Radiation continued to leak from an earthquake-stricken nuclear power station in Japan on Sunday as engineers worked to cool its overheated fuel, while thousands of people along the country’s northeastern coast remained missing after Friday’s quake and tsunami.
Conditions at the Number Three reactor at Tokyo Electric Power’s (Tepco) Fukushima Daiichi nuclear power facility, 240km north of Tokyo, deteriorated overnight as its coolant systems failed, forcing operators to pump seawater into the reactor vessel. The same emergency measure was employed on Saturday at the Number One reactor.
Yukio Edano, Japan’s chief cabinet secretary, said there was a “significant possibility” that a meltdown had occurred at both the Number One and Number Three reactors at the facility. “We are acting under the assumption that it has,” he told a televised news conference.
Radiation levels at the site spiked as engineers vented contaminated steam from both reactors to relieve pressure building up inside. “Tiny amounts” of radioactive material had escaped into the air during the ventilations, Mr Edano said.
At least 1,500 people were reported to have died and thousands more were still unaccounted for. Nearly 400,000 people had been evacuated to temporary shelters.
On Saturday, the steel and concrete building housing the Fukushima Daiichi Number One nuclear reactor was blown apart by an explosion, but officials said the blast had not breached the reactor’s core. Scientists said the use of sea water in the attempt to cool the Number One reactor was a highly unusual step, suggesting that more conventional options for bringing the situation under control had been exhausted.
There were reports that about 160 local residents may have been exposed to radiation. Thirteen people were diagnosed with possible radiation exposure, according to local media.
The Japanese government doubled the radius of the evacuation zone around the power plant to 20km after the blast.
People living and working near the plant were being evacuated on Saturday night and the International Atomic Energy Agency said the government was preparing to distribute iodine tablets, a treatment that can prevent the body from absorbing radiation in the event of a leak.
Television footage showed a large explosion at 3:36pm local time on Saturday, with plumes of grey smoke pouring from the site. Tepco said four workers at the site were injured in the explosion.
At the time Mr Edano said the blast had “destroyed the roof of the outer building but the reactor containment vessel did not explode”.
The level of radiation was higher than normal before the blast because engineers had been venting contaminated steam from the reactor vessel, in an effort to relieve pressure that had been building since the cooling system failed on Friday. The venting process triggered the explosion when combustible hydrogen released by the steam mixed with oxygen in the air, officials said.
Japan’s Nuclear and Industrial Safety Agency (Nisa) confirmed the presence of caesium and iodine, both radioactive elements, in the vicinity of Fukushima Daiichi Unit 1. Nisa reported an initial increase in levels of radioactivity around the plant earlier on Saturday, but these levels have been observed to lessen in recent hours.
The stricken Fukushima Daiichi facility has six reactors in total, but three were shut for maintenance when the earthquake occurred. The other plant, Fukushima Daini, also experienced coolant problems, and authorities have instructed people living within 10km of that facility to evacuate.
Earlier on Saturday, Naoto Kan, Japan’s prime minister, flew to the Fukushima power plant.
