Only two of Japan's 50 reactors are online. The rest are suspended for checks after the Fukushima meltdowns.
Checks have been also made for seismic faults at several other plants following criticism that past investigations of faults by utilities were faulty. Although the government, desperate to stabilize Japan's energy supply and cost, has said reactors that have passed strict safety checks can resume operations, fresh investigations into faults could further delay the process.
Hiroshi Sato, a University of Tokyo seismologist, said the NRA should make a safety-first decision.
He said to ensure safety, experts should expand the investigation into faults in the northern Aomori district, home to other major nuclear facilities including a spent fuel reprocessing plant.
Although the NRA is designed to have more independence and power than its predecessors, under Japan's lax nuclear safety law, neither the regulator nor the government has legal power to order operators to shut down or take specific action with their reactors.