An explosion rocked one of Japan’s nuclear power plants, causing a portion of a building to crumble, sending white smoke billowing into the air and prompting Japanese officials to warn those in the vicinity to cover their mouths and stay indoors.
In what may be the most serious nuclear power crisis since the Chernobyl disaster, the explosion followed large tremors at the Fukushima Daiichi number one reactor Saturday afternoon, injuring four workers who were struggling to get the quake-stricken unit under control.
Earlier, Japan’s Nuclear and Industrial Safety Agency had warned that the reactor, whose cooling system had been crippled by the giant earthquake on Friday, could be nearing a meltdown and that two radioactive substances, cesium and radioactive iodine, had already been detected nearby.
The extent of the blast remained unclear, but it is likely that at the very least it damaged the containment building surrounding the reactor vessel. The government ordered an evacuation of residents living within a 12.5-mile radius of the power plant.
The unit, built 40 years ago by General Electric, is just one of five reactors severely imperiled by the earthquake and subsequent disruptions in the power supply the reactors used for cooling systems.
Earlier, Japanese authorities had declared a state of emergency for the five reactors at two nuclear power complexes as military and utility officials scrambled to tame rising pressure and radioactivity levels inside the units and stabilize the systems used to cool the plants’ hot reactor cores.
Radiation had earlier surged to around 1,000 times the normal level in the control room of one reactor, Japan’s Nuclear and Industrial Safety Agency (NISA) said. Meanwhile, Tokyo Electric Power Co. said Saturday that the temperatures at two other reactors at a different power plant were rising and that it had lost control over pressure in three reactors there.
The explosion at the reactor is certain to rattle confidence in nuclear power in Japan, victim of the only nuclear weapons explosions and where people have long been sensitized to the dangers of radioactive releases. In the United States, it will deal a severe blow to advocates of a nuclear power renaissance.
In Tokyo late Saturday afternoon, news of the explosion sparked a run on bottled water supplies. At a Tokyo convenience store that had been well-stocked earlier in the day, a line of a half-dozen customers were picking up the last bottles.
“I saw a chain letter e-mail from my friend telling about the explosion in Fukushima,” said one shopper who, as is typical there, wanted only to give his first name, Masahito. “Right now they’re saying it’s a nuclear accident. I have been trying to buy enough water for one week, just in case, but I can’t find it anywhere. I’ve already been to four places, including a supermarket.”
The earthquake has led to the shutdown of 11 of the Japan’s 55 nuclear power plants, representing nearly 20 percent of the country’s capacity. It will deal an economic blow to Japan, which relies on nuclear power for one-third of its electricity generation, and could complicate economic recovery efforts.
“It’s a very serious situation for the reactors and might ultimately render those reactors unusable,” said Howard Shaffer, a former Navy submarine engineer and a member of the American Nuclear Society’s public information committee.
Japanese authorities initially evacuated about 3,000 residents living within a 1.9-mile radius of the Fukushima Daiichi plant on the east coast about 200 miles north of Tokyo and south of the heavily damaged city of Sendai. Later they widened that evacuation to a six-mile radius and, after the explosion, extended the evacuation area to 12.5 miles. People within a 16.2-mile radius were told to remain indoors, said the Web site of the International Atomic Energy Agency’s (IAEA) Incident and Emergency Center.
According to NHK news, the Japanese health ministry had already dispatched an emergency medical team, including experts on radiation exposure, to the Fukushima Daiichi complex nuclear plant.
Tokyo Electric, which owns the Fukushima Daiichi complex, has also said that it was also having trouble controlling three of the four reactors it owns at its nearby Fukushima Daina plant.
Earlier, NISA said no dangerous radioactive material had been released, but the government evacuated people as a precaution nonetheless.
The problems at the nuclear plants came in waves, starting with two of the six Daiichi units.
The quake disrupted the electric power the reactors used to run their cooling facilities, which pump water into the reactor core to cool the fuel rods there. The reactors switched to backup diesel generators, but the tsunami then swept in and shut down the generators used for the No. 2 reactor at Fukushima Daiichi. The unit then tapped excess steam in the core to power a turbine and switched to battery power, which would last only a few hours.
