The cooling system for the spent fuel storage at one of the reactors of Japan's stricken Fukushima Daiichi Nuclear Power Plant stopped working Friday, a news report said.
An alarm went off at 2:27 pm indicating a problem with electrical equipment in reactor number 3, Kyodo News agency quoted the Nuclear Regulation Authority as saying, dpa reported.
Reactors 1, 2 and 3 of the plant's six were severely damaged in the March 2011 earthquake and tsunami, which cut off the cooling to the main reactor cores, leading to explosions and radiation leaks.
Plant operator Tokyo Electric Power Co (TEPCO) said that no leaks have been confirmed so far and the cooling system was expected to be restored later Friday.
On March 20, the cooling was interrupted for a day to the spent rod storage at reactors 1, 3 and 4. The fault was tracked down to a switchboard, which may have been damaged by a rat, TEPCO said.