Japan's Nuclear Industrial Safety Agency said there was no change in radiation levels outside the plants.
The problems were reported at two nuclear plants run by Tohoku Electric Power Co. One is in Onagawa and the other is in Higashidori, some distance north of the Fukushima Daiichi nuclear power station. Loss of power was reported at a nuclear fuel reprocessing facility in Rokkasho.
In Onagawa, radioactive water from the spent fuel pools spilled in the wake of the magnitude 7.1 temblor. Kyodo News reports that the aftershocks caused the plant to also lose the ability to cool the spent fuel rods for anywhere from 20 to 80 minutes.
That is not enough time to cause the kinds of problems that resulted from loss of cooling at the Fukushima Daiichi plant, but it does raise further concerns about the safety of spent fuel facilities during earthquakes.
The spill at Onagawa was small, though contaminated water was seen on the floors of all three reactor buildings, according to Tohoku Electric power Co., the operator of the plant. One spilled up to 3.8 liters of water with high levels of radioactive contamination.
Meanwhile, the Higashidori nuclear power station in Aomori prefecture, lost power completely, according to NISA. The plant switched to emergency diesel power for some hours before some power was restored.
The nuclear reprocessing facility in Rokkasho, Aomori prefecture, as of Friday afternoon was still running on emergency power. The reprocessing plant is operated by Japan Nuclear Fuel Ltd. JNFL said that as the pools where spent fuel is kept are located at ground level it is possible to keep pumping water into them even when all external power is lost. A tsunami would not affect the plant, JNFL says, because it is five kilometers from the shoreline and 55 meters above sea level. The reprocessing plant stores some 3,258 tons of spent fuel.