THE explosion at the Fukushima plant is the third worst nuclear incident in history, after Chernobyl and Three Mile Island.
Major design flaws were blamed for Chernobyl in April 1986, when overheating caused two massive explosions at the Ukraine plant.
Huge clouds of radioactive material escaped into the atmosphere and travelled hundreds of miles across Europe.
The disaster produced 100 times more radiation than the Nagasaki and Hiroshima bombs and has been blamed for 200,000 deaths from cancer and other diseases. The March 1979 Three Mile Island accident in Pennsylvania in the US was similar to Fukushima because a fault caused overheating. Although the plant suffered a “severe core meltdown” only small amounts of radiation escaped.
Tokyo Electric Power Co.(TEPOC), operator and owner of the Fukushima plants, has injected sea water into the reactor to prevent it from overheating, said Edano, who acknowledged the core of the reactor may have been deformed due to overheating.
Backup cooling systems failed, leaving the core to glow unchecked and sparking fears that fuel could breach the containment shell, leaking dangerous radiation into the densely-populated region that houses 30 million people.
About 200,000 residents were evacuated from a 20-kilometre radius around the plant, which was built in the 1970s and is one of 54 nuclear plants providing about 30 per cent of Japan's power.
Operator Tokyo Electric Power Co (TEPCO) insisted radiation was still within safe levels, but mounting internal pressure meant that some vapour had to be released, and it warned another blast might take place in a second reactor.
