More than 1,000 people were feared dead and authorities scrambled to prevent meltdown at two nuclear plants after a monster tsunami devastated a swathe of northeast Japan.
Reactor cooling systems failed after Friday's record 8.9-magnitude earthquake hit, unleashing a terrifying 10-metre (33-foot) high wave that tore through coastal towns and cities and destroying all in its path.
Radiation 1,000 times above normal was detected in the control room of one nuclear plant, although authorities said levels outside the facility's gates were only eight times above normal, spelling "no immediate health hazard".
Tens of thousands of people were evacuated from around the the plants as Tokyo Electric Power, which runs the facilities, said it had released some radioactive vapour at both locations to relieve building reactor pressure.
"We are not in a situation in which residents face health damage," Chief Cabinet Secretary Yukio Edano told reporters, according to Jiji news agency.
The two nuclear plants affected are the Fukushima No. 1 and No. 2 plants, both located about 250 kilometres (160 miles) northeast of Tokyo.
The atomic emergency came as the country struggled to assess the full extent of the devastation wrought by the massive tsunami, which was unleashed by the strongest quake ever recorded in Japan off the eastern coast.
The towering wall of water pulverised the northeastern city of Sendai, where police reportedly said 200-300 bodies had been found on the coast.
There has been speculation that a meltdown may occur at one reactor, with this Bloomberg report being a good example - Explosion Destroys Walls of Japanese Nuclear Reactor Building, NHK Reports.
An explosion occurred at the Fukushima Dai-Ichi power station north of Tokyo, destroying the walls of the No. 1 reactor building, NHK Television said. The report came after the government said a reactor may be melting.
Smoke was rising around the nuclear reactor after an aftershock from yesterday’s quake struck, Ryohei Shiomi, a spokesman at the country’s nuclear safety agency said by phone.
The spokesman said several people were injured during an aftershock that struck around 3:30 p.m. Japan time, adding he had no further information. Tokyo Electric Power Co., which operates the plant, said it had no information, when contacted by Bloomberg News.
Japan’s Nuclear and Industrial Safety Agency said earlier that a nuclear reactor in the Fukushima Dai-Ichi power station, about 220 kilometers (140 miles) north of Tokyo, may be starting to melt down after Japan’s biggest earthquake on record hit the area yesterday.
Fuel rods at the No. 1 reactor at the plant run by Tokyo Electric Power Co. may be melting after radioactive Cesium material left by atomic fission was detected near the site, Nuclear and Industrial Safety Agency, spokesman Yuji Kakizaki said by phone today.
“If the fuel rods are melting and this continues, a reactor meltdown is possible,” Kakizaki said. A meltdown refers to a heat buildup in the core of such an intensity it melts the floor of the reactor containment housing.
Tokyo Electric, Asia’s biggest power company, started releasing radioactive gas and steam into the atmosphere to reduce pressure in the containment housing after yesterday’s magnitude 8.9 earthquake, Akitsuka Kobayashi, a company spokesman, said by phone earlier today