The Nuclear and Industrial Safety Agency of Japan, has asked three nuclear power plants to inspect their reactors for damage.  This after the agency realized that the 11 March earthquake was stronger than what many nuclear power plants were designed to withstand.

Since then Japan has had more than 400 aftershocks, several in the 5 to 6 magnitude range, and at least two of magnitude 7.  There is concern that nuclear plants already damaged by the 9.0 quake, will be further weakened by the aftershocks.

Work at the damaged Fukushima Daiichi plant has been continually interrupted by aftershocks.  Currently employees are moving diesel generators to higher ground, because there is concern that there could be another big quake caused tsunami.

Fukushima Daiichi is not the only nuke plant damaged by the 11 March quake.  Fukushima DaiNi, just a few miles away, has been struggling to keep its reactors cool, using external power.  Also, in Miyagi Prefecture, there is Onagawa nuclear plant (owned by Tohoku Electric, not to be confused with Tokyo Electric).  It too, has been struggling to keep its fuel pools cool with external power.  One aftershock cut the power lines running to the plant.  Onagawa had all its reactors shut down for maintenance prior to 11 March, so all the active fuel rods are in the spent fuel pools.