“There’s a basic cooling system that requires power, which they don’t have,” said Glenn McCullough, former chairman of the Tennessee Valley Authority, who was tracking the Japan situation.
Japanese utility and government officials raced to get another generator to the site to prevent a possible partial meltdown similar to what took place in 1979 at Three Mile Island in Pennsylvania. By Saturday morning they said they had succeeded. The utility said it had restored power from the grid, but the IAEA said power was restored from “mobile electricity supplies.”
Later Saturday an official with Japan’s nuclear safety commission said a meltdown was possible because of the overheating, the Associated Press reported. Ryohei Shiomi added that even if there were a meltdown, it wouldn’t affect residents outside the evacuated six-mile radius.
Meanwhile, Tokyo Electric said it had decided to vent slightly radioactive steam and gas to relieve pressure that had increased sharply in the containment building at unit No. 1. The company said on its Web site that the increase was “assumed to be due to leakage of reactor coolant.” It remained unclear where the leak was. The company said it did not think there was leakage of reactor coolant in the containment vessel “at this moment.”
The purpose of a containment building, which surrounds the reactor core, is to contain unplanned releases of steam or gases from the core. If there is not enough water in the reactor core, water turns to steam and is released through special valves into the containment building, nuclear experts said.
That could cause an increase in pressure inside the sealed containment building and ultimately force a release of gas and steam through filters meant to keep most, though not all, of the radiation inside the building.
There were also reports of elevated radiation levels inside the control room of that reactor unit. NISA said levels were 1,000 times the norm . The AP later quoted an official from NISA as saying that a measurement of radiation levels outside the plant was eight times as high as normal. Even that level of radiation still posed little danger to residents, nuclear experts said. They also said the release of steam and gas from containment buildings posed little danger.
The status of Tokyo Electric’s Daina plants remained unclear. Earlier, they had been said to have completed automatic shutdowns. But Saturday, Tokyo Electric suggested that they were having problems similar to the ones at the other nuclear complex because of disruptions in the power supply needed to run cooling facilities.
“The danger is the very thermally hot reactor cores at the plant must be continuously cooled for 24 to 48 hours,” said Kevin Kamps, a specialist in nuclear waste at Beyond Nuclear, a group devoted to highlighting the perils of nuclear power. “Without any electricity, the pumps won’t be able to pump water through the hot reactor cores to cool them.”
President Obama said at a news conference that he had told Energy Secretary Steven Chu to offer help to Japan.
In a statement that confused nuclear experts, Secretary of State Hillary Rodham Clinton said Friday morning that U.S. Air Force planes in Japan had delivered “coolant” to a nuclear power plant affected by the quake. Nuclear reactors do not require special coolants, only large amounts of pumped water.
“They have very high engineering standards, but one of their plants came under a lot of stress with the earthquake and didn’t have enough coolant,” she said, “and so Air Force planes were able to deliver that.”
An Air Force spokesman at the Pentagon, however, said he was unaware of any deliveries being made by Air Force planes related to the reactor issues.
“To our knowledge, we have delivered nothing in support of the nuclear power plant,” Lt. Col. John Haynes said. “Obviously, we stand by to assist with anything they might need.” He said the Air Force had received no formal request for help.
State Department officials later said Clinton misspoke.
In addition to the efforts to get Tokyo Electric’s nuclear reactors under control, Japan’s NISA said Friday that a fire had broken out at the Onagawa nuclear power plant but was later extinguished. The three reactors at the Onagawa site remained closed.
The key buildings in the Onagawa plant are about 45 feet above sea level, according to the Web site of Tohoku Electric Power, owner of the plant. The company said that was about twice the height of the previous highest tsunami.
The IAEA said it is seeking details on Japan’s nuclear power plants and research reactors, including information on off-site and on-site electrical power supplies, cooling systems and the condition of the reactor buildings.
Nuclear fuel requires continued cooling even after a plant is shut down, the IAEA noted.
“This is the most challenging seismic event on record, so it is a severe test,” McCullough said. “Clearly the Japanese government is taking this very seriously.”
Staff writers Chico Harlan in Tokyo and Mary Beth Sheridan contributed to this report.