1
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Legasov : Dyatlov broke every rule we have.

2
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He pushed the reactor
to the brink of destruction.

3
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He did these things believing
there was a fail-safe.

4
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AZ-5, A simple button to
shut it all down.

5
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But, in the circumstances, he created.

6
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- There wasn't.

7
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The shutdown system had a fatal flaw.

8
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At 1 : 23 : 40,
Akimov engages AZ-5(AЗ-5).

9
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The fully withdrawn control rods begin
moving back in to the reactor,

10
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These rods are made of boron - which reduces reactivity.

11
00:00:55,766 --> 00:00:57,208
But not the tips.

12
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The tips - are made of graphite.

13
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Which accelerates reactivity.

14
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- Why?

15
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- ...Why?

16
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For the same reason... Our reactors do not have
containment buildings around them.

17
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Like those in the West.

18
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For the same reason, We don't use
properly enriched fuel in our cores.

19
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For the same reason, we are the only nation

20
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that builds water-cooled graphite-moderated reactors

21
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with a positive void coefficient.

22
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Because cheaper.

23
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The first part of the rods
that enter the core

24
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are the graphite tips. And when they do,

25
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The reaction in the core which had been rising,

26
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Skyrockets.

27
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Every last molecule of liquid water
instantly converts to steam,

28
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which expands and ruptures
a series of fuel rod channels,

29
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The control rods in those channels
can move no further.

30
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The graphite tips are fixed in position.

31
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Endlessly accelerating the reaction.

32
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Chernobyl Reactor 4 - is now a Nuclear Bomb.

33
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1 : 23 : 42,

34
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P. Yuvchenko looks down of the enormous
steel lid of the reactor,

35
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And sees the impossible.

36
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The control rods and fuel channel caps
which each weight 350 kilograms

37
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are jumping up and down.

38
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He runs to warn the control room,

39
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But there's nothing he can do
to stop what is coming.

40
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1 : 23 : 44,

41
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The steam blows more fuel channels apart,

42
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You do not know how high the power went,

43
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We only know the final reading.

44
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- Reactor 4,

45
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Designed to operate at 3,200 Megawatts,

46
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Went beyond 33,000.

47
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The pressure inside the core,
can no longer be hold back.

48
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at long last we've arrived,

49
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1 : 23 : 45.

50
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Explosion.

51
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(core explodes)

52
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In the instant, the lid is thrown off the reactor,

53
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Oxygen rushes in.

54
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It combines these hydrogen and super-heated graphite.

55
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The chain of disaster is now complete.

56
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No one in the room that night knew,

57
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The shutdown button can act as a detonator.

58
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They didn't know it.

59
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Because it was kept from them.

60
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- Comrade Legasov, you're contradicting
your own testimony in Vienna.

61
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The testimony in Vienna was a lie!

62
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I lied!
To the world.

63
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Not the only one who kept the secrets,

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There are many,