The strongest aftershock to hit since the day of the March 11 earthquake and tsunami in Japan rocked a wide section of the country’s northeast Thursday night, prompting a tsunami alert, raising fears of further damage to the already crippled Fukushima Daiichi nuclear plant and knocking out external power at three other nuclear facilities.
People in coastal areas across north-east Japan were told to evacuate to higher ground after the magnitude 7.4 earthquake, while public broadcaster NHK issued warnings of a tsunami of up to three feet along more than 300 miles of coastline north of Tokyo.
Workers at the Fukushima nuclear plant were evacuated by the operator, Tokyo Electric Power Co., which said there were no reports of injuries among the emergency crews at the plant after the earthquake. The company added that there were no reports of additional problems at the plant, while other nuclear facilities in Ibaraki and Miyagi prefectures also appeared to be operating normally.
The tremor struck just hours before the one-month anniversary of the magnitude 9 earthquake that triggered a tsunami and subsequent nuclear crisis. To date, police have confirmed that 12,596 people died as a result of the March 11 quake, while a further 14,747 are listed as missing presumed dead.
Naoto Kan, the prime minister, summoned his senior officials before midnight and was informed by the Meteorological Agency that the tremor was an aftershock – the largest to date – from the March 11 earthquake.
He was also informed that five northern prefectures were experiencing power blackouts and that authorities had closed major expressways in northern Japan as a precaution, but that no spikes in radiation levels had been detected close to the Fukushima nuclear plant and that work to inject coolant water into the facility was continuing.
This latest earthquake will cause renewed concern about the fragile condition of the crippled facility, which continues to leak radiation into the ocean and atmosphere.
In a confidential risk-assessment study completed in late March, the United States’ Nuclear Regulatory Commission warned that the containment structures around the four damaged reactors at the Fukushima Daiichi plant are under great stresses as they fill up with radioactive cooling water, making them extremely vulnerable to rupturing in the event of a major aftershock.
The document, reported in The New York Times, also said there was an increased possibility fo explosions within the containment structures due to the release of hydrogen and oxygen from seawater pumped into the reactors.
The report concluded that the plant is facing a growing array of new threats that could persists indefinitely and that some of the actions being taken by TEPCO to ameliorate the crisis may be worsening the longer-term situation.[via NY Times and the Telegraph (UK)]