0:00:07.935,0:00:10.545
Legasov : Dyatlov broke every rule we have.

0:00:13.741,0:00:17.091
He pushed the reactor[br]to the brink of destruction.

0:00:21.101,0:00:23.531
He did these things believing[br]there was a fail-safe.

0:00:23.883,0:00:26.983
AZ-5, A simple button to[br]shut it all down.

0:00:27.090,0:00:29.630
But, in the circumstances, he created.

0:00:29.895,0:00:31.635
- There wasn't.

0:00:31.680,0:00:35.224
The shutdown system had a fatal flaw.

0:00:36.733,0:00:41.813
At 1 : 23 : 40,[br]Akimov engages AZ-5(AЗ-5).

0:00:49.132,0:00:52.729
The fully withdrawn control rods begin[br]moving back in to the reactor,

0:00:52.964,0:00:55.744
These rods are made of boron - which reduces reactivity.

0:00:55.766,0:00:57.208
But not the tips.

0:00:57.569,0:00:59.736
The tips - are made of graphite.

0:00:59.736,0:01:01.917
Which accelerates reactivity.

0:01:02.311,0:01:04.281
- Why?

0:01:08.040,0:01:10.520
- ...Why?

0:01:11.556,0:01:15.556
For the same reason... Our reactors do not have[br]containment buildings around them.

0:01:16.526,0:01:17.626
Like those in the West.

0:01:17.626,0:01:22.184
For the same reason, We don't use[br]properly enriched fuel in our cores.

0:01:22.593,0:01:24.773
For the same reason, we are the only nation

0:01:24.773,0:01:28.483
that builds water-cooled graphite-moderated reactors

0:01:28.639,0:01:31.779
with a positive void coefficient.

0:01:33.015,0:01:34.315
Because cheaper.

0:01:40.719,0:01:43.088
The first part of the rods[br]that enter the core

0:01:43.088,0:01:45.611
are the graphite tips. And when they do,

0:01:45.611,0:01:47.878
The reaction in the core which had been rising,

0:01:47.878,0:01:49.649
Skyrockets.

0:01:49.649,0:01:54.505
Every last molecule of liquid water[br]instantly converts to steam,

0:01:54.505,0:01:57.696
which expands and ruptures[br]a series of fuel rod channels,

0:01:57.869,0:02:01.395
The control rods in those channels[br]can move no further.

0:02:01.832,0:02:04.175
The graphite tips are fixed in position.

0:02:04.175,0:02:07.022
Endlessly accelerating the reaction.

0:02:07.022,0:02:11.022
Chernobyl Reactor 4 - is now a Nuclear Bomb.

0:02:11.343,0:02:13.836
1 : 23 : 42,

0:02:13.836,0:02:17.394
P. Yuvchenko looks down of the enormous[br]steel lid of the reactor,

0:02:17.394,0:02:19.516
And sees the impossible.

0:02:19.695,0:02:23.475
The control rods and fuel channel caps[br]which each weight 350 kilograms

0:02:23.475,0:02:25.672
are jumping up and down.

0:02:25.762,0:02:27.742
He runs to warn the control room,

0:02:27.853,0:02:31.103
But there's nothing he can do[br]to stop what is coming.

0:02:31.211,0:02:34.001
1 : 23 : 44,

0:02:34.128,0:02:37.738
The steam blows more fuel channels apart,

0:02:37.799,0:02:39.599
You do not know how high the power went,

0:02:39.599,0:02:41.501
We only know the final reading.

0:02:43.393,0:02:44.503
- Reactor 4,

0:02:44.582,0:02:48.332
Designed to operate at 3,200 Megawatts,

0:02:48.359,0:02:52.359
Went beyond 33,000.

0:02:56.122,0:03:00.122
The pressure inside the core,[br]can no longer be hold back.

0:03:00.356,0:03:02.346
at long last we've arrived,

0:03:02.409,0:03:04.327
1 : 23 : 45.

0:03:04.801,0:03:05.981
Explosion.

0:03:06.199,0:03:07.359
(core explodes)

0:03:07.649,0:03:10.224
In the instant, the lid is thrown off the reactor,

0:03:10.314,0:03:11.954
Oxygen rushes in.

0:03:12.194,0:03:15.941
It combines these hydrogen and super-heated graphite.

0:03:17.281,0:03:20.554
The chain of disaster is now complete.

0:04:00.048,0:04:02.918
No one in the room that night knew,

0:04:02.992,0:04:06.442
The shutdown button can act as a detonator.

0:04:07.618,0:04:09.488
They didn't know it.

0:04:10.597,0:04:12.287
Because it was kept from them.

0:04:12.287,0:04:16.966
- Comrade Legasov, you're contradicting[br]your own testimony in Vienna.

0:04:17.413,0:04:20.287
The testimony in Vienna was a lie!

0:04:20.615,0:04:23.835
I lied![br]To the world.

0:04:23.852,0:04:25.742
Not the only one who kept the secrets,

0:04:25.742,0:04:27.782
There are many,