Rebuilding reactors could be a boon for the likes of General Electric (which designed the Fukushima reactor) as well as French nuclear giant Areva.

FORBES: Reports Claim Meltdown At Japanese Reactor

Because this was a reactor that operated on water that was already at its boiling point, this also meant that the pressure inside the reactor was rising as well.

FORBES: Explainer: What Caused The Incident At Fukushima-Daiichi

As of 14:00 local time (05:00 GMT) on Friday, the temperature of water inside the cooling pool at reactor 3 was 15.1C, well below the safety limit of 65C, Tepco said.

BBC: Fukushima nuclear plant: Cooling system power restored