Japanese nuclear experts have restored the cooling system at the generating units 5 and 6 of the Fukushima Dai-ichi nuclear complex, which was badly affected by a powerful earthquake and tsunami.
The cooling system at units 1 and 2 is due to be restored today, while on Sunday, the cooling system is expected to be brought back to normal at units 3 and 4, where the situation is seen as the most dangerous.
All signs are that the core zone of reactor 3 has melted down, and a massive release of radiation is quite likely there.
To avoid this, water is being poured on the reactor.
The reactor of generating unit 4 has no fuel, but it contains spent fuel rods that are a threat.