The head of the Nuclear Regulation Authority said Wednesday that regulators are unlikely to complete safety checks on any of the country's reactors by the end of March, a key process toward reactivating the facilities.

"I think none (of the checks) will be completed by the end of this fiscal year," NRA Chairman Shunichi Tanaka told a press conference, referring to the process that started after nuclear regulations were revamped in light of the three meltdowns at the Fukushima No. 1 complex in 2011.

Of 16 reactors for which applications for NRA safety checks have been submitted, the assessments for 10 units, mainly in western Japan, are closer to completion.

But a number of items have to be addressed at the 10 reactors, including estimating the maximum possible seismic motion at each plant site for purposes of designing quake resistance.

During a meeting of the NRA commissioners earlier in the day, Kunihiko Shimazaki, who is in charge of assessments related to earthquakes and tsunami, said he sees differences in utilities' approaches to the issue.

"Some utilities have come to us without changing their style (from before the nuclear crisis), while others have actively used the latest method. Differences occur in such areas," Shimazaki said.

The 10 units include reactor 3 at Shikoku Electric Power Co.'s Ikata plant in Ehime Prefecture, and reactors 3 and 4 at the Genkai plant in Saga Prefecture and units 1 and 2 at the Sendai plant in Kagoshima Prefecture. Both are owned by Kyushu Electric Power Co.

The nation's remaining 48 commercial reactors still viable remain offline amid heightened safety concerns that stemmed from the Fukushima No. 1 plant catastrophe, which was triggered by the Great East Japan Earthquake and tsunami on March 11, 2011.