UPDATE AS OF 11:30 A.M. EDT, MONDAY, APRIL 11:
No damage to Japan's nuclear power plants was reported today after another strong aftershock hit the northeast coast. The temblor, measured at magnitude 6.6 by the U.S. Geological Survey, rocked the country one month after the magnitude 9.0 earthquake and tsunami struck March 11, damaging the Fukushima Daiichi nuclear power plant. A magnitude 7.1 aftershock rattled Japan April 7.
The Monday earthquake prompted the temporary evacuation of workers at the plant and interrupted the offsite electric power supply for less than an hour. Injection of cooling water to reactors 1, 2, and 3 resumed within an hour. Officials reported no new damage or increased radiation levels. Workers continued to spray water into the spent fuel pools of reactors 1-4 as needed.
As an additional safety measure, Tokyo Electric Power Co. (TEPCO) has brought additional diesel generators to the site as a backup in case offsite power is disabled.
Preparations are being made to transfer highly radioactive water from reactor 2 to a water storage tank. Workers are inspecting the tank to ensure there will be no leaks.
TEPCO is injecting nitrogen gas into the reactor 1 containment vessel to reduce the possibility of a hydrogen explosion. TEPCO plans to inject nitrogen into the containment vessels of reactors 2 and 3, the Japan Atomic Industrial Forum reported.
TEPCO used a drone helicopter to take aerial pictures of reactor buildings that are highly contaminated. TEPCO also is using remote-controlled heavy equipment to remove radioactive debris.
Japanese authorities announced that residents of some municipalities outside the 12.5-mile radius evacuation zone will be relocated to reduce long-term radiation exposure. Radiation can accumulate in some places based on weather and geographical factors. The relocation orders will apply to areas where there is a possibility of residents receiving a dose of 2,000 millirem over the course of a year.