Legasov : Dyatlov broke every rule we have.
He pushed the 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.
But, in the circumstances, he created.
- There wasn't.
The shutdown system had a fatal flaw.
At 1 : 23 : 40, Akimov engages AZ-5(AЗ-5).
The fully withdrawn control rods begin moving back in to the reactor,
These rods are made of boron - which reduces reactivity.
But not the tips.
The tips - are made of graphite.
Which accelerates reactivity.
- Why?
- ...Why?
For the same reason... Our reactors do not have containment buildings around them.
Like those in the West.
For the same reason, We don't use properly enriched fuel in our cores.
For the same reason, we are the only nation
that builds water-cooled graphite-moderated reactors
with a positive void coefficient.
Because cheaper.
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,
Skyrockets.
Every last molecule of liquid water instantly converts to steam,
which expands and ruptures a series of fuel rod channels,
The control rods in those channels can move no further.
The graphite tips are fixed in position.
Endlessly accelerating the reaction.
Chernobyl Reactor 4 - is now a Nuclear Bomb.
1 : 23 : 42,
P. Yuvchenko looks down of the enormous steel lid of the reactor,
And sees the impossible.
The control rods and fuel channel caps which each weight 350 kilograms
are jumping up and down.
He runs to warn the control room,
But there's nothing he can do to stop what is coming.
1 : 23 : 44,
The steam blows more fuel channels apart,
You do not know how high the power went,
We only know the final reading.
- Reactor 4,
Designed to operate at 3,200 Megawatts,
Went beyond 33,000.
The pressure inside the core, can no longer be hold back.
at long last we've arrived,
1 : 23 : 45.
Explosion.
(core explodes)
In the instant, the lid is thrown off the reactor,
Oxygen rushes in.
It combines these hydrogen and super-heated graphite.
The chain of disaster is now complete.
No one in the room that night knew,
The shutdown button can act as a detonator.
They didn't know it.
Because it was kept from them.
- Comrade Legasov, you're contradicting your own testimony in Vienna.
The testimony in Vienna was a lie!
I lied! To the world.
Not the only one who kept the secrets,
There are many,