(Adds earlier reports from fourth paragraph. See EXT2 for news on quake.)
March 12 (Bloomberg) -- 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. Pressure has started to fall in the containment housing, said Yoshihiro Sugiyama, a spokesman at the country’s nuclear safety agency.
Winds in the area of the Fukushima plant are blowing at less than 18 kilometers per hour mostly in an offshore direction, according to a 4 p.m. update from the Japan Meteorological Association.
The government earlier today widened the evacuation zone around the reactor to 10 kilometers from 3 kilometers, affecting thousands of people. The quake and the tsunami that followed is estimated to have killed at least 500 people with hundreds more missing, the National Police Agency said.
“When the pressure starts building up, the emergency procedure is to start venting,” Dave Lochbaum, director of the nuclear safety project at the Union for Concerned Scientists, said in a telephone interview. “They’ve essentially entered a beat the clock game. As long as there is no fuel damage, there will be radioactivity, but it will be very low.”
Radiation spread by the venting won’t be at a level dangerous to health, said Ryohei Shiomi, a spokesman at the government’s nuclear agency said earlier.
Tokyo Electric started venting gas from a containment section of the No. 1 reactor at Fukushima Dai-ichi at about 9 a.m. local time. The company is preparing to do the same at the Dai-Ni nuclear plant nearby, a spokesman said.
Tokyo Electric earlier said it had lost control of pressure building up in three reactors at the Dai-Ichi power plant. Temperatures in the control room rose to higher than 100 Celsius (212 Fahrenheit), said Naoki Tsunoda, a company spokesman.
The plant’s operators need to connect to the electricity grid, fix emergency diesel generators or bring in more batteries to power a backup system that pumps the water needed to cool the reactor, said Lochbaum, a nuclear engineer who has worked at nuclear power plants for 17 years.
The air cooling system in the containment building probably failed due to the power loss, allowing pressure to increase inside, Lochbaum said.
The main barrier between a reactor and outside areas is the containment building, Lochbaum said. Without an air cooling system the air heats, causing pressure to rise inside the building, with the risk that radioactive air will escape.
Tokyo Electric has also started preparing to vent gas from the containment areas of four reactors at the Fukushima Dai-ni nuclear plant, Kobayashi said.
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