I recently watched the HBO mini-series ‘Chernobyl’. Particularly in episode 2, the (fictional) character Khomyuk says that if the corium melted through the concrete and reached the water in the bubbler pool beneath, the resultant explosion would be somewhere between 2-4 megatons. This is way off the mark of any possible outcome, the upper bound being probably 0.00015 megatons as it is calculated here.
My questions are the following. Did the show include this number (2-4 megatons) because that is what was believed at the time or is the show just plain wrong? Could they be talking about the following fallout rather than the explosion itself? (In other words, maybe they were comparing the fallout that a 2-4 megaton nuclear bomb would produce).
Thank you in advance.
I really have no idea where the writers got those numbers from. They are not present in any of the Chernobyl literature I am familiar with, nor anything similar to them. The explosion numbers, and the effects of the explosion, are vastly inflated (the effects are vastly inflated even for the inflated numbers). Personally I would not spend much time trying to dissect where the error came from: it seems entirely invented in a writer's head. For whatever reasons, fans of the show seem to want to assume the best about this kind of line, but it's nonsense, and likely just invented for the purpose of heightening the tension, and not run by any kind of technical expert.
(You can see some more of my thoughts on the show and its source material in the comments to this question, but you have to expand the deleted comment to see them.)