Blast, radiation leak at Japanese nuclear plant

NBC, msnbc.com and news services

updated 7 minutes ago

BREAKING NEWS

TOKYO — Japanese authorities confirmed Saturday that radiation had leaked from a quake-hit nuclear plant after an explosion rocked the site.

The blast at the Fukushima Daiichi nuclear facility occurred just hours after officials said they feared a reactor could melt down.

Footage on Japanese TV showed that the walls of one building had crumbled, leaving only a skeletal metal frame standing. Plumes of smoke were spewing out of the plant.

It was not clear if the damaged building housed the reactor.

Several workers were injured by the blast at Fukushima Unit 1, Japanese TV station NHK reported.

The hourly amount of radiation leaking from Fukushima was equal to the amount permitted in one year, an official told the Kyodo news agency.

Area residents were told to stay indoors, not to drink tap water and to cover their faces with masks or wet towels, Britain's Sky News reported.

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

Authorities had warned Friday of a failure of a cooling system resulting from a powerful earthquake and tsunami.

'Radioactive vapors' 
Pressure had been building up in the reactor and Japan's Nuclear and Industrial Safety Agency told reporters Saturday that it was venting "radioactive vapors" to relieve that pressure. Officials said they were measuring radiation levels in the area.

Before the blast, the reactor in trouble had already leaked radiation: Operators at the Fukushima Daiichi plant's Unit 1 detected eight times the normal radiation levels outside the facility and 1,000 times normal inside Unit 1's control room.

 Video: Japanese nuclear plants under meltdown threat (on this page)

Two reactors had lost cooling ability and a meltdown was possible at one of the reactors because of the overheating, said Ryohei Shiomi, an official with Japan's nuclear safety commission.

Speaking before the explosion, he said that ven if there was a meltdown, it wouldn't affect people outside a six-mile radius. Most of the 51,000 residents living within the danger area had been evacuated, Shiomi added.

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Jiji news agency quoted nuclear authorities as saying that there was a high possibility that nuclear fuel rods at No. 1 reactor may be melting or have melted.

Experts said earlier that if that is the case, it means the reactor is heating up. If that is not halted, such as by venting steam which releases small amounts of radiation, there is a chance it would result in a rupture of the reactor pressure vessel.

But the risk of contamination can be minimized as long as the external container structure is intact, they said. The worry then becomes whether the quake has weakened the structure.

There has been no official word so far on whether the structure was damaged by the quake.

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The 8.9 magnitude quake and the tsunami that followed cut off electricity to the site and disabled emergency generators, knocking out the main cooling system.

'No Chernobyl is possible' 
The Tokyo Electric Power Co. (TEPCO), which operates the six-reactor Daiichi site, said Friday that it had also lost cooling ability at a second reactor there and three units at its nearby Fukushima Daini site.

The government declared state of emergency at all those units.

Prior to the blast, Japanese officials and experts were at pains to say that while there would be radiation leaks, they would be very small and have dismissed suggestions of a repeat of a Chernobyl-type disaster.

"No Chernobyl is possible at a light water reactor. Loss of coolant means a temperature rise, but it also will stop the reaction," said Naoto Sekimura, a professor at the University of Tokyo.

"Even in the worst-case scenario, that would mean some radioactive leakage and equipment damage, but not an explosion. If venting is done carefully, there will be little leakage. Certainly not beyond the 3-km (1.8-mile) radius."

Edwin Lyman, a senior scientist with the Union of Concerned Scientists, which opposes nuclear energy, told msnbc.com Friday that TEPCO was facing a potential catastrophe.

"It's just as bad as it sounds," he said. "What they have not been able to do is restore cooling of the radioactive core to prevent overheating and that's causing a variety of problems, including a rise in temperature and pressure with the containment (buildings).

"What's critical is, are they able to restore cooling and prevent fuel damage? If the fuel starts to get damaged, eventually it will melt through the reactor vessel and drop to the floor of the containment building," raising the odds that highly radioactive materials could be released into the environment, he said.

 Video: Japan in shock: 'Nothing compares to what happened' (on this page)

But Steve Kerekes, spokesman for the U.S.-based Nuclear Energy Institute, said that while the situation was serious, a meltdown remains unlikely and, even if it occurred would not necessarily pose a threat to public health and safety.

"Obviously that wouldn't be a good thing, but at Three Mile Island about half the core melted and, at the end of the day … there were no adverse impacts to the public," he said.

Earlier, experts downplayed the seriousness of the trace levels of radiation detected at the Fukushima Daiichi plant.

Japan's Asahi Shimbun newspaper reported Friday that radiation levels per hour in the area near the front entrance of the No. 1 Fukushima plant reached 0.59 micro Sievert, which is eight times the normal levels. The central control room of the reactor recorded radiation levels 1,000 times the normal level, which would be approximately 70 microsieverts per hour, or 7 millirems, according to calculations by msnbc.com.

Generally it would take much higher levels of outside exposure to cause health problems in humans. Radiation exposure is often measured in units called "millirem," which is 1/1000 of a rem. The average American is exposed to about 620 millirem each year, with about half from natural sources and half from manmade sources, according to the Nuclear Regulatory Commission.

A chest X-ray results in an exposure of about 8 to 10 millirems per film. A cross-country airplane flight results in a dose of 4 millirems.

Exposures of less than 50 millirem typically produce changes in blood chemistry, but no symptoms, according to the U.S. Environmental Protection Agency.

By comparison, normal exposure rates range from approximately 0.03 microsieverts per hour to 0.23 microsieverts per hour in La Paz, Bolivia, the highest city in the world.

 Video: Northern Japan engulfed in destruction (on this page)

Dr. Fred Mettler, emeritus professor of radiology at the University of New Mexico, studied the health effects of the Chernobyl explosions in Ukraine and has spent decades researching and writing about radiation exposure.

Mettler said the plants in the U.S. and Japan are far advanced from Chernobyl, which he likened to an airplane hangar with the nuclear reactor core sitting out in the open.

Japanese scientists have had more than 60 years since World War II to study the health effects of radiation poisoning and they won't take any step lightly, including releasing radioactive vapors into the atmosphere to ease building pressure in a reactor, he said.

"These people are more knowledgeable about radiation than anyone," Mettler said.

"People don't become acutely sick until they're over 50 rem and more like 100 rem," Mettler said.

However, he noted that Japanese scientists studying health effects since Hiroshima have determined that some health effects can start to occur at exposures of 15 rem, even if the results aren't apparent for 10 years.

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There were about 80,000 survivors of the atomic bomb, for instance, with an average exposure of 23 rem, Mettler said. During the next 50 years about 9,000 of those survivors died of cancer. However, Japanese scientists concluded that the toll included about 500 excess deaths, that is, deaths that would not otherwise have been expected.

The Daiichi site is located in Onahama city. The 460-megawatt Unit 1 began operating in 1971 and is the oldest at the facility. It is a boiling water reactor that drives the turbine with radioactive water, unlike pressurized water reactors usually found in the United States. Japanese regulators decided in February to allow it to run another 10 years. The reactors were manufactured by GE. (Msnbc.com is a joint venture between NBC Universal and Microsoft. GE is a part owner of NBC Universal.)

The quake, the most powerful since Japan started keeping records 140 years ago, sparked at least 80 fires in cities and towns along the coast.

Oil refineries were shut down and one refinery was ablaze. Power to millions of homes and businesses was knocked out.

Severe power shortages were also expected over the weekend.

NBC News, msnbc.com staff, Reuters and The Associated Press contributed to this report.