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Tuesday, March 15, 2011

Container damaged, radiation leak feared at Fukushima No. 2 reactor | The Japan Times Online

South-Yokohama Powerplant (Yokohama,Japan)Image via WikipediaContainer damaged, radiation leak feared at Fukushima No. 2 reactor | The Japan Times Online

Radiation is feared to have leaked after part of a container vessel was apparently damaged by an explosion at the troubled No. 2 reactor of the quake-hit Fukushima nuclear plant Tuesday morning, its operator said, triggering fears that the problem could develop into a critical "meltdown" situation.

The government's Nuclear and Industrial Safety Agency said that radiation levels at the plant shot up after the apparent blast at 6:10 a.m., and the operator Tokyo Electric Power Co. ordered some workers at the site to temporarily evacuate the area.

Prime Minister Naoto Kan urged people living between 20 and 30 kilometers of the plant to stay indoors. Residents within a 20 km radius have already been ordered to vacate the area following Saturday's hydrogen blast at the plant's No. 1 reactor, and Kan stressed all people within the area must evacuate.

"The radiation level has risen substantially. The risk that radiation will leak from now on has risen," Kan said.

The blast at the No. 2 reactor appears to be a hydrogen explosion, Chief Cabinet Secretary Yukio Edano said.

A fire also occurred around 9:40 a.m. at the plant's No. 4 reactor, Tepco said.

The agency said the explosion at the No. 2 reactor may have damaged the "suppression chamber," a facility connected to the reactor's container which is designed to cool down radiation steam and lower the pressure in the reactor. It said a sharp decline in the pressure level of the chamber suggests damage.

Following the incident, the radiation level near the main gate of the Fukushima No. 1 plant exceeded the legal limit to reach 965.5 micro sievert per hour at 7:00 a.m. and jumped to 8,217 micro sievert at 8:31 a.m., the agency said. The latter amount is more than eight times the 1,000 micro sievert level to which people can safely be exposed in one year.

Given that the building housing the reactor has already been damaged by Monday's hydrogen blast at the neighboring No. 3 reactor, a spread of radiation outside the plant has become a serious threat, experts say.

The possibility of a meltdown, in which fuel rods melt and are destroyed, "cannot be ruled out" as the fuel rods have been damaged, the utility said.

In Ibaraki Prefecture, just south of Fukushima, an amount of radiation up to about 100 times the usual level was measured Tuesday morning. The wind was blowing from north to south when the incident occurred at the Fukushima plant.

The cores of the three reactors are believed to have partially melted following Friday's magnitude 9.0 earthquake that hit northeastern and eastern Japan, causing the No. 1, 2 and 3 reactors — all that were operating at the plant at the time — to automatically shut down. The plant has six reactors.

Kan said earlier in the morning that the government and Tepco will set up an integrated headquarters, headed by himself, to address issues at the Fukushima No. 1 plant.

"A worrisome situation remains but I hope to take the lead in overcoming this crisis," Kan said of the nuclear power plant. "I will take all measures so that damage will not expand."

At the headquarters set up at the Tepco head office, with the company's president and the economy, trade and industry minister serving as its deputy chiefs, Kan confronted Tepco officials about their delay in reporting the initial blast.

The development follows hydrogen blasts at both of the plant's No. 1 and No. 3 reactors, whose cores are believed to have partially melted.

The cooling system for the No. 2 reactor broke down on Monday, causing water levels to rapidly fall and fully exposing its fuel rods for several hours.

Although workers have been pouring seawater into the reactor to prevent overheating and further damage to the container, its core is also believed to have been partially melting.

As of 6:28 a.m., the water level had recovered to cover about 1.2 meters of the fuel rods, about one-third of their height, Tepco said.

Japan has asked the United States to provide more cooling equipment to help stabilize the plant, Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission, said in Washington. The NRC has already sent two technological experts and is fully supporting Japanese efforts, he said.

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