NISA has reported that the magnitude 7.1 earthquake that hit northeastern Japan Thursday, resulted in losing power on 2 of the 3 off-site power lines to the Onagawa Nuclear Power Plant. The plant is using the remaining off-site line to maintain cooling function at its nuclear reactors. It said that the cooling systems of three spent fuel pools also stopped, but have since been restored.
After the March 11 earthquake all the reactiors at Onagawa were shut down (control rods were inserted to stop the uranium chain reaction). Also a fire was reported at the Onagawa plant and an Article 10 emergency was declared at the plant for a brief period when elevated radiation levels were detected.
At the Higashidori nuclear power plant in Aomori Prefecture, the earthquake shut down all off-site power lines, and the plant has had to switch to emergency diesel power generators.
A nuclear fuel reprocessing plant in Rokkasho, Aomori Prefecture has also lost all outside power and is operating on emergency diesel generators.
No new deevlopments at the the damaged nuclear power plant at Fukushima Daiichi as a result of the earthquake have been reported. The US NRC has suggested that severe earth tremors like this could further damage reactor pressure vessels.