TOKYO —
Radiation levels shot up in Tokyo and its vicinity Tuesday following the nuclear accident at the Fukushima No. 1 nuclear power plant in northeastern Japan that was triggered by last week’s massive earthquake and subsequent tsunami, local governments said.
But those levels did not pose immediate danger to human health, the Ministry of Education, Culture, Sports, Science and Technology said.
In Tokyo, small amounts of radioactive substances, such as iodine and cesium, were detected, the metropolitan government said.
In Ibaraki Prefecture, adjacent to Fukushima Prefecture where the troubled Fukushima No. 1 nuclear power plant is located, the amount of radiation at one stage reached 5 microsievert per hour, 100 times higher than usual, the Ibaraki prefectural government said.
In Kanagawa Prefecture, the radiation level shot up 10 times higher than usual.
In Saitama, capital of Saitama Prefecture, the amount of radiation reached 1,222 nanosievert per hour—a figure about 40 times higher than usual.
In Ichihara, Chiba Prefecture, the amount of radiation showed a two- to four-fold increase, the Chiba prefectural government said.
The amount of radiation rose to 1.318 micro sievert per hour—a figure 33 times bigger than usual—in Tochigi Prefecture’s capital of Utsunomiya, the Tochigi prefectural government said.
The science ministry said it had asked prefectural governments to observe radiation levels as frequently as possible.
Meanwhile, Chief Cabinet Secretary Yukio Edano said the radiation level reached 400 millisievert per hour near the No. 3 reactor at the Fukushima No. 1 plant Tuesday morning. The amount is 400 times higher than the allowable limit for citizens in a year.
On Monday, the radiation level near the No. 3 reactor peaked at 3,130 microsievert or about 3 millisievert per hour.
Steam containing radioactive substances was released from the Fukushima No. 1 nuclear power plant as part of efforts to reduce pressures within the reactor container there.
Northerly winds brought radioactive substances from Fukushima Prefecture to Tokyo and its vicinity, nuclear experts said.
The crisis at the quake-hit Fukushima No. 1 nuclear plant reached a critical phase Tuesday with radiation feared to have leaked after apparent hydrogen blasts at two more reactors, triggering growing fears of widespread contamination.
In a televised address to the nation, Prime Minister Naoto Kan urged people living between 20 and 30 kilometers of the plant to stay indoors, after radiation equivalent to 400 times the level to which people can safely be exposed in one year was detected near the No. 3 reactor in the plant.
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.
‘‘The danger of further radiation leaks (from the plant) is increasing.’’ Kan warned the public at a press conference, while asking people to ‘‘act calmly.’‘
Edano said the high radiation level detected at 10:22 a.m. after the explosions at the No. 2 and No. 4 reactors ‘‘would certainly have negative effects on the human body.’‘
Plant operator Tokyo Electric Power Co (TEPCO) said the problem could develop into a critical ‘‘meltdown’’ situation after part of the No. 2 reactor’s container vessel was damaged following the apparent hydrogen explosion at 6:10 a.m.
TEPCO ordered some workers at the site to temporarily evacuate the area, but the utility has been continuing operations to pour seawater into the troubled No. 2 reactor to prevent overheating and further damage to its container.
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.
Also, a fire occurred around 9:40 a.m. at the plant’s No. 4 reactor, where spent nuclear fuels are stored, but it was extinguished later, according to TEPCO. Edano said it was likely caused by another hydrogen explosion.
The nuclear 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.
Given that the building that houses the No. 2 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 cores of the No. 1, No. 2 and No. 3 reactors at the plant are believed to have partially melted following Friday’s magnitude 9.0 earthquake that hit northeastern and eastern Japan.
The country’s biggest recorded quake, which is also one of the largest in global history, caused the three reactors, which were all operating at the time, to automatically shut down. The No. 4 reactor and two others at the plant were not then in service.
Earlier in the day, the government and TEPCO set up an integrated headquarters, headed by Kan, to tackle the nuclear crisis.
‘‘A worrisome situation remains but I hope we can overcome this crisis,’’ Kan said of the nuclear power plant. ‘‘I will take all measures so that damage will not expand.’‘
Kan also strongly criticized TEPCO for its handling of the stricken Fukushima No. 1 nuclear power plant.
‘‘The TV reported an explosion. But nothing was said to the premier’s office for about an hour,’’ a reporter overheard Kan saying during a meeting with executives of the power company at its head office. ‘‘What is going on?’‘
Kan strongly ordered the company not to withdraw its employees from the power plant, which has been facing a series of problems since Friday’s massive quake, ranging from explosions to radiation leaks.
‘‘In the event of withdrawal from there, I’m 100% certain that the company will collapse,’’ Kan said. ‘‘I want you all to be determined.’‘
The government, as well as the public, has been dissatisfied with the company’s way of releasing information regarding the crippled nuclear plant.
In an attempt to work more closely together, the government and the company launched Tuesday a joint headquarters of the crisis involving the Fukushima No. 1 plant.
The headquarters set up at the company’s head office is headed by Kan, with industry minister Banri Kaieda and TEPCO President Masataka Shimizu serving as its deputy chiefs.
The development follows hydrogen blasts at both of the plant’s No. 1 and No. 3 reactors on Saturday and Monday.
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.
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.
The No. 4 reactor of TEPCO’s Fukushima No. 2 nuclear plant, which is adjacent to the No. 1 plant, has successfully cooled down, meaning the plant no longer has a reactor in an emergency situation after three of its four reactors were once in that state after the quake, the firm said.
Japan has asked the United States to provide more cooling equipment to help deal with the crisis, 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.
Meanwhile, the transport ministry banned aircraft on Tuesday from flying within 30 kilometers of the Fukushima No. 1 nuclear power plant.
The move, imposed under the Civil Aeronautics Law, excludes aircraft engaged in search and rescue operations, and is not expected to have a large impact on scheduled commercial flights in the country, according to the Land, Infrastructure, Transport and Tourism Ministry.
Similar irregular flight bans have been imposed three times before, including one for the Group of Eight summit meeting in Hokkaido in 2008 and another for meetings of the Asia-Pacific Economic Cooperation forum in Yokohama last October.
