TOKYO, Dec. 7 (Kyodo) — The Nuclear Regulation Authority Secretariat is considering starting preliminary safety checks on offline nuclear reactors in Japan next spring, allowing some to be restarted next summer, sources close to the matter said Thursday.

The authority plans to adopt new safety standards for nuclear power plants next July in response to the March 2011 Fukushima Daiichi nuclear plant accident, while 48 of Japan's 50 commercial nuclear reactors are left offline due to safety concerns. The remaining two are in operation under tentative standards.

In a bid to make safety checks under the new standards efficient, the secretariat is planning to launch preliminary checks next spring as an outline of the new standards becomes available, the sources said.

A bill was enacted earlier this year to require all existing nuclear reactors from next July to fit safety standards based on the latest knowledge before being allowed to restart operation.

If they fail to fit the standards, they will have to undergo improvement measures including their modification and the construction of additional facilities.

Given the time needed to build new facilities, the regulatory body has indicated that all necessary improvement measures would not necessarily have to be completed before the relevant reactors are allowed to restart operation.

The authority, while vowing to take responsibility for the safety of nuclear reactors, also noted that the government needs to decide which reactors are restarted.