A second explosion has hit a Japanese nuclear plant that was damaged in Friday’s earthquake, but Japanese officials are reporting that the reactor core is still intact.
A huge column of smoke billowed from Fukushima reactor 3, two days after a blast hit reactor 1.
Like the previous one, the latest explosion is believed to have been caused by a hydrogen build-up after the reactor lost its cooling system.
The US said it had moved one of its aircraft carriers from the area after detecting low-level radiation 100 miles (160km) offshore.
The Government said the plant’s reactor 2 is also a cause for concern after water levels began falling there, meaning it was not being cooled effectively. A similar cooling system breakdown preceded the explosions at reactors 1 and 3.
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However, scientists said this morning that although dramatic, the explosions do not appear to have damaged the containment chamber and that the reactor core appeared to be intact.
“The explosion seen this morning does evoke the idea of an atomic mushroom cloud, but it is important to stress that this isn’t what it is,” said Paddy Regan, professor of nuclear physics at the University of Surrey.
It is clear that some radiation was released in the blast, suggesting that a “partial meltdown” may have occurred.
However, this is likely to have involved the cooling rods that were inserted into the core to stop the nuclear reactions that generate energy, rather than a melting of the reactor core itself or its containment vessel.
“Again, the word meltdown sounds dramatic, but it could have been a single rod, out of perhaps several hundred, that was compromised,” said Professor Regan. “If this were a litmus test for nuclear power, so far the reactors in Japan have passed. You can’t imagine a bigger natural disaster than this. Japan has more than 50 nuclear power stations and so far all the reactor vessels appear to have maintained their integrity.”