Explosion at Japan’s Fukushima nuclear plant

An explosion occurred at the Fukushima Dai-Ichi power station north of Tokyo, destroying the walls of the No. 1 reactor building. “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.

Bloomberg News quoted Tokyo Electric Power Co., the plant’s operator, as saying the explosion happened “near” the No. 1 reactor at around 3:40 p.m. Japan time on Saturday. Four people were reported injured. The explosion came roughly 26 and a half hours after an 8.9-magnitude earthquake caused a deadly tsunami that killed hundreds and caused both plants to be shut down.

Authorities issued broad evacuation orders on Saturday for people living near the plants and warned that small amounts of radioactive material were likely to leak out. Officials said even before the explosion that they had detected cesium, an indication that some of the fuel was already damaged.

Friday’s double disaster, which pulverized Japan’s northeastern coast, has left 574 people dead by official count, although local media reports said at least 1,300 people may have been killed.

Tokyo Power Electric Co., the utility that runs the Fukushima Dai-ichi plant, said four workers had suffered fractures and bruises and were being treated at a hospital. A nuclear expert said a meltdown may not pose widespread danger.

Footage on Japanese TV showed that the walls of the reactor’s building had crumbled, leaving only a skeletal metal frame standing. Puffs of smoke were spewing out of the plant in Fukushima, 30 kilometers from Iwaki.

"We are now trying to analyze what is behind the explosion," said government spokesman Yukio Edano, stressing that people should quickly evacuate a 10-kilometer radius. "We ask everyone to take action to secure safety."

The trouble began at the plant’s Unit 1 after the massive 8.9-magnitude earthquake and the tsunami it spawned knocked out power there. According to official figures, 586 people are missing and 1,105 injured. In addition, police said between 200 and 300 bodies were found along the coast in Sendai, the biggest city in the area near the quake’s epicenter.

The true scale of the destruction was still not known more than 24 hours after the quake since washed-out roads and shut airports have hindered access to the area. An untold number of bodies were believed to be buried in the rubble and debris.

In another disturbing development that could substantially raise the death toll, Kyodo news agency said rail operators lost contact with four trains running on coastal lines on Friday and still had not found them by Saturday afternoon.

East Japan Railway Co. said it did not know how many people were aboard the trains.

Adding to worries was the fate of nuclear power plants. Japan has declared states of emergency for five nuclear reactors at two power plants after the units lost cooling ability.

The most troubled one, Fukushima Dai-ichi, is facing meltdown, officials have said.

A "meltdown" is not a technical term. Rather, it is an informal way of referring to a very serious collapse of a power plant’s systems and its ability to manage temperatures. It is not immediately clear if a meltdown would cause serious radiation risk, and if it did how far the risk would extend.

Yaroslov Shtrombakh, a Russian nuclear expert, said a Chernobyl-style meltdown was unlikely.

"It’s not a fast reaction like at Chernobyl," he said. "I think that everything will be contained within the grounds, and there will be no big catastrophe."

In 1986, the Chernobyl nuclear reactor exploded and caught fire, sending a cloud of radiation over much of Europe.

Pressure has been building up in Fukushima reactor — it’s now twice the normal level — and Japan’s Nuclear and Industrial Safety Agency told reporters Saturday that the plant was venting "radioactive vapors." Officials said they were measuring radiation levels in the area. Wind in the region is weak and headed northeast, out to sea, according to the Meteorological Agency.

The reactor in trouble has already leaked some radiation: Operators have detected eight times the normal radiation levels outside the facility and 1,000 times normal inside Unit 1’s control room.

Ryohei Shiomi, a nuclear official, said that each hour the plant was releasing the amount of radiation a person normal absorbs in a year.

He has said that even if there were a meltdown, it wouldn’t affect people outside a 10-kilometer radius — an assertion that might need revising if the situation deteriorates. Most of the 51,000 residents living within the danger area had been evacuated, he said.

Meanwhile, the first wave of military rescuers began arriving by boats and helicopters.

Prime Minister Naoto Kan said 50,000 troops would join rescue and recovery efforts following the quake that unleashed one of the greatest disasters Japan has witnessed — a 7-meter tsunami that washed far inland over fields, smashing towns, airports and highways in its way.

Technologically advanced Japan is well prepared for quakes and its buildings can withstand strong jolts, even a temblor like Friday’s, which was the strongest the country has experienced since official records started in the late 1800s. What was beyond human control was the killer tsunami that followed.

President Barack Obama pledged U.S. assistance following what he called a potentially "catastrophic" disaster. He said one U.S. aircraft carrier was already in Japan and a second was on its way. A U.S. ship was also heading to the Marianas Islands to assist as needed, he said.

Japan’s worst previous quake was a magnitude 8.3 temblor in Kanto that killed 143,000 people in 1923, according to the USGS. A magnitude 7.2 quake in Kobe killed 6,400 people in 1995.

Japan lies on the "Ring of Fire" — an arc of earthquake and volcanic zones stretching around the Pacific where about 90 percent of the world’s quakes occur, including the one that triggered the Dec. 26, 2004, Indian Ocean tsunami that killed an estimated 230,000 people in 12 countries. A magnitude-8.8 quake that shook central Chile in February 2010 also generated a tsunami and killed 524 people.

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.

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.

Environmental watchdog Greenpeace has expressed its condolences to victims of Friday’s 8.9 earthquake-cum-tsunami in northeastern Japan.

In a statement, Greenpeace said that it is deeply concerned about the potential safety and environmental impacts of both the earthquake and tsunami on Japanese nuclear installations, as well as other hazardous industries such as chemical or oil refineries.

According to media reports, twenty reactors at four power generation plants have been shut down, and so far no release of radiation has been reported.

Greenpeace said it is concerned about tsunami damage to nuclear installations such as the Fukushima nuclear power plant, which could affect reactor cooling systems and damage highly radioactive waste storage.

It warned that even if immediately shut down, the reactors require active cooling and large amounts of cooling water to avoid the risk of overheating and meltdown.

It said that it would continue to monitor what is clearly a rapidly unfolding situation.

"We hope that future investigations into the impacts on the nuclear installations, and how they affect the population and surrounding environment will be conducted independently and reported to the public," it said.

By José Santamarta, www.evwind.com/noticias.php