NHK : Earthquake Destroy Fukushima Reactor

An explosion near a nuclear power station north of Tokyo destroyed the walls of a reactor building and injured four people. Japanese officials said the reactor may melt down following yesterday’s record earthquake.
Tokyo Electric Power Co., Asia’s biggest utility, said there was an explosion near the No. 1 reactor at the Fukushima Dai-Ichi nuclear power station at 3:40 p.m. Japan time today. Four people were injured and radioactivity levels are rising, spokesman Taisuke Tomikawa said in by telephone.
Serious damage to the container of the reactor is believed to be unlikely, Kyodo News reported, citing unidentified nuclear safety agency officials. Fuel rods at the reactor 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 earlier 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 intensity it melts the floor of the reactor containment housing.
“If they cannot get the nuclear reactor back under control during the day, this may end up being the biggest problem of all,” said Ken Courtis, former vice chairman of Goldman Sachs Group Inc. in Asia. “A meltdown, which would cause massive immediate damage, would also set the nuclear industry back decades. This would have vast implications for the global energy equation and perforce the world economy.”

Death Toll

Japan’s central bank yesterday pledged to ensure financial stability after the earthquake forced Toyota Motor Corp. to shut some plants, shut down oil refineries and sparked a plunge in stocks. The quake and the tsunami that followed are estimated to have killed at least 500 people with hundreds more missing, the National Police Agency said.
The disaster may curb Japan’s recovery from an economic slump in the fourth quarter as Prime Minister Naoto Kan struggles to convince investors about his ability to tackle the world’s largest public-debt burden. While the Finance Ministry said it’s too soon to gauge the quake’s economic impact, the Nikkei 225 Stock Average dropped 1.7 percent yesterday.

Tokyo Electric

Tokyo Electric started releasing radioactive gas and steam into the atmosphere about 9 a.m. local time to reduce pressure in the containment housing after yesterday’s magnitude 8.9 earthquake, Akitsuka Kobayashi, a company spokesman, said by phone earlier today. The utility has also started preparing to vent gas from the containment areas of four reactors at the nearby Fukushima Dai-Ni nuclear plant, he said.
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 evacuation zone will be maintained at 10 kilometers from Dai-Ni plant and will be extended to 20 kilometers from Dai-Ichi plant, said Toshihiro Murakamia, spokesman for the Fukushima prefecture government.
“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.”

Pressure Control

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.

Nuclear Meltdown

Lack of adequate cooling for a reactor may cause a core meltdown, the most dangerous kind of nuclear power accident, according to the U.S. Nuclear Regulatory Commission.
A meltdown could potentially breach a reactor’s containment building, releasing massive amounts of radiation, according to information on the agency’s website. The 1979 accident at the Three Mile Island reactor in Pennsylvania resulted in a partial meltdown, without a breach in the containment building, according to the commission.
The 1986 Chernobyl accident in Russia caused the release of at least 5 percent of the radioactive reactor core, according to the World Nuclear Association, which represents the industry.