What /Actually/ Happened at Chernobyl
Channel: vlogbrothers
Date: 2019-06-14

This video was so dang fun to research, which, of course, I feel super guilty about because, like, real people died. But, after watching the HBO miniseries, I knew there was more to the science of this. I've also heard a lot of stuff from both credible and non-credible sources that just doesn't hold up to scrutiny. The idea of the "graphite tipped rods" for example is just a simplification for broad audiences. But I've also heard smart folks talk about how RBMK reactors have a positive /fuel/ temperature coefficient, which is not true. No nuclear reactors do, since fuel that reacted more as it got hot would be the kind of thing that would explode every time. 

However, for a moment, because water had become such a vital part of the neutron absorption in the reactor, it did have a positive temperature coefficient...meaning that getting hotter made it hotter which made it hotter which made it hotter. That's a coefficient for the entire reactor, and it's due to the "positive void coefficient" where, as the water got hotter, it got less good at absorbing neutrons. 

Usually that would be more than counter-acted by the negative fuel temperature coefficient, which is why they thought it couldn't explode...but it was not in this particular circumstance. 

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