FIRST came a violent earthquake. Then a devastating tsunami followed. Now an explosion at a nuclear power plant—and the release of radioactive material—has added to Japan's woes. But there was a momentary sense of relief on Saturday evening when the government assured the public that the explosion had not been caused by the meltdown of the reactor.
Two aftershocks of yesterday's quake rattled northeastern Japan between 10:20 and 10:40 pm, measuring 4.8 and 6.0 in magnitude. Yesterday's 8.9-magnitude earthquake set off the automatic shut-down systems in ten of Japan's 55 nuclear power plants, from which the country gets a third of its electricity. But the cooling systems malfunctioned in numerous reactors at the Fukushima plant. As the temperatures rose, so did the pressure inside two reactors. Radioactive vapour was released into the air on Saturday to ease the pressure. The control room reported radiation levels at 1,000 times the norm.
At 3:36pm the Fukushima Dai-ichi (number one) building exploded following reported tremors, billowing plumes of smoke into the atmosphere. Yukio Edano, the government's chief cabinet secretary, said that the reactor's nuclear containment vessel did not suffer a meltdown or explode, citing the plant's operator, Tokyo Electric Power Company (TEPCO).
The explosion, he said, was due to hydrogen buildup in the steam piping that mixed with oxygen, and that there was no damage to the container with the nuclear fuel. TEPCO has been filling the container with seawater combined with boric acid to cool the reactor, which Mr Edano called an "unprecedented" remedy. Boric acid is a strong neutron absorber which will help prevent the nuclear fuel from overheating. But the corrosive mixture of boric acid and seawater will also make the reactor much harder to get running again. That may be academic, though, because the elderly reactor was due for decommissioning anyway.
Four workers were injured in the explosion and another person is reported dead. The hourly radiation following the blast was 1,015 microsieverts, a level of exposure that is considered acceptable per person per year. But it has since been falling steadily, according to TEPCO. The government has ordered the evacuation of people within a 20km radius of Fukushima Dai-ichi, and a 10km radius of a second reactor nearby. "We wanted to play it safe," Mr Edano said.
Yet Japan has a spotty record for nuclear safety. In previous cases of suspected contamination, the government and industry has not been fully transparent—though it improved its response, such as after the release of small amounts of radioactive water following an earthquake near Niigata in 2007 that closed the Kashiwazaki-Kariwa Nuclear Power Plant.
The nuclear crisis adds to a day of chaos and cleanup for the country. The earthquake decimated cities and towns throughout northeastern Japan, followed by a crushing tsunami with four-metre high waves. Torrents of muddy water and firery debris washed away cars and buildings, flooding towns and farmland. The government has mobilized all self-defense forces personnel, with 50,000 directly dispatched for rescue efforts. More than 3,000 people have been rescued, including many by helicopters from building roofs, where people went to escape the floods. Around 9,500 people remain unaccounted for in the town of Minamisanriku in Miyagi Prefecture, say prefectural officials—more than half of the population of the coastal town. In all, at least 600 people have been declared dead and another 650 missing.
So powerful was the quake—off the coast of Japan and 24km under water—that Italy's National Institute of Geophysics and Volcanology said the Earth's axis shifted 25 centimeters as a result, and the US Geological Survey said the main island of Japan had shifted 2.4 meters. Tsunami warnings were issued throughout the Pacific basin and as far away as Chile. The devastation has forced power cuts to 5.6m households in the most stricken region, and more than 1m households lost their water supply, according to the Japanese news agency Kyodo.
Businesses are being disrupted. Nissan plans suspend operations at all of six of its Japanese factories until its supply chain can be assured. Honda will suspend four of its five domestic plants and Toyota said that two of its subsidiaries shut their factories in region. Sony suspended operations at six components factories in the area, and Toshiba halted a chip plant.