Alvin set for upgrade

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Few research tools in the history of science can match the achievements of Alvin, the US manned deep-submersible.

It was this 46-year-old vessel which discovered the hot volcanic vents on the ocean floor that transformed ideas about where and how life could exist.

The sub is also famed for finding an H-bomb lost at sea and for making one of the first surveys of the Titanic.

But this veteran of the abyss has been withdrawn from service this week as it gets ready for a major re-fit.

Alvin is to undergo a two-phase, $40m (