Fires, leakages of water and oil, misplaced duct pipes and broken equipment, have been recorded since the 6.8 magnitude quake hit the area of the Kashiwazaki-Kariwa facility on Monday, its operator said.
Tokyo Electric Power Co said a total of 50 operating faults had been detected at the sprawling nuclear site in central Japan, thought to be the world's largest.
Prime Minister Shinzo Abe earlier chided Tokyo Electric, saying its reports to authorities were "not quick enough."
"I sternly told the company to strictly, swiftly and immediately report such incidents," said Abe.
Tokyo Electric said it had detected radiation particles in the filter of a reactor halted in the earthquake. But it said the particles were a only one-ten millionth of what is legally deemed dangerous.
Rescue teams, who had spent the night digging through rubble, turned their attention to the 12,000 people who have sought refuge at shelters in the hard-hit coastal city of Kashiwazaki, many of them elderly.
