[The Kremlin, Moscow: Legasov and Ulana Khomyuk explain the consequences of a nuclear meltdown with full water tanks]
Ulana Khomyuk: When the lava enters these tanks, it will instantly superheat and vaporize approximately 7,000 cubic meters of water, causing a significant thermal explosion.
Gorbachev: How significant?
Khomyuk: We estimate between two and four megatons. Everything within a thirty-kilometer radius will be completely destroyed, including the three remaining reactors at Chernobyl. The entirety of the radioactive material in all of the cores will be ejected at force and dispersed by a massive shock wave, which will extend approximately two hundred kilometers and likely be fatal to the entire population of Kiev, as well as a portion of Minsk. The release of radiation will be severe, and will impact all of Soviet Ukraine, Latvia, Lithuania, Byelorussia, as well as Poland, Czechoslovakia, Hungary, Romania, and most of East Germany.
Gorbachev: What do you mean, ‘impact’?
Legasov: For much of the area, a nearly permanent disruption of the food and water supply, a steep increase in the rates of cancer and birth defects. I don't know how many deaths there will be, but many. For Byelorussia and the Ukraine, ‘impact’ means completely uninhabitable for a minimum of one hundred years.
Gorbachev: [visibly shaken] There are more than fifty million people living in Byelorussia and Ukraine.
Legasov: Sixty, yes.
Gorbachev: And how long before this happens?
Legasov: Approximately 48 to 72 hours. But we may have a solution. We can pump the water from the tanks. Unfortunately, the tanks are sealed shut by a sluice gate, and the gate can only be opened manually from within the duct system itself. So we need to find three plant workers who know the facility well enough to enter the basement here, find their way through all these duct ways, get to the sluice gate valve here, and give us the access we need to pump out the tanks. Of course, we will need your permission.
Gorbachev: My permission for what?
Legasov: Um, the water in these tanks... the level of radioactive contamination—
Khomyuk: They'll likely be dead in a week.
Legasov: We're asking for your permission to... kill three men.
Gorbachev: Comrade Legasov... all victories inevitably come at a cost.