The operators watch their panels. None of them notice the power output display. 205... 210... 220...
544 INT. TRIAL ROOM - NOW 544
LEGASOV
Inside the core, the remaining water is quickly converting to steam. A void is being created. There is no fresh water to replace it.
As he speaks, he adds multiple RED PLACARDS to the right column. "Positive Void Coefficient" (R2), "Nuclear Fission" (R3), "Positive Void Coefficient" (R4), "Nuclear Fission" (R5).
LEGASOV
Steam increases reactivity increases heat increases steam increases reactivity. The fuel is too cold to counter the vicious cycle. The remaining xenon decays away.
Legasov removes both blue "Xenon Poisoning" placards (B4, B5). There are NONE on the left side now. And five RED ones on the right.
LEGASOV
The power is rising. And nothing left to stop it. 1:23 and 35 seconds...
545 INT. CONTROL ROOM - REACTOR #4 - 1:23:35 545
Akimov and Toptunov watch the panel. Then Toptunov notices: LIGHTS blinking on, one after another in quick succession on the large CIRCULAR FUEL CHANNEL display.
Oh god. He looks up at the power output display.
320... 360... 400...
TOPTUNOV We have a power surge! Sasha!
Everyone turns at once to look at the power output.
440... 500...
DYATLOV (in shock) What did you-- ?
546 INT. TRIAL ROOM - NOW 546
CLOSE ON LEGASOV.
LEGASOV
1:23 and 40 seconds. The power is surging. The men in Control Room 4 have only one option left. (MORE)
LEGASOV (cont'd) In every control room of every nuclear reactor in the world, there is a button with one single purpose-- to "scram" or instantly shut down the reaction. In Soviet reactors, that button is called "AZ- 5". You press AZ-5, all of the control rods insert at once, and the reaction is stopped dead. (beat)
But.
He stops. Glances over at Khomyuk, who knows that the moment is almost upon them. Then the SIX SCIENTISTS.
And Khomyuk realizes— he's going to do it. He's finally going to tell the truth. But before he can say a word:
DYATLOV
What are you waiting for Legasov? Tell your lies.
A hushed gasp from the room. Legasov turns in disbelief to the defendant BOX, where Dyatlov glares back at him.
JUDGE KADNIKOV Comrade Dyatlov, you will not be warned again.
DYATLOV
Or what?
BRYUKHANOV (shut up!) For god's sake, Dyatlov—
DYATLOV
Legasov's already given it away. He said before there was no way to avoid what was coming. He knows something.
(points to Khomyuk) She knows something.
JUDGE KADNIKOV Strike that from the record.
Dyatlov rises, jabbing his finger toward a stunned Legasov.
DYATLOV I know what you are, Valery Alexeyevich. You're a liar. You're a liar and a coward.
The soldiers grab Dyatlov's arms to pull him away, but:
JUDGE KADNIKOV We've heard enough for today. The defendants will be remanded to custody. Court will—
Legasov finds his voice.
LEGASOV I haven't finished.
Stepashin turns his dark gaze on Legasov. How dare he?
LEGASOV
I have more evidence to give.
Shcherbina leans forward. Impossible for us to tell what he's thinking...
STEPASHIN It is not necessary. Your testimony is concluded.
(to Kadnikov) Your honor.
Legasov deflates. Turns back to Khomyuk. He tried. He tried to do the right thing.
JUDGE KADNIKOV Court is now adjourned. We will resume tomorrow with--
Shcherbina rises. That wonderful, terrible look in his eyes. The last stand of the stubborn, impossible Ukrainian.
SHCHERBINA The trial continues.
Judge Kadnikov begins to sweat. This is different. He looks at Stepashin, who falters.
JUDGE KADNIKOV Comrade Shcherbina--
SHCHERBINA Let him finish.
Stepashin is outranked. He glances at the CAMERAS. The dead faces of the "press." The audience. KGB scattered among them, no doubt. The show must go on. He gestures to Legasov. Very well. It's your funeral.
Shcherbina nods to Legasov. He knows what Legasov has decided to do. If we go down, we go down together. Legasov nods back. Gratitude.
Now he looks out into the audience. There are the SIX SCIENTISTS. Listening intently. Almost as if they, too, know the choice he is about to make.
LEGASOV
Dyatlov broke every rule we have, and pushed a reactor to the brink of destruction. He did these things believing there was a fail-safe. AZ- 5. A simple button to shut it all down.
(beat)
But in the circumstance he created-- there wasn't. The shut-down system had a fatal flaw.
Dyatlov listens in stunned horror. What did they not tell him? What did he not know?
LEGASOV
At 1:23 and 40 seconds, Akimov engages AZ-5.
547 INT. CONTROL ROOM - REACTOR #4 - 1:23:40 547
Akimov flips the cover off the AZ-5 switch and PRESSES IT.
548 INT. TRIAL ROOM - NOW 548
LEGASOV
The fully-withdrawn control rods begin moving back into the reactor. These rods are made of boron, which reduces reactivity. But not their tips. The tips are made of graphite, which accelerates reactivity.
JUDGE KADNIKOV (disbelief)
Why?
LEGASOV Why? For the same reason our reactors do not have containment buildings around them like those in the West.
(MORE)
LEGASOV (cont'd) The same reason we don't use properly enriched fuel in our cores. The same reason we are the only nation that builds water-cooled graphite moderated reactors with a positive void coefficient.
(beat) It's cheaper.
Legasov turns back to the room. And to his jury.
LEGASOV
The first part of the rods that enter the core are the graphite tips. And when they do, the reaction in the core, which had been rising-- now skyrockets. Every last molecule of liquid water instantly converts to steam, which expands and ruptures a series of fuel rod channels. (beat)
The control rods in those channels can move no further. The tips are fixed in position, endlessly accelerating the reaction.
He lets it sink in.
LEGASOV
Chernobyl reactor 4 is now a nuclear bomb.
(beat) 1:23 and 42 seconds.
549 INT. REACTOR HALL - 1:23:42 549
Perevozchenko is in the observation room, making notes on a clipboard. He hears a terrible CLUNKING and HISSING.
He looks out through the window, and his jaw drops.
LEGASOV (V.O.) Perevozchenko looks down on the enormous steel lid of the reactor, and sees the impossible.
THE LID - DOZENS of individual STEEL SQUARES are JOSTLING UP AND DOWN like popcorn... now more of them. And MORE.
LEGASOV (V.O.) The fuel channel caps, which each weigh 350 kilograms, are jumping up and down.
Perevozchenko DROPS his clipboard in horror, and RUNS out of the room onto the catwalk... racing for the stairs...
LEGASOV (V.O.) The pressure required to do this is unimaginable. He runs to warn the control room.
Perevozchenko half runs, half falls down the catwalks stairs, scrambles back to his feet, and keeps running.
LEGASOV (V.O.) But there's nothing he can do to stop what is coming. 1:23:44.
550 INT. PUMP ROOM - 1:23:44 550
KHODEMCHUK backs away from the pumps. They are ROCKING in place... valves begin to POP OFF like BULLETS...
551 INT. CONTROL ROOM - REACTOR #4 - 1:23:44 551
Akimov's hand is still on the AZ-5 button. But the LED DISPLAY is climbing. 700... 1000... 1800...