absorbed by the water and that created a cascade reaction where the water became steam at a faster rate than it could cool the reactor fuel, then that overwhelmingly fast accumulation of steam is what made the reactor itself explode
The engineers thought it was actually a tank where the steam and hydrogen generated from the molecular division of water by the radiation was being stored blew up, they didnt knew that the reactor could blow up the way it did, they knew it was dangerous to operate the reactor in low energy production, they didnt knew it could blow up
In short, the best way to keep RKMB reactors stable is to keep them working, if you try to produce low amounts of energy they overheat, what happened is that they tried to keep it producing too low energy for too long, core overheated, and when they tried to stabilize with Graphite and other Neutron Absorbing Rods they pushed away the water that was keeping it cool and that created the critical overheating and overpressure that blew up the reactor itself, it didnt help that the absorving rods didnt actually go in all the way in and got stuck like a meter in when they are like 7 meters long...
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If anybody has links to RBMK documentation, id love to read it, hopefully I did good job explaining the problem with the Chernobyl reactors and if it is any error let me know and I'll correct it
If anyone wants to hear more, in The Chernobyl Podcast episode 1, lead producer gives extra explanations of the failures of RMBK reactor at chernobyl
Posted May 16, 2019, 7:19 PM UTC · edited